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Vitamin E and drug metabolism
1Department of Vitamins and Atherosclerosis, German Institute of Human Nutrition, University of Potsdam, Potsdam-Rehbruecke, Germany. flohe@mail.dife.de
Biochemical and Biophysical Research Communications
|May 24, 2003
Summary
Vitamin E compounds, like tocotrienols, are metabolized by cytochrome P450 enzymes. These vitamin E forms can influence drug metabolism by inducing CYP3A4 and CYP3A5, potentially causing complications.
Area of Science:
- Biochemistry
- Pharmacology
- Nutritional Science
Background:
- Tocopherols and tocotrienols undergo metabolism via side chain degradation, starting with CYP-catalyzed omega-hydroxylation and beta-oxidation.
- Alpha-tocopherol is poorly metabolized, but other tocols yield significant carboxyethyl hydroxychroman (CEHC) in HepG2 cells and human urine.
- Cytochrome P450 enzymes CYP3A4 and CYP4F2 are implicated in tocopherol degradation.
Purpose of the Study:
- To investigate the role of tocopherols and tocotrienols in drug metabolism.
- To explore the interaction between vitamin E compounds and the pregnane X receptor (PXR) pathway.
- To understand the implications of vitamin E's influence on drug-metabolizing enzymes.
Main Methods:
- Analysis of tocopherol and tocotrienol metabolism pathways.
- Investigating CYP3A4 and CYP4F2 involvement in tocopherol degradation.
- Assessing the induction of PXR-driven reporter genes and endogenous CYP3A4/CYP3A5 by vitamin E compounds.
Main Results:
- Tocopherols and tocotrienols are metabolized by CYP-catalyzed omega-hydroxylation and beta-oxidation.
- Tocotrienols, in particular, induce the expression of PXR, CYP3A4, and CYP3A5.
- Evidence suggests a link between vitamin E compounds and drug-metabolizing enzyme induction over 30 years.
Conclusions:
- Vitamin E compounds, especially tocotrienols, can modulate drug metabolism through PXR activation.
- The induction of CYP3A4 and CYP3A5 by vitamin E may lead to drug interactions.
- Potential complications arising from vitamin E's interference with drug metabolism, similar to herbal remedies, warrant consideration.