Skeletal muscle energetics during submaximal contractions are linked to metabolic performance during ambulatory exercise: A pilot study in male adults.

Skeletal muscle's capacity for oxidative energy production can be measured in vivo by phosphocreatine (PCr) recovery following maximal contractions inside a magnetic resonance scanner. However, muscle energetic characteristics during submaximal contractions of similar intensity as used in free-living activities may be more relevant to the energetic support of ambulatory tasks during daily life. We measured vastus lateralis muscle oxidative capacity, acidification, submaximal oxidative energy production, and acetylcarnitine accumulation in response to an incremental contraction protocol (6%-15% maximal torque).

Does lower oxidative capacity influence the relative contributions of ATP-producing pathways during muscular work in aging?

Although the capacity of skeletal muscle to produce ATP via oxidative phosphorylation may decrease in some muscles in older age, the influence of a lower capacity on relative use of oxidative and non-oxidative ATP production pathways in vivo during contractions is unclear. To test the hypothesis that lower oxidative capacity would yield greater non-oxidative ATP production, 19 young (10F) and 17 older (9F) adults performed knee extensor muscle contractions in a 3-tesla magnetic resonance system. Phosphorus metabolites were used to calculate oxidative capacity (rate constant of phosphocreatine recovery; kPCr, s-1) and estimate the maximal rate of oxidative ATP production (Vmax, mM·s-1) following a 24-s dynamic contraction protocol.

Mitochondrial efficiency in resting skeletal muscle in vivo: a novel non-invasive approach using multinuclear magnetic resonance spectroscopy in humans.

Mitochondrial efficiency is a critical metabolic parameter with far-reaching implications for tissue homeostasis. However, the direct measurement of oxygen consumption (VO) and ATP production from a large tissue sample in vivo remains challenging. Using phosphorus (P) and proton (H) magnetic resonance spectroscopy (MRS), this study aimed to non-invasively quantify the skeletal muscle ATP synthesis rate and VO to determine mitochondrial efficiency at rest and during muscle contraction in humans.

Repeatability of alkaline inorganic phosphate quantification in the skeletal muscle using P-magnetic resonance spectroscopy at 3 T.

The detection of a secondary inorganic phosphate (Pi) resonance, a possible marker of mitochondrial content in vivo, using phosphorus magnetic resonance spectroscopy (P-MRS), poses technical challenges at 3 Tesla (T). Overcoming these challenges is imperative for the integration of this biomarker into clinical research. To evaluate the repeatability and reliability of measuring resting skeletal muscle alkaline Pi (Pi) using with P-MRS at 3 T.

Frontal cortex neurometabolites and mobility in older adults: a preliminary study.

Background: The frontal cortex, relevant to global cognition and motor function, is recruited to compensate for mobility dysfunction in older adults. However, the in vivo neurophysiological (e.g.

Postcontraction [acetylcarnitine] reflects interindividual variation in skeletal muscle ATP production patterns in vivo.

In addition to its role in substrate selection (carbohydrate vs. fat) for oxidative metabolism in muscle, acetylcarnitine production may be an important modulator of the energetic pathway by which ATP is produced. A combination of noninvasive magnetic resonance spectroscopy measures of cytosolic acetylcarnitine and ATP production pathways was used to investigate the link between [acetylcarnitine] and energy production in vivo.

Measurements of in vivo skeletal muscle oxidative capacity are lower following sustained isometric compared with dynamic contractions.

Human skeletal muscle oxidative capacity can be quantified non-invasively using 31-phosphorus magnetic resonance spectroscopy (P-MRS) to measure the rate constant of phosphocreatine (PCr) recovery () following contractions. In the quadricep muscles, several studies have quantified following 24-30 s of sustained maximal voluntary isometric contraction (MVIC). This approach has the advantage of simplicity but is potentially problematic because sustained MVICs inhibit perfusion, which may limit muscle oxygen availability or increase the intracellular metabolic perturbation, and thus affect .

Assessing the Dose-Dependent Effects of tDCS on Neurometabolites using Magnetic Resonance Spectroscopy.

Concurrent transcranial direct current stimulation (tDCS) and proton Magnetic Resonance Spectroscopy ( H MRS) experiments have shown up- or downregulation of neurotransmitter concentration. However, effects have been modest applying mostly lower current doses and not all studies found significant effects. Dose of stimulation might be an important variable in eliciting a consistent response.

Alterations of gray and white matter volumes and cortical thickness in treated HIV-positive patients.

Brain structural changes in HIV identified by voxel-based morphometry (VBM) alone could arise from a variety of causes that are difficult to distinguish without further information, such as cortical thickness (CT), gyrification index (GI) or sulcal depth (SD). Hence, our goal was to assess these additional metrics in HIV using high-resolution 3D T-weighted images and investigate if surface-based morphometric (SBM) analysis would reveal significant changes in the gray matter (GM) and white matter (WM) volumes combined with alterations in cortical thickness (CT), gyrification index (GI), sulcal depth (SD). T1-w magnetization-prepared-rapid-acquisition gradient-echo (MP-RAGE) scans were acquired in 27 HIV-infected individuals on antiretroviral therapy (ART) and 15 HIV-uninfected healthy controls using a 3T MRI scanner equipped with a 16-channel head "receive" and a quadrature body "transmit" coil.

Dictionary learning compressed sensing reconstruction: pilot validation of accelerated echo planar J-resolved spectroscopic imaging in prostate cancer.

Objectives: This study aimed at developing dictionary learning (DL) based compressed sensing (CS) reconstruction for randomly undersampled five-dimensional (5D) MR Spectroscopic Imaging (3D spatial + 2D spectral) data acquired in prostate cancer patients and healthy controls, and test its feasibility at 8x and 12x undersampling factors.

Materials And Methods: Prospectively undersampled 5D echo-planar J-resolved spectroscopic imaging (EP-JRESI) data were acquired in nine prostate cancer (PCa) patients and three healthy males. The 5D EP-JRESI data were reconstructed using DL and compared with gradient sparsity-based Total Variation (TV) and Perona-Malik (PM) methods.

Effects of old age and contraction mode on knee extensor muscle ATP flux and metabolic economy in vivo.

Key Points: We used 31-phosphorus magnetic resonance spectroscopy to quantify in vivo skeletal muscle metabolic economy (ME; mass-normalized torque or power produced per ATP consumed) during three 24 s maximal-effort contraction protocols: (1) sustained isometric (MVIC), (2) intermittent isokinetic (MVDC ), and (3) intermittent isotonic (MVDC ) in the knee extensor muscles of young and older adults. ME was not different between groups during the MVIC but was lower in older than young adults during both dynamic contraction protocols. These results are consistent with an increased energy cost of locomotion, but not postural support, with age.

Validity and accuracy of calculating oxidative ATP synthesis in vivo during high-intensity skeletal muscle contractions.

Several methods have been developed for using P-MRS to calculate rates of oxidative ATP synthesis (ATP ) during muscular contractions based on assumptions that (1) the ATP cost of force generation (ATP ) remains constant or (2) Michaelis-Menten coupling between cytosolic ADP and ATP does not change. However, growing evidence suggests that one, or both, of these assumptions are invalid during high-intensity fatigue protocols. Consequently, there is a need to examine the validity and accuracy of traditional ATP calculation methods under these conditions.

Oxidative ATP synthesis in human quadriceps declines during 4 minutes of maximal contractions.

Key Points: During maximal exercise, skeletal muscle metabolism and oxygen consumption remain elevated despite precipitous declines in power. Presently, it is unclear whether these responses are caused by an increased ATP cost of force generation (ATP ) or mitochondrial uncoupling; a process that reduces the efficiency of oxidative ATP synthesis (ATP ). To address this gap, we used 31-phosphorus magnetic resonance spectroscopy to measure changes in ATP and ATP in human quadriceps during repeated trials of maximal intensity knee extensions lasting up to 4 min.

Nuclear magnetic resonance spectroscopy of human body fluids and in vivo magnetic resonance spectroscopy: Potential role in the diagnosis and management of prostate cancer.

Prostate cancer is the most common solid organ cancer in men, and the second most common cause of male cancer-related mortality. It has few effective therapies, and is difficult to diagnose accurately. Prostate-specific antigen (PSA), which is currently the most effective diagnostic tool available, cannot reliably discriminate between different pathologies, and in fact only around 30% of patients found to have elevated levels of PSA are subsequently confirmed to actually have prostate cancer.

Assessment of Lipid and Metabolite Changes in Obese Calf Muscle Using Multi-Echo Echo-planar Correlated Spectroscopic Imaging.

Obesity-related conditions including heart disease, stroke, and type 2 diabetes are leading causes of preventable death. Recent evidence suggests that altered myocellular lipid metabolism in obesity may lead to increased insulin resistance (IR) that predisposes to these disorders. To test the hypothesis that muscles rich in type I vs.

Echo-Planar J-resolved Spectroscopic Imaging using Dual Read-outs: Implementation and Quantitation of Human Brain Metabolites.

Attempts have been made to reduce the total scan time in multi-dimensional J-resolved spectroscopic imaging (JRESI) using an echo-planar (EP) readout gradient, but acquisition duration remains a limitation for routine clinical use in the brain. We present here a significant acceleration achieved with a 4D EP-JRESI sequence that collects dual phase encoded lines within a single repetition time (TR) using two bipolar read-out trains. The performance and reliability of this novel 4D sequence, called Multi-Echo based Echo-Planar J-resolved Spectroscopic Imaging (ME-EP-JRESI), was evaluated in 10 healthy controls and a brain phantom using a 3 T MRI/MRS scanner.

Non-uniformly weighted sampling for faster localized two-dimensional correlated spectroscopy of the brain in vivo.

Two-dimensional localized correlated spectroscopy (2D L-COSY) offers greater spectral dispersion than conventional one-dimensional (1D) MRS techniques, yet long acquisition times and limited post-processing support have slowed its clinical adoption. Improving acquisition efficiency and developing versatile post-processing techniques can bolster the clinical viability of 2D MRS. The purpose of this study was to implement a non-uniformly weighted sampling (NUWS) scheme for faster acquisition of 2D-MRS.

Non-invasive detection of 2-hydroxyglutarate in IDH-mutated gliomas using two-dimensional localized correlation spectroscopy (2D L-COSY) at 7 Tesla.

Background: Mutations in the isocitrate dehydrogenase enzyme are present in a majority of lower-grade gliomas and secondary glioblastomas. This mis-sense mutation results in the neomorphic reduction of isocitrate dehydrogenase resulting in an accumulation of the "oncometabolite" 2-hydroxyglutarate (2HG). Detection of 2HG can thus serve as a surrogate biomarker for these mutations, with significant translational implications including improved prognostication.

Accelerated Echo Planer J-resolved Spectroscopic Imaging of Putamen and Thalamus in Obstructive Sleep Apnea.

Unlabelled: Obstructive sleep apnea syndrome (OSAS) leads to neurocognitive and autonomic deficits that are partially mediated by thalamic and putamen pathology. We examined the underlying neurochemistry of those structures using compressed sensing-based 4D echo-planar J-resolved spectroscopic imaging (JRESI), and quantified values with prior knowledge fitting. Bilaterally increased thalamic mI/Cr, putamen Glx/Cr, and Glu/Cr, and bilaterally decreased thalamic and putamen tCho/Cr and GABA/Cr occurred in OSAS vs healthy subjects (p < 0.

Obstructive sleep apnea is associated with low GABA and high glutamate in the insular cortex.

The insular cortex is injured in obstructive sleep apnea (OSA) and responds inappropriately to autonomic challenges, suggesting neural reorganization. The objective of this study was to assess whether the neural changes might result from γ-aminobutyric acid (GABA) and glutamate alterations. We studied 14 OSA patients [mean age ± standard deviation (SD): 47.

Accelerated echo planar J-resolved spectroscopic imaging in prostate cancer: a pilot validation of non-linear reconstruction using total variation and maximum entropy.

The overlap of metabolites is a major limitation in one-dimensional (1D) spectral-based single-voxel MRS and multivoxel-based MRSI. By combining echo planar spectroscopic imaging (EPSI) with a two-dimensional (2D) J-resolved spectroscopic (JPRESS) sequence, 2D spectra can be recorded in multiple locations in a single slice of prostate using four-dimensional (4D) echo planar J-resolved spectroscopic imaging (EP-JRESI). The goal of the present work was to validate two different non-linear reconstruction methods independently using compressed sensing-based 4D EP-JRESI in prostate cancer (PCa): maximum entropy (MaxEnt) and total variation (TV).

Neuroimaging abnormalities, neurocognitive function, and fatigue in patients with hepatitis C.

Objective: This study examined neurologic abnormalities (as measured by proton magnetic resonance spectroscopy imaging and diffusion tensor imaging), neurocognitive performance, and fatigue among a sample of adults with hepatitis C virus (HCV). We hypothesized that HCV+ individuals would demonstrate structural brain abnormalities and neurocognitive compromise consistent with frontostriatal dysfunction as well as increased fatigue compared to controls.

Method: Participants were 76 individuals diagnosed with HCV and 20 controls who underwent a comprehensive neurocognitive evaluation and clinical assessments.

A pilot validation of multi-echo based echo-planar correlated spectroscopic imaging in human calf muscles.

A current limitation of MR spectroscopic imaging of multiple skeletal muscles is prolonged scan duration. A significant reduction in the total scan duration using the echo-planar correlated spectroscopic imaging (EP-COSI) sequence was accomplished using two bipolar readout trains with different phase-encoded echoes for one of two spatial dimensions within a single repetition time (TR). The second bipolar readout was used for spatially encoding the outer k-space, whereas the first readout was used for the central k-space only.

Regional brain gray and white matter changes in perinatally HIV-infected adolescents.

Despite the success of antiretroviral therapy (ART), perinatally infected HIV remains a major health problem worldwide. Although advance neuroimaging studies have investigated structural brain changes in HIV-infected adults, regional gray matter (GM) and white matter (WM) volume changes have not been reported in perinatally HIV-infected adolescents and young adults. In this cross-sectional study, we investigated regional GM and WM changes in 16 HIV-infected youths receiving ART (age 17.