Resveratrol exerts anti-obesity effects via mechanisms involving down-regulation of adipogenic and inflammatory processes in mice

Self-emulsifying drug delivery systems as a tool to improve solubility and bioavailability of resveratrol

Resveratrol is a nonflavonoid polyphenolic compound which has a broad range of desirable biological actions which include antioxidant, anti-inflammatory, antidiabetic, cardioprotective, and antitumor activities. However, there is concern that the bioavailability of resveratrol may limit some of its clinical utility. So, the aim of this study was to enhance the dissolution rate and oral hypoglycemic and hypolipidemic effect of resveratrol. This was achieved using self-emulsifying drug delivery system. The solubility of resveratrol was determined in various oils, surfactants, and cosurfactants. Phase diagram was plotted to identify the efficient self-emulsification regions using olive oil, Tween 80, and propylene glycol. The prepared self-emulsifying drug delivery system formulations were tested for thermodynamic stability, emulsification efficiency, droplet size, zeta potential, and in vitro drug release. Self-emulsification time averaged 17-99 seconds without precipitation and the mean droplet sizes ranged from 285 to 823 nm with overall zeta potential of -2.24 to -15.4 mv. All formulations improved drug dissolution in relation to unprocessed drug with a trend of decreased dissolution parameters with increasing oil content. The optimized formula, F19, with dissolution efficiency of 94% compared to only 42% of pure drug was used to study the in vivo hypoglycemic and hypolipidemic effects of resveratrol in diabetic-induced albino rats and comparing these effects with that of pure resveratrol in different doses. Treatment with the optimized formula, F19, at 10 mg/kg had significant hypoglycemic and hypolipidemic effects in diabetic-induced albino rats which were nearly similar to the high dose (20 mg/kg) of unprocessed resveratrol. From the study, it was concluded that formulation F19 has good emulsification property with uniform globule size, satisfactory in vitro drug release profile, and significant in vivo hypoglycemic effects which identify future opportunities for resveratrol delivery.

Brazilian Red Propolis Attenuates Inflammatory Signaling Cascade in LPS-Activated Macrophages

Although previous studies suggested an anti-inflammatory property of Brazilian red propolis (BRP), the mechanisms involved in the anti-inflammatory effects of BRP and its activity on macrophages were still not elucidated. This study aimed to evaluate whether BRP attenuates the inflammatory effect of LPS on macrophages and to investigate its underlying mechanisms. BRP was added to RAW 264.7 murine macrophages after activation with LPS. NO production, cell viability, cytokines profile were evaluated. Activation of inflammatory signaling pathways and macrophage polarization were determined by RT-qPCR and Western blot. BRP at 50 μg/ml inhibited NO production by 78% without affecting cell viability. Cd80 and Cd86 were upregulated whereas mrc1 was down regulated by BRP indicating macrophage polarization at M1. BRP attenuated the production of pro-inflammatory mediators IL-12, GM-CSF, IFN-Ɣ, IL-1β in cell supernatants although levels of TNF- α and IL-6 were slightly increased after BRP treatment. Levels of IL-4, IL-10 and TGF-β were also reduced by BRP. BRP significantly reduced the up-regulation promoted by LPS of transcription of genes in inflammatory signaling (Pdk1, Pak1, Nfkb1, Mtcp1, Gsk3b, Fos and Elk1) and of Il1β and Il1f9 (fold-change rate > 5), which were further confirmed by the inhibition of NF-κB and MAPK signaling pathways. Furthermore, the upstream adaptor MyD88 adaptor-like (Mal), also known as TIRAP, involved in TLR2 and TLR4 signaling, was down- regulated in BRP treated LPS-activated macrophages. Given that BRP inhibited multiple signaling pathways in macrophages involved in the inflammatory process activated by LPS, our data indicated that BRP is a noteworthy food-source for the discovery of new bioactive compounds and a potential candidate to attenuate exhacerbated inflammatory diseases.

Resveratrol-Related Polymethoxystilbene Glycosides: Synthesis, Antiproliferative Activity, and Glycosidase Inhibition

A small library of polymethoxystilbene glycosides (20-25) related to the natural polyphenol resveratrol have been synthesized and subjected, together with their aglycones 17-19, to an antiproliferative activity bioassay toward Caco-2 and SH-SY5Y cancer cells. Six of the compounds exhibit antiproliferative activity against at least one cell line. In particular, compounds 17 and 18 proved highly active on at least one of the two cell cultures. Compound 18 showed a GI50 value of 3 μM against Caco-2 cells, a value comparable to that of the anticancer drug 5-fluorouracil. The closely related compound 19 proved inactive, and its conjugates 22 and 25 showed weak cell growth inhibition. The results indicate that minimal differences in the structure of both polymethoxystilbenes and their glycosides can substantially affect the antiproliferative activity. The possible hydrolytic release of the aglycones 17-19 by β-glucosidase or β-galactosidase was also evaluated. Compounds 20-25 were also tested as potential β-glucosidase, β-galactosidase, and α-glucosidase inhibitors. A promising inhibitory activity toward α-glucosidase was observed for 21 (IC50 = 78 μM) and 25 (IC50 = 70 μM), which might be indicative of their potential as lead compounds for development of antidiabetic or antiobesity agents.

Impact of Nutrition on Cerebral Circulation and Cognition in the Metabolic Syndrome

The increasing prevalence of Metabolic Syndrome (MetS), defined as the clustering of abdominal obesity, dyslipidemia, hypertension, and hyperglycemia, appears to be driving the global epidemics cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM). Nutrition has a major impact on MetS and plays an important role in the prevention, development, and treatment of its features. Structural and functional alterations in the vasculature, associated with MetS, might form the link between MetS and the increased risk of developing CVD and T2DM. Not only does the peripheral vasculature seem to be affected, but the syndrome has a profound impact on the cerebral circulation and thence brain structure as well. Furthermore, strong associations are shown with stroke, cognitive impairment, and dementia. In this review the impact of nutrition on the individual components of MetS, the effects of MetS on peripheral and cerebral vasculature, and its consequences for brain structure and function will be discussed.

Cell Systems to Investigate the Impact of Polyphenols on Cardiovascular Health

Polyphenols are a diverse group of micronutrients from plant origin that may serve as antioxidants and that contribute to human health in general. More specifically, many research groups have investigated their protective effect against cardiovascular diseases in several animal studies and human trials. Yet, because of the excessive processing of the polyphenol structure by human cells and the residing intestinal microbial community, which results in a large variability between the test subjects, the exact mechanisms of their protective effects are still under investigation. To this end, simplified cell culture systems have been used to decrease the inter-individual variability in mechanistic studies. In this review, we will discuss the different cell culture models that have been used so far for polyphenol research in the context of cardiovascular diseases. We will also review the current trends in cell culture research, including co-culture methodologies. Finally, we will discuss the potential of these advanced models to screen for cardiovascular effects of the large pool of bioactive polyphenols present in foods and their metabolites.

Functional foods as potential therapeutic options for metabolic syndrome

Obesity as part of metabolic syndrome is a major lifestyle disorder throughout the world. Current drug treatments for obesity produce small and usually unsustainable decreases in body weight with the risk of major adverse effects. Surgery has been the only treatment producing successful long-term weight loss. As a different but complementary approach, lifestyle modification including the use of functional foods could produce a reliable decrease in obesity with decreased comorbidities. Functional foods may include fruits such as berries, vegetables, fibre-enriched grains and beverages such as tea and coffee. Although health improvements continue to be reported for these functional foods in rodent studies, further evidence showing the translation of these results into humans is required. Thus, the concept that these fruits and vegetables will act as functional foods in humans to reduce obesity and thereby improve health remains intuitive and possible rather than proven.

Effect of Hibiscus sabdariffa extract on high fat diet-induced obesity and liver damage in hamsters

Background

Obesity is a chronic metabolic disorder associated with an increase in adipogenesis and often accompanied with fatty liver disease.

Objective

In this study, we investigated the anti-obesity effects of Hibiscus sabdariffa water extract (HSE) in vivo.

Method

Eight-weeks-old male mice were divided into six groups (n=8 per group) and were fed either normal feed, a high fat diet (HFD), HFD supplemented with different concentrations of HSE, or HFD supplemented with anthocyanin. After 10 weeks of feeding, all the blood and livers were collected for further analysis.

Results

Mesocricetus auratus hamster fed with a high-fat diet developed symptoms of obesity, as determined from their body weight change and from their plasma lipid levels. Meanwhile, HSE treatment reduced fat accumulation in the livers of hamsters fed with HFD in a concentration-dependent manner. Administration of HSE reduced the levels of liver cholesterol and triglycerides, which were elevated by HFD. Analysis of the effect of HSE on paraoxonase 1, an antioxidant liver enzyme, revealed that HSE potentially regulates lipid peroxides and protects organs from oxidation-associated damage. The markers of liver damage such as serum alanine aminotransferase and aspartate aminotransferase levels that were elevated by HFD were also reduced on HSE treatment. The effects of HSE were as effective as treatment with anthocyanin; therefore the anthocyanins present in the HSE may play a crucial role in the protection established against HFD-induced obesity.

Conclusions

In conclusion HSE administration constitutes an effective and viable treatment strategy against the development and consequences of obesity.

Can metabolically healthy obesity be explained by diet, genetics, and inflammation?

A substantial proportion of obese individuals do not present cardiometabolic complications such as diabetes, hypertension, or dyslipidemia. Some, but not all, prospective studies observe similar risk of cardiovascular events and all-cause mortality among individuals with this so-called "metabolically healthy obese" (MHO) phenotype, compared to the metabolically healthy normal weight or metabolically healthy non-obese phenotypes. Compared to the metabolically unhealthy obese (MUO) phenotype, MHO is often characterized by a more favorable inflammatory profile, less visceral fat, less infiltration of macrophages into adipose tissue, and smaller adipocyte cell size. Tipping the inflammation balance in adipose tissue might be particularly important for metabolic health in the obese. While the potential role of genetic predisposition or lifestyle factors such as diet in the MHO phenotype is yet to be clarified, it is well known that diet affects inflammation profile and contributes to the functionality of adipose tissue. This review will discuss genetic predisposition and the molecular mechanisms underlying the potential effect of food on the development of the metabolic phenotype characteristic of obesity.

Oleuropein-Rich Diet Attenuates Hyperglycemia and Impaired Glucose Tolerance in Type 2 Diabetes Model Mouse

Oleuropein, a phenolic compound found in abundance in olive leaves, has beneficial effects on various diseases. However, it is unknown whether an oleuropein-rich diet is efficacious against type 2 diabetic phenotypes. In this study, we investigated the effects of the oleuropein-containing supplement OPIACE, whose oleuropein content exceeds 35% (w/w), on the diabetic phenotypes in type 2 diabetes model Tsumura Suzuki Obese Diabetes (TSOD) mouse. TSOD mice were fed OPIACE at 4 weeks of age, i.e., before the TSOD mice exhibited diabetic phenotypes. We revealed that OPIACE attenuated hyperglycemia and impaired glucose tolerance in TSOD mice over the long-term (from 10 to 24 weeks of age) but had no effect on obesity. Furthermore, we demonstrated that OPIACE mildly reduced oxidative stress in TSOD mice by 26.2% and attenuated anxiety-like behavioral abnormality in aged TSOD mice. The results suggest that oleuropein suppresses the progression of type 2 diabetes and diabetes-related behavioral abnormality over the long-term.

Skeletal muscle interleukin-6 regulates metabolic factors in iWAT during HFD and exercise training

OBJECTIVE

To investigate the role of skeletal muscle (SkM) interleukin (IL)-6 in the regulation of adipose tissue metabolism.

METHODS

Muscle-specific IL-6 knockout (IL-6 MKO) and IL-6(loxP/loxP) (Floxed) mice were subjected to standard rodent diet (Chow), high-fat diet (HFD), or HFD in combination with exercise training (HFD ExTr) for 16 weeks.

RESULTS

Total fat mass increased (P < 0.05) in both genotypes with HFD. However, HFD IL-6 MKO mice had lower (P < 0.05) inguinal adipose tissue (iWAT) mass than HFD Floxed mice. Accordingly, iWAT glucose transporter 4 (GLUT4) protein content, 5'AMP activated protein kinase (AMPK)(Thr172) phosphorylation, and fatty acid synthase (FAS) mRNA content were lower (P < 0.05) in IL-6 MKO than Floxed mice on Chow. In addition, iWAT AMPK(Thr172) and hormone-sensitive lipase (HSL)(Ser565) phosphorylation as well as perilipin protein content was higher (P < 0.05) in HFD IL-6 MKO than HFD Floxed mice, and pyruvate dehydrogenase E1α (PDH-E1α) protein content was higher (P < 0.05) in HFD ExTr IL-6 MKO than HFD ExTr Floxed mice.

CONCLUSIONS

These findings indicate that SkM IL-6 affects iWAT mass through regulation of glucose uptake capacity as well as lipogenic and lipolytic factors.

Insulin-independent reversal of type 1 diabetes in nonobese diabetic mice with brown adipose tissue transplant

Traditional therapies for type 1 diabetes (T1D) involve insulin replacement or islet/pancreas transplantation and have numerous limitations. Our previous work demonstrated the ability of embryonic brown adipose tissue (BAT) transplants to establish normoglycemia without insulin in chemically induced models of insulin-deficient diabetes. The current study sought to extend the technique to an autoimmune-mediated T1D model and document the underlying mechanisms. In nonobese diabetic (NOD) mice, BAT transplants result in complete reversal of T1D associated with rapid and long-lasting euglycemia. In addition, BAT transplants placed prior to the onset of diabetes on NOD mice can prevent or significantly delay the onset of diabetes. As with streptozotocin (STZ)-diabetic models, euglycemia is independent of insulin and strongly correlates with decrease of inflammation and increase of adipokines. Plasma insulin-like growth factor-I (IGF-I) is the first hormone to increase following BAT transplants. Adipose tissue of transplant recipients consistently express IGF-I compared with little or no expression in controls, and plasma IGF-I levels show a direct negative correlation with glucose, glucagon, and inflammatory cytokines. Adipogenic and anti-inflammatory properties of IGF-I may stimulate regeneration of new healthy white adipose tissue, which in turn secretes hypoglycemic adipokines that substitute for insulin. IGF-I can also directly decrease blood glucose through activating insulin receptor. These data demonstrate the potential for insulin-independent reversal of autoimmune-induced T1D with BAT transplants and implicate IGF-I as a likely mediator in the resulting equilibrium.

Dual effects of a mixture of grape pomace (Campbell Early) and Omija fruit ethanol extracts on lipid metabolism and the antioxidant defense system in diet-induced obese mice

BACKGROUND/OBJECTIVES

We investigated the effects of a combination of grape pomace (Vitis labrusca, Campbell Early) and Omija fruit (Schizandra chinensis, Baillon) ethanol extracts on lipid metabolism and antioxidant defense system in diet-induced obese mice.

MATERIALS/METHODS

Forty male C57BL/6J mice were divided into four groups and fed high-fat diet (control group, CON) or high-fat diet added 0.5% grape pomace extract (GPE), 0.05% Omija fruit extract (OFE) or 0.5% GPE plus 0.05% OFE (GPE+OFE) for 12 weeks.

RESULTS

In contrast to the GPE- or OFE-supplemented groups, the GPE+OFE group showed significantly lower body weight and white adipose tissue weights than the CON group. Moreover, GPE+OFE supplementation significantly decreased plasma total cholesterol and increased the plasma HDL-cholesterol/total-cholesterol ratio (HTR) compared to the control diet. The hepatic triglyceride level was significantly lower in the GPE+OFE and GPE groups by increasing β-oxidation and decreasing lipogenic enzyme compared to the CON group. Furthermore, GPE+OFE supplementation significantly increased antioxidant enzyme activities with a simultaneous decrease in liver H₂O₂ content compared to the control diet.

CONCLUSIONS

Together our results suggest that supplementation with the GPE+OFE mixture may be more effective in improving adiposity, lipid metabolism and oxidative stress in high-fat diet-fed mice than those with GPE and OFE alone.

Effect of resveratrol and orchidectomy on the vasorelaxing influence of perivascular adipose tissue

Perivascular adipose tissue (PVAT) releases several adipo(cyto)kines. Some are vasoactive substances that elicit a net beneficial anticontractile effect. Resveratrol and testosterone are known to modulate adipo(cyto)kine release from adipose tissue and could therefore influence the anticontractile effect of PVAT. In vitro tension measurements were performed using thoracic aorta segments with and without adipose tissue from sham-operated or orchidectomized male Swiss mice. Concentration-response curves to norepinephrine (NOR) were constructed in the presence and absence of resveratrol (10 μM, 15 min) or the relaxant effect of resveratrol (10-100 μM) was investigated after inducing tone with NOR (5 μM). Aortas with PVAT displayed significantly attenuated contractions to NOR compared with aortas without PVAT. In aortas without PVAT, resveratrol (10 μM) significantly decreased NOR responses and elicited concentration-dependent (10-100 µM) relaxations. However, in aortas with adherent PVAT, resveratrol (10 μM) neither decreased NOR responses, nor did resveratrol (10-100 µM) induce arterial relaxations. The anticontractile effect of PVAT was less pronounced in the presence of resveratrol and unaltered by orchidectomy. Orchidectomy did not influence contractions induced by NOR. Orchidectomy does not modulate the anticontractile capacity of PVAT, while resveratrol decreases the vasorelaxing influence of PVAT. The positive effects associated with resveratrol addition are neutralized by the presence of PVAT. This is thought to result from a dual effect of resveratrol: (1) inhibition of the influence of vasodilatory adipo(cyto)kines and (2) a direct relaxant effect on the vascular smooth muscle. Overall, the beneficial relaxing effect of resveratrol is lost in mice thoracic aorta surrounded by PVAT.

Inhibitory Effects of Chemical Compounds Isolated from the Rhizome of Smilax glabra on Nitric Oxide and Tumor Necrosis Factor- α Production in Lipopolysaccharide-Induced RAW264.7 Cell

The rhizome of Smilax glabra has been used for a long time as both food and folk medicine in many countries. The present study focused on the active constituents from the rhizome of S. glabra, which possess potential anti-inflammatory activities. As a result, nine known compounds were isolated from the rhizome of S. glabra with the bioassay-guiding, and were identified as syringaresinol (1), lasiodiplodin (2), de-O-methyllasiodiplodin (3), syringic acid (4), 1,4-bis(4-hydroxy-3,5-dimethoxyphenyl)-2,3-bis(hydroxymethyl)-1,4-butanediol (5), lyoniresinol (6), trans-resveratrol (7), trans-caffeic acid methyl ester (8), and dihydrokaempferol (9). Among these compounds, 2 and 3 were isolated for the first time from S. glabra. In addition, the potential anti-inflammatory activities of the isolated compounds were evaluated in vitro in lipopolysaccharide- (LPS-) induced RAW264.7 cells. Results indicated that 4 and 7 showed significant inhibitory effects on NO production of RAW264.7 cells, and 1, 2, 3, and 5 showed moderate suppression effects on induced NO production. 1, 7, and 5 exhibited high inhibitory effects on TNF-α production, with the IC₅₀ values less than 2.3, 4.4, and 16.6 μM, respectively. These findings strongly suggest that compounds 1, 2, 3, 4, 5, 7, and 9 were the potential anti-inflammatory active compositions of S. glabra.

Resveratrol improves insulin resistance, glucose and lipid metabolism in patients with non-alcoholic fatty liver disease: a randomized controlled trial

BACKGROUND

Non-alcoholic fatty liver disease is a major health problem worldwide. Resveratrol is a natural polyphenol found in edible plants that has a variety of biochemical and physiological effects.

AIMS

To evaluate the effect of resveratrol on insulin resistance, glucose and lipid metabolism in non-alcoholic fatty liver disease.

METHODS

Double-blind, randomized, placebo-controlled trial: 60 subjects with non-alcoholic fatty liver disease were given 2 placebo capsules (placebo group) or 2 150mg resveratrol capsules (resveratrol group) twice daily for three months. Liver ultrasound imaging, anthropometric profile, serum liver enzymes, insulin, glucose, C-peptide, lipid profile, and inflammation-related cytokines were compared pre and post-treatment.

RESULTS

Compared with the placebo group, resveratrol significantly decreased aspartate aminotransferase, glucose and low-density lipoprotein cholesterol [-6.00 (-9.00, -3.00) IU/L, -0.64±0.31mmol/L, and -0.41±0.35mmol/L, respectively, P≤0.001] alanine aminotransferase, total cholesterol [-7.00 (-11.0, -2.50) IU/L and -0.67±0.50mmol/L, respectively, P=0.002], and homeostasis model assessment insulin resistance index (-0.60±1.15, P=0.016). In the resveratrol group significant reductions of the levels of tumour necrosis factor-alpha, cytokeratin 18 fragment, and fibroblast growth factor 21 [-0.53±1.30pg/mL, -26.9 (-70.3, 5.12) IU/L and -23.3 (-43.0, 0.31) pg/mL, respectively, P<0.05] and elevation of adiponectin level [1.22 (-0.37, 1.60) ng/mL, P=0.025] were observed.

CONCLUSION

Resveratrol supplementation may benefit patients with non-alcoholic fatty liver disease.

Regulatory effects of resveratrol on glucose metabolism and T-lymphocyte subsets in the development of high-fat diet-induced obesity in C57BL/6 mice

High-fat diet (HFD)-induced obesity is often associated with immune dysfunction. Resveratrol (trans-3,5,4'-trihydroxystilbene), which has well-founded immunity-related beneficial properties, was used to elucidate the regulatory effect on glucose metabolism and T-lymphocyte subsets in the development of HFD-induced obesity. Resveratrol, being associated with decreases of plasma leptin and plasma lipids and the release of oxidative stress, significantly decreased the body weight and fat masses in HF mice after 26 weeks of feeding. Furthermore, resveratrol decreased the fasting blood glucose and fasting plasma insulin and increased the CD3(+)CD4(+)/CD3(+)CD8(+) subsets percentages and the regulatory T cells (Tregs) production after 13 and 26 weeks of feeding. The results indicate that resveratrol, as an effective supplement for HFD, maintained glucose homeostasis by activating the PI3K and SIRT1 signaling pathways. Moreover, resveratrol activated the Nrf2 signaling pathway-mediated antioxidant enzyme expression to alleviate inflammation by protecting against oxidative damage and T-lymphocyte subset-related chronic inflammatory response in the development of HFD-induced obesity.

Brown Alga Ecklonia cava polyphenol extract ameliorates hepatic lipogenesis, oxidative stress, and inflammation by activation of AMPK and SIRT1 in high-fat diet-induced obese mice

Obesity is considered to be a metaflammatory condition. Ecklonia cava, brown algae rich in polyphenols, has shown strong antioxidant activity in vitro. This study investigated the effect of E. cava polyphenol extract (ECPE) on the regulation of fat metabolism, inflammation, and the antioxidant defense system in high fat diet-induced obese mice. After obesity was induced by a high-fat diet (HFD), the mice were administered ECPE by gavage for 5 days/12 weeks. ECPE supplementation reduced body weight gain, adipose tissue mass, plasma lipid profiles, hepatic fat deposition, insulin resistance, and the plasma leptin/adiponectin ratio derived from HFD-induced obesity. Moreover, ECPE supplementation selectively ameliorated hepatic protein levels associated with lipogenesis, inflammation, and the antioxidant defense system as well as activation of AMPK and SIRT1. Collectively, ECPE supplement might have potential antiobesity effects via regulation of AMPK and SIRT1 in HFD-induced obesity.

Resveratrol enhances palmitate-induced ER stress and apoptosis in cancer cells

Background

Palmitate, a saturated fatty acid (FA), is known to induce toxicity and cell death in various types of cells. Resveratrol (RSV) is able to prevent pathogenesis and/or decelerate the progression of a variety of diseases. Several in vitro and in vivo studies have also shown a protective effect of RSV on fat accumulation induced by FAs. Additionally, endoplasmic reticulum (ER) stress has recently been linked to cellular adipogenic responses. To address the hypothesis that the RSV effect on excessive fat accumulation promoted by elevated saturated FAs could be partially mediated by a reduction of ER stress, we studied the RSV action on experimentally induced ER stress using palmitate in several cancer cell lines.

Principal Findings

We show that, unexpectedly, RSV promotes an amplification of palmitate toxicity and cell death and that this mechanism is likely due to a perturbation of palmitate accumulation in the triglyceride form and to a less important membrane fluidity variation. Additionally, RSV decreases radical oxygen species (ROS) generation in palmitate-treated cells but leads to enhanced X-box binding protein-1 (XBP1) splicing and C/EBP homologous protein (CHOP) expression. These molecular effects are induced simultaneously to caspase-3 cleavage, suggesting that RSV promotes palmitate lipoapoptosis primarily through an ER stress-dependent mechanism. Moreover, the lipotoxicity reversion induced by eicosapentaenoic acid (EPA) or by a liver X receptor (LXR) agonist reinforces the hypothesis that RSV-mediated inhibition of palmitate channeling into triglyceride pools could be a key factor in the aggravation of palmitate-induced cytotoxicity.

Conclusions

Our results suggest that RSV exerts its cytotoxic role in cancer cells exposed to a saturated FA context primarily by triglyceride accumulation inhibition, probably leading to an intracellular palmitate accumulation that triggers a lipid-mediated cell death. Additionally, this cell death is promoted by ER stress through a CHOP-mediated apoptotic process and may represent a potential anticancer strategy.

Resveratrol: anti-obesity mechanisms of action

Resveratrol is a non-flavonoid polyphenol which belongs to the stilbenes group and is produced naturally in several plants in response to injury or fungal attack. Resveratrol has been recently reported as preventing obesity. The present review aims to compile the evidence concerning the potential mechanisms of action which underlie the anti-obesity effects of resveratrol, obtained either in cultured cells lines and animal models. Published studies demonstrate that resveratrol has an anti-adipogenic effect. A good consensus concerning the involvement of a down-regulation of C/EBPα and PPARγ in this effect has been reached. Also, in vitro studies have demonstrated that resveratrol can increase apoptosis in mature adipocytes. Furthermore, different metabolic pathways involved in triacylglycerol metabolism in white adipose tissue have been shown to be targets for resveratrol. Both the inhibition of de novo lipogenesis and adipose tissue fatty acid uptake mediated by lipoprotein lipase play a role in explaining the reduction in body fat which resveratrol induces. As far as lipolysis is concerned, although this compound per se seems to be unable to induce lipolysis, it increases lipid mobilization stimulated by β-adrenergic agents. The increase in brown adipose tissue thermogenesis, and consequently the associated energy dissipation, can contribute to explaining the body-fat lowering effect of resveratrol. In addition to its effects on adipose tissue, resveratrol can also acts on other organs and tissues. Thus, it increases mitochondriogenesis and consequently fatty acid oxidation in skeletal muscle and liver. This effect can also contribute to the body-fat lowering effect of this molecule.

Cross-talk between SIRT1 and endocrine factors: effects on energy homeostasis

The mammalian sirtuins (SIRT1-7) are a family of highly conserved nicotine adenine dinucleotide (NAD(+))-dependent deacetylases that act as cellular sensors to detect energy availability. SIRT1 is a multifaceted protein that is involved in a wide variety of cellular processes. SIRT1 is activated in response to caloric restriction, acting on multiple targets in a wide range of tissues. SIRT1 regulates the role of multiple hormones implicated in energy balance, including glucose and lipid metabolism. Here, we review the relevant role of SIRT1 as a mediator of endocrine function of several hormones to modulate energy balance. In addition, we analyze the potential of targeting SIRT1 for the treatment of obesity and type 2 diabetes mellitus.

Resveratrol and diabetes: from animal to human studies

Diabetes mellitus is a serious disease affecting about 5% of people worldwide. Diabetes is characterized by hyperglycemia and impairment in insulin secretion and/or action. Moreover, diabetes is associated with metabolic abnormalities and serious complications. Resveratrol is a natural, biologically active polyphenol present in different plant species and known to have numerous health-promoting effects in both animals and humans. Anti-diabetic action of resveratrol has been extensively studied in animal models and in diabetic humans. In animals with experimental diabetes, resveratrol has been demonstrated to induce beneficial effects that ameliorate diabetes. Resveratrol, among others, improves glucose homeostasis, decreases insulin resistance, protects pancreatic β-cells, improves insulin secretion and ameliorates metabolic disorders. Effects induced by resveratrol are strongly related to the capability of this compound to increase expression/activity of AMPK and SIRT1 in various tissues of diabetic subjects. Moreover, anti-oxidant and anti-inflammatory effects of resveratrol were shown to be also involved in its action in diabetic animals. Preliminary clinical trials show that resveratrol is also effective in type 2 diabetic patients. Resveratrol may, among others, improve glycemic control and decrease insulin resistance. These results show that resveratrol holds great potential to treat diabetes and would be useful to support conventional therapy. This article is part of a Special Issue entitled: Resveratrol: Challenges in translating pre-clincial findigns to improved patient outcomes.

Effects of yerba maté, a plant extract formulation ("YGD") and resveratrol in 3T3-L1 adipogenesis

We aimed to evaluate the in vitro effects of yerba maté, YGD (a herbal preparation containing yerba maté, guarana and damiana), and resveratrol on adipogenesis. The anti-adipogenic effects of yerba mate, YGD, resveratrol and YGD + resveratrol and yerba mate + resveratrol combinations were evaluated in 3T3-L1 cells by Oil Red staining, cellular triglyceride content, and PCR quantitative array. The results demonstrated that all of the tested compounds inhibited adipogenesis. Yerba maté extract significantly down-regulated the expression of genes that play an important role in regulating adipogenesis, such as Adig, Axin, Cebpa, Fgf10, Lep, Lpl, and Pparγ2. In addition, these genes, YGD also repressed Bmp2, Ccnd1, Fasn, and Srebf1. Resveratrol also modulated the expression of Adig, Bmp2, Ccnd1, C/EBPα, Fasn, Fgf10, Lep, Lpl, and Pparγ2. Moreover, resveratrol repressed Cebpb, Cdk4, Fgf2, and Klf15. The yerba maté extract and YGD up-regulated the expression of genes involved in inhibiting adipogenesis, such as Dlk-1, Klf2, and Ucp1. Resveratrol also induced the expression of Klf2 and Ucp1. In addition resveratrol modulated the Ddit3, Foxo1, Sirt1, and Sirt2. The combined effects of these compounds on gene expression showed similar results observed from individual treatments. Our data indicates that the synergy between the compounds favors the inhibition of adipogenesis.

Resveratrol and cardiovascular health--promising therapeutic or hopeless illusion?

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a natural polyphenolic compound that exists in Polygonum cuspidatum, grapes, peanuts and berries, as well as their manufactured products, especially red wine. Resveratrol is a pharmacologically active compound that interacts with multiple targets in a variety of cardiovascular disease models to exert protective effects or induce a reduction in cardiovascular risks parameters. This review attempts to primarily serve to summarize the current research findings regarding the putative cardioprotective effects of resveratrol and the molecular pathways underlying these effects. One intent is to hopefully provide a relatively comprehensive resource for clues that may prompt ideas for additional mechanistic studies which might further elucidate and strengthen the role of the stilbene family of compounds in cardiovascular disease and cardioprotection. Model systems that incorporate a significant functional association with tissues outside of the cardiovascular system proper, such as adipose (cell culture, obesity models) and pancreatic (diabetes) tissues, were reviewed, and the molecular pathways and/or targets related to these models and influenced by resveratrol are discussed. Because the body of work encompassing the stilbenes and other phytochemicals in the context of longevity and the ability to presumably mitigate a plethora of afflictions is replete with conflicting information and controversy, especially so with respect to the human response, we tried to remain as neutral as possible in compiling and presenting the more current data with minimal commentary, permitting the reader free reign to extract the knowledge most helpful to their own investigations.

Novel insights of dietary polyphenols and obesity

The prevalence of obesity has steadily increased over the past three decades both in the United States and worldwide. Recent studies have shown the role of dietary polyphenols in the prevention of obesity and obesity-related chronic diseases. Here, we evaluated the impact of commonly consumed polyphenols, including green tea catechins, especially epigallocatechin gallates, resveratrol and curcumin, on obesity and obesity-related inflammation. Cellular studies demonstrated that these dietary polyphenols reduce viability of adipocytes and proliferation of preadipocytes, suppress adipocyte differentiation and triglyceride accumulation, stimulate lipolysis and fatty acid β-oxidation, and reduce inflammation. Concomitantly, the polyphenols modulate signaling pathways including the adenosine-monophosphate-activated protein kinase, peroxisome proliferator activated receptor γ, CCAAT/enhancer binding protein α, peroxisome proliferator activator receptor gamma activator 1-alpha, sirtuin 1, sterol regulatory element binding protein-1c, uncoupling proteins 1 and 2, and nuclear factor-κB that regulate adipogenesis, antioxidant and anti-inflammatory responses. Animal studies strongly suggest that commonly consumed polyphenols described in this review have a pronounced effect on obesity as shown by lower body weight, fat mass and triglycerides through enhancing energy expenditure and fat utilization, and modulating glucose hemostasis. Limited human studies have been conducted in this area and are inconsistent about the antiobesity impact of dietary polyphenols probably due to the various study designs and lengths, variation among subjects (age, gender, ethnicity), chemical forms of the dietary polyphenols used and confounding factors such as other weight-reducing agents. Future randomized controlled trials are warranted to reconcile the discrepancies between preclinical efficacies and inconclusive clinic outcomes of these polyphenols.

Antidiabetic effect of nepodin, a component of Rumex roots, and its modes of action in vitro and in vivo

Many active components derived from edible natural resources such as plant extracts have recently attracted attention for their potential use as functional foods or drugs for preventing and treating metabolic diseases such as diabetes. To obtain a novel modulator of glucose metabolism, we conducted screening of a small compound library in cultured L6 myotubes. We identified nepodin that stimulated glucose uptake dose-dependently in differentiated L6 myotubes. The stimulatory effect of nepodin on glucose uptake was abrogated by a 5'-adenosine monophosphate-activated protein kinase (AMPK) inhibitor. In addition, nepodin stimulated the phosphorylation of AMPK. Nepodin also stimulated the translocation of GLUT4 to the plasma membrane in L6 myoblasts transfected with a Glut4 cDNA-coding vector and in differentiated L6 myotubes. In in vivo study, nepodin suppressed the increases in fasting blood glucose levels and improved the glucose intolerance of C57BL/KsJ-db/db mice, a type 2 diabetic animal model. Nepodin rescued the impaired phosphorylation of AMPK in the skeletal muscle of db/db mice. These results suggest that nepodin has an antidiabetic effect, which is at least partly mediated by stimulation of GLUT4 translocation via AMPK activation by nepodin.

Effects of resveratrol and other polyphenols in hepatic steatosis

Non-alcoholic fatty liver disease covers a wide spectrum of liver pathologies which range from simple steatosis to non-alcoholic steatohepatitis. Polyphenols are members of a very large family of plant-derived compounds that can have beneficial effects on human health, and thus their study has become an increasingly important area of human nutrition research. The aim of the present review is to compile published data concerning the effects of both isolated polyphenols as well as polyphenol extracts, on hepatocyte and liver fat accumulation under different steatosis-inducing conditions. The results reported clearly show that this group of biomolecules is able to reduce fat accumulation, but further studies are needed to establish the optimal dose and treatment period length. With regard to the potential mechanisms of action, there is a good consensus. The anti-lipidogenic effect of polyphenols is mainly due to reduced fatty acid and triacylglycerol synthesis, increased in fatty acid oxidation, and reduced of oxidative stress and inflammation. As a general conclusion, it can be stated that polyphenols are biomolecules which produce hepatoprotective effects. To date, these beneficial effects have been demonstrated in cultured cells and animal models. Thus, studies performed in humans are needed before these molecules can be considered as truly useful tools in the prevention of liver steatosis.

Cross talk between angiotensin-(1-7)/Mas axis and sirtuins in adipose tissue and metabolism of high-fat feed mice

Angiotensin-(1-7) and resveratrol have been described as new potential therapeutic tools on treating and preventing metabolic disorders. In the present study we aimed to evaluate the effect of an oral formulation of angiotensin-(1-7) [Ang-(1-7)] included in HPB-cyclodextrin and resveratrol (RSV), in modulation of sirtuin and renin-angiotensin system (RAS) in adipose tissue of mice treated with a high-fat diet (HFD). We observed that HFD+Ang-(1-7) and HFD+RSV groups presented marked decrease in the adipose tissue mass. Furthermore, these animals showed improved insulin-sensitivity and glucose tolerance as well as lower plasma levels of fasting glucose and lipids. The RT-PCR analysis revealed decreased expression of ACE and an increase of ACE2 [Ang-(1-7) marker] in group treated with resveratrol and also an increased expression of SIRT1 in groups that received Ang-(1-7). We showed for the first time that improved metabolic profile is associated with increased expression of GLUT4 and high expression of AMPK/FOXO1/PPAR-γ pathway in adipose-tissue. Finally, adipocyte primary cell-culture incubated with and without sirtuin and Ang-(1-7)/Mas antagonists pointed out for a cross-talking between RAS and sirtuins. We conclude that oral administration of Ang-(1-7) and RSV improved metabolic profile through a cross-modulation between RAS and Sirtuins.

Influence of nutrition in PCB-induced vascular inflammation

The nutritional profile of an individual can influence the toxicity of persistent environmental toxicants. Polychlorinated biphenyls (PCBs), prevalent environmental pollutants, are highly lipid-soluble toxic compounds that biomagnify through trophic levels and pose cancer, neurocognitive, and atherosclerotic risk to human populations. There is a growing body of knowledge that PCBs can initiate inflammatory responses in vivo, and this inflammation can be either exacerbated or ameliorated by nutrition. Data indicate that diets high in certain dietary lipids such as omega-6 fatty acids can worsen PCB-induced vascular toxicity while diets enriched with bioactive food components such as polyphenols and omega-3 polyunsaturated fatty acids can improve the toxicant-induced inflammation. There is evidence that bioactive nutrients protect through multiple cell signaling pathways, but we have shown that lipid raft caveolae and the antioxidant defense controller nuclear factor (erythroid-derived 2)-like 2 (Nrf2) both play a predominant role in nutritional modulation of PCB-induced vascular toxicity. Interestingly, there appears to be an intimate cross-talk between caveolae-related proteins and cellular Nrf2, and focusing on the use of specific bioactive food components that simultaneously alter both pathways may produce a more effective and efficient cytoprotective response to toxicant exposure. The use of nutrition as a protective tool is an economically beneficial means to address the toxicity of persistent environmental toxicants and may become a sensible means to protect human populations from PCB-induced vascular inflammation and associated chronic diseases.

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

The prevalence of obesity and related conditions like non-alcoholic fatty liver disease (NAFLD) is increasing worldwide and therapeutic options are limited. Alternative treatment options are therefore intensively sought after. An interesting candidate is the natural polyphenol resveratrol (RSV) that activates adenosinmonophosphate-activated protein kinase (AMPK) and silent information regulation-2 homolog 1 (SIRT1). In addition, RSV has known anti-oxidant and anti-inflammatory effects. Here, we review the current evidence for RSV-mediated effects on NAFLD and address the different aspects of NAFLD and non-alcoholic steatohepatitis (NASH) pathogenesis with respect to free fatty acid (FFA) flux from adipose tissue, hepatic de novo lipogenesis, inadequate FFA β-oxidation and additional intra- and extrahepatic inflammatory and oxidant hits. We review the in vivo evidence from animal studies and clinical trials. The abundance of animal studies reports a decrease in hepatic triglyceride accumulation, liver weight and a general improvement in histological fatty liver changes, along with a reduction in circulating insulin, glucose and lipid levels. Some studies document AMPK or SIRT1 activation, and modulation of relevant markers of hepatic lipogenesis, inflammation and oxidation status. However, AMPK/SIRT1-independent actions are also likely. Clinical trials are scarce and have primarily been performed with a focus on overweight/obese participants without a focus on NAFLD/NASH and histological liver changes. Future clinical studies with appropriate design are needed to clarify the true impact of RSV treatment in NAFLD/NASH patients.

Effects of resveratrol on gut microbiota and fat storage in a mouse model with high-fat-induced obesity

Recent studies have investigated the anti-obesity effect of resveratrol, but the pathways through which resveratrol resists obesity are not clear. In the present study, we hypothesize that resveratrol exerts anti-obesity effects that are likely mediated by mechanisms of regulating gut microbes, and in turn, improving fat storage and metabolism. Gut microbes, glucose and lipid metabolism in high-fat diet (HF) mice in vivo are investigated after resveratrol treatment. Several biochemical markers are measured. Fluorescence in situ hybridization and flow cytometry are used to monitor and quantify the changes in gut microbiota. The key genes related to fat storage and metabolism in the liver and visceral adipose tissues are measured by real-time PCR. The results show that resveratrol (200 mg per kg per day) significantly lowers both body and visceral adipose weights, and reduces blood glucose and lipid levels in HF mice. Resveratrol improves the gut microbiota dysbiosis induced by the HF diet, including increasing the Bacteroidetes-to-Firmicutes ratios, significantly inhibiting the growth of Enterococcus faecalis, and increasing the growth of Lactobacillus and Bifidobacterium. Furthermore, resveratrol significantly increases the fasting-induced adipose factor (Fiaf, a key gene negatively regulated by intestinal microbes) expression in the intestine. Resveratrol significantly decreases mRNA expression of Lpl, Scd1, Ppar-γ, Acc1, and Fas related to fatty acids synthesis, adipogenesis and lipogenesis, which may be driven by increased Fiaf expression. The Pearson's correlation coefficient shows that there is a negative correlation between the body weight and the ratios of Bacteroidetes-to-Firmicutes. Therefore, resveratrol mediates the composition of gut microbes, and in turn, through the Fiaf signaling pathway, accelerates the development of obesity.

Development and validation of a sensitive and selective LC-MS/MS method for the determination of trans δ-veniferin, a resveratrol dehydrodimer, in rat plasma and its application to pharmacokinetics and bioavailability studies

In this study, an accurate and reliable LC-MS/MS assay was firstly developed and validated for the quantitative determination of trans δ-veniferin (TVN) in rat plasma. Chlorzoxazone was used as the internal standard (IS). After one-step protein precipitation with methanol, the analyte and IS were separated on an ODS column by gradient elution with mobile phase of acetonitrile-0.2% formic acid at a flow rate of 0.3mL/min. Negative electrospray ionization was performed using multiple reactions monitoring (MRM) mode with transitions of m/z 453.0>410.9 for TVN, and m/z 168.0>132.0 for IS. Good linearity (R≥0.996) was observed over the concentration range of 5-5000ng/mL for TVN with a lower limit of quantification (LLOQ) of 5ng/mL. The mean recoveries for TVN and IS were 91.05% and 96.68%, respectively. The intra- and inter-day precisions (RSD) were no more than 10.5% and accuracies (RE) were within the range of -6.3% to 2.1%. The validated method was suitable for quantification of TVN and successfully applied to the pharmacokinetic study of TVN after oral and intravenous administration to rats. The oral absolute bioavailability of TVN was 14.2% in rat.

Resveratrol and clinical trials: the crossroad from in vitro studies to human evidence

Resveratrol (3,5,4’-trihydroxy-trans-stilbene) is a non-flavonoid polyphenol that may be present in a limited number of food-stuffs such as grapes and red wine. Resveratrol has been reported to exert a plethora of health benefits through many different mechanisms of action. This versatility and presence in the human diet have drawn the worldwide attention of many research groups over the past twenty years, which has resulted in a huge output of in vitro and animal (preclinical) studies. In line with this expectation, many resveratrol-based nutraceuticals are consumed all over the world with questionable clinical/scientific support. In fact, the confirmation of these benefits in humans through randomized clinical trials is still very limited. The vast majority of preclinical studies have been performed using assay conditions with a questionable extrapolation to humans, i.e. too high concentrations with potential safety concerns (adverse effects and drug interactions), short-term exposures, in vitro tests carried out with non-physiological metabolites and/or concentrations, etc. Unfortunately, all these hypothesis-generating studies have contributed to increased the number of ‘potential’ benefits and mechanisms of resveratrol but confirmation in humans is very limited. Therefore, there are many issues that should be addressed to avoid an apparent endless loop in resveratrol research. The so-called ‘Resveratrol Paradox’, i.e., low bioavailability but high bioactivity, is a conundrum not yet solved in which the final responsible actor (if any) for the exerted effects has not yet been unequivocally identified. It is becoming evident that resveratrol exerts cardioprotective benefits through the improvement of inflammatory markers, atherogenic profile, glucose metabolism and endothelial function. However, safety concerns remain unsolved regarding chronic consumption of high RES doses, specially in medicated people. This review will focus on the currently available evidence regarding resveratrol’s effects on humans obtained from randomized clinical trials. In addition, we will provide a critical outlook for further research on this molecule that is evolving from a minor dietary compound to a possible multi-target therapeutic drug.

Exercise training is more effective than resveratrol supplementation on alleviation of inflammation in peritoneal macrophages of high fat diet mice

[Purpose]

This study investigated the effect of exercise training and resveratrol supplementation with low fat diet on proinflammatory profiles by Lipopolysaccharide (LPS)-stimulation in peritoneal macrophage of high fat diet mice.

[Methods]

To accomplish the purpose of this study, C57BL/6 male mice were fed high fat diet (45% fat diet) for 8 weeks. Then these mice were divided into 3 groups; HLC (high fat diet and low fat diet for 8 weeks as the control, n=10), HLR (high fat diet and low fat diet for 8 weeks with resveratrol supplementation, n=10). HLE (high fat diet and low fat diet for 8 weeks with moderate exercise training, n=10). Resveratrol (10 mg/kg) was administrated once a day, 5 days/week for 8 weeks. Exercise training was performed for 8 weeks on a treadmill running for 30-60 min/day at 10-22 m/min, 0% grade, 5 days/week. After exercise training, all the peritoneal macrophage was collected and LPS (0, 0.5, 1.0 μg/ml) were used to stimulate the cells. Then peritoneal macrophage TNF-α, IL-6, MCP-1, IL12p70, IFN-γ, IL-10 were measured by BD cytometric bead array mouse inflammation kit.

[Results]

As a result, body weight and total cholesterol were significantly reduced in HLE compared with HLC (p<.05). Also, TNF-α and MCP-1 were decreased in HLE compared with HLC (p<.05) by LPS-stimulation (0, 0.5, 1.0 μg/ml) and IL-6, IL-12p70 and IFN-r were decreased in HLE compared with HLC (p<.05) by LPS-stimulation (1.0 μg/ml). But resveratrol supplementation did not affect the result.

[Conclusion]

These findings suggest that exercise training has beneficial effects on body weight, total cholesterol, peritoneal macrophage and proinflammatory cytokine in high fat diet mice.