PASSCLAIM--diet-related cancer

The comet assay for the evaluation of gut content genotoxicity: Use in human studies as an early biomarker of colon cancer risk

This short narrative review describes the use of the comet assay to evaluate the formation of genotoxic compounds in the gut lumen in human studies. The fecal water genotoxicity assay is based on ability of the gut content to induce genotoxicity in a cellular model, employing the aqueous component of the feces (fecal water) as this is supposed to contain most of the reactive species and to convey them to the intestinal epithelium. This non-invasive and low-cost assay has been demonstrated to be associated with colon cancer risk in animal models, and although the final validation against human tumors is lacking, it is widely used as a colo-rectal cancer risk biomarker in human nutritional intervention studies. The contribution given to the field of nutrition and cancer by the FW genotoxicity assay is highlighted, particularly in conjunction with other risk biomarkers, to shed light on the complex relationship among diet, microbiota, individual subject characteristics and the formation of genotoxic compounds in the gut.

Mechanism Analysis of Antiangiogenic d-Isofloridoside from Marine Edible Red algae Laurencia undulata in HUVEC and HT1080 cell

Laurencia undulata, as one of the most biologically active species in the genus Laurencia, is an edible folk herb red algae. Among them, d-isofloridoside (DIF, 940.68 Da) is isolated from Laurencia undulata, which has antioxidant and matrix metalloproteinases (MMP) inhibitory activities. However, its mechanism of action on tumor angiogenesis has not yet been reported. In this study, we have studied the mechanism of DIF on tumor metastasis and angiogenesis in HT1080 cell and human vascular endothelial cell (HUVEC). The results show that DIF can reduce the activity of MMP-2/9, and can inhibit the expression of hypoxia-inducible factor-1α (HIF-1α) by regulating the downstream PI3K/AKT and mitogen-activated protein kinases (MAPK) pathways, thereby down-regulating the production of vascular endothelial growth factor (VEGF) in CoCl₂-induced HT1080 cell. In addition, DIF can inhibit the activation of VEGF receptor (VEGFR-2), regulate downstream PI3K/AKT, MAPK, nuclear factor-kappa B (NF-κB) signal pathways, activate apoptosis, and thus down-regulate the production of platelet-derived growth factor (PDGF) in VEGF-induced HUVEC. In conclusion, our research shows that DIF has the potential to develop into a tumor-preventing functional food and tumor angiogenesis inhibitor, and it can provide theoretical guidance for the high-value comprehensive utilization of edible red algae Laurencia undulata.

Pharmacokinetic alterations of rhubarb anthraquinones in experimental colitis induced by dextran sulfate sodium in the rat

ETHNOPHARMACOLOGICAL RELEVANCE

Rhubarb (Rhei Rhizoma et Radix) is used for the treatment of digestive diseases in traditional medicinal practice in China. Recent studies also support its beneficial activities in alleviating ulcerative colitis (UC).

AIM OF THE STUDY

This study aimed to characterize the oral pharmacokinetics of rhubarb anthraquinones, the main bioactive components of this herb, in the experimental chronic colitis rat model induced by dextran sulfate sodium (DSS) and to identify the factors causing the pharmacokinetic alterations.

MATERIALS AND METHODS

Rats received drinking water (normal group) or 5% DSS for the first 7 days and 3% DSS for additional 14 days (UC group). On day 21 both groups received an oral dose of the rhubarb extract (equivalent to 5.0g crude drug/kg body weight). Plasma anthraquinone aglycones levels were determined directly by an LC-MS/MS method and the total of each anthraquinone (aglycone+conjugates) was quantified after β-glucuronidases hydrolysis.

RESULTS

Rhubarb anthraquinones predominantly existed as conjugates in plasma samples from both groups and only free aloe-emodin, rhein and emodin were detected. Compared to the normal rats, both C_max and AUC of the three free anthraquinones were increased, while the systemic exposure (AUC) of the total (aglycone+conjugates) of most anthraquinones decreased by UC accompanied by the disappearance of multiple-peak phenomenon in the plasma concentration-time profiles. Gut bacteria from UC rats exhibited a decreased activity in hydrolyzing anthraquinone glycosides to form respective aglycone and there were significant decreases in microbial β-glucosidases and β-glucuronidases activities. Moreover, the intestinal microsomes from UC rats catalyzed glucuronidation of free anthraquinones with higher activities, while the activities of hepatic microsomes were comparable to normal rats.

CONCLUSIONS

The decreases of β-glucuronidases activity in DSS-induced chronic rat colitis should mainly account for the decreases in systemic exposure and abrogation of enterohepatic recirculation of most rhubarb anthraquinones after oral intake.

High dose of prebiotics reduces fecal water cytotoxicity in healthy subjects

SCOPE

In vitro and animal studies have shown differential colonic fermentation of structurally different prebiotics. We evaluated the impact of two structurally different prebiotics (wheat bran extract (WBE, containing arabinoxylan-oligosaccharides) and oligofructose) on colonic fermentation and markers of bowel health in healthy volunteers.

METHODS AND RESULTS

Nineteen healthy subjects completed a double-blind, cross-over randomized controlled trial. Interventions with WBE, oligofructose or placebo for 2 wk (week 1: 15 g/day; week 2: 30 g/day) were separated by 2-wk wash-out periods. At the end of each study period, colonic fermentation was characterized through a metabolomics approach. Fecal water genotoxicity and cytotoxicity were determined using the comet and WST-1 assay, respectively, as parameters of gut health. Cluster analysis revealed differences in effects of WBE and oligofructose on colonic fermentation. WBE, but not oligofructose, reduced fecal p-cresol (p = 0.009) and isovaleric acid concentrations (p = 0.022), markers of protein fermentation. Fecal water cytotoxicity was significantly lower after intake of WBE (p = 0.015). Both WBE- and oligofructose-intake tended to reduce fecal water genotoxicity compared to placebo (WBE: p = 0.060; oligofructose: p = 0.057). Changes in fermentation were not related to changes in fecal water toxicity.

CONCLUSION

Structurally different prebiotics affect colonic fermentation and gut health in a different way.

Plant polyphenols and oxidative metabolites of the herbal alkenylbenzene methyleugenol suppress histone deacetylase activity in human colon carcinoma cells

Evidence has been provided that diet and environmental factors directly influence epigenetic mechanisms associated with cancer development in humans. The inhibition of histone deacetylase (HDAC) activity and the disruption of the HDAC complex have been recognized as a potent strategy for cancer therapy and chemoprevention. In the present study, we investigated whether selected plant constituents affect HDAC activity or HDAC1 protein status in the human colon carcinoma cell line HT29. The polyphenols (-)-epigallocatechin-3-gallate (EGCG) and genistein (GEN) as well as two oxidative methyleugenol (ME) metabolites were shown to inhibit HDAC activity in intact HT29 cells. Concomitantly, a significant decrease of the HDAC1 protein level was observed after incubation with EGCG and GEN, whereas the investigated ME metabolites did not affect HDAC1 protein status. In conclusion, dietary compounds were found to possess promising HDAC-inhibitory properties, contributing to epigenetic alterations in colon tumor cells, which should be taken into account in further risk/benefit assessments of polyphenols and alkenylbenzenes.

Enzyme deactivation treatments did not decrease the beneficial role of oat food in intestinal microbiota and short-chain fatty acids: an in vivo study

BACKGROUND

Steaming and roasting treatments are widely used enzyme deactivation methods in the oat food industry in China. Whether or not the enzyme deactivation treatments affect the nutritional function of oat foods is unknown. In the current study, we examined the effects of 4-week ingestion of steamed or roasted oat foods on the intestinal bacteria and short-chain fatty acids of rats.

RESULTS

Compared with rats taking no oat foods, rats taking normal oat foods or enzyme-deactivated oat foods showed significantly higher (P < 0.05) counts of Lactobacillus spp. and Bifidobacterium spp. in colon, significantly lower (P < 0.05) counts of Enterococcus spp. and coliforms in colon, and significantly higher (P < 0.05) levels of butyrate and acetate in colonic digesta. In addition, rats taking infrared roasting (IR)-treated oat foods also demonstrated significantly higher (P < 0.05) fecal Lactobacillus spp. counts and significantly lower (P < 0.05) cecal and fecal counts of E. coli, Enterococcus spp. and coliforms than rats taking no oat foods. As for the comparison between the enzyme-undeactivated oat group and the three enzyme-deactivated oat groups, there were no significant differences in most of the parameters (P > 0.05), though a few exceptions did exist.

CONCLUSION

Enzyme deactivation treatments did not decrease the beneficial role of oat food in the intestinal microbes and short-chain fatty acids of rats.

Potential role of probiotics on colorectal cancer prevention

Background

Colorectal cancer represents the most common malignancy of the gastrointestinal tract. Owing to differences in dietary habits and lifestyle, this neoplasm is more common in industrialized countries than in developing ones. Evidence from a wide range of sources supports the assumption that the link between diet and colorectal cancer may be due to an imbalance of the intestinal microflora.

Discussion

Probiotic bacteria are live microorganisms that, when administered in adequate amounts, confer a healthy benefit on the host, and they have been investigated for their protective anti-tumor effects. In vivo and molecular studies have displayed encouraging findings that support a role of probiotics in colorectal cancer prevention.

Summary

Several mechanisms could explain the preventive action of probiotics against colorectal cancer onset. They include: alteration of the intestinal microflora; inactivation of cancerogenic compounds; competition with putrefactive and pathogenic microbiota; improvement of the host’s immune response; anti-proliferative effects via regulation of apoptosis and cell differentiation; fermentation of undigested food; inhibition of tyrosine kinase signaling pathways.

Phylogenetic distribution of genes encoding β-glucuronidase activity in human colonic bacteria and the impact of diet on faecal glycosidase activities

Bacterial β-glucuronidase in the human colon plays an important role in cleaving liver conjugates of dietary compounds and xenobiotics, while other glycosidase activities are involved in the conversion of dietary plant glycosides. Here we detected an increase in β-glucuronidase activity in faecal samples from obese volunteers following a high-protein moderate carbohydrate weight-loss diet, compared with a weight maintenance diet, but little or no changes were observed when the type of fermentable carbohydrate was varied. Other faecal glycosidase activities showed little or no change over a fivefold range of dietary NSP intake, although α-glucosidase increased on a resistant starch-enriched diet. Two distinct groups of gene, gus and BG, have been reported to encode β-glucuronidase activity among human colonic bacteria. Degenerate primers were designed against these genes. Overall, Firmicutes were found to account for 96% of amplified gus sequences, with three operational taxonomic units particularly abundant, whereas 59% of amplified BG sequences belonged to Bacteroidetes and 41% to Firmicutes. A similar distribution of operational taxonomic units was found in a published metagenome dataset involving a larger number of volunteers. Seven cultured isolates of human colonic bacteria that carried only the BG gene gave relatively low β-glucuronidase activity that was not induced by 4-nitrophenyl-β-D-glucuronide. By comparison, in three of five isolates that possessed only the gus gene, β-glucuronidase activity was induced.

In vitro fermented nuts exhibit chemopreventive effects in HT29 colon cancer cells

It is proven that nuts contain essential macro- and micronutrients, e.g. fatty acids, vitamins and dietary fibre (DF). Fermentation of DF by the gut microflora results in the formation of SCFA which are recognised for their chemopreventive potential, especially by influencing cell growth. However, little is known about cellular response to complex fermentation samples of nuts. Therefore, we prepared and analysed (pH, SCFA, bile acids, tocopherol, antioxidant capacity) fermentation supernatant (fs) fractions of nuts (almonds, macadamias, hazelnuts, pistachios, walnuts) after in vitro fermentation and determined their effects on growth of HT29 cells as well as their genotoxic/anti-genotoxic potential. The fermented nut samples contained 2- to 3-fold higher amounts of SCFA than the faeces control, but considerable reduced levels of bile acids. While most of the investigated native nuts comprised relatively high amounts of tocopherol (α-tocopherol in almonds and hazelnuts and γ- and δ-tocopherol in pistachios and walnuts), rather low concentrations were found in the fs. All nut extracts and nut fs showed a strong antioxidant potential. Furthermore, all fs, except the fs pistachio, reduced growth of HT29 cells significantly. DNA damage induced by H₂O₂ was significantly reduced by the fs of walnuts after 15 min co-incubation of HT29 cells. In conclusion, this is the first study which presents the chemopreventive effects (reduction of tumour-promoting desoxycholic acid, rise in chemopreventive SCFA, protection against oxidative stress) of different nuts after in vitro digestion and fermentation, and shows the potential importance of nuts in the prevention of colon cancer.

Dietary patterns and risk of oral and pharyngeal cancer: a case-control study in Rio de Janeiro, Brazil

The study investigated the association between dietary patterns and oral cancer as part of a Latin American multicenter hospital-based case-control study, and included 210 incident cases of oral cancer and 251 controls. Dietary data were collected using a Food Frequency Questionnaire (FFQ). Factor analysis was used to define dietary patterns, which were categorized into terciles. Odds ratios (OR) with 95% confidence intervals (95%CI) were calculated using unconditional multiple logistic regression. The patterns "prudent", characterized mainly by vegetables and fruits, and "traditional", by rice, and pulses showed an inverse association with oral cancer for the higher tercile, respectively, OR = 0.44; 95%CI: 0.25-0.75, p value for trend (p tend) = 0.03; OR = 0.53; 95%CI: 0.30-0.93, p tend = 0.06. The "snacks pattern" was not associated with oral cancer. Besides the protective effect of a diet rich in vegetables and fruit, our data suggest that the traditional Brazilian diet, consisting mostly of rice and beans, may improve protection against oral cancer.

Glucosinolates in Brassica vegetables: the influence of the food supply chain on intake, bioavailability and human health

Glucosinolates (GLSs) are found in Brassica vegetables. Examples of these sources include cabbage, Brussels sprouts, broccoli, cauliflower and various root vegetables (e.g. radish and turnip). A number of epidemiological studies have identified an inverse association between consumption of these vegetables and the risk of colon and rectal cancer. Animal studies have shown changes in enzyme activities and DNA damage resulting from consumption of Brassica vegetables or isothiocyanates, the breakdown products (BDP) of GLSs in the body. Mechanistic studies have begun to identify the ways in which the compounds may exert their protective action but the relevance of these studies to protective effects in the human alimentary tract is as yet unproven. In vitro studies with a number of specific isothiocyanates have suggested mechanisms that might be the basis of their chemoprotective effects. The concentration and composition of the GLSs in different plants, but also within a plant (e.g. in the seeds, roots or leaves), can vary greatly and also changes during plant development. Furthermore, the effects of various factors in the supply chain of Brassica vegetables including breeding, cultivation, storage and processing on intake and bioavailability of GLSs are extensively discussed in this paper.

Diet, fecal water, and colon cancer--development of a biomarker

Colorectal cancer (CRC) is a leading cause of cancer incidence worldwide. Lifestyle factors, especially dietary intake, affect the risk of CRC development. Suitable risk biomarkers are required in order to assess the effect that specific dietary components have on CRC risk. The relationship between dietary intake and indicators of fecal water activity has been assessed using cell and animal models as well as human studies. This review summarizes the literature on fecal water and dietary components with a view to establishing further the potential role of fecal water as a source of CRC risk biomarkers. The literature indicates that fecal water activity markers are affected by specific dietary components linked with CRC risk: red meat, saturated fats, bile acids, and fatty acids are associated with an increase in fecal water toxicity, while the converse appears to be true for calcium, probiotics, and prebiotics. However, it must be acknowledged that the study of fecal water is still in its infancy and a number of issues need to be addressed before its usefulness can be truly gauged.

Chemopreventive effect of raw and cooked lentils (Lens culinaris L) and soybeans (Glycine max) against azoxymethane-induced aberrant crypt foci

Although lentils (Lens culinaris L) contain several bioactive compounds that have been linked to the prevention of cancer, the in vivo chemopreventive ability of lentils against chemically induced colorectal cancer has not been examined. Our present study examined the hypothesis that lentils could suppress the early carcinogenesis in vivo by virtue of their bioactive micro- and macroconstituents and that culinary thermal treatment could affect their chemopreventive potential. To accomplish this goal, we used raw whole lentils (RWL), raw split lentils (RSL), cooked whole lentils (CWL), and cooked split lentils (CSL). Raw soybeans (RSB; Glycine max) were used for the purpose of comparison with a well-studied chemopreventive agent. Sixty weanling Fischer 344 male rats, 4 to 5 weeks of age, were randomly assigned to 6 groups (10 rats/group): the control group (C) received AIN-93G diet, and treatment leguminous groups of RWL, CWL, RSL, CSL, and RSB received the treatment diets containing AIN-93G+5% of the above-mentioned legumes. After acclimatization for 1 week (at 5th to 6th week of age), all animals were put on the control and treatment diets separately for 5 weeks (from 6th to 11th week of age). At the end of the 5th week of feeding (end of 11th week of age), all rats received 2 subcutaneous injections of azoxymethane carcinogen at 15 mg/kg rat body weight per dose once a week for 2 consecutive weeks. After 17 weeks of the last azoxymethane injection (from 12th to 29th week of age), all rats were euthanized. Chemopreventive ability was assessed using colonic aberrant crypt foci and activity of hepatic glutathione-S-transferases. Significant reductions (P < .05) were found in total aberrant crypt foci number (mean +/- SEM) for RSB (27.33 +/- 4.32), CWL (33.44 +/- 4.56), and RSL (37.00 +/- 6.02) in comparison with the C group (58.33 +/- 8.46). Hepatic glutathione-S-transferases activities increased significantly (P < .05) in rats fed all treatment diets (from 51.38 +/- 3.66 to 67.94 +/- 2.01 micromol mg(-1) min(-1)) when compared with control (C) diet (26.13 +/- 1.01 micromol mg(-1) min(-1)). Our findings indicate that consumption of lentils might be protective against colon carcinogenesis and that hydrothermal treatment resulted in an improvement in the chemopreventive potential for the whole lentils.

Overview of experimental data on reduction of colorectal cancer risk by inulin-type fructans

Colorectal cancer is related to diet, lifestyle, physical inactivity, and obesity. The responsible carcinogens cause mutations or enhance cell growth. Inulin-type fructans may counteract the effects via their gut flora-mediated fermentation products in vitro and in vivo. Important products formed by fermentation of inulin-type fructans with human gut flora are short-chain fatty acids. Of these, butyrate and propionate inhibit growth of colon tumor cells and histone deacetylases. Butyrate also causes apoptosis, reduces metastasis in colon cell lines, and protects from genotoxic carcinogens by enhancing expression of enzymes involved in detoxification. Fermentation supernatants of inulin have similar growth-inhibitory effects on colon adenoma and carcinoma cells and induce histone hyperacetylation by inhibiting histone deacetylases. In animal models inulin-type fructans prevent and retard colorectal carcinogenesis. Several studies reported the reduction of chemically induced preneoplastic lesions or tumors in the colon of rodents treated with inulin-type fructans. The human intervention study (SYNCAN project) sought to provide the experimental evidence for risk reduction by inulin-type fructans in humans. One group of polypectomized people at high risk for colon cancer and another of colon cancer volunteers after curative resection were given a synbiotic preparation. There were clear functional effects of the synbiotic because numerous different cancer risk markers were favorably altered. In conclusion, there is considerable experimental evidence that inulin modulates parameters of colon cancer risks in human colon cells, in animals, and in a human intervention trial. The involved mechanisms possibly include reduction of exposure to risk factors and suppression of tumor cell survival.

Effect of fecal water on an in vitro model of colonic mucosal barrier function

Fecal water (FW) has been shown to exert, in cultured cells, cytotoxic and genotoxic effects that have implications for colorectal cancer (CRC) risk. We have investigated a further biological activity of FW, namely, the ability to affect gap junctions in CACO2 cell monolayers as an index of mucosal barrier function, which is known to be disrupted in cancer. FW samples from healthy, free-living, European subjects that were divided into two broad age groups, adult (40+/-9.7 yr; n=53) and elderly (76+/-7.5 yr; n=55) were tested for effects on gap junction using the transepithelial resistance (TER) assay. Overall, treatment of CACO2 cells with FW samples from adults increased TER (+4%), whereas FW from elderly subjects decreased TER (-5%); the difference between the two groups was significant (P<0.05). We also measured several components of FW potentially associated with modulation of TER, namely, short-chain fatty acid (SCFA) and ammonia. SCFAs (propionic, acetic, and n-butyric) were significantly lower in the elderly population (-30%, -35%, and -21%, respectively, all P A pound 0.01). We consider that FW modulation of in vitro epithelial barrier function is a potentially useful noninvasive biomarker, but it requires further validation to establish its relationship to CRC risk.

Enhanced estrogenic responses and sensitivity to azoxymethane following dietary soy isoflavone supplementation in older female rats

Soy isoflavones are popular supplements among middle-aged and older women based on their potential protection against cancer and their use as alternative hormone replacement therapy. The purpose of this study was to investigate the effects of dietary soy isoflavones on early stage colon cancer in various ages of female rats. Young (1month), mature (11month) and old (22month) female Fisher 344 rats were fed either the control diet or a diet containing 0.4% soy isoflavone isolate for 1week, injected once with 20mg/kg azoxymethane (AOM) and maintained on the diets for another 15weeks. The concentration of isoflavones in the diet was 2g/kgdiet, composed of 1.2g/kg genistin, 0.7g/kg daidzin and 0.1g/kg other isoflavones including glycitin, acetylgenistin, acetyldaidzin, genistein, daidzein, and glycitein. There was no difference over all ages in the development of preneoplastic colonic aberrant crypt foci between rats fed the soy compared to the control diet, indicating that the soy diet did not provide protection against early stage colonic carcinogenesis. On the contrary, several adverse effects of soy supplementation in female AOM-treated rats were observed. Soy-supplemented rats had greater weight loss and a slower recovery of body weight following the AOM injection compared to rats fed the control diet and these changes increased with age. Five of the 21 rats fed the soy supplement died before the end of the experiment while all animals on the control diet survived to term. The density of normal crypts lining the colonic mucosa was reduced in rats fed the soy compared to control diet, indicating gastrointestinal damage. Uterine weights, serum estradiol and serum isoflavone levels were increased in mature and old female rats fed the soy-supplemented diets compared to age-matched controls, suggesting an increasing estrogenic response with age to isoflavone supplementation. These adverse effects of soy isoflavones in aged female animals need further examination because women, and particularly older women, are the prime target population for consumption of soy supplements.

Dietary synbiotics reduce cancer risk factors in polypectomized and colon cancer patients

BACKGROUND

Animal studies suggest that prebiotics and probiotics exert protective effects against tumor development in the colon, but human data supporting this suggestion are weak.

OBJECTIVE

The objective was to verify whether the prebiotic concept (selective interaction with colonic flora of nondigested carbohydrates) as induced by a synbiotic preparation-oligofructose-enriched inulin (SYN1) + Lactobacillus rhamnosus GG (LGG) and Bifidobacterium lactis Bb12 (BB12)-is able to reduce the risk of colon cancer in humans.

DESIGN

The 12-wk randomized, double-blind, placebo-controlled trial of a synbiotic food composed of the prebiotic SYN1 and probiotics LGG and BB12 was conducted in 37 colon cancer patients and 43 polypectomized patients. Fecal and blood samples were obtained before, during, and after the intervention, and colorectal biopsy samples were obtained before and after the intervention. The effect of synbiotic consumption on a battery of intermediate bio-markers for colon cancer was examined.

RESULTS

Synbiotic intervention resulted in significant changes in fecal flora: Bifidobacterium and Lactobacillus increased and Clostridium perfringens decreased. The intervention significantly reduced colorectal proliferation and the capacity of fecal water to induce necrosis in colonic cells and improve epithelial barrier function in polypectomized patients. Genotoxicity assays of colonic biopsy samples indicated a decreased exposure to genotoxins in polypectomized patients at the end of the intervention period. Synbiotic consumption prevented an increased secretion of interleukin 2 by peripheral blood mononuclear cells in the polypectomized patients and increased the production of interferon gamma in the cancer patients.

CONCLUSIONS

Several colorectal cancer biomarkers can be altered favorably by synbiotic intervention.

Effect of azoxymethane and curcumin on transcriptional levels of cyclooxygenase-1 and -2 during initiation of colon carcinogenesis

BACKGROUND

Curcumin is well documented as an effective colonic chemopreventive agent in preclinical studies. Inhibition of arachidonic acid metabolism has been considered one of anticarcinogenic mechanisms of curcumin. We recently reported resistance of middle-aged F344 male rats to inhibition of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) by curcumin (Nutr Cancer, 48, 37-43). It was important to confirm this finding and to find potential mechanisms responsible, as loss of preventive activity of curcumin due to aging was a novel finding, with important implications for human intervention trials.

METHODS

To confirm our previous findings, and investigate arachidonic acid metabolism as a potential mechanism of age-related differences in response to curcumin, middle-aged F344 male rats were given AOM injections after being fed their experimental diets, 0.6% curcumin or control diet. Colonic ACF were evaluated and colonic levels of cyclooxygenase (COX)-1 and 2 mRNA and prostaglandin E2 (PGE2) were measured. Next, we investigated the short-term effect of AOM and curcumin on arachidonic acid metabolism in young rats. Six week-old rats were given injections of either AOM or untreated following their experimental diets. Colonic COX-1 and COX-2 mRNA as well as PGE2 levels were measured shortly after AOM treatment. Lastly, three different ages of F344 rats were treated with either AOM or saline, and colonic COX-1 and COX-2 mRNA levels were measured shortly after the injections to find if aging alters the effect of AOM on COX mRNA expression.

RESULTS

In middle-aged rats, dietary curcumin did not reduce the number of ACF and surprisingly increased colonic levels of COX-2 mRNA. Colonic COX-2 and PGE2 levels were also significantly increased in young rats fed curcumin after AOM injections. Interestingly, AOM did not affect COX-2 but decreased COX-1 expression in all ages.

CONCLUSIONS

Our study suggests that during initiation, AOM inhibits colonic COX-1 expression without affecting COX-2 and dietary curcumin may increase COX-2 expression to compensate AOM-induced reduction of COX-1 expression.

Anthocyanin-Rich Extracts Inhibit Multiple Biomarkers of Colon Cancer in Rats

The aim of the present study was to investigate the chemoprotective activity of anthocyanin-rich extracts (AREs) from bilberry (Vaccinium myrtillus L.), chokeberry (Aronia meloncarpa E.), and grape (Vitis vinifera) by assessing multiple biomarkers of colon cancer in male rats treated with a colon carcinogen, azoxymethane. Fischer 344 male rats were fed the AIN-93 diet (control) or AIN-93 diet supplemented with AREs for 14 wk. Biomarkers that were evaluated included the number and multiplicity of colonic aberrant crypt foci (ACF), colonic cell proliferation, urinary levels of oxidative DNA damage, and expression of cyclooxygenase (COX) genes. To assess the bioavailability, levels of anthocyanins in serum, urine, and feces were evaluated. Total ACF were reduced (P<0.05) in bilberry, chokeberry, and grape diet groups compared with the control group. The number of large ACF was also reduced (P<0.05) in bilberry and chokeberry ARE-fed rats. Colonic cellular proliferation was decreased in rats fed bilberry ARE and chokeberry ARE diets. Rats fed bilberry and grape ARE diets had lower COX-2 mRNA expression of gene. High levels of fecal anthocyanins and increased fecal mass and fecal moisture occurred in ARE-fed rats. There was also a significant reduction (P<0.05) in fecal bile acids in ARE-fed rats. The levels of urinary 8-hydroxyguanosine were similar among rats fed different diets. These results support our previous in vitro studies suggesting a protective role of AREs in colon carcinogenesis and indicate multiple mechanisms of action.

Review article: bifidobacteria as probiotic agents -- physiological effects and clinical benefits

Bifidobacteria, naturally present in the dominant colonic microbiota, represent up to 25% of the cultivable faecal bacteria in adults and 80% in infants. As probiotic agents, bifidobacteria have been studied for their efficacy in the prevention and treatment of a broad spectrum of animal and/or human gastrointestinal disorders, such as colonic transit disorders, intestinal infections, and colonic adenomas and cancer. The aim of this review is to focus on the gastrointestinal effects of bifidobacteria as probiotic agents in animal models and man. The traditional use of bifidobacteria in fermented dairy products and the GRAS ('Generally Recognised As Safe') status of certain strains attest to their safety. Some strains, especially Bifidobacterium animalis strain DN-173 010 which has long been used in fermented dairy products, show high gastrointestinal survival capacity and exhibit probiotic properties in the colon. Bifidobacteria are able to prevent or alleviate infectious diarrhoea through their effects on the immune system and resistance to colonization by pathogens. There is some experimental evidence that certain bifidobacteria may actually protect the host from carcinogenic activity of intestinal flora. Bifidobacteria may exert protective intestinal actions through various mechanisms, and represent promising advances in the fields of prophylaxis and therapy.

Kinetics of biomarkers: biological and technical validity of isoprostanes in plasma

Isoprostanes, non-enzymatic peroxidation products of arachidonic acid, are attractive biomarkers of oxidative stress in research in biology, medicine and nutrition. For the appropriate use of biomarkers it is required that these are both biologically and technically valid. Whereas the biological validity of isoprostanes is well-established, it is technically quite complicated to measure isoprostanes and its metabolites in body fluids, and its rapid disappearance from plasma may hamper practical application. This paper shortly introduces isoprostanes as a biomarker for studies with humans, describes a novel fast and sensitive method for measuring isoprostanes in plasma by high-performance liquid chromatography and tandem mass spectrometry, and provides several examples of the use of the method in studies in humans. By taking care of the biological and technical validity of this biomarker it is possible to establish the antioxidant effects of some food ingredients in studies with human volunteers.