Receptor-mediated activation of ceramidase activity initiates the pleiotropic actions of adiponectin

Abstract

The adipocyte-derived secretory factor adiponectin promotes insulin sensitivity, decreases inflammation and promotes cell survival. To date, no unifying mechanism explains how adiponectin can exert such a variety of beneficial systemic effects. Here, we show that adiponectin potently stimulates a ceramidase activity associated with its two receptors, adipoR1 and adipoR2, and enhances ceramide catabolism and formation of its anti-apoptotic metabolite – sphingosine-1-phosphate (S1P), independently of AMPK. Using models of inducible apoptosis in pancreatic β-cells and cardiomyocytes, we show that transgenic overproduction of adiponectin decreases caspase-8 mediated death, while genetic adiponectin ablation enhances apoptosis in vivo through a sphingolipid-mediated pathway. Ceramidase activity is impaired in cells lacking both adiponectin receptor isoforms, leading to elevated ceramide levels and enhanced susceptibility to palmitate-induced cell death. Combined, our observations suggest a novel unifying mechanism of action for the beneficial systemic effects exerted by adiponectin, with sphingolipid metabolism as its core upstream component.