Soyasaponin ameliorates obesity and reduces hepatic triacylglycerol accumulation by suppressing lipogenesis in high‐fat diet‐fed mice

Soyasaponins are triterpenoid glycosides found in soybean. We investigated whether soyasaponin ameliorates lipid metabolism and its possible mechanisms. In C57BL/6J mice fed a high-fat diet (HFD), soyasaponin (SAP) was orally administered for 9 weeks. Additionally, we evaluated the effect of soyasapogenols on 3T3-L1 adipocytes. In HFD-fed mice, the SAP significantly reduced body weight by 7% and relative adipose tissue weight by 35%. X-ray computed tomography demonstrated that the SAP reduced visceral and subcutaneous adipose tissue weights during week 3 of feeding. The SAP reduced sterol regulatory element-binding protein-1c (SREBP-1c) mRNA levels by 32% in the epididymal adipose tissue, significantly decreasing the triacylglycerol (TAG) content by 37% and SREBP-1c and fatty acid synthase mRNA levels by 52% and 61%, respectively, in the liver. In 3T3-L1 adipocytes, soyasapogenol B significantly decreased lipid droplets. The SAP containing soyasaponin A and B as conjugates demonstrate anti-obesity effects by suppressing adipocyte differentiation and lipogenesis, with a preventive effect on hepatic TAG accumulation by suppressing lipogenesis. PRACTICAL APPLICATION: Soyasaponin is one of the oleanane triterpenoids in soybeans. We have demonstrated that soyasaponin potently reduces body weight and white adipose tissue weight, and hepatic triacylglycerol accumulation in high-fat diet-fed mice. Thus, soyasaponin is a beneficial compound to prevent obesity and fatty liver.