2012-08-012024-05-14https://scholars.lib.ntu.edu.tw/handle/123456789/657111摘要：同半胱胺酸(homocysteine) 是體內一種內生性的含硫胺基酸，是methionine 胺基酸代謝途徑的中間產物，目前已知血漿中同半胱胺酸濃度過高，是冠狀動脈心臟病、腦中風、周邊動脈硬化及靜脈栓塞重要的危險因子。同半胱胺酸造成粥狀動脈硬化的原因雖然還不是很清楚，但眾多證據顯示是源自其對內皮細胞的損害。同半胱胺酸不僅抑制細胞週期的循環，也同時加速細胞的凋亡，這種現象使它成為抑制血管生成的一個重要的因子。由於 B 群維生素可以有效的降低病患血漿中同半胱胺酸濃度，因此臨床醫師常會使用B 群維生素來治療高同半胱胺酸病人，以期減少心血管疾病的發生。然而令人意外的是，許多臨床試驗顯示當受試者服用B 群維生素之後固然成功的降低血漿中同半胱胺酸濃度，但整體而言對心血管疾病發生率及死亡率並無影響。這些與傳統觀念迥異的觀察在最近激起一個新的理論：同半胱胺酸很可能並不是引起心血管疾病的危險因子；同半胱胺酸的前身，S-腺苷同半胱胺酸（S-adenosylhomocysteine），比同半胱胺酸更能預測心血管疾病的風險。我們在2008 年Circulation Research 發表一篇有關同半胱胺酸的研究，發現動脈內皮細胞暴露於高濃度的同半胱胺酸並不會加速細胞的凋亡。反之，若設法提高細胞內S-腺苷同半胱胺酸濃度，則動脈內皮細胞的傷害明顯增加，這是因為S-腺苷同半胱胺酸影響細胞DNA 甲基化（DNA methylation）的緣故。因此，我們提出這個研究計劃的目的是要探討S-腺苷同半胱胺酸在臨床應用的價值，特別是其與急性心肌梗塞的相關性。本計劃的第一個目標是建立以串聯質譜儀（Tandem LC-MS/MS）偵測血液中S-腺苷同半胱胺酸的方法，用以探討急性心肌梗塞患者血中S-腺苷同半胱胺酸的變化，並用於追蹤病患治療之預後。第二個目標是，由於S-腺苷同半胱胺酸與細胞甲基化（DNAmethylation）有關，因此我們也將探討冠狀動脈疾病患者白血球甲基化的程度，以了解心血管疾病與細胞甲基化的關係。第三個目標是，建立體外細胞培養系統，探討S-腺苷同半胱胺酸對血管生成的影響。這個研究是國際間第一個探討S-腺苷同半胱胺酸調節急性心肌梗塞患者細胞甲基化及血管生成的研究，其結果將有助於我們瞭解S-腺苷同半胱胺酸造成心血管疾病的機轉，藉由這些認識我們也可能發展出預防及治療同半胱胺酸代謝異常導致動脈硬化疾病的新策略。<br> Abstract: Homocysteine, a sulfhydryl-containing amino acid, is a key branch-point intermediatemetabolite of methionine. Elevated plasma total homocysteine level has been known as animportant risk factor for atherosclerosis. The mechanisms underlying homocysteine-inducedatherosclerosis, while still incompletely understood, can be attributed in large part toendothelial cell (EC) damage. The resultant growth inhibition in combination with impairedEC migration and vascular tubular formation incurred with high concentrations ofhomocysteine explain why homocysteine may also be regarded as an angiostatic molecule.Abundant clinical and epidemiological studies have associated hyperhomocysteinemiawith heightened risks of arterial diseases, yet not all prospective studies have reached thisconclusion. Likewise, not all clinical trials testing homocysteine-lowering strategies find adiminished recurrence of cardiovascular events such as restenosis, stroke, or venousthromboembol. Unlike homocysteine, plasma concentrations of S-adenosylhomocysteine(SAH) were not related to vitamin B6, vitamin B12 or folic acid, and more and more data areemerging in favor of SAH as a better indicator for cardiovascular disease than homocysteine.Our recent data published in Circulation Research 2008 show that human coronary arteryendothelial cells exposed to homocysteine alone did not alter cell integrity including cellsurvival, cell cycle transition and growth factor expression. On the contrary, increasedintracellular SAH levels resulted in significant cytotoxic changes, the early signs ofatherosclerosis. This study is therefore designed to define clinical significance of SAH incoronary artery disease, especially in acute myocardial infarction.There are three specific aims of this proposal. The first aim is to measure plasma SAHlevels by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) andestablish the correlation of SAH with acute myocardial infarction. The second aim is toelucidate the molecular mechanism of atherosclerosis by investigating DNA methylationstatus of leucocytes in coronary artery disease. The third aim is to investigate the effects ofSAH on vascular tube formation in vitro. Results of the proposed study will be the first todemonstrate in vivo DNA methylation status by SAH in acute myocardial infarction. Theseresults can also further our understanding of SAH-induced endothelial damage, and mayenable new approaches to the prevention and treatment of patients with abnormalhomocysteine metabolism.同半胱胺酸S-腺苷同半胱胺酸急性心肌梗塞細胞甲基化血管生成homocysteineS-adenosylhomocysteineacute myocardial infarctionDNA methylationvasculogenesis