FOREARM RESISTANCE VESSEL ABNORMALITIES AND INSULIN RESISTANCE IN OBESE ADOLESCENTS

To determine if structural changes in forearm resistance vessels are associated with insulin resistance, we evaluated the relation between minimum forearm vascular resistance and insulin resistance in 95 obese adolescents before and after weight loss. Insulin resistance was assessed by fasting insulin levels and sum of insulin values after an oral glucose tolerance test in all 95 subjects and whole body glucose uptake during euglycemic hyperinsulinemia in 35 of 95 subjects. Structural changes in forearm vessels were assessed by measurement of minimum forearm vascular resistance during 10 minutes of ischemic exercise. As compared with our normal values, obese adolescents had a significantly (p<0.01) decreased maximal forearm blood flow (41.6+/-1.4 versus 67.1+/-2.4 ml/min/100 ml) and increased minimum forearm vascular resistance (2.9+/-0.4 versus 1.6+/-0.7 mm Hg/ml/min/100 ml). There was a significant relation (p<0.01) between minimum forearm vascular resistance and fasting insulin, sum of insulins, and whole body glucose uptake. After a 20-week weight-loss program, minimum forearm vascular resistance decreased (3.0+/-0.3 versus 2.0+/-0.2, p<0.01), maximal forearm blood How increased (41+/-2.3 versus 57.4+/-3.9, p<0.01), and forearm volume remained unchanged. We also observed a significant (p<0.01) relation between the decrease in minimum forearm vascular resistance and the decrease in fasting insulin (r=0.29), decrease in sum of insulins (r=0.42), and increase in whole body glucose uptake (r=0.63). In summary, obese adolescents not only appear to have structural changes in forearm vessels, but these changes also correlate with the degree of insulin resistance.