Reduced glucose incorporation to triglycerides following chronic exposure of human fat cells to growth hormone

Using the tissue culture technique we have recently demonstrated that long-term exposure of human adipose tissue to human growth hormone (GH) in vitro leads to an impairment in glucose incorporation into triglycerides. This effect was further studied in the present investigation. Biopsies of human adipose tissue which had been cultured for one week with or without GH were studied in subsequent short-term incubations where the conversion of glucose to CO2 and to total lipids was determined. The formation of CO2 was not changed by previous exposure of the biopsies to GH whereas the incorporation of glucose into triglycerides was reduced by about one third. Total glucose metabolism, as determined from the sum of the two pathways, was significantly reduced. The activities of three glycolytic enzymes were determined in biopsies of human adipose tissue which had been cultured with or without GH for one week. The activity of phosphofructokinase was reduced, while the hexokinase and the glucose-6-phosphate dehydrogenase activities were unchanged. The diminished activity of phosphofructokinase, the enzyme considered to be rate-limiting for glycolysis in human fat cells, may be responsible for the decreased rate of glucose metabolism found.