568 Small Intestinal Bacterial Overgrowth (SIBO) and Lipoploysaccharide (LPS) Receptors in Non-Alcoholic Steatohepatitis (NASH)

Abstract

Background: Experimental and clinical studies suggest an association between SIBO and NASH. Liver injury and fibrosis could be related to exposure to a bacterial burden, notably endotoxins, of intestinal origin. Moreover, the gut microbiota and endotoxemia have been described to play a contributory role in metabolic dysfunction, particularly insulin resistance, which is a key factor in NASH development. The extracellular receptor molecules for LPS are Lipopolysaccharide Binding Protein (LBP), CD14, toll-like receptor-4 (TLR-4) and myeloid differentiation-2 (MD-2). Endotoxaemia also induces proinflammatory cytokine release from immune cells. Aim: To investigate the prevalence of small intestinal bacterial overgrowth (SIBO) and relationships to LPS receptors and systemic cytokines in NASH. Methods: 18 NASH patients (8 males and 10 females) and 16 ageand gender-matched healthy volunteers were studied. SIBO was assessed by the lactulose breath hydrogen test (LHBT), plasma LBP levels were measured by ELISA and expression (as a %) of TLR-2 and 4 on CD14 positive cells determined by flow cytometry. Proinflammatory mediators (IL-1β, IL-6, IL-8 and TNFα) were measured in plasma by MSD (Meso Scale Discovery). Results: SIBO was more common in NASH patients (71%) than in control subjects (35.7%). This was mainly due to H2 production which was significantly greater in NASH than control at time points 45, 60, 75 and 90minutes during the LHBT (p=0.0241, 0.0476, 0.0470 and 0.0139 respectively). On the other hand, CH4 production was similar in NASH and control groups. No significant differences were detected between NASH and controls for LBP levels, p=0.5448. TLR-4/ MD-2 expression on CD14 positive was significantly higher among NASH patients than in control subjects: % expression, mean ± SEM, NASH vs control: 20.95± 2.91% vs 12.73 ± 2.29%, p=0.048 while TLR-2 expression was not significantly different. Among the cytokines studied, IL-8 levels were significantly higher in patients than control (p=0.0413) and correlated positively with TLR-4 (r=0.5123, p=0.0355) expression but not with TLR-2 expression. Conclusion: Small intestinal bacterial overgrowth is common in NASH, largely related to excess production of H2 and is associated with increased circulating levels of IL-8 and upregulation of TLR-4/MD2.