Title: Lactobacillus casei strain Shirota protects against non-alcoholic steatohepatitis

33 34 Gut microbiota alterations are 35 associated with various disorders. In 36 this study, gut microbiota changes were 37 investigated in a methionine-choline 38 deficient (MCD) diet-induced 39 non-alcoholic steatohepatitis (NASH) 40 rodent model, and the effects of 41 administering Lactobacillus casei strain 42 Shirota (LcS) on the development of 43 NASH were also investigated. Mice 44 were divided into three groups, given 45 the normal chow diet (NCD), MCD 46 diet, or the MCD diet plus daily oral 47 administration of LcS for 6 weeks. Gut 48 microbiota analyses for the three 49 groups revealed that lactic acid bacteria 50 such as Bifidobacterium and 51 Lactobacillus in feces were markedly 52 reduced by the MCD diet. Interestingly, 53 oral administration of LcS to MCD 54 diet-fed mice increased not only the 55 L.casei subgroup but also other lactic 56 acid bacteria. Subsequently, NASH 57 development was evaluated based on 58 hepatic histochemical findings, serum 59 parameters and various mRNA and/or 60 protein expression levels. LcS 61 intervention markedly suppressed 62 MCD-diet induced NASH development, 63 with reduced serum lipopolysaccharide 64 concentrations, suppression of 65 inflammation and fibrosis in the liver, 66 and reduced colon inflammation. 67 Therefore, reduced populations of 68 lactic acid bacteria in the colon may be 69 involved in the pathogenesis of MCD 70 diet-induced NASH, suggesting 71 normalization of gut microbiota to be 72 effective for treating NASH. 73 74 75