Beneficial effects of heat-treated Enterococcus faecalis FK-23 on high-fat diet-induced hepatic steatosis in mice

A high-fat diet (HFD) is one of the causes of hepatic steatosis. We previously demonstrated that Enterococcus faecalis FK-23 (FK-23), a type of lactic acid bacteria, exhibits an anti-obesity effect in mice fed a HFD. In the present study, we examined the effects of FK-23 on HFD-induced hepatic steatosis. Male C57BL/6 mice were divided into four groups and given one of four treatments: standard diet (SD); standard diet supplemented with FK-23 (SD + FK); HFD; or HFD supplemented with FK-23 (HFD + FK). For the administration of FK-23, the drinking water was supplemented with FK-23 at a concentration of 2% (w/w). After 11 weeks, histological findings revealed hepatic steatosis in the liver of HFD-fed mice; however, this effect was attenuated by the administration of FK-23. The expression levels of genes involved in fatty acid oxidation in the liver tissue were significantly reduced in the HFD group compared with the SD group, but FK-23 supplementation tended to up-regulate the expression levels of these genes. Our findings show that the inhibitory effect of FK-23 against hepatic steatosis in HFD-fed mice can be explained by the prevention of fat accumulation in the liver through the modulation of the activities of genes involved in hepatic fatty acid oxidation.