Evidence for the importance of adiponectin in the cardioprotective effects of pioglitazone

The favorable effects of the peroxisome proliferator-activated receptor-gamma ligand pioglitazone on glucose metabolism are associated with an increase in the fat-derived hormone adiponectin in the bloodstream. A recent clinical trial, Prospective Pioglitazone Clinical Trial in Macrovascular Events, demonstrated that pioglitazone improved cardiovascular outcomes in patients with type 2 diabetes mellitus. However, the functional role of adiponectin in cardioprotection by pioglitazone has not been examined experimentally. Here we investigated the effect of pioglitazone on angiotensin II (Ang II)-induced cardiac hypertrophy and assessed the potential contribution of adiponectin to the action of pioglitazone on the heart. Wild-type or adiponectin-deficient mice were treated with pioglitazone as food admixture at a concentration of 0.01% for 1 week followed by 2 weeks of infusion with Ang II at 3.2 mg/kg per day. Ang II infusion in wild-type mice resulted in exacerbated myocyte hypertrophy and increased interstitial fibrosis, which were accompanied by elevated phosphorylation of extracellular signal-regulated kinase and expression of transforming growth factor-beta1 in the heart. Treatment of wild-type mice with pioglitazone attenuated cardiac hypertrophy and fibrosis, extracellular signal-regulated kinase phosphorylation, and transforming growth factor-beta1 expression in response to Ang II. Pioglitazone also increased the plasma adiponectin level and phosphorylation of cardiac AMP-activated protein kinase in wild-type mice in the presence of Ang II. The suppressive effects of pioglitazone on Ang II-induced cardiac hypertrophy and fibrosis were diminished in adiponectin-deficient mice. Furthermore, pioglitazone had no effects on the phosphorylation of extracellular signal-regulated kinase and AMP-activated protein kinase in the Ang II-infused heart of adiponectin-deficient mice. These data provide direct evidence that pioglitazone protects against Ang II-induced pathological cardiac remodeling via an adiponectin-dependent mechanism.

Obesity genotype score and cardiovascular risk in women with type 2 diabetes mellitus

OBJECTIVE

To investigate the associations between obesity-predisposing genetic variants, cardiovascular biomarkers, and cardiovascular disease (CVD) risk in women with preexisting type 2 diabetes mellitus.

METHODS AND RESULTS

We genotyped polymorphisms at nine established obesity loci in 1,395 women with diabetes from the Nurses' Health Study: 449 women developed CVD, and 946 women did not develop CVD. A genetic risk score (GRS) was derived by summing risk alleles for each individual. Four polymorphisms (rs9939609 [FTO], rs11084753 [KCTD15], rs10838738 [MTCH2], and rs10938397 [GNPDA2]) showed nominally significant associations with CVD. The GRS combining all obesity loci was linearly related to CVD risk (P = 0.013 for trend). The odds ratio was 1.08 per risk allele (95% confidence interval, 1.02-1.15; P = 0.01) after adjustment for body mass index and other conventional risk factors. Women with the highest quartile of GRS had 53% (95% confidence interval, 6%-122%) increased CVD risk, compared with those in the lowest quartile of GRS (P = 0.024). In addition, a higher GRS was associated with lower adiponectin levels (P = 0.02). Further adjustment for body mass index and other covariates did not change the association (P = 0.006). A higher GRS was also correlated with lower levels of high-density lipoprotein (P = 0.01).

CONCLUSIONS

Obesity-predisposing variants may jointly affect CVD risk among women with diabetes.

Interaction of ADIPOQ genetic polymorphism with blood pressure and plasma cholesterol level on the risk of coronary artery disease

BACKGROUND

The protective effect of +45T >G polymorphism in the adiponectin gene (ADIPOQ) on coronary artery disease (CAD) has been demonstrated in European populations, so this study investigated the effect of +45T >G polymorphism on the risk of CAD and its interactions with other metabolic risk factors in a Chinese population.

METHODS AND RESULTS

The +45T >G polymorphism (rs2241766) of ADIPOQ was genotyped in 600 patients with angiographically diagnosed CAD and in 718 controls. The G allele at the +45T >G polymorphism was associated with a lower risk of CAD (odds ratio (OR), 0.76; 95% confidence interval (CI), 0.64-0.89; P=0.001). The protective effect of the G allele at +45T >G polymorphism was magnified at blood pressure <140/90 mmHg (OR, 0.65; 95%CI, 0.51-0.82; P=0.0004), but disappeared at blood pressure >or=140/90 mmHg (OR, 0.98; 95%CI, 0.76-1.28; P=0.93), indicating an interaction between +45T >G polymorphism and blood pressure on CAD risk (P=0.02 for interaction). A similar interaction was also observed between plasma cholesterol level and the +45T >G polymorphism.

CONCLUSIONS

An association of ADIPOQ genetic polymorphism with CAD risk is modified by traditional risk factors, such as blood pressure and plasma cholesterol level.

Perspectives on adipose tissue, chagas disease and implications for the metabolic syndrome

The contribution of adipose tissue an autocrine and endocrine organ in the pathogenesis of infectious disease and metabolic syndrome is gaining attention. Adipose tissue and adipocytes are one of the major targets of T. cruzi infection. Parasites are detected 300 days postinfection in adipose tissue. Infection of adipose tissue and cultured adipocytes triggered local expression of inflammatory mediators resulting in the upregulation of cytokine and chemokine levels. Adipose tissue obtained from infected mice display an increased infiltration of inflammatory cells. Adiponectin, an adipocyte specific protein, which exerts antiinflammatory effects, is reduced during the acute phase of infection. The antiinflammatory regulator peroxisome proliferator activated receptor-γ (PPAR-γ) is downregulated in infected cultured adipocytes and adipose tissue. T. cruzi infection is associated with an upregulation of signaling pathways such as MAPKs, Notch and cyclin D, and reduced caveolin-1 expression. Adiponectin null mice have a cardiomyopathy and thus we speculate that the T. cruzi-induced reduction in adiponectin contributes to the T. cruzi-induced cardiomyopathy. While T. cruzi infection causes hypoglycemia which correlates with mortality, hyperglycemia is associated with increased parasitemia and mortality. The T. cruzi-induced increase in macrophages in adipose tissue taken together with the reduction in adiponectin and the associated cardiomyopathy is reminiscent of the metabolic syndrome.