Enhanced mitochondrial activity reshapes a gut microbiota profile that delays NASH progression.

BACKGROUND AND AIMS: Recent studies suggest that mitochondrial dysfunction promotes progression to NASH by aggravating the gut-liver status. However, the underlying mechanism remains unclear. Herein, we hypothesized that enhanced mitochondrial activity might reshape a specific microbiota signature that, when transferred to germ-free (GF) mice, could delay NASH progression. APPROACH AND RESULTS: Wild-type and methylation-controlled J protein knockout (MCJ-KO) mice were fed for 6 weeks with either control or a choline-deficient, L-amino acid-defined, high-fat diet (CDA-HFD). One mouse of each group acted as a donor of cecal microbiota to GF mice, who also underwent the CDA-HFD model for 3 weeks. Hepatic injury, intestinal barrier, gut microbiome, and the associated fecal metabolome were then studied. Following 6 weeks of CDA-HFD, the absence of methylation-controlled J protein, an inhibitor of mitochondrial complex I activity, reduced hepatic injury and improved gut-liver axis in an aggressive NASH dietary model. This effect was transferred to GF mice through cecal microbiota transplantation. We suggest that the specific microbiota profile of MCJ-KO, characterized by an increase in the fecal relative abundance of Dorea and Oscillospira genera and a reduction in AF12 , Allboaculum , and [ Ruminococcus ], exerted protective actions through enhancing short-chain fatty acids, nicotinamide adenine dinucleotide (NAD + ) metabolism, and sirtuin activity, subsequently increasing fatty acid oxidation in GF mice. Importantly, we identified Dorea genus as one of the main modulators of this microbiota-dependent protective phenotype. CONCLUSIONS: Overall, we provide evidence for the relevance of mitochondria-microbiota interplay during NASH and that targeting it could be a valuable therapeutic approach.

Idiosyncratic Drug-Induced Liver Injury and Amoxicillin-Clavulanate: Spotlight on Gut Microbiota, Fecal Metabolome and Bile Acid Profile in Patients.

Several hepatic disorders are influenced by gut microbiota, but its role in idiosyncratic drug-induced liver injury (iDILI), whose main causative agent is amoxicillin-clavulanate, remains unknown. This pioneering study aims to unravel particular patterns of gut microbiota composition and associated metabolites in iDILI and iDILI patients by amoxicillin-clavulanate (iDILI-AC). Thus, serum and fecal samples from 46 patients were divided into three study groups: healthy controls (n = 10), non-iDILI acute hepatitis (n = 12) and iDILI patients (n = 24). To evaluate the amoxicillin-clavulanate effect, iDILI patients were separated into two subgroups: iDILI non-caused by amoxicillin-clavulanate (iDILI-nonAC) (n = 18) and iDILI-AC patients (n = 6). Gut microbiota composition and fecal metabolome plus serum and fecal bile acid (BA) analyses were performed, along with correlation analyses. iDILI patients presented a particular microbiome profile associated with reduced fecal secondary BAs and fecal metabolites linked to lower inflammation, such as dodecanedioic acid and pyridoxamine. Moreover, certain taxa like Barnesiella, Clostridia UCG-014 and Eubacterium spp. correlated with significant metabolites and BAs. Additionally, comparisons between iDILI-nonAC and iDILI-AC groups unraveled unique features associated with iDILI when caused by amoxicillin-clavulanate. In conclusion, specific gut microbiota profiles in iDILI and iDILI-AC patients were associated with particular metabolic and BA status, which could affect disease onset and progression.

An altered fecal microbiota profile in patients with non-alcoholic fatty liver disease (NAFLD) associated with obesity.

INTRODUCTION: increasing evidence suggests a role of intestinal dysbiosis in obesity and non-alcoholic fatty liver disease (NAFLD). The advances in recent years with regard to the role of the gut microbiota raise the potential utility of new therapeutic approaches based on the modification of the microbiome. OBJECTIVE: the aim of this study was to compare the bacterial communities in obese patients with or without NAFLD to those of healthy controls. PATIENTS AND METHODS: the fecal microbiota composition of 20 healthy adults, 36 obese patients with NAFLD and 17 obese patients without NAFLD was determined by 16S ribosomal RNA sequencing using the Illumina MiSeq system. RESULTS: the results highlighted significant differences in the phylum Firmicutes between patients with and without NAFLD, which was a determining factor of the disease and supported its possible role as a marker of NAFLD. At the genus level, the relative abundance of Blautia, Alkaliphilus, Flavobacterium and Akkermansia was reduced in obese patients, both with or without NAFLD, compared to healthy controls. Furthermore, the number of sequences from the genus Streptococcus was significantly higher in patients with NAFLD in comparison with individuals without the disease, constituting another possible marker. Comparison of bacterial communities at the genus level by a principal coordinate analysis indicated that the bacterial communities of patients with NAFLD were dispersed and did not form a group. CONCLUSION: in conclusion, these results indicate the role of intestinal dysbiosis in the development of NAFLD associated with obesity. There was a differential microbiota profile between obese patients, with and without NAFLD. Thus, supporting gut microbiota modulation as a therapeutic alternative for the prevention and treatment of NAFLD.

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.

A gluten metabolism study in healthy individuals shows the presence of faecal glutenasic activity.

PURPOSE: To study the gluten metabolism in healthy individuals and its effect over the intestinal microbial activity. METHODS: The faeces of eleven healthy subjects were analysed under 4 diet regimens: their normal gluten diet, a strict gluten-free diet (GFD), a GFD with a supplemental intake of 9 g gluten/day and a GFD with a supplemental intake of 30 g gluten/day. Gluten content, faecal tryptic activity (FTA), short-chain fatty acids (SCFAs) and faecal glutenasic activity (FGA) were analysed in faecal samples. RESULTS: Faecal gluten contents, FTA, SCFAs and FGA varied significantly with different levels of gluten intake in the diet. When high gluten doses (30 g/day) were administered in the diet, SCFA concentrations (70.5 mmoles/kg faeces) were significantly different from those from the GFD period (33.8 mmoles/kg faeces) of the experiment. However, the FTA showed significant differences between the GFD (34 units) and the normal gluten-containing diet (60 units) and also between the GFD and the GFD + 30 g of gluten/day (67 units). When gluten was present in the diet, gluten was detected in the faeces, showing that at least a portion of the gluten ingested is eliminated in the large intestine, providing a substrate for intestinal microbial proteases. We have also shown the presence of faecal glutenasic activity that increased proportionally with the gluten intake in the diet, showing an enzymatic activity of 993 units in DSG, 2,063 units in DSG + 9 g and 6,090 units in DSG + 30 g. CONCLUSIONS: The activity of the intestinal microbiota is modified by gluten intake in the diet. The incorporation of gluten in the diet increases the activity of a gluten proteolytic activity in the faeces.

Dynamics of non-conventional intraepithelial lymphocytes-NK, NKT, and γδ T-in celiac disease: relationship with age, diet, and histopathology.

BACKGROUND: Intraepithelial lymphocytes (IEL) are a heterogeneous population of lymphocytes raised in celiac disease (CD), whose role in CD pathogenesis remains to be defined. AIMS: To investigate how the age of diagnosis, diet, and the severity of the histological lesions are related to the changes observed in unconventional IEL populations. METHODS: Prospective analysis of 101 confirmed celiac patients from a single center, including 66 at diagnosis (45 children, 21 adults) and 112 non-celiac controls (12 children, 100 adults). IEL from duodenal biopsies were studied by six-color flow cytometry. The results were analyzed in relationship with age, diet (gluten intake), and histopathology (Marsh type). RESULTS: In comparison with respective age controls, both children and adult patients showed duodenal intraepithelial lymphocytosis with significant differences in every single non-conventional IEL population: CD3+ TCR γδ, NK (CD3-, CD16+, CD56+), NKT (CD3+, CD161+, CD56+), and iNKT (CD3+ Vα24) (P < 0.001 for all). Gluten intake was not only directly associated with severe atrophy, but also with decreased percentages of NK (P = 0.02), NKT (P = 0.003), and iNKT (P = 0.03). Changes in iNKT and γδ IEL were more marked in celiac children compared with celiac adults (P = 0.02 and 0.01, respectively). In contrast, increased CD3+ TCR γδ were diet- and Marsh grade-independent. CONCLUSIONS: The typical phenotypical profile of intraepithelial lymphocytosis in untreated pediatric and adult celiacs consists of increased CD3+ TCR γδ populations with decreased NK, NKT, and iNKT cells. NK, NKT, and iNKT IEL, but not γδ IEL, are dynamic populations associated with diet, age, and histopathology.

The Synbiotic Combination of Akkermansia muciniphila and Quercetin Ameliorates Early Obesity and NAFLD through Gut Microbiota Reshaping and Bile Acid Metabolism Modulation.

Gut microbiota plays a key role in obesity and non-alcoholic fatty liver disease (NAFLD), so synbiotics could be a therapeutic alternative. We aim to evaluate a nutritional intervention together with the administration of the bacteria Akkermansia muciniphila and the antioxidant quercetin in an in vivo model of early obesity and NAFLD. 21-day-old rats were fed with control or high-fat diet for six weeks. Then, all animals received control diet supplemented with/without quercetin and/or A. muciniphila for three weeks. Gut microbiota, NAFLD-related parameters, circulating bile acids (BAs) and liver gene expression were analyzed. The colonization with A. muciniphila was associated with less body fat, while synbiotic treatment caused a steatosis remission, linked to hepatic lipogenesis modulation. The synbiotic promoted higher abundance of Cyanobacteria and Oscillospira, and lower levels of Actinobacteria, Lactococcus, Lactobacillus and Roseburia. Moreover, it favored elevated unconjugated hydrophilic BAs plasma levels and enhanced hepatic expression of BA synthesis and transport genes. A. muciniphila correlated with circulating BAs and liver lipid and BA metabolism genes, suggesting a role of this bacterium in BA signaling. Beneficial effects of A. muciniphila and quercetin combination are driven by gut microbiota modulation, the shift in BAs and the gut-liver bile flow enhancement.

Long-Term Effects of Bariatric Surgery on Gut Microbiota Composition and Faecal Metabolome Related to Obesity Remission.

Obesity is one of the main worldwide public health concerns whose clinical management demands new therapeutic approaches. Bariatric surgery is the most efficient treatment when other therapies have previously failed. Due to the role of gut microbiota in obesity development, the knowledge of the link between bariatric surgery and gut microbiota could elucidate new mechanistic approaches. This study aims to evaluate the long-term effects of bariatric surgery in the faecal metagenome and metabolome of patients with severe obesity. Faecal and blood samples were collected before and four years after the intervention from patients with severe obesity. Biochemical, metagenomic and metabolomic analyses were performed and faecal short-chain fatty acids were measured. Bariatric surgery improved the obesity-related status of patients and significantly reshaped gut microbiota composition. Moreover, this procedure was associated with a specific metabolome profile characterized by a reduction in energetic and amino acid metabolism. Acetate, butyrate and propionate showed a significant reduction with bariatric surgery. Finally, correlation analysis suggested the existence of a long-term compositional and functional gut microbiota profile associated with the intervention. In conclusion, bariatric surgery triggered long-lasting effects on gut microbiota composition and faecal metabolome that could be associated with the remission of obesity.

Aging, Gut Microbiota and Metabolic Diseases: Management through Physical Exercise and Nutritional Interventions.

Gut microbiota (GM) is involved in the maintenance of physiological homeostasis, thus the alteration of its composition and functionality has been associated with many pathologies such as metabolic diseases, and could also be linked with the progressive degenerative process in aging. Nowadays, life expectancy is continuously rising, so the number of elder people and the consequent related pathologies demand new strategies to achieve healthy aging. Besides, actual lifestyle patterns make metabolic diseases a global epidemic with increasing trends, responsible for a large mortality and morbidity in adulthood and also compromising the health status of later stages of life. Metabolic diseases and aging share a profile of low-grade inflammation and innate immunity activation, which may have disturbances of GM composition as the leading mechanism. Thus, GM emerges as a therapeutic target with a double impact in the elderly, counteracting both aging itself and the frequent metabolic diseases in this population. This review summarizes the role and compositional changes of the GM in aging and its modulation through nutritional interventions and physical exercise as a strategy to counteract the aging process and the related metabolic diseases.

Exercise training modulates the gut microbiota profile and impairs inflammatory signaling pathways in obese children.

Childhood obesity has reached epidemic levels and is a serious health concern associated with metabolic syndrome, nonalcoholic fatty liver disease, and gut microbiota alterations. Physical exercise is known to counteract obesity progression and modulate the gut microbiota composition. This study aims to determine the effect of a 12-week strength and endurance combined training program on gut microbiota and inflammation in obese pediatric patients. Thirty-nine obese children were assigned randomly to the control or training group. Anthropometric and biochemical parameters, muscular strength, and inflammatory signaling pathways in mononuclear cells were evaluated. Bacterial composition and functionality were determined by massive sequencing and metabolomic analysis. Exercise reduced plasma glucose levels and increased dynamic strength in the upper and lower extremities compared with the obese control group. Metagenomic analysis revealed a bacterial composition associated with obesity, showing changes at the phylum, class, and genus levels. Exercise counteracted this profile, significantly reducing the Proteobacteria phylum and Gammaproteobacteria class. Moreover, physical activity tended to increase some genera, such as Blautia, Dialister, and Roseburia, leading to a microbiota profile similar to that of healthy children. Metabolomic analysis revealed changes in short-chain fatty acids, branched-chain amino acids, and several sugars in response to exercise, in correlation with a specific microbiota profile. Finally, the training protocol significantly inhibited the activation of the obesity-associated NLRP3 signaling pathway. Our data suggest the existence of an obesity-related deleterious microbiota profile that is positively modified by physical activity intervention. Exercise training could be considered an efficient nonpharmacological therapy, reducing inflammatory signaling pathways induced by obesity in children via microbiota modulation.

A Network Involving Gut Microbiota, Circulating Bile Acids, and Hepatic Metabolism Genes That Protects Against Non-Alcoholic Fatty Liver Disease.

SCOPE: Gut microbiota contributes to non-alcoholic fatty liver disease (NAFLD) pathogenesis by multiple mechanisms not yet completely understood. Novel differential features between germ-free mice (GFm) transplanted with protective or non-protective cecal microbiota against NAFLD are investigated. METHODS AND RESULTS: Gut microbiota composition, plasma, and fecal bile acids (BAs) and liver mRNAs are quantified in GFm recipients from four donor mice differing in NAFLD severity (control diet, high-fat diet [HFD]-responder, HFD-non-responder, and quercetin-supplemented HFD). Transplanted GFm are on control or HFD for 16-weeks. Multivariate analysis shows that GFm colonized with microbiota from HFD-non-responder and quercetin supplemented-HFD donors (protected against NAFLD) clusters together, whereas GFm colonized with microbiota from control and HFD-responder mice (non-protected against NAFLD) establishes another cluster. Protected phenotype is associated with increased gut Desulfovibrio and Oscillospira, reduced gut Bacteroides and Oribacterium, lower primary and higher secondary BAs in plasma and feces, induction of hepatic BA transporters, and repression of hepatic lipogenic and BA synthesis genes. CONCLUSION: Protective gut microbiota associates with increased specific secondary BAs, which likely inhibit lipogenic pathways and enhance bile flow in the liver. This novel cross-talk between gut and liver, via plasma BAs, that promotes protection against NAFLD may have clinical and nutritional relevance.

Beneficial effects of exercise on gut microbiota functionality and barrier integrity, and gut-liver crosstalk in an in vivo model of early obesity and non-alcoholic fatty liver disease.

Childhood obesity has reached epidemic levels, representing one of the most serious public health concerns associated with metabolic syndrome and non-alcoholic fatty liver disease (NAFLD). There is limited clinical experience concerning pediatric NAFLD patients, and thus the therapeutic options are scarce. The aim of this study was to evaluate the benefits of exercise on gut microbiota composition and functionality balance, and consequent effects on early obesity and NAFLD onset in an in vivo model. Juvenile (21-day-old) male Wistar rats fed a control diet or a high-fat diet (HFD) were subjected to a combined aerobic and resistance training protocol. Fecal microbiota was sequenced by an Illumina MiSeq system, and parameters related to metabolic syndrome, fecal metabolome, intestinal barrier integrity, bile acid metabolism and transport, and alteration of the gut-liver axis were measured. Exercise decreased HFD-induced body weight gain, metabolic syndrome and hepatic steatosis, as a result of its lipid metabolism modulatory capacity. Gut microbiota composition and functionality were substantially modified as a consequence of diet, age and exercise intervention. In addition, the training protocol increased Parabacteroides, Bacteroides and Flavobacterium genera, correlating with a beneficial metabolomic profile, whereas Blautia, Dysgonomonas and Porphyromonas showed an opposite pattern. Exercise effectively counteracted HFD-induced microbial imbalance, leading to intestinal barrier preservation, which, in turn, prevented deregulation of the gut-liver axis and improved bile acid homeostasis, determining the clinical outcomes of NAFLD. In conclusion, we provide scientific evidence highlighting the benefits of gut microbiota composition and functionality modulation by physical exercise protocols in the management of early obesity and NAFLD development.

Functional Interactions between Gut Microbiota Transplantation, Quercetin, and High-Fat Diet Determine Non-Alcoholic Fatty Liver Disease Development in Germ-Free Mice.

SCOPE: Modulation of intestinal microbiota has emerged as a new therapeutic approach for non-alcoholic fatty liver disease (NAFLD). Herein, it is addressed whether gut microbiota modulation by quercetin and intestinal microbiota transplantation can influence NAFLD development. METHODS AND RESULTS: Gut microbiota donor mice are selected according to their response to high-fat diet (HFD) and quercetin in terms of obesity and NAFLD-related biomarkers. Germ-free recipients displayed metabolic phenotypic differences derived from interactions between microbiota transplanted, diets, and quercetin. Based on the evaluation of hallmark characteristics of NAFLD, it is found that gut microbiota transplantation from the HFD-non-responder donor and the HFD-fed donor with the highest response to quercetin results in a protective phenotype against HFD-induced NAFLD, in a mechanism that involves gut-liver axis alteration blockage in these receivers. Gut microbiota from the HFD-responder donor predisposed transplanted germ-free mice to NAFLD. Divergent protective and deleterious metabolic phenotypes exhibited are related to definite microbial profiles in recipients, highlighting the predominant role of Akkermansia genus in the protection from obesity-associated NAFLD development. CONCLUSIONS: The results provide scientific support for the prebiotic capacity of quercetin and the transfer of established metabolic profiles through gut microbiota transplantation as a protective strategy against the development of obesity-related NAFLD.

Intestinal Microbiota Modulation in Obesity-Related Non-alcoholic Fatty Liver Disease.

Obesity and associated comorbidities, including non-alcoholic fatty liver disease (NAFLD), are a major concern to public well-being worldwide due to their high prevalence among the population, and its tendency on the rise point to as important threats in the future. Therapeutic approaches for obesity-associated disorders have been circumscribed to lifestyle modifications and pharmacological therapies have demonstrated limited efficacy. Over the last few years, different studies have shown a significant role of intestinal microbiota (IM) on obesity establishment and NAFLD development. Therefore, modulation of IM emerges as a promising therapeutic strategy for obesity-associated diseases. Administration of prebiotic and probiotic compounds, fecal microbiota transplantation (FMT) and exercise protocols have shown a modulatory action over the IM. In this review we provide an overview of current approaches targeting IM which have shown their capacity to counteract NAFLD and metabolic syndrome features in human patients and animal models.

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'.

Protective effect of quercetin on high-fat diet-induced non-alcoholic fatty liver disease in mice is mediated by modulating intestinal microbiota imbalance and related gut-liver axis activation.

Gut microbiota is involved in obesity, metabolic syndrome and the progression of nonalcoholic fatty liver disease (NAFLD). It has been recently suggested that the flavonoid quercetin may have the ability to modulate the intestinal microbiota composition, suggesting a prebiotic capacity which highlights a great therapeutic potential in NAFLD. The present study aims to investigate benefits of experimental treatment with quercetin on gut microbial balance and related gut-liver axis activation in a nutritional animal model of NAFLD associated to obesity. C57BL/6J mice were challenged with high fat diet (HFD) supplemented or not with quercetin for 16 weeks. HFD induced obesity, metabolic syndrome and the development of hepatic steatosis as main hepatic histological finding. Increased accumulation of intrahepatic lipids was associated with altered gene expression related to lipid metabolism, as a result of deregulation of their major modulators. Quercetin supplementation decreased insulin resistance and NAFLD activity score, by reducing the intrahepatic lipid accumulation through its ability to modulate lipid metabolism gene expression, cytochrome P450 2E1 (CYP2E1)-dependent lipoperoxidation and related lipotoxicity. Microbiota composition was determined via 16S ribosomal RNA Illumina next-generation sequencing. Metagenomic studies revealed HFD-dependent differences at phylum, class and genus levels leading to dysbiosis, characterized by an increase in Firmicutes/Bacteroidetes ratio and in Gram-negative bacteria, and a dramatically increased detection of Helicobacter genus. Dysbiosis was accompanied by endotoxemia, intestinal barrier dysfunction and gut-liver axis alteration and subsequent inflammatory gene overexpression. Dysbiosis-mediated toll-like receptor 4 (TLR-4)-NF-κB signaling pathway activation was associated with inflammasome initiation response and reticulum stress pathway induction. Quercetin reverted gut microbiota imbalance and related endotoxemia-mediated TLR-4 pathway induction, with subsequent inhibition of inflammasome response and reticulum stress pathway activation, leading to the blockage of lipid metabolism gene expression deregulation. Our results support the suitability of quercetin as a therapeutic approach for obesity-associated NAFLD via its anti-inflammatory, antioxidant and prebiotic integrative response.

Factors Determining Colorectal Cancer: The Role of the Intestinal Microbiota.

The gastrointestinal tract, in particular the colon, holds a complex community of microorganisms, which are essential for maintaining homeostasis. However, in recent years, many studies have implicated microbiota in the development of colorectal cancer (CRC), with this disease considered a major cause of death in the western world. The mechanisms underlying bacterial contribution in its development are complex and are not yet fully understood. However, there is increasing evidence showing a connection between intestinal microbiota and CRC. Intestinal microorganisms cause the onset and progression of CRC using different mechanisms, such as the induction of a chronic inflammation state, the biosynthesis of genotoxins that interfere with cell cycle regulation, the production of toxic metabolites, or heterocyclic amine activation of pro-diet carcinogenic compounds. Despite these advances, additional studies in humans and animal models will further decipher the relationship between microbiota and CRC, and aid in developing alternate therapies based on microbiota manipulation.

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.

Monitoring of gluten-free diet compliance in celiac patients by assessment of gliadin 33-mer equivalent epitopes in feces.

BACKGROUND: Certain immunotoxic peptides from gluten are resistant to gastrointestinal digestion and can interact with celiac-patient factors to trigger an immunologic response. A gluten-free diet (GFD) is the only effective treatment for celiac disease (CD), and its compliance should be monitored to avoid cumulative damage. However, practical methods to monitor diet compliance and to detect the origin of an outbreak of celiac clinical symptoms are not available. OBJECTIVE: We assessed the capacity to determine the gluten ingestion and monitor GFD compliance in celiac patients by the detection of gluten and gliadin 33-mer equivalent peptidic epitopes (33EPs) in human feces. DESIGN: Fecal samples were obtained from healthy subjects, celiac patients, and subjects with other intestinal pathologies with different diet conditions. Gluten and 33EPs were analyzed by using immunochromatography and competitive ELISA with a highly sensitive antigliadin 33-mer monoclonal antibody. RESULTS: The resistance of a significant part of 33EPs to gastrointestinal digestion was shown in vitro and in vivo. We were able to detect gluten peptides in feces of healthy individuals after consumption of a normal gluten-containing diet, after consumption of a GFD combined with controlled ingestion of a fixed amount of gluten, and after ingestion of <100 mg gluten/d. These methods also allowed us to detect GFD infringement in CD patients. CONCLUSIONS: Gluten-derived peptides could be sensitively detected in human feces in positive correlation with the amount of gluten intake. These techniques may serve to show GFD compliance or infringement and be used in clinical research in strategies to eliminate gluten immunotoxic peptides during digestion. This trial was registered at clinicaltrials.gov as NCT01478867.

Differences in faecal bacteria populations and faecal bacteria metabolism in healthy adults and celiac disease patients.

UNLABELLED: Differences in the intestinal microbiota between children and adults with celiac disease (CD) have been reported; however, differences between healthy adults and adults with CD have not been clearly demonstrated. The aim of this study was to evaluate the differences in the intestinal microbiota between adults with CD and healthy individuals. Microbial communities in faecal samples were evaluated by PCR-denaturing gradient gel electrophoresis (DGGE) and gas-liquid chromatography of short chain fatty acids (SCFAs). The study group included 10 untreated CD patients, 11 treated CD patients and 11 healthy adults (in normal gluten diet and in GFD). UPGMA clustered the dominant microbial communities of healthy individuals together and separated them from the dominant microbial communities of the untreated CD patients. Most of the dominant microbial communities of the treated CD patients clustered together with those of healthy adults. The treated CD patients showed a reduction in the diversity of Lactobacillus and Bifidobacterium species. The presence of Bifidobacterium bifidum was significantly higher in untreated CD patients than healthy adults. There was a significant difference between untreated CD patients and healthy adults, as well as between treated CD patients and healthy adults, regarding acetic acid, propionic acid, butyric acid, and total SCFAs. IN CONCLUSION: healthy adults have a different faecal microbiota from that of untreated CD patients. A portion of the treated CD patients displayed a restored "normal" microbiota. The treated CD patients significantly reduce the Lactobacillus and Bifidobacterium diversity. Healthy adults have a different faecal SCFAs content from that of CD patients.