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Open research questions in Circadian rhythm and melatonin

63 unresolved questions extracted from the limitations and future-work sections of 465 Circadian rhythm and melatonin papers in our library. Each links back to the study that raised it.

What the literature leaves open

  • Future research should focus on prospective clinical studies, validation of noninvasive circadian biomarkers, and integration of temporal information into precision oncology frameworks.

    Circadian Gene Networks and Transcriptome Oscillations in Prostate Cancer: Insights From RNA Sequencing and Implications for Chronotherapy · 2026 · DOI

  • Although AR-V7 is a clinically relevant biomarker of resistance, a causal circadian mechanism for its generation has not been established. Similarly, clinical evidence supporting chronotherapy in prostate cancer remains insufficient, and standardized treatment-timing protocols are not currently available.

    Circadian Gene Networks and Transcriptome Oscillations in Prostate Cancer: Insights From RNA Sequencing and Implications for Chronotherapy · 2026 · DOI

  • Future research should focus on the prospective characterization of circadian regulation in prostate cancer using standardized and time-resolved study designs. Longitudinal transcriptomic profiling, repeated liquid biopsy sampling, and the integration of genomic, epigenomic, proteomic, and metabolomic data may help distinguish stable tumor-associated alterations from time-dependent molecular variation. Such approaches could also support the development of validated circadian biomarkers reflecting individual biological phase, tumor rhythmicity, and treatment response. Wearable devices capable of continuously monitoring rest-activity cycles, sleep, body temperature, and other physiological parameters may provide complementary information on systemic circadian organization. Integration of these data with blood-based biomarkers and tumor transcriptomic profiles could facilitate individualized assessment of circadian phase. Computational modeling and machine-learning methods may subsequently assist in identifying clinically relevant temporal patterns and optimizing treatment schedules [25-27,29]. The clinical implementation of precision chronomedicine will require prospective trials incorporating predefined administration times, standardized circadian measurements, and clinically relevant efficacy and toxicity endpoints. Circadian biomarkers and AI-guided scheduling should be evaluated within established precision-oncology frameworks rather than as independent approaches. Until such strategies undergo analytical and clinical validation, their use in prostate cancer should remain investigational.

    Circadian Gene Networks and Transcriptome Oscillations in Prostate Cancer: Insights From RNA Sequencing and Implications for Chronotherapy · 2026 · DOI

  • Phosphorylation of the CLOCK/BMAL1 complex is a reversible post-translational modification that plays a central role in regulating circadian oscillations; however, its underlying mechanistic basis remains poorly understood.

    Phosphorylation-dependent Remodeling of the CLOCK/BMAL1/nucleosome Complex · 2026 · DOI

  • Although biochemical studies have shown that phosphorylation modulates CLOCK/BMAL1 binding to DNA, yet it remains unclear whether these effects are confined to local perturbation or also propagate through allosteric effects.

    Phosphorylation-dependent Remodeling of the CLOCK/BMAL1/nucleosome Complex · 2026 · DOI

  • Data availability No datasets were generated or analysed during the current study. In summary, the timing of drug administration has both biological foundation and clinical significance in determining hepatic detoxification capacity and hepatotoxicity risk. Hepatic detoxification function exhibits intrinsic circadian rhythmicity, a temporal program driven by transcriptional-translational feedback loops constituted by intracellular CCGs.

    Circadian regulation of hepatic detoxification: implications for drug-induced liver injury · 2026 · DOI

  • Hypertension is the most common cardiovascular disease and is also the leading contributor to multiple fatal illnesses. In recent decades, scientists have explored the potential mechanisms of BP modulation and focused on curing hypertension. Consequently, the ANS has been proposed as an important factor that regulates BP in a circadian pattern. Using techniques of histology, scientists have decon- structed circadian clocks and discovered that the ANS is the bridge between the central clock and peripheral clocks. Although the ANS is a considerable factor involved in the occurrence of hypertension, the molecular mechanisms underlying ANS tone changes during the day remain to be clarified. Fortunately, with the development of molecular biology, genes that modulate fluctuations in ANS activity will be iden- tified, and whether these genes contribute to BP disorders will be ascertained. It is predictable that the above genes will act as effective targets for treating hypertension in clinical practice and that therapies targeting these genes will surely provide hope for patients with hypertension.

    Autonomic nervous system: an integrative regulator in circadian rhythm of blood pressure · 2026 · DOI

  • Moderate changes, such as small timing jitter, limited data loss, or modest threshold shifts, kept estimates stable within ±10 min, whereas pronounced alterations to sampling schedules, large multi-point deletions, or substantial threshold changes delayed estimates by over 40 min or prevented estimation.

    dlmoR: An open-source R package for the dim-light melatonin onset (DLMO) hockey-stick method · 2026

  • Melatonin has shown potent effects on improving plant stress resistance and phytoremediation upon HM stress, however, the systematic discussion of these extensive mechanisms and the gaps to practical applications remain elusive.

    Melatonin‐Mediated Alleviation of Plant Response to Heavy Metals: From Integrative Mechanisms to Potential Applications · 2026 · DOI

  • Circadian rhythms in behavior depend on the suprachiasmatic nucleus (SCN), but how SCN timekeeping is transmitted to downstream circuits that organize daily behavioral rhythms remains poorly defined.

    A direct SCN-to-DMH output pathway organizes circadian behavioral timing · 2026 · DOI

  • Circadian dysregulation is increasingly linked to prostate cancer (PCa) progression, yet its role in directing DNA damage response (DDR) pathway selection remains poorly understood.

    Stage-Specific Regulation of DNA Damage Repair by the Circadian Regulator, CRY1, in Prostate Cancer · 2026 · DOI

  • 1. Technical limitations of current organoid platforms Despite the substantial advances described above, intestinal organoid systems retain technical limitations that must be addressed before they can serve as standardized evaluation platforms. The most fundamental challenge is the absence of non-epithelial cell populations: current epithelial-only models lack vascular endothelial cells, resident immune cells, enteric neurons, and stromal fibroblasts. Among these omissions, the absence of immune components is particularly consequential for chronobiotic research. Diurnal oscillations in IgA secretion and rhythmic antimicrobial peptide production are key regu- lators of microbiota composition and host–microbiome circa- dian synchrony [84,87], and their absence prevents accurate modeling of circadian mucosal immunity. Emerging co-culture systems incorporating autologous immune compartments or macrophage populations have begun to address this gap, but their systematic integration into chronobiotic evaluation work- flows has not yet been validated [35,36,53]. Batch-to-batch variability also remains a substantial barrier. Differences in Matrigel composition, growth factor concen- trations, and passage number introduce stochastic variation in clock amplitude and cellular diversity [28,38,88]. Transcriptom- ic heterogeneity among organoid lines derived from different donors further complicates interpretation of subtle chronobiot- ic effects, reinforcing the need for reference organoid biobanks and single-cell-level quality metrics [29,81,89]. Moreover, the absence of an aerobic–anaerobic interface under standard culture conditions limits co-culture with strictly anaerobic com- mensal bacteria that produce most intestinal SCFAs, a critical limitation for microbiota-dependent chronobiotic evaluation [45,77]. Overcoming these constraints through defined syn- thetic matrices, automated culture systems, and oxygen-gradient microfluidic platforms will be essential for systematic chronobi- otic evaluation [24,90].

    Organoids for evaluating chronobiotics and functional foods · 2026 · DOI

  • Although existing research contributes towards elucidating the regulatory mechanisms of uterine circadian rhythms, the present review must still consider a number of limitations. First, the majority of existing evidence comes from nocturnal rodents, whereas humans are diurnal species. There are funda‑ mental differences between the two in activity‑rest patterns under light‑dark cycles, as well as in hormone secretion and metabolic rhythms. Therefore, conclusions drawn from animal studies cannot be directly extrapolated to humans. Second, animal experiments are typically conducted under strictly controlled conditions of light exposure and feeding schedules, whereas clinical populations exhibit more complex lifestyles, increasing translational uncertainty. Third, circadian patterns vary across species. For example, during the luteal phase, CLOCK expression decreases in the human endometrium but markedly increases in the endometrium of Small‑tail Han sheep (12,73), suggesting that physiological differences such as reproductive cycle length and endometrial shedding mecha‑ nisms may limit the extrapolation of mechanisms. Fourth, the reproducibility of in vitro studies is insufficient. For example, marked differences in circadian rhythm alterations of clock genes exist between primary and immortalized HESCs before MOLECULAR MEDICINE REPORTS 33: 178, 2026 13 Figure 5. Schematic diagram illustrating the role of circadian rhythms in uterine‑related diseases. Factors such as night shift work and nocturnal light exposure can disrupt circadian rhythms, subsequently affecting the central clock SCN and pineal melatonin secretion, thereby further disturbing the circadian rhythms of uterine clock genes and sex hormone levels. These alterations may regulate endometrial decidualization and rhythmic contractions of the uterine myometrium, thereby affecting endometrial receptivity and timing of labor. Ultimately, they contribute to the development and progression of uterine disorders including EMS, EC and menstrual irregularities. EMS, endometriosis; EC, endometrial cancer; CLOCK, circadian locomotor output cycles kaput; SCN, suprachiasmatic nucleus; BMAL1, brain and muscle ARNT‑like 1; PER, period; CRY, cryptochrome. and after decidualization treatment (13,76), indicating that the high sensitivity of results stems from model type and intervention method. Future studies should aim to enhance physiological relevance and clinical translational potential by utilizing diurnal animal models, uterine organoids and 3D co‑culture systems, combined with human cohort studies and in vivo monitoring research.

    Research progress and future directions in circadian rhythms for uterine‑related diseases (Review) · 2026 · DOI

  • If validated, this framework suggests that PBM represents the restoration of an evolutionarily ancient, lightdependent protective system rather than the introduction of a novel therapy. However, this therapeutic framing is contingent on the experimental validation of the central hypothesis, that NIR radiation triggers mitochondrial melatonin synthesis, which remains the least-established link in the proposed framework. The practical implications include non-invasive, targeted neuroprotection with minimal adverse effect potential. The mechanistic framework suggests that treatment optimization should consider timing (morning exposure aligned with CCO responsiveness peaks), dosing (within the optimal therapeutic window avoiding biphasic inhibition), frequency (permitting adequate inter-treatment recovery), and substrate status (concurrent glycine/NAC supplementation to ensure glutathione synthesis capacity). Although this paper focuses on neuroprotection, the proposed NIR-melatonin-glutathione cascade should theoretically operate in any mitochondria-rich tissue, suggesting potential applications in cardiac protection, renal protection, and other contexts that warrant future investigation. The evolutionary context deserves emphasis. Modern indoor living has eliminated the NIR exposure humans experienced throughout evolutionary history. If NIR serves as a physiological stimulus for endogenous 2026 Mercola et al. Cureus 18(3): e105322. DOI 10.7759/cureus.105322 27 of 33 protective mechanisms, contemporary humans may be experiencing a novel form of environmental deficiency with consequences for brain health. PBM would then represent not the introduction of a novel therapy but the restoration of an ancient, sun-dependent protective system that modern lifestyles have inadvertently disrupted.

    Optimizing Brain Biology Through Near-Infrared-Induced Mitochondrial Melatonin Synthesis: A Hypothesis Paper · 2026 · DOI

  • A critical communication barrier exists between circadian researchers and clinical practitioners, with insufficient education of circadian health among clinicians limiting the translation of basic circadian research findings into clinical practice for aging populations.

    Emerging Life Sciences Series: Q&A with the Editor Circadian Biology · 2022 · DOI

  • Only a limited number of NIH institutions (NHLBI, NIA, NIDDS, NIDA) currently provide dedicated funding for circadian biology and aging research, creating a gap in sustained research support for interdisciplinary circadian aging investigations that integrate aging biology with chronobiological mechanisms.

    Emerging Life Sciences Series: Q&A with the Editor Circadian Biology · 2022 · DOI

  • While circadian dysfunction's role in Alzheimer's disease development and progression is being investigated through multidisciplinary collaborations, the specific mechanistic pathways linking circadian system dysregulation to neurodegenerative processes in AD remain incompletely characterized and require integrated circadian physiology and neuropathology studies.

    Emerging Life Sciences Series: Q&A with the Editor Circadian Biology · 2022 · DOI

  • Current circadian aging research relies on molecular and genetic studies alongside physiological and person-population studies, but new experimental technologies, mathematical theories, and modeling and analytical tools specifically designed to capture circadian dysfunction interactions at different biological levels and time scales remain underdeveloped.

    Emerging Life Sciences Series: Q&A with the Editor Circadian Biology · 2022 · DOI

  • The study only measured peripheral clock gene expression in blood; tissue-specific effects of meal timing on clock gene expression in metabolically relevant tissues (liver, adipose tissue, skeletal muscle) have not been directly characterized in humans. Invasive or imaging-based approaches are needed to establish whether peripheral clock entrainment extends uniformly across metabolic tissues.

    Circadian Biology: Uncoupling Human Body Clocks by Food Timing · 2017 · DOI

  • Earlier meal timing has been associated with more effective weight-loss therapy in overweight and obese patients, but the mechanistic role of peripheral clock synchronization in mediating these effects has not been directly tested. Research must determine whether meal timing's effects on weight loss operate through peripheral clock gene expression changes or through alternative metabolic pathways.

    Circadian Biology: Uncoupling Human Body Clocks by Food Timing · 2017 · DOI

  • The mechanistic basis for why a 5-hour shift in meal timing did not alter subjective hunger levels, despite evidence that endogenous circadian modulation of hunger peaks in the biological evening, remains unexplained. Studies investigating the relationship between peripheral clock entrainment in metabolic tissues and hunger signaling pathways are needed.

    Circadian Biology: Uncoupling Human Body Clocks by Food Timing · 2017 · DOI

  • The translatability of meal timing-induced peripheral clock shifts to circadian rhythm sleep disorder patients and shift workers has not been tested. Future studies must evaluate whether manipulating meal timing can restore internal synchrony between the SCN-driven central clock and peripheral clocks in these populations, and whether this improves cardiometabolic outcomes.

    Circadian Biology: Uncoupling Human Body Clocks by Food Timing · 2017 · DOI

  • The study employed a fixed order design (early meal timing condition followed by late meal timing condition), which may confound the observed decrease in 24-hour glucose concentrations due to duration effects or adaptation over time. Randomized counterbalanced meal timing conditions are needed to isolate the independent effect of meal timing on glucose metabolism from temporal confounders.

    Circadian Biology: Uncoupling Human Body Clocks by Food Timing · 2017 · DOI

  • The effects of meal timing on sleep architecture were assessed only by actigraphy, which cannot detect polysomnographic sleep parameters. Direct measurement using polysomnography is required to determine whether meal timing influences sleep duration, fragmentation, latency, and efficiency, particularly for meals consumed close to bedtime.

    Circadian Biology: Uncoupling Human Body Clocks by Food Timing · 2017 · DOI

  • BACKGROUND: Sleep disturbances comparable with insomnia occur in up to 80% of people with schizophrenia, but very little is known about the contribution of circadian coordination to these prevalent disruptions.

    Sleep and circadian rhythm disruption in schizophrenia · 2011 · DOI

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63 open questions have been extracted from the limitations and future-work passages of 465 Circadian rhythm and melatonin papers in our library. Each one below links back to the study that raised it, so you can read the original claim in context.

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