Alteration in sympathoadrenergic activity at rest and during intense exercise despite normal aerobic fitness in late pubertal adolescent girls with type 1 diabetes.

BACKGROUND: An impaired sympathoadrenergic response to hypoglycaemic episodes has been described in young Type 1 diabetic subjects. It is unknown if this altered response occurs with exercise, and if it could influence aerobic power.
METHODS: Body composition (skinfold thickness), physical activity (questionnaire) and aerobic power (PWC170 and VO2max) were assessed in 19 post-menarcheal Type 1 diabetic (T1D) girls (13.3-18.2 years) and 19 healthy siblings. At rest and at each stage of the graded exhaustive exercise, plasma glucose, insulin, epinephrine and norepinephrine, were monitored via an intravenous catheter.
RESULTS: Only when expressed per kilograms of body weight, was aerobic power impaired in T1D girls compared to controls, probably because they were overweight. Throughout exercise, plasma glucose remained stable while plasma insulin decreased in the healthy girls, whereas glucose diminished significantly with no change in plasma insulin in T1D girls. During exercise catecholamines increased in the same way in both groups. However, at rest and throughout all stages of exercise, norepinephrine levels were significantly lower by a mean difference of 1.2 nmol/L, while epinephrine levels were significantly higher by a mean difference of 0.14 nmol/L, in T1D girls compared to healthy girls. Heart rates of T1D girls were not affected by the sympathoadrenergic alteration.
CONCLUSION: T1D adolescent girls display an altered sympathoadrenergic activity at rest and during intense exercise. Their reduced sympathetic activity, albeit probably compensated for by higher adrenomedullary responsiveness or sensitivity, does not affect their heart rate adaptations to exercise.