Postprandial Hyperglucagonemia Research Articles

The Regulation and Secretion of Glucagon in Response to Nutrient Composition: Unraveling Their Intricate Mechanisms.

Glucagon was initially regarded as a hyperglycemic substance; however, recent research has revealed its broader role in metabolism, encompassing effects on glucose, amino acids (AAs), and lipid metabolism. Notably, the interplay of glucagon with nutrient intake, particularly of AAs, and non-nutrient components is central to its secretion. Fasting and postprandial hyperglucagonemia have long been linked to the development and progression of type 2 diabetes (T2DM). However, recent studies have brought to light the positive impact of glucagon agonists on lipid metabolism and energy homeostasis. This review explores the multifaceted actions of glucagon, focusing on its regulation, signaling pathways, and effects on glucose, AAs, and lipid metabolism. The interplay between glucagon and other hormones, including insulin and incretins, is examined to provide a mechanistic understanding of its functions. Notably, the liver-α-cell axis, which involves glucagon and amino acids, emerges as a critical aspect of metabolic regulation. The dysregulation of glucagon secretion and its impact on conditions such as T2DM are discussed. The review highlights the potential therapeutic applications of targeting the glucagon pathway in the treatment of metabolic disorders.

Implication of sugar, protein and incretins in excessive glucagon secretion in type 2 diabetes after mixed meals

Amino acids powerfully release glucagon but their contribution to postprandial hyperglucagonemia in type 2 diabetes remains unclear. Exogenously applied GIP stimulates, while GLP-1 inhibits, glucagon secretion in humans. However, their role in mixed meals is unclear, which we therefore characterized. In three experiments, participants with type 2 diabetes and obese controls randomly received different loads of sugars and/or proteins. In the first experiment, participants ingested the rapidly cleaved saccharose (SAC) or slowly cleaved isomaltulose (ISO) which is known to elicit opposite profiles of GIP and GLP-1 secretion. In the second one participants received test meals which contained saccharose or isomaltulose in combination with milk protein. The third set of participants underwent randomized oral protein tests with whey protein or casein. Incretins, glucagon, C-peptide, and insulin were profiled by specific immunological assays. 50g of the sugars alone suppressed glucagon in controls but slightly less in type 2 diabetes patients. Participants with type 2 diabetes showed excessive glucagon responses within 15min and lasting over 3h, while the obese controls showed small initial and delayed greater glucagon responses to mixed meals. The release of GIP was significantly faster and greater with SAC compared to ISO, while GLP-1 showed an inverse pattern. The glucagon responses to whey or casein were only moderately increased in type 2 diabetes patients without a left shift of the dose response curve. The rapid hypersecretion of glucagon after mixed meals in type 2 diabetes patients compared to controls is unaffected by endogenous incretins. The defective suppression of glucagon by glucose combined with hypersecretion to protein is required for the exaggerated response. NCT03806920, NCT02219295, NCT04564391.

Postprandial hyperglucagonemia accompanies morbid obesity even in non-diabetic patients

Background and aims: Hyperglucagonemia is one of the pathophysiological mechanisms for type 2 diabetes development. Whether glucagon is increased in obese patients without glucose disturbances is less known.

The glucagon receptor antagonist LY2409021 has no effect on postprandial glucose in type 2 diabetes.

Type 2 diabetes (T2D) pathophysiology includes fasting and postprandial hyperglucagonemia, which has been linked to hyperglycemia via increased endogenous glucose production (EGP). We used a glucagon receptor antagonist (LY2409021) and stable isotope tracer infusions to investigate the consequences of hyperglucagonemia in T2D. A double-blinded, randomized, placebo-controlled crossover study was conducted. Ten patients with T2D and ten matched non-diabetic controls underwent two liquid mixed meal tests preceded by single-dose administration of LY2409021 (100 mg) or placebo. Double-tracer technique was used to quantify EGP. Antagonist selectivity toward related incretin receptors was determined in vitro. Compared to placebo, LY2409021 lowered the fasting plasma glucose (FPG) from 9.1 to 7.1 mmol/L in patients and from 5.6 to 5.0 mmol/L in controls (both P < 0.001) by mechanisms involving reduction of EGP. Postprandial plasma glucose excursions (baseline-subtracted area under the curve) were unaffected by LY2409021 in patients and increased in controls compared to placebo. Glucagon concentrations more than doubled during glucagon receptor antagonism. The antagonist interfered with both glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide receptors, complicating the interpretation of the postprandial data. LY2409021 lowered FPG concentrations but did not improve postprandial glucose tolerance after a meal in patients with T2D and controls. The metabolic consequences of postprandial hyperglucagonemia are difficult to evaluate using LY2409021 because of its antagonizing effects on the incretin receptors.

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.

A Review of the Efficacy and Cardiovascular Safety of Amylin Analogues.

A large proportion of persons with type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) do not reach the glycosylated haemoglobin (HbA1c) target of < 7% (53 mmol/- mol), with an increasing proportion of them being overweight or obese. In both T1DM and T2DM, there is accelerated gastric emptying and postprandial hyperglucagonemia. Furthermore, insulin therapy itself is associated with risk of hypoglycemia and weight-gain both of which are barriers to achieving good control. Medications which can achieve significant HbA1c and weight reduction associated with an ability to delay gastric emptying and suppress the glucagon secretion with minimal/ no hypoglycemia are of particular interest as an adjuvant to insulin. A synthetic amylin analogue, pramlintide is a drug with above mentioned properties. Other medications with similar properties are glucagon-like peptide-1 receptor agonists (GLP-1 RAs). In this article, we will review the efficacy of pramlintide when given with insulin in improving HbA1c, weight, and cognition with- /without GLP-1 RAs as well as its cardiovascular (CV) safety.

Association of Glucagon With Obesity, Glycemic Control and Renal Function in Adults With Type 2 Diabetes Mellitus

ObjectivesIn this study, we used a double-antibody sandwich enzyme-linked immunosorbent assay to assess the association between blood glucagon levels and indices of obesity, glycemic control and renal function in patients with type 2 diabetes mellitus (T2DM). MethodsThis investigation was a cross-sectional study on inpatients with T2DM who had plasma glucagon levels measured during hospitalization. Associations of fasting glucagon levels (G0), 120-minute postbreakfast plasma glucagon (G120), fasting glucagon/C-peptide ratio (G0/CPR0) and postbreakfast glucagon/C-peptide ratio (G120/CPR120) with clinical data were evaluated using multiple regression analysis. ResultsA total of 345 patients were enrolled in the study. G0, and G120 were significantly and positively associated with serum C-peptide levels. Moreover, G0 and G120 were positively associated with waist circumference, and G0 was negatively associated with duration of diabetes mellitus. Interestingly, both G0 and G120 were negatively associated with the estimated glomerular filtration rate. In addition, G120/CPR120 was positively associated with duration of diabetes mellitus and glycoalbumin levels. ConclusionsThe balance between glucagon and insulin secretion is significantly associated with abdominal obesity and important for maintaining glucose homeostasis. Postprandial hyperglucagonemia could also be related to deterioration of renal function.

1917-P: Alpha-Cell Function in Patients with Type 1 Diabetes Is Compromised with Different Levels of Residual C-Peptide

Objective: It is poorly understood α-cell function changes to respond to the different detectable C-peptide levels in patients with type 1 diabetes (T1D). This study aims to investigate the relationship between glucagon secretion and declining β-cell function in patients with T1D. Methods: Eighty-seven subjects [68, autoimmune type 1 diabetes (T1AD); 4, fulminant type 1 diabetes (FT1D); 15 healthy controls] were enrolled. All participants underwent a 100g steamed bread meal tests (SBMT). T1AD patients were divided into C-peptide negative (CPN), C-peptide middle (CPM) and C-peptide high (CPH) group based on peak C-peptide levels. Both fasting and postprandial of glucose, C-peptide and glucagon were measured. Glucagon among groups were compared by a linear mixed-effects model. The relationship between C-peptide, glucose and glucagon responses was evaluated by regression analysis. Results: At baseline, fasting glucagon concentrations were comparable between CPN, CPM and CPH group (F=0.099, P=0.906). After SBMT, 180min-glucagon in CPN group were higher than in CPM (P=0.004) and in CPH group (P&amp;lt;0.001). The iAUC30-180 of glucagon was lower in CPH than in CPN (P=0.001) and in CPM group (P=0.034), whereas the iAUC0-30 glucagon did not differ among CPN, CPM and CPH group (F=1.246, P=0.295). The same results were observed in iAUC of glucagon/glucose. After adjustment for age, BMI and diabetes duration, the iAUC30-180 glucagon in T1AD was inversely related to peak C-peptide and positively related to peak glucose levels (Radj2=0.315, P&amp;lt;0.001); however, the iAUC0-30 glucagon in T1AD was only positively related to 30min-glucose (Radj2=0.466, P&amp;lt;0.001). Conclusions: This study demonstrates α-cell function in patients with T1D are compromised with different levels of residual C-peptide. Glucose is also a contributor factor for postprandial hyperglucagonemia. Disclosure L. Zhang: None. Y. Shi: None. Y. Huang: None. Q. Hu: None. Y. Qin: None. M. Zhang: None. Funding National Natural Science Foundation of China (81670756, 81974103), Provincial Key Research and Development Foundation of Jiangsu (BE2018748)

1980-P: A Characterization of Postprandial Glucose Metabolism and Incretin Hormone Responses in Patients with Bile Acid Malabsorption

Bile acid malabsorption (BAM) is characterized by an excessive spill-over of bile acids to the colon leading to bile acid-induced diarrhea; the condition is usually treated with bile acid sequestrants. Bile acids have been demonstrated to modulate the secretion of the incretin hormone glucagon-like peptide 1 (GLP-1) and the aim of this study was to characterize postprandial glucose metabolism and incretin hormone responses in patients with BAM. Twelve patients with BAM (6 women; mean age 39.1 (SD 13.2); mean BMI 28.4 kg/m2 (SD 1.2); HbA1c 31.4 (SD 3.7)) and 12 healthy gender, age, BMI and HbA1c-matched controls (6 women; mean age 39.3 (SD 15.6); mean BMI 29,1 kg/m2 (SD 1.1); HbA1c 31.0 (SD 2.8)) were subjected to two 4-hour standardized liquid meal tests with double-blinded single-dose administration of the bile acid sequestrant colesevelam (3.75 g) and placebo, respectively, performed on separate days, and in randomized order. Fasting and postprandial plasma GIP and GLP-1 concentrations were comparable among patients with BAM and control subjects and unaffected by colesevelam administration. Peak plasma glucose concentrations were higher in BAM patients vs. control subjects, but area under curve for plasma glucose did not differ between the two groups. Patients with BAM exhibited significantly higher postprandial serum C-peptide concentrations and hyperglucagonemia compared to controls. Single-dose colesevelam had no effect on postprandial glucose or glucagon excursions in any of the groups but decreased the postprandial C-peptide response in BAM patients. Patients with BAM are characterized by elevated serum C-peptide concentrations and hyperglucagonemia whereas postprandial glucose tolerance and GLP-1 and GIP responses are similar to healthy controls. Disclosure M.L. Kårhus: None. D.P. Sonne: None. M.L. Thomasen: None. J.J. Holst: Advisory Panel; Self; Novo Nordisk A/S. T. Vilsbøll: None. A. Brønden: Other Relationship; Self; AstraZeneca. 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. Funding Novo Nordisk Foundation

Improved Glycemic Control due to Reduction in Glucagon Levels by the Administration of Once-Weekly Dulaglutide in a Non-Obese Patient With Type 2 Diabetes

Treatment with glucagon-like peptide-1 receptor agonists (GLP-1RAs) is a cornerstone for the management of obesity and type 2 diabetes. GLP-1RAs improve the glycemic control by suppressing glucagon secretion and stimulating insulin secretion in patients with type 2 diabetes. Here, we report the case of a patient with type 2 diabetes with postprandial hyperglucagonemia who was successfully treated by the administration of once-weekly dulaglutide. A 67-year-old, non-obese woman was admitted to our hospital for preoperative glycemic control. Her glycemic control significantly improved after the administration of dulaglutide. Both fasting and postprandial plasma glucagon levels were effectively suppressed by dulaglutide, which ameliorated hyperglycemia. Thus, to achieve an optimal glycemic control, clinicians should consider suppressing glucagon secretion in addition to improving insulin secretion and sensitivity. J Endocrinol Metab. 2018;8(1):6-9 doi: https://doi.org/10.14740/jem486w

Improved Glycemic Control due to Reduction in Glucagon Levels by the Administration of Once-Weekly Dulaglutide in a Non-Obese Patient With Type 2 Diabetes

Treatment with glucagon-like peptide-1 receptor agonists (GLP-1RAs) is a cornerstone for the management of obesity and type 2 diabetes. GLP-1RAs improve the glycemic control by suppressing glucagon secretion and stimulating insulin secretion in patients with type 2 diabetes. Here, we report the case of a patient with type 2 diabetes with postprandial hyperglucagonemia who was successfully treated by the administration of once-weekly dulaglutide. A 67-year-old, non-obese woman was admitted to our hospital for preoperative glycemic control. Her glycemic control significantly improved after the administration of dulaglutide. Both fasting and postprandial plasma glucagon levels were effectively suppressed by dulaglutide, which ameliorated hyperglycemia. Thus, to achieve an optimal glycemic control, clinicians should consider suppressing glucagon secretion in addition to improving insulin secretion and sensitivity. J Endocrinol Metab. 2018;8(1):6-9 doi: https://doi.org/10.14740/jem486w

Extrapancreatic contribution to glucose regulation by dipeptidyl peptidase 4 inhibition

Dipeptidyl peptidase 4 (DPP-4) inhibitors are now being clinically utilized as glucose-lowering medications for the treatment of type 2 diabetes. Their widespread use and effective glucose-lowering properties have led to great interest in the mechanism of action of this class of drug. Although it has been well accepted that DPP-4 inhibitors lower glucose in part by increasing postprandial insulin secretion and suppressing fasting and postprandial hyperglucagonemia, recent studies have suggested that DPP-4 inhibition has other metabolically beneficial properties that are extrapancreatic in nature. This review explores the changes in DPP-4 expression and activity in metabolic disease states and discusses the metabolic consequences of DPP-4 inhibition on a systemic and tissue-specific basis. It concludes that there is considerable scientific evidence and a growing body of clinical evidence to suggest that DPP-4 inhibition would be beneficial in a number of metabolic disorders in addition to type 2 diabetes. (Less)

Effects of endogenous GLP-1 and GIP on glucose tolerance after Roux-en-Y gastric bypass surgery.

Exaggerated secretion of glucagon-like peptide 1 (GLP-1) is important for postprandial glucose tolerance after Roux-en-Y gastric bypass (RYGB), whereas the role of glucose-dependent insulinotropic polypeptide (GIP) remains to be resolved. We aimed to explore the relative importance of endogenously secreted GLP-1 and GIP on glucose tolerance and β-cell function after RYGB. We used DPP-4 inhibition to enhance concentrations of intact GIP and GLP-1 and the GLP-1 receptor antagonist exendin-(9-39) (Ex-9) for specific blockage of GLP-1 actions. Twelve glucose-tolerant patients were studied after RYGB in a randomized, placebo-controlled, 4-day crossover study with standard mixed-meal tests and concurrent administration of placebo, oral sitagliptin, Ex-9 infusion, or combined Ex-9-sitagliptin. GLP-1 receptor antagonism increased glucose excursions, clearly attenuated β-cell function, and aggravated postprandial hyperglucagonemia compared with placebo, whereas sitagliptin had no effect despite two- to threefold increased concentrations of intact GLP-1 and GIP. Similarly, sitagliptin did not affect glucose tolerance or β-cell function during GLP-1R blockage. This study confirms the importance of GLP-1 for glucose tolerance after RYGB via increased insulin and attenuated glucagon secretion in the postprandial state, whereas amplification of the GIP signal (or other DPP-4-sensitive glucose-lowering mechanisms) did not appear to contribute to the improved glucose tolerance seen after RYGB.

Glucagon and type 2 diabetes: the return of the alpha cell.

In normal physiology, glucagon from pancreatic alpha cells plays an important role in maintaining glucose homeostasis via its regulatory effect on hepatic glucose production. Patients with type 2 diabetes suffer from fasting and postprandial hyperglucagonemia, which stimulate hepatic glucose production and, thus, contribute to the hyperglycemia characterizing these patients. Although this has been known for years, research focusing on alpha cell (patho)physiology has historically been dwarfed by research on beta cells and insulin. Today the mechanisms behind type 2 diabetic hyperglucagonemia are still poorly understood. Preclinical and clinical studies have shown that the gastrointestinal hormone glucose-dependent insulinotropic polypeptide (GIP) might play an important role in this pathophysiological phenomenon. Furthermore, it has become apparent that suppression of glucagon secretion or antagonization of the glucagon receptor constitutes potentially effective treatment strategies for patients with type 2 diabetes. In this review, we focus on the regulation of glucagon secretion by the incretin hormones glucagon-like peptide-1 (GLP-1) and GIP. Furthermore, potential advantages and limitations of suppressing glucagon secretion or antagonizing the glucagon receptor, respectively, in the treatment of patients with type 2 diabetes will be discussed.

First proof of pharmacology in humans of a novel glucagon receptor antisense drug.

Fasting and postprandial hyperglucagonemia in type 2 diabetes mellitus (T2DM) patients cause excessive hepatic glucose production (HGP), suggesting that attenuation of hepatic glucagon action could be a therapeutic strategy for T2DM. In this study we evaluated the safety, tolerability, PK, and pharmacodynamics in healthy human volunteers of single and multiple doses (50-400 mg) ISIS 325568, a 2'-O-MOE antisense (ASO) developed to reduce hepatic glucagon receptor (GCGR) mRNA expression. In the multiple dose cohorts, treatment consisted of eight doses of ISIS 325568 or placebo over 6-weeks. Drug effects were assessed using serial fasting glucagon measurements and the glycemic response to a glucagon challenge at baseline and at the end of 6-week treatment. ISIS 325568 was not associated with clinically relevant changes. Dose-dependent predominantly mild injection site reactions were the most common side-effect. Active treatment caused a gradual increase in fasting glucagon levels and, compared to placebo, a significantly blunted glucagon-induced increase in plasma glucose AUC (24%, P < 0.0001) and HGP (13%, P = 0.007) at the 400 mg/week dose. Six weeks treatment with ISIS 325568 in healthy volunteers attenuated glucagon-stimulated HGP and glucose excursions, supporting further evaluation of the GCGR antisense approach in patients with T2DM.

Does dipeptidyl peptidase-4 inhibition prevent the diabetogenic effects of glucocorticoids in men with the metabolic syndrome? A randomized controlled trial

Anti-inflammatory glucocorticoid (GC) therapy often induces hyperglycemia due to insulin resistance and islet-cell dysfunction. Incretin-based therapies may preserve glucose tolerance and pancreatic islet-cell function. In this study, we hypothesized that concomitant administration of the dipeptidyl peptidase-4 inhibitor sitagliptin and prednisolone in men at high risk to develop type 2 diabetes could protect against the GC-induced diabetogenic effects. Men with the metabolic syndrome but without diabetes received prednisolone 30 mg once daily plus sitagliptin 100 mg once daily (n=14), prednisolone (n=12) or sitagliptin alone (n=14) or placebo (n=12) for 14 days in a double-blind 2 × 2 randomized-controlled study. Glucose, insulin, C-peptide, and glucagon were measured in the fasted state and following a standardized mixed-meal test. β-cell function parameters were assessed both from a hyperglycemic-arginine clamp procedure and from the meal test. Insulin sensitivity (M-value) was measured by euglycemic clamp. Prednisolone increased postprandial area under the curve (AUC)-glucose by 17% (P<0.001 vs placebo) and postprandial AUC-glucagon by 50% (P<0.001). Prednisolone reduced 1st and 2nd phase glucose-stimulated- and combined hyperglycemia-arginine-stimulated C-peptide secretion (all P ≤ 0.001). When sitagliptin was added, both clamp-measured β-cell function (P=NS for 1st and 2nd phase vs placebo) and postprandial hyperglucagonemia (P=NS vs placebo) remained unaffected. However, administration of sitagliptin could not prevent prednisolone-induced increment in postprandial glucose concentrations (P<0.001 vs placebo). M-value was not altered by any treatment. Fourteen-day treatment with high-dose prednisolone impaired postprandial glucose metabolism in subjects with the metabolic syndrome. Concomitant treatment with sitagliptin improved various aspects of pancreatic islet-cell function, but did not prevent deterioration of glucose tolerance by GC treatment.

Impaired Crosstalk between Pulsatile Insulin and Glucagon Secretion in Prediabetic Individuals

Postprandial hyperglucagonemia is frequently found in patients with diabetes. Recently, a loss of the inverse relationship between pulsatile insulin and glucagon secretion has been reported in patients with type 2 diabetes. The crosstalk between pulsatile islet hormone secretion in prediabetic individuals has not yet been examined. Eleven individuals with impaired glucose tolerance and/or impaired fasting glucose and 13 nondiabetic controls were examined after mixed meal ingestion. Glucose, insulin, and glucagon levels were determined frequently and analyzed by deconvolution and cross-correlation methods. Postprandial glucose levels were higher in prediabetic individuals (P = 0.017). Insulin concentrations were not different between the groups (P = 0.29). Postprandial glucagon levels were higher in the impaired glucose tolerance/impaired fasting glucose individuals (P = 0.039). Pulsatile insulin and glucagon secretion was apparent in both groups, but there were no differences in the frequency or mass of insulin and glucagon pulses between the groups. An inverse relationship between the insulin and glucagon concentration time curves was found in the control subjects (P < 0.05). This association was not detectable in the prediabetic individuals. Increased postprandial glucagon concentrations in prediabetic individuals are accompanied by a loss of the pulsatile insulin-glucagon crosstalk. This suggests that disturbances in islet hormone pulsatility precede the actual manifestation of hyperglycemia.

Long-Term Metabolic and Hormonal Effects of Exenatide on Islet Transplant Recipients with Allograft Dysfunction

The initial success of islet transplantation (ITx) is followed by graft dysfunction (GDF) and insulin reintroduction. Exenatide, a GLP-1 agonist, increases insulin and decreases glucagon secretion and has potential for beta-cell regeneration. To improve functional islet mass, exenatide treatment was given to ITx recipients with GDF. The objective of this study was to assess metabolic and hormonal effects of exenatide in GDF. In this prospective, single-arm, nonrandomized study, 11 type 1 diabetes recipients of ITx with GDF had HbA1c, weight, insulin requirements, and 5-h mixed meal tolerance test (MMTT; with/without exenatide given before test) at baseline, 3, 6, and 12 months after initiating exenatide treatment. Baseline MMTT showed postprandial hyperglycemia and hyperglucagonemia. Daily exenatide treatment resulted in improved glucose, increased amylin/insulin ratio, and decreased proinsulin/insulin ratio as assessed by MMTT. Glucagon responses remained unchanged. Exenatide administration 1 h before MMTT showed decreased glucagon and glucose at 0 min and attenuation in their postprandial rise. Time-to-peak glucose was delayed, followed by insulin, proinsulin, amylin, and C-peptide, indicating glucose-driven insulin secretion. Five subjects completed 12-month follow-up. Glucose and glucagon suppression responses after MMTT with exenatide were no longer observed. Retrospective 3-month analysis of these subjects revealed higher and sustained glucagon levels that did not suppress as profoundly with exenatide administration, associated with higher glucose levels and increased C-peptide responses. In conclusion, Exenatide suppresses the abnormal postprandial hyperglucagonemia and hyperglycemia observed in GDF. Changes in amylin and proinsulin secretion may reflect more efficient insulin processing. Different degrees of responsiveness to exenatide were identified. These may help guide the clinical management of ITx recipients.

Long-term insulin independence and improvement in insulin secretion after supplemental islet infusion under exenatide and etanercept.

Progressive graft dysfunction (GDF) and loss of insulin independence (II) have been invariably observed in islet transplant recipients under the "Edmonton protocol." To reestablish II, we performed supplemental islet infusions (SI) in recipients of allogeneic islet transplant alone, displaying GDF. To improve the engraftment and long-term graft function of SI, exenatide (EXN) and etanercept treatment at islet infusion, and long-term EXN treatment were tested in a non-randomized pilot clinical trial. Patients with GDF received SI under Edmonton-like immunosuppression with daclizumab induction, either without interventions (SI-control; n=5) or with EXN and etanercept treatment (SI-EXN; n=4). Clinical and metabolic profiles were assessed during 18-month follow-up. Long-term II (18 months) was observed in 100% of SI-EXN and in 20% of SI-control (P=0.04). SI-EXN subjects demonstrated restoration of function better than that seen after initial islet infusions. Comparison of SI-EXN and SI-control groups demonstrated better responses in SI-EXN subjects at 3 months post-SI. During the 18 months of follow-up, function was sustained in the SI-EXN subjects better than in SI-controls. Acute effects of EXN during mixed meal tolerance test and intravenous glucose tolerance test results in improved first and second phase insulin release in response to intravenous glucose tolerance test and suppressed postprandial hyperglucagonemia after mixed meal tolerance test. These results suggest that the combination of EXN and etanercept improve engraftment and long-term islet survival and function in subjects undergoing SI. This data, however, must be interpreted with some caution because of small sample size, lack of randomization, and sequential comparison with historical controls.

Too Much Glucagon, Too Little Insulin

OBJECTIVE—To determine the time course of changes in glucagon and insulin secretion in children with recently diagnosed type 1 diabetes.RESEARCH DESIGN AND METHODS—Glucagon and C-peptide concentrations were determined in response to standard mixed meals in 23 patients with type 1 diabetes aged 9.4 ± 4.6 years, beginning within 6 weeks of diagnosis, and every 3 months thereafter for 1 year.RESULTS—Glucagon secretion in response to a physiologic stimulus (mixed meal) increased by 37% over 12 months, while C-peptide secretion declined by 45%. Fasting glucagon concentrations remained within the normal (nondiabetic) reference range.CONCLUSIONS—Postprandial hyperglucagonemia worsens significantly during the first year after diagnosis of type 1 diabetes and may represent a distinct therapeutic target. Fasting glucagon values may underestimate the severity of hyperglucagonemia. The opposing directions of abnormal glucagon and C-peptide secretion over time support the link between dysregulated glucagon secretion and declining β-cell function.