Editing Retinoid (section)

== Pharmacokinetics ==
The major source of retinoids in human diet are plant pigments such as [[carotene]]s and retinyl esters derived from animal sources.<ref>{{cite journal | vauthors = Hall JA, Grainger JR, Spencer SP, Belkaid Y | title = The role of retinoic acid in tolerance and immunity | journal = Immunity | volume = 35 | issue = 1 | pages = 13–22 | date = July 2011 | pmid = 21777796 | pmc = 3418663 | doi = 10.1016/j.immuni.2011.07.002 }}</ref> Retinyl esters are transported through the [[chylomicron]] pathway to the liver or fat tissue while [[retinol]] or [[carotene]]s are transported from the enterocytes to the liver and are processed into retinyl esters by [[Lecithin retinol acyltransferase|LRAT]] for storage.<ref>{{cite journal | vauthors = Burri BJ, Clifford AJ | title = Carotenoid and retinoid metabolism: insights from isotope studies | journal = Archives of Biochemistry and Biophysics | volume = 430 | issue = 1 | pages = 110–119 | date = October 2004 | pmid = 15325918 | doi = 10.1016/j.abb.2004.04.028 | series = Highlight issue on Carotenoids }}</ref> Most synthetic retinoids are absorbed when taken orally while topical retinoids cannot diffuse through the skin barrier unless it is compromised.<ref name = "Mukherjee_2006" />

All classes of retinoid bind to many proteins. Natural retinoids such as [[retinol]] and retinyl esters bind to carrier proteins such as [[Retinol binding protein 4|RBP4]], [[chylomicron]]s and [[VLDL]] while synthetic retinoids likely bind to these and other proteins.<ref>{{cite journal | vauthors = Burri BJ, Clifford AJ | title = Carotenoid and retinoid metabolism: insights from isotope studies | journal = Archives of Biochemistry and Biophysics | volume = 430 | issue = 1 | pages = 110–119 | date = October 2004 | pmid = 15325918 | doi = 10.1016/j.abb.2004.04.028 | series = Highlight issue on Carotenoids }}</ref> First generation retinoids are rapidly metabolized by [[Cytochrome P450|Cytochrome p450]] enzymes, typically of the [[CYP26 family|Cyp26 family]].<ref>{{cite journal | vauthors = Esposito M, Amory JK, Kang Y | title = The pathogenic role of retinoid nuclear receptor signaling in cancer and metabolic syndromes | journal = The Journal of Experimental Medicine | volume = 221 | issue = 9 | date = September 2024 | pmid = 39133222 | doi = 10.1084/jem.20240519 | doi-access = free | pmc = 11318670 }}</ref>