Insulin secretion and action and the response of endogenous glucose production to a lack of glucagon suppression in nondiabetic subjects.

Type 2 diabetes is a disease characterized by impaired insulin secretion and defective glucagon suppression in the postprandial period. We examined the effect of impaired glucagon suppression on glucose concentrations and endogenous glucose production (EGP) at different degrees of insulin secretory impairment. The contribution of anthropometric characteristics, peripheral, and hepatic insulin action to this variability was also examined. To do so, we studied 54 nondiabetic subjects on two occasions in which endogenous hormone secretion was inhibited by somatostatin, with glucagon infused at a rate of 0.65 ng/kg/min, at 0 min to prevent a fall in glucagon (nonsuppressed day) or at 120 min to create a transient fall in glucagon (suppressed day). Subjects received glucose (labeled with [3-3H]-glucose) infused to mimic the systemic appearance of 50-g oral glucose. Insulin was infused to mimic a prandial insulin response in 18 subjects, another 18 received 80% of the dose, and the remaining 18 received 60%. EGP was measured using the tracer-dilution technique. Decreased prandial insulin resulted in greater % increase in peak glucose but not in integrated glucose concentrations attributable to nonsuppressed glucagon. The % change in integrated EGP was unaffected by insulin dose. Multivariate regression analysis, adjusted for age, sex, weight, and insulin dose, did not show a relationship between the EGP response to impaired suppression of glucagon and insulin action as measured at the time of screening by oral glucose tolerance. A similar analysis for hepatic insulin action also did not show a relationship with the EGP response. These data indicate that the effect of impaired glucagon suppression on EGP is independent of anthropometric characteristics and insulin action.NEW & NOTEWORTHY In prediabetes, anthropometric characteristics as well as insulin action do not alter the hepatic response to glucagon. The postprandial suppression or lack of suppression of glucagon secretion is an important factor governing postprandial glucose tolerance independent of insulin secretion.

Mathematical Model of Glucagon Kinetics for the Assessment of Insulin-Mediated Glucagon Inhibition During an Oral Glucose Tolerance Test.

Glucagon is secreted from the pancreatic alpha cells and plays an important role in the maintenance of glucose homeostasis, by interacting with insulin. The plasma glucose levels determine whether glucagon secretion or insulin secretion is activated or inhibited. Despite its relevance, some aspects of glucagon secretion and kinetics remain unclear. To gain insight into this, we aimed to develop a mathematical model of the glucagon kinetics during an oral glucose tolerance test, which is sufficiently simple to be used in the clinical practice. The proposed model included two first-order differential equations -one describing glucagon and the other describing C-peptide in a compartment remote from plasma - and yielded a parameter of possible clinical relevance (i.e., SGLUCA(t), glucagon-inhibition sensitivity to glucose-induced insulin secretion). Model was validated on mean glucagon data derived from the scientific literature, yielding values for SGLUCA(t) ranging from -15.03 to 2.75 (ng of glucagon·nmol of C-peptide-1). A further validation on a total of 100 virtual subjects provided reliable results (mean residuals between -1.5 and 1.5 ng·L-1) and a negative significant linear correlation (r = -0.74, p < 0.0001, 95% CI: -0.82 - -0.64) between SGLUCA(t) and the ratio between the areas under the curve of suprabasal remote C-peptide and glucagon. Model reliability was also proven by the ability to capture different patterns in glucagon kinetics. In conclusion, the proposed model reliably reproduces glucagon kinetics and is characterized by sufficient simplicity to be possibly used in the clinical practice, for the estimation in the single individual of some glucagon-related parameters.

Glucagon blockade restores functional ß-cell mass in type 1 diabetic mice and enhances function of human islets.

We evaluated the potential for a monoclonal antibody antagonist of the glucagon receptor (Ab-4) to maintain glucose homeostasis in type 1 diabetic rodents. We noted durable and sustained improvements in glycemia which persist long after treatment withdrawal. Ab-4 promoted ß-cell survival and enhanced the recovery of insulin+ islet mass with concomitant increases in circulating insulin and C peptide. In PANIC-ATTAC mice, an inducible model of ß-cell apoptosis which allows for robust assessment of ß-cell regeneration following caspase-8-induced diabetes, Ab-4 drove a 6.7-fold increase in ß-cell mass. Lineage tracing suggests that this restoration of functional insulin-producing cells was at least partially driven by α-cell-to-ß-cell conversion. Following hyperglycemic onset in nonobese diabetic (NOD) mice, Ab-4 treatment promoted improvements in C-peptide levels and insulin+ islet mass was dramatically increased. Lastly, diabetic mice receiving human islet xenografts showed stable improvements in glycemic control and increased human insulin secretion.

Structure-Activity Relationship and Biological Investigation of SR18292 (16), a Suppressor of Glucagon-Induced Glucose Production.

Despite a myriad of available pharmacotherapies for the treatment of type 2 diabetes (T2D), challenges still exist in achieving glycemic control. Several novel glucose-lowering strategies are currently under clinical investigation, highlighting the need for more robust treatments. Previously, we have shown that suppressing peroxisome proliferator-activated receptor gamma coactivator 1-alpha activity with a small molecule (SR18292, 16) can reduce glucose release from hepatocytes and ameliorate hyperglycemia in diabetic mouse models. Despite structural similarities in 16 to known ß-blockers, detailed structure-activity relationship studies described herein have led to the identification of analogues lacking ß-adrenergic activity that still maintain the ability to suppress glucagon-induced glucose release from hepatocytes and ameliorate hyperglycemia in diabetic mouse models. Hence, these compounds exert their biological effects in a mechanism that does not include adrenergic signaling. These probe molecules may lead to a new therapeutic approach to treat T2D either as a single agent or in combination therapy.

The mediation by GLP-1 receptors of glucagon-induced insulin secretion revisited in GLP-1 receptor knockout mice.

To study whether activation of GLP-1 receptors importantly contributes to the insulinotropic action of exogenously administered glucagon, we have performed whole animal experiments in normal mice and in mice with GLP-1 receptor knockout. Glucagon (1, 3 or 10 µg/kg), the GLP-1 receptor antagonist exendin 9-39 (30 nmol/kg), glucose (0.35 g/kg) or the incretin hormone glucose-dependent insulinotropic polypeptide (GIP; 3 nmol/kg) was injected intravenously or glucose (75 mg) was given orally through gavage. Furthermore, islets were isolated and incubated in the presence of glucose with or without glucagon. It was found that the insulin response to intravenous glucagon was preserved in GLP-1 receptor knockout mice but that glucagon-induced insulin secretion was markedly suppressed in islets from GLP-1 receptor knockout mice. Similarly, the GLP-1 receptor antagonist markedly suppressed glucagon-induced insulin secretion in wildtype mice. These data suggest that GLP-1 receptors contribute to the insulinotropic action of glucagon and that there is a compensatory mechanism in GLP-1 receptor knockout mice that counteracts a reduced effect of glucagon. Two potential compensatory mechanisms (glucose and GIP) were explored. However, neither of these seemed to explain why the insulin response to glucagon is not suppressed in GLP-1 receptor knockout mice. Based on these data we confirm the hypothesis that glucagon-induced insulin secretion is partially mediated by GLP-1 receptors on the beta cells and we propose that a compensatory mechanism, the nature of which remains to be established, is induced in GLP-1 receptor knockout mice to counteract the expected impaired insulin response to glucagon in these mice.

Regulation of islet glucagon secretion: Beyond calcium.

The islet of Langerhans plays a key role in glucose homeostasis through regulated secretion of the hormones insulin and glucagon. Islet research has focused on the insulin-secreting ß-cells, even though aberrant glucagon secretion from α-cells also contributes to the aetiology of diabetes. Despite its importance, the mechanisms controlling glucagon secretion remain controversial. Proper α-cell function requires the islet milieu, where ß- and δ-cells drive and constrain α-cell dynamics. The response of glucagon to glucose is similar between isolated islets and that measured in vivo, so it appears that the glucose dependence requires only islet-intrinsic factors and not input from blood flow or the nervous system. Elevated intracellular free Ca2+ is needed for α-cell exocytosis, but interpreting Ca2+ data is tricky since it is heterogeneous among α-cells at all physiological glucose levels. Total Ca2+ activity in α-cells increases slightly with glucose, so Ca2+ may serve a permissive, rather than regulatory, role in glucagon secretion. On the other hand, cAMP is a more promising candidate for controlling glucagon secretion and is itself driven by paracrine signalling from ß- and δ-cells. Another pathway, juxtacrine signalling through the α-cell EphA receptors, stimulated by ß-cell ephrin ligands, leads to a tonic inhibition of glucagon secretion. We discuss potential combinations of Ca2+ , cAMP, paracrine and juxtacrine factors in the regulation of glucagon secretion, focusing on recent data in the literature that might unify the field towards a quantitative understanding of α-cell function.

Endogenous Glucose Production and Hormonal Changes in Response to Canagliflozin and Liraglutide Combination Therapy.

The decrement in plasma glucose concentration with SGLT2 inhibitors (SGLT2i) is blunted by a rise in endogenous glucose production (EGP). We investigated the ability of incretin treatment to offset the EGP increase. Subjects with type 2 diabetes (n = 36) were randomized to 1) canagliflozin (CANA), 2) liraglutide (LIRA), or 3) CANA plus LIRA (CANA/LIRA). EGP was measured with [3-3H]glucose with or without drugs for 360 min. In the pretreatment studies, EGP was comparable and decreased (2.2 ± 0.1 to 1.7 ± 0.2 mg/kg ⋅ min) during a 300- to 360-min period (P < 0.01). The decrement in EGP was attenuated with CANA (2.1 ± 0.1 to 1.9 ± 0.1 mg/kg ⋅ min) and CANA/LIRA (2.2 ± 0.1 to 2.0 ± 0.1 mg/kg ⋅ min), whereas with LIRA it was the same (2.4 ± 0.2 to 1.8 ± 0.2 mg/kg ⋅ min) (all P < 0.05 vs. baseline). After CANA, the fasting plasma insulin concentration decreased (18 ± 2 to 12 ± 2 µU/mL, P < 0.05), while it remained unchanged in LIRA (18 ± 2 vs. 16 ± 2 µU/mL) and CANA/LIRA (17 ± 1 vs. 15 ± 2 µU/mL). Mean plasma glucagon did not change during the pretreatment studies from 0 to 360 min, while it increased with CANA (69 ± 3 to 78 ± 2 pg/mL, P < 0.05), decreased with LIRA (93 ± 6 to 80 ± 6 pg/mL, P < 0.05), and did not change in CANA/LIRA. LIRA prevented the insulin decline and blocked the glucagon rise observed with CANA but did not inhibit the increase in EGP. Factors other than insulin and glucagon contribute to the stimulation of EGP after CANA-induced glucosuria.

Glucagon receptor signaling in metabolic diseases.

Glucagon is a peptide hormone secreted from the pancreatic alpha cells in response to hypoglycemia but in some patients with type 2 diabetes a paradoxical hypersecretion results from the intake of glucose. In rodent, antagonizing the actions of glucagon have been shown to be effective for lowering blood glucose levels and this has recently have been solidified in patients with type 2 diabetes. Although the reported increases of liver enzymes, hyperglucagonemia, and alpha cell hyperplasia resulting from glucagon receptor antagonism may potentially limit the clinical applicability of glucagon receptor antagonists, they may serve as an instrumental toolbox for delineating the physiology of glucagon. Agonizing glucagon receptor signaling may be relevant, in particular when combined with glucagon-like peptide-1 receptor analogues in the perspective of body weight lowering therapy. Here, we will focus on new conceptual aspects of glucagon biology and how this may led to new diagnostics and treatment of metabolic diseases.

Glucose-Sensitive CFTR Suppresses Glucagon Secretion by Potentiating KATP Channels in Pancreatic Islet α Cells.

The secretion of glucagon by islet α cells is normally suppressed by high blood glucose, but this suppressibility is impaired in patients with diabetes or cystic fibrosis (CF), a disease caused by mutations in the gene encoding CF transmembrane conductance regulator (CFTR), a cyclic adenosine monophosphate-activated Cl- channel. However, precisely how glucose regulates glucagon release remains controversial. Here we report that elevated glucagon secretion, together with increased glucose-induced membrane depolarization and Ca2+ response, is found in CFTR mutant (DF508) mice/islets compared with the wild-type. Overexpression of CFTR in AlphaTC1-9 cells results in membrane hyperpolarization and reduced glucagon release, which can be reversed by CFTR inhibition. CFTR is found to potentiate the adenosine triphosphate-sensitive K+ (KATP) channel because membrane depolarization and whole-cell currents sensitive to KATP blockers are significantly greater in wild-type/CFTR-overexpressed α cells compared with that in DF508/non-overexpressed cells. KATP knockdown also reverses the suppressive effect of CFTR overexpression on glucagon secretion. The results reveal that by potentiating KATP channels, CFTR acts as a glucose-sensing negative regulator of glucagon secretion in α cells, a defect of which may contribute to glucose intolerance in CF and other types of diabetes.

Balanced Coagonist of GLP-1 and Glucagon Receptors Corrects Dyslipidemia by Improving FGF21 Sensitivity in Hamster Model.

Hyperlipidemia is often associated with obesity and diabetes, and can lead to serious complications like atherosclerosis and fatty liver disease. Coagonist of GLP-1 and glucagon receptors is a therapy under clinical investigation for treatment of obesity and diabetes. In this study, we have characterized the mechanism of hypolipidemic effect of a balanced coagonist using high cholesterol-fed hamsters. Tyloxapol-induced hypertriglyceridemia, lipolysis in adipose tissue, and bile homeostasis were assessed after repeated dose treatment of the coagonist of GLP-1 and glucagon receptors (Aib2 C24 chimera 2, SC). Antagonists of GLP-1, glucagon, and FGF21 receptors were coadministered, and FGF21 sensitivity was determined in liver and adipose tissue. Repeated dose treatment of coagonist reduced cholesterol and increased FGF21 in blood and liver. Coagonist treatment reduced hepatic triglyceride secretion, increased lipolysis and reduced body weight. Antagonism of GLP-1 and glucagon receptors partially blocked the effect of the coagonist on lipid metabolism in circulation and liver, while FGF21 receptor antagonist completely abolished it. Glucagon and GLP-1 receptors antagonists blocked the action of coagonist on cholesterol excretion and bile flow in liver, but FGF21 antagonist was not effective. Treatment with the coagonist increased expression of FGF21, FGF21R and cofactor ßKlotho in liver and adipose. In conclusion, coagonist of GLP-1 and glucagon receptors improved lipid metabolism in liver of dyslipidemic hamsters. This effect is partially mediated by GLP-1 and glucagon receptors, and the improved FGF21 sensitivity could be the mechanism of hypolipidemic action of the coagonist of GLP-1/glucagon receptors.

Suppression of Extrapancreatic Glucagon by Octreotide May Reduce the Fasting and Postprandial Glucose Levels in a Diabetic Patient after Total Pancreatectomy.

A 52-year-old woman was treated with sensor augmented pump therapy after undergoing total pancreatectomy for a nonfunctional pancreatic neuroendocrine tumor (NET). The secretion of both endogenous insulin and pancreatic glucagon were completely depleted. Octreotide long acting repeatable (Oct-LAR) was administered for the treatment of liver metastasis of NET. Both the fasting and postprandial glucagon levels decreased immediately after the administration of Oct-LAR. In a continuous glucose monitoring analysis, episodes of nocturnal hypoglycemia was found to increase and an improvement of postprandial hyperglycemia was observed. This case suggests that octreotide may reduce the glucose level in both the fasting and postprandial states, in part by the suppression of extrapancreatic glucagon.

Selection and characterization of DNA aptamer against glucagon receptor by cell-SELEX.

Excessive secretion of glucagon, a functional insulin antagonist, significantly contributes to hyperglycemia. Glucagon exerts its physiological functions through activation of the glucagon receptor (GCGR). Inhibition of GCGR activity represents a potential therapeutic approach for reducing excess glucose production in diabetes mellitus. Aptamers are short DNA or RNA oligonucleotides evolved from systematic evolution of ligands by exponential enrichment (SELEX). Here, we have successfully selected a DNA aptamer against GCGR by cell-SELEX, which can specifically bind membrane protein of CHO-GCGR cells with a K d of 52.7 ± 5.1 nM. Aptamer-mediated pull-down and gcgr knockdown assay verified that GCGR was the target of aptamer GR-3. Binding analysis revealed that GR-3 could recognize other cells with different affinity according to the level of GCGR protein expressed in these cells. Hepatic tissue imaging suggested that GR-3 could bind the cell membrane of hepatic tissues. With the advantages of small size, high binding affinity, good stability, lack of immunogenicity, and easy synthesis, aptamer GR-3 against GCGR can be a promising tool with the potential to attenuate hyperglycemia in diabetes mellitus.

FAM3D inhibits glucagon secretion via MKP1-dependent suppression of ERK1/2 signaling.

Dysregulated glucagon secretion is a hallmark of type 2 diabetes (T2D). To date, few effective therapeutic agents target on deranged glucagon secretion. Family with sequence similarity 3 member D (FAM3D) is a novel gut-derived cytokine-like protein, and its secretion timing is contrary to that of glucagon. However, the roles of FAM3D in metabolic disorder and its biological functions are largely unknown. In the present study, we investigated whether FAM3D modulates glucagon production in mouse pancreatic alpha TC1 clone 6 (αTC1-6) cells. Glucagon secretion, prohormone convertase 2 (PC2) activity, and mitogen-activated protein kinase (MAPK) pathway were assessed. Exogenous FAM3D inhibited glucagon secretion, PC2 activity, as well as extracellular-regulated protein kinase 1/2 (ERK1/2) signaling and induced MAPK phosphatase 1 (MKP1) expression. Moreover, knockdown of MKP1 and inhibition of ERK1/2 abolished and potentiated the inhibitory effect of FAM3D on glucagon secretion, respectively. Taken together, FAM3D inhibits glucagon secretion via MKP1-dependent suppression of ERK1/2 signaling. These results provide rationale for developing the therapeutic potential of FAM3D for dysregulated glucagon secretion and T2D.

Insulin and Glucagon: Partners for Life.

In August 2016, several leaders in glucagon biology gathered for the European Association for the Study of Diabetes Hagedorn Workshop in Oxford, England. A key point of discussion focused on the need for basal insulin to allow for the therapeutic benefit of glucagon blockade in the treatment of diabetes. Among the most enlightening experimental results presented were findings from studies in which glucagon receptor-deficient mice were administered streptozotocin to destroy pancreatic ß cells or had undergone diphtheria toxin-induced ß cell ablation. This article summarizes key features of the discussion as a consensus was reached. Agents that antagonize glucagon may be of great benefit for the treatment of diabetes; however, sufficient levels of basal insulin are required for their therapeutic efficacy.

Liraglutide acutely suppresses glucagon, lipolysis and ketogenesis in type 1 diabetes.

In view of the occurrence of diabetic ketoacidosis associated with the use of sodium-glucose transport protein-2 inhibitors in patients with type 1 diabetes (T1DM) and the relative absence of this complication in patients treated with liraglutide in spite of reductions in insulin doses, we investigated the effect of liraglutide on ketogenesis. Twenty-six patients with inadequately controlled T1DM were randomly divided into 2 groups of 13 patients each. After an overnight fast, patients were injected, subcutaneously, with either liraglutide 1.8 mg or with placebo. They were maintained on their basal insulin infusion and were followed up in our clinical research unit for 5 hours. The patients injected with placebo maintained their glucose and glucagon concentrations without an increase, but there was a significant increase in free fatty acids (FFA), acetoacetate and ß-hydoxybutyrate concentrations. In contrast, liraglutide significantly reduced the increase in FFA, and totally prevented the increase in acetoacetate and ß-hydroxybutyrate concentrations while suppressing glucagon and ghrelin concentrations. Thus, a single dose of liraglutide is acutely inhibitory to ketogenesis.

Niclosamide reduces glucagon sensitivity via hepatic PKA inhibition in obese mice: Implications for glucose metabolism improvements in type 2 diabetes.

Type 2 diabetes (T2D) is a global pandemic. Currently, the drugs used to treat T2D improve hyperglycemic symptom of the disease but the underlying mechanism causing the high blood glucose levels have not been fully resolved. Recently published data showed that salt form of niclosamide improved glucose metabolism in high fat fed mice via mitochondrial uncoupling. However, based on our previous work we hypothesised that niclosamide might also improve glucose metabolism via inhibition of the glucagon signalling in liver in vivo. In this study, mice were fed either a chow or high fat diet containing two different formulations of niclosamide (niclosamide ethanolamine salt - NENS or niclosamide - Nic) for 10 weeks. We identified both forms of niclosamide significantly improved whole body glucose metabolism without altering total body weight or body composition, energy expenditure or insulin secretion or sensitivity. Our study provides evidence that inhibition of the glucagon signalling pathway contributes to the beneficial effects of niclosamide (NENS or Nic) on whole body glucose metabolism. In conclusion, our results suggest that the niclosamide could be a useful adjunctive therapeutic strategy to treat T2D, as hepatic glucose output is elevated in people with T2D and current drugs do not redress this adequately.

[Glucagon antagonists open a new way in treatment of type 2 diabetes Mellitus]. / Antagonisté glukagonu otevírají novou cestu v lécbe diabetu 2. typu.

UNLABELLED: Excessive hepatic glucose production resulting from dysregulated glucagon secretion associated with inappropriate fasting and postprandial hyperglucagonemia is common feature in type 2 diabetes (DM2T). The effects of some currently widely used anti-diabetic agents, especially concerning metformin, GLP1 agonists and inhibitors of DPP4, comprise partial supression of glucagon secretion and/or action. Complete supression of glucagon action is recently widely investigated in experiments, and also results of phase 1 and 2 of the clinical trials are available. The experimental studies proved expected therapeutical potential of this approach. Blockade of glucagon action in diabetic animals resulted in decreased hepatic glucose production, reduction of fasting and prandial hyperglycemia, and improved glucose tolerance. On the other hand, the complete supression of glucagon action is associated with possible risk of pancreatic A-cell hyperplasia, hyperglucagonemia, increased sensitivity to the development of liver steatosis or other liver damage, higher risk of hypoglycemia and other potential side effects. Thus evaluation of safety profile must represent the high priority in the development of new molecules affecting glucagon secretion and intracellular action. A number of molecules antagonising glucagon action were prepared in recent years; some of them are already reviewed successfully in phase 2 of clinical testing; however no molecule is used in clinical practice so far. The presented article briefly sums up contemporary knowledge about glucagon dysregulation in T2DM, and gained experience with pharmacological supression of glucagon action in those patients. Anti-sense oligo-nucleotides, and monoclonal anti-bodies against glucagon and glucagon receptor are mentioned. The glucagon receptor antagonists are discussed in a greater detail as well. KEY WORDS: glucagon antagonism - potential side effects - type 2 diabetes mellitus.

Glucagon therapeutics: Dawn of a new era for diabetes care.

Although insulin monotherapy prevents death from ketoacidosis, it does not prevent either the hyperglycemic surges or the hypoglycemic plunges of glucose levels that plague the majority of patients with type 1 diabetes. However, significant improvements have occurred with the combination of continuous insulin delivery matched by continuous glucose monitoring, but the technology is not available for all patients, requires extensive education, is expensive and moreover, while much better than standard care, it almost never reduces haemoglobin A1c (HbA1c ) to below 6%. This may indicate that an improved diabetes therapy involving antagonism of glucagon action will for the first time control glucose levels to normal and eradicate the long-term complications of diabetes. Although one can never predict that results in animals will be reproduced in humans, the available evidence suggests that patients with type 1 and type 2 diabetes may expect far superior control of the metabolic abnormalities without the need for significant monitoring of glucose, a very important but expensive part of any insulin regimen.

An AlphaScreen Assay for the Discovery of Synthetic Chemical Inhibitors of Glucagon Production.

Glucose homeostasis is primarily controlled by two opposing hormones, insulin and glucagon, and diabetes results when insulin fails to inhibit glucagon action. Recent efforts to control glucagon in diabetes have focused on antagonizing the glucagon receptor, which is effective in lowering blood glucose levels but leads to hyperglucogonemia in rodents. An alternative strategy would be to control glucagon production with small molecules. In pursuit of this goal, we developed a homogeneous AlphaScreen assay for measuring glucagon in cell culture media and used this in a high-throughput screen to discover synthetic compounds that inhibited glucagon secretion from an alpha cell-like cell line. Some of these compounds inhibited transcription of the glucagon gene.

Acute disruption of glucagon secretion or action does not improve glucose tolerance in an insulin-deficient mouse model of diabetes.

AIMS/HYPOTHESIS: Normal glucose metabolism depends on pancreatic secretion of insulin and glucagon. The bihormonal hypothesis states that while lack of insulin leads to glucose underutilisation, glucagon excess is the principal factor in diabetic glucose overproduction. A recent study reported that streptozotocin-treated glucagon receptor knockout mice have normal glucose tolerance. We investigated the impact of acute disruption of glucagon secretin or action in a mouse model of severe diabetes by three different approaches: (1) alpha cell elimination; (2) glucagon immunoneutralisation; and (3) glucagon receptor antagonism, in order to evaluate the effect of these on glucose tolerance. METHODS: Severe diabetes was induced in transgenic and wild-type mice by streptozotocin. Glucose metabolism was investigated using OGTT in transgenic mice with the human diphtheria toxin receptor expressed in proglucagon producing cells allowing for diphtheria toxin (DT)-induced alpha cell ablation and in mice treated with either a specific high affinity glucagon antibody or a specific glucagon receptor antagonist. RESULTS: Near-total alpha cell elimination was induced in transgenic mice upon DT administration and resulted in a massive decrease in pancreatic glucagon content. Oral glucose tolerance in diabetic mice was neither affected by glucagon immunoneutralisation, glucagon receptor antagonism, nor alpha cell removal, but did not deteriorate further compared with mice with intact alpha cell mass. CONCLUSIONS/INTERPRETATION: Disruption of glucagon action/secretion did not improve glucose tolerance in diabetic mice. Near-total alpha cell elimination may have prevented further deterioration. Our findings support insulin lack as the major factor underlying hyperglycaemia in beta cell-deficient diabetes.