The Human Digestive Tract Is Capable of Degrading Gluten from Birth.

The human gastrointestinal system has the capacity to metabolize dietary gluten. The capacity to degrade gliadin-derived peptide is present in humans from birth and increases during the first stages of life (up to 6-12 months of age). Fecal samples from 151 new-born and adult non-celiac disease (NCD) volunteers were collected, and glutenase and glianidase activities were evaluated. The capacity of total fecal proteins to metabolize 33-mer, 19-mer, and 13-mer gliadin peptides was also evaluated by high-performance liquid chromatography (HPLC). Feces from new-borns (meconium) showed glutenase and gliadinase activities, and peptidase activity against all three gliadin peptides. Maximal gluten degradative activity was observed in fecal samples from the youngest volunteers (0-12 months old). After the age of nine months, the gluten digestive capacity of gastrointestinal tract decreases and, from ±8 years old, individuals lose the ability to completely degrade toxic peptides. The gastrointestinal proteases involved in gluten digestion: elastase 2A, elastase 3B, and carboxipeptidase A1 are present from earlier stages of life. The human digestive tract contains the proteins capable of metabolizing gluten from birth, even before starting gluten intake. Humans are born with the ability to digest gluten and to completely degrade the potentially toxic gliadin-derived peptides (33-, 19-, and 13-mer).

The human digestive tract has proteases capable of gluten hydrolysis.

OBJECTIVE: To identify, purify, and characterize the proteins responsible for glutenase activity in the feces of healthy subjects and patients with celiac disease (CD). METHODS: Sixteen subjects were included in this study; 8 were healthy with no known food intolerances, and 8 were treated CD patients on a gluten-free diet. Fecal samples were homogenized, and precipitated proteins were purified by chromatography. Glutenase activity was evaluated by bioassays, zymography, and high-performance liquid chromatography with immunogenic 33-mer, 19-mer, and 13-mer gliadin peptides. RESULTS: The gastrointestinal elastase 3B (CEL3B), elastase 2A (CEL2A), and carboxypeptidase A1 (CBPA1) enzymes degraded human gluten. These proteins fully hydrolyzed 13-mer and 19-mer gliadin peptides that trigger immune-mediated enteropathy in individuals genetically predisposed to CD and partially digested a 33-mer. Feces from patients with CD showed more glutenase activity than feces from individuals without CD (171-466% higher). Peptidase activity against the gliadin peptides also increased in patients with CD. CONCLUSION: The digestive tracts of patients with CD and healthy subjects have enzymatic machinery needed for gluten degradation. Patients with CD showed more gluten hydrolysis than did healthy individuals, although, in both cases, a fraction of 33-mer peptide remained intact. Gliadin peptides derived from gastrointestinal digestion, especially the 33-mer, can potentially be used by commensal microbiota from both CD-positive and CD-negative individuals, and differences in bacterial hydrolysis can modify its immunogenic capacity.

Gluten-degrading bacteria are present in the human small intestine of healthy volunteers and celiac patients.

Gluten is the only known environmental factor that triggers celiac disease. Several studies have described an imbalance between the intestinal microbiota of different individuals based on diagnoses. Moreover, recent studies have suggested that human bacteria may play an important role in gluten hydrolysis. However, there has been no research focusing on the small intestine. This study aimed to characterize the adult small intestine microbiota possibly implicated in gluten hydrolysis. Duodenal biopsies from different diagnosed individuals were cultured in a gluten-containing medium, and the grown microbiota was analyzed by culture dependent/independent methods. Results showed that gluten-degrading bacteria can be found in the human small intestine. Indeed, 114 bacterial strains belonging to 32 species were isolated; 85 strains were able to grow in a medium containing gluten as the sole nitrogen source, 31 strains showed extracellular proteolytic activity against gluten protein and 27 strains showed peptidolytic activity towards the 33 mer peptide, an immunogenic peptide for celiac disease patients. We found that there are no differences based on the diagnosis, but each individual has its own population of gluten-hydrolyzing bacteria. These bacteria or their gluten-degrading enzymes could help to improve the quality of life of celiac disease patients'.

Differences in gluten metabolism among healthy volunteers, coeliac disease patients and first-degree relatives.

Coeliac disease (CD) is an immune-mediated enteropathy resulting from exposure to gluten in genetically predisposed individuals. Gluten proteins are partially digested by human proteases generating immunogenic peptides that cause inflammation in patients carrying HLA-DQ2 and DQ8 genes. Although intestinal dysbiosis has been associated with patients with CD, bacterial metabolism of gluten has not been studied in depth thus far. The aim of this study was to analyse the metabolic activity of intestinal bacteria associated with gluten intake in healthy individuals, CD patients and first-degree relatives of CD patients. Faecal samples belonging to twenty-two untreated CD patients, twenty treated CD patients, sixteen healthy volunteers on normal diet, eleven healthy volunteers on gluten-free diet (GFD), seventy-one relatives of CD patients on normal diet and sixty-nine relatives on GFD were tested for several proteolytic activities, cultivable bacteria involved in gluten metabolism, SCFA and the amount of gluten in faeces. We detected faecal peptidasic activity against the gluten-derived peptide 33-mer. CD patients showed differences in faecal glutenasic activity (FGA), faecal tryptic activity (FTA), SCFA and faecal gluten content with respect to healthy volunteers. Alterations in specific bacterial groups metabolising gluten such as Clostridium or Lactobacillus were reported in CD patients. Relatives showed similar parameters to CD patients (SCFA) and healthy volunteers (FTA and FGA). Our data support the fact that commensal microbial activity is an important factor in the metabolism of gluten proteins and that this activity is altered in CD patients.

Diversity of the cultivable human gut microbiome involved in gluten metabolism: isolation of microorganisms with potential interest for coeliac disease.

Gluten, a common component in the human diet, is capable of triggering coeliac disease pathogenesis in genetically predisposed individuals. Although the function of human digestive proteases in gluten proteins is quite well known, the role of intestinal microbiota in the metabolism of proteins is frequently underestimated. The aim of this study was the isolation and characterisation of the human gut bacteria involved in the metabolism of gluten proteins. Twenty-two human faecal samples were cultured with gluten as the principal nitrogen source, and 144 strains belonging to 35 bacterial species that may be involved in gluten metabolism in the human gut were isolated. Interestingly, 94 strains were able to metabolise gluten, 61 strains showed an extracellular proteolytic activity against gluten proteins, and several strains showed a peptidasic activity towards the 33-mer peptide, an immunogenic peptide in patients with coeliac disease. Most of the strains were classified within the phyla Firmicutes and Actinobacteria, mainly from the genera Lactobacillus, Streptococcus, Staphylococcus, Clostridium and Bifidobacterium. In conclusion, the human intestine exhibits a large variety of bacteria capable of utilising gluten proteins and peptides as nutrients. These bacteria could have an important role in gluten metabolism and could offer promising new treatment modalities for coeliac disease.