Objective It has been mentioned that myocardial fibrosis which contributes to cardiac dysfunctions is one of the hall markers of diabetic cardiomyopathy. Up-regulation of reactive oxidative species (ROS)/TGF- beta 1/Smad signalling was described to enhance collagen synthesis and fibroblasts proliferation through activating connective tissue growth factor (CTGF). As an essential trace element, selenium (Se) has cardioprotective effects because of its antioxidant property. However, its role in diabetic cardiomyopathy against myocardial fibrosis has not been elucidated. In this study, we investigated effects of Se on myocardial fibrosis and its possible mechanisms.
Methods I.p. injection of streptozotocin (STZ) at 50mg/Kg was administrated to induce type 1 diabetes in rats. Supplementation of Se was performed by i.p. injection of sodium selenite. Animals were divided into 4 groups: control group (Ctrl), diabetic group (D), normal animal with Se treatment (N+Se) and diabetic animal with Se treatment (D+Se). Intracellular generation of ROS was detected by 2’7- dichlorofluorescein staining. Activity of cellular glutathione peroxidase (GPx) was measured by spectrophotometrical method. Sirius red and Masson staining, gene expression examination of collagen type I (Coll-I) and fibronectin (FN) were employed to detect myocaridal fibrosis. Gene expression examination of TGF-beta 1, phosphorylated- Smad2, Smad2, phosphorylated- Smad3, Smad3 and CTGF was aimed to demonstrate the expression of Smad- CTGF signalling pathway.
Results Significant myocardial fibrosis characterised by Mason staining, Sirius red staining, up-regulation of Coll-I and FN gene expression was found in diabetic rats (D), which was then attenuated by Se treatment (D+Se). Mechanically, accompanied by myocardial fibrosis, intracellular GPx activity decreased significantly in D compared with Ctrl and N+Se, resulting in increased formation of intracellular ROS. Meanwhile, activation of Smad-CTGF signalling pathway marked by up- regulation of TGF-beta 1, phosphorylated- Smad2/Smad2, phosphorylated-Smad3/Smad3 and CTGF was detected in D. However, after treatment of Se, down- regulation of Smad-CTGF signalling pathway in D+Se compared with D resulted in alleviation of myocardial fibrosis.
Conclusions These results demonstrate that Se supplementation ameliorates myocardial fibrosis in diabetic cardiomyopathy through modulating GPx/ROS/Smad/CTGF signalling pathway, whose activation may participate in myocardial fibrosis in diabetes.