Description: Accumulating evidence supports the role of miR-122 in fatty liver disease. We investigated miR-122 expression in a steatotic hepatocyte model, the effect of miR-122 over-expression and inhibition in the pathogenesis. Human hepatic cell line L02 was induced with oleic acid to establish the steatotic hepatocyte model. Intracellular lipid content was observed with laser scanning confocal microscope (LSCM), and triglyceride content was determined with kits. Total RNA was extracted and reversely transcribed into cDNA. miR-122 expression was measured using qRT-PCR. Subsequently, miR-122 mimic and miR-122 inhibitor were transfected into steatotic hepatocytes to observe their effect on intracellular lipid content. The lipid fluorescence intensity and triglyceride content within the steatotic hepatocytes were significantly higher than those in normal control (860.01 ± 26.52 vs 257.77 ± 29.69 and 3.47 ± 0.12 vs 1.85 ± 0.02 at 24 hours) (p 〈 0.01). miR-122 expression in steatotic hepatocytes was down-regulated compared with that in control (2 －△Ct value: 0.0286 ± 0.0078 vs 0.0075 ± 0.0012) (p〈〈0.01). After transfection, miR-122 expression (2 －△Ct value) in the miR-122 mimic group increased 2.96-fold compared with that in control, and its lipid fluorescence intensity was significantly lower than that in control (790.92 ± 46.72 vs 1022.16 ± 49.66) (p 〈 0.01). Nevertheless, miR-122 expression decreased 3.45-fold in the miR-122 inhibitor group compared with that in control, and its fluorescence intensity was significantly higher than that in control (1386.49 ± 40.34 vs 1022.16 ± 49.66) (p 〈〈0.01). We concluded that miR-122 was down-regulated in steatotic hepatocytes model. The pathogenesis of hepatocyte steatosis was enhanced by miR-122 mimic and reduced with miR-122 inhibitor. J. Cell. Biochem. © 2013 Wiley Periodicals, Inc.