ABC | Volume 112, Nº5, May 2019

Original Article Effting et al RE Effects: heart and obesity Arq Bras Cardiol. 2019; 112(5):545-552 Figure 2 – Redox balance and inflammatory parameters in cardiac tissue of animals fed standard or high-fat diet and subsequently submitted to resistance training. A - DCFH oxidation; B - MDA content; C - SOD enzyme activity; D - CAT enzyme activity; E - Total glutathione content (reduced and oxidized); F - levels of TNF-α. *p < 0.05, **p < 0.01 and ***p < 0.001 vs. respective untrained; # p < 0.05, ## p < 0.01 and ### p < 0.001 vs. respective SD. Untrained Resistance training Untrained Resistance training Untrained Resistance training Untrained Resistance training Untrained Resistance training Untrained Resistance training ### # ## * ## # ** * * *** * * 15 12 9 6 3 5 0.5 1.5 2.5 1.0 2.0 0.5 2 25 50 75 100 125 150 4 6 8 1.5 2.5 1.0 2.0 3.0 10 15 20 25 30 35 SD DIO SD DIO SD DIO SD DIO SD DIO SD DIO DCFH oxidization (nM DCF/mg of protein) MDA (µmol/mg of protein) SOD (U/mg of protein) Catalase (U/mg of protein) Total glutathione (nM/min/mg of protein) TNF-α (pg/mL/mg of protein) The initial results of our study show that DIO animals have elevated levels of DCF, an indirect indicator of hydrogen peroxide production. 29 These data were also observed by a recent study published in 2017 by Zeng et al. 23 The authors showed high myocardial susceptibility to oxidative stress, with a significant increase in DCFH oxidation, both in vitro and in vivo , mediated by a high-fat diet. These increased DCF values, observed in DIO animals, were significantly reduced after resistance training, which suggests an important role of this type of training in the regulation of cell oxidant levels. Such effect may be associated to the fact that resistance training has a modulatory role on endogenous antioxidant enzymes. This observation is based on previous studies of our group in other experimental models of inflammation, which show the important role of resistance training on the enzymatic antioxidant system in different tissues. 30,31 SOD and CAT are two enzymes that act synergistically in the formation (via superoxide radical dismutation) and catalysis of hydrogen peroxide, respectively. DIO animals showed no changes in SOD activity, suggesting that an increased production of DCF may be associated with other stimuli independent from SOD. One of the factors responsible for it is that, although the oxidation of DCFH to DCF is widely used as an indicator of hydrogen peroxide production, studies have observed that DCFH can also be oxidized by other reactive species, on a smaller scale, such as hydroxyl, peroxyl, nitric oxide and peroxide nitrite. 29 It is also noteworthy that the formation of hydrogen peroxide is not totally dependent on SOD activity. On a smaller scale, auto-oxidation events of biomolecules also contribute to the formation of hydrogen peroxide. 32 These conditions would limit SOD activity, which may justify the results found. Catalases constitute a group of enzymes that catalyze the decomposition of hydrogen peroxide into water and oxygen. Our results show a reduction in the activity of this enzyme after resistance training in the group exposed to SD. As observed, SOD activity was increased in this same group, thus generating higher levels of hydrogen peroxide. However, the decrease in enzyme activity suggests a lower hydrogen peroxide catalysis, but it is worth noting that hydrogen peroxide can be catalyzed under these conditions by other cell detoxification systems, such as glutathione and peroxins, 33 which could justify our results since the glutathione system showed an increase in this group (SD + RE). Furthermore, we observed reduced levels of CAT after resistance training in the DIO + RE group and, therefore, considering that the diet significantly increases the production of cell oxidants such as hydrogen peroxide, a reduced CAT activity could have an impact on the possible oxidative damages in the myocardium, if hydrogen peroxide were not catalyzed by other aforementioned systems (not investigated in the present study, although they deserve attention in future studies). Aiming to observe the effects of RE on oxidative damage in the myocardium induced by the DIO model, we evaluated the levels of MDA, a byproduct of lipoperoxidation, and observed that DIO animals showed greater lipid damage in relation to the SD group and that the RE was able to reverse these effects. These effects of the DIO model on lipoperoxidation levels were also observed in a study with BL6/C57 mice performed by Muthulakshmi and Saravanan (2013). 34 Positive RE results are possibly associated with the exercise capacity to promote the modulation of antioxidant systems, in addition to the activity of primary antioxidant enzymes such as SOD and CAT. One of the mechanisms 549