在大白鼠急性心肌梗塞模式下探討Ghrelin基因表現之調控

Abstract

心臟冠狀動脈栓塞所引起的急性心肌梗塞，是世界各國常見的十大死因之一，而1999年Kojima等人從大鼠胃臟內分泌細胞中新發現的一種蛋白質『Ghrelin』則被研究證明具有保護心臟的功能。它是由28個胺基酸所組成的醯基化多胜，主要在胃臟、腦垂腺與下視丘存在，而在其他多種組織內也有少量發現。它引人注目的主要原因是與身體能量調節以及體重恆定有關，可以刺激生長激素釋放，增加食慾與肥胖發生。 此外，Ghrelin也具有其他多種作用，包括：抑制心肌細胞因AraC造成的細胞凋零；在健康的志願者中發現，在不會增加心跳速率的情況下可以減少心臟afterload與增加心輸出量；減少血管擴張；改善慢性心臟衰竭病人（CHF）的血液動力學；調節敗血性休克大鼠的心臟血管作用。 根據前人研究顯示，Ghrelin對心臟血管是有益的。然而，Ghrelin在心肌梗塞所扮演的調節角色卻少有人知，因此本論文的目的在探討心肌梗塞的模式中Ghrelin所扮演的調節角色。在本實驗中，利用Wistar雄性大白鼠在2.5月齡時，在其心臟冠狀動脈的左前下降支以手術方式結紮，引發其急性心肌梗塞，之後再依時間點取下心肌組織，做Ghrelin基因變化情形的分析。藉此瞭解此動物模式是否能提供作為ghrelin基因的研究，進而評估此基因的變化及其與心臟功能降低間的關係。 本研究證明Ghrelin會隨著心肌梗塞時間延長而在心肌缺血一天後至四週的左心室組織當中會增加表現，在五天時達到最高表現量。免疫組織染色加上血液動力學與超音波學之檢測可以確認北方墨點與西方墨點轉印法的結果，表示ghrelin可以持續表現，即使是在急性心肌梗塞的情況下。 使用ghrelin的基因治療將會被研究對於心肌梗塞是否成為有效的治療方式。本篇研究或許可以提供一項基礎資料，作為未來發展對於急性心肌梗塞，能夠提供更具療效的治療方式。

The acute myocardial infarction caused by coronary artery embolism is one of the common diseases around the world. A protein called ‘ghrelin’ was first isolated from rat stomach endocrine cells by kojima et al.in 1999 and its function of cardiac protection been proved found.It is a 28-amino-acid acylated peptide. It is found mainly in the stomach, pituitary and hypothalamus, but also found in numerous other tissues at lower levels. It could stimulate the release of growth hormone (GH) and also promote appetite and adiposity. In addition to other effects, it is involved in the regulation of energy balance and body weight homeostasis. In addition, ghrelin also has many effects, such as inhibiting cardiomyocyte AraC-induced apoptosis, reducing cardiac afterload and increasing cardiac output without increasing heart rate in healthy volunteers, inducing vasodilation, improving the haemodynamics of patients with chronic heart failure (CHF), and regulating cardiovascular function in rats suffering septic shock. According to previous studies, the fact that ghrelin has beneficial cardiovascular effects was confirmed. However, little is known about the regulation of ghrelin in response to myocardial infarction. The purpose of this study was to investigate the role of the ghrelin in myocardial infarction. In this experiment, acute myocardial infarction ( AMI ) is going to be produced in 2.5 month-old male Wistar rats by ligating proximal left anterior descending ( LAD ) coronary artery with 6-0 silk suture. Rat cardiac ventricular tissues will be collected for analyszing the change of ghrelin gene to realize whether such a murine model can be a used as a model of AMI for ghrelin and evaluate the relationship between the chage of ghrelin and decline of cardiac function ? After ligation of the left anterior descending coronary artery, expression of ghrelin significantly increased from 1 day to 4 weeks at left ventricle, and reached maximum at 5 days. Findings of Immuno- histochemical stain、hemodynamics and echocardiography can be confirmed the findings from Northern and Western blots. So it suggested that ghrelin could consist express even in AMI situation. Gene therapy with ghrelin gene will be studied to see whether such a treatment is effective for myocardial infarction. This study may provide a fundamental basis for the development of more effective therapies in AMI treatment.