Pioglitazone increases adiponectin levels in nondiabetic patients with coronary artery disease

The vascular endothelium in diabetes--a therapeutic target?

Insulin resistance affects the vascular endothelium, and contributes to systemic insulin resistance by directly impairing the actions of insulin to redistribute blood flow as part of its normal actions driving muscle glucose uptake. Impaired vascular function is a component of the insulin resistance syndrome, and is a feature of type 2 diabetes. On this basis, the vascular endothelium has emerged as a therapeutic target where the intent is to improve systemic metabolic state by improving vascular function. We review the available literature presenting studies in humans, evaluating the effects of metabolically targeted and vascular targeted therapies on insulin action and systemic metabolism. Therapies that improve systemic insulin resistance exert strong concurrent effects to improve vascular function and vascular insulin action. RAS-acting agents and statins have widely recognized beneficial effects on vascular function but have not uniformly produced the hoped-for metabolic benefits. These observations support the notion that systemic metabolic benefits can arise from therapies targeted at the endothelium, but improving vascular insulin action does not result from all treatments that improve endothelium-dependent vasodilation. A better understanding of the mechanisms of insulin's actions in the vascular wall will advance our understanding of the specificity of these responses, and allow us to better target the vasculature for metabolic benefits.

Relationship of adiponectin and leptin to coronary artery disease, classical cardiovascular risk factors and atherothrombotic biomarkers in the IARS cohort

Adiponectin and leptin link metabolic disorders and coronary artery disease (CAD). We analysed their relationship with CAD, classical risk factors and biomarkers in 287 CAD patients (cases) and 477 unaffected family members (controls) selected from the Indian Atherosclerosis Research Study (IARS). Classical risk factors included diabetes, hypertension, dyslipidaemia and obesity markers. Novel biomarkers were measured according to manufacturer recommendations. Adverse clinical events were recorded through telephonic follow-up. Cases showed lower adiponectin levels (4684.62 ± 190.73 ng/ml) than controls (5768.86 ± 152.87 ng/ml) (p=1.58X10(-5)); Leptin levels were higher in affected males (12.47 ± 1.32 ng/ml) than in male controls (9.53 ± 1.19 ng/ml, p=0.017). Adiponectin 1st quartile showed significant protection against CAD in females when compared to 3rd (odds ratio [OR] 0.39, 0.16-0.92, p=0.032) or 4th (OR 0.32, 0.14-0.72; p=0.006) quartile group. Leptin 3rd quartile showed higher CAD risk in males as compared to 1st quartile group (OR 2.09, 1.09-4.01, p=0.028). Subjects with metabolic syndrome showed low adiponectin and high leptin levels. Adipokines showed opposing association trend with lipids, inflammatory and coagulation markers and strong correlation (r=-0.14 to 0.52) with obesity markers. Cases with recurrent event and controls who developed new cardiac event during follow up showed high adiponectin levels (p<0.05). A model that combined adiponectin, leptin and conventional risk factors yielded the best 'C' index (0.890, 0.067-0.912). CAD patients in the top adiponectin tertile showed relatively poor survival curve as compared to the bottom Adiponectin tertile group. In conclusion, our findings strengthen the reported association between low adiponectin, high leptin, obesity-related metabolic disturbances and incident CAD in Asian Indians.

PPAR-γ as a therapeutic target in cardiovascular disease: evidence and uncertainty

Peroxisome proliferator-activated receptor γ (PPAR-γ) is a key regulator of fatty acid metabolism, promoting its storage in adipose tissue and reducing circulating concentrations of free fatty acids. Activation of PPAR-γ has favorable effects on measures of adipocyte function, insulin sensitivity, lipoprotein metabolism, and vascular structure and function. Despite these effects, clinical trials of thiazolidinedione PPAR-γ activators have not provided conclusive evidence that they reduce cardiovascular morbidity and mortality. The apparent disparity between effects on laboratory measurements and clinical outcomes may be related to limitations of clinical trials, adverse effects of PPAR-γ activation, or off-target effects of thiazolidinedione agents. This review addresses these issues from a clinician's perspective and highlights several ongoing clinical trials that may help to clarify the therapeutic role of PPAR-γ activators in cardiovascular disease.

Peroxisome proliferator-activated receptor-γ and the endothelium: implications in cardiovascular disease

Peroxisome proliferator-activated receptors-γ (PPARγs) are ligand-activated transcription factors that play a crucial regulatory role in the transcription of a large number of genes involved in lipid metabolism and inflammation. In addition to physiological ligands, synthetic ligands (the thiazoledinediones) have been developed. In spite of the much publicized adverse cardiovascular effects of one such thiazoledinedione (rosiglitazone), PPARγ activation may have beneficial cardiovascular effects. In this article we review the effects of PPARγ activation on the endothelium with special emphasis on the possible implications in cardiovascular disease. We discuss its possible role in inflammation, vasomotor function, thrombosis, angiogenesis, vascular aging and vascular rhythm. We also briefly review the clinical implications of these lines of research.

Screening of dried plant seed extracts for adiponectin production activity and tumor necrosis factor-alpha inhibitory activity on 3T3-L1 adipocytes

To search for dried plant seeds with potent anti-diabetes activity, we conducted a large scale screening for inhibitory activity on tumor necrosis factor-alpha and facilitating activity on adiponectin production in vitro. These activities in 3T3-L1 adipocytes were screened from ethanol extracts of 20 kinds of dried plant seed marketed in Japan. komatsuna (Brassica rapa var. perviridis), common bean (Phaseolus vulgaris L.), qing geng cai (Brassica rapa var. chinensis), green soybean (Glycine max), spinach (Spinacia oleracea L.) and sugar snap pea (Pisum sativum L.) markedly enhanced adiponectin production (11.3 ~ 12.7 ng/ml) but Japanese radish (Raphanus sativus), edible burdock (Arctium lappa L.), bitter melon (Momordica charantia) and broccoli (Brassica oleracea var. italica) did not (0.9 ~ 2.7 ng/ml). All adiponectin-production-enhancing seeds except spinach (2.7 pg/ml) and okra (Abelmoschus esculentus) (6.6 pg/ml) effectively decreased tumor necrosis factor-alpha levels (0.0 pg/ml). We further examined the effects on free radical scavenging activities in the dried seed extracts. Although scavenging activity correlated well with total phenolic content of samples, no correlation was observed with adiponectin production. These results point to the potential of dried seed extracts as a means to modify the activity of tumor necrosis factor-alpha for the adiponectin production.

The peroxisome proliferator-activated receptor gamma agonist pioglitazone improves cardiometabolic risk and renal inflammation in murine lupus

Individuals with systemic lupus erythematosus (SLE) have a striking increase in the risk of premature atherosclerosis, a complication preceded by significant subclinical vascular damage. A proposed mechanism leading to accelerated vascular disease in SLE is an imbalance between vascular damage and repair, as patients with this disease display significant abnormalities in phenotype and function of endothelial progenitor cells. In addition, individuals with SLE have a higher incidence of insulin resistance which may further contribute to the increased cardiovascular risk. This study examined the role of the peroxisome proliferator activated receptor gamma agonist pioglitazone in improving endothelial function, endothelial progenitor cell numbers and functional capacity, metabolic parameters, and disease activity in the lupus-prone murine model New Zealand Black/New Zealand White (NZB x NZW)F(1). Ten-week-old prenephritic female NZB/NZW F(1) mice were exposed to 10 or 25 mg/kg/day of oral pioglitazone or vehicle for 15 or 24 wk. Mice exposed to pioglitazone exhibited pronounced enhancement in endothelial-dependent vasorelaxation of thoracic aortas and in endothelial progenitor cell function, as assessed by the capacity of bone marrow-derived endothelial progenitor cells to differentiate into mature endothelial cells. Pioglitazone-treated mice showed improvement in insulin resistance, adipokine, and lipid profile. Kidneys from pioglitazone-treated mice showed significant decreases in immune complex deposition, renal inflammation, T cell glomerular infiltration, and intrarenal synthesis of TNF-alpha, IL-1beta, and VCAM-1. These results indicate that peroxisome proliferator-activated receptor gamma agonists could serve as important tools in the prevention of premature cardiovascular disease and organ damage in SLE.