Antidiabetic activity of resveratrol, a known SIRT1 activator in a genetic model for type-2 diabetes

Medicinal chemistry perspective on the structure-activity relationship of stilbene derivatives

Stilbenes are a small family of polyphenolic secondary metabolites produced in a variety of closely related plant species. These compounds function as phytoalexins, aiding plant defense against phytopathogens and plants' adaptation to abiotic environmental factors. Structurally, some important phenolic compounds have a 14-carbon skeleton and usually have two isomeric forms, Z and E. Stilbenes contain two benzene rings linked by a molecule of ethanol or ethylene. Some derivatives of natural (poly)phenolic stilbenes such as resveratrol, pterostilbene, and combretastatin A-4 have shown various biological activities, such as anti-microbial, anti-cancer, and anti-inflammatory properties as well as protection against heart disease, Alzheimer's disease, and diabetes. Among stilbenes, resveratrol is certainly the most popular and extensively studied for its health properties. In recent years, an increasing number of stilbene compounds have been investigated for their bioactivity. This review focuses on the assessment of synthetic stilbene derivatives in terms of their biological activities and structure-activity relationship. The goal of this study is to consider the structural changes and different substitutions on phenyl rings that can improve the desired medicinal effects of stilbene-based compounds beyond the usual standards and subsequently discover biological activities by identifying effective alternatives of the evaluated compounds.

Clinical applications and mechanism insights of natural flavonoids against type 2 diabetes mellitus

Diabetes is a complex disease that affects a large percentage of the world's population, and it is associated with several risk factors. Self-management poses a significant challenge, but natural sources have shown great potential in providing effective glucose reducing solutions. Flavonoids, a class of bioactive substances found in different natural sources including medicinal plants, have emerged as promising candidates in this regard. Indeed, several flavonoids, including apigenin, arbutin, catechins, and cyanidin, have demonstrated remarkable anti-diabetic properties. The clinical effectiveness of these flavonoids is linked to their potential to decrease blood glucose concentration and increase insulin concentration. Thus, the regulation of certain metabolic pathways such as glycolysis and neoglycogenesis has also been demonstrated. In vitro and in vivo investigations revealed different mechanisms of action related to flavonoid compounds at subcellular, cellular, and molecular levels. The main actions reside in the activation of glycolytic signaling pathways and the inhibition of signaling that promotes glucose synthesis and storage. In this review, we highlight the clinical efficiency of natural flavonoids as well as the molecular mechanisms underlying this effectiveness.

The effects of resveratrol and melatonin on biochemical and molecular parameters in diabetic old female rat hearts

The roles of melatonin and resveratrol-enhanced activation of SIRT1 (silent information regulator 1), GLUT4 (glucose transporter type 4), and PGC-1α (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) in mediating the protective effects on the heart in aged female rats with streptozotocin-induced diabetes were investigated. 16-month-old 48 Wistar female rats were separated into 8 groups with equal numbers. Group 1: Control, Group 2: Resveratrol Control, Group 3: Melatonin Control, Group 4: Resveratrol and Melatonin Control, Group 5: Diabetes, Group 6: Diabetes Resveratrol, Group 7: Diabetes Melatonin, Group 8: Diabetes Resveratrol and Melatonin. A single dose of 40 mg/kg intraperitoneal streptozotocin was injected into the rats of Groups 5, 6, 7, and 8 to induce experimental diabetes. Blood glucose levels were measured from the tail veins of the animals six days after the injections, using a diagnostic glucose kit. Rats with a blood glucose levels ≥300 mg/dl were considered diabetic. 5 mg/kg/day of resveratrol (intraperitoneal) and melatonin (subcutaneous) were administered for four weeks. At the end of the applications, SIRT1, GLUT4, PGC-1α gene expression as well as MDA and GSH levels in the heart tissues were determined by the PCR method from heart tissue samples taken under general anesthesia. The findings of our study show that suppressed antioxidant activity and decreased GLUT4, SIRT1, and PGC-1α gene expression in heart tissue can be reversed by the combination of resveratrol, melatonin, and resveratrol + melatonin in a diabetic aged female rat model. Resveratrol and melatonin supplementation may have a protective effect on cardiac functions in the diabetic aged female rat model.

Resveratrol in Treating Diabetes and Its Cardiovascular Complications: A Review of Its Mechanisms of Action

Diabetes mellitus (DM) is one of the most prevalent chronic diseases worldwide. High morbidity and mortality caused by DM are closely linked to its complications in multiple organs/tissues, including cardiovascular complications, diabetic nephropathy, and diabetic neuropathy. Resveratrol is a plant-derived polyphenolic compound with pleiotropic protective effects, ranging from antioxidant and anti-inflammatory to hypoglycemic effects. Recent studies strongly suggest that the consumption of resveratrol offers protection against diabetes and its cardiovascular complications. The protective effects of resveratrol involve the regulation of multiple signaling pathways, including inhibition of oxidative stress and inflammation, enhancement of insulin sensitivity, induction of autophagy, regulation of lipid metabolism, promotion of GLUT4 expression, and translocation, and activation of SIRT1/AMPK signaling axis. The cardiovascular protective effects of resveratrol have been recently reviewed in the literature, but the role of resveratrol in preventing diabetes mellitus and its cardiovascular complications has not been systematically reviewed. Therefore, in this review, we summarize the pharmacological effects and mechanisms of action of resveratrol based on in vitro and in vivo studies, highlighting the therapeutic potential of resveratrol in the prevention and treatment of diabetes and its cardiovascular complications.

Efficacy and safety of vitamin supplements with resveratrol in diabetic macular edema: Long-term results of a comparative study

PURPOSE

To investigate the adjunct efficacy and safety of vitamin supplements, including resveratrol, in patients with diabetic macular edema (DME) treated with intravitreal anti-vascular endothelial factor (anti-VEGF) agents.

METHODS

Participants in this prospective study were 45 patients with DME, who were treated with either intravitreal anti-VEGF injections (n = 23, Group I) or with combination of intravitreal anti-VEGF injections and vitamin supplements, including resveratrol (n = 22, Group II). All patients underwent visual acuity measurement, slit-lamp examination and spectral domain-optical coherence tomography (SD-OCT) at baseline and monthly after the loading phase of three-monthly anti-VEGF injections, following a PRN protocol.

RESULTS

There was a statistically significant improvement in visual acuity in both groups at month 12 compared to baseline, although the mean change in visual acuity did not differ between the two groups (p = 0.183). Accordingly, there was a statistically significant decrease in central retinal thickness in both groups at month 12 compared to baseline, while the mean difference in central retinal thickness was significantly greater in the "combination" group. The mean number of intravitreal anti-VEGF injection was less in Group II (6.45 ± 1.12 in Group II vs. 7.39 ± 1.31 in Group I, p = 0.018).

CONCLUSIONS

Vitamin supplements with resveratrol was found to be an effective adjunct to intravitreal anti-VEGF injections in patients with DME, offering better anatomic restoration with less injections at the 12-month follow-up.

ε-Viniferin, a promising natural oligostilbene, ameliorates hyperglycemia and hyperlipidemia by activating AMPK in vivo

ε-Viniferin (VNF), a naturally occurring oligostilbene (a resveratrol dimer), is mainly found in grapes and red wines. However, unlike resveratrol, the biological activity of VNF has not been widely studied. This study was conducted to investigate the beneficial effects of VNF on hyperglycemia and hyperlipidemia and further to reveal the underlying mechanism. The ameliorative effects of VNF in high-fat-diet and streptozotocin-induced type 2 diabetic rats were assessed physiologically, biochemically and histologically after oral administration of VNF (30 mg kg-1 and 60 mg kg-1) for 8 weeks. Western blotting and immunohistochemistry experiments were performed to determine the effects of VNF on the AMPK phosphorylation levels in the livers of diabetic rats. Molecular docking and molecular dynamics simulation were further performed to study the molecular-level interaction between VNF and AMPK. Meanwhile, the protective effects of VNF on the liver and kidney were also evaluated. The results showed that the VNF treatment caused a significant decrease in the concentrations of fasting blood glucose (FBG), total cholesterol (TC), triglyceride (TG), and low density lipoprotein-cholesterol (LDL-C), and improved the glucose tolerance of diabetic rats. In addition, the liver and kidney damage indices such as alanine aminotransferase (ALT), aspartate aminotransaminase (AST), creatinine (CR), and blood urea nitrogen (BUN) were also lowered and improved. Moreover, VNF could increase the AMPK activation and attenuate histopathological changes in the liver of diabetic rats. The molecular docking and molecular dynamics simulation results revealed for the first time that VNF bound to the hinge region between the α- and β-units of AMPK and interacted with the active site of AMPK. In conclusion, VNF can effectively improve hyperglycemia and hyperlipidemia and exhibit protective effects on the liver and kidney functions. The underlying mechanism of VNF in hyperglycemia and hyperlipidemia may be related to the activation of AMPK in vivo. Our findings indicate that VNF is a potentially useful natural agent for the treatment of metabolic diseases, especially type 2 diabetes and hyperlipidemia.

Unravelling the involvement of gut microbiota in type 2 diabetes mellitus

Type 2 diabetes mellitus is the most prevalent metabolic disorder characterized by hyperglycemia, hyperlipidemia as well as insulin resistance and is affecting the lives of a huge population across the globe. Genetic mutations, obesity and lack of physical activity constitute the possible factors that can lead to onset and progression of this disorder. However, there is another major factor that can be the root cause of type 2 diabetes mellitus and that is an imbalance in the microorganisms that inhabit the gut. The gut microbiome is a vital component that needs to be given significant attention because any "dysbiosis" in the colonic microorganisms can transform the host from a state of health to a state of disease. This transformation is quite obvious since the gut barrier integrity, host metabolism such as sensitivity to insulin and maintaining blood glucose level are carried out by the tiny organisms inhabiting our intestine. In fact, the normal functioning of the human body is accredited to the microbes, particularly the bacteria, because they generate their metabolites that communicate with host cells and maintain normal physiology. Giving importance to gut health is, therefore, necessary to prevent metabolic diseases that can be maintained by the intake of prebiotics, probiotics, synbiotics along with healthy diet. The tiny microorganisms in the gut that keep our body free of disorders such as type 2 diabetes mellitus need to be in a state of 'eubiosis', else the consequences of disturbance in gut microbes can progress to serious complications in the host.

In Silico Identification of Type III PKS Chalcone and Stilbene Synthase Homologs in Marine Photosynthetic Organisms

Marine microalgae are photosynthetic microorganisms at the base of the marine food webs. They are characterized by huge taxonomic and metabolic diversity and several species have been shown to have bioactivities useful for the treatment of human pathologies. However, the compounds and the metabolic pathways responsible for bioactive compound synthesis are often still unknown. In this study, we aimed at analysing the microalgal transcriptomes available in the Marine Microbial Eukaryotic Transcriptome Sequencing Project (MMETSP) database for an in silico search of polyketide synthase type III homologs and, in particular, chalcone synthase (CHS) and stilbene synthase (STS), which are often referred to as the CHS/STS family. These enzymes were selected because they are known to produce compounds with biological properties useful for human health, such as cancer chemopreventive, anti-inflammatory, antioxidant, anti-angiogenic, anti-viral and anti-diabetic. In addition, we also searched for 4-Coumarate: CoA ligase, an upstream enzyme in the synthesis of chalcones and stilbenes. This study reports for the first time the occurrence of these enzymes in specific microalgal taxa, confirming the importance for microalgae of these pathways and giving new insights into microalgal physiology and possible biotechnological applications for the production of bioactive compounds.

Natural Products Derived from the Mediterranean Diet with Antidiabetic Activity: from Insulin Mimetic Hypoglycemic to Nutriepigenetic Modulator Compounds

BACKGROUND

The Mediterranean diet is a healthy eating pattern that protects against the development of Type 2 diabetes mellitus (T2DM), a metabolic disease characterized by elevated blood sugar levels due to pancreatic beta-cell functional impairment and insulin resistance in various tissues. Inspired by the ancient communities, this diet emphasizes eating primarily plant-based foods, including vegetables, legumes, fruits, cereals, and nuts. Importantly, virgin olive oil is used as the principal source of fat. Red meat is consumed in low amounts while wine and fish are consumed moderately.

OBJECTIVE

Here, we review the most beneficial components of the Mediterranean Diet and tentative mechanisms of action for prevention and/or management of T2DM, based on research conducted within the last decade.

METHODS

The references over the last five years have been reviewed and they have been selected properly according to inclusion/ exclusion criteria.

RESULTS

Several bioactive diet components were evaluated to prevent inflammation and cytokine-induced oxidative damage, reduce glucose concentration, carbohydrate absorption and increase insulin sensitivity and related gene expression.

CONCLUSION

The adherence to a healthy lifestyle, including diet, exercise and habits remains the best approach for the prevention of diabetes as well as frequent check-ups and education. Though diabetes has a strong genetic component, in recent years many reports strongly point to the critical role of lifestyle specific epigenetic modifications in the development of T2DM. It remains to be established how different components of the Mediterranean Diet interact and influence the epigenetic landscape to prevent or treat the disease.

From role of gut microbiota to microbial-based therapies in type 2-diabetes

The incidence of type 2 diabetes mellitus (T2DM) has increased dramatically at an alarming level around the world.T2DM is associated with changeable risk factors in lifestyle as well as genetic and family associated risk factors. More importantly, imbalanced or impaired gut microbial distribution (dysbiosis) has been reported as a contributing risk factor in insulin resistance progression in T2DM. Dysbiosis may restructure the metabolic and functional pathways in the intestine which are involved in the development of T2DM. However, several studies have indicated the constructive and helpful effect of prebiotics, probiotics, and fecal microbiota transplantation (FMT) on the improvement of gut microbiota (GM) and accordingly host metabolism. In this review, the association between GM and T2DM have been evaluated and the role of prebiotics, probiotics and FMT, as potential therapeutic approaches have been discussed. Relevant studies were obtained randomly from online databases such as PubMed/Medline and ISI Web of Science.

A review on the potential of Resveratrol in prevention and therapy of diabetes and diabetic complications

Diabetes mellitus (DM) is a major world health problem and one of the most studied diseases, which are highly prevalent in the whole world, it is frequently associated with severe clinical complications, such as diabetic cardiomyopathy, nephropathy, retinopathy, neuropathy etc. Scientific research is continuously casting about for new monomer molecules from Chinese herbal medicine that could be invoked as candidate drugs for fighting against diabetes and its complications. Resveratrol (RES), a polyphenol phytoalexin, possesses diverse biochemical and physiological actions, including antiplatelet, estrogenic, and anti-inflammatory properties. It is recently gaining scientific interest for RES in controlling blood sugar and fighting against diabetes and its complications properties in various types of diabetic models. These beneficial effects seem to be due to the multiple actions of RES on cellular functions, which make RES become a promising molecule for the treatment of diabetes and diabetic complications. Here, we review the mechanism of action and potential therapeutic use of RES in prevention and mitigation of these diseases in recent ten years to provide a reference for further research and development of RES.

Ramadan diurnal intermittent fasting modulates SOD2, TFAM, Nrf2, and sirtuins (SIRT1, SIRT3) gene expressions in subjects with overweight and obesity

AIM

A growing body of evidence supports the impact of intermittent fasting on normalizing body metabolism and lowering oxidative stress and inflammation. Mounting evidence confirms that oxidative stress and chronic inflammation trigger the way for the development of metabolic diseases, such as diabetes. This research was conducted to evaluate the impact of Ramadan intermittent fasting (RIF) on the expression of cellular metabolism (SIRT1 and SIRT3) and antioxidant genes (TFAM, SOD2, and Nrf2).

METHODS

Fifty-six (34 males and 22 females) overweight and obese subjects and six healthy body weight controls were recruited and monitored before and after Ramadan.

RESULTS

Results showed that the relative gene expressions in obese subjects in comparison to counterpart expressions of controls for the antioxidant genes (TFAM, SOD2, and Nrf2) were significantly increased at the end of Ramadan, with percent increments of 90.5%, 54.1% and 411.5% for the three genes, respectively. However, the metabolism-controlling gene (SIRT3) showed a highly significant (P < 0.001) downregulation accompanied with a trend for reduction in SIRT1 gene at the end of Ramadan month, with percent decrements of 61.8% and 10.4%, respectively. Binary regression analysis revealed significant positive correlation (P < 0.05) between high energy intake (>2000 Kcal/day vs. <2000 Kcal/day) and expressions of SOD2 and TFAM (r = 0.84 and r = 0.9, respectively).

CONCLUSION

Results suggest that RIF ameliorates the genetic expression of antioxidant and anti-inflammatory, and metabolic regulatory genes. Thus, RIF presumably may entail a protective impact against oxidative stress and its adverse metabolic-related derangements in non-diabetic obese patients.

Inositol and antioxidant supplementation: Safety and efficacy in pregnancy

Pregnancies complicated by diabetes have largely increased in number over the last 50 years. Pregnancy is characterized by a physiologic increase in insulin resistance, which, associated with increased oxidative stress and inflammations, could induce alterations of glucose metabolism and diabetes. If not optimally controlled, these conditions have a negative impact on maternal and foetal outcomes. To date, one can resort only to diet and lifestyle to treat obesity and insulin resistance during pregnancy, and insulin remains the only therapeutic option to manage diabetes during pregnancy. However, in the last years, in a variety of experimental models, inositol and antioxidants supplementation have shown insulin-sensitizing, anti-inflammatory, and antioxidant properties, which could be mediated by some possible complementary mechanism of action. Different isomers and multiple combinations of these compounds are presently available: Aim of the present review article is to examine the existing evidence in order to clarify and/or define the effects of different inositol- and antioxidant-based supplements during pregnancy complicated by insulin resistance and/or by diabetes. This could help the clinician's evaluation and choice of the appropriate supplementation regimen.

Effects of Resveratrol on FOXO1 and FOXO3a Genes Expression in Adipose Tissue, Serum Insulin, Insulin Resistance and Serum SOD Activity in Type 2 Diabetic Rats

Induced oxidative stress in diabetes mellitus (DM) plays a critical role in insulin resistance. Fork head-related transcription factor (FOXO) proteins are important transcriptional factors involved in oxidative stress and insulin resistance. Resveratrol (RSV) is a polyphenol with hypoglycemic and antioxidant properties. The aims of the present study were to examine the effects of RSV on FOXO gene expression, serum superoxide dismutase (SOD) activity, insulin level, and insulin resistance in type 2 diabetic (T2DM) rats. Thirty male Wistar rats were used in this study. DM was induced in rats (n=24) using streptozotocin (STZ) and nicotinamide; then, they were divided into 4 groups of 6 rats each. Six untreated normal rats were used as normal control group; diabetic rats in groups 2 to 5 were treated with 0, 1, 5 and 10 mg /kg body weight of RSV, respectively for 30 days. At the end of the experimental period, the rats were sacrificed, their sera were separated, and adipose tissues were obtained and stored at −80 °C. Serum glucose and SOD activity levels were determined biochemically, and serum insulin level was determined by ELISA method. Gere expression in FOXO1 and FOXO3a in adipose tissue was evaluated using real‐time PCR. Results indicated that RSV significantly reduced blood glucose level, increased insulin level and improved insulin sensitivity. RSV resulted in an increased serum SOD activity and caused decreased FOXO1 and FOXO3a expression in adipose tissue of rats with T2DM. Therefore, by attenuation of FOXO expression in adipose tissue of T2DM rats, RSV showed a hypoglycemic potential and antioxidant properties, and consequently ameliorated insulin resistance.

Mitochondria, the NLRP3 Inflammasome, and Sirtuins in Type 2 Diabetes: New Therapeutic Targets

SIGNIFICANCE

Type 2 diabetes mellitus and hyperglycemia can lead to the development of comorbidities such as atherosclerosis and microvascular/macrovascular complications. Both type 2 diabetes and its complications are related to mitochondrial dysfunction and oxidative stress. Type 2 diabetes is also a chronic inflammatory condition that leads to inflammasome activation and the release of proinflammatory mediators, including interleukins (ILs) IL-1β and IL-18. Moreover, sirtuins are energetic sensors that respond to metabolic load, which highlights their relevance in metabolic diseases, such as type 2 diabetes. Recent Advances: Over the past decade, great progress has been made in clarifying the signaling events regulated by mitochondria, inflammasomes, and sirtuins. Nod-like receptor family pyrin domain containing 3 (NLRP3) is the best characterized inflammasome, and the generation of oxidant species seems to be critical for its activation. NLRP3 inflammasome activation and altered sirtuin levels have been observed in type 2 diabetes. Critical Issue: Despite increasing evidence of the relationship between the NLRP3 inflammasome, mitochondrial dysfunction, and oxidative stress and of their participation in type 2 diabetes physiopathology, therapeutic strategies to combat type 2 diabetes that target NLRP3 inflammasome and sirtuins are yet to be consolidated.

FUTURE DIRECTIONS

In this review article, we attempt to provide an overview of the existing literature concerning the crosstalk between mitochondrial impairment and the inflammasome, with particular attention to cellular and mitochondrial redox metabolism and the potential role of the NLRP3 inflammasome and sirtuins in the pathogenesis of type 2 diabetes. In addition, we discuss potential targets for therapeutic intervention based on these molecular interactions. Antioxid. Redox Signal. 29, 749-791.

Antiangiogenic cytokines as potential new therapeutic targets for resveratrol in diabetic retinopathy

Diabetes mellitus (DM) affects >350 million people worldwide. With many complications that can reduce the patient’s quality of life, vision loss is one of the most debilitating disorders it can cause. Active research in the field of diabetes includes microvascular complications in diabetic retinopathy (DR). Disturbances in the balance of pro-angiogenesis and anti-angiogenesis factors can lead to the progression of DR. The retinal pigment epithelium (RPE) is the outermost layer of the retina, and it is essential in maintaining the visual function. The RPE produces and secretes growth factors as well as protective agents which maintain structural integrity of the retina. Small natural molecules, such as resveratrol, may influence neurotrophic factors of the retina. The pigment epithelium-derived factor (PEDF) and thrombospondin-1 (TSP-1) are secreted by RPE cells. These two proteins inhibit angiogenesis and inflammation in RPE cells. An alteration of their production contributes to various eye diseases. There is a critical balance between two important factors secreted on opposite sides of the RPE: at the basal side, vascular endothelial growth factor (VEGF; acts on the choroidal endothelium) and, on the apical side, PEDF (acts on neurons and photoreceptors). Resveratrol inhibits VEGF expression in human adult RPE cells and limits the development of proliferative vitreoretinopathy, by attenuating transforming growth factor-β2-induced wound closure and cell migration. Possible new mechanisms could include PEDF and TSP-1 expression alterations under physiological and pathological conditions. Resveratrol is currently of interest due to its capacity to influence the cell’s secretory activity. Some limitations arise from its low bioavailability. Several drug delivery systems are currently tested, promising to improve tissue concentrations. This article reviews biological pathways involved in the pathogenesis of DR that could be influenced by resveratrol. A study of these pathways could identify new potential targets for the reduction of diabetic complications.

Antidiabetic properties of Capparis spinosa L. and its components

An increasing line of evidence confirmed that apart from conventional hypoglycemic drugs, diet and medicinal plants have beneficial effects on diabetes. Capparis spinosa L. (Caper) is a perennial shrub in the Capparidaceae family. It grows in different regions of the world, particularly in Asian and African countries. A wide range of biological activities such as antioxidant, anti-inflammatory, anticancer, antimicrobial, and antidiabetic effects have been reported for this plant. In this review, it is focused on beneficial effects of C. spinosa on diabetes. Several studies have showed the antihyperglycemic and hypolipidemic activities of C. spinosa. The putative mechanisms involved in the antihyperglycemic effects of C. spinosa include reducing carbohydrate absorption from the small intestine, inhibiting gluconeogenesis in the liver, enhancing glucose uptake by tissues, and beta cell protection/regeneration. This plant also ameliorates cardiovascular disorders, liver damage, and nephropathy in animal models of diabetes, which are attributed to its antioxidant phytochemicals such as phenolic compounds, flavonoids, carotenoids, tocopherols, and terpenes. Antihyperglycemic and hypolipidemic activities of C. spinose, along with its beneficial effects on diabetic complications, make it a good candidate for the management of diabetes. Well-designed clinical trials are necessary to define the advantages and disadvantages of C. spinose for diabetic patients.

Resveratrol Attenuates Copper and Zinc Homeostasis and Ameliorates Oxidative Stress in Type 2 Diabetic Rats

Diabetes is a common metabolic disorder characterized by elevated blood glucose level. Trace element homeostasis causes disturbances in diabetes due to hyperglycemia. Superoxide dismutase (SOD), an antioxidant enzyme, contains zinc and copper ions as its cofactors. Defects in SOD level and activity have been observed in diabetes. Resveratrol (RSV) has displayed hypoglycemic effects and is proven to improve oxidative stress. The aim of the present study was to examine the possible effects of RSV on blood glucose level, serum copper and zinc levels, SOD, and a number of other oxidative markers in type 2 diabetic rats. Diabetes was induced in male Wistar rats with administration of streptozotocin and nicotine amide. The studied groups containing six animals per group were as follows: group 1 normal control group; group 2 diabetic control group; groups 3, 4, and 5 diabetic rats that received 1, 5, and 10 mg/kg body weight of RSV, respectively for 30 days. Serum glucose, copper, zinc, SOD activity, total oxidant status (TOS) as well as thiol groups were all measured. Blood glucose in RSV treated groups significantly decreased. Similarly, copper significantly decreased in diabetic groups treated with RSV. Treatment with 10 mg/kg RSV resulted in significantly increased serum zinc. Furthermore, Cu/Zn ratio was observed to decrease in treated groups compared with untreated diabetic control group. RSV treated groups revealed an increased level of SOD activity as well as improved oxidative status. In summary, the results showed that RSV has potential hypoglycemic effect, attenuates trace element homeostasis, and consequently increases SOD activity level.

Pterostilbene, a dimethylated analog of resveratrol, promotes energy metabolism in obese rats

Pterostilbene (trans-3,5-dimethoxy-4-hydroxystilbene) is a dimethylated analog of resveratrol and has been reported to exert various pharmacological effects. In this study, we evaluated the effect of pterostilbene on the pathogenesis of obesity and energy metabolism in obese rats. Pterostilbene significantly activates silent mating type information regulation 2 homolog-1 and peroxisome proliferator-activated receptor-alpha in vitro. At 4 weeks a 0.5% pterostilbene diet markedly suppressed the abdominal white adipose tissue (WAT) accumulation in obese rats. The oxygen consumption and energy expenditure were significantly higher in the pterostilbene group, and pterostilbene increased the fat metabolism rather than the carbohydrate metabolism in obese rats. The mRNA level of uncoupling protein, a thermogenic regulator, was increased and the mRNA levels of fatty acid synthase and leptin, which are involved in lipogenesis and fat storage, were markedly decreased in WAT after the pterostilbene feeding. These results suggest that pterostilbene prevents WAT accumulation through the enhancement of energy metabolism and partly the suppression of lipogenesis in obese OLETF rats.

The Current State of NAD+ -Dependent Histone Deacetylases (Sirtuins) as Novel Therapeutic Targets

Sirtuins are NAD⁺ -dependent protein deacylases that cleave off acetyl, as well as other acyl groups, from the ε-amino group of lysines in histones and other substrate proteins. Seven sirtuin isotypes (Sirt1-7) have been identified in mammalian cells. As sirtuins are involved in the regulation of various physiological processes such as cell survival, cell cycle progression, apoptosis, DNA repair, cell metabolism, and caloric restriction, a dysregulation of their enzymatic activity has been associated with the pathogenesis of neoplastic, metabolic, infectious, and neurodegenerative diseases. Thus, sirtuins are promising targets for pharmaceutical intervention. Growing interest in a modulation of sirtuin activity has prompted the discovery of several small molecules, able to inhibit or activate certain sirtuin isotypes. Herein, we give an update to our previous review on the topic in this journal (Schemies, 2010), focusing on recent developments in sirtuin biology, sirtuin modulators, and their potential as novel therapeutic agents.

The effect of lead exposure on expression of SIRT1 in the rat hippocampus

Based on how the silent information regulator 2 homolog 1 (SIRT1) regulates the cyclic AMP response element binding protein (CREB), which is the molecular switch of long-term memory that maintains cognitive function, it is postulated that the impact of lead (Pb) on SIRT1 is one of the mechanisms leading to Pb-induced cognitive and learning deficits. Hence, the purpose of this study was to investigate the effect of Pb exposure on the expression of SIRT1, and the reversion effect of resveratrol, which is an activator of SIRT1. We examined the effects of maternal rat ingestion of Pb in drinking water during gestation and lactation on the expression of SIRT1 and CREB in the hippocampus of their offspring at postnatal week 3 (PNW3) and 52 (PNW52), and then reexamined these effects in offspring after intragastric administration of resveratrol for 4 weeks. Pb exposure decreased SIRT1 and CREB phosphorylation in a dose-dependent manner in the rat hippocampus at both PNW3 and 52, and resveratrol reversed those losses. These results indicated that SIRT1 might be a novel target to prevent Pb neurotoxicity.

Assessing Colonic Exposure, Safety, and Clinical Activity of SRT2104, a Novel Oral SIRT1 Activator, in Patients with Mild to Moderate Ulcerative Colitis

BACKGROUND

Sirtuins are a class of proteins with important physiologic roles in metabolism and inflammation. Sirtuin (silent mating type information regulation 2 homolog) 1, or SIRT1, activation is an unexplored therapeutic approach for the treatment of ulcerative colitis (UC).

METHODS

Patients with mild to moderately active UC were blindly randomized to 50 mg or 500 mg daily of SRT2104, a selective activator of SIRT1, for 8 weeks. Colonic exposure and safety were assessed, as well as blinded endoscopic scoring and disease activity by Mayo score, Simple Clinical Colitis Activity Index and fecal calprotectin.

RESULTS

Across both SRT2104 groups, only 3 of 26 evaluable subjects achieved remission on blinded endoscopic assessment. Clinical remission (Mayo score ≤2, no subscore >1) was achieved in 4 patients (2 of 13 evaluable patients in each dose group). Fecal calprotectin levels declined with treatment in both groups, but after 56 days of treatment subjects were still found to have levels approximately 4-fold elevated above normal. One subject experienced an SAE requiring study withdrawal and another was withdrawn for a severe UC flare; 19 subjects (61%) across both treatment groups experienced at least 1 treatment emergent adverse event. Average drug exposure increased in a dose-dependent manner for escalating doses of SRT2104, and colonic exposure was 140 to 160 times higher than plasma exposures.

CONCLUSIONS

SRT2104 did not demonstrate significant clinical activity in mild to moderately active UC. This suggests that further evaluation of SRT2104 as a therapeutic strategy for the treatment of UC is not warranted.

Sirtuins Link Inflammation and Metabolism

Sirtuins (SIRT), first discovered in yeast as NAD+ dependent epigenetic and metabolic regulators, have comparable activities in human physiology and disease. Mounting evidence supports that the seven-member mammalian sirtuin family (SIRT1–7) guard homeostasis by sensing bioenergy needs and responding by making alterations in the cell nutrients. Sirtuins play a critical role in restoring homeostasis during stress responses. Inflammation is designed to “defend and mend” against the invading organisms. Emerging evidence supports that metabolism and bioenergy reprogramming direct the sequential course of inflammation; failure of homeostasis retrieval results in many chronic and acute inflammatory diseases. Anabolic glycolysis quickly induced (compared to oxidative phosphorylation) for ROS and ATP generation is needed for immune activation to “defend” against invading microorganisms. Lipolysis/fatty acid oxidation, essential for cellular protection/hibernation and cell survival in order to “mend,” leads to immune repression. Acute/chronic inflammations are linked to altered glycolysis and fatty acid oxidation, at least in part, by NAD+ dependent function of sirtuins. Therapeutically targeting sirtuins may provide a new class of inflammation and immune regulators. This review discusses how sirtuins integrate metabolism, bioenergetics, and immunity during inflammation and how sirtuin-directed treatment improves outcome in chronic inflammatory diseases and in the extreme stress response of sepsis.

Comparison of antidiabetic potential of (+) and (−)-hopeaphenol, a pair of enantiomers isolated from Ampelocissus indica (L.) and Vateria indica Linn., with respect to inhibition of digestive enzymes and induction of glucose uptake in L6 myotubes

The remarkable α-glucosidase inhibition exhibited by the acetone extract of the rhizome of Ampelocissus indica (L.) and stem bark of Vateria indica Linn. (IC₅₀ 23.2 and 1.47 μg mL⁻¹) encouraged us to isolate the phytochemicals from these plants.

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.

Anti-inflammatory properties of resveratrol in the retinas of type 2 diabetic rats

Resveratrol (trans-3,5,4'-trihydroxystilbene) is a nutritional supplement with anti-inflammatory properties. The present study investigated the long-term anti-inflammatory property of resveratrol in the retinas of type 2 diabetic rats. Male Wistar rats were divided into four groups: normal control, diabetic control, resveratrol-treated normal rats and resveratrol-treated diabetic rats. Type 2 diabetes was induced by a single dose injection of streptozotocin (50 mg/kg; i.p.) 15 min after the administration of nicotinamide (110 mg/kg; i.p.) in 12-h fasted rats (the streptozotocin-nicotinamide type 2 diabetic model). Oral resveratrol administration (5 mg/kg per day for 4 months) significantly improved glucose tolerance, and alleviated hyperglycemia and weight loss in diabetic rats. Furthermore, resveratrol administration significantly decreased the elevated levels of nuclear factor-κB activity, and mRNA expression, tumour necrosis factor alpha level and apoptotic cells in the retinas of the diabetic rats. Furthermore, resveratrol did not significantly affect plasma insulin levels. Long-term resveratrol administration has beneficial anti-inflammatory properties in a rat model of diabetes. However, whether resveratrol exerts its effects directly or through reducing blood glucose levels requires further investigation.

Effects of resveratrol on ovarian response to controlled ovarian hyperstimulation in ob/ob mice

OBJECTIVE

To evaluate antidiabetic and anti-inflammatory effects of resveratrol on the ovarian response to controlled ovarian hyperstimulation (COH) in obesity-related infertility.

DESIGN

Experimental.

SETTING

University laboratory.

ANIMAL(S)

Sixteen female ob/ob mice and 16 female C57BL/6J mice undergoing COH.

INTERVENTION(S)

Wild-type placebo group; wild-type resveratrol group; ob/ob mice placebo group; ob/ob mice resveratrol group. Resveratrol 3.75 mg/kg daily for 20 days and undergoing COH protocol.

MAIN OUTCOME MEASURE(S)

Body and reproductive system weight, food intake, fasting blood glucose, plasma insulin and T levels, and Homeostatic Index of Insulin Resistance; interleukin-6 and tumor necrosis factor-α levels in adipose tissue by Western blot; assessment of quality and quantity of oocytes retrieved; and quantitative analysis of ovarian follicles.

RESULT(S)

Plasma insulin and T levels decreased and Homeostatic Index of Insulin Resistance improved in ob/ob mice treated with resveratrol. Interleukin-6 and tumor necrosis factor-α levels were significantly reverted back to near normalcy after resveratrol treatment in obese mice. Administration of resveratrol resulted in a significantly higher number of oocytes collected in wild-type mice. The number of primary, growing, preovulatory, and atretic follicles was found to be decreased in the group of obese mice treated with resveratrol when compared with the obese control group.

CONCLUSION(S)

Resveratrol administration could exert benefits against loss of ovarian follicles, and these actions may be mediated, at least in part, via anti-inflammatory, insulin-sensitizing, and antihyperandrogenism effects. These observations further validate the therapeutic potential of resveratrol to preserve ovarian reserve in conditions associated with obesity. Our results suggest the possible clinical use of resveratrol to enhance the ovarian response to COH in normal-weight females.

Maternal obesity, inflammation, and developmental programming

The prevalence of obesity, especially in women of child-bearing age, is a global health concern. In addition to increasing the immediate risk of gestational complications, there is accumulating evidence that maternal obesity also has long-term consequences for the offspring. The concept of developmental programming describes the process in which an environmental stimulus, including altered nutrition, during critical periods of development can program alterations in organogenesis, tissue development, and metabolism, predisposing offspring to obesity and metabolic and cardiovascular disorders in later life. Although the mechanisms underpinning programming of metabolic disorders remain poorly defined, it has become increasingly clear that low-grade inflammation is associated with obesity and its comorbidities. This review will discuss maternal metainflammation as a mediator of programming in insulin sensitive tissues in offspring. Use of nutritional anti-inflammatories in pregnancy including omega 3 fatty acids, resveratrol, curcumin, and taurine may provide beneficial intervention strategies to ameliorate maternal obesity-induced programming.

Resveratrol: review on therapeutic potential and recent advances in drug delivery

INTRODUCTION

Natural products have seen a wide range of acceptability for the prevention and treatment of diseases throughout history. Resveratrol, a member of the stilbene family, has been found to potentially exhibit anticancer, antiangiogenic, immunomodulatory and cardioprotective activities as well as being an antioxidant. This is in addition to its usefulness in the treatment of neurodegenerative disease, diabetes and cardiac ailments. Currently, various studies have revealed that resveratrol is a potential drug candidate with multi-spectrum therapeutic application.

AREAS COVERED

This review aims to describe the various studies supporting the wide range of pharmacological activities of resveratrol. In addition, it includes a section devoted to discussing the challenges associated with the drug and strategies to improve the properties of resveratrol such as solubility, stability and bioavailability.

EXPERT OPINION

Resveratrol demonstrated its ability to be a potential drug candidate for the treatment of different ailments due to its potent antioxidant properties. To improve the drug stability, increase the bioavailability and minimize side-effects of resveratrol, novel drug delivery systems have been formulated to bring this potential candidate to the first line of disease treatment.

Resveratrol ameliorates hepatic metaflammation and inhibits NLRP3 inflammasome activation

OBJECTIVE

Resveratrol (RSV) regulates NAD bioavailability and sirtuin-related metabolism, which relates to aging, metabolic syndrome and non-alcoholic fatty liver disease. The purpose of this study was to investigate the effects of resveratrol on hepatic metaflammation in a rodent model of high-fat (HF) diet-induced obesity (DIO).

MATERIALS/METHODS

DIO was induced in a subset of mice given an HF diet (45% kcal fat). After 6weeks of HF diet feeding, RSV was delivered via an osmotic pump for 4weeks. The experimental groups were as follows: 1) lean control fed with a standard diet, 2) HF diet-induced obese control, and 3) HF_RSV (8mg/kg/day). After 4weeks of each treatment, blood and liver tissues were collected and the indices of glucose control, serum and liver triglyceride (TG), sirtuin pathway, inflammation, and NOD-like receptor family, pryin domain containing 3 (NLRP3) inflammasome were analyzed.

RESULTS

Body weight and food intake were not altered by administering resveratrol. Glucose control was impaired, and serum and liver TG levels were increased by the HF diet. Hepatic inflammation was aggravated in mice fed with the HF diet, as shown by the increased levels of the pro-inflammatory markers interleukin-1 (IL-1), IL-6 and tumor necrosis factor-alpha in the liver. However, resveratrol administration significantly improved glucose control, and serum and liver TG contents. Also, resveratrol treatment reduced the levels of the pro-inflammatory markers. These improvements were accompanied by alterations in sirtuin pathway and NLRP3 inflammasome activation.

CONCLUSION

These results demonstrate that resveratrol ameliorates hepatic metaflammation, accompanied by alterations in NLRP3 inflammasome.

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.

Resveratrol protects the brain of obese mice from oxidative damage

Resveratrol (3,5,4′-trihydroxy-trans-stilbene) is a polyphenolic phytoalexin that exerts cardioprotective, neuroprotective, and antioxidant effects. Recently it has been shown that obesity is associated with an increase in cerebral oxidative stress levels, which may enhance neurodegeneration. The present study evaluates the neuroprotective action of resveratrol in brain of obese (ob/ob) mice. Resveratrol was administered orally at the dose of 25 mg kg⁻¹ body weight daily for three weeks to lean and obese mice. Resveratrol had no effect on body weight or blood glucose levels in obese mice. Lipid peroxides were significantly increased in brain of obese mice. The enzymatic antioxidants superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and nonenzymatic antioxidants tocopherol, ascorbic acid, and glutathione were decreased in obese mice brain. Administration of resveratrol decreased lipid peroxide levels and upregulated the antioxidant activities in obese mice brain. Our findings indicate a neuroprotective effect of resveratrol by preventing oxidative damage in brain tissue of obese mice.

Antihyperglycemic effects of short term resveratrol supplementation in type 2 diabetic patients

The objective of this study was to examine the effectiveness of resveratrol in lowering blood glucose in the presence of standard antidiabetic treatment in patients with type 2 diabetes, in a randomized placebo-controlled double-blinded parallel clinical trial. A total of 66 subjects with type 2 diabetes were enrolled in this study and randomly assigned to intervention group which was supplemented with resveratrol at a dose 1 g/day for 45 days and control group which received placebo tablets. Body weight, blood pressure, fasting blood glucose, haemoglobin A1c, insulin, homeostatic assessments for insulin resistance, triglycerides, total cholesterol, low density lipoprotein, high density lipoprotein, and markers of liver and kidney damage were measured at baseline and after 45 days of resveratrol or placebo supplementation. Resveratrol treatment significantly decreased systolic blood pressure, fasting blood glucose, haemoglobin A1c, insulin, and insulin resistance, while HDL was significantly increased, when compared to their baseline levels. On the other hand, the placebo group had slightly increased fasting glucose and LDL when compared to their baseline levels. Liver and kidney function markers were unchanged in the intervention group. Overall, this study showed that resveratrol supplementation exerted strong antidiabetic effects in patients with type 2 diabetes.

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.

Probing antioxidant activity of 2'-hydroxychalcones: crystal and molecular structures, in vitro antiproliferative studies and in vivo effects on glucose regulation

In order to better understand the antioxidant behavior of a series of polyphenolic 2'-hydroxychalcones, we describe the results of several chemical and biological studies, in vitro and in vivo. Single crystal X-ray methods elucidated their molecular structures and important intermolecular interactions such as H-bonding and molecular stacking in the crystal structures that contribute to our knowledge in explaining antioxidant activity. The results of experiments using the 1,1-diphenyl-2-dipicrylhydrazyl (DPPH) UV-vis spectroscopic method indicate that a hydroxyl group in position 5' induces the highest antioxidant activity. Consequently, 2,2',5'-trihydroxychalcone was selected for further study in vitro towards ROS scavenging in L-6 myoblasts and THP-1 human monocytes, where it shows an excellent antioxidant activity in a concentration range lower than that reported by most studies of related molecules. In addition, this chalcone shows a very selective activity: it inhibits the proliferation of leukemic cells, but it does not affect the normal L-6 myoblasts and human fibroblasts. In studying 2,2',5'-trihydroxychalcone's effect on weight gain and serum glucose and insulin levels in Zucker fatty (fa(-)/fa(-)) rats we found that supplementing the diet with a 10 mg/kg dose of this chalcone (3 times weekly) blunted the increase in glucose that co-occurs with weight gain over the 6-week treatment period. It is concluded that 2,2',5'-trihydroxychalcone has the potential to serve as a protective agent for some debilitating diseases.

Diabetic complications in pregnancy: is resveratrol a solution?

Diabetes is a metabolic disorder that, during pregnancy, may affect fetal development. Fetal outcome depends on the type of diabetes present, the concentration of blood glucose and the extent of fetal exposure to elevated or frequently fluctuating glucose concentrations. The result of some diabetic pregnancies will be embryonic developmental abnormalities, a condition referred to as diabetic embryopathy. Tight glycemic control in type 1 diabetes during pregnancy using insulin therapy together with folic acid supplementation are partially able to prevent diabetic embryopathy; however, the protection is not complete and additional interventions are needed. Resveratrol, a polyphenol found largely in the skins of red grapes, is known to have antidiabetic action and is in clinical trials for the treatment of diabetes, insulin resistance, obesity and metabolic syndrome. Studies of resveratrol in a rodent model of diabetic embryopathy reveal that it significantly improves the embryonic outcome in terms of diminishing developmental abnormalities. Improvements in maternal and embryonic outcomes observed in rodent models may arise from resveratrol's antioxidative potential, antidiabetic action and antidyslipidemic nature. Whether resveratrol will have similar actions in human diabetic pregnancy is unknown. Here, we review the potential therapeutic use of resveratrol in diabetes and diabetic pregnancy.

Diabetic complications in pregnancy: is resveratrol a solution?

Diabetes is a metabolic disorder that, during pregnancy, may affect fetal development. Fetal outcome depends on the type of diabetes present, the concentration of blood glucose and the extent of fetal exposure to elevated or frequently fluctuating glucose concentrations. The result of some diabetic pregnancies will be embryonic developmental abnormalities, a condition referred to as diabetic embryopathy. Tight glycemic control in type 1 diabetes during pregnancy using insulin therapy together with folic acid supplementation are partially able to prevent diabetic embryopathy; however, the protection is not complete and additional interventions are needed. Resveratrol, a polyphenol found largely in the skins of red grapes, is known to have antidiabetic action and is in clinical trials for the treatment of diabetes, insulin resistance, obesity and metabolic syndrome. Studies of resveratrol in a rodent model of diabetic embryopathy reveal that it significantly improves the embryonic outcome in terms of diminishing developmental abnormalities. Improvements in maternal and embryonic outcomes observed in rodent models may arise from resveratrol's antioxidative potential, antidiabetic action and antidyslipidemic nature. Whether resveratrol will have similar actions in human diabetic pregnancy is unknown. Here, we review the potential therapeutic use of resveratrol in diabetes and diabetic pregnancy.

The cytotoxic effects of Scilla nervosa (Burch.) Jessop (Hyacinthaceae) aqueous extract on cultured HepG2 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Bulbs of Scilla nervosa, a medicinal plant indigenous to Southern Africa, are traditionally used in aqueous decoctions to treat a diverse range of illnesses. The bulbs contain homoisoflavanones and stilbenoids. Little information is known about the plant's toxicity on the liver, a major detoxifying organ. This study investigated the effects of an aqueous extract of the bulbs in cultured HepG2 liver cells, a model system for investigating the toxicity of xenobiotics.

MATERIALS AND METHODS

The concentration that reduced cell viability to 50% (IC(50)) after 24h treatment was derived. Potential mechanisms of toxicity using the IC(50) were investigated as changes in metabolic activity, apoptosis, oxidative damage and DNA fragmentation. In addition, cytochrome P450 3A4 (CYP3A4) activity, which is implicated in drug metabolism and interactions, was also assayed.

RESULTS

Cell viability decreased in a concentration-dependent manner and the IC(50) was determined as 0.03 mg/mL. Treating the cells at the IC(50) for 24h resulted in increased intracellular ATP levels, no significant change in phosphatidylserine externalisation, increased caspase-8 activity, decreased caspase-9 activity, no significant change in mitochondrial membrane potential, increased lipid peroxidation, evidence for genotoxicity as demonstrated by DNA fragmentation, and slightly induced CYP3A4 activity.

CONCLUSION

Results suggest that liver cells are sensitive to an aqueous extract of the bulbs and there is an increased potential to induce apoptosis, oxidative stress and genotoxicity in vitro.

Chronic resveratrol treatment protects pancreatic islets against oxidative stress in db/db mice

Resveratrol (RSV) has anti-inflammatory and anti-oxidant actions which may contribute to its cardiovascular protective effects. We examined whether RSV has any beneficial effects on pancreatic islets in db/db mice, an animal model of type 2 diabetes. The db/db and db/dm mice (non-diabetic control) were treated with (db-RSV) or without RSV (db-control) (20 mg/kg daily) for 12 weeks. After performing an intraperitoneal glucose tolerance test and insulin tolerance test, mice were sacrificed, the pancreas was weighed, pancreatic β-cell mass was quantified by point count method, and the amount of islet fibrosis was determined. 8-Hydroxydeoxyguanosine (8-OHdG), an oxidative stress marker, was determined in 24 h urine and pancreatic islets. RSV treatment significantly improved glucose tolerance at 2 hrs in db/db mice (P = 0.036), but not in db/dm mice (P = 0.623). This was associated with a significant increase in both pancreas weight (P = 0.011) and β-cell mass (P = 0.016). Islet fibrosis was much less in RSV-treated mice (P = 0.048). RSV treatment also decreased urinary 8-OHdG levels (P = 0.03) and the percentage of islet nuclei that were positive for 8-OHdG immunostaining (P = 0.019). We conclude that RSV treatment improves glucose tolerance, attenuates β-cell loss, and reduces oxidative stress in type 2 diabetes. These findings suggest that RSV may have a therapeutic implication in the prevention and management of diabetes.

Attenuation of insulin resistance, metabolic syndrome and hepatic oxidative stress by resveratrol in fructose-fed rats

Metabolic syndrome and oxidative stress are common complications of type 2 diabetes mellitus. The present study was designed to determine whether resveratrol, a widely used nutritional supplement, can improve insulin sensitivity, metabolic complication as well as hepatic oxidative stress in fructose-fed rats. Male Sprague Dawley rats (180-200 g) were divided into four groups with 8 animals each. Fructose-fed insulin resistant group (Dia) animals were fed 65% fructose (Research diet, USA) for a period of 8 weeks, whereas control group (Con) animals were fed 65% cornstarch (Research Diet, USA). Resveratrol, 10 mg/kg/day (Dia+Resv) or metformin 300 mg/kg/day (Dia+Met) were administered orally to the 65% fructose-fed rats for 8 weeks. At the end of the feeding schedule, Dia group had insulin resistance along with increased blood glucose, triglyceride, uric acid and nitric oxide (NO) levels. Significant (p<0.05) increase in hepatic TBARS and conjugated dienes, and significant (p<0.05) decrease in hepatic SOD and vitamin C was observed in Dia group compared to Con group. Administration of metformin or resveratrol significantly (p<0.05) normalized all the altered metabolic parameters. However, a marked insulin sensitizing action was only observed in the Dia+Resv group. Similarly, while metformin administration failed to normalize the increased TBARS levels and decreased SOD activity, resveratrol showed a more promising effect of all oxidative stress parameters measured in the present study. Attenuation of hepatic oxidative stress in fructose-fed rat liver after resveratrol administration was associated with significant (p<0.05) increase in nuclear level of NRF2 compared with other groups. The present study demonstrates that resveratrol is more effective than metformin in improving insulin sensitivity, and attenuating metabolic syndrome and hepatic oxidative stress in fructose-fed rats.

SIRT1 as a therapeutic target in inflammaging of the pulmonary disease

OBJECTIVE

Chronic inflammation and cellular senescence are intertwined in the pathogenesis of premature aging, which is considered as an important contributing factor in driving chronic obstructive pulmonary disease (COPD). Sirtuin1 (SIRT1), a nicotinamide adenine dinucleotide (NAD(+))-dependent protein/histone deacetylase, regulates inflammation, senescence/aging, stress resistance, and deoxyribonucleic acid (DNA) damage repair via deacetylating intracellular signaling molecules and chromatin histones. The present review describes the mechanism and regulation of SIRT1 by environmental agents/oxidants/reactive aldehydes and pro-inflammatory stimuli in lung inflammation and aging. The role of dietary polyphenols in regulation of SIRT1 in inflammaging is also discussed.

METHODS

Analysis of current research findings on the mechanism of inflammation and senescence/aging (i.e., inflammaging) and their regulation by SIRT1 in premature aging of the lung.

RESULTS

COPD is a disease of the lung inflammaging, which is associated with the DNA damage response, transcription activation and chromatin modifications. SIRT1 regulates inflammaging via regulating forkhead box class O 3, p53, nuclear factor kappa B, histones and various proteins involved in DNA damage and repair. Polyphenols and its analogs have been shown to activate SIRT1 although they have anti-inflammatory and antioxidant properties.

CONCLUSIONS

Targeting lung inflammation and cellular senescence as well as premature lung aging using pharmacological SIRT1 activators or polyphenols would be a promising therapeutic intervention for COPD/emphysema.