Modulation of intestinal immune system by dietary fat intake: Relevance to Crohn's disease

Dietary acid load, alternative healthy eating index score, and bacterial vaginosis: is there any association? A case-control study

Background:

Changing the dietary pattern may be an alternative treatment for bacterial vaginosis, the prevalent vaginal infection in women.

Methods:

One hundred and forty-three bacterial vaginosis-affected women diagnosed by Amsel criteria and 151 healthy controls aged 18 to 45 entered the current case-control research. To calculate the alternative healthy eating index and dietary acid load score, food consumption was recorded with an accurate and precise food frequency questionnaire. The dietary acid load was measured by potential renal acid load (PRAL) and net endogenous acid production (NEAP) indices. Using logistic regression models, the association between the alternative healthy eating index and dietary acid load score with bacterial vaginosis was investigated.

Results:

The last tertile of the alternative healthy eating index had a 75% decreased odds of experiencing bacterial vaginosis in the adjusted model (adjusted odds ratio (aOR) = 0.25, 95% confidence interval (CI) = 0.12–0.53, P for trend = 0.001). Besides, vegetables (aOR = 0.34, 95% CI = 0.17–0.69, P for trend = 0.003), nuts and legumes (aOR = 0.44, 95% CI = 0.23–0.87, P for trend = 0.028), and meats (aOR = 0.31, 95% CI = 0.16–0.60, P for trend = 0.001) intake was linked to a decreased bacterial vaginosis odds. However, sugar-sweetened beverages and fruit juice (aOR = 3.47, 95% CI = 1.68–7.17, P for trend < 0.001), trans fatty acids (aOR = 2.29, 95% CI = 1.18–4.43, P for trend = 0.005), and sodium (aOR = 3.44, 95% CI = 1.67–7.06, P for trend = 0.002) intake were directly associated with bacterial vaginosis odds. There was no evidence of a link between dietary acid load and bacterial vaginosis.

Conclusion:

According to the present study’s findings, there is no correlation between dietary acid load and the likelihood of developing bacterial vaginosis. However, following a plant-based dietary pattern based on the healthy eating index may lead to a lower odds of bacterial vaginosis.

Diet-related changes of basal lamina fenestrations in the villous epithelium of the rat small intestine: Statistical analysis on scanning electron microscopy

The epithelial basal lamina of the small intestine has numerous fenestrations for intraepithelial migration of leukocytes. We have reported dynamic changes of fenestrations in dietary conditions. To investigate this phenomenon, we performed statistical analyses using scanning electron microscopy images of the epithelial basal lamina of rat intestinal villi after removal of the villous epithelium by osmium maceration. We examined structural changes in the number and size of fenestrations in the rat jejunum and ileum under fasted and fed states for 24 h. Our findings revealed that, in the jejunum, the number of free cells migrating into the epithelium through fenestrations increased from 2 h after feeding, resulting in an increase in the fenestration size of intestinal villi; the number of free cells then tended to decrease at 6 h after feeding, and the fenestration size also gradually decreased. By contrast, the increase in the fenestration size by feeding was not statistically significant in the ileum. These findings indicate that the number of migrating cells increases in the upper part of the small intestine under dietary conditions, which may influence the absorption efficiency of nutrients including lipids, as well as the induction of nutrient-induced inflammation.

The Role of Interstitial Matrix and the Lymphatic System in Gastrointestinal Lipid and Lipoprotein Metabolism

This review emphasizes the events that take place after the chylomicrons are secreted by the enterocytes through exocytosis. First, we will discuss the journey of how chylomicrons cross the basement membrane to enter the lamina propria. Then the chylomicrons have to travel across the lamina propria before they can enter the lacteals. To understand the factors affecting the trafficking of chylomicron particles across the lamina propria, it is important to understand the composition and properties of the lamina propria. With different degree of hydration, the pores of the lamina propria (sponge) changes. The greater the hydration, the greater the pore size and thus the easier the diffusion of the chylomicron particles across the lamina propria to enter the lacteals. The mechanism of the entry of lacteals is discussed in considerable details. We and others have demonstrated that intestinal fat absorption, but not the absorption of protein or carbohydrates, activates the intestinal mucosal mast cells to release many products including mucosal mast cell protease II in the rat. The activation of intestinal mucosal mast cells by fat absorption involves the process of chylomicron formation since the absorption of both medium and short-chain fatty acids do not activate the mast cells. Fat absorption has been associated with increased intestinal permeability. We hypothesize that there is a link between fat absorption, activation of mucosal mast cells, and the leaky gut phenomenon (increased intestinal permeability). Microbiome may also be involved in this chain of events associated with fat absorption. This review is presented in sequence under the following headings: (1) Introduction; (2) Structure and properties of the gut epithelial basement membrane; (3) Composition and physical properties of the interstitial matrix of the lamina propria; (4) The movement of chylomicrons across the interstitial matrix of the lamina propria and importance of the hydration of the interstitial matrix of the lamina propria and the movement of chylomicrons; (5) Entry of the chylomicrons into the intestinal lacteals; (6) Activation of mucosal mast cells by fat absorption and the metabolic consequences; and (7) Link between chylomicron transport, mucosal mast cell activation, leaky gut, and the microbiome.

High-fat diet induced central adiposity (visceral fat) is associated with increased fibrosis and decreased immune cellularity of the mesenteric lymph node in mice

PURPOSE

Accumulation of visceral, but not subcutaneous, adipose tissue is highly associated with metabolic disease. Inflammation inciting from adipose tissue is commonly associated with metabolic disease risk and comorbidities. However, constituents of the immune system, lymph nodes, embedded within these adipose depots remain under-investigated. We hypothesize that, lymph nodes are inherently distinct and differentially respond to diet-induced obesity much like the adipose depots they reside in.

METHODS

Adipose tissue and lymph nodes were collected from the visceral and inguinal depots of male mice fed 13 weeks of standard CHOW or high fat diet (HFD). Immune cells were isolated from tissues, counted and characterized by flow cytometry or plated for proliferative capacity following Concanavalin A stimulation. Lymph node size and fibrosis area were also characterized.

RESULTS

In HFD fed mice visceral adipose tissue accumulation was associated with significant enlargement of the lymph node encased within. The subcutaneous lymph node did not change. Compared with mice fed CHOW for 13 weeks, mice fed HFD had a decline in immune cell populations and immune cell proliferative ability, as well as, exacerbated fibrosis accumulation, within the visceral, but not subcutaneous, lymph node.

CONCLUSIONS

Obesity-induced chronic low-grade inflammation is associated with impaired immunity and increased susceptibility to disease. Excessive visceral adiposity and associated inflammation driven by diet likely leads to obesity-induced immune suppression by way of lymph node/lymphatic system pathophysiology.

Dynamic changes in basal lamina fenestrations in rat intestinal villous epithelium under high-fat diet condition

The basal lamina of the villous epithelium in the small intestine has numerous fenestrations, which are produced by leukocytes for their intraepithelial migration. We previously showed that these fenestrations change due to the dynamics of migrating leukocytes in response to dietary conditions and suggested the possibility that this change is related to the regulation of the absorption of large-sized nutrients such as chylomicrons. The present study was, thus, designed to investigate structural changes in basal lamina fenestrations in response to a high-fat diet. The ultrastructure of the intestinal villi in the rat upper jejunum was investigated by electron microscopy of tissue sections in both the normal and the high-fat diet groups, and the fenestrations in the villous epithelium of rat upper jejunum were studied by scanning electron microscopy of osmium macerated/ ultrasonicated tissues. The present study showed that free cells adhering to the fenestrations increased in the upper jejunum two hours after feeding high-fat diet and the size of the fenestrations in this region also increased after feeding high-fat diet for 2 days. This enlargement of fenestrations may play an important role in increasing the efficiency of lipid absorption by facilitating the movement of chylomicrons from the intercellular space to the lamina propria.

Lipophilic activated ester prodrug approach for drug delivery to the intestinal lymphatic system

The intestinal lymphatic system plays an important role in the pathophysiology of multiple diseases including lymphomas, cancer metastasis, autoimmune diseases, and human immunodeficiency virus (HIV) infection. It is thus an important compartment for delivery of drugs in order to treat diseases associated with the lymphatic system. Lipophilic prodrug approaches have been used in the past to take advantage of the intestinal lymphatic transport processes to deliver drugs to the intestinal lymphatics. Most of the approaches previously adopted were based on very bulky prodrug moieties such as those mimicking triglycerides (TG). We now report a study in which a lipophilic prodrug approach was used to efficiently deliver bexarotene (BEX) and retinoic acid (RA) to the intestinal lymphatic system using activated ester prodrugs. A range of carboxylic ester prodrugs of BEX were designed and synthesised and all of the esters showed improved association with chylomicrons, which indicated an improved potential for delivery to the intestinal lymphatic system. The conversion rate of the prodrugs to BEX was the main determinant in delivery of BEX to the intestinal lymphatics, and activated ester prodrugs were prepared to enhance the conversion rate. As a result, an 4-(hydroxymethyl)-1,3-dioxol-2-one ester prodrug of BEX was able to increase the exposure of the mesenteric lymph nodes (MLNs) to BEX 17-fold compared to when BEX itself was administered. The activated ester prodrug approach was also applied to another drug, RA, where the exposure of the MLNs was increased 2.4-fold through the application of a similar cyclic activated prodrug. Synergism between BEX and RA was also demonstrated in vitro by cell growth inhibition assays using lymphoma cell lines. In conclusion, the activated ester prodrug approach results in efficient delivery of drugs to the intestinal lymphatic system, which could benefit patients affected by a large number of pathological conditions.

Adipose tissue extrinsic factor: Obesity-induced inflammation and the role of the visceral lymph node

Obesity-related adverse health consequences occur predominately in individuals with upper body fat distribution commonly associated with increased central adiposity. Visceral adipose tissue accumulation is described to be the greatest driver of obesity-induced inflammation, however evidence also supports that the intestines fundamentally contribute to the development of obesity-induced metabolic disease. The visceral adipose depot shares the same vasculature and lymph drainage as the small intestine. We hypothesize that the visceral lymph node, which drains adipose tissue and the gastrointestinal tract, is central to the exacerbation of systemic pro-inflammation. Male C57BL/6 mice were fed CHOW or high fat diet (HFD) for 7 weeks. At termination the mesenteric depot, visceral lymph node and ileum, jejunum and Peyer's patches were collected. Cytokine concentration was determined in adipose tissue whereas immune cell populations where investigated in the visceral lymph node and intestinal segments by flow cytometry. Visceral adipose tissue and the gastrointestinal tract mutually influence immune cells enclosed within the visceral lymph node. HFD increased visceral lymph node immune cell number. This likely resulted from 1.) an increase in immune cells migration from the small intestines likely from activated dendritic cells that travel to the lymph node and 2.) cytokine effluent from visceral adipose tissue that promoted expansion, survival and retention of pro-inflammatory immune cells. Overall, the visceral lymph node, the immune nexus of visceral adipose tissue and the small intestines, likely plays a fundamental role in exacerbation of systemic pro-inflammation by HFD-induced obesity. The research of Tim Bartness greatly enhanced the understanding of adipose tissue regulation. Studies from his laboratory significantly contributed to our awareness of extrinsic factors that influence body fatness levels. Specifically, the work he produced eloquently demonstrated that adipose tissue was more complex than an insulating storage center; it was connected to our brains via the sympathetic and sensory nervous system. Mapping studies demonstrated that adipose tissue both receives and sends information to the brain. Further, his lab demonstrated that nervous system connections contributed to lipolysis, thermogenesis and adipocyte proliferation and growth. The work of Tim Bartness will continue to influence adipose tissue research. As such, Tim Bartness directly inspired the following research. Adipose tissue extrinsic factors are not limited to the peripheral nervous system. The lymphatic system is an additional extrinsic factor that cross talks with adipose tissue, however its role in this context is under emphasized. Here we begin to elucidate how the lymphatic system may contribute to the comorbidities associated with visceral adipose tissue accumulation.

Oral administration of cannabis with lipids leads to high levels of cannabinoids in the intestinal lymphatic system and prominent immunomodulation

Cannabidiol (CBD) and ∆⁹-tetrahydrocannabinol (THC) have well documented immunomodulatory effects in vitro, but not following oral administration in humans. Here we show that oral co-administration of cannabinoids with lipids can substantially increase their intestinal lymphatic transport in rats. CBD concentrations in the lymph were 250-fold higher than in plasma, while THC concentrations in the lymph were 100-fold higher than in plasma. Since cannabinoids are currently in clinical use for the treatment of spasticity in multiple sclerosis (MS) patients and to alleviate nausea and vomiting associated with chemotherapy in cancer patients, lymphocytes from those patients were used to assess the immunomodulatory effects of cannabinoids. The levels of cannabinoids recovered in the intestinal lymphatic system, but not in plasma, were substantially above the immunomodulatory threshold in murine and human lymphocytes. CBD showed higher immunosuppressive effects than THC. Moreover, immune cells from MS patients were more susceptible to the immunosuppressive effects of cannabinoids than those from healthy volunteers or cancer patients. Therefore, administering cannabinoids with a high-fat meal or in lipid-based formulations has the potential to be a therapeutic approach to improve the treatment of MS, or indeed other autoimmune disorders. However, intestinal lymphatic transport of cannabinoids in immunocompromised patients requires caution.

Epithelial cell specific Raptor is required for initiation of type 2 mucosal immunity in small intestine

Intestinal tuft cells are one of 4 secretory cell linages in the small intestine and the source of IL-25, a critical initiator of the type 2 immune response to parasite infection. When Raptor, a critical scaffold protein for mammalian target of rapamycin complex 1 (mTORC1), was acutely deleted in intestinal epithelium via Tamoxifen injection in Tritrichomonas muris (Tm) infected mice, tuft cells, IL-25 in epithelium and IL-13 in the mesenchyme were significantly reduced, but Tm burden was not affected. When Tm infected mice were treated with rapamycin, DCLK1 and IL-25 expression in enterocytes and IL-13 expression in mesenchyme were diminished. After massive small bowel resection, tuft cells and Tm were diminished due to the diet used postoperatively. The elimination of Tm and subsequent re-infection of mice with Tm led to type 2 immune response only in WT, but Tm colonization in both WT and Raptor deficient mice. When intestinal organoids were stimulated with IL-4, tuft cells and IL-25 were induced in both WT and Raptor deficient organoids. In summary, our study reveals that enterocyte specific Raptor is required for initiating a type 2 immune response which appears to function through the regulation of mTORC1 activity.

Targeting Immunomodulatory Agents to the Gut-Associated Lymphoid Tissue

In addition to fluid haemostasis and lipid absorption, the lymphatic system and lymphoid tissues serve as the major host of immune cells where immune responses are evoked. Impaired function of the immune system might lead to serious diseases which are often treated by immunomodulators. This chapter briefly explores the physiology of an important part of the lymphatic system, the gut-associated lymphoid tissues (GALT). Currently used strategies for targeting GALT by immunomodulators for enhanced activity and/or decreased side effects are discussed. Strategies range from simple oral co-administration of immunomodulators with lipids to more advanced lipid-based formulations, polymer-based nanoparticle formulations and prodrugs. These targeting approaches successfully increase the concentration of immunomodulators achieved in the GALT and, more importantly, enhance immunomodulatory effects. Therefore, targeting immunomodulators to GALT represent a promising approach in the treatment of diseases where the immune system is actively involved.

Trans fatty acids exacerbate dextran sodium sulphate-induced colitis by promoting the up-regulation of macrophage-derived proinflammatory cytokines involved in T helper 17 cell polarization

Numerous reports have shown that a diet containing large amounts of trans fatty acids (TFAs) is a major risk factor for metabolic disorders. Although recent studies have shown that TFAs promote intestinal inflammation, the underlying mechanisms are unknown. In this study, we examined the effects of dietary fat containing TFAs on dextran sodium sulphate (DSS)-induced colitis. C57 BL/6 mice were fed a diet containing 1·3% TFAs (mainly C16:1, C18:1, C18:2, C20:1, C20:2 and C22:1), and then colitis was induced with 1·5% DSS. Colonic damage was assessed, and the mRNA levels of proinflammatory cytokines and major regulators of T cell differentiation were measured. The TFA diet reduced survival and exacerbated histological damage in mice administered DSS compared with those fed a TFA-free diet. The TFA diet significantly elevated interleukin (IL)-6, IL-12p40, IL-23p19 and retinoic acid-related orphan receptor (ROR)γt mRNA levels in the colons of DSS-treated animals. Moreover, IL-17A mRNA levels were elevated significantly by the TFA diet, with or without DSS treatment. We also examined the expression of proinflammatory cytokines in lipopolysaccharide (LPS)-stimulated RAW264.7 cells and peritoneal macrophages. These cells were exposed to TFAs (linoelaidic acid or elaidic acid) with or without LPS and the mRNA levels of various cytokines were measured. IL-23p19 mRNA levels were increased significantly by TFAs in the absence of LPS. Cytokine expression was also higher in LPS-stimulated cells exposed to TFAs than in unexposed LPS-stimulated cells. Collectively, our results suggest that TFAs exacerbate colonic inflammation by promoting Th17 polarization and by up-regulating the expression of proinflammatory cytokines in the inflamed colonic mucosa.

Effect of dietary fat on intestinal inflammatory diseases

Dietary fat has multiple roles on human health, and some dietary fat is used to treat organic diseases because of its anti-inflammatory effect. It is commonly accepted that omega-3 polyunsaturated fatty acid (PUFA) is beneficial on ischemic heart disease or rheumatic arthritis. On the contrary, effect of omega-3-PUFA on Crohn's disease remained controversial. That effect of omega-3 PUFA differs according to the location of inflamed intestine was hypothesized. To elucidate this hypothesis, to investigate the role of dietary fat on disease activity in different kind of murine models of intestinal inflammatory diseases was planned. The effect of omega-3 PUFA on small intestinal Crohn's disease model and large intestinal Crohn's disease model of mice. Chronic colitis model C57BL/6 mice received two cycles of dextran sodium sulfate solution treatment to induce chronic colitis. Feeding of omega-3 fat-rich diets exacerbated colitis with decrease in adiponectin expression. Chronic small intestinal inflammation model: SAMP1/Yit mice showed remarkable inflammation of the terminal ileum spontaneously. Feeding of omega-3 fat-rich diets for 16 weeks significantly ameliorated the inflammation of the terminal ileum. Enhanced infiltration of leukocytes and expression of mucosal addressin cell adhesion molecule-1 in intestinal mucosa was significantly decreased by omega-3 fat-rich diets treatment. Omega-3 PUFA has dual role, pro-/anti-inflammatory, on intestinal inflammatory diseases. The role of omega-3 fat and the potential for immunonutrition in inflammatory conditions of the gastrointestinal tract will be discussed.

Anti-inflammatory effect of elemental diets with different fat composition in experimental colitis

The aim of the present study was to evaluate the effectiveness of two isoenergetic elemental formulae with different fat content in the rat model of trinitrobenzene sulphonic acid (TNBS) colitis that mimics human inflammatory bowel disease. A total of forty-five male Wistar rats were assigned to five groups: (1) control group; (2) TNBS-induced colitis group; (3) TNBS-induced colitis group fed a long-chain TAG (LCT)-rich diet; (4) TNBS-induced colitis group fed a medium-chain TAG (MCT)-rich diet; (5) TNBS-induced colitis group fed a baseline diet and administered infliximab. Nutritional management lasted 12 d before and 4 d after rectal administration of TNBS. Subsequently, the rats were killed, and colonic tissue samples were collected for the assessment of histology, inflammation and oxidative stress. The MCT-rich diet decreased IL-6, IL-8 and intercellular adhesion molecule-1 (ICAM-1) levels and glutathione S-transferase (GST) activity, while the LCT-rich diet reduced only ICAM-1 levels and GST activity (P< 0·05). Neither elemental formula affected IL-10 levels. Infliximab reduced IL-8 and ICAM-1 levels and GST activity and increased IL-10 levels (P< 0·05). No significant differences were detected in oxidative stress. Histological damage scores differed significantly only between the control and the TNBS-induced colitis group. A MCT-rich formula seems to exert stronger anti-inflammatory effects than a LCT-rich formula in TNBS colitis.

Lymphatic diamine oxidase secretion stimulated by fat absorption is linked with histamine release

Diamine oxidase (DAO) is abundantly expressed in mammalian small intestine catalyzing the oxidative breakdown of polyamines and histamine. The aim of this study was to determine the relationship between stimulation of intestinal diamine oxidase secretion with intestinal fat absorption and histamine release. Conscious intestinal lymph fistula rats were used. The mesenteric lymph ducts were cannulated and intraduodenal tubes were installed for the infusion of Liposyn II 20% (an intralipid emulsion). Lymphatic DAO activity and protein secretion were analyzed by radiometric assay and Western blot, respectively. Lymphatic histamine concentration was measured by ELISA. Infusion of Liposyn II (4.43 kcal/3 ml) resulted in a ~3.5-fold increase in lymphatic DAO protein secretion and DAO activity, peaking at 1 h and lasting for 3 h. Liposyn II infusion also increased the lymphatic histamine release, a substrate for DAO. To determine the relationship of DAO release with histamine release, histamine was administered intraperitoneally (10 mg/kg) in fasting rats and resulted in a significant doubling in lymphatic DAO activity, supporting a link between histamine and DAO. In addition, ip administration of the histamine H4 receptor antagonist JNJ7777120 significantly reduced the Liposyn II-induced DAO output by 65.9%, whereas H(1) (pyrilamine maleate), H(2) (ranitidine), and H(3) (thioperamide maleate) receptor antagonists had little effect. We conclude that DAO secretion may contribute to the catabolism of histamine released during fat absorption and this is probably mediated through the histamine H(4) receptor.

Dietary lipids and sweeteners regulate glucagon-like peptide-2 secretion

Glucagon-like peptide-2 (GLP-2) is a potent intestinal growth factor derived from enteroendocrine L cells. Although food intake is known to increase GLP-2 secretion, its regulatory mechanisms are largely unknown as a result of its very short half-life in venules. The aims of this study were to compare the effects of luminal nutrients on the stimulation of GLP-2 secretion in vivo using lymph samples and to clarify the involvement of the sweet taste receptor in this process in vitro. Lymph samples were collected from the thoracic duct after bolus administration of dietary lipids or sweetening agents into the duodenum of rats. Human enteroendocrine NCI-H716 cells were also used to compare the effects of various nutrients on GLP-2 secretion. GLP-2 concentrations were measured by ELISA in vivo and in vitro. GLP-2 secretion was enhanced by polyunsaturated fatty acid- and monounsaturated fatty acid-rich dietary oils, dietary carbohydrates, and some kinds of sweeteners in rats; this effect was reproduced in NCI-H716 cells using α-linolenic acid (αLA), glucose, and sweeteners. GLP-2 secretion induced by sweetening agents was inhibited by lactisole, a sweetness-antagonizing inhibitor of T1R3. In contrast, lactisole was unable to inhibit GLP-2 secretion induced by αLA alone. Our results suggested that fatty acid- and sweetener-induced GLP-2 secretion may be mediated by two different pathways, with the sweet taste receptor involved in the regulation of the latter.

Methods for studying rodent intestinal lipoprotein production and metabolism

Lipid absorption begins with the digestion of dietary triacylglycerol and ultimately results in the secretion of triacylglycerol in chylomicrons into the lymphatics. Additionally, the intestine also secretes numerous proteins and peptides involved in lipid and lipoprotein metabolism in response to food. Ultimately, chylomicrons and these proteins, peptides, and hormones are found in lymph. The lymph fistula rat model has traditionally been used to study this intestinal absorption of nutrients, especially lipids, but recently, this model has also been used for studying the secretion of hormones by the small intestine. The protocols described in this article include the lymph fistula rat and mouse model, as well as in vivo chylomicron metabolism studies. These experimental models are helpful for the study of metabolic phenotypes, the characterization of intestinal lipid absorption and transport, and determining peripheral metabolism of intestinally derived lipoproteins.

Activation of rat intestinal mucosal mast cells by fat absorption

Previous studies have linked certain types of gut mucosal immune cells with fat intake. We determined whether fat absorption activates intestinal mucosal mast cells (MMC), a key component of the gut mucosal immune system. Conscious intestinal lymph fistula rats were used. The mesenteric lymph ducts were cannulated, and the intraduodenal (i.d.) tubes were installed for the infusion of Liposyn II 20% (an intralipid emulsion). Lymphatic concentrations of histamine, rat MMC protease II (RMCPII), a specific marker of rat intestinal MMC degranulation, and prostaglandin D(2) (PGD(2)) were measured by ELISA. Intestinal MMC degranulation was visualized by immunofluorescent microscopy of jejunum sections taken at 1 h after Liposyn II gavage. Intraduodenal bolus infusion of Liposyn II 20% (4.4 kcal/3 ml) induced approximately a onefold increase in lymphatic histamine and PGD(2), ∼20-fold increase in lymphatic RMCPII, but only onefold increase in peripheral serum RMCPII concentrations. Release of RMCPII into lymph increased dose dependently with the amount of lipid fed. In addition, i.d. infusion of long-chain triacylglycerol trilinolein (C18:2 n-6, the major composite in Liposyn II) significantly increased the lymphatic RMCPII concentration, whereas medium-chain triacylglycerol tricaprylin (C8:0) did not alter lymph RMCPII secretion. Immunohistochemistry image revealed the degranulation of MMC into lamina propria after lipid feeding. These novel findings indicate that intestinal MMC are activated and degranulate to release MMC mediators to the circulation during fat absorption. This action of fatty acid is dose and chain length dependent.

Interaction of early diet and the development of the immune system

The present review focuses on the specific effects of nutrients on the development of the immune system in early life. There is a big gap regarding the specific mechanisms that regulate immunity at the intestinal level and their impact in the systemic immune function. For this reason, during the last few years there has been great interest in ascertaining the mechanisms that regulate the intestinal immune function, as well as to understand how specific nutrients interact with the gut-associated lymphoid tissue. We have reviewed this topic with special emphasis on how human milk, and its components, influence the early development of intestinal immunity in breast-fed infants compared with formula-fed infants. Interactions between nutrients and intestinal microbiota have also been reviewed. Some micronutrients such as nucleotides and gangliosides, which are present in human milk and also in most foods, are able to influence immune functionality at very low concentrations. The specific action of these micronutrients on some parameters of immunity, as well as their potential mechanisms of action, have been considered in detail. However, there are limited data on how other specific nutrients, namely protein and non-protein N-containing compounds, lipids, carbohydrates, and others, such as minerals, vitamins, fibre, non-nutritional dietary compounds (flavonoids, carotenoids, phyto-oestrogens, etc), influence immunity. In the present review we have provided data regarding the potential effects of these compounds on the immune response in early life. The increasing use of functional foods by the public to improve their general health and prevent the incidence of chronic diseases has become a major area of interest within the nutrition community. Of the many functional foods available, probiotics have been most studied in infancy and childhood, particularly with regard to the prevention of allergic diseases. Infant formulae and fermented milks containing large quantities of probiotics are produced and consumed by Europeans and in other industrialized countries. In the present review we cover the clinical effects of probiotics in preventing disease during early life, as well as the potential mechanisms of interaction between probiotics and the gastrointestinal tract.

Omega-3 polyunsaturated fatty acids ameliorate the severity of ileitis in the senescence accelerated mice (SAM)P1/Yit mice model

Clinical studies using omega-3 polyunsaturated fatty acids (omega3-PUFA) to Crohn's disease (CD) are conflicting. Beneficial effects of dietary omega3-PUFA intake in various experimental inflammatory bowel disease (IBD) models have been reported. However, animal models of large intestinal inflammation have been used in all previous studies, and the effect of omega3 fat in an animal model of small intestinal inflammation has not been reported. We hypothesized that the effects of omega3 fat are different between large and small intestine. The aim of this study was to determine whether the direct effect of omega3 fat is beneficial for small intestinal inflammation. Senescence accelerated mice (SAM)P1/Yit mice showed remarkable inflammation of the terminal ileum spontaneously. The numbers of F4/80-positive monocyte-macrophage cells as well as beta7-integrin-positive lymphocytes in the intestinal mucosa were increased significantly compared with those in the control mice (AKR-J mice). The area of mucosal addressin cell adhesion molecule-1 (MAdCAM-1)-positive vessels was also increased. The degree of expression levels of monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-6 and interferon (IFN)-gamma mRNA were increased significantly compared with those in the control mice. The feeding of two different kinds of omega3 fat (fish-oil-rich and perilla-oil-rich diets) for 16 weeks to SAMP1/Yit mice ameliorated inflammation of the terminal ileum significantly. In both the omega3-fat-rich diet groups, enhanced infiltration of F4/80-positive monocytes/macrophages in intestinal mucosa of SAMP1/Yit mice cells and the increased levels of MCP-1, IL-6 and IFN-gamma mRNA expression were ameliorated significantly compared with those in the control diet group. The results suggest that omega3 fat is beneficial for small intestinal inflammation by inhibition of monocyte recruitment to inflamed intestinal mucosa.

Cholesterol metabolism in active Crohn's disease

Hypocholesterolemia has been investigated as a typical feature of critical illness and is connected with poor prognosis. Crohn's disease is an inflammatory process and is associated with several metabolic disturbances. In recent decades clinical studies have established a link between lipid metabolism and systemic inflammation. In our study we examined the serum profile of cholesterol (total cholesterol, LDL- and HDL-cholesterol) and changes in the cholesterol absorption/synthesis process by determination of plasma non-cholesterol sterol (squalene, lathosterol, campesterol, sitosterol) concentrations. Serum concentrations of total cholesterol, LDL- and HDL-cholesterol and non-cholesterol sterols were evaluated in 24 patients with active Crohn's disease during a period of 28 days. We detected lower serum levels of total cholesterol (P < 0.001), LDL- and HDL-cholesterol (P < 0.05) in the patients with active Crohn's disease than in the control group. In addition, the patients had significantly lower plasma levels of lathosterol (P < 0.001) and higher concentrations of squalene, although without significant differences. A significant decrease of campesterol plasma levels (P < 0.001) was detected, but lower plasma concentrations of sitosterol were without statistical significance. The active phase of Crohn's disease is characterized by altered metabolism of lipids, mainly of cholesterol. Our results show abnormalities in plasma concentrations of non-cholesterol sterols and provide evidence that the process of cholesterol synthesis and absorption is altered in active Crohn's disease.

The effect of dietary fish oil on survival after infection with Klebsiella pneumoniae or Streptococcus pneumoniae

Dietary fish oil is believed to have a beneficial effect in various infections and in autoimmune disorders. This effect may correspond to an altered immune response. In order to discover whether the effect of dietary fish oil is different in various infections, we studied the survival of mice fed fish oil or corn oil supplemented diets and infected in the lungs with either Klebsiella pneumoniae or Streptococcus pneumoniae. 120 NMRI mice were divided into 4 groups, of which 2 groups were fed a fish oil supplemented diet and 2 a corn oil supplemented diet. After 6 weeks the mice were infected in the lungs with Klebsiella pneumoniae (fish oil groups and corn oil groups) or with Streptococcus pneumoniae serotype 3 (both groups). The survival rate was monitored. The experiment was performed twice. The survival of the mice fed fish oil enriched diet and infected with Klebsiella pneumoniae was significantly better compared with the mice fed corn oil enriched diet (p = 0.0001 and p = 0.0013). No difference was found between the mice fed corn oil enriched diet or fish oil enriched diet and infected with Streptococcus pneumoniae serotype 3 (p = 0.74 and p = 0.15). Our results indicate that dietary fish oil has a beneficial effect on survival of mice after experimental pneumoniae when infected with Klebsiella pneumoniae, but not after infection with Streptococcus pneumoniae serotype 3.

Omega-3 fatty acids exacerbate DSS-induced colitis through decreased adiponectin in colonic subepithelial myofibroblasts

BACKGROUND

Although the immunoregulatory effects of omega-3 fatty acid and adiponectin have been postulated, their role in intestinal inflammation is controversial. The aim of this study was to determine whether dietary fat intake influences activity of colonic inflammation through modulating this system.

METHODS

C57BL/6 mice received dextran sulfate sodium for induction of colitis. Mice were fed a control diet, omega-3 fat-rich diet, omega-6 fat-rich diet, or saturated fat-rich diet. Some mice were administered a peroxisome proliferator activated receptor-gamma; agonist, pioglitazone. Messenger RNA expression of adiponectin and its receptors were analyzed. Adiponectin expression in colonic mucosa of ulcerative colitis patients was also analyzed.

RESULTS

The receptors for adiponectin were found to be ubiquitously expressed in epithelial cells, intraepithelial lymphocytes, lamina proprial mononuclear cells, and subepithelial myofibroblasts from colonic tissue, but adiponectin was only expressed in myofibroblasts. Induction of colitis significantly decreased the expression of adiponectin in colonic mucosa. The omega-3 fat diet group, but not the other fat diet groups, showed exacerbated colitis with a further decrease of adiponectin expression. Pioglitazone treatment ameliorated the level of decrease in adiponectin expression and improved colonic inflammation induced by the omega-3 fat-rich diet. In patients with ulcerative colitis, the expression level of adiponectin in colonic mucosa was also decreased compared with that in control mucosa.

CONCLUSIONS

Adiponectin was found to be expressed in myofibroblasts. Adiponectin expression was significantly suppressed by induction of colitis, and aggravation of colitis after exposure to omega-3 fat may be due to a further decrease in the expression level of adiponectin.

Chylomicrons promote intestinal absorption of lipopolysaccharides

Recent data suggest that dietary fat promotes intestinal absorption of lipopolysaccharides (LPS) from the gut microflora, which might contribute to various inflammatory disorders. The mechanism of fat-induced LPS absorption is unclear, however. Intestinal-epithelial cells can internalize LPS from the apical surface and transport LPS to the Golgi. The Golgi complex also contains newly formed chylomicrons, the lipoproteins that transport dietary long-chain fat through mesenteric lymph and blood. Because LPS has affinity for chylomicrons, we hypothesized that chylomicron formation promotes LPS absorption. In agreement with our hypothesis, we found that CaCo-2 cells released more cell-associated LPS after incubation with oleic-acid (OA), a long-chain fatty acid that induces chylomicron formation, than with butyric acid (BA), a short-chain fatty acid that does not induce chylomicron formation. Moreover, the effect of OA was blocked by the inhibitor of chylomicron formation, Pluronic L-81. We also observed that intragastric triolein (TO) gavage was followed by increased plasma LPS, whereas gavage with tributyrin (TB), or TO plus Pluronic L-81, was not. Most intestinally absorbed LPS was present on chylomicron remnants (CM-R) in the blood. Chylomicron formation also promoted transport of LPS through mesenteric lymph nodes (MLN) and the production of TNFalpha mRNA in the MLN. Together, our data suggest that intestinal epithelial cells may release LPS on chylomicrons from cell-associated pools. Chylomicron-associated LPS may contribute to postprandial inflammatory responses or chronic diet-induced inflammation in chylomicron target tissues.

Dietary intake of selected nutrients affects bacterial vaginosis in women

Bacterial vaginosis (BV), a condition of altered vaginal flora, is associated with various adverse reproductive health outcomes. We evaluated the association between diet and the presence of BV in a subset of 1521 women (86% African-American) from a larger study of vaginal flora. Participants completed the Block Food Questionnaire and clinical assessments and self-report measures of sexual and hygiene behavior. A total of 42% of the women were classified as having BV (Nugent score > or = 7). Severe BV (Nugent score > or = 9 and vaginal pH > or = 5) was present in 14.9% of the women. BV was associated [adjusted OR (AOR)] with increased dietary fat (1.5, 1.1-2.4) after adjusting for other energy nutrients and behavioral and demographic covariates. Severe BV was associated with total fat (2.3, 1.3-4.3), saturated fat (2.1, 1.2-3.9), and monounsaturated fat (2.2, 1.2-4.1). Energy intake was only marginally associated (P = 0.05) with BV (1.4, 1.0-1.8). There were significant inverse associations between severe BV and intakes of folate (0.4, 0.2-0.8), vitamin E (0.4, 0.2-0.8), and calcium (0.4, 0.3-0.7). We conclude that increased dietary fat intake is associated with increased risk of BV and severe BV, whereas increased intake of folate, vitamin A, and calcium may decrease the risk of severe BV.

Treatment inferred disease severity in Crohn's disease: evidence for a European gradient of disease course

OBJECTIVE

Geographic differences in disease course of Crohn's disease (CD) might possibly be related to differences in genetic and environmental factors encountered in different parts of the world. The aim of this study was to assess differences in treatment regimens within a European cohort of CD patients as a reflection of disease course, and to identify associated phenotypic risk factors at diagnosis.

MATERIAL AND METHODS

A prospective European population-based inception cohort of 380 CD patients was studied. The patients were classified for phenotype according to the Vienna classification. Differences between Northern and Southern European centres in treatment over the first 10 years of disease were analysed using a competing risks survival analysis method.

RESULTS

Patients in the North were more likely to have had surgery (p<0.01), whereas patients in the South were more likely to have been treated medically (p<0.01). Phenotype at diagnosis was not predictive of differences in treatment regimens between North and South.

CONCLUSIONS

In this study, a difference in management of CD was observed between Northern and Southern European centres. This suggests that there may be a North-South disease severity gradient across Europe. Phenotypic differences between patients in the North and South did not explain this observed difference.

Fatty acid compositions of lipids in mesenteric adipose tissue and lymphoid cells in patients with and without Crohn's disease and their therapeutic implications

BACKGROUND

The physiological bases for roles of adipose tissue and fatty acids in the symptoms and dietary treatments of Crohn's disease (CD) are poorly understood. The hypothesis developed from experiments on rodents that perinodal adipocytes are specialized to provision adjacent lymphoid tissues was tested by comparing the composition of triacylglycerol and phospholipid fatty acids in homologous samples of mesenteric adipose tissue and lymph nodes from patients with or without CD.

METHODS

Mesenteric perinodal and other adipose tissue and lymph nodes were collected during elective surgery for CD and other conditions. Fatty acids were extracted, identified, and quantified by thin-layer and gas-liquid chromatography.

RESULTS

Perinodal adipose tissue contained more unsaturated fatty acids than other adipose tissue in controls, as reported for other mammals, but site-specific differences were absent in CD. Lipids from adipose and lymphoid tissues had more saturated fatty acids but fewer polyunsaturates in patients with CD than controls. In adipose tissue samples, depletion of n-3 polyunsaturates was greatest, but n-6 polyunsaturates, particularly arachidonic acid, were preferentially reduced in lymphoid cells. Ratios of n-6/n-3 polyunsaturates were higher in adipose tissue but lower in lymphoid cells in patients with CD than in controls.

CONCLUSIONS

Site-specific differences in fatty acid composition in normal human mesentery are consistent with local interactions between lymph node lymphoid cells and adjacent adipose tissue. These site-specific properties are absent in CD, causing anomalies in composition of lymphoid cell fatty acids, which may explain the efficacy of elemental diets containing oils rich in n-6 polyunsaturates.

Enteral nutrition in Crohn's disease: fat in the formula

Enteral nutrition is effective in inducing remission in active Crohn's disease. Speculation on the underlying mechanism of action has moved away from the presentation of nitrogen and towards the fat content of the various enteral feeds. Evidence is accumulating that additional long-chain triglyceride in such feeds impairs the response rate in active Crohn's disease, whereas no deleterious effects of additional medium-chain triglyceride have been identified. It has been proposed that long-chain triglycerides composed from n-6 fatty acids may be the most harmful, since such fatty acids are substrates for inflammatory eicosanoid production. However, recent studies comparing different enteral feeds are not consistent in identifying which additional fatty acids impair response rates to the greatest extent. Despite meta-analyses concluding that polymeric diets (typically containing large amounts of fat) are as effective as elemental diets, it would seem sensible to use enteral feeds with minimal fat content when treating active Crohn's disease.

Effect of dietary fatty acids on the intestinal permeability of marker drug compounds in excised rat jejunum

The aim of this study was to explore the effects of diets containing saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and omega-3 and omega-6 polyunsaturated fatty acids (omega-3 and omega-6 PUFA, respectively) on the passive and active transport properties of rat jejunum using marker compounds. Rats were fed diets supplemented with 18.4% (w/w) lipid (4 groups) or standard rat chow (1 group) for a period of 30 days. At the end of the dietary period, mucosal scrapings were taken for the determination of membrane phospholipids, and the apparent jejunal permeability of radiolabelled marker compounds was determined using modified Ussing chambers. Changes in the phospholipid content of the brush border membrane reflected the different lipid content of the diets. The passive paracellular permeability of mannitol was not significantly affected by the fatty acid composition of the diet, although there was a trend toward decreased mannitol permeability in the rats fed both the omega-3 and omega-6 PUFA diets. In comparison, the transcellular diffusion of diazepam was reduced by 20% (P < 0.05) in rats fed diets supplemented with omega-3 and omega-6 PUFA. In the lipid-fed rats, the serosal to mucosal flux of digoxin, an intestinal P-glycoprotein substrate, was reduced by 20% (P < 0.05) relative to the chow-fed group, however there were no significant differences between the different lipid groups. The active absorption of D-glucose via the Na+-dependent transport pathway was highest in the SFA, MUFA and PUFA omega-3 dietary groups, intermediate in the low-fat chow group and lowest in the PUFA omega-6 group, and was positively correlated with short-circuit current. These studies indicate that dietary fatty acid changes can result in moderate changes to the active and passive transport properties of excised rat jejunum.

The intestinal mucosa as a target for dietary polyunsaturated fatty acids

Several studies have reported beneficial effects of dietary polyunsaturated fatty acids (PUFA) on various aspects of both human and animal health, and particular reference has been made to their effects on systemic immune responses. Both immune stimulation and immune suppression have been reported, with the outcome dependent on the type of PUFA, the target cell, as well as the immune competence of the cells before exposure. The systemic and the mucosal immune systems are discrete entities, which have evolved specific approaches in the defense of the host. The latter comprises several interconnected tissues, which communicate with one another through the action of soluble mediators and the trafficking of cellular components. After the oral mucosa, the intestinal epithelium and its associated gut-associated lymphoid tissue are the primary targets of dietary components. Absorption of dietary PUFA and its incorporation into intestinal tissues has been well studied, but the consequences of these events in relation to local immune responses have received little attention. This article describes some of the immune mechanisms operating at this barrier and, where possible, pinpoints areas for which a modulatory role for PUFA has already been demonstrated. Although not an exhaustive treatise of the subject, it is hoped that this review will foster research into the specific interaction between dietary PUFA and cell populations comprising the intestinal barrier.

Review article: the management of severe Crohn's disease

The treatment of severe and active Crohn's disease is currently based on immunosuppression, but also involves the management of nutrition, appropriate selection of patients for surgery, and maintenance of remission in the long term. Corticosteroids remain the drug of the first choice, particularly in the acute setting. However, there is evolving understanding of the role of other immunosuppressants and immune modifiers, as major concerns regarding side-effects and efficacy of steroids in the medium to long-term drive the search for alternatives.

Nutrition in Crohn's disease

Nutrition plays an important role in Crohn's disease. This review provides further insights into the relationship between nutrition and Crohn's disease and focuses on three different aspects: dietary aetiological factors, nutritional status and nutritional therapy in Crohn's disease.