Role of MMP-2 and MMP-9 in the Relationship between Inflammation, Fibrosis, and Apoptosis during Progression of Non-Alcoholic Fatty Liver Disease and Diagnostic Significance of Plasma Levels of Their Active Forms

MMP-2 and MMP-9 play an important role in pathogenesis of chronic liver diseases, participating in the processes of inflammation and fibrosis. Their role in progression of non-alcoholic fatty liver disease (NAFLD) is poorly understood. Analysis of MMP-2, -9 levels in the blood plasma of patients with different forms of NAFLD [liver steatosis (LS) and non-alcoholic steatohepatitis (NASH) of weak (-WA), moderate (MA), high (-HA) activity without pronounced fibrosis] was performed. Correlations between the levels of MMP-2, -9 and mRNA of the genes MMP2, MMP9, ADAM17, NLRP3, caspase 3 activity in peripheral blood leukocytes (PBL), TNFα, IL-6, sIL-6R, cytokeratin-18 fragments in plasma were assessed. In steatosis, the levels of MMP2 gene mRNA in PBL and MMP-2 in plasma are lower than in the control, and expression of the NLRP3 gene in PBL is increased relative to other groups. In the NASH-WA, the level of MMP-9 is higher than in the control, in LS, and in NASH-MA, which could be associated with activation of inflammation during transformation of LS into NASH. The plasma level of MMP-9 over 389.50 pg/ml has been shown to be diagnostically significant for identification of NASH-WA among the patients with steatosis (AUC ROC = 0.818, 95% CI = 0.689-0.948, p < 0.001). In NAFLD, the level of MMP-9 could be associated not only with inflammation, but also with apoptosis. ADAM17 probably plays a certain role in this regard. In the advanced NASH, hepatocyte apoptosis is increased, the level of caspase 3 activity in PBL is increased, the level of MMP-9 in the blood is reduced to the level of the control and LS. In the NASH-HA, the level of mRNA of the ADAM17 gene in PBL is increased compared to the control, NASH-WA, and NASH-MA. Thus, MMP-2 and MMP-9 are involved in pathogenesis of NAFLD already at the early stages and their level in blood could be associated with the presence and severity of inflammation in the liver parenchyma.