Modulação do metabolismo muscular em camundongos exercitados e suplementados com leucina / Modulation of muscle metabolism by exercise and leucine supplementation in mice

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

03/02/2012

RESUMO

We investigated the effects of chronic physical training, associated or not with leucine supplementation, on protein and glucose metabolism in soleus muscle of Swiss mice. Half of the mice (T) performed a 12 weeks protocol of swimming exercise, 1h/day, 5 days/week, bearing no overload, and the other half remained sedentary (C). Additionally, half of the C and T mice were supplemented with leucine (1,5%) into the drinking water (groups CL and TL, respectively) throughout the experiment. Data were analysed by Two-Way ANOVA (variables exercise and leucine supplementation) and the Newman-Keus post hoc test was used in the cases of interaction between the variables. A p<0,05 was considered statistically significant. Results: The area under glucose curve during glucose tolerance test was increased in the leucine supplemented groups (CL and TL). Insulin sensitivity, estimated by kITT, was higher as an effect of exercise. AS160 phosphorylation, a distal step in the signaling pathway which leads to muscle glucose uptake, was increased in the T group compared to the others in both basal and insulin-stimulated condition, probably via AMPK, whose phosphorylation was increased by exercise in both conditions, but it was reduced by an effect of leucine supplementation following insulin stimulation. Akt phosphorylation was not affected by exercise, but it was reduced in the CL group compared to the other groups. Despite the increased weight of soleus muscle caused by an effect of exercise, protein synthesis was similar among the groups, even with the increased mTOR phosphorylation at the basal condition in the CL group, and the reduction caused by exercise following insulin stimulation. Protein degradation in the soleus muscle was reduced by an effect of exercise. Gene expression of specific isoforms of E2 and E3 ligases, members of the ubiquitin-proteosome proteolytic pathway, was also reduced by an effect of exercise. All the indicators of response to aerobic training were increased by exercise: time to exhaustion in the effort test, maximal oxygen uptake and citrate synthase enzyme activity. Some of these indicators were also affected by leucine supplementation. We conclude that leucine supplementation may impair glucose homeostasis and reduce the positive effects of exercise on insulin signaling. Exercise increased soleus muscle weight by reducing protein degradation via an inhibition of the ubiquitin-proteasome proteolytic pathway, whereas protein synthesis was not affected by either of the treatments (exercise or leucine supplementation).

ASSUNTO(S)

leucina insulina proteínas - síntese glicose camundongo mice leucine insulin proteins glucose

ACESSO AO ARTIGO

Documentos Relacionados