Human colonocyte detoxification

Effects of temperature-humidity index on blood metabolites of German dairy cows and their female calves

Heat stress (HS) impairs productivity, health, and welfare in dairy cows, and additionally causes metabolic changes. Hence, specific metabolites could be used as HS biomarkers. Consequently, the aim of the present study was to compare blood metabolite concentrations of German Holstein dairy cows and of their female calves suffering from high temperature-humidity index (THI) during late gestation (cows) or during their first week of life (calves) or not. According to the mean daily THI (mTHI) at the day before blood sampling, animals were classified into 2 groups: high mTHI ≥60 (hmTHI) and low mTHI <60 (lmTHI). To perform a standard cross-sectional 2-group study, cow groups (n = 48) and calf groups (n = 47) were compared separately. Differences in metabolite concentrations between hmTHI and lmTHI animals were inferred based on a targeted metabolomics approach. In the first step, processed metabolomics data were evaluated by multivariate data analysis techniques, and were visualized using the web-based platform MetaboAnalyst V5.0. The most important metabolites with pronounced differences between groups were further analyzed in a second step using linear mixed models. We identified 9 thermally sensitive metabolites for the cows [dodecanedioic acid; 3-indolepropionic acid; sarcosine; triglycerides (14:0_34:0), (16:0_38:7), (18:0_32:1), and (18:0_36:2); phosphatidylcholine aa C38:1; and lysophosphatidylcholine a C20:3] and for the calves [phosphatidylcholines aa C38:1, ae C38:3, ae C36:0, and ae C36:2; cholesteryl esters (17:1) and (20:3); sphingomyelins C18:0 and C18:1; and p-cresol sulfate], most of them related to lipid metabolism. Apart from 2 metabolites (3-indolepropionic acid and sarcosine) in cows, the metabolite plasma concentrations were lower in hmTHI than in lmTHI groups. In our heat-stressed dry cows, results indicate an altered lipid metabolism compared with lactating heat-stressed cows, due to the missing antilipolytic effect of HS. The results also indicate alterations in lipid metabolism of calves due to high mTHI in the first week of life. From a cross-generation perspective, high mTHI directly before calving seems to reduce colostrum quality, with detrimental effects on metabolite concentrations in offspring.

A Pilot Study on Across-Generation Impacts of Maternal Heat Stress on Blood Metabolites of Female Holstein Dairy Calves

Heat stress (HS) during late gestation implies unfavorable effects on dairy cows and their in-utero heat stressed offspring. The objective of the present study was to elucidate the effect of intrauterine (maternal) HS during the last week of gestation on blood metabolite concentrations of female dairy calves during their first week of life. We defined the mean temperature humidity index (mTHI) during the last gestation week of ≥60 as threshold for maternal HS. In this regard, we compared differences in metabolite concentrations of maternally heat stressed (MHSCALVES) (n = 14) and not heat stressed (NMHSCALVES) (n = 33) calves. We identified 15 metabolites from five different biochemical classes (phosphatidylcholines, cholesteryl esters, sphingomyelins, cresols and hexoses) as potential biomarkers for maternal HS in calves. The plasma concentrations of all significantly affected metabolites were lower in MHSCALVES when compared to NMHSCALVES. The effect of maternal HS during the last week of gestation on blood metabolite concentrations of the female offspring during the first week after birth might be due to HS induced intergenerational physiological alterations, impaired colostrum quality or epigenetic modifications of the calf genome. The results of this pilot study should be validated in ongoing fully standardized studies.

Forming 4-Methylcatechol as the Dominant Bioavailable Metabolite of Intraruminal Rutin Inhibits p-Cresol Production in Dairy Cows

Rutin, a natural flavonol glycoside, elicits its diverse health-promoting effects from the bioactivities of quercetin, its aglycone. While widely distributed in the vegetables and fruits of human diet, rutin is either absent or inadequate in common animal feed ingredients. Rutin has been supplemented to dairy cows for performance enhancement, but its metabolic fate in vivo has not been determined. In this study, plasma, urine, and rumen fluid samples were collected before and after the intraruminal dosing of 100 mg/kg rutin to 4 Holsteins, and then characterized by both targeted and untargeted liquid chromatography-mass spectrometry (LC-MS)-based metabolomic analysis. In plasma and urine, 4-methylcatechol sulfate was identified as the most abundant metabolite of rutin, instead of quercetin and its flavonol metabolites, and its concentration was inversely correlated with the concentration of p-cresol sulfate. In rumen fluid, the formation of 3,4-dihydroxyphenylacetic acid (DHPAA) and 4-methylcatechol after rapid degradation of rutin and quercetin concurred with the decrease of p-cresol and the increase of its precursor, 4-hydroxyphenylacetic acid. Overall, the formation of 4-methylcatechol, a bioactive microbial metabolite, as the dominant bioavailable metabolite of rutin and quercetin, could contribute to their beneficial bioactivities in dairy cows, while the decrease of p-cresol, a microbial metabolite with negative biological and sensory properties, from the competitive inhibition between microbial metabolism of rutin and tyrosine, has the potential to reduce environmental impact of dairy operations and improve the health of dairy cattle.

Microbiome response to diet: focus on obesity and related diseases

Numerous studies in humans and animal models describe disturbances of the gut microbial ecosystem associated with adiposity and hallmarks of the metabolic syndrome, including hepatic and cardiovascular diseases. The manipulation of the microbiome, which is largely influenced by the diet, appears as an innovative therapeutic tool to prevent or control obesity and related diseases. This review describes the impact of nutrients on the gut microbiota composition and/or function and when available, the consequences on host physiology. A special emphasis is made on the contribution of bacterial-derived metabolites in the regulation of key gut functions that may explain their systemic effect.

Hydrogen sulfide: An endogenous regulator of the immune system

Hydrogen sulfide (H₂S) is now recognized as an endogenous signaling gasotransmitter in mammals. It is produced by mammalian cells and tissues by various enzymes - predominantly cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) - but part of the H₂S is produced by the intestinal microbiota (colonic H₂S-producing bacteria). Here we summarize the available information on the production and functional role of H₂S in the various cell types typically associated with innate immunity (neutrophils, macrophages, dendritic cells, natural killer cells, mast cells, basophils, eosinophils) and adaptive immunity (T and B lymphocytes) under normal conditions and as it relates to the development of various inflammatory and immune diseases. Special attention is paid to the physiological and the pathophysiological aspects of the oral cavity and the colon, where the immune cells and the parenchymal cells are exposed to a special "H₂S environment" due to bacterial H₂S production. H₂S has many cellular and molecular targets. Immune cells are "surrounded" by a "cloud" of H₂S, as a result of endogenous H₂S production and exogenous production from the surrounding parenchymal cells, which, in turn, importantly regulates their viability and function. Downregulation of endogenous H₂S producing enzymes in various diseases, or genetic defects in H₂S biosynthetic enzyme systems either lead to the development of spontaneous autoimmune disease or accelerate the onset and worsen the severity of various immune-mediated diseases (e.g. autoimmune rheumatoid arthritis or asthma). Low, regulated amounts of H₂S, when therapeutically delivered by small molecule donors, improve the function of various immune cells, and protect them against dysfunction induced by various noxious stimuli (e.g. reactive oxygen species or oxidized LDL). These effects of H₂S contribute to the maintenance of immune functions, can stimulate antimicrobial defenses and can exert anti-inflammatory therapeutic effects in various diseases.

Activating the pregnane X receptor by imperatorin attenuates dextran sulphate sodium-induced colitis in mice

BACKGROUND AND PURPOSE

Activation of the human pregnane X receptor (PXR; NR1I2) has potential therapeutic uses for inflammatory bowel disease (IBD). Imperatorin (IMP), a naturally occurring coumarin, is the main bioactive ingredient of Angelica dahurica Radix, which is regularly used to treat the common cold and intestinal disorders. However, there are no data on the protective effects of IMP against IBD.

EXPERIMENTAL APPROACH

The effects of IMP on PXR-modulated cytochrome P450 3A4 (CYP3A4) expression were assessed using a PXR transactivation assay, a mammalian two-hybrid assay, a competitive ligand-binding assay, analysis of CYP3A4 mRNA and protein expression levels and measurement of CYP3A4 activity using a cell-based reporter gene assay and in vitro model. The inhibitory effects of IMP on NF-κB activity were evaluated by a reporter assay and NF-κB p65 nuclear translocation. The anti-IBD effects of IMP were investigated in a dextran sulphate sodium (DSS)-induced colitis mouse model. Colon inflammatory cytokines were assessed by elisa.

KEY RESULTS

IMP activated CYP3A4 promoter activity, recruited steroid receptor coactivator 1 to the ligand-binding domain of PXR and increased the expression and activity of CYP3A4. PXR knockdown substantially reduced IMP-induced increase in CYP3A4 expression. Furthermore, IMP-mediated PXR activation suppressed the nuclear translocation of NF-κB and down-regulated LPS-induced expression of pro-inflammatory genes. Nevertheless, PXR knockdown partially reduced the IMP-mediated inhibition of NF-κB. IMP ameliorated DSS-induced colitis by PXR/NF-κB signalling.

CONCLUSIONS AND IMPLICATIONS

IMP acts as a PXR agonist to attenuate DSS-induced colitis by suppression of the NF-κB-mediated pro-inflammatory response in a PXR/NF-κB-dependent manner.

Protein fermentation in the gut; implications for intestinal dysfunction in humans, pigs, and poultry

The amount of dietary protein is associated with intestinal disease in different vertebrate species. In humans, this is exemplified by the association between high-protein intake and fermentation metabolite concentrations in patients with inflammatory bowel disease. In production animals, dietary protein intake is associated with postweaning diarrhea in piglets and with the occurrence of wet litter in poultry. The underlying mechanisms by which dietary protein contributes to intestinal problems remain largely unknown. Fermentation of undigested protein in the hindgut results in formation of fermentation products including short-chain fatty acids, branched-chain fatty acids, ammonia, phenolic and indolic compounds, biogenic amines, hydrogen sulfide, and nitric oxide. Here, we review the mechanisms by which these metabolites may cause intestinal disease. Studies addressing how different metabolites induce epithelial damage rely mainly on cell culture studies and occasionally on mice or rat models. Often, contrasting results were reported. The direct relevance of such studies for human, pig, and poultry gut health is therefore questionable and does not suffice for the development of interventions to improve gut health. We discuss a roadmap to improve our understanding of gut metabolites and microbial species associated with intestinal health in humans and production animals and to determine whether these metabolite/bacterial networks cause epithelial damage. The outcomes of these studies will dictate proof-of-principle studies to eliminate specific metabolites and or bacterial strains and will provide the basis for interventions aiming to improve gut health.

In vivo imaging of leucine aminopeptidase activity in drug-induced liver injury and liver cancer via a near-infrared fluorescent probe

The liver, a main detoxification organ, has evolved a complex enzymatic system to respond to multiple pathological conditions, in which leucine aminopeptidase (LAP) has been reported to participate in detoxifying cisplatin in hepatoma cells and contribute to the intrinsic drug resistance. In vivo imaging of LAP activity in liver disease models is thus helpful to further understand the function of LAP in detoxification and medicine, but such an imaging approach is still lacking. Herein, we develop a selective and sensitive near-infrared fluorescent probe (HCAL) for this purpose. Using the probe, combined with confocal fluorescence imaging, we disclose the upregulations of LAP in acetaminophen-induced liver injury and tumor-bearing mice models. Supplementary acetylcysteine can suppress this upregulation, revealing that the LAP increase may be connected with a deficiency in biothiols. Moreover, HCAL has been used to image LAP in hepatoma cells, tumor tissues and xenograft tumor mice models successfully. These results demonstrate that HCAL may be a promising tool for studying the function of LAP in LAP-associated liver diseases.

Effect of pistachio consumption on the modulation of urinary gut microbiota-related metabolites in prediabetic subjects

The specific nutritional composition of nuts could affect different metabolic pathways involved in a broad range of metabolic diseases. We therefore investigated whether chronic consumption of pistachio nuts modifies the urine metabolome in prediabetic subjects. We designed a randomized crossover clinical trial in 39 prediabetic subjects. They consumed a pistachio-supplemented diet (PD, 50% carbohydrates, 33% fat, including 57 g/d of pistachios daily) and a control diet (CD, 55% carbohydrates, 30% fat) for 4 months each, separated by a 2-week wash-out. Nuclear magnetic resonance (NRM) was performed to determine changes in 24-h urine metabolites. Significant changes in urine metabolites according to the different intervention periods were found in uni- and multivariate analysis. Score plot of the first two components of the multilevel partial least squares discriminant analysis (ML-PLS-DA) showed a clear separation of the intervention periods. Three metabolites related with gut microbiota metabolism (i.e., hippurate, p-cresol sulfate and dimethylamine) were found decreased in PD compared with CD (P<.05). Moreover, cis-aconitate [intermediate of the tricarboxylic acid (TCA)] was also found decreased following PD compared with CD. Intragroup analysis showed that creatinine levels were significantly increased in PD (P=.023), whereas trimethylamine N-oxide (TMAO) was found significantly reduced following PD (P=.034). Our results suggest that chronic pistachio consumption may modulate some urinary metabolites related to gut microbiota metabolism and the TCA cycle; all associated with metabolic derangements associated with insulin resistance and Type 2 diabetes.

Integrative Network-based Analysis of Colonic Detoxification Gene Expression in Ulcerative Colitis According to Smoking Status

BACKGROUNDS AND AIMS

The effect of cigarette smoking [CS] is ambivalent since smoking improves ulcerative colitis [UC] while it worsens Crohn's disease [CD]. Although this clinical relationship between inflammatory bowel disease [IBD] and tobacco is well established, only a few experimental works have investigated the effect of smoking on the colonic barrier homeostasis focusing on xenobiotic detoxification genes.

METHODS

A comprehensive and integrated comparative analysis of the global xenobiotic detoxification capacity of the normal colonic mucosa of healthy smokers [n = 8] and non-smokers [n = 9] versus the non-affected colonic mucosa of UC patients [n = 19] was performed by quantitative real-time polymerase chain reaction [qRT PCR]. The detoxification gene expression profile was analysed in CD patients [n = 18], in smoking UC patients [n = 5], and in biopsies from non-smoking UC patients cultured or not with cigarette smoke extract [n = 8].

RESULTS

Of the 244 detoxification genes investigated, 65 were dysregulated in UC patients in comparison with healthy controls or CD patients. The expression of ≥ 45/65 genes was inversed by CS in biopsies of smoking UC patients in remission and in colonic explants of UC patients exposed to cigarette smoke extract. We devised a network-based data analysis approach for differentially assessing changes in genetic interactions, allowing identification of unexpected regulatory detoxification genes that may play a major role in the beneficial effect of smoking on UC.

CONCLUSIONS

Non-inflamed colonic mucosa in UC is characterised by a specifically altered detoxification gene network, which is partially restored by tobacco. These mucosal signatures could be useful for developing new therapeutic strategies and biomarkers of drug response in UC.

The protective effect of piperine on dextran sulfate sodium induced inflammatory bowel disease and its relation with pregnane X receptor activation

ETHNOPHARMACOLOGICAL RELEVANCE

Inflammatory bowel disease (IBD) is associated with chronic inflammation of the intestinal tract. Piperine (1-peperoylpiperidine), the primary lipophilic component in black pepper (Piper nigrum) and long pepper (Piper longum), has been reported to be effective for anti-inflammatory. Rencently, several ethnopharmacological purity compounds, such as baicalin and artemisinin, are reported to have potentially therapeutic role in treating IBD. In the present study, the effects of piperine on pregnane X receptor (PXR)-mediated CYP3A expression and its therapeutic role in IBD were investigated.

MATERIALS AND METHODS

LS174T cells and C57BL/6J mice were treated by the piperine. Gene expressions were analyzed by real-time PCR, Western blot analysis, transient transfections assay and histological analysis.

RESULTS

Data indicated that treatment of LS174T cells with piperine markedly increased both CYP3A4 and PXR mRNA and protein. Transient transfection experiments indicated that transcriptional activation of the CYP3A4 gene via piperine was PXR-dependent. Data show that pre-administration of piperine decreased clinical hallmarks of colitis in DSS-treated PXR mice as measured by body weight loss and assessment of diarrhea, rectal bleeding, colon length, and histology. Inflammatory mediators (CCR2, ICAM-1, IL-1β, IL-6, IL-10, iNOS, MCP-1, and TNFα) after DSS treatment were significantly decreased in mice pretreated with piperine but corresponding conditions did not occur in mice with down-regulation of PXR by small interfering RNA (siRNA).

CONCLUSION

Piperine is a potential agonist of PXR and an inducer of PXR, which may induce CYP3A4 gene expression at the mRNA and protein levels. These results establish that piperine may contribute to prevention or reduction of colonic inflammation.

Towards microbial fermentation metabolites as markers for health benefits of prebiotics

Available evidence on the bioactive, nutritional and putative detrimental properties of gut microbial metabolites has been evaluated to support a more integrated view of how prebiotics might affect host health throughout life. The present literature inventory targeted evidence for the physiological and nutritional effects of metabolites, for example, SCFA, the potential toxicity of other metabolites and attempted to determine normal concentration ranges. Furthermore, the biological relevance of more holistic approaches like faecal water toxicity assays and metabolomics and the limitations of faecal measurements were addressed. Existing literature indicates that protein fermentation metabolites (phenol, p-cresol, indole, ammonia), typically considered as potentially harmful, occur at concentration ranges in the colon such that no toxic effects are expected either locally or following systemic absorption. The endproducts of saccharolytic fermentation, SCFA, may have effects on colonic health, host physiology, immunity, lipid and protein metabolism and appetite control. However, measuring SCFA concentrations in faeces is insufficient to assess the dynamic processes of their nutrikinetics. Existing literature on the usefulness of faecal water toxicity measures as indicators of cancer risk seems limited. In conclusion, at present there is insufficient evidence to use changes in faecal bacterial metabolite concentrations as markers of prebiotic effectiveness. Integration of results from metabolomics and metagenomics holds promise for understanding the health implications of prebiotic microbiome modulation but adequate tools for data integration and interpretation are currently lacking. Similarly, studies measuring metabolite fluxes in different body compartments to provide a more accurate picture of their nutrikinetics are needed.

Linear growth faltering in infants is associated with Acidaminococcus sp. and community-level changes in the gut microbiota

BACKGROUND

Chronic malnutrition, termed stunting, is defined as suboptimal linear growth, affects one third of children in developing countries, and leads to increased mortality and poor developmental outcomes. The causes of childhood stunting are unknown, and strategies to improve growth and related outcomes in children have only had modest impacts. Recent studies have shown that the ecosystem of microbes in the human gut, termed the microbiota, can induce changes in weight. However, the specific changes in the gut microbiota that contribute to growth remain unknown, and no studies have investigated the gut microbiota as a determinant of chronic malnutrition.

RESULTS

We performed secondary analyses of data from two well-characterized twin cohorts of children from Malawi and Bangladesh to identify bacterial genera associated with linear growth. In a case-control analysis, we used the graphical lasso to estimate covariance network models of gut microbial interactions from relative genus abundances and used network analysis methods to select genera associated with stunting severity. In longitudinal analyses, we determined associations between these selected microbes and linear growth using between-within twin regression models to adjust for confounding and introduce temporality. Reduced microbiota diversity and increased covariance network density were associated with stunting severity, while increased relative abundance of Acidaminococcus sp. was associated with future linear growth deficits.

CONCLUSIONS

We show that length growth in children is associated with community-wide changes in the gut microbiota and with the abundance of the bacterial genus, Acidaminococcus. Larger cohorts are needed to confirm these findings and to clarify the mechanisms involved.

Aluminum enhances inflammation and decreases mucosal healing in experimental colitis in mice

The increasing incidence of inflammatory bowel diseases (IBDs) in developing countries has highlighted the critical role of environmental pollutants as causative factors in their pathophysiology. Despite its ubiquity and immune toxicity, the impact of aluminum in the gut is not known. This study aimed to evaluate the effects of environmentally relevant intoxication with aluminum in murine models of colitis and to explore the underlying mechanisms. Oral administration of aluminum worsened intestinal inflammation in mice with 2,4,6-trinitrobenzene sulfonic acid- and dextran sodium sulfate-induced colitis and chronic colitis in interleukin 10-negative (IL10(-/-)) mice. Aluminum increased the intensity and duration of macroscopic and histologic inflammation, colonic myeloperoxidase activity, inflammatory cytokines expression, and decreased the epithelial cell renewal compared with control animals. Under basal conditions, aluminum impaired intestinal barrier function. In vitro, aluminum induced granuloma formation and synergized with lipopolysaccharide to stimulate inflammatory cytokines expression by epithelial cells. Deleterious effects of aluminum on intestinal inflammation and mucosal repair strongly suggest that aluminum might be an environmental IBD risk factor.

Beneficial effects of an amino acid mixture on colonic mucosal healing in rats

BACKGROUND

Mucosal healing (MH) decreases the relapse risk in patients with inflammatory bowel disease, but the role of dietary supplementation in this process has been poorly investigated. Here, we investigated the effect of an amino acid mixture supplement on rat MH.

METHODS

Colitis was induced using 5% of dextran sodium sulfate for 6 days. Then, rats received a mixture of threonine (0.50 g/d), methionine (0.31 g/d), and monosodium glutamate (0.57 g/d) or an isonitrogenous amount of alanine (control group). Colons were recovered after colitis induction and after dietary supplementation for measuring colon characteristics, myeloperoxidase, cytokine gene expression, glutathione content, protein synthesis rate, and for histological analysis. Short-chain fatty acids were measured in the colonic content.

RESULTS

Colitis induction resulted in anorexia, thickening and shortening of the colon, and ulceration. Colonic cytokine expression and neutrophil infiltration were increased. An increased amount of water and a decreased amount of butyrate, propionate, and acetate were measured in the colonic content. Supplementation with the amino acid mixture coincided with a reduced protein synthesis rate in the colon compatible with the observed increased colonic MH. Mucosal regeneration/re-epithelialization was visible within 3 days after colitis induction at a time when mucosal inflammation was severe. Histological analysis revealed an increased regeneration/re-epithelialization after 10-day supplementation. In contrast, the spontaneous resolution of inflammation was not affected by the supplementation.

CONCLUSIONS

Amino acid supplementation ameliorates colonic MH but not mucosal inflammatory status. Our data sustain the use of adjuvant dietary intervention on initiated intestinal MH.

Constitutive expression of MMP9 in intestinal epithelium worsens murine acute colitis and is associated with increased levels of proinflammatory cytokine Kc

Inflammatory bowel disease (IBD), which includes ulcerative colitis and Crohn's disease, is a chronic inflammatory disease associated with an increased risk for colon cancer. Matrix metalloproteinases (MMPs) are the predominant proteinases expressed in the gut mucosa during active IBD. Our laboratory has previously demonstrated that epithelial-derived MMP9 is absent in normal colonic tissue but is upregulated during IBD. In this study MMP9 transgenic mice (Tg-villin-MMP9) are generated specifically to overexpress MMP9 in intestinal epithelium to examine the role and underlying mechanism by which it modulates the pathogenesis of acute colitis. Dextran sodium sulfate (3% DSS)- and Salmonella typhimurium (S.T.)-induced colitis models were used to study gut inflammation in Tg-villin-MMP9 and wild-type littermates (WT). Colonic tissue was analyzed via Western blot, histology, myeloperoxidase (MPO) assay, and quantitative PCR. Tg-villin-MMP9 mice expressed significantly increased MMP9 mRNA and protein expression at basal level. There was a significant decrease in the goblet cells, but a significant increase in proliferation and apoptosis were observed among Tg-villin-MMP9 mice compared with WT mice. There was also a significant increase in the proinflammatory chemokine Kc among Tg-villin-MMP9 compared with WT mice. Tg-villin-MMP9 exhibited a severe inflammatory response than WT mice in both DSS- and S.T.-induced colitis models as evident by greater weight loss and higher clinical score, histological score, and MPO activity, which correlated with relative levels of Kc mRNA. MMP9 expressed by intestinal epithelial cells mediates inflammation in colitis with simultaneous increase in proinflammatory cytokine Kc.

Gut microbial activity, implications for health and disease: the potential role of metabolite analysis

Microbial metabolism of proteins and amino acids by human gut bacteria generates a variety of compounds including phenol, indole, and sulfur compounds and branched chain fatty acids, many of which have been shown to elicit a toxic effect on the lumen. Bacterial fermentation of amino acids and proteins occurs mainly in the distal colon, a site that is often fraught with symptoms from disorders including ulcerative colitis (UC) and colorectal cancer (CRC). In contrast to carbohydrate metabolism by the gut microbiota, proteolysis is less extensively researched. Many metabolites are low molecular weight, volatile compounds. This review will summarize the use of analytical methods to detect and identify compounds in order to elucidate the relationship between specific dietary proteinaceous substrates, their corresponding metabolites, and implications for gastrointestinal health.

Animal models of colitis-associated carcinogenesis

Inflammatory bowel disease (IBD) is a group of chronic inflammatory disorders that affect individuals throughout life. Although the etiology and pathogenesis of IBD are largely unknown, studies with animal models of colitis indicate that dysregulation of host/microbial interactions are requisite for the development of IBD. Patients with long-standing IBD have an increased risk for developing colitis-associated cancer (CAC), especially 10 years after the initial diagnosis of colitis, although the absolute number of CAC cases is relatively small. The cancer risk seems to be not directly related to disease activity, but is related to disease duration/extent, complication of primary sclerosing cholangitis, and family history of colon cancer. In particular, high levels and continuous production of inflammatory mediators, including cytokines and chemokines, by colonic epithelial cells (CECs) and immune cells in lamina propria may be strongly associated with the pathogenesis of CAC. In this article, we have summarized animal models of CAC and have reviewed the cellular and molecular mechanisms underlining the development of carcinogenic changes in CECs secondary to the chronic inflammatory conditions in the intestine. It may provide us some clues in developing a new class of therapeutic agents for the treatment of IBD and CAC in the near future.

Metabolism and functions of L-glutamate in the epithelial cells of the small and large intestines

l-Glutamate is one of the most abundant amino acids in alimentary proteins, but its concentration in blood is among the lowest. This is largely because l-glutamate is extensively oxidized in small intestine epithelial cells during its transcellular journey from the lumen to the bloodstream and after its uptake from the bloodstream. This oxidative capacity coincides with a high energy demand of the epithelium, which is in rapid renewal and responsible for the nutrient absorption process. l-Glutamate is a precursor for glutathione and N-acetylglutamate in enterocytes. Glutathione is involved in the enterocyte redox state and in the detoxication process. N-acetylglutamate is an activator of carbamoylphosphate synthetase 1, which is implicated in l-citrulline production by enterocytes. Furthermore, l-glutamate is a precursor in enterocytes for several other amino acids, including l-alanine, l-aspartate, l-ornithine, and l-proline. Thus, l-glutamate can serve both locally inside enterocytes and through the production of other amino acids in an interorgan metabolic perspective. Intestinal epithelial cell capacity to oxidize l-glutamine and l-glutamate is already high in piglets at birth and during the suckling period. In colonocytes, l-glutamate also serves as a fuel but is provided from the bloodstream. Alimentary and endogenous proteins that escape digestion enter the large intestine and are broken down by colonic bacterial flora, which then release l-glutamate into the lumen. l-Glutamate can then serve in the colon lumen as a precursor for butyrate and acetate in bacteria. l-Glutamate, in addition to fiber and digestion-resistant starch, can thus serve as a luminally derived fuel precursor for colonocytes.

Nuclear pregnane X receptor single nucleotide polymorphism (-25385C/T) is not associated with inflammatory bowel disease in pediatric patients

OBJECTIVE

Studies in adults characterized the role of the pregnane X receptor (PXR) in the pathophysiology of inflammatory bowel disease (IBD) with conflicting results; pediatric studies are still lacking.

PATIENTS AND METHODS

Genotyping for the -25385C/T polymorphism of the PXR gene in 187 white children with IBD and 185 controls. Determination of colonic PXR expression in selected patients with IBD.

RESULTS

Minor allele frequency was seen in 35.6% patients with IBD and 40.5% controls (P = 0.174), although no significant differences were seen between the genotypes (P = 0.366). PXR was underexpressed in colonic tissue of 7 out of 11 Crohn disease and in 4 out of 5 patients with ulcerative colitis.

CONCLUSIONS

We could not confirm an association of the -25385C/T polymorphism in pediatric patients with IBD.

Role of the PXR gene locus in inflammatory bowel diseases

BACKGROUND

The pregnane X receptor gene (PXR/NR1I2) has been recently associated with an increased risk for inflammatory bowel disease (IBD), although a subsequent case-control study failed to replicate the original association in an independent population. This nuclear receptor regulates genes involved in the detoxification process in the liver and intestine, like ABCB1/MDR1. PXR expression was significantly reduced in the colon of patients with ulcerative colitis (UC), but remained unaffected in Crohn's disease (CD) patients. Considering previous results, we aimed at investigating the impact of this locus on IBD predisposition in the Spanish population.

METHODS

Three PXR polymorphisms, including the 1 more strongly correlated with IBD risk in the initial study at -25385C/T (rs3814055) and the 6 haplotypes conformed by them, were analyzed in 365 UC and 331 CD patients and compared with 550 ethnically matched controls.

RESULTS

The overall haplotypic distribution showed a significant difference between UC and CD patients (P = 0.05; chi(2) = 10.84). Among UC patients a significant difference was seen between those with extensive colitis and controls (P = 0.004; chi(2) = 17.04), mainly due to the presence of a risk haplotype (rs3814055*T//rs6784598*C//rs2276707*C: P = 0.001; odds ratio [OR] = 1.66, 95% confidence interval [CI] 1.20-2.30). Patients with extensive UC carrying the -25385T allele showed increased susceptibility compared with left-sided colitis patients and with healthy subjects. In patients with extensive UC a significantly different distribution of genotypes of the MDR1 G/A change located in intron 3 (rs3789243) was observed between carriers/noncarriers of the -25385T risk allele (P = 0.005).

CONCLUSIONS

Our data seem to support the association of the PXR locus with extensive UC and the interaction between PXR and MDR1 genes.

Microsomal glutathione S-transferase gene polymorphisms and colorectal cancer risk in a Han Chinese population

BACKGROUND AND AIMS

Glutathione S-transferases (GSTs) are phase II detoxification enzymes. Human GSTs have been classified into cytosolic, mitochondrial, and microsomal families. Several studies reported the association of colorectal cancer (CRC) risk with the genetic polymorphisms of cytosolic GSTs. The microsomal GSTs are structurally distinct but functionally similar to cytosolic GSTs; their association with CRC has not been reported. In this report, we summarized the result of a case-control study aimed at investigating the association of MGST1 gene locus polymorphisms with CRC risk among Han Chinese.

PATIENT/METHODS

Three hundred and seventy-two healthy controls and 238 sporadic CRC patients participated in this study. DNA resequencing was conducted for the 3.4 kb genomic DNA region containing the promoter, exons, exon-intron junctions, and the 5' and 3' untranslated regions.

RESULTS

We detected 13 single nucleotide polymorphisms (SNPs) including four novel SNPs not reported in database/literature. The gene shows a much higher nucleotide diversity than most human genes. The linkage and recombination analysis revealed 24 common haplotypes (13% > or = freq > or = 1%) and identified extensive intragenic recombination throughout the MGST1 locus (R = 81.8). Significant CRC association (P < or = 0.005) was not detected for each individual SNP. However, SNPs 102G>A and 16416G>A reached a marginal level of statistical significance with P values of 0.016 and 0.078, respectively. A combined genotype analysis detected a statistically significant CRC association for individuals carrying 102G>A/16416G>A (GG/GG) genotype (adjusted OR, 1.682; 95% confidence interval (CI), 1.177-2.404; P = 0.004). Consistent with the results of genotype analysis, the GG haplotype (102G>A/16416G>A) with two risk alleles was associated with a significantly higher CRC risk comparing with the haplotypes with one or no risk allele (adjusted OR 1.744; 95% CI 1.309-2.322; P = 0.0001).

CONCLUSION

The results suggest that MGST1 polymorphisms may contribute to CRC risk among Han Chinese.

Enterocyte proliferation and apoptosis in the caudal small intestine is influenced by the composition of colonizing commensal bacteria in the neonatal gnotobiotic pig

We previously reported marked differences in small intestinal morphology, including changes in crypt depth and villous height, after inoculation of germ-free pigs with different bacterial species. In an attempt to identify the mechanisms governing changes in villous morphology associated with bacterial colonization, 2 gnotobiotic experiments were performed. In each experiment, 16 piglets were allocated to 4 treatment groups including germ-free (GF), monoassociation with Lactobacillus fermentum (LF) or Escherichia coli (EC), or conventionalized with sow feces (SF). Piglets were reared under gnotobiotic conditions until 14 d of age, at which time whole intestinal tissue and enterocytes were collected for histological, gene expression, and protein analysis. Proliferating cell nuclear antigen, tumor necrosis factor alpha (TNFalpha), Fas ligand (FasL), CD3epsilon, caspase 3 (casp3), and toll-like receptors (TLR)2, 4, and 9 expression were measured by quantitative PCR. Activated casp3 was measured by Western blot. Increased abundance of activated casp3 and transcripts encoding proliferating cell nuclear antigen, TNFalpha, CD3epsilon, and FasL was observed in SF and EC treatment groups compared with GF and LF. Expression of TLR2 was increased (P < 0.05) in the SF treatment and tended to be greater (P < 0.08) in EC relative to LF and GF. Results indicate that conventional bacteria and E. coli but not L. fermentum increase overall cell turnover by stimulating increased apoptosis through the expression of FasL and TNFalpha and by increasing cell proliferation. The differential regulation of TLR expression indicates that microbially induced changes may be mediated in part by these receptors. Induction of inflammatory responses and activation of apoptosis through death receptors appears to play a significant role in enterocyte turnover mediated by commensal bacteria.

Pregnane X receptor activation ameliorates DSS-induced inflammatory bowel disease via inhibition of NF-kappaB target gene expression

Pregnane X receptor (PXR) expression was shown to be protective in inflammatory bowel disease (IBD). However, the mechanism by which PXR provides protection remains unclear. Wild-type and Pxr-null mice were treated with the PXR agonist pregnenolone-16alpha-carbonitrile or vehicle and administered 2.5% dextran sulfate sodium (DSS) in drinking water to induce IBD. Typical clinical symptoms were evaluated on a daily basis. In vivo intestinal permeability assays and proinflammatory cytokine analysis were performed. PXR agonist-treated mice were protected from DSS-induced colitis compared with vehicle-treated mice, as defined by body weight loss, diarrhea, rectal bleeding, colon length, and histology. Pregnenolone-16alpha-carbonitrile did not decrease the severity of IBD in Pxr-null mice. PXR agonist treatment did not increase epithelial barrier function but did decrease mRNA expression of several NF-kappaB target genes in a PXR-dependent manner. The present study clearly demonstrates a protective role for PXR agonist in DSS-induced IBD. The data suggest that PXR-mediated repression of NF-kappaB target genes in the colon is a critical mechanism by which PXR activation decreases the susceptibility of mice to DSS-induced IBD.

Low colonic glutathione detoxification capacity in patients at risk for colon cancer

BACKGROUND

Colon carcinogenesis is a multifactorial process influenced by hereditary as well as environmental factors. The glutathione/glutathione S-transferase detoxification system in the colon is important for protection against carcinogens. We investigated the levels of glutathione/glutathione S-transferase in normal colon mucosa of patients with colorectal cancer and in patients at high risk for colorectal cancer compared with those in healthy controls.

MATERIALS AND METHODS

Glutathione content was analyzed by high-performance liquid chromatography, and glutathione S-transferase enzyme activity by spectrophotometric determination with 1-chloro 2,4-dinitrobenzene. Normal colon tissue of patients with colon adenoma (n = 64), colorectal cancer (n = 37), familial adenomatous polyposis (FAP; n = 19), hereditary non-polyposis colorectal cancer families with (HNPCC+Ad; n = 34) or without (HNPCC-Ad; n = 33) adenoma was investigated.

RESULTS

Glutathione levels were significantly lower in the normal colon mucosa of patients with cancer, FAP, HNPCC-Ad or HNPCC+Ad compared with adenoma patients or healthy controls. Glutathione S-transferase enzyme activity in the distal colon was significantly lower in patients with cancer or FAP compared with the adenoma patients or healthy controls, whereas values in carcinoma patients were significantly lower compared with both the HNPCC-Ad and HNPCC+Ad groups.

CONCLUSIONS

An association of low colonic glutathione/glutathione S-transferase activity levels and high clinical risk for the development of colorectal cancer was observed. This low glutathione detoxification capacity might contribute to the colon cancer risk.

Clinical implications of oxidative stress and antioxidant therapy

Oxidative stress occurs when there is an imbalance between generation of reactive oxygen species and inadequate antioxidant defense systems. Oxidative stress can cause cell damage either directly or through altering signaling pathways. Oxidative stress is a unifying mechanism of injury in many types of disease processes, including gastrointestinal diseases. For example, in alcoholic liver disease, reactive oxygen species have been detected through direct spin-trapping techniques and through indirect markers, such as products of lipid peroxidation. A host of antioxidants have protected against liver injury in animal models of alcoholic liver disease. Similarly, in inflammatory bowel disease, oxidative stress has been postulated to play a role in disease initiation and progression, and antioxidant therapy, such as green tea polyphenols and gene therapy with superoxide dismutase, has a markedly attenuated disease. Downregulation of specific detoxification genes may play a role in the pathogenesis of inflammatory bowel disease, especially in ulcerative colitis. Oxidative stress is postulated to play a sustaining role in acute and chronic pancreatitis. Antioxidant supplementation has been used with some success in the treatment of chronic pancreatitis. This review covers recent findings related to oxidative stress in liver disease, inflammatory bowel disease, and pancreatitis.

The potential mechanisms involved in the anti-carcinogenic action of probiotics

Probiotic bacteria are live microbial food ingredients that provide a health benefit to the consumer. In the past it was suggested that they served to benefit the host primarily through the prevention of intestinal infections. More recent studies have implicated probiotic bacteria in a number of other beneficial effects within the host including: *The suppression of allergies. *Control of blood cholesterol levels. *Modulation of immune function. *And the prevention of cancers of the colon. The reputed anti-carcinogenic effect of probiotics arises from in vivo studies in both animals and to a limited extent in man; this evidence is supported by in vitro studies with carcinoma cell lines and anti-mutagenicity assays. However, the mechanisms involved in any effect have thus far been difficult to elucidate; studies offer evidence for a variety of mechanisms; we have reviewed these and come to the opinion that, the anti-carcinogenic effect may not be attributable to a single mechanism but rather to a combination of events not yet fully elucidated or understood.

Radical induction theory of ulcerative colitis

To propose a new pathogenesis called Radical Induction to explain the genesis and progression of ulcerative colitis (UC). UC is an inflammatory bowel disease. Colonic inflammation in UC is mediated by a buildup of white blood cells (WBCs) within the colonic mucosal lining; however, to date there is no answer for why WBCs initially enter the colonic mucosa to begin with. A new pathogenesis termed “Radical Induction Theory” is proposed to explain this and states that excess un-neutralized hydrogen peroxide, produced within colonic epithelial cells as a result of aberrant cellular metabolism, diffuses through cell membranes to the extracellular space where it is converted to the highly damaging hydroxyl radical resulting in oxidative damage to structures comprising the colonic epithelial barrier. Once damaged, the barrier is unable to exclude highly immunogenic fecal bacterial antigens from invading the normally sterile submucosa. This antigenic exposure provokes an initial immune response of WBC infiltration into the colonic mucosa. Once present in the mucosa, WBCs are stimulated to secrete toxins by direct exposure to fecal bacteria leading to mucosal ulceration and bloody diarrhea characteristic of this disease.

Loss of detoxification in inflammatory bowel disease: dysregulation of pregnane X receptor target genes

BACKGROUND & AIMS

Phase 1, phase 2, and cellular efflux transporters are critical components in intestinal barrier function against xenobiotics and bacteria. We therefore performed global gene expression profiling in patients with ulcerative colitis (UC) and Crohn's disease as well as control specimens, with a special emphasis on genes involved in detoxification and epithelial membrane integrity.

METHODS

Mucosal biopsy specimens from nonaffected regions of the colon and the terminal ileum were subjected to DNA microarray analysis and pathway-related data mining. Real-time reverse-transcription polymerase chain reaction was used for verification of selected regulated candidate genes in larger inflammatory bowel disease sample numbers and intestinal cell lines.

RESULTS

Several dysregulated genes were identified in both disease groups and tissues. A set of genes coordinately down-regulated in the colon of patients with UC was composed of cellular detoxification and defense genes, which are target genes for the transcription factor pregnane X receptor (PXR). Messenger RNA expression of ABCB1 (MDR1) and PXR was significantly reduced in the colon of patients with UC but was unaffected in patients with Crohn's disease. In contrast to some of its target genes, the expression of PXR was not sensitive to tumor necrosis factor alpha stimulation of intestinal cell lines.

CONCLUSIONS

A disease- and tissue-specific decrease in the expression of detoxification enzymes and ABC transporters was observed, which may be explained by a loss of PXR expression. Thus, dysregulation of xenobiotic metabolism and PXR activity in the gut is likely to contribute to the pathophysiology of UC.

Colonic epithelial functional phenotype varies with type and phase of experimental colitis

BACKGROUND & AIMS

Colonic crypt elongation occurs during both chronic colitis and in the recovery phase of acute colitis. The impact of these alterations on epithelial cell functions is not fully defined.

METHODS

DNA microarray analysis of freshly isolated colonic epithelial cells (CECs) from acute and chronic colitis was performed, and the results were confirmed by reverse transcription polymerase chain reaction. Localization of the selected molecules was examined by immunohistochemistry using newly generated antibodies. The function of selected molecules detected in this study was examined by administering the specific inhibitors in dextran sodium sulfate (DSS) colitis.

RESULTS

Several detoxification-associated molecules, which contribute to prevent inflammation by regulating physiological balance under normal conditions, were markedly down-regulated, and anti-inflammatory molecules, which are not normally expressed, were up-regulated in the CEC under the chronic colitis. Among the detoxification-associated molecules, carbonic anhydrase IV was specifically down-regulated in CEC of Th2- but not Th1-mediated colitis. Functionally, inhibition of carbonic anhydrase activity led to the enhancement of recovery from DSS-induced acute colitis by directly stimulating CEC proliferation. Increased expression of regeneration-associated molecules such as regenerating gene-III gamma was detectable in the CEC of acute and chronic colitis but not in the recovery phase of colitis. The expression of this molecule was restricted in surface epithelium and upper crypts but not lower crypts.

CONCLUSIONS

These studies suggest that functional alterations, which result in either the exacerbation or the suppression of colitis, coexist in the CEC during chronic colitis. CEC functions are likely to be differentially regulated in the context of the stage and mechanism of colitis.

Genetic polymorphisms in biotransformation enzymes in Crohn's disease: association with microsomal epoxide hydrolase

BACKGROUND

Mucosal biotransformation enzymes can modify toxic compounds in the gut. As chemical or oxidative stress may be involved in the aetiology of Crohn's disease, genes encoding for enzymes involved in the prevention of such stress may be candidates for genetic susceptibility to Crohn's disease.

AIM

To assess the association of Crohn's disease with genetic polymorphisms in cytochrome P450 1A1, glutathione S-transferases mu-1, pi-1, and theta-1, and epoxide hydrolase.

METHODS

chi(2) square analysis was used to compare frequencies of polymorphisms between 151 patients with Crohn's disease and 149 healthy controls.

RESULTS

In patients, a genetic polymorphism in exon 3 of the microsomal epoxide hydrolase gene was distributed significantly different compared with controls (chi(2)=23.7; p<0.0001). All other polymorphisms tested were equally distributed between patients and controls.

CONCLUSIONS

Microsomal epoxide hydrolase may play a role in the pathophysiology of Crohn's disease. Furthermore, the epoxide hydrolase gene is located on chromosome 1q, close to a region previously linked to Crohn's disease.

Hydrogen sulfide and colonic epithelial metabolism: implications for ulcerative colitis

Hydrogen sulfide (HS-) impairs the oxidation of butyrate in colonocytes and is found in excess in feces of patients with ulcerative colitis. The possible pathogenic role of HS- in ulcerative colitis was further investigated. To investigate the metabolic effect of free and bound fecal HS-, isolated rat colonocytes were incubated in the presence of butyrate without and with the addition of (1) HS- in water, (2) sterile filtrates of fecal homogenates supplemented and incubated with HS- and known sources of fecal HS- production, and (3) HS- incubated with fecal agents known to bind HS-. Oxidation rates were obtained by quantifying the production of CO2. Total and free HS-, as well as the fecal ability to bind HS-, were determined in health and ulcerative colitis. Compared to the production of CO2 by colonocytes incubated with 2 mmol/liter of butyrate, the further addition of 1.25 and 2.5 mmol/liter of HS- in water reduced the production of CO2 by 57.6+/-10.0 and 98.9+/-1.4%, respectively. However, when adding fecal filtrate of homogenate supplemented with HS- corresponding to 1.25 and 2.5 mmol/liter of HS- in water, the reduction of CO2 production was only 30.7+/-12.0 and 53.2+/-14.0%, respectively. Neither the fecal level of total or free HS- nor the remarkable fecal ability to bind HS- differed in health or quiescent and active ulcerative colitis. Bound HS- had no or little effect on CO2 production. Addition of fecal filtrate of nonsupplemented homogenate to colonocytes significantly reduced the oxidation of butyrate to CO2 about 25%, which could not be ascribed to fecal HS-. In conclusion, fecal HS- has little effect on butyrate oxidation in colonocytes and does not seem to play a pathogenic role for UC by impairing colonic epithelial metabolism. Other fecal agents seem to be more potent metabolic inhibitors than fecal HS-. The role of colonic contents in the pathogenesis of ulcerative colitis remains circumstantial.

Thiol methyltransferase activity in inflammatory bowel disease

BACKGROUND

Luminal anionic sulphide may contribute to epithelial damage in ulcerative colitis. Thiol methyltransferase (TMT) governs sulphide detoxification by the colonic mucosa and circulating erythrocytes.

AIMS

To measure levels of TMT activity in erythrocytes of surgically treated cases of colitis or in rectal biopsies of defined groups of colitis.

PATIENTS

Venepuncture blood was obtained from 37 blood donors and 27 subjects who had previously undergone a proctocolectomy for colitis: 18 for ulcerative colitis and nine for Crohn's colitis. Rectal biopsies from 122 cases were obtained: 47 without mucosal disease, 33 post-colon resection for cancer, 14 with moderate to severe ulcerative colitis, 15 with quiescent ulcerative colitis, seven with acute Crohn's colitis, and six with radiation proctitis.

METHODS

TMT activity was measured by high performance liquid chromatography with radioactive detection to measure (14)C methylmercaptoethanol formation, the reaction product of cell extracts incubated with mercaptoethanol and (14)C S-adenosylmethionine.

RESULTS

Erythrocyte TMT activity of surgically treated cases of colitis was significantly elevated (p<0. 001) compared with control cases. TMT activity of rectal biopsies was significantly decreased (p<0.02) in acute but not quiescent ulcerative colitis, Crohn's colitis, or radiation colitis.

CONCLUSIONS

Erythrocyte TMT activity was persistently elevated after proctocolectomy for Crohn's disease and ulcerative colitis. No primary defect of TMT activity was found in any case of unoperated colitis but mucosal activity was diminished with disease progression of ulcerative colitis. Studies of genetic control of TMT activity of erythrocytes in inflammatory bowel disease appear worthwhile.

A simple method to establish short-term cultures of normal human colonic epithelial cells from endoscopic biopsy specimens. Comparison of isolation methods, assessment of viability and metabolic activity

BACKGROUND

Abnormalities in colonic epithelial cell function have been implicated in the pathogenesis of various intestinal disorders, especially inflammatory bowel disease (IBD). The mechanisms, however, remain obscure owing to the lack of representative human colonic epithelial cell models. The aim of this study was to develop and validate a method for establishment of short-term culture of normal human colonic epithelial cells from endoscopic biopsies.

METHODS

Epithelial cells were isolated from colonoscopic biopsies by means of ethylenediaminetetraacetic acid/ethylene glycol tetraacetic acid (EDTA/EGTA) (10 or 60 min) or by enzyme treatment and cultured in collagen-coated wells. Viability was measured with a methyltetrazoleum conversion assay, confocal laser, and electron microscopy. Metabolic function was measured by means of butyrate oxidation, 14C-leucine and 3H-glucosamine incorporation; DNA synthesis by means of 3H-thymidine incorporation, and apoptosis with an enzyme-linked immunosorbent assay (ELISA) for histone-associated DNA fragments. Cell types were identified by immunocytochemistry.

RESULTS

Ten minutes of EDTA/EGTA treatment released intact crypts and was superior to both the 60-min treatment and enzymatic treatment in terms of viability and nonepithelial cell contamination, respectively. Despite activation of detachment-induced apoptosis, a median 51% of the isolated cells was viable after 24 h of culture and metabolically active as judged by 3H-thymidine, 14C-leucine, and 3H-glucosamine incorporation. Butyrate oxidation followed more complex kinetics (substrate activation) than observed previously in other models. The apparent Km values (medians) were 0.7 mM and 4.5 mM in low and high concentration ranges, respectively.

CONCLUSION

We report a simple method to establish culture of human colonic epithelial cells from endoscopically obtained biopsy specimens, producing sufficient viable cells to perform metabolic studies pertinent to the pathogenesis of IBD and related human disorders.