Beta2-Adrenergic Sensitivity Preserved in Diabetics With Hypoglycemia Unawarenes

Sensitivity to stimulation by beta2-adrenergic receptor agonists is preserved in type 1 diabetics who have hypoglycemia unawareness. Beta2-adrenergic receptor agonists have been proposed for the treatment of hypoglycemia unawareness, the authors explain, but previous reports have suggested a reduction in beta-adrenergic sensitivity among type 1 diabetic patients with hypoglycemia unawareness.

Dr. Bastiaan E. De Galan and colleagues from Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands compared beta2-adrenergic sensitivity in 10 type 1 diabetic patients with hypoglycemia unawareness, 12 type 1 diabetic patients with intact hypoglycemia awareness, and 11 healthy controls.

Sensitivity to beta2-adrenergic stimulation was determined by measuring the forearm vasodilator response to an intraarterial infusion of salbutamol.

Maximal forearm blood flow responses to salbutamol in the infused arm did not differ between the three groups, the authors report. Salbutamol infusion also induced an increase in forearm blood flow in the noninfused arm of healthy controls and diabetics with intact hypoglycemia awareness, the results indicate, but not in the noninfused arm of diabetics with hypoglycemia unawareness.

"Our finding of similar vasodilator responses does not support a role for the beta2-adrenergic receptor in reduced beta-adrenergic sensitivity," the researchers say. "When the data were expressed as fold increase from baseline, salbutamol elicited even higher responses in unaware diabetic patients than the other two groups, although the differences did not reach statistical significance."

"This observation may be of potential value when treatment with beta2-adrenergic agonists is considered to support glucose counterregulation," the authors conclude. "Whether reduced beta-adrenergic sensitivity in hypoglycemia unawareness is mediated through the beta1-adrenergic receptor or impairments in the baroreflex response pathway requires further study."

J Clin Endocrinol Metab 2006;91:2878-2881.

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