Objective: Soybean phytoestrogens, such as genistein and daidzein, have become a popular alternative for women undergoing the treatment of menopause symptoms. These isoflavones are also commonly used in traditional medicine in the prevention and treatment of osteoporosis, cardiovascular diseases and cancer Despite the widespread use of soybean preparations as functional foods and dietary supplements, data regarding the safety as well as interactions between herbal medicines and synthetic drugs, especially with antineoplastic agents, remain scarce. Therefore, the aim of the present study was to determine the influence of soybean extract on the expression levels of CYP3A and PXR genes using real-time PCR (RT-PCR).
Materials and methods: Male Wistar rats were given a standardized soybean extract (100 mg/kg p.o.) for 3 and 10 days. Total RNA isolated from the liver tissue was transcribed into cDNA. The level of CYP3A 1/2 and PXR mRNAs expression was analyzed by real-time quantitative PCR using SYBR Green I dye.
Results: Our findings showed that soybean extract containing 37% isoflavones resulted in a significant decrease of CYP3A1 expression level by almost 35% (p<0.05), both after 3 and 10 days, when compared with the control group. No statistically significant differences were noted for CYP3A2 enzyme and the PXR nuclear factor.
Conclusions: These results suggest that soybean extract can decrease the CYP3A1 (homolog to human CYP3A4) expression and may participate in clinically significant interactions with drugs metabolized by CYP3A4 enzyme. Moreover it is postulated that gene expression of CYP3A1 and CYP3A2 (homolog to human CYP3A5) can be regulated indirectly by the PXR transcription factor.