Circadian physiology of metabolism

Partially unraveling mechanistic underpinning and weight loss effects of time-restricted eating across diverse adult populations: A systematic review and meta-analyses of prospective studies

Time-restricted eating (TRE) is a promising and cost-effective dietary approach for weight management. This study aimed to evaluate the effects of TRE on weight loss in three adult populations using pre- and post-intervention analyses while also investigating its underlying mechanism. A systematic search was conducted across four databases (PubMed, Web of Science, Scopus, and the CENTRAL) up until January 28, 2024, specifically focusing on prospective studies that examined the efficacy of TRE in achieving weight loss. A random effects model was employed to conduct meta-analyses, while heterogeneity was assessed using the I2 statistic (PROSPERO: CRD42023439317). The study encompassed 36 selected studies involving 44 effect sizes and 914 participants. The effectiveness of the TRE was found to vary across health conditions, with modest weight loss observed in healthy individuals (pooled effect size -1.04 Kg, 95% CI: -1.42 to -0.65) and more significant weight reduction seen in participants with chronic diseases (pooled effect size -3.33 Kg, 95% CI: -5.05 to -1.62) and overweight/obesity (pooled effect size -4.21 Kg, 95% CI: -5.23 to -3.10). The observed decrease in body weight could be partially attributed to factors influencing energy balance, as evidenced by the significantly lower mean calorie intake at the end of the intervention (1694.71 kcal/day, 95% CI: 1498.57-1890.85) compared to the baseline intake (2000.64 kcal/day, 95% CI: 1830-2172.98), despite the absence of intentional efforts to restrict energy intake by the participants. These findings support the efficacy of this lifestyle intervention for weight loss maintenance and guide the development of its clinical guidelines.

Effects of time-of-day on the noradrenaline, adrenaline, cortisol and blood lipidome response to an ice bath

While the effect of time-of-day (morning versus evening) on hormones, lipids and lipolysis has been studied in relation to meals and exercise, there are no studies that have investigated the effects of time-of-day on ice bath induced hormone and lipidome responses. In this crossover-designed study, a group of six women and six men, 26 ± 5 years old, 176 ± 7 cm tall, weighing 75 ± 10 kg, and a BMI of 23 ± 2 kg/m2 had an ice bath (8-12 °C for 5 min) both in the morning and evening on separate days. Absence from intense physical exercise, nutrient intake and meal order was standardized in the 24 h prior the ice baths to account for confounders such as diet or exercise. We collected venous blood samples before and after (5 min and 30 min) the ice baths to measure hormones (noradrenaline, adrenaline, and cortisol) and lipid levels in plasma via liquid chromatography mass spectrometry shotgun lipidomics. We found that ice baths in the morning increase plasma fatty acids more than in the evening. Overall plasma lipid composition significantly differed in-between the morning and evening, and only in the morning ice bathing is accompanied by significantly increased plasma fatty acids from 5.1 ± 2.2% to 6.0 ± 2.4% (P = 0.029) 5 min after and to 6.3 ± 3.1% (P = 0.008) 30 min after. Noradrenaline was not affected by time-of-day and increased significantly immediately after the ice baths in the morning by 127 ± 2% (pre: 395 ± 158 pg/ml, post 5 min: 896 ± 562 pg/ml, P = 0.025) and in the evening by 144 ± 2% (pre: 385 ± 146 pg/ml, post 5 min: 937 ± 547 pg/ml, P = 0.015). Cortisol was generally higher in the morning than in the evening (pre: 179 ± 108 pg/ml versus 91 ± 59 pg/ml, P = 0.013; post 5 min: 222 ± 96 pg/ml versus 101 ± 52 pg/ml, P = 0.001; post 30 min: 190 ± 96 pg/ml versus 98 ± 54 pg/ml, P = 0.009). There was no difference in the hormonal and lipidome response to an ice bath between women and men. The main finding of the study was that noradrenaline, adrenaline, cortisol and plasma lipidome responses are similar after an ice bath in the morning and evening. However, ice baths in the morning increase plasma fatty acids more than in the evening.

Epigenetic Mechanisms in the Transcriptional Regulation of Circadian Rhythm in Mammals

Almost all organisms, from the simplest bacteria to advanced mammals, havea near 24 h circadian rhythm. Circadian rhythms are highly conserved across different life forms and are regulated by circadian genes as well as by related transcription factors. Transcription factors are fundamental to circadian rhythms, influencing gene expression, behavior in plants and animals, and human diseases. This review examines the foundational research on transcriptional regulation of circadian rhythms, emphasizing histone modifications, chromatin remodeling, and Pol II pausing control. These studies have enhanced our understanding of transcriptional regulation within biological circadian rhythms and the importance of circadian biology in human health. Finally, we summarize the progress and challenges in these three areas of regulation to move the field forward.

The Effect of Sleep Disruption on Cardiometabolic Health

Sleep disruption has emerged as a significant public health concern with profound implications for metabolic health. This review synthesizes current evidence demonstrating the intricate relationships between sleep disturbances and cardiometabolic dysfunction. Epidemiological studies have consistently demonstrated that insufficient sleep duration (<7 h) and poor sleep quality are associated with increased risks of obesity, type 2 diabetes, and cardiovascular disease. The underlying mechanisms are multifaceted, involving the disruption of circadian clock genes, alterations in glucose and lipid metabolism, the activation of inflammatory pathways, and the modulation of the gut microbiome. Sleep loss affects key metabolic regulators, including AMPK signaling and disrupts the secretion of metabolic hormones such as leptin and ghrelin. The latest evidence points to the role of sleep-induced changes in the composition and function of gut microbiota, which may contribute to metabolic dysfunction through modifications in the intestinal barrier and inflammatory responses. The NLRP3 inflammasome and NF-κB signaling pathways have been identified as crucial mediators linking sleep disruption to metabolic inflammation. An understanding of these mechanisms has significant implications for public health and clinical practice, suggesting that improving sleep quality could be an effective strategy for preventing and treating cardiometabolic disorders in modern society.

Circadian disruption of feeding-fasting rhythm and its consequences for metabolic, immune, cancer, and cognitive processes

The circadian system is composed by a central hypothalamic clock at the suprachiasmatic nuclei (SCN) that communicates with peripheral circadian oscillators for daily coordination of behavior and physiology. The SCN entrain to the environmental 24-h light-dark (LD) cycle and drive daily rhythms of internal synchronizers such as core body temperature, hypothalamic-hypophysary hormones, sympathetic/parasympathetic activity, as well as behavioral and feeding-fasting rhythms, which supply signals setting core molecular clocks at central and peripheral tissues. Steady phase relationships between the SCN and peripheral oscillators keep homeostatic processes such as microbiota/microbiome composition/activity, metabolic supply/demand, energy balance, immunoinflammatory process, sleep amount and quality, psychophysiological stress, etc. Indeed, the risk of health alterations increase when these phase relationships are chronically changed prompting circadian disruption (CD), as occurring after sudden LD cycle changes (so-called jet-lag), or due to changes of activity/feeding-rest/fasting rhythm with respect to LD cycles (as humans subjected to nightwork, or restricting food access at rest in mice). Typical pathologies observed in animal models of CD and epidemiological studies include metabolic syndrome, type-2 diabetes, obesity, chronic inflammation, cancer, sleep disruption, decrease in physical and cognitive performance, and mood, among others. The present review discusses different aspects of such physiological dysregulations observed in animal models of CD having altered feeding-fasting rhythms, with potential translation to human health.

Effectiveness of Early Versus Late Time-Restricted Eating Combined with Physical Activity in Overweight or Obese Women

AIMS

To evaluate the effectiveness of a dual approach involving time-restricted eating (TRE) at different times of the day combined with physical activity (PA) on functional capacity and metabolic health in overweight or obese women.

METHODS

Random allocation of sixty-one participants into four groups: early time-restricted eating plus physical activity (ETRE-PA, n = 15, 31.8 ± 10.76 years, 89.68 ± 13.40 kg, 33.5 ± 5.53 kg/m2), late time-restricted eating with physical activity (LTRE-PA, n = 15, 30.60 ± 7.94 years, 94.45 ± 15.36 kg, 34.37 ± 7.09 kg/m2), late time-restricted eating only (LTRE, n = 15, 27.93 ± 9.79 years, 88.32 ± 10.36 kg, 32.71 ± 5.15 kg/m2) and a control group (CG, n = 15, 36.25 ± 11.52 years, 89.01 ± 11.68 kg, 33.66 ± 6.18 kg/m2). The intervention lasted for 12 weeks in all groups. Both the ETRE-PA and LTRE-PA groups engaged in a rigorous combined aerobic and resistance-training program.

RESULTS

Significant reductions in body weight and body mass index were observed in the ETRE-PA and LTRE-PA groups compared to the CG and LTRE groups post-intervention (p < 0.0005). Only the ETRE-PA group exhibited a significant decrease in fat mass (p = 0.02), low-density lipoprotein cholesterol (p = 0.01), and aspartate aminotransferase (p = 0.002). Significant reductions in alanine aminotransferase levels were observed in the ETRE-PA (p = 0.004) and LTRE-PA (p = 0.02) groups. These two latter groups achieved higher performances in the 6-min walking test, bench press, 30-s squat, crunch test, vertical jump (p < 0.0005 for both), and leg extension (p < 0.02 for both) when compared to the LTRE and CG groups.

CONCLUSION

The integration of TRE with PA leads to greater improvements in body composition, lipid profile, and physical performance, with no significant differences between the ETRE-PA and LTRE-PA approaches. This combined strategy offers a promising solution for overweight and obese women.

Leptin Receptor Deficiency-Associated Diabetes Disrupts Lacrimal Gland Circadian Rhythms and Contributes to Dry Eye Syndrome

Purpose

This study investigated the impact of hyperglycemia in type 2 diabetes mellitus (T2DM) on the circadian rhythms and function of lacrimal glands (LGs) in contributing to dry eye syndrome. We assessed the effects of hyperglycemia on circadian gene expression, immune cell recruitment, neural activity, and metabolic pathways, and evaluated the effectiveness of insulin in restoring normal LG function.

Methods

Using a T2DM mouse model (db/db mice), circadian transcriptomic changes in LGs were analyzed through RNA sequencing over a 24-hour period. Rhythmic expression of core clock genes, immune and neural activity, and metabolic pathways were evaluated. The effects of insulin treatment on these parameters were also assessed.

Results

Hyperglycemia disrupted the circadian expression of core clock genes in LGs, leading to a 50% reduction in rhythmic gene expression. This was associated with altered immune cell recruitment, impaired neural activity, and metabolic changes. Insulin treatment lowered blood glucose levels but did not restore normal circadian function or tear secretion, exacerbating dry eye syndrome in diabetic mice.

Conclusions

T2DM significantly disrupts circadian rhythms and function in lacrimal glands, contributing to dry eye syndrome. The limited efficacy of insulin in restoring circadian regulation suggests that hyperglycemia-induced dysfunction in LGs is not solely dependent on blood glucose levels, highlighting the need for therapies targeting circadian rhythms in diabetic ocular complications.

Light Environment of Arctic Solstices is Coupled With Melatonin Phase-Amplitude Changes and Decline of Metabolic Health

Light environment in the Arctic differs widely with the seasons. Studies of relationships between objectively measured circadian phase and amplitude of light exposure and melatonin in community-dwelling Arctic residents are lacking. This investigation combines cross-sectional (n = 24-62) and longitudinal (n = 13-27) data from week-long actigraphy (with light sensor), 24-h salivary melatonin profiles, and proxies of metabolic health. Data were collected within the same week bracketing spring equinox (SE), and winter/summer solstices (WS/SS). Drastic seasonal differences in blue light exposure (BLE) corresponded to seasonal changes in the 24-h pattern of melatonin, which was phase delayed and reduced in normalized amplitude (NA) during WS/SS compared to SE. The extent of individual melatonin's acrophase and Dim Light Melatonin Onset (DLMO) change from SE to WS correlated with that from SE to SS. Although similar in extent and direction, melatonin phase changes versus SE were linked to morning BLE deficit in WS, contrasting to evening BLE excess in SS. Seasonal changes in sleep characteristics were closely associated with changes in the phases of BLE and melatonin. Proxies of metabolic health included triglycerides (TG), high-density lipoprotein cholesterol (HDL), TG/HDL ratio, and cortisol. Adverse seasonal changes in these proxies were associated with delayed acrophases of BLE and melatonin during WS and SS. TG and TG/HDL were higher in WS and SS than in SE, and cross-sectionally correlated with later melatonin and BLE acrophases, while lower HDL was associated with later BLE onset and later melatonin acrophase. Overall, this study shows that optimal 24-h patterns of light exposure during SE is associated with an earlier acrophase and a larger 24-h amplitude of melatonin, and that both features are linked to better metabolic health. Improving light hygiene, in particular correcting winter morning light deficit and summer evening light excess may help maintain metabolic health at high latitudes. Novel solutions for introducing proper circadian light hygiene such as human-centric light technologies should be investigated to address these issues in future studies.

Association of circadian syndrome with risk of hyperuricemia among middle-aged and older adults in China: The first nationwide cohort study

OBJECTIVES

No studies have been conducted to explore the association of circadian syndrome (CircS) and hyperuricemia. We addressed the gap by investigating the association of CircS and the risk of hyperuricemia among middle-aged and older adults in China.

STUDY DESIGN

Prospective cohort study.

METHODS

We utilized a nationwide cohort from the China Health and Retirement Longitudinal Study, 7009 adults aged at least 45 years were enrolled at baseline in 2011, and 4415 participants followed up to 2015. CircS was assessed using seven components including five components used to define metabolic syndrome and two components of lack of sleep and depression. Multivariable logistic regression analysis was applied to examine the association of CircS and hyperuricemia. Stratified analyses were used to identify the vulnerable subgroup.

RESULTS

Among the 7009 participants (mean age: 60.6 [SD: 9.8] years), 52.8 % were women. Compared to participants without CircS, those with CircS had a higher risk of hyperuricemia (adjusted odds ratio, aOR 2.246, 95 % CI:1.819-2.773). After 4-year follow-up, 457 (10.4 %) cases developed as hyperuricemia. The longitudinal analyses showed that CircS had a higher risk of incident hyperuricemia (aOR 2.136, 1.740-2.620). The association was stronger in women and those with kidney disease. Sensitivity analysis showed that individuals with ≥ six CircS components had the highest risk of hyperuricemia.

CONCLUSIONS

This nationwide cohort first revealed that CircS was related to an increased risk of hyperuricemia among Chinese adults. Our findings provide epidemiological evidence regarding the importance of CircS management as a preventative strategy for hyperuricemia.

Dietary patterns to promote cardiometabolic health

Multiple professional societies recommend the Mediterranean and/or Dietary Approaches to Stop Hypertension dietary patterns in their cardiovascular disease prevention guidelines because these diets can improve cardiometabolic health and reduce the risk of cardiovascular events. Furthermore, low sodium intake can be particularly beneficial for patients with hypertension. Carbohydrate restriction, with an emphasis on including high-quality carbohydrates and limiting refined starches and foods and beverages with added sugars, can promote weight loss and cardiometabolic benefits in the short term, compared with higher carbohydrate intake. Evidence is lacking for sustained, long-term effects of low carbohydrate and very low carbohydrate intake on cardiometabolic risk and cardiovascular outcomes. Time-restricted eating, in the context of an overall healthy dietary pattern, can promote cardiometabolic health by aligning food intake with the circadian rhythm, although its effect on hard clinical outcomes remains to be proven. Although there is no one dietary pattern that is appropriate for all patients, engaging in shared decision-making with patients, utilizing behaviour-change principles and engaging members of the health-care team, such as registered dietitian nutritionists, can lead to substantial improvement in the lifestyle and overall health trajectory of a patient. Emphasizing the similarities, rather than differences, of recommended dietary patterns, which include an emphasis on vegetables, fruits, legumes, nuts, whole grains and minimally processed protein foods, such as fatty fish or plant-based proteins, can simplify the process for both patients and clinicians alike.

Intermittent fasting shifts the diurnal transcriptome atlas of transcription factors

Intermittent fasting remains a safe and effective strategy to ameliorate various age-related diseases, but its specific mechanisms are not fully understood. Considering that transcription factors (TFs) determine the response to environmental signals, here, we profiled the diurnal expression of 600 samples across four metabolic tissues sampled every 4 over 24 h from mice placed on five different feeding regimens to provide an atlas of TFs in biological space, time, and feeding regimen. Results showed that 1218 TFs exhibited tissue-specific and temporal expression profiles in ad libitum mice, of which 974 displayed significant oscillations at least in one tissue. Intermittent fasting triggered more than 90% (1161 in 1234) of TFs to oscillate somewhere in the body and repartitioned their tissue-specific expression. A single round of fasting generally promoted TF expression, especially in skeletal muscle and adipose tissues, while intermittent fasting mainly suppressed TF expression. Intermittent fasting down-regulated aging pathway and upregulated the pathway responsible for the inhibition of mammalian target of rapamycin (mTOR). Intermittent fasting shifts the diurnal transcriptome atlas of TFs, and mTOR inhibition may orchestrate intermittent fasting-induced health improvements. This atlas offers a reference and resource to understand how TFs and intermittent fasting may contribute to diurnal rhythm oscillation and bring about specific health benefits.

The Role of the Chronotype in Developing an Excessive Body Weight and Its Complications-A Narrative Review

The chronotype, the personal predisposition towards morning or evening activities, significantly influences health conditions, sleep, and eating regulations. Individuals with evening chronotypes are often at a higher risk for weight gain due to misalignment between their natural tendencies of functioning and social schedules, resulting in insufficient sleep, disruptions in eating habits, and decreased physical activity levels. Often, impaired glucose tolerance and changes in melatonin, adiponectin, and leptin secretion, along with alterations in the clock gene functions in subjects with evening preferences, may be predisposed to obesity. These disturbances contribute to metabolic dysregulation, which may lead to the subsequent onset of obesity complications, such as hypertension, type 2 diabetes, sleep apnea, and liver diseases. Targeting critical components of the circadian system and synchronizing people's chronotypes with lifestyle conditions could deliver potential strategies for preventing and treating metabolic disorders. Thus, it is recommended to take a personalized chronobiological approach to maintain a normal body weight and metabolic health. Nevertheless, future studies are needed to identify the clear mechanisms between the chronotype and human health. This article provides a narrative review and discussion of recent data to summarize studies on the circadian rhythm in the context of obesity. The manuscript represents a comprehensive overview conducted between August and November 2024 using the National Library of Medicine browser (Medline, Pub-Med, Web of Science).

Insufficient Sleep Syndrome in Childhood

Sleep disorders in children have a negative impact on mental and physical development, and a lack of sleep is one of the most important problems in infancy. At the age when naps are commonly accepted, the judgment of whether the amount of sleep is adequate has been based on the total amount of sleep per day. In other words, the idea is that even if the amount of sleep at night is insufficient, it is not considered insufficient if it is compensated for by taking a long nap or sleeping late on weekend mornings. However, these lifestyle habits disrupt the circadian rhythm and cause social jet lag, which is not appropriate for healthy mental and physical development. Therefore, in this review, I present the average required nighCime basic sleep duration (NBSD) of 10 h for Japanese and 11 h for Caucasian children as a judgment standard. (1) If the child sleeps less than 8 h at night, and (2) if the child sleeps less than 9 h at night or 30 to 60 min less than the required NBSD, immediate treatment is recommended. I also discuss briefly how to address sleep insufficiency in childhood.

Comparative Impact of Alternate-Day Fasting and Time-Restricted Feeding on Placental Function and Fetal Development in Maternal Obesity

BACKGROUND

Maternal obesity detrimentally affects placental function and fetal development. Both alternate-day fasting (ADF) and time-restricted feeding (TRF) are dietary interventions that can improve metabolic health, yet their comparative effects on placental function and fetal development remain unexplored.

OBJECTIVES

This study aims to investigate the effects of ADF and TRF on placental function and fetal development during maternal consumption of a high-fat diet (HFD).

METHODS

One hundred 8-week-old female mice were assigned to one of four dietary regimens: (1) normal diet with ad libitum feeding (NA); (2) HFD with ad libitum feeding (HA); (3) HFD with ADF (HI); and (4) HFD with TRF (HT), administered both before and during pregnancy. On gestational day 18.5, serum and placental samples were collected from both mothers and fetuses to examine placental function and fetal development.

RESULTS

During gestation, both ADF and TRF substantially alleviated the metabolic impairments caused by an HFD in obese maternal mice. TRF mice demonstrated enhanced placental nutrient transport and fetal development, associated with reduced endoplasmic reticulum (ER) stress and inflammatory responses. In contrast, ADF markedly intensified placental stress and inflammatory responses, diminished placental nutrient transport efficiency, and consequently induced fetal growth restriction.

CONCLUSIONS

Both ADF and TRF during pregnancy significantly mitigated metabolic impairments in obese dams on an HFD. TRF mice demonstrated enhanced placental nutrient transport and fetal development, associated with reduced endoplasmic reticulum (ER) stress and inflammatory responses. In contrast, ADF markedly intensified placental stress and inflammatory responses, diminished placental nutrient transport efficiency, and consequently induced fetal growth restriction.

Sexual dimorphism on the acute effect of exercise in the morning vs. evening: A randomized crossover study

BACKGROUND

Mammalian cells possess molecular clocks, the adequate functioning of which is decisive for metabolic health. Exercise is known to modulate these clocks, potentially having distinct effects on metabolism depending on the time of day. This study aimed to investigate the impact of morning vs. evening moderate-intensity aerobic exercise on glucose regulation and energy metabolism in healthy men and women. It also aimed to elucidate molecular mechanisms within skeletal muscle.

METHODS

Using a randomized crossover design, healthy men (n = 18) and women (n = 17) performed a 60-min bout of moderate-intensity aerobic exercise in the morning and evening. Glucose regulation was continuously monitored starting 24 h prior to the exercise day and continuing until 48 h post-exercise for each experimental condition. Energy expenditure and substrate oxidation were measured by indirect calorimetry during exercise and at rest before and after exercise for 30 min. Skeletal muscle biopsies were collected immediately before and after exercise to assess mitochondrial function, transcriptome, and mitochondrial proteome.

RESULTS

Results indicated similar systemic glucose, energy expenditure, and substrate oxidation during and after exercise in both sexes. Notably, transcriptional analysis, mitochondrial function, and mitochondrial proteomics revealed marked sexual dimorphism and time of day variations.

CONCLUSION

The sexual dimorphism and time of day variations observed in the skeletal muscle in response to exercise may translate into observable systemic effects with higher exercise-intensity or chronic exercise interventions. This study provides a foundational molecular framework for precise exercise prescription in the clinical setting.

Neuropeptide-dependent spike time precision and plasticity in circadian output neurons

Circadian rhythms influence various physiological and behavioral processes such as sleep-wake cycles, hormone secretion, and metabolism. In Drosophila, an important set of circadian output neurons are called pars intercerebralis (PI) neurons, which receive input from specific clock neurons called DN1. These DN1 neurons can further be subdivided into functionally and anatomically distinctive anterior (DN1a) and posterior (DN1p) clusters. The neuropeptide diuretic hormones 31 (Dh31) and 44 (Dh44) are the insect neuropeptides known to activate PI neurons to control activity rhythms. However, the neurophysiological basis of how Dh31 and Dh44 affect circadian clock neural coding mechanisms underlying sleep in Drosophila is not well understood. Here, we identify Dh31/Dh44-dependent spike time precision and plasticity in PI neurons. We first find that a mixture of Dh31 and Dh44 enhanced the firing of PI neurons, compared to the application of Dh31 alone and Dh44 alone. We next find that the application of synthesized Dh31 and Dh44 affects membrane potential dynamics of PI neurons in the precise timing of the neuronal firing through their synergistic interaction, possibly mediated by calcium-activated potassium channel conductance. Further, we characterize that Dh31/Dh44 enhances postsynaptic potentials in PI neurons. Together, these results suggest multiplexed neuropeptide-dependent spike time precision and plasticity as circadian clock neural coding mechanisms underlying sleep in Drosophila.

A miR-219-5p-bmal1b negative feedback loop contributes to circadian regulation in zebrafish

MicroRNAs post-transcriptionally regulate gene expression and contribute to numerous life processes, including circadian rhythms. However, whether miRNAs contribute to zebrafish circadian regulation has not yet been investigated. Here, we showed that mature miR-219-5p, and its three pre-miRNAs, mir-219-1, mir-219-2, and mir-219-3, are rhythmically expressed primarily in Tectum opticum (TeO), Corpus cerebelli (CCe), and Crista cerellaris (CC) of the zebrafish brain. While mir-219-1 and mir-219-2 are regulated by the circadian clock through the E-like box, mir-219-3 is regulated by light via the D-box. Deleting mir-219-1, mir-219-2, or mir-219-3 individually or knocking down miR-219-5p all results in a shortened period of locomotor rhythms and up-regulation of bmal1b. RIP assays with Ago2 and miRNA pull-down assays show that miR-219-5p binds to bmal1b in the RISC. Cell transfection and in Vivo assays show that miR219-5p inhibits bmal1b through binding to its 3'UTR. Further, transcriptome analysis of miR-219-5p knockdown zebrafish adult brain reveals possible roles of miR-219-5p in phototransduction and neuroactive ligand-receptor interaction. Together, our findings demonstrate that mir-219-1, mir-219-2, and mir-219-3 are controlled directly by the circadian clock; and in turn, miR-219-5p contributes to circadian regulation by targeting bmal1b, highlighting a miR-219-5p-bmal1b negative feedback loop in the zebrafish circadian circuit.

The Functional Connectome Mediating Circadian Synchrony in the Suprachiasmatic Nucleus

Circadian rhythms in mammals arise from the spatiotemporal synchronization of ~20,000 neuronal clocks in the Suprachiasmatic Nucleus (SCN). While anatomical, molecular, and genetic approaches have revealed diverse cell types and signaling mechanisms, the network wiring that enables SCN cells to communicate and synchronize remains unclear. To overcome the challenges of revealing functional connectivity from fixed tissue, we developed MITE (Mutual Information & Transfer Entropy), an information theory approach that infers directed cell-cell connections with high fidelity. By analyzing 3447 hours of continuously recorded clock gene expression from 9011 cells in 17 mice, we found that the functional connectome of SCN was highly conserved bilaterally and across mice, sparse, and organized into a dorsomedial and a ventrolateral module. While most connections were local, we discovered long-range connections from ventral cells to cells in both the ventral and dorsal SCN. Based on their functional connectivity, SCN cells can be characterized as circadian signal generators, broadcasters, sinks, or bridges. For example, a subset of VIP neurons acts as hubs that generate circadian signals critical to synchronize daily rhythms across the SCN neural network. Simulations of the experimentally inferred SCN networks recapitulated the stereotypical dorsal-to-ventral wave of daily PER2 expression and ability to spontaneously synchronize, revealing that SCN emergent dynamics are sculpted by cell-cell connectivity. We conclude that MITE provides a powerful method to infer functional connectomes, and that the conserved architecture of cell-cell connections mediates circadian synchrony across space and time in the mammalian SCN.

Exenatide administration time-dependently affects the hepatic circadian clock through glucagon-like peptide-1 receptors in the central nervous system

Accumulating evidence indicates that disruption of the circadian clock contributes to the development of lifestyle-related diseases. We have previously shown that exenatide, a glucagon-like peptide-1 (GLP-1) receptor agonist, can strongly affect the molecular clocks in the peripheral tissues. This study aimed to investigate the effects of its dosing time and the central nervous system-specific GLP-1 receptor knockdown (GLP1RKD) on the hepatic clock in mice treated with exenatide. Male C57BL/6J and GLP1RKD mice were housed under a 12-h/12-h light/dark cycle, and feeding was restricted to either the light period (L-TRF) or the first 4 h in the dark period (D-TRF). In parallel, exenatide was administered 4-5 times, once daily either at the beginning of the dark (ZT 12) or light period (ZT 0), and we assessed the mRNA expression rhythms of clock genes in the liver thereafter. Exenatide administration at ZT 12 counteracted the phase shift effect of the L-TRF on the hepatic clock of wild-type mice, whereas the dosing at ZT 0 enhanced its effect. However, exenatide did not influence the phase of the hepatic clock under D-TRF regardless of the dosing time. The effect of exenatide in wild-type mice weakened in GLP1RKD mice. These results showed that exenatide dosing time-dependently affects the hepatic circadian clock through the central GLP-1 system. Exenatide administration at the beginning of the active period (i.e., in the morning for humans) might prevent disruption of the peripheral clocks caused by irregular eating habits.

Comparison of the Effects of Inappropriate Meal Timing-Induced and Genetic Models of Circadian Clock Disruption on Uterine mRNA Expression Profiles

BACKGROUND

Accumulating evidence reveals that inappropriate meal timing contributes to the development of lifestyle-related diseases. An underlying mechanism is thought to be the disruption of the intracellular circadian clock in various tissues based on observations in both systemic and tissue-specific clock gene-deficient mice. However, whether the effects of conditional clock gene knockout are comparable to those of inappropriate meal timing remains unclear.

OBJECTIVES

This study aimed to compare the effects of a recently developed 28-h feeding cycle model with those of a core clock gene Bmal1 uterine conditional knockout (Bmal1 cKO) model on uterine mRNA expression profiles.

METHODS

The models were generated by subjecting C57BL/6J mice to an 8-h/20-h feeding/fasting cycle for 2 wk and crossing Bmal1-floxed mice with PR-Cre mice. Microarray analyses were conducted using uterine samples obtained at the beginning of the dark and light periods.

RESULTS

The analyses identified 516 and 346, significantly 4-fold and 2-fold, up- or downregulated genes in the 28-h feeding cycle and Bmal1 cKO groups, respectively, compared with each control group. Among these genes, only 7 (1.4%) and 63 (18.2%) were significantly up- or downregulated in the other model. Moreover, most (n = 44, 62.9%) of these genes were oppositely regulated. These findings were confirmed by gene set enrichment analyses.

CONCLUSIONS

This study reveals that a 28-h feeding cycle and Bmal1 cKO differently affect gene expression profiles and highlights the need for considering this difference to assess the pathophysiology of diseases associated with inappropriate meal timing.

Rhythmic IL-17 production by γδ T cells maintains adipose de novo lipogenesis

The circadian rhythm of the immune system helps to protect against pathogens1-3; however, the role of circadian rhythms in immune homeostasis is less well understood. Innate T cells are tissue-resident lymphocytes with key roles in tissue homeostasis4-7. Here we use single-cell RNA sequencing, a molecular-clock reporter and genetic manipulations to show that innate IL-17-producing T cells-including γδ T cells, invariant natural killer T cells and mucosal-associated invariant T cells-are enriched for molecular-clock genes compared with their IFNγ-producing counterparts. We reveal that IL-17-producing γδ (γδ17) T cells, in particular, rely on the molecular clock to maintain adipose tissue homeostasis, and exhibit a robust circadian rhythm for RORγt and IL-17A across adipose depots, which peaks at night. In mice, loss of the molecular clock in the CD45 compartment (Bmal1∆Vav1) affects the production of IL-17 by adipose γδ17 T cells, but not cytokine production by αβ or IFNγ-producing γδ (γδIFNγ) T cells. Circadian IL-17 is essential for de novo lipogenesis in adipose tissue, and mice with an adipocyte-specific deficiency in IL-17 receptor C (IL-17RC) have defects in de novo lipogenesis. Whole-body metabolic analysis in vivo shows that Il17a-/-Il17f-/- mice (which lack expression of IL-17A and IL-17F) have defects in their circadian rhythm for de novo lipogenesis, which results in disruptions to their whole-body metabolic rhythm and core-body-temperature rhythm. This study identifies a crucial role for IL-17 in whole-body metabolic homeostasis and shows that de novo lipogenesis is a major target of IL-17.

Glycaemic Response to Acute Aerobic and Anaerobic Exercise Performed in the Morning or Afternoon in Healthy Subjects: A Crossover Trial

BACKGROUND

The regular practice of physical activity is considered a health promoter and appears to be one of the main contributors to the prevention of chronic diseases. However, the potential effects of exercise on health depending on the time of day at which it is performed have not yet been fully elucidated.

OBJECTIVES

To evaluate the effect of physical exercise (aerobic or anaerobic) and chronobiology (morning or afternoon) on the glycemic metabolism of healthy subjects.

METHODS

Healthy subjects participated in aerobic or anaerobic physical exercise sessions, either in the morning or in the afternoon. Blood was drawn from the subjects before, at the end of the exercise and 2 hours after the end of the exercise. Glycemic parameters were analyzed at these time points. A general linear model test was performed after verifying the normal distribution of the raw data (as assessed by the Shapiro-Wilk test) or after a logarithmic/square root transformation, considering aerobic or anaerobic exercise and morning or afternoon exercise as independent variables.

RESULTS

Twenty-three subjects (14 women and 9 men) were included in the study. The rate of change in glucose levels was significantly higher at the end of anaerobic exercise compared to aerobic exercise (1.19 ± 0.04 vs. 0.98 ± 0.02, respectively), with a more pronounced decrease in insulin and C-peptide levels following aerobic exercise. In addition, the increase of glucose was higher after the exercise in the morning compared with the afternoon (1.14 ± 0.03 vs. 1.03 ± 0.03, respectively).

CONCLUSIONS

The type of exercise and chronobiology influence short-term glucose metabolism.

Different time-restricted feeding patterns potentially modulate metabolic health by altering tryptophan metabolism of gut microbes in pigs

Time-restricted feeding has emerged as a preferred approach for alleviating metabolic disorders, but the potential microbiological mechanism remains poorly understood. This study used a growing pig model to mimic common-sense eating habits. Four feeding patterns were set up, including ad libitum feeding (ALF) for daily irregulated eating habits, time-restricted feeding (TRF) for three meals a day, early time-restricted feeding (eTRF) for skipping dinner and mid-day time-restricted feeding (mTRF) for skipping breakfast. The results showed that the three time-restricted feeding patterns (TRF, eTRF and mTRF) resulted in a reduction of hepatic fat accumulation and a decrease in hepatic function markers compared to the ALF pattern. However, this was independent of food consumption. Transcriptome analysis of the liver showed that the three time-restricted feeding patterns downregulated the expression of genes related to gluconeogenesis, β-oxidation, lipid accumulation, and urea cycle, and upregulated the expression of genes related to lipogenesis and glycolysis compared to the ALF pattern. Microbiome and metabolome analyses showed that Lactobacillus enriched in the colon of pigs in three time-restricted groups were negatively correlated with serum triglyceride. Meanwhile, three time-restricted feeding patterns elevated the levels of the microbial metabolite indole-3-lactic acid, which was further confirmed to reduce excessive hepatic lipid accumulation in vitro. Overall, time-restricted feeding potentially improved metabolic health by modulating gut microbiota and metabolites.

Neuronal Progenitors Suffer Genotoxic Stress in the Drosophila Clock Mutant per0

The physiological role and the molecular architecture of the circadian clock in fully developed organisms are well established. Yet, we have a limited understanding of the function of the clock during ontogenesis. We have used a null mutant (per0) of the clock gene period (per) in Drosophila melanogaster to ask whether PER may play a role during normal brain development. In third-instar larvae, we have observed that the absence of functional per results in increased genotoxic stress compared to wild-type controls. We have detected increased double-strand DNA breaks in the central nervous system and chromosome aberrations in dividing neuronal precursor cells. We have demonstrated that reactive oxygen species (ROS) are causal to the genotoxic effect and that expression of PER in glia is necessary and sufficient to suppress such a phenotype. Finally, we have shown that the absence of PER may result in less condensed chromatin, which contributes to DNA damage.

Impact of Circadian Clock PER2 Gene Overexpression on Rumen Epithelial Cell Dynamics and VFA Transport Protein Expression

The circadian gene PER2 is recognized for its regulatory effects on cell proliferation and lipid metabolism across various non-ruminant cells. This study investigates the influence of PER2 gene overexpression on goat rumen epithelial cells using a constructed pcDNA3.1-PER2 plasmid, assessing its impact on circadian gene expression, cell proliferation, and mRNA levels of short-chain fatty acid (SCFA) transporters, alongside genes related to lipid metabolism, cell proliferation, and apoptosis. Rumen epithelial cells were obtained every four hours from healthy dairy goats (n = 3; aged 1.5 years; average weight 45.34 ± 4.28 kg), cultured for 48 h in vitro, and segregated into control (pcDNA3.1) and overexpressed (pcDNA3.1-PER2) groups, each with four biological replicates. The study examined the potential connection between circadian rhythms and nutrient assimilation in ruminant, including cell proliferation, apoptosis, cell cycle dynamics, and antioxidant activity and the expression of circadian-related genes, VFA transporter genes and regulatory factors. The introduction of the pcDNA3.1-PER2 plasmid drastically elevated PER2 expression levels by 3471.48-fold compared to controls (p < 0.01), confirming effective overexpression. PER2 overexpression resulted in a significant increase in apoptosis rates (p < 0.05) and a notable reduction in cell proliferation at 24 and 48 h post-transfection (p < 0.05), illustrating an inhibitory effect on rumen epithelial cell growth. PER2 elevation significantly boosted the expression of CCND1, WEE1, p21, and p16 (p < 0.05) while diminishing CDK4 expression (p < 0.05). While the general expression of intracellular inflammation genes remained stable, TNF-α expression notably increased. Antioxidant marker levels (SOD, MDA, GSH-Px, CAT, and T-AOC) exhibited no significant change, suggesting no oxidative damage due to PER2 overexpression. Furthermore, PER2 overexpression significantly downregulated AE2, NHE1, MCT1, and MCT4 mRNA expressions while upregulating PAT1 and VH+ ATPase. These results suggest that PER2 overexpression impairs cell proliferation, enhances apoptosis, and modulates VFA transporter-related factors in the rumen epithelium. This study implies that the PER2 gene may regulate VFA absorption through modulation of VFA transporters in rumen epithelial cells, necessitating further research into its specific regulatory mechanisms.

Circadian rhythms in muscle health and diseases

All major life forms from bacteria to humans have internal clocks that regulate essential biological processes in a roughly 24-h cycle. In mammals, the central clock in the suprachiasmatic nucleus (SCN) is historically considered the top of a hierarchical organisation that dominates subordinate clocks in peripheral tissues and dictates the circadian behaviours of an organism. Recent studies, however, underscore the importance of the local circadian oscillators, such as the skeletal muscle clock, in regulating local metabolism and physiology. Studies in animal models show that the muscle peripheral clock per se is required for the expression of genes involved in glucose, lipid, and amino acid metabolism. Disruption of the muscle clock leads to glucose intolerance, insulin resistance, and alterations in muscle size and force. This highlights the vital role of the muscle clock in controlling muscle physiology and metabolism. In humans, a perturbation in the muscle circadian rhythms is seen in metabolic disorders such as type 2 diabetes, and muscle diseases such as dystrophies. Disruption of muscle metabolism is also seen when the internal rhythms are misaligned with the external rhythms (circadian misalignments) as in shift work. Understanding the mechanisms by which the muscle clock regulates circadian functions may help the development of new strategies, such as chronotherapy, to potentially prevent or treat muscle pathologies and maintain muscle health.

Dexamethasone is a regulator of clock genes in testicular peritubular cells

BACKGROUND

We recently found that peritubular cells of the human testis are a dominant site of expression of the glucocorticoid receptor (GR; encoded by NR3C1). Activation of GR by dexamethasone (Dex) strongly influences the phenotype of cultured human testicular peritubular cells (HTPCs), causing massive changes of their proteome and secretome. As glucocorticoids (GC) are also known to set the internal clock of peripheral organs by regulating clock genes, we tested such an influence of Dex in HTPCs.

METHODS

We performed cellular studies with HTPCs and immortalized nonhuman primate (Callithrix jacchus; Cj)-derived peritubular cells, organotypic incubations of testicular fragments of Cj, qPCR and proteomic, as well as immunohistochemical studies.

RESULTS

Basal clock gene expression levels, when monitored by qPCR under standard culture conditions, showed alterations over 24 h, suggesting an endogenous circadian rhythm, especially for BMAL1. Dex (1 µM) when added to cells, caused a strong and significant increase of PER1, followed by elevations of BMAL1, and other clock genes. This action was observed as early as 4 h after the addition of Dex. Immunohistochemistry and data mining revealed GR in testicular peritubular cells and other somatic cells of Cj, in situ. We therefore performed organotypic incubations of testicular fragments of Cj (n = 3) and found that upon addition of Dex (1 µM), mRNA levels of BMAL1 and PER1 also increased in samples of two out of three animals after 6 h. Mass spectrometry did, however, not reveal significant alterations of the testicular proteome, possibly due to the short time point and/or the fact that the somatic GR-expressing cells represent only a small portion of the testis. In support for this assumption, Dex (1 µM; 6 h) significantly increased mRNA levels of BMAL1 and PER1 in Cj-derived immortalized testicular peritubular cells.

CONCLUSION

The results indicate that an internal clock system likely exists in peritubular cells of the testis and that Dex, via testicular GR expressed by peritubular cells and other somatic cells, is a strong regulator of this system. In a physiological situation, GC thus may be important regulators of the testicular clock, while in a situation of prolonged stress or GC-medication, derangements in clock gene expression may result.

Getting in the zone: Metabolite transport across liver zones

The liver has many functions including the regulation of nutrient and metabolite levels in the systemic circulation through efficient transport into and out of hepatocytes. To sustain these functions, hepatocytes display large functional heterogeneity. This heterogeneity is reflected by zonation of metabolic processes that take place in different zones of the liver lobule, where nutrient-rich blood enters the liver in the periportal zone and flows through the mid-zone prior to drainage by a central vein in the pericentral zone. Metabolite transport plays a pivotal role in the division of labor across liver zones, being either transport into the hepatocyte or transport between hepatocytes through the blood. Signaling pathways that regulate zonation, such as Wnt/β-catenin, have been shown to play a causal role in the development of metabolic dysfunction-associated steatohepatitis (MASH) progression, but the (patho)physiological regulation of metabolite transport remains enigmatic. Despite the practical challenges to separately study individual liver zones, technological advancements in the recent years have greatly improved insight in spatially divided metabolite transport. This review summarizes the theories behind the regulation of zonation, diurnal rhythms and their effect on metabolic zonation, contemporary techniques used to study zonation and current technological challenges, and discusses the current view on spatial and temporal metabolite transport.

Breakfast Protein Intake of One-third of Daily Requirement Can Maintain Lean Body Mass Post-distal Gastrectomy

BACKGROUND/AIM

Post-gastrectomy lean body mass (LBM) decrease has a significant negative impact on postoperative survival in patients with cancer. This study investigated the effect of intake of at least one-third of the daily protein requirement at breakfast on the maintenance of LBM in patients during the first month post-gastrectomy.

PATIENTS AND METHODS

Among patients with gastric cancer who underwent curative distal gastrectomy between April 2011 and December 2018, without adjuvant chemotherapy, we evaluated 401 patients who had consumed more than the daily protein requirement in the first month postoperatively, using the FFQW82 nutrition intake questionnaire. Patients were divided into those who consumed more (≥1/3 intake group, n=160) and those who consumed less than one-third of the daily protein requirement at breakfast (<1/3 intake group, n=241). We compared the LBM reduction rate at one month postoperatively between groups. Univariate and multivariate analyses were performed to determine clinicopathological factors predicting LBM reduction at one month postoperatively.

RESULTS

The LBM reduction rate at one month post-curative distal gastrectomy was significantly higher in the <1/3 intake group than in the ≥1.3 intake group (p=0.01) at breakfast. Multivariate analysis showed that morning protein intake below one-third of the daily requirement independently predicted LBM reduction (odds ratio=1.75, 95% confidence interval=1.14-2.68, p<0.01).

CONCLUSION

Consuming at least one-third of the daily protein requirement at breakfast may be effective in maintaining LBM in patients undergoing curative distal gastrectomy. These results may be very important for prognosis, since maintaining LBM influences the continuation of adjuvant chemotherapy and thus survival after curative resection in patients with gastric cancer.

Resilience to Chronic Stress Is Characterized by Circadian Brain-Liver Coordination

Background

Chronic stress has a profound impact on circadian regulation of physiology. In turn, disruption of circadian rhythms increases the risk of developing both psychiatric and metabolic disorders. To explore the role of chronic stress in modulating the links between neural and metabolic rhythms, we characterized the circadian transcriptional regulation across different brain regions and the liver as well as serum metabolomics in mice exposed to chronic social defeat stress, a validated model for studying depressive-like behaviors.

Methods

Male C57BL/6J mice underwent chronic social defeat stress, and subsequent social interaction screening identified distinct behavioral phenotypes associated with stress resilience and susceptibility. Stressed mice and their control littermates were sacrificed every 4 hours over the circadian cycle for comprehensive analyses of the circadian transcriptome in the hypothalamus, hippocampus, prefrontal cortex, and liver together with assessments of the circadian circulatory metabolome.

Results

Our data demonstrate that stress adaptation was characterized by reprogramming of the brain as well as the hepatic circadian transcriptome. Stress resiliency was associated with an increase in cyclic transcription in the hypothalamus, hippocampus, and liver. Furthermore, cross-tissue analyses revealed that resilient mice had enhanced transcriptional coordination of circadian pathways between the brain and liver. Conversely, susceptibility to social stress resulted in a loss of cross-tissue coordination. Circadian serum metabolomic profiles corroborated the transcriptome data, highlighting that stress-resilient mice gained circadian rhythmicity of circulating metabolites, including bile acids and sphingomyelins.

Conclusions

This study reveals that resilience to stress is characterized by enhanced metabolic rhythms and circadian brain-liver transcriptional coordination.

Site of breast cancer metastasis is independent of single nutrient levels

Cancer metastasis is a major contributor to patient morbidity and mortality1, yet the factors that determine the organs where cancers can metastasize are incompletely understood. In this study, we quantify the absolute levels of over 100 nutrients available across multiple tissues in mice and investigate how this relates to the ability of breast cancer cells to grow in different organs. We engineered breast cancer cells with broad metastatic potential to be auxotrophic for specific nutrients and assessed their ability to colonize different organs. We then asked how tumor growth in different tissues relates to nutrient availability and tumor biosynthetic activity. We find that single nutrients alone do not define the sites where breast cancer cells can grow as metastases. Additionally, we identify purine synthesis as a requirement for tumor growth and metastasis across many tissues and find that this phenotype is independent of tissue nucleotide availability or tumor de novo nucleotide synthesis activity. These data suggest that a complex interplay of multiple nutrients within the microenvironment dictates potential sites of metastatic cancer growth, and highlights the interdependence between extrinsic environmental factors and intrinsic cellular properties in influencing where breast cancer cells can grow as metastases.

Effects of the Fungicide Prothioconazole on Lipid Metabolism in Mice: Whitening Alterations of Brown Adipose Tissue

With considerable concerns about the associations between metabolic disorders and agricultural biocides, there are scattered data suggesting that the triazole fungicide prothioconazole (PTC) at lower doses than the no observed adverse effect level of 5000 μg/kg/d possibly has the potential to disrupt glycolipid metabolism in mammals. Here, we investigated the effects of 50, 500, and 5000 μg/kg/d of PTC on glycolipid metabolism in mice following 8 weeks of administration via drinking water, with specific attention on brown adipose tissue (BAT) and white adipose tissue (WAT) in addition to the liver. We found that along with the increased serum triglyceride level in the 5000 μg/kg/d group, small fatty vacuoles occurred in livers in all treatment groups, indicating lipid accumulation. No change in WAT was observed, but PTC caused BAT whitening, characterized by adipocyte hypertrophy, more unilocular adipocytes with enlarged lipid droplets, reduced UCP1 levels, and down-regulated Doi2 expression, and even the dose of 50 μg/kg/d was effective. Transcriptomic analysis revealed immune inhibition and circadian rhythm disturbance in BAT from the 5000 μg/kg/d group, which are in agreement with BAT whitening and inactivation. On employing the C3H10T1/2 cells in vitro, we found that PTC treatment concentration-dependently promoted lipid accumulation in brown adipocytes, along with altered expression of thermogenesis-related and circadian genes. Taken together, our study shows that low doses of PTC caused BAT whitening, calling for much attention to the new target by pollutants.

Dual-Approach Co-expression Analysis Framework (D-CAF) Enables Identification of Novel Circadian Regulation From Multi-Omic Timeseries Data

The circadian clock is a central driver of many biological and behavioral processes, regulating the levels of many genes and proteins, termed clock controlled genes and proteins (CCGs/CCPs), to impart biological timing at the molecular level. While transcriptomic and proteomic data has been analyzed to find potential CCGs and CCPs, multi-omic modeling of circadian data, which has the potential to enhance the understanding of circadian control of biological timing, remains relatively rare due to several methodological hurdles. To address this gap, a Dual-approach Co-expression Analysis Framework (D-CAF) was created to perform perturbation-robust co-expression analysis on time-series measurements of both transcripts and proteins. Applying this D-CAF framework to previously gathered transcriptomic and proteomic data from mouse macrophages gathered over circadian time, we identified small, highly significant clusters of oscillating transcripts and proteins in the unweighted similarity matrices and larger, less significant clusters of of oscillating transcripts and proteins using the weighted similarity network. Functional enrichment analysis of these clusters identified novel immunological response pathways that appear to be under circadian control. Overall, our findings suggest that D-CAF is a tool that can be used by the circadian community to integrate multi-omic circadian data to improve our understanding of the mechanisms of circadian regulation of molecular processes.

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.

Circadian time-dependent effects of experimental colitis on theophylline disposition and toxicity

BACKGROUND AND PURPOSE

Drug disposition undergoes significant alteration in patients with inflammatory bowel disease (IBD), yet circadian time-dependency of these changes remains largely unexplored. In this study, we aimed to determine the temporal effects of experimental colitis on drug disposition and toxicity.

EXPERIMENTAL APPROACH

RNA-sequencing was used to screen genes relevant to colitis induced by dextran sodium sulfate in mice. Liver microsomes and pharmacokinetic analysis were used to analyze the activity of key enzymes. Dual luciferase assays and chromatin immunoprecipitation (ChIP) were employed to elucidate regulatory mechanisms.

KEY RESULTS

RNA sequencing analysis revealed that colitis markedly influenced expression of cytochrome P450 (CYP) enzymes. Specifically, a substantial down-regulation of CYP1A2 and CYP2E1 was observed in livers of mice with colitis at Zeitgeber Time 8 (ZT8), with no significant changes detected at ZT20. At ZT8, the altered expression corresponded to diminished metabolism and enhanced incidence of hepato-cardiac toxicity of theophylline, a substrate specifically metabolized by these enzymes. A combination of assays, integrating liver-specific Bmal1 knockout and targeted activation of BMAL1 showed that dysregulation in CYP1A2 and CYP2E1 during colitis was attributable to perturbed BMAL1 functionality. Luciferase reporter and ChIP assays collectively substantiated the role of BMAL1 in regulating Cyp1a2 and Cyp2e1 transcription through its binding affinity to E-box-like sites.

CONCLUSION AND IMPLICATION

Our findings establish a strong link between colitis and chronopharmacology, shedding light on how IBD affects drug disposition and toxicity over time. This research provides a theoretical foundation for optimizing drug dosage in patients with IBD.

Time of day dependent changes in embryonic heart rate are detectable after maturation of rhythmic circadian gene expression in the eye, but before the heart in Xenopus laevis tadpoles cultured in LD

We systematically characterized onset of expression of circadian genes in the embryonic eye and heart of Xenopus laevis tadpoles. We found that period1 (per1) and nr1d1 ( rev-erbα) were the first circadian genes to display significant 24-hour rhythms in the developing eye and heart in a 12-hour light-dark cycle (LD). Rhythmic expression of both oscillator and output genes were present in the eye by 2.75 days post fertilization (dpf), but not in 15 dpf hearts. Surprisingly, rhythmic oscillation of heart rate occurred after 3.2 dpf suggesting that heart rate may be controlled directly by light or indirectly by the pineal in LD.

Hepatic BMAL1 and HIF1α regulate a time-dependent hypoxic response and prevent hepatopulmonary-like syndrome

The transcriptional response to hypoxia is temporally regulated, yet the molecular underpinnings and physiological implications are unknown. We examined the roles of hepatic Bmal1 and Hif1α in the circadian response to hypoxia in mice. We found that the majority of the transcriptional response to hypoxia is dependent on either Bmal1 or Hif1α, through shared and distinct roles that are daytime determined. We further show that hypoxia-inducible factor (HIF)1α accumulation upon hypoxia is temporally regulated and Bmal1 dependent. Unexpectedly, mice lacking both hepatic Bmal1 and Hif1α are hypoxemic and exhibit increased mortality upon hypoxic exposure in a daytime-dependent manner. These mice display mild liver dysfunction with pulmonary vasodilation likely due to extracellular signaling regulated kinase (ERK) activation, endothelial nitric oxide synthase, and nitric oxide accumulation in lungs, suggestive of hepatopulmonary syndrome. Our findings indicate that hepatic BMAL1 and HIF1α are key time-dependent regulators of the hypoxic response and can provide molecular insights into the pathophysiology of hepatopulmonary syndrome.

Long-term high fructose intake reprograms the circadian transcriptome and disrupts homeostasis in mouse extra-orbital lacrimal glands

This study aims to explore the effects of long-term high fructose intake (LHFI) on the structure, functionality, and physiological homeostasis of mouse extra-orbital lacrimal glands (ELGs), a critical component of ocular health. Our findings reveal significant reprogramming of the circadian transcriptome in ELGs following LHFI, alongside the activation of specific inflammatory pathways, as well as metabolic and neural pathways. Notably, LHFI resulted in increased inflammatory infiltration, enhanced lipid deposition, and reduced nerve fiber density in ELGs compared to controls. Functional assessments indicated a marked reduction in lacrimal secretion following cholinergic stimulation in LHFI-treated mice, suggesting impaired gland function. Overall, our results suggest that LHFI disrupts lacrimal gland homeostasis, potentially leading to dry eye disease by altering its structure and secretory function. These insights underscore the profound impact of dietary choices on ocular health and highlight the need for strategies to mitigate these risks.

Energy Intake and Dietary Glycemic Load in Late Morning and Risk of Type 2 Diabetes: The Hispanic Community Health Study/Study of Latinos-A Multicenter Prospective Cohort Study

OBJECTIVE

To evaluate the association between meal timing and type 2 diabetes risk in U.S. Hispanic/Latino adults.

RESEARCH DESIGN AND METHODS

The Hispanic Community Health Study/Study of Latinos (HCHS/SOL) is a multicenter, community-based, prospective cohort study. This study included 8,868 HCHS/SOL adults without diabetes at baseline (2008-2011) and attending the visit 2 examination (2014-2017). Energy intake and glycemic load (GL) in each meal timing were assessed at baseline using two 24-h dietary recalls. Incident diabetes was identified through annual follow-up calls or at visit 2. Hazard ratios (HRs) for incident diabetes were estimated using Cox models, accounting for the complex survey design.

RESULTS

The study population (50.9% female) had a baseline mean age of 39.0 (95% CI, 38.4-39.5) years. Over a median (range) follow-up of 5.8 (0.8-9.6) years, 1,262 incident diabetes cases were documented. Greater energy intake and GL in late morning (9:00-11:59 a.m.) were associated with a lower diabetes risk, whereas greater energy intake and GL in other meal timings were not. After accounting for diet quantity and quality, sociodemographic characteristics, lifestyle factors, and chronic conditions, the HRs were 0.94 (95% CI, 0.91-0.97) per 100-kcal energy intake increment and 0.93 (0.89-0.97) per 10-unit GL increment in late morning. Replacing energy intake or GL from early morning (6:00-8:59 a.m.), afternoon (12:00-5:59 p.m.), or evening (6:00-11:59 p.m.) with late-morning equivalents was associated with a comparably lower diabetes risk.

CONCLUSIONS

This study identified late morning as a favorable meal timing in Hispanic/Latino adults, providing a novel perspective on type 2 diabetes prevention that warrants confirmation.

An atlas of the human liver diurnal transcriptome and its perturbation by hepatitis C virus infection

Chronic liver disease and cancer are global health challenges. The role of the circadian clock as a regulator of liver physiology and disease is well established in rodents, however, the identity and epigenetic regulation of rhythmically expressed genes in human disease is less well studied. Here we unravel the rhythmic transcriptome and epigenome of human hepatocytes using male human liver chimeric mice. We identify a large number of rhythmically expressed protein coding genes in human hepatocytes of male chimeric mice, which includes key transcription factors, chromatin modifiers, and critical enzymes. We show that hepatitis C virus (HCV) infection, a major cause of liver disease and cancer, perturbs the transcriptome by altering the rhythmicity of the expression of more than 1000 genes, and affects the epigenome, leading to an activation of critical pathways mediating metabolic alterations, fibrosis, and cancer. HCV-perturbed rhythmic pathways remain dysregulated in patients with advanced liver disease. Collectively, these data support a role for virus-induced perturbation of the hepatic rhythmic transcriptome and pathways in cancer development and may provide opportunities for cancer prevention and biomarkers to predict HCC risk.

Glucose Challenge Uncovers Temporal Fungibility of Metabolic Homeostasis over a day:night cycle

Rhythmicity is a cornerstone of behavioral and biological processes, especially metabolism, yet the mechanisms behind metabolite cycling remain elusive. This study uncovers a robust oscillation in key metabolite pathways downstream of glucose in humans. A purpose-built 13C6-glucose isotope tracing platform was used to sample Drosophila every 4h and probe these pathways, revealing a striking peak in biosynthesis shortly after lights-on in wild-type flies. A hyperactive mutant (fumin) demonstrates increased Krebs cycle labelling and dawn-specific glycolysis labelling. Surprisingly, neither underlying feeding rhythms nor the presence of food availability explain the rhythmicity of glucose processing across genotypes, suggesting a robust internal mechanism for metabolic control of glucose processing. These results align with clinical data highlighting detrimental effects of mistimed energy intake. Our approach offers a unique insight into the dynamic range of daily metabolic processing and provides a mechanistic foundation for exploring circadian metabolic homeostasis in disease contexts.

Regulation of metabolism by circadian rhythms: Support from time-restricted eating, intestinal microbiota & omics analysis

Circadian oscillatory system plays a key role in coordinating the metabolism of most organisms. Perturbation of genetic effects and misalignment of circadian rhythms result in circadian dysfunction and signs of metabolic disorders. The eating-fasting cycle can act on the peripheral circadian clocks, bypassing the photoperiod. Therefore, time-restricted eating (TRE) can improve metabolic health by adjusting eating rhythms, a process achieved through reprogramming of circadian genomes and metabolic programs at different tissue levels or remodeling of the intestinal microbiota, with omics technology allowing visualization of the regulatory processes. Here, we review recent advances in circadian regulation of metabolism, focus on the potential application of TRE for rescuing circadian dysfunction and metabolic disorders with the contribution of intestinal microbiota in between, and summarize the significance of omics technology.

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.

Light-Dependent Circadian Rhythm Governs O-GlcNAc Cycling to Influence Cognitive Function in Adult Zebrafish

This study explores the 24-h rhythmic cycle of protein O-GlcNAcylation within the brain and highlights its crucial role in regulating the circadian cycle and neuronal function based on zebrafish as an animal model. In our experiments, disruption of the circadian rhythm, achieved through inversion of the light-dark cycle or daytime melatonin treatment, not only impaired the rhythmic changes of O-GlcNAcylation along with altering expression patterns of O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) in zebrafish brain but also significantly impeded learning and memory function. In particular, circadian disruption affected rhythmic expression of protein O-GlcNAcylation and OGT in the nuclear fraction. Notably, the circadian cycle induces rhythmic alterations in O-GlcNAcylation of H2B histone protein that correspond to changes in H3 trimethylation. Disruption of the cycle interfered with these periodic histone code alterations. Pharmacological inhibition of OGT with OSMI-1 disrupted the wake-sleep patterns of zebrafish without affecting expression of circadian rhythm-regulating genes. OSMI-1 inhibited the expression of c-fos, bdnf, and calm1, key genes associated with brain function and synaptic plasticity, and decreased the binding of O-GlcNAcylated H2B and OGT to promoter regions of these genes. The collective findings support the potential involvement of circadian cycling of the O-GlcNAc histone code in regulating synaptic plasticity and brain function. Overall, data from this study provide evidence that protein O-GlcNAcylation serves as a pivotal posttranslational mechanism integrating circadian signals and neuronal function to regulate rhythmic physiology.

Dopamine production in neurotensin receptor 1 neurons is required for diet-induced obesity and increased day eating on a high-fat diet

OBJECTIVE

This study aimed to determine a dopaminergic circuit required for diet-induced obesity in mice.

METHODS

We created conditional deletion mutants for tyrosine hydroxylase (TH) using neurotensin receptor 1 (Ntsr1) Cre and other Cre drivers and measured feeding and body weight on standard and high-fat diets. We then used an adeno-associated virus to selectively restore TH to the ventral tegmental area (VTA) Ntsr1 neurons in conditional knockout (cKO) mice.

RESULTS

Mice with cKO of Th using Vglut2-Cre, Cck-Cre, Calb1-Cre, and Bdnf-Cre were susceptible to obesity on a high-fat diet; however, Ntsr1-Cre Th cKO mice resisted weight gain on a high-fat diet and did not experience an increase in day eating unlike their wild-type littermate controls. Restoration of TH to the VTA Ntsr1 neurons of the Ntsr1-Cre Th cKO mice using an adeno-associated virus resulted in an increase in weight gain and day eating on a high-fat diet.

CONCLUSIONS

Ntsr1-Cre Th cKO mice failed to increase day eating on a high-fat diet, offering a possible explanation for their resistance to diet-induced obesity. These results implicate VTA Ntsr1 dopamine neurons as promoting out-of-phase feeding behavior on a high-fat diet that could be an important contributor to diet-induced obesity in humans.

Circadian metabolites for evaluating the timing of bloodstain deposition: A preliminary study

Metabolites, as products of cellular metabolism, can provide a wealth of biological information and are less susceptible to degradation than other biomarkers due to their low molecular weight. Due to these properties, metabolites can be used as valuable biomarkers for forensic investigations. Knowing the timing of deposition of bloodstain could help to reconstruct crime scenes, draw conclusions about the time of the crime, and narrow down the circle of possible suspects. Previous studies have indicated that the concentration of some metabolites in blood is subject to circadian changes. However, the circadian metabolites of bloodstains have been still unclear. A total of sixty-four bloodstain samples were prepared under real conditions in three time categories (morning/noon (09:00 h ∼ 17:00 h), afternoon/evening (18:00 h ∼ 23:00 h) and night/early morning (24:00 h ∼ 08:00 h)). Fifty metabolites of bloodstains with significant differences were identified in the three time categories. Twenty-eight of these metabolites exhibited significant circadian changes. Finally, three independently contributing circadian metabolites were selected to build the logistic regression model, with an area under the curve of 0.91, 0.84 and 0.87 for the prediction of bloodstain deposition time in the morning/noon, afternoon/evening and night/early morning, respectively. The study indicated that circadian metabolites can be used for evaluating the timing of bloodstain deposition. This would provide a valuable perspective for analyzing the deposition time of biological traces in forensic investigations.

Research advances in the therapy of metabolic syndrome

Metabolic syndrome refers to the pathological state of metabolic disorder of protein, fat, carbohydrate, and other substances in the human body. It is a syndrome composed of a group of complex metabolic disorders, whose pathogenesis includes multiple genetic and acquired entities falling under the category of insulin resistance and chronic low-grade inflammationand. It is a risk factor for increased prevalence and mortality from diabetes and cardiovascular disease. Cardiovascular diseases are the predominant cause of morbidity and mortality globally, thus it is imperative to investigate the impact of metabolic syndrome on alleviating this substantial disease burden. Despite the increasing number of scientists dedicating themselves to researching metabolic syndrome in recent decades, numerous aspects of this condition remain incompletely understood, leaving many questions unanswered. In this review, we present an epidemiological analysis of MetS, explore both traditional and novel pathogenesis, examine the pathophysiological repercussions of metabolic syndrome, summarize research advances, and elucidate the mechanisms underlying corresponding treatment approaches.

Associations between Dietary Intake and Cardiovascular Disease Risk in American Career Firefighters: An Observational Study

Firefighters have demanding jobs, requiring high levels of fitness in stressful situations for operational readiness, yet many firefighters are at an increased risk of developing cardiovascular disease (CVD). Diet is an important factor contributing to the development of CVD. The purpose of this study was to describe the dietary intake of firefighters and examine the associations between dietary intake and the CVD risk. Forty-six male career firefighters (age = 41.2 ± 11.2 years; BMI = 29.2 ± 4.1 kg/m2; body fat = 21.7 ± 6.1%) enrolled in a fitness-focused wellness program completed a health survey and a fitness assessment. The survey responses and fitness assessment were used to calculate the Framingham CVD Risk Score. Data were analyzed using R, the residual assumptions were verified, and the alpha level was set at 0.05. The results revealed that firefighters consume a standard American diet, with the overconsumption of meat and underconsumption of fruits and vegetables. The average CVD risk approached the upper limit of low risk. The results also indicate that meat servings and preparation fat affect the CVD risk (R2 = 0.21, p = 0.006). The outcomes of this study can inform investigations aimed at improving operational readiness and reducing the CVD risk in firefighters by implementing a holistic approach combining dietary interventions with physical training.

Hypermetabolic state is associated with circadian rhythm disruption in mouse and human cancer cells

Crosstalk between metabolism and circadian rhythms is a fundamental building block of multicellular life, and disruption of this reciprocal communication could be relevant to disease. Here, we investigated whether maintenance of circadian rhythms depends on specific metabolic pathways, particularly in the context of cancer. We found that in adult mouse fibroblasts, ATP levels were a major contributor to signal from a clock gene luciferase reporter, although not necessarily to the strength of circadian cycling. In contrast, we identified significant metabolic control of circadian function across a series of pancreatic adenocarcinoma cell lines. Metabolic profiling of congenic tumor cell clones revealed substantial diversity among these lines that we used to identify clones to generate circadian reporter lines. We observed diverse circadian profiles among these lines that varied with their metabolic phenotype: The most hypometabolic line [exhibiting low levels of oxidative phosphorylation (OxPhos) and glycolysis] had the strongest rhythms, while the most hypermetabolic line had the weakest rhythms. Pharmacological enhancement of OxPhos decreased the amplitude of circadian oscillation in a subset of tumor cell lines. Strikingly, inhibition of OxPhos enhanced circadian rhythms only in the tumor cell line in which glycolysis was also low, thereby establishing a hypometabolic state. We further analyzed metabolic and circadian phenotypes across a panel of human patient-derived melanoma cell lines and observed a significant negative association between metabolic activity and circadian cycling strength. Together, these findings suggest that metabolic heterogeneity in cancer directly contributes to circadian function and that high levels of glycolysis or OxPhos independently disrupt circadian rhythms in these cells.

Autonomous Oscillatory Mitochondrial Respiratory Activity: Results of a Systematic Analysis Show Heterogeneity in Different In Vitro-Synchronized Cancer Cells

Circadian oscillations of several physiological and behavioral processes are an established process in all the organisms anticipating the geophysical changes recurring during the day. The time-keeping mechanism is controlled by a transcription translation feedback loop involving a set of well-characterized transcription factors. The synchronization of cells, controlled at the organismal level by a brain central clock, can be mimicked in vitro, pointing to the notion that all the cells are endowed with an autonomous time-keeping system. Metabolism undergoes circadian control, including the mitochondrial terminal catabolic pathways, culminating under aerobic conditions in the electron transfer to oxygen through the respiratory chain coupled to the ATP synthesis according to the oxidative phosphorylation chemiosmotic mechanism. In this study, we expanded upon previous isolated observations by utilizing multiple cell types, employing various synchronization protocols and different methodologies to measure mitochondrial oxygen consumption rates under conditions simulating various metabolic stressors. The results obtained clearly demonstrate that mitochondrial respiratory activity undergoes rhythmic oscillations in all tested cell types, regardless of their individual respiratory proficiency, indicating a phenomenon that can be generalized. However, notably, while primary cell types exhibited similar rhythmic respiratory profiles, cancer-derived cell lines displayed highly heterogeneous rhythmic changes. This observation confirms on the one hand the dysregulation of the circadian control of the oxidative metabolism observed in cancer, likely contributing to its development, and on the other hand underscores the necessity of personalized chronotherapy, which necessitates a detailed characterization of the cancer chronotype.