Depot-Specific Differences in the Effects of IGF-1, HGF and VEGF on Human Preadipocytes Proliferation and Differentiation

Introduction Accumulating evidence suggests that adipose tissue is a dynamic organ that undergoes expansion and contraction in response to energy demands and obesity-associated tissue injury. The dynamic nature of the adipose tissue is achieved via changes in both size and number of mature adipocytes through adipocyte hypertrophy and preadipocytes proliferation and differentiation respectively. These changes are mediated through various growth factors and cytokines secreted by cells within the adipose tissues (Spalding et al. 2008). Hypertrophied adipocytes secrete cytokines such as IL-6 that can trigger macrophage infiltration and secretion of IL-1β, TNFα and IL-8 (Bjorntorp 1974; Kobashi et al. 2009), causing impairment of preadipocytes differentiation and induction of insulin resistance (Gustafson et al. 2007; Veilleux et al. 2009). TNFα-stimulates HGF release from fibroblasts and monocytes within the adipose tissue serving as a potent mitogenic factor (Bell et al. 2008). Mature adipocytes secrete IGF-...