Colonic paracellular permeability and circulating zonulin-related proteins

Abstract

Objective: Irritable bowel syndrome (IBS) is a gut-brain disorder associated with increased gut permeability. Zonulin has been suggested to regulate the gut barrier and claimed to be pre-haptoglobin 2 (pre-HP2) and circulating zonulin is often used as a proxy for gastrointestinal permeability. This study investigated the correlation between colonic paracellular permeability and levels of circulating zonulin and pre-HP2. Materials and Methods: Colonic biopsies from 32 patients with IBS and 15 healthy controls (HC) were used to measure permeability in Ussing chambers and levels of zonulin (Cusabio ELISA). Zonulin was also measured in blood samples from 40 HC, 78 patients with IBS and 20 patients with celiac disease (CeD), before and after a gluten-free diet. In addition, we verified HP genotype and circulating pre-HP2 using a monoclonal pre-HP2 antibody (Bio-Rad) by ELISA. Results: Increased colonic paracellular permeability correlated positively with zonulin levels in IBS biopsies, but negatively with plasma zonulin. We found no agreement between circulating zonulin and pre-HP2. Genotyping revealed non-specificity of the zonulin kit, as all pre-HP2 non-producers presented detectable levels. Patients with CeD displayed higher pre-HP2 and zonulin levels compared to HC. A gluten-free diet in patients with CeD led to lower serum zonulin and pre-HP2 concentrations. Conclusions: Our study suggests that neither circulating zonulin nor pre-HP2 mirror colonic permeability. Our data corroborate previous reports showing the inability of the Cusabio zonulin kit to target zonulin and highlights that the results of studies using this kit must be reexamined with caution.

Perfluoroalkyl substances are increased in patients with late-onset ulcerative colitis and induce intestinal barrier defectsex vivoin murine intestinal tissue

“…A recent study, using zonulin as surrogate marker of intestinal permeability stated that there was no significant correlation between exposure to PFAS and zonulin levels among 179 patients/individuals [33], in contrast with our findings. However, the use of zonulin as a potential marker of intestinal permeability have recently been questioned [34,35]. Currently, the Ussing Chamber is the most advanced methodology for investigation of the intestinal barrier function where both the electrophysiology and macropmolecular passage can be monitored.…”

Perfluoroalkyl Substances are increased in patients with Late-Onset Ulcerative colitis and induce Intestinal Barrier defects ex vivo in Murine Intestinal tissue

“…A recent study, using zonulin as surrogate marker of intestinal permeability stated that there was no significant correlation between exposure to PFAS and zonulin levels among 179 patients/individuals [32], in contrast with our findings. However, the use of zonulin as a potential marker of intestinal permeability have recently been questioned ([33,34]. Currently, the Ussing Chamber is the most advanced methodology for investigation of the intestinal barrier function where both the electrophysiology and macropmolecular passage can be monitored, however it is important to acknowledge that our results are based on experiments in mice.…”

The Role of Leaky Gut in Functional Dyspepsia

“…Besides a correlation between neuronal changes and mucosal eosinophils or mast cells ( Cirillo et al, 2015 ), upregulated glial cell line-derived neurotrophic factor (GDNF) may also play a role in the protection of a disturbed epithelial barrier in FD ( Tanaka et al, 2016 ). In IBS, reactive enteric glial cells have been linked to bacterial translocation in the colon via mast cells with different profiles in health ( MeiradeFaria et al, 2021 ), suggesting a role for neuro-immune interactions. While no link was found between ex vivo permeability and symptoms ( Vanheel et al, 2014 ; Wauters et al, 2021b ), the central interactions are complex as illustrated by an inverse association with increased functional and structural connectivity in endogenous pain facilitation regions in IBS patients ( Witt et al, 2019 ).…”