Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada.
J Physiol Pharmacol. 2011 Feb;62(1):13-9.
Human life span, with or without modern medicine is around 85-95 years. All living creatures have their inner clock that measures their daily (circadian) and their seasonal (circannual) time. These time changes are mediated by the alteration of levels of melatonin, an evolutionary ancient hormone, which is produced in many body tissues, including the pineal gland, retina and the gastrointestinal tract (GIT). Light is blocking the production of melatonin in the pineal gland, darkness is stimulating it. So, the diurnal changes of light intensity of melatonin, provide a "daily clock" and the seasonal changes provide a "seasonal clock". Finally, the reduction of melatonin observed with aging, may indicate the presence of an "age clock". Melatonin is a strong antioxidant (often it is called scavenger of free radicals), which protects the body from the effects of noxious compounds. Therefore it was hypothesized that the reduction of melatonin levels with age contributes to the aging process. So far, the only remedy to extend the life span was a 40% reduction in caloric intake, which prolonged the life in mice, rats, dogs and monkeys by 30-50%. A large group of people imitate these experiments performed on animals, but the results of these experiments will not be known for several decades. How is being hungry prolonging the life span? There is a connection between caloric reduction and melatonin levels in GIT. Several experiments indicate that fasting in animals substantially increased their production of GIT melatonin. Therefore, instead of being permanently hungry, a prolongation of human life could be achieved by a replacement melatonin therapy. A daily intake of melatonin before bed time might achieve the same effect as fasting e.g. an increase of body melatonin levels, which will protect the individual from the ravages of old age. That includes Parkinson's disease and Alzheimer's disease. There is a large group of people taking melatonin daily who believe that melatonin is the "fountain of youth". Those are the subjects which will one day provide an experimental evidence of the efficacy of melatonin.
人类的寿命，无论是否有现代医学的干预，都在 85-95 岁左右。所有生物都有自己的生物钟，它可以测量它们的日常（昼夜节律）和季节性（年节律）时间。这些时间变化是由褪黑素水平的改变介导的，褪黑素是一种古老的进化激素，存在于许多身体组织中，包括松果体、视网膜和胃肠道（GIT）。光会抑制松果体中褪黑素的产生，而黑暗则会刺激褪黑素的产生。因此，褪黑素的日强度变化提供了一个“日常时钟”，而季节性变化则提供了一个“季节性时钟”。最后，随着年龄的增长而观察到的褪黑素减少，可能表明存在一个“年龄时钟”。褪黑素是一种强大的抗氧化剂（通常被称为自由基清除剂），可以保护身体免受有害物质的影响。因此，有人假设褪黑素水平随年龄的降低导致了衰老过程。到目前为止，延长寿命的唯一方法是减少 40%的热量摄入，这使老鼠、大鼠、狗和猴子的寿命延长了 30-50%。一大批人模仿这些在动物身上进行的实验，但这些实验的结果还需要几十年的时间才能知道。饥饿如何延长寿命？热量摄入的减少和 GIT 中的褪黑素水平之间存在联系。多项实验表明，动物的禁食会大大增加其 GIT 褪黑素的产生。因此，与其永久饥饿，不如通过褪黑素替代疗法来延长人类的寿命。在睡前摄入褪黑素可能会产生与禁食相同的效果，例如增加体内褪黑素水平，从而保护个体免受老年的摧残。这包括帕金森病和阿尔茨海默病。有一大群人每天都在服用褪黑素，他们相信褪黑素是“青春之泉”。这些人将有一天为褪黑素的疗效提供实验证据。
