Stimulatory and Inhibitory regulation of lipolysis by the NPR-A/cGMP/PKG and NPR-C/G i pathways in rat cultured adipocytes

Abstract

Objective Recent studies have suggested the abundant expression of natriuretic peptide receptor in adipose tissue. This study was designed to investigate the levels of natriuretic receptor-A (NPR-A) and NPR-C gene expression during the process of preadipocyte differentiation and its role in adipogenesis and lipid metabolism. Methods We measured mRNA levels of NPR-A and NPR-C during the process of rat preadipocyte differentiation in vitro. We also measured the effects of ANP and C-ANP, a ligand for NPR-C, on preadipocyte differentiation. In addition, we assessed the effects of ANP and C-ANP on lipolysis and the cellular mechanism. Results The mRNA levels of NPR-A and NPR-C on day 3, 6, 10 are (− 26%, + 226%), (+ 6%, + 568%), and (+ 207%, + 3232%) respectively as compared with day 1. ANP (10 − 7 M) and 8-bromo-cGMP (10 − 4 M) significantly increased Oil Red positive area and cell number of matured-adipocytes. ANP and 8-bromo-cGMP also increased the mRNA levels of adipocyte-related genes such as PPARγ, leptin, and adiponectin on day 3, whereas C-ANP did not change these parameters. ANP (10 − 9–10 − 6 M) increased intracellular cGMP levels and promoted lipolysis in adipocytes and the effects were abolished by HS-142-1, and KT5823. Conversely C-ANP (10 − 6 M) decreased intracellular cAMP levels and lipolysis and its effect was inhibited by PTX. Conclusion Results suggest that ANP may promote adipocyte differentiation and lipolysis via the NPR-A/cGMP/PKG pathway. Direct action of ANP via NPR-C in adipogenesis may be either absent or barely present, but ANP may play a counter regulatory role in lipolysis via NPR-C/Gi pathway.