Sex differences in mitochondrial respiratory function in human skeletal muscle

Area of Science:

• Human skeletal muscle physiology
• Mitochondrial bioenergetics
• Sex-based metabolic differences

Background:

• Mitochondrial function is crucial for skeletal muscle metabolism.
• Sex-based differences in human metabolism are not fully understood.
• Investigating mitochondrial bioenergetics can elucidate these sex differences.

Purpose of the Study:

• To compare mitochondrial respiratory kinetics between young men and women.
• To identify sex-specific differences in human skeletal muscle mitochondrial function.
• To establish a baseline for future research on metabolic diseases.

Main Methods:

• Analysis of mitochondrial respiratory kinetics in permeabilized human skeletal muscle fibers.
• Measurement of maximal respiration rates and ADP sensitivity.
• Assessment of protein abundance for mitochondrial/adenosine diphosphate (ADP) transport and carnitine palmitoyl transferase-I.
• Evaluation of sensitivity to malonyl-CoA-mediated respiratory inhibition.

Main Results:

• No significant sex differences in maximal respiration rates or mitochondrial/ADP transport protein abundance.
• Women showed significantly lower mitochondrial ADP sensitivity (higher apparent Km) and absolute respiration at 100 μM ADP.
• Women exhibited increased sensitivity to malonyl-CoA inhibition of respiration.
• Similar carnitine palmitoyl transferase-I protein content and palmitoyl-CoA supported respiration between sexes.

Conclusions:

• Baseline sex differences in human skeletal muscle mitochondrial bioenergetics are established.
• Women's skeletal muscle mitochondria display altered ADP sensitivity and malonyl-CoA response.
• These findings provide a foundation for understanding sex-specific metabolic disease mechanisms.