Dipeptidyl peptidase IV resistant analogues of glucagon-like peptide-1 which have extended metabolic stability and improved biological activity
Abstract
Glucagon-like peptide 1 (GLP-1) has great potential in diabetes therapy due to its glucose-dependent stimulation of insulin secretion, but this is limited by its rapid degradation, primarily by dipeptidyl peptidase IV. Four analogues, N-terminally substituted with threonine, glycine, serine or alpha-aminoisobutyric acid, were synthesised and tested for metabolic stability. All were more resistant to dipeptidyl peptidase IV in porcine plasma in vitro, ranging from a t1/2 of 159 min (Gly8 analogue) to undetectable degradation after 6 h (Aib8 analogue; t1/2 for GLP-1 (7-36) amide, 28 min). During i. v. infusion in anaesthetised pigs, over 50% of each analogue remained undegraded compared to 22.7 % for GLP-1 (7-36) amide. In vivo, analogues had longer N-terminal t1/2 (intact peptides: means, 3.3-3.9 min) than GLP-1 (7-36) amide (0.9 min; p < 0.01), but these did not exceed the C-terminal t1/2 (intact plus metabolite: analogues, 3.5-4.4 min; GLP-1 (7-36) amide, 4.1 min). Analogues were assessed for receptor binding using a cell line expressing the cloned receptor, and for ability to stimulate insulin or inhibit glucagon secretion from the isolated perfused porcine pancreas. All bound to the receptor, but only the Aib8 and Gly8 analo...Continue Reading
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