No abstract

Obesity is a highly prevalent condition associated with several diseases. Physical exercise has been considered as a non-pharmacological tool in the treatment of obesity. However, several aspects underlying exercise evaluation and prescription in obesity and associated pathologies are still under investigation. Although many research involving exercise have been performed in animal models, there is a lack of protocols for aerobic capacity assessment in obese animals, such as the ob/ob mice. This study aimed the following: (i) to verify the possibility of determining the lactate threshold (LT) on swimming exercise in ob/ob mice and in non-obese heterozygote mice (ob/OB), through visual inspection (vLT) and polynomial adjustment (pLT); and (ii) to verify if the LT determined through these protocols corresponds to the maximal lactate steady state (MLSS). Eight ob/ob and ten ob/OB mice performed an incremental exercise test to determine vLT and pLT as well as constant-load exercise bouts to determine MLSS. There were no within-group differences between vLT, pLT and MLSS [ob/ob: ~5.3% body weight (BW); ob/OB: ~3·6%BW] with a high agreement among protocols. In conclusion, the identification of the LT and MLSS intensities was possible for both groups. These data suggest that the proposed protocols may be used in new research on the effects of different exercise intensities on some aspects of obesity.

Exercise is recognized to prevent and attenuate several metabolic and cardiovascular disorders. Obesity is commonly related to cardiovascular diseases, frequently resulting in heart failure and death. To elucidate the effects of acute exercise in heart tissue from obese animals, 12-week-old C57BL6/J obese (ob/ob) and non-obese (ob/OB) mice were submitted to a single bout of swimming and had their hearts analyzed by proteomic techniques. Mice were divided into three groups: control (ob/ob, n = 3; ob/OB, n = 3); a moderate intensity consisting of 20 min of swimming around 90% of Maximal Lactate Steady State (ob/ob, n = 3; ob/OB, n = 3), and a high intensity exercise performed as an incremental overload test (ob/ob, n = 3; ob/OB, n = 3). Obesity modulations were analyzed by comparing ob/ob and ob/OB control groups. Differential 2-DE analysis revealed that single session of exercise was able to up-regulate: myoglobin (ob/ob), aspartate aminotransferase (ob/OB) and zinc finger protein (ob/OB) and down-regulate: nucleoside diphosphate kinase B (ob/OB), mitochondrial aconitase (ob/ob and ob/OB) and fatty acid binding protein (ob/ob). Zinc finger protein and α-actin were up-regulated by the effect of obesity on heart proteome. These data demonstrate the immediate response of metabolic and stress-related proteins after exercise so as contractile protein by obesity modulation on heart proteome.

RESUMOObjetivo: Analisar em ratos idosos os efeitos de oito semanas de treinamento aeróbio em carga correspondente ao limiar de lactato. Métodos: Dezessete ratos idosos (~ 478 dias/vida) foram divididos em Treinados (T; n=11) e Controle (C; n=6). Foram submetidos a um teste incremental antes e após 8 semanas de treinamento de natação (30 min/dia, 5/semanais, a ~5% do peso corporal) ou controle sem exercícios. O teste foi realizado com incrementos de 1% do peso corporal a cada 3 minutos até a exaustão. O limiar de lactato foi identificado por ajuste polinomial da resposta da razão lactato/carga. Após período experimental os animais foram sacrificados para cálculo da razão peso do coração/peso corporal. Resultados: O limiar de lactato não demonstrou diferença significativa com o treinamento em ambos os grupos (T:pré=5,1±0,7/pós=5,3±0,7%PC; C:pré=6,1±0,4/pós=6,4±0,6%PC;p>0,05). Quando calculada a variação do peso corporal do pré para o pós-experimento, constatou-se diferença significativa entre os grupos (T= -1,5±2,4% vs. C=6,4±3,3%;p<0,0001). Observou-se diferença de 13% da razão peso do coração/peso corporal entre grupos (T=0,29±0,04 vs. C=0,25±0,03;p<0,05). Conclusão: Embora alterações na razão peso do coração/peso corporal indiquem possíveis benefícios de eficiência cardiovascular decorrente do treinamento, a metodologia utilizada não resultou em melhora da capacidade aeróbia mensurada pelo limiar de lactato em ratos idosos.Palavras-chave: limiar anaeróbio, natação, animais idosos, treinamento ABSTRACT Eight weeks of moderate exercise training does not change the load corresponding to lactate threshold in old-age ratsObjective: To analyze in elderly rats the effect of eight weeks of aerobic training in corresponding load to the lactate threshold. Methods: Seventeen elderly rats (~ 478 days/life) had been divided in Trained (T; n=11) and Control (C; n=6). They underwent an incremental test before and after 8 weeks of swimming training (30 min/day, 5/weekly, 5% body weight) or control without exercise. Incremental test was carried out with increments of 1% body weight each 3 minutes until exhaustion. Lactate threshold was identified by polynomial adjustment of the ratio lactate/workload. After experimental period animals were sacrificed for calculation of the ratio weight of the heart/body weight. Results: lactate threshold did not demonstrate significant difference with training in both groups (T:pre=5.1±0.7/post=5.3±0.7%PC;C:pre=6.1±0.4/post=6.4±0.6 %PC;p>0.05). When calculated the variation of the body weight before and after training, significant difference between groups was evidenced (T=-1.5±2.4% vs. C=6.4±3.3%;p<0.0001). A 13% difference was observed in the ratio weight of heart/body weight between groups (T=0.29±0.04 vs. C=0.25±0.03;p<0.05). Conclusion: Although alterations in the ratio weight of heart/body weight indicate possible cardiovascular benefits because of training, the used protocol did not result in improvement of aerobic capacity evaluated by lactate threshold in elderly rats.

Type 2 diabetes mellitus (T2D) results in several metabolic and cardiovascular dysfunctions, clinically characterized by hyperglycaemia due to lower glucose uptake and oxidation. Physical exercise is an effective intervention for glycaemic control. However, the effects of exercising at different intensities have not yet been addressed. The present study analysed the effects of 8 weeks of training performed at different exercise intensities on type 4 glucose transporters (GLUT4) content and glycaemic control of T2D (ob/ob) and non-diabetic mice (ob/OB). The animals were divided into six groups, with four groups being subjected either to low-intensity (ob/obL and ob/OBL: 3% body weight, three times/week/40 min) or high-intensity (ob/obH and ob/OBH: 6% body weight, three times per week per 20 min) swimming training. An incremental swimming test was performed to measure aerobic fitness. After the training intervention period, glycaemia and the content of GLUT4 were quantified. Although both training intensities were beneficial, the high-intensity regimen induced a more significant improvement in GLUT4 levels and glycaemic profile compared with sedentary controls (p < 0.05). Only animals in the high-intensity exercise group improved aerobic fitness. Thus, our study shows that high-intensity training was more effective for increasing GLUT4 content and glycaemia reduction in insulin-resistant mice, perhaps because of a higher metabolic demand imposed by this form of exercise.