AIM: To explore the relationship between small intestinalmotility and small intestinal bacteria overgrowth(SIBO) in Nonalcoholic steatohepatitis (NASH), andto investigate the effect of SIBO on the pathogenesisof NASH in rats. The effect of cidomycin in alleviatingseverity of NASH is also studied. METHODS: Forty eight rats were randomly dividedinto NASH group (n = 16), cidomycin group (n = 16)and control group (n = 16). Then each group weresubdivided into small intestinal motility group (n = 8),bacteria group (n = 8) respectively. A semi-solid coloredmarker was used for monitoring small intestinal transit.The proximal small intestine was harvested under sterilecondition and processed for quantitation for aerobes(E. coli) and anaerobes (Lactobacilli). Liver pathologicscore was calculated to qualify the severity of hepatitis.Serum ALT, AST levels were detected to evaluate theseverity of hepatitis. RESULTS: Small intestinal transit was inhibited inNASH group (P < 0.01). Rats treated with cidomycinhad higher small intestine transit rate than rats in NASHgroup (P < 0.01). High fat diet resulted in quantitativealterations in the aerobes (E. coli ) but not in theanoerobics (Lactobacill). There was an increase in thenumber of E. coli in the proximal small intestinal florain NASH group than in control group (1.70 ± 0.12 log10(CFU/g) vs 1.28 ± 0.07 log10 (CFU/g), P < 0.01). TNF-αconcentration was significantly higher in NASH groupthan in control group (1.13 ± 0.15 mmol/L vs 0.57 ±0.09 mmol/L, P < 0.01). TNF-α concentration was lowerin cidomycin group than in NASH group (0.63 ± 0.09mmol/L vs 1.13 ± 0.15 mmol/L, P < 0.01). Treatmentwith cidomycin showed its effect by significantly loweringserum ALT, AST and TNF-α levels of NASH rats. CONCLUSION: SIBO may decrease small intestinalmovement in NASH rats. SIBO may be an importantpathogenesis of Nash. And treatment with cidomycin by mouth can alleviate the severity of NASH. AIM: To explore the relationship between small intestinal motility and small intestinal bacteria overgrowth (SIBO) in Nonalcoholic steatohepatitis (NASH), and investigate the effect of SIBO on the pathogenesis of NASH in rats. METHODS The effect of cidomycin in alleviating severity of NASH is also studied. METHODS : Forty eight rats were randomly dividedinto NASH group (n = 16), cidomycin group (n = 16) and control group (n = 16). Then each group weresubdivided into small intestinal motility group = 8) respectively. A semi-solid colored marker was used for monitoring small intestinal transit. The proximal small intestine was harvested under sterile condition and processed for quantitation for aerobes (E. coli) and anaerobes (Lactobacilli). Liver pathology was calculated to qualify the severity of hepatitis. Serum ALT, AST levels were detected to evaluate theseverity of hepatitis. RESULTS: Small intestinal transit was inhibited in NASH group (P <0.01). Rats treated with c idomycinhad higher small intestine transit rate than rats in NASHgroup (P <0.01). High fat diet resulted in quantitativealterations in the aerobes (E. coli) but not in theanoerobics (Lactobacill). There was an increase in thenumber of E. coli in the proximal small intestinal florain NASH group than in control group (1.70 ± 0.12 log10 CFU / g vs 1.28 ± 0.07 log10 CFU / g, P <0.01). TNF-αconcentration was significantly higher in NASH groupthan in control group (1.13 ± 0.15 mmol / L vs 0.57 ± 0.09 mmol / L, P <0.01). TNF-α concentration was lower in cidomycin group than in NASH group (0.63 ± 0.09 mmol / L vs 1.13 ± 0.15 mmol / L, P <0.01). Treatment with cidomycin showed its effect by significantly lowering serum ALT, AST and TNF-α levels of NASH rats. CONCLUSION: SIBO may decrease small intestinal motility in NASH rats. SIBO may be important pathogenesis of Nash. And treatment with cidomycin by mouth can alleviate the severity of NASH.