Identification of Cell Type-Specific Insulin Responsive Quantitative Trait Loci (QTL) in Human Skeletal Muscle

The study investigators seek to find the relationship between basal and insulin stimulated Quantitative trait loci (QTL's) by utilizing vastus lateralis muscle biopsies before and after a euglycemic/hyperinsulinemic clamp. Each participant will have a catheter placed into an antecubital vein for the infusion of all test substances. A second catheter will be inserted retrogradely into a vein on the dorsum of the hand, and the hand will be placed into a thermoregulated box heated to 45 to 50 degrees Celsius. All participants will receive an infusion of [3-3H]glucose. After a 2-h basal tracer equilibration period, participants will receive a prime-continuous insulin infusion at the rate of 80mU/m2*min. During the last 30 min of the basal equilibration period and throughout the insulin infusion, plasma samples will be taken at 5-10 min intervals for the determination of plasma glucose and insulin concentrations and tritiated glucose radioactivity. During the insulin infusion, a variable in-fusion of 20% glucose will be adjusted, based on the negative feedback principle, to maintain the plasma glucose concentration at ~100mg/dL with a coefficient of variation <5%. Skeletal muscle biopsies will be obtained from the vastus lateralis muscle approximately 1h prior to and at the end of the insulin clamp, and will be snap frozen in liquid nitrogen for nuclei isolation.