Abstract Aims: The purpose of the present study was to evaluate the effects of the resistance training (RT) on the lipid profile and metabolism, oxidative stress, and activity of metalloproteinase-2 (MMP-2) in the left ventricle (LV) of diet-induced obesity rats. Methods: Forty males Wistar rats 90 days-old were grouped into four groups (n=10): i) Sedentary group (SED); ii) Obese sedentary group, feed with high-fat diet (Ob-SED); iii) Resistance Trained group (RT), and iv) Obese Resistance trained group (Ob-RT). The LV was assayed to Obesity index, LV lipid content, citrate synthase activity, lipid peroxidation (TBARS), enzymatic and non-enzymatic antioxidant systems, lipid profile, cardio-metabolic parameters, and activity of MMP-2. Results: High-fat diet was associated with manifestations of the obesity, body mass gain, and increased obesity index, accompanied by an alteration in the lipid profile. On the other hand, RT was able to prevent body weight gain, to reduce the obesity index and to improve the lipid profile, to elevate the activation of the citrate synthase, and to decrease MMP-2 activity in the LV of obese rats. Conclusion: RT positively modulated blood lipid profile and antioxidant enzymes preventing the increased activity of MMP-2 in the left ventricle from rats fed with high-fat diet.

Methylmercury (MeHg) is present in the environment because of natural and anthropogenic causes. MeHg can reach the central nervous system (CNS) and cause neurological damage in humans and animals. Electric organ discharges (EODs) in the weak electric fish Gymnotus sylvius are produced by the electric organ and modulated by the CNS. These discharges are used for electrolocation and communication. The purpose of the present study was to investigate the effects of dietary MeHg exposure on EOD rate in G. sylvius. An oscilloscope was used to record the EOD rate. Two treatments were investigated: chronic MeHg administration (4 µg/kg MeHg every 2 days, with a total of nine dietary exposures to MeHg) and acute MeHg administration (a single dose of 20 µg/kg MeHg). The control data for both treatments were collected every 2 days for 18 days, with a total of nine sessions (day 1 until day 18). Data of fish exposed to MeHg were collected every 2 days, totaling nine sessions (day 19 until day 36). Chronic treatment significantly increased the EOD rate in G. sylvius (p < .05), especially with the final treatment (day 32 until day 36). Acute treatment resulted in an initial increase in the EOD rate, which was maintained midway through the experiment (day 26 until day 30; p < .05). The present study provides the first insights into the effects of MeHg on EODs in weak electric fish. The EOD rate is a novel response of the fish to MeHg administration.