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.
Female ; Humans ; Pregnancy ; Blood Glucose/metabolism* ; Diabetes, Gestational/metabolism* ; Glucose/metabolism* ; Melatonin/metabolism* ; Polymorphism, Genetic ; PPAR gamma ; Receptor, Melatonin, MT2/genetics*

OBJECTIVE: To investigate the effects of melatonin on the growth and metastasis of MDA-MB-231 breast cancer cells and explore the mechanism. METHODS: MDA-MB-231 cells were treated with 1, 3 or 5 mmol/L melatonin, and the changes in cell proliferation were examined using CCK-8 assay. Colony-forming assay and wound healing assay were used to assess the effects of melatonin treatmnent on colony-forming ability and migration of the cells. Flow cytometry and immunofluoresnce assay were employed to examine apoptosis and positive staining for autophagy-related proteins in the cells treated with 3 mmol/L melatonin. The effects of melatonin treatment alone or in combination with 3-methyladenine (3-MA) on the expressions of the proteins associated with autophagy (LC3, P62 and Beclin1), apoptosis (Bcl2 and Bax) and epithelial-mesenchymal transition (E-cadherin and Snail) were examined with Western blotting. RESULTS: Melatonin treatment significantly inhibited the proliferation of breast cancer cells in a concentration- and time-dependent manner (P < 0.05), suppressed colony-forming ability and migration (P < 0.01), and promoted apoptosis of the cells (P < 0.01). Melatonin treatment alone significantly increased the expressions of Bax (P < 0.05), E-cadherin, LC3-II/LC3-I, and Beclin1 and lowered the expressions of Bcl2 (P < 0.05), Snail, P62 (P < 0.05), and Bcl2/Bax ratio (P < 0.01) in the cells, and caused enhanced positive staining of Beclin1 protein and attenuated staining of P62 protein. Compared with melatonin treatment alone, melatonin treatment combined with 3-MA significantly decreased the expressions of Beclin1 (P < 0.001), LC3-II/LC3-I (P < 0.05), Bax (P < 0.01), and E-cadherin (P < 0.001) and increased the expressions of Bcl2 (P < 0.05), Snail, and Bcl2/Bax ratio (P < 0.01). CONCLUSION Melatonin can induce autophagy of MDA-MB-231 breast cancer cells to inhibit cell proliferation and metastasis and promote cell apoptosis, and suppressing autophagy can weaken the inhibitory effect of melatonin on the growth and metastasis of breast cancer cells.
Autophagy ; Autophagy-Related Proteins/metabolism* ; Breast Neoplasms ; Cell Line, Tumor ; Female ; Humans ; Melatonin/pharmacology*

Depression is a debilitating psychiatric disorder with a huge socioeconomic burden, and its treatment relies on antidepressants including selective serotonin reuptake inhibitors (SSRIs). Recently, the melatonergic system that is closely associated with the serotonergic system has been implicated in the pathophysiology and treatment of depression. However, it remains unknown whether combined treatment with SSRI and melatonin has synergistic antidepressant effects. In this study, we applied a sub-chronic restraint stress paradigm, and evaluated the potential antidepressant effects of combined fluoxetine and melatonin in adult male mice. Sub-chronic restraint stress (6 h/day for 10 days) induced depression-like behavior as shown by deteriorated fur state, increased latency to groom in the splash test, and increased immobility time in the forced-swim test. Repeated administration of either fluoxetine or melatonin at 10 mg/kg during stress exposure failed to prevent depression-like phenotypes. However, combined treatment with fluoxetine and melatonin at the selected dose attenuated stress-induced behavioral abnormalities. Moreover, we found that the antidepressant effects of combined treatment were associated with the normalization of brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling in the hippocampus, but not in the prefrontal cortex. Our findings suggest that combined fluoxetine and melatonin treatment exerts synergistic antidepressant effects possibly by restoring hippocampal BDNF-TrkB signaling.
Animals ; Antidepressive Agents ; pharmacology ; Behavior, Animal ; drug effects ; Brain-Derived Neurotrophic Factor ; drug effects ; metabolism ; Depression ; Drug Synergism ; Drug Therapy, Combination ; Fluoxetine ; pharmacology ; Hippocampus ; drug effects ; metabolism ; Male ; Melatonin ; pharmacology ; Membrane Glycoproteins ; drug effects ; metabolism ; Mice, Inbred C57BL ; Protein-Tyrosine Kinases ; drug effects ; metabolism ; Restraint, Physical ; Signal Transduction ; drug effects

OBJECTIVETo investigate the effects of Liuwei Dihuang (LWDH) decoction on serotonine (5-HTs), melatonin and the activity of the rate-limiting enzymes ANNAT and HIOMT in cultured human melanocytes and in melanocytes co-cultured with keratinocytes.

METHODSCCK-8 assay was used to assess the proliferation of melanocytes and melanocytes co-cultured with keratinocytes after treatment with the serum from rabbits fed with LWDH decoction. High-performance liquid chromatography was used to determine 5-HT and melatonin contents, and real-time fluorescent PCR was employed to evaluate the ANNAT and HIOMT activities in the cell cultures.

RESULTSThe serum from rabbits fed with LWDH Decoction at low doses did not affect the proliferation of melanocytes co-cultured with keratinocytes, but at the concentrations of 20%-40%, the serum significantly inhibited the proliferation of melanocytes, and the effect was optimal with a concentration of 40% (P<0.05). 5-HT and melatonin contents in the cell culture decreased as the serum concentration increased (P<0.05), which was the most obvious with a serum concentration of 40% (P<0.01). Exposure of the cells to low and moderate doses of the serum caused a dose-dependent decrease in AANAT activity (P<0.05), but the serum produced no significant changes in the level of HIOMT mRNA expression in the cells.

COUCLUSIONSThe serotoninergic/melatoninergic system mediate the regulation of melanin metabolism by LWDH Decoction, the mechanism of which may involve 5-HTs, melatonin and ANNAT.

Animals ; Cells, Cultured ; Coculture Techniques ; Drugs, Chinese Herbal ; pharmacology ; Humans ; Keratinocytes ; Melanins ; metabolism ; Melanocytes ; drug effects ; metabolism ; Melatonin ; metabolism ; Rabbits ; Serotonin ; metabolism ; Serum ; chemistry

OBJECTIVETo explore the effects of Kaixin Powder (, KXP) on melatonin receptor (MR) expression and (125)I-Mel binding affinity in a depression rat model.

METHODSSeventy-two male Wistar rats were divided into six groups: a blank control group, model group, ramelteon group, KXP high-dosage group (HKXP), medium-dosage group (MKXP) and low-dosage group (LKXP). To establish the depression model, all groups except the blank control group were singly housed and exposed to chronic unpredictable mild stress. Weight gain, sucrose consumption and the open-field test were used to evaluate induction of depression. KXP at 260, 130 and 65 mg/(kg•d) was also respectively administered to the rats in the HKXP, MKXP and LKXP groups for 21 days. Ramelteon [0.83 mg/(kg•d)] was given to the positive drug control group. An equivalent volume of physiological saline was given to the blank and model groups. The liquid chip method was used to measure the concentration of plasma melatonin (MT). Mel1a (MT1) and Mel1b (MT2) expression levels were determined by Western blotting. In addition, a radioactive ligand-binding assay was used to analyze the specific binding properties and dynamic characteristics between MR and (125)I-Mel.

RESULTSThe results of weight gain, sucrose consumption and the open-field test showed that our model successfully produced depressive symptoms and depressive-like behavior. The concentration of plasma MT in the model group decreased significantly at night but increased in the MKXP group (P<0.05). The HKXP group showed significantly increased expression of MT1 (P<0.05); however, the expression of MT2 in all groups exhibited no significant differences (P>0.05). The maximum binding capacity (B(max)) for specific binding between MR and 125I-Mel in the MKXP group was significantly higher than that in the model group (P<0.05), but no significant differences were found in the equilibrium dissociation constant (K(d)) of each group (P>0.05).

CONCLUSIONSKXP may have a similar effect as ramelteon. KXP improved depressive-like behavior by increasing the concentration of plasma MT and MT1 expression, thereby increasing three B(max) of MR to achieve the desired antidepressant effect.

Animals ; Brain ; drug effects ; metabolism ; pathology ; Depression ; blood ; drug therapy ; metabolism ; Disease Models, Animal ; Drinking Behavior ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; Gene Expression Regulation ; drug effects ; Indenes ; Iodine Radioisotopes ; Male ; Melatonin ; blood ; metabolism ; Rats, Wistar ; Receptors, Melatonin ; genetics ; metabolism ; Weight Gain ; drug effects

OBJECTIVETo investigate the expressions of P38 mitogen-activated protein kinases (P38 MAPK), JNK mitogen-activated protein kinases (JNK MAPK) and the therapeutical effects of melatonin in the renal tissue of acute acuteparaquat-induced rats.

METHODSSeventy-eight healthy adult Sprague-Dawley (SD) rats (39 male, 39 female) were randomly divided into three groups: (1) Control group (group A): 6 rats, (2) Poisoned group (group B): 36 rats, (3) Therapeutical group (group C): 36 rats. At 1, 3, 5, 7, 10 and 14 days after poisoning, six rats in Group B and group C were used to assess renal pathological changes and the expression of P38 MAPK, JNK MAPK in kidney were evaluated by immunohistochemistry.

RESULTSCompared with control group, the expression of P38MAPK in renal tissue of poisoned group significantly rose at the first day, reached the peak at the 10th day and afterwards decreased slowly. Expression of JNK MAPK reached the peak at the first day, and kept at relatively high levels up to the 14th day. Melatonin weakened markedly the expressions of P38 MAPK and JNK MAPK in renal tissue of acute acuteparaquat-induced rats.

CONCLUSIONP38 MAPK and JNK MAPK play an important role in renal injury of acute paraquat -poisoning rats. Melatonin takes a significant effect on the activation of them.

Animals ; Female ; JNK Mitogen-Activated Protein Kinases ; metabolism ; Kidney ; drug effects ; metabolism ; physiopathology ; Male ; Melatonin ; therapeutic use ; Paraquat ; poisoning ; Rats ; Rats, Sprague-Dawley ; p38 Mitogen-Activated Protein Kinases ; metabolism

The worldwide prevalence of obesity is steadily increasing, nearly doubling between 1980 and 2008. Obesity is often associated with insulin resistance, a major risk factor for type 2 diabetes mellitus (T2DM): a costly chronic disease and serious public health problem. The underlying cause of T2DM is a failure of the beta cells of the pancreas to continue to produce enough insulin to counteract insulin resistance. Most current T2DM therapeutics do not prevent continued loss of insulin secretion capacity, and those that do have the potential to preserve beta cell mass and function are not effective in all patients. Therefore, developing new methods for preventing and treating obesity and T2DM is very timely and of great significance. There is now considerable literature demonstrating a link between inhibitory guanine nucleotide-binding protein (G protein) and G protein-coupled receptor (GPCR) signaling in insulin-responsive tissues and the pathogenesis of obesity and T2DM. These studies are suggesting new and emerging therapeutic targets for these conditions. In this review, we will discuss inhibitory G proteins and GPCRs that have primary actions in the beta cell and other peripheral sites as therapeutic targets for obesity and T2DM, improving satiety, insulin resistance and/or beta cell biology.
Animals ; Diabetes Mellitus, Type 2/drug therapy/*metabolism ; GTP-Binding Protein alpha Subunits/genetics/*metabolism ; Humans ; Insulin-Secreting Cells/metabolism ; Obesity/drug therapy/*metabolism ; Receptor, Melatonin, MT2/genetics/*metabolism ; Receptors, Adrenergic, alpha-1/genetics/*metabolism ; Receptors, Prostaglandin/genetics/*metabolism

OBJECTIVETo investigate the effect of melatonin (MT) on p38 mitogen-activated protein kinase (MAPK) signaling pathway in rats with phosgene-induced lung injury.

METHODSFifty specific pathogen-free male Sprague-Dawley rats were randomly divided into phosgene inhalation group, air control group, saline control group, MT treatment group, and SB203580 (specific inhibitor of p38 MAPK) group, with 10 mice in each group. All groups except the air control group were exposed to phosgene, and the animals were sacrificed 6 h later. Lung wet/dry weight (W/D) ratio and the content of malondialdehyde (MDA) and nitric oxide (NO) and activity of myeloperoxidase (MPO) in bronchoalveolar lavage fluid (BALF) were measured. The qualitative and quantitative expression of p38 MAPK and phospho-p38 MAPK (p-p38) was measured by immunohistochemistry (IHC) and Western blot, respectively. Inducible nitric oxide synthase (iNOS) level in lung tissue was determined by Western blot.

RESULTSCompared with the air control group, the phosgene inhalation group had significantly increased lung W/D ratio and neutrophil count in BALF (P < 0.01); the MT treatment group had significantly lower neutrophil count and lung W/D ratio than the phosgene inhalation group (P < 0.05). IHC demonstrated that the air control group had relatively weak expression of p-p38 in lung tissue; the expression of p-p38 was significantly up-regulated after phosgene inhalation, and it was mainly distributed in infiltrating inflammatory cells and vascular endothelial cells, positive in the cytoplasm and nucleus of many cells. The distribution of p-p38-positive cells in the MT treatment and SB203580 groups was similar to that in the phosgene inhalation group, but the MT treatment and SB203580 groups had a significantly reduced number of cells with p-p38-positive nuclei and a significantly reduced intensity of p-p38 expression signals. The phosgene inhalation group had significantly increased content of MDA and NO and activity of MPO compared with the air control group (P < 0.01); the MT treatment and SB203580 groups had significantly reduced content of MDA and NO and activity of MPO compared with the phosgene inhalation group (P < 0.05), but had higher content of MDA and NO and activity of MPO than the air control group. The Western blot showed that the phosgene inhalation group had significantly increased expression of iNOS and p-p38 compared with the air control group (P < 0.01); the MT treatment and SB203580 groups had lower expression of iNOS and p-p38 than the phosgene inhalation group (P < 0.05).

CONCLUSIONMT and SB203580 have a significant protective effect in rats with phosgene-induced lung injury, and the mechanism may be associated with scavenging free radicals and inhibiting activation of p38 MAPK and expression of iNOS.

Animals ; Bronchoalveolar Lavage Fluid ; Chemical Warfare Agents ; toxicity ; Imidazoles ; Lung ; drug effects ; Lung Injury ; chemically induced ; Male ; Malondialdehyde ; adverse effects ; Melatonin ; physiology ; Mice ; Nitric Oxide ; adverse effects ; Nitric Oxide Synthase Type II ; metabolism ; Phosgene ; toxicity ; Pyridines ; Rats, Sprague-Dawley ; Respiratory Distress Syndrome, Adult ; metabolism ; Signal Transduction ; p38 Mitogen-Activated Protein Kinases ; metabolism

In order to investigate the role of melatonin in inhibiting the proliferation of murine gastric cancer and the underlying molecular mechanism, we performed an in vivo study by inoculating murine foregastric carcinoma (MFC) cells in mice, and then tumor-bearing mice were treated with different concentrations of melatonin (i.p.). The changes of Bcl-2, Bax, p21 and p53 expressions in tumor tissue were detected by using real-time fluorescence quantitative RT-PCR and Western blot. We found that: (1) melatonin resulted in reductions of tumor's volume and weight in the gastric cancer-bearing mice and thus showed anti-cancer effect; (2) melatonin reduced Bcl-2 expression, but increased the expression of Bax, p53 and p21 in tumor tissue. Our results suggest that melatonin could inhibit the growth of tumors in gastric cancer-bearing mice through accelerating the apoptosis of tumor cells.
Animals ; Apoptosis ; Melatonin ; pharmacology ; Mice ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; Stomach Neoplasms ; drug therapy ; metabolism ; Tumor Suppressor Protein p53 ; metabolism ; bcl-2-Associated X Protein ; metabolism

Melatonin (N-acetyl-5-methoxytryptamine, MT) is a hormone synthesized and secreted by the pineal gland. Recent studies show that melatonin plays an essential role in the pathogenesis of many reproductive processes. High-concentration melatonin exists in human preovulatory follicular fluid and melatonin receptors are present in ovarian granulosa cells, which indicates the direct effects of melatonin on ovarian function. Reactive oxygen species are involved in a number of reproductive events, including folliculogenesis, follicular atresia, ovulation, oocyte maturation, and corpus luteum formation. Melatonin and its metabolites, as powerful antioxidants and free radical scavengers, can potentially inhibit premature ovarian failure. Literature published in recent years shows the essential roles of melatonin in improving human ovarian function and oocyte quality as well as in the management of infertility. Researches on the action mechanisms of melatonin may provide a theoretical basis for the prevention and treatment of some clinical diseases.
Female ; Granulosa Cells ; metabolism ; physiology ; Humans ; Melatonin ; metabolism ; physiology ; Ovarian Follicle ; growth & development ; metabolism ; Ovary ; physiology ; Reactive Oxygen Species ; metabolism