Resveratrol attenuates steatosis in obese Zucker rats by decreasing fatty acid availability and reducing oxidative stress. Br J Nutr. 2012;107:202-210. [PMID: 21733326 DOI: 10.1017/s0007114511002753]

Treatment Options and Continuity of Care in Metabolic-associated Fatty Liver Disease: A Multidisciplinary Approach

The terms non-alcoholic fatty liver disease and non-alcoholic steatohepatitis have some limitations as they use exclusionary confounder terms and the use of potentially stigmatising language. Recently, a study with content experts and patients has been set to change this nomenclature. The term chosen to replace non-alcoholic fatty liver disease was metabolic dysfunction-associated steatotic liver disease (MASLD), which avoids stigmatising and helps improve awareness and patient identification. MASLD is the most common cause of chronic liver disease with an increasing prevalence, accounting for 25% of the global population. It is considered the hepatic manifestation of the metabolic syndrome with lifestyle playing a fundamental role in its physiopathology. Diet change and physical activity are the cornerstones of treatment, encompassing weight loss and healthier behaviours and a holistic approach. In Europe, there is no approved drug for MASLD to date and there is a substantial unmet medical need for effective treatments for patients with MASLD. This review not only provides an update on advances in evidence for nutrition and physical activity interventions but also explores the different therapeutic options that are being investigated and whose development focuses on the restitution of metabolic derangements and halting inflammatory and fibrogenic pathways.

Integrative evidence construction for resveratrol treatment of nonalcoholic fatty liver disease: preclinical and clinical meta-analyses

Background: Resveratrol, a polyphenol found in various plants, is known for its diverse bioactivities and has been explored in relation to nonalcoholic fatty liver disease (NAFLD). However, no high-quality evidence exists regarding its efficacy. Objective: a meta-analysis was conducted to evaluate the potential efficacy of resveratrol in treating nonalcoholic fatty liver disease by analyzing both preclinical studies and clinical trials. Method: PubMed, Embase and Web of Science were searched for the included literature with the criteria for screening. Quantitative synthesis and meta-analyses were performed by STATA 16.0. Results: Twenty-seven studies were included, and the results indicated that resveratrol effectively improved liver function, reduced fatty liver indicators, and affected other indices in preclinical studies. The effective dosage ranged from 50 mg/kg-200 mg/kg, administered over a period of 4-8 weeks. While there were inconsistencies between clinical trials and preclinical research, both study types revealed that resveratrol significantly reduced tumor necrosis factor-α levels, further supporting its protective effect against nonalcoholic fatty liver disease. Additionally, resveratrol alleviated nonalcoholic fatty liver disease primarily via AMPK/Sirt1 and anti-inflammatory signaling pathways. Conclusion: Current meta-analysis could not consistently verify the efficacy of resveratrol in treating nonalcoholic fatty liver disease, but demonstrated the liver-protective effects on nonalcoholic fatty liver disease. The large-sample scale and single region RCTs were further needed to investigate the efficacy.

Protective Effects of Gnetin C from Melinjo Seed Extract against High-Fat Diet-Induced Hepatic Steatosis and Liver Fibrosis in NAFLD Mice Model

Nonalcoholic fatty liver disease (NAFLD), the most common form of chronic liver disease, can progress to hepatic steatosis, inflammation, and advanced fibrosis, increasing the risk of cirrhosis. Resveratrol, a natural polyphenol with antioxidant and anti-inflammatory properties, is beneficial in treating multiple metabolic diseases. Gnetin C, a resveratrol derivative obtained from Melinjo seed extract (MSE), shares similar health-promoting properties. We investigated the role of gnetin C in preventing NAFLD in a mouse model and compared it with resveratrol. Male C57BL/6J mice were fed a control diet (10% calories from fat), a high-fat choline-deficient (HFCD) diet (46% calories from fat) and HFCD diet supplemented with gnetin C (150 mg/kg BW·day-1) or resveratrol (150 mg/kg BW·day-1) for 12 weeks. Gnetin C supplementation reduced body and liver weight, and improved blood glucose levels and insulin sensitivity. Both gnetin C- and resveratrol reduced hepatic steatosis, with gnetin C also decreasing liver lipid content. Gnetin C and resveratrol ameliorated HFCD diet-induced hepatic fibrosis. The mRNA expression results, and western blot analyses showed that gnetin C and, to some extent, resveratrol downregulated fibrosis markers in the TGF-β1 signaling pathway, indicating a possible safeguarding mechanism against NAFLD. These results suggest that gnetin C supplementation may protect against lipid deposition and hepatic fibrosis.

Targeting Oxidative Stress with Polyphenols to Fight Liver Diseases

Reactive oxygen species (ROS) are important second messengers in many metabolic processes and signaling pathways. Disruption of the balance between ROS generation and antioxidant defenses results in the overproduction of ROS and subsequent oxidative damage to biomolecules and cellular components that disturb cellular function. Oxidative stress contributes to the initiation and progression of many liver pathologies such as ischemia-reperfusion injury (LIRI), non-alcoholic fatty liver disease (NAFLD), and hepatocellular carcinoma (HCC). Therefore, controlling ROS production is an attractive therapeutic strategy in relation to their treatment. In recent years, increasing evidence has supported the therapeutic effects of polyphenols on liver injury via the regulation of ROS levels. In the current review, we summarize the effects of polyphenols, such as quercetin, resveratrol, and curcumin, on oxidative damage during conditions that induce liver injury, such as LIRI, NAFLD, and HCC.

Effects of Pomegranate Peel Polyphenols Combined with Inulin on Gut Microbiota and Serum Metabolites of High-Fat-Induced Obesity Rats

Pomegranate peel polyphenols (PPPs) and inulin have been reported to have lipid-lowering effects. Here, the effects of PPPs combined with inulin on obesity traits and the change of the gut microbiota, short-chain fatty acids (SCFAs), and serum metabolomics profiles in rats with a high-fat diet (HFD) were investigated. According to the experimental results, PPPs were most effective in reducing the body weight and serum and liver lipid levels. Besides, PPPs ameliorated the disorder of gut microbiota, in particular, the enrichment of SCFA producers, such as Lactobacillus, Roseburia, Christensenellaceae_R-7_group, Ruminococcaceae_UCG-005, Bacteroides, and Allobaculum, and the depletion of the Blautia and unclassified Lachnospiraceae population. PPPs also regulated the levels of metabolites changed by HFD feeding via tryptophan metabolism, valine, leucine, and isoleucine biosynthesis, and arachidonic acid metabolism pathways. The correlation analysis showed that PPPs remitted HFD-induced elevation in triglycerides (TGs), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) levels and lowered high-density lipoprotein (HDL) levels through regulating the gut microbiota, SCFAs, and related metabolites. These findings elucidated that PPPs have a good anti-obesity effect. This study extends the understanding of PPP effects on high-fat-induced obesity, which includes the relationship among gut microbiota, SCFAs, serum metabolites, and TG-, IL-6- and TNF-α- lowering and HDL-elevating functions.

The effect of resveratrol supplementation on biomarkers of liver health: A systematic review and meta-analysis of randomized controlled trials

This study aimed to evaluate the effect of resveratrol on liver biomarkers in adult participants, using systematic review and meta-analysis of randomized controlled trials. PubMed, Scopus, Web of Science and Cochran Library was searched, up to October 2021. The pooled effects were calculated using a random-effects model and expressed as weighted mean difference and 95% confidence interval. The methodological quality of studies as well as certainty of evidence were assessed by standard tools. Thirty-seven relevant trials were found. Although overall analysis found no significant change, subgroup analysis showed a significant improvement in alanine aminotransferase (ALT; -7.79 U/L) and glutamyl transferase (-6.0 U/L) in patients with liver disorders, and ALT (-2.22 U/L) in younger adults; however, high-dose supplementation (>1,000 mg/day) appeared to increase alkaline phosphatase concentration (+5.07 U/L). ALT also increased in older adults (+2.33 U/L) following resveratrol supplementation. We found resveratrol did not have a significant effect on liver health in the general population. However, resveratrol could be effective in patients with liver disorders. Our findings also suggest that high-dose resveratrol administration and supplementation in older adults should be performed with caution. Further high-quality clinical trials are also needed to firmly establish the clinical efficacy of resveratrol.

Independent, but not co-supplementation, with nitrate and resveratrol improves glucose tolerance and reduces markers of cellular stress in high-fat-fed male mice

Independent supplementation with nitrate (NIT) and resveratrol (RSV) enriches various aspects of mitochondrial biology in key metabolic tissues. Although RSV is known to activate Sirt1 and initiate mitochondrial biogenesis, the metabolic benefits elicited by dietary nitrate appear to be dependent on 5'-adenosine monophosphate-activated protein kinase (AMPK)-mediated signaling events, a process also linked to the activation of Sirt1. Although the benefits of individual supplementation with these compounds have been characterized, it is unknown if co-supplementation may produce superior metabolic adaptations. Thus, we aimed to determine if treatment with combined +NIT and +RSV (+RN) could additively alter metabolic adaptations in the presence of a high-fat diet (HFD). Both +RSV and +NIT improved glucose tolerance compared with HFD (P < 0.05); however, this response was attenuated following combined +RN supplementation. Within skeletal muscle, all supplements increased mitochondrial ADP sensitivity compared with HFD (P < 0.05), without altering mitochondrial content. Although +RSV and +NIT decreased hepatic lipid deposition compared with HFD (P < 0.05), this effect was abolished with +RN, which aligned with significant reductions in Sirt1 protein content (P < 0.05) after combined treatment, in the absence of changes to mitochondrial content or function. Within epididymal white adipose tissue (eWAT), all supplements reduced crown-like structure accumulation compared with HFD (P < 0.0001) and mitochondrial reactive oxygen species (ROS) emission (P < 0.05), alongside reduced adipocyte cross-sectional area (CSA) (P < 0.05), with the greatest effect observed after +RN treatment (P = 0.0001). Although the present data suggest additive changes in adipose tissue metabolism after +RN treatment, concomitant impairments in hepatic lipid homeostasis appear to prevent improvements in whole body glucose homeostasis observed with independent treatment, which may be Sirt1 dependent.

Epigenetic Aspects and Prospects in Autoimmune Hepatitis

The observed risk of autoimmune hepatitis exceeds its genetic risk, and epigenetic factors that alter gene expression without changing nucleotide sequence may help explain the disparity. Key objectives of this review are to describe the epigenetic modifications that affect gene expression, discuss how they can affect autoimmune hepatitis, and indicate prospects for improved management. Multiple hypo-methylated genes have been described in the CD4⁺ and CD19⁺ T lymphocytes of patients with autoimmune hepatitis, and the circulating micro-ribonucleic acids, miR-21 and miR-122, have correlated with laboratory and histological features of liver inflammation. Both epigenetic agents have also correlated inversely with the stage of liver fibrosis. The reduced hepatic concentration of miR-122 in cirrhosis suggests that its deficiency may de-repress the pro-fibrotic prolyl-4-hydroxylase subunit alpha-1 gene. Conversely, miR-155 is over-expressed in the liver tissue of patients with autoimmune hepatitis, and it may signify active immune-mediated liver injury. Different epigenetic findings have been described in diverse autoimmune and non-autoimmune liver diseases, and these changes may have disease-specificity. They may also be responses to environmental cues or heritable adaptations that distinguish the diseases. Advances in epigenetic editing and methods for blocking micro-ribonucleic acids have improved opportunities to prove causality and develop site-specific, therapeutic interventions. In conclusion, the role of epigenetics in affecting the risk, clinical phenotype, and outcome of autoimmune hepatitis is under-evaluated. Full definition of the epigenome of autoimmune hepatitis promises to enhance understanding of pathogenic mechanisms and satisfy the unmet clinical need to improve therapy for refractory disease.

Effect of resveratrol supplementation on hepatic steatosis and cardiovascular indices in overweight subjects with type 2 diabetes: a double-blind, randomized controlled trial

BACKGROUND

Patients with type 2 diabetes mellitus (T2DM) are prone to develop non-alcoholic fatty liver disease (NAFLD) and cardiovascular diseases (CVD). We aimed to investigate whether the resveratrol supplementation improves novel hepatic and cardiovascular indices in these patients.

METHODS

We conducted a double-blind, randomized controlled trial for 8 weeks. Seventy-six patients with T2DM were randomly assigned to receive 1000 mg/day resveratrol or placebo. Levels of lipid accumulation product (LAP), visceral adiposity index (VAI), Castelli risk index I (CRI-I), CRI-II and atherogenic coefficient (AC) were measured at the beginning and after intervention.

RESULTS

A total of 71 participants completed the trial. After adjusting for confounding factors including medications, diabetes duration, energy intake and physical activity, no significant difference was found between the intervention group and the control group in LAP (mean change: - 2.46 ± 23.3 vs. 1.43 ± 14.3; P = 0.43), VAI (mean change: - 0.25 ± 1.1 vs. - 0.02 ± 0.6; P = 0.47), CRI-I (mean change: - 0.25 ± 0.9 vs. - 0.09 ± 0.5; P = 0.79), CRI-II (mean change: - 0.23 ± 0.7 vs. - 0.06 ± 0.6; P = 0.38) and AC (mean change: - 0.25 ± 0.9 vs. - 0.09 ± 0.5; P = 0.79).

CONCLUSIONS

Resveratrol supplementation had no effect on hepatic steatosis and cardiovascular indices. Further clinical trials, especially among subjects with dyslipidemia are needed to reach a firm conclusion. In addition, taking all medications should be controlled in future studies. Trial registration The protocol was registered on 29/12/2017 at the Iranian clinical trials website (IRCT20171118037528N1) with URL: https://en.irct.ir/trial/27734 .

Therapeutic Effects of Resveratrol on Nonalcoholic Fatty Liver Disease Through Inflammatory, Oxidative Stress, Metabolic, and Epigenetic Modifications

The prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing around the world, in association with the progressive elevation in overweight and obesity. The accumulation of lipids in NAFLD patients contributes to the development of insulin resistance, inflammation and oxidative stress in hepatocytes, and alteration of blood lipids and glycaemia. There are currently no effective pharmacological therapies for NAFLD, although lifestyle and dietary modifications targeting weight reduction are among the prevailing alternative approaches. For this reason, new approaches should be investigated. The natural polyphenol resveratrol represents a potential new treatment for management of NAFLD due to anti-inflammatory and antioxidant properties. Although preclinical trials have demonstrated promising results of resveratrol against NALFD, the lack of conclusive results creates the need for more trials with larger numbers of patients, longer time courses, and standardized protocols.

The Anti-Obesity Effect of Traditional Chinese Medicine on Lipid Metabolism

With the improvement of living conditions and the popularity of unhealthy eating and living habits, obesity is becoming a global epidemic. Obesity is now recognized as a disease that not only increases the risk of metabolic diseases such as type 2 diabetes (T2D), non-alcoholic fatty liver disease (NAFLD), cardiovascular disease (CVD), and cancer but also negatively affects longevity and the quality of life. The traditional Chinese medicines (TCMs) are highly enriched in bioactive compounds and have been used for the treatment of obesity and obesity-related metabolic diseases over a long period of time. In this review, we selected the most commonly used anti-obesity or anti-hyperlipidemia TCMs and, where known, their major bioactive compounds. We then summarized their multi-target molecular mechanisms, specifically focusing on lipid metabolism, including the modulation of lipid absorption, reduction of lipid synthesis, and increase of lipid decomposition and lipid transportation, as well as the regulation of appetite. This review produces a current and comprehensive understanding of integrative and systematic mechanisms for the use of TCMs for anti-obesity. We also advocate taking advantage of TCMs as another therapy for interventions on obesity-related diseases, as well as stressing the fact that more is needed to be done, scientifically, to determine the active compounds and modes of action of the TCMs.

Resveratrol and endoplasmic reticulum stress: A review of the potential protective mechanisms of the polyphenol

The endoplasmic reticulum (ER) is an organelle that performs a set of essential functions in cellular biology. These include synthesis of lipids, homeostasis of calcium, and controlling the folding of proteins. Inflammation and oxidative stress are two important reasons behind the accumulation of misfolded or unfolded proteins in the ER. In such circumstances, a series of measures are undertaken in the cell which are collectively called unfolded protein response (UPR). The aim of UPR is to reduce the burden of protein aggregates and promote survival. However, extended and unrestricted ER stress (ERS) can induce further inflammation and apoptosis. ERS and the UPR are involved in different diseases such as neurodegenerative and cardiovascular diseases. Resveratrol (RSV), a natural polyphenol, has well-documented evidence supporting its numerous biological properties including antioxidant, antiinflammatory, antiobesity, antidiabetic, and antiischemic activities. The compound is also known for its potential beneficial effects on cognitive function and liver, kidney, and lung health. In this review, the role of ERS in several pathological conditions and the potential protective effects of RSV are discussed. However, the scarcity of clinical data means that more research needs to be conducted to gain a lucid understanding of RSV's effects on endoplasmic reticulum stress (ERS) in humans.

Açaí (Euterpe oleracea Martius) supplementation improves oxidative stress biomarkers in liver tissue of dams fed a high-fat diet and increases antioxidant enzymes' gene expression in offspring

Lipids excess from an uterine environment can increase free radicals production of and thus induce oxidative status imbalance, a key factor for progression of non-alcoholic fatty liver disease (NAFLD) in offspring. Food antioxidant components in maternal diet may play an important role in preventing offspring metabolic disorders. The objective of the study was to evaluate the effects of açaí pulp supplementation on maternal high-fat diet, by assessing activity and expression of antioxidant enzymes and biomarkers of oxidative stress in the liver. Female Fisher rats were divided into four groups and fed a control diet (C), a high-fat diet (HF), a control diet supplemented with açaí (CA) and a high-fat diet supplemented with açaí (HFA) before mating, during gestation and lactation. The effects of açaí supplementation on oxidative stress biomarkers and antioxidant enzymes expression were evaluated in dams and male offspring after weaning. HFA diet increased body weight in dams, however reduced absolute and relative liver weight. There was a reduction in liver biomarkers of oxidative stress, malondialdehyde and carbonyl protein, as well as in catalase, glutathione peroxidase and superoxide dismutase activity. In offspring, HFA diet reduced liver weight and increased Gpx1, Gpx4 and Sod1 mRNA expression. These results suggest that açaí is able to restore redox status, preventing oxidative damage in dams by a direct mechanism and to promote beneficial effects on expression of antioxidant defences related genes in offspring.

Antioxidative Stress Mechanisms behind Resveratrol: A Multidimensional Analysis

Over the past decade, oxidative stress was shown to be a key factor for various diseases. The term “antioxidant” also rapidly gained attention worldwide, viewed as beneficial in disease prevention. Resveratrol (RSV), a natural polyphenol, is a plant antitoxin formed in response to harmful environmental factors such as infection and injury. This antitoxin is found in grapes, strawberries, peanuts, or herbal medicines and exhibits many pharmacological effects involved in antitumor, anti-inflammatory, antiaging, and antioxidation stress mechanisms. Recently, numerous in vitro and in vivo experiments have shown that RSV harbors antioxidative stress properties and can be used as an antioxidant. Here, we review the free radical scavenging ability, antioxidant properties, signaling pathways, expression and regulation of antioxidant enzymes, and oxidative stress-related diseases associated with RSV.

Effects of resveratrol supplementation on liver enzymes: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

The available evidence regarding the possible effects of resveratrol on liver function is inconsistent. Therefore, the present meta-analysis was performed to investigate the overall effects of resveratrol supplementation on liver enzymes in adults.

METHODS

A systematic and comprehensive search of the online medical databases including PubMed, Scupos, Web of Science and Cochran Library was performed up to February 2020. All RCTs using resveratrol supplements in adults were included in this systematic review and meta-analysis. The overall effect was presented as weighted mean difference (WMD) and 95% confidence interval (CI) in a random-effects meta-analysis model.

RESULTS

Finally, 15 randomised trials including 714 participants were selected for the present meta-analysis. Pooled analysis did not show any significant changes in alanine aminotransferase (ALT) (WMD: 0 IU/L, 95% CI: -3.17 to 3.17, P = .99; I² = 74.2%), aspartate aminotransferase (AST) (WMD: -2.40 IU/L, 95% CI: -5.45 to 0.65, P = .11; I² = 82.9%), gamma-glutamyl transferase (GGT) (WMD: -1.26 IU/L, 95% CI: -4.64 to 2.13, P = .64; I² = 23.7%), alkaline phosphatase (ALP) (WMD: 3.80 IU/L, 95% CI: -4.65 to 12.25, P = .37; I² = 29.9%) and bilirubin (WMD: 0.13 IU/L, 95% CI: -0.43 to 0.17, P = .39; I² = 8.9%) after supplementation with resveratrol.

CONCLUSION

Overall, in our study, resveratrol does not affect liver enzyme levels significantly, but subgroup analysis indicates that these results may be influenced by resveratrol dose, duration of the study and population status, so future high-quality studies are necessary to get definitive results.

Efficacy of Polyphenols in the Management of Dyslipidemia: A Focus on Clinical Studies

Polyphenols (PLPs), phytochemicals found in a wide range of plant-based foods, have gained extensive attention in view of their antioxidant, anti-inflammatory, immunomodulatory and several additional beneficial activities. The health-promoting effects noted in animal models of various non-communicable diseases explain the growing interest in these molecules. In particular, in vitro and animal studies reported an attenuation of lipid disorders in response to PLPs. However, despite promising preclinical investigations, the effectiveness of PLPs in human dyslipidemia (DLP) is less clear and necessitates revision of available literature. Therefore, the present review analyzes the role of PLPs in managing clinical DLP, notably by dissecting their potential in ameliorating lipid/lipoprotein metabolism and alleviating hyperlipidemia, both postprandially and in long-term interventions. To this end, PubMed was used for article search. The search terms included polyphenols, lipids, triglycerides, cholesterol, LDL-cholesterol and /or HDL-cholesterol. The critical examination of the trials published to date illustrates certain benefits on blood lipids along with co-morbidities in participant’s health status. However, inconsistent results document significant research gaps, potentially owing to study heterogeneity and lack of rigor in establishing PLP bioavailability during supplementation. This underlines the need for further efforts in order to elucidate and support a potential role of PLPs in fighting DLP.

Acute oral treatment with resveratrol and Lactococcus Lactis Subsp. Lactis decrease body weight and improve liver proinflammatory markers in C57BL/6 mice

The present study aimed to evaluate the effects of resveratrol, a nutraceutical polyphenol, and Lactococcus lactis (bacteria probiotic), on metabolic parameters and hepatic proinflammatory markers expression. C57BL/6 mice were divided into 4 groups: Standard (ST), Lactococcus lactis (LL), Resveratrol (RSV), and Lactococcus lactis plus resveratrol (LL + RSV). Lactococcus lactis and resveratrol were administered by orogastric gavage. Blood parameters were assessed (total cholesterol, triglycerides, ALT and AST). IL-6 mRNA expression was evaluated by Real-time PCR and TNF-α protein expression was assessed by immunohistochemistry. The main findings showed that resveratrol and Lactococcus lactis association decreased body weight, aspartate aminotransferase and total cholesterol levels. LL and LL + RSV decreased triglycerides levels and IL-6 and TNF-α expression. These results open a perspective of using resveratrol and Lactococcus lactis to improve metabolic parameters and Lactococcus lactis in preventing inflammation and the hepatic diseases development.

Hypolipidemic properties of Chlorella pyrenoidosa organic acids via AMPK/HMGCR/SREBP-1c pathway in vivo

The aim of this study was to explore the effects and mechanisms of 95% ethanol extract of Chlorella pyrenoidosa (CPE95) on lipid metabolism in hyperlipidemic rats. For the sake of chemical composition analysis of CPE95, liquid chromatography-mass spectrometry (LC-MS) was used for determination. After treatment with CPE95, serum high-density lipoprotein cholesterol content of the hyperlipidemic rats was increased, while the contents of cholesterol, triglyceride, and low-density lipoprotein cholesterol were decreased strikingly. Moreover, the result of histopathology analysis showed that the accumulation and fatty deformation of the livers were relieved. Real-time quantitative PCR and Western blotting were used to determine the expression levels of lipid metabolism-related genes. The gene expression level of adenosine 5'-monophosphate-activated protein kinase was descended, and expressions of sterol regulatory element-binding protein-1c, acetyl-CoA carboxylase, and 3-hydroxy-3-methylglutaryl coenzyme A reductase were all downregulated in the CPE95-treated rats. It suggested that CPE95 may effectively improve the hyperlipidemia in rats and would be potential for functional food component to reduce blood lipid.

Natural Product Heme Oxygenase Inducers as Treatment for Nonalcoholic Fatty Liver Disease

Heme oxygenase (HO) is a critical component of the defense mechanism to a wide variety of cellular stressors. HO induction affords cellular protection through the breakdown of toxic heme into metabolites, helping preserve cellular integrity. Nonalcoholic fatty liver disease (NAFLD) is a pathological condition by which the liver accumulates fat. The incidence of NAFLD has reached all-time high levels driven primarily by the obesity epidemic. NALFD can progress to nonalcoholic steatohepatitis (NASH), advancing further to liver cirrhosis or cancer. NAFLD is also a contributing factor to cardiovascular and metabolic diseases. There are currently no drugs to specifically treat NAFLD, with most treatments focused on lifestyle modifications. One emerging area for NAFLD treatment is the use of dietary supplements such as curcumin, pomegranate seed oil, milk thistle oil, cold-pressed Nigella Satvia oil, and resveratrol, among others. Recent studies have demonstrated that several of these natural dietary supplements attenuate hepatic lipid accumulation and fibrosis in NAFLD animal models. The beneficial actions of several of these compounds are associated with the induction of heme oxygenase-1 (HO-1). Thus, targeting HO-1 through dietary-supplements may be a useful therapeutic for NAFLD either alone or with lifestyle modifications.

Whole Red Raspberry (Rubus idaeus)-Enriched Diet Is Hepatoprotective in the Obese Zucker Rat, a Model of the Metabolic Syndrome

Non-alcoholic fatty liver disease is a major risk factor of the metabolic syndrome (MetS). The effect of whole red raspberry (WRR) consumption on lipid metabolism was investigated in the obese Zucker rat (OZR), a model for the MetS. Male OZRs (n = 16) and their lean littermates (lean Zucker rat) (n = 16) at 8 weeks of age were placed on a control or an 8% WRR-enriched diet for 8 weeks. Plasma triglycerides (TGs), total cholesterol, high-density lipoprotein cholesterol (HDL-C), and non-HDL-C levels, and hepatic concentration of TG were measured. The expression of nine genes related to lipid metabolism was evaluated, both in liver and adipose tissue. A WRR-enriched diet reduced plasma cholesterol and HDL-C and increased plasma TG, while it decreased hepatic TG accumulation in the OZR. The OZR assigned to a WRR exhibited upregulation of microsomal triglyceride transfer protein (Mttp) and downregulation of fatty acid synthase (Fas) expression in the liver. Results showed a decrease in accumulation of liver TG and gene expression modulation of enzymes and transcription factors associated with lipid metabolism, suggesting a possible hepatoprotective role of a WRR-enriched diet.

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.

Efficacy of Dietary Supplements to Reduce Liver Fat

Liver fat accumulation is an important pathophysiological feature of non-alcoholic fatty liver disease that may be modulated by dietary supplements (DS). A systematic search of the literature was conducted for randomized controlled trials (RCTs) pertaining to the effect of a DS on liver fat as assessed using quantitative tomographic imaging in human adults. Where feasible, data were pooled, and meta-analyses conducted using random-effect model. Quality assessment was done according the Cochrane Collaboration's tool for assessing risk of bias. Twenty RCTs, involving 1171 overweight and obese adults, of which 36% were females, with or without comorbidities, were included. Only RCTs assessing omega-3 fatty acids (n = 4) and resveratrol (n = 4) qualified for meta-analysis. Results did neither favor omega-3 (effect size -1.17; weighted mean difference (WMD) (95% confidence interval (CI)) -3.62, 1.28; p < 0.001) nor resveratrol supplementation (0.18; 95% CI -1.08, 1.43; p = 0.27). The findings of the qualitatively summarized RCTs suggested that catechins (n = 1), Lactobacillus reuteri (n = 1), and carnitine (n = 1) may reduce liver fat. All other DS did not show any influence. The current evidence is scarce, of limited quality and does not support DS use to reduce liver fat. Further well-designed trials are warranted.

Resveratrol attenuates metabolic, sperm, and testicular changes in adult Wistar rats fed a diet rich in lipids and simple carbohydrates

High-fat diets affect male reproduction and sexual function. Therefore, we evaluated the effects of prolonged resveratrol administration on the metabolic, sperm, and testicular parameters of rats fed a cafeteria diet. Male Wistar rats were divided at weaning into control (C, n = 20) and cafeteria (CAF, n = 16) groups. At 3 months, half of them were given daily supplementations of resveratrol (C-R, n = 10; CAF-R, n = 8) at a dosage of 30 mg kg^-1 body mass for 2 months. Animals were killed at 5 months of age, and blood, spermatozoa, and testes were collected for further analysis. Data were analyzed by one-way ANOVA, and P < 0.05 was considered statistically significant. The CAF diet promoted hyperglycemia (P < 0.0001), and treatment with resveratrol reversed this condition (P < 0.0001). The CAF diet reduced sperm viability and motility, while resveratrol improved these parameters (P < 0.05). Regarding testicular morphology, the height of the seminiferous epithelium was reduced in the CAF group compared with that of the C group (P = 0.0007). Spermatogenic cell proliferation was also reduced in the CAF group compared with that of the C group. However, the CAF-R showed an increase in cell proliferation rate compared with that of the untreated CAF group (P = 0.0024). Although it did not modify body mass, the consumption of a CAF diet promoted hyperglycemia, adverse testicular morphology remodeling, and abnormal sperm, which were attenuated by treatment with resveratrol, thus suggesting a protective effect of this antioxidant on spermatogenesis.

Targeting the gut microbiota with resveratrol: a demonstration of novel evidence for the management of hepatic steatosis

Resveratrol is a natural polyphenol that has been reported to reduce the risk of obesity and nonalcoholic fatty liver disease (NAFLD). Recent evidence has demonstrated that the gut microbiota plays an important role in the protection against NAFLD and other metabolic diseases. The present study aimed to investigate the relationship between the gut microbiota and the beneficial effects of resveratrol on the amelioration of NAFLD in mice. We observed marked decreases in body weight and liver steatosis and improved insulin resistance in high-fat diet (HFD)-fed mice treated with resveratrol. Furthermore, we found that resveratrol treatment alleviated NAFLD in HFD-fed mice by improving the intestinal microenvironment, including gut barrier function and gut microbiota composition. On the one hand, resveratrol improved gut intestinal barrier integrity through the repair of intestinal mucosal morphology and increased the expression of physical barrier- and physiochemical barrier-related factors in HFD-fed mice. On the other hand, in HFD-fed mice, resveratrol supplementation modulated the gut bacterial composition. The resveratrol-induced gut microbiota was characterized by a decreased abundance of harmful bacteria, including Desulfovibrio, Lachnospiraceae_NK4A316_group and Alistipes, as well as an increased abundance of short-chain fatty acid (SCFA)-producing bacteria, such as Allobaculum, Bacteroides and Blautia. Moreover, transplantation of the HFDR-microbiota into HFD-fed mice sufficiently decreased body weight, liver steatosis and low-grade inflammation and improved hepatic lipid metabolism. Collectively, resveratrol would provide a potentially dietary intervention strategy against NAFLD through modulating the intestinal microenvironment.

Effects of excess sugars and lipids on the growth and development of Caenorhabditis elegans

Background

Excessive intake of carbohydrates and fats causes over-nutrition, leading to a variety of diseases and complications. Here, we characterized the effects of different types of sugar and lipids on the growth and development of Caenorhabditis elegans.

Methods

We measured the lifespan, reproductive capacity, and length of nematodes after sugars and lipids treatment alone and co-treatment of sugars and lipids. Furthermore, we studied the mechanisms underlying the damage caused by high-sucrose and high-stearic acid on C.elegans by using transcriptome sequencing technology.

Results

The results showed that a certain concentration of sugar and lipid promoted the growth and development of nematodes. However, excessive sugars and lipids shortened the lifespan and length of nematodes and destroyed their reproductive capacity. Based on the results of the orthogonal test, we selected 400 mmol/L sucrose and 500 μg/mL stearic acid to model a high-sugar and high-lipid diet for C. elegans.

Conclusion

High-sugar and high-lipid intake altered the expression of genes involved in biofilm synthesis, genes that catalyze the synthesis and degradation of endogenous substances, and genes involved in innate immunity, resulting in physiological damage. Furthermore, we explored the protective effect of resveratrol on high-sugar and high-lipid damage to nematodes. Resveratrol plays a role in repairing by participating in the metabolism of foreign substances and reducing cellular oxidative stress.

The influence of dietary conditions in the effects of resveratrol on hepatic steatosis

Non-alcoholic fatty liver disease (NAFLD) is considered the major cause for the development of chronic liver alterations.

An energy restriction-based weight loss intervention is able to reverse the effects of obesity on the expression of liver tumor-promoting genes

The epidemiological evidence regarding the association of obesity with liver disease and possibly hepatocellular carcinoma highlights the need for investigations of whether obesity itself could induce the differential expression of genes commonly associated with the initial phase of liver tumorigenesis, and whether such phenomenon could be reversed after a weight loss intervention. In this study, obese Zucker rats were found to have dysregulated cell proliferation, antioxidative defenses, and tumor suppressor gene expression in association with liver dysfunction parameters, as well as oxidative stress and inflammation. Importantly, after a 4-week weight loss protocol of energy restriction and/or exercise, this effect on the liver carcinogenesis-related genes was reversed concomitantly with reductions in the fat mass, hepatic lipid content, oxidative stress, and inflammation. The findings indicate that the oxidative stress and inflammation associated with excess adiposity promote dysregulation of the genes involved in liver tumorigenesis. This is clinically relevant because these effects were detectable in the liver without evidence of a tumoral mass and were reversed after weight loss. Consequently, this study reveals the susceptibility of obese individuals to the initiation of a hepatocarcinogenic process, and how this can be prevented by achieving a healthy body weight.

Moderate Alcohol Intake in Non-Alcoholic Fatty Liver Disease: To Drink or Not to Drink?

Nonalcoholic fatty liver disease (NAFLD) is defined by hepatic steatosis in the presence of alcohol intake within safe limits, defined by guidelines of scientific associations (usually 20 g or 2 units/day in women, 30 g or 3 units in men). The diagnosis is usually followed by medical counseling of total abstinence, in order to prevent disease progression. This policy has been challenged by epidemiological studies, suggesting that the risk of liver disease and disease progression is lower in modest drinkers than in total abstainers. We revised the literature on the effects of modest alcohol intake on disease burden. Epidemiological data may suffer from several potential biases (recall bias for retrospective analyses, difficulties in the calculation of g/day), limiting their validity. Prospective data suggest that NAFLD patients with regular alcohol intake, although within the safe thresholds, are at higher risk of liver disease progression, including hepatocellular carcinoma; a detrimental effect of modest alcohol drinking is similarly observed in liver disease of viral etiology. Alcohol intake is also a risk factor for extrahepatic cancers, particularly breast, oral, and pharyngeal cancers, with gender difference and no floor effect, which outweigh the possible beneficial effects on cardiovascular system, also derived from retrospective studies. Finally, the negative effects of the calorie content of alcohol on dietary restriction and weight loss, the pivotal intervention to reduce NAFLD burden, should be considered. In summary, the policy of counseling NAFLD patients for alcohol abstinence should be maintained.

The Fluid Aspect of the Mediterranean Diet in the Prevention and Management of Cardiovascular Disease and Diabetes: The Role of Polyphenol Content in Moderate Consumption of Wine and Olive Oil

A growing interest has emerged in the beneficial effects of plant-based diets for the prevention of cardiovascular disease, diabetes and obesity. The Mediterranean diet, one of the most widely evaluated dietary patterns in scientific literature, includes in its nutrients two fluid foods: olive oil, as the main source of fats, and a low-to-moderate consumption of wine, mainly red, particularly during meals. Current mechanisms underlying the beneficial effects of the Mediterranean diet include a reduction in inflammatory and oxidative stress markers, improvement in lipid profile, insulin sensitivity and endothelial function, as well as antithrombotic properties. Most of these effects are attributable to bioactive ingredients including polyphenols, mono- and poly-unsaturated fatty acids. Polyphenols are a heterogeneous group of phytochemicals containing phenol rings. The principal classes of red wine polyphenols include flavonols (quercetin and myricetin), flavanols (catechin and epicatechin), anthocyanin and stilbenes (resveratrol). Olive oil has at least 30 phenolic compounds. Among them, the main are simple phenols (tyrosol and hydroxytyrosol), secoroids and lignans. The present narrative review focuses on phenols, part of red wine and virgin olive oil, discussing the evidence of their effects on lipids, blood pressure, atheromatous plaque and glucose metabolism.

A Unique Formulation of Cardioprotective Bio-Actives: An Overview of Their Safety Profile

The burden of cardiovascular disease (CVD) remains high globally and in the United States despite the availability of pharmaceuticals aimed at its prevention and treatment. An invention by Summit Innovation Labs, which is a formula consisting of a unique blend of select polyphenols (i.e., curcumin, quercetin, resveratrol), vitamin K2 as menaquinone-7, and magnesium, was recently developed to modulate the impact of the specific drivers of CVD, namely, vascular calcification, oxidative stress, and chronic inflammation. The SIL formulation is a dietary supplement that was designed leveraging the more bioavailable forms of ingredients with poor absorption, such as curcumin and quercetin. Each ingredient within the SIL formulation has been shown to contribute to CVD risk reduction by moderating the effect of CVD triggers, thereby providing a holistic prevention strategy for CVD in the healthy population. This review focuses on recently published clinical data to support the safety profile of these ingredients following oral administration. The preponderance of clinical trial data reviewed support the overall safety of the bioactives when used singly or in combination. The most commonly reported adverse effects were generally mild dose-related gastrointestinal disturbances, which may be alleviated with diet in some cases. In light of these, we conclude that the combination of the ingredients in the SIL formulation is reasonably expected to be safe.

Resveratrol shifts energy metabolism to increase lipid oxidation in healthy old mice

OBJECTIVES

The objective of this work was to determine the specific mechanisms by which resveratrol inhibits lipogenesis and stimulates lipolysis.

METHODS

Twelve male mice were individually introduced into a metabolic cage for 24 h to measure basal metabolic rate, prior to intervention. They were randomly divided into two groups, resveratrol (RSV) and control (C), and administered resveratrol intraperitoneally or vehicle, respectively, for two consecutive days. After 24 h, the metabolic energy expenditure was again determined for 24 h, before mice were sacrificed. Protein and gene expression of different enzymes related to metabolism in the hepatic tissue, adipose tissue and gastrocnemius of mice were analyzed by RT-PCR, western blot or ELISA.

RESULTS

We report that resveratrol lowers the respiratory quotient in old mice and that this may be due to the activation of fatty acid mobilization from white adipose tissue (because hormone-activated lipase expression is increased) and fatty acid transport into mitochondria and eventual oxidation in muscle and liver (because transport enzymes and beta oxidation enzymes are also increased). Indeed, we have observed that resveratrol in vivo causes an increase in the expression and phosphorylation of AMPKα in liver, muscle and adipose tissue and an increase in the expression of acyl-CoA synthetase, of carnitine palmitoyl transferase 1 and of carnitine acylcarnitine translocase, all enzymes involved in lipid catabolism. On the other hand, the levels of acetyl-CoA carboxylase as well as those its product, i.e. malonyl CoA, are decreased.

CONCLUSIONS

We conclude that a controlled dose of resveratrol activates fatty acid mobilization and degradation and inhibits fatty acid synthesis in old mice. This is the first time that these effects of resveratrol in lipid metabolism in healthy old (non-obese) animals are reported.

Resveratrol Treatment Ameliorates Leptin Resistance and Adiposity Programed by the Combined Effect of Maternal and Post-Weaning High-Fat Diet

SCOPE

Prenatal high-fat (HF) and postnatal HF diet are both associated with obesity and metabolic disturbances in adults. Leptin resistance induced by obesity limits its biological effects. The anti-obesity mechanism of resveratrol in visceral adiposity is investigated here.

METHODS AND RESULTS

During mating and lactation, Sprague-Dawley dams are fed either control or a HF diet. Subsequently, the offspring are fed chow or an HF diet. A fifth group that received maternal/postnatal HF diet and resveratrol after weaning (HHR) is used to study the effects of resveratrol treatment. Resveratrol treatment alleviates adiposity programed by maternal and postnatal HF diet by decreasing feed intake or inducing metabolic changes. Resveratrol treatment is also found to ameliorate the decrease in SIRT1 abundance observed in retroperitoneal adipose tissue, programed by maternal and postnatal HF diet. Moreover, resveratrol therapy decreases plasma leptin level and increases leptin receptor expression in retroperitoneal adipose tissue through DNA methylation modification.

CONCLUSION

These results suggest that resveratrol can alleviate peripheral leptin resistance programed by the combined effect of prenatal and postnatal HF diet through epigenetic regulation of genes coding leptin and its receptor. It provides insights into a novel mechanism explaining the beneficial effects of resveratrol in obesity management.

Resveratrol protects against nonalcoholic fatty liver disease by improving lipid metabolism and redox homeostasis via the PPARα pathway

Resveratrol (RSV), a well-known bioactive compound, has been reported to exert a broad range of health benefits. Accumulating evidence suggests that RSV is beneficial for many metabolic diseases, including nonalcoholic fatty liver disease (NAFLD). This study investigated the preventive and therapeutic effects of RSV on high-fat diet (HFD)-induced NAFLD in rats and palmitate acid (PA)-induced hepatocyte steatosis in HepG2 cells. Hepatocytes were incubated with inhibitors of peroxisome proliferator-activated receptor α (PPARα) or short interfering RNAs (siRNAs) targeting PPARα, AMP-activated protein kinase (AMPK), and protein kinase A (PKA) to determine the underlying mechanisms. We found that RSV noticeably ameliorated HFD-induced hepatic steatosis in rats and inhibited PA-induced lipid accumulation in HepG2 cells. Moreover, RSV improved lipid metabolism, enhanced antioxidant capacity, and restored mitochondrial respiratory chain activities. Incubation with inhibitors of PPARα or PPARα siRNA abolished the protective effects of RSV on lipid metabolism and redox homeostasis. Furthermore, RSV activated the PKA/AMPK/PPARα signaling pathway. Our results provided direct evidence for a novel, PPARα-mediated mechanism responsible for the beneficial effects of RSV on hepatic steatosis. These findings may have important theoretical and application prospects for the prevention and treatment of NAFLD. Novelty RSV improved lipid metabolism and redox homeostasis and oxidative stress in NAFLD via the PKA/AMPK/PPARα signaling pathway. RSV may have a greater beneficial effect in the early prevention of hepatic steatosis.

Effect of resveratrol on non-alcoholic fatty liver disease

The aim of the present study was to investigate the effect of a micronized formulation of trans-resveratrol in humans with non-alcoholic fatty liver disease (NAFLD). Trans-Resveratrol has been used in the form of micronized formulation, which is better absorbed, has strong antioxidants effects, is more effective than plain resveratrol formulations and is circulated on the market as a food supplement. Resveratrol (3,5,4′-trihydroxy-trans-stilbene) is a stilbenoid and a phytoalexin produced by several plants. NAFLD is an increasing clinical problem involving the liver for which effective treatments are required. The present study was based on two patient groups. The study, which commenced on April 2013 and finished on April 2015, included 44 patients, aged 29–70 years, with an average weight of 84.6 kg (n=22 per group; 28 men and 16 women) who were randomly assigned to groups and given 50 mg Evelor capsule (n=22) and 200 mg Evelor H tablet (n=22) correspondingly on a daily basis. The patients were followed up for 6 months. Quantity fat measurements, with ultrasound on the liver and kidney, were carried out. There was an initial measurement (time 1) and one after six months (time 2). The study results showed the effects of Trans-resveratrol micronized formulation in reducing the liver fat, as well as decreasing hepatic enzymes, serum glutamate pyruvic transaminase (SGPT) and gamma-glutamyl transpeptidase (g-GT) and insulin resistance. At the end of the study, the statistical analysis showed a statistically significant reduction on the liver fat. These data demonstrate that use of Trans-resveratrol micronized formulation improves features of NAFLD, and prevents liver damage. Thus, Trans-resveratrol micronized formulation can be a new treatment method for NAFLD.

Peanut Sprout Extracts Attenuate Triglyceride Accumulation by Promoting Mitochondrial Fatty Acid Oxidation in Adipocytes

Peanut sprouts (PS), which are germinated peanut seeds, have recently been reported to have anti-oxidant, anti-inflammatory, and anti-obesity effects. However, the underlying mechanisms by which PS modulates lipid metabolism are largely unknown. To address this question, serial doses of PS extract (PSE) were added to 3T3-L1 cells during adipocyte differentiation. PSE (25 µg/mL) significantly attenuated adipogenesis by inhibiting lipid accumulation in addition to reducing the level of adipogenic protein and gene expression with the activation of AMP-activated protein kinase (AMPK). Other adipocyte cell models such as mouse embryonic fibroblasts C3H10T1/2 and primary adipocytes also confirmed the anti-adipogenic properties of PSE. Next, we investigated whether PSE attenuated lipid accumulation in mature adipocytes. We found that PSE significantly suppressed lipogenic gene expression, while fatty acid (FA) oxidation genes were upregulated. Augmentation of FA oxidation by PSE in mature 3T3-L1 adipocytes was confirmed via a radiolabeled-FA oxidation rate experiment by measuring the conversion of [³H]-oleic acid (OA) to [³H]-H₂O. Furthermore, PSE enhanced the mitochondrial oxygen consumption rate (OCR), especially maximal respiration, and beige adipocyte formation in adipocytes. In summary, PSE was effective in reducing lipid accumulation in 3T3-L1 adipocytes through mitochondrial fatty acid oxidation involved in AMPK and mitochondrial activation.

No beneficial effects of resveratrol supplementation on atherogenic risk factors in patients with nonalcoholic fatty liver disease

Introduction: Cardiovascular disease (CVD) accounts as a major cause of mortality among patients with nonalcoholic fatty liver disease (NAFLD). Resveratrol, a natural polyphenol compound, is known for its antioxidant and antiatherogenic properties and is purported to be beneficial in decreasing CVD risk factors in NAFLD patients. Objectives: This study aimed to investigate the effects of resveratrol on atherogenic risk factors in patients with NAFLD. Methods: This randomized, double-blind, placebo-controlled clinical trial was performed on 50 patients with NAFLD aged 20-60 years. Subjects were randomly assigned to receive a daily dose of 600 mg resveratrol (n = 25) or placebo (n = 25) for 12 wk. Serum liver enzymes, lipid profile and atherogenic indices, blood pressure and anthropometric values were assessed pre and post-treatment. Results: Resveratrol supplementation reduced body weight (from 88.75 ± 11.41 to 87.54 ± 11.18 kg, P = 0.005) and BMI (from 31.00 ± 3.16 to 30.60 ± 3.26 kg/m², P = 0.01) significantly compared to the placebo group. A significant reduction in waist circumference was observed within resveratrol group (from 102.70 ± 7.68 to 101.39 ± 7.62 cm, P = 0.02). There were no significant changes in lipid profile (ox-LDL, ApoA1 and ApoB), serum atherogenic indices (LDL-C/HDL-C, ApoB/ApoA1, ox-LDL/ApoB, LDL-C/ox-LDL and AIP), liver enzymes (AST, ALT, ALP and GGT), hip circumference, waist-to-hip ratio and blood pressure in either group (P > 0.05 for all). Conclusion: These findings indicated that resveratrol supplementation in dose and duration used in this study did not affect most of the CVD risk factors in NAFLD patients. Further studies are warranted to explain more effects of resveratrol on CVD complications of NAFLD. Registration ID in IRCT: IRCT201511233664N16.

Modulation of fat metabolism and gut microbiota by resveratrol on high-fat diet-induced obese mice

PURPOSE

The antioxidant resveratrol (RSV) has low bioavailability and can reach the colon to access the gut microbial ecosystem. RSV administration together with high-fat diet prevented abnormal changes of intestinal microbiota. However, whether or not RSV can reshape the intestinal microbiota of obese mice and alleviate obesity-related diseases remains to be studied. This study aimed to explore the role of RSV in alleviating high-fat-induced obesity and its relationship with oxidative stress and gut microbiota.

METHODS

Male C57BL/6 mice were divided into five groups and administered for 16 weeks with: standard diet (CON), high-fat diet (60% energy for lard, HFD), and HFD with low, medium, and high dose of RSV, 50, 75, and 100 mg/kg body weight administered daily via drinking water, respectively.

RESULTS

Medium and high RSV treatment significantly prevented body weight gain, decreased relative weight of liver and adipose tissue compared with HFD (P<0.05). All doses significantly prevented HFD-induced increase of serum triglyceride, low density lipoprotein cholesterol, glucose, and endotoxemia (P<0.05). Medium and high dose also prevented chronic inflammation by decreasing serum interleukin-1 and tumor necrosis factor-alpha (P<0.05), and oxidative stress in liver and brain indicated by increase in superoxide dismutase, catalase, glutathione peroxidase activity (P<0.05). Formation of malondialdehyde was prevented by all doses compared with HFD (P<0.05). Both medium and high doses of RES increased alpha diversity of gut microbiota according to the Chao1 and Shannon indices (P<0.05). Medium dose induced obvious shift in gut microbiota composition according to principal component analysis. High dose of RSV effectively prevented HFD-induced increase of Coriobacteriaceae and Desulfovi-brionaceae (P<0.05), which show a significant correlation with body weight (r>0.8 P<0.00).

CONCLUSION

RSV prevented HFD-induced endotoxemia, oxidative stress, and gut microbiota change.

Resveratrol, Metabolic Syndrome, and Gut Microbiota

Resveratrol is a polyphenol which has been shown to have beneficial effects on metabolic syndrome-related alterations in experimental animals, including glucose and lipid homeostasis improvement and a reduction in fat mass, blood pressure, low-grade inflammation, and oxidative stress. Clinical trials have been carried out to address its potential; however, results are still inconclusive. Even though resveratrol is partly metabolized by gut microbiota, the relevance of this “forgotten organ” had not been widely considered. However, in the past few years, data has emerged suggesting that the therapeutic potential of this compound may be due to its interaction with gut microbiota, reporting changes in bacterial composition associated with beneficial metabolic outcomes. Even though data is still scarce and for the most part observational, it is promising nevertheless, suggesting that resveratrol supplementation could be a useful tool for the treatment of metabolic syndrome and its associated conditions.

Sinapic acid and resveratrol alleviate oxidative stress with modulation of gut microbiota in high-fat diet-fed rats

High-fat diet (HFD) consumption induces oxidative stress and microbial dysbiosis, the latter of which plays a vital role in the development of metabolic syndrome. We hypothesized that sinapic acid and resveratrol treatment might be a potential strategy to ameliorate the redox state and gut microbiota composition imbalance. In this study, rats were randomised into five groups and fed a high-fat diet supplemented with resveratrol (400 mg/kg), sinapic acid (200 mg/kg) or a combination of both polyphenols. Administration of resveratrol effectively reduced fasting blood glucose levels (p < 0.05) and increased the HDL-c levels (p < 0.05). Reactive oxygen species and malondialdehyde levels were decreased in the colon (p < 0.05), total antioxidant capacity was increased in liver (p < 0.05) by sinapic acid consumption in HFD rats. Moreover, polyphenol supplementation impacted the intestinal microbiome at different taxonomic levels by improving the proportion of butyrate producer Blautia (p < 0.05) and Dorea (p < 0.01) in the Lachaospiraceae family and inhibiting the growth of bacterial species associated with diseases and inflammation such as Bacteroides (p < 0.05) and Desulfovibrionaceaesp (p < 0.01). Spearman correlation analysis showed that some oxidative stress variables were directly correlated with changes in gut microbiota. Our findings demonstrated qualitative differences between the treatments in their abilities to alleviate HFD-induced oxidative stress and modulate the gut microbiota. These findings might be helpful to better understand the effects of bioactive constituents on nutrition for human health.

Pepsin egg white hydrolysate modulates gut microbiota in Zucker obese rats

There is limited information that relates the intake of food-derived bioactive peptides and the gut microbiota. We have previously described a pepsin hydrolysate of egg white (EWH) that ameliorates fat accumulation and dyslipidemia, while reducing oxidative stress and inflammation markers in obese Zucker rats. The aim of this study was to associate the beneficial effects of EWH with gut microbiota changes in these animals. Obese Zucker rats received daily 750 mg kg^-1 EWH in drinking water for 12 weeks and faeces were analysed for microbial composition and metabolic compounds in comparison with Zucker lean rats and obese controls. EWH supplementation modulated the microbiological characteristics of the obese rats to values similar to those of the lean rats. Specifically, counts of total bacteria, Lactobacillus/Enterococcus and Clostridium leptum in EWH fed obese Zucker rats were more similar to the lean rats than to the obese controls. Besides, feeding the obese Zucker rats with EWH reduced (P < 0.05) the faecal concentration of lactic acid. The physiological benefits of EWH in the improvement of obesity associated complications of Zucker rats could be associated with a more lean-like gut microbiota and a tendency to diminish total short-chain fatty acids (SCFA) production and associated obesity complications. The results warrant the use of pepsin egg white hydrolysate as a bioactive food ingredient.

Catalase and nonalcoholic fatty liver disease

Obesity and insulin resistance are considered the main causes of nonalcoholic fatty liver disease (NAFLD), and oxidative stress accelerates the progression of NAFLD. Free fatty acids, which are elevated in the liver by obesity or insulin resistance, lead to incomplete oxidation in the mitochondria, peroxisomes, and microsomes, leading to the production of reactive oxygen species (ROS). Among the ROS generated, H₂O₂ is mainly produced in peroxisomes and decomposed by catalase. However, when the H₂O₂ concentration increases because of decreased expression or activity of catalase, it migrates to cytosol and other organelles, causing cell injury and participating in the Fenton reaction, resulting in serious oxidative stress. To date, numerous studies have been shown to inhibit the pathogenesis of NAFLD, but treatment for this disease mainly depends on weight loss and exercise. Various molecules such as vitamin E, metformin, liraglutide, and resveratrol have been proposed as therapeutic agents, but further verification of the dose setting, clinical application, and side effects is needed. Reducing oxidative stress may be a fundamental method for improving not only the progression of NAFLD but also obesity and insulin resistance. However, the relationship between NAFLD progression and antioxidants, particularly catalase, which is most commonly expressed in the liver, remains unclear. Therefore, this review summarizes the role of catalase, focusing on its potential therapeutic effects in NAFLD progression.

Effects of Pharmacologic Dose of Resveratrol Supplementation on Oxidative/Antioxidative Status Biomarkers in Nonalcoholic Fatty Liver Disease Patients: A Randomized, Double-Blind, Placebo-Controlled Trial

Purpose: Despite a proposed role for oxidative stress in the pathogenesis of nonalcoholic fatty liver disease (NAFLD), antioxidant approaches have not been sufficiently investigated in human NAFLD management. Resveratrol has been reported to possess a wide range of biological functions, including antioxidant activities. This study aimed to evaluate the effects of resveratrol supplementation on oxidative/anti-oxidative status in patients with NAFLD.

Methods: This randomized, double-blind, placebo-controlled clinical trial was conducted on 60 patients with NAFLD (males and females) aged 20 to 60 years, and body mass index (BMI) of 25-35 kg/m2. Subjects were randomly assigned to receive a daily dose of 600 mg resveratrol (2×300 mg pure trans-resveratrol capsules; n=30) or placebo capsules (n=30) for 12 wk. Fasting blood samples, anthropometric measurements, and dietary intakes were collected for all patients at baseline and at the end of the trial. Oxidative stress was evaluated by measurement of serum malondialdehyde (MDA), oxidized low-density lipoprotein (ox-LDL), total antioxidant capacity (TAC), and erythrocyte superoxide dismutase (SOD) as well as glutathione peroxidase (GSH-Px) activities. Changes in the outcomes were analyzed using analysis of covariance (ANCOVA).

Results: Resveratrol supplementation did not significantly affect neither serum MDA, ox-LDL, and TAC levels, nor erythrocyte SOD and GSH-Px activities, compared to placebo group (All P>0.05). Moreover, changes in serum levels of liver enzymes (ALT, AST, GGT, and ALP) were not significant in neither of the study groups (All P>0.05).

Conclusion: Resveratrol supplementation did not modify oxidative/anti-oxidative status in patients with NAFLD.

Magnolol Alleviates Inflammatory Responses and Lipid Accumulation by AMP-Activated Protein Kinase-Dependent Peroxisome Proliferator-Activated Receptor α Activation

Magnolol (MG) is a kind of lignin isolated from Magnolia officinalis, which serves several different biological functions, such as antifungal, anticancer, antioxidant, and hepatoprotective functions. This study aimed to evaluate the protective effect of MG against oleic acid (OA)-induced hepatic steatosis and inflammatory damage in HepG2 cells and in a tyloxapol (Ty)-induced hyperlipidemia mouse model. Our findings indicated that MG can effectively inhibit OA-stimulated tumor necrosis factor α (TNF-α) secretion, reactive oxygen species generation, and triglyceride (TG) accumulation. Further study manifested that MG significantly suppressed OA-activated mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways and that these inflammatory responses can be negated by pretreatment with inhibitors of extracellular regulated protein kinase and c-Jun N-terminal kinase (U0126 and SP600125, respectively). In addition, MG dramatically upregulated peroxisome proliferator-activated receptor α (PPARα) translocation and reduced sterol regulatory element-binding protein 1c (SREBP-1c) protein synthesis and excretion, both of which are dependent upon the phosphorylation of adenosine monophosphate (AMP)-activated protein kinase (AMPK), acetyl-CoA carboxylase, and AKT kinase (AKT). However, MG suspended the activation of PPARα expression and was thus blocked by pretreatment with LY294002 and compound c (specific inhibitors of AKT and AMPK). Furthermore, MG clearly alleviated serum TG and total cholesterol release; upregulated AKT, AMPK, and PPARα expression; suppressed SREBP-1c generation; and alleviated hepatic steatosis and dyslipidemia in Ty-induced hyperlipidemia mice. Taken together, these results suggest that MG exerts protective effects against steatosis, hyperlipidemia, and the underlying mechanism, which may be closely associated with AKT/AMPK/PPARα activation and MAPK/NF-κB/SREBP-1c inhibition.

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.