Loss of microRNA-27a induces cardiac dysfunction through activating FoxO1.

OBJECTIVE:To elucidate how microRNA-27a and FoxO1 regulate cardiac dysfunction in mice. MATERIALS AND METHODS:Expression levels of ANP, BNP, β-MHC, α-SMA, Fn1, and Periostin in myocardial tissues of 2-month-old and 8-month-old microRNA-27a-KO mice and age-matched wild-type mice were determined by quantitative Real (qRT-PCR) and Western blot. Dual-luciferase reporter gene assay was conducted in H9C2 cells to verify the binding condition between microRNA-27a and FoxO1. By transfection of microRNA-27a mimics or inhibitor, FoxO1 expression in H9C2 cells was determined at the mRNA and protein levels. HW/BW [ratio of heart weight (mg) and body weight (mg)], HW/TL [ratio of heart weight (mg) and tibial length (mm)], LVPWDT [left ventricular posterior wall diastolic thickness (mm)], LVEDD [left ventricular end-diastolic dimension (mm)], and FS (fractional shortening) in mice treated with or without FoxO1 inhibitor AS1842856 were accessed through echocardiography. RESULTS:MicroRNA-27a-KO mice had larger LVEDD, HW/BW, and HW/TL, but lower FS and LVPWDT than those of age-matched wild-type mice. Besides, higher levels of ANP, BNP, β-MHC, α-SMA, Fn1, and Periostin were observed in myocardial tissues of microRNA-27a-KO mice compared with those of age-matched wild-type mice. Dual-luciferase reporter gene assay revealed lower luciferase activity in H9C2 cells co-transfected with microRNA-27a mimics and wild-type FoxO1 than that of controls. The expression level of FoxO1 was negatively regulated by microRNA-27a in H9C2 cells at the mRNA and protein levels. After AS1842856 injection, HW/BW, HW/TL, and LVEDD in microRNA-27a-KO mice markedly decreased, whereas FS and LVPWDT elevated. By comparison, AS1842856 injection did not influence cardiac development in wild-type mice. CONCLUSIONS:MicroRNA-27a knockout could induce cardiac dysfunction in mice through upregulating FoxO1 expression.

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