Cruciferous vegetables, genetic polymorphisms in glutathione S-transferases M1 and T1, and prostate cancer risk

Cruciferous vegetables contain anticarcinogenic isothiocyanates (ITCs), particularly the potent sulforaphane, which may decrease risk of prostate cancer through induction of phase II enzymes, including glutathione S-transferases (GSTs). We evaluated this hypothesis in a population-based, case-control study of prostate cancer, including 428 men with incident prostate cancer and 537 community controls. An in-person interview included an extensive food-frequency questionnaire. Genotyping for deletions in GSTM1 and GSTT1 was performed in a subset of men who provided blood. Intakes of cruciferous vegetables and of broccoli, the greatest source of sulforaphane, were associated with decreased prostate cancer risk at all levels above the lowest consumers [adjusted 4th quartile odds ratio (OR)=0.58; 95% confidence interval (CI)=0.38, 0.89, and 0.72 (95% CI=0.49, 1.06)], respectively. In relation to genotypes, there was a nonsignificant increase in risk with the GSTT1 null genotype (OR=1.51; 95% CI=0.98, 2.31) but no effects of GSTM1 genotype. However, men with GSTM1-present genotype and high broccoli intake had the greatest reduction in risk (OR=0.49; 95% CI=0.27, 0.89). Our findings provide evidence that two or more servings per month of cruciferous vegetables may reduce risk of prostate cancer, especially among men with GSTM1-present alleles, and are consistent with a role of dietary ITCs as chemopreventive agents against prostate cancer.     

中国汉族人口三种谷胱甘肽S-转移酶基因多态性分析

目的：分析中国汉族人口谷胱甘肽S－转移酶（GSTs)基因多态性分布。方法：样本为450名中国汉族人口,采用多重等位基因特异聚合酶链反应（PCR）方法分析GSTM1和GSTT1基因多态性,采用PCR－限制性片段长度多态性方法分析GSTP1＋313核苷酸位点的基因多态性。结果：GSTM1缺失型和GSTT1缺失型基因型频率分别为57％和45％,同时具有GSTM1缺失型和GSTT1缺失型基因型的人个体频率为28．92％;而GSTP1＋313位点G等位基因频率为18．7％,并发现该人群中同时具有3种危险基因型（GSTM1缺失型、GSTT1缺失型和GSTP1＋313A／A）的个体频率为18．04％。GSTs基因型分布不受性别和年龄的影响。结论：中国汉族人口GSTM1、GSTT1和GSTP1基因呈多态性分布,其等位基因和基因型频率不同于其他种族。     

Green tea and black tea consumption and prostate cancer risk: an exploratory meta-analysis of observational studies

Observational studies on tea consumption and prostate cancer (PCa) risk are still inconsistent. The authors conducted a meta-analysis to investigate the association between green tea and black tea consumption with PCa risk. Thirteen studies providing data on green tea or black tea consumption were identified by searching PubMed and ISI Web of Science databases and secondary referencing qualified for inclusion. A random-effects model was used to calculate the summary odds ratios (OR) and their corresponding 95% confidence intervals (CIs). For green tea, the summary OR of PCa indicated a borderline significant association in Asian populations for highest green tea consumption vs. non/lowest (OR = 0.62; 95% CI: 0.38-1.01); and the pooled estimate reached statistically significant level for case-control studies (OR = 0.43; 95% CI: 0.25-0.73), but not for prospective cohort studies (OR = 1.00; 95% CI: 0.66-1.53). For black tea, no statistically significant association was observed for the highest vs. non/lowest black tea consumption (OR = 0.99; 95% CI: 0.82-1.20). In conclusion, this meta-analysis supported that green tea but not black tea may have a protective effect on PCa, especially in Asian populations. Further research regarding green tea consumption across different regions apart from Asia is needed.     

Significance of genetic polymorphisms in glutathione S-transferase multigene family and lung cancer risk

A vast number of studies are focused on investigating genetic polymorphism in order to estimate genetic contribution to the development of cancer. Possible cancer susceptibility genes have been sought among oncogenes, tumor suppressor genes, DNA repair genes and genes encoding phase I and phase II enzymes. Large individual differences in the biotransformation of xenobiotics have been explained on the basis of genetic polymorphisms in some detoxifying enzymes, regardless of environmental and occupational exposure. Among these enzymes, glutathione S-transferases (GST) constitute a large multigene family of phase II enzymes involved in detoxification of potentially genotoxic chemicals. Five genetic polymorphisms of GST have been well documented. Total or partial deletions and (or) single nucleotide polymorphisms in alleles encoding GSTM1, GSTM3, GSTPI, GSTT1, GSTZ1 are associated with reduction of enzymatic activity toward several substrates of different GST isoenzymes. In addition, molecular epidemiology studies indicate that a single genetic polymorphism of glutathione S-transferase appears to be a moderate lung cancer risk factor. However, the risk is higher when interactions with more GST polymorphisms and other risk factors (e.g. cigarette smoking) occur. Individuals with decreased rate of detoxification, with "high risk" glutathione S-transferase genotypes have a slightly higher level of carcinogen-DNA adducts and more cytogenetic damages.     

Green tea consumption and prostate cancer risk in Japanese men: a prospective study

The incidence of prostate cancer is much lower in Asian than Western populations. Given that environmental factors such as dietary habits may play a major role in the causation of prostate cancer and the high consumption of green tea in Asian populations, this low incidence may be partly due to the effects of green tea. The JPHC Study (Japan Public Health Center-based Prospective Study) was established in 1990 for cohort I and in 1993 for cohort II. The subjects were 49,920 men aged 40-69 years who completed a questionnaire that included their green tea consumption habit at baseline and were followed until the end of 2004. During this time, 404 men were newly diagnosed with prostate cancer, of whom 114 had advanced cases, 271 were localized, and 19 were of an undetermined stage. Green tea was not associated with localized prostate cancer. However, consumption was associated with a dose-dependent decrease in the risk of advanced prostate cancer. The multivariate relative risk was 0.52 (95% confidence interval: 0.28, 0.96) for men drinking 5 or more cups/day compared with less than 1 cup/day (p(trend) = 0.01). Green tea may be associated with a decreased risk of advanced prostate cancer.     

Interaction of soy food and tea consumption with CYP19A1 genetic polymorphisms in the development of endometrial cancer

Certain polyphenols inhibit the activity of aromatase, a critical enzyme in estrogen synthesis that is coded by the CYP19A1 gene. Consumption of polyphenol-rich foods and beverages, thus, may interact with CYP19A1 genetic polymorphisms in the development of endometrial cancer. The authors tested this hypothesis in the Shanghai Endometrial Cancer Study (1997-2003), a population-based case-control study of 1,204 endometrial cancer cases and 1,212 controls. Dietary information was obtained by use of a validated food frequency questionnaire. Genotypes of CYP19A1 at rs28566535, rs1065779, rs752760, rs700519, and rs1870050 were available for 1,042 cases and 1,035 controls. Unconditional logistic regression models were used to calculate odds ratios and their 95% confidence intervals after adjustment for potential confounding factors. Higher intake of soy foods and tea consumption were both inversely associated with the risk of endometrial cancer, with odds ratios of 0.8 (95% confidence interval: 0.6, 1.0) for the highest versus the lowest tertiles of intake of soy and 0.8 (95% confidence interval: 06, 0.9) for ever tea consumption. The association of single nucleotide polymorphisms rs1065779, rs752760, and rs1870050 with endometrial cancer was modified by tea consumption (p(interaction) < 0.05) but not by soy isoflavone intake. The authors' findings suggest that tea polyphenols may modify the effect of CYP19A1 genetic polymorphisms on the development of endometrial cancer.     

Green tea composition, consumption, and polyphenol chemistry.

Tea is grown in about 30 countries but is consumed worldwide, although at greatly varying levels. It is the most widely consumed beverage aside from water with a per capita worldwide consumption of approximately 0.12 liter per year. Tea is manufactured in three basic forms. Green tea is prepared in such a way as to preclude the oxidation of green leaf polyphenols. During black tea production oxidation is promoted so that most of these substances are oxidized. Oolong tea is a partially oxidized product. Of the approximately 2.5 million metric tons of dried tea manufactured, only 20% is green tea and less than 2% is oolong tea. Green tea is consumed primarily in China, Japan, and a few countries in North Africa and the Middle East. Fresh tea leaf is unusually rich in the flavanol group of polyphenols known as catechins which may constitute up to 30% of the dry leaf weight. Other polyphenols include flavanols and their glycosides, and depsides such as chlorogenic acid, coumarylquinic acid, and one unique to tea, theogallin (3-galloylquinic acid). Caffeine is present at an average level of 3% along with very small amounts of the other common methylxanthines, theobromine and theophylline. The amino acid theanine (5-N-ethylglutamine) is also unique to tea. Tea accumulates aluminum and manganese. In addition to the normal complement of plant cell enzymes, tea leaf contains an active polyphenol oxidase which catalyzes the aerobic oxidation of the catechins when the leaf cell structure is disrupted during black tea manufacture. The various quinones produced by the enzymatic oxidations undergo condensation reactions which result in a series of compounds, including bisflavanols, theaflavins, epitheaflavic acids, and thearubigens, which impart the characteristic taste and color properties of black tea. Most of these compounds readily form complexes with caffeine. There is no tannic acid in tea. Thearubigens constitute the largest mass of the extractable matter in black tea but their composition is not well known. Proanthocyanidins make up part of the complex. Tea peroxidase may be involved in their generation. The catechin quinones also initiate the formation of many of the hundreds of volatile compounds found in the black tea aroma fraction. Green tea composition is very similar to that of the fresh leaf except for a few enzymatically catalyzed changes which occur extremely rapidly following plucking. New volatile substances are produced during the drying stage. Oolong tea is intermediate in composition between green and black teas.     

Green tea consumption and serum malondialdehyde-modified LDL concentrations in healthy subjects

OBJECTIVE: Green tea was shown to inhibit LDL oxidation, platelet aggregation, and matrix metalloproteinases (MMPs) activities in vitro. We tried to elucidate whether or not green tea consumption may have these effects in vivo, which may be protective against atherosclerotic disease. METHODS: We measured serum malondialdehyde-modified LDL (MDA-LDL) concentrations and urine 8-epi-prostaglandin (PG) F(2alpha) in 22 healthy male nonsmokers. They drank 7 cups/day of water for 2 weeks and drank 7 cups/day of green tea for the next 2 weeks. Regarding platelet aggregation, plasma thromboxane B(2) (TXB(2)) and 6-keto-PGF(1alpha) concentrations and ex vivo platelet aggregation were evaluated. Plasma MMP-2 and -9 concentrations were also measured. RESULTS: Of the 22 subjects, 20 had been in the habit of drinking green tea before the study. Plasma catechins concentrations significantly decreased at the end of the water period and then increased at the end of the green tea period. Although no change in plasma LDL-cholesterol concentrations (110 +/- 33 vs. 113 +/- 28 mg/dL, p = NS) was found, MDA-LDL concentrations (84 +/- 45 vs. 76 +/- 40 IU/L, p < 0.05) and the ratio of MDA-LDL/LDL-cholesterol (0.74 +/- 0.21 vs. 0.65 +/- 0.20, p < 0.02) significantly decreased at the end of the green tea period. However, no significant changes were observed in urine 8-epi-PGF(2alpha) concentrations, in platelet aggregation, nor in plasma TXB(2), 6-keto-PGF(1alpha) or MMP concentrations. CONCLUSION: Daily consumption of green tea decreased serum MDA-LDL concentrations, but it had no significant effects on platelet aggregation, platelet TX production or plasma MMPs concentrations. Our results suggest that green tea consumption may inhibit LDL oxidation in vivo.     

Cigarette smoking and risk of adult leukemia

A case-control study investigated the relation between cigarette smoking and histologic subtypes of adult leukemia in Missouri in 1984-1990. Among males, elevated risks associated with ever smoking were observed for acute nonlymphocytic leukemia (odds ratio (OR) = 1.5; 95% confidence interval (CI) 1.1-2.0) and acute myelocytic leukemia (OR = 1.5; 95% CI 1.1-2.1). Females also showed an increased risk of acute nonlymphocytic leukemia associated with ever smoking (OR = 1.4; 95% CI 1.0-1.9), with an increasing trend in risk by level of smoking (p less than 0.01). Attributable risk estimates of the proportion of acute nonlymphocytic leukemia caused by smoking were 33 percent in males and 29 percent in females. Elevations in risk were not apparent for chronic forms of leukemia. The findings support the hypothesis that some types of leukemia may be etiologically related to cigarette smoking.     

Effect of acrylamide on chick embryonic liver glutathione S-transferases

Glutathione S-transferases (GSTs, EC 2.5.1.18), as the detoxifying enzymes, play an important protective role in embryonic tissues. The GSTs of eleventh-day chick embryonic liver were purified to electrophoretic homogeneity with an overall yield of 31%. The SDS-PAGE analysis of chick embryonic liver GSTs resolved in to three bands, CL1, CL2 and CL3, with relative molecular weights of 27.0, 26.0 and 25.0 kDa respectively. On 72 hours of treatment with acrylamide (AC) (0.1, 0.2 and 0.3 mg) the specific activities of GSTs with CDNB, pNBC, EPNP, BSP, Δ⁵5A and pNPA increased significantly. Total GPx levels were decreased with CHP in liver samples. Immunoblot analysis of AC-treated liver samples showed a dose-dependent increase in the induction of GSTs. CL1 of theta class, CL2 of Mu class and CL3 of alpha class were induced with AC treatment. The theta, mu and alpha classes induced by AC might inhibit the initiation of carcinogenesis.     

Black tea consumption and risk of stroke in women and men

PurposeOur aim was examine the association between black tea consumption and risk of total stroke and stroke types in a prospective study.MethodsA total of 74,961 Swedish women and men who were free of cardiovascular disease and cancer at baseline in 1997 were followed up through December 2008. Tea consumption was assessed with a questionnaire at baseline. Stroke cases were ascertained from the Swedish Hospital Discharge Registry.ResultsDuring a mean follow-up of 10.2 years, we ascertained 4089 cases of first stroke, including 3159 cerebral infarctions, 435 intracerebral hemorrhages, 148 subarachnoid hemorrhages, and 347 unspecified strokes. After adjustment for other risk factors, high tea consumption was associated with a significantly lower risk of total stroke; however, there was no dose–response relation (P for trend = .36). Compared with no tea consumption, the multivariable relative risk for four or more cups per day (median, 5) was 0.79 (95% confidence interval [CI], 0.62–0.998). The corresponding relative risks were 0.80 (95% CI, 0.61–1.04) for cerebral infarction and 0.68 (95% CI, 0.35–1.30) for hemorrhagic stroke.ConclusionsThese findings suggest that daily consumption of four or more cups of black tea is inversely associated with risk of stroke.     

Black tea consumption and risk of rectal cancer in Moscow population

PURPOSE: This population-based case-control study (663 cases and 323 controls) examined the effect of black tea intake on the risk of rectal cancer in Moscow residents. The Moscow population was selected for its wide range of black tea consumption. METHODS: This study used three measures of tea consumption: the volume of beverage (l/month), zavarka (tea concentrate, l/month), and dry tea (g/month). We calculated the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for these three parameters of tea intake using logistic regression. RESULTS: Greater use of dry tea was associated with lower risk of rectal cancer in women (high vs. low: OR = 0.40; 95% CI, 0.23-0.70) and in men (high vs. low: OR = 0.77; 95% CI, 0.42-1.43). The observed effect was weaker when tea was measured as zavarka (high vs. low in women: OR = 0.47; 95% CI, 0.26-0.83; in men: OR = 0.99; 95% CI, 0.52-1.96) and as beverage volume (high vs. low in women: OR = 0.68; 95% CI, 0.39-1.19; in men: OR = 1.03; 95% CI, 0.53-2.09). CONCLUSIONS: These findings support the hypothesis that black tea consumption reduces the risk of rectal cancer. The attenuation of the effect across the three measures of tea intake can be explained by an increasing degree of exposure misclassification from dry tea to zavarka and beverage volume.     

Green tea consumption and chronic atrophic gastritis: a cross-sectional study in a green tea production village

Chronic atrophic gastritis (CAG) is well known as a precancerous lesion of the stomach, and Helicobacter pylori (H. pylori) infection increases the risk of CAG. While recent studies have reported that green tea consumption decreases the risk of gastric cancer, there has been no study analyzing the relationship between green tea consumption and the both risks H. pylori infection and CAG. We conducted a cross-sectional study on 636 subjects living in a farming village in Japan to examine the relationship among green tea consumption, H. pylori infection, and CAG. Smoking, alcohol drinking, consumption of four beverages, including green tea, and of five foods were investigated as lifestyle factors that may affect H. pylori infection and CAG. The measurement of H. pylori-IgG antibodies was used to define H. pylori infection, and serum pepsinogens were used to define of CAG. The unconditional logistic regression model was used for analyzing each odds ratio (OR). H. pylori infection was positively associated with the risk of CAG (OR = 3.73; 95% confidence interval [CI], 2.59-5.36). High green tea consumption (more than 10 cups per day) was negatively associated with the risk of CAG, even after adjustment for H. pylori infection and lifestyle factors associated with green tea consumption (OR = 0.63; 95% CI, 0.43-0.93). These results support the hypothesis that high green tea consumption prevents CAG.     

Green tea supplementation increases glutathione and plasma antioxidant capacity in adults with the metabolic syndrome

Green tea, a popular polyphenol-containing beverage, has been shown to alleviate clinical features of the metabolic syndrome. However, its effects in endogenous antioxidant biomarkers are not clearly understood. Thus, we tested the hypothesis that green tea supplementation will upregulate antioxidant parameters (enzymatic and nonenzymatic) in adults with the metabolic syndrome. Thirty-five obese participants with the metabolic syndrome were randomly assigned to receive one of the following for 8 weeks: green tea (4 cups per day), control (4 cups water per day), or green tea extract (2 capsules and 4 cups water per day). Blood samples and dietary information were collected at baseline (0 week) and 8 weeks of the study. Circulating carotenoids (α-carotene, β-carotene, lycopene) and tocopherols (α-tocopherol, γ-tocopherol) and trace elements were measured using high-performance liquid chromatography and inductively coupled plasma mass spectroscopy, respectively. Serum antioxidant enzymes (glutathione peroxidase, glutathione, catalase) and plasma antioxidant capacity were measured spectrophotometrically. Green tea beverage and green tea extract significantly increased plasma antioxidant capacity (1.5 to 2.3 μmol/L and 1.2 to 2.5 μmol/L, respectively; P < .05) and whole blood glutathione (1783 to 2395 μg/g hemoglobin and 1905 to 2751 μg/g hemoglobin, respectively; P < .05) vs controls at 8 weeks. No effects were noted in serum levels of carotenoids and tocopherols and glutathione peroxidase and catalase activities. Green tea extract significantly reduced plasma iron vs baseline (128 to 92μg/dL, P < .02), whereas copper, zinc, and selenium were not affected. These results support the hypothesis that green tea may provide antioxidant protection in the metabolic syndrome.     

Green tea and gastric cancer risk: meta-analysis of epidemiologic studies

OBJECTIVE: To evaluate the association between green tea consumption and the risk of gastric cancer. METHODS: Electronic search of the Cochrane Library, MEDLINE, EMBASE and Chinese Bio-medicine Database, which have articles published between (1966 and 2006), was conducted to select studies for this meta-analysis. RESULTS: This meta-analysis included 14 epidemiologic studies, with a total number of 6123 gastric cancer cases and 134006 controls. The combined results based on all studies showed that green tea consumption was not associated with the risk of gastric cancer [odds ratio (OR)=0.98, 95% confidence interval (CI)=0.77-1.24]. The summary OR from all population-based case-control studies showed a minor inverse association between green tea consumption and risk of gastric cancer (OR=0.68, 95% CI=0.49-0.92), while no associations were noted from hospital-based case-control studies (OR=1.12, 95% CI=0.70-1.77) and cohort studies (OR=1.56, 95% CI=0.93-2.60). No associations were noted both in males (OR=1.10, 95% CI=0.76-1.60) and females (OR=0.99, 95% CI=0.64-1.51). The summary OR from seven studies suggest that the highest consumption level of green tea was more than 5 cups per day and no associations were noted (OR=0.99, 95% CI=0.78-1.27). CONCLUSIONS: The results of this meta-analysis indicated that there is no clear epidemiological evidence to support the suggestion that green tea plays a role in the prevention of gastric cancer.     

A review of genetic polymorphisms and prostate cancer risk

In this study, we review a variety of genetic polymorphisms that may have an etiologic role in prostate cancer. We include associations identified in molecular epidemiology studies and the consistency of findings reported to date. Suggestions for further research are also offered. For the purposes of this review, we identified relevant articles through a MEDLINE search for the period of January 1987 through March 2001. The searches were limited to articles published in English. Medical subject headings were used to scan titles, abstracts, and subject headings in the databases using the keywords "prostate neoplasms," "genetics," and "polymorphisms."     

Food consumption by children and the risk of childhood acute leukemia

The possible relation between child's early diet and risk of childhood leukemia has remained largely unexplored. The authors' objective was to determine what particular foods consumed early in life (first 2 years) are associated with risk of childhood leukemia in a 1995-2002 case-control study of a diverse California population. Dietary data were obtained from a questionnaire administered to the child's caregiver. Conditional logistic regression was used to analyze 328 case-control sets matched on age, sex, Hispanic status, and maternal race. Regular consumption of oranges/bananas (odds ratio = 0.49, 95% confidence interval: 0.26, 0.94) and orange juice (odds ratio = 0.54, 95% confidence interval: 0.31, 0.94) during the first 2 years of life was associated with a reduction in risk of childhood leukemia diagnosed between the ages of 2 and 14 years. Restricting the analysis to leukemia diagnosed between the ages of 2 and 5 years reflected a similar pattern of reduced risk. No association between eating hot dogs/lunch meats and risk of leukemia was found. These results suggest that fruits or fruit juices that contain vitamin C and/or potassium may reduce the risk of childhood leukemia, especially if they are consumed on a regular basis during the first 2 years of life.     

Environmental tobacco smoke and risk of adult leukemia

BACKGROUND: The role of environmental tobacco smoke (ETS) in the causation of lung and breast cancer has been repeatedly evaluated over recent years. In contrast, its impact on the risk of adult leukemia has received little attention. METHODS: We used the lifetime residential and occupational ETS exposure histories from a population-based sample of 1068 incident and histologically confirmed adult leukemia cases and 5039 population controls age 20 to 74 years to evaluate the relationship between ETS exposure and adult leukemia risk among nonsmokers in Canada. The duration of exposure and smoker-years index were used as indices of ETS exposure. We restricted our analysis to the 266 case and 1326 control subjects who reported being lifetime nonsmokers and provided residential ETS exposure history for at least 75% of their lifetime. RESULTS: No association was found for most leukemia subtypes, and in particular for acute myeloid leukemia. In contrast, the risk for chronic lymphocytic leukemia was clearly associated with ETS exposure, with an adjusted odds ratio of 2.3 (95% confidence interval = 1.2-4.5) for more than 83 smoker-years of residential exposure and 2.4 (1.3-4.3) for more than 72 smoker-years of occupational exposure. There was a dose-response relationship for chronic lymphocytic leukemia with both indices of exposure. Risk was not higher with recent exposure, using time-window-exposure analyses. CONCLUSIONS: Regular long-term ETS exposure may be a risk factor for chronic lymphocytic leukemia.