Mucosal DNA methylome alteration in Crohn's disease: surgical and non-surgical groups.

Crohn's disease (CD) is characterized as a chronic, relapsing, and progressive disorder with a complex etiology involving interactions between host, microbiome, and the external environment. Genome wide association studies (GWAS) suggest several genetic variations in the diseased individuals but that explains only a small proportion of susceptibility to disease conditions. This indicates the possible role of epigenome which links environmental factors to the genetic variation in the disease etiology. The current study is focused on the DNA methylome evolution with disease progression. We performed Reduced Representation Bisulfite Sequencing (RRBS) to analyze differential DNA methylation in the diseased and healthy mucosal tissues of 2 different groups of CD patients: non-surgical and surgical, categorized based on the severity of disease and standard of care needed. Patients in both groups have unique DNA methylation signature compared to the healthy tissue. After removing single nucleotide polymorphisms (SNPs), 1,671 differentially methylated loci were found in the non-surgical and 3,334 in the surgical group of which only 206 were found overlapping in both groups. Furthermore, differential DNA methylation was noted in some of the GWAS associated genes implicated in CD. Also, functional enrichment analysis showed high representation of several key pathways where differential methylations were observed, and these can be implicated in CD pathogenesis. We identified specific DNA methylation patterns in the mucosal DNA of surgical and non-surgical CD patients which indicates evolution of the methylome as the disease progresses from initial to the advance stage. These unique patterns can be used as DNA methylation signatures to identify different stages of the disease.

Abundance and diversity of mucosa-associated hydrogenotrophic microbes in the healthy human colon.

Hydrogenotrophic microbiota have a significant impact on colonic health; however, little is known about their diversity and ecology in situ. Here, molecular-based methods and multivariate analyses were used to examine the abundance and diversity of mucosa-associated hydrogenotrophic microbes in 90 biopsies collected from right colon, left colon and rectum of 25 healthy subjects. Functional genes of all three hydrogenotrophic groups were detected in at least one colonic region of all subjects. Methanogenic archaea (MA) constituted approximately one half of the hydrogenotrophic microbiota in each colonic region. Sulfate-reducing bacteria (SRB) were more abundant than acetogens in right colon, while acetogens were more abundant than SRB in left colon and rectum. MA genotypes exhibited low diversity, whereas SRB genotypes were diverse and generally similar across the three regions within subject but significantly variable among subjects. Multivariate cluster analysis defined subject-specific patterns for the diversity of SRB genotypes; however, neither subject- nor region-specific clusters were observed for the abundance of hydrogenotrophic functional genes. Sequence analyses of functional gene clones revealed that mucosa-associated SRB were phylogenetically related to Desulfovibrio piger, Desulfovibrio desulfuricans and Bilophila wadsworthia; whereas MA were related to Methanobrevibacter spp., Mb. smithii and the order Methanomicrobiales. Together these data demonstrate for the first time that the human colonic mucosa is persistently colonized by all three groups of hydrogenotrophic microbes, which exhibit segmental and interindividual variation in abundance and diversity.

Lower gastrointestinal bleeding in chronic hemodialysis patients.

Gastrointestinal (GI) bleeding is more common in patients with chronic kidney disease and is associated with higher mortality than in the general population. Blood losses in this patient population can be quite severe at times and it is important to differentiate anemia of chronic diseases from anemia due to GI bleeding. We review the literature on common causes of lower gastrointestinal bleeding (LGI) in chronic kidney disease (CKD) and end-stage renal disease (ESRD) patients. We suggest an approach to diagnosis and management of this problem.

Pyrosequencing-based analysis of the mucosal microbiota in healthy individuals reveals ubiquitous bacterial groups and micro-heterogeneity.

This study used 16S rRNA-based pyrosequencing to examine the microbial community that is closely associated with the colonic mucosa of five healthy individuals. Spatial heterogeneity in microbiota was measured at right colon, left colon and rectum, and between biopsy duplicates spaced 1 cm apart. The data demonstrate that mucosal-associated microbiota is comprised of Firmicutes (50.9% ± 21.3%), Bacteroidetes (40.2% ± 23.8%) and Proteobacteria (8.6%± 4.7%), and that interindividual differences were apparent. Among the genera, Bacteroides, Leuconostoc and Weissella were present at high abundance (4.6% to 41.2%) in more than 90% of the studied biopsy samples. Lactococcus, Streptococcus, Acidovorax, Acinetobacter, Blautia, Faecalibacterium, Veillonella, and several unclassified bacterial groups were also ubiquitously present at an abundance <7.0% of total microbial community. With the exception of one individual, the mucosal-associated microbiota was relatively homogeneous along the colon (average 61% Bray-Curtis similarity). However, micro-heterogeneity was observed in biopsy duplicates within defined colonic sites for three of the individuals. A weak but significant Mantel correlation of 0.13 was observed between the abundance of acidomucins and mucosal-associated microbiota (P-value = 0.04), indicating that the localized biochemical differences may contribute in part to the micro-heterogeneity. This study provided a detailed insight to the baseline mucosal microbiota along the colon, and revealed the existence of micro-heterogeneity within defined colonic sites for certain individuals.

On the relationship between sialomucin and sulfomucin expression and hydrogenotrophic microbes in the human colonic mucosa.

The colonic mucus layer is comprised primarily of acidomucins, which provide viscous properties and can be broadly classified into sialomucins or sulfomucins based on the presence of terminating sialic acid or sulfate groups. Differences in acidomucin chemotypes have been observed in diseases such as colorectal cancer and inflammatory bowel disease, and variation in sialo- and sulfomucin content may influence microbial colonization. For example, sulfate derived from sulfomucin degradation may promote the colonization of sulfate-reducing bacteria (SRB), which through sulfate respiration generate the genotoxic gas hydrogen sulfide. Here, paired biopsies from right colon, left colon, and rectum of 20 subjects undergoing routine screening colonoscopies were collected to enable parallel histochemical and microbiological studies. Goblet cell sialo- and sulfomucins in each biopsy were distinguished histochemically and quantified. Quantitative PCR and multivariate analyses were used to examine the abundance of hydrogenotrophic microbial groups and SRB genera relative to acidomucin profiles. Regional variation was observed in sialomucins and sulfomucins with the greatest abundance of each found in the rectum. Mucin composition did not appear to influence the abundance of SRB or other hydrogenotrophic microbiota but correlated with the composition of different SRB genera. A higher sulfomucin proportion correlated with higher quantities of Desulfobacter, Desulfobulbus and Desulfotomaculum, relative to the predominant Desulfovibrio genus. Thus, acidomucin composition may influence bacterial sulfate respiration in the human colon, which may in turn impact mucosal homeostasis. These results stress the need to consider mucus characteristics in the context of studies of the microbiome that target intestinal diseases.

Microbial DNA extraction from intestinal biopsies is improved by avoiding mechanical cell disruption.

Currently, standard protocols for microbial DNA extraction from intestinal tissues do not exist. We assessed the efficiency of a commercial kit with and without mechanical disruption. Better quality DNA was obtained without mechanical disruption. Thus, it appears that bead-beating is not required for efficient microbial DNA extraction from intestinal biopsies.

An uncommon etiology of cholestatic jaundice: intraductal mucinous papillary tumor of the bile duct.

Intraductal papillary mucinous tumors (IPMT) are known to occur in the pancreas but rarely can occur in the bile ducts. These tumors secrete mucin that may form mucous plugs resulting in biliary stasis, biliary duct obstruction and dilation. We report a case of IPMT of the biliary tract that presented with fatigue and a persistent cholestatic pattern of liver enzyme elevation and required a high index of suspicion to make the final diagnosis. The early recognition and treatment of these tumors is important, as unlike other bile duct tumors, these have a good prognosis.

Tacrolimus for the treatment of fistulas in patients with Crohn's disease: a randomized, placebo-controlled trial.

BACKGROUND & AIMS: This study determined the effectiveness of tacrolimus for the treatment of Crohn's disease fistulas. METHODS: The study was a randomized, double-blind, placebo-controlled, multicenter clinical trial. Forty-eight patients with Crohn's disease and draining perianal or enterocutaneous fistulas were randomized to treatment with oral tacrolimus 0.2 mg. kg(-1). day(-1) or placebo for 10 weeks. The primary outcome measure was fistula improvement as defined by closure of >/=50% of particular fistulas that were draining at baseline and maintenance of that closure for at least 4 weeks. A secondary outcome measure was fistula remission as defined by closure of all fistulas and maintenance of that closure for at least 4 weeks. RESULTS: Forty-three percent of tacrolimus-treated patients had fistula improvement compared with 8% of placebo-treated patients (P = 0.004). Ten percent of tacrolimus-treated patients had fistula remission compared with 8% of placebo-treated patients (P = 0.86). Adverse events significantly associated with tacrolimus, including headache, increased serum creatinine level, insomnia, leg cramps, paresthesias, and tremor, were managed with dose reduction. CONCLUSIONS: Oral tacrolimus 0.2 mg. kg(-1). day(-1) is effective for fistula improvement, but not fistula remission, in patients with perianal Crohn's disease. Adverse events associated with tacrolimus can be managed by dose reduction. Lower doses of tacrolimus should be evaluated.