Stimulated Insulin Secretion Research Articles

Is glucose‐induced hypersecretion of glicentin after the revision surgery using Roux‐en‐Y gastric bypass related to improved glycemic control due to insulin hypersecretion in a type 2 diabetes patient without diabetes remission after laparoscopic sleeve gastrectomy?

ABSTRACTWe report case details of a morbidly obese patient with type 2 diabetes mellitus (T2DM) who became a failure of diabetes remission after laparoscopic sleeve gastrectomy (LSG). He had a marked improvement of hyperglycemia after the revision surgery using Roux‐en‐Y gastric bypass (RYGB), where passage failure of a solid food intake at the gastric angle portion disappeared after the revision surgery. Interestingly, he showed improvements of insulin and a marked glicentin secretions with minor changes in glucagon related peptide 1 (GLP‐1) and glucose‐dependent insulinotropic polypeptide (GIP) secretions in the oral glucose tolerance test OGTT after the RYGB surgery compared with post‐LSG. Although a marked increase in glucose‐induced glicentin secretion after RYGB surgery with increased insulin secretion, further studies are needed to confirm if the increased glicentin secretion after RYGB surgery is linked to stimulation of insulin secretion.

Impact of glucagon-Like peptide-1 agonists in optimizing abdominal wall Reconstruction patients.

Pre-optimization of obese patients prior to abdominal wall reconstruction (AWR) is essential in mitigating their increased preoperative risks. Traditionally diet, exercising, bariatric surgery are the tools typically prescribed for weight loss. The advent of glucagon-like peptide-1 agonists (GLP-1A) which stimulate insulin secretion and inhibit gastric emptying have improved the weight loss armamentarium. However, there is a limited amount of literature on GLP-1A effectiveness and postoperative outcomes in AWR patients. This study compares the efficacy of GLP-1A to Bariatric Surgery (BAS) in perioperative AWR patient. A prospectively maintained database was retrospectively reviewed to identify all patients undergoing AWR at our institution between January 2021 and March 2024. We included patients who required GLP-1A or BAS for weight optimization prior to AWR. We excluded patients on GLP1-A or history BAS not performed for AWR preoptimization. Basic demographics such as age, sex, race, weight and BMI at initial clinic visit and at surgery were compared. Primary endpoints included time to surgery, time to bowel recovery and length of stay (LOS). Time to surgery was defined as the number of months between the initial clinic visit and AWR. Time to bowel recovery was defined as the number of days it took for the first postoperative bowel function. Secondary endpoints included standard 30-days postoperative variables. Nominal variables were analyzed using a Fisher exact test and continuous variables were analyzed with Student's T test. 35 patients were included in this study (GLP-1A: 17, BAS: 18). The GLP-1A cohort had a lesser BMI at the initial clinic visit (40.8 vs 43.4, p = 0.188). GLP-1A cohort made it to the operating room faster (9.1 months vs 13.5 months, p = 0.06) from the first clinic visit; and (7.9 months vs 9.7 months, p = 0.4) from initiation of weight loss intervention. Albeit losing less weight (14.9 kg vs 27.1 kg, p = 0.008) with a lesser reduction in the BMI (4.69 vs 9.23, p = 0.004). The GLP-1A cohort showed a non-significant elevated LOS (5.2 days vs 3.6 days, p = 0.25) and an increased ileus rate (17.6% vs 0%, p = 0.1). However, there were no differences noted in time to bowel recovery (2.9 days vs 3.1 days, p = 0.76). GLP-1A is effective in optimizing patients needing weight loss before AWR. They shorten the timeline to AWR intervention and have comparable peri-operative outcomes to BAS patients.

Metformin Preserves Insulin Secretion in Pancreatic β-cells through FGF21/Akt Pathway In vitro and In vivo.

In our previous studies, it was found that metformin can elevate the expression of FGF21 in the peripheral blood of type 2 diabetic rats and improve insulin sensitivity in diabetic rats. However, whether this effect is mediated by increased FGF21 expression in pancreatic islet β-cells is still unknown. Therefore, this study focuses on the effect of metformin on insulin secretion in pancreatic β-cells. Metformin can effectivly improve insulin resistance. Metformin influencing pancreatic β- cell function is inclusive. In this study, we sought to analyze possible variations in insulin secretion and possible signaling mechanisms after metformin intervention. The study employed an in vivo model of a high-fat diet in streptozocin-induced diabetic rats and an in vitro model of rat pancreatic β-cells (INS-1 cells) that were subjected to damage caused by hyperglycemia and hyperlipidemia. After treating INS-1 cells in normal, high-glucose, and high-glucose+metformin, we measured insulin secretion by glucose-stimulated insulin secretion (GSIS). Insulin was measured using an enzyme-linked immunosorbent assay. FGF21 expression was detected by RT-PCR and Western blot, as well as that p-Akt and t-Akt expression were detected by Western blot in INS-1 cells and diabetic rat islets. Finally, to verify the regulation of the FGF21 /Akt axis in metformin administration, additional experiments were carried out in metformin-stimulated INS-1 cells. High-glucose could significantly stimulate insulin secretion while metformin preserved insulin secretion. Expression of FGF21 and p-Akt was decreased in high-glucose, however, metformin could reverse this effect in INS-1 cells and diabetic rat islets. Our results demonstrate a protective role of metformin in preserving insulin secretion through FGF21/Akt signaling in T2DM.

Dipeptidyl Peptidase-4 Inhibitors: A Systematic Review of Structure-Activity Relationship Studies

Context: Dipeptidyl peptidase 4 (DPP-4) is a serine exopeptidase enzyme that hydrolyzes the amide bond at the N-terminal of peptides. This enzyme converts incretins, such as glucagon-like peptide I and glucose-dependent insulinotropic peptide, into their inactive forms, thereby preventing them from stimulating insulin secretion. Numerous studies have confirmed the role of DPP-4 in the pathophysiology of type 2 diabetes, leading to the development of various DPP-4 inhibitors. In recent years, research on DPP-4 inhibitors has expanded significantly, resulting in the creation of both non-peptidomimetic heterocyclic compounds and peptidomimetic scaffolds. Evidence Acquisition: This systematic review summarizes all recent advances related to DPP-4 inhibitors up to 2024. It begins by outlining the biochemical characteristics of DPP-4 and general pharmacological principles of DPP-4 inhibition, followed by an overview of the latest developments from recent publications. The review provides valuable insights into the pharmacophores necessary for ligand-protein interactions, aimed at understanding the structure-activity relationship of novel DPP-4 inhibitors. Data for this review was collected from sources including ScienceDirect, PubMed, and Scopus. Results: This review highlights various chemical scaffolds that have been explored in the development of novel DPP-4 inhibitors. It emphasizes scaffolds with significant DPP-4 inhibitory activity, including azoles, azines, sulfonamides, and quinolone motifs. The article also details the structure-activity relationships of newly developed analogs, providing a comprehensive overview of recent advancements in this area. Conclusions: Despite moderate progress in the development of novel DPP-4 inhibitors, emerging molecular aspects of DPP-4 intervention show great promise for future therapeutic developments.

A metabolic dysfunction-associated steatotic liver acinus biomimetic induces pancreatic islet dysfunction in a coupled microphysiology system

Preclinical and clinical studies suggest that lipid-induced hepatic insulin resistance is a primary defect that predisposes to dysfunction in islets, implicating a perturbed liver-pancreas axis underlying the comorbidity of T2DM and MASLD. To investigate this hypothesis, we developed a human biomimetic microphysiological system (MPS) coupling our vascularized liver acinus MPS (vLAMPS) with pancreatic islet MPS (PANIS) enabling MASLD progression and islet dysfunction to be assessed. The modular design of this system (vLAMPS-PANIS) allows intra-organ and inter-organ dysregulation to be deconvoluted. When compared to normal fasting (NF) conditions, under early metabolic syndrome (EMS) conditions, the standalone vLAMPS exhibited characteristics of early stage MASLD, while no significant differences were observed in the standalone PANIS. In contrast, with EMS, the coupled vLAMPS-PANIS exhibited a perturbed islet-specific secretome and a significantly dysregulated glucose stimulated insulin secretion response implicating direct signaling from the dysregulated liver acinus to the islets. Correlations between several pairs of a vLAMPS-derived and a PANIS-derived factors were significantly altered under EMS, as compared to NF conditions, mechanistically connecting MASLD and T2DM associated hepatic-factors with islet-derived GLP-1 synthesis and regulation. Since vLAMPS-PANIS is compatible with patient-specific iPSCs, this platform represents an important step towards addressing patient heterogeneity, identifying disease mechanisms, and advancing precision medicine.

7700 Two Years Of Testosterone Therapy Reduces Glycemia In Males At High Risk Of Type 2 Diabetes Without Affecting Beta Cell Function: Results From A Randomised Controlled Trial And Cellular Model

Abstract Disclosure: M. Umapathysivam: None. S. Nawaz: None. K. Robledo: None. C.A. Allan: None. K. Bracken: None. M. Grossmann: None. D.J. Handelsman: None. W.J. Inder: None. D. Jesudason: None. B. Stuckey: None. B. Yeap: None. A. Januszewski: None. A. Jenkins: None. A. Conway: None. B. Hastoy: None. G.A. Wittert: Consulting Fee; Self; I-Nova. Grant Recipient; Self; Lawley pharmaceuticals, Bayer, Weight Watchers, Eli Lilly & Company. Speaker; Self; Bayer, Inc., Amgen Inc, Besin Health Care. Background: In the Testosterone for the prevention of type 2 diabetes (T4DM) Study, treatment with testosterone (T)-undecanoate (1000 mg IM 3 monthly) vs placebo decreased fat mass and reduced the risk of T2D by 40% after 2 years. However, the mechanism(s) by which T therapy prevents or reverts T2D remain unclear. Aim: To assess (1) the impact of T treatment on insulin resistance (IR) and beta-cell function in the T4DM study and (2) the in-vitro effect of graded T exposure on glucose stimulated insulin secretion (GSIS) from the human beta-cell line EndoC-βH1. Methods: (1) T4DM study: Men (n= 1007) from the T4DM study aged, 50-74 years, waist circumference (WC) >95cm, with prediabetes, or newly diagnosed T2D (by OGTT) and serum testosterone (T) ≤ 14 nmol/L (chemiluminescent assay) treated with T-undecanoate (1000 mg IM 3 monthly) or placebo for 2 years. Men were included if they had fasting bloods at baseline, weeks 18, 66, and 102 (N=743). We compared the change in glycated albumin, and derived measures of beta-cell function (HOMA2-B) and insulin resistance (HOMA-IR) using fasting glucose and c-peptide in T and placebo treated men using linear regression models.(2) EndoC-βH1 were incubated with T 5nM, 10nM and 15nM for 20 min and 15nM T for 2-days. Insulin secretion and content were measured at baseline (1mM glucose) and after 20 min exposure 20mM glucose. Results: Treatment with T compared to placebo reduced glycated albumin (-3.4 umol/L; 95%CI:1.4-5.4, p<0.001) maximally at week 66, along with C-peptide (corrected for baseline C-peptide and change in fasting glucose) (-0.12 nmol/L;-0.22,-0.02; p=0.01), HOMA2-B (-6.1; 95%CI: -16, 3.7; p=0.2) and HOMA-IR (-0.20; 95%CI: -0.59,0.20; p=0.3). In-vitro, acute exposure of EndoC-βH1 to 5nM and 10nM of T had no effect on GSIS, and 15nM T reduced GSIS (<20%, p=0.002). T, at 15nM for 2 days was without effect on GSIS. EndoC-βH1 insulin content was not altered at any concentration or timeframe of T exposure. Conclusion: In men with pre-diabetes or early T2D, T treatment reduces glycemia without evidence either in vivo or in-vitro of an affect to increase insulin secretion. Presentation: 6/1/2024

9366 The Rnf20 Histone Modifier Is A Crucial Mediator Of Pancreatic Beta Cell Identity And Function

Abstract Disclosure: T.H. Pierre: None. Y. Liu: None. M.M. Bethea: None. K. Coutinho: None. C. Hunter: None. Diabetes is characterized by the loss of pancreatic β-cell mass. As diabetes incidence continues to elevate, it is critical that we develop a better understanding of the factors that define functional β-cells in order to improve current therapeutics. One approach is through the study of transcription factors (TFs), which are essential for β-cell development and function. Prior work from our lab and others has examined Islet-1 (Isl1) a LIM-homeodomain TF that is required for the maturation of the endocrine pancreas and adult β-cell function. We have also extensively characterized several Isl1-interacting co-regulators (e.g., Ldb1 and SSBP3) that facilitate its roles in maintaining glucose homeostasis. Most recently, we have identified that Isl1 interacts with the ubiquitin ligases Ring Finger 20 (Rnf20) and Rnf40, whose histone H2B monoubiquitation (H2Bub1) activity support the gene regulatory functions of Isl1. With in vitro experiments, we demonstrated that Rnf20 and Rnf40 are important for glucose stimulated insulin secretion (GSIS) and mediate the expression of β-cell identity genes. Based on these findings, we hypothesize that Isl1-Rnf complexes modify histones to regulate β-cell gene expression and function. To address this hypothesis in vivo, we developed an adult inducible β-cell knockout of Rnf20 (Rnf20Δβ-cell). Rnf20Δβ-cell mice display fasting hyperglycemia and severe glucose intolerance that is driven by impaired GSIS, reduced insulin content, and the dysregulation of critical β-cell genes including Ins1, Ucn3, and Slc2a2. Additionally, loss of Rnf20 perturbs insulin processing and overall β-cell maturation as observed by measurement of proinsulin:insulin ratios, C-peptide levels, and whole islet RNA-seq. Phenotypes exhibited by Rnf20Δβ-cell mice are similar to those observed in Isl1 β-cell knockout mice, and comparative transcriptomics revealed an overlap of 570 genes involved in metabolism, zinc homeostasis, and islet proliferation including Slc30a8 and Matn2, both of which we found are occupied by Isl1 and Rnf20. Collectively, our findings demonstrate the importance of the Rnf20 histone modifier in regulating β-cell function and expand our understanding of the Isl1 regulatory network. Presentation: 6/2/2024

6989 Novel Use of Dual GIP/GLP-1 Receptor Agonist in HNF4A-MODY

Abstract Disclosure: A. Mehdi: None. M.C. Foss de Freitas: Advisory Board Member; Self; PTC Pharmaceuticals. Other; Self; Scientific presenter in a symposium funded by Amryt Pharmaceuticals. C.L. Martin: None. B.E. Gregg: None. N. Nachawi: None. E. Frontera: None. E.A. Oral: Consulting Fee; Self; Amryt Pharmaceuticals, Akcea Therapeutics, Ionis Pharmaceuticals Inc., Regeneron Pharmaceuticals. Grant Recipient; Self; Amryt Pharmaceuticals (now part of Cheisi, manufacturer of metreleptin), Akcea Therapeutics, Ionis Pharmaceuticals Inc., Regeneron Pharmaceuticals, Novo Nordisk, Rhythm Pharmaceuticals, Fractyl Laboratories, GI Dynamics (now Morfic Medical. Other; Self; Royalty rights from the use of Metreleptin in lipodystrophy. W.H. Herman: Advisory Board Member; Self; Member of the Data Safety and Monitoring Board for Merck Sharp & Dohme, LLC, Memer of the Data Safety and Monitoring Board for Rivus Pharmaceuticals. Other; Self; Chair for the National Committee for Quality Assurance (NCQA) Healthcare Effectiveness Data and Information Set (HEDIS) Workgroup. D.T. Broome: Consulting Fee; Self; Tayco, Inc. Research Investigator; Self; Novo Nordisk, Fractyl Laboratories, Rhythm Pharmaceuticals, Inc. HNF4A-MODY (formerly MODY-1) is an autosomal dominant form of diabetes caused by a mutation in the transcription factor HNF4A[1],2. Affected patients are initially very sensitive to the anti-hyperglycemic effect of sulfonylureas, but become unresponsive to sulfonylureas at a rate of 1-4% per year3. Recently, the efficacy of glucagon-like peptide-1 receptor agonists has been demonstrated in HNF4A-MODY2, but there have been no reports on the use of dual gastric inhibitory polypeptide/glucagon-like peptide-1 receptor agonists (dual GIP/GLP-1 RA) in HNF4A-MODY. This report describes a patient with HNF4A-MODY who was treated with a dual GIP/GLP-1 RA. A 42-year-old White male with a pathogenic heterozygous mutation in Q268X was diagnosed with HNF4A-MODY at the age of 10 years (part of the RW pedigree)3. He was diagnosed with diabetes at age 20, treated with metformin from age 20 to age 30, and had glipizide extended release added at age 30. His dose of glipizide was titrated over 9-years to the maximum therapeutic dose. At the age of 40, when his HbA1c was no longer controlled, dulaglutide 1.5 mg once weekly was added. Thereafter, his HbA1c was well controlled between 5.5-7.0%, until it increased to 7.7%. He was then transitioned from dulaglutide to tirzepatide 5 mg once weekly for 4 weeks, 7.5 mg once weekly for 4 weeks, then 10 mg once weekly. He has been maintained on tirzepatide 10 mg once weekly, glipizide extended release 10 mg once daily, and metformin 1,000 mg twice daily without significant side effects. His HbA1c improved from 7.7% to 5.8% and he lost 7 lbs since transitioning from dulaglutide to tirzepatide (while on tirzepatide for 4 months in total). During his recent visit, he was without significant hyper- or hypoglycemia and his BMI was 31.2 kg/m2. (down from 32.32 kg/m2). To our knowledge, this is the first case report demonstrating preliminary efficacy of dual GIP/GLP-1 receptor agonist in HNF4A-MODY. While it is known that GIP and GLP-1 can cause glucose stimulated insulin secretion, and the mechanism of GLP-1 was previously described in MODY4, the differential effects and/or predominance of GIP or GLP-1 in MODY requires further investigation.

8330 Pancreatic neurons in neuron-islet complexes and activation of these neurons promotes insulin secretion under high glucose level

Abstract Disclosure: Y. Liu: None. Z. Yang: None. Q. Feng: None. M. Hu: None. L. Sha: None. Islets are rich in pancreatic nerve innervation. Pancreatic ganglionic neurons, as an integrating center, receive central and peripheral nerve innervation regulating endocrine and exocrine of pancreas. Neurons in pancreatic ganglia have been studied intensely in our lab and a few other labs. Neurons located in islets forming neuron-islet complexes have been demonstrated. However, the properties and function of these neurons has not been studied. In this study, pancreatic neurons in the neuron-islet complex and the effects of activation of these neurons on insulin release were investigated. Methods: Eight week old rats were used. Pancreas was digested and a method was developed to identify neuron-islet complexes from islets. Results: CHAT and TUBB3 were co-localized in nearly all neurons in the neuron-islet complex indicating that these neurons were mainly cholinergic neurons. A small portion (<10%) of TUBB3 positive cells were also positive for nNOS. Nicotinic tartrate was used to activate neurons in the complexes. After one hour of administration of nicotinic tartrate, with 5.6 mM glucose, ACh level was increased significantly from 15.26±5.46 μM to 23.24±4.18 μM and insulin level were slightly increased from 37.21±2.04 μM to 39.27±1.23μM (P > 0.05). With 16.7 mM glucose, ACh level were increased significantly from 23.83±2.28 μM to 30.92±1.03 μM and insulin increased significantly from 41.93±1.30 μM to 49.04±1.68 μM. Conclusion: The neurons in neuron-islet complexes are mainly cholinergic neurons and activation of these neuron under high glucose level stimulate insulin secretion. Presentation: 6/2/2024

7971 The Role of PDX1 In Beta Cell Response To GLP1

Abstract Disclosure: C. Bheeman: None. K. Vann: None. O. Astapova: None. Mature Onset of Diabetes of the Young Type 4 is a rare form of diabetes mellitus caused by a defect in the Pancreatic and Duodenal homeobox 1 (PDX-1) gene, which is predominantly expressed in β-cells and is an important factor in insulin gene transcription. We aim to study the impact that a PDX1 mutation (modeled after a patient) has on the beta cell response to GLP1. This was a 33-year-old nonobese man who presented to the clinic with new onset diabetes without ketosis. He was treated with insulin and metformin and his hemoglobin A1c decreased from 16% to 6.1% in six months. Other labs showed c-peptide of 8.9 ng/mL in setting of a blood glucose of 231 mg/dL, negative islet cell antibodies and glutamic acid antibodies. Of note, patient also had significant family history of diabetes. Due to high probability of MODY, genetic testing was obtained. He was found to have a heterozygous frameshift mutation in codons 228 -233 leading to a 17 base pair deletion in the PDX1 gene causing replacement of the 56 C- terminal amino acids with a shorter, missense C-terminal tail. Patient was started on dulaglutide 0.75 mg weekly but was hypoglycemic on the smallest dose so he was then switched to Semaglutide and has been maintained on less than 0.25 mg weekly. The clinical question we aim to answer was why was this patient so sensitive to GLP1 agonist activity. To study how the mutation affects response to GLP1 we are using mouse beta-TC-6 cell as they are insulin secreting, and regulated by glucose. The PDX-1 gene is highly conserved among species and the mouse PDX gene is comparable to the human gene. We used CRISPR-Cas9 to introduce the same 17 base-pair deletion into the mouse PDX-1 gene in beta-TC-6 cells. We first measured the glucose stimulated insulin secretion in control cells to examine first and second phases of insulin secretion, determining that the first phase of insulin occurs in twenty minutes and the second phase starts at about two hours. We also evaluated if these cells responded GLP-1 by increasing insulin secretion. We found that these cells respond to glucose and GLP1 in an additive manner. Insulin was measured by enzyme-linked immunosorbent assay (ELIZA). In the next phase of the experiment we aim to determine the effect of the GLP-1 in cell lines with the PDX1 deletion mutation as compared to control cell line. We will measure insulin secretion by ELISA in both mutant and the control cells treated with and without glucose and GLP1. We will measure insulin at 0 minutes and 30 minutes and insulin mRNA at 0 minutes and 6 hours to determine the first and second phases of insulin production. Our results will help guide personalized treatment for patients with MODY type 4 and improve our understanding of beta cell response to GLP1. Presentation: 6/2/2024

8010 Potent MSB-61 as Type 1 Diabetes (T1D) therapy: mechanism of action in insulin secretion

Abstract Disclosure: N. Ajmal: None. M. Bogart: None. K. Corbin: None. P. Khan: None. M. Shafqat: None. S. Bergmeier: None. G. Gu: None. X. Tong: None. C.S. Nunemaker: None. Type 1 diabetes (T1D) is a chronic autoimmune disorder caused by proinflammatory cytokines (Interleukin 1-beta; IL1-β, Tumor Necrosis Factor-alpha; TNF-α, and Interferon-gamma; IFN-ϒ) from immune cells that destroy insulin-producing beta cells in pancreatic islets and lead to hyperglycemia. The development of possible treatments to cure T1D is needed besides intensive insulin therapy that does not halt disease progression. We have identified a small molecule called MSB-61 that can protect islet cells from endoplasmic reticulum stressors (66% protection) and cytokines (33% protection) as measured by propidium iodide in islets isolated from mice using 50uM MSB-61. Importantly, we observed large increases in insulin secretion during overnight exposure to 50uM MSB-61. Insulin secretion began to increase in response to MSB-61 at ∼4h, reaching a plateau at ∼8h of greater than 4-fold insulin release compared to controls. The Kegg pathway analysis of RNA-seq data on MSB-61 suggested that multiple genes upregulated by MSB-61 are involved in insulin secretion through an amplifying pathway that includes cAMP/PKA and Pi3k/Akt signaling cascades. Based on RNA sequencing data, this study aimed to test MSB-61 for identifying pathway by which it potentiates insulin secretion. Islets from CD-1 mice and mouse insulinoma Min-6 cell lines were used to test amplifying pathways by using cAMP/PKA and Pi3k/Akt analogs and antagonists with and without MSB-61, and overnight insulin secretion and insulin content will be measured by enzyme-linked immunosorbent assay (ELISA). MSB-61 showed no potential effects on insulin secretion when tested for Pi3k/Akt pathway in the presence of analogs and antagonists such as 740-Y-P and wortmannin. It further suggests MSB-61 might potentiate insulin secretion through the cAMP/PKA pathway, which is still under investigation. RNA sequencing analysis of mouse islets showed several genes that belong to Ras family member-2 and have GTPase activity. Genes with GTPase activity will be further investigated to help identify if MSB-61 stimulates insulin secretion through an amplifying pathway involving the cAMP/PKA downstream signaling cascade. Identifying the mechanism of action and signaling pathway by which MSB-61 potentiates insulin secretion will open new ways of identifying T1D therapeutic interventions that would help replace standard insulin therapy. Presentation: 6/3/2024

9317 Diabetogenic Stress-Mediated Beta Cell Extracellular Vesicle:Autophagy Pathway Crosstalk

Abstract Disclosure: A. Roy: None. G. Ariyaratne: None. A. Matveyenko: None. N. Javeed: None. Diabetogenic stressors including elevated free fatty acids (lipotoxicity), low-grade systemic inflammation, and proteotoxicity are central to the development of Type 2 Diabetes (T2D). Due to their high protein synthetic burden, β-cells employ autophagy and endo/lysosomal pathways to reduce protein aggregates, and protect β-cell mass and function. Recently, extracellular vesicles (EVs; 30-150 nm sized nanoparticles) have been shown to work in tandem with autophagy to facilitate cellular adaptation and intercellular communication. As diabetogenic stressors have been shown to perturb autophagy via lysosomal defects, our group has noted enhanced EV secretion. Thus, we hypothesize that diabetogenic factors enhance EV secretion through activation of an EV-based secretory autophagy pathway and that re-balancing of both pathways could improve β-cell function in T2D. To test this, MIN6 cells were exposed to free fatty acid palmitate (PAL; 24h), or pro-inflammatory cytokines IL-1β, TNFα, and IFNγ (CYTO; 48h). Expression of autophagic markers, LC3 and p62 were increased in CYTO and PAL conditions suggesting defects in auto/lysosomal function. Upon PAL/CYTO treatment in MIN6 cells, conditioned media EVs were isolated using differential ultracentrifugation. We noted enhanced protein expression of LC3-II and p62 in PAL- and cytoEVs, suggesting a diversion of immature autophagosome components into EVs due to lysosomal inhibition. To restore balance between autophagy:EV flux, we used EV biogenesis inhibitor, GW4869 (GW; 24h) or autophagy inducer, rapamycin (Rapa; 24h) on MIN6 cells exposed to PAL or CYTO. Isolated EVs were subjected to Nanoparticle Tracking Analysis (NTA) which showed a significant reduction in EV concentration with GW or Rapa addition (p<.05). Isolated mouse islet exposed to CYTO+GW/Rapa or PAL+GW/Rapa showed significant improvements in glucose stimulated insulin secretion (vs. CYTO or PAL; p<.05). Taken together, these data implicate activation of EV-based secretory autophagy in response to diabetogenic stressors and thus, potential targets to improve functional β-cell mass. Presentation: 6/2/2024

Mammalian D-Cysteine controls insulin secretion in the pancreas

D-amino acids are being recognized as important molecules in mammals with function. This is a first identification of endogenous D-cysteine in mammalian pancreas. D-cysteine is synthesized by serine racemase (SR) and SR−/− mice produce 6–10 fold higher levels of insulin in the pancreas and plasma including higher glycogen and ketone bodies in the liver. The excess insulin is stored as amyloid in secretory vesicles and exosomes. In glucose stimulated insulin secretion in mouse and human islets, equimolar amount of D-cysteine showed higher inhibition of insulin secretion compared to D-serine, another closely related stereoisomer synthesized by SR. In mouse models of diabetes (Streptozotocin (STZ) and Non Obese Diabetes (NOD) and human pancreas, the diabetic state showed increased expression of D-cysteine compared to D-serine followed by increased expression of SR. SR−/− mice show decreased cAMP in the pancreas, lower DNA methyltransferase enzymatic and promoter activities followed by reduced phosphorylation of CREB (S133), resulting in decreased methylation of the Ins1 promoter. D-cysteine is efficiently metabolized by D-amino acid oxidase and transported by ASCT2 and Asc1. Dietary supplementation with methyl donors restored the high insulin levels and low DNMT enzymatic activity in SR−/− mice. Our data show that endogenous D-cysteine in the mammalian pancreas is a regulator of insulin secretion.

Abdominal Normothermic Regional Perfusion after Donation after Circulatory Death Improves Pancreatic Islet Isolation Yield

Abdominal Normothermic Regional Perfusion (aNRP) is an in-situ normothermic oxygenated donor perfusion technique before procurement during controlled donation after circulatory death (cDCD) procedures and allows for organ quality evaluation. There are few data on the effect of aNRP on pancreatic islet isolation and subsequent transplantation outcomes. We aim to evaluate the impact of aNRP on cDCD pancreatic islet isolation and transplantation.A retrospective analysis was performed on pancreatic islet isolation outcomes from aNRP, cDCD, and Donation after Brain death (DBD) pancreases. Isolations were compared to previous donor age (60-75) matched isolations. Islet function was asses by a dynamic Glucose Stimulated Insulin Secretion (dGSIS).Donor baseline characteristics did not differ among groups. Isolations from aNRP pancreases (471,739 IEQ [655,435 – 244,851]) yielded more islets compared to cDCD (218,750 IEQ [375,951 – 112,364, p<0.01) and to DBD (206,522 IEQ [385,544 – 142,446, p=0.03) pancreases. dGSIS tests in seven aNRP islet preparations showed a mean stimulation index of 4.91, indicating good functionality. Bilirubin and alanine aminotransferase during aNRP correlated with islet yield (r2=0.685, p=0.002; r2=0.491, p=0.016 respectively).Islet isolation after aNRP in cDCD donors results in a high islet yield with viable functional islets. aNRP could increase the utilization of pancreases for islet transplantation.

Preparation of bee venom-loaded chitosan nanoparticles for treatment of streptozotocin-induced diabetes in male Sprague Dawley rats

BackgroundDiabetes mellitus (DM) can be defined as an increase in the blood sugar level and a disturbance in protein, fat and carbohydrate metabolism. Bee venom (BV) is useful for treating and preventing diabetic rats’ histological and biochemical problems. Although the medical advantages of BV have been identified, its safety has remained a substantial barrier for its application. Consequently, the goal of our work was to prepare bee venom-loaded chitosan (BV-CS) nanoparticles (NPs), which would then be physically characterized. This was followed by examining the effect of the synthetized BV-CS NPs on oxidation, inflammation and coagulation in vitro. In diabetic rats’ model [induced by streptozotocin (STZ)], the produced BV-CS NPs were tested as an anti-diabetic medication.ResultsIn vivo testing on pancreatic tissue homogenates showed that BV-CS NPs have antioxidant and anti-inflammatory properties. The results showed that BV-CS NPs can be used as a safe and efficient therapy for diabetes. Up to a concentration of 250 µg/ml, the generated NPs demonstrated potential antioxidant, membrane stabilizing, and non-cytotoxic capabilities. Our findings indicated that the administration of BV-CS NPs significantly controlled blood glucose levels and metabolic abnormalities that accompanied diabetes induction.ConclusionsBV-CS NPs were successful in treating STZ-induced diabetes in rats, stimulated insulin secretion and were safe to be used in vivo.Graphical abstract

Therapeutic benefits of incretin hormones beyond glycemic control from a primary care perspective: A Narrative Review

The parallel rise in the prevalence of obesity and T2DM is a global health challenge. One of the pathogenesis involved in development and progression of type-2 diabetes mellitus is beta cell dysfunction. Until now, diabetes treatments could not restore the reduced function of pancreatic β cell, necessitating the need for advanced treatment options. This led to discovery of incretin hormones in the small intestine, which stimulates insulin secretion in response to glucose. Glucagon-like peptide 1 (GLP-1) and glucosedependent insulinotropic polypeptide (GIP) are two such incretin hormones, secreted by the small intestine in response to food ingestion. Important physiological effects of GLP-1 include enhancement of the insulinotropic response of beta cells to intake of nutrients, reduced gastrointestinal secretion and motility, as well as induction of satiety and ensuing reduction of food intake. Recent evidence suggests that in addition to its established glucose-lowering actions, GLP-1 RAs may also exert several beneficial actions extending beyond glycemic control. The recent finding that GIP/GLP-1 receptor co-agonists like tirzepatide have superior efficacy compared to selective GLP-1 receptor agonists with respect to glycaemic control as well as body weight has renewed interest in GIP, which previously was thought to lack therapeutic potential. This is a narrative review examining some of the ‘beyond-glycemic” benefits of incretin hormones, focusing predominantly on GLP-1 RAs including blood pressure lowering, improvements in the lipid profile, improvements in myocardial and endothelial function. We explore how those effects may help reduce the cardiovascular burden in patients with diabetes. The aim is to encourage use of GLP-1 RA early in patients with established CVD risk factors to prevent CVD related complications and mortality. Keywords: glucagon-like peptide-1 receptor agonist, cardiovascular diseases, major adverse cardiovascular events, type 2 diabetes mellitus, obesity, GIP receptor.

Nutritional and Organoleptic Value in the Formula Enteral of Growol and Germinated Mung Bean Flour as an Alternative Enteral Type 2 Diabetes Mellitus

Background: Type 2 Diabetes Mellitus (T2DM) is a metabolic disease characterized by increased blood glucose. Nutritional support rich in dietary fiber and high protein can stimulate insulin secretion, thereby inhibiting increased blood glucose. Enteral of Growol-Germinated Mung Bean Flour (ENGROCAJO) is a formula developed from growol flour and germinated mung bean flour. It contains high dietary fiber with protein and is an alternative nutritional therapy for people with T2DM. Hospital Diabetes Mellitus (DM) enteral formula administered to patients is limited to dietary fiber. Objectives: This study aimed to analyze the nutritional value and organoleptic value of the ENGROCAJO formula and compare it with the hospital DM enteral formula. Methods: This was an observational laboratory study developed an enteral formula from growol and germinated mung bean flour. It analyzed the nutritional value using proximate and dietary fiber analysis. The organoleptic assessment utilized a hedonic test with 20 participants. The nutritional and organoleptic contents were compared with hospital DM enteral formula. The difference test between formulas was tested using Kruskal-Wallis with a significant value of p&lt;0.05. Results: The nutritional content in 100 g of ENGROCAJO formula and hospital DM enteral formula includes energy of 386.86 and 329.49 kcal, protein of 41.38% and 20.43%, fat of 2.78% and 8.88%, carbohydrate of 49.08% and 38.55% with dietary fiber of 22.43% and 3.62%. Organoleptic assessment of aroma, color, flavor, and thickness showed that the ENGROCAJO formula had higher quality than the hospital DM enteral formula. However, the flavor aspect showed significant difference (p=0.038). Conclusions: ENGROCAJO formula contains higher protein and dietary fiber compared to the hospital DM enteral formula. There was a significant difference in the organoleptic taste between the ENGROCAJO formula and the hospital DM enteral formula.

Expression of Glucagon-Like Peptide-1 Receptors in the Submandibular Gland of Mice and Its Implications in Type 2 Diabetes.

Introduction Type 2 diabetes mellitus (T2DM) not only affects the pancreas directly involved in glucose metabolism but also impairs salivary gland function. Glucagon-like peptide-1 (GLP-1) is a gastrointestinal hormone that lowers postprandial blood glucose levels by stimulating insulin secretion from the pancreas. Previous studies have revealed the presence of GLP-1 receptors (GLP-1R) in salivary glands. However, the effect of diabetes on salivary gland GLP-1R remains unclear. This study aimed to observe the impact of T2DM on GLP-1R in the submandibular gland (SMG). Materials and methods Twenty-five-week-old mice were randomly divided into four groups (n=5 each): 11w and 13w control groups (CON), and 11w and 13wdiabetes mellitusgroups (DM). After a five-day adaptation period, the DM group mice were subjected to a high-fat diet, while the CON group received a standard diet. The DM group mice were then induced into a state of T2DM by a single low-dose streptozotocin injection at nine weeks of age. Oral glucose tolerance tests (OGTT) were conducted to evaluate mouse glucose tolerance. At 11 and 13 weeks of age, SMG was excised under general anesthesia, and the morphology of SMG was evaluated by hematoxylin-eosin staining, while the distribution and expression of GLP-1R were assessed by immunohistochemical staining. The data obtained were subjected to the Shapiro-Wilk test to confirm normal distribution, the t-test for the OGTTresults, and statistical analysis for other results by one-way analysis of variance. Results Consistent with previous reports, the mice in the DM group showed higher body weight and lower glucose tolerance.Histological analysis revealed an increase in the acinar area and a decrease in the ductal area of the SMG in the DM group. Although there was no significant decrease in the cell count regarding the ductal area, a tendency towardluminal dilation was observed. Interestingly, the expression pattern of GLP-1R was limited to the ductal portion of the SMG, with a decrease in anti-GLP-1R-positive areas observed in the DM group compared to the CON group.While there was no significant difference in anti-GLP-1R-positive areas between the CON11w and CON13w groups, the DM13w group exhibited a significant decrease compared to the DM11w group. These data suggest that diabetes induces both structural changes in the SMG and a reduction in GLP-1R expression, particularly in the ductal regions. Conclusions We found that the expression level of GLP-1R in SMG was decreased in the DM group mice. This data demonstrates the potential relationship between T2DM and GLP-1R expression. Moreover, there was an indication of a temporal decrease in anti-GLP-1R positive areas over time.Thisresult may suggest the involvement of salivary gland GLP-1R in the mechanism of impaired SMG function caused by T2DM, potentially mediated through the decrease in blood GLP-1 levels.

Insulin Signaling Pathway Mediates FoxO-Pepck Axis Regulation of Glucose Homeostasis in Drosophila suzukii.

The agricultural pest Drosophila suzukii exhibits a strong preference for feeding on fresh fruits, demonstrating high adaptability to sugary environments. Meanwhile, high sugar levels stimulate insulin secretion, thereby regulating the steady state of sugar metabolism. Understanding the mechanisms related to sugar metabolism in D. suzukii is crucial due to its adaptation to these specific environmental conditions. The insulin signaling pathway is an evolutionarily conserved phosphorylation cascade with significant roles in development and metabolism. We observed that the activation of the insulin signaling pathway inhibited FoxO activity and downregulated the expression of Pepck, thereby activating glycolysis and reducing glucose levels. By contrast, inhibiting insulin signaling increased the FoxO activity and upregulated the expression of Pepck, which activated gluconeogenesis and led to increased glucose levels. Our findings demonstrated the crucial role of the insulin signaling pathway in mediating glucose metabolism through the FoxO-Pepck axis, which supports the ecological adaptation of D. suzukii to high-sugar niches, thereby providing insights into its metabolic control and suggesting potential strategies for pest management. Elucidating these molecular processes is important for understanding metabolic regulation and ecological specialization in D. suzukii.

Beta cell specific ZnT8 gene deficiency and resulting loss in zinc content significantly improve insulin secretion

Zinc transporter 8 (ZnT8) is highly expressed in pancreatic beta cells, localizes to insulin secretory granules (ISG), and regulates zinc content. ZnT8 gene polymorphisms have revealed a relationship between ZnT8 activity and type 2 diabetes (T2D) risk, however, the role of beta-cell ZnT8 is not well understood.A beta cell specific ZnT8 knockout (ZnT8 BKO) mouse model was investigated. ZnT8 BKO islets showed significantly reduced ZnT8 gene expression and reduced zinc content. Compared to controls, ZnT8 BKO mice displayed significantly elevated plasma insulin levels and improved glucose tolerance following acute insulin resistance induced via S961. Glucose stimulated insulin secretion from isolated ZnT8 BKO pancreatic islets revealed enhanced insulin secretion capacity. The difference in insulin secretion between ZnT8 BKO and control islets was negated upon zinc supplementation, and the inhibitory effect of zinc on insulin secretion was confirmed in human islets.These results indicate that the loss of ZnT8 activity and accompanying reduced cellular zinc are associated with increased insulin secretion capacity. The reduction in secreted insulin content upon zinc supplementation in ZnT8 BKO islets suggests that ISG-released zinc normally tempers insulin secretion.