Biological activities of glucagon-like peptide-1 analogues in vitro and in vivo.
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.
Xiao
Q
Q
Department of Medicine and Physiology, University of Toronto, Toronto, Ontario, Canada.
Giguere
J
J
Parisien
M
M
Jeng
W
W
St-Pierre
S A
SA
Brubaker
P L
PL
Wheeler
M B
MB
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001667:Binding, Competitive; D016466:CHO Cells; D006224:Cricetinae; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000188:drug therapy; D005260:Female; D005934:Glucagon / Q000008:administration & dosage / Q000138:chemical synthesis / Q000378:metabolism*; D052216:Glucagon-Like Peptide 1; D000067757:Glucagon-Like Peptide-1 Receptor; D005951:Glucose Tolerance Test; D006801:Humans; D007274:Injections, Intraperitoneal; D007279:Injections, Subcutaneous; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000008:administration & dosage / Q000138:chemical synthesis / Q000378:metabolism*; D011498:Protein Precursors / Q000008:administration & dosage / Q000138:chemical synthesis / Q000378:metabolism*; D011869:Radioligand Assay; D018027:Receptors, Glucagon / Q000378:metabolism; D017384:Sequence Deletion; D013329:Structure-Activity Relationship
C000593833:GLP1R protein, human; C000593834:Glp1r protein, mouse; D000067757:Glucagon-Like Peptide-1 Receptor; D010446:Peptide Fragments; D011498:Protein Precursors; D018027:Receptors, Glucagon; D052216:Glucagon-Like Peptide 1; D005934:Glucagon