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PubMed2001

Expression of p21Waf1/Cip1 and cyclin D1 is increased in butyrate-resistant HeLa cells.

Sodium butyrate induced cell cycle arrest in mammalian cells through an increase in p21Waf1/Cip1, although another study showed that this arrest is related to pRB signaling. We isolated variants of HeLa cells adapted to growth in 5 mm butyrate. One of these variants, clone 5.1, constitutively expressed elevated levels of p21Waf1/Cip1 when incubated in regular growth medium and in the presence of butyrate. Despite this elevated level of p21Waf1/Cip1, the cells continue to proliferate, albeit at a slower rate than parental HeLa cells. Western blot analyses showed that other cell cycle regulatory proteins were not up-regulated to compensate for the elevated expression of p21Waf1/Cip1. However, cyclin D1 was down-regulated by butyrate in HeLa cells but not in clone 5.1. We conclude that continued expression of cyclin D1 allowed clone 5.1 to grow in the presence of butyrate and elevated levels of p21Waf1/Cip1.

Blotting, Western↗
PubMed2004

Leptin counteracts sodium butyrate-induced apoptosis in human colon cancer HT-29 cells via NF-kappaB signaling.

This study shows that leptin induced a rapid phosphorylation of p42/44 mitogen-activated protein kinase, an enhancement of both NF-kappaB DNA binding and transcriptional activities, and a concentration-dependent increase of HT-29 cell proliferation. These effects are consistent with the presence of leptin receptors on cell membranes. The leptin induction of cell growth was associated with an increase of cell population in S and G2/M phase compared with control cells found in G0/G1 phase of the cell cycle. Moreover, cyclin D1 immunoreactivity was enhanced in leptin-treated HT-29 cells and this increase was essentially associated with cell population in G0/G1 phase. On the other hand, we observed that sodium butyrate inhibited cell proliferation by blocking HT-29 cells in G0/G1 phase of the cell cycle. Interestingly, at physiological concentration, leptin prevented sodium butyrate-induced morphological nucleus changes, DNA laddering and suppressed butyrate-induced cell cycle arrest. This anti-apoptotic effect of leptin was associated with HT-29 cell proliferation and activation NF-kappaB pathways. However, the phosphorylation of p42/44 MAP kinase in response to leptin was reduced in butyrate-treated cells. These data demonstrated that leptin is a potent mitogenic factor for intestinal epithelial cells through the MAP kinase and NF-kappaB pathways. They also showed, for the first time, that leptin promotes colon cancer HT-29 cell survival upon butyrate challenge by counteracting the apoptotic programs initiated by this short chain fatty acid probably through the NF-kappaB pathways. Although further studies are required to unravel the precise mechanism, these data may have significance in the pathogenesis of colorectal cancer and ulcerative colitis diseases.

Apoptosis↗
PubMed2005

A novel role of sodium butyrate in the regulation of cancer-associated aromatase promoters I.3 and II by disrupting a transcriptional complex in breast adipose fibroblasts.

The aromatase gene encodes the key enzyme for estrogen formation. Aromatase enzyme inhibitors eliminate total body estrogen production and are highly effective therapeutics for postmenopausal breast cancer. A distal promoter (I.4) regulates low levels of aromatase expression in tumor-free breast adipose tissue. Two proximal promoters (I.3/II) strikingly induce in vivo aromatase expression in breast fibroblasts surrounding malignant cells. Treatment of breast fibroblasts with medium conditioned with malignant breast epithelial cells (MCM) or a surrogate hormonal mixture (dibutyryl (Bt2)cAMP plus phorbol diacetate (PDA)) induces promoters I.3/II. The mechanism of promoter-selective expression, however, is not clear. Here we reported that sodium butyrate profoundly decreased MCM- or Bt2cAMP + PDA-induced promoter I.3/II-specific aromatase mRNA. MCM, Bt2cAMP + PDA, or sodium butyrate regulated aromatase mRNA or activity only via promoters I.3/II but not promoters I.1 or I.4 in breast, ovarian, placental, and hepatic cells. Mechanistically, recruitment of phosphorylated ATF-2 by a CRE (-211/-199, promoter I.3/II) conferred inductions by MCM or Bt2cAMP + PDA. Chromatin immunoprecipitation-PCR and immunoprecipitation-immunoblotting assays indicated that MCM or Bt2cAMP + PDA stabilized a complex composed of phosphorylated ATF-2, C/EBPbeta, and cAMP-response element-binding protein (CREB)-binding protein in the common regulatory region of promoters I.3/II. Overall, histone acetylation patterns of promoters I.3/II did not correlate with sodium butyrate-dependent silencing of promoters I.3/II. Sodium butyrate, however, consistently disrupted the activating complex composed of phosphorylated ATF-2, C/EBPbeta, and CREB-binding protein. This was mediated, in part, by decreased ATF-2 phosphorylation. Together, these findings represent a novel mechanism of sodium butyrate action and provide evidence that aromatase activity can be ablated in a signaling pathway- and cell-specific fashion.

Activating Transcription Factor 2↗
PubMed2001

Butyric acid stimulates rumen mucosa development in the calf mainly by a reduction of apoptosis.

In ruminants the stimulation of papillar growth by butyric acid is well described but effects on mitosis and apoptosis are not known. To clarify the effect of short chain fatty acids three groups of three calves received a basic ration of 100 g hay per day for 6 weeks and additionally milk replacer. From these, two groups were fed with increasing amounts of the salts of either propionic acid (53 to 390 g) or butyric acid up to (54 to 326 g). The control group instead received an additional isocaloric amount of milk replacer. Mitosis was characterized by Ki67 immunoreactivity, apoptosis by a modified TUNEL assay and by electron microscopy. The feeding regimes led to significant differences of papillar length, increasing from 1.0 mm (controls) to 2.2 mm (propionic acid) and 4 mm (butyric acid). This enlargement was partly explained by an increased mitotic rate for the two fatty acid groups. The difference between the fatty acid groups was mainly explained by different apoptotic rates which were only one third for butyric acid compared to propionic acid (P < 0.001). In conclusion, butyric acid is a specific inhibitor of ruminal apoptosis in vivo.

Animal Feed↗
PubMed2001

HMG-CoA reductase inhibitor mevastatin enhances the growth inhibitory effect of butyrate in the colorectal carcinoma cell line Caco-2.

Mevastatin is an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme in cholesterol synthesis. Butyrate, a short-chain fatty acid, reduces proliferation and induces differentiation of human colon cancer cells. The aim of our study was to determine the effect of mevastatin, alone or in combination with butyrate, on proliferation, the cell cycle and apoptosis in the human colorectal carcinoma cell line Caco-2. In this report we show that mevastatin combined with butyrate synergistically suppressed growth of Caco-2 cells in a dose- and time-dependent manner. In addition, incubation with mevastatin arrested cells in the G1 phase of the cell cycle after 24 h with a switch to the G2/M phase after 72 h. This was accompanied by a down-regulation of cyclin-dependent kinases (cdk) 4 and cdk 6 as well as cyclin D1, while cdk 2 and cyclin E protein levels remained unchanged during mevastatin treatment. Cell cycle inhibitors p21 and p27 were significantly upregulated by mevastatin. The proapoptotic properties of mevastatin were further enhanced by co-incubation with butyrate. Lastly, the effects of mevastatin could be reversed by addition of mevalonate, but not farnesyl- or geranylgeranylpyrophosphate, intermediate products of cholesterol synthesis, to the medium. These results suggest that HMG-CoA reductase inhibitors like mevastatin may enhance the antiproliferative effect of butyrate in colon cancer cells via induction of apoptosis together with a G0/G1 cell cycle arrest.

Butyrates↗
PubMed1984

Effect of Brij 58 on the hydrolysis of methyl butyrate by lipase from Pseudomonas fluorescens.

Purified Pseudomonas fluorescens lipase [EC 3.1.1.3] exhibited slight activity on water-soluble esters such as methyl butyrate, and this activity was increased on addition of Brij 58 (20 oxyethylene hexadecyl ether) to the solution. This stimulating effect of Brij 58 on hydrolysis of various esters (dimethyl succinate, butyl n-acetate, and tributyrin) in aqueous solution was unspecific. Hydrolysis of methyl butyrate depended on the molecular ratio of Brij 58 to lipase, being maximal (about 8 times the basal level at 37 degrees C with 80 mM substrate in 0.1 M NaCl solution) with 30 mol of Brij 58 per mol of lipase. Comparative studies showed that all polyoxyethylene (POE) alkyl ethers tested, stimulated the methyl butyrate hydrolyzing activity and that the Adekatol SO series (dihydric normal alcohol ethoxylate) also stimulated the appreciably active, whereas Triton X-100, sodium cholate, sodium deoxycholate, sodium dodecylsulfate, POE, and fatty acids had no effect. Comparison of the effects of Brij 58 on the methyl butyrate hydrolyzing activities of various lipolytic enzymes indicated that its effect was specific for this lipase. Brij 58 had no detectable effect with emulsified esters, such as supersaturated methyl butyrate and triolein.

Animals↗
PubMed2005

Genotoxicity of 4-hydroxy-2-nonenal in human colon tumor cells is associated with cellular levels of glutathione and the modulation of glutathione S-transferase A4 expression by butyrate.

The cellular production of 4-hydroxy-2-nonenal (HNE), a product of endogenous lipid peroxidation, constitutes a genotoxic risk factor for carcinogenesis. Our previous studies have shown that human HT29 colon cells developed resistance toward HNE injury after treatment with butyrate, a diet-associated gut fermentation product. This resistance was attributed to the induction of certain glutathione S-transferases (hGSTP1-1, hGSTM2-2, and hGSTA1-1) and also for the tripeptide glutathione (GSH) synthesizing enzymes. In the present study, we have investigated in HT29 cells whether hGSTA4-4, which has a high substrate specificity for HNE, was also inducible by butyrate and, thus, could contribute to the previously observed chemoresistance. In addition, we investigated if cellular depletion of GSH by L-buthionine-S,R-sulfoximine (BSO) enhances chemosensitivity to HNE injury in HT29 cells. Incubation of HT29 cells with butyrate (2-4 mM) significantly elicited a 1.8 to 3-fold upregulation of steady state hGSTA4 mRNA over 8-24 h after treatment. Moreover, 4 mM butyrate tended to increase hGSTA4-4 protein concentrations. Incubation with 100 microM BSO decreased cellular GSH levels by 77% without significant changes in cell viability. Associated with this was a 2-fold higher level of HNE-induced DNA damage as measured by the comet assay. Collectively, the results of this study and our previous work indicate that the genotoxicity of HNE is highly dependent on cellular GSH status and those GSTs that contribute toward HNE conjugation, including hGSTA4-4. Since HNE contributes to colon carcinogenesis, the favorable modulation of the GSH/GST system by butyrate may contribute to chemoprevention and reduction of the risks.

Aldehydes↗
PubMed2000

Anti-inflammatory effects of sodium butyrate on human monocytes: potent inhibition of IL-12 and up-regulation of IL-10 production.

Cytokines are critical in regulating unresponsiveness versus immunity towards enteric antigens derived from the intestinal flora and ingested food. There is increasing evidence that butyrate, a major metabolite of intestinal bacteria and crucial energy source for gut epithelial cells, also possesses anti-inflammatory properties. Its influence on cytokine production, however, is not established. Here, we report that butyrate strongly inhibits interleukin-12 (IL-12) production by suppression of both IL-12p35 and IL-12p40 mRNA accumulation, but massively enhances IL-10 secretion in Staphylococcus aureus cell-stimulated human monocytes. The effect of butyrate on IL-12 production was irreversible upon the addition of neutralizing antibodies to IL-10 or transforming growth factor b1 and of indomethacin. In anti-CD3-stimulated peripheral blood mononuclear cells, butyrate enhanced IL-10 and IL-4 secretion but reduced the release of IL-2 and interferon-g. The latter effect was in part a result of suppressed IL-12 production but also a result of inhibition of IL-12 receptor expression on T cells. These data demonstrate a novel anti-inflammatory property of butyrate that may have broad implications for the regulation of immune responses in vivo and could be exploited as new therapeutic approach in inflammatory conditions.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2004

The butyrate story: old wine in new bottles?

PURPOSE OF REVIEW: Short-chain fatty acids are important end products of bacterial carbohydrate fermentation in the colon. In particular, n-butyrate is thought to play a regulatory role in the maintenance of a physiological environment. Disturbances in the interplay between the microflora and the lining epithelium may lead to mucosal inflammation and promote carcinogenesis. The purpose of this article is to review the literature between March 2003 and February 2004 and to determine if recent studies have improved the understanding of butyrate effects in health and disease. RECENT FINDINGS: Preclinical studies (cell culture experiments, animal studies) using modern molecular biological tools (including cDNA arrays) have provided new insights into the action of butyrate on colonic epithelial, vascular endothelial and extracolonic cell types. The new information adds pieces of evidence to the assumption that butyrate may ameliorate colonic inflammation and may be chemopreventive in carcinogenesis. In contrast, new data from clinical studies have been limited in the review period. SUMMARY: In the era of molecular biology our understanding of subcellular processes that ultimately lead to inflammatory bowel disease or colorectal cancer has widened considerably. The new powerful technology of genomics and proteomics, however, raises new questions without easy answers. With this new information in mind, we will have to go back to human intervention trials to test the hypotheses generated in vitro. The preclinical data from the review period justify the need for carefully designed clinical trials to test the benefits derived from butyrate production.

Animals↗
PubMed2006

A novel class of CoA-transferase involved in short-chain fatty acid metabolism in butyrate-producing human colonic bacteria.

Bacterial butyryl-CoA CoA-transferase activity plays a key role in butyrate formation in the human colon, but the enzyme and corresponding gene responsible for this activity have not previously been identified. A novel CoA-transferase gene is described from the colonic bacterium Roseburia sp. A2-183, with similarity to acetyl-CoA hydrolase as well as 4-hydroxybutyrate CoA-transferase sequences. The gene product, overexpressed in an Escherichia coli lysate, showed activity with butyryl-CoA and to a lesser degree propionyl-CoA in the presence of acetate. Butyrate, propionate, isobutyrate and valerate competed with acetate as the co-substrate. Despite the sequence similarity to 4-hydroxybutyrate CoA-transferases, 4-hydroxybutyrate did not compete with acetate as the co-substrate. Thus the CoA-transferase preferentially uses butyryl-CoA as substrate. Similar genes were identified in other butyrate-producing human gut bacteria from clostridial clusters IV and XIVa, while other candidate CoA-transferases for butyrate formation could not be detected in Roseburia sp. A2-183. This suggests strongly that the newly identified group of CoA-transferases described here plays a key role in butyrate formation in the human colon.

Acyl Coenzyme A↗
PubMed2005

Oral butyrate for mildly to moderately active Crohn's disease.

BACKGROUND: Butyrate exerts anti-inflammatory effects in experimental colitis and on Crohn's disease lamina propria mononuclear cells in vitro. AIM: To explore the efficacy and safety of oral butyrate in Crohn's disease. METHODS: Thirteen patients with mild-moderate ileocolonic Crohn's disease received 4 g/day butyrate as enteric-coated tablets for 8 weeks. Full colonoscopy and ileoscopy were performed before and after treatment. Endoscopical and histological score, laboratory data, Crohn's disease activity index and mucosal interleukin (IL)-1beta, IL-6, IL-12, interferon-gamma, tumour necrosis factor-alpha and nuclear factor-kappa B (NF-kappaB) were assessed before and after treatment. RESULTS: One patient withdrew from the study, and three patients did not experience clinical improvement. Among the nine patients (69%) who responded to treatment, seven (53%) achieved remission and two had a partial response. Endoscopical and histological score significantly improved after treatment at ileocaecal level (P < 0.05). Leucocyte blood count, erythrocyte sedimentation rate and mucosal levels of NF-kappaB and IL-1beta significantly decreased after treatment (P < 0.05). CONCLUSIONS: Oral butyrate is safe and well tolerated, and may be effective in inducing clinical improvement/remission in Crohn's disease. These data indicate the need for a large investigation to extend the present findings, and suggest that butyrate may exert its action through downregulation of NF-kappaB and IL-1beta.

Administration, Oral↗
PubMed2006

Studies on a kinetic model for butyric acid bioproduction by Clostridium butyricum.

AIMS: This paper discusses the establishment of a kinetic model for cell growth, butyric acid production and substrate consumption of Clostridium butyricum ZJUCB in batch cultivation. METHODS AND RESULTS: Mathematic simulations were proposed by the logistic equation for the cell growth, the Luedeking-Piret equation for butyric acid production and the Luedeking-Piret-like equation for glucose consumption. CONCLUSION: We compared the performance of our model against that obtained by the empirically experimental design. The experiment-validated model was found suitable for studying butyric acid fermentation kinetics in a complex dynamic behaviour of C. butyricum, especially for its singular growth phenomenon. SIGNIFICANCE AND IMPACT OF THE STUDY: The model parameters are estimated from the data fitting and evaluated for simulation of the time courses of the concentrations of cell biomass, butyric acid and glucose and the model appears to fit the experimental data well. The results may be useful for butyric acid production by microbial fermentation.

Biomass↗
PubMed2002

The microbiology of butyrate formation in the human colon.

Butyrate arising from microbial fermentation is important for the energy metabolism and normal development of colonic epithelial cells and has a mainly protective role in relation to colonic disease. While certain dietary substrates such as resistant starch appear to be butyrogenic in the colon, it is not known to what extent these stimulate butyrate production directly, e.g. by promoting amylolytic species, or indirectly, e.g. through cross-feeding of fermentation products. Cultural and molecular studies indicate that the most numerous butyrate-producing bacteria found in human faeces are highly oxygen-sensitive anaerobes belonging to the Clostridial clusters IV and XIVa. These include many previously undescribed species related to Eubacterium, Roseburia, Faecalibacterium and Coprococcus whose distribution and metabolic characteristics are under investigation. A better understanding of the microbial ecology of colonic butyrate-producing bacteria will help to explain the influence of diet upon butyrate supply, and to suggest new approaches for optimising microbial activity in the large intestine.

Anaerobiosis↗
PubMed2002

Acetate utilization and butyryl coenzyme A (CoA):acetate-CoA transferase in butyrate-producing bacteria from the human large intestine.

Seven strains of Roseburia sp., Faecalibacterium prausnitzii, and Coprococcus sp. from the human gut that produce high levels of butyric acid in vitro were studied with respect to key butyrate pathway enzymes and fermentation patterns. Strains of Roseburia sp. and F. prausnitzii possessed butyryl coenzyme A (CoA):acetate-CoA transferase and acetate kinase activities, but butyrate kinase activity was not detectable either in growing or in stationary-phase cultures. Although unable to use acetate as a sole source of energy, these strains showed net utilization of acetate during growth on glucose. In contrast, Coprococcus sp. strain L2-50 is a net producer of acetate and possessed detectable butyrate kinase, acetate kinase, and butyryl-CoA:acetate-CoA transferase activities. These results demonstrate that different functionally distinct groups of butyrate-producing bacteria are present in the human large intestine.

Acetates↗
PubMed1974

Comparison of butyric type of fermentation in sporogenic and asporogenic mutants of Clostridium botulinum.

Glucose-adapted cells of a sporogenic mutant. MSp(+), and an asporogenic mutant, RSpoIIIa, of Clostridium botulinum type E rapidly fermented glucose, fructose, maltose, and sucrose, resulting in cytoplasmic granulation, heavy growth, a pH of <6.0, and sporulation of the MSp(+) mutant ranging from 60 to 80%. In Trypticase peptone glucose broth, the MSp(+) mutant formed >80% refractile endospores in 25 h, whereas the RSpoIIIa mutant which was blocked at early forespore stage had commenced to lyse. Both mutants accumulated acetate and intracellular granules, reaching maximal levels at early stationary phase of growth. In MSp(+), as the levels of acetokinase, phosphotransacetylase, and butyryl-coenzyme A dehydrogenase reached a maximum, butyrate accumulation continued concurrently with an increase of endospore formation, whereas the levels of poly-beta-hydroxybutyrate decreased simultaneously with its precursor, acetate. Butyrate biosynthesis was blocked in the asporogenic mutant. As shown by isotopic assays, butyrate and acetate serve as precursors of spore lipids. beta-Phenethyl alcohol, fluoroacetic acid, and 2-picolinic acid inhibited anaerobic sporogenesis almost completely, butyrate biosynthesis by >87%, and acetate accumulation by 50 to 62%, showing a direct relationship between butyric type of fermentation and anaerobic sporulation.

Acetates↗
PubMed1996

The human clotting factor VIII cDNA contains an autonomously replicating sequence consensus- and matrix attachment region-like sequence that binds a nuclear factor, represses heterologous gene expression, and mediates the transcriptional effects of sodium butyrate.

Expression of the human blood-clotting factor VIII (FVIII) cDNA is hampered by the presence of sequences located in the coding region that repress transcription. We have previously identified a 305-bp fragment within the FVIII cDNA that is involved in the repression (R.C. Hoeben, F.J. Fallaux, S.J. Cramer, D.J.M. van den Wollenberg, H. van Ormondt, E. Briet, and A.J. van der Eb, Blood 85:2447-2454, 1995). Here, we show that this 305-bp region of FVIII cDNA contains sequences that resemble the yeast (Saccharomyces cerevisiae) autonomously replicating sequence consensus. Two of these DNA elements coincide with AT-rich sequences that are often found in matrix attachment regions or scaffold-attached regions. One of these elements, consisting of nucleotides 1569 to 1600 of the FVIII cDNA (nucleotide numbering is according to the system of Wood et al. (W.I. Wood, D.J. Capon, C.C. Simonsen, D.L. Eaton, J. Gitschier, D. Keyt, P.H. Seeburg, D.H. Smith, P. Hollingshead, K.L. Wion, et al., Nature [London] 312:330-337,1984), binds a nuclear factor in vitro but loses this capacity after four of its base pairs have been changed. A synthetic heptamer of this segment can repress the expression of a chloramphenicol acetyltransferase (CAT) reporter gene and also loses this capacity upon mutation. Furthermore, we demonstrate that repression by FVIII sequences can be relieved by sodium butyrate. We demonstrate that the synthetic heptamer (FVIII nucleotides 1569 to 1600), when placed upstream of the Moloney murine leukemia virus long terminal repeat promoter that drives the CAT reporter, can render the CAT reporter inducible by butyrate. This effect was absent when the same element was mutated. The stimulatory effect of butyrate could not be attributed to butyrate-responsive elements in the studied long terminal repeat promoters. Our data provide a functional characterization of the sequences that repress expression of the FVIII cDNA. These data also suggest a link between transcriptional repression by FVIII cDNA elements and the stimulatory effect of butyrate on FVIII cDNA expression.

Base Sequence↗
PubMed1996

Mucosal enzyme activity for butyrate oxidation; no defect in patients with ulcerative colitis.

BACKGROUND: Butyrate is an important energy source for the colon and its metabolism has been reported to be defective in ulcerative colitis. One mechanism for defective butyrate metabolism in patients with ulcerative colitis could be an enzyme deficiency in the beta-oxidation pathway of butyrate. AIMS: This study was undertaken to measure the activity of each enzyme involved in the beta-oxidation pathway of butyrate in colonic epithelium. PATIENTS: Patients with ulcerative colitis (n = 33), Crohn's colitis (n = 10), and control subjects with colorectal cancer or diverticular disease (n = 73) were studied. METHODS: Analysis was carried out using fluorometric and spectrophotometric techniques on homogenised epithelial biopsy specimens. RESULTS: Significantly increased butyryl CoA dehydrogenase activity was found in mucosa from patients with ulcerative colitis (33.2 (28.3, 38.1) mumol/g wet weight/min:mean (95% CI)) compared with activity in mucosa from control patients (24.3 (20.9, 27.7) mumol/g wet weight/min:mean (95% CI)) p < 0.02. No significant increase in activity of the enzymes butyryl-CoA synthetase, crotonase or hydroxybutyryl-CoA dehydrogenase was found in patients with ulcerative colitis. In contrast the mucosal thiolase activity was significantly lower in those patients with quiescent colitis (3.21 (2.61, 3.81) mumol/g wet weight/min:mean (95% CI)) when compared with control mucosa (5.69 (5.09, 6.29) mumol/g wet weight/min:mean (95% CI)) p < 0.001. However, mucosal thiolase activity increases with the age of the donor patient and differences in the age range of the patient groups probably account for this finding. CONCLUSIONS: This study shows no substantial deficiency of enzyme activity in the beta-oxidation pathway of butyrate in the mucosa of patients with ulcerative colitis in histological remission.

Adolescent↗
PubMed2001

Only fibres promoting a stable butyrate producing colonic ecosystem decrease the rate of aberrant crypt foci in rats.

BACKGROUND: Dietary fibres have been proposed as protective agents against colon cancer but results of both epidemiological and experimental studies are inconclusive. AIMS: Hypothesising that protection against colon cancer may be restricted to butyrate producing fibres, we investigated the factors needed for long term stable butyrate production and its relation to susceptibility to colon cancer. METHODS: A two part randomised blinded study in rats, mimicking a prospective study in humans, was performed using a low fibre control diet (CD) and three high fibre diets: starch free wheat bran (WB), type III resistant starch (RS), and short chain fructo-oligosaccharides (FOS). Using a randomised block design, 96 inbred rats were fed for two, 16, 30, or 44 days to determine the period of adaptation to the diets, fermentation profiles, and effects on the colon, including mucosal proliferation on day 44. Subsequently, 36 rats fed the same diets for 44 days were injected with azoxymethane and checked for aberrant crypt foci 30 days later. RESULTS: After fermentation had stabilised (44 days), only RS and FOS produced large amounts of butyrate, with a trophic effect in the large intestine. No difference in mucosal proliferation between the diets was noted at this time. In the subsequent experiment one month later, fewer aberrant crypt foci were present in rats fed high butyrate producing diets (RS, p=0.022; FOS, p=0.043). CONCLUSION: A stable butyrate producing colonic ecosystem related to selected fibres appears to be less conducive to colon carcinogenesis.

Animals↗