Secretion of melatonin

Melatonin is a hormone produced by the mysterious pineal gland in reaction to darkness, earning it the nickname “hormone of darkness.” It has sparked a lot of attention as a treatment option for a variety of ailments, including sleep problems. In addition to endothelium protection, this pleiotropic chemical exhibits anti-inflammatory, antioxidant, and anticoagulopathic activities. Melatonin secretion and methods of action, as well as therapeutic rationale, are discussed in this article.

Melatonin synthesis:

Melatonin is the sole hormone known to be produced by the pineal gland, and it is released in reaction to darkness, therefore the moniker “hormone of darkness.” Melatonin sends a circadian and seasonal signal to vertebrate creatures. Melatonin is synthesised from serotonin (which is derived from tryptophan) by a series of enzyme processes. 

The enzyme arylalkylamine N acetyltransferase (AANAT) catalyses the conversion of serotonin to N-acetylserotonin (NAS), which is followed by the enzyme hydroxyl-indole-O-methyltransferase catalysing the conversion of N-acetylserotonin to melatonin (HIOMT).

Melatonin’s functions:

• Stabilises and increases circadian rhythm coupling, particularly of core temperature and sleep-wake cycles.
• Immunological and antioxidant defences 
• Haemostasis, and glucose control
• The distinction between physiological and pharmaceutical melatonin effects is not always evident, but it is dependent on dosage rather than the length of the hormone message.

Note- A “physiological” dosage is acknowledged to give plasma melatonin levels in the same order of magnitude as a nocturnal peak. Because the melatonin secretion regulating mechanism is complicated, including both cerebral and autonomic routes, melatonin secretion can be disrupted in a variety of pathological circumstances.

Melatonin secretion is influenced by several factors:
Several studies have found that dietary factors alter the production or concentration of melatonin.

Energy Restriction: Food has a strong impact on melatonin production, as evidenced by studies of participants who fasted for a length of time. Although the number of human research confirming this is limited, energy restriction affects melatonin release during the night. From 2 to 7 days, deliberate fasting by a total rejection of food or extremely reduced calorie intake (300 kcal per day) reduces melatonin content in the blood by roughly 20%.

Plants and plant-based products that are edible:
Melatonin and its precursor TRP are found in several foods, particularly edible plants. Melatonin is found everywhere in plants, however at varying amounts ranging from picograms to micrograms per gramme of plant tissue. Tomatoes, olives, barley, rice, and walnuts have all been found to contain significant quantities of melatonin.

Night-Time Milk:
Melatonin is a natural substance found in milk that helps you sleep at night. Melatonin concentrations in milk have a distinct diurnal rhythm, with higher quantities in milk produced at night. This appears to be a universal phenomenon across animals.
Because milk is the most important part of an infant’s diet and overnight nursing ensures nutritional sufficiency, the melatonin concentration of nocturnal milk may have additional physiological significance.

Although further research is needed, it is feasible that maternal melatonin may travel through milk to the newborn, resulting in increased nighttime sleep, even though this notion is based on a small number of data.

Alcohol: Researchers have shown that the effects of alcohol on melatonin levels are inconsistent. In three small investigations of healthy volunteers, acute and chronic use of alcohol at a level similar to social drinking’ (10–100 g of ethanol per day) reduced melatonin levels in the blood and saliva, but not in the fourth research. Other features of alcoholic beverages, in addition to the actual amount of ethanol, may have an impact on the overall effect.

Nutrient availability: 

• Evidence of nutrients’ impact on melatonin production varies. Several studies show the significance of B vitamins, magnesium, zinc, and polyunsaturated fatty acids, based primarily on animal data.
• Folate, magnesium, and zinc deficiencies have been linked to lower melatonin levels in rodents, and vitamin B6, alone or in combination with zinc, increased plasma melatonin levels in one rodent study. 
• Folate and B6 vitamins are thought to help TRP coenzymes produce more serotonin.
• Zinc and magnesium, on the other hand, are thought to boost the production of melatonin from serotonin by binding to the AANAT enzyme, activating it and boosting serotonin’s affinity for binding to it. In humans, the significance of these vitamins and minerals in this link is less well understood.

Conclusion:

Melatonin secretion is inversely proportional to the length of darkness. Its most important physiological function is to provide information regarding day duration to the body for a range of physiological activities. In addition to its action as an endogenous synchronizer, accumulating evidence shows that melatonin has antioxidant properties and may play a role in immune response modulation.