Skeletal muscle bioenergetics in vivo using combined 31P-1H Magnetic Resonance Spectroscopy
Presenter Type
UNO Graduate Student (Doctoral)
Major/Field of Study
Health and Kinesiology
Other
Exercise Physiology
Author ORCID Identifier
https://orcid.org/0009-0006-1037-7399
Advisor Information
Layec, Gwenael
Location
CEC RM #231
Presentation Type
Oral Presentation
Start Date
22-3-2024 9:00 AM
End Date
22-3-2024 10:15 AM
Abstract
Introduction: Mitochondrial efficiency is a critical functional parameter for metabolic phenotyping with important implications for both exercise tolerance and whole-body physiological function. However, the direct measurement of both oxygen consumption (VO2) and ATP production from the same region of the contracting muscle in vivo remains a great technical challenge. Purpose: Using an innovative approach combining noninvasive phosphorus and proton magnetic resonance spectroscopy (31P/1H-MRS), the present study aimed to characterize skeletal muscle ATP synthesis rate and muscle VO2 at rest and during a graded dynamic plantar flexion exercise to determine mitochondrial efficiency in the gastrocnemius muscle. Method: We assessed mitochondrial efficiency in the gastrocnemius muscles of 12 healthy adults (21±1 yrs.). 31P and 1H magnetic resonance spectroscopy (MRS) was performed using a whole-body 3T MR system (Skyra, Siemens) at rest and during a series of constant workloads coupled to brief transient ischemia to quantify both oxidative ATP synthesis (ATPox) rate and myoglobin-derived oxygen consumption (Mb-derived VO2). The MRS data were acquired with a dual-tuned 31P/1H surface coil with linear polarization positioned over the gastrocnemius muscle. Results: As expected, the end-exercise PCr concentration decreased from 29 ± 2 mM of WRmax to 18 ± 1 mM, and the end-exercise Mb oxygenation level declined linearly with increasing workload. The ATPox synthesis rate increased linearly with exercise workload (r2 = 0.45), whereas there was no significant change in Mb-derived VO2. At rest, the estimated P/O ratio in the gastrocnemius muscle was 1.95 ± 0.68, whereas non-physiological values were obtained during exercise (>3). Conclusion: The results indicate that combined 31P/1H-MRS noninvasive techniques in human gastrocnemius muscle at rest offer a specific approach for accurately quantifying mitochondrial efficiency, thereby emerging as a valuable potential endpoint to evaluate mitochondrial function in vivo. In contrast, Mb-derived VO2 during exercise was likely limited by O2 availability with the methodology employed and the slow recording time resolution, which precluded the quantification of mitochondrial efficiency and required additional technical refinement.
Skeletal muscle bioenergetics in vivo using combined 31P-1H Magnetic Resonance Spectroscopy
CEC RM #231
Introduction: Mitochondrial efficiency is a critical functional parameter for metabolic phenotyping with important implications for both exercise tolerance and whole-body physiological function. However, the direct measurement of both oxygen consumption (VO2) and ATP production from the same region of the contracting muscle in vivo remains a great technical challenge. Purpose: Using an innovative approach combining noninvasive phosphorus and proton magnetic resonance spectroscopy (31P/1H-MRS), the present study aimed to characterize skeletal muscle ATP synthesis rate and muscle VO2 at rest and during a graded dynamic plantar flexion exercise to determine mitochondrial efficiency in the gastrocnemius muscle. Method: We assessed mitochondrial efficiency in the gastrocnemius muscles of 12 healthy adults (21±1 yrs.). 31P and 1H magnetic resonance spectroscopy (MRS) was performed using a whole-body 3T MR system (Skyra, Siemens) at rest and during a series of constant workloads coupled to brief transient ischemia to quantify both oxidative ATP synthesis (ATPox) rate and myoglobin-derived oxygen consumption (Mb-derived VO2). The MRS data were acquired with a dual-tuned 31P/1H surface coil with linear polarization positioned over the gastrocnemius muscle. Results: As expected, the end-exercise PCr concentration decreased from 29 ± 2 mM of WRmax to 18 ± 1 mM, and the end-exercise Mb oxygenation level declined linearly with increasing workload. The ATPox synthesis rate increased linearly with exercise workload (r2 = 0.45), whereas there was no significant change in Mb-derived VO2. At rest, the estimated P/O ratio in the gastrocnemius muscle was 1.95 ± 0.68, whereas non-physiological values were obtained during exercise (>3). Conclusion: The results indicate that combined 31P/1H-MRS noninvasive techniques in human gastrocnemius muscle at rest offer a specific approach for accurately quantifying mitochondrial efficiency, thereby emerging as a valuable potential endpoint to evaluate mitochondrial function in vivo. In contrast, Mb-derived VO2 during exercise was likely limited by O2 availability with the methodology employed and the slow recording time resolution, which precluded the quantification of mitochondrial efficiency and required additional technical refinement.