Long-term exercise prevents hepatic steatosis: a novel role of FABP1 in regulation of autophagy-lysosomal machinery

Gut microbiota-bile acid crosstalk and metabolic fatty liver in spotted seabass (Lateolabrax maculatus): The role of a cholesterol, taurine and glycine supplement

The prevalent practice of substituting fishmeal with plant protein frequently leads to disturbances in bile acid metabolism, subsequently increasing the incidence of metabolic liver diseases. Bile acid nutrients such as cholesterol, taurine and glycine have been shown to enhance bile acid synthesis and confer beneficial effects on growth. Therefore, this study aimed to investigate the effects of cholesterol-taurine-glycine (Ch-Tau-Gly) supplement on bile acid metabolism and liver health in spotted seabass (Lateolabrax maculatus) fed a plant-based diet. Two isonitrogenous and isolipidic diets were formulated: (1) plant protein-based diet (PP); (2) PP supplemented 0.5% cholesterol, 0.5% taurine and 1.3% glycine (CTG). Each experimental diet was randomly fed to quadruplicate groups of 30 feed-trained spotted seabass in each tank. The results revealed that supplementing plant-based diet with Ch-Tau-Gly supplement led to an increase in carcass ratio (meat yield) in spotted seabass (P < 0.05), indirectly contributing positively to their growth. The dietary supplement effectively suppressed endogenous cholesterol synthesis in the liver, promoted the expression of bile acid synthesis enzyme synthesis, and simultaneously the expression of intestinal fxr and its downstream genes, including hnf4α and shp (P < 0.05). The reduction in Lactobacillus_salivarius and bile salt hydrolase (BSH) were observed in CTG group with concurrently increased conjugated chenodeoxycholic acid (CDCA) bile acids (P < 0.05), suggesting the enhancement of the hydrophilicity of the bile acid pool. In CTG group, fatty liver was alleviated with a corresponding increase in lipid metabolism, characterized by a downregulation of genes associated with lipogenesis and lipid droplet deposition, along with an upregulation of genes related to lipolysis. Our study underscored the ability of Ch-Tau-Gly supplement to influence the gut microbiota, leading to an increase in the levels of conjugated CDCA (P < 0.05) in the bile acid pool of spotted seabass. The interplay between the gut microbiota and bile acids might constitute a crucial pathway in the promotion of liver health. These findings offer a promising solution, suggesting that Ch-Tau-Gly supplement have the potential to promote the growth of aquatic species and livestock fed on plant-based diets while addressing issues related to metabolic fatty liver.

Would Combination Be Better: Swimming Exercise and Intermittent Fasting Improve High-Fat Diet-Induced Nonalcoholic Fatty Liver Disease in Obese Rats via the miR-122-5p/SREBP-1c/CPT1A Pathway

Background

Swimming and intermittent fasting can both improve obesity-induced NAFLD, but which of the two is more effective and whether the combination of the two has a superimposed effect is inconclusive.

Methods

The model of NAFLD in obese rats was established by a high-fat diet and performed swimming, intermittent fasting, and a combination of both interventions for 8 weeks. Serum lipids and enzyme activity were measured by an automatic biochemical analyzer. Liver morphostructural analysis was observed by transmission electron microscopy, and morphology was observed by HE staining. RT‒PCR was used to detect the mRNA level.

Results

Morphology and microstructure of the liver of model rats were impaired, with the upregulation of miR-122-5p, SREBP-1c, FASN and ACC1. Eight weeks of swimming exercise, intermittent fasting and the combination of both attenuate these effects, manifested by the downregulation of miR-122-5p and upregulation of CPT1A mRNA levels. There was no significant stacking effect of the combination of the swimming and intermittent fasting interventions.

Conclusion

NAFLD leads to pathology in model rats. Eight weeks of swimming exercise, intermittent fasting and the combination of both can inhibit miR-122-5p and improve hepatic lipid metabolism, while no significant additive effects of combining the interventions were found.

Early-life exercise induces immunometabolic epigenetic modification enhancing anti-inflammatory immunity in middle-aged male mice

Exercise is usually regarded to have short-term beneficial effects on immune health. Here we show that early-life regular exercise exerts long-term beneficial effects on inflammatory immunity. Swimming training for 3 months in male mice starting from 1-month-old curbs cytokine response and mitigates sepsis when exposed to lipopolysaccharide challenge, even after an 11-month interval of detraining. Metabolomics analysis of serum and liver identifies pipecolic acid, a non-encoded amino acid, as a pivotal metabolite responding to early-life regular exercise. Importantly, pipecolic acid reduces inflammatory cytokines in bone marrow-derived macrophages and alleviates sepsis via inhibiting mTOR complex 1 signaling. Moreover, early-life exercise increases histone 3 lysine 4 trimethylation at the promoter of Crym in the liver, an enzyme responsible for catalyzing pipecolic acid production. Liver-specific knockdown of Crym in adult mice abolishes this early exercise-induced protective effects. Our findings demonstrate that early-life regular exercise enhances anti-inflammatory immunity during middle-aged phase in male mice via epigenetic immunometabolic modulation, in which hepatic pipecolic acid production has a pivotal function.

Complementary yet divergent effects of exercise and an exercise mimetic on microbiome in high-fat diet-induced obesity

Exercise is beneficial for obesity, partially through increased mitochondrial activity and raised nicotinamide adenine dinucleotide (NAD), a coenzyme critical for mitochondrial function and metabolism. Recent work has shown that increasing the availability of NAD through pharmacological means improves metabolic health in rodent models of diet-induced obesity and that the effect of these supplements when administered orally may be modulated by the gut microbiome. The gut microbiome is altered by both diet and exercise and is thought to contribute to some aspects of high-fat diet-induced metabolic dysfunction. We examined the independent and combined effects of treadmill exercise and nicotinamide mononucleotide (NMN) supplementation on the gut microbiome of female C57Bl6/J mice chronically fed a high-fat diet. We showed that 8 wk of treadmill exercise, oral-administered NMN, or combined therapy exert unique effects on gut microbiome composition without changing bacterial species richness. Exercise and NMN exerted additive effects on microbiota composition, and NMN partially or fully restored predicted microbial functions, specifically carbohydrate and lipid metabolism, to control levels. Further research is warranted to better understand the mechanisms underpinning the interactions between exercise and oral NAD+ precursor supplementation on gut microbiome.NEW & NOTEWORTHY Exercise and NAD+ precursor supplementation exerted additive and independent effects on gut microbiota composition and inferred function in female mice with diet-induced obesity. Notably, combining exercise and oral nicotinamide mononucleotide supplementation restored inferred microbial functions to control levels, indicating that this combination may improve high-fat diet-induced alterations to microbial metabolism.

Dysfunction of autophagy in high-fat diet-induced non-alcoholic fatty liver disease

ABBREVIATIONS

ACOX1: acyl-CoA oxidase 1; ADH5: alcohol dehydrogenase 5 (class III), chi polypeptide; ADIPOQ: adiponectin, C1Q and collagen domain containing; ATG: autophagy related; BECN1: beclin 1; CRTC2: CREB regulated transcription coactivator 2; ER: endoplasmic reticulum; F2RL1: F2R like trypsin receptor 1; FA: fatty acid; FOXO1: forkhead box O1; GLP1R: glucagon like peptide 1 receptor; GRK2: G protein-coupled receptor kinase 2; GTPase: guanosine triphosphatase; HFD: high-fat diet; HSCs: hepatic stellate cells; HTRA2: HtrA serine peptidase 2; IRGM: immunity related GTPase M; KD: knockdown; KDM6B: lysine demethylase 6B; KO: knockout; LAMP2: lysosomal associated membrane protein 2; LAP: LC3-associated phagocytosis; LDs: lipid droplets; Li KO: liver-specific knockout; LSECs: liver sinusoidal endothelial cells; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAP3K5: mitogen-activated protein kinase kinase kinase 5; MED1: mediator complex subunit 1; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin complex 1; NAFLD: non-alcoholic fatty liver disease; NASH: non-alcoholic steatohepatitis; NFE2L2: NFE2 like bZIP transcription factor 2; NOS3: nitric oxide synthase 3; NR1H3: nuclear receptor subfamily 1 group H member 3; OA: oleic acid; OE: overexpression; OSBPL8: oxysterol binding protein like 8; PA: palmitic acid; RUBCNL: rubicon like autophagy enhancer; PLIN2: perilipin 2; PLIN3: perilipin 3; PPARA: peroxisome proliferator activated receptor alpha; PRKAA2/AMPK: protein kinase AMP-activated catalytic subunit alpha 2; RAB: member RAS oncogene family; RPTOR: regulatory associated protein of MTOR complex 1; SCD: stearoyl-CoA desaturase; SIRT1: sirtuin 1; SIRT3: sirtuin 3; SNARE: soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SQSTM1/p62: sequestosome 1; SREBF1: sterol regulatory element binding transcription factor 1;SREBF2: sterol regulatory element binding transcription factor 2; STING1: stimulator of interferon response cGAMP interactor 1; STX17: syntaxin 17; TAGs: triacylglycerols; TFEB: transcription factor EB; TP53/p53: tumor protein p53; ULK1: unc-51 like autophagy activating kinase 1; VMP1: vacuole membrane protein 1.

Mechanisms and therapeutic implications of selective autophagy in nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide, whereas there is no approved drug therapy due to its complexity. Studies are emerging to discuss the role of selective autophagy in the pathogenesis of NAFLD, because the specificity among the features of selective autophagy makes it a crucial process in mitigating hepatocyte damage caused by aberrant accumulation of dysfunctional organelles, for which no other pathway can compensate.

AIM OF REVIEW

This review aims to summarize the types, functions, and dynamics of selective autophagy that are of particular importance in the initiation and progression of NAFLD. And on this basis, the review outlines the therapeutic strategies against NAFLD, in particular the medications and potential natural products that can modulate selective autophagy in the pathogenesis of this disease.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The critical roles of lipophagy and mitophagy in the pathogenesis of NAFLD are well established, while reticulophagy and pexophagy are still being identified in this disease due to the insufficient understanding of their molecular details. As gradual blockage of autophagic flux reveals the complexity of NAFLD, studies unraveling the underlying mechanisms have made it possible to successfully treat NAFLD with multiple pharmacological compounds that target associated pathways. Overall, it is convinced that the continued research into selective autophagy occurring in NAFLD will further enhance the understanding of the pathogenesis and uncover novel therapeutic targets.

Cell-type specific role of autophagy in the liver and its implications in non-alcoholic fatty liver disease

Autophagy, a cellular degradative process, has emerged as a key regulator of cellular energy production and stress mitigation. Dysregulated autophagy is a common phenomenon observed in several human diseases, and its restoration offers curative advantage. Non-alcoholic fatty liver disease (NAFLD), more recently renamed metabolic dysfunction-associated steatotic liver disease, is a major metabolic liver disease affecting almost 30% of the world population. Unfortunately, NAFLD has no pharmacological therapies available to date. Autophagy regulates several hepatic processes including lipid metabolism, inflammation, cellular integrity and cellular plasticity in both parenchymal (hepatocytes) and non-parenchymal cells (Kupffer cells, hepatic stellate cells and sinusoidal endothelial cells) with a profound impact on NAFLD progression. Understanding cell type-specific autophagy in the liver is essential in order to develop targeted treatments for liver diseases such as NAFLD. Modulating autophagy in specific cell types can have varying effects on liver function and pathology, making it a promising area of research for liver-related disorders. This review aims to summarize our present understanding of cell-type specific effects of autophagy and their implications in developing autophagy centric therapies for NAFLD.

Quantitative proteomics analysis based on data-independent acquisition reveals the effect of Shenling Baizhu powder (SLP) on protein expression in MAFLD rat liver tissue

BACKGROUND

Metabolic associated fatty liver disease (MAFLD) has become the most common chronic liver disease worldwide, and it is also a high-risk factor for the development of other metabolic diseases. Shenling Baizhu powder (SLP) is a traditional Chinese herbal formula with good clinical efficacy against MAFLD. However, its molecular mechanism for the treatment of MAFLD is still not fully understood. This study used quantitative proteomics analysis to reveal the SLP action mechanism in the treatment of MAFLD by discovering the effect of SLP on protein expression in the liver tissue of MAFLD rats.

MATERIALS AND METHODS

Q-Orbitrap LC-MS/MS was used to identify the incoming blood compounds of SLP. The 18 SD male rats were randomly divided into 3 groups (n = 6): control group, HFD group and SLP group. The HFD group and SLP group were established as MAFLD rat models by feeding them a high-fat diet for 4 weeks. Afterwards, the SLP group was treated with SLP (10.89 g/kg/d) for 3 weeks. Biochemical parameters and liver pathological status were measured. Rat liver tissue was analyzed using DIA-based quantitative proteomics and the DEPs were validated by western blotting analysis.

RESULTS

A total of 18 active compounds of SLP were identified and isolated to enter the bloodstream. Comparison of DEPs between control group vs. HFD group and HFD group vs. SLP group revealed that SLP restored the expression of 113 DEPs. SLP catalyzes oxidoreductase activity and binding activity on mitochondria and endoplasmic reticulum to promote lipid oxidative catabolism, maintain oxoacid metabolic homeostasis in vivo and mitigate oxidative stress-induced hepatocyte injury. And 52 signaling pathways including PPAR signaling, arachidonic acid metabolism and glycine, serine and threonine metabolism were enriched by KEGG. PPI topology analysis showed that Cyp4a2, Agxt2, Fabp1, Pck1, Acsm3, Aldh1a1, Got1 and Hmgcs2 were the core DEPs. The western blotting analysis verified that SLP was able to reverse the increase in Fabp1 and Hmgcs2 and the decrease in Pck1 induced by HFD, and the results were consistent proteomic data.

CONCLUSION

SLP ameliorates hepatic steatosis to exert therapeutic effects on MAFLD by inhibiting the expression of lipid synthesis genes and inhibiting lipid peroxidation in mitochondria. This study provides a new idea and basis for the study of SLP in the treatment of MAFLD and provides an experimental basis for the clinical application of SLP.

Physical Activity Protocols in Non-Alcoholic Fatty Liver Disease Management: A Systematic Review of Randomized Clinical Trials and Animal Models

Non-alcoholic fatty liver disease (NAFLD) is closely associated with other metabolic disease and cardiovascular disease. Regular exercise reduces hepatic fat content and could be the first-line treatment in the management of NAFLD. This review aims to summarize the current evidence of the beneficial effects of exercise training and identify the molecular pathways involved in the response to exercise to define their role in the resolution of NAFLD both in animal and human studies. According to the inclusion criteria, 43 animal studies and 14 RCTs were included in this systematic review. Several exercise modalities were demonstrated to have a positive effect on liver function. Physical activity showed a strong association with improvement in inflammation, and reduction in steatohepatitis and fibrosis in experimental models. Furthermore, both aerobic and resistance exercise in human studies were demonstrated to reduce liver fat, and to improve insulin resistance and blood lipids, regardless of weight loss, although aerobic exercises may be more effective. Resistance exercise is more feasible for patients with NAFLD with poor cardiorespiratory fitness. More effort and awareness should be dedicated to encouraging NAFLD patients to adopt an active lifestyle and benefit from it its effects in order to reduce this growing public health problem.

p16 INK4A drives nonalcoholic fatty liver disease phenotypes in high fat diet fed mice through biliary E2F1/FOXO1/IGF-1 signaling

BACKGROUND AND AIMS

NAFLD is characterized by steatosis, hepatic inflammation, and fibrosis, which can develop into NASH. Patients with NAFLD/NASH have increased ductular reaction (DR) and biliary senescence. High fat/high cholesterol diet feeding increases biliary senescence, DR, and biliary insulin-like growth factor-1 (IGF-1) expression in mice. p16/IGF-1 converges with fork-head box transcription factor O1 (FOXO1) through E2F1. We evaluated p16 inhibition on NAFLD phenotypes and biliary E2F1/FOXO1/IGF-1 signaling.

APPROACH AND RESULTS

4-week wild-type (C57BL/6J) male mice were fed a control diet (CD) or high fat/high cholesterol diet and received either p16 or control Vivo Morpholino (VM) by tail vein injection 2× during the 16th week of feeding. We confirmed p16 knockdown and examined: (i) NAFLD phenotypes; (ii) DR and biliary senescence; (iii) serum metabolites; and (iv) biliary E2F1/FOXO1/IGF-1 signaling. Human normal, NAFLD, and NASH liver samples and isolated cholangiocytes treated with control or p16 VM were evaluated for p16/E2F1/FOXO1/IGF-1 signaling. p16 VM treatment reduced cholangiocyte and hepatocyte p16. In wild-type high fat/high cholesterol diet mice with control VM, there were increased (i) NAFLD phenotypes; (ii) DR and biliary senescence; (iii) serum metabolites; and (iv) biliary E2F1/FOXO1/IGF-1 signaling; however, p16 VM treatment reduced these parameters. Biliary E2F1/FOX-O1/IGF-1 signaling increased in human NAFLD/NASH but was blocked by p16 VM. In vitro , p16 VM reduced biliary E2f1 and Foxo1 transcription by inhibiting RNA pol II binding and E2F1 binding at the Foxo1 locus, respectively. Inhibition of E2F1 reduced biliary FOXO1 in vitro.

CONCLUSION

Attenuating hepatic p16 expression may be a therapeutic approach for improving NAFLD/NASH phenotypes.

Exercise against nonalcoholic fatty liver disease: Possible role and mechanism of lipophagy

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease worldwide. NAFLD is prevalent in about 30% of people worldwide. The lack of physical activity is considered as one of the risks for NAFLD, and approximately one-third of NAFLD patients hardly engage in physical activity. It is acknowledged that exercise is one of the optimal non-pharmacological methods for preventing and treating NAFLD. Different forms of exercise such as aerobic exercise, resistance exercise and even simply physical activity in a higher level can be beneficial in reducing liver lipid accumulation and disease progression for NAFLD patients. In NAFLD patients, exercise is helpful in lowering steatosis and enhancing liver function. The mechanisms underlying the prevention and treatment of NAFLD by exercise are various and complex. Current studies on the mechanisms have focused on the pro-lipolytic, anti-inflammatory, and antioxidant and lipophagy. Promotion of lipophagy is regarded as an important mechanism for prevention and improvement of NAFLD by exercise. Recent studies have investigated the above mechanism, yet the potential mechanism has not been completely elucidated. Thus, in this review, we cover the recent advances of exercise-promoted lipophagy in NAFLD treatment and prevention. Furthermore, given the fact that exercise activates SIRT1, we discuss the possible regulatory mechanisms of lipophagy by SIRT1 during exercise. These mechanisms need to be verified by further experimental studies.

Autophagy: A Cellular Guardian against Hepatic Lipotoxicity

Lipotoxicity is a phenomenon of lipid-induced cellular injury in nonadipose tissue. Excess of free saturated fatty acids (SFAs) contributes to hepatic injury in nonalcoholic fatty liver disease (NAFLD), which has been growing at an unprecedented rate in recent years. SFAs and their derivatives such as ceramides and membrane phospholipids have been shown to induce intrahepatic oxidative damage and ER stress. Autophagy represents a cellular housekeeping mechanism to counter the perturbation in organelle function and activation of stress signals within the cell. Several aspects of autophagy, including lipid droplet assembly, lipophagy, mitophagy, redox signaling and ER-phagy, play a critical role in mounting a strong defense against lipotoxic lipid species within the hepatic cells. This review provides a succinct overview of our current understanding of autophagy-lipotoxicity interaction and its pharmacological and nonpharmacological modulation in treating NAFLD.

Acupoint Catgut Embedding Improves Lipid Metabolism in Exercise-Induced Fatigue Rats via the PPAR Signaling Pathway

To improve the phenomenon of exercise-induced fatigue that often occurs during horse racing, we previously studied the improvement in exercise tolerance by acupoint catgut embedding preconditioning in an exercise-induced fatigue rat model. We found that acupoint catgut embedding pretreatment effectively improved animal exercise tolerance. Here, by combining transcriptomics and metabolomics, we aimed to explore the underlying mechanisms of this improvement. We used blood biochemical detection combined with ELISA to detect triglyceride (TG), total cholesterol (TC), lactate dehydrogenase (LDH), high-density lipoprotein (HDL), alanine transaminase (ALT), aspartate aminotransferase (AST), and glucose (GLU), arachidonic acid (AA), and free fatty acid (FFA) content and found that acupoint embedding can correct FFA, AA, TG, LDH, and AST in the blood. We used RT-qPCR to measure the expression of genes in tissue from the quadriceps femoris muscle. We found that solute carrier family 27 member 2 (Slc27a2), fatty acid binding protein 1 (Fabp1), apolipoprotein C3 (Apoc3), and lipoprotein lipase (Lpl) genes in the peroxisome proliferator-activated receptor (PPAR) signaling pathway were important. The regulation of lipid metabolism through the PPAR signaling pathway was important for improving the exercise endurance of rats in our exercise-induced fatigue model. Therefore, we conclude that acupoint catgut embedding can not only promote body fat decomposition and reduce lactic acid accumulation but also promote the repair of tissue damage and liver damage caused by exercise fatigue. Acupoint catgut embedding regulates the PPAR signaling pathway by upregulating Lpl expression and downregulating Slc27a2, Fabp1, and Apoc3 expression to further improve body fat metabolism.

The natural flavone acacetin protects against high-fat diet-induced lipid accumulation in the liver via the endoplasmic reticulum stress/ferroptosis pathway

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. To date, no medication has been approved to treat NAFLD. In this study, we evaluated the therapeutic effect of the natural flavone acacetin on high-fat diet (HFD)-induced NAFLD in mice and the underlying mechanisms. We found that acacetin (10, 20, 50 mg/kg/day) suppressed the increase in body weight, serum total cholesterol, triglycerides, low-density lipoprotein, aspartate aminotransferase, and alanine aminotransferase levels in mice fed with HFD with a dose-dependent manner. Hepatic lipid accumulation, iron overload, and lipid peroxidation were significantly alleviated by acacetin. Quantitative PCR and western blotting revealed that acacetin inhibited endoplasmic reticulum (ER) stress, ferroptosis, and expressions of lipid acid synthesis-related genes in the livers of HFD mice. Similar results were observed in HepG2 cells treated with oleic acid and lipopolysaccharide. The suppressive effects of acacetin on triglycerides and expression of lipid acid synthesis genes were abolished by ER stress and the ferroptosis activators, erastin or TU. Interestingly, the action of TU was more potent than that of erastin. Treatment with the ER stress inhibitor GSK and the ferroptosis inhibitor Fer-1 revealed that ER stress was the upstream signal of ferroptosis for hepatic lipid accumulation. These findings suggest the protective effect of acacetin against lipid accumulation via suppressing ER stress and ferroptosis and provide evidence that ER stress is an upstream signal of ferroptosis in lipid accumulation. Acacetin may be a promising candidate agent for NAFLD treatment.

Exercise-Induced ADAR2 Protects against Nonalcoholic Fatty Liver Disease through miR-34a

Nonalcoholic fatty liver disease (NAFLD) is a growing health problem that is closely associated with insulin resistance and hereditary susceptibility. Exercise is a beneficial approach to NAFLD. However, the relief mechanism of exercise training is still unknown. In this study, mice on a normal diet or a high-fat diet (HFD), combined with Nω-nitro-L-arginine methyl ester, hydrochloride (L-NAME) mice, were either kept sedentary or were subjected to a 12-week exercise running scheme. We found that exercise reduced liver steatosis in mice with diet-induced NAFLD. The hepatic adenosine deaminases acting on RNA 2 (ADAR2) were downregulated in NAFLD and were upregulated in the liver after 12-week exercise. Next, overexpression of ADAR2 inhibited and suppression promoted lipogenesis in HepG2 cells treated with oleic acid (OA), respectively. We found that ADAR2 could down-regulate mature miR-34a in hepatocytes. Functional reverse experiments further proved that miR-34a mimicry eliminated the suppression of ADAR2 overexpression in lipogenesis in vitro. Moreover, miR-34a inhibition and mimicry could also affect lipogenesis in hepatocytes. In conclusion, exercise-induced ADAR2 protects against lipogenesis during NAFLD by editing miR-34a. RNA editing mediated by ADAR2 may be a promising therapeutic candidate for NAFLD.

Concurrent betaine administration enhances exercise-induced improvements to glucose handling in obese mice

BACKGROUND AND AIMS

Betaine supplementation has been shown to enhance hepatic lipid metabolism in obese mice and improve exercise performance in healthy populations. We examined effects of betaine supplementation, alone or in combination with treadmill exercise, on the metabolic consequences of high fat diet (HFD)-induced obesity in mice.

METHODS AND RESULTS

Male C57BL/6 J mice were fed chow or HFD. After 15 weeks, HFD mice were split into: HFD, HFD with betaine (1.5% w/v), HFD with treadmill exercise, and HFD with both betaine and exercise (15 m/min for 45min, 6 days/week; n = 12/group) for 10 weeks. Compared to HFD mice, body weight was significantly reduced in exercise and exercise-betaine mice, but not in mice given betaine alone. Similarly, adiposity was reduced by exercise but not by betaine alone. HFD-induced glucose intolerance was slightly improved by exercise, but not with betaine alone. Significantly greater benefits were observed in exercise-betaine mice, compared to exercise alone, such that GTT-outcomes were similar to controls. This was associated with reduced insulin levels during ipGTT, suggesting enhanced insulin sensitivity. Modest benefits were observed in fatty acid metabolism genes in skeletal muscle, whilst limited effects were observed in the liver. HFD-induced increases in hepatic Mpc1 (mitochondrial pyruvate carrier 1) were normalized by all treatments, suggesting potential links to altered glucose metabolism.

CONCLUSIONS

Our data show that drinking 1.5% betaine was sufficient to augment metabolic benefits of exercise in obese mice. These processes appear to be facilitated by altered glucose metabolism, with limited effects on hepatic lipid metabolism.

Fatty Acid-Binding Proteins: Their Roles in Ischemic Stroke and Potential as Drug Targets

Stroke is among the leading causes of death and disability worldwide. However, despite long-term research yielding numerous candidate neuroprotective drugs, there remains a lack of effective neuroprotective therapies for ischemic stroke patients. Among the factors contributing to this deficiency could be that single-target therapy is insufficient in addressing the complex and extensive mechanistic basis of ischemic brain injury. In this context, lipids serve as an essential component of multiple biological processes and play important roles in the pathogenesis of numerous common neurological diseases. Moreover, in recent years, fatty acid-binding proteins (FABPs), a family of lipid chaperone proteins, have been discovered to be involved in the onset or development of several neurodegenerative diseases, including Alzheimer’s and Parkinson’s disease. However, comparatively little attention has focused on the roles played by FABPs in ischemic stroke. We have recently demonstrated that neural tissue-associated FABPs are involved in the pathological mechanism of ischemic brain injury in mice. Here, we review the literature published in the past decade that has reported on the associations between FABPs and ischemia and summarize the relevant regulatory mechanisms of FABPs implicated in ischemic injury. We also propose candidate FABPs that could serve as potential therapeutic targets for ischemic stroke.

Roles of organelle-specific autophagy in hepatocytes in the development and treatment of non-alcoholic fatty liver disease

ABSTRACT

Non-alcoholic fatty liver disease (NAFLD) is a disorder of lipid metabolism. The lipotoxic intermediates of lipid metabolism cause mitochondrial dysfunction and endoplasmic reticulum stress. Organelle-specific autophagy is responsible for the removal of dysfunctional organelles to maintain intracellular homeostasis. Lipophagy contributes to lipid turnover by degrading lipid droplets. The level of autophagy changes during the course of NAFLD, and the activation of hepatocyte autophagy might represent a method of treating NAFLD.

The Correlations of Plasma Liver-Type Fatty Acid-Binding Protein with Amyloid-β and Tau Levels in Patients with Alzheimer’s Disease

Background: The dysregulation of lipid metabolism plays an important role in the pathogenesis of Alzheimer’s disease (AD). Liver-type fatty acid-binding protein (L-FABP, also known as FABP1) is critical for fatty acid transport and may be involved in AD. Objective: To investigate whether the FABP1 level is altered in patients with AD, and its associations with levels of amyloid-β (Aβ) and tau in the plasma and cerebrospinal fluid (CSF). Methods: A cross-sectional study was conducted in a Chinese cohort consisting of 39 cognitively normal controls and 47 patients with AD. The levels of FABP1 in plasma, and Aβ and tau in CSF, were measured by enzyme-linked immunosorbent assay (ELISA). A single-molecule array (SIMOA) was used to detect plasma Aβ levels. Results: The level of plasma FABP1 was significantly elevated in the AD group (p = 0.0109). Further analysis showed a positive correlation of FABP1 with CSF total tau (t-tau) and phosphorylated tau (p-tau) levels. Besides, plasma FABP1/Aβ 42 (AUC = 0.6794, p = 0.0071) and FABP1/t-tau (AUC = 0.7168, p = 0.0011) showed fair diagnostic efficacy for AD. When combined with other common AD biomarkers including plasma Aβ 42, Aβ 40, and t-tau, both FABP1/Aβ 42 and FABP1/t-tau showed better diagnostic efficacy than using these biomarkers alone. Among all AUC analyses, the combination of plasma FABP1/t-tau and Aβ 42 had the highest diagnostic value (AUC = 0.8075, p <  0.0001). Conclusion: These findings indicate that FABP1 may play a role in AD pathogenesis and be worthy of further investigation in the future.

The Role of Hydrogen Sulfide Regulation of Autophagy in Liver Disorders

Autophagy is a complex process of degradation of senescent or dysfunctional organelles in cells. Dysfunctional autophagy is associated with many diseases such as cancers, immune dysfunction, and aging. Hydrogen sulfide (H₂S) is considered to be the third gas signal molecule after nitrous oxide and carbon monoxide. In recent years, H₂S has been found to have a variety of important biological functions, and plays an important role in a variety of physiological and pathological processes. In this review, we review the recent role and mechanism of H₂S in regulating autophagy in liver disorders, in order to provide a basis for further research in the future.

Effects of the Phytochemical Combination PB123 on Nrf2 Activation, Gene Expression, and the Cholesterol Pathway in HepG2 Cells

There has been a long history of human usage of the biologically-active phytochemicals in Salvia rosmarinus, Zingiber officinale, and Sophora japonica for health purposes, and we recently reported on a combination of those plant materials as the PB123 dietary supplement. In the present work we extended those studies to evaluate activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor and differential gene expression in cultured HepG2 (hepatocellular carcinoma) cells treated with PB123. We determined transcriptome changes using mRNA-seq methods, and analyzed the affected pathways using Ingenuity Pathway Analysis and BioJupies, indicating that primary effects included increasing the Nrf2 pathway and decreasing the cholesterol biosynthesis pathway. Pretreatment of cultured HepG2 cells with PB123 upregulated Nrf2-dependent cytoprotective genes and increased cellular defenses against cumene hydroperoxide-induced oxidative stress. In contrast, pretreatment of cultured HepG2 cells with PB123 downregulated cholesterol biosynthesis genes and decreased cellular cholesterol levels. These findings support the possible beneficial effects of PB123 as a healthspan-promoting dietary supplement.

Association between liver-type fatty acid-binding protein and hyperuricemia before and after laparoscopic sleeve gastrectomy

BACKGROUND

Liver-type fatty acid-binding protein (FABP1) contributes to metabolic disorders. However, the relationship between FABP1 and hyperuricemia remains unknown. We aimed to evaluate the correlation between serum FABP1 and hyperuricemia in patients with obesity before and after laparoscopic sleeve gastrectomy (LSG).

METHODS

We enrolled 105 patients (47 men and 58 women) with obesity who underwent LSG. They were divided into two groups: normal levels of uric acid (UA) (NUA, n = 44) and high levels of UA (HUA, n = 61) with matching sexes. FABP1 levels and other biochemical parameters were measured at baseline and 3, 6, and 12 months after LSG.

RESULTS

Serum FABP1 levels were significantly higher in the HUA group than in the NUA group (34.76 ± 22.69 ng/mL vs. 25.21 ± 21.68 ng/mL, P=0.024). FABP1 was positively correlated with UA (r=0.390, P=0.002) in the HUA group. The correlation still existed after adjusting for confounding factors. Preoperative FABP1 levels were risk factors for hyperuricemia at baseline. UA and FABP1 levels decreased at 3, 6, and 12 months postoperatively. FABP1 showed a more significant decrease in the HUA group than in the NUA group at 12 months (27.06 ± 10.98 ng/mL vs. 9.54 ± 6.52 ng/mL, P=0.003). Additionally, the change in FABP1 levels positively correlated with changes in UA levels in the HUA group 12 months postoperatively (r=0.512, P=0.011).

CONCLUSIONS

FABP1 was positively associated with UA and may be a risk factor for hyperuricemia in obesity. FABP1 levels were higher but decreased more after LSG in obese patients with hyperuricemia than in those without hyperuricemia.

Autophagy in metabolic disease and ageing

Autophagy is an evolutionarily conserved, lysosome-dependent catabolic process whereby cytoplasmic components, including damaged organelles, protein aggregates and lipid droplets, are degraded and their components recycled. Autophagy has an essential role in maintaining cellular homeostasis in response to intracellular stress; however, the efficiency of autophagy declines with age and overnutrition can interfere with the autophagic process. Therefore, conditions such as sarcopenic obesity, insulin resistance and type 2 diabetes mellitus (T2DM) that are characterized by metabolic derangement and intracellular stresses (including oxidative stress, inflammation and endoplasmic reticulum stress) also involve the accumulation of damaged cellular components. These conditions are prevalent in ageing populations. For example, sarcopenia is an age-related loss of skeletal muscle mass and strength that is involved in the pathogenesis of both insulin resistance and T2DM, particularly in elderly people. Impairment of autophagy results in further aggravation of diabetes-related metabolic derangements in insulin target tissues, including the liver, skeletal muscle and adipose tissue, as well as in pancreatic β-cells. This Review summarizes the role of autophagy in the pathogenesis of metabolic diseases associated with or occurring in the context of ageing, including insulin resistance, T2DM and sarcopenic obesity, and describes its potential as a therapeutic target.

Prevalence and Independent Factors for Fatty Liver and Significant Hepatic Fibrosis Using B-Mode Ultrasound Imaging and Two Dimensional-Shear Wave Elastography in Health Check-up Examinees

BACKGROUND AND AIM

Exercise is beneficial for metabolic syndrome. Fatty liver and significant hepatic fibrosis, hepatic manifestations of metabolic syndrome, are becoming an epidemic. We aimed to investigate the prevalence of fatty liver and significant fibrosis and examined the independent factors for these conditions.

SUBJECTS AND METHODS

We enrolled 1,361 health check-up examinees (median age, 53 years; female/male, 813/548). Fatty liver and fibrosis were evaluated by B-mode ultrasound imaging and shear wave elastography. Factors associated with fatty liver and significant fibrosis were analyzed by logistic regression analysis.

RESULTS

Fatty liver and significant fibrosis were observed in 50.5% and 42.7% of enrolled subjects, respectively. Independent factors associated with fatty liver were BMI (OR 1.46; 95%CI 1.397-1.537; P<0.0001) and no exer cise habits (OR 1.47; 95% CI 1.101-1.984; P=0.0093). Independent factors associated with significant fibrosis were age, female, BMI (OR 1.37; 95%CI 1.311-1.436; P<0.0001), and no exercise habits (OR 1.49; 95% CI 1.102-2.031; P=0.0097).

CONCLUSIONS

Fatty liver and significant fibrosis were frequently seen in health check-up examinees and the common independent factors were higher BMI and no exercise habits. Thus, weight loss and exercise may ameliorate fatty liver and significant hepatic fibrosis in the general population.

NAC antagonizes arsenic-induced neurotoxicity through TMEM179 by inhibiting oxidative stress in Oli-neu cells

Arsenic is one of the most common environmental pollutants. Neurotoxicity induced by arsenic has become a major public health concern. However, the effects of arsenic-induced neurotoxicity in the brain and the underlying molecular mechanisms are not well understood. N-acetyl-cysteine (NAC) is a thiol-based antioxidant that can antagonize heavy metal-induced neurotoxicity by scavenging reactive oxygen species (ROS). Here, we used the mouse oligodendrocyte precursor cell (OPC) line Oli-neu to explore the neurotoxic effects of arsenic and the protective effects of NAC. We found that arsenic exposure decreased cell viability, increased oxidative stress, caused mitochondrial dysfunction, and led to apoptosis of Oli-neu cells. Furthermore, we revealed that NAC treatment reversed these neurotoxic effects of arsenic. TMEM179, a key membrane protein, was found highly expressed in OPCs and to be an important factor in maintaining mitochondrial functions. We found that TMEM179 played a critical role in mediating the neurotoxic effects of arsenic and the protective role of NAC. PKCβ is a downstream factor through which TMEM179 regulates the expression of apoptosis-related proteins. This study improves our understanding of the neurotoxic effects and mechanisms of arsenic exposure and the protective effects of NAC. It also identifies a potential molecular target, TMEM179, for the treatment of arsenic-induced neurotoxicity.

Mitochondrial Lipid Homeostasis at the Crossroads of Liver and Heart Diseases

The prevalence of NAFLD (non-alcoholic fatty liver disease) is a rapidly increasing problem, affecting a huge population around the globe. However, CVDs (cardiovascular diseases) are the most common cause of mortality in NAFLD patients. Atherogenic dyslipidemia, characterized by plasma hypertriglyceridemia, increased small dense LDL (low-density lipoprotein) particles, and decreased HDL-C (high-density lipoprotein cholesterol) levels, is often observed in NAFLD patients. In this review, we summarize recent genetic evidence, proving the diverse nature of metabolic pathways involved in NAFLD pathogenesis. Analysis of available genetic data suggests that the altered operation of fatty-acid β-oxidation in liver mitochondria is the key process, connecting NAFLD-mediated dyslipidemia and elevated CVD risk. In addition, we discuss several NAFLD-associated genes with documented anti-atherosclerotic or cardioprotective effects, and current pharmaceutical strategies focused on both NAFLD treatment and reduction of CVD risk.

The ménage à trois of autophagy, lipid droplets and liver disease

Autophagic pathways cross with lipid homeostasis and thus provide energy and essential building blocks that are indispensable for liver functions. Energy deficiencies are compensated by breaking down lipid droplets (LDs), intracellular organelles that store neutral lipids, in part by a selective type of autophagy, referred to as lipophagy. The process of lipophagy does not appear to be properly regulated in fatty liver diseases (FLDs), an important risk factor for the development of hepatocellular carcinomas (HCC). Here we provide an overview on our current knowledge of the biogenesis and functions of LDs, and the mechanisms underlying their lysosomal turnover by autophagic processes. This review also focuses on nonalcoholic steatohepatitis (NASH), a specific type of FLD characterized by steatosis, chronic inflammation and cell death. Particular attention is paid to the role of macroautophagy and macrolipophagy in relation to the parenchymal and non-parenchymal cells of the liver in NASH, as this disease has been associated with inappropriate lipophagy in various cell types of the liver.Abbreviations: ACAT: acetyl-CoA acetyltransferase; ACAC/ACC: acetyl-CoA carboxylase; AKT: AKT serine/threonine kinase; ATG: autophagy related; AUP1: AUP1 lipid droplet regulating VLDL assembly factor; BECN1/Vps30/Atg6: beclin 1; BSCL2/seipin: BSCL2 lipid droplet biogenesis associated, seipin; CMA: chaperone-mediated autophagy; CREB1/CREB: cAMP responsive element binding protein 1; CXCR3: C-X-C motif chemokine receptor 3; DAGs: diacylglycerols; DAMPs: danger/damage-associated molecular patterns; DEN: diethylnitrosamine; DGAT: diacylglycerol O-acyltransferase; DNL: de novo lipogenesis; EHBP1/NACSIN (EH domain binding protein 1); EHD2/PAST2: EH domain containing 2; CoA: coenzyme A; CCL/chemokines: chemokine ligands; CCl_4: carbon tetrachloride; ER: endoplasmic reticulum; ESCRT: endosomal sorting complexes required for transport; FA: fatty acid; FFAs: free fatty acids; FFC: high saturated fats, fructose and cholesterol; FGF21: fibroblast growth factor 21; FITM/FIT: fat storage inducing transmembrane protein; FLD: fatty liver diseases; FOXO: forkhead box O; GABARAP: GABA type A receptor-associated protein; GPAT: glycerol-3-phosphate acyltransferase; HCC: hepatocellular carcinoma; HDAC6: histone deacetylase 6; HECT: homologous to E6-AP C-terminus; HFCD: high fat, choline deficient; HFD: high-fat diet; HSCs: hepatic stellate cells; HSPA8/HSC70: heat shock protein family A (Hsp70) member 8; ITCH/AIP4: itchy E3 ubiquitin protein ligase; KCs: Kupffer cells; LAMP2A: lysosomal associated membrane protein 2A; LDs: lipid droplets; LDL: low density lipoprotein; LEP/OB: leptin; LEPR/OBR: leptin receptor; LIPA/LAL: lipase A, lysosomal acid type; LIPE/HSL: lipase E, hormone sensitive type; LIR: LC3-interacting region; LPS: lipopolysaccharide; LSECs: liver sinusoidal endothelial cells; MAGs: monoacylglycerols; MAPK: mitogen-activated protein kinase; MAP3K5/ASK1: mitogen-activated protein kinase kinase kinase 5; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MCD: methionine-choline deficient; MGLL/MGL: monoglyceride lipase; MLXIPL/ChREBP: MLX interacting protein like; MTORC1: mechanistic target of rapamycin kinase complex 1; NAFLD: nonalcoholic fatty liver disease; NAS: NAFLD activity score; NASH: nonalcoholic steatohepatitis; NPC: NPC intracellular cholesterol transporter; NR1H3/LXRα: nuclear receptor subfamily 1 group H member 3; NR1H4/FXR: nuclear receptor subfamily 1 group H member 4; PDGF: platelet derived growth factor; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PLIN: perilipin; PNPLA: patatin like phospholipase domain containing; PNPLA2/ATGL: patatin like phospholipase domain containing 2; PNPLA3/adiponutrin: patatin like phospholipase domain containing 3; PPAR: peroxisome proliferator activated receptor; PPARA/PPARα: peroxisome proliferator activated receptor alpha; PPARD/PPARδ: peroxisome proliferator activated receptor delta; PPARG/PPARγ: peroxisome proliferator activated receptor gamma; PPARGC1A/PGC1α: PPARG coactivator 1 alpha; PRKAA/AMPK: protein kinase AMP-activated catalytic subunit; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; PTEN: phosphatase and tensin homolog; ROS: reactive oxygen species; SE: sterol esters; SIRT1: sirtuin 1; SPART/SPG20: spartin; SQSTM1/p62: sequestosome 1; SREBF1/SREBP1c: sterol regulatory element binding transcription factor 1; TAGs: triacylglycerols; TFE3: transcription factor binding to IGHM enhancer 3; TFEB: transcription factor EB; TGFB1/TGFβ: transforming growth factor beta 1; Ub: ubiquitin; UBE2G2/UBC7: ubiquitin conjugating enzyme E2 G2; ULK1/Atg1: unc-51 like autophagy activating kinase 1; USF1: upstream transcription factor 1; VLDL: very-low density lipoprotein; VPS: vacuolar protein sorting; WIPI: WD-repeat domain, phosphoinositide interacting; WDR: WD repeat domain.

Exercise improves lipid droplet metabolism disorder through activation of AMPK-mediated lipophagy in NAFLD

AIM

To emphasize the mechanism of the effect of exercise on lipid droplet (LD) metabolism disorder in nonalcoholic fatty liver disease (NAFLD).

MAIN METHODS

C57BL/6J mice were randomly divided into three groups: The first group was fed with a normal diet (CON), the second group was fed a high-fat diet (HF), and finally group with a high-fat diet intervention and swim training (HF-EX). The total intervention period was 16 weeks. RT-PCR and Western blot were performed to evaluate the effect of exercise on LDs metabolism and the AMPK pathway. Histopathological examinations and immunofluorescence were performed to evaluate the lipid deposition and lipophagy in the liver.

KEY FINDINGS

Exercise reduced liver steatosis and insulin resistance along with the stimulation of AMPK/SIRT1 signaling and downstream regulation of lipid metabolism. In addition, exercise increased the expression of autophagy marker and colocalization of LC3 and LAMP1 with LDs.

SIGNIFICANCE

Exercise stimulated AMPK/SIRT1 and activated lipophagy in NAFLD. Enhancing lipophagy may be one of the key mechanisms of regulation and resolution of NAFLD by exercise.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Liraglutide Alleviates Hepatic Steatosis by Activating the TFEB-Regulated Autophagy-Lysosomal Pathway

Liraglutide, a glucagon-like peptide-1 receptor agonist (GLP-1RA), has been demonstrated to alleviate non-alcoholic fatty liver disease (NAFLD). However, the underlying mechanism has not been fully elucidated. Increasing evidence suggests that autophagy is involved in the pathogenesis of hepatic steatosis. In this study, we examined whether liraglutide could alleviate hepatic steatosis through autophagy-dependent lipid degradation and investigated the underlying mechanisms. Herein, the effects of liraglutide on NAFLD were evaluated in a high-fat diet (HFD)-induced mouse model of NAFLD as well as in mouse primary and HepG2 hepatocytes exposed to palmitic acid (PA). The expression of the GLP-1 receptor (GLP-1R) was measured in vivo and in vitro. Oil red O staining was performed to detect lipid accumulation in hepatocytes. Electron microscopy was used to observe the morphology of autophagic vesicles and autolysosomes. Autophagic flux activity was measured by infecting HepG2 cells with mRFP-GFP-LC3 adenovirus. The roles of GLP-1R and transcription factor EB (TFEB) in autophagy-lysosomal activation were explored using small interfering RNA. Liraglutide treatment alleviated hepatic steatosis in vivo and in vitro. In models of hepatic steatosis, microtubule-associated protein 1B light chain-3-II (LC3-II) and SQSTM1/P62 levels were elevated in parallel to blockade of autophagic flux. Liraglutide treatment restored autophagic activity by improving lysosomal function. Furthermore, treatment with autophagy inhibitor chloroquine weakened liraglutide-induced autophagy activation and lipid degradation. TFEB has been identified as a key regulator of lysosome biogenesis and autophagy. The protein levels of nuclear TFEB and its downstream targets CTSB and LAMP1 were decreased in hepatocytes treated with PA, and these decreases were reversed by liraglutide treatment. Knockdown of TFEB expression compromised the effects of liraglutide on lysosome biogenesis and hepatic lipid accumulation. Mechanistically, GLP-1R expression was decreased in HFD mouse livers as well as PA-stimulated hepatocytes, and liraglutide treatment reversed the downregulation of GLP-1R expression in vivo and in vitro. Moreover, GLP-1R inhibition could mimic the effect of the TFEB downregulation-mediated decrease in lysosome biogenesis. Thus, our findings suggest that liraglutide attenuated hepatic steatosis via restoring autophagic flux, specifically the GLP-1R-TFEB-mediated autophagy-lysosomal pathway.

Effects of Long-Term Exercise on Liver Cyst in Polycystic Liver Disease Model Rats

BACKGROUND

Polycystic liver disease (PLD) is a hereditary liver disease with progressive enlargement of fluid-filled liver cysts, which causes abdominal discomfort and worsens quality of life. Long-term exercise has beneficial effects in various organs, but the effects of long-term exercise on PLD are unclear. Therefore, the aim of this study was to investigate whether long-term exercise inhibits liver cyst formation and fibrosis.

METHODS

Polycystic kidney (PCK) rats, a model of PLD, were randomly divided into a sedentary group and a long-term exercise group, which underwent treadmill running for 12 wk (28 m·min, 60 min·d, 5 d·wk). Sprague-Dawley (SD) rats were set as a control group. After 12 wk, exercise capacity, histology, and signaling cascades of PLD were examined.

RESULTS

Compared with control SD rats, PCK rats showed a low exercise capacity before exercise protocol. After 12 wk, the exercise improved the exercise capacity and ameliorated liver cyst formation and fibrosis. The exercise significantly decreased the number of Ki-67-positive cells; the expression of cystic fibrosis transmembrane conductance regulator, aquaporin 1, transforming growth factor β, and type 1 collagen; and the phosphorylation of extracellular signal-regulated kinase, mammalian target of rapamycin and S6. It also increased the phosphorylation of AMP-activated protein kinase in the liver of PCK rats.

CONCLUSIONS

The present results indicated that long-term moderate-intensity exercise ameliorates liver cyst formation and fibrosis with the inhibition of signaling cascades responsible for cellular proliferation and fibrosis in PCK rats.

Glycochenodeoxycholic acid impairs transcription factor E3 -dependent autophagy-lysosome machinery by disrupting reactive oxygen species homeostasis in L02 cells

Cholestasis represents pathophysiologic syndromes defined as impaired bile flow from the liver. As an outcome, bile acids accumulate and promote hepatocyte injury, followed by liver cirrhosis and liver failure. Glycochenodeoxycholic acid (GCDCA) is relatively toxic and highly concentrated in bile and serum after cholestasis. However, the mechanism underlying GCDCA-induced hepatotoxicity remains unclear. In this study, we found that GCDCA inhibits autophagosome formation and impairs lysosomal function by inhibiting lysosomal proteolysis and increasing lysosomal pH, contributing to defects in autophagic clearance and subsequently leading to the death of L02 human hepatocyte cells. Notably, through tandem mass tag (TMT)-based quantitative proteomic analysis and database searches, 313 differentially expressed proteins were identified, of which 71 were increased and 242 were decreased in the GCDCA group compared with those in the control group. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that GCDCA suppressed the signaling pathway of transcription factor E3 (TFE3), which was the most closely associated with autophagic flux impairment. In contrast, GCDCA-inhibited lysosomal function and autophagic flux were efficiently attenuated by TFE3 overexpression. Specifically, the decreased expression of TFE3 was closely related to the disruption of reactive oxygen species (ROS) homeostasis, which could be prevented by inhibiting intracellular ROS with N-acetyl cysteine (NAC). In summary, our study is the first to demonstrate that manipulation of ROS/TFE3 signaling may be a therapeutic approach for antagonizing GCDCA-induced hepatotoxicity.

Sex-dependent metabolic effects of pregestational exercise on prenatally stressed mice

Stressful events during the prenatal period have been related to hyperactive hypothalamic-pituitary-adrenal (HPA) axis responses as well as metabolic changes in adult life. Moreover, regular exercise may contribute to the improvement of the symptoms associated with stress and stress-related chronic diseases. Therefore, this study aims to investigate the effects of exercise, before the gestation period, on the metabolic changes induced by prenatal stress in adult mice. Female Balb/c mice were divided into three groups: control (CON), prenatal restraint stress (PNS) and exercise before the gestational period plus PNS (EX + PNS). When adults, the plasmatic biochemical analysis, oxidative stress, gene expression of metabolic-related receptors and sex differences were assessed in the offspring. Prenatal stress decreased neonatal and adult body weight when compared to the pregestational exercise group. Moreover, prenatal stress was associated with reduced body weight in adult males. PNS and EX + PNS females showed decreased hepatic catalase. Pregestational exercise prevented the stress-induced cholesterol increase in females but did not prevent the liver mRNA expression reduction on the peroxisome proliferator-activated receptors (PPARs) α and γ in PNS females. Conversely, PNS and EX + PNS males showed an increased PPARα mRNA expression. In conclusion, pregestational exercise prevented some effects of prenatal stress on metabolic markers in a sex-specific manner.

Different training intensities induced autophagy and histopathology appearances potentially associated with lipid metabolism in wistar rat liver

Introduction

Aerobic training has a beneficial effect on enhancing liver functions. Autophagy might potentially play a role in preventing excessive lipid accumulation, regulating oxidative stress, and inflammation in the liver.

Objective

To investigate the potential linking role of autophagy-related gene expressions and protein levels with histopathology changes in Wistar rat livers after treadmill training under different intensities.

Methods

20 rats were divided into 4 groups (control, low intensity, moderate intensity, and high intensity). 8 weeks of treadmill training was conducted with a frequency of 5 days per week, for a duration of 30 min per day. Liver histopathology was studied using hematoxylin-eosin, and oil red O staining. RNA and protein from the liver tissues were extracted to examine the autophagy-related gene (LC3, p62) and protein levels (Beclin, ATG5, LC3, p62). The gene expressions of CPT1a, CD36, FATP 2,3,5, GLUT2, and FGF21 were also studied.

Results

Different intensities of training might potentially modulate autophagy-related gene expressions in rat livers. LC3 and p62 mRNA expressions in moderate and high intensities decreased compared to control. Beclin, ATG5, and LC3 protein level increased compared to control, while p62 protein level decreased compared to control. Whereas for the other genes, we found an increase in CPT1a, but we did not observed any changes in the expression of the other genes. Interestingly, autophagy-related gene expressions might be correlated with the changes of sinusoidal dilatation, cloudy swelling, inflammation, and lipid droplets of the liver tissues.

Conclusion

Moderate and high intensities of training induce autophagy activity, combined with a shift in metabolic zonation in liver that might be potentially correlated with lipophagy. Our results showed the potential interplay role between autophagy and liver histopathology appearances as a part of the adaptation process to training.

The Role of Lipophagy in the Development and Treatment of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) or metabolic (dysfunction) associated liver disease (MAFLD), is, with a global prevalence of 25%, the most common liver disorder worldwide. NAFLD comprises a spectrum of liver disorders ranging from simple steatosis to steatohepatitis, fibrosis, cirrhosis and eventually end-stage liver disease. The cause of NAFLD is multifactorial with genetic susceptibility and an unhealthy lifestyle playing a crucial role in its development. Disrupted hepatic lipid homeostasis resulting in hepatic triglyceride accumulation is an hallmark of NAFLD. This disruption is commonly described based on four pathways concerning 1) increased fatty acid influx, 2) increased de novo lipogenesis, 3) reduced triglyceride secretion, and 4) reduced fatty acid oxidation. More recently, lipophagy has also emerged as pathway affecting NAFLD development and progression. Lipophagy is a form of autophagy (i.e. controlled autolysosomal degradation and recycling of cellular components), that controls the breakdown of lipid droplets in the liver. Here we address the role of hepatic lipid homeostasis in NAFLD and specifically review the current literature on lipophagy, describing its underlying mechanism, its role in pathophysiology and its potential as a therapeutic target.