The Role of Circadian Clocks in Muscle Health and Aging in Shift Workers

Recent research highlights the critical role of circadian clocks within muscle cells in maintaining muscle integrity and delaying aging. This study, published in the Proceedings of the National Academy of Sciences, reveals that disruption of these internal timers, especially common in shift workers, can accelerate muscle deterioration and aging processes.

Muscle cells possess autonomous circadian mechanisms that regulate essential functions like protein turnover, which is vital for muscle growth and repair. Typically, during nighttime rest, these clocks activate the breakdown of defective proteins, ensuring muscle health. However, when these clocks are disrupted—as occurs in shift work—the regular clearance of damaged proteins is impaired, leading to their accumulation. This buildup contributes to sarcopenia, the age-related decline in muscle mass and strength.

Researchers from King's College London employed zebrafish models to understand these mechanisms better. Zebrafish share about 70% of their genes with humans and allow for detailed observation due to their transparency and genetic modifiability. The scientists impaired muscle clock function in zebrafish by overexpressing a faulty clock protein and observed the effects over two years. While young fish appeared unaffected, older fish lacking proper muscle circadian regulation demonstrated signs of premature aging, including reduced size, weight, and mobility, mirroring effects seen in human shift workers.

Further analysis showed that the muscle clock's nighttime activity is crucial for degradation of defective proteins. Disruption of this process accelerates muscle decline, emphasizing how circadian misalignment can contribute to aging. This insight opens new avenues for protecting shift workers against muscle deterioration. Potential strategies include developing drugs that target clock proteins to restore normal circadian functions.

Dr. Jeffrey Kelu, lead researcher, emphasized the practical implications: "Approximately four million shift workers in the UK play essential roles around the clock. Our findings suggest that circadian disruption directly impacts muscle health, and interventions aimed at restoring circadian rhythms could help mitigate age-related muscle loss."

Professor Simon Hughes, a co-author, added that studying these processes in simple models like fish larvae provides valuable insights that could translate into human health benefits, paving the way for future therapies to promote healthy aging in shift workers.