Increased Plasma Glucagon Research Articles

Increased hepatic glucagon sensitivity in totally pancreatectomised patients.

The metabolic phenotype of totally pancreatectomised patients includes hyperaminoacidaemia and predisposition to hypoglycaemia and hepatic lipid accumulation. We aimed to investigate whether the loss of pancreatic glucagon may be responsible for these changes. Nine middle-aged, normal-weight totally pancreatectomised patients, nine patients with type 1 diabetes (C-peptide negative), and nine matched controls underwent two separate experimental days, each involving a 150-min intravenous infusion of glucagon (4 ng/kg/min) or placebo (saline) under fasting conditions while any basal insulin treatment was continued. Glucagon infusion increased plasma glucagon to similar high physiological levels in all groups. The infusion increased hepatic glucose production and decreased plasma concentration of most amino acids in all groups, with more pronounced effects in the totally pancreatectomised patients compared with the other groups. Glucagon infusion diminished fatty acid re-esterification and tended to decrease plasma concentrations of fatty acids in the totally pancreatectomised patients but not in the type 1 diabetes patients. Totally pancreatectomised patients were characterised by increased sensitivity to exogenous glucagon at the level of hepatic glucose, amino acid, and lipid metabolism, suggesting that the metabolic disturbances characterising these patients may be rooted in perturbed hepatic processes normally controlled by pancreatic glucagon.

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.

Role of Glucagon in The Metabolic Response

Historically, glucagon is the counter-regulatory hormone of insulin. Glucagon secretion is induced by fasting conditions or hypoglycaemia to increase glucose levels. Glucagon is the dominant product of alpha cells in the islet and was first identified in 1923 during an attempt to purify insulin, where it was identified as a contaminant hyperglycaemia factor. Further research determined that the hyperglycaemic action of glucagon is mediated by increased hepatic glycogenolysis and gluconeogenesis to increase endogenous glucose production. Insulin and glucagon as opposing hormones work together for glycaemic control. Diabetic hyperglycaemia is caused by increased impaired insulin action and inappropriately elevated glucagon levels. This review summarizes an important function of glucagon is its role as a regulator of glucose homeostasis. Increased plasma glucagon levels lead to increased hepatic glucose production. The balance between insulin and glucagon is responsible for maintaining euglycaemia conditions. In conditions of hypoglycaemia, increased glucagon secretion leads to increased hepatic glucose production through a number of cellular mechanisms including suppression of glycogenesis and glycolysis and stimulation of glycogenolysis and gluconeogenesis

Chronic, Mild Hypothermic Environmental Temperature Does Not Ameliorate Cognitive Deficits in an Alzheimer's DiseaseMouse.

Metabolic dysfunction increases with age and is a contributing factor to Alzheimer's disease (AD) development. We have previously observed impaired insulin sensitivity and glucose homeostasis in the APP/PS1 model of AD. To improve these parameters, we chronically exposed male and female mice to mild hypothermic environmental temperature (eT), which positively modulates metabolism. Although a hypothermic eT normalized insulin sensitivity, glucose tolerance was still impaired in both sexes of AD mice. We observed increased plasma glucagon and B-cell activating factor in both sexes, but additional sexually dimorphic mechanisms may explain the impaired glucose homeostasis in AD mice. Hepatic Glut2 was decreased in females while visceral adipose tissue TNFα was increased in male APP/PS1 mice. Amild hypothermic eT did not improve spatial learning and memory in either sex and increased amyloid plaque burden in male APP/PS1 mice. Overall, plasma markers of glucose homeostasis and AD pathology were worse in females compared to male APP/PS1 mice suggesting a faster disease progression. This could affect the therapeutic outcomes if interventional strategies are administered at the same chronological age to male and female APP/PS1 mice. Furthermore, this data suggests a dichotomy exists between mechanisms to improve metabolic function and cognitive health that may be further impaired inAD.

Urotensin II receptor knockout alleviates streptozotocin‐induced hyperglucagonemia and diabetic kidney disease

Plasma and urinary levels of UII, a potent vasoactive peptide, are elevated in diabetes mellitus (DM) patients. UII receptor (UT) expression levels are also increased in the kidneys of humans and animals with DM. Palosuran, an orally active UT antagonist, increased insulin levels and improved renal function in uninephrectomized streptozotocin (STZ)‐treated rats. However, human studies on the potential use of palosuran for kidney protection in diabetes were inconclusive. In addition to UT antagonism, palosuran can activate somatostatin receptors. Also, the reduced affinity of palosuran for UT in intact cells and tissues suggests that it may not be an optimal UT antagonist. Thus, using non‐selective and less potent UT antagonists constitutes a weakness in the scientific rigor of the prior attempts to dissect UT as a potential therapeutic target in DKD. Hence, studies using genetic animal models and highly selective and potent pharmacological antagonists are needed to fill the gaps of understanding on the pathophysiological significance of the UII system in DM. In the present study, we examine the development of hyperglycemia and DKD in the wild‐type (WT) and UT knockout (KO) mouse model of type 1 DM.STZ‐treated mice showed increased blood glucose levels, glucosuria, decreased plasma insulin levels, and diabetic kidney disease (DKD), which UT KO attenuated. However, UT KO failed to reverse STZ‐induced insulin deficiency. To understand the underlying mechanism for alleviating hyperglycemia and DKD in UT KO despite the uncorrected insulin deficiency, we tested the role of the primary insulin counterregulatory hormone, glucagon. We found that STZ treatment increased plasma glucagon levels in WT mice but not in UT KO mice. This finding was supported by double immunohistochemistry of pancreatic islet sections, where STZ treatment reduced insulin and increased glucagon staining. UT KO reversed only the effect of STZ on glucagon staining. These findings suggest that UT KO protects the glucagon‐producing alpha cells but not the insulin‐producing beta cells.UII increased glucagon secretion in a cultured pancreatic alpha cell line, which UT inhibition reversed. Next, to determine how UII triggers glucagon secretion, we performed membrane potential recordings in alpha cells using the perforated‐patch clamp technique. UII produced depolarization of alpha cells. This effect was abolished by UT inhibition. Calcium (Ca2+) imaging demonstrated that UII stimulates intracellular Ca2+ ([Ca2+]i) elevation in alpha cells, which T‐ and L‐type Ca2+ channel blockers attenuated.Taken together, the results of this study suggest that: (1) STZ‐treatment causes insulin deficiency, hyperglycemia, glucosuria, DKD, and hyperglucagonemia. (2) UT KO reverses STZ effects, except insulin deficiency. (3) UII increases glucagon secretion by alpha cells, mediated by UII‐induced membrane depolarization and Ca2+ influx via T‐ and L‐type Ca2+ channels. Therefore, the reversal of hyperglycemia, glucosuria, and DKD in UT KO might be linked to the reversal of hyperglucagonemia.

Arginine-vasopressin mediates counter-regulatory glucagon release and is diminished in type 1 diabetes.

Insulin-induced hypoglycemia is a major treatment barrier in type-1 diabetes (T1D). Accordingly, it is important that we understand the mechanisms regulating the circulating levels of glucagon. Varying glucose over the range of concentrations that occur physiologically between the fed and fuel-deprived states (8 to 4 mM) has no significant effect on glucagon secretion in the perfused mouse pancreas or in isolated mouse islets (in vitro), and yet associates with dramatic increases in plasma glucagon. The identity of the systemic factor(s) that elevates circulating glucagon remains unknown. Here, we show that arginine-vasopressin (AVP), secreted from the posterior pituitary, stimulates glucagon secretion. Alpha-cells express high levels of the vasopressin 1b receptor (V1bR) gene (Avpr1b). Activation of AVP neurons in vivo increased circulating copeptin (the C-terminal segment of the AVP precursor peptide) and increased blood glucose; effects blocked by pharmacological antagonism of either the glucagon receptor or V1bR. AVP also mediates the stimulatory effects of hypoglycemia produced by exogenous insulin and 2-deoxy-D-glucose on glucagon secretion. We show that the A1/C1 neurons of the medulla oblongata drive AVP neuron activation in response to insulin-induced hypoglycemia. AVP injection increased cytoplasmic Ca2+ in alpha-cells (implanted into the anterior chamber of the eye) and glucagon release. Hypoglycemia also increases circulating levels of AVP/copeptin in humans and this hormone stimulates glucagon secretion from human islets. In patients with T1D, hypoglycemia failed to increase both copeptin and glucagon. These findings suggest that AVP is a physiological systemic regulator of glucagon secretion and that this mechanism becomes impaired in T1D.

The liver-alpha-cell axis after a mixed meal and during weight loss in type 2 diabetes.

ObjectiveGlucagon and amino acids may be regulated in a feedback loop called the liver-alpha-cell axis with alanine or glutamine as suggested signal molecules. We assessed this concept in individuals with type 2 diabetes in the fasting state, after ingestion of a protein-rich meal, and during weight loss. Moreover, we investigated if postprandial glucagon secretion and hepatic insulin sensitivity were related.MethodsThis is a secondary analysis of a 12-week weight-loss trial (Paleolithic diet ± exercise) in 29 individuals with type 2 diabetes. Before and after the intervention, plasma glucagon and amino acids were measured in the fasting state and during 180 min after a protein-rich mixed meal. Hepatic insulin sensitivity was measured using the hyperinsulinemic-euglycemic clamp with [6,6-2H2]glucose as a tracer.ResultsThe postprandial increase of plasma glucagon was associated with the postprandial increase of alanine and several other amino acids but not glutamine. In the fasted state and after the meal, glucagon levels were negatively correlated with hepatic insulin sensitivity (rS = −0.51/r = −0.58, respectively; both P < 0.05). Improved hepatic insulin sensitivity with weight loss was correlated with decreased postprandial glucagon response (r = −0.78; P < 0.001).ConclusionsSeveral amino acids, notably alanine, but not glutamine could be key signals to the alpha cell to increase glucagon secretion. Amino acids may be part of a feedback mechanism as glucagon increases endogenous glucose production and ureagenesis in the liver. Moreover, postprandial glucagon secretion seems to be tightly related to hepatic insulin sensitivity.

Abstract 2951: Anti-GCGR in vivo efficacy evaluated in a novel humanized B-hGCGR mouse model

Abstract GCGR (glucagon receptor) is a G-protein-coupled seven-transmembrane protein, a typical representative of the class B GPCR family. Animals homozygous for a targeted mutation in this gene exhibit reduced blood glucose levels, increased plasma glucagon and amino acid levels associated with alpha-cell hyperplasia. Glucagon activates intracellular adenylate cyclase by specifically binding to GCGR on the surface of target cells in the liver. This results in an increase in intracellular cAMP levels, playing a role in promoting glycogenolysis and gluconeogenesis, and promoting blood glucose elevation. The crucial role in regulation of blood glucose levels and glucose homeostasis is posing GCGR as a potential drug target for type 2 diabetes and related diseases. Currently, much attention and many resources are directed towards research and development of antibody drugs targeting the glucagon receptor. Joining these efforts, Biocytogen has developed a GCGR humanized mouse model (B-hGCGR mouse). Human GCGR protein and mRNA were detected in liver tissue of homozygous B-hGCGR mice, but not in wild type mice. Physiological indexes have been analyzed. Results indicated that the random blood glucose, fasting blood glucose, and glucose tolerance were comparable to the wild type mice. In addition, we characterized the ability of glucagon to stimulate production of cAMP. We observed that glucagon elicits a dose specific increase of cAMP in membranes prepared from the humanized GCGR mice comparable to the cAMP levels observed in membranes prepared from wild type mice. In pharmacodynamic experiments using B-hGCGR mice we showed that an anti-GCGR antibody (Crotedumab) was able to effectively reduce random blood glucose and fasting blood glucose levels and improve the glucose tolerance, validating our humanized mouse model. This antibody also blocked the functional response to glucagon in B-hGCGR mice more efficiently than what can be observed in an approach targeting the wild type murine receptor using antagonists. These data demonstrate that B-hGCGR mice are a promising model for preclinical in vivo pharmacodynamic assessment of anti-GCGR antibodies. Citation Format: Rufeng Zhang, Chengzhang Shang, Yuting Hu, Veronika Chromikova, Qingcong Lin. Anti-GCGR in vivo efficacy evaluated in a novel humanized B-hGCGR mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2951.

Disordered branched chain amino acid catabolism in pancreatic islets is associated with postprandial hypersecretion of glucagon in diabetic mice

Dysregulation of glucagon is associated with the pathophysiology of type 2 diabetes. We previously reported that postprandial hyperglucagonemia is more obvious than fasting hyperglucagonemia in type 2 diabetes patients. However, which nutrient stimulates glucagon secretion in the diabetic state and the underlying mechanism after nutrient intake are unclear. To answer these questions, we measured plasma glucagon levels in diabetic mice after oral administration of various nutrients. The effects of nutrients on glucagon secretion were assessed using islets isolated from diabetic mice and palmitate-treated islets. In addition, we analyzed the expression levels of branched chain amino acid (BCAA) catabolism-related enzymes and their metabolites in diabetic islets. We found that protein, but not carbohydrate or lipid, increased plasma glucagon levels in diabetic mice. Among amino acids, BCAAs, but not the other essential or nonessential amino acids, increased plasma glucagon levels. BCAAs also directly increased the intracellular calcium concentration in α cells. When BCAAs transport was suppressed by an inhibitor of system L-amino acid transporters, glucagon secretion was reduced even in the presence of BCAAs. We also found that the expression levels of BCAA catabolism-related enzymes and their metabolite contents were altered in diabetic islets and palmitate-treated islets compared to control islets, indicating disordered BCAA catabolism in diabetic islets. Furthermore, BCKDK inhibitor BT2 suppressed BCAA-induced hypersecretion of glucagon in diabetic islets and palmitate-treated islets. Taken together, postprandial hypersecretion of glucagon in the diabetic state is attributable to disordered BCAA catabolism in pancreatic islet cells.

282-OR: The Effect of Glucagon on Rates of Hepatic Mitochondrial Oxidation and Pyruvate Carboxylase Flux in Man Assessed by Positional Isotopomer NMR Tracer Analysis (PINTA)

Dual GLP-1/glucagon agonists are now in clinical trials for the treatment of T2D and NASH. In addition to promoting further reduction in food intake on top of GLP-1, the glucagon component of these dual agonists may also promote increased rates of hepatic mitochondrial fat oxidation. In order to investigate this possibility we assessed the glucagon-specific effects of a dual agonist on rates of hepatic mitochondrial oxidation (VCS) and pyruvate carboxylase flux (VPC) in humans by infusing glucagon to achieve a physiological increase in plasma glucagon concentrations in combination with a novel 13C PINTA method to assess rates of hepatic VCS and VPC in 15 healthy volunteers using a paired study design. Following an overnight fast a 3-h IV infusion of [3-13C]lactate (4.3 μmol/Kg-min) and [1,2,3,4,5,6,6-2H7]glucose (0.22 μmol/Kg-min) was begun and during the last 2 hours glucagon (GLG) was co-infused [6 ng/(Kg-min)] or no GLG (CON). The GLG infusion resulted in a ~2.4 fold increase in plasma GLG conc. (from 75±11 to 183±20 pg/mL; P&amp;lt;0.0001), which was associated with an ~20% increase in both plasma C-peptide (from 1.89±0.17 to 2.30±0.26 ng/mL; P=0.02) and plasma insulin conc. (from 9.9±2.0 to 12.0±2.4 μU/mL; P=0.06). Plasma glucose conc. increased from 4.90±0.16 to 5.64±0.19 mmol/L (P=0.0001) which was associated with a tendency for increased rates of glucose production (CON:1042±123 vs. GLG:1148±122 μmol/min; p=0.086) despite no change in rates of VPC flux (CON: 403±69 vs. GLG: 373±55 μmol/min; p=NS). In contrast, this physiological increase in plasma GLG concentrations caused an 85% increase in rates of hepatic VCS (P&amp;lt;0.05). Conclusion: Taken together these studies demonstrate that a physiological increase in plasma glucagon promotes increased rates of hepatic mitochondrial oxidation in humans, which may provide additional benefits to the anorexic effects of dual GLP-1/glucagon agonists to reduce hepatic steatosis. Disclosure K. Petersen: Advisory Panel; Spouse/Partner; AstraZeneca, iMetabolic Biopharma Corporation, Janssen Research &amp; Development, LLC, Merck &amp; Co., Inc., Consultant; Spouse/Partner; Aegerion Pharmaceuticals Inc., Novo Nordisk, Research Support; Self; Gilead Sciences, Inc., Merck &amp; Co., Inc. G. I. Shulman: Consultant; Self; 89bio, Inc., BridgeBio, Ionis Pharmaceuticals, Maze Therapeutics, Novo Nordisk, Other Relationship; Self; AstraZeneca, Esperion Therapeutics, Inc, Generian Pharmaceuticals, Inc., Gilead Sciences, Inc., iMetabolic Biopharma Corporation, Janssen Research &amp; Development, LLC, Merck &amp; Co., Inc., The Liver Company. Funding Merck &amp; Co., Inc. (MISP583402); National Institutes of Health (R01DK113984)

133-OR: Somatostatin Receptor Type 2 Antagonism (SSTR2a) Augments Glucagon Counterregulation and Delays Hypoglycemia Onset in Type 2 Diabetic (T2D), Sprague-Dawley Rats

Background: SSTR2a rescues glucagon counterregulation in type 1 diabetic rats. Here, we investigated its potential for resisting hypoglycemic onset in insulin-treated rats with T2D.Methods: T2D was induced in 8-9-week-old, male, Sprague-Dawley rats (n=20) via 3-weeks of high-fat feeding and low-dose streptozotocin (35 mg/kg). After 1 week of basal insulin maintenance, N=10 healthy and N=20 T2D rats were treated with SSTR2a (3 mg/kg ZT-01, SC) or vehicle in a crossover design (1 wk apart), 60 min prior to hypoglycemic induction via insulin aspart bolus (6 U/kg).Results: SSTR2a increased plasma glucagon levels for up to 120 min after insulin challenge, with a 2.2-fold increase in glucagon AUC (32167 ± 6658 vs. 14428 ± 3673 pg*min/mL; p<0.01). Blood glucose was significantly elevated in treated, T2D rats for ∼30 min, and hypoglycemia onset was delayed by 17 ± 4 min (p<0.001). Neither effect was observed in SSTR2a-treated, healthy rats.Conclusions: SSTR2a increased glucagon secretion following insulin overdose and delayed the onset of hypoglycemia in T2D rats. SSTR2a may be a promising therapeutic tool for alleviating hypoglycemic risk in intensively-treated T2D.View largeDownload slideView largeDownload slide DisclosureE. G. Hoffman: None. N. Dsouza: None. J. Aiken: None. R. Liggins: Employee; Self; Zucara Therapeutics Inc. M. Riddell: Advisory Panel; Self; Zealand Pharma A/S, Consultant; Self; Lilly Diabetes, Research Support; Self; Dexcom, Inc., Insulet Corporation, Speaker’s Bureau; Self; Novo Nordisk Inc., Sanofi, Stock/Shareholder; Self; Zucara Therapeutics Inc. FundingGlycoNet

1191-P: Increased Glucagon Sensitivity in Totally Pancreatectomized Patients

Glucagon secretion and signaling are affected in several metabolic disorders including different types of diabetes. To understand these mechanisms better, we investigated the effect of exogeneous glucagon in participants deprived of endogenous glucagon and/or insulin. We included nine middle-aged, normal-weight patients who had undergone total pancreatectomy (PX), eight patients with type 1 diabetes (T1D) and nine healthy controls in a randomized, double-blinded crossover study (groups were matched by age, gender and BMI). Participants received a 2.5-hour intravenous infusion of glucagon (4 ng/kg/min) and placebo (saline), respectively, under fasting conditions with usual basal insulin administration. Glucagon infusion increased plasma glucagon to similar supraphysiologic levels in all groups and increased glucose levels as assessed by baseline-subtracted area under the curve (bsAUC) by 2.2 and 3.5-fold, respectively, in the PX group compared to the T1D group (P=0.015) and control group (P In conclusion, well-known actions of glucagon are more pronounced in PX patients compared to matched T1D patients and healthy controls indicating an increased sensitivity to glucagon in response to the underlying loss of pancreatic glucagon secretion in PX patients. Disclosure I. Rix: Employee; Self; Zealand Pharma A/S. A. Lund: Speaker9s Bureau; Self; Novo Nordisk, Sanofi. L. F. Garvey: None. K. Owen: Employee; Self; Zealand Pharma A/S. C. Hansen: None. G. Van hall: n/a. J. J. Holst: Consultant; Self; Novo Nordisk, Other Relationship; Self; Antag Therapeutics, Bainan Biotech, MSD Corporation, Novo Nordisk, Other Relationship; Spouse/Partner; Antag Therapeutics, Bainan Biotech, Synklino ApS. T. Vilsboll: Consultant; Self; Amgen Inc., AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Bristol-Myers Squibb Company, Gilead Sciences, Inc., Lilly Diabetes, Merck Sharp & Dohme Corp., Mundipharma International, Novo Nordisk, Sanofi, Sun Pharmaceutical Industries Ltd. F. K. Knop: Advisory Panel; Self; MSD Corporation, Novo Nordisk A/S, Sanofi, Consultant; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, Novo Nordisk A/S, Pharmacosmos, Zealand Pharma A/S, Research Support; Self; Novo Nordisk A/S, Zealand Pharma A/S, Speaker9s Bureau; Self; AstraZeneca, Bayer AG, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, MSD Corporation, Novo Nordisk A/S. Funding Innovation Fund Denmark; Novo Nordisk Foundation; A.P. Moller Foundation; Aase and Ejnar Danielsen Foundation; Inge & Per Refhall9s Research Grant; Augustinus Foundation

Do sodium-glucose co-transporter-2 inhibitors increase plasma glucagon by direct actions on the alpha cell? And does the increase matter for the associated increase in endogenous glucose production?

Sodium-glucose co-transporter-2 inhibitors (SGLT2is) lower blood glucose and are used for treatment of type 2 diabetes. However, SGLT2is have been associated with increases in endogenous glucose production (EGP) by mechanisms that have been proposed to result from SGLT2i-mediated increases in circulating glucagon concentrations, but the relative importance of this effect is debated, and mechanisms possibly coupling SGLT2is to increased plasma glucagon are unclear. A direct effect on alpha-cell activity has been proposed, but data on alpha-cell SGLT2 expression are inconsistent, and studies investigating the direct effects of SGLT2 inhibition on glucagon secretion are conflicting. By contrast, alpha-cell sodium-glucose co-transporter-1 (SGLT1) expression has been found more consistently and appears to be more prominent, pointing to an underappreciated role for this transporter. Nevertheless, the selectivity of most SGLT2is does not support interference with SGLT1 during therapy. Paracrine effects mediated by secretion of glucagonotropic/static molecules from beta and/or delta cells have also been suggested to be involved in SGLT2i-induced increase in plasma glucagon, but studies are few and arrive at different conclusions. It is also possible that the effect on glucagon is secondary to drug-induced increases in urinary glucose excretion and lowering of blood glucose, as shown in experiments with glucose clamping where SGLT2i-associated increases in plasma glucagon are prevented. However, regardless of the mechanisms involved, the current balance of evidence does not support that SGLT2 plays a crucial role for alpha-cell physiology or that SGLT2i-induced glucagon secretion is important for the associated increased EGP, particularly because the increase in EGP occurs before any rise in plasma glucagon.

Glucagon, insulin, adrenocorticotropic hormone, and cortisol in response to carbohydrates and fasting in healthy neonatal foals.

BackgroundThe endocrine pancreas and hypothalamic‐pituitary‐adrenal axis (HPAA) are central to energy homeostasis, but information on their dynamics in response to energy challenges in healthy newborn foals is lacking.ObjectivesTo evaluate glucagon, insulin, ACTH, and cortisol response to fasting and carbohydrate administration in healthy foals.AnimalsTwenty‐two healthy Standardbred foals ≤4 days of age.MethodsFoals were assigned to fasted (n = 6), IV glucose (IVGT; n = 5), PO glucose (OGT; n = 5), and PO lactose (OLT; n = 6) test groups. Blood samples were collected frequently for 210 minutes. Nursing was allowed from 180 to 210 minutes. Plasma glucagon, ACTH, serum insulin, and cortisol concentrations were measured using immunoassays.ResultsPlasma glucagon concentration decreased relative to baseline at 45, 90, and 180 minutes during the OLT (P = .03), but no differences occurred in other test groups. Nursing stimulated marked increases in plasma glucagon, serum insulin, and glucose concentrations in all test groups (P < .001). Plasma ACTH concentration increased relative to baseline at 180 minutes (P < .05) during fasting and OLT, but no differences occurred in other test groups. Serum cortisol concentration increased relative to baseline during OLT at 180 minutes (P = .04), but no differences occurred in other test groups. Nursing resulted in decreased plasma ACTH and serum cortisol concentrations in all test groups (P < .01).Conclusions and Clinical ImportanceThe endocrine response to enterally and parenterally administered carbohydrates, including the major endocrine response to nursing, suggests that factors in milk other than carbohydrates are strong stimulators (directly or indirectly) of the endocrine pancreas and HPAA.

Counterregulatory responses to postprandial hypoglycemia after Roux-en-Y gastric bypass.

Postbariatric hypoglycemia (PBH) is a potentially serious complication after Roux-en-Y gastric bypass (RYGB), and impaired counterregulatory hormone responses have been suggested to contribute to the condition. We evaluated counterregulatory responses during postprandial hypoglycemia in individuals with PBH who underwent RYGB. University hospital. Eleven women with documented PBH who had RYGB underwent a baseline liquid mixed meal test (MMT) followed by 5 MMTs preceded by treatment with (1) acarbose 50 mg, (2) sitagliptin 100 mg, (3) verapamil 120 mg, (4) liraglutide 1.2 mg, and (5) pasireotide 300 μg. Blood was collected at fixed time intervals. Plasma and serum were analyzed for glucose, insulin, glucagon, epinephrine, norepinephrine, pancreatic polypeptide (PP), and cortisol. During the baseline MMT, participants had nadir blood glucose concentrations of 3.3 ± .2mmol/L. At the time of nadir glucose, there was a small but significant increase in plasma glucagon. Plasma epinephrine concentrations were not increased at nadir glucose but were significantly elevated by the end of the MMT. There were no changes in norepinephrine, PP, and cortisol concentrations in response to hypoglycemia. After treatment with sitagliptin, 8 individuals had glucose nadirs <3.2 mmol/L (versus 4 individuals at baseline), and significant increases in glucagon, PP, and cortisol responses were observed. In response to postprandial hypoglycemia, individuals with PBH who underwent RYGB only had minor increases in counterregulatory hormones, while larger hormone responses occurred when glucose levels were lowered during treatment with sitagliptin. The glycemic threshold for counterregulatory activation could be altered in individuals with PBH, possibly explained by recurrent hypoglycemia.

1919-P: Dysfunction of BCAA Catabolism in Pancreatic Alpha Cells Is Associated with Higher Glucagon Secretion in Diabetic Mice

Background: Circulating plasma glucagon level is known to increase in diabetic state. We found that postprandial plasma glucagon level significantly increased in diabetic mice more than that in the control group. However, it’s still unknown which nutrient stimulates glucagon secretion as well as the underlying mechanism of glucagon secretion enhancement in diabetic state. Therefore, we aimed to answer these questions by using diabetic mouse models and isolated islets. Methods: Plasma glucagon levels were measured by sandwich ELISA in several diabetic model mice after oral administration of various nutrients. The effects of nutrients on glucagon secretion were assessed using isolated islets from diabetic mice. The expression levels of nutrient catabolism-related factors were analyzed in diabetic mice compared with control mice. Results and Discussions: Rather than carbohydrate or lipid, protein increased plasma glucagon levels in all diabetic models including high-fat diet mice, STZ mice, and db/db mice. Among amino acids, branched-chain amino acids (BCAA), but not the other essential or nonessential amino acids, increased plasma glucagon. BCAA directly stimulated glucagon secretion in isolated islets from diabetic mice, which was suppressed by amino acid transporter inhibitor (BCH) or branched-chain alpha-ketoacid dehydrogenase (BCKDK) inhibitor (BT2). This suggests that BCAA’s stimulation of glucagon secretion is mediated by BCAA catabolism in alpha cells. We also found that the expression level of BCKDK was higher, while branched-chain amino acid transaminase 2 (BCAT2) was lower, in diabetic islets than control islets. Considering that dysfunction of BCAA catabolism has been reported in both adipocytes and hepatocytes of diabetic mice, the dysfunction of BCAA catabolism might be a common pathogenesis for metabolic disorders observed in diabetes. Disclosure E. Wada: None. M. Kobayashi: None. O. Kikuchi: None. D. Kohno: None. T. Kitamura: None.

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.

Evidence Against an Important Role of Plasma Insulin and Glucagon Concentrations in the Increase in EGP Caused by SGLT2 Inhibitors.

Sodium–glucose cotransport 2 inhibitors (SGLT2i) lower plasma glucose but stimulate endogenous glucose production (EGP). The current study examined the effect of dapagliflozin on EGP while clamping plasma glucose, insulin, and glucagon concentrations at their fasting level. Thirty-eight patients with type 2 diabetes received an 8-h measurement of EGP ([3-3H]-glucose) on three occasions. After a 3-h tracer equilibration, subjects received 1) dapagliflozin 10 mg (n = 26) or placebo (n = 12); 2) repeat EGP measurement with the plasma glucose concentration clamped at the fasting level; and 3) repeat EGP measurement with inhibition of insulin and glucagon secretion with somatostatin infusion and replacement of basal plasma insulin and glucagon concentrations. In study 1, the change in EGP (baseline to last hour of EGP measurement) in subjects receiving dapagliflozin was 22% greater (+0.66 ± 0.11 mg/kg/min, P < 0.05) than in subjects receiving placebo, and it was associated with a significant increase in plasma glucagon and a decrease in the plasma insulin concentration compared with placebo. Under glucose clamp conditions (study 2), the change in plasma insulin and glucagon concentrations was comparable in subjects receiving dapagliflozin and placebo, yet the difference in EGP between dapagliflozin and placebo persisted (+0.71 ± 0.13 mg/kg/min, P < 0.01). Under pancreatic clamp conditions (study 3), dapagliflozin produced an initial large decrease in EGP (8% below placebo), followed by a progressive increase in EGP that was 10.6% greater than placebo during the last hour. Collectively, these results indicate that 1) the changes in plasma insulin and glucagon concentration after SGLT2i administration are secondary to the decrease in plasma glucose concentration, and 2) the dapagliflozin-induced increase in EGP cannot be explained by the increase in plasma glucagon or decrease in plasma insulin or glucose concentrations.

1952-P: Glucagon Receptor Antagonism Increases Plasma Amino Acids and Glucagon

Hyperglucagonemia in type 2 diabetes (T2D) may result from impaired hepatic glucagon signaling and consequent reduced glucagon-induced amino acid (AA) turnover leading to higher AA concentrations and stimulation of glucagon secretion. In a double-blinded, cross-over study, blood was sampled from 10 overnight fasted patients with T2D (BMI [mean±SD]: 33.0±5.4 kg/m2; HbA1c: 46.2±6.1 mmol/mol, 6.4±0.6%) and 10 matched healthy controls (BMI: 31.7±4.2 kg/m2; HbA1c: 33.9±3.0 mmol/mol, 5.3±0.3%) after a single-dose of the glucagon receptor antagonist (GRA) LY2409021 or placebo. Total AA and glucagon concentrations are means of 3 samples (15 minutes apart) on 3 GRA and 3 placebo days. Fractioned AA were analyzed from one sample per day. Total AA concentrations were increased by GRA compared to placebo by 1.4 fold in T2D and 1.3 fold in controls (P≤0.001) with threonine, proline and the glucagonotropic AAs alanine and tyrosine exhibiting the greatest increases in T2D (1.6-2 fold) and controls (1.4-1.5 fold). GRA also increased plasma glucagon concentrations by more than 3-fold (P≤0.0001), and the glucagonotropic AAs alanine (R2 0.24, P=0.0012) and tyrosine (R2 0.30, P=0.0002) were correlated to glucagon. In conclusion, acute inhibition of glucagon receptor signaling by GRA causes hyperaminoacidemia linked to hyperglucagonemia, supporting the importance of the liver-alpha cell axis in regulating circulating glucagon and AA in humans. Disclosure S. Haedersdal: None. N.J. Wewer Albrechtsen: Research Support; Self; Mercodia, Novo Nordisk A/S. Speaker's Bureau; Self; Merck Sharp &amp; Dohme Corp. A.B. Lund: None. K.D. Galsgaard: None. M. Winther-Soerensen: None. J.J. Holst: Advisory Panel; Self; Novo Nordisk A/S. 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. T. Vilsbøll: None. Funding Novo Nordisk Foundation

1951-P: Prolonged (12-Hour) Glucagon Infusion Leads to Transient Elevation of Plasma Glucose but Sustained Elevation of Hepatic Glucose Production

Recently, novel non-glycemic effects of glucagon have been described. Although short-term glucagon infusion is well known to elevate plasma glucose levels, long-term effect of increased plasma glucagon on glucose and lipid metabolism is unclear. The aim of the present study was to evaluate the effect of 12-hour glucagon infusion on hepatic glucose production and lipid metabolism in healthy NGT individuals. 8 NGT subjects (5M/3F, age=35± 5 years, BMI = 24 ± 1 kg/m2, HbA1c 5.2± 0.1%) received an 2-hour (75gram) OGTT. On a different day subjects received a 12-hour (6PM to 6 AM) glucagon infusion (3ng/kg/minutes) with the measurement of hepatic glucose production (HGP) with 3-3H-glucose on the following morning from 6-10 AM. HGP in glucagon infused subjects was compared to values in 20 age/gender/weight matched NGT subjects studied after an overnight fast from 6-10 AM. Plasma glucose, insulin, C-peptide, glucagon, and FFA concentrations were obtained every 15 minutes during OGTT. Plasma glucagon concentrations increased from 40 ± 4 to 120 ± 34 pg/ml at 6 AM. Plasma glucose increased 2 hours after the start of infusion from 95 ± 6 to 111 ± 6 mg/dl (p&amp;lt;0.005); after 12 hours of glucagon infusion the plasma glucose concentration declined to the mean baseline levels. After 12-hour glucagon infusion (6 AM), plasma insulin and C-peptide were not significantly changed. Basal hepatic glucose production was significantly higher following prolonged (12-hour) glucagon infusion compared to NGT control subjects following 12-hour overnight fast (3.1 ± 0.1 vs. 2.2 ± 0.2 mg/kg/minutes, p&amp;lt;0.05). Plasma FFA concentrations did not change following 12-hour glucagon infusion (0.629±0.1 vs. 0.670±0.2mml/l, p=ns). Thus 12-hour glucagon infusion led to higher basal rate of HGP, but unchanged plasma FFA levels. These results demonstrate that prolonged physiologic hyperglucagonemia results in a transient elevation of plasma glucose concentration but sustained increase in hepatic glucose production. Disclosure X. Chen: None. A. Merovci: None. E. Case: None. R.A. DeFronzo: Advisory Panel; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Elcelyx Therapeutics, Inc., Intarcia Therapeutics, Inc., Janssen Pharmaceuticals, Inc., Novo Nordisk Inc. Research Support; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Janssen Pharmaceuticals, Inc., Merck &amp; Co., Inc. Speaker's Bureau; Self; AstraZeneca, Novo Nordisk Inc. D. Tripathy: None.