Circadian rhythm dysfunction in glaucoma: A hypothesis

Parental and Child Sleep: Children with Vision Impairment, Autistic Children, and Children with Comorbid Vision Impairment and Autism

BACKGROUND

Parents report associations between children's sleep disturbances and behaviors. Children with neurodevelopmental conditions (e.g., Williams Syndrome and autism) are consistently reported to experience increased sleeping problems. Sleep in children with vision impairment and children with a dual diagnosis of vision impairment and autism remains understudied.

METHODS

Our exploratory study compared sleep profiles in 52 children (aged 4-12 years) and their parents (n = 37), across four groups: children with vision impairment (VI; n = 9), autism (n = 10), comorbid vision impairment + autism (n = 6), and typically developing children (n = 27). Childhood sleep was measured using the parental report Childhood Sleep Habits Questionnaire and sleep diaries. Children's cognitive functioning was measured using digit span, semantic, and phonemic verbal fluency measures. Parental sleep was measured via the Pittsburgh Sleep Quality Index and Epworth Sleepiness Scale.

RESULTS

Clinically disordered sleep was reported in all child groups (p ≤ 0.001), particularly children with VI + autism. Age, not sleep quality/quantity, predicted cognitive task performance in TD and autistic groups, but not in VI and VI + autism groups. The child's diagnosis affected parental sleep, particularly in children with a dual diagnosis of VI + autism.

CONCLUSIONS

All participants experienced problematic sleep to varying degrees. Those most affected were children and parents in the VI + autism group, suggesting that autism may be the main driver of sleep problems in our sample.

Preservation of Intrinsically Photosensitive Retinal Ganglion Cells (ipRGCs) in Late Adult Mice: Implications as a Potential Biomarker for Early Onset Ocular Degenerative Diseases

Purpose

Intrinsically photosensitive retinal ganglion cells (ipRGCs) play a crucial role in non-image-forming visual functions. Given their significant loss observed in various ocular degenerative diseases at early stages, this study aimed to assess changes in both the morphology and associated behavioral functions of ipRGCs in mice between 6 (mature) and 12 (late adult) months old. The findings contribute to understanding the preservation of ipRGCs in late adults and their potential as a biomarker for early ocular degenerative diseases.

Methods

Female and male C57BL/6J mice were used to assess the behavioral consequences of aging to mature and old adults, including pupillary light reflex, light aversion, visual acuity, and contrast sensitivity. Immunohistochemistry on retinal wholemounts from these mice was then conducted to evaluate ipRGC dendritic morphology in the ganglion cell layer (GCL) and inner nuclear layer (INL).

Results

Morphological analysis showed that ipRGC dendritic field complexity was remarkably stable through 12 months old of age. Similarly, the pupillary light reflex, visual acuity, and contrast sensitivity were stable in mature and old adults. Although alterations were observed in ipRGC-independent light aversion distinct from the pupillary light reflex, aged wild-type mice continuously showed enhanced light aversion with dilation. No effect of sex was observed in any tests.

Conclusions

The preservation of both ipRGC morphology and function highlights the potential of ipRGC-mediated function as a valuable biomarker for ocular diseases characterized by early ipRGC loss. The consistent stability of ipRGCs in mature and old adult mice suggests that detected changes in ipRGC-mediated functions could serve as early indicators or diagnostic tools for early-onset conditions such as Alzheimer's disease, Parkinson's disease, and diabetes, where ipRGC loss has been documented.

Towards improving the prognosis of stroke through targeting the circadian clock system

Rhythmicity of the circadian system is a 24-hour period, driven by transcription-translation feedback loops of circadian clock genes. The central circadian pacemaker in mammals is located in the hypothalamic suprachiasmatic nucleus (SCN), which controls peripheral circadian clocks. In general, most physiological processes are regulated by the circadian system, which is modulated by environmental cues such as exposure to light and/or dark, temperature, and the timing of sleep/wake and food intake. The chronic circadian disruption caused by shift work, jetlag, and/or irregular sleep-wake cycles has long-term health consequences. Its dysregulation contributes to the risk of psychiatric disorders, sleep abnormalities, hypothyroidism and hyperthyroidism, cancer, and obesity. A number of neurological conditions may be worsened by changes in the circadian clock via the SCN pacemaker. For stroke, different physiological activities such as sleep/wake cycles are disrupted due to alterations in circadian rhythms. Moreover, the immunological processes that affect the evolution and recovery processes of stroke are regulated by the circadian clock or core-clock genes. Thus, disrupted circadian rhythms may increase the severity and consequences of stroke, while readjustment of circadian clock machinery may accelerate recovery from stroke. In this manuscript, we discuss the relationship between stroke and circadian rhythms, particularly on stroke development and its recovery process. We focus on immunological and/or molecular processes linking stroke and the circadian system and suggest the circadian rhythm as a target for designing effective therapeutic strategies in stroke.

AUTOPHAGY IN THE EYE: FROM PHYSIOLOGY TO PATHOPHYSOLOGY

Autophagy is a catabolic self-degradative pathway that promotes the degradation and recycling of intracellular material through the lysosomal compartment. Although first believed to function in conditions of nutritional stress, autophagy is emerging as a critical cellular pathway, involved in a variety of physiological and pathophysiological processes. Autophagy dysregulation is associated with an increasing number of diseases, including ocular diseases. On one hand, mutations in autophagy-related genes have been linked to cataracts, glaucoma, and corneal dystrophy; on the other hand, alterations in autophagy and lysosomal pathways are a common finding in essentially all diseases of the eye. Moreover, LC3-associated phagocytosis, a form of non-canonical autophagy, is critical in promoting visual cycle function. This review collects the latest understanding of autophagy in the context of the eye. We will review and discuss the respective roles of autophagy in the physiology and/or pathophysiology of each of the ocular tissues, its diurnal/circadian variation, as well as its involvement in diseases of the eye.

Structural Basis for Agonistic Activity and Selectivity toward Melatonin Receptors hMT1 and hMT2

Glaucoma, a major ocular neuropathy originating from a progressive degeneration of retinal ganglion cells, is often associated with increased intraocular pressure (IOP). Daily IOP fluctuations are physiologically influenced by the antioxidant and signaling activities of melatonin. This endogenous modulator has limited employment in treating altered IOP disorders due to its low stability and bioavailability. The search for low-toxic compounds as potential melatonin agonists with higher stability and bioavailability than melatonin itself could start only from knowing the molecular basis of melatonergic activity. Thus, using a computational approach, we studied the melatonin binding toward its natural macromolecular targets, namely melatonin receptors 1 (MT1) and 2 (MT2), both involved in IOP signaling regulation. Besides, agomelatine, a melatonin-derivative agonist and, at the same time, an atypical antidepressant, was also included in the study due to its powerful IOP-lowering effects. For both ligands, we evaluated both stability and ligand positioning inside the orthosteric site of MTs, mapping the main molecular interactions responsible for receptor activation. Affinity values in terms of free binding energy (ΔG_bind) were calculated for the selected poses of the chosen compounds after stabilization through a dynamic molecular docking protocol. The results were compared with experimental in vivo effects, showing a higher potency and more durable effect for agomelatine with respect to melatonin, which could be ascribed both to its higher affinity for hMT2 and to its additional activity as an antagonist for the serotonin receptor 5-HT2c, in agreement with the in silico results.

Indoor lighting design for healthier workplaces: natural and electric light assessment for suitable circadian stimulus

Light, especially daylight, plays a critical role in human health as the main timer for circadian rhythms. Indoor environments usually lack the correct exposure to daylight and are highly dependent on electric lighting, disrupting the circadian rhythm and compromising the health of occupants. The methodology proposed assesses the combination of natural and electric lighting on circadian rhythms for operational environments. The case study chosen examines a 24/7 laboratory area representing an open-plan shift-work area. Several electric lighting scenarios under different sky conditions have been assessed, considering a variable window size and resulting in a spectrum which establishes the indoor circadian regulation performance according to the amount of light perceived. A set of configurations is presented to determine optimal electric lighting configuration based on natural light conditions in order to ensure a suitable circadian stimulus and the electric lighting flux threshold for different scenarios, benefiting occupants' health while also ensuring energy conservation.

Melatonin mitigates disrupted circadian rhythms, lowers intraocular pressure, and improves retinal ganglion cells function in glaucoma

Glaucoma is a progressive optic neuropathy associated with damage to retinal ganglion cells (RGCs) and disrupted circadian rhythms. Melatonin is a promising substance to ameliorate glaucoma-associated compromised circadian rhythms, sleep, mood, and retinal cells function. However, studies estimating melatonin effects in glaucoma are currently lacking. Therefore, In this study, we investigated the effect of long-term (daily at 10:30 pm for 90 days) oral melatonin administration on systemic (Tb) and local to the organ of vision (IOP) circadian rhythms, pattern electroretinogram (PERG), sleep, and mood, depending on glaucoma stage in patients diagnosed with stable or advanced primary open-angle glaucoma. In a laboratory study in 15 of them, 24-hour records of salivary melatonin were obtained and MTNR1B receptor gene polymorphism was assessed. Melatonin increased the stability of the Tb circadian rhythm by improving its phase alignment and alignment with IOP. Melatonin time-dependently decreased IOP and IOP standard deviation (SD). IOP 24-hour mean and IOP SD decreases were more pronounced in individuals with the higher initial 24-hour IOP mean. Melatonin improved RGCs function in advanced glaucoma; N95 amplitude increase correlated positively with RGCs loss. The beneficial effects of melatonin on sleep and mood were greater in advanced glaucoma. Finally, delayed salivary melatonin and Tb phases were observed in MTNR1B G-allele carriers with advanced glaucoma. Combined, these results provide evidence for melatonin efficiency in restoring disrupted circadian rhythms in glaucoma with different effects of melatonin on systemic vs. local circadian rhythms, indicating that a personalized strategy of melatonin administration may further refine its treatment benefits.

Lights Out: Examining Sleep in Children with Vision Impairment

Sleep is crucial for development across cognitive, physical, and social-emotional domains. Sleep quality and quantity impact domains of daytime functioning, attainment, and global development. Previous work has explored sleep profiles in typically developing children and children with developmental disorders such as Down syndrome and Williams Syndrome, yet there is a complete absence of published work regarding the sleep profiles of children with vision impairment aged 4–11 years. This is the first known study that examines the sleep profiles in children with vision impairment (n = 58) in comparison to 58 typically developing children (aged 4–11 years) in the UK. Sleep was measured using the Childhood Sleep Habits Questionnaire (CSHQ; parental report), actigraphy and sleep diaries. Results showed group differences in subjective CSHQ scores but not objective actigraphy measures. Surprisingly, the findings revealed disordered sleep (namely, poor sleep quantity) in both groups. Discordance between CSHQ and actigraphy measures could represent heightened awareness of sleeping problems in parents/caregivers of children with vision impairment. The implications of this study extend beyond group comparison, examining disordered sleep in ‘typically developing’ children, exploring the potential role of light perception and the importance of sleep quality and quantity in both groups.

Influence of Circadian Rhythm in the Eye: Significance of Melatonin in Glaucoma

Circadian rhythm and the molecules involved in it, such as melanopsin and melatonin, play an important role in the eye to regulate the homeostasis and even to treat some ocular conditions. As a result, many ocular pathologies like dry eye, corneal wound healing, cataracts, myopia, retinal diseases, and glaucoma are affected by this cycle. This review will summarize the current scientific literature about the influence of circadian patterns on the eye, focusing on its relationship with increased intraocular pressure (IOP) fluctuations and glaucoma. Regarding treatments, two ways should be studied: the first one, to analyze if some treatments could improve their effect on the ocular disease when their posology is established in function of circadian patterns, and the second one, to evaluate new drugs to treat eye pathologies related to the circadian rhythm, as it has been stated with melatonin or its analogs, that not only could be used as the main treatment but as coadjutant, improving the circadian pattern or its antioxidant and antiangiogenic properties.

Disruption of 24-Hour Rhythm in Intraocular Pressure Correlates with Retinal Ganglion Cell Loss in Glaucoma

Parameters of 24-h rhythm in intraocular pressure (IOP) were assessed in patients with stable or advanced primary open-angle glaucoma (S-POAG/A-POAG) and referenced to the phase of “marker” circadian temperature rhythm of each patient. Body temperature and IOP were measured over a 72-h span in 115 participants (65 S-POAG and 50 A-POAG). Retinal Ganglion Cell (RGC) damage was assessed by high-definition optical coherence tomography. The 24-h IOP rhythm in A-POAG patients peaked during the night, opposite to the daytime phase position in S-POAG patients (p < 0.0001). The 24-h IOP phase correlated with RGC loss (p < 0.0001). The internal phase shift between IOP and body temperature gradually increased with POAG progression (p < 0.001). Angiotensin converting enzyme Alu-repeat deletion/insertion (ACE I/D) emerged as a candidate gene polymorphism, which may play a role in the alteration of the circadian IOP variability in advanced glaucoma. To conclude, a reliable estimation of the 24-h rhythm in IOP requires the degree of RGC damage to be assessed. In advanced POAG, the 24-h phase of IOP tended to occur during the night and correlated with RGC loss, being progressively delayed relative to the phase of temperature.

Recent advances in modulators of circadian rhythms: an update and perspective

Circadian rhythm is a universal life phenomenon that plays an important role in maintaining the multiple physiological functions and regulating the adaptability to internal and external environments of flora and fauna. Circadian alignment in humans has the greatest effect on human health, and circadian misalignment is closely associated with increased risk for metabolic syndrome, cardiovascular diseases, neurological diseases, immune diseases, cancer, sleep disorders, and ophthalmic diseases. The recent description of clock proteins and related post-modification targets was involved in several diseases, and numerous lines of evidence are emerging that small molecule modulators of circadian rhythms can be used to rectify circadian disorder. Herein, we attempt to update the disclosures about the modulators targeting core clock proteins and related post-modification targets, as well as the relationship between circadian rhythm disorders and human health as well as the therapeutic role and prospect of these small molecule modulators in circadian rhythm related disease.

Effects of primary glaucoma on sleep quality and daytime sleepiness of patients residing at an equatorial latitude

AIM

To investigate the impact of primary glaucoma on sleep quality and daytime sleepiness of patients.

METHODS

Prospective cross-sectional study with consecutive sampling in South-East Asian population was performed. Validated questionnaires: the Pittsburg Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS) were administered prospectively. Subjects with non-glaucomatous optic neuropathy or concomitant retinal pathology were excluded. Glaucoma severity was based on HVF 24-2 perimetry. Binocular single vision was represented based on the better eye. Frequency of and predictive factors for poor sleep quality and excessive daytime sleepiness were compared.

RESULTS

A total of 79 primary open angle glaucoma (POAG), 27 primary angle-closure glaucoma (PACG) patients, and 89 controls were recruited. PACG patients had higher median PSQI scores (P=0.004) and poorer sleep quality (P<0.001). Compared to controls, PACG patients were 3.34 times more likely to have poor sleep quality (P=0.008), which remained significant after adjustment for demographics (P=0.016) and predictive variables (P=0.013). PACG patients have poorer sleep quality when visual acuity (VA) was 6/15 or worse (P=0.009). Univariate and multivariate analysis of predictive variables for poor sleep quality and daytime sleepiness did not find statistical significance.

CONCLUSION

PACG patients have poorer sleep quality but not daytime sleepiness. This is important in South-East Asian population with heavy disease burden. Evaluations on sleep disturbances can be considered to provide more holistic care.

Circadian regulation in the retina: From molecules to network

The mammalian retina is the most unique tissue among those that display robust circadian/diurnal oscillations. The retina is not only a light sensing tissue that relays light information to the brain, it has its own circadian "system" independent from any influence from other circadian oscillators. While all retinal cells and retinal pigment epithelium (RPE) possess circadian oscillators, these oscillators integrate by means of neural synapses, electrical coupling (gap junctions), and released neurochemicals (such as dopamine, melatonin, adenosine, and ATP), so the whole retina functions as an integrated circadian system. Dysregulation of retinal clocks not only causes retinal or ocular diseases, it also impacts the circadian rhythm of the whole body, as the light information transmitted from the retina entrains the brain clock that governs the body circadian rhythms. In this review, how circadian oscillations in various retinal cells are integrated, and how retinal diseases affect daily rhythms.

Photosensitive Melanopsin-Containing Retinal Ganglion Cells in Health and Disease: Implications for Circadian Rhythms

Melanopsin-containing retinal ganglion cells (mRGCs) represent a third class of retinal photoreceptors involved in regulating the pupillary light reflex and circadian photoentrainment, among other things. The functional integrity of the circadian system and melanopsin cells is an essential component of well-being and health, being both impaired in aging and disease. Here we review evidence of melanopsin-expressing cell alterations in aging and neurodegenerative diseases and their correlation with the development of circadian rhythm disorders. In healthy humans, the average density of melanopsin-positive cells falls after age 70, accompanied by age-dependent atrophy of dendritic arborization. In addition to aging, inner and outer retinal diseases also involve progressive deterioration and loss of mRGCs that positively correlates with progressive alterations in circadian rhythms. Among others, mRGC number and plexus complexity are impaired in Parkinson's disease patients; changes that may explain sleep and circadian rhythm disorders in this pathology. The key role of mRGCs in circadian photoentrainment and their loss in age and disease endorse the importance of eye care, even if vision is lost, to preserve melanopsin ganglion cells and their essential functions in the maintenance of an adequate quality of life.

Chronotyping glaucoma patients with the Munich ChronoType Questionnaire: A case-control study

Purpose

The circadian clock is entrained to light by the intrinsically photosensitive retinal ganglion cells. Loss of these cells in glaucoma, an eye disease with loss of retinal ganglion cells as its key feature, might thus result in a change in chronotype. We aimed to compare the chronotype between glaucoma patients and healthy subjects.

Methods

We sent the Munich ChronoType Questionnaire to 221 glaucoma patients (response rate 81%); controls (primary control group) were primarily their spouses. After exclusion of shift workers and participants who woke-up due to an alarm clock on days off, 159 glaucoma patients (88 early, 21 moderate, 23 severe) and 163 controls remained. We calculated chronotype as the mid-sleep on days off, corrected for workweek accumulated sleep debt (MSF_sc). We compared means and variances between groups using Welch’s tests and F-tests, respectively. A secondary control group was recruited from participants in a citizen-science project (n = 17073) who completed an online questionnaire. A resampling method was applied to enable an age- and gender- matched comparison with the glaucoma patients.

Results

Compared to the primary control group, glaucoma did not affect the mean MSF_sc (controls 3:47; early, moderate, and severe glaucoma 3:40, 3:45, and 3:33, respectively [P = 0.62]). Chronotype variability seemed to increase with increasing disease severity (severe glaucoma versus controls: P = 0.023). The mean MSF_sc of the secondary control group was 3:50 (95% confidence interval 3:48 to 3:52); significantly later than that of the glaucoma patients (3:40; P = 0.024). Mean MSF_sc did not differ significantly between the control groups (P = 0.42).

Conclusions

No clear changes were found in the chronotype as determined by sleep phase in patients with glaucoma, especially not in early and moderate glaucoma. In severe glaucoma, chronotype variability seems to increase, possibly alongside a small advancement.

Progressive retinal ganglion cell loss in primary open-angle glaucoma is associated with temperature circadian rhythm phase delay and compromised sleep

Advanced primary open-angle glaucoma (POAG) is characterized by progressive retinal ganglion cell complex (RGCC) damage that may cause subsequent disruption of the circadian rhythms. Therefore, we evaluated circadian body temperature (BT) rhythm and sleep characteristics of 115 individuals (38 men and 77 women) diagnosed with POAG. GLV (global loss volume; %), a measure of RGCC damage, was estimated by high-definition optical coherence tomography, and RGC functional ability was assessed by pattern electroretinogram amplitude (PERGA). Depending on dynamics of POAG progression criteria, two groups were formed that were distinctively different in GLV: Stable POAG group (S-POAG; GLV = 5.95 ± 1.84, n = 65) and Progressive POAG group (P-POAG; GLV = 24.27 ± 5.09, n = 50). S-POAG and P-POAG groups were not different in mean age (67.61 ± 7.56 versus 69.98 ± 8.15) or body mass index (24.66 ± 3.03 versus 24.77 ± 2.90). All subjects performed 21 around-the-clock BT self-measurements during a 72-h period and kept activity/sleep diaries. Results showed pronounced disruption of circadian physiology in POAG and its progression with increasing severity of the disease. The daily mean of BT was unusually low, compared to age-matched controls. Moreover, our results revealed distinctive features of BT circadian rhythm alterations in POAG development and POAG progression. S-POAG is associated with lowered BT circadian rhythm robustness and inter-daily phase stability compared to controls. In the P-POAG group, the mean phase of the circadian BT rhythm was delayed by about 5 h and phases were highly scattered among individual patients, which led to reduced group mean amplitude. Circadian amplitudes of individuals were not different between the groups. Altogether, these results suggest that the body clock still works in POAG patients, but its entrainment to the 24-h environment is compromised. Probably because of the internal desynchronization, bedtime is delayed, and sleep duration is accordingly shortened by about 55 min in P-POAG compared to S-POAG patients. In the entire POAG cohort (both groups), later sleep phase and shorter mean sleep duration correlate with the delayed BT phase (r = 0.215; p = 0.021 and r = 0.322; p = 0.0004, respectively). An RGCC GLV of 15% apparently constitutes a threshold above which a delay of the circadian BT rhythm and a shortening of sleep duration occur.

Melatonin concentrations in serum of primary glaucoma patients

AIM

To determine whether glaucoma patients exhibit an abnormal melatonin concentration in serum and the effects of psychiatric disorders caused by glaucoma in melatonin secretion.

METHODS

A sample of 80 primary angle-closure glaucoma (PACG) patients, 120 primary open angle glaucoma (POAG) patients, and 120 normal controls were enrolled in this study. All the participants were asked to complete the following questionnaires: Pittsburgh sleep quality index (PSQI), self-rating anxiety scale (SAS), and self-rating depression scale (SDS). Variance analysis was used to compare the subscores between the groups. After that, we chose 58 patients with primary glaucoma and 20 non-glaucoma control patients to collect their serum samples at 7-10 a.m. Serum melatonin levels were measured using enzyme linked immunosorbent assay (ELISA).

RESULTS

Of all participants, the scores of PSQI, SAS, and SDS in PACG and POAG group were 9.38±0.40, 46.08±8.99, 51.11±10.72 and 7.43±0.35, 45.42±9.87, 49.04±12.24 respectively, significantly higher than those in control group (4.16±0.28, 35.49±9.18, 40.31±13.08). The serum melatonin levels in PACG (37.29±2.99 pg/mL) and POAG (35.97±3.64 pg/mL) were significantly higher than the controls (29.96±3.94 pg/mL) (P<0.001). But no difference was found between the PACG and POAG (P=0.216). Glaucoma patients with sleep disorders, anxiety and depression were more likely resulting in the increase of melatonin levels.

CONCLUSION

There is a significant increase in serum melatonin levels in glaucoma patients compared to the controls especially in glaucoma patients with psychiatric disorders such as sleep disorders, anxiety and depression.

A nonparametric methodological analysis of rest-activity rhythm in type 2 diabetes

The purpose of this study was to analyze the rest-activity rhythm of type 2 diabetics mellitus (T2DM) and compare it to healthy controls using the nonparametric analytic approach. Twenty-one diabetics and 21 healthy subjects matched for gender and age were recruited to participate in the study. Data were analyzed using the Independent t-test, Mann-Whitney U test, and Spearmans correlation. T2DM subjects demonstrate lower interdaily stability (IS) (p=.03), higher intradaily variability (p=.046) and lower rhythm amplitude (p=.02) when compared to healthy controls. Also, there was a positive correlation between IS and most active 10 hr (M10) in the average of 24 hours pattern (r =.44; p=.046) in the diabetes group and a negative correlation between IV and M10 in the healthy group (r =-.57; p=.007). These data together suggest that T2DM exhibits a dysfunction in the rest-activity rhythm due to alterations in the circadian function as well as in the homeostatic capacity to maintain sleep; mainly characterized by less consistency across days of the daily circadian signal, higher rhythm fragmentation and lower rhythm amplitude. Future approaches may be developed considering the influence of circadian glucose variations throughout the day on the coupling of the rest-activity rhythm to zeitgeber and rhythm fragmentation.

Effect of Circadian Rhythm Disruption and Alcohol on the Oxidative Stress Level in Rat Brain

Alcohol abuse is often associated with disrupted circadian rhythms and sleep, and the link seems to be bidirectional. In addition, it has been shown that exposure to constant illumination may increase lipid peroxidation in tissues. In this study, we investigated the effects of circadian rhythm disruption (CRD) and chronic alcohol intake (A) alone and in combination (CRD+A), on the oxidative stress in total rat brain homogenate. Our results demonstrated that lipid peroxidation was increased in the brain samples of all experimental animals compared with the control ones. The oxidative stress levels increased in the order: C<CRD<A<(CRD+A). Furthermore, xanthine oxidase activity changed in the order: C<CRD<A=CRD+A. It was proposed that chronic alcohol intake, if accompanied with CRD, might lead to significantly higher lipid peroxidation in the brain, than if present alone. Our data suggest that ethanol metabolites may be involved in the increase of the brain xanthine oxidase activity in rats with chronic alcohol intake.

Associations of sleep duration with open angle glaucoma in the Korea national health and nutrition examination survey

The aim of this study is to investigate the relationship between sleep duration and glaucoma, stratified by obesity status.This study was conducted using data from the Korean National Health and Nutrition Examination Survey V 2010 to 2012. Open-angle glaucoma was diagnosed according to the International Society of Geographical and Epidemiological Ophthalmology criteria. Subjects were divided into subgroups based on those who were overweight (body mass index ≥25 kg/m or <25 kg/m) or with abdominal obesity (based on waist circumference). Multiple logistic regression analysis was done to estimate the magnitude of the association between sleep duration (<7 h, 7-<9, or ≥9 hours) and prevalence of glaucoma in the total population and in the subgroups.Individuals who slept <5 hours per night had the highest prevalence of glaucoma (5.55 ± 1.09%), followed by those who slept ≥9 hours per night (4.56 ± 0.10%), and then by those who slept 5 to <6 hours per night (4.15 ± 0.68%), which revealed a U-shaped pattern (P for trend = 0.072). Among overweight individuals, subjects who slept <7 hours and those who slept ≥9 hours were significantly more likely to have glaucoma compared with subjects who slept 7 to <9 hours after adjusting for survey year, age, sex, smoking, drinking, exercise, education level, household income, hypertension, intraocular pressure, stress, and depression (odds ratio, 2.41; 95% confidence interval, 1.14-5.03). Unlike for overweight individuals, sleep duration in nonoverweight individuals was not statistically significantly associated with glaucoma.Our results reveal a U-shaped association between sleep duration and the prevalence of glaucoma. An effect of sleep duration on glaucoma was present in the subgroup of overweight patients.

Relationship between Daytime Sleepiness and Intrinsically Photosensitive Retinal Ganglion Cells in Glaucomatous Disease

Patients with glaucoma showed to have higher daytime sleepiness measured by Epworth sleepiness scale. In addition, this symptom was associated with pupillary reflex and polysomnography parameters. These ipRGC functions might be impaired in patients with glaucoma, leading to worse quality of life.

High prevalence of seasonal affective disorder among persons with severe visual impairment

BACKGROUND

Light severely affects the occurrence of seasonal affective disorder (SAD).

AIMS

To compare the prevalence of SAD in persons with severe visual impairment and persons with full sight, and in persons with severe visual impairment with or without light perception.

METHOD

This cross-sectional study assessed the Global Seasonality Score (GSS) and the prevalence of SAD among 2781 persons with visual impairment and 4099 persons with full sight using the Seasonal Pattern Assessment Questionnaire (SPAQ).

RESULTS

Respondents with visual impairment had significantly higher GSS and prevalence of SAD compared with full sight controls, P<0.001. Light perception respondents were more vulnerable to seasonal change than both full sight and no light perception respondents.

CONCLUSIONS

The study showed a highly significant association between visual impairment and SPAQ-defined SAD parameters, supporting the hypothesis that decreased retinal light input plays a role in the pathogenesis of SAD.

Genetic advances in ophthalmology: the role of melanopsin-expressing, intrinsically photosensitive retinal ganglion cells in the circadian organization of the visual system

Daily changes in the light-dark cycle are the principal environmental signal that enables organisms to synchronize their internal biology with the 24-hour day-night cycle. In humans, the visual system is integral to photoentrainment and is primarily driven by a specialized class of intrinsically photosensitive retinal ganglion cells (ipRGCs) that express the photopigment melanopsin (OPN4) in the inner retina. These cells project through the retinohypothalamic tract (RHT) to the suprachiasmatic nuclei (SCN) of the hypothalamus, which serves as the body's master biological clock. At the same time, the retina itself possesses intrinsic circadian oscillations, exemplified by diurnal fluctuations in visual sensitivity, neurotransmitter levels, and outer segment turnover rates. Recently, it has been noted that both central and peripheral oscillators share a molecular clock consisting of an endogenous, circadian-driven, transcription-translation feedback loop that cycles with a periodicity of approximately 24 hours. This review will cover the role that melanopsin and ipRGCs play in the circadian organization of the visual system.

Changes in the circadian rhythm in patients with primary glaucoma

Purpose

The current study was undertaken to investigate whether glaucoma affects the sleep quality and whether there is any difference between patients with primary glaucoma (primary open angle glaucoma, POAG and primary angle-closure glaucoma, PACG) and healthy subjects, using a validated self-rated questionnaire, the Pittsburgh Sleep Quality Index (PSQI).

Methods

The sleep quality of patients with POAG and PACG was tested against normal controls. Subjects were divided into three sub-groups according to age. Differences in the frequency of sleep disturbances (PSQI score >7) were assessed. The differences of sleep quality within the three groups and within the POAG group depending on the patients’ intraocular pressure (IOP) and impairment of visual field (VF) were also studied.

Results

92 POAG patients, 48 PACG patients and 199 controls were included. Sleep quality declined with age in control and POAG group (tendency chi-square, P<0.05). The prevalence of sleep disturbances was higher in POAG and PACG group than in the control group, the differences were statistically significant. The prevalence of sleep disturbances was higher in patients with PACG, compared to POAG patients in the age interval of 61–80. In POAG group, the ratio of patients with sleep disorders increased with augmented impairment of VF, but the differences were not statistically significant (χ²-test, P>0.05). No significant differences were found in POAG group between patients with a highest IOP in daytime and at nighttime (χ²-test, P>0.05).

Conclusions

The prevalence of sleep disorders was higher in patients with POAG and PACG than in controls. PACG patients seemed to have a more serious problem of sleep disorders than POAG patients between 61 to 80 years old. No correlation was found between the prevalence of sleep disorders and impairment of VF or the time when POAG patients showed a highest IOP.

FMR1, circadian genes and depression: suggestive associations or false discovery?

Background

There are several indications that malfunctions of the circadian clock contribute to depression. To search for particular circadian gene polymorphisms associated with depression, diverse polymorphisms were genotyped in two samples covering a range of depressed volunteers and participants with normal mood.

Methods

Depression mood self-ratings and DNA were collected independently from a sample of patients presenting to a sleep disorders center (1086 of European origin) and from a separate sample consisting of 399 participants claiming delayed sleep phase symptoms and 406 partly-matched controls. A custom Illumina Golden Gate array of 768 selected single nucleotide polymorphisms (SNPs) was assayed in both samples, supplemented by additional SNPlex and Taqman assays, including assay of 41 ancestry-associated markers (AIMs) to control stratification.

Results

In the Sleep Clinic sample, these assays yielded Bonferroni-significant association with depressed mood in three linked SNPs of the gene FMR1: rs25702 (nominal P=1.77E-05), rs25714 (P=1.83E-05), and rs28900 (P=5.24E-05). This FMR1 association was supported by 8 SNPs with nominal significance and a nominally-significant gene-wise set test. There was no association of depressed mood with FMR1 in the delayed sleep phase case–control sample or in downloaded GWAS data from the GenRED 2 sample contrasting an early-onset recurrent depression sample with controls. No replication was located in other GWAS studies of depression. Our data did weakly replicate a previously-reported association of depression with PPARGC1B rs7732671 (P=0.0235). Suggestive associations not meeting strict criteria for multiple testing and replication were found with GSK3B, NPAS2, RORA, PER3, CRY1, MTNR1A and NR1D1. Notably, 16 SNPs nominally associated with depressed mood (14 in GSK3B) were also nominally associated with delayed sleep phase syndrome (P=3E10^-6).

Conclusions

Considering the inconsistencies between samples and the likelihood that the significant three FMR1 SNPs might be linked to complex polymorphisms more functionally related to depression, large gene resequencing studies may be needed to clarify the import for depression of these circadian genes.

Polymorphisms in melatonin synthesis pathways: possible influences on depression

Background

It has been reported that rs4446909, a single nucleotide polymorphism (SNP) in the promoter of acetylserotonin methyltransferase (ASMT), influences the expression of the ASMT enzyme. The common G allele is associated with lower ASMT activity, and therefore, diminishes conversion of N-acetylserotonin to melatonin. The G allele was associated with recurrent depressive disorder in a Polish group. ASMT might also affect bipolar relapse, given evidence that N-acetylserotonin might stimulate TRKB receptors, and TRKB may influence mood relapse in bipolar disorder. Additionally, arylalkylamine N-acetyltransferase (AANAT) polymorphisms have been reported associated with depression, perhaps through their influence upon N-acetylserotonin or melatonin synthesis.

Results

To replicate and further explore these ideas, rs4446909 was genotyped in four research groups, as part of a panel of 610 SNPs surveyed by an Illumina Golden Gate assay. In 768 cases with delayed sleep phase disorder or matched controls, rs4446909 was indeed associated with the depressive symptoms on a self-report scale (P = 0.01, R² = 0.007). However, there was no significant association of rs4446909 with self-reported depression in a sleep clinic patient group or with two groups of elderly men and women from multicenter studies, nor was the response to lithium treatment associated with rs4446909 in bipolar patients. No associations of two AANAT SNPs with depression were found.

Conclusions

The evidence did not support a strong influence of rs4446909 upon mood, but the partial replication may be consistent with a modest effect. It is possible that larger or younger subject groups with improved phenotype ascertainment might demonstrate more persuasive replication.

Circadian dysfunction in P23H rhodopsin transgenic rats: effects of exogenous melatonin

This study focuses on the effects of retinal degeneration on the circadian patterns of P23H rats, as well as on the effect of exogenous melatonin administration. To this end, the body temperature of P23H and Sprague-Dawley rats was continuously monitored and their retinas examined at different stages of degeneration, by means of histological labeling and electroretinogram recordings. Melatonin (2 mg/kg BW/day) was supplied ad libitum throughout the experiment to a subset of animals. The body temperature recordings from wild-type and mutant animals showed no differences in the periodogram and the pattern of the mean waveform. However, a progressive decrease in the relative amplitude of the rhythm (RA), a decline in the coupling strength of the rhythm to environmental zeitgebers (interdaily stability, IS) and increased rhythm fragmentation (intradaily variability, IV) were observed in P23H rats, when compared to wild-type animals. The P23H animals showed a progressive decrease in light-induced retinal responses until reaching 18 months of age. By this age, all photoreceptors had already disappeared, and no responses were found in the EGRs. Exogenous administration of melatonin improved the visual response of P23H rats. In fact, the maximum b-wave recorded at 14 months of age was significantly higher in melatonin-treated P23H rats than in the control animals. Furthermore, the maximum b-wave recorded for P23H rats at the age of 14 months significantly correlated with RA, IS, and IV. This leads us to conclude that vision loss in P23H rats is correlated with a progressive fragmentation of their circadian patterns. Both effects are partially reversed by melatonin administration.

The role of melatonin in glaucoma: implications concerning pathophysiological relevance and therapeutic potential

Glaucoma is a frequent ophthalmologic condition leading to chronic progressive optic neuropathy, which can result in visual impairment and blindness. In addition, glaucoma is associated with a dysregulation of circadian rhythms, as well as with a high incidence of sleep disorders, depression, and anxiety. However, because of their high comorbidity in older age, these conditions have not received much scientific attention and are often undertreated. In the current paper, we review the available literature on the role of melatonergic mechanisms in glaucoma, regulation of circadian rhythms, and depression. The literature is presented as a narrative review, providing an overview on the most important and clinically relevant publications. Recently, there has been evidence for a progressive loss of intrinsically photosensitive retinal ganglion cells (ipRGC) because of oxidative stress in glaucoma. As ipRGC are responsible for the photic transduction to the circadian system and subsequent melatonin secretion, and melatonin is involved in the pathophysiology of circadian desynchronization, sleep disorder, and depression, an impairment of photo-dependent melatonergic signaling may be a common pathway connecting glaucoma with these comorbidities. This fact, as well as the proven retinal neuroprotective role of melatonin, suggests that melatonergic drugs provide a potentially promising treatment strategy supplementing the management of intraocular pressure by pharmacological and surgical measures. Additionally, multidisciplinary treatment focusing on depression and normalization of circadian rhythms might be beneficial for glaucoma patients. Furthermore, glaucoma might be a useful model for studying the pathophysiological interactions between the melatonergic, circadian, and mood systems.

Physiology of circadian entrainment

Mammalian circadian rhythms are controlled by endogenous biological oscillators, including a master clock located in the hypothalamic suprachiasmatic nuclei (SCN). Since the period of this oscillation is of approximately 24 h, to keep synchrony with the environment, circadian rhythms need to be entrained daily by means of Zeitgeber ("time giver") signals, such as the light-dark cycle. Recent advances in the neurophysiology and molecular biology of circadian rhythmicity allow a better understanding of synchronization. In this review we cover several aspects of the mechanisms for photic entrainment of mammalian circadian rhythms, including retinal sensitivity to light by means of novel photopigments as well as circadian variations in the retina that contribute to the regulation of retinal physiology. Downstream from the retina, we examine retinohypothalamic communication through neurotransmitter (glutamate, aspartate, pituitary adenylate cyclase-activating polypeptide) interaction with SCN receptors and the resulting signal transduction pathways in suprachiasmatic neurons, as well as putative neuron-glia interactions. Finally, we describe and analyze clock gene expression and its importance in entrainment mechanisms, as well as circadian disorders or retinal diseases related to entrainment deficits, including experimental and clinical treatments.

Melanopsin-expressing retinal ganglion cells: implications for human diseases

In the last decade, there was the seminal discovery of melanopsin-expressing retinal ganglion cells (mRGCs) as a new class of photoreceptors that subserve the photoentrainment of circadian rhythms and other non-image forming functions of the eye. Since then, there has been a growing research interest on these cells, mainly focused on animal models. Only recently, a few studies have started to address the relevance of the mRGC system in humans and related diseases. We recently discovered that mRGCs resist neurodegeneration in two inherited mitochondrial disorders that cause blindness, i.e. Leber hereditary optic neuropathy and dominant optic atrophy. The mechanism leading to mRGCs sparing in these blinding disorders, characterized by extensive and selective loss of RGCs, is currently unknown and under investigation. Other studies reported on mRGCs in glaucoma, on genetic variation of the melanopsin gene (OPN4) in seasonal affective disorder and on the role of mRGCs in migraineous photophobia. Our own data and studies from others have shown a significant reduction of mRGCs with aging. We anticipate that these studies will lead to many other investigations addressing the role of mRGCs and circadian photoreception in the pathogenesis of circadian and sleep abnormalities in neurodegenerative disorders.