Effect of monochromatic light on circadian rhythmic expression of clock genes and arylalkylamine N-acetyltransferase in chick retina

Green Light Mitigates Cyclic Chronic Heat-Stress-Induced Liver Oxidative Stress and Inflammation via NF-κB Pathway Inhibition in Geese

Heat stress (HS) induces various physiological disorders in poultry, negatively impacting feed intake, feed efficiency, and growth performance. Considering the documented anti-stress and growth-promoting benefits of monochromatic green light in poultry, we aimed to investigate its effects on cyclic chronic HS-induced oxidative stress (OS) and inflammation in geese. We established three treatment groups-geese exposed to white light (W), white light with HS treatment (WH), and green light with HS treatment (GH)-treated over a six-week period with daily HS sessions. The results revealed that cyclic chronic HS induced liver OS and inflammation, leading to hepatocellular injury and reduced growth performance and feed intake. In comparison, the growth performance of geese under green light significantly improved. Additionally, liver index, serum, liver malondialdehyde (MDA), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumour necrosis factor-α (TNF-α) levels were reduced. Serum total antioxidant capacity (T-AOC), liver catalase (CAT), and superoxide dismutase (SOD) activity were enhanced, reducing hepatic OS and inflammation. Liver transcriptomic analysis indicated that green light alleviates cyclic chronic HS-induced liver injury and promotes geese growth performance by suppressing NF-κB pathway activation.

One Health: Circadian Medicine Benefits Both Non-human Animals and Humans Alike

Circadian biology's impact on human physical health and its role in disease development and progression is widely recognized. The forefront of circadian rhythm research now focuses on translational applications to clinical medicine, aiming to enhance disease diagnosis, prognosis, and treatment responses. However, the field of circadian medicine has predominantly concentrated on human healthcare, neglecting its potential for transformative applications in veterinary medicine, thereby overlooking opportunities to improve non-human animal health and welfare. This review consists of three main sections. The first section focuses on the translational potential of circadian medicine into current industry practices of agricultural animals, with a particular emphasis on horses, broiler chickens, and laying hens. The second section delves into the potential applications of circadian medicine in small animal veterinary care, primarily focusing on our companion animals, namely dogs and cats. The final section explores emerging frontiers in circadian medicine, encompassing aquaculture, veterinary hospital care, and non-human animal welfare and concludes with the integration of One Health principles. In summary, circadian medicine represents a highly promising field of medicine that holds the potential to significantly enhance the clinical care and overall health of all animals, extending its impact beyond human healthcare.

Effects of different light-emitting diode light on hatch performance, embryo development, eye structure, and plasma melatonin in layer incubation

Light intensity, wavelength, and photoperiod have a combined effect on chicken incubation. This study was conducted to evaluate the effect of 12-h light, 12-h dark (12L:12D) photoperiod of white light (380-780 nm, WL), blue light (455/447.5-462.5 nm, BL), and green light (525/515-535 nm, GL) in chicken perceived light intensity during layer incubation on hatching performance, embryo development, eye structure, and melatonin concentration. Three batches of eggs from Jinghong No. 1 layer breeder were used in this experiment. Light stimulation had no effect on hatchability, and no consistent effect on embryo weight and newly hatched chick weight. However, the average hatching time of white light group and green light group was 7.3 h and 5.5 h later than that of the control group. Therefore, the holding period of chicks was significantly shortened (P = 0.001) in these 2 light groups. Light stimulation had a significant effect on the thickness of retinal layers (P < 0.05), retinal layers of white light group was thicker than that of the other 3 groups. Melatonin levels of chicks hatched in the green light and blue light were significantly higher than that of chicks hatched in the white light and darkness (P < 0.05). It indicated that the monochrome green and blue light promoted the expression of melatonin in chicken embryos. No significant diurnal rhythms were found at the level of plasma melatonin in 4 groups on d 21 using cosine analysis. It was concluded that green light has a positive effect on embryo development and melatonin secretion, while white light probably has positive effect on eye development. Furthermore, both green and white light stimulation resulted in late hatch for layer egg incubation. The obtained results are important in determining the light protocol for chicken incubation.

The impact of biological clock and sex hormones on the risk of disease

Molecular clocks are responsible for defining 24-h cycles of behaviour and physiology that are called circadian rhythms. Several structures and tissues are responsible for generating these circadian rhythms and are named circadian clocks. The suprachiasmatic nucleus of the hypothalamus is believed to be the master circadian clock receiving light input via the optic nerve and aligning internal rhythms with environmental cues. Studies using both in vivo and in vitro methodologies have reported the relationship between the molecular clock and sex hormones. The circadian system is directly responsible for controlling the synthesis of sex hormones and this synthesis varies according to the time of day and phase of the estrous cycle. Sex hormones also directly interact with the circadian system to regulate circadian gene expression, adjust biological processes, and even adjust their own synthesis. Several diseases have been linked with alterations in either the sex hormone background or the molecular clock. So, in this chapter we aim to summarize the current understanding of the relationship between the circadian system and sex hormones and their combined role in the onset of several related diseases.

Role of Melatonin in Daily Variations of Plasma Insulin Level and Pancreatic Clock Gene Expression in Chick Exposed to Monochromatic Light

To clarify the effect of monochromatic light on circadian rhythms of plasma insulin level and pancreatic clock gene expression and its mechanism, 216 newly hatched chicks were divided into three groups (intact, sham operation and pinealectomy) and were raised under white (WL), red (RL), green (GL) or blue (BL) light for 21 days. Their plasma and pancreas were sampled at six four-hour intervals. For circadian rhythm analysis, measurements of plasma melatonin, insulin, and clock gene expression (cClock, cBmal1, cBmal2, cCry1, cCry2, cPer2, and cPer3) were made. Plasma melatonin, insulin, and the pancreatic clock gene all expressed rhythmically in the presence of monochromatic light. Red light reduced the mesor and amplitude of plasma melatonin in comparison to green light. The mesor and amplitude of the pancreatic clock gene in chickens exposed to red light were dramatically reduced, which is consistent with the drop in plasma melatonin levels. Red light, on the other hand, clearly raised the level of plasma insulin via raising the expression of cVamp2, but not cInsulin. After the pineal gland was removed, the circadian expressions of plasma melatonin and pancreatic clock gene were significantly reduced, but the plasma insulin level and the pancreatic cVamp2 expression were obviously increased, resulting in the disappearance of differences in insulin level and cVamp2 expression in the monochromatic light groups. Therefore, we hypothesize that melatonin may be crucial in the effect of monochromatic light on the circadian rhythm of plasma insulin level by influencing the expression of clock gene in chicken pancreas.

Effect of artificial light at night on sleep and metabolism in weaver birds

Artificial light at night is constantly minimizing the span of dark nights from the natural light-dark cycle of earth. Over the past century, the "lightscape" of earth has completely changed owing to technological advancements which subsequently changed the lifestyle of human as well as the nearby animal species. This motivated the present study, wherein we investigated the impact of light at night (LAN) on behavior and physiology of a diurnal passerine finch, baya weaver (Ploceus philippinus). A group of bird (N=10) exposed to 12L:12D photoperiod was initially subjected to dark nights (0 lux) for a period of 1.5 weeks followed by 5 lux, night light for a span of 4 weeks. The first week in LAN served as acute treatment with respect to the fourth week (chronic). The results reveal significant increase in nighttime activity and sleep loss with respect to acute LAN, while significant inclusion of drowsiness behavior during the day in response to chronic LAN. Besides these behavioral alterations, changes in physiological parameters such as reduction in body mass, loss of gradient between pre- and post- prandial blood glucose levels, and elevation in plasma corticosterone levels were more prominent during acute exposure of LAN. Plasma metabolites such as triglycerides, total protein, serum glutamic-oxaloacetic transaminase (SGOT), and creatinine concentrations also hiked in response to acute LAN treatment. Thus, acute exposure of LAN seems to serve as a novel environment for the bird leading to more pronounced impacts on behavioral and physiological observations during the experiment. In chronic exposure, the birds sort of adapted themselves to the prevailing circumstances as evident by decreased nighttime activity, rebound of sleep and corticosterone levels, etc. Thus, the study clearly demonstrates the differential impact of acute and chronic exposure of LAN on behavior and physiology of birds.

Light regimen on health and growth of broilers: an update review

The importance of lighting regimen is increasing with the industrialization of poultry production, as lighting has been intimately associated with not only the establishment of rhythm and synchronous physiology of broiler chickens, but also the secretion of hormones associated with broiler maturation and growth. In recent years, increasing attention has been paid to the effects of lighting management on growth performance, immune status, and welfare of broilers. An appropriate lighting regimen, including proper source of lighting, intensity, duration, and wavelength (color) of light, is crucial to improve the growth performance and welfare of broilers. In this review, we updated the impacts of different light regimens on health and growth performance of broilers.

Light, Sleep and Performance in Diurnal Birds

Sleep has a multitude of benefits and is generally considered necessary for optimal performance. Disruption of sleep by extended photoperiods, moonlight and artificial light could therefore impair performance in humans and non-human animals alike. Here, we review the evidence for effects of light on sleep and subsequent performance in birds. There is accumulating evidence that exposure to natural and artificial sources of light regulates and suppresses sleep in diurnal birds. Sleep also benefits avian cognitive performance, including during early development. Nevertheless, multiple studies suggest that light can prolong wakefulness in birds without impairing performance. Although there is still limited research on this topic, these results raise intriguing questions about the adaptive value of sleep. Further research into the links between light, sleep and performance, including the underlying mechanisms and consequences for fitness, could shed new light on sleep evolution and urban ecology.

The Influence of Melatonin and Light on VEGF Secretion in Primary RPE Cells

(1) Background: Retinal pigment epithelial cells (RPE) cells constitutively secrete vascular endothelial growth factor (VEGF) in the retina, protecting the neuronal cells and the choroid. Increased VEGF secretion, however, can result in neovascularization and edema. Many factors regulate VEGF secretion. In this study, we investigated the effect of external stimuli in relation to diurnal rhythm on constitutive VEGF secretion. (2) Methods: Single-eye RPE cell culture was prepared from porcine eyes. RPE cells were cultured in darkness, treated with daylight or room light, and treated with melatonin at different time frames, either respectively or in combination. Supernatants were collected and VEGF content evaluated using ELISA. Expression of the clock protein BMAL1 was evaluated with Western blot. (3) Results: VEGF secretion of the RPE shows a diurnal rhythm. While the rhythm is not influenced by either light or melatonin, the amount of secreted VEGF can be increased by nocturnal melatonin, especially in combination with morning daylight. These findings disclose another layer of VEGF regulation in the retina.

The in vitro effects of melatonin and Cry gene on the secretion of estradiol from camel ovarian granulosa cells

Bactrian camel as endemic economic species to the Northwest of China, its seasonal reproduction severely limits litter rates. In addition to melatonin, seasonal reproduction of animals is also regulated by the biological clock, but the specific molecular mechanism is not clear. To investigate the effects of melatonin and Cryptochrome (Cry) genes on seasonal reproduction, they were placed in ovarian granulosa cells, and their effects on reproduction were determined by measuring the concentrations of estradiol. Immunohistochemistry revealed that melatonin receptor protein (MT) was expressed in the cytosol and membrane of the ovarian granulosa cells, and the highest levels of CRY were expressed in the nuclei. The concentrations of estradiol in the cell culture supernatant were increased after the addition of exogenous melatonin or overexpression of MT, but these were decreased after MT was over expressed, and exogenous melatonin was added to the cells. In addition, there was a significant increase in the concentrations of estradiol after the Cry genes were overexpressed; however, the estradiol concentrations were decreased after the Cry genes were silenced. Our findings demonstrate that the MT and Cry genes play important roles in ovarian granulosa cell production of estradiol in a seasonally breeding species.

Role of BMAL1 and CLOCK in regulating the secretion of melatonin in chick retina under monochromatic green light

As the circadian pacemaker of birds, the retina possesses the ability to receive light information, generate circadian oscillation, and secrete melatonin. Previous studies have confirmed that monochromatic green light can accelerate the circadian rhythmic expression of clock genes in the chick retina, thereby increasing cAanat mRNA level and melatonin secretion. However, as the core components of the transcriptional-translational negative feedback loop, the role that cBmal1 and cClock plays in the regulation of the retinal molecular clock system and melatonin secretion under monochromatic green light is unknown. To explore their in these processes, embryonic chick retinal cells at six embryo ages were isolated and cultured under light-dark (LD) 12:12 monochromatic green light with, and the role of cBmal1 and cClock in the regulation of the retinal molecular clock and melatonin secretion in the chick retina was explored by siRNA interference and overexpression. The results showed siRNA interference and overexpression of cBmal1 obliterated the circadian rhythm of cCry1, cPer2, cPer3, cAanat, and melatonin secretion. Moreover, the siRNA interference of cBmal1 significantly reduced the average expression levels of the positive clock genes cBmal2 and cClock, positive clock protein CLOCK, negative clock genes cCry1, cCry2, cPer2, cPer3, as well as cAanat and retinal melatonin. The over-expression of cBmal1 increased the average levels of the above-detected targets. However, siRNA interference and overexpression of cClock did not change the rhythm of all of the clock genes, clock proteins, cAanat, and melatonin secretion, while it only affected the circadian mesors (24 h time series means), amplitudes, and acrophases (peak times) of cCry1, cPer2, cPer3, cAanat, and melatonin, as well as the average levels of arrhythmic cBmal2 and cCry2. Moreover, interference and overexpression of cClock did not affect cBmal1 mRNA level and BMAL1 protein expression. The above results reveal interference and overexpression of cBmal1 completely abolished the molecular circadian oscillation and the rhythm of melatonin output signal of chick retinal cells, indicating that cBmal1 is on the top of the avian retinal molecular clock feedback loop and regulates the downstream molecular clock oscillation and output under monochromatic green light. cClock plays a subordinate role in maintaining the circadian oscillation of the molecular clock and melatonin secretion in retinal cells, and it has a stabilizing and amplifying effect on molecular clock oscillation.

Visual Image Quality Impacts Circadian Rhythm-Related Gene Expression in Retina and in Choroid: A Potential Mechanism for Ametropias

Purpose

Stimulated by evidence implicating diurnal/circadian rhythms and light in refractive development, we studied the expression over 24 hours of selected clock and circadian rhythm-related genes in retina/retinal pigment epithelium (RPE) and choroid of experimental ametropias in chicks.

Methods

Newly hatched chicks, entrained to a 12-hour light/dark cycle for 12 to 14 days, either experienced nonrestricted vision OU (i.e., in both eyes) or received an image-blurring diffuser or a minus 10-diopter (D) or a plus 10-D defocusing lens over one eye. Starting 1 day later and at 4-hour intervals for 24 hours, the retina/RPE and choroid were separately dissected. Without pooling, total RNA was extracted, converted to cDNA, and assayed by quantitative PCR for the expression of the following genes: Opn4m, Clock, Npas2, Per3, Cry1, Arntl, and Mtnr1a.

Results

The expression of each gene in retina/RPE and in choroid of eyes with nonrestricted vision OU varied over 24 hours, with equal levels OU for most genes and times. Altered visual input influenced gene expression in complex patterns that varied by gene, visual input, time, and eye, affecting experimental eyes with altered vision and also contralateral eyes with nonrestricted vision.

Discussion

Altering visual input in ways known to induce ametropias alters the retinal/RPE and choroidal expression of circadian rhythm-related genes, further linking circadian biology with eye growth regulation. While further investigations are needed, studying circadian processes may help understand refractive mechanisms and the increasing myopia prevalence in contemporary societies where lighting patterns can desynchronize endogenous rhythms from the natural environmental light/dark cycle.

Effect of monochromatic light on the temporal expression of N-acetyltransferase in chick pineal gland

The avian pineal gland is an independent molecular oscillator that receives external light information that regulates the synthesis and secretion of melatonin. Arylalkylamine N-acetyltransferase plays an important role in the pineal gland by controlling the rhythmic production of melatonin. Previous study showed that monochromatic light influences the secretion of melatonin, which is regulated by the molecular circadian clock genes in chick pineal gland. This study was designed to investigate the effect of monochromatic light on the circadian rhythm of levels of cAanat, clock protein (CLOCK and BMAL1), cCreb, and opsins (cOpnp, Pinopsin; cOpn4-1, Melanopsin-1; cOpn4-2, Melanopsin-2) in chick pineal gland. A total of 240 post-hatching day (P) 0 broiler chickens were reared under white (WL), red (RL), green (GL), and blue light (BL) with light (L)-dark (D) cycle of 12L:12D for 14 d. The results show significant circadian rhythms in the expression of cAanat, CLOCK, BMAL1, cCreb, cOpnp, cOpn4-1, and cOpn4-2, but not for cOpnp under RL. Compared with WL, GL increased the level of cAanat mRNA, while RL decreased it. Meanwhile, CLOCK and BMAL1 proteins were expressed at high levels in GL. Furthermore, the peak of the 24 h pattern of cOpnp mRNA in GL was earlier than that of in WL, RL, and BL. These results demonstrated that monochromatic light affects the daily expression of cAanat in the chick pineal gland via the biological clock. GL activates the transcription of cAanat, while RL suppresses the transcription of cAanat. Meanwhile, GL appears to induce the peak of cOpnp mRNA in advance to affect the transmission of light. Thus, monochromatic light regulates cAanat in the chick pineal gland by affecting the levels of clock regulators via entraining the expression of pineal gland opsins.

Effect of monochromatic light on the circadian clock of cultured chick retinal tissue

The central biological clock system of bird is formed by hypothalamus suprachiasmatic nucleus, pineal gland and retina thereby interacting with each other in a neuroendocrine loop. Previous results have confirmed that monochromatic light can influence the clock genes in the pineal gland, hypothalamus and retina of chicks in vivo. The present work was conducted to study whether the cultured retinal tissue of chick could maintain the circadian oscillation and whether the monochromatic light affect the expression level of cultured retinal circadian clock in vitro. Retinal tissues of 0-day-old chicks were cultured in vitro under 4 light treatments (white, red, green and blue lights) with light dark cycle 12:12 and constant dark. The tissues and culture medium were collected every each 4 h. Melanopsin, clock genes, cAanat, the positive-regulating clock proteins and melatonin were measured. The results showed that cOpn4-1, cOpn4-2, cBmal1, cCry1, cPer2, cPer3, cAanat and melatonin concentrations possessed a significant circadian rhythm in cultured chick retina tissues under different monochromatic lights; while, in constant dark, cBmal1, cCry1, cPer2, cPer3, cAanat and melatonin concentration possessed a significant circadian rhythm. Green light promoted the circadian expression level of cOpn4-1, cOpn4-2, cBmal1, cAanat and BMAL1 proteins and the circadian rhythm of melatonin secretion of retina by increasing the mesors and amplitudes. In addition, green light significantly increased the average expression levels of cClock, cBmal2 and CLOCK proteins which were expressed arrhythmically. Results suggested that the retina is a central oscillator with autonomous circadian rhythm. In isolated retina tissues, green light activated the expression of melanopsin and promoted the expression of positive-regulating clock genes, thereby up-regulating the expression of cAanat and resulting the increasing of the synthesis and secretion of melatonin.

Effect of melatonin on monochromatic light-induced changes in clock gene circadian expression in the chick liver

Light is the most prominent zeitgeber of the circadian system, which contains central and peripheral oscillators. Our previous studies found that light wavelength could influence the rhythms of melatonin synthesis and clock gene expression in the central oscillator of chicks. However, the effect of monochromatic light on the peripheral oscillator and the role of melatonin have yet to be clarified. In this study, 216 newly hatched chicks were divided into three groups (intact, sham operation and pinealectomy) and were raised under white (WL), red (RL), green (GL) or blue (BL) light for 14 days. Their plasma and livers were sampled at 6 time points with 4-h intervals. Plasma melatonin concentration and liver clock gene expression (cClock, cBmal1, cBmal2, cCry1, cCry2, cPer2, cPer3) were measured for circadian rhythm analysis. In intact and sham operation chicks under WL, all liver clock genes showed circadian expression along with oscillations in plasma melatonin. However, positive clock genes peaked at subjective night along with melatonin, while negative clock genes peaked at subjective day or the shifting time of day-night. Chick exposure to monochromatic light led to an unaltered circadian rhythmicity in plasma melatonin and liver clock genes; however, their rhythmic parameters were notably influenced. Compared to WL, GL enhanced the mesor and amplitude of melatonin and all kinds of clock genes, whereas RL had the opposite effect. Pinealectomy significantly decreased expression of liver clock genes, which was consistent with the reduction in plasma melatonin concentration, especially for the GL group, and resulted in the expression of liver clock genes showing low-mesor and low-amplitude oscillations as well as no statistically significant differences among the monochromatic light groups. Thus, we speculated that melatonin plays a key role in the effects of light wavelength on clock gene rhythm in the chick liver.

Effect of pinealectomy on the circadian clock of the chick retina under different monochromatic lights

The avian circadian rhythm pacemaker is composed of the retina, pineal gland and suprachiasmatic nucleus. As an intact input-pacemaker-output system, each of these structures is linked within a neuroendocrine loop to influence downstream processes and peripheral oscillations. While our previous study found that monochromatic light affected the circadian rhythms of clock genes in the chick retina, the effect of the pineal gland on the response of the retinal circadian clock under monochromatic light still remains unclear. In this study, a total of 144 chicks, including sham-operated and pinealectomized groups, were exposed to white, red, green or blue light. After 2 weeks of light illumination, the circadian expression of six core clock genes (cClock, cBmal1, cCry1, cCry2, cPer2 and cPer3), melanopsin (cOpn4-1, cOpn4-2), Arylalkylamine N-acetyltransferase (cAanat) and melatonin was examined in the retina. The cBmal1, cCry1, cPer2, cPer3, cOpn4-1, cOpn4-2 and cAanat genes as well as melatonin had circadian rhythmic expression in both the sham-operated and pinealectomized groups under different monochromatic lights, while cClock and cCry2 had arrhythmic 24 h profiles in all of the light-treated groups. After pinealectomy, the rhythmicity of the clock genes, melanopsins, cAanat and melatonin in the chick retina did not change, especially the mesors, amplitudes and phases of cBmal1, cOpn4-1, cOpn4-2, cAanat and melatonin. Compared to the white light group, however, green light increased the mRNA expression of the positive-regulating clock genes cBmal1, cAanat, cOpn4-1 and cOpn4-2 as well as the melatonin content in pinealectomized chicks, whereas red light decreased their expression. These results suggest that the chick retina is a relatively independent circadian oscillator from the pineal gland, whose circadian rhythmicity (including photoreception, molecular clock and melatonin output) is not altered after pinealectomization. Moreover, green light increases ocular cAanat expression and melatonin synthesis by accelerating the expression of melanopsin and positive-regulating clock genes cBmal1 and cClock.

BMAL1 but not CLOCK is associated with monochromatic green light-induced circadian rhythm of melatonin in chick pinealocytes

The avian pineal gland, an independent circadian oscillator, receives external photic cues and translates them for the rhythmical synthesis of melatonin. Our previous study found that monochromatic green light could increase the secretion of melatonin and expression of CLOCK and BMAL1 in chick pinealocytes. This study further investigated the role of BMAL1 and CLOCK in monochromatic green light-induced melatonin secretion in chick pinealocytes using siRNAs interference and overexpression techniques. The results showed that si-BMAL1 destroyed the circadian rhythms of AANAT and melatonin, along with the disruption of the expression of all the seven clock genes, except CRY1. Furthermore, overexpression of BMAL1 also disturbed the circadian rhythms of AANAT and melatonin, in addition to causing arrhythmic expression of BMAL1 and CRY1/2, but had no effect on the circadian rhythms of CLOCK, BMAL2 and PER2/3. The knockdown or overexpression of CLOCK had no impact on the circadian rhythms of AANAT, melatonin, BMAL1 and PER2, but it significantly deregulated the circadian rhythms of CLOCK, BMAL2, CRY1/2 and PER3. These results suggested that BMAL1 rather than CLOCK plays a critical role in the regulation of monochromatic green light-induced melatonin rhythm synthesis in chicken pinealocytes. Moreover, both knockdown and overexpression of BMAL1 could change the expression levels of CRY2, it indicated CRY2 may be involved in the BMAL1 pathway by modulating the circadian rhythms of AANAT and melatonin.

Effect of Monochromatic Light on Circadian Rhythm of Clock Genes in Chick Pinealocytes

The avian circadian system is a complex of mutually coupled pacemakers residing in pineal gland, retina and suprachiasmatic nucleus. In this study, the self-regulation mechanism of pineal circadian rhythm was investigated by culturing chick primary pinealocytes exposed to red light (RL), green light (GL), blue light (BL), white light (WL) and constant darkness (DD), respectively. All illuminations were set up with a photoperiod of 12 light: 12 dark. The 24-h expression profiles of seven core clock genes (cBmal1/2, cClock, cCry1/2 and cPer2/3), cAanat and melatonin showed significant circadian oscillation in all groups, except for the loss of cCry1 rhythm in BL. Compared to WL, GL increased the amplitudes and mesors of positive elements (cClock and cBmal1/2) and reduced those of negative elements (cCry1/2 and cPer2/3), in contrast to RL. The temporal patterns of cAanatmRNA and melatonin secretion have always been consistent with the positive genes. Besides, GL advanced the acrophases of the positive elements, cAanat and melatonin, but RL and BL showed the opposite effect. Thereby, GL could promote the secretion of melatonin by enhancing the expressions of positive clock genes and repressing the expressions of negative clock genes.