IAPP and type 1 diabetes: implications for immunity, metabolism and islet transplants

Exploration of Immune Targets for Type 1 Diabetes and Latent Autoimmune Disease Immunotherapy

Type 1 diabetes (T1D) is an autoimmune disease that destroys pancreatic beta cells, which produce insulin in the islets of Langerhans. The risk of developing T1D is influenced by environmental factors, genetics, and autoantibodies. Latent autoimmune diabetes in adults (LADA) is a type of T1D that is genetically and phenotypically distinct from classic T1D. This review summarizes the accumulated information on the risk factors for T1D and LADA, and immunotherapy trials that offer insights into potential future combined therapeutic interventions for both T1D and LADA to slow the rate of islet cell loss and preserve beta cell function. Future research should also focus on improving intervention doses, conducting more thorough examinations of intervention responders, and/or combining minimally effective single-target immunotherapies to slow the rate of islet cell loss and preserve beta cell function.

Interaction of Proteins Involved in Neuronal Proteinopathies

Proteinopathy is characterized by the accumulation of aggregates of a specific protein in a target organ, tissue, or cell. The aggregation of the same protein can cause different pathologies as single protein can adopt various amyloidogenic, disease-specific conformations. The conformation governs the interaction of amyloid aggregates with other proteins that are prone to misfolding and, thus, determines disease-specific spectrum of concomitant pathologies. In this regard, a detailed description of amyloid protein conformation as well as spectrum of its interaction with other proteins become a key point for drafting of precise description of the disease. The majority of clinical cases of neuronal proteinopathies is caused by the aggregation of rather limited range of amyloidogenic proteins. Here, we provided the characterization of pathologies, related to the aggregation of amyloid β peptide, tau protein, α-synuclein, TDP-43, and amylin, giving a short description of pathologies themselves, recent advances in elucidation of misfolded protein conformation, with emphasis on those protein aggregates extracted from biological samples, what is known about the interaction of this proteins, and the influence of this interaction on the progression of underlying disease and comorbidities.

Oxidant-modified amylin fibrils and aggregates alter the inflammatory profile of multiple myeloid cell types, but are non-toxic to islet β cells

Diabetes mellitus currently affects ∼10% of the population worldwide, with Type 2 predominating, and this incidence is increasing steadily. Both Type 1 and 2 are complex diseases, involving β-cell death and chronic inflammation, but the pathways involved are unresolved. Chronic inflammation is characterized by increased oxidant formation, with this inducing protein modification, altered function and immunogenicity. Amylin, a peptide hormone co-secreted with insulin by β-cells, has attracted considerable interest for its amyloidogenic properties, however, the effects that oxidants have on amylin aggregation and function are poorly understood. Amylin was exposed in vitro to hypochlorous acid, hydrogen peroxide and peroxynitrous acid/peroxynitrite to investigate the formation of post-translational oxidative modifications (oxPTMs, via mass spectrometry) and fibril formation (via transmission electron microscopy). Amylin free acid (AFA) was also examined to investigate the role of the C-terminal amide in amylin. Oxidant exposure led to changes in aggregate morphology and abundance of oxPTMs in a concentration-dependent manner. The toxicity and immunogenic potential of oxidant-modified amylin or AFA on pancreatic islet cells (INS-1E), human monocyte cell line (THP-1) and monocyte-derived dendritic cells (moDCs) were examined using metabolic activity and cytokine assays, and flow cytometry. No significant changes in vitality or viability were detected, but exposure to oxidant-modified amylin or AFA resulted in altered immunogenicity when compared to the native proteins. THP-1 and moDCs show altered expression of activation markers and changes in cytokine secretion. Furthermore, oxidant-treated amylin and AFA promoted maturation of THP-1 and pre-mature moDCs, as determined by changes in size, and maturation markers.

Identification of key immune genes of osteoporosis based on bioinformatics and machine learning

Introduction

Immunity is involved in a variety of bone metabolic processes, especially osteoporosis. The aim of this study is to explore new bone immune-related markers by bioinformatics method and evaluate their ability to predict osteoporosis.

Methods

The mRNA expression profiles were obtained from GSE7158 in Gene expression Omnibus (GEO), and immune-related genes were obtained from ImmPort database (https://www.immport.org/shared/). immune genes related to bone mineral density(BMD) were screened out for differential analysis. protein-protein interaction (PPIs) networks were used to analyze the interrelationships between different immune-related genes (DIRGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of DIRGs function were performed. A least absolute shrinkage and selection operation (LASSO) regression model and multiple Support Vector Machine-Recursive Feature Elimination (mSVM-RFE) model were constructed to identify the candidate genes for osteoporosis prediction The receiver operator characteristic (ROC) curves were used to validate the performances of predictive models and candidate genes in GEO database (GSE7158,GSE13850).Through the RT - qPCR verify the key genes differentially expressed in peripheral blood mononuclear cells Finally, we constructed a nomogram model for predicting osteoporosis based on five immune-related genes. CIBERSORT algorithm was used to calculate the relative proportion of 22 immune cells.

Results

A total of 1158 DEGs and 66 DIRGs were identified between high-BMD and low-BMD women. These DIRGs were mainly enriched in cytokine-mediated signaling pathway, positive regulation of response to external stimulus and the cellular components of genes are mostly localized to external side of plasma membrane. And the KEGG enrichment analysis were mainly involved in Cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, Neuroactive ligand-receptor interaction,Natural killer cell mediated cytotoxicity. Then five key genes (CCR5, IAPP, IFNA4, IGHV3-73 and PTGER1) were identified and used as features to construct a predictive prognostic model for osteoporosis using the GSE7158 dataset.

Conclusion

Immunity plays an important role in the development of osteoporosis.CCR5, IAPP, IFNA4, IGHV3-73 and PTGER1were play an important role in the occurrences and diagnosis of OP.

Mechanisms of ag85a/b DNA vaccine conferred immunotherapy and recovery from Mycobacterium tuberculosis-induced injury

Our previous research developed a novel tuberculosis (TB) DNA vaccine ag85a/b that showed a significant therapeutic effect on the mouse tuberculosis model by intramuscular injection (IM) and electroporation (EP). However, the action mechanisms between these two vaccine immunization methods remain unclear. In a previous study, 96 Mycobacterium tuberculosis (MTB) H₃₇ Rv-infected BALB/c mice were treated with phosphate-buffered saline, 10, 50, 100, and 200 μg ag85a/b DNA vaccine delivered by IM and EP three times at 2-week intervals, respectively. In this study, peripheral blood mononuclear cells (PBMCs) from three mice in each group were isolated to extract total RNA. The gene expression profiles were analyzed using gene microarray technology to obtain differentially expressed (DE) genes. Finally, DE genes were validated by real-time reverse transcription-quantitive polymerase chain reaction and the GEO database. After MTB infection, most of the upregulated DE genes were related to the digestion and absorption of nutrients or neuroendocrine (such as Iapp, Scg2, Chga, Amy2a5), and most of the downregulated DE genes were related to cellular structural and functional proteins, especially the structure and function proteins of the alveolar epithelial cell (such as Sftpc, Sftpd, Pdpn). Most of the abnormally upregulated or downregulated DE genes in the TB model group were recovered in the 100 and 200 μg ag85a/b DNA IM groups and four DNA EP groups. The pancreatic secretion pathway downregulated and the Rap1 signal pathway upregulated had particularly significant changes during the immunotherapy of the ag85a/b DNA vaccine on the mouse TB model. The action targets and mechanisms of IM and EP are highly consistent. Tuberculosis infection causes rapid catabolism and slow anabolism in mice. For the first time, we found that the effective dose of the ag85a/b DNA vaccine immunized whether by IM or EP could significantly up-regulate immune-related pathways and recover the metabolic disorder and the injury caused by MTB.

Nanothin Conformal Coating with Poly(N-vinylpyrrolidone) and Tannic Acid (PVPON/TA) Preserves Murine and Human Pancreatic Islets Function

Beta cell replacement therapies can restore glycemic control to select individuals living with type 1 diabetes. However, the obligation of lifelong immunosuppression restricts cell therapies from replacing exogenous insulin administration. Encapsulation strategies can reduce the inherent adaptive immune response; however, few are successfully translated into clinical testing. Herein, we evaluated if the conformal coating of islets with poly(N-vinylpyrrolidone) (PVPON) and tannic acid (TA) (PVPON/TA) could preserve murine and human islet function while conferring islet allograft protection. In vitro function was evaluated using static glucose-stimulated insulin secretion, oxygen consumption rates, and islet membrane integrity. In vivo function was evaluated by transplanting human islets into diabetic immunodeficient B6.129S7-Rag1tm1Mom/J (Rag-/-) mice. The immunoprotective capacity of the PVPON/TA-coating was assessed by transplanting BALB/c islets into diabetic C57BL/6 mice. Graft function was evaluated by non-fasting blood glucose measurements and glucose tolerance testing. Both coated and non-coated murine and human islets exhibited indistinguishable in vitro potency. PVPON/TA-coated and control human islets were able to restore euglycemia post-transplant. The PVPON/TA-coating as monotherapy and adjuvant to systemic immunosuppression reduced intragraft inflammation and delayed murine allograft rejection. This study demonstrates that PVPON/TA-coated islets may be clinically relevant as they retain their in vitro and in vivo function while modulating post-transplant immune responses.

Mammalian models of diabetes mellitus, with a focus on type 2 diabetes mellitus

Although no single animal model replicates all aspects of diabetes mellitus in humans, animal models are essential for the study of energy balance and metabolism control as well as to investigate the reasons for their imbalance that could eventually lead to overt metabolic diseases such as type 2 diabetes mellitus. The most frequently used animal models in diabetes mellitus research are small rodents that harbour spontaneous genetic mutations or that can be manipulated genetically or by other means to influence their nutrient metabolism and nutrient handling. Non-rodent species, including pigs, cats and dogs, are also useful models in diabetes mellitus research. This Review will outline the advantages and disadvantages of selected animal models of diabetes mellitus to build a basis for their most appropriate use in biomedical research.

Selected Serum Markers Associated with Pathogenesis and Clinical Course of Type 1 Diabetes in Pediatric Patients—The Effect of Disease Duration

Biochemical abnormalities in the course of type 1 diabetes (T1D) may cause the production/activation of various proteins and peptides influencing treatment and causing a risk of complications. The aim of this study was to assess concentrations of selected serum substances involved in the pathogenesis and course of T1D and to correlate their concentrations with the duration of T1D. The study included patients with T1D (n = 156) at the age of 3–17, who were divided according to the duration of the disease into those newly diagnosed (n = 30), diagnosed after 3–5 (n = 77), 6–7 (n = 25), and over 7 (n = 24) years from the onset of T1D, and age-matched healthy controls (n = 30). Concentrations of amylin (IAPP), proamylin (proIAPP), catestatin (CST), chromogranin A (ChgA), nerve growth factor (NFG), platelet-activating factor (PAF), uromodulin (UMOD), and intestinal fatty acid binding protein (I-FABP) were measured in sera using immunoenzymatic tests. There were significant differences in concentrations of all the substances except UMOD and NGF between T1D patients and healthy children. The duration of the disease affected concentrations of CST, ChgA, PAF, and NGF, i.e., proteins/peptides which could have an impact on the course of T1D and the development of complications. In long-term patients, a decrease in concentrations of CST and ChgA, and an increase in PAF concentrations were found. In the case of NGF, a decrease was observed after the initial high values, followed by an increase over 7 years after T1D diagnosis. Concluding, the results show that concentrations of selected serum indicators may change in the course of T1D. Further studies are needed to establish whether these indicators could be used in the context of predicting long-term complications.

Acute Recurrent Pancreatitis in a Child With INS-Related Monogenic Diabetes and a Heterozygous Pathogenic CFTR Mutation

Given the close anatomical and physiological links between the exocrine and endocrine pancreas, diseases of 1 compartment often affect the other through mechanisms that remain poorly understood. Pancreatitis has been associated with both type 1 and type 2 diabetes, but its association with monogenic diabetes is unknown. Patients heterozygous for pathogenic CFTR variants are cystic fibrosis carriers and have been reported to have an increased risk of acute pancreatitis. We describe a 12-year-old patient with monogenic neonatal diabetes due to a pathogenic heterozygous paternally inherited mutation of the insulin gene (INS), c.94 G > A (p.Gly32Ser), who experienced 3 recurrent episodes of acute pancreatitis over 7 months in conjunction with poor glycemic control, despite extensive efforts to improve glycemic control in the past 4 years. Intriguingly, the maternal side of the family has an extensive history of adult-onset pancreatitis consistent with autosomal dominant inheritance and the proband is heterozygous for a maternally inherited, CFTR variant c.3909C > G (p.Asn1303Lys). Paternally inherited monogenic neonatal diabetes may have promoted earlier age-of-onset of pancreatitis in this pediatric patient compared to maternal relatives with adult-onset acute pancreatitis. Further study is needed to clarify how separate pathophysiologies associated with INS and CFTR mutations influence interactions between the endocrine and exocrine pancreas.

The unique pathophysiological features of diabetes mellitus secondary to total pancreatectomy: proposal for a new classification distinct from diabetes of the exocrine pancreas

INTRODUCTION

Diabetes of the exocrine pancreas (DEP; a.k.a. pancreatic diabetes or pancreatogenic diabetes or type 3c diabetes mellitus or T3cDM) refers to different diabetes types resulting from disorders of the exocrine pancreas. DEP is characterized by the structural and functional loss of glucose-normalizing insulin secretion in the context of exocrine pancreatic dysfunction. Among these forms, new-onset diabetes mellitus secondary to total pancreatectomy (TP) has unique pathophysiological and clinical features, for which we propose a new nomenclature such as post-total pancreatectomy diabetes mellitus (PTPDM).

AREAS COVERED

TP results in the complete loss of pancreatic parenchyma, with subsequent absolute insulinopenia and lifelong need for exogenous insulin therapy. Patients with PTPDM also exhibit deficiency of glucagon, amylin and pancreatic polypeptide. These endocrine abnormalities, coupled with increased peripheral insulin sensitivity, deficiency of pancreatic enzymes and TP-related modifications of gastrointestinal anatomy, can lead to marked glucose variability and increased risk of iatrogenic (insulin-induced) severe hypoglycemic episodes ('brittle diabetes').

EXPERT OPINION

We believe that diabetes mellitus secondary to TP should not be included in the DEP spectrum in light of its peculiar pathophysiological and clinical features. Therefore, we propose a new classification for this entity, that would likely provide more accurate prognosis and treatment strategies.

Calcitonin gene-related peptide is a potential autoantigen for CD4 T cells in type 1 diabetes

The calcitonin gene-related peptide (CGRP) is a 37-amino acid neuropeptide with critical roles in the development of peripheral sensitization and pain. One of the CGRP family peptides, islet amyloid polypeptide (IAPP), is an important autoantigen in type 1 diabetes. Due to the high structural and chemical similarity between CGRP and IAPP, we expected that the CGRP peptide could be recognized by IAPP-specific CD4 T cells. However, there was no cross-reactivity between the CGRP peptide and the diabetogenic IAPP-reactive T cells. A set of CGRP-specific CD4 T cells was isolated from non-obese diabetic (NOD) mice. The T-cell receptor (TCR) variable regions of both α and β chains were highly skewed towards TRAV13 and TRBV13, respectively. The clonal expansion of T cells suggested that the presence of activated T cells responded to CGRP stimulation. None of the CGRP-specific CD4 T cells were able to be activated by the IAPP peptide. This established that CGRP-reactive CD4 T cells are a unique type of autoantigen-specific T cells in NOD mice. Using IAg7-CGRP tetramers, we found that CGRP-specific T cells were present in the pancreas of both prediabetic and diabetic NOD mice. The percentages of CGRP-reactive T cells in the pancreas of NOD mice were correlated to the diabetic progression. We showed that the human CGRP peptide presented by IAg7 elicited strong CGRP-specific T-cell responses. These findings suggested that CGRP is a potential autoantigen for CD4 T cells in NOD mice and probably in humans. The CGRP-specific CD4 T cells could be a unique marker for type 1 diabetes. Given the ubiquity of CGRP in nervous systems, it could potentially play an important role in diabetic neuropathy.

Pramlintide: A Novel Therapeutic Approach for Osteosarcoma through Metabolic Reprogramming

Despite aggressive combination chemotherapy and surgery, outcomes for patients with osteosarcoma have remained stagnant for more than 25 years, and numerous clinical trials have identified no new therapies. p53 deletion or mutation is found in more than 80% of osteosarcoma tumors. In p53-deficient cancers with structurally altered p63 and p73, interfering with tumor cell metabolism using Pramlintide (an FDA-approved drug for type 2 diabetes) results in tumor regression. Pramlintide response is mediated through upregulation of islet amyloid polypeptide (IAPP). Here, we showed that osteosarcoma cells have altered p63, p73, and p53, and decreased IAPP expression but have the two main IAPP receptors, CalcR and RAMP3, which inhibit glycolysis and induce apoptosis. We showed that in osteosarcoma cells with high- or mid-range glycolytic activity, Pramlintide decreased cell glycolysis, resulting in decreased proliferation and increased apoptosis in vitro. In contrast, Pramlintide had no effect in osteosarcoma cells with low glycolytic activity. Using a subcutaneous osteosarcoma mouse model, we showed that intratumoral injection of Pramlintide-induced tumor regression. Tumor sections showed increased apoptosis and a decrease in Ki-67 and HIF-1α. These data suggest that in osteosarcoma cells with altered p53, p63, and p73 and a high glycolytic function, Pramlintide therapy can modulate metabolic programming and inhibit tumor growth.

Proteins Do Not Replicate, They Precipitate: Phase Transition and Loss of Function Toxicity in Amyloid Pathologies

Protein aggregation into amyloid fibrils affects many proteins in a variety of diseases, including neurodegenerative disorders, diabetes, and cancer. Physicochemically, amyloid formation is a phase transition process, where soluble proteins are transformed into solid fibrils with the characteristic cross-β conformation responsible for their fibrillar morphology. This phase transition proceeds via an initial, rate-limiting nucleation step followed by rapid growth. Several well-defined nucleation pathways exist, including homogenous nucleation (HON), which proceeds spontaneously; heterogeneous nucleation (HEN), which is catalyzed by surfaces; and seeding via preformed nuclei. It has been hypothesized that amyloid aggregation represents a protein-only (nucleic-acid free) replication mechanism that involves transmission of structural information via conformational templating (the prion hypothesis). While the prion hypothesis still lacks mechanistic support, it is also incompatible with the fact that proteins can be induced to form amyloids in the absence of a proteinaceous species acting as a conformational template as in the case of HEN, which can be induced by lipid membranes (including viral envelopes) or polysaccharides. Additionally, while amyloids can be formed from any protein sequence and via different nucleation pathways, they invariably adopt the universal cross-β conformation; suggesting that such conformational change is a spontaneous folding event that is thermodynamically favorable under the conditions of supersaturation and phase transition and not a templated replication process. Finally, as the high stability of amyloids renders them relatively inert, toxicity in some amyloid pathologies might be more dependent on the loss of function from protein sequestration in the amyloid state rather than direct toxicity from the amyloid plaques themselves.

Anti-IAPP Monoclonal Antibody Improves Clinical Symptoms in a Mouse Model of Type 2 Diabetes

Type 2 Diabetes Mellitus (T2DM) is a chronic progressive disease, defined by insulin resistance and insufficient insulin secretion to maintain normoglycemia. Amyloidogenic aggregates are a hallmark of T2DM patients; they are cytotoxic for the insulin producing β-cells, and cause inflammasome-dependent secretion of IL-1β. To avoid the associated β-cell loss and inflammation in advanced stage T2DM, we developed a novel monoclonal therapy targeting the major component of aggregates, islet amyloid polypeptide (IAPP). The here described monoclonal antibody (mAb) m81, specific for oligomeric and fibrils, but not for soluble free IAPP, is able to prevent oligomer growth and aggregate formation in vitro, and blocks islet inflammation and disease progression in vivo. Collectively, our data show that blocking fibril formation and prevention of new amyloidogenic aggregates by monoclonal antibody therapy may be a potential therapy for T2DM.

Amyloidogenicity of peptides targeting diabetes and obesity

Since the discovery of insulin, a century ago, the repertoire of therapeutic polypeptides targeting diabetes - and now also obesity - have increased substantially. The focus on quality has shifted from impure and unstable preparations of animal insulin to highly pure, homologous recombinant insulin, along with other peptide-based hormones and analogs such as amylin analogs (pramlintide, davalintide, cagrilintide), glucagon and glucagon-like peptide-1 receptor agonists (GLP-1, liraglutide, exenatide, semaglutide). Proper formulation, storage, manipulation and usage by professionals and patients are required in order to avoid agglomeration into high molecular weight products (HMWP), either amorphous or amyloid, which could result in potential loss of biological activity and short- or long-term immune reaction and silent inactivation. In this narrative review, we present perspective of the aggregation of therapeutic polypeptides used in diabetes and other metabolic diseases, covering the nature and mechanisms, analytical techniques, physical and chemical stability, strategies aimed to hamper the formation of HMWP, and perspectives on future biopharmaceutical developments.

Islet amyloid toxicity: From genesis to counteracting mechanisms

Islet amyloid polypeptide (IAPP or amylin) is a hormone co-secreted with insulin by pancreatic β-cells and is the major component of islet amyloid. Islet amyloid is found in the pancreas of patients with type 2 diabetes (T2D) and may be involved in β-cell dysfunction and death, observed in this disease. Thus, investigating the aspects related to amyloid formation is relevant to the development of strategies towards β-cell protection. In this sense, IAPP misprocessing, IAPP overproduction, and disturbances in intra- and extracellular environments seem to be decisive for IAPP to form islet amyloid. Islet amyloid toxicity in β-cells may be triggered in intra- and/or extracellular sites by membrane damage, endoplasmic reticulum stress, autophagy disruption, mitochondrial dysfunction, inflammation, and apoptosis. Importantly, different approaches have been suggested to prevent islet amyloid cytotoxicity, from inhibition of IAPP aggregation to attenuation of cell death mechanisms. Such approaches have improved β-cell function and prevented the development of hyperglycemia in animals. Therefore, counteracting islet amyloid may be a promising therapy for T2D treatment.

Altered islet prohormone processing: A cause or consequence of diabetes?

Peptide hormones are first produced as larger precursor prohormones that require endoproteolytic cleavage to liberate the mature hormones. A structurally conserved but functionally distinct family of nine prohormone convertase enzymes (PCs) are responsible for cleavage of protein precursors of which PC1/3 and PC2 are known to be exclusive to neuroendocrine cells and responsible for prohormone cleavage. Differential expression of PCs within tissues define prohormone processing; whereas glucagon is the major product liberated from proglucagon via PC2 in pancreatic α-cells, proglucagon is preferentially processed by PC1/3 in intestinal L cells to produce glucagon-like peptides 1 and 2 (GLP-1, GLP-2). Beyond our understanding of processing of islet prohormones in healthy islets, there is convincing evidence that proinsulin, proIAPP, and proglucagon processing is altered during prediabetes and diabetes. There is predictive value of elevated circulating proinsulin or proinsulin : C-peptide ratio for progression to type 2 diabetes and elevated proinsulin or proinsulin : C-peptide is predictive for development of type 1 diabetes in at risk groups. After onset of diabetes, patients have elevated circulating proinsulin and proIAPP and proinsulin may be an autoantigen in type 1 diabetes. Further, preclinical studies reveal that α-cells have altered proglucagon processing during diabetes leading to increased GLP-1 production. We conclude that despite strong associative data, current evidence is inconclusive on the potential causal role of impaired prohormone processing in diabetes, and suggest that future work should focus on resolving the question of whether altered prohormone processing is a causal driver or merely a consequence of diabetes pathology.

Dual-hormone artificial pancreas for management of type 1 diabetes: Recent progress and future directions

Over the last few years, technological advances have led to tremendous improvement in the management of type 1 diabetes (T1D). Artificial pancreas systems have been shown to improve glucose control compared with conventional insulin pump therapy. However, clinically significant hypoglycemic and hyperglycemic episodes still occur with the artificial pancreas. Postprandial glucose excursions and exercise-induced hypoglycemia represent major hurdles in improving glucose control and glucose variability in many patients with T1D. In this regard, dual-hormone artificial pancreas systems delivering other hormones in addition to insulin (glucagon or amylin) may better reproduce the physiology of the endocrine pancreas and have been suggested as an alternative tool to overcome these limitations in clinical practice. In addition, novel ultra-rapid-acting insulin analogs with a more physiological time-action profile are currently under investigation for use in artificial pancreas devices, aiming to address the unmet need for further improvements in postprandial glucose control. This review article aims to discuss the current progress and future outlook in the development of novel ultra-rapid insulin analogs and dual-hormone closed-loop systems, which offer the next steps to fully closing the loop in the artificial pancreas.

The Role of Interleukin-1β in Destruction of Transplanted Islets

Islet transplantation is a promising β-cell replacement therapy for type 1 diabetes, which can reduce glucose lability and hypoglycemic episodes compared with standard insulin therapy. Despite the tremendous progress made in this field, challenges remain in terms of long-term successful transplant outcomes. The insulin independence rate remains low after islet transplantation from one donor pancreas. It has been reported that the islet-related inflammatory response is the main cause of early islet damage and graft loss after transplantation. The production of interleukin-1β (IL-1β) has considered to be one of the primary harmful inflammatory events during pancreatic procurement, islet isolation, and islet transplantation. Evidence suggests that the innate immune response is upregulated through the activity of Toll-like receptors and The NACHT Domain-Leucine-Rich Repeat and PYD-containing Protein 3 inflammasome, which are the starting points for a series of signaling events that drive excessive IL-1β production in islet transplantation. In this review, we show recent contributions to the advancement of knowledge of IL-1β in islet transplantation and discuss several strategies targeting IL-1β for improving islet engraftment.

Citrullination and PAD Enzyme Biology in Type 1 Diabetes - Regulators of Inflammation, Autoimmunity, and Pathology

The generation of post-translational modifications (PTMs) in human proteins is a physiological process leading to structural and immunologic variety in proteins, with potentially altered biological functions. PTMs often arise through normal responses to cellular stress, including general oxidative changes in the tissue microenvironment and intracellular stress to the endoplasmic reticulum or immune-mediated inflammatory stresses. Many studies have now illustrated the presence of 'neoepitopes' consisting of PTM self-proteins that induce robust autoimmune responses. These pathways of inflammatory neoepitope generation are commonly observed in many autoimmune diseases including systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, and type 1 diabetes (T1D), among others. This review will focus on one specific PTM to self-proteins known as citrullination. Citrullination is mediated by calcium-dependent peptidylarginine deiminase (PAD) enzymes, which catalyze deimination, the conversion of arginine into the non-classical amino acid citrulline. PADs and citrullinated peptides have been associated with different autoimmune diseases, notably with a prominent role in the diagnosis and pathology of rheumatoid arthritis. More recently, an important role for PADs and citrullinated self-proteins has emerged in T1D. In this review we will provide a comprehensive overview on the pathogenic role for PADs and citrullination in inflammation and autoimmunity, with specific focus on evidence for their role in T1D. The general role of PADs in epigenetic and transcriptional processes, as well as their crucial role in histone citrullination, neutrophil biology and neutrophil extracellular trap (NET) formation will be discussed. The latter is important in view of increasing evidence for a role of neutrophils and NETosis in the pathogenesis of T1D. Further, we will discuss the underlying processes leading to citrullination, the genetic susceptibility factors for increased recognition of citrullinated epitopes by T1D HLA-susceptibility types and provide an overview of reported autoreactive responses against citrullinated epitopes, both of T cells and autoantibodies in T1D patients. Finally, we will discuss recent observations obtained in NOD mice, pointing to prevention of diabetes development through PAD inhibition, and the potential role of PAD inhibitors as novel therapeutic strategy in autoimmunity and in T1D in particular.

Altered β-Cell Prohormone Processing and Secretion in Type 1 Diabetes

Analysis of data from clinical cohorts, and more recently from human pancreatic tissue, indicates that reduced prohormone processing is an early and persistent finding in type 1 diabetes. In this article, we review the current state of knowledge regarding alterations in islet prohormone expression and processing in type 1 diabetes and consider the clinical impact of these findings. Lingering questions, including pathologic etiologies and consequences of altered prohormone expression and secretion in type 1 diabetes, and the natural history of circulating prohormone production in health and disease, are considered. Finally, key next steps required to move forward in this area are outlined, including longitudinal testing of relevant clinical populations, studies that probe the genetics of altered prohormone processing, the need for combined functional and histologic testing of human pancreatic tissues, continued interrogation of the intersection between prohormone processing and autoimmunity, and optimal approaches for analysis. Successful resolution of these questions may offer the potential to use altered prohormone processing as a biomarker to inform therapeutic strategies aimed at personalized intervention during the natural history of type 1 diabetes and as a pathogenic anchor for identification of potential disease-specific endotypes.

Optimal allogeneic islet dose for transplantation in insulin-dependent diabetic Macaca fascicularis monkeys

Many groups are working to improve the results of clinical allogeneic islet transplantation in a primate model. However, few studies have focused on the optimal islet dose for achieving normal glycemia without exogenous insulin after transplantation in primate models or on the relationship between rejection and islet amyloid polypeptide (IAPP) expression. We evaluated the dose (10,000, 20,000, and > 25,000 islet equivalents (IEQ)/kg) needed to achieve normal glycemia without exogenous insulin after transplantation using eleven cynomolgus monkeys, and we analyzed the characteristics exhibited in the islets after transplantation. 10,000 IEQ/kg (N = 2) failed to control blood glucose level, despite injection with the highest dose of exogenous insulin, and 20,000 IEQ/kg group (N = 5) achieved unstable control, with a high insulin requirement. However, 25,000 IEQ/kg (N = 4) achieved normal glycemia without exogenous insulin and maintained it for more than 60 days. Immunohistochemistry results from staining islets found in liver biopsies indicated that as the number of transplanted islets decreased, the amount of IAPP accumulation within the islets increased, which accelerated CD3⁺ T cell infiltration. In conclusion, the optimal transplantation dose for achieving a normal glycemia without exogenous insulin in our cynomolgus monkey model was > 25,000 IEQ/kg, and the accumulation of IAPP early after transplantation, which depends on the transplanted islet dose, can be considered one factor in rejection.

Optimized experimental pre-treatment strategy for temporary inhibition of islet amyloid polypeptide aggregation

Islet amyloid polypeptide (IAPP) is a neuroendocrine hormone from pancreatic β-cells. Misfolded, aggregated IAPP is believed to be toxic to islet cells and amyloid deposits in the pancreas are pathological hallmarks of type 2 diabetes. Rapid fibrillization of this peptide makes it difficult to study in its soluble form, impeding a better understanding of its role. In this study, a variety of popular pretreatment methods were tested for their ability to delay aggregation of IAPP, including solutions of hexafluoroisopropanol, sodium hydroxide, hydrochloric acid, phosphate buffered saline, ammonium hydroxide, as well as tris buffer at different pH and containing either calcium (II), zinc (II), or iron (II). Aggregation was assessed using the thioflavin T fluorescence assay as well as by transmission electron microscopy. Tris buffer at pH 8.1 containing Zn(II) was found to have the best balance of temporary inhibition of aggregation and biological relevance.

Type 1 diabetes mellitus as a disease of the β-cell (do not blame the immune system?)

Type 1 diabetes mellitus is believed to result from destruction of the insulin-producing β-cells in pancreatic islets that is mediated by autoimmune mechanisms. The classic view is that autoreactive T cells mistakenly destroy healthy ('innocent') β-cells. We propose an alternative view in which the β-cell is the key contributor to the disease. By their nature and function, β-cells are prone to biosynthetic stress with limited measures for self-defence. β-Cell stress provokes an immune attack that has considerable negative effects on the source of a vital hormone. This view would explain why immunotherapy at best delays progression of type 1 diabetes mellitus and points to opportunities to use therapies that revitalize β-cells, in combination with immune intervention strategies, to reverse the disease. We present the case that dysfunction occurs in both the immune system and β-cells, which provokes further dysfunction, and present the evidence leading to the consensus that islet autoimmunity is an essential component in the pathogenesis of type 1 diabetes mellitus. Next, we build the case for the β-cell as the trigger of an autoimmune response, supported by analogies in cancer and antitumour immunity. Finally, we synthesize a model ('connecting the dots') in which both β-cell stress and islet autoimmunity can be harnessed as targets for intervention strategies.

Nonhuman IAPP Variants Inhibit Human IAPP Aggregation

AIM

To identify naturally occurring variants of IAPP capable of inhibiting the aggregation of human IAPP and protecting living cells from the toxic effects of human IAPP.

BACKGROUND

The loss of insulin-producing β-cells and the overall progression of type 2 diabetes appears to be linked to the formation of toxic human IAPP (hIAPP, Islet Amyloid Polypeptide, amylin) amyloid in the pancreas. Inhibiting the initial aggregation of hIAPP has the potential to slow, if not stop entirely, the loss of β-cells and halt the progression of the disease.

OBJECTIVE

To identify and characterize naturally occurring variants of IAPP capable of inhibiting human IAPP aggregation.

METHODS

Synthetic human IAPP was incubated with synthetic IAPP variants identified from natural sources under conditions known to promote amyloid-based aggregation. To identify IAPP variants capable of inhibiting human IAPP aggregation, Thioflavin T-binding fluorescence, atomic force microscopy, and cell-rescue assays were performed.

RESULTS

While most IAPP variants showed little to no ability to inhibit human IAPP aggregation, several variants showed some ability to inhibit aggregation, with two variants showing substantial inhibitory potential.

CONCLUSION

Several naturally occurring IAPP variants capable of inhibiting human IAPP aggregation were identified and characterized.

Protein Supramolecular Structures: From Self-Assembly to Nanovaccine Design

Life-inspired protein supramolecular assemblies have recently attracted considerable attention for the development of next-generation vaccines to fight against infectious diseases, as well as autoimmune diseases and cancer. Protein self-assembly enables atomic scale precision over the final architecture, with a remarkable diversity of structures and functionalities. Self-assembling protein nanovaccines are associated with numerous advantages, including biocompatibility, stability, molecular specificity and multivalency. Owing to their nanoscale size, proteinaceous nature, symmetrical organization and repetitive antigen display, protein assemblies closely mimic most invading pathogens, serving as danger signals for the immune system. Elucidating how the structural and physicochemical properties of the assemblies modulate the potency and the polarization of the immune responses is critical for bottom-up design of vaccines. In this context, this review briefly covers the fundamentals of supramolecular interactions involved in protein self-assembly and presents the strategies to design and functionalize these assemblies. Examples of advanced nanovaccines are presented, and properties of protein supramolecular structures enabling modulation of the immune responses are discussed. Combining the understanding of the self-assembly process at the molecular level with knowledge regarding the activation of the innate and adaptive immune responses will support the design of safe and effective nanovaccines.

Analysis of Proline Substitutions Reveals the Plasticity and Sequence Sensitivity of Human IAPP Amyloidogenicity and Toxicity

Pancreatic amyloid formation by the polypeptide IAPP contributes to β-cell dysfunction in type 2 diabetes. There is a 1:1 correspondence between the ability of IAPP from different species to form amyloid in vitro and the susceptibility of the organism to develop diabetes. Rat IAPP is non-amyloidogenic and differs from human IAPP at six positions, including three proline replacements: A25P, S28P, and S29P. Incorporation of these proline residues into human IAPP leads to a non-amyloidogenic analogue that is used clinically. The role of the individual proline residues is not understood. We examine the three single and three double proline substitutions in the context of human IAPP. An S28P substitution significantly decreases amyloidogenicity and toxicity, while an S29P substitution has very modest effects despite being an identical replacement just one residue away. The consequences of the A25P substitution are between those of the two Ser to Pro substitutions. Double analogues containing an S28P replacement are less amyloidogenic and less toxic than the IAPP_A25P S29P double analogue. Ion mobility mass spectrometry reveals that there is no correlation between the monomer or dimer conformation as reported by collision cross section measurements and the time to form amyloid. The work reveals both the plasticity of IAPP amyloid formation and the exquisite sequence sensitivity of IAPP amyloidogenicity and toxicity. The study highlights the key role of the S28P substitution and provides information that will aid in the rational design of soluble variants of IAPP. The variants studied here offer a system for further exploring features that control IAPP toxicity.

pH-Dependent Aggregation in Intrinsically Disordered Proteins Is Determined by Charge and Lipophilicity

Protein aggregation is associated with an increasing number of human disorders and premature aging. Moreover, it is a central concern in the manufacturing of recombinant proteins for biotechnological and therapeutic applications. Nevertheless, the unique architecture of protein aggregates is also exploited by nature for functional purposes, from bacteria to humans. The relevance of this process in health and disease has boosted the interest in understanding and controlling aggregation, with the concomitant development of a myriad of algorithms aimed to predict aggregation propensities. However, most of these programs are blind to the protein environment and, in particular, to the influence of the pH. Here, we developed an empirical equation to model the pH-dependent aggregation of intrinsically disordered proteins (IDPs) based on the assumption that both the global protein charge and lipophilicity depend on the solution pH. Upon its parametrization with a model IDP, this simple phenomenological approach showed unprecedented accuracy in predicting the dependence of the aggregation of both pathogenic and functional amyloidogenic IDPs on the pH. The algorithm might be useful for diverse applications, from large-scale analysis of IDPs aggregation properties to the design of novel reversible nanofibrillar materials.

Type 1 Diabetes: an Association Between Autoimmunity, the Dynamics of Gut Amyloid-producing E. coli and Their Phages

The etiopathogenesis of type 1 diabetes (T1D), a common autoimmune disorder, is not completely understood. Recent studies suggested the gut microbiome plays a role in T1D. We have used public longitudinal microbiome data from T1D patients to analyze amyloid-producing bacterial composition and found a significant association between initially high amyloid-producing Escherichia coli abundance, subsequent E. coli depletion prior to seroconversion, and T1D development. In children who presented seroconversion or developed T1D, we observed an increase in the E. coli phage/E. coli ratio prior to E. coli depletion, suggesting that the decrease in E. coli was due to prophage activation. Evaluation of the role of phages in amyloid release from E. coli biofilms in vitro suggested an indirect role of the bacterial phages in the modulation of host immunity. This study for the first time suggests that amyloid-producing E. coli, their phages, and bacteria-derived amyloid might be involved in pro-diabetic pathway activation in children at risk for T1D.

The Evolving Landscape of Autoantigen Discovery and Characterization in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease that is caused, in part, by T cell-mediated destruction of insulin-producing β-cells. High risk for disease, in those with genetic susceptibility, is predicted by the presence of two or more autoantibodies against insulin, the 65-kDa form of glutamic acid decarboxylase (GAD65), insulinoma-associated protein 2 (IA-2), and zinc transporter 8 (ZnT8). Despite this knowledge, we still do not know what leads to the breakdown of tolerance to these autoantigens, and we have an incomplete understanding of T1D etiology and pathophysiology. Several new autoantibodies have recently been discovered using innovative technologies, but neither their potential utility in monitoring disease development and treatment nor their role in the pathophysiology and etiology of T1D has been explored. Moreover, neoantigen generation (through posttranslational modification, the formation of hybrid peptides containing two distinct regions of an antigen or antigens, alternative open reading frame usage, and translation of RNA splicing variants) has been reported, and autoreactive T cells that target these neoantigens have been identified. Collectively, these new studies provide a conceptual framework to understand the breakdown of self-tolerance, if such modifications occur in a tissue- or disease-specific context. A recent workshop sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases brought together investigators who are using new methods and technologies to identify autoantigens and characterize immune responses toward these proteins. Researchers with diverse expertise shared ideas and identified resources to accelerate antigen discovery and the detection of autoimmune responses in T1D. The application of this knowledge will direct strategies for the identification of improved biomarkers for disease progression and treatment response monitoring and, ultimately, will form the foundation for novel antigen-specific therapeutics. This Perspective highlights the key issues that were addressed at the workshop and identifies areas for future investigation.

Navigating Two Roads to Glucose Normalization in Diabetes: Automated Insulin Delivery Devices and Cell Therapy

Incredible strides have been made since the discovery of insulin almost 100 years ago. Insulin formulations have improved dramatically, glucose levels can be measured continuously, and recently first-generation biomechanical "artificial pancreas" systems have been approved by regulators around the globe. However, still only a small fraction of patients with diabetes achieve glycemic goals. Replacement of insulin-producing cells via transplantation shows significant promise, but is limited in application due to supply constraints (cadaver-based) and the need for chronic immunosuppression. Over the past decade, significant progress has been made to address these barriers to widespread implementation of a cell therapy. Can glucose levels in people with diabetes be normalized with artificial pancreas systems or via cell replacement approaches? Here we review the road ahead, including the challenges and opportunities of both approaches.

A Novel Pentapeptide Inhibitor Reduces Amyloid Deposit Formation by Direct Interaction with hIAPP

BACKGROUNDS

The presence of amyloid deposits of human islet amyloid polypeptide (hIAPP) in islet β-cells has been associated with type 2 diabetes occurrence and islet graft failure. Self-assembly into oligomers and fibrils during the process of aggregation by hIAPP can lead to failure and depletion of β-cells. Studies have shown that some critical regions of hIAPP might contribute to the aggregation. Thus, many studies focused on finding the effective molecules, especially the short-peptide inhibitors, that bind to these regions and disrupt the aggregation of hIAPP. In the present study, a novel pentapeptide inhibitor Phe-Leu-Pro-Asn-Phe (FLPNF) was designed and its effectiveness on the inhibition of the formation of amyloid deposits was examined.

METHODS

The binding mode between FLPNF and hIAPP was performed using molecular docking. The effectiveness of FLPNF on inhibiting hIAPP amyloid aggregation was tested by Thioflavin T (ThT) staining. Furthermore, negative stain electron microscopy was used to observe hIAPP fibrils. A biolayer interferometry analysis was used to identify the interaction between FLPNF and hIAPP. In addition, the cytotoxicity toward INS-1 cells was tested by a cell proliferation assay.

RESULTS

FLPNF was predicted to have a compact conformation to bind at the site of hIAPP. FLPNF strongly inhibited the amyloid aggregation of hIAPP at a 10 : 1 molar ratio in vitro. Coincubation of FLPNF with hIAPP decreased the amount of hIAPP fibrils. Furthermore, a direct interaction between FLPNF and hIAPP was confirmed. FLPNF could also decrease the cytotoxic effect of hIAPP.

CONCLUSIONS

The novel pentapeptide inhibitor FLPNF was constructed and inhibited the aggregation through direct binding to hIAPP. It is considered a suitable inhibitor for hIAPP amyloid deposit formation.

Islet amyloidosis in a child with type 1 diabetes

Histopathology based studies of the pancreas obtained from organ donors are increasing our awareness of islet phenotypic heterogeneity during development and aging, as well as in settings of type 1 diabetes, type 2 diabetes, monogenic diabetes or other forms of this metabolic disease. Islet amyloidosis represents a histopathological feature classically ascribed to patients with type 2 diabetes. Herein, the occurrence of islet amyloidosis and its severity are reported in a child with type 1 diabetes along with histological comparisons of islet amyloidosis in two young adults with recent-onset type 1 diabetes. Islet amyloidosis was infrequent yet widely distributed throughout the pancreas in the child with type 1 diabetes and both adults with type 1 diabetes, with no such pathology seen in matched control donors. Analysis of these cases add to the increasing appreciation of islet heterogeneity in children and young adults with type 1 diabetes. Such knowledge also supports a notion that multiple pathophysiological mechanisms underlie the loss of functional β-cell mass in the spectrum of clinical phenotypes in patients with type 1 diabetes.

The receptor for advanced glycation endproducts is a mediator of toxicity by IAPP and other proteotoxic aggregates: Establishing and exploiting common ground for novel amyloidosis therapies

Proteotoxicity plays a key role in many devastating human disorders, including Alzheimer's, Huntington's and Parkinson's diseases; type 2 diabetes; systemic amyloidosis; and cardiac dysfunction, to name a few. The cellular mechanisms of proteotoxicity in these disorders have been the focus of considerable research, but their role in prevalent and morbid disorders, such as diabetes, is less appreciated. There is a large body of literature on the impact of glucotoxicity and lipotoxicity on insulin-producing pancreatic β-cells, and there is increasing recognition that proteotoxicty plays a key role. Pancreatic islet amyloidosis by the hormone IAPP, the production of advanced glycation endproducts (AGE), and insulin misprocessing into cytotoxic aggregates are all sources of β-cell proteotoxicity in diabetes. AGE, produced by the reaction of reducing sugars with proteins and lipids are ligands for the receptor for AGE (RAGE), as are the toxic pre-fibrillar aggregates of IAPP produced during amyloid formation. The mechanisms of amyloid formation by IAPP in vivo or in vitro are not well understood, and the cellular mechanisms of IAPP-induced β-cell death are not fully defined. Here, we review recent findings that illuminate the factors and mechanisms involved in β-cell proteotoxicity in diabetes. Together, these new insights have far-reaching implications for the establishment of unifying mechanisms by which pathological amyloidoses imbue their injurious effects in vivo.