Objective To investigate the effect of sodium-glucose cotransporter 2 inhibitor (empagliflozin, EMPA) on myocardial remodeling in a mouse uremic cardiomyopathy (UCM) model induced by 5/6 nephrectomy, through the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (PKB/AKT)/p65 signaling pathway.
Methods The animals were divided into three groups: Sham group (n=6), UCM group (n=8), and UCM＋EMPA group (n=8). A UCM model was established in C57BL/6N mice using the 5/6 nephrectomy. Starting from 5 weeks post-surgery, EMPA or a placebo was administered. After 16 weeks, blood pressure, serum creatinine, blood urea nitrogen, 24-hour urine glucose and urine sodium were measured. Cardiac structure and function were assessed by echocardiography. Hematoxylin-eosin (HE) staining and Masson trichrome staining were used to observe pathological changes in the heart and kidneys. Wheat germ agglutinin (WGA) staining was used to evaluate myocardial hypertrophy. The real-time quantitative PCR (RT-qPCR) was used to detect the expression levels of myocardial hypertrophy- and fibrosis-related mRNAs. Western blotting was used to detect the expression levels of PI3K, AKT and p65 in myocardial tissues.
Results After 16 weeks, UCM group exhibited significantly higher blood pressure, serum creatinine, blood urea nitrogen than sham group (P＜0.01); UCM＋EMPA group exhibited lower blood pressure, serum creatinine, blood urea nitrogen, and higher 24 h urine sodium and glucose than UCM group (P＜0.05). Echocardiographic results showed ventricular remodeling in the UCM group, evidenced by left ventricular wall thickening, left ventricular enlargement, increased left ventricular mass, and decreased systolic function (P＜0.05); ventricular remodeling was alleviated (P＜0.05), though there was no significant improvement in systolic function in UCM＋EMPA group. HE and Masson stainings revealed myocardial degeneration, necrosis, and interstitial fibrosis in UCM group (P＜0.01); the myocardial pathology improved with reduced collagen deposition in UCM＋EMPA group (P＜0.01). WGA staining confirmed myocardial hypertrophy in UCM group (P＜0.01), while myocardial hypertrophy was alleviated in UCM＋EMPA group (P＜0.01). RT-qPCR results showed myocardial hypertrophy- and fibrosis-related genes (NPPA, NPPB, MYH7, COL1A1, COL3A1, TGF-β1) were upregulated in UCM group (P＜0.05), but downregulated in UCM＋EMPA group. Western blotting showed PI3K, p-AKT/AKT ratio, and p-p65/p65 ratio were increased in UCM group, but decreased in UCM＋EMPA group (P＜0.05).
Conclusion EMPA can improve myocardial hypertrophy and fibrosis in the UCM mouse model, and it may play the role through inhibiting the PI3K/AKT/p65 signaling pathway.
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