Enzymes related to lipogenesis in the adipose tissue of obese subjects.
In a group of ten adult obese subjects, maintained for 15 days on a normal caloric intake and balanced diet, the activity of hexokinase (EC 2.7.1.1),6-phosphofructokinase (EC 2.7.1.11), and ATP citratelyase (EC 4.1.3.8) in the adipose tissue was significantly increased, both on a protein and on a fat cell number basis, compared to matched normal subjects. The activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49), malate dehydrogenase (EC 1.1.1.37), and malate dehydrogenase (decarboxylating) (NADP) (EC 1.1.1.40), on the other hand, was unchanged. Since both hexokinase and 6-phosphofructokinase are rate-limiting in glycolysis, their enhanced activity would indicate the occurrence of an increased capacity to metabolize glucose and therefore to generate alpha-glycerophosphate. The elevation of ATP citrate-lyase would suggest increased lipogenesis, owing to the regulatory role that this enzyme plays in fatty acid synthesis. The normal activity of glucose-6-phosphate dehydrogenase and malate dehydrogenase (decarboxylating) (NADP), which supply NADPH for the reduction of acetyl-CoA to fatty acids, would suggest that the change in lipogenesis is of moderate degree, thereb) affecting only the most rate-limiting enzyme, ATP citrate-lyase. These data, on the whole, are consistent with the occurrence of enhanced triglyceride formation. Whether the enzyme changes observed are adaptive or genetic in nature remains to be clarified.
D001275:ATP Citrate (pro-S)-Lyase / Q000378:metabolism; D000273:Adipose Tissue / Q000201:enzymology*; D000328:Adult; D000368:Aged; D002986:Clinical Trials as Topic; D005260:Female; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism; D006801:Humans; D008055:Lipids / Q000096:biosynthesis*; D008291:Malate Dehydrogenase / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000201:enzymology* / Q000235:genetics; D010732:Phosphofructokinase-1 / Q000378:metabolism
D008055:Lipids; D008291:Malate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D001275:ATP Citrate (pro-S)-Lyase; D006593:Hexokinase; D010732:Phosphofructokinase-1