日期：2015-09-17 期刊：Science Translational Medicine
DOI：
10.1126/scitranslmed.aac5125 作者：T.M. Burke
有些人是天生的云雀，他们会在清晨醒来。另外一些人则是猫头鹰，他们喜欢晚睡。在睡前摄取与两份意式浓咖啡所含咖啡因量相同的咖啡因会推迟人体生物钟近1个小时，这意味着晚上喝咖啡的人容易在第二天较晚醒来。这表示晚间摄取咖啡因会让人更像“夜猫子”。
喜欢喝咖啡的人要注意了：晚上喝相当于2份(double shots)意式浓咖啡所含咖啡因量的咖啡会让人体生物钟推迟达40分钟。一项新的研究揭示了咖啡因是如何干扰我们体内的计时系统并破坏睡眠的，咖啡因是全世界使用最广泛的致精神兴奋性化合物。这些结果为治疗某些昼夜睡眠-觉醒障碍铺设了道路，它们表明深夜喝咖啡可能促成了近来睡眠问题的增加，而在恰当的时候摄取咖啡因或能帮助人们在倒时差时调整生物钟。咖啡因已知会影响许多物种的生物钟，但这种情况在人体中是否也如此则仍然未知。为了弄清楚，Tina Burke和同事对5位健康人进行了一项有仔细对照的、为期49天的研究，这些人在睡觉前3小时服用一颗咖啡因药片，其所含的咖啡因量与2份意式浓咖啡中所含咖啡因量相同。研究人员对晚上摄取咖啡因会如何影响人体生物钟进行了调查，并与晚间接触强光进行比较，后者是一种行之有效的已知会破坏睡眠的环境刺激。他们发现，咖啡因会强力延长受试者的生物钟周期达40分钟，或相当于在夜晚接触强光时所引起的生物钟推迟时间的几乎一半。为了探索咖啡因在细胞水平的作用，研究人员在长期接触咖啡因的培养的人类细胞中分析了分子振荡。他们发现，咖啡因所施加的破坏睡眠影响是通过阻止促睡眠激素腺苷无法与其受体结合并刺激cAMP信号传导而实现的，而cAMP信号传导是细胞生物钟和睡眠调节因子的一个核心组分。
原文链接：
Effects of caffeine on the human circadian clock in vivo and in vitro
原文摘要：
Your morning cup of coffee may be shifting your circadian clock. Burke et al. show that caffeine—widely available, legal, and psychoactive—inserts a delay into the ~24-hour metabolic rhythm that keeps your body running in time with the world.In a sensitive, within-subject experimental design, five people were kept under highly controlled conditions for 49 days. Before bedtime, they were given various treatments: either a double-espresso caffeine dose, exposure to bright or dim light, or a placebo. The caffeine delayed their internal clock by 40 min, a shift about half as long as bright light, a stimulus known to robustly lengthen the circadian phase.The authors used cultured cells to determine that the drug acted directly on the adenosine receptor, which increases the intracellular messenger molecule cyclic AMP. The fact that cyclic AMP forms a key cog in the inner workings of the clock links caffeine’s biochemical effects to its delay of the circadian rhythm.Not only do these results reinforce the common advice to avoid caffeine in the evening, but they also raise the intriguing possibility that caffeine may be useful for resetting the circadian clock to treat jet lag induced by international time zone travel.