High-fat diet modulates non-CD1d-restricted natural killer T cells and regulatory T cells in mouse colon and exacerbates experimental colitis

Curcumin Attenuates Dextran Sodium Sulfate Induced Colitis in Obese Mice

SCOPE

Curcumin (Cur), with diverse pharmacological properties, shows anti-obesity, immunomodulatory, and anti-inflammatory effects. Its role in ulcerative colitis complicated by obesity remains unclear.

METHODS AND RESULTS

Here, colitis is induced in obese mice using dextran sulfate sodium (DSS), followed by administration of Cur at a dosage of 100 mg kg-1 for 14 days. Cur effectively alleviates DSS-induced colitis in obese mice, accompanied by an increase in body weight and survival rate, reduction in disease activity index, elongation of the colon, decrease in colonic weight, and improvements in ulcer formation and inflammatory cell infiltration in colonic tissues. Additionally, Cur effectively improves lipid metabolism and the composition of the gut microbiota, and enhances mucosal integrity and boosts anti-oxidative stress capacity in obese mice with colitis. Importantly, Cur is effective in improving the homeostasis of memory T cells in obese mice with colitis. Furthermore, Cur regulates inflammatory cytokines expression and inhibits activation of the JAK2/STAT signaling pathway in colonic tissues of obese mice with colitis.

CONCLUSIONS

Cur alleviates colitis in obese mice through a comprehensive mechanism that improves lipid metabolism, modulates gut microbiota composition, enhances mucosal integrity and anti-oxidative stress, balances memory T cell populations, regulates inflammatory cytokines, and suppresses the JAK2/STAT signaling pathway.

Experimental colonization with H. hepaticus, S. aureus and R. pneumotropicus does not influence the metabolic response to high-fat diet or incretin-analogues in wildtype SOPF mice

OBJECTIVES

We here assessed whether typical pathogens of laboratory mice affect the development of diet-induced obesity and glucose intolerance, and whether colonization affects the efficacy of the GLP-1R agonist liraglutide and of the GLP-1/GIP co-agonist MAR709 to treat obesity and diabetes.

METHODS

Male C57BL/6J mice were experimentally infected with Helicobacter hepaticus, Rodentibacter pneumotropicus and Staphylococcus aureus and compared to a group of uninfected specific and opportunistic pathogen free (SOPF) mice. The development of diet-induced obesity and glucose intolerance was monitored over a period of 26 weeks. To study the influence of pathogens on drug treatment, mice were then subjected for 6 days daily treatment with either the GLP-1 receptor agonist liraglutide or the GLP-1/GIP co-agonist MAR709.

RESULTS

Colonized mice did not differ from SOPF controls regarding HFD-induced body weight gain, food intake, body composition, glycemic control, or responsiveness to treatment with liraglutide or the GLP-1/GIP co-agonist MAR709.

CONCLUSIONS

We conclude that the occurrence of H. hepaticus, R. pneumotropicus and S. aureus does neither affect the development of diet-induced obesity or type 2 diabetes, nor the efficacy of GLP-1-based drugs to decrease body weight and to improve glucose control in mice.

Role of CD1d and iNKT cells in regulating intestinal inflammation

Invariant natural killer T (iNKT) cells, a subset of unconventional T cells that recognize glycolipid antigens in a CD1d-dependent manner, are crucial in regulating diverse immune responses such as autoimmunity. By engaging with CD1d-expressing non-immune cells (such as intestinal epithelial cells and enterochromaffin cells) and immune cells (such as type 3 innate lymphoid cells, B cells, monocytes and macrophages), iNKT cells contribute to the maintenance of immune homeostasis in the intestine. In this review, we discuss the impact of iNKT cells and CD1d in the regulation of intestinal inflammation, examining both cellular and molecular factors with the potential to influence the functions of iNKT cells in inflammatory bowel diseases such as Crohn's disease and ulcerative colitis.

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.

Acute high-fat diet impairs macrophage-supported intestinal damage resolution

Chronic exposure to high-fat diets (HFD) worsens intestinal disease pathology, but acute effects of HFD in tissue damage remain unclear. Here, we used short-term HFD feeding in a model of intestinal injury and found sustained damage with increased cecal dead neutrophil accumulation, along with dietary lipid accumulation. Neutrophil depletion rescued enhanced pathology. Macrophages from HFD-treated mice showed reduced capacity to engulf dead neutrophils. Macrophage clearance of dead neutrophils activates critical barrier repair and antiinflammatory pathways, including IL-10, which was lost after acute HFD feeding and intestinal injury. IL-10 overexpression restored intestinal repair after HFD feeding and intestinal injury. Macrophage exposure to lipids from the HFD prevented tethering and uptake of apoptotic cells and Il10 induction. Milk fat globule-EGF factor 8 (MFGE8) is a bridging molecule that facilitates macrophage uptake of dead cells. MFGE8 also facilitates lipid uptake, and we demonstrate that dietary lipids interfere with MFGE8-mediated macrophage apoptotic neutrophil uptake and subsequent Il10 production. Our findings demonstrate that HFD promotes intestinal pathology by interfering with macrophage clearance of dead neutrophils, leading to unresolved tissue damage.

High-fat diet promotes the effect of fructo-oligosaccharides on the colonic luminal environment, including alkaline phosphatase activity in rats

We recently reported that fermentable nondigestible carbohydrates such as oligosaccharides, commonly increase colonic alkaline phosphatase (ALP) activity and the gene expression of Alpi-1, coding for rat intestinal alkaline phosphatase-I isozyme in rats and that the effect of oligosaccharides on colonic ALP activity is affected by the quality of dietary fats. We hypothesized that the amount of dietary fat would modulate the effect of oligosaccharides on colonic ALP and luminal environment in rats. In experiment 1, male Sprague-Dawley rats were fed a low-fat (LF, 5% lard) or high-fat (HF, 30% lard) diet with or without 4% fructo-oligosaccharides (FOS). In experiment 2, they were fed a 2.5%, 7%, 20%, or 40% fat (lard) diet with 4% FOS for 2 weeks. Dietary FOS in the HF diet (HF-FOS) significantly increased ALP activity in the colon and cecal digesta and colonic expression of Alpi-1, but not in the LF diet with FOS groups (LF-FOS). In comparison to the LF-FOS group, the increases in fecal mucins, Lactobacillus ratio, as well as cecal n-butyrate, and the decrease in fecal Clostridium coccoides, were more pronounced in the HF-FOS group. Compared with the 2.5% or 7% fat + FOS diet, the 20% fat + FOS diet significantly increased colonic ALP activity, Alpi-1 expression, and fecal mucins. These factors did not differ significantly between 20% and 40% fat + FOS diets. To exert the maximum effect of FOS on the colonic luminal environment, including ALP activity in rats, significantly more fat may be required than that contained present a LF diet.

New insights into the mechanisms of high-fat diet mediated gut microbiota in chronic diseases

High-fat diet (HFD) has been recognized as a primary factor in the risk of chronic disease. Obesity, diabetes, gastrointestinal diseases, neurodegenerative diseases, and cardiovascular diseases have long been known as chronic diseases with high worldwide incidence. In this review, the influences of gut microbiota and their corresponding bacterial metabolites on the mechanisms of HFD-induced chronic diseases are systematically summarized. Gut microbiota imbalance is also known to increase susceptibility to diseases. Several studies have proven that HFD has a negative impact on gut microbiota, also exacerbating the course of many chronic diseases through increased populations of Erysipelotrichaceae, facultative anaerobic bacteria, and opportunistic pathogens. Since bile acids, lipopolysaccharide, short-chain fatty acids, and trimethylamine N-oxide have long been known as common features of bacterial metabolites, we will explore the possibility of synergistic mechanisms among those metabolites and gut microbiota in the context of HFD-induced chronic diseases. Recent literature concerning the mechanistic actions of HFD-mediated gut microbiota have been collected from PubMed, Google Scholar, and Scopus. The aim of this review is to provide new insights into those mechanisms and to point out the potential biomarkers of HFD-mediated gut microbiota.

Dietary Considerations for Inflammatory Bowel Disease Are Useful for Treatment of Checkpoint Inhibitor-Induced Colitis

Checkpoint molecules are cell surface receptors on immune cells that mitigate excessive immune responses, but they have increased expression levels in cancer to facilitate immune escape. Checkpoint blockade therapies (e.g., anti-PD-1, anti-CTLA-4, and anti-LAG-3 therapy, among others) have been developed for multiple cancers. Colitis associated with checkpoint blockade therapy has pathophysiological similarities to inflammatory bowel disease (IBD), such as Crohn's disease and ulcerative colitis. Current therapeutic guidelines for checkpoint blockade-induced colitis include corticosteroids and, if the patient is refractory to steroids, immunomodulating antibodies, such as anti-TNF and anti-integrin agents. Interestingly, immunomodulatory molecules, such as TNFα, are upregulated in both IBD and checkpoint-mediated colitis. The inflammatory colitis toxicity symptoms from checkpoint blockade are similar to clinical symptoms experienced by patients with IBD. The pathophysiologic, dietary, and genetic factors associated with IBD will be reviewed. We will then explain how the principles developed for the treatment of IBD can be applied to patients experiencing inflammatory bowel toxicity secondary to checkpoint blockade.

Defects in the expression of colonic host defense factors associate with barrier dysfunction induced by a high-fat/high-cholesterol diet

The effect of Western diets in the gastrointestinal system is largely mediated by their ability to promote alterations in the immunity and physiology of the intestinal epithelium, and to affect the composition of the commensal microbiota. To investigate the response of the colonic epithelium to high-fat/high-cholesterol diets (HFHCDs), we evaluated the synthesis of host defense factors involved in the maintenance of the colonic homeostasis. C57BL/6 mice were fed an HFHCD for 3 weeks and their colons were evaluated for histopathology, gene expression, and microbiota composition. In addition, intestinal permeability and susceptibility to Citrobacter rodentium were also studied. HFHCD caused colonic hyperplasia, loss of goblet cells, thinning of the mucus layer, moderate changes in the composition of the intestinal microbiota, and an increase in intestinal permeability. Gene expression analyses revealed significant drops in the transcript levels of Muc1, Muc2, Agr2, Atoh1, Spdef, Ang4, Camp, Tff3, Dmbt1, Fcgbp, Saa3, and Retnlb. The goblet cell granules of HFHCD-fed mice were devoid of Relmβ and Tff3, indicating defective production of those two factors critical for intestinal epithelial defense and homeostasis. In correspondence with these defects, colonic bacteria were in close contact with, and invading the epithelium. Fecal shedding of C. rodentium showed an increased bacterial burden in HFHCD-fed animals accompanied by increased epithelial damage. Collectively, our results show that HFHCD perturbs the synthesis of colonic host defense factors, which associate with alterations in the commensal microbiota, the integrity of the intestinal barrier, and the host's susceptibility to enteric infections.

Sugars and Gastrointestinal Health

Sugar overconsumption is linked to a rise in the incidence of noncommunicable diseases such as diabetes, cardiovascular diseases, and cancer. This increased incidence is becoming a real public health problem that is more severe than infectious diseases, contributing to 35 million deaths annually. Excessive intake of free sugars can cause many of the same health problems as excessive alcohol consumption. Many recent international recommendations have expressed concerns about sugar consumption in Westernized societies, as current consumption levels represent quantities with no precedent during hominin evolution. In both adults and children, the World Health Organization strongly recommends reducing free sugar intake to <10% of total energy intake and suggests a further reduction to below 5%. Most studies have focused on the deleterious effects of Western dietary patterns on global health and the intestine. Whereas excessive dietary fat consumption is well studied, the specific impact of sugar is poorly described, while refined sugars represent up to 40% of caloric intake within industrialized countries. However, high sugar intake is associated with multiple tissue and organ dysfunctions. Both hyperglycemia and excessive sugar intake disrupt the intestinal barrier, thus increasing gut permeability and causing profound gut microbiota dysbiosis, which results in a disturbance in mucosal immunity that enhances infection susceptibility. This review aims to highlight the roles of different types of dietary carbohydrates and the consequences of their excessive intake for intestinal homeostasis.

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.

Nutraceuticals for the Treatment of IBD: Current Progress and Future Directions

Inflammatory bowel disease (IBD) is a chronic relapsing-remitting inflammatory disease of the gastrointestinal tract. Patients are usually diagnosed in adolescence and early adulthood and need lifelong treatment. In recent years, it has been found that diet plays an important role in the pathogenesis of IBD. Diet can change intestinal barrier function, affect the structure and function of intestinal flora, and promote immune disorder, thus promoting inflammation. Many patients believe that diet plays a role in the onset and treatment of the disease and changes their diet spontaneously. This review provides some insights into how nutraceuticals regulate intestinal immune homeostasis and improve intestinal barrier function. We reviewed the research results of dietary fiber, polyphenols, bioactive peptides, and other nutraceuticals in the prevention and treatment of IBD and sought better alternative or supplementary treatment methods for IBD patients.

Dietary Patterns and Gut Microbiota: The Crucial Actors in Inflammatory Bowel Disease

It is widely believed that diet and the gut microbiota are strongly related to the occurrence and progression of inflammatory bowel disease (IBD), but the effects of the interaction between dietary patterns and the gut microbiota on IBD have not been well elucidated. In this article, we aim to explore the complex relation between dietary patterns, gut microbiota, and IBD. We first comprehensively summarized the dietary patterns associated with IBD and found that dietary patterns can modulate the occurrence and progression of IBD through various signaling pathways, including mammalian target of rapamycin (mTOR), mitogen-activated protein kinases (MAPKs), signal transducer and activator of transcription 3 (STAT3), and NF-κB. Besides, the gut microbiota performs a vital role in the progression of IBD, which can affect the expression of IBD susceptibility genes, such as dual oxidase 2 (DUOX2) and APOA-1 , the intestinal barrier (in particular, the expression of tight junction proteins), immune function (especially the homeostasis between effector and regulatory T cells) and the physiological metabolism, in particular, SCFAs, bile acids (BAs), and tryptophan metabolism. Finally, we reviewed the current knowledge on the interaction between dietary patterns and the gut microbiota in IBD and found that dietary patterns modulate the onset and progression of IBD, which is partly attributed to the regulation of the gut microbiota (especially SCFAs-producing bacteria and Escherichia coli). Faecalibacteria as "microbiomarkers" of IBD could be used as a target for dietary interventions to alleviate IBD. A comprehensive understanding of the interplay between dietary intake, gut microbiota, and IBD will facilitate the development of personalized dietary strategies based on the regulation of the gut microbiota in IBD and expedite the era of precision nutritional interventions for IBD.

Immunity and Nutrition: The Right Balance in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an increasingly urgent medical problem that strongly impairs quality of life for patients. A global rise in incidence has been observed over the last few decades, with the highest incidence rates recorded in North America and Europe. Still, an increased incidence has been reported in the last ten years in newly industrialized countries in Asia, including China and India, both with more than one billion inhabitants. These data underline that IBD is an urgent global health problem. In addition, it is estimated that between 20% and 30% of IBD patients will develop colorectal cancer (CRC) within their lifetime and CRC mortality is approximately 50% amongst IBD patients. Although the exact etiology of IBD is still being defined, it is thought to be due to a complex interaction between many factors, including defects in the innate and adaptive immune system; microbial dysbiosis, i.e., abnormal levels of, or abnormal response to, the gastrointestinal microbiome; a genetic predisposition; and several environmental factors. At present, however, it is not fully understood which of these factors are the initiators of inflammation and which are compounders. The purpose of this review is to analyze the complex balance that exists between these elements to maintain intestinal homeostasis and prevent IBD or limit adverse effects on people’s health.

Diet and microbiome in the beginning of the sequence of gut inflammation

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the gastrointestinal tract due, at least partially, to an aberrant and excessive mucosal immune response to gut bacteria in genetically-predisposed individuals under certain environmental factors. The incidence of IBD is rising in western and newly industrialized countries, paralleling the increase of westernized dietary patterns, through new antigens, epithelial function and permeability, epigenetic mechanisms (e.g., DNA methylation), and alteration of the gut microbiome. Alteration in the composition and functionality of the gut microbiome (including bacteria, viruses and fungi) seems to be a nuclear pathogenic factor. The microbiome itself is dynamic, and the changes in food quality, dietary habits, living conditions and hygiene of these western societies, could interact in a complex manner as modulators of dysbiosis, thereby influencing the activation of immune cells' promoting inflammation. The microbiome produces diverse small molecules via several metabolic ways, with the fiber-derived short-chain fatty acids (i.e., butyrate) as main elements and having anti-inflammatory effects. These metabolites and some micronutrients of the diet (i.e., vitamins, folic acid, beta carotene and trace elements) are regulators of innate and adaptive intestinal immune homeostasis. An excessive and unhealthy consumption of sugar, animal fat and a low-vegetable and -fiber diet are risk factors for IBD appearance. Furthermore, metabolism of nutrients in intestinal epithelium and in gut microbiota is altered by inflammation, changing the demand for nutrients needed for homeostasis. This role of food and a reduced gut microbial diversity in causing IBD might also have a prophylactic or therapeutic role for IBD. The relationship between dietary intake, symptoms, and bowel inflammation could lead to dietary and lifestyle recommendations, including diets with abundant fruits, vegetables, olive oil and oily fish, which have anti-inflammatory effects and could prevent dysbiosis and IBD. Dietary modulation and appropriate exclusion diets might be a new complementary management for treatment at disease flares and in refractory patients, even reducing complications, hospitalizations and surgery, through modifying the luminal intestinal environment.

A High-Fat Western Diet Attenuates Intestinal Changes in Mice with DSS-Induced Low-Grade Inflammation

BACKGROUND

A Western diet (WD) is associated with increased inflammation in the large intestine, which is often ascribed to the high dietary fat content. Intestinal inflammation in rodents can be induced by oral administration of dextran sodium sulfate (DSS). However, most studies investigating effects of WD and DSS have not used appropriate low-fat diets (LFDs) as control.

OBJECTIVES

To compare the effects of a WD with those of an LFD on colon health in a DSS-induced low-grade colonic inflammation mouse model.

METHODS

Six-week-old male C57BL/6JRj mice were fed an LFD (fat = 10.3% energy, n = 24) or a WD (fat = 41.2% energy, n = 24) for 15 wk [Experiment 1 (Exp.1)]. Half the mice on each diet (n = 12) then received 1% DSS in water for 6 d with the remainder (n = 12 in each diet) administered water. Disease activity, proinflammatory genes, inflammatory biomarkers, and fecal microbiota (16S rRNA) were assessed (Exp.1). Follow-up experiments (Exp.2 and Exp.3) were performed to investigate whether fat source (milk or lard; Exp.2) affected outcomes and whether a shift from LFD to WD 1 d prior to 1% DSS exposure caused an immediate effect on DSS-induced inflammation (Exp.3).

RESULTS

In Exp.1, 1% DSS treatment significantly increased disease score in the LFD group compared with the WD group (2.7 compared with 0.8; P < 0.001). Higher concentrations of fecal lipocalin (11-fold; P < 0.001), proinflammatory gene expression (≤82-fold), and Proteobacteria were observed in LFD-fed mice compared with the WD group. The 2 fat sources in WDs (Exp.2) revealed the same low inflammation in WD+DSS mice compared with LFD+DSS mice. Finally, the switch from LFD to WD just before DSS exposure resulted in reduced colonic inflammation (Exp.3).

CONCLUSIONS

Herein, WDs (with milk or lard) protected mice against DSS-induced colonic inflammation compared with LFD-fed mice. Whether fat intake induces protective mechanisms against DSS-mediated inflammation or inhibits establishment of the DSS-induced colitis model is unclear.

Diet in Intestinal Fibrosis: A Double-Edged Sword

The natural history of inflammatory bowel diseases, especially Crohn’s disease, is frequently complicated by intestinal fibrosis. Because of the lack of effective treatments for intestinal fibrosis, there is an urgent need to develop new therapies. Factors promoting intestinal fibrosis are currently unclear, but diet is a potential culprit. Diet may influence predisposition to develop intestinal fibrosis or alter its natural history by modification of both the host immune response and intestinal microbial composition. Few studies have documented the effects of dietary factors in modulating IBD-induced intestinal fibrosis. As the mechanisms behind fibrogenesis in the gut are believed to be broadly similar to those from extra-intestinal organs, it may be relevant to investigate which dietary components can inhibit or promote fibrosis factors such as myofibroblasts progenitor activation in other fibrotic diseases.

Low dietary fiber promotes enteric expansion of a Crohn's disease-associated pathobiont independent of obesity

Obesity is associated with metabolic, immunological, and infectious disease comorbidities, including an increased risk of enteric infection and inflammatory bowel disease such as Crohn's disease (CD). Expansion of intestinal pathobionts such as adherent-invasive Escherichia coli (AIEC) is a common dysbiotic feature of CD, which is amplified by prior use of oral antibiotics. Although high-fat, high-sugar diets are associated with dysbiotic expansion of E. coli, it is unknown if the content of fat or another dietary component in obesogenic diets is sufficient to promote AIEC expansion. Here, we found that administration of an antibiotic combined with feeding mice an obesogenic low-fiber, high-sucrose, high-fat diet (HFD) that is typically used in rodent-obesity studies promoted AIEC intestinal expansion. Even a short-term (i.e., 1 day) pulse of HFD feeding before infection was sufficient to promote AIEC expansion, indicating that the magnitude of obesity was not the main driver of AIEC expansion. Controlled-diet experiments demonstrated that neither dietary fat nor sugar were the key determinants of AIEC colonization, but that lowering dietary fiber from approximately 13% to 5%-6% was sufficient to promote the intestinal expansion of AIEC when combined with antibiotics in mice. When combined with antibiotics, lowering fiber promoted AIEC intestinal expansion to a similar extent as widely used HFDs in mice. However, lowering dietary fiber was sufficient to promote AIEC intestinal expansion without affecting body mass. Our results show that low dietary fiber combined with oral antibiotics are environmental factors that promote the expansion of Crohn's disease-associated pathobionts in the gut.NEW & NOTEWORTHY It is commonly thought that obesity or a high-fat diet alters pathogenic bacteria and promotes inflammatory gut diseases. We found that lower dietary fiber is a key factor that expands a gut pathobiont linked to Crohn's disease, independent of obesity status in mice.

Kaempferol reduces obesity, prevents intestinal inflammation, and modulates gut microbiota in high-fat diet mice

Kaempferol, a flavonoid identified in a wide variety of dietary sources, has been reported to possess anti-obesity properties; however, its underlying mechanism was poorly understood. Chronic, low-grade gut inflammation and dysbacteria are proposed as underlying factors as well as novel treatment approaches for obesity-associated pathologies. This present study aims to investigate the benefits of experimental treatment with kaempferol on intestinal inflammation and gut microbial balance in animal model of obesity. High fat diet (HFD) was applied to C57BL/6J mice for 16 weeks, during which the supplement of kaempferol served as a variable. Clearly, HFD induced obesity, fat accumulation, glucose intolerance and adipose inflammation, the metabolic syndrome of which was the main finding. All these metabolic disorders can be alleviated through kaempferol supplementation. In addition, increased intestinal permeability, infiltration of immunocytes (macrophage, dendritic cells and neutrophils) and overexpression of inflammatory cytokines (tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, monocyte chemoattractant protein-1) were also found in the HFD-induced mice. Kaempferol supplementation improved intestinal barrier integrity and inhibited gut inflammation, by reducing the activation of TLR4/NF-κB pathway. Furthermore, the characterization of the cecal microbiota by sequencing showed that kaempferol supplementation was able to counteract the dysbiosis associated to obesity. Our study delineated the multiple mechanism of action underlying the anti-obesity effect of kaempferol, and provide scientific evidence to support the development of kaempferol as a dietary supplement for obesity treatment.

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.

Diet-Microbiota Interactions in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract. Although the precise etiology of IBD is largely unknown, it is widely thought that diet contributes to the development of IBD. Diet shapes the composition of the gut microbiota, which plays critical roles in intestinal homeostasis. In contrast, intestinal inflammation induces gut dysbiosis and may affect the use of dietary nutrients by host cells and the gut microbiota. The interaction of diet and the gut microbiota is perturbed in patients with IBD. Herein, we review the current knowledge of diet and gut microbiota interaction in intestinal homeostasis. We also discuss alterations of diet and gut microbiota interaction that influence the outcome and the nutritional treatment of IBD. Understanding the complex relationships between diet and the gut microbiota provides crucial insight into the pathogenesis of IBD and advances the development of new therapeutic approaches.

Blockage of protease-activated receptor 2 exacerbates inflammation in high-fat environment partly through autophagy inhibition

Protease-activated receptor 2 (PAR2) regulates inflammatory responses and lipid metabolism. However, its precise role in colitis remains unclear. In this study, we aimed to investigate the function of PAR2 in high-fat diet-fed mice with colitis and its potential role in autophagy. PAR2^+/+ and PAR2^-/- mice were fed a high-fat diet (HFD) for 7 days before colitis induction with dextran sodium sulfate. Deletion of PAR2 and an HFD significantly exacerbated colitis, as shown by increased mortality, body weight loss, diarrhea or bloody stools, colon length shortening, and mucosal damage. Proinflammatory cytokine levels were elevated in HFD-fed PAR2^-/- mice and in cells treated with the PAR2 antagonist GB83, palmitic acid (PA), and a cytokine cocktail (CC). Damaging effects of PAR2 blockage were associated with autophagy regulation by reducing the levels of YAP1, SIRT1, PGC-1α, Atg5, and LC3A/B-I/II. In addition, mitochondrial dysfunction was demonstrated only in cells treated with GB83, PA, and CC. Reduced cell viability and greater induction of apoptosis, as shown by increased levels of cleaved caspase-9, cleaved caspase-3, and cleaved poly(ADP-ribose) polymerase (PARP), were observed in cells treated with GB83, PA, and CC but not in those treated with only PA and CC. Collectively, protective effects of PAR2 were elucidated during inflammation accompanied by a high-fat environment by promoting autophagy and inhibiting apoptosis, suggesting PAR2 as a therapeutic target for inflammatory bowel disease co-occurring with metabolic syndrome.NEW & NOTEWORTHY Deletion of PAR2 with high-fat diet feeding exacerbates colitis in a murine colitis model. Proinflammatory effects of PAR2 blockage in a high-fat environment were associated with an altered balance between autophagy and apoptosis. Increased colonic levels of PAR2 represent as a therapeutic strategy for IBD co-occurring with metabolic syndrome.

Nutrition Regulates Innate Immunity in Health and Disease

Nutrient content and nutrient timing are considered key regulators of human health and a variety of diseases and involve complex interactions with the mucosal immune system. In particular, the innate immune system is emerging as an important signaling hub that modulates the response to nutritional signals, in part via signaling through the gut microbiota. In this review we elucidate emerging evidence that interactions between innate immunity and diet affect human metabolic health and disease, including cardiometabolic disorders, allergic diseases, autoimmune disorders, infections, and cancers. Furthermore, we discuss the potential modulatory effects of the gut microbiota on interactions between the immune system and nutrition in health and disease, namely how it relays nutritional signals to the innate immune system under specific physiological contexts. Finally, we identify key open questions and challenges to comprehensively understanding the intersection between nutrition and innate immunity and how potential nutritional, immune, and microbial therapeutics may be developed into promising future avenues of precision treatment.

High-fat diet-derived free fatty acids impair the intestinal immune system and increase sensitivity to intestinal epithelial damage

In Japan and other Asian countries, increased fat uptake induced by a westernized diet is thought to be associated with an increased incidence of inflammatory bowel disease, colorectal cancer and food allergies; however, the mechanism for this remains unclear. High-fat diet (HFD)-fed mice are common animal models used to examine the effect of fat intake in vivo. HFDs are reported to exacerbate DSS-induced colitis and intestinal tumorigenesis, but the effect of HFDs on the intestines before disease induction is often overlooked. We found that the intestinal and gut-associated lymphoid tissue (GALT) morphology of HFD-fed mice differed from that of standard diet (SD)-fed mice. To clarify the mechanism by which fat intake increases intestinal diseases, we analyzed the morphological and immunological aspects of the intestines of HFD-fed mice as well as the molecular mechanisms and physiology. Feeding an HFD for 3 weeks induced atrophy of the small intestine, colon and GALT and reduced the number of small intestinal intraepithelial lymphocytes (IELs) and lamina propria lymphocytes (LPLs). Feeding an HFD for only one day reduced the number of small intestinal (SI)-IELs and SI-LPLs. The effect of feeding a 3-week HFD continued for 2 weeks after returning to the SD. The effect of the HFD on the intestinal immune system was independent of the gut microbes. We hypothesized that the cytotoxicity of the abundant HFD-derived free fatty acids in the intestinal lumen impairs the intestinal immune system. Both saturated and unsaturated free fatty acids were toxic to intestinal T-cells in vitro. Orally administering free fatty acids reduced the number of SI-IELs and LPLs. Using a lipase inhibitor to reduce the luminal free fatty acids attenuated the HFD-induced changes in the intestinal immune system, while using a statin to reduce the serum free fatty acids did not. Thus, HFD-induced free fatty acids damaged the intestines; this effect was termed "intestinal lipotoxicity". Because sustained reduction of SI-LPLs after HFD feeding exacerbated indomethacin-induced small intestinal damage, lipotoxicity to the human intestines incurred by consuming a westernized diet in Japan may increase intestinal diseases such as IBD, colorectal cancer or food allergies.

Phytic acid actions on hepatic lipids and gut microbiota in rats fed a diet high in sucrose is influenced by dietary fat level

Phytic acid (PA) or myoinositol intake was recently reported by our group to suppress hepatic lipogenic gene expression and modulate gut microbiota in rats fed a high-sucrose diet (HSC). The aim of this study was to investigate the effect of PA and dietary fat level on fatty liver and gut microbiota in rats fed an HSC diet. Male Sprague-Dawley rats were fed a high-fat (HF), HSC diet or a low-fat (LF), HSC diet with or without 1.02% sodium PA for 12 days. Hepatic lipid levels, hepatic enzyme activity, and expression of the enzymes and transcriptional factors related to lipid metabolism, cecal organic acids, and fecal microbiota were evaluated. PA intake depressed hepatic total lipid and triglyceride levels; reduced hepatic activity and expression of lipogenic enzymes; elevated fecal proportion of Lactobacillus spp; and increased cecal succinate level in rats fed the LF diet. The HF diet, when compared with the LF diet, depressed hepatic total lipid and triglyceride levels; reduced hepatic activity and expression of lipogenic enzymes; increased hepatic expression of carnitine palmitoyl-transferase 1a and cAMP-responsive element binding protein 3-like 3; and elevated fecal proportions of Lactobacillus spp and Bifidobacterium spp. In the HF diet groups, PA intake did not affect the factors associated with hepatic lipid metabolism and gut microbiota. In conclusion, dietary fat level could change the effect of PA on hepatic lipid metabolism and gut microbiota and, in turn, could alter the degree of nutritional importance of PA in rats fed an HSC diet.

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.

Nutritional interventions for the treatment of IBD: current evidence and controversies

Environmental factors, particularly diet, are the focus of current research as potential triggers of inflammatory bowel disease (IBD). Epidemiological cohort data showing a rapid increase of IBD in western countries and the emergence of IBD in developing countries paralleling the introduction of a western diet are indirect arguments linking food and food behaviour to intestinal inflammation. The successful use of exclusive enteral nutrition (EEN), now considered as first-line induction therapy for paediatric Crohn's disease (CD), is the strongest argument for a link between diet and IBD. Mechanistic studies revealed that EEN impacts intestinal microbiota composition and together with the exclusion of potentially harmful food ingredients this allows the control of intestinal inflammation and induces mucosal healing. However, the exclusivity character of EEN is a major drawback. Based on the data of EEN, the search for more tolerable and still effective diets has begun. Recent reports on the new CD exclusion diet (CDED), CD-TREAT, as well as the specific carbohydrate diet (SCD) provide the first promising results, further underlining the potential of diet to control inflammation in patients with CD by excluding certain food components. Ongoing research is trying to combine nutritional interventions with analyses of intestinal microbiota and their metabolic functions with the aim of correcting the intestinal dysbiosis that characterizes IBD. This research is promising and gives new hope to patients that have been looking for decades for nutritional interventions with the aim of stabilizing their disease course. There might even be potential for disease prevention in high-risk patients by excluding potentially harmful food components.

Dietary Composition and Effects in Inflammatory Bowel Disease

Dramatic changes in the environment and human lifestyle have been associated with the rise of various chronic complex diseases, such as inflammatory bowel disease (IBD). A dysbiotic gut microbiota has been proposed as a crucial pathogenic element, contributing to immune imbalances and fostering a proinflammatory milieu, which may be associated with disease relapses or even the initiation of IBD. In addition to representing important regulators of the mucosal immunity and the composition of the gut microbiota, food components have been shown to be potential environmental triggers of epigenetic modifications. In the context of chronic intestinal inflammation, dietary habits and specific food components have been implicated as important modulators of epigenetic mechanisms, including DNA methylation, which may predispose a person to the increased risk of the initiation and evolution of IBD. This review provides novel insights about how dietary factors may interact with the intestinal mucosa and modulate immune homeostasis by shaping the intestinal ecosystem, as well as the potential influence of diet in the etiopathogenesis and management of IBD.

Bases for the Adequate Development of Nutritional Recommendations for Patients with Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic and relapsing inflammatory condition of the gastrointestinal tract; it is a heterogeneous and multifactorial disorder resulting from a complex interplay between genetic variation, intestinal microbiota, the host immune system and environmental factors such as diet, drugs, breastfeeding and smoking. The interactions between dietary nutrients and intestinal immunity are complex. There is a compelling argument for environmental factors such as diet playing a role in the cause and course of IBD, given that three important factors in the pathogenesis of IBD can be modulated and controlled by diet: intestinal microbiota, the immune system and epithelial barrier function. The aim of this review is to summarize the epidemiological findings regarding diet and to focus on the effects that nutrients exert on the intestinal mucosa-microbiota-permeability interaction. The nature of these interactions in IBD is influenced by alterations in the nutritional metabolism of the gut microbiota and host cells that can influence the outcome of nutritional intervention. A better understanding of diet-host-microbiota interactions is essential for unravelling the complex molecular basis of epigenetic, genetic and environmental interactions underlying IBD pathogenesis as well as for offering new therapeutic approaches for the treatment of IBD.

The role of obesity in inflammatory bowel disease

In just over a generation overweight and obesity has become a worldwide health concern. The ramifications for this on future health care costs and longevity are consequent, whilst increased adiposity is a harbinger for diabetes, kidney and bone failure, and cancer. An area of intense interest where the role of adiposity is avidly discussed is in inflammatory bowel disease (IBD), which presents mainly as Crohn's disease (CD) and ulcerative colitis (UC). Studies in patients associating IBD with a western diet are divergent. Nevertheless, elegant studies have found gene polymorphisms in humans that in murine models parallel the inflammatory and gut microbiome changes seen in IBD patients. However, an area not to be ignored are the alterations in adipocyte function with ensuing adiposity, in particular and a focus of this review, the dysregulation of the levels of adipocytokines such as leptin and adiponectin. Herein, we present and discuss the known influences of a western diet on IBD in patients and rodent models and how adipocytokines could influence the IBD disease process.

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.

Research Gaps in Diet and Nutrition in Inflammatory Bowel Disease. A Topical Review by D-ECCO Working Group [Dietitians of ECCO]

Although the current doctrine of IBD pathogenesis proposes an interaction between environmental factors and gut microbiota in genetically susceptible individuals, dietary exposures have attracted recent interest and are, at least in part, likely to explain the rapid rise in disease incidence and prevalence. The D-ECCO working group along with other ECCO experts with expertise in nutrition, microbiology, physiology, and medicine reviewed the evidence investigating the role of diet and nutritional therapy in the onset, perpetuation, and management of IBD. A narrative topical review is presented where evidence pertinent to the topic is summarised collectively under three main thematic domains: i] the role of diet as an environmental factor in IBD aetiology; ii] the role of diet as induction and maintenance therapy in IBD; and iii] assessment of nutritional status and supportive nutritional therapy in IBD. A summary of research gaps for each of these thematic domains is proposed, which is anticipated to be agenda-setting for future research in the area of diet and nutrition in IBD.

Recipe for IBD: can we use food to control inflammatory bowel disease?

The mucosal immune system and the microbiota in the intestinal tract have recently been shown to play a key role in the pathogenesis of inflammatory bowel disease (IBD). Both of these can be influenced by food. Thus, we propose dietary intervention as a therapeutic option for IBD. In this review, we discuss the interaction of the intestinal mucosal immune system and the intestinal microbiota in the context of IBD. In addition, we discuss the impact of food components on immune responses in IBD. Finally, we address the current evidence of how this interaction (i.e., immune system-microbiota) can be modulated by food components, pre/probiotics, and fecal microbiota transplantation (FMT) and how these approaches can support intestinal homeostasis. By gathering the vast amount of literature available on the impact of food on IBD, we aim to distinguish between scientifically sound data and theories, which have not been included in this review.

Sentinels at the frontline: the role of intraepithelial lymphocytes in inflammatory bowel disease

Purpose of review

Intestinal mucosal immunity is tightly regulated to ensure effective host defense against invasive microorganisms while limiting the potential for aberrant damage. In inflammatory bowel disease (IBD), an imbalance between effector and regulatory T cell populations results in an uncontrolled inflammatory response to commensal bacteria. Intraepithelial lymphocytes (IEL) are perfectly positioned within the intestinal epithelium to provide the first line of mucosal defense against luminal microbes or rapidly respond to epithelial injury. This review will highlight how IELs promote protective intestinal immunity and discuss the evidence indicating that altered IEL responses contribute to the pathogenesis of IBD.

Recent findings

Although the role of IELs in mucosal homeostasis has been largely underappreciated, many of the same factors that contribute to the dysregulation of host defense in IBD also adversely affect IELs. For example, IL-23 and the endoplasmic reticulum stress response can enhance IEL lytic activity toward enterocytes. Microbial dysbiosis or defective microbial recognition results in the loss of regulatory IELs, further amplifying these pro-inflammatory effects. Migration of T cells into or within the intraepithelial compartment has a profound effect on their differentiation or effector function demonstrating that IELs are exquisitely sensitive to changes in the local intestinal microenvironment.

Summary

Enhanced mechanistic insight into the regulation of IEL survival, differentiation and effector function may provide useful tools to modulate IEL surveillance or enhance IEL regulatory function. Elucidation of these processes may result in the development of novel therapeutics to reduce intestinal inflammation and reinforce the mucosal barrier in IBD.

Protective Effect of Dietary Lily Bulb on Dextran Sulfate Sodium-Induced Colitis in Rats Fed a High-Fat Diet

Lily bulb is traditionally consumed in East Asia and contains high amounts of glucomannan. This study investigated the effect of dietary lily bulb on dextran sulfate sodium (DSS)-induced colitis in rats fed a high-fat (HF) diet. Male Sprague-Dawley rats were fed a diet containing 30% beef tallow with or without 7% steamed lily bulb powder for 17 d. Experimental colitis was induced by replacing drinking water with DSS during the last 7 d. The disease activity index (DAI) was significantly lower in the lily bulb+DSS group than in the DSS group on day 17. The fecal abundance of Bifidobacterium was significantly reduced in the DSS group compared with that in the control group, but it was recovered by lily bulb intake. Cecal butyrate, fecal mucins, and alkaline phosphatase (ALP) activity were significantly higher in the DSS group than in the control group. Dietary lily bulb potentiated the increase in cecal butyrate, fecal mucins, and the ALP activity caused by DSS treatment. These results indicate that lily bulb attenuates DSS-induced colitis by modulating colonic microflora, organic acids, mucins, and ALP activity in HF diet-fed rats.

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.

Fat intake and risk of ulcerative colitis: Systematic review and dose-response meta-analysis of epidemiological studies

BACKGROUND AND AIM

Fat intake is generally thought as a risk factor for onset of ulcerative colitis (UC), while epidemiological data had been controversial. This study aimed to evaluate the role of fat intake in the development of UC.

METHODS

Comprehensive search in PubMed and Embase was conducted to identify all relevant studies, and the role of fat intake in the development of UC was quantitatively assessed by dose-response meta-analysis.

RESULTS

Nine studies (four case-control and five prospective cohort) were indentified with a total of 966 UC cases and 171 589 controls. No evidence of a nonlinear dose-response association was found between fat intake and UC risk. Overall, the summary relative risks (RR) for per 30 g increment/day were 1.023 (95%confidence interval [CI]: 0.963-1.087; I²  = 24%; n = 6) for total fat intake, 1.063 (95%CI: 0.845-1.337; I²  = 44.5%; n = 4) for saturated fat intake, 1.214 (95%CI: 0.911-1.618; I²  = 63.1%; n = 4) for monounsaturated fat (MUFA) intake, and 1.247 (95%CI: 0.948-1.640; I²  = 25.4%; n = 4) for polyunsaturated fat (PUFA) intake, respectively. Subgroup and sensitivity analyses showed inconsistent results on PUFA intake, which was significantly related with UC risk after adjusting for smoking (RR: 1.617, 95%CI: 1.045-2.502; I²  = 0%; n = 3). For PUFA and MUFA subtypes, no subtypes were significantly associated with UC risk (P > 0.05), and only docosahexaenoic acid showed a potential protective effect in the development of UC (RR for the highest versus lowest intake level: 0.642, 95%CI: 0.403-1.024; I²  = 34.4%; n = 3) CONCLUSIONS: This meta-analysis suggested a lack of association between fat intake and UC risk, and large-scale prospective designed studies are warranted to confirm our findings.

High fat diet exacerbates dextran sulfate sodium induced colitis through disturbing mucosal dendritic cell homeostasis

Epidemiological studies have shown that fat rich western diet contributes to the high incidence of inflammatory bowel disease (IBD). Moreover, accumulated data indicated that fat dietary factor might promote the change of the composition and metabolism in commensal flora. But, the exact mechanisms for fatty diet in gut inflammation are not well demonstrated. In this study, we found that high fat diet (HFD) promoted inflammation and exacerbated the disease severity of dextran sulfate sodium (DSS) induced colitis in mice. Compared with low fat diet (LFD)/DSS mice, shorter colon length, more epithelial loss and crypt destruction and more Gr-1⁺ myeloid inflammatory cells infiltration in colons were observed in HFD/DSS cohorts. Interestingly, such HFD mediated inflammation accompanied with the dys-regulation of hematopoiesis, and more hematopoiesis stem and progenitor cells were detected in colon and spleen. We further analyzed the effects of HFD and DSS treatment on mucosal DC subsets, and found that DSS treatment in LFD mice mainly dramatically increased the percentage of CD11c⁺CD103^-CD11b⁺ DCs in lamina propria (LP). While, in HFD/DSS mice, HFD pre-treatment not only increased the percentage of CD11c⁺CD103^-CD11b⁺ DCs, but also decreased CD11c⁺CD103⁺CD11b⁺ in both LP and mesenteric lymph nodes (MLN) in mice with colitis. This disequilibrium of mucosal dendritic cells in HFD/DSS mice may depend on the reduced levels of buytrate and retinoic acid. Thus, this study declared the effects of HFD on gut microenviroment, and further indicated its potential role in the development of DSS induced colitis.

Environmental risk factors for inflammatory bowel diseases: Evidence based literature review

AIM: Advances in genetics and immunology have contributed to the current understanding of the pathogenesis of inflammatory bowel diseases (IBD).

METHODS: The current opinion on the pathogenesis of IBD suggests that genetically susceptible individuals develop intolerance to dysregulated gut microflora (dysbiosis) and chronic inflammation develops as a result of environmental insults. Environmental exposures are innumerable with varying effects during the life course of individuals with IBD. Studying the relationship between environmental factors and IBD may provide the missing link to increasing our understanding of the etiology and increased incidence of IBD in recent years with implications for prevention, diagnosis, and treatment. Environmental factors are heterogeneous and genetic predisposition, immune dysregulation, or dysbiosis do not lead to the development of IBD in isolation.

RESULTS: Current challenges in the study of environmental factors and IBD are how to effectively translate promising results from experimental studies to humans in order to develop models that incorporate the complex interactions between the environment, genetics, immunology, and gut microbiota, and limited high quality interventional studies assessing the effect of modifying environmental factors on the natural history and patient outcomes in IBD.

CONCLUSION: This article critically reviews the current evidence on environmental risk factors for IBD and proposes directions for future research.

High-fat diets rich in saturated fat protect against azoxymethane/dextran sulfate sodium-induced colon cancer

High-fat-diet (HFD) consumption is associated with colon cancer risk. However, little is known about how the lipid composition of a HFD can influence prooncogenic processes. We examined the effects of three HFDs differing in the percentage of total calories from saturated fat (SF) (6, 12, and 24% of total caloric intake), but identical in total fat (40%), and a commercially available Western diet (26 and 41% saturated and total fat, respectively) on colon cancer development using the azoxymethane (AOM)/dextran sulfate sodium (DSS) murine model. A second dose-response experiment was performed using diets supplemented with the saturated-fatty-acid (SFA)-rich coconut oil. In experiment 1, we found an inverse association between SF content and tumor burden. Furthermore, increased SF content was associated with reduced inflammation, increased apoptosis, and decreased proliferation. The second dose-response experiment was performed to test whether this effect may be attributed to the SF content of the diets. Consistent with the initial experiment, we found that high SF content was protective, at least in male mice; there was a decrease in mortality in mice consuming the highest concentration of SFAs. To explore a potential mechanism for these findings, we examined colonic mucin 2 (Muc2) protein content and found that the HFDs with the highest SF content had the greatest concentration of Muc2. Our data suggest that high dietary SF is protective in the AOM/DSS model of colon cancer, which may be due, at least in part, to the ability of SF to maintain intestinal barrier integrity through increased colonic Muc2.

Crosstalk between intestinal microbiota, adipose tissue and skeletal muscle as an early event in systemic low-grade inflammation and the development of obesity and diabetes

Obesity is associated with a systemic chronic low-grade inflammation that contributes to the development of metabolic disorders such as cardiovascular diseases and type 2 diabetes. However, the etiology of this obesity-related pro-inflammatory process remains unclear. Most studies have focused on adipose tissue dysfunctions and/or insulin resistance in skeletal muscle cells as well as changes in adipokine profile and macrophage recruitment as potential sources of inflammation. However, low-grade systemic inflammation probably involves a complex network of signals interconnecting several organs. Recent evidences have suggested that disturbances in the composition of the gut microbial flora and alterations in levels of gut peptides following the ingestion of a high-fat diet may be a cause of low-grade systemic inflammation that may even precede and predispose to obesity, metabolic disorders or type 2 diabetes. This hypothesis is appealing because the gastrointestinal system is first exposed to nutrients and may thereby represent the first link in the chain of events leading to the development of obesity-associated systemic inflammation. Therefore, the present review will summarize the latest advances interconnecting intestinal mucosal bacteria-mediated inflammation, adipose tissue and skeletal muscle in a coordinated circuitry favouring the onset of a high-fat diet-related systemic low-grade inflammation preceding obesity and predisposing to metabolic disorders and/or type 2 diabetes. A particular emphasis will be given to high-fat diet-induced alterations of gut homeostasis as an early initiator event of mucosal inflammation and adverse consequences contributing to the promotion of extended systemic inflammation, especially in adipose and muscular tissues.

Dietary fatty acid intakes are related to the risk of ulcerative colitis: a case-control study

INTRODUCTION

The role of dietary fatty acids in ulcerative colitis (UC) pathogenesis has been shown in animal models; however, human studies are rare. We hypothesized that there might be a relationship between dietary fatty acid composition and the risk of developing incident UC.

MATERIAL AND METHODS

Overall, 62 new cases of UC and 124 healthy age and sex-matched controls were studied. Information on usual diet was measured by a validated country-specific food frequency questionnaire (FFQ). Logistic regression analysis adjusting for potential confounding variables was carried out to compare dietary fatty acid intakes between cases and controls.

RESULTS

We found positive associations between dietary intake of total fat (P value for trend <0.01), oleic acid (P value for trend <0.01), saturated fatty acid (SAFA) (P value for trend = 0.02), total polyunsaturated fatty acid (PUFA) (P value for trend = 0.04), and trans fat (P value for trend <0.01).

CONCLUSION

Our results showed that higher consumptions of total fats, oleic acid, SAFAs, total PUFAs, trans fat, MUFAs, and linoleic acid are significantly associated with increased risk for UC; however, no statistically significant associations were detected between the risk of disease and n-3 PUFAs and cholesterol intake.

Effects of obesity on severity of colitis and cytokine expression in mouse mesenteric fat. Potential role of adiponectin receptor 1

In inflammatory bowel disease (IBD), obesity is associated with worsening of the course of disease. Here, we examined the role of obesity in the development of colitis and studied mesenteric fat-epithelial cell interactions in patients with IBD. We combined the diet-induce obesity with the trinitrobenzene sulfonic acid (TNBS) colitis mouse model to create groups with obesity, colitis, and their combination. Changes in the mesenteric fat and intestine were assessed by histology, myeloperoxidase assay, and cytokine mRNA expression by real-time PCR. Medium from human mesenteric fat and cultured preadipocytes was obtained from obese patients and those with IBD. Histological analysis showed inflammatory cell infiltrate and increased histological damage in the intestine and mesenteric fat of obese mice with colitis compared with all other groups. Obesity also increased the expression of proinflammatory cytokines including IL-1β, TNF-α, monocyte chemoattractant protein 1, and keratinocyte-derived chemokine, while it decreased the TNBS-induced increases in IL-2 and IFN-γ in mesenteric adipose and intestinal tissues. Human mesenteric fat isolated from obese patients and those with and IBD demonstrated differential release of adipokines and growth factors compared with controls. Fat-conditioned media reduced adiponectin receptor 1 (AdipoR1) expression in human NCM460 colonic epithelial cells. AdipoR1 intracolonic silencing in mice exacerbated TNBS-induced colitis. In conclusion, obesity worsens the outcome of experimental colitis, and obesity- and IBD-associated changes in adipose tissue promote differential mediator release in mesenteric fat that modulates colonocyte responses and may affect the course of colitis. Our results also suggest an important role for AdipoR1 for the fat-intestinal axis in the regulation of inflammation during colitis.

Strengthening of the intestinal epithelial tight junction by Bifidobacterium bifidum

Epithelial barrier dysfunction has been implicated as one of the major contributors to the pathogenesis of inflammatory bowel disease. The increase in intestinal permeability allows the translocation of luminal antigens across the intestinal epithelium, leading to the exacerbation of colitis. Thus, therapies targeted at specifically restoring tight junction barrier function are thought to have great potential as an alternative or supplement to immunology-based therapies. In this study, we screened Bifidobacterium, Enterococcus, and Lactobacillus species for beneficial microbes to strengthen the intestinal epithelial barrier, using the human intestinal epithelial cell line (Caco-2) in an in vitro assay. Some Bifidobacterium and Lactobacillus species prevented epithelial barrier disruption induced by TNF-α, as assessed by measuring the transepithelial electrical resistance (TER). Furthermore, live Bifidobacterium species promoted wound repair in Caco-2 cell monolayers treated with TNF-α for 48 h. Time course (1)H-NMR-based metabonomics of the culture supernatant revealed markedly enhanced production of acetate after 12 hours of coincubation of B. bifidum and Caco-2. An increase in TER was observed by the administration of acetate to TNF-α-treated Caco-2 monolayers. Interestingly, acetate-induced TER-enhancing effect in the coculture of B. bifidum and Caco-2 cells depends on the differentiation stage of the intestinal epithelial cells. These results suggest that Bifidobacterium species enhance intestinal epithelial barrier function via metabolites such as acetate.

Diet and inflammatory bowel disease: review of patient-targeted recommendations

Patients have strong beliefs about the role of diet in the cause of inflammatory bowel disease (IBD) and in exacerbating or alleviating ongoing symptoms from IBD. The rapid increase in the incidence and prevalence of IBD in recent decades strongly suggests an environmental trigger for IBD, one of which may be dietary patterns. There are several pathways where diet may influence intestinal inflammation, such as direct dietary antigens, altering the gut microbiome, and affecting gastrointestinal permeability. However, data that altering diet can change the natural history of IBD are scarce, and evidence-based dietary guidelines for patients with IBD are lacking. Patients, therefore, seek nonmedical resources for dietary guidance, such as patient support groups and unverified sources on the Internet. The aim of this review is to identify patient-targeted dietary recommendations for IBD and to critically appraise the nutritional value of these recommendations. We review patient-targeted dietary information for IBD from structured Internet searches and popular defined diets. Patient-targeted dietary recommendations focus on food restrictions and are highly conflicting. High-quality dietary intervention studies are needed to facilitate creation of evidence-based dietary guidelines for patients with IBD.

Intrauterine growth restriction and prematurity influence regulatory T cell development in newborns

PURPOSE

The aim of this study was to determine the relationship of birth weight and gestational age with regulatory T cells (Tregs) in cord blood of human newborns.

METHODS

Cord blood mononuclear cells (CBMCs) of 210 newborns were analyzed using flow cytometry to identify Tregs (CD3(+), CD4(+), CD25(high), FoxP3(high)) and measure FoxP3 mean fluorescence intensity (MFI). Suppressive index (SI) was calculated as FoxP3 MFI per Treg.

RESULTS

Mode of delivery had no significant effect on Tregs at birth. Term babies with growth restriction had fewer Tregs than their appropriate weight counterparts but equivalent SI. Preterm babies had higher percentages of Tregs, but lower SI than term controls. SI steadily increased through gestation.

CONCLUSIONS

Intrauterine growth restriction is correlated with fewer circulating Tregs and prematurity with decreased functionality of Tregs compared to term appropriate weight infants. This may have implications in diseases such as necrotizing enterocolitis that disproportionately affect premature and lower birth weight infants.