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Carotene Utilization and Cholesterol Metabolism as Influenced by Added Choline and Vitamin B₁₂ to Diets Containing Yeast or a Synthetic Vitamin Mixture¹

Department of Home Economics Research, Montana State College Agricultural Experiment Station, Bozeman

The feeding of 0, 30, 60, 100, 250 or 350 mg of choline or 3000 mµg of vitamin B₁₂ per 100 gm of diet to male or female rats receiving a synthetic-vitamin-mix diet and 60 µg of carotene daily for 14 days did not change the rats' utilization of carotene and the resulting liver and kidney storage of vitamin A.

Male rats fed the yeast diet with 350 mg of choline per 100 gm of diet stored significantly more vitamin A than did those receiving the synthetic-vitamin-mix diet with 350 mg of choline (P < 0.01), or more than those fed the unsupplemented yeast diet with 30 mg of choline from the yeast (P < 0.01). These differences were not significant for the females.

Both male and female rats receiving the yeast-containing diet supplemented with 3000 mµg of vitamin B₁₂ per 100 gm of diet stored significantly more vitamin A than did those receiving the unsupplemented yeast diet (P < 0.01) or those fed the synthetic-vitamin-mix diet with 3000 mµg of vitamin B₁₂ (P < 0.01).

The results indicate the presence in yeast of some factors (or factor) which, together with vitamin B₁₂, but not alone, bring about greater utilization of carotene and larger storage of vitamin A in the livers and kidneys of rats than when vitamin B₁₂ is fed with a synthetic-vitamin-mix diet. It is also suggested that the protein composition of the yeast may be such that the amino acid balance of the yeast containing diet when supplemented with vitamin B₁₂ but not alone, provides for greater utilization of carotene.

The serum cholesterol of female rats receiving no choline for 18 days was not significantly different from that of rats receiving 30, 60, 100, 250 or 350 mg of choline per 100 gm of diet. Male rats receiving no choline had significantly lower serum cholesterols than did those receiving the choline supplements (P < 0.05). Both male and female rats receiving 0, 30 or 60 mg of choline per 100 gm of diet had lower serum cholesterols than did those receiving the higher levels of choline 100, 250 or 350 mg (P < 0.01).

Feeding 3000 mµg of vitamin B₁₂ to female rats receiving 250 mg of choline and a synthetic-vitamin-mix diet caused a significant lowering of serum cholesterol when compared with that of females receiving the same amount of choline but no vitamin B₁₂. Male rats did not respond in a like manner to the feeding of vitamin B₁₂.

Male rats receiving the unsupplemented yeast diet had lower serum cholesterol than did those receiving the syntheticvitamin-mix diet with the same amount of choline (P < 0.01). This difference was not significant for the females.

Male and female rats receiving no choline in their diet for 18 days had more total cholesterol in their livers than did those rats receiving either 30, 60, 100, 250 or 350 mg of choline per 100 gm of diet.

The addition of 3000 mµg of vitamin B₁₂ per 100 gm to the synthetic-vitamin-mix diet or the yeast-containing diet did not affect the liver cholesterol of male or female rats.

There were no correlations between storage of vitamin A in the liver and serum or liver cholesterol or between serum and liver cholesterol.

Manuscript received 4 November 1957.