Mechanisms of primary cancer prevention by butyrate and other products formed during gut flora-mediated fermentation of dietary fibre

Epigenetics Offer New Horizons for Colorectal Cancer Prevention

In recent years, colorectal cancer (CRC) incidence has been increasing to become a major cause of morbidity and mortality worldwide from cancers, with high rates in westernized societies and increasing rates in developing countries. Epigenetic modifications including changes in DNA methylation, histone modifications, and non-coding RNAs play a critical role in carcinogenesis. Epidemiological data suggest that, in comparison to other cancers, these alterations are particularly common within the gastrointestinal tract. To explain these observations, environmental factors and especially diet were suggested to both prevent and induce CRC. Epigenetic alterations are, in contrast to genetic modifications, potentially reversible, making the use of dietary agents a promising approach in CRC for the development of chemopreventive strategies targeting epigenetic mechanisms. This review focuses on CRC-related epigenetic alterations as a rationale for various levels of prevention strategies and their potential modulation by natural dietary compounds.

Histone deacetylase inhibitors upregulate MMP11 gene expression through Sp1/Smad complexes in human colon adenocarcinoma cells

MMP-11 (stromelysin-3) is a matrix metalloproteinase associated with tumor progression and poor prognosis. Its expression was initially described exclusively in stromal cells surrounding tumors, but more recently it has also been detected in macrophages and hepatocarcinoma cells. Here we show MMP-11 expression in human epithelial colon adenocarcinoma cell lines (Caco-2, HT-29 and BCS-TC2). Treatment of BCS-TC2 cells with butyrate and trichostatin A (TSA) (histone deacetylase inhibitors) increases MMP11 promoter activity and protein expression. Using electrophoretic mobility shift assay (EMSA) and supershift assays, we demonstrate for the first time that Sp1 is able to bind to the GC-boxes within the MMP11 proximal promoter region; this binding has been confirmed by chromatin immunoprecipitation. Sp1 is involved in MMP11 basal expression and it is essential for the upregulation of transcription by histone deacetylase inhibitors as deduced from mutant constructs lacking the Sp1 sites and by inhibition of its binding to the promoter with mithramycin. This regulation requires the formation of Sp1/Smad2 heterocomplexes, which is stimulated by an increase in the acetylation status of Smad after butyrate or TSA treatments. We have also found that ERK1/2-mitogen-activated protein kinase (MAPK), but not p38-MAPK or JNK, is involved in the upregulation of MMP11 by HDAC inhibitors.

Partially hydrolyzed guar gum affects the expression of genes involved in host defense functions and cholesterol absorption in colonic mucosa of db/db male mice

Biomedical evidence in the last 20 years has shown that the consumption of partially hydrolyzed guar gum may influence lipid and/or carbohydrate metabolism at many levels. Since intestine represents the first interface to interact with dietary partially hydrolyzed guar gum in vivo, we evaluated gene expression profiles in small intestinal mucosa of db/db mice fed with partially hydrolyzed guar gum in an effort to delineate its effect on the small intestine. DNA microarray and real-time PCR analyses were performed to evaluate the gene expression profiles in mice small intestinal mucosa. Among the 28,853 transcripts represented on the GeneChip® microarray, no more than 20 genes exhibited up- or down-regulation by 1.5-fold or more after four weeks following partially hydrolyzed guar gum consumption. No adverse effects were apparent. We detected up- or down-regulation of some genes known to be involved in host defense functions and cholesterol absorption.

Lignan transformation by gut bacteria lowers tumor burden in a gnotobiotic rat model of breast cancer

High dietary lignan exposure is implicated in a reduced breast cancer risk in women. The bacterial transformation of plant lignans to enterolignans is thought to be essential for this effect. To provide evidence for this assumption, gnotobiotic rats were colonized with the lignan-converting bacteria Clostridium saccharogumia, Eggerthella lenta, Blautia producta and Lactonifactor longoviformis (LCC rats). Germ-free rats were used as the control. All animals were fed a lignan-rich flaxseed diet and breast cancer was induced with 7,12-dimethylbenz(a)anthracene. The lignan secoisolariciresinol diglucoside was converted into the enterolignans enterodiol and enterolactone in the LCC but not in the germ-free rats. This transformation did not influence cancer incidence at the end of the 13 weeks experimental period but significantly decreased tumor numbers per tumor-bearing rat, tumor size, tumor cell proliferation and increased tumor cell apoptosis in LCC rats. No differences between LCC and control rats were observed in the expression of the genes encoding the estrogen receptors (ERs) α, ERβ and G-coupled protein 30. The same was true for IGF-1 and EGFR involved in tumor growth. The activity of selected enzymes involved in the degradation of oxidants in plasma and liver was significantly increased in the LCC rats. However, plasma and liver concentrations of reduced glutathione and malondialdehyde, considered as oxidative stress markers, did not differ between the groups. In conclusion, our results show that the bacterial conversion of plant lignans to enterolignans beneficially influences their anticancer effects.

Chemopreventive effects of in vitro digested and fermented bread in human colon cells

PURPOSE

Bread as a staple food product represents an important source for dietary fibre consumption. Effects of wheat bread, wholemeal wheat bread and wholemeal rye bread on mechanisms which could have impact on chemoprevention were analysed in colon cells after in vitro fermentation.

METHODS

Effects of fermented bread samples on gene expression, glutathione S-transferase activity and glutathione content, differentiation, growth and apoptosis were investigated using the human colon adenoma cell line LT97. Additionally, apoptosis was studied in normal and tumour colon tissue by determination of caspase activities.

RESULTS

The expression of 76 genes (biotransformation, differentiation, apoptosis) was significantly upregulated (1.5-fold) in LT97 cells. The fermented bread samples were able to significantly increase glutathione S-transferase activity (1.8-fold) and glutathione content (1.4-fold) of the cells. Alkaline phosphatase activity as a marker of differentiation was also significantly enhanced (1.7-fold). The fermented bread samples significantly inhibited LT97 cell growth and increased the level of apoptotic cells (1.8-fold). Only marginal effects on apoptosis in tumour compared to normal tissue were observed.

CONCLUSIONS

This is the first study which presents chemopreventive effects of different breads after in vitro fermentation. In spite of differences in composition, the results were comparable between the bread types. Nevertheless, they indicate a potential involvement of this staple food product regarding the prevention of colon cancer.

Impact of butyrate on PKM2 and HSP90β expression in human colon tissues of different transformation stages: a comparison of gene and protein data

Due to protection of oncogenic proteins from degradation and enhancement of glycolytic phosphometabolites for synthetic processes, respectively, heat shock protein 90 (HSP90) and pyruvate kinase type M2 (PKM2) are important proteins for tumor growth. The present study was undertaken to investigate the susceptibility of both proteins and their encoding genes to the chemopreventive agent butyrate in human colon cells. Matched tissue of different transformation stages derived from 20 individual colon cancer patients was used for the experiments. The results of quantitative real-time PCR revealed a moderate increase of HSP90β and PKM2 mRNA in colon tumors (P < 0.01) compared to normal tissues without relation to clinical parameters. The expression pattern could be confirmed for PKM2 protein by Western blot but not for HSP90β. During culturing with butyrate, the amount of PKM2 transcripts decreased in all three tissue types with the strongest effects observed in tumors (median fold decrease 45%, P < 0.05). The protein data have not reflected this influence supposing a more gradual degradation rate due to a longer half-life of PKM2. In contrast, the mRNA expression of HSP90β in normal tissue was found 1.38-fold increased by butyrate (P < 0.05), but not the corresponding protein level. HSP90β expression in adenomas and tumors remained generally insensitive. Only in malignant tissue, however, a significant correlation was found between the individual effects observed on gene and protein expression level. In conclusion, the present study identified PKM2 as a potential direct target of butyrate in neoplastic colon tissue, whereas HSP90β is none of it.

[Serrated precursor lesions]

The so-called serrated pathway has in recent years been well established as a second route of colorectal carcinogenesis. Sessile serrated polyps, especially sessile serrated adenomas (SSA) and traditional serrated adenomas (TSA) were identified as precursor lesions of this pathway. Activating mutations in either the BRAF (in SSAs) or the KRAS oncogene (in TSAs) have been determined as the initiating molecular alterations, followed by epigenetic methylation of CpG islands in promoter regions of genes which are implicated in cell cycle control or DNA repair. These findings have led to a paradigm shift in gastrointestinal pathology as lesions without cytological dysplasia, such as SSAs and certain forms of hyperplastic polyps, are now accepted to be precancerous lesions. In addition, carcinomas that have developed through the serrated pathway of colorectal carcinogenesis show varying biological behavior relevant for the clinical management of these tumors depending on the molecular aberrations.

Konjac glucomannan and inulin systematically modulate antioxidant defense in rats fed a high-fat fiber-free diet

The aim of this study was to investigate the effects of konjac glucomannan (KGM) and inulin on the balance between pro-oxidative status and antioxidative defense systems in the colon, liver, and plasma of rats fed a high-fat fiber-free diet. Male Sprague-Dawley rats (n = 8 animals per group) were fed a high-fat (25% corn oil, w/w) fiber-free diet or that supplemented with KGM or inulin fiber (5%, w/w) for 4 weeks. The index of pro-oxidative status, malondialdehyde (MDA), and blood lymphocyte DNA damage; the antioxidative defense, that is, antioxidant enzymes (glutathione peroxidase, superoxide dismutase, catalase) in the colonic mucosa and liver; and the plasma antioxidant levels were determined. The fermentation of fiber was shown in fecal short-chain fatty acids. Incorporation of KGM and inulin into the high-fat fiber-free diet beneficially reduced the MDA levels of the colon and liver and DNA damage in blood lymphocytes. On the other hand, both fibers enhanced the antioxidative defense systems by up-regulating the gene expressions of glutathione peroxidase and catalase in the colonic mucosa and of superoxide dismutase and catalase in the liver. Furthermore, KGM and inulin promoted antioxidative status in the blood by elevating the α-tocopherol level. KGM and inulin were well-fermented in rats and increased the concentration and daily excretion of fecal short-chain fatty acids, especially acetate and butyrate. These results suggest that in vivo utilization of KGM and inulin stimulated both local and systemic antioxidative defense systems in rats.

Impact of polyphenol metabolites produced by colonic microbiota on expression of COX-2 and GSTT2 in human colon cells (LT97)

Polyphenols may play an important role in colon cancer prevention. After entering the colon, they are subjected to metabolism by the human gut microbiota. The objective of the present study was to analyze the impact of selected intestinal metabolites on modulation of enzymes involved in detoxification and inflammation in human adenoma cells LT97. LT97 cells were incubated with 3,4-dihydroxyphenylacetic acid (ES) and 3-(3,4-dihydroxyphenyl)-propionic acid (PS), metabolites of quercetin and chlorogenic acid/caffeic acid, respectively. The effect on cell number was analyzed using 4'- 6-diamino-2-phenylindole-dihydrochloride (DAPI)-staining. Modulation of glutathione S-transferase T2 (GSTT2) and cyclooxygenase-2 (COX-2) was measured by real-time PCR and Western blot. Comet assay was performed to assess the impact on DNA damage caused by the GSTT2 substrate cumene hydroperoxide (CumOOH). Polyphenol metabolites did not affect cell number but significantly upregulated GSTT2 expression and decreased COX-2. The latter was confirmed via Western blot. CumOOH-induced DNA damage was significantly reduced compared to the control. An upregulation of GSTT2 and downregulation of COX-2 could possibly contribute to the chemopreventive potential of polyphenols after degradation in the gut. Working with polyphenol metabolites is an important prerequisite to better understand the in vivo effects of pure polyphenols.

The intestinal microbiota, gastrointestinal environment and colorectal cancer: a putative role for probiotics in prevention of colorectal cancer?

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the United States, and, even though 5-15% of the total CRC cases can be attributed to individual genetic predisposition, environmental factors could be considered major factors in susceptibility to CRC. Lifestyle factors increasing the risks of CRC include elevated body mass index, obesity, and reduced physical activity. Additionally, a number of dietary elements have been associated with higher or lower incidence of CRC. In this context, it has been suggested that diets high in fruit and low in meat might have a protective effect, reducing the incidence of colorectal adenomas by modulating the composition of the normal nonpathogenic commensal microbiota. In addition, it has been demonstrated that changes in abundance of taxonomic groups have a profound impact on the gastrointestinal physiology, and an increasing number of studies are proposing that the microbiota mediates the generation of dietary factors triggering colon cancer. High-throughput sequencing and molecular taxonomic technologies are rapidly filling the knowledge gaps left by conventional microbiology techniques to obtain a comprehensive catalog of the human intestinal microbiota and their associated metabolic repertoire. The information provided by these studies will be essential to identify agents capable of modulating the massive amount of gut bacteria in safe noninvasive manners to prevent CRC. Probiotics, defined as "live microorganisms which, when administered in adequate amounts, confer a health benefit on the host" (219), are capable of transient modulation of the microbiota, and their beneficial effects include reinforcement of the natural defense mechanisms and protection against gastrointestinal disorders. Probiotics have been successfully used to manage infant diarrhea, food allergies, and inflammatory bowel disease; hence, the purpose of this review was to examine probiotic metabolic activities that may have an effect on the prevention of CRC by scavenging toxic compounds or preventing their generation in situ. Additionally, a brief consideration is given to safety evaluation and production methods in the context of probiotics efficacy.

Structural segregation of gut microbiota between colorectal cancer patients and healthy volunteers

Despite a long-suspected role in the development of human colorectal cancer (CRC), the composition of gut microbiota in CRC patients has not been adequately described. In this study, fecal bacterial diversity in CRC patients (n=46) and healthy volunteers (n=56) were profiled by 454 pyrosequencing of the V3 region of the 16S ribosomal RNA gene. Both principal component analysis and UniFrac analysis showed structural segregation between the two populations. Forty-eight operational taxonomic units (OTUs) were identified by redundancy analysis as key variables significantly associated with the structural difference. One OTU closely related to Bacteroides fragilis was enriched in the gut microbiota of CRC patients, whereas three OTUs related to Bacteroides vulgatus and Bacteroides uniformis were enriched in that of healthy volunteers. A total of 11 OTUs belonging to the genera Enterococcus, Escherichia/Shigella, Klebsiella, Streptococcus and Peptostreptococcus were significantly more abundant in the gut microbiota of CRC patients, and 5 OTUs belonging to the genus Roseburia and other butyrate-producing bacteria of the family Lachnospiraceae were less abundant. Real-time quantitative PCR further validated the significant reduction of butyrate-producing bacteria in the gut microbiota of CRC patients by measuring the copy numbers of butyryl-coenzyme A CoA transferase genes (Mann-Whitney test, P<0.01). Reduction of butyrate producers and increase of opportunistic pathogens may constitute a major structural imbalance of gut microbiota in CRC patients.

Effects of synbiotic fermentation products on primary chemoprevention in human colon cells

The consumption of synbiotics, a mixture of probiotics and indigestible food constituents such as dietary fiber, has been reported to reduce colon cancer risk. We investigated the effects of fermented wheat aleurone enriched with the probiotics Lactobacillus rhamnosus GG/Bifidobacterium animalis supsp. lactis on the gene expression and functional end points related to cellular defence in HT29 and primary human colon cells. Aleurone was digested and fermented in vitro with/without probiotics. The resulting fermentation supernatants (fs) were analyzed for concentrations of deoxycholic acid and ammonia. The cells were treated with the fs, and effects on gene expression of catalase, GSTP1 and SULT2B1, enzyme activity of catalase and glutathione S-transferase as well as H₂O₂-induced DNA damage were examined. Fermentation of aleurone reduced deoxycholic acid concentration by 84%, while the probiotics enhanced this effect. Ammonia was increased by fs aleurone, whereas a reduction occurred by the addition of L. rhamnosus GG/B. animalis supsp. lactis 12. GSTP1 expression tended to result in an increase by the fs aleurone in both cell types, whereas the probiotics could not additionally increase the effect. Catalase was not modulated by fs aleurone enriched with probiotics. Only in HT29 cells, expression of SULT2B1 was enhanced by fs aleurone. Enzyme activity of catalase and glutathione S-transferase was induced (2-3.6 fold, 72 h) in HT29 cells only. Addition of probiotics had no influence on this effect. In HT29 cells, a reduced H₂O₂-induced DNA damage by the fs aleurone after 48 h, enhanced by the addition of probiotics, was detected. The observed effects could improve detoxification of xenobiotics and therefore may lower colon cancer risk.

Sodium butyrate does not decrease the evolution of precancerous lesions in rats

PURPOSE

To evaluate the preventive effect of sodium butyrate in the appearance of aberrant crypt foci (ACF) in rats after induction with the carcinogen 1,2-dimethylhydrazine (DMH).

METHODS

Forty Wistar rats were separated into four groups (n=10) distributed as follows: control 1, control 2, butyrate 1 and butyrate 2. The groups control 1 and butyrate 1 remained under experimentation for 4 weeks, while the groups control 2 and butyrate 2 remained for 8 weeks. In the first four weeks, the animals of the control groups received water ad libitum and the animals of the butyrate groups received a sodium butyrate solution (3.4%) ad libitum. Injections of the drug 1,2-dimethylhydrazine were applied during the two first weeks of the experiment in all the animals, concurrently with the application of sodium butyrate. The large intestine of the animals was removed, for the analysis of the ACF and of the content of polyamines. The animal feces were collected for the analysis of the SCFA profile.

RESULTS

The spermidine presented a higher concentration in the group butyrate 2 in comparison to the group control 2. There was a significant difference in the concentration value (µmol/mL) of acetate in comparison to the groups control 2 and butyrate 2.

CONCLUSION

The use of sodium butyrate together with the induction of colorectal cancer was not effective in the prevention of the disease progression.

The short-chain fatty acid butyrate is a substrate of breast cancer resistance protein

Colorectal cancer is one of the most common cancers worldwide. Butyrate (BT) plays a key role in colonic epithelium homeostasis. The aim of this work was to investigate the possibility of BT being transported by P-glycoprotein (MDR1), multidrug resistance proteins (MRPs), or breast cancer resistance protein (BCRP). Uptake and efflux of (14)C-BT and (3)H-folic acid were measured in Caco-2, IEC-6, and MDA-MB-231 cell lines. mRNA expression of BCRP was detected by RT-PCR. Cell viability, proliferation, and differentiation were quantified with the lactate dehydrogenase, sulforhodamine B, and alkaline phosphatase activity assays, respectively. In both IEC-6 cells and Caco-2 cells, no evidence was found for the involvement of either MDR1 or MRPs in (14)C-BT efflux from the cells. In contrast, several lines of evidence support the conclusion that BT is a substrate of both rat and human BCRP. Indeed, BCRP inhibitors reduced (14)C-BT efflux in IEC-6 cells, both BT and BCRP inhibitors significantly decreased the efflux of the known BCRP substrate (3)H-folic acid in IEC-6 cells, and BCRP inhibitors reduced (14)C-BT efflux in the BCRP-expressing MDA-MB-231 cell line. In IEC-6 cells, combination of BT with a BCRP inhibitor significantly potentiated the effect of BT on cell proliferation. The results of this study, showing for the first time that BT is a BCRP substrate, are very important in the context of the high levels of BCRP expression in the human colon and the anticarcinogenic and anti-inflammatory role of BT at that level. So, interaction of BT with BCRP and with other BCRP substrates/inhibitors is clearly of major importance.

Inhibition of the cytotoxic effect of Clostridium difficile in vitro by Clostridium butyricum MIYAIRI 588 strain

In contrast to most modern pharmaceuticals, probiotics are used in many parts of the world with little or no research data on the complex system of interactions that each strain may elicit in the human body. Research on probiotics has recently become more significant, as probiotics have begun to be prescribed by clinicians as an alternative for some gut infections, especially when antibiotics are contraindicated. This study attempted to elucidate the inhibitory interaction between the Japanese probiotic strain Clostridium butyricum MIYAIRI 588 (CBM588) and the hospital pathogen Clostridium difficile, which is responsible for a large proportion of antibiotic-associated diarrhoea and colitis. CBM588 has previously shown effectiveness against C. difficile in vivo, and here it was found that the toxicity of C. difficile in in vitro co-culture with CBM588 was greatly decreased or absent. This was dependent on the inoculation ratio and was not accounted for by the small degree of growth and mRNA inhibition observed. CBM588 and its cell-free supernatant also had no effect on toxin already secreted into the culture medium, and culture of the two strains separated by a semi-permeable membrane resulted in loss of the inhibition. Therefore, it was concluded that the detoxification probably occurred by the inhibition of toxin protein production and that this required close proximity or contact between the two species. The low-pH conditions caused by organic acid secretion were also observed to have inhibitory effects on C. difficile growth, metabolism and toxicity.

Butyrate induces expression of 17β-hydroxysteroid dehydrogenase type 1 in HT29 and SW707 colorectal cancer cells

Epidemiological studies have revealed that butyrate and 17β-estradiol (E2) may decrease the incidence of colorectal cancer (CRC). In peripheral tissue, E2 can be produced locally by 17β-hydroxysteroid dehydrogenase 1 (HSD17B1) estrone (E1) reduction. Using quantitative real-time polymerase chain reaction and western blotting analysis, we found that sodium butyrate significantly upregulates HSD17B1 long and short transcripts and protein levels in HT29 and SW707 CRC cells. Chromatin immunoprecipitation analysis showed that upregulation of these transcript levels correlated with an increase in binding of Polymerase II to proximal and distal promoters of HSD17B1. Moreover, we observed that upregulation of HSD17B1 protein levels was associated with increased conversion of E1 to E2 in HT29 and SW707 CRC cells. Since sodium butyrate increases the conversion of E1 to E2, our findings may support the validity of butyrate in the prophylaxis of CRC incidence.

Butyrate suppresses mRNA increase of osteopontin and cyclooxygenase-2 in human colon tumor tissue

The short chain fatty acid (SCFA) butyrate, a product of fermentation of dietary fiber in the human colon, is found to exert multiple regulatory processes in colon carcinogenesis. The aim of this study was to find out whether butyrate affects the tumor-promoting genes osteopontin (OPN) and cyclooxygenase (COX)-2, their respective proteins and/or their functional activity in matched normal, adenoma and tumor colon tissues obtained from 20 individuals at colon cancer surgery. Quantitative real-time polymerase chain reaction experiments showed increased levels of OPN and COX-2 messenger RNA in tumor tissues when compared with the adjacent normal samples (P < 0.001). The addition of butyrate reduced OPN and COX-2 mRNA expression in all tissue types compared with the related medium controls (tumor: P < 0.05). In tumor samples, a downregulation of up to median 35% (COX-2) and 50% (OPN) was observed, respectively. Thereby, tumors with lower levels of OPN basal expression were more sensitive to inhibition and vice versa for COX-2 in normal tissue. At the protein and enzyme level, which were determined by using western blot and enzyme immunometric assays, the impact of the SCFA was not clearly visible anymore. The active proteins of OPN and COX-2 (determined by prostaglandin E(2)) were found to correlate with their respective mRNA expression only in 50-63% of analyzed donors. For the first time, our data reveal new insights into the chemoprotective potential of butyrate by showing the suppression of OPN and COX-2 mRNA in primary human colon tissue with the strongest effects observed in tumors.

Potential beneficial effects of butyrate in intestinal and extraintestinal diseases

The multiple beneficial effects on human health of the short-chain fatty acid butyrate, synthesized from non-absorbed carbohydrate by colonic microbiota, are well documented. At the intestinal level, butyrate plays a regulatory role on the transepithelial fluid transport, ameliorates mucosal inflammation and oxidative status, reinforces the epithelial defense barrier, and modulates visceral sensitivity and intestinal motility. In addition, a growing number of studies have stressed the role of butyrate in the prevention and inhibition of colorectal cancer. At the extraintestinal level, butyrate exerts potentially useful effects on many conditions, including hemoglobinopathies, genetic metabolic diseases, hypercholesterolemia, insulin resistance, and ischemic stroke. The mechanisms of action of butyrate are different; many of these are related to its potent regulatory effects on gene expression. These data suggest a wide spectrum of positive effects exerted by butyrate, with a high potential for a therapeutic use in human medicine.

Effects of konjac glucomannan on putative risk factors for colon carcinogenesis in rats fed a high-fat diet

The aim of this study was to determine effects of konjac glucomannan (KGM) in a high fat corn oil diet on risk factors of colon carcinogenesis, that is, fecal β-glucuronidase, mucinase, and bile acids, and on preventive factors, that is, fecal microflora and cecal short-chain fatty acids (SCFAs). Sprague-Dawley rats (n = 8 animals per group) were fed a normal-fat fiber-free (5% corn oil, w/w) or high-fat (25% corn oil, w/w) diet containing no fiber, KGM (5%, w/w), or inulin (5%, w/w, as a prebiotic control) for 4 weeks. Results indicated that the high-fat fiber-free diet significantly elevated the fecal β-glucuronidase and mucinase activities and total bile acid concentration and decreased cecal SCFA contents, as compared with its normal-fat counterpart. The incorporation of KGM, as well as inulin, into the high-fat fiber-free diet beneficially reduced the fecal β-glucuronidase and mucinase activities and lithocholic acid (secondary bile acid) concentration. Although KGM elevated the daily fecal total bile acid excretion, the change was due to the primary, instead of the secondary, bile acids. In addition, KGM beneficially promoted the daily fecal excretion of bifidobacteria and lactobacilli and cecal SCFA contents, as compared with the high-fat fiber-free diet. Therefore, the present study suggests that KGM potentially attenuated the high fat-induced risk in colon carcinogenesis.

Modification of anin vitromodel simulating the whole digestive process to investigate cellular endpoints of chemoprevention

In vitrogut fermentation systems are relevant tools to study health benefits of foodstuffs. Most of them are commonly used to investigate the degradation of nutrients or the development of gut flora. Using these models, strong cytotoxic effects of the resulting samples on cultured cells were observed. Hence, the aim of the present study was to develop a modifiedin vitrofermentation model that simulates the whole digestive tract and generates fermented samples that are suitable for testing in cell culture experiments. Wholemeal wheat flour (wwf) was digested and fermentedin vitrowith a fermentation model using different ox gall concentrations (41·6 and 0·6 g/l). The resulting fermentation supernatants (fs) were characterised for metabolites and biological effects in HT29 cells. The fermentation of wwf increased chemopreventive SCFA and decreased carcinogenic deoxycholic acid (DCA). The strong cytotoxic effects of the fs, which were partly due to cholic acid and DCA, were diminished by lowering the ox gall concentration, allowing the use of the samples in cell culture experiments. In conclusion, anin vitrodigestion model, which can be used to study the effects of foodstuffs on chemoprevention and gut health in colon cells, is introduced and its physiological relevance is demonstrated.

Colorectal cancer prevention through dietary and lifestyle modifications

Several studies indicate that Western dietary and lifestyle factors are responsible for the high incidence of colorectal cancer in industrialized countries. Diets rich in red and processed meat, refined starches, sugar, and saturated and trans-fatty acids but poor in fruits, vegetables, fiber, omega-3 fatty acids and whole grains are closely associated with an increased risk of colorectal cancer. Other main features of the western lifestyle, such as excess body mass and sedentary behaviours, are also strongly associated with higher risk of developing this cancer. Modifications of the western diet, notably increasing consumption of foods from plant origin and reducing that of red meat intake, and maintenance of physical activity and appropriate body mass could substantially reduce colorectal cancer incidence and mortality.

Effects of short-chain fatty acids on colonopathies and mechanisms involved

Short-chain fatty acids (SCFAs), primarily acetate, propionate and butyrate, are produced by anaerobic bacterial fermentation of undigested carbohydrates. They are not only the major source of energy for the colonic mucosa, but also can maintain the normal physiological functions of the colon, keep the homeostasis of the colonic mucosal barrier and prevent the occurrence of dysfunction, inflammation and canceration. In pathological state, SCFAs also play a role in inhibiting inflammation and tumor growth.

Gene expression profiles of colonic mucosa in healthy young adult and senior dogs

Background

We have previously reported the effects of age and diet on nutrient digestibility, intestinal morphology, and large intestinal fermentation patterns in healthy young adult and senior dogs. However, a genome-wide molecular analysis of colonic mucosa as a function of age and diet has not yet been performed in dogs.

Methodology/Principal Findings

Colonic mucosa samples were collected from six senior (12-year old) and six young adult (1-year old) female beagles fed one of two diets (animal protein-based vs. plant protein-based) for 12 months. Total RNA in colonic mucosa was extracted and hybridized to Affymetrix GeneChip® Canine Genome Arrays. Results indicated that the majority of gene expression changes were due to age (212 genes) rather than diet (66 genes). In particular, the colonic mucosa of senior dogs had increased expression of genes associated with cell proliferation, inflammation, stress response, and cellular metabolism, whereas the expression of genes associated with apoptosis and defensive mechanisms were decreased in senior vs. young adult dogs. No consistent diet-induced alterations in gene expression existed in both age groups, with the effects of diet being more pronounced in senior dogs than in young adult dogs.

Conclusion

Our results provide molecular insight pertaining to the aged canine colon and its predisposition to dysfunction and disease. Therefore, our data may aid in future research pertaining to age-associated gastrointestinal physiological changes and highlight potential targets for dietary intervention to limit their progression.

Fermented wheat aleurone induces enzymes involved in detoxification of carcinogens and in antioxidative defence in human colon cells

Dietary fibre is fermented by the human gut flora resulting mainly in the formation of SCFA, for example, acetate, propionate and butyrate. SCFA, in particular butyrate, may be important for secondary cancer prevention by inducing apoptosis and inhibiting cell growth of cancer cells, thereby inhibiting the promotion and/or progression of cancer. Furthermore, SCFA could also act on primary cancer prevention by activation of detoxifying and antioxidative enzymes. We investigated the effects of fermented wheat aleurone on the expression of genes involved in stress response and toxicity, activity of drug-metabolising enzymes and anti-genotoxic potential. Aleurone was digested and fermented in vitro to obtain samples that reflect the content of the colon. HT29 cells and colon epithelial stripes were incubated with the resulting fermentation supernatant fractions (fs) and effects on mRNA expression of CAT, GSTP1 and SULT2B1 and enzyme activity of glutathione S-transferase (GST) and catalase (CAT) were measured. Fermented aleurone was also used to study the protection against H2O2-induced DNA damage in HT29 cells. The fs of aleurone significantly induced the mRNA expression of CAT, GSTP1 and SULT2B1 (HT29) and GSTP1 (epithelial stripes), respectively. The enzyme activities of GST (HT29) and CAT (HT29, epithelial stripes) were also unambiguously increased (1·4- to 3·7-fold) by the fs of aleurone. DNA damage induced by H2O2 was significantly reduced by the fs of aleurone after 48 h, whereupon no difference was observed compared with the faeces control. In conclusion, fermented aleurone is able to act on primary prevention by inducing mRNA expression and the activity of enzymes involved in detoxification of carcinogens and antioxidative defence.

Post-translational modulation of CD133 expression during sodium butyrate-induced differentiation of HT29 human colon cancer cells: implications for its detection

The CD133 molecule has been proposed as a surface marker of cancer stem cells in several human malignancies, including colon cancers. The function and the mechanisms regulating CD133 expression remain unknown. The HT29 human colon cancer cells undergo differentiation following treatment with various agents and represent a useful in vitro model of colon differentiation. This study evaluated the behavior of CD133 during sodium butyrate-induced differentiation of HT29 cells. Treatment with sodium butyrate induced a progressive decrease of CD133 expression, as assessed by flow cytometry using the AC133 monoclonal antibody. Indeed, expression of CD133, which was about 47% in untreated control cells, gradually decreased down to about 3% after 72 h in a time- and dose-dependent manner. No relationship was observed between CD133 protein evaluated by flow cytometry and mRNA expression level, and no changes were detected in the methylation status of the CD133 gene promoter during HT29 differentiation. Moreover, the expression of the CD133 protein, evaluated by Western blot analysis using a specific anti-CD133 antibody directed against the C-terminal intracytoplasmic region of human CD133 protein, did not correlate with flow cytometry results. Different results were also obtained using the two antibodies to analyze the expression of the CD133 molecule in human colon cancers. These findings demonstrate that membrane expression of the CD133 stem cell marker might undergo a complex regulation during differentiation of colon cells and suggest that HT29 cells are a useful in vitro model to study the mechanisms involved in this regulation which likely occurs at a post-transcriptional level.

Modifier-concept of colorectal carcinogenesis: Lipidomics as a technical tool in pathway analysis

In the modifier concept of intestinal carcinogenesis, lipids have been established as important variables and one focus is given to long-chain fatty acids. Increased consumption of long-chain fatty acids is in discussion to modify the development of colorectal carcinoma in humans. Saturated long-chain fatty acids, in particular, are assumed to promote carcinogenesis, whereas polyunsaturated forms are likely to act in the opposite way. At present, the molecular mechanisms behind these effects are not well understood. Recently, it has been demonstrated by lipidomics and associated molecular techniques, that activation and metabolic channeling of long-chain fatty acids are important mechanisms to modify colorectal carcinogenesis. In this Editorial, an overview about the present concept of long-chain fatty acids and its derivatives in colorectal carcinogenesis as well as technical algorithms in lipid analysis is given.

Butyrate increases the formation of anti-angiogenic vascular endothelial growth factor variants in human lung microvascular endothelial cells

The primary transcript of vascular endothelial growth factor (VEGF) can be alternatively spliced and translated to pro-angiogenic and anti-angiogenic VEGF variants. We investigated the effect of sodium butyrate (NaB) on pro-angiogenic and anti-angiogenic VEGF variants production in immortalized human lung microvascular endothelial cells (HLMEC). These cells were cultured in the absence or in the presence of NaB, followed by total RNA and protein isolation. The transcript and protein levels of pro-angiogenic and anti-angiogenic VEGF variants were evaluated by reverse transcription, real-time quantitative PCR and western blot analysis. We found that NaB significantly increased the anti-angiogenic transcript and protein levels of the VEGF 121b, VEGF165b and VEGF189b variants in HLMEC cells. We did not find the pro-angiogenic VEGF189a transcript variant either in control or NaB treated cells. By contrast, the pro-angiogenic VEGF121a and VEGF165a transcript variants were present in HLMEC cells, but their levels were slightly modulated in the cells treated with NaB compared to controls. Since anti-angiogenic VEGF variants inhibit angiogenesis and tumour progression, and NaB is considered an anticancer drug, our findings may have clinical significance.

Fermentation supernatants of wheat ( Triticum aestivum L.) aleurone beneficially modulate cancer progression in human colon cells

Wheat aleurone contains high amounts of dietary fibers that are fermented by the microflora, resulting in the formation of short-chain fatty acids (SCFA), which are recognized for their chemopreventive potential. This study investigated the effects of fermented aleurone on growth, apoptosis, differentiation, and expression of several genes using two different human colon cell lines (LT97 and HT29). In LT97 cells, the fermentation supernatant (fs) aleurone reduced significantly the cell growth (EC(50) after 48 h = 7.6-8.3%), whereas the level of apoptotic cells was significantly increased (2.1-2.3-fold). Differentiation was enhanced in HT29 cells (1.8-fold) more than in LT97 cells (1.6-fold). Cell growth and apoptosis-related genes, namely WNT2B and p21, were induced by the fs (LT97, 1.7-3.3-fold; HT29, 7.9-22.2-fold). In conclusion, fermented wheat aleurone is able to act as a secondary chemopreventive agent by modulating parameters of cell growth and survival, whereas cells of an early transformation stage are more sensitive.