Effects of Soybean Extracts Prepared with Bionuruk on Adipogenesis in 3T3-L1 Adipocytes

Soybean isoflavone aglycones are more readily absorbed by humans than isoflavone glycosides and can inhibit adipogenesis. Various methods are used to convert isoflavone glycosides to their corresponding aglycones. However, few studies have used enzyme complexes to achieve this conversion. The present study examined the changes in the isoflavone profile of soybean extract prepared with Bionuruk, a fermentation starter (SE-B), and investigated its effects on lipid accumulation. SE-B was obtained by reacting soybean with Bionuruk at 37°C for 24 h. High-performance liquid chromatography was used to analyze the isoflavone profile of SE-B. The effects of SE-B on adipogenesis were assessed in 3T3-L1 adipocytes. Cytotoxicity and lipid accumulation were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and Oil Red O assay, respectively. The mRNA and protein expression levels of adipogenesis-related transcription factors were measured by quantitative reverse transcription polymerase chain reaction and Western blot analysis. The isoflavone glycosides in SE-B were converted to their corresponding aglycones through the reaction with Bionuruk. Notably, the highest conversion rate was observed in SE-B10 (SE-B prepared with 10% Bionuruk), which exhibited the strongest inhibition of lipid accumulation (50.3% at 5.4 µg/mL). Furthermore, the mRNA and protein expression levels of peroxisome proliferator-activated receptor gamma, CCAAT/enhancer-binding protein-alpha, and adipocyte protein 2 were lower in cells treated with SE-B10 than in those with other treatments, and the effects were dose-dependent. In conclusion, isoflavone glycosides in soybeans were efficiently converted to their corresponding aglycones through the reaction with 10% Bionuruk, and SE-B10 inhibited lipid accumulation in 3T3-L1 adipocytes, suggesting its potential role in regulating adipogenesis in humans.