Serum alkylresorcinols as biomarkers of dietary gluten exposure in coeliac disease

Selective determination of 3,5-dihydroxycinnamic acid in urine samples as gluten intake biomarker: high-performance thin-layer chromatography combined with colorimetric detection

The determination of biomarkers is a significant field of analytical chemistry research under continuous evolution that contributes to enhance diagnostics and enable more personalized medicine. Celiac disease is a systemic autoimmune disorder caused by the ingestion of gluten (Glu) proteins found in various cereals. Currently, the only effective way to prevent and manage potential complications is through a strict gluten-free diet (GFD). However, both intentional and unintentional dietary transgressions can occur, often leading to persistent symptoms and ineffective treatment. In this scenario, the development of analytical strategies to detect biomarkers of gluten intake and monitor adherence to a GFD is of significant interest. Herein, we present an analytical strategy based on high-performance thin-layer chromatography (HPTLC) combined with colorimetric detection to estimate 3,5-dihydroxycinnamic acid (3,5-DHCA) as selective biomarker of Glu intake in urine. The approach combined Fast Blue (FB)-doped polydimethylsiloxane (PDMS) membrane with colorimetric HPTLC (RP-C18) giving rise to a selective method to isolate 3,5-DHCA response in urine samples. Detection by visual inspection, image analysis, and spectroscopic response was evaluated and compared. Analytical parameters were estimated showing a good sensitivity (limit of detection (LOD) ≤ 0.8 mg L-1) and precision, relative standard deviation (RSD) values < 7%. Analysis of urine samples of celiac patients and control patients was performed, and recovery studies showed satisfactory values (R > 80%). The preliminary results indicated correlation between Glu intake and positive 3,5-DHCA responses. This study demonstrated that FB-doped PDMS membranes-HPTLC is a promising tool for detecting dietary transgressions to the GFD by visual inspection, and subsequent quantitative analysis by image analysis and spectroscopic techniques. Hence, the proposed analytical method contributes to the advance of knowledge about celiac disease, which still remains an important challenge to our society.

Plasma Alkylresorcinols is an objective biomarker for gluten intake in young children

BACKGROUND

Alkylresorcinols are a well-established biomarker for whole grain intake. There is evidence suggesting that total plasma alkylresorcinol concentration may also be used as a biomarker for gluten intake in adults.

OBJECTIVE

The aim of the study was to evaluate if total alkylresorcinol concentration is a valid biomarker for gluten intake in young children.

METHODS

Non-fasting plasma alkylresorcinol concentrations were analyzed by normal-phase ultra-high pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) in 65 children aged 18 months included in a randomized controlled trial. The intervention group was following a gluten-free diet (n=21, 31.3%), while the diet was unrestricted in the control group (n=44, 65.7%). Alkylresorcinol concentrations in the 65 children were validated against simultaneously collected 3-day food records estimating total gluten intake.

RESULTS

Gluten intake in controls was median 5.8 grams (g)/day (inter quartile range [IQR] 2.8-9.4, max 17.1) compared to 0.0 g/day (IQR 0.0-0.0, max 0.7, p<0.001) in the intervention group. In the control group, wheat accounted for mean 85% (standard deviations [SD] 0.1) of the gluten intake. The intervention group had lower alkylresorcinol levels (median 7.2 nmol/L, IQR 4.0-10.5) compared to controls (median 269, IQR 116-505 nmol/L, p<0.001). The correlation between alkylresorcinol concentrations and gluten intake was rho=0.68 (p<0.001). Alkylresorcinol concentrations increased by 35.7% (95% confidence interval [CI] 25.9, 46.2, p<0.001) for every g/day increase of gluten intake. The Cohen's weighted kappa between quartiles of alkylresorcinol and gluten intake was 0.73 (95% CI 0.59, 0.86).

CONCLUSIONS

Alkylresorcinol concentrations increased with gluten intake in young non-fasting children. The findings suggest that alkylresorcinol concentrations may be a useful biomarker for gluten intake in young children.

CLINICAL TRIAL REGISTRY

ClinicalTrials.gov Identifier NCT03562221.

Randomised controlled trial: effects of gluten-free diet on symptoms and the gut microenvironment in irritable bowel syndrome

BACKGROUND

A gluten-free diet reduces symptoms in some patients with irritable bowel syndrome (IBS) through unclear mechanisms.

AIMS

To assess the effects of gluten-free versus gluten-containing diet on symptoms and the gut microenvironment, and to identify predictors of response to the gluten-free diet in IBS METHODS: Twenty patients with IBS and 18 healthy controls (HC) followed a gluten-free diet during two 14-day intervention periods where they sprinkled either gluten (14 g/day) or rice flour powder over their meals. Primary outcomes included effects of the interventions on IBS symptoms (IBS-SSS) and bowel habits. Secondary outcomes included effects of gluten-free diet on faecal microbiota and metabolite profile.

RESULTS

IBS symptoms improved during the gluten-free (p = 0.02), but not the gluten-containing period, with no difference between the interventions. IBS patients reported fewer loose stools during the gluten-free intervention (p = 0.01). Patients with IBS and HC presented distinct metabolite profiles based on the effects of the gluten-free diet (p < 0.001). True responders (reduced IBS-SSS by ≥50 solely after gluten-free period) and non-responders were discriminated based on the effects of the gluten-free diet on the microbiota (p < 0.01) and metabolite profiles (p < 0.001). The response to the gluten-free diet could be predicted by the metabolite profile before the intervention (p < 0.001).

CONCLUSIONS

A gluten-free diet may influence symptoms in a subset of patients with IBS, with a particular effect on bowel habits. A gluten-free diet seems to impact the gut microenvironment. Responsiveness to the gluten-free diet may be predicted by the metabolite profile.

CLINICALTRIALS

gov: NCT03869359.

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.

Plasma IL-2 and Symptoms Response after Acute Gluten Exposure in Subjects With Celiac Disease or Nonceliac Gluten Sensitivity

INTRODUCTION

Treated patients with celiac disease (CeD) and nonceliac gluten sensitivity (NCGS) report acute, transient, incompletely understood symptoms after suspected gluten exposure. To determine whether (i) blinded gluten exposure induces symptoms, (ii) subjects accurately identify gluten exposure, and (iii) serum interleukin-2 (IL-2) levels distinguish CeD from NCGS subjects after gluten exposure.

METHODS

Sixty subjects (n = 20 treated, healed CeD; n = 20 treated NCGS; n = 20 controls) were block randomized to a single, double-blind sham (rice flour) or 3-g gluten challenge with 72-hours follow-up. Twelve serial questionnaires (100 mm visual analog scale; pain, bloating, nausea, and fatigue) and 10 serial plasma samples were collected. Mucosal permeability was assessed using both urinary lactulose-13C mannitol ratios and endoscopic mucosal impedance.

RESULTS

Thirty-five of 40 (83%) subjects with CeD and NCGS reported symptoms with gluten (8 CeD, 9 NCGS) and sham (9 CeD, 9 NCGS) compared with 9 of 20 (45%) controls after gluten (n = 6) and sham (n = 3). There was no significant difference in symptoms among groups. Only 2 of 10 subjects with CeD and 4 of 10 NCGS identified gluten, whereas 8 of 10 subjects with CeD and 5 of 10 NCGS identified sham. A significant plasma IL-2 increase occurred only in subjects with CeD after gluten, peaking at 3 hours and normalizing within 24 hours postchallenge despite no significant intestinal permeability change from baseline.

DISCUSSION

Symptoms do not reliably indicate gluten exposure in either subjects with CeD or NCGS. IL-2 production indicates a rapid-onset gluten-induced T-cell activation in CeD despite long-standing treatment. The effector site is unknown, given no increased intestinal permeability after gluten.

Community-Based Study of Celiac Disease Autoimmunity Progression in Adults

BACKGROUND & AIMS

Celiac disease can develop at any age, but outcomes of adults with positive results from serologic tests for tissue transglutaminase antibodies (tTGA) without endoscopic determination of celiac disease (called celiac autoimmunity) have not been thoroughly evaluated. We investigated the proportion of adults with celiac autoimmunity at a community medical center and their progression to celiac disease.

METHODS

We analyzed waste blood samples from a community clinic from 15,551 adults for tTGA and, if titer results were above 2 U/mL, for endomysial antibody. The blood samples had been collected at 2 time points (median interval, 8.8 years) from 2006 through 2017. We collected data from the clinic on diagnoses of celiac disease based on duodenal biopsy analysis.

RESULTS

Of the serum samples collected at the first time point, 15,398 had negative results for tTGA, and 153 had positive results for tTGA (>4 U/mL). Based on medical records, 6 individuals received a diagnosis of celiac disease, for a cumulative incidence of celiac disease diagnosis of 0.06% (95% confidence interval, 0.01-0.11). Forty-nine (0.32%) individuals with a negative result from the first serologic test for tTGA had a positive result from the second test. Among the 153 adults who were tTGA positive at the first time point, 31 (20%) had a subsequent diagnosis of celiac disease, 81 (53%) remained positive for tTGA without a clinical diagnosis of celiac disease, and 41 (27%) had negative test results for tTGA at the second time point. Higher initial tTGA titers, female sex, and a history of hypothyroidism and autoimmune disease were associated with increased risks of subsequent diagnosis of celiac disease. Interestingly, adults whose first blood sample had a positive test result but second blood sample had a negative result for tTGA were older, had lower-than-average initial tTGA titer results, and had a higher mean body mass index than adults whose blood samples were positive for tTGA at both time points and adults later diagnosed with celiac disease.

CONCLUSIONS

In an analysis of serum samples collected from a community clinic an average of 8.8 years apart, we found that fewer than 1% of adults with negative results from an initial test for tTGA have a positive result on a second test. Of adults with positive results from the test for tTGA, only 20% are later diagnosed with celiac disease; the remaining individuals maintain persistent increases in tTGA without diagnoses of celiac disease or have negative results from second tests.

Coeliac disease

Coeliac disease is an immune-mediated enteropathy against dietary gluten present in wheat, rye and barley and is one of the most common lifelong food-related disorders worldwide. Coeliac disease is also considered to be a systemic disorder characterized by a variable combination of gluten-related signs and symptoms and disease-specific antibodies in addition to enteropathy. The ingestion of gluten leads to the generation of harmful gluten peptides, which, in predisposed individuals, can induce adaptive and innate immune responses. The clinical presentation is extremely variable; patients may have severe gastrointestinal symptoms and malabsorption, extraintestinal symptoms or have no symptoms at all. Owing to the multifaceted clinical presentation, diagnosis remains a challenge and coeliac disease is heavily underdiagnosed. The diagnosis of coeliac disease is achieved by combining coeliac disease serology and small intestinal mucosal histology during a gluten-containing diet. Currently, the only effective treatment for coeliac disease is a lifelong strict gluten-free diet; however, the diet is restrictive and gluten is difficult to avoid. Optimizing diagnosis and care in coeliac disease requires continuous research and education of both patients and health-care professionals.

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.