Effects of beta-conglycinin intake on circulating FGF21 levels and brown adipose tissue activity in Japanese young men: a single intake study and a randomized controlled trial

Background: Human brown adipose tissue (BAT) activity has beneficial effects on body composition and glucose metabolism. A previous study reported that beta-conglycinin intake induced postprandial fibroblast growth factor 21 (FGF21) secretion, thereby promoting adipose tissue thermogenesis in mice. Since it has not been evaluated whether beta-conglycinin intake is associated with induced FGF21 secretion and BAT thermogenesis in humans, the current study examined the effects of beta-conglycinin intake on circulating FGF21 level and BAT activity. Methods: Twenty-two healthy young male subjects participated. This study consisted of 2 interventional studies. In one of them, the effects of single beta-conglycinin intake at thermoneutral temperature on circulating FGF21 levels were examined (n= 7). The other study was a single-blinded randomized crossover trial of 2 weeks (n= 14). The subjects were exposed to mild cold conditions using a climatic chamber, and BAT activity was analyzed using thermography. Serum FGF21 level was determined by ELISA in these studies. Results: In the single intake study, serum FGF21 level was the highest before beta-conglycinin intake and gradually and significantly decreased throughout the 2-h experimental period (P< 0.05). The randomized crossover trial showed that 2-week beta-conglycinin intake did not affect serum FGF21 level and BAT activity, whereas changes (Delta) in baseline levels of serum FGF21 were positively correlated with Delta BAT activity (P< 0.05). In addition, analysis of each group revealed that there was significant correlation between the Delta serum FGF21 level and Delta BAT activity in the beta-conglycinin group (P< 0.05), but not in the placebo group. Conclusions: This study reveals that although serum FGF21 levels are not increased by a single or short-term intake of beta-conglycinin, the Delta basal FGF21 level is associated with Delta BAT activity. These results suggest that human FGF21 responsiveness is different from that of rodents and support the importance of FGF21 in human BAT thermogenesis.