APOE Gene
The APOE gene provides instructions for making a protein called apolipoprotein E. The official name of this gene is “apolipoprotein E.” APOE is the gene's official symbol. Apolipoprotein E combines with fats (lipids) in the body and is known as a lipoprotein. Lipoproteins are responsible for packaging cholesterol and other fats, carrying them through the bloodstream, and delivering them to the appropriate locations in the body for processing and use. In particular, apolipoprotein E is a major component of specific lipoproteins called very low-density lipoproteins (VLDLs). A key function of very low-density lipoproteins is to remove excess cholesterol from the blood and carry it to the liver for processing. Maintaining normal levels of cholesterol is essential for the prevention of disorders that affect the heart and blood vessels (cardiovascular diseases), including heart attack and stroke.
APOE Gene and increased risk of Alzheimer’s:
Mutations in the APP, PSEN1, and PSEN2 genes cause Alzheimer’s disease and it has been found that variations of the APOE Gene increase the risk of developing Alzheimer’s disease. The e4 version of the APOE gene seems to increase an individual's risk for developing type 2 Alzheimer’s disease, the late-onset form of this disorder. People who inherit one copy of the APOE e4 allele have an increased chance of developing the disease; those who inherit two copies of the allele are at even greater risk. It is not known how this allele affects a person's risk of Alzheimer’s disease.
Four major types of familial Alzheimer’s disease have been identified. Types 1, 3, and 4 are classified as early-onset Alzheimer disease because their signs and symptoms appear before age 65. Type 2 is classified as late-onset Alzheimer’s disease because its signs and symptoms appear after age 65. Other cases of Alzheimer’s disease are classified as sporadic or nonfamilial, which means they do not appear to run in families. Researchers have found that the APOE e4 allele is associated with an increased number of protein clumps, called amyloid plaques, in the brain tissue of people with Alzheimer disease. It is important to note that not all people with Alzheimer’s disease have the e4 allele, and not all people who have the e4 allele will develop Alzheimer’s disease.
APOE gene – relationship to other health conditions
There are other disorders associated with the APOE gene: Apolipoprotein E is also associated with cardiovascular disorders. People who carry at least one copy of the APOE e4 allele are at increased risk for atherosclerosis, which is an accumulation of fatty deposits and scar-like tissue in the lining of the arteries. This progressive narrowing of the arteries increases the risk of heart attack and stroke.
hyper-lipoproteinemia type III. This condition is characterized by increased levels of cholesterol, certain fats called triglycerides, and molecules called beta-very low-density lipoproteins (beta-VLDLs), which carry cholesterol and lipoproteins in the bloodstream (Sources: National Library of Medicine 2007.)
