Melatonin improves non-alcoholic fatty liver disease via MAPK-JNK/P38 signaling in high-fat-diet-induced obese mice

Melatonin partially restores hepatic nocturnin oscillations in experimental models of MASLD

Melatonin, a pleiotropic neurohormone, is recognized for its hepatoprotective role in metabolic dysfunction-associated steatotic liver disease (MASLD) triggered by diet and/or chronodisruption. Nocturnin (Noct), a circadian clock output regulating hepatic lipid metabolism, has an unclear role in MASLD. This study explores circadian oscillations of Noct in MASLD and its synergy with melatonin. Differential gene expression analysis identified key lipogenic genes (HNF-4A and SCD) as targets of Noct enzymatic activity. Male C57BL/6J mice were subjected to high-fat-high-fructose (H) diet with or without chronodisruption (CD) for 16 weeks. Noct mRNA peaked at ZT12 in Control and H groups, while CD and HCD groups showed peaks at ZT6, alongside increased % relative amplitude, cumulative expression, and shifted Centre of Gravity (CoG). Melatonin treatment in H, CD, and HCD groups significantly reduced Noct amplitude and cumulative expression. In OA-treated HepG2 cells, Noct mRNA and protein levels rose at 36 h and 32 h, respectively, with CoG shifts. Melatonin reduced Noct mRNA but increased protein levels while correcting rhythmicity. Collectively, MASLD induces elevation and phase shifts in hepatic Noct expression, and melatonin demonstrates corrective effects on Noct circadian phasing, underscoring its therapeutic potential.   .

Unraveling the triglyceride-glucose index: a key predictor of liver fat content and the amplifying role of BMI: evidence from a large physical examination data

Background

The triglyceride-glucose (TyG) index is associated with the severity of metabolic-associated fatty liver disease (MASLD), but its link to liver fat content is not fully understood. This study investigates the relationship between the TyG index and liver fat content and explores the role of body mass index (BMI) as a mediator.

Methods

This cross-sectional study analyzed data from 12,750 participants who underwent health screenings at the first affiliated hospital of Xinxiang Medical University between January 2018 and December 2023. The TyG index, derived as Ln [triglycerides (mg/dl) * fasting plasma glucose (mg/dl)/2], was the independent variable, while liver fat content, measured by quantitative computed tomography (QCT), was the dependent variable. Participants were grouped into tertiles based on their TyG index. Univariate and multivariate analyses, smooth curve fitting (generalized additive models), threshold effect analysis, and subgroup analyses were used to assess the TyG-liver fat content relationship. BMI's mediating effect was also examined.

Results

Liver fat content increased steadily across TyG index tertiles. After adjusting for confounders, the TyG index remained independently associated with liver fat content [β = 1.42, 95% CI: 1.26-1.57]. Participants in the highest TyG tertile (T3) had a 1.58-fold higher liver fat content compared to those in the lowest tertile (T1) (95% CI: 1.37-1.80, P<0.001). A generalized additive model showed a nonlinear relationship between TyG index and liver fat content. When the TyG index ≤ 7.39, liver fat content increased gradually (β = 0.74, 95% CI: 0.50-0.99, P<0.001). Beyond this threshold, liver fat content rose sharply (β = 2.19, 95% CI: 1.92-2.46, P<0.001). Subgroup analysis indicated that the association between TyG index and liver fat content was stronger at higher BMI levels (P for interaction < 0.001). Mediation analysis revealed that BMI accounted for 26.68% of the observed effect.

Conclusion

The TyG index is positively associated with liver fat content in a nonlinear manner, with BMI amplifying this effect. These results suggest that the TyG index may be a useful marker for predicting liver fat content, and managing weight could help slow the progression of MASLD.

A comparative study on the effect of melatonin and orlistat combination versus orlistat alone on high fat diet-induced hepatic changes in the adult male albino rats (a histological and morphometric study)

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the extremely usual reason of chronic liver disease, extending from simple hepatic steatosis (HS), nonalcoholic steatohepatitis (NASH) to advanced hepatic fibrosis and cirrhosis. Though orlistat is a Food and Drug Administration (FDA) approved drug for long-duration management of obesity, few cases of severe hepatic insult were declared. Melatonin is an efficient antioxidant; it also regulates metabolic processes that lead to fat accumulation and obesity.

AIM OF THE WORK

The current research aimed to compare the impact of orlistat, melatonin, and their combination on the structural changes of the hepatic tissue of adult male albino rats supplied with high fat diet (HFD).

MATERIAL AND METHODS

Thirty adult male albino rats divided into five groups. Liver specimens were divided into two parts. One-half was processed to obtain paraffin blocks, and the other half was processed to obtain semithin sections. Morphometric study and statistical analysis were done.

RESULTS

Hepatic tissue from the HFD group showed steatosis, ballooning, and inflammation and all these parameters were moderately improved - except for inflammation which worsened with therapy. Combined orlistat and melatonin-treated groups showed marked improvement of all parameters as well as marked improvement in the hepatic fibrosis.Orlistat/Melatonin combination therapy is both safe and effective in comparison to orlistat and melatonin monotherapy.

Melatonin-Supplemented Obese Female Mice Show Less Inflammation in Ovarian Adipocytes and Browning in Subcutaneous Adipocytes

We hypothesized that melatonin (Mel) supplementation may offer therapeutic benefits for obesity, particularly in women. Therefore, the study evaluated Mel's effects on white adipose tissue (WAT) in diet-induced obese female mice. Four-week-old C57BL/6 females were assigned to either a control diet (C group) or a high-fat diet (HF group) for 6 weeks (n = 20/group). Following this, Mel was administered (10 mg/kg/day) for 8 weeks (n = 10/group), resulting in four groups: C, CMel, HF, and HFMel. The HF group developed obesity. HFMel displayed reduced fat pad size, lower plasma insulin, and improved glucose tolerance and insulin resistance compared to HF. In ovarian WAT (oWAT), HFMel versus HF showed reduced pro-inflammatory markers, less endoplasmic reticulum (ER) stress, and smaller adipocyte size. In subcutaneous WAT (sWAT), HFMel versus HF demonstrated increased adipocyte multiloculation, higher uncoupling protein-1 expression, and elevated thermogenic gene expression. Principal component analysis of gene expressions in oWAT and sWAT revealed significant differences: in oWAT, ER stress and inflammation markers were linked to the HF group, while HFMel and CMel clustered together, indicating a beneficial Mel effect. In sWAT, HFMel and CMel clustered on the opposite side of HF, which is associated with thermogenic gene expressions. In conclusion, the findings demonstrate that Mel supplementation in obese female mice, even when maintained on an HF diet, effectively modulated weight gain and reduced ovarian and subcutaneous fat accumulation. Mel supplementation positively influenced insulin resistance, inflammation, and ER stress while promoting thermogenesis in WAT in obese female mice.

Disruption of Melatonin Signaling Leads to Lipids Accumulation in the Liver of Melatonin Proficient Mice

Melatonin signaling via melatonin receptor type 1 (MT1) and type 2 (MT2) plays an important role in the regulation of several physiological functions. Studies in rodents and humans have demonstrated that disruption of melatonin signaling may affect glucose metabolism, insulin sensitivity, and leptin levels. Accumulating experimental evidence also indicates that in rodents the administration of exogenous melatonin has a beneficial effect on the blood lipid levels. However, the molecular mechanism by which melatonin signaling may regulate lipids is still unclear. In addition, most of the studies with mice have been performed in melatonin-deficient mice by administering exogenous melatonin at supraphysiological doses. Hence the results of these studies may be greatly affected by these two factors. In this study, we report the effects of melatonin signaling removal on the liver biology and transcriptome using melatonin-proficient mice (C3H-f+/f+) in which MT1 or MT2 have been genetically ablated. Our data indicate that the absence of MT1 or MT2 signaling leads to disruption of the blood lipids profile and an increase in lipids deposition in the liver. These effects were more pronounced in the mice lacking MT1 than MT2. The gene expression profiles obtained with RNA-seq from the livers of the three genotypes revealed that removal of MT1 affected the transcription of 4255 genes (i.e., 40.6%). Conversely, the removal of MT2 affected the transcription of 1864 transcripts (i.e., 17.2%). Finally, we identified a group of 13 genes involved in lipids biology that may play a key role in the accumulation of lipids in the liver when melatonin signaling is disrupted. In conclusion, our study indicates that melatonin signaling is an important modulator of liver physiology and metabolism. Our study also indicated that the removal of MT1 signaling is more deleterious than MT2 removal.

Therapeutic applications of melatonin in disorders related to the gastrointestinal tract and control of appetite

Most animals have large amounts of the special substance melatonin, which is controlled by the light/dark cycle in the suprachiasmatic nucleus. According to what is now understood, the gastrointestinal tract (GIT) and other areas of the body are sites of melatonin production. According to recent studies, the GIT and adjacent organs depend critically on a massive amount of melatonin. Not unexpectedly, melatonin's many biological properties, such as its antioxidant, anti-inflammatory, pro-apoptotic, anti-proliferative, anti-metastasis, and antiangiogenic properties, have drawn the attention of researchers more and more. Because melatonin is an antioxidant, it produces a lot of secretions in the GIT's mucus and saliva, which shields cells from damage and promotes the development of certain GIT-related disorders. Melatonin's ability to alter cellular behavior in the GIT and other associated organs, such as the liver and pancreas, is another way that it functions. This behavior alters the secretory and metabolic activities of these cells. In this review, we attempted to shed fresh light on the many roles that melatonin plays in the various regions of the gastrointestinal tract by focusing on its activities for the first time.

Therapeutic potential of traditional Chinese medicine in the prevention and treatment of digestive inflammatory cancer transformation: Portulaca oleracea L. as a promising drug

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine (TCM) has been used for centuries to treat various types of inflammation and tumors of the digestive system. Portulaca oleracea L. (POL), has been used in TCM for thousands of years. The chemical composition of POL is variable and includes flavonoids, alkaloids, terpenoids and organic acids and other classes of natural compounds. Many of these compounds exhibit powerful anti-inflammatory and anti-cancer-transforming effects in the digestive system.

AIM OF STUDY

In this review, we focus on the potential therapeutic role of POL in NASH, gastritis and colitis and their associated cancers, with a focus on the pharmacological properties and potential mechanisms of action of the main natural active compounds in POL.

METHODS

The information and data on Portulaca oleracea L. and its main active ingredients were collated from various resources like ethnobotanical textbooks and literature databases such as CNKI, VIP (Chinese literature), PubMed, Science Direct, Elsevier and Google Scholar (English literatures), Wiley, Springer, Tailor and Francis, Scopus, Inflibnet.

RESULTS

Kaempferol, luteolin, myricetin, quercetin, genistein, EPA, DHA, and melatonin were found to improve NASH and NASH-HCC, while kaempferol, apigenin, luteolin, and quercetin played a therapeutic role in gastritis and gastric cancer. Apigenin, luteolin, myricetin, quercetin, genistein, lupeol, vitamin C and melatonin were found to have therapeutic effects in the treatment of colitis and its associated cancers. The discovery of the beneficial effects of these natural active compounds in POL supports the idea that POL could be a promising novel candidate for the treatment and prevention of inflammation-related cancers of the digestive system.

CONCLUSION

The discovery of the beneficial effects of these natural active compounds in POL supports the idea that POL could be a promising novel candidate for the treatment and prevention of inflammation-related cancers of the digestive system. However, clinical data describing the mode of action of the naturally active compounds of POL are still lacking. In addition, pharmacokinetic data for POL compounds, such as changes in drug dose and absorption rates, cannot be extrapolated from animal models and need to be measured in patients in clinical trials. On the one hand, a systematic meta-analysis of the existing publications on TCM containing POL still needs to be carried out. On the other hand, studies on the hepatic and renal toxicity of POL are also needed. Additionally, well-designed preclinical and clinical studies to validate the therapeutic effects of TCM need to be performed, thus hopefully providing a basis for the validation of the clinical benefits of POL.

Melatonin supplementation in obese mothers reduces hypothalamic inflammation and enhances thermogenesis in mice progeny

Maternal obesity might induce obesity and metabolic alterations in the progeny. The study aimed to determine the effect of supplementing obese mothers with Mel (Mel) on thermogenesis and inflammation. C57BL/6 female mice (mothers) were fed from weaning to 12 weeks control diet (C, 17% kJ as fat) or a high-fat diet (HF, 49% kJ as fat) and then matted with male mice fed the control diet. Melatonin (10 mg/kg daily) was supplemented to mothers during gestation and lactation, forming the groups C, CMel, HF, and HFMel (n = 10/group). Twelve-week male offspring were studied (plasma biochemistry, immunohistochemistry, protein, and gene expressions at the hypothalamus - Hyp, subcutaneous white adipose tissue - sWAT, and interscapular brown adipose tissue - iBAT). Comparing HFMel vs. HF offspring, fat deposits and plasmatic proinflammatory markers decreased. Also, HFMel showed decreased Hyp proinflammatory markers and neuropeptide Y (anabolic) expression but improved proopiomelanocortin (catabolic) expression. Besides, HFMel sWAT adipocytes changed to a beige phenotype with-beta-3 adrenergic receptor and uncoupling protein-1 activation, concomitant with browning genes activation, triggering the iBAT thermogenic activity. In conclusion, compelling evidence indicated the beneficial effects of supplementing obese mothers with Mel on the health of their mature male offspring. Mel led to sWAT browning-related gene enhancement, increased iBAT thermogenis, and mitigated hypothalamic inflammation. Also, principal component analysis of the data significantly separated the untreated obese mother progeny from the progeny of treated obese mothers. If confirmed in humans, the findings encourage a future guideline recommending Mel supplementation during pregnancy and breastfeeding.

12-week melatonin administration had no effect on diabetes risk markers and fat intake in overweight women night workers

Introduction

Interactions between circadian clocks and key mediators of chronic low-grade inflammation associated with fat consumption may be important in maintaining metabolic homeostasis and may pose a risk for the development of obesity-associated comorbidities, especially type 2 diabetes (T2DM).

Objective

The aims of the present study were to evaluate the effects of melatonin administration on diabetes risk markers according to dietary lipid profile (pro-inflammatory versus anti-inflammatory) in excessive weight night workers, and to determine the effect of administration on fat consumption profile.

Methods

A randomized, controlled, double-blind, crossover clinical trial involving 27 nursing professionals working permanent night shifts under a 12×36-hour system. The melatonin group (12 weeks) used synthetic melatonin (3 mg) only on days off and between shifts, while the placebo group (12 weeks) was instructed to take a placebo, also on days off and between shifts. For inflammatory characteristics, participants were divided into pro-inflammatory (saturated fats, trans fats and cholesterol) and anti-inflammatory (monounsaturated, polyunsaturated fats and EPA + DHA) groups according to fatty acid determinations. At baseline and at the end of each phase, blood glucose, insulin, glycosylated hemoglobin plasma concentrations were collected, and HOMA-IR was calculated.

Conclusion

Melatonin administration for 12 weeks had no effect on T2DM risk markers according to dietary lipid profile (pro-inflammatory or anti-inflammatory potential) in excessive weight night workers. Among the limitations of the study include the fact that the low dose may have influenced the results expected in the hypothesis, and individual adaptations to night work were not evaluated. The insights discussed are important for future research investigating the influence of melatonin and fats considered anti- or pro-inflammatory on glucose and insulin homeostasis related to night work.

Role of Mitogen-Activated Protein (MAP) Kinase Pathways in Metabolic Diseases

Physiological processes that govern the normal functioning of mammalian cells are regulated by a myriad of signalling pathways. Mammalian mitogen-activated protein (MAP) kinases constitute one of the major signalling arms and have been broadly classified into four groups that include extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), p38, and ERK5. Each signalling cascade is governed by a wide array of external and cellular stimuli, which play a critical part in mammalian cells in the regulation of various key responses, such as mitogenic growth, differentiation, stress responses, as well as inflammation. This evolutionarily conserved MAP kinase signalling arm is also important for metabolic maintenance, which is tightly coordinated via complicated mechanisms that include the intricate interaction of scaffold proteins, recognition through cognate motifs, action of phosphatases, distinct subcellular localisation, and even post-translational modifications. Aberration in the signalling pathway itself or their regulation has been implicated in the disruption of metabolic homeostasis, which provides a pathophysiological foundation in the development of metabolic syndrome. Metabolic syndrome is an umbrella term that usually includes a group of closely associated metabolic diseases such as hyperglycaemia, hyperlipidaemia, and hypertension. These risk factors exacerbate the development of obesity, diabetes, atherosclerosis, cardiovascular diseases, and hepatic diseases, which have accounted for an increase in the worldwide morbidity and mortality rate. This review aims to summarise recent findings that have implicated MAP kinase signalling in the development of metabolic diseases, highlighting the potential therapeutic targets of this pathway to be investigated further for the attenuation of these diseases.

Melatonin as a Repairing Agent in Cadmium- and Free Fatty Acid-Induced Lipotoxicity

(1) Background: Cadmium (Cd) is a potentially toxic element with a long half-life in the human body (20-40 years). Cytotoxicity mechanisms of Cd include increased levels of oxidative stress and apoptotic signaling, and recent studies have suggested that these aspects of Cd toxicity contribute a role in the pathobiology of non-alcoholic fatty liver disease (NAFLD), a highly prevalent ailment associated with hepatic lipotoxicity and an increased generation of reactive oxygen species (ROS). In this study, Cd toxicity and its interplay with fatty acid (FA)-induced lipotoxicity have been studied in intestinal epithelium and liver cells; the cytoprotective function of melatonin (MLT) has been also evaluated. (2) Methods: human liver cells (HepaRG), primary murine hepatocytes and Caco-2 intestinal epithelial cells were exposed to CdCl2 before and after induction of lipotoxicity with oleic acid (OA) and/or palmitic acid (PA), and in some experiments, FA was combined with MLT (50 nM) treatment. (3) Results: CdCl2 toxicity was associated with ROS induction and reduced cell viability in both the hepatic and intestinal cells. Cd and FA synergized to induce lipid droplet formation and ROS production; the latter was higher for PA compared to OA in liver cells, resulting in a higher reduction in cell viability, especially in HepaRG and primary hepatocytes, whereas CACO-2 cells showed higher resistance to Cd/PA-induced lipotoxicity compared to liver cells. MLT showed significant protection against Cd toxicity either considered alone or combined with FFA-induced lipotoxicity in primary liver cells. (4) Conclusions: Cd and PA combine their pro-oxidant activity to induce lipotoxicity in cellular populations of the gut-liver axis. MLT can be used to lessen the synergistic effect of Cd-PA on cellular ROS formation.

Melatonin targets ferroptosis through bimodal alteration of redox environment and cellular pathways in NAFLD model

Ferroptosis is a non-conventional cellular death caused by lipid peroxide induced iron deposition. Intracellular lipid accumulation followed by generation of lipid peroxides is an hallmark of non-alcoholic fatty liver disease (NAFLD). Melatonin (MLT) is an important pineal hormone with tremendous antioxidant and anti-inflammatory properties. Various studies targeted ferroptosis in different diseases using melatonin. However, none of them focused the intrinsic mechanism of MLT's action to counteract ferroptosis in NAFLD. Hence, the present study investigated the role of MLT in improvement of NAFLD-induced ferroptosis. HepG2 cells were treated with free fatty acids (FFAs) to induce in vitro NAFLD state and C57BL/6 mice were fed with high-fat diet (HFD) followed by MLT administration. The results indicated that MLT administration caused the recovery from both FFA- and HFD-induced ferroptotic state via increasing GSH and SOD level, decreasing lipid reactive oxygen species (ROS) and malondialdehyde (MDA) level, increasing Nrf2 and HO-1 level to defend cells against an oxidative environment. MLT also altered the expression of two key proteins GPX4 and SLC7A11 back to their normal levels, which would otherwise cause ferroptosis. MLT also protected against histopathological damage of both liver tissue and HepG2 cells as depicted by Oil Red O, HE staining and immunofluorescence microscopy. MLT also had control over pAMPKα as well as PPARγ and PPARα responsible for lipid homeostasis and lipogenesis. In brief, MLT exerted its multifaceted effect in FFA- and HFD-induced NAFLD by retrieving cellular oxidative environment, reducing lipogenesis and lipid peroxidation and modulating Nrf2/HO-1 and GPX4/SLC7A11 axis to combat ferroptosis.

Melatonin Ameliorates Hepatic Ferroptosis in NAFLD by Inhibiting ER Stress via the MT2/cAMP/PKA/IRE1 Signaling Pathway

Ferroptosis, an iron-dependent cell death form, has recently been observed in the development of non-alcoholic fatty liver disease (NAFLD). Melatonin (Mel) shows potential benefits for preventing and treating liver diseases. Whether and how Mel ameliorates hepatic ferroptosis in NAFLD is not fully understood. Here we established a mouse model of NAFLD induced by long-term high-fat diet (HFD) feeding. We found that Mel treatment ameliorated global metabolic abnormalities and inhibited the progression of NAFLD in mice. Most importantly, Mel supplementation significantly improved HFD-induced iron homeostasis disorders in the liver, including iron overload and ferritin transport disorders. For another, Mel ameliorated HFD-induced hepatic lipid peroxidation. The recuperative role of exogenous Mel on hepatocyte ferroptosis was also observed in PA- or Erastin-treated HepG2 cells. Mechanistically, MT2, but not MT1, was involved in the effect of Mel. Furthermore, Mel treatment inhibited HFD or Erastin-activated ER stress and activated the PKA/IRE1 signaling pathway. Co-expression of p-PKA and p-IRE1 was enhanced by the MT2 antagonist. Inhibitions of PKA and IRE1 respectively improved hepatocyte ferroptosis, and activations of cAMP/PKA reversed Mel's effect on ferroptosis. Collectively, these findings suggest that exogenous Mel inhibits hepatic ferroptosis in NAFLD by ameliorating ER stress through the MT2/cAMP/PKA/IRE1 pathway, proving that Mel is a promising candidate drug for the treatment of hepatic ferroptosis in NAFLD.

Experimental Data on the Role of Melatonin in the Pathogenesis of Nonalcoholic Fatty Liver Disease

Despite the increasing prevalence of nonalcoholic fatty liver disease (NAFLD) worldwide, its complex pathogenesis remains incompletely understood. The currently stated hypotheses cannot fully clarify the interrelationships between individual pathogenetic mechanisms of the disease. No appropriate health strategies have been developed for treating NAFLD. NAFLD is characterized by an accumulation of triglycerides in hepatic cells (steatosis), with the advanced form known as nonalcoholic steatohepatitis. In the latter, superimposed inflammation can lead to fibrosis. There are scientific data on NAFLD's association with components of metabolic syndrome. Hormonal factors are thought to play a role in the development of metabolic syndrome. Endogenous melatonin, an indoleamine hormone synthesized by the pineal gland mainly at night, is a powerful chronobiotic that probably regulates metabolic processes and has antioxidant, anti-inflammatory, and genomic effects. Extrapineal melatonin has been found in various tissues and organs, including the liver, pancreas, and gastrointestinal tract, where it likely maintains cellular homeostasis. Melatonin exerts its effects on NAFLD at the cellular, subcellular, and molecular levels, affecting numerous signaling pathways. In this review article, we discuss the experimental scientific data accumulated on the involvement of melatonin in the intimate processes of the pathogenesis of NAFLD.

Anti-Angiogenic Effects of Natural Compounds in Diet-Associated Hepatic Inflammation

Alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) are the most common causes of chronic liver disease and are increasingly emerging as a global health problem. Such disorders can lead to liver damage, resulting in the release of pro-inflammatory cytokines and the activation of infiltrating immune cells. These are some of the common features of ALD progression in ASH (alcoholic steatohepatitis) and NAFLD to NASH (non-alcoholic steatohepatitis). Hepatic steatosis, followed by fibrosis, lead to a continuous progression accompanied by angiogenesis. This process creates hypoxia, which activates vascular factors, initiating pathological angiogenesis and further fibrosis. This forms a vicious cycle of ongoing damage and progression. This condition further exacerbates liver injury and may contribute to the development of comorbidities, such as metabolic syndrome as well as hepatocellular carcinoma. Increasing evidence suggests that anti-angiogenic therapy may have beneficial effects on these hepatic disorders and their exacerbation. Therefore, there is a great interest to deepen the knowledge of the molecular mechanisms of natural anti-angiogenic products that could both prevent and control liver diseases. In this review, we focus on the role of major natural anti-angiogenic compounds against steatohepatitis and determine their potential therapeutic benefits in the treatment of liver inflammation caused by an imbalanced diet.

Role of targeting TLR4 signaling axis in liver-related diseases

Toll-like receptor 4 (TLR4) plays an important role as a key signal-receiving transmembrane protein molecule in the liver, and substances that target the liver exert therapeutic effects via TLR4-related signaling pathways. This article provides a comprehensive review of targeting the TLR4 signaling axis to play an important role in the liver based on endogenous substances. Articles were divided into 5 major types of liver disease, acute liver injury, viral hepatitis, alcoholic and non-alcoholic liver disease, cirrhosis, and liver cancer, to elucidate how various endogenous substances affect the liver via the TLR4 pathway and the important role of the pathway itself in liver-related diseases to discover the potential therapeutic implications of the TLR4-related pathway in the liver. The results indicate that activation of the TLR4-related signaling axis primarily plays a role in promoting disease progression in liver-related diseases, and the TLR4/MyD88/NF-κB axis plays the most dominant role. Therefore, exploring the full effects of drugs targeting the TLR4-related signaling axis in the liver and the new use of old drugs may be a new research direction.

Melatonin alleviates alcoholic liver disease via EGFR-BRG1-TERT axis regulation

Chronic alcohol consumption causes liver steatosis, cell death, and inflammation. Melatonin (MLT) is reported to alleviate alcoholic liver disease (ALD)-induced injury. However, its direct regulating targets in hepatocytes are not fully understood. In the current study, a cell-based screening model and a chronic ethanol-fed mice ALD model were used to test the protective mechanisms of MLT. MLT ameliorated ethanol-induced hepatocyte injury in both cell and animal models (optimal doses of 10 μmol/L and 5 mg/kg, respectively), including lowered liver steatosis, cell death, and inflammation. RNA-seq analysis and loss-of-function studies in AML-12 cells revealed that telomerase reverse transcriptase (TERT) was a key downstream effector of MLT. Biophysical assay found that epidermal growth factor receptor (EGFR) on the hepatocyte surface was a direct binding and regulating target of MLT. Liver specific knock-down of Tert or Egfr in the ALD mice model impaired MLT-mediated liver protection, partly through the regulation of nuclear brahma-related gene-1 (BRG1). Long-term administration (90 days) of MLT in healthy mice did not cause evident adverse effect. In conclusion, MLT is an efficacious and safe agent for ALD alleviation. Its direct regulating target in hepatocytes is EGFR and downstream BRG1-TERT axis. MLT might be used as a complimentary agent for alcoholics.

Adult mice offspring of obese mothers supplemented with melatonin show lessened liver steatosis, inflammation, oxidative stress, and endoplasmic reticulum stress

AIMS

To investigate, in the liver of adult offspring, the possible effects of melatonin supplementation in the obese mother during pregnancy and lactation.

MAIN METHODS

C57BL/6 females were fed with a control (C) or a high-fat (HF) diet and supplemented with melatonin (Mel) during the pregnancy and lactation, forming the groups: C, CMel, HF, and HFMel. After weaning until three months old, the offspring only received the C diet.

KEY FINDINGS

The HF mothers and their offspring showed higher body weight (BW) than the C mothers and offspring. However, at 3-mo-old, BW was reduced in HFMel vs. HF offspring. Also, plasmatic and liver lipid markers increased in HF vs. C offspring but were reduced in HFMel vs. HF offspring. Liver lipid content was lessened in HFMel vs. HF offspring by 50 %. Also, lipid metabolism, pro-inflammatory and endoplasmic reticulum (ER) stress genes were higher expressed in HF vs. C offspring but reduced in HFMel vs. HF offspring. Contrarily, beta-oxidation and antioxidant enzyme genes were less expressed in HF vs. C offspring but improved in HFMel vs. HF offspring. Finally, AMPK/mTOR pathway genes, initially dysregulated in the HF, were restored in the HFMel offspring.

SIGNIFICANCE

The obese mother leads to liver alterations in the offspring. Current findings demonstrated the maternal melatonin supplementation during pregnancy and lactation in adult offspring's liver. Consequently, the effects were seen in mitigating the liver's AMPK/mTOR pathway genes, lipogenesis, beta-oxidation, inflammation, oxidative stress, and ER stress, preventing liver disease progression in the offspring.

Effects of melatonin on intestinal function and bacterial compositions in sucking piglets

Melatonin has been reported to affect intestinal function by targeting microbiome, morphological structure, barrier integrity and nutrient absorptive system. While the effect of melatonin on intestinal development in newborn infants is obscure, thus, this study firstly attempted to investigate the hypothesis that melatonin treatment improves intestinal development in sucking piglets. 14 healthy newborn piglets received 10 ml melatonin solution (1 mg/ml) or drinking water (n = 7) for 21 days. The results showed that oral administration of melatonin increased liver relative weight (p < 0.05) but failed to affect growth performance in sucking piglets (p > 0.05). Immunostaining jejunal samples from melatonin group showed high expressions of nnos and claudin1, indicating that melatonin improved intestinal neural development and barrier integrity. Also, melatonin promoted intestinal absorptive function evidenced by the increased serum proline concentration in melatonin-treated piglets compared with the control (p < 0.05). Gut microbiota compositions were tested by 16S rDNA sequencing and the results showed that melatonin increased the relative abundance of Actinobacteria compared with the control (p < 0.05) at the phylum level. However, Selenomonadales was markedly reduced compared with the control at the order level (p < 0.05). Gut and faecal volatile fatty acids were tested to evaluate the microbiota metabolism, but no difference was noticed in volatile fatty acid concentrations (p > 0.05). Melatonin improved intestinal development by affecting neural development, barrier integrity, nutrient absorption and microbiota in sucking piglets.

Identification of a novel probiotic and its protective effects on NAFLD via modulating gut microbial community

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is becoming the most common progressive liver diseases. Therapeutic strategy based on gut-liver axis and probiotics is a promising approach for the treatment of NAFLD. However, rare probiotics have been applied in NAFLD treatment, and the involved molecular mechanism is not entirely clear.

RESULTS

We initially identified a novel functional probiotic, Lactobacillus kefiranofaciens ZW3, on the lipid deposition by a simple and rapid zebrafish model. Supplementation with ZW3 to the methionine and choline deficient (MCD) diet induced NAFLD rats could improve the liver impairments and reduce inflammation through TLR4-MyD88 and JNK signaling pathways. Moreover, ZW3 modulated gut microbiota by promoting relative abundance of Firmicutes and Lactobacillus, decreasing the abundance of Escherichia-Shigella and Bacteroides. Functional prediction of microbiome showed ZW3 presented potential enhancement on carbohydrate and lipid metabolism, cell process control and signal transduction processes, and reduced several human diseases.

CONCLUSION

This present study identified a novel probiotic and its protective effects on NAFLD, and interpreted the interactions of ZW3 with the immune system and gut microbiota involved in gut-liver axis. © 2022 Society of Chemical Industry.

Breviscapine alleviates NASH by inhibiting TGF-β-activated kinase 1-dependent signaling

BACKGROUND AND AIMS

NAFLD is a key component of metabolic syndrome, ranging from nonalcoholic fatty liver to NASH, and is now becoming the leading cause of cirrhosis and HCC worldwide. However, due to the complex and unclear pathophysiological mechanism, there are no specific approved agents for treating NASH. Breviscapine, a natural flavonoid prescription drug isolated from the traditional Chinese herb Erigeron breviscapus, exhibits a wide range of pharmacological properties, including effects on metabolism. However, the anti-NASH efficacy and mechanisms of breviscapine have not yet been characterized.

APPROACH AND RESULTS

We evaluated the effects of breviscapine on the development of hepatic steatosis, inflammation, and fibrosis in vivo and in vitro under metabolic stress. Breviscapine treatment significantly reduced lipid accumulation, inflammatory cell infiltration, liver injury, and fibrosis in mice fed a high-fat diet, a high-fat/high-cholesterol diet, or a methionine- and choline-deficient diet. In addition, breviscapine attenuated lipid accumulation, inflammation, and lipotoxicity in hepatocytes undergoing metabolic stress. RNA-sequencing and multiomics analyses further indicated that the key mechanism linking the anti-NASH effects of breviscapine was inhibition of TGF-β-activated kinase 1 (TAK1) phosphorylation and the subsequent mitogen-activated protein kinase signaling cascade. Treatment with the TAK1 inhibitor 5Z-7-oxozeaenol abrogated breviscapine-mediated hepatoprotection under metabolic stress. Molecular docking illustrated that breviscapine directly bound to TAK1.

CONCLUSION

Breviscapine prevents metabolic stress-induced NASH progression through direct inhibition of TAK1 signaling. Breviscapine might be a therapeutic candidate for the treatment of NASH.

Melatonin Suppresses NLRP3 Inflammasome Activation via TLR4/NF-κB and P2X7R Signaling in High-Fat Diet-Induced Murine NASH Model

Background

NLRP3 inflammasome activation plays a critical role in mediating inflammation and NASH (non-alcoholic steatohepatitis) progression that ultimately leads to cirrhosis and hepatocellular carcinoma. Melatonin (MLT) controls high-fat diet-induced NASH in the murine model by modulating NLRP3 mediated inflammation. P2X7R-mediated inflammasome activation is reported in several inflammatory models including NASH.

Objective

The role of MLT in P2X7R-mediated inflammation in the NASH model has not yet been explored. The present study investigated the role of MLT in amending high-fat diet-induced nonalcoholic steatohepatitis in the murine liver.

Methods

To evaluate the hepatological changes, mice were divided into four groups to investigate the improvement potential of this MLT (10 and 20 mg/kg) and to assess the experimental findings. Histology, biochemical assays, ELISA, FACS analysis, Western blotting, and IF were performed to assess the physical and molecular changes upon melatonin treatment.

Results

The result demonstrated that MLT administration reduced HFD (high-fat diet)-induced non-alcoholic steatohepatitic indices, which successively restored the hepatic morphological architecture and other pathophysiological features too. Moreover, the application of MLT suppressed HFD-induced activation of the inflammasome and through TLR4/NF-κB signaling. Herein, we report that MLT significantly suppresses P2X7R expression and calcium influx along with inflammasome in both in vitro and in vivo. The docking study revealed a strong binding affinity of MLT with P2X7R. Moreover, the results also showed that the Nrf2 level was boosted which may normalize the expression of antioxidant proteins that safeguard against oxidative damage triggered by inflammation. Furthermore, some matrix metalloproteinases like MMP 2 and MMP 9 were repressed and TIMP-1 level was increased, which also signifies that MLT could improve liver fibrosis in this model.

Conclusion

Based on our findings, this study may conclude that MLT could be used as a therapeutic agent in the high-fat diet-induced NASH model as it has persuasive anti-inflammatory potential.

Osteocalcin reduces fat accumulation and inflammatory reaction by inhibiting ROS-JNK signal pathway in chicken embryonic hepatocytes

Osteocalcin (OCN) has a function in preventing fatty liver hemorrhagic syndrome (FLHS) in poultry. The aim of this study was to investigate the effects of OCN on fat emulsion stimulated chicken embryonic hepatocytes and related signaling pathways. The primary chicken embryonic hepatocytes were isolated from the incubated 15-day (E15) pathogen free eggs and cultured with dulbecco's modified eagle medium (DMEM). After the hepatocyte density reached 80%, the cells were divided into 5 groups: control group (CONT), fat emulsion group (FE, 10% FE, v/v), FE with ucOCN at 1 ng/mL (FE-LOCN), 3 ng/mL (FE-MOCN), and 9 ng/mL (FE-HOCN). In addition, 2 mM N-Acetyl-L-cysteine (NAC) a reactive oxygen species (ROS) scavenger, and 5 μM SP600125, a Jun N-terminal kinase (JNK) inhibitor, were added separately in to the DMEM with 10% FE to test effects of FE on the function of ROS-JNK signal pathway. The number of hepatocytes, cell ultra-microstructure, viability, and apoptosis were detected after 48 h treatment, and the protein expressions and enzyme concentrations were detected after 72 h treatment. The results showed that, compared to the control group, FE increased the triglyceride (TG) concentration and lipid droplets (LDs) in chicken embryonic hepatocytes (P < 0.05), and induced hepatocytic edema with obviously mitochondrial swelling, membrane damage, and cristae rupture. FE also decreased ATP concentration, increased ROS concentrations and mitochondrial DNA (mtDNA) copy number, promoted inflammatory interleukin-1 (IL-1), IL-6, tumor necrosis factor-alpha (TNF-α) concentrations and hepatocytic apoptosis rate, and raised phospho-c-Jun N-terminal kinase (p-JNK) protein expressions. Compared to the FE group, ucOCN significantly increased hepatocyte viability, reduced hepatocytic TG concentrations and LDs numbers, and alleviated hepatocytic edema and mitochondrial swelling. Furthermore, ucOCN significantly decreased ROS concentrations, increased ATP concentrations, reduced IL-1, IL-6, TNF-α concentrations and hepatocytic apoptosis rate, and inhibited p-JNK protein expressions (P < 0.05). NAC had the similar functions of ucOCN reduced the ROS concentration and inhibited the TNF-α protein expression and p-JNK/JNK ration. Similarly, SP600125 reduced p-JNK/JNK protein expression, IL-1, IL-6, TNF-α, and TG concentrations without effects on ROS concentration and hepatocytic apoptosis. These results suggest that ucOCN alleviates FE-induced mitochondrial damage, cellular edema, and apoptosis of hepatocytes. These results reveal that the functions of ucOCN in reducing fat accumulation and inflammatory reaction in chicken embryonic hepatocytes are mostly via inhibiting the ROS-JNK signal pathway.

Update of Indoles: Promising molecules for ameliorating metabolic diseases

Obesity and metabolic disorders have gradually become public health-threatening problems. The metabolic disorder is a cluster of complex metabolic abnormalities which are featured by dysfunction in glucose and lipid metabolism, and results from the increasing prevalence of visceral obesity. With the core driving factor of insulin resistance, metabolic disorder mainly includes type 2 diabetes mellitus (T2DM), micro and macro-vascular diseases, non-alcoholic fatty liver disease (NAFLD), dyslipidemia, and the dysfunction of gut microbiota. Strategies and therapeutic attention are demanded to decrease the high risk of metabolic diseases, from lifestyle changes to drug treatment, especially herbal medicines. Indole is a parent substance of numerous bioactive compounds, and itself can be produced by tryptophan catabolism to stimulate glucagon-like peptide-1 (GLP-1) secretion and inhibit the development of obesity. In addition, in heterocycles drug discovery, the indole scaffold is primarily found in natural compounds with versatile biological activity and plays a prominent role in drug molecules synthesis. In recent decades, plenty of natural or synthesized indole deriviatives have been investigated and elucidated to exert effects on regulating glucose hemeostasis and lipd metabolism. The aim of this review is to trace and emphasize the compounds containing indole scaffold that possess immense potency on preventing metabolic disorders, particularly T2DM, obesity and NAFLD, along with the underlying molecular mechanisms, therefore facilitate a better comprehension of their druggability and application in metabolic diseases.

Melatonin Alleviates Liver Fibrosis by Inhibiting Autophagy

OBJECTIVE

Melatonin has been reported to suppress inflammation and alleviate liver fibrosis, but its effect on autophagy in liver fibrosis has not been studied. This study investigated the effect of melatonin on autophagy in an animal model of liver fibrosis and the hepatic stellate cell (HSC)-T6 cell line.

METHODS

The model was established in rats through carbon tetrachloride treatment, and melatonin was administered at three doses (2.5, 5.0, and 10.0 mg/kg). Haematoxylin and eosin staining and Van Gieson's staining were performed to examine the pathological changes of liver. The expression of alpha-smooth muscle actin (α-SMA) and Beclin1 in liver tissues was detected by immunohistochemical staining. The protein levels of α-SMA, Beclin1 and LC3 in the animal model were detected by Western blot analysis, and gene levels of Beclin1 and LC3 were detected by quantitative real-time PCR (qRT-PCR) in the animal model. HSC-T6 cells were activated by platelet-derived growth factor-BB (PDGF-BB). The expression of α-SMA, Beclin1 and collagen I was detected by Western blot analysis, and the gene expression of Beclin1 and LC3 was detected by qRT-PCR.

RESULTS

Melatonin reduced the expression of α-SMA, Beclin1 and LC3 in liver tissues. In addition, melatonin inhibited the activation of HSC-T6 cells and the expression of α-SMA, Beclin1 and LC3 in these cells. These results revealed that melatonin could inhibit autophagy and HSC activation.

CONCLUSION

Melatonin might ameliorate liver fibrosis by regulating autophagy, suggesting that melatonin is a potential therapeutic agent for liver fibrosis.

Dexmedetomidine attenuates acute stress-induced liver injury in rats by regulating the miR-34a-5p/ROS/JNK/p38 signaling pathway

Dexmedetomidine (DEX) protects against acute stress-induced liver injury, but what's less clear lies in the specific mechanism. To elucidate the specific mechanism underlying DEX on acute stress-induced liver injury, an in vivo model was constructed on rats with acute stress-induced liver injury by 15 min of exhaustive swimming and 3 hr of immobilization. DEX (30 μg/kg) or miR-34a-5p agomir was injected into model rats. Open field test was used to verify the establishment of the model. Liver injury was observed by hematoxylin-eosin (H&E) staining. Contents of norepinephrine (NE), alanine aminotransfease (ALT) and aspartate aminotransferase (AST) in serum of rats were detected by enzyme-linked immunosorbent assay (ELISA) and those of oxidative stress markers (reactive oxygen species (ROS), Malondialdehyde (MDA), Glutathione (GSH), Superoxide Dismutase (SOD) and Glutathione Peroxidase (GPX)) were measured using commercial kits. Apoptosis of hepatocytes was detected by Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. Western blot was performed to detect the expressions of SOD2, COX-2, cytochrome C, Cleaved caspase 3, Bax, Bcl-2, P-JNK, JNK, P-p38, p38 and c-AMP, p-PKA and PKA in liver tissues. As a result, liver injury in model rat was alleviated by DEX. DEX attenuated the increase in the levels of NE, ALT, AST, MDA, ROS, apoptosis, SOD2, COX-2, Cytochrome C, cleaved caspase 3, Bax, and P-JNK, P-p38, c-AMP, P-PKA and miR-34a-5p, and the decrease in the levels of SOD, GPX, GSH and Bcl-2 in model rats. Furthermore, miR-34a-5p overexpression could partly reverse the effects of DEX. Collectively, DEX could alleviate acute stress-induced liver injury through ROS/JNK/p38 signaling pathway via downregulation of miR-34a-5p.

Melatonin as an antioxidant agent in disease prevention: A biochemical focus

Abstract:

In the recent years, free radicals and oxidative stress have been found to be associated with aging, cancer, atherosclerosis, neurodegenerative disorders, diabetes, and inflammatory diseases. Confirming the role of oxidants in numerous pathological situations including cancer, developing antioxidants as therapeutic platforms is needed. It has been well established that melatonin and its derived metabolites function as endogenous free-radical scavengers and broad spectrum antioxidants. To achieve this function, melatonin can directly detoxify reactive oxygen and reactive nitrogen species and indirectly overexpress antioxidant enzymes while suppressing the activity of pro-oxidant enzymes. Many investigations have also confirmed the role of melatonin and its derivatives in different physiological processes and therapeutic functions such as controlling the circadian rhythm and immune functions. This review aimed to focus on melatonin as a beneficial agent for the stimulation of antioxidant enzymes and inhibition of lipid peroxidation and to evaluate its contribution to protection against oxidative damages. In addition, the clinical application of melatonin in several diseases is discussed. Finally, the safety and efficacy of melatonin in clinical backgrounds is also reviewed.

Intestinal Dysbiosis, the Tryptophan Pathway and Nonalcoholic Steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) progresses from simple steatosis to steatohepatitis (NASH), which may then progress to the development of cirrhosis and hepatocarcinoma. NASH is characterized by both steatosis and inflammation. Control of inflammation in NASH is a key step for the prevention of disease progression to severe sequalae. Intestinal dysbiosis has been recognized to be an important causal factor in the pathogenesis of NASH, involving both the accumulation of lipids and aggravation of inflammation. The effects of gut dysbiosis are mediated by adverse shifts of various intestinal commensal bacterial genera and their associated metabolites such as butyrate, tryptophan, and bile acids. In this review, we focus on the roles of tryptophan and its metabolites in NASH in association with intestinal dysbiosis and discuss possible therapeutic implications.

Mechanisms of Melatonin in Obesity: A Review

Obesity and its complications have become a prominent global public health problem that severely threatens human health. Melatonin, originally known as an effective antioxidant, is an endogenous hormone found throughout the body that serves various physiological functions. In recent decades, increasing attention has been paid to its unique function in regulating energy metabolism, especially in glucose and lipid metabolism. Accumulating evidence has established the relationship between melatonin and obesity; nevertheless, not all preclinical and clinical evidence indicates the anti-obesity effect of melatonin, which makes it remain to conclude the clinical effect of melatonin in the fight against obesity. In this review, we have summarized the current knowledge of melatonin in regulating obesity-related symptoms, with emphasis on its underlying mechanisms. The role of melatonin in regulating the lipid profile, adipose tissue, oxidative stress, and inflammation, as well as the interactions of melatonin with the circadian rhythm, gut microbiota, sleep disorder, as well as the α7nAChR, the opioidergic system, and exosomes, make melatonin a promising agent to open new avenues in the intervention of obesity.

Melatonin Levels in Patients with Nonalcoholic Fatty Liver Disease Compared with Healthy Individuals according to Fibrosis Level

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is one of the most common diseases worldwide. Studies have shown that melatonin, as a regulatory hormone, is effective in different cell protective pathways. We aimed to compare serum melatonin levels of patients with NAFLD with different stages of fibrosis with that of healthy individuals.

METHODS

In this cross-sectional study patients, aged >20 years with elevated serum liver enzymes and trance abdominal sonographic diagnosis of fatty liver who met the exclusion criteria for NAFLD were included. The participants were categorized into three groups as follows: 1) severe fibrosis (fibrosis > 9.1 kPa and steatosis > 285 dbm), 2) mild-moderate fibrosis (fibrosis: 6-9.0 kPa and steatosis 240-285), and 3) normal group with fibrosis < 5.8 kPa and steatosis < 240 dbm based on Fibroscan evaluation. Five ml of fasting venous blood was taken from each patient and the control group for laboratory assessment. A questionnaire including demographic, anthropometric, laboratories (serum ALT, AST, triglyceride, total cholesterol and melatonin level), and clinical data was completed for all participants.

RESULTS

97 people with a mean±SD age of 42.21 ± 11 years were enrolled. 59 (60.0%) patients were women. we observed that the melatonin levels were increased by advancing fibrosis. Based on control- attenuated parameter results the melatonin levels significantly differed between the healthy individuals and patients with severe steatosis. There was a direct association between increased melatonin levels and liver enzymes.

CONCLUSION

As a regulatory hormone, melatonin may directly be associated with liver cell injuries. Therefore, considered regulatory substances such as melatonin either diagnostic or therapeutic can improve the patients’ outcome.

Melatonin induces Nrf2-HO-1 reprogramming and corrections in hepatic core clock oscillations in Non-alcoholic fatty liver disease

Melatonin pleiotropically regulates physiological events and has a putative regulatory role in the circadian clock desynchrony-mediated Non-alcoholic fatty liver disease (NAFLD). In this study, we investigated perturbations in the hepatic circadian clock gene, and Nrf2-HO-1 oscillations in conditions of high-fat high fructose (HFHF) diet and/or jet lag (JL)-mediated NAFLD. Melatonin treatment (100 µM) to HepG2 cells led to an improvement in oscillatory pattern of clock genes (Clock, Bmal1, and Per) in oleic acid (OA)-induced circadian desynchrony, while Cry, Nrf2, and HO-1 remain oblivious of melatonin treatment that was also validated by circwave analysis. C57BL/6J mice subjected to HFHF and/or JL, and treated with melatonin showed an improvement in the profile of lipid regulatory genes (CPT-1, PPARa, and SREBP-1c), liver function (AST and ALT) and histomorphology of fatty liver. A detailed scrutiny revealed that hepatic mRNA and protein profiles of Bmal1 (at ZT6) and Clock (at ZT12) underwent corrective changes in oscillations, but moderate corrections were recorded in other components of clock genes (Per1, Per2, and Cry2). Melatonin induced changes in oscillations of anti-oxidant genes (Nrf2, HO-1, and Keap1) subtly contributed in the overall improvement in NAFLD recorded herein. Taken together, melatonin induced reprograming of hepatic core clock and Nrf2-HO-1 genes leads to an improvement in HFHF/JL-induced NAFLD.

Melatonin ameliorates hepatic steatosis by inhibiting NLRP3 inflammasome in db/db mice

Introduction: Type 2 diabetes mellitus (T2DM) is commonly accompanied by obesity and non-alcoholic fatty liver disease (NAFLD), yet the mechanism underlying diabetes-related NAFLD is not fully understood. It has been reported that melatonin can regulate glucose and lipid metabolism. This study aims to investigate the actions and mechanisms of melatonin toward the development of diabetes-related NAFLD. Methods: Melatonin (bid, 30 mg/kg/day, i.p.) was administrated to db/db mice for 8 weeks, while saline was administrated to db/m mice. The metabolic parameters of mice were measured using an automatic biochemistry analyzer. The oxidative stress indexes and mitochondrial membrane potential (MMP) were determined with kits. Pathological assessment in liver tissues was used to analyze the effects of melatonin on hepatic steatosis. The levels of IL-1β and IL-18 were detected with ELISA kits. The mRNA levels of NLRP3 inflammasome were detected using quantitative real-time PCR assay, and protein expressions were estimated using Western blotting assay. Immunofluorescence staining was used to evaluate the caspase-1 expression in the liver. Results: Melatonin treatment significantly reduced blood glucose, serum insulin, body weight, related liver weight, serum lipids, and hepatic enzymes in db/db mice. Melatonin markedly corrected the NAFLD phenotypes, including lipid accumulation, steatohepatitis, fibrosis, and oxidative stress levels. Melatonin significantly improved the MMP level and decreased the serum IL-1β and IL-18 concentrations. The mRNA levels of the NLRP3 inflammasome could also be remarkably reversed by melatonin in the liver tissues. The activation of the NLRP3 inflammasome was also suppressed, evidenced by the downregulated proteins of NLRP3, caspase-1, IL-1β, and IL-18. The enhanced fluorescence intensity of caspase-1 in the liver tissues was also obviously weakened by the melatonin treatment. Conclusion: Our study concluded that melatonin could safeguard against NAFLD by improving hepatic steatosis in db/db mice, and this action could be associated with the regulation of the NLRP3 inflammasome activation.

The effects of melatonin therapy on the treatment of patients with Non-alcoholic steatohepatitis: A systematic review and Meta-analysis on clinical trial studies

Melatonin has shown promising effects in controlling the progress of non-alcoholic fatty liver disease (NAFLD), introducing it as a possible candidate for NAFLD treatment. In this context, the current study is aimed to evaluate melatonin's effect on the plasma levels of Gamma-glutamyl transpeptidase, cholesterol, triglyceride, and liver aminotransferases in NAFLD patients. NAFLD and melatonin, as well as their related terms, were searched in electronic databases, until May 1st, 2020. The initial search identified 1152 studies. Considering inclusion and exclusion criteria, the final seven articles were included in the study. The methodology of the articles was assessed by the Newcastle-Ottawa Scale. Alanine transaminase levels were significantly lowered with melatonin treatment but not earlier than the 4th week (P = 0.010 and 0.519, respectively). Aspartate aminotransferase levels didn't show significant alteration before 4 weeks, although exhibiting substantial decline in total (P = 0.697 and 0.008, respectively). Alkaline phosphatase changes under 4 weeks of follow-up were not significant (P = 0.3), however, it decreased significantly in total (P = 0.006). A significant decline was detected in triglyceride levels after melatonin treatment (P = 0.015). There was a significant reduction in cholesterol levels (P = 0.005). Gamma-glutamyl transpeptidase levels were also significantly different after the administration of melatonin (P < 0.001). Melatonin could reduce the progress of NAFLD. It might also decrement hepatic function parameters. Thus, it could be used for managing NAFLD and possibly as part of the treatment plan for patients with NAFLD.

Ovulation mitigates fatty liver associated with reproductive suppression and oxidative stress in Damaraland mole-rats (Fukomys damarensis)

Oxidative damage is often linked to reproduction; however, reproducing female Damaraland mole-rats (Fukomys damarensis) exhibit a reduction in oxidative damage relative to their non-reproductive, anovulatory, cohorts. Specifically, liver concentrations of malondialdehyde, a biomarker for lipid peroxidation, are significantly lower in reproducing females. We examined liver histology in reproductive, anovulatory and recently ovulating non-reproductive females, demonstrating an accumulation of lipid droplets only in the livers of anovulatory females and no fibrosis, cell death or inflammatory infiltrates in any group. Our observations suggest that anovulatory females experience a form of non-alcoholic fatty liver disease, which is reversed once they commence ovulation. We propose hormonal interactions that may underlie our observations.

Discovery of : A Novel Potent and Peripherally Preferred Melatonin Receptor Agonist that Reduces Liver Triglycerides and Steatosis in Diet-Induced Obese Rats

The modulation of melatonin signaling in peripheral tissues holds promise for treating metabolic diseases like obesity, diabetes, and nonalcoholic steatohepatitis. Here, several benzimidazole derivatives have been identified as novel agonists of the melatonin receptors MT1 and MT2. The lead compounds 10b, 15a, and 19a demonstrated subnanomolar potency at MT1/MT2 receptors, high oral bioavailability in rodents, peripherally preferred exposure, and excellent selectivity in a broad panel of targets. Two-month oral administration of 10b in high-fat diet rats led to a reduction in body weight gain similar to dapagliflozin with superior results on hepatic steatosis and triglyceride levels. An early toxicological assessment indicated that 10b (also codified as ACH-000143) was devoid of hERG binding, genotoxicity, and behavioral alterations at doses up to 100 mg/kg p.o., supporting further investigation of this compound as a drug candidate.

miR-125b promotes the NF-κB-mediated inflammatory response in NAFLD via directly targeting TNFAIP3

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) has a high incidence and mortality rate, and a rapid course of clinical development. Although miR-125b is closely associated with the pathogenesis of liver fibrosis and hepatocellular carcinoma, the role of miR-125b in NAFLD remains unknown.

METHODS

The levels of TNF-α, IL-6, and IL-1β expression were examined via ELISA assays. Real-time PCR was used to determine the levels of miR-125b and tumor necrosis factor alpha-induced protein 3 (TNFAIP3) expression. The related molecular mechanisms were examined by performing luciferase reporter, western blot, and immunofluorescence assays. Structural changes in the livers of mice with NAFLD were observed via H&E staining.

RESULTS

The levels of TNF-α, IL-6, and IL-1β in NAFLD patients were greatly increased, and miR-125b expression was significantly up-regulated. The phosphorylation of IκBα and p65, and secretion of inflammatory factors were all markedly decreased by miR-125b silencing, but greatly increased by miR-125b overexpression. We also demonstrated that downregulation of TNFAIP3 in NAFLD was negatively correlated with miR-125b. Interestingly, the influence of miR-125b inhibitors on nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-mediated inflammatory responses were greatly aggravated by co-treatment with TNFAIP siRNA; however, the opposite results were obtained after treatment with miR-125b mimics and TNFAIP plasmids. Furthermore, the HF-induced liver damage and inflammatory responses were greatly ameliorated by miR-125b inhibitors but further aggravated by co-treatment with TNFAIP3 siRNA.

CONCLUSION

MiR-125b promoted the NF-κB-mediated inflammatory response in NAFLD by directly targeting TNFAIP3, and that mechanism might be target for treating NAFLD.

Effects of Melatonin on Lipid Metabolism and Circulating Irisin in Sprague-Dawley Rats with Diet-Induced Obesity

Melatonin, a pivotal photoperiodic signal transducer, may work as a brown-fat inducer that regulates energy balance. Our study aimed to investigate the effects of melatonin treatment on the body fat accumulation, lipid profiles, and circulating irisin of rats with high-fat diet-induced obesity (DIO). Methods: 30 male Sprague-Dawley rats were divided into five groups and treated for 8 weeks: vehicle control (VC), positive control (PC), MEL10 (10 mg melatonin/kg body weight (BW)), MEL20 (20 mg/kg BW), and MEL50 (50 mg/kg BW). The vehicle control group was fed a control diet, and the other groups were fed a high-fat and high-calorie diet for 8 weeks to induce obesity before the melatonin treatment began. Melatonin reduced weight gain without affecting the food intake, reduced the serum total cholesterol level, enhanced the fecal cholesterol excretion, and increased the circulating irisin level. Melatonin downregulated the fibronectin type III domain containing 5 (FNDC5) and lipoprotein lipase (LPL) mRNA expressions of inguinal white adipose tissue (iWAT) and induced the browning of iWAT in both the MEL10 and MEL20 groups. Conclusion: Chronic continuous melatonin administration in drinking water reduced weight gain and the serum total cholesterol levels. Additionally, it enhanced the circulating irisin, which promoted brite/beige adipocyte recruitment together with cholesterol excretion and contributed to an anti-obesity effect.

Targeting DUSP7 signaling alleviates hepatic steatosis, inflammation and oxidative stress in high fat diet (HFD)-fed mice via suppression of TAK1

The non-alcoholic fatty liver disease (NAFLD), as a critical liver disease, is still lack of effective treatments because the molecular mechanism revealing the NAFLD pathogenesis remains unclear. Dual specific phosphatase 6 (DUSP7) shows effects on inflammatory response and is a negative feedback mechanism of the mitogen-activated protein kinase (MAPK) superfamily, which are critical factors in regulating NAFLD progression. However, the effects of DUSP7 on hepatic steatosis are still not fully understood. Here, we found that DUSP7 functioned as a negative regulator of NAFLD and in various metabolic disorders. DUSP7 expression was markedly reduced in liver samples from patients with simple hepatic steatosis or non-alcoholic steatohepatitis (NASH), as well as in liver tissues from high fat diet (HFD)-challenged mice or genetically obese (ob/ob) mice. DUSP7 knockout markedly accelerated insulin resistance, glucose intolerance, liver dysfunction, fibrosis and hepatic steatosis in HFD-fed mice. In addition, inflammatory response was significantly exacerbated in HFD-challenged mice with DUSP7 deletion, which was associated with the elevated activation of nuclear factor-κB (NF-κB) and MAPKs signaling pathways. Moreover, oxidative stress was detected in liver of HFD-induced mice, and this phenomenon was aggravated in mice with DUSP7 knockout. Importantly, we demonstrated that DUSP7 physically interacted with transforming growth factor β (TGF-β)-activated kinase (TAK1). DUSP7 deletion considerably promoted the activation of TAK1 in mice after HFD feeding, contributing to the lipid deposition, inflammatory response and reactive oxygen species (ROS) production. Taken together, DUSP7 might function as a protective factor against NAFLD development and metabolic disorder through alleviating dyslipidemia, inflammation and oxidative stress by directly interacting with TAK1 in hepatocytes, which was involved in the suppression of fibrosis. Thus, we may provide an effective strategy for the treatment of hepatic steatosis via targeting DUSP7.

GRHL2 induces liver fibrosis and intestinal mucosal barrier dysfunction in non-alcoholic fatty liver disease via microRNA-200 and the MAPK pathway

Non‐alcoholic fatty liver disease (NAFLD) serves as the most common subtype of liver diseases and cause of liver dysfunction, which is closely related to obesity and insulin resistance. In our study, we sought to investigate effect of transcription factor grainyhead‐like 2 (GRHL2) on NAFLD and the relevant mechanism. NAFLD mouse model was established with a high‐fat feed. Then, serum was extracted from NAFLD patients and mice, followed by ectopic expression and depletion experiments in NAFLD mice and L02 cells. Next, the correlation between GRHL2 and microRNA (miR)‐200 and between miR‐200 and sirtuin‐1 (SIRT1) was evaluated. The observations demonstrated that miR‐200 and GRHL2 were overexpressed in the serum of NAFLD patients and mice, while SIRT1 was poorly expressed. GRHL2 positively regulated miR‐200 by binding to miR‐200 promoter region, which negatively targeted SIRT1. The inhibition of miR‐200 and GRHL2 or SIRT1 overexpression lowered HA and LN in mouse liver tissue, occludin and ZO‐1 in mouse small intestine tissue, TNF‐α and IL‐6 in mouse serum, glucose, total cholesterol (TC), triglyceride (TG), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in mouse serum, and also inhibited liver fibrosis and intestinal mucosal barrier dysfunction. Meanwhile, GRHL2 induced activation of MAPK signalling pathway in NAFLD mice. Collectively, GRHL2 played a contributory role in NAFLD by exacerbating liver fibrosis and intestinal mucosal barrier dysfunction with the involvement of miR‐200‐dependent SIRT1 and the MAPK signalling pathway.

Piceatannol attenuates fat accumulation and oxidative stress in steatosis-induced HepG2 cells

Non-alcoholic fatty liver disease (NAFLD), which affects over 20% of the adult population, is the most common liver disease worldwide and can progress to inflammatory hepatitis, cirrhosis and liver cancer. The need to alleviate NAFLD is imperative, but there are limited pharmacological therapies available. Based on previous reports that piceatannol, a stilbenoid metabolite of resveratrol, exhibits anti-obesity, antioxidant and anti-inflammatory effects, the goal of this study was to determine the efficacy of piceatannol on prevention and/or treatment of NAFLD. The results showed that piceatannol significantly decreased fat accumulation and suppressed lipogenesis and fatty acids (FAs) uptake by decreasing sterol regulatory element-binding protein 1 (SREBP1) and cluster of differentiation 36 (CD36) in steatosis-induced HepG2 hepatocytes. Piceatannol treatment also promoted FAs β-oxidation by increasing farnesoid X receptor (FXR), peroxisome proliferator-activated receptor α (PPARα), and carnitine palmitoyltransferase 1α (CPT1α) under steatosis conditions. Moreover, piceatannol significantly suppressed FA-induced oxidative stress and inhibited phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinases 1/2 (ERK1/2). Overall, it is suggested that piceatannol reduced fat accumulation in steatosis-induced HepG2 cells by suppressing lipogenesis (SREBP1 and ACC) and FA uptake (CD36), and promoting FAs oxidation (FXR, PPARα and CPT1α).

Melatonin and circadian rhythms in liver diseases: Functional roles and potential therapies

Circadian rhythms and clock gene expressions are regulated by the suprachiasmatic nucleus in the hypothalamus, and melatonin is produced in the pineal gland. Although the brain detects the light through retinas and regulates rhythms and melatonin secretion throughout the body, the liver has independent circadian rhythms and expressions as well as melatonin production. Previous studies indicate the association between circadian rhythms with various liver diseases, and disruption of rhythms or clock gene expression may promote liver steatosis, inflammation, or cancer development. It is well known that melatonin has strong antioxidant effects. Alcohol drinking or excess fatty acid accumulation produces reactive oxygen species and oxidative stress in the liver leading to liver injuries. Melatonin administration protects these oxidative stress-induced liver damage and improves liver conditions. Recent studies have demonstrated that melatonin administration is not limited to antioxidant effects and it has various other effects contributing to the management of liver conditions. Accumulating evidence suggests that restoring circadian rhythms or expressions as well as melatonin supplementation may be promising therapeutic strategies for liver diseases. This review summarizes recent findings for the functional roles and therapeutic potentials of circadian rhythms and melatonin in liver diseases.

Elucidating the Regulatory Role of Melatonin in Brown, White, and Beige Adipocytes

The high prevalence of obesity and its associated metabolic diseases has heightened the importance of understanding control of adipose tissue development and energy metabolism. In mammals, 3 types of adipocytes with different characteristics and origins have been identified: white, brown, and beige. Beige and brown adipocytes contain numerous mitochondria and have the capability to burn energy and counteract obesity, while white adipocytes store energy and are closely associated with metabolic disorders and obesity. Thus, regulation of the development and function of different adipocytes is important for controlling energy balance and combating obesity and related metabolic disorders. Melatonin is a neurohormone, which plays multiple roles in regulating inflammation, blood pressure, insulin actions, and energy metabolism. This article summarizes and discusses the role of melatonin in white, beige, and brown adipocytes, especially in affecting adipogenesis, inducing beige formation or white adipose tissue browning, enhancing brown adipose tissue mass and activities, improving anti-inflammatory and antioxidative effects, regulating adipokine secretion, and preventing body weight gain. Based on the current findings, melatonin is a potential therapeutic agent to control energy metabolism, adipogenesis, fat deposition, adiposity, and related metabolic diseases.

Chinese Herbal Medicine Formula Shenling Baizhu San Ameliorates High-Fat Diet-Induced NAFLD in Rats by Modulating Hepatic MicroRNA Expression Profiles

Objective

The purpose of present study was to investigate the potential mechanism underlying the protective effect of Shenling Baizhu San (SLBZS) on nonalcoholic fatty liver disease (NAFLD) by microRNA (miRNA) sequencing.

Methods

Thirty male Wistar rats were randomly divided into a normal control (NC) group, a high-fat diet (HFD) group, and an SLBZS group. After 12 weeks, the biochemical parameters and liver histologies of the rats were assessed. The Illumina HiSeq 2500 sequencing platform was used to analyse the hepatic miRNA expression profiles. Representative differentially expressed miRNAs were further validated by qRT-PCR. The functions of the differentially expressed miRNAs were analysed by bioinformatics.

Results

Our results identified 102 miRNAs that were differentially expressed in the HFD group compared with the NC group. Among those differentially expressed miRNAs, the expression levels of 28 miRNAs were reversed by SLBZS administration, suggesting the modulation effect of SLBZS on hepatic miRNA expression profiles. The qRT-PCR results confirmed that the expression levels of miR-155-5p, miR-146b-5p, miR-132-3p, and miR-34a-5p were consistent with those detected by sequencing. Bioinformatics analyses indicated that the target genes of the differentially expressed miRNAs reversed by SLBZS were mainly related to metabolic pathways.

Conclusion

This study provides novel insights into the mechanism of SLBZS in protecting against NAFLD; this mechanism may be partly related to the modulation of hepatic miRNA expression and their target pathways.

Lipidomic biomarkers and mechanisms of lipotoxicity in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) represents the most common form of chronic liver disease worldwide (about 25% of the general population) and 3-5% of patients develop non-alcoholic steatohepatitis (NASH), characterized by hepatocytes damage, inflammation and fibrosis, which increase the risk of developing liver failure, cirrhosis and hepatocellular carcinoma. The pathogenesis of NAFLD, particularly the mechanisms whereby a minority of patients develop a more severe phenotype, is still incompletely understood. In this review we examine the available literature on initial mechanisms of hepatocellular damage and inflammation, deriving from toxic effects of excess lipids. Accumulating data indicate that the total amount of triglycerides stored in the liver cells is not the main determinant of lipotoxicity and that specific lipid classes act as damaging agents. These lipotoxic species affect the cell behavior via multiple mechanisms, including activation of death receptors, endoplasmic reticulum stress, modification of mitochondrial function and oxidative stress. The gut microbiota, which provides signals through the intestine to the liver, is also reported to play a key role in lipotoxicity. Finally, we summarize the most recent lipidomic strategies utilized to explore the liver lipidome and its modifications in the course of NALFD. These include measures of lipid profiles in blood plasma and erythrocyte membranes that can surrogate to some extent lipid investigation in the liver.

Melatonin Supplementation Attenuates the Pro-Inflammatory Adipokines Expression in Visceral Fat from Obese Mice Induced by A High-Fat Diet

Obesity is defined as a condition of abnormal or excessive fat accumulation in white adipose tissue that results from the exacerbated consumption of calories associated with low energy expenditure. Fat accumulation in both adipose tissue and other organs contributes to a systemic inflammation leading to the development of metabolic disorders such as type 2 diabetes, hypertension, and dyslipidemia. Melatonin is a potent antioxidant and improves inflammatory processes and energy metabolism. Using male mice fed a high-fat diet (HFD-59% fat from lard and soybean oil; 9:1) as an obesity model, we investigated the effects of melatonin supplementation on the prevention of obesity-associated complications through an analysis of plasma biochemical profile, body and fat depots mass, adipocytes size and inflammatory cytokines expression in epididymal (EPI) adipose depot. Melatonin prevented a gain of body weight and fat depot mass as well as adipocyte hypertrophy. Melatonin also reversed the increase of total cholesterol, triglycerides and LDL-cholesterol. In addition, this neurohormone was effective in completely decreasing the inflammatory cytokines leptin and resistin in plasma. In the EPI depot, melatonin reversed the increase of leptin, Il-6, Mcp-1 and Tnf-α triggered by obesity. These data allow us to infer that melatonin presents an anti-obesity effect since it acts to prevent the progression of pro-inflammatory markers in the epididymal adipose tissue together with a reduction in adiposity.

Protective role of melatonin in early-stage and end-stage liver cirrhosis

The liver is composed of hepatocytes, cholangiocytes, Kupffer cells, sinusoidal endothelial cells, hepatic stellate cells (HSCs) and dendritic cells; all these functional and interstitial cells contribute to the synthesis and secretion functions of liver tissue. However, various hepatotoxic factors including infection, chemicals, high‐fat diet consumption, surgical procedures and genetic mutations, as well as biliary tract diseases such as sclerosing cholangitis and bile duct ligation, ultimately progress into liver cirrhosis after activation of fibrogenesis. Melatonin (MT), a special hormone isolated from the pineal gland, participates in regulating multiple physiological functions including sleep promotion, circadian rhythms and neuroendocrine processes. Current evidence shows that MT protects against liver injury by inhibiting oxidation, inflammation, HSC proliferation and hepatocyte apoptosis, thereby inhibiting the progression of liver cirrhosis. In this review, we summarize the circadian rhythm of liver cirrhosis and its potential mechanisms as well as the therapeutic effects of MT on liver cirrhosis and earlier‐stage liver diseases including liver steatosis, nonalcoholic fatty liver disease and liver fibrosis. Given that MT is an antioxidative and anti‐inflammatory agent that is effective in eliminating liver injury, it is a potential agent with which to reverse liver cirrhosis in its early stage.

Combined Amelioration of Ginsenoside (Rg1, Rb1, and Rg3)-enriched Korean Red Ginseng and Probiotic Lactobacillus on Non-alcoholic Fatty Liver Disease

BACKGROUND

Red ginseng is a traditional medicine that has been used to treat numerous metabolic and inflammatory diseases. Probiotic administration has been established to have beneficial effects in non-alcoholic fatty liver disease (NAFLD). The purpose of this study was to determine whether a combination of Korean red ginseng (KRG) and probiotics could synergistically reduce NAFLD and liver inflammation compared with the effects reported for each individual product.

METHOD

db/db and C57BL/6 mice were fed a normal chow diet and high-fat diet (HFD), respectively, and were treated with KRG, probiotics, or both. Samples were examined for lipid content, kinase protein phosphorylation, and gene expression patterns.

RESULTS

KRG- and probiotic-treated HFD-fed mice exhibited a reduction in body weight and a decrease in inflammatory cytokine secretion compared with the non-treated control mice. The same treatment was less successful in improving NAFLD parameters in the db/db mice while the combination of both products did not enhance their therapeutic potential.

CONCLUSION

The results of this study indicate that KRG and probiotics administration ameliorated NAFLD symptoms in a mouse model of dyslipidemia by reducing weight gain and liver inflammation. Coadministration of both products did not enhance their efficacy, and further research should be conducted to clarify their mechanisms of action.

Reduced delivery of epididymal adipocyte-derived exosomal resistin is essential for melatonin ameliorating hepatic steatosis in mice

Adipocyte-derived exosomes (Exos) serve as bioinformation-containing messengers in cell-to-cell communications, and numerous reports demonstrate that resistin, an adipokine, is strongly associated with hepatic steatosis and other fatty liver diseases, suggesting that adipose dysfunction-generated altered pattern of exosomal cytokines may contribute to shaping the physiological activities in liver. Admittedly, melatonin-mediated positive effects on various tissues/organs have been respectively reported, but regulatory mechanisms of melatonin on the crosstalk between adipose tissue and liver have been investigated rarely. Overall, we hypothesize that the crosstalk originating from adipose tissue may be another worthy regulatory pathway for melatonin ameliorating of hepatic steatosis. Here, we first found the amount of adipocyte-derived exosomal resistin to be significantly decreased by melatonin supplementation. Compared to mice with Exos_HFD or Exos_resistin treatment, Exos_MT remarkably ameliorated hepatic steatosis. Further test demonstrated that resistin was a pivotal cytokine which repressed phosphorylation of 5' adenosine monophosphate-activated protein kinase α (pAMPKα Thr¹⁷² ) to trigger endoplasmic reticulum (ER) stress, resulting in hepatic steatosis, whereas Exos_MT reversed these risks in hepatocytes. In adipocytes, we identified melatonin to reduce the production of resistin through the brain and muscle arnt-like protein 1 (Bmal1) transcriptional inhibition. Notably, we also confirmed that melatonin enhanced N⁶ -Methyladenosine (m⁶ A) RNA demethylation to degrade resistin mRNA in adipocytes. Overall, melatonin decreases traffic volume of adipocyte-generated exosomal resistin from adipocytes to hepatocytes, which further alleviates ER stress-induced hepatic steatosis. Our findings illustrate a novel melatonin-mediated regulatory pathway from adipocytes to hepatocytes, indicating that adipocyte-derived exosome is a new potential target for treating obesity and related hepatorenal syndrome.