Abstract
Apelin is an adipokine secreted by adipocytes. Co-expression of apelin and apelin receptor (APJ) in adipocytes implies the autocrine regulations of apelin on adipocyte functions through yet unknown molecular mechanisms. In the present study, we provide evidence that apelin, through its interaction with APJ receptor, inhibits adipogenesis of pre-adipocytes and lipolysis in mature adipocytes. The detailed molecular pathways underlying apelin signaling is proposed based on our experimental observations. Specifically, we show that apelin suppresses adipogenesis through MAPK kinase/ERK dependent pathways. And by preventing lipid droplet fragmentation, apelin inhibits basal lipolysis through AMP kinase dependent enhancement of perilipin expression and inhibits hormone-stimulated acute lipolysis through decreasing perilipin phosphorylation. Apelin induced decrease of free fatty acid release can be attributed to its dual inhibition on adipogenesis and lipolysis. This study suggests that the autocrine signaling of apelin may serve as a novel therapeutic target for obesity and other metabolic disorders.