Estrogenic activity of fermented soymilk extracts and soy compounds

Abstract

To understand the complex mechanism of estrogen action, multiple assays based on different biological principles are necessary. The estrogenic activity of soymilk extracts was evaluated for soymilk extracts before and after fermentation using Lactobacillus delbrueckii, and the data were compared with major isoflavone constituents. Cell, protein, and transcription assays were used in this study to evaluate the estrogenic activity of soymilk extracts before and after fermentation, in addition to the activity of four soy compounds, namely genistein and daidzein and their glycosides, genistin and daidzin. These assays clearly demonstrated the estrogenic activity of these soymilk extracts and soy compounds, although the presence of complex mechanisms for the responses at the transcription level, presumably due to the differences in the mechanism of estrogen signaling. Furthermore, greater estrogenic activity was observed after fermentation of the soymilk extracts. The data obtained by RNA-sequencing were further examined using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases to determine cell functions, i.e., biological processes and metabolic pathways. Among the identified cell functions, the sets of genes for cell division/cell cycle and DNA replication/DNA repair were significantly up-regulated, whereas those for autophagy were significantly down-regulated, which explains the enhanced cell proliferation promoted by these materials. The estrogenic activity of soymilk extracts and soy flavonoids, and the contribution of fermentation, have multiple pharmacological benefits, including bone protection/bone regeneration, cancer chemoprevention, neuroprotection, and the treatment of menopausal syndromes.

Keywords

• Estrogenic activity
• Soy flavonoid
• Fermentation
• Cell functions
• Cell signaling pathway
• Gene expression