Résumé
In a rat model of metabolic syndrome (MS), our previous studies have shown that dietary sodium restriction prevents both metabolic and cardiac damages associated with MS. Our aim is now to investigate whether the beneficial effects of sodium restriction could be mediated by endothelial to mesenchymal (EndoMT) transition in the myocardium thereby preventing cardiac fibrosis.High fructose (60%) Sprague Dawley rats were divided into 2 groups: low sodium (<0.01% NaCl, N=20) or normal sodium (0.65% NaCl, N=20) diet for 8 weeks. EndoMT was investigated by q-PCR, WB, and IF on the left ventricles. Transcriptomic analysis was performed using Agilent Rat Gene Expression Microarray. After 8 weeks, fructose-fed rats on normal sodium diet were insulin-resistant and hypertensive, both abnormalities being significantly prevented by sodium restriction. In left ventricles, two mesenchymal proteins, α-smooth muscle actin (αSMA) and vimentin were found significantly reduced using qPCR and WB by sodium restriction (P<0.05), as compared to normal sodium diet. At the opposite, we observed a significant increase in Pecam-1, a specific protein of vascular endothelial cells (P<0.05). Using IF, we detected a co-expression of αSMA and Pecam-1 in 67.3%±4.9 (54 of 88) of cardiac vessels of rats fed normal sodium diet, as compared to 42.3%±3.8 (37 of 88) in rats fed low sodium diet (P<0.05). The transcriptomic study showed that 22 genes, involved in fibrosis, were down-regulated in left ventricles of sodium-restricted rats (P<0.05). By q-PCR, we confirmed that 17 of them were significantly reduced by the low sodium diet (P<0.05). Finally, we established an in vitro model of EndoMT, using primary human aortic endothelial (HAoE) cells that were transdifferentiated with TGF-β2 (10ng/ml). We evidenced in HAoE cells the co-expression of Pecam-1 and collagen-1, as a signature of EndoMT. Especially, fibulin 5, one of the genes identified by transcriptomics was found upregulated (13 folds) in the presence of TGF-β2, confirming its potential role in EndoMT. Our study shows that EndoMT is involved in the prevention of cardiac fibrosis by sodium restriction in our rat model of MS. We also confirmed the involvement of ew genes that could be of interest to improve the management of cardiac fibrosis.