Animals ; Humans ; Melatonin ; physiology ; Receptors, Melatonin ; physiology ; Signal Transduction ; physiology

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

The selective melatonin receptor agonism effect of ramelteon is useful for insomnia. Here we wanted to present a refractory chronic migraine case, who had significant improvements in migraine after using ramelteon. The possible mechanism for the ramelteon in the migraine relief might be related to melatonin effects.
Felodipine ; Melatonin ; Migraine Disorders* ; Receptors, Melatonin ; Sleep Initiation and Maintenance Disorders ; Sleep Wake Disorders

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.
Bipolar Disorder ; Depression ; Humans ; Melatonin ; Mood Disorders ; Pineal Gland ; Receptors, Melatonin

AIMTo observe the role of melatonin receptor and GABAA receptor in sleeping time prolonged by melatonin in mice.

METHODSThe absence of the righting reflex was considered as the sleep onset and the duration of the loss of the righting reflex was recorded as the sleeping time. The effects of receptor agonist and antagonist on hypnotic activity of melatonin were studied in the paper.

RESULTSPrazosin hydrochloride, the blocker of melatonin 3 receptor, didn't affect the sleeping time prolonged by melatonin in mice. GABA, the endogenous agonist of GABA receptor, significantly potentiated the hypnotic activity of melatonin. When picrotoxin, the ligand of picrotoxin site on GABAA receptor, used together with melatonin, it significantly antagonized the sleeping time prolonged by melatonin, however, bicuculline, the specific antagonist of GABA binding site in GABAA receptor, didn't affect the hypnotic activity of melatonin in mice.

CONCLUSIONMelatonin does not exhibit its potentiation sleeping time in mice through melatonin 3 receptor. Hypnotic activity of melatonin may be mediated through picrotoxin site on GABAA receptor.

Animals ; Bicuculline ; pharmacology ; Male ; Melatonin ; physiology ; Mice ; Mice, Inbred Strains ; Picrotoxin ; pharmacology ; Prazosin ; pharmacology ; Receptors, GABA-A ; physiology ; Receptors, Melatonin ; physiology ; Sleep ; physiology

The secretion of melatonin exhibits a circadian rhythm entrained with the sleep-wake cycle. An alteration of this secretory rhythm has been found in various psychiatric disorders. This review summarizes the regulation of melatonin and its relationship to the circadian rhythm, major depressive disorder, bipolar disorder, seasonal affective disorder, Alzheimer's disease and autism. The review also looks at the effect of melatonin and melatonin agonist on sleep and symptoms of depression, bipolar disorder and seasonal affective disorder. In Alzheimer's disease, the circadian rhythm alterations are associated with the change of melatonin levels and melatonin receptors. It has been reported that melatonin and melatonin synthetic enzyme levels decrease in autism spectrum disorder.
Alzheimer Disease ; Autistic Disorder ; Bipolar Disorder ; Child ; Autism Spectrum Disorder ; Circadian Rhythm ; Depression ; Depressive Disorder, Major ; Melatonin* ; Receptors, Melatonin ; Seasonal Affective Disorder

Animals ; Cytokines ; physiology ; Humans ; Immune System ; drug effects ; physiology ; Melatonin ; pharmacology ; Opioid Peptides ; physiology ; Receptors, Melatonin ; physiology ; Stress, Physiological ; immunology ; T-Lymphocytes ; drug effects ; physiology

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.
Androstadienes ; Animals ; Astrocytes ; Cell Death ; Cell Membrane ; Glial Cell Line-Derived Neurotrophic Factor ; Hippocampus ; Melatonin ; Mice ; Neurons ; Phosphorylation ; Rats ; Receptors, Melatonin ; Tryptamines

Major depression is a common mental illness, associated with high morbidity and mortality. Antidepressants have been the first-line therapies due to their confirmed efficacy, however, considering high rate of poor treatment response to these therapies, distressing side effects, and delayed onset of their efficacy, there has been much effort to find alternative treatments for major depression. Recently, evidence regarding disturbed circadian rhythms involved in the pathophysiology of major depression has emerged, the interest on this area has been increasing. Agomelatine is an emerging antidepressant, with a unique profile of selective antagonist at serotonin 2C (5-HT2C) receptors and melatonin receptor agonist. Previous studies have shown its superior efficacy over placebo in treating major depression. Previous trials have shown comparable antidepressant efficacy of agomelatine compared to other standard antidepressants including venlafaxine, sertraline, and fluoxetine. Regarding safety profile of agomelatine, it seems to be not associated with sexual dysfunction and it has less potential for serotonin syndrome or discontinuation syndrome than standard antidepressants including selective serotonin reuptake inhibitors. Considering favorable results on the efficacy and safety of agomelatine in treating depression, it could be a good, safe treatment alternative in the treatment of depression.
Antidepressive Agents ; Circadian Rhythm ; Depression ; Fluoxetine ; Mortality ; Receptors, Melatonin ; Serotonin ; Serotonin Syndrome ; Serotonin Uptake Inhibitors ; Sertraline ; Venlafaxine Hydrochloride

OBJECTIVES: To study the protective effect of melatonin (Mel) against oxygen-induced retinopathy (OIR) in neonatal mice and the role of the HMGB1/NF-κB/NLRP3 axis. METHODS: Neonatal C57BL/6J mice, aged 7 days, were randomly divided into a control group, a model group (OIR group), and a Mel treatment group (OIR+Mel group), with 9 mice in each group. The hyperoxia induction method was used to establish a model of OIR. Hematoxylin and eosin staining and retinal flat-mount preparation were used to observe retinal structure and neovascularization. Immunofluorescent staining was used to measure the expression of proteins and inflammatory factors associated with the HMGB1/NF-κB/NLRP3 axis and lymphocyte antigen 6G. Colorimetry was used to measure the activity of myeloperoxidase. RESULTS: The OIR group had destruction of retinal structure with a large perfusion-free area and neovascularization, while the OIR+Mel group had improvement in destruction of retinal structure with reductions in neovascularization and perfusion-free area. Compared with the control group, the OIR group had significant increases in the expression of proteins and inflammatory factors associated with the HMGB1/NF-κB/NLRP3 axis, the expression of lymphocyte antigen 6G, and the activity of myeloperoxidase (P<0.05). Compared with the OIR group, the OIR+Mel group had significant reductions in the above indices (P<0.05). Compared with the control group, the OIR group had significant reductions in the expression of melatonin receptors in the retina (P<0.05). Compared with the OIR group, the OIR+Mel group had significant increases in the expression of melatonin receptors (P<0.05). CONCLUSIONS Mel can alleviate OIR-induced retinal damage in neonatal mice by inhibiting the HMGB1/NF-κB/NLRP3 axis and may exert an effect through the melatonin receptor pathway.
Animals ; Mice ; HMGB1 Protein ; Melatonin/therapeutic use* ; Mice, Inbred C57BL ; NF-kappa B ; NLR Family, Pyrin Domain-Containing 3 Protein ; Oxygen/adverse effects* ; Peroxidase ; Receptors, Melatonin ; Retinal Diseases/drug therapy*