Saxagliptin alleviates non-alcoholic fatty liver disease with comorbid diabetes through reducing the expression of integrin avβ5 hereby

Abstract

Objective To observe the effect of saxagliptin on the expression of integrin avβ5 in serum and liver tissues of type 2 diabetes mellitus (T2DM) with non-alcoholic fatty liver disease (NAFLD) and the sinusoidal capillarization, and to explore the pathogenesis of diabetes mellitus complicated with fatty liver and the possible protective mechanism of saxagliptin on diabetes with fatty liver. Methods Rats models of T2DM with NAFLD were established by feeding on a high-fat diet combined with low-dose streptozotocin (STZ) intraperitoneal injection. Fifty male SPF Wistar rats (10 in each group) at 10 weeks of age were divided into 5 groups: normal control (NC), NAFLD, T2DM with NAFLD model control group, integrin avβ5 inhibitor intervention group and saxagliptin intervention group. The rats of the avβ5 inhibitor intervention group were injected with the integrin avβ5 inhibitor lentiviral plasmid (109 TU/ml, 20 μl/day) via the tail vein. The rats of saxagliptin intervention group were treated with saxagliptin (daily dose of 10 mg/kg) gavage for 6 weeks, and the rats of the control group were given the same volume of normal saline. After the treatment for 6 weeks, fasting blood glucose, serum insulin, blood lipids, liver function, liver index and pathological changes were evaluated in all the rats, and the expressions of integrin avβ5 and Vn in the liver tissue were detected with immunohistochemistry and western blotting. Ultrastructure of the liver was detected by transmission electron microscopy. The expression levels of integrin avβ5 and Vn mRNA were detected by RT-PCR. The serum levels of integrin avβ5 in the rat were detected by ELISA. T test was used for comparison between groups. Results (1) Compared with the model group, saxagliptin significantly reduced the serum level of integrin avβ5 in the rats (0.47±0.06 vs 0.96±0.12, t=3.36, all P<0.05); (2) The protein expression levels of integrin avβ5 and Vn in the liver tissue of diabetic rats with fatty liver were significantly higher than those in the normal control group, but the levels were significantly decreased after the treatment with saxagliptin (t=3.16-9.86, all P<0.05). The mRNA expression levels of integrin avβ5 and Vn were consistent with those protein expression (t=3.50-8.33, all P<0.05); (3) Transmission electron microscopy results show: in the model group, the basement membrane of sinusoidal endothelial cells is thickened, continuous and windowless. Moreover, the endoplasmic reticulum in the cytoplasm of hepatocytes proliferates or expands, the mitochondrial sputum decreases or dissolves, and the Disse′s gap widens. And a large amount of collagen fibrosis can be seen in the gap. The basement membrane gradually returns to a basement membrane with a window or discontinuity or thinning, and the expanded endoplasmic reticulum and swollen mitochondria are significantly improved after the treatment with integrin avβ5 inhibitor or saxagliptin; (4) Compared with the model group, the levels of liver coefficient, aspartate aminotransferase, alanine aminotransferase, fasting insulin, and homeostatic model assessment for insulin resistance were significantly decreased in the integrin avβ5 inhibitor or sax intervention group (t=6.11-9.7, all P<0.05). Conclusions Saxagliptin protects diabetes with nonalcoholic fatty liver disease by inhibiting the expression of integrin avβ5 in serum or liver tissue of the rats and integrin avβ5-induced sinusoidal capillarization. Key words: Diabetes mellitus, type 2; Non-alcoholic fatty liver disease; Saxagliptin; Integrin avβ5; Sinusoidal capillarization