FoxO1 inhibitor restored Mfn2-mediated mitochondrial fusion and enhanced cardiac function in the Dox-treated mice. (A) Representative blots and quantitative data of total FoxO1 protein level in the heart tissues. (B) Representative blots and quantitative data of Mfn2 protein level. The blotting experiments were conducted 6 times independently per group in Figure A–B. (C) Quantitative data of Mfn2 mRNA expression. (D) Representative M-mode echocardiography images. (Quantitative data are presented in E-F) (E) EF, ejection fraction. (F) LVESV, left ventricular end-systolic volume. (G) Quantitative data of mean mitochondrial size. (H) Representative mitochondrial images obtained by transmission electron microscope (Quantitative data are presented in G and I). Original magnification × 15000. Representative mitochondria on the bottom images (local magnifications of top images) were marked with light green pseudo-color to highlight the changes of the mitochondria. (I) The proportion of mitochondria in a specific area categorized into three size groups (< 0.6 μm2, within 0.6–1.0 μm2, >1.0 μm2) was counted. n = 6 independent experiments per group in Figure C–I. One-way ANOVA with Turkey's multiple comparison test was used. *P < 0.05, **P < 0.01, ***P < 0.001. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)