Catecholamines and Metabolism of Human Adipose Tissue

Human omental adipose tissue under basal incubation conditions incorporates glucose‐l‐ 14 C in glycerideglycerol (62%) and glyceride‐fatty acids (38%). Studies either on incorporation of glucose‐l‐ 14 C into lipids or on re‐esterification of FFA show that noradrenaline and adrenaline prominently stimulate the synthesis of triglycerides in human omental tissue in vitro. The stimulation on conversion of glucose‐l‐ 14 C into glyceride‐fatty acid was at least as pronounced as on the incorporation of label into glyceride‐glycerol. The increase in lipogenesis (glucose incorporation into adipose glycerides measured in vitro) was attributed to the enhanced triglyceride breakdown, since other lipolytic agents, isopropylnoradrenaline, dibutyryl‐cAMP, and addition of low concentration of phentolamine to noradrenaline‐containing medium produced similar changes. Furthermore, lipogenesis was diminished when either noradrenaline‐induced lipolysis was inhibited by propranolol or when the effect of other lipolytic agents was suppressed by high concentration of phentolamine. The only lipolytic agent which had no stimulating effect on lipogenesis, and even inhibited this process when added at high concentration, was theophylline. The inhibitory effect of theophylline was not prevented by the addition of different concentrations of 5′AMP, and the mechanism for its effect on lipogenesis remains unknown.