Role of melatonin receptor 1B gene polymorphism and its effect on the regulation of glucose transport in gestational diabetes mellitus / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Melatonin receptor 1B (MT2, encoded by the MTNR1B gene), a high-affinity receptor for melatonin, is associated with glucose homeostasis including glucose uptake and transport. The rs10830963 variant in the MTNR1B gene is linked to glucose metabolism disorders including gestational diabetes mellitus (GDM); however, the relationship between MT2-mediated melatonin signaling and a high birth weight of GDM infants from maternal glucose abnormality remains poorly understood. This article aims to investigate the relationship between rs10830963 variants and GDM development, as well as the effects of MT2 receptor on glucose uptake and transport in trophoblasts. TaqMan-MGB (minor groove binder) probe quantitative real-time polymerase chain reaction (qPCR) assays were used for rs10930963 genotyping. MT2 expression in the placenta of GDM and normal pregnant women was detected by immunofluorescence, western blot, and qPCR. The relationship between MT2 and glucose transporters (GLUTs) or peroxisome proliferator-activated receptor γ (PPARγ) was established by western blot, and glucose consumption of trophoblasts was measured by a glucose assay kit. The results showed that the genotype and allele frequencies of rs10830963 were significantly different between GDM and normal pregnant women (P<0.05). The fasting, 1-h and 2-h plasma glucose levels of G-allele carriers were significantly higher than those of C-allele carriers (P<0.05). Besides, the protein and messenger RNA (mRNA) expression of MT2 in the placenta of GDM was significantly higher than that of normal pregnant women (P<0.05). Melatonin could stimulate glucose uptake and GLUT4 and PPARγ protein expression in trophoblasts, which could be attenuated by MT2 receptor knockdown. In conclusion, the rs10830963 variant was associated with an increased risk of GDM. The MT2 receptor is essential for melatonin to raise glucose uptake and transport, which may be mediated by PPARγ.

Changes of the Melatonergic System in Bipolar Disorder: A Literature Review / 우울ㆍ조울병

Recently, melatonergic agents have been gaining much interest in the treatment of mood disorders. The elucidation of the underlying biological mechanisms related to the melatonergic system in mood disorders is warranted to ensure the proper use of melatonergic agents. Changes of the melatonergic system have been investigated in several studies of patients with bipolar disorder (BP) and depression. Accumulating evidence has indicated that patients with BP might exhibit abnormal melatonin secretion patterns, increased light-induced melatonin suppression, altered pineal gland volume, genetically abnormal melatonin synthesis enzyme, and modified melatonin receptors. In this review, the findings of studies performed to explore the association between the melatonergic system and BP are discussed. Moreover, the interpretations and limitations of these findings are described.

The receptor-dependent and non-receptor-dependent mechanism of melatonin activated BK channels in middle cerebral artery myocyte / 中国应用生理学杂志

OBJECTIVE@#To investigate the mechanisms through which myocyte large-conductance Ca-activated K (BK) channels mediate the vasodilation effects of melatonin on cerebral arteries (CAs).@*METHODS@#Middle cerebral arteries (MCA) were obtained from 8-week-old male Wistar rats after anaesthetized. Middle cerebral arterial smooth muscle cells were enzymatically isolated. Whole cell recording mode of patch clamp technique was used to measure the current density of BK channel and voltage-gated potassium (K) channel before and after adding melatonin. Currents density of melatonin on BK channels with melatonin receptor inhibitor 2-phenyl-N-acetyl (luzindole) was recorded using whole cell recording mode and open probability (Po) was recorded using single-channel attached recording mode. The conductance (G) and average open time (To) and off time (Tc) of the BK channel were detected before and after the addition of melatonin in the internal-outward mode.@*RESULTS@#① Melatonin markedly increased the whole-cell BK channel current density but not the voltage-gated potassium (K) channel current density. ② Luzindole (1 μmol/L) greatly suppressed melatonin-induced increase of BK channel current density. ③ The Po of BK channel was significantly increased by melatonin (100 μmol/L) under cell attached recording mode, which was markedly inhibited by luzindole (1 μmol/L). ④ In inside-outside recording mode, melatonin (1 μmol/L, 100 μmol/L) reduced both To and Tc of BK channel, and Tc was reduced much more than To.@*CONCLUSIONS@#Melatonin mediates vasodilation of MCA through the activation of BK channels both melatonin receptor dependent and independent mode.

Serum melatonin and hippocampus MT1 overexpression in asthmatic rat models / 中国药理学通报

Aim ToinvestigatetheexpressionofMT1 in the hippocampus and serum melatonin in the asth-matic rats, and explore the mechanism in the develop-mentofasthma.Methods SixtyadultSDratswere randomly divided into two groups: control group ( n=20 ) and asthma group ( n=40 ) . Asthma rat model was established by sensitization and stimulation with ovalbumin ( OVA ) . Immunohistochemistry, Western blot, and reverse transcription PCR ( RT-PCR ) were used to evaluate the expression of MT1 in hippocam-pus. Enzyme linked immunosorbent assay ( ELISA ) was used to detect serum melatonin level. Results TheexpressionofMT1inhippocampusatgeneand protein levels were significantly elevated in asthmatic group ( P 0.05).Conclusions MelatoninandMT1maybe involved in the pathogenesis of asthma. The up-regula-tion of MT1 in hippocampus with time-dependent pat-tern may be a compensatory response to decreased pe-ripheral melatonin levels for augmenting melatoninˊs neuroprotective and neuroimmunomodulatory effects a-gainst inflammatory reaction and stress in asthma.

Comparison of arylalkylamine N-acetyltransferase and melatonin receptor type 1B immunoreactivity between young adult and aged canine spinal cord

Melatonin affects diverse physiological functions through its receptor and plays an important role in the central nervous system. In the present study, we compared immunoreactivity patterns of arylalkylamine N-acetyltransferase (AANAT), an enzyme essential for melatonin synthesis, and melatonin receptor type 1B (MT2) in the spinal cord of young adult (2~3 years) and aged (10~12 years) beagle dogs using immunohistochemistry and Western blotting. AANAT-specific immunoreactivity was observed in the nuclei of spinal neurons, and was significantly increased in aged dog spinal neurons compared to young adult spinal neurons. MT2-specific immunoreactivity was found in the cytoplasm of spinal neurons, and was predominantly increased in the margin of the neuron cytoplasm in aged spinal cord compared to that in the young adult dogs. These increased levels of AANAT and MT2 immunoreactivity in aged spinal cord might be a feature of normal aging and associated with a feedback mechanism that compensates for decreased production of melatonin during aging.

The expression and binding property of melatonin receptor in adult hepatoma tissue / 中国药理学通报

Aim To determine whether there existed melatonin receptor (MR) in adult hepatoma tissue and to observe its property of binding.Methods Immuno-histochemistry was used to detect MR and identify its subcellular distribution. Specific binding and kinetic analyses of melatonin receptor were measured by radioligand binding assay.Results The results of immunohistochemistry showed that MT1 and MT2 existed in membrane, cytosol and nucleus of the hepatoma cells, but the expression of them principally localized in the membrane and cytosol. The specific binding assay properties of MR were presented as follows: the maximum binding capacity (B_(max)) was (0.29±0.07) pmol·g~(-1) protein. Equilibrium dissociation constant (K_d) was (48.7±6.5) pmol·L~(-1). The trait of MR, saturation and reversibility, was detected by ~(125)I-Mel specific binding kinetic analyses.Conclusions MR exists in adult hepatoma cells, furthermore, the subtypes of MR (MT1 and MT2) coexist in the membrane and cytosol, respectively,whose characters of the specific binding sites were low binding capacity,high affinity,saturation and reversibility.

Melatonin Induces Akt Phosphorylation through Melatonin Receptor- and PI3K-Dependent Pathways in Primary Astrocytes

Melatonin has been reported to protect neurons from a variety of neurotoxicity. However, the underlying mechanism by which melatonin exerts its neuroprotective property has not yet been clearly understood. We previously demonstrated that melatonin protected kainic acid-induced neuronal cell death in mouse hippocampus, accompanied by sustained activation of Akt, a critical mediator of neuronal survival. To further elucidate the neuroprotective action of melatonin, we examined in the present study the causal mechanism how Akt signaling pathway is regulated by melatonin in a rat primary astrocyte culture model. Melatonin resulted in increased astrocytic Akt phosphorylation, which was significantly decreased with wortmannin, a specific inhibitor of PI3K, suggesting that activation of Akt by melatonin is mediated through the PI3K-Akt signaling pathway. Furthermore, increased Akt activation was also significantly decreased with luzindole, a non-selective melatonin receptor antagonist. As downstream signaling pathway of Akt activation, increased levels of CREB phoshorylation and GDNF expression were observed, which were also attenuated with wortmannin and luzindole. These results strongly suggest that melatonin exerts its neuroprotective property in astrocytes through the activation of plasma membrane receptors and then PI3K-Akt signaling pathway.

DETECTION AND LOCATION OF MELATONIN RECEPTOR IN HUMAN SKIN AND ITS MOLECULAR FEATURE / 解放军医学杂志

In order to detect and localize melatonin receptor and its mRNA expression in the human skin, human skin was obtained from healthy volunteers. Immunohistochemistry and RT-PCR were applied to detect MR in human skin and to identify its subcellular distribution. Electrophoresis of RT-PCR product showed positive band of mt 1 subtype in human skin. The subtype of MR, mt 1was present in the membrane, cytosol and nucleus of skin cells as shown by immunohistochemistry. It is suggested that skin is the target organ of melatonin.

THE DISTRIBUTION DIFFERENCE BETWEEN Mel 1a AND Mel 1b MELATONIN RECEPTORS IN THE CENTRAL NERVOUS SYSTEM OF RATS / 解剖学报

Objective To exam the expression and the distribution difference between melatonin membrane receptor subtype Mel 1a and Mel 1b in the central nervous system of rats. Methods In situ hybridization technique was used. Results (1)The Mel 1a mRNA positive cells were mainly detected in the hippocampus,cerebral cortex,supraoptic nucleus,paraventricular nucleus,suprachiasmatic nucleus,inferior olivary nucleus,cortex and fastigial nucleus of cerebellar,ventral horn of the spinal cord,facial nerve nucleus,gigantocellular reticular nucleus,striatum cortex and trigeminal nerve nucleus,etc.(2)The Mel 1b mRNA positive cells were mainly observed in the cerebellar cortex,fastigial nucleus,global nucleus,emboliform nucleus of the medullaris cerebelli,hippocampus,cerebral cortex,ventral horn of the spinal cord,supraoptic nucleus and suprachiasmatic nucleus.Conclusion\ Mel 1a mRNA positive neurons were abundant and distributed widely in the CNS,while Mel 1b mRNA\|positive neurons distributed comparatively localized.However,the hippocampus and the cortex were two regions which were rich in both Mel 1a and Mel 1b mRNA positive neurons.\;[