Abstract
To evaluate the influence of the incidence and unawareness of hypoglycemia
on lymphocyte beta2-adrenoceptor densities, we measured beta2-adrenoceptor
density using 125I-iodocyanopindolol and CGP 12177 before and after
1 week of treatment optimization in 33 adults with type-1 diabetes
mellitus. Diabetes treatment of all patients was modified to improve
their glycemic control. During this week, all patients had to complete
a protocol with 7 daily glucose measurements, one of which was at
night. The subjective symptoms were evaluated in case of hypoglycemia.
A significant correlation between a hypoglycemia incidence below
(but not above) the threshold of 2.75 mmol/l (50 mg/dl) and beta2-adrenoceptor
densities on lymphocytes was found after the study week (r = -0.72,
p < 0.00001). Nine patients suffering from hypoglycemia unawareness
had a significantly higher incidence of hypoglycemia (p < 0.002)
and lower beta2-adrenoceptor densities on lymphocytes compared to
24 patients who recognized all of their hypoglycemic episodes (p
< 0.004). We conclude that downregulation of beta2-adrenoceptor densities
on lymphocytes occurs as a result of recurrent hypoglycemia defined
as glucose levels of < 2.75 mmol/l. Beta2-adrenoceptor densities
are decreased in patients with subjective hypoglycemia unawareness
and might contribute to the reduced beta-adrenergic sensitivity in
this subgroup of patients.
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