The study revealed that the total amounts of protein, lipids and cholesterol were significantly reduced in the myelin of Alzheimer's patients in comparison to the control group. This erosion of the myelin sheath is referred to as demyelination. "These profound white matter alterations undoubtedly contribute to the origin and development of Alzheimer's disease, and might possibly be the initiating step," Roher says. There are multiple reasons for arriving at this conclusion, according to Roher, but two in particular stand out.

First, previous studies have demonstrated that patients with pre-clinical Alzheimer's disease show deterioration in the white matter before the gray matter. Second, the current study suggests that white matter degeneration might be caused by a disease of the oligodendrocytes, whose main job is to produce the myelin sheath. A defective myelin coating could leave the axons unprotected, resulting in serious disturbances in nerve conduction and damage to brain functions, Roher says.

Because neurons in the gray matter are vital to cognitive activity, scientists have generally assumed that Alzheimer's disease with its memory loss and other cognitive debilitations must begin in the gray matter. But Roher says the white matter is just as critical to cognitive function. White matter axons play a major role in controlling mental activities like emotion, and all mental functions are fully expressed only when the axons are transmitting properly.

An analogy can be drawn from the recent energy crisis in California, Roher says. One of the many issues facing Californians was a short supply of power attributable, in part, to an unusually cold winter and a dry summer at hydroelectric dams. A sugg
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Contact: Beverly Hassell
b_hassell@acs.org
202-872-4065
American Chemical Society
18-Sep-2002