title: Phytanic acid and docosahexaenoic acid increase the metabolism of all-trans-retinoic acid and CYP26 gene expression in intestinal cells.
abstract: Retinoids are essential for growth and cell differentiation of epithelial tissues. The effects of the food compounds phytol, the phytol metabolite phytanic acid, and the fatty acid docosahexaenoic acid (DHA) on the retinoid signaling pathway in intestinal cells were studied. Phytol inhibited the formation of all-trans-retinoic acid (RA) from dietary retinol in intestinal cells. Phytanic acid, a known retinoic X receptor (RXRalpha) and peroxisome proliferator activating receptor (PPARalpha) activator, also activated PPARdelta, and to a lesser degree PPARgamma, in a transactivation assay. Phytanic acid had no effect on intestinal RA hydroxylase CYP26 (also named P450RAI) gene expression and metabolism of all-trans-RA in intestinal Caco-2 cells. However, in combination with retinoic acid receptor (RAR)-ligands (all-trans-RA or synthetic Am580) phytanic acid enhanced the induction of CYP26 and RA-metabolism in comparison to treatments with all-trans-RA or Am580 alone. Also treatment with DHA did not affect CYP26 gene expression and RA-metabolism but cotreatment of the cells with DHA and all-trans-RA or Am580 enhanced the induction of CYP26, in comparison to the induction caused by all-trans-RA or Am580 alone. This study indicates that food compounds such as phytanic acid and DHA that are RXR-agonists and have an impact on intestinal CYP26 gene expression and metabolism of all-trans-RA in intestinal cells.
authors.affiliation: Zentrumsabteilung für Lebensmitteltoxikologie, Tierärztliche Hochschule Hannover, Bischofsholer Damm 15, D-30173, Hannover, Germany. alfonso.lampen@tiho-hannover.de
authors.forename: A
authors.initials: A
authors.lastname: Lampen
authors.forename: S
authors.initials: S
authors.lastname: Meyer
authors.forename: H
authors.initials: H
authors.lastname: Nau
mesh_terms: D001565:Benzoates / Q000494:pharmacology; D018938:Caco-2 Cells / Q000187:drug effects / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006801:Humans; D010831:Phytanic Acid / Q000494:pharmacology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects; D018168:Receptors, Retinoic Acid / Q000819:agonists*; D000072516:Retinoic Acid 4-Hydroxylase; D047488:Retinoid X Receptors; D015398:Signal Transduction / Q000187:drug effects; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D014157:Transcription Factors / Q000819:agonists* / Q000187:drug effects; D014212:Tretinoin / Q000032:analysis / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D001565:Benzoates; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D013764:Tetrahydronaphthalenes; D014157:Transcription Factors; C068073:Am 580; D010831:Phytanic Acid; D004281:Docosahexaenoic Acids; D014212:Tretinoin; D003577:Cytochrome P-450 Enzyme System; D000072516:Retinoic Acid 4-Hydroxylase