抄録
成長ホルモン分泌促進因子受容体の内因性リガンドとして探索がなされ,ラットの胃から発見されたプレリンは,強力な成長ホルモン分泌刺激作用を有するばかりでなく,摂食も強力に亢進させ,他に循環器系や中枢神経系,骨代謝系などでさまざまな生理作用を有することが判明している.特に,飢餓や空腹において,胃を中心にグレリンの多くが未梢臓器で分泌されて全身循環の中で,延髄の迷走神経核を介して末梢から視床下部への求心路と,胃に向かう遠心路の双方向性に末梢と中枢神経系をつなぐと考えられている.さらに,食欲調節系の中枢でもある弓状核にはブレリン分泌細胞も存在し,NPY//AgRPニューロンで摂食抑制作用を有するレフチンと拮抗的に作用する.臨床研究において,その血中濃度は体重と逆相関し,食事摂取直後から減少するなどの動態が判明しているが,摂食障害においては習慣化した嘔吐が血中濃度を上昇させることも判明しており,さらなる未知の生理作用や作用機序が想定されている.末梢と中枢を結び,心身の情報を双方向性に伝えてバランスを取るこのホルモンの作用は,心身相関の観点からも大いに興味を抱かせる.
Ghrelin which has been searched as a specific endogenous ligand for the growth hormone secretagogue receptor (GHS-R) and which was isolated from the stomach of a rat at last has a naturally powerful stimulus action growth hormone secretion. Furthermore, it was shown clearly that ghrelin had various physiological functions such as powerful appetite rise action, and other actions in the circulatory organ system, in the central nervous and the bone metabolism systems. Especially, in starvation, much of ghrelin, which is secreted by peripheral internal organs mainly in the stomach, reaches to vagal nuclei of the medulla oblongata through the whole body circulation and connects both directions of the afferent way going to hypothalamus and the efferent way going to the stomach. Furthermore, ghrelin-producing cells also exist in the arcuate nucleus which is also the center of an appetite regulation system. They act competitively on the leptin which has an appetite reduction action by the NPY/AgRP neuron. In clinical research, in was clarified that the concentration in the blood was reverse-correlated with weight, and decreasing from immediately after meal ingestion. In eating disorders, it is also made clear that habitual vomiting raises the concentration in blood. Thus, further unknown physiological functions of ghrelin are assumed. I think that these actions play an important role in the mind-and-body correlation by connecting the center to the tip, maintaining various physiological functions.
