Fat composition may be a clue to explain the primary therapeutic effect of enteral nutrition in Crohn's disease: results of a double blind randomised multicentre European trial

Enteral nutrition in the management of Crohn's disease

Exclusive feeding of defined formula diets has been used successfully as an alternative to corticosteroid treatment of active Crohn's disease, but the mechanism of efficacy remains conjectural. Recognition that polymorphisms in the NOD2/CARD15 gene confer susceptibility to Crohn's disease has increased appreciation of the interactions between the innate immune system and enteric bacteria, which lead to chronic intestinal inflammation. The 2 major goals of this workshop are: first, in light of current understanding of pathogenesis, to examine possible mechanisms of action of enteral nutrition as primary therapy; and second, to make evidence-based recommendations concerning its use in the new era of biologic therapies, when mucosal healing has become a realistic goal. Factors influencing efficacy, including duration, location of intestinal inflammation, and formula composition require consideration.

Control of systemic and local inflammation with transforming growth factor beta containing formulas

Enteral nutrition therapy with liquid diet has been shown to be effective in achieving clinical remission in intestinal Crohn's disease. The mechanism of action of this therapy, however, is still poorly understood. As part of our assessment of the action of 3 related polymeric enteral therapies, we have used a variety of techniques to document the histological and cytokine responses, in the mucosa and, systemically, to these treatments. The feeds studied (AL110, Modulen IBD and ACD004 [Nestle, Vevey, Switzerland]) all have casein as the protein source, are lactose free and are rich in transforming growth factor beta (TGF-beta). They have all been shown to induce clinical remission associated with mucosal healing. In the case of Modulen IBD, as well as mucosal macroscopic and histological healing there was a fall in mucosal proinflammatory cytokines: interleukin-1 mRNA in colonic and ileal, interleukin-8 mRNA in the colon and interferon gamma mRNA in the ileum, but a rise in the regulatory cytokine TGF-beta mRNA in the ileum. These results indicate that these formulas are influencing the disease process itself, and thus suggest that the clinical remission achieved is a result of a reduction in inflammation, rather than a consequence of some other nutrition effect.

The potential interactions between polyunsaturated fatty acids and colonic inflammatory processes

n-3 Polyunsaturated fatty acids (PUFAs) are recognized as having an anti-inflammatory effect, which is initiated and propagated via a number of mechanisms involving the cells of the immune system. These include: eicosanoid profiles, membrane fluidity and lipid rafts, signal transduction, gene expression and antigen presentation. The wide-range of mechanisms of action of n-3 PUFAs offer a number of potential therapeutic tools with which to treat inflammatory diseases. In this review we discuss the molecular, animal model and clinical evidence for manipulation of the immune profile by n-3 PUFAs with respect to inflammatory bowel disease. In addition to providing a potential therapy for inflammatory bowel disease there is also recent evidence that abnormalities in fatty acid profiles, both in the plasma phospholipid membrane and in perinodal adipose tissue, may be a key component in the multi-factorial aetiology of inflammatory bowel disease. Such abnormalities are likely to be the result of a genetic susceptibility to the changing ratios of n-3 : n-6 fatty acids in the western diet. Evidence that the fatty acid components of perinodal adipose are fuelling the pro- or anti-inflammatory bias of the immune response is also reviewed.

Insulin-like growth factors (IGFs) and IGF binding proteins in active Crohn's disease treated with omega-3 or omega-6 fatty acids and corticosteroids

OBJECTIVE

Catabolism and growth impairment are well-known complications of inflammatory bowel disease (IBD). This may be caused by the disease activity itself and/or the medical treatment, and both may lead to changes in the growth hormone (GH)/insulin-like growth factor I (IGF-I) axis. The aim of the present study was to examine the effects of enteral nutrition, Impact Powder, as adjuvant therapy to corticosteroid treatment on changes in the GH/IGF-I axis in patients with Crohn's disease (CD).

MATERIAL AND METHODS

The patients were randomized to 3-IP (omega-3-fatty acid (FA), 3 g/day) or 6-IP (omega-6-FA, 9 g/day). Changes in total IGF-I (tIGF-I) and total IGF-II (tIGF-II), free IGF-I (fIGF-I), IGF binding proteins (IGFBP-1 and IGFBP-3), IGFBP-3 protease activity and insulin levels were examined in 31 patients with active CD (CDAI: 186-603) during treatment with prednisolone (40 mg for 1 week) and tapering the dose by 5 mg/week. Clinical and biochemical markers of inflammation were studied at day 0, and after 5 and 9 weeks.

RESULTS

There were no differences at baseline between the two groups. During the treatment period, tIGF-I, fIGF-I and IGFBP-3 increased significantly in both groups compared to baseline (p<0.05) without differences between the groups. Insulin and IGFBP-1 showed no significant changes throughout the treatment period.

CONCLUSIONS

There was no difference between 3-IP and 6-IP as adjuvant enteral nutrition on the GH/IGF-I axis. The changes observed in the GH/IGF-I axis are in line with previously published studies and may be explained by corticosteroid treatment; however, we cannot exclude an additional effect of omega3-/omega6 FA as adjuvant enteral nutrition.

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.

Interventions for growth failure in childhood Crohn's disease

BACKGROUND

Crohn's disease in childhood is a chronic relapsing condition. Fifteen to forty per cent of children with Crohn's disease have growth retardation (Griffiths 1993a). Some treatment modalities including corticosteroids have been implicated in growth failure but it is thought mainly to be secondary to uncontrolled disease activity (Motil 1993; Markowitz 1993). Growth is fundamental to the practice of pediatrics, so by taking growth as the primary outcome measure we address issues important to both patients, their families and pediatricians.

OBJECTIVES

To evaluate the effectiveness of the different modalities available for the treatment of childhood Crohn's disease with regard to the reversal of growth failure and the promotion of normal growth.

SEARCH STRATEGY

Searches were made of the following databases using the Collaborative Review Group Search Strategy: EMBASE (1984-2004), MEDLINE (1966-2004), The Cochrane Central Register of Controlled Trials, The Cochrane Inflammatory Bowel Disease and Functional Bowel Disorders Group Specialized Trials Register and the Science Citation Index. Abstracts from the major gastrointestinal research meetings and references from published articles were also reviewed.

SELECTION CRITERIA

Randomized controlled trials pertaining to children less than 18 years of age with Crohn's disease were selected. Those with growth as an outcome measure were included in the review.

DATA COLLECTION AND ANALYSIS

Data extraction and assessment of the methodological quality of each trial was independently reviewed by two reviewers. Only one good quality randomized controlled trial was included in the review and therefore no statistical analysis was possible.

MAIN RESULTS

Three randomized controlled trials were identified. One was of good methodological quality (Markowitz 2000). This study looked at the use of 6-mercaptopurine (6-MP) as a steroid sparing agent. No difference in linear growth was observed between the intervention and placebo groups, although the total steroid dose received over the 18 month follow up period was reduced in the group receiving 6-MP. The two remaining randomized controlled trials (Sanderson 1987; Thomas 1993a) consider the use of enteral feeding versus corticosteroids for induction of remission, with height velocity standard deviation score at 6 months as an outcome measure. Although of less rigorous methodological quality, the results of these studies are discussed in detail in the review. In both studies height velocity standard deviation scores were significantly increased in the enteral feeding group compared with the corticosteroid group.

AUTHORS' CONCLUSIONS

In addition to these randomized controlled trials, a body of lower quality evidence does exist relevant to two other important interventions; the use of supplemental enteral nutrition (Morin 1980; Belli 1988; Israel 1995) and the judicious use of surgical interventions in pre-pubertal children with refractory disease (Alperstein 1985; Lipson 1990; McLain 1990). Newer treatments, such as infliximab, are now becoming more widely used and may offer advantages in promoting growth. These effects are as yet unstudied. This review highlights the need for large, multi centre studies of the different treatment options in paediatric Crohn's disease and the importance of standardised measurements of growth, such as height velocity standard deviation scores and height standard deviation scores as outcome measures.

Nutritional therapy for Crohn's disease in Japan

In Japan, nutritional therapy as both a primary and as a secondary treatment is widely used for Crohn's disease (CD). The rationale for its use is based on a variety of reasons. The first is its ability to induce remission and to ameliorate the activity of intestinal lesions in the short term by enteral (EN) or by parenteral nutritional therapy in which overexpressions of chemokine receptors in an active stage are decreased significantly in the remission stage. Second is its ability to maintain remission over the long term through home-based enteral nutrition in which tube feeding during the nighttime is encouraged. Third is its ability to reduce the steroid dosage over the period of a long-term treatment course. However, several disadvantages of this therapy such as unpalatability and sluggish effect have been pointed out. Several studies have attempted to resolve this issue and determine the best components of EN, especially in fat composition. Some data have been suggestive of too much long-chained fatty acid having a hazardous effect on EN's clinical efficacy because it works as a precursor of inflammatory prostaglandins. Our recent data show that medium-chained triglyceride did not have such a hazardous effect on clinical efficacy. Several studies suggested that the patient factors that were resistant to inducing remission in the short term were a long period of suffering CD, a high activity (on Crohn's Disease Activity Index, CDAI), hemorrhagic colitis, and colitis with marked cobblestoning. Japanese guidelines for the treatment of CD recommended nutritional therapy as a first-line therapy and as a maintenance therapy after inducing remission. This treatment policy has led to Japanese CD patients having lower mortality rates than that of patients who do not receive EN. If this therapy could be combined with other drug therapies, including strong immunosuppressants, treatment strategies would be improved over those we have at present.

Review article: the role of nutrition in the treatment of inflammatory bowel disease

Nutrients may be involved in the modulation of the immune response through at least three different mechanisms. First, the intestinal ecosystem plays a pivotal role in the pathogenesis of inflammatory bowel disease, triggering the uncontrolled inflammatory response in genetically predisposed individuals. Nutrients, together with bacteria, are major components of, and can therefore influence, the intestinal environment. Second, as components of cell membranes, nutrients can mediate the expression of proteins involved in the immune response, such as cytokines, adhesion molecules and nitric oxide synthase. The composition of lipids in the cell membrane is modified by dietary changes and can influence cellular responses. Indeed, various epidemiological, experimental and clinical data suggest that the immune response may be sensitive to changes in dietary composition. Finally, suboptimal levels of micronutrients are often found in both children and adults with inflammatory bowel disease, although, with the exception of iron and folate, it is unusual to discover symptoms attributable to these deficits. However, subclinical deficits may have a pathophysiological significance, as they may favour the self-perpetuation of the disease (due to defects in the mechanisms of tissue repair), cause defective defence against damage produced by oxygen free radicals and facilitate lipid peroxidation. These events can occur even in clinically inactive or mildly active disease, as well as in the development of dysplasia in the intestinal mucosa. Some dietary manipulations have been attempted as primary treatment for rheumatoid arthritis, and specially formulated diets for enteral nutrition have proved to be an effective treatment for Crohn's disease. Most trials, although lacking sufficient patient numbers, have demonstrated a role for dietary manipulation as primary therapy for inflammatory disease. Dietary lipids are one of the most active nutritional substrates modulating the immune response. Recently, it has been demonstrated that lipids may be a key factor explaining the therapeutic effect of clinical nutrition in Crohn's disease.

Nutrition support for pediatric patients with inflammatory bowel disease: a clinical report of the North American Society for Pediatric Gastroenterology, Hepatology And Nutrition

Impairment of growth and malnutrition are significant complications of inflammatory bowel disease (IBD) in pediatric patients. Since this topic was last reviewed in these pages (), a number of studies have further explored the epidemiology and pathogenesis of these nutritional complications of IBD in an effort to provide more effective interventions to prevent the long-term consequences of chronic nutrient deficiencies in childhood. In addition, during the past 15 years, the use of selected nutrients and microorganisms (probiotics) as primary or adjunctive therapy for the treatment of IBD has become an emerging area of great interest. The following is a Clinical Report from the Nutrition and Inflammatory Bowel Disease Committees of the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition.

Nutritional Therapy in Inflammatory Bowel Disease

Nutritional intervention is an important adjunctive therapy for patients with inflammatory bowel disease (IBD). The correction and maintenance of nutritional status, achieved by careful nutritional monitoring and intervention, should be an integral part of the multidisciplinary management of IBD throughout all stages of the disease. In acute Crohn's disease, enteral nutrition (polymeric and elemental) is an effective and safe primary therapy for many patients. Enteral diets should be considered as primary therapy in pediatric Crohn's disease patients, especially in children with poor nutritional status or growth impairment and in patients with severe drug-induced side effects. Total parenteral nutrition does not have a primary therapeutic role in IBD.

Immunomodulation by polyunsaturated fatty acids: mechanisms and effects

Polyunsaturated fatty acids (PUFAs) modulate immune responses, thereby exerting beneficial effects in a variety of inflammatory disorders. PUFAs of the n-3 series that are found in marine fish oils are particularly effective. A variety of molecular mechanisms have been found to explain how PUFAs could interfere with immune cell function. PUFAs alter eicosanoid (prostaglandin, leukotriene) synthesis, orphan nuclear receptor activation (e.g. peroxisome proliferator-activated receptors, liver X receptors) and T lymphocyte signaling by changing the molecular composition of special signaling platforms called lipid rafts. This review discusses these mechanisms in detail with respect to their probable relevance in vivo. In addition, the effects of PUFAs on the immune system in general are summarized, as are clinical effects in rheumatoid arthritis, inflammatory bowel disease and sepsis.

Medical management of Crohn's disease

Current evidence strongly suggests that Crohn's disease is caused by an abnormal response to enteric flora. This review examines the current evidence for medical management of Crohn's disease, particularly focusing on alternative therapies to corticosteroids in managing disease relapses and preventing long-term complications.

Trophic and cytoprotective nutrition for intestinal adaptation, mucosal repair, and barrier function

Intestinal epithelial cell turnover (proliferation, migration, differentiation, and apoptosis) and gut barrier functions are dynamic processes that are markedly affected by nutritional status, the route of feeding, and the adequacy of specific nutrients in the diet. Emerging studies are defining potential therapeutic roles for specific nutrients and diet-derived compounds (including arginine, glutamate, glutamine, glutathione, glycine, vitamin A, zinc, and specific lipids) in gut mucosal turnover, repair, adaptation after massive bowel resection, and barrier function. The role and regulation of endogenous bowel flora in generating short-chain fatty acids from diet-derived fiber and other diet-derived compounds and the effects of these agents on gut function are increasingly being elucidated. Results of these investigations should define new nutritional methods for trophic and cytoprotective effects on the intestine in conditions such as inflammatory bowel disease, malnutrition, and short bowel syndrome.

Lipids and the immune response: from molecular mechanisms to clinical applications

PURPOSE OF REVIEW

This review critically evaluates recent studies investigating the effects of fatty acids on immune and inflammatory responses in both healthy individuals and in patients with inflammatory diseases, with some reference to animal studies where relevant. It examines recent findings describing the cellular and molecular basis for the modulation of immune function by fatty acids. The newly emerging area of diet-genotype interactions will also be discussed, with specific reference to the anti-inflammatory effects of fish oil.

RECENT FINDINGS

Fatty acids are participants in many intracellular signalling pathways. They act as ligands for nuclear receptors regulating a host of cell responses, they influence the stability of lipid rafts, and modulate eicosanoid metabolism in cells of the immune system. Recent findings suggest that some or all of these mechanisms may be involved in the modulation of immune function by fatty acids.

SUMMARY

Human studies investigating the relationship between dietary fatty acids and some aspects of the immune response have been disappointingly inconsistent. This review presents the argument that most studies have not been adequately powered to take into account the influence of variation (genotypic or otherwise) on parameters of immune function. There is well-documented evidence that fatty acids modulate T lymphocyte activation, and recent findings describe a range of potential cellular and molecular mechanisms. However, there are still many questions remaining, particularly with respect to the roles of nuclear receptors, for which fatty acids act as ligands, and the modulation of eicosanoid synthesis, for which fatty acids act as precursors.

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.

Nutrition and inflammatory bowel disease: its relation to pathophysiology, outcome and therapy

Nutritional deficiencies are frequent in patients with ulcerative colitis and Crohn's disease, and negatively influence the outcome of the disease. Growth retardation, osteopenia and thromboembolic phenomena are some of the inflammatory bowel disease complications in which nutritional deficits are involved. Moreover, nutrients can play a role in the pathogenesis of the disease and, in some cases, can be a primary therapeutic tool. Enteral nutrition has proven to play a therapeutic role in Crohn's disease. The nutrient(s) responsible for this effect are not well identified but dietary fat appears to be a major factor. In ulcerative colitis, unabsorbable carbohydrates can modulate the intestinal microbial environment, thus contributing to improve colonic inflammation.