AKT keeps the beat in CLOCK's circadian rhythm

Effects of (Poly)phenols on Circadian Clock Gene-Mediated Metabolic Homeostasis in Cultured Mammalian Cells: A Scoping Review

Circadian clocks regulate metabolic homeostasis. Disruption to our circadian clocks, by lifestyle behaviors such as timing of eating and sleeping, has been linked to increased rates of metabolic disorders. There is now considerable evidence that selected dietary (poly)phenols, including flavonoids, phenolic acids and tannins, may modulate metabolic and circadian processes. This review evaluates the effects of (poly)phenols on circadian clock genes and linked metabolic homeostasis in vitro, and potential mechanisms of action, by critically evaluating the literature on mammalian cells. A systematic search was conducted to ensure full coverage of the literature and identified 43 relevant studies addressing the effects of (poly)phenols on cellular circadian processes. Nobiletin and tangeretin, found in citrus, (-)-epigallocatechin-3-gallate from green tea, urolithin A, a gut microbial metabolite from ellagitannins in fruit, curcumin, bavachalcone, cinnamic acid, and resveratrol at low micromolar concentrations all affect circadian molecular processes in multiple types of synchronized cells. Nobiletin emerges as a putative retinoic acid-related orphan receptor (RORα/γ) agonist, leading to induction of the circadian regulator brain and muscle ARNT-like 1 (BMAL1), and increased period circadian regulator 2 (PER2) amplitude and period. These effects are clear despite substantial variations in the protocols employed, and this review suggests a methodological framework to help future study design in this emerging area of research.

Molecular mechanisms of tumour development in glioblastoma: an emerging role for the circadian clock

Glioblastoma is one of the most lethal cancers with current therapeutic options lacking major successes. This underlines the necessity to understand glioblastoma biology on other levels and use these learnings for the development of new therapeutic concepts. Mounting evidence in the field of circadian medicine points to a tight interplay between disturbances of the circadian system and glioblastoma progression. The circadian clock, an internal biological mechanism governing numerous physiological processes across a 24-h cycle, also plays a pivotal role in regulationg key cellular functions, including DNA repair, cell cycle progression, and apoptosis. These processes are integral to tumour development and response to therapy. Disruptions in circadian rhythms can influence tumour growth, invasion, and response to treatment in glioblastoma patients. In this review, we explore the robust association between the circadian clock, and cancer hallmarks within the context of glioblastoma. We further discuss the impact of the circadian clock on eight cancer hallmarks shown previously to link the molecular clock to different cancers, and summarize the putative role of clock proteins in circadian rhythm disturbances and chronotherapy in glioblastoma. By unravelling the molecular mechanisms behind the intricate connections between the circadian clock and glioblastoma progression, researchers can pave the way for the identification of potential therapeutic targets, the development of innovative treatment strategies and personalized medicine approaches. In conclusion, this review underscores the significant influence of the circadian clock on the advancement and understanding of future therapies in glioblastoma, ultimately leading to enhanced outcomes for glioblastoma patients.

Diurnal variations in the expression of core-clock genes correlate with resting muscle properties and predict fluctuations in exercise performance across the day

Objectives

In this study, we investigated daily fluctuations in molecular (gene expression) and physiological (biomechanical muscle properties) features in human peripheral cells and their correlation with exercise performance.

Methods

21 healthy participants (13 men and 8 women) took part in three test series: for the molecular analysis, 15 participants provided hair, blood or saliva time-course sampling for the rhythmicity analysis of core-clock gene expression via RT-PCR. For the exercise tests, 16 participants conducted strength and endurance exercises at different times of the day (9h, 12h, 15h and 18h). Myotonometry was carried out using a digital palpation device (MyotonPRO), five muscles were measured in 11 participants. A computational analysis was performed to relate core-clock gene expression, resting muscle tone and exercise performance.

Results

Core-clock genes show daily fluctuations in expression in all biological samples tested for all participants. Exercise performance peaks in the late afternoon (15–18 hours for both men and women) and shows variations in performance, depending on the type of exercise (eg, strength vs endurance). Muscle tone varies across the day and higher muscle tone correlates with better performance. Molecular daily profiles correlate with daily variation in exercise performance.

Conclusion

Training programmes can profit from these findings to increase efficiency and fine-tune timing of training sessions based on the individual molecular data. Our results can benefit both professional athletes, where a fraction of seconds may allow for a gold medal, and rehabilitation in clinical settings to increase therapy efficacy and reduce recovery times.

Phosphorylation and Circadian Molecular Timing

Endogenous circadian rhythms are biological processes generated by an internal body clock. They are self-sustaining, and they govern biochemical and physiological processes. However, circadian rhythms are influenced by many external stimuli to reprogram the phase in response to environmental change. Through their adaptability to environmental changes, they synchronize physiological responses to environmental challenges that occur within a sidereal day. The precision of this circadian system is assured by many post-translational modifications (PTMs) that occur on the protein components of the circadian clock mechanism. The most ancient example of circadian rhythmicity driven by phosphorylation of clock proteins was observed in cyanobacteria. The influence of phosphorylation on the circadian system is observed through different kingdoms, from plants to humans. Here, we discuss how phosphorylation modulates the mammalian circadian clock, and we give a detailed overview of the most critical discoveries in the field.

Time-of-day dependent effects of contractile activity on the phase of the skeletal muscle clock

Key points

Disruptions in circadian rhythms across an organism are associated with negative health outcomes, such as cardiometabolic and neurodegenerative diseases.

Exercise has been proposed as a time cue for the circadian clock in rodents and humans.

In this study, we assessed the effect of a single bout of endurance exercise on the skeletal muscle clock in vivo and a bout of muscle contractions in vitro.

Timing of exercise or contractions influences the directional response of the muscle clock phase in vivo and in vitro.

Our findings demonstrate that muscle contractions, as a component of exercise, can directly modulate the expression of muscle clock components in a time‐of‐day dependent manner.

Abstract

Exercise has been proposed to be a zeitgeber for the muscle circadian clock mechanism. However, this is not well defined and it is unknown if exercise timing induces directional shifts of the muscle clock. Our purpose herein was to assess the effect of one bout of treadmill exercise on skeletal muscle clock phase changes. We subjected PERIOD2::LUCIFERASE mice (n = 30F) to one 60 min treadmill exercise bout at three times of day. Exercise at ZT5, 5 h after lights on, induced a phase advance (100.2 ± 25.8 min; P = 0.0002), whereas exercise at ZT11, 1 h before lights off, induced a phase delay (62.1 ± 21.1 min; P = 0.0003). Exercise at ZT17, middle of the dark phase, did not alter the muscle clock phase. Exercise induces diverse systemic changes so we developed an in vitro model system to examine the effects of contractile activity on muscle clock phase. Contractions applied at peak or trough Bmal1 expression induced significant phase delays (applied at peak: 27.2 ± 10.2 min; P = 0.0017; applied at trough: 64.6 ± 6.5 min, P < 0.0001). Contractions applied during the transition from peak to trough Bmal1 expression induced a phase advance (49.8 ± 23.1 min; P = 0.0051). Lastly, contractions at different times of day resulted in differential changes of core clock gene expression, demonstrating an exercise and clock interaction, providing insight into potential mechanisms of exercise‐induced phase shifts. These data demonstrate that muscle contractions, as part of exercise, are sufficient to shift the muscle circadian clock phase, likely through changes in core clock gene expression. Additionally, our findings that exercise induces directional muscle clock phase changes confirms that exercise is a bona fide environmental time cue for skeletal muscle.

Disruptions in circadian rhythms across an organism are associated with negative health outcomes, such as cardiometabolic and neurodegenerative diseases.

Exercise has been proposed as a time cue for the circadian clock in rodents and humans.

In this study, we assessed the effect of a single bout of endurance exercise on the skeletal muscle clock in vivo and a bout of muscle contractions in vitro.

Timing of exercise or contractions influences the directional response of the muscle clock phase in vivo and in vitro.

Our findings demonstrate that muscle contractions, as a component of exercise, can directly modulate the expression of muscle clock components in a time‐of‐day dependent manner.

Magnesium Extravaganza: A Critical Compendium of Current Research into Cellular Mg2+ Transporters Other than TRPM6/7

Magnesium research has boomed within the last 20 years. The real breakthrough came at the start of the new millennium with the discovery of a plethora of possible Mg homeostatic factors that, in particular, included putative Mg²⁺ transporters. Until that point, Mg research was limited to biochemical and physiological work, as no target molecular entities were known that could be used to explore the molecular biology of Mg homeostasis at the level of the cell, tissue, organ, or organism and to translate such knowledge into the field of clinical medicine and pharmacology. Because of the aforementioned, Mg²⁺ and Mg homeostasis, both of which had been heavily marginalized within the biomedical field in the twentieth century, have become overnight a focal point of many studies ranging from primary biomedical research to translational medicine.The amount of literature concerning cellular Mg²⁺ transport and cellular Mg homeostasis is increasing, together with a certain amount of confusion, especially about the function(s) of the newly discovered and, in the majority of instances, still only putative Mg²⁺ transporters/Mg²⁺ homeostatic factors. Newcomers to the field of Mg research will thus find it particularly difficult to orient themselves.Here, we briefly but critically summarize the status quo of the current understanding of the molecular entities behind cellular Mg²⁺ homeostasis in mammalian/human cells other than TRPM6/7 chanzymes, which have been universally accepted as being unspecific cation channel kinases allowing the flux of Mg²⁺ while constituting the major gateway for Mg²⁺ to enter the cell.