Current Pharmaceutical Design - Volume 19, Issue 32, 2013

Cardiovascular disease (CVD) is one of the major lifestyle associated disorders and leading causes of death worldwide. The incidence of CVD in diabetic patients has increased up to 3 folds and it became the major risk for diabetes associated morbidity and mortality. Insulin resistance and oxidative stress both play a central role in the pathogenesis and progression of diabetes. The high prevalence of CVD among diabetic patients suggests the role of insulin resistance and oxidative stress in developing cardiovascular complications. Finding molecular mechanisms which could control both insulin resistance and oxidative stress would be more efficacious in improving the cardiovascular complications. Recent literatures show that an epigenetic mechanism could control or regulate the cardiovascular complications in diabetes. Sirtuins, a group of enzymes, modulate epigenetic changes by deacetylating histone and non-histone proteins. These enzymes are distributed in different cell organelles and are found to regulate different biological processes. Recent findings showed that sirtuins modulate different important proteins related to insulin signaling pathway and oxidative stress. This review summarizes how sirtuins could affect the insulin resistance and oxidative stress pathways in cardiovascular system and thus attenuate the cardiovascular complications. Understanding the role of sirtuins in insulin resistance and oxidative stress will increase the prospects for controlling or preventing cardiovascular complications in the future.

Insulin resistance and inflammation are recognized as important links between obesity and cardiovascular disease (CVD). Plasma free fatty acids (FFA), either released from the abnormally enlarged adipose tissue or as part of the excessive nutrient intake, produce insulin resistance and inflammation. Both insulin resistance and inflammation are tightly linked to several independent CVD risk factors such as type 2 diabetes (T2DM), hypertension, dyslipidemia and disorders of blood coagulation. Several hypotheses have been proposed to explain how increased plasma FFA levels can cause insulin resistance including a) the lipid metabolite hypothesis, b) the inflammation hypothesis, c) the hyperinsulinemia hypothesis and d) the endoplasmic reticulum (ER) stress hypothesis. The latter does not require presence of elevated plasma FFA levels and thus provides a mechanism to explain the development of insulin resistance and inflammation in all obese individuals, i.e., those with and without elevated plasma FFA levels. Hyperinsulinemia per se has been suspected to cause CVD based on epidemiologic studies which have associated chronic hyperinsulinemia with CVD without, however, establishing a cause and effect relationship. There are, however, newer results which support the hypothesis that chronic hyperinsulinemia per se can promote the development of CVD. For instance, hyperinsulinemia can activate triglyceride formation, several matrix metalloproteinases (MMP), and the tissue factor pathway of blood coagulation, all of which are known to be associated with CVD, even in the presence of “metabolic insulin resistance”.

Intrinsic cardiac aging is an independent risk factor for cardiovascular disease and is associated with structural and functional changes that impede cardiac responses to stress and to cardio-protective mechanisms. Although systemic insulin resistance and the associated risk factors exacerbate cardiac aging, cardiac-specific insulin resistance without confounding systemic alterations, could prevent cardiac aging. Thus, strategies aimed to reduce insulin/insulin-like growth factor (IGF) signaling in the heart prevent cardiac aging in lower organisms and in mammals but the mechanisms underlying this protection are not fully understood. In this review, we describe the impact of aging on the cardiovascular system and discuss the mounting evidence that reduced insulin/IGF signaling in the heart could alleviate age-associated alterations and preserve cardiac performance.

Diabetes mellitus is associated to an increased risk of cardiovascular diseases. Hyperglycemia is an important factor in cardiovascular damage, working through different mechanisms such as activation of protein kinase C, polyol and hexosamine pathways, advanced glycation end products production. All of these pathways, in association to hyperglycemia-induced mitochondrial dysfunction and endoplasmic reticulum stress, promote reactive oxygen species (ROS) accumulation that, in turn, promote cellular damage and contribute to the diabetic complications development and progression. ROS can directly damage lipids, proteins or DNA and modulate intracellular signaling pathways, such as mitogen activated protein kinases and redox sensitive transcription factors causing changes in protein expression and, therefore, irreversible oxidative modifications. Hyperglycemia-induced oxidative stress induces endothelial dysfunction that plays a central role in the pathogenesis of micro- and macro-vascular diseases. It may also increase pro-inflammatory and pro-coagulant factors expression, induce apoptosis and impair nitric oxide release. Oxidative stress induces several phenotypic alterations also in vascular smooth-muscle cell (VSMC). ROS is one of the factors that can promote both VSMC proliferation/migration in atherosclerotic lesions and VSMC apoptosis, which is potentially involved in atherosclerotic plaque instability and rupture. Currently, there are contrasting clinical evidences on the benefits of antioxidant therapies in the prevention/treatment of diabetic cardiovascular complications. Appropriate glycemic control, in which both hypoglycemic and hyperglycemic episodes are reduced, in association to the treatment of dyslipidemia, hypertension, kidney dysfunction and obesity, conditions which are also associated to ROS overproduction, can counteract oxidative stress and, therefore, both microvascular and macrovascular complications of diabetes mellitus.

The increasing prevalence of obesity has significant implications for healthcare, more particularly since it is a major risk factor for type 2 diabetes and cardiovascular diseases. However, not every obese patient is at the same risk of developing future metabolic and cardiovascular complications. Therefore, there is an urgent need for novel biomarkers for early identification of obese patients at high risk. Possible candidate biomarkers are microRNAs, which are highly conserved non-coding RNA molecules of approximately 22 nucleotides that exert post-transcriptional effects on gene expression. They are expressed in a tissue- and cell-type specific manner, play essential roles in many biological and pathological processes and are released in human peripheral blood in a disease-specific manner where they remain stable due to association with lipoprotein and phospholipids. All these characteristics suggest that they are putative diagnostic biomarkers. This review summarizes microRNAs with a functional role in the pathogenesis of atherosclerosis, myocardial infarction, ischemia/reperfusion injury and cardiac remodeling. It emphasizes those which have already been deregulated in association with obesity-related risk factors clustered in the metabolic syndrome. It demonstrates that several microRNAs which have been claimed to be biomarkers for cardiovascular diseases have already been deregulated in association with metabolic disorders prior to cardiovascular diseases. Finally, it summarizes which of these functionally validated microRNAs are deregulated in the circulation making them easily accessible for detection and thus into candidate biomarkers for early diagnosis of obesity-induced cardiovascular events.

Morbid obesity is a chronic multifunctional disease characterized by an accumulation of fat. Epidemiological studies have shown that obesity is associated with cardiovascular and metabolic disorders. Endothelial dysfunction, as defined by an imbalance between relaxing and contractile endothelial factors, plays a central role in the pathogenesis of these cardiometabolic diseases. Diminished bioavailability of nitric oxide (NO) contributes to endothelial dysfunction and impairs endothelium- dependent vasodilatation. But this is not the only mechanism that drives to endothelial dysfunction. Obesity has been associated with a chronic inflammatory process, atherosclerosis, and oxidative stress. Moreover levels of asymmetrical dimethyl-L-arginine (ADMA), an endogenous inhibitor of endothelial nitric oxide synthase (eNOS), are elevated in obesity. On the other hand, increasing prostanoid-dependent vasoconstriction and decreasing vasodilator prostanoids also lead to endothelial dysfunction in obesity. Other mechanisms related to endothelin-1 (ET-1) or endothelium derived hyperpolarizing factor (EDHF) have been proposed. Bariatric surgery (BS) is a safe and effective means to achieve significant weight loss, but its use is limited only to patients with severe obesity including morbid obesity. BS also proved efficient in endothelial dysfunction reduction improving cardiovascular and metabolic comorbidities associated with morbid obesity such as diabetes, coronary artery disease, nonalcoholic fatty liver disease and cancer. This review will provide a brief overview of the mechanisms that link obesity with endothelial dysfunction, and how weight loss is a cornerstone treatment for cardiovascular comorbidities obesity-related. A better understanding of the mechanisms of obesity-induced endothelial dysfunction may help develop new therapeutic strategies to reduce cardiovascular morbidity and mortality.

Evidence is mounting of the involvement of mitochondrial dysfunction in insulin resistance, diabetes and associated complications. This review aims to provide an overview of the effects of insulin resistance on mitochondrial function in several tissues. We consider the pathogenesis of insulin resistance from a mitochondrial perspective and contemplate potential beneficial effects of strategies aimed at modulating mitochondrial function in insulin resistance, including insulin and insulin-sensitizing drugs, antioxidants, and selectively targeting antioxidants to mitochondria.

Insulin resistance is associated with the impairment of the response of insulin receptor to insulin, resulting in the reduction of glucose uptake, leading to the alteration of myocardial glucose metabolism, impairment of cardiac electrophysiology, and increased susceptibility to ischemia-induced myocardial injury. Insulin resistance is associated with the impairment of the intracellular insulin signal transduction pathway. Among the MAPK family, p38-MAPK is a serine/threonine protein kinase, which has been shown to play an important role in cellular responses to various kinds of stress, including insulin resistance. Since growing evidence indicates the involvement of p38-MAPK in cardiovascular dysfunction, it is possible that the activation of p38-MAPK is responsible in part as a causative mechanism for cardiovascular complications in the insulin resistant heart. In addition, several anti-diabetic drugs have been shown to affect the myocardial p38-MAPK pathway. The effect of these drugs on p38-MAPK could be associated with their cardiovascular results in patients with insulin resistance. In this article, the signal transduction pathways of myocardial p38-MAPK activation in the insulin resistant heart, as well as the effects of anti-diabetic drugs on the myocardial p38-MAPK pathway, are comprehensively reviewed. Furthermore, the possible therapeutic approach regarding the utilization of a p38-MAPK inhibitor in diabetes patients to prevent cardiovascular complications is also addressed.

Adiponectin, a secretory protein specifically expressed by adipose tissue, has been shown to play a critical role in the maintenance of metabolic homeostasis. A deficiency of adiponectin has been linked to a wide variety of metabolic abnormalities, including obesity and associated disorders such as insulin resistance, hyperglycemia, dyslipidemia, hypertension and nonalcoholic fatty liver disease, collectively referred to as the “metabolic syndrome”. Conversely, increased expression of adiponectin corrects these abnormalities, as revealed by the positive metabolic effects observed in genetic over expression studies or by administration of recombinant adiponectin. This has led to widespread interest in its role as a therapeutic target for treatment of a range of metabolic disorders such as diabetes mellitus, obesity, inflammatory and cardiovascular diseases. Various therapeutic approaches targeted at increasing adiponectin levels, or its activity, are being explored. These consist of increasing expression of adiponectin or its receptors by inducers, increasing circulating levels of adiponectin by administering recombinant protein, peptide mimetic approaches, or increasing expression/activity of its downstream effectors such as AMPK or PPAR alpha. Many of these approaches have achieved therapeutic benefits in animal models of metabolic diseases. Despite the profusion of research on adiponectin and ways to modulate it, there are limited number of studies focused on smallmolecule based-therapeutic approaches. In this review, we summarize what is currently known with respect to the therapeutic potential of adiponectin and discuss the challenges in designing small molecule-based therapies.

Polycystic ovary syndrome (PCOS) is a heterogeneous syndrome of reproductive and metabolic derangements. The combination of anovulation and hyperandrogenism signifies the classic form of PCOS which displays the adverse metabolic phenotype of the syndrome. This phenotype includes visceral obesity and insulin resistance as well as a constellation of other traditional cardiovascular risk factors, mainly low grade inflammation, disturbances of glucose metabolism and dyslipidemia. The resultant increased risk for cardiovascular disease may affect not only obese but also lean women with classic PCOS. The mechanisms underlying the increased cardiovascular risk in the context of PCOS may include not only metabolic aberrations, but also hormonal factors, in particular hyperandrogenemia. However, the consequences in terms of CV morbidity remain questionable due to the difficulties in conducting long-term, prospective studies aimed at identifying potential late-arriving clinical outcomes.

Chronic low-grade subclinical inflammation has been increasingly recognized as an interposer in the endocrine, metabolic and reproductive disturbances that characterize the polycystic ovary syndrome (PCOS). Abdominal adiposity and obesity are often present in PCOS. Mounting evidence indicates that adipose tissue is involved in innate and adaptive immune responses. Continuous release of inflammatory mediators such as cytokines, acute phase proteins, and adipokines perpetuates the inflammatory condition associated with obesity in women with PCOS, possibly contributing to insulin resistance and other long-term cardiometabolic risk factors. Genetic variants in the genes encoding inflammation-related mediators underlie the development of PCOS and their interaction with environmental factors may contribute to the heterogeneous clinical phenotype of this syndrome. In the future, strategies ameliorating inflammation may prove useful for the management of PCOS and associated conditions.

Stroke is the third leading cause of death and the leading cause of disability in contemporary society. Aneurysmal subarachnoid hemorrhage (aSAH) is a hemorrhagic stroke which accounts for 7% of all stroke cases and 22 to 25% of cerebrovascular deaths. Aneurysmal subarachnoid hemorrhage is a very complex disease and many controversies on its pathophysiology and management have not yet been settled. The aim of this review is to present the most recent evidence-based advances in the pathophysiology and perioperative management of aSAH.

Rapid increase in the emergence and spread of microbes resistant to conventionally used antibiotics has become a major threat to global health care. Antimicrobial peptides (AMPs) are considered as a potential source of novel antibiotics because of their numerous advantages such as broad-spectrum activity, lower tendency to induce resistance, immunomodulatory response and unique mode of action. However, AMPs have several drawbacks such as; susceptibility to protease degradation, toxicity and high costs of manufacturing. Therefore, extensive research efforts are underway to explore the therapeutic potential of these fascinating natural compounds. This review highlights the potential of small cationic antimicrobial peptidomimetics (SCAMPs; M.W. ≈ 700 Da) as new generation antibiotics. In particular, we focused on recently identified small active pharmacophore from bulky templates of native AMPs, β-peptides, and lipopeptides. In addition, various design strategies recently undertaken to improve the physicochemical properties (proteolytic stability & plasma protein binding) of small cationic peptides have also been discussed.

The aim of this study was to determine the impact of mean platelet volume (MPV) on the strategy for treatment of atrial fibrillation (AF) with respect to stroke prevention. MPV was analyzed in 265 patients with AF who were undergoing treatment using rhythm or rate control. The primary endpoint was ischemic stroke or a transient ischemic attack (TIA) event. Kaplan-Meier analysis revealed a significantly higher stroke rate in the rate control group compared to the rhythm control group. A significantly higher stroke rate was observed in the higher tertile MPV group (≥7.9 fL) compared to the lower tertile MPV group (<7.3 fL). When the MPV cut-off level was set to 7.85 fL using the receiver operating characteristic curve, the sensitivity was 80.0% and the specificity was 70.4% for differentiating between the group with stroke and the group without stroke. In the Cox proportional hazard analysis, after adjusting for sex, treatment strategy for AF, high MPV level, antithrombotic treatment, and high CHADS2 score, higher MPV, rate control strategy for treatment of AF, and high CHADS2 score were found to be independent predictors of stroke risk. In addition, patients with AF who were treated using rate control had high stroke risk with an MPV over 7.85 fL and high CHADS2 score. The results of this study demonstrate that the MPV and the rate control strategy for treatment of AF were predictive markers for stroke; its predictive power for stroke was independent of female sex and high CHADS2 score in patients with AF.

Objective: The mechanisms by which bariatric surgeries, including gastric bypass (GB) and sleeve gastrectomy (SG), achieve remission of type 2 diabetes mellitus (T2DM) and sustained weight reduction are unknown. We hypothesized that the novel anorexic hormone nesfatin-1 and another new hormone obestatin might contribute to the marked improvement in glycemic homeostasis and weight loss in diabetics after GB and SG. Methods: A hospital-based, prospective study was conducted. Overnight fasting plasma concentrations of nesfatin-1 and obestatin were analyzed in T2DM patients before surgery, and at 3 and 12 months after laparoscopic GB (n =12) and SG (n = 6). Results: At 12 months, reductions of body mass index (BMI), fasting blood glucose, and glycated hemoglobin were similar between GB and SG groups (P all > 0.05). Plasma nesfatin-1 levels in patients undergoing GB or SG significantly decreased after surgeries (P both < 0.05). In contrast, plasma obestatin concentrations significantly increased in patients after SG (P < 0.05) but without any alteration after GB. The alterations of plasma nesfatin-1 were significantly and negatively associated with the reduction of fasting blood glucose (P <0.05) at 12 months after GB and SG. In the SG group, the reduction of nesfatin-1 significantly and positively correlated with the decrease of BMI (P < 0.05). Conclusions: GB and SG produce differential influences with regards to circulating nesfatin-1 and obestatin levels in non-morbidly obese, T2DM patients. Circulating nesfatin-1 may modulate glucose homeostasis in two surgical procedures, and participate in regulating body weight in SG.