Short-chain fatty acids inhibit invasive human colon cancer by modulating uPA, TIMP-1, TIMP-2, mutant p53, Bcl-2, Bax, p21 and PCNA protein expression in an in vitro cell culture model

Carbohydrate Digestibility Predicts Colon Carcinogenesis in Azoxymethane-Treated Rats

The purpose of this study was to compare the effect of carbohydrate structure and digestibility on azoxymethane (AOM)-induced colon carcinogenesis. Five groups of male Fischer 344 rats each comprising 30 animals were injected with AOM and fed a high-fat diet with 15% of various carbohydrates. The carbohydrate sources used were sucrose, cornstarch (a linear starch, reference group), potato starch (a branched starch), a short-chained oligofructose (Raftilose), and a long-chained inulin-type fructan (Raftiline). An interim sacrifice was performed after 9 wk to investigate markers of carbohydrate digestibility, including caecal fermentation (caecum weight and pH) and glucose and lipid metabolism [glucose, fructoseamine, HbA1c, triglycerides, and insulin-like growth factor (IGF) 1]. In addition potential early predictors of carcinogenicity [cell proliferation and aberrant crypt foci (ACF)] at 9 wk and their correlation to colon cancer risk after 32 wk were investigated. Tumor incidence was significantly reduced in animals fed oligofructose, and the number of tumors per animal was significantly reduced in animals fed inulin and oligofructose at 32 wk after AOM induction compared to the reference group fed sucrose. Increased caecum weight and decreased caecal pH were seen in groups fed oligofructose, inulin, and potato starch. Plasma triglyceride was decreased in rats fed oligofructose and inulin. Cell proliferation was increased in the proximal colon of rats fed sucrose, oligofructose, and inulin, and the number of cells per crypt decreased in rats fed oligofructose and inulin. The total number of ACF's was unaffected by treatment, and the size and multiplicity of ACF was unrelated to tumor development. It was concluded that less digestible carbohydrates with an early effect on caecum fermentation and plasma triglyceride decreased subsequent tumor incidence and multiplicity. This was unrelated to ACF, cell proliferation, and other markers of glucose and lipid metabolism.

Development of a Low Glycemic Maize Starch: Preparation and Characterization

A low glycemic index starch was developed by partial alpha-amylase treatment, and its fine structure responsible for slowly digestible and resistant properties was investigated. Different digestion rates were obtained for gelatinized, retrograded starch by varying the enzyme dosage and reaction time. Analysis by high performance size-exclusion chromatography (HPSEC) coupled with multiangle laser-light scattering indicated that the molecular weighs of amylopectin and amylose were reduced during the digestion, to less than 100 kDa. A debranched chain length study using high performance anion-exchange chromatography equipped with an amyloglucosidase reactor and a pulsed amperometric detector and HPSEC revealed that short chains of amylopectin and noncrystalline amylose were rapidly digested, while DPn 121 chains showed resistance, followed by DPn 46 chains. X-ray diffraction analysis revealed that the crystalline structure in the treated starches survived cooking. These starches not only have slowly digestible and resistant character, but also retain some branched structure for adequate functionality.

Interactions of high amylose starch and deoxycholic acid on gut functions in rats

OBJECTIVE

This study evaluated whether high amylose cornstarch (HAS) could prevent adverse physiologic effects induced by deoxycholic acid (DCA) in the gut of rats.

METHODS

Thirty-two male Sprague-Dawley rats were provided with a low amylose cornstarch (LAS) diet or a 50/50 mixture of LAS and HAS diets for 4 wk; each of these diets was supplemented with 0 or 2 g of DCA per kilogram of diet. Therefore, there were four groups.

RESULTS

Cecal content pH was lower in rats fed the HAS diets compared with rats fed the LAS diets (P < 0.05). Bifidobacteria number in cecal contents, cecal pools of acetate, butyrate, and total short-chain fatty acids were highest in rats fed the HAS diet; moreover, the HAS/DCA diet resulted in increased Bifidobacteria growth and short-chain fatty acid production numerically compared with the LAS/DCA diets (P = 0.06). Production of prostaglandin-E2 in colonic mucosa was highest in rats fed the LAS/DCA diet, and the intake of HAS significantly decreased prostaglandin-E2 levels (P < 0.05).

CONCLUSIONS

In this study, DCA may have inhibited fermentation in the large intestine and increased prostaglandin-E2 production, and concurrent administration of HAS and DCA may have decreased the adverse effects on the gut induced by DCA.

Comparative toxicity of oleic and linoleic acid on human lymphocytes

Commercially available lipid emulsions for parenteral nutrition are mainly composed by long chain triacylglycerol containing a high proportion of linoleic acid (LA) or oleic acid (OA). The immunological impact of such therapy is particularly important because parenteral diets are often administered to critically ill patients as a mechanism to supply adequate nutrition during catabolic stress conditions. The comparative toxicity of OA and LA on human lymphocytes and the type of cell death induced by these fatty acids were determined in vitro. Parameters of cell death were investigated by flow cytometry-cell viability, DNA fragmentation, phosphatidylserine externalization, mitochondrial depolarization, neutral lipid accumulation and production of reactive oxygen species-and by fluorescence microscopy-chromatin condensation. Additionally a spectrofluorometric assay was employed to determine the activities of caspase--3, 6 and 8. Evidence is presented herein that OA is less toxic to human lymphocytes than LA. However, both fatty acids promoted apoptosis and necrosis of these cells. The mechanism of cell death induced by OA involved activation of caspase 3 while the mechanism of death induced by LA involved mitochondrial depolarization and ROS production. Importantly, neutral lipid accumulation may be a mechanism to protect lymphocytes against the toxicity induced by OA. OA may offer an immunological less problematic alternative to LA with respect to fatty acid composition of parenteral nutritional emulsions.

Comparative toxicity of oleic acid and linoleic acid on Jurkat cells

BACKGROUND

Lipid emulsions for parenteral nutrition commercially available are mainly composed of long-chain triacylglycerol containing a high proportion of alpha-6 polyunsaturated fatty acids or alpha-9 monounsaturated fatty acids. The immunological impact of such therapy is particularly important because parenteral and enteral diets are often administered to critical ill patients. The comparative toxicity of oleic acid and linoleic acid on Jurkat cells, a human T lymphocyte cell line, and the type of cell death induced by these fatty acids were determined.

METHODS

Cell death was investigated by cytometry: decrease in cell volume, increase of granularity, DNA fragmentation, phosphatidylserine externalization, mitochondrial depolarization, lipid accumulation; by fluorescence microscopy: chromatin condensation and acridine orange/ethidium bromide assay; and by RT-PCR: mRNA expression of apoptotic genes.

RESULTS

Evidence is presented herein that oleic acid is much less toxic to Jurkat cells than linoleic acid. Both fatty acids promote apoptosis and necrosis of these cells. The mechanism of cell death induced by these fatty acids seem to involve with mitochondrial depolarization, lipid accumulation and the levels of C-MYC and P53 mRNA expression.

CONCLUSION

Therefore, oleic acid may offer an immunological less harmful alternative to linoleic acid for parenteral and enteral diets preparation.

Prolonged butyrate treatment inhibits the migration and invasion potential of HT1080 tumor cells

Butyrate, a normal constituent of the colonic luminal contents, is produced by the bacterial fermentation of dietary fibers and resistant starches. It has been hypothesized that butyrate may inhibit the invasion of tumor cells. The purpose of the present study was to investigate the effects of butyrate treatment on the growth, migration, and invasion characteristics of tumor HT1080 cells. HT1080 cells cultured in the presence of 0.5 and 1 mmol/L butyrate for 14 d exhibited an increase in the G(1) and G(2) fractions with a concomitant drop in the S-phase, thus showing slower cell growth. Interestingly, 0.5 and 1 mmol/L butyrate inhibited the migration and invasion rate of the tumor cells compared with the untreated (control) cells. The protein and mRNA levels of the tissue inhibitors of metalloproteinase-1 (TIMP-1) and TIMP-2 were significantly increased in HT1080 cells cultured with 0.5 and 1 mmol/L butyrate. Enzymatic activities and the mRNA level of the latent forms of matrix metalloproteinase (MMP), pro-MMP-2 and pro-MMP-9, were also increased in HT1080 cells cultured with 0.5 and 1 mmol/L butyrate. In contrast, the active form of MMP-2 was detectable by zymographic analysis in control but not butyrate-conditioned media. Collectively, these results demonstrate that prolonged and low-dose butyrate treatment increases both prometastasis MMP-2, -9 and antimetastasis TIMP-1, -2 expression, and the net effect of these increases is the inhibition of pro-MMP-2 activation and of tumor cell migration/invasion potential.

Do aberrant crypt foci have predictive value for the occurrence of colorectal tumours? Potential of gene expression profiling in tumours

The effects of different dietary compounds on the formation of aberrant crypt foci (ACF) and colorectal tumours and on the expression of a selection of genes were studied in rats. Azoxymethane-treated male F344 rats were fed either a control diet or a diet containing 10% wheat bran (WB), 0.2% curcumin (CUR), 4% rutin (RUT) or 0.04% benzyl isothiocyanate (BIT) for 8 months. ACF were counted after 7, 15 and 26 weeks. Tumours were scored after 26 weeks and 8 months. We found that the WB and CUR diets inhibited the development of colorectal tumours. In contrast, the RUT and BIT diets rather enhanced (although not statistically significantly) colorectal carcinogenesis. In addition, the various compounds caused different effects on the development of ACF. In most cases the number or size of ACF was not predictive for the ultimate tumour yield. The expression of some tumour-related genes was significantly different in tumours from the control group as compared to tumours from the treated groups. It was concluded that WB and CUR, as opposed to RUT and BIT, protects against colorectal cancer and that ACF are unsuitable as biomarker for colorectal cancer. Effects of the different dietary compounds on metalloproteinase 1 (TIMP-1) expression correlated well with the effects of the dietary compounds on the ultimate tumour yield.

Short chain fatty acid regulation of signaling genes expressed by the intestinal epithelium

Changes in diet greatly affect the mucosal immune system, particularly in diseases such as Crohn's disease and necrotizing enterocolitis. This review examines the hypothesis that alterations in the luminal environment of the intestine regulate the expression of genes in the epithelium responsible for signaling to immune cells. Increasing chemokine expression in the mouse intestinal epithelium using transgenic techniques enhances the recruitment of neutrophils and lymphocytes into the intestine. Furthermore, SCFA concentrations in the intestinal lumen vary markedly with diet. SCFAs alter chemokine expression by inhibiting histone deacetylase activity in the enterocyte. The review therefore describes a molecular pathway explaining how changes in diet may alter leukocyte recruitment by regulating enterocyte gene expression. It is likely that other similar pathways remain to be discovered.

Time- and dose-dependent effects of curcumin on gene expression in human colon cancer cells

BACKGROUND: Curcumin is a spice and a coloring food compound with a promising role in colon cancer prevention. Curcumin protects against development of colon tumors in rats treated with a colon carcinogen, in colon cancer cells curcumin can inhibit cell proliferation and induce apoptosis, it is an anti-oxidant and it can act as an anti-inflammatory agent. The aim of this study was to elucidate mechanisms and effect of curcumin in colon cancer cells using gene expression profiling. METHODS: Gene expression changes in response to curcumin exposure were studied in two human colon cancer cell lines, using cDNA microarrays with four thousand human genes. HT29 cells were exposed to two different concentrations of curcumin and gene expression changes were followed in time (3, 6, 12, 24 and 48 hours). Gene expression changes after short-term exposure (3 or 6 hours) to curcumin were also studied in a second cell type, Caco-2 cells. RESULTS: Gene expression changes (>1.5-fold) were found at all time points. HT29 cells were more sensitive to curcumin than Caco-2 cells. Early response genes were involved in cell cycle, signal transduction, DNA repair, gene transcription, cell adhesion and xenobiotic metabolism. In HT29 cells curcumin modulated a number of cell cycle genes of which several have a role in transition through the G2/M phase. This corresponded to a cell cycle arrest in the G2/M phase as was observed by flow cytometry. Functional groups with a similar expression profile included genes involved in phase-II metabolism that were induced by curcumin after 12 and 24 hours. Expression of some cytochrome P450 genes was downregulated by curcumin in HT29 and Caco-2 cells. In addition, curcumin affected expression of metallothionein genes, tubulin genes, p53 and other genes involved in colon carcinogenesis. CONCLUSIONS: This study has extended knowledge on pathways or processes already reported to be affected by curcumin (cell cycle arrest, phase-II genes). Moreover, potential new leads to genes and pathways that could play a role in colon cancer prevention by curcumin were identified.

Butyrate inhibits leukocyte adhesion to endothelial cells via modulation of VCAM-1

BACKGROUND

Leukocyte recruitment to areas of inflammation depends on Integrin-VCAM/ICAM interaction. Blocking the vascular cell adhesion molecule (VCAM-1) and the intracellular adhesion molecule (ICAM-1) may have therapeutic benefit for the inflammatory component of bowel disease. Notably, the induction of ICAM and VCAM is mediated by a nuclear factor kappaB (NF-kappaB)-dependent mechanism. We investigated whether the anti-inflammatory properties of butyrate are mediated via the modulation of VCAM and ICAM on human endothelial cells.

METHODS

VCAM-1 and ICAM-1 expression on human endothelial cells upon tumor necrosis factor-alpha (TNF-alpha) stimulation was assessd by FACS analysis. A monocyte adhesion assay was performed to evaluate the relevance of a modulated CAM-expression. Electrophoretic mobility shift assays were applied to investigate NF-kappaB activation.

RESULTS

The observed butyrate-associated inhibition of monocyte adhesion to endothelial cells is associated with an inhibition of NF-kappaB activation in human endothelial cells. In this context, the observed suppression of the TNF-alpha induced VCAM-1 expression is likely to play an essential role.

CONCLUSIONS

Butyrate inhibits VCAM-1 mediated leukocyte adhesion to human endothelial cells. This inhibition may contribute to the anti-inflammatory effects of butyrate in patients with distal ulcerative colitis.

Functional identification of SLC5A8, a tumor suppressor down-regulated in colon cancer, as a Na(+)-coupled transporter for short-chain fatty acids

SLC5A8, a tumor suppressor gene down-regulated in human colon cancer, codes for a transporter in the Na(+)/glucose cotransporter gene family, but the definitive functional identity of the transporter protein is not known. Since this gene is expressed abundantly in the colon where short-chain fatty acids are generated by bacterial fermentation, we tested the hypothesis that it codes for a Na(+)-coupled transporter for these fatty acids. The coding region of SLC5A8 mRNA was amplified from human intestine and expressed heterologously in Xenopus laevis oocytes. Transport function was monitored by uptake of radiolabeled substrates and by substrate-induced currents under voltage-clamp conditions. Uptake of short-chain fatty acids (lactate, pyruvate, acetate, propionate, and butyrate) in oocytes expressing SLC5A8 was severalfold higher than in uninjected oocytes. Exposure of SLC5A8-expressing oocytes to these fatty acids induced inward currents under voltage-clamp conditions in a Na(+)-dependent manner. These currents were saturable and the substrate concentrations needed for half-maximal induction of the current were in the range of 0.08-2.5 mm. The substrate-induced currents decreased as the carbon chain length of the substrates increased. The Na(+)-activation kinetics indicated involvement of more than one Na(+) ion in the activation process. Direct measurements of substrate (propionate) and charge transfer showed that three positive charges are transferred into oocytes per substrate molecule. These studies establish the functional identity of SLC5A8 as a Na(+)-coupled transporter for short-chain fatty acids.

Sodium Butyrate Inhibits Cell Growth and Stimulates p21WAF1/CIP1 Protein in Human Colonic Adenocarcinoma Cells Independently of p53 Status

Butyric acid, one of the short-chain fatty acids produced by microbial fermentation in the colon, exhibits antiproliferative activities in various cancer cell lines. The initial objective of the study was to assess whether the effect of sodium butyrate (NaB) on cell growth differed by p53 status of the cells. Four human colorectal adenocarcinoma cell lines were used: HT29 (p53 point mutation), Caco2 (p53 truncation), LS513 (p53 wild type), and Lovo (p53 wild type). NaB significantly inhibited cell growth in all four cell lines. NaB arrested HT29 and LS513 cells in G0/G1 and Caco2 and Lovo in G2-phase. A second objective was to determine whether NaB similarly affected the cyclin-dependent kinase inhibitor, p21WAF1/CIP1. In all cell lines, p21 mRNA levels were immediately elevated after NaB exposure, and p21 protein levels were increased within 6 h. NaB increased p21 promoter activity in both Caco2 and Lovo, suggesting p53 independence. NaB did not influence p21 mRNA stability. Although three DNase I hypersensitivity sites were identified in the region of the p21 gene, induction of p21 mRNA by NaB was not accompanied by relaxation of the chromatin in the region of the p21 gene.

Inhibition of histone deacetylase activity by butyrate

This article reviews the effects of the short-chain fatty acid butyrate on histone deacetylase (HDAC) activity. Sodium butyrate has multiple effects on cultured mammalian cells that include inhibition of proliferation, induction of differentiation and induction or repression of gene expression. The observation that butyrate treatment of cells results in histone hyperacetylation initiated a flurry of activity that led to the discovery that butyrate inhibits HDAC activity. Butyrate has been an essential agent for determining the role of histone acetylation in chromatin structure and function. Interestingly, inhibition of HDAC activity affects the expression of only 2% of mammalian genes. Promoters of butyrate-responsive genes have butyrate response elements, and the action of butyrate is often mediated through Sp1/Sp3 binding sites (e.g., p21(Waf1/Cip1)). We demonstrated that Sp1 and Sp3 recruit HDAC1 and HDAC2, with the latter being phosphorylated by protein kinase CK2. A model is proposed in which inhibition of Sp1/Sp3-associated HDAC activity leads to histone hyperacetylation and transcriptional activation of the p21(Waf1/Cip1) gene; p21(Waf1/Cip1) inhibits cyclin-dependent kinase 2 activity and thereby arrests cell cycling. Pending the cell background, the nonproliferating cells may enter differentiation or apoptotic pathways. The potential of butyrate and HDAC inhibitors in the prevention and treatment of cancer is presented.