Exploration of Perturbed Liver Fibrosis-Related Factors and Collagen Type I in Animal Model of Non-Alcoholic Fatty Liver Disease

Abstract

To determine their involvement in the onset of the disease, we investigated the changing levels of liver fibrosis-related proteins, namely, type-I collagen, α-smooth muscle actin (α-SMA), and transforming growth factor β1 and β3 (TGF-β1, β3). The four groups of Sprague-Dawley (SD) rats were involved in the study, namely, (i) normal control group, (ii) high-fat diet group (HFD), (iii) carbon tetrachloride (CCl₄) group, and (iv) NAFLD group (animal model) which were chosen at random. The NAFLD model received HFD combined with subcutaneous injection of small doses of CCl₄. Histopathological examination confirmed extent of liver fibrosis, while other immunological and molecular methods were used to evaluate expression and distribution of α-SMA, type I collagen TGF-β1 and TGF-β3, at both m-RNA and protein levels. In contrast to the normal control group, the NAFLD group showed moderately elevated expressions of TGF-β1, α-SMA, and type I collagen, which was proportional on temporal scale of NAFLD persistence in the model (P < 0.05). In the early phage of NAFLD, enhancement in the mRNA transcripts and, henceforth, protein expression of TGF-β3 was observed. However, these were found to be downregulated in case of liver fibrosis (P < 0.05). This NAFLD rat model shows the histopathologic changes of human NAFLD and is suitable for the study of NAFLD pathogenesis. These findings suggest that type I collagen and the liver fibrosis-related factors TGF- β1, TGF- β3, and α-SMA may be significant contributors to NAFLD. Although NAFLD model is previously demonstrated by other researchers, our study is novel in terms of exploration of involvement of fibrosis-related factors and in particular aforementioned proteins at the early stage of NAFLD vis-à-vis dynamics of type-I collagen distribution.

Keywords: Liver fibrosis; Non-alcoholic fatty liver disease; TGF-β1; TGF-β3; α-SMA.