Abstract
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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Deaminase / metabolism
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Amino Acid Substitution
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Animals
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Binding, Competitive
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Blood Glucose / drug effects
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Blood Glucose / metabolism
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Cell Line, Tumor
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Cricetinae
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Cyclic AMP / metabolism*
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Diabetes Mellitus, Type 2 / drug therapy
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Diabetes Mellitus, Type 2 / metabolism
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Dipeptidyl Peptidase 4*
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Fibroblasts / metabolism
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Glucagon / genetics
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Glucagon / metabolism*
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Glucagon / pharmacology
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Glucagon-Like Peptide 1
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Glucagon-Like Peptide-1 Receptor
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Glucose / pharmacology
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Glutamine / chemistry
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Glycoproteins / metabolism
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Humans
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Hypoglycemic Agents / metabolism*
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Hypoglycemic Agents / pharmacology
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Insulin / blood
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Insulin / metabolism*
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Insulin Secretion
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Islets of Langerhans / drug effects
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Islets of Langerhans / metabolism
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Mice
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Mice, Obese
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Peptide Fragments / genetics
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Peptide Fragments / metabolism*
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Peptide Fragments / pharmacology
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Phenylalanine / chemistry
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Proline / chemistry
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Protein Precursors / genetics
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Protein Precursors / metabolism*
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Protein Precursors / pharmacology
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Rats
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Receptors, Glucagon / metabolism
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Spectrometry, Mass, Electrospray Ionization
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Transformation, Genetic
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Tyrosine / chemistry
Substances
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Blood Glucose
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GLP1R protein, human
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Glp1r protein, mouse
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Glp1r protein, rat
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Glucagon-Like Peptide-1 Receptor
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Glycoproteins
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Hypoglycemic Agents
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Insulin
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Peptide Fragments
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Protein Precursors
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Receptors, Glucagon
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Glutamine
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Tyrosine
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Phenylalanine
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Glucagon-Like Peptide 1
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Glucagon
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Proline
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Cyclic AMP
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DPP4 protein, human
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Dipeptidyl Peptidase 4
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Adenosine Deaminase
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Glucose