Fatty acid composition of myelin isolated from the brain of a patient with cellular deficiency of co-enzyme forms of vitamin B12.

Myelin fractionation and subsequent lipid isolation have been carried out on a brain from a patient who suffered from a cellular deficiency of the adenosylcobalamin and methylcobalamin co-enzyme forms of vitamin B12. Examination of the fatty acid composition of choline and ethanolamine glycerophospholipids indicated a relative enrichment of odd-chain fatty acids which were identified by gas-liquid chromatography-mass spectroscopy as C15, C15:1, C17 and C17:1. A mixture of methyl branched C17 fatty acids was also identified. Odd-chain fatty acids accounted for 9.8% of the total fatty acid in the myelin choline phospholipid conpared to control values of 1.2%. The affected brain myelin phospholipids had a lower unsaturated fatty acid content. Examination of the myelin sphingolipids, sphingomyelin, cerebroside and sulfatide, yielded abnormal fatty acid profiles. The sphingomyelin contained only small amounts of C24:1 fatty acid. Both normal and hydroxy fatty acid containing cerebroside and sulfatide had reduced levels of C24 fatty acid. Determination of the relative hydroxy and normal fatty acid content of the galactolipids indicated an abnormally high hydroxy fatty acid level. Abnormal fatty acid profiles of brain cerebral sphingolipids have not been previously described in cases of vitamin B12 deficiency. Whether or not these alterations are characteristic will only be established by estimating sphingolipids in other such cases.