Metabolic dysfunction-associated steatotic liver disease (MASLD) is a series of obesity-related metabolic liver diseases, ranging from relatively benign hepatic steatosis to metabolic-associated steatohepatitis (MASH). With the changes in lifestyle, its incidence and prevalence have risen to epidemic proportions globally. In recent years, an increasing amount of evidence has indicated that the hepatic microenvironment is involved in the pathophysiological processes of MASH-induced liver fibrosis and the formation of hepatocellular carcinoma (HCC). The hepatic microenvironment is composed of various parenchymal and non-parenchymal cells, which communicate with each other through various factors. In this review, we focus on the changes in hepatocytes, cholangiocytes, liver sinusoidal endothelial cells (LSECs), hepatic stellate cells (HSCs), Kupffer cells (KC), dendritic cells (DC), neutrophils, monocytes, T and B lymphocytes, natural killer cells (NK), natural killer T cells (NKT), mucosal-associated invariant T cells (MAIT), γδT cells, and gut microbiota during the progression of MASLD. Furthermore, we discuss promising therapeutic strategies targeting the microenvironment of MASLD-MASH-HCC.

High fibrosis of the tumor microenvironment (TME) not only impedes the effective infiltration of T cells but also serves as a physical barrier to inhibit the penetration of chemotherapy drugs. Triple-negative breast cancer (TNBC) is characterized by significant infiltration of tumor-associated macrophages (TAMs) and high fibrosis. However, the mechanism of high fibrosis in such tumors is still under debate.

We first investigated the correlation between tumor-derived osteopontin (OPN) and tumor fibrosis as well as TAM enrichment using a tumor model characterized by OPN genetic inactivation or overexpression. We further compared the effects of macrophage depletion on tumor fibrosis in mice bearing TNBC tumors (4T1WT or 4T1Spp1 - KO). To elucidate the mechanism by which TAMs promote tumor fibrosis, we evaluated their potential to recruit cancer-associated fibroblasts (CAFs) through in vitro migration assays and compared the production of transforming growth factor-beta 1 (TGFβ1) among different TAM subpopulations.

Our study revealed that OPN secretion by tumor cells correlates positively with both tumor fibrosis and TAM enrichment. Specifically, within the enriched TAM population, Ly6C+CD206- TAMs recruit CAFs via CCL5 secretion, while Ly6C-CD206high TAMs secrete TGFβ1 to activate CAFs. Blocking the tumor cell-derived OPN can effectively prevent tumor fibrosis.

This study shows that tumor-derived OPN primarily drives TAM enrichment in mouse cancer model, indirectly promoting tumor fibrosis through Ly6C+CD206-/low and Ly6C-CD206high TAMs. Our findings have potential application in preventing tumors from excessive fibrosis and enhancing the efficacy of immunotherapy and chemotherapy.

The nuclear factor of activated T cells (NFAT) is a novel renoprotective transcription factor in an inactive form in the cytoplasm and an active form in the nucleus. NFAT is expressed in T cells, heart, kidney and lymphocytes. NFAT plays an essential role in inducing apoptosis of renal tubular epithelial cells. NFAT levels have been observed to increase significantly during kidney diseases. Further, downregulation or silencing of endogenous NFAT mitigates kidney diseases. NFAT regulation depends upon the intricate interplay between calcium ions and calcineurin (CaN), thus orchestrating the NFAT/calcineurin signalling pathway. When CaN is activated, it induces dephosphorylation of NFAT and localises the active NFAT into the nucleus, which ultimately leads to inflammation, fibrosis and apoptosis of kidney cells. Further, the global incidence (> 800 million) due to kidney disease imposes a significant economic burden on the healthcare system. Therefore, it is crucial to comprehend the pathways involved in the pathophysiology of kidney diseases to develop targeted interventions. Ongoing studies indicate potential therapies, including anandamide, 11R-VIVIT and maxacalcitol to regulate NFAT levels in kidney disease. The present review discusses the role and regulation of NFAT in the pathogenesis of kidney diseases. This is focused on various preclinical studies that have shown NFAT downregulation as a potential therapeutic strategy against kidney disease setting the foundation for future clinical investigations.

Primary sclerosing cholangitis (PSC) is a chronic heterogenous cholangiopathy with unknown etiology where chronic inflammation of the bile ducts leads to multifocal biliary strictures and biliary fibrosis with consecutive cirrhosis development. We here aimed to identify a PSC-specific gene signature associated with biliary fibrosis development.

We performed RNA-sequencing of 47 liver biopsies from people with PSC (n = 16), primary biliary cholangitis (PBC, n = 15), and metabolic dysfunction-associated steatotic liver disease (MASLD, n = 16) with different fibrosis stages to identify a PSC-specific gene signature associated with biliary fibrosis progression. For validation, we compared an external transcriptome data set of liver biopsies from people with PSC (n = 73) with different fibrosis stages (baseline samples from NCT01672853).

Differential gene expression analysis of the liver transcriptome from patients with PSC with advanced vs. early fibrosis revealed 431 genes associated with fibrosis development. Of those, 367 were identified as PSC-associated when compared with PBC or MASLD. Validation against an external data set of 73 liver biopsies from patients with PSC with different fibrosis stages led to a condensed set of 150 (out of 367) differentially expressed genes. Cell type specificity assignment of those genes by using published single-cell RNA-Seq data revealed genetic disease drivers expressed by cholangiocytes (e.g. CXCL1, SPP1), fibroblasts, innate, and adaptive immune cells while deconvolution along fibrosis progression of the PSC, PBC, and MASLD samples highlighted an early involvement of macrophage- and neutrophil-associated genes in PSC fibrosis.

We reveal a PSC-attributed gene signature associated with biliary fibrosis development that may enable the identification of potential new biomarkers and therapeutic targets in PSC-related fibrogenesis.

Primary sclerosing cholangitis (PSC) is an inflammatory liver disease that is characterized by multifocal inflammation of bile ducts and subsequent biliary fibrosis. Herein, we identify a PSC-specific gene set of biliary fibrosis progression attributing to a uniquely complex milieu of different cell types, including innate and adaptive immune cells while neutrophils and macrophages showed an earlier involvement in fibrosis initiation in PSC in contrast to PBC and metabolic dysfunction-associated steatotic liver disease. Thus, our unbiased approach lays an important groundwork for further mechanistic studies for research into PSC-specific fibrosis.

Osteopontin (OPN) is a multifunctional glycoprotein with various structural domains that enable it to perform diverse functions in both physiological and pathological states. This review comprehensively examines OPN from multiple perspectives, including its protein structure, interactions with receptors, interactions with immune cells, and roles in kidney diseases and transplantation. This review explores the immunological duality of OPN and its significance and value as a biomarker and therapeutic target in kidney transplantation. In cancer, OPN typically promotes tumor evasion by suppressing the immune system. Conversely, in immune-related kidney diseases, particularly kidney transplantation, OPN activates the immune system by enhancing the migration and activation of immune cells, thereby exacerbating kidney damage. This immunological duality may stem from different OPN splice variants and the exposure, after cleavage, of different structural domains, which play distinct biological roles in cellular interactions. Additionally, OPN has a significant biological impact posttransplantation and on chronic kidney disease and, highlighting its importance as a biomarker and potential therapeutic target. Future research should further explore the specific mechanisms of OPN in kidney transplantation to improve treatment strategies and enhance patient quality of life.

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most widespread chronic liver disease that poses significant threats to public health due to changes in dietary habits and lifestyle patterns. The transition from simple steatosis to nonalcoholic steatohepatitis (NASH) markedly increases the risk of developing cirrhosis, hepatocellular carcinoma, and liver failure in patients. However, there is only one Food and Drug Administration-approved therapeutic drug in the world, and the clinical demand is huge. There is significant clinical heterogeneity among patients with NAFLD, and it is challenging to fully understand human NAFLD using only a single animal model. Interestingly, felines, like humans, are particularly prone to spontaneous fatty liver disease. This review summarized and compared the etiology, clinical features, pathological characteristics, and molecular pathogenesis between human fatty liver and feline hepatic lipidosis (FHL). We analyzed the key similarities and differences between those two species, aiming to provide theoretical foundations for developing effective strategies for the treatment of NAFLD in clinics.

Peroxisome proliferator-activated receptors (PPARs) constitute a small family of three nuclear receptors that act as lipid sensors, and thereby regulate the transcription of genes having key roles in hepatic and whole-body energy homeostasis, and in other processes (e.g., inflammation), which have far-reaching health consequences. Peroxisome proliferator-activated receptor isotype α (PPARα) is expressed in oxidative tissues, particularly in the liver, carrying out critical functions during the adaptive fasting response. Advanced omics technologies have provided insight into the vast complexity of the regulation of PPAR expression and activity, as well as their downstream effects on the physiology of the liver and its associated metabolic organs. Here, we provide an overview of the gene regulatory networks controlled by PPARα in the liver in response to fasting. We discuss impacts on liver metabolism, the systemic repercussions and benefits of PPARα-regulated ketogenesis and production of fibroblast growth factor 21 (FGF21), a fasting- and stress-inducible metabolic hormone. We also highlight current challenges in using novel methods to further improve our knowledge of PPARα in health and disease.

Hepatic steatosis, a common liver disorder, can progress to severe conditions such as nonalcoholic steatohepatitis and cirrhosis. While olfactory receptors are primarily known for detecting odorants, emerging evidence suggests that they also influence liver lipid metabolism. This study generated a mouse model with a specific knockout of olfactory receptor 23 (MOR23) to investigate its role in hepatic steatosis. MOR23 knockout mice on a normal diet showed a slight increase in liver weight compared to wild-type (WT) mice. When fed a high-fat diet (HFD), these knockout mice exhibited accelerated hepatic steatosis, indicated by increased liver weight and hepatic triglyceride levels. Our findings suggest that the cyclic adenosine monophosphate/protein kinase A/AMP-activated protein kinase pathway is involved in the role of MOR23, leading to the upregulation of peroxisome proliferator-activated receptor α, peroxisome proliferator-activated receptor-γ coactivator 1-α, and their target β-oxidation genes in the liver. MOR23 also appeared to regulate lipogenesis and free fatty acid uptake in HFD-fed mice, potentially by influencing sterol regulatory element-binding protein 1 activity. Notably, administering a potential MOR23 ligand, cedrene, attenuated hepatic steatosis in WT mice, but these effects were largely nullified in MOR23 knockout mice. These findings provide valuable insights into the in vivo role of MOR23 in hepatic steatosis development.

Berberine (BBR) is the main active component from Coptidis rhizome, a well-known Chinese herbal medicine used for metabolic diseases, especially diabetes for thousands of years. BBR has been reported to cure various metabolic disorders, such as nonalcoholic fatty liver disease (NAFLD). However, the direct proteomic targets and underlying molecular mechanism of BBR against NAFLD remain less understood.

To investigate the direct target and corresponding molecular mechanism of BBR on NAFLD is the aim of the current study.

High-fat diet (HFD)-fed mice and oleic acid (OA) stimulated HepG2 cells were utilized to verify the beneficial impacts of BBR on glycolipid metabolism profiles. The click chemistry in proteomics, DARTS, CETSA, SPR and fluorescence co-localization analysis were conducted to identify the targets of BBR for NAFLD. RNA-seq and shRNA/siRNA were used to investigate the downstream pathways of the target.

BBR improved hepatic steatosis, ameliorated insulin resistance, and reduced TG levels in the NAFLD models. Importantly, Aldo-keto reductase 1B10 (AKR1B10) was first proved as the target of BBR for NAFLD. The gene expression of AKR1B10 increased significantly in the NAFLD patients' liver tissue. We further demonstrated that HFD and OA increased AKR1B10 expression in the C57BL/6 mice's liver and HepG2 cells, respectively, whereas BBR decreased the expression and activities of AKR1B10. Moreover, the knockdown of AKR1B10 by applying shRNA/siRNA profoundly impacted the beneficial effects on the pathogenesis of NAFLD by BBR. Meanwhile, the changes in various proteins (ACC1, CPT-1, GLUT2, etc.) are responsible for hepatic lipogenesis, fatty acid oxidation, glucose uptake, etc. by BBR were reversed by the knockdown of AKR1B10. Additionally, RNA-seq was used to identify the downstream pathway of AKR1B10 by examining the gene expression of liver tissues from HFD-fed mice. Our findings revealed that BBR markedly increased the protein levels of PPARα while downregulating the expression of PPARγ. However, various proteins of PPAR signaling pathways remained unaffected post the knockdown of AKR1B10.

BBR alleviated NAFLD via mediating PPAR signaling pathways through targeting AKR1B10. This study proved that AKR1B10 is a novel target of BBR for NAFLD treatment and helps to find new targets for the treatment of NAFLD by using active natural compounds isolated from traditional herbal medicines as the probe.

Dysregulated lipid oxidation occurs in several pathological processes characterized by cell proliferation and migration. Nonetheless, the molecular mechanism of lipid oxidation is not well appreciated in liver fibrosis, which is accompanied by enhanced fibroblast proliferation and migration.

We investigated the causes and consequences of lipid oxidation in liver fibrosis using cultured cells, animal models, and clinical samples.

Increased ecto-nucleotide pyrophosphatase/phosphodiesterase (ENPP1) expression caused increased lipid oxidation, resulting in the proliferation and migration of hepatic stellate cells (HSCs) that lead to liver fibrosis, whereas fibroblast-specific ENPP1 knockout reversing these results. Elevated ENPP1 and N6-methyladenosine (m6A) levels were associated with high expression of Wilms tumor 1 associated protein (WTAP). Mechanistically, WTAP-mediated m6A methylation of the 3'UTR of ENPP1 mRNA and induces its translation dependent of YTH domain family proteins 1 (YTHDF1). Additionally, ENPP1 could interact with hypoxia inducible lipid droplet associated (HILPDA) directly; overexpression of ENPP1 further recruits HILPDA-mediated lipid oxidation, thereby promotes HSCs proliferation and migration, while inhibition of ENPP1 expression produced the opposite effect. Clinically, increased expression of WTAP, YTHDF1, ENPP1, and HILPDA, and increased m6A mRNA content, enhanced lipid oxidation, and increased collagen deposition in human liver fibrosis tissues.

We describe a novel mechanism in which WTAP catalyzes m6A methylation of ENPP1 in a YTHDF1-dependent manner to enhance lipid oxidation, promoting HSCs proliferation and migration and liver fibrosis.

Increasing attention to liver-bone crosstalk has spurred interest in targeted interventions for various forms of osteoporosis. Liver injury induced by different liver diseases can cause an imbalance in bone metabolism, indicating a novel regulatory paradigm between the liver and bone. However, the role of the liver-bone axis in both primary and secondary osteoporosis remains inadequately elucidated. Therefore, exploring the exact regulatory mechanisms of the liver-bone axis may offer innovative clinical approaches for treating diseases associated with the liver and bone.

Here, we summarize the latest research on the liver-bone axis by searching the PubMed and Web of Science databases and discuss the possible mechanism of the liver-bone axis in different types of osteoporosis. The literature directly reporting the regulatory role of the liver-bone axis in different types of osteoporosis from the PubMed and Web of Science databases has been included in the discussion of this review (including but not limited to the definition of the liver-bone axis, clinical studies, and basic research). In addition, articles discussing changes in bone metabolism caused by different etiologies of liver injury have also been included in the discussion of this review (including but not limited to clinical studies and basic research).

Several endocrine factors (IGF-1, FGF21, hepcidin, vitamin D, osteocalcin, OPN, LCAT, Fetuin-A, PGs, BMP2/9, IL-1/6/17, and TNF-α) and key genes (SIRT2, ABCB4, ALDH2, TFR2, SPTBN1, ZNF687 and SREBP2) might be involved in the regulation of the liver-bone axis. In addition to the classic metabolic pathways involved in inflammation and oxidative stress, iron metabolism, cholesterol metabolism, lipid metabolism and immunometabolism mediated by the liver-bone axis require more research to elucidate the regulatory mechanisms involved in osteoporosis.

During primary and secondary osteoporosis, the liver-bone axis is responsible for liver and bone homeostasis via several hepatokines and osteokines as well as biochemical signaling. Combining multiomics technology and data mining technology could further advance our understanding of the liver-bone axis, providing new clinical strategies for managing liver and bone-related diseases.The translational potential of this article is as follows: Abnormal metabolism in the liver could seriously affect the metabolic imbalance of bone. This review summarizes the indispensable role of several endocrine factors and biochemical signaling pathways involved in the liver-bone axis and emphasizes the important role of liver metabolic homeostasis in the pathogenesis of osteoporosis, which provides novel potential directions for the prevention, diagnosis, and treatment of liver and bone-related diseases.

Chronic inflammation of adipose tissue is a prominent characteristic of many metabolic diseases. Lipid metabolism in adipose tissue is consistently dysregulated during inflammation, which is characterized by substantial infiltration by proinflammatory cells and high cytokine concentrations. Adipose tissue inflammation is caused by a variety of endogenous factors, such as mitochondrial dysfunction, reactive oxygen species (ROS) production, endoplasmic reticulum (ER) stress, cellular senescence, ceramides biosynthesis and mediators of lipopolysaccharides (LPS) signaling. Additionally, the gut microbiota also plays a crucial role in regulating adipose tissue inflammation. Essentially, adipose tissue inflammation arises from an imbalance in adipocyte metabolism and the regulation of immune cells. Specific inflammatory signals, including nuclear factor-κB (NF-κB) signaling, inflammasome signaling and inflammation-mediated autophagy, have been shown to be involved in the metabolic regulation. The pathogenesis of metabolic diseases characterized by chronic inflammation (obesity, insulin resistance, atherosclerosis and nonalcoholic fatty liver disease [NAFLD]) and recent research regarding potential therapeutic targets for these conditions are also discussed in this review.

Non-alcoholic fatty liver disease (NAFLD) has become one of the most frequent chronic liver diseases worldwide in recent decades. Metabolic diseases like excessive blood glucose, central obesity, dyslipidemia, hypertension, and liver function abnormalities cause NAFLD. NAFLD significantly increases the likelihood of liver cancer, heart disease, and mortality, making it a leading cause of liver transplants. Non-alcoholic steatohepatitis (NASH) is a more advanced form of the disease that causes scarring and inflammation of the liver over time and can ultimately result in cirrhosis and hepatocellular carcinoma. In this review, we briefly discuss NAFLD's pathogenic mechanisms, their progression into NASH and afterward to NASH-related cirrhosis. It also covers disease epidemiology, metabolic mechanisms, glucose and lipid metabolism in the liver, macrophage dysfunction, bile acid toxicity, and liver stellate cell stimulation. Additionally, we consider the contribution of intestinal microbiota, genetics, epigenetics, and ecological factors to fibrosis progression and hepatocellular carcinoma risk in NAFLD and NASH patients.

Chronic interstitial fibrosis presents a significant challenge to the long-term survival of transplanted kidneys. Our research has shown that reduced expression of acyl-coenzyme A oxidase 1 (ACOX1), which is the rate-limiting enzyme in the peroxisomal fatty acid β-oxidation pathway, contributes to the development of fibrosis in renal allografts. ACOX1 deficiency leads to lipid accumulation and excessive oxidation of polyunsaturated fatty acids (PUFAs), which mediate epithelial-mesenchymal transition (EMT) and extracellular matrix (ECM) reorganization respectively, thus causing fibrosis in renal allografts. Furthermore, activation of Toll-like receptor 4 (TLR4)-nuclear factor kappa-B (NF-κB) signaling induced ACOX1 downregulation in a DNA methyltransferase 1 (DNMT1)-dependent manner. Overconsumption of PUFA resulted in endoplasmic reticulum (ER) stress, which played a vital role in facilitating ECM reorganization. Supplementation with PUFAs contributed to delayed fibrosis in a rat model of renal transplantation. The study provides a novel therapeutic approach that can delay chronic interstitial fibrosis in renal allografts by targeting the disorder of lipid metabolism.

Metabolic dysfunction-associated steatohepatitis (MASH) is a severe form of liver disease that poses a global health threat because of its potential to progress to advanced fibrosis, leading to cirrhosis and liver cancer. Recent advances in single-cell methodologies, refined disease models, and genetic and epigenetic insights have provided a nuanced understanding of MASH fibrogenesis, with substantial cellular heterogeneity in MASH livers providing potentially targetable cell-cell interactions and behavior. Unlike fibrogenesis, mechanisms underlying fibrosis regression in MASH are still inadequately understood, although antifibrotic targets have been recently identified. A refined antifibrotic treatment framework could lead to noninvasive assessment and targeted therapies that preserve hepatocellular function and restore the liver's architectural integrity.

Identifying immune cells and anatomical tissues that contribute to the establishment of viral reservoirs is of central importance in HIV-1 cure research. Herein, we used rhesus macaques (RMs) infected with SIVmac251 to analyze viral seeding in the liver and lungs of either untreated or early antiretroviral therapy-treated (ART-treated) RMs. Consistent with viral replication and sensing, transcriptomic analyses showed higher levels of inflammation, pyroptosis, and chemokine genes as well as of interferon-stimulating gene (ISG) transcripts, in the absence of ART. Our results highlighted the infiltration of monocyte-derived macrophages (HLA-DR+CD11b+CD14+CD16+) in inflamed liver and lung tissues associated with the expression of CD183 and CX3CR1 but also with markers of tissue-resident macrophages (CD206+ and LYVE+). Sorting of myeloid cell subsets demonstrated that CD14+CD206-, CD14+CD206+, and CD14-CD206+ cell populations were infected, in the liver and lungs, in SIVmac251-infected RMs. Of importance, early ART drastically reduced viral seeding consistent with the absence of ISG detection but also of genes related to inflammation and tissue damage. Viral DNA was only detected in CD206+HLA-DR+CD11b+ cells in ART-treated RMs. The observation of pulmonary and hepatic viral rebound after ART interruption reinforces the importance of early ART implementation to limit viral seeding and inflammatory reactions.

Chronic environmental exposure to polychlorinated biphenyls (PCBs) is associated with non-alcoholic fatty liver disease (NAFLD) and exacerbated by a high fat diet (HFD). Here, chronic (34 wks.) exposure of low fat diet (LFD)-fed male mice to Aroclor 1260 (Ar1260), a non-dioxin-like (NDL) mixture of PCBs, resulted in steatohepatitis and NAFLD. Twelve hepatic RNA modifications were altered with Ar1260 exposure including reduced abundance of 2'-O-methyladenosine (Am) and N(6)-methyladenosine (m6A), in contrast to increased Am in the livers of HFD-fed, Ar1260-exposed mice reported previously. Differences in 13 RNA modifications between LFD- and HFD- fed mice, suggest that diet regulates the liver epitranscriptome. Integrated network analysis of epitranscriptomic modifications identified a NRF2 (Nfe2l2) pathway in the chronic, LFD, Ar1260-exposed livers and an NFATC4 (Nfatc4) pathway for LFD- vs. HFD-fed mice. Changes in protein abundance were validated. The results demonstrate that diet and Ar1260 exposure alter the liver epitranscriptome in pathways associated with NAFLD.

Ginsenoside Rb1 (GRb1), a dammarane-type triterpene saponin compound mainly distributed in ginseng (Panax ginseng), has been demonstrated to ameliorate cardiovascular diseases. However, it remains unclear whether GRb1 alleviates heart failure (HF) by maintaining cardiac energy metabolism balance. Therefore, this work aimed to investigate the cardiac benefits of GRb1 against cardiac energy deficit and explore its mechanism of action.

Isoproterenol (ISO) induced HF Sprague-Dawley rats were administrated with GRb1 or fenofibrate for 6 weeks. ISO-induced primary neonatal rat cardiomyocytes (NRCMs) were used as the in vitro model. In vivo, GRb1 significantly improved the structural and metabolic disorder, as demonstrated by the restoration of cardiac function, inhibition of cardiac hypertrophy and fibrosis, and increased adenosine triphosphate (ATP) generation. In vitro, GRb1 effectively protected mitochondrial function and scavenged excessive reactive oxygen species. Moreover, in ISO-induced NRCMs, GRb1 significantly inhibited the abnormal upregulation of Fas-associated death domain (FADD), promoted transcriptional activation of peroxisome proliferator-activated receptor-alpha (PPARα), improved the aberrant expression of cardiac energy metabolism-related enzymes and cardiac fatty acid oxidation, and subsequently increased the synthesis of ATP. Noticeably, GRb1 could inhibit the increased binding between FADD and PPARα, which contributed to the activation of PPARα. Furthermore, GRb1 strengthened the thermal stabilization of FADD and might bind to FADD directly.

Collectively, it's part of the in-depth mechanism of GRb1's cardio-protection that GRb1 could directly bind to FADD and counteract its negative role in the transcription of PPARα thus ameliorating cardiac energy derangement and HF.

Osteoporosis is a common complication of many types of chronic liver diseases (CLDs), such as cholestatic liver disease, viral hepatitis, and alcoholic liver disease. Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent metabolic liver disease, affecting almost one third of adults around the world, and is emerging as the dominant cause of CLDs. Liver serves as a hub for nutrient and energy metabolism in the body, and its crosstalk with other tissues, such as adipose tissue, heart, and brain, has been well recognized. However, much less is known about the crosstalk that occurs between the liver and bone. Moreover, the mechanisms by which CLDs increase the risk for osteoporosis remain unclear. This review summarizes the latest research on the liver-bone axis and discusses the relationship between NAFLD and osteoporosis. We cover key signaling molecules secreted by liver, such as insulin-like growth factor-1 (IGF-1), fibroblast growth factor 21 (FGF21), insulin-like growth factor binding protein 1 (IGFBP1), fetuin-A, tumor necrosis factor-alpha (TNF-α), and osteopontin (OPN), and their relevance to the homeostasis of bone metabolism. Finally, we consider the disordered liver metabolism that occurs in patients with NAFLD and how this disrupts signaling to the bone, thereby perturbing the balance between osteoclasts and osteoblasts and leading to osteoporosis or hepatic osteodystrophy (HOD).

Nonalcoholic steatohepatitis (NASH) is closely related to liver fibrosis. The role of coiled-coil-helix-coiled-coil-helix domain-containing 2 (CHCHD2) in NASH remains unknown. CHCHD2's functions as a transcription factor have received much less attention than those in mitochondria. Herein, we systematically characterized the role of CHCHD2 as a transcription factor by chromatin immunoprecipitation sequencing and found its target genes were enriched in nonalcoholic fatty liver disease (NAFLD). Overall, CHCHD2 expression was found to be increased in the livers of patients with NAFLD and those of NASH mice. In line with these findings, CHCHD2 deficiency ameliorated NASH- and thioacetamide-induced liver fibrosis, whereas hepatocyte-specific CHCHD2 overexpression promoted liver fibrosis in NASH mice via Notch signaling. Specifically, CHCHD2-overexpressing hepatocytes activated hepatic stellate cells by upregulating osteopontin levels, a downstream mediator of Notch signals. Moreover, Notch inhibition attenuated CHCHD2 overexpression-induced liver fibrosis in vivo and in vitro. Then we found lipopolysaccharide-induced CHCHD2 expression in hepatocytes was reverted by verteporfin, an inhibitor that disrupts the interaction between Yes-associated protein (YAP) and transcriptional enhanced associate domains (TEADs). In addition, CHCHD2 levels were positively correlated with those of TEAD1 in human samples. In conclusion, CHCHD2 is upregulated via YAP/TAZ-TEAD in NASH livers and consequently promotes liver fibrosis by activating the Notch pathway and enhancing osteopontin production.

Non-alcoholic fatty liver disease (NAFLD) can persist in the stage of simple hepatic steatosis or progress to steatohepatitis (NASH) with an increased risk for cirrhosis and cancer. We examined the mechanisms controlling the progression to severe NASH in order to develop future treatment strategies for this disease.

NFATc1 activation and regulation was examined in livers from patients with NAFLD, cultured and primary hepatocytes and in transgenic mice with differential hepatocyte-specific expression of the transcription factor (Alb-cre, NFATc1^c.a . and NFATc1^Δ/Δ ). Animals were fed with high-fat western diet (WD) alone or in combination with tauroursodeoxycholic acid (TUDCA), a candidate drug for NAFLD treatment. NFATc1-dependent ER stress-responses, NLRP3 inflammasome activation and disease progression were assessed both in vitro and in vivo.

NFATc1 expression was weak in healthy livers but strongly induced in advanced NAFLD stages, where it correlates with liver enzyme values as well as hepatic inflammation and fibrosis. Moreover, high-fat WD increased NFATc1 expression, nuclear localisation and activation to promote NAFLD progression, whereas hepatocyte-specific depletion of the transcription factor can prevent mice from disease acceleration. Mechanistically, NFATc1 drives liver cell damage and inflammation through ER stress sensing and activation of the PERK-CHOP unfolded protein response (UPR). Finally, NFATc1-induced disease progression towards NASH can be blocked by TUDCA administration.

NFATc1 stimulates NAFLD progression through chronic ER stress sensing and subsequent activation of terminal UPR signalling in hepatocytes. Interfering with ER stress-responses, for example, by TUDCA, protects fatty livers from progression towards manifest NASH.

Nuclear factor of activated T-cells, cytoplasmic 4 (NFATc4), a transcription factor of NFAT family, which is activated by Ca²⁺/calcineurin signaling. Recently, it is reported that aberrantly activated NFATc4 participated and modulated in the initiation, proliferation, invasion, and metastasis of various cancers (including cancers of the lung, breast, ovary, cervix, skin, liver, pancreas, as well as glioma, primary myelofibrosis and acute myelocytic leukemia). In this review, we cover the latest knowledge on NFATc4 expression pattern, post-translational modification, epigenetic regulation, transcriptional activity regulation and its downstream targets. Furthermore, we perform database analysis to reveal the prognostic value of NFATc4 in various cancers and discuss the current unexplored areas of NFATc4 research. All in all, the result from these studies strongly suggest that NFATc4 has the potential as a molecular therapeutic target in multiple human cancer types.

Infection with influenza A virus (IAV) can trigger pulmonary inflammation and lung damage. Osteopontin (OPN) is an essential regulator of cell death and immunity. However, the role and underlying mechanism of OPN in cell death in IAV-induced pulmonary injury remain poorly understood. Here, we demonstrated that OPN-deficient (OPN^-/-) mice were insensitive to IAV, exhibiting decreased viral loads and attenuated lung injury after IAV infection compared to those in wild-type (WT) mice. Moreover, macrophage necroptosis was significantly reduced in OPN^-/- mice infected with IAV compared to that in infected WT mice. OPN increased the expression of necroptosis-related genes and exacerbated macrophage necroptosis in IAV-infected THP1 cells. Notably, adoptive transfer of WT bone marrow-derived macrophages (BMDMs) or OPN^-/- BMDMs into mice restored resistance to influenza infection, and the rescue effect of OPN^-/- BMDMs was better than that of WT BMDMs. Collectively, these results suggest that OPN deficiency in macrophages reduces necroptosis, which leads to a decrease in viral titers and protects against IAV infection. Therefore, OPN is a potential target for the treatment of IAV infection.

Non-alcoholic fatty liver disease develops from simple steatosis to non-alcoholic steatohepatitis (NASH), which then potentially develops into liver cirrhosis. It is a serious threat to human health. Therefore, investigating the formation and development mechanism of non-alcoholic fatty liver disease (NAFLD) is of great significance. Herein, an early model of NAFLD was successfully established by feeding rats with a high-fat and choline-deficient diet. Liver tissue samples were obtained from rats in the fatty liver model group (NAFL) and normal diet control group (CON). Afterward, transcriptome and lipidomic analysis was performed. Transcriptome results revealed that 178 differentially expressed genes were detected in NAFL and CON groups. Out of which, 105 genes were up-regulated, 73 genes were downregulated, and 8 pathways were significantly enriched. A total of 982 metabolites were detected in lipidomic analysis. Out of which 474 metabolites were significantly different, 273 were up-regulated, 201 were downregulated, and 7 pathways were significantly enriched. Based on the joint analysis, 3 common enrichment pathways were found, including cholesterol metabolism and fat digestion and absorption metabolic pathways. Overall, in the early stage of NAFLD, a small number of genetic changes caused a strong response to lipid components. The strongest reflection was glycerides and glycerophospholipids. A significant increase in fatty acid uptake accompanied by cholesterol metabolism is the most prominent metabolic feature of the liver in the early stage of NAFLD. In the early stage of fatty liver, the liver had shown the characteristics of NASH.

Receptor-interacting protein kinase (RIPK) 3-dependent necroptosis plays a critical role in alcoholic liver disease. RIPK3 also facilitates steatosis, oxidative stress, and inflammation. Pterostilbene (PTS) has favorable hepatoprotective activities. The present study was aimed to reveal the therapeutic effects of PTS on ethanol-induced hepatocyte necroptosis and further illustrate possible molecular mechanisms. Human hepatocytes LO2 were incubated with 100 mM ethanol for 24 h to mimic alcoholic hepatocyte injury. Results showed that PTS at 20 μM reduced damage-associated molecular patterns (DAMPs) release, including IL-1α and high-mobility group box 1 (HMGB1), and blocked necroptotic signaling, evidenced by decreased RIPK1 and RIPK3 expression. Trypan blue staining visually showed that PTS reduced nonviable hepatocytes after ethanol exposure, which was counteracted by adenovirus-mediated ectopic overexpression of RIPK3 but not RIPK1. Besides, PTS inhibited ethanol-induced hepatocyte steatosis via restricting lipogenesis and enhancing lipolysis, decreased oxidative stress via rescuing mitochondrial membrane potential, reducing oxidative system, and enhancing antioxidant system, and relieved inflammation evidenced by decreased expression of proinflammatory factors. Notably, RIPK3 overexpression diminished these protective effects of PTS. Subsequent work indicated that PTS suppressed the expression and nuclear translocation of nuclear factor of activated T-cells 4 (NFATc4), an acetylated protein, in ethanol-exposed hepatocytes, while NFATc4 overexpression impaired the negative regulation of PTS on RIPK3 and DAMPs release. Further, PTS rescued sirtuin 2 (SIRT2) expression, and SIRT2 knockdown abrogated the inhibitory effects of PTS on nuclear translocation and acetylation status of NFATc4 in ethanol-incubated hepatocytes. In conclusion, PTS attenuated RIPK3-dependent hepatocyte necroptosis after ethanol exposure via SIRT2-mediated NFATc4 deacetylation.

Hepatocyte senescence is a core event that mediates the occurrence and development of alcoholic liver disease. Nuclear factor of activated T-cells 4 (NFATc4) is a key driver of nonalcoholic steatohepatitis. However, little was known about the implication of NFATc4 for alcoholic liver disease. This study was aimed to investigate the role of NFATc4 in hepatocyte senescence and further elucidate the underlying mechanism.

Real-time PCR, Western blot, immunofluorescence staining, and enzyme-linked immunosorbent assay were performed to explore the role of NFATc4 in hepatocyte senescence.

NFATc4 was induced in ethanol-incubated hepatocytes. NFATc4 knockdown recovered cell viability and reduced the release of aspartate transaminase, alanine transaminase, and lactic dehydrogenase from ethanol-incubated hepatocytes. NFATc4 knockdown protected mice from alcoholic liver injury and inflammation. NFATc4 knockdown counteracted ethanol-induced hepatocyte senescence, evidenced by decreased senescence-associated β-galactosidase positivity and reduced p16, p21, HMGA1, and γH2AX, which was validated in in vivo studies. Peroxisome proliferator-activated receptor (PPAR)γ was inhibited by NFATc4 in ethanol-treated hepatocytes. PPARγ deficiency abrogated the inhibitory effects of NFATc4 knockdown on hepatocyte senescence, oxidative stress, and hepatic steatosis in mice with alcoholic liver disease.

This work discovered that ethanol enhanced NFATc4 expression, which further triggered hepatocyte senescence via repression of PPARγ.

Nuclear factor of activated T cells, cytoplasmic 4 (NFATc4), a nuclear transcription factor, has been implicated in cardiac hypertrophy through the enhancement of hypertrophic gene expression. However, the role of NFATc4 in mitochondrial modulation is mostly unknown. The current study aimed to investigate the role of NFATc4 in regulating mitochondrial function during phenylephrine (PE)-induced cardiac hypertrophy. Our results showed that overexpression of NFATc4 aggravated the PE-induced decrease in mitochondrial genesis, membrane potential, and mitochondrial gene expression as well as impaired mitochondrial respiration. However, knockdown of NFATc4 relieved PE-induced perturbations in mitochondria and cardiomyocyte hypertrophy. Mechanistically, by activating phosphoinositide-dependent kinase 1 and promoting a combination of AKT and phosphoinositide-dependent kinase 1, phosphorylation and sequential acetylation of PGC-1α were aggravated by NFATc4 and suppressed the activity of PGC-1α. In conclusion, NFATc4-regulated factors were shown to be associated with mitochondrial function and exacerbated PE-induced mitochondrial dysfunction. These findings revealed new roles of NFATc4 in cardiac hypertrophy.