Posts Tagged ‘apoe’

Alzheimer’s Disease

May 11, 2010

Alzheimer’s disease is the most common form of dementia. Common symptoms include memory loss, confusion, irritability and aggression, mood swings and language breakdown. It is often misdiagnosed as senility. Progression of the disease varies widely. About 26.6 million people were diagnosed with Alzheimer’s in 2006.

There are two types of Alzheimer’s. Late-onset, or sporadic, Alzheimer’s is more common and is diagnosed in people 65 years of age or older. Early-onset, or familial Alzheimer’s disease (FAD), usually develops in adults in their 30’s and 40’s. This type only occurs in about 1 out of every 1000 Alzheimer’s cases. These individuals have a family history of FAD. Genetics has been linked to Alzheimer’s.

Genetics of Alzheimer’s

Genetics and Alzheimer’s are linked but the relationship is not completely understood. If a parent has been diagnosed with FAD, 50% of his offspring will develop it. It is due to autosomal dominant mutations. Therefore, even if a person has only one copy of the gene, he will develop that type. A person who has not developed the disease can not pass it on. Late-onset Alzheimer’s, on the other hand, is not inherited. There are, however, families in which clusters of cases exist.

Three genes have been discovered that influence a person’s risk of getting FAD. These include an amyloid precursor protein (APP) gene and two presenilin genes (PSEN-1 and PSEN-2). These genes exist on chromosomes 1, 14 and 21. A mutation on chromosome 21 causes a build-up in the amount of amyloid protein in the brain. An increase in the amount of amyloid protein has been linked to FAD. Mutations in all of these genes cause senile plaques.

Many genes affect a person’s chances of getting late-onset Alzheimer’s. Some genes are thought to have protective influence. A combination of multiple genes increases the risk of developing it. Only one gene has been identified so far. Apolipoprotein E (APOE) mutations are the cause of about 50% of all late-onset Alzheimer’s. It is found in three forms:

  • APOE2 gives a person some protection against getting Alzheimer’s.
  • APOE3 gives an individual an “average risk” of developing Alzheimer’s.
  • APOE4 increases a person’s risk of getting Alzheimer’s. People with one copy are four times more likely and those with two copies are ten times more likely to develop the disease. Having two copies, however, does not mean that a person will definitely get the disease.

Recent research has, however, made it possible to determine which genes have an influence on developing this disorder. It will only take time to identify these genes. The role of each gene will then be determined. It may then be possible to treat and prevent the disease.

Treatment of Alzheimer’s

Treatment is targeted at alleviating the symptoms of Alzheimer’s. Research has not yet discovered a way to prevent or delay the onset or progression of this condition. Clinical trials are ongoing. Some lifestyle changes that may help include exercise, mental stimulation and a healthy diet. Cardiovascular health and pharmaceutical products may also have an influence on one’s risk.