Effects of Melatonin: Basics Studies and Clinical Applications

Melatonin is a somewhat mysterious substance. In animals, melatonin is secreted from the pineal gland during the night. It acts as a hormone, functioning as a circadian mediator for time information over the course of each day, and is also able to eliminate free radicals (reactive oxygen species). Melatonin also exists in higher plants (edible plants), and is inadvertently obtained from daily meals 1,2). This substance was isolated by chance from the pineal gland, an endocrine organ, and is therefore named a hormone. Regarding the effect of melatonin in inducing synchronization of circadian rhythms, which is generally regarded as a sleep-promoting effect, melatonin administration lowers deep body temperatures not only in those with rhythm disorders but also in healthy individuals, from children to elderly people 3); shortens the time required to fall asleep; and improves sleep 4). In addition, melatonin functions as an antioxidative substance (Review: Reiter, 2000) 5) and acts on bone metabolism 6). Melatonin thus has a variety of activities. In a rat model, melatonin inhibited age-related visceral adiposity 7). These findings may indicate that in addition to meals and physical exercise, sleep is deeply involved in metabolic syndrome, which has become of increasing concern in recent years. In the Current Concept Session “Melatonin” at the 9th Scientific Meeting of the Japanese Society of Anti-Aging Medicine in 2009, three speakers presented basic data and their interpretations and applications in clinical settings from the viewpoints of brain functions, sleep medicine, and reproductive functions, namely “Melatonin and Brain Functions” by Kazuyoshi Tsutsui, “Sleep Medicine and Melatonin” by Masako Okawa, and “Melatonin and Reproductive Functions” by Bunpei Ishizuka. This Session was co-held with the Society of Anti-Aging Endocrinology. In the future, we intend to introduce new basic and clinical research studies on melatonin and propose a lifestyle that will not decrease but rather lead to an increase in melatonin. Synthesis and Distribution of Melatonin