Effects of 6-months' Exercise on Cardiac Function, Structure and Metabolism in Female Hypertensive Rats–The Decisive Role of Lysyl Oxidase and Collagen III

Figures

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  Figure 1. Microrespiratory measurements on permeabilized heart and skeletal muscle fibers. (A) Running training improved complex I respiration and did not influence complex II activity in the LV. (B) The efficiency of complex I as well as complex II respiration was increased in the soleus muscle of both running groups. Data are means ± S.D. of n = 6 animals. *p < 0.05 vs. Wistar sed., #p < 0.05 vs. SHR sed.

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  Figure 2. Effects of running training on muscle growth. (A) A comparable increase in muscle weight (red and white fraction of the gastrocnemius muscle) was found in both running groups. Data are means ± S.D. of n = 6 animals. *p < 0.05 vs. Wistar sed., #p < 0.05 vs. SHR sed. (B) Gains in BW could be observed in all groups over the study period, however, the largest increase could be determined in running SHR. Data are means ± S.D. of n = 6 animals. *p < 0.05 vs. first week, #p < 0.05 vs. 26th week SHR sed.

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  Figure 3. Development of the BP and the resting HR. Neither the temporal development nor the level of the systolic or diastolic BP were affected by 6-months' voluntary aerobic training in (A) Wistar rats and (B) pre-hypertensive SHR. Blood pressure values of non-runners are represented by a solid line, values of runners are represented by a broken line. Data are means ± S.D. of n = 6 animals. *p < 0.05 vs. Wistar sed., #p < 0.05 vs. SHR sed. (C) HR was lowered over the entire course of the training in the running animals compared to the non-running controls. Data are means ± S.D. of n = 6 animals. *p < 0.05 vs. first week, #p < 0.05 vs. 26th week sed.

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  Figure 4. Effects of running training on cardiac hypertrophy. (A) The wet weight of the LV was normalized to the TL. (B) Left ventricular hypertrophy is also marked by the corresponding expression of ANP. Data are means ± S.D. of n = 6 animals. *p < 0.05 vs. Wistar sed., #p < 0.05 vs. SHR sed.

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  Figure 5. Regulation of reactive oxygen species in the LV. DHE staining was performed to measure the formation of O2-• in heart tissue from the LV of all treatment groups. Slides were imaged by fluorescence microscopy using an excitation wavelength of 488 nm and an emission wavelength of 540 nm. Data are means ± S.D. of n = 4 hearts. *p < 0.05 vs. Wistar sed., #p < 0.05 vs. SHR sed.

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  Figure 6. Remodeling of the extracellular collagen matrix. (A) The running training did not affect the expression of Col-I but markedly increased the expression of Col-III notably in SHR. (B,C) PCR results for collagen could be verified subsequently using both Sirius Red staining of histological sections and western blot. (D) The expression of pro-fibrotic factors (TGF-β1, CTGF, and FGF2) was reduced in both exercise groups. Data are means ± S.D. of n = 6 animals. *p < 0.05 vs. Wistar sed., #p < 0.05 vs. SHR sed.

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  Figure 7. LOX as a critical risk factor for cardiac remodeling during a 6-months' aerobic running training. (A) The mRNA expression of LOX was analyzed in tissue from the LV using real-time RT PCR. The expression of HPRT was used for normalization. (B,C) Representative immunoblots and densitometric analysis of the pre-LOX (50 kDa) and the catalytically active mature LOX (30 kDa). Immunoblot bands were all normalized to GAPDH (S, sed.; R, run.). (D–F) A significant correlation was found between LOX expression and the expression of Col-III (R2 = 0.83) as well as the LV/TL ratio (R2 = 0.84) in SHR. However, LOX does not correlate with the mRNA expression of the Col-I isoform (R2 = 0.18). (G) There is also a significant correlation between the E/A ratio and the Col-III expression in SHR (R2 = 0.66). Data are means ± S.D. of n = 6 animals. *p < 0.05 vs. Wistar sed., #p < 0.05 vs. SHR sed.

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  Figure 8. Regulatory mechanisms in cardiac fibroblasts. (A) By incubating cardiac fibroblasts with OPN, the mRNA expression of LOX and Col-III increased after 24 and 48 h, respectively. (B) OPN expression in cardiac fibroblasts could be induced by Ang-II and NAC. (C–E) Ang-II increased the expression of LOX and Col-III, however, Col-III expression depends on the presence of LOX (si-LOX, siRNA against LOX; sc-LOX, control siRNA). Data are means ± S.D. of n = 6 hearts. *p < 0.05 vs. control, #p < 0.05 vs. Ang-II. (F) Downregulation of OPN reduced the expression of LOX in both unstimulated and Ang-II stimulated cells after 48 h (si-OPN, siRNA against OPN). Data are means ± S.D. of n = 6 hearts. *p < 0.05 vs. control. (G) OPN mRNA was primarily elevated in left ventricular tissue of trained SHR. The expression of HPRT was used for normalization. Data are means ± S.D. of n = 6 animals. *p < 0.05 vs. Wistar sed., #p < 0.05 vs. SHR sed.

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  Figure 9. Aerobic endurance training in the concomitant presence of hypertension. Despite desired functional and metabolic adaptation reactions, running training in combination with arterial hypertension induced a myocardial hypertrophy as well as significant fibrosis, and thus, a diastolic functional disorder, which critically affects the prognosis in the medium to long term.