Accumulation of visceral fat, more so than subcutaneous fat, is strongly associated with severe metabolic complications. However, the factors regulating depot-specific adipogenesis are poorly understood. In this study, we show differential expression of pregnancy-associated plasma protein-A (PAPP-A), a secreted regulator of local insulin-like growth factor (IGF) action, in adipose tissue of mice. PAPP-A mRNA expression was 5-fold higher in visceral (mesenteric) fat compared to subcutaneous (inguinal, subscapular), peri-renal, and brown fat of mice. To investigate the possible role of depot-specific PAPP-A expression in fat accumulation, wild-type (WT) and PAPP-A knock-out (KO) mice were fed a high-fat diet (HFD) for up to 20 weeks. Adipocyte size increased in subcutaneous and peri-renal depots similarly in WT and PAPP-A KO mice. However, fat cell size and in vivo lipid uptake were significantly reduced in mesenteric fat of PAPP-A KO compared to WT mice. After 20 weeks on HFD, phosphorylation of AKT, a downstream signaling intermediate of IGF-I and insulin receptor activation, was significantly decreased by 50% in mesenteric compared to subcutaneous fat in WT mice, but was significantly increased 3-fold in mesenteric compared to subcutaneous fat in PAPP-A KO mice. This appeared to be due to enhanced insulin-stimulated signaling in mesenteric fat of PAPP-A KO mice. These data establish fat depot-specific expression of PAPP-A, and indicate preferential impact of PAPP-A deficiency on visceral fat in the mouse that is associated with enhanced insulin receptor signaling. Thus, PAPP-A may be a potential target for treatment and/or prevention strategies for visceral obesity and related morbidities.
- pregnancy-associated plasma protein-A
- visceral fat
- adipose tissue
- Copyright © 2013, American Journal of Physiology - Endocrinology and Metabolism