Capsinoids suppress diet-induced obesity through uncoupling protein 1-dependent mechanism in mice

•Capsinoids repressed HFD-induced increase in body weight and adiposity in WT mice.•Anti-obesity effects of capsinoids were not observed in UCP1-KO mice.•Capsinoids increased UCP1 expression in BAT but not in WAT of WT mice. Capsinoids are less pungent capsaicin analogues that increase whole body energy expenditure and hence reduce fat. Several studies have suggested that capsinoids activate brown adipose tissue (BAT), a major site of adaptive thermogenesis, but the actual contribution of BAT and uncoupling protein 1 (UCP1), a thermogenic protein expressed in BAT, to the fat-reducing effect of capsinoids has not yet been determined. Here, we investigated the effect of capsinoids on high-fat diet (HFD)-induced obesity using wild-type (WT) and UCP1-deficient (KO) mice. Capsinoids feeding potently suppressed HFD-induced increase in body weight, adiposity, and fatty liver development in WT mice. In contrast, such effects of capsinoids were completely abolished in UCP1-KO mice. Moreover, capsinoids significantly increased UCP1 protein expression in BAT without its apparent induction in white adipose tissue (WAT) in WT mice. These results indicate that capsinoids suppress diet-induced obesity of mice through the UCP1 function in BAT but not in WAT.