The age-related inverse relationship between ob and lipogenic enzymes genes expression in rat white adipose tissue

To determine whether increase of serum leptin (the known natural inhibitor of lipogenic enzymes gene expression) concentration would account for the age-related decrease in lipogenesis (a) serum leptin concentration; (b) leptin mRNA abundance; (c) the rate of fatty acid synthesis in vivo; (d) lipogenic enzymes activity and (e) mRNA levels were assayed in white adipose tissue (WAT) of male young and old rats. We found that leptin mRNA abundance in WAT and serum leptin concentration was much lower in young than in old animals. In contrast, the rate of fatty acid synthesis in WAT was much higher in young animals. The old rats displayed much lower lipogenic enzymes activities (acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), ATP-citrate lyase (ACL), malic enzyme (ME), glucose 6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase 6PGDH) and mRNA abundance as compared to young rats. Considering the inverse relationship between serum leptin concentration and lipogenic enzymes genes expression and known inhibitory effect of leptin on lipogenic enzymes gene expression, one can conclude that the increase of ob gene expression could at least partly account for the reduced WAT lipogenic enzymes genes expression in old animals.