Retro-age: A unique epigenetic biomarker of aging captured by DNA methylation states of retroelements.

Reactivation of retroelements in the human genome has been linked to aging. However, whether the epigenetic state of specific retroelements can predict chronological age remains unknown. We provide evidence that locus-specific retroelement DNA methylation can be used to create retroelement-based epigenetic clocks that accurately measure chronological age in the immune system, across human tissues, and pan-mammalian species. We also developed a highly accurate retroelement epigenetic clock compatible with EPICv.2.0 data that was constructed from CpGs that did not overlap with existing first- and second-generation epigenetic clocks, suggesting a unique signal for epigenetic clocks not previously captured. We found retroelement-based epigenetic clocks were reversed during transient epigenetic reprogramming, accelerated in people living with HIV-1, and responsive to antiretroviral therapy. Our findings highlight the utility of retroelement-based biomarkers of aging and support a renewed emphasis on the role of retroelements in geroscience.

Reciprocal Coupling of Circadian Clocks in the Compound Eye and Optic Lobe in the Cricket Gryllus bimaculatus.

The circadian system comprises multiple clocks, including central and peripheral clocks. The central clock generally governs peripheral clocks to synchronize circadian rhythms throughout the animal body. However, whether the peripheral clock influences the central clock is unclear. This issue can be addressed through a system comprising a peripheral clock (compound eye clock [CE clock]) and central clock (the optic lobe [OL] clock) in the cricket Gryllus bimaculatus. We previously found that the compound eye regulates the free-running period (τ) and the stability of locomotor rhythms driven by the OL clock, as measured by the daily deviation of τ at 30°C. However, the role of the CE clock in this regulation remains unexplored. In this study, we investigated the importance of the CE clock in this regulation using RNA interference (RNAi) of the period (per) gene localized to the compound eye (perCE-RNAi). The perCE-RNAi abolished the compound eye rhythms of the electroretinogram (ERG) amplitude and clock gene expression but the locomotor rhythm driven by the OL clock was maintained. The locomotor rhythm of the tested crickets showed a significantly longer τ and greater daily variation of τ than those of control crickets treated with dsDsRed2. The variation of τ was comparable with that of crickets with the optic nerve severed. The τ was considerably longer but was comparable with that of crickets with the optic nerve severed. These results suggest that the CE clock regulates the OL clock to maintain and stabilize τ.

Phenotypic correlates between clock genes and phenology among populations of Diederik cuckoo, Chrysococcyx caprius.

The Diederik cuckoo, Chrysococcyx caprius, is a small Afrotropical bird in the family Cuculidae. It is taxonomically related to 13 other species within the genus Chrysococcyx and is migratory in sub-Saharan Africa. It has a unique breeding behaviour of being a brood parasite: Breeding pairs lay their eggs in the nests of a host species and hatchlings expel the eggs of the host species. The aim of the present study was to investigate diversity in two circadian clock genes, Clock and Adcyap1, to probe for a relationship between genetic polymorphisms and their role in circannual timing and habitat selection (phenology) in intra-African migrants. DNA extracted from blood was used for the PCR amplification and sequencing of clock genes in 30 Diederik cuckoos. Three alleles were detected for Clock with similar genotypes between individuals from the Northern and Southern breeding ranges while 10 alleles were detected for Adcyap1, having shorter alleles in the North and longer alleles in the South. Population genetic analyses, including allele frequency and zygosity analysis, showed distinctly higher frequencies for the most abundant Clock allele, containing 10 polyglutamine repeats, as well as a high degree of homozygosity. In contrast, all individuals were heterozygous for Adcyap1 and alleles from both regions showed distinct differences in abundance. Comparisons between both clock genes and phenology found several phenotypic correlations. This included evidence of a relationship between the shorter alleles and habitat selection as well as a relationship between longer alleles and timing. In both instances, evidence is provided that these effects may be sex-specific. Given that these genes drive some of the synchronicity between environments and the life cycles of birds, they provide valuable insight into the fitness of species facing global challenges including climate change, urbanisation and expanding agricultural practices.

Grey modelling and real-time forecasting for the approximate non-homogeneous white exponential law BDS clock bias sequences.

Precise forecasting of satellite clock bias is crucial for ensuring service quality and enhancing the efficiency of real-time precise point positioning (PPP).The grey model with many benefits is an excellent choice for predicting real-time clock bias. However, the absolute prediction error of a small number of satellites is very high in actual forecasting process. In order to address this issue, a non-homogeneous white exponential law grey model has been constructed specifically for predicting clock bias sequences with non-homogeneous class ratio approximating constants. Considering that any model is difficult to apply to different kinds of satellite clocks and clock bias signals, an adaptive selection strategy for forecast model is proposed to ensure more excellent prediction accuracy. Afterwards, a prediction scenario based on the observed products of the BeiDou satellite navigation system (BDS) is created to demonstrate the effectiveness of the approach described in this article. The outcomes of the method are then compared with those of a single grey model and the ultra-rapid predicted products. The outcomes demonstrate that this strategy's prediction accuracy is less than 1 ns/day and that its prediction uncertainty is much decreased, which may improve data selection for real-time applications like real-time kinematics (RTK) and PPP.

Transcriptomic Plasticity of the Circadian Clock in Response to Photoperiod: A Study in Male Melatonin-Competent Mice.

Seasonal daylength, or circadian photoperiod, is a pervasive environmental signal that profoundly influences physiology and behavior. In mammals, the central circadian clock resides in the suprachiasmatic nuclei (SCN) of the hypothalamus where it receives retinal input and synchronizes, or entrains, organismal physiology and behavior to the prevailing light cycle. The process of entrainment induces sustained plasticity in the SCN, but the molecular mechanisms underlying SCN plasticity are incompletely understood. Entrainment to different photoperiods persistently alters the timing, waveform, period, and light resetting properties of the SCN clock and its driven rhythms. To elucidate novel candidate genes for molecular mechanisms of photoperiod plasticity, we performed RNA sequencing on whole SCN dissected from mice raised in long (light:dark [LD] 16:8) and short (LD 8:16) photoperiods. Fewer rhythmic genes were detected in mice subjected to long photoperiod, and in general, the timing of gene expression rhythms was advanced 4-6 h. However, a few genes showed significant delays, including Gem. There were significant changes in the expression of the clock-associated gene Timeless and in SCN genes related to light responses, neuropeptides, gamma aminobutyric acid (GABA), ion channels, and serotonin. Particularly striking were differences in the expression of the neuropeptide signaling genes Prokr2 and Cck, as well as convergent regulation of the expression of 3 SCN light response genes, Dusp4, Rasd1, and Gem. Transcriptional modulation of Dusp4 and Rasd1 and phase regulation of Gem are compelling candidate molecular mechanisms for plasticity in the SCN light response through their modulation of the critical NMDAR-MAPK/ERK-CREB/CRE light signaling pathway in SCN neurons. Modulation of Prokr2 and Cck may critically support SCN neural network reconfiguration during photoperiodic entrainment. Our findings identify the SCN light response and neuropeptide signaling gene sets as rich substrates for elucidating novel mechanisms of photoperiod plasticity. Data are also available at http://circadianphotoperiodseq.com/, where users can view the expression and rhythmic properties of genes across these photoperiod conditions.

Annelid methylomes reveal ancestral developmental and aging-associated epigenetic erosion across Bilateria.

BACKGROUND: DNA methylation in the form of 5-methylcytosine (5mC) is the most abundant base modification in animals. However, 5mC levels vary widely across taxa. While vertebrate genomes are hypermethylated, in most invertebrates, 5mC concentrates on constantly and highly transcribed genes (gene body methylation; GbM) and, in some species, on transposable elements (TEs), a pattern known as "mosaic". Yet, the role and developmental dynamics of 5mC and how these explain interspecies differences in DNA methylation patterns remain poorly understood, especially in Spiralia, a large clade of invertebrates comprising nearly half of the animal phyla. RESULTS: Here, we generate base-resolution methylomes for three species with distinct genomic features and phylogenetic positions in Annelida, a major spiralian phylum. All possible 5mC patterns occur in annelids, from typical invertebrate intermediate levels in a mosaic distribution to hypermethylation and methylation loss. GbM is common to annelids with 5mC, and methylation differences across species are explained by taxon-specific transcriptional dynamics or the presence of intronic TEs. Notably, the link between GbM and transcription decays during development, alongside a gradual and global, age-dependent demethylation in adult stages. Additionally, reducing 5mC levels with cytidine analogs during early development impairs normal embryogenesis and reactivates TEs in the annelid Owenia fusiformis. CONCLUSIONS: Our study indicates that global epigenetic erosion during development and aging is an ancestral feature of bilateral animals. However, the tight link between transcription and gene body methylation is likely more important in early embryonic stages, and 5mC-mediated TE silencing probably emerged convergently across animal lineages.

Circadian clock component PER2 negatively regulates CD4+ T cell IFN-γ production in ulcerative colitis.

Period circadian clock 2 (PER2) is involved in the pathogenesis of various inflammatory and autoimmune diseases. However, there are gaps in our understanding of the role of PER2 in regulating CD4+ T cells beyond its time-keeping function in ulcerative colitis (UC) pathogenesis. Our findings revealed PER2 was predominantly expressed in CD4+ T cells, while it was significantly decreased in the inflamed mucosa and peripheral blood CD4+ T cells of UC patients compared with that in Crohn's disease (CD) patients and healthy controls (HC). Notably, PER2 expression was significantly recovered in UC patients in remission (R-UC) compared to that in active UC patients (A-UC) but not in CD patients. It was negatively correlated with the Ulcerative Colitis Endoscopic Index of Severity (UCEIS), Crohn's Disease Activity Index (CDAI), Simple Endoscopic Score for Crohn's disease (SES-CD), and C-reactive protein (CRP), respectively. Overexpression of PER2 markedly inhibited IFN-γ production in UC CD4+ T cells. RNA-seq analysis showed that overexpression of PER2 could repress the expression of a disintegrin and metalloproteinase 12 (ADAM12), a costimulatory molecule that determines Th1 cell fate. Mechanistically, cleavage under targets and tagmentation (CUT&Tag) analysis revealed that PER2 down-regulated ADAM12 expression by reducing its binding activity, thereby suppressing IFN-γ production in UC CD4+ T cells. Additionally, our data further demonstrated that ADAM12 was upregulated in CD4+ T cells and inflamed mucosa of A-UC patients compared to HC. Our study reveals a critical role of PER2 in regulating CD4+ T cell differentiation and highlights its potential as a therapeutic target for UC treatment.

Five years of change in adult twins: longitudinal changes of genetic and environmental influence on epigenetic clocks.

BACKGROUND: Epigenetic clocks were known as promising biomarkers of aging, including original clocks trained by individual CpG sites and principal component (PC) clocks trained by PCs of CpG sites. The effects of genetic and environmental factors on epigenetic clocks are still unclear, especially for PC clocks. METHODS: We constructed univariate twin models in 477 same-sex twin pairs from the Chinese National Twin Registry (CNTR) to estimate the heritability of five epigenetic clocks (GrimAge, PhenoAge, DunedinPACE, PCGrimAge, and PCPhenoAge). Besides, we investigated the longitudinal changes of genetic and environmental influences on epigenetic clocks across 5 years in 134 same-sex twin pairs. RESULTS: Heritability of epigenetic clocks ranged from 0.45 to 0.70, and those for PC clocks were higher than those for original clocks. For five epigenetic clocks, the longitudinal stability was moderate to high and was largely due to genetic effects. The genetic correlations between baseline and follow-up epigenetic clocks were moderate to high. Special unique environmental factors emerged both at baseline and at follow-up. PC clocks showed higher longitudinal stability and unique environmental correlations than original clocks. CONCLUSIONS: For five epigenetic clocks, they have the potential to identify aging interventions. High longitudinal stability is mainly due to genetic factors, and changes of epigenetic clocks over time are primarily due to changes in unique environmental factors. Given the disparities in genetic and environmental factors as well as longitudinal stability between PC and original clocks, the results of studies with original clocks need to be further verified with PC clocks.

Circadian misalignment disrupts biomarkers of cardiovascular disease risk and promotes a hypercoagulable state.

The circadian system regulates 24-h time-of-day patterns of cardiovascular physiology, with circadian misalignment resulting in adverse cardiovascular risk. Although many proteins in the coagulation-fibrinolysis axis show 24-h time-of-day patterns, it is not understood if these temporal patterns are regulated by circadian or behavioral (e.g., sleep and food intake) cycles, or how circadian misalignment influences these patterns. Thus, we utilized a night shiftwork protocol to analyze circadian versus behavioral cycle regulation of 238 plasma proteins linked to cardiovascular physiology. Six healthy men aged 26.2 ± 5.6 years (mean ± SD) completed the protocol involving two baseline days with 8-h nighttime sleep opportunities (circadian alignment), a transition to shiftwork day, followed by 2 days of simulated night shiftwork with 8-h daytime sleep opportunities (circadian misalignment). Plasma was collected for proteomics every 4 h across 24 h during baseline and during daytime sleep and the second night shift. Cosinor analyses identified proteins with circadian or behavioral cycle-regulated 24-h time-of-day patterns. Five proteins were circadian regulated (plasminogen activator inhibitor-1, angiopoietin-2, insulin-like growth factor binding protein-4, follistatin-related protein-3, and endoplasmic reticulum resident protein-29). No cardiovascular-related proteins showed regulation by behavioral cycles. Within the coagulation pathway, circadian misalignment decreased tissue factor pathway inhibitor, increased tissue factor, and induced a 24-h time-of-day pattern in coagulation factor VII (all FDR < 0.10). Such changes in protein abundance are consistent with changes observed in hypercoagulable states. Our analyses identify circadian regulation of proteins involved in cardiovascular physiology and indicate that acute circadian misalignment could promote a hypercoagulable state, possibly contributing to elevated cardiovascular disease risk among shift workers.

Methylation of SSTR4 promoter region in multiple mental health disorders.

The existence of a shared genetic basis for mental disorders has long been documented, yet research on whether acquired epigenetic modifications exhibit common alterations across diseases is limited. Previous studies have found that abnormal methylation of cg14631053 at the SSTR4 promoter region mediates the onset of alcohol use disorder. However, whether aberrant methylation of the SSTR4 gene promoter is involved in other mental health disorders remains unclear. In this study, leveraging publicly available data, we identified that changes in methylation of cg14631053 from the SSTR4 promoter region are involved in the development of bipolar disorder and schizophrenia. Furthermore, the direction of methylation changes in the SSTR4 promoter region is disease-specific: hypomethylation is associated with the onset of bipolar disorder and schizophrenia, rather than major depressive disorder. Methylation levels of cg14631053 correlate with chronological age, a correlation that can be disrupted in patients with mental health disorders including schizophrenia and bipolar disorder. In conclusion, SSTR4 promoter methylation may serve as a marker for identifying bipolar disorder and schizophrenia, providing insights into a transdiagnostic mechanism for precision medicine in the future.

Biological aging of different blood cell types.

Biological age (BA) captures detrimental age-related changes. The best-known and most-used BA indicators include DNA methylation-based epigenetic clocks and telomere length (TL). The most common biological sample material for epidemiological aging studies, whole blood, is composed of different cell types. We aimed to compare differences in BAs between blood cell types and assessed the BA indicators' cell type-specific associations with chronological age (CA). An analysis of DNA methylation-based BA indicators, including TL, methylation level at cg16867657 in ELOVL2, as well as the Hannum, Horvath, DNAmPhenoAge, and DunedinPACE epigenetic clocks, was performed on 428 biological samples of 12 blood cell types. BA values were different in the majority of the pairwise comparisons between cell types, as well as in comparison to whole blood (p < 0.05). DNAmPhenoAge showed the largest cell type differences, up to 44.5 years and DNA methylation-based TL showed the lowest differences. T cells generally had the "youngest" BA values, with differences across subsets, whereas monocytes had the "oldest" values. All BA indicators, except DunedinPACE, strongly correlated with CA within a cell type. Some differences such as DNAmPhenoAge-difference between naïve CD4 + T cells and monocytes were constant regardless of the blood donor's CA (range 20-80 years), while for DunedinPACE they were not. In conclusion, DNA methylation-based indicators of BA exhibit cell type-specific characteristics. Our results have implications for understanding the molecular mechanisms underlying epigenetic clocks and underscore the importance of considering cell composition when utilizing them as indicators for the success of aging interventions.

Overlapping Central Clock Network Circuitry Regulates Circadian Feeding and Activity Rhythms in Drosophila.

The circadian system coordinates multiple behavioral outputs to ensure proper temporal organization. Timing information underlying circadian regulation of behavior depends on a molecular circadian clock that operates within clock neurons in the brain. In Drosophila and other organisms, clock neurons can be divided into several molecularly and functionally discrete subpopulations that form an interconnected central clock network. It is unknown how circadian signals are coherently generated by the clock network and transmitted across output circuits that connect clock cells to downstream neurons that regulate behavior. Here, we have exhaustively investigated the contribution of clock neuron subsets to the control of two prominent behavioral outputs in Drosophila: locomotor activity and feeding. We have used cell-specific manipulations to eliminate molecular clock function or induce electrical silencing either broadly throughout the clock network or in specific subpopulations. We find that clock cell manipulations produce similar changes in locomotor activity and feeding, suggesting that overlapping central clock circuitry regulates these distinct behavioral outputs. Interestingly, the magnitude and nature of the effects depend on the clock subset targeted. Lateral clock neuron manipulations profoundly degrade the rhythmicity of feeding and activity. In contrast, dorsal clock neuron manipulations only subtly affect rhythmicity but produce pronounced changes in the distribution of activity and feeding across the day. These experiments expand our knowledge of clock regulation of activity rhythms and offer the first extensive characterization of central clock control of feeding rhythms. Despite similar effects of central clock cell disruptions on activity and feeding, we find that manipulations that prevent functional signaling in an identified output circuit preferentially degrade locomotor activity rhythms, leaving feeding rhythms relatively intact. This demonstrates that activity and feeding are indeed dissociable behaviors, and furthermore suggests that differential circadian control of these behaviors diverges in output circuits downstream of the clock network.

Childhood trauma is linked to epigenetic age deceleration in young adults with previous youth residential care placements.

Background: Early adversity increases the risk for mental and physical disorders as well as premature death. Epigenetic processes, and altered epigenetic aging in particular, might mediate these effects. While the literature that examined links between early adversity and epigenetic aging is growing, results have been heterogeneous.Objective: In the current work, we explored the link between early adversity and epigenetic aging in a sample of formerly out-of-home placed young adults.Method: A total of N = 117 young adults (32% women, age mean = 26.3 years, SD = 3.6 years) with previous youth residential care placements completed the Childhood Trauma Questionnaire (CTQ) and the Life Events Checklist (LEC-R) and provided blood samples for the analysis of DNA methylation using the Illumina Infinium MethylationEPIC BeadChip Microarray. Epigenetic age was estimated using Hovarth's and Hannum's epigenetic clocks. Furthermore, Hovarth's and Hannum's epigenetic age residuals were calculated as a proxy of epigenetic aging by regressing epigenetic age on chronological age. The statistical analysis plan was preregistered (https://osf.io/b9ev8).Results: Childhood trauma (CTQ) was negatively associated with Hannum's epigenetic age residuals, ß = -.23, p = .004 when controlling for sex, BMI, smoking status and proportional white blood cell type estimates. This association was driven by experiences of physical neglect, ß = -.25, p = .001. Lifetime trauma exposure (LEC-R) was not a significant predictor of epigenetic age residuals.Conclusion: Childhood trauma, and physical neglect in particular, was associated with decelerated epigenetic aging in our sample. More studies focusing on formerly institutionalized at-risk populations are needed to better understand which factors affect stress-related adaptations following traumatic experiences.

Growing literature links early adversity to altered epigenetic aging, yet results have been heterogeneous.We assessed childhood and lifetime trauma exposure using the Childhood Trauma Questionnaire and the Life Events Checklist and estimated epigenetic aging by obtaining Horvath's and Hannum's epigenetic age residuals in a sample of formerly out-of-home placed young adults.In this high-risk sample, childhood trauma, physical neglect in particular, but not lifetime trauma was negatively related to epigenetic aging.

Olanzapine suppresses mPFC activity-norepinephrine releasing to alleviate CLOCK-enhanced cancer stemness under chronic stress.

BACKGROUND: Olanzapine (OLZ) reverses chronic stress-induced anxiety. Chronic stress promotes cancer development via abnormal neuro-endocrine activation. However, how intervention of brain-body interaction reverses chronic stress-induced tumorigenesis remains elusive. METHODS: KrasLSL-G12D/WT lung cancer model and LLC1 syngeneic tumor model were used to study the effect of OLZ on cancer stemness and anxiety-like behaviors. Cancer stemness was evaluated by qPCR, western-blotting, immunohistology staining and flow-cytometry analysis of stemness markers, and cancer stem-like function was assessed by serial dilution tumorigenesis in mice and extreme limiting dilution analysis in primary tumor cells. Anxiety-like behaviors in mice were detected by elevated plus maze and open field test. Depression-like behaviors in mice were detected by tail suspension test. Anxiety and depression states in human were assessed by Hospital Anxiety and Depression Scale (HADS). Chemo-sensitivity of lung cancer was assessed by in vivo syngeneic tumor model and in vitro CCK-8 assay in lung cancer cell lines. RESULTS: In this study, we found that OLZ reversed chronic stress-enhanced lung tumorigenesis in both KrasLSL-G12D/WT lung cancer model and LLC1 syngeneic tumor model. OLZ relieved anxiety and depression-like behaviors by suppressing neuro-activity in the mPFC and reducing norepinephrine (NE) releasing under chronic stress. NE activated ADRB2-cAMP-PKA-CREB pathway to promote CLOCK transcription, leading to cancer stem-like traits. As such, CLOCK-deficiency or OLZ reverses NE/chronic stress-induced gemcitabine (GEM) resistance in lung cancer. Of note, tumoral CLOCK expression is positively associated with stress status, serum NE level and poor prognosis in lung cancer patients. CONCLUSION: We identify a new mechanism by which OLZ ameliorates chronic stress-enhanced tumorigenesis and chemoresistance. OLZ suppresses mPFC-NE-CLOCK axis to reverse chronic stress-induced anxiety-like behaviors and lung cancer stemness. Decreased NE-releasing prevents activation of ADRB2-cAMP-PKA-CREB pathway to inhibit CLOCK transcription, thus reversing lung cancer stem-like traits and chemoresistance under chronic stress.

Genome-wide identification of PAR domain protein 1 (PDP1) targets through ChIP-seq reveals the regulation of diapause-specific characteristics in Culex pipiens.

Insects use seasonal diapause as an alternative strategy to endure adverse seasons. This developmental trajectory is induced by environmental cues like short-day lengths in late summer and early fall, but how insects measure day length is unknown. The circadian clock has been implicated in regulating photoperiodic or seasonal responses in many insects, including the Northern house mosquito, Culex pipiens, which enters adult diapause. To investigate the potential control of diapause by circadian control, we employed ChIP-sequencing to identify the downstream targets of a circadian transcription factor, PAR domain protein 1 (PDP1), that contribute to the hallmark features of diapause. We identified the nearest genes in a 10 kb region of the anticipated PDP1 binding sites, listed prospective targets and searched for PDP1-specific binding sites. By examining the functional relevance to diapause-specific behaviours and modifications such as metabolic pathways, lifespan extension, cell cycle regulation and stress tolerance, eight genes were selected as targets and validated using ChIP-qPCR. In addition, qRT-PCR demonstrated that the mRNA abundance of PDP1 targets increased in the heads of diapausing females during the middle of the scotophase (ZT17) compared with the early photophase (ZT1), in agreement with the peak and trough of PDP1 abundance. Thus, our investigation uncovered the mechanism by which PDP1 might generate a diapause phenotype in insects.

Circadian rhythm disruption upregulating Per1 in mandibular condylar chondrocytes mediating temporomandibular joint osteoarthritis via GSK3ß/ß-CATENIN pathway.

BACKGROUND: Temporomandibular joint osteoarthritis (TMJOA) has a high incidence rate, but its pathogenesis remains unclear. Circadian rhythm is an important oscillation in the human body and influences various biological activities. However, it is still unclear whether circadian rhythm affects the onset and development of TMJOA. METHODS: We disrupted the normal rhythm of rats and examined the expression of core clock genes in the mandibular condylar cartilage of the jaw and histological changes in condyles. After isolating rat mandibular condylar chondrocytes, we upregulated or downregulated the clock gene Per1, examined the expression of cartilage matrix-degrading enzymes, tested the activation of the GSK3ß/ß-CATENIN pathway and verified it using agonists and inhibitors. Finally, after downregulating the expression of Per1 in the mandibular condylar cartilage of rats with jet lag, we examined the expression of cartilage matrix-degrading enzymes and histological changes in condyles. RESULTS: Jet lag led to TMJOA-like lesions in the rat mandibular condyles, and the expression of the clock gene Per1 and cartilage matrix-degrading enzymes increased in the condylar cartilage of rats. When Per1 was downregulated or upregulated in mandibular condylar chondrocytes, the GSK3ß/ß-CATENIN pathway was inhibited or activated, and the expression of cartilage matrix-degrading enzymes decreased or increased, which can be rescued by activator and inhibitor of the GSK3ß/ß-CATENIN pathway. Moreover, after down-regulation of Per1 in mandibular condylar cartilage in vivo, significant alleviation of cartilage degradation, cartilage loss, subchondral bone loss induced by jet lag, and inhibition of the GSK3ß/ß-CATENIN signaling pathway were observed. Circadian rhythm disruption can lead to TMJOA. The clock gene Per1 can promote the occurrence of TMJOA by activating the GSK3ß/ß-CATENIN pathway and promoting the expression of cartilage matrix-degrading enzymes. The clock gene Per1 is a target for the prevention and treatment of TMJOA.

Effect of electroacupuncture pre-conditioning on the expression rhythm of core clock gene Bmal1 in uterine tissue of controlled hyperstimulation rats. / ç”µé’ˆé¢„å¤„ç†å¯¹ä¿ƒæŽ’åµå¤§é¼ å­å®«ç»„ç»‡æ ¸å¿ƒæ—¶é’ŸåŸºå› Bmal1表达节律的影响.

OBJECTIVES: To observe the effect of electroacupuncture (EA) pre-conditioning on the expression rhythm of clock gene Bmal1 in the uterine tissue of rats with controlled ovarian hyperstimulation(COH), so as to explore its mechanisms underlying improvement of the endometrial receptivity of ovarian superovulation during implantation. METHODS: Seventy-two female SD rats with typical estrous cycles were randomly divided into normal control, model and EA pre-conditioning (pre-EA) groups, with 24 rats in each group. The COH model was established by giving the rats with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (HCG) by intraperitoneal injection. The rats of the pre-EA group received EA stimulation (1 Hz/5 Hz, a tolerable strength) of "Guanyuan"(CV4) and "Sanyinjiao"(SP6) for 15 min each time, once daily (at 21：00 every day). After successive EA intervention during the first two estrous cycles, the modeling began in the third estrus cycle and the EA intervention was continued till the end of modeling, followed by raising the rats with superovulation induction and male rats undergoing vasoligation in one cage (1∶1). The rats during the estrum in the normal control group or those of the model group at the end of modeling were raised together with the male rats undergoing vasoligation in one cage. On the 5th day (04：00 AM) after raising in one cage, the rats in the three groups were sacrificed in six batches every 4 hours, with 4 rats in each group in each batch. The H.E. staining was used for revealing alterations of the endometrial thickness, number of glands and blood vessels and tissue histology, and ELISA employed to ascertain the contents of estradiol (E2) and progesterone (Pg) in serum. The expression rhythm of core clock gene Bmal1 ［In the present study, Zeitgeber time (ZT) is an artificially set laboratory time, i.e., ZT7 (07：00) is light on and ZT19 (19：00) is light off.］ and the expression of endometrial HoxA10 and leukemia inhibitory factor (LIF) mRNAs were detected by quantitative real-time PCR. The Western blot was employed to detect the expression levels of HoxA10 and LIF proteins. RESULTS: Findings of the clock gene Bmal1 level showed that the expression peak was at ZT12 and the valley value at ZT20 in the normal control group, and that of the peak value was at ZT20 and valley value at ZT12 in the model group, while in the pre-EA group, the peak value was at ZT8, and the valley value at ZT4. The difference of Bmal1 levels among the three groups was most significant at ZT12 (12：00), therefore, the tissue samples were taken at ZT12 in this study for comparison of the levels of different indexes among the 3 groups. Compared with the control group, the endometrial thickness, number of glands and blood vessels, HoxA10 and LIF mRNAs and proteins were significantly down-regulated (P<0.01, P<0.05), and contents of serum E2 and Pg were considerably up-regulated in the model group (P<0.01, P<0.05). Relevant to the model group, the pre-EA group had an apparent increase in the endometrial thickness, number of glands and blood vessels, and expression levels of HoxA10 and LIF mRNAs and proteins (P<0.05, P<0.01), and a marked decrease in the serum Pg (P<0.05). At the ZT12 (12：00 noon), compared with the normal control group, the mRNA level of Bmal1 was significantly decreased in the model group (P<0.01)；and compared with the model group, the level of Bmal1 mRNA was significantly increased in the pre-EA group (P<0.05). In addition, at the node of ZT16, the mRNA level of Bmal1 was significantly decreased in the model group in comparison with the normal control group (P<0.01). CONCLUSIONS: EA preconditioning can improve the endometrial receptivity during the implantation window period in rats with COH, which may be related to its functions in regulating the expression of clock gene Bmal1 in the uterine tissue and in correcting the disturbance of clock gene rhythm.

Unlocking Nature's Rhythms: Insights into Secondary Metabolite Modulation by the Circadian Clock.

Plants, like many other living organisms, have an internal timekeeper, the circadian clock, which allows them to anticipate photoperiod rhythms and environmental stimuli to optimally adjust plant growth, development, and fitness. These fine-tuned processes depend on the interaction between environmental signals and the internal interactive metabolic network regulated by the circadian clock. Although primary metabolites have received significant attention, the impact of the circadian clock on secondary metabolites remains less explored. Transcriptome analyses revealed that many genes involved in secondary metabolite biosynthesis exhibit diurnal expression patterns, potentially enhancing stress tolerance. Understanding the interaction mechanisms between the circadian clock and secondary metabolites, including plant defense mechanisms against stress, may facilitate the development of stress-resilient crops and enhance targeted management practices that integrate circadian agricultural strategies, particularly in the face of climate change. In this review, we will delve into the molecular mechanisms underlying circadian rhythms of phenolic compounds, terpenoids, and N-containing compounds.

Effects of Dietary Protein Intake Levels on Peripheral Circadian Rhythm in Mice.

The regulation of the circadian clock plays an important role in influencing physiological conditions. While it is reported that the timing and quantity of energy intake impact circadian regulation, the underlying mechanisms remain unclear. This study investigated the impact of dietary protein intake on peripheral clocks. Firstly, transcriptomic analysis was conducted to investigate molecular targets of low-protein intake. Secondly, mPer2::Luc knock-in mice, fed with either a low-protein, normal, or high-protein diet for 6 weeks, were analyzed for the oscillation of PER2 expression in peripheral tissues and for the expression profiles of circadian and metabolic genes. Lastly, the candidate pathway identified by the in vivo analysis was validated using AML12 cells. As a result, using transcriptomic analysis, we found that the low-protein diet hardly altered the circadian rhythm in the central clock. In animal experiments, expression levels and period lengths of PER2 were different in peripheral tissues depending on dietary protein intake; moreover, mRNA levels of clock-controlled genes and endoplasmic reticulum (ER) stress genes were affected by dietary protein intake. Induction of ER stress in AML12 cells caused an increased amplitude of Clock and Bmal1 and an advanced peak phase of Per2. This result shows that the intake of different dietary protein ratios causes an alteration of the circadian rhythm, especially in the peripheral clock of mice. Dietary protein intake modifies the oscillation of ER stress genes, which may play key roles in the regulation of the circadian clock.

Systemic Inflammation Disrupts Circadian Rhythms and Diurnal Neuroimmune Dynamics.

Circadian rhythms regulate physiological processes in approximately 24 h cycles, and their disruption is associated with various diseases. Inflammation may perturb circadian rhythms, though these interactions remain unclear. This study examined whether systemic inflammation induced by an intraperitoneal injection of lipopolysaccharide (LPS) could alter central and peripheral circadian rhythms and diurnal neuroimmune dynamics. Mice were randomly assigned to two groups: the saline control group and the LPS group. The diurnal expression of circadian clock genes and inflammatory cytokines were measured in the hypothalamus, hippocampus, and liver. Diurnal dynamic behaviors of microglia were also assessed. Our results revealed that the LPS perturbed circadian gene oscillations in the hypothalamus, hippocampus, and liver. Furthermore, systemic inflammation induced by the LPS could trigger neuroinflammation and perturb the diurnal dynamic behavior of microglia in the hippocampus. These findings shed light on the intricate link between inflammation and circadian disruption, underscoring their significance in relation to neurodegenerative diseases.