Diabetes, Vol 36, Issue 11 1320-1328, Copyright © 1987 by American Diabetes Association
Different effects of glyburide and glipizide on insulin secretion and hepatic glucose production in normal and NIDDM subjects
L Groop, L Luzi, A Melander, PH Groop, K Ratheiser, DC Simonson and RA DeFronzo
Yale University School of Medicine, New Haven, Connecticut.
Glyburide (GB) and glipizide (GZ) differ in their pharmacokinetics, but it
is not known whether they also differ in mode of action. To examine this
question, 10 young healthy subjects and 6 non-insulin-dependent diabetic
(NIDDM) patients participated in each of three studies: 1) infusion of
saline for 120 min followed by a 100-min hyperglycemic (125 mg/dl) clamp;
2) 120-min primed continuous infusion of GZ followed by a 100-min
hyperglycemic clamp; and 3) 120-min primed continuous infusion of GB
followed by a 100-min hyperglycemic clamp. The GB and GZ infusions were
continued throughout the hyperglycemic clamp. Similar plasma concentrations
of GB and GZ were obtained in both groups. All studies were performed with
[3-3H]glucose to allow quantification of hepatic glucose production. When
administered under basal conditions of glycemia, the acute phase (0-10 min)
of plasma insulin and C-peptide increase in both control and NIDDM subjects
was twice as great with GZ compared with GB (P less than .01). During the
hyperglycemic-clamp studies performed in normal subjects, both GB and GZ
increased the first- (1.6-fold) and second- (2.2-fold) phase plasma insulin
responses more than hyperglycemia alone. During the hyperglycemic clamp in
NIDDM subjects, the first-phase plasma insulin response was absent, and the
second-phase insulin response was markedly impaired. Neither GB nor GZ
improved first-phase insulin secretion in the NIDDM patients. In both NIDDM
and control subjects, the effects of hyperglycemia and sulfonylurea drugs
(both GB and GZ) on the first- and second-phase plasma insulin responses
were simply additive.(ABSTRACT TRUNCATED AT 250 WORDS)