Effect of a bovine hypothalamic extract on glucose utilization by rat adipocytes

This study was undertaken to assess whether a hypothalamic extract has any direct metabolic action on adipose and muscle tissues. An acid bovine hypothalamic extract (HE) was tested for its effect on the utilization of D[U-14C]glucose by isolated rat adipocytes and rat hemidiaphragms. The HE was ineffective in stimulating the conversion of labeled glucose into CO2 and glycogen by rat hemidiaphragm. However, in isolated adipocytes, the HE had significant lipogenic activity. This lipogenic effect was independent of insulin and nonsuppressible by insulin antibodies. The dose-response curve was linear and saturable. That insulin and the HE were not additive at maximal concentrations suggests that they act through a common rate-limiting step, possibly a receptor site. Other hypothalamic substances tested (thyrotropin-releasing hormone, luteinizing hormone-releasing hormone, and substance P) showed no lipogenic activity. Somatostatin (6 microgram/ml) was an insulin potentiator but only when preincubated with the fat cells. It is concluded that the hypothalamic regulation of body weight may be mediated by a neurohumoral mechanism affecting adipose tissue stores.