Soybean meal fermented by Aspergillus awamori increases the cytochrome P-450 content of the liver microsomes of mice

The effect of soybean meal fermented by Aspergillus awamori on the acute le thality of acetaldehyde, pentobarbital sleeping time, and cytochrome P-450 content of the hepatic microsomes was studied in mice. Most of the daidzin and genistin in soybean meal (SBM) were converted into the respective aglyc ones, daidzein and genistein, by fermentation. In experiment 1, mice were f ed isonitrogenic test diets with one of the following five protein sources for 28 d: casein, SBM, fermented and hot-air-dried SBM (FSBM-HD), fermented and freeze-dried SBM (FSBM-FD), or methanol-extracted FSBM-FD (FSMB-FD-R). The acute lethality of acetaldehyde in mice fed the FSBM-FD diet was signi ficantly lower than that in mice fed the SBM, FSBM-HD, or FSBM-FD-R diet. I n experiments 2 and 3, mice were fed isonitrogenic test diets with one of t he following four protein sources for 28 d: casein, SBM, FSBM-FD, and FSBM- FD-R. The pentobarbital sleeping time was significantly shorter and the cyt ochrome P-450 content was significantly higher in the mice fed the FSBM-FD diet than the respective value in mice fed the other test diets. In experim ent 4, mice were fed one of eight diets which contained different levels of aglycone obtained by varying the proportion of FSBM-FD and FSBM-FD-R, for 28 d. The cytochrome P-450 content in hepatic microsomes increased as the d ietary level of isoflavonoid aglycones increased, but there was a saturatio n phenomenon. These results suggest that soy isoflavonoid aglycones are mor e potent inducers of cytochrome P-450 than isoflavonoid glycosides.