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.
Medical studies on the relationship of ApoE gene and Alzheimer’s
Alzheimer’s is a kind of brain disorder. Brain cells of people with Alzheimer’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.
Implication of different forms of Apoe gene
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.
Genes aren’t the only factor
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’.