The role of small intestinal bacterial overgrowth, intestinal permeability, endotoxaemia, and tumour necrosis factor α in the pathogenesis of non-alcoholic steatohepatitis

Background-Small intestinal bacterial overgrowth may contribute to the development of non-alcoholic steatohepatitis, perhaps by increasing intestinal permeability and promoting the absorption endotoxin or other enteric bacterial products. Aims-To investigate the prevalence small intestinal bacterial overgrowth, increased intestinal permeability, elevated endotoxin, and tumour necrosis factor alpha (TNF-alpha) levels in patients with nonalcoholic steatohepatitis and in control subjects. Patients and methods-Twenty two patients with non-alcoholic steatohepatitis and 23 control subjects were studied. Small intestinal bacterial overgrowth was assessed by a combined C-14-D-xylose and lactulose breath test. Intestinal permeability was assessed by a dual lactuloserhamnose sugar test. Serum endotoxin levels were determined using the limulus amoebocyte lysate assay and TNF-alpha levels using an ELISA. Results-Small intestinal bacterial overgrowth was present in 50% of patients with non-alcoholic steatosis and 22% of control subjects (p=0.048). Mean TNF-alpha levels in non-alcoholic steatohepatitis patients and control subjects were 14.2 and 7.5 pg/ml, respectively (p=0.001). Intestinal permeability and serum endotoxin levels were similar in the two groups. Conclusions-Patients with non-alcoholic steatohepatitis have a higher prevalence of small intestinal bacterial overgrowth, as assessed by the C-14-D -xylose-lactulose breath test, and higher TNF-alpha levels in comparison with control subjects. This is not accompanied by increased intestinal permeability or elevated endotoxin levels.