American Journal of Clinical Nutrition, Vol 9, 27-35, Copyright © 1961 by The American Society for Clinical Nutrition, Inc.

Vitamin A Function in Ubiquinone and Cholesterol Biosynthesis

¹ From the Department of Vitamin and Nutritional Research of F. Hoffmann-La Roche and Company, Ltd., Basle, Switzerland

After administration of ¹⁴C-labeled mevalonic acid to rats it could be shown by isolation and chemical degradation of the biosynthetically labeled ubiquinone that mevalonic acid is the precursor of the side-chain of ubiquinone. After dosing ¹⁴C-methyl labeled methionine, radioactivity was incorporated into the methoxy groups of ubiquinone in the liver of rats. No conclusive results have been obtained up to now on the precursor of the benzoquinone part of ubiquinone.

The biosynthesis of ubiquinone was found to be increased in vitamin A deficient rats, whereas that of cholesterol was depressed. Squalene is enriched in the liver of the deficient animals. This alteration in biosynthesis of cholesterol and ubiquinone takes place in a very early stage of vitamin A deficiency and can be reversed by administration of vitamin A to deficient rats even in a rather severe deficiency state. The influence of vitamin A deficiency on cholesterol biosynthesis could also be demonstrated in experiments with rat liver homogenate preparations by statistical evaluation. A possible mechanism for the interaction between vitamin A deficiency and cholesterol, squalene and ubiquinone synthesis is discussed.