Biological activities of glucagon-like peptide-1 analogues in vitro and in vivo

Biochemistry. 2001 Mar 6;40(9):2860-9. doi: 10.1021/bi0014498.

Abstract

Studies support a role for glucagon-like peptide 1 (GLP-1) as a potential treatment for diabetes. However, since GLP-1 is rapidly degraded in the circulation by cleavage at Ala(2), its clinical application is limited. Hence, understanding the structure-activity of GLP-1 may lead to the development of more stable and potent analogues. In this study, we investigated GLP-1 analogues including those with N-, C-, and midchain modifications and a series of secretin-class chimeric peptides. Peptides were analyzed in CHO cells expressing the hGLP-1 receptor (R7 cells), and in vivo oral glucose tolerance tests (OGTTs) were performed after injection of the peptides in normal and diabetic (db/db) mice. [D-Ala(2)]GLP-1 and [Gly(2)]GLP-1 showed normal or relatively lower receptor binding and cAMP activation but exerted markedly enhanced abilities to reduce the glycemic response to an OGTT in vivo. Improved biological effectiveness of [D-Ala(2)]GLP-1 was also observed in diabetic db/db mice. Similarly, improved biological activity of acetyl- and hexenoic-His(1)-GLP-1, glucagon((1-5)-, glucagon((1-10))-, PACAP(1-5)-, VIP(1-5)-, and secretin((1-10))-GLP-1 was observed, despite normal or lower receptor binding and activation in vitro. [Ala(8/11/12/16)] substitutions also increased biological activity in vivo over wtGLP-1, while C-terminal truncation of 4-12 amino acids abolished receptor binding and biological activity. All other modified peptides examined showed normal or decreased activity in vitro and in vivo. These results indicate that specific N- and midchain modifications to GLP-1 can increase its potency in vivo. Specifically, linkage of acyl-chains to the alpha-amino group of His(1) and replacement of Ala(2) result in significantly increased biological effects of GLP-1 in vivo, likely due to decreased degradation rather than enhanced receptor interactions. Replacement of certain residues in the midchain of GLP-1 also augment biological activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Animals
  • Binding, Competitive
  • CHO Cells
  • Cricetinae
  • Diabetes Mellitus, Type 2 / blood
  • Diabetes Mellitus, Type 2 / drug therapy
  • Female
  • Glucagon / administration & dosage
  • Glucagon / chemical synthesis
  • Glucagon / metabolism*
  • Glucagon-Like Peptide 1
  • Glucagon-Like Peptide-1 Receptor
  • Glucose Tolerance Test
  • Humans
  • Injections, Intraperitoneal
  • Injections, Subcutaneous
  • Mice
  • Mice, Inbred C57BL
  • Mice, Obese
  • Molecular Sequence Data
  • Peptide Fragments / administration & dosage
  • Peptide Fragments / chemical synthesis
  • Peptide Fragments / metabolism*
  • Protein Precursors / administration & dosage
  • Protein Precursors / chemical synthesis
  • Protein Precursors / metabolism*
  • Radioligand Assay
  • Receptors, Glucagon / metabolism
  • Sequence Deletion
  • Structure-Activity Relationship

Substances

  • GLP1R protein, human
  • Glp1r protein, mouse
  • Glucagon-Like Peptide-1 Receptor
  • Peptide Fragments
  • Protein Precursors
  • Receptors, Glucagon
  • Glucagon-Like Peptide 1
  • Glucagon