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Vitamin A is required for several vital functions in the body. Some of the most important functions of Vitamin A are described below.
Vitamin A is required for the maintenance of normal vision. A deficiency in vitamin A can lead to visual disturbances. In the eyes, a form of vitamin A called retinal is combined with a protein called opsin to give rhodopsin, an essential light absorbing molecule needed for color vision and seeing in dim light.
Vitamin A is essential for maintaining healthy immune function and deficiency can lead to an impaired response to infection.
One form of Vitamin A, retinoic acid is, a key hormone-like growth factor for epithelial cells and other cell types in the body.
Vitamin A in the form of retinoic acid is essential for gene transcription. Retinol is taken up by the cell where it is oxidized to retinaldehyde (by retinol dehydrogenases), which is then oxidized to give retinoic acid. The conversion of retinal to retinoic acid is irreversible and the process is therefore tightly regulated because retinoic acid functions as a ligand for nuclear receptors. Retinoic acid binds to these nuclear receptors called in order to regulate gene transcription.
Retinoic acid also maintains skin health by activating genes that cause immature skin cells to develop into mature epidermal cells. The exact mechanism behind this is currently being researched to help develop treatments for dermatolgical diseases. Currently, the retinoic drug isotretinoin is the most commonly prescribed agent in the treatment of acne. This drug decreases the size of sebaceous glands and reduces their secretions. The agent also reduces the amount of bacteria present in the ducts and surface of the skin, which occurs as a result of reduced sebum, which bacteria rely on as a source of nutrients.