我們的基因控制著身體細胞的功能。有些基因決定了我們身體的基本特徵，例如頭髮及眼珠的顏色；有些基因則會令我們患上某些疾病的風險。
載脂蛋白E(Apolipoprotein E, 簡稱ApoE)基因位於人體的第19對染色體上，負責生產攜帶膽固醇的去脂蛋白。因此ApoE基因在調節血脂及膽固醇方面發揮著重要的作用。醫學界早已確定ApoE基因的不同形態與腦退化症，以及其他大腦損傷的疾病有非常密切的關係。
腦退化症是一種腦部疾病，患者腦細胞死亡的速度很快，並且會出現腦部萎縮，引致腦部功能嚴重衰退。
而ApoE4並非引致腦退化症的直接基因，它是個易感基因(Susceptibility gene)，反映著人們患病的先天傾向。據香港中文大學的研究發現，臨床病例中，有60至70%的腦退化症病人帶有最少一個ApoE4基因；而在屍檢的病例當中，腦退化症病人帶有ApoE4基因的機會是正常人的十倍。根據外國文獻，超過一半帶有一個ApoE4基因的人在70歲後患有腦退化症。
 ApoE基因可為三種形態：E2、E3及E4。一般人會從父母遺傳到各一種形態的ApoE基因，因此個人的ApoE基因可以有六種組合分別是：E2/E2、E2/E3、E3/E3、E3/E4，以及E4/E4。
E2：具有保護的作用。擁有Apo E2基因的人，血液中的總體膽固醇和 LDL（壞膽固醇）數值較一般人低。
E3：是ApoE基因的正常形態，最為常見的ApoE基因型態。基本上，ApoE3不會增加或減少心臟病、腦中風以及阿爾滋海默氏症等疾病罹患的機率。
E4：是ApoE各種基因型中危險性最高的一種。只要您遺傳到兩個ApoE4，比遺傳到一個ApoE4具有更高的患病風險。
帶有E3/E4或E4/E4基因形態的人，比E3/E3的人具有更大的風險患上腦退化症。而假若ApoE4擕帶者吸煙及經常飲酒，會大大增加ApoE4基因健康的負面影響。但就算是帶有E3/E4或E4/E4基因，只要多注意飲食、盡可能少吸煙、少喝酒，並增加運動，E4基因帶來的壞影響是可以被抵消的。
現有的醫學科技，可以通過基因類型分析從唾液或口腔組織區別出個人的基因型。如果您想了解我們這項新服務，歡迎致電熱線電話+852 2763 1488查詢！
Genes control the function of every cell in our body. Some genes determine basic characteristics; other genes can make you more likely to develop certain diseases – including Alzheimer’s.
ApoE (Apolippprotein E) gene locates on chromosome 19. It plays an important role in the metabolism regulation of cholesterol and fatty acids. In recent years, scientists have discovered one of the several forms (polymorphism) of a gene, ApoE4, is closely associated with Alzheimer’s disease.
Alzheimer’s is a kind of brain disorder. Brain cells of people with Alzhimer’s die quickly and their brain will shrink, causing severing deterioration of brain functions.
ApoE4 is not the causative gene; it is a susceptibility gene and reflects a degree of risk for the disease. In studies of CUHK, among the clinical samples, 60-70% of patients with Alzheimer's disease carry at least one ApoE4 gene. Among post-mortem samples, the prevalence of one E4 gene among Alzheimer's disease is 10 times that of the normal controls. In the west, it has been estimated that half of those who carry one ApoE4 gene may develop Alzheimer's disease by the age of 70.
 
ApoE gene exists in three different forms: E2, E3 and E4. You inherit two ApoE genes each from your parents. Therefore there are six possible combinations of the ApoE genotypes: E2/E2, E2/E3, E2/E4, E3/E3, E3/E4 and E4/E4.
E2: carries a protective role to Alzheimer’s. Individuals with ApoE2, the level of total cholesterol and low density lipoprotein are lower than the majority.
E3: it is considered to be the most common and normal form, doesn’t seems to affect the risk of Alzheimer’s in either direction.
E4: the most dangerous form. Having one ApoE4 gene increases your risk of developing Alzheimer’s, and if you have two ApoE4 genes, your risk is even higher.
ApoE gene affects disease risk, but other environmental factors are likely involved in the development of Alzheimer’s. Individuals with E3/E4 or E4/E4 combination will have greater risk to develop Alzheimer’s than those with E3/E3. A balanced diet, regular exercise, not to smoke or drink frequently can help to cancel out the negative effect brought by the ‘bad-genes’.
Current medical technology can help to identify the personal genotype of a particular gene with a sample of saliva or oral cell. Please call +852 2763 1488 if you want to more about our new service on genes!
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