Glucagon Hormone Research Articles

Enteropancreatic hormone changes in caloric-restricted diet interventions associate with post-intervention weight maintenance

Background & AimsTo explore enteropancreatic hormone changes during isocaloric-restricted dietary interventions and their impact on post-intervention weight maintenance. Methods253 individuals with overweight / obesity and prediabetes were randomly assigned to 25% isocaloric-restricted diets: Control diet, Traditional Jiangnan diet or Mediterranean diet. Serum hormones and clinical indices were evaluated at 0, 3 and 6 months. Body weight values were collected again 6 months after completing interventions. ResultsWe observed decreased fasting and post-glucose load levels of glucagon, amylin, peptide YY, and glucagon-like peptide-1 (GLP-1) while increased ghrelin at three months after 25% caloric restriction (CR) of three dietary interventions, and most of these changes sustained to six month-treatment. Interestingly, changes in appetite-inhibitory hormones glucagon, amylin and GLP-1 showed positive associations with body weight change while appetite-promoting hormone ghrelin showed inverse association during intervention. Furthermore, subjects with more reduction in amylin and GLP-1, or more increase in ghrelin during intervention showed greater increase in body weight after completing intervention. ConclusionsCR intervention results in consistent hormone signatures regardless of dietary patterns. More changes in amylin, GLP-1 or ghrelin levels during CR is associated with poor weight maintenance after intervention, supporting that CR-induced hormone changes as biomarkers for predicting weight maintenance after intervention. Trial registrationClinicaltrials.gov NCT03856762

Phosphoproteomics-directed manipulation reveals SEC22B as a hepatocellular signaling node governing metabolic actions of glucagon

The peptide hormone glucagon is a fundamental metabolic regulator that is also being considered as a pharmacotherapeutic option for obesity and type 2 diabetes. Despite this, we know very little regarding how glucagon exerts its pleiotropic metabolic actions. Given that the liver is a chief site of action, we performed in situ time-resolved liver phosphoproteomics to reveal glucagon signaling nodes. Through pathway analysis of the thousands of phosphopeptides identified, we reveal “membrane trafficking” as a dominant signature with the vesicle trafficking protein SEC22 Homolog B (SEC22B) S137 phosphorylation being a top hit. Hepatocyte-specific loss- and gain-of-function experiments reveal that SEC22B was a key regulator of glycogen, lipid and amino acid metabolism, with SEC22B-S137 phosphorylation playing a major role in glucagon action. Mechanistically, we identify several protein binding partners of SEC22B affected by glucagon, some of which were differentially enriched with SEC22B-S137 phosphorylation. In summary, we demonstrate that phosphorylation of SEC22B is a hepatocellular signaling node mediating the metabolic actions of glucagon and provide a rich resource for future investigations on the biology of glucagon action.

Larval density can be used to predict genetic modifiers of glucagon signaling in Drosophila melanogaster.

Obesity is a growing concern. 42.3% of people in the U.S were considered obese between 2017-2018. Much is still unknown about the genetic components that contribute to weight gain. In humans, the hormone glucagon is a major contributor to the body's energy regulation as it signals for the breakdown of lipids. Treatments targeting the glucagon pathway have helped patients with both weight loss and appetite suppression. Understanding the genetic modifiers of glucagon signaling and its downstream pathways could enable the development of a wider variety of effective therapeutics. In this study, we blocked the glucagon pathway in Drosophila melanogaster by reducing the expression of the fly ortholog of the glucagon receptor (AKHR). We then crossed our model to the Drosophila Genetic Reference Panel (DGRP) and looked for natural variation in fat content. We used variation in larval density to identify candidate modifier genes through a genome-wide association study. We then tested these modifier genes by increasing or decreasing their expression in the AKHR model. We screened these candidates initially with the same density assay used in the original study to narrow down to four candidate genes that substantially impacted the density of the larvae: THADA, AmyD, GluRIIC, and CG9826. We further characterized these candidates using biochemical assays to analyze stored metabolites such as triglycerides, glucose, glycogen, and protein under control, high sugar, and high fat conditions to see if the larvae are resistant to environmental changes. Our results indicate consistency between the results of the density assay and direct measurement of metabolite levels. In particular, THADA and AmyD are highlighted as interesting genes for additional study. We hope to improve our understanding of the glucagon signaling pathway, obesity, and lipid metabolism. We also aim to provide candidate genes that can be regarded as future therapeutic targets.

Fish-hunting cone snail disrupts prey’s glucose homeostasis with weaponized mimetics of somatostatin and insulin

Venomous animals have evolved diverse molecular mechanisms to incapacitate prey and defend against predators. Most venom components disrupt nervous, locomotor, and cardiovascular systems or cause tissue damage. The discovery that certain fish-hunting cone snails use weaponized insulins to induce hypoglycemic shock in prey highlights a unique example of toxins targeting glucose homeostasis. Here, we show that, in addition to insulins, the deadly fish hunter, Conus geographus, uses a selective somatostatin receptor 2 (SSTR2) agonist that blocks the release of the insulin-counteracting hormone glucagon, thereby exacerbating insulin-induced hypoglycemia in prey. The native toxin, Consomatin nG1, exists in several proteoforms with a minimized vertebrate somatostatin-like core motif connected to a heavily glycosylated N-terminal region. We demonstrate that the toxin’s N-terminal tail closely mimics a glycosylated somatostatin from fish pancreas and is crucial for activating the fish SSTR2. Collectively, these findings provide a stunning example of chemical mimicry, highlight the combinatorial nature of venom components, and establish glucose homeostasis as an effective target for prey capture.

Gut-Liver-Pancreas Axis Crosstalk in Health and Disease: From the Role of Microbial Metabolites to Innovative Microbiota Manipulating Strategies.

The functions of the gut are closely related to those of many other organs in the human body. Indeed, the gut microbiota (GM) metabolize several nutrients and compounds that, once released in the bloodstream, can reach distant organs, thus influencing the metabolic and inflammatory tone of the host. The main microbiota-derived metabolites responsible for the modulation of endocrine responses are short-chain fatty acids (SCFAs), bile acids and glucagon-like peptide 1 (GLP-1). These molecules can (i) regulate the pancreatic hormones (insulin and glucagon), (ii) increase glycogen synthesis in the liver, and (iii) boost energy expenditure, especially in skeletal muscles and brown adipose tissue. In other words, they are critical in maintaining glucose and lipid homeostasis. In GM dysbiosis, the imbalance of microbiota-related products can affect the proper endocrine and metabolic functions, including those related to the gut-liver-pancreas axis (GLPA). In addition, the dysbiosis can contribute to the onset of some diseases such as non-alcoholic steatohepatitis (NASH)/non-alcoholic fatty liver disease (NAFLD), hepatocellular carcinoma (HCC), and type 2 diabetes (T2D). In this review, we explored the roles of the gut microbiota-derived metabolites and their involvement in onset and progression of these diseases. In addition, we detailed the main microbiota-modulating strategies that could improve the diseases' development by restoring the healthy balance of the GLPA.

Hyperglycemia influences the cell proliferation and death of the rat endocrine pancreas in the neonatal period

AimsTo evaluate the cell proliferation and death, and structural morphology of the pancreatic islet cells of the rats with hyperglycemia in the first month of life and compare to those of the control rats. Main methodsFemale Sprague-Dawley newborn rats received Streptozotocin (a beta-cytotoxic drug) at birth for diabetes induction. Control and hyperglycemic animals were euthanized on different days of life: 5, 10, 15, and 30. The pancreas was collected and processed for immunohistochemical analysis of cleaved Caspase-3 (cell death), Ki-67 (cell proliferation), PDX-1 (transcription factor responsible for insulin synthesis), and endocrine hormones (insulin, glucagon, and somatostatin). Key findingsControl females showed a higher percentage (%) of Ki-67-positive(+) cells on D10 and D15, a higher % of insulin+ and somatostatin+ cells on D15 and D30, a lower % of PDX-1+ cells on D10, and a higher % of glucagon+ cells on D10 and D30. Hyperglycemic females showed a lower % of Ki-67+ cells on D15, a higher % of cleaved Caspase-3+ cells on D15, and insulin+ cells on D15 and D30. In the comparison among the experimental groups, the hyperglycemic females showed an increased % of cleaved Caspase-3+ and Ki-67+ cells and a lower % of PDX-1+ cells. SignificanceThis study enabled a better understanding of the abnormal pancreas development regarding cellular proliferation, apoptosis, and hormonal synthesis in the neonatal period. Thus, the pancreatic islets of hyperglycemic rats do not reestablish the normal endocrine cell population, and cellular apoptosis overcame the proliferative activity of these cells.

Neuronal glucose sensing mechanisms and circuits in the control of insulin and glucagon secretion.

Glucose homeostasis is mainly under the control of the pancreatic islet hormones insulin and glucagon, which, respectively, stimulate glucose uptake and utilization by liver, fat, and muscle and glucose production by the liver. The balance between the secretions of these hormones is under the control of blood glucose concentrations. Indeed, pancreatic islet β-cells and α-cells can sense variations in glycemia and respond by an appropriate secretory response. However, the secretory activity of these cells is also under multiple additional metabolic, hormonal, and neuronal signals that combine to ensure the perfect control of glycemia over a lifetime. The central nervous system (CNS), which has an almost absolute requirement for glucose as a source of metabolic energy and thus a vital interest in ensuring that glycemic levels never fall below ∼5 mM, is equipped with populations of neurons responsive to changes in glucose concentrations. These neurons control pancreatic islet cell secretion activity in multiple ways: through both branches of the autonomic nervous system, through the hypothalamic-pituitary-adrenal axis, and by secreting vasopressin (AVP) in the blood at the level of the posterior pituitary. Here, we present the autonomic innervation of the pancreatic islets; the mechanisms of neuron activation by a rise or a fall in glucose concentration; how current viral tracing, chemogenetic, and optogenetic techniques allow integration of specific glucose sensing neurons in defined neuronal circuits that control endocrine pancreas function; and, finally, how genetic screens in mice can untangle the diversity of the hypothalamic mechanisms controlling the response to hypoglycemia.

Fasting and post prandial pancreatic and enteroendocrine hormone levels in obese and non-obese participants

Circulating insulin levels are known to be increased in people with higher body mass index (BMI) due to effects of adiposity on insulin resistance, whilst gut hormones have a more complex relationship, with fasting peptideYY (PYY) reported to be inversely related to BMI. This study aimed to further explore fasting and post prandial pancreatic and gut hormone concentrations in plasma samples from obese and non-obese participants. Participants with healthy BMI (n=15), overweight BMI (n=29) and obesity (n=161) had samples taken fasting and 30 min post mixed liquid meal for analysis of glucagon-like peptide-1 (GLP-1), PYY, glucose-dependent insulinotropic polypeptide (GIP), insulin and glucagon. Data visualiation used linear discriminant analysis for dimensionality reduction, to visualise the data and assess scaling of each hormone. Fasting levels of insulin, GIP and PYY were shown to be key classifiers between the 3 groups on ANCOVA analysis, with an observation of increased GIP levels in overweight, but not obese participants. In non-obese subjects, fasting GIP, PYY and insulin correlated with BMI, whereas in subjects with obesity only the pancreatic hormones glucagon and insulin correlated with BMI. Concentrations of total GLP-1 in the fasting state correlated strongly with glucagon levels, highlighting potential assay cross-reactivities. The study, which included a relatively large number of subjects with severe obesity, supported previous evidence of BMI correlating negatively with fasting PYY and positively with fasting insulin. The observation of increased fasting GIP levels in overweight but not obese participants deserves further validation and mechanistic investigation.

Bihormonal fully closed-loop system for the treatment of type 1 diabetes: a real-world multicentre, prospective, single-arm trial in the Netherlands

Management of insulin administration for intake of carbohydrates and physical activity can be burdensome for people with type 1 diabetes on hybrid closed-loop systems. Bihormonal fully closed-loop (FCL) systems could help reduce this burden. In this trial, we assessed the long-term performance and safety of a bihormonal FCL system. The FCL system (Inreda AP; Inreda Diabetic, Goor, Netherlands) that uses two hormones (insulin and glucagon) was assessed in a 1 year, multicentre, prospective, single-arm intervention trial in adults with type 1 diabetes. Participants were recruited in eight outpatient clinics in the Netherlands. We included adults with type 1 diabetes aged 18-75 years who had been using flash glucose monitoring or continuous glucose monitors for at least 3 months. Study visits were integrated into standard care, usually every three months, to evaluate glycaemic control, adverse events, and person-reported outcomes. The primary endpoint was time in range (TIR; glucose concentration 3·9-10·0 mmol/L) after 1 year. The study is registered in the Dutch Trial Register, NL9578. Between June 1, 2021, and March 2, 2022, we screened 90 individuals and enrolled 82 participants; 78 were included in the analyses. 79 started the intervention and 71 were included in the 12 month analysis. Mean age was 47.7 (SD 12·4) years and 38 (49%) were female participants. The mean preintervention TIR of participants was 55·5% (SD 17·2). After 1 year of FCL treatment, mean TIR was 80·3% (SD 5·4) and median time below range was 1·36% (IQR 0·80-2·11). Questionnaire scores improved on Problem Areas in Diabetes (PAID) from 30·0 (IQR 18·8-41·3) preintervention to 10·0 (IQR 3·8-21·3; p<0·0001) at 12 months and on World Health Organization-Five Well-Being Index (WHO-5) from 60·0 (IQR 44·0-72·0) preintervention to 76·0 (IQR 60·0-80·0; p<0·0001) at 12 months. Five serious adverse events were reported (one cerebellar stroke, two severe hypoglycaemic, and two hyperglycaemic events). Real-world data obtained in this trial demonstrate that use of the bihormonal FCL system was associated with good glycaemic control in patients who completed 1 year of treatment, and could help relieve these individuals with type 1 diabetes from making treatment decisions and the burden of carbohydrate counting. Inreda Diabetic.

Endocrine disorders in burn disease. Literature review

The purpose of the review is to highlight clinically hidden variants of hormonal dysfunctions in burn disease, which strongly determine the peculiarities of the course of the pathological condition but are often overlooked by clinicians. Based on available literary sources, this study provides a comprehensive analysis of specialised medical reports from both domestic and foreign researchers. The focus of this analysis was on compensatory and pathological shifts in hormonal regulation of the body in individuals suffering from local heat injury. The collected scientific data is expected to be useful to practitioners in the field of combustiology in their practical activities. Damage to the endocrine glands is one of the key pathogenetic factors of local thermal injury, but the intracellular mechanisms of the influence of burn disease on these processes remain poorly understood. The criticality of burn injuries often leads to hypodiagnosis of endocrine disorders, which are indeed typical and rapidly developing. The neuroendocrine response to severe burns is a multisystem coordinated response of the body, which can not only maintain homeostasis and play a protective role in critical conditions but also cause tissue damage, realising the properties of a «double‑edged sword». Burns covering more than 40% of the total surface area of the body are accompanied by a stress reaction and hyperinflammation with a steady increase in the secretion of catecholamines, glucocorticoids, and cytokines. Classic studies confirm that a sharp post‑burn increase in stress hormones (adrenaline, norepinephrine, glucagon, and cortisol) contributes to the development of hyperglycemia, a systemic catabolic state, and multiple organ dysfunction. It has been established that the hypothalamic‑pituitary axis is responsible for fluctuations in the content of pituitary hormones in the blood serum of patients with local thermal lesions. After severe burns, the plasma renin‑angiotensin‑aldosterone system is activated, and the level of some hormones increases for more than 2 months after the injury.

Preterm Delivery in Obese Mothers Predicts Tumor Necrosis Factor-α Levels in Breast Milk.

Background: Breast milk (BM) is a nutritive fluid that is rich in bioactive components such as hormones and cytokines that can shape the newborn's feeding habits and program the newborn's immature immune system. BM components can change under different scenarios that include maternal body mass index (BMI) and premature birth. This study aimed to study the interaction of premature status or maternal obesity on the hormonal and cytokine profile in BM according to the sex of the offspring. Materials and Methods: We recruited 31 women with preterm births from the Centro de Alta Especialidad Dr. Rafael Lucio in Mexico. Luminex multiplexing assay was used for quantifying cytokine profile of monocyte chemoattractant protein-1, tumor necrosis factor (TNF)-α, interferon-γ, interleukin (IL)1-β, IL-2, IL-4, IL-6, IL-7, and hormones insulin, ghrelin, leptin, and glucagon in mature BM samples. Biological modeling was performed to predict the interaction between cytokines and hormones, maternal BMI status, infant birth sex, parity, and gestational age. Results: BM multiplex analysis showed positive correlations for TNF-α and increasing prematurity and for higher maternal BMI and IL-2, IL-4, and IL-6 cytokines. Multiple regression models identified an interaction between maternal BMI and gestational weeks in male infants that is associated to TNF-α accumulation in BM. Biological modeling predicts that preterm delivery in mothers with obesity modulates TNF- α levels in mature BM of women with male offspring. Conclusion: Prematurity and obesity modify BM's immune profile. TNF- α expression increases as prematurity increases, and maternal BMI correlates positively with increases in IL-2, IL-6, and IL-4. Our multiple regression model also shows that maternal BMI and gestational weeks in male infants predict TNF-α.

Serotonergic neurons are involved in the counter-regulatory response to hypoglycemia.

Intensive insulin therapy provides optimal glycemic control in patients with diabetes. However, intensive insulin therapy causes so-called iatrogenic hypoglycemia as a major adverse effect. The ventromedial hypothalamus (VMH) has been described as the primary brain area initiating the counter-regulatory response (CRR). Nevertheless, the VMH receives projections from other brain areas which could participate in the regulation of the CRR. In particular, studies suggest a potential role of the serotonin (5-HT) network. Thus, the objective of this study was to determine the contribution of 5-HT neurons in CRR control. Complementary approaches have been used to test this hypothesis in quantifying the level of 5-HT in several brain areas by HPLC in response to insulin-induced hypoglycemia, measuring the electrical activity of dorsal raphe (DR) 5-HT neurons in response to insulin or decreased glucose level by patch-clamp electrophysiology; and measuring the CRR hormone glucagon as an index of the CRR to the modulation of the activity of 5-HT neurons using pharmacological or pharmacogenetic approaches. HPLC measurements show that the 5HIAA/5HT ratio is increased in several brain regions including the VMH in response to insulin-induced hypoglycemia. Patch-clamp electrophysiological recordings show that insulin, but not decreased glucose level, increases the firing frequency of DR 5-HT neurons in the DR. In vivo, both the pharmacological inhibition of 5-HT neurons by intraperitoneal injection of the 5-HT1A receptor agonist 8-OH-DPAT or the chemogenetic inhibition of these neurons reduce glucagon secretion, suggesting an impaired CRR. Taken together, these data highlight a new neuronal network involved in the regulation of the CRR. In particular, this study shows that DR 5-HT neurons detect iatrogenic hypoglycemia in response to the increased insulin level and may play an important role in the regulation of CRR.

Diabetes Risk Prediction using Feature Importance Extreme Gradient Boosting (XGBoost)

Diabetes results from impaired pancreatic function as a producer of insulin and glucagon hormones, which regulate glucose levels in the blood. People with diabetes today are not only experienced adults, but pre-diabetes has been identified since the age of children and adolescents. Early prediction of diabetes can make it easier for doctors and patients to intervene as soon as possible so that the risk of complications can be reduced. One of the uses of medical data from diabetes patients is to produce a model that medical personnel can use to predict and identify diabetes in patients. Various techniques are used to provide the earliest possible prediction of diabetes based on the symptoms experienced by diabetic patients, including the use of machine learning. People can use machine learning to generate models based on historical data from diabetic patients, and predictions are made with the model. In this study, extreme gradient boosting is the machine learning technique for predicting diabetes (xgboost) using XGBoost with importance features. The diabetes dataset used in this study comes from the early stage diabetes risk prediction dataset published by UCI Machine Learning, which has 520 records and 16 attributes. The diabetes prediction model using xgboost is displayed as a tree. The model precision result in this study was 98.71%, for the F1 score was 98.18%. The accuracy obtained based on the best 10 attributes using the importance of the XGBoost feature is 98.72%.&#x0D;

The effect of hormones insulin and glucagon on ubiquitin modifications elucidated by proteomics in liver cells

AimsInsulin action is intertwined with changing levels of glucose and counter-regulatory hormone glucagon. While insulin lowers blood sugar level, glucagon raises it by promoting the breakdown of the stored glycogen in liver and releases glucose into the bloodstream. The hormones insulin and glucagon are key in the pathogenesis of type 2 diabetes (T2D). Insulin resistance is a primary predisposing factor for diabetes. Phosphorylation of insulin signaling molecules is altered in the insulin-resistant state. However, ubiquitin (Ub) modifications in insulin-resistant state are relatively understudied. To dissect the underlying mechanisms, we performed a proteomics study on hepatoma cells to study the regulation of ubiquitination by insulin and glucagon. Materials and methodsWe performed western blotting, immunoprecipitations, and affinity pull down using tandem Ub binding entities (TUBE) reagents on hepatoma cells treated with insulin or glucagon. Next, we performed MS/MS analysis on Ub-linkage specific affinity pull down samples. Gene ontology analysis and protein-protein interaction network analysis was performed using DAVID GO and STRING db, respectively. Key findingsThe ubiquitination pattern of total Ub, K48-linked Ub, and K63-linked Ub was altered with the treatment of hormones insulin and glucagon. Ubiquitination in immunoprecipitated samples showed enrichment with total Ub and K48-linked Ub but not with K63-linked Ub. Ubiquitination by treatment with hormones mainly enriched key signaling pathways MAPK, Akt, oxidative stress etc. SignificanceOur study identified key altered proteins and signal transduction pathways which aids in understanding the mechanisms of hormonal action on ubiquitination and identify new therapeutic targets for T2D.

Renal neuroendocrine tumors: clinical and molecular pathology with an emphasis on frequent association with ectopic Cushing syndrome

Renal neuroendocrine tumors (RenNETs) are rare malignancies with largely unknown biology, hormone expression, and genetic abnormalities. This study aims to improve our understanding of the RenNETs with emphasis of functional, hormonal, and genetic features. Surgically resected RenNETs (N = 13) were retrieved, and immunohistochemistry and next-generation sequencing (NGS) were performed in all cases. In addition, all published RenNETs were systematically reviewed. Our cohort (4 men and 9 women, mean age 42, mean tumor size 7.6 cm) included 2 patients with Cushing syndrome (CS). WHO grade (23% G1, 54% G2, and 23% G3) and tumor progression did not correlate. CS-associated RenNETs (CS-RenNETs) showed a solid and eosinophilic histology and stained for ACTH, while the remaining non-functioning tumors had a trabecular pattern and expressed variably hormones somatostatin (91%), pancreatic polypeptide (63%), glucagon (54%), and serotonin (18%). The transcription factors ISL1 and SATB2 were expressed in all non-functioning, but not in CS-RenNETs. NGS revealed no pathogenic alterations or gene fusions. In the literature review (N = 194), 15 (8%) of the patients had hormonal syndromes, in which CS being the most frequent (7/15). Large tumor size and presence of metastasis were associated with shorter patients’ survival (p < 0.01). RenNETs present as large tumors with metastases. CS-RenNETs differ through ACTH production and solid-eosinophilic histology from the non-functioning trabecular RenNETs that produce pancreas-related hormones and express ISL1 and SATB2. MEN1 or DAXX/ARTX abnormalities and fusion genes are not detected in RenNETs, indicating a distinct yet unknown molecular pathogenesis.

100 years of glucagon and 100 more.

The peptide hormone glucagon, discovered in late 1922, is secreted from pancreatic alpha cells and is an essential regulator of metabolic homeostasis. This review summarises experiences since the discovery of glucagon regarding basic and clinical aspects of this hormone and speculations on the future directions for glucagon biology and glucagon-based therapies. The review was based on the international glucagon conference, entitled 'A hundred years with glucagon and a hundred more', held in Copenhagen, Denmark, in November 2022. The scientific and therapeutic focus of glucagon biology has mainly been related to its role in diabetes. In type 1 diabetes, the glucose-raising properties of glucagon have been leveraged to therapeutically restore hypoglycaemia. The hyperglucagonaemia evident in type 2 diabetes has been proposed to contribute to hyperglycaemia, raising questions regarding underlying mechanism and the importance of this in the pathogenesis of diabetes. Mimicry experiments of glucagon signalling have fuelled the development of several pharmacological compounds including glucagon receptor (GCGR) antagonists, GCGR agonists and, more recently, dual and triple receptor agonists combining glucagon and incretin hormone receptor agonism. From these studies and from earlier observations in extreme cases of either glucagon deficiency or excess secretion, the physiological role of glucagon has expanded to also involve hepatic protein and lipid metabolism. The interplay between the pancreas and the liver, known as the liver-alpha cell axis, reflects the importance of glucagon for glucose, amino acid and lipid metabolism. In individuals with diabetes and fatty liver diseases, glucagon's hepatic actions may be partly impaired resulting in elevated levels of glucagonotropic amino acids, dyslipidaemia and hyperglucagonaemia, reflecting a new, so far largely unexplored pathophysiological phenomenon termed 'glucagon resistance'. Importantly, the hyperglucagonaemia as part of glucagon resistance may result in increased hepatic glucose production and hyperglycaemia. Emerging glucagon-based therapies show a beneficial impact on weight loss and fatty liver diseases and this has sparked a renewed interest in glucagon biology to enable further pharmacological pursuits.

Hypoglycaemia frequency and physiological response after double or triple doses of once-weekly insulin icodec vs once-daily insulin glargine U100 in type 2 diabetes: a randomised crossover trial

Aims/hypothesisThis study compared the frequency of hypoglycaemia, time to hypoglycaemia and recovery from hypoglycaemia after double or triple doses of once-weekly insulin icodec vs once-daily insulin glargine U100. Furthermore, the symptomatic and counterregulatory responses to hypoglycaemia were compared between icodec and glargine U100 treatment.MethodsIn a randomised, single-centre (Department of Internal Medicine, Division of Endocrinology and Diabetology, Medical University of Graz, Graz, Austria), open-label, two-period crossover trial, individuals with type 2 diabetes (age 18–72 years, BMI 18.5–37.9 kg/m2, HbA1c ≤75 mmol/mol [≤9.0%]) treated with basal insulin with or without oral glucose-lowering drugs received once-weekly icodec (for 6 weeks) and once-daily glargine U100 (for 11 days). Total weekly doses were equimolar based on individual titration of daily glargine U100 during the run-in period (target fasting plasma glucose [PG]: 4.4–7.2 mmol/l). Randomisation was carried out by assigning a randomisation number to each participant in ascending order, which encoded to one of two treatment sequences via a randomisation list prepared prior to the start of the trial. At steady state, double and triple doses of icodec and glargine U100 were administered followed by hypoglycaemia induction: first, euglycaemia was maintained at 5.5 mmol/l by variable i.v. infusion of glucose; glucose infusion was then terminated, allowing PG to decrease to no less than 2.5 mmol/l (target PGnadir). The PGnadir was maintained for 15 min. Euglycaemia was restored by constant i.v. glucose (5.5 mg kg−1 min−1). Hypoglycaemic symptoms score (HSS), counterregulatory hormones, vital signs and cognitive function were assessed at predefined PG levels towards the PGnadir.ResultsHypoglycaemia induction was initiated in 43 and 42 participants after double dose of icodec and glargine U100, respectively, and in 38 and 40 participants after triple doses, respectively. Clinically significant hypoglycaemia, defined as PGnadir <3.0 mmol/l, occurred in comparable proportions of individuals treated with icodec vs glargine U100 after double (17 [39.5%] vs 15 [35.7%]; p=0.63) and triple (20 [52.6%] vs 28 [70.0%]; p=0.14) doses. No statistically significant treatment differences were observed in the time to decline from PG values of 5.5 mmol/l to 3.0 mmol/l (2.9–4.5 h after double dose and 2.2–2.4 h after triple dose of the insulin products). The proportion of participants with PGnadir ≤2.5 mmol/l was comparable between treatments after double dose (2 [4.7%] for icodec vs 3 [7.1%] for glargine U100; p=0.63) but higher for glargine U100 after triple dose (1 [2.6%] vs 10 [25.0%]; p=0.03). Recovery from hypoglycaemia by constant i.v. glucose infusion took <30 min for all treatments. Analyses of the physiological response to hypoglycaemia only included data from participants with PGnadir <3.0 mmol/l and/or the presence of hypoglycaemic symptoms; in total 20 (46.5%) and 19 (45.2%) individuals were included after a double dose of icodec and glargine U100, respectively, and 20 (52.6%) and 29 (72.5%) individuals were included after a triple dose of icodec and glargine U100, respectively. All counterregulatory hormones (glucagon, adrenaline [epinephrine], noradrenaline [norepinephrine], cortisol and growth hormone) increased during hypoglycaemia induction with both insulin products at both doses. Following triple doses, the hormone response was greater with icodec vs glargine U100 for adrenaline at PG3.0 mmol/l (treatment ratio 2.54 [95% CI 1.69, 3.82]; p<0.001), and cortisol at PG3.0 mmol/l (treatment ratio 1.64 [95% CI 1.13, 2.38]; p=0.01) and PGnadir (treatment ratio 1.80 [95% CI 1.09, 2.97]; p=0.02). There were no statistically significant treatment differences in the HSS, vital signs and cognitive function.Conclusions/interpretationDouble or triple doses of once-weekly icodec lead to a similar risk of hypoglycaemia compared with double or triple doses of once-daily glargine U100. During hypoglycaemia, comparable symptomatic and moderately greater endocrine responses are elicited by icodec vs glargine U100.Trial registrationClinicalTrials.gov NCT03945656.FundingThis study was funded by Novo Nordisk A/S.Graphical

Ghrelin does not impact the blunted counterregulatory response to recurrent hypoglycemia in mice.

Recurrent episodes of insulin-induced hypoglycemia in patients with diabetes mellitus can result in hypoglycemia-associated autonomic failure (HAAF), which is characterized by a compromised response to hypoglycemia by counterregulatory hormones (counterregulatory response; CRR) and hypoglycemia unawareness. HAAF is a leading cause of morbidity in diabetes and often hinders optimal regulation of blood glucose levels. Yet, the molecular pathways underlying HAAF remain incompletely described. We previously reported that in mice, ghrelin is permissive for the usual CRR to insulin-induced hypoglycemia. Here, we tested the hypothesis that attenuated release of ghrelin both results from HAAF and contributes to HAAF. C57BL/6N mice, ghrelin-knockout (KO) + control mice, and GhIRKO (ghrelin cell-selective insulin receptor knockout) + control mice were randomized to one of three treatment groups: a "Euglycemia" group was injected with saline and remained euglycemic; a 1X hypoglycemia ("1X Hypo") group underwent a single episode of insulin-induced hypoglycemia; a recurrent hypoglycemia ("Recurrent Hypo") group underwent repeated episodes of insulin-induced hypoglycemia over five successive days. Recurrent hypoglycemia exaggerated the reduction in blood glucose (by ~30%) and attenuated the elevations in plasma levels of the CRR hormones glucagon (by 64.5%) and epinephrine (by 52.9%) in C57BL/6N mice compared to a single hypoglycemic episode. Yet, plasma ghrelin was equivalently reduced in "1X Hypo" and "Recurrent Hypo" C57BL/6N mice. Ghrelin-KO mice exhibited neither exaggerated hypoglycemia in response to recurrent hypoglycemia, nor any additional attenuation in CRR hormone levels compared to wild-type littermates. Also, in response to recurrent hypoglycemia, GhIRKO mice exhibited nearly identical blood glucose and plasma CRR hormone levels as littermates with intact insulin receptor expression (floxed-IR mice), despite higher plasma ghrelin in GhIRKO mice. These data suggest that the usual reduction of plasma ghrelin due to insulin-induced hypoglycemia is unaltered by recurrent hypoglycemia and that ghrelin does not impact blood glucose or the blunted CRR hormone responses during recurrent hypoglycemia.

Glucagon receptor family in GtoPdb v.2023.1

The glucagon family of receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on the Glucagon receptor family [165]) are activated by the endogenous peptide (27-44 aa) hormones glucagon, glucagon-like peptide 1, glucagon-like peptide 2, glucose-dependent insulinotropic polypeptide (also known as gastric inhibitory polypeptide), GHRH and secretin. One common precursor (GCG) generates glucagon, glucagon-like peptide 1 and glucagon-like peptide 2 peptides [121]. For a recent review on the current understanding of the structures of GLP-1 and GLP-1R, the molecular basis of their interaction, and the associated signaling events see de Graaf et al., 2016 [90].

The ubiquitination status of the glucagon receptor determines signal bias

The pancreatic hormone glucagon activates the glucagon receptor (GCGR), a class B seven-transmembrane G protein-coupled receptor that couples to the stimulatory heterotrimeric G protein and provokes PKA-dependent signaling cascades vital to hepatic glucose metabolism and islet insulin secretion. Glucagon-stimulation also initiates recruitment of the endocytic adaptors, βarrestin1 and βarrestin2, which regulate desensitization and internalization of the GCGR. Unlike many other G protein-coupled receptors, the GCGR expressed at the plasma membrane is constitutively ubiquitinated and upon agonist-activation, internalized GCGRs are deubiquitinated at early endosomes and recycled via Rab4-containing vesicles. Herein we report a novel link between the ubiquitination status and signal transduction mechanism of the GCGR. In the deubiquitinated state, coupling of the GCGR to Gs is diminished, while binding to βarrestin is enhanced with signaling biased to a βarrestin1-dependent p38 mitogen activated protein kinase (MAPK) pathway. This ubiquitin-dependent signaling bias arises through the modification of lysine333 (K333) on the cytoplasmic face of transmembrane helix V. Compared with the GCGR-WT, the mutant GCGR-K333R has impaired ubiquitination, diminished G protein coupling, and PKA signaling but unimpaired potentiation of glucose-stimulated-insulin secretion in response to agonist-stimulation, which involves p38 MAPK signaling. Both WT and GCGR-K333R promote the formation of glucagon-induced βarrestin1-dependent p38 signaling scaffold that requires canonical upstream MAPK-Kinase3, but is independent of Gs, Gi, and βarrestin2. Thus, ubiquitination/deubiquitination at K333 in the GCGR defines the activation of distinct transducers with the potential to influence various facets of glucagon signaling in health and disease.