Endocrine Abstracts

Obesity is linked to the development of insulin resistance, diabetes and an increased risk of cardiovascular disease and the metabolic syndrome. Adipose tissue-derived proteins so termed ‘adipokines’ have been implicated in cardiovascular disease and the metabolic syndrome although the molecular mechanisms are not fully understood. Adiponectin, unlike other adipokines, has been shown to have anti-inflammatory, anti-atherogenic, and insulin-sensitising effects. Importantly, circulating adiponectin levels are inversely correlated with cardiovascular risk factors such as C-reactive protein (CRP), and hypercholesterolemia. Adiponectin exerts its effects by activating two families of seven transmembrane domain receptors, functionally distinct from G protein-coupled receptors, termed AdipoR1 and AdipoR2. Given the widespread distribution of adiponectin receptors and the observation that adiponectin is synthesised in other tissues, including skeletal muscle we hypothesised that adiponectin is present in the human heart and may therefore act locally. Therefore, in this study we investigated the expression of adiponectin and its receptors across the regions of the human heart.

To assess adiponectin receptor expression in the adult heart, we used a human cardiovascular multiple tissue cDNA panel. RT-PCR analysis revealed aberrant expression of both adipoR1 and adipoR2 genes in whole fetal and adult heart and in the following compartments of the adult human heart: aorta, apex of the heart, left atrium, right atrium, right auricle, left auricle, left ventricle, right ventricle, interventricular septum, and atrioventricular node. Interestingly, adiponectin expression was more confined in left atrium and right atrium and in the left ventricle and right ventricle. Immunohistochemical analysis confirmed protein expression of both adiponectin receptors in human adult and fetal hearts. These novel data demonstrate the presence of both adiponectin receptors across the human heart, with interesting regional the adiponectin gene. Our study potentially implicates adiponectin and its receptors in signalling mechanisms in the heart.