Potential of magnetic resonance spectroscopy in assessing the effect of fatty acids on inflammatory bowel disease in an animal model

Plant- and Fish-Derived n-3 PUFAs Suppress Citrobacter Rodentium-Induced Colonic Inflammation

SCOPE

Marine-derived n-3 PUFAs may ameliorate inflammation associated with inflammatory bowel diseases. Plant-derived n-3 PUFAs are thought to be inferior owing to shorter chain lengths. The aim of this study is to compare the impact of plant- and fish-derived PUFAs on murine colitis.

METHODS AND RESULTS

C57BL/6 mice are fed high fat (36% kcal) diets with either 2.5% w/w sunflower oil (SO), flaxseed oil (FSO), ahiflower oil (AO), or fish oil (FO). After 4 weeks, mice are orogastrically challenged with Citrobacter rodentium (10⁸ CFU) or sham gavaged. Fecal shedding is assayed at 2, 7, 10, and 14 days post infection (PI), and fecal microbiota at 14 days PI. Colonic inflammation and lipid mediators are measured. Supplementation regulates intestinal inflammation with crypt lengths being 66, 73, and 62 ±17 µm shorter (compared to SO) for FSO, AO, and FO respectively, p < 0.01. FSO blunts pathogen shedding at the peak of infection and FSO and AO both enhance fecal microbial diversity. FO attenuates levels of lipoxin and leukotriene B₄ while plant oils increase pro-resolving mediator concentrations including D, E, and T-series resolvins.

CONCLUSION

Plant and fish n-3 PUFAs attenuate colitis-induced inflammation while exhibiting characteristic pro-resolving lipid mediator metabolomes. Plant oils additionally promote microbial diversity.

Extra virgin olive oil and flaxseed oil have no preventive effects on DSS-induced acute ulcerative colitis

OBJECTIVES

The aim of this study was to evaluate the preventive effects of extra virgin olive oil (EVOO) or flaxseed oil (FO) on dextran sodium sulfate (DSS)-induced acute ulcerative colitis in female mice.

METHODS

Eighty C57BL/6J mice of 8-weeks-old were divided in four groups: Control (SO), 10%EVOO, 10%FO and 5%EVOO+5%FO. The oils were given through the AIN-93M diet. After 30 days, animals were divided in four more groups, in which half received 3%DSS in water for 5 days. Body weight loss, bleeding and stool consistency were verified for the Disease Activity Index (DAI). Animals were euthanized and their colon and spleen weighted and measured. Histopathological analysis, the concentrations of TNF-α, IL-1β, and IL-10 and the iNOS expression were evaluated in the colon samples.

RESULTS

Animals that received DSS presented with elevated disease activity index values; increased colon weight-to-length ratio; augmented leukocyte infiltration into the lamina propria and submucosa; and increased production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6, and greater inducible nitric oxide synthase expression in the distal colon. Individually or in combination, the oils were not able to reverse or mitigate any of the DSS-induced symptoms or damage. Additionally, the group of animals treated with DSS and supplemented with FO displayed increased spleen weight-to-body weight ratio, and the group that received a combination of EVOO and FO presented increased TNF-α levels compared with the respective control group.

CONCLUSION

Consumption of large amounts of EVOO and FO as a treatment for or prevention against ulcerative colitis could potentially elicit unwanted adverse effects.

Eosinophil-mediated signalling attenuates inflammatory responses in experimental colitis

OBJECTIVE

Eosinophils reside in the colonic mucosa and increase significantly during disease. Although a number of studies have suggested that eosinophils contribute to the pathogenesis of GI inflammation, the expanding scope of eosinophil-mediated activities indicate that they also regulate local immune responses and modulate tissue inflammation. We sought to define the impact of eosinophils that respond to acute phases of colitis in mice.

DESIGN

Acute colitis was induced in mice by administration of dextran sulfate sodium, 2,4,6-trinitrobenzenesulfonic acid or oxazolone to C57BL/6J (control) or eosinophil deficient (PHIL) mice. Eosinophils were also depleted from mice using antibodies against interleukin (IL)-5 or by grafting bone marrow from PHIL mice into control mice. Colon tissues were collected and analysed by immunohistochemistry, flow cytometry and reverse transcription PCR; lipids were analysed by mass spectroscopy.

RESULTS

Eosinophil-deficient mice developed significantly more severe colitis, and their colon tissues contained a greater number of neutrophils, than controls. This compensatory increase in neutrophils was accompanied by increased levels of the chemokines CXCL1 and CXCL2, which attract neutrophils. Lipidomic analyses of colonic tissue from eosinophil-deficient mice identified a deficiency in the docosahexaenoic acid-derived anti-inflammatory mediator 10, 17- dihydroxydocosahexaenoic acid (diHDoHE), namely protectin D1 (PD1). Administration of an exogenous PD1-isomer (10S, 17S-DiHDoHE) reduced the severity of colitis in eosinophil-deficient mice. The PD1-isomer also attenuated neutrophil infiltration and reduced levels of tumour necrosis factor-α, IL-1β, IL-6 and inducible NO-synthase in colons of mice. Finally, in vitro assays identified a direct inhibitory effect of PD1-isomer on neutrophil transepithelial migration.

CONCLUSIONS

Eosinophils exert a protective effect in acute mouse colitis, via production of anti-inflammatory lipid mediators.

Serum and urine metabolomic fingerprinting in diagnostics of inflammatory bowel diseases

AIM: To evaluate the utility of serum and urine metabolomic analysis in diagnosing and monitoring of inflammatory bowel diseases (IBD).

METHODS: Serum and urine samples were collected from 24 patients with ulcerative colitis (UC), 19 patients with the Crohn’s disease (CD) and 17 healthy controls. The activity of UC was assessed with the Simple Clinical Colitis Activity Index, while the activity of CD was determined using the Harvey-Bradshaw Index. The analysis of serum and urine samples was performed using proton nuclear magnetic resonance (NMR) spectroscopy. All spectra were exported to Matlab for preprocessing which resulted in two data matrixes for serum and urine. Prior to the chemometric analysis, both data sets were unit variance scaled. The differences in metabolite fingerprints were assessed using partial least-squares-discriminant analysis (PLS-DA). Receiver operating characteristic curves and area under curves were used to evaluate the quality and prediction performance of the obtained PLS-DA models. Metabolites responsible for separation in models were tested using STATISTICA 10 with the Mann-Whitney-Wilcoxon test and the Student’s t test (α = 0.05).

RESULTS: The comparison between the group of patients with active IBD and the group with IBD in remission provided good PLS-DA models (P value 0.002 for serum and 0.003 for urine). The metabolites that allowed to distinguish these groups were: N-acetylated compounds and phenylalanine (up-regulated in serum), low-density lipoproteins and very low-density lipoproteins (decreased in serum) as well as glycine (increased in urine) and acetoacetate (decreased in urine). The significant differences in metabolomic profiles were also found between the group of patients with active IBD and healthy control subjects providing the PLS-DA models with a very good separation (P value < 0.001 for serum and 0.003 for urine). The metabolites that were found to be the strongest biomarkers included in this case: leucine, isoleucine, 3-hydroxybutyric acid, N-acetylated compounds, acetoacetate, glycine, phenylalanine and lactate (increased in serum), creatine, dimethyl sulfone, histidine, choline and its derivatives (decreased in serum), as well as citrate, hippurate, trigonelline, taurine, succinate and 2-hydroxyisobutyrate (decreased in urine). No clear separation in PLS-DA models was found between CD and UC patients based on the analysis of serum and urine samples, although one metabolite (formate) in univariate statistical analysis was significantly lower in serum of patients with active CD, and two metabolites (alanine and N-acetylated compounds) were significantly higher in serum of patients with CD when comparing jointly patients in the remission and active phase of the diseases. Contrary to the results obtained from the serum samples, the analysis of urine samples allowed to distinguish patients with IBD in remission from healthy control subjects. The metabolites of importance included in this case up-regulated acetoacetate and down-regulated citrate, hippurate, taurine, succinate, glycine, alanine and formate.

CONCLUSION: NMR-based metabolomic fingerprinting of serum and urine has the potential to be a useful tool in distinguishing patients with active IBD from those in remission.

Characterization of the gastrointestinal microbiota in health and inflammatory bowel disease

The enteric bacterial flora play a key role in maintaining health. Inflammatory bowel disease is associated with quantitative and qualitative alterations in the microbiota. Early characterization of the microbiota involved culture-dependent techniques. The advent of metagenomic techniques, however, allows for structural and functional characterization using culture-independent methods. Changes in diversity, together with quantitative alterations in specific bacterial species, have been identified. The functional significance of these changes, and their pathogenic role, remain to be elucidated.