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Essay: Rhythmic melatonin release controlled by the SCN and its consequences for glucose homeostasis

Groendijk, I. (2016) Essay: Rhythmic melatonin release controlled by the SCN and its consequences for glucose homeostasis. Bachelor's Thesis, Biology.

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The regulation of glucose homeostasis by melatonin starts in the suprachiasmatic nucleus (SCN). Here, two neurotransmitters are produced which indirectly influence melatonin synthesis by the pineal gland. GABA inhibits the sympathetic input from the paraventricular nucleus (PVN) to the pineal gland during the light period, and glutamate, in contrast, stimulate the PVN whereby the signal can be transmitted to the pineal gland resulting in melatonin synthesis. Nocturnal melatonin secretion is an output signal of the circadian clock able to convey photoperiodic, as well as circadian signals to multiple structures/organs possessing melatonin receptors within the brain or the periphery. There is probably an endogenous rhythm, generated by the SCN, responsible for the rhythmic entrainment of the pineal gland. Melatonin is a time messenger candidate to entrain all the clocks in the body, which is especially important in glucose homeostasis. It is shown that a lack of clock genes in the liver results in impaired glycogenesis, reduced hepatic glucose production and increased glucose tolerance, while a lack of melatonin signalling displays glucose intolerance and a desynchronized circadian pattern of gluconeogenesis, hallmarked by increased night time glucose levels. Plasma insulin levels show a daily rhythm as well as it follows on food intake. Ablation of the peripheral clock in the pancreas caused hyperglycemia and diabetes mellitus type 2 due to disturbed β-cell function. Is has been made clear that melatonin has an inhibitory effect on these pancreatic β-cells via its MT1 and MT2 receptors. Melatonin has its receptors not only in the periphery, but also in the brain. Stimulation of the MT1 receptor in the SCN has a stimulatory effect on the neuronal activity. Melatonin has also antioxidant and anti-inflammatory functions, which can be helpful in the treatment against obesity and diabetes through the JAK-STAT3-SOCS3 pathway. The aim of this literature study is to evaluate the effect of the SCN on melatonin release and the consequences on glucose homeostasis. In conclusion, melatonin is a promising candidate for a variety of disorders related to glucose metabolism, with or without the influence of circadian rhythms.

Item Type: Thesis (Bachelor's Thesis)
Degree programme: Biology
Thesis type: Bachelor's Thesis
Language: English
Date Deposited: 15 Feb 2018 08:14
Last Modified: 15 Feb 2018 08:14

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