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 (Δ) in baseline levels of serum FGF21 were positively correlated with Δ BAT activity (P < 0.05). In addition, analysis of each group revealed that there was significant correlation between the Δ serum FGF21 level and Δ 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 Δ basal FGF21 level is associated with Δ 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. TRIAL REGISTRATION: This study is registered with University Hospital Medical Information Network in Japan (number 000038723, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000043942).