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1
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Richter EA, Bilan PJ, Klip A. A comprehensive view of muscle glucose uptake: regulation by insulin, contractile activity, and exercise. Physiol Rev 2025; 105:1867-1945. [PMID: 40173020 DOI: 10.1152/physrev.00033.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2024] [Revised: 11/07/2024] [Accepted: 03/08/2025] [Indexed: 04/04/2025] Open
Abstract
Skeletal muscle is the main site of glucose deposition in the body during meals and the major glucose utilizer during physical activity. Although in both instances the supply of glucose from the circulation to the muscle is of paramount importance, in most conditions the rate-limiting step in glucose uptake, storage, and utilization is the transport of glucose across the muscle cell membrane. This step is dependent upon the translocation of the insulin- and contraction-responsive glucose transporter GLUT4 from intracellular storage sites to the sarcolemma and T tubules. Here, we first analyze how glucose can traverse the capillary wall into the muscle interstitial space. We then review the molecular processes that regulate GLUT4 translocation in response to insulin and muscle contractions and the methodologies utilized to unravel them. We further discuss how physical activity and inactivity, respectively, lead to increased and decreased insulin action in muscle and touch upon sex differences in glucose metabolism. Although many key processes regulating glucose uptake in muscle are known, the advent of newer and bioinformatics tools has revealed further molecular signaling processes reaching a staggering level of complexity. Much of this molecular mapping has emerged from cellular and animal studies and more recently from application of a variety of -omics in human tissues. In the future, it will be imperative to validate the translatability of results drawn from experimental systems to human physiology.
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Affiliation(s)
- Erik A Richter
- Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Philip J Bilan
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Amira Klip
- Cell Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
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2
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Winn NC, Cappel DA, Pollack ED, Lantier L, Riveros JK, Bracy DP, Beckman JA, Wasserman DH. Increased cGMP improves microvascular exercise training adaptations in diet-induced obesity. Am J Physiol Endocrinol Metab 2025; 328:E711-E722. [PMID: 40204283 PMCID: PMC12070609 DOI: 10.1152/ajpendo.00368.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2024] [Revised: 10/15/2024] [Accepted: 04/02/2025] [Indexed: 04/11/2025]
Abstract
With the development of atherosclerosis, impaired microvascular function can result in diminished capacity for ambulation and is a risk factor for type 2 diabetes. Dynamic changes in vascular tone are determined, in large part, by the endothelial nitric oxide synthase (eNOS)/nitric oxide (NO)/cGMP axis. We used pharmacological gain of function of the eNOS/NO/cGMP axis in diet-induced obese (DIO) mice and reduced function in lean mice to test the hypothesis that functionality of this vascular control mechanism parallels the benefits of an exercise training regimen. DIO mice have 50% lower exercise capacity (P < 0.0001) than lean mice and were used for pharmacological gain of function. The phosphodiesterase-5a (PDE-5a) inhibitor, sildenafil, increases cGMP and was administered to DIO mice daily. In sedentary mice, neither acute nor chronic sildenafil improves exercise capacity. In contrast, chronic sildenafil synergizes with exercise training to improve performance during an incremental exercise test. Improved exercise performance was accompanied by a 40% increase in basal skeletal muscle capillary flow velocity and ∼20% increase in plasma-perfused capillary density measured via intravital microscopy. Loss of function was tested in lean mice hemizygous for endothelial cell (EC) specific eNOS creating an EC-eNOS knockdown (KD). EC-eNOS KD decreases capillary density and exercise tolerance in sedentary mice; however, it did not prevent exercise-training-induced improvements in endurance capacity. These data show that 1) increasing cGMP with sildenafil enhances microcirculatory function and exercise work tolerance that results from training; 2) eNOS KD does not prevent the microcirculatory or improvements in exercise tolerance with training. PDE-5a inhibitors combined with physical exercise are a potential mechanism for improving ambulation in patients with circulatory limitations.NEW & NOTEWORTHY This study used pharmacological gain-of-function and genetic loss-of-function approaches to test the hypothesis that the eNOS/NO/cGMP axis is central to exercise training adaptations in microcirculatory function and exercise capacity. Chronic but not acute treatment with the PDE5 inhibitor, sildenafil, synergizes with exercise training to improve performance with incremental exercise in obese mice; whereas endothelium-specific knockdown in eNOS does not blunt the microcirculatory adaptations and improvements in exercise tolerance with training.
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Affiliation(s)
- Nathan C. Winn
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - David A. Cappel
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Ethan D. Pollack
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Louise Lantier
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
- Vanderbilt Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, Tennessee, USA
| | - Jillian K. Riveros
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Deanna P. Bracy
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Joshua A. Beckman
- Division of Vascular Medicine, UT Southwestern Medical Center, Dallas, TX
| | - David H. Wasserman
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
- Vanderbilt Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, Tennessee, USA
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3
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Arif I, Rasheed A, Nazeer S, Shahid F. Physiological and morphological impact of physical activity and nutritional interventions to offset disuse-induced skeletal muscle atrophy. Eur J Transl Myol 2025. [PMID: 40231413 DOI: 10.4081/ejtm.2025.13177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2024] [Accepted: 01/31/2025] [Indexed: 04/16/2025] Open
Abstract
Skeletal muscle tissue acts as a functional unit for physical movements, energy metabolism, thermogenesis, and metabolic homeostasis. In this literature review, the underlying mechanisms of skeletal muscle atrophy and the prevention strategies, including vigorous training and nutritional modifications are focused. Furthermore, the comparative analysis of multiple interventions is briefly explained. Ageing is an inevitable process often associated with cognitive impairment and physical decline due to muscular atrophy. Skeletal muscle atrophy is characterized by low muscle mass due to multiple underlying factors, i.e., genetic predisposition, ageing, inflammation, and trauma. The structural alterations include myofiber shrinkage, changes in myosin isoforms, decrease in myofiber diameter, and total protein loss. Furthermore, there is an imbalance in protein anabolic and catabolic reactions. This may be due to changes in multiple signal transduction pathways of protein degradation (i.e., caspase, calpain, ubiquitin protein degradation system, autophagy) and protein anabolism via the mTOR pathway. Consequently, certain pathophysiological factors associated with health disparities may reduce mobility and functional capacity to perform ADLs. To tackle this issue, novel strategies linked to physical movement, and dietary intake must be incorporated in life. Exercise poses multiple health benefits, including improved muscle mass and mobility. Diet diversification [particularly protein-rich meals] and the "whole food" approach (based on non-protein nutrients) may enhance intramuscular anabolic signaling and tissue remodeling. However, there is a pressing need to fund large-scale evidence-based trials based on modern machine learning techniques (AI-driven nutrition). Additionally, entrepreneurial platforms for commercialization of consumer-friendly food products must be initiated in future.
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Affiliation(s)
- Irfan Arif
- Department of Health and Medical Sciences, University of Southern Queensland, Toowoomba.
| | - Ayesha Rasheed
- Department of Medical and Dental Sciences, University of Birmingham, Birmingham.
| | - Sadia Nazeer
- Department of Food Science and Technology, Government College University Faisalabad, Faisalabad.
| | - Fareeha Shahid
- Department of National Institute of Food Science and Technology, University of Agriculture Faisalabad, Faisalabad.
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4
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Bahadoran Z, Mirmiran P, Ghasemi A. Type 2 diabetes-related sarcopenia: role of nitric oxide. Nutr Metab (Lond) 2024; 21:107. [PMID: 39695784 DOI: 10.1186/s12986-024-00883-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2024] [Accepted: 11/28/2024] [Indexed: 12/20/2024] Open
Abstract
Sarcopenia, characterized by progressive and generalized loss of skeletal muscle (SkM) mass, strength, and physical performance, is a prevalent complication in type 2 diabetes (T2D). Nitric oxide (NO), a multifunctional gasotransmitter involved in whole-body glucose and insulin homeostasis, plays key roles in normal SkM physiology and function. Here, we highlight the role of NO in SkM mass maintenance and its potential contribution to the development of T2D-related sarcopenia. Physiologic NO level, primarily produced by sarcolemmal neuronal nitric oxide synthase (nNOSμ isoform), is involved in protein synthesis in muscle fibers and maintenance of SkM mass. The observed effect of nNOSμ on SkM mass is muscle-type specific and sex-dependent. Impaired NO homeostasis [due to a diminished nNOSμ-NO availability and excessive NO production through inducible NOS (iNOS) in response to atrophic stimuli, e.g., inflammatory cytokines] in SkM occurred during the development and progression of T2D, may cause sarcopenia. Theoretically, restoration of NO through nNOS overexpression, supplying NOS substrates (e.g., L-arginine and L-citrulline), phosphodiesterase (PDE) inhibition, and supplementation with NO donors (e.g., inorganic nitrate) may be potential therapeutic approaches to preserve SkM mass and prevents sarcopenia in T2D.
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Affiliation(s)
- Zahra Bahadoran
- Micronutrient Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
- Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Parvin Mirmiran
- Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Asghar Ghasemi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, No. 24, Sahid-Erabi St, Yemen St, Chamran Exp, P.O. Box 19395-4763, Tehran, Iran.
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5
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Craige SM, Mammel RK, Amiri N, Willoughby OS, Drake JC. Interplay of ROS, mitochondrial quality, and exercise in aging: Potential role of spatially discrete signaling. Redox Biol 2024; 77:103371. [PMID: 39357424 PMCID: PMC11474192 DOI: 10.1016/j.redox.2024.103371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2024] [Revised: 09/05/2024] [Accepted: 09/23/2024] [Indexed: 10/04/2024] Open
Affiliation(s)
- Siobhan M Craige
- Department of Human Nutrition, Foods, and Exercise, Virginia Tech, Blacksburg, 24061, USA.
| | - Rebecca K Mammel
- Department of Human Nutrition, Foods, and Exercise, Virginia Tech, Blacksburg, 24061, USA
| | - Niloufar Amiri
- Department of Human Nutrition, Foods, and Exercise, Virginia Tech, Blacksburg, 24061, USA; Institute for Critical Technology and Applied Science, Virginia Tech, Blacksburg, 24061, USA
| | - Orion S Willoughby
- Department of Human Nutrition, Foods, and Exercise, Virginia Tech, Blacksburg, 24061, USA
| | - Joshua C Drake
- Department of Human Nutrition, Foods, and Exercise, Virginia Tech, Blacksburg, 24061, USA.
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6
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Winn NC, Cappel DA, Pollock ED, Lantier L, Riveros JK, Debrow P, Bracy DP, Beckman JA, Wasserman DH. Increased cGMP improves microvascular exercise training adaptations independent of endothelial nitric oxide synthase. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.09.18.612717. [PMID: 39345415 PMCID: PMC11429803 DOI: 10.1101/2024.09.18.612717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 10/01/2024]
Abstract
Impaired microvascular function is a hallmark of pre-diabetes. With development of atherosclerosis this impaired microvascular function can result in diminished capacity for ambulation and is a risk factor for Type 2 Diabetes. Dynamic changes in vascular tone are determined, in large part, by the eNOS/NO/cGMP axis. We used gain of function of the eNOS/NO/cGMP axis in diet-induced obese (DIO) mice and reduced function in lean mice to test the hypothesis that functionality of this vascular control mechanism parallels the benefits of an exercise training regimen. DIO mice have lower exercise capacity than lean mice and were used for pharmacological gain of function. The PDE-5a inhibitor - sildenafil - increases cGMP and was administered to DIO mice daily. In sedentary mice, we find that sildenafil does not improve exercise capacity. In contrast, it amplifies the microcirculatory effects of exercise training. Sildenafil synergizes with exercise training to improve performance during an incremental exercise test. Improved exercise performance was accompanied by increased skeletal muscle capillary flow velocity and capillary density measured via intravital microscopy. Loss of function was tested in lean mice hemizygous for endothelial cell (EC) specific eNOS creating an EC-eNOS knockdown (KD). EC-eNOS KD decreases capillary density and exercise tolerance in sedentary mice; however, it did not prevent exercise-training induced improvements in endurance capacity. These data show that 1) increasing cGMP with sildenafil enhances microcirculatory function and exercise work tolerance that results from training; 2) eNOS KD does not prevent the microcirculatory or improvements in exercise tolerance with training. PDE-5a inhibitors combined with physical exercise are a potential mechanism for improving ambulation in patients with circulatory limitations.
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Affiliation(s)
- Nathan C. Winn
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - David A. Cappel
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Ethan D. Pollock
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Louise Lantier
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
- Vanderbilt Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, Tennessee, USA
| | - Jillian K. Riveros
- Department of Molecular Metabolism; Sabri Ülker Center for Metabolic Research, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Payton Debrow
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Deanna P. Bracy
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Joshua A. Beckman
- Division of Vascular Medicine, UT Southwestern Medical Center, Dallas, TX
| | - David H. Wasserman
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA
- Vanderbilt Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, Tennessee, USA
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7
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Tan R, Baranauskas MN, Karl ST, Ortiz de Zevallos J, Shei RJ, Paris HL, Wiggins CC, Bailey SJ. Effects of dietary nitrate supplementation on peak power output: Influence of supplementation strategy and population. Nitric Oxide 2023; 138-139:105-119. [PMID: 37438201 DOI: 10.1016/j.niox.2023.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
Increasing evidence indicates that dietary nitrate supplementation has the potential to increase muscular power output during skeletal muscle contractions. However, there is still a paucity of data characterizing the impact of different nitrate dosing regimens on nitric oxide bioavailability and its potential ergogenic effects across various population groups. This review discusses the potential influence of different dietary nitrate supplementation strategies on nitric oxide bioavailability and muscular peak power output in healthy adults, athletes, older adults and some clinical populations. Effect sizes were calculated for peak power output and absolute and/or relative nitrate doses were considered where applicable. There was no relationship between the effect sizes of peak power output change following nitrate supplementation and when nitrate dosage when considered in absolute or relative terms. Areas for further research are also recommended including a focus on nitrate dosing regimens that optimize nitric oxide bioavailability for enhancing peak power at times of increased muscular work in a variety of healthy and disease populations.
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Affiliation(s)
- Rachel Tan
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA.
| | - Marissa N Baranauskas
- Department of Human Physiology & Nutrition, University of Colorado, Colorado Springs, CO, 80918, USA
| | - Sean T Karl
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA
| | | | - Ren-Jay Shei
- Indiana University Alumni Association, Indiana University, Bloomington, IN, 47408, USA
| | - Hunter L Paris
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA
| | - Chad C Wiggins
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Stephen J Bailey
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, LE11 3TU, UK
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8
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Tan R, Baranauskas MN, Karl ST, Ortiz de Zevallos J, Shei RJ, Paris HL, Wiggins CC, Bailey SJ. Effects of dietary nitrate supplementation on muscular power output: Influence of supplementation strategy and population. Nitric Oxide 2023:S1089-8603(23)00047-2. [PMID: 37244391 DOI: 10.1016/j.niox.2023.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 05/18/2023] [Indexed: 05/29/2023]
Abstract
Increasing evidence indicates that dietary nitrate supplementation has the potential to increase muscular power output during skeletal muscle contractions. However, there is still a paucity of data characterizing the impact of different nitrate dosing regimens on nitric oxide bioavailability its potential ergogenic effects across various population groups. This narrative review discusses the potential influence of different dietary nitrate supplementation strategies on nitric oxide bioavailability and muscular power output in healthy adults, athletes, older adults and some clinical populations. Areas for further research are also recommended including a focus individualized nitrate dosing regimens to optimize nitric oxide bioavailability and to promote muscular power enhancements in different populations.
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Affiliation(s)
- Rachel Tan
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA.
| | - Marissa N Baranauskas
- Department of Human Physiology & Nutrition, University of Colorado, Colorado Springs, CO, 80918, USA
| | - Sean T Karl
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA
| | | | - Ren-Jay Shei
- Indiana University Alumni Association, Indiana University, Bloomington, IN, 47408, USA
| | - Hunter L Paris
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA
| | - Chad C Wiggins
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Stephen J Bailey
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, LE11 3TU, UK
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9
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Abstract
Obesity has reached epidemic proportions and is a major contributor to insulin resistance (IR) and type 2 diabetes (T2D). Importantly, IR and T2D substantially increase the risk of cardiovascular (CV) disease. Although there are successful approaches to maintain glycemic control, there continue to be increased CV morbidity and mortality associated with metabolic disease. Therefore, there is an urgent need to understand the cellular and molecular processes that underlie cardiometabolic changes that occur during obesity so that optimal medical therapies can be designed to attenuate or prevent the sequelae of this disease. The vascular endothelium is in constant contact with the circulating milieu; thus, it is not surprising that obesity-driven elevations in lipids, glucose, and proinflammatory mediators induce endothelial dysfunction, vascular inflammation, and vascular remodeling in all segments of the vasculature. As cardiometabolic disease progresses, so do pathological changes in the entire vascular network, which can feed forward to exacerbate disease progression. Recent cellular and molecular data have implicated the vasculature as an initiating and instigating factor in the development of several cardiometabolic diseases. This Review discusses these findings in the context of atherosclerosis, IR and T2D, and heart failure with preserved ejection fraction. In addition, novel strategies to therapeutically target the vasculature to lessen cardiometabolic disease burden are introduced.
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10
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Angiotensin II inhibition: a potential treatment to slow the progression of sarcopenia. Clin Sci (Lond) 2021; 135:2503-2520. [PMID: 34751393 DOI: 10.1042/cs20210719] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 10/21/2021] [Accepted: 10/29/2021] [Indexed: 02/07/2023]
Abstract
Sarcopenia is defined as the progressive and generalized loss of skeletal muscle mass and strength, which is associated with increased likelihood of adverse outcomes including falls, fractures, physical disability, and mortality. The etiology of sarcopenia has been postulated to be multifactorial with genetics, aging, immobility, nutritional deficiencies, inflammation, stress, and endocrine factors all contributing to the imbalance of muscle anabolism and catabolism. The prevalence of sarcopenia is estimated to range from 13 to 24% in adults over 60 years of age and up to 50% in persons aged 80 and older. As the population continues to age, the prevalence of sarcopenia continues to increase and is expected to affect 500 million people by the year 2050. Sarcopenia impacts the overall health of patients through limitations in functional status, increase in hospital readmissions, poorer hospital outcomes, and increase in overall mortality. Thus, there exists a need to prevent or reduce the occurrence of sarcopenia. Here, we explore the potential mechanisms and current studies regarding angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme (ACE) inhibitors on reducing the development of sarcopenia through the associated changes in cardiovascular function, renal function, muscle fiber composition, inflammation, endothelial dysfunction, metabolic efficiency, and mitochondrial function.
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11
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Roberts FL, Markby GR. New Insights into Molecular Mechanisms Mediating Adaptation to Exercise; A Review Focusing on Mitochondrial Biogenesis, Mitochondrial Function, Mitophagy and Autophagy. Cells 2021; 10:cells10102639. [PMID: 34685618 PMCID: PMC8533934 DOI: 10.3390/cells10102639] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 09/27/2021] [Accepted: 09/29/2021] [Indexed: 12/25/2022] Open
Abstract
Exercise itself is fundamental for good health, and when practiced regularly confers a myriad of metabolic benefits in a range of tissues. These benefits are mediated by a range of adaptive responses in a coordinated, multi-organ manner. The continued understanding of the molecular mechanisms of action which confer beneficial effects of exercise on the body will identify more specific pathways which can be manipulated by therapeutic intervention in order to prevent or treat various metabolism-associated diseases. This is particularly important as exercise is not an available option to all and so novel methods must be identified to confer the beneficial effects of exercise in a therapeutic manner. This review will focus on key emerging molecular mechanisms of mitochondrial biogenesis, autophagy and mitophagy in selected, highly metabolic tissues, describing their regulation and contribution to beneficial adaptations to exercise.
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12
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Almannai M, El-Hattab AW. Nitric Oxide Deficiency in Mitochondrial Disorders: The Utility of Arginine and Citrulline. Front Mol Neurosci 2021; 14:682780. [PMID: 34421535 PMCID: PMC8374159 DOI: 10.3389/fnmol.2021.682780] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 06/21/2021] [Indexed: 11/21/2022] Open
Abstract
Mitochondrial diseases represent a growing list of clinically heterogeneous disorders that are associated with dysfunctional mitochondria and multisystemic manifestations. In spite of a better understanding of the underlying pathophysiological basis of mitochondrial disorders, treatment options remain limited. Over the past two decades, there is growing evidence that patients with mitochondrial disorders have nitric oxide (NO) deficiency due to the limited availability of NO substrates, arginine and citrulline; decreased activity of nitric oxide synthase (NOS); and NO sequestration. Studies evaluating the use of arginine in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) presenting with stroke-like episodes showed symptomatic improvement after acute administration as well as a reduction in the frequency and severity of stroke-like episodes following chronic use. Citrulline, another NO precursor, was shown through stable isotope studies to result in a greater increase in NO synthesis. Recent studies showed a positive response of arginine and citrulline in other mitochondrial disorders besides MELAS. Randomized-controlled studies with a larger number of patients are warranted to better understand the role of NO deficiency in mitochondrial disorders and the efficacy of NO precursors as treatment modalities in these disorders.
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Affiliation(s)
- Mohammed Almannai
- Section of Medical Genetics, Children's Hospital, King Fahad Medical City, Riyadh, Saudi Arabia.,College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Ayman W El-Hattab
- Department of Clinical Sciences, College of Medicine, University of Sharjah, Sharjah, United Arab Emirates.,Clinical Genetics, University Hospital Sharjah, Sharjah, United Arab Emirates
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13
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Luse MA, Heiston EM, Malin SK, Isakson BE. Cellular and Functional Effects of Insulin Based Therapies and Exercise on Endothelium. Curr Pharm Des 2021; 26:3760-3767. [PMID: 32693765 DOI: 10.2174/1381612826666200721002735] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 06/04/2020] [Indexed: 12/24/2022]
Abstract
Endothelial dysfunction is a hallmark of type 2 diabetes that can have severe consequences on vascular function, including hypertension and changes in blood flow, as well as exercise performance. Because endothelium is also the barrier for insulin movement into tissues, it acts as a gatekeeper for transport and glucose uptake. For this reason, endothelial dysfunction is a tempting area for pharmacological and/or exercise intervention with insulin-based therapies. In this review, we describe the current state of drugs that can be used to treat endothelial dysfunction in type 2 diabetes and diabetes-related diseases (e.g., obesity) at the molecular levels, and also discuss their role in exercise.
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Affiliation(s)
- Melissa A Luse
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Virginia, United States
| | - Emily M Heiston
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Virginia, United States
| | - Steven K Malin
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Virginia, United States
| | - Brant E Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Virginia, United States
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14
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Biochemical adaptations in white adipose tissue following aerobic exercise: from mitochondrial biogenesis to browning. Biochem J 2020; 477:1061-1081. [PMID: 32187350 DOI: 10.1042/bcj20190466] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 02/24/2020] [Accepted: 02/28/2020] [Indexed: 02/07/2023]
Abstract
Our understanding of white adipose tissue (WAT) biochemistry has evolved over the last few decades and it is now clear that WAT is not simply a site of energy storage, but rather a pliable endocrine organ demonstrating dynamic responsiveness to the effects of aerobic exercise. Similar to its established effects in skeletal muscle, aerobic exercise induces many biochemical adaptations in WAT including mitochondrial biogenesis and browning. While past research has focused on the regulation of these biochemical processes, there has been renewed interest as of late given the potential of harnessing WAT mitochondrial biogenesis and browning to treat obesity and type II diabetes. Unfortunately, despite increasing evidence that innumerable factors, both exercise induced and pharmacological, can elicit these biochemical adaptations in WAT, the underlying mechanisms remain poorly defined. Here, we begin with a historical account of our understanding of WAT exercise biochemistry before presenting detailed evidence in favour of an up-to-date model by which aerobic exercise induces mitochondrial biogenesis and browning in WAT. Specifically, we discuss how aerobic exercise induces increases in WAT lipolysis and re-esterification and how this could be a trigger that activates the cellular energy sensor 5' AMP-activated protein kinase to mediate the induction of mitochondrial biogenesis and browning via the transcriptional co-activator peroxisome proliferator-activated receptor gamma co-activator-1 alpha. While this review primarily focuses on mechanistic results from rodent studies special attention is given to the translation of these results, or lack thereof, to human physiology.
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15
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Behrens CE, Ahmed K, Ricart K, Linder B, Fernández J, Bertrand B, Patel RP, Fisher G. Acute beetroot juice supplementation improves exercise tolerance and cycling efficiency in adults with obesity. Physiol Rep 2020; 8:e14574. [PMID: 33063953 PMCID: PMC7556310 DOI: 10.14814/phy2.14574] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/16/2020] [Accepted: 08/19/2020] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Exercise training improves health outcomes in individuals with obesity (IO); however, it remains challenging for IO to adhere to exercise. Thus, it is critical to identify novel strategies that improve exercise tolerance (ET) and adherence in IO. Beetroot juice (BRJ), high in inorganic dietary nitrate, consistently improves exercise performance in athletes, individuals with cardiopulmonary diseases, and nonobese lean individuals. These improvements may be explained by reduced oxygen uptake (VO2 ) during exercise, enhanced blood flow, and greater mitochondrial efficiency. To date, we are aware of no studies that have compared the effects of BRJ, sodium nitrate (NaNO3), and nitrate-depleted BRJ (PLA) for improving ET and cardiometabolic health in IO. PURPOSE Determine if BRJ improves ET, exercise efficiency (EE), and cardiometabolic health in IO and identify possible mechanisms of action. METHODS Vascular hemodynamic, submaximal- and maximal-exercise VO2 , and time to exhaustion (TTE) were assessed in 16 participants 2.5 hr following consumption of: 1) BRJ, 2) NaNO3 , 3) PLA, or 4) CON. RESULTS A significant treatment effect was observed for submaximal exercise VO2 (p = .003), and TTE (p < .001). Post hoc analyses revealed lower VO2 during submaximal exercise in BRJ compared to PLA (p = .009) NaNO3 (p = .042) and CON (0.009), equating to an average improvement of ~ 7% with BRJ. TTE was greater for BRJ compared to other treatment arms, PLA (p = .008), NaNO3 (p = .038), and CON (p=<0.001), equating to ~ 15% improvement with BRJ. No significant changes were observed for other outcomes. CONCLUSIONS Consumption of BRJ improved EE during submaximal exercise by 7%, and TTE by 15% compared to other conditions. These results suggest that BRJ may improve EE and exercise tolerance in IO.
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Affiliation(s)
- Christian E. Behrens
- Department of Nutrition SciencesThe University of Alabama at BirminghamBirminghamALUSA
| | - Khandaker Ahmed
- Department of Pathology and Center for Free Radical BiologyThe University of Alabama at BirminghamBirminghamALUSA
| | - Karina Ricart
- Department of Pathology and Center for Free Radical BiologyThe University of Alabama at BirminghamBirminghamALUSA
| | - Braxton Linder
- Department of Human StudiesThe University of Alabama at BirminghamBirminghamALUSA
| | - José Fernández
- Department of Nutrition SciencesThe University of Alabama at BirminghamBirminghamALUSA
| | - Brenda Bertrand
- Department of Nutrition SciencesThe University of Alabama at BirminghamBirminghamALUSA
| | - Rakesh P. Patel
- Department of Pathology and Center for Free Radical BiologyThe University of Alabama at BirminghamBirminghamALUSA
| | - Gordon Fisher
- Department of Human StudiesThe University of Alabama at BirminghamBirminghamALUSA
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16
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Cunningham RP, Sheldon RD, Rector RS. The Emerging Role of Hepatocellular eNOS in Non-alcoholic Fatty Liver Disease Development. Front Physiol 2020; 11:767. [PMID: 32719616 PMCID: PMC7350778 DOI: 10.3389/fphys.2020.00767] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 06/11/2020] [Indexed: 12/29/2022] Open
Abstract
Non-alcoholic fatty liver disease (NAFLD) is comprised of a spectrum of liver injury ranging from excess fat accumulation in the liver (steatosis), to steatohepatitis (NASH), to its end stage of cirrhosis. A hallmark of NAFLD progression is the decline in function of hepatic mitochondria, although the mechanisms remain unresolved. Given the important role endothelial nitric oxide synthase (eNOS) plays in mitochondrial dynamics in other tissues, it has emerged as a potential mediator of maintaining mitochondrial function in the liver. In this mini review, we summarize the most relevant findings that extends current understanding of eNOS as a regulator of mitochondrial biogenesis, and identifies a potential additional role in mitochondrial turnover and attenuating inflammation during NAFLD development and progression.
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Affiliation(s)
- Rory P Cunningham
- Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, United States.,Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, United States
| | - Ryan D Sheldon
- Metabolic and Nutritional Programming, Center for Cancer and Cell Biology, Van Andel Institute, Grand Rapids, MI, United States
| | - R Scott Rector
- Research Service, Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, United States.,Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, United States.,Medicine-Division of Gastroenterology and Hepatology, University of Missouri, Columbia, MO, United States
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17
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Glutathione and Nitric Oxide: Key Team Players in Use and Disuse of Skeletal Muscle. Nutrients 2019; 11:nu11102318. [PMID: 31575008 PMCID: PMC6836164 DOI: 10.3390/nu11102318] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 09/11/2019] [Accepted: 09/16/2019] [Indexed: 02/07/2023] Open
Abstract
Glutathione (GSH) is the main non-enzymatic antioxidant playing an important role in detoxification, signal transduction by modulation of protein thiols redox status and direct scavenging of radicals. The latter function is not only performed against reactive oxygen species (ROS) but GSH also has a fundamental role in buffering nitric oxide (NO), a physiologically-produced molecule having-multifaceted functions. The efficient rate of GSH synthesis and high levels of GSH-dependent enzymes are characteristic features of healthy skeletal muscle where, besides the canonical functions, it is also involved in muscle contraction regulation. Moreover, NO production in skeletal muscle is a direct consequence of contractile activity and influences several metabolic myocyte pathways under both physiological and pathological conditions. In this review, we will consider the homeostasis and intersection of GSH with NO and then we will restrict the discussion on their role in processes related to skeletal muscle function and degeneration.
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18
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TaheriChadorneshin H, Rostamkhani F, Shirvani H. Long-term effects of sprint interval training on expression of cardiac genes involved in energy efficiency. SPORT SCIENCES FOR HEALTH 2019. [DOI: 10.1007/s11332-018-0480-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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19
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Normal increases in insulin-stimulated glucose uptake after ex vivo contraction in neuronal nitric oxide synthase mu (nNOSμ) knockout mice. Pflugers Arch 2019; 471:961-969. [DOI: 10.1007/s00424-019-02268-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 02/20/2019] [Accepted: 02/26/2019] [Indexed: 11/25/2022]
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20
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Matsumoto T, Tanaka M, Ikeji T, Maeshige N, Sakai Y, Akisue T, Kondo H, Ishihara A, Fujino H. Application of transcutaneous carbon dioxide improves capillary regression of skeletal muscle in hyperglycemia. J Physiol Sci 2019; 69:317-326. [PMID: 30478742 PMCID: PMC10717691 DOI: 10.1007/s12576-018-0648-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 11/14/2018] [Indexed: 12/17/2022]
Abstract
The purpose of the present study was to determine the effects of transcutaneous CO2 application on the blood flow and capillary architecture of the soleus muscle in rats with streptozotocin (STZ)-induced hyperglycemia. Wistar rats were randomly divided into four groups: control, control + CO2-treated, STZ-induced hyperglycemia, and STZ-induced hyperglycemia + CO2-treated groups. Blood flow in soleus muscle increased during the transcutaneous CO2 exposure, and continued to increase for 30 min after the treatment. In addition, the transcutaneous CO2 attenuated a decrease in capillary and the expression level of eNOS and VEGF protein, and an increase in the expression level of MDM-2 and TSP-1 protein of soleus muscle due to STZ-induced hyperglycemia. These results indicate that the application of transcutaneous CO2 could improve capillary regression via the change of pro- and anti-angiogenesis factors, which might be induced by an increase in blood flow.
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Affiliation(s)
- Tomohiro Matsumoto
- Department of Rehabilitation Science, Kobe University Graduate School of Health Sciences, 7-10-2 Tomogaoka, Suma-ku, Kobe, Hyogo, 654-0142, Japan
| | - Masayuki Tanaka
- Department of Physical Therapy, Faculty of Human Sciences, Osaka University of Human Sciences, 1-4-1 Shojaku, Settsu, Osaka, 566-8501, Japan
| | - Takuya Ikeji
- Department of Rehabilitation Science, Kobe University Graduate School of Health Sciences, 7-10-2 Tomogaoka, Suma-ku, Kobe, Hyogo, 654-0142, Japan
| | - Noriaki Maeshige
- Department of Rehabilitation Science, Kobe University Graduate School of Health Sciences, 7-10-2 Tomogaoka, Suma-ku, Kobe, Hyogo, 654-0142, Japan
| | - Yoshitada Sakai
- Division of Rehabilitation Medicine, Kobe University Graduate School of Medicine, Kobe, 650-0017, Japan
| | - Toshihiro Akisue
- Department of Rehabilitation Science, Kobe University Graduate School of Health Sciences, 7-10-2 Tomogaoka, Suma-ku, Kobe, Hyogo, 654-0142, Japan
| | - Hiroyo Kondo
- Department of Food Science and Nutrition, Nagoya Women's University, 4-21 Shioji-cho, Mizuho-ku, Nagoya, Aichi, 467-8611, Japan
| | - Akihiko Ishihara
- Laboratory of Cell Biology and Life Science, Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatsu-cho, Sakyo-ku, Kyoto-shi, Kyoto, 606-8501, Japan
| | - Hidemi Fujino
- Department of Rehabilitation Science, Kobe University Graduate School of Health Sciences, 7-10-2 Tomogaoka, Suma-ku, Kobe, Hyogo, 654-0142, Japan.
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21
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Fiorenza M, Gunnarsson TP, Ehlers TS, Bangsbo J. High-intensity exercise training ameliorates aberrant expression of markers of mitochondrial turnover but not oxidative damage in skeletal muscle of men with essential hypertension. Acta Physiol (Oxf) 2019; 225:e13208. [PMID: 30339318 DOI: 10.1111/apha.13208] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Revised: 09/18/2018] [Accepted: 10/14/2018] [Indexed: 12/21/2022]
Abstract
AIM To examine whether hypertensive individuals exhibit altered muscle mitochondrial turnover and redox homeostasis compared with healthy normotensive counterparts, and whether the antihypertensive effect of high-intensity exercise training is associated with improved mitochondrial quality and enhanced anti-oxidant defence. METHODS In a cross-sectional and longitudinal parallel design, 24 essential hypertensive (HYP) and 13 healthy normotensive (NORM) men completed 6 weeks of high-intensity interval training (HIIT). Twenty four-hour ambulatory blood pressure, body composition, cardiorespiratory fitness, exercise capacity and skeletal muscle characteristics were examined before and after HIIT. Expression of markers of mitochondrial turnover, anti-oxidant protection and oxidative damage was determined in vastus lateralis muscle biopsies. Muscle protein levels of eNOS and VEGF, and muscle capillarity were also evaluated. RESULTS At baseline, HYP exhibited lower expression of markers of mitochondrial volume/biogenesis, mitochondrial fusion/fission and autophagy along with depressed eNOS expression compared with NORM. Expression of markers of anti-oxidant protection was similar in HYP and NORM, whereas oxidative damage was higher in HYP than in NORM. In HYP, HIIT lowered blood pressure, improved body composition, cardiorespiratory fitness and exercise capacity, up-regulated markers of mitochondrial volume/biogenesis and autophagy and increased eNOS and VEGF protein content. Furthermore, in HYP, HIIT induced divergent responses in markers of mitochondrial fusion and anti-oxidant protection, did not affect markers of mitochondrial fission, and increased apoptotic susceptibility and oxidative damage. CONCLUSION The present results indicate aberrant muscle mitochondrial turnover and augmented oxidative damage in hypertensive individuals. High-intensity exercise training can partly reverse hypertension-related impairments in muscle mitochondrial turnover, but not redox imbalance.
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Affiliation(s)
- Matteo Fiorenza
- Department of Nutrition, Exercise and Sports University of Copenhagen Copenhagen Denmark
- Department of Neurosciences, Biomedicine and Movement Sciences University of Verona Verona Italy
| | - Thomas P. Gunnarsson
- Department of Nutrition, Exercise and Sports University of Copenhagen Copenhagen Denmark
| | - Thomas S. Ehlers
- Department of Nutrition, Exercise and Sports University of Copenhagen Copenhagen Denmark
| | - Jens Bangsbo
- Department of Nutrition, Exercise and Sports University of Copenhagen Copenhagen Denmark
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22
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Mitochondrial dynamics in exercise physiology. Pflugers Arch 2019; 472:137-153. [DOI: 10.1007/s00424-019-02258-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Accepted: 01/17/2019] [Indexed: 12/11/2022]
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23
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Sidorenko S, Klimanova E, Milovanova K, Lopina OD, Kapilevich LV, Chibalin AV, Orlov SN. Transcriptomic changes in C2C12 myotubes triggered by electrical stimulation: Role of Ca2+i-mediated and Ca2+i-independent signaling and elevated [Na+]i/[K+]i ratio. Cell Calcium 2018; 76:72-86. [DOI: 10.1016/j.ceca.2018.09.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 09/18/2018] [Accepted: 09/26/2018] [Indexed: 12/25/2022]
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24
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Kodippili K, Hakim CH, Yang HT, Pan X, Yang NN, Laughlin MH, Terjung RL, Duan D. Nitric oxide-dependent attenuation of noradrenaline-induced vasoconstriction is impaired in the canine model of Duchenne muscular dystrophy. J Physiol 2018; 596:5199-5216. [PMID: 30152022 DOI: 10.1113/jp275672] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 08/08/2018] [Indexed: 12/31/2022] Open
Abstract
KEY POINTS We developed a novel method to study sympatholysis in dogs. We showed abolishment of sarcolemmal nNOS, and reduction of total nNOS and total eNOS in the canine Duchenne muscular dystrophy (DMD) model. We showed sympatholysis in dogs involving both nNOS-derived NO-dependent and NO-independent mechanisms. We showed that the loss of sarcolemmal nNOS compromised sympatholysis in the canine DMD model. We showed that NO-independent sympatholysis was not affected in the canine DMD model. ABSTRACT The absence of dystrophin in Duchenne muscular dystrophy (DMD) leads to the delocalization of neuronal nitric oxide synthase (nNOS) from the sarcolemma. Sarcolemmal nNOS plays an important role in sympatholysis, a process of attenuating reflex sympathetic vasoconstriction during exercise to ensure blood perfusion in working muscle. Delocalization of nNOS compromises sympatholysis resulting in functional ischaemia and muscle damage in DMD patients and mouse models. Little is known about the contribution of membrane-associated nNOS to blood flow regulation in dystrophin-deficient DMD dogs. We tested the hypothesis that the loss of sarcolemmal nNOS abolishes protective sympatholysis in contracting muscle of affected dogs. Haemodynamic responses to noradrenaline in the brachial artery were evaluated at rest and during contraction in the absence and presence of NOS inhibitors. We found sympatholysis was significantly compromised in DMD dogs, as well as in normal dogs treated with a selective nNOS inhibitor, suggesting that the absence of sarcolemmal nNOS underlies defective sympatholysis in the canine DMD model. Surprisingly, inhibition of all NOS isoforms did not completely abolish sympatholysis in normal dogs, suggesting sympatholysis in canine muscle also involves NO-independent mechanism(s). Our study established a foundation for using the dog model to test therapies aimed at restoring nNOS homeostasis in DMD.
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Affiliation(s)
- Kasun Kodippili
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, USA
| | - Chady H Hakim
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, USA.,National Center for Advancing Translational Sciences (NCATS), Bethesda, MD, USA
| | - Hsiao T Yang
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, USA.,Department of Veterinary Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA
| | - Xiufang Pan
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, USA
| | - N Nora Yang
- National Center for Advancing Translational Sciences (NCATS), Bethesda, MD, USA
| | - Maurice H Laughlin
- Department of Veterinary Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA
| | - Ronald L Terjung
- Department of Veterinary Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA
| | - Dongsheng Duan
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO, USA.,Department of Veterinary Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA.,Department of Neurology, School of Medicine, University of Missouri, Columbia, MO, USA.,Department of Bioengineering, University of Missouri, Columbia, MO, USA
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25
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Hughey CC, James FD, Bracy DP, Donahue EP, Young JD, Viollet B, Foretz M, Wasserman DH. Loss of hepatic AMP-activated protein kinase impedes the rate of glycogenolysis but not gluconeogenic fluxes in exercising mice. J Biol Chem 2017; 292:20125-20140. [PMID: 29038293 PMCID: PMC5724001 DOI: 10.1074/jbc.m117.811547] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 10/10/2017] [Indexed: 11/06/2022] Open
Abstract
Pathologies including diabetes and conditions such as exercise place an unusual demand on liver energy metabolism, and this demand induces a state of energy discharge. Hepatic AMP-activated protein kinase (AMPK) has been proposed to inhibit anabolic processes such as gluconeogenesis in response to cellular energy stress. However, both AMPK activation and glucose release from the liver are increased during exercise. Here, we sought to test the role of hepatic AMPK in the regulation of in vivo glucose-producing and citric acid cycle-related fluxes during an acute bout of muscular work. We used 2H/13C metabolic flux analysis to quantify intermediary metabolism fluxes in both sedentary and treadmill-running mice. Additionally, liver-specific AMPK α1 and α2 subunit KO and WT mice were utilized. Exercise caused an increase in endogenous glucose production, glycogenolysis, and gluconeogenesis from phosphoenolpyruvate. Citric acid cycle fluxes, pyruvate cycling, anaplerosis, and cataplerosis were also elevated during this exercise. Sedentary nutrient fluxes in the postabsorptive state were comparable for the WT and KO mice. However, the increment in the endogenous rate of glucose appearance during exercise was blunted in the KO mice because of a diminished glycogenolytic flux. This lower rate of glycogenolysis was associated with lower hepatic glycogen content before the onset of exercise and prompted a reduction in arterial glucose during exercise. These results indicate that liver AMPKα1α2 is required for maintaining glucose homeostasis during an acute bout of exercise.
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Affiliation(s)
- Curtis C Hughey
- Department of Molecular Physiology and Biophysics, Nashville, Tennessee 37232
| | - Freyja D James
- Department of Molecular Physiology and Biophysics, Nashville, Tennessee 37232; Mouse Metabolic Phenotyping Center, Nashville, Tennessee 37232
| | - Deanna P Bracy
- Department of Molecular Physiology and Biophysics, Nashville, Tennessee 37232; Mouse Metabolic Phenotyping Center, Nashville, Tennessee 37232
| | - E Patrick Donahue
- Department of Molecular Physiology and Biophysics, Nashville, Tennessee 37232
| | - Jamey D Young
- Department of Molecular Physiology and Biophysics, Nashville, Tennessee 37232; Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37232
| | - Benoit Viollet
- INSERM, U1016, Institut Cochin, 75014 Paris, France; CNRS, UMR 8104, 75014 Paris, France; Université Paris Descartes, Sorbonne Paris Cité, 75014 Paris, France
| | - Marc Foretz
- INSERM, U1016, Institut Cochin, 75014 Paris, France; CNRS, UMR 8104, 75014 Paris, France; Université Paris Descartes, Sorbonne Paris Cité, 75014 Paris, France
| | - David H Wasserman
- Department of Molecular Physiology and Biophysics, Nashville, Tennessee 37232; Mouse Metabolic Phenotyping Center, Nashville, Tennessee 37232.
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26
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Guers JJ, Zhang J, Campbell SC, Oydanich M, Vatner DE, Vatner SF. Disruption of adenylyl cyclase type 5 mimics exercise training. Basic Res Cardiol 2017; 112:59. [PMID: 28887652 DOI: 10.1007/s00395-017-0648-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 08/30/2017] [Indexed: 02/07/2023]
Abstract
Exercise training is key to healthful longevity. Since exercise training compliance is difficult, it would be useful to have a therapeutic substitute that mimicked exercise training. We compared the effects of exercise training in wild-type (WT) littermates with adenylyl cyclase type 5 knock out (AC5 KO) mice, a model of enhanced exercise performance. Exercise performance, measured by maximal distance and work to exhaustion, was increased in exercise-trained WT to levels already attained in untrained AC5 KO. Exercise training in AC5 KO further enhanced their exercise performance. The key difference in untrained AC5 KO and exercise-trained WT was the β-adrenergic receptor signaling, which was decreased in untrained AC5 KO compared to untrained WT but was increased in WT with exercise training. Despite this key difference, untrained AC5 KO and exercise-trained WT mice shared similar gene expression, determined by deep sequencing, in their gastrocnemius muscle with 183 genes commonly up or down-regulated, mainly involving muscle contraction, metabolism and mitochondrial function. The SIRT1/PGC-1α pathway partially mediated the enhanced exercise in both AC5 KO and exercise-trained WT mice, as reflected in the reduced exercise responses after administering a SIRT1 inhibitor, but did not abolish the enhanced exercise performance in the AC5 KO compared to untrained WT. Increasing oxidative stress with paraquat attenuated exercise performance more in untrained WT than untrained AC5 KO, reflecting the augmented oxidative stress protection in AC5 KO. Blocking nitric oxide actually reduced the enhanced exercise performance in untrained AC5 KO and trained WT to levels below untrained WT, demonstrating the importance of this mechanism. These results suggest that AC5 KO mice, without exercise training, share similar mechanisms responsible for enhanced exercise capacity with chronic exercise training, most importantly increased nitric oxide, and demonstrate more reserve with the addition of exercise training. A novel feature of the enhanced exercise performance in untrained AC5 KO mice is their decreased sympathetic tone, which is also beneficial to patients with cardiovascular disease.
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Affiliation(s)
- John J Guers
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, New Jersey Medical School, Rutgers University, 185 South Orange Avenue, MSB G609, Newark, NJ, 07103, USA
| | - Jie Zhang
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, New Jersey Medical School, Rutgers University, 185 South Orange Avenue, MSB G609, Newark, NJ, 07103, USA
| | - Sara C Campbell
- Department of Kinesiology and Health, Rutgers University, New Brunswick, NJ, USA
| | - Marko Oydanich
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, New Jersey Medical School, Rutgers University, 185 South Orange Avenue, MSB G609, Newark, NJ, 07103, USA
| | - Dorothy E Vatner
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, New Jersey Medical School, Rutgers University, 185 South Orange Avenue, MSB G609, Newark, NJ, 07103, USA.
- Department of Medicine, New Jersey Medical School, Rutgers University, 185 South Orange Avenue, MSB G659, Newark, NJ, 07103, USA.
| | - Stephen F Vatner
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, New Jersey Medical School, Rutgers University, 185 South Orange Avenue, MSB G609, Newark, NJ, 07103, USA.
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27
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Tyml K, Swarbreck S, Pape C, Secor D, Koropatnick J, Feng Q, Veldhuizen RAW, Gill SE. Voluntary running exercise protects against sepsis-induced early inflammatory and pro-coagulant responses in aged mice. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2017; 21:210. [PMID: 28789683 PMCID: PMC5549433 DOI: 10.1186/s13054-017-1783-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 06/29/2017] [Indexed: 01/10/2023]
Abstract
Background Despite many animal studies and clinical trials, mortality in sepsis remains high. This may be due to the fact that most experimental studies of sepsis employ young animals, whereas the majority of septic patients are elderly (60 − 70 years). The objective of the present study was to examine the sepsis-induced inflammatory and pro-coagulant responses in aged mice. Since running exercise protects against a variety of diseases, we also examined the effect of voluntary running on septic responses in aged mice. Methods Male C57BL/6 mice were housed in our institute from 2–3 to 22 months (an age mimicking that of the elderly). Mice were prevented from becoming obese by food restriction (given 70–90% of ad libitum consumption amount). Between 20 and 22 months, a subgroup of mice ran voluntarily on wheels, alternating 1–3 days of running with 1–2 days of rest. At 22 months, mice were intraperitoneally injected with sterile saline (control) or 3.75 g/kg fecal slurry (septic). At 7 h post injection, we examined (1) neutrophil influx in the lung and liver by measuring myeloperoxidase and/or neutrophil elastase in the tissue homogenates by spectrophotometry, (2) interleukin 6 (IL6) and KC in the lung lavage by ELISA, (3) pulmonary surfactant function by measuring percentage of large aggregates, (4) capillary plugging (pro-coagulant response) in skeletal muscle by intravital microscopy, (5) endothelial nitric oxide synthase (eNOS) protein in skeletal muscle (eNOS-derived NO is putative inhibitor of capillary plugging) by immunoblotting, and (6) systemic blood platelet counts by hemocytometry. Results Sepsis caused high levels of pulmonary myeloperoxidase, elastase, IL6, KC, liver myeloperoxidase, and capillary plugging. Sepsis also caused low levels of surfactant function and platelet counts. Running exercise increased eNOS protein and attenuated the septic responses. Conclusions Voluntary running protects against exacerbated sepsis-induced inflammatory and pro-coagulant responses in aged mice. Protection against pro-coagulant responses may involve eNOS upregulation. The present discovery in aged mice calls for clinical investigation into potential beneficial effects of exercise on septic outcomes in the elderly. Electronic supplementary material The online version of this article (doi:10.1186/s13054-017-1783-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Karel Tyml
- Centre for Critical Illness Research, London, Ontario, Canada.,Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
| | - Scott Swarbreck
- Centre for Critical Illness Research, London, Ontario, Canada
| | - Cynthia Pape
- Centre for Critical Illness Research, London, Ontario, Canada.,Department of Medicine, University of Western Ontario, London, Ontario, Canada
| | - Dan Secor
- Centre for Critical Illness Research, London, Ontario, Canada
| | - James Koropatnick
- Cancer Research Program, Lawson Health Research Institute, London, Ontario, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.,Department of Oncology, University of Western Ontario, London, Ontario, Canada.,Department of Pathology, University of Western Ontario, London, Ontario, Canada
| | - Qingping Feng
- Centre for Critical Illness Research, London, Ontario, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Ruud A W Veldhuizen
- Centre for Critical Illness Research, London, Ontario, Canada.,Division of Respirology, University of Western Ontario, London, Ontario, Canada.,Department of Medicine, University of Western Ontario, London, Ontario, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| | - Sean E Gill
- Centre for Critical Illness Research, London, Ontario, Canada. .,Division of Respirology, University of Western Ontario, London, Ontario, Canada. .,Department of Medicine, University of Western Ontario, London, Ontario, Canada. .,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.
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28
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Sylow L, Kleinert M, Richter EA, Jensen TE. Exercise-stimulated glucose uptake - regulation and implications for glycaemic control. Nat Rev Endocrinol 2017; 13:133-148. [PMID: 27739515 DOI: 10.1038/nrendo.2016.162] [Citation(s) in RCA: 289] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Skeletal muscle extracts glucose from the blood to maintain demand for carbohydrates as an energy source during exercise. Such uptake involves complex molecular signalling processes that are distinct from those activated by insulin. Exercise-stimulated glucose uptake is preserved in insulin-resistant muscle, emphasizing exercise as a therapeutic cornerstone among patients with metabolic diseases such as diabetes mellitus. Exercise increases uptake of glucose by up to 50-fold through the simultaneous stimulation of three key steps: delivery, transport across the muscle membrane and intracellular flux through metabolic processes (glycolysis and glucose oxidation). The available data suggest that no single signal transduction pathway can fully account for the regulation of any of these key steps, owing to redundancy in the signalling pathways that mediate glucose uptake to ensure maintenance of muscle energy supply during physical activity. Here, we review the molecular mechanisms that regulate the movement of glucose from the capillary bed into the muscle cell and discuss what is known about their integrated regulation during exercise. Novel developments within the field of mass spectrometry-based proteomics indicate that the known regulators of glucose uptake are only the tip of the iceberg. Consequently, many exciting discoveries clearly lie ahead.
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Affiliation(s)
- Lykke Sylow
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Maximilian Kleinert
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Erik A Richter
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Thomas E Jensen
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
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Kanuri BN, Kanshana JS, Rebello SC, Pathak P, Gupta AP, Gayen JR, Jagavelu K, Dikshit M. Altered glucose and lipid homeostasis in liver and adipose tissue pre-dispose inducible NOS knockout mice to insulin resistance. Sci Rep 2017; 7:41009. [PMID: 28106120 PMCID: PMC5247703 DOI: 10.1038/srep41009] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 12/14/2016] [Indexed: 12/15/2022] Open
Abstract
On the basis of diet induced obesity and KO mice models, nitric oxide is implied to play an important role in the initiation of dyslipidemia induced insulin resistance. However, outcomes using iNOS KO mice have so far remained inconclusive. The present study aimed to assess IR in iNOS KO mice after 5 weeks of LFD feeding by monitoring body composition, energy homeostasis, insulin sensitivity/signaling, nitrite content and gene expressions changes in the tissues. We found that body weight and fat content in KO mice were significantly higher while the respiratory exchange ratio (RER), volume of carbon dioxide (VCO2), and heat production were lower as compared to WT mice. Furthermore, altered systemic glucose tolerance, tissue insulin signaling, hepatic gluconeogenesis, augmented hepatic lipids, adiposity, as well as gene expression regulating lipid synthesis, catabolism and efflux were evident in iNOS KO mice. Significant reduction in eNOS and nNOS gene expression, hepatic and adipose tissue nitrite content, circulatory nitrite was also observed. Oxygen consumption rate of mitochondrial respiration has remained unaltered in KO mice as measured using extracellular flux analyzer. Our findings establish a link between the NO status with systemic and tissue specific IR in iNOS KO mice at 5 weeks.
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Affiliation(s)
- Babu Nageswararao Kanuri
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow - 226031, India.,Academy of Scientific and Innovative Research, New Delhi - 110001, India
| | - Jitendra S Kanshana
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow - 226031, India
| | - Sanjay C Rebello
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow - 226031, India
| | - Priya Pathak
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow - 226031, India
| | - Anand P Gupta
- Pharmacokinetics and Metabolism Division, CSIR-Central Drug Research Institute, Lucknow - 226031, India
| | - Jiaur R Gayen
- Pharmacokinetics and Metabolism Division, CSIR-Central Drug Research Institute, Lucknow - 226031, India
| | - Kumaravelu Jagavelu
- Pharmacology Division, CSIR-Central Drug Research Institute, Lucknow - 226031, India
| | - Madhu Dikshit
- Academy of Scientific and Innovative Research, New Delhi - 110001, India
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Fu J, Han Y, Wang J, Liu Y, Zheng S, Zhou L, Jose PA, Zeng C. Irisin Lowers Blood Pressure by Improvement of Endothelial Dysfunction via AMPK-Akt-eNOS-NO Pathway in the Spontaneously Hypertensive Rat. J Am Heart Assoc 2016; 5:e003433. [PMID: 27912206 PMCID: PMC5210324 DOI: 10.1161/jaha.116.003433] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 09/06/2016] [Indexed: 12/13/2022]
Abstract
BACKGROUND Exercise is a major nonpharmacological treatment for hypertension, but its underlying mechanisms are still not completely elucidated. Irisin, a polypeptide containing 112 amino acids, which is secreted mainly by skeletal muscle cells during exercise, exerts a protective role in metabolic diseases, such as diabetes mellitus and obesity. Because of the close relationship between irisin and metabolic diseases, we hypothesized that irisin may play a role in the regulation of blood pressure. METHODS AND RESULTS Blood pressures of male Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs) were monitored through the carotid artery. Our study found that acute intravenous injection of irisin reduced blood pressure in SHRs, but not WKY rats. Irisin, by itself, had no direct vasorelaxing effect in phenylephrine-preconstricted mesenteric arteries from SHRs. However, irisin augmented the acetylcholine-induced vasorelaxation in mesenteric arteries from SHRs that could be reversed by Nω-nitro-l-arginine-methyl ester (L-NAME; 100 μmol/L), indicating a role of nitric oxide (NO) in this action. Indeed, irisin increased NO production and phosphorylation of endothelial nirtic oxide synthase (eNOS) in endothelial cells. 5'-AMP-activated protein kinase (AMPK) was involved in the vasorelaxing effect of irisin because compound C (20 μmol/L), an AMPK inhibitor, blocked the irisin-mediated increase in phosphorylation of eNOS and protein kinase B (Akt) in endothelial cells and vasodilation in mesenteric arteries. CONCLUSIONS We conclude that acute administration of irisin lowers blood pressure of SHRs by amelioration of endothelial dysfunction of the mesenteric artery through the AMPK-Akt-eNOS-NO signaling pathway.
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Affiliation(s)
- Jinjuan Fu
- Department of Cardiology, Daping Hospital, Chongqing Institute of Cardiology, The Third Military Medical University, Chongqing, China
| | - Yu Han
- Department of Cardiology, Daping Hospital, Chongqing Institute of Cardiology, The Third Military Medical University, Chongqing, China
| | - Jialiang Wang
- Department of Cardiology, Daping Hospital, Chongqing Institute of Cardiology, The Third Military Medical University, Chongqing, China
| | - Yukai Liu
- Department of Cardiology, Daping Hospital, Chongqing Institute of Cardiology, The Third Military Medical University, Chongqing, China
| | - Shuo Zheng
- Department of Cardiology, Daping Hospital, Chongqing Institute of Cardiology, The Third Military Medical University, Chongqing, China
| | - Lin Zhou
- Department of Cardiology, Daping Hospital, Chongqing Institute of Cardiology, The Third Military Medical University, Chongqing, China
| | - Pedro A Jose
- Division of Renal Diseases & Hypertension, Department of Medicine, The George Washington University School of Medicine & Health Sciences, Washington, DC
| | - Chunyu Zeng
- Department of Cardiology, Daping Hospital, Chongqing Institute of Cardiology, The Third Military Medical University, Chongqing, China
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Lee-Young RS, Hoffman NJ, Murphy KT, Henstridge DC, Samocha-Bonet D, Siebel AL, Iliades P, Zivanovic B, Hong YH, Colgan TD, Kraakman MJ, Bruce CR, Gregorevic P, McConell GK, Lynch GS, Drummond GR, Kingwell BA, Greenfield JR, Febbraio MA. Glucose-6-phosphate dehydrogenase contributes to the regulation of glucose uptake in skeletal muscle. Mol Metab 2016; 5:1083-1091. [PMID: 27818934 PMCID: PMC5081409 DOI: 10.1016/j.molmet.2016.09.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 08/29/2016] [Accepted: 09/05/2016] [Indexed: 12/25/2022] Open
Abstract
Objective The development of skeletal muscle insulin resistance is an early physiological defect, yet the intracellular mechanisms accounting for this metabolic defect remained unresolved. Here, we have examined the role of glucose-6-phosphate dehydrogenase (G6PDH) activity in the pathogenesis of insulin resistance in skeletal muscle. Methods Multiple mouse disease states exhibiting insulin resistance and glucose intolerance, as well as obese humans defined as insulin-sensitive, insulin-resistant, or pre-diabetic, were examined. Results We identified increased glucose-6-phosphate dehydrogenase (G6PDH) activity as a common intracellular adaptation that occurs in parallel with the induction of insulin resistance in skeletal muscle and is present across animal and human disease states with an underlying pathology of insulin resistance and glucose intolerance. We observed an inverse association between G6PDH activity and nitric oxide synthase (NOS) activity and show that increasing NOS activity via the skeletal muscle specific neuronal (n)NOSμ partially suppresses G6PDH activity in skeletal muscle cells. Furthermore, attenuation of G6PDH activity in skeletal muscle cells via (a) increased nNOSμ/NOS activity, (b) pharmacological G6PDH inhibition, or (c) genetic G6PDH inhibition increases insulin-independent glucose uptake. Conclusions We have identified a novel, previously unrecognized role for G6PDH in the regulation of skeletal muscle glucose metabolism.
Defective skeletal muscle G6PDH activity in multiple insulin resistant animal models. Demonstration of defective skeletal muscle G6PDH activity in pre-diabetic individuals. Identification of nNOSμ as a regulator of G6PDH activity in skeletal muscle. G6PDH activity modulates insulin-independent glucose uptake in skeletal muscle.
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Affiliation(s)
- Robert S Lee-Young
- Cellular and Molecular Metabolism Laboratory, Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia.
| | - Nolan J Hoffman
- Diabetes & Metabolism Division, Garvan Institute of Medical Research, NSW, Australia
| | - Kate T Murphy
- Basic and Clinical Myology Laboratory, Department of Physiology, The University of Melbourne, Melbourne, VIC, Australia
| | - Darren C Henstridge
- Cellular and Molecular Metabolism Laboratory, Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - Dorit Samocha-Bonet
- Diabetes & Metabolism Division, Garvan Institute of Medical Research, NSW, Australia
| | - Andrew L Siebel
- Metabolic and Vascular Physiology Laboratory, Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - Peter Iliades
- Cellular and Molecular Metabolism Laboratory, Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - Borivoj Zivanovic
- Cellular and Molecular Metabolism Laboratory, Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - Yet H Hong
- Institute for Sports, Exercise and Active Living, Victoria University, Footscray, VIC, Australia
| | - Timothy D Colgan
- Muscle Research and Therapeutics Laboratory, Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - Michael J Kraakman
- Cellular and Molecular Metabolism Laboratory, Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - Clinton R Bruce
- School of Exercise and Nutrition Sciences, Deakin University, Burwood, VIC, Australia
| | - Paul Gregorevic
- Muscle Research and Therapeutics Laboratory, Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - Glenn K McConell
- Institute for Sports, Exercise and Active Living, Victoria University, Footscray, VIC, Australia
| | - Gordon S Lynch
- Basic and Clinical Myology Laboratory, Department of Physiology, The University of Melbourne, Melbourne, VIC, Australia
| | - Grant R Drummond
- Vascular Biology and Immunopharmacology Group, Department of Pharmacology, Monash University, Clayton, VIC, Australia
| | - Bronwyn A Kingwell
- Metabolic and Vascular Physiology Laboratory, Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia
| | - Jerry R Greenfield
- Diabetes & Metabolism Division, Garvan Institute of Medical Research, NSW, Australia
| | - Mark A Febbraio
- Cellular and Molecular Metabolism Laboratory, Baker IDI Heart & Diabetes Institute, Melbourne, VIC, Australia; Diabetes & Metabolism Division, Garvan Institute of Medical Research, NSW, Australia.
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Hong YH, Yang C, Betik AC, Lee-Young RS, McConell GK. Skeletal muscle glucose uptake during treadmill exercise in neuronal nitric oxide synthase-μ knockout mice. Am J Physiol Endocrinol Metab 2016; 310:E838-45. [PMID: 27006199 DOI: 10.1152/ajpendo.00513.2015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 03/17/2016] [Indexed: 11/22/2022]
Abstract
Nitric oxide influences intramuscular signaling that affects skeletal muscle glucose uptake during exercise. The role of the main NO-producing enzyme isoform activated during skeletal muscle contraction, neuronal nitric oxide synthase-μ (nNOSμ), in modulating glucose uptake has not been investigated in a physiological exercise model. In this study, conscious and unrestrained chronically catheterized nNOSμ(+/+) and nNOSμ(-/-) mice either remained at rest or ran on a treadmill at 17 m/min for 30 min. Both groups of mice demonstrated similar exercise capacity during a maximal exercise test to exhaustion (17.7 ± 0.6 vs. 15.9 ± 0.9 min for nNOSμ(+/+) and nNOSμ(-/-), respectively, P > 0.05). Resting and exercise blood glucose levels were comparable between the genotypes. Very low levels of NOS activity were detected in skeletal muscle from nNOSμ(-/-) mice, and exercise increased NOS activity only in nNOSμ(+/+) mice (4.4 ± 0.3 to 5.2 ± 0.4 pmol·mg(-1)·min(-1), P < 0.05). Exercise significantly increased glucose uptake in gastrocnemius muscle (5- to 7-fold) and, surprisingly, more so in nNOSμ(-/-) than in nNOSμ(+/+) mice (P < 0.05). This is in parallel with a greater increase in AMPK phosphorylation during exercise in nNOSμ(-/-) mice. In conclusion, nNOSμ is not essential for skeletal muscle glucose uptake during exercise, and the higher skeletal muscle glucose uptake during exercise in nNOSμ(-/-) mice may be due to compensatory increases in AMPK activation.
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Affiliation(s)
- Yet Hoi Hong
- College of Health and Biomedicine, Victoria University, Melbourne, Victoria, Australia; Clinical Exercise Science Program, Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Victoria, Australia; Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia; and
| | - Christine Yang
- Cellular and Molecular Metabolism, Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Andrew C Betik
- College of Health and Biomedicine, Victoria University, Melbourne, Victoria, Australia; Clinical Exercise Science Program, Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Victoria, Australia
| | - Robert S Lee-Young
- Cellular and Molecular Metabolism, Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Glenn K McConell
- College of Health and Biomedicine, Victoria University, Melbourne, Victoria, Australia; Clinical Exercise Science Program, Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Victoria, Australia
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Fallahi AA, Shekarfroush S, Rahimi M, Jalali A, Khoshbaten A. Alteration in cardiac uncoupling proteins and eNOS gene expression following high-intensity interval training in favor of increasing mechanical efficiency. IRANIAN JOURNAL OF BASIC MEDICAL SCIENCES 2016; 19:258-64. [PMID: 27114795 PMCID: PMC4834115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES High-intensity interval training (HIIT) increases energy expenditure and mechanical energy efficiency. Although both uncoupling proteins (UCPs) and endothelial nitric oxide synthase (eNOS) affect the mechanical efficiency and antioxidant capacity, their effects are inverse. The aim of this study was to determine whether the alterations of cardiac UCP2, UCP3, and eNOS mRNA expression following HIIT are in favor of increased mechanical efficiency or decreased oxidative stress. MATERIALS AND METHODS Wistar rats were divided into five groups: control group (n=12), HIIT for an acute bout (AT1), short term HIIT for 3 and 5 sessions (ST3 and ST5), long-term training for 8 weeks (LT) (6 in each group). The rats of the training groups were made to run on a treadmill for 60 min in three stages: 6 min running for warm-up, 7 intervals of 7 min running on treadmill with a slope of 5° to 20° (4 min with an intensity of 80-110% VO2max and 3 min at 50-60% VO2max), and 5-min running for cool-down. The control group did not participate in any exercise program. Rats were sacrificed and the hearts were extracted to analyze the levels of UCP2, UCP3 and eNOS mRNA by RT-PCR. RESULTS UCP3 expression was increased significantly following an acute training bout. Repeated HIIT for 8 weeks resulted in a significant decrease in UCPs mRNA and a significant increase in eNOS expression in cardiac muscle. CONCLUSION This study indicates that Long term HIIT through decreasing UCPs mRNA and increasing eNOS mRNA expression may enhance energy efficiency and physical performance.
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Affiliation(s)
| | - Shahnaz Shekarfroush
- Department of Physiology, Arsanjan Branch, Islamic Azad University, Fars, Iran,Corresponding author: Shahnaz Shekarforoush. Islamic Azad University, Arsanjan, Iran, Fars. Tel: 09173376859; Fax 071-43522483; ;
| | - Mostafa Rahimi
- Department of Physical Education, University of Kashan, Iran
| | - Amirhossain Jalali
- Institute of Biotechnology and Bioengineering, Isfahan University of Technology, Isfahan, Iran
| | - Ali Khoshbaten
- Sport Physiology Research Center, Baghiyatallah University of Medical Sciences, Tehran, Iran
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Kapilevich LV, Kironenko TA, Zaharova AN, Kotelevtsev YV, Dulin NO, Orlov SN. Skeletal muscle as an endocrine organ: Role of [Na +] i/[K +] i-mediated excitation-transcription coupling. Genes Dis 2015; 2:328-336. [PMID: 27610402 PMCID: PMC5012537 DOI: 10.1016/j.gendis.2015.10.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 10/21/2015] [Indexed: 01/20/2023] Open
Abstract
During the last two decades numerous research teams demonstrated that skeletal muscles function as an exercise-dependent endocrine organ secreting dozens of myokines. Variety of physiological and pathophysiological implications of skeletal muscle myokines secretion has been described; however, upstream signals and sensing mechanisms underlying this phenomenon remain poorly understood. It is well documented that in skeletal muscles intensive exercise triggers dissipation of transmembrane gradient of monovalent cations caused by permanent activation of voltage-gated Na+ and K+ channels. Recently, we demonstrated that sustained elevation of the [Na+]i/[K+]i ratio triggers expression of dozens ubiquitous genes including several canonical myokines, such as interleukin 6 and cyclooxygenase 2, in the presence of intra- and extracellular Ca2+ chelators. These data allowed us to suggest a novel [Na+]i/[K+]i-sensitive, Ca2+i-independent mechanism of excitation-transcription coupling which triggers myokine production. This pathway exists in parallel with canonical signaling mediated by Ca2+i, AMP-activated protein kinase and hypoxia-inducible factor 1α (HIF-1α). In our mini-review we briefly summarize data supporting this hypothesis as well as unresolved issues aiming to forthcoming studies.
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Affiliation(s)
| | | | | | | | | | - Sergei N. Orlov
- National Research Tomsk State University, Tomsk, Russia
- Siberian Medical University, Tomsk, Russia
- M.V. Lomonosov Moscow State University, Moscow, Russia
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Zeng Y, Zhang Y, Zhang L, Cui S, Sun Y. Structural characterization and antioxidant and immunomodulation activities of polysaccharides from the spent rice substrate of Cordyceps militaris. Food Sci Biotechnol 2015. [DOI: 10.1007/s10068-015-0205-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Kinugawa S, Takada S, Matsushima S, Okita K, Tsutsui H. Skeletal Muscle Abnormalities in Heart Failure. Int Heart J 2015; 56:475-84. [PMID: 26346520 DOI: 10.1536/ihj.15-108] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Exercise capacity is lowered in patients with heart failure, which limits their daily activities and also reduces their quality of life. Furthermore, lowered exercise capacity has been well demonstrated to be closely related to the severity and prognosis of heart failure. Skeletal muscle abnormalities including abnormal energy metabolism, transition of myofibers from type I to type II, mitochondrial dysfunction, reduction in muscular strength, and muscle atrophy have been shown to play a central role in lowered exercise capacity. The skeletal muscle abnormalities can be classified into the following main types: 1) low endurance due to mitochondrial dysfunction; and 2) low muscle mass and muscle strength due to imbalance of protein synthesis and degradation. The molecular mechanisms of these skeletal muscle abnormalities have been studied mainly using animal models. The current review including our recent study will focus upon the skeletal muscle abnormalities in heart failure.
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Affiliation(s)
- Shintaro Kinugawa
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine
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Dyakova EY, Kapilevich LV, Shylko VG, Popov SV, Anfinogenova Y. Physical exercise associated with NO production: signaling pathways and significance in health and disease. Front Cell Dev Biol 2015; 3:19. [PMID: 25883934 PMCID: PMC4382985 DOI: 10.3389/fcell.2015.00019] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 03/07/2015] [Indexed: 12/20/2022] Open
Abstract
Here we review available data on nitric oxide (NO)-mediated signaling in skeletal muscle during physical exercise. Nitric oxide modulates skeletal myocyte function, hormone regulation, and local microcirculation. Nitric oxide underlies the therapeutic effects of physical activity whereas the pharmacological modulators of NO-mediated signaling are the promising therapeutic agents in different diseases. Nitric oxide production increases in skeletal muscle in response to physical activity. This molecule can alter energy supply in skeletal muscle through hormonal modulation. Mitochondria in skeletal muscle tissue are highly abundant and play a pivotal role in metabolism. Considering NO a plausible regulator of mitochondrial biogenesis that directly affects cellular respiration, we discuss the mechanisms of NO-induced mitochondrial biogenesis in the skeletal muscle cells. We also review available data on myokines, the molecules that are expressed and released by the muscle fibers and exert autocrine, paracrine and/or endocrine effects. The article suggests the presence of putative interplay between NO-mediated signaling and myokines in skeletal muscle. Data demonstrate an important role of NO in various diseases and suggest that physical training may improve health of patients with diabetes, chronic heart failure, and even degenerative muscle diseases. We conclude that NO-associated signaling represents a promising target for the treatment of various diseases and for the achievement of better athletic performance.
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Affiliation(s)
- Elena Y Dyakova
- Department of Sporting Health Tourism, Physiology, and Medicine, National Research Tomsk State University Tomsk, Russia
| | - Leonid V Kapilevich
- Department of Sporting Health Tourism, Physiology, and Medicine, National Research Tomsk State University Tomsk, Russia ; Institute of Physics and Technology, National Research Tomsk Polytechnic University Tomsk, Russia
| | - Victor G Shylko
- Department of Sporting Health Tourism, Physiology, and Medicine, National Research Tomsk State University Tomsk, Russia
| | - Sergey V Popov
- Federal State Budgetary Scientific Institution "Research Institute for Cardiology," Tomsk, Russia
| | - Yana Anfinogenova
- Institute of Physics and Technology, National Research Tomsk Polytechnic University Tomsk, Russia ; Federal State Budgetary Scientific Institution "Research Institute for Cardiology," Tomsk, Russia
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Hong YH, Frugier T, Zhang X, Murphy RM, Lynch GS, Betik AC, Rattigan S, McConell GK. Glucose uptake during contraction in isolated skeletal muscles from neuronal nitric oxide synthase μ knockout mice. J Appl Physiol (1985) 2015; 118:1113-21. [PMID: 25749441 DOI: 10.1152/japplphysiol.00056.2015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 02/28/2015] [Indexed: 01/25/2023] Open
Abstract
Inhibition of nitric oxide synthase (NOS) significantly attenuates the increase in skeletal muscle glucose uptake during contraction/exercise, and a greater attenuation is observed in individuals with Type 2 diabetes compared with healthy individuals. Therefore, NO appears to play an important role in mediating muscle glucose uptake during contraction. In this study, we investigated the involvement of neuronal NOSμ (nNOSμ), the main NOS isoform activated during contraction, on skeletal muscle glucose uptake during ex vivo contraction. Extensor digitorum longus muscles were isolated from nNOSμ(-/-) and nNOSμ(+/+) mice. Muscles were contracted ex vivo in a temperature-controlled (30°C) organ bath with or without the presence of the NOS inhibitor N(G)-monomethyl-l-arginine (L-NMMA) and the NOS substrate L-arginine. Glucose uptake was determined by radioactive tracers. Skeletal muscle glucose uptake increased approximately fourfold during contraction in muscles from both nNOSμ(-/-) and nNOSμ(+/+) mice. L-NMMA significantly attenuated the increase in muscle glucose uptake during contraction in both genotypes. This attenuation was reversed by L-arginine, suggesting that L-NMMA attenuated the increase in muscle glucose uptake during contraction by inhibiting NOS and not via a nonspecific effect of the inhibitor. Low levels of NOS activity (~4%) were detected in muscles from nNOSμ(-/-) mice, and there was no evidence of compensation from other NOS isoform or AMP-activated protein kinase which is also involved in mediating muscle glucose uptake during contraction. These results indicate that NO regulates skeletal muscle glucose uptake during ex vivo contraction independently of nNOSμ.
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Affiliation(s)
- Yet Hoi Hong
- College of Health and Biomedicine and Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia; Department of Physiology, Faculty of Medicine, University of Malaya, Malaysia
| | - Tony Frugier
- Department of Pharmacology and Therapeutics, University of Melbourne, Melbourne, Australia
| | - Xinmei Zhang
- Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia
| | - Robyn M Murphy
- Department of Zoology, La Trobe University, Melbourne, Australia
| | - Gordon S Lynch
- Department of Physiology, University of Melbourne, Melbourne, Australia; and
| | - Andrew C Betik
- College of Health and Biomedicine and Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia
| | - Stephen Rattigan
- Menzies Research Institute Tasmania, University of Tasmania, Hobart, Australia
| | - Glenn K McConell
- College of Health and Biomedicine and Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia;
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Valerio A, Nisoli E. Nitric oxide, interorganelle communication, and energy flow: a novel route to slow aging. Front Cell Dev Biol 2015; 3:6. [PMID: 25705617 PMCID: PMC4319459 DOI: 10.3389/fcell.2015.00006] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 01/12/2015] [Indexed: 12/14/2022] Open
Abstract
The mitochondrial lifecycle (mitochondrial biogenesis, dynamics, and removal by mitophagy) is carefully orchestrated to ensure the efficient generation of cellular energy and to maintain reactive oxygen species (ROS) production within an optimal range for cellular health. Based on latest research, these processes largely depend on mitochondrial interactions with other cell organelles, so that the ER- and peroxisome-mitochondrial connections might intervene in the control of cellular energy flow. Damaged organelles are cleared by autophagic mechanisms to assure the quality and proper function of the intracellular organelle pool. Nitric oxide (NO) generated through the endothelial nitric oxide synthase (eNOS) acts a gas signaling mediator to promote mitochondrial biogenesis and bioenergetics, with a favorable impact in diverse chronic diseases of the elderly. Obesity, diabetes and aging share common pathophysiological mechanisms, including mitochondrial impairment and dysfunctional eNOS. Here we review the evidences that eNOS-dependent mitochondrial biogenesis and quality control, and possibly the complex interplay among cellular organelles, may be affected by metabolic diseases and the aging processes, contributing to reduce healthspan and lifespan. Drugs or nutrients able to sustain the eNOS-NO generating system might contribute to maintain organelle homeostasis and represent novel preventive and/or therapeutic approaches to chronic age-related diseases.
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Affiliation(s)
- Alessandra Valerio
- Department of Molecular and Translational Medicine, University of Brescia Brescia, Italy
| | - Enzo Nisoli
- Department of Medical Biotechnology and Translational Medicine, Center for Study and Research on Obesity, University of Milan Milan, Italy
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Valgas da Silva CP, Delbin MA, La Guardia PG, Moura CS, Davel APC, Priviero FB, Zanesco A. Improvement of the physical performance is associated with activation of NO/PGC-1α/mtTFA signaling pathway and increased protein expressions of electron transport chain in gastrocnemius muscle from rats supplemented with L-arginine. Life Sci 2015; 125:63-70. [PMID: 25636591 DOI: 10.1016/j.lfs.2014.12.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 12/11/2014] [Accepted: 12/26/2014] [Indexed: 11/16/2022]
Abstract
AIM To examine the influence of l-arginine supplementation in combination with physical training on mitochondrial biomarkers from gastrocnemius muscle and its relationship with physical performance. MAIN METHODS Male Wistar rats were divided into four groups: control sedentary (SD), sedentary supplemented with l-arginine (SDLA), trained (TR) and trained supplemented with l-arginine (TRLA). Supplementation of l-arginine was administered by gavage (62.5mg/ml/day/rat). Physical training consisted of 60min/day, 5days/week, 0% grade, speed of 1.2km/h. The study lasted 8weeks. Skeletal muscle mitochondrial enriched fraction as well as cytoplasmic fractions were obtained for Western blotting and biochemical analyses. Protein expressions of transcriptor coactivator (PGC-1α), transcriptor factors (mtTFA), ATP synthase subunit c, cytochrome oxidase (COXIV), constitutive nitric oxide synthases (eNOS and nNOS), Cu/Zn-superoxide dismutase (SOD) and manganese-SOD (Mn-SOD) were evaluated. We also assessed in plasma: lipid profile, glycemia and malondialdehyde (MDA) levels. The nitrite/nitrate (NOx(-)) levels were measured in both plasma and cytosol fraction of the gastrocnemius muscle. KEY FINDINGS 8-week l-arginine supplementation associated with physical training was effective in promoting greater tolerance to exercise that was accompanied by up-regulation of the protein expressions of mtTFA, PGC-1α, ATP synthase subunit c, COXIV, Cu/Zn-SOD and Mn-SOD. The upstream pathway was associated with improvement of NO bioavailability, but not in NO production since no changes in nNOS or eNOS protein expressions were observed. SIGNIFICANCE This combination would be an alternative approach for preventing cardiometabolic diseases given that in overt diseases a profound impairment in the physical performance of the patients is observed.
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Affiliation(s)
- Carmem Peres Valgas da Silva
- Laboratory of cardiovascular Physiology and physical activity, Institute of Bioscience, Univ Estadual Paulista (UNESP), Rio Claro, SP, Brazil
| | - Maria Andréia Delbin
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas, SP, Brazil
| | - Paolo G La Guardia
- Clinical Pathology, FCM, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil
| | - Carolina Soares Moura
- Department of Food and Nutrition, Faculty of Food Engineering, State University of Campinas, Campinas, SP, Brazil
| | - Ana Paula Couto Davel
- Department of Structural and Functional Biology, Institute of Biology, University of Campinas, Campinas, SP, Brazil
| | - Fernanda Bruschi Priviero
- Laboratory of cardiovascular Physiology and physical activity, Institute of Bioscience, Univ Estadual Paulista (UNESP), Rio Claro, SP, Brazil
| | - Angelina Zanesco
- Laboratory of cardiovascular Physiology and physical activity, Institute of Bioscience, Univ Estadual Paulista (UNESP), Rio Claro, SP, Brazil.
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Blaauw B, Schiaffino S, Reggiani C. Mechanisms modulating skeletal muscle phenotype. Compr Physiol 2014; 3:1645-87. [PMID: 24265241 DOI: 10.1002/cphy.c130009] [Citation(s) in RCA: 177] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mammalian skeletal muscles are composed of a variety of highly specialized fibers whose selective recruitment allows muscles to fulfill their diverse functional tasks. In addition, skeletal muscle fibers can change their structural and functional properties to perform new tasks or respond to new conditions. The adaptive changes of muscle fibers can occur in response to variations in the pattern of neural stimulation, loading conditions, availability of substrates, and hormonal signals. The new conditions can be detected by multiple sensors, from membrane receptors for hormones and cytokines, to metabolic sensors, which detect high-energy phosphate concentration, oxygen and oxygen free radicals, to calcium binding proteins, which sense variations in intracellular calcium induced by nerve activity, to load sensors located in the sarcomeric and sarcolemmal cytoskeleton. These sensors trigger cascades of signaling pathways which may ultimately lead to changes in fiber size and fiber type. Changes in fiber size reflect an imbalance in protein turnover with either protein accumulation, leading to muscle hypertrophy, or protein loss, with consequent muscle atrophy. Changes in fiber type reflect a reprogramming of gene transcription leading to a remodeling of fiber contractile properties (slow-fast transitions) or metabolic profile (glycolytic-oxidative transitions). While myonuclei are in postmitotic state, satellite cells represent a reserve of new nuclei and can be involved in the adaptive response.
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Affiliation(s)
- Bert Blaauw
- Department of Biomedical Sciences, University of Padova, Padova, Italy
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42
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Asano RY, Sales MM, Browne RAV, Moraes JFVN, Coelho Júnior HJ, Moraes MR, Simões HG. Acute effects of physical exercise in type 2 diabetes: A review. World J Diabetes 2014; 5:659-665. [PMID: 25317243 PMCID: PMC4138589 DOI: 10.4239/wjd.v5.i5.659] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 07/09/2014] [Accepted: 07/29/2014] [Indexed: 02/05/2023] Open
Abstract
The literature has shown the efficiency of exercise in the control of type 2 diabetes (T2D), being suggested as one of the best kinds of non-pharmacological treatments for its population. Thus, the scientific production related to this phenomenon has growing exponentially. However, despite its advances, still there is a lack of studies that have carried out a review on the acute effects of physical exercise on metabolic and hemodynamic markers and possible control mechanisms of these indicators in individuals with T2D, not to mention that in a related way, these themes have been very little studied today. Therefore, the aim of this study was to organize and analyze the current scientific production about the acute effects of physical exercise on metabolic and hemodynamic markers and possible control mechanisms of these indicators in T2D individuals. For such, a research with the following keywords was performed: -exercise; diabetes and post-exercise hypotension; diabetes and excess post-exercise oxygen consumption; diabetes and acute effects in PUBMED, SCIELO and HIGHWIRE databases. From the analyzed studies, it is possible to conclude that, a single exercise session can promote an increase in the bioavailability of nitric oxide and elicit decreases in postexercise blood pressure. Furthermore, the metabolic stress from physical exercise can increase the oxidation of carbohydrate during the exercise and keep it, in high levels, the post exercise consumption of O², this phenomenon increases the rate of fat oxidation during recovery periods after exercise, improves glucose tolerance and insulin sensitivity and reduces glycemia between 2-72 h, which seems to be dependent on the exercise intensity and duration of the effort.
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43
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Hong YH, Betik AC, McConell GK. Role of nitric oxide in skeletal muscle glucose uptake during exercise. Exp Physiol 2014; 99:1569-73. [PMID: 25192731 DOI: 10.1113/expphysiol.2014.079202] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Nitric oxide is produced within skeletal muscle fibres and has various functions in skeletal muscle. There is evidence that NO may be essential for normal increases in skeletal muscle glucose uptake during contraction/exercise. Although there have been some discrepant results, it has been consistently demonstrated that inhibition of NO synthase (NOS) attenuates the increase in skeletal muscle glucose uptake during contraction in mouse and rat muscle ex vivo, during in situ contraction in rats and during exercise in humans. The NO-mediated increase in skeletal muscle glucose uptake during contraction/exercise is probably due to the modulation of intramuscular signalling that ultimately increases glucose transporter 4 (GLUT4) translocation and is, surprisingly, independent of blood flow. In this review, we discuss the evidence for and against a role of NO in regulating skeletal muscle glucose uptake during contraction/exercise and outline the possible mechanism(s) involved. Emerging findings regarding the role of neuronal NOS mu (nNOSμ) in this process are also discussed.
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Affiliation(s)
- Yet Hoi Hong
- College of Health and Biomedicine, Victoria University, Melbourne, Victoria, Australia Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia Department of Physiology, Faculty of Medicine, University of Malaya, Malaysia
| | - Andrew C Betik
- College of Health and Biomedicine, Victoria University, Melbourne, Victoria, Australia Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia
| | - Glenn K McConell
- College of Health and Biomedicine, Victoria University, Melbourne, Victoria, Australia Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia
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44
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Sansbury BE, Hill BG. Regulation of obesity and insulin resistance by nitric oxide. Free Radic Biol Med 2014; 73:383-99. [PMID: 24878261 PMCID: PMC4112002 DOI: 10.1016/j.freeradbiomed.2014.05.016] [Citation(s) in RCA: 186] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 05/16/2014] [Accepted: 05/17/2014] [Indexed: 02/07/2023]
Abstract
Obesity is a risk factor for developing type 2 diabetes and cardiovascular disease and has quickly become a worldwide pandemic with few tangible and safe treatment options. Although it is generally accepted that the primary cause of obesity is energy imbalance, i.e., the calories consumed are greater than are utilized, understanding how caloric balance is regulated has proven a challenge. Many "distal" causes of obesity, such as the structural environment, occupation, and social influences, are exceedingly difficult to change or manipulate. Hence, molecular processes and pathways more proximal to the origins of obesity-those that directly regulate energy metabolism or caloric intake-seem to be more feasible targets for therapy. In particular, nitric oxide (NO) is emerging as a central regulator of energy metabolism and body composition. NO bioavailability is decreased in animal models of diet-induced obesity and in obese and insulin-resistant patients, and increasing NO output has remarkable effects on obesity and insulin resistance. This review discusses the role of NO in regulating adiposity and insulin sensitivity and places its modes of action into context with the known causes and consequences of metabolic disease.
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Affiliation(s)
- Brian E Sansbury
- Diabetes and Obesity Center, Institute of Molecular Cardiology, University of Louisville School of Medicine, Louisville, KY 40202, USA; Department of Physiology and Biophysics, University of Louisville School of Medicine, Louisville, KY 40202, USA
| | - Bradford G Hill
- Diabetes and Obesity Center, Institute of Molecular Cardiology, University of Louisville School of Medicine, Louisville, KY 40202, USA; Department of Physiology and Biophysics, University of Louisville School of Medicine, Louisville, KY 40202, USA; Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, Louisville, KY 40202, USA.
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Trevellin E, Scorzeto M, Olivieri M, Granzotto M, Valerio A, Tedesco L, Fabris R, Serra R, Quarta M, Reggiani C, Nisoli E, Vettor R. Exercise training induces mitochondrial biogenesis and glucose uptake in subcutaneous adipose tissue through eNOS-dependent mechanisms. Diabetes 2014; 63:2800-11. [PMID: 24622799 DOI: 10.2337/db13-1234] [Citation(s) in RCA: 136] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Insulin resistance and obesity are associated with a reduction of mitochondrial content in various tissues of mammals. Moreover, a reduced nitric oxide (NO) bioavailability impairs several cellular functions, including mitochondrial biogenesis and insulin-stimulated glucose uptake, two important mechanisms of body adaptation in response to physical exercise. Although these mechanisms have been thoroughly investigated in skeletal muscle and heart, few studies have focused on the effects of exercise on mitochondria and glucose metabolism in adipose tissue. In this study, we compared the in vivo effects of chronic exercise in subcutaneous adipose tissue of wild-type (WT) and endothelial NO synthase (eNOS) knockout (eNOS(-/-)) mice after a swim training period. We then investigated the in vitro effects of NO on mouse 3T3-L1 and human subcutaneous adipose tissue-derived adipocytes after a chronic treatment with an NO donor: diethylenetriamine-NO (DETA-NO). We observed that swim training increases mitochondrial biogenesis, mitochondrial DNA content, and glucose uptake in subcutaneous adipose tissue of WT but not eNOS(-/-) mice. Furthermore, we observed that DETA-NO promotes mitochondrial biogenesis and elongation, glucose uptake, and GLUT4 translocation in cultured murine and human adipocytes. These results point to the crucial role of the eNOS-derived NO in the metabolic adaptation of subcutaneous adipose tissue to exercise training.
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Affiliation(s)
- Elisabetta Trevellin
- Internal Medicine 3, Endocrine-Metabolic Laboratory, Department of Medicine DIMED, University of Padua, Padua, Italy
| | - Michele Scorzeto
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Massimiliano Olivieri
- Internal Medicine 3, Endocrine-Metabolic Laboratory, Department of Medicine DIMED, University of Padua, Padua, Italy
| | - Marnie Granzotto
- Internal Medicine 3, Endocrine-Metabolic Laboratory, Department of Medicine DIMED, University of Padua, Padua, Italy
| | - Alessandra Valerio
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Laura Tedesco
- Center for Study and Research on Obesity, Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - Roberto Fabris
- Internal Medicine 3, Endocrine-Metabolic Laboratory, Department of Medicine DIMED, University of Padua, Padua, Italy
| | - Roberto Serra
- Internal Medicine 3, Endocrine-Metabolic Laboratory, Department of Medicine DIMED, University of Padua, Padua, Italy
| | - Marco Quarta
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Carlo Reggiani
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Enzo Nisoli
- Center for Study and Research on Obesity, Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy
| | - Roberto Vettor
- Internal Medicine 3, Endocrine-Metabolic Laboratory, Department of Medicine DIMED, University of Padua, Padua, Italy
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Hughey CC, Wasserman DH, Lee-Young RS, Lantier L. Approach to assessing determinants of glucose homeostasis in the conscious mouse. Mamm Genome 2014; 25:522-38. [PMID: 25074441 DOI: 10.1007/s00335-014-9533-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 07/04/2014] [Indexed: 01/11/2023]
Abstract
Obesity and type 2 diabetes lessen the quality of life of those afflicted and place considerable burden on the healthcare system. Furthermore, the detrimental impact of these pathologies is expected to persist or even worsen. Diabetes is characterized by impaired insulin action and glucose homeostasis. This has led to a rapid increase in the number of mouse models of metabolic disease being used in the basic sciences to assist in facilitating a greater understanding of the metabolic dysregulation associated with obesity and diabetes, the identification of therapeutic targets, and the discovery of effective treatments. This review briefly describes the most frequently utilized models of metabolic disease. A presentation of standard methods and technologies on the horizon for assessing metabolic phenotypes in mice, with particular emphasis on glucose handling and energy balance, is provided. The article also addresses issues related to study design, selection and execution of metabolic tests of glucose metabolism, the presentation of data, and interpretation of results.
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Affiliation(s)
- Curtis C Hughey
- Department of Molecular Physiology and Biophysics, School of Medicine, Vanderbilt University, 823 Light Hall, 2215 Garland Ave, Nashville, TN, 37232, USA,
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Baltgalvis KA, White K, Li W, Claypool MD, Lang W, Alcantara R, Singh BK, Friera AM, McLaughlin J, Hansen D, McCaughey K, Nguyen H, Smith IJ, Godinez G, Shaw SJ, Goff D, Singh R, Markovtsov V, Sun TQ, Jenkins Y, Uy G, Li Y, Pan A, Gururaja T, Lau D, Park G, Hitoshi Y, Payan DG, Kinsella TM. Exercise performance and peripheral vascular insufficiency improve with AMPK activation in high-fat diet-fed mice. Am J Physiol Heart Circ Physiol 2014; 306:H1128-45. [PMID: 24561866 DOI: 10.1152/ajpheart.00839.2013] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Intermittent claudication is a form of exercise intolerance characterized by muscle pain during walking in patients with peripheral artery disease (PAD). Endothelial cell and muscle dysfunction are thought to be important contributors to the etiology of this disease, but a lack of preclinical models that incorporate these elements and measure exercise performance as a primary end point has slowed progress in finding new treatment options for these patients. We sought to develop an animal model of peripheral vascular insufficiency in which microvascular dysfunction and exercise intolerance were defining features. We further set out to determine if pharmacological activation of 5'-AMP-activated protein kinase (AMPK) might counteract any of these functional deficits. Mice aged on a high-fat diet demonstrate many functional and molecular characteristics of PAD, including the sequential development of peripheral vascular insufficiency, increased muscle fatigability, and progressive exercise intolerance. These changes occur gradually and are associated with alterations in nitric oxide bioavailability. Treatment of animals with an AMPK activator, R118, increased voluntary wheel running activity, decreased muscle fatigability, and prevented the progressive decrease in treadmill exercise capacity. These functional performance benefits were accompanied by improved mitochondrial function, the normalization of perfusion in exercising muscle, increased nitric oxide bioavailability, and decreased circulating levels of the endogenous endothelial nitric oxide synthase inhibitor asymmetric dimethylarginine. These data suggest that aged, obese mice represent a novel model for studying exercise intolerance associated with peripheral vascular insufficiency, and pharmacological activation of AMPK may be a suitable treatment for intermittent claudication associated with PAD.
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Heinonen I, Saltin B, Kemppainen J, Nuutila P, Knuuti J, Kalliokoski K, Hellsten Y. Effect of nitric oxide synthase inhibition on the exchange of glucose and fatty acids in human skeletal muscle. Nutr Metab (Lond) 2013; 10:43. [PMID: 23773265 PMCID: PMC3686616 DOI: 10.1186/1743-7075-10-43] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 06/10/2013] [Indexed: 12/03/2022] Open
Abstract
Background The role of nitric oxide in controlling substrate metabolism in humans is incompletely understood. Methods The present study examined the effect of nitric oxide blockade on glucose uptake, and free fatty acid and lactate exchange in skeletal muscle of eight healthy young males. Exchange was determined by measurements of muscle perfusion by positron emission tomography and analysis of arterial and femoral venous plasma concentrations of glucose, fatty acids and lactate. The measurements were performed at rest and during exercise without (control) and with blockade of nitric oxide synthase (NOS) with NG-monomethyl-l-arginine (L-NMMA). Results Glucose uptake at rest was 0.40 ± 0.21 μmol/100 g/min and increased to 3.71 ± 2.53 μmol/100 g/min by acute one leg low intensity exercise (p < 0.01). Prior inhibition of NOS by L-NMMA did not affect glucose uptake, at rest or during exercise (0.40 ± 0.26 and 4.74 ± 2.69 μmol/100 g/min, respectively). In the control trial, there was a small release of free fatty acids from the limb at rest (−0.05 ± 0.09 μmol/100 g/min), whereas during inhibition of NOS, there was a small uptake of fatty acids (0.04 ± 0.05 μmol/100 g/min, p < 0.05). During exercise fatty acid uptake was increased to (0.89 ± 1.07 μmol/100 g/min), and there was a non-significant trend (p = 0.10) for an increased FFA uptake with NOS inhibition 1.23 ± 1.48 μmol/100 g/min) compared to the control condition. Arterial concentrations of all substrates and exchange of lactate over the limb at rest and during exercise remained unaltered during the two conditions. Conclusion In conclusion, inhibition of nitric oxide synthesis does not alter muscle glucose uptake during low intensity exercise, but affects free fatty acid exchange especially at rest, and may thus be involved in the modulation of energy metabolism in the human skeletal muscle.
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Miller MW, Knaub LA, Olivera-Fragoso LF, Keller AC, Balasubramaniam V, Watson PA, Reusch JEB. Nitric oxide regulates vascular adaptive mitochondrial dynamics. Am J Physiol Heart Circ Physiol 2013; 304:H1624-33. [PMID: 23585138 PMCID: PMC3680775 DOI: 10.1152/ajpheart.00987.2012] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Accepted: 04/11/2013] [Indexed: 01/06/2023]
Abstract
Cardiovascular disease risk factors, such as diabetes, hypertension, dyslipidemia, obesity, and physical inactivity, are all correlated with impaired endothelial nitric oxide synthase (eNOS) function and decreased nitric oxide (NO) production. NO-mediated regulation of mitochondrial biogenesis has been established in many tissues, yet the role of eNOS in vascular mitochondrial biogenesis and dynamics is unclear. We hypothesized that genetic eNOS deletion and 3-day nitric oxide synthase (NOS) inhibition in rodents would result in impaired mitochondrial biogenesis and defunct fission/fusion and autophagy profiles within the aorta. We observed a significant, eNOS expression-dependent decrease in mitochondrial electron transport chain (ETC) protein subunits from complexes I, II, III, and V in eNOS heterozygotes and eNOS null mice compared with age-matched controls. In response to NOS inhibition with NG-nitro-L-arginine methyl ester (L-NAME) treatment in Sprague Dawley rats, significant decreases were observed in ETC protein subunits from complexes I, III, and IV as well as voltage-dependent anion channel 1. Decreased protein content of upstream regulators of mitochondrial biogenesis, cAMP response element-binding protein and peroxisome proliferator-activated receptor-γ coactivator-1α, were observed in response to 3-day L-NAME treatment. Both genetic eNOS deletion and NOS inhibition resulted in decreased manganese superoxide dismutase protein. L-NAME treatment resulted in significant changes to mitochondrial dynamic protein profiles with decreased fusion, increased fission, and minimally perturbed autophagy. In addition, L-NAME treatment blocked mitochondrial adaptation to an exercise intervention in the aorta. These results suggest that eNOS/NO play a role in basal and adaptive mitochondrial biogenesis in the vasculature and regulation of mitochondrial turnover.
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Affiliation(s)
- Matthew W Miller
- University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
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50
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Lee-Young RS, Bonner JS, Mayes WH, Iwueke I, Barrick BA, Hasenour CM, Kang L, Wasserman DH. AMP-activated protein kinase (AMPK)α2 plays a role in determining the cellular fate of glucose in insulin-resistant mouse skeletal muscle. Diabetologia 2013; 56:608-17. [PMID: 23224579 PMCID: PMC4075509 DOI: 10.1007/s00125-012-2787-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Accepted: 11/01/2012] [Indexed: 12/25/2022]
Abstract
AIMS/HYPOTHESIS We determined whether: (1) an acute lipid infusion impairs skeletal muscle AMP-activated protein kinase (AMPK)α2 activity, increases inducible nitric oxide synthase (iNOS) and causes peripheral insulin resistance in conscious, unstressed, lean mice; and (2) restoration of AMPKα2 activity during the lipid infusion attenuates the increase in iNOS and reverses the defect in insulin sensitivity in vivo. METHODS Chow-fed, 18-week-old C57BL/6J male mice were surgically catheterised. After 5 days they received: (1) a 5 h infusion of 5 ml kg(-1) h(-1) Intralipid + 6 U/h heparin (Lipid treatment) or saline (Control); (2) Lipid treatment or Control, followed by a 2 h hyperinsulinaemic-euglycaemic clamp (insulin clamp; 4 mU kg(-1) min(-1)); and (3) infusion of the AMPK activator, 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR) (1 mg kg(-1) min(-1)), or saline during Lipid treatment, followed by a 2 h insulin clamp. In a separate protocol, mice producing a muscle-specific kinase-dead AMPKα2 subunit (α2-KD) underwent an insulin clamp to determine the role of AMPKα2 in insulin-mediated muscle glucose metabolism. RESULTS Lipid treatment decreased AMPKα2 activity, increased iNOS abundance/activation and reduced whole-body insulin sensitivity in vivo. AICAR increased AMPKα2 activity twofold; this did not suppress iNOS or improve whole-body or tissue-specific rates of glucose uptake during Lipid treatment. AICAR caused a marked increase in insulin-mediated glycogen synthesis in skeletal muscle. Consistent with this latter result, lean α2-KD mice exhibited impaired insulin-stimulated glycogen synthesis even though muscle glucose uptake was not affected. CONCLUSIONS/INTERPRETATION Acute induction of insulin resistance via lipid infusion in healthy mice impairs AMPKα2, increases iNOS and causes insulin resistance in vivo. However, these changes do not appear to be interrelated. Rather, a functionally active AMPKα2 subunit is required for insulin-stimulated muscle glycogen synthesis.
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Affiliation(s)
- R S Lee-Young
- Cellular and Molecular Metabolism Laboratory, Division of Metabolism and Obesity, Baker IDI Heart and Diabetes Institute, 75 Commercial Rd, Melbourne, VIC 3004, Australia.
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