Inhibition of adipogenesis by ghrelin

Ghrelin, a novel gastric hormone, regulates food intake and energy metabolism via central mechanisms. The peripheral effect of ghrelin on adiposity is poorly understood. We established a stable 3T3-L1 cell line expressing ghrelin to study the direct effect of ghrelin on adipogenesis. Cells overexpressing ghrelin demonstrate significantly attenuated differentiation of preadipocytes into adipocytes. Expression of peroxisome proliferator-activator receptor-gamma is significantly inhibited as demonstrated by decrease of peroxisome proliferator-activator receptor-gamma mRNA and protein. Both ghrelin overexpression and exogenous ghrelin stimulate cell proliferation. Phosphorylation of mitogen-activated protein kinase is increased after treatment of cells with ghrelin. Ghrelin binding activity is demonstrated in both native and ghrelin-overexpressing 3T3-L1 cells by radiolabeled ghrelin, although reverse transcription-polymerase chain reaction with the primer sequence of the previously identified ghrelin receptor subtypes detected no signal. Our results demonstrate that ghrelin inhibits adipogenesis by stimulation of cell proliferation via the mediation of a ghrelin receptor, likely a novel unidentified subtype.