Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome

Role of the Gut Microbiome in the Pathogenesis of Obesity and Obesity-Related Metabolic Dysfunction

The potential role of intestinal microbiota in the etiology of various human diseases has attracted massive attention in the last decade. As such, the intestinal microbiota has been advanced as an important contributor in the development of obesity and obesity-related metabolic dysfunctions, amongst others. Experiments in animal models have produced evidence for a causal role of intestinal microbiota in the etiology of obesity and insulin resistance. However, with a few exceptions, such causal relation is lacking for humans and most publications merely report associations between intestinal microbial composition and metabolic disorders such as obesity and type 2 diabetes. Thus, the reciprocal relationship between the bacteria and these metabolic disorders remains a matter of debate. The main objective of this review is to critically assess the driving role of intestinal microbe composition in the etiology, prevention, and treatment of obesity and obesity-related metabolic dysfunction, including type 2 diabetes.

Crohn's disease

Crohn's disease is a chronic inflammatory disease of the gastrointestinal tract, with increasing incidence worldwide. Crohn's disease might result from a complex interplay between genetic susceptibility, environmental factors, and altered gut microbiota, leading to dysregulated innate and adaptive immune responses. The typical clinical scenario is a young patient presenting with abdominal pain, chronic diarrhoea, weight loss, and fatigue. Assessment of disease extent and of prognostic factors for complications is paramount to guide therapeutic decisions. Current strategies aim for deep and long-lasting remission, with the goal of preventing complications, such as surgery, and blocking disease progression. Central to these strategies is the introduction of early immunosuppression or combination therapy with biologicals in high-risk patients, combined with a tight and frequent control of inflammation, and adjustment of therapy on the basis of that assessment (treat to target strategy). The therapeutic armamentarium for Crohn's disease is expanding, and therefore the need to develop biomarkers that can predict response to therapies will become increasingly important for personalised medicine decisions in the near future. In this Seminar, we provide a physician-oriented overview of Crohn's disease in adults, ranging from epidemiology and cause to clinical diagnosis, natural history, patient stratification and clinical management, and ending with an overview of emerging therapies and future directions for research.

The Gut Microbiome: Connecting Spatial Organization to Function

The first rudimentary evidence that the human body harbors a microbiota hinted at the complexity of host-associated microbial ecosystems. Now, almost 400 years later, a renaissance in the study of microbiota spatial organization, driven by coincident revolutions in imaging and sequencing technologies, is revealing functional relationships between biogeography and health, particularly in the vertebrate gut. In this Review, we present our current understanding of principles governing the localization of intestinal bacteria, and spatial relationships between bacteria and their hosts. We further discuss important emerging directions that will enable progressing from the inherently descriptive nature of localization and -omics technologies to provide functional, quantitative, and mechanistic insight into this complex ecosystem.

Colonic Microbiota Encroachment Correlates With Dysglycemia in Humans

BACKGROUND AND AIMS

Mucoid structures that coat the epithelium play an essential role in keeping the intestinal microbiota at a safe distance from host cells. Encroachment of bacteria into the normally almost-sterile inner mucus layer has been observed in inflammatory bowel disease and in mouse models of colitis. Moreover, such microbiota encroachment has also been observed in mouse models of metabolic syndrome, which are associated low-grade intestinal inflammation. Hence, we investigated if microbiota encroachment might correlate with indices of metabolic syndrome in humans.

METHODS

Confocal microscopy was used to measure bacterial-epithelial distance of the closest bacteria per high-powered field in colonic biopsies of all willing participants undergoing cancer screening colonoscopies.

RESULTS

We observed that, among all subjects, bacterial-epithelial distance was inversely correlated with body mass index, fasting glucose levels, and hemoglobin A_1C. However, this correlation was driven by dysglycemic subjects, irrespective of body mass index, whereas the difference in bacterial-epithelial distance between obese and nonobese subjects was eliminated by removal of dysglycemic subjects.

CONCLUSIONS

We conclude that microbiota encroachment is a feature of insulin resistance-associated dysglycemia in humans.

Resolution of inflammation in inflammatory bowel disease

Treatment of inflammatory bowel disease at present mainly targets mediators of inflammation to stop or suppress pro-inflammatory processes. Typical examples are steroids, suppression of T cells by thioguanine nucleotides, or antibodies against cytokines such as tumour necrosis factor, interleukin 12, or interleukin 23. In addition to suppression of inflammation, development of therapeutic strategies that support resolution of inflammation or that actively resolve inflammation might be desirable. Resolution of inflammation is now seen as an active process involving specific mediators (eg, lipid mediators or specific cytokines) that is mandatory to restore organ function and completely shut down inflammation. The molecular pathways involved in resolution of inflammation have been investigated in recent years and could be adopted in treatment strategies for inflammatory bowel disease. Among these approaches are anti-integrin strategies and means to produce or locally increase restitution or resolution factors, such as restoration of the activity of transforming growth factor-β by anti-SMAD7 antisense oligonucleotides. The potential role of inflammation-resolving lipid mediators (eg, resolvins), however, still warrants further study and clinical development. This Review focuses on the specific role of active resolution of inflammation in inflammatory bowel disease pathophysiology. Potential therapeutic targets based on these pathways are also discussed.

A Dietary Fiber-Deprived Gut Microbiota Degrades the Colonic Mucus Barrier and Enhances Pathogen Susceptibility

Despite the accepted health benefits of consuming dietary fiber, little is known about the mechanisms by which fiber deprivation impacts the gut microbiota and alters disease risk. Using a gnotobiotic mouse model, in which animals were colonized with a synthetic human gut microbiota composed of fully sequenced commensal bacteria, we elucidated the functional interactions between dietary fiber, the gut microbiota, and the colonic mucus barrier, which serves as a primary defense against enteric pathogens. We show that during chronic or intermittent dietary fiber deficiency, the gut microbiota resorts to host-secreted mucus glycoproteins as a nutrient source, leading to erosion of the colonic mucus barrier. Dietary fiber deprivation, together with a fiber-deprived, mucus-eroding microbiota, promotes greater epithelial access and lethal colitis by the mucosal pathogen, Citrobacter rodentium. Our work reveals intricate pathways linking diet, the gut microbiome, and intestinal barrier dysfunction, which could be exploited to improve health using dietary therapeutics.

Chemical signaling between gut microbiota and host chromatin: What is your gut really saying?

Mammals and their gut microbial communities share extensive and tightly coordinated co-metabolism of dietary substrates. A large number of microbial metabolites have been detected in host circulation and tissues and, in many cases, are linked to host metabolic, developmental, and immunological states. The presence of these metabolites in host tissues intersects with regulation of the host's epigenetic machinery. Although it is established that the host's epigenetic machinery is sensitive to levels of endogenous metabolites, the roles for microbial metabolites in epigenetic regulation are just beginning to be elucidated. This review focuses on eukaryotic chromatin regulation by endogenous and gut microbial metabolites and how these regulatory events may impact host developmental and metabolic phenotypes.

Insulin, glucose and beta-hydroxybutyrate responses to a medium-chain triglyceride-based sports supplement: A pilot study

There is a current trend in endurance sports to move athletes towards a low-carbohydrate diet or use periods of low carbohydrate consumption to increase both health and performance. As a result, a market is developing for sports supplements to provide nutritional support during training and racing for athletes who follow a low-carbohydrate lifestyle. PHAT FIBRE (PF) is a powdered sports supplement that includes medium-chain triglycerides suspended in a digestion-resistant carbohydrate and is tailored to the needs of low-carb athletes. Eleven healthy participants were administered 25 g of PF after an overnight fast. After 30 minutes, median blood glucose increased by 6 mg/dl from 94 mg/dl to 100 mg/dl (p = 0.002). At the same time points, median blood beta-hydroxybutyrate (BHB) increased from 0.3 mmol/L to 0.5 mmol/L. The increase in BHB was significant (p = 0.02) after excluding one outlier who had elevated levels of fasting BHB. Insulin levels did not change significantly at any point during the study. In a single participant, a revised formulation of PF (PFv2) produced a 0.6 mmol/L increase in BHB with no effect on blood glucose. These data suggest that PF can provide a source of energy for the low-carb athlete by supporting ketone production without negatively impacting insulin or blood glucose levels.

Adsorption and Distribution of Edible Gliadin Nanoparticles at the Air/Water Interface

Edible gliadin nanoparticles (GNPs) were fabricated using the anti-solvent method. They possessed unique high foamability and foam stability. An increasing concentration of GNPs accelerated their initial adsorption speed from the bulk phase to the interface and raised the viscoelastic modulus of interfacial films. High foamability (174.2 ± 6.4%) was achieved at the very low concentration of GNPs (1 mg/mL), which was much better than that of ovalbumin and sodium caseinate. Three stages of adsorption kinetics at the air/water interface were characterized. First, they quickly diffused and adsorbed at the interface, resulting in a fast increase of the surface pressure. Then, nanoparticles started to fuse into a film, and finally, the smooth film became a firm and rigid layer to protect bubbles against coalescence and disproportionation. These results explained that GNPs had good foamability and high foam stability simultaneously. That provides GNPs as a potential candidate for new foaming agents applied in edible and biodegradable products.

The Microbiome and Human Biology

Over the past few years, microbiome research has dramatically reshaped our understanding of human biology. New insights range from an enhanced understanding of how microbes mediate digestion and disease processes (e.g., in inflammatory bowel disease) to surprising associations with Parkinson's disease, autism, and depression. In this review, we describe how new generations of sequencing technology, analytical advances coupled to new software capabilities, and the integration of animal model data have led to these new discoveries. We also discuss the prospects for integrating studies of the microbiome, metabolome, and immune system, with the goal of elucidating mechanisms that govern their interactions. This systems-level understanding will change how we think about ourselves as organisms.

The Gut Microbiome, Obesity, and Weight Control in Women's Reproductive Health

The microbes residing in the human gut, referred to as the microbiome, are intricately linked to energy homeostasis and subsequently obesity. Integral to the origins of obesity, the microbiome is believed to affect not only health of the human gut but also overall health. This microbiome-obesity association is mediated through the process of energy extraction, metabolism, and cross talk between the brain and the gut microbiome. Host exposures, including diet, that potentially modify genetic predisposition to obesity and affect weight management are reviewed. The higher prevalence of obesity among women and recent evidence linking obesity during pregnancy with offspring health make this topic particularly relevant. Current limitations in microbiome research to address obesity and future advances in this field are described. Applications of this science with respect to applied nursing and overall health care in general are included, with emphasis on the reproductive health of women and their offspring.

[Modulation of the intestinal microbiota by nutritional interventions]

Humans live in symbiosis with billions of commensal bacteria. The so-called microbiota live on different biological interfaces such as the skin, the urogenital tract and the gastrointestinal tract. Commensal bacteria replace potentially pathogenic microbes, synthesize vitamins and ferment dietary fibre. An imbalance in the bacterial composition of the intestinal microbiota has been associated with various diseases including gut-associated disorders such as inflammatory bowel diseases, colorectal cancer and nonalcoholic fatty liver disease. Furthermore, a shift in the microbiota composition appears to be of pathophysiological relevance which renders the specific modulation of the intestinal microbiota a promising approach in the treatment of the above mentioned diseases. Our intestinal microbiota composition is mainly modulated by dietary macro- and micronutrients but also by secondary plant compounds and synthetic food additives such as emulsifiers and artificial sweeteners. Nutritional interventions with the purpose to modulate the intestinal microbiota show only limited therapeutic potential in the treatment of gut-associated disorders, which may be due to individual differences in the intestinal microbiota composition and a lack of specificity. A combination of newly established technical analytic approaches involving a machine-learning algorithm may bridge the currently existing limitations by providing a personalized, highly-specific and consequently therapeutically effective microbiota modulation.

The gut microbiome and microbial translocation in multiple sclerosis

Individuals with multiple sclerosis (MS) have a distinct intestinal microbial community (microbiota) and increased low-grade translocation of bacteria from the intestines into the circulation. The observed change of intestinal bacteria in MS patients regulate immune functions involved in MS pathogenesis. These functions include: systemic and central nervous system (CNS) immunity (including peripheral regulatory T cell function), the blood-brain barrier (BBB) permeability and CNS-resident cell activity. This review discusses the MS intestinal microbiota implication on MS systemic- and CNS-immunopathology. We introduce the possible contributions of MS low-grade microbial translocation (LG-MT) to the development of MS, and end on a discussion on microbiota therapies for MS patients.

Low-dose penicillin exposure in early life decreases Th17 and the susceptibility to DSS colitis in mice through gut microbiota modification

Antibiotic exposure in early life can lead to a significant change of the gut microbiota and may contribute to later onset of inflammatory bowel disease (IBD). However, the relationship between early-life antibiotic treatment and IBD is ambiguous, according to contradicting results of epidemiologic studies. In the present study, we demonstrated that low-dose penicillin pre-treatment had a unique protective effect against mouse colitis induced by dextran sodium sulfate (DSS). Low-dose penicillin also suppressed the expression of pro-inflammatory cytokine IL-17 in various intestinal tissues, and decreased the amount of Th17 cells in small-intestine lamina propria. Neither metronidazole nor enrofloxacin had a similar effect. We further confirmed that low-dose penicillin could cause specific changes of the gut microbiota, especially the eradication of segmented filamentous bacteria (SFB). Mice without SFB inoculation showed no disparity when treated with penicillin or water. Taken together, the results showed that low-dose penicillin can achieve a highly specific manipulation of sensitive bacteria and interfere with development of intestinal immune system in early life. The study may further indicate the possibility of achieving a favorable immune state among a certain group of patients with IBD, or other autoimmune diseases, by fine-tuning the gut microbiota.

Diet and the Microbiome

The gut microbiota provides a range of ecologic, metabolic, and immunomodulatory functions relevant to health and well-being. The gut microbiota not only responds quickly to changes in diet, but this dynamic equilibrium may be managed to prevent and/or treat acute and chronic diseases. This article provides a working definition of the term "microbiome" and uses two examples of dietary interventions for the treatment of large bowel conditions to emphasize the links between diet and microbiome. There remains a need to develop a better functional understanding of the microbiota, if its management for clinical utility is to be fully realized.

Effects of environmental pollutants on gut microbiota

Environmental pollutants have become an increasingly common health hazard in the last several decades. Recently, a number of studies have demonstrated the profound relationship between gut microbiota and our health. Gut microbiota are very sensitive to drugs, diet, and even environmental pollutants. In this review, we discuss the possible effects of environmental pollutants including antibiotics, heavy metals, persistent organic pollutants, pesticides, nanomaterials, and food additives on gut microbiota and their subsequent effects on health. We emphasize that gut microbiota are also essential for the toxicity evaluation of environmental pollution. In the future, more studies should focus on the relationship between environmental pollution, gut microbiota, and human health.

Nutritional Psychiatry: Where to Next?

The nascent field of 'Nutritional Psychiatry' offers much promise for addressing the large disease burden associated with mental disorders. A consistent evidence base from the observational literature confirms that the quality of individuals' diets is related to their risk for common mental disorders, such as depression. This is the case across countries and age groups. Moreover, new intervention studies implementing dietary changes suggest promise for the prevention and treatment of depression. Concurrently, data point to the utility of selected nutraceuticals as adjunctive treatments for mental disorders and as monotherapies for conditions such as ADHD. Finally, new studies focused on understanding the biological pathways that mediate the observed relationships between diet, nutrition and mental health are pointing to the immune system, oxidative biology, brain plasticity and the microbiome-gut-brain axis as key targets for nutritional interventions. On the other hand, the field is currently limited by a lack of data and methodological issues such as heterogeneity, residual confounding, measurement error, and challenges in measuring and ensuring dietary adherence in intervention studies. Key challenges for the field are to now: replicate, refine and scale up promising clinical and population level dietary strategies; identify a clear set of biological pathways and targets that mediate the identified associations; conduct scientifically rigorous nutraceutical and 'psychobiotic' interventions that also examine predictors of treatment response; conduct observational and experimental studies in psychosis focused on dietary and related risk factors and treatments; and continue to advocate for policy change to improve the food environment at the population level.

Sex-Dependent Effects of Cadmium Exposure in Early Life on Gut Microbiota and Fat Accumulation in Mice

BACKGROUND

Environmental cadmium, with a high average dietary intake, is a severe public health risk. However, the long-term health implications of environmental exposure to cadmium in different life stages remain unclear.

OBJECTIVES

We investigated the effects of early exposure to cadmium, at an environmentally relevant dosage, on adult metabolism and the mechanism of action.

METHODS

We established mouse models with low-dose cadmium (LDC) exposure in early life to examine the long-term metabolic consequences. Intestinal flora measurement by 16S rDNA sequencing, microbial ecological analyses, and fecal microbiota transplant was conducted to explore the potential underlying mechanisms.

RESULTS

Early LDC exposure (100 nM) led to fat accumulation in adult male mice. Hepatic genes profiling revealed that fatty acid and lipid metabolic processes were elevated. Gut microbiota were perturbed by LDC to cause diversity reduction and compositional alteration. Time-series studies indicated that the gut flora at early-life stages, especially at 8 weeks, were vulnerable to LDC and that an alteration during this period could contribute to the adult adiposity, even if the microbiota recovered later. The importance of intestinal bacteria in LDC-induced fat accumulation was further confirmed through microbiota transplantation and removal experiments. Moreover, the metabolic effects of LDC were observed only in male, but not female, mice.

CONCLUSIONS

An environmental dose of cadmium at early stages of life causes gut microbiota alterations, accelerates hepatic lipid metabolism, and leads to life-long metabolic consequences in a sex-dependent manner. These findings provide a better understanding of the health risk of cadmium in the environment. Citation: Ba Q, Li M, Chen P, Huang C, Duan X, Lu L, Li J, Chu R, Xie D, Song H, Wu Y, Ying H, Jia X, Wang H. 2017. Sex-dependent effects of cadmium exposure in early life on gut microbiota and fat accumulation in mice. Environ Health Perspect 125:437-446; http://dx.doi.org/10.1289/EHP360.

Re-evaluation of polyglycerol polyricinoleate (E 476) as a food additive

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re-evaluating the safety of polyglycerol polyricinoleate (PGPR, E 476) used as a food additive. In 1978, the Scientific Committee for Food (SCF) established an acceptable daily intake (ADI) of 7.5 mg/kg body weight (bw) per day for PGPR. PGPR is hydrolysed in the gut resulting in the liberation of free polyglycerols, polyricinoleic acid and ricinoleic acid. Di- and triglycerol are absorbed and excreted unchanged in the urine; long-chain polyglycerols show lower absorption and are mainly excreted unchanged in faeces. Acute oral toxicity of PGPR is low, and short-term and subchronic studies indicate PGPR is tolerated at high doses without adverse effects. PGPR (E 476) is not of concern with regard to genotoxicity or carcinogenicity. The single reproductive toxicity study with PGPR was limited and was not an appropriate study for deriving a health-based guidance value. Human studies with PGPR demonstrated that there is no indication of significant adverse effect. The Panel considered a 2-year combined chronic toxicity/carcinogenicity study for determining a reference point and derived a no observed adverse effect level (NOAEL) for PGPR (E 476) of 2,500 mg/kg bw per day, the only dose tested. Therefore, the Panel concluded that the present data set give reason to revise the ADI of 7.5 mg/kg bw per day allocated by SCF to 25 mg/kg bw per day. Exposure estimates did not exceed the ADI of 25 mg/kg bw per day and a proposed extension of use would not result in an exposure exceeding this ADI. The Panel recommended modification of the EU specifications for PGPR (E 476).

Influence of nutrition therapy on the intestinal microbiome

PURPOSE OF REVIEW

This review describes the relationship between nutritional therapies and the intestinal microbiome of critically ill patients.

RECENT FINDINGS

The intestinal microbiome of the critically ill displays a near complete loss of health-promoting microbiota with overgrowth of virulent healthcare-associated pathogens. Early enteral nutrition within 24 h of admission to the ICU has been advocated in medical and surgical patients to avoid derangements of the intestinal epithelium and the microbiome associated with starvation. Contrary to previous dogma, permissive enteral underfeeding has recently been shown to have similar outcomes to full feeding in the critically ill, whereas overfeeding has been shown to be deleterious in those patients who are not malnourished at baseline. Randomized clinical trials suggest that peripheral nutrition can be used safely either as the sole or supplemental source of nutrition even during the early phases of critical care. The use of probiotics has been associated with a significant reduction in infectious complications in the critically ill without a notable mortality benefit.

SUMMARY

Focus of research is shifting toward strategies that augment the intestinal environment to facilitate growth of beneficial microorganisms, strengthen colonization resistance, and maintain immune homeostasis.

Inhibitory effects of dietary soyasaponin on 2,4-dinitrofluorobenzene-induced contact hypersensitivity in mice

Soyasaponins (SSs) abundant in soybean have anti-inflammatory activities; however, their therapeutic effects on allergic contact dermatitis (ACD) remain unknown. To assess the effects of SS-enriched diets on ACD, we used a mouse model of contact hypersensitivity (CHS). Mice were fed low-dose or high-dose SS-containing diets for 3 weeks prior to CHS induction with 2,4-dinitrofluorobenzene (DNFB). The low-dose SS diet attenuated DNFB-induced ear swelling and tissue oedema, and reduced the number of infiltrating Gr-1-positive myeloid cells. Low-dose, but not high-dose, SSs decreased chemokine (C-X-C motif) ligand 2 (CXCL2) and triggering receptor expressed on myeloid cells (TREM)-1 production in ear tissues, compared to a control. Taxonomic 16S rRNA analysis revealed significant alterations in faecal microbiota caused by CHS, which were reversed by low-dose SSs. The low-dose SS and non-CHS groups clustered together, while the high-dose SS group split between CHS and non-CHS clusters. Our results demonstrated that low-dose SSs alleviated CHS symptoms by attenuating inflammation and improving the intestinal microbiota composition, suggesting that dietary SSs may have beneficial effects on ACD.

Gelatin-Based Nanocomplex-Stabilized Pickering Emulsions: Regulating Droplet Size and Wettability through Assembly with Glucomannan

Particle size and surface wettability play leading roles in the distribution of particles on the oil-water interface and the stability of emulsions. This work utilized nanocomplexes assembled from gelatin and tannic acid to stabilize Pickering emulsions. The sizes and surface wettability of particles were further regulated by using a polysaccharide. The sizes of nanocomplexes ranged from 205.8 to 422.2 nm and increased with the addition of polysaccharide. Their contact angles decreased from 84.1° to 59.3°, revealing their hydrophilic nature. Results of fluorescence microscopy and cryo-scanning electron microscopy indicated that nanocomplexes were located at the oil-water interface. Interfacial shear and dilatational rheological data revealed a fast and irreversible adsorption behavior, which differed from rearrangement of gelatin molecules at the oil-water interface. The minimal concentration of nanocomplexes required to stabilize emulsions was 0.1 wt %. Our results demonstrated that protein-polyphenol-polysaccharide nanocomplexes had the potential to be applied to form stable surfactant-free food emulsions for the delivery of nutraceuticals.

Food: a new form of personalised (gut microbiome) medicine for chronic diseases?

Filling in the knowledge gaps between what we eat and the diseases we develop may lie in our guts, literally. The human large intestine houses the largest reservoir of microorganisms in or on the human body. With a 100-fold greater gene count than humans, the gut microbiome has huge potential to place a large metabolic burden (or advantage) on its host. The number of diverse gut microbial species is diminished in nearly all modern chronic conditions studied. The 'Western diet', rich in animal protein, fats and artificial additives, and lacking in fibre, beneficial microbes, plant phytochemicals, vitamins and minerals, is thought to drive these conditions by encouraging gut dysbiosis. Evidence from recent dietary intervention studies suggest adopting a plant-based, minimally processed high-fibre diet may rapidly reverse the effects of meat-based diets on the gut microbiome. However, recent work has shown that individual diet responses may be complicated by host genetics and the wide variation in the gut microbiome. Now that we measure genes and microbes more accurately, we are embarking on an exciting era of using both food and microbes as potential therapies.

Diet as a Trigger or Therapy for Inflammatory Bowel Diseases

The most common question asked by patients with inflammatory bowel disease (IBD) is, "Doctor, what should I eat?" Findings from epidemiology studies have indicated that diets high in animal fat and low in fruits and vegetables are the most common pattern associated with an increased risk of IBD. Low levels of vitamin D also appear to be a risk factor for IBD. In murine models, diets high in fat, especially saturated animal fats, also increase inflammation, whereas supplementation with omega 3 long-chain fatty acids protect against intestinal inflammation. Unfortunately, omega 3 supplements have not been shown to decrease the risk of relapse in patients with Crohn's disease. Dietary intervention studies have shown that enteral therapy, with defined formula diets, helps children with Crohn's disease and reduces inflammation and dysbiosis. Although fiber supplements have not been shown definitively to benefit patients with IBD, soluble fiber is the best way to generate short-chain fatty acids such as butyrate, which has anti-inflammatory effects. Addition of vitamin D and curcumin has been shown to increase the efficacy of IBD therapy. There is compelling evidence from animal models that emulsifiers in processed foods increase risk for IBD. We discuss current knowledge about popular diets, including the specific carbohydrate diet and diet low in fermentable oligo-, di-, and monosaccharides and polyols. We present findings from clinical and basic science studies to help gastroenterologists navigate diet as it relates to the management of IBD.

Understanding and Preventing the Global Increase of Inflammatory Bowel Disease

The inflammatory bowel diseases (IBDs) are contemporary conditions of industrialized societies. The prevalence of IBD continues to increase steadily in Western countries, and newly industrialized countries have a rapidly increasing incidence. The global spread of IBD appears to associate with Westernization of diets and environments, which affects the intestinal microbiome and increases the risk of IBD in genetically susceptible individuals. It is important to increase our understanding of these events to slow progression of IBD. We present a long-term plan to develop interventions that slow or stop the global increase in the incidence of IBD.

The Importance and Challenges of Dietary Intervention Trials for Inflammatory Bowel Disease

Inflammatory bowel disease is believed to be caused by a combination of genetic and environmental stimuli such as our diet. Diets high in meat and fats and low in fruits and vegetables have been associated with new-onset inflammatory bowel disease. This has triggered interest in using dietary modification as a treatment. The 3 principle models of dietary intervention are supplementation with selected dietary components, exclusion of selected dietary components, or use of dietary formulas in place of a normal diet. Despite the high level of interest in dietary interventions as a treatment for inflammatory bowel disease, few well-designed clinical trials have been conducted to firmly establish the optimal diet to induce or maintain remission. This may be in part related to the challenges of conducting dietary intervention trials. This review examines these challenges and potential approaches to be used in dietary intervention trials.

Transglutaminases in Dysbiosis As Potential Environmental Drivers of Autoimmunity

Protein-glutamine γ-glutamyltransferases (transglutaminases, Tgs) belong to the class of transferases. They catalyze the formation of an isopeptide bond between the acyl group at the end of the side chain of protein- or peptide-bound glutamine residues and the first order 𝜀-amine groups of protein- or peptide-bound lysine. The Tgs are considered to be universal protein cross-linkers, and they play an essential role in a number of human diseases. In this review, we discuss mainly the bacterial Tgs in terms of the functionality of the enzymes and a potential role they may play in bacterial survival. Since microbial transglutaminases (mTgs) are functionally similar to the human homologs, they may be involved in the human disease provocation. We suggest here a potential involvement of Tgs in the pathologies such as autoimmune diseases. In this hypothesis, the endogenous mTgs that are secreted by the gut microbiota, especially in a dysbiotic configuration, are potential drivers of systemic autoimmunity, via the enzymatic posttranslational modification of peptides in the gut lumen. These mTg activities directed toward cross-linking of naïve proteins can potentially generate neo-epitopes that are not only immunogenic but may also activate some immune response cascades leading to the pathological autoimmune processes.

Identification and Characterization of Ana o 3 Modifications on Arginine-111 Residue in Heated Cashew Nuts

Raw and roasted cashew nut extracts were evaluated for protein modifications by mass spectrometry. Independent modifications on the Arg-111 residue of Ana o 3 were observed in roasted but not raw cashew nuts. The mass changes of 72.0064 or 53.9529 Da are consistent with the formation of carboxyethyl and hydroimidazolone modifications at the Arg-111 residue. These same modifications were observed in Ana o 3 purified from roasted but not raw cashew nuts, albeit at a relatively low occurrence. Circular dichroism indicated that Ana o 3 purified from raw and roasted cashew nuts had similar secondary structure, and dynamic light scattering analysis indicated there was no observable difference in particle size. The stability of Ana o 3 purified from raw and roasted cashew nuts to trypsin was similar in the absence of or following treatment with a reducing agent. Only minor differences in IgE binding to Ana o 3 were observed by ELISA among a cohort of cashew-allergic patient sera.

A minimal length rigid helical peptide motif allows rational design of modular surfactants

Extensive work has been invested in the design of bio-inspired peptide emulsifiers. Yet, none of the formulated surfactants were based on the utilization of the robust conformation and self-assembly tendencies presented by the hydrophobins, which exhibited highest surface activity among all known proteins. Here we show that a minimalist design scheme could be employed to fabricate rigid helical peptides to mimic the rigid conformation and the helical amphipathic organization. These designer building blocks, containing natural non-coded α-aminoisobutyric acid (Aib), form superhelical assemblies as confirmed by crystallography and microscopy. The peptide sequence is amenable to structural modularity and provides the highest stable emulsions reported so far for peptide and protein emulsifiers. Moreover, we establish the ability of short peptides to perform the dual functions of emulsifiers and thickeners, a feature that typically requires synergistic effects of surfactants and polysaccharides. This work provides a different paradigm for the molecular engineering of bioemulsifiers.

Emulsifiers are used in the pharmaceutical, food, cosmetic, and biomedical industry. Here the authors fabricate rigid helical peptides that can perform as emulsifiers and thickeners, which typically requires synergistic effects of surfactants and polysaccharides.

Immunologic impact of the intestine in metabolic disease

Obesity and diabetes are associated with increased chronic low-grade inflammation and elevated plasma glucose levels. Although inflammation in the fat and liver are established features of obesity-associated insulin resistance, the intestine is emerging as a new site for immunologic changes that affect whole-body metabolism. Specifically, microbial and dietary factors incurred by diet-induced obesity influence underlying innate and adaptive responses of the intestinal immune system. These responses affect the maintenance of the intestinal barrier, systemic inflammation, and glucose metabolism. In this Review we propose that an understanding of the changes to the intestinal immune system, and how these changes influence systemic immunity and glucose metabolism in a whole-body integrative and a neuronal-dependent network, will unveil novel intestinal pathologic and therapeutic targets for diabetes and obesity.

Biological fate of food nanoemulsions and the nutrients they carry – internalisation, transport and cytotoxicity of edible nanoemulsions in Caco-2 intestinal cells

Internalisation of edible food nanoemulsions by CaCo-2 intestinal cells. The structure of edible nanoemulsions increases five times upon incorporation of reactive/ROS producing nutrients/APIs.

The Role of Carrageenan and Carboxymethylcellulose in the Development of Intestinal Inflammation

Although the exact pathophysiology remains unknown, the development of inflammatory bowel disease (IBD) is influenced by the interplay between genetics, the immune system, and environmental factors such as diet. The commonly used food additives, carrageenan and carboxymethylcellulose (CMC), are used to develop intestinal inflammation in animal models. These food additives are excluded from current dietary approaches to induce disease remission in Crohn's disease such as exclusive enteral nutrition (EEN) using a polymeric formula. By reviewing the existing scientific literature, this review aims to discuss the role that carrageenan and CMC may play in the development of IBD. Animal studies consistently report that carrageenan and CMC induce histopathological features that are typical of IBD while altering the microbiome, disrupting the intestinal epithelial barrier, inhibiting proteins that provide protection against microorganisms, and stimulating the elaboration of pro-inflammatory cytokines. Similar trials directly assessing the influence of carrageenan and CMC in humans are of course unethical to conduct, but recent studies of human epithelial cells and the human microbiome support the findings from animal studies. Carrageenan and CMC may trigger or magnify an inflammatory response in the human intestine but are unlikely to be identified as the sole environmental factor involved in the development of IBD or in disease recurrence after treatment. However, the widespread use of carrageenan and CMC in foods consumed by the pediatric population in a "Western" diet is on the rise alongside a corresponding increase in IBD incidence, and questions are being raised about the safety of frequent usage of these food additives. Therefore, further research is warranted to elucidate the role of carrageenan and CMC in intestinal inflammation, which may help identify novel nutritional strategies that hinder the development of the disease or prevent disease relapse post-EEN treatment.

Therapeutic modulation of gut microbiota in inflammatory bowel disease: More questions to be answered

Patients with inflammatory bowel disease (IBD) exhibit impaired control of the microbiome in the gut, and 'dysbiosis' is commonly observed. Western diet is a risk factor for the development of IBD, but it may have different effects on gut microbiota between IBD and non-IBD individuals. Exclusive enteral nutrition (EEN) can induce remission in pediatric Crohn's disease with a decrease in gut microbial diversity. Although there are some theoretical benefits, actual treatment effects of prebiotics and probiotics in IBD vary. High-quality studies have shown that VSL#3 (a high-potency probiotic medical food containing eight different strains) exhibits benefits in treating ulcerative colitis, and gut microbial diversity is reduced after treated with VSL#3 in animal models. The effect of fecal microbiome transplantation on IBD is controversial. Increasing microbial diversity compared with impaired handling of bacteria presents a dilemma. Antibiotics are the strongest factors in the reduction of microbiome ecological diversity. Some antibiotics may help to induce remission of the disease. Microbiome alteration has been suggested to be an intrinsic property of IBD and a potential predictor in diagnosis and prognosis. However, the effects of therapeutic modulations are variable; thus, more questions remain to be answered.

Diet-Microbiota Interactions Mediate Global Epigenetic Programming in Multiple Host Tissues

Histone-modifying enzymes regulate transcription and are sensitive to availability of endogenous small-molecule metabolites, allowing chromatin to respond to changes in environment. The gut microbiota produces a myriad of metabolites that affect host physiology and susceptibility to disease; however, the underlying molecular events remain largely unknown. Here we demonstrate that microbial colonization regulates global histone acetylation and methylation in multiple host tissues in a diet-dependent manner: consumption of a "Western-type" diet prevents many of the microbiota-dependent chromatin changes that occur in a polysaccharide-rich diet. Finally, we demonstrate that supplementation of germ-free mice with short-chain fatty acids, major products of gut bacterial fermentation, is sufficient to recapitulate chromatin modification states and transcriptional responses associated with colonization. These findings have profound implications for understanding the complex functional interactions between diet, gut microbiota, and host health.

Effects of Tween 80 on Growth and Biofilm Formation in Laboratory Media

Tween 80 is a widely used non-ionic emulsifier that is added to cosmetics, pharmaceuticals, and foods. Because of its widespread use we need to understand how it affects bacteria on our skin, in our gut, and in food products. The aim of this study is to investigate how Tween 80 affects the growth and antimicrobial susceptibility of Staphylococcus aureus, Listeria monocytogenes, and Pseudomonas fluorescens, which are common causes of spoilage and foodborne illnesses. Addition of 0.1% Tween 80 to laboratory growth media increased the growth rate of planktonic S. aureus batch cultures, and it also increased the total biomass when S. aureus was grown as biofilms. In contrast, Tween 80 had no effect on batch cultures of L. monocytogenes, it slowed the growth rate of P. fluorescens, and it led to formation of less biofilm by both L. monocytogenes and P. fluorescens. Furthermore, Tween 80 lowered the antibacterial efficacy of two hydrophobic antimicrobials: rifampicin and the essential oil isoeugenol. Our findings underline the importance of documenting indirect effects of emulsifiers when studying the efficacy of hydrophobic antimicrobials that are dispersed in solution by emulsification, or when antimicrobials are applied in food matrixes that include emulsifiers. Furthermore, the species-specific effects on microbial growth suggests that Tween 80 in cosmetics and food products could affect the composition of skin and gut microbiota, and the effect of emulsifiers on the human microbiome should therefore be explored to uncover potential health effects.

Globalisation of inflammatory bowel disease: perspectives from the evolution of inflammatory bowel disease in the UK and China

The UK and China provide unique historical perspectives on the evolution of the incidence of inflammatory bowel disease, which might provide insight into its pathogenesis. Historical records from the UK document the emergence of ulcerative colitis during the mid-1800s, which was later followed by the recognition of Crohn's disease in 1932. During the second half of the 20th century, the incidence of inflammatory bowel disease rose dramatically in high-income countries. Globalisation at the turn of the 21st century led to rapid economic development of newly industrialised countries such as China. In China, the modernisation of society was accompanied by the recognition of a sharp rise in the incidence of inflammatory bowel disease. The prevalence of inflammatory bowel disease is expected to continue to rise in high-income countries and is also likely to accelerate in the developing world. An understanding of the shared and different environmental determinants underpinning the pathogenesis of inflammatory bowel disease in western and eastern countries is essential to implement interventions that will blunt the rising global burden of inflammatory bowel disease.

Antimicrobial effect of emulsion-encapsulated isoeugenol against biofilms of food pathogens and spoilage bacteria

Food-related biofilms can cause food-borne illnesses and spoilage, both of which are problems on a global level. Essential oils are compounds derived from plant material that have a potential to be used in natural food preservation in the future since they are natural antimicrobials. Bacterial biofilms are particularly resilient towards biocides, and preservatives that effectively eradicate biofilms are therefore needed. In this study, we test the antibacterial properties of emulsion-encapsulated and unencapsulated isoeugenol against biofilms of Lis. monocytogenes, S. aureus, P. fluorescens and Leu. mesenteroides in tryptic soy broth and carrot juice. We show that emulsion encapsulation enhances the antimicrobial properties of isoeugenol against biofilms in media but not in carrot juice. Some of the isoeugenol emulsions were coated with chitosan, and treatment of biofilms with these emulsions disrupted the biofilm structure. Furthermore, we show that addition of the surfactant Tween 80, which is commonly used to disperse oils in food, hampers the antibacterial properties of isoeugenol. This finding highlights that common food additives, such as surfactants, may have an adverse effect on the antibacterial activity of preservatives. Isoeugenol is a promising candidate as a future food preservative because it works almost equally well against planktonic bacteria and biofilms. Emulsion encapsulation has potential benefits for the efficacy of isoeugenol, but the effect of encapsulation depends on the properties of food matrix in which isoeugenol is to be applied.

Dietary Emulsifier-Induced Low-Grade Inflammation Promotes Colon Carcinogenesis

The increased risks conferred by inflammatory bowel disease (IBD) to the development of colorectal cancer gave rise to the term "colitis-associated cancer" and the concept that inflammation promotes colon tumorigenesis. A condition more common than IBD is low-grade inflammation, which correlates with altered gut microbiota composition and metabolic syndrome, both present in many cases of colorectal cancer. Recent findings suggest that low-grade inflammation in the intestine is promoted by consumption of dietary emulsifiers, a ubiquitous component of processed foods, which alter the composition of gut microbiota. Here, we demonstrate in a preclinical model of colitis-induced colorectal cancer that regular consumption of dietary emulsifiers, carboxymethylcellulose or polysorbate-80, exacerbated tumor development. Enhanced tumor development was associated with an altered microbiota metagenome characterized by elevated levels of lipopolysaccharide and flagellin. We found that emulsifier-induced alterations in the microbiome were necessary and sufficient to drive alterations in major proliferation and apoptosis signaling pathways thought to govern tumor development. Overall, our findings support the concept that perturbations in host-microbiota interactions that cause low-grade gut inflammation can promote colon carcinogenesis. Cancer Res; 77(1); 27-40. ©2016 AACR.

When pathogenic bacteria meet the intestinal microbiota

The intestinal microbiota is a large and diverse microbial community that inhabits the intestinal tract, containing about 100 trillion bacteria from 500-1000 distinct species that, collectively, provide multiple benefits to the host. The gut microbiota contributes to nutrient absorption and maturation of the immune system, and also plays a central role in protection of the host from enteric bacterial infection. On the other hand, many enteric pathogens have developed strategies in order to be able to outcompete the intestinal community, leading to infection and/or chronic diseases. This review will summarize findings describing the complex relationship occurring between the intestinal microbiota and enteric pathogens, as well as how future therapies can ultimately benefit from such discoveries.This article is part of the themed issue 'The new bacteriology'.