Insulin stimulates the expression of basic fibroblast growth factor in rat brown adipocyte primary culture

The effect of insulin on the hyperplasia of brown adipose tissue (BAT) was investigated using the primary culture of rat brown adipocyte precursor cells (RBAC). Results showed insulin to significantly increase the number of RBAC, but not bovine capillary endothelial cells, in the presence of fetal bovine serum. Insulin also increased the expression of basic fibroblast growth factor (bFGF) mRNA and the related protein in the primary culture of RBAC. In addition, insulin enhanced the capillary growth in an in vitro angiogenesis model in which microvascular fragments and RBAC isolated from rat BAT were grown in coculture. The level of bFGF-related protein in the coculture was higher in the presence of insulin than in the absence of insulin. These findings suggest that insulin may play an important role in the proliferation as well as in the differentiation of brown adipocytes, with resulting hyperplasia of BAT (including the formation of new capillaries) through increased production of bFGF in brown adipocytes.