Glycation of glucagon-like peptide-1(7-36)amide: characterization and impaired action on rat insulin secreting cells.
Glucagon-like peptide-1(7-36)amide(truncated GLP-1, tGLP-1) is a potent insulin releasing hormone of the enteroinsular axis. This study has examined glycation of tGLP-1 and effects of such structural modification on insulin secretion. Monoglycated tGLP-1 (M(r) 3463.8, determined by plasma desorption mass spectrometry) was prepared by incubation with glucose under reducing conditions and purified by reversed-phase high performance liquid chromatography. Automated Edman degradation indicated that tGLP-1 was specifically glycated at the amino terminal His7 site. In extracts from mouse small intestine, glycated tGLP-1 represented approximately 14% of the total tGLP-1 content. Effects of glycated and non-glycated tGLP-1 on insulin secretion were examined using glucose-responsive clonal BRIN-BD11 cells. In acute (20 min) incubations, 10(-9) mol/l tGLP-1 enhanced insulin release by 2.2-fold and 1.5-fold at 5.6 and 11.1 mmol/l glucose, respectively. In contrast, 10(-9) mol/l glycated tGLP-1 failed to stimulate secretion and insulin output was decreased by 34-73% following glycation. At 5.6 mmol/l glucose, non-glycated tGLP-1 (3 x 10(-10) mol/l-10(-8) mol/l) exerted a 2.3-fold to 3.2-fold increase in insulin secretion compared with controls. The effect of glycated tGLP-1 at 10(-9) mol/l and 3 x 10(-9) mol/l was reduced by 51-55% compared with non-glycated peptide, and its insulinotropic action was effectively abolished. These data indicate that when tGLP-1 is glycated at the amino terminal His7, this modification substantially reduces the glucose-dependent insulinotropic action of the peptide.
O'Harte
F P
FP
School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, UK.
Abdel-Wahab
Y H
YH
Conlon
J M
JM
Flatt
P R
PR
D000595:Amino Acid Sequence; D000818:Animals; D000918:Antibody Specificity; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D005934:Glucagon; D052216:Glucagon-Like Peptide 1; D004763:Glucagon-Like Peptides; D006031:Glycosylation; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007421:Intestine, Small / Q000737:chemistry; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000032:analysis / Q000737:chemistry* / Q000494:pharmacology*; D011863:Radioimmunoassay; D051381:Rats; D017421:Sequence Analysis; D013329:Structure-Activity Relationship
D007328:Insulin; D010446:Peptide Fragments; C055453:glucagon-like peptide 1 (7-36)amide; D004763:Glucagon-Like Peptides; D052216:Glucagon-Like Peptide 1; D005934:Glucagon