Protection Of Islets Research Articles

Muted fibrosis from protected islets.

Transplanting allogeneic pancreatic islets intraperitoneally by first encapsulating the islets within an alginate-based formulation results in reduced fibrosis and capsule clumping, and thus in improved islet survival.

Extending Remission and Reversing New-Onset Type 1 Diabetes by Targeted Ablation of Autoreactive T Cells.

Preserving endogenous insulin production is clinically advantageous and remains a vital unmet challenge in the treatment and reversal of type 1 diabetes. Although broad immunosuppression has had limited success in prolonging the so-called remission period, it comes at the cost of compromising beneficial immunity. Here, we used a novel strategy to specifically deplete the activated diabetogenic T cells that drive pathogenesis while preserving not only endogenous insulin production but also protective immunity. Effector T (Teff) cells, such as diabetogenic T cells, are naturally poised on the edge of apoptosis because of activation-induced DNA damage that stresses the p53 regulation of the cell cycle. We have found that using small molecular inhibitors that further potentiate p53 while inhibiting the G2/M cell cycle checkpoint control drives apoptosis of activated T cells in vivo. When delivered at the onset of disease, these inhibitors significantly reduce diabetogenic Teff cells, prolong remission, preserve functional islets, and protect islet allografts while leaving naive, memory, and regulatory T-cell populations functionally untouched. Thus, the targeted manipulation of p53 and cell cycle checkpoints represents a new therapeutic modality for the preservation of islet β-cells in new-onset type 1 diabetes or after islet transplant.

Role and Cytotoxicity of Amylin and Protection of Pancreatic Islet β-Cells from Amylin Cytotoxicity.

Amylin, (or islet amyloid polypeptide; IAPP), a 37-amino acid peptide hormone, is released in response to nutrients, including glucose, lipids or amino acids. Amylin is co-stored and co-secreted with insulin by pancreatic islet β-cells. Amylin inhibits food intake, delays gastric emptying, and decreases blood glucose levels, leading to the reduction of body weight. Therefore, amylin as well as insulin play important roles in controlling the level of blood glucose. However, human amylin aggregates and human amylin oligomers cause membrane disruption, endoplasmic reticulum (ER) stress and mitochondrial damage. Since cytotoxicity of human amylin oligomers to pancreatic islet β-cells can lead to diabetes, the protection of pancreatic islet β cells from cytotoxic amylin is crucial. Human amylin oligomers also inhibit autophagy, although autophagy can function to remove amylin aggregates and damaged organelles. Small molecules, including β-sheet breaker peptides, chemical chaperones, and foldamers, inhibit and disaggregate amyloid formed by human amylin, suggesting the possible use of these small molecules in the treatment of diabetes. In this review, we summarize recent findings regarding the role and cytotoxicity of amylin and the protection of pancreatic islet β-cells from cytotoxicity of amylin.

Conformal coating by multilayer nano-encapsulation for the protection of human pancreatic islets: In-vitro and in-vivo studies

To improve the efficiency of pancreatic islet transplantation, we performed in-vitro and in-vivo experiments with isolated human pancreatic islets coated by multi-layer nano-encapsulation using differently charged polymers [chitosan and poly(sodium styrene sulfonate)] to obtain up to 9 layers. The islet coating (thickness: 104.2 ± 4.2 nm) was uniform, with ≥ 90% cell viability and well preserved beta- and alpha-cell ultrastructure. Nano-encapsulated islets maintained physiological glucose-stimulated insulin secretion by both static incubation and perifusion studies. Notably, palmitate- or cytokine-induced toxicity was significantly reduced in nano-coated islets. Xenotransplantation of nano-encapsulated islets under the kidney capsule of streptozotocin-induced C57Bl/6J diabetic mice allowed long term normal or near normal glycemia, associated with minimal infiltration of immune cell into the grafts, well preserved islet morphology and signs of re-vascularization. In summary, the multi-layer nano-encapsulation approach described in the present study provides a promising tool to effectively protect human islets both in-vitro andin-vivo conditions.

Extending remission and reversing new onset type 1 diabetes by targeted ablation of autoreactive T cells

Abstract Preserving endogenous insulin production is clinically advantageous and remains a vital unmet challenge in the treatment and reversal of type 1 diabetes (T1D). While broad immunosuppression has had limited success in prolonging the so-called remission period, it comes at the cost of compromising beneficial immunity. Here, we employed an alternate strategy to specifically deplete the activated diabetogenic T cells that drive pathogenesis while preserving not only endogenous insulin production but also protective immunity. Effector T cells, such as diabetogenic T cells, are naturally poised on the edge of apoptosis because of activation-induced DNA damage that stresses the p53 regulation of cell cycle. We have found that the combined use of small molecular inhibitors that further potentiates p53 while inhibiting G2/M cell cycle checkpoint control drives apoptosis of activated T cells in vivo. When delivered at the onset of T1D these inhibitors eliminate diabetogenic effector T cells, prolong remission, preserve functional islets, and protect islet allografts while leaving naïve, memory, and regulatory T cell populations functionally untouched. Thus, the targeted manipulation of p53 and cell cycle checkpoints represents a new therapeutic modality for the preservation of islet beta cells in new onset type 1 diabetes or after islet transplant.

Islet protection and amelioration of type 2 diabetes mellitus by treatment with quercetin from the flowers of <em>Edgeworthia gardneri</em>

Background and purposeThe traditional Chinese medicine – the flower of Edgeworthia gardneri – is reported as an effective therapeutic for type 2 diabetes mellitus (T2DM). Nevertheless, most constituents of the flowers of E. gardneri have not yet been studied. This study was conducted to investigate the effect of quercetin extracted from the flowers of E. gardneri on islet protection and amelioration in T2DM and explore its mechanism.MethodQuercetin was extracted from the flowers of E. gardneri and verified by high-performance liquid chromatography. Quercetin or crude extract’s effect on insulin secretion was investigated. ERK1/2 and phospho-ERK1/2 were detected by Western blot analysis, and fluo-3 AM was used to detect intracellular Ca2+. The anti-apoptosis effect of quercetin or crude extract on MIN-6 cells was investigated by thiazolyl blue tetrazolium bromide (MTT) assay and flow cytometry analysis. Activation of caspases and expression of Bcl-2 and BAX were tested by Western blot analysis. In addition, the mitochondrial membrane potential was determined by JC-1 probe. Moreover, in vivo activity was also tested in db/db mice.ResultsA quercetin level of >10 μmol/L could induce insulin secretion. Intracellular Ca2+ and ERK1/2 were involved in the signaling pathway of quercetin-induced insulin secretion. We also observed that quercetin could inhibit palmitic acid-induced cell apoptosis via suppressing the activation of caspase-3, -9, -12; increasing the ratio of Bcl-2/BAX and reversing the impaired mitochondrial membrane potential. Crude extract’s effect on insulin secretion was similar to that of pure extracted quercetin, while it possessed higher anti-apoptosis activity. Additionally, intraperitoneal glucose tolerance, plasma insulin level, hepatic triglyceride, hepatic glycogen and the pathological histology of both pancreatic islet and liver in db/db mice were significantly improved by the administration of the extracted quercetin.ConclusionOur study indicated that quercetin extracted from the flowers of E. gardneri exerted excellent properties in islet protection and amelioration.

Role of osteopontin and its regulation in pancreatic islet

Osteopontin (OPN) is involved in various physiological processes and also implicated in multiple pathological states. It has been suggested that OPN may have a role in type 2 diabetes (T2D) by protecting pancreatic islets and interaction with incretins. However, the regulation and function of OPN in islets, especially in humans, remains largely unexplored. In this study, we performed our investigations on both diabetic mouse model SUR1-E1506K+/+ and islets from human donors. We demonstrated that OPN protein, secretion and gene expression was elevated in the diabetic SUR1-E1506K+/+ islets. We also showed that high glucose and incretins simultaneously stimulated islet OPN secretion. In islets from human cadaver donors, OPN gene expression was elevated in diabetic islets, and externally added OPN significantly increased glucose-stimulated insulin secretion (GSIS) from diabetic but not normal glycemic donors. The increase in GSIS by OPN in diabetic human islets was Ca2+ dependent, which was abolished by Ca2+-channel inhibitor isradipine. Furthermore, we also confirmed that OPN promoted cell metabolic activity when challenged by high glucose. These observations provided evidence on the protective role of OPN in pancreatic islets under diabetic condition, and may point to novel therapeutic targets for islet protection in T2D.

Protective effects of dietary polyphenols from black soybean seed coats on islet and renal function in streptozotocin-induced diabetic rats.

The aim of this study was to investigate the antidiabetic effects of the crude polyphenol extract (BSCP) from black soybean seed coats (BSC) and the whole flour of BSC and illustrate the mechanism in terms of islet and renal protection. BSCP and BSC effectively controlled the increased blood glucose level and impaired glucose tolerance in streptozotocin (STZ)-induced diabetic rats after 8 weeks of treatment. They increased the concentrations of serum insulin, C-peptide and Glp-1 (P < 0.05) by improving the STZ-induced damage of islet β-cells and increasing their insulin expression (P < 0.05). Lipid profiles and antioxidant activities were also improved. Moreover, BSCP and BSC tended to decrease serum creatinine (0.05 < P < 0.1), and blood urea nitrogen was decreased by BSC significantly (P < 0.05). They also led to significantly lower glomerular volume (P < 0.05). Long-term intervention with BSC at a low dose of polyphenols plays a role in controlling blood glucose and lipids levels by promoting insulin secretion and restoring islet β-cell function, the same as BSCP. These benefits are accompanied by their potential protection of diabetic renal dysfunction. BSCP is mainly responsible for the antidiabetic effect of BSC. © 2017 Society of Chemical Industry.

Advances of mechanism research on procyanidin in prevention and treatment of type 2 diabetes mellitus

Diabetes mellitus, a chronic disease, is characterized by high blood glucose that could induce various complications. Procyanidin, a kind of polyphenol compounds existing in many plants, have shown to be effective in preventing and treating type 2 diabetes mellitus as they may lower blood glucose, moderate insulin resistance and protect islet β cells. This review focused on the research advances on the preventive and therapeutic application of procyanidin in promoting glucose absorption, protecting islet β cells, modulating intestinal microbiota and regulating diabetic complications of type 2 diabetes mellitus, which should provide useful reference for subsequent studies.

Mechanisms related to the anti-diabetic properties of mango (Mangifera indica L.) juice by-product

This study aimed to determine the nutraceutical composition of mango by-product (BP) and to evaluate the mechanisms related to its antidiabetic properties. Mango BP reduced (p<0.05) serum glucose in streptozotocin-induced diabetic rats, which was not associated with a decreased glucose intestinal absorption or to the protection of Langerhans islets. Mango BP showed insulin mimetic effects in 3T3-L1 adipocyte cells, increasing Glut4, Irs1 and Pi3k expression. Mango BP reduced (p<0.05) serum triacylglycerides in diabetic rats, which was associated to a decreased lipid intestinal absorption, and ameliorated diabetic nephropathy due to its renal antioxidant activity. The anti-diabetic effect of mango BP was associated to its high content of soluble fiber, as well as several polyphenols and carotenoids, like ellagic acid, gallic acid, quercetin, epicatechin gallate, and β-carotene. Therefore, these results suggest that mango BP could be used as a functional supplement for diabetes treatment.

STEAP4 expression in human islets is associated with differences in body mass index, sex, HbA1c, and inflammation.

STEAP4 (six-transmembrane epithelial antigen of the prostate 4) is a metalloreductase that has been shown previously to protect cells from inflammatory damage. Genetic variants in STEAP4 have been associated with numerous metabolic disorders related to obesity, including putative defects in the acute insulin response to glucose in type 2 diabetes. We examined whether obesity and/or type 2 diabetes altered STEAP4 expression in human pancreatic islets. Human islets were isolated from deceased donors at two medical centers and processed for quantitative polymerase chain reaction. Organ donors were selected by status as non-diabetic or having type 2 diabetes. Site 1 (Edmonton): N = 13 type 2 diabetes donors (7M, 6F), N = 20 non-diabetic donors (7M, 13F). Site 2 (Virginia): N = 6 type 2 diabetes donors (6F), N = 6 non-diabetic donors (3M, 3F). STEAP4 showed reduced islet expression with increasing body mass index among all donors (P < 0.10) and non-diabetic donors (P < 0.05) from Site 1; STEAP4 showed reduced islet expression among type 2 diabetes donors with increasing hemoglobin A1c. Islet STEAP4 expression was also marginally higher in female donors (P < 0.10). Among type 2 diabetes donors from Site 2, islet insulin expression was reduced, STEAP4 expression was increased, and white blood cell counts were increased compared to non-diabetic donors. Islets from non-diabetic donors that were exposed overnight to 5 ng/ml IL-1β displayed increased STEAP4 expression, consistent with STEAP4 upregulation by inflammatory signaling. These findings suggest that increased STEAP4 mRNA expression is associated with inflammatory stimuli, whereas lower STEAP4 expression is associated with obesity in human islets. Given its putative protective role, downregulation of STEAP4 by chronic obesity suggests a mechanism for reduced islet protection against cellular damage.

The effect of G-CSF and AMD3100 on mice treated with streptozotocin: Expansion of alpha-cells and partial islet protection

Administration of streptozotocin (STZ) is one of the most used experimental models of diabetes (STZ-DT). STZ induces beta-cell damage in pancreatic islets. It is known that hematopoietic stem progenitor cells (HSPCs) are mobilized from bone marrow to damaged tissues. In this work, we evaluated the effects of the hematopoietic mobilizers G-CSF (250μg/kg; for five consecutive days) and AMD3100 (5mg/kg; single s.c injection) in mice treated with STZ (175mg/kg). Mice injected with STZ showed a significant reduction in the number and area of islets and in the number of beta- and alpha-cells. Concurrently, they had hyperglycemia (blood glucose over 300mg/dl) associated with very low levels of insulin in plasma. The number and area of islets from STZ-DT mice treated with G-CSF and/or AMD3100 were similar to the controls. However, these mice had neither a reduction of hyperglycemia nor an improvement in the insulin levels. Analysis of islet cellularity showed a large reduction in beta-cells with a significant expansion of alpha-cells. These results indicate that G-CSF and AMD3100 induce partial protection of islet tissues and expansion of alpha-cells in mice treated with STZ but do not protect beta-cells from the damage induced by this compound.

Ethylene carbodiimide-fixed donor splenocytes combined with α-1 antitrypsin induce indefinite donor-specific protection to mice cardiac allografts.

Peritransplant infusion of ethylene carbodiimide-fixed donor splenocytes (ECDI-SPs) induces protection of islet and cardiac allografts. However, pro-inflammatory cytokine production during the peritransplantation period may negate the effect of ECDI-SPs. Therefore, we hypothesized that blocking pro-inflammatory cytokine secretion while increasing levels of anti-inflammatory cytokines would enhance the tolerance-induced efficacy of ECDI-SPs. The objective of this study was to determine the effectiveness of using ECDI-SPs combined with a short course of α1-antitrypsin (AAT) for induction of tolerance. Using a mice cardiac transplant model, we demonstrated that ECDI-SPs+AAT effectively induced indefinite mice cardiac allograft protection in a donor-specific fashion. This effect was accompanied by modulation of cytokines through decreasing levels of pro-inflammatory cytokines (including IFN-γ, TNF-α, IL-1β, IL-6, IL-17, and IL-23) and increasing levels of anti-inflammatory cytokines (including IL-10, IL-13, and TGF-β), and by inhibition of effector T cells (Teff) and expansion of regulatory T cells (Tregs). Therefore, we concluded that combined ECDI-SPs and AAT appeared to modulate the expression of cytokines and regulate the Teff:Treg balance to create a support milieu for graft protection. Our strategy of combining ECDI-SPs and AAT provides a promising approach for inducing donor-specific transplant tolerance.

Prolonged Survival of Subcutaneous Allogeneic Islet Graft by Donor Chimerism without Immunosuppressive Treatment.

The aim of this study was to investigate whether tolerance-induced protection of islets in the renal subcapsular space can also prevent subcutaneous allogeneic islets from being rejected. We used bone marrow stem cells from C57BL/6 (H2b) mice to construct donor chimerism in conditioned diabetic BALB/c (H2d) mice and investigated the effect of donor chimerism on engraftment and survival of subcutaneously transplanted allogeneic islets in streptozotocin-induced diabetic mice. We also studied the anti-inflammatory effect of mesenchymal stem cell on islet engraftment. Full but not low-grade or no donor chimerism was associated with successful engraftment of allogeneic islets and restoration of normoglycemia in the treated diabetic mice. The temporary hyperglycemia was 11 ± 1 versus 19 ± 5 days (p < 0.05) for the mice with full donor chimerism with transplanted islets in the renal subcapsular space versus the subcutaneous space, respectively. Cotransplantation of mesenchymal stem cell did not enhance alloislet engraftment. Full multilineage donor chimerism was associated with a higher transient expansion of CD11b+ and Gr-1+ myeloid progenitor cells and effector memory CD4 and CD8 T cells. In conclusion, full donor chimerism protected both renal subcapsular and subcutaneous allogeneic islets in this rodent transplantation model.

Synergistic effect of PEGylation and pentoxifylline addition on immunoprotection of pancreatic islets

In this study, a method is proposed to reduce immunological response of immune system against Langerhans islets by PEGylation of islets combined with adjuvant therapy. For this purpose, the best composition for a mixture of succinimidyl valeric acid activated mPEG (mPEG-SVA) with different molecular weights (MWs) and for a mixture of succinimidyl carbonate activated mPEG (mPEG-SC) with different MWs was determined separately. Then, the effect of pentoxifylline (PTX) as an adjuvant drug on immunological response against PEGylated islets at best mPEG composition was studied. The extent of mPEGs reaction, the amount of interlukin-2 (IL-2) and perforin secretion, and the viability of lymphocytes and islets in homo and co-cultures in the presence of PTX at different concentrations were considered for the in vitro evaluation of the proposed method. It was found, that a mixture of mPEG-SVA with MWs of 10 and 5 kDa at a composition of 75 and 25%, respectively, was the best formulation. Also, the addition of PTX drug to co-culture medium increased the protection of PEGylated islets against immune system and a concentration of 75 μg mL−1 of PTX was suitable for islet protection with no adverse effect on immune cells.

Macroporous biohybrid cryogels for co-housing pancreatic islets with mesenchymal stromal cells.

Intrahepatic transplantation of allogeneic pancreatic islets offers a promising therapy for type 1 diabetes. However, long-term insulin independency is often not achieved due to severe islet loss shortly after transplantation. To improve islet survival and function, extrahepatic biomaterial-assisted transplantation of pancreatic islets to alternative sites has been suggested. Herein, we present macroporous, star-shaped poly(ethylene glycol) (starPEG)-heparin cryogel scaffolds, covalently modified with adhesion peptides, for the housing of pancreatic islets in three-dimensional (3D) co-culture with adherent mesenchymal stromal cells (MSC) as accessory cells. The implantable biohybrid scaffolds provide efficient transport properties, mechanical protection, and a supportive extracellular environment as a desirable niche for the islets. MSC colonized the cryogel scaffolds and produced extracellular matrix proteins that are important components of the natural islet microenvironment known to facilitate matrix-cell interactions and to prevent cellular stress. Islets survived the seeding procedure into the cryogel scaffolds and secreted insulin after glucose stimulation in vitro. In a rodent model, intact islets and MSC could be visualized within the scaffolds seven days after subcutaneous transplantation. Overall, this demonstrates the potential of customized macroporous starPEG-heparin cryogel scaffolds in combination with MSC to serve as a multifunctional islet supportive carrier for transplantation applications. Diabetes results in the insufficient production of insulin by the pancreatic β-cells in the islets of Langerhans. Transplantation of pancreatic islets offers valuable options for treating the disease; however, many transplanted islets often do not survive the transplantation or die shortly thereafter. Co-transplanted, supporting cells and biomaterials can be instrumental for improving islet survival, function and protection from the immune system. In the present study, islet supportive hydrogel sponges were explored for the co-transplantation of islets and mesenchymal stromal cells. Survival and continued function of the supported islets were demonstrated in vitro. The in vivo feasibility of the approach was shown by transplantation in a mouse model.

Protection of Human Pancreatic Islets from Lipotoxicity by Modulation of the Translocon.

Type 2 diabetes is characterized by peripheral insulin resistance and pancreatic beta cell dysfunction. Elevated free fatty acids (FFAs) may impair beta cell function and mass (lipotoxicity). Altered calcium homeostasis may be involved in defective insulin release. The endoplasmic reticulum (ER) is the major intracellular calcium store. Lipotoxicity induces ER stress and in parallel an ER calcium depletion through unknown ER calcium leak channels. The main purposes of this study is first to identify one of these channels and secondly, to check the opportunity to restore beta cells function (i.e., insulin secretion) after pharmacological inhibition of ER calcium store depletion. We investigated the functionality of translocon, an ER calcium leak channel and its involvement on FFAs-induced alterations in MIN6B1 cells and in human pancreatic islets. We evidenced that translocon acts as a functional ER calcium leak channel in human beta cells using anisomycin and puromycin (antibiotics), respectively blocker and opener of this channel. Puromycin induced a significant ER calcium release, inhibited by anisomycin pretreatment. Palmitate treatment was used as FFA model to induce a mild lipotoxic effect: ER calcium content was reduced, ER stress but not apoptosis were induced and glucose induced insulin secretion was decreased in our beta cells. Interestingly, translocon inhibition by chronic anisomycin treatment prevented dysfunctions induced by palmitate, avoiding reticular calcium depletion, ER stress and restoring insulin secretion. Our results provide for the first time compelling evidence that translocon actively participates to the palmitate-induced ER calcium leak and insulin secretion decrease in beta cells. Its inhibition reduces these lipotoxic effects. Taken together, our data indicate that TLC may be a new potential target for the treatment of type 2 diabetes.

Peptide micelle-mediated curcumin delivery for protection of islet β-cells under hypoxia

Islet transplantation is one of many therapeutic approaches for the treatment of diabetes. During transplant procedures, the isolated islets are subjected to hypoxic conditions, and undergo the apoptotic process. Curcumin has a cytoprotective effect, and may therefore be useful for the protection of islets under hypoxia. However, curcumin is hydrophobic, and an efficient curcumin carrier is required for effective treatment. In this study, R3V6 peptide micelles, composed of a 3-arginine stretch and 6-valine stretch, were evaluated as a curcumin carrier to INS-1 insulinoma cells. Curcumin was loaded into R3V6 micelles at a weight ratio of 10:3 (R3V6:curcumin). The size and surface charge of the curcumin-loaded R3V6 micelles (R3V6-curcumin) were approximately 250 nm and 17.49 mV, respectively. R3V6-curcumin delivered curcumin to the INS-1 cells more efficiently than either curcumin alone or a simple mixture of R3V6 and curcumin. MTT assay indicated that under hypoxia, R3V6-curcumin protected INS-1 cells more efficiently than curcumin alone. TUNEL and reactive oxygen species (ROS) assays suggested that R3V6-curcumin reduced INS-1 cell apoptosis under hypoxia. These results demonstrate that R3V6 peptide micelles are an effective carrier of curcumin, and that R3V6-curcumin may improve the viability of pancreatic β-cells in islet transplantation.

Alginate composition, temperature, and presence of islet tissue influence microcapsule permeability

Alginate composition, temperature, and presence of islet tissue influence microcapsule permeability

Activation of imidazoline-I3 receptors ameliorates pancreatic damage.

Agmatine, an endogenous ligand of imidazoline receptors, is reported to exhibit anti-hyperglycaemic and many other effects. It has been established that the imidazoline I3 receptor is involved in insulin secretion. The current study characterizes the role of the imidazoline I3 receptor in the protection of pancreatic islets. The activity effect of agmatine against on streptozotocin (STZ)-induced (5mmol/L) rat β cell apoptosis was examined by using ApoTox-Glo triplex assay, live/dead cell double staining assay, flow cytometric analysis, and western blot. Imidazoline I3 receptors antagonist KU14R and the phospholipase C inhibitor named U73122 were treated in β cells to investigate the potential signalling pathways. The serum glucose and recovery of insulin secretion were measured in STZ-treated rats after continuously injected agmatine. The apoptosis in rat β cells was reduced by agmatine in a dose-dependent manner, cell viability was improved after treatment with agmatine and these effects were suppressed after the blockade of KU14R and U73122. Western blot analysis confirmed that agmatine could decrease caspase-3 expression and increase the p-BAD levels. In STZ-treated rats, injection of agmatine for 4weeks may significantly lower the serum glucose and recovery of insulin secretion. This improvement of pancreatic islets induced by agmatine was deleted by KU14R invivo. Agmatine can activate the imidazoline I3 receptor linked with the phospholipase C pathway to induce cell protection against apoptosis induced by a low dose of STZ. This finding provides new insight into the prevention of early stage pancreatic islet damage.