RESUMO
Cytochrome P450 2B6 (CYP2B6) is a human enzyme important in chemical detoxification, steroid and fatty acid metabolism that is primarily hepatic. Therefore, induction or inhibition of CYP2B6 may perturb endo- and xenobiotic metabolism and cause adverse reactions. Recent research indicates that mice lacking Cyp2b enzymes are obese with liver steatosis [1] (Heintz et al., J Nutr Biochem, 70:125-137, 2019). Current work is underway to determine the role of CYP2B6 in obesity and fatty acid metabolism, and CYP2B6 fluorescent inhibition assays were used to determine the IC50s of multiple industrial chemicals, pesticides, bile acids, steroids, and fatty acids. In many cases, inhibition of CYP3A4 was also performed in comparison because CYP3A4 is the most abundant hepatic detoxification CYP and therefore by abundance alone may also play a key role in the chemical's metabolism. Further, using the ratio of comparative potency of these compounds for CYP2B6 and CYP3A4, specificity can be estimated for these CYP2B6 inhibitors. These results indicate strong preferential inhibition (greater than 10-fold) of CYP2B6 and include lithocholic acid, arachidonic acid, atrazine, chlorpyrifos, endosulfan, parathion, and nonylphenol. Estradiol was a strong preferential inhibitor of CYP3A4. Other screened CYP2B6 inhibitors include triclosan, ticlopidine, jet fuel, docosahexaenoic acid, linoleic acid, linolenic acid, oleic acid, lithocholic acid, butylate, hexachlorocyclohexane, vinclozolin, pentachlorophenol, metalachlor, butylate, diazinon, avermectin, tribufos, ticlopidine, and bisphenol A. Documentation of xenobiotic and endobiotic inhibition by these CYPs is necessary for proper modeling of the effects of diet, chemical exposure or even mixtures on drug metabolism and potential adverse reactions.
RESUMO
Multiple factors in addition to over consumption lead to obesity and non-alcoholic fatty liver disease (NAFLD) in the United States and worldwide. CYP2B6 is the only human detoxification CYP whose loss is associated with obesity, and Cyp2b-null mice show greater diet-induced obesity with increased steatosis than wildtype mice. However, a putative mechanism has not been determined. LC-MS/MS revealed that CYP2B6 metabolizes PUFAs, with a preference for metabolism of ALA to 9-HOTrE and to a lesser extent 13-HOTrE with a preference for metabolism of PUFAs at the 9- and 13-positions. To further study the role of CYP2B6 in vivo, humanized-CYP2B6-transgenic (hCYP2B6-Tg) and Cyp2b-null mice were fed a 60% high-fat diet for 16 weeks. Compared to Cyp2b-null mice, hCYP2B6-Tg mice showed reduced weight gain and metabolic disease as measured by glucose tolerance tests, however hCYP2B6-Tg male mice showed increased liver triglycerides. Serum and liver oxylipin metabolite concentrations increased in male hCYP2B6-Tg mice, while only serum oxylipins increased in female hCYP2B6-Tg mice with the greatest increases in LA oxylipins metabolized at the 9 and 13-positions. Several of these oxylipins, specifically 9-HODE, 9-HOTrE, and 13-oxoODE, are PPAR agonists. RNA-seq data also demonstrated sexually dimorphic changes in gene expression related to nuclear receptor signaling, especially CAR > PPAR with qPCR suggesting PPARγ signaling is more likely than PPARα signaling in male mice. Overall, our data indicates that CYP2B6 is an anti-obesity enzyme, but probably to a lesser extent than murine Cyp2b's. Therefore, the inhibition of CYP2B6 by xenobiotics or dietary fats can exacerbate obesity and metabolic disease potentially through disrupted PUFA metabolism and the production of key lipid metabolites.