In vitro evaluation of the microbiota modulation abilities of different sized whole oat grain flakes

Epidemiological studies and healthy eating guidelines suggest a positive correlation between ingestion of whole grain cereal and food rich in fibre with protection from chronic diseases. The prebiotic potential of whole grains may be related, however, little is known about the microbiota modulatory capability of oat grain or the impact processing has on this ability. In this study the fermentation profile of whole grain oat flakes, processed to produce two different sized flakes (small and large), by human faecal microbiota was investigated in vitro. Simulated digestion and subsequent fermentation by gut bacteria was investigated using pH controlled faecal batch cultures inoculated with human faecal slurry. The different sized oat flakes, Oat 23’s (0.53–0.63 mm) and Oat 25’s/26’s (0.85–1.0 mm) were compared to oligofructose, a confirmed prebiotic, and cellulose, a poorly fermented carbohydrate. Bacterial enumeration was carried out using the culture independent technique, fluorescent in situ hybridisation, and short chain fatty acid (SCFA) production monitored by gas chromatography. Significant changes in total bacterial populations were observed after 24 h incubation for all substrates except Oat 23’s and cellulose. Oats 23’s fermentation resulted in a significant increase in the Bacteroides–Prevotella group. Oligofructose and Oats 25’s/26’s produced significant increases in Bifidobacterium in the latter stages of fermentation while numbers declined for Oats 23’s between 5 h and 24 h. This is possibly due to the smaller surface area of the larger flakes inhibiting the simulated digestion, which may have resulted in increased levels of resistant starch (Bifidobacterium are known to ferment this dietary fibre). Fermentation of Oat 25’s/26’s resulted in a propionate rich SCFA profile and a significant increase in butyrate, which have both been linked to benefiting host health. The smaller sized oats did not produce a significant increase in butyrate concentration. This study shows for the first time the impact of oat grain on the microbial ecology of the human gut and its potential to beneficially modulate the gut microbiota through increasing Bifidobacterium population.     

Evening rather than morning increased physical activity alters the microbiota in mice and is associated with increased body temperature and sympathetic nervous system activation

Voluntary training and food modulate the fecal microbiota in humans and mice. Although there are some reports of the timing effects of voluntary training and feeding on metabolism, the timing effects of these factors on microbiota have not been investigated. Therefore, we investigated the effects of the timing of voluntary training and feeding on the gut microbiota.The ICR mice were housed under conditions with an early (in the morning) or late (evening) active phase of increased physical activity. Furthermore, to investigate why voluntary training affects the gut microbiota, mice were housed in a cold environment and received propranolol administration with increased physical activity. After that, we collected cecal contents and feces and measured cecal pH. Short-chain fatty acids (SCFA) were measured from cecal contents. Microbiota was determined using sequencing of the V3-V4 region of the 16S rDNA gene.This study found that increased evening physical activity rather than morning activity decreases cecal pH, increases SCFA, and changes the microbiota. It is especially important that increased evening physical activity is induced under the post-prandial voluntary training condition. Also, we found that cold room housing, sympathetic blockade, or both suppressed the increased physical activity-induced changes in cecal pH, SCFA, and microbiota. Allobaculum responded to increased physical activity through body temperature increases and sympathetic activation.Post-prandial increased physical activity, rather than pre-prandial increased physical activity by evening voluntary wheel training, altered the microbiota composition, which may be related to the increase in body temperature and sympathetic nervous system activation.     

The Effect of Selected Synbiotics on Microbial Composition and Short-Chain Fatty Acid Production in a Model System of the Human Colon

Background

Prebiotics, probiotics and synbiotics can be used to modulate both the composition and activity of the gut microbiota and thereby potentially affecting host health beneficially. The aim of this study was to investigate the effects of eight synbiotic combinations on the composition and activity of human fecal microbiota using a four-stage semicontinuous model system of the human colon.

Methods and Findings

Carbohydrates were selected by their ability to enhance growth of the probiotic bacteria Lactobacillus acidophilus NCFM (NCFM) and Bifidobacterium animalis subsp. lactis Bl-04 (Bl-04) under laboratory conditions. The most effective carbohydrates for each probiotic were further investigated, using the colonic model, for the ability to support growth of the probiotic bacteria, influence the composition of the microbiota and stimulate formation of short-chain fatty acids (SCFA).The following combinations were studied: NCFM with isomaltulose, cellobiose, raffinose and an oat β-glucan hydrolysate (OBGH) and Bl-04 with melibiose, xylobiose, raffinose and maltotriose. All carbohydrates showed capable of increasing levels of NCFM and Bl-04 during fermentations in the colonic model by 10³–10⁴ fold and 10–10² fold, respectively. Also the synbiotic combinations decreased the modified ratio of Bacteroidetes/Firmicutes (calculated using qPCR results for Bacteroides-Prevotella-Porphyromonas group, Clostridium perfringens cluster I, Clostridium coccoides - Eubacterium rectale group and Clostridial cluster XIV) as well as significantly increasing SCFA levels, especially acetic and butyric acid, by three to eight fold, as compared to the controls. The decreases in the modified ratio of Bacteroidetes/Firmicutes were found to be correlated to increases in acetic and butyric acid (p = 0.04 and p = 0.03, respectively).

Conclusions

The results of this study show that all synbiotic combinations investigated are able to shift the predominant bacteria and the production of SCFA of fecal microbiota in a model system of the human colon, thereby potentially being able to manipulate the microbiota in a way connected to human health.     

Intake of Meat Proteins Substantially Increased the Relative Abundance of Genus Lactobacillus in Rat Feces

Diet has been shown to have a critical influence on gut bacteria and host health, and high levels of red meat in diet have been shown to increase colonic DNA damage and thus be harmful to gut health. However, previous studies focused more on the effects of meat than of meat proteins. In order to investigate whether intake of meat proteins affects the composition and metabolic activities of gut microbiota, feces were collected from growing rats that were fed with either meat proteins (from beef, pork or fish) or non-meat proteins (casein or soy) for 14 days. The resulting composition of gut microbiota was profiled by sequencing the V4-V5 region of the 16S ribosomal RNA genes and the short chain fatty acids (SCFAs) were analyzed using gas chromatography. The composition of gut microbiota and SCFA levels were significantly different between the five diet groups. At a recommended dose of 20% protein in the diet, meat protein-fed rats had a higher relative abundance of the beneficial genus Lactobacillus, but lower levels of SCFAs and SCFA-producing bacteria including Fusobacterium, Bacteroides and Prevotella, compared with the soy protein-fed group. Further work is needed on the regulatory pathways linking dietary protein intake to gut microbiota.     

More than one way to be an herbivore: convergent evolution of herbivory using different digestive strategies in prickleback fishes (Stichaeidae)

In fishes, the evolution of herbivory has occured within a spectrum of digestive strategies, with two extremes on opposite ends: (i) a rate-maximization strategy characterized by high intake, rapid throughput of food through the gut, and little reliance on microbial digestion or (ii) a yield-maximization strategy characterized by measured intake, slower transit of food through the gut, and more of a reliance on microbial digestion in the hindgut. One of these strategies tends to be favored within a given clade of fishes. Here, we tested the hypothesis that rate or yield digestive strategies can arise in convergently evolved herbivores within a given lineage. In the family Stichaeidae, convergent evolution of herbivory occured in Cebidichthys violaceus and Xiphister mucosus, and despite nearly identical diets, these two species have different digestive physiologies. We found that C. violaceus has more digesta in its distal intestine than other gut regions, has comparatively high concentrations (>11 mM) of short-chain fatty acids (SCFA, the endpoints of microbial fermentation) in its distal intestine, and a spike in β-glucosidase activity in this gut region, findings that, when coupled to long retention times (>20 h) of food in the guts of C. violaceus, suggest a yield-maximizing strategy in this species. X. mucosus showed none of these features and was more similar to its sister taxon, the omnivorous Xiphister atropurpureus, in terms of digestive enzyme activities, gut content partitioning, and concentrations of SCFA in their distal intestines. We also contrasted these herbivores and omnivores with other sympatric stichaeid fishes, Phytichthys chirus (omnivore) and Anoplarchus purpurescens (carnivore), each of which had digestive physiologies consistent with the consumption of animal material. This study shows that rate- and yield-maximizing strategies can evolve in closely related fishes and suggests that resource partitioning can play out on the level of digestive physiology in sympatric, closely related herbivores.     

Effects of semi-purified diet on depressive behaviors in aged mice

Diet is a key modifiable factor influencing the composition of gut microbiota. There are two types of commercially available diets for experimental animals: non-purified and semi-purified diets. Non-purified diets are composed of complex ingredients from multiple sources, while semi-purified diets are formulated with refined ingredients. Accumulating evidence has demonstrated a link between the gut microbiota and depression, and feed ingredients may influence depressive physiology and behaviors. To test this hypothesis, we examined how chronic non-purified (CRF-1) and semi-purified (AIN-93G) diets affected phenotypes, including depressive behaviors, plasma corticosterone levels, and small-intestine microbiota in young (2 months old) and aged (22 months old) inbred C57BL/JJcl mice. In young mice, similar phenotypes were associated with non-purified and semi-purified diets. However, in aged mice, semi-purified diets increased depressive behaviors in the tail suspension (P < 0.05) and forced swimming tests (P < 0.01). The corticosterone levels were similar between the two diets under normal rearing conditions. However, immediately after exposure to the stressful conditions of the forced swimming test, the corticosterone levels in the aged mice fed the semi-purified diet were higher than those of mice fed the non-purified diet (P < 0.05). There were fewer Lactobacillales in the small intestines of aged mice fed the semi-purified diet compared to those fed the non-purified diet (P < 0.01). Further, α-diversity was lower in aged mice fed the semi-purified versus non-purified diet (P < 0.01). Our results indicate that host physiology and gut microbiota differed according to whether the aged mice were fed a non-purified or semi-purified diet. Specifically, those fed the semi-purified diet were more vulnerable to stress than age-matched mice fed the non-purified diet. Our findings indicate that researchers should consider the effects of feed ingredients on depressive physiology and behaviors, and select diets that are appropriate for their particular research design. Further, identification of the ingredients in non-purified diets could facilitate examination of the mechanisms by which gut microbiota composition might increase resistance to stress and depression.     

The potential role of the gut microbiota in modulating renal function in experimental diabetic nephropathy murine models established in same environment

Recent studies have shown that laboratory murine autoimmunity models under the same environment display different outcomes. We established diabetic nephropathy model mice under the same environment using the classic streptozotocin method. Renal dysfunction was different among the mice. Proteinuria was more significant in the severe proteinuria group (SP) than in the mild proteinuria group (MP). We hypothesized a role for the gut microbiota in the outcome and reproducibility of induced DN models. 16S rDNA gene sequencing technology was used to analyze the differences in the gut microbiota between the two groups. Here, through fecal microbiota transplantation (FMT) and gas chromatography mass spectrometry (GC–MS), we verified the role of the gut microbiota and its short-chain fatty acid (SCFA) generation in DN mouse renal dysfunction. In the SP group, there was a reduced abundance of Firmicutes (P < 0.0001), and the dominant genus Allobaculum [linear discriminant analysis (LDA) >3, P < 0.05] was positively correlated with body weight (Rho = 0.767, P < 0.01) and blood glucose content (Rho = 0.648, P < 0.05), while the dominant genus Anaerosporobacter (LDA > 3, P < 0.05) was positively correlated with 24-hour urinary protein content (Rho = 0.773, P < 0.01). In the MP group, the dominant genus Blautia (LDA > 3, P < 0.05) was negatively correlated with 24-hour urinary protein content (Rho = −0.829, P < 0.05). The results indicated that Allobaculum and Anaerosporobacter may worsen renal function, while Blautia may be a protective factor in DN. These findings suggested that the gut microbiota may contribute to the heterogeneity of the induced response since we observed potential disease-associated microbial taxonomies and correlations with DN.     

Stability of the Maternal Gut Microbiota During Late Pregnancy and Early Lactation

Scarce research has been performed to assess whether the human maternal gut microbiota undergoes changes during the perinatal period. Therefore, in the present study, gut microbiota composition of seven healthy mothers(to-be) was assessed at different time points during the perinatal period (i.e. weeks 3–7 prepartum and days 3–6, 9–14, and 25–30 postpartum) using quantitative polymerase chain reaction (qPCR) and pyrosequencing, and was complemented by short-chain fatty acids (SCFA) and calprotectin quantification using high-performance liquid chromatography and enzyme-linked immunosorbent assay, respectively. qPCR revealed the predominance of members of the Firmicutes, Bacteroides, and Bifidobacterium without detectable changes over the perinatal period. Pyrosequencing supported these data in terms of microbiota stability for any population at any taxonomic level, although ratios of members of the Actinobacteria and Bacteroidetes differed between the two methods. However, the number of operational taxonomic units observed by pyrosequencing was subjected to fluctuations and the relative abundance of Streptococcus decreased numerically postpartum (P = 0.11), which may indicate that aberrancies in subdominant populations occur perinatally. Furthermore, total fecal SCFA concentrations, particularly the branched-chain fatty acids isobutyrate and isovalerate, were higher than for non-pregnant subjects throughout the perinatal period. This suggests metabolic changes and increased energy extraction via proteolytic, in addition to saccharolytic fermentation, accompanied by low-grade inflammation based on fecal calprotectin levels. Our data show that the maternal gut microbiota remained stable over the perinatal period despite altered metabolic activity and low-grade inflammation; however, it remains to be confirmed whether changes preceded earlier during pregnancy and succeeded later postpartum.     

Cyclocarya paliurus polysaccharides alleviate type 2 diabetic symptoms by modulating gut microbiota and short-chain fatty acids

BackgroundCyclocarya paliurus polysaccharide (CCPP), a primary active component in the leaves of Cyclocarya paliurus (Batal.) Iljinsk (C. paliurus), has the ability to treat type 2 diabetes mellitus (T2DM), but cannot be digested by our digestive system. Therefore, mechanisms of regulating the gut microbiota and intestinal metabolites might exist.PurposeTo reveal the potential mechanism of CCPP treatment, this study aimed to investigate the alterations of the gut microbiota and intestinal metabolites especially short chain fatty acids (SCFAs) in type 2 diabetic rats.Study design and methodsType 2 diabetic rat models were developed, and the therapeutic effects of CCPP were evaluated. Metagenomics analysis was utilized to analyze the alterations to the gut microbiota, and UHPLC-QTOF/MS-based untargeted metabolomics analysis of colon contents was used to identify the differential intestinal metabolites. GC/MS was used to measure the SCFAs in rat's colon contents and human fecal inoculums. Furthermore, the expression of SCFA receptors including GPR41, GPR43 and GPR109a was verified by qRT-PCR and the concentration of glucagon-like peptide-1(GLP-1) and peptide tyrosinetyrosine (PYY) was measured by Elisa.ResultsInhibition of the blood glucose levels and improvements in glucose tolerance and serum lipid parameters were observed after CCPP treatment. Eleven SCFA-producing species including Ruminococcus_bromii, Anaerotruncus_colihominis, Clostridium_methylpentosum, Roseburia_intestinalis, Roseburia_hominis, Clostridium_asparagiforme, Pseudoflavonifractor_capillosus, Intestinimonas_butyriciproducens, Intestinimonas_sp._GD2, Oscillibacter_valericigenes and Oscillibacter_ruminantium were clearly increased in the CCPP group. Furthermore, our study indicated that CCPP increases the production of SCFAs both in vivo and in vitro, and the gut microbiota are the key factor of this process. The SCFA receptors including GPR41, GPR43 and GPR109a, were significantly stimulated in the CCPP treated rats, which was accompanied by the upregulated expression of GLP-1 and PYY.ConclusionThese results demonstrated that CCPP could alleviate type 2 diabetic symptoms by increasing the SCFA-producing bacteria, promoting the production of SCFAs and upregulating SCFA-GLP1/PYY associated sensory mediators.     

Formation of propionate and butyrate by the human colonic microbiota

The human gut microbiota ferments dietary non‐digestible carbohydrates into short‐chain fatty acids (SCFA). These microbial products are utilized by the host and propionate and butyrate in particular exert a range of health‐promoting functions. Here an overview of the metabolic pathways utilized by gut microbes to produce these two SCFA from dietary carbohydrates and from amino acids resulting from protein breakdown is provided. This overview emphasizes the important role played by cross‐feeding of intermediary metabolites (in particular lactate, succinate and 1,2‐propanediol) between different gut bacteria. The ecophysiology, including growth requirements and responses to environmental factors, of major propionate and butyrate producing bacteria are discussed in relation to dietary modulation of these metabolites. A detailed understanding of SCFA metabolism by the gut microbiota is necessary to underpin effective strategies to optimize SCFA supply to the host.     

Pediococcus pentosaceus LI05 alleviates DSS-induced colitis by modulating immunological profiles,the gut microbiota and short-chain fatty acid levels in a mouse model

The gut microbiota is considered a key factor in pathogenesis and progression of inflammatory bowel disease (IBD). The bacterium Pediococcus pentosaceus LI05 alleviated host inflammation by maintaining the gut epithelial integrity, modulating the host immunity, gut microbiota and metabolism, but its effect on IBD remains unclear. The present study aimed to investigate the role and mechanisms of P. pentosaceus LI05. Mice were administered P. pentosaceus LI05 or phosphate-buffered saline once daily by oral gavage for 14 days, and colitis was induced by providing mice 2% DSS-containing drinking water for 7 days. P. pentosaceus LI05 ameliorated colitis in mice and reduced the body weight loss, disease activity index (DAI) scores, colon length shortening, intestinal permeability and the proinflammatory cytokine levels. Furthermore, a significantly altered gut microbiota composition with increased diversity and short-chain fatty acid (SCFA) production was observed in mice treated with P. pentosaceus LI05. Several genera, including Akkermansia and Faecalibacterium, were differentially enriched in the P. pentosaceus LI05-treated mice and were negatively correlated with colitis indices and positively correlated with gut barrier markers and SCFA levels. The P. pentosaceus LI05 treatment alleviated intestinal inflammation by maintaining the intestinal epithelial integrity and modulating the immunological profiles, gut microbiome and metabolite composition. Based on our findings, P. pentosaceus LI05 might be applied as potential preparation to ameliorate colitis.     

Indigenous Bacteria and Fungi Drive Traditional Kimoto Sake Fermentations

Sake (Japanese rice wine) production is a complex, multistage process in which fermentation is performed by a succession of mixed fungi and bacteria. This study employed high-throughput rRNA marker gene sequencing, quantitative PCR, and terminal restriction fragment length polymorphism to characterize the bacterial and fungal communities of spontaneous sake production from koji to product as well as brewery equipment surfaces. Results demonstrate a dynamic microbial succession, with koji and early moto fermentations dominated by Bacillus, Staphylococcus, and Aspergillus flavus var. oryzae, succeeded by Lactobacillus spp. and Saccharomyces cerevisiae later in the fermentations. The microbiota driving these fermentations were also prevalent in the production environment, illustrating the reservoirs and routes for microbial contact in this traditional food fermentation. Interrogating the microbial consortia of production environments in parallel with food products is a valuable approach for understanding the complete ecology of food production systems and can be applied to any food system, leading to enlightened perspectives for process control and food safety.     

A critical review on the impacts of β-glucans on gut microbiota and human health

The β-glucans are the glucose polymers present in the cells walls of yeast, fungi and cereals. β-Glucans are the major compositions of various nutritional diets such as oats, barley, seaweeds and mushrooms. Various biological activities of β-glucans have been reported such as anticancer, antidiabetic, anti-inflammatory and immune-modulating effects. The importance of β-glucans in food processing industries such as bread preparation, yogurt and pasta have been well elucidated. In recent findings on food science research gut microbiota plays a significant role and vastly studied for its intermediate role in regulating health. Several reports have suggested that β-glucans should have a significant impact on the gut microbiota changes and in turn on human health. The review was aimed to accumulate the evidence on types of β-glucans, their functional properties and the mechanism by how the β-glucans regulate the gut microbiota and human health. The various in vitro, in vivo and clinical studies, have been summarized, in particular, the changes happening upon the β-glucans supplementation on the gut microbiota. Overall, this review updates the recent studies on β-glucans and gut microbiota and also inputs the demanding questions to be addressed in β-glucans–microbiota research in the future.     

Cranberries attenuate animal-based diet-induced changes in microbiota composition and functionality: a randomized crossover controlled feeding trial

Cranberries have multiple health effects but their impact on gut microbiota has not been examined in randomized controlled feeding trials. We evaluated the relationship between the microbiota and cranberries in the context of an animal-based diet. In a randomized, double-blind, cross-over, controlled design trial, 11 healthy adults consumed for 5 days each a control diet (animal-based diet plus 30 g/day placebo powder) and a cranberry diet (animal-based diet plus 30 g/day freeze-dried whole cranberry powder). The animal-based diet included meats, dairy products, and simple sugars. Stool, urine, and blood samples were obtained before and after each intervention phase. As compared to the pre-control diet, control diet modified 46 taxonomic clades, including an increase in the abundance of Firmicutes and decrease in Bacteroidetes. Moreover, it increased bacteria-derived deoxycholic acid and decreased acetate and butyrate in stool. As compared to the post-intervention phase of control diet, the cranberry diet modified 9 taxonomic clades, including a decrease in the abundance of Firmicutes and increase in Bacteroidetes. Further, the cranberry diet attenuated control diet-induced increase in secondary bile acids and decrease in short-chain fatty acids (SCFA), and increased urinary anthocyanins and bacterially derived phenolic acids. No changes were found in fecal trimethylamine and plasma cytokines. In conclusion, an animal-based diet altered the microbiota composition to a less favorable profile, increased carcinogenic bile acids, and decreased beneficial SCFA. Cranberries attenuated the impact of the animal-based diet on microbiota composition, bile acids, and SCFA, evidencing their capacity to modulate the gut microbiota.     

Key bacterial taxa and metabolic pathways affecting gut short-chain fatty acid profiles in early life

Infant gut microbiota development affects the host physiology throughout life, and short-chain fatty acids (SCFAs) are promising key metabolites mediating microbiota-host relationships. Here, we investigated dense longitudinally collected faecal samples from 12 subjects during the first 2 years (n = 1048) to identify early life gut SCFA patterns and their relationships with the microbiota. Our results revealed three distinct phases of progression in the SCFA profiles: early phase characterised by low acetate and high succinate, middle-phase characterised by high lactate and formate and late-phase characterised by high propionate and butyrate. Assessment of the SCFA–microbiota relationships revealed that faecal butyrate is associated with increased Clostridiales and breastfeeding cessation, and that diverse and personalised assemblage of Clostridiales species possessing the acetyl-CoA pathway play major roles in gut butyrate production. We also found an association between gut formate and some infant-type bifidobacterial species, and that human milk oligosaccharides (HMO)-derived fucose is the substrate for formate production during breastfeeding. We identified genes upregulated in fucose and fucosylated HMO utilisation in infant-type bifidobacteria. Notably, bifidobacteria showed interspecific and intraspecific variation in the gene repertoires, and cross-feeding of fucose contributed to gut formate production. This study provides an insight into early life SCFA–microbiota relationships, which is an important step for developing strategies for modulating lifelong health.Subject terms: Microbial ecology, Microbiome, Bacterial genetics     

The association of fecal microbiota and fecal,blood serum and urine metabolites in myalgic encephalomyelitis/chronic fatigue syndrome

Introduction

The human gut microbiota has the ability to modulate host metabolism. Metabolic profiling of the microbiota and the host biofluids may determine associations significant of a host–microbe relationship. Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a long-term disorder of fatigue that is poorly understood, but has been linked to gut problems and altered microbiota.

Objectives

Find changes in fecal microbiota and metabolites in ME/CFS and determine their association with blood serum and urine metabolites.

Methods

A workflow was developed that correlates microbial counts with fecal, blood serum and urine metabolites quantitated by high-throughput ¹H NMR spectroscopy. The study consists of thirty-four females with ME/CFS (34.9?±?1.8 SE years old) and twenty-five non-ME/CFS female (33.0?±?1.6 SE years old).

Results

The workflow was validated using the non-ME/CFS cohort where fecal short chain fatty acids (SCFA) were associated with serum and urine metabolites indicative of host metabolism changes enacted by SCFA. In the ME/CFS cohort a decrease in fecal lactate and an increase in fecal butyrate, isovalerate and valerate were observed along with an increase in Clostridium spp. and a decrease in Bacteroides spp. These differences were consistent with an increase in microbial fermentation of fiber and amino acids to produce SCFA in the gut of ME/CFS patients. Decreased fecal amino acids positively correlated with substrates of gluconeogenesis and purine synthesis in the serum of ME/CFS patients.

Conclusion

Increased production of SCFA by microbial fermentation in the gut of ME/CFS patients may be associated with deleterious effects on the host energy metabolism.

     

Pediatric obesity is associated with an altered gut microbiota and discordant shifts in Firmicutes populations

An altered gut microbiota has been linked to obesity in adulthood, although little is known about childhood obesity. The aim of this study was to characterize the composition of the gut microbiota in obese (n = 42) and normal‐weight (n = 36) children aged 6 to 16. Using 16S rRNA gene‐targeted sequencing, we evaluated taxa with differential abundance according to age‐ and sex‐normalized body mass index (BMI z‐score). Obesity was associated with an altered gut microbiota characterized by elevated levels of Firmicutes and depleted levels of Bacteroidetes. Correlation network analysis revealed that the gut microbiota of obese children also had increased correlation density and clustering of operational taxonomic units (OTUs). Members of the Bacteroidetes were generally better predictors of BMI z‐score and obesity than Firmicutes, which was likely due to discordant responses of Firmicutes OTUs. In accordance with these observations, the main metabolites produced by gut bacteria, short chain fatty acids (SCFAs), were higher in obese children, suggesting elevated substrate utilisation. Multiple taxa were correlated with SCFA levels, reinforcing the tight link between the microbiota, SCFAs and obesity. Our results suggest that gut microbiota dysbiosis and elevated fermentation activity may be involved in the etiology of childhood obesity.     

Intestinal Microbiota and Microbial Metabolites Are Changed in a Pig Model Fed a High-Fat/Low-Fiber or a Low-Fat/High-Fiber Diet

The intestinal microbiota and its metabolites appear to be an important factor for gastrointestinal function and health. However, research is still needed to further elaborate potential relationships between nutrition, gut microbiota and host’s health by means of a suitable animal model. The present study examined the effect of two different diets on microbial composition and activity by using the pig as a model for humans. Eight pigs were equally allotted to two treatments, either fed a low-fat/high-fiber (LF), or a high-fat/low-fiber (HF) diet for 7 weeks. Feces were sampled at day 7 of every experimental week. Diet effects on fecal microbiota were assessed using quantitative real-time PCR, DNA fingerprinting and metaproteomics. Furthermore, fecal short-chain fatty acid (SCFA) profiles and ammonia concentrations were determined. Gene copy numbers of lactobacilli, bifidobacteria (P<0.001) and Faecalibacterium prausnitzii (P<0.05) were higher in the LF pigs, while Enterobacteriaceae were more abundant in the HF pigs (P<0.001). Higher numbers of proteins affiliated to Enterobacteriaceae were also present in the HF samples. Proteins for polysaccharide breakdown did almost exclusively originate from Prevotellaceae. Total and individual fecal SCFA concentrations were higher for pigs of the LF treatment (P<0.05), whereas fecal ammonia concentrations did not differ between treatments (P>0.05). Results provide evidence that beginning from the start of the experiment, the LF diet stimulated beneficial bacteria and SCFA production, especially butyrate (P<0.05), while the HF diet fostered those bacterial groups which have been associated with a negative impact on health conditions. These findings correspond to results in humans and might strengthen the hypothesis that the response of the porcine gut microbiota to a specific dietary modulation is in support of using the pig as suitable animal model for humans to assess diet-gut-microbiota interactions.Data are available via ProteomeXchange with identifier PXD003447.     

Epithelial Cell Proliferation Arrest Induced by Lactate and Acetate from Lactobacillus casei and Bifidobacterium breve

In an attempt to identify and characterize how symbiotic bacteria of the gut microbiota affect the molecular and cellular mechanisms of epithelial homeostasis, intestinal epithelial cells were co-cultured with either Lactobacillus or Bifidobacterium as bona fide symbionts to examine potential gene modulations. In addition to genes involved in the innate immune response, genes encoding check-point molecules controlling the cell cycle were among the most modulated in the course of these interactions. In the m-ICcl2 murine cell line, genes encoding cyclin E1 and cyclin D1 were strongly down regulated by L. casei and B. breve respectively. Cell proliferation arrest was accordingly confirmed. Short chain fatty acids (SCFA) were the effectors of this modulation, alone or in conjunction with the acidic pH they generated. These results demonstrate that the production of SCFAs, a characteristic of these symbiotic microorganisms, is potentially an essential regulatory effector of epithelial proliferation in the gut.