Differential effect of prolonged food restriction and fasting on hypothalamic malonyl-CoA concentration and expression of orexigenic and anorexigenic neuropeptides genes in rats

Abstract

Several lines of evidence suggest that malonyl-CoA in the hypothalamus plays an important role in monitoring and modulating body energy balance. In fasted state the level of malonyl-CoA concentration significantly decreases. Simultaneously, orexigenic neuropeptides (NPY - neuropeptide Y, AgRP - agouti-related peptide) genes are expressed at high level, whereas anorexigenic neuropeptides (CART - cocaine-and amphetamine-regulated transcript, POMC - proopiomelanocortin) genes are expressed at low level. When food intake resumes, opposite effect is observed. This study examined the effect of prolonged food restriction, common in humans trying to lose body weight on expression of orexigenic and anorexigenic neuropeptides genes and on malonyl-CoA content in rat whole hypothalamus. We observed an increase of NPY and AgRP mRNA levels in hypothalamus of rats kept on 30 days-long food restriction (50% of the amount of food consumed by controls). Simultaneously, a decrease of CART and POMC mRNA levels occurred. Refeeding caused a decrease in NPY and POMC mRNA levels without effect on AgRP and CART mRNA. Surprisingly, both prolonged food restriction and food restriction/refeeding caused the increase of malonyl-CoA level in whole hypothalamus. In contrast, fasting for 24h caused the decrease of malonyl-CoA level, which was associated with the up-regulation of NPY and AgRP genes expression and down-regulation of CART and POMC genes expression. After refeeding opposite effect was observed. These results indicate that prolonged food restriction and acute fasting, conditions in which energy expenditure exceeds intake, differentially affect malonyl-CoA concentration and similarly affect orexigenic and anorexigenic neuropeptide genes expression in whole rat hypothalamus.