Changes in fatty acid composition of peripheral nerve myelin in essential fatty acid deficiency

Severe essential fatty acid deficiency (EFAD) was induced by feeding weanling rats a diet free of essential fatty acids 8 months after weaning. The fatty acid compositions of phospholipids and glycosphingolipids in peripheral nerve myelin were compared in rats with and without EFAD. With the deficient diet, 20:3ω9 was found in the major myelin phospholipids. The level of 18:1 was increased and the levels of 18:2ω6, 20:4ω6, and 22:4ω6 were decreased. Both sphingomyelin and cerebroside showed higher proportion of 24:1 and lower proportions of 24:0 in EFA-deficient rats than in control rats. The fatty acid chain elongating system in myelin cerebroside was also depressed by EFAD. A two- to sevenfold increase of the ratio 20:4ω6 to 20:3ω6 was found in myelin phospholipids of regenerated nerve from rats fed control diet. However, this ratio was suppressed by EFAD diet. The biochemical index (20:3ω9/20:4ω6) for EFAD was not affected by crush injury. These results suggest that dietary EFAD in postweaning rats can induce fatty acid alterations in peripheral nerve myelin without resulting in detectable changes in function or structure and that myelin lipids may be sequestered and reused during nerve degeneration and regeneration.