Luciana Oquendo Pereira

Effect of insulin and contraction up on glucose transport in skeletal muscle

The major glucose transporter protein expressed in skeletal muscle is GLUT4. Both muscle contraction and insulin induce translocation of GLUT4 from the intracellular pool to the plasma membrane. The intracellular pathways that lead to contraction- and insulin-stimulated GLUT4 translocation seem to be different, allowing the attainment of a maximal effect when acting together. Insulin utilizes a phosphatidylinositol 3-kinase-dependent mechanism, whereas the exercise signal may be initiated by calcium release from the sarcoplasmic reticulum or from autocrine- or paracrine-mediated activation of glucose transport. During exercise skeletal muscle utilizes more glucose than when at rest. However, endurance training leads to decreased glucose utilization during sub-maximal exercise, in spite of a large increase in the total GLUT4 content associated with training. The mechanisms involved in this reduction have not been totally elucidated, but appear to cause the decrease of the amount of GLUT4 translocated to the plasma membrane by altering the exercise-induced enhancement of glucose transport capacity. On the other hand, the effect of resistance training is controversial. Recent studies, however, demonstrated the improvement in insulin sensitivity correlated with increasing muscle mass. New studies should be designed to define the molecular basis for these important adaptations to skeletal muscle. Since during exercise the muscle may utilize insulin-independent mechanisms to increase glucose uptake, the mechanisms involved should provide important knowledge to the understanding and managing peripheral insulin resistance.

Obesidade: atualização sobre sua etiologia, morbidade e tratamento

The trend in nutritional transition in this century leads to an occidentalized diet, which, allied to a decrease in physical activity, results in increasing of obesity all over the world. It raises the risk of morbidity and mortality, since obesity is the first step to several diseases such as Diabetes type II, hypertension, cardiovascular and gallbladder diseases. Obesity is not only a scientific and public health problem, but also an industry of pharmacos, special foods and governmental strategies to encourage people to be more active and to provide more food information in order to promote better habits. Several studies all around the world discuss the causes and treatments for obesity. In this way, this paper summarizes these researches, approaching the elements associated with higher obesity incidence and prevalence, the diseases related to overweight and the treatments for reducing body fat.

Obesidade: hábitos nutricionais, sedentarismo e resistência à insulina

A obesidade ja e considerada uma epidemia mundial independente de condicoes economicas e sociais. O risco aumentado de mortalidade e morbidade associado a obesidade tem sido alvo de muitos estudos que tentam elucidar os aspectos da sindrome X como consequencia da obesidade. Esta sindrome e caracterizada por algumas doencas metabolicas, como resistencia a insulina, hipertensao, dislipidemia. Esta bem estabelecido que fatores geneticos tem influencia neste aumento dos casos de obesidade. No entanto, o aumento significativo nos casos de obesidade nos ultimos 20 anos dificilmente poderia ser explicado por mudancas geneticas que tenham ocorrido neste espaco de tempo. Sendo assim, os principais fatores envolvidos no desenvolvimento da obesidade tem sido relacionados com fatores ambientais, como ingestao alimentar inadequada e reducao no gasto calorico diario. Na tentativa de desencadear obesidade em animais e permitir o estudo desta doenca de maneira mais completa, diversos modelos experimentais de obesidade tem sido desenvolvidos. Ainda que nao possam ser considerados exatamente iguais aos modelos de obesidade humana, sao de grande valor no estudo dos diversos aspectos que contribuem para este excessivo acumulo de adiposidade e suas consequencias.

The effect of 5 days of aspartate and asparagine supplementation on glucose transport activity in rat muscle

The consumption of protein supplements containing amino acids is increasing around the world. Aspartate (Asp) and asparagine (Asn) are amino acids metabolized by skeletal muscle. This metabolism involves biochemical pathways that are involved in increasing Krebs cycle activity via anaplerotic reactions, resulting in higher glutamine concentrations. A connection between amino acid supplementation, glycogen concentration, and glucose uptake has been previously demonstrated. The purpose of this study was to evaluate the effect of Asp and Asn supplementation on glucose uptake in rats using three different glycogen concentrations. The results indicate that Asp and Asn supplementation in rats with high glycogen concentrations (fed state) further increased the glycogen concentration in the muscle, and decreased in vitro 2‐deoxyglucose (a glucose analog) uptake by the muscle at maximal insulin concentrations. When animals had a medium glycogen concentration (consumed lard for 3 days), glucose uptake was higher in the supplemented group at sub‐maximal insulin concentrations. We conclude that supplementation of Asp and Asn reduced glucose transport in rat muscle only at higher levels of glycogen. The ingestion of lard for 3 days changed the responsiveness and sensitivity to insulin, and that group had higher levels of insulin sensitivity with Asp and Asn supplementation. Copyright