ABC | Volume 115, Nº1, July 2020

Original Article Silva-Bertani et al. Mechanism of decreased heart collagen I in obesity Arq Bras Cardiol. 2020; 115(1):61-70 obese animals. This finding is consistent with some previous researchers who investigated SBP in obese animals fed a high- fat diet 38 and in disagreement with others. 27 The main objective of this study was to investigate whether increased MMP-2 activity by leptin is responsible for the reduction in myocardial collagen type I in obese rats. The results of this investigation indicated that there was a reduction of protein levels of collagen type I accompanied by an increase in MMP-2 activity and leptin protein levels and a decrease in TIMP-1 and TIMP-2 protein levels in the heart. As previously stated, few studies have evaluated the behavior of collagen type I in the myocardium of animals with obesity induced by a high-fat diet; while Carroll 12 and Martínez-Martínez 39 found an increase, Silva et al. 13 found a decrease in myocardial type I collagen. Table 2 – Systolic blood pressure and cardiac morphological profile Variables Groups Control (n = 20) Obese (n = 21) p value SBP 127 ± 11.0 134 ± 12.0 0.04 Heart (g) 1.10 ± 0.10 1.17 ± 0.13 0.06 ATW (g) 0.093 ± 0.018 0.094 ± 0.021 0.80 LVW (g) 0.81 ± 0.09 0.82 ± 0.10 0.62 RVW (g) 0.22 ± 0.03 0.24 ± 0.03 0.04 ATW/FBW. 10-3 0.20 ± 0.03 0.18 ± 0.03 0.14 LVW/FBW. 10-3 1.72 ± 0.11 1.71 ± 0.12 0.44 RVW/FBW. 10-3 0.48 ± 0.09 0.47 ± 0.05 0.64 Values are means ± SD. SBP: systolic blood pressure; LVW: left ventricle weight; RVW: right ventricle weight; ATW: atrial weight; FBW: final body weight; ATW/FBW; LVW/FBW; RVW/FBW ratio; 10 -3 = 0.001. Student’s t-test. Figure 2 – Representative western blots and quantification of myocardial collagen type I, TIMP-1, TIMP-2, and leptin from control and obese rats (n = 6 per group). Western blot bands were normalized to β-actin. Data are presented as mean ± SD. Student’s t-test. *: p < 0.05. 66