Summary: Steven Vanhoutvin (born 1979) graduated from his study, Health Sciences at the University of Maastricht, in March 2003. After his graduation he worked as a research assistent for NutriScience, a research and consultancy organization specialized in functional foods. Afther that he worked as a research assistant for WCFS (presently, TI Food and Nutrition), validating a non invasive marker for colon integrity. In januari 2005 he started his PhD in the TI Food and Nutrition project C-012 "Microbe-mediated Gut Metabolism" were he studied the effects of butyrate (a short chain fatty acid) on different parameters of colonic health with special emphasis on validation of in vivo sampling techniques. From March 2010 Steven started as a clinical research associate for the gastroenterology department at the Netherlands Cancer institute (NKI-AVL). He facilitates the logistics of research projects, from protocol writing and protocol submissions to patient recruitment and datamanagement. In June 2010, Steven joined the NKI-young-academics group.
In his spare time, Steven joins and initiates several activities related to outdoor, winter sports and volunteers work.
Specialties: -In vivo sampling in humans -Oro-cecal intubation technique for sampling and delivery -Ussing Chambers for ex vivo measurements in human tissue -Barostat measurements for visceral perception and rectal compliance -short chain fatty acids and gut health
Abstract: Abstract
Objectives: Self-expanding metal stents (SEMS) provide effective palliation in patients with malignant dysphagia. However, although life expectancy is generally limited, reintervention rates due to stent dysfunction are significant. New SEMS are being designed to overcome this drawback. In the present study, we investigated whether results of SEMS placement could be improved with a new SEMS design.
Methods: In a multi-center randomized clinical trial consecutive patients with dysphagia due to a malignant esophageal stenosis were randomized to placement of a conventional Ultraflex® stent or the new Evolution® stent. Patients were followed by scheduled telephone calls at one and three 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. Reintervention rate was 15/40 [38%] for the Ultraflex and 4/39 [10%] for the Evolution stent (p=0.004). Major complications including aspiration pneumonia and bleeding occurred more frequently with the Ultraflex (10/40 [25%]) compared to the Evolution group (3/39 [8%]) (p=0.04). There was no difference in overall survival between the two groups.
Conclusions: The Ultraflex stent and Evolution stent are equally effective in the relief of malignant dysphagia and sealing fistulae. Ultraflex stent is associated with more stent dysfunction and a significantly higher major complication rate. Patients treated with an Evolution stent also needed significantly fewer reinterventions than those treated with an Ultraflex stent. This sets the preference for the Evolution stent over the Ultraflex stent for patients with malignant esophageal disease.
Abstract: 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.
Abstract: BACKGROUND: Barostat methodology is widely used for assessing visceral perception. Different barostat protocols are described with respect to the measurement of rectal compliance and visceral perception. The choice of protocols affects the duration, which is normally 60-90Â min, and accuracy of the procedure. This study aimed to shorten the procedure by using the semi-random distension protocol for both compliance and visceral perception measurement and a correction based on rectal capacity (RC) instead of minimal distension pressure (MDP). METHODS: Twelve irritable bowel syndrome (IBS) patients (7 females) and 11 healthy controls (8 females) underwent a barostat procedure. Compliance was determined during both a staircase distension and a semi-random protocol. Visceral perception data were compared as a function of pressure or relative volume, corrected for MDP or RC, respectively. RESULTS: Compliance measurement using the semi-random protocol instead of the staircase distension protocol resulted in an overestimation in healthy volunteers, but not in IBS patients. The overall conclusion that IBS patients had a lower compliance compared to controls was not different between protocols. Data presentation of the visceral perception scores as a function of corrected volume instead of pressures corrected for MDP did not alter the conclusion that sensation scores in IBS patients were higher as compared to healthy controls. CONCLUSIONS: This study showed that barostat procedures may be shortened by approximately 20Â min, without losing the ability to discriminate between healthy controls and IBS patients. A correction for RC instead of MDP may improve the accuracy of the procedure.
Abstract: Butyrate, produced by colonic fermentation of dietary fibers is often hypothesized to beneficially affect colonic health. This study aims to assess the effects of butyrate on inflammation and oxidative stress in subjects with chronically mildly elevated parameters of inflammation and oxidative stress.
Abstract: 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.
Abstract: 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.
Abstract: 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.
Abstract: 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.
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.
Abstract: 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. AIM: To provide an overview on the present knowledge of the bioactivity of butyrate, emphasizing effects and possible mechanisms of action in relation to human colonic function. METHODS: A PubMed search was performed to select relevant publications using the search terms: 'butyrate, short-chain fatty acid, fibre, colon, inflammation, carcinogenesis, barrier, oxidative stress, permeability and satiety'. RESULTS: Butyrate exerts potent effects on a variety of colonic mucosal functions such as inhibition of inflammation and carcinogenesis, reinforcing various components of the colonic defence barrier and decreasing oxidative stress. In addition, butyrate may promote satiety. Two important mechanisms include the inhibition of nuclear factor kappa B activation and histone deacetylation. However, the observed effects of butyrate largely depend on concentrations and models used and human data are still limited. CONCLUSION: Although most studies point towards beneficial effects of butyrate, more human in vivo studies are needed to contribute to our current understanding of butyrate-mediated effects on colonic function in health and disease.
Abstract: This study attempted to contribute to standardization of blood testing in sport, and to investigate the effect of artificial dilution with saline. In 10 healthy, physically active males and 3 healthy physically active females hemoglobin (Hb), hematocrit (Ht), and % reticulocytes (%retics) were measured at different time points to look for possible fluctuations during day time, while the subjects had regular coffee breaks and lunch. In 7 of the subjects in a separate experiment 500 ml of saline were infused around 8 am and Hb, Ht, and %retics were measured before and every hour thereafter until 7 hours after infusion. In addition Ht was measured on a hematological analyzer as well as with a centrifuge. In a separate experiment the effect of tourniquet duration on Hb and Ht was studied in 9 of the subjects. The results show that Hb, Ht, and %retics are stable from 8 am to 4 pm, but that infusion of 500 ml of saline induces an acute decrease in Hb and Ht within one hour (Hb decreased from 15.2+/-0.9 g/dl to 14.5+/-1.0 g/dl, and Ht from 45.6+/-2.8 % to 44.0+/-2.5 %). The decline in Hb and Ht was maintained during the 7-hour observation period. Ht values of the same samples measured with a hematological analyzer and a centrifuge were not different. Application of the tourniquet did significantly affect Hb and Ht values only from two minutes, and thereafter Hb and Ht remained stable during the rest of the 5-minute tourniquet. With blood testing in sport these results have to be taken into consideration.
Abstract: Introduction: Rectal hypersensitivity is a hallmark of a subgroup of patients with irritable
bowel syndrome (IBS). In these patients symptoms are often provoked by meal ingestion
and enhanced colorectal sensitivity has been demonstrated after duodenal lipid administration.
Aim of the present study was to investigate in a large cohort of IBS patients whether
rectal (hyper)sensitivity is more pronounced after meal ingestion. Methods: Sixty five IBS
patients were included according to the Rome III criteria (20 men, mean age 39 years, range
18-65 years) and underwent a rectal barostat measurement 1) in fasting state and 2) after
a mixed liquid meal (370 kcal; 215 mL; 19.3 g fat). Rectal barostat recording was performed
according to a standard pressure distention protocol (intermittent random staircase procedure,
pressure range from 0 to 50 mmHg above MDP, stepwise increase by 3 mmHg). During
the procedure subjects scored pain, discomfort and urge using a visual analogue scale (VAS).
According to previous data from our group obtained in healthy controls, a score >10 mm
on the VAS-score for pain at a pressure ≤23 mmHg indicates visceral hypersensitivity. Pain
threshold is defined as the first pressure level at which the VAS-score is >10 mm. Results:
Under fasting conditions, 37 (57%) patients were found to be hypersensitive for pain. After
meal ingestion this percentage increased to 72% (47 patients). When separating IBS patients
in a normosensitive (n=28) and hypersensitive group (n=37), pain thresholds were significant
lower after the meal in normosensitive patients (fasting vs. postprandial threshold: 35.4 ±
2.2 vs. 29.5 ± 3.0 mmHg, p=0.01) but not in hypersensitive patients (8.0 ± 1.1 vs. 8.6 ±
1.4 mmHg, p=NS). Ten out of 28 (35.7%) normosensitive patients became hypersensitive
after the meal (p<0.01). In normosensitive patients, VAS-scores for pain were significantly
higher postprandial vs. fasting at pressure steps from 5-29 mmHg. In hypersensitive patients
(scored in fasting state) VAS-scores for pain were similar under fasting and postprandial
conditions. In the whole IBS group, early termination of the test procedure due to intolerable
symptoms was significantly more frequent under postprandial vs. fasting conditions at
pressure steps from 29-41 mmHg (at 29 mmHg pressure: 38.5% vs. 20%, p=0.03). Conclusions:
Assessment of rectal sensitivity by barostat procedure under postprandial conditions
results in a higher percentage of IBS patients classified as hypersensitive. These data support
the strategy to evaluate visceral perception in the fed state.
Abstract: Introduction: When incubated with lactose in vitro, the fecal microbiota from symptomatic lactose-
maldigesters produced more short-chain fatty acids (SCFA) at a faster rate than that from asymptomatic
maldigesters. In vivo studies are needed to verify the role of colonic fermentation in lactose intolerance.
The objective of the present study was to develop methods to study colonic fermentation of lactose in
vivo.
Methods: A multilumen feeding catheter was introduced in two healthy adults (male, Caucasian).
Progression of the catheter was aided by inflating the distal balloon and monitored by fluoroscopy. When
the catheter was located in the terminal ileum, an isotonic solution containing 500 mg of U-13C-lactose,
19.5 g of unlabelled lactose and 200 mg of 2H3-acetate was infused through the catheter at a rate of 4.5
ml/min for 45 min. Breath and peripheral blood samples were collected at a 15-min interval for 4 h.
Plasma 13C-acetate and 13C-glucose, and breath 13C-CO2 were analyzed with Gas Chromatography (GC)-
Combustion-Isotope Ratio Mass Spectrometry (MS), plasma 2H3-acetate with GC/ MS, and breath hydrogen with GC. The ratios of 13C/2H3-acetate in plasma were calculated as reflections of acetate production from colonic fermentation of lactose.
Results: Breath hydrogen and 13C-CO2 and plasma 13C/2H3-acetate increased synchronously, and plasma 13C-glucose increased slightly in subject A. These indicate that the infused lactose was fermented in the colon. In subject B, the increase in breath hydrogen lagged behind that in breath 13C-CO2.
Plasma 13C-glucose increased sharply. Increases in breath hydrogen and plasma13C/2H3-acetate were lower in subjectB than in subject A.
These suggest that in subject B, the infused lactose was partially digested in the small intestine and partially fermented in the colon.
Conclusions: The applied approach provides a promising methodology to study colonic fermentation of
lactose and other carbohydrates in humans. Further development of the methodology include, e.g.
inclusion of electromagnetic imaging devices to improve monitoring of progression of the catheter, and
sampling from the intestine via the catheter.
Abstract: Introduction: The colonic mucus layer is an important dynamic component of the epithelial
barrier, which can be affected by dietary intake and intestinal disorders. The mucus layer
contains mucin glycoproteins, intestinal trefoil factor (ITF) and many other compounds
secreted by the intestinal epithelium, such as secretory IgA (sIgA). To determine changes
in the human mucus layer, standardized In Vivo sampling is required. In this study, mucus was
collected with a cytology brush during sigmoidoscopy in order to assess the reproducibility of
the sampling technique and the inter-individual variability of mucus composition. In addition,
attention was paid to standardization of mucus sampling and feasibility of proteomic analysis.
Method: From 11 healthy volunteers triplicate colonic mucus samples were collected from
the same region during sigmoidoscopy using cytology brushes. The total mucin concentration
was determined by measuring the amount of liberated oligosaccharide side chains and
monosaccharides (galactosamine, glucosamine, fucose, galactose). Also sIgA and total protein
concentration were determined and proteomic analysis was performed using SELDI-TOF
MS. Results: The amount of oligosaccharide side chains correlated significantly with both
the galactosamine concentration (R2= 0.91; p<0.001) and the sum of monosaccharides (R2=
0.97; p<0.001). A significant correlation was also found between total protein concentration
and the amount of oligosaccharide side chains (R2= 0.12; p<0.05), but the correlation between
the galactosamine concentration and total protein did not reach statistical significance (R2=
0.11; p=0.06). Mean triplicate values of sIgA ranged from 0.16 to 1.81 gram sIgA/mmol
oligosaccharide side chains. The mean variation coefficient of triplicate samples per subject
was 41.3 ±17.9%. Duplicate proteomic analyses of one mucus sample resulted in highly
reproducible profiles. Using a hierarchical cluster analysis, it was shown that all three replicate
samples clustered in five out of 11 subjects, and two out of three replicate samples clustered
in another five different subjects. Conclusion: The liberated oligosaccharide side chain
concentration can be used to standardize the amount of mucus obtained with cytology
brushes during endoscopy. Secretory IgA concentrations can be measured in the mucus
samples. Proteomic analysis of intestinal mucus is feasible and yields information on many
proteins. The cluster analysis showed that subject specific profiles can be obtained. However,
the differences between some triplicates indicate that analyzing only one mucus sample can
result in an observation bias.
Abstract: Introduction/aims: In Vivo research on the human colon gives rise to challenges caused by
the limited accessibility of the human colon for delivering drugs or for sampling. A variety
of tools are nowadays available for colon delivery in scientific intervention studies such as
catheters and remote controlled capsules. However, these are expensive and/or not userfriendly.
Alternatively, capsules can be used after applying a pressure, pH or time sensitive
or microbially degradable coating. However, the appropriate equipment and training for
coating is often lacking. Moreover, as only small batches are required, they cannot be
produced on industrial scale. Huyghebaert et al. described a new protocol for the production
of ready-to-use enteric coated capsule, which can be easily filled prior to oral consumption(
Huyghebaert et al., Eur. J. Pharm. Biopharm. 21 (2004) 617-623). The aim of this
study was to evaluate and validate In Vivo these capsules, coated with the pH sensitive
polymer Eudragit® FS30D, which dissolves from pH 7.4 for delivering a substance in
the terminal ileum or proximal colon. Materials and methods: HPMC capsules size 00
(Capsugel,VCaps) were coated with Eudragit® FS30D (Röhm) and filled with radio labelled
Indium (111In, 3.7 MBq). Next, they were administered to seven healthy volunteers (age 30
± 15y) (16 capsules in total). Gamma camera recordings were performed with two-hour
intervals starting from the moment of administration (8:00 AM) until 5:00 PM. Subjects
were in a fasted state up to five hours after administration of the capsules. From that moment
subjects were allowed to eat and drink ad libitum. The final recording for the evaluation
of the capsule opening was performed 24 hours after administration. For comparison of the
consecutive recordings a technetium marker was placed on the volunteers umbilicus. Results
and discussion: From the 16 capsules that were tested, three capsules opened distal to the
target area (transverse and/or descending colon). The remaining 13 capsules opened in the
target area (11 in terminal ileum and 2 in the proximal ascending colon). None of the
capsules opened proximal to the target area. The three capsules with the deviating opening
locations were all in the same volunteer. In conclusion this study has shown that the readyto-
use enteric-coated capsules provide a reliable, cheap and easy tool for terminal ileum/
proximal colon delivery of a broad range of substances (substrates and/or drugs) for
research purposes.
Abstract: Introduction: Butyrate, produced by colonic microbial fermentation, is the prime energy
substrate for colonocytes. In addition, it has an anti-carcinogenic potential and is suggested
to inhibit inflammation. Cancer and inflammation are associated with oxidative stress to the
mucosa. In Vitro studies showed that butyrate increased glutathione-S-transferase activity
and reduced H2O2-induced DNA damage, suggesting a role for butyrate on oxidative stress.
Therefore, the effect of butyrate on several parameters of oxidative damage and anti-oxidant
defense were studied in the colon of healthy human volunteers. Methods: A randomized,
double blind, placebo controlled, crossover study was performed in 16 healthy volunteers
(age: 24(16-63)). Treatments consisted of daily rectal administration of a 60 ml enema
containing 100 mM sodium-butyrate or placebo (saline) for two weeks with a two weeks
wash-out period. After each treatment, biopsies were taken from the sigmoid colon. Nonprotein
trolox equivalent antioxidant capacity (TEAC), uric acid (UA), reduced glutathione
(GSH) and oxidized glutathione (GSSG) levels and the enzyme activity of glutathione-Stransferase
(GST) were determined. Malondialdehyde (MDA) was measured as a parameter
of lipid peroxidation and the GSH/GSSG ratio was calculated as a marker of oxidative stress.
Results: Butyrate resulted in a higher (p<0.05) amount of GSH (26.5 (20.4-35.2) vs. 22.9
(12.0-31.5) nmol/mg protein), and in a significantly lower (p<0.01) amount of UA (2.4
(1.6-3.7) vs. 3.1 (1.9-3.3) nmol/mg protein) compared to placebo. Between butyrate and
placebo no statistical differences were found in TEAC (136.2 (116.2-207.6) vs. 137.2 (112.6-
210.7) nmol trolox Eq/mg protein), GST (0.3 (0.4-0.4) vs. 0.3 (0.2-0.5) U/mg protein),
GSSG (0.3 (0.1-2.7) vs. 0.4 (0.2-2.1) nmol/mg protein), MDA (0.8 (0.4-1.4) vs. 1.1 (0.7-
2.2) nmol/mg protein) and GSH/GSSG ratio (90.8 (7.6-333.9) vs. 70.1 (8.1-127.0)). In
addition, a significant positive correlation was found between MDA and GSSG (R2=0.35,
p<0.01), and a significant negative correlation between MDA and the GSH/GSSG ratio (R2=
0.27, p<0.01). Conclusion: Butyrate enhances the anti-oxidant defense capacity as indicated
by the increase in the amount of GSH. Also a decrease in the amounts of UA was found,
which might be due to an inhibitory effect of butyrate on xanthine oxidase, the enzyme
that catalyzes the production of UA. In addition, the correlations between the MDA and
the GSH/GSSG ratio and GSSG support the validity of these assessments in colonic biopsy
samples from healthy individuals.
