(Journal Article): Pancreatic and intestinal processing of proglucagon in man.
0rskov C, Holst JJ, Poulsen S, Kirkegaard P (Institute of Medical Physiology C, University of Copenhagen, Denmark.)
IN:
Diabetologia
1987; 30:874-881
Impact Factor(s) of Diabetologia: 5.583 (2004), 5.689 (2003), 5.136 (2002), 6.299 (2001)
ABSTRACT: We developed antisera and radioimmunoassays against synthetic replicas of glucagon-like peptide-1 (1-36) and -2, predicted products of the glucagon precursor, and against glucagon-like peptide-1 (7-36) identical to the sequence of glucagon-like peptide-1, but lacking its first six N-terminal amino acids. With these tools, we studied the localisation and molecular nature of glucagon-like immunoreactivity in human pancreas, small intestine and plasma. By immunohistochemistry glucagon-like peptide-1, and glucagon-like peptide-2 immunoreactivity coexisted with glucagon in pancreatic islet cells and with enteroglucagon in small intestinal enteroglucagon-producing cells. By chromatography of tissue extracts we found that glucagon-like peptide-1 and glucagon-like peptide-2-immunoreactivities in the human pancreas (307 +/- 51 and 107 +/- 37 pmol/g tissue) were mainly contained in a large peptide, whereas in the small intestine glucagon-like peptide-1 and glucagon-like peptide-2 immunoreactivities were found in separate smaller molecules (49 +/- 21 and 77 +/- 28/g tissue). By isocratic high pressure liquid chromatography of the large pancreatic glucagon-like peptide we found that this peptide is heterogeneous. By chromatographic analysis glucagon-like peptide-1 immunoreactivity in fasting plasma was mainly found in a large peptide corresponding to the pancreatic form, while after a meal a smaller molecular form coeluting by gel filtration with glucagon-like peptide-1 predominated.
TYPE OF PUBLICATION: Original article
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(Journal Article): Effect of glucagon-like peptide-1 (proglucagon 78-107amide) on hepatic glucose production in healthy man.
Hvidberg A, Nielsen MT, Hilsted J, 0rskov C, Holst JJ (Department of Endocrinology, Hvidovre Hospital, Copenhagen, Denmark.)
IN:
Metabolism
1994; 43(1):104-108
Impact Factor(s) of Metabolism: 2.143 (2004), 2.013 (2003), 1.931 (2001)
Fulltext: HTML
ABSTRACT: The newly discovered intestinal hormone, glucagon-like peptide-1 (GLP-1) (proglucagon 78-107amide), stimulates insulin secretion and inhibits glucagon secretion in man and may therefore be anticipated to influence hepatic glucose production. To study this, we infused synthetic GLP-1 sequentially at rates of 25 and 75 pmol.kg-1.h-1 into eight healthy volunteers after an overnight fast and measured plasma concentrations of glucose, insulin, and glucagon and glucose turnover by a technique involving infusion of 3-3H-glucose. Plasma levels of GLP-1 increased by 21.3 +/- 3.1 and 75.4 +/- 3.2 pmol/L during the infusion, changes that were within physiologic limits. In a control experiment only saline was infused. During GLP-1 infusion, plasma glucose level decreased significantly (from 5.3 +/- 0.1 to 4.7 +/- 0.1 and 4.3 +/- 0.1 pmol/L at the end of the two infusion periods). Despite this, plasma insulin level increased significantly (from 20.5 +/- 2.9 to a peak value of 33.5 +/- 5.2 pmol/L during the second period), and plasma glucagon level decreased (from 9.3 +/- 1.7 to 7.1 +/- 1.0 pmol/L). Glucose rate of appearance (Ra) decreased significantly to 75% +/- 6% of the preinfusion values during GLP-1 infusion. Glucose disappearance rate (Rd) did not change significantly, but glucose clearance increased significantly compared with saline. All parameters of glucose turnover remained constant during saline infusion. We conclude that GLP-1 may potently control hepatic glucose production and glucose clearance through its effects on the pancreatic glucoregulatory hormones. The effect of GLP-1 on glucose production is consistent with its proposed use in the treatment of type II diabetes.
TYPE OF PUBLICATION: Original article
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(Journal Article): Glucagon-like peptide I analogues: effects on insulin secretion and adenosine 3',5'-monophosphate formation.
Gefel D, Hendrick GK, Mojsov S, Habener J, Weir GE (Joslin Diabetes Center, Boston, Massachusetts 02215.)
IN:
Endocrinology
1990; 126:2164-2168
Impact Factor(s) of Endocrinology: 5.151 (2004), 5.063 (2003), 5.095 (2002), 4.971 (2001)
ABSTRACT: Glucagon-like peptide 1-(7-37) [GLP-I-(7-37)] is a 31-amino acid hormone which may have an important role in the regulation of insulin secretion, It is processed from preproglucagon and found in the pancreas, brain, and, in highest quantity, intestine. In previous studies we found that GLP-I-(7-37) is a potent insulin secretagogue, and its effect was indistinguishable from that of GLP-I-(7-36) amide at concentrations of 10(-11) M. Herein we report insulinotropic effects of additional GLP-I analogs. GLP-I-(7-34) had no stimulatory effect on insulin release at 10(-10) M, but had a partial effect at 10(-9) M and was as active as GLP-I-(7-37) at 10(-8) M. GLP-I-(7-33) had no effect at any concentration tested. GLP-I-(8-37) caused no significant effect on insulin release at 10(-9) and 10(-8) M, but did have an effect at the high concentration of 10(-7) M. Similar results were found with cAMP formation in the beta TC1 line. In this system GLP-I-(7-34) was less potent than GLP-I-(7-37) at a concentration of 5 x 10(-9) M. GLP-I-(7-33) had only about 0.1% the potency of GLP-I-(7-37); thus, there is good agreement between cAMP formation in the beta-cell line and insulin secretion from the perfused pancreas experiments. We conclude that histidine in the 7 position in the N-terminus of GLP-I-(7-37) is crucial for cAMP formation and insulin secretion, and that removal of the last three C-terminus residues of GLP-I-(7-37) results in only partial loss of activity; the residue in the 34 position is, however, essential for the insulinotropic action.
TYPE OF PUBLICATION: Original article
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(Journal Article): Glucagon-like peptide 1(7-36)amide: characterization of the domain responsible for binding to its receptor on rat insulinoma RINm5F cells.
Gallwitz B, Schmidt WE, Conlon JM, Creutzfeldt W (Division of Gastroenterology and Endocrinology, Georg August University, Gottingen, Federal Republic of Germany.)
IN:
J Mol Endocrinol
1990; 5:33-39
Impact Factor(s) of J Mol Endocrinol: 3.855 (2004), 3.701 (2003), 4.359 (2002), 3.649 (2001)
ABSTRACT: Glucagon-like peptide-1(7-36)amide (GLP-1(7-36)amide) is a potent stimulator of insulin secretion. Receptors for this hormone have been found on different insulinoma-derived cell lines, e.g. the RINm5F cell line which is derived from a radiation-induced rat insulinoma. To characterize the part of the GLP-1(7-36)amide molecule that is responsible for binding to its receptor on RINm5F cells, binding studies with synthetic C-terminal (GLP-1(21-36)amide) and synthetic N-terminal (GLP-1(7-25] GLP-1 fragments were carried out. GLP-1(21-36)amide showed dose-dependent binding to the GLP-1(7-36)amide receptor but was approximately 1500 times less potent in inhibiting binding of 125I-labelled GLP-1(7-36)amide than the intact hormone. GLP-1(7-25) at concentrations up to 10 mumol/l did not inhibit binding of label. Neither fragment changed intracellular cyclic AMP concentrations, in contrast to GLP-1(7-36)amide which increased intracellular cyclic AMP. GLP-1(21-36)amide, however, acted as a weak partial antagonist of GLP-1(7-36)amide with respect to GLP-1(7-36)amide-dependent stimulation of cyclic AMP production.
TYPE OF PUBLICATION: Original article
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(Journal Article): Structure-activity studies of glucagon-like peptide-l.
Adelhorst K, Hedegaard BB, Knudsen LB, Kirk O (Novo Nordisk A/S, Novo Alle, Bagsvaerd, Denmark.)
IN:
J Biol Chem
1994; 269:6275-6278
Impact Factor(s) of J Biol Chem: 6.355 (2004), 6.482 (2003), 7.258 (2001)
ABSTRACT: A series of analogs of glucagon-like peptide-1 (GLP-1) was made replacing each amino acid with L-alanine to identify side-chain functional groups required for interaction with the GLP-1 receptor. In the case of L-alanine being the parent amino acid, substitution was made with the amino acid found in the corresponding position in glucagon. Binding assays were performed using the cloned rat GLP-1 receptor, and receptor activation was monitored using RIN 2A18 plasma membranes. The analogs that showed the weakest receptor binding were further compared with native GLP-1 by circular dichroism spectroscopy to investigate possible conformational changes. We conclude that the side chains in positions 7, 10, 12, 13, and 15 are directly involved in the receptor interaction while positions 28 and 29 are important for GLP-1 to adapt the conformation recognized by the receptor.
TYPE OF PUBLICATION: Original article
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(Journal Article): Is GLP-l (9-36)amide an endogenous antagonist at GLP-l receptors?
Grandt D, Sieburg B, Sievert J,
IN:
Digestion
1994; 55:302.-
Impact Factor(s) of Digestion: 1.473 (2004), 1.672 (2002), 1.89 (2001)
ABSTRACT: n.a.
TYPE OF PUBLICATION: Original article
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(Journal Article): GLP-1 (glucagon-like peptide 1) and truncated GLP-1, fragments of human proglucagon, inhibit gastric acid secretion in humans.
Schjoldager BT, Mortensen PE, Christiansen J, 0rskov C, Holst JJ (Institute of Medical Physiology C, Panum Institute, Copenhagen, Denmark.)
IN:
Dig Dis Sei
1989; 34(5):703-708
Fulltext: HTML
ABSTRACT: Glucagon-like peptide 1 amide (GLP-1 amide), a predicted product of the glucagon gene (proglucagon 72-107-amide), and truncated GLP-1 (proglucagon 78-107-amide), recently isolated from porcine small intestine, were infused in doses of 100 and 400 ng/kg/hr and 12.5 and 50 ng/kg/hr, respectively, into eight volunteers to study pharmacokinetics and effects on pentagastrin-stimulated gastric acid secretion (plateau stimulation with pentagastrin at D50: 100 ng/kg/hr). The concentration of GLP-1 in plasma increased from 64 +/- 12 to 189 +/- 23 and 631 +/- 76 pmol/liter, respectively. The concentration of truncated GLP increased from approximately 7 pmol/liter to 28 +/- 3 pmol/liter during the high rate of infusion. A similar increase was seen in response to a mixed meal in eight normal volunteers. The metabolic clearance rate (MCR) of GLP-1 was 2.2 +/- 0.3 and 2.6 +/- 0.3 ml/kg/min, respectively, and the half-life in plasma was 17 +/- 2 min. The MCR of truncated GLP-1 was 13 +/- 2.8 ml/kg/min and the half-life 11.4 +/- 2.1 min. GLP-1 reduced the pentagastrin-stimulated acid secretion 16 +/- 9% during the low-rate infusion and 23 +/- 12% during the high rate (P less than 0.05). Truncated GLP-1 caused a 36 +/- 3% inhibition during the high infusion rate. Thus truncated GLP-1, a naturally occurring peptide, is a potent inhibitor of acid secretion in man and more so than GLP-1.
TYPE OF PUBLICATION: Original article
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(Journal Article): Biologieal effects and metabolic rates of glucagon-like peptide-1 7-36 amide and glucagon-like peptide-1 7-37 in healthy subjects are indistinguishable.
0rskov C, Wettergren A, Holst JJ (Department of Clinical Biochemistry, Rigshospitalet, Copenhagen, Denmark.)
IN:
Diabetes
1993; 42:658-661
Impact Factor(s) of Diabetes: 8.848 (2004), 8.298 (2003), 8.256 (2002), 7.7 (2001)
ABSTRACT: The biological effects and the metabolism of the intestinal hormone glucagonlike peptide-1 7-36 amide and glucagonlike peptide-1 7-37 were studied in normal healthy subjects. GLP-1 7-36 amide and GLP-1 7-37 equipotently stimulated insulin secretion (integrated hormone response 0-60 min, 631 +/- 211 vs. 483 +/- 177 pmol/h x L-1) and C-peptide secretion (integrated hormone response 9064 +/- 1804 vs. 9954 +/- 2031 pmol/h x L-1) and equipotently lowered plasma glucose (integrated decrease 48.3 +/- 5.7 vs. 46.2 +/- 8.4 mmol/h x L-1) and plasma glucagon (integrated decrease 80.4 +/- 24.3 vs. 156.0 +/- 34.6 pmol/h x L-1). Both GLP-1 7-36 amide and GLP-1 7-37 lowered the plasma concentration of free fatty acids significantly. The plasma half-lives of GLP-1 7-36 amide and GLP-1 7-37 were 5.3 +/- 0.4 vs. 6.1 +/- 0.8 min, and the metabolic clearance rates of the two peptides also were similar (14.6 +/- 2.4 vs. 12.2 +/- 1.0 pmol/kg x min). In conclusion, COOH-terminal amidation is neither important for the metabolism of GLP-1 nor for its effects on the endocrine pancreas.
TYPE OF PUBLICATION: Original article
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