Physical Inactivity and Insulin Resistance in Skeletal Muscle.
The purpose of this study is to determine how a decline in physical activity acutely leads to a decrease in insulin sensitivity in skeletal muscle. The hypothesis is that the loss of insulin sensitivity following physical inactivity is caused by a rapid reduction in skeletal muscle mitochondrial oxidative capacity.
Metabolic Syndrome X
|Study Design:||Allocation: Randomized
Endpoint Classification: Efficacy Study
Intervention Model: Single Group Assignment
Masking: Double Blind (Subject, Investigator, Outcomes Assessor)
Primary Purpose: Treatment
|Official Title:||Physical Inactivity and Insulin Resistance in Skeletal Muscle.|
- Insulin sensitivity; following 12 weeks of exercise training and 1 and 3 days of detraining and + or - Metformin. [ Time Frame: 12 weeks and 3 days ] [ Designated as safety issue: No ]
- PGC-1 alpha transcription and mitochondrial fatty acid oxidation and enzyme activity in skeletal muscle; following 12 weeks of exercise training and 1, 2, and 3 days of detraining and + or - Metformin. [ Time Frame: 12 weeks and 3 days ] [ Designated as safety issue: No ]
|Study Start Date:||June 2009|
|Estimated Study Completion Date:||December 2011|
|Estimated Primary Completion Date:||October 2011 (Final data collection date for primary outcome measure)|
Exercise training will consist of walking and/or jogging on a treadmill 5 out of 7 d each week at ~60% of each subject's predetermined VO2max (75% maximal heart rate as monitored by heart rate monitors), 45 min/session, for 12 weeks. The exercise training will follow a three-stage progression: 1. wk 1 = 30 min, 3 d/wk, 60% VO2max; 2. wk 2 = 30 min, 5 d/wk, 60% VO2max; and 3. wk 3-12 = 45 min, 5 d/wk, 60% VO2max.
Active Comparator: 2
oral tablet, 1000 mg daily for 17 days
In this project we will study two diverse groups of subjects. Group 1 will be subjects who are sedentary, insulin resistant, and have the Metabolic Syndrome. These subjects will be tested for insulin sensitivity at the whole body level, and for key changes in skeletal muscle metabolism at baseline, following 12 weeks of exercise training, and during an acute (1-3 days) period of time following the cessation of exercise training. The design allows us to study the effects of exercise on improving insulin sensitivity and make direct comparisons to a period when insulin sensitivity quickly decreases because of the removal of exercise training. Metformin is a drug commonly prescribed to control insulin resistance and type 2 diabetes. Metformin is thought to have exercise like effects on muscle metabolism and is known to activate a molecule that is de-activated during inactivity. Thus, half of the Metabolic Syndrome subjects will cease exercise training with no treatment while another half will quite exercise training while taking the drug Metformin.
Group 2 subjects will be highly trained endurance athletes. Endurance athletes display high levels of insulin sensitivity that can drop in the hours and days following the cessation of exercise. Thus we will take the same measurements in endurance athletes at baseline during their normal training regimen and in the acute (1-3 days) period following the cessation of exercise training. Again, half of the subjects will be take Metformin during the cessation of exercise in the same fashion as done in group 1.
Studies in both groups seek to determine the event(s) which cause insulin resistance in skeletal muscle following a decrease in physical activity levels. Comparisons between healthy, active individuals and sedentary Metabolic Syndrome subjects may provide additional information about the underlying events that cause insulin resistance.
|United States, Missouri|
|Harry S. Truman Memorial Veterans' Hospital|
|Columbia, Missouri, United States, 65201|
|Principal Investigator:||John P Thyfault, PhD||University of Missouri-Columbia|