mTOR as Mediator of Insulin Sensitivity Study

Insulin Sensitivity

Exercise, Muscle insulin Sensitivity, Muscle Glucose uptake, Muscle protein synthesis, mTOR

The study investigates the role of mTOR in mediating enhancement of muscle insulin sensitivity following a single bout of exercise. This will be investigated in young healthy male subjects by administering the pharmacological mTOR inhibitor Rapamycin in a crossover blinded experimental setup known to enhance muscle insulin sensitivity following one-legged knee-extensor exercise.

Trial A: During trial A the study subject will arrive at the research laboratory and eat a morning meal at 6:30 a.m. corresponding to 5% of the daily energy requirements. It is requested that the study subject will arrive in a car or with public transportation. At the same time, the subject will ingest 16 mg of Rapamycin or placebo (800 mg Calcium) in pill form. Following ingestion, the study subject will rest for 2 hour and at that time catheters are inserted in both femoral veins, the femoral artery in one of the legs and in each forearm vein (antecubital veins) for later blood sampling and intravenous infusion of insulin, glucose, stable D2-glucose and stable 13C6-phenylalanine. At 8:30 a.m. the study subjects will perform one-leg knee extension exercise for 1 hour at an intensity of 80% of maximal work capacity. In this work protocol there are inserted 3 intervals of 5 minutes duration where the study subject works at 100% of maximal intensity with the purpose of securing a full activation/recruiting of all muscle fibers. Immediately following conclusion of the exercise bout 13C6-phenylalanine is infused for later determination of muscle protein synthesis. 2 hours into the recovery from exercise D2-glucose is infused for later determination of hepatic glucose production. 4 hours into the recovery from exercise an euglycaemic hyperinsulinemic clamp will be initiated for 2 hours for determination of insulin stimulated muscle glucose uptake. Muscle biopsies from the m. vastus lateralis muscle in one or both legs will be taken before, immediately after, as well as 2, 4 and 6 hours after conclusion of exercise. Pulmonary oxygen uptake is measured with the use of an online system before, during and after exercise and is used for determination of substrate metabolism. Blood samples from the femoral veins in both legs and the femoral artery in one of the legs are drawn before, during exercise, and during the recovery period after exercise. At the same time blood flow is measured in the femoral arteries in both legs with the use of Doppler technique. Determination of arteriovenous difference (AV difference) by simultaneous measurement of blood flow enables us to calculate skeletal muscle glucose uptake and uptake/release of relevant substances (proteins, peptides and metabolites etc.). The experimental part of trial A is completed at 15:30 p.m. The study subject will be given food and drink and will be observed for one hour before they may leave the research laboratory. Trial B is an identical protocol, except that the subject will receive opposite drug from trial A (Rapamycin or placebo). Trial A and B will be separated by a minimum of 14 days.

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