Dietary polyphenols: focus on resveratrol, a promising agent in the prevention of cardiovascular diseases and control of glucose homeostasis

Resveratrol does not increase body fat loss induced by energy restriction

Resveratrol (RSV) is known to have an antiobesogenic effect because it mimics energy restriction. However, hardly any evidence exists concerning the combined effects of RSV and energy restriction on body fat reduction. So, the aim of the present study was to determine whether RSV increases body fat reduction induced by energy restriction. Male Wistar rats were fed a high-fat, high-sucrose diet for 6 weeks to obtain a diet-induced obesity model. Then they were submitted to a mild energy restriction (25%) without or with RSV supplementation (30 mg/kg body weight/day) for 2 weeks. Final body weight, subcutaneous and intra-abdominal white adipose tissues weights, Adipose Index, and serum triacylglycerol, cholesterol, glucose, and insulin were assessed. Lipoprotein lipase (LPL), fatty acid synthase (FAS), and acetyl coenzyme A carboxylase (ACC) activities, as well as their genetic expressions, were measured in white adipose tissue. Final body weight, white adipose tissue weights, Adipose Index, and serum triacylglycerol, cholesterol, and insulin were reduced in both groups, but no differences were found among them. FAS, ACC, and LPL activities and expressions were also similar in both groups. These results suggest a lack of any adjuvant effect of RSV on energy restriction for obesity treatment purposes.

Ethanol inhibits activation of NLRP3 and AIM2 inflammasomes in human macrophages--a novel anti-inflammatory action of alcohol

Objective

In the pathogenesis of coronary atherosclerosis, local macrophage-driven inflammation and secretion of proinflammatory cytokines, interleukin-1β (IL-1β) in particular, are recognized as key factors. Moderate alcohol consumption is associated with a reduced risk of coronary artery disease mortality. Here we examined in cultured human macrophages whether ethanol modulates the intracellular processes involved in the secretion of IL-1β.

Results

Ethanol decreased dose-dependently the production of mature IL-1β induced by activators of the NLRP3 inflammasome, i.e. ATP, cholesterol crystals, serum amyloid A and nigericin. Ethanol had no significant effect on the expression of NLRP3 or IL1B mRNA in LPS-primed macrophages. Moreover, secretion of IL-1β was decreased in parallel with reduction of caspase-1 activation, demonstrating that ethanol inhibits inflammasome activation instead of synthesis of pro-IL-1β. Acetaldehyde, a highly reactive metabolite of ethanol, had no effect on the ATP-induced IL-1β secretion. Ethanol also attenuated the secretion of IL-1β triggered by synthetic double-stranded DNA, an activator of the AIM2 inflammasome. Ethanol conferred the inhibitory functions by attenuating the disruption of lysosomal integrity and ensuing leakage of the lysosomal protease cathepsin B and by reducing oligomerization of ASC.

Conclusion

Ethanol-induced inhibition of the NLRP3 inflammasome activation in macrophages may represent a biological pathway underlying the protective effect of moderate alcohol consumption on coronary heart disease.

Randomized cross-over trial of short-term water-only fasting: metabolic and cardiovascular consequences

BACKGROUND AND AIMS

Routine, periodic fasting is associated with a lower prevalence of coronary artery disease (CAD). Animal studies show that fasting may increase longevity and alter biological parameters related to longevity. We evaluated whether fasting initiates acute changes in biomarker expression in humans that may impact short- and long-term health.

METHODS AND RESULTS

Apparently-healthy volunteers (N = 30) without a recent history of fasting were enrolled in a randomized cross-over trial. A one-day water-only fast was the intervention and changes in biomarkers were the study endpoints. Bonferroni correction required p ≤ 0.00167 for significance (p < 0.05 was a trend that was only suggestively significant). The one-day fasting intervention acutely increased human growth hormone (p = 1.1 × 10⁻⁴), hemoglobin (p = 4.8 × 10⁻⁷), red blood cell count (p = 2.5 × 10⁻⁶), hematocrit (p = 3.0 × 10⁻⁶), total cholesterol (p = 5.8 × 10⁻⁵), and high-density lipoprotein cholesterol (p = 0.0015), and decreased triglycerides (p = 1.3 × 10⁻⁴), bicarbonate (p = 3.9 × 10⁻⁴), and weight (p = 1.0 × 10⁻⁷), compared to a day of usual eating. For those randomized to fast the first day (n = 16), most factors including human growth hormone and cholesterol returned to baseline after the full 48 h, with the exception of weight (p = 2.5 × 10⁻⁴) and (suggestively significant) triglycerides (p = 0.028).

CONCLUSION

Fasting induced acute changes in biomarkers of metabolic, cardiovascular, and general health. The long-term consequences of these short-term changes are unknown but repeated episodes of periodic short-term fasting should be evaluated as a preventive treatment with the potential to reduce metabolic disease risk. Clinical trial registration (ClinicalTrials.gov): NCT01059760 (Expression of Longevity Genes in Response to Extended Fasting [The Fasting and Expression of Longevity Genes during Food abstinence {FEELGOOD} Trial]).

Protective effects of chronic resveratrol treatment on vascular inflammatory injury in streptozotocin-induced type 2 diabetic rats: Role of NF-kappa B signaling

Type 2 diabetes mellitus (T2DM) is associated with an increased risk of macrovascular disease. Epidemiological studies suggest that plant polyphenol resveratrol (REV) is associated with reduced risk of cardiovascular diseases. Since chronic inflammatory and endothelial cell activation play a critical role in vascular aging and atherogenesis, we evaluated whether REV can inhibit inflammatory-induced vascular injury in T2DM. We found that REV (50mg/kg/d) can regulate glucose and lipid metabolism, improve insulin resistance and vascular permeability, and protect against the foam cells and cholesterol crystals formation in arterial vessel walls of T2DM rats. The protective effects of REV were consistent with the decrease in nuclear translocation of nuclear factor kappa B (NF-kappa B) and the downregulation of interleukin-1 beta (IL-1β) and interleukin-6 (IL-6) levers in blood and tumor necrosis factor-alpha (TNF-α), intercellular adhesion molecule-1 (ICAM-1), and monocyte chemoattractant protein-1 (MCP-1) expressions in vascular wall. In addition, REV (10 and 100nmol/L) treatment protected cultured endothelial cells against increases in the expression of TNF-α, ICAM-1, and MCP-1 mRNA and protein induced by high glucose via inhibiting nuclear translocation of NF-kappa B p65. The specific NF-kappa B inhibitor pyrrolidine dithiocarbamate- (PDTC-) or small interfering RNA directed against NF-kappa B p65-mediated downregulation of NF-kappa B p65 was further enhanced by REV (100nmol/L) in the human endothelial cell line EA. hy926. In conclusion, these observations suggest that chronic treatment of T2DM rats with REV attenuates the inflammatory injury of the vascular wall and the effects are associated with down-regulation of the NF-kappa B signal pathway.

Resveratrol inhibits hydrogen peroxide-induced apoptosis in endothelial cells via the activation of PI3K/Akt by miR-126

AIM

Resveratrol(RSV) is an edible polyphenolic phytoalexin present in different plant species that plays an important role in improving endothelial dysfunction. However, the molecular mechanisms underlying these effects are unknown. In the present study, the mechanism underlying the protection of CRL-1730 cells by RSV against oxidative stress was examined.

METHODS

We first assessed the effects of RSV on the cell viability and apoptosis of CRL-1730 cells exposed to hydrogen peroxide(H2O2). Real-time PCR was used to determine the microRNA-126(miR-126) expression in cells treated with RSV and/or H2O2. We also evaluated the PI3K/Akt signaling pathway in CRL-1730 cells following upregulation of the miR-126 expression. Finally, we determined the effects of miR-126 on RSV against oxidative injury using an miR-126 inhibitor.

RESULTS

Treatment with RSV resulted in a significant increase in survival and a decrease in the apoptosis of CRL-1730 cells exposed to H2O2. We also found that H2O2 significantly suppressed the expression of miR-126, which was reversed by RSV in a dose-dependent manner. The overexpression of miR-126 decreased PIK3R2(p85-β) and enhanced Akt phosphorylation, which resulted in an increase in the survival of CRL-1730 cells exposed to H2O2. More importantly, the downregulation of the miR-126 expression reversed the effects of RSV on the survival and apoptosis of CRL-1730 cells exposed to H2O2. In addition, the knockdown of Ets-1 reversed the effects of RSV on the miR-126 expression in CRL-1730 cells exposed to H2O2.

CONCLUSIONS

In this study, we demonstrated that the protection of endothelial cells by RSV against oxidative injury is due to the activation of PI3K/Akt by miR-126.

Polyphenols: benefits to the cardiovascular system in health and in aging

Numerous studies have demonstrated the importance of naturally occurring dietary polyphenols in promoting cardiovascular health and emphasized the significant role these compounds play in limiting the effects of cellular aging. Polyphenols such as resveratrol, epigallocatechin gallate (EGCG), and curcumin have been acknowledged for having beneficial effects on cardiovascular health, while some have also been shown to be protective in aging. This review highlights the literature surrounding this topic on the prominently studied and documented polyphenols as pertaining to cardiovascular health and aging.

Transferrin modified PEG-PLA-resveratrol conjugates: in vitro and in vivo studies for glioma

Glioblastoma is one of the most malignant brain tumors with a poor prognosis. In this study, we examined the effects of transferrin (Tf)-modified poly ethyleneglycol-poly lactic acid (PEG-PLA) nanoparticles conjugated with resveratrol (Tf-PEG-PLA-RSV) to glioma therapy in vitro and in vivo. The cell viability of Tf-PEG-PLA-RSV on C6 and U87 glioma cells was determined by the MTT assay. In vivo biodistribution and antitumor activity were investigated in Brain glioma bearing rat model of C6 glioma by i.p. administration of RSV-polymer conjugates. We found that the average diameter of each Tf-PEG-PLA-RSV is around 150 nm with 32 molecules of Tf on surface. In vitro cytotoxicity of PEG-PLA-RSV against C6 and U87 cells was higher than that of free RSV, and further the modification of Tf enhanced the cytotoxicity of the RSV-polymer conjugates as a result of the increased cellular uptake of the RSV-modified conjugates by glioma cells. In comparison with free RSV, RSV conjugates could significantly decrease tumor volume and accumulate in brain tumor, which resulted in prolonging the survival of C6 glioma-bearing rats. These results suggest that Tf-NP-RSV had a potential of therapeutic effect to glioma both in vitro and in vivo and might be a potential candidate for targeted therapy of glioma and worthy of further investigation.

Polyphenols, inflammation, and cardiovascular disease

Polyphenols are compounds found in foods such as tea, coffee, cocoa, olive oil, and red wine and have been studied to determine if their intake may modify cardiovascular disease (CVD) risk. Historically, biologic actions of polyphenols have been attributed to antioxidant activities, but recent evidence suggests that immunomodulatory and vasodilatory properties of polyphenols may also contribute to CVD risk reduction. These properties will be discussed, and recent epidemiological evidence and intervention trials will be reviewed. Further identification of polyphenols in foods and accurate assessment of exposures through measurement of biomarkers (i.e., polyphenol metabolites) could provide the needed impetus to examine the impact of polyphenol-rich foods on CVD intermediate outcomes (especially those signifying chronic inflammation) and hard endpoints among high risk patients. Although we have mechanistic insight into how polyphenols may function in CVD risk reduction, further research is needed before definitive recommendations for consumption can be made.

Antioxidant effects of resveratrol in cardiovascular, cerebral and metabolic diseases

Resveratrol-a natural polyphenolic compound-was first discovered in the 1940s. Although initially used for cancer therapy, it has shown beneficial effects against most cardiovascular and cerebrovascular diseases. A large part of these effects are related to its antioxidant properties. Here we review: (a) the sources, the metabolism, and the bioavailability of resveratrol; (b) the ability of resveratrol to modulate redox signalling and to interact with multiple molecular targets of diverse intracellular pathways; (c) its protective effects against oxidative damage in cardio-cerebro-vascular districts and metabolic disorders such as diabetes; and (d) the evidence for its efficacy and toxicity in humans. The overall aim of this review is to discuss the frontiers in the field of resveratrol's mechanisms, bioactivity, biology, and health-related use.

Resveratrol repressed viability of U251 cells by miR-21 inhibiting of NF-κB pathway

Resveratrol (RSV), a polyphenol, is known to play an important role in inhibiting proliferation and inducing apoptosis of glioma cells. The aim of this study was to explore the mechanism of RSV on U251 cells apoptosis. RSV showed a dose-dependent decrease in U251 cell viability. It could reduce IκB phosphorylation, nuclear P65 protein levels and NF-κB transcriptional activity, which suggested that signaling pathway are involved in RSV-induced apoptosis. In addition, RSV could inhibit miR-21 expression and down-regulation of miR-21 expression could suppress NF-κB activity. Interestingly, over-expression of miR-21 can reverse the effect of RSV on NF-κB activity and apoptosis in U251 cells. These results suggest that RSV can effectively induce apoptosis of U251 cells and modulation of miR-21 possibly contributes to this antitumor action.

HS-1793, a recently developed resveratrol analogue protects rat heart against hypoxia/reoxygenation injury via attenuating mitochondrial damage

Resveratrol is known to exert a cardioprotective effect against hypoxia/reoxygenation (H/R) injury. HS-1793 is a novel, more stable resveratrol analog, but its cardioprotective effects were unknown. The present study aimed to test the cardioprotective effect of HS-1793 against H/R injury and investigate the role of mitochondria in Sprague Dawley rat heart damage using an ex vivo Langendorff system. HS-1793 ameliorated H/R-induced mitochondrial dysfunction by reducing mitochondrial reactive oxygen species production, improving mitochondrial oxygen consumption and suppressing mitochondrial calcium (Ca(2+)) overload during reperfusion. Moreover, HS-1793-treated rat heart showed reduced infarct size. Our data suggest that HS-1793 can protect cardiac against mitochondrial damage following H/R, thereby suppressing injury.

Resveratrol prevents interleukin-1β-induced dysfunction of pancreatic β-cells

Objective

Interleukin-1β (IL-1β) plays an important role in the development of type 1 and type 2 diabetes mellitus. Resveratrol, a polyphenol, is known to have a wide range of pharmacological properties in vitro. In this research, we examined the effects of resveratrol on IL-1β-induced β-cell dysfunction.

Methods

We first evaluated the effect of resveratrol on nitric oxide (NO) formation in RINm5F cells stimulated with IL-1β using the Griess method. Next, we performed transient transfection and reporter assays to measure the transcriptional activity of peroxisome proliferator-activated receptor-γ (PPAR-γ). We also used Western blotting analysis to assess the effect of resveratrol on inducible nitric oxide synthase (iNOS) expression and nuclear factor-κB (NF-κB) translocation to the nuclei in cells treated with IL-1β. In addition, we assessed the transcriptional activity of NF-κB using an electrophoretic mobility shift assay (EMSA). Finally, we evaluated the effect of resveratrol on IL-1β–induced inhibition of glucose-stimulated insulin secretion in freshly isolated rat pancreatic islets.

Results

Resveratrol significantly suppressed IL-1β-induced NO production, a finding that correlated well with reduced levels of iNOS mRNA and protein. The molecular mechanism by which resveratrol inhibited iNOS gene expression appeared to involve increased PPAR-γ activity, which resulted in the inhibition of NF-κB activation. Further analysis showed that resveratrol could prevent IL-1β-induced inhibition of glucose-stimulated insulin secretion in rat islets.

Conclusion

In this study, we demonstrated that resveratrol could protect against pancreatic β-cell dysfunction caused by IL-1β.

Oxidative stress and cardiovascular health: therapeutic potential of polyphenols

Reactive oxygen species (ROS) are important in normal cellular function and physiology. However, oxidative stress resulting from an accumulation of ROS has a detrimental impact on cellular function, and ROS has been implicated in the pathogenesis of a number of diseases, including cardiovascular diseases. This review provides a summary of the impact of ROS on cardiovascular health and diseases, highlighting the therapeutic use of antioxidants. In addition, this review summarizes the health benefits of polyphenols, and the recent progress on understanding the cellular and physiological actions by which polyphenols may impart their beneficial properties on cardiovascular health.

Protection against recurrent stroke with resveratrol: endothelial protection

Despite increased risk of a recurrent stroke following a minor stroke, information is minimal regarding the interaction between injurious mild cerebral ischemic episodes and the possible treatments which might be effective. The aim of the current study was to investigate recurrent ischemic stroke and whether resveratrol, a nutritive polyphenol with promising cardio- and neuro- protective properties, could ameliorate the associated brain damage. Experiments in adult rats demonstrated that a mild ischemic stroke followed by a second mild cerebral ischemia exacerbated brain damage, and, daily oral resveratrol treatment after the first ischemic insult reduced ischemic cell death with the recurrent insult (P<0.002). Further investigation demonstrated reduction of both inflammatory changes and markers of oxidative stress in resveratrol treated animals. The protection observed with resveratrol treatment could not be explained by systemic effects of resveratrol treatment including effects either on blood pressure or body temperature measured telemetrically. Investigation of resveratrol effects on the blood-brain barrier in vivo demonstrated that resveratrol treatment reduced blood-brain barrier disruption and edema following recurrent stroke without affecting regional cerebral blood flow. Investigation of the mechanism in primary cell culture studies demonstrated that resveratrol treatment significantly protected endothelial cells against an in vitro ‘ischemia’ resulting in improved viability against oxygen and glucose deprivation (39.6±6.6% and 81.3±9.5% in vehicle and resveratrol treated cells, respectively). An inhibition of nitric oxide synthesis did not prevent the improved cell viability following oxygen glucose deprivation but SIRT-1 inhibition with sirtinol partially blocked the protection (P<0.001) suggesting endothelial protection is to some extent SIRT-1 dependent. Collectively, the results support that oral resveratrol treatment provides a low risk strategy to protect the brain from enhanced damage produced by recurrent stroke which is mediated in part by a protective effect of resveratrol on the endothelium of the cerebrovasculature.

Transcriptomic and metabonomic profiling reveal synergistic effects of quercetin and resveratrol supplementation in high fat diet fed mice

Dietary quercetin and resveratrol have been frequently used in treating various diseases, but the underlying mechanisms are not entirely clear. Here, we report combined transcriptomic and metabonomic profiling that showed that the combined supplementation with quercetin and resveratrol produced synergistic effects on a high-fat diet-induced metabolic phenotype in mice. Histological and phenotypic improvements in serum and hepatic total cholesterol, insulin, fasting blood glucose, and HbA1c were also observed in mice receiving combined quercetin and resveratrol supplementation. This combined quercetin and resveratrol supplementation resulted in significant restoration of gene sets in functional pathways of glucose/lipid metabolism, liver function, cardiovascular system, and inflammation/immunity, which were altered by high fat diet feeding. The integration of transcriptomic and metabonomic data indicated quercetin and resveratrol supplementation enhanced processes of glycolysis and fatty acid oxidation, as well as suppressed gluconeogenesis. These alterations discovered at both the transcriptional and metabolic levels highlight the significance of combined "omics" platforms for elucidating mechanistic pathways altered by dietary polyphenols, such as quercetin and resveratrol, in a synergistic manner.

Plant phytochemicals as new potential drugs for immune disorders and cancer therapy: really a promising path?

Plant phytochemicals represent an exciting opportunity to maintain best health conditions through a balanced and properly administered daily nutrition or dietary supplement and have often been considered a good option for obtaining a few promising, expensive new drugs from plants. Several polyphenolic compounds, such as resveratrol, tea catechins and flavonoids, which are commonly found in vegetables, fruits and plant-derived juices or beverages, exert well-evidenced cardioprotective, neuroprotective, chemopreventive and anti-inflammatory properties, but, nevertheless, further clinical and epidemiological research is required. Most of these botanical byproducts are produced as noxious components by plants, in order to prevent pathogen colonization, insect-mediated damage and also to discourage animals from eating them. An evolutionary theory of stress adaptation would explain how these toxic substances from nature act as protective molecules. A future challenge to achieve a rather complete understanding of these chemical phenol derivatives for human health should deal with the complexity of cellular signalling networks, the epigenetic machinery endowment of the cell and the nonlinear relationship between dose and effectiveness.

Impact of short-term intake of red wine and grape polyphenol extract on the human metabolome

Red wine and grape polyphenols are considered to promote cardiovascular health and are involved in multiple biological functions. Their overall impact on the human metabolome is not known. Therefore, exogenous and endogenous metabolic effects were determined in fasting plasma and 24 h urine from healthy male adults consuming a mix of red wine and grape juice extracts (WGM) for 4 days in a placebo-controlled, crossover study. Syringic acid, 3-hydroxyhippuric acid, pyrogallol, 3-hydroxyphenylacetic acid, and 3-hydroxyphenylpropionic acid were confirmed as the strongest urinary markers of WGM intake. Overall, WGM had a mild impact on the endogenous metabolism. Most noticeable were changes in several amino acids deriving from tyrosine and tryptophan. Reductions in the microbial metabolites p-cresol sulfate and 3-indoxylsulfuric acid and increases in indole-3-lactic acid and nicotinic acid were observed in urine. In plasma, tyrosine was reduced. The results suggest that short-term intake of WGM altered microbial protein fermentation and/or amino acid metabolism.

The role of oxidative stress in the pathophysiology of gestational diabetes mellitus

Normal human pregnancy is considered a state of enhanced oxidative stress. In pregnancy, it plays important roles in embryo development, implantation, placental development and function, fetal development, and labor. However, pathologic pregnancies, including gestational diabetes mellitus (GDM), are associated with a heightened level of oxidative stress, owing to both overproduction of free radicals and/or a defect in the antioxidant defenses. This has important implications on the mother, placental function, and fetal well-being. Animal models of diabetes have confirmed the important role of oxidative stress in the etiology of congenital malformations; the relative immaturity of the antioxidant system facilitates the exposure of embryos and fetuses to the damaging effects of oxidative stress. Of note, there are only a few clinical studies evaluating the potential beneficial effects of antioxidants in GDM. Thus, whether or not increased antioxidant intake can reduce the complications of GDM in both mother and fetus needs to be explored. This review provides an overview and updated data on our current understanding of the complications associated with oxidative changes in GDM.

Natural polyphenols in cancer therapy

Natural polyphenols are secondary metabolites of plants involved in defense against different types of stress. Extracts containing these compounds have been used for thousands of years in traditional eastern medicine. Polyphenols act on multiple targets in pathways and mechanisms related to carcinogenesis, tumor cell proliferation and death, inflammation, metastatic spread, angiogenesis, or drug and radiation resistance. Nevertheless, reported effects claimed for polyphenols are controversial, since correlations between in vitro effects and in vivo evidence are poorly established. The main discrepancy between health claims versus clinical observations is the frequent use of nonphysiologically relevant concentrations of these compounds and their metabolites in efficacy and mechanistic studies. The present review will discuss how in vivo administration correlates with polyphenol metabolism, toxicity, and bioavailability. Analysis of the general application of polyphenols in cancer therapy will be complemented by potential applications in the therapy of specific tumors, including melanoma, colorectal and lung cancers. Possible pharmaceutical formulations, structural modifications, combinations, and delivery systems aimed to increase bioavailability and/or biological effects will be discussed. Final remarks will include recommendations for future research and developments.

Synergism between resveratrol and other phytochemicals: implications for obesity and osteoporosis

Resveratrol, a phytoalexin, has gained much attention recently due to its effects on sirtuins. While the anti-cancer properties of resveratrol have been extensively investigated, the anti-adipogenic and osteogenic effects of resveratrol are also gaining considerable interest. The finding that resveratrol supplementation mimics caloric restriction prompted researchers to study the effects of resveratrol on lipid metabolism. Mesenchymal stem cells are the precursors for both adipocytes and osteoblasts. In the aging population, differentiation to adipocytes dominates over the differentiation to osteoblasts in bone marrow, contributing to the increased tendency for fractures to occur in the elderly. Thus, an inverse relationship exists between adipocytes and osteoblasts in the bone marrow. Resveratrol acts on several molecular targets in adipocytes and osteoblasts leading to a decrease in adipocyte number and size and an increase in osteogenesis. Furthermore, resveratrol in combination with genistein and quercetin synergistically decreased adipogenesis in murine and human adipocytes. A recent in vivo study showed that phytochemicals including resveratrol in combination with vitamin D prevented weight gain and bone loss in a postmenopausal rat model. Therefore, combinations of resveratrol with other phytochemicals may lead to potential novel potent therapies for both obesity and osteoporosis.