Molecular mechanisms of glucose uptake in skeletal muscle at rest and in response to exercise

Abstract Glucose uptake is an important phenomenon for cell homeostasis and for organism health. Under resting conditions, skeletal muscle is dependent on insulin to promote glucose uptake.Insulin, after binding to its membrane receptor, triggers a cascade of intracellular reactions culminating in activation of the glucose transporter 4, GLUT4, among other outcomes.This transporter migrates to the plasma membrane and assists in glucose internalization.However, under special conditions such as physical exercise, alterations in the levels of intracellular molecules such as ATP and calcium actto regulate GLUT4 translocation and glucose uptake in skeletal muscle, regardless of insulinlevels.Regular physical exercise, due to stimulating pathways related to glucose uptake, is an important non-pharmacological intervention for improving glycemic control in obese and diabetic patients. In this mini-review the main mechanisms involved in glucose uptake in skeletal muscle in response to muscle contraction will be investigated.(AU)

Influência de dfferentes protocolos de treinameto físico sobre a fosforilação da proteína akt em músculo esquelético e sensibilidade à insulina de ratos obesos / Influences of dffferent protocols of physical training on the posphorylation oof akt protein in skeletal muscle and insulin sensitivity of obese rats

RESUMOO Objetivo deste estudo foi investigar os efeitos de diferentes protocolos de treinamento físico (TF) sobre a sensibilidade à insulina (SI) e a fosforilação da Akt (p-Akt) no músculo de ratos obesos. Os animais foram distribuídos em quatro grupos: Controle: recebeu dieta padrão (C); Obeso sedentário: recebeu dieta hiperlipídica (DHL) por 12 semanas (OS); Obeso treinado-1: recebeu DHL por 12 semanas e TF sem sobrecarga por 6 semanas (OT-1); Obeso treinado-2: recebeu DHL por 12 semanas e TF por 6 semanas com sobrecarga de 5% da massa corporal (OT -2). O teste de tolerância à insulina foi realizado para estimar a SI. A p-Akt e Akt total no músculo gastrocnêmio foram determinadas por Western Blot. Os resultados apontam que o TF com sobrecarga induziu maior p-Akt, porém não houve diferença na SI se comparado ao TF sem sobrecarga. Como conclusão as diferenças na p-Akt não induziram respostas mais significativas de SI em ratos obesos induzidos por DHL.

ABSTRACTInvestigate the effects of different protocols of physical training (PT) on insulin sensibility (IS) and Akt phosphorylation (p-Akt) in skeletal muscle of obese rats. Animals were distributed in four groups according to the diet and physical training: Control: received standard chow (C); Sedentary obese: received high fat diet (HFD) for 12 weeks (OS); Obese Trained 1: received HFD for 12 weeks and PT without overload for 6 weeks (OT-1); Obese Trained 2: received HFD for 12 weeks and PT with overload of 5% body weight (OT-2). Insulin tolerance test was used to evaluate the IS. Western blotting was performed to evaluate p-Akt and total Akt in gastrocnemius muscle. Results: The PT with overload induced greater p-Akt, however there isn't difference in SI when compared with the training without overload. Conclusion: Differences in p-Akt not induced better responses of IS in obese rats induced by HFD.