Non-canonical Wnt signaling contributes to development of non-alcoholic steatohepatitis in a rat model of type 2 diabetes mellitus

Abstract

To investigate the role of the non-canonical Wnt signaling pathway in development of non-alcoholic steatohepatitis (NASH) related to type 2 diabetes mellitus (T2DM) using a rat model. Twenty-four male Sprague-Dawley rats were randomly divided into two equal groups: control group, fed a stand diet; T2DM-NASH model group, fed a high sucrose and fat diet for 4 weeks and intraperitoneally injected with streptozotocin (30 mg/kg). Twelve weeks after model establishment, all rats were sacrificed. Serum levels of glucose, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were detected by biochemical analysis. Liver pathological changes were assessed microscopically by hematoxylin-eosin and oil red O staining. The liver expression of Wnt5a and NF-kB p65 were detected by immunohistochemistry and western blotting (protein), and quantitative real-time PCR (mRNA). The T2DM-NASH model group showed significantly higher levels of glucose (control group: 6.25 +/- 1.28 vs. 31.21 +/- 0.86 mmol/L, t = -36.204, P less than 0.01), ALT (31.00 +/- 3.69 vs. 301.50 +/- 8.62 U/L, t = -99.94, P less than 0.01), and AST (77.58 +/- 1.83 vs. 344.75 +/- 1.82 U/L, t = -358.85, P less than 0.01). The T2DM-NASH group also showed remarkable signs of steatosis and inflammation in hepatic tissues. The T2DM-NASH group had significantly higher integral optical density (IOD) detection of Wnt5a (control group: 1.15E4 +/- 577.45 vs. 4.04E5 +/- 2.42E4, t = -56.24, P less than 0.01) and NF-kB p65 (1.28E4 +/- 1.59E3 vs. 4.21E5 +/- 1.68E4, t = -83.895, P less than 0.01), as well as protein levels detected by western blot (Wnt5a: 4.21 +/- 0.34 vs. 1.00 +/- 0.25, t = 17.030, P less than 0.01; NF-kB p65: 4.93 +/- 0.76 vs. 1 +/- 0.13, t = 11.438, P less than 0.01). The hepatic mRNA levels followed the same trend (Wnt5a: 9.53 +/- 0.64 vs. 1.04 +/- 0.35, t = 20.165, P less than 0.01; NF-kB p65: 0.60 +/- 0.13 vs. 0.74 +/- 0.10, t = -1.802, P = 0.125). In the T2DM-NASH group, hepatic Wnt5a protein expression was positively correlated with ALT (r = 0.64, P less than 0.05), AST (r = 0.59, P less than 0.05), and NF-kB p65 protein expression (r = 0.58, P less than 0.05). Wnt5a may activate NF-kB to stimulate an inflammatory response leading to development of NASH related to T2DM.