Serum I-FABP Detects Gluten Responsiveness in Adult Celiac Disease Patients on a Short-Term Gluten Challenge

The follow-up of patients with celiac disease

Celiac disease (CD) is a very common immune-mediated enteropathy resulting from the interaction between dietary gluten and the immune system in genetically predisposed individuals. The immune response leads to intestinal damage, malabsorption and, ultimately, to a broad spectrum of both intestinal and extra-intestinal symptoms. According to current criteria, a proper diagnosis of CD requires an initial phase consisting of clinical case identification and serological screening that, over time, has increased in importance. In most adults and in selected children, the diagnosis is subsequently defined by histological evidence of intestinal damage as a confirmatory test, which usually returns to normal after a suitable period of a gluten-free diet (GFD). The clinical remission and disappearance of circulating antibodies after a GFD further confirm the diagnosis and represent a goal to be achieved to improve the quality of life and reduce the risk of long-term complications. However, although the diagnostic criteria for CD are well defined and described in specific guidelines, the monitoring of CD patients undergoing GFD has been less studied and, consequently, specific guidelines for this phase are still lacking. The aim of this report was to evaluate the classical tools used to monitor the adherence and response to GFD, other non-invasive biomarkers that have been proposed for CD monitoring, and the histological follow-up of CD patients in order to provide a starting point for future discussions on this specific topic.

Past, Present, and Future of Noninvasive Tests to Assess Gluten Exposure, Celiac Disease Activity, and End-Organ Damage

Although many biomarkers have been proposed, and several are in widespread clinical use, there is no single readout or combination of readouts that correlates tightly with gluten exposure, disease activity, or end-organ damage in treated patients with celiac disease. Challenges to developing and evaluating better biomarkers include significant interindividual variability-related to immune amplification of gluten exposure and how effects of immune activation are manifest. Furthermore, the current "gold standard" for assessment of end-organ damage, small intestinal biopsy, is itself highly imperfect, such that a marker that is a better reflection of the "ground truth" may indeed appear to perform poorly. The goal of this review was to analyze past and present efforts to establish robust noninvasive tools for monitoring treated patients with celiac disease and to highlight emerging tools that may prove to be useful in clinical practice.

Global Approach to Follow-Up of Celiac Disease

Celiac disease, an autoimmune disorder induced by the ingestion of gluten, affects approximately 1.4% of the population. Gluten damages the villi of the small intestine, producing symptoms such as abdominal pain, bloating and a subsequent loss of nutrient absorption, causing destabilization of the nutritional status. Moreover, gluten can trigger extra intestinal symptoms, such as asthma or dermatitis, but also mental disorders such as depression or anxiety. Moreover, people suffering from celiac disease sometimes feel misunderstood by society, mainly due to the lack of knowledge about the disease and the gluten-free diet. Thus, the treatment and follow-up of patients with celiac disease should be approached from different perspectives, such as the following: (1) a clinical perspective: symptomatology and dietary adherence monitorization; (2) nutritional assessment: dietary balance achievement; (3) psychological assistance: mental disorders avoidance; and (4) social inclusion: educating society about celiac disease in order to avoid isolation of those with celiac disease. The aim of this narrative review is to gain deep insight into the different strategies that currently exist in order to work on each of these perspectives and to clarify how the complete approach of celiac disease follow-up should be undertaken so that the optimum quality of life of this collective is reached.

Monitoring patients with celiac disease on gluten free diet: different outcomes comparing three tissue transglutaminase IgA assays

OBJECTIVES

Tissue transglutaminase (tTG) IgA antibodies are a hallmark for celiac disease (CD). In CD patients on gluten free diet (GFD) these antibodies are transient. Few studies are available comparing the tTG-IgA assay characteristics for monitoring response to GFD. Since discrepant results were reported in patients on GFD after switching tTG-IgA assays, we conducted a retrospective observational study to monitor GFD response using three different tTG-IgA assays.

METHODS

Diagnostic samples from 44 adults and 17 children with CD were included. Of most patients two follow-up samples after introduction of GFD were available. In all samples tTG-IgA were assessed using one fluorochrome-enzyme immuno-assay (FEIA) and two chemiluminescence immuno-assays (CLIA) and intestinal fatty acid binding protein (i-FABP) as surrogate marker for intestinal epithelial damage was measured.

RESULTS

Using CLIA assays, normalization of antibody levels was delayed compared to FEIA (p<0.001). Of all samples taken after at least 6 months on GFD with elevated i-FABP indicating intestinal epithelial damage, 40 % had positive tTG-IgA according to the FEIA, 85 and 90 % according to the two CLIA.

CONCLUSIONS

Normalization of tTG-IgA in patients on GFD depends on the assay used. Both CLIA appear to be more sensitive in detecting suboptimal treatment response in CD-indicated by elevated i-FABP - when applying the manufacturer's recommended cut-off for the diagnosis of CD.

Gastrointestinal cell injury and perceived symptoms after running the Boston Marathon

Gastrointestinal (GI) disturbances are a prevalent cause of marathon related complaints, and in extreme cases can promote life-threatening conditions such as exertional heat stroke. Our aim was to study intestinal cell injury [via intestinal fatty acid binding protein (I-FABP)] and perceived GI distress symptoms among marathon runners. We also examined potential risk factors (e.g., inadequate sleep) that could exacerbate GI disturbances in healthy, trained endurance runners. This was a parallel mixed-methods study design. 2019 Boston Marathon participants were recruited via email and subjects completed surveys before the race describing demographics and training history. Participants completed a GI questionnaire to assess presence and severity of symptoms, a survey regarding risk factors (e.g., recent illness, medications) that could promote GI disturbances, and provided a urine sample at three time points (immediately pre-race, post-race, and 24-h post-race). Due to weather, blood samples were only collected immediately and 24-h post-race. A total of 40 runners (males: n = 19, age = 44.9 ± 10.8 years; females: n = 21, age = 44.8 ± 10.6 years) completed this study. I-FABP significantly decreased from post-race (3367.5 ± 2633.5 pg/mL) to 24-h post-race (1657.3 ± 950.7 pg/mL, t (39) = -4.228, p < .001, d = -.669). There was a significant difference in overall GI symptom scores across the three time points (F (2, 39) = 41.37, p < .001). The highest average score occurred post-race (.84 ± .68), compared to pre-race (.09 ± .12) and 24-h post-race (.44 ± .28). Post-race I-FABP (r = .31, p = .048) and post-race urine specific gravity (r = .33, p = .041) were significantly correlated with post-race GI symptom scores. Our study provides further support to the individualized nature of GI disturbances, with participants experiencing a wide range of risk factors that can influence the extent of GI damage and perceived symptoms during and after exercise.

sCD14 and Intestinal Fatty Acid Binding Protein Are Elevated in the Serum of Patients With Idiopathic Anaphylaxis

BACKGROUND

Intestinal epithelial integrity compromise has been identified in gastrointestinal (GI), atopic, and autoimmune diseases.

OBJECTIVE

Episodes of idiopathic anaphylaxis (IA) are often accompanied by GI manifestations. We, therefore, sought to determine whether surrogate markers of GI permeability were aberrant in this patient population.

METHODS

Serum concentrations of zonulin, intestinal fatty acid binding protein (I-FABP), and soluble CD14 (sCD14) measured in 54 patients with IA were compared with concentrations in healthy controls (HCs); and correlated with clinical and laboratory parameters.

RESULTS

The I-FABP was elevated in sera of patients with IA compared with HCs (median 1,378.0 pg/mL vs 479.0 pg/mL, respectively; P < .001). The sCD14 was also elevated compared with HCs (median 2,017.0 ng/mL and 1,189.0 ng/mL, respectively; P < .001), whereas zonulin was comparable between patients with IA and HCs (median 49.6 ng/mL vs 52.4 ng/mL, respectively; P = .40). The I-FABP was elevated in patients with IA who experienced vomiting and/or diarrhea compared with patients with IA who did not (P = .0091).

CONCLUSIONS

The I-FABP and sCD14 are elevated in the serum of patients with IA. Elevations in these biomarkers of IA provides evidence that increased GI permeability, as is observed in other allergic conditions such as food allergy, is a common finding in those with IA and offers possible insight into the pathogenesis of this disease.

Intestinal fatty acid binding protein (I-FABP) and CXC3L1 evaluation as biomarkers for patients at high-risk for coeliac disease in Johannesburg, South Africa

Coeliac disease (CD) is an autoimmune disorder and one of the few gastroenteropathies with accurate serological testing. CD serology has decreased accuracy for patients on a gluten-free diet and for monitoring mucosal healing. New ancillary tests would, therefore, be useful. Intestinal Fatty Acid Binding Protein (I-FABP) and CX3CL1 (Fractalkine) are two promising biomarkers for CD but haven't been examined in patients who are at a high-risk for CD such as patients with type one diabetes (TID). This study, therefore, aimed to investigate serum levels of I-FABP and CX3CL1 in a cohort of South African patients with TID at a high-risk of developing CD. The serum I-FABP levels were significantly higher in CD-positive patients compared to CD-negative individuals (p = 0.03). No significant differences in the serum CX3CL1 levels were detected although this may reflect the impact of the comorbid autoimmune diseases had on the serum CX3CL1 levels. In conclusion, this study is the first to assess the levels of these biomarkers in a multiethnic population with comorbid autoimmune disease and determined I-FABP to be the more promising biomarker in such clinical contexts. Future research should focus on a diverse biomarker panel and longitudinal follow-up of patients at a high-risk for CD.

Coeliac disease

Coeliac disease is an autoimmune disorder that primarily affects the small intestine, and is caused by the ingestion of gluten in genetically susceptible individuals. Prevalence in the general population ranges from 0·5% to 2%, with an average of about 1%. The development of the coeliac enteropathy depends on a complex immune response to gluten proteins, including both adaptive and innate mechanisms. Clinical presentation of coeliac disease is highly variable and includes classical and non-classical gastrointestinal symptoms, extraintestinal manifestations, and subclinical cases. The disease is associated with a risk of complications, such as osteoporosis and intestinal lymphoma. Diagnosis of coeliac disease requires a positive serology (IgA anti-transglutaminase 2 and anti-endomysial antibodies) and villous atrophy on small-intestinal biopsy. Treatment involves a gluten-free diet; however, owing to the high psychosocial burden of such a diet, research into alternative pharmacological treatments is currently very active.

Intestinal fatty acid binding protein is a disease biomarker in paediatric coeliac disease and Crohn's disease

Background

There is a clinical need to develop biomarkers of small bowel damage in coeliac disease and Crohn’s disease. This study evaluated intestinal fatty acid binding protein (iFABP), a potential biomarker of small bowel damage, in children with coeliac disease and Crohn’s disease.

Methods

The concentration iFABP was measured in plasma and urine of children with ulcerative colitis, coeliac disease, and Crohn’s disease at diagnosis and from the latter two groups after treatment with gluten free diet (GFD) or exclusive enteral nutrition (EEN), respectively. Healthy children (Controls) were also recruited.

Results

138 children were recruited. Plasma but not urinary iFABP was higher in patients with newly diagnosed coeliac disease than Controls (median [Q1, Q3] coeliac disease: 2104 pg/mL 1493, 2457] vs Controls: 938 pg/mL [616, 1140], p = 0.001). Plasma or urinary iFABP did not differ between patients with coeliac on GFD and Controls. Baseline iFABP in plasma decreased by 6 months on GFD (6mo GFD: 1238 pg/mL [952, 1618], p = 0.045). By 12 months this effect was lost, at which point 25% of patients with coeliac disease had detectable gluten in faeces, whilst tissue transglutaminase IgA antibodies (TGA) continued to decrease. At diagnosis, patients with Crohn’s disease had higher plasma iFABP levels than Controls (EEN Start: 1339 pg/mL [895, 1969] vs Controls: 938 pg/mL [616, 1140], p = 0.008). iFABP did not differ according to Crohn’s disease phenotype. Induction treatment with EEN tended to decrease (p = 0.072) iFABP in plasma which was no longer different to Controls (EEN End: 1114 pg/mL [689, 1400] vs Controls: 938 pg/mL [616, 1140], p = 0.164). Plasma or urinary iFABP did not differ in patients with ulcerative colitis from Controls (plasma iFABP, ulcerative colitis: 1309 pg/mL [1005, 1458] vs Controls: 938 pg/mL [616, 1140], p = 0.301; urinary iFABP ulcerative colitis: 38 pg/mg [29, 81] vs Controls: 53 pg/mg [27, 109], p = 0.605).

Conclusions

Plasma, but not urinary iFABP is a candidate biomarker with better fidelity in monitoring compliance during GFD than TGA. The role of plasma iFABP in Crohn’s disease is promising but warrants further investigation.

Trial registration: Clinical Trials.gov, NCT02341248. Registered on 19/01/2015.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-022-02334-6.

Celiac Disease Revisited

Celiac disease (CD) is a systemic disease triggered by gluten ingestion in genetically predisposed individuals. It manifests primarily as an autoimmune enteropathy associated with specific circulating autoantibodies and a human leukocyte antigen haplotype (HLA-DQ2 or HLA-DQ8). It afflicts roughly 1% of the population, though the majority of patients remain undiagnosed. Diarrhea and malabsorption are classic manifestations of CD; however, both children and adults can be paucisymptomatic and present extraintestinal manifestations such as anemia, osteoporosis, and abnormal liver tests. CD screening is not recommended for the general population, and it should be focused on high-risk groups. CD diagnosis is challenging and relies on serological tests, duodenal histology, and genetic testing. Particularly difficult presentations to manage are seronegative patients, seropositive patients without villus atrophy, and patients who have started a gluten-free diet before the diagnostic workup. The only proven treatment is a lifelong gluten-free diet. We present an in-depth review on the physiopathology and management of CD, with a particular emphasis on diagnostic challenges.

Monocyte transcriptomes from patients with axial spondyloarthritis reveal dysregulated monocytopoiesis and a distinct inflammatory imprint

BACKGROUND

In patients with axial spondyloarthritis (axSpA), monocytes show a pre-activated phenotype. Gut inflammation is a trigger of monocyte activation and may also affect their development in the bone marrow (BM). As gut inflammation is commonly observed in axSpA patients, we performed a detailed analysis of monocyte transcriptomes of axSpA patients in two cohorts and searched for signs of activation and developmental adaptations as putative imprints of gut inflammation.

METHODS

Transcriptomes of blood CD14+ monocytes of HLA-B27+ axSpA patients and healthy controls (HC) were generated by microarrays from cohort 1 and by RNA-sequencing from cohort 2. Differentially expressed genes from both analyses were subjected to gene set enrichment analysis (GSEA) and to co-expression analysis in reference transcriptomes from BM cells, blood cells and activated monocytes. As serological markers of translocation, 1,3 beta-glycan, intestinal fatty acid binding protein, and lipopolysaccharide binding protein (LBP) were determined by LAL and ELISA.

RESULTS

Transcriptome analysis identified axSpA-specific monocyte signatures showing an imprint of LPS/cytokine-activated monocytes, late granulopoietic BM cells, blood neutrophils, and G-CSF-mobilized blood cells, which suggests LPS/TNF activation and more prominent BM adaptation promoting a neutrophil-like phenotype. GSEA mapped axSpA upregulated genes to inflammatory responses and TNFα signaling and downregulated probe-sets to metabolic pathways. Among translocation markers, LBP levels were significantly increased in axSpA patients vs. HC (p < 0.001). Stratified analysis by disease activity and stage identified an "active disease signature" (BASDAI ≥ 4) with an imprint of LPS/cytokine-activated monocytes and CD16+ monocyte subsets. The "AS signature" (vs. non-radiographic axSpA) showed a reinforced neutrophil-like phenotype due to deprivation of dendritic cell transcripts.

CONCLUSIONS

The neutrophil-like phenotype of axSpA monocytes points towards a biased monocytopoiesis from granulocyte-monocyte progenitors. This shift in monocytopoiesis and the LPS/cytokine imprint as well as the elevated LBP levels are indicators of systemic inflammation, which may result from bacterial translocation. The BM adaptation is most prominent in AS patients while disease activity appears to be linked to activation and trafficking of monocytes.

Accuracy of citrulline, I-FABP and D-lactate in the diagnosis of acute mesenteric ischemia

Early diagnosis of acute mesenteric ischemia (AMI) remains a clinical challenge, and no biomarker has been consistently validated. We aimed to assess the accuracy of three promising circulating biomarkers for diagnosing AMI-citrulline, intestinal fatty acid-binding protein (I-FABP), and D-lactate. A cross-sectional diagnostic study enrolled AMI patients admitted to the intestinal stroke center and controls with acute abdominal pain of another origin. We included 129 patients-50 AMI and 79 controls. Plasma citrulline concentrations were significantly lower in AMI patients compared to the controls [15.3 μmol/L (12.0-26.0) vs. 23.3 μmol/L (18.3-29.8), p = 0.001]. However, the area under the receiver operating curves (AUROC) for the diagnosis of AMI by Citrulline was low: 0.68 (95% confidence interval = 0.58-0.78). No statistical difference was found in plasma I-FABP and plasma D-lactate concentrations between the AMI and control groups, with an AUROC of 0.44, and 0.40, respectively. In this large cross-sectional study, citrulline, I-FABP, and D-lactate failed to differentiate patients with AMI from patients with acute abdominal pain of another origin. Further research should focus on the discovery of new biomarkers.

Diagnosing coeliac disease: A literature review

Coeliac disease (CD) is an autoimmune gastroenteropathy triggered by gliadin and gliadin-tissue transglutaminase (tTG) complexes. CD is one of the few autoimmune diseases with an accurate, non-invasive serological test. Anti-endomysial, anti-tTG and anti-deaminated gliadin peptides (DGP) antibodies are currently used for serological tests with tTG ELISAs being the superior test. Duodenal biopsy, although invasive, is the gold standard for CD diagnosis. HLA genotyping and flow cytometry can also be used as supplementary tests. The incidence of CD is rising globally although the reasons for this remain unclear. In addition, the true incidence of coeliac disease in African populations remains unknown although recent work suggests that South African populations express the alleles associated with this disease. This review examines the pathogenesis and diagnosis of coeliac disease and considers novel and innovative biomarkers in its diagnosis specifically in an African population.

Apolipoprotein A4 Defines the Villus-Crypt Border in Duodenal Specimens for Celiac Disease Morphometry

Histological evaluation of the small intestinal mucosa is the cornerstone of celiac disease diagnostics and an important outcome in scientific studies. Gluten-dependent injury can be evaluated either with quantitative morphometry or grouped classifications. A drawback of mucosal readings is the subjective assessment of the border where the crypt epithelium changes to the differentiated villus epithelium. We studied potential immunohistochemical markers for the detection of the villus-crypt border: apolipoprotein A4 (APOA4), Ki-67, glucose transporter 2, keratin 20, cytochrome P450 3A4 and intestinal fatty-acid binding protein. Among these, villus-specific APOA4 was chosen as the best candidate for further studies. Hematoxylin-eosin (H&E)- and APOA4 stained duodenal biopsy specimens from 74 adult patients were evaluated by five observers to determine the villus-to-crypt ratio (VH : CrD). APOA4 delineated the villus to crypt epithelium transition clearly, and the correlation coefficient of VH : CrD values between APOA4 and H&E was excellent (r=0.962). The VH : CrD values were lower in APOA4 staining (p<0.001) and a conversion factor of 0.2 in VH : CrD measurements was observed to make the two methods comparable to each other. In the intraobserver analysis, the doubled standard deviations, representing the error ranges, were 0.528 for H&E and 0.388 for APOA4 staining, and the ICCs were 0.980 and 0.971, respectively. In the interobserver analysis, the average error ranges were 1.017 for H&E and 0.847 for APOA4 staining, and the ICCs were better for APOA4 than for H&E staining in all analyses. In conclusion, the reliability and reproducibility of morphometrical VH : CrD readings are improved with the use of APOA4 staining.

Intestinal Fatty Acid Binding Protein Levels in Pediatric Celiac Patients in Transition From Active Disease to Clinical and Serological Remission

Celiac disease (CD) is increasingly diagnosed without endoscopy. As such, the need for accurate serological markers to aid in the diagnosis and follow-up of CD has increased. Intestinal fatty acid binding protein (I-FABP) is a cytosolic protein present in enterocytes, whose blood levels reflect mucosal damage in a reliable and quantifiable way. The aim of this study was to compare I-FABP levels in newly diagnosed patients with CD and to examine changes in levels following 6 months of gluten-free diet (GFD).

Methods

A prospective observational case control study of pediatric patients diagnosed with CD, with measurements of tissue transglutaminase IgA (TTG-IgA) and I-FABP levels at diagnosis and after 6 months of gluten free diet were compared to a control group of nonceliac patients.

Results

This study included 35 patients and 32 controls. The CD group had higher I-FABP levels at diagnosis compared with the control group (median 641.7 pg/mL versus 334 pg/mL; P < 0.05). I-FABP levels significantly differed between patients presenting with TTG-IgA level 3-10 times the upper limit of normal (ULN) compared with those presenting with values >10 times ULN (median 432.2 pg/mL versus 796.2 pg/mL; P < 0.05). Patients with CD had a significant decrease in median I-FABP levels after 6 months of GFD (median 268.2 pg/mL), paralleling a decrease in TTG-IgA and GFD adherence.

Conclusions

I-FABP levels are increased in patients with CD at diagnosis compared with controls and decrease significantly while patients adhere to GFD.

Evaluating Responses to Gluten Challenge: A Randomized, Double-Blind, 2-Dose Gluten Challenge Trial

BACKGROUND & AIMS

Gluten challenge is used to diagnose celiac disease (CeD) and for clinical research. Sustained gluten exposure reliably induces histologic changes but is burdensome. We investigated the relative abilities of multiple biomarkers to assess disease activity induced by 2 gluten doses, and aimed to identify biomarkers to supplement or replace histology.

METHODS

In this randomized, double-blind, 2-dose gluten-challenge trial conducted in 2 US centers (Boston, MA), 14 adults with biopsy-proven CeD were randomized to 3 g or 10 g gluten/d for 14 days. The study was powered to detect changes in villous height to crypt depth, and stopped at planned interim analysis on reaching this end point. Additional end points included gluten-specific cluster of differentiation (CD)4 T-cell analysis with HLA-DQ2-gluten tetramers and enzyme-linked immune absorbent spot, gut-homing CD8 T cells, interleukin-2, symptoms, video capsule endoscopy, intraepithelial leukocytes, and tissue multiplex immunofluorescence.

RESULTS

All assessments showed changes with gluten challenge. However, time to maximal change, change magnitude, and gluten dose-response relationship varied. Villous height to crypt depth, video capsule endoscopy enteropathy score, enzyme-linked immune absorbent spot, gut-homing CD8 T cells, intraepithelial leukocyte counts, and HLA-DQ2-restricted gluten-specific CD4 T cells showed significant changes from baseline at 10 g gluten only; symptoms were significant at 3 g. Symptoms and plasma interleukin-2 levels increased significantly or near significantly at both doses. Interleukin-2 appeared to be the earliest, most sensitive marker of acute gluten exposure.

CONCLUSIONS

Modern biomarkers are sensitive and responsive to gluten exposure, potentially allowing less invasive, lower-dose, shorter-duration gluten ingestion. This work provides a preliminary framework for rational design of gluten challenge for CeD research. ClinicalTrials.gov number, NCT03409796.

Molecular Biomarkers for Celiac Disease: Past, Present and Future

Celiac disease (CeD) is a complex immune-mediated disorder that is triggered by dietary gluten in genetically predisposed individuals. CeD is characterized by inflammation and villous atrophy of the small intestine, which can lead to gastrointestinal complaints, malnutrition, and malignancies. Currently, diagnosis of CeD relies on serology (antibodies against transglutaminase and endomysium) and small-intestinal biopsies. Since small-intestinal biopsies require invasive upper-endoscopy, and serology cannot predict CeD in an early stage or be used for monitoring disease after initiation of a gluten-free diet, the search for non-invasive biomarkers is ongoing. Here, we summarize current and up-and-coming non-invasive biomarkers that may be able to predict, diagnose, and monitor the progression of CeD. We further discuss how current and emerging techniques, such as (single-cell) transcriptomics and genomics, can be used to uncover the pathophysiology of CeD and identify non-invasive biomarkers.

Noninvasive Biomarkers of Gut Barrier Function in Patients Suffering from Diarrhea Predominant-IBS: An Update

The intestinal barrier plays a crucial role in the absorption of nutrients and in preventing the entry of pathogenic microorganisms and toxic molecules. Several studies have shown a compromised intestinal barrier associated with low-grade inflammation in the small intestinal mucosa in celiac disease, inflammatory bowel disease, and irritable bowel syndrome (IBS), particularly in IBS with diarrhea (IBS-D). In light of these new data, IBS is no longer considered a functional disease but rather a heterogeneous syndrome that has yet to be carefully studied. Therefore, investigating the integrity and function of the intestinal barrier is now essential to improving knowledge of the pathophysiology of IBS-D and to improving the management of IBS-D patients. However, the study of the intestinal barrier must clarify some still unsolved methodological aspects and propose standardised assays before becoming a useful diagnostic tool. In this framework, this review will discuss data about the tests that noninvasively evaluate the integrity and functionality of the human intestinal barrier, paying particular attention to patients with IBS-D, in both clinical and research situations.

New celiac disease biomarkers

Advances in the knowledge regarding celiac disease have enabled the development of diagnostic markers, such as anti-tissue transglutaminase and anti-deaminated gliadin antibodies. The wide availability of these antibodies, genetic studies of HLA-DQ and duodenal biopsies constitute the pillars necessary for a definitive diagnosis. However, difficulties sometimes arise in both the diagnosis and follow-up of celiac patients, which cannot be resolved using these tools. This article reviews the scientific evidence and possible clinical utility of different biomarkers. This review is structured according to biomarkers that have been evaluated pathophysiologically in relation to intestinal damage or immune response and their potential clinical utility in the diagnosis and follow-up of celiac disease patients.

An open-label randomised pilot trial on safety of wheat variety C273 in patients with adult celiac disease

BACKGROUND

The only effective treatment for celiac disease (CeD) is gluten free diet (GFD). However, GFD is restrictive and efforts are being made to explore alternative therapies including safer wheat varieties. Wheat variety C273 has been previously identified to have reduced load of intact T-cell stimulatory epitopes via in silico and in vitro analysis.

METHODS

Adult patients diagnosed with CeD and recovered on GFD were included in the study. Patients were randomised into two groups in a 2:1 ratio. Patients in group I had graded introduction of C273 wheat in diet, maintained for 24 weeks; in Group II, wheat was restricted with continuation of GFD. Clinical symptoms, serology [anti-tissue transglutaminase (anti-tTG), anti-endomysial antibody (anti-EMA)], circulating inflammatory biomarkers [intestinal fatty-acid binding protein (I-FABP), plasma citrulline, interferon-γ (IFN-γ)] and histology were evaluated periodically. Final evaluation was performed at week 28.

RESULTS

A total of 15 patients were enrolled (Group I: n = 10, Group II: n = 5). All patients except two in Group I remained compliant. None of the remaining eight patients in group I developed symptoms. No significant changes in serology (anti-tTG, anti-EMA) and histology were observed between the two groups at 28 weeks (p > 0.05). Significant changes in plasma citrulline(29.87 ± 8.98 versus 36.58 ± 3.09, p = 0.049) and IFN-γ (44.56 ± 9.74 versus 33.50 ± 3.68; p = 0.031) were observed in Group I.

CONCLUSION

Consumption of C273 wheat did not result in development of symptoms or evident changes in serology and histology at 28 weeks. However, variations in circulating inflammatory markers were noted. Larger randomised trials are needed to corroborate these findings.

CLINICAL TRIALS REGISTRY-INDIA

CTRI/2018/06/014521.

Coeliac Disease Pathogenesis: The Uncertainties of a Well-Known Immune Mediated Disorder

Coeliac disease is a common small bowel enteropathy arising in genetically predisposed individuals and caused by ingestion of gluten in the diet. Great advances have been made in understanding the role of the adaptive immune system in response to gluten peptides. Despite detailed knowledge of these adaptive immune mechanisms, the complete series of pathogenic events responsible for development of the tissue lesion remains less certain. This review contributes to the field by discussing additional mechanisms which may also contribute to pathogenesis. These include the production of cytokines such as interleukin-15 by intestinal epithelial cells and local antigen presenting cells as a pivotal event in the disease process. A subset of unconventional T cells called gamma/delta T cells are also persistently expanded in the coeliac disease (CD) small intestinal epithelium and recent analysis has shown that these cells contribute to pathogenic inflammation. Other unconventional T cell subsets may play a local immunoregulatory role and require further study. It has also been suggested that, in addition to activation of pathogenic T helper cells by gluten peptides, other peptides may directly interact with the intestinal mucosa, further contributing to the disease process. We also discuss how myofibroblasts, a major source of tissue transglutaminase and metalloproteases, may play a key role in intestinal tissue remodeling. Contribution of each of these factors to pathogenesis is discussed to enhance our view of this complex disorder and to contribute to a wider understanding of chronic immune-mediated disease.

The Role of Gastrointestinal-Related Fatty Acid-Binding Proteins as Biomarkers in Gastrointestinal Diseases

The fatty acid-binding proteins play a major role in intracellular transportation of long-chain fatty acids. Nine fatty acid-binding proteins have been identified, with each having individual tissue-specific functions in addition to regulation of fatty acids. This review focuses on the three fatty acid-binding proteins found in the gastrointestinal tract and discusses their role as diagnostic or disease monitoring markers in neonatal necrotizing enterocolitis, acute mesenteric ischemia, celiac disease, and inflammatory bowel disease. Of these three fatty acid-binding proteins, intestinal fatty acid-binding protein is of the most interest due to its exclusive expression in the gastrointestinal tract. The elevation of intestinal fatty acid-binding protein in blood and urine reflects enterocyte damage, regardless of the underlying cause. The short half-life of intestinal fatty acid-binding protein also means it is a relatively sensitive marker. In contrast, there is currently less evidence to support liver fatty acid-binding protein and ileal bile acid-binding protein as sensitive biomarkers in these conditions. More extensive studies with specific endpoints are required to validate the roles of these fatty acid-binding proteins in gastrointestinal diseases.

Non-Invasive Biomarkers for Celiac Disease

Once thought to be uncommon, celiac disease has now become a common disease globally. While avoidance of the gluten-containing diet is the only effective treatment so far, many new targets are being explored for the development of new drugs for its treatment. The endpoints of therapy include not only reversal of symptoms, normalization of immunological abnormalities and healing of mucosa, but also maintenance of remission of the disease by strict adherence of the gluten-free diet (GFD). There is no single gold standard test for the diagnosis of celiac disease and the diagnosis is based on the presence of a combination of characteristics including the presence of a celiac-specific antibody (anti-tissue transglutaminase antibody, anti-endomysial antibody or anti-deamidated gliadin peptide antibody) and demonstration of villous abnormalities. While the demonstration of enteropathy is an important criterion for a definite diagnosis of celiac disease, it requires endoscopic examination which is perceived as an invasive procedure. The capability of prediction of enteropathy by the presence of the high titer of anti-tissue transglutaminase antibody led to an option of making a diagnosis even without obtaining mucosal biopsies. While present day diagnostic tests are great, they, however, have certain limitations. Therefore, there is a need for biomarkers for screening of patients, prediction of enteropathy, and monitoring of patients for adherence of the gluten-free diet. Efforts are now being made to explore various biomarkers which reflect different changes that occur in the intestinal mucosa using modern day tools including transcriptomics, proteomics, and metabolomics. In the present review, we have discussed comprehensively the pros and cons of available biomarkers and also summarized the current status of emerging biomarkers for the screening, diagnosis, and monitoring of celiac disease.

(Outcome) Measure for (Intervention) Measures: A Guide to Choosing the Appropriate Noninvasive Clinical Outcome Measure for Intervention Studies in Celiac Disease

There is an unmet need for diagnostic and treatment interventions for celiac disease. Both clinical trials and real-world studies require careful selection of clinical outcome measures. Often, neither serology nor histology is an appropriate primary outcome. This article reviews various measures of intestinal function and nutrition, patient-reported outcome measures for symptoms and for health-related quality of life, and measures of sickness burden as they apply to intervention studies for celiac disease. A series of case studies is presented to illustrate key considerations in selecting outcome measures for dietary interventions, pharmacologic interventions, and real-world studies.

Comparison of Clinical Methods With the Faecal Gluten Immunogenic Peptide to Assess Gluten Intake in Coeliac Disease

OBJECTIVES

Detection of faecal gluten immunogenic peptides (GIP) is a biomarker of recent gluten consumption. GIP levels can be used to monitor gluten intake and compliment clinical methods to evaluate compliance to gluten-free diet (GFD). In the present study, recent gluten intake was measured by GIP in children with coeliac disease (CD) and compared to routine clinical measures to evaluate GFD compliance.

METHODS

GIP was measured in 90 samples from 63 CD children (44 previously and 19 newly diagnosed with follow-up samples at 6 and 12 months on GFD). Compliance to GFD was evaluated based on clinical assessment, tissue transglutaminase (tTG) levels, and Biagi score.

RESULTS

GIP was detectable in 16% of patients with previous CD diagnosis on GFD. Body mass index z score (P = 0.774), height z score (P = 0.723), haemoglobin concentration (P = 0.233), age (P = 0.448), sex (P = 0.734), or disease duration (P = 0.488) did not differ between those with detectable and nondetectable GIP. In newly diagnosed patients, on gluten-containing diet, GIP was detectable in 95% of them. Following GFD initiation, GIP decreased (P < 0.001); 17% and 27% had detectable levels at 6 and 12 months, respectively. Compared to GIP, the Biagi score, tTG, and clinical assessment presented sensitivity of 17%, 42%, and 17%, respectively. Likewise, GIP was detectable in 16%, 16%, and 14% of patients evaluated as GFD compliant according to the Biagi score, tTG, and clinical assessment, respectively. A combination of methods did not improve identification of patients who were noncompliant.

CONCLUSIONS

Inclusion of faecal GIP measurements is likely to improve identification of GFD recent noncompliance in CD management and could be incorporated into current follow-up strategies.

The Role of a Low Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyol Diet in Nonceliac Gluten Sensitivity

Background

Nonceliac gluten sensitivity (NCGS) is a recently defined clinical entity characterized by intestinal and extraintestinal symptoms associated with gluten ingestion in individuals in whom celiac disease (CD) or wheat allergy (WA) has been excluded. Despite its name and definition, gluten has been shown to precipitate symptoms in only 16–30% of these patients. In addition to gluten, other components of wheat, including fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs), alpha-amylase trypsin inhibitors (ATIs) and wheat germ agglutinin have been implicated in the causation of the symptoms of NCGS, with FODMAPs garnering the most attention. We present a review of the existing literature evaluating the role of FODMAPs in NCGS symptomatology.

Methods

A systematic review of PubMed, Cochrane, EMBASE, and Google Scholar for keywords fructans, non-celiac gluten sensitivity, NCGS, FODMAPs, and gluten-free diet (GFD) was conducted through a series of advanced searches. Articles related to the use of fructans or FODMAPs were analyzed.

Results

FODMAPs were found to be associated with gastrointestinal and extraintestinal symptoms in NCGS.

Conclusions

A low FODMAP diet has potential for improvement of clinical symptoms in NCGS. In addition, some evidence suggests an additional benefit to simultaneous adherence to both low FODMAP diet and GFD.

Characterization of the Small Intestinal Lesion in Celiac Disease by Label-Free Quantitative Mass Spectrometry

Global characterization of tissue proteomes from small amounts of biopsy material has become feasible because of advances in mass spectrometry and bioinformatics tools. In celiac disease (CD), dietary gluten induces an immune response that is accompanied by pronounced remodeling of the small intestine. Removal of gluten from the diet abrogates the immune response, and the tissue architecture normalizes. In this study, differences in global protein expression of small intestinal biopsy specimens from CD patients were quantified by analyzing formalin-fixed, paraffin-embedded material using liquid chromatography-mass spectrometry and label-free protein quantitation. Protein expression was compared in biopsy specimens collected from the same patients before and after 1-year treatment with gluten-free diet (n = 10) or before and after 3-day gluten provocation (n = 4). Differential expression of proteins in particular from mature enterocytes, neutrophils, and plasma cells could distinguish untreated from treated CD mucosa, and Ig variable region IGHV5-51 expression was found to serve as a CD-specific marker of ongoing immune activation. In patients who had undergone gluten challenge, coordinated up-regulation of wound response proteins, including the CD autoantigen transglutaminase 2, was observed. Our study provides a global and unbiased assessment of antigen-driven changes in protein expression in the celiac intestinal mucosa.

The acute effects on duodenal gene expression in healthy men following consumption of a low-fat meal enriched with theobromine or fat

Increasing apoA-I synthesis may improve HDL functionality and lower CVD risk. As theobromine and fat increase fasting apoA-I concentrations, and the intestine is involved in apoA-I production, the acute effects of both were studied on duodenal gene transcription to better understand underlying mechanisms. In this crossover study, 8 healthy men received once a low fat (LF) meal, a LF meal plus theobromine (850 mg), or a high fat (HF) meal. Five hours after meal intake duodenal biopsies were taken for microarray analysis. Theobromine and HF consumption did not change duodenal apoA-I expression. Theobromine did not change gene expression related to lipid and cholesterol metabolism, whereas those related to glycogen/glucose breakdown were downregulated. HF consumption increased gene expression related to lipid and cholesterol uptake and transport, and to glucose storage, while it decreased those related to glucose uptake. Furthermore, genes related to inflammation were upregulated, but inflammation markers in plasma were not changed. In healthy men, acute theobromine and fat consumption did not change duodenal apoA-I mRNA, but inhibited expression of genes related to glucose metabolism. Furthermore, HF intake activated in the duodenum expression of genes related to lipid and cholesterol metabolism and to inflammation.

The Role of an IgA/IgG-Deamidated Gliadin Peptide Point-of-Care Test in Predicting Persistent Villous Atrophy in Patients With Celiac Disease on a Gluten-Free Diet

OBJECTIVES

Mucosal healing is important in celiac disease (CD) for the prevention of complications. However, obtaining duodenal biopsies is invasive, and there is currently no reliable surrogate marker for histological remission in clinical practice. We aimed to assess the role of a point-of-care test (POCT) based on IgA/IgG-deamidated gliadin peptide, in detecting persistent villous atrophy (VA) in CD.

METHODS

We prospectively recruited patients with CD attending endoscopy for the assessment of histological remission. All patients had IgA-endomysial (EMA) antibodies, IgA-tissue transglutaminase (TTG) antibodies, and the POCT performed, and completed a validated dietary adherence questionnaire. A gastroscopy was performed in all patients, with four biopsies taken from the second part of the duodenum and one from the duodenal bulb. We compared the diagnostic performance of the surrogate markers against duodenal histology as the reference standard.

RESULTS

A total of 217 patients with CD (70% female, age range 16-83 years, median age 53 years) on a gluten-free diet (median duration 6 years) were recruited from 2013 to 2017. Eighty-five (39.2%) patients had persistent VA. The sensitivities of the POCT, TTG, EMA, and the adherence score in detecting VA were 67.1%, 44.7%, 37.7%, and 24.7% respectively (P=0.0005). The combination of the POCT and adherence score only marginally increased the sensitivity to 70.6% (59.7-80.0%).

CONCLUSIONS

The sensitivity of the POCT was higher than the other surrogate markers in predicting VA. A POCT may provide the additional advantage of an immediate objective assessment of mucosal healing at the time of an office-based follow-up consultation.

Gluten-related disorders: certainties, questions and doubts

In the last decade, the ingestion of gluten, a heterogeneous complex of proteins present in wheat, rice, barley and probably in oats, has been associated with clinical disorders, such as celiac disease, wheat allergy and recently to non-celiac gluten sensitivity or wheat intolerance syndrome. Gluten-related disorders, which are becoming epidemiologically relevant with an estimated global prevalence of about 5%, require the exclusion of gluten from the diet. For the past 5 years, an important shift in the availability of gluten-free products, together with increased consumption in the general population, has been recorded and is estimated to be about 12-25%. Many people follow a self-prescribed gluten-free diet, despite the fact that the majority have not first been previously excluded, or confirmed, as having gluten disorders. They rely on claims that a gluten-free diet improves general health. In this review, we provide an overview of the clinical disorders related to gluten or wheat ingestion, pointing out the current certainties, open questions, possible answers and several doubts in the management of these conditions. KEY MESSAGE Incidence of gluten-related disorders is increased in the last decade and self-diagnosis is frequent with inappropriate starting of a gluten-free diet. Gluten and wheat are considered as the most important triggers to coeliac disease, wheat allergy and non-celiac gluten sensitivity. Pediatricians, allergologist and gastroenterologist are involved in the management of these conditions and appropriate diagnostic protocols are required.

Understanding Celiac Disease From Genetics to the Future Diagnostic Strategies

Celiac disease (CD) is an autoimmune disorder characterized by the permanent inflammation of the small bowel, triggered by the ingestion of gluten. It is associated with a number of symptoms, the most common being gastrointestinal. The prevalence of this illness worldwide is 1%. One of the main problems of CD is its difficulty to be diagnosed due to the various presentations of the disease. Besides, in many cases, CD is asymptomatic. Celiac disease is a multifactorial disease, HLA-DQ2 and HLA-DQ8 haplotypes are predisposition factors. Nowadays, molecular markers are being studied as diagnostic tools. In this review, we explore CD from its basic concept, manifestations, types, current and future methods of diagnosis, and associated disorders. Before addressing the therapeutic approaches, we also provide a brief overview of CD genetics and treatment.

Recent advances in pediatric celiac disease

The incidence of celiac disease (CD) has increased over the last half-century, resulting in rising interest in identifying risk factors for CD. The necessity of duodenal biopsies in the diagnosis of CD has recently been challenged. Areas covered: This review covers the recent literature regarding the role of infant feeding practices, including breastfeeding and timing of gluten introduction, and the microbiota in the development of CD. Additionally, the application of the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition guidelines for a non-biopsy approach to the diagnosis of CD is reviewed. Expert commentary: Recent investigations have not revealed any significant effect of breastfeeding or timing of gluten introduction on the risk of CD in at-risk populations. There are alterations in the microbiota of CD patients. However, the role of the microbiome and whether its manipulation has a clinical effect are unknown. Preliminary data suggests a non-biopsy approach to diagnosis of pediatric CD can be applied to several populations, although additional studies are needed. Prospective investigations are underway to examine the interplay of infant feeding practices and the microbiome and to identify particular CD-specific biomarkers that may aid in the diagnosis and ultimately prevention of CD.

Optimizing the diagnosis of celiac disease

PURPOSE OF REVIEW

The diagnostic approach in celiac disease is continuously evolving as our understanding of its pathophysiology improves. This review aims to provide a summary of contemporary work that supports optimization of the diagnosis of this common yet underdiagnosed condition.

RECENT FINDINGS

The recently updated National Institute of Clinical Excellence and European Society for Pediatric Gastroenterology, Hepatology, and Nutrition guidelines and the contentious biopsy-free diagnostic approach will be discussed. We will review the evidence advocating optimal biopsy techniques such as single bite biopsy and controversial bulb biopsy sampling to increase diagnostic yield. Recent data providing phenotypical characterization and clinical outcomes of celiac subtypes such as potential celiac disease, seronegative celiac disease and ultrashort celiac disease will be covered. We will present emerging evidence on novel case finding strategies with point of care tests. Promising novel markers for celiac disease such as serum intestinal fatty acid binding protein and in-vitro gluten challenge will be included.

SUMMARY

Recent work has demonstrated the clinical significance of the celiac disease subtypes, emphasizing the importance of careful diagnosis and recognition. There is a move toward a less invasive and perhaps more cost-effective diagnostic approach in celiac disease, but duodenal biopsy remains the gold standard at present for all adults and the majority of pediatric patients.

Soluble Syndecan-1: A Novel Biomarker of Small Bowel Mucosal Damage in Children with Celiac Disease

BACKGROUND

Syndecan-1 (SDC1) is essential for maintaining normal epithelial barrier. Shedding of SDC1 ectodomain, reflected by serum soluble syndecan-1 (SSDC1) levels, is regulated by inflammation. Increased intestinal permeability plays a central role in celiac disease (CD). The association between SSDC1 levels and mucosal damage in CD has not been evaluated.

AIMS

To evaluate serum SSDC1 levels in children with CD and to determine its relationship with histological grading classified by modified Marsh criteria.

METHODS

This is a cross-sectional, pilot study, in which serum SSDC1 was analyzed by ELISA in a cohort of 49 untreated children with CD and 15 children with nonspecific abdominal pain (AP). CD was diagnosed based on positive celiac serology and small intestinal biopsy. SSDC1 levels at the time of biopsy were correlated with Marsh grading. Controls were defined by AP, negative celiac serology, normal upper endoscopy, and small intestinal biopsies.

RESULTS

SSDC1 levels were significantly higher in CD patients compared to AP controls (116.2 ± 161 vs. 41.3 ± 17.5 ng/ml, respectively, p < 0.01). SSDC1 levels were significantly higher in patients with Marsh 3c lesion compared to AP controls (170.6 ± 201 vs. 41.3 ± 17.5 ng/ml, respectively, p < 0.05). SSDC1 concentrations displayed a significant correlation with mucosal damage defined by Marsh (r = 0.39, p < 0.05).

CONCLUSION

This is the first study demonstrating elevated levels of serum SSDC1 in children with CD. Our results suggest that SSDC1 is a potentially novel marker of intestinal mucosal damage in patients with CD. Its applicability as a surrogate biomarker in CD remains to be determined.

Suspected Nonceliac Gluten Sensitivity Confirmed in Few Patients After Gluten Challenge in Double-Blind, Placebo-Controlled Trials

A double-blind, placebo-controlled, gluten challenge has been proposed to confirm a diagnosis of nonceliac gluten sensitivity (NCGS) in patients without celiac disease who respond to a gluten-free diet. To determine the accuracy of this approach, we analyzed data from 10 double-blind, placebo-controlled, gluten-challenge trials, comprising 1312 adults. The studies varied in the duration of the challenge (range, 1 d to 6 wk), daily doses for the gluten challenge (range, 2-52 g; 3 studies administered <8 g/d), and composition of the placebo (gluten-free products, xylose, whey protein, rice, or corn starch containing fermentable carbohydrates). Most of the studies found gluten challenge to significantly increase symptom scores compared with placebo. However, only 38 of 231 NCGS patients (16%) showed gluten-specific symptoms. Furthermore, 40% of these subjects had a nocebo response (similar or increased symptoms in response to placebo). These findings reveal heterogeneity and potential methodology flaws among studies of gluten challenge, cast doubt on gluten as the culprit food component in most patients with presumptive NCGS, and highlight the importance of the nocebo effect in these types of studies.