Skeletal muscle miR-34a/SIRT1:AMPK axis is activated in experimental and human non-alcoholic steatohepatitis

Empagliflozin Plays Vasoprotective Role in Spontaneously Hypertensive Rats via Activation of the SIRT1/AMPK Pathway

Empagliflozin (EMPA), a sodium-glucose co-transporter 2 (SGLT2) inhibitor, prevents endothelial dysfunction, but its effects on vascular tone in hypertension remain unclear. This study investigated whether EMPA modulates vasomotor tone via sirtuin 1 (SIRT1) and AMP-activated protein kinase (AMPK) pathways in spontaneously hypertensive rats (SHR) and controls (Wistar Kyoto rats, WKY). Functional (wire myography, organ bath) and biochemical (Western blot) studies were conducted on the third-order of the superior mesenteric arteries (sMAs) and/or aortas. EMPA induced concentration-dependent relaxation of preconstricted sMAs in both groups. In SHR, EMPA enhanced acetylcholine (Ach)-induced relaxation in sMAs and aortas and reduced constriction induced by phenylephrine (Phe) and U46619 in sMAs. The SIRT1 inhibitor (EX527) abolished EMPA's effects on Ach-mediated relaxation and U46619-induced vasoconstriction, while AMPK inhibition reduced Ach-mediated relaxation and Phe-induced vasoconstriction. SHR showed increased SGLT2 and SIRT1 expression and decreased pAMPK/AMPK levels in sMAs. In conclusion, EMPA might exert vasoprotective effects in hypertension by enhancing endothelium-dependent relaxation and reducing constriction via AMPK/SIRT1 pathways. These properties could improve vascular health in patients with hypertension and related conditions. Further studies are needed to explore new indications for SGLT2 inhibitors.

Lipotoxicity-driven metabolic dysfunction-associated steatotic liver disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD) encompasses a spectrum of liver lesions, ranging from simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH), that may further progress to cirrhosis. MASLD is estimated to affect more than one third of the general population and it represents a risk factor for end-stage liver failure and liver cancer, substantially contributing to liver-related morbidity and mortality. Although the pathogenesis of MASLD is incompletely understood, it is known to consist of a multifactorial process influenced by extrinsic and intrinsic factors such as metabolic, environmental and demographic features, gut microbiota and genetics. Dysregulation of both extracellular and intracellular lipid composition is known to promote the generation of toxic lipid species, thereby triggering lipotoxicity and cellular stress. These events ultimately lead to the activation of distinct cell death pathways, resulting in inflammation, fibrogenesis and, eventually, carcinogenesis. In this manuscript, we provide a comprehensive review of the role of lipotoxicity during MASLD pathogenesis, discussing the most relevant lipid species and related molecular mechanisms, summarizing the cell type-specific effects and highlighting the most promising putative therapeutic strategies for modulating lipotoxicity and lipid metabolism in MASLD.

MicroRNAs in metabolic dysfunction-associated diseases: Pathogenesis and therapeutic opportunities

Metabolic dysfunction-associated diseases often refer to various diseases caused by metabolic problems such as glucose and lipid metabolism disorders. With the improvement of living standards, the increasing prevalence of metabolic diseases has become a severe public health problem, including metabolic dysfunction-associated steatotic liver disease (MASLD), alcohol-related liver disease (ALD), diabetes and obesity. These diseases are both independent and interdependent, with complex and diverse molecular mechanisms. Therefore, it is urgent to explore the molecular mechanisms and find effective therapeutic targets of these diseases. MicroRNAs (miRNAs) have emerged as key regulators of metabolic homoeostasis due to their multitargets and network regulatory properties within the past few decades. In this review, we discussed the latest progress in the roles of miRNA-mediated regulatory networks in the development and progression of MASLD, ALD, diabetes and obesity.

Extracellular Vesicles as Delivery Vehicles for Non-Coding RNAs: Potential Biomarkers for Chronic Liver Diseases

In recent years, EVs have emerged as promising vehicles for coding and non-coding RNAs (ncRNAs), which have demonstrated remarkable potential as biomarkers for various diseases, including chronic liver diseases (CLDs). EVs are small, membrane-bound particles released by cells, carrying an arsenal of ncRNAs, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and other ncRNA species, such as piRNAs, circRNAs, and tsRNAs. These ncRNAs act as key regulators of gene expression, splicing, and translation, providing a comprehensive molecular snapshot of the cells of origin. The non-invasive nature of EV sampling, typically via blood or serum collection, makes them highly attractive candidates for clinical biomarker applications. Moreover, EV-encapsulated ncRNAs offer unique advantages over traditional cell-free ncRNAs due to their enhanced stability within the EVs, hence allowing for their detection in circulation for extended periods and enabling more sensitive and reliable biomarker measurements. Numerous studies have investigated the potential of EV-enclosed ncRNAs as biomarkers for CLD. MiRNAs, in particular, have gained significant attention due to their ability to rapidly respond to changes in cellular stress and inflammation, hallmarks of CLD pathogenesis. Elevated levels of specific miRNAs have been consistently associated with various CLD subtypes, including metabolic dysfunction-associated steatotic liver disease (MASLD), metabolic dysfunction-associated steatohepatitis (MASH), and chronic hepatitis B and C. LncRNAs have also emerged as promising biomarkers for CLD. These transcripts are involved in a wide range of cellular processes, including liver regeneration, fibrosis, and cancer progression. Studies have shown that lncRNA expression profiles can distinguish between different CLD subtypes, providing valuable insights into disease progression and therapeutic response. Promising EV-enclosed ncRNA biomarkers for CLD included miR-122 (elevated levels of miR-122 are associated with MASLD progression and liver fibrosis), miR-21 (increased expression of miR-21 is linked to liver inflammation and fibrosis in CLD patients), miR-192 (elevated levels of miR-192 are associated with more advanced stages of CLD, including cirrhosis and HCC), LncRNA HOTAIR (increased HOTAIR expression is associated with MASLD progression and MASH development), and LncRNA H19 (dysregulation of H19 expression is linked to liver fibrosis and HCC progression). In the present review, we focus on the EV-enclosed ncRNAs as promising tools for the diagnosis and monitoring of CLD of various etiologies.

Short-term fructose feeding alters tissue metabolic pathways by modulating microRNAs expression both in young and adult rats

Dietary high fructose (HFrD) is known as a metabolic disruptor contributing to the development of obesity, diabetes, and dyslipidemia. Children are more sensitive to sugar than adults due to the distinct metabolic profile, therefore it is especially relevant to study the metabolic alterations induced by HFrD and the mechanisms underlying such changes in animal models of different ages. Emerging research suggests the fundamental role of epigenetic factors such as microRNAs (miRNAs) in metabolic tissue injury. In this perspective, the aim of the present study was to investigate the involvement of miR-122-5p, miR-34a-5p, and miR-125b-5p examining the effects induced by fructose overconsumption and to evaluate whether a differential miRNA regulation exists between young and adult animals. We used young rats (30 days) and adult rats (90 days) fed on HFrD for a short period (2 weeks) as animal models. The results indicate that both young and adult rats fed on HFrD exhibit an increase in systemic oxidative stress, the establishment of an inflammatory state, and metabolic perturbations involving the relevant miRNAs and their axes. In the skeletal muscle of adult rats, HFrD impair insulin sensitivity and triglyceride accumulation affecting the miR-122-5p/PTP1B/P-IRS-1(Tyr612) axis. In liver and skeletal muscle, HFrD acts on miR-34a-5p/SIRT-1: AMPK pathway resulting in a decrease of fat oxidation and an increase in fat synthesis. In addition, liver and skeletal muscle of young and adult rats exhibit an imbalance in antioxidant enzyme. Finally, HFrD modulates miR-125b-5p expression levels in liver and white adipose tissue determining modifications in de novo lipogenesis. Therefore, miRNA modulation displays a specific tissue trend indicative of a regulatory network that contributes in targeting genes of various pathways, subsequently yielding extensive effects on cell metabolism.

Noncoding RNAs as additional mediators of epigenetic regulation in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most common cause of chronic liver disorder worldwide. It represents a spectrum that includes a continuum of different clinical entities ranging from simple steatosis to nonalcoholic steatohepatitis, which can evolve to cirrhosis and in some cases to hepatocellular carcinoma, ultimately leading to liver failure. The pathogenesis of NAFLD and the mechanisms underlying its progression to more pathological stages are not completely understood. Besides genetic factors, evidence indicates that epigenetic mechanisms occurring in response to environmental stimuli also contribute to the disease risk. Noncoding RNAs (ncRNAs), including microRNAs, long noncoding RNAs, and circular RNAs, are one of the epigenetic factors that play key regulatory roles in the development of NAFLD. As the field of ncRNAs is rapidly evolving, the present review aims to explore the current state of knowledge on the roles of these RNA species in the pathogenesis of NAFLD, highlight relevant mechanisms by which some ncRNAs can modulate regulatory networks implicated in NAFLD, and discuss key challenges and future directions facing current research in the hopes of developing ncRNAs as next-generation non-invasive diagnostics and therapies in NAFLD and subsequent progression to hepatocellular carcinoma.

Advances of microRNAs in regulating mitochondrial function: new potential application in NAFLD treatment

Nonalcoholic fatty liver disease (NAFLD) is one of the most common metabolic diseases and closely associated with lipid disorder. Mitochondrion has been recognized to play a key role in lipid metabolism as the main site of energy metabolism in cells, and its dysfunction is involved in the progression of NAFLD. MicroRNAs (miRNAs), one of regulators in the pathogenesis of NAFLD, are discovered to modulate mitochondrial function by targeting mitochondrial proteins or mitochondrial-related factors, thereby improving or deteriorating NAFLD-associated pathologies. This review summarizes the differentially expressed miRNAs from clinical and experimental models of NAFLD with abilities in regulating mitochondrial function, expounds their underlying molecular mechanism and discusses their prospect and future research direction.

Mitochondria homeostasis: Biology and involvement in hepatic steatosis to NASH

Mitochondrial biology and behavior are central to the physiology of liver. Multiple mitochondrial quality control mechanisms remodel mitochondrial homeostasis under physiological and pathological conditions. Mitochondrial dysfunction and damage induced by overnutrition lead to oxidative stress, inflammation, liver cell death, and collagen production, which advance hepatic steatosis to nonalcoholic steatohepatitis (NASH). Accumulating evidence suggests that specific interventions that target mitochondrial homeostasis, including energy metabolism, antioxidant effects, and mitochondrial quality control, have emerged as promising strategies for NASH treatment. However, clinical translation of these findings is challenging due to the complex and unclear mechanisms of mitochondrial homeostasis in the pathophysiology of NASH.

Comparative Analysis of miRNA Expression Profiles in Skeletal Muscle of Bian Chickens at Different Embryonic Ages

MicroRNAs (miRNAs) are widely involved in the growth and development of skeletal muscle through the negative regulation of target genes. In order to screen out the differentially expressed miRNAs (DEMs) associated with skeletal muscle development of Bian chickens at different embryonic ages, we used the leg muscles of fast-growing and slow-growing Bian chickens at the 14th and 20th embryonic ages (F14, F20, S14 and S20) for RNA-seq. A total of 836 known miRNAs were identified, and 121 novel miRNAs were predicted. In the F14 vs. F20 comparison group, 127 DEMs were screened, targeting a total of 2871 genes, with 61 miRNAs significantly upregulated and 66 miRNAs significantly downregulated. In the S14 vs. S20 comparison group, 131 DEMs were screened, targeting a total of 3236 genes, with 60 miRNAs significantly upregulated and 71 miRNAs significantly downregulated. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the predicted target genes were significantly enriched in 706 GO terms and 6 KEGG pathways in the F14 vs. F20 group and 677 GO terms and 5 KEGG pathways in the S14 vs. S20 group. According to the interaction network analysis, we screened five coexpressed DEMs (gga-miR-146a-3p, gga-miR-2954, gga-miR-34a-5p, gga-miR-1625-5p and gga-miR-18b-3p) with the highest connectivity degree with predicted target genes between the two comparison groups, and five hub genes (HSPA5, PKM2, Notch1, Notch2 and RBPJ) related to muscle development were obtained as well. Subsequently, we further identified nine DEMs (gga-let-7g-3p, gga-miR-490-3p, gga-miR-6660-3p, gga-miR-12223-5p, novel-miR-327, gga-miR-18a-5p, gga-miR-18b-5p, gga-miR-34a-5p and gga-miR-1677-3p) with a targeting relationship to the hub genes, suggesting that they may play important roles in the muscle development of Bian chickens. This study reveals the miRNA differences in skeletal muscle development between 14- and 20-day embryos of Bian chickens from fast- and slow-growing groups and provides a miRNA database for further studies on the molecular mechanisms of the skeletal muscle development in Bian chickens.

Gestational Exercise Increases Male Offspring's Maximal Workload Capacity Early in Life

Mothers’ antenatal strategies to improve the intrauterine environment can positively decrease pregnancy-derived intercurrences. By challenging the mother–fetus unit, gestational exercise (GE) favorably modulates deleterious stimuli, such as high-fat, high-sucrose (HFHS) diet-induced adverse consequences for offspring. We aimed to analyze whether GE alters maternal HFHS-consumption effects on male offspring’s maximal workload performance (MWP) and in some skeletal muscle (the soleus—SOL and the tibialis anterior—TA) biomarkers associated with mitochondrial biogenesis and oxidative fitness. Infant male Sprague-Dawley rats were divided into experimental groups according to mothers’ dietary and/or exercise conditions: offspring of sedentary control diet-fed or HFHS-fed mothers (C–S or HFHS–S, respectively) and of exercised HFHS-fed mothers (HFHS–E). Although maternal HFHS did not significantly alter MWP, offspring from GE dams exhibited increased MWP. Lower SOL AMPk levels in HFHS–S were reverted by GE. SOL PGC-1α, OXPHOS C-I and C-IV subunits remained unaltered by maternal diet, although increased in HFHS–E offspring. Additionally, GE prevented maternal diet-related SOL miR-378a overexpression, while upregulated miR-34a expression. Decreased TA C-IV subunit expression in HFHS–S was reverted in HFHS–E, concomitantly with the downregulation of miR-338. In conclusion, GE in HFHS-fed dams increases the offspring’s MWP, which seems to be associated with the intrauterine modulation of SM mitochondrial density and functional markers.

The CD38 glycohydrolase and the NAD sink: implications for pathological conditions

Nicotinamide adenine dinucleotide (NAD) acts as a cofactor in several oxidation-reduction (redox) reactions and is a substrate for a number of nonredox enzymes. NAD is fundamental to a variety of cellular processes including energy metabolism, cell signaling, and epigenetics. NAD homeostasis appears to be of paramount importance to health span and longevity, and its dysregulation is associated with multiple diseases. NAD metabolism is dynamic and maintained by synthesis and degradation. The enzyme CD38, one of the main NAD-consuming enzymes, is a key component of NAD homeostasis. The majority of CD38 is localized in the plasma membrane with its catalytic domain facing the extracellular environment, likely for the purpose of controlling systemic levels of NAD. Several cell types express CD38, but its expression predominates on endothelial cells and immune cells capable of infiltrating organs and tissues. Here we review potential roles of CD38 in health and disease and postulate ways in which CD38 dysregulation causes changes in NAD homeostasis and contributes to the pathophysiology of multiple conditions. Indeed, in animal models the development of infectious diseases, autoimmune disorders, fibrosis, metabolic diseases, and age-associated diseases including cancer, heart disease, and neurodegeneration are associated with altered CD38 enzymatic activity. Many of these conditions are modified in CD38-deficient mice or by blocking CD38 NADase activity. In diseases in which CD38 appears to play a role, CD38-dependent NAD decline is often a common denominator of pathophysiology. Thus, understanding dysregulation of NAD homeostasis by CD38 may open new avenues for the treatment of human diseases.

MiR-195 promotes pancreatic β-cell dedifferentiation by targeting Mfn2 and impairing Pi3k/Akt signaling in type 2 diabetes

OBJECTIVE

The aim of this study was to research the role and underlying mechanism of miR-195 involved in pancreatic β-cell dedifferentiation induced by hyperlipemia in type 2 diabetes mellitus.

METHODS

High-fat-diet-induced obese C57BL/6J mice and palmitate-stimulated Min6 cells were used as the models of β-cell dedifferentiation in vivo and in vitro, respectively. The expression of miR-195 and insulin secretion during β-cell dedifferentiation were measured. Also, the influence of regulated miR-195 expression on β-cell dedifferentiation was examined. Meanwhile, the IRS-1/2/Pi3k/Akt pathway and mitofusin-2 (Mfn2) expression were investigated during β-cell dedifferentiation.

RESULTS

MiR-195 was upregulated during lipotoxicity-induced β-cell dedifferentiation in both in vivo and in vitro experiments, and miR-195 functionally contributed to lipotoxicity-induced β-cell dedifferentiation. Furthermore, miR-195 inhibited IRS-1/2/Pi3k/Akt pathway activation, which accompanied β-cell dedifferentiation. Mfn2, a target of miR-195, was found to be downregulated and was associated with increased mitochondrial production of reactive oxygen species during β-cell dedifferentiation. Instructively, inhibition of miR-195, at least partially, reversed the downregulation of Mfn2, restored IRS-1/2/Pi3k/Akt pathway activation, and prevented β-cell dedifferentiation.

CONCLUSIONS

MiR-195 promoted β-cell dedifferentiation through negatively regulating Mfn2 expression and inhibiting the IRS-1/2/Pi3k/Akt pathway, providing a promising treatment for type 2 diabetes mellitus.

Therapeutic Metabolic Reprograming Using microRNAs: From Cancer to HIV Infection

MicroRNAs (miRNAs) are crucial regulators of cellular processes, including metabolism. Attempts to use miRNAs as therapeutic agents are being explored in several areas, including the control of cancer progression. Recent evidence suggests fine tuning miRNA activity to reprogram tumor cell metabolism has enormous potential as an alternative treatment option. Indeed, cancer growth is known to be linked to profound metabolic changes. Likewise, the emerging field of immunometabolism is leading to a refined understanding of how immune cell proliferation and function is governed by glucose homeostasis. Different immune cell types are now known to have unique metabolic signatures that switch in response to a changing environment. T-cell subsets exhibit distinct metabolic profiles which underlie their alternative differentiation and phenotypic functions. Recent evidence shows that the susceptibility of CD4+ T-cells to HIV infection is intimately linked to their metabolic activity, with many of the metabolic features of HIV-1-infected cells resembling those found in tumor cells. In this review, we discuss the use of miRNA modulation to achieve metabolic reprogramming for cancer therapy and explore the idea that the same approach may serve as an effective mechanism to restrict HIV replication and eliminate infected cells.

Concerted regulation of non-alcoholic fatty liver disease progression by microRNAs in apolipoprotein E-deficient mice

The prevalence of non-alcoholic fatty liver disease (NAFLD) is constantly increasing, and altered expression of microRNAs (miRNAs) fosters the development and progression of many pathologies, including NAFLD. Therefore, we explored the role of new miRNAs involved in the molecular mechanisms that trigger NAFLD progression and evaluated them as biomarkers for diagnosis. As a NAFLD model, we used apolipoprotein E-deficient mice administered a high-fat diet for 8 or 18 weeks. We demonstrated that insulin resistance and decreased lipogenesis and autophagy observed after 18 weeks on the diet are related to a concerted regulation carried out by miR-26b-5p, miR-34a-5p, miR-149-5p and miR-375-3p. We also propose circulating let-7d-5p and miR-146b-5p as potential biomarkers of early stages of NAFLD. Finally, we confirmed that circulating miR-34a-5p and miR-375-3p are elevated in the late stages of NAFLD and that miR-27b-3p and miR-122-5p are increased with disease progression. Our results reveal a synergistic regulation of key processes in NAFLD development and progression by miRNAs. Further investigation is needed to unravel the roles of these miRNAs for developing new strategies for NAFLD treatment.

This article has an associated First Person interview with the joint first authors of the paper.

Summary:Apoe^−/− mice administered a high-fat diet represent a model of non-alcoholic fatty liver disease, revealing the synergistic regulation of key processes in disease progression by miRNAs and indicating some miRNAs as biomarkers for diagnosis.

Exercise Intervention Mitigates Pathological Liver Changes in NAFLD Zebrafish by Activating SIRT1/AMPK/NRF2 Signaling

Non-alcoholic fatty liver disease (NAFLD) is a common disease that causes serious liver damage. Exercise is recognized as a non-pharmacological tool to improve the pathology of NAFLD. However, the antioxidative effects and mechanisms by which exercise ameliorates NAFLD remain unclear. The present study conducted exercise training on zebrafish during a 12-week high-fat feeding period to study the antioxidant effect of exercise on the liver. We found that swimming exercise decreased lipid accumulation and improved pathological changes in the liver of high-fat diet-fed zebrafish. Moreover, swimming alleviated NOX4-derived reactive oxygen species (ROS) overproduction and reduced methanedicarboxylic aldehyde (MDA) levels. We also examined the anti-apoptotic effects of swimming and found that it increased the expression of antiapoptotic factor bcl2 and decreased the expression of genes associated with apoptosis (caspase3, bax). Mechanistically, swimming intervention activated SIRT1/AMPK signaling-mediated lipid metabolism and inflammation as well as enhanced AKT and NRF2 activation and upregulated downstream antioxidant genes. In summary, exercise attenuates pathological changes in the liver induced by high-fat diets. The underlying mechanisms might be related to NRF2 and mediated by SIRT1/AMPK signaling.

C1q/tumor necrosis factor-related protein-6 attenuates TNF-α-induced apoptosis in salivary acinar cells via AMPK/SIRT1-modulated miR-34a-5p expression

C1q/tumor necrosis factor-related protein-6 (CTRP6) is a newly identified adipokine involved in diverse biological processes. However, its role in salivary glands remains unknown. Here, we demonstrated that CTRP6 was mainly distributed in the nuclei, apicolateral membranes, and cytoplasm of human submandibular glands (SMGs), serous cells of parotid glands, and ducts and apicolateral membranes of serous cells in rats and mice. CTRP6 inhibited the apoptosis rate and reversed the increased levels of cleaved caspase 3, caspase 8, caspase 9, and cytochrome C and the decreased Bcl-2 expression induced by tumor necrosis factor (TNF)-α in both SMG-C6 cells and cultured human SMG tissues. Microarray analysis identified 43 differentially expressed microRNAs (miRNAs) in the SMGs of nonobese diabetic mice. miR-34a-5p was selected due to its upregulation by TNF-α, which was abolished by CTRP6. The miR-34a-5p inhibitor promoted whereas the miR-34a-5p mimic suppressed the effects of CTRP6 on TNF-α-induced apoptosis. CTRP6 increased AMP-activated protein kinase (AMPK) phosphorylation and reversed TNF-α-induced SIRT1 downregulation in salivary cells. AraA, an AMPK inhibitor, reversed the effects of CTRP6 on TNF-α-induced alterations in the levels of SIRT1, miR-34a-5p, Bcl-2, and cleaved caspase 3 in vitro and ex vivo, whereas activating AMPK by AICAR reversed the decrease in SIRT1 expression and increase in miR-34a-5p expression induced by TNF-α. Inhibition of SIRT1 by EX527 suppressed the effects of CTRP6 on TNF-α-induced changes in miR-34a-5p and apoptosis-related proteins. Our findings indicate that salivary glands are novel sites for CTRP6 synthesis and secretion. CTRP6 protects acinar cells against TNF-α-induced apoptosis via AMPK/SIRT1-modulated miR-34a-5p expression.

Plant sterol ester of α-linolenic acid ameliorates high-fat diet-induced nonalcoholic fatty liver disease in mice: association with regulating mitochondrial dysfunction and oxidative stress via activating AMPK signaling

Plant sterol ester of α-linolenic acid prevents nonalcoholic fatty liver disease by improving mitochondrial function, modifying lipid metabolism, and inhibiting oxidative stress via AMPK signaling.

The Inhibitory Effects of Juglanin on Adipogenesis in 3T3-L1 Adipocytes

INTRODUCTION

Deregulation of adipogenesis plays an important role in obesity and other metabolism disorders. PPAR, C/EBP and SREBP1c are key transcriptional factors involved in adipogenesis and lipogenesis. Juglanin is a natural compound belonging to flavonoids, and it has been reported that juglanin has a potent inhibitory effect on inflammation and certain type of cancers. However, the effects of juglanin in adipogenesis have not been reported before.

MATERIALS AND METHODS

3T3-L1 preadipocytes were incubated with differentiation induction medium in the presence or absence of 0.5, 2.5, or 5 µM juglanin for an 8-day differentiation period. The lipid droplets accumulated in the cytoplasm were monitored by Oil Red O staining on days 0, 2, 5, and 8. The regulatory effects of juglanin on adipogenesis-related genes and proteins were investigated by real-time polymerase chain reaction and Western blot analysis.

RESULTS

Juglanin significantly decreased lipid accumulation in differentiated adipocytes. Our findings show that juglanin reduced the expression of C/EBPα, C/EBPβ, and SREBP-1c without affecting PPARα or PPARγ expression. Additionally, juglanin increased the activation of the SIRT1/AMPK signaling pathway through the phosphorylation of AMPKα. Finally, we performed an AMPK inhibitor experiment, which revealed that the inhibitory effects of juglanin on adipogenesis are mediated through AMPK.

DISCUSSION

Juglanin can prevent adipogenesis by suppressing lipid accumulation and the differentiation of preadipocytes. The mechanism of juglanin regulating adipogenesis requires further investigation. Future clinical study in vivo could shed more light on its implication in modulating obesity and metabolic disorders.

Saturated Fatty Acids Promote Hepatocytic Senecence through Regulation of miR-34a/Cyclin-Dependent Kinase 6

SCOPE

Obesity increases intracellular lipid accumulation in hepatocytes, which can induce non-alcoholic fatty liver disease (NAFLD). With progression of NAFLD, a sizable fraction of patients develop non-alcoholic steatohepatitis (NASH), eventually leading to cirrhosis and hepatocellular carcinoma (HCC). The mechanism involved in obesity-induced NAFLD remains unclear. Free fatty acids and high-fat diets, which induce hepatocyte senescence, are major risk factors for NAFLD. Therefore in this study, the mechanism of lipotoxicity-induced hepatocyte senescence is investigated.

METHODS AND RESULTS

The mice are fed a high-fat diet (HFD) and BNL CL.2 cells are treated with palmitate acid (PA) to establish in vivo and in vitro models of lipotoxicity, respectively. SA-β-gal staining is used to analyze the positively stained senescent hepatocytes. The results show that both PA and HFD induce cellular senescence. Real-time-PCR quantitative analysis reveals that miR-34a is significantly upregulated in the liver tissues of the HFD mice and in the PA-treated BNL CL.2 cells. Western blotting analysis shows that cyclin-dependent kinase inhibitor 1 (CDKN1, also known as p21) is upregulated, while cyclin-dependent kinase 6 (CDK6) is downregulated. Further investigation of the mechanism reveals that CDK6 is a target of miR-34a, which binds to the 3' UTR of CDK6 and inhibits its expression.

CONCLUSION

The findings reveal that miR-34a is upregulated in a high-fat environment in the liver, and induces hepatocyte senescence by targeting CDK6. The miR-34a-CDK6 signaling axis may promote NAFLD development in a high-fat environment and therefore represents a potential target for NAFLD therapy.

Ferroptosis mediated by the interaction between Mfn2 and IREα promotes arsenic-induced nonalcoholic steatohepatitis

Exposure to arsenic is a risk factor for nonalcoholic steatohepatitis (NASH). Ferroptosis is a form of regulated cell death defined by the accumulation of lipid peroxidation. In the current study, we observed the occurrence of ferroptosis in arsenic-induced NASH by assessing ferroptosis related hallmarks. In vitro, we found that ferrostatin-1 effectively attenuated the executing of ferroptosis and NASH. Simultaneously, the expression of ACSL4 (acyl-CoA synthetase long-chain family member 4) was upregulated in rat's liver and L-02 cells exposed to arsenic. While, suppression of ACSL4 with rosiglitazone or ACSL4 siRNA remarkably alleviated arsenic-induced NASH and ferroptosis through diminishing 5-hydroxyeicosatetraenoic acid (5-HETE) content. Additionally, Mitofusin 2 (Mfn2), a physical tether between endoplasmic reticulum and mitochondria, has rarely been explored in the ferroptosis. Using Mfn2 siRNA or inositol-requiring enzyme 1 alpha (IRE1α) inhibitor, we found NASH and ferroptosis were obviously mitigated through reducing 5-HETE content. Importantly, Co-IP assay indicated that Mfn2 could interact with IRE1α and promoted the production of 5-HETE, ultimately led to ferroptosis and NASH. Collectively, our data showed that ferroptosis is involved in arsenic-induced NASH. These data provide insightful viewpoints into the mechanism of arsenic-induced NASH.

Processes exacerbating apoptosis in non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is a significant public health concern, owing to its high prevalence, progressive nature and lack of effective medical therapies. NAFLD is a complex and multifactorial disease involving the progressive and concerted action of factors that contribute to the development of liver inflammation and eventually fibrosis. Here, we summarize fundamental molecular mechanisms underlying the pathogenesis of non-alcoholic steatohepatitis (NASH), how they are interrelated and possible translation to clinical applications. We focus on processes triggering and exacerbating apoptotic signalling in the liver of NAFLD patients and their metabolic and pathological implications. Indeed, liver injury and inflammation are cardinal histopathological features of NASH, a duo in which derailment of apoptosis is of paramount importance. In turn, the liver houses a very high number of mitochondria, crucial metabolic unifiers of both extrinsic and intrinsic signals that converge in apoptosis activation. The role of lifestyle options is also dissected, highlighting the management of modifiable risk factors, such as obesity and harmful alcohol consumption, influencing apoptosis signalling in the liver and ultimately NAFLD progression. Integrating NAFLD-associated pathologic mechanisms in the cell death context could provide clues for a more profound understating of the disease and pave the way for novel rational therapies.

The Emerging Role of MicroRNAs in NAFLD: Highlight of MicroRNA-29a in Modulating Oxidative Stress, Inflammation, and Beyond

Non-alcoholic fatty liver disease (NAFLD) is a common cause of chronic liver disease and ranges from steatosis to steatohepatitis and to liver fibrosis. Lipotoxicity in hepatocytes, elevated oxidative stress and the activation of proinflammatory mediators of Kupffer cells, and fibrogenic pathways of activated hepatic stellate cells can contribute to the development of NAFLD. MicroRNAs (miRs) play a crucial role in the dysregulated metabolism and inflammatory signaling connected with NAFLD and its progression towards more severe stages. Of note, the protective effect of non-coding miR-29a on liver damage and its versatile action on epigenetic activity, mitochondrial homeostasis and immunomodulation may improve our perception of the pathogenesis of NAFLD. Herein, we review the biological functions of critical miRs in NAFLD, as well as highlight the emerging role of miR-29a in therapeutic application and the recent advances in molecular mechanisms underlying its liver protective effect.