The HLA complex and coeliac disease

Genetic correlation, pleiotropic loci and shared risk genes between major depressive disorder and gastrointestinal tract disorders

BACKGROUND

Major depressive disorder (MDD) is associated with gastrointestinal tract (GIT) disorders, while genetic correlation, pleiotropic loci and shared risk genes remain to be explored.

METHODS

Leveraging genome-wide association study statistics for MDD (n = 170,756), peptic ulcer disease (PUD; n = 16,666), gastroesophageal reflux disease (GORD; n = 54,854), PUD and/or GORD and/or medications (PGM; n = 90,175), irritable bowel syndrome (IBS; n = 28,518), and inflammatory bowel disease (IBD; n = 7045), we determined global and local genetic correlations, identified pleiotropic loci, performed gene-level evaluations, and inferred causal associations using bidirectional Mendelian randomization.

RESULTS

We found global correlation of MDD with PUD (rg = 0.444, P = 3.135 × 10-24), GORD (rg = 0.459, P = 2.568 × 10-65), PGM (rg = 0.498, P = 6.094 × 10-114), IBS (rg = 0.621, P = 2.483 × 10-63), and IBD (rg = 0.171, P = 1.824 × 10-5). We identified 12 locally correlated regions between MDD and GIT disorders except for IBD, and one shared region (chr11:111985737-113,103,996) for PGM, GORD, and IBS. We found one pleiotropic locus for PUD, 12 for GORD, 30 for PGM, eight for IBS, and seven for IBD, and five shared loci (rs138786869, rs2284189, rs3130063, rs35789010, rs7568369) for GORD and PGM. We respectively observed 14 and 20 overlapping genes for MDD-GORD and MDD-PGM. We showed genetic liabilities to GORD, PGM, and IBS causally increase MDD risk, while all reverse causalities are significant.

CONCLUSIONS

Our work identifies genetic architectures shared between MDD and GIT disorders, contributes genetic insights to understand depression in the context of gut-brain interactions, and provides potential targets to treat gastrointestinal symptoms in depressive patients.

Can flow cytometry be a key in the difficult diagnosis of coeliac disease?

We present the clinical case of a 39-year-old woman with a medical history of juvenile idiopathic arthritis and uveitis, evaluated for abdominal pain and distension, difficulty gaining weight, and diarrhea. Blood tests were requested, including antibodies which were negative and common genetic markers, showing positivity for HLA DQ 7.5. A gastroscopy with duodenal biopsies revealed findings consistent with stage 3b of the modified Marsh classification. Due to diagnostic uncertainty, an IEL study was performed, showing a characteristic CD pattern, leading to the initiation of a strict gluten-free diet (GFD). During follow-up, the patient showed partial improvement, with persistent digestive symptoms. A repeat endoscopic study revealed persistent atrophy, but refractory disease type 2 was ruled out. During a flare of rheumatologic disease, Tocilizumab was initiated by Rheumatology, resulting in improvement of duodenal atrophy.

The frequency of HLA-DQ7 in patients at risk of coeliac disease: A haplotype to be reckoned with for screening?

HLA-DQ2 and -DQ8 carriers are genetically predisposed to develop coeliac disease (CD). Testing negative for HLA-DQ2/DQ8 has a high negative predictive value. Full HLA-DQ genotyping as well as tests only typing for HLA-DQ2/DQ8 are therefore used for screening at-risk populations. However, HLA-DQ7 positive and HLA-DQ2/DQ8 negative CD patients have been described in various populations. In this study we examine the relevance for HLA-DQ7 typing in a large at-risk CD population. The HLA-DQ status of all paediatric and adult patients at-risk of CD that were typed in a tertiary medical centre laboratory between 2012 and 2016 (n = 3983) was obtained. HLA-DQ7 (HLA-DQB1*03:01) positive and HLA-DQ2/DQ8 negative patients were selected. We gathered information on serology, histology and dietary status, and CD diagnosis. In total, 489/3983 patients were HLA-DQ7-positive and HLA-DQ2/DQ8 negative, and after exclusion (missing data on diet or serology/histology), 325 were included. Only one adult patient was diagnosed with CD, based on a duodenal biopsy and a clinical response to a gluten-free diet. Homozygosity was observed in 14.8 %. Based on the current cohort additional typing of HLA-DQ7 does not seem relevant for screening at-risk populations for CD in the Netherlands. It should be considered in patients with a high suspicion of CD.

Vitamin D: An Essential Nutrient in the Dual Relationship between Autoimmune Thyroid Diseases and Celiac Disease-A Comprehensive Review

Autoimmune thyroid diseases (AITD) are among the most frequent autoimmune disorders, with a multifactorial etiology in which both genetic and environmental determinants are probably involved. Celiac disease (CeD) also represents a public concern, given its increasing prevalence due to the recent improvement of screening programs, leading to the detection of silent subtypes. The two conditions may be closely associated due to common risk factors, including genetic setting, changes in the composition and diversity of the gut microbiota, and deficiency of nutrients like vitamin D. This comprehensive review discussed the current evidence on the pivotal role of vitamin D in modulating both gut microbiota dysbiosis and immune system dysfunction, shedding light on the possible relevance of an adequate intake of this nutrient in the primary prevention of AITD and CeD. While future technology-based strategies for proper vitamin D supplementation could be attractive in the context of personalized medicine, several issues remain to be defined, including standardized assays for vitamin D determination, timely recommendations on vitamin D intake for immune system functioning, and longitudinal studies and randomized controlled trials to definitely establish a causal relationship between serum vitamin D levels and the onset of AITD and CeD.

Coeliac disease in the Trøndelag Health Study (HUNT), Norway, a population-based cohort of coeliac disease patients

PURPOSE

Coeliac disease (CD) is a common disorder and affects about 1% of the population worldwide. CD in the Trøndelag Health Study (HUNT) is a population-based cohort study which was established to provide new knowledge about CD that can improve the diagnostics and management, prevent the onset or progression and expand the knowledge about the role of genetics of the disease.

PARTICIPANTS

The cohort is based on the fourth wave of the population-based HUNT study (HUNT4), Norway, performed during 2017-2019, also including linkage to hospital records and the Norwegian Patient Registry (NPR). A total of 54 541 HUNT4 participants with available sera were screened for CD by serology. All seropositive participants were invited to a clinical assessment, including endoscopy with duodenal biopsies, during 2019-2023.

FINDINGS TO DATE

A total of 1107 HUNT4 participants (2%) were seropositive for CD and 1048 were eligible for clinical assessment, including biopsy. Of these, 724 participants attended the clinical assessment and 482 were identified with CD. In addition, 371 participants with CD were identified through the hospital records and NPR. In total, 853 participants in HUNT4 with biopsy-verified CD diagnosis were identified.

FUTURE PLANS

All participants in the study will be invited to a follow-up assessment after at least 1 year, including repeated standard serological testing, endoscopy and tissue sampling. The collected data and material will be used to establish the true population-based prevalence of CD. The consequences of CD, including symptoms, deficiencies and comorbidity, will be investigated and possible triggers and predictors, will be studied. With access to serum samples from the previous HUNT surveys in HUNT Biobank, serological signs of CD in prediagnostic samples of seropositive individuals will be used. Genetic studies will identify new CD markers, assess genotype-phenotype links and explore gene-environment correlations.

REGISTRATION

clinicaltrials.gov identifier: NCT04041622.

Extra-intestinal manifestations of Celiac disease in children: their prevalence and association with human leukocyte antigens and pathological and laboratory evaluations

BACKGROUND

Celiac disease (CD) is an autoimmune disease caused by gluten intake. Traditionally CD was believed to be a disease of the gut, although a wide range of extra-intestinal manifestations (EIM) was recognized. The exact prevalence of EIM and the associated risk factors have not been well studied.

AIM

We aimed to assess the prevalence of EIM in children with CD and their association with human leukocyte antigen (HLA) typing, and pathological and laboratory indices.

METHOD

We conducted a cross-sectional study on children and adolescents with a definite diagnosis of CD. They were followed in the main Celiac Clinic of Southern Iran.

RESULTS

We included 204 children who were visited between 2012 and 2017. Nearly 85% of them were positive for HLA-DQ2 and 40.6% for HLA-DQ8. The most prevalent intestinal complaints reported were abdominal pain (42.6%) and chronic constipation (19.1%). Failure-to-thrive (32.7%), iron deficiency anemia (25%), short stature (20.5%), and eczema (18.6%) were the most common EIMs. However, failure-to-thrive and short stature were presented at significantly younger ages, whereas those patients with concomitant type 1 diabetes mellitus (DM) were significantly older. We also found significant relationships between autoimmune thyroid disease and HLA-DQ5, and the presence of headaches with HLA-DQ7. The prevalence of HLA types of DQ2, DQ8, DQ6, and DQ7 significantly varied among different Marsh groups. Patients who were positive for HLA-DQ8, were significantly older, taller, and weightier. No significant association was found between HLA types and any of the gastrointestinal symptoms, anti-tTG and compliance to gluten free diet. Moreover, there were no statistically significant differences detected between the presence of each individual EIM, the level of IgA anti-tTG, sex, and Marsh typing.

CONCLUSION

This study highlights the presence of EIM in CD and their associated factors. We show the potential role of HLA typing in some EIMs, which may shed light for future studies.

Celiac Disease and Gallbladder: Pathophysiological Aspects and Clinical Issues

Background: Celiac Disease (CD) is an immune-mediated disorder which primarily affects the small intestine; however, extra-intestinal organs are often affected by the pathological process, too. As regards the digestive system, liver alterations in CD patients have been widely described, which can also extend to the biliary tract. Notably, gallbladder function can be altered in CD patients. In this review, we specifically analyze and summarize the main pathophysiological aspects and clinical evidence of gallbladder dysfunction in CD patients, in order to discuss the potential medical complications and clinical research gaps. In addition to some perturbations of bile composition, CD patients can develop gallbladder dysmotility, which mainly expresses with an impaired emptying during the digestive phase. The main pathophysiological determinant is a perturbation of cholecystokinin secretion by the specific duodenal enteroendocrine cells in response to the appropriate nutrient stimulation in CD patients. This situation appears to be reversible with a gluten-free diet in most cases. Despite this gallbladder impairment, CD patients do not seem to be more predisposed to gallbladder complications, such as calculous and acalculous cholecystitis. However, very few clinical studies have actively investigated these clinical aspects, which may not be completely evidenced so far; alternatively, the substantial improvements in the last two decades regarding CD diagnosis, which have reduced the diagnostic delay (and related dietary treatment), may have lessened the potential clinical consequences of CD-related gallbladder dysfunction. Specific clinical studies focused on these aspects are needed for a better understanding of the clinical implications of gallbladder alterations in CD patients.

Posttranslational modifications in diabetes: Mechanisms and functions

As one of the most widespread chronic diseases, diabetes and its accompanying complications affect approximately one tenth of individuals worldwide and represent a growing cause of morbidity and mortality. Accumulating evidence has proven that the process of diabetes is complex and interactive, involving various cellular responses and signaling cascades by posttranslational modifications (PTMs). Therefore, understanding the mechanisms and functions of PTMs in regulatory networks has fundamental importance for understanding the prediction, onset, diagnosis, progression, and treatment of diabetes. In this review, we offer a holistic summary and illustration of the crosstalk between PTMs and diabetes, including both types 1 and 2. Meanwhile, we discuss the potential use of PTMs in diabetes treatment and provide a prospective direction for deeply understanding the metabolic diseases.

HLA Associations in pediatric autoimmune liver diseases: Current state and future research initiatives

The strongest genetic association with autoimmunity is within chromosome 6p21, where the human leukocyte antigen (HLA) complex resides. This review will focus on the HLA associations within pediatric autoimmune hepatitis, autoimmune sclerosing cholangitis and primary sclerosing cholangitis. In general, there is considerable overlap in HLA genotypes conferring susceptibility to pediatric autoimmune liver diseases, however unique HLA associations and protective HLA genotypes exist. There are numerous areas for future research initiatives in pediatric autoimmune liver diseases and HLA associations with clinical outcomes, autoantigen discovery and novel therapeutics targeting the HLA- autoantigen- T cell pathway will be highlighted.

HLA class II immunopeptidomics reveals that co-inherited HLA-allotypes within an extended haplotype can improve proteome coverage for immunosurveillance

Human leucocyte antigen (HLA) class II molecules in humans are encoded by three different loci, HLA-DR, -DQ, and -DP. These molecules share approximately 70% sequence similarity and all present peptide ligands to circulating T cells. While the peptide repertoires of numerous HLA-DR, -DQ, and -DP allotypes have been examined, there have been few reports on the combined repertoire of these co-inherited molecules expressed in a single cell as an extended HLA haplotype. Here we describe the endogenous peptide repertoire of a human B lymphoblastoid cell line (C1R) expressing the class II haplotype HLA-DR12/DQ7/DP4. We have identified 71350 unique naturally processed peptides presented collectively by HLA-DR12, HLA-DQ7, or HLA-DP4. The resulting "haplodome" is complemented by the cellular proteome defined by standard LC-MS/MS approaches. This large dataset has shed light on properties of these class II ligands especially the preference for membrane and extracellular source proteins. Our data also provides insights into the co-evolution of these conserved haplotypes of closely linked and co-inherited HLA molecules; which together increase sequence coverage of cellular proteins for immune surveillance with minimal overlap between each co-inherited HLA-class II allomorph.