4.1. Retinol metabolism
The main function of retinol is cell signal transduction through binding to the 2 types of retinol receptors in the nuclear hormone receptor family, RARs, and RXRs. These receptors are transcription factors regulated by ligands and are essential for embryonic development and adult physiology. It has been found that the embryo quality of adult oocytes was improved after the addition of retinol.As for the synthesis and decomposition of retinol, it has been reported that retinol is transformed into retinaldehyde through 2 oxidation steps, and then into all-trans retinoic acid. All-trans retinoic acid is present in high levels in embryonic and adult tissues and effectively binds to RARs. It is the main bioactive retinoic acid in vivo and could be having important biological functions.