Melatonin, endocrine pancreas and diabetes
1Institute of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Germany. elmar.Peschke@medizin.uni-halle.de
Journal of Pineal Research
|December 15, 2007
Summary
Melatonin, a hormone, regulates insulin secretion and exhibits protective effects against diabetes-related oxidative stress. It influences circadian rhythms in pancreatic islets and shows altered levels in diabetic conditions, highlighting its role in metabolic health.
Area of Science:
- Endocrinology
- Chronobiology
- Molecular Biology
Background:
- Melatonin is a key hormone involved in regulating physiological processes, including metabolic functions.
- Insulin secretion and pancreatic beta-cell function are crucial for glucose homeostasis.
- Disruptions in melatonin signaling and oxidative stress are implicated in diabetes pathogenesis.
Purpose of the Study:
- To elucidate the mechanisms by which melatonin influences insulin secretion via specific receptor pathways.
- To investigate the role of melatonin in the circadian regulation of insulin release from pancreatic islets.
- To assess the protective effects of melatonin against oxidative stress in beta-cells and its implications in diabetes.
Main Methods:
- Investigated melatonin's effects on insulin secretion in vivo and in vitro, focusing on MT(1)/MT(2) receptor-mediated pathways (cAMP, cGMP, IP3).
- Analyzed the circadian rhythm of insulin secretion and the influence of melatonin on this rhythm in isolated islets.
- Examined the impact of diabetogens (alloxan, streptozotocin) on beta-cells and melatonin's protective role against reactive oxygen species (ROS).
- Compared plasma melatonin levels and arylalkylamine-N-acetyltransferase (AANAT) activity in diabetic and non-diabetic subjects.
Main Results:
- Melatonin, acting through MT(1)/MT(2) receptors and G(i)-proteins, inhibits cAMP and cGMP pathways, decreasing insulin release, while potentially increasing it via the IP(3) pathway.
- Insulin secretion exhibits a circadian rhythm influenced by melatonin, which induces phase shifts.
- Melatonin demonstrates protective effects against ROS-induced damage to beta-cells, suggesting a therapeutic potential in diabetes.
- Diabetic rats and humans show lower plasma melatonin levels and AANAT activity, alongside increased pineal AANAT mRNA and decreased insulin receptor mRNA.
Conclusions:
- Melatonin significantly modulates insulin secretion through complex receptor-mediated signaling pathways.
- Melatonin plays a critical role in the circadian regulation of pancreatic islet function and insulin release.
- Pharmacological doses of melatonin may offer protection against diabetes-associated oxidative stress.
- Alterations in melatonin metabolism and signaling are closely linked to insulin resistance and diabetes.
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