Gli enzimi digestivi gastro-intestinali riducono “spezzettano” il glutine in frammenti piccoli o/e singoli aminoacidi che vengono assorbiti nell’intestino tenue o piccolo intestino attraverso i villi intestinali. Ma solo i più piccoli potranno essere digeriti, gli altri, in individui sani, attraversano l’intestino crasso [1] dove, partre di essi, verranno fermentati dalla flora batterica e trasformati in nutrienti; altri verranno eliminati con le feci.
1 – La ricerca “Diversity of the cultivable human gut microbiome involved in gluten metabolism: isolation of microorganisms with potential interest for coeliac disease” ha evidenziato come alcuni di questi batteri riescano a degradare il glutine trasformandolo in nutrienti utili per l’intestino stesso.
Abstract. “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. Twentytwo 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 [2], [3]. These bacteria could have an important role in gluten metabolism and could offer promising new treatment modalities for coeliac disease.” Diversity of the cultivable human gut microbiome involved in gluten metabolism: isolation of microorganisms with potential interest for coeliac disease. Alberto Caminero et al. Final version published online 3 March 2014. DOI: 10.1111/1574-6941.12295
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[1]- “Alimentary protein digestion followed by amino acid and peptide absorption in the small intestinal epithelium is considered an efficient process. Nevertheless, unabsorbed dietary proteins enter the human large intestine as a complex mixture of protein and peptides.53,63 The incomplete assimilation of some dietary proteins in the small intestine has been previously demonstrated, even with proteins that are known to be easily digested (e.g., egg protein).64,65 The high proline content of wheat gluten and related proteins renders these proteins resistant to complete digestion in the small intestine. As a result, many high molecular weight gluten oligopeptides arrive in the lower gastrointestinal tract.66 While gluten peptides pass through the large intestine, proteolytic bacteria could participate in the hydrolysis of these peptides. 81Gluten Metabolism in Humans. Alberto Caminero, … Javier Casqueiro, in Wheat and Rice in Disease Prevention and Health, 2014”
[2], [3] – “Considering the characteristics of gut microbiota such as the large diversity, the stability and resilience, and the symbiotic interaction with the host, we can define the host and the microorganisms inhabiting it as a “superorganism” [8,9] which performs immune and metabolic functions [1]. Gut bacteria are key regulators of digestion along the gastrointestinal tract; commensal bacteria play an important role in the extraction, synthesis, and absorption of many nutrients and metabolites, including bile acids, lipids, amino acids, vitamins, and short-chain fatty acids (SCFAs). Gut microbiota have a crucial immune function against pathogenic bacteria colonization inhibiting their growth, consuming available nutrients and/or producing bacteriocins. Gut microbiota also prevent bacteria invasion by maintaining the intestinal epithelium integrity [10]. Microorganisms prevent pathogenic colonization by many competition processes: nutrient metabolism, pH modification, antimicrobial peptide secretions, and effects on cell signaling pathways. Moreover, recent studies have identified a critical role for commensal bacteria and their products in regulating the development, homeostasis, and function of innate and adaptive immune cells [11]. It is paradoxical to note that the gut microbiota functions are highly preserved between individuals, whereas each individual’s gut microbiota are characterized by a specific combination of bacterial species due to inter-individual and intra-individual variations throughout human life. What is the Healthy Gut Microbiota Composition? A Changing Ecosystem across Age, Environment, Diet, and Diseases. Emanuele Rinninella et al. Published online 2019 Jan 10. doi: 10.3390/microorganisms7010014. PMCID: PMC6351938”