Glucose-sensitive Insulin Research Articles

Glucose-sensitive insulin adjusts to blood sugar

Glucose-sensitive insulin adjusts to blood sugar

Glucose-sensitive insulin with attenuation of hypoglycaemia

The risk of inducing hypoglycaemia (low blood glucose) constitutes the main challenge associated with insulin therapy for diabetes1,2. Insulin doses must be adjusted to ensure that blood glucose values are within the normal range, but matching insulin doses to fluctuating glucose levels is difficult because even a slightly higher insulin dose than needed can lead to a hypoglycaemic incidence, which can be anything from uncomfortable to life-threatening. It has therefore been a long-standing goal to engineer a glucose-sensitive insulin that can auto-adjust its bioactivity in a reversible manner according to ambient glucose levels to ultimately achieve better glycaemic control while lowering the risk of hypoglycaemia3. Here we report the design and properties of NNC2215, an insulin conjugate with bioactivity that is reversibly responsive to a glucose range relevant for diabetes, as demonstrated in vitro and in vivo. NNC2215 was engineered by conjugating a glucose-binding macrocycle4 and a glucoside to insulin, thereby introducing a switch that can open and close in response to glucose and thereby equilibrate insulin between active and less-active conformations. The insulin receptor affinity for NNC2215 increased 3.2-fold when the glucose concentration was increased from 3 to 20 mM. In animal studies, the glucose-sensitive bioactivity of NNC2215 was demonstrated to lead to protection against hypoglycaemia while partially covering glucose excursions.

Ectopic expression of insulin in a type 1 diabetic rat model by injection of manipulated mesenchymal stem cells with an insulin construct driven by a glucose-sensitive promoter in the port vein.

The treatment of type 1 diabetes through islet cell transplantation is a complex process, facing challenges such as allograft rejections and a limited supply of donors. One potential solution is to utilize the liver as an alternative for natural insulin production, as hepatocytes can secrete proteins and respond to glucose levels. Recent research has shown promising results in using mesenchymal stem cells as a potential cure for diabetes. The study utilized a diabetic rat model, confirmed through blood sugar measurement. A plasmid vector was designed with specific genetic components, synthesized by biotech company, and then Inserted vector into a plasmid with resistance genes and bacterial origin. Bone marrow-derived mesenchymal stem cells (BM-MSCs) were cultured and transfected with the plasmid using Lipofectamine 3000. Polymerase chain reaction wasemployed to confirm successful transfection using specific primers. For the animal study, 30 male Wistar rats were divided into six groups, each comprising five rats. The control group did not receive any treatment, while the second group received MSCs via Portal Vein Injection. The third group received MSCs transfected with a specific construct via Portal Vein Injection. The fourth group was induced to develop diabetes through streptozotocin(STZ) injection, the fifth group developed diabetes and received untransfected MSCs via Portal Vein Injection, and the sixth group received MSCs transfected with the specific construct via Portal Vein Injection. To manage Pain, appropriate pain control was administered to the rats for 3 days after the surgery. Fixed liver tissues obtained from the euthanized rats were utilized for immunohistochemistry. In this study, immunohistochemical techniques were used to examine insulin expression in different groups of rats. The control groups showed high levels of insulin expression, while the diabetic groups exhibited lower expression. However, there was a significant difference between the diabetic groups treated with MSC and transgenic MSC cells. All groups had similar baseline glucose levels, but the diabetic groups showed a significant increase after STZ injection, whereas the control and MSC groups did not. Postintervention, both the control and MSC groups had similar glucose levels to the post-STZ levels. However, diabetes-induced groups experienced a significant decrease in glucose levels, with the transfected MSCs showing a greater decrease than the untransfected MSCs. The study suggested that treatment with MSCs, especially transfected ones, can effectively reduce glucose levels in rats with diabetes. In this research, rat BM-MSCs were utilized to create insulin-producing mesenchymal cells with glucose-sensitive insulin expression. The cells were transferred to the liver of diabetic rats via portal vein injection, leading to an increase in insulin expression. This study proposes a novel approach for cell therapy and delivery in the treatment of type 1 diabetes.

Aberrant metabolite trafficking and fuel sensitivity in human pluripotent stem cell-derived islets

Pancreatic islets regulate blood glucose homeostasis through the controlled release of insulin; however, current metabolic models of glucose-sensitive insulin secretion are incomplete. A comprehensive understanding of islet metabolism is integral to studies of endocrine cell development as well as diabetic islet dysfunction. Human pluripotent stem cell-derived islets (SC-islets) are a developmentally relevant model of human islet function that have great potential in providing a cure for type 1 diabetes. Using multiple 13C-labeled metabolic fuels, we demonstrate that SC-islets show numerous divergent patterns of metabolite trafficking in proposed insulin release pathways compared with primary human islets but are still reliant on mitochondrial aerobic metabolism to derive function. Furthermore, reductive tricarboxylic acid cycle activity and glycolytic metabolite cycling occur in SC-islets, suggesting that non-canonical coupling factors are also present. In aggregate, we show that many facets of SC-islet metabolism overlap with those of primary islets, albeit with a retained immature signature.

Pharmacological inhibition of human EZH2 can influence a regenerative β-like cell capacity with in vitro insulin release in pancreatic ductal cells

BackgroundTherapeutic replacement of pancreatic endocrine β-cells is key to improving hyperglycaemia caused by insulin-dependent diabetes . Whilst the pool of ductal progenitors, which give rise to the endocrine cells, are active during development, neogenesis of islets is repressed in the human adult. Recent human donor studies have demonstrated the role of EZH2 inhibition in surgically isolated exocrine cells showing reactivation of insulin expression and the influence on the H3K27me3 barrier to β-cell regeneration. However, those studies fall short on defining the cell type active in transcriptional reactivation events. This study examines the role of the regenerative capacity of human pancreatic ductal cells when stimulated with pharmacological inhibitors of the EZH2 methyltransferase.ResultsHuman pancreatic ductal epithelial cells were stimulated with the EZH2 inhibitors GSK-126, EPZ6438, and triptolide using a 2- and 7-day protocol to determine their influence on the expression of core endocrine development marker NGN3, as well as β-cell markers insulin, MAFA, and PDX1. Chromatin immunoprecipitation studies show a close correspondence of pharmacological EZH2 inhibition with reduced H3K27me3 content of the core genes, NGN3, MAFA and PDX1. Consistent with the reduction of H3K27me3 by pharmacological inhibition of EZH2, we observe measurable immunofluorescence staining of insulin protein and glucose-sensitive insulin response.ConclusionThe results of this study serve as a proof of concept for a probable source of β-cell induction from pancreatic ductal cells that are capable of influencing insulin expression. Whilst pharmacological inhibition of EZH2 can stimulate secretion of detectable insulin from ductal progenitor cells, further studies are required to address mechanism and the identity of ductal progenitor cell targets to improve likely methods designed to reduce the burden of insulin-dependent diabetes.

Adiponectin reverses β-Cell damage and impaired insulin secretion induced by obesity.

Obesity significantly decreases life expectancy and increases the incidence of age-related dysfunctions, including β-cell dysregulation leading to inadequate insulin secretion. Here, we show that diluted plasma from obese human donors acutely impairs β-cell integrity and insulin secretion relative to plasma from lean subjects. Similar results were observed with diluted sera from obese rats fed ad libitum, when compared to sera from lean, calorically restricted, animals. The damaging effects of obese circulating factors on β-cells occurs in the absence of nutrient overload, and mechanistically involves mitochondrial dysfunction, limiting glucose-supported oxidative phosphorylation and ATP production. We demonstrate that increased levels of adiponectin, as found in lean plasma, are the protective characteristic preserving β-cell function; indeed, sera from adiponectin knockout mice limits β-cell metabolic fluxes relative to controls. Furthermore, oxidative phosphorylation and glucose-sensitive insulin secretion, which are completely abrogated in the absence of this hormone, are restored by the presence of adiponectin alone, surprisingly even in the absence of other serological components, for both the insulin-secreting INS1 cell line and primary islets. The addition of adiponectin to cells treated with plasma from obese donors completely restored β-cell functional integrity, indicating the lack of this hormone was causative of the dysfunction. Overall, our results demonstrate that low circulating adiponectin is a key damaging element for β-cells, and suggest strong therapeutic potential for the modulation of the adiponectin signaling pathway in the prevention of age-related β-cell dysfunction.

Glucose-sensitive poly(ether sulfone) composite membranes blended with phenylboronic acid-based amphiphilic block copolymer for self-regulated insulin release.

Glucose-sensitive membranes have promising applications in insulin release. Phenylboronic acid (PBA) is an important glucose reporter. Most of PBA-based glucose-sensitive materials are expansion-type, which cannot act as chemical valves in porous membranes for self-regulated insulin release. In this study, a glucose-sensitive membrane with PBA-based contraction-type amphiphilic block copolymer polystyrene-b-poly(N-isopropylacrylamide-co-2-(acrylamido) phenylboronic acid) (PSNB) as chemical valves was constructed through non-solvent induced phase separation (NIPS) method. Due to surface segregation, hydrophobic polystyrene (PS) component can anchor in the membrane matrix to improve the stability of the membrane, and glucose-sensitive hydrophilic poly(N-isopropylacrylamide-co-2-(acrylamido) phenylboronic acid) (PNB) component can expose on the surfaces of the membrane and the channels to provide glucose-sensitivity of the membrane. With increasing the polymer content or chain length of the hydrophilic component, the glucose sensitivity of the membrane was improved. The blend membrane showed glucose-sensitive insulin release behavior in simulated body fluids (SBF) and fetal bovine serum (FBS). The membrane also exhibited good antifouling properties and biocompatibility.

Adiponectin Promotes Glucose-Sensitive Insulin Secretion and Prevents Beta-Cell Damage by Obesity

Adiponectin Promotes Glucose-Sensitive Insulin Secretion and Prevents Beta-Cell Damage by Obesity

A comprehensive review on glucokinase activators: Promising agents for the treatment of Type 2 diabetes.

Glucokinase is a key enzyme which converts glucose into glucose-6-phosphate in the liver and pancreatic cells of the human. In the liver, glucokinase promotes the synthesis of glycogen, and in the pancreas, it helps in glucose-sensitive insulin release. It serves as a "glucose sensor" and thereby plays an important role in the regulation of glucose homeostasis. Due to this activity, glucokinase is considered as an attractive drug target for type 2 diabetes. It created a lot of interest among the researchers, and several small molecules were discovered. The research work was initiated in 1990. However, the hypoglycemic effect, increased liver burden, and loss of efficacy over time were faced during clinical development. Dorzagliatin, a novel glucokinase activator that acts on both the liver and pancreas, is in the late-stage clinical development. TTP399, a promising hepatoselective GK activator, showed a clinically significant and sustained reduction in glycated hemoglobin with a low risk of adverse effects. The successful findings generated immense interest to continue further research in finding small molecule GK activators for the treatment of type 2 diabetes. The article covers different series of GK activators reported over the past decade and the structural insights into the GK-GK activator binding which, we believe will stimulate the discovery of novel GK activators to treat type 2 diabetes.

Glucose- and pH-Responsive Supramolecular Polymer Vesicles Based on Host-Guest Interaction for Transcutaneous Delivery of Insulin.

Smart insulin delivery platforms having the ability of mimicking pancreatic cells are highly expected for diabetes treatment. Herein, a smart glucose-sensitive insulin delivery platform on the basis of transcutaneous microneedles has been designed. The as-prepared microneedles are composed of glucose- and pH-responsive supramolecular polymer vesicles (PVs) as the drug storage and water soluble polymers as the matrix. The well-defined PVs are constructed from the host-guest inclusion complex between water-soluble pillar[5]arene (WP5) with pH-responsiveness and paraquat-ended poly(phenylboronic acid) (PPBA-G) with glucose-sensitivity. The drug-loaded PVs, including insulin and glucose oxidase (GOx) can quickly respond to elevated glucose level, accompanied by the disassociation of PVs and fast release of encapsulated insulin. Moreover, the insulin release rate is further accelerated by GOx, which generates gluconic acid at high glucose levels, thus decreasing the local pH. Therefore, the host-guest interaction between WP5 and PPBA-G is destroyed and a total structure disassociation of PVs takes place, contributing to a fast release of encapsulated insulin. The in vivo insulin delivery to diabetic rats displays a quick response to hyperglycemic levels and then can fast regulate the blood glucose concentrations to normal levels, which demonstrates that the obtained smart insulin device has a highly potential application in the treatment of diabetes.

Visible-Light-Triggered Cyanoalkylation of para-Quinone Methides and Its Application to the Synthesis of GPR40 Agonists.

Cyanoalkylated diarylmethanes with biological and pharmacological potentials were synthesized from para-quinone methides and cyanoalkylating reagents through a photocatalytic process. This protocol is operationally simple and mild and has high efficiency, which gave the corresponding products in moderate to good yields. The synthetic utility of this work has been illustrated in the efficient synthesis of GPR40 agonists, which play an important role in FA-induced glucose-sensitive insulin secretion.

An Intelligent Nanoscale Insulin Delivery System.

Insulin injection relies on strict blood glucose monitoring. However, existing techniques and algorithms for blood glucose monitoring cannot be completed in a timely way. In this study, we have developed a new intelligent glucose-sensitive insulin delivery system to stabilize blood glucose levels in the body. This system does not require real-time detection of blood glucose. First, we successfully synthesized a nanoscale material called PAM-PAspPBA-b-PEG by using chemical methods. We then conducted TEM, DLS, and 1H-NMR analyses to characterize the physicochemical properties, such as size, molecular composition, and configuration of the nanomaterial. We verified the glucose responsibility of the insulin loading nanoscale material in vitro and evaluated its safety and effect on mice in vivo. Results showed that insulin-loaded PAM-PAspPBA-b-PEG is glucose-sensitive, safer and more effective than regular insulin injection. This study provides a basis for future development of smart insulin delivery systems.

Insulin delivery to the brain using intracranial implantation of alginate-encapsulated pancreatic islets.

There is increasing evidence supporting a link between cognitive dysfunctions and impaired brain insulin signalling. Insulin therapy has previously been tested as an approach to ameliorate brain insulin resistance and deficiency in patients with various brain disorders. However, current strategies for insulin delivery to the brain may induce severe hypoglycaemia when injected peripherally or show poor uptake when delivered intranasally. Recently, we have shown that intracranial transplantation of naked pancreatic islets increased insulin content in the brain and attenuated cognitive dysfunctions without altering peripheral glucose homeostasis in rats with schizophrenia-like syndrome. In this study, we show that intracranial implantation of 50 pancreatic islets encapsulated in disc-shaped alginate is sufficient to elevate insulin content in the rat brain. Three weeks after implantation, the islets displayed intact morphology, intensive hormone staining and glucose-sensitive insulin release. The ultrapure alginate with high guluronic acid content used for islet encapsulation demonstrated good biocompatibility and stability after intracranial implantation. All implanted animals were normoglycaemic and normoinsulinaemic. In conclusion, the intracranial implantation of a small amount of alginate-encapsulated islets is an efficient tool for metabolically regulated insulin delivery to the brain. Copyright © 2017 John Wiley & Sons, Ltd.

4-Phenylureido/thioureido-substituted 2,2-dimethylchroman analogs of cromakalim bearing a bulky ‘carbamate’ moiety at the 6-position as potent inhibitors of glucose-sensitive insulin secretion

The synthesis of 2,2-dimethylchromans bearing a 3/4-chloro/cyano-substituted phenylureido or phenylthioureido moiety at the 4-position and an alkoxycarbonylamino (‘carbamate’) group at the 6-position is described. These new analogs of the potassium channel opener (±)-cromakalim were further tested on rat pancreatic islets as putative inhibitors of insulin release and on rat aorta rings as putative vasorelaxants. All compounds inhibited insulin secretion and induced a myorelaxant activity. Compound 14o [R/S-N-3-cyanophenyl-N’-(6-tert-butoxycarbonylamino-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4-yl)urea; BPDZ 711] emerged as the most potent inhibitor of the glucose-sensitive insulin releasing process (IC50 = 0.24 μM) and displayed selectivity towards the pancreatic endocrine tissue. Radioisotopic, fluorimetric and pharmacological investigations were performed on rat pancreatic islet and rat vascular smooth muscle cells in order to decipher its mechanism of action. Our findings suggest that the mechanism of action of 14o is rather unspecific. The compound behaves as a KATP channel opener, a Ca2+ entry blocker, and promotes an intracellular calcium translocation.

Chemical synthesis of peptides within the insulin superfamily.

The synthesis of insulin has inspired fundamental advances in the art of peptide science while simultaneously revealing the structure-function relationship of this centrally important metabolic hormone. This review highlights milestones in the chemical synthesis of insulin that can be divided into two separate approaches: (i) disulfide bond formation driven by protein folding and (ii) chemical reactivity-directed sequential disulfide bond formation. Common to the two approaches are the persistent challenges presented by the hydrophobic nature of the individual A-chain and B-chain and the need for selective disulfide formation under mildly oxidative conditions. The extension and elaboration of these synthetic approaches have been ongoing within the broader insulin superfamily. These structurally similar peptides include the insulin-like growth factors and also the related peptides such as relaxin that signal through G-protein-coupled receptors. After a half-century of advances in insulin chemistry, we have reached a point where synthesis is no longer limiting structural and biological investigation within this family of peptide hormones. The future will increasingly focus on the refinement of structure to meet medicinal purposes that have long been pursued, such as the development of a glucose-sensitive insulin. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

The fabrication of glucose-sensitive insulin carriers with layer-by-layer assembly technique

The fabrication of glucose-sensitive insulin carriers with layer-by-layer assembly technique

Phenylboronic Acid Appended Pyrene-Based Low-Molecular-Weight Injectable Hydrogel: Glucose-Stimulated Insulin Release.

A pyrene-containing phenylboronic acid (PBA) functionalized low-molecular-weight hydrogelator was synthesized with the aim to develop glucose-sensitive insulin release. The gelator showed the solvent imbibing ability in aqueous buffer solutions of pH values, ranging from 8-12, whereas the sodium salt of the gelator formed a hydrogel at physiological pH 7.4 with a minimum gelation concentration (MGC) of 5 mg mL(-1) . The aggregation behavior of this thermoreversible hydrogel was studied by using microscopic and spectroscopic techniques, including transmission electron microscopy, FTIR, UV/Vis, luminescence, and CD spectroscopy. These investigations revealed that hydrogen bonding, π-π stacking, and van der Waals interactions are the key factors for the self-assembled gelation. The diol-sensitive PBA part and the pyrene unit in the gelator were judiciously used in fluorimetric sensing of minute amounts of glucose at physiological pH. The morphological change of the gel due to addition of glucose was investigated by scanning electron microscopy, which denoted the glucose-responsive swelling of the hydrogel. A rheological study indicated the loss of the rigidity of the native gel in the presence of glucose. Hence, the glucose-induced swelling of the hydrogel was exploited in the controlled release of insulin from the hydrogel. The insulin-loaded hydrogel showed thixotropic self-recovery property, which hoisted it as an injectable soft composite. Encouragingly, the gelator was found to be compatible with HeLa cells.

BLX-1002 restores glucose sensitivity and enhances insulin secretion stimulated by GLP-1 and sulfonylurea in type 2 diabetic pancreatic islets.

BLX‐1002 is a novel thiazolidinedione with no peroxisome proliferator‐activated receptor (PPAR) activity that has been shown to improve glycemia in type 2 diabetes without weight gain. We previously found that BLX‐1002 selectively augments glucose‐sensitive (but not basal) insulin secretion in normal mouse β‐cells. We have now extended these observations to other insulin secretagogues and to diabetic rat islets. To this end, dynamics of insulin secretion stimulated by glucose, GLP‐1, and the sulfonylurea tolbutamide were examined in pancreatic islets from nondiabetic Wistar and type 2 diabetic Goto‐Kakizaki rats ex vivo. BLX‐1002 restored normal glucose‐sensitive insulin secretion in otherwise “glucose‐blind” islets from GK rats, but did not affect basal or glucose‐stimulated secretion in normal Wistar rat islets. The stimulatory effect of BLX‐1002 on insulin secretion at high glucose required Ca2+ and involved phosphatidylinositol 3‐kinase (PI3K) activity. Consistent with its effects on insulin secretion, BLX‐1002 also augmented insulin secretion and cytoplasmic‐free Ca2+ concentrations ([Ca2+]i) stimulated by high glucose, GLP‐1, and tolbutamide in islets from GK, but not Wistar, rats. The inactive analog BLX‐1237 had no effects. In conclusion, our findings suggest that BLX‐1002 potentiates insulin secretion by different stimuli in diabetic β‐cells only, in a Ca2+‐dependent manner and involving PI3K.

Protein phosphatases in pancreatic islets

The prevalence of diabetes is increasing rapidly worldwide. A cardinal feature of most forms of diabetes is the lack of insulin-producing capability, due to the loss of insulin-producing β-cells, impaired glucose-sensitive insulin secretion from the β-cell, or a combination thereof, the reasons for which largely remain elusive. Reversible phosphorylation is an important and versatile mechanism for regulating the biological activity of many intracellular proteins, which, in turn, controls a variety of cellular functions. For instance, significant changes in protein kinase activities and in protein phosphorylation patterns occur subsequent to the stimulation of insulin release by glucose. Therefore, the molecular mechanisms regulating the phosphorylation of proteins involved in the insulin secretory process by the β-cell have been extensively investigated. However, far less is known about the role and regulation of protein dephosphorylation by various protein phosphatases. Herein, we review extant data implicating serine/threonine and tyrosine phosphatases in various aspects of healthy and diabetic islet biology, ranging from control of hormonal stimulus-secretion coupling to mitogenesis and apoptosis.

Lixisenatide resensitizes the insulin‐secretory response to intravenous glucose challenge in people with type 2 diabetes – a study in both people with type 2 diabetes and healthy subjects

AimsGlucagon-like peptide-1 (GLP-1) receptor agonists improve blood glucose control by enhancing glucose-sensitive insulin release, delaying gastric emptying and reducing postprandial glucagon secretion. The studies reported here investigated the insulin response to an intravenous (iv) glucose challenge after injection of lixisenatide (LIXI) 20 µg or placebo.MethodsTwo single-centre, double-blind, randomized, placebo-controlled, single-dose, crossover studies were performed in healthy subjects (HS) and people with type 2 diabetes mellitus (T2DM). Participants received subcutaneous LIXI or placebo 2 h before an iv glucose challenge. Study endpoints included first- and second-phase insulin response, insulin concentration (INS), glucagon response and glucose disposal rate (Kglucose). LIXI exposure was measured over 12 h.ResultsLIXI 20 µg reached maximum concentration after 2 h and resensitized first-phase insulin secretion by 2.8-fold in T2DM to rates comparable with those in HS on placebo, and raised second-phase insulin secretion by 1.6-fold in T2DM. INS rose correspondingly and glucose disposal was accelerated by 1.8-fold in T2DM. First-phase insulin secretion and glucose disposal were also augmented by LIXI in HS, whereas second-phase insulin secretion reduced blood glucose concentrations to below fasting levels and then ceased, accompanied by a rapid, short-lasting rise in glucagon. Otherwise, suppression of glucagon release subsequent to augmentation of insulin release was unaffected in T2DM and in HS.ConclusionsLIXI resensitized the insulin response to an iv glucose challenge in people with T2DM, thereby accelerating glucose disposal to nearly physiological intensity, and did not impair counter-regulation to low glucose levels by glucagon.