The molecular pathogenesis of non-alcoholic steatohepatitis (NASH) is not well defined. The objective of the present study was to identify disease progression-related cytokines and investigate the molecular pathogenesis of such changes in NASH.

A study population of 20 non-alcoholic fatty liver (NAFL) and 59 NASH patients diagnosed by liver biopsy and 15 healthy volunteers was recruited. The serum pro- and anti-inflammatory cytokines were measured by a multiple enzyme-linked immunosorbent assay. The hepatic mRNA expressions of cytokines were measured by real-time PCR. A monocyte cell line was stimulated with Toll-like receptor (TLR) ligand under a high glucose and insulin condition, and cellular cytokine mRNA expression was quantified.

One group of cytokines was higher in NAFL and NASH than in controls, while another group was higher in NASH than in NAFL and controls. The NASH-specific second group included interleukin (IL)-15 and interferon-γ-inducible protein (IP)-10. In particular, IP-10 was higher in NAFL than in controls and higher in NASH than in NAFL and controls. The sensitivity to diagnose NASH was 90%, with specificity of 50%. Insulin resistance reflecting a high glucose and insulin condition resulted in higher IP-10 mRNA expression in the monocyte cell line only with concomitant TLR-2 stimulation.

IP-10 is a sensitive marker of the need for liver biopsy. Insulin resistance with bacteria-related TLR-2 stimulation might induce IP-10 production from monocytes. Insulin resistance and intestinal barrier function should be intensively controlled to prevent progression from NAFL to NASH.