Browsing by Subject "Glucagon"

Now showing 1 - 10 of 14
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    Bioengineering Against Fibrils and Hypoglycemia: Studies on Insulin, Glucagon and the Fusion of Both
    (2024-12) Molina, Nicolas Varas; Weiss, Michael; Georgiadis, Millie; Hurley, Thomas; Wells, Clark; Dahlem, Andrew
    Insulin drugs are vital for blood glucose control in type 1 and late-stage type 2 diabetes mellitus. Unfortunately, however, they have two notable problems: (1) an intrinsic propensity to physical degradation (amyloid-like fibrillation), which reduces potency and can lead to occlusion of insulin pumps’ catheters, impairing timely drug administration; and (2) an ever-present risk for iatrogenic hypoglycemia with potential acute (or even fatal) consequences and chronic sequelae. The risk of hypoglycemia, its immediate and long-term complications, and associated anxiety can confound efforts to achieve effective glycemic control. Further, insulin’s physical instability impacts worldwide distribution by imposing a refrigeration requirement—often a barrier to global access. A combined solution to these two problems could benefit patients worldwide. To circumvent these limitations, glucose-responsive technologies have been sought to reduce hypoglycemic risk; diverse strategies have focused on novel devices, delivery modes, or protein engineering. In the present doctoral work, we describe an alternative glucose-responsive approach that exploits an endogenous glucose-dependent switch in hepatic physiology: preferential insulin signaling (under hyperglycemic conditions) versus preferential counter-regulatory glucagon signaling (under hypoglycemic conditions). Glucagon, traditionally regarded as a counter-regulatory hormone, has been underutilized in routine glucose control due to a marked propensity to fibrillation. Motivated by the pilot success of a counterintuitive strategy—co-infusion of insulin and glucagon—we have bioengineered and tested a fibrillation-resistant insulin-glucagon fusion protein with favorable relative hormonal activities. The N-terminal glucagon moiety was stabilized as a partial α-helix by Lys13-Glu17 lactam bridge and fused to a C-terminal insulin moiety stabilized as a single chain with a foreshortened C domain. Our in vitro studies demonstrated (a) marked resistance to fibrillation on prolonged agitation at 37 °C and (b) unaffected dual hormonal signaling activity. Glucodynamic responses were monitored in rats relative to control fusion proteins lacking one or the other hormonal activity. Results showed that insulin’s efficacy in hyperglycemia was unaffected, but enhanced endogenous glucose production was observed under hypoglycemic conditions. Together, these findings provide proof of principle for the translational application of a novel glucose-responsive insulin formulation with augmented physical stability, addressing two major problems of insulin replacement therapy in a single molecule.
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    Dasiglucagon, a next-generation ready-to-use glucagon analog, for treatment of severe hypoglycemia in children and adolescents with type 1 diabetes: Results of a phase 3, randomized controlled trial
    (Wiley, 2021) Battelino, Tadej; Tehranchi, Ramin; Bailey, Timothy; Dovc, Klemen; Melgaard, Anita; Yager Stone, Jenine; Woerner, Stephanie; von dem Berge, Thekla; DiMeglio, Linda; Danne, Thomas; Pediatrics, School of Medicine
    Background: Dasiglucagon, a next-generation, ready-to-use aqueous glucagon analog formulation, has been developed to treat severe hypoglycemia in individuals with diabetes. Objective: The aim of this trial was to evaluate the safety and efficacy of dasiglucagon in pediatric individuals with type 1 diabetes (T1DM). Participants were children and adolescents (6-17 years) with T1DM. Methods: In this randomized double-blind trial, 42 participants were randomly allocated (2:1:1) to a single subcutaneous (SC) injection of dasiglucagon (0.6 mg), placebo, or reconstituted glucagon (GlucaGen; dosed per label) during insulin-induced hypoglycemia. The primary endpoint was time to plasma glucose (PG) recovery (first PG increase ≥20 mg/dL after treatment initiation without rescue intravenous glucose). The primary comparison was dasiglucagon vs. placebo; glucagon acted as a reference. Results: The median time (95% confidence interval) to PG recovery following SC injection was 10 min (8-12) for dasiglucagon vs. 30 min (20 to -) for placebo (P < .001); the median time for glucagon was 10 min (8-12), which did not include the time taken to reconstitute the lyophilized powder. PG recovery was achieved in all participants in the dasiglucagon and glucagon groups within 20 min of dosing compared to 2 out of 11 patients (18%) with placebo. The most frequent adverse events were nausea and vomiting, as expected with glucagon treatment. Conclusions: Consistent with adult phase 3 trials, dasiglucagon rapidly and effectively restored PG levels following insulin-induced hypoglycemia in children and adolescents with T1DM, with an overall safety profile similar to glucagon.
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    Evaluation of a Mixed Meal Test for Diagnosis and Characterization of PancrEaTogEniC DiabeTes Secondary to Pancreatic Cancer and Chronic Pancreatitis: Rationale and Methodology for the DETECT Study From the Consortium for the Study of Chronic Pancreatitis, Diabetes, and Pancreatic Cancer
    (Wolters Kluwer, 2018-11) Hart, Phil A.; Andersen, Dana K.; Mather, Kieren J.; Castonguay, Alicia C.; Bajaj, Mandeep; Bellin, Melena D.; Bradley, David; Contreras, Noemy; Habtezion, Aida; Korc, Murray; Kudva, Yogish; Petrov, Maxim S.; Whitcomb, David C.; Yadav, Dhiraj; Yuan, Ying; Rinaudo, Jo Ann; Srivastava, Sudhir; Serrano, Jose; Medicine, School of Medicine
    Pancreatogenic diabetes mellitus is most commonly the result of chronic pancreatitis but can also occur secondary to pancreatic cancer. The early identification of pancreatogenic diabetes and distinction from the more prevalent type 2 diabetes are clinically significant; however, currently, there is no validated method to differentiate these diabetes subtypes. We describe a study, "Evaluation of a Mixed Meal Test for Diagnosis and Characterization of PancrEaTogEniC DiabeTes Secondary to Pancreatic Cancer and Chronic Pancreatitis: the DETECT study," that seeks to address this knowledge gap. The DETECT study is a multicenter study that will examine differences in hormone and glucose excursions after a mixed meal test. The study will also create a biorepository that will be used to evaluate novel diagnostic biomarkers for differentiating these diabetes subtypes.
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    Glucagon is essential for alpha cell transdifferentiation and beta cell neogenesis
    (The Company of Biologists, 2015-04-15) Ye, Lihua; Robertson, Morgan A.; Hesselson, Daniel; Stainier, Didier Y. R.; Anderson, Ryan M.; Department of Pediatrics, IU School of Medicine
    The interconversion of cell lineages via transdifferentiation is an adaptive mode of tissue regeneration and an appealing therapeutic target. However, its clinical exploitation is contingent upon the discovery of contextual regulators of cell fate acquisition and maintenance. In murine models of diabetes, glucagon-secreting alpha cells transdifferentiate into insulin-secreting beta cells following targeted beta cell depletion, regenerating the form and function of the pancreatic islet. However, the molecular triggers of this mode of regeneration are unknown. Here, using lineage-tracing assays in a transgenic zebrafish model of beta cell ablation, we demonstrate conserved plasticity of alpha cells during islet regeneration. In addition, we show that glucagon expression is upregulated after injury. Through gene knockdown and rescue approaches, we also find that peptides derived from the glucagon gene are necessary for alpha-to-beta cell fate switching. Importantly, whereas beta cell neogenesis was stimulated by glucose, alpha-to-beta cell conversion was not, suggesting that transdifferentiation is not mediated by glucagon/GLP-1 control of hepatic glucose production. Overall, this study supports the hypothesis that alpha cells are an endogenous reservoir of potential new beta cells. It further reveals that glucagon plays an important role in maintaining endocrine cell homeostasis through feedback mechanisms that govern cell fate stability.
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    Integration of metabolic flux with hepatic glucagon signaling and gene expression profiles in the conscious dog
    (American Physiological Society, 2024) Coate, Katie C.; Ramnanan, Christopher J.; Smith, Marta; Winnick, Jason J.; Kraft, Guillaume; Irimia-Dominguez, Jose; Farmer, Ben; Donahue, E. Patrick; Roach, Peter J.; Cherrington, Alan D.; Edgerton, Dale S.; Biochemistry and Molecular Biology, School of Medicine
    Glucagon rapidly and profoundly stimulates hepatic glucose production (HGP), but for reasons that are unclear, this effect normally wanes after a few hours, despite sustained plasma glucagon levels. This study characterized the time course of glucagon-mediated molecular events and their relevance to metabolic flux in the livers of conscious dogs. Glucagon was either infused into the hepato-portal vein at a sixfold basal rate in the presence of somatostatin and basal insulin, or it was maintained at a basal level in control studies. In one control group, glucose remained at basal, whereas in the other, glucose was infused to match the hyperglycemia that occurred in the hyperglucagonemic group. Elevated glucagon caused a rapid (30 min) and largely sustained increase in hepatic cAMP over 4 h, a continued elevation in glucose-6-phosphate (G6P), and activation and deactivation of glycogen phosphorylase and synthase activities, respectively. Net hepatic glycogenolysis increased rapidly, peaking at 15 min due to activation of the cAMP/PKA pathway, then slowly returned to baseline over the next 3 h in line with allosteric inhibition by glucose and G6P. Glucagon's stimulatory effect on HGP was sustained relative to the hyperglycemic control group due to continued PKA activation. Hepatic gluconeogenic flux did not increase due to the lack of glucagon's effect on substrate supply to the liver. Global gene expression profiling highlighted glucagon-regulated activation of genes involved in cellular respiration, metabolic processes, and signaling, as well as downregulation of genes involved in extracellular matrix assembly and development. NEW & NOTEWORTHY: Glucagon rapidly stimulates hepatic glucose production, but these effects are transient. This study links the molecular and metabolic flux changes that occur in the liver over time in response to a rise in glucagon, demonstrating the strength of the dog as a translational model to couple findings in small animals and humans. In addition, this study clarifies why the rapid effects of glucagon on liver glycogen metabolism are not sustained.
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    Potential Role for the Use of Gliptins in Cystic Fibrosis-related Diabetes
    (Endocrine Society, 2021-10-21) Ismail, Heba M.; Pediatrics, School of Medicine