The metabolic effects of ghrelin on muscle, adipose and liver.

胃饥饿素是一种胃肽，以其促氧（食欲刺激）作用而闻名。血浆胃饥饿素浓度在进餐前急剧上升，在进食后下降。胃饥饿素以两种亚型存在，酰化（AG）和去酰化（DAG）胃饥饿素。AG被认为是生物活性形式的促氧作用，虽然DAG最近被证明对外周组织有代谢作用。AG是生长激素促分泌受体亚型1a （GHS-R1a）的配体，并启动生长激素（GH）的释放。许多研究表明，胃促生长素输注会损害血液中葡萄糖的清除；然而，这些研究使用的剂量范围很广，通常是非生理性的，并且无法区分生长素的直接作用和由于生长激素的继发性增加而产生的作用。据推测，胃饥饿素是一个重要机制的一部分，通过刺激生长激素释放，从而促进脂肪分解和血糖保存，在长时间禁食期间防止极端低血糖。令人惊讶的是,

Ghrelin is a gastric peptide best known for its orexigenic (appetite-stimulating) effects. Plasma ghrelin concentrations rise sharply prior to entrained mealtimes and decline following the consumption of food. Ghrelin exists as two isoforms, acylated (AG) and deacylated (DAG) ghrelin. AG is considered the bioactive form in terms of orexigenic actions, although DAG has recently been demonstrated to have metabolic effects on peripheral tissues. AG is a ligand for the growth hormone secretagogue receptor subtype 1a (GHS-R1a) and initiates growth hormone (GH) release. A number of studies suggest that ghrelin infusion impairs the clearance of glucose from the blood; however, these studies utilize a wide range of dosages which are often nonphysiological, and are unable to distinguish between the direct effects of ghrelin vs. those due to the secondary increase in GH. It has been postulated that ghrelin is part of an important mechanism to prevent extreme hypoglycemia during a prolonged fast by stimulating GH release and thereby facilitating lipolysis and the preservation of blood glucose. Surprisingly, the