Diabetes Care, Vol 10, Issue 5 545-554, Copyright © 1987 by American Diabetes Association
Glyburide decreases insulin requirement, increases beta-cell response to mixed meal, and does not affect insulin sensitivity: effects of short- and long-term combined treatment in secondary failure to sulfonylurea
M Gutniak, SG Karlander and S Efendic
Department of Endocrinology, Karolinska Hospital, Stockholm, Sweden.
In 20 patients with non-insulin-dependent diabetes mellitus (NIDDM) and
secondary failure to sulfonylurea, a double-blind randomized study was
performed comparing two regimes: insulin plus placebo (IP) and insulin plus
glyburide (IG). The protocol included two hospitalization periods (days
1-18 and 78-85) and follow-up at the outpatient clinic for 325 days. The
metabolic control was kept as tight as possible. The subjects underwent
normoglycemic clamp studies and meal tests with determination of insulin,
C-peptide, glucagon, somatostatin, and gastric inhibitory polypeptide in
plasma. On IG, they demonstrated marked and long-lasting improvement of
metabolic control: HbA1c decreased from 11.1 +/- 0.3% on day 3 to 8.3 +/-
0.4% (P less than .001) on day 78 and 9.1 +/- 0.5% (P less than .001) on
day 325. In subjects on IP, the corresponding values were 10.3 +/- 0.5, 8.4
+/- 0.4 (P less than .001), and 8.9 +/- 0.5% (P less than .05). Body weight
increased by 6.0 +/- 1.5 kg (P less than .005) on IG and 2.9 +/- 2.1 kg
(NS) on IP. The daily insulin requirement decreased on IG from 62.5 +/-
12.9 U/day on day 7 to 33.5 +/- 8.8 U/day on day 83 and 34.6 +/- 8.9 U/day
on day 325. On IP the insulin requirement was almost constant: 62.0 +/-
10.7 U/day on day 7, 55.5 +/- 7.7 U/day on day 83, and 54.7 +/- 7.9 U/day
on day 325. Insulin sensitivity measured with the hyperinsulinemic clamp
(plasma insulin approximately equal to 130 microU/ml) was similar on IP and
IG at the initiation of the study and was unchanged on days 18 and 85. A
key observation of this study, although the mechanism is unclear, is that
isoglycemic-meal-related insulin requirement was diminished by insulin
treatment, indicating improvement of meal-related insulin sensitivity.
Glyburide increased basal and meal-but not glucagon-stimulated insulin and
C-peptide levels, and also augmented the effect of meals on somatostatin
release. We conclude that in NIDDM, IG regime promptly and continuously
decreased insulin requirement and improved metabolic control. This effect
is, at least during the first 3 mo, mainly due to enhanced insulin
secretion. IG and IP treatment had no effect on insulin sensitivity during
hyperinsulinemic-normoglycemic clamp, whereas meal-related insulin
sensitivity was augmented.