Circadian modulation by time-restricted feeding rescues brain pathology and improves memory in mouse models of Alzheimer's disease

Exercise-mediated muscle-hypothalamus crosstalk: Improvement for cognitive dysfunction caused by disrupted circadian rhythm

In contemporary societal evolution, the increasing disruption of the natural sleep-wake cycle, attributable to factors such as shift work and overexposure to artificial light, has been paralleled by a marked escalation in the incidence of cognitive impairments and the prevalence of neurodegenerative diseases. Current management strategies for cognitive impairments include pharmacological and non-pharmacological interventions. Pharmacological interventions for cognitive impairments typically involve medications to manage cognitive symptoms and improve neurological functions. However, these drugs show limited long-term efficacy in slowing disease progression and may cause side effects. Given the widespread occurrence of cognitive dysfunction, it is crucial to develop accessible non-pharmacological interventions. Physical activity and exercise have emerged as pivotal lifestyle determinants known to exert a modulatory effect on the risk profile for cognitive dysfunction caused by disrupted circadian rhythms. The skeletal muscle, a dynamic tissue, undergoes a profound morphological and metabolic reconfiguration in response to physical exertion, along with the secretion of myokines. Additionally, the hypothalamus, particularly the ventromedial nuclei, arcuate nuclei, and the suprachiasmatic nucleus, have crucial functions in regulating physical activity, influencing energy metabolism, and managing circadian cycles. Nevertheless, the communication between the hypothalamus and skeletal muscle during exercise is not fully understood. This narrative review integrates current knowledge on the interaction between the hypothalamus and skeletal muscle during exercise, emphasizing its neuroendocrine effects and potential therapeutic implications for alleviating cognitive dysfunction associated with disrupted circadian rhythms.

Nanoparticles targeting the central circadian clock: Potential applications for neurological disorders

Circadian rhythms and their involvement with various human diseases, including neurological disorders, have become an intense area of research for the development of new pharmacological treatments. The location of the circadian clock machinery in the central nervous system makes it challenging to reach molecular targets at therapeutic concentrations. In addition, a timely administration of the therapeutic agents is necessary to efficiently modulate the circadian clock. Thus, the use of nanoparticles in circadian clock dysfunctions may accelerate their clinical translation by addressing these two key challenges: enhancing brain penetration and/or enabling their formulation in chronodelivery systems. This review describes the implications of the circadian clock in neurological pathologies, reviews potential molecular targets and their modulators and suggests how the use of nanoparticle-based formulations could improve their clinical success. Finally, the potential integration of nanoparticles into chronopharmaceutical drug delivery systems will be described.

Intermittent Fasting Enhances Motor Coordination Through Myelin Preservation in Aged Mice

Integrating dietary interventions have been extensively studied for their health benefits, such as Alzheimer's disease, Huntington's disease, and aging. However, it is necessary to fully understand the mechanisms of long-term effects and practical applications of these dietary interventions for health. A 10-week intermittent fasting (IMF) regimen was implemented on the aging animals in the current study. The variations of cerebral functions were analyzed employing a comprehensive experimental design that includes behavioral tests, neuroimaging, and ultrastructural analysis, such as resting-state functional MRI (rsfMRI), EEG/EMG recordings, transmission electron microscopy, and immunohistochemistry. Over a 10-week regimen, IMF significantly improved locomotor activity, motor coordination, and muscle strength compared to controls (p < 0.01). Resting-state fMRI (rsfMRI) demonstrated that IMF modulates brain-wide functional connectivity, enhancing communication between key brain regions. Advanced imaging techniques revealed increased expression of myelin-related proteins, including myelin basic protein (MBP), and myelin-associated glycoprotein (MAG), indicating enhanced myelin integrity and repair, particularly in axons with diameters < 400 nm (p < 0.01). These findings suggest that IMF may mitigate age-related declines by promoting better neuronal signaling. This study highlights the potential function of IMF as a non-pharmacological intervention to promote brain health and mitigate cognitive decline in aging populations.

Circadian rhythm disturbances in Alzheimer's disease: insights from plaque-free and plaque-burdened stages in APPSWE/PS1dE9 mice

BACKGROUND

Disruptions in circadian rhythms are commonly observed in patients with Alzheimer's disease (AD) and could potentially accelerate the progression of the condition. However, the relationship between circadian rhythm disruptions and AD development, as well as the mechanisms involved, remain poorly understood.

METHODS

This study investigated the circadian behavior, rhythmic gene expression in multiple brain regions, and its correlation with sleep architecture of AD mice at two disease stages: plaque-free stage (2-month-old) and plaque-burdened stage (10-month-old) as compared to age-matched wild-type (WT) mice.

RESULTS

Two-month-old AD mice already displayed alteration in the activity patterns compared to WT mice, showing increased activity during the light phase and decreased activity during the dark phase, and the change in the activity pattern of 10-month-old AD mice was more significant. Further, electroencephalogram (EEG) examination showed increased wakefulness and reduced non-rapid eye movement (NREM) sleep in 2- and 10-month-old AD mice. In addition, we documented a significant change in circadian core clock genes in the suprachiasmatic nucleus (SCN), hippocampus, and cortex of 2- and 10-month-old AD mice. Correlation analyses demonstrated the close relationship between circadian clock gene expression level and specific sleep-wake parameters, especially within the SCN and hippocampus.

CONCLUSIONS

These findings revealed that circadian rhythm disturbances in AD mice preceded Aβ deposition. The circadian rhythm disturbances observed in the early AD might be attributed to the abnormal expression of core clock genes in the brain regions involved in circadian rhythm regulation.

Sleep abnormalities are associated with greater cognitive deficits and disease activity in Huntington's disease: a 12-year polysomnographic study

Increasing evidence suggests that the sleep pathology associated with neurodegenerative diseases can in turn exacerbate both the cognitive deficits and underlying pathobiology of these conditions. Treating sleep may therefore bear significant, even disease-modifying, potential for these conditions, but how best and when to do so remains undetermined. Huntington's disease, by virtue of being an autosomal dominant neurodegenerative disease presenting in mid-life, presents a key 'model' condition through which to advance this field. To date, however, there has been no clinical longitudinal study of sleep abnormalities in Huntington's disease and no robust interrogation of their association with disease onset, cognitive deficits and markers of disease activity. Here, we present the first such study. Huntington's disease gene carriers (n = 28) and age- and sex-matched controls (n = 21) were studied at baseline and 10- and 12-year follow-up. All Huntington's disease gene carriers were premanifest at baseline and were stratified at follow-up into 'prodromal/manifest' versus 'premanifest' groups. Objective sleep abnormalities were assessed through two-night inpatient polysomnography and 2-week domiciliary actigraphy, and their association was explored against Montreal Cognitive Assessment, Trail A/B task, Symbol Digit Modalities Task (SDMT), Hopkins Verbal Learning Task (HVLT) and Montgomery-Asberg Depression Rating Scale (MADRS) scores, plus serum neurofilament light levels. Statistical analysis incorporated cross-sectional ANOVA, longitudinal repeated measures linear models and regressions adjusted for multiple confounders including disease stage. Fifteen Huntington's disease gene carriers phenoconverted to prodromal/early manifest Huntington's disease by study completion. At follow-up, these gene carriers showed more frequent sleep stage changes (P ≤ 0.001, ηp 2 = 0.62) and higher levels of sleep maintenance insomnia (defined by wake after sleep onset, P = 0.002, ηp 2 = 0.52). The latter finding was corroborated by nocturnal motor activity patterns on follow-up actigraphy (P = 0.004, ηp 2 = 0.32). Greater sleep maintenance insomnia was associated with greater cognitive deficits (Trail A P ≤ 0.001, R 2 = 0.78; SDMT P = 0.008, R 2 = 0.63; Trail B P = 0.013, R 2 = 0.60) and higher levels of neurofilament light (P = 0.015, R 2 = 0.39). Longitudinal modelling suggested that sleep stage instability accrues from the early premanifest phase, whereas sleep maintenance insomnia emerges closer to phenoconversion. Baseline sleep stage instability was able to discriminate those who phenoconverted within the study period from those who remained premanifest (area under curve = 0.81, P = 0.024). These results demonstrate that the key sleep abnormalities of premanifest/early Huntington's disease are sleep stage instability and sleep maintenance insomnia and suggest that the former bears value in predicting disease onset, while the latter is associated with greater disease activity and cognitive deficits. Intervention studies to interrogate causation within this association could not only benefit patients with Huntington's disease but also help provide fundamental proof-of-concept findings for the wider sleep-neurodegeneration field.

Time-restricted feeding mitigates Alzheimer's disease-associated cognitive impairments via a B. pseudolongum-propionic acid-FFAR3 axis

Time-restricted feeding (TRF) holds promise for alleviating cognitive decline in aging, albeit the precise mechanism via the gut-brain axis remains elusive. In a clinical trial, we observed, for the first time, that a 4-month TRF ameliorated cognitive impairments among Alzheimer's disease (AD) patients. Experiments in 5xFAD mice corroborated the gut microbiota-dependent effect of TRF on mitigating cognitive dysfunction, amyloid-beta deposition, and neuroinflammation. Multi-omics integration linked Bifidobacterium pseudolongum (B. pseudolongum) and propionic acid (PA) with key genes in AD pathogenesis. Oral supplementation of B. pseudolongum or PA mimicked TRF's protective effects. Positron emission tomography imaging confirmed PA's blood-brain barrier penetration, while knockdown of the free fatty acid receptor 3 (FFAR3) diminished TRF's cognitive benefits. Notably, we observed a positive correlation between fecal PA and improved cognitive function in an AD cohort, further indicating that TRF enhanced PA production. These findings highlight the microbiota-metabolites-brain axis as pivotal in TRF's cognitive benefits, proposing B. pseudolongum or PA as potential AD therapies.

The cyclic metabolic switching theory of intermittent fasting

Intermittent fasting (IF) and ketogenic diets (KDs) have recently attracted much attention in the scientific literature and in popular culture and follow a longer history of exercise and caloric restriction (CR) research. Whereas IF involves cyclic metabolic switching (CMS) between ketogenic and non-ketogenic states, KDs and CR may not. In this Perspective, I postulate that the beneficial effects of IF result from alternating between activation of adaptive cellular stress response pathways during the fasting period, followed by cell growth and plasticity pathways during the feeding period. Thereby, I establish the cyclic metabolic switching (CMS) theory of IF. The health benefits of IF may go beyond those seen with continuous CR or KDs without CMS owing to the unique interplay between the signalling functions of the ketone β-hydroxybutyrate, mitochondrial adaptations, reciprocal activation of autophagy and mTOR pathways, endocrine and paracrine signalling, gut microbiota, and circadian biology. The CMS theory may have important implications for future basic research, clinical trials, development of pharmacological interventions, and healthy lifestyle practices.

Biological Effects of Dietary Restriction on Alzheimer's Disease: Experimental and Clinical Investigations

BACKGROUNDS

Dementia can impose a heavy economic burden on both society and families. Alzheimer's disease (AD), the most prevalent form of dementia, is a complex neurodegenerative disease characterized by the abnormal deposition of extracellular amyloid β-protein (Aβ) and the aggregation of intracellular Tau protein to form neurofibrillary tangles (NFTs). Given the limited efficacy of pharmacological treatment, scientists have already paid more attention to non-pharmacological strategies, including dietary restriction (DR). DR refers to a nutritional paradigm aimed at promoting overall health by modifying the balance between energy consumption and expenditure. Studies have demonstrated that DR effectively extends the healthy lifespan, delays the aging process, and achieves promising results in the prevention and treatment of AD in preclinical studies.

METHODS

In this review we collected related studies and viewpoints by searching on PubMed database using the keywords. Most of the citations were published between 2015 and 2025. A few older literatures were also included due to their relevance and significance in this field.

RESULTS

We first provide a concise overview of the current therapeutic and preventive strategies for AD. Then, we introduce several specific DR protocols and their favorable effects on AD. Furthermore, the potential mechanisms underlying the benefits of DR on AD are discussed. Finally, we briefly highlight the role of DR in maintaining brain health.

CONCLUSION

This review may offer valuable insights into the development of innovative non-pharmacological strategies for AD treatment.

Circadian clock communication during homeostasis and ageing

Maintaining homeostasis is essential for continued health, and the progressive decay of homeostatic processes is a hallmark of ageing. Daily environmental rhythms threaten homeostasis, and circadian clocks have evolved to execute physiological processes in a manner that anticipates, and thus mitigates, their effects on the organism. Clocks are active in almost all cell types; their rhythmicity and functional output are determined by a combination of tissue-intrinsic and systemic inputs. Numerous inputs for a specific tissue are produced by the activity of circadian clocks of other tissues or cell types, generating a form of crosstalk known as clock communication. In mammals, the central clock in the hypothalamus integrates signals from external light-dark cycles to align peripheral clocks elsewhere in the body. This regulation is complemented by a tissue-specific milieu of external, systemic and niche inputs that modulate and cooperate with the cellular circadian clock machinery of a tissue to tailor its functional output. These mechanisms of clock communication decay during ageing, and growing evidence suggests that this decline might drive ageing-related morbidities. Dietary, behavioural and pharmacological interventions may offer the possibility to overcome these changes and in turn improve healthspan.

Intermittent fasting and neurocognitive disorders: What the evidence shows

INTRODUCTION

Intermittent fasting (IF) has emerged as a potential lifestyle intervention for mitigating cognitive decline and enhancing brain health in individuals with mild to major neurocognitive disorders. Unlike preventive strategies, this review evaluates IF as a therapeutic approach, focusing on its effects on neuroplasticity, inflammation, and cognitive function.

METHODS

A narrative review was conducted using a comprehensive PubMed search with the terms "intermittent fasting AND neurocognition" and "intermittent fasting AND neuroplasticity". Studies published in English within the last ten years involving human and animal models were included. Exclusion criteria focused on studies primarily examining mood disorders or unrelated metabolic outcomes.

RESULTS

Preclinical evidence demonstrates that IF enhances hippocampal neurogenesis and synaptic plasticity through pathways involving BDNF and CREB. IF also reduces neuroinflammation, as shown in animal models of Alzheimer's disease, vascular cognitive impairment, and high-fat diet-induced cognitive impairment. Human studies, though limited, suggest that regular IF may improve cognitive function and reduce markers of oxidative stress and inflammation in individuals with mild cognitive impairment.

CONCLUSION

Current findings highlight the therapeutic potential of IF for individuals with existing cognitive impairment. While preclinical studies provide robust evidence of neuroprotective mechanisms, human studies remain sparse and require standardization. Further clinical research is necessary to confirm long-term safety and efficacy and to refine IF protocols for broader clinical application.

IL-17A Induces Circadian Disruptions Through the Epigenetic Repression of BMAL1 in Mice With Alzheimer's Disease

Circadian disruptions and neuroinflammation impact nearly all people with Alzheimer's disease (AD), but their relationships with each other and the impact of their interaction on AD remain to be addressed. Here, we found that amyloid (A)-β treatment downregulated brain and muscle aryl hydrocarbon receptor nuclear translocator-like (BMAL) 1 through the hypermethylation of its promoter region in HT22 cells and that the inhibition of DNA methylation ameliorated circadian rhythm disorders and restored BMAL1 protein expression by reversing its hypermethylation in APPswe/PSEN1dE9 (APP/PS1) mice. Critically, increased levels of interleukin (IL)-17A contributed to BMAL1 downregulation through the hypermethylation of its promoter region, thus leading to circadian disruptions in APP/PS1 mice. Moreover, we revealed that the mitogen-activated protein kinase (MAPK) pathway was responsible for IL-17A-induced DNA methyltransferase (DNMT) 1 upregulation. Taken together, we elucidate a new mechanism connecting IL-17A with altered DNA methylation of Bmal1, which results in circadian disturbances in an AD mouse model.

Review on pathogenesis and treatment of Alzheimer's disease

The rising incidence of Alzheimer's disease (AD) and the associated economic impacts has prompted a global focus in the field. In recent years, there has been a growing understanding of the pathogenic mechanisms of AD, including the aggregation of β-amyloid, hyperphosphorylated tau, and neuroinflammation. These processes collectively lead to neurodegeneration and cognitive decline, which ultimately results in the loss of autonomy in patients. Currently, there are three main types of AD treatments: clinical tools, pharmacological treatment, and material interventions. This review provides a comprehensive analysis of the underlying etiology and pathogenesis of AD, as well as an overview of the current prevalence of AD treatments. We believe this article can help deepen our understanding of the AD mechanism, and facilitate the clinical translation of scientific research or therapies, to address this global problem of AD.

Long-24-h ahemeral light cycle improved eggshell quality of hens in late laying period

Previous study indicated that long-24-h ahemeral light cycle could ameliorate the deterioration of eggshell quality, a significant issue in the later stages of egg production; nevertheless, the underlying process remains unclear. This study explored the mechanism of the long-24-h ahemeral light cycle improving eggshell quality of hens in late laying stage. Two sets of 260 Hy-Line brown laying hens, aged 74 weeks, were randomized, with 65 chickens in each group. One was treated to a standard light cycle (24 h, 16L:8D), whereas the other was subjected to a long-24 h ahemeral light cycle (28 h, 16L:12D). The experimental cycle was 12 weeks. The results indicated that the long-24 h ahemeral light cycle did not influence laying performance (P > 0.05); however, eggshell strength and thickness was dramatically enhanced (P < 0.05). The serum levels of 1,25(OH)2D3 and ALP exhibited comparable changes, whereas PTH, PCT, and OT displayed contrasting variations between the two groups. Transcriptome sequencing revealed 889 common genes exhibiting rhythmic expression in both groups, with an average phase advance of 7.41 h. In comparison to the 16L:8D group, 97.41 % of genes exhibited phase advancement in the 16L:12D group. Based on the findings of the functional analysis, we identified four genes associated with bone metabolism and examined their expression patterns: CTNNB1, BMPR2, BMP7, and PDIA3. The expression trend of BMPR2 gene was similar to that of serum 1,25(OH)2D3, and the expression trend of BMP7 gene was similar to that of serum OT. The mRNA expression patterns of PDIA3 and BMP7 were inversely related, whereas CTNNB1 and BMPR2 exhibited comparable trends. The mRNA expression of CTNNB1, PDIA3, and BMP7 correlated with eggshell formation. The mRNA expression of BMPR2 significantly elevated during eggshell formation in the 16L:8D group, whereas it remained low during the daylight in comparison to darkness in the 16L:12D group. In summary, the change of light cycle affects the biological rhythm of laying hens, and we found four genes related to bone metabolism, CTNNB1, BMPR2, BMP7 and PDIA3, which specifically responded to the long-24 h ahemeral light cycle and possibly participated in the improvement of eggshell quality.

Scheduled feeding improves behavioral outcomes and reduces inflammation in a mouse model of Fragile X syndrome

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by the abnormal expansion of CGG repeats in the fragile X mental retardation 1 (FMR1) gene. Many FXS patients experience sleep disruptions, and we sought to explore these symptoms along with the possible benefits of a scheduled feeding intervention using the Fmr1 knockout (KO) mouse model. These mutants displayed clear evidence for sleep and circadian disturbances including delay in the onset of sleep and fragmented activity rhythms with increases in cycle-to-cycle variability. Importantly, the Fmr1 KO mice exhibited deficits in their circadian behavioral response to light with reduced masking, longer time to resetting to shifts in the Light-Dark cycle, altered synchronization to a skeleton photoperiod and lower magnitude light-induced phase shifts of activity rhythms. Investigation of the retinal input to the surprachiasmatic nucleus (SCN) with the neurotracer cholera toxin (β subunit) and quantification of the light-evoked cFos expression in the SCN revealed an abnormal retinal innervation of the SCN in the Fmr1 KO, providing a possible mechanistic explanation for the observed behavioral deficits. Interestingly, disruptions in social and repetitive behaviors correlated with sleep duration and fragmentation. Understanding the nature of the deficits, we decided to apply a scheduled feeding regimen (6-hr/18-hr feed/fast cycle) as a circadian-based strategy to boast circadian rhythms independently of light. This intervention significantly improved the activity rhythms and sleep in the mutants. Strikingly, the scheduled feeding ameliorated social interactions and reduced repetitive behaviors as well as the levels of Interferon-gamma and Interleukin-12 in the Fmr1 KO mutants, suggesting that timed eating may be an effective way to lessen inflammation. Collectively, this work adds support to efforts to develop circadian based interventions to help with symptoms of neurodevelopmental disorders.

Regulation of lipid dysmetabolism and neuroinflammation linked with Alzheimer's disease through modulation of Dgat2

Alzheimer's disease (AD) is a progressive neurodegenerative disorder marked by amyloid-β (Aβ) plaque accumulation, cognitive decline, lipid dysregulation, and neuroinflammation. While mutations in the Amyloid Precursor Protein (APP) and Aβ42 accumulation contribute to AD, the mechanisms linking Aβ to lipid metabolism and neuroinflammation remain unclear. Using Drosophila models, we show that App NLG and Aβ42 expression causes locomotor deficits, disrupted sleep, memory impairments, lipid accumulation, synaptic loss, and neuroinflammation. Similar lipid and inflammatory changes are observed in the App NLG-F knock-in mouse model, reinforcing their role in AD pathogenesis. We identify diacylglycerol O-acyltransferase 2 (Dgat2), a key lipid metabolism enzyme, as a modulator of AD phenotypes. In Drosophila and mouse AD models, Dgat2 levels and its transcription factors are altered. Dgat2 knockdown in Drosophila reduced lipid accumulation, restored synaptic integrity, improved locomotor and cognitive function, and mitigated neuroinflammation. Additionally, Dgat2 modulation improved sleep and circadian rhythms. In App NLG-F mice, Dgat2 inhibition decreased neuroinflammation and reduced AD risk gene expression. These findings highlight the intricate link between amyloid pathology, lipid dysregulation, and neuroinflammation, suggesting that targeting Dgat2 may offer a novel therapeutic approach for AD. Conserved lipid homeostasis mechanisms across species provide valuable translational insights.

Antiageing strategy for neurodegenerative diseases: from mechanisms to clinical advances

In the context of global ageing, the prevalence of neurodegenerative diseases and dementia, such as Alzheimer's disease (AD), is increasing. However, the current symptomatic and disease-modifying therapies have achieved limited benefits for neurodegenerative diseases in clinical settings. Halting the progress of neurodegeneration and cognitive decline or even improving impaired cognition and function are the clinically meaningful goals of treatments for neurodegenerative diseases. Ageing is the primary risk factor for neurodegenerative diseases and their associated comorbidities, such as vascular pathologies, in elderly individuals. Thus, we aim to elucidate the role of ageing in neurodegenerative diseases from the perspective of a complex system, in which the brain is the core and peripheral organs and tissues form a holistic network to support brain functions. During ageing, the progressive deterioration of the structure and function of the entire body hampers its active and adaptive responses to various stimuli, thereby rendering individuals more vulnerable to neurodegenerative diseases. Consequently, we propose that the prevention and treatment of neurodegenerative diseases should be grounded in holistic antiageing and rejuvenation means complemented by interventions targeting disease-specific pathogenic events. This integrated approach is a promising strategy to effectively prevent, pause or slow down the progression of neurodegenerative diseases.

A novel O,N,O-coordinated organofluoroboron probe for amyloid detection: insight from experiment and theory

This work presents the results of photophysical studies for a newly synthesized BF-based organoboron dye of D-A-D topology. The one- and two-photon properties of the dye are compared with the D-A parent compound and commercially available amyloid marker: methoxy-X04. We demonstrate that the new dye exhibits better optical properties upon binding to amyloids than methoxy-X04, including emission above 600 nm, higher values of 2PA cross section, broader excitation range and higher increment of emission intensity upon binding to amyloids. All these data demonstrate that the new probe is an interesting scaffold for application in two-photon microscopy and amyloid staining.

Circadian rhythm, microglia-mediated neuroinflammation, and Alzheimer's disease

Microglia, the brain's resident macrophages, are key mediators of neuroinflammation, responding to immune pathogens and toxins. They play a crucial role in clearing cellular debris, regulating synaptic plasticity, and phagocytosing amyloid-β (Aβ) plaques in Alzheimer's disease (AD). Recent studies indicate that microglia not only exhibit intrinsic circadian rhythms but are also regulated by circadian clock genes, influencing specific functions such as phagocytosis and the modulation of neuroinflammation. Disruption of the circadian rhythm is closely associated with AD pathology. In this review, we will provide an overview of how circadian rhythms regulate microglia-mediated neuroinflammation in the progression of AD, focusing on the pathway from the central nervous system (CNS) and the peripheral immune system. We also discuss potential therapeutic targets, including hormone modulation, lifestyle interventions, and anti-inflammatory therapies, aimed at maintaining brain health in AD. This will shed light on the involvement of circadian rhythm in AD and explore new avenues for AD treatment.

I "Gut" Rhythm: the microbiota as a modulator of the stress response and circadian rhythms

Modern habits are becoming more and more disruptive to health. As our days are often filled with circadian disruption and stress exposures, we need to understand how our responses to these external stimuli are shaped and how their mediators can be targeted to promote health. A growing body of research demonstrates the role of the gut microbiota in influencing brain function and behavior. The stress response and circadian rhythms, which are essential to maintaining appropriate responses to the environment, are known to be impacted by the gut microbiota. Gut microbes have been shown to alter the host's response to stress and modulate circadian rhythmicity. Although studies demonstrated strong links between the gut microbiota, circadian rhythms and the stress response, such studies were conducted in an independent manner not conducive to understanding the interface between these factors. Due to the interconnected nature of the stress response and circadian rhythms, in this review we explore how the gut microbiota may play a role in regulating the integration of stress and circadian signals in mammals and the consequences for brain health and disease.

Daytime-Restricted Feeding Alleviates D-Galactose-Induced Aging in Mice and Regulates the AMPK and mTORC1 Activities

Time-restricted feeding (TRF) is a distinct regimen of intermittent fasting advocated for health improving. Although nighttime TRF (NRF) in rodents is analogous to daytime TRF (DRF) in humans and has health benefits, the effects of DRF on rodent's health remain uncertain. The adverse health effects of DRF in rodents are primarily attributed to its implementation-induced temporal shift in the expression of circadian rhythm-related genes. However, studies also demonstrate the health-beneficial effect of restricted feeding itself on metabolic homeostasis, particularly in periphery tissues. Moreover, the direct effects of DRF on aging progression in rodents are underexplored, highlighting a gap in current research. To explore the overall health effects of long-term DRF in rodents, especially its influence on aging progression, we investigated the impact of long-term DRF on mice under a progeric aging condition. Results showed that both 4-h and 8-h DRF regimens exerted positive effects on aging retardation; these effects were manifested as improved physical and memory capacities, enhanced liver and kidney functions, and reduced oxidative damage and inflammatory response. These DRF regimens also lowered the manifestation of aging-related markers in peripheral tissues, with decreased SA-β-gal staining and p16 expression. Mechanistically, DRF regimens, especially DRF8, upregulated AMPK signaling and downregulated mTORC1 signaling. Interestingly, the health benefits of DRF are similar to those of metformin intervention. In conclusion, our study demonstrates for the first time that DRF effectively counteracts oxidative stress-induced aging progression in mice, supporting the viewpoint that TRF as a promising strategy for preventing aging and aging-related disorders.

Longitudinal characterization reveals behavioral impairments in aged APP knock in mouse models

APP knock-in (KI) mice serve as an exciting new model system to understand amyloid beta (Aβ) pathology, overcoming many of the limitations of previous overexpression-based model systems. The APPSAA mouse model (containing the humanized APP with three familial Alzheimer's disease mutations) and the APPWT control (containing wildtype humanized APP) are the first commercially available APP KI mice within the United States. While APPSAA mice have been shown to develop progressive Aβ pathology and neuroinflammation, the age at which behavioral and cognitive impairments begin to develop has yet to be described. Therefore, we performed an in-depth longitudinal study over 16 months, assessing cognition in these two strains, as well as assessments of motor function. While no cognitive deficits are observed in either genotype throughout the first year of life, 16-month-old APPSAA, but not APPWT mice show initial signs of spatial memory decline. In addition, both genotypes display impaired motor function at the same age. Together, this data identifies a timeframe where behavioral deficits appear, providing an essential foundation for future studies using these model systems.

The influence of time-restricted eating/feeding on Alzheimer's biomarkers and gut microbiota

OBJECTIVES

Alzheimer's disease (AD) is a progressive neurodegenerative disorder affecting approximately 55 million individuals globally. Diagnosis typically occurs in advanced stages, and there are limited options for reversing symptoms. Preventive strategies are, therefore, crucial. Time Restricted Eating (TRE) or Time Restricted Feeding (TRF) is one such strategy. Here we review recent research on AD and TRE/TRF in addition to AD biomarkers and gut microbiota.

METHODS

A comprehensive review of recent studies was conducted to assess the impact of TRE/TRF on AD-related outcomes. This includes the analysis of how TRE/TRF influences circadian rhythms, beta-amyloid 42 (Aß42), pro-inflammatory cytokines levels, and gut microbiota composition.

RESULTS

TRE/TRF impacts circadian rhythms and can influence cognitive performance as observed in AD. It lowers beta-amyloid 42 deposition in the brain, a key AD biomarker, and reduces pro-ininflammatory cytokines. The gut microbiome has emerged as a modifiable factor in AD treatment. TRE/TRF changes the structure and composition of the gut microbiota, leading to increased diversity and a decrease in harmful bacteria.

DISCUSSION

These findings underscore the potential of TRE/TRF as a preventive strategy for AD. By reducing Aß42 plaques, modulating pro-inflammatory cytokines, and altering gut microbiota composition, TRE/TRF may slow the progression of AD. Further research is needed to confirm these effects and to understand the mechanisms involved. This review highlights TRE/TRF as a promising non-pharmacological intervention in the fight against AD.

Effects of aging on diurnal transcriptome change in the mouse corpus callosum

The corpus callosum, a major white matter region central to cognitive function, is vulnerable to aging. Using zeitgeber time (ZT) aligned with environmental light/dark cycles, we investigated temporal gene expression patterns in the corpus callosum of young (5-month-old) and aged (24-month-old) mice using RNA-seq. Comparative analysis revealed more differentially expressed genes across ZT pairs in young mice than aged mice. In addition, complement pathway genes, including C4b, C3, C1qa, C1qb, and C1qc, were consistently upregulated in aged mice regardless of ZT. Furthermore, genes such as Etnppl, Tinagl1, Hspa12b, Ppp1r3c, Thbd, Pla2g3, and Tsc22d3 exhibited ZT-dependent rhythmicity in young mice, but their rhythmic patterns were altered with age. This study provides an important dataset of the interplay between aging, diurnal rhythms, and gene expression in the corpus callosum, highlighting potential molecular mechanisms mediating white matter aging. Further investigation is warranted to dissect these gene's specific roles in neurological health during aging.

Dysregulation of the molecular clock by blood-borne factors in Alzheimer's disease patients

BACKGROUND

Circadian disruptions are increasingly recognized in Alzheimer's disease (AD) patients and may influence disease onset and progression. This study examines how AD pathology affects blood-borne factors that regulate circadian rhythms.

METHODS

Eighty-five participants from the Sino Longitudinal Study on Cognitive Decline were enrolled: 35 amyloid-beta negative normal controls (Aβ- NCs), 23 amyloid-beta positive normal controls (Aβ+ NCs), 15 patients with amnestic mild cognitive impairment (aMCI), and 12 with Alzheimer's disease dementia (ADD). Patients with aMCI and ADD were grouped as cognitively impaired (CI). Cellular circadian period length was assessed using a serum-based assay. Expression levels of clock genes in serum-treated cells and in leukocytes of participants were measured via real-time PCR. Plasma biomarkers were quantified using a single-molecule array immunoassay. Pineal parenchymal and hippocampal volumes were determined by magnetic resonance imaging.

RESULTS

The cellular circadian period length was significantly extended by serum from CI patients than by that from Aβ- NCs (p < 0.01). Treatment of cells with serum from the CI patients resulted in suppressed expression of the clock genes Bmal1 and Nr1d1. Strong relationships between the expression levels of clock genes observed in leukocytes of the Aβ- NC group did not appear in those of the Aβ+ NC or CI groups. The significant correlation of cellular circadian period length and the pineal volume was only observed in the Aβ- NC group, but not in the Aβ+ NC or CI groups.

CONCLUSIONS

This study indicates the presence of significant changes in blood-borne factors that could affect the circadian rhythms in AD, starting even at preclinical stages. These alterations could precede cognitive decline and contribute to AD pathogenesis.

TRIAL REGISTRATION

The cohort is registered at ClinicalTrials.gov (SILCODE: NCT03370744; Registered on Mar 15th, 2017).

BMAL1 ameliorates type 2 diabetes-induced cognitive impairment via AREG upregulation and PI3K/Akt/GSK-3β pathway activation

Cognitive impairment is a significant complication of type 2 diabetes mellitus (T2DM). However, the mechanisms underlying the development of cognitive dysfunction in individuals with T2DM remain elusive. Herein, we discussed the role of Bmal1, a core circadian rhythm-regulating gene, in the process of T2DM-associated cognitive dysfunction. We identified a marked decrease in BMAL1 levels in the hippocampus of db/db mice, followed by gain- and loss-of-function studies to explore the impact of BMAL1 on cognitive function. Our findings indicated that BMAL1 downregulation led to cognitive deficits, characterized by tau hyperphosphorylation and accumulated amyloid plaque. Conversely, BMAL1 overexpression mitigated these Alzheimer-like pathologies. Further investigation revealed that BMAL1 directly activated the transcription of Areg, thereby activating the PI3K/Akt/GSK-3β pathway and ameliorating cognitive dysfunction. Moreover, these effects of BMAL1 were attenuated by LY294002, a PI3K inhibitor. Collectively, these results underscore the significant role of BMAL1 in T2DM-associated cognitive impairment, proposing a novel intervention strategy for individuals exposed to risk factors of T2DM.

Fasting the brain for mental health

Unfavorable socioeconomic and geopolitical conditions such as poverty, violence and inequality increase vulnerability to mental disorders. Also, exposure to a poor nutrition such as high-energy dense (HED) diets has been linked to alterations in brain function, leading to anxiety, addiction, and depression. HED diets rich in saturated fatty acids or obesity can activate the innate immune system in the brain, especially microglia, increasing proinflammatory cytokines such as interleukin 1 beta (IL1-β) and interleukin 6 (IL-6), in part, by the stimulation of toll-like receptor 4 (TLR4) and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway. Intermittent fasting (IF), an eating protocol characterized by alternating periods of fasting with periods of eating, has gained recognition as a weight-management strategy to reduce obesity. Accordingly, during IF inflammation and brain function can be modulated by production of ketone bodies and modulation of the intestinal microbiota, which also promote the induction of brain-derived neurotrophic factor (BDNF), which is involved in neurogenesis and neuronal plasticity. Although IF has contributed to reduce body weight and improve metabolic profiles, its influence on mental health remains an evolving field of research. Here, we provide experimental evidence supporting the role of IF reducing neuroinflammation as a valuable approach to improve mental health.

Bmi-1 plays an important role in preventing bone aging by regulating the bone microenvironment

BACKGROUND

B-cell specific Moloney MLV insertion site-1 (Bmi-1) belongs to the polycomb group (PcG) gene and is a transcriptional suppressor to maintain appropriate gene expression patterns during development. To investigate whether the Bmi-1 gene has a corrective effect on bone senescence induced in Bmi-1-/- mice through regulating the bone microenvironment.

METHODS

Littermate heterozygous male and female mice (Bmi-1+/-) were used in this study. Related experiments were performed in wild type mice (10 mice, WT group) and Bmi-1 knock out mice (10 mice, BKO group) for analysis of phenotype, skeletal radiography, micro-computed tomography, histology, immunohistochemical staining, western blot analysis, and detection of ROS levels.

RESULTS

Our results indicated that the Bmi-1 gene could proportionally rescued mice suffering from bone aging induced by Bmi-1 gene defects. Bmi-1 plays an anti-aging effect in bone through multiple aspects, such as increasing osteoblast bone formation and decreascing osteoclast bone absorption, stimulating proliferation, reducing apoptosis, inhibiting reactive oxygen species (ROS) and delaying DNA damage.

CONCLUSIONS

Our results suggested that Bmi-1 may play a fundamental and important role in correcting bone senescence in BKO mice. At the same time, it may provide theoretical basis for the clinical application of Bmi-1 in anti-aging in bone.

Time-restricted feeding does not prevent adverse effects of palatable cafeteria diet on adiposity, cognition and gut microbiota in rats

Time-restricted feeding (TRF) is a popular dietary strategy whereby daily food intake is limited to a <12h window. As little is known about the effects of TRF on cognitive and behavioral measures, the present study examined the effects of time-restricted (8h/day; zeitgeber time [ZT]12-20) or continuous access to a high-fat, high-sugar cafeteria-style diet (Caf; Caf and Caf-TRF groups; n=12 adult male Sprague-Dawley rats) or standard chow (Chow and Chow-TRF groups) on short-term memory, anxiety-like behavior, adiposity and gut microbiota composition over 13-weeks with daily food intake measures. TRF significantly reduced daily energy intake in Caf- but not chow-fed groups. In Caf-fed groups, TRF reduced the proportion of energy derived from sugar while increasing that derived from protein. Caf diet significantly increased weight gain, adiposity and fasting glucose within 4 weeks; TRF partially reduced these effects. Caf diet increased anxiety-like behavior in the Elevated Plus Maze in week 3 but not week 12, and impaired hippocampal-dependent place recognition memory in week 11; neither measure was affected by TRF. Global microbiota composition differed markedly between chow and Caf groups, with a small effect of TRF in rats fed chow. In both chow and Caf diet groups, TRF reduced microbiota alpha diversity measures of Shannon diversity and evenness relative to continuous access. Results indicate only limited benefits of TRF access to an obesogenic diet under these conditions, suggesting that more severe time restriction may be required to offset adverse metabolic and cognitive effects when using highly palatable diets.

Blood osmolytes such as sugar can drive brain fluid flows in a poroelastic model

The glymphatic system of fluid flow through brain tissue may clear amyloid-β during sleep and as such underlie the need for sleep. Dysfunctional glymphatic transport has been implicated in pathological conditions ranging from stroke and dementia to psychiatric illnesses. To date, the fastest observed in-vivo brain flows have been reported after the manipulation of blood osmotic pressures. Surprisingly, the brain seems to shrink while receiving more influx. Though influx of an incompressible fluid might expand the tissue, no physical theory for these observations has been proposed. We here present a minimal mathematical model of brain pressure, deformation, and fluid flows due to vascular osmotic pressures. The model is based on Darcy flow, linear poroelasticity theory and conservation of mass. We propose that a screened Poisson equation holds for interstitial pressure because vascular filtration corresponds to fluid divergence. The model resolves the apparent paradox of combined fluid influx with tissue shrinkage by showing that fluid absorption into the blood can drive both. In this model, small glucose concentration differences between plasma and brain can drive brain flow velocities observed in recent in-vivo assays. Osmosis may therefore drive brain fluid flow under physiological conditions and provide an explanation for the known correlations between diabetes and dementia.

Health impacts of a remotely delivered prolonged nightly fasting intervention in stressed adults with memory decline and obesity: A nationwide randomized controlled pilot trial

Objective/Goals

Cognitive decline is intricately linked to various factors such as obesity, stress, poor sleep, and circadian rhythm misalignment, which are interrelated in their impact on cognitive health. Irregular food-intake timing further compounds these issues. The practice of prolonged nightly fasting (PNF) may help synchronize food intake with circadian rhythms, potentially mitigating adverse effects of cognitive decline and associated factors.

Methods

A pilot nationwide, remotely delivered, 2-arm randomized controlled trial was conducted to assess the 8-week outcomes of cognition, stress, and sleep, after a PNF intervention (14-hr nightly fast, 6 nights/week, no calories after 8 pm) compared to a health education (HED) control condition. Participants were living with memory decline, stress, and obesity and had weekly check-in calls to report fasting times (PNF) or content feedback (HED).

Results

Participants were enrolled from 37 states in the US; N = 58, 86% women, 71% white, 93% non-Latinx, mean (SD) age 50.1 (5.1) years and BMI 35.6 (3.6) kg/m2. No group differences existed at baseline. Linear mixed-effects models were used to compare outcome change differences between groups. Compared to the HED control, the PNF intervention was associated with improved sleep quality (B = -2.52; SE = 0.90; 95% CI -4.30--0.74; p = 0.006). Perceived stress and everyday cognition significantly changed over time (p < 0.02), without significant difference by group.

Discussion

Changing food intake timing to exclude nighttime eating and promote a fasting period may help individuals living with obesity, memory decline, and stress to improve their sleep. Improved sleep quality may lead to additional health benefits.

Time-restricted feeding prevents memory impairments induced by obesogenic diet consumption, via hippocampal thyroid hormone signaling

OBJECTIVE

The early consumption of calorie-rich diet disrupts circadian rhythms and has adverse effects on memory, yet the effects of time-restricted feeding (TRF) and the underlying molecular mechanisms are unknown. Here, we set out to identify the behavioral and molecular circadian rhythms disruptions generated by juvenile obesogenic diet consumption and their restoration by TRF in male mice.

METHODS

Metabolic rhythms were measured by indirect calorimetry and memory performances by behavioral tasks. Hippocampal translatome (pS6_TRAP), enrichment and co-regulated gene network analyses were conducted to identify the molecular pathways involved in memory impairments and their restoration by TRF. Differential exon usage analyses, mass spectrometry and pharmacological intervention were used to confirm thyroid hormone signaling involvement.

RESULTS

We show that four weeks of TRF restore the rhythmicity of metabolic parameters and prevents memory impairments in mice fed a high fat-high sucrose (HFS) diet since weaning, independently of body fat levels. Hippocampal translatome and differential exon usage analyses indicate that impaired memory of mice under ad libitum HFS diet is accompanied by reduced thyroid hormone signaling and altered expression of astrocytic genes regulating glutamate neurotransmission. TRF restored the diurnal expression variation of part of these genes and intra-hippocampal infusion of T3, the active form of thyroid hormone, rescues memory performances and astrocytic gene expression of ad libitum HFS diet-fed mice.

CONCLUSIONS

Thus, thyroid hormones contribute to the TRF positive effects on both metabolism and memory in mice fed an obesogenic diet, highlighting this nutritional approach as a powerful tool in addressing obesity brain comorbidities and paving the way for further mechanistic studies on hippocampal thyroid signaling.

Apolipoprotein E Induces Lipid Accumulation Through Dgat2 That Is Prevented with Time-Restricted Feeding in Drosophila

Background: Apolipoprotein E (ApoE) is the leading genetic risk factor for late-onset Alzheimer's disease (AD), which is the leading cause of dementia worldwide. Most people have two ApoE-ε3 (ApoE3) alleles, while ApoE-ε2 (ApoE2) is protective from AD, and ApoE-ε4 (ApoE4) confers AD risk. How these alleles modulate AD risk is not clearly defined, and ApoE's role in lipid metabolism is also not fully known. Lipid droplets increase in AD. However, how ApoE contributes to lipid accumulation in the brain remains unknown. Methods: Here, we use Drosophila to study the effects of ApoE alleles on lipid accumulation in the brain and muscle in a cell-autonomous and non-cell-autonomous manner. Results: We report that pan-neuronal expression of each ApoE allele induces lipid accumulation specifically in the brain, but not in the muscle. However, this was not the case when expressed with muscle-specific drivers. ApoE2- and ApoE3-induced lipid accumulation is dependent on the expression of Dgat2, a key regulator of triacylglycerol production, while ApoE4 still induces lipid accumulation even with knock-down of Dgat2. Additionally, we find that implementation of time-restricted feeding (TRF), a dietary intervention in which food access only occurs in the active period (day), prevents ApoE-induced lipid accumulation in the brain of flies and modulates lipid metabolism genes. Conclusions: Altogether, our results demonstrate that ApoE induces lipid accumulation in the brain, that ApoE4 is unique in causing lipid accumulation independent of Dgat2, and that TRF prevents ApoE-induced lipid accumulation. These results support the idea that lipid metabolism is critical in AD, and that TRF could be a promising therapeutic approach to prevent ApoE-associated dysfunction in lipid metabolism.

Microglia, circadian rhythm and lifestyle factors

Microglia, a vital homeostasis-keeper of the central nervous system, perform critical functions such as synaptic pruning, clearance of cellular debris, and participation in neuroinflammatory processes. Recent research has shown that microglia exhibit strong circadian rhythms that not only actively regulate their own immune activity, but also affect neuronal function. Disruptions of the circadian clock have been linked to a higher risk of developing a variety of diseases. In this article we will provide an overview of how lifestyle factors impact microglial function, with a focus on disruptions caused by irregular sleep-wake patterns, reduced physical activity, and eating at the wrong time-of-day. We will also discuss the potential connection between these lifestyle factors, disrupted circadian rhythms, and the role of microglia in keeping brain health. This article is part of the Special Issue on "Microglia".

Cognitive impairment induced by circadian rhythm disorders involves hippocampal brain-derived neurotrophic factor reduction and amyloid-β deposition

Circadian rhythm disruptions have been implicated in numerous health issues, including cognitive decline and the exacerbation of neurodegenerative diseases, like Alzheimer disease (AD). Brain-derived neurotrophic factor (BDNF), vital for neuronal plasticity and cognitive function, is regulated by the circadian clock and exerts protective effects against AD. Thus, we investigated the impact of circadian rhythm disorders (CRDs) on cognitive impairment and explored the underlying neurobiological mechanisms by assessing BDNF and amyloid-β (Aβ) levels. We divided male C57BL/6 mice into three groups (n = 30): a control group (normal 12/12 hour light-dark cycle) and two CRD model groups (3/3 and 22/22 hour cycles, respectively). After 12 weeks, we assessed cognitive functions using the Morris water maze. Following behavioral tests, hippocampal levels of BDNF and Aβ were quantified using enzyme-linked immunosorbent assays. CRDs significantly impaired learning and memory, as evidenced by longer times to reach and find the platform in the CRD groups (p < 0.01). Furthermore, BDNF levels were notably decreased and Aβ levels increased in the CRD groups compared with the control group (p < 0.01). Thus, CRDs elicit cognitive impairment by reducing BDNF levels and increasing Aβ deposition in the hippocampus.

Melatonin Supplementation Alleviates Impaired Spatial Memory by Influencing Aβ1-42 Metabolism via γ-Secretase in the icvAβ1-42 Rat Model with Pinealectomy

In the search for Alzheimer's disease (AD) therapies, most animal models focus on familial AD, which accounts for a small fraction of cases. The majority of AD cases arise from stress factors, such as oxidative stress, leading to neurological changes (sporadic AD). Early in AD progression, dysfunction in γ-secretase causes the formation of insoluble Aβ1-42 peptides, which aggregate into senile plaques, triggering neurodegeneration, cognitive decline, and circadian rhythm disturbances. To better model sporadic AD, we used a new AD rat model induced by intracerebroventricular administration of Aβ1-42 oligomers (icvAβ1-42) combined with melatonin deficiency via pinealectomy (pin). We validated this model by assessing spatial memory using the radial arm maze test and measuring Aβ1-42 and γ-secretase levels in the frontal cortex and hippocampus with ELISA. The icvAβ1-42 + pin model experienced impaired spatial memory and increased Aβ1-42 and γ-secretase levels in the frontal cortex and hippocampus, effects not seen with either icvAβ1-42 or the pin alone. Chronic melatonin treatment reversed memory deficits and reduced Aβ1-42 and γ-secretase levels in both structures. Our findings suggest that our icvAβ1-42 + pin model is extremely valuable for future AD research.

Updates in Alzheimer's disease: from basic research to diagnosis and therapies

Alzheimer's disease (AD) is the most common neurodegenerative disorder, characterized pathologically by extracellular deposition of β-amyloid (Aβ) into senile plaques and intracellular accumulation of hyperphosphorylated tau (pTau) as neurofibrillary tangles. Clinically, AD patients show memory deterioration with varying cognitive dysfunctions. The exact molecular mechanisms underlying AD are still not fully understood, and there are no efficient drugs to stop or reverse the disease progression. In this review, we first provide an update on how the risk factors, including APOE variants, infections and inflammation, contribute to AD; how Aβ and tau become abnormally accumulated and how this accumulation plays a role in AD neurodegeneration. Then we summarize the commonly used experimental models, diagnostic and prediction strategies, and advances in periphery biomarkers from high-risk populations for AD. Finally, we introduce current status of development of disease-modifying drugs, including the newly officially approved Aβ vaccines, as well as novel and promising strategies to target the abnormal pTau. Together, this paper was aimed to update AD research progress from fundamental mechanisms to the clinical diagnosis and therapies.

Circadian Interventions in Preclinical Models of Huntington's Disease: A Narrative Review

Huntington's Disease (HD) is a neurodegenerative disorder caused by an autosomal-dominant mutation in the huntingtin gene, which manifests with a triad of motor, cognitive and psychiatric declines. Individuals with HD often present with disturbed sleep/wake cycles, but it is still debated whether altered circadian rhythms are intrinsic to its aetiopathology or a consequence. Conversely, it is well established that sleep/wake disturbances, perhaps acting in concert with other pathophysiological mechanisms, worsen the impact of the disease on cognitive and motor functions and are a burden to the patients and their caretakers. Currently, there is no cure to stop the progression of HD, however, preclinical research is providing cementing evidence that restoring the fluctuation of the circadian rhythms can assist in delaying the onset and slowing progression of HD. Here we highlight the application of circadian-based interventions in preclinical models and provide insights into their potential translation in clinical practice. Interventions aimed at improving sleep/wake cycles' synchronization have shown to improve motor and cognitive deficits in HD models. Therefore, a strong support for their suitability to ameliorate HD symptoms in humans emerges from the literature, albeit with gaps in our knowledge on the underlying mechanisms and possible risks associated with their implementation.

Scheduled feeding improves sleep in a mouse model of Huntington's disease

Sleep disturbances are common features of neurodegenerative disorders including Huntington's disease (HD). Sleep and circadian disruptions are recapitulated in animal models, providing the opportunity to evaluate the effectiveness of circadian interventions as countermeasures for neurodegenerative disease. For instance, time restricted feeding (TRF) successfully improved activity rhythms, sleep behavior and motor performance in mouse models of HD. Seeking to determine if these benefits extend to physiological measures of sleep, electroencephalography (EEG) was used to measure sleep/wake states and polysomnographic patterns in male and female wild-type (WT) and bacterial artificial chromosome transgenic (BACHD) adult mice, under TRF and ad lib feeding (ALF). Our findings show that male, but not female, BACHD mice exhibited significant changes in the temporal patterning of wake and non-rapid eye movement (NREM) sleep. The TRF intervention reduced the inappropriate early morning activity by increasing NREM sleep in the male BACHD mice. In addition, the scheduled feeding reduced sleep fragmentation (# bouts) in the male BACHD mice. The phase of the rhythm in rapid-eye movement (REM) sleep was significantly altered by the scheduled feeding in a sex-dependent manner. The treatment did impact the power spectral curves during the day in male but not female mice regardless of the genotype. Sleep homeostasis, as measured by the response to six hours of gentle handling, was not altered by the diet. Thus, TRF improves the temporal patterning and fragmentation of NREM sleep without impacting sleep homeostasis. This work adds critical support to the view that sleep is a modifiable risk factor in neurodegenerative diseases.

The impacts of sex and the 5xFAD model of Alzheimer's disease on the sleep and spatial learning responses to feeding time

Introduction

The relationships between the feeding rhythm, sleep and cognition in Alzheimer's disease (AD) are incompletely understood, but meal time could provide an easy-to-implement method of curtailing disease-associated disruptions in sleep and cognition. Furthermore, known sex differences in AD incidence could relate to sex differences in circadian rhythm/sleep/cognition interactions.

Methods

The 5xFAD transgenic mouse model of AD and non-transgenic wild-type controls were studied. Both female and male mice were used. Food access was restricted each day to either the 12-h light phase (light-fed groups) or the 12-h dark phase (dark-fed groups). Sleep (electroencephalographic/electromyographic) recording and cognitive behavior measures were collected.

Results

The 5xFAD genotype reduces NREM and REM as well as the number of sleep spindles. In wild-type mice, light-fed groups had disrupted vigilance state amounts, characteristics, and rhythms relative to dark-fed groups. These feeding time differences were reduced in 5xFAD mice. Sex modulates these effects. 5xFAD mice display poorer spatial memory that, in female mice, is curtailed by dark phase feeding. Similarly, female 5xFAD mice have decreased anxiety-associated behavior. These emotional and cognitive measures are correlated with REM amount.

Discussion

Our study demonstrates that the timing of feeding can alter many aspects of wake, NREM and REM. Unexpectedly, 5xFAD mice are less sensitive to these feeding time effects. 5xFAD mice demonstrate deficits in cognition which are correlated with REM, suggesting that this circadian-timed aspect of sleep may link feeding time and cognition. Sex plays an important role in regulating the impact of feeding time on sleep and cognition in both wild-type and 5xFAD mice, with females showing a greater cognitive response to feeding time than males.

Prolonged Sleep Deprivation Induces a Reprogramming of Circadian Rhythmicity with the Hepatic Metabolic Transcriptomic Profile

Sleep disturbances can disrupt the overall circadian rhythm. However, the impact of sleep deprivation on the circadian rhythm of the liver and its underlying mechanisms still requires further exploration. In this study, we subjected male mice to 5 days of sleep deprivation and performed liver transcriptome sequencing analysis at various time points within a 24-h period. Subsequently, we monitored the autonomic activity and food intake in these male mice for six days post-sleep deprivation. We observed alterations in sleep-wake and feeding rhythms in the first two days following sleep deprivation. Additionally, we also observed a decrease in 24-h serum-glucose levels. Liver transcriptome sequencing has shown that sleep deprivation induces the rhythmic transcription of a large number of genes, or alters the rhythmic properties of genes, which were then significantly enriched in the carbohydrate, lipid, and protein metabolism pathways. Our findings suggest that under conditions of prolonged sleep deprivation, the expression of metabolic-related genes in the liver was reset, leading to changes in the organism's metabolic state to ensure energy supply to sustain prolonged wakefulness.

Genomic Convergence in Hibernating Mammals Elucidates the Genetics of Metabolic Regulation in the Hypothalamus

Elucidating the genetic basis of mammalian metabolism could help define mechanisms central to health and disease. Here, we define conserved cis-regulatory elements (CREs) and programs for mammalian metabolic control. We delineate gene expression and chromatin responses in the mouse hypothalamus for 7 steps of the Fed-to-Fasted-to-Refed (FFR) response process. Comparative genomics of hibernating versus non-hibernating lineages then illuminates cis-elements showing convergent changes in hibernators. Hibernators accumulated loss-of-function effects for specific CREs regulating hypothalamic FFR responses. Multi-omics approaches pinpoint key CREs, genes, regulatory programs, and cell types in the divergence of hibernating and homeothermic lineages. The refeeding period after extended fasting is revealed as one critical period of chromatin remodeling with convergent genomic changes. This genetic framework is a step toward harnessing hibernator adaptations in medicine.

A circadian clock regulates the blood-brain barrier across phylogeny

As the central regulatory system of an organism, the brain is responsible for overseeing a wide variety of physiological processes essential for an organism's survival. To maintain the environment necessary for neurons to function, the brain requires highly selective uptake and elimination of specific molecules through the blood-brain barrier (BBB). As an organism's activities vary throughout the day, how does the BBB adapt to meet the changing needs of the brain? A mechanism is through temporal regulation of BBB permeability via its circadian clock, which will be the focal point of this chapter. To comprehend the circadian clock's role within the BBB, we will first examine the anatomy of the BBB and the transport mechanisms enabling it to fulfill its role as a restrictive barrier. Next, we will define the circadian clock, and the discussion will encompass an introduction to circadian rhythms, the Transcription-Translation Feedback Loop (TTFL) as the mechanistic basis of circadian timekeeping, and the organization of tissue clocks found in organisms. Then, we will cover the role of the circadian rhythms in regulating the cellular mechanisms and functions of the BBB. We discuss the implications of this regulation in influencing sleep behavior, the progression of neurodegenerative diseases, and finally drug delivery for treatment of neurological diseases.

Scheduled feeding improves sleep in a mouse model of Huntington's disease

Sleep disturbances are common features of neurodegenerative disorders including Huntington's disease (HD). The sleep and circadian disruptions are recapitulated in animal models, and these models provide the opportunity to evaluate whether circadian interventions can be effective countermeasures for neurodegenerative disease. Time restricted feeding (TRF) interventions successfully improve activity rhythms, sleep behavior and motor performance in mouse models of HD. Seeking to determine if these benefits of scheduled feeding extend to physiological measures of sleep, electroencephalography (EEG) was used to measure sleep/wake states and polysomnographic patterns in adult mice (six mo-old) under TRF and ad lib feeding (ALF). With each diet, both male and female wild-type (WT) and bacterial artificial chromosome transgenic (BACHD) mice were evaluated. Our findings show that male, but not female, BACHD mice exhibited significant changes in the temporal patterning of wake and nonrapid eye movement (NREM) sleep. The TRF intervention reduced the inappropriate early morning activity by increasing NREM sleep in the male BACHD mice. In addition, the scheduled feeding reduced sleep fragmentation (# bouts) in the male BACHD mice. The phase of the rhythm in rapid-eye movement (REM) sleep was significantly altered by the scheduled feeding. The treatment did impact the power spectral curves during the day in male but not female mice. Sleep homeostasis, as measured by the response to six hours of gentle handling, was not altered by the diet. Thus, TRF improves the temporal patterning and fragmentation of NREM sleep without impacting sleep homeostasis. This work adds critical support to the view that sleep is a modifiable risk factor in neurodegenerative diseases.

Transient anticonvulsant effects of time-restricted feeding in the 6-Hz mouse model

INTRODUCTION

Intermittent fasting enhances neural bioenergetics, is neuroprotective, and elicits antioxidant effects in various animal models. There are conflicting findings on seizure protection, where intermittent fasting regimens often cause severe weight loss resembling starvation which is unsustainable long-term. Therefore, we tested whether a less intensive intermittent fasting regimen such as time-restricted feeding (TRF) may confer seizure protection.

METHODS

Male CD1 mice were assigned to either ad libitum-fed control, continuous 8 h TRF, or 8 h TRF with weekend ad libitum food access (2:5 TRF) for one month. Body weight, food intake, and blood glucose levels were measured. Seizure thresholds were determined at various time points using 6-Hz and maximal electroshock seizure threshold (MEST) tests. Protein levels and mRNA expression of genes, enzyme activity related to glucose metabolism, as well as mitochondrial dynamics were assessed in the cortex and hippocampus. Markers of antioxidant defence were evaluated in the plasma, cortex, and liver.

RESULTS

Body weight gain was similar in the ad libitum-fed and TRF mouse groups. In both TRF regimens, blood glucose levels did not change between the fed and fasted state and were higher during fasting than in the ad libitum-fed groups. Mice in the TRF group had increased seizure thresholds in the 6-Hz test on day 15 and on day 19 in a second cohort of 2:5 TRF mice, but similar seizure thresholds at other time points compared to ad libitum-fed mice. Continuous TRF did not alter MEST seizure thresholds on day 28. Mice in the TRF group showed increased maximal activity of pyruvate dehydrogenase in the cortex, which was accompanied by increased protein levels of mitochondrial pyruvate carrier 1 in the cortex and hippocampus. There were no other major changes in protein or mRNA levels associated with energy metabolism and mitochondrial dynamics in the brain, nor markers of antioxidant defence in the brain, liver, or plasma.

CONCLUSIONS

Both continuous and 2:5 TRF regimens transiently increased seizure thresholds in the 6-Hz model at around 2 weeks, which coincided with stability of blood glucose levels during the fed and fasted periods. Our findings suggest that the lack of prolonged anticonvulsant effects in the acute electrical seizure models employed may be attributed to only modest metabolic and antioxidant adaptations found in the brain and liver. Our findings underscore the potential therapeutic value of TRF in managing seizure-related conditions.

Increased cysteinyl-tRNA synthetase drives neuroinflammation in Alzheimer's disease

BACKGROUND

Microglia-mediated neuroinflammation in Alzheimer's disease (AD) is not only a response to pathophysiological events, but also plays a causative role in neurodegeneration. Cytoplasmic cysteinyl-tRNA synthetase (CARS) is considered to be a stimulant for immune responses to diseases; however, it remains unknown whether CARS is involved in the pathogenesis of AD.

METHODS

Postmortem human temporal cortical tissues at different Braak stages and AD patient-derived serum samples were used to investigate the changes of CARS levels in AD by immunocytochemical staining, real-time PCR, western blotting and ELISA. After that, C57BL/6J and APP/PS1 transgenic mice and BV-2 cell line were used to explore the role of CARS protein in memory and neuroinflammation, as well as the underlying mechanisms. Finally, the associations of morphological features among CARS protein, microglia and dense-core plaques were examined by immunocytochemical staining.

RESULTS

A positive correlation was found between aging and the intensity of CARS immunoreactivity in the temporal cortex. Both protein and mRNA levels of CARS were increased in the temporal cortex of AD patients. Immunocytochemical staining revealed increased CARS immunoreactivity in neurons of the temporal cortex in AD patients. Moreover, overexpression of CARS in hippocampal neurons induced and aggravated cognitive dysfunction in C57BL/6J and APP/PS1 mice, respectively, accompanied by activation of microglia and the TLR2/MyD88 signaling pathway as well as upregulation of proinflammatory cytokines. In vitro experiments showed that CARS treatment facilitated the production of proinflammatory cytokines and the activation of the TLR2/MyD88 signaling pathway of BV-2 cells. The accumulation of CARS protein occurred within dense-core Aβ plaques accompanied by recruitment of ameboid microglia. Significant upregulation of TLR2/MyD88 proteins was also observed in the temporal cortex of AD.

CONCLUSIONS

The findings suggest that the neuronal CARS drives neuroinflammation and induces memory deficits, which might be involved in the pathogenesis of AD.

Gut microbiota defined epigenomes of Alzheimer's and Parkinson's diseases reveal novel targets for therapy

The origins of Alzheimer's disease (AD) and Parkinson's disease (PD) involve genetic mutations, epigenetic changes, neurotoxin exposure and gut microbiota dysregulation. The gut microbiota's dynamic composition and its metabolites influence intestinal and blood-brain barrier integrity, contributing to AD and PD development. This review explores protein misfolding, aggregation and epigenetic links in AD and PD pathogenesis. It also highlights the role of a leaky gut and the microbiota-gut-brain axis in promoting these diseases through inflammation-induced epigenetic alterations. In addition, we investigate the potential of diet, probiotics and microbiota transplantation for preventing and treating AD and PD via epigenetic modifications, along with a discussion related to current challenges and future considerations. These approaches offer promise for translating research findings into practical clinical applications.

Fasting and Cognitive Impairment

Fasting is a nutritional practice involving complete food restriction for a varying length of time [...].