[Biochemistry of brain lipids (especially fatty acids). In situ synthesis and exogenous origin during development. Various aspects of nutritional effects].

In contrast with other tissues, the nervous system is very rich in lipids, most of which are found in membranes. Fatty acids thus play a role in membrane structure and function: sphingolipids are essentially found in myelin and present original fatty acid patterns. Saturated and monounsaturated fatty acids are synthesized in microsomes by 3 different systems which differ at the level of the condensing enzyme. The activities of these systems are directly related to myelination. Mitochondria are also able to synthesize fatty acids but the pathways are totally different and unrelated to myelination. Moreover, the brain does not elaborate all its membrane fatty acids whose exogenous origin is demonstrated by injecting labelled non-essential fatty acids. The relationship between blood and brain vary during brain development; the uptake of fatty acids is quantitatively very important during glial cell multiplication and myelination. Nutrition alters the fatty acid composition of brain membranes; the fatty acids are largely altered in an opposite way in the neurons and oligodendrocytes of hypotrophic animals.