Effect of glucagon-like peptide 1(7-36) amide on glucose effectiveness and insulin action in people with type 2 diabetes.
Although it is well established that glucagon-like peptide 1(7-36) amide (GLP-1) is a potent stimulator of insulin secretion, its effects on insulin action and glucose effectiveness are less clear. To determine whether GLP-1 increases insulin action and glucose effectiveness, subjects with type 2 diabetes were studied on two occasions. Insulin was infused during the night on both occasions to ensure that baseline glucose concentrations were comparable. On the morning of study, either GLP-1 (1.2 pmol x kg(-1) x min(-1)) or saline were infused along with somatostatin and replacement amounts of glucagon. Glucose also was infused in a pattern mimicking that typically observed after a carbohydrate meal. Insulin concentrations were either kept constant at basal levels (n = 6) or varied so as to create a prandial insulin profile (n = 6). The increase in glucose concentration was virtually identical on the GLP-1 and saline study days during both the basal (1.21 +/- 0.15 vs. 1.32 +/- 0.19 mol/l per 6 h) and prandial (0.56 +/- 0.14 vs. 0.56 +/- 0.10 mol/l per 6 h) insulin infusions. During both the basal and prandial insulin infusions, glucose disappearance promptly increased after initiation of the glucose infusion to rates that did not differ on the GLP-1 and saline study days. Suppression of endogenous glucose production also was comparable on the GLP-1 and saline study days during both the basal (-2.7 +/- 0.3 vs. -3.1 +/- 0.2 micromol/kg) and prandial (-3.1 +/- 0.4 vs. -3.0 +/- 0.6 pmol/kg) insulin infusions. We conclude that when insulin and glucagon concentrations are matched, GLP-1 has negligible effects on either insulin action or glucose effectiveness in people with type 2 diabetes. These data strongly support the concept that GLP-1 improves glycemic control in people with type 2 diabetes by increasing insulin secretion, by inhibiting glucagon secretion, and by delaying gastric emptying rather than by altering extrapancreatic glucose metabolism.
Vella
A
A
Department of Internal Medicine, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
Shah
P
P
Basu
R
R
Basu
A
A
Holst
J J
JJ
Rizza
R A
RA
D001786:Blood Glucose / Q000378:metabolism*; D002096:C-Peptide / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000188:drug therapy*; D005502:Food; D005746:Gastric Emptying / Q000187:drug effects; D005934:Glucagon / Q000008:administration & dosage / Q000097:blood; D052216:Glucagon-Like Peptide 1; D004763:Glucagon-Like Peptides; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007328:Insulin / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*; D007700:Kinetics; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D013004:Somatostatin
D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D010446:Peptide Fragments; C055453:glucagon-like peptide 1 (7-36)amide; D019382:Human Growth Hormone; D013004:Somatostatin; D004763:Glucagon-Like Peptides; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D006854:Hydrocortisone