Current Pharmaceutical Design - Volume 19, Issue 27, 2013

The metabolic syndrome (MetS) is characterized by a cluster of cardiovascular risk factors, including central obesity, hyperglycemia, dyslipidemia and hypertension, which are highly associated with increased morbidity and mortality of cardiovascular diseases (CVD). The association between these metabolic disorders and the development of CVD is believed to be multifactorial, where insulin resistance, oxidative stress, low-grade inflammation and vascular maladaptation act as the major contributors. Therefore, multipronged therapeutic strategies should be taken for the management of patients with MetS. Lifestyle changes including weight control, healthy heart diet and regular exercises have been proposed as first line treatment to decrease CVD risks in MetS individuals. In addition, improving insulin resistance and glucose metabolism, controlling blood pressure as well as modulating dyslipidemia can also delay or reverse the progression of CVD in MetS. This review will first address the complicated interactions between MetS and CVD¸ followed by discussion about the optimal strategy in the prevention and treatment of CVD in MetS patients and the updated results from newly released clinical trials.

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.

Glucocorticoids include steroid hormones released from the adrenal cortex or synthetic analogues developed for various inflammatory and immune disorders. GCs are known to play an important role in maintaining the body’s metabolic balance, but their irregular activity has been associated with complications like Cushing’s syndrome, insulin resistance, and heart disease. Conventional GC action is through their nuclear receptor activation, but specific and non-specific membrane bound receptor mediated non-genomic actions have also been reported. GCs increase AMPK phosphorylation at Thr172, in addition to augmenting AMPK protein and gene expressions. AMPK is insulin mimetic in many of its actions like glucose uptake and inhibition of lipolysis, and these properties of AMPK are made used in conditions like insulin resistance and diabetes. Nevertheless, if AMPK is activated by GC in the absence of diabetes or decreased insulin signaling, accumulation of substrates in the form of glycogen and triglycerides could precipitate cardiac abnormalities. Glycogen storage can lead to many disorders like hypertrophy, conduction system disease and Wolff Parkinson White syndrome. TG accumulation is associated with generation of free radicals, ceramide formation, mitochondrial dysfunction and cardiac cell death. In this review, we outline the cardiometabolic changes associated with GC, especially related to augmentation in AMPK, and link these changes to cardiac dysfunction.

The melanocortin-3 receptor (MC3R) is a G protein-coupled receptor involved in regulating energy metabolism, cardiovascular function, and inflammation. To gain a better understanding of the structure-function relationship of the MC3R, we used alaninescanning mutagenesis to investigate the functions of residues 247–273 in the third intracellular loop (ICL3) of the human MC3R (hMC3R). Ligand binding and signaling parameters of the mutants were measured. The results showed that six mutants at the N terminus of ICL3 had decreased receptor occupancy (an estimate of relative binding capacity) whereas six mutants at the C terminus of ICL3 had increased receptor occupancy. M247A, R252A, H254A, and K256A had decreased maximal responses (M247A also had increased EC50) whereas F250A, P262A, and H272A had increased maximal responses. None of the mutants was constitutively active. The binding and signaling properties of the other mutants were not significantly different from that of the wild type hMC3R. In summary, we presented detailed functional data on the functions of the residues in ICL3 of hMC3R, providing important constraints for modeling ligand binding and G protein coupling/activation in the hMC3R.

Patients with diabetes exhibit significantly altered renin-angiotensin system (RAS) control. Recently, it has been determined that hyperglycemic conditions induce an increase in angiotensin II (AT II) expression; specifically by cardiomyocytes. Altered RAS has been shown to be associated with an increase in oxidative stress and cardiac dysfunction leading to the development of cardiac hypertrophy. The transient outward potassium current (Ito) in cardiac myocytes is mainly mediated by members of the Kv subfamily of voltage gated potassium channels and has been shown to be altered in cellular localization and expression during the development of cardiac hypertrophy. However it is not clear as to how AT II affects the pore forming complex at the cell membrane and thus directly affects the Ito current. In the current study, we explored the protective effect of PPARγ ligands on cardiomyocyte Ito by preventing NADPH Oxidase activation and the ensuing ROS formation. Furthermore, short term PPARγ activation in diabetic leptin deficient db/db mice displayed improvements in the membrane association of the molecular components of Ito as well as prolonged QT interval. These findings demonstrate that PPARγ agonists have the potential to attenuate cardiomyocyte dysfunction associated with diabetes.

Metabolic syndrome is well known to increase the risk of cardiovascular disease and diabetes. As the key feature of metabolic syndrome, insulin resistance occurs when target tissues cannot respond properly to insulin and develops in multiple organs, including the vasculature and heart. Accumulating evidence has suggested insulin-induced PI3K-Akt-eNOS survival signaling as a potent therapeutic target for cardiovascular disorders and highlighted the impaired survival signaling as a key link between insulin resistance and cardiovascular disease. However, long-term insulin treatment is inconvenient and may increase the risk of hypoglycemia. More importantly, the effects of insulin are significantly blunted in patients with insulin resistance due to the pathway-specific impairment of PI3K-Akt signaling, and exogenous chronic insulin administration may lead to the over-activation of Ras-MAPK signaling which may result in unwanted side effects. Our recent study has shown that some Chinese medicinal herbs can directly activate PI3K-Akt-eNOS survival signals and improve tissue insulin sensitivity to exert endothelial and cardiac protective effects in diabetic animals. These herbs or phytoinsulins as we named, targeting insulin-activated cell survival signals and exert insulin-like actions, have promising beneficial effects on prevention and treatment of diabetes- and insulin resistance-induced cardiovascular disorders. Another advantage of phytoinsulins is that they generally exert multiple actions, including mild blood glucose-lowering effect, pancreatic β cells protection and adipogenesis reduction, for better cardiovascular protection. In this review, we discussed our strategies of searching for phytoinsulins and their potential beneficial effects in the treatment of metabolic syndrome, especially their values in prevention of diabetic cardiovascular disease.

Chloride (Cl-) channels participate in the regulation of cardiac function in response to stress although the underlying regulatory mechanism remains poorly understood. This study was designed to examine the impact of the pro-apoptotic stimulus staurosporine (STS) on the volume-sensitive outwardly rectifying Cl- current (ICl,Vol) in cardiomyocytes and possible regulatory mechanism involved with a focus on phosphatidylinositol-3 kinase (PI3K)/Akt. Primary cultured rat neonatal cardiomyocytes were subjected to hypotonic and isotonic environment in the presence or absence of STS prior to whole-cell voltage-clamp evaluation of Cl- current. Whole-cell recordings revealed that STS activated an outwardly rectifying Cl- current with phenotypic properties reminiscent of ICl,Vol. These currents were outwardly rectifying with a time-dependent inactivation at positive potentials and were sensitive to 4,4'-diisothiocya-natostilbene- 2,2'- disulfonicacid (DIDS), a non-selective Cl- channel blocker, and 4-(2-butyl-6,7-dichlor-2-cyclopentyl-indan-1-on-5-yl)oxybutyric acid (DCPIB), a selective VSOR Cl- channel blocker. DIDS and DCPIB inhibited ICl,Vol by 92.6% ± 7.3% and 78.4% ± 5.5%, respectively. Our data further revealed that the PI3K inhibitor LY294002 facilitated the current with the peak amplitude of 19.54 ± 2.70 pA/pF. To the contrary, insulin partially inhibited the current amplitude with the peak current amplitude of 15.4 ± 2.13 pA/pF. Taken together, our data depicted staurosporine is capable of activating ICl,Vol channel in cardiomyocytes via possibly a PI3K/Akt-dependent mechanism.

MicroRNA-34a (miR-34a) promotes apoptosis via down-regulating many anti-apoptotic proteins. Aldehyde dehydrogenase 2 (ALDH2) is an anti-apoptotic enzyme whose activity decline associates with myocardial injury. We tested hypothesis that miR-34a might play a pro-apoptotic role in myocardial infarction (MI) by down-regulating ALDH2. MiR-34a was highly increased while ALDH2 expression was decreased after experimental MI. Overexpression of miR-34a in neonatal rat cardiomyocyte could significantly enhance apoptosis and down-regulate ALDH2 expression. In 293 cells, luciferase reporter assay results demonstrated that ALDH2 was a direct target of miR-34a. Serum miR-34a levels in acute myocardial infarction (AMI) patients and rats were significantly higher than healthy subjects and sham rats. Our results proved that miR-34a could promote cardiomyocyte apoptosis via negatively regulating ALDH2 and circulating miR-34a was increased in the condition of MI. Thus, miR-34a may constitute a new therapeutic target and diagnostic marker for patients with MI.

This study was designed to evaluate the role of ULK1 in AMPK-mediated myocardial autophagy and contractile dysfunction following acute alcohol challenge. Wild-type and AMPK knockout mice were challenged with ethanol (3 g/kg/d, i.p.) for 3 days. Myocardial function was evaluated using echocardiography and edge-detection. Western blot analysis was employed to evaluate the levels of AMPK, Raptor, mTOR, the AMPK downstream signal ULK1 and autophagy markers Beclin-1 and LC3-II. siRNA was used to knockdown ULK1 in H9C2 myoblasts. GFP-LC3 puncta was used to evaluate autophagosome formation. Alcohol challenge compromised cardiac function as evidenced by decreased fractional shortening, peak shortening and intracellular Ca2+ rise, prolonged relengthening and intracellular Ca2+ decay in WT mice, the effects of which were mitigated by AMPK knockout. Ethanol exposure facilitated myocardial autophagy as evidenced by enhanced LC3-II level, as well as phosphorylation of AMPK, Raptor, and dephosphorylation of mTOR and ULKI in WT hearts, which were alleviated by AMPK knockout. Pharmacological inhibition of AMPK using compound C attenuated ethanol-induced autophagosome formation, AMPK phosphorylation, ULK1 dephosphorylation and apoptosis. Ethanol exposure-induced cardiomyocyte contractile defects and autophagosome accumulation were reversed by the autophagy inhibitor 3-MA. Similarly, knockdown of ULK1 using siRNA in H9C2 cells ablated ethanol-induced autophagosome accumulation, LC3-II expression and cell death. Lysosomal inhibition using bafilomycin, E64-D and pepstatin A potentiated ethanol-induced increase in autophagosome formation. Taken together, our results suggest that ULK1 may play a critical role in AMPK-mediated myocardial autophagy, apoptosis and contractile dysfunction following acute alcohol challenge.

The metabolic syndrome (MetS) is a constellation of multiple metabolic risk factors including obesity, glucose intolerance, insulin resistance, dyslipidemia and hypertension. Individuals with MetS are found to be afflicted with an increased risk of type 2 diabetes mellitus and overall cardiovascular diseases. One of the common comorbidities of MetS is the impairment of heart function en route to loss of cardiomyocytes and ultimately heart failure. Although it is accepted that cardiomyocytes are terminally differentiated, recent evidence has challenged this concept to indicate the ability of cardiomyocytes to regenerate from progenitor cells of the heart and other organs. Moreover, it has been suggested that pathological conditions such as MetS may play a role in the regulation of cardiomyocyte regeneration. This mini-review will discuss the role of MetS in the regulatory machineries of cardiomyocyte regeneration.

This study was designed to evaluate the distribution of Tregs/Th17/Th1 cells in type 2 diabetic patients with foot disease before and after human umbilical cord blood mesenchymal stem cell (hUCB-MSCs) transplantation. Fifteen diabetic patients with foot disease under insulin therapy received hUCB-MSC transplantation. The hUCB-MSCs were directly injected into the quadriceps thigh muscles in patients with foot disease (cell quantity at 2x106 per point). Physical attributes, blood cytokines, blood glucose and insulin dosage were evaluated before treatment and 1, 2, 4, 8, and 12 weeks thereafter. The ratios of Treg/Th17, Treg/Th1, and Th17/Th1 cells were measured using flow cytometry and their correlation with various cytokines (FoxP3, IL-17, INF-γ, C-RP, TNF-α, and VEGF) was scrutinized. Levels of blood glucose and insulin dosage were significantly reduced in all 15 patients following hUCB-MSC transplantation. The ratios of CD4+CD25hiFoxP3+ Treg/Th17 and CD4+CD25hiFoxP3+ Treg/Th1 cells were significantly increased 4 weeks after transplantation (p < 0.01), while the ratio of Th17/Th1 cells remained unchanged. Serum levels of VEGF peaked at 4 weeks following transplantation. Levels of C-RP and TNF-α were significantly reduced 4 weeks after transplantation. Intriguingly, the ratios of Treg/Th17 were positively correlated with VEGF levels, and were inversely correlated with plasma IL-6 levels. Our data indicated that immune disorders are associated with the development of type 2 diabetes and its complications. Levels of blood glucose and required insulin dosage were reduced after hUCB-MSC transplantation accompanied with improved clinical profiles in diabetic patients. These data favor a role for Treg cells in the onset and progression of T2D.

Despite positive effects on the plasma lipid profile and vascular events, statin use is associated with various side effects. Among these, statins might cause a disruption of a number of regulatory pathways including insulin signaling. This may affect insulin sensitivity, pancreatic beta-cell function and adipokine secretion. The statin-associated risk of new-onset diabetes (NOD) appears to be a dose-dependent class effect. It still remains unclear whether statin treatment is associated with increased risk of NOD in the general population or if there are groups of individuals at particular risk. However, according to the available data it seems that cardiovascular (CV) benefits in high-risk individuals strongly favor statin therapy since it outweighs other risks. Whether statins should be used for primary prevention among patients with a relatively low baseline CV risk is still questionable, however the results of primary prevention trials have shown reductions in mortality in this population. Thus, there is a need for randomized, placebo-controlled statin studies with carefully selected groups of patients and NOD as a key end point in order to resolve queries concerning this issue.

After the withdrawal of troglitazone and rosiglitazone, pioglitazone remains the sole thiazolidinedione (TZD) still available. Pioglitazone is efficacious in improving glycemic control and reduce the risk of cardiovascular events. Although generally well-tolerated, pioglitazone was withdrawn by some national medicines agencies (e.g. in France and Germany) due to reports of increased incidence of bladder cancer. In this article, we review the literature on the association between pioglitazone and cancer in several sites, including the bladder. Pioglitazone, like other TZDs, increased differentiation, inhibited growth and proliferation, while provoked apoptosis in various cancer cells, including bladder cancer, in vitro and in vivo. However, a rat-specific carcinogenic effect of pioglitazone on the bladder was noted in vivo. Clinical data for the risk of various cancer sites mostly come from observational studies and are subject to bias. An increased risk for bladder cancer by pioglitazone was suggested by retrospective analyses. This risk was associated with the time of exposure and the age, by identifying 24 months and 65 years, respectively, as time ‘thresholds’ above which this risk becomes relevant. In contrast, no increased risk for bladder cancer was associated with pioglitazone in randomized clinical trials. Pioglitazone was associated with increased incidence of melanoma and non-Hodgkin lymphoma and decreased risk of renal cancer in one cohort study. These findings need to be re-evaluated on a prospective basis. There is no convincing evidence that pioglitazone increases or decreases the risk of cancer in other sites. In contrast, it was suggested that this drug may be useful either in the treatment of cancer complications or as an adjunct to chemotherapeutic agents. Considering the clinical benefit from the use of pioglitazone it is reasonable to wait until data from ongoing clinical trials are available before reaching definitive conclusions. Nevertheless, the potential for increased risk of bladder cancer should be taken into consideration, especially in the presence of other risk factors for bladder carcinogenesis (e.g. smoking).

Elevated serum uric acid (SUA) levels (i.e. hyperuricaemia) have been associated with metabolic syndrome (MetS) and cardiovascular disease (CVD) morbidity and mortality. Elevated SUA levels predict the onset of type 2 diabetes (T2DM). SUA levels are increased during the early stages of impaired glucose metabolism. Furthermore, in diabetic patients, hyperuricaemia has been linked to both micro- and macrovascular complications. The present review considers: (1) SUA levels in patients with MetS, type 1 diabetes and T2DM; (2) the mechanisms that influence SUA levels in these patients; (3) the potential links between SUA and diabetic complications. The effect on SUA levels of drugs commonly prescribed for T2DM and the risk of uric acid nephrolithiasis in patients with MetS or DM are also briefly discussed.

Although the obesity epidemic is constantly expanding at very high costs for health care systems, the currently available options for the pharmacotherapy of obesity are very limited. This is not due to lack of interest or research on the subject but rather to the poor efficacy and/or safety profile of the majority of the antiobesity drugs developed up to now. Since the late fifties, various medications were brought to advanced states of clinical development but either never made it to the market or were initially approved only to be withdrawn some years later because of safety issues. However, our understanding of the pathophysiology of obesity has been steadily increasing and new, promising drugs targeting various selected obesity-associated and energy-homeostasis-related pathways are now under development. Nonetheless, obesity remains a disease mainly caused by an excess of caloric intake in relation to energy expenditure and on that basis, its treatment should be a healthy diet and physical activity. When these options alone are not sufficient, then additional pharmacotherapy with an acceptable efficacy and safety profile could provide a useful option.

Ghrelin is a peptide hormone produced mainly in the stomach that has widespread tissue distribution and diverse hormonal, metabolic and cardiovascular activities. The circulating ghrelin concentration increases during fasting and decreases after food intake. Ghrelin secretion may thus be initiated by food intake and is possibly controlled by nutritional factors. Lean subjects have increased levels of circulating ghrelin compared with obese subjects. Recent reports show that low plasma ghrelin is associated with elevated fasting insulin levels, insulin resistance and type 2 diabetes mellitus. Factors involved in the regulation of ghrelin secretion have not yet been defined; however, it is assumed that blood glucose levels represent a significant regulator. Recent evidence indicates that ghrelin can increase myocardial contractility, enhance vasodilatation, and has protective effect from myocardial damage. It has been shown that ghrelin may improve cardiac function through growth hormone (GH)-dependent mechanisms but there is also evidence to suggest that ghrelin's cardioprotective activity is independent of GH. Recent data demonstrate that ghrelin can influence key events in atherogenesis. Thus, ghrelin may be a new target for the treatment of some cardiovascular diseases. In this review, we consider the current literature focusing on ghrelin as a potential antiatherogenic agent in the treatment of various pathophysiological conditions.

Microalbuminuria (MA), excessive albumin excretion in the urine, is defined in different ways. MA is more prevalent among patients with diabetes mellitus (DM) and/or hypertension and correlates with adverse renal and cardiovascular (CV) outcomes. Several cross-sectional and prospective studies have demonstrated a positive association between MA and CV outcomes in the general population but also specific populations such as patients with previous MI and hypertensives. The relationship between MA and hypertension is of particular importance. Increased urine albumin excretion (UAE) has been associated with left ventricular hypertrophy (LVH), subclinical markers of atherosclerosis and vascular dysfunction. Metabolic syndrome (MetS), insulin resistance (IR), inflammatory markers, lipid parameters and measures of obesity also correlate with increased UAE. Accumulating evidence suggests that a UAE value lower than the “traditionally” considered microalbuminuric threshold is associated with increased CV risk. The revision of MA definition according to the levels which confer increased CV risk in the general population should probably be considered. Further prospective studies with uniform methods of urine collection and UAE measurement as well as consistent threshold values and units may provide additional information regarding MA (or low-grade albuminuria) as a predictor of CV outcomes.

We aimed to summarise recent advances in the therapy of diabetic neuropathy. Although all therapeutic choices in the treatment of diabetes mellitus itself are based on clear pathophysiological basis, this approach is less present in the treatment of the “forgotten complication”, diabetic neuropathy. As part of pathogenetic oriented treatment, the role of glycemic control and cardiovascular risk factors are reviewed. The mode of action of benfotiamine is based on inhibition of key alternative pathways, including the polyol, hexosamine, protein-kinase-C pathways, and inhibition of advanced glycation end products formation, just as on activation of transketolase. Alpha- lipoic-acid is considered as the most potent antioxidant. Other forms of pathogenetic oriented treatment, including actovegin, will be summarised. The anticonvulsants gabapentin and pregabalin, as well as the antidepressant duloxetine represent the most important new drugs among agents for symptomatic relief. Most likely, we should offer combination treatment to our patients much more often, first of all combination of pathogenetic and symptomatic drugs. Finally, the broad spectrum of non-pharmacological treatment will be reviewed.