Cvs Melatonin: Melatonin Wikipedia

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Cvs Melatonin: Melatonin Wikipedia

Melatonin – Wikipedia

In humans, melatonin is synthesized from the amino acid tryptophan, which is involved in the synthesis of the neurotransmitter (neurotransmitter) serotonin, and it, in turn, is transformed into melatonin by the action of the enzyme N-acetyltransferase. It has been shown that melatonin is an indole derivative of serotonin and is synthesized at night by the enzymes N-acetyltransferase and hydroxyindole-O-methyltransferase. In an adult, about 30 μg is synthesized per day [a source is not indicated for 1395 days] of melatonin, its concentration in blood serum at night is 30 times greater than during the day, and the maximum concentration in an average of many observations falls at about 2 am [1] [ 3] local solar time. Melatonin is transported by serum albumin, after release from albumin, binds to specific receptors on the membrane of target cells, penetrates into the nucleus and performs its action there. Melatonin is rapidly hydrolyzed in the liver and excreted in the urine, the main metabolite is 6-hydroxymelatonin sulfate (6-COMT), the content of which allows you to indirectly judge the production of melatonin by the epiphysis.

Melatonin is present in the body and is formed outside the epiphysis. This discovery in 1974 was made by Russian scientists N. T. Raikhlin and I. M. Kvetnoy – they discovered that melatonin is synthesized in cells of the vermiform process of the intestine. Then it turned out that melatonin is formed in other parts of the gastrointestinal tract, as well as in many other organs [1].

Melatonin secretion is subject to the daily rhythm, which, in turn, determines the rhythm of gonadotropic effects and sexual function. Synthesis and secretion of melatonin depend on the illumination – an excess of light reduces its formation, and a decrease in illumination increases the synthesis and secretion of the hormone. A person with a normal daily routine (sleeping at night) has about 70% of the daily melatonin production at night. In clinical conditions, it has been established that sleep deprivation at night leads to a disruption of the daily rhythm of melatonin production — production at night decreases and approaches day level [4].

Studies by Russian scientists under the guidance of Doctor of Medical Sciences S.I. Rapoport, conducted on patients with coronary heart disease and arterial hypertension, showed a significant decrease in melatonin production during geomagnetic storms [5] [6].

Melatonin receptors [edit | edit code]

Melatonin is a rare example of a hormone that has both membrane and nuclear receptors. Mammals have two melatonin membrane receptors, MTNR1A (MT1), which are mainly expressed on the cells of the anterior pituitary and the suprachiasm nuclei of the hypothalamus, but also present in many peripheral organs, and MTNR1B (MT2), which is expressed in some other brain regions, retina and in the lungs. Birds, amphibians, and fish have a third receptor, MTNR1C (MT3), which has not yet been cloned in mammals. Melatonin receptors belong to the family of receptors associated with G-proteins, and act through the Gαi-protein, reducing the level of cAMP.

The ramelteon insomnia remedy, manufactured in the United States under the trade name Rozerem, is associated with both types of melatonin receptors. The antidepressant agomelatine, registered in Russia under the trade name Valdoxan, binds to these receptors.

Recently discovered nuclear melatonin receptors belong to the RZR / ROR subfamily of retinoid receptors. Apparently, many immunostimulating and antitumor effects of melatonin are mediated through them.

Basic functions [edit | edit code]

Regulates the activity of the endocrine system, blood pressure, sleep frequency

Reduces emotional, intellectual and physical activity.

Regulates the seasonal rhythm of many animals

Slows down growth and sexual development in children

Reduces calcium intake to bone

Decreases bleeding speed

Increases antibody production

Slows down the aging process

Enhances the efficiency of the immune system

It has antioxidant properties.

Affects adaptation processes during a fast change of time zones

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In addition, melatonin is involved in the regulation

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functions of the digestive tract,

brain cell work.

Effect on the secretion of other hormones and neurotransmitters [edit | edit code]

The main effect of melatonin on the endocrine system in many species is inhibition of gonadotropin secretion. In addition, the secretion of other tropic hormones of the anterior pituitary – corticotropin, thyrotropin, somatotropin – is reduced to a lesser extent. Melatonin reduces the sensitivity of the anterior lobe cells to the gonadotropin release factor and can suppress its secretion.

Experimental data suggests that, under the influence of melatonin, GABA levels increase in the CNS and serotonin in the midbrain and hypothalamus. It is known that GABA is an inhibitory mediator in the central nervous system, and a decrease in the activity of serotonergic mechanisms may be important in the pathogenesis of depressive states.

At night, melatonin reduces leptin secretion.

Effect on seasonal rhythm and reproduction [edit | edit code]

Since melatonin production depends on the length of daylight, many animals use it as a “seasonal clock”. In humans, as in animals, melatonin production is less in summer than in winter. Thus, melatonin can regulate the functions depending on the photoperiod – reproduction, migration behavior, seasonal molting. In species of birds and mammals that multiply during a long day, melatonin inhibits the secretion of gonadotropins and reduces the level of sexual activity. In animals that reproduce at a short daylight, melatonin stimulates sexual activity.

The effect of melatonin on reproductive function in humans is not well understood. At puberty, the peak (night) concentration of melatonin decreases sharply. In winter, the number of menstrual cycles that do not end in ovulation is, on average, higher than in summer. In women with pituitary amenorrhea, melatonin concentration is significantly higher than in healthy ones. These data suggest that melatonin inhibits reproductive function in women. [Source not specified 912 days]

Circadian rhythm and sleep [edit | edit code]

One of the main actions of melatonin is the regulation of sleep. Melatonin is the main component of the body system that sets the pace. He takes part in the creation of the circadian (circadian) rhythm: it directly affects the cells and changes the level of secretion of other hormones and biologically active substances, the concentration of which depends on the time of day. The effect of the light cycle on the melatonin secretion rhythm is shown in monitoring the blind. Most of them have a rhythmic secretion of the hormone, but with a freely changing period, which differs from the daily (25-hour cycle compared with the 24-hour daily). That is, for most blind people, the melatonin secretion rhythm has the appearance of a circadian melatonin wave, “running freely” in the absence of a change of light-dark cycles. A shift in the rhythm of melatonin secretion occurs during the flight to other time zones.

The role of pineal gland and epiphyseal melatonin in the daily and seasonal rhythm, sleep-wakefulness mode today seems beyond doubt. In diurnal (diurnal) animals (including humans), the secretion of melatonin by the epiphysis coincides with the usual hours of sleep. Studies have shown that increasing the level of melatonin is not a mandatory signal to start sleeping. In most subjects, receiving physiological doses of melatonin caused only mild sedation and reduced reactivity to normal surrounding stimuli.

There is a hypothesis that melatonin plays a role in the opening of the so-called sleep gates, in the inhibition of wakefulness regimes, and not in the direct effect on somogenic brain structures. According to the physiologists-somnologists, the opening of the “sleep gate” is preceded by a period of increased human activation – the “forbidden period” (“forbidden zone”) for sleep, which is quite abruptly replaced by the “opening of the gate”.

With age, the activity of the pineal gland is reduced, so the amount of melatonin decreases, sleep becomes shallow and restless, insomnia is possible. Melatonin helps to eliminate insomnia, prevents the violation of the daily regime of the body and biorhythm. Insomnia and lack of sleep give way to healthy and deep sleep, which relieves fatigue and irritability. During a quiet deep sleep in the body, the work of all internal organs and systems is normalized, the muscles relax, the nervous system rests, the brain manages to process the information accumulated during the day. As a result, a person feels fit and healthy.

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Disruption of the normal mode of production of melatonin is associated with disorders of circadian rhythms and pathologies such as jet lag; insomnia due to shift work; weekend insomnia; sleep phase delay syndrome and others [7].

Antioxidant effect [edit | edit code]

Melatonin neutralizes the damaging effects of oxidative processes, which are the main cause of skin aging and fading.

The most important function of melatonin is antioxidant activity, which is manifested throughout the body, since melatonin penetrates into all organs and tissues. The mechanism of antioxidant action is manifested in the fact that melatonin has a pronounced ability to bind free radicals, including hydroxyl radicals formed during lipid peroxidation, and exogenous carcinogens, it also activates glutathione peroxidase, a factor that protects the body from free radical damage. The main functions of the antioxidant effect of melatonin are aimed at protecting DNA. To a lesser extent – the protection of proteins and lipids.

Melatonin is the most powerful of the known endogenous free radical scavengers. In recent years, there has been evidence that melatonin can be located not only in plasma, but also in cell nuclei and protect the macromolecules of the nucleus from oxidative damage in all subcellular structures.

Antitumor effect [edit | edit code]

Cvs Melatonin: Melatonin Wikipedia

In the early stages of embryonic development, biogenic amines, including melatonin, play the role of specialized cellular signaling molecules that regulate cell renewal processes. It has been established that melatonin can suppress cell proliferation, while its strength is not inferior to colchicine, a powerful cytotoxic agent. In a number of studies on laboratory animals and in systems of tumor tissue cultures, it was found that melatonin has an antitumor, oncostatic effect.

The mechanisms of action of melatonin on tumor growth are diverse: it can affect the synthesis and secretion of pituitary and sex hormones, can modulate the immune response in the presence of tumor cells and have a direct cytotoxic effect.

There are suggestions that melatonin may enhance the expression of adhesion molecules and thereby inhibit tumor growth, since it is known that in most malignant tumors there are abnormalities in cell adhesion and defects in intercellular cellular connections.

The melatonin metabolite is significantly positively correlated with a reliable marker of the proliferative activity of tumor cells – the nuclear antigen of proliferating cells (PCNA). This indicator reflects the degree of tumor progression, that is, melatonin metabolites can serve as a reliable diagnostic factor.

Under the influence of melatonin, in some forms of cancer (breast, ovary, prostate, etc.) a decrease in the proliferative capacity of cells was observed and the number of cells dying in the form of apoptosis (oncostatic effect) increased. Targets for the implementation of the antitumor effects of melatonin can serve as nuclear receptors of cancer cells.

In vitro, melatonin suppressed the growth of melanoma cells, although the effect of the hormone depended on the intensity of tumor proliferation: growth was inhibited with moderate, but not with high cell proliferative activity. The effects of melatonin were dose-dependent, but the mechanism of oncostatic action at the moment is still not completely clear.

Epidemiological data show that women working on night shifts, aviation employees (flight attendants, dispatchers), radio and telegraph operators, have an increased risk of developing breast cancer, while women who are primarily blind (i.e. having light deprivation) have this risk 2 times less.

Anti-stress effect [edit | edit code]

After experiments and direct clinical observations, the concept was formulated that the pineal gland and its hormone melatonin are included in the body’s defense system against adverse effects. Epiphysis and melatonin play a nonspecific role, but epiphyseal support is provided at all levels of stress management. In the case of a prolonged stressful situation, a two-phase reaction is observed: the initial decline in epiphyseal activity during the resistant phase of stress with its further sharp rise.

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In experiments on rats, it was shown that melatonin is capable of changing the negative emotional state, reducing anxiety, which is triggered by various stressors.

According to numerous observations, the hormone stabilizes the activity of various endocrine systems disorganized by stress, including eliminating excessive stress adrenal hypercorticism.

When melatonin is oversupplied, depression can develop.

Immunostimulating effect [edit | edit code]

An important consequence of prolonged stress is stress immunodeficiency. Melatonin contributes to the normalization of immunological parameters.

Melatonin and other epiphyseal hormones can be classified as geroprotective. A relationship has been established between the degree of age-related involution of the pineal gland and the decrepitude of tissues. It is known that during aging the degree of immunological protection decreases, and melatonin, as has been repeatedly stated, has immunomodulating activity.

Melatonin stimulates the immune system (immunostimulant), as it participates in the regulation of the function of the thymus and thyroid gland, increasing the activity of T-cells and phagocytes, which is a warning for a number of diseases and, as laboratory studies show, slows the growth of seven types of cancer cells, including cancer cells mammary and prostate glands.

Melatonin deficiency in the body [edit | edit code]

Experiments on laboratory animals showed [1] that with a lack of melatonin caused by the removal of receptors, animals began to age faster: menopause started earlier, free radical cell damage accumulated, insulin sensitivity decreased, and obesity and cancer developed.

Extrapineal melatonin synthesis [edit | edit code]

The amount of hormone that is produced in the pineal gland is not enough to ensure the many biological effects of melatonin. Studies have shown that after removal of the pineal gland in experimental animals significant amounts of melatonin are detected in the blood. At present, it has been firmly established that the pineal gland is not the monopoly organ of melatonin production [8]. Extrapineal sources of melatonin synthesis are enterochromaffin cells of the gastrointestinal tract (EC-cells), the main depot cells of serotonin (containing up to 95% of the total endogenous serotonin) – the precursor of melatonin. Synthesis of this hormone was detected in a large number of neuroendocrine cells of the airways, lungs, in the cortical layer of the kidneys and along the border between the cortical and cerebral layer of the adrenal glands, under the hepatic capsule, in the paraganglia, ovaries, endometrium, prostate gland, placenta, gallbladder and inner ear. Melatonin synthesis is also found in non-endocrine cells:

in blood cells – mast cells,

lymphocytes – natural killers,

platelets

eosinophilic leukocytes,

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in the thymus

pancreas,

the cerebellum

retina,

in some endothelial cells.

Functionally, many cells producing melatonin belong to the so-called diffuse neuroendocrine system – the universal system of adaptation and maintenance of homeostasis of the body.

Within this system, two links of melatonin-producing cells are distinguished:

central (includes the pineal gland and cells of the visual system), in which the melatonin secretion rhythm coincides with the light-dark rhythm;

peripheral – all other cells, where the secretion of the hormone does not depend on light.

Pharmacology [edit | edit code]

Available in tablets, in the US it is considered a dietary supplement. Melatonin tablets are available for over-the-counter sales in almost all countries of the world [9]. In Russia, it is available as a drug under the names Melaxen, Sonnovan, Melapur, Melatonin, Yukalin, Cirkadin, Malarena [10]. Also available in sports nutrition stores, most often under the name Melatonin.

In culture [edit | edit code]

In July 2011, an icon depicting the structural formula of melatonin appeared on the fields of Wiltshire (England): http://cropcircles.lucypringle.co.uk/photos/2011/roundway-hill-cropcircle-2011.shtml.

Melatonin is mentioned in the song Melanie Martinez “Milk and Cookies”: [1]

See also [edit | edit code]

Circadian rhythm

Gamma-melanocyte-stimulating hormone

Notes [edit | edit code]