[Vitamin E: protection of membrane polyunsaturated fatty acids against radical peroxidation in the course of cerebral aging, particularly in cerebral capillaries and microvessels].

Nerve tissue (as well as capillaries and cerebral microvessels) has a very high concentration in polyunsaturated fatty acids belonging to linoleic and alpha-linolenic series. Nerve tissue also requires large amounts of oxygen. Radical peroxidation of the polyunsaturated fatty acids represents a serious risk to the biochemistry and physiology of the membranes: it can be a cause of cellular death. During aging, the capillaries and cerebral microvessels undergo extensive modifications at the level of the polyunsaturated fatty acids: for example, the concentration of arachidonic acid decreases by half. In brain in general, vitamin E is very well protected: after oxidation, it is rapidly regenerated; it seems to undergo only slight degradation. In case of dietary deficiency, the brain loses much less vitamin E, and at a slower rate, than other non-nerve tissue. During aging, there is a relation between the content in vitamin E and the concentration of polyunsaturated fatty acids of the linoleic series, but not of the alpha-linolenic series. In addition, vitamin E deficiency also leads to a decrease in the enzymatic activities that protect against peroxidation of fatty acids.