Resveratrol modifies risk factors for coronary artery disease in swine with metabolic syndrome and myocardial ischemia

High-fidelity porcine models of metabolic syndrome: a contemporary synthesis

This review aims to describe and compare porcine models of metabolic syndrome. This syndrome and its associated secondary comorbidities are set to become the greatest challenge to healthcare providers and policy makers in the coming century. However, an incomplete understanding of the pathogenesis has left significant knowledge gaps in terms of efficacious therapeutics. To further our comprehension and, in turn, management of metabolic syndrome, appropriate high-fidelity models of the disease complex are of great importance. In this context, our review aims to assess the most promising porcine models of metabolic syndrome currently available for their similarity to the human phenotype. In addition, we aim to highlight the strengths and shortcomings of each model in an attempt to identify the most appropriate application of each. Although no porcine model perfectly recapitulates the human metabolic syndrome, several pose satisfactory approximations. The Ossabaw miniature swine in particular represents a highly translatable model that develops each of the core parameters of the syndrome with many of the associated secondary comorbidities. Future high-fidelity porcine models of metabolic syndrome need to focus on secondary sequelae replication, which may require extended induction period to reveal.

Mechanistic Basis for the Role of Phytochemicals in Inflammation-Associated Chronic Diseases

Chronic inflammatory diseases occur in a large portion of the population and are associated with a poor diet. Key natural products found in fruits and vegetables may assist in lowering inflammation associated with chronic diseases such as obesity, diabetes, cardiovascular diseases, and cancer. This review seeks to examine the roles of several natural products, resveratrol (RES), quercetin (QUE), curcumin (CUR), piperine (PIP), epigallocatechin gallate (EGCG), and gingerol (GIN), in their ability to attenuate inflammatory markers in specific diseases states. Additionally, we will discuss findings in past and ongoing clinical trials, detail possible phytochemical–drug interactions, and provide a brief resource for researchers and healthcare professionals on natural product and supplement regulation as well as names of databases with information on efficacy, indications, and natural product–drug interactions. As diet and over-the-counter supplement use are modifiable factors and patients are interested in using complementary and alternative therapies, understanding the mechanisms by which natural products have demonstrated efficacy and the types of drugs they interact with and knowing where to find information on herbs and supplements is important for practicing healthcare providers and researchers interested in this field.

Peroxisome Proliferator-Activated Receptor-Gamma (PPAR-ɣ): Molecular Effects and Its Importance as a Novel Therapeutic Target for Cerebral Ischemic Injury

Cerebral ischemic injury is a leading cause of death and long-term disability throughout the world. Peroxisome proliferator-activated receptor gamma (PPAR-ɣ) is a ligand-activated nuclear transcription factor that is a member of the PPAR family. PPAR-ɣ has been shown in several in vitro and in vivo models to prevent post-ischemic inflammation and neuronal damage by negatively controlling the expression of genes modulated by cerebral ischemic injury, indicating a neuroprotective effect during cerebral ischemic injury. A extensive literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on the mechanistic role of Peroxisome proliferator activated receptor gamma and its modulation in Cerebral ischemic injury. PPAR-ɣ can interact with specific DNA response elements to control gene transcription and expression when triggered by its ligand. It regulates lipid metabolism, improves insulin sensitivity, modulates antitumor mechanisms, reduces oxidative stress, and inhibits inflammation. This review article provides insights on the current state of research into the neuroprotective effects of PPAR-ɣ in cerebral ischemic injury, as well as the cellular and molecular mechanisms by which these effects are modulated, such as inhibition of inflammation, reduction of oxidative stress, suppression of pro-apoptotic production, modulation of transcription factors, and restoration of injured tissue through neurogenesis and angiogenesis.

Natural and synthetic antioxidants targeting cardiac oxidative stress and redox signaling in cardiometabolic diseases

Cardiometabolic diseases (CMDs) are metabolic diseases (e.g., obesity, diabetes, atherosclerosis, rare genetic metabolic diseases, etc.) associated with cardiac pathologies. Pathophysiology of most CMDs involves increased production of reactive oxygen species and impaired antioxidant defense systems, resulting in cardiac oxidative stress (OxS). To alleviate OxS, various antioxidants have been investigated in several diseases with conflicting results. Here we review the effect of CMDs on cardiac redox homeostasis, the role of OxS in cardiac pathologies, as well as experimental and clinical data on the therapeutic potential of natural antioxidants (including resveratrol, quercetin, curcumin, vitamins A, C, and E, coenzyme Q10, etc.), synthetic antioxidants (including N-acetylcysteine, SOD mimetics, mitoTEMPO, SkQ1, etc.), and promoters of antioxidant enzymes in CMDs. As no antioxidant indicated for the prevention and/or treatment of CMDs has reached the market despite the large number of preclinical and clinical studies, a sizeable translational gap is evident in this field. Thus, we also highlight potential underlying factors that may contribute to the failure of translation of antioxidant therapies in CMDs.

Oral resveratrol supplementation improves Metabolic Syndrome features in obese patients submitted to a lifestyle-changing program

AIMS

The aim of the present study was to evaluate the oral resveratrol effects associated with diet and physical training changes on anthropometric and biochemical parameters.

MAIN METHODS

25 individuals aged from 30 to 60 years old; with Body Mass Index (BMI) ≥ 30 kg/m² were included in the study. Following the primary evaluation (anthropometric and clinical), the patients were randomly divided into 2 groups: (1) Placebo: Physical activity program + Diet + Placebo; (2) Resveratrol: Physical activity program + Diet + Resveratrol (RVS) (250 mg/day) for three months. Anthropometric and biochemical parameters were evaluated at baseline and after the treatment period.

KEY FINDINGS

The main findings showed that the resveratrol supplementation improved total cholesterol (TC), High-density Lipoprotein cholesterol (HDL-c), Very-low density Lipoprotein cholesterol (VLDL-c), urea, creatinine and albumin serum levels.

SIGNIFICANCE

These findings indicate that this polyphenol may be an option to potentiate the beneficial effects induced by dietary and physical activity programs in the Metabolic Syndrome (MetS) treatment.

Pathobiological mechanisms underlying metabolic syndrome (MetS) in chronic obstructive pulmonary disease (COPD): clinical significance and therapeutic strategies

Chronic obstructive pulmonary disease (COPD) is a major incurable global health burden and is currently the 4th largest cause of death in the world. Importantly, much of the disease burden and health care utilisation in COPD is associated with the management of its comorbidities (e.g. skeletal muscle wasting, ischemic heart disease, cognitive dysfunction) and infective viral and bacterial acute exacerbations (AECOPD). Current pharmacological treatments for COPD are relatively ineffective and the development of effective therapies has been severely hampered by the lack of understanding of the mechanisms and mediators underlying COPD. Since comorbidities have a tremendous impact on the prognosis and severity of COPD, the 2015 American Thoracic Society/European Respiratory Society (ATS/ERS) Research Statement on COPD urgently called for studies to elucidate the pathobiological mechanisms linking COPD to its comorbidities. It is now emerging that up to 50% of COPD patients have metabolic syndrome (MetS) as a comorbidity. It is currently not clear whether metabolic syndrome is an independent co-existing condition or a direct consequence of the progressive lung pathology in COPD patients. As MetS has important clinical implications on COPD outcomes, identification of disease mechanisms linking COPD to MetS is the key to effective therapy. In this comprehensive review, we discuss the potential mechanisms linking MetS to COPD and hence plausible therapeutic strategies to treat this debilitating comorbidity of COPD.

Biomarkers of Oxidative Stress in Metabolic Syndrome and Associated Diseases

Metabolic syndrome (MS) represents worldwide public health issue characterized by a set of cardiovascular risk factors including obesity, diabetes, dyslipidemia, hypertension, and impaired glucose tolerance. The link between the MS and the associated diseases is represented by oxidative stress (OS) and by the intracellular redox imbalance, both caused by the persistence of chronic inflammatory conditions that characterize MS. The increase in oxidizing species formation in MS has been accepted as a major underlying mechanism for mitochondrial dysfunction, accumulation of protein and lipid oxidation products, and impairment of the antioxidant systems. These oxidative modifications are recognized as relevant OS biomarkers potentially able to (i) clarify the role of reactive oxygen and nitrogen species in the etiology of the MS, (ii) contribute to the diagnosis/evaluation of the disease's severity, and (iii) evaluate the utility of possible therapeutic strategies based on natural antioxidants. The antioxidant therapies indeed could be able to (i) counteract systemic as well as mitochondrial-derived OS, (ii) enhance the endogenous antioxidant defenses, (iii) alleviate MS symptoms, and (iv) prevent the complications linked to MS-derived cardiovascular diseases. The focus of this review is to summarize the current knowledge about the role of OS in the development of metabolic alterations characterizing MS, with particular regard to the occurrence of OS-correlated biomarkers, as well as to the use of therapeutic strategies based on natural antioxidants.

Elastic aortic wrap reduced aortic stiffness by partially alleviating the impairment of cholesterol efflux capacity in pigs

Purpose

Metabolic syndrome patients exhibit impaired cholesterol efflux capacity. Previous studies have shown a positive association between aortic stiffness and metabolic syndrome. However, it is unknown whether cholesterol efflux capacity participates in the process of aortic stiffness. This study sought to determine the effect of metabolic syndrome on aortic stiffening, and to investigate the effectiveness of aortic wraps on aortic compliance and the underlying mechanisms.

Methods

In a swine model of metabolic syndrome, we compared the cholesterol efflux capacity and aortic compliance responding to diet modifications and aortic wrap applications.

Results

Metabolic syndrome induced by high cholesterol diet significantly decreased cholesterol efflux capacity and aortic compliance. Elastic aortic wrap application increased aortic compliance and partially restored cholesterol efflux capacity via ATP binding cassette transporter A1 (ABCA1) pathway.

Conclusions

Cholesterol efflux plays a role in aortic stiffening. Elastic aortic wrap application could be a potential treatment for aortic stiffness related to metabolic syndrome.

The Effects of Resveratrol in the Treatment of Metabolic Syndrome

Resveratrol, also known as 3,5,4′-trihydroxystilbene, is a natural polyphenol that occurs as a phytoalexin. It is produced by plant sources such as grapes, apples, blueberries, plums, peanuts, and other oilseeds. This compound has a variety of effects on human health and diseases. This review summarizes the mounting evidence that resveratrol is helpful in treating metabolic syndrome and related disorders. Resveratrol can be provided either early as a reprogramming agent or later as part of treatment. A few of the main mechanisms underlying the beneficial effects of resveratrol on metabolic syndrome are outlined. This review also discusses the potential of resveratrol derivatives as a complementary or alternative medicine. In conclusion, resveratrol could be a useful regimen for the prevention and treatment of metabolic syndrome and its related conditions.

Cardiovascular Protective Effects and Clinical Applications of Resveratrol

Resveratrol is a naturally occurring phenol that is generated by plant species following injury or attack by bacterial and fungal pathogens. This compound was first described as the French Paradox in 1992. Later in 2003, resveratrol was reported to activate sirtuins in yeast cells. Recent experimental studies have found that resveratrol offers a variety of benefits that include both anticarcinogenic and anti-inflammatory effects in addition to the ability to reverse obesity, attenuate hyperglycemia and hyperinsulinemia, protect heart and endothelial function, and increase the life span. Multiple molecular targets are associated with the cardioprotective capabilities of resveratrol, and therefore, resveratrol has potential for a wide range of new therapeutic strategies for atherosclerosis, ischemia/reperfusion, metabolic syndrome, cardiac failure, and inflammatory alterations during aging. Expectations for application in human patients, however, suffer from a lack of sufficient clinical evidence in support of these beneficial effects. This article reviews recently reported basic research results that describe the beneficial effects of resveratrol in an attempt to condense the evidence observed in clinical trials and provide support for the future development of novel clinical therapeutics in patients with cardiovascular diseases.

Challenges in Analyzing the Biological Effects of Resveratrol

The suggested health effects (e.g., disease prevention) of dietary bioactive compounds such as resveratrol are challenging to prove in comparison to man-made drugs developed for therapeutic purposes. Dietary bioactive compounds have multiple cellular targets and therefore have a variety of biological effects. Extrapolating the biological effects of dietary compounds from in vitro and in vivo animal experiments to humans may lead to over- or under-estimation of the effect and role of these compounds. The present paper will discuss a few of these challenges and suggest directions for future research. Questions we address include: (1) Is the combinatorial effect of resveratrol and other compounds real? (2) What are the real and relevant doses of resveratrol after administration? and (3) Is it possible to estimate the preventive effect of resveratrol by clinical trials using standard experimental designs? The examples concerning resveratrol taken from the scientific literature are mainly from 2010 and later. The challenges pointed out in this review are similar to most naturally occurring bioactive compounds.

Resveratrol and Cardiovascular Diseases

The increased incidence of cardiovascular diseases (CVDs) has stimulated research for substances that could improve cardiovascular health. Among them, resveratrol (RES), a polyphenolic compound notably present in grapes and red wine, has been involved in the “French paradox”. RES is known for its antioxidant and anti-inflammatory properties and for its ability to upregulate endothelial NO synthase (eNOS). RES was able to scavenge ^•OH/O₂^•− and peroxyl radicals, which can limit the lipid peroxidation processes. Moreover, in bovine aortic endothelial cells (BAEC) under glucose-induced oxidative stress, RES restored the activity of dimethylargininedimethylaminohydrolase (DDAH), an enzyme that degrades an endogenous inhibitor of eNOS named asymmetric dimethylarginine (ADMA). Thus, RES could improve ^•NO availability and decrease the endothelial dysfunction observed in diabetes. Preclinical studies have made it possible to identify molecular targets (SIRT-1, AMPK, Nrf2, NFκB…); however, there are limited human clinical trials, and difficulties in the interpretation of results arise from the use of high-dose RES supplements in research studies, whereas low RES concentrations are present in red wine. The discussions on potential beneficial effects of RES in CVDs (atherosclerosis, hypertension, stroke, myocardial infarction, heart failure) should compare the results of preclinical studies with those of clinical trials.

Novel nutraceutic therapies for the treatment of metabolic syndrome

Nutraceutic therapies such as berberine, bitter melon, Gymnema sylvestre, Irvingia gabonensis, resveratrol and ursolic acid have been shown to help control metabolic syndrome (MetS). The effect of berberine on glucose and lipid metabolism, hypertension, obesity and MetS has been evaluated in animal models and humans. Most clinical trials involving bitter melon have been conducted to evaluate its effect on glucose metabolism; nevertheless, some studies have reported favorable effects on lipids and blood pressure although there is little information about its effect on body weight. Gymnema sylvestre helps to decrease body weight and blood sugar levels; however, there is limited information on dyslipidemia and hypertension. Clinical trials of Irvingia gabonensis have shown important effects decreasing glucose and cholesterol concentrations as well decreasing body weight. Resveratrol acts through different mechanisms to decrease blood pressure, lipids, glucose and weight, showing its effects on the population with MetS. Finally, there is evidence of positive effects with ursolic acid in in vitro and in vivo studies on glucose and lipid metabolism and on body weight and visceral fat. Therefore, a review of the beneficial effects and limitations of the above-mentioned nutraceutic therapies is presented.

Early Cellular Changes in the Ascending Aorta and Myocardium in a Swine Model of Metabolic Syndrome

Background

Metabolic syndrome is associated with pathological remodeling of the heart and adjacent vessels. The early biochemical and cellular changes underlying the vascular damage are not fully understood. In this study, we sought to establish the nature, extent, and initial timeline of cytochemical derangements underlying reduced ventriculo-arterial compliance in a swine model of metabolic syndrome.

Methods

Yorkshire swine (n = 8 per group) were fed a normal diet (ND) or a high-cholesterol (HCD) for 12 weeks. Myocardial function and blood flow was assessed before harvesting the heart. Immuno-blotting and immuno-histochemical staining were used to assess the cellular changes in the myocardium, ascending aorta and left anterior descending artery (LAD).

Results

There was significant increase in body mass index, blood glucose and mean arterial pressures (p = 0.002, p = 0.001 and p = 0.024 respectively) in HCD group. At the cellular level there was significant increase in anti-apoptotic factors p-Akt (p = 0.007 and p = 0.002) and Bcl-xL (p = 0.05 and p = 0.01) in the HCD aorta and myocardium, respectively. Pro-fibrotic markers TGF-β (p = 0.01), pSmad1/5 (p = 0.03) and MMP-9 (p = 0.005) were significantly increased in the HCD aorta. The levels of pro-apoptotic p38MAPK, Apaf-1 and cleaved Caspase3 were significantly increased in aorta of HCD (p = 0.03, p = 0.04 and p = 0.007 respectively). Similar changes in coronary arteries were not observed in either group. Functionally, the high cholesterol diet resulted in significant increase in ventricular end systolic pressure and–dp/dt (p = 0.05 and p = 0.007 respectively) in the HCD group.

Conclusion

Preclinical metabolic syndrome initiates pro-apoptosis and pro-fibrosis pathways in the heart and ascending aorta, while sparing coronary arteries at this early stage of dietary modification.

Modulation of Hypercholesterolemia-Induced Oxidative/Nitrative Stress in the Heart

Hypercholesterolemia is a frequent metabolic disorder associated with increased risk for cardiovascular morbidity and mortality. In addition to its well-known proatherogenic effect, hypercholesterolemia may exert direct effects on the myocardium resulting in contractile dysfunction, aggravated ischemia/reperfusion injury, and diminished stress adaptation. Both preclinical and clinical studies suggested that elevated oxidative and/or nitrative stress plays a key role in cardiac complications induced by hypercholesterolemia. Therefore, modulation of hypercholesterolemia-induced myocardial oxidative/nitrative stress is a feasible approach to prevent or treat deleterious cardiac consequences. In this review, we discuss the effects of various pharmaceuticals, nutraceuticals, some novel potential pharmacological approaches, and physical exercise on hypercholesterolemia-induced oxidative/nitrative stress and subsequent cardiac dysfunction as well as impaired ischemic stress adaptation of the heart in hypercholesterolemia.

Retinol binding protein 4 in relation to diet, inflammation, immunity, and cardiovascular diseases

Retinol binding protein 4 (RBP4), previously called retinol binding protein (RBP), is considered a specific carrier of retinol in the blood. It is also an adipokine that has been implicated in the pathophysiology of insulin resistance. RBP4 seems to be correlated with cardiometabolic markers in inflammatory chronic diseases, including obesity, type 2 diabetes, metabolic syndrome, and cardiovascular diseases (CVDs). It has recently been suggested that inflammation produced by RBP4 induces insulin resistance and CVD. The clinical relevance of this hypothesis is discussed in this review. Knowledge concerning the association of RBP4 with inflammation markers, oxidative stress, and CVDs as well as concerning the role of diet and antioxidants in decreasing RBP4 concentrations are discussed. Special attention is given to methodologies used in previously published studies and covariates that should be controlled when planning new studies on this adipokine.

Investigating the effects of resveratrol on chronically ischemic myocardium in a swine model of metabolic syndrome: a proteomics analysis

Resveratrol has been shown to improve cardiac perfusion and ventricular function after chronic ischemic injury. Using proteomic analysis, we sought to objectively investigate potential mechanisms, by which resveratrol exerts its cardioprotective effects in the setting of metabolic syndrome and chronic myocardial ischemia. Yorkshire swine were divided into two groups based on diet: high cholesterol (n=7) or a high-cholesterol diet with supplemental resveratrol (n=6). Four weeks later, all animals underwent surgical placement of an ameroid constrictor to their left circumflex artery. Diets were continued for another 7 weeks, and then the ischemic myocardium was harvested for proteomics analysis. Proteomic analysis identified 669 common proteins between the two groups. Of these proteins, 76 were statistically different, of which 41 were characterized (P<.05). Pathway analysis demonstrated that in animals supplemented with resveratrol, there was a downregulation in several proteins involved with mitochondrial dysfunction, cell death, and unfavorable cardiac remodeling. Furthermore, there was an upregulation in proteins involved in free radical elimination. We conclude that resveratrol supplementation significantly alters several critical protein markers in the chronically ischemic myocardium. Further investigation of these proteins may help elucidate the mechanisms by which resveratrol exerts its cardioprotective effects.

The effects of resveratrol in rats with simultaneous type 2 diabetes and renal hypertension: a study of antihypertensive mechanisms

BACKGROUND

Resveratrol has beneficial effects on cardiovascular system. This study aimed at examining antidiabetic and antihypertensive effects of resveratrol in rats with simultaneous type 2 diabetes and renal hypertension.

METHODS

Eight groups (8-10 each) of male Spargue-Dawley rats, including a control, a diabetic (induced by streptozotocin and nicotinamide), a renal hypertensive (induced by placing plexiglas clips on the left renal arteries), a sham, a simultaneously hypertensive-diabetic receiving vehicle, and 3 simultaneous hypertensive-diabetic receiving resveratrol at 5, 10 or 20 mg/kg/day were used. Four weeks after the induction of diabetes, renal hypertension was induced and animals were given vehicle or resveratrol for the next four weeks. Afterwards, blood pressure and glucose, serum markers of oxidative stress were measured and animal's aortic rings were used for isolated studies.

RESULTS

Serum malondialdehyde, systolic blood pressure, heart rate, fasting blood glucose, maximal response and effective concentration 50 of phenylephrine, and inhibitory concentration 50 of acetylcholine of hypertensive-diabetic group receiving vehicle were significantly higher than those of the control group, and treatment with resveratrol caused significant reduction of these variables. Moreover, serum superoxide dismutase, glutathione reductase, and maximal response to acetylcholine of hypertensive-diabetic group receiving vehicle were significantly lower than those of the control group, and treatment with resveratrol caused significant increase of these variables.

CONCLUSION

The findings indicate that resveratrol has antidiabetic and antihypertensive effects, which may be partly due to antioxidant mechanism. They also show that antihypertensive effect of resveratrol may be additionally mediated by improving the release of nitric oxide and sympathoplegic activities.

The pharmacology of resveratrol in animals and humans

In addition to thousands of research papers related to resveratrol (RSV), approximately 300 review articles have been published. Earlier research tended to focus on pharmacological activities of RSV related to cardiovascular systems, inflammation, and carcinogenesis/cancer development. More recently, the horizon has been broadened by exploring the potential effect of RSV on the aging process, diabetes, neurological dysfunction, etc. Herein, we primarily focus on the in vivo pharmacological effects of RSV reported over the past 5 years (2009-2014). In addition, recent clinical intervention studies performed with resveratrol are summarized. Some discrepancies exist between in vivo studies with animals and clinical studies, or between clinical studies, which are likely due to disparate doses of RSV, experimental settings, and subject variation. Nevertheless, many positive indications have been reported with mammals, so it is reasonable to advocate for the conduct of more definitive clinical studies. Since the safety profile is pristine, an added advantage is the use of RSV as a dietary supplement. This article is part of a Special Issue entitled: Resveratrol: Challenges in translating pre-clinical findings to improved patient outcomes.

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.

Synergistic effects of polyphenols and methylxanthines with Leucine on AMPK/Sirtuin-mediated metabolism in muscle cells and adipocytes

The AMPK-Sirt1 pathway is an important regulator of energy metabolism and therefore a potential target for prevention and therapy of metabolic diseases. We recently demonstrated leucine and its metabolite β-hydroxy-β-methylbutyrate (HMB) to synergize with low-dose resveratrol (200 nM) to activate sirtuin signaling and stimulate energy metabolism. Here we show that leucine exerts a direct effect on Sirt1 kinetics, reducing its Km for NAD⁺ by >50% and enabling low doses of resveratrol to further activate the enzyme (p = 0.012). To test which structure elements of resveratrol are necessary for synergy, we assessed potential synergy of structurally similar and dissimilar polyphenols as well as other compounds converging on the same pathways with leucine using fatty acid oxidation (FAO) as screening tool. Dose-response curves for FAO were constructed and the highest non-effective dose (typically 1–10 nM) was used with either leucine (0.5 mM) or HMB (5 µM) to treat adipocytes and myotubes for 24 h. Significant synergy was detected for stilbenes with FAO increase in adipocytes by 60–70% (p<0.05) and in myotubes >2000% (p<0.01). Sirt1 and AMPK activities were stimulated by ∼65% (p<0.001) and ∼50% (p<0.03), respectively. Similarly, hydroxycinnamic acids and derivatives (chlorogenic, cinnamic, and ferulic acids) combined with leucine/HMB increased FAO (300–1300%, p<0.01), AMPK activity (50–150%, p<0.01), and Sirt1 activity (∼70%, p<0.001). In contrast, more complex polyphenol structures, such as ellagic acid and epigallocatechin gallate required higher concentrations (>1 µM) and exhibited little or no synergy. Thus, the six-carbon ring structure bound to a carboxylic group seems to be a necessary element for leucine/HMB synergy with other stilbenes and hydroxycinnamic acids to stimulate AMPK/Sirt1 dependent FAO; these effects occur at concentrations that produce no independent effects and are readily achievable via oral administration.

Resveratrol regulates autophagy signaling in chronically ischemic myocardium

OBJECTIVE

Autophagy is a cellular process by which damaged components are removed. Although autophagy can result in cell death, when optimally regulated, it might be cardioprotective. Resveratrol is a naturally occurring polyphenol also believed to be cardioprotective. Using a clinically relevant swine model of metabolic syndrome, we investigated the effects of resveratrol on autophagy in the chronically ischemic myocardium.

METHODS

Yorkshire swine were fed a regular diet (n = 7), a high cholesterol diet (n = 7), or a high cholesterol diet with supplemental resveratrol (n = 6). After 4 weeks, an ameroid constrictor was surgically placed on the left circumflex artery to induce chronic myocardial ischemia. The diets were continued another 7 weeks, and then the ischemic and nonischemic myocardium were harvested for protein analysis.

RESULTS

In the ischemic myocardium, a high cholesterol diet partly attenuated the autophagy, as determined by an increase in phosphorylated mammalian target of rapamycin (p-mTOR) and a decrease in p70 S6 kinase (P70S6K), lysosome-associated membrane protein (LAMP)-2, and autophagy-related gene 12-5 conjugate (ATG 12-5; P < .05). The addition of resveratrol blunted many of these changes, because the p-mTOR, P70S6K, and LAMP-2 levels were not significantly altered from those of the pigs fed a regular diet. Other autophagy markers were increased with a high cholesterol diet, including light chain 3A-II and beclin 1 (P < .05). In the nonischemic myocardium, beclin 1 was decreased in the high cholesterol-fed pigs (P < .05); otherwise no significant changes in protein expression were noted among the 3 groups.

CONCLUSIONS

In the chronically ischemic myocardium, resveratrol partly reversed the effects of a high cholesterol diet on autophagy. This might be a mechanism by which resveratrol exerts its cardioprotective effects.

Effects of the PPAR-β/δ agonist GW0742 during resuscitated porcine septic shock

Background

In un-resuscitated rodent models of septic shock, the peroxisome proliferator-activated receptor-β/δ (PPAR-β/δ) agonist GW0742 improved visceral organ function. Therefore, we tested the hypothesis whether GW0742 would attenuate kidney injury during long-term, resuscitated, porcine polymicrobial septic shock.

Methods

Six, 12, and 18 h after the induction of fecal peritonitis by inoculation of autologous feces, anesthetized, mechanically ventilated, and instrumented male pigs with pre-existing atherosclerosis resulting from familial hypercholesteremia and atherogenic diet randomly received either vehicle (dimethyl sulfoxide, n = 12) or GW0742 (n = 10). Resuscitation comprised hydroxyethyl starch and norepinephrine infusion titrated to maintain mean arterial pressure at baseline values.

Results

Despite aggressive fluid resuscitation, fecal peritonitis was associated with arterial hypotension requiring norepinephrine infusion, ultimately resulting in progressive lactic acidosis and acute kidney injury. GW0742 did not beneficially affect any parameter of systemic and regional hemodynamics, gas exchange, metabolism, or organ function. The parameters of inflammation, oxidative and nitrosative stress, and organ injury (post-mortem analysis for histomorphology and markers of apoptosis) were not influenced either. Immunohistochemistry of pre-shock kidney biopsies from a previous study in this swine strain showed markedly lower PPAR-β/δ receptor expression than in healthy animals.

Conclusions

In swine with pre-existing atherosclerosis, the PPAR-β/δ agonist GW0742 failed to attenuate septic shock-induced circulatory failure and kidney dysfunction, most likely due to reduced receptor expression coinciding with cardiovascular and metabolic co-morbidity.

Electronic supplementary material

The online version of this article (doi:10.1186/2197-425X-1-9) contains supplementary material, which is available to authorized users.

Resveratrol in primary and secondary prevention of cardiovascular disease: a dietary and clinical perspective

Primary prevention of cardiovascular disease (CVD) aims to avoid a first event in subjects that are at risk but have not yet been diagnosed with heart disease. Secondary prevention of CVD aims to avoid new events in patients with established heart disease. Both approaches involve clinical intervention and implementation of healthy lifestyles. The grape and wine polyphenol resveratrol (3,5,4'-trihydroxy-trans-stilbene) has shown cardioprotective benefits in humans. Most of these approaches deal with rather high doses and short follow-ups, and do not address the issue of long-term resveratrol consumption safety, especially in medicated individuals. Here, we review the trials conducted with resveratrol in patients at risk for or with established CVD, focusing on the two longest human clinical trials reported so far (1-year follow-up). We also discuss the expectations for resveratrol from a dietary and clinical perspective in relation to CVD. However, statistically significant changes in CVD-risk markers do not necessarily equal clinical significance in the daily care of patients.

Does resveratrol improve insulin signaling in chronically ischemic myocardium?

BACKGROUND

Resveratrol is a naturally occurring polyphenol believed to be cardioprotective. We previously demonstrated that resveratrol improves insulin signaling and glucose metabolism in liver and skeletal muscle of swine with metabolic syndrome. Although resveratrol has metabolic benefits in peripheral tissues, its effect on insulin signaling in ischemic myocardium (IM) is unclear. Therefore, we developed a clinically relevant swine model of metabolic syndrome and chronic myocardial ischemia to investigate the effects of resveratrol on insulin signaling in cardiac tissue.

MATERIALS AND METHODS

Thirteen male Yorkshire swine were fed a high-cholesterol diet for 4 wk then underwent surgical placement of an ameroid constrictor to their circumflex artery to induce chronic myocardial ischemia. The high-cholesterol control group was given no drug (n = 7). The experimental group was provided the same diet and received supplemental resveratrol (100 mg/kg/d) (n = 6). Tissue was harvested 7 wk after ameroid placement for western blot and histological analyses.

RESULTS

In IM, there was no significant difference between the two groups in the insulin signaling markers studied. In nonischemic myocardium, there was a significant decrease in phosphorylated AMP-activated protein kinase α (P = 0.021) in the group treated with resveratrol; otherwise, there were no significant differences between the groups. Immunostaining for glucose transporter 4 and Periodic acid-Schiff staining for myocardial glycogen stores was similar between the groups.

CONCLUSIONS

Resveratrol has complex effects on glucose metabolism. Although prior studies demonstrated that resveratrol supplementation improves insulin sensitivity in peripheral tissues, in chronically IM, there are no significant alterations.

Arterial insulin resistance in Yucatan micropigs with diet-induced obesity and metabolic syndrome

AIM

Metabolic syndrome affects a large proportion of the population and increases cardiovascular disease risk. Because metabolic syndrome often co-exists clinically with atherosclerosis, it is difficult to distinguish the respective contributions of the components to vascular abnormalities. Accordingly, we utilized a porcine dietary model of metabolic syndrome without atherosclerosis to investigate early abnormalities of vascular function and signaling.

METHODS

Thirty-two Yucatan micropigs were fed either a high-fat, high-simple-sugar, high-calorie (HFHS) or standard chow diet (STD) for 6 months. Neither diet contained added cholesterol. Blood pressure and flow-mediated vasodilatation were assessed at baseline and 6 months. Aortas were harvested at 6 months to assess histology, insulin signaling, and endothelial nitric oxide (eNOS) phosphorylation.

RESULTS

HFHS pigs developed characteristics of metabolic syndrome including obesity, dyslipidemia, and insulin resistance, but without histologic evidence of atherosclerosis. Although arterial intima-media thickness did not differ between groups, vascular dysfunction in HFHS was manifest by increased blood pressure and impaired flow-mediated vasodilation of the femoral artery. Compared with STD, aortas from HFHS exhibited increased p85α expression and Ser307 IRS-1 phosphorylation, and blunted insulin-stimulated IRS-1-associated phosphatidylinositol (PI) 3-kinase activity. In the absence of insulin stimulation, aortic Akt Ser473-phosphorylation was greater in HFHS than in STD. With insulin stimulation, Akt phosphorylation increased in STD, but not HFHS. Insulin-induced Ser1177-phosphorylation of eNOS was decreased in HFHS, compared with STD.

CONCLUSIONS

Pigs with metabolic syndrome develop early vascular dysfunction and aortic insulin signaling abnormalities, and could be a useful model for early human vascular abnormalities in this condition.

Metabolic syndrome is not a predictor for cardiovascular events in Japanese patients with diabetes mellitus asymptomatic for coronary artery disease: a retrospective analysis of the J-ACCESS-2 study

PURPOSE

Patients with metabolic syndrome (MetS) have potentially higher risk for cardiovascular events. The aim of this study was to evaluate the effect of MetS on cardiac events in type-2 diabetic patients asymptomatic for coronary artery disease (CAD) in a Japanese population.

METHODS

A total of 485 patients from a J-ACCESS-2 investigation with stress-gated myocardial perfusion imaging (MPI) and quantitative-gated MPI analysis were examined. Cardiovascular hard events (cardiac death and acute coronary syndrome) and total events during a 3-year follow-up were analyzed.

RESULTS

The MetS group (n = 229) had higher incidence of hypertension, dyslipidemia, and ventricular dilatation than the non-MetS group (n = 256). The hard events were 8 and 12 for the MetS and non-MetS groups (P = n.s.), and total events were 31 and 31 for each of these groups, respectively (P = n.s.). Significant variables related to total cardiovascular events included age, current smoking, insulin use, total cholesterol, ejection fraction, summed stress score ≥ 9, and summed difference score ≥ 2. Cox proportional hazard analysis and Kaplan-Meier survival analysis showed that only the summed stress score was related to total events (P = .01), and the presence and the number of items for MetS criteria were not.

CONCLUSION

In patients with type 2 diabetes asymptomatic for CAD, cardiovascular events and ischemia are as common in diabetic patients without MetS as in those with MetS. A high MPI defect score is related to total events including cardiac and cerebrovascular events.

Potential therapeutic effects of natural heme oxygenase-1 inducers in cardiovascular diseases

SIGNIFICANCE

Many physiological effects of natural antioxidants, their extracts or their major active components, have been reported in recent decades. Most of these compounds are characterized by a phenolic structure, similar to that of α-tocopherol, and present antioxidant properties that have been demonstrated both in vitro and in vivo. Polyphenols may increase the capacity of endogenous antioxidant defenses and modulate the cellular redox state. Such effects may have wide-ranging consequences for cellular growth and differentiation.

CRITICAL ISSUES

The majority of in vitro and in vivo studies conducted so far have attributed the protective effect of bioactive polyphenols to their chemical reactivity toward free radicals and their capacity to prevent the oxidation of important intracellular components. One possible protective molecular mechanism of polyphenols is nuclear factor erythroid 2-related factor (Nrf2) activation, which in turn regulates a number of detoxification enzymes.

RECENT ADVANCES

Among the latter, the heme oxygenase-1 (HO-1) pathway is likely to contribute to the established and powerful antioxidant/anti-inflammatory properties of polyphenols. In this context, it is interesting to note that induction of HO-1 expression by means of natural compounds contributes to prevention of cardiovascular diseases in various experimental models.

FUTURE DIRECTIONS

The focus of this review is on the role of natural HO-1 inducers as a potential therapeutic strategy to protect the cardiovascular system against various stressors in several pathological conditions.

Cardiac dysfunction and oxidative stress in the metabolic syndrome: an update on antioxidant therapies

The metabolic syndrome (MetS) is a cluster of risk factors including obesity, insulin resistance, dyslipidemia, elevated blood pressure and glucose intolerance. The MetS increases the risk for cardiovascular disease (CVD) and type 2 diabetes. Each component of the MetS causes cardiac dysfunction and their combination carries additional risk. The mechanisms underlying cardiac dysfunction in the MetS are complex and might include lipid accumulation, increased fibrosis and stiffness, altered calcium homeostasis, abnormal autophagy, altered substrate utilization, mitochondrial dysfunction and increased oxidative stress. Mitochondrial and extra-mitochondrial sources of reactive oxygen species (ROS) and reduced antioxidant defense mechanisms characterize the myocardium of humans and animals with the MetS. The mechanisms for increased cardiac oxidative stress in the MetS are not fully understood but include increased fatty acid oxidation, mitochondrial dysfunction and enhanced NADPH oxidase activity. Therapies aimed to reduce oxidative stress and enhance antioxidant defense have been employed to reduce cardiac dysfunction in the MetS in animals. In contrast, large scale clinical trials using antioxidants therapies for the treatment of CVD have been disappointing because of the lack of efficacy and undesired side effects. The focus of this review is to summarize the current knowledge about the mechanisms underlying cardiac dysfunction in the MetS with a special interest in the role of oxidative stress. Finally, we will update the reader on the results obtained with natural antioxidant and mitochondria-targeted antioxidant therapies for the treatment of CVD in the MetS.

Autophagy, myocardial protection, and the metabolic syndrome

Autophagy is a housekeeping process that helps to maintain cellular energy homeostasis and remove damaged organelles. In the heart, autophagy is an adaptive process that is activated in response to stress including acute and chronic ischemia. Given the evidence that autophagy is suppressed in energy-rich conditions, the objective of this review is to examine autophagy and cardioprotection in the setting of the metabolic syndrome. Clinical approaches that involve the induction of cardiac autophagy pharmacologically to enhance the heart's tolerance to ischemia are also discussed.

Vodka and wine consumption in a swine model of metabolic syndrome alters insulin signaling pathways in the liver and skeletal muscle

BACKGROUND

The purpose of this study was to examine the effects of alcohol in the context of metabolic syndrome on insulin signaling pathways in the liver and skeletal muscle.

METHODS

Twenty-six Yorkshire swine were fed a hypercaloric, high-fat diet for 4 weeks then split into 3 groups: hypercholesterolemic diet alone (HCC, n = 9), hypercholesterolemic diet with vodka (HCVOD, n = 9), and hypercholesterolemic diet with wine (HCW, n = 8) for 7 weeks. Animals underwent intravenous dextrose challenge before euthanasia and tissue collection.

RESULTS

HCC, HCVOD, and HCW groups had similar blood fasting glucose levels, liver function test, and body mass index. Thirty and 60 minutes after dextrose infusion, HCVOD and HCW groups had significantly increased blood glucose levels compared with the HCC group. The HCW group had significantly increased levels of insulin compared with the HCC group. Immunoblotting in skeletal muscle demonstrated that alcohol up-regulates p-IRS1, IRS2, AKT, AMPKα, PPARα, Fox01, and GLUT4. In the liver, HCW had up-regulation of AKT, AMPKα, and GLUT4 compared with HCC. Skeletal muscle immunohistochemistry demonstrated increased sarcolemmal expression of GLUT4 in both alcohol groups compared with HCC.

CONCLUSION

Moderate alcohol consumption in a swine model of metabolic syndrome worsens glucose metabolism by altering activation of the insulin signaling pathway in the liver and skeletal muscle.

Neuropeptide Y improves myocardial perfusion and function in a swine model of hypercholesterolemia and chronic myocardial ischemia

Pharmacologically induced angiogenesis could be a promising option in clinical situations with diffuse inoperable coronary artery disease e.g. metabolic syndrome and diabetes mellitus. The failure of focused cytokine, stem cell and gene therapies to achieve both perfusion and functional improvement in clinical trials suggests a more centralized control mechanism. Neuropeptide-Y (NPY) is one such natural neurotransmitter that is known to exert a multifaceted role during neo-angiogenesis and can possibly act as the central control. To date, the ability to harness the 'master switch' nature of NPY in a specific experimental model of metabolic syndrome and chronic myocardial ischemia has not been conclusively demonstrated. We hypothesized that infiltration of NPY into an area of chronic ischemia in a metabolic syndrome swine model would induce angiogenesis and improve myocardial perfusion and function. An osmotic pump was inserted three weeks after surgical induction of focal myocardial ischemia. We delivered either NPY or placebo for five weeks, after which the myocardial tissue was harvested for analysis. Assessments of myocardial perfusion and function were performed at each stage of the experiment. Local infiltration of NPY significantly improved collateral vessel formation, blood flow and myocardial function. We believe activation of NPY receptors may be a potential target therapy for patients with diffuse coronary artery disease.

Synergistic effects of leucine and resveratrol on insulin sensitivity and fat metabolism in adipocytes and mice

BACKGROUND

Sirtuins are important regulators of glucose and fat metabolism, and sirtuin activation has been proposed as a therapeutic target for insulin resistance and diabetes. We have shown leucine to increase mitochondrial biogenesis and fat oxidation via Sirt1 dependent pathways. Resveratrol is a widely recognized activator of Sirt; however, the biologically-effective high concentrations used in cell and animal studies are generally impractical or difficult to achieve in humans. Accordingly, we sought to determine whether leucine would exhibit synergy with low levels of resveratrol on sirtuin-dependent outcomes in adipocytes and in diet-induced obese (DIO) mice.

METHODS

3T3-L1 mouse adipocytes were treated with Leucine (0.5 mM), β-hydroxy-β-methyl butyrate (HMB) (5 μM) or Resveratrol (200 nM) alone or in combination. In addition, diet-induced obese mice were treated for 6-weeks with low (2 g/kg diet) or high (10 g/kg diet) dose HMB, Leucine (24 g/kg diet; 200% of normal level) or low (12.5 mg/kg diet) or high (225 mg/kg diet) dose resveratrol, alone or as combination with leucine-resveratrol or HMB-resveratrol.

RESULTS

Fatty acid oxidation, AMPK, Sirt1 and Sirt3 activity in 3T3-L1 adipocytes and in muscle cells, were significantly increased by the combinations compared to the individual treatments. Similarly, 6-week feeding of low-dose resveratrol combined with either leucine or its metabolite HMB to DIO mice increased adipose Sirt1 activity, muscle glucose and palmitate uptake (measured via PET/CT), insulin sensitivity (HOMAIR), improved inflammatory stress biomarkers (CRP, IL-6, MCP-1, adiponectin) and reduced adiposity comparable to the effects of high dose resveratrol, while low-dose resveratrol exerted no independent effect.

CONCLUSION

These data demonstrate that either leucine or its metabolite HMB may be combined with a low concentration of resveratrol to exert synergistic effects on Sirt1-dependent outcomes; this may result in more practical dosing of resveratrol in the management of obesity, insulin-resistance and diabetes.

Resveratrol preserves myocardial function and perfusion in remote nonischemic myocardium in a swine model of metabolic syndrome

BACKGROUND

Resveratrol has been shown to reverse some of the detrimental effects of metabolic syndrome (MetS). We sought to define the impact of supplemental resveratrol on normal myocardium remote from an ischemic territory in a swine model of MetS and chronic myocardial ischemia.

STUDY DESIGN

Yorkshire swine were fed a normal diet (control), a high cholesterol diet (HCD), or a high cholesterol diet with orally supplemented resveratrol (HCD-R; 100 mg/kg/day). Four weeks after diet modification, myocardial ischemia was induced by ameroid constrictor placement. Seven weeks later, myocardial tissue from a territory remote from the ischemia was harvested. Animals in the HCD and HCD-R groups underwent functional cardiac MRI before ischemia and before sacrifice. Tissue was harvested for protein expression analysis.

RESULTS

After 7 weeks of ischemia, regional left ventricular systolic function was significantly increased in HCD-R as compared with HCD animals. During ventricular pacing the HCD group had significantly decreased flow (p = 0.03); perfusion in the HCD-R was preserved as compared with the control. There was no difference in microvascular relaxation. Expression of metabolic proteins Sirt-1 (p = 0.002), AMPkinase (p = 0.02), and carnitine palmitoyltransferase-I (p = 0.002) were upregulated in the HCD-R group. Levels of protein oxidative stress were significantly increased in the HCD and HCD-R groups, as compared with the controls (p = 0.003). Activated endothelial nitric oxide synthase (eNOS) was increased in the HCD-R group (p = 0.01). There was no difference in myocardial endothelial cell density between the groups; however, dividing endothelial cells were decreased in the HCD and HCD-R groups (p = 0.006).

CONCLUSIONS

Resveratrol supplementation improves regional left ventricular function and preserves perfusion to myocardium remote from an area of ischemia in an animal model of metabolic syndrome and chronic myocardial ischemia.

Are sirtuins viable targets for improving healthspan and lifespan?

Although the increased lifespan of our populations illustrates the success of modern medicine, the risk of developing many diseases increases exponentially with old age. Caloric restriction is known to retard ageing and delay functional decline as well as the onset of disease in most organisms. Studies have implicated the sirtuins (SIRT1-SIRT7) as mediators of key effects of caloric restriction during ageing. Two unrelated molecules that have been shown to increase SIRT1 activity in some settings, resveratrol and SRT1720, are excellent protectors against metabolic stress in mammals, making SIRT1 a potentially appealing target for therapeutic interventions. This Review covers the current status and controversies surrounding the potential of sirtuins as novel pharmacological targets, with a focus on SIRT1.

Unique vascular protective properties of natural products: supplements or future main-line drugs with significant anti-atherosclerotic potential?

Natural health products (NHP) which include minerals, vitamins and herbal remedies are not generally considered by medical practitioners as conventional medicines and as such are not frequently prescribed by health centre's as either main-line or supplemental treatments. In the field of cardiovascular medicine, studies have shown that typically, less than half of patients suffering from coronary syndromes chose to take any form of NHP supplement and these products are rarely recommended by their medical practitioner. Vascular/endothelial cell damage is a key instigator of coronary arterial plaque development which often culminates in thrombosis and myocardial infarction (MI). Current treatment for patients known to be at risk of primary or secondary (MI) includes lipid lowering statins, anti-clotting agents (e.g. tissue plasminogen activator; tPA) and drugs for stabilization of blood pressure such as beta-blockers. However, evidence has been building which suggests that components of at least several NHP (e.g. aged garlic extract (AGExt), resveratrol and green tea extracts (GTE)) may have significant vascular protective effects through reduction of oxidative stress, lowering of blood pressure, reduction in platelet aggregation, vasodilation and inhibition of abnormal angiogenesis. Therefore, in this review we will discuss in detail the potential of these substances (chosen on the basis of their potency and complimentarity) as anti-atherosclerotic agents and the justification for their consideration as main-line additional supplements or prescriptions.