Gostner J M, Becker K, Croft K D, Woodman R J, Puddey I B, Fuchs D, Hodgson J M
Division of Medical Biochemistry, Medical University of Innsbruck, Austria.
Division of Biological Chemistry, Medical University of Innsbruck, Austria.
BBA Clin. 2014 Dec 4;3:31-5. doi: 10.1016/j.bbacli.2014.11.007. eCollection 2015 Jun.
Circulating neopterin and the ratio of kynurenine to tryptophan (KYN/TRP) concentrations are biomarkers of immune activation that have been linked to cardiovascular and total mortality. Several in vitro studies indicated that tea flavonoids and other antioxidants can modulate tryptophan breakdown rates and neopterin production in immune cells. We aimed to assess the effects of regular black tea consumption on tryptophan and neopterin metabolisms in vivo.
Participants were healthy individuals, with no major illnesses and having normal to mildly elevated systolic blood pressure. They were randomly assigned to consume 3 cups/day of either powdered black tea solids (tea; n = 45) or a flavonoid-free caffeine-matched beverage (control; n = 49). Serum concentrations of tryptophan, kynurenine and neopterin were assessed at baseline and again at 3 and 6 months after daily ingestion of the respective beverage.
Regular consumption of tea over 6 months, compared to control, did not significantly alter neopterin (p = 0.13) or tryptophan (p = 0.85) concentrations, but did result in significantly higher kynurenine (p = 0.016) and KYN/TRP (p = 0.012). Relative to the control group, in the tea group kynurenine and KYN/TRP increased during the treatment period by 0.28 μmol/L (95% CI: - 0.04, 0.60) and 3.2 μmol/mmol (95% CI: - 1.6, 8.0), respectively at 3 months, and by 0.48 μmol/L (95% CI: 0.16, 0.80) and 7.5 μmol/mmol (95% CI: 2.5, 12.5), respectively at 6 months.
Increased circulation of kynurenine and KYN/TRP following regular black tea consumption may indicate enhanced tryptophan breakdown, possibly due to immune activation-induced tryptophan degrading enzyme indoleamine 2,3-dioxygenase.
The influence of black tea consumption on biomarkers of immune system activation could relate to its general health benefits. Data suggests that the net effect strongly depends on the individual immune state, being stimulatory in healthy individuals, while acting more immune dampening in situations with an inflammatory background.
循环新蝶呤以及犬尿氨酸与色氨酸的浓度比值（KYN/TRP）是免疫激活的生物标志物，与心血管疾病死亡率和全因死亡率相关。多项体外研究表明，茶黄酮类化合物和其他抗氧化剂可调节免疫细胞中色氨酸的分解速率和新蝶呤的生成。我们旨在评估长期饮用红茶对体内色氨酸和新蝶呤代谢的影响。
参与者为健康个体，无重大疾病，收缩压正常或轻度升高。他们被随机分为两组，一组每天饮用3杯红茶固体粉末（茶组；n = 45），另一组饮用不含黄酮类化合物但咖啡因含量匹配的饮料（对照组；n = 49）。在基线时以及每天饮用相应饮料3个月和6个月后，评估血清中色氨酸、犬尿氨酸和新蝶呤的浓度。
与对照组相比，连续6个月饮用红茶并没有显著改变新蝶呤（p = 0.13）或色氨酸（p = 0.85）的浓度，但确实导致犬尿氨酸（p = 0.016）和KYN/TRP（p = 0.012）显著升高。相对于对照组，茶组在治疗3个月时，犬尿氨酸和KYN/TRP分别增加了0.28 μmol/L（95% CI：-0.04，0.60）和3.2 μmol/mmol（95% CI：-1.6，8.0）；在6个月时分别增加了0.48 μmol/L（95% CI：0.16，0.80）和7.5 μmol/mmol（95% CI：2.5，12.5）。
长期饮用红茶后犬尿氨酸和KYN/TRP循环水平升高可能表明色氨酸分解增强，这可能是由于免疫激活诱导色氨酸降解酶吲哚胺2,3-双加氧酶所致。
饮用红茶对免疫系统激活生物标志物的影响可能与其对总体健康的益处有关。数据表明，其净效应在很大程度上取决于个体的免疫状态，对健康个体具有刺激作用，而在有炎症背景的情况下则具有更多的免疫抑制作用。
