Signalling mechanisms underlying the metabolic and other effects of adipokines on the heart

Adipokines represent a family of proteins released by adipocytes that affect various biological processes including metabolism, satiety, inflammation, and cardiovascular function. The first adipokine to be identified is leptin, a product of the obesity gene whose primary function is to act as a satiety factor. However, it is now recognized that leptin and many of the newly discovered adipokines produce effects on numerous organ systems including the heart. Indeed, various adipokines including leptin, adiponectin, and apelin exert potent and diverse cardiovascular effects which are mediated by their specific receptors and involve complex and multifaceted cell-signalling pathways. Among these are effects on the heart as well as blood pressure where leptin has been proposed to potentially contribute to obesity-related hypertension. In this review, we focus primarily on the diverse effects of adipokines on the heart and discuss the potential cell-signalling mechanisms underlying their actions. The potential role of adipokines in the regulation of cardiac metabolism and function is discussed. Discussion is also presented on the emerging role, both deleterious and salutary, of various adipokines in heart disease with an examination of the possible underlying mechanisms which contribute to these effects.