Obese reversal by a chronic energy restricted diet leaves an increased Arc NPY/AgRP, but no alteration in POMC/CART, mRNA expression in diet-induced obese mice.

Weight regain after weight loss is a major hurdle for combating obesity. The aim of this study is to examine orexigenic and anorectic neuropeptides of the hypothalamic arcuate nucleus (Arc) in response to weight loss after chronic energy intake restriction. Thirty mice were fed with a high-fat diet for 8 weeks and then classified as diet-induced obese (DIO; n=10) or diet-resistant (DR; n=10) mice according to the highest and lowest body weight gainers. Five mice from DIO and DR groups were placed on an energy restricted diet or continued on their high-fat diet ad libitum for 6 weeks. An additional five mice were on a LF diet throughout the course of this study as controls. Results showed that a six-week energy restricted diet completely reversed the increased body weight, fat mass and leptin in the DIO mice to the levels of the LF and DR mice. Arc neuropeptide Y (NPY) and agouti-related protein (AgRP) mRNA expression in DIO mice after obesity reversal were significantly higher than DIO mice without obesity reversal (17%, 47%, both p<0.05), while the Arc pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) mRNA showed no difference. Both NPY and AgRP expression in DIO mice were negatively correlated with plasma leptin (R=-0.78, p<0.05; R=-0.72, p<0.05). In conclusion, while chronic energy restriction will lead to weight loss, it can up-regulate hypothalamic orexigenic peptides, which may be an important contributing factor to weight regain after a weight loss program from an energy restricted diet.