Effects of resveratrol in experimental and clinical non-alcoholic fatty liver disease

Effects of polyphenol supplementation on hepatic steatosis, intima-media thickness and non-invasive vascular elastography in obese adolescents: a pilot study protocol

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) is increasingly prevalent in obese adolescents. Increased systemic inflammation and decreased gut microbial diversity linked to obesity affect the liver and are also associated with cardiovascular diseases in adulthood. However, NAFLD and vascular alterations are reversible.

METHODS AND ANALYSIS

This pilot study evaluated the feasibility of a prospective open-label randomised controlled trial evaluating the effects of polyphenols on NAFLD and vascular parameters in obese adolescents. Children aged 12-18 years with hepatic steatosis (n=60) will be recruited. The participants will be randomised with a 1:1 allocation ratio to receive polyphenol supplementation one time per day for 8 weeks along with the clinician-prescribed treatment (group B, n=30) or to continue the prescribed treatment without taking any polyphenols (group A, n=30). The outcome measures will be collected from both the groups at day 1 before starting polyphenol supplementation, at day 60 after 8 weeks of supplementation and at day 120, that is, 60 days after supplementation. The changes in hepatic steatosis and vascular parameters will be measured using liver and vascular imaging. Furthermore, anthropometric measures, blood tests and stool samples for gut microbiome analysis will be collected. After evaluating the study's feasibility, we hypothesise that, as a secondary outcome, compared with group A, the adolescents in group B will have improved NAFLD, vascular parameters, systemic inflammation and gut microbiome.

ETHICS AND DISSEMINATION

This study is approved by Health Canada and the hospital ethics. Participants and their parents/tutors will both provide consent. Trial results will be communicated to the collaborating gastroenterologists who follow the enrolled participants. Abstracts and scientific articles will be submitted to high-impact radiological societies and journals.

CLINICALTRIALS

gov ID: NCT03994029. Health Canada authorisation referral number: 250 811. Protocole version 13, 2 June 2023.

TRIAL REGISTRATION NUMBER

NCT03994029.

Molecular Mechanisms of Oxidative Stress in Acute Kidney Injury: Targeting the Loci by Resveratrol

Reactive oxygen species are a group of cellular molecules that stand as double-edged swords, their good and bad being discriminated by a precise balance. Several metabolic reactions in the biological system generate these molecules that interact with cellular atoms to regulate functions ranging from cell homeostasis to cell death. A prooxidative state of the cell concomitant with decreased clearance of such molecules leads to oxidative stress, which contributes as a prime pathophysiological mechanism in various diseases including renal disorders, such as acute kidney injury. However, targeting the generation of oxidative stress in renal disorders by an antioxidant, resveratrol, is gaining considerable therapeutic importance and is known to improve the condition in preclinical studies. This review aims to discuss molecular mechanisms of oxidative stress in acute kidney injury and its amelioration by resveratrol. The major sources of data were PubMed and Google Scholar, with studies from the last five years primarily included, with significant earlier data also considered. Mitochondrial dysfunction, various enzymatic reactions, and protein misfolding are the major sources of reactive oxygen species in acute kidney injury, and interrupting these loci of generation or intersection with other cellular components by resveratrol can mitigate the severity of the condition.

A novel combination of metformin and resveratrol alleviates hepatic steatosis by activating autophagy through the cAMP/AMPK/SIRT1 signaling pathway

Nonalcoholic fatty liver disease (NAFLD) is a prevalent liver disorder that is associated with the accumulation of triglycerides (TG) in hepatocytes. Resveratrol (RSV), as a natural product, and metformin have been reported to have potential lipid-lowering effects for the treatment of NAFLD via autophagy, but the combined effects of both have not yet been studied. The current study aimed to investigate the role of autophagy in the lipid-lowering effects of RSV, alone and in combination with metformin, on the hepatic steatosis model of HepG2 cells and elucidate the mechanism of action. Triglyceride measurement and real-time PCR showed that RSV-metformin reduced lipid accumulation and the expression of lipogenic genes in palmitic acid (PA)-induced HepG2 cells. Additionally, the LDH release assay indicated that this combination protected HepG2 cells against PA-induced cell death through autophagy. The western blotting analysis revealed that RSV-metformin induced autophagy by reducing the expression of p62 and increasing LC3-I and LC3-II proteins. This combination also enhanced cAMP, phosphorylated AMP-activated protein kinase (p-AMPK), and Beclin-1 levels in HepG2 cells. Furthermore, SIRT1 inhibitor treatment inhibited autophagy induced by RSV-metformin, which indicated the autophagy induction is SIRT1-dependent. This study demonstrated for the first time that RSV-metformin reduced hepatic steatosis by triggering autophagy via the cAMP/AMPK/SIRT1 signaling pathway.

Therapeutic Potential of Resveratrol and Atorvastatin Following High-Fat Diet Uptake-Induced Nonalcoholic Fatty Liver Disease by Targeting Genes Involved in Cholesterol Metabolism and miR33

The present study was designed to evaluate the effects of resveratrol, atorvastatin, and a combination of resveratrol and atorvastatin on expression levels of genes involved in the cholesterol metabolic pathway in the fatty liver of C57/BL6 mice. A high-fat diet was used to induce fatty liver in C57/BL6 mice treated with resveratrol, atorvastatin, or a combination of resveratrol and atorvastatin. Pathological and biochemical studies were performed. In addition, hepatic gene expressions of ATP-binding cassette transporter A1 (ABCA1), ABCG1, liver X receptor (LXR)α, scavenger receptor B1 (SR-B1), low-density lipoprotein receptor (LDLR), and miR33 were evaluated by the real-time PCR method, and the Western blot method was used to measure the ABCA1, ABCG1, and LXRα protein levels. Resveratrol and atorvastatin reduced fat accumulation in the liver of mice with fatty liver, and this effect was correlated with decreased blood glucose levels, triglyceride, cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol blood levels compared with the positive control (PC) group. In contrast to the animals of the PC group, fatty liver groups that received resveratrol and atorvastatin had a significant effect on the mRNA levels of the ABCA1, ABCG1, LXRα, SR-B1, LDLR, and miR33 genes. Moreover, resveratrol and atorvastatin administration elevated ABCA1 and ABCG1 and reduced LXRα protein expression. Obtained results showed that resveratrol and atorvastatin combination therapy can improve nonalcoholic fatty liver disease by targeting genes involved in cholesterol metabolism and miR33.

Resveratrol therapy improves liver function via estrogen-receptors after hemorrhagic shock in rats

Background

Resveratrol may improve organ dysfunction after experimental hemorrhagic or septic shock, and some of these effects appear to be mediated by estrogen receptors. However, the influence of resveratrol on liver function and hepatic microcirculation after hemorrhagic shock is unknown, and a presumed mediation via estrogen receptors has not been investigated in this context.

Methods

Male Sprague-Dawley rats (200-300g, n = 14/group) underwent hemorrhagic shock for 90 min (MAP 35±5 mmHg) and were resuscitated with shed blood and Ringer’s solution. Animals were treated intravenously with vehicle (1% EtOH), resveratrol (0.2 mg/kg), the unselective estrogen receptor antagonist ICI 182,780 (0.05 mg/kg) or resveratrol + ICI 182,780 prior to retransfusion. Sham-operated animals did not undergo hemorrhage but were treated likewise. After 2 hours of reperfusion, liver function was assessed either by plasma disappearance rate of indocyanine green (PDR_ICG) or evaluation of hepatic perfusion and hepatic integrity by intravital microscopy, serum enzyme as well as cytokine levels.

Results

Compared to vehicle controls, administration of resveratrol significantly improved PDR_ICG, hepatic perfusion index and hepatic integrity after hemorrhagic shock. The co-administration of ICI 182,780 completely abolished the protective effect only with regard to liver function.

Conclusions

This study shows that resveratrol may improve liver function and hepatocellular integrity after hemorrhagic shock in rats; estrogen receptors mediate these effects at least partially.

Tamoxifen induced hepatic steatosis in high-fat feeding rats through SIRT1-Foxo1 suppression and LXR-SREBP1c activation

Background

Clinically, long-term use of tamoxifen (TAM) would lead to fatty liver disease in breast cancer patients, especially obese women. However, the exact mechanism of TAM-induced hepatic steatosis is still unclear. Meanwhile, there is no drug to prevent and treat it.

Aims and Methods

In view of silent information regulator 1 (SIRT1) playing a key role in hepatic lipid metabolism regulation, this study was conducted to investigate whether SIRT1 is a potential therapeutic target for TAM-induced hepatic steatosis. In this study, obese female Wistar rats fed with high-fat diet (HFD) for 15 weeks were given TAM (4, 8 mg/kg, intragastric) for 14 days. In vitro, human hepatocarcinoma cell line HepG2 was used to establish a high-fat model with 50 μM oleic acid and TAM (10 μM) was treated simultaneously for 72 h.

Results

The results showed that TAM was more likely to upregulate the expression of lipid synthetase that caused the increase of lipid content in HepG2 cells and rat liver. The expression of SIRT1 was downregulated both in vitro and in vivo. SIRT1 agonist SRT1720 (15 mg/kg, 30 mg/kg, i.p.) could resist TAM-induced hepatic lipid synthetase overexpression to relieve TAM-induced hepatic steatosis. Meanwhile, the upregulation of p-forkhead box O1 and LXRα induced by TAM was reversed by SRT1720.

Conclusions

These results indicated that TAM-induced hepatic steatosis was based on SIRT1-p-FoxO/LXRα-sterol regulatory element binding protein 1c pathway under HFD condition. SIRT1 agonist might be a potential therapeutic drug to relieve this side effect.

Highlights

Tamoxifen increased lipid synthesis and regulated lipid transport in HFD rat liver.p-FoxO1/LXRα-SREBP1c signaling was upregulated through the inhibition of SIRT1 in tamoxifen-induced hepatic steatosis under HFD condition.SIRT1 agonist SRT1720 could relieve tamoxifen-induced hepatic steatosis.

Resveratrol Alleviates Acute Campylobacter jejuni Induced Enterocolitis in a Preclinical Murine Intervention Study

The polyphenolic compound resveratrol has been shown to exert health-beneficial properties. Given globally emerging Campylobacter infections in humans, we addressed potential anti-pathogenic, immuno-modulatory and intestinal epithelial barrier preserving properties of synthetic resveratrol in the present preclinical intervention study applying a murine acute campylobacteriosis model. Two days following peroral C. jejuni infection, secondary abiotic IL-10^−/− mice were either subjected to resveratrol or placebo via the drinking water. Whereas placebo mice suffered from acute enterocolitis at day 6 post-infection, resveratrol treatment did not only lead to improved clinical conditions, but also to less pronounced colonic epithelial apoptosis as compared to placebo application. Furthermore, C. jejuni induced innate and adaptive immune cell responses were dampened in the large intestines upon resveratrol challenge and accompanied by less colonic nitric oxide secretion in the resveratrol versus the placebo cohort. Functional analyses revealed that resveratrol treatment could effectively rescue colonic epithelial barrier function in C. jejuni infected mice. Strikingly, the disease-alleviating effects of resveratrol could additionally be found in extra-intestinal and also systemic compartments at day 6 post-infection. For the first time, our current preclinical intervention study provides evidence that peroral resveratrol treatment exerts potent disease-alleviating effects during acute experimental campylobacteriosis.

Administration of low-dose resveratrol attenuated hepatic inflammation and lipid accumulation in high cholesterol-fructose diet-induced rat model of nonalcoholic fatty liver disease

Resveratrol (RSV) has been demonstrated to ameliorate nonalcoholic fatty liver disease (NAFLD) in animal studies. However, RSV was given with the dosage that ranged from 7 to 300 mg/kg body weight (BW). Hence, the study aimed to investigate the efficacy of RSV at a lower dosage on high cholesterol-fructose diet (HCFD)-induced rat model of NAFLD. In the study, male Sprague-Dawley rats were fed with HCFD for 15 weeks. RSV was also given at a daily dose of 1 mg/kg BW for 15 days or 15 weeks by oral delivery. At sacrifice, plasma and liver specimens were acquired for detections of alanine and aspartate aminotransferases, proinflammatory cytokines, and lipid contents. Histological examinations and Western blotting analysis were performed using liver tissues. The results showed that RSV administration reduced plasma levels of aminotransferases and proinflammatory cytokines including interleukin-1 beta (IL-1β), IL-6, and tumor necrosis factor-alpha (TNF-α) in HCFD-induced NAFLD. RSV also mitigated hepatic lipid accumulation and expression of IL-1β, IL-6, and TNF-α. Besides, phosphorylation of signal transducer and activator of transcription 3 (STAT3) was reduced with RSV supplementation in the liver of HCFD-fed rats. We concluded that low-dose RSV supplementation attenuated hepatic inflammation and lipid accumulation in HCFD-induced NAFLD. The ameliorative effect of RSV on NAFLD could be associated with downregulation of phosphorylated STAT3.

Resveratrol Metabolites Are Able to Reduce Steatosis in Cultured Hepatocytes

Steatosis is characterized primarily by excessive lipid accumulation in the form of triglycerides in the liver. Although resveratrol shows a low bioavailability, it has significant positive effects on steatosis. The aim of this study was to analyze whether some phase II and microbial resveratrol metabolites (trans-resveratrol-4'-O-glucuronide (R-4G); trans-resveratrol-3-O-glucuronide (R-3G); trans-resveratrol-3-O-sulfate (R-S) and dihydro-resveratrol (DH-R) were effective in reducing hepatocyte fat accumulation. An in vitro model mimicking the hepatocyte situation in fatty liver was developed by incubating mouse AML12 hepatocytes with palmitic acid (PA). For cell treatments, hepatocytes were incubated with 1, 10, or 25 µM resveratrol or its metabolites. Triglycerides and cell viability were assessed using commercial kits. Protein expression of enzymes and transporters involved in triglyceride metabolism were analyzed by western blot. We show for the first time that resveratrol and all the tested metabolites, at 1 µM, partially prevented lipid accumulation induced by the saturated fatty acid PA in AML12 hepatocytes. This effect was mainly due to the inhibition of de novo lipogenesis. This demonstrates that the low bioavailability of resveratrol is not as big a problem as it was thought to be, because resveratrol metabolites contribute to the delipidating effects of the parent compound.

Cardiolipin deficiency elevates susceptibility to a lipotoxic hypertrophic cardiomyopathy

Cardiolipin (CL) is a unique tetra-acyl phospholipid localized to the inner mitochondrial membrane and essential for normal respiratory function. It has been previously reported that the failing human heart and several rodent models of cardiac pathology have a selective loss of CL. A rare genetic disease, Barth syndrome (BTHS), is similarly characterized by a cardiomyopathy due to reduced levels of cardiolipin. A mouse model of cardiolipin deficiency was recently developed by knocking-down the cardiolipin biosynthetic enzyme tafazzin (TAZ KD). These mice develop an age-dependent cardiomyopathy due to mitochondrial dysfunction. Since reduced mitochondrial capacity in the heart may promote the accumulation of lipids, we examined whether cardiolipin deficiency in the TAZ KD mice promotes the development of a lipotoxic cardiomyopathy. In addition, we investigated whether treatment with resveratrol, a small cardioprotective nutraceutical, attenuated the aberrant lipid accumulation and associated cardiomyopathy. Mice deficient in tafazzin and the wildtype littermate controls were fed a low-fat diet, or a high-fat diet with or without resveratrol for 16 weeks. In the absence of obesity, TAZ KD mice developed a hypertrophic cardiomyopathy characterized by reduced left-ventricle (LV) volume (~36%) and 30-50% increases in isovolumetric contraction (IVCT) and relaxation times (IVRT). The progression of cardiac hypertrophy with tafazzin-deficiency was associated with several underlying pathological processes including altered mitochondrial complex I mediated respiration, elevated oxidative damage (~50% increase in reactive oxygen species, ROS), the accumulation of triglyceride (~250%) as well as lipids associated with lipotoxicity (diacylglyceride ~70%, free-cholesterol ~44%, ceramide N:16-35%) compared to the low-fat fed controls. Treatment of TAZ KD mice with resveratrol maintained normal LV volumes and preserved systolic function of the heart. The beneficial effect of resveratrol on cardiac function was accompanied by a significant improvement in mitochondrial respiration, ROS production and oxidative damage to the myocardium. Resveratrol treatment also attenuated the development of cardiac steatosis in tafazzin-deficient mice through reduced de novo fatty acid synthesis. These results indicate for the first time that cardiolipin deficiency promotes the development of a hypertrophic lipotoxic cardiomyopathy. Furthermore, we determined that dietary resveratrol attenuates the cardiomyopathy by reducing ROS, cardiac steatosis and maintaining mitochondrial function.

The Epigenetic Drug Discovery Landscape for Metabolic-associated Fatty Liver Disease

Despite decades of research, effective therapies for metabolic (dysfunction)-associated fatty liver disease (MAFLD) are lacking. An increasing body of evidence suggests that epigenetic dysregulation is frequent in MAFLD, and orchestrates many aspects of its development and progression. Furthermore, the high plasticity of epigenetic modifications in response to environmental cues renders epigenetics a novel area for therapeutic drug discovery. Over recent years, several epigenetics-based drugs and diagnostic biomarkers have entered clinical development and/or obtained regulatory approval. Here, we review recent advances in our understanding of epigenetic regulation and programming during MAFLD, including DNA methylation, histone modifications, chromatin remodelling, transcriptional control, and noncoding (nc)RNAs. We also discuss the potential translational implications and challenges of epigenetics in the context of MAFLD.

Influence of Resveratrol on Sphingolipid Metabolism in Hepatocellular Carcinoma Cells in Lipid Overload State

Background:

Obesity is characterized by increased long chain fatty acids (LCFA) uptake and impaired lipid metabolism in hepatocytes. Consequently, an enhanced intracellular lipid content, including sphingolipids, may lead to lipotoxicity. It is believed that resveratrol (RSV), one of the most extensively studied plant-derived polyphenols, and its interaction with sphingolipid metabolism may constitute one of the major therapeutic targets for cancer and metabolic diseases treatment.

Objective:

The aim of this study was to ascertain, whether resveratrol may affect sphingolipid metabolic pathways, enzymes and transporters in a lipid overload state.

Methods:

The experiments were conducted on hepatocellular carcinoma cells (HepG2) incubated with RSV and/or Palmitic Acid (PA) at the concentration of 0.5 mM and 50 µM, respectively for 16h. Intra- and extracellular sphingolipid concentrations were assessed by high-performance liquid chromatography and gas liquid chromatography. Moreover, the expression of caspase 3, selected fatty acid transporters and sphingolipid metabolism pathway proteins were estimated by Western Blot.

Results:

RSV alone and together with PA significantly increased the intracellular concentration of ceramide, sphinganine and sphingosine as well as the expression of enzymes related to de novo ceramide synthesis pathway. Moreover, in our study, we observed augmented ceramide and sphingomyelin efflux into the incubation media in these groups. In addition, RSV substantially reduced intracellular triacylglycerols accumulation in lipid overload conditions.

Conclusion:

The above-mentioned findings suggest that RSV, at least partially, demonstrates a potential protective effect on HepG2 cells in a lipid overload state.

Effect of sodium-glucose cotransporter 2 inhibitor, empagliflozin, and α-glucosidase inhibitor, voglibose, on hepatic steatosis in an animal model of type 2 diabetes

OBJECTIVE

We investigated the effects of sodium-glucose cotransporter 2 inhibitor, empagliflozin, and α-glucosidase inhibitor, voglibose, on hepatic steatosis in an animal model of type 2 diabetes (T2DM).

METHODS

Empagliflozin (OLETF-EMPA) or voglibose (OLETF-VOG) was administered to Otsuka Long-Evans Tokushima fatty (OLETF) rats once daily for 12 weeks. Control Long-Evans Tokushima Otsuka (LETO) and OLETF (OLETF-C) rats received saline.

RESULTS

Blood glucose levels were significantly suppressed in OLETF-EMPA and OLETF-VOG compared with the OLETF-C group. The liver fat content was significantly higher in the OLETF-C group than in the OLETF-EMPA and OLETF-VOG. Hepatic gene expressions involved in gluconeogenesis (glucose 6-phosphatase [G6Pase], fructose-1,6-bisphosphatase [FBP1], and phosphoenolpyruvate carboxykinase [PEPCK]) and lipogenesis (acetyl-CoA carboxylase [ACC], fatty acid synthase [FAS], and sterol regulatory element-binding transcription factor 1c [SREBP-1c]) were significantly decreased in the OLETF-EMPA group compared with other OLETF groups (OLETF-C and OLETF-VOG). Sirtuin 1 (SIRT1) expression level and SIRT1 activity were markedly reduced in OLETF-C rats; however, its expression increased in the OLETF-EMPA and OLETF-VOG. AMP-activated protein kinase (AMPK) phosphorylation level was remarkably increased by empagliflozin treatment in OLETF rats compared with other OLETF groups. Long-term empagliflozin and voglibose treatment reduced hepatic steatosis with suppression of gluconeogenesis and lipogenesis pathway in OLETF rats.

CONCLUSION

We suggest that this metabolic improvement might be related to SIRT1 and AMPK pathway in T2DM. But empagliflozin is thought to have more advantage to prevent hepatic steatosis than voglibose in T2DM.

Resveratrol protects against hepatic insulin resistance in a rat's model of non-alcoholic fatty liver disease by down-regulation of GPAT-1 and DGAT2 expression and inhibition of PKC membranous translocation

Non-alcoholic fatty liver disease (NAFLD) is associated with hepatic insulin resistance (IR). Resveratrol (RES) a potent hypolipidemic dietary polyphenol has been identified for its ability to prevent hepatic steatosis and hepatic IR in high-fat diet (HFD)-fed murine models of NAFLD. In the present study, we have carried an in vivo animal experiment to identify a novel mechanism for RES protective action. Sub-chronic (45 days) RES pretreatment in 3 days HFD-fed adult Wistar rats prevented early hepatic IR through inhibiting PKC/JNK activation; decreasing p-IRS (Ser³⁰⁷ ) and increasing p-IRS(Tyr⁶¹² ), p-Akt(Ser⁴⁷³ ) and p-GSK3(Ser⁹ ). These effects of RES were associated with reduced expression of acyl-CoA:glycerol-sn-3-phosphate acyltransferase (GPAT-1) and diacylglycerol:acyl-CoA acyltransferase (DGAT2), two critical enzymes in the glycerol-3-phosphate pathway for de novo triglycerides synthesis. These data indicate that RES protects against NAFLD, initially, by inhibiting the early development of hepatic IR.

Health benefits of resveratrol: Evidence from clinical studies

Resveratrol is a polyphenolic nutraceutical that exhibits pleiotropic activities in human subjects. The efficacy, safety, and pharmacokinetics of resveratrol have been documented in over 244 clinical trials, with an additional 27 clinical trials currently ongoing. Resveretrol is reported to potentially improve the therapeutic outcome in patients suffering from diabetes mellitus, obesity, colorectal cancer, breast cancer, multiple myeloma, metabolic syndrome, hypertension, Alzheimer's disease, stroke, cardiovascular diseases, kidney diseases, inflammatory diseases, and rhinopharyngitis. The polyphenol is reported to be safe at doses up to 5 g/d, when used either alone or as a combination therapy. The molecular basis for the pleiotropic activities of resveratrol are based on its ability to modulate multiple cell signaling molecules such as cytokines, caspases, matrix metalloproteinases, Wnt, nuclear factor-κB, Notch, 5'-AMP-activated protein kinase, intercellular adhesion molecule, vascular cell adhesion molecule, sirtuin type 1, peroxisome proliferator-activated receptor-γ coactivator 1α, insulin-like growth factor 1, insulin-like growth factor-binding protein 3, Ras association domain family 1α, pAkt, vascular endothelial growth factor, cyclooxygenase 2, nuclear factor erythroid 2 like 2, and Kelch-like ECH-associated protein 1. Although the clinical utility of resveratrol is well documented, the rapid metabolism and poor bioavailability have limited its therapeutic use. In this regard, the recently produced micronized resveratrol formulation called SRT501, shows promise. This review discusses the currently available clinical data on resveratrol in the prevention, management, and treatment of various diseases and disorders. Based on the current evidence, the potential utility of this molecule in the clinic is discussed.

The therapeutic effects of resveratrol on hepatic steatosis in high-fat diet-induced obese mice by improving oxidative stress, inflammation and lipid-related gene transcriptional expression

So far, the majority of the previous animal studies have focused on the preventive effects of resveratrol (RSV) on non-alcoholic fatty liver disease (NAFLD) rather than the therapeutic effects. In this study, the therapeutic effects of RSV on hepatic oxidative stress (OS), inflammation, and lipid metabolism-related gene expression of obese mice induced by a high-fat diet (HFD) were investigated. Male C57BL/6 mice were fed a HFD for 8 weeks to induce obesity-related NAFLD model. And then, NAFLD mice were treated with daily RSV oral gavage at the dose of 100 mg/kg body weight for an additional 4 weeks. HFD-induced the elevation of serum total cholesterol, high-density lipoprotein cholesterol, glucose, insulin, aspartate aminotransferase and alanine aminotransferase levels, and homeostasis model assessment of insulin resistance, hepatic histology changes, the increases in hepatic triglyceride, malondialdehyde and tumor necrosis factor alpha concentrations, as well as the higher mRNA expression of hepatic toll-like receptor 4 and cluster of differentiation 36 in mice, were restored by RSV. The therapeutic effects of RSV against hepatic steatosis of HFD obese mice were attributed to the reduction of OS, inflammation and free fatty acid uptake.

Involvement of 5'-Activated Protein Kinase (AMPK) in the Effects of Resveratrol on Liver Steatosis

This review focuses on the role of 5′AMP-activated protein kinase (AMPK) in the effects of resveratrol (RSV) and some RSV derivatives on hepatic steatosis. In vitro studies, performed in different hepatic cell models, have demonstrated that RSV is effective in preventing liver TG accumulation by activating AMPK, due to its phosphorylation. These preventive effects have been confirmed in studies conducted in animal models, such as mice and rats, by administering the phenolic compound at the same time as the diet which induces TG accumulation in liver. The literature also includes studies focused on other type of models, such as animals showing alcohol-induced steatosis or even steatosis induced by administering chemical products. In addition to the preventive effects of RSV on hepatic steatosis, other studies have demonstrated that it can alleviate previously developed liver steatosis, thus its role as a therapeutic tool has been proposed. The implication of AMPK in the delipidating effects of RSV in in vivo models has also been demonstrated.

Resveratrol improves high-fat diet induced fatty liver and insulin resistance by concomitantly inhibiting proteolytic cleavage of sterol regulatory element-binding proteins, free fatty acid oxidation, and intestinal triglyceride absorption

Resveratrol (RES) has the ability to ameliorate nonalcoholic fatty liver disease (NAFLD) and the mechanism remains unclear. Hence, using high-fat diet (HFD) obese rat model, we investigated the effect of a low dose of RES (20 mg/kg) on the hepatic sterol regulatory element-binding protein (SREBPs) – lipogenesis pathway, enzymes involved in β-oxidation and activity of pancreatic lipase. Four groups of rats (n = 8) of control (12% of calories as fat) and HFD (40% of calories as fat) were administered orally with either normal saline as a vehicle or RES as a concomitant treatment for 8 weeks on a daily basis. Then, various biochemical, histological, and molecular experiments were carried out. RES prevented the development and progression of NAFLD and significantly improved insulin sensitivity through (1) inhibiting the proteolytic cleavage of SREBPs-1 and SREBPs-2 without affecting their precursor mRNA or protein levels, (2) inhibiting free fatty acid β-oxidation and generation of reactive oxygen species through significant inhibition of CPT-1 and UCP-2, and (3) decreasing activity of pancreatic lipase in vivo and in vitro. In conclusion, our findings are the first in the literature to show new mechanisms of the hepatoprotective effect of RES against HFD induced NAFLD in rats.

Resveratrol modifies biliary secretion of cholephilic compounds in sham-operated and cholestatic rats

AIM

To investigate the effect of resveratrol on biliary secretion of cholephilic compounds in healthy and bile duct-obstructed rats.

METHODS

Resveratrol (RSV) or saline were administered to rats by daily oral gavage for 28 d after sham operation or reversible bile duct obstruction (BDO). Bile was collected 24 h after the last gavage during an intravenous bolus dose of the Mdr1/Mrp2 substrate azithromycin. Bile acids, glutathione and azithromycin were measured in bile to quantify their level of biliary secretion. Liver expression of enzymes and transporters relevant for bile production and biliary secretion of major bile constituents and drugs were analyzed at the mRNA and protein levels using qRT-PCR and Western blot analysis, respectively. The TR-FRET PXR Competitive Binding Assay kit was used to determine the agonism of RSV at the pregnane X receptor.

RESULTS

RSV increased bile flow in sham-operated rats due to increased biliary secretion of bile acids (BA) and glutathione. This effect was accompanied by the induction of the hepatic rate-limiting transporters for bile acids and glutathione, Bsep and Mrp2, respectively. RSV also induced Cyp7a1, an enzyme that is crucial for bile acid synthesis; Mrp4, a transporter important for BA secretion from hepatocytes to blood; and Mdr1, the major apical transporter for xenobiotics. The findings were supported by increased biliary secretion of azithromycin. The TR-FRET PXR competitive binding assay confirmed RSV as a weak agonist of the human nuclear receptor PXR, which is a transcriptional regulator of Mdr1/Mrp2. RSV demonstrated significant hepatoprotective properties against BDO-induced cirrhosis. RSV also reduced bile flow in BDO rats without any corresponding change in the levels of the transporters and enzymes involved in RSV-mediated hepatoprotection.

CONCLUSION

Resveratrol administration for 28 d has a distinct effect on bile flow and biliary secretion of cholephilic compounds in healthy and bile duct-obstructed rats.

Resveratrol in Hepatitis C Patients Treated with Pegylated-Interferon-α-2b and Ribavirin Reduces Sleep Disturbance

Background: Hepatitis C virus infection and interferon treatment have shown to be risk factors for sleep disorder health-related quality of life. Aim: To determine whether the effects of resveratrol on sleep disorders were associated with different tests in subjects with chronic hepatitis C treated with Peg-IFN-α and RBV. Patients and Methods: In this prospective, randomized, placebo controlled, double blind clinical trial, 30 subjects (Group A) with chronic hepatitis received Pegylated-Interferon-α2b (1.5 mg/kg per week), Ribavirin and placebo (N-acetylcysteine 600 mg and lactoferrin 23.6 g), while 30 subjects (Group B) received the same dosage of Pegylated-Interferon-α2b, Ribavirin and association of N-acetylcysteine 600 mg, lactoferrin 23.6 g and Resveratrol 19.8 mg for 12 months. All subjects underwent laboratory exams and questionnaires to evaluate mood and sleep disorders (General Health Questionnaire (GHQ), Profile of Mood States (POMS), Pittsburgh Sleep Quality Inventory (PSQI), Epworth Sleepiness Scale (ESS)). Results: The comparison between Group A and Group B showed significant differences after six months in C-reactive protein (p < 0.0001); after 12 months in aspartate aminotransferase (AST) (p < 0.0001) Viremia (p < 0.0001), HAI (p < 0.0012) and C-reactive protein (p < 0.0001); and at follow up in AST (p < 0.0001), Viremia (p < 0.0026) and C-reactive protein (p < 0.0001). Significant differences were observed after 12 month and follow-up in General Health Questionnaire, after 1, 6, 12 and follow-up in Profile of Mood States, after 6, 12, follow-up in Pittsburgh Sleep Quality Inventory and Epworth Sleepiness Scale. Conclusions: Supplementation with Resveratrol decreased General Health Questionnaire score and reduced sleep disorders in patients treated with Peg–IFN-α and RBV.

Traditional Chinese herbal extracts inducing autophagy as a novel approach in therapy of nonalcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is one of the leading causes of chronic liver diseases around the world due to the modern sedentary and food-abundant lifestyle, which is characterized by excessive fat accumulation in the liver related with causes other than alcohol abuse. It is widely acknowledged that insulin resistance, dysfunctional lipid metabolism, endoplasmic reticulum stress, oxidative stress, inflammation, and apoptosis/necrosis may all contribute to NAFLD. Autophagy is a protective self-digestion of intracellular organelles, including lipid droplets (lipophagy), in response to stress to maintain homeostasis. Lipophagy is another pathway for lipid degradation besides lipolysis. It is reported that impaired autophagy also contributes to NAFLD. Some studies have suggested that the histological characteristics of NAFLD (steatosis, lobular inflammation, and peri-sinusoid fibrosis) might be improved by treatment with traditional Chinese herbal extracts, while autophagy may be induced. This review will provide insights into the characteristics of autophagy in NAFLD and the related role/mechanisms of autophagy induced by traditional Chinese herbal extracts such as resveratrol, Lycium barbarum polysaccharides, dioscin, bergamot polyphenol fraction, capsaicin, and garlic-derived S-allylmercaptocysteine, which may inhibit the progression of NAFLD. Regulation of autophagy/lipophagy with traditional Chinese herbal extracts may be a novel approach for treating NAFLD, and the molecular mechanisms should be elucidated further in the near future.

Comprehensive Metabolomic Analysis in Blood, Urine, Fat, and Muscle in Men with Metabolic Syndrome: A Randomized, Placebo-Controlled Clinical Trial on the Effects of Resveratrol after Four Months' Treatment

Resveratrol possesses several beneficial metabolic effects in rodents, while the effects of resveratrol in humans remain unclear. Therefore, we performed a non-targeted comprehensive metabolomic analysis on blood, urine, adipose tissue, and skeletal muscle tissue in middle-aged men with metabolic syndrome randomized to either resveratrol or placebo treatment for four months. Changes in steroid hormones across all four matrices were the most pronounced changes observed. Resveratrol treatment reduced sulfated androgen precursors in blood, adipose tissue, and muscle tissue, and increased these metabolites in urine. Furthermore, markers of muscle turnover were increased and lipid metabolism was affected, with increased intracellular glycerol and accumulation of long-chain saturated, monounsaturated, and polyunsaturated (n3 and n6) free fatty acids in resveratrol-treated men. Finally, urinary derivatives of aromatic amino acids, which mainly reflect the composition of the gut microbiota, were altered upon resveratrol treatment. In conclusion, the non-targeted metabolomics approach applied to four different matrices provided evidence of subtle but robust effects on several metabolic pathways following resveratrol treatment for four months in men with metabolic syndrome—effects that, for the most part, would not have been detected by routine analyses. The affected pathways should be the focus of future clinical trials on resveratrol’s effects, and perhaps particularly the areas of steroid metabolism and the gut microbiome.

Placebo-controlled, randomised clinical trial: high-dose resveratrol treatment for non-alcoholic fatty liver disease

OBJECTIVE

"The obesity epidemic" has led to an increase in obesity-related conditions including non-alcoholic fatty liver disease (NAFLD), for which effective treatments are in demand. The polyphenol resveratrol prevents the development of experimental NAFLD through modulation of cellular pathways involved in calorie restriction. We aimed to test the hypothesis that resveratrol alleviates NAFLD in a randomised, clinical trial.

MATERIALS AND METHODS

A total of 28 overweight patients with transaminasemia and histological NAFLD were randomised 1:1 to placebo or resveratrol 1.5 g daily for 6 months. Twenty-six participants completed the trial and underwent repeated clinical investigation, blood work, MR spectroscopy; and 19 participants agreed to a repeat liver biopsy.

RESULTS

Resveratrol treatment was generally not superior to placebo in improving plasma markers of liver injury (primary outcome: alanine transaminase, p = 0.51). Resveratrol-treated patients showed a 3.8% decrease in liver lipid content (p = 0.03), with no difference between the two treatment arms (p = 0.38) and no improvement of histological features. Resveratrol treatment was not associated with improvements in insulin sensitivity or markers of the metabolic syndrome, except for a transient decrease in systolic BP. Microarray analysis and qRT-PCR revealed no major changes in expression profile. Also, we report a serious adverse event in a patient who developed fever and bicytopenia.

CONCLUSIONS

In this placebo-controlled, high-dose and long-term study, resveratrol treatment had no consistent therapeutic effect in alleviating clinical or histological NAFLD, though there may be a small ameliorating effect on liver function tests and liver fat accumulation.

Protective effects of resveratrol and its analogs on age-related macular degeneration in vitro

Damage of retinal pigment epithelial (RPE) cells by A2E may be critical for age-related macular degeneration (AMD) management. Accumulation and photooxidation of A2E are known to be one of the critical causes in AMD. Here, we evaluated the protective effect of resveratrol (RES), piceatannol (PIC) and RES glycones on blue-light-induced RPE cell death caused by A2E photooxidation. A2E treatment followed by blue light exposure caused significant damages on human RPE cells (ARPE-19). But the damages were attenuated by post- and pre-treatment of RES and PIC in our in vitro models. The results of cell free system and FAB-MS analysis clearly showed that the reduction of A2E by blue light exposure was significantly rescued, and that oxidized forms of A2E were significantly reduced by RES or PIC treatment. Besides, RES or PIC inhibited the intracellular accumulation of A2E. Not only RES and PIC but RES glycones showed protection of ARPE-19 cells against A2E and blue-light-induced photo-damage. These findings demonstrate that RES and its analogs may have protective effects against A2E and blue-light-induced ARPE-19 cell death through regulation of A2E accumulation as well as photooxidation of A2E. Thus RES and its analogs may be beneficial for AMD treatment.

The Effects of Resveratrol Supplementation in Overweight and Obese Humans: A Systematic Review of Randomized Trials

BACKGROUND

Obesity and metabolic syndrome are significant global health issues, with current public health messages predominately focused on altering dietary and physical activity behaviors. Resveratrol is a polyphenol (stilbenoid) commonly found in grapes, and human trials to date have shown conflicting and limited beneficial effects with respect to health. The aim of this study was to determine the effect of resveratrol supplementation on reducing body weight and modifying associated inflammatory markers.

METHODS

A systematic review was undertaken following the PRISMA guidelines and using five indexed databases (OVID MEDLINE, Cochrane Library, Web of Science, SCOPUS, and CINAHL). A search strategy was formulated to select randomized, double-blind, placebo-controlled human trials investigating the effects of resveratrol supplementation on obesity or overweight, including body weight, metabolic and inflammatory markers.

RESULTS

Five thousand five hundred sixty-nine studies published from 1990 to November 2015 were identified, with only nine papers meeting the inclusion criteria. The studies involved 208 participants (aged 49.2 ± 8.3 years) and utilized a substantial range of resveratrol doses (75-3000 mg/day). Study durations were a minimum of 2 weeks (14-90 days). Seven studies indicated no significant change in body mass index or body weight (P > 0.05), and three studies showed no improvements in fat mass, fat volume, or abdominal fat distribution (P > 0.05). Four studies included measurements of inflammatory markers, with three of these finding resveratrol supplementation to have a significant positive effect (P > 0.05).

CONCLUSION

Based on the included studies, there is currently insufficient evidence to support the recommendation of resveratrol supplements in management of obesity. However, there were significant but not entirely consistent anti-inflammatory effects after resveratrol supplementation in overweight and obese individuals.

Resveratrol Attenuates Aβ25-35 Caused Neurotoxicity by Inducing Autophagy Through the TyrRS-PARP1-SIRT1 Signaling Pathway

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulation of β-amyloid peptide (Aβ) and loss of neurons. Resveratrol (RSV) is a natural polyphenol that has been found to be beneficial for AD through attenuation of Aβ-induced toxicity in neurons both in vivo and in vitro. However, the specific underlying mechanisms remain unknown. Recently, autophagy was found to protect neurons from toxicity injuries via degradation of impaired proteins and organelles. Therefore, the aim of this study was to determine the role of autophagy in the anti-neurotoxicity effect of RSV in PC12 cells. We found that RSV pretreatment suppressed β-amyloid protein fragment 25-35 (Aβ25-35)-induced decrease in cell viability. Expression of light chain 3-II, degradation of sequestosome 1, and formation of autophagosomes were also upregulated by RSV. Suppression of autophagy by 3-methyladenine abolished the favorable effects of RSV on Aβ25-35-induced neurotoxicity. Furthermore, RSV promoted the expression of sirtuin 1 (SIRT1), auto-poly-ADP-ribosylation of poly (ADP-ribose) polymerase 1 (PARP1), as well as tyrosyl transfer-RNA (tRNA) synthetase (TyrRS). Nevertheless, RSV-mediated autophagy was markedly abolished with the addition of inhibitors of SIRT1 (EX527), nicotinamide phosphoribosyltransferase (STF-118804), PARP1 (AG-14361), as well as SIRT1 and TyrRS small interfering RNA transfection, indicating that the action of RSV on autophagy induction was dependent on TyrRS, PARP1 and SIRT1. In conclusion, RSV attenuated neurotoxicity caused by Aβ25-35 through inducing autophagy in PC12 cells, and the autophagy was partially mediated via activation of the TyrRS-PARP1-SIRT1 signaling pathway.

Effect of resveratrol on experimental non-alcoholic fatty liver disease depends on severity of pathology and timing of treatment

BACKGROUND AND AIM

Non-alcoholic steatohepatitis (NASH) is a leading cause of chronic liver disease with few therapeutic options. Resveratrol (RSV) prevents the development of steatosis in a number of experimental fatty liver (non-alcoholic fatty liver [NAFL]) models, but the preventive or therapeutic effects on experimental NASH are not yet clarified, and clinical results on non-alcoholic fatty liver disease are ambiguous. Thus, we aimed to compare the RSV-mediated preventive and therapeutic effects on experimental NAFL and NASH.

METHODS

We used a high-fat (HF) diet to generate a rat NAFL model and a high-fat, high-cholesterol (HFC) diet to generate a rat NASH model. The preventive and therapeutic potential of RSV was tested by adding RSV to the HF and HFC diet from study start or after 1 week of the diets. Animals were sacrificed after 8 weeks with appropriate controls. Blood and liver were harvested for analysis, including measurement of RSV metabolites.

RESULTS

Resveratrol reduced the development of histological steatosis (P = 0.03) and partly triglyceride accumulation (fold change reduced from 3.6 to 2.4, P = 0.08) in the male NAFL model, although effects were moderate. In NASH prevention, RSV reduced the accumulation of triglyceride in hepatic tissue (P < 0.01), while there was no effect on biochemical, histopathological, or transcriptional NASH changes. Further, RSV had no therapeutic effect on established NASH. We found RSV metabolites but no parent RSV in serum or liver tissue, confirming low bioavailability.

CONCLUSIONS

These experimental findings suggest that a weak hepatic benefit of RSV treatment is seen in prevention of steatosis only.

A Combination of Leucine, Metformin, and Sildenafil Treats Nonalcoholic Fatty Liver Disease and Steatohepatitis in Mice

Sirt1, AMPK, and eNOS modulate hepatic energy metabolism and inflammation and are key players in the development of NASH. L-leucine, an allosteric Sirt1 activator, synergizes with low doses of metformin or sildenafil on the AMPK-eNOS-Sirt1 pathway to reverse mild NAFLD in preclinical mouse models. Here we tested a possible multicomponent synergy to yield greater therapeutic efficacy in NAFLD/NASH. Liver cells and macrophages or an atherogenic diet induced NASH mouse model was treated with two-way and three-way combinations. The three-way combination Sild-Met-Leu increased hepatic fatty acid oxidation and reduced lipogenic gene expression and inflammatory marker in vitro. In mice, Sild-Met-Leu reduced the diet induced increases of ALT, TGFβ, PAI-1, IL1β, and TNFα, hepatic collagen expression, and nearly completely reversed hepatocyte ballooning and triglyceride accumulation, while all two-way combinations had only modest effects. Therefore, these data provide preclinical evidence for therapeutic efficacy of Sild-Met-Leu in the treatment of NAFLD and NASH.

Critical review of resveratrol in xenobiotic-induced hepatotoxicity

Use of natural products is increasingly popular. In fact, many patients with liver diseases self-medicate with herbal supplements. Resveratrol (RSV), in particular, is a common natural product that can reduce injury in experimental models of liver disease. Xenobiotic hepatotoxicity is a particularly important area-of-need for therapeutics. Drug-induced liver injury, for example, is the most common cause of acute liver failure (ALF) and ALF-induced deaths in many countries. Importantly, RSV protects against hepatotoxicity in animal models in vivo caused by several drugs and chemicals and may be an effective intervention. Although many mechanisms have been proposed to explain the protection, not all are consistent with other data. Furthermore, RSV suffers from other issues, including limited bioavailability due to extensive hepatic metabolism. The purpose of this article is to summarize recent findings on the protective effects of RSV in xenobiotic-induced liver injury and other forms of liver injury and to provide a critical review of the underlying mechanisms. New mechanisms that are more consistent with data emerging from the toxicology field are suggested. Efforts to move RSV into clinical use are also considered. Overall, RSV is a promising candidate for therapeutic use, but additional studies are needed to better understand its effects.

Resveratrol attenuates the progress of liver fibrosis via the Akt/nuclear factor-κB pathways

Liver fibrosis is a wound-healing response to chronic liver injury that results in the accumulation of extracellular matrix proteins. It eventually leads to cirrhosis of the liver and liver failure, and it is a critical threat to the health and lives of patients with chronic liver diseases. No effective treatment is currently available. Resveratrol is a polyphenol with antioxidant, anti‑cancer and anti‑inflammatory properties. It has been reported that resveratrol prevents liver fibrosis, possibly by inhibiting NF‑κB activation. The present study investigated the mechanisms by which resveratrol prevented liver fibrosis, focusing on the possible involvement of the NF‑κB pathway. Mice with carbon tetrachloride (CCl4)‑induced liver fibrosis were treated with various concentrations of resveratrol. Serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and tumor necrosis factor (TNF)‑α were detected by ELISAs. Expression of α‑smooth muscle actin (α‑SMA), collagen I, inhibitor of NF‑κB (IκB) and NF‑κB were detected by western blot analysis. In addition, the present study examined the effects of resveratrol on the expression of fibrosis markers in LX‑2 cells. Western blot analysis was further used to detect the levels of Akt and phosphorylated Akt, as well as the nuclear levels of IκB, phosphorylated IκB and NF‑κB p65. The expression of α‑SMA in resveratrol‑treated LX‑2 cells was detected by immunofluorescence and flow cytometry, which demonstrated that resveratrol decreased the expression of α‑SMA in LX‑2 cells. Resveratrol also decreased CCl4‑induced upregulation of serum AST, ALT, TNF‑α, α‑SMA and collagen I. Finally, resveratrol prevented the activation of NF‑κB and Akt. The results of the present study therefore indicated that resveratrol attenuates liver fibrosis via the Akt/NF-κB pathways.

Anti-Inflammatory and Organ-Protective Effects of Resveratrol in Trauma-Hemorrhagic Injury

Resveratrol, a natural polyphenolic compound of grape and red wine, owns potential anti-inflammatory effects, which results in the reduction of cytokines overproduction, the inhibition of neutrophil activity, and the alteration of adhesion molecules expression. Resveratrol also possesses antioxidant, anti-coagulation and anti-aging properties, and it may control of cell cycle and apoptosis. Resveratrol has been shown to reduce organ damage following traumatic and shock-like states. Such protective phenomenon is reported to be implicated in a variety of intracellular signaling pathways including the activation of estrogen receptor, the regulation of the sirtuin 1/nuclear factor-kappa B and mitogen-activated protein kinases/hemeoxygenase-1 pathway, and the mediation of proinflammatory cytokines and reactive oxygen species formation and reaction. In the recent studies, resveratrol attenuates hepatocyte injury and improves cardiac contractility due to reduction of proinflammatory mediator expression and ameliorates hypoxia-induced liver and kidney mitochondrial dysfunction following trauma and hemorrhagic injuries. Moreover, through anti-inflammatory effects and antioxidant properties, the resveratrol is believed to protect organ function in trauma-hemorrhagic injury. In this review, the organ-protective and anti-inflammatory effects of resveratrol in trauma-hemorrhagic injury will be discussed.

Resveratrol improves hepatic steatosis by inducing autophagy through the cAMP signaling pathway

SCOPE

Resveratrol (RSV), a natural polyphenol, has been reported to attenuate nonalcoholic fatty liver disease (NAFLD); however, its underlying mechanism is unclear. Autophagy was recently identified as a critical protective mechanism during NAFLD development. Therefore, we investigated the role of autophagy in the beneficial effects of RSV on hepatic steatosis.

METHODS AND RESULTS

Via Oil red O staining, triglyceride, and β-hydroxybutyrate detection, we found that RSV decreased palmitate-induced lipid accumulation and stimulated fatty acid β-oxidation in hepatocytes. Based on Western blot assay, confocal microscopy and transmission electron microscopy, we found that RSV induced autophagy in hepatocytes, whereas autophagy inhibition markedly abolished RSV-mediated hepatic steatosis improvement. Moreover, RSV increased cAMP levels and the levels of SIRT1 (sirtuin 1), pPRKA (phosphorylated protein kinase A), and pAMPK (phosphorylated AMP-activated protein kinase), as well as SIRT1 activity in HepG2 cells. Incubation with inhibitors of AC (adenylyl cyclase), PRKA, AMPK, SIRT1, or with AC, PRKA, AMPK, or SIRT1 siRNA abolished RSV-mediated autophagy. Similar results were obtained in mice with hepatic steatosis.

CONCLUSION

RSV improved hepatic steatosis partially by inducing autophagy via the cAMP-PRKA-AMPK-SIRT1 signaling pathway, which provides new evidence regarding RSV's effects on NAFLD treatment.

Resveratrol prevents hepatic steatosis and endoplasmic reticulum stress and regulates the expression of genes involved in lipid metabolism, insulin resistance, and inflammation in rats

Previous research demonstrated that resveratrol possesses promising properties for preventing obesity. Endoplasmic reticulum (ER) stress was proposed to be involved in the pathophysiology of both obesity and hepatic steatosis. In the current study, we hypothesized that resveratrol could protect against high-fat diet (HFD)-induced hepatic steatosis and ER stress and regulate the expression of genes related to hepatic steatosis. Rats were fed either a control diet or a HFD for 12 weeks. After 4 weeks, HFD-fed rats were treated with either resveratrol or vehicle for 8 weeks. Body weight, serum metabolic parameters, hepatic histopathology, and hepatic ER stress markers were evaluated. Moreover, an RT2 Profiler Fatty Liver PCR Array was performed to investigate the mRNA expressions of 84 genes related to hepatic steatosis. Our work showed that resveratrol prevented dyslipidemia and hepatic steatosis induced by HFD. Resveratrol significantly decreased activating transcription factor 4, C/EBP-homologous protein and immunoglobulin binding protein levels, which were elevated by the HFD. Resveratrol also decreased PKR-like ER kinase phosphorylation, although it was not affected by the HFD. Furthermore, resveratrol increased the expression of peroxisome proliferator-activated receptor δ, while decreasing the expression of ATP citrate lyase, suppressor of cytokine signaling-3, and interleukin-1β. Our data suggest that resveratrol can prevent hepatic ER stress and regulate the expression of peroxisome proliferator-activated receptor δ, ATP citrate lyase, suppressor of cytokine signaling-3, tumor necrosis factor α, and interleukin-1β in diet-induced obese rats, and these effects likely contribute to resveratrol's protective function against excessive accumulation of fat in the liver.

The role of fibroblast growth factor 21 in the pathogenesis of non-alcoholic fatty liver disease and implications for therapy

Non-alcoholic fatty liver disease (NAFLD) includes a cluster of liver disorders ranging from simple fatty liver to non-alcoholic steatohepatitis (NASH) and cirrhosis. Due to its liver and vascular complications, NAFLD has become a public health problem with high morbidity and mortality. The pathogenesis of NAFLD is considered a "multi-hit hypothesis" that involves lipotoxicity, oxidative stress, endoplasmic reticulum stress, a chronic inflammatory state and mitochondrial dysfunction. Fibroblast growth factor 21 (FGF21) is a member of the fibroblast growth factor family with multiple metabolic functions. FGF21 directly regulates lipid metabolism and reduces hepatic lipid accumulation in an insulin-independent manner. Several studies have shown that FGF21 can ameliorate the "multi-hits" in the pathogenesis of NAFLD. The administration of FGF21 reverses hepatic steatosis, counteracts obesity and alleviates insulin resistance in rodents and nonhuman primates. Using several strategies, we show that the reversal of simple fatty liver and NASH is mediated by activation of the FGF21 signaling pathway. In this review, we describe the molecular mechanisms involved in the onset and/or progression of NAFLD, and review the current literature to highlight the therapeutic procedures associated with the FGF21 signaling pathway for simple fatty liver and NASH, which are the two most important types of NAFLD.

Recent advances in dietary supplementation, in treating non-alcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is currently known as the most common liver problem, characterized by excessive lipid accumulation in hepatocytes, which may progress to other liver diseases such as nonalcoholic steatohepatitis, hepatic tissue fibrosis, liver cirrhosis, and failure or hepatocellular carcinoma. Since NAFLD is positively associated with the development of obesity, insulin resistance, and ultimately type 2 diabetes mellitus, it is often regarded as the hepatic manifestation of the metabolic syndrome. No pharmacologic treatment has yet been proven for this disease. For most patients with presumed or confirmed NAFLD, the only proven strategy is to offer lifestyle advice that can lead to sustained weight loss. Since insulin resistance, oxidative stress, inflammation, and necro-apoptosis are involved in NAFLD pathogenesis, it seems that every potential therapeutic agent should target one or some of these pathologic events. There are many well known anti-oxidants, anti-inflammatory, and insulin sensitizer dietary supplements which have shown beneficial effects on NAFLD improvement in animal and human studies. The purpose of this review is to explore the existing evidences on dietary supplements considered to have hepatoprotective properties, and to present some proposed mechanisms by which they may protect against NAFLD.