Age-related declines in energy metabolism, muscle strength, and physical performance have been linked to lower mitochondrial respiratory capacity. This study investigates whether mitochondrial respiration in peripheral blood mononuclear cells (PBMC) is associated with metabolic flexibility and physical performance in healthy older adults.
What this study does not show
This research does not establish a causal relationship between PBMC respiration and improved physical performance or metabolic flexibility.
Evidence scorecard
- Analytic validity: established
- Clinical validity: partial
- Clinical utility: not established
The evidence is based on primary research involving human subjects.
The study involved fifty community-dwelling older adults (22 men, 28 women; age 70 ± 4 years). PBMC mitochondrial respiratory capacity was quantified using high-resolution respirometry, which assessed 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 as a lower respiratory exchange ratio (RER) and higher relative fat oxidation at a fixed workload. Muscle strength was determined through handgrip dynamometry and one-repetition maximum leg extension tests, while physical function was evaluated by gait speed and five-repetition chair rise time.
Associations were tested using linear and logistic regression, adjusted for age, sex, skeletal muscle index, physical activity, and high-sensitive C-reactive protein concentrations. The study also employed exploratory K-means clustering to identify mitochondrial respiration phenotypes.
The results indicated that higher ROUTINE respiration correlated with a lower RER (rho = -0.335, p = 0.020), greater fat utilization (rho = -0.334, p = 0.019), improved grip strength (rho = 0.302, p = 0.033), and faster 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 noted for ATP-linked respiration.
Cluster analysis revealed 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, the study suggests that higher PBMC ROUTINE respiration is associated with a more fat-dominant substrate utilization profile during submaximal exercise, greater muscle strength, and faster gait speed in healthy older adults. This indicates that PBMC respiratory capacity may serve as a reflection of systemic bioenergetic status relevant to exercise substrate utilization and physical performance in ageing.