Skeletal muscle alkaline Pi pool is decreased in overweight-to-obese sedentary subjects and relates to mitochondrial capacity and phosphodiester content
Abstract:Defects in skeletal muscle energy metabolism are indicative of systemic disorders such as obesity or type 2 diabetes. Phosphorus magnetic resonance spectroscopy (31P-MRS), in particularly dynamic 31P-MRS, provides a powerful tool for the non-invasive investigation of muscular oxidative metabolism. The increase in spectral and temporal resolution of 31P-MRS at ultra high fields (i.e., 7T) uncovers new potential for previously implemented techniques, e.g., saturation transfer (ST) or highly resolved static spect… Show more
“…3), and, thus, supported this hypothesis. Significantly lower Pi 2 concentrations and Pi 2 /Pi ratios have also been reported in the overweight-to-obese sedentary subjects when compared to a group of lean, active individuals [92].Fig. 3Bar plot showing a significantly higher Pi 2 /Pi (marked here as Pi 2 /Pi 1 ) in the endurance trained athletes compared to the normal physical active group.…”
Section: P-mrs Of Skeletal Musclementioning
confidence: 71%
“…3Bar plot showing a significantly higher Pi 2 /Pi (marked here as Pi 2 /Pi 1 ) in the endurance trained athletes compared to the normal physical active group. Similarly, the Pi 2 /Pi was found lower in overweight-to-obese sedentary subjects than in lean, active individuals [92]. Figure was reproduced from Ref.…”
Section: P-mrs Of Skeletal Musclementioning
confidence: 91%
“…At ultra-high fields (i.e., 7 T), or by using 1 H decoupling, the main phosphodiester in human skeletal muscle – GPC – can be separately evaluated and used directly rather than the total PDE signal [92]. A sedentary lifestyle, in particular, if accompanied by overweight, gives rise to significantly higher PDE levels [92].…”
In addition to direct assessment of high energy phosphorus containing metabolite content within tissues, phosphorus magnetic resonance spectroscopy (31P-MRS) provides options to measure phospholipid metabolites and cellular pH, as well as the kinetics of chemical reactions of energy metabolism in vivo. Even though the great potential of 31P-MR was recognized over 30 years ago, modern MR systems, as well as new, dedicated hardware and measurement techniques provide further opportunities for research of human biochemistry. This paper presents a methodological overview of the 31P-MR techniques that can be used for basic, physiological, or clinical research of human skeletal muscle and liver in vivo. Practical issues of 31P-MRS experiments and examples of potential applications are also provided. As signal localization is essential for liver 31P-MRS and is important for dynamic muscle examinations as well, typical localization strategies for 31P-MR are also described.
“…3), and, thus, supported this hypothesis. Significantly lower Pi 2 concentrations and Pi 2 /Pi ratios have also been reported in the overweight-to-obese sedentary subjects when compared to a group of lean, active individuals [92].Fig. 3Bar plot showing a significantly higher Pi 2 /Pi (marked here as Pi 2 /Pi 1 ) in the endurance trained athletes compared to the normal physical active group.…”
Section: P-mrs Of Skeletal Musclementioning
confidence: 71%
“…3Bar plot showing a significantly higher Pi 2 /Pi (marked here as Pi 2 /Pi 1 ) in the endurance trained athletes compared to the normal physical active group. Similarly, the Pi 2 /Pi was found lower in overweight-to-obese sedentary subjects than in lean, active individuals [92]. Figure was reproduced from Ref.…”
Section: P-mrs Of Skeletal Musclementioning
confidence: 91%
“…At ultra-high fields (i.e., 7 T), or by using 1 H decoupling, the main phosphodiester in human skeletal muscle – GPC – can be separately evaluated and used directly rather than the total PDE signal [92]. A sedentary lifestyle, in particular, if accompanied by overweight, gives rise to significantly higher PDE levels [92].…”
In addition to direct assessment of high energy phosphorus containing metabolite content within tissues, phosphorus magnetic resonance spectroscopy (31P-MRS) provides options to measure phospholipid metabolites and cellular pH, as well as the kinetics of chemical reactions of energy metabolism in vivo. Even though the great potential of 31P-MR was recognized over 30 years ago, modern MR systems, as well as new, dedicated hardware and measurement techniques provide further opportunities for research of human biochemistry. This paper presents a methodological overview of the 31P-MR techniques that can be used for basic, physiological, or clinical research of human skeletal muscle and liver in vivo. Practical issues of 31P-MRS experiments and examples of potential applications are also provided. As signal localization is essential for liver 31P-MRS and is important for dynamic muscle examinations as well, typical localization strategies for 31P-MR are also described.
“…The τ
PCr was used to calculate the initial PCr recovery rate ( V
PCr ), as reported before 15. The maximal rate of oxidative phosphorylation ( Q
max ) was calculated according to the adenosine diphosphate (ADP)‐based model of Michaelis and Menten, for which the ADP concentration was calculated according to Kemp et al43
…”
Section: Methodsmentioning
confidence: 99%
“…In particular, phosphorus MRS ( 31 P–MRS) has been established as a powerful tool for studies of energy metabolism 10, 11, 12, 13, 14, 15. More specifically, dynamic 31 P–MRS, during exercise and recovery, allows direct estimation of the oxidative adenosine triphosphate (ATP) synthesis rate in challenged muscle, which reflects maximal mitochondrial capacity 12.…”
Phosphorus MRSI (31P–MRSI) using a spiral‐trajectory readout at 7 T was developed for high temporal resolution mapping of the mitochondrial capacity of exercising human skeletal muscle.The sensitivity and localization accuracy of the method was investigated in phantoms. In vivo performance was assessed in 12 volunteers, who performed a plantar flexion exercise inside a whole‐body 7 T MR scanner using an MR‐compatible ergometer and a surface coil. In five volunteers the knee was flexed (~60°) to shift the major workload from the gastrocnemii to the soleus muscle.Spiral‐encoded MRSI provided 16–25 times faster mapping with a better point spread function than elliptical phase‐encoded MRSI with the same matrix size. The inevitable trade‐off for the increased temporal resolution was a reduced signal‐to‐noise ratio, but this was acceptable. The phosphocreatine (PCr) depletion caused by exercise at 0° knee angulation was significantly higher in both gastrocnemii than in the soleus (i.e. 64.8 ± 19.6% and 65.9 ± 23.6% in gastrocnemius lateralis and medialis versus 15.3 ± 8.4% in the soleus).Spiral‐encoded 31P–MRSI is a powerful tool for dynamic mapping of exercising muscle oxidative metabolism, including localized assessment of PCr concentrations, pH and maximal oxidative flux with high temporal and spatial resolution.
Magnetic resonance (MR) imaging (MRI) is routinely used to evaluate organ morphology and pathology in the human body at rest or in combination with pharmacological stress as an exercise surrogate. With MR during actual physical exercise, we can assess functional characteristics of tissues and organs under real‐life stress conditions. This is particularly relevant in patients with limited exercise capacity or exercise intolerance, and where complaints typically present only during physical activity, such as in neuromuscular disorders, inherited metabolic diseases, and heart failure. This review describes practical and physiological aspects of exercise MR of skeletal muscles, the heart, and the brain. The acute effects of physical exercise on these organs are addressed in the light of various dynamic quantitative MR readouts, including phosphorus‐31 MR spectroscopy (31P‐MRS) of tissue energy metabolism, phase‐contrast MRI of blood flow and muscle contraction, real‐time cine MRI of cardiac performance, and arterial spin labeling MRI of muscle and brain perfusion. Exercise MR will help advancing our understanding of underlying mechanisms that contribute to exercise intolerance, which often proceed structural and anatomical changes in disease. Its potential to detect disease‐driven alterations in organ function, perfusion, and metabolism under physiological stress renders exercise MR stress testing a powerful noninvasive imaging modality to aid in disease diagnosis and risk stratification. Although not yet integrated in most clinical workflows, and while some applications still require thorough validation, exercise MR has established itself as a comprehensive and versatile modality for characterizing physiology in health and disease in a noninvasive and quantitative way.Evidence Level5Technical EfficacyStage 1
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