高血脂症病人的分子基因學研究及相關脂蛋白之表現

Molecular Analysis of the Taiwanese Patients with Hypertriglyceridemia and Expression of the Associated Apolipoprotein

陳彥心(Yen-Hsin Chen)

指導教授 ： 李銘仁

國立臺灣大學/醫學院/分子醫學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.00595

摘要

由於現代人的飲食習慣與以往大為不同，加上忙碌的生活導致缺乏運動，以及一些抽菸、喝酒等生活習慣，使得代謝症候群的病人越來越多。其中常見的高血脂症(Hypertriglyceridemia，HTG)的發生不單單只受到後天環境因素的影響，先天遺傳基因也會造成三酸甘油脂(Triglycerides，TGs)升高；而TGs升高與心血管疾病(Coronary Artery Disease，CAD)及腦血管疾病(Cerebrovascular Disease)的相關性相當顯著(4,7,10,,17,24,31,55)。因此探究高血脂症的發生原因和先天性基因型的相互作用為我們重要之課題。

首先，我們在代謝門診經專科醫師之診斷與協助，收集Controls (TGs<2.26mmol/L, n=285)，Moderate HTG (2.26≦TGs<5.65 mmol/L, n=216)，以及Severe HTG (TGs≧5.65mmol/L, n=169)三組之病患及對照組的檢體，並加以瞭解其基本資料和生活模式後，發現在年齡、BMI、腰圍、抽菸習慣和有無高血壓病史和HTG具有統計學的顯著相關(p-value<0.0001)，推論這些因素都可能會造成TGs升高，而引發高血脂症。接著，從臨床生化的檢驗數值發現，Severe HTG的病人在膽固醇(CHO)、TGs、飯前血糖(Glucose AC)和飯前胰島素(Insulin AC)上的表現比Moderate HTG和Control的病人較高(p-value<0.0001)，由此可見，血脂越高的病人在這些生化數值上的表現也都相對提高。

探討後天環境的影響和臨床表徵之後，我們根據文獻選取與高血脂症發生有關的APOA5、APOE、APOC3三個候選基因(Candidate Gene)進行分析。若在APOA5基因上出現553G>T的polmorphism(APOA5:T(+))時，脂蛋白A5 (Apoliprotein A5)無法調節TGs的運輸，導致TGs升高；在APOC3基因的三端未轉錄區若有3238C>G的置換(S2基因型)時，脂蛋白C3 (Apolipoprotein C3)失去調控TGs代謝的功能，造成TGs升高；而在APOE基因上，倘若為APOE4的基因型態，在運送和代謝TGs、CHO的能力會變差，而使得血液中TGs的濃度升高。我們發現血脂表現越高，有APOA5之”T” allele及APOE4 allele的比例，在統計上明顯地增高(p-value<0.0001)。

因為APOA5、APOE4和APOC3皆可能與高血脂症之發生有相關，所以利用Univariate and Multivariate Logistic Regression Aalysis去分析三個基因之間是否有交互作用，結果發現為APOA5:T(+)、APOC3:S2和APOE4基因型態時，最有機會造成高血脂症之發生，推論APOA5蛋白和APOE4同時存在，會造成TGs的調控不好，導致TGs升高。

在脂蛋白元E4、C3和A5的表現上，發現脂蛋白C3的濃度與Lipid Profile(CHO、TGs、NHDL)的表現，具有統計意義(p-value<0.0001)，且脂蛋白元C3在TGs大於500 mg/dl的HTG表現會比血脂小於500 mg/dl的群體來的高。所以脂蛋白元C3的濃度與高血脂症有相關。

在發現APOA5、APOC3和APOE4與高血脂症之關係後，我們可以建議高血脂症的病人進行基因型態之分析，幫助高血脂症病人之家屬改變飲食習慣和生活作息，以降低體內的血脂濃度，避免高血脂症之發生。對於病人，可以找到其高血脂症發生的原因，在併發症和情形尚未惡化之前，就接受治療，控制血脂，改善生活品質，並預防心血管疾病之發生。

關鍵字

高血脂症 ； 三酸甘油脂 ； 心血管疾病 ； 候選基因 ； 多型態 ； 脂蛋白元A5 ； 脂蛋白元C3 ； 脂蛋白元E4

並列摘要

The differences in eating habits and less exercise influence people’s health condition. The increasing people suffered from metabolic syndrome including Hypertriglyceridemia (HTG) which results from genetic and environmental factors. Some researches say that the elevated triglycerides (TGs) are related to coronary artery disease (CAD) and cerebrovascular disease. We supposed to do is consider what caused HTG and clarify the interaction of genotypes.

We collect three groups of Controls (TGs<2.26mmol/L, n=285), Moderate HTG (2.26≦TGs<5.65 mmol/L, n=216), and Severe HTG (TGs≧5.65mmol/L, n=169) from Dr. Su’s metabolic clinic in National Taiwan University Hospital. Get information of their age, BMI, waist, smoking habit and the history of hypertension associated with HTG patients, and identify their significance in statistics (p-value<0.0001). And then consider the biochemical analysis, we find the expressions of cholesterol (CHO), TGs, Glucose AC, Insulin AC in severe HTG are higher than moderate HTG and Controls (p-valus<0.0001).

According to previous papers, we pick up three candidate gene (APOA5, APOE and APOC3) to do genetic analysis. If we find the 553G>T polymorphism in APOA5 gene, apolipoprotin A5 cannot modulate the transport of TGs and cause TGs increase. The replacement of C to G occurred in 3’ untranslated region at 3238 site of APOC3 gene, which make apolipoprotein C3 fail to regulate TGs metabolism. The consequence is TGs elevated. And if the genotype is APOE4, the function of TGs transport and metabolism will not work well and the concentration of TGs will be high. There are statistic significances (p-value<0.0001) in high ratio of T allele in APOA5 and APOE4 allele.

Consequently, APOA5, APOE4 and APOC3 may be related to HTG. Therefore we use univariate and multivariate logistic regression analysis to analyze the interaction between these three genes. We postulate the co-existence of apoliprotein A5 and apolipoprotein E4 influence the function of TGs regulation and then TGs increase.

Otherwise, we also observe the protein level of apolipoprotein E4, C3 and A5. Then, we find that the concentration of apolipoprotein C3 is associated with lipid profile (p-value<0.0001). As a result, we assume that the level of apolipoprotein C3 is associated with TGs level in HTG patients.

Clarify APOA5, APOE4, and APOC3 are associated with HTG. What we should do is suggest the patients with HTG do genetic analysis to confirm genotype, and then help them change their life style to control TGs level and avoid coronary artery disease.

並列關鍵字

hypertriglyceridemia (HTG) ； triglycerides (TGs) ； coronary artery disease (CAD) ； cerebrovascular disease ； candidate gene ； APOA5 ； APOC3 ； APOE4 ； polymorphism

參考文獻

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