Lipid metabolism in the vitamin-B12-deprived rat

Rats were deprived of vitamin B12 in order to study the effect of this deprivation on the metabolism of lipids in the liver and the nervous system. Serum vitamin B12 concentrations of 102.7 and 78 pg/ml were found at sacrifice after 5 and 6 months, respectively. Neurological testing failed to reveal signs of neuropathy. The total liver lipids were decreased in the vitamin-B12-deprived animals, but no changes were detected in the lipid concentration or in the phospholipid composition of the nervous system. Some animals were given propionate, and in these, contrary to expectations, pentadecanoic acid and heptadecanoic acid were found in smaller amounts in the liver triglycerides of the vitamin B12-deprived rats than in the control rats. This could be due to the inhibitory effect of methylmalonyl CoA on fatty-acid synthesis, demonstrated by others in vitro.