Deregulation of Melatonin Receptors and Differential Modulation of After-Hyperpolarization and Ih Currents Using Melatonin Treatment Due to Amyloid-ß-Induced Neurotoxicity in the Hippocampus.

Treatment with melatonin is routinely prescribed for its potent antioxidant and cognitive-promoting effects, nevertheless, it has yet to find neuromodulatory effects in normal and disease conditions. Therefore, to investigate its neuromodulatory mechanisms, melatonin was systemically administered over 10 consecutive days to both intracortical normal saline- and amyloid-ß 1-42 (Aß) peptide-injected rats. At the behavioral level, treatment with melatonin was associated with reduced efficacy in restoring Aß-induced deficit in passive-avoidance memory. Whole-cell patch-clamp recordings from CA1 pyramidal neurons revealed that melatonin treatment reduced spontaneous and evoked intrinsic excitability in control rats while exerting a reduction of spontaneous, but not evoked activity, in the Aß-injected group. Interestingly, treatment with melatonin enhances after-hyperpolarization in control, but not Aß-injected rats. In contrast, our voltage-clamp study showed that Ih current is significantly enhanced by Aß injection, and this effect is further strengthened by treatment with melatonin in Aß-injected rats. Finally, we discovered that the transcription of melatonin receptors 1 (MT1) and 2 (MT2) is significantly upregulated in the hippocampi of Aß-injected rats. Collectively, our study demonstrates that systemic treatment with melatonin has differential neuromodulation on CA1 neuronal excitability, at least in part, via differential effects on after-hyperpolarization and Ih currents due to Aß-induced neurotoxicity.

Validated UPLC-MS/MS method for quantification of melatonin receptor agonists and dual orexin receptor antagonists in human plasma and breast milk: Application to quantify suvorexant and lemborexant in clinical samples.

Pharmaceutical care is important for mental health during the perinatal period, which is often characterized by insomnia. In recent years, prescriptions of melatonin receptor agonists (MRAs) and dual orexin receptor antagonists (DORAs) for insomnia have increased; however, their use during the perinatal period has scarcely been reported. In the present study, we developed a UPLC-MS/MS method for the quantification of ramelteon, its metabolite M-II, suvorexant, and lemborexant in human plasma and breast milk to accumulate information on the safety and transfer of MRAs and DORAs into breast milk. Samples of MRAs (ramelteon and M-II) in plasma and breast milk were prepared using liquid-liquid extraction (LLE) with ethyl acetate. For DORAs (suvorexant and lemborexant), LLE with ethyl acetate was applied to plasma samples. For breast milk samples, significant ion suppression was observed for LLE with ethyl acetate. Solid-phase extraction (SPE) cartridges capable of removing phospholipids improved the matrix effects. Finally, protein precipitation with methanol and an SPE cartridge, InertSep® Phospholipid Remover, were selected for breast milk sample preparation. An ACQUITY UPLC BEH C18 column was used for analyte separation. MRAs and DORAs were eluted using isocratic and gradient elution, respectively, and analyzed using electrospray ionization in the positive mode with multiple reaction monitoring. The range of calibration curve for MRAs and DORAs was 0.1-25 and 0.5-50 ng/ml, respectively. Both the plasma and breast milk samples exhibited good linearity over this range. The method was validated by evaluating its accuracy and precision, matrix effect, recovery, carry-over, stability, and dilution integrity. The validated method was successfully applied to clinical samples donated by breastfeeding women and the milk/plasma (M/P) ratio and relative infant dose (RID) of lemborexant (one case) and suvorexant (two cases) were estimated. The M/P ratio of lemborexant was <1, and the RID was 1.05 %. The M/P ratio of suvorexant was <0.1, and RID was 0.11-0.20 %. This method will be useful for future studies evaluating the safety of these drugs during breastfeeding.

Relationship Between Melatonin Receptor Agonists and Parkinson's Disease.

Parkinson's disease affects millions of people worldwide, and without significant progress in disease prevention and treatment, its incidence and prevalence could increase by more than 30% by 2030. Researchers have focused on targeting sleep and the circadian system as a novel treatment strategy for Parkinson's disease. This study investigated the association between melatonin receptor agonists and Parkinson's disease, using the Food and Drug Administration (FDA) Adverse Events Reporting System (FAERS). The target drugs were melatonin receptor agonists including ramelteon, tasimelteon, and agomelatine. Parkinson's disease cases were defined according to the Medical Dictionary for Regulatory Activities (MedDRA) 25.0; Standardized MedDRA Query (SMQ) using both the "narrow" and "broad" preferred terms (PTs) associated with Parkinson's disease. The association between melatonin receptor agonists (ramelteon, tasimelteon, and agomelatine) and Parkinson's disease was evaluated by the reporting odds ratio. Upon analyzing the data from all patients registered in the FAERS, ramelteon (ROR: 0.66, 95% confidence interval [95% CI]: 0.51-0.84) and tasimelteon (ROR: 0.49, 95% CI: 0.38-0.62) showed negative correlations with Parkinson's disease. Conversely, only agomelatine was positively correlated with Parkinson's disease (ROR: 2.63, 95% CI: 2.04-3.40). These results suggest that among the melatonin receptor agonists, ramelteon and tasimelteon are negatively correlated with Parkinson's disease. In contrast, agomelatine was shown to be positively correlated with Parkinson's disease. These results should be used in research to develop drugs for the treatment of Parkinson's disease, fully considering the limitations of the spontaneous reporting system.

Melatonin targets the paraventricular thalamus to promote non-rapid eye movement sleep in C3H/HeJ mice.

Melatonin (MLT) is an important circadian signal for sleep regulation, but the neural circuitries underlying the sleep-promoting effects of MLT are poorly understood. The paraventricular thalamus (PVT) is a critical thalamic area for wakefulness control and expresses MLT receptors, raising a possibility that PVT neurons may mediate the sleep-promoting effects of MLT. Here, we found that MLT receptors were densely expressed on PVT neurons and exhibited circadian-dependent variations in C3H/HeJ mice. Application of exogenous MLT decreased the excitability of PVT neurons, resulting in hyperpolarization of membrane potential and reduction of action potential firing. MLT also inhibited the spontaneous activity of PVT neurons at both population and single-neuron levels in freely behaving mice. Furthermore, pharmacological manipulations revealed that local infusion of exogeneous MLT into the PVT promoted non-rapid eye movement (NREM) sleep and increased NREM sleep duration, whereas MLT receptor antagonists decreased NREM sleep. Moreover, we found that selectively knocking down endogenous MLT receptors in the PVT decreased NREM sleep and correspondingly increased wakefulness, with particular changes shortly after the onset of the dark or light phase. Taken together, these results demonstrate that PVT is an important target of MLT for promoting NREM sleep.

Ramelteon protects against social defeat stress-associated abnormal behaviors.

Psychological stress affects the neuroendocrine regulation, which modulates mental status and behaviors. Melatonin, a hormone synthesized primarily by the pineal gland, regulates many brain functions, including circadian rhythms, pain, sleep, and mood. Selective pharmacological melatonin agonist ramelteon has been clinically used to treat mood and sleep disorders. Posttraumatic stress disorder (PTSD) is a psychiatric condition associated with severe trauma; it is generally triggered by traumatic events, which lead to severe anxiety and uncontrollable trauma recall. We recently reported that repeated social defeat stress (RSDS) may induce robust anxiety-like behaviors and social avoidance in mice. In the present study, we investigated whether melatonin receptor activation by melatonin and ramelteon regulates RSDS-induced behavioral changes. Melatonin treatment improved social avoidance and anxiety-like behaviors in RSDS mice. Moreover, treatment of the non-selective MT1/MT2 receptor agonist, ramelteon, markedly ameliorated RSDS-induced social avoidance and anxiety-like behaviors. Moreover, activating melatonin receptors also balanced the expression of monoamine oxidases, glucocorticoid receptors, and endogenous antioxidants in the hippocampus. Taken together, our findings indicate that the activation of both melatonin and ramelteon regulates RSDS-induced anxiety-like behaviors and PTSD symptoms. The current study also showed that the regulatory effects of neuroendocrine mechanisms and cognitive behaviors on melatonin receptor activation in repeated social defeat stress.

Sperm melatonin receptors, seminal plasma melatonin and semen freezability in goats.

Goat bucks are seasonal breeders that show variation in sperm quality, endogenous melatonin (MLT), and presumably in the expression of MLT receptors on the sperm throughout the year, which may modify sperm freezability. The aim of this study was to determine whether sperm freezability is associated with (i) endogenous melatonin levels in seminal plasma and (ii) the expression of sperm plasma membrane melatonin receptors (MT1, MT2). To evaluate this, spermatozoa from seven Saanen goat bucks were cryopreserved throughout the year in Mexico using a standard freezing protocol. Seminal plasma MLT concentrations were determined by ELISA and the expression and localization of MT1 and MT2 were detected by immunocytochemistry and confirmed by western blotting. The recovery rate of progressive motility after thawing was higher in spring than autumn and winter; in contrast, the F pattern (CTC assay) was higher in winter than in the other seasons. A proportional increase in the AR pattern (CTC assay) was smaller in winter than in the other seasons and the proportion of sperm showing high plasma membrane fluidity was higher in spring than in summer and autumn. The seminal plasma MLT concentrations showed no significant interseasonal differences. The MT1 receptor was immunolocalised at the apical region of the sperm head, while MT2 was mainly localised in the neck. The relative expression of MLT receptors showed significant differences between summer and winter for all bands, except at 75 kDa of MT2. In conclusion, there was an association between the relative expression of MT1 and MT2 receptors throughout the year and sperm freezability in goat bucks in México. Post-thaw sperm quality is enhanced in semen samples collected during breeding season.

Overexpression of cassava melatonin receptor PMTR1 plays dual roles in development under light and dark conditions in Arabidopsis.

KEY MESSAGE: MePMTR1 is involved in plant development and production as well as photosynthesis in plant. Melatonin is widely involved in plant growth and development as well as stress responses. Compared with the extending studies of melatonin in stress responses, the direct link between melatonin and plant development in the whole stages remains unclear. With the identification of phytomelatonin receptor PMTR1 in plants, melatonin signalling is becoming much clearer. However, the function of MePMTR1 in tropical crop cassava remains elusive. In this study, we found that overexpression of MePMTR1 showed larger biomass than wild type (WT), including higher number and area of leaves, weight, and accompanying with higher photosynthetic efficiency. Consistently, exogenous melatonin accelerated photosynthetic rate in Arabidopsis. In addition, MePMTR1-overexpressed plants exhibited more resistance to dark-induced senescence compared with WT, demonstrated by higher chlorophyll, lower hydrogen peroxide and superoxide content. In summary, this study illustrated that melatonin and its receptor regulate growth, development and senescence in plants, highlighting the potential application of melatonin and its receptor in improving crop yield and photosynthesis.

Melatonin in the mammalian retina: Synthesis, mechanisms of action and neuroprotection.

Melatonin is an important player in the regulation of many physiological functions within the body and in the retina. Melatonin synthesis in the retina primarily occurs during the night and its levels are low during the day. Retinal melatonin is primarily synthesized by the photoreceptors, but whether the synthesis occurs in the rods and/or cones is still unclear. Melatonin exerts its influence by binding to G protein-coupled receptors named melatonin receptor type 1 (MT1) and type 2 (MT2). MT1 and MT2 receptors activate a wide variety of signaling pathways and both receptors are present in the vertebrate photoreceptors where they may form MT1/MT2 heteromers (MT1/2h). Studies in rodents have shown that melatonin signaling plays an important role in the regulation of retinal dopamine levels, rod/cone coupling as well as the photopic and scotopic electroretinogram. In addition, melatonin may play an important role in protecting photoreceptors from oxidative stress and can protect photoreceptors from apoptosis. Critically, melatonin signaling is involved in the modulation of photoreceptor viability during aging and other studies have implicated melatonin in the pathogenesis of age-related macular degeneration. Hence melatonin may represent a useful tool in the fight to protect photoreceptors-and other retinal cells-against degeneration due to aging or diseases.

Industrial and academic approaches to the search for alternative melatonin receptor ligands: An historical survey.

The search for melatonin receptor agonists formed the main part of melatonin medicinal chemistry programs for the last three decades. In this short review, we summarize the two main aspects of these programs: the development of all the necessary tools to characterize the newly synthesized ligands at the two melatonin receptors MT1 and MT2, and the medicinal chemist's approaches to find chemically diverse ligands at these receptors. Both strategies are described. It turns out that the main source of tools were industrial laboratories, while the medicinal chemistry was mainly carried out in academia. Such complete accounts are interesting, as they delineate the spirits in which the teams were working demonstrating their strength and innovative character. Most of the programs were focused on nonselective agonists and few of them reached the market. In contrast, discovery of MT1-selective agonists and melatonergic antagonists with proven in vivo activity and MT1 or MT2-selectivity is still in its infancy, despite the considerable interest that subtype selective compounds may bring in the domain, as the physiological respective roles of the two subtypes of melatonin receptors, is still poorly understood. Poly-pharmacology applications and multitarget ligands have also been considered.

Melatonin's effect on hair follicles in a goat (Capra hircus) animal model.

Introduction: Melatonin can treat androgenetic alopecia in males. Goats can be used as animal models to study melatonin treatment for human alopecia. In this study, a meta-analysis of melatonin's effects on goat hair follicles was pursued. Methods: Literature from the last 20 years was searched in Scopus, Science Direct, Web of Science and PubMed. Melatonin's effect on goat hair follicles and litter size were performed through a traditional meta-analysis and trial sequential analysis. A network meta-analysis used data from oocyte development to blastocyst. The hair follicle genes regulated by melatonin performed KEGG and PPI. We hypothesized that there are differences in melatonin receptors between different goats, and therefore completed melatonin receptor 1A homology modelling and molecular docking. Results: The results showed that melatonin did not affect goat primary follicle or litter size. However, there was a positive correlation with secondary follicle growth. The goat melatonin receptor 1A SNPs influence melatonin's functioning. The wild type gene defect MR1 is a very valuable animal model. Discussion: Future studies should focus on the relationship between goat SNPs and the effect of embedded melatonin. This study will provide theoretical guidance for the cashmere industry and will be informative for human alopecia research.

Melatonin receptor structure and signaling.

Melatonin (5-methoxy-N-acetyltryptamine) binds with high affinity and specificity to membrane receptors. Several receptor subtypes exist in different species, of which the mammalian MT1 and MT2 receptors are the best-characterized. They are members of the G protein-coupled receptor superfamily, preferentially coupling to Gi/o proteins but also to other G proteins in a cell-context-depending manner. In this review, experts on melatonin receptors will summarize the current state of the field. We briefly report on the discovery and classification of melatonin receptors, then focus on the molecular structure of human MT1 and MT2 receptors and highlight the importance of molecular simulations to identify new ligands and to understand the structural dynamics of these receptors. We then describe the state-of-the-art of the intracellular signaling pathways activated by melatonin receptors and their complexes. Brief statements on the molecular toolbox available for melatonin receptor studies and future perspectives will round-up this review.

Binding and unbinding of potent melatonin receptor ligands: Mechanistic simulations and experimental evidence.

The labeled ligand commonly employed in competition binding studies for melatonin receptor ligands, 2-[125I]iodomelatonin, showed slow dissociation with different half-lives at the two receptor subtypes. This may affect the operational measures of affinity constants, which at short incubation times could not be obtained in equilibrium conditions, and structure-activity relationships, as the Ki values of tested ligands could depend on either interaction at the binding site or the dissociation path. To address these issues, the kinetic and saturation binding parameters of 2-[125I]iodomelatonin as well as the competition constants for a series of representative ligands were measured at a short (2 h) and a long (20 h) incubation time. Concurrently, we simulated by molecular modeling the dissociation path of 2-iodomelatonin from MT1 and MT2 receptors and investigated the role of interactions at the binding site on the stereoselectivity observed for the enantiomers of the subtype-selective ligand UCM1014. We found that equilibrium conditions for 2-[125I]iodomelatonin binding can be reached only with long incubation times, particularly for the MT2 receptor subtype, for which a time of 20 h approximates this condition. On the other hand, measured Ki values for a set of ligands including agonists, antagonists, nonselective, and subtype-selective compounds were not significantly affected by the length of incubation, suggesting that structure-activity relationships based on data collected at shorter time reflect different interactions at the binding site. Molecular modeling simulations evidenced that the slower dissociation of 2-iodomelatonin from the MT2 receptor can be related to the restricted mobility of a gatekeeper tyrosine along a lipophilic path from the binding site to the membrane bilayer. The enantiomers of the potent, MT2-selective agonist UCM1014 were separately synthesized and tested. Molecular dynamics simulations of the receptor-ligand complexes provided an explanation for their stereoselectivity as due to the preference shown by the eutomer at the binding site for the most abundant axial conformation adopted by the ligand in solution. These results suggest that, despite the slow-binding kinetics occurring for the labeled ligand, affinity measures at shorter incubation times give robust results consistent with known structure-activity relationships and with interactions taken at the receptor binding site.

Melatonin Alleviates BPA-Induced Testicular Apoptosis and Endoplasmic Reticulum Stress.

BACKGROUND: The impact of melatonin on bisphenol A (BPA)-induced testicular apoptosis and endoplasmic reticulum (ER) stress was explored. METHODS: The mice received BPA (50 mg/kg) by gavage for 30 days while being injected with 20 mg/kg melatonin. Protein expressions were detected with western blotting. The Terminal Deoxynucleotidyl Transferase dUTP Nick End Labeling (TUNEL) assay measured testicular cell apoptosis. Testosterone was quantified by employing enzyme-linked immunosorbent assay (ELISA). RESULTS: Melatonin promoted the development of seminiferous tubules, restored the orderly arrangement of the germ cells, and increased epithelial layers in the seminiferous tubules in BPA-treated mice. Moreover, in BPA-treated mouse testicular cells, melatonin markedly upregulated melatonin receptor 1A (MTNR1A) and melatonin Receptor 2 (MTNR2) expressions while downregulating ER molecular chaperones glucose-regulated protein 78 (GRP78) and glucose-regulated protein 94 (GRP94). Furthermore, it decreased p-PERK, p-IRE1, and ATF6α, as well as the apoptotic proteins cysteine-containing aspartate-specific proteases-12 (caspase-12) and cleaved cysteine-containing aspartate-specific proteases-3 (cleaved caspase-3), causing the suppression of testicular cell apoptosis. Additionally, melatonin increased the levels of cytochrome P450 17α-hydroxylase/20-lyase (CYP17A1), 17ß-hydroxysteroid dehydrogenase 3 (17ß-HSD3), and 3ß-hydroxysteroid dehydrogenase 4 (3ß-HSD4), in the ER, and elevated testosterone levels in testicular tissue. CONCLUSIONS: Melatonin can significantly alleviate testicular apoptosis and ER stress induced by BPA, which is because of the upregulation of melatonin receptor expression in testicular cells, inhibition of ER stress-related pathways, and enhancement of testosterone synthesis.

Melatonin facts: Melatonin lacks immuno-inflammation boosting capacities at the molecular and cellular levels.

Among the properties melatonin is claimed to possess, are the immuno-inflammation inductive capacities that would be responsible of some of the paramount of activities melatonin is reported to have in most of the human pathological conditions. In the present paper, we measured the effect of melatonin on established cellular models of immuno-inflammation, and found none. The discrepancies are discussed, especially because those properties are reported at pharmacological concentration (1 µM and beyond) at which the melatonin receptors are desensitized by internalization, leading to putative non-receptor-dependent mechanism of action.

Melatonin and melatonin receptor agonists in the treatment of nocturia: A systematic review.

AIM: Causes of nocturia may extend beyond primary bladder pathology and it has been commonly associated as a side effect of sleep disorders. This has led to the study of melatonin and melatonin receptor agonists as a primary treatment for nocturia hypothesized to be secondary to sleep disorders. We aim to systematically review the efficacy and reported safety of melatonin and melatonin receptor agonists in the treatment of nocturia. METHODS: A search strategy of EMBASE and Pubmed/Medline databases was utilized to identify eligible studies. Two thousand and twenty-eight unique references were identified in concordance with the Preferred Reporting Items of Systematic Reviews and Meta-Analyses guidelines for systematic reviews, of which nine papers met the inclusion criteria. The Cochrane Collaboration risk of bias criteria in the open label and nonplacebo studies was used to assess bias. RESULTS: The nine studies identified included 3 randomized double-blinded placebo-controlled trials, 2 randomized non-placebo trial, and 4 prospective open-label trials. Three utilized the melatonin-receptor agonist ramelteon (8 mg) and six utilized melatonin (four 2 mg extended release, two 2 mg normal release). Nocturia improved in 8 studies varying from moderate to low efficacy related to reduction in nocturia episodes. Five studies evaluated sleep parameters finding improvement in both nocturia and sleep quality. Male subjects represented 76.8% of 371 total subjects in prospective and randomized trials. Ramelteon and melatonin were both reported as well tolerated during nocturia treatment. A meta-analysis was not able to be performed due to the heterogeneity of bladder diagnoses. CONCLUSIONS: At this time, there is insufficient evidence to routinely recommend melatonin as an effective treatment for nocturia given the limitations of current clinical studies. Randomized placebo-controlled trials and prospective open label studies in non-neurogenic populations report a trend towards nocturia improvement with good tolerability and rare side effects. Therefore, further larger scale randomized trials with focused urologic diagnoses in well-characterized patient populations are warranted.

Real-Time Determination of Intracellular cAMP Reveals Functional Coupling of Gs Protein to the Melatonin MT1 Receptor.

Melatonin is a neuroendocrine hormone that regulates the circadian rhythm and many other physiological processes. Its functions are primarily exerted through two subtypes of human melatonin receptors, termed melatonin type-1 (MT1) and type-2 (MT2) receptors. Both MT1 and MT2 receptors are generally classified as Gi-coupled receptors owing to their well-recognized ability to inhibit cAMP accumulation in cells. However, it remains an enigma as to why melatonin stimulates cAMP production in a number of cell types that express the MT1 receptor. To address if MT1 can dually couple to Gs and Gi proteins, we employed a highly sensitive luminescent biosensor (GloSensorTM) to monitor the real-time changes in the intracellular cAMP level in intact live HEK293 cells that express MT1 and/or MT2. Our results demonstrate that the activation of MT1, but not MT2, leads to a robust enhancement on the forskolin-stimulated cAMP formation. In contrast, the activation of either MT1 or MT2 inhibited cAMP synthesis driven by the activation of the Gs-coupled ß2-adrenergic receptor, which is consistent with a typical Gi-mediated response. The co-expression of MT1 with Gs enabled melatonin itself to stimulate cAMP production, indicating a productive coupling between MT1 and Gs. The possible existence of a MT1-Gs complex was supported through molecular modeling as the predicted complex exhibited structural and thermodynamic characteristics that are comparable to that of MT1-Gi. Taken together, our data reveal that MT1, but not MT2, can dually couple to Gs and Gi proteins, thereby enabling the bi-directional regulation of adenylyl cyclase to differentially modulate cAMP levels in cells that express different complements of MT1, MT2, and G proteins.

Have All of the Phytohormonal Properties of Melatonin Been Verified?

Melatonin is a ubiquitous regulator in plants and performs a variety of physiological roles, including resistance to abiotic stress, regulation of growth and development, and enhancement of plant immunity. Melatonin exhibits the characteristics of a phytohormone with its pleiotropic effects, biosynthesis, conjugation, catabolism, effective concentration, and the shape and location of its dose-response curves. In addition, CAND2/PMTR1, a phytomelatonin receptor candidate belonging to the G protein-coupled receptors (GPCRs), supports the concept of melatonin as a phytohormone. However, the biochemistry of plant melatonin receptors needs to be further characterized. In particular, some of the experimental findings to date cannot be explained by known GPCR signaling mechanisms, so further studies are needed to explore the possibility of novel signaling mechanisms.

Rs4862705 in the melatonin receptor 1A gene is associated with renal function decline in type 1 diabetes individuals.

Aim: The pathogenesis of chronic diabetes complications has oxidative stress as one of the major elements, and single-nucleotide polymorphisms (SNPs) in genes belonging to antioxidant pathways modulate susceptibility to these complications. Considering that melatonin is a powerful antioxidant compound, our aim was to explore, in a longitudinal cohort study of type 1 diabetes (T1D) individuals, the association of microvascular complications and SNPs in the gene encoding melatonin receptor 1A (MTNR1A). Methods: Eight SNPs in MTNR1A were genotyped in 489 T1D individuals. Besides cross-sectional analyses of SNPs with each one of the microvascular complications (distal polyneuropathy, cardiovascular autonomic neuropathy, retinopathy, and diabetic kidney disease), a longitudinal analysis evaluated the associations of SNPs with renal function decline in 411 individuals followed up for a median of 8 years. In a subgroup of participants, the association of complications with urinary 6-sulfatoxymelatonin (aMT6s) concentration was investigated. Results: The group of individuals with a renal function decline ≥ 5 mL min-1 1.73 m-2 year-1 presented a higher frequency of the A allele of rs4862705 in comparison with nondecliners, even after adjustment for confounding variables (OR = 1.84, 95% CI = 1.20-2.82; p = 0.0046). No other significant associations were found. Conclusions: This is the first study showing an association between a variant in a gene belonging to the melatonin system and renal function decline in the diabetic setting.

Melatonin injection and red light irradiation affect the antioxidant response and cell damage in disk abalone (Haliotis discus hannai) exposed to high water temperatures.

The effects of red light-emitting diode (LED) light irradiation (630 nm, 0.5 W/m2) and melatonin (10-8 and 10-7 M) on oxidative stress and physiological responses in abalones exposed to high temperatures (28°C) were investigated. Changes in messenger RNA (mRNA) expressions of melatonin receptor (MT-R), heat shock protein 70 (HSP70), and antioxidant enzymes, as well as alterations in H2O2 levels in the hemolymph, were examined. The results revealed that high-temperature-stressed abalones treated with melatonin injections or exposed to red LED light showed a significant increase in MT-R mRNA expression, while HSP70 mRNA expression decreased. Notably, HSP70 mRNA expression levels in the red LED light-irradiated group were similar to those in the group injected with 10-8 M melatonin after 24 h exposure. Abalones treated with melatonin at 20°C or irradiated with red LED light exhibited decreased H2O2 levels and reduced antioxidant enzyme mRNA expression compared with those of the control group. However, the high-temperature environment induced oxidative stress in abalones, leading to increased antioxidant enzyme mRNA expression compared with that under 20°C conditions. Moreover, abalones exposed to high-temperature stress exhibited hepatopancreatic DNA damage, which was attenuated by melatonin treatment or red LED light irradiation. Hence, red LED light reduces oxidative stress, boosts antioxidant enzymes, and alleviates DNA damage in high-temperature-stressed abalones, akin to 10-8 M melatonin treatment. Therefore, considering the practical challenges of continuous melatonin administration to abalones, utilizing red LED light emerges as a practical, effective alternative to protect abalones from oxidative stress compared to 10-8 M melatonin treatment.