Age-related declines in energy metabolism, muscle strength, and physical performance have been linked to lower mitochondrial respiratory capacity. This study investigates the relationship between mitochondrial respiration in peripheral blood mononuclear cells (PBMCs) and whole-body metabolic flexibility in healthy older adults.
What this study does not show
This study does not establish a causal relationship between PBMC respiratory capacity and improved physical performance or metabolic flexibility.
Evidence scorecard
- Evidence class: primary_research
- Human status: unclassified
- Publication type: Journal Article
The study involved fifty community-dwelling older adults (22 men, 28 women; age 70 ± 4 years). Mitochondrial respiratory capacity was quantified using high-resolution respirometry to assess ROUTINE, LEAK, and MAX states. The researchers measured postprandial substrate oxidation during steady-state treadmill walking at 60% of VO2max using indirect calorimetry, calculating fat and carbohydrate oxidation rates with 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 using gait speed and five-repetition chair rise time. The associations were tested using linear and logistic regression, adjusted for age, sex, skeletal muscle index, physical activity, and high-sensitive C-reactive protein concentrations.
Results showed that higher ROUTINE respiration correlated with RER (rho = -0.335, p = 0.020), fat utilization (rho = -0.334, p = 0.019), grip strength (rho = 0.302, p = 0.033), and gait speed (rho = 0.324, p = 0.022). Adjusted regression analyses confirmed that ROUTINE respiration was associated with greater fat oxidation (β = 0.212, 95% CI 0.049; 0.375), lower RER (β = -0.160, 95% CI -0.300; -0.020), and higher gait speed (β = 0.153, 95% CI 0.028; 0.277). Similar associations were found for ATP-linked respiration.
Cluster analysis identified high- and low-respiration phenotypes. The low-respiration group exhibited lower counter-movement jump (CMJ) height (OR: 0.204, 95% CI 0.055; 0.763) and quadriceps strength (OR: 0.373, 95% CI 0.155; 0.897) compared to the high-respiration group.
In conclusion, higher PBMC ROUTINE respiration in healthy older adults was associated with a more fat-dominant substrate utilization profile during submaximal exercise, greater muscle strength, and faster gait speed. This suggests that PBMC respiratory capacity may reflect systemic bioenergetic status relevant to exercise substrate utilization and physical performance in ageing.