Expression of Notch family is altered in non-alcoholic fatty liver disease

The aim of the present study was to explore the dynamic relationship between Notch and non-alcoholic fatty liver disease (NAFLD), both in vitro and in vivo. The LX2, Huh7 and MIHA hepatic cell lines were used to establish a cell steatosis model induced by palmitic acid (PA) at different concentrations (0.1, 0.25 and 0.5 mM). Cell proliferation and migration were assessed using a 5-bromo-2′-deoxyuridine kit and a wound healing assay. The dosage of 0.25 mM PA for 36–48 h treatment was chosen for subsequent experiments. Steatotic cells were identified by Oil Red O staining. Feeding mice a methionine-choline-deficient (MCD) diet is known induce a model of NAFLD, compared with a methionine-choline-sufficient (MCS) diet. Therefore, Notch family mRNA expression was evaluated in the liver of MCD-fed mice at varying time points (days 5, 10, 21 and 70) using reverse transcription-quantitative PCR. Notch expression levels were also assessed in cell lines at 12, 24, 36 and 48 h after PA treatment. Notch signaling molecules changed in the PA or MCD model over time. In vitro, the mRNA levels of Notch1, −2 and −4 increased in all cell lines after 12-h PA treatment. At 24 h, these genes were upregulated only in LX2 cells, while showing a ‘down-up’ pattern in MIHA cells (i.e. these genes were downregulated at 24 h but upregulated at 36 h). However, expression of Notch1, −2, −3 and −4 mRNA rose significantly in the early stage (day 10) of NAFLD. At week 3, the levels of Notch1 and −2 were higher in the MCD group than in the MCS group, while the reverse was observed for Notch3 and −4. Expression of these four genes increased again in the late stage (day 70) of NAFLD. Therefore, these results indicated that Notch family members Notch1-4 were involved in the development of NAFLD and played an important role in steatosis in this model.