Cholangiopathy After Severe COVID-19: Clinical Features and Prognostic Implications.

INTRODUCTION: Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 virus, is a predominantly respiratory tract infection with the capacity to affect multiple organ systems. Abnormal liver tests, mainly transaminase elevations, have been reported in hospitalized patients. We describe a syndrome of cholangiopathy in patients recovering from severe COVID-19 characterized by marked elevation in serum alkaline phosphatase (ALP) accompanied by evidence of bile duct injury on imaging. METHODS: We conducted a retrospective study of COVID-19 patients admitted to our institution from March 1, 2020, to August 15, 2020, on whom the hepatology service was consulted for abnormal liver tests. Bile duct injury was identified by abnormal liver tests with serum ALP > 3x upper limit of normal and abnormal findings on magnetic resonance cholangiopacreatography. Clinical, laboratory, radiological, and histological findings were recorded in a Research Electronic Data Capture database. RESULTS: Twelve patients were identified, 11 men and 1 woman, with a mean age of 58 years. Mean time from COVID-19 diagnosis to diagnosis of cholangiopathy was 118 days. Peak median serum alanine aminotransferase was 661 U/L and peak median serum ALP was 1855 U/L. Marked elevations of erythrocyte sedimentation rate, C-reactive protein, and D-dimers were common. Magnetic resonance cholangiopacreatography findings included beading of intrahepatic ducts (11/12, 92%), bile duct wall thickening with enhancement (7/12, 58%), and peribiliary diffusion high signal (10/12, 83%). Liver biopsy in 4 patients showed acute and/or chronic large duct obstruction without clear bile duct loss. Progressive biliary tract damage has been demonstrated radiographically. Five patients were referred for consideration of liver transplantation after experiencing persistent jaundice, hepatic insufficiency, and/or recurrent bacterial cholangitis. One patient underwent successful living donor liver transplantation. DISCUSSION: Cholangiopathy is a late complication of severe COVID-19 with the potential for progressive biliary injury and liver failure. Further studies are required to understand pathogenesis, natural history, and therapeutic interventions.

Intestinal Spirochetosis: To Treat or Not to Treat.

Spirochete colonization of the gastrointestinal tract is a poorly understood phenomenon presenting with varying signs and symptoms. Due to the lack of a unified approach and its varying presentations, the management decision for intestinal spirochetosis (IS) has always been challenging. While metronidazole is the commonly preferred antimicrobial treatment, it remains unclear if therapeutic intervention is indicated for everyone, especially asymptomatic patients. We present three patients, diagnosed with IS. They presented with varying demographics, clinical presentations, and past medical histories and underwent different clinical managements. Our decisions for treatment not only included presenting symptoms but also factors like history of pre-existing gastrointestinal diseases, age, and immune status.

Enhanced Complement Expression in the Tumor Microenvironment Following Neoadjuvant Therapy: Implications for Immunomodulation and Survival in Pancreatic Ductal Adenocarcinoma.

Background: Neoadjuvant therapy (NAT) is increasingly being used for pancreatic ductal adenocarcinoma (PDAC) treatment. However, its specific effects on carcinoma cells and the tumor microenvironment (TME) are not fully understood. This study aims to investigate how NAT differentially impacts PDAC's carcinoma cells and TME. Methods: Spatial transcriptomics was used to compare gene expression profiles in carcinoma cells and the TME between 23 NAT-treated and 13 NAT-naïve PDAC patients, correlating with their clinicopathologic features. Analysis of an online single-nucleus RNA sequencing (snRNA-seq) dataset was performed for validation of the specific cell types responsible for NAT-induced gene expression alterations. Results: NAT not only induces apoptosis and inhibits proliferation in carcinoma cells but also significantly remodels the TME. Notably, NAT induces a coordinated upregulation of multiple key complement genes (C3, C1S, C1R, C4B and C7) in the TME, making the complement pathway one of the most significantly affected pathways by NAT. Patients with higher TME complement expression following NAT exhibit improved overall survival. These patients also exhibit increased immunomodulatory and neurotrophic cancer-associated fibroblasts (CAFs); more CD4+ T cells, monocytes, and mast cells; and reduced immune exhaustion gene expression. snRNA-seq analysis demonstrates C3 complement was specifically upregulated in CAFs but not in other stroma cell types. Conclusions: NAT can enhance complement production and signaling within the TME, which is associated with reduced immunosuppression in PDAC. These findings suggest that local complement dynamics could serve as a novel biomarker for prognosis, evaluating treatment response and resistance, and guiding therapeutic strategies in NAT-treated PDAC patients.

Histologic Predictors of Clinical Outcomes and Healthcare Utilization in Patients With Ileal Pouch-Anal Anastomosis.

BACKGROUND: The prognostic significance of histology in ileal pouch-anal anastomosis (IPAA) remains unclear. The aim of this study was to evaluate if histologic variables are predictive of IPAA clinical outcomes and healthcare utilization. METHODS: This was a retrospective cohort study of patients with IPAA undergoing surveillance pouchoscopy at a tertiary care institution. Pouch body biopsies were reviewed by gastrointestinal pathologists, who were blinded to clinical outcomes, for histologic features of acute or chronic inflammation. Charts were reviewed for clinical outcomes including development of acute pouchitis, chronic pouchitis, biologic or small molecule initiation, hospitalizations, and surgery. Predictors of outcomes were analyzed using univariable and multivariable logistic and Cox regression. RESULTS: A total of 167 patients undergoing surveillance pouchoscopy were included. Polymorphonuclear leukocytes (odds ratio [OR], 1.67), ulceration and erosion (OR, 2.44), chronic inflammation (OR, 1.97), and crypt distortion (OR, 1.89) were associated with future biologic or small molecule initiation for chronic pouchitis. Loss of goblet cells was associated with development of chronic pouchitis (OR, 4.65). Pyloric gland metaplasia was associated with hospitalizations (OR, 5.24). No histologic variables were predictive of development of acute pouchitis or surgery. In an exploratory subgroup analysis of new IPAA (<1 year), loss of goblet cells was associated with acute pouchitis (OR, 14.86) and chronic pouchitis (OR, 12.56). Pyloric gland metaplasia was again associated with hospitalizations (OR, 13.99). CONCLUSIONS: Histologic findings may be predictive of IPAA outcomes. Pathologists should incorporate key histologic variables into pouchoscopy pathology reports. Clinicians may need to more closely monitor IPAA patients with significant histologic findings.

In this retrospective cohort study, histologic variables of acute and chronic inflammation were associated with future development of chronic pouchitis, need for biologic or small molecule treatment for chronic pouchitis, and hospitalization.

The pancreatic islet ß-cell-enriched transcription factor Pdx-1 regulates Slc30a8 gene transcription through an intronic enhancer.

The SLC30A8 gene encodes the zinc transporter ZnT-8, which provides zinc for insulin-hexamer formation. Genome-wide association studies have shown that a polymorphic variant in SLC30A8 is associated with altered susceptibility to Type 2 diabetes and we recently reported that glucose-stimulated insulin secretion is decreased in islets isolated from Slc30a8-knockout mice. The present study examines the molecular basis for the islet-specific expression of Slc30a8. VISTA analyses identified two conserved regions in Slc30a8 introns 2 and 3, designated enhancers A and B respectively. Transfection experiments demonstrated that enhancer B confers elevated fusion gene expression in both ßTC-3 cells and αTC-6 cells. In contrast, enhancer A confers elevated fusion gene expression selectively in ßTC-3 and not αTC-6 cells. These data suggest that enhancer A is an islet ß-cell-specific enhancer and that the mechanisms controlling Slc30a8 expression in α- and ß-cells are overlapping, but distinct. Gel retardation and ChIP (chromatin immunoprecipitation) assays revealed that the islet-enriched transcription factor Pdx-1 binds enhancer A in vitro and in situ respectively. Mutation of two Pdx-1-binding sites in enhancer A markedly reduces fusion gene expression suggesting that this factor contributes to Slc30a8 expression in ß-cells, a conclusion consistent with developmental studies showing that restriction of Pdx-1 to pancreatic islet ß-cells correlates with the induction of Slc30a8 gene expression and ZnT-8 protein expression in vivo.

Recurrent Liver Allograft Injury in Patients With Donor-Derived Malignancy Treated With Immunosuppression Cessation and Retransplantation.

OBJECTIVES: Donor-derived malignancy of the liver allograft is a rare but serious condition in the setting of necessary immunosuppression. Retransplantation after abrupt immunosuppression cessation has been performed with durable cancer-free survival. METHODS: We present 2 cases of patients with donor-derived malignancy who were treated with complete immunosuppression cessation, which induced rapidly progressive liver allograft rejection and failure, with a need for subsequent retransplantation. We reviewed all serial liver biopsies and explants from both patients and performed C4d immunostaining. RESULTS: Initial explants of both patients showed severe allograft rejection, with unusual features of sinusoidal obstruction syndrome and C4d positivity. Malignant tumors in the explants were necrotic, related to rejection of donor-derived cancer cells and tissue. Follow-up of both patients has shown long-term cancer-free survival but issues with recurrent allograft failure requiring a third transplant. The reasons for retransplantation in both cases were related to allograft failure from antibody-mediated rejection. CONCLUSIONS: Clinicians should be aware of a potentially increased risk of rejection and recurrent allograft failure when strategizing treatment of donor-derived malignancy with immunosuppression cessation and retransplantation.

Primary small bowel adenocarcinoma with loss of nuclear expression of PMS2 after resection of mucinous cholangiocarcinoma.

Mucinous cholangiocarcinoma is an extremely rare form of intrahepatic cholangiocarcinoma that has been characterized by rapid growth, widespread metastasis and poor prognosis. These tumors have been shown to be a part of the Lynch syndrome tumor spectrum, however, the role of DNA mismatch repair (MMR) deficiency in their development is poorly understood. We present the case of a 74-year-old male with cholangiocarcinoma, who underwent Roux-en-Y hepaticojejunostomy and extended left hepatectomy and was diagnosed with a primary small bowel adenocarcinoma 2 years later. Immunohistochemistry testing for mismatch repair proteins was significant for the loss of nuclear expression of PMS2. Taken together, the cause of both the mucinous cholangiocarcinoma and primary small bowel adenocarcinoma with PMS2 loss in the patient presented here is likely genetic, suggestive of a cancer syndrome.

Clinical and Intestinal Histopathological Findings in SARS-CoV-2/COVID-19 Patients with Hematochezia.

Gastrointestinal (GI) symptoms of SARS-CoV-2/COVID-19 in the form of anorexia, nausea, vomiting, abdominal pain and diarrhea are usually preceded by respiratory manifestations and are associated with a poor prognosis. Hematochezia is an uncommon clinical presentation of COVID-19, and we hypothesize that older patients with significant comorbidities (obesity and cardiovascular) and prolonged hospitalization are susceptible to ischemic injury to the bowel. We reviewed the clinical course, key laboratory data including acute-phase reactants, and drug/medication history in 2 elderly male patients admitted for COVID-19 respiratory failure. Both patients had a complicated clinical course and suffered from hematochezia, acute blood loss, and anemia which led to hemodynamic instability requiring blood transfusion around day 40 of their hospitalization. Colonoscopic impressions were correlated with the histopathological findings in the colonic biopsies that included changes compatible with ischemia and nonspecific acute inflammation, edema, and increased eosinophils in the lamina propria. Both patients were hemodynamically stable, on prophylactic anticoagulants, multiple antibiotics, and antifungal agents due to respiratory infections at the time of lower GI bleeding. Hematochezia resolved spontaneously with supportive care. Both patients eventually recovered and were discharged. Elderly patients with significant comorbid conditions are uniquely at risk for ischemic injury to the bowel. This case report highlights hematochezia as an uncommon GI manifestation of spectrum of COVID-19 complications. The causes of bleeding in these COVID-19 associated cases are likely multifactorial and can be attributed to concomitant etiologies based on their age, multiple comorbid conditions, prolonged hospitalization compounded by lung injury, and hypoxia precipitated by the virus. We hypothesize that rather than a direct viral cytopathic effect, ischemia and hypoperfusion may be unleashed due to the cytokine storm orchestrated by the virus that leads to abnormal coagulation profile. Additional factors that may contribute to ischemic injury are prophylactic use of anticoagulants and polypharmacy. There were no other causes to explain the brisk lower GI bleeding. Presentation of hematochezia was followed by hemodynamic instability that may further increase the mortality and morbidity of COVID-19 patients, and prompt consultation and management by gastroenterology is therefore warranted.

Deletion of the mouse Slc30a8 gene encoding zinc transporter-8 results in impaired insulin secretion.

The Slc30a8 gene encodes the islet-specific zinc transporter ZnT-8, which provides zinc for insulin-hexamer formation. Polymorphic variants in amino acid residue 325 of human ZnT-8 are associated with altered susceptibility to Type 2 diabetes and ZnT-8 autoantibody epitope specificity changes in Type 1 diabetes. To assess the physiological importance of ZnT-8, mice carrying a Slc30a8 exon 3 deletion were analysed histologically and phenotyped for energy metabolism and pancreatic hormone secretion. No gross anatomical or behavioural changes or differences in body weight were observed between wild-type and ZnT-8-/- mice, and ZnT-8-/- mouse islets were indistinguishable from wild-type in terms of their numbers, size and cellular composition. However, total zinc content was markedly reduced in ZnT-8-/- mouse islets, as evaluated both by Timm's histochemical staining of pancreatic sections and direct measurements in isolated islets. Blood glucose levels were unchanged in 16-week-old, 6 h fasted animals of either gender; however, plasma insulin concentrations were reduced in both female (approximately 31%) and male (approximately 47%) ZnT-8-/- mice. Intraperitoneal glucose tolerance tests demonstrated no impairment in glucose clearance in male ZnT-8-/- mice, but glucose-stimulated insulin secretion from isolated islets was reduced approximately 33% relative to wild-type littermates. In summary, Slc30a8 gene deletion is accompanied by a modest impairment in insulin secretion without major alterations in glucose metabolism.

DNA microarray analysis for the identification of innate immune pathways implicated in virus-induced autoimmune diabetes.

We have recently demonstrated that upregulation of the innate immune system plays a key role in KRV-induced autoimmune diabetes in the BBDR rat, but the nature of this proinflammatory reaction has not yet been addressed. Using a DNA microarray approach, we identified 569 genes upregulated in pancreatic lymph nodes following virus infection. Among the most highly activated are IL-1 pathways, IFN-gamma-induced chemokines, and genes associated with interferon production and signaling. Ex vivo and in vitro studies indicate that KRV upregulates proinflammatory cytokines and chemokines in B lymphocytes and Flt-3L-induced plasmacytoid DCs (pDCs). Finally, in contrast to KRV, infection of BBDR rats with the non-diabetogenic KRV homologue H-1 parvovirus fails to induce a robust proinflammatory response in pancreatic lymph nodes. Our findings provide new insights into KRV-induced innate immune pathways that may play a role in early mechanisms leading to islet inflammation and diabetes.

Induction of indoleamine 2,3-dioxygenase by interferon-gamma in human islets.

Indoleamine 2,3-dioxygenase (IDO) catalyzes the initial, rate-limiting step of tryptophan (Trp) catabolism along the kynurenine (KYN) pathway, and its induction in cells of the immune system in response to cytokines has been implicated in the regulation of antigen presentation and responses to cell-mediated immune attack. Microarray and quantitative PCR analyses of isolated human islets incubated with interferon (IFN)-gamma for 24 h revealed increased expression of IDO mRNA (>139-fold) and Trp-tRNA synthase (WARS) (>17-fold) along with 975 other transcripts more than threefold, notably the downstream effectors janus kinase (JAK)2, signal transducer and activator of transcription (STAT)1, IFN-gamma regulatory factor-1, and several chemokines (CXCL9/MIG, CXCL10/IP10, CXCL11/1-TAC, CCL2, and CCL5/RANTES) and their receptors. IDO protein expression was upregulated in IFN-gamma-treated islets and accompanied by increased intracellular IDO enzyme activity and the release of KYN into the media. The response to IFN-gamma was countered by interleukin-4 and 1alpha-methyl Trp. Immunohistochemical localization showed IDO to be induced in cells of both endocrine, including pancreatic duodenal homeobox 1-positive beta-cells, and nonendocrine origin. We postulate that in the short term, IDO activation may protect islets from cytotoxic damage, although chronic exposure to various Trp metabolites could equally lead to beta-cell attrition.

Modulation of c-myc, max, and mad gene expression during neural differentiation of embryonic stem cells by all-trans-retinoic acid.

c-Myc regulates cellular proliferation, differentiation, and apoptosis. Temporal expression of c-Myc during all-trans-retinoic acid (RA)-mediated neural differentiation in murine embryonic stem cell (ES) was investigated. Correlation to the modulation of dimerizing partners Max and Mad that may influence c-Myc signaling and transcription regulation was elucidated for the first time in these cells. In RA-treated cells, increase in c-myc mRNA was detected by reverse transcriptase polymerase chain reaction on days 11 and 14 of differentiation compared with the vehicle-treated controls. The results were further corroborated by ribonuclease protection assay (RPA). Western blots revealed an increase in c-Myc protein only on day 14 of differentiation in RA-treated cells. Increases in max and mad gene transcription detected by RPA at times of elevated c-Myc in RA-treated ES cells suggest that a transient increase in c-Myc protein expression may influence differential dimerization of Myc partners needed for signaling in the neural differentiation of ES cells.

Expression of c-Myc and other apoptosis-related genes in Swiss Webster mouse fetuses after maternal exposure to all trans-retinoic acid.

The Myc family of genes regulates proliferation, differentiation, and apoptosis. Temporal expression of Myc family genes and several pro-apoptotic genes were investigated during Swiss Webster mice organogenesis after maternal treatment with an oral dose of 100 mg/kg trans-retinoic acid (RA) or vehicle on day 10 post-coitum. Reverse transcriptase-polymerase chain reaction and ribonuclease protection assay revealed decreased c-myc expression at 48 h followed by an increase at 72 h in fetuses from RA-treated dams. Increased c-Myc protein was detected at 72 h in the RA-treated group. In utero RA-treatment resulted in decreased expression of max, mad, caspases, bax, and bad genes at 48 h. Terminal uridinetriphosphate nick end-labeling (TUNEL) analysis revealed increased apoptosis at 24-48 h, followed by decreased apoptosis 72 h after in utero RA-exposure, which correlated with the decreased expression of pro-apoptotic genes noted at 48 h. Further investigations are needed to understand the role of Myc family genes during RA-mediated teratogenesis.

Synergizing genomic analysis with biological knowledge to identify and validate novel genes in pancreatic development.

OBJECTIVE: This study investigated the utility of advanced computational techniques to large-scale genome-based data to identify novel genes that govern murine pancreatic development. METHODS: An expression data set for mouse pancreatic development was complemented with high-throughput data analyzer to identify and prioritize novel genes. Quantitative real-time polymerase chain reaction, in situ hybridization, and immunohistochemistry were used to validate selected genes. RESULTS: Four new genes whose roles in the development of murine pancreas have not previously been established were identified: cystathionine ß-synthase (Cbs), Meis homeobox 1, growth factor independent 1, and aldehyde dehydrogenase 18 family, member A1. Their temporal expression during development was documented. Cbs was localized in the cytoplasm of the tip cells of the epithelial chords of the undifferentiated progenitor cells at E12.5 and was coexpressed with the pancreatic and duodenal homeobox 1 and pancreas-specific transcription factor, 1a-positive cells. In the adult pancreas, Cbs was localized primarily within the acinar compartment. CONCLUSIONS: In silico analysis of high-throughput microarray data in combination with background knowledge about genes provides an additional reliable method of identifying novel genes. To our knowledge, the expression and localization of Cbs have not been previously documented during mouse pancreatic development.

Expression and regulation of chemokines in murine and human type 1 diabetes.

More than one-half of the ~50 human chemokines have been associated with or implicated in the pathogenesis of type 1 diabetes, yet their actual expression patterns in the islet environment of type 1 diabetic patients remain, at present, poorly defined. Here, we have integrated a human islet culture system, murine models of virus-induced and spontaneous type 1 diabetes, and the histopathological examination of pancreata from diabetic organ donors with the goal of providing a foundation for the informed selection of potential therapeutic targets within the chemokine/receptor family. Chemokine (C-C motif) ligand (CCL) 5 (CCL5), CCL8, CCL22, chemokine (C-X-C motif) ligand (CXCL) 9 (CXCL9), CXCL10, and chemokine (C-X3-C motif) ligand (CX3CL) 1 (CX3CL1) were the major chemokines transcribed (in an inducible nitric oxide synthase-dependent but not nuclear factor-κB-dependent fashion) and translated by human islet cells in response to in vitro inflammatory stimuli. CXCL10 was identified as the dominant chemokine expressed in vivo in the islet environment of prediabetic animals and type 1 diabetic patients, whereas CCL5, CCL8, CXCL9, and CX3CL1 proteins were present at lower levels in the islets of both species. Of importance, additional expression of the same chemokines in human acinar tissues emphasizes an underappreciated involvement of the exocrine pancreas in the natural course of type 1 diabetes that will require consideration for additional type 1 diabetes pathogenesis and immune intervention studies.

The physiological effects of deleting the mouse SLC30A8 gene encoding zinc transporter-8 are influenced by gender and genetic background.

OBJECTIVE: The SLC30A8 gene encodes the islet-specific transporter ZnT-8, which is hypothesized to provide zinc for insulin-crystal formation. A polymorphic variant in SLC30A8 is associated with altered susceptibility to type 2 diabetes. Several groups have examined the effect of global Slc30a8 gene deletion but the results have been highly variable, perhaps due to the mixed 129SvEv/C57BL/6J genetic background of the mice studied. We therefore sought to remove the conflicting effect of 129SvEv-specific modifier genes. METHODS: The impact of Slc30a8 deletion was examined in the context of the pure C57BL/6J genetic background. RESULTS: Male C57BL/6J Slc30a8 knockout (KO) mice had normal fasting insulin levels and no change in glucose-stimulated insulin secretion (GSIS) from isolated islets in marked contrast to the ∼50% and ∼35% decrease, respectively, in both parameters observed in male mixed genetic background Slc30a8 KO mice. This observation suggests that 129SvEv-specific modifier genes modulate the impact of Slc30a8 deletion. In contrast, female C57BL/6J Slc30a8 KO mice had reduced (∼20%) fasting insulin levels, though this was not associated with a change in fasting blood glucose (FBG), or GSIS from isolated islets. This observation indicates that gender also modulates the impact of Slc30a8 deletion, though the physiological explanation as to why impaired insulin secretion is not accompanied by elevated FBG is unclear. Neither male nor female C57BL/6J Slc30a8 KO mice showed impaired glucose tolerance. CONCLUSIONS: Our data suggest that, despite a marked reduction in islet zinc content, the absence of ZnT-8 does not have a substantial impact on mouse physiology.

Characterization of the human SLC30A8 promoter and intronic enhancer.

Genome-wide association studies have shown that a polymorphic variant in SLC30A8, which encodes zinc transporter-8, is associated with altered susceptibility to type 2 diabetes (T2D). This association is consistent with the observation that glucose-stimulated insulin secretion is decreased in islets isolated from Slc30a8 knockout mice. In this study, immunohistochemical staining was first used to show that SLC30A8 is expressed specifically in pancreatic islets. Fusion gene studies were then used to examine the molecular basis for the islet-specific expression of SLC30A8. The analysis of SLC30A8-luciferase expression in ßTC-3 cells revealed that the proximal promoter region, located between -6154 and -1, relative to the translation start site, was only active in stable but not transient transfections. VISTA analyses identified three regions in the SLC30A8 promoter and a region in SLC30A8 intron 2 that are conserved in the mouse Slc30a8 gene. Additional fusion gene experiments demonstrated that none of these Slc30a8 promoter regions exhibited enhancer activity when ligated to a heterologous promoter whereas the conserved region in SLC30A8 intron 2 conferred elevated reporter gene expression selectively in ßTC-3 but not in αTC-6 cells. Finally, the functional effects of a single nucleotide polymorphism (SNP), rs62510556, in this conserved intron 2 enhancer were investigated. Gel retardation studies showed that rs62510556 affects the binding of an unknown transcription factor and fusion gene analyses showed that it modulates enhancer activity. However, genetic analyses suggest that this SNP is not a causal variant that contributes to the association between SLC30A8 and T2D, at least in Europeans.

Deletion of the G6pc2 gene encoding the islet-specific glucose-6-phosphatase catalytic subunit-related protein does not affect the progression or incidence of type 1 diabetes in NOD/ShiLtJ mice.

OBJECTIVE: Islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP), now known as G6PC2, is a major target of autoreactive T cells implicated in the pathogenesis of type 1 diabetes in both mice and humans. This study aimed to determine whether suppression of G6p2 gene expression might therefore prevent or delay disease progression. RESEARCH DESIGN AND METHODS: G6pc2(-/-) mice were generated on the NOD/ShiLtJ genetic background, and glycemia was monitored weekly up to 35 weeks of age to determine the onset and incidence of diabetes. The antigen specificity of CD8(+) T cells infiltrating islets from NOD/ShiLtJ G6pc2(+/+) and G6pc2(-/-) mice at 12 weeks was determined in parallel. RESULTS: The absence of G6pc2 did not affect the time of onset, incidence, or sex bias of type 1 diabetes in NOD/ShiLtJ mice. Insulitis was prominent in both groups, but whereas NOD/ShiLtJ G6pc2(+/+) islets contained CD8(+) T cells reactive to the G6pc2 NRP peptide, G6pc2 NRP-reactive T cells were absent in NOD/ShiLtJ G6pc2(-/-) islets. CONCLUSIONS: These results demonstrate that G6pc2 is an important driver for the selection and expansion of islet-reactive CD8(+) T cells infiltrating NOD/ShiLtJ islets. However, autoreactivity to G6pc2 is not essential for the emergence of autoimmune diabetes. The results remain consistent with previous studies indicating that insulin may be the primary autoimmune target, at least in NOD/ShiLtJ mice.

Replication and further characterization of a Type 1 diabetes-associated locus at the telomeric end of the major histocompatibility complex.

BACKGROUND: We recently reported an association between Type 1 diabetes and the telomeric major histocompatibility complex (MHC) single nucleotide polymorphism (SNP) rs1233478. As further families have been analyzed in the Type 1 Diabetes Genetics Consortium (T1DGC), we tested replication of the association and, with more data, analyzed haplotypic associations. METHODS: An additional 2717 case and 1315 control chromosomes have been analyzed from the T1DGC, with human leukocyte antigen (HLA) typing and data for 2837 SNPs across the MHC region. RESULTS: We confirmed the association of rs1233478 (new data only: P=2.2E-5, OR=1.4). We also found two additional SNPs nearby that were significantly associated with Type 1 diabetes (new data only rs3131020: P=8.3E-9, OR=0.65; rs1592410: P=2.2E-8, OR=1.5). For studies of Type 1 diabetes in the MHC region, it is critical to account for linkage disequilibrium with the HLA genes. Logistic regression analysis of these new data indicated that the effects of rs3131020 and rs1592410 on Type 1 diabetes risk are independent of HLA alleles (rs3131020: P=2.3E-3, OR=0.73; rs1592410: P=2.1E-3, OR=1.4). Haplotypes of 12 SNPs (including the three highly significant SNPs) stratify diabetes risk (high risk, protective, and neutral), with high-risk haplotypes limited to approximately 20,000 bp in length. The 20,000-bp region is telomeric of the UBD gene and contains LOC729653, a hypothetical gene. CONCLUSIONS: We believe that polymorphisms of the telomeric MHC locus LOC729653 may confer risk for Type 1 diabetes.