Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 19, 1999
Publication Date: December 19, 1999
Interpretive Summary: Consumption of soybeans is thought to provide health benefits. This study describes the effects of soy protein on 2 important areas necessary to maintain health, called CYP3A and CYP2B. CYP3A and CYP2B are enzymes that breakdown medications and toxins. Therefore, any changes in them will affect health of people taking drugs or exposed to environmental compounds. We have shown in this experiment that rats fed a soy diet will have different ability to breakdown drugs and other compounds that might get into the body. These data also suggest that if a person is taking a medication while eat a soy diet, they will breakdown drugs differently that a non-soy eater.
Technical Abstract: Hepatic CYP3A and CYP2B enzymes were studied in male Sprague-Dawley rats derived from 5-7 litters fed diets in which the protein source was either casein or soy protein isolate. At age 65 d, rats were gavaged with corn oil (vehicle) or 50 mg/kg dexamethasone. Hepatic expression of CYP3A and CYP2B1 mRNA, apoprotein and associated monooxygenase activities were measured. Consumption of soy diets significantly increased monooxygenase activity toward the following: the CYP3A substrates erythromycin and ethylmorphine N-demethylase; corticosterone and testosterone 6-alpha-hydroxylase; and apoprotein and mRNA express of CYP3A (P<0.05). Dexamethasone significantly induced turnover of erythromycin and testosterone, expression of CYP3A apoprotein, and expression of CYP3A1 and CYP3A2 mRNA (P<0.05). In addition, significant diet-inducer interactions were observed in the expression of CYP3A apoprotein and activities toward ethylmorphine, corticosterone and testosterone (P<0.05). Significant diet-inducer interactions were also observed on CYP2B1-dependent pentoxyresorufin O-depentylase activity (P<0.05). However, although dexamethasone significantly induced CYP2B1 expression at the apoprotein and mRNA level (P<0.05), no significant diet effects were observed. These data suggest potential effects of soy consumption on the metabolism of a wide variety of CYP3A and CYP2B1 substrates, especially in situations involving co-exposure to CYP inducers.