Article Text

  1. K. J. Nadeau1,
  2. L. B. Ehlers1,
  3. P. S. Zeitler1,
  4. B. Draznin1,
  5. J. G. Regensteiner1,
  6. J. E.B. Reusch1
  1. 1VA Medical Center and University of Colorado Health Sciences Center, Denver, CO.


Purpose Despite the knowledge that exercise increases longevity and is beneficial for people with type 2 diabetes (T2D), adults with T2D do not exercise sufficiently. One explanation is that adults with T2D have a reduced maximal exercise capacity (VO2max), making exercise more difficult. T2D is now increasingly common in the pediatric population, but it is unknown whether exercise dysfunction is already present in youth since they lack the other comorbidities often seen in adults with long-standing T2D. Pediatric subjects are especially important to study as exercise dysfunction at such an early age predicts poor outcomes. We hypothesized that adolescents with T2D would have a reduced VO2max, which can be partly explained by insulin resistance, endothelial function, and inflammation.

Methods Thirty adolescents, 10 with T2D, 10 with obesity (similar BMI), and 10 lean controls, were matched for age, sex, Tanner stage, and physical activity level. All subjects underwent anthropomorphic measurements, fasting blood draw, autonomic function testing and assessment of VO2max by cycle ergometer, blood flow by venous plethysmography, body composition by DEXA scan, and insulin sensitivity by hyperinsulinemic (80 mU/m2) euglycemic clamp (mg/kg/min).

Results VO2max (21.9 ± 4.2 vs 28.7 ± 5.2 mL/kg/min, p = .04) and workload (145 ± 32 vs 186 ± 40 watts, p = .036) were significantly lower in T2D subjects versus obese subjects and significantly lower in T2D and obese subject versus lean subjects (41.2 ± 10.2 mL/kg/min, 204 watts, p < .0001). VO2max/kg was significantly correlated with insulin sensitivity (r = .83, p < .0001) and significantly inversely correlated with blood flow (r= −.63, p < .0001), HbA1c (r = −.55, p < .0001), c-peptide (r = −.51, p = .003), C-reactive protein (r = −.50, p = .003), fasting glucose (r = −.42, p = .013, p < .0001).

Conclusion Of concern, VO2max and workload are already significantly reduced in adolescents with T2D, not explainable by body weight or inactivity. As predicted, VO2max correlates with markers of insulin sensitivity, endothelial function, and inflammation. Unlike studies in adults, VO2max in adolescents also correlates with glycemia. Future intervention studies should target these potentially modifiable determinants of exercise function to decrease morbidity and mortality in youth with T2D.

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