Proliferating bovine intramuscular preadipocyte cells synthesize leptin.

Leptin is thought to be not only a satiety factor but also a stimulator of angiogenesis. We examined leptin, PPARγ2, and vascular endothelial growth factor (VEGF) expression in bovine intramuscular preadipocyte (BIP) cells during proliferation. The cells were seeded at 0.85 × 10(4) cells/cm(2) and collected every day until the fifth day after passage. Leptin mRNA was present in the cells between days 2 and 4, as indicated by RT-PCR analysis. Western blot analysis showed a band for leptin at approximately 16 kDa on all of the days during growth, and the cytoplasmic concentration of leptin was highest on day 2 and decreased gradually thereafter. A PPARγ2 band at approximately 54 kDa was also observed on all days. The concentration was highest on day 2 and decreased thereafter, which is similar to the expression pattern of leptin. In constant, the expression level of VEGF protein did not change while in culture. We have demonstrated that BIP cells can synthesize both leptin and PPARγ2, with maximal synthesis occurring during maximal proliferation. Given the role of leptin in angiogenesis, we speculate that leptin is involved in the neovascularization of adipose tissue, because new organization of adipose tissue requires the growth of new blood vessels.