HYPOGLYCEMIC SYMPTOM VARIATION IS RELATED TO EPINEPHRINE AND NOT PERIPHERAL MUSCLE SYMPATHETIC-NERVE RESPONSE

Hypoglycemic unawareness may be due to diminished adrenal and/or perip heral sympathochromaffin responses to hypoglycemia. To determine wheth er hypoglycemic symptom awareness is more closely related to adrenal o r nonadrenal sympathetic activity, we studied the relationship between symptoms and the epinephrine, norepinephrine, and muscle sympathetic nerve activity (MSNA) responses to hypoglycemia in ten IDDM and ten co ntrol subjects. MSNA was measured continuously using microneurography during hyperinsulinemic (720 pmol m(-2) min(-1)), glucose clamp with 6 0 min of euglycemia, 30 min of hypoglycemia, and 30 min of recovery. S ubjects were asked to rate a series of symptoms every 10 min during th e last 30 min of each period and were unaware of their plasma glucose concentration. MSNA increased significantly in both groups during insu lin clamp (p < 0.05) and further increased during hypoglycemia (p < 0. 01). Both epinephrine and norepinephrine levels significantly increase d during hypoglycemia (p < 0.02). The increase in adrenergic symptom r esponses during hypoglycemia positively correlated with epinephrine (r = 0.75, p < 0.01), but not with MSNA in the control subjects. A simil ar near significant relationship for epinephrine was seen in IDDM subj ects (r = 0.65, p = 0.056). No significant predictors were found for n euroglycopenic or cholinergic symptoms. Thus, the variation in hypogly cemic symptoms is not related to the MSNA response to hypoglycemia. Ad renergic symptom variation is due to differences in adrenal epinephrin e secretion. (C) Elsevier Science inc., 1997.