beta-Cell death during progression to diabetes

Cardiovascular Health Benefits of Exercise Training in Persons Living with Type 1 Diabetes: A Systematic Review and Meta-Analysis

Exercise is advocated in the management of type 1 diabetes (T1D), but the effects of different forms of exercise training on cardiovascular risk factors in T1D still remain unclear. The aim of this study was to conduct a systematic review and meta-analysis on exercise training for cardiovascular risk factors in T1D. Six electronic databases were systematically searched for randomized or non-randomized controlled studies reporting associations between exercise training and cardiovascular risk factors in T1D. Weighted mean differences (WMD) of each cardiovascular risk factor between exercise groups and control groups were calculated using a random effects model. A total of 24 studies reported the effects of exercise training on cardiovascular risk factors. Exercise training increased maximal aerobic power (3.01 mL·kg⁻¹·min⁻¹, 95% confidence interval, CI, 0.94 to 6.38) and reduced glycated hemoglobin (HbA1c; −0.45%, 95% CI −0.73 to −0.17), daily insulin dosage (−0.88 U·kg⁻¹, 95% CI −1.27 to −0.48), and total cholesterol (−0.38 mmol·L⁻¹, 95% CI −0.71 to −0.04). Exercise training did not lead to consistent changes in body mass index (BMI), blood pressure, triglycerides, high-density lipoprotein cholesterol (HDL-C), or low-density lipoprotein cholesterol (LDL-C). In persons living with T1D, exercise training is associated with a beneficial cardiovascular profile, including improvements in lipid profile, glycemic control (decreased daily insulin dosage and HbA1c), and aerobic fitness.

Streptozotocin-Induced Diabetes Mellitus in Neonatal Rats: An Insight into its Applications to Induce Diabetic Complications

BACKGROUND

Diabetic complications are the major contributor in the mortality of diabetic patients despite controlling blood glucose level. In the journey of new drug discovery, animal models have to play a major role. A large number of chemical-induced and genetically modified animal models have been investigated to induce diabetic complications but none of them was found to be mimicking the pathophysiology of the human. Therefore, the search and identification of the appropriate animal model become essential.

OBJECTIVE

In the present review, we have made an attempt to understand the pathophysiology of diabetic complication in the neonatal streptozotocin-diabetic rat model and tried to identify the targets for therapeutic agents. The review will help the researchers to explore the animal model to induce diabetic complications, to identify targets and further to find lead molecules for treatment or prevention of diabetic complications.

METHODS

We have compiled the available research work from 1974 by using prominent databases, organized the available information and analyzed the data to improve the understanding of the pathophysiology of streptozotocin-induced diabetic complications in neonates of rats.

RESULTS

The neonatal streptozotocin-diabetic rat model is frequently used and well-established animal model for type 2 diabetes mellitus. We have found that this model has been used to study the pathogenesis of various micro and macrovascular diabetic complications and also investigated for its effects on the liver, thymus gland, and brain. The underlying pathophysiology for complications had a resemblance to the human.

CONCLUSION

The neonatal streptozotocin-diabetic rat model may demonstrate symptomatic diabetic complications due to persistent hyperglycemia at the age of approximately 18-24 weeks. Critical interpretations of available research work showed that the researcher can explore split dose STZ (90- 100mg/kg b.w) model to induce Type 2 DM in neonates of rats at 2nd or 3rd postnatal day.

PARP-14 Promotes Survival of Mammalian α but Not β Pancreatic Cells Following Cytokine Treatment

PARP-14 (poly-ADP Ribose Polymerase-14), a member of the PARP family, belongs to the group of Bal proteins (B Aggressive Lymphoma). PARP-14 has recently appeared to be involved in the transduction pathway mediated by JNKs (c Jun N terminal Kinases), among which JNK2 promotes cancer cell survival. Several pharmacological PARP inhibitors are currently used as antitumor agents, even though they have also proved to be effective in many inflammatory diseases. Cytokine release from immune system cells characterizes many autoimmune inflammatory disorders, including type I diabetes, in which the inflammatory state causes β cell loss. Nevertheless, growing evidence supports a concomitant implication of glucagon secreting α cells in type I diabetes progression. Here, we provide evidence on the activation of a survival pathway, mediated by PARP-14, in pancreatic α cells, following treatment of αTC1.6 glucagonoma and βTC1 insulinoma cell lines with a cytokine cocktail: interleukin 1 beta (IL-1β), interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α). Through qPCR, western blot and confocal analysis, we demonstrated higher expression levels of PARP-14 in αTC1.6 cells with respect to βTC1 cells under inflammatory stimuli. By cytofluorimetric and caspase-3 assays, we showed the higher resistance of α cells compared to β cells to apoptosis induced by cytokines. Furthermore, the ability of PJ-34 to modulate the expression of the proteins involved in the survival pathway suggests a protective role of PARP-14. These data shed light on a poorly characterized function of PARP-14 in αTC1.6 cells in inflammatory contexts, widening the potential pharmacological applications of PARP inhibitors.

Phosphorylation of extracellular signal-regulated kinase 1/2 in subepidermal nerve fibers mediates hyperalgesia following diabetic peripheral neuropathy

Peripheral neuropathy, a chronic complication of diabetes mellitus (DM), is often accompanied by the onset of severe pain symptoms that affect quality of life. However, the underlying mechanisms remain elusive. In the present study, we used Sprague-Dawley rats to establish a rodent model of the human type 1 DM by a single intraperitoneal (i.p.) injection with streptozotocin (STZ) (60 mg/kg). Hypersensitivity, including hyperalgesia and allodynia, developed in the STZ-induced diabetic rats. Cutaneous innervation exhibited STZ-induced reductions of protein gene product 9.5-, peripherin-, and neurofilament 200-immunoreactivity (IR) subepidermal nerve fibers (SENFs). Moreover, the decreases of substance P (SP)- and calcitonin gene-related peptide (CGRP)-IR SENFs were distinct gathered from the results of extracellular signal-regulated kinase 1 and 2 (ERK1/2)- and phosphorylated ERK1/2 (pERK1/2)-IR SENFs in STZ-induced diabetic rats. Double immunofluorescence studies demonstrated that STZ-induced pERK1/2-IR was largely increased in SENFs where only a small portion was colocalized with SP- or CGRP-IR. By an intraplantar (i. pl.) injection with a MEK inhibitor, U0126 (1,4-Diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene), hyperalgesia was attenuated in a dose-responsive manner. Botulinum toxin serotype A had dose-dependent analgesic effects on STZ-induced hyperalgesia and allodynia, which exhibited equivalent results as the efficacy of transient receptor potential vanilloid (TRPV) channel antagonists. Morphological evidence further confirmed that STZ-induced SP-, CGRP- and pERK1/2-IR were reduced in SENFs after pharmacological interventions. From the results obtained in this study, it is suggested that increases of pERK1/2 in SENFs may participate in the modulation of TRPV channel-mediated neurogenic inflammation that triggers hyperalgesia in STZ-induced diabetic rats. Therefore, ERK1/2 provides a potential therapeutic target and efficient pharmacological strategies to address hyperglycemia-induced neurotoxicity.

The Glucose Lowering Effect of Zornia gibbosa Span Extracts in Diabetic Rats

Objectives

Diabetes mellitus is a chronic, lifelong condition that affects our body physiology. Untreated diabetes mellitus causes diseases such as diabetic retinopathy, diabetic nephropathy and diabetic neuropathy, auto immune diseases, polyuria, polydipsia, loss of weight, and cardiovascular diseases. The use of medications for the treatment of diabetes mellitus causes adverse effects with long-term use, and sometimes leads to death. Today, researchers are working on the discovery of new anti-diabetes drugs from plants with low or no adverse effects. From this point of view, the present work was conducted to evaluate the anti-diabetic activity of Zornia gibbosa Span.

Materials and Methods

This acute toxicity study was conducted for ethyl acetate and ethanol (70%v/v) extracts of Z. gibbosa as per OECD guidelines. The anti-diabetic activity of selected plant extracts were tested using alloxan-induced diabetes in a rat model.

Results

No mortality was observed in the administered doses of Zornia gibbosa Span extracts. The tested extracts significantly (p≤0.01) restored the physiologic changes that occurred due to the alloxan-induced diabetes mellitus. The hydroalcoholic extracts at 500 mg/kg body weight concentration showed more activity compared with other extracts at different concentrations along with standard drug (glibenclamide). Zornia gibbosa significantly decreased glucose concentrations and restored the altered enzymes levels caused by damage to different organs by diabetes.

Conclusion

The results of the present study indicate that Z. gibbosa has a significant anti-diabetic activity. Therefore, it may be capable of use as an alternate medicine along with allopathic medicine in the treatment of diabetes as well as its health problems.

Redox-Sensitive Innate Immune Pathways During Macrophage Activation in Type 1 Diabetes

SIGNIFICANCE

Type 1 diabetes (T1D) is an autoimmune disease resulting in β-cell destruction mediated by islet-infiltrating leukocytes. The role of oxidative stress in human and murine models of T1D is highly significant as these noxious molecules contribute to diabetic complications and β-cell lysis, but their direct impact on dysregulated autoimmune responses is highly understudied. Pro-inflammatory macrophages play a vital role in the initiation and effector phases of T1D by producing free radicals and pro-inflammatory cytokines to facilitate β-cell destruction and to present antigen to autoreactive T cells. Recent Advances: Redox modulation of macrophage functions may play critical roles in autoimmunity. These include enhancing pro-inflammatory innate immune signaling pathways in response to environmental triggers, enforcing an M1 macrophage differentiation program, controlling antigen processing, and altering peptide recognition by oxidative post-translational modification. Therefore, an oxidative environment may act on multiple macrophage functions to orchestrate T1D pathogenesis.

CRITICAL ISSUES

Mechanisms involved in the initiation of T1D remain unclear, making preventive and early therapeutics difficult to develop. Although many of these advances in the redox regulation of macrophages are in their infancy, they provide insight into how oxidative stress aids in the precipitating event of autoimmune activation.

FUTURE DIRECTIONS

Future studies should be aimed at mechanistically determining which redox-regulated macrophage functions are pertinent in T1D pathogenesis, as well as at investigating potential targetable therapeutics to halt and/or dampen innate immune activation in T1D.

An important step towards a prevascularized islet microencapsulation device: in vivo prevascularization by combination of mesenchymal stem cells on micropatterned membranes

Extrahepatic transplantation of islets of Langerhans could aid in better survival of islets after transplantation. When islets are transfused into the liver 60-70% of them are lost immediately after transplantation. An important factor for a successful extrahepatic transplantation is a well-vascularized tissue surrounding the implant. There are many strategies known for enhancing vessel formation such as adding cells with endothelial potential, the combination with angiogenic factors and / or applying surface topography at the exposed surface of the device. Previously we developed porous, micropatterned membranes which can be applied as a lid for an islet encapsulation device and we showed that the surface topography induces human umbilical vein endothelial cell (HUVEC) alignment and interconnection. This was achieved without the addition of hydrogels, often used in angiogenesis assays. In this work, we went one step further towards clinical implementation of the device by combining this micropatterned lid with Mesenchymal Stem Cells (MSCs) to facilitate prevascularization in vivo. As for HUVECs, the micropatterned membranes induced MSC alignment and organization in vitro, an important contributor to vessel formation, whereas in vivo (subcutaneous rat model) they contributed to improved implant prevascularization. In fact, the combination of MSCs seeded on the micropatterned membrane induced the highest vessel formation score in 80% of the sections.

Inhibition of mTORC1 by ER stress impairs neonatal β-cell expansion and predisposes to diabetes in the Akita mouse

Unresolved ER stress followed by cell death is recognized as the main cause of a multitude of pathologies including neonatal diabetes. A systematic analysis of the mechanisms of β-cell loss and dysfunction in Akita mice, in which a mutation in the proinsulin gene causes a severe form of permanent neonatal diabetes, showed no increase in β-cell apoptosis throughout life. Surprisingly, we found that the main mechanism leading to β-cell dysfunction is marked impairment of β-cell growth during the early postnatal life due to transient inhibition of mTORC1, which governs postnatal β-cell growth and differentiation. Importantly, restoration of mTORC1 activity in neonate β-cells was sufficient to rescue postnatal β-cell growth, and to improve diabetes. We propose a scenario for the development of permanent neonatal diabetes, possibly also common forms of diabetes, where early-life events inducing ER stress affect β-cell mass expansion due to mTOR inhibition.

β-Cell mass restoration by α7 nicotinic acetylcholine receptor activation

Although it is well-established how nutrients, growth factors, and hormones impact functional β-cell mass (BCM), the influence of the central nervous system in this regard, and especially in the context of islet immune modulation, has been understudied. Here we investigated the expression and activity of pancreatic islet α7 nicotinic acetylcholine receptor (α7nAChR) in islet anti-inflammatory and prosurvival signaling. Systemic administration of α7nAChR agonists in mice improved glucose tolerance and curtailed streptozotocin-induced hyperglycemia by retaining BCM, in part through maintaining Pdx1 and MafA expression and reducing apoptosis. α7nAChR activation of mouse islets ex vivo led to reduced inflammatory drive through a JAK2-STAT3 pathway that couples with CREB/Irs2/Akt survival signaling. Because the vagus nerve conveys anti-inflammatory signals to immune cells of the spleen and other nonneural tissues in the viscera by activating α7nAChR agonists, our study suggests a novel role for β-cell α7nAChR that functions to maintain β-cell survival and mass homeostasis through modulating islet cytokine and phosphatidylinositol 3-kinase-dependent signaling pathways. Exploiting these pathways may have therapeutic potential for the treatment of autoimmune diabetes.

The biologic effect of hydrogen sulfide and its function in various diseases

INTRODUCTION

Hydrogen sulfide (H2S), a colorless, water soluble, flammable gas with a characteristic smell of rotten eggs, has been known as a highly toxic gas for several years. However, much like carbon monoxide (CO) and nitric oxide (NO), the initial negative perception of H2S has developed with the discovery that H2S is generated enzymatically in animals under normal conditions. With the result of this discovery, much more work is needed to elucidate the biologic effects of H2S. In recent years, its cytoprotective properties have been recognized in multiple organs and tissues. In particular, H2S plays important roles in combating oxidative species such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) and protect the body from oxidative stress. Therefore, this review discusses the biologic effect of H2S and how it protects cells in various diseases by acting as an antioxidant that reduces excessive amounts of ROS and RNS.

ETHICS AND DISSEMINATION

Ethical approval and informed consent are not required, as the study will be a literature review and will not involve direct contact with patients or alterations to patient care.

CONCLUSION

H2S has been found to be cytoprotective in oxidative stress in a wide range of physiologic and pathologic conditions, an increasing number of therapeutic potentials of H2S also have been revealed. However, there is still much debate on the clear mechanism of action of H2S, so that the mechanisms of cell signaling that promote cellular survival and organ protection need to be further investigated to provide better H2S-based therapeutics.

Endothelin-1 traps potently reduce pathologic markers back to basal levels in an in vitro model of diabetes

Background

Diabetes mellitus is a group of metabolic disorders in which there are high blood glucose levels over a prolonged period. Diabetes is one of many diseases associated with pathologically elevated levels of endothelin (ET)-1. We have recently proposed the development of ET-traps, which are an antibody - based fusion protein that potently bind and sequester pathologically elevated levels of endothelin-1.

Methods

We constructed ET-traps that were found to be very potent binders to ET-1, with a K_D of 32.5ρM. We then treated human retinal microvascular endothelial cells (HRMECs), which are an in vitro model of glucose induced cellular damage, with 10 nM ET-1 or high glucose levels (25 mM).

Results

In this study, we investigated the effects of our ET-trap constructs on the expression levels of both collagen 4α1 and fibronectin, which are both important pathologic markers in diabetes. Treating HRMECs with 10 nM ET-1 or 25 mM glucose significantly induces the expression of the ECM proteins fibronectin and collagen 4α1, as is found in chronic diabetic complications; Incubation of the cells with the ET-traps significantly prevented the increased expression of fibronectin and collagen 4α1 back to basal levels. This was found with both mRNA and protein expression levels of the two ECM proteins.

Conclusion

Our results provide the first evidence of the efficacy of ET-traps in reducing pathologic markers in an in vitro model (of diabetes). Further research is warranted to determine the efficacy of ET-traps as a therapeutic tool for diabetes, which is a major public health burden around the world.

Dietary Cows' Milk Protein A1 Beta-Casein Increases the Incidence of T1D in NOD Mice

The contribution of cows’ milk containing beta-casein protein A1 variant to the development of type 1 diabetes (T1D) has been controversial for decades. Despite epidemiological data demonstrating a relationship between A1 beta-casein consumption and T1D incidence, direct evidence is limited. We demonstrate that early life exposure to A1 beta-casein through the diet can modify progression to diabetes in non-obese diabetic (NOD) mice, with the effect apparent in later generations. Adult NOD mice from the F0 generation and all subsequent generations (F1 to F4) were fed either A1 or A2 beta-casein supplemented diets. Diabetes incidence in F0–F2 generations was similar in both cohorts of mice. However, diabetes incidence doubled in the F3 generation NOD mice fed an A1 beta-casein supplemented diet. In F4 NOD mice, subclinical insulitis and altered glucose handling was evident as early as 10 weeks of age in A1 fed mice only. A significant decrease in the proportion of non-conventional regulatory T cell subset defined as CD4⁺CD25⁻FoxP3⁺ was evident in the F4 generation of A1 fed mice. This feeding intervention study demonstrates that dietary A1 beta-casein may affect glucose homeostasis and T1D progression, although this effect takes generations to manifest.

Effects of proinsulin misfolding on β-cell dynamics, differentiation and function in diabetes

ER stress due to proinsulin misfolding has an important role in the pathophysiology of rare forms of permanent neonatal diabetes (PNDM) and probably also of common type 1 (T1D) and type 2 diabetes (T2D). Accumulation of misfolded proinsulin in the ER stimulates the unfolded protein response (UPR) that may eventually lead to apoptosis through a process called the terminal UPR. However, the β-cell ER has an incredible ability to cope with accumulation of misfolded proteins; therefore, it is not clear whether in common forms of diabetes the accumulation of misfolded proinsulin exceeds the point of no return in which terminal UPR is activated. Many studies showed that the UPR is altered in both T1D and T2D; however, the observed changes in the expression of different UPR markers are inconsistent and it is not clear whether they reflect an adaptive response to stress or indeed mediate the β-cell dysfunction of diabetes. Herein, we critically review the literature on the effects of proinsulin misfolding and ER stress on β-cell dysfunction and loss in diabetes with emphasis on β-cell dynamics, and discuss the gaps in understanding the role of proinsulin misfolding in the pathophysiology of diabetes.

Type 2 diabetes - An autoinflammatory disease driven by metabolic stress

Type 2 diabetes has traditionally been viewed as a metabolic disorder characterised by chronic high glucose levels, insulin resistance, and declining insulin secretion from the pancreas. Modern lifestyle, with abundant nutrient supply and reduced physical activity, has resulted in dramatic increases in the rates of obesity-associated disease conditions, including diabetes. The associated excess of nutrients induces a state of systemic low-grade chronic inflammation that results from production and secretion of inflammatory mediators from the expanded pool of activated adipocytes. Here, we review the mechanisms by which obesity induces adipose tissue dysregulation, detailing the roles of adipose tissue secreted factors and their action upon other cells and tissues central to glucose homeostasis and type 2 diabetes. Furthermore, given the emerging importance of adipokines, cytokines and chemokines in disease progression, we suggest that type 2 diabetes should now be viewed as an autoinflammatory disease, albeit one that is driven by metabolic dysregulation.

Phagocytosis Deficiency of Macrophages in NOD.H-2h4 Mice Accelerates the Severity of Iodine-Induced Autoimmune Thyroiditis

Apoptosis occurs in many autoimmune diseases. Excess iodine induces thyrocyte apoptosis and increases the incidence and prevalence of autoimmune thyroiditis (AIT). However, the sequence of events between the appearance of thyrocyte apoptosis and the occurrence of thyroiditis remains uncharacterized. Furthermore, few studies have investigated the role of macrophage phagocytosis in the development of AIT. Therefore, we evaluated the relationship between apoptosis and inflammatory infiltration in NOD.H-2^h4 mouse thyroids by comparing the sequence of events in tissue samples. We also investigated the role of macrophages by comparing macrophage phagocytosis function in BALB/c, C57BL/6, and NOD.H-2^h4 mice treated with different levels of iodine. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays and thyroid inflammatory scores revealed that apoptosis (2 weeks) occurred before inflammatory infiltration (4 weeks). Phosphatidylserine (PS) expression on the extracellular surface of the cell membrane and double-stranded DNA fragments associated with apoptosis appeared at 2 and 8 weeks, respectively. Additionally, although apoptosis was enhanced in the thyroids of mice supplemented with excess iodine (0.05 ± 0.12 vs 1.63 ± 0.82% for BALB/c, 0.09 ± 0.14 vs 1.51 ± 0.34% for C57BL/6, and 0.07 ± 1.11 vs 4.72 ± 0.62% for NOD.H-2^h4 mice), only NOD.H-2^h4 mouse thyroids presented with inflammation. Furthermore, macrophages from NOD.H-2^h4 mice (44.46 ± 1.79%) exhibited decreased phagocytotic activity relative to that in BALB/c (54.21 ± 4.58%) and C57BL/6 (58.96 ± 4.04%) mice. There were no differences in phagocytosis function between NOD.H-2^h4 mice supplemented with excess iodine or left untreated (24.50 ± 2.66 vs 21.71 ± 1.79%, p = 0.06). In conclusion, deficiencies in the apoptosis clearance of macrophages in NOD.H-2^h4 mice may constitute an early pathogenic mechanism in AIT that is not influenced by iodine intake.

Phthalates and type 1 diabetes: is there any link?

Phthalates are a group of chemical compounds used as plasticizers in the manufacture of plastic materials. They can be present in many commonly used products. There seems to be a relationship between exposure to phthalates and the occurrence of metabolic dysfunctions, such as a decrease in glucose tolerance, oxidative stress, loss of beta cells, and a decrease in insulin synthesis. As beta cells play a key role in the onset of type 1 diabetes mellitus (T1DM), we sought to investigate the relationship between exposure to phthalates and the diagnosis of T1DM in prepubertal children. Design concentrations of phthalate metabolites were compared in the urine of a population of prepubertal children with new-onset diabetes, patients with T1DM diagnosed more than 6 months previously, and healthy control children. Although the concentrations of DBP and DiBP metabolites were statistically identical in the new-onset diabetes, diabetes, and control groups, there was a clear trend for higher levels of DiBP metabolites in the children with new-onset diabetes. In our sample, there was a trend for higher levels of DiBP metabolites in children with new-onset diabetes.

Role of Egr1 on Pancreatic Endoderm Differentiation

The low efficiency of in vitro differentiation of human embryonic stem cells (hESCs) or human-induced pluripotent stem cells (iPSCs) into insulin-producing cells is a crucial hurdle for the clinical implementation of human pluripotent stem cells (PSCs). Our previous investigation into the key factors for the differentiation of PSCs into insulin-producing cells suggested that the expression of GATA binding protein 6 (GATA6) and Gremlin 1 (GREM1) and inhibition of early growth response protein 1 (Egr1) may be important factors. In this study, we investigated the role of Egr1 in pancreas development. The transfection of small interfering RNA (siRNA) of Egr1 in the early phase induced the differentiation of iPSCs derived from fibroblasts (FiPSCs) into pancreatic endoderm and insulin-producing cells. In contrast, the downregulation of Egr1 in the late phase suppressed the differentiation of FiPSCs into pancreatic endoderm and insulin-producing cells. In addition, the overexpression of Egr1 suppressed the differentiation of iPSCs derived from pancreatic cells into pancreatic endoderm and insulin-producing cells. These data suggest that the downregulation of Egr1 in the early phase can efficiently induce the differentiation of iPSCs into insulin-producing cells.

Potential differentiation of islet-like cells from pregnant cow-derived placental stem cells

OBJECTIVE

Type 1 diabetes is an autoimmune disease that destroys islet cells and results in insufficient insulin secretion by pancreatic β-cells. Islet transplantation from donors is an approach used for treating patients with diabetes; however, this therapy is difficult to implement because of the lack of donors. Nevertheless, several stem cells have the potential to differentiate from islet-like cells and enable insulin secretion for treating diabetes in animal models. For example, placenta is considered a waste material and can be harvested noninvasively during delivery without ethical or moral concerns. To date, the differentiation of islet-like cells from cow-derived placental stem cells (CPSCs) has yet to be demonstrated.

MATERIALS AND METHODS

The investigation of potential differentiation of islet-like cells from CPSCs was conducted by supplementation with nicotinamide, exendin-4, glucose, and poly-d-lysine and was detected through reverse transcription polymerase chain reaction, dithizone staining, and immunocytochemical methods.

RESULTS

Our results indicated that CPSCs are established and express mesenchymal stem cell surface antigen markers, such as CD73, CD166, β-integrin, and Oct-4, but not hematopoietic stem cell surface antigen markers, such as CD45. After induction, the CPSCs successfully differentiated into islet-like cells. The CPSC-derived islet-like cells expressed islet cell development-related genes, such as insulin, glucagon, pax-4, Nkx6.1, pax-6, and Fox. Moreover, CPSC-derived islet-like cells can be stained with zinc ions, which are widely distributed in the islet cells and enable insulin secretion.

CONCLUSION

Altogether, islet-like cells have the potential to be differentiated from CPSCs without gene manipulation, and can be used in diabetic animal models in the future for preclinical and drug testing trial investigations.

Diabetes pathogenic mechanisms and potential new therapies based upon a novel target called TXNIP

PURPOSE OF REVIEW

Thioredoxin-interacting protein has emerged as a major factor regulating pancreatic β-cell dysfunction and death, key processes in the pathogenesis of type 1 and type 2 diabetes. Accumulating evidence based on basic, preclinical, and retrospective epidemiological research suggests that TXNIP represents a promising therapeutic target for diabetes. The present review is aimed at providing an update regarding these developments.

RECENT FINDINGS

TXNIP has been shown to be induced by glucose and increased in diabetes and to promote β-cell apoptosis, whereas TXNIP deletion protected against diabetes. More recently, TXNIP inhibition has also been found to promote insulin production and glucagon-like peptide 1 signaling via regulation of a microRNA. β-Cell TXNIP expression itself was found to be regulated by hypoglycemic agents, carbohydrate-response-element-binding protein, and cytosolic calcium or the calcium channel blocker, verapamil. Retrospective studies now further suggest that verapamil use might be associated with a lower incidence of type 2 diabetes in humans.

SUMMARY

TXNIP has emerged as a key factor in the regulation of functional β-cell mass and TXNIP inhibition has shown beneficial effects in a variety of studies. Thus, the inhibition of TXNIP may provide a novel approach to the treatment of diabetes.

Loss of Deubiquitinase USP1 Blocks Pancreatic β-Cell Apoptosis by Inhibiting DNA Damage Response

Impaired pancreatic β-cell survival contributes to the reduced β-cell mass in diabetes, but underlying regulatory mechanisms and key players in this process remain incompletely understood. Here, we identified the deubiquitinase ubiquitin-specific protease 1 (USP1) as an important player in the regulation of β-cell apoptosis under diabetic conditions. Genetic silencing and pharmacological suppression of USP1 blocked β-cell death in several experimental models of diabetes in vitro and ex vivo without compromising insulin content and secretion and without impairing β-cell maturation/identity genes in human islets. Our further analyses showed that USP1 inhibition attenuated DNA damage response (DDR) signals, which were highly elevated in diabetic β-cells, suggesting a USP1-dependent regulation of DDR in stressed β-cells. Our findings highlight a novel function of USP1 in the control of β-cell survival, and its inhibition may have a potential therapeutic relevance for the suppression of β-cell death in diabetes.

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Genetic and chemical inhibition of USP1 promoted β-cell survival

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USP1 inhibitors blocked β-cell death in human islets without affecting β-cell function

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USP1 inhibition reduced DDR signals in stressed β-cells

Differential role of MyD88 and TRIF signaling in myeloid cells in the pathogenesis of autoimmune diabetes

Type 1 diabetes (T1D) is caused by the autoimmune destruction of the insulin-producing pancreatic beta cells. While the role of adaptive immunity has been extensively studied, the role of innate immune responses and particularly of Toll- like Receptor (TLR) signaling in T1D remains poorly understood. Here we show that myeloid cell-specific MyD88 deficiency considerably protected mice from the development of streptozotocin (STZ)-induced diabetes. The protective effect of MyD88 deficiency correlated with increased expression of the immunoregulatory enzyme indoleamine 2,3-dioxygenase (IDO) in pancreatic lymph nodes from STZ-treated mice and in bone marrow-derived dendritic cells (BMDC) stimulated with apoptotic cells. Mice with myeloid cell specific TIR-domain-containing adapter-inducing interferon-β (TRIF) knockout showed a trend towards accelerated onset of STZ-induced diabetes, while TRIF deficiency resulted in reduced IDO expression in vivo and in vitro. Moreover, myeloid cell specific MyD88 deficiency delayed the onset of diabetes in Non-Obese Diabetic (NOD) mice, whereas TRIF deficiency had no effect. Taken together, these results identify MyD88 signaling in myeloid cells as a critical pathogenic factor in autoimmune diabetes, which is antagonized by TRIF-dependent responses. This differential function of MyD88 and TRIF depends at least in part on their opposite effects in regulating IDO expression in phagocytes exposed to apoptotic cells.

Neutralization Versus Reinforcement of Proinflammatory Cytokines to Arrest Autoimmunity in Type 1 Diabetes

As physiological pathways of intercellular communication produced by all cells, cytokines are involved in the pathogenesis of inflammatory insulitis as well as pivotal mediators of immune homeostasis. Proinflammatory cytokines including interleukins, interferons, transforming growth factor-β, tumor necrosis factor-α, and nitric oxide promote destructive insulitis in type 1 diabetes through amplification of the autoimmune reaction, direct toxicity to β-cells, and sensitization of islets to apoptosis. The concept that neutralization of cytokines may be of therapeutic benefit has been tested in few clinical studies, which fell short of inducing sustained remission or achieving disease arrest. Therapeutic failure is explained by the redundant activities of individual cytokines and their combinations, which are rather dispensable in the process of destructive insulitis because other cytolytic pathways efficiently compensate their deficiency. Proinflammatory cytokines are less redundant in regulation of the inflammatory reaction, displaying protective effects through restriction of effector cell activity, reinforcement of suppressor cell function, and participation in islet recovery from injury. Our analysis suggests that the role of cytokines in immune homeostasis overrides their contribution to β-cell death and may be used as potent immunomodulatory agents for therapeutic purposes rather than neutralized.

mTORC1 Signaling: A Double-Edged Sword in Diabetic β Cells

The mechanistic target of rapamycin complex 1 (mTORC1) is a central regulator of metabolic and nutrient cues that integrates environmental inputs into downstream signaling pathways to control cellular metabolism, growth, and survival. While numerous in vitro and in vivo studies reported the positive functions of mTORC1 in the regulation of β cell survival and proliferation under physiological conditions, more recent work demonstrates the opposite in the long term; this is exemplified by the constitutive inappropriate hyper-activation of mTORC1 in diabetic islets or β cells under conditions of increased β cell stress and metabolic demands. These recent findings uncover mTORC1's importance as an emerging significant player in the development and progression of β cell failure in type 2 diabetes and suggest that mTORC1 may act as a "double edge sword" in the regulation of β cell mass and function in response to metabolic stress such as nutrient overload and insulin resistance.

The Hippo Signaling Pathway in Pancreatic β-Cells: Functions and Regulations

Hippo signaling is an evolutionarily conserved pathway that critically regulates development and homeostasis of various tissues in response to a wide range of extracellular and intracellular signals. As an emerging important player in many diseases, the Hippo pathway is also involved in the pathophysiology of diabetes on the level of the pancreatic islets. Multiple lines of evidence uncover the importance of Hippo signaling in pancreas development as well as in the regulation of β-cell survival, proliferation, and regeneration. Hippo therefore represents a potential target for therapeutic agents designed to improve β-cell function and survival in diabetes. In this review, we summarize recent data on the regulation of the Hippo signaling pathway in the pancreas/in pancreatic islets, its functions on β-cell homeostasis in physiology and pathophysiology, and its contribution toward diabetes progression. The current knowledge related to general mechanisms of action and the possibility of exploiting the Hippo pathway for therapeutic approaches to block β-cell failure in diabetes is highlighted.

Hyperspectral imaging for simultaneous measurements of two FRET biosensors in pancreatic β-cells

Fluorescent protein (FP) biosensors based on Förster resonance energy transfer (FRET) are commonly used to study molecular processes in living cells. There are FP-FRET biosensors for many cellular molecules, but it remains difficult to perform simultaneous measurements of multiple biosensors. The overlapping emission spectra of the commonly used FPs, including CFP/YFP and GFP/RFP make dual FRET measurements challenging. In addition, a snapshot imaging modality is required for simultaneous imaging. The Image Mapping Spectrometer (IMS) is a snapshot hyperspectral imaging system that collects high resolution spectral data and can be used to overcome these challenges. We have previously demonstrated the IMS’s capabilities for simultaneously imaging GFP and CFP/YFP-based biosensors in pancreatic β-cells. Here, we demonstrate a further capability of the IMS to image simultaneously two FRET biosensors with a single excitation band, one for cAMP and the other for Caspase-3. We use these measurements to measure simultaneously cAMP signaling and Caspase-3 activation in pancreatic β-cells during oxidative stress and hyperglycemia, which are essential components in the pathology of diabetes.

Type 1 diabetes genome-wide association studies: not to be lost in translation

Genetic studies have identified >60 loci associated with the risk of developing type 1 diabetes (T1D). The vast majority of these are identified by genome-wide association studies (GWAS) using large case-control cohorts of European ancestry. More than 80% of the heritability of T1D can be explained by GWAS data in this population group. However, with few exceptions, their individual contribution to T1D risk is low and understanding their function in disease biology remains a huge challenge. GWAS on its own does not inform us in detail on disease mechanisms, but the combination of GWAS data with other omics-data is beginning to advance our understanding of T1D etiology and pathogenesis. Current knowledge supports the notion that genetic variation in both pancreatic β cells and in immune cells is central in mediating T1D risk. Advances, perspectives and limitations of GWAS are discussed in this review.

The small RNA miR-375 - a pancreatic islet abundant miRNA with multiple roles in endocrine beta cell function

The pathophysiology of diabetes is complex and recent research put focus on the pancreatic islets of Langerhans and the insulin-secreting beta cells as central in the development of the disease. MicroRNAs (miRNAs), the small non-coding RNAs regulating post-transcriptional gene expression, are significant regulators of beta cell function. One of the most abundant miRNAs in the islets is miR-375. This review focus on the role of miR-375 in beta cell function, including effects in development and differentiation, proliferation and regulation of insulin secretion. It also discusses the regulation of miR-375 expression, miR-375 as a potential circulating biomarker in type 1 and type 2 diabetes, and the need for the beta cell to keep expression of miR-375 within optimal levels. The summed picture of miR-375 is a miRNA with multiple functions with importance in the formation of beta cell identity, control of beta cell mass and regulation of insulin secretion.

GPNMB Induces BiP Expression by Enhancing Splicing of BiP Pre-mRNA during the Endoplasmic Reticulum Stress Response

Glycoprotein nonmetastatic melanoma protein B (GPNMB) has a neuroprotective effect against neuronal cell death caused by the accumulation of abnormal mutated proteins. It is known that the accumulation of pathological proteins induces endoplasmic-reticulum (ER) stress leading to cell damage. The aim of this study was to determine the role of GPNMB in the ER stress response. GPNMB was greatly up-regulated by thapsigargin-induced ER stress. Under the ER stress conditions, GPNMB relocated to the nucleus and specifically up-regulated expression of BiP at the mRNA level by promoting the BiP pre-mRNA splicing, not through the pathways initiated by the three major transducers of the unfolded protein response: IRE1, PERK, and ATF6. Furthermore, we found that the protein level of BiP and the infarction were increased and attenuated, respectively, in Gpnmb-transgenic mice after occlusion of the middle cerebral artery, in comparison with wild-type mice. Thus, our findings indicate that GPNMB enhances the BiP expression by promoting the splicing (thereby preventing cell death caused by ER stress) and could be a therapeutic target in ER stress-related disorders.

Intestinal type 1 regulatory T cells migrate to periphery to suppress diabetogenic T cells and prevent diabetes development

Growing insight into the pathogenesis of autoimmune diseases and numerous studies in preclinical models highlights the potential of regulatory T cells to restore tolerance. By using non-obese diabetic (NOD) BDC2.5 TCR-transgenic (Tg), and IL-10 and Foxp3 double-reporter mice, we demonstrate that alteration of gut microbiota during cohousing experiments or treatment with anti-CD3 mAb significantly increase intestinal IL-10-producing type 1 regulatory T (Tr1) cells and decrease diabetes incidence. These intestinal antigen-specific Tr1 cells have the ability to migrate to the periphery via a variety of chemokine receptors such as CCR4, CCR5, and CCR7 and to suppress proliferation of Th1 cells in the pancreas. The ability of Tr1 cells to cure diabetes in NOD mice required IL-10 signaling, as Tr1 cells could not suppress CD4⁺ T cells with a dominant-negative IL-10R. Taken together, our data show a key role of intestinal Tr1 cells in the control of effector T cells and development of diabetes. Therefore, modulating gut-associated lymphoid tissue to boost Tr1 cells may be important in type 1 diabetes management.

Pancreatic-β-cell survival and proliferation are promoted by protein kinase G type Iα and downstream regulation of AKT/FOXO1

Early studies showed nitric oxide as a pro-inflammatory-cytokine-induced toxin involved in pancreatic β-cell destruction during pathogenesis of type-1 diabetes. However, nitric oxide has both cytotoxic and cytoprotective effects on mammalian cells, depending on concentration and micro-environmental surroundings. Our studies have shown that low/physiological-level nitric oxide selectively activates protein kinase G type Iα isoform, promoting cytoprotective/pro-cell-survival effects in many cell types. In bone marrow-derived stromal/mesenchymal stem cells, protein kinase G type Iα mediates autocrine effects of nitric oxide and atrial natriuretic peptide, promoting DNA-synthesis/proliferation and cell survival. In this study, endothelial nitric oxide synthase/neuronal nitric oxide synthase inhibitor L-NIO (L-N(5)-(1-iminoethyl)ornithine), soluble guanylyl cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3,-a] quinoxalin-1-one), atrial natriuretic peptide-receptor inhibitor A71915 and protein kinase G type Iα kinase activity inhibitor DT-2 all increased apoptosis and decreased insulin secretion in RINm5F pancreatic β-cells, suggesting autocrine regulatory role for endogenous nitric oxide- and atrial natriuretic peptide-induced activation of protein kinase G type Iα. In four pancreatic β-cell lines, Beta-TC-6, RINm5F, INS-1 and 1.1B4, protein kinase G type Iα small-interfering RNA decreased phospho-serine-239-VASP (indicator of endogenous protein kinase G type Iα kinase activity), increased apoptosis and decreased proliferation. In protein kinase G type Iα-knockdown β-cell lines, expressions of phospho-protein kinase B (PKB/AKT) (AKT), phospho-Forkhead box protein O1 (FOXO1) (transcriptional repressor of pancreas duodenum homobox-1) and pancreas duodenum homobox-1 were decreased, suppressing proliferation and survival in pancreatic β-cells. The data suggest autocrine nitric oxide/atrial natriuretic peptide-induced activation of protein kinase G type Iα/p-AKT/p-FOXO1 promotes survival and proliferation in pancreatic β-cells, providing therapeutic implications for development of new therapeutic agents for diabetes.

Isoform-selective inhibitor of histone deacetylase 3 (HDAC3) limits pancreatic islet infiltration and protects female nonobese diabetic mice from diabetes

Preservation of insulin-secreting β-cells is an important goal for therapies aimed at restoring normoglycemia in patients with diabetes. One approach, the inhibition of histone deacetylases (HDACs), has been reported to suppress pancreatic islet inflammation and β-cell apoptosis in vitro In this report, we demonstrate the efficacy of HDAC inhibitors (HDACi) in vivo We show that daily administration of BRD3308, an isoform-selective HDAC3 inhibitor, for 2 weeks to female nonobese diabetic (NOD) mice, beginning at 3 weeks of age, followed by twice-weekly injections until age 25 weeks, protects the animals from diabetes. The preservation of β-cells was because of a significant decrease in islet infiltration of mononuclear cells. Moreover, the BRD3308 treatment increased basal insulin secretion from islets cultured in vitro All metabolic tissues tested in vehicle- or BRD3308-treated groups showed virtually no sign of immune cell infiltration, except minimal infiltration in white adipose tissue in animals treated with the highest BRD3308 dose (10 mg/kg), providing additional evidence of protection from immune attack in the treated groups. Furthermore, pancreata from animals treated with 10 mg/kg BRD3308 exhibited significantly decreased numbers of apoptotic β-cells compared with those treated with vehicle or low-dose BRD3308. Finally, animals treated with 1 or 10 mg/kg BRD3308 had enhanced β-cell proliferation. These in vivo results point to the potential use of selective HDAC3 inhibitors as a therapeutic approach to suppress pancreatic islet infiltration and prevent β-cell death with the long-term goal of limiting the progression of type 1 diabetes.

Early prediction of autoimmune (type 1) diabetes

Underlying type 1 diabetes is a genetic aetiology dominated by the influence of specific HLA haplotypes involving primarily the class II DR-DQ region. In genetically predisposed children with the DR4-DQ8 haplotype, exogenous factors, yet to be identified, are thought to trigger an autoimmune reaction against insulin, signalled by insulin autoantibodies as the first autoantibody to appear. In children with the DR3-DQ2 haplotype, the triggering reaction is primarily against GAD signalled by GAD autoantibodies (GADA) as the first-appearing autoantibody. The incidence rate of insulin autoantibodies as the first-appearing autoantibody peaks during the first years of life and declines thereafter. The incidence rate of GADA as the first-appearing autoantibody peaks later but does not decline. The first autoantibody may variably be followed, in an apparently non-HLA-associated pathogenesis, by a second, third or fourth autoantibody. Although not all persons with a single type of autoantibody progress to diabetes, the presence of multiple autoantibodies seems invariably to be followed by loss of functional beta cell mass and eventually by dysglycaemia and symptoms. Infiltration of mononuclear cells in and around the islets appears to be a late phenomenon appearing in the multiple-autoantibody-positive with dysglycaemia. As our understanding of the aetiology and pathogenesis of type 1 diabetes advances, the improved capability for early prediction should guide new strategies for the prevention of type 1 diabetes.

High glucose-induced ROS activates TRPM2 to trigger lysosomal membrane permeabilization and Zn2+-mediated mitochondrial fission

Diabetic stress increases the production of reactive oxygen species (ROS), leading to mitochondrial fragmentation and dysfunction. We hypothesized that ROS-sensitive TRPM2 channels mediated diabetic stress-induced mitochondrial fragmentation. We found that chemical inhibitors, RNAi silencing, and genetic knockout of TRPM2 channels abolished the ability of high glucose to cause mitochondrial fission in endothelial cells, a cell type that is particularly vulnerable to diabetic stress. Similar to high glucose, increasing ROS in endothelial cells by applying H₂O₂ induced mitochondrial fission. Ca²⁺ that entered through TRPM2 induced lysosomal membrane permeabilization, which led to the release of lysosomal Zn²⁺ and a subsequent increase in mitochondrial Zn²⁺ Zn²⁺ promoted the recruitment of the fission factor Drp-1 to mitochondria to trigger their fission. This signaling pathway may operate in aging-associated illnesses in which excessive mitochondrial fragmentation plays a central role.

BACE2 suppression promotes β-cell survival and function in a model of type 2 diabetes induced by human islet amyloid polypeptide overexpression

BACE2 (β-site APP-cleaving enzyme 2) is a protease expressed in the brain, but also in the pancreas, where it seems to play a physiological role. Amyloidogenic diseases, including Alzheimer's disease and type 2 diabetes (T2D), share the accumulation of abnormally folded and insoluble proteins that interfere with cell function. In T2D, islet amyloid polypeptide (IAPP) deposits have been shown to be a pathogenic key feature of the disease. The aim of the present study was to investigate the effect of BACE2 modulation on β-cell alterations in a mouse model of T2D induced by IAPP overexpression. Heterozygous mice carrying the human transcript of IAPP (hIAPP-Tg) were used as a model to study the deleterious effects of IAPP upon β-cell function. These animals showed glucose intolerance and impaired insulin secretion. When crossed with BACE2-deficient mice, the animals presented a significant improvement in glucose tolerance accompanied with an enhanced insulin secretion, as compared to hIAPP-Tg mice. BACE2 deficiency also partially reverted gene expression changes observed in islets from hIAPP-Tg mice, including a set of genes related to inflammation. Moreover, homozygous hIAPP mice presented a severe hyperglycemia and a high lethality rate from 8 weeks onwards due to a massive destruction of β-cell mass. This process was significantly reduced when crossed with the BACE2-KO model, improving the survival rate of the animals. Altogether, the absence of BACE2 ameliorates glucose tolerance defects induced by IAPP overexpression in the β-cell and promotes β-cell survival. Thus, targeting BACE2 may represent a promising therapeutic strategy to improve β-cell function in T2D.

Monomeric cocoa catechins enhance β-cell function by increasing mitochondrial respiration

A hallmark of type 2 diabetes (T2D) is β-cell dysfunction and the eventual loss of functional β-cell mass. Therefore, mechanisms that improve or preserve β-cell function could be used to improve the quality of life of individuals with T2D. Studies have shown that monomeric, oligomeric and polymeric cocoa flavanols have different effects on obesity, insulin resistance and glucose tolerance. We hypothesized that these cocoa flavanols may have beneficial effects on β-cell function. INS-1 832/13-derived β-cells and primary rat islets cultured with a monomeric catechin-rich cocoa flavanol fraction demonstrated enhanced glucose-stimulated insulin secretion, while cells cultured with total cocoa extract and with oligomeric or polymeric procyanidin-rich fraction demonstrated no improvement. The increased glucose-stimulated insulin secretion in the presence of the monomeric catechin-rich fraction corresponded with enhanced mitochondrial respiration, suggesting improvements in β-cell fuel utilization. Mitochondrial complex III, IV and V components are up-regulated after culture with the monomer-rich fraction, corresponding with increased cellular ATP production. The monomer-rich fraction improved cellular redox state and increased glutathione concentration, which corresponds with nuclear factor, erythroid 2 like 2 (Nrf2) nuclear localization and expression of Nrf2 target genes including nuclear respiratory factor 1 (Nrf1) and GA binding protein transcription factor alpha subunit (GABPA), essential genes for increasing mitochondrial function. We propose a model by which monomeric cocoa catechins improve the cellular redox state, resulting in Nrf2 nuclear migration and up-regulation of genes critical for mitochondrial respiration, glucose-stimulated insulin secretion and ultimately improved β-cell function. These results suggest a mechanism by which monomeric cocoa catechins exert their effects as an effective complementary strategy to benefit T2D patients.

Hispidin rescues palmitate‑induced insulin resistance in C2C12 myotubes

Skeletal muscle serves an important role in the utilization of glucose during insulin‑stimulated conditions. Excessive saturated fatty acids are considered to be a major contributing factor to insulin resistance in skeletal muscle cells. The present study investigated the effects of hispidin on palmitate‑induced insulin resistance in C2C12 skeletal muscle myotubes via an MTT assay, glucose uptake assay, Oil‑Red‑O staining and western blot analysis. Hispidin reversed the palmitate‑induced inhibition of glucose uptake, and inhibited palmitate‑induced intracellular lipid accumulation. Hispidin suppressed insulin receptor substrate‑1 Ser307 phosphorylation, and significantly promoted the activation of phosphatidylinositol‑3‑kinase and Akt, via inhibition of protein kinase C theta. Furthermore, hispidin treatment of C2C12 muscle cells increased glucose uptake via activation of adenosine monophosphate‑activated protein kinase. These findings indicated that hispidin may improve palmitate‑induced insulin resistance in skeletal muscle myotubes, and therefore hispidin treatment may be beneficial for patients with diabetes.

Changes in the Pancreas in Experimental Diabetes and the Effect of Lycopene on These Changes: Proliferating, Apoptotic, and Estrogen Receptor α Positive Cells

This study aimed to investigate the changes occurring in estrogen receptor (ER) α-positive cells, proliferating cells, apoptotic cells and malondialdehyde (MDA) expression in the pancreas of experimentally induced adult diabetic rats and to determine the effect of orally administered lycopene on these changes. Experimental diabetes was induced using a single dose of 50 mg/kg streptozotocin (STZ). Following the administration of STZ, four groups of animals were established: Control + corn oil, control + lycopene, diabetic + corn oil and diabetic + lycopene. The expressions of ER α, Ki-67, and MDA were determined through immunohistochemistry in sections taken from pancreas tissue samples at the end of the experiment. Apoptotic cells were determined through the TUNEL method. In the diabetic groups, the densities of ER α expression in islets and ER α-positive cells in exocrine parts increased. Whereas the number of proliferating Ki-67 positive cells was higher in the diabetic groups, no significant difference was observed in terms of apoptotic cell number between the control and diabetic groups. Lycopene in general did not have any effect on any of the parameters analyzed in the study. The presence of ER α-positive cells around the islets was demonstrated for the first time in diabetic groups. Based on these observations, demonstrating the antioxidant effects of lycopene in the pancreas of diabetic rats may be possible by increasing the dose and/or the duration of lycopene. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 300:2000-2007, 2017. © 2017 Wiley Periodicals, Inc.

Modulation of hippocampal gene expression of microRNA-146a/microRNA-155-nuclear factor-kappa B inflammatory signaling by troxerutin in healthy and diabetic rats

Objectives:

Inflammation plays a critical role in the progression of diabetic complications such as neurological disorders. Previous reports have indicated the memory-improving effect of troxerutin, in rat hippocampus, but the underlying mechanisms are unclear. Hence, we have investigated the effect of troxerutin pretreatment on gene expressions of inflammation-related microRNAs (miRs), miR-146a and miR-155, and nuclear factor-kappa B (NF-κB) signaling pathway in the hippocampus of healthy and diabetic rats.

Materials and Methods:

Wistar rats were randomly divided into four groups (control, control + troxerutin, diabetic, and diabetic + troxerutin). Diabetes was induced by a single i.p. injection of streptozotocin (50 mg/kg). Troxerutin (150 mg/kg) was orally administered in animals for 1 month. After 10 weeks of diabetes, animals were anesthetized and decapitated for the isolation of hippocampus. The expression of miR-146a and miR-155 and the messenger RNA (mRNA) expressions of NF-κB, interleukin-1 receptor-associated kinase-1 (IRAK-1), and tumor necrosis factor receptor-associated factor-6 (TRAF-6) were analyzed by real-time polymerase chain reaction.

Results:

Diabetes significantly increased hippocampal mRNA levels of NF-κB, IRAK-1, and TRAF-6 compared with nondiabetic rats (P < 0.05); however, pretreatment with troxerutin decreased them in both diabetic and nondiabetic animals, independent of its glycemic effect (P < 0.05). The expression levels of miR-146a and miR-155 were decreased in diabetic group as compared to the control (P < 0.01).

Conclusion:

These findings showed that troxerutin could inhibit the inflammatory NF-κB pathway in the hippocampus of diabetic rats, which may be due to the negative feedback loop regulated by miR-146a.

The Inhibitory G Protein α-Subunit, Gαz, Promotes Type 1 Diabetes-Like Pathophysiology in NOD Mice

The α-subunit of the heterotrimeric Gz protein, Gαz, promotes β-cell death and inhibits β-cell replication when pancreatic islets are challenged by stressors. Thus, we hypothesized that loss of Gαz protein would preserve functional β-cell mass in the nonobese diabetic (NOD) model, protecting from overt diabetes. We saw that protection from diabetes was robust and durable up to 35 weeks of age in Gαz knockout mice. By 17 weeks of age, Gαz-null NOD mice had significantly higher diabetes-free survival than wild-type littermates. Islets from these mice had reduced markers of proinflammatory immune cell infiltration on both the histological and transcript levels and secreted more insulin in response to glucose. Further analyses of pancreas sections revealed significantly fewer terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL)-positive β-cells in Gαz-null islets despite similar immune infiltration in control mice. Islets from Gαz-null mice also exhibited a higher percentage of Ki-67-positive β-cells, a measure of proliferation, even in the presence of immune infiltration. Finally, β-cell-specific Gαz-null mice phenocopy whole-body Gαz-null mice in their protection from developing hyperglycemia after streptozotocin administration, supporting a β-cell-centric role for Gαz in diabetes pathophysiology. We propose that Gαz plays a key role in β-cell signaling that becomes dysfunctional in the type 1 diabetes setting, accelerating the death of β-cells, which promotes further accumulation of immune cells in the pancreatic islets, and inhibiting a restorative proliferative response.

Glial fibrillary acidic protein (GFAP) is a novel biomarker for the prediction of autoimmune diabetes

Glial fibrillary acidic protein (GFAP) is expressed in peri-islet Schwann cells, as well as in glia cells, and has been reported to be an autoantigen candidate for type 1 diabetes mellitus (T1DM). We confirmed that the production of the autoantibodies GFAP and glutamic acid decarboxylase 65 (GAD65) was increased and inversely correlated with the concentration of secreted C peptide in female nonobese diabetic mice (T1DM model). Importantly, the development of T1DM in female nonobese diabetic mice at 30 wk of age was predicted by the positive GFAP autoantibody titer at 17 wk. The production of GFAP and GAD65 autoantibodies was also increased in KK-A^y mice [type 2 diabetes mellitus (T2DM) model]. In patients with diabetes mellitus, GFAP autoantibody levels were increased in patients with either T1DM or T2DM, and were significantly associated with GAD65 autoantibodies but not zinc transporter 8 autoantibodies. Furthermore, we identified a B-cell epitope of GFAP corresponding to the GFAP autoantibody in both mice and patients with diabetes. Thus, these results indicate that autoantibodies against GFAP could serve as a predictive marker for the development of overt autoimmune diabetes.-Pang, Z., Kushiyama, A., Sun, J., Kikuchi, T., Yamazaki, H., Iwamoto, Y., Koriyama, H., Yoshida, S., Shimamura, M., Higuchi, M., Kawano, T., Takami, Y., Rakugi, H., Morishita, R., Nakagumi, H. Glial fibrillary acidic protein (GFAP) is a novel biomarker for the prediction of autoimmune diabetes.

Plant-Produced Asialo-Erythropoietin Restores Pancreatic Beta-Cell Function by Suppressing Mammalian Sterile-20-like Kinase (MST1) and Caspase-3 Activation

Pancreatic beta-cell death adversely contributes to the progression of both type I and II diabetes by undermining beta-cell mass and subsequently diminishing endogenous insulin production. Therapeutics to impede or even reverse the apoptosis and dysfunction of beta-cells are urgently needed. Asialo-rhuEPO, an enzymatically desialylated form of recombinant human erythropoietin (rhuEPO), has been shown to have cardioprotective and neuroprotective functions but with no adverse effects like that of sialylated rhuEPO. Heretofore, the anti-apoptotic effect of asialo-rhuEPO on pancreatic beta-cells has not been reported. In the current study, we investigated the cytoprotective properties of plant-produced asialo-rhuEPO (asialo-rhuEPO^P) against staurosporine-induced cell death in the pancreatic beta-cell line RIN-m5F. Our results showed that 60 IU/ml asialo-rhuEPO^P provided 41% cytoprotection while 60 IU/ml rhuEPO yielded no effect. Western blotting results showed that asialo-rhuEPO^P treatment inhibited both MST1 and caspase-3 activation with the retention of PDX1 and insulin levels close to untreated control cells. Our study provides the first evidence indicating that asialo-rhuEPO^P-mediated protection involves the reduction of MST1 activation, which is considered a key mediator of apoptotic signaling in beta-cells. Considering the many advantages its plant-based expression, asialo-rhuEPO^P could be potentially developed as a novel and inexpensive agent to treat or prevent diabetes after further performing studies in cell-based and animal models of diabetes.

Perfluorooctanoic acid induces oxidative damage and mitochondrial dysfunction in pancreatic β-cells

Several environmental contaminants have been linked to the development of diabetes and increased diabetes‑associated mortality. Perfluorooctanoic acid (PFOA) is a widely used perfluoroalkane found in surfactants and lubricants, and in processing aids used in the production of polymers. Furthermore, PFOA has been detected in humans, wildlife and the environment. The present study investigated the toxic effects of PFOA on rat pancreatic β‑cell‑derived RIN‑m5F cells. Cell viability, apoptosis, reactive oxygen and nitrogen species, cytokine release and mitochondrial parameters, including membrane potential collapse, reduced adenosine triphosphate levels, cardiolipin peroxidation and cytochrome c release were assessed. PFOA significantly decreased RIN‑m5F cell viability and increased apoptosis. Exposure to PFOA increased the formation of reactive oxygen species, mitochondrial superoxide, nitric oxide and proinflammatory cytokines. Furthermore, PFOA induced mitochondrial membrane potential collapse and reduced adenosine triphosphate levels, cardiolipin peroxidation and cytochrome c release. These results indicate that PFOA is associated with the induction of apoptosis in RIN-m5F cells, and induces cytotoxicity via increased oxidative stress and mitochondrial dysfunction.

Impairment of endoplasmic reticulum is involved in β-cell dysfunction induced by microcystin-LR

Microcystins (MCs) widely distributed in freshwaters have posed a significant risk to human health. Previous studies have demonstrated that exposure to MC-LR impairs pancreatic islet function, however, the underlying mechanisms still remain unclear. In the present study, we explored the role of endoplasmic reticulum (ER) impairment in β-cell dysfunction caused by MC-LR. The result showed that MC-LR modified ER morphology evidenced by increased ER amount and size at low doses (15, 30 or 60 μM) and vacuolar and dilated ER ultrastructure at high doses (100 or 200 μM). Also, insulin content showed increased at 15 or 30 μM but declined at 60, 100, or 200 μM, which was highly accordant with ER morphological alteration. Transcriptomic analysis identified a number of factors and several pathways associated with ER protein processing, ER stress, apoptosis, and diabetes mellitus in the cells treated with MC-LR compared with non-treated cells. Furthermore, MC-LR-induced ER stress significantly promoted the expression of PERK/eIF2α and their downstream targets (ATF4, CHOP, and Gadd34), which indicates that PERK-eIF2α-ATF4 pathway is involved in MC-LR-induced insulin deficiency. These results suggest that ER impairment is an important contributor to MC-LR-caused β-cell failure and provide a new insight into the association between MCs contamination and the occurrence of human diseases.

Broad induction of immunoregulatory mechanisms after a short course of anti-IL-7Rα antibodies in NOD mice

BACKGROUND

Type 1 diabetes is an autoimmune disease caused by T cell-mediated destruction of the insulin-producing β-cells in the pancreas. Therefore, approaches that effectively halt the pathogenic T cell response are predicted to have preventive or therapeutic benefit for type 1 diabetes patients. We previously demonstrated that long-term blocking of IL-7 signaling, which is critical for the survival and function of T cells, prevented and reversed type 1 diabetes in non-obese diabetic mice. However, such persistent inhibition of T cell responses raises concerns about causing immunodeficiency. Here, we asked whether a reduced duration of the treatment with anti-IL-7Rα antibodies retained efficacy in preventing diabetes. Moreover, we sought to identify immunoregulatory mechanisms induced by anti-IL-7Rα administration.

RESULTS

Anti-IL-7Rα antibodies were administered to prediabetic NOD mice for 3 weeks and blood samples were taken at the end of treatment and 2 weeks later to analyze changes in T cell phenotypes in response to IL-7Rα blockade. We found that the co-inhibitory receptors LAG-3, Tim-3 and PD-1 were increased on peripheral blood CD4⁺ and CD8⁺ T cells from anti-IL-7Rα-treated mice. Expression of these receptors contributed to reduced T cell cytokine production in response to TCR stimulation. In addition, the frequency of Tregs within the circulating CD4⁺ T cells was increased at the end of anti-IL-7Rα antibody treatment and these Tregs showed a more activated phenotype. In vitro restimulation assays revealed that effector T cells from anti-IL-7Rα-treated mice were more sensitive to co-inhibitory receptor induction after TCR stimulation. Importantly, these changes were accompanied by delayed type 1 diabetes disease kinetics.

CONCLUSIONS

Together, our data show that short-term blockade of IL-7Rα induces detectable changes in co-inhibitory receptor expression and Treg frequencies in peripheral blood of NOD mice. These changes appear to have long-lasting effects by delaying or preventing type 1 diabetes incidence. Hence, our study provides further support for using anti-IL-7Rα antibodies to modulate autoreactive T cell responses.