CATECHOLAMINES AND METABOLISM OF HUMAN ADIPOSE TISSUE

Abstract

Abstract. The influence of glucose on the in vitro lipolysis of human omental adipose tissue has been studied. Omental tissue obtained at surgery during general anesthesia was incubated in Krebs‐Henseleit bicarbonate buffer containing 3% bovine albumin with and without added glucose (2 mg/ml). Glycerol release into the medium was considered as an index of lipolysis. Glucose enhanced the basal lipolysis and potentiated significantly the adipokinetic effects of noradrenaline, isopropylnoradrenaline and N6‐2′0‐dibutyryl cAMP (dibutyryl cAMP). The slope of glycerol release obtained for dibutyryl cAMP in glucose‐free versus glucose‐containing medium was significantly different from those obtained for noradrenaline and isopropylnoradrenaline. This difference might be explained if it is admitted that glucose stimulates lipolysis by acting on two different sites: (a) close to the triglyceride‐splitting enzyme system, and (b) close to the beta‐adrenergic receptor.In a second series of experiments the effect of glucose on the level of FFA was studied in tissue and in medium with noradrenaline present. No changes in the net release of FFA were observed, whereas a slight increase in the tissue level of FFA was demonstrated. These findings in human tissue are not in accordance with those previously described in rat epididymal fat pad, and do not justify the assumption that a decrease in the tissue level of FFA is the “trigger mechanism” for the lipolysis‐promoting effect of glucose.A marked decrease in the glycerol release was noticed when 2‐deoxy‐d‐glucose was added to medium containing noradrenaline, isopropylnoradrenaline and dibutyryl cAMP. The data are consistent with the view that glucose metabolism and the activity of triglyceride lipase are closely related.