Vitamin B6 and Lipid Metabolism in Monkeys

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Abstract
Graded levels of butter fat and of safflower oil (0, 2, 10 and 20 per cent) were fed to rhesus monkeys maintained for successive periods on graded levels of pyridoxine·HC1 (0.05, 0.10, 0.50, 1 and 2 mg. daily). Effects of these regimens were observed in reference to clinical condition, food consumption, weight response, plasma lipids and hematology. The intake of food decreased in all groups during the periods of feeding 0.05 and 0.10 mg. of pyridoxine. A slight increase was noted at the 0.50 mg. level in some groups and sustained increases were seen throughout the period of feeding 1 and 2 mg. In general, the intake of food increased with the caloric content of the diet. Only the animals receiving 20 per cent butter fat and 10 and 20 per cent safflower oil maintained or slightly exceeded their initial weights during the period in which 0.05 mg. of pyridoxine was fed. Alopecia and ataxia developed in all groups. Increasing the intake of pyridoxine to 0.10 mg. daily for two months did not appreciably change the growth responses. Inconsistent improvement was noted at the 0.50 mg. level of pyridoxine intake; however, the alopecia and ataxia persisted. Fourteen (of an initial twenty-six) monkeys died during the periods of feeding of 0.10 and 0.50 mg. of pyridoxine: eight of these had convulsive seizures. Two additional animals with convulsions recovered spontaneously. The groups on the 10 per cent level of the two fats were discontinued and the remaining animals served as replacements in other groups. The growth responses and the general condition of the monkeys including growth of hair and increase in activity improved during the period of feeding 1 mg. of pyridoxine. Further increases in weight occurred when the level of pyridoxine was raised to 2 mg. daily. Groups receiving the rations containing 2 per cent butter fat and 2 per cent safflower oil showed the greatest growth responses. The levels of free and total plasma cholesterol, sterol esters and phospholipids increased with the intake of pyridoxine. These fractions, in general, were highest on the diets containing 20 per cent butter fat and lowest for the fat-deficient and the 20 per cent safflower oil diets. The total lipids followed a similar pattern. Total and free plasma cholesterol values for the monkeys given 20 per cent butter fat were greater than for the control period at all levels of pyridoxine intake except the lowest level. At the 1 mg. level of pyridoxine feeding the increment was 33 per cent over the control period and 65 per cent at the 2 mg. level of pyridoxine intake. Corresponding increases for the monkeys receiving safflower oil were 7 per cent and 15 per cent, respectively. Mild to definite normocytic anemia was observed in some monkeys in each group other than at the 2 mg. level of pyridoxine intake. The elevation of plasma lipids and their fractions appeared to be dependent upon the intake of pyridoxine and the level and type of fat in the diets.