Effects of fat depot site on differentiation-dependent gene expression in rat preadipocytes

Variability in physiological characteristics among adipose depots could be caused, in part, by mechanisms intrinsic to cells comprising the depots. To evaluate the contribution of intrinsic mechanisms to depot variability, we studied levels of differentiation-dependent mRNAs in differentiating cultured rat epididymal and perirenal preadipocytes and in fat cells isolated from these depots. The magnitude of the change in levels of adipsin and glycerol-3 phosphate dehydrogenase mRNAs, which increase late during differentiation, was greater in perirenal than epididymal preadipocytes. The magnitude of the change in beta-actin mRNA, which decreases early during differentiation, was not site-dependent. Effects of anatomic site on changes in differentiation-dependent mRNAs observed in differentiating preadipocytes in vitro were similar to effects of site on these mRNAs in freshly isolated fat cells: those mRNA species whose levels increase late during preadipocyte differentiation were present in greater abundance in perirenal than epididymal fat cells. Hence, mechanisms which underlie site-dependent variability in adipose function may be intrinsic and could become evident midway through the differentiation process.