Comparison Between the Effect of Mid-Late-Life High-Intensity Interval Training and Continuous Moderate-Intensity Training in Old Mouse Hearts

Figures

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  Figure 1.. The effects of high-intensity interval training group (HIIT) and continuous moderate-intensity training group (CMIT) on weight, survival rate, exercise capacity, and cardiac function. (A) Treadmill training plan for old mice. (B) The relative change of weight after 8 weeks: calculated as (weight after 8 weeks − baseline weigh)/baseline weight. (C) Survival curves for mice among old control (CON), CMIT, and HIIT groups. (D) Evaluation of exercise capacity using maximum speed. (E) Representative echocardiography graphs displaying M-mode ultrasound in left ventricular long-axis section and pulsed Doppler of mitral valve region in apical four-chamber section from Y, CON, CMIT, and HIIT groups. (F–M) Measurement of average left ventricular ejection fraction (LVEF), ratio of mitral velocity E and A peak (MV E/A), TEI index, left ventricular posterior wall diameter at end-diastole (LVPWd), interventricular septal thickness at end-diastole (IVSd), relative wall thickness (RWT), left ventricular internal diameter at end-diastole (LVIDd), and LV mass. TEI index is calculated as (isovolumic relaxation time + isovolumic contraction time)/ejection time. RWT is calculated as (LVPWd +…

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  Figure 2.. The effects of high-intensity interval training group (HIIT) and continuous moderate-intensity training group (CMIT) on ventricular hypertrophy, deposition of myocardial collagen fibers, and angiogenesis in old mice. (A) HE staining scan of heart coronal section, ×0.8. (B) WGA staining depicting the area of myocardial cells, ×63. (C) Ratio of heart weight to body weight (HW/BW). (D) The mean area of myocardial cells stained with WGA. (E, F) Gene expression related to hypertrophy in cardiac tissue. E, mRNA expression of Nppa; F, mRNA expression of Myh7. N = 4 per group. (G) Masson staining section, ×0.8 and ×63. (H) Quantitative analysis of collagen fiber area as revealed by Masson staining. (I) Picrosirius red staining section examined by ordinary and polarized light microscope. Type I collagen fibers are displayed as orange light, type III collagen fiber are displayed as yellow-green light under polarized microscope, ×40. (J, K) Quantitative analysis of collagen fiber area shown by Picrosirius red staining and the ratio of type I to type III collagen fiber. (L) Immunohistochemical staining of CD31 in mouse cardiac tissue and immunofluorescence staining of isolectin B4 in mouse…

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  Figure 3.. The effects of high-intensity interval training group (HIIT) and continuous moderate-intensity training group (CMIT) on cardiac electrophysiology ex vivo. (A) Electrocardiogram for mice among young (Y), old control (CON), CMIT, and HIIT groups. (B) Electrocardiogram parameters: heart rate, P wave, and QRS duration. (C) Typical right atrial isochronal conduction electrical mapping in sinus rhythm, and corresponding conduction parameters (D). (E) Typical right atrial isochronal conduction maps under programmed electrical stimulation, and corresponding conduction parameters (F). (G) Typical ventricular isochronal conduction optical mapping in sinus rhythm, with corresponding conduction parameters (H). (I) Typical ventricular isochronal conduction optical mapping under S1-S2 ventricular pacing, with corresponding conduction parameters (J). Data represent mean ± SEM. *p < .05 vs CON group, #p < .05 vs CMIT group. ns represents no significant difference. N = 6–8 per group.

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  Figure 4.. The effects of high-intensity interval training group (HIIT) and continuous moderate-intensity training group (CMIT) on action potential and Ca2+ handling. (A) Representative optical mapping recording of APD90 in sinus rhythm and the corresponding quantitative analysis of APD90, APD80, and APD50 in (B), accompanied by optical AP traces (C). (D) Sign of APD triangulation: calculated as APD90 minus APD50 in sinus rhythm. (E) Representative optical mapping recording of APD90 under S1-S2 ventricular pacing. (F) Recording and programmed stimulation configuration for APD90 (G). Quantitative analysis of APD90, APD80, and APD50 under S1-S2 ventricular pacing, and the corresponding optical AP traces (H), along with sign of APD triangulation: APD90 minus APD50 (I). (J) Representative optical mapping recording of Ca2+ transient duration in sinus rhythm, and corresponding conduction parameters (K). (L) Representative optical mapping recording of Ca2+ transient duration under S1-S2 ventricular pacing, and corresponding conduction parameters (M). (N) CSNRT for mice among young (Y), old control (CON), CMIT, and HIIT groups. CSNRT was measured from the last pacing pulse (high-frequency…

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  Figure 5.. The effects of high-intensity interval training group (HIIT) and continuous moderate-intensity training group (CMIT) on aging biomarkers. (A) Serum concentration of senescence-associated secretory phenotype (SASP) across different samples. (B–E) Gene expression of SASP in cardiac tissue. B, mRNA expression of IL1β; C, mRNA expression of IL6; D, mRNA expression of Mmp3; E, mRNA expression of Tnfα. (F, H–K) Expression and quantification of p16, p21, p53, and TERT proteins in the left ventricle using WB. (G) Quantification of telomere relative length (telomere and single-copy gene 36B4 in DNA). Y = young; CON = old control. Data represent mean ± SEM. *p < .05 vs CON group, #p < .05 vs CMIT group. N = 6–14 per group.

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  Figure 6.. The effects of high-intensity interval training group (HIIT) and continuous moderate-intensity training group (CMIT) on myocardial apoptosis and mitochondrial morphology. (A) TUNEL staining of mouse myocardium. Scattered green fluorescent labeled apoptotic nuclei were only observed in the old control group. Blue, DAPI; green, TUNEL; red, α-actin. The magnification of those figures was ×40, the local magnification of CON group was ×200. (B, C) Expression and quantification of BAX and BCL2 in the left ventricle. Data represent mean ± SEM. ns represents no significant difference. N = 8 per group. (D, E) Gene expression of apoptosis markers in cardiac tissue. D, mRNA expression of Bax/Bcl2; E, mRNA expression of Cytochrome C. (F) Ultrastructure of mouse myocardium obtained by transmission electron microscopy. AP = autophagic body; ASS = autophagic lysosome; CL = capillary lumen; LD = lipid drop; M = mitochondria; yellow double arrow = intercalated disc; yellow single arrow = Z-line. Young group (Y), mitochondria were distributed along muscle fibers, with orderly arrangement of mitochondrial cristae and even matrix. Old control group (CON), the intercalated discs were disarrayed.…

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  Figure 7.. The effects of high-intensity interval training group (HIIT) and continuous moderate-intensity training group (CMIT) on energy metabolism, mitochondrial biogenesis, motility, and autophagy. (A, B) Expression and quantification of GLUT1, GLUT4, and CPT1B proteins in the left ventricle detected by WB; (C) ATP contents of cardiac tissue; (D) Relative quantity of mitochondrial DNA = Nd1/Lpl detected by RT-PCR; (E, F) Expression and quantification of PGC1α, NRF1, TFAM, and CS proteins in the left ventricle detected by WB; (G, H) Expression and quantification of DRP1, FIS1, MFN1, and MFN2 proteins in the left ventricle detected by WB; (I, J) Expression and quantification of P62, Beclin1, Parkin, and PINK1 proteins in the left ventricle detected by WB; (K) Immunofluorescence staining of myocardial tissue. Red, DRP1; pink, MFN2; blue, DAPI; green, WGA. The magnification of those figures was ×40. Y, young; CON, old control. Data represent mean ± SEM. *p < .05 vs CON group, #p < .05 vs CMIT group. N = 3–17 per group.