Influence Gut Microbiota Composition Research Articles

Genetic determinants of gut microbiota composition and bile acid profiles in mice.

The microbial communities that inhabit the distal gut of humans and other mammals exhibit large inter-individual variation. While host genetics is a known factor that influences gut microbiota composition, the mechanisms underlying this variation remain largely unknown. Bile acids (BAs) are hormones that are produced by the host and chemically modified by gut bacteria. BAs serve as environmental cues and nutrients to microbes, but they can also have antibacterial effects. We hypothesized that host genetic variation in BA metabolism and homeostasis influence gut microbiota composition. To address this, we used the Diversity Outbred (DO) stock, a population of genetically distinct mice derived from eight founder strains. We characterized the fecal microbiota composition and plasma and cecal BA profiles from 400 DO mice maintained on a high-fat high-sucrose diet for ~22 weeks. Using quantitative trait locus (QTL) analysis, we identified several genomic regions associated with variations in both bacterial and BA profiles. Notably, we found overlapping QTL for Turicibacter sp. and plasma cholic acid, which mapped to a locus containing the gene for the ileal bile acid transporter, Slc10a2. Mediation analysis and subsequent follow-up validation experiments suggest that differences in Slc10a2 gene expression associated with the different strains influences levels of both traits and revealed novel interactions between Turicibacter and BAs. This work illustrates how systems genetics can be utilized to generate testable hypotheses and provide insight into host-microbe interactions.

Impact of different hypercaloric diets on obesity features in rats: a metagenomics and metabolomics integrative approach

Diet is considered a key influencing agent affecting the gut microbiome. Dysbiosis of microbial communities contributes to the development of metabolic diseases such as obesity. We aimed to characterize the physiological, microbial and metabolic changes induced by different obesogenic diets to understand the diet-specific modulation of the host–microbiota co-metabolism in rodents. For this purpose, Wistar rats were fed standard, cafeteria (CAF), low-fat (LF), high-fat (HF) and high-fat high-sucrose (HFS) diets for 10 weeks. The CAF diet strongly induced an obese phenotype accompanied by dyslipidemia, hyperleptinemia, insulin resistance and hepatic steatosis, whereas both HF and HFS diets promoted overweight. Concerning the microbiome, CAF feeding induced a rise of the Bacteroidetes-to-Firmicutes ratio, while few microbial genera were altered in the HF or HFS group. Changes in microbial activity according to dietary treatment were also reflected in the disruption of short-chain fatty acid production and bile acid metabolism, which were mainly associated with fiber intake. Urinary metabolomics revealed a significant increase in metabolites related to oxidative stress and metabolic inflammation together with an altered excretion of host–microbiota co-metabolites only in the CAF group. Moreover, several associations between metabolic patterns, physiological status and specific microbial communities were described, helping to elucidate the crucial role of the microbiota in host homeostasis. Overall, our study suggests that different hypercaloric dietary models distinctively influence gut microbiota composition and reveals robust and similar clustering patterns concerning both cecal microbiome and urinary metabolome profiles.

Composition of Human Gut Microbiota After a Mediterranean Diet Intervention Among Fire Fighters (OR23-05-19)

ObjectivesWhile it is known that specific components of diet namely fiber, fatty acids, or polyphenols can modulate the gut microbiota, literature describing the influence of a specific dietary pattern such as the Mediterranean Diet (MD) on enteric microbiota especially in relation to health are scarce. The aim of this study was to evaluate whether a MD intervention and the adherence to MD influences the gut fecal microbial composition in firefighters participating in Feeding America’s Bravest, a randomized control trial. MethodsParticipants were firefighters who received a MD Nutritional Intervention (n = 22) or standard dietary advice (n = 24) as part of a cluster-randomized, controlled trial for 12 months. A lifestyle and food frequency questionnaire was administered and adherence scores to the MD were calculated (PREDIMED and Modified MD Score). Bacterial 16S rRNA sequencing was performed from fecal samples, and the microbial composition was analyzed with a bioinformatics pipeline implemented using QIIME 2. R software was used for linear modeling. ResultsThe predominant bacteria phyla in both groups were Firmicutes (52.9%), Bacteroidetes (39.8%), Proteobacteria (3.5%), and Actinobacteria (2.0%). A significant increase in the genus Prevotella was found in those in the intervention group (1.45 log-fold, P = 0.018) compared to controls. Furthermore, linear modeling revealed that higher adherence to MD was associated with lower abundance of Lachnospiriceae UCG-010 (R2 = 0.205, P < 0.001) and Eubacterium ventriosum group (R2 = 0.101, P = 0.016). There were no significant differences in alpha or beta diversity between the control and intervention group. ConclusionsA MD intervention as well as higher adherence influence gut microbiota composition; specifically, Prevotella, a genus previously associated with plant-rich diets, was significantly higher in the intervention group. Additionally, higher adherence to MD was associated with multiple genera of bacteria previously involved in SCFA production, which may help elucidate the beneficial effects of the Mediterranean Diet. Funding SourcesGrant support: EMW-2014-FP-00612, US Department of Homeland Security and Ohio University Startup funds.Trial Registration Number: NCT02941757

Exploring the effects of COLOSTRONONI on the mammalian gut microbiota composition.

COLOSTRONONI is a dietary supplement consisting of bovine colostrum and Morinda citrifolia fruit (Noni). In this study, we tested the capability of COLOSTRONONI to influence gut microbiota composition using an in vivo evaluation in rats. Furthermore, we analyzed the effect of COLOSTRONONI on the systemic inflammatory responses as well as on the gut permeability of the animals. Altogether, our analyses supported the concept of COLOSTRONONI as a natural food supplement that doesn't affect (neither negatively nor positively) gut microbiota homeostasis in healthy conditions. Moreover, COLOSTRONONI highlighted a lower effect in the expression of genes coding for IL-10, Il-12 and TNF-α response allowing us to hypothesize an immunomodulatory activity of this dietary supplement.

A descriptive analysis of gut microbiota composition in differentially reared infant rhesus monkeys (Macaca mulatta) across the first 6 months of life.

The gastrointestinal microbiome is recognized as a critical component in host immune function, physiology, and behavior. Early life experiences that alter diet and social contact also influence these outcomes. Despite the growing number of studies in this area, no studies to date have examined the contribution of early life experiences on the gut microbiome in infants across development. Such studies are important for understanding the biological and environmental factors that contribute to optimal gut microbial colonization and subsequent health. We studied infant rhesus monkeys (Macaca mulatta) across the first 6 months of life that were pseudo-randomly assigned to one of two different rearing conditions at birth: mother-peer-reared (MPR), in which infants were reared in social groups with many other adults and peers and nursed on their mothers, or nursery-reared (NR), in which infants were reared by human caregivers, fed formula, and given daily social contact with peers. We analyzed the microbiome from rectal swabs (total N = 97; MPR = 43, NR = 54) taken on the day of birth and at postnatal Days 14, 30, 90, and 180 using 16S rRNA gene sequencing. Bacterial composition differences were evident as early as 14 days, with MPR infants exhibiting a lower abundance of Bifidobacterium and a higher abundance of Bacteroides than NR infants. The most marked differences were observed at 90 days, when Bifidobacterium, Lactobacillus, Streptococcus, Bacteroides, Clostridium, and Prevotella differed across rearing groups. By Day 180, no differences in the relative abundances of the bacteria of interest were observed. These novel findings in developing primate neonates indicate that the early social environment as well as diet influence gut microbiota composition very early in life. These results also lay the groundwork for mechanistic studies examining the effects of early experiences on gut microbiota across development with the ultimate goal of understanding the clinical significance of developmental changes.

High dietary salt consumption in advanced age influences gut microbiota composition, metabolic flexibility, and cardiovascular response in exercise‐resistant rat model

AimsPopulations of older (&gt;age 65) adults are among the most varied for predicting beneficial outcomes to exercise and most vulnerable to environmental stressors (i.e., dietary change). Growing evidence suggests that inter‐individual variation in response to exercise plays a role in sustaining metabolic fitness and maintenance of healthspan. Given the importance of exercise capacity in predicting complex disease risk, we hypothesized that exercise‐resistant individuals with low response to exercise training are more vulnerable to the ill‐effects of dietary change and gut microbiota perturbation during aging when compared to exercise‐sensitive individuals with high response to exercise training.MethodsTo test our hypothesis, we fed 22–23‐months old male high response trainer (HRT) and low response trainer (LRT) rats with a high salt diet (2% NaCl, HSD) for 32 days. HRT and LRT rat models were developed by selectively breeding for low and high gain in running distance after 8 weeks of standardized treadmill exercise. Fecal microbial communities of HRT and LRT rats before and after HSD were profiled using 16S rRNA sequences. To test the effects of high dietary salt consumption on metabolic flexibility and cardiovascular risks, whole body metabolism was measured by indirect calorimetry (n = 10 per group, generation 24 of breeding selection). Cardiovascular response (e.g. blood pressure, heart rate) to HSD was monitored weekly using radiotelemetry (n = 11–12 per group, generation 23 of breeding selection) over the span of 24 hours.Results and ConclusionWe observed significant change in the composition of gut microbiota before and after HSD (i.e., increased Firmicutes/Bacteroidetes ratio). HSD consumption significantly altered energy metabolism in LRT rats as indicated by progressive decreases in both RER and glucose oxidation, and increases in fat oxidation. Interestingly, high salt intake appeared to decrease drinking and food consumption in LRT animals without any change in body weight. LRT rats also exhibited significantly decreased heart rate after HSD, especially during dark phase. However, we did not observe a significant increase in blood pressure during the course of the study in either LRT or HRT. Overall, our data suggests that high dietary salt consumption induces symbiosis of gut microbiota, reprioritizes energy metabolism, and triggers cardiovascular response in aged, exercise‐resistant rats over exercise‐sensitive rats, which may be associated with a decline of healthspan in exercise‐resistant individuals. Our study demonstrates HRT and LRT rats are a valuable contrasting animal model system for the study on the impacts of lifestyles and aging on metabolic fitness and cardiovascular risks.Support or Funding InformationResearch support: NIH Office of Research Infrastructure Programs grant P40OD021331.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Microbe and host interaction in gastrointestinal homeostasis

RationaleResearchers in psychiatry and neuroscience are increasingly recognizing the importance of gut-brain communication in mental health. Both genetics and environmental factors influence gut microbiota composition and function. This study examines host-microbe signaling at the gastrointestinal barrier to identify bottom-up mechanisms of microbiota-brain communication.ObjectivesWe examined differences in gut microbiota composition and fecal miRNA profiles in BALB/c and C57BL/6 mice, in relation to gastrointestinal homeostasis and evaluated the response to perturbation of the gut microbiota by broad-spectrum antibiotic treatment.Methods and resultsDifferences in the gut microbiota composition between BALB/c and C57BL/6 mice, evaluated by fecal 16S rRNA gene sequencing, included significant differences in genera Prevotella, Alistipes, Akkermansia, and Ruminococcus. Significant differences in fecal miRNA profiles were determined using the nCounter NanoString platform. A BLASTn analysis identified conserved fecal miRNA target regions in bacterial metagenomes with 14 significant correlations found between fecal miRNA and predicted taxa relative abundance in our dataset. Treatment with broad-spectrum antibiotics for 2 weeks resulted in a host-specific physiological response at the gastrointestinal barrier including a decrease in barrier permeability in BALB/c mice and alterations in the expression of barrier regulating genes in both strains. Genera Parabacteroides and Bacteroides were associated with changes in barrier function.ConclusionsThe results of this study provide insight into how specific taxa influence gut barrier integrity and function. More generally, these data in the context of recent published studies makes a significant contribution to our understanding of host-microbe interactions providing new knowledge that can be harnessed by us and others in future mechanistic studies.

Low Salivary Amylase Gene (AMY1) Copy Number Is Associated with Obesity and Gut Prevotella Abundance in Mexican Children and Adults.

Genome-wide association studies (GWAS) have identified copy number variants (CNVs) associated with obesity in chromosomal regions 1p31.1, 10q11.22, 11q11, 16p12.3, and recently 1p21.1, which contains the salivary amylase gene (AMY1). Recent evidence suggests this enzyme may influence gut microbiota composition through carbohydrate (mainly starch) degradation. The role of these CNVs in obesity has been scarcely explored in the Latino population, and thus the aim of our study was to evaluate the association of 1p31.1, 10q11.22, 11q11, 16p12.3 and 1p21.1 CNVs with obesity in 921 Mexican children, to replicate significant associations in 920 Mexican adults, and to analyze the association of AMY1 copy number with gut microbiota in 75 children and 45 adults. Of the five CNVs analyzed, 1q11 CNV was significantly associated with obesity in children, but not in adults. Only AMY1 CNV was significantly associated with obesity in both age groups. Moreover, gut microbiota analyses revealed a positive correlation between AMY1 copy number and Prevotella abundance. This genus has enzymes and gene clusters essential for complex polysaccharide degradation and utilization. To our knowledge, this is the first study to analyze the association of these five CNVs in the Mexican population and to report a correlation between AMY1 CN and gut microbiota in humans.

The Influence of Habitual Food Intake on Fecal Microbiota in Mexican School‐Age Children

BackgroundDiet has been considered as a major modifiable factor influencing gut microbiota composition and function. However this knowledge arises mainly from intervention studies in humans and animal models, where drastic changes in diet are made. In addition, it is important to study the diet not only at nutrient level but through food groups that comprise it, since it takes into account the food integrity. Yet there is insufficient evidence from observational studies addressing how consumption of certain food groups can influence gut microbiota composition, specifically in children of developing countries like Mexico. Therefore, the aim of this study was to evaluate the influence of food intake on the gut microbiota composition in Mexican school‐age children.MethodsThis study was a cross‐sectional study and included 382 children of Mexico City, between 5 and 12 years old (9.68; DE ± 1.8). Habitual dietary intake was assessed through a previously validated semi quantitative Food Frequency Questionnaire of 107 food items that were classified into 17 groups. Analysis of the fecal microbiota was performed through 16S rRNA sequencing, in the Illumina MiSeq platform. Association of fecal microbiota composition with food intake was performed using non‐parametric statistics. The study was performed in accordance with the Basic Principles of the Declaration of Helsinki.ResultsIn this study the intake of certain food groups; fruit, vegetables and legumes showed a positive correlation with the gut microbiota alpha diversity (Shannon index), after adjusting for age and sex (p &lt; 0.05). Higher intake of vegetables, legumes and yogurt further correlated at phyla level with higher relative abundance of Firmicutes (p &lt; 0.05). Yogurt also positively correlated with Actinobacteria relative abundance, specifically to higher abundance of Bifidobacterium. This is in accordance with other trials where yogurt intake has shown to increase Bifidobacteria number. Vegetable intake positively correlated with abundance of Lachnospiraceae, while higher consumption of legumes with increased abundance of Ruminococcaceae and Erysipelothrichaceae. The effect seen in Ruminococcaceae could be influenced by the fiber content of legumes.ConclusionThis study demonstrates that the consumption of vegetables, legumes, and yogurt was related to fecal microbiota composition. To our knowledge this is the first study in Mexican children evaluating the association of food groups with fecal microbiota composition. However it is necessary to continue the research to evaluate the effect of these associations with the metabolic phenotype.Support or Funding InformationThis work was supported by CONACYT grant 248765 to SM‐R

The enteric nervous system promotes intestinal health by constraining microbiota composition.

Sustaining a balanced intestinal microbial community is critical for maintaining intestinal health and preventing chronic inflammation. The gut is a highly dynamic environment, subject to periodic waves of peristaltic activity. We hypothesized that this dynamic environment is a prerequisite for a balanced microbial community and that the enteric nervous system (ENS), a chief regulator of physiological processes within the gut, profoundly influences gut microbiota composition. We found that zebrafish lacking an ENS due to a mutation in the Hirschsprung disease gene, sox10, develop microbiota-dependent inflammation that is transmissible between hosts. Profiling microbial communities across a spectrum of inflammatory phenotypes revealed that increased levels of inflammation were linked to an overabundance of pro-inflammatory bacterial lineages and a lack of anti-inflammatory bacterial lineages. Moreover, either administering a representative anti-inflammatory strain or restoring ENS function corrected the pathology. Thus, we demonstrate that the ENS modulates gut microbiota community membership to maintain intestinal health.

Impact of dietary pattern of the fecal donor on in vitro fermentation properties of whole grains and brans

Because diet influences gut microbiota composition and function, the purpose of this study was to determine how fecal donor diet impacts in vitro fermentation properties of whole grain flours and brans from corn, oats, rye, and wheat. Samples were fermented with fecal microbiota from subjects with similar energy intakes but differing in intakes of several beneficial nutrients (G1>G2). Shifts in the microbiota during fermentation were a function of diet group and time. Fecal microbiota from G1 subjects showed less decrease in diversity during fermentation and these microbiotas showed higher carbohydrate utilization and butyrate production compared with microbiota from G2 subjects. More carbohydrates were fermented from whole grains than brans. Rye induced high carbohydrate fermentability and butyrate production accompanied by low ammonia production, but only when using fecal microbiota from G1 subjects. Thus, diet quality influences the ability of the microbiota to ferment carbohydrates, differentiate among grains, and produce butyrate.

Fiber utilizing capacity varies with Prevotella versus Bacteroides enterotypes

The human gut microbiota is highly individualized because of the forces of diverse hosts’ genetic background, living environment and dietary habit. Population data on human gut microbiota show distinctive enterotypes (Prevotella, Bacteroides or Ruminococcus dominant) that are associated with long‐term diet patterns. Yet, enterotypes have not been linked with health status. Short chain fatty acids (SCFAs), generated by dietary fiber fermentation, are biologically active and are an important target related to colon and whole body health. Here, we were interested in understanding whether fibers produce different SCFA amounts and ratios in different enterotypes. A study was designed to explore how the different fiber structures influence gut microbiota composition and SCFA production in two enterotypes using an in vitro batch human fecal fermentation model.The dominance of Prevotella versus Bacteroides in the initial enterotypes had a large impact on SCFA products from fermentation of fibers of different types and with different chemical complexity. A single Prevotella OTU was exclusively promoted in the microbiome of the Prevotella enterotype when fed fructooligosaccharides (FOS) or sorghum or corn arabinoxylans (SAX, CAX), while in the Bacteroides enterotype different OTUs were enriched by each fiber (Lactobacillus by FOS, Bacteroides with different OTUs by SAX and CAX). SCFA production by the two enterotypes on the three fibers was substantially different. Propionate was initially 2–3 fold higher in the stool of the Prevotella compared to the Bacteroides enterotype, and had up to 4 fold higher increase with the fiber treatments. Furthermore, The total amount of SCFA generated by SAX and CAX matched at 24 h in each microbiota, but the fermentation rate varied with the simpler SAX structure fermenting fast in both enterotypes and the more complex CAX fermenting as fast as SAX in the Prevotella enterotype but much slower in the Bacteroides enterotype. Overall, the dominant fiber‐using bacteria and the type of dietary fiber together determined the SCFA profile generated by fermentation. This study shows the possibility to design fibers for future personalized medicine.

Diet, Gut Microbiota and Obesity

Increasing evidence suggests that alteration of gut microbiota ('dysbiosis') can lead to a number of diseases, including obesity, which affects a large population in the world and is now a global health issue. The mechanisms of gut microbiota-mediated obesity are just being explored and characterized in recent years. It has been suggested that dysbiosis of gut microbiota contributes to obesity development mainly in three ways: affecting energy harvest, altering host gene expression, and triggering chronic inflammation. Among the factors that determine and influence gut microbiota composition, diet is one of the best characterized in human and animal studies, and has been long linked with weight gain or loss. In this review, we will discuss recent advances of mechanisms through which gut microbiota dysbiosis leads to obesity. We will further discuss the underlying causes of obesity-related gut microbiota, highlighting dietary effects.

Intestinal Microbiota and Celiac Disease: Cause, Consequence or Co-Evolution?

It is widely recognized that the intestinal microbiota plays a role in the initiation and perpetuation of intestinal inflammation in numerous chronic conditions. Most studies report intestinal dysbiosis in celiac disease (CD) patients, untreated and treated with a gluten-free diet (GFD), compared to healthy controls. CD patients with gastrointestinal symptoms are also known to have a different microbiota compared to patients with dermatitis herpetiformis and controls, suggesting that the microbiota is involved in disease manifestation. Furthermore, a dysbiotic microbiota seems to be associated with persistent gastrointestinal symptoms in treated CD patients, suggesting its pathogenic implication in these particular cases. GFD per se influences gut microbiota composition, and thus constitutes an inevitable confounding factor in studies conducted in CD patients. To improve our understanding of whether intestinal dysbiosis is the cause or consequence of disease, prospective studies in healthy infants at family risk of CD are underway. These studies have revealed that the CD host genotype selects for the early colonizers of the infant’s gut, which together with environmental factors (e.g., breast-feeding, antibiotics, etc.) could influence the development of oral tolerance to gluten. Indeed, some CD genes and/or their altered expression play a role in bacterial colonization and sensing. In turn, intestinal dysbiosis could promote an abnormal response to gluten or other environmental CD-promoting factors (e.g., infections) in predisposed individuals. Here, we review the current knowledge of host-microbe interactions and how host genetics/epigenetics and environmental factors shape gut microbiota and may influence disease risk. We also summarize the current knowledge about the potential mechanisms of action of the intestinal microbiota and specific components that affect CD pathogenesis.

The gut microbiome and diet in psychiatry: focus on depression.

With depressive disorders the leading source of disability globally, the identification of new targets for prevention and management is imperative. A rapidly emerging field of research suggests that the microbiome-gut-brain axis is of substantial relevance to mood and behaviour. Similarly, unhealthy diet has recently emerged as a significant correlate of and risk factor for depression. This review provides evidence for the gut microbiota as a key factor mediating the link between diet and depressive illness. The development of new technologies is affording a better understanding of how diet influences gut microbiota composition and activity and how this may, in turn, influence depressive illness. New interventions are also suggesting the possible utility of pre and probiotic formulations and fermented food in influencing mental health. Although in its early stages, the emerging field of research focused on the human microbiome suggests an important role for the gut microbiota in influencing brain development, behaviour and mood in humans. The recognition that the gut microbiota interacts bidirectionally with other environmental risk factors, such as diet and stress, suggests promise in the development of interventions targeting the gut microbiota for the prevention and treatment of common mental health disorders.

The gut microbiota appears to compensate for seasonal diet variation in the wild black howler monkey (Alouatta pigra).

For most mammals, including nonhuman primates, diet composition varies temporally in response to differences in food availability. Because diet influences gut microbiota composition, it is likely that the gut microbiota of wild mammals varies in response to seasonal changes in feeding patterns. Such variation may affect host digestive efficiency and, ultimately, host nutrition. In this study, we investigate the temporal variation in diet and gut microbiota composition and function in two groups (N = 13 individuals) of wild Mexican black howler monkeys (Alouatta pigra) over a 10-month period in Palenque National Park, Mexico. Temporal changes in the relative abundances of individual bacterial taxa were strongly correlated with changes in host diet. For example, the relative abundance of Ruminococcaceae was highest during periods when energy intake was lowest, and the relative abundance of Butyricicoccus was highest when young leaves and unripe fruit accounted for 68 % of the diet. Additionally, the howlers exhibited increased microbial production of energy during periods of reduced energy intake from food sources. Because we observed few changes in howler activity and ranging patterns during the course of our study, we propose that shifts in the composition and activity of the gut microbiota provided additional energy and nutrients to compensate for changes in diet. Energy and nutrient production by the gut microbiota appears to provide an effective buffer against seasonal fluctuations in energy and nutrient intake for these primates and is likely to have a similar function in other mammal species.

Long-term dietary pattern of fecal donor correlates with butyrate production and markers of protein fermentation during in vitro fecal fermentation

Diet influences gut microbiota composition. Therefore, we hypothesized that diet would impact the extent of dietary fiber utilization and the types of metabolic end-products produced by the microbiota during in vitro fecal fermentation. By obtaining long-term dietary records from fecal donors, we aimed to determine the correlations between dietary intake variables and dietary fiber degradation and short-/branched-chain fatty acid (BCFA) and ammonia production during in vitro fecal fermentation. Eighteen subjects completed 1-year diet history questionnaires and provided fecal samples that were used for in vitro fermentation of a whole wheat substrate. The percentage of dietary fiber fermented was not correlated with nutrient intakes; however, butyrate production was correlated with fecal donor intake of many nutrients of which principal component analysis revealed were mostly contributed by grain-, nut-, and vegetable-based foods. Negative correlations were found for propionate with intake of total carbohydrate, added sugar, and sucrose and for ammonia and BCFA production with intake of unsaturated fats. Thus, our analysis did not support our first hypothesis: the percentage of dietary fiber fermented during in vitro fermentation was not correlated with dietary records. However, production of butyrate; BCFA; ammonia; and, to a lesser extent, propionate was correlated with the diet records of fecal donors, thus supporting our second hypothesis. These results suggest that diets high in plant-based foods and high in unsaturated fats are associated with microbial metabolism that is consistent with host health.

Major Histocompatibility Complex class IIb polymorphism influences gut microbiota composition and diversity.

Animals harbour diverse communities of symbiotic bacteria, which differ dramatically among host individuals. This heterogeneity poses an immunological challenge: distinguishing between mutualistic and pathogenic members of diverse and host-specific microbial communities. We propose that Major Histocompatibility class II (MHC) genotypes contribute to recognition and regulation of gut microbes, and thus, MHC polymorphism contributes to microbial variation among hosts. Here, we show that MHC IIb polymorphism is associated with among-individual variation in gut microbiota within a single wild vertebrate population of a small fish, the threespine stickleback. We sampled stickleback from Cedar Lake, on Vancouver Island, and used next-generation sequencing to genotype the sticklebacks' gut microbiota (16S sequencing) and their MHC class IIb exon 2 sequences. The presence of certain MHC motifs was associated with altered relative abundance (increase or decrease) of some microbial Families. The effect sizes are modest and entail a minority of microbial taxa, but these results represent the first indication that MHC genotype may affect gut microbiota composition in natural populations (MHC-microbe associations have also been found in a few studies of lab mice). Surprisingly, these MHC effects were frequently sex-dependent. Finally, hosts with more diverse MHC motifs had less diverse gut microbiota. One implication is that MHC might influence the efficacy of therapeutic strategies to treat dysbiosis-associated disease, including the outcome of microbial transplants between healthy and diseased patients. We also speculate that macroparasite-driven selection on MHC has the potential to indirectly alter the host gut microbiota, and vice versa.

Luminal ATP: the missing link between intestinal alkaline phosphatase, the gut microbiota, and inflammation?

gut dysbiosis is a common feature to many inflammatory diseases but the cause-and-effect relationships between the gut microbiota and host inflammation are poorly understood. For metabolic disorders and obesity, however, bacterial lipopolysaccharide (LPS), an emblematic member of pathogen-associated

Gut microbiota and the development of obesity.

Advances in tools for molecular investigations have allowed deeper understanding of how microbes can influence host physiology. A very interesting field of research that has gained attention recently is the possible role of gut microbiota in the development of obesity and metabolic disorders. The aim of this review is to discuss mechanisms that explain the influence of gut microbiota on host metabolism. The gut microbiota is important for normal physiology of the host. However, differences in their composition may have different impacts on host metabolism. It has been shown that obese and lean subjects present different microbiota composition profile. These differences in microbiota composition may contribute to weight imbalance and impaired metabolism. The evidences from animal models suggest that it is possible that the microbiota of obese subjects has higher capacity to harvest energy from the diet providing substrates that can activate lipogenic pathways. In addition, microorganisms can also influence the activity of lipoprotein lipase interfering in the accumulation of triglycerides in the adipose tissue. The interaction of gut microbiota with the endocannabinoid system provides a route through which intestinal permeability can be altered. Increased intestinal permeability allows the entrance of endotoxins to the circulation, which are related to the induction of inflammation and insulin resistance in mice. The impact of the proposed mechanisms for humans still needs further investigations. However, the fact that gut microbiota can be modulated through dietary components highlights the importance to study how fatty acids, carbohydrates, micronutrients, prebiotics, and probiotics can influence gut microbiota composition and the management of obesity. Gut microbiota seems to be an important and promising target in the prevention and treatment of obesity and its related metabolic disturbances in future studies and in clinical practice.