Enhancing the anti-adipogenic activity of soy protein by limited hydrolysis with Flavourzyme and ultrafiltration

Limited hydrolysis of soy protein isolate (SPI) with Flavourzyme for 2 h to obtain the hydrolysate (FH2h) revealed much higher suppression of glycerol-3-phosphate dehydrogenase (GPDH) activity and relative lipid accumulation (RLA) than intact SPI in 3T3-L1 preadipocytes during differentiation. Lower GPDH activity or RLA indicates higher anti-adipogenic activity. The GPDH significantly decreased from 673 to 477 U/mg protein (p < 0.05). Sequentially fractionating FH2h with 30–1 kDa (kilo-daltons) molecular weight cut-off (MWCO) membranes to obtain the 1 kDa permeate resulted in further reduction of 59% GPDH activity. When comparing the high-performance size-exclusion chromatography (HPSEC) profiles, the most active peptide fraction for the anti-adipogenic activity was primarily composed of small peptides with molecular weight less than 1300 Da. According to the Western immunoblot analysis, 1 kDa permeate inhibits adipogenesis by affecting the expression of peroxisome proliferators-activated receptor γ (PPARγ) and the CCAAT/enhancer binding protein α (C/EBPα) during 3T3-L1 cells differentiation.