• Aging
• Butyrate-producing bacteria
• Gut microbiota, methanogenic archaea
• Metagenome

• Humans
• Gastrointestinal Microbiome
• Middle Aged
• Adult
• Aged
• Archaea/classification
• Archaea/genetics
• Archaea/metabolism
• Archaea/isolation & purification
• Methane/metabolism
• Feces/microbiology
• Aged, 80 and over
• Young Adult
• Female
• Male
• Aging
• Age Factors
• Methanobrevibacter/genetics
• Metagenomics
• Phylogeny
• Bacteria/classification
• Bacteria/genetics
• Bacteria/metabolism

• P 32697 Austrian Science Fund

• archaea
• archaeome
• gut microbiome
• human microbiome
• multiple sclerosis

• Humans
• Multiple Sclerosis/microbiology
• Multiple Sclerosis/drug therapy
• Female
• Middle Aged
• Gastrointestinal Microbiome
• Adult
• Male
• Aged
• Archaea/classification
• Archaea/genetics
• Archaea/metabolism
• Archaea/isolation & purification
• Methanobrevibacter/genetics
• Methanobrevibacter/isolation & purification
• Methanobrevibacter/metabolism
• Methanobrevibacter/classification
• Metagenomics
• Methane/metabolism

• F83, P32697, COE7 Austrian Science Fund (FWF)

• small intestinal bacterial overgrowth
• sibo
• breath test
• supercrescimento bacteriano no intestino delgado
• teste respiratório

• Humans
• Brazil
• Intestine, Small/microbiology
• Blind Loop Syndrome/diagnosis
• Blind Loop Syndrome/therapy
• Breath Tests
• Anti-Bacterial Agents/therapeutic use

• breath analysis
• respiratory monitoring
• vocs
• nonvolatile substance
• exhaled breath condensate
• personalized medicine
• wearable biosensor

• Humans
• Breath Tests/methods
• Breath Tests/instrumentation
• Wearable Electronic Devices
• Exhalation/physiology

• R01 HL155815 NHLBI NIH HHS
• R21 DK132666 NIDDK NIH HHS

• Hemorrhagic shock
• Mesenteric perfusion
• Monitoring blood loss
• Multiple trauma
• Photoacoustic spectroscopy (pas)
• methane

• Humans
• Shock, Hemorrhagic/physiopathology
• Shock, Hemorrhagic/metabolism
• Methane/analysis
• Methane/metabolism
• Hemodynamics/physiology
• Multiple Trauma/physiopathology
• Multiple Trauma/complications
• Male
• Exhalation/physiology
• Breath Tests/methods
• Adult
• Injury Severity Score
• Mesenteric Artery, Superior

• archaea
• microbial communities

• Methanobrevibacter/genetics
• Methanobrevibacter/isolation & purification
• Methanobrevibacter/metabolism
• Humans
• Feces/microbiology
• Gastrointestinal Microbiome/genetics
• Genome, Archaeal
• Methane/metabolism
• Phylogeny
• Adult
• Male
• Female
• Gastrointestinal Tract/microbiology

• P 30796 Austrian Science Fund (Fonds zur Förderung der Wissenschaftlichen Forschung)
• SFB F-83 Austrian Science Fund (Fonds zur Förderung der Wissenschaftlichen Forschung)
• COE 7 Austrian Science Fund (Fonds zur Förderung der Wissenschaftlichen Forschung)

• breath analysis
• gas sensor
• gold nanosheet
• hydrogen sulfide
• ppb-level detection

• Humans
• Hydrogen Sulfide/analysis
• Oxides/chemistry
• Breath Tests

• Japan Society for the Promotion of Science
• Co-creation place formation support program
• Core Research for Evolutional Science and Technology

• Inflammatory Bowel Disease (IBD)
• archaeome
• cobalamin
• innate immunity
• metabolite
• microbiome
• mycobiome
• sulfate reduction
• vitamin
• vitamin B12
• vitamin D receptor

• 1 I101BX004824-01 VA
• R01 DK134343 NIDDK NIH HHS
• R01DK134343, R01 DK105118, and R01DK114126 NIH HHS
• I01 BX004824 BLRD VA
• R01 DK105118 NIDDK NIH HHS
• R01 DK114126 NIDDK NIH HHS

• Coculture
• acetate
• formate
• hydrogen
• methanogen
• sulfide

• Methanobrevibacter/physiology
• Ecosystem
• Gastrointestinal Microbiome
• Hydrogen
• Sulfates

• antioxidant defense system
• dimethyl sulfoxide
• endogenously produced methane
• methyl donors
• methyl radicals
• oxidative stress
• reactive oxygen species
• stable carbon and hydrogen isotope labeling

• Butyrate
• Fermentation
• Gut microbiota
• Hydrogen gas
• Methanogen
• Resistant starch

• Humans
• Butyrates/metabolism
• Fermentation
• Gastrointestinal Microbiome
• Hydrogenase/metabolism
• Microbiota
• Acetates/metabolism
• Lactic Acid/metabolism
• Formates

• U2C DK110768 NIDDK NIH HHS
• Howard Hughes Medical Institute
• P01 HL149633 NHLBI NIH HHS

• small intestinal bacterial overgrowth
• intestinal methanogen overgrowth
• lactulose breath test
• breath tracker

• Humans
• Intestine, Small/microbiology
• Intestines
• Blind Loop Syndrome/diagnosis
• Blind Loop Syndrome/epidemiology
• Bacterial Infections
• Lactulose
• Breath Tests

• gas infusion
• reliability
• spectroscopy
• validation
• whole room indirect calorimeter

• Humans
• Reproducibility of Results
• Energy Metabolism
• Diet
• Energy Intake
• Intestines

• R01 DK105829 NIDDK NIH HHS
• HHS | NIH | National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

• Breath tests
• Irritable bowel syndrome
• Metano
• Methane
• Mexico
• México
• Obesidad
• Obesity
• Pruebas de aliento
• Síndrome de intestino irritable

• Humans
• Female
• Male
• Irritable Bowel Syndrome/epidemiology
• Prevalence
• Mexico/epidemiology
• Overweight
• Obesity

• acetogens
• fecal microbiota composition
• hydrogenotrophic functional groups
• qPCR
• sulfate-reducing bacteria

• Humans
• Adult
• Irritable Bowel Syndrome/microbiology
• Quality of Life
• Longitudinal Studies
• Gastrointestinal Microbiome/genetics
• Feces/microbiology
• Microbiota
• Hydrogen

• diagnostic tests
• irritable bowel syndrome
• metabolites
• microbiome

• Dysbiosis
• Fungicides, Industrial
• Gastrointestinal Microbiome/physiology
• Humans
• Irritable Bowel Syndrome/diagnosis
• Irritable Bowel Syndrome/drug therapy
• Microbiota

• Atmospheric emissions
• CH(4)
• CO(2)
• Dermal
• Exhaled
• Whole-body

• Atmosphere
• Carbon Dioxide/analysis
• Greenhouse Gases
• Humans
• Methane/analysis
• Nitrous Oxide
• Temperature

• gastroenterology
• diagnostic markers

• Breath Tests/methods
• Carbohydrates
• Humans
• Hydrogen
• Malabsorption Syndromes
• Retrospective Studies

• breath tests
• functional dyspepsia
• functional gastrointestinal disorders
• small bowel aspirate and culture
• small intestinal bacterial overgrowth
• small intestinal dysbiosis

• National Health and Medical Research Council

• abdominal MRI
• colonic fermentation
• dietary fibre
• irritable bowel syndrome

• Breath Tests
• Fermentation
• Humans
• Hydrogen/analysis
• Inulin/metabolism
• Irritable Bowel Syndrome
• Magnetic Resonance Imaging
• Psyllium

• Medical Research Council
• Biotechnology and Biological Sciences Research Council
• Consejo Nacional de Ciencia y Tecnología

• Irritable bowel syndrome
• breath tests
• inflammatory bowel disease
• methane
• small intestinal bacterial overgrowth

• Breath Tests/methods
• Child
• Consensus
• Gastroenterology/methods
• Helicobacter Infections/diagnosis
• Helicobacter Infections/drug therapy
• Humans
• Systematic Reviews as Topic

The hydrogen (H₂) breath test is a non-invasive investigation used to diagnose lactose intolerance (LI). Patients with LI may also expire increased amounts of methane (CH₄) during a lactose test. The aim of this study is to evaluate the contribution of CH₄ measurements. We tested 209 children (1–17 years old) with symptoms suggesting LI with lactose H₂ and CH₄ breath tests. The result was positive when the H₂ excretion exceeded 20 parts per million (ppm) and the CH₄ was 10 ppm above the baseline. A clinician, blinded for the results of the breath test, registered the symptoms. Of the patient population, 101/209 (48%) were negative for both H₂ and CH₄; 96/209 (46%) had a positive H₂ breath test result; 31/96 (32%) were also positive for CH₄; 12/209 (6%) patients were only positive for CH₄. The majority of hydrogen producers showed symptoms, whereas this was only the case in half of the H₂-negative CH₄ producers. Almost all patients treated with a lactose-poor diet reported significant symptom improvement. These results indicate that CH₄ measurements may possibly be of additional value for the diagnosis of LI, since 5.7% of patients were negative for H₂ and positive for CH₄, and half of them experienced symptoms during the test.

• hydrogen breath test
• lactose intolerance
• methane

• Biogas
• Methane fermentation
• Psychrophilic methanogens
• Sweet whey

• Biofuels
• Bioreactors
• Fermentation
• Methane/analysis
• Whey/chemistry

• Ministerstwo Nauki i Szkolnictwa Wyższego

Recent research demonstrates a reciprocal relationship between gut microbiota-derived metabolites and the host in controlling the energy homeostasis in mammals. On the one hand, to thrive, gut bacteria exploit nutrients digested by the host. On the other hand, the host utilizes numerous products of gut bacteria metabolism as a substrate for ATP production in the colon. Finally, bacterial metabolites seep from the gut into the bloodstream and interfere with the host’s cellular bioenergetics machinery. Notably, there is an association between alterations in microbiota composition and the development of metabolic diseases and their cardiovascular complications. Some metabolites, like short-chain fatty acids and trimethylamine, are considered markers of cardiometabolic health. Others, like hydrogen sulfide and nitrite, demonstrate antihypertensive properties. Scientific databases were searched for pre-clinical and clinical studies to summarize current knowledge on the role of gut microbiota metabolites in the regulation of mammalian bioenergetics and discuss their potential involvement in the development of cardiometabolic disorders. Overall, the available data demonstrates that gut bacteria products affect physiological and pathological processes controlling energy and vascular homeostasis. Thus, the modulation of microbiota-derived metabolites may represent a new approach for treating obesity, hypertension and type 2 diabetes.

• H2S
• Metabolic syndrome
• Mitochondria
• Nitrate
• Nitric oxide
• SCFAs
• TMAO

Methane levels in methane‐positive lactulose breath tests are frequently elevated at time zero. We hypothesized that baseline methane level is sufficient to detect excessive methane production and thereby avoid extended testing. Our aim was to determine if baseline methane levels were sufficient to identify methane‐positive individuals as defined by current guidelines.

A retrospective study of lactulose breath tests was conducted at an open access motility lab. A methane‐positive study was defined as a methane level ≥10 ppm at any time. Small intestinal bacterial overgrowth (SIBO) was defined as a ≥20 ppm rise in hydrogen from baseline by 90 min. Dual‐positive SIBO and methane studies were identified. Demographics, symptoms, and indications were recorded.

Of 745 tests, 33.1%, 15.0%, and 3.1% were SIBO, methane, and dual‐positive, respectively. Precisely 96.4% of methane‐positive studies had methane levels ≥10 ppm within 90 min and 75.9% had levels ≥10 ppm at time 0. An additional elevation of ≥20 ppm over baseline within 90 min was observed in 32.1%. Of 22 methane‐positive patients with constipation, methane levels were ≥10 ppm at baseline in 81.8% and were ≥10 ppm within 90 min in all cases.

Nearly 25% of methane‐positive studies were not identified by a fasting methane level, but 96% were identified within 90 min. Most methane‐positive studies did not have a rise of 20 ppm above baseline. Our findings suggest the lactulose breath test for hydrogen and methane can be complete at 90 min.

• breath tests
• lactulose
• obesity
• zonulin

• Adolescent
• Breath Tests
• Carbon Dioxide
• Child
• Fructose
• Humans
• Hydrogen
• Lactose Intolerance/diagnosis
• Malabsorption Syndromes/diagnosis
• Methane

Background: Internal hemorrhage is a medical emergency, which requires immediate causal therapy, but the recognition may be difficult. The reactive changes of the mesenteric circulation may be part of the earliest hemodynamic responses to bleeding. Methane is present in the luminal atmosphere; thus, we hypothesized that it can track the intestinal circulatory changes, induced by hemorrhage, non-invasively. Our goal was to validate and compare the sensitivity of this method with an established technique using sublingual microcirculatory monitoring in a large animal model of controlled, graded hemorrhage and the early phase of following fluid resuscitation.

Materials and Methods: The experiments were performed on anesthetized, ventilated Vietnamese minipigs (approval number: V/148/2013; n = 6). The animals were gradually bled seven times consecutively of 5% of their estimated blood volume (BV) each, followed by gradual fluid resuscitation with colloid (hydroxyethyl starch; 5% of the estimated BV/dose) until 80 mmHg mean arterial pressure was achieved. After each step, macrohemodynamic parameters were recorded, and exhaled methane level was monitored continuously with a custom-built photoacoustic laser-spectroscopy unit. The microcirculation of the sublingual area, ileal serosa, and mucosa was examined by intravital videomicroscopy (Cytocam-IDF, Braedius).

Results: Mesenteric perfusion was significantly reduced by a 5% blood loss, whereas microperfusion in the oral cavity deteriorated after a 25% loss. A statistically significant correlation was found between exhaled methane levels, superior mesenteric artery flow (r = 0.93), or microcirculatory changes in the ileal serosa (ρ = 0.78) and mucosa (r = 0.77). After resuscitation, the ileal mucosal microcirculation increased rapidly [De Backer score (DBS): 2.36 ± 0.42 vs. 8.6 ± 2.1 mm⁻¹], whereas serosal perfusion changed gradually and with a lower amplitude (DBS: 2.51 ± 0.48 vs. 5.73 ± 0.75). Sublingual perfusion correlated with mucosal (r = 0.74) and serosal (r = 0.66) mesenteric microperfusion during the hemorrhage phase but not during the resuscitation phase.

Conclusion: Detection of exhaled methane levels is of diagnostic significance during experimental hemorrhage as it indicates blood loss earlier than sublingual microcirculatory changes and in the early phase of fluid resuscitation, the exhaled methane values change in association with the mesenteric perfusion and the microcirculation of the ileum.

• diagnostic significance
• exhaled methane
• hemorrhage
• resuscitation
• small intestinal microcirculation

• head and neck cancer
• translational research
• cancer
• immunology
• microbiology
• biomarkers
• medical research
• oncology

• Adult
• Aged
• Aged, 80 and over
• Biomarkers/analysis
• Breath Tests/methods
• Carbohydrate Metabolism
• Case-Control Studies
• Dysbiosis/diagnosis
• Fasting
• Fatty Acids, Volatile/analysis
• Female
• Head and Neck Neoplasms/metabolism
• Head and Neck Neoplasms/microbiology
• Head and Neck Neoplasms/pathology
• Humans
• Hydrogen/analysis
• Male
• Methane/analysis
• Middle Aged
• Risk Factors
• Squamous Cell Carcinoma of Head and Neck/metabolism
• Squamous Cell Carcinoma of Head and Neck/microbiology
• Squamous Cell Carcinoma of Head and Neck/pathology

• Garnett Passe and Rodney Williams Memorial Foundation
• Australia and New Zealand Head and Neck Cancer Society Foundation

Renal transplant recipients (RTRs) often suffer from posttransplant diarrhea. The observed dysbiosis in RTR may influence the fermentation processes in the gut. In this study, we aimed to investigate whether fermentation differs between RTRs and healthy controls (HCs), by measuring breath H₂ and CH₄ concentrations. Additionally, we determined the fecal presence of the methanogen Methanobrevibacter smithii (M. smithii), which plays a main role in the process of methanogenesis. Data from the TransplantLines Biobank and Cohort Study (NCT03272841) was used. A total of 142 RTRs and 77 HCs were included. Breath H₂ concentrations in RTRs were not significantly different from HCs. Breath CH₄ concentrations in RTRs were significantly lower compared with HCs (median [interquartile range (IQR)] 7.5 [3.9–10.6] ppm vs. 16.0 [8.0–45.5] ppm, p < 0.001). M. smithii was less frequently present in the feces of RTRs compared to HCs (28.6% vs. 86.4% resp., p < 0.001). Our findings regarding the altered methanogenesis in the gut of RTRs show similarities with previous results in inflammatory bowel disease patients. These findings provide novel insight into the alterations of fermentation after renal transplantation, which may contribute to understanding the occurrence of posttransplant diarrhea.

• Methanosphaera stadtmanae
• methanogenesis
• mucins
• posttransplant diarrhea
• sulfate-reducing bacteria

• Breath tests
• Difference
• Irritable bowel syndrome
• Lactulose
• sex

• Adolescent
• Adult
• Aged
• Aged, 80 and over
• Body Mass Index
• Breath Tests/methods
• Female
• Humans
• Hydrogen/metabolism
• Irritable Bowel Syndrome/diagnosis
• Irritable Bowel Syndrome/pathology
• Logistic Models
• Male
• Methane/metabolism
• Middle Aged
• Odds Ratio
• Sex Factors
• Young Adult

• Bioactivity
• Exogenous methane
• Ischemia/reperfusion
• Methanogenesis
• Sepsis

The human intestinal tract harbors diverse and complex microbial communities that have a vast metabolic capacity including the breakdown of complex carbohydrates into short chain fatty acids, acetate, propionate, and butyrate. As butyrate is beneficial for gut health there is much attention on butyrogenic bacteria and their role in the colonic anaerobic food chain. However, our understanding how production of butyrate by gut microorganisms is controlled by interactions between different species and environmental nutrient availability is very limited. To address this, we set up experimental in vitro co-culture systems to study the metabolic interactions of Anaerostipes rhamnosivorans, a butyrate producer with each of its partners; Blautia hydrogenotrophica, an acetogen; Methanobrevibacter smithii, a methanogen and Bacteroides thetaiotaomicron, a versatile degrader of plant cell wall pectins; through corresponding specific cross-feeding. In all co-cultures, A. rhamnosivorans was able to benefit from its partner for enhanced butyrate formation compared to monocultures. Interspecies transfer of hydrogen or formate from A. rhamnosivorans to the acetogen B. hydrogenotrophica and in turn of acetate from the acetogen to the butyrogen were essential for butyrate formation. A. rhamnosivorans grown on glucose supported growth of M. smithii via interspecies formate/hydrogen transfer enhancing butyrate formation. In the co-culture with pectin, lactate was released by B. thetaiotaomicron which was concomitantly used by A. rhamnosivorans for the production of butyrate. Our findings indicate enhanced butyrate formation through microbe-microbe interactions between A. rhamnosivorans and an acetogen, a methanogen or a pectin-degrader. Such microbial interactions enhancing butyrate formation may be beneficial for colonic health.

• Anaerostipes
• butyrate
• butyrate-producing bacteria
• gut microbes
• microbial interaction

Biological methane formation is associated with anoxic environments and the activity of anaerobic prokaryotes (Archaea). However, recent studies have confirmed methane release from eukaryotes, including plants, fungi, and animals, even in the absence of microbes and in the presence of oxygen. Furthermore, it was found that aerobic methane emission in plants is stimulated by a variety of environmental stress factors, leading to reactive oxygen species (ROS) generation. Further research presented evidence that molecules with sulfur and nitrogen bonded methyl groups such as methionine or choline are carbon precursors of aerobic methane formation. Once generated, methane is widely considered to be physiologically inert in eukaryotes, but several studies have found association between mammalian methanogenesis and gastrointestinal (GI) motility changes. In addition, a number of recent reports demonstrated anti-inflammatory potential for exogenous methane-based approaches in model anoxia-reoxygenation experiments. It has also been convincingly demonstrated that methane can influence the downstream effectors of transiently increased ROS levels, including mitochondria-related pro-apoptotic pathways during ischemia-reperfusion (IR) conditions. Besides, exogenous methane can modify the outcome of gasotransmitter-mediated events in plants, and it appears that similar mechanism might be active in mammals as well. This review summarizes the relevant literature on methane-producing processes in eukaryotes, and the available results that underscore its bioactivity. The current evidences suggest that methane liberation and biological effectiveness are both linked to cellular redox regulation. The data collectively imply that exogenous methane influences the regulatory mechanisms and signaling pathways involved in oxidative and nitrosative stress responses, which suggests a modulator role for methane in hypoxia-linked pathologies.

• bioactive gases
• ischemia-reperfusion
• methanogenesis
• mitochondria
• nitroxidative stress

• breath tests
• irritable bowel syndrome
• methane
• sensitivity and specificity

• CH4 overproduction
• H2 overproduction
• breath test with lactulose

• Breath Tests
• Case-Control Studies
• Humans
• Intestine, Small
• Irritable Bowel Syndrome/microbiology
• Lactulose
• Methanobrevibacter/pathogenicity

• Amyotrophic lateral sclerosis
• dysbiosis
• gut microbiota
• metagenomics
• microbiome
• neurodegeneration

• Animals
• Male
• Rats
• Breath Tests
• Disease Models, Animal
• Hemodynamics/drug effects
• Mesenteric Ischemia/physiopathology
• Methane/pharmacology
• Rats, Sprague-Dawley
• Regional Blood Flow
• Reperfusion Injury/physiopathology
• Swine