H.-H. Sherry Chow

Pharmacokinetic and chemoprevention studies on tea in humans

Green tea and its major polyphenols constituents, tea catechins, have been shown to have many health benefits including cancer prevention. Tea catechins and tea catechin metabolites/catabolites are bioavailable in the systemic circulation after oral intake of green tea or green tea catechins. The metabolites/catabolites identified in humans include glucuronide/sulfate conjugates, methylated tea catechin conjugates, and microflora-mediated ring fission products and phenolic acid catabolites. Plasma levels of unchanged tea catechins in humans are mostly in the sub-μM or nM concentration range, which is much lower than the effective concentrations determined in most in vitro studies. However, some of the catechin metabolites/catabolites are present in the systemic circulation at levels much higher than those of the parent catechins. The contribution of catechin derived metabolites/catabolites to the biological effects associated with green tea is yet to be defined. A limited number of chemoprevention trials of green tea or green tea catechins have been conducted to date and have observed potential preventive activity for oral, prostate, and colorectal cancer. Emerging data from multiple ongoing intervention trials will further contribute to defining the cancer preventive activity of green tea or green tea catechins.

Modulation of human glutathione s-transferases by polyphenon e intervention.

Purpose: Green tea consumption has been associated with decreased risk of certain types of cancers in humans. Induction of detoxification enzymes has been suggested as one of the biochemical mechanisms responsible for the cancer-preventive effect of green tea. We conducted this clinical study to determine the effect of repeated green tea polyphenol administration on a major group of detoxification enzymes, glutathione S-transferases (GST). Methods: A total of 42 healthy volunteers underwent a 4-week washout period by refraining from tea or tea-related products. At the end of the washout period, a fasting blood sample was collected, and plasma and lymphocytes were isolated for assessment of GST activity and level. Following the baseline evaluation, study participants underwent 4 weeks of green tea polyphenol intervention in the form of a standardized Polyphenon E preparation at a dose that contains 800 mg epigallocatechin gallate (EGCG) once a day. Polyphenon E was taken on an empty stomach to optimize the oral bioavailability of EGCG. Upon completion of the intervention, samples were collected for postintervention GST assessment. Results: Four weeks of Polyphenon E intervention enhanced the GST activity in blood lymphocytes from 30.7 ± 12.2 to 35.1 ± 14.3 nmol/min/mg protein, P = 0.058. Analysis based on baseline activity showed that a statistically significant increase (80%, P = 0.004) in GST activity was observed in individuals with baseline activity in the lowest tertile, whereas a statistically significant decrease (20%, P = 0.02) in GST activity was observed in the highest tertile. In addition, Polyphenon E intervention significantly increased the GST-π level in blood lymphocytes from 2,252.9 ± 734.2 to 2,634.4 ± 1,138.3 ng/mg protein, P = 0.035. Analysis based on baseline level showed that this increase was only significant (P = 0.003) in individuals with baseline level in the lowest tertile, with a mean increase of 80%. Repeated Polyphenon E administration had minimal effects on lymphocyte GST-μ and plasma GST-α levels. There was a small but statistically significant decrease (8%, P = 0.003) in plasma GST-α levels in the highest tertile. Conclusions: We conclude that 4 weeks of Polyphenon E administration resulted in differential effects on GST activity and level based on baseline enzyme activity/level, with GST activity and GST-π level increased significantly in individuals with low baseline enzyme activity/level. This suggests that green tea polyphenol intervention may enhance the detoxification of carcinogens in individuals with low baseline detoxification capacity. (Cancer Epidemiol Biomarkers Prev 2007;16(8):1662–6)

Selenium supplementation for prevention of colorectal adenomas and risk of associated type 2 diabetes

BACKGROUND Selenium supplementation may help to prevent colorectal cancer; as precursors of colorectal cancer, colorectal adenomas are a surrogate for colorectal cancer. Selenium supplementation may increase risk of type 2 diabetes (T2D). METHODS The Selenium and Celecoxib (Sel/Cel) Trial was a randomized, placebo controlled trial of selenium 200 µg daily as selenized yeast and celecoxib 400 mg once daily, alone or together, for colorectal adenoma prevention. Men and women between age 40 and 80 years were eligible following colonoscopic removal of colorectal adenomas. The primary outcome was adenoma development. Celecoxib was suspended because of cardiovascular toxicity in other trials, but accrual continued to selenium and placebo. A total of 1621 participants were randomly assigned to selenium or placebo, of whom 1374 (84.8%) were available for analysis. All statistical tests were two-sided. RESULTS In the respective placebo and selenium arms of 689 and 685 participants, adenoma detection after medians of 33.6 (range = 0.0-85.1 months) and 33.0 months (range = 0.0-82.6 months) were 42.8% and 44.1% (relative risk [RR] = 1.03, 95% confidence interval [CI] = 0.91 to 1.16, P = .68). In participants with baseline advanced adenomas, adenoma recurrence was reduced by 18% with selenium (RR = 0.82, 95% CI = 0.71 to 0.96, P = .01). In participants receiving selenium, the hazard ratio for new-onset T2D was 1.25 (95% CI = 0.74 to 2.11, P = .41), with a statistically significantly increased risk of selenium-associated T2D among older participants (RR = 2.21; 95% CI = 1.04 to 4.67, P = .03). CONCLUSIONS Overall, selenium did not prevent colorectal adenomas and showed only modest benefit in patients with baseline advanced adenomas. With limited benefit and similar increases in T2D to other trials, selenium is not recommended for preventing colorectal adenomas in selenium-replete individuals.

Results of a phase II randomized, double-blind, placebo-controlled trial of Polyphenon E in women with persistent high-risk HPV infection and low-grade cervical intraepithelial neoplasia

OBJECTIVE In vitro data and pilot data suggest that green tea catechins may possess chemopreventive activity for cervical cancer and precursor lesions. We conducted a randomized, double-blind, placebo-controlled trial of Polyphenon E (decaffeinated and enriched green tea catechin extract) in women with persistent human papillomavirus (HPV) infection and low-grade cervical intraepithelial neoplasia (CIN1) to evaluate the potential of Polyphenon E for cervical cancer prevention. METHODS Ninety-eight eligible women were randomized to receive either Polyphenon E (containing 800 mg epigallocatechin gallate) or placebo once daily for 4 months. The primary study outcome was oncogenic HPV clearance and clearance of CIN1. RESULTS Polyphenon E was shown to be acceptable, safe and well tolerated. There was no difference in the response rate by treatment allocation. Complete response, defined as negative for high-risk HPV and normal histopathology, was noted in 7 (17.1%) and 6 (14.6%) women in the Polyphenon E and placebo arms, respectively. Progression, defined as persistent oncogenic HPV with histopathologic evidence of progression, was more common in the Polyphenon E group than in the placebo group [6 (14.6%) vs. 3 (7.7%)]. CONCLUSION Based on the largest randomized placebo-controlled trial of a green tea extract for HPV related cervical disease, we conclude that 4 months of Polyphenon E intervention did not promote the clearance of persistent high-risk HPV and related CIN1. Further studies may be necessary to better delineate the risk factors for persistent HPV infection and biology of the disease to facilitate the evaluation of chemopreventive strategies.

Safety and Feasibility of Topical Application of Limonene as a Massage Oil to the Breast.

BACKGROUND Limonene, a major component in citrus oil, has demonstrated anti-cancer effects in preclinical mammary cancer models. However, the effective oral dose translates to a human dose that may not be feasible for chronic dosing. We proposed to evaluate topical application of limonene to the breast as an alternative dosing strategy. MATERIALS AND METHODS We conducted a mouse disposition study to determine whether limonene would be bio available in the mammary tissue after topical application. SKH-1 mice received topical or oral administration of limonene in the form of orange oil every day for 4 weeks. Plasma and mammary pads were collected 4 hrs after the final dosing. We also conducted an exploratory clinical study to evaluate the safety and feasibility of topically applied limonene in the form of orange oil to the breast. Healthy women were recruited to apply orange oil containing massage oil to their breasts daily for four weeks. Safety and feasibility were assessed by reported adverse events, clinical labs, and usage compliance. Pre and post-intervention nipple aspirate fluid (NAF) and plasma were collected for limonene concentration determination. RESULTS The mouse disposition study showed that topical and oral orange oil administration resulted in similar mammary tissue disposition of limonene with no clinical signs of toxicity. In the clinical study, the topical application of limonene containing massage oil to the breast was found to be safe with high levels of usage compliance for daily application, although NAF and plasma limonene concentrations were not significantly changed after the massage oil application. CONCLUSIONS Our studies showed that limonene is bio available in mammary tissue after topical orange oil application in mice and this novel route of administration to the breast is safe and feasible in healthy women.

Design and baseline characteristics of participants in a phase III randomized trial of celecoxib and selenium for colorectal adenoma prevention

COX inhibitors reduce colorectal adenoma recurrence by up to 45% and selenium supplementation may prevent colorectal cancer. Following colonoscopic adenoma resection, 1,600 men and women, ages 40 to 80 years, were randomized to celecoxib (400 mg daily), a selective COX-2 inhibitor, and/or selenium (200 μg daily as selenized yeast), or double placebo. The trial was initiated in November 2001. The primary trial endpoint is adenoma recurrence in each intervention group compared with placebo, as determined by surveillance colonoscopy conducted three to five years after baseline. Randomization was stratified by use of low-dose aspirin (81 mg) and clinic site. Following reports of cardiovascular toxicity associated with COX-2 inhibitors, the celecoxib arm was discontinued in December 2004 when 824 participants had been randomized. Accrual continued with randomization to selenium alone or placebo. Randomization of the originally planned cohort (n = 1,621) was completed in November 2008. A further 200 patients with one or more advanced adenomas (denoting increased risk for colorectal cancer) were accrued to enhance statistical power for determining intervention efficacy in this higher-risk subgroup. Accrual of the total cohort (n = 1,824) was completed in January 2011. Baseline cohort characteristics include: mean age 62.9 years; 65% male; body mass index (BMI) 29.1 ± 5.1; 47% taking low-dose aspirin while on trial; 20% with three or more adenomas; and 38% with advanced adenomas. Intervention effects on adenoma recurrence will be determined, and their modification by genetic background and baseline selenium level. The effect of selenium supplementation on risk for type II diabetes will also be reported. Cancer Prev Res; 5(12); 1381–93. ©2012 AACR.

Determination of d-limonene in adipose tissue by gas chromatography-mass spectrometry.

We developed a novel method for analyzing d-limonene levels in adipose tissue. Fat samples were subjected to saponification followed by solvent extraction. d-Limonene in the sample extract was analyzed using gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring. Linear calibration curves were established over the mass range of 79.0-2529 ng d-limonene per 0.1g of adipose tissue. Satisfactory within-day precision (R.S.D. 6.7-9.6%) and accuracy (%difference of -2.7 to 3.8%) and between-day precision (R.S.D. 6.0-10.7%) and accuracy (%difference of 1.8-2.6%) were achieved. The assay was successfully applied to human fat biopsy samples from a d-limonene feeding trial.

Metabolomic Characterization of Nipple Aspirate Fluid by 1H NMR Spectroscopy and GC-MS

Nipple aspirate fluid (NAF) is a noninvasively obtained biofluid from the duct openings of the breast. NAF components are constantly secreted, metabolized, and reabsorbed by the epithelial lining of the lactiferous ducts of the breast. NAF has been studied as a potential breast tissue surrogate for the discovery of novel breast cancer risk, early detection, and treatment response biomarkers. We report the first unsupervised metabolite characterization of nipple aspirate fluid using NMR and GC-MS using convenience samples previously collected from four premenopausal and four postmenopausal women. A total of 38 metabolites were identified using the two analytical techniques, including amino acids, organic acids, fatty acids, and carbohydrates. Analytical reproducibility of metabolites in NAF by GC-MS was high across different extraction and analysis days. Overall, 31 metabolites had a coefficient of variation below 20%. By GC-MS, there were eight metabolites unique to NAF, 19 unique to plasma, and 24 shared metabolites. Correlative analysis of shared metabolites between matched NAF and plasma samples from pre- and postmenopausal women shows almost no correlations, with the exception being lactic acid, which was significantly negatively correlated (R(2) = 0.57; P = 0.03). These results suggest that NAF is metabolically distinct from plasma and that the application of metabolomic strategies may be useful for future studies investigating breast cancer risk and intervention response biomarkers.

Smoking Status Effect on Inflammatory Markers in a Randomized Trial of Current and Former Heavy Smokers

Background. The level of systemic inflammation as measured by circulating levels of C-reactive protein (CRP) and interleukin-6 (IL-6) is linked to an increased risk for cardiovascular diseases (CVD) and cancer. Methods. We recruited 154 current and former smokers between 40 and 80 years of age with 25 or more pack-years of smoking history to study the relationship between inflammatory markers (CRP and IL-6) and smoking status. Results. Our results show that male smokers had significantly higher levels of serum IL-6 compared to male former smokers. We did not find any gender specific differences for smoking and CRP levels but the IL-6 levels were slightly lower in females compared to males. Additionally, our results show that CRP is significantly associated with IL-6 regardless of smoking status. Modelling indicates that the significant predictors of CRP levels were biomarkers of the metabolic syndrome while the significant predictors of IL-6 levels were age and plasma triglycerides among former smokers and the numbers of smoked packs of cigarettes per year among smokers. Conclusions. In conclusion, our study showed that CRP levels were not associated with markers of smoking intensity. However, IL-6 levels were significantly associated with smoking especially among current smokers.

hOGG1 Genotype, Green Tea and Oxidative DNA Damage among Heavy Smokers

DNA is susceptible to damage by reactive oxygen species, and 8-hydroxydeoxyguanosine (8-OHdG) is probably one of the most abundant DNA lesions formed during oxidative stress. Several pathways exist for the removal or repair of this lesion from mammalian DNA. The most established is via the base excision repair enzyme, human 8-oxoguanine glycosylase (hOGG1). Several polymorphisms in the hOGG1 gene have been detected in human populations. We were interested in whether there were differences in increased oxidative stress susceptibility to smoking within the hOGG1 genotypes and the impact of high tea drinking on this. A phase IIb randomised, controlled, tea intervention trial was designed to study the effect of high consumption (four cups per day) of decaffeinated green or black tea on oxidative DNA damage, as measured by urinary 8-OHdG, among smokers over a 4-month period and to evaluate the role of the hOGG1 genotype as an effect modifier. A total of 120 smokers with hOGG1 data completed the 4-month intervention. The hOGG1 genotype status was determined with a polymerase chain reaction-based approach. Multiple linear regression models were used to estimate the main effects and interaction effect of green and black tea consumption on creatinine-adjusted urinary 8-OHdG, with or without adjustment for potential confounders. Finally, we studied whether the effect of treatment varied by hOGG1 status of the individual. Assessment of urinary 8-OHdG after adjustment for baseline measurements and other potential confounders revealed a highly significant decrease in urinary 8-OHdG after 4 months of drinking decaffeinated green tea (p = 0.001). No change in urinary 8-OHdG was seen among smokers assigned to the black tea group. We found the distribution of hOGG1 Ser326Cys genotypes among smokers to be 62%, 28% and 10% for Ser/Ser, Ser/Cys and Cys/Cys genotypes, respectively. Because the homozygous Cys/Cys genotype was present in only 10% of the study population, the mutant types (Ser/Cys and Cys/Cys) were combined and compared with the Ser/Ser genotype. We found no significant interaction between smoking, hOGG1 genotypes and tea intervention in terms of levels of urinary 8-OHdG. This finding suggests that green tea intervention might be effective in decreasing levels of urinary 8-OHdG among smokers regardless of their hOGG1 genotype.