褪黑素(N-乙酰基-5-甲氧基色胺)是一种吲哚胺,由脊椎动物松果体中的色氨酸通过四种酶促反应合成。褪黑素是一种非常独特的生物活性物质,以受体介导和受体非依赖性作用的组合为特征,促进褪黑激素的多种作用。褪黑素的主要功能之一,通过它的膜受体,是调节昼夜节律或季节节律。在哺乳动物中,光信息,控制褪黑激素的合成,是在眼睛里收到的,并传播到松果体,通过视交叉上核,中央时钟的位置。或者,在哺乳动物以外的许多脊椎动物中,松果体细胞,它们参与褪黑激素的合成和分泌以及昼夜节律,直接接收光。最近,据报道,褪黑激素具有多种代谢功能,涉及骨骼和葡萄糖,除了调节昼夜节律。褪黑素通过抑制破骨细胞活性来改善骨强度。还已知通过增加夜间葡萄糖摄取来维持睡眠期间的大脑活动,以不依赖胰岛素的方式。此外,作为一种非受体介导的作用,褪黑激素具有抗氧化特性。褪黑激素已被证明是一种有效的自由基清除剂和广谱抗氧化剂,甚至保护生物体免受来自太空的辐射。褪黑激素是一种广泛分布的分子,存在于细菌中,单细胞生物,真菌,和植物。假设褪黑激素最初是一种抗氧化剂,然后,在脊椎动物中,它将这种作用与调节节奏和新陈代谢的能力结合在一起,通过它的受体。
Melatonin (N-acetyl-5-methoxytryptamine) is an indolamine that is synthesized from tryptophan in the pineal glands of vertebrates through four enzymatic reactions. Melatonin is a quite unique bioactive substance, characterized by a combination of both receptor-mediated and receptor-independent actions, which promote the diverse effects of melatonin. One of the main functions of melatonin, via its membrane receptors, is to regulate the circadian or seasonal rhythm. In mammals, light information, which controls melatonin synthesis, is received in the eye, and transmitted to the pineal gland, via the suprachiasmatic nucleus, where the central clock is located. Alternatively, in many vertebrates other than mammals, the pineal gland cells, which are involved in melatonin synthesis and secretion and in the circadian clock, directly receive light. Recently, it has been reported that melatonin possesses several metabolic functions, which involve bone and glucose, in addition to regulating the circadian rhythm. Melatonin improves bone strength by inhibiting osteoclast activity. It is also known to maintain brain activity during sleep by increasing glucose uptake at night, in an insulin-independent manner. Moreover, as a non-receptor-mediated action, melatonin has antioxidant properties. Melatonin has been proven to be a potent free radical scavenger and a broad-spectrum antioxidant, even protecting organisms against radiation from space. Melatonin is a ubiquitously distributed molecule and is found in bacteria, unicellular organisms, fungi, and plants. It is hypothesized that melatonin initially functioned as an antioxidant, then, in vertebrates, it combined this role with the ability to regulate rhythm and metabolism, via its receptors.