The metabolite generated by dipeptidyl-peptidase 4 metabolism of glucagon-like peptide-1 has no influence on plasma glucose levels in patients with type 2 diabetes.
OBJECTIVE
Glucagon-like peptide-1 (GLP-1) is metabolised by the enzyme dipeptidyl-peptidase 4 (DPP-4), generating a metabolite with potential antagonistic properties. This study was conducted to evaluate the effect of that metabolite on plasma glucose levels in patients with type 2 diabetes.


METHODS
The randomised crossover study consisted of five regimens: (1) i.v. infusion of GLP-1 (1.2 pmol kg(-1) min(-1); IV); (2 and 3) s.c. infusion of GLP-1 (2.4 and 9.6 pmol kg(-1) min(-1); LSC, HSC); (4) s.c. infusion of GLP-1 (2.4 pmol kg(-1) min(-1)) in combination with a DPP-4 inhibitor (IB); and (5) s.c. infusion of saline (154 mmol NaCl/l; SAL). Seven patients with type 2 diabetes participated in all protocols.


RESULTS
Plasma levels of intact GLP-1 increased from 7+/-1 (SAL) to 17+/-3 (LSC), 61+/-7 (IB), 62+/-5 (IV) and 94+/-10 (9.6 s.c.) pmol/l, p<0.0001. Plasma concentrations of the metabolite increased from 1+/-3 (SAL) and 2+/-6 (IB) pmol/l to 42+/-4 (LSC), 64+/-8 (IV) and 327+/-16 (HSC) pmol/l, p<0.0001. Mean plasma glucose levels at 6 h decreased from 12.4+/-1.1 (SAL) mmol/l to 10.4+/-1.1 (LSC), 8.6+/-0.6 (IB), 8.8+/-0.8 (IV) and 9.1+/-0.9 (HSC) mmol/l, p<0.0001.


CONCLUSIONS
At approximately similar concentrations of intact GLP-1 (IV, IB, HSC), but with widely ranging metabolite concentrations, the effect on plasma glucose levels was equal, indicating that the presence of the metabolite does not antagonise the glucose-lowering effect of GLP-1.
Zander
M
M
Department of Endocrinology, Hvidovre Hospital, Kettegaards Allé 30, 2650 Hvidovre, Denmark. m.zander@dadlnet.dk
Madsbad
S
S
Deacon
C F
CF
Holst
J J
JJ
D001786:Blood Glucose / Q000032:analysis*; D002096:C-Peptide / Q000097:blood; D018592:Cross-Over Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000503:physiopathology; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism*; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005934:Glucagon / Q000097:blood; D052216:Glucagon-Like Peptide 1 / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D008875:Middle Aged; D009570:Nitriles / Q000494:pharmacology; D010455:Peptides / Q000378:metabolism*; D011759:Pyrrolidines / Q000494:pharmacology
C121834:1-(((2-((5-cyanopyridin-2-yl)amino)ethyl)amino)acetyl)-2-cyano-(S)-pyrrolidine; D001786:Blood Glucose; D002096:C-Peptide; D004791:Enzyme Inhibitors; D007328:Insulin; D009570:Nitriles; D010455:Peptides; D011759:Pyrrolidines; C114437:glucagon-like peptide-1 (9-36)-amide; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D018819:Dipeptidyl Peptidase 4