High fat diet accelerates pathogenesis of murine Crohn's disease-like ileitis independently of obesity

No causal relationship between glucose and inflammatory bowel disease: a bidirectional two-sample mendelian randomization study

BACKGROUND

Association between glucose and inflammatory bowel disease (IBD) was found in previous observational studies and in cohort studies. However, it is not clear whether these associations reflect causality. Thus, this study investigated whether there is such a causal relation between elevated glucose and IBD, Crohn's disease (CD) and ulcerative colitis (UC).

METHODS

We performed a two-sample Mendelian Randomization (MR) with the independent genetic instruments identified from the largest available genome-wide association study (GWAS) for IBD (5,673 cases; 213,119 controls) and its main subtypes, CD and UC. Summarized data for glucose which included 200,622 cases and glycemic traits including HbA1c and type 2 diabetes(T2DM) were obtained from different GWAS studies. Primary and secondary analyses were conducted by preferentially using the radial inverse-variance weighted (IVW) approach. A number of other meta-analysis approach and sensitivity analyses were carried out to assess the robustness of the results.

RESULTS

We did not find a causal effect of genetically predicted glucose on IBD as a whole (OR 0.858; 95% CI 0.649-1.135; P = 0.286). In subtype analyses glucose was also suggestively not associated with Crohn's disease (OR 0.22; 95% CI 0.04-1.00; P = 0.05) and ulcerative colitis (OR 0.940; 95% CI 0.628-1.407; P = 0.762). In the other direction, IBD and its subtypes were not related to glucose and glycemic traits.

CONCLUSIONS

This MR study is not providing any evidence for a causal relationship between genetically predicted elevated glucose and IBD as well as it's subtypes UC and CD. Regarding the other direction, no causal associations could be found. Future studies with robust genetic instruments are needed to confirm this conclusion.

Pterostilbene: a potential therapeutic agent for fibrotic diseases

Fibrosis is a prevailing pathology in chronic diseases and accounts for 45% of deaths in developed countries. This condition is primarily identified by the transformation of fibroblasts into myofibroblasts and the overproduction of extracellular matrix (ECM) by myofibroblasts. Pterostilbene (PTS) is a natural analogue of resveratrol and is most commonly found in blueberries. Research has shown that PTS exerts a wide range of pharmacological effects, such as antioxidant, anti-inflammatory, and anticancer effects. As a result, PTS has the potential to prevent and cure numerous diseases. Emerging evidence has indicated that PTS can alleviate myocardial fibrosis, renal fibrosis, pulmonary fibrosis, hepatic fibrosis, and colon fibrosis via the inhibition of inflammation, oxidative stress, and fibrogenesis effects in vivo and in vitro, and the potential mechanisms are linked to various pathways, including transforming growth factor-β1 (TGF-β1)/small mother against decapentaplegic proteins (Smads) signalling, the reactive oxygen species (ROS)-driven Pitx2c/mir-15b pathway, nuclear factor kappa B (NF-κB) signalling, Kelch-like epichlorohydrin-associated protein-1 (Keap-1)/NF-E2-related factor-2 (Nrf2) cascade, the NLR family pyridine structure domain 3 (NLRP3) pathway, the Janus kinase-2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway, and the Src/STAT3 pathway. In this review, we comprehensively summarize the antifibrotic effects of PTS both in vivo and in vitro and the pharmacological mechanisms, pharmacokinetics, and toxicology of PTS and provide insights into and strategies for exploring promising agents for the treatment of fibrosis.

The TNF∆ARE Model of Crohn's Disease-like Ileitis

Crohn's disease (CD) is one of the 2 main phenotypes of inflammatory bowel diseases (IBDs); CD ischaracterized by a discontinuous, spontaneously recurring, transmural immunopathology that largely affects the terminal ileum. Crohn's disease exhibits both a relapsing and progressive course, and its prevalence is on the rise globally, mirroring the trends of industrialization. While the precise pathogenesis of CD remains unknown, various factors including immune cell dysregulation, microbial dysbiosis, genetic susceptibility, and environmental factors have been implicated in disease etiology. Animal models, particularly ileitis mouse models, have provided valuable tools for studying the specific mechanisms underlying CD, allowing longitudinal assessment and sampling in interventional preclinical studies. Furthermore, animal models assess to evaluate the distinct role that bacterial and dietary antigens play in causing inflammation, using germ-free animals, involving the introduction of individual bacteria (monoassociation studies), and experimenting with well-defined dietary components. An ideal animal model for studying IBD, specifically CD, should exhibit an inherent intestinal condition that arises spontaneously and closely mimics the distinct transmural inflammation observed in the human disease, particularly in the terminal ileum. We have recently characterized the impact of disease-relevant, noninfectious microbiota and specific bacteria in a mouse model that replicates CD-like ileitis, capturing the intricate nature of human CD, namely the TNF∆ARE mouse model. Using germ-free mice, we studied the impact of different diets on the expansion of disease-relevant pathobionts and on the severity of inflammation. In this review article, we review some of the currently available ileitis mouse models and discuss in detail the TNF∆ARE model of CD-like Ileitis.

Obesity alters immunopathology in cancers and inflammatory diseases

Obesity is characterized by chronic low-grade inflammation and is strongly associated with multiple immunological diseases, including cancer and inflammatory diseases. Recent animal studies revealed that obesity-induced immunological changes worsen immune-driven diseases and cause resistance to immunotherapy. Here, we discuss the role of obesity in the immunopathology and treatment responses of cancers, respiratory and allergic diseases, and IL-17-mediated inflammatory diseases. We summarize the unique features of the inflammatory state of these diseases, which are orchestrated by obesity. In particular, obesity alters the immune landscape in cancers with a reprogrammed metabolic profile of tumor-infiltrating immune cells. Obesity exacerbates airway inflammation by dysregulating multiple immune-cell subsets. Obesity also dysregulates Th17, IL-17-producing mucosal-associated invariant T (MAIT), and γδ T cells, which contribute to IL-17-mediated inflammatory response in multiple sclerosis, inflammatory bowel disease, psoriasis, atopic dermatitis, and rheumatoid arthritis. By identifying the effects of obesity on immunological diseases, new strategies could be devised to target immune dysregulation caused by obesity.

Fatty acids and lipid mediators in inflammatory bowel disease: from mechanism to treatment

Inflammatory Bowel Disease (IBD) is a chronic, relapsing inflammatory disorder of the gastrointestinal tract. Though the pathogenesis of IBD remains unclear, diet is increasingly recognized as a pivotal factor influencing its onset and progression. Fatty acids, essential components of dietary lipids, play diverse roles in IBD, ranging from anti-inflammatory and immune-regulatory functions to gut-microbiota modulation and barrier maintenance. Short-chain fatty acids (SCFAs), products of indigestible dietary fiber fermentation by gut microbiota, have strong anti-inflammatory properties and are seen as key protective factors against IBD. Among long-chain fatty acids, saturated fatty acids, trans fatty acids, and ω-6 polyunsaturated fatty acids exhibit pro-inflammatory effects, while oleic acid and ω-3 polyunsaturated fatty acids display anti-inflammatory actions. Lipid mediators derived from polyunsaturated fatty acids serve as bioactive molecules, influencing immune cell functions and offering both pro-inflammatory and anti-inflammatory benefits. Recent research has also highlighted the potential of medium- and very long-chain fatty acids in modulating inflammation, mucosal barriers, and gut microbiota in IBD. Given these insights, dietary intervention and supplementation with short-chain fatty acids are emerging as potential therapeutic strategies for IBD. This review elucidates the impact of various fatty acids and lipid mediators on IBD and delves into potential therapeutic avenues stemming from these compounds.

Zingerone attenuates intestinal injury and colitis caused by a high-fat diet through Nrf2 signaling regulation

This study examined the protective effect of Zingerone against a high-fat diet (HFD)-induced intestinal damage. Control and HFD rats were treated with the vehicle or Zingerone (100 mg/kg, orally) (n = 8 rats/groups). An extra group, HFD + Zingerone + brusatol (an Nrf2 inhibitor). This study treatment lasted four weeks. Zingerone reduced the nuclear levels of NF-B p65 in control and HFD-fed rats while increasing SOD, CAT, GSH, levels of mRNA, cytoplasmic levels, and Nrf2 nuclear levels. Zingerone treatment attenuated the duodenal epithelial damage and maintained the mucosal barrier by reducing plasma FITC-DX and serum LPS in rats fed with HFD. Concomitantly, it lowered the duodenal MDA, TNF-α, IL-6, and IL-1β levels. These impacts included changes in body weight, duodenal lipid levels, and Keap-1 expression, a natural Nrf2 inhibitor. We concluded that Zingerone reduces HFD-induced duodenal injury. These findings support Zingerone's clinical applicability against various inflammatory diseases of the intestine.

The Effects of a High-Fat Diet on Inflammatory Bowel Disease

The interactions among diet, intestinal immunity, and microbiota are complex and play contradictory roles in inflammatory bowel disease (IBD). An increasing number of studies has shed light on this field. The intestinal immune balance is disrupted by a high-fat diet (HFD) in several ways, such as impairing the intestinal barrier, influencing immune cells, and altering the gut microbiota. In contrast, a rational diet is thought to maintain intestinal immunity by regulating gut microbiota. In this review, we emphasize the crucial contributions made by an HFD to the gut immune system and microbiota.

Diet-induced obesity alters intestinal monocyte-derived and tissue-resident macrophages and increases intestinal permeability in female mice independent of tumor necrosis factor

Macrophages are essential for homeostatic maintenance of the anti-inflammatory and tolerogenic intestinal environment, yet monocyte-derived macrophages can promote local inflammation. Proinflammatory macrophage accumulation within the intestines may contribute to the development of systemic chronic inflammation and immunometabolic dysfunction in obesity. Using a model of high-fat diet-induced obesity in C57BL/6J female mice, we assessed intestinal paracellular permeability by in vivo and ex vivo assays and quantitated intestinal macrophages in ileum and colon tissues by multicolor flow cytometry after short (6 wk), intermediate (12 wk), and prolonged (18 wk) diet allocation. We characterized monocyte-derived CD4^-TIM4^- and CD4⁺TIM4^- macrophages, as well as tissue-resident CD4⁺TIM4⁺ macrophages. Diet-induced obesity had tissue- and time-dependent effects on intestinal permeability, as well as monocyte and macrophage numbers, surface marker phenotype, and intracellular production of the cytokines IL-10 and tumor necrosis factor (TNF). We found that obese mice had increased paracellular permeability, in particular within the ileum, but this did not elicit recruitment of monocytes nor a local proinflammatory response by monocyte-derived or tissue-resident macrophages in either the ileum or colon. Proliferation of monocyte-derived and tissue-resident macrophages was also unchanged. Wild-type and TNF^-/- littermate mice had similar intestinal permeability and macrophage population characteristics in response to diet-induced obesity. These data are unique from reported effects of diet-induced obesity on macrophages in metabolic tissues, as well as outcomes of acute inflammation within the intestines. These experiments also collectively indicate that TNF does not mediate effects of diet-induced obesity on paracellular permeability or intestinal monocyte-derived and tissue-resident intestinal macrophages in young female mice.NEW & NOTEWORTHY We found that diet-induced obesity in female mice has tissue- and time-dependent effects on intestinal paracellular permeability as well as monocyte-derived and tissue-resident macrophage numbers, surface marker phenotype, and intracellular production of the cytokines IL-10 and TNF. These changes were not mediated by TNF.

Insights into diet-associated oxidative pathomechanisms in inflammatory bowel disease and protective effects of functional amino acids

There has been a substantial rise in the incidence and prevalence of clinical patients presenting with inflammatory bowel disease (IBD), which includes Crohn's disease and ulcerative colitis. Accumulating evidence has corroborated the view that dietary factors (particularly diets with high levels of saturated fat or sugar) are involved in the development and progression of IBD, which is predominately associated with changes in the composition of the gut microbiota and an increase in the generation of reactive oxygen species. Notably, the ecological imbalance of the gut microbiome exacerbates oxidative stress and inflammatory responses, leading to perturbations of the intestinal redox balance and immunity, as well as mucosal integrity. Recent findings have revealed that functional amino acids, including L-glutamine, glycine, L-arginine, L-histidine, L-tryptophan, and hydroxyproline, are effectively implicated in the maintenance of intestinal redox and immune homeostasis. These amino acids and their metabolites have oxygen free-radical scavenging and inflammation-relieving properties, and they participate in modulation of the microbial community and the metabolites in the gut. The principal focus of this article is a review of recent advances in the oxidative pathomechanisms of IBD development and progression in relation to dietary factors, with a particular emphasis on the redox and signal transduction mechanisms of host cells in response to unbalanced diets and enterobacteria. In addition, an update on current understanding of the protective effects of functional amino acids against IBD, together with the underlying mechanisms for this protection, have been provided.

Sex hormones, intestinal inflammation, and the gut microbiome: Major influencers of the sexual dimorphisms in obesity

Obesity is defined as the excessive accumulation of body fat and is associated with an increased risk of developing major health problems such as cardiovascular disease, diabetes and stroke. There are clear sexual dimorphisms in the epidemiology, pathophysiology and sequelae of obesity and its accompanying metabolic disorders, with females often better protected compared to males. This protection has predominantly been attributed to the female sex hormone estrogen and differences in fat distribution. More recently, the sexual dimorphisms of obesity have also been attributed to the differences in the composition and function of the gut microbiota, and the intestinal immune system. This review will comprehensively summarize the pre-clinical and clinical evidence for these sexual dimorphisms and discuss the interplay between sex hormones, intestinal inflammation and the gut microbiome in obesity. Major gaps and limitations of this rapidly growing area of research will also be highlighted in this review.

Influence of Foods and Nutrition on the Gut Microbiome and Implications for Intestinal Health

Food components in our diet provide not only necessary nutrients to our body but also substrates for the mutualistic microbial flora in our gastrointestinal tract, termed the gut microbiome. Undigested food components are metabolized to a diverse array of metabolites. Thus, what we eat shapes the structure, composition, and function of the gut microbiome, which interacts with the gut epithelium and mucosal immune system and maintains intestinal homeostasis in a healthy state. Alterations of the gut microbiome are implicated in many diseases, such as inflammatory bowel disease (IBD). There is growing interest in nutritional therapy to target the gut microbiome in IBD. Investigations into dietary effects on the composition changes in the gut microbiome flourished in recent years, but few focused on gut physiology. This review summarizes the current knowledge regarding the impacts of major food components and their metabolites on the gut and health consequences, specifically within the GI tract. Additionally, the influence of the diet on the gut microbiome-host immune system interaction in IBD is also discussed. Understanding the influence of the diet on the interaction of the gut microbiome and the host immune system will be useful in developing nutritional strategies to maintain gut health and restore a healthy microbiome in IBD.

Diet-Induced Host-Microbe Interactions: Personalized Diet Strategies for Improving Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an idiopathic inflammatory disease. Environmental sanitization, modern lifestyles, advanced medicines, ethnic origins, host genetics and immune systems, mucosal barrier function, and the gut microbiota have been delineated to explain how they cause mucosal inflammation. However, the pathogenesis of IBD and its therapeutic targets remain elusive. Recent studies have highlighted the importance of the human gut microbiota in health and disease, suggesting that the pathogenesis of IBD is highly associated with imbalances of the gut microbiota or alterations of epithelial barrier function in the gastrointestinal (GI) tract. Moreover, diet-induced alterations of the gut microbiota in the GI tract modulate immune responses and perturb metabolic homeostasis. This review summarizes recent findings on IBD and its association with diet-induced changes in the gut microbiota; furthermore, it discusses how diets can modulate host gut microbes and immune systems, potentiating the impact of personalized diets on therapeutic targets for IBD.

Reactive Oxygen Species/Reactive Nitrogen Species as Messengers in the Gut: Impact on Physiology and Metabolic Disorders

Significance: The role of reactive oxygen/nitrogen species as "friend" or "foe" messengers in the whole body is well characterized. Depending on the concentration in the tissue considered, these molecular actors exert beneficial or deleterious impacts leading to a pathological state, as observed in metabolic disorders such as type 2 diabetes and obesity. Recent Advances: Among the tissues impacted by oxidation and inflammation in this pathological state, the intestine is a site of dysfunction that can establish diabetic symptoms, such as alterations in the intestinal barrier, gut motility, microbiota composition, and gut/brain axis communication. In the intestine, reactive oxygen/nitrogen species (from the host and/or microbiota) are key factors that modulate the transition from physiological to pathological signaling. Critical Issues: Controlling the levels of intestinal reactive oxygen/nitrogen species is a complicated balance between positive and negative impacts that is in constant equilibrium. Here, we describe the synthesis and degradation of intestinal reactive oxygen/nitrogen species and their interactions with the host. The development of novel redox-based therapeutics that alter these processes could restore intestinal health in patients with metabolic disorders. Future Directions: Deciphering the mode of action of reactive oxygen/nitrogen species in the gut of obese/diabetic patients could result in a future therapeutic strategy that combines nutritional and pharmacological approaches. Consequently, preventive and curative treatments must take into account one of the first sites of oxidative and inflammatory dysfunctions in the body, that is, the intestine. Antioxid. Redox Signal. 37, 394-415.

Use of polyunsaturated fatty acids in prevention and treatment of gastrointestinal diseases, obesity and cancer

Fatty acids are important structural and functional elements of human body. We can distinguish several types: among others polyunsaturated fatty acids, which include omega-3 fatty acids (ω-3PUFA) and omega-6 fatty acids(ω-6PUFA). The first group has pleiotropic health-promoting effects, while the second group, ω-6PUFA, negatively affects the homeostasis of the human body and contributes to the development of numerous diseases. Both the amount and the relative ratio of these acids in the diet is an important factor affecting health and quality of life.

Laboratory and clinical studies indicate that ω-3PUFA have a positive effect on the therapy of illnesses such as obesity and inflammatory bowel disease (IBD). ω-3 PUFA supplementation also appears to have a helpful effect in the adjuvant treatment of colorectal cancer and recovery.

Food as Treatment of Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD), namely, Crohn's disease (CD) and ulcerative colitis (UC), are lifelong and incurable chronic inflammatory diseases affecting 6.8 million people worldwide. By 2030, the prevalence of IBD is estimated to reach 1% of the population in Western countries, and thus there is an urgent need to develop effective therapies to reduce the burden of this disease. Microbiome dysbiosis is at the heart of the IBD pathophysiology, and current research and development efforts for IBD treatments have been focused on gut microbiome regulation. Diet can shape the intestinal microbiome. Diet is also preferred over medication, is safe, and has been proven to be an effective strategy for the management of IBD. Therefore, although often overlooked, dietary interventions targeting the microbiome represent ideal treatments for IBD. Here, I summarize the latest research on diet as a treatment for IBD from infancy to adulthood, compile evidence of the mechanisms of action behind diet as treatment, and, lastly, provide insights into future research focusing on culturally tailored diets for ethnic minority groups with increased incidence of IBD yet underrepresented in nutrition research.

When fat meets the gut-focus on intestinal lipid handling in metabolic health and disease

The regular overconsumption of energy‐dense foods (rich in lipids and sugars) results in elevated intestinal nutrient absorption and consequently excessive accumulation of lipids in the liver, adipose tissue, skeletal muscles, and other organs. This can eventually lead to obesity and obesity‐associated diseases such as type 2 diabetes (T2D), non‐alcoholic fatty liver disease (NAFLD), cardiovascular disease, and certain types of cancer, as well as aggravate inflammatory bowel disease (IBD). Therefore, targeting the pathways that regulate intestinal nutrient absorption holds significant therapeutic potential. In this review, we discuss the molecular and cellular mechanisms controlling intestinal lipid handling, their relevance to the development of metabolic diseases, and emerging therapeutic strategies.

The Combination of Intestinal Alkaline Phosphatase Treatment with Moderate Physical Activity Alleviates the Severity of Experimental Colitis in Obese Mice via Modulation of Gut Microbiota, Attenuation of Proinflammatory Cytokines, Oxidative Stress Biomarkers and DNA Oxidative Damage in Colonic Mucosa

Inflammatory bowel diseases (IBD) are commonly considered as Crohn's disease and ulcerative colitis, but the possibility that the alterations in gut microbiota and oxidative stress may affect the course of experimental colitis in obese physically exercising mice treated with the intestinal alkaline phosphatase (IAP) has been little elucidated. Mice fed a high-fat-diet (HFD) or normal diet (ND) for 14 weeks were randomly assigned to exercise on spinning wheels (SW) for 7 weeks and treated with IAP followed by intrarectal administration of TNBS. The disease activity index (DAI), grip muscle strength test, oxidative stress biomarkers (MDA, SOD, GSH), DNA damage (8-OHdG), the plasma levels of cytokines IL-2, IL-6, IL-10, IL-12p70, IL-17a, TNF-α, MCP-1 and leptin were assessed, and the stool composition of the intestinal microbiota was determined by next generation sequencing (NGS). The TNBS-induced colitis was worsened in obese sedentary mice as manifested by severe colonic damage, an increase in DAI, oxidative stress biomarkers, DNA damage and decreased muscle strength. The longer running distance and weight loss was observed in mice given IAP or subjected to IAP + SW compared to sedentary ones. Less heterogeneous microbial composition was noticed in sedentary obese colitis mice and this effect disappeared in IAP + SW mice. Absence of Alistipes, lower proportion of Turicibacter, Proteobacteria and Faecalibacterium, an increase in Firmicutes and Clostridium, a decrease in oxidative stress biomarkers, 8-OHdG content and proinflammatory cytokines were observed in IAP + SW mice. IAP supplementation in combination with moderate physical activity attenuates the severity of murine colitis complicated by obesity through a mechanism involving the downregulation of the intestinal cytokine/chemokine network and oxidative stress, the modulation of the gut microbiota and an improvement of muscle strength.

Characterization and Analysis of the Temporal and Spatial Dynamic of Several Enteritis Modeling Methodologies

Inflammatory bowel disease (IBD), such as Crohn’s disease and ulcerative colitis, is a complex disease involving genetic, immune, and microbiological factors. A variety of animal models of IBD have been developed to study the pathogenesis of human IBD, but there is no model that can fully represent the complexity of IBD. In this study, we established two acute enteritis models by oral 3% DSS or intraperitoneal injection of anti-CD3 antibody, and two chronic enteritis models by feeding 3 cycles of 1.5% DSS or 3 months of the high-fat diet, respectively, and then examined the clinical parameters, histological changes, and cytokine expression profiles after the successful establishment of the models. Our results indicated that in 3% DSS-induced acute enteritis, the colorectal injury was significantly higher than that of the small intestine, while in anti-CD3 antibody-induced acute enteritis, the small intestine injury was significantly higher than that of colorectal damage. Besides, in the 1.5% DSS-induced chronic enteritis, the damage was mainly concentrated in the colorectal, while the damage caused by long-term HFD-induced chronic enteritis was more focused on the small intestine. Therefore, our work provides a reference for selecting appropriate models when conducting research on factors related to the pathogenesis of IBD or evaluating the potential diagnosis and treatment possibilities of pharmaceuticals.

Pediococcus pentosaceus PP04 improves high-fat diet-induced liver injury by the modulation of gut inflammation and intestinal microbiota in C57BL/6N mice

In this study, Pediococcus pentococcus PP04 (PP04) isolated from the Northeast pickled cabbage was given to C57BL/6N mice for eight weeks, aiming to investigate the ameliorative effects of PP04 on liver injury induced by a high-fat diet. The western blot results suggested that PP04 ameliorated the increase of intestinal permeability by dramatically increasing the expressions of tight junction proteins, such as Occludin, Claudin-1 and ZO-1, which decreased hepatic lipopolysaccharides (LPS), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) concentrations to effectively alleviate the liver injury. Furthermore, PP04 relieved the high-fat diet-caused gut inflammation by the NF-κB/Nrf2 signaling pathway, which regulated the expression of inflammatory cytokines and antioxidants, to positively improve the liver injury. In addition, the 16S rDNA sequencing results inferred that PP04 had the potential to rebalance intestinal flora disorders through regulating the relative abundance of inflammation and obesity-related bacteria in mice.

Pterostilbene Attenuates High-Fat Diet and Dextran Sulfate Sodium-Induced Colitis via Suppressing Inflammation and Intestinal Fibrosis in Mice

The worldwide prevalence of obesity has significantly increased over the past few decades. It is currently believed that obesity is a risk factor for developing inflammatory bowel disease. Pterostilbene (PTS), a naturally occurring stilbene from blueberries, is known to have anticancer, anti-inflammation, antifibrosis, and antiobesity effects. The preventive effect of PTS on the susceptibility of high-fat diet (HFD) to dextran sulfate sodium (DSS)-induced colitis in mice was investigated. Beginning at 5 weeks of age, C57BL/6J mice were fed a normal diet, 50% HFD alone, or containing PTS, and DSS (2.5%, w/v) was given in drinking water at week 9 and week 11. The results demonstrated that PTS significantly attenuated HFD and DSS-induced plasma interleukin-6 accumulation. Moreover, PTS suppressed HFD/DSS-induced formation of aberrant crypt foci and reduced the colon weight-to-length ratio in HFD/DSS-induced colitis mice. Furthermore, PTS inhibited interleukin-1β (IL-1β), the C/EBP homologous protein (CHOP), cyclooxygenase-2, and transforming growth factor beta-1 (TGF-β1)/mothers against decapentaplegic homolog 2 expression and maintained mucin2 (Muc2) and E-cadherin expressions. In addition, post-treatment with PTS also decreased the colon weight-to-length ratio and loss of Muc2. Moreover, the CHOP, IL-1β, matrix metalloproteinase-2, and TGF-β1 expressions were significantly decreased in HFD/DSS-induced colitis mice after post-treatment with PTS. In conclusion, the results of the present study suggest that PTS is of significant interest for the prevention of HFD/DSS-induced colitis in C57BL/6J mice.

Dietary simple sugars alter microbial ecology in the gut and promote colitis in mice

The higher prevalence of inflammatory bowel disease (IBD) in Western countries points to Western diet as a possible IBD risk factor. High sugar, which is linked to many noncommunicable diseases, is a hallmark of the Western diet, but its role in IBD remains unknown. Here, we studied the effects of simple sugars such as glucose and fructose on colitis pathogenesis in wild-type and Il10^-/- mice. Wild-type mice fed 10% glucose in drinking water or high-glucose diet developed severe colitis induced by dextran sulfate sodium. High-glucose-fed Il10^-/- mice also developed a worsened colitis compared to glucose-untreated Il10^-/- mice. Short-term intake of high glucose or fructose did not trigger inflammatory responses in healthy gut but markedly altered gut microbiota composition. In particular, the abundance of the mucus-degrading bacteria Akkermansia muciniphila and Bacteroides fragilis was increased. Consistently, bacteria-derived mucolytic enzymes were enriched leading to erosion of the colonic mucus layer of sugar-fed wild-type and Il10^-/- mice. Sugar-induced exacerbation of colitis was not observed when mice were treated with antibiotics or maintained in a germ-free environment, suggesting that altered microbiota played a critical role in sugar-induced colitis pathogenesis. Furthermore, germ-free mice colonized with microbiota from sugar-treated mice showed increased colitis susceptibility. Together, these data suggest that intake of simple sugars predisposes to colitis and enhances its pathogenesis via modulation of gut microbiota in mice.

Current recommendations on the role of diet in the aetiology and management of IBD

Diet is a key modifier of risk of inflammatory bowel disease development and potentially a treatment option in patients with established disease. International organisations in gastroenterology and inflammatory bowel disease have published guidelines for the role of diet in disease onset and its management. Here, we discuss the major overarching themes arising from these guidelines and appraise recent literature on the role of diet for inflammatory bowel disease prevention, treatment of active disease and maintenance of remission, considering these themes. Except for exclusive enteral nutrition in active Crohn's disease, we currently possess very little evidence to make any further dietary recommendations for the management of inflammatory bowel disease. There is also currently uncertainty on the extrapolation of epidemiological dietary signals on risk of disease development and preclinical experiments in animal models to management, once disease is established. Until high-quality evidence from clinical research becomes available, the only specific recommendations for inflammatory bowel disease we might safely give are those of healthy eating which apply for the general population for overall health and well-being.

Modeling microbe-host interaction in the pathogenesis of Crohn's disease

Alterations in the gut microbiota structure and function are thought to play an important role in the pathogenesis of Crohn's disease (CD). The rapid advancement of high-throughput sequencing technologies led to the identification of microbiome risk signatures associated with distinct disease phenotypes and progressing disease entities. Functional validation of the identified microbiome signatures is essential to understand the underlying mechanisms of microbe-host interactions. Germfree mouse models are available to study the functional role of disease-conditioning complex gut microbial ecosystems (dysbiosis) or pathobionts (single bacteria) in the pathogenesis of CD-like inflammation. Here, we discuss the clinical and mechanistic relevance and limitations of gnotobiotic mouse models in the context of CD. In addition, we will address the role of diet as an essential external factor modulating microbiome changes, potentially underlying disease initiation and development.

Regulation of Intestinal Inflammation by Dietary Fats

With the epidemic of human obesity, dietary fats have increasingly become a focal point of biomedical research. Epidemiological studies indicate that high-fat diets (HFDs), especially those rich in long-chain saturated fatty acids (e.g., Western Diet, National Health Examination survey; NHANES 'What We Eat in America' report) have multi-organ pro-inflammatory effects. Experimental studies have confirmed some of these disease associations, and have begun to elaborate mechanisms of disease induction. However, many of the observed effects from epidemiological studies appear to be an over-simplification of the mechanistic complexity that depends on dynamic interactions between the host, the particular fatty acid, and the rather personalized genetics and variability of the gut microbiota. Of interest, experimental studies have shown that certain saturated fats (e.g., lauric and myristic fatty acid-rich coconut oil) could exert the opposite effect; that is, desirable anti-inflammatory and protective mechanisms promoting gut health by unanticipated pathways. Owing to the experimental advantages of laboratory animals for the study of mechanisms under well-controlled dietary settings, we focus this review on the current understanding of how dietary fatty acids impact intestinal biology. We center this discussion on studies from mice and rats, with validation in cell culture systems or human studies. We provide a scoping overview of the most studied diseases mechanisms associated with the induction or prevention of Inflammatory Bowel Disease in rodent models relevant to Crohn's Disease and Ulcerative Colitis after feeding either high-fat diet (HFD) or feed containing specific fatty acid or other target dietary molecule. Finally, we provide a general outlook on areas that have been largely or scarcely studied, and assess the effects of HFDs on acute and chronic forms of intestinal inflammation.

Fungal lysozyme leverages the gut microbiota to curb DSS-induced colitis

Colitis is characterized by colonic inflammation and impaired gut health. Both features aggravate obesity and insulin resistance. Host defense peptides (HDPs) are key regulators of gut homeostasis and generally malfunctioning in above-mentioned conditions. We aimed here to improve bowel function in diet-induced obesity and chemically induced colitis through daily oral administration of lysozyme, a well-characterized HDP, derived from Acremonium alcalophilum.C57BL6/J mice were fed either low-fat reference diet or HFD ± daily gavage of lysozyme for 12 weeks, followed by metabolic assessment and evaluation of colonic microbiota encroachment. To further evaluate the efficacy of intestinal inflammation, we next supplemented chow-fed BALB/c mice with lysozyme during Dextran Sulfate Sodium (DSS)-induced colitis in either conventional or microbiota-depleted mice. We assessed longitudinal microbiome alterations by 16S amplicon sequencing in both models.Lysozyme dose-dependently alleviated intestinal inflammation in DSS-challenged mice and further protected against HFD-induced microbiota encroachment and fasting hyperinsulinemia. Observed improvements of intestinal health relied on a complex gut flora, with the observation that microbiota depletion abrogated lysozyme's capacity to mitigate DSS-induced colitis.Akkermansia muciniphila associated with impaired gut health in both models, a trajectory that was mitigated by lysozyme administration. In agreement with this notion, PICRUSt2 analysis revealed specific pathways consistently affected by lysozyme administration, independent of vivarium, disease model and mouse strain.Taking together, lysozyme leveraged the gut microbiota to curb DSS-induced inflammation, alleviated HFD-induced gastrointestinal disturbances and lowered fasting insulin levels in obese mice. Collectively, these data present A. alcalophilum-derived lysozyme as a promising candidate to enhance gut health.

Gut epithelial TSC1/mTOR controls RIPK3-dependent necroptosis in intestinal inflammation and cancer

Although Western diet and dysbiosis are the most prominent environmental factors associated with inflammatory bowel diseases (IBDs), the corresponding host factors and cellular mechanisms remain poorly defined. Here we report that the TSC1/mTOR pathway in the gut epithelium represents a metabolic and innate immune checkpoint for intestinal dysfunction and inflammation. mTOR hyperactivation triggered by Western diet or Tsc1 ablation led to epithelium necroptosis, barrier disruption, and predisposition to dextran sulfate sodium-induced colitis and inflammation-associated colon cancer. Mechanistically, our results uncovered a critical role for TSC1/mTOR in restraining the expression and activation of RIPK3 in the gut epithelium through TRIM11-mediated ubiquitination and autophagy-dependent degradation. Notably, microbiota depletion by antibiotics or gnotobiotics attenuated RIPK3 expression and activation, thereby alleviating epithelial necroptosis and colitis driven by mTOR hyperactivation. mTOR primarily impinged on RIPK3 to potentiate necroptosis induced by TNF and by microbial pathogen-associated molecular patterns (PAMPs), and hyperactive mTOR and aberrant necroptosis were intertwined in human IBDs. Together, our data reveal a previously unsuspected link between the Western diet, microbiota, and necroptosis and identify the mTOR/RIPK3/necroptosis axis as a driving force for intestinal inflammation and cancer.

Are Fried Foods Unhealthy? The Dietary Peroxidized Fatty Acid, 13-HPODE, Induces Intestinal Inflammation In Vitro and In Vivo

Inflammatory Bowel Disease (IBD) is a chronic inflammatory disorder characterized by progressive inflammation and the erosion of the gut mucosa. Although the exact cause of IBD is unknown, multiple factors contribute to its complex pathogenesis. Diet is one such factor and a strong correlation exists between the western-style, high fat diets (HFDs) and IBD incidence rates. In this study, we propose that the peroxidized fatty acid components of HFDs could contribute to inflammation of the gut. The inflammatory nature of peroxidized linoleic acid (13-HPODE), was confirmed in vitro by analyzing pro-inflammatory gene expression in Caco-2 cells via RT-PCR and ELISA. Additionally, peroxide induced apoptosis was tested by Annexin-V fluorescent staining, while permeability was tested by FITC-dextran flux and TEER. The 13-HPODE-induced inflammation of intestinal epithelium was evaluated in vivo by analyzing pro-inflammatory cytokines under acute and chronic conditions after feeding 13-HPODE to C57BL/6J mice. Our data show that 13-HPODE significantly induced pro-inflammatory gene expression of TNF-α and MCP-1 in vitro, most notably in differentiated Caco-2 cells. Further, acute and chronic 13-HPODE treatments of mice similarly induced pro-inflammatory cytokine expression in the epithelium of both the proximal and distal small intestines, resident immune cells in Peyer's patches and peritoneal macrophages. The results of this study not only confirm the pro-inflammatory properties of peroxidized fats on the gut mucosa, but for the first time demonstrate their ability to differentially induce pro-inflammatory gene expression and influence permeability in the intestinal epithelium and mucosal cells. Collectively, our results suggest that the immunogenic properties of HFD's in the gut may be partly caused by peroxide derivatives, providing potential insight into how these diets contribute to exacerbations of IBD.

Maternal high fat diet-induced obesity affects trophoblast differentiation and placental function in mice†

Evidence suggests that maternal obesity (MO) can aggravate placental function causing severe pathologies during the perinatal window. However, molecular changes and mechanisms of placental dysfunction remain largely unknown. This work aimed to decipher structural and molecular alterations of the placental transfer zone associated with MO. To this end, mice were fed a high fat diet (HFD) to induce obesity before mating, and pregnant dams were sacrificed at E15.5 to receive placentas for molecular, histological, and ultrastructural analysis and to assess unidirectional materno-fetal transfer capacity. Laser-capture microdissection was used to collect specifically placental cells of the labyrinth zone for proteomics profiling. Using BeWo cells, fatty acid-mediated mechanisms of adherens junction stability, cell layer permeability, and lipid accumulation were deciphered. Proteomics profiling revealed downregulation of cell adhesion markers in the labyrinth zone of obese dams, and disturbed syncytial fusion and detachment of the basement membrane (BM) within this zone was observed, next to an increase in materno-fetal transfer in vivo across the placenta. We found that fetuses of obese dams develop a growth restriction and in those placentas, labyrinth zone volume-fraction was significantly reduced. Linoleic acid was shown to mediate beta-catenin level and increase cell layer permeability in vitro. Thus, MO causes fetal growth restriction, molecular and structural changes in the transfer zone leading to impaired trophoblast differentiation, BM disruption, and placental dysfunction despite increased materno-fetal transfer capacity. These adverse effects are probably mediated by fatty acids found in HFD demonstrating the need for obesity treatment to mitigate placental dysfunction and prevent offspring pathologies.

Nutritional Management of Paediatric Crohn’s Disease

For many people with Crohn’s disease (CD), onset occurs in childhood or adolescence. Treatment for CD has moved from predominantly surgical to, more often, pharmacological. While successful for many, others have tried various medications and combinations without long-term success and, for all, drug treatment needs to be balanced with potential therapy risks. Findings that diet can impact pathogenesis of CD to cause and exacerbate symptoms have inspired studies of dietary interventions. The Crohn’s Disease Exclusion Diet (CDED) was developed following the observation that certain dietary components were linked to inflammation and gut dysbiosis found in those with CD. This three-phase diet included two periods of a highly-controlled and prescribed diet, followed by a maintenance diet in which patients had a wider choice of foods. The diet limited ingestion of foods that may trigger inflammation and/or dysbiosis in CD, such as saturated fats, wheat, carrageenan, and some dairy products, and included healthy choices, such as fruits, vegetables, lean protein sources, and complex carbohydrates. It was nutritionally balanced, science-based, and included foods that were widely accessible. Based on findings from clinical trials and case studies, four experts (Prof Lionetti, Prof Martín-de-Carpi, Mrs Sigall-Boneh, and Prof Wine) discussed the background of CD, current treatment options, the utility of dietary therapies including CDED, and how all healthcare professionals (HCP) looking after children and adolescents with CD should consider the use of diet as part of their therapy.

High-Fat Diet and Antibiotics Cooperatively Impair Mitochondrial Bioenergetics to Trigger Dysbiosis that Exacerbates Pre-inflammatory Bowel Disease

The clinical spectra of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) intersect to form a scantily defined overlap syndrome, termed pre-IBD. We show that increased Enterobacteriaceae and reduced Clostridia abundance distinguish the fecal microbiota of pre-IBD patients from IBS patients. A history of antibiotics in individuals consuming a high-fat diet was associated with the greatest risk for pre-IBD. Exposing mice to these risk factors resulted in conditions resembling pre-IBD and impaired mitochondrial bioenergetics in the colonic epithelium, which triggered dysbiosis. Restoring mitochondrial bioenergetics in the colonic epithelium with 5-amino salicylic acid, a PPAR-γ (peroxisome proliferator-activated receptor gamma) agonist that stimulates mitochondrial activity, ameliorated pre-IBD symptoms. As with patients, mice with pre-IBD exhibited notable expansions of Enterobacteriaceae that exacerbated low-grade mucosal inflammation, suggesting that remediating dysbiosis can alleviate inflammation. Thus, environmental risk factors cooperate to impair epithelial mitochondrial bioenergetics, thereby triggering microbiota disruptions that exacerbate inflammation and distinguish pre-IBD from IBS.

What's new in IBD therapy: An "omics network" approach

The industrial revolution that began in the late 1800s has resulted in dramatic changes in the environment, human lifestyle, dietary habits, social structure, and so on. Almost certainly because this rapid evolution has outpaced the ability of the body to adapt to a number of environmental and behavioral changes, there has been a parallel emergence of several chronic inflammatory diseases, among which are inflammatory bowel diseases (IBD), primarily ulcerative colitis and Crohn's disease. The ability to treat these conditions has progressively improved in the last 50 years, particularly in the last couple of decades with the introduction of biological therapy targeting primarily soluble mediators produced by inflammatory cells. A large number of biologics are now available, but all of them induce similarly unsatisfactory (<50%) rates of clinical response and remission, and most of them lose efficacy over time, requiring dose escalation or switching from one biologic to another. So, treatment of IBD still needs improvement that will occur only if different approaches are taken. A reason why even the most recent forms of IBD therapy are unsatisfactory is because they target only selected components of an exceedingly complex pathophysiological process, a reality that must be honestly considered if better IBD therapies are to be achieved. Brand new approaches must integrate all relevant factors in their totality - the "omes" - and identify the key controllers of biological responses. This can be accomplished by using systems biology-based approaches and advanced bioinformatics tools, which together represent the essence of network medicine. This review looks at the past and the present of IBD pathogenesis and therapy, and discusses how to develop new therapies based on a network medicine approach.

Negative Effects of a High-Fat Diet on Intestinal Permeability: A Review

The intestinal tract is the largest barrier between a person and the environment. In this role, the intestinal tract is responsible not only for absorbing essential dietary nutrients, but also for protecting the host from a variety of ingested toxins and microbes. The intestinal barrier system is composed of a mucus layer, intestinal epithelial cells (IECs), tight junctions (TJs), immune cells, and a gut microbiota, which are all susceptible to external factors such as dietary fats. When components of this barrier system are disrupted, intestinal permeability to luminal contents increases, which is implicated in intestinal pathologies such as inflammatory bowel disease, necrotizing enterocolitis, and celiac disease. Currently, there is mounting evidence that consumption of excess dietary fats can enhance intestinal permeability differentially. For example, dietary fat modulates the expression and distribution of TJs, stimulates a shift to barrier-disrupting hydrophobic bile acids, and even induces IEC oxidative stress and apoptosis. In addition, a high-fat diet (HFD) enhances intestinal permeability directly by stimulating proinflammatory signaling cascades and indirectly via increasing barrier-disrupting cytokines [TNFα, interleukin (IL) 1B, IL6, and interferon γ (IFNγ)] and decreasing barrier-forming cytokines (IL10, IL17, and IL22). Finally, an HFD negatively modulates the intestinal mucus composition and enriches the gut microflora with barrier-disrupting species. Although further research is necessary to understand the precise role HFDs play in intestinal permeability, current data suggest a stronger link between diet and intestinal disease than was first thought to exist. Therefore, this review seeks to highlight the various ways an HFD disrupts the gut barrier system and its many implications in human health.

The dietary peroxidized lipid, 13-HPODE, promotes intestinal inflammation by mediating granzyme B secretion from natural killer cells

The dietary peroxidized lipid, 13-HPODE, stimulates natural killer cell granzyme B production and secretion, with potential implications for intestinal inflammation.

Role of Obesity, Mesenteric Adipose Tissue, and Adipokines in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBDs) are a group of disorders which include ulcerative colitis and Crohn's disease. Obesity is becoming increasingly more common among patients with inflammatory bowel disease and plays a role in the development and course of the disease. This is especially true in the case of Crohn's disease. The recent results indicate a special role of visceral adipose tissue and particularly mesenteric adipose tissue, also known as "creeping fat", in pathomechanism, leading to intestinal inflammation. The involvement of altered adipocyte function and the deregulated production of adipokines, such as leptin and adiponectin, has been suggested in pathogenesis of IBD. In this review, we discuss the epidemiology and pathophysiology of obesity in IBD, the influence of a Western diet on the course of Crohn's disease and colitis in IBD patients and animal's models, and the potential role of adipokines in these disorders. Since altered body composition, decrease of skeletal muscle mass, and development of pathologically changed mesenteric white adipose tissue are well-known features of IBD and especially of Crohn's disease, we discuss the possible crosstalk between adipokines and myokines released from skeletal muscle during exercise with moderate or forced intensity. The emerging role of microbiota and the antioxidative and anti-inflammatory enzymes such as intestinal alkaline phosphatase is also discussed, in order to open new avenues for the therapy against intestinal perturbations associated with IBD.

Food Components and Dietary Habits: Keys for a Healthy Gut Microbiota Composition

The gut microbiota is a changing ecosystem, containing trillions of bacteria, continuously shaped by many factors, such as dietary habits, seasonality, lifestyle, stress, antibiotics use, or diseases. A healthy host-microorganisms balance must be respected in order to optimally maintain the intestinal barrier and immune system functions and, consequently, prevent disease development. In the past several decades, the adoption of modern dietary habits has become a growing health concern, as it is strongly associated with obesity and related metabolic diseases, promoting inflammation and both structural and behavioral changes in gut microbiota. In this context, novel dietary strategies are emerging to prevent diseases and maintain health. However, the consequences of these different diets on gut microbiota modulation are still largely unknown, and could potentially lead to alterations of gut microbiota, intestinal barrier, and the immune system. The present review aimed to focus on the impact of single food components (macronutrients and micronutrients), salt, food additives, and different dietary habits (i.e., vegan and vegetarian, gluten-free, ketogenic, high sugar, low FODMAP, Western-type, and Mediterranean diets) on gut microbiota composition in order to define the optimal diet for a healthy modulation of gut microbiota.

High-fat diet promotes experimental colitis by inducing oxidative stress in the colon

Diets high in animal fats are associated with increased risks of inflammatory bowel disease, but the mechanism remains unclear. In this study, we investigated the effect of high-fat diet (HFD) on the development of experimental colitis in mice. Relative to mice fed low-fat diet (LFD), HFD feeding for 4 wk increased the levels of triglyceride, cholesterol, and free fatty acids in the plasma as well as within the colonic mucosa. In an experimental colitis model induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS), mice on 4-wk HFD exhibited more severe colonic inflammation and developed more severe colitis compared with the LFD counterparts. HFD feeding resulted in higher production of mucosal pro-inflammatory cytokines, greater activation of the myosin light chain kinase (MLCK) tight junction regulatory pathway, and greater increases in mucosal barrier permeability in mice following TNBS induction. HFD feeding also induced gp91, an NADPH oxidase subunit, and promoted reactive oxygen species (ROS) production in both colonic epithelial cells and lamina propria cells. In HCT116 cell culture, palmitic acid or palmitic acid and TNF-α combination markedly increased ROS production and induced the MLCK pathway, and these effects were markedly diminished in the presence of a ROS scavenger. Taken together, these data suggest that HFD promotes colitis by aggravating mucosal oxidative stress, which rapidly drives mucosal inflammation and increases intestinal mucosal barrier permeability.NEW & NOTEWORTHY This study demonstrates high-fat diet feeding promotes colitis in a 2,4,6-trinitrobenzenesulfonic acid-induced experimental colitis model in mice. The underlying mechanism is that high-fat diet induces oxidative stress in the colonic mucosa, which increases colonic epithelial barrier permeability and drives colonic mucosal inflammation. These observations provide molecular evidence that diets high in saturated fats are detrimental to patients with inflammatory bowel diseases.

Importance of nutritional therapy in the management of intestinal diseases: beyond energy and nutrient supply

The gut is an immune-microbiome-epithelial complex. Gut microbiome-host interactions have widespread biological implications, and the role of this complex system extends beyond the digestion of food and nutrient absorption. Dietary nutrients can affect this complex and play a key role in determining gut homeostasis to maintain host health. In this article, we review various dietary nutrients and their contribution to the pathogenesis and treatment of various intestinal diseases including inflammatory bowel disease, irritable bowel syndrome, colorectal cancer, and diverticulitis, among other such disorders. A better understanding of diet-host-gut microbiome interactions is essential to provide beneficial nutrients for gut health and to limit nutritional hazards to ensure successful nutritional management of gastrointestinal conditions in clinical practice.

Docosahexaenoic and Eicosapentaenoic Acids Prevent Altered-Muc2 Secretion Induced by Palmitic Acid by Alleviating Endoplasmic Reticulum Stress in LS174T Goblet Cells

Diets high in saturated fatty acids (FA) represent a risk factor for the development of obesity and associated metabolic disorders, partly through their impact on the epithelial cell barrier integrity. We hypothesized that unsaturated FA could alleviate saturated FA-induced endoplasmic reticulum (ER) stress occurring in intestinal secretory goblet cells, and consequently the reduced synthesis and secretion of mucins that form the protective mucus barrier. To investigate this hypothesis, we treated well-differentiated human colonic LS174T goblet cells with palmitic acid (PAL)—the most commonly used inducer of lipotoxicity in in vitro systems—or n-9, n-6, or n-3 unsaturated fatty acids alone or in co-treatment with PAL, and measured the impact of such treatments on ER stress and Muc2 production. Our results showed that only eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids protect goblet cells against ER stress-mediated altered Muc2 secretion induced by PAL, whereas neither linolenic acid nor n-9 and n-6 FA are able to provide such protection. We conclude that EPA and DHA could represent potential therapeutic nutrients against the detrimental lipotoxicity of saturated fatty acids, associated with type 2 diabetes and obesity or inflammatory bowel disease. These in vitro data remain to be explored in vivo in a context of dietary obesity.

Effects of Fish n-3 PUFAs on Intestinal Microbiota and Immune System

Studies over several decades have documented the beneficial actions of n-3 polyunsaturated fatty acids (PUFAs), which are plentiful in fish oil, in different disease states. Mechanisms responsible for the efficacy of n-3 PUFAs include: (1) Reduction of triglyceride levels; (2) anti-arrhythmic and antithrombotic effects, and (3) resolution of inflammatory processes. The human microbiota project and subsequent studies using next-generation sequencing technology have highlighted that thousands of different microbial species are present in the human gut, and that there has been a significant variability of taxa in the microbiota composition among people. Several factors (gestational age, mode of delivery, diet, sanitation and antibiotic treatment) influence the bacterial community in the human gastrointestinal tract, and among these diet habits play a crucial role. The disturbances in the gut microbiota composition, i.e., gut dysbiosis, have been associated with diseases ranging from localized gastrointestinal disorders to neurologic, respiratory, metabolic, ocular, and cardiovascular illnesses. Many studies have been published about the effects of probiotics and prebiotics on the gut microbiota/microbioma. On the contrary, PUFAs in the gut microbiota have been less well defined. However, experimental studies suggested that gut microbiota, n-3 PUFAs, and host immune cells work together to ensure the intestinal wall integrity. This review discussed current evidence concerning the links among gut microbiota, n-3 PUFAs intake, and human inflammatory disease.

Dietary interventions for induction and maintenance of remission in inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD), comprised of Crohn's disease (CD) and ulcerative colitis (UC), is characterized by chronic mucosal inflammation, frequent hospitalizations, adverse health economics, and compromised quality of life. Diet has been hypothesised to influence IBD activity.

OBJECTIVES

To evaluate the efficacy and safety of dietary interventions on IBD outcomes.

SEARCH METHODS

We searched the Cochrane IBD Group Specialized Register, CENTRAL, MEDLINE, Embase, Web of Science, Clinicaltrials.gov and the WHO ICTRP from inception to 31 January 2019. We also scanned reference lists of included studies, relevant reviews and guidelines.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) that compared the effects of dietary manipulations to other diets in participants with IBD. Studies that exclusively focused on enteral nutrition, oral nutrient supplementation, medical foods, probiotics, and parenteral nutrition were excluded.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, extracted data and assessed bias using the risk of bias tool. We conducted meta-analyses where possible using a random-effects model and calculated the risk ratio (RR) and corresponding 95% confidence interval (CI) for dichotomous outcomes. We assessed the certainty of evidence using GRADE.

MAIN RESULTS

The review included 18 RCTs with 1878 participants. The studies assessed different dietary interventions for active CD (six studies), inactive CD (seven studies), active UC (one study) and inactive UC (four studies). Dietary interventions involved either the consumption of low amounts or complete exclusion of one or more food groups known to trigger IBD symptoms. There was limited scope for data pooling as the interventions and control diets were diverse. The studies were mostly inadequately powered. Fourteen studies were rated as high risk of bias. The other studies were rated as unclear risk of bias.The effect of high fiber, low refined carbohydrates, low microparticle diet, low calcium diet, symptoms-guided diet and highly restricted organic diet on clinical remission in active CD is uncertain. At 4 weeks, remission was induced in: 100% (4/4) of participants in the low refined carbohydrates diet group compared to 0% (0/3) of participants in the control group (RR 7.20, 95% CI 0.53 to 97.83; 7 participants; 1 study; very low certainty evidence). At 16 weeks, 44% (23/52) of participants in the low microparticle diet achieved clinical remission compared to 25% (13/51) of control-group participants (RR 3.13, 95% CI 0.22 to 43.84; 103 participants; 2 studies; I² = 73%; very low certainty evidence). Fifty per cent (16/32) of participants in the symptoms-guided diet group achieved clinical remission compared to 0% (0/19) of control group participants (RR 20.00, 95% CI 1.27 to 315.40; 51 participants ; 1 study; very low certainty evidence) (follow-up unclear). At 24 weeks, 50% (4/8) of participants in the highly restricted organic diet achieved clinical remission compared to 50% (5/10) of participants in the control group (RR 1.00, 95% CI 0.39 to 2.53; 18 participants; 1 study; very low certainty evidence). At 16 weeks, 37% (16/43) participants following a low calcium diet achieved clinical remission compared to 30% (12/40) in the control group (RR 1.24, 95% CI 0.67 to 2.29; 83 participants; 1 study; very low certainty evidence).The effect of low refined carbohydrate diets, symptoms-guided diets and low red processed meat diets on relapse in inactive CD is uncertain. At 12 to 24 months, 67% (176/264) of participants in low refined carbohydrate diet relapsed compared to 64% (193/303) in the control group (RR 1.04, 95% CI 0.87 to 1.25; 567 participants; 3 studies; I² = 35%; low certainty evidence). At 6 to 24 months, 48% (24/50) of participants in the symptoms-guided diet group relapsed compared to 83% (40/48) participants in the control diet (RR 0.53, 95% CI 0.28 to 1.01; 98 participants ; 2 studies; I² = 54%; low certainty evidence). At 48 weeks, 66% (63/96) of participants in the low red and processed meat diet group relapsed compared to 63% (75/118) of the control group (RR 1.03, 95% CI 0.85 to 1.26; 214 participants; 1 study; low certainty evidence). At 12 months, 0% (0/16) of participants on an exclusion diet comprised of low disaccharides / grains / saturated fats / red and processed meat experienced clinical relapse compared to 26% (10/38) of participants on a control group (RR 0.11, 95% CI 0.01 to 1.76; 54 participants; 1 study; very low certainty evidence).The effect of a symptoms-guided diet on clinical remission in active UC is uncertain. At six weeks, 36% (4/11) of symptoms-guided diet participants achieved remission compared to 0% (0/10) of usual diet participants (RR 8.25, 95% CI 0.50 to 136.33; 21 participants; 1 study; very low certainty evidence).The effect of the Alberta-based anti-inflammatory diet, the Carrageenan-free diet or milk-free diet on relapse rates in inactive UC is uncertain. At 6 months, 36% (5/14) of participants in the Alberta-based anti-inflammatory diet group relapsed compared to 29% (4/14) of participants in the control group (RR 1.25, 95% CI 0.42 to 3.70; 28 participants; 1 study; very low certainty evidence). Thirty per cent (3/10) of participants following the carrageenan-free diet for 12 months relapsed compared to 60% (3/5) of the participants in the control group (RR 0.50, 95% CI 0.15 to 1.64; 15 participants; 1 study; very low certainty evidence). At 12 months, 59% (23/39) of milk free diet participants relapsed compared to 68% (26/38) of control diet participants (RR 0.83, 95% CI 0.60 to 1.15; 77 participants; 2 studies; I² = 0%; low certainty evidence).None of the included studies reported on diet-related adverse events.

AUTHORS' CONCLUSIONS

The effects of dietary interventions on CD and UC are uncertain. Thus no firm conclusions regarding the benefits and harms of dietary interventions in CD and UC can be drawn. There is need for consensus on the composition of dietary interventions in IBD and more RCTs are required to evaluate these interventions. Currently, there are at least five ongoing studies (estimated enrollment of 498 participants). This review will be updated when the results of these studies are available.

The role of dietary factors in inflammatory bowel diseases: New perspectives

The current review aimed to elucidate the role of diet in every stage of inflammatory bowel diseases, from aspects of prevention, treatment and rehabilitation. Western diet, characterized by overconsumption of refined sugar and saturated fat and low consumption of dietary fiber, may partly be blamed for its pathogenesis. Some immune-modulated nutrients (fibers, monounsaturated fatty acids, n-3 polyunsaturated fatty acids and vitamin D) exert their potential beneficial effects on gut microbiota and immune function, resulting in clinical remission and/or preventing relapse. However, data is limited to conclude optimal micronutrient levels and therapeutic implications. Further, diet itself is complex; therefore, it is reasonable to evaluate diet as a whole rather than a single type of food. Some specific dietary patterns are generated for the management of inflammatory bowel diseases with controversial results. Only exclusive enteral nutrition has been widely recommended for pediatric patients with non-stricturing active Crohn's disease. Self-monitoring, avoidance of certain types of foods, limited intake of alcohol and smoking, supplementation of minerals and vitamins if deficiency is confirmed, and adherence to the diet enriched in vegetables and fruits and low in animal food and un-digested fiber during flares are the most common dietary recommendation. Further clinical trials with a high evidence rank are warranted.

Inflammatory Links Between High Fat Diets and Diseases

In recent years, chronic overnutrition, such as consumption of a high-fat diet (HFD), has been increasingly viewed as a significant modifiable risk factor for diseases such as diabetes and certain types of cancer. However, the mechanisms by which HFDs exert adverse effects on human health remains poorly understood. Here, this paper will review the recent scientific literature about HFD-induced inflammation and subsequent development of diseases and cancer, with an emphasis on mechanisms involved. Given the expanding global epidemic of excessive HFD intake, understanding the impacts of a HFD on these medical conditions, gaining great insights into possible underlying mechanisms, and developing effective therapeutic strategies are of great importance.

Evolving role of diet in the pathogenesis and treatment of inflammatory bowel diseases

Recent advances in basic and clinical science over the last 3 years have dramatically altered our appreciation of the role of diet in inflammatory bowel diseases (IBD). The marked increase in incidence of these diseases along with the important role of non-genetic susceptibility among patients with IBD has highlighted that these diseases have a strong environmental component. Progress in the field of microbiome and IBD has demonstrated that microbiome appears to play an important role in pathogenesis, and that diet may in turn impact the composition and functionality of the microbiome. Uncontrolled clinical studies have demonstrated that various dietary therapies such as exclusive enteral nutrition and newly developed exclusion diets might be potent tools for induction of remission at disease onset, for patients failing biologic therapy, as a treatment for disease complications and in reducing the need for surgery. We review these advances from bench to bedside, along with the need for better clinical trials to support these interventions.