Consumption of acidic water alters the gut microbiome and decreases the risk of diabetes in NOD mice

Zamzam Water Mitigates Cardiac Toxicity Risk through Modulation of GUT Microbiota and the Renin-angiotensin System

BACKGROUND

Cardiovascular diseases (CVDs) continue to exert a substantial global influence in specific areas due to population growth, aging, microbiota, and genetic/environmental factors. Drinking water has a strong impact on the health of an individual. Further, emerging evidence has highlighted the therapeutic potential and benefits of Zamzam water (Zam).

OBJECTIVE

We investigated the influence of Zam on doxorubicin-induced cardiac toxicity, elucidating its consequential effects on GUT microbiota dysbiosis and hepatic and renal functions.

METHODS

Male rats were categorized into four groups: Group 1 as Normal control (NC), Group 2 as Zamzam control (ZC), Group 3 Disease control (DC) and Group 4 as Therapeutic control (DZ) treated with Zam against doxorubicin-induced disease at a dose of 1mg/kg boy weight) intraperitoneally (i.p).

RESULTS

Significant dysbiosis in the composition of GM was observed in the DC group along with a significant decrease (p < 0.05) in serum levels of Zinc, interleukin-10 (IL-10), IL-6 and Angiotensin II (Ang II), while C-reactive protein (CRP), fibrinogen, and CKMB increased significantly (restoration of Zinc ions (0.72 ± 0.07 mcg/mL) compared to NC. Treatment with Zamzam exhibited a marked abundance of 18-times to 72% in Romboutsia, a genus of firmicutes, along with lowering of Proteobacteria in DZ followed by significant restoration of Zinc ions (0.72 ± 0.07 mcg/mL), significant (p ˂ 0.05) reduction in CRP (7.22 ± 0.39 mg/dL), CKMB (118.8 ± 1.02 U/L) and Fibrinogen (3.18 ± 0.16 mg/dL), significant (p < 0.05) increase in IL-10 (7.22 ± 0.84 pg/mL) and IL-6 (7.18 ± 0.40 pg/ml), restoration of Ang II (18.62 ± 0.50 nmol/mL/min), marked increase in renin with normal myocyte architecture and tissue orientation of kidney, and restoration of histological architecture of hepatocyte.

CONCLUSION

Zam treatment mitigated cardiac toxicity risk through the modulation of GUT microbiota and the renin-angiotensin system and tissue histology effectively.

A Review of the Effects of Some Extrinsic Factors on Mice Used in Research

Animals have been used in research for over 2,000 y. From very crude experiments conducted by ancient scholars, animal research, as a science, was refined over hundreds of years to what we know it as today. However, the housing conditions of animals used for research did not improve significantly until less than 100 years ago when guidelines for housing research animals were first published. In addition, it was not until relatively recently that some extrinsic factors were recognized as a research variable, even when animals were housed under recommended guidelines. For example, temperature, humidity, light, noise, vibration, diet, water, caging, bedding, etc., can all potentially affect research using mice, contributing the inability of others to reproduce published findings. Consequently, these external factors should be carefully considered in the design, planning, and execution of animal experiments. In addition, as recommended by others, the housing and husbandry conditions of the animals should be described in detail in publications resulting from animal research to improve study reproducibility. Here, we briefly review some common, and less common, external factors that affect research in one of the most popular animal models, the mouse.

Acidified drinking water attenuates motor deficits and brain pathology in a mouse model of a childhood neurodegenerative disorder

We recently demonstrated that HCl-acidified drinking water, which is widely used in laboratory animal facilities, had some beneficial effects in the Cln3−/− mouse model of juvenile Batten disease, a neurodegenerative lysosomal storage disorder1. Here we tested if acidified drinking water has therapeutic effects in Cln1R151X nonsense mutant mice, a model of the infantile form of Batten disease. In Cln1R151X mice, acidified drinking water received from weaning prevented the impairment in pole climbing ability measured at 3 and 6 months of age. Histopathological analysis of the brain at 6 months showed that acidified drinking water decreased the amount of lysosomal storage material, reduced astrocytosis in the striatum and somatosensory barrelfield cortex, and attenuated microglial activation in the thalamus. Compared to wild-type mice, the gut microbiota of Cln1R151X mice was markedly different. Acidified drinking water significantly altered the gut microbiota composition of Cln1R151X mice, indicating a contribution of gut bacteria to the therapeutic effects of acidified water. Our results in Cln1R151X mice suggest that acidified drinking water may have beneficial effects for patients with infantile Batten disease. This study also verifies that acidified drinking water can modify disease phenotypes in mouse models, contributing to the inter-laboratory variations in neurological and pathological findings.

Kidney metabolism and acid-base control: back to the basics

Kidneys are central in the regulation of multiple physiological functions, such as removal of metabolic wastes and toxins, maintenance of electrolyte and fluid balance, and control of pH homeostasis. In addition, kidneys participate in systemic gluconeogenesis and in the production or activation of hormones. Acid-base conditions influence all these functions concomitantly. Healthy kidneys properly coordinate a series of physiological responses in the face of acute and chronic acid-base disorders. However, injured kidneys have a reduced capacity to adapt to such challenges. Chronic kidney disease patients are an example of individuals typically exposed to chronic and progressive metabolic acidosis. Their organisms undergo a series of alterations that brake large detrimental changes in the homeostasis of several parameters, but these alterations may also operate as further drivers of kidney damage. Acid-base disorders lead not only to changes in mechanisms involved in acid-base balance maintenance, but they also affect multiple other mechanisms tightly wired to it. In this review article, we explore the basic renal activities involved in the maintenance of acid-base balance and show how they are interconnected to cell energy metabolism and other important intracellular activities. These intertwined relationships have been investigated for more than a century, but a modern conceptual organization of these events is lacking. We propose that pH homeostasis indissociably interacts with central pathways that drive progression of chronic kidney disease, such as inflammation and metabolism, independent of etiology.

Drinking Water Source and Intake Are Associated with Distinct Gut Microbiota Signatures in US and UK Populations

BACKGROUND

The microbiome of the digestive tract exerts fundamental roles in host physiology. Extrinsic factors including lifestyle and diet are widely recognized as key drivers of gut and oral microbiome compositions. Although drinking water is among the food items consumed in the largest amount, little is known about its potential impact on the microbiome.

OBJECTIVES

We explored the associations of plain drinking water source and intake with gut and oral microbiota compositions in a population-based cohort.

METHODS

Microbiota, health, lifestyle, and food intake data were extracted from the American Gut Project public database. Associations of drinking water source (bottled, tap, filtered, or well water) and intake with global microbiota composition were evaluated using linear and logistic models adjusted for anthropometric, diet, and lifestyle factors in 3413 and 3794 individuals, respectively (fecal samples; 56% female, median [IQR] age: 48 [36-59] y; median [IQR] BMI: 23.3 [20.9-26.3] kg/m2), and in 283 and 309 individuals, respectively (oral samples).

RESULTS

Drinking water source ranked among the key contributing factors explaining the gut microbiota variation, accounting for 13% [Faith's phylogenetic diversity (Faith's PD)] and 47% (Bray-Curtis dissimilarity) of the age effect size. Drinking water source was associated with differences in gut microbiota signatures, as revealed by β diversity analyses (P < 0.05; Bray-Curtis dissimilarity, weighted UniFrac distance). Subjects drinking mostly well water had higher fecal α diversity (P < 0.05; Faith's PD, observed amplicon sequence variants), higher Dorea, and lower Bacteroides, Odoribacter, and Streptococcus than the other groups. Low water drinkers also exhibited gut microbiota differences compared with high water drinkers (P < 0.05; Bray-Curtis dissimilarity, unweighted UniFrac distance) and a higher abundance of Campylobacter. No associations were found between oral microbiota composition and drinking water consumption.

CONCLUSIONS

Our results indicate that drinking water may be an important factor in shaping the human gut microbiome and that integrating drinking water source and intake as covariates in future microbiome analyses is warranted.

Host genetic control of gut microbiome composition

The gut microbiome plays a significant role in health and disease, and there is mounting evidence indicating that the microbial composition is regulated in part by host genetics. Heritability estimates for microbial abundance in mice and humans range from (0.05-0.45), indicating that 5-45% of inter-individual variation can be explained by genetics. Through twin studies, genetic association studies, systems genetics, and genome-wide association studies (GWAS), hundreds of specific host genetic loci have been shown to associate with the abundance of discrete gut microbes. Using genetically engineered knock-out mice, at least 30 specific genes have now been validated as having specific effects on the microbiome. The relationships among of host genetics, microbiome composition, and abundance, and disease is now beginning to be unraveled through experiments designed to test causality. The genetic control of disease and its relationship to the microbiome can manifest in multiple ways. First, a genetic variant may directly cause the disease phenotype, resulting in an altered microbiome as a consequence of the disease phenotype. Second, a genetic variant may alter gene expression in the host, which in turn alters the microbiome, producing the disease phenotype. Finally, the genetic variant may alter the microbiome directly, which can result in the disease phenotype. In order to understand the processes that underlie the onset and progression of certain diseases, future research must take into account the relationship among host genetics, microbiome, and disease phenotype, and the resources needed to study these relationships.

Establishing Pediatric Mouse Models of the Hematopoietic Acute Radiation Syndrome and the Delayed Effects of Acute Radiation Exposure

Medical countermeasures (MCMs) for hematopoietic acute radiation syndrome (H-ARS) should be evaluated in well-characterized animal models, with consideration of at-risk populations such as pediatrics. We have developed pediatric mouse models of H-ARS and delayed effects of acute radiation exposure (DEARE) for efficacy testing of MCMs against radiation. Male and female C57BL/6J mice aged 3, 4, 5, 6, 7 and 8 weeks old (±1 day) were characterized for baseline hematopoietic and gastrointestinal parameters, radiation response, efficacy of a known MCM, and DEARE at six and 12 months after total-body irradiation (TBI). Weanlings (age 3 weeks) were the most radiosensitive age group with an estimated LD50/30 of 712 cGy, while mice aged 4 to 8 weeks were more radioresistant with an estimated LD50/30 of 767-787 cGy. Female weanlings were more radiosensitive than males at 3 and 4 weeks old but became significantly more radioresistant after the pubertal age of 5 weeks. The most dramatic increase in body weight, RBC counts and intestinal circumference length occurred from 3 to 5 weeks of age. The established radiomitigator Neulasta® (pegfilgrastim) significantly increased 30-day survival in all age groups, validating these models for MCM efficacy testing. Analyses of DEARE among pediatric survivors revealed depressed weight gain in males six months post-TBI, and increased blood urea nitrogen at 12 months post-TBI which was more severe in females. Hematopoietic DEARE at six months post-TBI appeared to be less severe in survivors from the 3- and 4-week-old groups but was equally severe in all age groups by 12 months of age. Similar to our other acute radiation mouse models, there was no appreciable effect of Neulasta used as an H-ARS MCM on the severity of DEARE. In summary, these data characterize a pediatric mouse model useful for assessing the efficacy of MCMs against ARS and DEARE in children.

The acidified drinking water-induced changes in the behavior and gut microbiota of wild-type mice depend on the acidification mode

Acidification of drinking water to a pH between 2.5 and 3.0 is widely used to prevent the spread of bacterial diseases in animal colonies. Besides hydrochloric acid (HCl), sulfuric acid (H₂SO₄) is also used to acidify drinking water. Here we examined the effects of H₂SO₄-acidified drinking water (pH = 2.8) received from weaning (postnatal day 21) on the behavior and gut microflora of 129S6/SvEv mice, a mouse strain commonly used in transgenic studies. In contrast to HCl-acidified water, H₂SO₄-acidified water only temporarily impaired the pole-descending ability of mice (at 3 months of age), and did not change the performance in an accelerating rotarod test. As compared to 129S6/SvEv mice receiving non-acidified or HCl-acidified drinking water, the gut microbiota of 129S6/SvEv mice on H₂SO₄-acidified water displayed significant alterations at every taxonomic level especially at 6 months of age. Our results demonstrate that the effects of acidified drinking water on the behavior and gut microbiota of 129S6/SvEv mice depends on the acid used for acidification. To shed some light on how acidified drinking water affects the physiology of 129S6/SvEv mice, we analyzed the serum and fecal metabolomes and found remarkable, acidified water-induced alterations.

Dietary Indole-3-Carbinol Activates AhR in the Gut, Alters Th17-Microbe Interactions, and Exacerbates Insulitis in NOD Mice

The diet represents one environmental risk factor controlling the progression of type 1 diabetes (T1D) in genetically susceptible individuals. Consequently, understanding which specific nutritional components promote or prevent the development of disease could be used to make dietary recommendations in prediabetic individuals. In the current study, we hypothesized that the immunoregulatory phytochemcial, indole-3-carbinol (I3C) which is found in cruciferous vegetables, will regulate the progression of T1D in nonobese diabetic (NOD) mice. During digestion, I3C is metabolized into ligands for the aryl hydrocarbon receptor (AhR), a transcription factor that when systemically activated prevents T1D. In NOD mice, an I3C-supplemented diet led to strong AhR activation in the small intestine but minimal systemic AhR activity. In the absence of this systemic response, the dietary intervention led to exacerbated insulitis. Consistent with the compartmentalization of AhR activation, dietary I3C did not alter T helper cell differentiation in the spleen or pancreatic draining lymph nodes. Instead, dietary I3C increased the percentage of CD4+RORγt+Foxp3- (Th17 cells) in the lamina propria, intraepithelial layer, and Peyer's patches of the small intestine. The immune modulation in the gut was accompanied by alterations to the intestinal microbiome, with changes in bacterial communities observed within one week of I3C supplementation. A transkingdom network was generated to predict host-microbe interactions that were influenced by dietary I3C. Within the phylum Firmicutes, several genera (Intestinimonas, Ruminiclostridium 9, and unclassified Lachnospiraceae) were negatively regulated by I3C. Using AhR knockout mice, we validated that Intestinimonas is negatively regulated by AhR. I3C-mediated microbial dysbiosis was linked to increases in CD25high Th17 cells. Collectively, these data demonstrate that site of AhR activation and subsequent interactions with the host microbiome are important considerations in developing AhR-targeted interventions for T1D.

The gut microbiome of laboratory mice: considerations and best practices for translational research

Just as the gut microbiota (GM) is now recognized as an integral mediator of environmental influences on human physiology, susceptibility to disease, and response to pharmacological intervention, so too does the GM of laboratory mice affect the phenotype of research using mouse models. Multiple experimental factors have been shown to affect the composition of the GM in research mice, as well as the model phenotype, suggesting that the GM represents a major component in experimental reproducibility. Moreover, several recent studies suggest that manipulation of the GM of laboratory mice can substantially improve the predictive power or translatability of data generated in mouse models to the human conditions under investigation. This review provides readers with information related to these various factors and practices, and recommendations regarding methods by which issues with poor reproducibility or translatability can be transformed into discoveries.

The Influence of Feed and Drinking Water on Terrestrial Animal Research and Study Replicability

For more than 50 years, the research community has made strides to better determine the nutrient requirements for many common laboratory animal species. This work has resulted in high-quality animal feeds that can optimize growth, maintenance, and reproduction in most species. We have a much better understanding of the role that individual nutrients play in physiological responses. Today, diet is often considered as an independent variable in experimental design, and specialized diet formulations for experimental purposes are widely used. In contrast, drinking water provided to laboratory animals has rarely been a consideration in experimental design except in studies of specific water-borne microbial or chemical contaminants. As we advance in the precision of scientific measurements, we are constantly discovering previously unrecognized sources of experimental variability. This is the nature of science. However, science is suffering from a lack of experimental reproducibility or replicability that undermines public trust. The issue of reproducibility/replicability is especially sensitive when laboratory animals are involved since we have the ethical responsibility to assure that laboratory animals are used wisely. One way to reduce problems with reproducibility/replicability is to have a strong understanding of potential sources of inherent variability in the system under study and to provide "…a clear, specific, and complete description of how the reported results were reached [1]." A primary intent of this review is to provide the reader with a high-level overview of some basic elements of laboratory animal nutrition, methods used in the manufacturing of feeds, sources of drinking water, and general methods of water purification. The goal is to provide background on contemporary issues regarding how diet and drinking water might serve as a source of extrinsic variability that can impact animal health, study design, and experimental outcomes and provide suggestions on how to mitigate these effects.

Metagenomic insights into the effects of nanobubble water on the composition of gut microbiota in mice

The particular physicochemical and biological properties of nanobubbles (NBs) have prompted many researchers to conduct an in-depth study on their potential application in various fields. This study aims to investigate the effects of nanobubble water (NBW) on the community structure of the gut microbiota in mice. In this study, supplementation with nitrogen NBW (SD-N₂ group), hydrogen NBW (SD-H₂ group) and deionized water (SD-C group) to a standard diet of mice was performed for five weeks. The composition of fecal microbiota was analyzed by using 16S rRNA gene sequencing. Compared with the SD-C group, the species diversity of the fecal microbiota in mice in NBW groups was significantly increased. At the genus level, supplementation with nitrogen NBW to mice significantly increased the relative abundance of two beneficial genera Clostridium and Coprococcus (mean growth 6.3 times and 9.7 times, respectively), while supplementation with hydrogen NBW significantly decreased the relative abundance of two pathogenic genera Mucispirillum and Helicobacter (mean reduction rate 86% and 60%, respectively). These results demonstrate that supplementation with NBW might optimize the composition of gut microbiota in mice.

Dissociation of Adaptive Thermogenesis from Glucose Homeostasis in Microbiome-Deficient Mice

Recent studies suggest that a key mechanism whereby the gut microbiome influences energy balance and glucose homeostasis is through the recruitment of brown and beige adipocytes, primary mediators of the adaptive thermogenic response. To test this, we assessed energy expenditure and glucose metabolism in two complementary mouse models of gut microbial deficiency, which were exposed to a broad range of thermal and dietary stresses. Neither ablation of the gut microbiome, nor the substantial microbial perturbations induced by cold ambient temperatures, influenced energy expenditure during cold exposure or high-fat feeding. Nevertheless, we demonstrated a critical role for gut microbial metabolism in maintaining euglycemia through the production of amino acid metabolites that optimized hepatic TCA (tricarboxylic acid) cycle fluxes in support of gluconeogenesis. These results distinguish the dispensability of the gut microbiome for the regulation of energy expenditure from its critical contribution to the maintenance of glucose homeostasis.

The Interplay between Immune System and Microbiota in Diabetes

Diabetes is not a single and homogeneous disease, but a cluster of metabolic diseases characterized by the common feature of hyperglycemia. The pathogenesis of type 1 diabetes (T1D) and type 2 diabetes (T2D) (and all other intermediate forms of diabetes) involves the immune system, in terms of inflammation and autoimmunity. The past decades have seen an increase in all types of diabetes, accompanied by changes in eating habits and consequently a structural evolution of gut microbiota. It is likely that all these events could be related and that gut microbiota alterations might be involved in the immunomodulation of diabetes. Thus, gut microbiota seems to have a direct, even causative role in mediating connections between the environment, food intake, and chronic disease. As many conditions that increase the risk of diabetes modulate gut microbiota composition, it is likely that immune-mediated reactions, induced by alterations in the composition of the microbiota, can act as facilitators for the onset of diabetes in predisposed subjects. In this review, we summarize recent evidence in the field of gut microbiota and the role of the latter in modulating the immune reactions involved in the pathogenesis of diabetes.

Long-Term Potable Effects of Alkalescent Mineral Water on Intestinal Microbiota Shift and Physical Conditioning

BACKGROUND

An alkalescent (pH 8.3) mineral water (AMW) of Hita basin, located in the northwestern part of Kyushu island in Japan, has been recognized for the unique quality of ingredients including highly concentrated silicic acid, sodium, potassium, and hydrogen carbonate. The biological effects of AMW intake were evaluated with a particular focus on its "antiobesity" properties through its modulation of the gut microbiota population.

METHODS

Two groups of C57BL6/J mice (8-week-old male) were maintained with a standard diet and tap water (control: TWC group) or AMW (AMW group) for 6 months and the following outputs were quantitated: (1) food and water intake, (2) body weight (weekly), (3) body fat measurements by CT scan (monthly), (4) sera biochemical values (TG, ALT, AST, and ALP), and (5) UCP-1 mRNA in fat tissues (terminal point). Two groups of ICR mice (7-week-old male) were maintained with the same method and their feces were collected at the 0, 1st, 3rd, and 6th month at which time the population rates of gut microbiota were quantitated using metagenomic sequencing analysis of 16S-rRNA.

RESULTS

Among all antiobesity testing items, even though a weekly dietary consumption was increased (p=0.012), both ratios of weight gain (p=1.21E - 10) and visceral fat accumulation (p=0.029) were significantly reduced in the AMW group. Other criteria including water intake (p=0.727), the amounts of total (p=0.1602), and subcutaneous fat accumulation (p=0.052) were within the margin of error and UCP-1 gene expression level (p=0.171) in the AMW group was 3.89-fold higher than that of TWC. Among 8 major gut bacteria families, Lactobacillaceae (increased, p=0.029) and Clostridiaceae (decreased, p=0.029) showed significant shift in the whole population.

CONCLUSION

We observed significantly reduced (1) weight gaining ratio (average -1.86%, up to -3.3%), (2) visceral fat accumulation ratio (average -4.30%, up to -9.1%), and (3) changes in gut microbiota population. All these consequences could support the "health benefit" functionality of AMW.

Changes in motor behavior, neuropathology, and gut microbiota of a Batten disease mouse model following administration of acidified drinking water

CLN3 mutations cause the fatal neurodegenerative disorder, CLN3 Batten disease. The Cln3^−/− mouse model displays characteristic features of the human disease including motor deficits. When mice received acidified drinking water (pH 2.5–2.9) instead of normal tap water (pH 8.4) for several generations, the motor skills of Cln3^−/− mice normalized to control levels, indicating a disease-modifying effect of acidified water. Here we investigated if acidified water administered from postnatal day 21 has therapeutic benefits in Cln3^−/− mice. Indeed, acidified water temporarily attenuated the motor deficits, had beneficial effects on behavioral parameters and prevented microglial activation in the brain of Cln3^−/− mice. Interestingly, in control mice, acidified drinking water caused brain region-specific glial activation and significant changes in motor performance. Since the gut microbiota can influence neurological functions, we examined it in our disease model and found that the gut microbiota of Cln3^−/− mice was markedly different from control mice, and acidified water differentially changed the gut microbiota composition in these mice. These results indicate that acidified water may provide therapeutic benefit to CLN3 Batten disease patients, and that the pH of drinking water is a major environmental factor that strongly influences the results of murine behavioral and pathological studies.

Gut Microbiota and IL-17A: Physiological and Pathological Responses

IL-17A is a cytokine which is produced by several immune and non-immune cells. The cytokine plays dual roles from protection from microbes and protection from pro-inflammatory based diseases to induction of the pro-inflammatory based diseases. The main mechanisms which lead to the controversial roles of IL-17A are yet to be clarified. Gut microbiota (GM) are the resident probiotic bacteria in the gastrointestinal tracts which have been introduced as a plausible regulator of IL-17A production and functions. This review article describes the recent information regarding the roles played by GM in determination of IL-17A functions outcome.

Gut microbiome interventions in human health and diseases

Ongoing studies have determined that the gut microbiota is a major factor influencing both health and disease. Host genetic factors and environmental factors contribute to differences in gut microbiota composition and function. Intestinal dysbiosis is a cause or a contributory cause for diseases in multiple body systems, ranging from the digestive system to the immune, cardiovascular, respiratory, and even nervous system. Investigation of pathogenesis has identified specific species or strains, bacterial genes, and metabolites that play roles in certain diseases and represent potential drug targets. As research progresses, gut microbiome-based diagnosis and therapy are proposed and applied, which might lead to considerable progress in precision medicine. We further discuss the limitations of current studies and potential solutions.

Microbe-metabolite-host axis, two-way action in the pathogenesis and treatment of human autoimmunity

The role of microorganism in human diseases cannot be ignored. These microorganisms have evolved together with humans and worked together with body's mechanism to maintain immune and metabolic function. Emerging evidence shows that gut microbe and their metabolites open up new doors for the study of human response mechanism. The complexity and interdependence of these microbe-metabolite-host interactions are rapidly being elucidated. There are various changes of microbial levels in models or in patients of various autoimmune diseases (AIDs). In addition, the relevant metabolites involved in mechanism mainly include short-chain fatty acids (SCFAs), bile acids (BAs), and polysaccharide A (PSA). Meanwhile, the interaction between microbes and host genes is also a factor that must be considered. It has been demonstrated that human microbes are involved in the development of a variety of AIDs, including organ-specific AIDs and systemic AIDs. At the same time, microbes or related products can be used to remodel body's response to alleviate or cure diseases. This review summarizes the latest research of microbes and their related metabolites in AIDs. More importantly, it highlights novel and potential therapeutics, including fecal microbial transplantation, probiotics, prebiotics, and synbiotics. Nonetheless, exact mechanisms still remain elusive, and future research will focus on finding a specific strain that can act as a biomarker of an autoimmune disease.

Citizen science charts two major "stomatotypes" in the oral microbiome of adolescents and reveals links with habits and drinking water composition

BACKGROUND

The oral cavity comprises a rich and diverse microbiome, which plays important roles in health and disease. Previous studies have mostly focused on adult populations or in very young children, whereas the adolescent oral microbiome remains poorly studied. Here, we used a citizen science approach and 16S profiling to assess the oral microbiome of 1500 adolescents around Spain and its relationships with lifestyle, diet, hygiene, and socioeconomic and environmental parameters.

RESULTS

Our results provide a detailed snapshot of the adolescent oral microbiome and how it varies with lifestyle and other factors. In addition to hygiene and dietary habits, we found that the composition of tap water was related to important changes in the abundance of several bacterial genera. This points to an important role of drinking water in shaping the oral microbiota, which has been so far poorly explored. Overall, the microbiome samples of our study can be clustered into two broad compositional patterns (stomatotypes), driven mostly by Neisseria and Prevotella, respectively. These patterns show striking similarities with those found in unrelated populations.

CONCLUSIONS

We hypothesize that these stomatotypes represent two possible global optimal equilibria in the oral microbiome that reflect underlying constraints of the human oral niche. As such, they should be found across a variety of geographical regions, lifestyles, and ages.

Considerations for best practices in studies of fiber or other dietary components and the intestinal microbiome

A 2-day workshop organized by the National Institutes of Health and U.S. Department of Agriculture included 16 presentations focused on the role of diet in alterations of the gastrointestinal microbiome, primarily that of the colon. Although thousands of research projects have been funded by U.S. federal agencies to study the intestinal microbiome of humans and a variety of animal models, only a minority addresses dietary effects, and a small subset is described in sufficient detail to allow reproduction of a study. Whereas there are standards being developed for many aspects of microbiome studies, such as sample collection, nucleic acid extraction, data handling, etc., none has been proposed for the dietary component; thus this workshop focused on the latter specific point. It is important to foster rigor in design and reproducibility of published studies to maintain high quality and enable designs that can be compared in systematic reviews. Speakers addressed the influence of the structure of the fermentable carbohydrate on the microbiota and the variables to consider in design of studies using animals, in vitro models, and human subjects. For all types of studies, strengths and weaknesses of various designs were highlighted, and for human studies, comparisons between controlled feeding and observational designs were discussed. Because of the lack of published, best-diet formulations for specific research questions, the main recommendation is to describe dietary ingredients and treatments in as much detail as possible to allow reproduction by other scientists.

H2Oh No! The importance of reporting your water source in your in vivo microbiome studies

Water is a fundamental part of any in vivo microbiome experiment however, it is also one of the most overlooked and underreported variables within the literature. Currently there is no established standard for drinking water quality set by the Canadian Council on Animal Care. Most water treatment methods focus on inhibiting bacterial growth within the water while prolonging the shelf-life of bottles once poured. When reviewing the literature, it is clear that some water treatment methods, such as water acidification, alter the gut microbiome of experimental animals resulting in dramatic differences in disease phenotype progression. Furthermore, The Jackson Lab, one of the world's leading animal vendors, provides acidified water to their in-house animals and is often cited in the literature as having a dramatically different gut microbiome than animals acquired from either Charles River or Taconic. While we recognize that it is impossible to standardize water across all animal facilities currently conducting microbiome research, we hope that by drawing attention to the issue in this commentary, researchers will consider water source as an experimental variable and report their own water sources to facilitate experimental reproducibility. Moreover, researchers should be cognisant of potential phenotypic differences observed between commercial animal vendors due to changes in the gut microbiome as a result of various sources of water used.

The effect of drinking water pH on the human gut microbiota and glucose regulation: results of a randomized controlled cross-over intervention

Studies in rodent models have shown that alterations in drinking water pH affect both the composition of the gut microbiota and host glucose regulation. To explore a potential impact of electrochemically reduced alkaline (pH ≈ 9) versus neutral (pH ≈ 7) drinking water (2 L/day) on human intestinal microbiota and host glucose metabolism we conducted a randomized, non-blinded, cross-over study (two 2-week intervention periods, separated by a 3-week wash-out) in 29 healthy, non-smoking Danish men, aged 18 to 35 years, with a body mass index between 20.0 to 27.0 kg m-2. Volunteers were ineligible if they had previously had abdominal surgery, had not been weight stabile for at least two months, had received antibiotic treatment within 2 months, or had a habitual consumption of caloric or artificially sweetened beverages in excess of 1 L/week or an average intake of alcohol in excess of 7 units/week. Microbial DNA was extracted from faecal samples collected at four time points, before and after each intervention, and subjected to 16S rRNA gene amplicon sequencing (Illumina MiSeq, V4 region). Glycaemic regulation was evaluated by means of an oral glucose tolerance test.No differential effect of alkaline versus neutral drinking water was observed for the primary outcome, overall gut microbiota diversity as represented by Shannon's index. Similarly, neither a differential effect on microbiota richness or community structure was observed. Nor did we observe a differential effect on the abundance of individual operational taxonomic units (OTUs) or genera. However, analyses of within period effects revealed a significant (false discovery rate ≤5%) increase in the relative abundance of 9 OTUs assigned to order Clostridiales, family Ruminococcaceae, genus Bacteroides, and species Prevotella copri, indicating a potential effect of quantitative or qualitative changes in habitual drinking habits. An increase in the concentration of plasma glucose at 30 minutes and the incremental area under the curve of plasma glucose from 0 30 and 0 120 minutes, respectively, was observed when comparing the alkaline to the neutral intervention. However, results did not withstand correction for multiplicity. In contrast to what has been reported in rodents, a change in drinking water pH had no impact on the composition of the gut microbiota or glucose regulation in young male adults. The study is registered at www.clinicaltrials.gov (NCT02917616).

Effects of water decontamination methods and bedding material on the gut microbiota

Rodent models are invaluable to understanding health and disease in many areas of biomedical research. Unfortunately, many models suffer from lack of phenotype reproducibility. Our laboratory has shown that differences in gut microbiota (GM) can modulate phenotypes of models of colon cancer and inflammatory bowel disease. We and others have also shown that a number of factors associated with rodent research, including vendor, cage system, and bedding can alter GM. The objective of this study was to expand these studies to examine the effect of additional bedding materials and methods of water decontamination on GM diversity and composition. To this end, Crl:CD1 (ICR) mice were housed on corn cob or compressed paper chip bedding and provided water that was decontaminated by four different methods: autoclaving with reverse osmosis, autoclaving with hydrochloric acid, autoclaving with sulfuric acid, and autoclaving alone. Feces was collected at day 0, and at day 28 (endpoint), fecal and cecal samples were collected. DNA was extracted from samples, amplified by PCR using conserved bacterial primer sets and subjected to next generation sequencing. Sequence data were analyzed using Qiime and groups were compared using principal coordinate analysis (PCoA) and permutational multivariate analysis of variance (PERMANOVA). Two factor PERMANOVA of cecal GM data revealed significant changes when comparing bedding and water decontamination methods, while no significant effects were noted in the fecal GM data. Subsequent PERMANOVA and PCoA of cecal data revealed that several combinations of bedding and water decontamination methods resulted in differing GM, highlighting the complexity by which environmental factors interact to modulate GM.

Evaluation of different mucosal microbiota leads to gut microbiota-based prediction of type 1 diabetes in NOD mice

Type 1 diabetes (T1D) is a progressive autoimmune disease in which the insulin-producing beta cells are destroyed by auto-reactive T cells. Recent studies suggest that microbiota are closely associated with disease development. We studied gut, oral and vaginal microbiota longitudinally in non-obese diabetic (NOD) mice. We showed that the composition of microbiota is very different at the different mucosal sites and between young and adult mice. Gut microbiota are more diverse than oral or vaginal microbiota and the changes were more evident in the mice before and after onset of diabetes. Using alpha-diversity, Gram-positive/Gram-negative ratio as well as the relative abundance of Bacteroidetes and Erysipelotrichaceae in the gut microbiota, at 8 weeks of age, we formulated a predictive algorithm for T1D development in a cohort of 63 female NOD mice. Using this algorithm, we obtained 80% accuracy of prediction of diabetes onset, in two independent experiments, totaling 29 mice, with Area Under the Curve of 0.776 by ROC analysis. Interestingly, we did not find differences in peripheral blood mononuclear cells of the mice at 8 weeks of age, regardless of later diabetes development. Our results suggest that the algorithm could potentially be used in early prediction of future T1D development.

Gut microbiome in type 1 diabetes: A comprehensive review

Type 1 diabetes (T1D) is an autoimmune disease, which is characterized by the destruction of islet β cells in the pancreas triggered by genetic and environmental factors. In past decades, extensive familial and genome-wide association studies have revealed more than 50 risk loci in the genome. However, genetic susceptibility cannot explain the increased incidence of T1D worldwide, which is very likely attributed by the growing impact of environmental factors, especially gut microbiome. Recently, the role of gut microbiome in the pathogenesis of T1D has been uncovered by the increasing evidence from both human subjects and animal models, strongly indicating that gut microbiome might be a pivotal hub of T1D-triggering factors, especially environmental factors. In this review, we summarize the current aetiological and mechanism studies of gut microbiome in T1D. A better understanding of the role of gut microbiome in T1D may provide us with powerful prognostic and therapeutic tools in the near future.

Standardization in host-microbiota interaction studies: challenges, gnotobiology as a tool, and perspective

Considering the increasing list of diseases linked to the commensal microbiota, experimental studies of host-microbe interactions are of growing interest. Axenic and differently colonized animal models are inalienable tools to study these interactions. Factors, such as host genetics, diet, antibiotics and litter affect microbiota composition and can be confounding factors in many experimental settings. The use of gnotobiotic mice harboring defined microbiotas of different complexity plus additional housing standardization have thus become a gold standard to study the influence of the microbiome on the host. We highlight here the recent advances, challenges and outstanding goals in gnotobiology with the ambition to contribute to the generation of reliable, reproducible and transferrable results, which form the basis for advances in biomedical research.

Type 1 diabetes: Through the lens of human genome and metagenome interplay

Diabetes is a genetic- and epigenetic-related disease from which a large population worldwide suffers. Some genetic factors along with various mutations related to the immune system for disease mechanism(s) have contrastively been determined. However, sometimes mechanisms have not been fully managed for the clarification of the initiation and/or progression of diseases to help patients. In the recent years, due to familiarity with the role of gut microbiota in the health, it has been found that the changes of the microbial balance in the industrialized societies can cause a battery of modern diseases, for which we have no specific definition of how they emerge. This work aims to explore the relationship between the human gut microbiota and the immune system along with their possible role in avoiding/emerging of type 1 diabetes (T1D) accompanied with the relation between genome and metagenome and their imbalance in causing T1D. Moreover, it provides novel view on how to balance the intestinal microbiota by lifestyle to hinder the mechanisms leading to T1D.

Training Rats Using Water Rewards Without Water Restriction

High-throughput behavioral training of rodents has been a transformative development for systems neuroscience. Water or food restriction is typically required to motivate task engagement. We hypothesized a gap between physiological water need and hedonic water satiety that could be leveraged to train rats for water rewards without water restriction. We show that when Citric Acid (CA) is added to water, female rats drink less, yet consume enough to maintain long term health. With 24 h/day access to a visual task with water rewards, rats with ad lib CA water performed 84% ± 18% as many trials as in the same task under water restriction. In 2-h daily sessions, rats with ad lib CA water performed 68% ± 13% as many trials as under water restriction. Using reward sizes <25 μl, rats with ad lib CA performed 804 ± 285 trials/day in live-in sessions or 364 ± 82 trials/day in limited duration daily sessions. The safety of CA water amendment was previously shown for male rats, and the gap between water need and satiety was similar to what we observed in females. Therefore, it is likely that this method will generalize to male rats, though this remains to be shown. We conclude that at least in some contexts rats can be trained using water rewards without water restriction, benefitting both animal welfare and scientific productivity.

On the pathogenesis of insulin-dependent diabetes mellitus: the role of microbiota

Type 1 diabetes (T1D) is an autoimmune disorder characterized by the selective destruction of insulin-producing β cells as result of a complex interplay between genetic, stochastic and environmental factors in genetically susceptible individuals. An increasing amount of experimental data from animal models and humans has supported the role played by imbalanced gut microbiome in T1D pathogenesis. The commensal intestinal microbiota is fundamental for several physiologic mechanisms, including the establishment of immune homeostasis. Alterations in its composition have been correlated to changes in the gut immune system, including defective tolerance to food antigens, intestinal inflammation and enhanced gut permeability. Early findings reported differences in the intestinal microbiome of subjects affected by prediabetes or overt disease compared to healthy individuals. The present review focuses on microbiota-host homeostasis, its alterations, factors that influence microbiome composition and discusses their putative correlation with T1D development. Further studies are necessary to clarify the role played by microbiota modifications in the processes that cause enhanced permeability and the autoimmune mechanisms responsible for T1D onset.

Gut Microbiota-Immune System Crosstalk and Pancreatic Disorders

Gut microbiota is key to the development and modulation of the mucosal immune system. It plays a central role in several physiological functions, in the modulation of inflammatory signaling and in the protection against infections. In healthy states, there is a perfect balance between commensal and pathogens, and microbiota and the immune system interact to maintain gut homeostasis. The alteration of such balance, called dysbiosis, determines an intestinal bacterial overgrowth which leads to the disruption of the intestinal barrier with systemic translocation of pathogens. The pancreas does not possess its own microbiota, and it is believed that inflammatory and neoplastic processes affecting the gland may be linked to intestinal dysbiosis. Increasing research evidence testifies a correlation between intestinal dysbiosis and various pancreatic disorders, but it remains unclear whether dysbiosis is the cause or an effect. The analysis of specific alterations in the microbiome profile may permit to develop novel tools for the early detection of several pancreatic disorders, utilizing samples, such as blood, saliva, and stools. Future studies will have to elucidate the mechanisms by which gut microbiota is modulated and how it tunes the immune system, in order to be able to develop innovative treatment strategies for pancreatic disorders.

Long-Term Provision of Acidified Drinking Water Fails to Influence Autoimmune Diabetes and Encephalomyelitis

Induction of autoimmune diseases is predisposed by background genetics and influenced by environmental factors including diet and infections. Since consumption of acidified drinking water leads to eradication of gastrointestinal pathogens in animals, we tested whether it may also influence the development of autoimmune diseases. The frequency of spontaneously occurring type 1 diabetes in female NOD mice that were maintained on acidified drinking water by the vendor did not alter after switching to neutral water in our facility. In addition, experimentally induced autoimmune encephalomyelitis was also unaffected by the pH of the drinking water. Interestingly, administration of complete Freund's adjuvant alone or emulsified with a neuronal peptide to induce neurodegenerative disease during the prediabetic stage completely prevented the onset of diabetes regardless of the pH of the drinking water. However, exposure to microbial products later in life had only a partial blocking effect on diabetes induction, which was also not influenced by the ionic content of the drinking water. Taken together, these data indicate that the onset of autoimmune diseases is not influenced by the gastrointestinal pathogen-depleting treatment, acidified drinking water. Thus, administration of acidic drinking water does not appear to be an option for treating autoimmune diseases.

Alpinia oxyphylla Miq. Extract Prevents Diabetes in Mice by Modulating Gut Microbiota

Recently, the role of gut microbiota in the development of obesity and type 2 diabetes mellitus (T2DM) has been highlighted. We performed an 8-week administration protocol on T2DM (C57BL/6J db-/db-) mice and fecal samples were collected. Comparisons of fecal bacterial communities were performed between db-/db- mice and normal mice (DB/DB) and between the db-/db mice treated and untreated with AOE using next-generation sequencing technology. Our results showed that the db-/db-AOE group had improved glycemic control and renal function compared with the db-/db-H₂O group. Compared with the db-/db-H₂O group, AOE administration resulted in significantly increased ratio of Bacteroidetes-to-Firmicutes in db-/db- mice. In addition, the abundance of Akkermansia was significantly increased, while Helicobacter was significantly suppressed in the db-/db-AOE group compared with the db-/db-H₂O group. Our data suggest that AOE treatment decreased blood glucose levels and significantly reduced damage of renal pathology in the T2DM mice by modulating gut microbiota composition.

Effect of Early-life Gut Mucosal Compromise on Disease Progression in NOD Mice

Disease expression in spontaneous nonobese diabetic (NOD) mice depends on environmental stimuli such as stress, diet, and gut microbiota composition. We evaluated a brief, early-life gut intervention in which pups were weaned to low-dose dextran sulfate sodium (DSS). We hypothesized that the mucus-reducing effect of this compound and subsequent increased host-bacterial contact would delay disease onset and decrease insulitis due to enhanced oral tolerance. However, disease incidence did not differ between groups, although median survival (time point when 50% of the mice are still alive) of the control group was 184 d compared with 205 d for DSS-treated mice. Mean age at disease onset (that is, blood glucose of at least 12 mmol/L) was 164 d for control mice and 159 d for DSS-treated mice. In addition, 62.5% of control mice reached a blood glucose of 12 mmol/L before 30 wk of age compared with 59% in DSS-treated mice, which had a significant transient increase in serum insulin in week 4. No changes were found in immune cells collected from spleen, pancreatic lymph nodes, and mesenteric lymph nodes. Although mice received a low dose of DSS, the subsequent reduction in the diversity of the microbiota during weeks 4 through 6 led to increased cecal length and weight and, in week 13, a tendency toward decreased colon length, with increased leakage of LPS to the blood. We conclude that mucus reduction and subsequent increased host-bacterial contact did not affect overall disease progression in NOD mice.

Vasopressin deletion is associated with sex-specific shifts in the gut microbiome

Brattleboro rats harbor a spontaneous deletion of the arginine-vasopressin (Avp) gene. In addition to diabetes insipidus, these rats exhibit low levels of anxiety and depressive behaviors. Recent work on the gut-brain axis has revealed that gut microbiota can influence anxiety behaviors. Therefore, we studied the effects of Avp gene deletion on gut microbiota. Since Avp gene expression is sexually different, we also examined how Avp deletion affects sex differences in gut microbiota. Males and females show modest but differentiated shifts in taxa abundance across 3 separate Avp deletion genotypes: wildtype (WT), heterozygous (Het) and AVP-deficient Brattleboro (KO) rats. For each sex, we found examples of taxa that have been shown to modulate anxiety behavior, in a manner that correlates with anxiety behavior observed in homozygous knockout Brattleboro rats. One prominent example is Lactobacillus, which has been reported to be anxiolytic: Lactobacillus was found to increase in abundance in inverse proportion to increasing gene dosage (most abundant in KO rats). This genotype effect of Lactobacillus abundance was not found when females were analyzed independently. Therefore, Avp deletion appears to affect microbiota composition in a sexually differentiated manner.

Antibiotic-associated Manipulation of the Gut Microbiota and Phenotypic Restoration in NOD Mice

Segmented filamentous bacterium (SFB) a gram-positive, anaerobic, and intestinal commensal organism directly influences the development of Th17 helper cells in the small intestine of mice. In NOD mice, SFB colonization interferes with the development of type 1 diabetes (T1D), a T-cell-mediated autoimmune disease, suggesting that SFB may influence Th17 cells to inhibit Th1 populations associated with the anti-β-cell immune response. This effect is a serious concern for investigators who use NOD mice for diabetes research because the expected incidence of disease decreases markedly when they are colonized by SFB. A room housing mice for T1D studies at The Jackson Laboratory was determined by fecal PCR testing to have widespread SFB colonization of multiple NOD strains after a steady decline in the incidence of T1D was noted. Rederivation of all NOD-related mouse strains was not feasible; therefore an alternative treatment using antibiotics to eliminate SFB from colonized mice was undertaken. After antibiotic treatment, soiled bedding from NOD mouse strains housed in SFB-free high-health-status production barrier rooms was used to reintroduce the gastrointestinal microbiota. Over the past 16 mo since treating the mice and disinfecting the mouse room, regular PCR testing has shown that no additional SFB colonization of mice has occurred, and the expected incidence of T1D has been reestablished in the offspring of treated mice.

Factors Shaping the Human Exposome in the Built Environment: Opportunities for Engineering Control

The "exposome" is a term describing the summation of one's lifetime exposure to microbes and chemicals. Such exposures are now recognized as major drivers of human health and disease. Because humans spend ∼90% of their time indoors, the built environment exposome merits particular attention. Herein we utilize an engineering perspective to advance understanding of the factors that shape the built environment exposome and its influence on human wellness and disease, while simultaneously informing development of a framework for intentionally controlling the exposome to protect public health. Historically, engineers have been focused on controlling chemical and physical contaminants and on eradicating microbes; however, there is a growing awareness of the role of "beneficial" microbes. Here we consider the potential to selectively control the materials and chemistry of the built environment to positively influence the microbial and chemical components of the indoor exposome. Finally, we discuss research gaps that must be addressed to enable intentional engineering design, including the need to define a "healthy" built environment exposome and how to control it.

pH-Mediated Microbial and Metabolic Interactions in Fecal Enrichment Cultures

The human gut is a dynamic environment in which microorganisms consistently interact with the host via their metabolic products. Some of the most important microbial metabolic products are fermentation products such as short-chain fatty acids. Production of these fermentation products and the prevalence of fermenting microbiota depend on pH, alkalinity, and available dietary sugars, but details about their metabolic interactions are unknown. Here, we show that, for in vitro conditions, pH was the strongest driver of microbial community structure and function and microbial and metabolic interactions among pH-sensitive fermentative species. The balance between bicarbonate alkalinity and formation of fatty acids by fermentation determined the pH, which controlled microbial community structure. Our results underscore the influence of pH balance on microbial function in diverse microbial ecosystems such as the human gut.

pH and fermentable substrates impose selective pressures on gut microbial communities and their metabolisms. We evaluated the relative contributions of pH, alkalinity, and substrate on microbial community structure, metabolism, and functional interactions using triplicate batch cultures started from fecal slurry and incubated with an initial pH of 6.0, 6.5, or 6.9 and 10 mM glucose, fructose, or cellobiose as the carbon substrate. We analyzed 16S rRNA gene sequences and fermentation products. Microbial diversity was driven by both pH and substrate type. Due to insufficient alkalinity, a drop in pH from 6.0 to ~4.5 clustered pH 6.0 cultures together and distant from pH 6.5 and 6.9 cultures, which experienced only small pH drops. Cellobiose yielded more acidity than alkalinity due to the amount of fermentable carbon, which moved cellobiose pH 6.5 cultures away from other pH 6.5 cultures. The impact of pH on microbial community structure was reflected by fermentative metabolism. Lactate accumulation occurred in pH 6.0 cultures, whereas propionate and acetate accumulations were observed in pH 6.5 and 6.9 cultures and independently from the type of substrate provided. Finally, pH had an impact on the interactions between lactate-producing and -consuming communities. Lactate-producing Streptococcus dominated pH 6.0 cultures, and acetate- and propionate-producing Veillonella, Bacteroides, and Escherichia dominated the cultures started at pH 6.5 and 6.9. Acid inhibition on lactate-consuming species led to lactate accumulation. Our results provide insights into pH-derived changes in fermenting microbiota and metabolisms in the human gut.

IMPORTANCE The human gut is a dynamic environment in which microorganisms consistently interact with the host via their metabolic products. Some of the most important microbial metabolic products are fermentation products such as short-chain fatty acids. Production of these fermentation products and the prevalence of fermenting microbiota depend on pH, alkalinity, and available dietary sugars, but details about their metabolic interactions are unknown. Here, we show that, for in vitro conditions, pH was the strongest driver of microbial community structure and function and microbial and metabolic interactions among pH-sensitive fermentative species. The balance between bicarbonate alkalinity and formation of fatty acids by fermentation determined the pH, which controlled microbial community structure. Our results underscore the influence of pH balance on microbial function in diverse microbial ecosystems such as the human gut.

Modeling month-season of birth as a risk factor in mouse models of chronic disease: from multiple sclerosis to autoimmune encephalomyelitis

Month-season of birth (M-SOB) is a risk factor in multiple chronic diseases, including multiple sclerosis (MS), where the lowest and greatest risk of developing MS coincide with the lowest and highest birth rates, respectively. To determine whether M-SOB effects in such chronic diseases as MS can be experimentally modeled, we examined the effect of M-SOB on susceptibility of C57BL/6J mice to experimental autoimmune encephalomyelitis (EAE). As in MS, mice that were born during the M-SOB with the lowest birth rate were less susceptible to EAE than mice born during the M-SOB with the highest birth rate. We also show that the M-SOB effect on EAE susceptibility is associated with differential production of multiple cytokines/chemokines by neuroantigen-specific T cells that are known to play a role in EAE pathogenesis. Taken together, these results support the existence of an M-SOB effect that may reflect seasonally dependent developmental differences in adaptive immune responses to self-antigens independent of external stimuli, including exposure to sunlight and vitamin D. Moreover, our documentation of an M-SOB effect on EAE susceptibility in mice allows for modeling and detailed analysis of mechanisms that underlie the M-SOB effect in not only MS but in numerous other diseases in which M-SOB impacts susceptibility.-Reynolds, J. D., Case, L. K., Krementsov, D. N., Raza, A., Bartiss, R., Teuscher, C. Modeling month-season of birth as a risk factor in mouse models of chronic disease: from multiple sclerosis to autoimmune encephalomyelitis.

Microbiota composition of simultaneously colonized mice housed under either a gnotobiotic isolator or individually ventilated cage regime

Germ-free rodents colonized with microbiotas of interest are used for host-microbiota investigations and for testing microbiota-targeted therapeutic candidates. Traditionally, isolators are used for housing such gnotobiotic rodents due to optimal protection from the environment, but research groups focused on the microbiome are increasingly combining or substituting isolator housing with individually ventilated cage (IVC) systems. We compared the effect of housing systems on the gut microbiota composition of germ-free mice colonized with a complex microbiota and housed in either multiple IVC cages in an IVC facility or in multiple open-top cages in an isolator during three generations and five months. No increase in bacterial diversity as assessed by 16S rRNA gene sequencing was observed in the IVC cages, despite not applying completely aseptic cage changes. The donor bacterial community was equally represented in both housing systems. Time-dependent clustering between generations was observed in both systems, but was strongest in the IVC cages. Different relative abundance of a Rikenellaceae genus contributed to separate clustering of the isolator and IVC communities. Our data suggest that complex microbiotas are protected in IVC systems, but challenges related to temporal dynamics should be addressed.

Is there a role for gut microbiota in type 1 diabetes pathogenesis?

Type 1 diabetes mellitus (T1D) is an autoimmune disease characterized by insufficient insulin production due to the destruction of insulin secreting β-cells in the Langerhans islets. A variety of factors, including chemicals, viruses, commensal bacteria and diet have been proposed to contribute to the risk of developing the disorder. In the last years, gut microbiota has been proposed as a main factor in T1D pathogenesis. Several alterations of gut microbiota composition were described both in animal model and in humans. The decrease of Firmicutes/Bacteroides ratio was the most frequent pattern described, in particular, in human studies. Furthermore, Bacteroides, Clostridium cluster XIVa, Lactobacillus, Bifidobacterium, and Prevotella relative abundances were different in healthy and affected subjects. Dysbiosis would seem to increase intestinal permeability and thus promote the development of a pro-inflammatory niche that stimulates β-cell autoimmunity in predisposed subjects. Preliminary studies on animal models were realized to investigate the role of gut microbiota modulation as therapy or prevention approach in predisposed animals: promising and stimulating results have been reported. Key message Dietary antigens and microbiota-derived products might act as triggers of T1D by causing a pro-inflammatory and metabolic dysfunctional environment.

Microbial antigen mimics activate diabetogenic CD8 T cells in NOD mice

Both animal model and human studies indicate that commensal bacteria may modify type 1 diabetes (T1D) development. However, the underlying mechanisms by which gut microbes could trigger or protect from diabetes are not fully understood, especially the interaction of commensal bacteria with pathogenic CD8 T cells. In this study, using islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)-reactive CD8 T cell receptor NY8.3 transgenic nonobese diabetic mice, we demonstrated that MyD88 strongly modulates CD8(+) T cell-mediated T1D development via the gut microbiota. Some microbial protein peptides share significant homology with IGRP. Both the microbial peptide mimic of Fusobacteria and the bacteria directly activate IGRP-specific NY8.3 T cells and promote diabetes development. Thus, we provide evidence of molecular mimicry between microbial antigens and an islet autoantigen and a novel mechanism by which the diabetogenicity of CD8(+) T cells can be regulated by innate immunity and the gut microbiota.

The Mammalian Microbiome and Its Importance in Laboratory Animal Research

In this issue are assembled 10 fascinating, well-researched papers that describe the emerging field centered on the microbiome of vertebrate animals and how these complex microbial populations play a fundamental role in shaping homeostasis of the host. The content of the papers will deal with bacteria and, because of relative paucity of information on these organisms, will not include discussions on viruses, fungus, protozoa, and parasites that colonize various animals. Dissecting the number and interactions of the 500-1000 bacterial species that can inhabit the intestines of animals is made possible by advanced DNA sequencing methods, which do not depend on whether the organism can be cultured or not. Laboratory animals, particularly rodents, have proven to be an indispensable component in not only understanding how the microbiome aids in digestion and protects the host against pathogens, but also in understanding the relationship of various species of bacteria to development of the immune system. Importantly, this research elucidates purported mechanisms for how the microbiome can profoundly affect initiation and progression of diseases such as type 1 diabetes, metabolic syndromes, obesity, autoimmune arthritis, inflammatory bowel disease, and irritable bowel syndrome. The strengths and limitations of the use of germfree mice colonized with single species of bacteria, a restricted flora, or most recently the use of human-derived microbiota are also discussed.

The role of the intestinal microbiota in type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is a chronic immune-mediated disease with a subclinical prodromal period, characterized by selective loss of insulin-producing-β cells in the pancreatic islets of genetically susceptible individuals. The incidence of T1DM has increased several fold in most developed countries since World War II, in conjunction with other immune-mediated diseases. Rapid environmental changes and modern lifestyles are probably the driving factors that underlie this increase. These effects might be mediated by changes in the human microbiota, particularly the intestinal microbiota. Research on the gut microbiome of individuals at risk of developing T1DM and in patients with established disease is still in its infancy, but initial findings indicate that the intestinal microbiome of individuals with prediabetes or diabetes mellitus is different to that of healthy individuals. The gut microbiota in individuals with preclinical T1DM is characterized by Bacteroidetes dominating at the phylum level, a dearth of butyrate-producing bacteria, reduced bacterial and functional diversity and low community stability. However, these changes seem to emerge after the appearance of autoantibodies that are predictive of T1DM, which suggests that the intestinal microbiota might be involved in the progression from β-cell autoimmunity to clinical disease rather than in the initiation of the disease process.

Insights into environmental factors impacting celiac disease: microbiota modulation of disease pathogenesis

This commentary highlights the article by Galipeau et al exploring the role of microbiota in modulating gluten immune response and celiac disease-like pathology in a humanized mouse model.

Role of the gastrointestinal ecosystem in the development of type 1 diabetes

A new emphasis has been put on the role of the gastrointestinal (GI) ecosystem in autoimmune diseases; however, there is limited knowledge about its role in type 1 diabetes (T1D). Distinct differences have been observed in intestinal permeability, epithelial barrier function, commensal microbiota, and mucosal innate and adaptive immunity of patients and animals with T1D, when compared with healthy controls. The non-obese diabetic (NOD) mouse and the BioBreeding diabetes prone (BBdp) rat are the most commonly used models to study T1D pathogenesis. With the increasing awareness of the importance of the GI ecosystem in systemic disease, it is critical to understand the basics, as well as the similarities and differences between rat and mouse models and human patients. This review examines the current knowledge of the role of the GI ecosystem in T1D and indicates the extensive opportunities for further investigation that could lead to biomarkers and therapeutic interventions for disease prevention and/or modulation.