Objective: The object of this study was to investigate the in vivo antioxidant effect of green tea and dosage effect of green tea on antioxidant effect. Design: We tested 10 healthy subjects (aged 23 ± 25 y, ®ve women and ®ve men) with overnight fasting. The total antioxidant capacity of plasma was measured at baseline and 60 min and 120 min after ingestion of 150 ml green tea. Green tea was prepared by infusing 2.5 g of dried green tea leaves for 2 min at 80 C in 150 ml of water. In the second week, they took 300 ml of tea (5.0 g of green tea leaves) and, in the third week, 450 ml of tea (7.5 g of green tea leaves). The total antioxidant capacities of plasma were determined with a Total Antioxidant Kit (Randox Laboratories Ltd, UK) using a Cobas Mira analyser (Roche Diagnostic Systems Inc., Switzerland). The mean intra-assay coef®cient of variation was 1.2%. Results: The total antioxidant capacity of plasma increased by 1.1% at 60 min and 2.1% at 120 min over baseline value in subjects consuming 150 ml of green tea, which was statistically not signi®cant. However, total antioxidant capacity of plasma after consuming 300 ml of green tea showed a signi®cant increase of 7.0% after 60 min and 6.2% after 120 min (P`0.0001), and after consuming 450 ml 12.0% after 60 min and 12.7% after 120 min over baseline value (P`0.0001). Conclusions: Total antioxidant capacity of plasma was signi®cantly increased after taking green tea in amounts of 300 and 450 ml. A positive increment according to green tea dosage was also observed. Sponsorship: This work was funded by the Paci®c Corporation (Korea).
Although obesity is a risk factor for colorectal cancer, the underlying mechanism is not clear. Adiponectin is an adipokine that binds to 2 types of receptors, AdipoR1 and AdipoR2. The plasma concentrations of adiponectin are reduced in obese individuals and adiponectin has been reported to have anticarcinogenic properties. Furthermore, AdipoR1 and AdipoR2 have been reported to be expressed in several malignancies. However, little is known about the expression of AdipoR1 and AdipoR2 in colorectal cancer and its clinicopathological implications. In addition, the relationship between adiponectin and colorectal cancer has not yet been determined. Here, we sought to investigate adiponectin and adiponectin receptors in relation to colorectal cancer. AdipoR1 and AdipoR2 immunostaining was detected in 72 and 68% of human colorectal cancer tissue, respectively. AdipoR1 and AdipoR2 expression levels were inversely related to T stage. The lowest AdipoR1 and AdipoR2 expression were detected in poorly differentiated adenocarcinoma. RT-PCR also showed the expression of AdipoR1 and AdipoR2 in HCT116 and SW620. MTT assay and TUNEL assay demonstrated the tendency of growth inhibition and apoptosis induction in both cell lines after full-length adiponectin treatment although statistically insignificant. Microarray analysis revealed several gene responses to full-length adiponectin, including upregulation of ENDOGL1 and MT1G.In conclusion, AdipoR1 and AdipoR2 may be intimately related to the progression of colorectal cancer. Further studies may be warranted to assess adiponectin and its receptors as a novel target for inhibition of colorectal cancer growth.Colorectal cancer has long been prevalent in Western populations and was estimated to comprise 10.4% of new cancer cases and be the second leading cause of cancer death in the United States in 2008. 1 Over the past few decades, the incidence of colorectal cancer has increased in Asia and it is now one of the most common malignancies worldwide. 2 Obesity is one of the risk factors for colorectal cancer. Several case-control studies assessing body mass index and colorectal cancer incidence have reported an increased risk of colorectal cancer in obese individuals compared with normal weight individuals. [3][4][5] In addition, prospective cohort investigations have reported a positive association between body mass index and colorectal cancer, with relative risks of 1.2-3.4. 6-9 Indices such as waist-to-hip ratio or waist circumference, which indicate abdominal or visceral adiposity, have also been suggested to be independent risk factors for colorectal cancer. [9][10][11] Together with other researchers, we have further demonstrated the importance of visceral adiposity to colorectal cancer risk by the direct measurement of visceral fat by computed tomography (CT) analysis. 12,13 Although the pathophysiological mechanism by which obesity is linked to colorectal cancer is not completely understood, several mechanisms have been proposed. Obesityinduced insulin resistance increases the...
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