Abstract
Vitamin A (retinol), which is also known as the retinoid, is one of fat-soluble vitamins. Vitamin A is required not only for the visual cycle but also for normal cell development and metabolism. Retinol is oxidatively metabolized to retinal and retinoic acid. Retinal is required for the visual cycle and retinoic acid regulates the expression of specific genes. In each case, the metabolism of vitamin A is regulated by specific proteins which are required for the function expression of vitamin A metabolites. To understand the regulatory mechanism of these vitamin A-mediated physiological actions, therefore, not only the concentration of vitamin A metabolites but also the behavior of specific proteins related to vitamin A such as enzymes, transport proteins, and nuclear receptors should be evaluated. This evaluation makes it possible to understand the complex reactions of vitamin A in vivo from the fluctuations of these proteins.
In this comprehensive paper, we have shown both how these binding proteins regulate the action of vitamin A and a possibility that nutritional status affects retinol metabolism and actions by altering the expression of proteins related to vitamin A metabolism.
