Fecal fermentation products of common bean-derived fiber inhibit C/EBPα and PPARγ expression and lipid accumulation but stimulate PPARδ and UCP2 expression in the adipogenesis of 3T3-L1 cells

Clinical and animal studies have suggested efficacies of common bean (Phaseolus vulgaris) consumption on weight loss. Fermentation of common bean-derived dietary fiber by gut microbiota is proposed to mitigate obesity; however, the mechanism of action is unclear. The objective of this study was to investigate whether and how fecal fermentation of common bean-derived dietary fiber impacts adipogenesis in a cell model. Dietary fiber was generated by in vitro digestion of cooked, lyophilized common bean flour, followed by anaerobic fermentation with the use of fresh feces from healthy mice without antibiotics treatment. The murine 3T3-L1 cells were induced to differentiate in the presence of the fermentation products. Treatment of the fecal fermentation products inhibited adipocyte differentiation and lipid accumulation in a dose- and time-dependent manner. The fermentation products decreased (P<.05) protein levels of two key transcription factors for adipogenesis, CCAAT/enhancer binding protein α and peroxisome proliferator-activated receptor γ by 79-92% and 78-90%, respectively, and one of their downstream targets fatty acid binding protein 4 by 49-86% and 63-98% at protein and mRNA levels, respectively, during the time course. In contrast, the fermentation products increased (P<.05) levels of two proteins promoting energy expenditure, peroxisome proliferator-activated receptor δ (71-91%) on days 2 and 4 and mitochondrial uncoupling protein 2 (1.1-1.2 fold) on days 4-8. Altogether, fecal fermentation of dietary fiber derived from in vitro digestion of common bean temporally and dose-dependently inhibits adipogenesis and key adipogenic transactivators, but activates two energy expenditure proteins in 3T3-L1 cells.