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[Summary] The neuropeptides orexin A and orexin B are involved in numerous central regulation processes such as energy homeostasis,sleeping behaviour,and neuroendocrine activities.Orexin receptors are expressed in a variety of tissues besides the brain,adrenal gland for example.The article reviews the effect of orexin on adrenal gland function.
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Objective To evaluate the relationships of the expression of orexin A in hypothalamus with hyperleptinemia, hyperinsulinism, and hyperlipidemia in alimentary obesity rats.Methods The alimentary obesity rat model was induced by high-fat diet in Wistar rats. The levels of leptin, insulin, C-peptide, total cholesterol (TC) and triglyeride (TG) were detected by luminescent immunoassay and biochemistry enzymic method. The gene expression of orexin A in rat hypothalamus was detected by real-time PCR. The correlation between orexin A and leptin was analyzed. Results After 8 weeks of high-fat diet feeding, the body weight, Lee's index, blood glucose, TG and TC significantly increased in obesity rat group (P＜0. 01). The levels of serum leptin, insulin and C-peptide were significantly higher in obesity rats than in controls [( 1.74±0. 36)μg/Lvs. (1.27±0.11) μg/L, (35±5) MIU/L vs. (23±4) MIU/L, (0.21±0.04) μg/L vs.(0. 14±0. 03) μg/L respectively, P＜0.01]. However, the level of orexin A mRNA was lower in obesity rats than in controls (6.8±2.3 vs. 14.5±3.6, t=-8.06, P＜0.01). The correlation coefficient (r) of orexin A mRNA with serum leptin, insulin, and C-peptide in alimentary obesity rat were -0. 726 (P＜0.01), -0. 506 (P＜0.01) and -0. 664 (P＜0.01), respectively. Conclusions High-fat diet can induce leptin-resistance and alimentary obesity in Wistar rat. The down-regulation of orexin A in rat hypothalamus would be correlated closely to the leptin and insulin resistance in alimentary obesity.