Melatonin Uptake by Cells: An Answer to Its Relationship with Glucose?

Melatonin Uptake by Cells: An Answer to Its Relationship with Glucose?

Melatonin, -acetyl-5-methoxytryptamine, is an indole mainly synthesized from tryptophan in the pineal gland and secreted exclusively during the night in all the animals reported to date. While the pineal gland is the major source responsible for this night rise, it is not at all the exclusive produc...

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Bibliographic Details
Published in:Molecules (Basel, Switzerland) Vol. 23; no. 8; p. 1999
Main Authors: Mayo, Juan C, Aguado, Arturo, Cernuda-Cernuda, Rafael, Álvarez-Artime, Alejandro, Cepas, Vanesa, Quirós-González, Isabel, Hevia, David, Sáinz, Rosa M
Format: Journal Article
Language:English
Published: Switzerland MDPI AG 10-08-2018
MDPI
Subjects:
Animals
Antioxidants
Beta cells
Biological Transport
Cell Membrane - metabolism
Circadian rhythms
Cytoplasm
Dark adaptation
Endocrine system
Energy Metabolism
Free radicals
Glucose
Glucose - metabolism
GLUT/SLC2A
Historic artifacts
Homeostasis
Humans
Immunomodulation
Indoles
Insulin
Insulin - metabolism
Insulin secretion
Internalization
Melatonin
Melatonin - metabolism
metabolism
Organic chemistry
Organs
Pancreas
Pineal gland
Pineal Gland - metabolism
Protein Transport
Protozoa
Review
Scavenging
Secretory Vesicles - metabolism
Tryptophan
Vertebrates
GLUT/SLC2A
glucose
metabolism
insulin
melatonin
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Summary:Melatonin, -acetyl-5-methoxytryptamine, is an indole mainly synthesized from tryptophan in the pineal gland and secreted exclusively during the night in all the animals reported to date. While the pineal gland is the major source responsible for this night rise, it is not at all the exclusive production site and many other tissues and organs produce melatonin as well. Likewise, melatonin is not restricted to vertebrates, as its presence has been reported in almost all the phyla from protozoa to mammals. Melatonin displays a large set of functions including adaptation to light: dark cycles, free radical scavenging ability, antioxidant enzyme modulation, immunomodulatory actions or differentiation⁻proliferation regulatory effects, among others. However, in addition to those important functions, this evolutionary 'ancient' molecule still hides further tools with important cellular implications. The major goal of the present review is to discuss the data and experiments that have addressed the relationship between the indole and glucose. Classically, the pineal gland and a pinealectomy were associated with glucose homeostasis even before melatonin was chemically isolated. Numerous reports have provided the molecular components underlying the regulatory actions of melatonin on insulin secretion in pancreatic beta-cells, mainly involving membrane receptors MTNR1A/B, which would be partially responsible for the circadian rhythmicity of insulin in the organism. More recently, a new line of evidence has shown that glucose transporters GLUT/SLC2A are linked to melatonin uptake and its cellular internalization. Beside its binding to membrane receptors, melatonin transportation into the cytoplasm, required for its free radical scavenging abilities, still generates a great deal of debate. Thus, GLUT transporters might constitute at least one of the keys to explain the relationship between glucose and melatonin. These and other potential mechanisms responsible for such interaction are also discussed here.
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ISSN:1420-3049
1420-3049
DOI:10.3390/molecules23081999