The patients had median of 7 (range 4-11) disease components of APECED. to evaluate whether the intestinal microbiota composition, predicted functions or fungal abundance differ Palmitic acid between Finnish patients with APECED and healthy controls, and whether these associate to the patients clinical phenotype and gastrointestinal symptoms. Methods DNA was isolated from fecal samples from 15 patients with APECED (median age 46.4 years) together with 15 samples from body mass index matched healthy controls. DNA samples were subjected to analysis of the gut microbiota using 16S rRNA gene amplicon sequencing, imputed metagenomics using the PICRUSt2 algorithm, and quantitative PCR for fungi. Extensive correlations of the microbiota with patient characteristics were determined. Results Analysis of gut microbiota indicated that both alpha- and beta-diversity were altered in patients with APECED compared to healthy controls. The fraction of was reduced in patients with APECED while that of spp. and several gram-negative genera previously implicated in biofilm formation, e.g. and antibodies (ASCA) and severity of gastrointestinal symptoms. Conclusions Gut microbiota of patients with APECED is altered and enriched with predominantly gram-negative bacterial taxa that may promote biofilm formation and lead to increased exposure to LPS in the patients. The most pronounced alterations in the microbiota were associated with more severe gastrointestinal symptoms. Keywords: dysbiosis, gut microbiota, immune dysregulation, lps, autoantibodies, atopobium, faecalibacterium, autoimmunity Highlights APECED is a rare autoimmune disease caused by mutations in the Autoimmune Regulator gene. A significant proportion of patients have gastrointestinal symptoms, including malabsorption, Palmitic acid chronic diarrhea, and obstipation that lead to decrease in the quality of life. The pathological background of the gastrointestinal symptoms remains incompletely understood. We have previously found that patients with APECED have increased immune responses against gut commensals, but previous smaller studies have found only small alterations Palmitic acid in the microbiota of the gut of the patients. Our objective was to evaluate whether the intestinal microbiota composition differs between patients with APECED (N=15) and healthy controls, and whether these are associated with the patients clinical phenotype and gastrointestinal symptoms. We found both alpha- and beta-diversity to be altered in patients with APECED compared to healthy controls. Several gram-negative genera previously implicated in biofilm formation were increased in patients, in parallel with lipopolysaccharide (LPS) synthesis in imputed metagenomics. Interestingly, the most pronounced changes in the microbiota were associated with more severe?gastrointestinal symptoms in patients with APECED, suggesting that gut microbiota is a factor to consider when contemplating therapy. Introduction APECED (autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy, OMIM #240300) is a rare autoimmune disease caused by autosomal recessive mutations in the gene encoding the Autoimmune Regulator (AIRE) (1). AIRE is expressed in medullary thymic epithelial cells where it regulates the expression of tissue-restricted antigens, most likely contributing to thymic negative selection. The lack of a fully functioning AIRE leads to autoimmunity against multiple endocrine organs, resulting in hormonal deficiencies of which hypoparathyroidism and primary adrenal Rabbit polyclonal to EpCAM insufficiency are the most common manifestations (1). Practically all patients with APECED have neutralizing anti-cytokine antibodies some of which have been linked susceptibility to infections (2). A significant proportion of patients with APECED present with gastrointestinal (GI) symptoms, such Palmitic acid as malabsorption, chronic diarrhea, obstipation, and gastritis (3). The pathological background of the GI symptoms remains incompletely understood, but they have been attributed to multiple factors with autoimmunity being the most common underlying cause. About half of patients with APECED have autoimmunity against gut neuroendocrine cells associated with antibodies against tryptophan hydroxylase (TPH) (4). The loss of neuroendocrine cells leads to decreased serum serotonin levels, which in turn is associated with symptoms of obstipation (5). In addition, around a quarter of the patients exhibit autoimmunity against defensins, culminating in a loss of Paneth cells Palmitic acid (6). Anti-defensin antibodies are linked to gut microbiota dysbiosis in Aire?-/- mice and diarrhea in humans (6). Autoimmune hepatitis, gastritis, and exocrine pancreatic malfunction also affect patients GI health. We have previously detected anti-antibodies.