PEGylated glucagon-like peptide-1 displays preserved effects on insulin release in isolated pancreatic islets and improved biological activity in db/db mice.
OBJECTIVE
The rapid degradation and clearance of glucagon-like peptide-1 (GLP-1) by the enzymes dipeptidyl peptidase-IV and neutral endopeptidase 24.11 are the main impediments to the development of GLP-1 as a potential glucose-lowering agent. In this study, new enzyme-resistant polyethylene glycol (PEG)-conjugated GLP-1 analogues were designed and examined for metabolic stability and biological potency.


METHODS
Two mono-PEGylated GLP-1 analogues, N-terminally modified N-PEG/GLP-1 and Lys-modified Lys-PEG/GLP-1, were prepared. Stability was tested in plasma and tissue extracts. In vitro insulin release studies were performed using isolated rat pancreatic islets, while in vivo glycaemic responses were measured in db/db mice.


RESULTS
The half-life of Lys-PEG/GLP-1 was 40-, 10- and 28-fold longer than that of GLP-1 in plasma, liver and kidney homogenates, respectively. Lys-PEG/GLP-1 stimulated insulin secretion in the islets in a dose- and glucose-dependent manner, and was as potent as GLP-1. In contrast, N-PEG/GLP-1 showed extended metabolic stability but had significantly lower biological activity. The administration of Lys-PEG/GLP-1 (9 nmol/kg i.p.) to non-fasted db/db mice stabilised glycaemia (p<0.001), whereas GLP-1 (9 nmol/kg) only caused small changes in glucose level. During OGTT in fasted db/db mice, Lys-PEG/GLP-1 administered at 1, 3 and 9 nmol/kg (i.p.) reduced the glucose AUC(0-3h) by 48.7+/-9.4, 55.0+/-2.9 and 63.4+/-2.5%, respectively, compared with placebo (p<0.01), whereas GLP-1 (9 nmol/kg) lowered the glucose level by 39.5+/-12.9% (p<0.01).


CONCLUSIONS
This study demonstrates that site-specific PEGylated GLP-1 analogues are resistant to degradation. The enhanced biological potencies of these analogues highlight their potential as new, GLP-1-like glucose-lowering agents.
College of Pharmacy, Seoul National University, San 56-1, Shillim-dong, Gwanak-gu, Seoul 151-742, South Korea.
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S
Lee
Y S
YS
Youn
S-H
SH
Lee
Y
Y
Byun
K C
KC
Lee
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D005260:Female; D052216:Glucagon-Like Peptide 1 / Q000737:chemistry / Q000494:pharmacology*; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011092:Polyethylene Glycols / Q000737:chemistry / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley
D001786:Blood Glucose; D007328:Insulin; D011092:Polyethylene Glycols; D052216:Glucagon-Like Peptide 1