Isoflavone Aglycones and Oligopeptides in Lactic Acid-Fermented Soy Milk Differentially Regulate Lipid Metabolism-Related Gene ExpressionReport as inadecuate




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We previously investigated the physiological effect of an ethanol extract of fermentedsoymilk on rats and clarified that this extract modulated their hepatic lipid metabolism.Although the soy isoflavones and oligopeptides are representative functionalcomponents of the ethanol extract, it remained unclear whether these substancesshare a role in lipid metabolism modulation. Therefore, we attempted to clarify theeffects of isoflavones and oligopeptides in lactic acid-fermented soymilk on lipid metabolism-related gene expression in rats and HepG2 cells. The fermented soymilkextract had a higher isoflavone aglycone content than the soymilk extract. Sevenweek-old male Sprague-Dawley rats were fed an AIN-93G diet, a diet plus 70% soymilkethanol extract, or a diet plus 70% fermented soymilk ethanol extract for 5weeks. Although both the soymilk and fermented soymilk ethanol extracts did notsignificantly affect plasma and hepatic lipid profiles, the expression levels of thegenes encoding CYP7a1 and SREBP-2 were significantly upregulated in the livers ofrats fed with the fermented soymilk extract. Whereas isoflavone aglycones upregulatedCYP7a1-encoding gene expression in HepG2, oligopeptides in soymilk andfermented soymilk downregulated this expression. Oligopeptides in fermented soymilkdownregulated the expression stronger than that observed with soymilk. On theother hand, no significant change in FAS expression was observed in the livers of ratsfed the fermented soymilk extract. Although isoflavone aglycones did not affect FASexpression in HepG2 cells, oligopeptides in fermented soymilk downregulated FASexpression. The downregulation of FAS with oligopeptides from fermented soymilkwas stronger than that from soymilk. In the present animal experiment, the effect onreduction of fat synthesis was not found because of insufficient amount of peptidesderived from digestion of soy protein. These results suggest that isoflavone aglycones increase CYP7a1 gene expression, whereas oligopeptides decrease FAS expression.Isoflavone glycosides and proteins in soymilk were converted to isoflavone aglyconesand oligopeptides by lactic acid fermentation, respectively, and these functionalcomponents independently improved the lipid metabolism. In the present study, itwas found that isoflavone aglycones and oligopeptides in fermented soymilk differentiallyregulate hepatic lipid metabolism-related gene expression. Therefore, theconsumption of fermented soymilk containing isoflavone aglycones and soy oligopeptidesmight prevent dyslipidemia more effectively than that of any other soy food.Fermented soymilk is a superior functional food modulating lipid metabolism.

KEYWORDS

Isoflavone, Oligopeptide, Fermented Soymilk, Lipid Metabolism

Cite this paper

Kobayashi, M. , Egusa, S. and Fukuda, M. 2016 Isoflavone Aglycones and Oligopeptides in Lactic Acid-Fermented Soy Milk Differentially Regulate Lipid Metabolism-Related Gene Expression. Food and Nutrition Sciences, 7, 989-1009. doi: 10.4236-fns.2016.711097.





Author: Maki Kobayashi1*, Shintaro Egusa2, Mitsuru Fukuda3

Source: http://www.scirp.org/



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