Diurnal variation in skeletal muscle mitochondrial function dictates time-of-day-dependent exercise capacity

Area of Science:

• Physiology
• Mitochondrial Biology
• Chronobiology

Background:

• Exercise performance exhibits a diurnal rhythm, typically peaking in the late active phase.
• The molecular and metabolic mechanisms driving time-of-day differences in exercise capacity are not fully understood.
• Mitochondrial energetics are crucial for cellular energy production during exercise.

Purpose of the Study:

• To investigate the role of diurnal variations in mitochondrial function in determining skeletal muscle exercise performance.
• To identify the molecular factors contributing to time-of-day differences in exercise capacity.
• To elucidate the causal relationship between mitochondrial diurnal variation and exercise output.

Main Methods:

• Comparative analysis of skeletal muscle metabolome and mitochondrial energetics at different times of day (ZT3 and ZT15).
• Assessment of exercise performance across different time points.
• Utilizing genetic manipulation to study the role of Sirtuin4 (SIRT4) in regulating mitochondrial diurnal variation.

Main Results:

• Muscle metabolome and mitochondrial energetics differ significantly between ZT3 and ZT15.
• Diurnal variations in mitochondrial function correlate with time-of-day-dependent exercise capacity.
• Loss of Sirtuin4 (SIRT4) eliminates mitochondrial diurnal variation and abolishes time-of-day differences in muscle output.

Conclusions:

• Diurnal variations in skeletal muscle mitochondrial function are critical determinants of exercise capacity.
• Sirtuin4 (SIRT4) plays a pivotal role in maintaining mitochondrial diurnal rhythms and time-of-day exercise performance.
• Baseline mitochondrial function is essential for dictating diurnal exercise capacity.