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Previous issue date: 2012 === Funda??o de Amparo ? Pesquisa do estado de Minas Gerais (FAPEMIG) === Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) === Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (Capes) === A maior quantidade de ?cidos graxos livres e de citocinas pr?-inflamat?rias plasm?tica presentes na obesidade, podem desencadear a resist?ncia a insulina, dentre outros fatores, pela fosforila??o inibit?ria do substrato do receptor de insulina 1 (IRS-1), via ativa??o de quinases relacionadas ao estresse, como a quinase C-jun N-terminal (JNK). Em obesos, a resist?ncia a insulina correlaciona-se com altera??es do sistema imune, e com a baixa express?o da prote?na de choque t?rmico de 72kDa (Hsp72) e aumento da ativa??o da JNK no m?sculo esquel?tico. Considerando que o exerc?cio f?sico aer?bico promove melhora da sensibilidade a insulina e tem um efeito anti-inflamat?rio. O objetivo desse estudo foi avaliar os efeitos de uma sess?o de exerc?cio f?sico aer?bico na express?o da HSP70, ativa??o da JNK e fosforila??o do IRS-1 no res?duo de serina 612 (IRS-1 ser612) no m?sculo esquel?tico de obesos. Al?m disso, foi avaliada a frequ?ncia dos linf?citos T auxiliares (CD4+) e citol?ticos (CD8+) e das subpopula??es de mon?citos cl?ssicos (CD14++CD16-), intermedi?rios (CD14++CD16+) e n?o cl?ssicos (CD14+CD16++). Os participantes do estudo (n=27) foram alocados em tr?s grupos experimentais (eutr?ficos sens?veis a insulina, obesos sens?veis a insulina, obesos resistentes a insulina) de acordo com a classifica??o do estado nutricional, de acordo com o ?ndice de massa corporal e presen?a ou n?o de resist?ncia a insulina, definida pelo modelo de avalia??o da homeostase (HOMA1-IR). Amostras de sangue venoso e do m?sculo vasto lateral foram obtidas antes e ap?s uma sess?o de exerc?cio f?sico aer?bico realizado a 60% do VO2pico,em cicloerg?metro, com dura??o de 60 minutos. Para avaliar a frequ?ncia das diferentes popula??es de mon?citos e linf?citos T circulantes utilizou-se a citometria de fluxo. As an?lises da express?o da HSP70, ativa??o da JNK e fosforila??o do IRS-1 ser612 no m?sculo esquel?tico foram feitas pelo procedimento de western blot. Nossos resultados demonstraram que obesos resistentes a insulina apresentam uma maior frequ?ncia de mon?citos intermedi?rios e maior fosforila??o do IRS-1 ser612 comparado aos eutr?ficos, maior ativa??o da JNK e menor express?o da HSP70 em rela??o aos demais grupos. Ap?s 1 hora do t?rmino da sess?o de exerc?cio aer?bico houve redu??o da frequ?ncia dos mon?citos intermedi?rios (CD14++CD16+) e dos linf?citos auxiliares (TCD4+) circulantes. Adicionalmente, a sess?o de exerc?cio induziu no m?sculo esquel?tico maior express?o da HSP70, redu??o da fosforila??o do IRS-1 ser612 nos grupos de indiv?duos obesos e menor atividade da JNK nos obesos resistentes a insulina. Conclui-se que uma sess?o de exerc?cio aer?bico promove altera??es que caracterizam redu??o da inflama??o e/ou estresse celular, que podem contribuir para a modula??o da sensibilidade a insulina promovida pelo exerc?cio f?sico. === Disserta??o (Mestrado) ? Programa Multic?ntrico de P?s-gradua??o em Ci?ncias Fisiol?gicas, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2012. === ABSTRACT
The great amount of free fatty acids and proinflammatory cytokines present in obese individuals may trigger insulin resistance, through the inhibitory phosphorylation of insulin receptor substrate 1 (IRS-1), via activation of kinases related to stress, such as kinase C-Jun N-terminal (JNK). In obese individuals, insulin resistance correlates with alterations of the immune system and lower expression of the heat shock protein of 72kDa (Hsp72) and increased activation of JNK in skeletal muscle. Considering that aerobic exercise improve insulin sensitivity and has an anti-inflammatory effect, the purpose of this study was to evaluate the effects of a bout of aerobic exercise in the expression of HSP70, activation of JNK and phosphorylation of IRS-1 in serine residue 612 (IRS-1 ser612) in skeletal muscle of obese patients. Furthermore, we assessed the frequency of helper T lymphocytes (CD4 +) and cytolytic (CD8 +) and subpopulations of classical (CD14 + + CD16-), intermediate (CD14 + + CD16 +) and non-classical (CD14 + CD16 + +) monocytes. Study participants (n = 27) were divided into three experimental groups (eutrophic sensitive to insulin, insulin-sensitive obese, insulin-resistant obese) according to the classification of nutritional status, according to the body mass index, and the presence or absence of insulin resistance, defined by the
homeostasis assessment model (HOMA1-IR). Venous blood and vastus lateralis samples were obtained before and after a bout of aerobic exercise performed at 60% of VO2peak on a cycle ergometer, lasting 60 minutes. To assess the frequency of the different populations of monocytes and T lymphocytes circulating we used flow cytometry. Analyses of of HSP70 expression, JNK activation and IRS-1 phosphorylation of ser612 in skeletal muscle were performed by western blot. Our results showed that obese insulin resistant subjects have an increased frequency of intermediate monocytes and higher phosphorylation of IRS-1 ser612 compared to normal weight individuals, and greater activation of JNK and lower expression of HSP70 than the other two groups. 1 hour after the exercise bout, we observed reductions on the frequency of intermediate circulating monocytes (CD14 + + CD16 +) and helper cells (CD4 +). Additionally, the exercise bout induced in the skeletal muscle higher expression of HSP70, decreased phosphorylation of IRS-1 ser612 in the obese groups and lower activity of JNK in the obese insulin resistant individuals. It is concluded that a bout of aerobic exercise promotes changes that characterize reduction of inflammation and / or cellular stress, which may contribute to the modulation of insulin sensitivity promoted by exercise.
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