Oxidative capacity and ageing in human muscle

Area of Science:

• Exercise physiology
• Aging biology
• Skeletal muscle metabolism

Background:

• Muscle oxidative capacity declines with age, impacting physical function.
• Mitochondria are key to cellular energy production and are affected by aging.
• Understanding age-related changes in muscle metabolism is crucial for healthspan.

Purpose of the Study:

• To quantify the age-related decline in human vastus lateralis muscle oxidative capacity.
• To determine the contribution of mitochondrial content and function to this decline.
• To compare oxidative capacity per muscle volume in adult versus elderly subjects.

Main Methods:

• Utilized (31)P magnetic resonance (MR) spectroscopy to measure creatine phosphate ([PCr]) kinetics during exercise recovery.
• Estimated maximal oxidative phosphorylation rate (oxidative capacity) using [PCr] recovery rate constant (k(PCr)) and an electrical circuit model.
• Analyzed muscle biopsy samples to determine mitochondrial volume density.

Main Results:

• Elderly subjects showed a 50% lower muscle oxidative capacity compared to adults (0.61 vs. 1.16 mM ATP s(-1)).
• Mitochondrial volume density was significantly reduced in elderly muscle (2.9% vs. 3.6%).
• Oxidative capacity per mitochondrial volume was also lower in elderly individuals (0.22 vs. 0.32 mM ATP (s %)(-1)).

Conclusions:

• Aging significantly reduces skeletal muscle oxidative capacity per unit volume.
• Both decreased mitochondrial content and reduced mitochondrial function contribute to age-related decline in muscle energy production.
• These findings highlight cellular mechanisms underlying age-associated reductions in muscle performance.