N-terminal glycation of cholecystokinin-8 abolishes its insulinotropic action on clonal pancreatic B-cells.
Monoglycated cholecystokinin octapeptide (Asp(1)-glucitol CCK-8) was prepared under hyperglycaemic reducing conditions and purified by reverse phase-high performance liquid chromatography. Electrospray ionisation mass spectrometry and automated Edman degradation demonstrated that CCK-8 was glycated specifically at the amino-terminal Asp(1) residue. Effects of Asp(1)-glucitol CCK-8 and CCK-8 on insulin secretion were examined using glucose-responsive clonal BRIN-BD11 cells. In acute (20 min) incubations, 10(-10) mol/l CCK-8 enhanced insulin release by 1.2-1.5-fold at 5.6-11.1 mmol/l glucose. The stimulatory effect induced by 10(-10) mol/l CCK-8 was abolished following glycation. At 5.6 mmol/l glucose, CCK-8 at concentrations ranging from 10(-11) to 10(-7) mol/l induced a significant 1.6-1.9-fold increase in insulin secretion. Insulin output in the presence of Asp(1)-glucitol CCK-8 over the concentration range 10(-11)-10(-7) mol/l was decreased by 21-35% compared with CCK-8, and its insulinotropic action was effectively abolished. Asp(1)-glucitol CCK-8 at 10(-8) mol/l also completely blocked the stimulatory effects of 10(-11)-10(-8) mol/l CCK-8. These data indicate that structural modification by glycation at the amino-terminal Asp(1) residue effectively abolishes and/or antagonises the insulinotropic activity of CCK-8.
Abdel-Wahab
Y H
YH
School of Biomedical Sciences, University of Ulster, Coleraine, UK. y.abdel-wahab@ulst.ac.uk
O'Harte
F P
FP
Mooney
M H
MH
Conlon
J M
JM
Flatt
P R
PR
D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D006031:Glycosylation; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D012844:Sincalide / Q000737:chemistry / Q000494:pharmacology*; D013012:Sorbitol / Q000737:chemistry
D007328:Insulin; D013012:Sorbitol; D012844:Sincalide