Oral L-theanine administration promotes fat browning and prevents obesity in mice fed high-fat diet associated with the modulation of gut microbiota

Abstract

• L-theanine (LTh) alleviated diet-induced obesity and hepatic steatosis in mice. • LTh enhanced brown fat thermogenic activity and promoted white fat browning. • LTh increased short-chain fatty acids (SCFA)-producing bacteria in feces. • LTh increased the fecal SCFA contents in obese mice. • The dominant bacterial taxa altered by LTh were related with improvement of obesity. L-theanine (LTh), a unique nonproteinic amino acid of tea, is known to possess beneficial effects on diet-induced obesity. This study aimed to evaluate whether orally administrated LTh could improve the adaptive thermogenesis of high-fat diet (HFD)-induced obese mice through regulating the composition of gut microbiota. Mice were fed control diet or a HFD with or without LTh for 12 weeks. Oral LTh administration ameliorated adiposity and hepatic steatosis in HFD mice. LTh increased the metabolic activities of brown fat and subcutaneous white fat by enhancing the expression of a series of thermogenic genes. More importantly, LTh improved the intestinal dysbiosis by decreasing the ratio of Firmicutes / Bacteroidetes , along with increases in the fecal short chain fatty acids concentrations. In conclusion, LTh ameliorates metabolic features of obesity by promoting fat browning and improving gut microbiota composition in HFD mice, which may be a mechanism of LTh-induced beneficial metabolic health.