Abbreviations: ANOVA, analysis of variance; FPG, fasting plasma glucose; GLP-1, glucagon-like peptide 1; RIA, radioimmunoassay.A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
Evaluation of -Cell Secretory Capacity Using Glucagon-Like Peptide 1 O R I G I N A L A R T I C L EOBJECTIVE --Cell secretory capacity is often evaluated with a glucagon test or a meal test. However, glucagon-like peptide 1 (GLP-1) is the most insulinotropic hormone known, and the effect is preserved in type 2 diabetic patients.RESEARCH DESIGN AND METHODS -We first compared the effects of intravenous bolus injections of 2.5, 5, 15, and 25 nmol GLP-1 with glucagon (1 mg intravenous) and a standard meal (566 kcal) in 6 type 2 diabetic patients and 6 matched control subjects. Next, we studied another 6 patients and 6 control subjects and, in addition to the above procedure, performed a combined glucose plus GLP-1 stimulation, where plasma glucose was increased to 15 mmol/l before injection of 2.5 nmol GLP-1. Finally, we compared the insulin response to glucose plus GLP-1 stimulation with that observed during a hyperglycemic arginine clamp (30 mmol/l) in 8 patients and 8 control subjects.RESULTS -Peak insulin and C-peptide concentrations were similar after the meal, after 2.5 nmol GLP-1, and after glucagon. Side effects were less with GLP-1 than with glucagon. Peak insulin and C-peptide concentrations were as follows (C-peptide concentrations are given in parentheses): for patients (n = 12): meal, 277 ± 42 pmol/l (2,181 ± 261 pmol/l); GLP-1 (2.5 nmol), 390 ± 74 pmol/l (2,144 ± 254 pmol/l); glucagon, 329 ± 50 pmol/l (1,780 ± 160 pmol/l); glucose plus GLP-1, 465 ± 87 pmol/l (2,384 ± 2,99 pmol/l); for control subjects (n = 12): meal, 543 ± 89 pmol/l (2,873 ± 210 pmol/l); GLP-1, 356 ± 51 pmol/l (2,001 ± 130 pmol/l); glucagon, 420 ± 61 pmol/l (1,995 ± 99 pmol/l); glucose plus GLP-1, 1,412 ± 187 pmol/l (4,391 ± 416 pmol/l). Peak insulin and C-peptide concentrations during the hyperglycemic arginine clamp and during glucose plus GLP-1 injection were as follows: for patients: 475 ± 141 pmol/l (2,295 ± 379 pmol/l) and 816 ± 268 pmol/l (3,043 ± 508 pmol/l), respectively; for control subjects: 1,403 ± 308 pmol/l (4,053 ± 533 pmol/l) and 2,384 ± 452 pmol/l (6,047 ± 652 pmol/l), respectively.CONCLUSIONS -GLP-1 (2.5 nmol = 9 µg) elicits similar secretory responses to 1 mg glucagon (but has fewer side effects) and a standard meal. Additional elevation of plasma glucose to 15 mmol/l did not enhance the response further. The incremental response was similar to that elicited by arginine, but hyperglycemia had an additional effect on the response to arginine. E m e r g i n g T r e a t m e n t s a n d T e c h n o l o g i e s
808DIABETES CARE, VOLUME 23, NUMBER 6, JUNE 2000 , and a GLP-1 bolus injection of 2.5 nmol GLP-1 were performed. In addition, in type 2 diabetic patients with fasting plasma glucose (FPG) Ͻ15 mmol/l (9 of the 12 patients) and in all healthy subjects, a combine...