Involvement of a cGMP-dependent pathway in the natriuretic peptide-mediated hormone-sensitive lipase phosphorylation in human adipocytes

Our previous studies have demonstrated that natriuretic peptides (NPs), peptide hormones with natriuretic, diuretic, and vasodilating properties, exert a potent control on the lipolysis in human adipocytes via the activation of the type A guanylyl cyclase receptor ( 1, 2). In the current study we investigated the intracellular mechanisms involved in the NP-stimulated lipolytic effect in human preadipocytes and adipocytes. We demonstrate that the atrial NP (ANP)-induced lipolysis in human adipocytes was associated with an enhanced serine phosphorylation of the hormone-sensitive lipase (HSL). Both ANP-mediated lipolysis and HSL phosphorylation were inhibited in the presence of increasing concentrations of the guanylyl cyclase inhibitor LY-83583. ANP did not modulate the activity of the cAMP-dependent protein kinase (PKA). Moreover, H-89, a PKA inhibitor, did not affect the ANP-induced lipolysis. On primary cultures of human preadipocytes, the ANP-mediated lipolytic effect was dependent on the differentiation process. On differentiated human preadipocytes, ANP-mediated lipolysis, associated with an increased phosphorylation of HSL and of perilipin A, was strongly decreased by treatment with the inhibitor of the cGMP-dependent protein kinase I ( cGKI), Rp-8-pCPT-cGMPS. Thus, ANP-induced lipolysis in human adipocytes is a cGMP-dependent pathway that induces the phosphorylation of HSL and perilipin A via the activation of cGKI. The present study shows that lipolysis in human adipocytes can be controlled by an independent cGKI-mediated signaling as well as by the classical cAMP/PKA pathway.