GLP-1 amidation efficiency along the length of the intestine in mice, rats and pigs and in GLP-1 secreting cell lines.
XXX: Measurements of plasma concentrations of the incretin hormone GLP-1 are complex because of extensive molecular heterogeneity. This is partly due to a varying and incompletely known degree of C-terminal amidation. Given that virtually all GLP-1 assays rely on a C-terminal antibody, it is essential to know whether or not the molecule one wants to measure is amidated. We performed a detailed analysis of extractable GLP-1 from duodenum, proximal jejunum, distal ileum, caecum, proximal colon and distal colon of mice (n=9), rats (n=9) and pigs (n=8) and determined the degree of amidation and whether this varied with the six different locations. We also analyzed the amidation in 3 GLP-1 secreting cell lines (GLUTag, NCI-H716 and STC-1). To our surprise there were marked differences between the 3 species with respect to the concentration of GLP-1 in gut. In the mouse, concentrations increased continuously along the intestine all the way to the rectum, but were highest in the distal ileum and proximal colon of the rat. In the pig, very little or no GLP-1 was present before the distal ileum with similar levels from ileum to distal colon. In the mouse, GLP-1 was extensively amidated at all sampling sites, whereas rats and pigs on average had around 2.5 and 4 times higher levels of amidated compared to non-amidated GLP-1, although the ratio varied depending upon the location. GLUTag, NCI-H716 and STC-1 cells all exhibited partial amidation with 2-4 times higher levels of amidated compared to non-amidated GLP-1.
NNF Center for Basic Metabolic Research, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 12.2, DK-2200, Copenhagen N, Denmark. Electronic address: kuhre@sund.ku.dk.
Rune Ehrenreich
RE
Kuhre
NNF Center for Basic Metabolic Research, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 12.2, DK-2200, Copenhagen N, Denmark. Electronic address: Nicolai.albrechtsen@sund.ku.dk.
Nicolai Wewer
NW
Albrechtsen
NNF Center for Basic Metabolic Research, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 12.2, DK-2200, Copenhagen N, Denmark. Electronic address: johannewi@sund.ku.dk.
Johanne Agerlin
JA
Windeløv
NNF Center for Basic Metabolic Research, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 12.2, DK-2200, Copenhagen N, Denmark. Electronic address: bsvendsen@sund.ku.dk.
Berit
B
Svendsen
NNF Center for Basic Metabolic Research, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 12.2, DK-2200, Copenhagen N, Denmark. Electronic address: bhartmann@sund.ku.dk.
Bolette
B
Hartmann
NNF Center for Basic Metabolic Research, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 12.2, DK-2200, Copenhagen N, Denmark. Electronic address: jjholst@sund.ku.
Jens Juul
JJ
Holst
D000818:Animals; D002460:Cell Line; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D008810:Mice, Inbred C57BL; D011499:Protein Processing, Post-Translational; D017208:Rats, Wistar; D013045:Species Specificity; D034421:Sus scrofa
D052216:Glucagon-Like Peptide 1
GLP-1; GLP-1 measurement; Peptide's assays