Abstract
AIMS/HYPOTHESIS: The incretin hormone glucagon-like peptide 1 (GLP-1) has antihyperglycaemic effects, but its therapeutic usefulness is limited by its metabolic instability. Dipeptidyl peptidase IV (DPP-IV) is established as the primary inactivating enzyme, but the roles of other enzymes remain unclear.
METHODS: The effect of candoxatril, a selective inhibitor of neutral endopeptidase (NEP) 24.11, on GLP-1 pharmacokinetics/pharmacodynamics with or without DPP-IV inhibition was examined in anaesthetised pigs.
RESULTS: During GLP-1 infusion, candoxatril doubled C-terminal immunoreactivity, improving the pharmacokinetics (t(1/2) 2.3+/-0.1 to 8.8+/-1.2 min; metabolic clearance rate [MCR] 20.4+/-3.4 to 4.8+/-0.4 ml.kg(-1). min(-1); p<0.01), but had no effect upon intact GLP-1 (t(1/2) 1.4+/-0.1 to 1.6+/-0.1 min; MCR 47.9+/-8.0 to 38.8+/-5.0 ml.kg(-1).min(-1)). Insulin responses to intravenous glucose were unaffected by candoxatril, but glucose tolerance was improved (DeltaAUC(min 27-87) 118+/-5 to 74+/-14 min.mmol.l(-1); glucose elimination rate [k] 6.6+/-0.5 to 8.6+/-0.5%; p<0.05). When candoxatril was co-administered with valine pyrrolidide (a DPP-IV inhibitor), changes in C-terminal GLP-1 pharmacokinetics mirrored those seen when candoxatril alone was administered (t(1/2) 2.7+/-0.3 and 7.7+/-0.8 min; MCR 17.3+/-2.6 and 6.5+/-0.8 ml.kg(-1).min(-1) for valine pyrrolidide without and with candoxatril, respectively). However, intact GLP-1 pharmacokinetics were improved (t(1/2) 2.8+/-0.3 and 7.5+/-0.6 min; MCR 18.3+/-0.6 and 9.4+/-0.9 ml.kg(-1).min(-1); p<0.02), potentiating the antihyperglycaemic/insulinotropic effects of GLP-1 (glucose deltaAUC(min 27- 87) 103+/-8 to 62+/-14 min.mmol.l(-1); k 6.8+/-0.4 to 11.4+/-1.4%; insulin deltaAUC(min 27-87) 3,680+/-738 to 7,201+/-1,183 min.pmol.l(-1); p<0.05).
CONCLUSIONS/INTERPRETATION: This study confirms a role for NEP-24.11 in GLP-1 metabolism in vivo, suggesting that up to 50% of GLP-1 entering the circulation may be degraded by NEP-24.11. Furthermore, combined inhibition of DPP-IV and NEP-24.11 is superior to DPP-IV inhibition alone in preserving intact GLP-1, which raises the possibility that the combination has therapeutic potential.
Original language | English |
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Journal | Diabetologia |
Volume | 48 |
Issue number | 9 |
Pages (from-to) | 1882-90 |
Number of pages | 9 |
ISSN | 0012-186X |
DOIs | |
Publication status | Published - Sep 2005 |
Keywords
- Animals
- Antihypertensive Agents
- Area Under Curve
- Dipeptidyl Peptidase 4
- Glucagon
- Indans
- Insulin
- Metabolic Clearance Rate
- Models, Animal
- Neprilysin
- Propionates
- Swine