Differential effect of long-term food restriction on fatty acid synthase and leptin gene expression in rat white adipose tissue.

Long-term food restriction (85%, 70% and 50% of ad libitum energy intake for one month) induced a substantial fall in serum leptin concentration and leptin mRNA levels in epididymal white adipose tissue in rats. Surprisingly, this suppression was not reversed by refeeding ad libitum for 48 h. The reduction in serum leptin concentration and leptin mRNA level did not strictly correlate with reduction in fat or body mass. Unlike serum leptin concentration and epididymal adipose tissue leptin mRNA levels, fatty acid synthase activity, fatty acid synthase protein abundance and fatty acid synthase mRNA levels increased significantly in white adipose tissue after refeeding rats subjected to food restriction. The increase in serum insulin concentration was observed in all groups on different degrees of food restriction and refed ad libitum for 48 h compared to controls. A decrease in serum insulin concentration was found in the rats not refed before sacrifice. Long-term food restriction did not significantly affect serum glucose concentrations in either refed or non-refed rats. The data reported in this paper indicate that there is no rapid rebound in serum leptin concentration or leptin gene expression in contrast to the increase in serum insulin concentration and fatty acid gene expression in white adipose tissue of rats refed ad libitum after one month's food restriction.