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ATP production rate via creatine kinase or ATP synthase in vivo: a novel superfast magnetization saturation transfer method.

ABSTRACT: ³¹P magnetization saturation transfer (MST) experiment is the most widely used method to study ATP metabolism kinetics. However, its lengthy data acquisition time greatly limits the wide biomedical applications in vivo, especially for studies requiring high spatial and temporal resolutions.We aimed to develop a novel superfast MST method that can accurately quantify ATP production rate constants (k(f)) through creatine kinase (CK) or ATP synthase (ATPase) with 2 spectra.The T?(nom) (T? nominal) method uses a correction factor to compensate the partially relaxed MST experiments, thus allowing measurement of enzyme kinetics with an arbitrary repetition time and flip angle, which consequently reduces the data acquisition time of a transmurally differentiated CK k(f) measurement by 91% as compared with the conventional method with spatial localization. The novel T?(nom) method is validated theoretically with numeric simulation, and further verified with in vivo swine hearts, as well as CK and ATPase activities in rat brain at 9.4 Tesla. Importantly, the in vivo data from swine hearts demonstrate, for the first time, that within an observation window of 30 minutes, the inhibition of CK activity by iodoacetamide does not limit left ventricular chamber contractile function.A novel MST method for superfast examination of enzyme kinetics in vivo has been developed and verified theoretically and experimentally. In the in vivo normal heart, redundant multiple supporting systems of myocardial ATP production, transportation, and utilization exist, such that inhibition of one mechanism does not impair the normal left ventricular contractile performance.

SUBMITTER: Xiong Q

PROVIDER: S-EPMC3090083 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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ATP production rate via creatine kinase or ATP synthase in vivo: a novel superfast magnetization saturation transfer method.

Xiong Qiang Q Du Fei F Zhu Xiaohong X Zhang Pengyuan P Suntharalingam Piradeep P Ippolito Joseph J Kamdar Forum D FD Chen Wei W Zhang Jianyi J

Circulation research 20110203 6

<h4>Rationale</h4>³¹P magnetization saturation transfer (MST) experiment is the most widely used method to study ATP metabolism kinetics. However, its lengthy data acquisition time greatly limits the wide biomedical applications in vivo, especially for studies requiring high spatial and temporal resolutions.<h4>Objective</h4>We aimed to develop a novel superfast MST method that can accurately quantify ATP production rate constants (k(f)) through creatine kinase (CK) or ATP synthase (ATPase) with ...[more]

PMID: 21293002

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Project description:New findingsWhat is the central question of this study? Humans with obesity have lower ATP synthesis in muscle along with lower content of the β-subunit of the ATP synthase (β-F1-ATPase), the catalytic component of the ATP synthase. Does lower synthesis rate of β-F1-ATPase in muscle contribute to these responses in humans with obesity? What is the main finding and its importance? Humans with obesity have a lower synthesis rate of β-F1 -ATPase and ATP synthase specific activity in muscle. These findings indicate that reduced production of subunits forming the ATP synthase in muscle may contribute to impaired generation of ATP in obesity.AbstractThe content of the β-subunit of the ATP synthase (β-F1 -ATPase), which forms the catalytic site of the enzyme ATP synthase, is reduced in muscle of obese humans, along with a reduced capacity for ATP synthesis. We studied 18 young (37 ± 8 years) subjects of which nine were lean (BMI = 23 ± 2 kg m-2 ) and nine were obese (BMI = 34 ± 3 kg m-2 ) to determine the fractional synthesis rate (FSR) and gene expression of β-F1 -ATPase, as well as the specific activity of the ATP synthase. FSR of β-F1 -ATPase was determined using a combination of isotope tracer infusion and muscle biopsies. Gene expression of β-F1 -ATPase and specific activity of the ATP synthase were determined in the muscle biopsies. When compared to lean, obese subjects had lower muscle β-F1 -ATPase FSR (0.10 ± 0.05 vs. 0.06 ± 0.03% h-1 ; P < 0.05) and protein expression (P < 0.05), but not mRNA expression (P > 0.05). Across subjects, abundance of β-F1 -ATPase correlated with the FSR of β-F1 -ATPase (P < 0.05). The specific activity of muscle ATP synthase was lower in obese compared to lean subjects (0.035 ± 0.004 vs. 0.042 ± 0.007 arbitrary units; P < 0.05), but this difference was not significant after the activity of the ATP synthase was adjusted to the β-F1 -ATPase content (P > 0.05). Obesity impairs the synthesis of β-F1 -ATPase in muscle at the translational level, reducing the content of β-F1 -ATPase in parallel with reduced capacity for ATP generation via the ATP synthase complex.

Dataset Information

ATP production rate via creatine kinase or ATP synthase in vivo: a novel superfast magnetization saturation transfer method.

Publications

ATP production rate via creatine kinase or ATP synthase in vivo: a novel superfast magnetization saturation transfer method.

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