Secretion Of Extrapancreatic Glucagon Research Articles

Gluco-metabolic response to exogenous oxytocin in totally pancreatectomized patients and healthy individuals

Oxytocin has been proposed to possess glucose-stabilizing effects through the release of insulin and glucagon from the pancreas. Also, exogenous oxytocin has been shown to stimulate extrapancreatic glucagon secretion in depancreatized dogs. Here, we investigated the effect of exogenous oxytocin on circulating levels of pancreatic and gut-derived glucose-stabilizing hormones (insulin [measured as C-peptide], glucagon, glucagon-like peptide 1 [GLP-1], and glucose-dependent insulinotropic polypeptide). We studied nine pancreatectomized (PX) patients and nine healthy controls (CTRLs) (matched on age and body mass index) before, during, and after an intravenous infusion of 10 IU of oxytocin administered over 12 min. Oxytocin did not increase plasma glucagon levels, nor induce any changes in plasma glucose, C-peptide, or GIP in any of the groups. Oxytocin decreased plasma glucagon levels by 19 ± 10 % in CTRLs (from 2.0 ± 0.5 [mean ± SEM] to 1.3 ± 0.2 pmol/l, P = 0.0025) and increased GLP-1 by 42 ± 22 % in PX patients (from 9.0 ± 1.0–12.7 ± 1.0 pmol/l, P = 0.0003). Fasting plasma glucose levels were higher in PX patients compared with CTRLs (13.1 ± 1.1 vs. 5.1 ± 0.1 mmol/l, P < 0.0001). In conclusion, the present findings do not support pancreas-mediated glucose-stabilizing effects of acute oxytocin administration in humans and warrant further investigation of oxytocin’s gluco-metabolic effects.

263-OR: Counterregulatory Responses to Hypoglycemia in Totally Pancreatectomized Patients

We have previously shown that totally pancreatectomized (PX) patients secrete substantial amounts of glucagon (most likely from enteroendocrine cells) during an oral glucose tolerance test (OGTT) whereas these patients suppress circulating glucagon concentrations during intravenous glucose infusions. Here, we investigated the effect of insulin-induced hypoglycemia on extrapancreatic glucagon secretion and other counterregulatory factors in PX patients and in healthy controls (CTRLs). On two separate days, 12 PX patients (age 65.5±5.5 [mean±SD] years; BMI: 23.8±3.6 kg/m2) and 12 matched, healthy CTRLs (age 64.8±6.5 years; BMI: 24.5±2.9 kg/m2) underwent 1) a 50-g OGTT with 1.5 g acetaminophen (for assessment of gastric emptying) and 2) an insulin-induced hypoglycemic clamp followed by a 30-minute recovery period and a subsequent 50-g OGTT with acetaminophen. Blood was intermittently sampled throughout both experimental days. Plasma glucagon responses to OGTT (as assessed by baseline-subtracted area under curve) were greater in PX patients compared to CTRLs (386±150 vs. -340±50 min×pmol/l [mean±SEM], P=0.0001). During the hypoglycemic clamp, PX patients did not increase plasma glucagon concentrations and, thus, glucagon responses to hypoglycemia were higher in CTRLs (903±104 vs. -21±16 min×pmol/l, P&amp;lt;0.001). Hypoglycemia-induced responses of catecholamines, growth hormone and cortisol were similar in the two groups. Gastric emptying was unaffected by hypoglycemia in CTRLs but was decelerated by hypoglycemia in PX patients. We conclude that 1) insulin-induced hypoglycemia, which powerfully stimulates glucagon secretion in CTRLs, does not stimulate extrapancreatic glucagon secretion in PX patients; 2) counterregulatory responses of catecholamines, growth hormone and cortisol were intact in PX patients, but hypoglycemia decelerated gastric emptying in these patients. This provides mechanistic insight into the high risk of hypoglycemia in PX patients. Disclosure M. Baekdal: None. A.B. Lund: Speaker’s Bureau; Self; AstraZeneca, Novo Nordisk A/S, Sanofi. M. Baldassarre: None. J.I. Egholk: None. K. Rose: None. C. Hansen: None. J.H. Storkholm: None. M.B. Christensen: None. B. Hartmann: None. J. Faber: None. J.J. Holst: Advisory Panel; Self; AstraZeneca, Merck Sharp &amp; Dohme Corp., Novo Nordisk A/S, Zealand Pharma A/S. Other Relationship; Spouse/Partner; Antag Therapeutics. T. Vilsbøll: Advisory Panel; Self; AstraZeneca, Mundipharma International, Novo Nordisk A/S, Sun Pharmaceutical Industries Ltd. Consultant; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Lilly Diabetes, Medscape, Merck Sharp &amp; Dohme Corp., Sanofi. F.K. Knop: Advisory Panel; Self; AstraZeneca, Merck Sharp &amp; Dohme Corp., Mundipharma International, Novo Nordisk A/S, Sanofi. Consultant; Self; Carmot Therapeutics, Inc., Eli Lilly and Company, Novo Nordisk A/S. Research Support; Self; AstraZeneca, Gubra, Novo Nordisk A/S, Sanofi, Zealand Pharma A/S. Speaker’s Bureau; Self; AstraZeneca, Lupin Pharmaceuticals, Inc., Merck Sharp &amp; Dohme Corp., Norgine B.V., Novo Nordisk A/S.

1 Involvement of Dipeptidyl Peptidase-4 and Sodium-glucose Co-transporter-2 in Extrapancreatic Glucagon Secretion

1 Involvement of Dipeptidyl Peptidase-4 and Sodium-glucose Co-transporter-2 in Extrapancreatic Glucagon Secretion

63-OR: The Physiological Effects of Extrapancreatic Glucagon in Totally Pancreatectomized Patients Evaluated Using Glucagon Receptor Antagonism

We have recently shown a hyperglucagonemic response to meal test and oral glucose tolerance test (OGTT) in totally pancreatectomized (PX) patients. Here, we employed a glucagon receptor antagonist (GRA) to determine the physiological implications of extrapancreatic glucagon secretion in PX patients. In a double-blinded, randomized, cross-over study, 9 PX patients (age: 61.3±4.3 [mean±SEM] years; BMI: 22.6±1.6 kg/m2) and 9 matched healthy controls (age 65.9±2.9 years; BMI: 23.9±0.9 kg/m2) were examined during two 3-hour 75-OGTTs. Before the tests, subjects ingested 300 mg of the GRA, LY2409021 (Eli Lilly and Company), and placebo, respectively. Patients received their regular dose of insulin the night before each experimental day, but no insulin was given during the experiments. In the healthy controls, the GRA resulted in lower fasting levels of glucose (4.3±0.1 vs. 5.2±0.1 mmol/l, P=0.001), but higher post-OGTT plasma glucose excursions (as assessed by baseline-subtracted area under the curve (bsAUC): 926±92 vs. 467±72 mmol/l×min, P=0.002) compared to placebo. In the PX patients, the GRA and placebo resulted in similar fasting plasma glucose concentrations (11.3±0.9 vs. 12.5±0.8 mmol/l, P=0.266) and post-OGTT glucose excursions (bsAUC: 1,671±96 vs. 1,693±152 mmol/l×min, P=0.398), respectively. In the healthy controls, the GRA resulted in significantly higher fasting concentrations of glucagon (33.1±5.5 vs. 13.0±3.7 pmol/l, P=0.023), which, nevertheless, were suppressed by OGTT to similarly low levels as observed with placebo. In the PX patients, equal fasting glucagon concentrations (3.2±0.7 vs. 4.7±1.9 pmol/l, P=0.373) and similarly exaggerated plasma glucagon responses to OGTT were observed with the GRA and placebo (bsAUC: 1,636±573 vs. 1,034±542 pmol/l×min, P=0.113). In this study, antagonizing the glucagon receptor in totally pancreatectomized patients did not influence fasting or post-OGTT glucose levels. Disclosure C.T.B. Juel: None. A.B. Lund: None. J.F. Rehfeld: None. N.J. Wewer Albrechtsen: Research Support; Self; Mercodia, Novo Nordisk A/S. Speaker's Bureau; Self; Merck Sharp &amp; Dohme Corp. J.J. Holst: Advisory Panel; Self; Novo Nordisk A/S. T. Vilsbøll: None. F.K. Knop: Advisory Panel; Self; AstraZeneca, MedImmune, Merck Sharp &amp; Dohme Corp., Mundipharma, Novo Nordisk A/S, Sanofi. Consultant; Self; Amgen Inc., Carmot Therapeutics, Novo Nordisk A/S. Research Support; Self; AstraZeneca, Novo Nordisk A/S. Speaker's Bureau; Self; AstraZeneca, MedImmune, Merck Sharp &amp; Dohme Corp., Mundipharma, Norgine, Novo Nordisk A/S.

Evidence of Extrapancreatic Glucagon Secretion in Man.

Glucagon is believed to be a pancreas-specific hormone, and hyperglucagonemia has been shown to contribute significantly to the hyperglycemic state of patients with diabetes. This hyperglucagonemia has been thought to arise from α-cell insensitivity to suppressive effects of glucose and insulin combined with reduced insulin secretion. We hypothesized that postabsorptive hyperglucagonemia represents a gut-dependent phenomenon and subjected 10 totally pancreatectomized patients and 10 healthy control subjects to a 75-g oral glucose tolerance test and a corresponding isoglycemic intravenous glucose infusion. We applied novel analytical methods of plasma glucagon (sandwich ELISA and mass spectrometry-based proteomics) and show that 29-amino acid glucagon circulates in patients without a pancreas and that glucose stimulation of the gastrointestinal tract elicits significant hyperglucagonemia in these patients. These findings emphasize the existence of extrapancreatic glucagon (perhaps originating from the gut) in man and suggest that it may play a role in diabetes secondary to total pancreatectomy.

Oxytocin increases extrapancreatic glucagon secretion and glucose production in pancreatectomized dogs.

Infusion of oxytocin into normal dogs increases plasma levels of insulin and glucagon and glucose production and uptake. To determine whether infused oxytocin also increases glucagon secretion from extrapancreatic sites, pancreatectomized dogs, off insulin for 18 hr, were infused with oxytocin and plasma glucagon, and glucose production and uptake were measured using the [6-3H]glucose primer-infusion technique. The diabetic dogs, in the control period, had elevated plasma glucose and glucagon levels, an increased rate of glucose production, and a relative decrease in glucose uptake (decreased clearance). Infusion of oxytocin (500 microU/kg/min) caused a rise in plasma glucagon and glucose levels, increased glucose production, and further decreased glucose clearance. It is concluded that oxytocin can stimulate secretion of extrapancreatic glucagon, which contributes to the increased glucose production.

Effect of pancreatic glucagon upon secretion of extrapancreatic glucagon in dogs.

Effect of pancreatic glucagon upon secretion of extrapancreatic glucagon in dogs.

Response of extrapancreatic glucagon to gastrointestinal hormones in pancreatectomized dogs.

In order to investigate the effect of gastrointestinal hormones upon the secretion of extrapancreatic glucagon, tetragastrin, secretin, caerulein and cholecytokinin-pancreozymin octapeptide (CCK-octa) were administered during saline or arginine infusion in pancreatectomized dogs. Intravenous administration of tetragastrin (7 micrograms/kg) did not elicit any changes in plasma glucagon during saline infusion, while the plasma glucagon increased significantly following tetragastrin infusion during arginine infusion. The administration of secretin (3 U/kg) did not affect the plasma level of glucagon during saline or arginine infusion at all. Plasma glucagon did not change after the administration of caerulein (0.5 microgram/kg) during saline infusion, whereas it increased significantly following caerulein administration during arginine infusion. Intravenous administration of CCK-octa in a dose of 20 U/kg did not affect the plasma level of glucagon during saline infusion but exerted a significant rise of extrapancreatic glucagon during arginine infusion. It is concluded from the present experiment that the administration of tetragastrin, caerulein or CCK-octa enhances the release of extrapancreatic glucagon stimulated by arginine infusion while secretin infusion does not affect the secretion of extrapancreatic glucagon.

Effect of insulin treatment upon response of extrapancreatic glucagon to arginine.

In order to investigate the effect of insulin treatment upon the secretion of extrapancreatic glucagon, arginine infusion was performed in normal dogs and alloxan diabetic dogs with or without insulin treatment at conscious and anesthetized states. In a series of experiments with conscious dogs, alloxan diabetic dogs revealed not only elevated fasting levels of plasma glucagon but also exaggerated glucagon response to arginine. Insulin treatment in the alloxan dogs reduced the fasting plasma glucagon levels as well as responsiveness of glucagon to arginine. In the experi-ments with anesthetized dogs, plasma glucagon in the portal vein of the normal dogs rose only slightly in response to arginine infused after total pancreatectomy. In contrast, the alloxan diabetic dogs revealed an increase in plasma glucagon following arginine infusion performed after pancreatectomy. The response of plasma glucagon to arginine was reduced after pancreatectomy in the alloxan diabetic dogs with insulin treatment. Total immunoreactive glucagon (IRG) measured by a non-specific antiserum, increased in response to arginine after pancreatectomy in both the normal and alloxan diabetic dogs. Insulin treatment reduced an exaggerated response of total IRG in alloxan diabetic dogs. From these experiments, it is concluded that alloxan diabetic dogs have an increased response of plasma glucagon and extrapancreatic glucagon, which is reduced by insulin treatment. Furthermore, the difference in response of plasma glucagon to arginine in alloxan diabetic dogs and depancreatized dogs indicates that deficiency of insulin as well as pancreatic glucagon plays an important role in the secretion of extrapancreatic glucagon.

Response of extrapancreatic glucagon to arginine in dogs.

In order to investigate secretion of extrapancreatic glucagon in dogs, plasma glucagon and total immunoreactive glucagon (IRG) in response to arginine were determined with antisera specific and non-specific for pancreatic glucagon, respectively. Only a tiny rise of plasma glucagon was observed in the portal vein following arginine infusion performed immediately after total pancreatectomy in a group of 5 normal dogs. In contrast, total IRG in the portal vein increased significantly after arginine infusion even after pancreatectomy. In alloxan diabetic dogs, arginine infusion after total pancreatectomy caused a rise in plasma glucagon in the portal vein, although not significantly. The response of total IRG to arginine in the portal vein was exaggerated in alloxan diabetic dogs. In a group of one-week post-pancreatectomized animals, plasma glucagon and total IRG increased significantly in response to arginine infusion. Furthermore, in these dogs, response of plasma glucagon and plasma total IRG to arginine infusion was abolished after gastrectomy. From the present results it is concluded that secretion of extrapancreatic glucagon increased in response to arginine infusion in the diabetic state, both alloxan diabetic dogs and one-week post-pancreatectomized dogs. In addition, a rise in extrapancreatic glucagon following arginine infusion in the chronically pancreatectomized dogs almost certainly derived from the stomach, as the rise was abolished by gastrectomy.

Failure of somatostatin to decrease blood glucose by suppression of extrapancreatic glucagon in severely diabetic depancreatized dogs.

Effects of somatostatin on extrapancreatic glucagon secretion in totally depancreatized dogs were examined. Somatostatin infusion at a rate of 3 microgram/min showed a rapid decrease of total glucagon-like immunoreactive materials (total GLI) measured by nonspecific antiserum, AGS 10, and gut glucagon immunoreactivity (gut GI) measured by specific antiserum, AGS 18, in systemic blood. Gut GLI calculated as the difference between total GLI and GI did not decrease significantly within 30 min. No changes of blood glucose were noted. Significant decreases of all glucagon fractions were observed when the rate of somatostatin infusion was increased to 10 microgram/min and prolonged for 90 min, whereas again blood glucose did not change at all. It is concluded that somatostatin inhibits both gut GI and GLI secretion, although gut GLI remains in circulation longer than gut GI. Suppression of gut GI is not effective for the reduction of blood glucose once an extreme hyperglycemia is brought about by insulin deficiency.