Department of Food and Nutritional Sciences, University of Reading, Whiteknights, PO Box 226, Reading, Berkshire RG6 6AP, UK.
Br J Nutr. 2011 Apr;105(8):1138-44. doi: 10.1017/S0007114510004836. Epub 2010 Dec 9.
The beneficial effects of green tea catechins, such as the proposed improvement in endothelial function, may be influenced by phase II metabolism during and after absorption. The methylation enzyme, catechol-O-methyltransferase (COMT), has a missense mutation rs4680 (G to A), proposed to result in a 40 % reduction in enzyme activity. In the present pilot study, twenty subjects (ten of each homozygous COMT genotype) were recruited. Green tea extract capsules (836 mg green tea catechins) were given in a fasted state, and a high-carbohydrate breakfast was given after 60 min. Blood samples and vascular function measurements were taken at regular intervals. The change in digital volume pulse stiffness index (SI) from baseline was shown to be different between genotype groups at 120 and 240 min, with a lower SI in the GG individuals (P ≤ 0·044). The change in blood pressure from baseline also differed between genotype groups, with a greater increase in systolic (P = 0·023) and diastolic (P = 0·034) blood pressure at 120 min in the GG group. The GG [corrected] group was shown to have a greater increase in insulin concentrations at 120 min (P = 0·019) and 180 min (P = 0·008) compared with baseline, despite similar glucose profiles. No genotypic differences were found in vascular reactivity measured using laser Doppler iontophoresis, total nitrite, lipids, plasma total antioxidant capacity or inflammatory markers after ingestion of the green tea extract. In conclusion, SI and insulin response to the glucose load differed between the COMT genotype groups, and this may be suggestive of a green tea extract and genotype interaction.
绿茶儿茶素的有益作用，如内皮功能的改善，可能受到吸收过程中和吸收后的 II 相代谢的影响。甲基转移酶，儿茶酚-O-甲基转移酶（COMT），有一种错义突变 rs4680（G 到 A），据推测会导致酶活性降低 40%。在本初步研究中，招募了二十名受试者（每种 COMT 基因型各十名）。空腹给予绿茶提取物胶囊（836 毫克绿茶儿茶素），60 分钟后给予高碳水化合物早餐。定期采集血样并测量血管功能。从基线开始，数字体积脉搏硬度指数（SI）的变化在 120 和 240 分钟时显示出在基因型组之间不同，GG 个体的 SI 较低（P ≤ 0.044）。从基线开始，血压的变化也在基因型组之间不同，在 GG 组中，收缩压（P = 0.023）和舒张压（P = 0.034）在 120 分钟时的增加更大。与基线相比，在 120 分钟（P = 0.019）和 180 分钟（P = 0.008）时，GG 组的胰岛素浓度增加更大，尽管葡萄糖谱相似。在摄入绿茶提取物后，使用激光多普勒离子电泳测量的血管反应性、总硝酸盐、脂质、血浆总抗氧化能力或炎症标志物均未发现基因型差异。总之，SI 和胰岛素对葡萄糖负荷的反应在 COMT 基因型组之间存在差异，这可能表明绿茶提取物和基因型之间存在相互作用。
