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Melatonin for sleep: how it works, adverse effects
Last reviewed: 23.04.2024
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Melatonin, a hormone produced by the pineal gland, regulates circadian rhythms. It is obtained from animals or manufactured artificially.
[How does melatonin work?
Some scientific evidence suggests the use of melatonin in minimizing the consequences of long flights, especially in people traveling eastward and crossing more than 2-5 time zones (see the summary of the Cochrane central register of controlled studies on the role of melatonin for the prevention and treatment of biorhythm failure when moving to another time zone).
The standard dosage is not established, varying within 0.5-5 mg orally taken 1 hour before the usual sleep time on the day of travel and 2-4 mg at night after arrival at the site. Evidence supporting the importance of using melatonin as a sleeping aid in adults and children with psychoneurological disorders (for example, developmental disorders) is less.
Antioxidant effects of melatonin
The physiological effects of melatonin for more than 20 years have been studied in animals. Only in recent years, research has begun to study the mechanisms of synthesis, regulation and functions of this hormone in the human body. Melatonin in the chemical structure is indole, mainly produced by the epiphysis from tryptophan. The rhythm of melatonin production by the epiphysis is of a circadian nature. Its level in the circulation begins to rise in the evening, reaching a maximum by the middle of the night, and then progressively decreases, reaching a minimum in the morning hours.
Unlike the biorhythmological effects of melatonin, which are carried out with the participation of receptors to it on cell membranes, the antioxidant properties of this hormone are not mediated through its receptors. In an in vitro study using the procedure for determining the presence of one of the most active OH free radicals in the medium under study, it was found that melatonin has significantly more activity in terms of inactivation of OH than such potent intracellular antioxidants as glutathione and mannitol. Also in vitro, it has been demonstrated that melatonin has stronger antioxidant activity against the peroxyl radical ROO than the well-known vitamin E antioxidant. The protective effect of exogenous melatonin on free radical damage caused by exposure to ionizing radiation was demonstrated in human leukocytes in vitro .
An interesting fact, indirectly indicative of the priority role of melatonin as a DNA protector, was revealed in the study of the activity of cell proliferation. The revealed phenomenon testifies to the predominant role of endogenous melatonin in the mechanisms of antioxidant protection.
The role of melatonin in protecting macromolecules from oxidative stress is not limited to nuclear DNA alone. When studying the effect of free radical damage on tissues in the experiment, it was revealed that it has a high efficiency in preventing the occurrence of degeneration (clouding) of the lens. Moreover, the protein-protective effects of this hormone are comparable to those of glutathione (one of the most potent endogenous antioxidants, therefore, melatonin also has protective properties for free radical damage to proteins.
Of course, studies of the role of this hormone in interrupting the processes of lipid oxidation of lipids (LPO) are of great interest. One of the most powerful lipid antioxidants until recently was considered to be vitamin E (a-tocopherol). In experiments in vitro and in vivo, when comparing the effectiveness of vitamin E and melatonin, it was shown that melatonin is 2 times more active in terms of ROO inactivation than vitamin E. The authors also noted that such a high antioxidant efficiency of this hormone can not be explained only by the ability melatonin interrupt the process of lipid peroxidation by inactivating ROO ', but also includes the inactivation of the OH radical, which is one of the initiators of the LPO process.
In addition to the high antioxidant activity of the hormone itself, in vitro experiments it was found that its metabolite 6-hydroxymelatonin, formed during its metabolism in the liver, gives a much more pronounced antioxidant effect on LPO than M. Consequently, in the body, the mechanisms of protection from free- radical damage include not only the effects of the hormone, but also at least one of its metabolites.
One of the factors that lead to toxic effects of bacteria on the human body is the stimulation of LPO processes by bacterial lipopolysaccharides. In the animal experiment, the high efficiency of the hormone against the oxidative stress caused by the lipopolysaccharide bacteria was demonstrated. The authors of the study emphasize that the antioxidant effect of the hormone is not limited to any one type of cell or tissue, but is of an organismic nature.
In addition to the fact that melatonin itself has antioxidant properties, it is able to stimulate glutathione peroxidase, involved in the conversion of reduced glutathione to its oxidized form. During this reaction, the H2O2 molecule, active in terms of producing an extremely toxic OH radical, turns into a water molecule, and the oxygen ion joins glutathione to form oxidized glutathione. It is also shown that melatonin can inhibit the enzyme (nitrikoksiksintstaza), which activates the processes of NO radical production.
The above hormone effects make it one of the most powerful endogenous antioxidants. Moreover, unlike most other intracellular antioxidants, localized predominantly in certain cellular structures, its presence and, consequently, its antioxidant activity are determined in all cellular structures, including the nucleus. This fact testifies to the universality of the antioxidant effect of melatonin, which is confirmed by the results of experiments already shown above, which demonstrated its protective properties in terms of free radical damage to DNA, proteins and lipids. Due to the fact that the antioxidant effects of the hormone are not mediated through its membrane receptors, melatonin can affect the free radical processes in any cell of the human body, and not only in cells that have receptors to it.
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