Effects of prolonged incubation and cell concentration on lipogenesis from glucose in isolated human omental fat cells

The behavior of human omental fat cells in vitro has been examined in order to define conditions under which glucose is converted to glyceride-glycerol and glyceride fatty acids. Synthesis of glyceride fatty acids from glucose reached maximal rates only after several hours of incubation in Krebs- Henseleit bicarbonate buffer, with or without added bovine albumin. Conversion of glucose to glyceride fatty acids was readily demonstrable with concentrated cell suspensions and was stimulated 3- to 8-fold by insulin. With dilute cell suspen- sions, little fatty acid was synthesized even after prolonged in- cubation in the presence of insulin. Conversion of glucose to glyceride-glycerol was linear dur- ing 6-hr incubations in buffer and unaffected by the concen- tration of the cell suspension. In the presence of bovine albu- min, glyceride-glycerol synthesis was readily demonstrable at all cell concentrations used, although synthesis was faster in dilute suspensions. Thus, different incubation conditions produce widely diver- gent patterns of glucose metabolism cells.