Effects of food restriction on the hypothalamic prepro-orexin gene expression in genetically obese mice

Orexins, which are identical to hypocretins, are novel hypothalamic orexige nic peptides. We examined the effects of food restriction on the expression of the prepro-orexin gene in control (C57Bl/6J) and genetically obese mice (ob/ob and db/db), using in situ hybridization histochemistry. Dry food wa s given 3 g/day to each obese mouse for 2 weeks. Food restriction caused a significant increase of the prepro-orexin gene expression in obese mice in comparison with ad libitum fed animals. Although the levels of the expressi on of the preproorexin gene in obese mice were significantly lower than tho se in C57Bl/6J mice during feeding ad libitum, food restriction caused an i ncrease in the expression of the prepro-orexin gene in the hypothalamus of obese mice. The expression of the neuropeptide Y (NPY) gene was increased s ignificantly in the arcuate nucleus of obese mice compared to that of contr ol mice during feeding ad libitum, Food restriction for 2 weeks also caused a significant increase of the expression in the NPY gene in all groups. Th ese results indicate that the hypothalamic prepro-orexin gene could be upre gulated by food restriction without leptin signal in genetically obese mice . (C) 2000 Elsevier Science Inc.