Effect of common Brassica vegetables (Brussels sprouts and red cabbage) on the development of preneoplastic lesions induced by 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in liver and colon of Fischer 344 rats

The hypolipidemic, anti-inflammatory and antioxidant effect of Kavolì® aqueous extract, a mixture of Brassica oleracea leaves, in a rat model of NAFLD

Herein we characterized the bioactive metabolites of the aqueous extract of Kavolì®, a commercial product composed of a mixture of Brassica oleracea leaves, and assessed its potential ameliorating effects in a rat model of non-alcoholic fatty liver disease (NAFLD). Kavolì® extract showed high levels of bioactive compounds and strong in vitro antioxidant activities. Chlorogenic and neochlorogenic acids were identified as the most representative polyphenols. The administration of brassica extract to steatotic rats significantly ameliorated the levels of blood lipids and transaminases, and lipid content and inflammatory markers in liver. Oxidative stress parameters were significantly improved in both liver and brain of steatotic rats. Moreover, plasma and feces levels of short chain fatty acids (SCFAs) were bring back close to control values by Kavolì® treatment, in spite of high fat diet/streptozotocin (HFD/STZ)-induced alterations. The efficacy of Kavolì® in treating hypercholesterolemia, reducing the level of inflammation and cardiovascular disease biomarkers, steatosis and oxidative stress parameters, as well as the ability in modulating SCFAs levels is probably related to the bioactive compounds of the water extract administered to the rat model of NAFLD. In particular, the ameliorating effects are largely attributable to the high content in polyphenols observed in our study.

Young shoots of red cabbage are a better source of selected nutrients and glucosinolates in comparison to the vegetable at full maturity

Cruciferous vegetables are a valuable source of ingredients with health benefits. The most characteristic compounds of cruciferous vegetables with identified anticancer properties are glucosinolates. Young shoots and sprouts of red cabbage are becoming a popular fresh food rich in nutrients and bioactive compounds. The objective of this research was to determine, for the first time in a comprehensive approach, whether young shoots of red headed cabbage are a better source of selected nutrients and glucosinolates in the human diet in comparison to the vegetable at full maturity. The proximate composition (protein, fat, digestible carbohydrates, fiber), fatty acids profile, minerals (calcium, magnesium, potassium, sodium, iron, zinc, manganese, copper), as well as glucosinolates were examined. The red headed cabbage was characterized by a significantly larger amount of dry matter, and total and digestible carbohydrates in comparison to young shoots. The ready-to-eat young shoots, which are in the phase of intensive growth, are a better source of protein, selected minerals, and especially glucosinolates. The level of some nutrients can be enhanced and the intake of pro-healthy glucosinolates can be significantly increased by including young shoots of red cabbage into the diet.

Cruciferous vegetables intake and the risk of colorectal cancer: a meta-analysis of observational studies

BACKGROUND

Epidemiological studies have reported inconsistent associations between cruciferous vegetable (CV) intake and colorectal cancer (CRC) risk. To our knowledge, a comprehensive and quantitative assessment of the association between CV intake and CRC has not been reported.

METHODS

Relevant articles were identified by searching MEDLINE. We pooled the relative risks (RR) from individual studies using a random-effect model and carried out heterogeneity and publication bias analyses.

RESULTS

Twenty-four case-control and 11 prospective studies were included in our analysis. When all studies were pooled, we yielded a significantly inverse association between CV (RR: 0.82; 95% confidence interval 0.75-0.90) intake and CRC risk. Specific analysis for cabbage and broccoli yielded similar result. When separately analyzed, case-control studies of CV intake yield similar results, and the results from the prospective studies showed borderline statistical significance. Moreover, significant inverse associations were also observed in colon cancer and its distal subsite both among prospective and case-control studies.

CONCLUSIONS

Findings from this meta-analysis provide evidence that high intake of CV was inversely associated with the risk of CRC and colon cancer in humans. Further analysis on other specific CV, food preparation methods, stratified results by anatomic cancer site, and subsite of colon cancer should be extended in future study.

Effect of polyphenols extracts from Brassica vegetables on erythrocyte membranes (in vitro study)

The aim of this work was to estimate the in vitro effects of polyphenol extracts from Brassica vegetables (Brussels sprouts and red cabbage) on erythrocyte membranes with normal and high concentration of cholesterol. To determine the effect of phenolic compounds we prospectively studied cholesterol concentration, lipid peroxidation, membrane fluidity and ATPase activity. Polyphenol extracts from Brassica vegetables resulted in statistically significant reductions in cholesterol concentrations in hypercholesterolemic erythrocytes. For control erythrocytes, no significant reduction of cholesterol levels was observed for both extracts. Decreases in lipid peroxidation intensity were observed after incubation of hypercholesterolemic erythrocytes with the extracts. No changes in membrane fluidity for both extracts were noted for normal and hypercholesterolemic erythrocytes. The activity of ATPase decreased after incubation of normal and hypercholesterolemic erythrocytes with extract from Brassica vegetables. Our results indicate that polyphenols from red cabbage and Brussels sprout may directly influence erythrocyte membrane properties.

Nuclear factor-erythroid 2-related factor 2 as a chemopreventive target in colorectal cancer

INTRODUCTION

Numerous epidemiological studies have linked consumption of cruciferous vegetables to a reduced risk of colorectal cancer (CRC) in individuals. It is currently well accepted that chronic inflammation is a contributing factor in 15 - 20% malignancies including CRC. Many chemopreventive compounds are effective in preclinical systems and many ongoing clinical trials are showing promising findings. Many of these compounds could activate the antioxidant responsive element (ARE), a critical regulatory element for Phase II protective/detoxification and antioxidative stress enzymes mediated by nuclear factor-erythroid 2-related factor 2 (Nrf2). Recently, Nrf2 has emerged as a novel target for the prevention of CRC.

AREAS COVERED

A full literature search was performed using PubMed with the key words 'ARE, Nrf2, colon, colorectal cancer, chemoprevention, cancer prevention', and all relevant publications are included.

EXPERT OPINION

The use of Nrf2 knockout mice has provided key insights into the toxicological and chemopreventive importance of this pathway. Mounting evidence has revealed that Nrf2 is a critical regulator of inflammation as well, a major driving force for CRC progression and formation. Targeting the Nrf2/ARE pathway may present a novel therapeutic approach for the treatment of not only colorectal inflammatory diseases but the frequent subsequent development of CRC as well.

Water extracts of cabbage and kale inhibit ex vivo H(2)O(2)-induced DNA damage but not rat hepatocarcinogenesis

The chemopreventive potential of water extracts of the Brassica vegetables cabbage and kale was evaluated by administering their aqueous extracts in drinking water ad libitum to Wistar rats submitted to Ito's hepatocarcinogenesis model (CB group and K group, respectively - 14 rats per group). Animals submitted to this same model and treated with water were used as controls (W group - 15 rats). Treatment with the vegetable extracts did not inhibit (P > 0.05) placental glutathione S-transferase-positive preneoplastic lesions (PNL). The number of apoptotic bodies did not differ (P > 0.05) among the experimental groups. Ex vivo hydrogen peroxide treatment of rat livers resulted in lower (P < 0.05) DNA strand breakage in cabbage- (107.6 +/- 7.8 microm) and kale- (110.8 +/- 10.0 microm) treated animals compared with control (120.9 +/- 12.7 microm), as evaluated by the single cell gel (comet) assay. Treatment with cabbage (2 +/- 0.3 microg/g) or kale (4 +/- 0.2 microg/g) resulted in increased (P < 0.05) hepatic lutein concentration compared with control (0.5 +/- 0.07 microg/g). Despite the absence of inhibitory effects of cabbage and kale aqueous extracts on PNL, these Brassica vegetables presented protection against DNA damage, an effect possibly related to increased hepatic lutein concentrations. However, it must be pointed out that the cause-effect relationship between lutein levels and protection is hypothetical and remains to be demonstrated.

Xanthohumol, a prenylated flavonoid contained in beer, prevents the induction of preneoplastic lesions and DNA damage in liver and colon induced by the heterocyclic aromatic amine amino-3-methyl-imidazo[4,5-f]quinoline (IQ)

Xanthohumol (XN) is a hop derived prenylated flavonoid contained in beer. Earlier findings indicated that it has promising chemopreventive properties and protects cells against DNA damage by carcinogens via inhibition of their activation. Furthermore, it was found that XN inhibits DNA synthesis and proliferation of cancer cells in vitro, inactivates oxygen radicals and induces apoptosis. Since evidence for its chemoprotective properties is restricted to results from in vitro experiments, we monitored the impact of XN on the formation of amino-3-methyl-imidazo[4,5-f]quinoline (IQ)-induced preneoplastic foci in livers and colons of rats (9/group). Additionally, we studied its effects on IQ-induced DNA damage in colonocytes and hepatocytes in single cell gel electrophoresis assays and on the activities of a panel of drug metabolising enzymes. Consumption of the drinking water supplemented with XN (71 microg/kg b.w.) before and during carcinogen treatment led to a significant reduction of the number of GST-p+ foci in the liver by 50% and also to a decrease of the foci area by 44%. DNA migration was decreased significantly in both, colon mucosa and liver cells, but no alterations of the activities of different phases I and II enzymes were found in hepatic tissue. Our findings indicate that XN protects against DNA damage and cancer induced by the cooked food mutagen. Since the effects were observed with low doses of XN which are reached after consumption of brews with high XN levels, our findings may be relevant for humans.

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.

Protective effects of epigallocatechin gallate on colon preneoplastic lesions induced by 2-amino-3-methylimidazo[4,5-f ] quinoline in mice

Epigallocatechin gallate (EGCG), a key active ingredient in green tea, has multiple anticarcinogenic effects. The aim of the present study was to investigate if EGCG could prevent the formation of colon aberrant crypt foci (ACF) induced by 2-amino-3-methylimidazo[4,5-f ]quinoline (IQ) and to explore possible mechanisms for resultant effects. Sixty male BALB/cA nude, immunodeficient mice were divided into six groups including a normal unexposed control, mice induced with IQ alone, three groups treated with varying doses of EGCG post-IQ induction, and a EGCG-treated control population. Six weeks later, the mice were killed, and tissues subjected to hematoxylin-eosin (H&E) and 0.2% methylene blue staining to observe histopathological alterations of colon mucus and the formation of ACF, respectively. Protein expression of NF-E2-related factor 2 (Nrf2) was assessed via immunohistochemistry (IHC) and Western analysis, and mRNA levels of Nrf2 and uridine 5'-diphosphate-glucuronosyltransferase (UGT)1A10 were determined in colon tissues. Our results demonstrate that, compared with IQ-induced controls, the degree of atypical hyperplasia decreased and the number of total ACF and total AC also decreased significantly (P < 0.05 and P < 0.01, respectively) in mice belonging to all EGCG dosing groups. At the same time, the protein levels of Nrf2 detected by IHC and Western blotting increased (both P < 0.01 compared with IQ group), and the mRNA levels of Nrf2 and UGT1A10 increased (both P < 0.01 compared with IQ group). In conclusion, EGCG had preventive effects on preneoplastic lesions induced by IQ. Our observations suggest that this effect may be the result of activation of the Nrf2-UGT1A10 signaling pathway.

Cruciferous vegetables reduce morphological markers of colon cancer risk in dimethylhydrazine-treated rats

Consumption of cruciferous vegetables has been associated with reduced colon cancer risk in human populations. However, little experimental evidence exists to support this association. Here, we report the effects of diets containing cruciferous vegetables on colon cancer risk. In Expt. 1, rats were fed a vegetable-free (basal) diet or diets containing different lyophilized cruciferous vegetables in concentrations between 4 and 10%. In Expt. 2, rats were fed the basal diet or diets containing 10-22.6% fresh cruciferous vegetables. Diets were fed for 2 wk (Expt. 1) or 3 wk (Expt. 2) before and 7 wk (Expt. 1) or 12 wk (Expt. 2) after administration of the colon carcinogen 1,2-dimethylhydrazine. Rats fed fresh vegetables were also injected with a low dose of carcinogen 18-24 h prior to termination. Groups fed lyophilized vegetables did not differ in aberrant crypt foci (ACF), sialomucin-producing foci, or mucin-depleted foci (MDF) numbers. However, all fresh vegetable diets significantly decreased ACF (approximately 40%) and MDF numbers. Activities of the hepatic phase I enzyme CYP2E1 did not differ among groups in either experiment. Hepatic glutathione S-transferase (GST) and quinone reductase activities did not differ among groups fed fresh vegetables, whereas the lyophilized cabbage diets decreased GST activity compared with the basal diet. Groups did not differ in apoptosis and cell proliferation labeling indices in colonic mucosa. This study indicates that fresh but not lyophilized cruciferous vegetables reduce colon cancer risk in rats. These results do not support changes in hepatic carcinogen metabolism or colonic crypt cytokinetics as a mechanism.