中文导读 人老了以后，体内常会出现一种长期存在、从未完全消退的低水平炎症，科学家称之为“炎性衰老”（inflammaging），它与许多老年疾病有关。耶鲁大学医学院 10 月 23 日（美国时间）在《细胞》（Cell）期刊发表的研究，把目光投向了牛磺酸（taurine）。此前有观点认为牛磺酸会随年龄下降并推动衰老，但这一说法仍有争议；研究者比较 20–40 岁与 60–99 岁人群的血液后却发现，牛磺酸其实随年龄升高，小鼠也是如此。研究者推测，这种升高可能是身体想压低炎症却没能成功的反应。实验中，巨噬细胞（身体第一道防线的免疫细胞）遇到细菌毒素等危险信号时，NLRP3 炎症小体会组装并引发炎症，同时细胞释放多达 80% 的牛磺酸；把牛磺酸补回细胞，炎症停止；降低牛磺酸，炎症在年轻小鼠身上也更强。老年小鼠额外补充牛磺酸后健康状况改善，败血症死亡减少。论文还报告，长期限制热量的人脂肪组织中牛磺酸升高、炎症较低，但大幅少吃并不现实。资深作者 Dixit 称这只是“解开谜题的第一步”：关键实验多在细胞和小鼠中完成，尚不能说明服用牛磺酸能减缓人类衰老。文章按“常见看法—新发现—机制实验—联系—局限”展开，阅读时可留意 though、however、instead、still 如何表达转折，以及 may、suggested、whether 如何限定结论。
正文 As people grow older , many of them live with a low level of inflammation that never fully goes away . Scientists call this “inflammaging ”, and it is linked to many diseases of old age . A new study from Yale School of Medicine published in the journal Cell on October 23, points to an unexpected helper : taurine , an amino acid found at high levels inside the body’s cells
本段译文 随着年龄增长，许多人身上会出现一种从未完全消退的低水平炎症。科学家称之为“炎性衰老”（inflammaging），它与许多老年疾病有关。耶鲁大学医学院 10 月 23 日发表在《细胞》（Cell）期刊上的一项新研究，指向了一个出人意料的“帮手”：牛磺酸——一种在人体细胞内含量很高的氨基酸。
Some scientists have suggested that taurine falls with age and that this decline may help drive ageing , though the idea is still debated . However , when the Yale team compared blood from young adults aged 20 to 40 with blood from people aged 60 to 99, they found that taurine actually increased with age . The same was true in mice . The first author , Chenyang Guan , said this suggested that taurine does not drive ageing .
本段译文 一些科学家曾提出，牛磺酸会随年龄下降，而这种下降可能推动衰老，不过这一观点仍有争议。然而，耶鲁团队把 20 至 40 岁年轻人的血液与 60 至 99 岁人群的血液进行比较后发现，牛磺酸实际上随年龄增加。小鼠身上也是如此。第一作者 Chenyang Guan 表示，这说明牛磺酸并不是推动衰老的原因。
So why would it rise ? The researchers think the increase may be the body’s failed attempt to reduce inflammation . To test this , they studied macrophages , immune cells that act as the body’s first line of defence . When these cells meet danger signals , such as poisons from bacteria , a group of proteins called the NLRP 3 inflammasome comes together inside them and starts inflammation . As this happened in the lab , the cells released up to 80% of their taurine .
本段译文 那么它为什么会升高？研究者认为，这种增加可能是身体减轻炎症的一次失败尝试。为了验证这一点，他们研究了巨噬细胞——充当身体第一道防线的免疫细胞。当这些细胞遇到危险信号（例如细菌产生的毒素）时，一组名为 NLRP3 炎症小体的蛋白质会在细胞内组装起来并引发炎症。在实验室中发生这一过程时，细胞释放了多达 80% 的牛磺酸。
This loss seemed to be part of how the cells sense danger . When the team put taurine back into the cells , the inflammation stopped . When they lowered taurine instead , inflammation grew stronger , even in young mice . In older mice , giving extra taurine improved their health in later life and reduced deaths from sepsis , a serious reaction to infection .
本段译文 这种流失似乎是细胞感知危险的方式之一。研究团队把牛磺酸重新补回细胞后，炎症就停止了；反过来降低牛磺酸时，即使在年轻小鼠身上炎症也会变得更强。在老年小鼠中，额外补充牛磺酸改善了它们晚年的健康状况，并减少了败血症（一种对感染的严重反应）造成的死亡。
The work also connects to an earlier finding . Senior author Vishwa Deep Dixit first became interested in taurine when he saw it rise in people who ate fewer calories for up to a year in a study called CALERIE . The new paper reports that in humans , long-term calorie restriction raises taurine in fat tissue and comes with lower inflammation . However , eating much less is not practical for most adults
本段译文 这项研究还与更早的一项发现有关。资深作者 Vishwa Deep Dixit 最初关注牛磺酸，是因为他在一项名为 CALERIE 的研究中看到，连续最长一年减少热量摄入的人体内牛磺酸升高。新论文报告，在人类中，长期限制热量会提高脂肪组织中的牛磺酸，并伴随较低的炎症水平。不过，大幅少吃对大多数成年人来说并不现实。
Dixit compared taurine to a brake that keeps the inflammasome in check . Still , he called the result only “the first step of the puzzle .” Most of the key tests were done on cells and mice , not on people . The team is now testing whether the findings could benefit older adults . For now , the study does not show that taking taurine will slow ageing in humans
本段译文 Dixit 把牛磺酸比作一个让炎症小体受到控制的“刹车”。但他也称这一结果只是“解开谜题的第一步”。大部分关键实验是在细胞和小鼠身上完成的，而不是在人身上。研究团队目前正在检验这些发现能否惠及老年人。就目前而言，这项研究并不能说明服用牛磺酸会减缓人类的衰老。
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