Abstract
The physiological roles of vitamin A have been elucidated based on a knowledge of the relatioships between vitamin A and health. However, this knowledge is not complete and it still remains to be studied what the actions of vitamin A are and the mechanisms behind its actions. Vitamin A, including β-carotene, is consumed from diet, are metabolized and transported within the body. Vitamin A is stored as retinyl ester in the liver, and vitamin A metabolites (retinal and retinoic acid) exert their actions in various target cells (organs). The mechanisms of action of these agents depend on nuclear retinoid receptors and protein modifications. This review provides a comprehensive survey of vitamin A and new insights into the latter's mechanisms of action.
