Efeito do treinamento com plataforma vibratória na morfologia do músculo diafragma em ratos com obesidade hipotalâmica

Abstract

Diaphragm muscle is presented as the main muscle related to respiratory mechanics, presenting remarkable plasticity, undergoing remodelling due to several conditions, such as obesity and physical exercise. Vibrating platform (VP) causes mechanical stimuli, which can promote muscle changes, however, little is known about its effects. Thus, the present study aims to investigate the effects of using VP on the diaphragm muscle morphology of obese rats by the monosodium glutamate (MSG). Newborn Wistar Rats were initially separated into: control group (CG; n=14) and obese group (OG; n =14); who received MSG (4 mg/g) in the first five days of life to induce obesity. At 70 days of age, the groups were divided into four; control (CG; n=7), exercised in VP (CGP; n=7), obese (OG; n=7) and obese exercised in VP (OGP; n=7), started the training protocol, at a frequency of 60 hertz (Hz) and two millimetres amplitude, three times a week for 10 minutes, over a period of eight weeks. At the end of the experimental period, at 130 days of age, the animals were euthanized and the retroperitoneal and peri-epididymal fats were collected, as well as the diaphragm muscle, which was divided into left and right antimeres to evaluate the morphology and morphometry of the muscle fibers, the different types of fibers, the percentages of connective tissue, morphometry of neuromuscular junctions (NMJs) and analysis of the activity of cholinesterase (ChE), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione reductase (GR) and lipoperoxidation reaction (LPO). Statistical analysis was performed using the Two-way ANOVA analysis of variance test, with Bonferroni's post-test (p <0.05). In all the studied groups the fibers’ morphology was preserved, however, in morphometry, obesity caused a decrease in the cross-sectional area and in the larger and smaller diameters, as well as an increase in the number of muscle fibers and a reduction in the core/fiber ratio. There was a reduction in the number of glycolytic fibers in trained animals and a reduction in the area of type IIA and IIB fibers in obese animals. The percentage of connective tissue was higher in obese animals, as well as in trained animals. In the analysis of neuromuscular junctions, there was a decrease in all of the analyzed parameters facing obesity, VP and the interaction of the two factors. Regarding oxidative stress, obesity caused a decrease in CAT activity and an increase in GST, an enzyme that was also increased in animals trained in VP, and also in the interaction between the two factors, where the interaction also promoted a reduction in GR. Therefore, it is concluded that exercise in VP was not able to reverse the effects caused by obesity in the studied muscle, although some changes were observed relating to this type of exercise.