Abstract

Despite the importance of adipocyte formation for adipose tissue physiology, current knowledge about the mechanisms that regulate the recruitment of progenitor cells to undergo adipogenic differentiation is limited. A role for locally generated angiotensin II emerged from studies with human and murine cells. Preadipose cells from different human fat depots show reduced response to adipogenic stimuli when exposed to angiotensin II. This investigation sought to gain an insight into the intracellular mechanisms involved in the anti-adipogenic response of human preadipose cells from omental fat to angiotensin II. Its effect was evaluated on cells stimulated to adipogenic differentiation in vitro, by assessment of glycerol-3-phosphate dehydrogenase activity and expression of early markers of adipogenesis. Extracellular signal-regulated kinase 1,2 (ERK 1,2) pathway activation was inferred from the phosphorylated to total ERK1,2 ratio determined by western blot. Exposure to angiotensin II throughout the 10-day differentiation period resulted in a reduced adipogenic response. A similar anti-adipogenic effect was observed when this hormone was present during the first 48 h of induction to differentiation. Angiotensin II treatment had no consequences on CCAAT/enhancer-binding protein b and peroxisome proliferator-activated receptor ? (PPARG) induction, but increased the phosphorylated form of the key adipogenic regulator PPARG. Upon angiotensin II exposure, a raise of phosphorylated ERK 1,2 was determined, which was more prominent 8-20 h after induction of adipogenesis (when controls reached negligible values). Chemical inhibition of ERK 1,2 phosphorylation prevented angiotensin II-dependent reduction in adipogenesis. These results support the participation of the mitogen-activated protein kinase/ERK 1,2 pathway in the anti-adipogenic effect of angiotensin II on preadipose cells from human omental adipose tissue. © 2010 Society for Endocrinology.