Inhibition Of Glucagon Secretion Research Articles

Liraglutide enhances the effect of checkpoint blockade in lung and liver cancers through the inhibition of neutrophil extracellular traps.

Glucagon-like peptide-1 (GLP-1) regulates glycemic excursions by augmenting insulin production and inhibiting glucagon secretion. Liraglutide, a long-acting GLP-1 analog, can improve glycemic control for treating type 2 diabetes and prevent neutrophil extravasation in inflammation. Here, we explored the role of liraglutide in the development and therapy of murine lung and liver cancers. In this study, liraglutide substantially decreased circulating neutrophil extracellular trap (NET) markers myeloperoxidase, elastase, and dsDNA in Lewis lung cancer (LLC) and Hepa1-6 tumor-bearing mice. Furthermore, liraglutide downregulated NETs and reactive oxygen species (ROS) of neutrophils in the tumor microenvironment. Functionally, in vitro experiments showed that liraglutide reduced NET formation by inhibiting ROS. In addition, we showed that liraglutide enhanced the anti-tumoral efficiency of programmed cell death-1 (PD-1) inhibition in LLC and Hepa1-6 tumor-bearing C57BL/6 mice. However, the removal of NETs significantly weakened the antitumor efficiency of liraglutide. We further demonstrated that the long-term antitumor CD8+ T cell responses induced by the combination therapy rejected rechallenges by respective tumor cell lines. Taken together, our findings suggest that liraglutide may promote the anti-tumoral efficiency of PD-1 inhibition by reducing NETs in lung and liver cancers.

Comparison of an oral mixed meal plus arginine and intravenous glucose, GLP-1 plus arginine to unmask residual islet function in longstanding type 1 diabetes.

Residual beta cells are present in most patients with longstanding type 1 diabetes but it is unknown whether these beta cells react normally to different stimuli. Moreover a defect in proinsulin conversion and abnormal alpha cell response are also part of the islet dysfunction. A three-phase [euglycemia, hyperglycemia, and hyperglycemia + glucagon-like peptide 1 (GLP-1)] clamp was performed in patients with longstanding type 1 diabetes. Intravenous arginine boluses were administered at the end of each phase. On another day, a mixed meal stimulation test with a subsequent intravenous arginine bolus was performed. C-peptide was detectable in a subgroup of subjects at baseline (2/15) or only after stimulation (3/15). When detectable, C-peptide increased 2.9-fold [95% CI: 1.2-7.1] during the hyperglycemia phase and 14.1-fold [95% CI: 3.1-65.2] during the hyperglycemia + GLP-1 phase, and 22.3-fold [95% CI: 5.6-89.1] during hyperglycemia + GLP-1 + arginine phase when compared with baseline. The same subset of patients with a C-peptide response were identified during the mixed meal stimulation test as during the clamp. There was an inhibition of glucagon secretion (0.72-fold, [95% CI: 0.63-0.84]) during the glucose clamp irrespective of the presence of detectable beta cell function. Proinsulin was only present in a subset of subjects with detectable C-peptide (3/15) and proinsulin mimicked the C-peptide response to the different stimuli when detectable. Residual beta cells in longstanding type 1 diabetes respond adequately to different stimuli and could be of clinical benefit.NEW & NOTEWORTHY If beta cell function is detectable, the beta cells react relatively normal to the different stimuli except for the first phase response to intravenous glucose. An oral mixed meal followed by an intravenous arginine bolus can identify residual beta cell function/mass as well as the more commonly used glucose potentiated arginine-induced insulin secretion during a hyperglycemic clamp.

The role of nanosystems in the delivery of glucose-lowering drugs for the preemption and treatment of diabetes-associated atherosclerosis.

Diabetes is one of the most prevalent diseases worldwide. In recent decades, type-2 diabetes has become increasingly common, particularly in younger individuals. Diabetes leads to many vascular complications, including atherosclerosis. Atherosclerosis is a cardiovascular disease characterized by lipid-rich plaques within the vasculature. Plaques develop over time, restricting blood flow, and can, therefore, be the underlying cause of major adverse cardiovascular events, including myocardial infarction and stroke. Diabetes and atherosclerosis are intrinsically linked. Diabetes is a metabolic syndrome that accelerates atherosclerosis and increases the risk of developing other comorbidities, such as diabetes-associated atherosclerosis (DAA). Gold standard antidiabetic medications focus on attenuating hyperglycemia. Though recent evidence suggests that glucose-lowering drugs may have broader applications, beyond diabetes management. This review mainly evaluates the role of glucagon-like peptide-1 receptor agonists (GLP-1 RAs), such as liraglutide and semaglutide in DAA. These drugs mimic gut hormones (incretins), which inhibit glucagon secretion while stimulating insulin secretion, thus improving insulin sensitivity. This facilitates delayed gastric emptying and increased patient satiety; hence, they are also indicated for the treatment of obesity. GLP-1 RAs have significant cardioprotective effects, including decreasing low-density lipoprotein (LDL) cholesterol and triglycerides levels. Liraglutide and semaglutide have specifically been shown to decrease cardiovascular risk. Liraglutide has displayed a myriad of antiatherosclerotic properties, with the potential to induce plaque regression. This review aims to address how glucose-lowering medications can be applied to treat diseases other than diabetes. We specifically focus on how nanomedicines can be used for the site-specific delivery of antidiabetic medicines for the treatment of diabetes-associated atherosclerosis.

Lowest Glucagon/Highest C-Peptide in Oral Glucose Tolerance Test: Clinical Utility in Monitoring Glucose Control in Type 2 Diabetes Mellitus.

Understanding factors that influence blood glucose levels in patients with type 2 diabetes mellitus (T2DM) is crucial for managing hyperglycemia. Currently, there is no standardized interpretation method for glucagon levels in oral glucose tolerance test (OGTT). This study aims to assess the relationship between the lowest glucagon/highest C-peptide ratio (Lglc/Hcp) in OGTT and glucose control levels in T2DM. Clinical data from 120 patients with T2DM were examined to compare the correlations of Lglc/Hcp and other pancreatic islet function-associated indices with fasting blood glucose (G0), glucose at 120 minutes in OGTT (G120), hemoglobin A1c (HbA1c), and the area under the glucose curve in OGTT (AUCglu). Additionally, the study investigated difference in Lglc/Hcp between patient groups based on the highest blood glucose levels (Hglu) in OGTT (Hglu ≥ 16.7 mmol/L vs Hglu < 16.7 mmol/L). The generalized linear model suggested that Lglc/Hcp significantly correlated with G0 (B = 0.85, P < 0.001), G120(B = 1.46, P < 0.001), HbA1c (B = 0.67, P < 0.001), and AUCglu (B = 3.46, P < 0.001). This correlation surpassed C-peptide and glucagon-related parameters, even after adjusting for confounding factors. Furthermore, Lglc/Hcp was notably higher in patients with Hglu ≥ 16.7 mmol/L compared to those with Hglu < 16.7 mmol/L (Z = -3.71, p < 0.001). Lglc/Hcp in OGTT closely relates to blood glucose control in patients with T2DM, potentially reflecting the overall pancreatic islet function in regulating glucose levels. Moreover, inhibiting glucagon secretion may be a crucial consideration for patients requiring insulin treatment.

GLP-1 metabolite GLP-1(9–36) is a systemic inhibitor of mouse and human pancreatic islet glucagon secretion

Aims/hypothesisDiabetes mellitus is associated with impaired insulin secretion, often aggravated by oversecretion of glucagon. Therapeutic interventions should ideally correct both defects. Glucagon-like peptide 1 (GLP-1) has this capability but exactly how it exerts its glucagonostatic effect remains obscure. Following its release GLP-1 is rapidly degraded from GLP-1(7–36) to GLP-1(9–36). We hypothesised that the metabolite GLP-1(9–36) (previously believed to be biologically inactive) exerts a direct inhibitory effect on glucagon secretion and that this mechanism becomes impaired in diabetes.MethodsWe used a combination of glucagon secretion measurements in mouse and human islets (including islets from donors with type 2 diabetes), total internal reflection fluorescence microscopy imaging of secretory granule dynamics, recordings of cytoplasmic Ca2+ and measurements of protein kinase A activity, immunocytochemistry, in vivo physiology and GTP-binding protein dissociation studies to explore how GLP-1 exerts its inhibitory effect on glucagon secretion and the role of the metabolite GLP-1(9–36).ResultsGLP-1(7–36) inhibited glucagon secretion in isolated islets with an IC50 of 2.5 pmol/l. The effect was particularly strong at low glucose concentrations. The degradation product GLP-1(9–36) shared this capacity. GLP-1(9–36) retained its glucagonostatic effects after genetic/pharmacological inactivation of the GLP-1 receptor. GLP-1(9–36) also potently inhibited glucagon secretion evoked by β-adrenergic stimulation, amino acids and membrane depolarisation. In islet alpha cells, GLP-1(9–36) led to inhibition of Ca2+ entry via voltage-gated Ca2+ channels sensitive to ω-agatoxin, with consequential pertussis-toxin-sensitive depletion of the docked pool of secretory granules, effects that were prevented by the glucagon receptor antagonists REMD2.59 and L-168049. The capacity of GLP-1(9–36) to inhibit glucagon secretion and reduce the number of docked granules was lost in alpha cells from human donors with type 2 diabetes. In vivo, high exogenous concentrations of GLP-1(9–36) (>100 pmol/l) resulted in a small (30%) lowering of circulating glucagon during insulin-induced hypoglycaemia. This effect was abolished by REMD2.59, which promptly increased circulating glucagon by >225% (adjusted for the change in plasma glucose) without affecting pancreatic glucagon content.Conclusions/interpretationWe conclude that the GLP-1 metabolite GLP-1(9–36) is a systemic inhibitor of glucagon secretion. We propose that the increase in circulating glucagon observed following genetic/pharmacological inactivation of glucagon signalling in mice and in people with type 2 diabetes reflects the removal of GLP-1(9–36)’s glucagonostatic action.Graphical

An extended minimal model of OGTT: estimation of α- and β-cell dysfunction, insulin resistance, and the incretin effect.

Loss of insulin sensitivity, α- and β-cell dysfunction, and impairment in incretin effect have all been implicated in the pathophysiology of type 2 diabetes (T2D). Parsimonious mathematical models are useful in quantifying parameters related to the pathophysiology of T2D. Here, we extend the minimum model developed to describe the glucose-insulin-glucagon dynamics in the isoglycemic intravenous glucose infusion (IIGI) experiment to the oral glucose tolerance test (OGTT). The extended model describes glucose and hormone dynamics in OGTT including the contribution of the incretin hormones, glucose-dependent insulinotropic polypeptide (GIP), and glucagon-like peptide-1 (GLP-1), to insulin secretion. A new function describing glucose arrival from the gut is introduced. The model is fitted to OGTT data from eight individuals with T2D and eight weight-matched controls (CS) without diabetes to obtain parameters related to insulin sensitivity, β- and α-cell function. The parameters, i.e., measures of insulin sensitivity, a1, suppression of glucagon secretion, k1, magnitude of glucagon secretion, γ2, and incretin-dependent insulin secretion, γ3, were found to be different between CS and T2D with P values < 0.002, <0.017, <0.009, <0.004, respectively. A new rubric for estimating the incretin effect directly from modeling the OGTT is presented. The average incretin effect correlated well with the experimentally determined incretin effect with a Spearman rank test correlation coefficient of 0.67 (P < 0.012). The average incretin effect was found to be different between CS and T2D (P < 0.032). The developed model is shown to be effective in quantifying the factors relevant to T2D pathophysiology.NEW & NOTEWORTHY A new extended model of oral glucose tolerance test (OGTT) has been developed that includes glucagon dynamics and incretin contribution to insulin secretion. The model allows the estimation of parameters related to α- and β-cell dysfunction, insulin sensitivity, and incretin action. A new function describing the influx of glucose from the gut has been introduced. A new rubric for estimating the incretin effect directly from the OGTT experiment has been developed. The effect of glucose dose was also investigated.

Zinc-Phthalocyanine Loaded PLGA-PVA-Chitosan Nanosystem for the Enhancement of Antidiabetic Activity.

Zinc, one of the most common nutraceutical agents, proved to be effective for diabetes as it regulates the blood glucose level by inhibiting glucagon secretion. However, the hepatotoxicity of zinc creates necrosis, hepatic glycogen depletion, and apoptosis of hepatocytes at the concentration of 10 μg/kg. Phthalocyanine, a blue-colored compound, is an aromatic macrocyclic compound with good antioxidant ability owing to its heterocyclic nitrogen conjugation. The conjugation of zinc with phthalocyanine aimed to reduce the toxicity associated with zinc and enhance the antidiabetic activity at a lower dose. Hence, the present research work possessed the insights of the synthetic aspect of zinc with phthalocyanine along with its entrapment in the poly(lactic-co-glycolic acid) (PLGA)-chitosan nanosystem via oral administration in the treatment of diabetes. A nanoprecipitation technique was implemented for the synthesis of PLGA chitosan nanoparticles, and formulation was further optimized using a central composite design. Twenty trials provided by the software selected optimum concentrations of PLGA, poly(vinyl alcohol) (PVA), and chitosan in consideration with particle size up to 335.6 nm, zeta potential 27.87 mV, and entrapment efficiency of 75.67 ± 8.13%. Addition of chitosan to the nanocarrier system for controlling the release of the drug for 3 days was accompanied by the improvement in the glucose level within 28 days. The delivery of the nanoparticles showed enhancement in the cholesterol, triglyceride, alkaline phosphatase (ALP), urine parameters, and pro-inflammatory cytokines. The application of DoE (design of experiments) for the optimization of the nanoparticles established a controlled release formulation for diabetes, which displayed safety and effectiveness in streptozotocin (STZ)-induced diabetic rats.

Conflicting Views About Interactions Between Pancreatic α-Cells and β-Cells.

In type 1 diabetes, the reduced glucagon response to insulin-induced hypoglycemia has been used to argue that β-cell secretion of insulin is required for the full glucagon counterregulatory response. For years, the concept has been that insulin from the β-cell core flows downstream to suppress glucagon secretion from the α-cells in the islet mantle. This core-mantle relationship has been supported by perfused pancreas studies that show marked increases in glucagon secretion when insulin was neutralized with antisera. Additional support comes from a growing number of studies focused on vascular anatomy and blood flow. However, in recent years this core-mantle view has generated less interest than the argument that optimal insulin secretion is due to paracrine release of glucagon from α-cells stimulating adjacent β-cells. This mechanism has been evaluated by knockout of β-cell receptors and impairment of α-cell function by inhibition of Gi designer receptors exclusively activated by designer drugs. Other studies that support this mechanism have been obtained by pharmacological blocking of glucagon-like peptide 1 receptor in humans. While glucagon has potent effects on β-cells, there are concerns with the suggested paracrine mechanism, since some of the supporting data are from isolated islets. The study of islets in static incubation or perifusion systems can be informative, but the normal paracrine relationships are disrupted by the isolation process. While this complicates interpretation of data, arguments supporting paracrine interactions between α-cells and β-cells have growing appeal. We discuss these conflicting views of the relationship between pancreatic α-cells and β-cells and seek to understand how communication depends on blood flow and/or paracrine mechanisms.

Identification of Dipeptidyl-Peptidase 4 (DPP-4) Inhibitors from Miracle Berry Fruit (Synsepalum dulcificum) Extract

Dipeptidyl-peptidase 4 is a novel targeted enzyme in type 2 diabetes mellitus (T2DM) therapy due to its regulatory effect on incretin; glucagon-like peptide 1 (GLP-1) that responsible for stimulating insulin and suppressing glucagon secretion. DPP-4 degrades GLP-1 to biologically inactive fragments. In incretin-based therapies, DPP-4 inhibitor helps to restrain the inactivation of GLP-1, which in turn prolonging GLP-1’s half-life in blood and subsequently reducing the blood sugar more effectively. Nowadays, researchers are focusing to replace the synthetic drugs with natural-based drugs since they exert less toxicity. In our attempt to discover the natural inhibitor for DPP-4, miracle berry fruit was sequentially extracted with different solvents such as hexane, dichloromethane, chloroform, ethyl acetate and methanol and screened for the DPP-4 inhibitory activity. The analyses on the extractions show dichloromethane yielded the highest number of phenolic compounds with 38.37 mg GAE/g, while the highest number of flavonoids was found in hexane extract with 142.269 mg QE/g. On the other hand, qualitative analyses showed that methanol was able to extract alkaloids, terpenoids, saponins, tannins, quinones and carbohydrate from miracle berry fruit. It was also found that ethyl acetate extract was able to completely inhibit the enzyme. For further identification of constituent responsible for DPP-4 inhibitory activity, ethyl acetate extract was then subjected to silica gel column chromatography and eluted with different solvents with increasing polarity. The active fraction was then subjected to LC-MS/MS analysis and the results show it contains astragalin, nialamide, n-acetyl-l-phenylalanine, (+)-6-gingerol, 9-nitro oleate and 4(3H)-quinazolinone. The study indicates that miracle berry fruit extract contains natural DPP-4 inhibitor that can potentially be used for treating T2DM.

Hyperglucagonaemia in diabetes: altered amino acid metabolism triggers mTORC1 activation, which drives glucagon production.

Hyperglycaemia is associated with alpha cell dysfunction, leading to dysregulated glucagon secretion in type 1 and type 2 diabetes; however, the mechanisms involved are still elusive. The nutrient sensor mammalian target of rapamycin complex 1 (mTORC1) plays a major role in the maintenance of alpha cell mass and function. We studied the regulation of alpha cell mTORC1 by nutrients and its role in the development of hyperglucagonaemia in diabetes. Alpha cell mTORC1 activity was assessed by immunostaining for phosphorylation of its downstream target, the ribosomal protein S6, and glucagon, followed by confocal microscopy on pancreatic sections and flow cytometry on dispersed human and mouse islets and the alpha cell line, αTC1-6. Metabolomics and metabolic flux were studied by 13C glucose labelling in 2.8 or 16.7 mmol/l glucose followed by LC-MS analysis. To study the role of mTORC1 in mediating hyperglucagonaemia in diabetes, we generated an inducible alpha cell-specific Rptor knockout in the Akita mouse model of diabetes and tested the effects on glucose tolerance by IPGTT and on glucagon secretion. mTORC1 activity was increased in alpha cells from diabetic Akita mice in parallel to the development of hyperglycaemia and hyperglucagonaemia (two- to eightfold increase). Acute exposure of mouse and human islets to amino acids stimulated alpha cell mTORC1 (3.5-fold increase), whereas high glucose concentrations inhibited mTORC1 (1.4-fold decrease). The mTORC1 response to glucose was abolished in human and mouse diabetic alpha cells following prolonged islet exposure to high glucose levels, resulting in sustained activation of mTORC1, along with increased glucagon secretion. Metabolomics and metabolic flux analysis showed that exposure to high glucose levels enhanced glycolysis, glucose oxidation and the synthesis of glucose-derived amino acids. In addition, chronic exposure to high glucose levels increased the expression of Slc7a2 and Slc38a4, which encode amino acid transporters, as well as the levels of branched-chain amino acids and methionine cycle metabolites (~1.3-fold increase for both). Finally, conditional Rptor knockout in alpha cells from adult diabetic mice inhibited mTORC1, thereby inhibiting glucagon secretion (~sixfold decrease) and improving diabetes, despite persistent insulin deficiency. Alpha cell exposure to hyperglycaemia enhances amino acid synthesis and transport, resulting in sustained activation of mTORC1, thereby increasing glucagon secretion. mTORC1 therefore plays a major role in mediating alpha cell dysfunction in diabetes. All sequencing data are available from the Gene Expression Omnibus (GEO) repository (accession no. GSE154126; https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE154126 ).

A New Hope for Treating Obesity Pandemic

A new class of drugs is transforming obesity treatment in an unprecedented manner. Scientists are amazed by their potency in the treatment of obesity. Glucagon-like peptide 1 (GLP-1) analogs are a class of medications used to treat type 2 diabetes mellitus. These analogs mimic the action of GLP-1, a hormone released by the intestine in response to food intake. GLP-1 analogs have been extensively studied, and scientists have made several important discoveries about their effects and potential therapeutic applications. GLP-1 analogs have shown significant efficacy in improving glycemic control in patients with type 2 diabetes. They stimulate insulin secretion from pancreatic beta cells, suppress glucagon secretion (which reduces hepatic glucose production), and slow down gastric emptying, leading to reduced postprandial glucose levels. Apart from their controlling glycemic index, GLP-1 analogs are shown to offer cardio-protective, reno-protective, and neuroprotective benefits. However, their most surprising and potent effects have been observed in the context of weight loss. Two drugs from this class, semaglutide, and tripeptide, have shown efficacy in recent clinical trials. Tirzepatide was effective in significantly reducing body weight in about half of the participants in a recent clinical trial. In another trial, semaglutide was able to reduce 20% of the body weight of about one-third of the participants. However, not everyone is benefiting from these medications. There are still significant challenges in determining who will benefit from these medications and to what extent. These challenges are currently being addressed. It has been observed that the new drugs work best in people who become hungry in between meals. People with obesity can be classified into four categories; those who need to eat more to reach fullness; those who reach fullness with a regular-sized meal but feel hungry again soon (hungry gut); those who eat to cope with emotions; and those with a relatively slow metabolism. It is not known why people with a ‘hungry gut’ respond most effectively to the new drugs, but one hypothesis suggests that these patients have low levels of GLP-1 hormones, and that’s why they have obesity. When they get a replacement in the form of GLP-1 analogs, they do extremely well. Another study with a GLP-1-mimicking drug called liraglutide found that patients with low GLP-1 levels reduced twice as much weight compared to the general population after using the drug for one year. Both semaglutide and tripeptide are given once weekly, thus increasing treatment compliance. Because of their weekly regimen, the drugs will also help people with erratic schedules and work shifts. Some of the other medications have to be taken at a certain time of day, which can be difficult for those with irregular sleep schedules. Another important question is to find out how long these drugs' weight loss benefits remain. One study concluded that semaglutide’s weight-reducing effects last as long as the patients remain on medication. This means that these drugs will be given chronically to obese patients. Whether ‘chronic’ means ‘life-long’ in this context is still to be determined. Perhaps an even more important question that clinicians face is determining how much weight loss is too much, especially when muscle loss is also involved. More research is needed to find a balance where these drugs are used not only for weight reduction but to treat a person for health, prevent disease, and improve quality of life.

26-OR: A Novel Drug That Normalizes Hyperglycemia in Type 1 Diabetes

Treatment of hyperglycemia in patients with type 1 diabetes (T1D) depends on insulin injections, which risk hypoglycemia and represent an unfavorable route of administration. Inhibition of EphA4 signaling in α-cells reduces glucagon hypersecretion, which suggests an alternative approach for the treatment of hyperglycemia in T1D. We have designed and synthesized a novel EphA4 agonist (Ki = 0.1 µM), termed WCDD301, that dose-dependently suppresses glucagon secretion (p&amp;lt;0.001) from mouse islets and dispersed α-cells at high glucose levels. Co-treatment of the EphA4 competitive inhibitor, Rhyncophylline (2.5µM) and WCDD301 (2.5µM or 5µM) substantially or partially, respectively, abolishes WCDD301 effects. Further, WCDD301 reduces glucagon secretion from nondiabetic human donor islet cells following 1h (p&amp;lt;0.05), 3h (p&amp;lt;0.01) and 6h (p&amp;lt;0.001) exposure. WCDD301 suppresses glucagon secretion (p&amp;lt;0.001) from isolated islets and dispersed islet cells from T1D subjects, comparable to the natural EphA4 ligand ephrinA5. Similar to ephrinA5 treatment, WCDD301 increases F-actin density in both human and mouse α-cells. WCDD301 exhibits good plasma (&amp;gt;289 and 105 min) and microsomal (&amp;gt;145 and 93.6 min) stability in human and mouse, respectively. In STZ-induced diabetic mice (initial blood glucose &amp;lt;300mg/dL, n=6), oral administration of WCDD301 (daily 10 mg/kg) substantially reduces blood glucose levels (140±31 mg/dL after four weeks). In diabetic NOD mice (initial blood glucose 249.6±13.1 mg/dL; n=7), oral administration of WCDD301 (daily 10 mg/kg) normalizes glucose (105±2.6 mg/dL after 3 weeks), which remains constant for &amp;gt;3 months (experiments on-going) accompanied by reduced plasma glucagon (16.6±7.9 pg/mL) compared to diabetic control (328.5±18.7 pg/ml). The data support our hypothesis that oral administration of WCDD301 suppresses glucagon secretion by an EphA4-dependent pathway. The recovery of euglycemia in T1D mouse models is promising for further evaluation towards potential treatment of T1D. Disclosure F. Asadi: None. S.C. Gunawardana: None. D.W. Piston: None. Funding The Leona M. and Harry B. Helmsley Charitable Trust (2305-06050); National Institutes of Health (R01DK123301, P30DK020579)

1653-P: Brown Adipocyte–Secreted Factors for Treating Type 1 Diabetes Mellitus

Hyperglycemia during type 1 Diabetes (T1D) is driven not only by a lack of insulin secretion due to autoimmune destruction of the pancreatic β-cells, but also by hypersecretion of glucagon from pancreatic α-cells. Insulin therapy can replace the lack of insulin secretion, but there is no effective therapeutic tool to counter the hyperglucagonemia. Brown adipose tissue (BAT) has gained attention for treating metabolic diseases due to its role as an endocrine organ and its effect on whole-body energy metabolism. Subcutaneous transplantation of embryonic BAT into T1D mouse models reverses hyperglycemia, independent of insulin but accompanied by reduced plasma glucagon levels, which suggests that lowering plasma glucagon plays a central role in restoring euglycemia. However, the molecular mechanism(s) underlying this action remain unclear. Towards discovering these mechanisms, we have examined the effects of secretions from immortalized brown adipocytes (imBAT) on pancreatic α-cells and mouse models of T1D. We show that the large molecule fraction (&amp;gt;100kDa) of imBAT-secreted factors suppresses glucagon secretion from both mouse and human pancreatic α-cells. Live cell fluorescence imaging shows that this fraction inhibits both intracellular Ca2+ and cAMP activities, and these inhibitions are ameliorated by blocking the insulin receptor, suggesting that imBAT-secreted factors act, at least in part, through these receptors. Injecting this imBAT-secreted fraction into the NOD mouse model reverses hyperglycemia (242 ± 47.4 to 146 ± 24.7mg/dL, n=8), suppresses hyperglucagonemia (77.6 ± 55.4 to 10.7 ± 4.75pg/mL, n=8), improves glucose tolerance (n=3), and increases thermogenic activity and differentiation of endogenous BAT (n=7). Our data provide insights into the mechanisms of long-term recovery of euglycemia by BAT transplants, and further fractionation experiments to isolate active factors are ongoing. Disclosure J.Lee: None. D.W.Piston: None. Funding The Leona M. and Harry B. Helmsley Charitable Trust (2305-06050); National Institutes of Health (R01DK123301, P30DK020579)

200-OR: Role of Insulin-Degrading Enzyme (IDE) in the Tubulin–Primary Cilium Axis to Regulate Glucagon Secretion

Hyperglucagonemia is a hallmark of T2D, although molecular mechanisms underlying glucagon secretion dysregulation are poorly understood. We have recently reported that genetic ablation of IDE in α-cells (A-IDE-KO mouse) leads to constitutive glucagon secretion, hypertrophy, hyperplasia and increased proliferation. αTC1.9-KD-IDE cells (~30% IDE-knock-down) displayed reduced tubulin and acetylated-α-tubulin protein levels, impaired primary cilium and increased proliferation. Thus, we aimed to elucidate the role of IDE in α-cells tubulin network and ciliogenesis, and how this axis may be part of the glucagon secretion machinery. We have studied by western-blot IDE, tubulin, acetylated-α-tubulin and Arl13b (primary cilium marker) levels in αTC1.9 cells under low- and high-glucose conditions. We have found that high-glucose lowers IDE protein levels by 50% compared to low-glucose conditions, leading to a similar decrease in tubulin, acetylated-α-tubulin and Arl13b protein levels. These findings agree with our previous results using αTC1.9-KD-IDE cells, suggesting a relevant role of IDE in microtubule dynamics to control glucagon granules exocytosis. On the other hand, αTC1.9-KD-Arl13b cells (~70% Arl13b-knock-down) were used as a model of impaired ciliogenesis, showing 50% decrease in tubulin, and dysregulated glucagon secretion, mimicking αTC1.9-KD-IDE cells phenotype. In parallel, insulin-mediated inhibition of glucagon secretion is lost and insulin receptor protein levels were decreased by 40% in both, αTC1.9-KD-IDE and αTC1.9-KD-Arl13b cells, showing the relevance of IDE and primary cilium in the paracrine regulation of α-cells. Furthermore, these results have been reproduced in A-IDE-KO mice isolated islets. In conclusion, our results show that IDE-tubulin-primary cilium axis is regulated during glucose-stimulated glucagon secretion, this axis is also required for the paracrine action of insulin on α-cells to inhibit glucagon secretion. Disclosure E.Casanueva-alvarez: None. A.Sanz-gonzález: None. B.Merino: None. G.Perdomo: None. I.Cozar-castellano: None. Funding Ministerio de Ciencia e Innovación-Spain (PID2019-110496RB-C21)

Hibiscus sabdariffa on Fibroblast Growth Factor 21 (FGF21) on Diabetes Mellitus Type 2 Patients

FGF21 has a role in modulating the uptake of macronutrients in the body. It is produced by the liver in response to high carbohydrate intake and acts as a signal to the brain to reduce carbohydrate intake. Liver is the main site for FGF21 production under the regulation of Unfolding Protein Response (UPR) in hepatocytes. FGF21 has an important role in regulating peripheral glucose tolerance as well as lipid metabolism. FGF21 expression in the liver depends on the PKR-like ER kinase (PERK)–eukaryotic initiation factor 2? (eIF2?)–activating transcription factor 4 (ATF4) pathway. FGF21 can regulate the expression of glucose transporter 1, and increase glucose uptake. In addition, research shows that FGF21 can reduce blood sugar levels and also body weight in mice1. FGF21 can also increase insulin sensitivity by suppressing hepatic glucose production and increasing hepatic glycogen content, so that this can improve systemic glucose intolerance and insulin resistance. The researchers attempted to discover the influence of Hibiscus sadariffa on FGF21 on Diabetes mellitus type 2 patients. The method used was literature review with data generated from various sources such as Google Scholar, Scopus, and Pubmed. FGF21 has an effect on the function of ? and ß cells in the pancreas organ. In the islets of the pancreatic organs of rats with DM, administration of FGF21 increased insulin levels, induced insulin secretion, and inhibited glucagon secretion.

Glucagon and Insulin Overview: An Odd Couple's History and Physiology.

Glucagon is a peptide hormone that is produced primarily by the alpha cells in the islet of Langerhans in the pancreas, but also in intestinal enteroendocrine cells and in some neurons. Approximately 100 years ago several research groups discovered that pancreatic extracts would cause a brief rise blood glucose before they observed the decrease in glucose attributed to insulin. An overall description of the regulation of glucagon secretion requires inclusion of its sibling insulin because they both are made primarily by the islet and they both regulate each other in different ways. For example, glucagon stimulates insulin secretion, whereas insulin suppresses glucagon secretion. The mechanism of action of glucagon on insulin secretion has been identified as a trimeric guanine nucleotide-binding protein (G-protein)-mediated event. The manner in which insulin suppresses glucagon release from the alpha cell is thought to be highly dependent on the peri-portal circulation of the islet through which blood flows downstream from beta cells to alpha cells. In this scenario, it is via the circulation that insulin is thought to suppresses the release of glucagon. However, high levels of glucose also have been shown to suppress glucagon secretion. Consequently, the glucose lowering effect of insulin may be additive to the direct effects of insulin to suppress alpha cell function, so that in vivo both the discontinuation of the insulin signal and the condition of low glucose jointly are responsible for induction of glucagon secretion.

Acanthopanax trifoliatus (L.) Merr polysaccharides ameliorates hyperglycemia by regulating hepatic glycogen metabolism in type 2 diabetic mice.

Drug monotherapy was inadequate in controlling blood glucose levels and other comorbidities. An agent that selectively tunes multiple targets was regarded as a new therapeutic strategy for type 2 diabetes. Acanthopanax trifoliatus (L.) Merr polysaccharide (ATMP) is a bio-macromolecule isolated from Acanthopanax trifoliatus (L.) Merr and has therapeutic potential for diabetes management due to its anti-hyperglycemia activity. Type 2 diabetes mellitus was induced in mice using streptozotocin, and 40 and 80 mg/kg ATMP was administered daily via the intragastric route for 8 weeks. Food intake, water intake, and body weight were recorded. The fasting blood glucose (FBG), fasting insulin (FINS) and an oral glucose tolerance test (OGTT) were performed. Histological changes in the liver and pancreas were analyzed by H&E staining. The mRNA and the protein levels of key factors involved in glycogen synthesis, glycogenolysis, and gluconeogenesis were measured by quantitative real time PCR and Western blotting. In this study, we found that ATMP could effectively improve glucose tolerance and alleviate insulin resistance by promoting insulin secretion and inhibiting glucagon secretion. In addition, ATMP decreases glycogen synthesis by inhibiting PI3K/Akt/GSK3β signaling, reduces glycogenolysis via suppressing cAMP/PKA signaling, and suppresses liver gluconeogenesis by activating AMPK signaling. Together, ATMP has the potential to be developed as a new multitargets therapeutics for type 2 diabetes.

Advances in GLP-1 receptor agonists for the treatment of type 2 diabetes

Glucagon-like peptide-1 (GLP-1), an incretin secreted by intestinal L cells, has become a critical target for the treatment of type 2 diabetes because of its physiological effects of augmenting insulin secretion, suppressing glucagon secretion, and decelerating gastric emptying. Human endogenous GLP-1 is found to be proteolytically degraded and inactivated by DPP-4, which considerably limits the therapeutic effects of GLP-1. In contrast, GLP-1RAs undergo significant improvement in drug stability. In this context, several successful strategies for the development of GLP-1RAs and the corresponding problems are fully elaborated. The assay gives a brief overview of the pharmacological effects, advantages and common adverse effects of GLP-1RAs, shedding light on the latest research progress of GLP-1RAs, including new dosage forms, new drug targets and new clinical applications.

Distribution and function of glucagon-like peptide 1 (GLP-1) in the digestive tract of mammals and the clinical use of its analogues

Recently, interest in glucagon-like peptide-1 (GLP-1) and other peptides derived from preproglucagon has increased significantly. GLP-1 is a 30-amino acid peptide hormone produced in L-type enteroendocrine cells as a response to food intake. GLP-1 is rapidly metabolized and inactivated by the dipeptidyl peptidase IV enzyme before the hormone leaves the intestine, which increases the likelihood that GLP-1 action is transmitted through sensory neurons in the intestine and liver through the GLP-1 receptor. The main actions of GLP-1 are to stimulate insulin secretion (i.e. act as incretin hormone) and inhibit glucagon secretion, thus contributing to the reduction of postprandial glucose spikes. GLP-1 also inhibits motility and gastrointestinal secretion, and therefore acts as part of the „small bowel brake” mechanism. GLP-1 also appears to be a physiological regulator of appetite and food intake. Because of these effects, GLP-1 or GLP-1 receptor agonists are now increasingly used to treat type 2 diabetes. Reduced GLP-1 secretion may contribute to the development of obesity, and excessive secretion may be responsible for postprandial reactive hypoglycemia. The use of GLP-1 agonists opens up new possibilities for the treatment of type 2 diabetes and other metabolic diseases. In the last two decades, many interesting studies covering both the physiological and pathophysiological role of GLP-1 have been published, and our understanding of GLP-1 has broadened significantly. In this review article, we have tried to describe our current understanding of how GLP-1 works as both a peripheral hormone and as a central neurotransmitter in health and disease. We focused on its biological effects on the body and the potential clinical application in relation to current research.

In Silico Analysis of Gene Expression Location and Single Nucleotide Polymorphisms (SNPs) of The Glucagon Like Peptide 1 Receptor (GLP-1R)

Association studies of SNPs have become very important in determining how genetic variants are linked to complex diseases, quantitative traits, and physiological responses. Genetic polymorphisms in the GLP-1R gene have potentially decreased protein stability and are associated with many diseases, especially diabetes and obesity. This study aimed to screen the expression and investigate the genetic polymorphism of the GLP-1R by using several beneficial bioinformatics tools. We observed database Ensembl, GTEx portal, and KEGG to identify the structure, expression, and molecular pathway of GLP-1R. In silico computational methods (SIFT, PolyPhen v2, PROVEAN, and PhD-SNP) were used to identify nsSNPs of the GLP-1R that potentially influence protein structure and function. I-Mutant was used to investigate possibly damaging nsSNPs, while GeneMANIA was used to investigate GLP-1R gene-gene interactions. GLP-1R is localized on chromosome 6p21, contains 13 exons, and has the regulation variant (CTCF, promotor, enhancer, and promotor flank region). GLP-1R is highly expressed in the pancreas to stimulate glucose-dependent insulin secretion and suppress glucagon secretion. Seven nsSNPs of the GLP-1R gene were found to be potentially deleterious: rs10305421, rs201672448, rs10305492, rs2295006, rs6923761, rs1042044, rs140642887, and rs10305510. I-Mutant server showed that nsSNPs rs140642887 was unstable, decreased GLP-1R protein stability, and impaired other genes' interaction and function (SP1, SP3, GNAS, and GCG). This study is the first in silico analysis of the polymorphic GLP-1R gene, and will serve as a great resource for developing precision medications to treat diseases associated with these polymorphisms.