Insulin Release In Response Research Articles

Metabolic Adaptions/Reprogramming in Islet Beta-Cells in Response to Physiological Stimulators-What Are the Consequences.

Irreversible pancreatic β-cell damage may be a result of chronic exposure to supraphysiological glucose or lipid concentrations or chronic exposure to therapeutic anti-diabetic drugs. The β-cells are able to respond to blood glucose in a narrow concentration range and release insulin in response, following activation of metabolic pathways such as glycolysis and the TCA cycle. The β-cell cannot protect itself from glucose toxicity by blocking glucose uptake, but indeed relies on alternative metabolic protection mechanisms to avoid dysfunction and death. Alteration of normal metabolic pathway function occurs as a counter regulatory response to high nutrient, inflammatory factor, hormone or therapeutic drug concentrations. Metabolic reprogramming is a term widely used to describe a change in regulation of various metabolic enzymes and transporters, usually associated with cell growth and proliferation and may involve reshaping epigenetic responses, in particular the acetylation and methylation of histone proteins and DNA. Other metabolic modifications such as Malonylation, Succinylation, Hydroxybutyrylation, ADP-ribosylation, and Lactylation, may impact regulatory processes, many of which need to be investigated in detail to contribute to current advances in metabolism. By describing multiple mechanisms of metabolic adaption that are available to the β-cell across its lifespan, we hope to identify sites for metabolic reprogramming mechanisms, most of which are incompletely described or understood. Many of these mechanisms are related to prominent antioxidant responses. Here, we have attempted to describe the key β-cell metabolic adaptions and changes which are required for survival and function in various physiological, pathological and pharmacological conditions.

Multivesicular Liposomes for Glucose-Responsive Insulin Delivery.

An intelligent insulin delivery system is highly desirable for diabetes management. Herein, we developed a novel glucose-responsive multivesicular liposome (MVL) for self-regulated insulin delivery using the double emulsion method. Glucose-responsive MVLs could effectively regulate insulin release in response to fluctuating glucose concentrations in vitro. Notably, in situ released glucose oxidase catalyzed glucose enrichment on the MVL surface, based on the combination of (3-fluoro-4-((octyloxy)carbonyl)phenyl)boronic acid and glucose. The outer MVL membrane was destroyed when triggered by the local acidic and H2O2-enriched microenvironment induced by glucose oxidase catalysis in situ, followed by the further release of entrapped insulin. Moreover, the Alizarin red probe and molecular docking were used to clarify the glucose-responsive mechanism of MVLs. Utilizing chemically induced type 1 diabetic rats, we demonstrated that the glucose-responsive MVLs could effectively regulate blood glucose levels within a normal range. Our findings suggest that glucose-responsive MVLs with good biocompatibility may have promising applications in diabetes treatment.

Spontaneous and iatrogenic hypoglycemia in cystic fibrosis

Spontaneous episodes of hypoglycemia can occur in people with cystic fibrosis (CF) without diabetes, who are not on glucose lowering medications. Spontaneous hypoglycemia in CF could occur both in the fasting or postprandial state (reactive hypoglycemia). The pathophysiology of fasting hypoglycemia is thought to be related to malnutrition and increased energy expenditure in the setting of inflammation and acute infections. Reactive hypoglycemia is thought to be due to impaired first phase insulin release in response to a glucose load, followed by a delayed and extended second phase insulin secretion; ineffective counterregulatory response to dropping glucose levels may also play a role. The overall prevalence of spontaneous hypoglycemia varies from 7 to 69% as examined with oral glucose tolerance test (OGTT) or with continuous glucose monitoring (CGM) under free living conditions. Spontaneous hypoglycemia in CF is associated with worse lung function, higher hospitalization rates, and worse clinical status. In addition, patients with CF related diabetes on glucose-lowering therapies are at risk for iatrogenic hypoglycemia. In this article, we will review the pathophysiology, prevalence, risk factors, clinical implications, and management of spontaneous and iatrogenic hypoglycemia in patients with CF.

Digital Assembly of Spherical Viscoelastic Bio‐Ink Particles

Abstract3D bioprinting additively assembles bio‐inks to manufacture tissue‐mimicking biological constructs, but with the typical building blocks limited to 1D filaments. Here, it is developed a voxelated bioprinting technique for the digital assembly of spherical particles (DASP), which are effectively 0D voxels—the basic unit of 3D structures. It is shown that DASP enables on‐demand generation, deposition, and assembly of viscoelastic bio‐ink droplets. A two‐parameter diagram is developed to outline the viscoelasticity of bio‐inks required for printing spherical particles of good fidelity. Moreover, a strategy is developed for engineering bio‐inks with independently controllable viscoelasticity and mesh size, two of the most important yet intrinsically coupled physical properties of biomaterials. Using DASP, mechanically robust, multiscale porous scaffolds composed of interconnected yet distinguishable hydrogel particles are created. Finally, it is demonstrated the application of the scaffolds in encapsulating human pancreatic islets for sustained responsive insulin release. Together with the knowledge of bio‐ink design, DASP might be used to engineer highly heterogeneous, yet tightly organized tissue constructs for therapeutic applications.

Glucose-induced [Ca2+]i oscillations in β cells are composed of trains of spikes within a subplasmalemmal microdomain

Electrical activity and oscillations of cytosolic Ca2+ concentrations ([Ca2+]i) that trigger insulin release in response to glucose are key functions of pancreatic β cells. Although oscillatory Ca2+ signals have been intensively studied in β cells, their lower frequency did not match that of electrical activity. In addition, the measured peak [Ca2+]i did not reach levels that are typically required by synaptotagmins to elicit the release of insulin-containing vesicles in live-cell experiments. We therefore sought to resolve the Ca2+ dynamics in the subplasmalemmal microdomain that is critical for triggering fast exocytosis. Applying total internal reflection fluorescence (TIRF) microscopy in insulin-producing INS-1E and primary mouse β cells, we resolved extraordinary fast trains of Ca2+ spiking (frequency > 3 s−1) in response to glucose exposure. Using a low-affinity [Ca2+]i indicator dye, we provide experimental evidence that Ca2+ spikes reach low micromolar apparent concentrations in the vicinity of the plasma membrane. Analysis of Ca2+ spikes evoked by repeated depolarization for 10 ms closely matched the Ca2+ dynamics observed upon glucose application. To our knowledge, this is the first study that experimentally demonstrates Ca2+ spikes in β cells with velocities that resemble those of bursting or continuously appearing trains of action potentials (APs) in non-patched cells.

Decreased KATP Channel Activity Contributes to the Low Glucose Threshold for Insulin Secretion of Rat Neonatal Islets.

Transitional hypoglycemia in normal newborns occurs in the first 3 days of life and has clinical features consistent with hyperinsulinism. We found a lower threshold for glucose-stimulated insulin secretion from freshly isolated embryonic day (E) 22 rat islets, which persisted into the first postnatal days. The threshold reached the adult level by postnatal day (P) 14. Culturing P14 islets also decreased the glucose threshold. Freshly isolated P1 rat islets had a lower threshold for insulin secretion in response to 2-aminobicyclo-(2, 2, 1)-heptane-2-carboxylic acid, a nonmetabolizable leucine analog, and diminished insulin release in response to tolbutamide, an inhibitor of β-cell KATP channels. These findings suggested that decreased KATP channel function could be responsible for the lower glucose threshold for insulin secretion. Single-cell transcriptomic analysis did not reveal a lower expression of KATP subunit genes in E22 compared with P14 β cells. The investigation of electrophysiological characteristics of dispersed β cells showed that early neonatal and cultured cells had fewer functional KATP channels per unit membrane area. Our findings suggest that decreased surface density of KATP channels may contribute to the observed differences in glucose threshold for insulin release.

Substantial PCSK9 inactivation in β-cells does not modify glucose homeostasis or insulin secretion in mice

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays an important role in cholesterol homeostasis by promoting the degradation of the LDL receptor (LDLR). PCSK9 loss-of-function mutations are associated with increased fasting plasma glucose levels and slightly elevated risk of type 2-diabetes. Considering the known detrimental effects of cholesterol accumulation in β-cell, and the widespread use of PCSK9 inhibitors to treat hypercholesterolemia, it is important to gain insight into the role of pancreatic PCSK9 in glucose homeostasis and β-cell function. We generated the first β-cell-specific KO of PCSK9 (βKO). PCSK9 mRNA and protein expression were reduced by 48% and 78% in βKO islets, respectively, indicating that β-cells constitute a major site of PCSK9 expression. In islets, loss of β-cell PCSK9 resulted in unchanged LDLR protein levels, but reduced LDLR mRNA, indicating that cholesterol internalization is enhanced and that β-cell PCSK9 promotes LDLR degradation. In contrast, whole body PCSK9 KO mice exhibited 2-fold higher LDLR protein levels in islets and a stable expression of cholesterogenic genes. Whole body KO and βKO mice presented normal glucose tolerance, insulin release in response to glucose load and insulin sensitivity. Ex vivo glucose-stimulated insulin secretion in presence or absence of fatty acids was similar in WT and KO islets. Like KO mice, individuals carrying loss-of-function PCSK9 variants may be protected from cholesterol-induced toxicity due to reduced circulating cholesterol levels. Using both whole body KO or βKO models, our data demonstrate that PCSK9 deletion in mouse does not have any toxic effect on β-cell function and glucose homeostasis.

Chronic binge alcohol impairs glucose‐insulin dynamics in SIV‐infected female rhesus macaques

Background Antiretroviral therapy (ART) has significantly reduced mortality of people living with HIV (PLWH). Older PLWH, especially post-menopausal women, experience complex interactions of HIV, ART, hormonal status, and lifestyle behaviors such as at-risk alcohol use, increasing the risk of metabolic comorbidities. We have previously shown that chronic binge alcohol (CBA) reduces the acute insulin response to a glucose challenge in SIV-infected male macaques and that at-risk alcohol use decreases HOMA-β (a marker for pancreatic beta cell function) in PLWH. Meanwhile, the role of estrogen in pancreatic health maintenance is not fully understood. The objective of this study was to determine the effect of CBA and ovarian hormone loss, resulting from ovariectomy (OVX), on glucose-insulin dynamics and pancreatic integrity in SIV-infected female rhesus macaques. Hypothesis We hypothesized that chronic binge alcohol and ovariectomy would decrease insulin response to a glucose challenge and impair insulin and glucagon expression in pancreatic islets. Methods 28 adult female macaques were used in the study. CBA or isovolumetric water (VEH) was administered through an intragastric catheter for 30 minutes, 5 days a week, with blood alcohol concentrations reaching 50-60 mM. Three months after initiation of CBA/VEH administration, macaques were infected with SIVMac251 and 2.5 months later initiated on ART. After 1 month of ART, macaques underwent sham surgery or ovariectomy. Using a modified frequently sampled intravenous glucose tolerance test (FSIVGTT), blood glucose and serum insulin values were measured. Glucose and insulin dynamic measures including the acute insulin response to glucose (AIRg), insulin sensitivity (Si), disposition index (DI), and glucose effectiveness (Sg) were determined using minimal model software. Insulin and glucagon expression was determined in formalin-fixed, paraffin-embedded pancreatic tissue collected at study endpoint. Corrected total cell fluorescence for insulin and glucagon were calculated using ImageJ software. To confirm these results, total RNA was isolated from pancreas and mRNA expression of insulin and glucagon determined using quantitative PCR. Results There was a main effect of CBA to decrease AIRg (p=0.02) and increase Si (p=0.01). There were no statistically significant effects of OVX on AIRg (p=0.06) or Si (p=0.4). There were also no statistically significant effects of CBA or OVX on DI or Sg. Neither CBA nor OVX altered the protein or mRNA expression of insulin and glucagon in pancreatic islets. Conclusion CBA decreased the acute endogenous insulin release in response to a glucose challenge without significantly altering basal pancreatic islet expression of insulin and glucagon, while OVX did not significantly alter any of these measures. These results indicate that CBA impairs the immediate release of insulin from beta cell insulin secretory vesicles, and we speculate that CBA dysregulates the metabolic signaling pathway of insulin secretion. Determining mechanisms of pancreatic endocrine dysfunction will inform therapeutic strategies to improve alcohol-mediated impaired glucose insulin dynamics in the context of SIV/HIV.

Wearable Glucose Monitoring and Implantable Drug Delivery Systems for Diabetes Management.

The global cost of diabetes care exceeds $1 trillion each year with more than $327 billion being spent in the United States alone. Despite some of the advances in diabetes care including continuous glucose monitoring systems and insulin pumps, the technology associated with managing diabetes has largely remained unchanged over the past several decades. With the rise of wearable electronics and novel functional materials, the field is well-poised for the next generation of closed-loop diabetes care. Wearable glucose sensors implanted within diverse platforms including skin or on-tooth tattoos, skin-mounted patches, eyeglasses, contact lenses, fabrics, mouthguards, and pacifiers have enabled noninvasive, unobtrusive, and real-time analysis of glucose excursions in ambulatory care settings. These wearable glucose sensors can be integrated with implantable drug delivery systems, including an insulin pump, glucose responsive insulin release implant, and islets transplantation, to form self-regulating closed-loop systems. This review article encompasses the emerging trends and latest innovations of wearable glucose monitoring and implantable insulin delivery technologies for diabetes management with a focus on their advanced materials and construction. Perspectives on the current unmet challenges of these strategies are also discussed to motivate future technological development toward improved patient care in diabetes management.

Injectable Biodegradable Polymeric Complex for Glucose-Responsive Insulin Delivery.

Insulin therapy is the central component of treatment for type 1 and advanced type 2 diabetes; however, its narrow therapeutic window is associated with a risk of severe hypoglycemia. A glucose-responsive carrier that demonstrates consistent and slow basal insulin release under a normoglycemic condition and accelerated insulin release in response to hyperglycemia in real-time could offer effective blood glucose regulation with reduced risk of hypoglycemia. Here, we describe a poly(l-lysine)-derived biodegradable glucose-responsive cationic polymer for constructing polymer-insulin complexes for glucose-stimulated insulin delivery. The effects of the modification degree of arylboronic acid in the synthesized cationic polymer and polymer-to-insulin ratio on the glucose-dependent equilibrated free insulin level and the associated insulin release kinetics have been studied. In addition, the blood glucose regulation ability of these complexes and the associated glucose challenge-triggered insulin release are evaluated in type 1 diabetic mice.

A dissolving and glucose-responsive insulin-releasing microneedle patch for type 1 diabetes therapy.

Diabetes and its complications have become crucial public health challenges worldwide. In this study, we aim to develop a dissolving and glucose-responsive insulin-releasing microneedle (MN) patch system, for minimally invasive and glucose-responsive insulin delivery for type 1 diabetes therapy. The MNs were composed of dissolving and biodegradable gelatin and starch materials, which encapsulated glucose-responsive insulin-releasing gold nanocluster (AuNC) nanocarriers. The fabricated MNs had a complete and uniform structure, consisting of an array of 11 × 11 conical needles, with a needle height of 756 μm, a bottom diameter of 356 μm, a tip diameter of 10 μm, and a tip-to-tip distance of 591 μm. The encapsulated AuNC nanocarriers as additives in the MNs enhanced the mechanical strength of the MNs, and facilitated the penetration of the MNs into the skins of mice. Moreover, the AuNC nanocarrier drugs in the MNs enabled MN patches with a glucose-responsive insulin releasing behavior. With one transdermal application of MN patches on the dorsal skin of mice, the MN patches effectively regulated the BG levels of mice in normoglycemic ranges for 1 to 2 days, and effectively alleviated the diabetic symptoms in type 1 diabetic mice. This dissolving and glucose-responsive insulin-releasing MN patch system realized a closed-loop administration of insulin with minimal invasion, providing great potential applications for type 1 diabetes therapy.

Control of Insulin Release by Transient Receptor Potential Melastatin 3 (TRPM3) Ion Channels.

The release of insulin in response to increased levels of glucose in the blood strongly depends on Ca2+ influx into pancreatic beta cells by the opening of voltage-gated Ca2+ channels. Transient Receptor Potential Melastatin 3 proteins build Ca2+ permeable, non-selective cation channels serving as pain sensors of noxious heat in the peripheral nervous system. TRPM3 channels are also strongly expressed in pancreatic beta cells that respond to the TRPM3 agonist pregnenolone sulfate with Ca2+ influx and increased insulin release. Therefore, we hypothesized that in beta cells TRPM3 channels may contribute to pregnenolone sulfate- as well as to glucose-induced insulin release. We used INS-1 cells as a beta cell model in which we analysed the occurrence of TRPM3 isoformes by immunoprecipitation and western blotting and by cloning of RT-PCR amplified cDNA fragments. We applied pharmacological as well as CRISPR/Cas9-based strategies to analyse the interplay of TRPM3 and voltage-gated Ca2+ channels in imaging experiments (FMP, Fura-2) and electrophysiological recordings. In immunoassays, we examined the contribution of TRPM3 channels to pregnenolone sulfate- and glucose-induced insulin release. To confirm our findings, we generated beta cell-specific Trpm3-deficient mice and compared their glucose clearance with the wild type in glucose tolerance tests. TRPM3 channels triggered the activity of voltage-gated Ca2+ channels and both channels together contributed to insulin release after TRPM3 activation. Trpm3-deficient INS-1 cells lacked pregnenolone sulfate-induced Ca2+ signals just like the pregnenolone sulfate-induced insulin release. Both, glucose-induced Ca2+ signals and the glucose-induced insulin release were strongly reduced. Accordingly, Trpm3-deficient mice displayed an impaired decrease of the blood sugar concentration after intraperitoneal or oral administration of glucose. The present study suggests an important role for TRPM3 channels in the control of glucose-dependent insulin release.

THE CORRELATION BETWEEN DIET PATTERN AND LIFESTYLE ON DIABETES MELITUS RISK AT PUBLIC HEALTH CENTRE PEMBINA PALEMBANG IN 2016

Diabetes Mellitus is an autoimmune disease characterized by hyperglycemia secondary toreduced pancreatic insulin production, reduced insulin release in response to a carbohydrate load, ordisruption cellular response to insulin. The aim of this study to know the correlation between diet patternand lifestyle on diabetes melitus risk at Public Health Centre Pembina Palembang in 2016. This study useda survey design analytic through cross sectional approach. The population of this study were all patientswho come for treatment at Publich Health Centre Pembina Palembang in 2016, the total sample of thisstudy was 60 respondents. The result of analysis found that there are relationship of diet pattern ondiabetes melitus risk at public health centre Pembina Palembang in 2016 (ρ value = 0.013). There isrelationship of lifestyle on diabetes melitus risk at Public Health Centre Pembina Palembang in 2016 (ρvalue = 0.032). It is suggested to health officer should provide councelling and blood sugar level treatmentregularly, especially health centers, to prevent rising numbers of diabetes mellitus, especially in PublicHealth Centre Pembina Palembang

Paracrine regulation of insulin secretion.

Pancreatic beta cells are the only cell type in our body capable of producing and secreting insulin to instruct the insulin-sensitive cells and tissues of our bodies to absorb nutrients after a meal. Accurate control of insulin release is of critical importance; too little insulin leads to diabetes, while an excess of insulin can cause potentially fatal hypoglycaemia. Yet, the pancreas of most people will control insulin secretion safely and effectively over decades and in response to glucose excursions driven by tens of thousands of meals. Because we only become aware of the important contributions of the pancreas when it fails to maintain glucose homeostasis, it is easy to forget just how well insulin release from a healthy pancreas is matched to insulin need to ensure stable blood glucose levels. Beta cells achieve this feat by extensive crosstalk with the rest of the endocrine cell types in the islet, notably the glucagon-producing alpha cells and somatostatin-producing delta cells. Here I will review the important paracrine contributions that each of these cells makes to the stimulation and subsequent inhibition of insulin release in response to a transient nutrient stimulation, and make the case that a breakdown of this local crosstalk contributes to the pathophysiology of diabetes. Graphical abstract.

Highly blood perfused, highly metabolically active pancreatic islets may be more susceptible for immune attack.

Differences in pancreatic islet susceptibility during type 1 diabetes development may be explained by interislet variations. This study aimed to investigate if heterogeneities in vascular support and metabolic activity in rat and human islets may explain why some islets are attacked earlier than other islets. In rats, highly blood perfused islets were identified by injection of microspheres into the ascending aorta, whereas a combination of anterograde and retrograde injections of microspheres into pancreas was used to determine the islet vascular drainage system. Highly blood perfused islets had superior function and lower glucose threshold for insulin release when compared with other islets. These islets had a preferential direct venous drainage to the portal vein, whereas other islets mainly were incorporated into the exocrine capillary system. In BioBreeding rats, the hypothesis that islets with high islet blood perfusion was more prone to immune cell infiltration was investigated. Indeed, highly blood perfused islets were the first affected by the immune attack. In human subjects, differences in glucose threshold for insulin (C‐peptide) secretion was evaluated in individuals recently diagnosed for type 1 diabetes and compared to control subjects. A preferential loss of capacity for insulin release in response to low glucose concentrations was observed at debut of type 1 diabetes. Our study indicates that highly blood perfused islets with direct venous drainage and lower glucose threshold for insulin release are of great importance for normal glucose homeostasis. At the same time, these highly metabolically active islets were the primary target of the immune system.

Lab-on-a-Chip System for Developing and Fluorescence Imaging a Three-Dimensional Model of Pancreatic Islets Under Flow Conditions

Introduction Diabetes mellitus is a group of metabolic diseases characterized by elevated blood sugar resulting from a defect in the production of insulin by pancreatic β-cells or tissue insensitivity for this peptide hormone [1]. The most common form of the disease is diabetes mellitus type 2 (insulin-dependent), which is diagnosed in about 80% of all patients [2]. In patients with this type of diabetes, both the efficiency and the secretion of insulin are disturbed [3]. For this reason, it is very important to thoroughly understand the kinetics of insulin release in response to various conditions, which can help develop effective therapy. The most important cells for this disease are insulin secreting β-cells and their antagonist - glucagon-secreting α-cells [4]. In our research, we focused on imitate the pancreatic islet structure, which can be a universal model for testing the impact of various environmental factors on disease development. The idea of using a Lab-on-a-chip system for three-dimensional islet cells culture came from the possibility of mimicking in vivo conditions. This can give a wider and more accurate view of the pancreatic islets function than the cell culture in static conditions. Lab-on-a-chip system In our research we present a Lab-on-a-chip system in which a pancreatic “pseudoislet” model will be developed. This system is composed of biocompatible, non-toxic and transparent materials, such as: poly(dimethylsiloxane) (PDMS) and thin glass. Thanks to this, it is possible to conduct cell culture and observe the results in various types of microscopes. The geometry of Lab-on-a-chip system consist of two elliptical cell culture chambers, one for the test sample and second for the reference sample. In in each of the chambers there are 15 round microtraps. Each of the microtraps is made of 6 micropillars. This solution forces the dense packing of cells and their aggregations. The geometry of the developed system is consistent with the culture wells on a standard multi-well plate, which allows measurements in a multi-well plate reader. Methods All experiments were performed using two commercially purchased pancreatic islets cell lines: β-cells (INS-1E) and α-cells (α-TC1-6). Appropriate α-cells and β-cells ratios were selected to reflect the morphology and composition of the pancreatic islet found in the body. The cells were introduced through the inlet to the Lab-on-a-chip system and placed for 24h in an incubator to form spherical aggregates (“pseudoislets”). In the next stage immunostaining protocol using primary and secondary antibody solutions was developed. Due to the use this method and confocal microscope it was possible to confirm the correct distribution of cells in the obtained aggregate. To confirm cells viability previously prepared solution of Calcein AM and Propidium Iodide were introduced through the microsystem inlet with a flow rate 5µL/min for 10 min. After 10 min incubation (37oC, 5% CO2) the viability of the cells was determined using fluorescence microscope. Proliferation of the ells was measured using spectrofluorimetric multi-well plate reader after incubation with AlamarBlue solution. The “pseudoislets” were then stimulated with various glucose concentrations (imitation of health and disease state). After this, the standard ELISA test procedure was adapted to the microfluidic conditions to examine the insulin secretion profile from the obtained “pseudoislets”. Results and Conclusions It was confirmed that 15 spherical α and β-cell aggregates with diameters of 160-180 µm were obtained in one culture chamber using the method described earlier. As was expected the participation of β-cells in the core and α-cells on the periphery of the aggregate was confirmed by the use of immunostaining method. Moreover, the compatibility of the designed microsystem with the multi-well plate reader allowed to monitor cell proliferation and viability in situ during the culture. A high viability after 24 and 48 hours of culture in the microchip was confirmed and was 97% and 95% respectively. The cells maintained their morphology, function and high level of proliferation for up to 48 hours of culture. Moreover, in the developed model health and disease conditions were simulated and the level of insulin secreted from this model was determined using the ELISA test. At this stage, a research model corresponding to the model in vivo conditions was obtained. The next step will be to develop a method for analyzing insulin secretion in real time (such as Surface Plasmon Resonance). This study presents basic research and in the future, this model could be utilized to simulate diabetes, testing new drugs and therapy in diabetes mellitus treatment.

A New Player in Glucose Counterregulation: the Glycemic Effects of Neuronostatin through GPR107 and Enhanced Glucagon Secretion

Regulation of blood glucose is a tightly controlled system with numerous players, woven by both hyperglycemic and hypoglycemic agents that interact in secretion and signaling mechanisms. However, this complex system is deranged in both Type 1 and Type 2 Diabetes, in the response to hyperglycemia (insulin) and hypoglycemia (counterregulatory factors such as glucagon). In treating diabetes with insulin and antidiabetic agents, there is significant risk of hypoglycemia due to improper dosing or inadequate food intake. In addition, repeated bouts of hypoglycemia diminish the counterregulatory response and blunt awareness of symptoms, creating a vicious cycle of unawareness and increasingly severe hypoglycemia. There is great need for better understanding of the players and mechanisms in blood glucose maintenance, and specifically in diabetic hypoglycemia.We recently identified a novel peptide, neuronostatin (NST), encoded in the somatostatin prohormone and found in all somatostatin‐positive tissues. However, the activity of NST is functionally distinct from other prosomatostatin products. Furthermore, it appears the physiologic stimuli of the peptides are different and that the peptides are sequestered in separate secretory vesicles. Our group identified the orphan GPCR, GPR107, as a cognate receptor of NST. Through an interaction with GPR107, NST enhanced glucagon release from isolated islets and immortalized alpha cells. NST also reduced release of insulin in response to high glucose conditions in isolated islets. Based off our findings, we hypothesized that NST is a component of the pancreatic arm of the counterregulatory response. In support of our hypothesis, an infusion of NST substantially increased plasma glucose levels over 30 minutes in male rats, and diminished the insulin response to hyperglycemia in a glucose tolerance test. Additionally, antagonism of the glucagon receptor did not prevent the hyperglycemic effects of NST, suggesting the peptide can act independent of glucagon to increase blood glucose. In insulin‐induced hypoglycemia, NST blunts the drop in blood glucose, further reinforcing the role of NST in counterregulation. The secretion of NST release also appears tied to glucose levels. Fasting blood glucose raised plasma NST levels in rats and humans, and exposure to low glucose stimulated NST release from human islets.Further experiments will confirm the regulatory mechanisms involved in the release of NST, and the importance of its receptor, GPR107. We propose that NST could represent a novel therapeutic target for the treatment and prevention of hypoglycemia in diabetes.Support or Funding InformationThis work was funded by the NIDDK and the Helmsley Charitable Trust.

The role of coffee derivatives in the regulation of pancreatic beta cell function in Type 2 Diabetes

AbstractCoffee contains several components other than caffeine such as chlorogenic acids (CGAs), which are a family of polyphenols. Non-caffeinated coffee has been shown to reduce the risk of Type 2 diabetes, but it is unclear whether this effect is primarily due to a beneficial action on glucose regulation in peripheral tissues or whether it is partly mediated via a direct, functional modulation of insulin-secreting beta cells from the pancreas. This study aims to explore the specific role of coffee compounds derived from the polyphenolic family of CGAs (caffeic acid (CA) and ferulic acid (FA)) and their metabolites (dihydroferulic acid (diFA) and ferulic acid 4-O-sulphate (FA-4-OS)) in the regulation of beta cell survival and secretory function. To investigate this role, the cells were initially exposed to conditions of glucotoxicity (30mmol/l glucose), lipotoxicity (0.5mmol/l palmitate), glucolipotoxicity (30mmol/l glucose + 0.5mmol/l palmitate) and cytokine-induced cell toxicity (25U/ml IL1b + 500U/ml TNFα) for 20 and 48 h. INS1 beta cells were subsequently treated with or without 100nmol/l of the CGA compounds for 48 h followed by 20 h exposure to glucolipotoxicity to measure cellular ATP content and 3/7 caspase activity, respectively, as an indication of cell viability and apoptosis. Additionally, insulin release was assessed by radioimmunoassay following 1 h static incubations with or without CA, FA and metabolites. Data were analysed by One-Way ANOVA using GraphPad prism software (version 8). Glucotoxicity, lipotoxicity and glucotoxicity or glucolipotoxicity combined with cytokines significantly reduced INS1 cell viability compared to control at 20 and 48 h (p < 0.001 vs 11mmol/l glucose, p < 0.05; Glucotoxicity vs 11mmol/l glucose at 20 h, n = 6), whereas cytokines alone did not significantly affect cellular ATP content. Moreover, pre-treatment for 48 h with CGAs alone or in combination did not affect INS1 beta-cell viability under basal conditions (n = 3, p > 0.2). Additional exposure to glucolipotoxicity for 20 h significantly decreased beta cell viability and survival and was not alleviated by pre- or co-treatment with CGAs (n = 3, p > 0.05). However, insulin release in response to 1 h incubation with 20 mmol/l glucose + 10μmol/l forskolin (FSK) + 100μmol/l 3-isobutyl-1-methylxanthine (IBMX) was significantly higher from cells pre-treated with CA and FA combined compared to controls (7.64 + 2.89pg insulin/5,000 cells/h vs 2.17 + 0.35pg insulin/5,000 cells/h; p < 0.01 vs. 20mmol/l glucose + 10μmol/l FSK + 100μmol/l IBMX only, n = 5). The results suggest that CGA derivatives from coffee do not directly modulate INS1 beta cell viability and apoptosis whereas the compounds may play a role in the regulation of beta cell secretory function.

Decreases in Circulating Concentrations of Long-Chain Acylcarnitines and Free Fatty Acids During the Glucose Tolerance Test Represent Tissue-Specific Insulin Sensitivity.

Background: Insulin plays a pivotal role in the regulation of both carbohydrate and lipid intermediate turnover and metabolism. In the transition from a fasted to fed state, insulin action inhibits lipolysis in adipocytes, and acylcarnitine synthesis in the muscles and heart. The aim of this study was to measure free fatty acid (FFA) and acylcarnitine levels during the glucose tolerance test as indicators of tissue-specific insulin resistance.Results: Insulin release in response to glucose administration decreased both FFA and long-chain acylcarnitine levels in plasma in healthy control animals by 30% (120 min). The glucose tolerance test and [3H]-deoxy-D-glucose uptake in tissues revealed that high fat diet-induced lipid overload in C57bl/6N mice evoked only adipose tissue insulin resistance, and plasma levels of FFAs did not decrease after glucose administration. In comparison, db/db mice developed type 2 diabetes with severely impaired insulin sensitivity and up to 70% lower glucose uptake in both adipose tissues and muscles (skeletal muscle and heart), and both plasma concentrations of FFAs and long-chain acylcarnitines did not decrease in response to glucose administration.Conclusions: These results link impaired adipose tissue insulin sensitivity with continuous FFA release in the transition from a fasted to postprandial state, while a blunted decrease in long-chain acylcarnitine levels is associated with muscle and heart insulin resistance.

Urocortin 2 Gene Transfer Improves Glycemic Control and Reduces Retinopathy and Mortality in Murine Insulin Deficiency

Type 1 diabetes affects 20 million patients worldwide. Insulin is the primary and commonly the sole therapy for type 1 diabetes. However, only a minority of patients attain the targeted glucose control and reduced adverse events. We tested urocortin 2 gene transfer as single-agent therapy for insulin deficiency using two mouse models. Urocortin 2 gene transfer reduced blood glucose for months after a single intravenous injection, through increased skeletal muscle insulin sensitivity, increased insulin release in response to glucose stimulation, and increased plasma insulin levels before and during euglycemic clamp. The combined increases in both insulin availability and sensitivity resulted in improved glycemic indices—events that were not anticipated in these insulin-deficient models. In addition, urocortin 2 gene transfer reduced ocular manifestations of long-standing insulin deficiency such as vascular leak and improved retinal function. Finally, mortality was reduced by urocortin 2 gene transfer. The mechanisms for these beneficial effects included increased activities of AMP-activated protein kinase and Akt (protein kinase B) in skeletal muscle, increased skeletal muscle glucose uptake, and increased insulin release. These data suggest that urocortin 2 gene transfer may be a viable therapy for new onset type 1 diabetes and might reduce insulin needs in later stage disease.