| First Author | Traber MG | Year | 2005 |
| Journal | Free Radic Biol Med | Volume | 38 |
| Issue | 6 | Pages | 773-85 |
| PubMed ID | 15721988 | Mgi Jnum | J:98008 |
| Mgi Id | MGI:3576952 | Doi | 10.1016/j.freeradbiomed.2004.11.027 |
| Citation | Traber MG, et al. (2005) Alpha-tocopherol modulates Cyp3a expression, increases gamma-CEHC production, and limits tissue gamma-tocopherol accumulation in mice fed high gamma-tocopherol diets. Free Radic Biol Med 38(6):773-85 |
| abstractText | Although all forms of vitamin E are absorbed, the liver preferentially secretes alpha-, but not gamma-tocopherol, into plasma. Liver alpha-tocopherol secretion is under the control of the alpha-tocopherol transfer protein (TTP). Therefore, to assess gamma-tocopherol bioactivities Ttpa-/-, +/- and +/+ mice were fed for 5 weeks diets containing gamma-tocopherol 550 (gamma-T550), gamma-tocopherol 60 (gamma-T60) mg/kg that also contained trace amounts of alpha-tocopherol, a vitamin E-deficient diet, or a control diet. Plasma and tissues from mice fed gamma-T550 diets were found to contain similar gamma- and alpha-tocopherol concentrations despite the high dietary gamma-tocopherol content; nervous tissues contained almost no gamma-tocopherol. Liver vitamin E metabolites (carboxyethyl hydroxychromans, CEHCs) were also measured. In mice with widely ranging liver alpha- (from 0.7 to 16 nmol/g) and gamma-tocopherol concentrations (0 to 13 nmol/g), hepatic alpha-CEHC was undetectable, but gamma-CEHC concentrations (0.1 to 0.8 nmol/g) were correlated with both alpha- and gamma-tocopherol concentrations (P < 0.004). Hepatic cytochrome P450s (CYPs) involved in vitamin E metabolism, Cyp4f and Cyp3a, were also measured. There were no variations in Cyp4f protein expression as related to diet or mouse genotype. However, Cyp3a was correlated (P < 0.0001) with liver alpha-, but not gamma-tocopherol concentrations. These data support the hypothesis that alpha-tocopherol modulates xenobiotic metabolism by increasing Cyp3a expression, gamma-CEHC formation, and the excretion of both gamma-tocopherol and gamma-CEHC. |
