Adiponectin expression and metabolic markers in obesity and Type 2 diabetes

Abstract

Adiponectin has emerged over the last decade as a key adipokine linking obesity, insulin resistance, and Type 2 diabetes. However, the molecular mechanisms controlling adiponectin expression in adipose tissue are not fully elucidated. Furthermore, increasing evidence indicates that peroxisome proliferator-activated receptor- γ (PPAR-γ) plays an important, and beneficial, role in modulating adiponectin expression. The aim of the present study was to assess the separate role of obesity and Type 2 diabetes in the relationship between endogenous PPAR-γ signaling and adiponectin expression in subcutaneous adipose tissue. Enzyme-linked immuno sor bent assay and real time quantitative PCR analysis were carried out in overweight, obese, and/or diabetic Tunisian patients who underwent an abdominal surgery. These results collectively indicate that circulating levels of adiponectin were decreased in all overweight, obese, and/or diabetic (p<0.001). However, the subcutaneous mRNA expression of adiponectin was reduced only in diabetics (p<0.01) but presents some discrepancies in obese individuals. Moreover, mRNA levels of adiponectin were positively correlated with levels of mRNA encoding PPARγ and its heterodimeric partner retinoid X receptor-α (RXR-α), in both obese and diabetic patients. Our study on Tunisian patients shows impaired regulation of circulating and mRNA adiponectin levels dependent of metabolic disorders in obesity and Type 2 diabetes. The data suggest that subcutaneous adipose tissue may play an important role in modulating adiponectin expression in diabetes and obesity. Moreover, adiponectin mRNA could be potentially regulated by endogenous PPARγ/RXRα-dependent pathways.