Islets Of Patients Research Articles

No Evidence for Persistent Enteroviral B Infection of Pancreatic Islets in Patients With Type 1 Diabetes and Prediabetes From RNA Sequencing Data.

Persistent enterovirus B infection has been proposed as an important contributor to the etiology of type 1 diabetes. We leveraged extensive bulk RNA-sequencing data from alpha, beta, and exocrine cells, as well as single cell islet RNA-Seq data from the Human Pancreas Analysis Program (HPAP), to evaluate the presence of enterovirus B sequences in the pancreas of type 1 diabetic and pre-diabetic (non-diabetic but auto-antibody positive) patients. We examined all available HPAP data for either assay type, including non-diabetic, type 1, and type 2 diabetic donors. To assess the presence of viral reads, we analyzed all reads not mapping to the human genome with the taxonomic classification system Kraken2 and its full viral database, augmented to encompass representatives for all (28) enterovirus B serotypes for which a complete genome is available. As a secondary approach, we input the same sequence reads into the STAR aligner using these 28 enterovirus B genomes as the reference. No enterovirus B sequences were detected by either approach in any of the 243 bulk RNA libraries nor in any of the 79 single cell RNA libraries. While we cannot rule out the possibility of a very low-grade persistent enterovirus B infection in the donors analyzed, our data do not support the notion of chronic viral infection by these viruses as a major driver of type 1 diabetes.

Clinical Trial Protocol for Porcine Islet Xenotransplantation in South Korea.

Islet transplantation holds promise for treating selected type 1 diabetes mellitus patients, yet the scarcity of human donor organs impedes widespread adoption. Porcine islets, deemed a viable alternative, recently demonstrated successful longterm survival without zoonotic risks in a clinically relevant pig-to-non-human primate islet transplantation model. This success prompted the development of a clinical trial protocol for porcine islet xenotransplantation in humans. A single-center, open-label clinical trial initiated by the sponsor will assess the safety and efficacy of porcine islet transplantation for diabetes patients at Gachon Hospital. The protocol received approval from the Gachon Hospital Institutional Review Board (IRB) and the Korean Ministry of Food and Drug Safety (MFDS) under the Investigational New Drug (IND) process. Two diabetic patients, experiencing inadequate glycemic control despite intensive insulin treatment and frequent hypoglycemic unawareness, will be enrolled. Participants and their family members will engage in deliberation before xenotransplantation during the screening period. Each patient will receive islets isolated from designated pathogen-free pigs. Immunosuppressants and systemic infection prophylaxis will follow the program schedule. The primary endpoint is to confirm the safety of porcine islets in patients, and the secondary endpoint is to assess whether porcine islets can reduce insulin dose and the frequency of hypoglycemic unawareness. A clinical trial protocol adhering to global consensus guidelines for porcine islet xenotransplantation is presented, facilitating streamlined implementation of comparable human trials worldwide.

Glucose metabolism disorders associated with COVID-19: clinical and morphological study

BACKGROUND. Glucose metabolism disorders (GMD) were detected both in acute and in post-COVID, however, its pathogenic aspects remain unclear.AIM. To analyze the occurrence of GMD in post-COVID patients who have had moderate and severe COVID-19 without previously known GMD disorders, and evaluate expression of SARS-CoV-2 proteins and its entry factors in pancreas in acute COVID-19.METHODS. Among 187 hospitalized patients with confirmed COVID-19 141 patients without previously diagnosed GMD underwent follow-up post-COVID visits. The examination for all patients included anthropometric measurement with calculation of BMI, level of HbA1c and fasting plasma glucose, for 106 patients level of insulin and HOMA-IR index was analyzed. For histological examination, pancreas fragments of 20 patients with fatal outcome were selected. Immunohistochemical study was performed with antibodies to SARS-CoV-2, ACE2, DPP4, as well as double-labeled immunofluorescence microscopy (insulin-SARS-CoV-2, insulin-ACE2, insulin-DPP4).RESULTS. Among 141 patients in post-COVID period, 9 (6.3%) had HbA1c or fasting plasma glucose levels that met criteria for diabetes mellitus, 38 (26.9%) — exceeded normal values (WHO), and 84 (59.6%) had GMD according to criteria of the ADA. In post-COVID, patients with GMD had a higher BMI and HOMA-IR index (p=0.001) compared to patients with normal glycemic levels. Only 40.4% of people had HOMA-IR index above 2.7. Patients with GMD had higher level of CRP (p=0.007) and a maximum glucose level (p=0.019) in the acute period. Positive relationship was found between BMI and HOMA index both in acute (p<0.001; r=0.389) and post-COVID (p<0.001; r=0.412) periods, as well as the level of HbA1c in acute period (p=0.019, r=0.202) and in post-COVID (p=0.004, r=0.242).Histological and immunohistochemical studies showed the expression of SARS-CoV-2 proteins in 1.85% [0–15.4] and 11.1% [5.3–14.8] cells of the Langerhans islets in patients who died on the second and third waves, respectively. The expression of ACE2 and DPP4 in the islets of Langerhans did not exceed 0.4% [0–1.7] and 0.5% [0–0.8] of cells, respectively. Double-labeled immunofluorescence microscopy showed co-localization of SARS-CoV-2, ACE2, DPP4 with insulin.CONCLUSION. Post-COVID Glucose metabolism disorders may be explained by direct cytotoxic effect of SARS-COV-2, increased glucose toxicity and insulin resistance because of the acute infection and its complex therapy.

Epigallocatechin gallate inhibits SNARE-dependent membrane fusion by blocking trans-SNARE assembly.

Insulin secretion is a signal-triggered process that requires membrane fusion between the secretory granules and plasma membrane in pancreatic β cells. The exocytosis of insulin is mediated by target-soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs) on the plasma membrane and vesicle-SNAREs on the vesicles, which assemble into a quaternary trans-SNARE complex to initiate the fusion. Expression of fusion proteins is reduced in the islets of patients with type II diabetes, indicating that SNARE-mediated fusion defect is closely related to insulin-based metabolic diseases. Previous studies have suggested that epigallocatechin gallate (EGCG) has an inhibitory effect on membrane fusion. In the present study, we performed in vitro reconstitution assays to unravel the molecular mechanisms of EGCG in SNARE-mediated insulin secretory vesicle fusion. Our data show that EGCG efficiently inhibits insulin secretory SNARE-mediated membrane fusion. Mechanistic studies indicated that EGCG blocks the formation of the trans-SNARE complex. Furthermore, calcium/synaptotagmin-7-stimulated fusion kinetics were largely reduced by EGCG, confirming that it is a potential regulator of SNARE-dependent insulin secretion. Our findings suggest that the trans-SNARE complex might be a promising target for controlling SNARE-dependent vesicle fusion.

Defective insulin maturation in patients with type 2 diabetes.

Progressive beta-cell dysfunction is a hallmark of type 2 diabetes (T2D). Increasing evidence indicates that over-stimulating proinsulin synthesis causes proinsulin misfolding and impairs insulin maturation and storage in db/db mice. However, defective insulin maturation in patients with T2D remains unknown. We examined intra-islet and intra-cellular distributions of proinsulin and insulin and proinsulin to insulin ratio in the islets of patients with T2D. The expression of transcription factor NKX6.1 and dedifferentiation marker ALDH1A3, as well as glucagon, were detected by immunofluorescence. We identified a novel subgroup of beta cells expressing only proinsulin but not insulin. Importantly, significantly increased proinsulin positive and insulin negative (PI+/INS-) cells were evident in T2D, and this increase was strongly correlated with levels of hemoglobin A1C (HbA1c) in T2D and prediabetes. The percentages of beta cells expressing prohormone convertase 1/3 and carboxypeptidase E were not reduced. Indeed, while proinsulin displayed a higher degree of co-localization with the golgi markers GM130/TGN46 in control beta cells, it appeared to be more diffused within the cytoplasm and less co-localized with GM130/TGN46 in PI+/INS- cells. Furthermore, the key functional transcription factor NKX6.1 markedly decreased in the islets of T2D, especially in the cells with PI+/INS-. The decreased NKX6.1+/PI+/INS+ was strongly correlated with levels of HbA1c in T2D. Almost all PI+/INS- cells showed absence of NKX6.1. Moreover, the percentages of PI+/INS- cells expressing ALDH1A3 were elevated along with an increased acquisition of glucagon immunostaining. Our data demonstrate defective insulin maturation in patients with T2D.

Viral infiltration of pancreatic islets in patients with COVID-19

Metabolic diseases are associated with an increased risk of severe COVID-19 and conversely, new-onset hyperglycemia and complications of preexisting diabetes have been observed in COVID-19 patients. Here, we performed a comprehensive analysis of pancreatic autopsy tissue from COVID-19 patients using immunofluorescence, immunohistochemistry, RNA scope and electron microscopy and detected SARS-CoV-2 viral infiltration of beta-cells in all patients. Using SARS-CoV-2 pseudoviruses, we confirmed that isolated human islet cells are permissive to infection. In eleven COVID-19 patients, we examined the expression of ACE2, TMPRSS and other receptors and factors, such as DPP4, HMBG1 and NRP1, that might facilitate virus entry. Whereas 70% of the COVID-19 patients expressed ACE2 in the vasculature, only 30% displayed ACE2-expression in beta-cells. Even in the absence of manifest new-onset diabetes, necroptotic cell death, immune cell infiltration and SARS-CoV-2 viral infection of pancreatic beta-cells may contribute to varying degrees of metabolic dysregulation in patients with COVID-19.

Fulminant type 1 diabetes: 20years of discovery and development.

Twenty years have passed since the first article on fulminant type 1 diabetes (FT1D) was published. FT1D is characterized by an extremely rapid onset of ketoacidosis, high plasma glucose and, conversely, a near-normal glycosylated hemoglobin level. Digestive or flu-like symptoms frequently precede the onset of ketoacidosis. Patients are usually negative for islet-related autoantibodies, with near-complete destruction of pancreatic β-cells, even at the onset of disease. Massive infiltration of immunocytes (insulitis) can be seen in the islets of patients with new-onset FT1D, but this subsides within a few weeks. Early discovery and development of research on FT1D were carried out in Japan, with some reports from Korea and China. Recently, the recognition of FT1D as an immune-related adverse effect of immune-checkpoint inhibitor therapy for various malignant tumors in some patients has drawn the attention of Western countries. The discovery and successful establishment of FT1D as a disease entity was the product of three essential factors: (1) accumulated research data spanning more than 10years; (2) fortuitous clinical observation; and (3) organization of a dedicated Japanese research committee. We anticipate that continued investigations of FT1D by a new generation of researchers will further elucidate the pathogenesis and yield new therapies.

NKG2D Signaling Within the Pancreatic Islets Reduces NOD Diabetes and Increases Protective Central Memory CD8+ T-Cell Numbers.

NKG2D is implicated in autoimmune diabetes. However, the role of this receptor in diabetes pathogenesis is unclear owing to conflicting results with studies involving global inhibition of NKG2D signaling. We found that NKG2D and its ligands are present in human pancreata, with expression of NKG2D and its ligands increased in the islets of patients with type 1 diabetes. To directly assess the role of NKG2D in the pancreas, we generated NOD mice that express an NKG2D ligand in β-islet cells. Diabetes was reduced in these mice. The reduction corresponded with a decrease in the effector to central memory CD8+ T-cell ratio. Further, NKG2D signaling during in vitro activation of both mouse and human CD8+ T cells resulted in an increased number of central memory CD8+ T cells and diabetes protection by central memory CD8+ T cells in vivo. Taken together, these studies demonstrate that there is a protective role for central memory CD8+ T cells in autoimmune diabetes and that this protection is enhanced with NKG2D signaling. These findings stress the importance of anatomical location when determining the role NKG2D signaling plays, as well as when developing therapeutic strategies targeting this pathway, in type 1 diabetes development.

Pancreatic ductal adenocarcinoma is associated with a unique endocrinopathy distinct from type 2 diabetes mellitus

IntroductionThe majority of patients with pancreatic ductal adenocarcinoma (PC) display either impaired fasting glucose/glucose intolerance or overt diabetes. However, the pathophysiologic basis of this association remains largely unexplained. MethodsIn this case-control study we aimed to study the morphological changes in the islets of patients with PC, compared to control patients with and without type 2 diabetes mellitus (T2DM). T2DM controls and PC cases had a lower β-cell area and average islet size and density compared to non-T2DM controls (p < 0.05). ResultsCompared to both T2DM and non-T2DM controls, mean α-cell area was significantly lower and β/α-ratio was higher in PC cases (p < 0.05). Furthermore, whereas islets in T2DM controls were characterized by disrupted islet architecture and presence of islet amyloid aggregates, islet composition in PC islets was not significantly different compared to non-T2DM controls (p > 0.05 vs. Control). ConclusionsOur data shows that PC is associated with a unique pattern of islet pathology characterized by preserved architecture, absence of amyloid aggregates, and relative α-cell loss indicating that distinct mechanisms are likely involved in the pathophysiology of islet failure in PC-induced DM. Insights into the mechanisms mediating β-cell failure in PC can be important for our understanding of pathophysiology of PC.

Adipose Triglyceride Lipase Is a Key Lipase for the Mobilization of Lipid Droplets in Human β-Cells and Critical for the Maintenance of Syntaxin 1a Levels in β-Cells.

Lipid droplets (LDs) are frequently increased when excessive lipid accumulation leads to cellular dysfunction. Distinct from mouse β-cells, LDs are prominent in human β-cells. However, the regulation of LD mobilization (lipolysis) in human β-cells remains unclear. We found that glucose increases lipolysis in nondiabetic human islets but not in islets in patients with type 2 diabetes (T2D), indicating dysregulation of lipolysis in T2D islets. Silencing adipose triglyceride lipase (ATGL) in human pseudoislets with shRNA targeting ATGL (shATGL) increased triglycerides (TGs) and the number and size of LDs, indicating that ATGL is the principal lipase in human β-cells. In shATGL pseudoislets, biphasic glucose-stimulated insulin secretion (GSIS), and insulin secretion to 3-isobutyl-1-methylxanthine and KCl were all reduced without altering oxygen consumption rate compared with scramble control. Like human islets, INS1 cells showed visible LDs, glucose-responsive lipolysis, and impairment of GSIS after ATGL silencing. ATGL-deficient INS1 cells and human pseudoislets showed reduced SNARE protein syntaxin 1a (STX1A), a key SNARE component. Proteasomal degradation of Stx1a was accelerated likely through reduced palmitoylation in ATGL-deficient INS1 cells. Therefore, ATGL is responsible for LD mobilization in human β-cells and supports insulin secretion by stabilizing STX1A. The dysregulated lipolysis may contribute to LD accumulation and β-cell dysfunction in T2D islets.

Pancreatic stellate cells in the islets as a novel target to preserve the pancreatic β-cell mass and function.

There are numerous lines of clinical evidence that inhibition of the renin–angiotensin system (RAS) can prevent and delay the development of diabetes. Also, the role of RAS in the pathogenesis of diabetes, including insulin resistance and β‐cell dysfunction, has been extensively investigated. Nevertheless, this role had not yet been fully shown. A variety of possible protective mechanisms for RAS blockers in the regulation of glucose homeostasis have been suggested. However, the direct effect on pancreatic islet fibrosis has only recently been spotlighted. Various degrees of islet fibrosis are often observed in the islets of patients with type 2 diabetes mellitus, which can be associated with a decrease in β‐cell mass and function in these patients. Pancreatic stellate cells are thought to be deeply involved in this islet fibrosis. In this process, the activation of RAS in islets is shown to transform quiescent pancreatic stellate cells into the activated form, stimulates their proliferation and consequently leads to islet fibrotic destruction. In this article, we introduce existing clinical and experimental evidence for diabetes prevention through inhibition of RAS, and review the responsible local RAS signaling pathways in pancreatic stellate cells. Finally, we propose possible targets for the prevention of islet fibrosis.

2161-P: Overexpression of UCP2 in Pancreatic Beta Cells Caused Impaired Insulin Secretion through Mitochondrial Dysfunction and Aldolase B Expression

Uncoupling protein 2 (UCP2), a mitochondrial protein, is known to be upregulated in pancreatic islets of patients with type 2 diabetes (T2DM); however, the pathological significance of the increase in UCP2 expression remained unclear. In this study, we investigated the regulatory mechanisms of UCP2 expression and its effects on β-cell functions. The mRNA expression of UCP2 in mouse islets was upregulated by the treatment with glucose, glucokinase activator, or insulin (p&amp;lt;0.05), while metformin downregulated it (p&amp;lt;0.01). Islets from db/db mice and insulin receptor substrate-2 knockout (IRS-2KO) mice showed the increment in the UCP2 expression. Transgenic mouse with specific UCP2 overexpression in β-cells (βUCP2Tg) demonstrated impaired glucose tolerance due to reduced insulin secretion. Adenoviral expression of UCP2 in MIN6-M9 β-cell line also attenuated glucose-induced insulin secretion. The ATP production in response to glucose and mitochondrial Complex I protein level were reduced (p&amp;lt;0.01) in βUCP2Tg islets. Dilatation (1.8-fold, p&amp;lt;0.05) and morphological alteration of mitochondria were observed in βUCP2Tg β-cells. Gene expression microarray analysis revealed 18 upregulated genes (1.5-fold, p&amp;lt;0.05) and 2 downregulated genes (&amp;lt;67%, p&amp;lt;0.05) in βUCP2Tg islets. The most upregulated mRNA by UCP2 expression encoded the aldolase B (Aldob) (77-fold), whose expression was reported to be negatively associated with insulin secretion in human islets (J Clin Endocrinol Metab. 103(12):4373-4383, 2018). We validated increased Aldob expression in islets from βUCP2Tg mice, db/db mice, and IRS-2KO mice. Taken together, UCP2 expression seemed to be increased under T2DM conditions including hyperglycemia or hyperinsulinemia. Our data also suggested that the increase in UCP2 expression in T2DM β-cells cell-autonomously attenuated glucose-induced insulin secretion, possibly via mitochondrial abnormality and Aldob expression. Disclosure R. Inoue: None. J. Shirakawa: None. Y. Togashi: None. Y. Terauchi: Advisory Panel; Self; AstraZeneca, Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp &amp; Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novo Nordisk A/S, Sanofi. Research Support; Self; Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp &amp; Dohme Corp., Novartis Pharmaceuticals Corporation, Novo Nordisk A/S, Ono Pharmaceutical Co., Ltd., Sanofi, Shionogi &amp; Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd. Speaker's Bureau; Self; Astellas Pharma Inc., AstraZeneca, Bayer Yakuhin, Ltd., Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp &amp; Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novartis Pharmaceuticals Corporation, Novo Nordisk A/S, Ono Pharmaceutical Co., Ltd., Sanofi, Sanwa Kagaku Kenkyusho, Shionogi &amp; Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd.

NKG2D signaling within the pancreas decreases NOD diabetes by enhancing CD8+ central memory T cell formation

Abstract The main drivers of type 1 diabetes are islet-specific T cells. These cells must escape a myriad of tolerance mechanisms that control their activation in healthy individuals. One pathway implicated in this process is signaling through Natural Killer Group 2 member D (NKG2D). We demonstrate that the mRNAs encoding both NKG2D and NKG2D ligands are increased in the islets of patients with type 1 diabetes, making discerning the role of NKG2D-ligand interaction in the pancreas during diabetes development of significant interest. To this end, we developed a novel mouse model to determine the role of NKG2D specifically within the pancreas. This is a NOD mouse that expresses a transgene driving expression of the NKG2D ligand RAE1ɛ in islets (RIP-RAE1ɛ NOD mice). Spontaneous diabetes development was significantly decreased in RIP-RAE1ɛ-NOD mice compared with control NOD mice, and RIP-RAE1ɛ mice contained decreased numbers of CD44hiCD62Llo(effector/effector memory, Tem, phenotype) CD8+ T cells in both the pancreas and spleen. This decrease correlated with increased numbers of CD44hiCD62Lhi(central memory T cell, Tcm, phenotype) CD8+ T cells, which is a cell population previously demonstrated to contain cells that inhibit the CD8+ Teff response. Further, we found that NKG2D signaling in both NOD and human CD8+ T cells increased CD8+ Tcm differentiation in vitro. Together, these novel results suggest that the NKG2D pathway in CD8+ T cells could be utilized to inhibit type 1 diabetes progression.

Functional Role and Mechanism of UCP2 Upregulation in Pancreatic ß Cells

Uncoupling protein 2 (UCP2) is a mitochondrial protein, which uncouples the oxidative phosphorylation. UCP2 protein level is reportedly upregulated in pancreatic islets of patients with type 2 diabetes; however, the functional role and mechanism of the upregulated UCP2 remain unclear. In this study, we undertook both in vitro regulation of gene expression and in vivo transgenic approaches to assess the significance of UCP2 in β cells. The expression of UCP2 was significantly upregulated by the stimulation with glucose, glucokinase activator, or insulin in mouse isolated islets (n=3-5, p &amp;lt;0.05). The islet UCP2 expression was also enhanced by the deletion of insulin receptor substrate 2 (IRS-2) (n=3, p &amp;lt;0.05). We generated β-cell-specific UCP2 transgenic (RIP-UCP2) mice, which had 40-fold higher UCP2 expression in islets (n=5, p &amp;lt;0.01), but not in hypothalamus. RIP-UCP2 mice developed glucose intolerance (n=13, p &amp;lt;0.01) in association with tendency to decrease insulin secretion (n=4, p=0.17, at 2 or 5 min after glucose loading), without alterations in insulin sensitivity and β cell mass, compared to the control. ATP/ADP ratio of RIP-UCP2 islets was significantly decreased after glucose stimulation (n=4, p &amp;lt;0.05). Next, we fed mice with high-fat diets (HFD) for 20 weeks. HFD-fed RIP-UCP2 mice initially showed hyperglycemia compared to the control; however, the difference in blood glucose was disappeared after 8 weeks. There were no changes in glucose tolerance, insulin secretion, and insulin sensitivity in HFD-fed RIP-UCP2 mice. β cell mass tended to be increased in HFD-fed RIP-UCP2 mice (1.5-fold compared with HFD-fed control, n=4-5, p=0.15). The IRS-2 expression level was significantly higher in the islets from HFD-fed RIP-UCP2 mice (n=4, p &amp;lt;0.05). Taken together, UCP2 upregulation potentially participates in the reduction in insulin secretion and β cell mass expansion by modulating ATP production and IRS-2 expression. Disclosure R. Inoue: None. J. Shirakawa: None. Y. Togashi: None. Y. Terauchi: Research Support; Self; MSD K.K.. Speaker's Bureau; Self; MSD K.K.. Advisory Panel; Self; MSD K.K.. Research Support; Self; Ono Pharmaceutical Co., Ltd.. Speaker's Bureau; Self; Ono Pharmaceutical Co., Ltd.. Research Support; Self; Novartis Pharma K.K., Boehringer Ingelheim GmbH. Speaker's Bureau; Self; Boehringer Ingelheim GmbH. Advisory Panel; Self; Boehringer Ingelheim GmbH. Research Support; Self; Mitsubishi Tanabe Pharma Corporation. Speaker's Bureau; Self; Mitsubishi Tanabe Pharma Corporation. Advisory Panel; Self; Mitsubishi Tanabe Pharma Corporation. Research Support; Self; Daiichi Sankyo Company, Limited. Speaker's Bureau; Self; Daiichi Sankyo Company, Limited. Advisory Panel; Self; Daiichi Sankyo Company, Limited. Research Support; Self; Sanwa Kagaku Kenkyusho Co., Ltd.. Speaker's Bureau; Self; Sanwa Kagaku Kenkyusho Co., Ltd.. Research Support; Self; Novo Nordisk Inc.. Speaker's Bureau; Self; Novo Nordisk Inc.. Advisory Panel; Self; Novo Nordisk Inc.. Research Support; Self; Eli Lilly and Company. Speaker's Bureau; Self; Eli Lilly and Company. Advisory Panel; Self; Eli Lilly and Company. Research Support; Self; Sanofi. Speaker's Bureau; Self; Sanofi. Advisory Panel; Self; Sanofi. Research Support; Self; Sumitomo Dainippon Pharma Co., Ltd.. Speaker's Bureau; Self; Sumitomo Dainippon Pharma Co., Ltd.. Research Support; Self; Shionogi &amp; Co., Ltd.. Speaker's Bureau; Self; Shionogi &amp; Co., Ltd., Bayer Yakuhin, Ltd., Astellas Pharma US, Inc., AstraZeneca. Advisory Panel; Self; AstraZeneca, Teijin Pharma Limited.

Tau ablation in mice leads to pancreatic β cell dysfunction and glucose intolerance

The microtubule-associated protein tau is highly expressed in pancreatic islets. Abnormally phosphorylated tau aggregates assemble into neurofibrillary tangles linked to Alzheimer's disease pathology and has also been found in islets of patients with type 2 diabetes. However, the significance of tau in islet function remains relatively unexplored. Therefore, we investigated the role of tau on β cell function and glucose homeostasis using tau knockout (tauKO) mice. TauKO mice were hyperglycemic and glucose intolerant at an early age. Islet insulin content was reduced and proinsulin levels were significantly elevated in tauKO mice, resulting in impaired glucose-stimulated insulin secretion. Loss of tau also resulted in increased epididymal fat mass and leptin levels, reduced glucose production, and insulin resistance at later ages, leading to complete onset of diabetes. Transgenic expression of human tau in islets was unable to rescue those defects in glucose regulation, indicating structural and/or functional differences between mouse and human tau. Cumulatively, these results suggest an important role for tau in the proper maintenance of pancreatic β cell function and glucose homeostasis.-Wijesekara, N., Gonçalves, R. A., Ahrens, R., De Felice, F. G., Fraser, P. E. Tau ablation in mice leads to pancreatic β cell dysfunction and glucose intolerance.

Type I Interferon Is a Catastrophic Feature of the Diabetic Islet Microenvironment.

A detailed understanding of the molecular pathways and cellular interactions that result in islet beta cell (β cell) destruction is essential for the development and implementation of effective therapies for prevention or reversal of type 1 diabetes (T1D). However, events that define the pathogenesis of human T1D have remained elusive. This gap in our knowledge results from the complex interaction between genetics, the immune system, and environmental factors that precipitate T1D in humans. A link between genetics, the immune system, and environmental factors are type 1 interferons (T1-IFNs). These cytokines are well known for inducing antiviral factors that limit infection by regulating innate and adaptive immune responses. Further, several T1D genetic risk loci are within genes that link innate and adaptive immune cell responses to T1-IFN. An additional clue that links T1-IFN to T1D is that these cytokines are a known constituent of the autoinflammatory milieu within the pancreas of patients with T1D. The presence of IFNα/β is correlated with characteristic MHC class I (MHC-I) hyperexpression found in the islets of patients with T1D, suggesting that T1-IFNs modulate the cross-talk between autoreactive cytotoxic CD8+ T lymphocytes and insulin-producing pancreatic β cells. Here, we review the evidence supporting the diabetogenic potential of T1-IFN in the islet microenvironment.

Type 1 Interferons Potentiate Human CD8+ T-Cell Cytotoxicity Through a STAT4- and Granzyme B-Dependent Pathway.

Events defining the progression to human type 1 diabetes (T1D) have remained elusive owing to the complex interaction between genetics, the immune system, and the environment. Type 1 interferons (T1-IFN) are known to be a constituent of the autoinflammatory milieu within the pancreas of patients with T1D. However, the capacity of IFNα/β to modulate human activated autoreactive CD8+ T-cell (cytotoxic T lymphocyte) responses within the islets of patients with T1D has not been investigated. Here, we engineer human β-cell–specific cytotoxic T lymphocytes and demonstrate that T1-IFN augments cytotoxicity by inducing rapid phosphorylation of STAT4, resulting in direct binding at the granzyme B promoter within 2 h of exposure. The current findings provide novel insights concerning the regulation of effector function by T1-IFN in human antigen-experienced CD8+ T cells and provide a mechanism by which the presence of T1-IFN potentiates diabetogenicity within the autoimmune islet.

In vivo pancreatic β-cell-specific expression of antiaging gene Klotho: a novel approach for preserving β-cells in type 2 diabetes.

Protein expression of an antiaging gene, Klotho, was depleted in pancreatic islets in patients with type 2 diabetes mellitus (T2DM) and in db/db mice, an animal model of T2DM. The objective of this study was to investigate whether in vivo expression of Klotho would preserve pancreatic β-cell function in db/db mice. We report for the first time that β-cell–specific expression of Klotho attenuated the development of diabetes in db/db mice. β-Cell–specific expression of Klotho decreased hyperglycemia and enhanced glucose tolerance. The beneficial effects of Klotho were associated with significant improvements in T2DM-induced decreases in number of β-cells, insulin storage levels in pancreatic islets, and glucose-stimulated insulin secretion from pancreatic islets, which led to increased blood insulin levels in diabetic mice. In addition, β-cell–specific expression of Klotho decreased intracellular superoxide levels, oxidative damage, apoptosis, and DNAJC3 (a marker for endoplasmic reticulum stress) in pancreatic islets. Furthermore, β-cell–specific expression of Klotho increased expression levels of Pdx-1 (insulin transcription factor), PCNA (a marker of cell proliferation), and LC3 (a marker of autophagy) in pancreatic islets in db/db mice. These results reveal that β-cell–specific expression of Klotho improves β-cell function and attenuates the development of T2DM. Therefore, in vivo expression of Klotho may offer a novel strategy for protecting β-cells in T2DM.

Human IAPP-induced pancreatic β cell toxicity and its regulation by autophagy.

Pancreatic islets in patients with type 2 diabetes mellitus (T2DM) are characterized by loss of β cells and formation of amyloid deposits derived from islet amyloid polypeptide (IAPP). Here we demonstrated that treatment of INS-1 cells with human IAPP (hIAPP) enhances cell death, inhibits cytoproliferation, and increases autophagosome formation. Furthermore, inhibition of autophagy increased the vulnerability of β cells to the cytotoxic effects of hIAPP. Based on these in vitro findings, we examined the pathogenic role of hIAPP and its relation to autophagy in hIAPP-knockin mice. In animals fed a standard diet, hIAPP had no toxic effects on β cell function; however, hIAPP-knockin mice did not exhibit a high-fat-diet-induced compensatory increase in β cell mass, which was due to limited β cell proliferation and enhanced β cell apoptosis. Importantly, expression of hIAPP in mice with a β cell-specific autophagy defect resulted in substantial deterioration of glucose tolerance and dispersed cytoplasmic expression of p62-associated toxic oligomers, which were otherwise sequestrated within p62-positive inclusions. Together, our results indicate that increased insulin resistance in combination with reduced autophagy may enhance the toxic potential of hIAPP and enhance β cell dysfunction and progression of T2DM.

Increased expression of IL-15 and IL-15Ra in the islets of patients with T1D (CCR3P.217)

Abstract We previously showed that transgenic mice with islet expression of IL-15 and IL-15Ra developed diabetes that mimics early human T1D. Inhibiting IL-15 signaling with anti-IL2/IL15Rβ (anti-CD122) or with the JAK 2/3 inhibitor tofacitinib reversed the diabetes. This suggested a causative role of IL-15 and IL-15Ra in the induction of insulin dependent diabetes in mice. To further investigate whether IL-15 and IL-15Ra play a role in the pathogenesis of human type 1 diabetes, we investigated the expression of IL-15 and IL-15Ra in the islets of patients with type 1 diabetes, anti-insulin autoantibodies and normal donors. Immunohistochemistry demonstrated IL-15 expression in the islets in all T1D patients examined whereas IL-15 was detected only in the pancreatic islets in one out of four normal donors and two out of five autoantibody positive donors. Interestingly, in two cases where IL-15 was positive, we also detected islet expression of MxA, a GTPase induced by type 1 IFN (α/β) that has been reported to interfere with virus multiplication and spread. Furthermore, IL-15 and IL-15Rα mRNA levels were also higher in the islets from T1D patients compared to that from autoantibody positive donors or normal donors. Moreover, the serum sIL-15Rα levels were significantly higher in patients with T1D compared with those of normal controls. Taken together, our data suggest that disordered IL-15 and IL-15Rα may be involved in the pathogenesis of human T1D.