title: Degradation, receptor binding, insulin secreting and antihyperglycaemic actions of palmitate-derivatised native and Ala8-substituted GLP-1 analogues.
abstract: The hormone glucagon-like peptide-1(7-36)amide (GLP-1) is released in response to ingested nutrients and acts to promote glucose-dependent insulin secretion ensuring efficient postprandial glucose homeostasis. Unfortunately, the beneficial actions of GLP-1 which give this hormone many of the desirable properties of an antidiabetic drug are short lived due to degradation by dipeptidyl-peptidase IV (DPP IV) and rapid clearance by renal filtration. In this study we have attempted to extend GLP-1 action through the attachment of palmitoyl moieties to the epsilon-amino group in the side chain of the Lys26 residue and to combine this modification with substitutions of the Ala8 residue, namely Val or amino-butyric acid (Abu). In contrast to native GLP-1, which was rapidly degraded, [Lys(pal)26]GLP-1, [Abu8, Lys(pal)26]GLP-1 and [Val8 Lys(pal)26]GLP-1 all exhibited profound stability during 12 h incubations with DPP IV and human plasma. Receptor binding affinity and the ability to increase cyclic AMP in the clonal beta-cell line BRIN-BD11 were decreased by 86- to 167-fold and 15- to 62-fold, respectively compared with native GLP-1. However, insulin secretory potency tested using BRIN-BD11 cells was similar, or in the case of [Val8,Lys(pal)26]GLP-1 enhanced. Furthermore, when administered in vivo together with glucose to diabetic (ob/ob) mice, [Lys(pal)26]GLP-1, [Abu8,Lys(pal)26]GLP-1 and [Val8,Lys(pal)26]GLP-1 did not demonstrate acute glucose-lowering or insulinotropic activity as observed with native GLP-1. These studies support the potential usefulness of fatty acid linked analogues of GLP-1 but indicate the importance of chain length for peptide kinetics and bioavailability.
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine BT52 1SA, Northern Ireland, UK. b.green@ulster.ac.uk
authors.forename: Brian D
authors.initials: BD
authors.lastname: Green
authors.forename: Victor A
authors.initials: VA
authors.lastname: Gault
authors.forename: Mark H
authors.initials: MH
authors.lastname: Mooney
authors.forename: Nigel
authors.initials: N
authors.lastname: Irwin
authors.forename: Patrick
authors.initials: P
authors.lastname: Harriott
authors.forename: Brett
authors.initials: B
authors.lastname: Greer
authors.forename: Cliff J
authors.initials: CJ
authors.lastname: Bailey
authors.forename: Finbarr P M
authors.initials: FP
authors.lastname: O'Harte
authors.forename: Peter R
authors.initials: PR
authors.lastname: Flatt
mesh_terms: D000409:Alanine / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000096:biosynthesis; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism; D005934:Glucagon / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology*; D052216:Glucagon-Like Peptide 1; D000067757:Glucagon-Like Peptide-1 Receptor; D006801:Humans; D007004:Hypoglycemic Agents / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism; D008239:Lysine / Q000737:chemistry; D051379:Mice; D008820:Mice, Obese; D010168:Palmitates / Q000737:chemistry* / Q000493:pharmacokinetics / Q000494:pharmacology; D010446:Peptide Fragments / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology*; D011498:Protein Precursors / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology*; D011869:Radioligand Assay; D018027:Receptors, Glucagon / Q000378:metabolism; D014633:Valine / Q000737:chemistry
chemical_list: D001786:Blood Glucose; C000593833:GLP1R protein, human; C000593834:Glp1r protein, mouse; D000067757:Glucagon-Like Peptide-1 Receptor; D007004:Hypoglycemic Agents; D007328:Insulin; D010168:Palmitates; D010446:Peptide Fragments; D011498:Protein Precursors; D018027:Receptors, Glucagon; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP; D018819:Dipeptidyl Peptidase 4; D014633:Valine; D008239:Lysine; D000409:Alanine