Venkata B. Pokkunuri

Intestinal Methanobrevibacter smithii but not total bacteria is related to diet-induced weight gain in rats.

It is increasingly understood that gastrointestinal (GI) methanogens, including Methanobrevibacter smithii, influence host metabolism.

Role of Cytolethal Distending Toxin in Altered Stool Form and Bowel Phenotypes in a Rat Model of Post-infectious Irritable Bowel Syndrome

Background/Aims Campylobacter jejuni infection is a leading cause of acute gastroenteritis, which is a trigger for post-infectious irritable bowel syndrome (PI-IBS). Cytolethal distending toxin (CDT) is expressed by enteric pathogens that cause PI-IBS. We used a rat model of PI-IBS to investigate the role of CDT in long-term altered stool form and bowel phenotypes. Methods Adult Sprague-Dawley rats were gavaged with wildtype C. jejuni (C+), a C. jejuni cdtB knockout (CDT-) or saline vehicle (controls). Four months after gavage, stool from 3 consecutive days was assessed for stool form and percent wet weight. Rectal tissue was analyzed for intraepithelial lymphocytes, and small intestinal tissue was stained with anti-c-kit for deep muscular plexus interstitial cells of Cajal (DMP-ICC). Results All 3 groups showed similar colonization and clearance parameters. Average 3-day stool dry weights were similar in all 3 groups, but day-to-day variability in stool form and stool dry weight were significantly different in the C+ group vs both controls (P < 0.01) and the CDT- roup (P < 0.01), but were not different in the CDT- vs controls. Similarly, rectal lymphocytes were significantly higher after C. jejuni (C+) infection vs both controls (P < 0.01) and CDT-exposed rats (P < 0.05). The counts in the latter 2 groups were not significantly different. Finally, c-kit staining revealed that DMP-ICC were reduced only in rats exposed to wildtype C. jejuni. Conclusions In this rat model of PI-IBS, CDT appears to play a role in the development of chronic altered bowel patterns, mild chronic rectal inflammation and reduction in DMP-ICC.

Gender distribution in irritable bowel syndrome is proportional to the severity of constipation relative to diarrhea.

BACKGROUND A significant gender disparity has been observed in individuals with irritable bowel syndrome (IBS), with females outnumbering males, especially in constipation-predominant IBS (C-IBS). However, this observation is based on Rome criteria categorization and does not take into account the severity of constipation or diarrhea. OBJECTIVE In a large prospective data set, gender differences across the severity of constipation and diarrhea were examined in patients with IBS. METHODS Consecutive adult patients with Rome I positive IBS who were referred to a tertiary care medical center (Cedars-Sinai Medical Center, Los Angeles, California) in 1999-2003 were given a questionnaire. The questionnaire asked subjects to rate their constipation and diarrhea according to perceived severity using a scale from 0 (none) to 5 (very severe). C-IBS was determined to be present if the severity of constipation was greater than the severity of diarrhea (sevC > sevD). If sevD > sevC, subjects were considered to have diarrhea-predominant IBS (D-IBS). To further categorize their symptoms, subjects were then grouped by the difference between the severity of constipation and diarrhea, creating a range of values from -5 to +5. For each of these 11 constipation/diarrhea severity values, the female:male ratio was determined. The severity of constipation to diarrhea was compared by Spearman rank correlation. RESULTS A total of 429 subjects with IBS (325 women: mean [SD] age, 42.5 [0.8] years; 104 men: mean age, 42.2 [1.7] years) completed the questionnaire. Constipation occurred more frequently in women (79.7%) compared with men (61.5%) (odds ratio [OR] = 2.49; 95% CI, 1.55-4.02). The prevalence of diarrhea was similar between the sexes. Whereas C-IBS was more common in women (31.8%) than in men (26.0%) (OR = 2.03; 95% CI, 1.24-3.30), D-IBS was more prevalent in men (62.5%) than in women (36.3%) (OR = 2.39; 95% CI, 1.53-3.75). When the female:male ratio was evaluated across the 11 severity score categories of constipation and diarrhea, the greater the sevC - sevD score, the higher the proportion of women (R = 0.80; P = 0.003). CONCLUSION In this study of patients with IBS, the observation of the association of constipation and gender in IBS is extended to indicate that the female:male ratio significantly increases according to the severity of constipation relative to the severity of diarrhea.

Effect of repeated Campylobacter jejuni infection on gut flora and mucosal defense in a rat model of post infectious functional and microbial bowel changes

Campylobacter jejuni infection is a leading cause of gastroenteritis and post infectious irritable bowel syndrome (PI‐IBS). Unanswered questions include the role of cytokines, effects on gut flora, and why IBS is not more prevalent in countries with higher gastroenteritis rates. Therefore, we determined the effects of early and repeat C. jejuni infections on post infectious phenotypes, gut flora, and cytokine levels in a rat model of functional bowel and microbial changes.

Su2020 Autoimmunity to Vinculin in Humans May Be Important in the Pathophysiology of IBS

G A A b st ra ct s tissue myeloperoxidase (MPO) activity and qPCR quantification of TLR4 gene expression, as markers for immune cell infiltration and host-gut flora interactions, respectively (6 samples/ mouse). Results: Our studies showed a strong, yet conditional, correlation between stereomicroscopy and histology, and treatment effect. For ileitis, there was a strong exponential correlation (y=6.7216*e0.1889x; R2=0.8919), which was explained by a plateau effect of histological scores between (10-12/18) as the severity of 3D-steromicroscopic abnormalities in SAMP increased. Such correlation differed from that of other studies with ileitis-free mice (R2<0.3), indicating that histological scores need to be validated or adjusted for a diverse categories of intestinal pathologies. For colitis, the correlation between stereomicroscopy and histology was strong as it correlated with the high histological scores observed in DSScolitis, and intermediate or low after dexamethasone or placebo treatments (y=8.03x+13.369; R2=0.908). The variability observed between the two methods, was explained by nonrandom segmental distribution of 3-D abnormal pathologies, not captured by the integer histological scoring system. Of immunological and statistical relevance, the ability for MPO and TLR4 to differentiate the groups was significantly enhanced when the analysis was stratified by the degree of 3-Dmucosal abnormalities (p<0.01). Conclusion: Stereomicroscopy is a very cost effective visualization tool that can be used as a complementary research and diagnostic tool in studies of therapeutic and intestinal pathology.

Tu1990 Expression of Mucosal Defense Mediators and Cytokines are Dependent on the Number of Exposures to C. Jejuni in a Rat Model of Post-Infectious IBS

Background and Aims: The question was raised, whether the herbal medicine STW 5 acts on contractions elicited after electrical field stimulation (EFS) and on intestinal slow wave activity in the small intestine of mice, in a new type of an In Vitro model of trinitrobenzene sulfonic acid (TNBS) triggered inflammation. Methods: In the organ bath, segments of distal ileum of Balb/C mice were used for registration of spontaneous and EFS stimulated contractions. In the electrophysiological studies, segments of distal ileum (with minimum 50% increase in EFS induced contraction after 90 min of intraluminal TNBS application) were used for intracellular recordings, after removal of mucosa and submucosa. STW 5 was tested in a dilution of 1:100 in an organ bath and compared to vehicle (31% ethanol solution diluted 1:100), following intraluminal application of TNBS (0,01M solution, 3 cm H2O pressure) or Krebs solution for 90 min. Results: TNBS induced a significant time dependent enhancement of contractility (90 min: 155.1 ± 6.5% vs. control, n=15). STW 5 applied into the organ bath reduced basal tone (-22.1±2.1% TNBS vs. -17.7±1.5% no TNBS n=15), EFS induced contractility (-61.3±3.5% TNBS vs. -67.6±3.7% no TNBS n=10) and significantly prevented TNBS induced increase of EFS induced contractions (97.4 ± 4.1% STW5+TNBS vs. TNBS/no STW 5 155.1 ± 6.5% n=10). Electrophysiological parameters were not significantly influenced in TNBS pretreated or control preparations. No significant effects on intracellular recordings of resting membrane potential, slow wave amplitude and frequency were observed making neuronal and muscular effects unlikely. Summary and Conclusions: Stimulation with TNBS results in inflammation induced changes of motility, which are reversed or prevented by STW 5. The underlying mechanisms may be of relevance in the treatment of functional gastrointestinal and subclinical inflammatory gastrointestinal diseases.