Plasma Melatonin Concentrations Research Articles

Effects of prenatal and postnatal melatonin supplementation on overall performance, male reproductive performance, and testicular hemodynamics in beef cattle.

Melatonin has been documented to alleviate compromised pregnancies and enhance livestock performance traits. The objective of this study was to determine the effect of prenatal and postnatal melatonin supplementation on overall calf performance and dam milking traits in relation to calves, molecular factors involved in growth and metabolism of calves, along with testicular physiology and fertility traits in subsequent bulls. At day 190, 220 and 250 of gestation, dams (n = 60) were administered either 2 subdermal ear melatonin implants (preMEL) or no implants (preCON). After parturition, birth weights were recorded and calves were blocked based on prenatal treatment and sex. Calves received either melatonin implants (posMEL) or none (posCON) on day 0, 30, and 60 of age. At day 60 of lactation, a subset of dams (n= 32) were selected based on age, weight and calf sex for milk collection and analysis. At weaning, (day 210 postnatally) calf weight, morphometric data, liver samples, and loin samples were collected. At 12 months of age, bull (n = 30) scrotal circumference, scrotal temperature, and testicular artery measurements were recorded. Milk yield and fat percent from dams tended to decrease in the preMEL group (P < 0.07) compared with preCON group. Prenatal melatonin administration did not affect (P = 0.95) calf birth weight and similarly calf weaning weight was unaffected (P < 0.10) by prenatal or postnatal melatonin supplementation. Blood analysis demonstrated that plasma concentrations of melatonin were not different (P = 0.12) in dams; however, an increase (P < 0.001) in plasma concentrations of melatonin was observed in posMEL versus posCON calves. A tendency (P < 0.10) for decreased MYF5 and MYOD1 expression in loin muscle was observed in the posMEL calves. Prenatal and postnatal melatonin administration did not affect subsequent bull scrotal measurements or testicular hemodynamics (P ≥ 0.14). Administering supplemental melatonin via implants during the prenatal and postnatal phase did not alter performance characteristics in offspring. In this study, dams were implanted in winter months, whereas calves were implanted in the spring months. Seasonal differences involving photoperiod and ambient temperature might have attributed to a lack of differences in melatonin levels during the prenatal phase. In the postnatal period, the level of developmental plasticity appears to be too low for melatonin properties to be effective.

Dietary supplementation with tryptophan increases the plasma concentrations of tryptophan, kynurenine, and melatonin in Yili mares

Context Tryptophan (Trp) is the precursor of melatonin (MT) and the latter plays vital physiological roles in mares. Aims The purpose of this experiment was to investigate the effects of dietary Trp supplementation on the plasma Trp, kynurenine (Kyn), 5-hydroxytryptophan (5-HT), and melatonin (MT) concentrations in female Yili horses. Methods Twenty Yili mares aged 2 years with mean bodyweight (BW) of 263.5 ± 14.77 kg and of similar stature were selected and randomly allocated to the control (CON; basal diet), basal diet plus Trp at 20 mg/kg BW (TRP1), basal diet plus Trp at 40 mg/kg BW (TRP2), or basal diet plus Trp at 60 mg/kg BW (TRP3) group. Key results The plasma total Trp, Kyn, and MT concentrations in all Trp groups steadily increased, reached their peak values, and gradually decreased after Trp supplementation between 0 h and 12 h. However, the plasma 5-HT concentration displayed the opposite trend. Peak plasma total Trp and 5-HT concentrations were attained between 1 h and 3 h, while those of KYN and MT appeared between 4 h and 6 h after Trp supplementation. The plasma total Trp and Kyn concentrations were significantly higher in TRP2 and TRP3 than in CON between 1 h and 12 h (P &lt; 0.05) after Trp supplementation. The plasma 5-HT concentration was significantly (P &lt; 0.05) lower in TRP1 than in CON at 3 h, 4 h, 6 h, 9 h, and 12 h after Trp supplementation. The plasma MT concentrations in TRP1 and TRP2 were significantly (P &lt; 0.05) higher than in CON at 3 h, 4 h, and 12 h, and at 0 h, 1 h, and 12 h after Trp supplementation (P &lt; 0.05). Conclusions Dietary Trp supplementation can increase the plasma total Trp, Kyn, and MT concentrations in Yili mares and the optimal Trp dosage was 20 mg/kg BW. Implication The addition of Trp to a basal diet or feed may increase the plasma total Trp, Kyn, and MT concentrations in female horses.

The effects of morning/afternoon surgeries on the early postoperative sleep quality of patients undergoing general anesthesia

ObjectiveThis study aimed to investigate the effects of morning and afternoon surgeries on the early postoperative sleep function in patients undergoing general anesthesia.MethodsFifty nine patients, aged 18–60 years, American society of anaesthesiologists (ASA) grade I or II, Body mass index of 18.5–28 kg/m2, undergoing laparoscopic myomectomy under total intravenous anesthesia, were included in the study. These patients were divided into two groups according to the start time of anesthesia: morning surgery group (group A, 8:00–12:00) and afternoon surgery group (group P, 14:00–18:00). The sleep conditions of the two groups of patients were evaluated by the Athens Insomnia Scale (AIS) one day before and one day after the operation. A total score of > 6 was regarded as postoperative sleep disturbance. The incidences of sleep disturbance one day after the operation in two groups were compared. The bispectral Index assessed the patient’s total sleep duration, sleep efficiency, and overall quality of sleep from 21:00 to 6:00 on the first night after surgery. Plasma concentrations of melatonin and cortisol at 6:00 am 1 day before surgery, 1 day after surgery were measured by ELISA, and rapid random blood glucose was measured.ResultsThe total AIS score, overall quality of sleep, total sleep duration, and final awakening earlier than desired scores of the two groups of patients on the first night after surgery were significantly increased compared with preoperative scores (P < 0.01). In group P, the sleep induction and the physical and mental functioning during the day scores increased significantly after surgery compared with preoperative scores (P < 0.05). The postoperative AIS scores in group P increased significantly compared with those in group A (P < 0.01). The incidence of postoperative sleep disturbances (70.0%) in group P was significantly higher than that in group A (37.9%) (P < 0.05). Compared with group A, the total sleep duration under BIS monitoring in group P was significantly shorter, the sleep efficiency and the overall quality of sleep was significantly reduced (P < 0.01). Compared with those in group A, the level of melatonin on 1 d after surgery in group P was significantly decreased, and the level of cortisol in group P was significantly increased. There were no significant differences between the two groups in the levels of postoperative blood glucose and pain.ConclusionBoth morning and afternoon surgeries have significant impacts on the sleep function in patients undergoing general anesthesia, while afternoon surgery has a more serious impact on sleep function.Trial registrationClinicalTrials, NCT04103528. Registered 24 September 2019—Retrospectively registered, http://www.ClinicalTrials.gov/ NCT04103528.

Chronic developmental hypoxia alters mitochondrial oxidative capacity and reactive oxygen species production in the fetal rat heart in a sex-dependent manner.

Insufficient oxygen supply (hypoxia) during fetal development leads to cardiac remodeling and a predisposition to cardiovascular disease in later life. Previous work has shown hypoxia causes oxidative stress in the fetal heart and alters the activity and expression of mitochondrial proteins in a sex‐dependent manner. However, the functional effects of these modifications on mitochondrial respiration remain unknown. Furthermore, while maternal antioxidant treatments are emerging as a promising new strategy to protect the hypoxic fetus, whether these treatments convey similar protection to cardiac mitochondria in the male or female fetus has not been investigated. Therefore, using an established rat model, we measured the sex‐dependent effects of gestational hypoxia and maternal melatonin treatment on fetal cardiac mitochondrial respiration, reactive oxygen species (ROS) production, and lipid peroxidation. Pregnant Wistar rats were subjected to normoxia or hypoxia (13% oxygen) during gestational days (GDs) 6–20 (term ~22 days) with or without melatonin treatment (5 µg/ml in maternal drinking water). On GD 20, mitochondrial aerobic respiration and H2O2 production were measured in fetal heart tissue, together with lipid peroxidation and citrate synthase (CS) activity. Gestational hypoxia reduced maternal body weight gain (p < .01) and increased placental weight (p < .05) but had no effect on fetal weight or litter size. Cardiac mitochondria from male but not female fetuses of hypoxic pregnancy had reduced respiratory capacity at Complex II (CII) (p < .05), and an increase in H2O2 production/O2 consumption (p < .05) without any changes in lipid peroxidation. CS activity was also unchanged in both sexes. Despite maternal melatonin treatment increasing maternal and fetal plasma melatonin concentration (p < .001), melatonin treatment had no effect on any of the mitochondrial parameters investigated. To conclude, we show that gestational hypoxia leads to ROS generation from the mitochondrial electron transport chain and affects fetal cardiac mitochondrial respiration in a sex‐dependent manner. We also show that maternal melatonin treatment had no effect on these relationships, which has implications for the development of future therapies for hypoxic pregnancies.

Transcutaneous auricular vagal nerve stimulation releases extrapineal melatonin and reduces thermal hypersensitivity in Zucker diabetic fatty rats.

Type 2 diabetes (T2D) is the most common comorbidity of COVID-19, and both are related to the lack of circulating melatonin. In addition, chronic pain is a common sequela of both COVID-19 and T2D. Using a neuropathic pain model produced by sciatic nerve chronic constriction injury in Zucker diabetic fatty rats, a verified preclinical genetic T2D neuropathy animal model, this study aimed to show that transcutaneous auricular vagal nerve stimulation (taVNS) could elevate plasma melatonin concentration, upregulate the expression of melatonin receptors (MTRs) in the amygdala, and relieve peripheral neuropathic pain. Furthermore, taVNS would restore melatonin levels and relieve pain even in pinealectomized rats. On the contrary, intraperitoneally injected luzindole, a melatonin receptor antagonist, would attenuate the antinociceptive effects of taVNS. In conclusion, the mechanism of the therapeutic effect of taVNS on chronic pain involves the release of extrapineal melatonin and the positive regulation of the expression of central MTRs. This beneficial efficacy should be considered during COVID-19 rehabilitation in individuals with diabetes.

Improvement of several stress response and sleep quality hormones in men and women after sleeping in a bed that protects against electromagnetic fields

BackgroundThe electromagnetic fields (EMFs) emitted by the technologies affect the homeostatic systems (nervous, endocrine, and immune systems) and consequently the health. In a previous work, we observed that men and women, after 2 months of using a bed with a registered HOGO system, that prevents and drain EMFs, improved their immunity, redox and inflammatory states and rejuvenated their rate of aging or biological age. Since, EMFs can act as a chronic stressor stimulus, and affect the sleep quality. The objective of this work was to study in men and women (23–73 years old) the effect of sleeping for 2 months on that bed in the blood concentrations of several hormones related to stress response and sleep quality as well as to corroborate the rejuvenation of their biological age.MethodsIn 18 men and women, plasma concentration of cortisol, dehydroepiandrosterone (DHEA), catecholamines (epinephrine, norepinephrine and dopamine), serotonin, oxytocin and melatonin were analyzed before and after 2 months of using the HOGO beds. A group of 10 people was used as placebo control. In another cohort of 25 men (20 experimental and 5 placebo), the effects of rest on the HOGO system on the concentration of cortisol and testosterone in plasma were studied. In all these volunteers, the biological age was analyzed using the Immunity Clock model.ResultsThere is a significant increase in plasma concentration of DHEA, norepinephrine, serotonin, oxytocin, and melatonin as well as in testosterone, after resting for 2 months in that bed with the EMFs avoiding system. In addition, decreases in Cortisol/DHEA and Testosterone/cortisol ratio and plasma dopamine concentration were observed. No differences were found in placebo groups. In all participants that slept on HOGO beds, the biological age was reduced.ConclusionsSleeping in a bed that isolates from EMFs and drain them can be a possible strategy to improve the secretion of hormones related to a better response to stress and sleep quality, which means a better endocrine system, and consequently better homeostasis and maintenance of health. This fact was confirmed with the slowdown in the rate of aging checked with a rejuvenation of the biological age.

Diurnal variation of clock genes expression and other sleep-wake rhythm biomarkers among acute ischemic stroke patients

There is accumulating evidence about sleep-wake rhythm disturbances as potential modifiable risk factors of both incident and recurrent stroke and less favorable outcomes after stroke. To our best knowledge this is the first study designed to investigate clock genes expression profiles in ischemic stroke patients and their relations to other biological and behavioral sleep-wake rhythm biomarkers, sleep structural and clinical stroke features. Altogether, 27 ischemic stroke patients (20 males) with the median age of 56 years and 25 gender and age matched controls were investigated with neurological and objective examination, scales, polysomnography, actigraphy and 24-h blood sampling for melatonin and clock genes profiles. Median melatonin plasma concentrations at four time points at 7, 11 p.m., 3 a.m. and 12 p.m. did not differ significantly between patients and controls, only early morning melatonin concentration at 7 a.m. was significantly lower and cortisol plasma concentration - significantly higher among stroke patients. All four clock genes (ARNTL (BMAL1), NR1D1 (Rev-erbα/β), PER1, and PER3) showed significant time-of-day variation in both patients' and controls’ groups, except expression of NR1D1 (Rev-erbα/β) at 7 a.m. and PER1 at 12 p.m. differed significantly. In conclusion, acute ischemic stroke patients tended to preserve most of diurnal variation of sleep-wake rhythm molecular patterns. Nevertheless, early morning time point showing higher cortisol and lower melatonin concentrations and lower NR1D1 (Rev-erbα/β) expression, as well as lower PER1 midday expression reflect specific circadian desynchrony features in different loops of the molecular circadian clock system.

0035 Enrichment of RAI1 genetic aberrations associated with sleep disturbances in SMS, in Autism Spectrum Disorder

Abstract Introduction Autism Spectrum Disorder (ASD) comprises a complex of neurodevelopmental disorders primarily characterized by deficits in verbal communication, impaired social interactions and repetitive behaviors. The profound clinical heterogeneity of ASD poses challenges in diagnosis and treatment. Genetic studies have pointed to hundreds of presumptive causative or susceptibility variants in ASD, making it difficult to find common underlying pathogenic mechanisms and suggesting that multiple different genetic etiologies for ASDs influence a continuum of traits. Smith–Magenis syndrome is a rare genetic disorder that results from an interstitial deletion of 17p11.2 and, in rare cases, from a retinoic acid induced 1 (RAI1) gene variant. The prevalence is estimated to be 1/15,000–25,000. Haploinsufficiency of RAI1 is the primary cause of the neurobehavioral and metabolic phenotype in SMS. Individuals with SMS present with a distinct pattern of mild to moderate intellectual disability, delayed speech and language skills, distinctive craniofacial and skeletal abnormalities, behavioral disturbances, and, almost uniformly, significant sleep disturbances. Alterations in RAI1 copy number has been also linked to a number of neurodevelopmental disorders including ASD. Methods We conducted a large-scale association analysis of the ASD MSSNG whole genome sequencing data to elucidate the prevalence of RAI1 SNVs and CNVs in the ASD population. We accessed the MSSNG database hosting over 11,000 genomes (6080 probands) and queried both SNVs and CNVs. Results Specifically, we focused on the prevalence of the classic deletions, microdeletions of (exon 3) and of the causative variants. We report a single case of a classic deletion (17p11.2 critical region), and an additional 3 cases of microdeletions in exon 3. Moreover, we report 2 frameshift mutations and one splicing variant. Given that the frequency of SMS is 1 in 15000 in the general population, we observe a 2.5x enrichment of the major deletion (1 in 6080 samples) and a &amp;gt;5x enrichment of the frameshift variants (2 in 6080 samples). In a set of 6080 probands we also observed 54 unique missense variants in 84 individuals within exon 3 of RAI1 gene. Conclusion Both ASD patients and SMS patients suffer from sleep disturbances. In this population of individuals with ASD, we report here an enrichment of variants known to cause SMS. We estimate the enrichment to be at least 2.5-fold and potentially higher than 10-fold enrichment, considering the types of variants observed in the population. Currently, the prevailing theory is that there is an underlying circadian pathophysiology causing sleep disturbances in SMS associated with RAI1 haploinsufficiency, as these patients exhibit low overall melatonin concentrations and abnormal timing of peak plasma melatonin concentrations. This abnormal inverted circadian rhythm is estimated to occur in 95% of individuals with SMS. The sleep disturbance seen in individuals with SMS may be also the underlying mechanism in at least a subset of individuals with ASD, especially in those individuals with consequential variants in the RAI1 gene Further studies will help delineate the role of RAI1 variants in sleep physiology. Support (If Any)

Melatonin dose: testicular and testosterone response in Border Leicester rams during spring

The negative effects of seasonality on ram fertility during the spring months (non-breeding season) can be addressed by administration of melatonin. Slow-release implants containing 18 mg of melatonin are available to improve reproductive responses in ewes but as far as we are aware nobody has examined the effects of dose on increasing testicular size and plasma testosterone levels. Mature Border Leicester rams were randomly allocated to four doses (0, 18, 36 and 54 mg) with treatment beginning in mid-September (spring). Measurements (scrotal size, testosterone and melatonin concentrations, live weight and body condition score) began before hormone administration and continued at monthly intervals until January (mid-summer). Scrotal circumference increased with increasing dose with 36 and 54 mg treatments producing larger responses than 0 and 18 mg treatments (p < 0.05). Plasma testosterone concentration was positively related (p ≤ 0.05) with plasma melatonin levels on days 60 and 90 after melatonin administration. There was a negative relationship (p < 0.01) between plasma melatonin concentration and liveweight on day 30. It is concluded that a higher dose of melatonin is required to maintain plasma melatonin levels in larger animals, and that at least 36 mg is required to elicit a threshold response in testicular size.

Melatonin Nuclear Receptors Mediate Green-and-Blue-Monochromatic-Light-Combinations-Inhibited B Lymphocyte Apoptosis in the Bursa of Chickens via Reducing Oxidative Stress and Nfκb Expression.

Previous studies found that melatonin modulates a combination of green-and-blue-light-induced B-lymphocyte proliferation via its membrane receptors Mel1a and Mel1c. However, in addition to its membrane-bound receptors, melatonin also functions through binding to nuclear receptors RORα/RORβ/RORγ. In this study, we raised 120 chicks under 400–700 nm white (WW), 660 nm red (RR), 560 nm green (GG) and 480 nm blue light (BB) from P0 to P26. From P27 to P42, half of the chickens in green, blue and red were switched to blue (G→B), green (B→G) and red (R→B), respectively. We used immunohistochemistry, Western blotting, qRT-PCR, Elisa and MTT to investigate the influence of various monochromatic light combinations on the bursal B lymphocyte apoptosis and oxidative stress levels as well as estimate whether melatonin and its nuclear receptors were involved in this process. Consistent with the increase in the plasma melatonin concentration and antioxidant enzyme activity, we observed that G→B significantly decreased the RORα, RORγ mRNA level, inhibited Bax, Caspase-3 and p-iκb, p-p65 protein expression, increased the IL-10 level and Nrf2, HO-1 protein expression, down-regulated the MDA and pro-inflammatory IL-6, TNF-α and IFN-γ levels in the bursa compared with WW, RR, GG, BB and R→B, respectively. Our in vitro results showed exogenous melatonin supplementation inhibited B-lymphocyte apoptosis, decreased IL-6, TNF-α, IFN-γ and ROS production, down-regulated RORα, RORγ mRNA level and p-iκb and p-p65 protein expression, whereas it improved the IL-10 level and Nrf2 and the HO-1 protein expression in bursal B lymphocyte. Moreover, these responses were abrogated by RORα agonist SR1078 but were mimicked by RORα antagonist SR3335 or RORγ antagonist GSK2981278. In addition, p65 antagonist BAY reversed RORα/RORγ-mediated G→B-inhibited bursal B lymphocyte apoptosis. Overall, we concluded that melatonin nuclear RORα/RORγ mediates G→B-inhibited bursal B lymphocyte apoptosis via reducing oxidative stress and Nfκb expression.

Unanticipated daytime melatonin secretion on a simulated night shift schedule generates a distinctive 24-h melatonin rhythm with antiphasic daytime and nighttime peaks.

The daily rhythm of plasma melatonin concentrations is typically unimodal, with one broad peak during the circadian night and near-undetectable levels during the circadian day. Light at night acutely suppresses melatonin secretion and phase shifts its endogenous circadian rhythm. In contrast, exposure to darkness during the circadian day has not generally been reported to increase circulating melatonin concentrations acutely. Here, in a highly-controlled simulated night shift protocol with 12-h inverted behavioral/environmental cycles, we unexpectedly found that circulating melatonin levels were significantly increased during daytime sleep (p < .0001). This resulted in a secondary melatonin peak during the circadian day in addition to the primary peak during the circadian night, when sleep occurred during the circadian day following an overnight shift. This distinctive diurnal melatonin rhythm with antiphasic peaks could not be readily anticipated from the behavioral/environmental factors in the protocol (e.g., light exposure, posture, diet, activity) or from current mathematical model simulations of circadian pacemaker output. The observation, therefore, challenges our current understanding of underlying physiological mechanisms that regulate melatonin secretion. Interestingly, the increase in melatonin concentration observed during daytime sleep was positively correlated with the change in timing of melatonin nighttime peak (p = .002), but not with the degree of light-induced melatonin suppression during nighttime wakefulness (p = .92). Both the increase in daytime melatonin concentrations and the change in the timing of the nighttime peak became larger after repeated exposure to simulated night shifts (p = .002 and p = .006, respectively). Furthermore, we found that melatonin secretion during daytime sleep was positively associated with an increase in 24-h glucose and insulin levels during the night shift protocol (p = .014 and p = .027, respectively). Future studies are needed to elucidate the key factor(s) driving the unexpected daytime melatonin secretion and the melatonin rhythm with antiphasic peaks during shifted sleep/wake schedules, the underlying mechanisms of their relationship with glucose metabolism, and the relevance for diabetes risk among shift workers.

The Effect of Chronic Intermittent Hypobaric Hypoxia on Sleep Quality and Melatonin Serum Levels in Chilean Miners.

High-altitude mining is an important economic resource for Chile. These workers are exposed to chronic intermittent hypobaric hypoxia (CIHH), which reduces their sleep quality and increases the risk of accidents and long-term illnesses. Melatonin, a hormone produced by the pineal gland, is a sleep inducer that regulates the circadian cycle and may be altered in populations subjected to CIHH. This work aimed to assess the relationship between altitude, sleep quality, and plasma melatonin concentrations in miners with CIHH exposure. 288 volunteers were recruited from five altitudes (0, 1,600, 2,500, 3,500, and 4,500 m). All volunteers worked for 7 days at altitude, followed by 7 days of rest at sea level. We performed anthropometric assessments, nocturnal oximetry, sleep quality and sleepiness surveys, and serum melatonin levels upon awakening. Although oxygen saturation progressively decreased and heart rate increased at higher altitudes, subjective perception of sleep quality was not significantly different, and sleepiness increased in all groups compared to population at sea level. Similarly, melatonin levels increased at all assessed altitudes compared to the population at sea level. These data confirm that sleep disturbances associated with CIHH increase morning melatonin levels. Therefore, this hormone and could potentially serve as a biomarker of sleep quality.

Melatonin as a Smart Protector of Pregnancy in Dairy Cows.

The experimental objective was to examine the role of melatonin and its pathways in the maintenance of pregnancy in lactating dairy cows. Blood samples were collected at days 0, 16 and 32 after timed AI from cows (n = 200) in order to consider plasma melatonin concentrations and to conduct AOPP (advanced oxidation products of proteins) and TBARS (thiobarbituric acid reactive substances) tests. Luminal endometrial cells were collected at day 16 using a Cytobrush in all cows to determine mRNA expressions of melatonin receptor 1 (MT1), mouse double minute 2 (MDM2), MDM2 binding protein (MTBP), BCL2-associated X, apoptosis Regulator (BAX), p53 upregulated modulator of apoptosis (PUMA, gene symbol BBC3), mucin 1 (MUC1) and leukemia inhibitory factor (LIF). Plasma concentrations of melatonin were significantly greater in pregnant cows diagnosed pregnant at day 16 who sustained pregnancy to day 32 compared to nonpregnant cows at day 16, or pregnant at day 16 and who lost embryos by days 32. Concentrations of AOPP and TBARS were greater in nonpregnant cows at day 16 or pregnant at day 16 and who lost embryos by days 32 compared to those diagnosed pregnant at day 16 and who sustained pregnancy to day 32. In pregnant cows, endometrial mRNA expressions of MDM2, MTBP, MTR1 and LIF were higher compared to pregnant–embryo-loss cows (p < 0.05). In contrast, mRNA expressions of BBC3 and MUC1 were greater at day 16 in pregnant–embryo-loss cows compared to pregnant cows (p < 0.05). In conclusion, melatonin status is a modulator of embryo well-being and maintenance of pregnancy in lactating dairy cows.

Dietary melatonin and L-tryptophan supplementation counteracts the effects of acute stress in Salmo salar

It has been suggested that supplementing fish diets with L-tryptophan (L-Trp) and melatonin (MEL) may attenuate stress; however, little clarity exists regarding the physiological effects of both additives and the associated mechanisms in attenuating the stress response. We investigated how MEL and L-Trp in the diet affects the physiology and acute stress responses in post-smolt Salmo salar. We supplemented in the fish diet with MEL and L-Trp for seven days and then used a chasing protocol to induce an acute stress response. After 0 (no stress), 5 and 15 min of chasing, we took plasma, gills, liver, and intestine samples. Our results suggest that MEL and L-Trp affect the physiology of S. salar differently. Plasma cortisol and lactate levels, in addition to branchial cortisol in fish fed with MEL decreased compared to controls; however, we did not observe any such differences in fish fed L-Trp. We detected significant increases in plasma MEL and L-Trp concentrations in fish fed MEL and L-Trp, respectively, but did not observe any changes in plasma MEL concentrations in fish fed L-Trp, while in the intestine we found that fish fed L-Trp increased MEL levels in pyloric caeca and hindgut, under stress and non-stress conditions, respectively. Serotonin (5-HT) levels in the intestine increased in fish fed MEL, while fish fed L-Trp increased their 5-HT levels in pyloric caeca and midgut under non-stress conditions. At the metabolic level, MEL generated hyperglycemia in plasma with greater glucose uptake in the gills, while L-Trp increased the levels of triglycerides, lactate and plasma proteins in non-stress conditions, in addition to a greater metabolism of amino acids in the liver. The modulation of glucocorticoid receptor transcription was similar in gills for MEL and L-Trp, while in liver, fish fed MEL had higher transcription of glucocorticoid receptors compared to fish fed L-Trp. In conclusion, dietary supplementation with MEL and L-Trp modulates the physiology of S. salar, but only MEL supplementation attenuates their acute stress response.

93 Melatonin and oxidative stress in the prevention of cardiovascular disease

Abstract Aims Arterial hypertension, especially if not well-controlled, is one of the main risk factors predisposing to fatal cardiovascular diseases (CVDs). Moreover, the diagnosis of essential hypertension are increasing, therefore oxidative stress and chronic inflammation have also been identified as potential responsible for the development of endothelial damage. Among all the molecules, melatonin (MT) was chosen for its role as a powerful antioxidant and anti-inflammatory endogenous molecule. This trial aims to evaluate the early intervention at the base of the inflammatory and oxidative cascade (that results in the development of hypertension), to restore an oxidative balance leading to positive results even at the endothelial and vascular level using MT in addition to anti-hypertensive therapy. Methods The trial is randomized, prospective and monocentric control. We enrolled 23 patients with hypertension in absence of other cardiovascular or autoimmune diseases that could alter the oxidative background, from March 2018 to April 2019 (recruitment period). Patients were randomly assigned to two groups: ‘melatonin group’ (in which 16 patients add 1 mg/day of melatonin for a year, to their already settled therapy), and a ‘control’ group (consisting of 7 patients with no changes in their therapy). The average follow-up was 1 year from randomisation. Patients were evaluated before and after a period of 1 year through MT plasma concentration and serum antioxidant capacity (TAC) by specific quantitative ELISA method. Therefore endothelial dysfunction and arterial stiffness were evaluated too (using the non-invasive methods of EndoPAT and SphygmoCor). Results In ‘melatonin group’ arterial stiffness index statistically decreased (P 0.022), according to a significant increase in plasma melatonin values (P 0.003) and significant decrease in TAC levels (P 0.041) despite the ‘control’ group. The improvement of endothelial function was not significant (P 0.688). Blood pressure had not a significative improvement too (P 0.401). Conclusions Data obtained could confirm the hypothesis of activation of plasma antioxidant system against a situation of altered oxidative balance. In fact, it is possible to hypothesize a correlation between TAC and arterial stiffness that confirm the antioxidant role of MT. The combination between antihypertensive therapy and antioxidant supplementation is able to improve the vascular stiffness. Data obtained are still preliminary and present some limitations but we can think of proposing this trial as a future basis for other extensive and prolonged studies.

Melatonin along with eCG improves fresh semen quality and plasma concentrations of melatonin and testosterone during non-breeding season in Beetal bucks

Under subtropical regions, the breeding activities of goats are restricted to a specific season. Several hormonal regimens have been used to improve reproductive performance. However, different hormonal protocols have certain limitations. The effect of melatonin + eCG therapy on fresh semen, plasma testosterone, and melatonin profiles of bucks was evaluated during the non-breeding season. Nine bucks were assigned to three treatments (control; normal saline, melatonin alone, and melatonin + eCG; n = 3 in each group). Except for control, all bucks were implanted melatonin subcutaneously and eCG was administered every fourth day to melatonin + eCG treated bucks. Weekly two fresh ejaculates per buck for 10 weeks (n = 180) were evaluated for sperm concentration, motility, kinematics (VCL, VSL, VAP, and ALH), non-viability, morphological abnormality, DNA fragmentation/damage, acrosomal and mitochondrial integrity. Weekly plasma profiles of testosterone and melatonin were monitored. From the 4th week onward, non-viable and morphological abnormal sperms and decreased (P < 0.05) while sperm progressive motility and kinematics, acrosomal and DNA integrity improved (P < 0.05) in melatonin + eCG than melatonin alone and control treatments. The concentrations of testosterone (ng/mL) increased (P < 0.05) from the 3rd week onward in melatonin + eCG (4.2 ± 0.2) than melatonin alone (1.2 ± 0.1) and control treatments (0.28 ± 0.1). An increase (P < 0.05) in the concentration of melatonin (pg/mL) was observed at 5th week in melatonin + eCG (12.5 ± 0.2) than melatonin alone (10.2 ± 0.1) and control treatments (3.89 ± 0.2); however, by 9th-week melatonin alone and melatonin + eCG had similar melatonin profiles. Compared to other treatments, melatonin + eCG therapy quickly improves and sustains fresh semen quality and plasma testosterone profile of bucks during the non-breeding season.

Melatonin MT2 receptor is expressed and potentiates contraction in human airway smooth muscle.

Nocturnal asthma is characterized by heightened bronchial reactivity at night, and plasma melatonin concentrations are higher in patients with nocturnal asthma symptoms. Numerous physiological effects of melatonin are mediated via its specific G protein-coupled receptors (GPCRs) named the MT1 receptor, which couples to both Gq and Gi proteins, and the MT2 receptor, which couples to Gi. We investigated whether melatonin receptors are expressed on airway smooth muscle; whether they regulate intracellular cyclic AMP (cAMP) and calcium concentrations ([Ca2+]i), which modulate airway smooth muscle tone; and whether they promote airway smooth muscle cell proliferation. We detected the mRNA and protein expression of the melatonin MT2 but not the MT1 receptor in native human and guinea pig airway smooth muscle and cultured human airway smooth muscle (HASM) cells by RT-PCR, immunoblotting, and immunohistochemistry. Activation of melatonin MT2 receptors with either pharmacological concentrations of melatonin (10-100 µM) or the nonselective MT1/MT2 agonist ramelteon (10 µM) significantly inhibited forskolin-stimulated cAMP accumulation in HASM cells, which was reversed by the Gαi protein inhibitor pertussis toxin or knockdown of the MT2 receptor by its specific siRNA. Although melatonin by itself did not induce an initial [Ca2+]i increase and airway contraction, melatonin significantly potentiated acetylcholine-stimulated [Ca2+]i increases, stress fiber formation through the MT2 receptor in HASM cells, and attenuated the relaxant effect of isoproterenol in guinea pig trachea. These findings suggest that the melatonin MT2 receptor is expressed in ASM, and modulates airway smooth muscle tone via reduced cAMP production and increased [Ca2+]i.

Effects of Duodenal 5-Hydroxytryptophan Perfusion on Melatonin Synthesis in GI Tract of Sheep.

The purpose of this study is to investigate the potential effects of 5-hydroxytryptophan (5-HTP) duodenal perfusion on melatonin (MT) synthesis in the gastrointestinal (GI) tract of sheep. 5-hydroxytryptophan is a precursor in the melatonin synthetic pathway. The results showed that this method significantly increased melatonin production in the mucosa of all segments in GI tract including duodenum, jejunum, ileum, cecum and colon. The highest melatonin level was identified in the colon and this indicates that the microbiota located in the colon may also participate in the melatonin production. In addition, portion of the melatonin generated by the GI tract can pass the liver metabolism and enters the circulation via portal vein. The current study provides further evidence to support that GI tract is the major site for melatonin synthesis and the GI melatonin also contributes to the circulatory melatonin level since plasma melatonin concentrations in 5-HTP treated groups were significantly higher than those in the control group. In conclusion, the results show that 10–50 mg of 5-HTP flowing into the duodenum within 6 h effectively improve the production of melatonin in the GI tract and melatonin concentration in sheep blood circulation during the day.

Supplementary Tryptophan Fed to Sows Prior to and after Farrowing to Improve Piglet Growth and Survival.

Simple SummaryPre-weaning mortality is a significant economic and welfare issue for the Australian pig industry. Tryptophan can increase serotonin and melatonin production. Serotonin can decrease stress and indirectly increase calcium, which may improve sow health. Meanwhile, melatonin may decrease stillbirths and improve piglet viability at birth and, in turn, increase survival to weaning. This study determined whether feeding 0.16%, 0.42% or 0.56% tryptophan (per kg of feed) to sows during late pregnancy until seven days of lactation could improve piglet survival and viability to weaning and increase the levels of calcium and melatonin in sows. Supplementing tryptophan at levels of 0.42 and 0.56% increased piglet survival compared to no supplementation but did not have an effect on piglet viability. Furthermore, tryptophan supplementation did not increase sow melatonin and calcium levels compared to 0.16%. Further research is required to understand how tryptophan may improve piglet survival, particularly through sow maternal behaviour, and if 5-hydroxytryptophan (the form of tryptophan that directly converts to serotonin and melatonin) would further improve piglet survival. Tryptophan indirectly increases plasma calcium levels, which may improve sow health, and melatonin production, which may improve piglet survival when supplemented during late gestation and lactation. It was hypothesised that tryptophan would increase piglet survival and increase sow circulating melatonin and calcium. Seventy-two multiparous (Landrace x Large White) sows were allocated to either control (0.16% tryptophan; n = 24), low tryptophan (0.42%; n = 24) or high tryptophan (0.56%; n = 24). Piglet viability measures consisted of weights, behaviour, meconium staining, rectal temperature, blood glucose and serum immunoglobulin G concentration. Blood samples collected from sows were analysed for melatonin (two daytime and three night-time samples; n = 17) and calcium (two samples pre- and post-farrowing; n = 14). Both tryptophan treatments increased piglet survival compared to the control group (p < 0.001). Tryptophan had no effect on piglet viability (p > 0.05) and no effect on sow plasma melatonin and calcium concentrations compared with the control group (p > 0.05) except at 21:00 when low tryptophan sows had higher melatonin concentration compared with high tryptophan (p = 0.011). Further research to understand the mediating effects of tryptophan (particularly 5-hydroxytryptophan) on piglet survival, including sow behaviour, is warranted.

Identification of the blue light intensity administered to one eye required to suppress bovine plasma melatonin and investigation into effects on milk production in grazing dairy cows

Long-day photoperiod is known to positively affect milk production in confinement dairy systems, and it has been hypothesized that pineal melatonin (MT) secretion plays a substantial role in this process. Specialized mammalian photoreceptors that regulate MT secretion are optimally stimulated by short wavelength blue light. We investigated the blue light intensity administered to one eye required to suppress MT secretion in nonlactating dairy cows, and subsequently examined effects on milk production in grazing dairy cows. Following a 14-d light-dark 8:16 h environmental conditioning period, 5 nonlactating Holstein-Friesian cows were exposed to treatments of <1, 70, 125, 175, and 225 lx for 8 additional hours using a 5 × 5 Latin square design. Light was administered via headpieces fitted with light-emitting diodes emitting blue light (465 nm) to the right eye. All cows were then exposed to a light-dark 16:8 h cycle for one night via the indoor lighting system (>200 lx white light). Plasma samples collected at regular intervals were assayed for MT. A dose-dependent effect of light treatment on mean circulating MT concentrations (and 95% CI) was observed [9.4 (7.2, 12.3), 5.0 (3.8, 6.6), 4.4 (3.3, 5.7), 3.3 (2.5, 4.3) and 1.7 (1.3, 2.3) pg/mL for treatments of 0, 70, 125, 175, and 225 lx, respectively. Only the 225 lx treatment acutely suppressed plasma melatonin concentration to levels similar to the light-dark 16:8 h treatment [1.9 (1.4, 2.5) pg/mL]. Forty spring-calving cows were blocked on parity, calving date and Economic Breeding Index for milk production and assigned to the control treatment or blue light to a single eye (LT) treatment from calving through 32 wk of lactation. The cows assigned to LT treatment were fitted with headpieces providing 225 lx of blue light to the right eye from 1700 until 0000 h. Mean milk production (and 95% CI) during 32 wk of lactation was not affected by treatment [20.3 (19.3, 21.3) vs. 20.9 (19.8, 22.0) kg/d, control and LT, respectively]. Within multiparous cows, a treatment by week interaction was detected, whereby LT treatment increased milk production during the first 12 wk of lactation [25.8 (24.3, 27.3) vs. 28.0 (26.5, 29.5) kg/d; +8.5%], but had no effect thereafter. Treatment did not affect plasma insulin-like growth factor 1. We identified the blue light intensity to one eye required to acutely suppress MT concentrations. Transient favorable effects on milk production were observed in multiparous cows. It remains unclear how single-eye blue light treatment affects galactopoiesis in grazing dairy cows, and further research is needed to explore whether this modality of light delivery represents a useful means to aid productivity in pasture-based dairy systems.