Metabolic stability, receptor binding, cAMP generation, insulin secretion and antihyperglycaemic activity of novel N-terminal Glu9-substituted analogues of glucagon-like peptide-1.
Glucagon-like peptide-1(7-36)amide (GLP-1) is an incretin hormone with therapeutic potential for type 2 diabetes. Rapid removal of the N-terminal dipeptide, His7-Ala8, by the ubiquitous enzyme dipeptidyl peptidase IV (DPP IV) curtails the biological activity of GLP-1. Chemical modifications or substitutions of GLP-1 at His7 or Ala8 improve resistance to DPP-IV action, but this often reduces potency. Little attention has focused on the metabolic stability and functional activity of GLP-1 analogues with amino acid substitution at Glu9, adjacent to the DPP IV cleavage site. We generated three novel Glu9-substituted GLP-1 analogues, (Pro9)GLP-1, (Phe9)GLP-1 and (Tyr9)GLP-1 and show for the first time that Glu9 of GLP-1 is important in DPP IV degradation, since replacing this amino acid, particularly with proline, substantially reduced susceptibility to degradation. All three novel GLP-1 analogues showed similar or slightly enhanced insulinotropic activity compared with native GLP-1 despite a moderate 4-10-fold reduction in receptor binding and cAMP generation. In addition, (Pro9)GLP-1 showed significant ability to moderate the plasma glucose excursion and increase circulating insulin concentrations in severely insulin resistant obese diabetic (ob/ob) mice. These observations indicate the importance of Glu9 for the biological activity of GLP-1 and susceptibility to DPP IV-mediated degradation.
Green
Brian D
BD
School of Biomedical Sciences, University of Ulster, Coleraine BT52 1SA, Northern Ireland, UK.
Gault
Victor A
VA
Irwin
Nigel
N
Mooney
Mark H
MH
Bailey
Clifford J
CJ
Harriott
Patrick
P
Greer
Brett
B
Flatt
Peter R
PR
O'Harte
Finbarr P M
FP
D000243:Adenosine Deaminase / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D001667:Binding, Competitive; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000378:metabolism; D018819:Dipeptidyl Peptidase 4; D005347:Fibroblasts / Q000378:metabolism; D005934:Glucagon / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D052216:Glucagon-Like Peptide 1; D000067757:Glucagon-Like Peptide-1 Receptor; D005947:Glucose / Q000494:pharmacology; D005973:Glutamine / Q000737:chemistry; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000378:metabolism* / Q000494:pharmacology; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008820:Mice, Obese; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D010649:Phenylalanine / Q000737:chemistry; D011392:Proline / Q000737:chemistry; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D018027:Receptors, Glucagon / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D014170:Transformation, Genetic; D014443:Tyrosine / Q000737:chemistry
D001786:Blood Glucose; C000593833:GLP1R protein, human; C000593834:Glp1r protein, mouse; C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D006023:Glycoproteins; D007004:Hypoglycemic Agents; D007328:Insulin; D010446:Peptide Fragments; D011498:Protein Precursors; D018027:Receptors, Glucagon; D005973:Glutamine; D014443:Tyrosine; D010649:Phenylalanine; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D011392:Proline; D000242:Cyclic AMP; C042807:DPP4 protein, human; D018819:Dipeptidyl Peptidase 4; D000243:Adenosine Deaminase; D005947:Glucose