Suppression Of Melatonin Secretion Research Articles

Sleep Deprivation and Subchronic Arsenite Exposure Synergistically Induced Skeletal Muscle Aging by Disrupting Melatonin and Cortisol Secretion in Mice

In recent years, the influence of environmental factors on organismal aging has garnered increasing attention. Studies have shown that sleep deprivation and environmental pollutants could accelerate the emergence of multiple organismal aging phenotypes. In addition, studies have shown that chronic exposure to sodium arsenite (iAs) induces skeletal muscle atrophy and the inhibition of melatonin secretion in rats. This study aimed to reveal the synergistic effect of sleep deprivation and arsenite exposure on skeletal muscle aging, including reduced limb grip strength and skeletal muscle mass, along with the serum levels of melatonin (MT) and cortisol (COR) in C57BL/6J mice. The results demonstrated that while exposure to arsenite for 12 weeks or sleep deprivation (SD) for 4 weeks did not exert significant effects on limb grip strength or skeletal muscle mass, their combination exhibited a synergistic effect on skeletal muscle aging. Notably, the iAs+SD group exhibited a significant decline in limb grip strength by Week 12, accompanied by a reduced gastrocnemius muscle mass and muscle index. The pathological analysis showed muscle fiber atrophy, a shift towards slow-twitch muscle fibers (type I), and shortened telomere length. Additionally, oxidative damage was increased in the SD and iAs+SD groups, with decreased levels of SOD and GPx and elevated levels of MDA in the iAs+SD group. The serum MT level and MT/COR ratio were significantly reduced, while the serum COR level was elevated in the iAs+SD group compared to the other groups. A correlation analysis further revealed that the serum MT level and the MT/COR ratio were positively correlated with limb grip strength, muscle index, and telomere length, whereas the serum COR level exhibited negative correlations with these parameters. These findings suggest that sleep deprivation and subchronic exposure to arsenite synergistically induce skeletal muscle aging, and that the disruption of the balance between MT and COR potentially serves as a significant risk factor.

Artificial light at night effects glucose metabolism in the developing jawbone by inhibiting melatonin secretion

Objective: To investigate the effects of artificial light at night on the growth of mandibles in mice and its regulatory mechanisms. Methods: A mouse model of artificial light at night (night light pollution group) and normal lighting (normal light group) was established by controlling light exposure time, with 4 mice in each group. Micro-CT was employed to analyze the differences in bone quantities of the mandibles between the two groups. Real-time fluorescence quantitative PCR (RT-qPCR) was used to examine the expression levels of osteogenic differentiation and metabolism-related genes in the cortical bone and condylar ossification center of the mandibles. Enzyme-linked immunosorbent assay was utilized to assess the diurnal variation of serum melatonin concentrations between the two groups. The artificial light at night experimental group received daily timed injections of a defined dose of melatonin to restore the diurnal variation of serum melatonin concentration in the mice, while the normal light group and the artificial light at night control group received the same volume of saline. Bone quantities, mandibular tissue morphologies, ossification differentiation in the condylar region and cortical bone, as well as glucose metabolism expression differences were assessed across the three groups. Results: The cortical bone thickness of the mandibles in the artificial light at night group [(0.196±0.017) mm] was significantly less than that in the control group [ (0.228±0.007) mm] (P=0.029). The bone volume fraction of the condylar ossification center in the artificial light at night group [(36.90±1.09) %] was significantly lower than that in the normal light group [(54.24±1.49) %] (P<0.001). The length of the mandible in the artificial light at night group [(10.86±0.17) mm] was significantly shorter than that in the normal light group [(11.41±0.32) mm] (P=0.032). RT-qPCR results indicated that the expressions of osteogenic-related genes alkaline phosphatase, liver/bone/kidney (Alpl), osteocalcin (Ocn), Runt-related transcription factor 2 (Runx2), and osterix (Osx) in the cortical bone and condylar ossification center of mice in the artificial light at night group were significantly lower than those in the normal light group (all P<0.05). The expression of metabolism-related genes protein kinase, AMP activated alpha 1 (Prkaa1), V-type proton ATPase subunit d 1 (Atp6v0d1), and cytochrome C oxidase subunit Ⅳ isoform 1 (Cox4i1) in the cortical bone and condylar ossification center of mice in the artificial light at night group were also significantly reduced compared to normal mice (all P<0.01). The serum melatonin concentration peaked 8 hours after lights off in the normal light group, whereas the artificial light at night group exhibited a significantly reduced nocturnal serum melatonin concentration with no apparent peak compared to the normal light group. Micro-CT results demonstrated that after artificial light at night group mice received timed melatonin supplementation daily, the thickness of cortical bone, the bone volume fraction of the condylar ossification center, and the length of the mandible were all significantly higher than those in the artificial light at night group (all P<0.05). Histological staining results indicated that the cortical bone structure of the mandibles in the melatonin supplementation group was more organized than that of the artificial light at night group, with higher brain and muscle ARNT-like 1 (BMAL1) expression (P=0.003). RT-qPCR results further showed that the expression levels of Prkaa1, Atp6v0d1, and Cox4i1 in the cortical bone and condylar ossification center significantly increased in the melatonin supplementation group compared to the artificial light at night group (all P<0.05), but still significantly lower than those in the normal light group (all P<0.05). Additionally, the RT-qPCR results further revealed that the expression levels of osteogenic differentiation-related genes Alpl, Ocn, and Runx2 in the cortical bone and condylar ossification center of the melatonin supplementation group were significantly higher than those in the artificial light at night group (all P<0.01). Western blotting analysis indicated that the expression levels of glucose metabolism and osteogenic-related proteins RUNX2, OSX, ATP6V0D1, and COX Ⅳ, along with the phosphorylation levels of AMPKα1/α2, were significantly higher in the melatonin supplementation group compared to the artificial light at night group (all P<0.01). Conclusions: Artificial light at night can inhibit melatonin secretion in mice, reduce glucose metabolism in mandibular tissues, and affect both intramembranous and chondrogenic ossification activities, ultimately leading to inadequate mandibular development.

Effect of Diurnal Light Conditions on Electroretinogram Responses to Red and Blue Flickering Light.

Bright light impacts the human circadian system such that exposure to bright light at night can suppress melatonin secretion, and exposure to bright light in the morning prevents light-induced melatonin suppression at night. The preventive effect of morning light may attenuate the prior history of light sensitivity of intrinsically photosensitive retinal ganglion cells (ipRGCs) that regulate the circadian system. In this study, we evaluated electroretinogram (ERG) responses to red and blue flickering lights following dim and bright daylight conditions. Eleven healthy females underwent ERG measurements during exposure to 33Hz flickering red or blue light under dim and bright daytime conditions. We averaged ERG waves for 50 flickering light pulses of the trigger signal data. We obtained the amplitude of the signal-averaged ERG by calculating the difference between the waves' peaks and bottoms. Although there was no significant dim and bright light difference in the amplitude of ERG waves, the ERG amplitude to flickering blue light under the bright light condition was significantly lower than to flickering blue light under the dim light condition. In this study, blue light stimulated mainly ipRGCs and S-cones. Since S-cones may contribute minimally to the light-adapted 33Hz flicker ERG results, our findings suggest that bright light during the daytime attenuates the sensitivity of human ipRGCs.

Melatonin and Vascular Function.

The indolamine hormone melatonin, also known as N-acetyl-5-methoxytrypamine, is frequently associated with circadian rhythm regulation. Light can suppress melatonin secretion, and photoperiod regulates melatonin levels by promoting its production and secretion at night in response to darkness. This hormone is becoming more and more understood for its functions as an immune-modulatory, anti-inflammatory, and antioxidant hormone. Melatonin may have a major effect on several diabetes-related disturbances, such as hormonal imbalances, oxidative stress, sleep disturbances, and mood disorders, according to recent research. This has raised interest in investigating the possible therapeutic advantages of melatonin in the treatment of diabetic complications. In addition, several studies have described that melatonin has been linked to the development of diabetes, cancer, Alzheimer's disease, immune system disorders, and heart diseases. In this review, we will highlight some of the functions of melatonin regarding vascular biology.

Do blue light filter applications improve sleep outcomes? A study of smartphone users’ sleep quality in an observational setting

ABSTRACT Exposure to blue light at bedtime, suppresses melatonin secretion, postponing the sleep onset and interrupting the sleep process. Some smartphone manufacturers have introduced night-mode functions, which have been claimed to aid in improving sleep quality. In this study, we evaluate the impact of blue light filter application on decreasing blue light emissions and improving sleep quality. Participants in this study recorded the pattern of using their mobile phones through a questionnaire. In order to evaluate sleep quality, we used a PSQI questionnaire. Blue light filters were used by 9.7% of respondents, 9.7% occasionally, and 80% never. The mean score of PSQI was more than 5 in 54.10% of the participants and less than 5 in 45.90%. ANOVA test was performed to assess the relationship between using blue light filter applications and sleep quality (p-value = 0.925). The findings of this study indicate a connection between the use of blue light filter apps and habitual sleep efficiency in the 31–40 age group. However, our results align only to some extent with prior research, as we did not observe sustained positive effects on all parameters of sleep quality from the long-term use of blue light filtering apps. Several studies have found that blue light exposure can suppress melatonin secretion, exacerbating sleep problems. Some studies have reported that physical blue light filters, such as lenses, can affect melatonin secretion and improve sleep quality. However, the impact of blue light filtering applications remains unclear and debatable.

Plasmonic Contact Lenses Based on Silver Nanoparticles for Blue Light Protection.

Constant exposure to blue light emanating from screens, lamps, digital devices, or other artificial sources at night can suppress melatonin secretion, potentially compromising both sleep quality and overall health. Daytime exposure to elevated levels of blue light can also lead to permanent damage to the eyes. Here, we have developed blue light protective plasmonic contact lenses (PCLs) to mitigate blue light exposure. Crafted from poly(hydroxyethyl methacrylate) (pHEMA) and infused with silver nanoparticles, these contact lenses serve as a protective barrier to filter blue light. Leveraging the plasmonic properties of silver nanoparticles, the lenses effectively filtered out the undesirable blue light (400-510 nm), demonstrating substantial protection (22-71%) while maintaining high transparency (80-96%) for the desirable light (511-780 nm). The maximum protection level reaches a peak of 79% at 455 nm, aligned with the emission peak for the blue light sourced from LEDs in consumer displays. The presence of silver nanoparticles was found to have an insignificant impact on the water content of the developed contact lenses. The lenses maintained high water retention levels within the range of 50-70 wt %, comparable to commercial contact lenses. The optical performance of the developed lenses remains unaffected in both artificial tears and contact lens storage solution over a month with no detected leakage of the nanoparticles. Additionally, the MTT assay confirmed that the lenses were biocompatible and noncytotoxic, maintaining cell viability at over 85% after 24 h of incubation. These lenses could be a potential solution to protect against the most intense wavelengths emitted by consumer displays and offer a remedy to counteract the deleterious effects of prolonged blue light exposure.

Role of melanocortin system in the locomotor activity rhythms and melatonin secretion as revealed by agouti-signalling protein (asip1) overexpression in zebrafish.

Temporal signals such as light and temperature cycles profoundly modulate animal physiology and behaviour. Via endogenous timing mechanisms which are regulated by these signals, organisms can anticipate cyclic environmental changes and thereby enhance their fitness. The pineal gland in fish, through the secretion of melatonin, appears to play a critical role in the circadian system, most likely acting as an element of the circadian clock system. An important output of this circadian clock is the locomotor activity circadian rhythm which is adapted to the photoperiod and thus determines whether animals are diurnal or nocturnal. By using a genetically modified zebrafish strain known as Tg (Xla.Eef1a1:Cau.asip1)iim04, which expresses a higher level of the agouti signalling protein 1 (Asip1), an endogenous antagonist of the melanocortin system, we observed a complete disruption of locomotor activity patterns, which correlates with the ablation of the melatonin daily rhythm. Consistent with this, in vitro experiments also demonstrated that Asip1 inhibits melatonin secretion from the zebrafish pineal gland, most likely through the melanocortin receptors expressed in this gland. Asip1 overexpression also disrupted the expression of core clock genes, including per1a and clock1a, thus blunting circadian oscillation. Collectively, these results implicate the melanocortin system as playing an important role in modulating pineal physiology and, therefore, circadian organisation in zebrafish.

The impact of cyanopic illuminance on evening light induced circadian effects

Circadian lighting aims to avoid the negative impacts of artificial lighting on the circadian system. Of particular concern are the negative effects induced by evening light exposure, such as the suppression of melatonin secretion and delayed circadian phase. The melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs) play a key role in the circadian phototransduction processes. Therefore, popular metrics for “circadian illuminance”, such as equivalent melanopic lux (EML) and melanopic equivalent daylight D65 illuminance (m-EDI), are based solely on melanopic illuminance. However, some recent studies suggested that visual photo-receptors could also participate in the circadian phototransduction process. Especially, the S-cone-related cyanopic illuminance may also contribute to the light-elicited circadian responses. To investigate the actual role of cyanopic illuminance and the accuracy of the m-EDI and EML metrics, we designed a pair of general-lighting spectra with equivalent melanopic and photopic illuminance but very different cyanopic illuminance (40.5% difference achieved). Human-factor studies were conducted using this pair of spectra, which showed that saliva melatonin concentration and sleep efficiency were significantly higher under the lighting condition with greater cyanopic illuminance. These results suggest that cyanopic illuminance plays an important role in evening-light-induced circadian effects with an inhibitory behavior. On the other hand, cyanopic illuminance alone does not affect KSS-rated subjective alertness. Our findings suggest that incorporating cyanopic illuminance, in addition to melanopic illuminance, can enhance the accuracy of circadian illuminance metrics. This balanced approach can help achieve both precise quantification and convenience in circadian lighting design.

Reducing nighttime light exposure in the urban environment to benefit human health and society.

Nocturnal light pollution can have profound effects on humans and other organisms. Recent research indicates that nighttime outdoor lighting is increasing rapidly. Evidence from controlled laboratory studies demonstrates that nocturnal light exposure can strain the visual system, disrupt circadian physiology, suppress melatonin secretion, and impair sleep. There is a growing body of work pointing to adverse effects of outdoor lighting on human health, including the risk of chronic diseases, but this knowledge is in a more nascent stage. In this Review, we synthesize recent research on the context-specific factors and physiology relevant to nocturnal light exposure in relation to human health and society, identify critical areas for future research, and highlight recent policy steps and recommendations for mitigating light pollution in the urban environment.

A Study on the Effect and Prevention of Blue Light on Eyes

Abstract: In recent years, large number of people complaining about rteh effects of light pollution on their eyes. Blue light with the wavelength range between 415nm and 455nm is much nearly related with eye damage in the visible range. High energy blue light damages the hormonal balance and negatively impacts sleep quality by passing from the cornea to retina. Here it led to many types of disease such as cataract, age related degeneration and dry eye. It also stimulates the brain, inhibits melatonin secretion, and increases the production of adrenocortical hormones. Consequently, the impact of Blu-rays on the eye is growing in significance going forward. The effects of blue light on ocular tissues are highlighted in this study, along with a summary of the studies on eye injuries, physical preventative measures, and medical care.

Design and Development of a Sustainable Environmentally Friendly and Human Centric Luminaire

Apart from the visual effects, light can also affect the human non-visual system, which includes a wide range of functions such as hormone secretion, alertness, mood etc. The non-image forming effects occur because light affects melanopsin, a photosensitive protein present in the receptive domain of retinal ganglion cells. These cells are responsible for generating nerve impulses that regulate the secretion of two hormones, cortisol and melatonin. Low-wavelength light at 460-480 nm inhibits melatonin secretion and activates brain activity. Aim of this paper is to create a sustainable and human centric luminaire suitable for office installations that will regulate the biological rhythm of the occupants and has the minimum environmental impact. The luminaire’s light source emits variable spectrum, with a collated colour temperature varying between 2700K and 6500K. For a 500K step of colour temperature values, the appropriate human centric lighting metrics are calculated: Equivalent Melanopic Lux, Melanopic Daylight Equivalent Illuminance, Circadian Stimulus. The development of the human centric luminaire considers not only the metrics of human centric lighting but energy efficiency and visual comfort as well. Conclusively, the proposed luminaire can provide a holistic approach to lighting design so as to integrate both visual and non-visual effects and produce sustainable and environmentally friendly lighting.

Sensitizer enabling long lifetime wet-processed candlelight OLEDs

Blue hazard-free candlelight-style light sources are friendly to human eyes and physiology, ecosystems, night skies, and artifacts . Wet-process enables devices to be fabricated cost-effectively. However, wet-processed organic devices typically exhibit poor lifetime. We demonstrate here a fairly long lifetime wet-processed candlelight OLED with a simple structure. The lifetime was increased by 2.8 times by using 4,4′,4″-tris(carbazol-9-yl) triphenylamine as host in lieu of the typical 4,4′-bis( N -carbazolyl)-1,1′-biphenyl. Incorporation of a robust sensitizer further increased the lifetime by 93 times. The reasons why the lifetime was markedly enhanced may be mainly attributed to the facts that the sensitizer is thermally and electrochemically more stable, besides being more favorable to the injection of both electron and hole. The device showed a color temperature of 1770 K. From retinal protection perspective, this candlelight OLED permits at 100 lx an exposure-limit of 13 h, 150 times friendlier than that of the 5500 K cold-white LED (320 s) and 170 times friendlier than that of the 5920 K cold-white CFL (286 s). Upon a 1.5 h exposure at night, it would suppress melatonin secretion only by 2%, 9 times better than the LED (20%) and 14 times better than the CFL (29%).

Constant light in early life induces fear-related behavior in chickens with suppressed melatonin secretion and disrupted hippocampal expression of clock- and BDNF-associated genes

BackgroundLight management plays an important role in the growth and behavior of broiler chickens. Constant light in early post hatch stage has been a common practice in broiler industry for improving growth performance, while whether and how constant light in early life affects the behavior of broiler chickens is rarely reported.ResultsIn this study, newly hatched chicks were kept in either constant (24 L:0 D, LL) or (12 L:12 D, LD) photoperiod for 7 d and then maintained in 12 L:12 D thereafter until 21 days of age. Constant light increased the average daily feed intake but not the body weight, which led to higher feed conversion ratio. Chickens in LL group exhibited fear-related behaviors, which was associated with higher corticosterone, lower melatonin and 5-HT levels. Concurrently, constant light exposure increased the mRNA expression of clock-related genes and suppressed the expression of antioxidative genes in the hippocampus. Moreover, brain derived neurotrophic factor/extracellular signal-regulated kinase (BDNF/ERK) pathway was suppressed in the hippocampus of chickens exposed to constant light in the first week post hatching.ConclusionsThese findings indicate that constant light exposure in early life suppress melatonin secretion and disrupts hippocampal expression of genes involved in circadian clock and BDNF/ERK pathway, thereby contributing to fear-related behaviors in the chicken.

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.

Effects of different light incident angles via a head-mounted device on the magnitude of nocturnal melatonin suppression in healthy young subjects

Bright light is a primary zeitgeber (synchronizer) for the central circadian pacemaker in humans. Recently, head-mounted devices for light therapy have been developed to treat patients suffering from circadian rhythm sleep disorders. In this study, to evaluate the influence of the light incident angle of head-mounted devices on the human circadian pacemaker, we examined the effects of bright light (ca.10000 lx) from two different angles (55° vs. 28°) on the suppression of melatonin secretion at night. Twenty-nine subjects (25.1 ± 6.3 SD years) participated in the present study. The subjects were kept under dim light conditions (< 5 lx) from 4 h before their habitual bedtime, followed by exposure to 1 h of bright light at two different angles during their habitual bedtime. Saliva samples were collected every hour under dim light conditions and then collected every 30 min during the bright light exposure. To assess the effect of the light incident angle on ipRGCs mediating light-evoked pupillary constriction, pupil size was measured in before and after exposure to bright light. Melatonin suppression in the group exposed to light at 28° was significantly higher than that in the group with light at 55° (p < 0.001). The pupillary constriction was significantly greater in the group exposed to light at 28° than that in the group with light at 55° (p < 0.001). The present findings suggest that the light incident angle is an important factor for bright light therapy and should be considered to effectively use head-mounted devices in home and clinical settings.

Prednisolone induces sleep disorders via inhibition of melatonin secretion by the circadian rhythm in zebrafish

Prednisolone (PN) is a glucocorticoid (GC) analog that is clinically used to treat allergic inflammation and autoimmune diseases. However, the long-term use of GC-like drugs results in many side effects, among which sleep disorders caused by PN have attracted much attention. Many studies have showed that GCs indirectly cause sleep disorders by disrupting the circadian rhythm of the peripheral biological clock. However, the detailed mechanism of this effect in zebrafish remains unclear. In the present study, we aimed to study the pharmacology and toxicology of PN by analyzing the sleep phenotype and internal circadian oscillation of zebrafish. Exposure of zebrafish to PN resulted in decreased melatonin secretion and shortened sleep time. Additionally, analysis of the internal circadian rhythm of the zebrafish revealed that the expression of per and cry was significantly upregulated, resulting in a significant delay in the phase of the zebrafish behavioral rhythm. A dual-luciferase reporter assay further revealed that PN repressed per2 and cry1aa expression via the GC receptor (GR), which inhibited aanat2 expression. This caused a decrease in melatonin secretion and led to sleep disorders. The findings of this study highlight the mechanisms underlying the effects of GCs on sleep.

Effects of working environments with minimum night lighting on night-shift nurses’ fatigue and sleep, and patient safety

ObjectiveNurses working rotating shifts often suffer from insomnia or similar disorders because exposure to room lighting at night inhibits melatonin secretion, resulting in a disturbed circadian rhythm. This study investigated...

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.

Behaviorally and environmentally induced non-24-hour sleep-wake rhythm disorder in sighted patients.

To determine whether there was evidence of circadian or sleep-regulatory dysfunction in sighted individuals with non-24-hour sleep-wake rhythm disorder. Three sighted individuals with signs and/or symptoms of non-24-hour sleep-wake rhythm disorder were studied. Thirty-five- to 332-day laboratory and home-based assessments of sleep-wake and circadian timing, endogenous circadian period, photic input to the circadian pacemaker, and/or circadian and sleep-wake-dependent regulation of sleep were conducted. No evidence of circadian dysfunction was found in these individuals. Instead, sleep-wake timing appeared to dissociate from the circadian timing system, and/or self-selected sleep-wake and associated light/dark timing shifted the circadian pacemaker later, rather than the circadian pacemaker determining sleep-wake timing. These findings suggest that the etiology of this disorder may be light- and/or behaviorally induced in some sighted people, which has implications for the successful treatment of this disorder. Emens JS, St Hilaire MA, Klerman EB, etal. Behaviorally and environmentally induced non-24-hour sleep-wake rhythm disorder in sighted patients. J Clin Sleep Med. 2022;18(2):453-459.

Effects of Organic Light-Emitting Diodes on Circadian Rhythm and Sleep.

ObjectiveOrganic light-emitting diodes (OLEDs) emit less blue light than traditional light-emitting diodes (LEDs), and we previously found that early-night OLED light exposure (LE) delays the melatonin phase by less than LED at a color temperature of 4,000 K. As a follow-up study, we investigated the effects of OLED and LED at a different color temperature (3,000 K) on melatonin profile, sleep, and vigilance. Methods24 healthy subjects (27.5±5.1 years) were exposed to three light conditions [OLED, LED, and dim light (DL)] from 17:30 to 24:00, in a random order and with a 1-week interval. Saliva samples for melatonin were taken every hour from 18:00 to 24:00. Polysomnography (PSG) and a psychomotor vigilance test (PVT) were performed. ResultsMelatonin onset time was significantly delayed under OLED and LED compared with DL, with no significant difference between OLED and LED. The mean melatonin level at 24:00 under LED was lower than that under DL, but there was no significant difference between OLED LE and DL. The percentage of slow wave sleep (N3) in LED was significantly lower than in OLED. ConclusionExposure to light in the evening can suppress melatonin secretion late at night and disturb deep sleep, and those effects are slightly worse under LED than OLED.