Serum Melatonin Concentrations Research Articles

Melatonin attenuates cardiac dysfunction and inflammation in dilated cardiomyopathy via M2 macrophage polarization.

Melatonin is a neuroendocrine hormone that exerts protective effects on the heart. Increasing evidence suggests that macrophage M2-type polarization improves myocardial regeneration and repair. Therefore, this study investigated whether melatonin ameliorates dilated cardiomyopathy (DCM) by modulating M2-type polarization. DCM mice were established by induction with doxorubicin and then treated with melatonin. Cardiac dysfunction was determined by measuring left ventricular ejection fraction (LVEF) and left ventricular internal dimensions at end-diastole and end-systole. Heart injury and fibrosis were determined by hematoxylin and eosin staining and Sirius Red staining, respectively. Serum concentrations of melatonin, tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6) were measured through enzyme-linked immunosorbent assays. M2-type macrophages were analyzed by flow cytometry. Relative mRNA and protein levels were determined by reverse transcription quantitative polymerase chain reaction and western blotting, respectively. Circulating melatonin levels were significantly decreased in DCM mice and were associated with LVEF. Treatment with melatonin markedly ameliorated cardiac dysfunction, improved survival, and alleviated pathological changes and collagen deposition in DCM mice. Furthermore, melatonin-treated DCM mice displayed lower serum and cardiac levels of IL-1β, IL-6, and TNF-α, as well as higher numbers of M2-type macrophages in cardiac tissue, indicating that melatonin treatment could decrease inflammatory responses and facilitate M2 macrophage polarization in DCM mice. Thus, melatonin treatment alleviated cardiac dysfunction and inflammatory responses by promoting M2 macrophage polarization in the DCM mouse model.

Impact of oral melatonin supplementation on urine and serum melatonin concentrations and quality-of-life measures in persons with relapsing multiple sclerosis

IntroductionMelatonin is an antioxidant and anti-inflammatory agent that modulates the immune system by scavenging free radicals, reducing the upregulation of pro-inflammatory cytokines, and reducing transendothelial cell migration. Therefore, melatonin may play a role in regulating multiple sclerosis (MS) disease activity. However, little is known about how melatonin supplementation effects individuals with MS. ObjectiveDetermine if there was a dose-dependent elevation in urine and serum melatonin concentrations. Determine if melatonin supplementation had an impact on patient reported outcomes. MethodsThis was a randomized, dose-blinded exploratory study. Adults (age 18–65) with relapsing forms of multiple sclerosis (RMS) treated with a stable dose of oral disease modifying therapy for at least 6 months were randomized into melatonin 3 mg or 5 mg daily. Urinary and serum melatonin levels and modified fatigue impact scale (MFIS), multiple sclerosis impact scale (MSIS-29), and Pittsburgh sleep quality index (PSQI), patient determined disease steps (PDDS) and performance scales (PS) were measured at baseline, 3, 6, and 12 months. Urinary and serum melatonin analyses was performed to estimate mean concentrations and their differences between treatment arms over time by a repeated measures linear mixed model. The model included treatment, assessment time, and treatment × time interaction. ResultsThirty patients, randomized 1:1, were analyzed in an intent to treat population. Twenty-three completed the study. The repeated measures linear mixed model analysis of all timepoints revealed higher melatonin concentrations in patients on 5 mg compared to 3 mg melatonin for both urinary 6-SMT (p = 0.03) and serum melatonin (p = 0.04). MFIS, MSIS-29, PSQI, and PDSS-PS scores did not significantly change from baseline to month 12. No significant differences in these measures were seen between the two doses. Five patients stopped melatonin (three on 5 mg and two on 3 mg) due to adverse events, including one patient who developed focal spongiotic dermatitis. One patient experienced three consecutive serious adverse events that were unrelated to melatonin supplementation. ConclusionsThe 5 mg melatonin supplementation group had higher concentrations of urinary 6-SMT and serum melatonin compared to the 3 mg group over 12 months of treatment. There was a correlation between 6-SMT and serum melatonin concentrations. This suggests that measuring serum melatonin is a reliable alternative to measuring urinary 6-SMT. However, no differences in clinical benefit between the two dosage groups were demonstrated in the patient reported outcomes. Trial Registration NumberNCT03498131

Clinical Use of Long-Term GnRH Agonist in Prepubertal Bitches: Effect on P4, E2 and Melatonin Serum Concentration before and During First Estrus

Abstract The aim of this study was to determine the length of the contraceptive period after the application of deslorelin implant (4.7 mg) in juvenile, prepubertal bitches and assess the effects on the hormonal status (P4, E2 and melatonin), as well as on the occurrence of normal physiological estrus. Twelve crossbred prepubertal female dogs (4 months of age) were divided into the two groups, the treated group (DESLO) and control (placebo) group (C). Hormone assays, vaginal microbiological and cytological smears and the measurements of electrical resistance of cervical mucus were performed once in 3 weeks until the first signs of proestrus, and every day during estrus. GnRH implant significantly postponed time of onset of estrus (633 ± 30,38 days vs. 143.80 ± 52,30 days, P<0.001). In estrus, DESLO group showed statistically higher E2 (34.58 pg/mL vs. 20.59 pg/mL, P<0.001) and melatonin serum concentration (45.86 pg/mL vs. 18.85 pg/mL, P<0.001) compared to the control group. The average P4 serum concentration had no statistically significant differences between groups. In conclusion, deslorelin implants do not cause “flare up” effect in perpubertal bitches, however, increase of E2 and especially melatonin serum concentrations show the need to explore the consequences and mutual influence of melatonin and deslorelin implants in the future.

Validation of a simple bioanalytical method for the determination of melatonin concentration in human serum using high-performance liquid chromatography with a fluorescent detector

Analysis of melatonin in biological samples is a challenge for the analyst both because of its low concentration and because of the numerous interfering substances. Therefore, chromatography, as a powerful analytical technique used for the separation, detection, and quantification of analytes, can be the method of choice for determining melatonin in biological samples for clinical use and pharmacokinetic research. The method was developed and validated according to the internal documents in accordance with Good Laboratory Practice. The concentrations of melatonin in human serum were determined using a high-performance liquid chromatography method with a fluorescence detector and mirtazapine as an internal standard. Preparation of serum samples was performed by liquid–liquid extraction with ethyl acetate: n-hexane (1:1 v/v). High linearity was exhibited over a concentration range of 25–10,000 pg/mL of melatonin, with a correlation coefficient higher than 0.999 during the course of method validation. Repeatability and intermediate precision show a relative standard deviation lower than 6.6 %, and accuracies were from 90.7 % to 110.3 %. The lower limit of quantitation was 30 pg/mL, and the limit of detection was 7.92 pg/mL. The in-house method is simple, fast, reproducible, and applicable for the determination of melatonin in human serum.

Potential Role of Bmal1 in Lipopolysaccharide-Induced Depression-Like Behavior and its Associated "Inflammatory Storm".

Inflammation plays an important role in the pathogenesis of depression; however, the underlying mechanisms remain unclear. Apart from the disordered circadian rhythm in animal models and patients with depression, dysfunction of clock genes has been reported to be involved with the progress of inflammation. This study aimed to investigate the role of circadian clock genes, especially brain and muscle ARNT-like 1 (Bmal1), in the linkage between inflammation and depression. Lipopolysaccharide (LPS)-challenged rats and BV2 cells were used in the present study. Four intraperitoneal LPS injections of 0.5mg/kg were administered once every other day to the rats, and BV2 cells were challenged with LPS for 24h at the working concentration of 1mg/L, with or without the suppression of Bmal1 via small interfering RNA. The results showed that LPS could successfully induce depression-like behaviors and an "inflammatory storm" in rats, as indicated by the increased immobility time in the forced swimming test and the decreased saccharin preference index in the saccharin preference test, together with hyperactivity of the hypothalamic-pituitary-adrenal axis, hyperactivation of astrocyte and microglia, and increased peripheral and central abundance of tumor necrosis factor-α, interleukin 6, and C-reactive protein. Moreover, the protein expression levels of brain-derived neurotrophic factor, triggering receptor expressed on myeloid cells 1, Copine6, and Synaptotagmin1 (Syt-1) decreased in the hippocampus and hypothalamus, whereas the expression of triggering receptor expressed on myeloid cells 2 increased. Interestingly, the fluctuation of temperature and serum concentration of melatonin and corticosterone was significantly different between the groups. Furthermore, protein expression levels of the circadian locomotor output cycles kaput, cryptochrome 2, and period 2 was significantly reduced in the hippocampus of LPS-challenged rats, whereas Bmal1 expression was significantly increased in the hippocampus but decreased in the hypothalamus, where it was co-located with neurons, microglia, and astrocytes. Consistently, apart from the reduced cell viability and increased phagocytic ability, LPS-challenged BV2 cells presented a similar trend with the changed protein expression in the hippocampus of the LPS model rats. However, the pathological changes in BV2 cells induced by LPS were reversed after the suppression of Bmal1. These results indicated that LPS could induce depression-like pathological changes, and the underlying mechanism might be partly associated with the imbalanced expression of Bmal1 and its regulated dysfunction of the circadian rhythm.

Дія мелатоніну та кверцетину на запалення i метаболізм за умов цілодобового освітлення та висококалорійної вуглеводно-ліпідної дієти

The study is aimed at investigating the impact of exogenous melatonin and quercetin on indices of systemic inflammatory response and indicators of carbohydrate and lipid metabolism in the blood serum of male rats exposed to round-the-clock lighting (RCL) with 1500 lx intensity during the last 30 days of being kept on a 60 day high-calorie carbohydrate-lipid diet (HCCLD, 20% fructose solution and the proper chow). The study has demonstrated that the restoration of serum melatonin concentration in rats by its exogenous administration during the RCL exposure and keeping them on HCCLD did not fully correct the indicators of the systemic inflammatory response such as the content of tumor necrosis factor α (TNF-α) and C-reactive protein (CRP), as well as indices of carbohydrate and lipid metabolism such as concentration of insulin, highdensity lipoprotein (HDL), very low-density lipoprotein (VLDL) and triglycerides, HOMA-IR insulin resistance index. The administration of quercetin under the experimental conditions was accompanied by a significant increase in the serum melatonin concentration (by 85.9%), a decrease in the content of TNF-α (by 53.9%), CRP (by 54.4%), glucose (by 49.2%), insulin (by 49.6%), VLDL (by 49, 2%) and triglycerides (by 49.3%), and an increase in HDL concentration (by twofold), but these indicators (with the exception of the HOMA-IR index, which decreased by 62.4%) did not reach the values of the intact group. The combined effect of melatonin and quercetin under RCL exposure and HLLD significantly improved the indicators of systemic inflammatory response, carbohydrate and lipid metabolism that is confirmed by a more significant decrease in serum levels of TNF-α, CRP, insulin, VLDL and triglycerides, an increase in HDL concentration, and a decrease in the HOMA-IR index compared with the separate use of melatonin and quercetin.

The association between melatonin hormone and reproductive hormones in polycystic ovary syndrome: A case–control study

Abstract Background: One of the common endocrine disorders is polycystic ovary syndrome (PCOS) with prevalence of about 5%–15% of women within reproductive age. It is related to androgen disturbance, obesity, and irregular menstrual cycle. Pineal gland secretes melatonin hormone, which is involved in the regulation of the circadian rhythm. Melatonin receptors in the ovary adjust sex steroid secretion. Furthermore, it is considered a strong antioxidant, which protects ovarian follicles during follicular maturation. Objectives: To evaluate the level of melatonin in patients with PCOS and its relation with reproductive hormones and anthropometric measures. Materials and Methods: A case-control study included 200 women in reproductive age (20–40 years), including 100 PCOS patients and 100 controls who appeared to be in generally good health. Anthropometric measurements were evaluated. Reproductive hormones and anti-Müllerian hormone (AMH) were evaluated using the mini VIDAS method. Human MT (Melatonin) ELISA Kit from Elabscience source (USA) was used for measuring melatonin levels. Results: Luteinizing hormone/follicle-stimulating hormone (FSH) ratio, AMH, and melatonin were significantly higher in PCOS women, whereas FSH level was significantly lower in PCOS compared with controls. There was an adverse relationship between melatonin levels with thigh circumference, waist circumference, and waist/hip ratio (P < 0.05). There was a significant adverse correlation between melatonin and testosterone hormone in PCOS patients (P < 0.05). Melatonin level showed an AUC of 0.755 at a cutoff point of 20 ng/mL and more, giving a sensitivity (78%) and specificity (75%). Conclusions: Although PCOS women had higher serum melatonin concentrations, their effect on ovarian hormones is diminished. Melatonin had a connection with androgen, and melatonin supplements may improve metabolic dysfunction in PCOS patients.

EFFECTIVENESS OF MELATONIN AND RESVERATROL COMBINED ADMINISTRATION IN ROUND-THE-CLOCK ILLUMINATION WITH HIGH-CALORIE CARBOHYDRATE-LIPID DIET

The purpose of this experiment was to investigate the combined effect of exogenous melatonin and resveratrol on the serum melatonin content in rats exposed to 30 day round-the-clock lighting (RCL) and kept on a high-calorie carbohydrate-lipid diet (HCCLD, 20% fructose solution, and standard chow). The combination of exogenous melatonin and resveratrol was administered for 60 days to 35 white male rats. Exogenous melatonin and resveratrol were administered daily during the last 30 days of the experiment intragastrically in a dose of 5 mg/kg (both). The findings obtained have revealed the combined effect of RCL and HCCLD reduced the serum melatonin content to 7.1±0.7 pg/ml that is 77.7% (p<0.001) lower than the control values (31.8±2.5 pg/ml). Applying exogenous melatonin restored the concentration of this hormone in the blood serum to normal values, 28.4±1.6 pg/ml. Resveratrol administration increased the melatonin content to 13.6±1.0 pg/ml, i.e. by 91.5% (p<0.001). The combined administration of exogenous melatonin and resveratrol increased the concentration of melatonin in the blood serum to 32.3±2.0 pg/ml. It can be concluded that the combined effect of exogenous melatonin and resveratrol under RCL and HCCLD is more effective in correcting hypomelatoninemia compared to the effect of the compounds used separately.

Rhythmicity in testicular melatonin and its correlation with the dynamics of spermatogenic cells in an annual reproductive cycle of Clarias batrachus under natural photo-thermal conditions

Melatonin, the pineal hormone, is synthesized and secreted rhythmically in accordance with various environmental cues especially photo-thermal conditions. The reproductive physiology of seasonal breeders is synchronized with the surroundings by melatonin as a neuroendocrine mediator to acts as an important factor in fish reproduction. However, the data on the participation of melatonin in male reproduction and the putative interaction with the process of spermatogenesis in fish is scarce till date. So, major objectives of the current study are to determine for the first time, the relationship, if any, between seasonal levels of melatonin and testicular development and maturation of the germ cells, and also the involvements of specific meteorological parameters in spermatogenesis under natural photo-thermal conditions. We measured the concentration of circulatory and testicular melatonin; value of gonadosomatic index (GSI), relative percentages of different developing spermatogenic cells, area and perimeter (size and shape) of seminiferous lobules along with the level/duration of rainfall, water temperature and day length in six reproductive phases throughout an annual cycle in adult male catfish (Clarias batrachus). Intra-testicular and serum melatonin concentration showed a similar seasonal pattern with a peak during “functional maturity” phase and trough during “slow spermatogenesis” phase. Correlation as well as regression analyses also supported this positive relationship. Interestingly, intra-testicular melatonin also showed a significant positive correlation with GSI and relative percentage as well as lobular size of mature stages (spermatid and spermatozoa) of germ cells in an annual cycle. Furthermore, meteorological factors exhibited as critical cues to regulate the dynamics (in %) of spermatogenic cells and the level of testicular melatonin throughout the annual gonadal cycle. Our results corroborated by principal component (PC) analysis and showed very clearly that active “functional maturity” state is characterized by GSI, testicular melatonin, relative abundance and lobular size of mature spermatogenic stages as key internal oscillators; and studied environmental variables as the external clues for the regulation of spawning process. Collectively, the present data revealed that there is a relationship between melatonin levels and testicular growth and development of germ cells in Clarias batrachus under natural photo-thermal conditions.

Seasonal variation of serum and intrafollicular concentrations of melatonin and estradiol in relation to follicular development

The main objective of this study was to compare the effect of season on serum and intrafollicular concentrations of melatonin (MT). The relationship between follicular size, MT and estradiol (E2) concentrations was also explored. Twelve mares were used. Aspiration of fluid from all follicles larger than 5 mm was carried out in each mare during the breeding season and during the anovulatory season. All aspirations were carried out between 7AM and 8AM, and a serum sample was obtained at the same time. Follicles were classified into small (≤ 15 mm); medium (16-30 mm); and large (> 30 mm). MT and E2 concentrations were measured by enzymatic immunoassay (Melatonin ELISA Mybiosource, MBS1603596; Estradiol ELISA DRG, EIA-2693). Analysis of Variance was used to evaluate the effects of season, fluid type (follicular vs serum) and follicle size. Intrafollicular concentrations of MT were higher than serum concentrations both in the reproductive season (127±1.41 vs 69.59±1.73 ng/L) and in the anovulatory season (118.5±2.93vs 115.45±3.06 ng/L). MT concentrations in serum were higher during the anovulatory season than during the reproductive season (p<0.05), but the opposite was the case for intrafollicular MT. During the ovulatory season MT was higher (p<0.05) in large follicles (141.39±2.13ng/L) than in medium (130.25±2.55 ng/L) and small follicles (109.36±2.57 ng/L). The difference between medium and small follicles was also significant(p<0.05). In contrast during the anovulatory season MT concentration was not different between small and medium follicles (123.43±3.79 vs 109.92±5.55 ng/mL). Intrafollicular levels of E2 were higher during the ovulatory season than during the anovulatory season in medium (211.89±20.4 vs 126.18±0.07) and small follicles (67.42±2.4 vs 14.78±1.06 ng/mL). E2 concentrations in large follicles during the ovulatory season was 4,312.83±65.8 ng/mL. The results of this study indicate that while serum MT concentrations were different between seasons due to the known negative correlation between pineal MT secretion and day length, this seasonal effect was not found in the case of intrafollicular MT concentrations. Also, in this study there was no correlation between serum and intrafollicular MT concentrations. Together, these findings suggest photoperiod-independent intrinsic follicular MT synthesis. E2 concentrations were correlated with follicle size in both ovulatory and anovulatory seasons but were always higher during the ovulatory season for a given size. During this season there was a positive correlation between intrafollicular MT and estradiol concentrations, thus suggesting that intrafollicular estradiol may stimulate intrafollicular melatonin synthesis. It is concluded that intrafollicular MT concentrations in the mare are at least in part of intrinsic origin and may be stimulated by estradiol.

Melatonin alleviates lung injury in H1N1-infected mice by mast cell inactivation and cytokine storm suppression.

Influenza A virus (IAV) H1N1 infection is a constant threat to human health and it remains so due to the lack of an effective treatment. Since melatonin is a potent antioxidant and anti-inflammatory molecule with anti-viral action, in the present study we used melatonin to protect against H1N1 infection under in vitro and in vivo conditions. The death rate of the H1N1-infected mice was negatively associated with the nose and lung tissue local melatonin levels but not with serum melatonin concentrations. The H1N1-infected AANAT-/- melatonin-deficient mice had a significantly higher death rate than that of the WT mice and melatonin administration significantly reduced the death rate. All evidence confirmed the protective effects of melatonin against H1N1 infection. Further study identified that the mast cells were the primary targets of melatonin action, i.e., melatonin suppresses the mast cell activation caused by H1N1 infection. The molecular mechanisms involved melatonin down-regulation of gene expression for the HIF-1 pathway and inhibition of proinflammatory cytokine release from mast cells; this resulted in a reduction in the migration and activation of the macrophages and neutrophils in the lung tissue. This pathway was mediated by melatonin receptor 2 (MT2) since the MT2 specific antagonist 4P-PDOT significantly blocked the effects of melatonin on mast cell activation. Via targeting mast cells, melatonin suppressed apoptosis of alveolar epithelial cells and the lung injury caused by H1N1 infection. The findings provide a novel mechanism to protect against the H1N1-induced pulmonary injury, which may better facilitate the progress of new strategies to fight H1N1 infection or other IAV viral infections.

A Pilot Study to Evaluate the Potential of Melatonin Implants to Control Cyclicity in the Bitch.

In short-day breeders such as the sheep, melatonin stimulates oestrus activity; in contrast, a high serum concentration of melatonin inhibits oestrus in long-day breeders such as the cat. Therefore, implants with melatonin have been used to suppress or induce oestrus depending on the species. The aim of this pilot study was to evaluate if melatonin could be an alternative to control the reproductive cycle in the bitch. Nine beagle bitches were observed for three oestrus cycles. Five beagle bitches were treated with 18 mg melatonin implants on average 27 days before the next expected oestrus based on the previous interoestrus interval. Four bitches served as untreated controls. Blood samples for evaluation of serum melatonin were collected at the time of assignment to treatment or control group and 1-4 weeks thereafter. Clinical signs and vaginal smears were used to follow the cycle. Melatonin varied significantly with bitch (p < 0.05) but not with treatment. Treatment did not affect the interoestrus interval (p > 0.05). In conclusion, treatment with 18 mg melatonin implants approximately one month before expected oestrus is not likely to be a useful method to control cyclicity in the bitch. It is still not known if melatonin is involved in regulation of the oestrus cycle in the domestic dog.

Вплив модуляторів факторів транскрипції NF-κB і Nrf2 на показники оксидативно–нітрозативного стресу в скелетних м’язах щурів за умов хронічної гіпомелатонінемії та вуглеводно-ліпідної дієти

This article describes the effect of NF-κB inhibitor ammonium pyrrolidine dithiocarbamate and Nrf2 inducer dimethylfumarate on indicators of oxidative-nitrosative stress in skeletal muscles of rats with chronic hypomelatoninemia, induced by roundthe-clock illumination with an intensity of 1500 lux for 30 days, against the background of a carbohydrate-lipid diet (20% fructose solution and appropriate food) for 60 days. The study demonstrated that the administration of ammonium pyrrolidine dithiocarbamate and dimethylfumarate under the experimental conditions impedes the development of hypomelatoninemia, this was accompanied by a two-fold increase in the blood serum melatonin concentration compared to the control group. Moreover, the administration of ammonium pyrrolidine dithiocarbamate and dimethylfumarate significantly reduces the production of superoxide anion radical by electron transport chains of mitochondria (by 47.9 and 51.3%) and sarcoplasmic reticulum (by 48.6 and 52.0%) in the homogenate of femoral muscles, the total activity of NO synthase (by 37.2 and 36.2%) and its inducible isoform (by 41.1 and 40.0%), the concentration of peroxynitrites of alkaline and alkaline earth metals (by 37.2 and 41.0 %), while the activity of constitutive NO-synthases (by 2.9 and 2.8 times) and their conjugation index (by 5.2 and 5.4 times) increases compared to the respective control values. We suggest that modulators of redox-sensitive transcription factors NF-κB and Nrf2 under conditions of chronic hypomelatoninemia and the exposure to the carbohydrate-lipid diet are effective means to restrain the development of oxidative-nitrosative stress in skeletal muscles.

The Influence of Circadian Rhythm on the Activity of Oxidative Stress Enzymes.

The circadian system synchronizes daily with the day-night cycle of our environment. Disruption of this rhythm impacts the emergence and development of many diseases caused, for example, by the overproduction of free radicals, leading to oxidative damage of cellular components. The goal of this study was to determine the activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), glutathione transferase (GST), glutathione reductase (R-GSSG), and the concentration of glutathione (GSH) in the circadian rhythm. The study group comprised 66 healthy volunteers (20-50 years; 33 women; 33 men). The blood was collected at 2, 8 a.m., and 2, 8 p.m. All samples marked the serum melatonin concentration to confirm the correct sleeping rhythm and wakefulness throughout the day. The activity of study enzymes and the concentration of GSH were measured by the spectrophotometric method. Confirmed the existence of circadian regulation of oxidative stress enzymes except for GST activity. The peak of activity of study enzymes and GSH concentration was observed at 2 a.m. The increased activity of enzymes and the increase in GSH concentration observed at night indicate that during sleep, processes allowing to maintain of the redox balance are intensified, thus limiting the formation of oxidative stress.

Prophylactic melatonin for delirium in critically ill patients: A systematic review and meta-analysis with trial sequential analysis.

Up to 80% of patients in the intensive care unit (ICU) suffer from delirium. Studies on the preventative use of melatonin in the ICU have produced mixed results. We performed a systematic review and meta-analysis to evaluate whether early administration of melatonin reduces the prevalence of delirium in critically ill patients. We searched Medline, Embase, and the Cochrane Library for randomized controlled trials comparing melatonin or melatonin agonists to placebo in ICU setting. The population included adult patients in the ICU. The primary outcome was the prevalence of delirium. Secondary outcomes included duration of delirium, delirium-free day, serum melatonin concentration, need for sedation, duration of mechanical ventilation, hospital and ICU length of stay (LOS), all-cause mortality, sleep quality, and adverse events. Trial sequential analysis (TSA) was performed on the primary outcome to prevent the risk of random error and multiplicity phenomenon as a result of repeated significance testing across all the included trials. Twelve trials with a total of 2538 patients were analyzed. When all trials were pooled, the incidence of delirium in ICU patients who received melatonin was significantly lower than in those who received placebo (risk ratio, 0.77; 95% confidence interval: 0.61-0.96; I2 = 56%). There were no significant differences in secondary outcomes including duration of delirium, duration of mechanical ventilation, ICU LOS, hospital LOS, and mortality. TSA indicated that Z-curve crossed the traditional boundary, but did not cross the monitoring boundary for benefit, which indicated that it is still inconclusive that melatonin affects the incidence of delirium. This meta-analysis found that early administration of melatonin may result in a decreased delirium prevalence in critically ill patients. However, the sensitivity analysis of high-quality studies did not support this finding. In addition, TSA demonstrated that the result may have false-positive error. Therefore, this finding should be interpreted with caution. Further studies are needed to examine the effectiveness of prophylactic melatonin on the prevalence and duration of ICU delirium in the future.

Effects of SNPs in AANAT and ASMT Genes on Milk and Peripheral Blood Melatonin Concentrations in Holstein Cows (Bos taurus).

Aralkylamine N-acetyltransferase (AANAT) and acetylserotonin O-methyltransferase (ASMT), the two rate-limiting enzymes for melatonin synthesis, regulate melatonin production in mammals. Through analysis of the milk melatonin level and dairy herd improvement (DHI) index, it was found that the melatonin concentration in milk was significantly negatively correlated with the 305 day milk yield (305M) and peak milk yield (PeakM) (p < 0.05), while it was significantly positively correlated with the serum melatonin concentration (p < 0.05). The full-length of AANAT and ASMT were sequenced and genotyped in 122 cows. Three SNPs in AANAT and four SNPs in ASMT were significantly related to MT levels in the milk and serum (p < 0.05). The SNPs in AANAT were temporarily denoted as N-SNP1 (g.55290169 T>C), N-SNP2 (g.55289357 T>C), and N-SNP3 (g.55289409 C>T). The SNPs in ASMT were temporarily denoted as M-SNP1 (g.158407305 G>A), M-SNP2 (g.158407477 A>G), M-SNP3 (g.158407874 G>A), and M-SNP4 (g.158415342 T>C). The M-SNP1, M-SNP2, and M-SNP3 conformed to the Hardy−Weinberg equilibrium (p > 0.05), while other SNPs deviated from the Hardy−Weinberg equilibrium (p < 0.05). The potential association of MT production and each SNP was statistically analyzed using the method of linkage disequilibrium (LD). The results showed that N-SNP2 and N-SNP3 had some degree of LD (D′ = 0.27), but M-SNP1 and M-SNP2 had a strong LD (D′ = 0.98). Thus, the DHI index could serve as a prediction of the milk MT level. The SNPs in AANAT and ASMT could be used as potential molecular markers for screening cows to produce high melatonin milk.

Influence of Light Phase Exposure to LED Lighting on Circadian Levels of Neuroendocrine Hormones in Sprague-Dawley Rats.

Light and lighting protocols of animal research facilities are critically important to the outcomes of biomedical research that uses animals. Previous studies from our laboratory showed that the wavelength (color) of light in animal housing areas affects the nocturnal melatonin signal that temporally coordinates circadian rhythms in rodents. Here, we tested the hypothesis that exposure to LED light enriched in the blue-appearing portion (460-480 nm) of the visible spectrum during the light phase (bLAD) influences circadian concentrations of select neuroendocrine hormones in adolescent Sprague-Dawley rats. Male and female rats (4 to 5 wk old) were housed on a novel IVC system under a 12L:12D in either cool-white fluorescent (control, n = 72) or bLAD (experimental, n = 72) lighting. Every third day, body weight and food and water consumption were measured. On Day 30, rats were anesthetized with ketamine/xylazine and terminal collection of arterial blood was performed to quantify serum concentrations of melatonin, corticosterone, insulin, and glucose at 6 circadian time points (0400, 0800, 1200, 1600, 2000, 2400). As compared with male and female rats housed under cool white fluorescent (CWF) lighting, rats in bLAD lighting showed a 6-fold higher peak in dark phase serum melatonin (P < 0.05). Effects on serum corticosterone were sex dependent, as CWF and bLAD females had significantly higher corticosterone levels than did CWF and bLAD males, respectively. CWF and bLAD females had significantly higher serum glucose overall as compared with males. However, serum insulin was not affected by sex (M or F) or lighting conditions (CWF or bLAD). These data show that housing Sprague-Dawley rats under bLAD lighting conditions increases circadian peaks of melatonin without increasing serum levels of corticosterone, glucose or insulin, indicating less variation of circadian cycling of key neuroendocrine hormones in bLAD-exposed rats.

Effects of long-term oral administration of melatonin on tear production, intraocular pressure, and tear and serum melatonin concentrations in healthy dogs.

To evaluate the effects of long-term (30-day) oral administration of melatonin on tear production, intraocular pressure (IOP), and concentration of melatonin in the tears and serum of healthy dogs. 20 healthy sexually intact adult male dogs. 10 dogs were given melatonin (0.3 mg/kg, PO, q 24 h, administered in food at 9 am), and 10 dogs were given a placebo. Tear and serum melatonin concentrations, IOP, and tear production (determined with a Schirmer tear test) were recorded before (baseline) and 30 minutes, 3 hours, and 5 hours after administration of melatonin or the placebo on day 1 and 30 minutes after administration of melatonin or the placebo on days 8, 15, and 30. Data collection time had significant effects on tear production, IOP, and tear melatonin concentration but not on serum melatonin concentration. Treatment (melatonin vs placebo) had a significant effect on tear melatonin concentration, but not on tear production, IOP, or serum melatonin concentration; however, tear melatonin concentration was significantly different between groups only 30 minutes after administration on day 1 and not at other times. In healthy dogs, long-term administration of melatonin at a dosage of 0.3 mg/kg, PO, every 24 hours did not have any clinically important effects on tear production, IOP, or serum or tear melatonin concentrations.

Anhedonia as target symptom in personalized therapy of patients with mood disorders and alcohol use disorder comorbidity

To estimate the efficacy of antidepressants in the treatment of anhedonia in mood disorders (MD) comorbid with alcohol use disorder (AUD), considering melatonin concentration in the patient's blood serum. Seventy patients, aged 18-65 years old, with MD, including patients with- (group F3+F10, n=36) or without comorbid AUD (group F3, n=34), were examined. Control group consisted of 26 healthy volunteers. Clinical-dynamic evaluation was carried out using SIGH-SAD and SHAPS-C. Melatonin concentration was measured with MAGPIX analyzer (Luminex, USA). The statistical analysis was carried out using the SPSS (V. 23.0) standard package. In the case of MD/AUD comorbidity anhedonia symptom does not respond well to psychopharmacotherapy during four weeks (p=0.192, Wilcoxon test) whereas anhedonia in «pure» MD does (p=0.007, Wilcoxon test). At the same time, only patients with «pure» MD have a statistically significant decrease in melatonin concentration in blood serum compared with the control group (p=0.025, p=0.031, Mann-Whitney test), on the contrary, in the case of MD/AUD comorbidity, a relative increase in melatonin concentration (p>0.05 Mann-Whitney test) was demonstrated. The relatively low response of anhedonia symptom in the case of MD/AUD comorbidity compared with the «pure» MD, makes perspective using antidepressants with prodophaminergic mechanism of action in this cohort of patients. Furthermore, in MD/AUD comorbidity, contrary to «pure» MD, a relative increase in melatonin concentration in blood serum was detected, therefore it could be a limitation to prescribing antidepressants directly or indirectly modulating melatoninergic system.

Reactivity of stress-implementing system under conditions of light regime change in experiment

Influence of light exposure duration (model 18:6) on hormonal indices of stress-implementing system in laboratory animals blood is studied. Activity of stress systems central link was evaluated based on data on concentration of adrenocorticotrophic hormone, melatonin and β-endorphin in blood serum, observed during enzyme immunoassay. Reaction of peripheric link of the stress-implementing system was evaluated in blood smears based on results of qualitative count of catecholamine granules in erythrocytes. It was established, that variations of hormonal indices of the stress systems for laboratory animals depend on trigger factor activity periods. With increase of the experiment duration to 21-st days the most pronounced reduction of melatonin, β-endorphin and increase of adrenocorticotrophic hormone concentration, as well as sharp increase of catecholamines level are observed in the blood serum. These hormonal changes develop as a result of failure of compensation mechanisms of the stress-implementing systems in connection with melatonin rhythms disturbance, that indicates the gradual development of the general adaptation syndrome. Keywords: endocrine profile, stress-implementing system, general adaptation syndrome, biorhythms, light desynchronosis.