Steven Vanhoutvin

Review article : the role of butyrate on colonic function

Background  Butyrate, a short‐chain fatty acid, is a main end‐product of intestinal microbial fermentation of mainly dietary fibre. Butyrate is an important energy source for intestinal epithelial cells and plays a role in the maintenance of colonic homeostasis.

Butyrate modulates oxidative stress in the colonic mucosa of healthy humans

BACKGROUND & AIMS Butyrate, a short-chain fatty acid produced by colonic microbial fermentation of undigested carbohydrates, has been implicated in the maintenance of colonic health. This study evaluates whether butyrate plays a role in oxidative stress in the healthy colonic mucosa. METHODS A randomized, double blind, cross-over study with 16 healthy volunteers was performed. Treatments consisted of daily rectal administration of a 60 ml enema containing 100 mM sodium butyrate or saline for 2 weeks. After each treatment, a blood sample was taken and mucosal biopsies were obtained from the sigmoid colon. In biopsies, the trolox equivalent antioxidant capacity, activity of glutathione-S-transferase, concentration of uric acid, glutathione (GSH), glutathione disulfide and malondialdehyde, and expression of genes involved in GSH and uric acid metabolism was determined. Secondary outcome parameters were CRP, calprotectin and intestinal fatty acid binding protein in plasma and histological inflammatory scores. RESULTS Butyrate treatment resulted in significantly higher GSH (p<0.05) and lower uric acid (p<0.01) concentrations compared to placebo. Changes in GSH and uric acid were accompanied by increased and decreased expression, respectively, of their rate limiting enzymes determined by RT-PCR. No significant differences were found in other parameters. CONCLUSIONS This study demonstrated that butyrate is able to beneficially affect oxidative stress in the healthy human colon.

Butyrate-induced transcriptional changes in human colonic mucosa.

Background Fermentation of dietary fiber in the colon results in the production of short chain fatty acids (mainly propionate, butyrate and acetate). Butyrate modulates a wide range of processes, but its mechanism of action is mostly unknown. This study aimed to determine the effects of butyrate on the transcriptional regulation of human colonic mucosa in vivo. Methodology/Principal Findings Five hundred genes were found to be differentially expressed after a two week daily butyrate administration with enemas. Pathway analysis showed that the butyrate intervention mainly resulted in an increased transcriptional regulation of the pathways representing fatty acid oxidation, electron transport chain and oxidative stress. In addition, several genes associated with epithelial integrity and apoptosis, were found to be differentially expressed after the butyrate intervention. Conclusions/Significance Colonic administration of butyrate in concentrations that can be achieved by consumption of a high-fiber diet enhances the maintenance of colonic homeostasis in healthy subjects, by regulating fatty acid metabolism, electron transport and oxidative stress pathways on the transcriptional level and provide for the first time, detailed molecular insight in the transcriptional response of gut mucosa to butyrate.

The effects of butyrate enemas on visceral perception in healthy volunteers

Abstract  Fermentation of dietary fibres by colonic microbes leads to the production of short chain fatty acids (mainly propionate, butyrate and acetate), which are utilized by the colonic mucosa. Previous studies showed positive effects of butyrate on parameters of oxidative stress, inflammation and apoptosis. Recent studies in rats, however, showed that butyrate increased visceral sensitivity. The aim of this study was to determine the effects of physiologically relevant concentrations of butyrate on visceral perception in healthy human subjects. Eleven healthy volunteers participated in this randomized double‐blind, placebo controlled cross‐over study. The study consisted of three periods of 1 week each, in which the volunteers daily self‐administered rectal enemas containing 100, 50 mmol L−1 butyrate, or placebo (saline) prior to sleeping. A rectal barostat measurement was performed at the start and the end of each test period for the measurement of pain, urge and discomfort. Butyrate treatment resulted in a dose‐dependent reduction of pain, urge and discomfort throughout the entire pressure range of the protocol. At a pressure of 4 mmHg, 50 and 100 mmol L−1 butyrate concentrations resulted in a 23.9% and 42.1% reduction of pain scores, respectively, and the discomfort scores decreased by 44.2% and 69.0% respectively. At a pressure of 67 mmHg, 50 and 100 mmol L−1 of butyrate decreased the pain scores by 23.8% and 42%, respectively, and discomfort scores 1.9% and 5.2% respectively. Colonic administration of butyrate, at physiologically relevant concentrations, dose‐dependently decreases visceral sensitivity in healthy volunteers.

Comparison of 2 expandable stents for malignant esophageal disease: a randomized controlled trial

BACKGROUND Self-expanding metal stents (SEMSs) provide effective palliation in patients with malignant dysphagia. However, although life expectancy is generally limited, reintervention rates because of stent dysfunction are significant. New SEMSs are being designed to overcome this drawback. OBJECTIVES To investigate whether the results of SEMS placement could be improved with a new SEMS design. PATIENTS Consecutive patients with dysphagia or leakage caused by malignant esophageal disease. METHODS In a multicenter randomized clinical trial, consecutive patients with dysphagia or leakage because of malignant esophageal disease were randomized to placement of a conventional stent or the new stent. Patients were followed up by scheduled telephone calls 1 and 3 months after SEMS insertion. RESULTS A total of 80 patients (73% male; median age, 67 years [range, 40-92 years]) were included. One patient refused follow-up. Technical success was 100% in both groups. The reintervention rate was 15/40 (38%) for the conventional stent and 4/39 (10%) for the new stent (P = .004). Major complications, including aspiration pneumonia and bleeding, occurred more frequently with the conventional stent (10/40, 25%) than with the new stent (3/39, 8%, P = .04). There was no difference in overall survival between the 2 groups. LIMITATIONS Inclusion of patients with a perforation or fistula. CONCLUSIONS The conventional stent and the new stent were equally effective in the relief of malignant dysphagia and sealing fistulae. The conventional stent was associated with more stent dysfunction and a significantly higher rate of major complications. Patients treated with the new stent also needed significantly fewer reinterventions than did those treated with a conventional stent. This sets the preference for the new stent over the conventional stent for patients with malignant esophageal disease.

Does meal ingestion enhance sensitivity of visceroperception assessment in irritable bowel syndrome

Background  Visceral hypersensitivity is frequently observed in irritable bowel syndrome (IBS). Previous studies have shown that administration of a meal can aggravate symptoms or increase visceroperception in IBS patients. We investigated whether meal ingestion could increase the sensitivity of the barostat procedure for the detection of visceral hypersensitivity in IBS patients.

Butyrate enemas do not affect human colonic MUC2 and TFF3 expression

Introduction The colonic mucus layer plays an important role in the protection of the intestinal epithelium and mainly consists of mucin glycoproteins (primarily MUC2 in the colon) trefoil factor 3 (TFF3) and secretory IgA. Butyrate is a major end product of fermentation of dietary fibres and is associated with beneficial effects on colonic health. Earlier in-vitro and animal studies showed that butyrate modulates MUC2 and TFF3 expression and mucin secretion, although data from human studies are not yet available. Methods Sixteen healthy volunteers and 35 ulcerative colitis (UC) patients in clinical remission self-administered a 60 ml rectal enema containing 100 mmol/l butyrate or placebo once daily for 2 and 3 weeks, respectively. After each treatment, biopsies were taken from the distal sigmoid for quantitative RT-PCR and immunohistochemical analysis of MUC2 and TFF3. In addition, mucosal sections were stained with high iron diamine-alcian blue to distinguish between sialomucins and sulphomucins. To analyse total mucin secretion and secretory IgA concentrations, 24 h faeces were collected during the day before the endoscopic examination. Results The butyrate intervention did not significantly modulate the expression of MUC2 (fold change: 1.04 and 1.05 in healthy volunteers and ulcerative colitis patients, respectively) or TFF3 (fold change: 0.91 and 0.94 in healthy volunteers and UC patients, respectively). Furthermore, the percentage of sialomucins, mucus secretion and secretory IgA concentrations were not affected by the butyrate intervention in both the groups. Conclusion Butyrate exposure in healthy volunteers and UC patients in remission did not affect the measured parameters of the colonic mucus layer.

Analyses of human colonic mucus obtained by an in vivo sampling technique.

BACKGROUND The mucus layer is an important dynamic component of the epithelial barrier. It contains mucin glycoproteins and other compounds secreted by the intestinal epithelium, such as secretory IgA. However, a standardized in vivo sampling technique of mucus in humans is not yet available. AIM To assess the validity and feasibility of mucin and protein determinations in human colonic mucus collected under physiological conditions. SUBJECTS AND METHODS Triplicate colonic mucus samples were collected in 11 healthy volunteers using cytology brushes during sigmoidoscopy. As an indication of the quantity of collected mucus, total protein and mucin concentrations were determined by measuring oligosaccharide equivalents and monosaccharides. Also secretory IgA and sialic acid concentrations were determined and proteomic analysis was performed using surface enhanced laser desorption/ionization-time of flight-mass spectrometry. RESULTS Mean values of secretory IgA and sialic acid corrected for the amount of mucus ranged from 0.16 to 1.81 g secretory IgA/mmol oligosaccharide equivalents and from 12.6 to 48.6g sialic acid/mmol oligosaccharide equivalents. Proteomic analysis of mucus is feasible and cluster analysis showed subject specific profiles. CONCLUSION Using cytology brushes, human colonic mucus can be sampled and under physiological conditions. These samples could give information on the composition and quality of the mucus layer.