ABSTRACT This study aims to investigate renal aquaporins (2 and 3) in the pinealectomy and exogenous melatonin administration. 50 rats were separated into 5 groups: Control, Sham Pinealectomy (Sham PiX), Melatonin (MLT), Pinealectomy (PiX), and PiX+MLT groups. PiX included groups operated on the first day of the experiment. The MLT groups received intraperitoneal MLT (10 mg/kg for 30 days) injections. At the end of 30 days, the kidneys of the rats were removed, and histometrical, immunohistochemical, biochemical, and qPCR analyses were performed. AQP 2 and 3 water channels had the highest expressions in the PiX group while experiencing the lowest levels in the MLT group for both immunohistochemical and qPCR results (P˂0.05). Malondialdehyde (MDA), interleukin-1β (IL-1β), blood urea nitrogen (BUN), and creatinine levels showed an increase in the renal tissue, while superoxide dismutase (SOD) and gluthation (GSH) levels decreased in the PiX group (P˂0.05). Glomerulus diameters of the PiX group showed substantial reduction compared to other groups while renal corpuscule diameters were found to be greater (P˂0.05). Pinealectomy results in elevated expressions of Aquaporin 2 and 3 in renal tissue, as evidenced by both immunohistochemistry analysis and qPCR data. The pinealectomy group has elevated levels of MDA, IL-1β, BUN, and creatinine, while exogenous melatonin treatment leads to a reduction in GSH and SOD levels in renal tissue.

ABSTRACT This study aims to explore the association between exposure to light at night (LAN) and ambulatory blood pressure (BP) profiles in college students. A school-based cross-sectional study was conducted in a university of Changsha, Hunan Province, China. We recruited 732 college students from September 2023 to June 2024. Abnormal BP phenotypes include abnormal daytime/nighttime/24 h/ambulatory BP. Abnormal ambulatory BP is defined by presence of abnormal daytime/nighttime/24 h BP. After exclusion, a total of 688 participants were included in the final analysis with an age of 19 years (IQR 18, 20), with 501 (72.8%) females. After adjustment of potential covariates, including age, sex, body mass index, chronotype, sedentary behavior, physical activity, and intake of fruits and vegetables, participants with LAN exposure had a significantly higher risk of abnormal daytime BP (OR = 5.12, 95%CI, 1.30–20.14), abnormal nighttime BP (OR = 2.61, 95%CI, 1.00–6.77), abnormal ambulatory BP (OR = 3.80, 95%CI, 1.55–9.30) and abnormal daytime SBP (OR = 4.28, 95%CI, 1.08–16.98), than the non-LAN exposure group. When the LAN exposure was categorized as high, moderate/low and non-exposure, similar results were obtained, especially for abnormal nighttime SBP. Light pollution at night is associated with abnormal ambulatory BP profiles among young adults, especially for abnormal nighttime SBP.

ABSTRACT Muscle strength is known to fluctuate across the day, typically peaking in the late afternoon. However, studies examining diurnal variation in hand-grip strength have produced inconsistent findings, likely due to methodological limitations such as short or sparsely sampled time series. Clarifying whether hand-grip strength exhibits a robust daily rhythm is essential for understanding the circadian modulation of motor performance. Our sample included 22 participants (11 men and 11 women) ranging in age from 21 to 90 years and residing in both Europe and the United States. Each participant conducted measurements at 12 time points scheduled every two hours across a 24-hour cycle and distributed over two or three days to avoid unintended sequential effects. We also measured sublingual temperature as a supplemental variable. Using ANOVAs and cosinor rhythmometry, we found that hand-grip strength and sublingual temperature exhibited robust daily rhythmicity with average peaks at 15:30 (grip strength) and 16:18 (temperature). We conclude that hand-grip strength exhibits robust daily rhythmicity in healthy individuals. Negative results in previous studies were likely due to inadequately short time series and insensitive data analysis procedures.

ABSTRACT This mini-review explores the role of circadian rhythm-related gene polymorphisms, particularly single-nucleotide polymorphisms (SNPs), in the development of various diseases, including cancer, chronic inflammatory diseases, cognitive decline, and mood disorders. We conducted a structured literature search across PubMed, Google Scholar, SCOPUS, and Web of Science to identify human studies examining associations between SNPs in circadian genes (e.g., CLOCK, BMAL1, PER2, MTNR1B) and disease susceptibility. The search strategy incorporated predefined keywords, Boolean operators, and specific inclusion/exclusion criteria, focusing exclusively on human research to ensure clinical and translational relevance. Alterations in circadian genes, especially SNPs, have been linked to cancers like lung, breast, and prostate by disrupting key cellular processes, including DNA repair and apoptosis. Additionally, these gene variations are associated with chronic inflammatory conditions, cognitive impairment, and mood disorders. Understanding circadian gene variations provides valuable insights into predicting disease risk and progression. The synthesis of human genetic evidence underscores the importance of integrating circadian biology into precision medicine and highlights the need for further human-focused research across diverse populations. This knowledge holds promise for developing personalized treatment strategies tailored to an individual’s genetic makeup.

ABSTRACT Seasonal variations in mental health represent a complex interplay between environmental photoperiod changes and neurobiological rhythms, affecting millions globally through conditions like seasonal affective disorder and bipolar seasonality. This narrative scoping review synthesizes current understanding of molecular and neural mechanisms underlying seasonal mental health fluctuations, from circadian clock gene regulation to neurotransmitter system adaptations. The suprachiasmatic nucleus orchestrates seasonal responses through melatonin-mediated pathways, while serotonergic and dopaminergic systems show pronounced seasonal variations correlating with mood and cognitive changes. Brain regions including the hippocampus, prefrontal cortex, and limbic structures demonstrate seasonal plasticity in structure and function. Light therapy (10,000 lux for 30 minutes daily) remains the primary evidence- based intervention, with response typically emerging within 1–2 weeks. Combination approaches incorporating cognitive-behavioral therapy, sleep schedule optimization, and pharmacological interventions are under investigation, though optimal protocols require validation. Emerging research explores personalized medicine strategies based on genetic polymorphisms and chronotype assessment, though clinical implementation awaits rigorous validation. Critical research gaps include biomarker validation for treatment selection, standardized neuroimaging protocols, and translational validation of precision chronotherapy approaches. Future directions prioritize large-scale longitudinal investigations and evidence-based personalization strategies addressing the growing burden of seasonal mood disorders.

ABSTRACT Sleep is crucial for brain development in children and melatonin is the main sleep-inducing hormone. However, the relationship between melatonin and academic achievement in children is not well understood. This study aimed to examine the associations between salivary melatonin levels, sleep habits, and academic achievement in elementary school children. The study comprised 63 children (26 boys and 37 girls) aged 9–12 years. Salivary melatonin levels were measured at two time points: morning (6:30 AM) and evening (9:30 PM). Sleep duration and social jetlag were assessed using self-report questionnaires. Teachers assessed the academic achievement (ranging from 21–63 points across seven school subjects). Morning salivary melatonin levels were negatively correlated with academic achievement (β = −0.312, p = 0.018), and the morning-to-evening salivary melatonin ratio was positively correlated with academic achievement (β = 0.291, p = 0.014). No correlation between evening salivary melatonin levels and academic achievement was observed. Sleep duration and social jetlag were also associated with academic achievement (p < 0.05 for all tests). Overall, morning salivary melatonin levels, morning-to-evening salivary melatonin ratios, sleep duration, and social jetlag were independently associated with academic achievement in elementary school children.

ABSTRACT This letter offers a critical commentary on the narrative review by de Mello et al. (2025) on sleep and performance across the lifespan. While the review provides a comprehensive synthesis of sleep requirements in athletes from childhood to older adulthood, this letter highlights areas for further clarification and development. These include the need for more empirical data on youth athletes, clearer operationalization of sleep metrics, and greater attention to sociocultural and sport-specific contexts. The commentary supports the authors’ call for age-specific sleep strategies and encourages future research to integrate longitudinal and interdisciplinary approaches to better inform athlete health and performance.

ABSTRACT Current sleep pharmacotherapies often target single neurotransmitter systems, yielding limited efficacy and high non-response rates. We propose a dual-pathway integration framework, combining circadian (melatonin-mediated) and GABAergic (botanical) modulation, as a hypothesis-generating model for precision sleep medicine. Grounded in foundational work (e.g. SCN as circadian pacemaker; Borbély’s two-process model), this review assessed evidence from five databases per PRISMA 2020 guidelines. Among GABAergic botanicals, Passiflora incarnata was selected for its clinical relevance and mechanistic data. Putative convergence is hypothesized at molecular nodes (e.g. cAMP/PKC pathways) and neuroanatomical sites (e.g. GABAergic SCN neurons). However, no studies have formally tested pharmacodynamic synergy between melatonin and Passiflora. Clinical evidence is limited to monotherapy trials, with one uncontrolled pilot (N = 43) showing subjective improvement. Meta-analyses of some phytotherapeutics (e.g. multi-ingredient or poorly standardized formulations) report extreme heterogeneity (I2 > 95%) due to variability in composition and study populations. The 2023 European Insomnia Guidelines conclude that evidence for herbal medicines (e.g. valerian, chamomile and passionflower) is insufficient to support recommendations for routine clinical use. Most data come from European-ancestry cohorts, despite known pharmacogenetic differences (e.g. CYP1A2, GABRA2 variants). We conclude that dual-pathway therapy remains hypothetical and requires empirical validation via biomarker-stratified, randomized trials in diverse populations before clinical use.

ABSTRACT The influence of lifestyle factors, such as light exposure and meal timing, on susceptibility to infectious diseases like COVID-19, remains an area of active investigation. This cross-sectional study analyzed self-reported data from 1147 healthy adults (aged 18–65 years), divided into COVID-19 negative (n = 797) and positive (n = 350) groups. Data collected were MEQ chronotype score, MCTQ (including outdoor light exposure (OLE), bedtime, mid-sleep, wake-up) and meal timing on work-days and free-days. Compared to COVID-19 positive participants, individuals who remained COVID-19 negative reported greater weekday OLE (+39 minutes, p = 0.006) and earlier mid-sleep on working days (9 min, p = 0.031). They also exhibited earlier latest meal timing on workdays (26 min, p = 0.016) and free-days (27 min, p = 0.015), and earlier main meal timing on free days (21 min, p = 0.025). Multivariate analysis corrected for age, sex, BMI and MEQ identified higher weekday OLE (β = 0.103, p = 0.001), earlier mid-sleep on workdays (β = 0.080, p = 0.010), and earlier main meal timing on free days (β = 0.065, p = 0.037) as independent predictors of COVID-19 negative status. This study suggests that greater OLE, earlier mid-sleep on workdays and earlier main meal timing, may be independently associated with a reduced risk of COVID-19 infection in healthy adults, underscoring the importance of circadian health in infectious disease susceptibility.

ABSTRACT This study aimed to clarify the effects of rotating night shift work on the circadian rhythm of heart rate among nurses. Continuous heart rate monitoring was conducted for approximately three months using a wearable device, and comparisons were made with nurses working only day shifts. The participants included 40 hospital nurses (27 in the rotating night shift group and 13 in the day-only shift group). Daily 24-h heart rate data were analyzed using single-component cosinor analysis to calculate the mesor, amplitude, and acrophase. Group-level comparisons were performed using a nonparametric bootstrap method and age-adjusted rank-based analysis of covariance. After adjusting for age, only the acrophase remained significantly different between groups, being delayed in the rotating night shift group compared with the day-only group. Intra-individual variability, measured as the standard deviation of the daily mesor, amplitude, and acrophase, was also significantly greater in the rotating night shift group. When standardized intra-individual variability was compared, the most pronounced group difference was observed in acrophase variability. These findings indicate that rotating night shift work affects both the phase and stability of heart rate rhythms, which may reflect behavioral and physiological irregularities associated with work schedules.