Inherited membranes predict Alzheimer's?

Inherited membranes predict Alzheimer's?

Isolating the diagnosis of Alzheimer's disease from other forms of dementia can be difficult; a definitive identification still depends on autopsy reports. But a new study suggests that an abnormality of blood-cell membranes found among families with a higher-than-normal incidence of Alzheimer's may help diagnose or even predict the disease. Focusing on the blood-clotting cells called platelets, scientists recently found that-- compared to randomly chosen controls--close relatives of Alzheimer patients were 3.2 to 11.5 times more likely to have platelet membranes that were less rigid than normal.

Researchers associated with the University of Pittsburgh, Carnegie-Mellon University in Pittsburgh and Harvard Medical School in Belmont, Mass., report in the Oct. 23 SCIENCE that this increased fluidity of platelet membranes can be found in a characteristic pattern among families affected by Alzheimer's disease. Earlier studies had shown that the disease begins earlier and progresses more rapidly in patients with increased fluidity of these membranes. Other evidence suggests that the risk of developing Alzheimer's is higher among certain families.

By including first-degree relatives of 38 Alzheimer patients, the current study examined the correlation between these physiological and genetic components. The authors say that the pattern of inheritance associated with the membrane abnormality closely matches that reported with Alzheimer's. If further studies confirm the membrane aberration as a specific biological marker for Alzheimer's, laboratory techniques to measure membrane rigidity may be incorporated into diagnostic strategies, say the scientists.

The latest findings also point to a change in research directions, says Zaven S. Khachaturian, director of the National Institute of Aging's Alzheimer research program, in Bethesda, Md. He told SCIENCE NEWS that scientists are beginning to look for Alzheimer-associated effects outside the nervous system. The fact that platelets are not neural tissue is exciting, he says, "because it means the disease may have a systemic effect, [which] creates all kinds of [research] possibilities.' He does caution, however, that the simple measure of membrane fluidity may not be adequate, and that useful diagnostic tests may need to include the relative concentrations of various membrane components like phospholipids.