#495: Circadian Clocks in Muscle & Exercise as a Time Cue – Prof. Karyn Esser

Introduction

The field of circadian biology has long been associated with regulating diurnal physiological processes, notably the sleep-wake cycle. However, recent advances have unveiled a broader role for circadian clocks across various tissues, including skeletal muscle.

Within this context, the investigation of circadian clocks within the skeletal muscle milieu has emerged as a frontier of scientific inquiry. These intrinsic timekeeping mechanisms exhibit multifaceted regulatory capacities beyond mere temporal synchronization.

This episode delves into the implications of “circadian clocks” operating within skeletal muscle tissue, with the esteemed Prof. Karyn Esser as this week’s guest. Her pioneering work has been instrumental in understanding the interplay between circadian rhythmicity and muscular physiology.

Guest Information

Prof. Karyn Esser

Prof. Karyn Esser, PhD, is chair of the department of physiology and aging at University of Florida. Prof. Esser was among the first researchers to recognize the importance of circadian rhythms to cell and muscle health.

Prof. Esser’s lab has pioneered research on the role of circadian rhythms and the molecular clock mechanism in skeletal muscle homeostasis and health.

Her work has shown that mutations of two different molecular clock genes, Clock and Bmal1, dramatically disrupt skeletal muscle structure and function.Esser’s lab is also pursuing the role of physical activity/exercise as a time cue for skeletal muscle and other tissues. And they have also shown that time of exercise can significantly alter the clock mechanism in skeletal muscle independent of lighting and the central clock in the brain.

Overview

• What is a “circadian clock”?
• The clock mechanism in skeletal muscle
• The role of physical activity/exercise as a time cue
• Circadian phase advance and delay with external cues
• Implications of these findings for time zone travel, chronic disease, and other applications in humans

Related Resources

• Studies mentioned in this episode:
  • Wolff & Esser, 2012 – Scheduled exercise phase shifts the circadian clock in skeletal muscle
  • Kemler et al., 2020 – Time-of-day dependent effects of contractile activity on the phase of the skeletal muscle clock
  • Savikj et al., 2019 – Afternoon exercise is more efficacious than morning exercise at improving blood glucose levels in individuals with type 2 diabetes
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