Effects of Vitamin B-12 Deprivation on Phospholipid Fatty Acid Patterns in Liver and Brain of Rats Fed High and Low Levels of Linoleate in Low Methionine Diets

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Abstract
Experiments were conducted to determine how 20 weeks of deprivation of vitamin B-12 (B-12) would influence polyunsaturated fatty acid (PUFA) patterns in cerebral and liver phospholipids of female rats. All experimental diets included 24% soybean protein and either 3.5 or 0.35% of linoleate (18:2). Deprivation of B-12 and restricted intakes of 18:2 significantly inhibited growth of the rats. Rats depleted of B-12 had 6.7 times more methylmalonic acid in their liver, and significantly more odd-numbered acids (15:0 + 17:0) were present in phosphatidyl choline (PC) of their liver and cerebrum. Deprivation of B-12 promoted 63.3 to 97.3% increases of 18:2 in PC and phosphatidyl ethanolamine (PE) of the liver. Rats deprived of B-12 had significantly less arachidonate (20:4ω6) and 22:5ω6 in their liver PC, as well as smaller amounts of 20:4ω6 and 22:6ω3 in their cerebral PC. Some of the observed changes appear to be due to a significant interaction between the effects of B-12 and linoleate. Changes in PUFA patterns of cerebral and hepatic PC suggest that B-12 deprivation may interfere with the conversion of 18:2ω6 → 20:4ω6 → 22:5ω6. Some of the observed changes may also be related to an inhibited ability to convert PE to PC.