Additive Glucose-Lowering Effects of Glucagon-Like Peptide-1 and Metformin in Type 2 Diabetes
- Mette Zander, MD12,
- Mustafa Taskiran, MD1,
- Mai-Britt Toft-Nielsen, MD1,
- Sten Madsbad, MD, PHD1 and
- Jens Juul Holst, MD, PHD2
- 1Department of Endocrinology, Hvidovre Hospital, Hvidovre, Denmark
- 2Department of Medical Physiology, The Panum Institute, University of Copenhagen, Copenhagen, Denmark
Abstract
OBJECTIVE—The incretin hormone glucagon-like peptide-1 (GLP-1) reduces plasma glucose in type 2 diabetic patients by stimulating insulin secretion and inhibiting glucagon secretion. The biguanide metformin is believed to lower plasma glucose without affecting insulin secretion. We conducted this study to investigate the effect of a combination therapy with GLP-1 and metformin, which could theoretically be additive, in type 2 diabetic patients.
RESEARCH DESIGN AND METHODS—In a semiblinded randomized crossover study, seven patients received treatment with metformin (1,500 mg daily orally) alternating with GLP-1 (continuous subcutaneous infusion of 2.4 pmol · kg–1 · min–1) alternating with a combination of metformin and GLP-1 for 48 h. Under fixed energy intake, we examined the effects on plasma glucose, insulin, C-peptide, glucagon, and appetite.
RESULTS—Fasting plasma glucose (day 2) decreased from 13.9 ± 1 (no treatment) to 11.2 ± 0.4 (metformin) and 11.5 ± 0.5 (GLP-1) and further decreased to 9.4 ± 0.7 (combination therapy) (P = 0.0005, no difference between monotherapy with GLP-1 and metformin). The 24-h mean plasma glucose (day 2) decreased from 11.8 ± 0.5 (metformin) and 11.7 ± 0.8 (GLP-1) to 9.8 ± 0.5 (combination) (P = 0.02, no difference between GLP-1 and metformin). Insulin levels were similar between the three regimens, but glucagon levels were significantly reduced with GLP-1 compared with metformin (P = 0.0003). Combination therapy had no additional effect on appetite scores.
CONCLUSIONS—Monotherapy with GLP-1 and metformin have equal effects on plasma glucose and additive effects upon combination.
Footnotes
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Address correspondence and reprint requests to Jens Juul Holst, MD, PhD, Department of Medical Physiology, The Panum Institute, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark. E-mail: holst{at}mfi.ku.dk.
Received for publication 19 September 2000 and accepted in revised form 8 December 2000.
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