Regional differences in the expression of genes involved in lipid metabolism in adipose tissue in response to short- and medium-term fasting and refeeding

The aim of this study was to analyze regional differences in the time-course response to fasting and refeeding in the expression of genes involved in lipid metabolism in retroperitoneal, mesenteric and inguinal adipose tissue. Rats were studied under different feeding conditions: feeding state; after 4, 8 or 24 h of fasting; and after 3 h of refeeding following 8 h of fasting. The expression of lipogenesis-related genes decreased by fasting in adipose tissue, and the retroperitoneal depot showed the fastest response: mRNA levels of peroxisome proliferator-activated receptor gamma 2 (PPARγ2) decreased after 4 h of fasting and those of sterol regulatory element binding protein 1c (SREBP1c), fatty acid synthase (FAS), GPAT and glucose transporter 4 (GLUT4) decreased after 8 h. In the inguinal depot, mRNA levels of SREBP1c, acetyl-coenzyme A carboxylase alpha, FAS and lipoprotein lipase decreased after 8 h of fasting, while in the mesenteric depot, only GLUT4 and FAS mRNA levels decreased after 8 and 24 h, respectively. Concerning lipolytic and fatty acid oxidation genes, only adipose triglyceride lipase and carnitine palmitoyltransferase 1a expression increased after 24 h of fasting in the retroperitoneal depot. Three hours of refeeding restored the expression of the lipogenic transcription factors PPARγ2 and SREBP1c in the retroperitoneal depot and of PPARγ2 in the inguinal depot. This period of refeeding was ineffective in changing the expression of genes related with lipid mobilization and fatty acid oxidation, except hormone-sensitive lipase, whose expression decreased in the mesenteric depot. It is suggested that different regulations of the expression of genes related with lipid metabolism between internal and subcutaneous depots to feeding and fasting conditions are site-specific metabolic features of white adipose tissue.