促食素对能量平衡代谢的调节作用

促食素(orexin)，也称作下丘脑分泌素(hypocretin)，是一种在下丘脑外侧区表达的神经肽。促食素能神经纤维终端在大脑内投射广泛，其受体在脑内也广泛分布。促食素信号涉及到多种生理过程的整合，如觉醒、摄食、自主活动、奖赏寻求以及自主神经功能控制等。促食素能神经通过对多种生理活动的调节而参与机体的能量代谢。本文基于促食素生理功能及其兴奋调节的研究进展，探讨了促食素能神经在能量代谢平衡中的调节作用。促食素受血糖、饥饿素及瘦素的调节，饥饿时血糖的降低及饥饿素的升高，或者消瘦时瘦素水平的降低均能提高促食素神经元的兴奋性，进而促进觉醒、自主活动及摄食动机。同时促食素通过交感神经升高血压、提高心率及葡萄糖的利用等为获取食物的行为做准备，另一方面还通过迷走神经促进胃酸分泌和胃运动为消化食物做好准备。进食后受血糖升高及活动期伴随能量消耗而积累的腺苷等信号的影响，促食素神经元兴奋性下降，促食素分泌减少，个体表现出意欲低下、少动及睡眠发生以利于节约及储存能量。可见，促食素功能系统为机体整合了合理的能量摄取和利用机制，为生命活动维持必要的能量代谢平衡。 

Actions of orexin in the regulation of energy balance metabolism

Orexin, also known as hypocretin, is a neuropeptide which is expressed by the neurons in the lateral hypothalamic area. The orexinergic nerve fiber terminals project widely in the brain and its receptors also widely distribute in the brain. The signal of orexin involves the integration of many physiological processes, such as arousal, feeding, spontaneous activity, reward seeking, as well as function control of autonomic nerve. Orexinergic nerve participates in the energy metabolism of the body through the regulation of multiple physiological activities. Based on the research progress on physiological functions of orexin and regulations of orexin neuron excitation, we have analyzed and explored the regulatory role of the orexin nerve in the balance of energy metabolism. Orexin is regulated by blood glucose, ghrelin and leptin. The decrease of blood glucose or the increase of ghrelin when an individual is hungry or decreases of leptin in an emaciation patient can all enhance excitability of orexin neurons, so as to promote awakening, activities and motivation of ingestion. Meanwhile, orexin makes the individual prepare for gaining food by increasing blood pressure, heart rate and the use of glucoses through sympathetic nerves. It can also make the digestive system ready for digesting food by promoting gastric acid secretion and gastric motion through vagus nerves. After feeding, following the increase of blood glucose and accumulation of adenosine which occurs while energy is consumed during activities, the excitability of orexin neurons decreases and the secretions of orexin reduces, leading to low desire, less movement and sleep of the individual, so as to save and store energy. Thus, orexinergic system has integrated a mechanism for the individual to intake and apply energy, and is maintaining the necessary balance of energy metabolism for life activities.