Effects of resveratrol on glucose control and insulin sensitivity in subjects with type 2 diabetes: systematic review and meta-analysis

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.

Metabolic syndrome, Mediterranean diet, and polyphenols: Evidence and perspectives

Metabolic syndrome (MetS) is defined as the co-occurrence of metabolic risk factors that includes insulin resistance, hyperinsulinemia, impaired glucose tolerance, type 2 diabetes mellitus, dyslipidemia, and visceral obesity. The clinical significance of MetS consists of identifying a subgroup of patients sharing a common physiopathological state predisposing to chronic diseases. Clinical and scientific studies pinpoint lifestyle modification as an effective strategy aiming to reduce several features accountable for the risk of MetS onset. Among the healthy dietary patterns, the Mediterranean diet (MedDiet) emerges in terms of beneficial properties associated with longevity. Current evidence highlights the protective effect exerted by MedDiet on the different components of MetS. Interestingly, the effect exerted by polyphenols contained within the representative MedDiet components (i.e., olive oil, red wine, and nuts) seems to be accountable for the beneficial properties associated to this dietary pattern. In this review, we aim to summarize the principal evidence regarding the effectiveness of MedDiet-polyphenols in preventing or delaying the physiopathological components accountable for MetS onset. These findings may provide useful insights concerning the health properties of MedDiet-polyphenols as well as the novel targets destined to a tailored approach to MetS.

Developmental Programming of the Metabolic Syndrome: Can We Reprogram with Resveratrol?

Metabolic syndrome (MetS) is a mounting epidemic worldwide. MetS can start in early life, in a microenvironment that is now known as the developmental origins of health and disease (DOHaD). The concept of DOHaD also offers opportunities for reprogramming strategies that aim to reverse programming processes in early life. Resveratrol, a polyphenolic compound has a wide spectrum of beneficial effects on human health. In this review, we first summarize the epidemiological and experimental evidence supporting the developmental programming of MetS. This review also presents an overview of the evidence linking different molecular targets of resveratrol to developmental programming of MetS-related disorders. This will be followed by studies documenting resveratrol as a reprogramming agent to protect against MetS-related disorders. Further clinical studies are required in order to bridge the gap between animal models and clinical trials in order to establish the effective dose and therapeutic duration for resveratrol as a reprogramming therapy on MetS disorders from developmental origins.

Resveratrol Counteracts Insulin Resistance-Potential Role of the Circulation

Pre-clinical data and human trials indicate that resveratrol supplementation may help to counteract diabetes. Several mechanisms of action have been proposed to explain its metabolic benefits, including activation of sirtuins and estrogen receptors (ER) to promote glucose transporter type-4 (GLUT4) translocation and increase glucose uptake. Resveratrol can also enhance vasodilator function, yet the possibility that this action might help to alleviate insulin resistance in type-2 diabetes mellitus has received little attention. In this brief review we propose that, by restoring impaired endothelium-dependent vasodilatation in insulin resistant individuals resveratrol increases blood perfusion of skeletal muscle, thereby facilitating glucose delivery and utilization with resultant improvement of insulin sensitivity. Thus, circulatory improvements by vasoactive nutrients such as resveratrol may play a role in preventing or alleviating insulin resistance.

Can resveratrol supplement change inflammatory mediators? A systematic review and meta-analysis on randomized clinical trials

BACKGROUND

Resveratrol as a polyphenolic compound might be able to reduce inflammatory mediators. Change in inflammatory state is identified by the measurement of inflammatory mediators such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP). The objective of this study is to conduct a systematic review and meta-analysis on randomized controlled trials that assessed the effect of resveratrol on concentration of serum inflammatory mediators.

METHOD

Systematic search was performed up to October 2017 using ISI web of science, PubMed, Scopus, EMBASE, and Google scholar. Weighted mean difference was estimated either by subtracting baseline values from post-intervention value or as the post-intervention values. Fixed effect model was applied to analyze data where heterogeneity was <25%; otherwise, random effects models were applied. The protocol was registered with PROSPERO (No. CRD42018085098).

RESULTS

The meta-analysis and systematic review considered 15 trials, involving 658 adults aged 18-75 years. Resveratrol significantly reduced serum CRP levels (WMD = -0.54; 95% CI: -0.78, -0.30; I² = 77.7%; P < 0.0001), but it had no significant effect on serum IL-6 (WMD = -0.06; 95% CI: -0.27, 0.14; I² = 62.0%; P = 0.005) and TNF-α levels (WMD = -0.20; 95% CI: -0.55, 0.16; I² = 87.2%; P < 0.0001). Resveratrol intake reduced TNF-α in young subjects (WMD = -0.34; 95% CI: -0.57, -0.12; I² = 60.5%; P = 0.038) and obese individuals (WMD = -1.52; 95% CI: -2.87, -0.16; I² = 74.1%; P = 0.004).

CONCLUSION

The analysis indicated possible decreasing effect of resveratrol on CRP, but it might not be able to change IL-6 and TNF-α concentrations. More studies, separately on males and females with obesity, and varied age, are necessary.

Resveratrol Prevents Diabetic Cardiomyopathy by Increasing Nrf2 Expression and Transcriptional Activity

OBJECTIVE

This study investigated if resveratrol ameliorates diabetic cardiomyopathy by targeting associated oxidative stress mechanisms.

METHOD

Type 1 diabetes mellitus (DM) in FVB mice was induced by several intraperitoneal injections of a low dose of streptozotocin. Hyperglycemic and age-matched control mice were given resveratrol (10 mg/kg per day) for 1 month and subsequently monitored for an additional 6 months. Mice were assigned to four groups: control, resveratrol, DM, and DM/resveratrol. Cardiac function and blood pressure were assessed at 1, 3, and 6 months after DM induction. Oxidative damage and cardiac fibrosis were analyzed by histopathology, real-time PCR, and Western blot.

RESULT

Mice in the DM group exhibited increased blood glucose levels, cardiac dysfunction, and high blood pressure at 1, 3, and 6 months after DM induction. Resveratrol did not significantly affect blood glucose levels and blood pressure; however, resveratrol attenuated cardiac dysfunction and hypertrophy in DM mice. Resveratrol also reduced DM-induced fibrosis. In addition, DM mice hearts exhibited increased oxidative damage, as evidenced by elevated accumulation of 3-nitrotyrosine and 4-hydroxynonenal, which were both attenuated by resveratrol. Mechanistically, resveratrol increased NFE2-related factor 2 (Nrf2) expression and transcriptional activity, as well as Nrf2's downstream antioxidative targets.

CONCLUSION

We demonstrated that resveratrol prevents DM-induced cardiomyopathy, in part, by increasing Nrf2 expression and transcriptional activity.

Maternal resveratrol consumption and its programming effects on metabolic health in offspring mechanisms and potential implications

A growing body of evidence has clearly demonstrated that maternal nutrition can strongly determine the susceptibility to the development of metabolic diseases in offspring. With the increasing prevalence of maternal overweight, obesity, and gestational diabetes mellitus, it yields enormous burden for individual and public health. Interventions during pregnancy have been proven to be challenging, with limited efficacy and low compliance. Resveratrol, as a natural polyphenolic compound, has a wide-range of beneficial properties, including potent antiobesogenic, antiatherosclerotic, and antidiabetic effects. However, the role of maternal resveratrol intake on metabolic health in offspring has not been extensively investigated. Therefore, the aim of this study was to review the effects of maternal resveratrol supplementation on metabolic health in offspring and its potential mechanisms.

Effect of resveratrol on blood pressure: A systematic review and meta-analysis of randomized, controlled, clinical trials

Introduction: Results of previous clinical trials evaluating the effect of resveratrol supplementation on blood pressure (BP) are controversial. Purpose: We aimed to assess the impact of resveratrol on BP through systematic review of literature and meta-analysis of available randomized, controlled clinical trials (RCTs). Methods: Literature search included SCOPUS, PubMed-Medline, ISI Web of Science and Google Scholar databases up to 17th October 2017 to identify RCTs investigating the impact of resveratrol on BP. Two review authors independently extracted data on study characteristics, methods and outcomes. Overall, the impact of resveratrol on BP was reported in 17 trials. Results: Administration of resveratrol did not significantly affect neither systolic BP [weighted mean difference (WMD): -2.5 95% CI:(-5.5, 0.6) mmHg; p=0.116; I²=62.1%], nor diastolic BP [WMD: -0.5 95% CI:(-2.2, 1.3) mmHg; p=0.613; I²=50.8], nor mean BP [MAP; WMD: -1.3 95% CI:(-2.8, 0.1) mmHg; p=0.070; I²=39.5%] nor pulse pressure [PP; WMD: -0.9 95% CI:(-3.1, 1.4) mmHg; p=0.449; I²=19.2%]. However, significant WMDs were detected in subsets of studies categorized according to high resveratrol daily dosage (≥300 mg/day) and presence of diabetes. Meta-regression analysis revealed a positive association between systolic BP-lowering resveratrol activity (slope: 1.99; 95% CI: 0.05, 3.93; two-tailed p= 0.04) and Body Mass Index (BMI) at baseline, while no association was detected neither between baseline BMI and MAP-lowering resveratrol activity (slope: 1.35; 95% CI: -0.22, 2.91; two-tailed p= 0.09) nor between baseline BMI and PP-lowering resveratrol activity (slope: 1.03; 95% CI: -1.33, 3.39; two-tailed p= 0.39). Resveratrol was fairly well-tolerated and no serious adverse events occurred among most of the eligible trials. Conclusion: The favourable effect of resveratrol emerging from the current meta-analysis suggests the possible use of this nutraceutical as active compound in order to promote cardiovascular health, mostly when used in high daily dose (≥300 mg/day) and in diabetic patients.

Effect of resveratrol on lipid profile: An updated systematic review and meta-analysis on randomized clinical trials

Despite the notion that resveratrol can significantly reduce plasma lipids, the result of randomized clinical trials (RCTs) on resveratrol effect and the serum lipid profile are contradictory. Our objective was to conduct a systematic review and meta-analysis on randomized clinical trials (RCTs) and assess the effect of resveratrol on lipids. ISI web of science, Ovid, PubMed/Medline, SCOPUS, and Google Scholar data bases were searched up to Jun 2017. RCTs that assessed resveratrol effects on lipid profile among adult participants were chosen. Treatment effects were considered as weighted mean difference (WMD) and the corresponding standard error (SE) in concentrations of serum lipids. To estimate the overall summary effect, we used random-effects model. The protocol was registered with PROSPERO (No. CRD42017072365). This meta-analysis was performed on twenty-one trials. Our results indicated that resveratrol can't significantly change total cholesterol (TC) (WMD = -0.08 mmol/l, 95% CI: -0.23, 0.08; P = .349, I² = 87.8%), low-density lipoprotein (LDL-C) (WMD: -0.04 mmol/l, 95% CI: -0.21, 0.12; P = .620, I² = 93.4%), and high density lipoprotein (HDL-C) (WMD: -0.01 mmol/l, 95% CI: -0.04, 0.02; P = .269, I² = 88.6%). Its effect on triacylglycerol (TG) (WMD: 0.58 mmol/l, 95% CI: 0.34, 0.82; P < .0001, I² = 99.8%), was significant, but after removing one study the significance was eliminated. We also found that sex, age, BMI, resveratrol dosage, and intervention duration could not change the results. We conclude that resveratrol does not change lipid profile concentration. Confirmation of this conclusion will require more studies exclusively on dyslipidemic patients in which the intake of lipid lowering agents is among the exclusion criteria.