Age-related declines in energy metabolism, muscle strength, and physical performance have been linked to lower mitochondrial respiratory capacity. This study investigates the association of peripheral blood mononuclear cell (PBMC) respiration with metabolic flexibility and physical performance in healthy older adults.
Methods
The researchers quantified PBMC mitochondrial respiratory capacity using high-resolution respirometry, assessing ROUTINE, LEAK, and MAX states. They measured postprandial substrate oxidation during steady-state treadmill walking at 60% of VO2max through indirect calorimetry, calculating fat and carbohydrate oxidation rates using standard stoichiometric equations. Metabolic flexibility was defined by a lower respiratory exchange ratio (RER) and higher relative fat oxidation at a fixed workload. Muscle strength was evaluated through handgrip dynamometry and one-repetition maximum leg extension, while physical function was assessed via gait speed and five-repetition chair rise time. The study included linear and logistic regression analyses adjusted for age, sex, skeletal muscle index, physical activity, and high-sensitive C-reactive protein concentrations.
Results
The study examined fifty community-dwelling older adults (22 men, 28 women; age 70 ± 4 years). Key findings included:
- Higher ROUTINE respiration correlated with a lower RER (rho = -0.335, p = 0.020) and greater fat utilization (rho = -0.334, p = 0.019).
- Grip strength showed a positive correlation with ROUTINE respiration (rho = 0.302, p = 0.033), as did gait speed (rho = 0.324, p = 0.022).
- Adjusted regression analyses confirmed associations of ROUTINE respiration with greater fat oxidation (β = 0.212, 95% CI 0.049; 0.375) and higher gait speed (β = 0.153, 95% CI 0.028; 0.277).
Cluster analysis revealed high- and low-respiration phenotypes, with the low-respiration group exhibiting lower countermovement jump height (OR: 0.204, 95% CI 0.055; 0.763) and quadriceps strength (OR: 0.373, 95% CI 0.155; 0.897).
Conclusions
This study concludes that in healthy older adults, higher PBMC ROUTINE respiration is associated with a more fat-dominant substrate utilization profile during submaximal exercise, greater muscle strength, and faster gait speed. PBMC respiratory capacity may reflect systemic bioenergetic status relevant to exercise substrate utilization and physical performance in ageing.
What this study does not show
This study does not establish a causal relationship between mitochondrial respiration and physical performance metrics, nor does it provide evidence for interventions based on these findings.
Evidence scorecard
- Analytic validity: Established
- Clinical validity: Partial
- Clinical utility: Not established
The evidence is based on primary research involving human participants.