Characterization of α-MSH browning effect in diverse mice white adipose tissue depots

Abstract

White adipose tissue (WAT) browning is a potent mechanism to dissipate energy as heat and, thus, its activation constitutes a promise therapeutic approach to obesity. We previously reported the melanocortin α-melanocyte stimulating hormone (α-MSH) ability to increase the number of beige cells in subcutaneous inguinal WAT (ingWAT) in high fat diet (HFD)-fed mice. The current study examined the browning effect of intraperitoneally administered α-MSH on diverse fat depots from mice fed with HFD or standard rodent diet (SD). For this, mRNA expression of browning hallmark genes was quantified concomitantly with histological examination of the adipose tissue samples (epidydimal - eWAT, mesenteric – mWAT, retroperitoneal – rpWAT or ingWAT). As well, α-MSH impact on body weight, serum profile, WAT mass and lipolytic rates were evaluated. In the visceral depots mWAT, eWAT and rpWAT from HFD-fed mice, α-MSH was not able to induce a browning mechanism. Surprisingly, in SD-fed mice, α-MSH decreased the expression of several beige-specific genes in rpWAT and promoted an increase of the size of lipid droplets. No browning effect was observed in ingWAT from SD-fed mice. We also verified that HFD ingestion per se stimulated the browning mechanisms in rpWAT, but not in mWAT and eWAT. In conclusion, the fat depots from diverse anatomical locations respond differently to α-MSH treatment when exposed to different diets.