Treatment Online

Early Advantage to Alzheimer's Gene?
> 8/27/2007 2:27:03 PM

When a grandparent is lost in the fog of Alzheimer's Disease, family members want to know why the person that they care about is breaking down. It is not enough to say that they got the disease because they were put at risk by the APOE4 allele. The question that remains is: why would such a detrimental gene survive through the generations to inflict so much devastation?

Sometimes there are no answers to such questions, but new research from the University of Zurich suggests that APOE4 might confer a health benefit in the first few decades of life. When humans rarely lived past 30, the negative effects of many dangerous genes did not have time to manifest, but now the life-span has extended to allow many of these problems to surface. This is in line with the theory of antagonistic pleiotropy, postulated by G.C. Williams to explain phenomena like the spread of a gene for testosterone that increased fitness in youth but also increased the risk of prostate cancer in old age. Dr. D.M. Alexander cites this theory as the explanation for the results of a study he published last month in Biological Psychology. He found that subjects with the APOE4 gene had greater verbal fluency and performed better on a visual working memory task using alphabetical stimuli.

More recently, Dr. Mondadori from Zurich tested the memory of a control group against subjects with the APOE4 gene. While the APOE4 group had a much higher risk of developing memory problems later in life along with Alzheimer's, they actually scored significantly higher on tests of episodic memory during the healthy years of their youth. In addition, the APOE4 group seemed to perform memory tasks with greater efficiency. fMRI scans showed that the APOE4 group needed less neural activation to retrieve memories with the same accuracy as the control group.

The scans are not detailed enough to reveal the exact difference between APOE4 and normal brains, but it is plausible that the two groups use different strategies to encode information. The APOE4 strategy may be more efficient in the short-term, but more prone to accumulate errors later in life.

While this memory benefit probably does not seem like a fair trade for those who develop Alzheimer's, it is at least some consolation. It is also a reminder that "bad genes" are often complex mixtures of gift and curse.

Comments

No comments yet.