MUSCLE GLUCOSE-UPTAKE DURING AND AFTER EXERCISE IS NORMAL IN INSULIN-RESISTANT RATS

It is not generally known whether impaired stimulation of muscle glucose metabolism in insulin-resistant states is specific to insulin stimulation. Our aim was to examine whether glucose uptake responded normally to exercise and postexercise recovery in insulin-resistant high-fat-fed (HFF) rats. Three-week HFF or Chow-fed [control (Con)] adult rats were studied 5 days after cannulation. Before, during, or immediately after (recovery) 50 min of treadmill exercise, bolus 2-deoxy-[H-3]glucose and [C-14]glucose were administered to estimate muscle glucose uptake (R(g)') and glycogen incorporation rates. Mean exercise and recovery plasma glucose levels were similar in HFF and Con rats. In hindlimb muscles sampled, exercise and recovery R(g)' were similar in HFF and Con (e.g., red quadriceps exercise 104 +/- 13 vs. 113 +/- 8, recovery 45.3 +/- 3.9 vs. 47.7 +/- 4.5 mumol . 100 g-1 . min-1, respectively). Moreover, muscle glucose transporter (GLUT-4) content was not reduced in HFF rats. Glycogen resynthesis accounted almost entirely for R(g)' during recovery and was equivalent between groups. We conclude that impaired muscle glucose uptake and glycogen synthesis in HFF rats are characteristic of insulin but not of exercise or postexercise stimulation.