31P Magnetic Resonance Spectroscopy Research Articles

Abstract 1431: Autophagic degradation of the endoplasmic reticulum leads to reduced phospholipid biosynthesis in mutant isocitrate dehydrogenase 1 gliomas

Abstract Introduction: Cancer cells up-regulate phospholipid biosynthesis in order to meet the demands of uncontrolled cell proliferation. Unusually, mutant isocitrate dehydrogenase 1 (IDHmut) gliomas down-regulate levels of the phospholipid precursors phosphocholine and phosphoethanolamine relative to wild-type IDH1 (IDHwt) gliomas. The goal of this study was therefore to investigate whether the phospholipids phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdE) are also down-regulated in IDHmut gliomas. Methods: Immortalized normal human astrocytes and U87 cells expressing IDHwt or IDHmut enzyme were studied. Steady-state phospholipid levels were measured by 31P-magnetic resonance spectroscopy (MRS) of cell extracts. De novo phospholipid biosynthesis was quantified by 13C-MRS of cells labeled with 56μM [1,2-13C]-choline and [1,2-13C]-ethanolamine. ER area was measured by STORM imaging of calnexin fluorescence. Results: Steady-state PtdCho and PtdE levels and de novo phospholipid biosynthesis were significantly reduced in IDHmut cells relative to IDHwt. Concomitantly, the activities of CTP:PC cytidylyltransferase (CCT) and CTP:PE cytidylyltransferase (ECT), the rate-limiting enzymes for phospholipid biosynthesis, were significantly reduced in IDHmut cells. CCT and ECT are localized to the endoplasmic reticulum (ER), the site of phospholipid biosynthesis. We therefore measured ER area by super-resolution STORM imaging and found a significant reduction in IDHmut cells relative to IDHwt while cell size remained unchanged. Autophagy of the ER (ER-phagy) can regulate ER area and we found that IDHmut cells showed increased expression of FAM134b, the ER-phagy receptor and higher autophagic flux. These results suggest that IDHmut cells undergo ER-phagy, leading to reduced phospholipid biosynthesis. Silencing FAM134b or the autophagy proteins Atg5 and Atg7 restored ER area and phospholipid biosynthesis and abrogated clonogenicity of IDHmut cells, linking ER-phagy to reduced phospholipid biosynthesis and pointing to a therapeutic opportunity. In the absence of specific ER-phagy inhibitors, we used the late-stage autophagy inhibitor chloroquine (CQ) to test proof-of-principle and found that CQ significantly inhibited orthotopic IDHmut glioma growth in vivo. Importantly, we observed ER-phagy and down-regulation of phospholipid levels in IDHmut glioma patient biopsies, highlighting the translational validity of our findings. Conclusions: We find that down-regulation of phospholipid biosynthesis is a unique metabolic outcome of ER-phagy in IDHmut gliomas. While autophagy has been linked to glucose and glutamine metabolism, this study is the first to link autophagy to phospholipid biosynthesis. Importantly, our study identifies a rationale for the development of novel therapies targeting ER-phagy in IDHmut gliomas. Citation Format: Pavithra Viswanath, Russell O. Pieper, Joanna J. Phillips, Sabrina M. Ronen. Autophagic degradation of the endoplasmic reticulum leads to reduced phospholipid biosynthesis in mutant isocitrate dehydrogenase 1 gliomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1431.

Differences in muscle metabolism in patients with type I diabetes - influence of gender and nephropathy studied by (31)P MR spectroscopy.

Type I diabetes mellitus (DM1) is a complex disease with adverse effects on organs and tissues despite compensation by insulin treatment. The goal of our study was to study how kidney diseases change (31)P MR parameters of muscle metabolism in DM1 patients with respect to gender. 51 DM1 patients (19 m/14 f without and 13 m/5 f with nephropathy) and 26 (14 m/12 f) healthy volunteers were examined using (31)P magnetic resonance spectroscopy at 3T tomograph at rest, and during and after a calf muscle exercise. The exercise consisted of a six-minute plantar flexion using a pedal ergometer followed by a six-minute recovery. It is reflected by reduced relative beta-ATP and increased Pi and phosphodiester signals to phosphocreatine (PCr) at rest and prolongation of the PCr recovery time after the exercise. Measurement on healthy volunteers indicated differences between males and females in pH at the rest and after the exercise only. These differences between patients groups were not significant. We have proven that nephropathy affects the metabolism in diabetic patients and our results confirm significant difference between patients with and without nephropathy. Gender differences in pH were observed only between male and female healthy volunteers.

Brain bioenergetics during resting wakefulness are related to neurobehavioral deficits in severe obstructive sleep apnea: a 31P magnetic resonance spectroscopy study.

Obstructive sleep apnea (OSA) is a well-established cause of impaired daytime functioning. However, there is a complex inter-individual variability in neurobehavioral performance in OSA patients. We previously reported compromised brain bioenergetics during apneic sleep in severe OSA. In this study, we investigate whether brain bioenergetics during resting wakefulness are related to neurobehavioral performance. Patients attended the sleep laboratory in the evening and were kept awake over-night. Repeated testing on the 10-minute psychomotor vigilance task (PVT, at 9 pm, 11 pm, 1 am, 3 am, 5 am) and 30-minute AusEd driving simulator task (9 pm and 5 am) was performed. Brain bioenergetics (inorganic phosphate/adenosine triphosphate ratio, Pi/ATP) were measured in the temporal lobe during resting wakefulness at 7 am in a 1.5T MRI scanner using phosphorus magnetic resonance spectroscopy (31P MRS). Fifteen males with severe OSA (age 47.7 ± 10.4 years, body mass index [BMI] 34 ± 6.6 kg/m2, apnea hypopnea index [AHI] 79.7 ± 21.8/hour) were investigated. A higher Pi/ATP ratio in the brain (lower phosphorylation potential) was correlated with worse PVT and driving simulator performance across the testing period (PVT lapses: r = 0.632, r2 = 0.399, p = 0.012; and AusEd braking reaction time: r = 0.609, p = 0.016). In contrast, the conventional AHI measure of disease severity was not significantly correlated with performance (PVT lapses: r = -0.084, p = 0.8; and AusEd braking reaction time: r = -0.326, p = 0.2). Lower phosphorylation potential was associated with worse performance. Compromised brain bioenergetics may in part underlie the neurobehavioral deficits in untreated OSA. We speculate that better brain bioenergetics may explain why some OSA patients are relatively asymptomatic compared with others.

Investigating Muscle Function After Stroke Rehabilitation with 31P-MRS: A Preliminary Study

BackgroundNew evidence reveals significant metabolic changes in skeletal muscle after stroke. However, it is unknown if 31P magnetic resonance spectroscopy (31P-MRS) can evaluate these metabolic changes. Our objective here was to investigate: (a) if muscle energy metabolism changes in the affected side; (b) if muscle energy metabolism changes after rehabilitation; and (c) if energy metabolism measured by 31P-MRS can reflect changes in the Modified Modified Ashworth Scale (MMAS) and Fugl-Meyer assessment-lower extremity (FMA-LE) scores after rehabilitation.Material/MethodsWe enrolled 13 patients with stroke symptoms and hemiplegia. Lower-limb motor status on the affected side was evaluated by FMA-LE and MMAS. The 31P-MRS measures included phosphocreatine (PCr), inorganic phosphate (Pi), PCr/Pi, and pH. We statistically compared these measures in the affected and unaffected lower leg muscles before rehabilitation and after rehabilitation on the affected side. Spearman correlational analyses was performed to determine correlations between change in energy metabolism and change in FMA-LE score and MMAS score after rehabilitation.ResultsPCr and PCr/Pi were significantly lower in the affected muscle compared to the unaffected muscle; however, there were no significant differences in Pi or pH. After rehabilitation, PCr, Pi, PCr/Pi, and pH did not significantly change. However, FMA-LE and MMAS score improved significantly after rehabilitation. Changes in energy metabolism measured by 31P-MRS had no correlation with FMA-LE change after rehabilitation. However, changes in PCr and PCr/Pi were correlated with change in MMAS score after rehabilitation.Conclusions31P-MRS can evaluate changes in muscle energy metabolism in patients with stroke. PCr measured by 31P-MRS can reflect changes in MMAS after rehabilitation.

Tai Chi Improves Brain Metabolism and Muscle Energetics in Older Adults.

ABSTRACTBACKGROUND AND PURPOSETai Chi is a mind‐body exercise that has been shown to improve both mental and physical health. As a result, recent literature suggests the use of Tai Chi to treat both physical and psychological disorders. However, the underlying physiological changes have not been characterized. The aim of this pilot study is to assess the changes in brain metabolites and muscle energetics after Tai Chi training in an aging population using a combined brain‐muscle magnetic resonance spectroscopy (MRS) examination.METHODSSix healthy older adults were prospectively recruited and enrolled into a 12‐week Tai Chi program. A brain 1H MRS and a muscle 31P MRS were scanned before and after the training, and postprocessed to measure N‐acetylaspartate to creatine (NAA/Cr) ratios and phosphocreatine (PCr) recovery time. Wilcoxon‐signed rank tests were utilized to assess the differences between pre‐ and post‐Tai Chi training.RESULTSA significant within‐subject increase in both the NAA/Cr ratios (P = .046) and the PCr recovery time (P = .046) was observed between the baseline and the posttraining scans. The median percentage changes were 5.38% and 16.51% for NAA/Cr and PCr recovery time, respectively.CONCLUSIONSOur pilot study demonstrates significant increase of NAA/Cr ratios in posterior cingulate gyrus and significantly improved PCr recovery time in leg muscles in older adults following short‐term Tai Chi training, and thus provides insight into the beneficial mechanisms.

Tracking disease progression non-invasively in Duchenne and Becker muscular dystrophies.

BackgroundAnalysis of muscle biopsies allowed to characterize the pathophysiological changes of Duchenne and Becker muscular dystrophies (D/BMD) leading to the clinical phenotype. Muscle tissue is often investigated during interventional dose finding studies to show in situ proof of concept and pharmacodynamics effect of the tested drug. Less invasive readouts are needed to objectively monitor patients' health status, muscle quality, and response to treatment. The identification of serum biomarkers correlating with clinical function and able to anticipate functional scales is particularly needed for personalized patient management and to support drug development programs.MethodsA large‐scale proteomic approach was used to identify serum biomarkers describing pathophysiological changes (e.g. loss of muscle mass), association with clinical function, prediction of disease milestones, association with in vivo 31P magnetic resonance spectroscopy data and dystrophin levels in muscles. Cross‐sectional comparisons were performed to compare DMD patients, BMD patients, and healthy controls. A group of DMD patients was followed up for a median of 4.4 years to allow monitoring of individual disease trajectories based on yearly visits.ResultsCross‐sectional comparison enabled to identify 10 proteins discriminating between healthy controls, DMD and BMD patients. Several proteins (285) were able to separate DMD from healthy, while 121 proteins differentiated between BMD and DMD; only 13 proteins separated BMD and healthy individuals. The concentration of specific proteins in serum was significantly associated with patients' performance (e.g. BMP6 serum levels and elbow flexion) or dystrophin levels (e.g. TIMP2) in BMD patients. Analysis of longitudinal trajectories allowed to identify 427 proteins affected over time indicating loss of muscle mass, replacement of muscle by adipose tissue, and cardiac involvement. Over‐representation analysis of longitudinal data allowed to highlight proteins that could be used as pharmacodynamic biomarkers for drugs currently in clinical development.ConclusionsSerum proteomic analysis allowed to not only discriminate among DMD, BMD, and healthy subjects, but it enabled to detect significant associations with clinical function, dystrophin levels, and disease progression.

31P-MR spectroscopy in patients with mild and serious lower limb ischemia.

31P-MR spectroscopy is a technique for undertaking a comprehensive evaluation of muscle metabolism. The goal of this study was to compare patients with mild and severe lower limb ischemia measured by 31P-MR spectroscopy at rest and during exercise. Sixteen non-diabetic mild peripheral arterial occlusive disease (PAOD) patients, 23 diabetic PAOD patients with severe ischemia and 19 healthy controls were examined by rest and dynamic 31P-MR spectroscopy with a 3T MR system equipped with an MR-compatible home-made pedal ergometer. Signal intensity ratios of phosphorous metabolites to the sum of all 31P intensities (Ptot) and pH were obtained at rest. The PCr drop (ΔPCr), time recovery constant of PCr (τPCr), pH at the end of the exercise (pHend), and mitochondrial capacity (Qmax) were calculated from dynamic MR spectra. Diabetic PAOD patients with severe ischemia differed from controls in both rest (PCr/Pi, βATP/Ptot, pH) and dynamic (Qmax, pHend, τPCr) parameters. PAOD patients with mild ischemia differed from controls only in Qmax and pHend. Rest parameters of the nondiabetic PAOD patients did not differ from control values excluding rest pH which was higher in both patient groups. A combination of rest and dynamic 31P-MR spectroscopy can distinguish among all three groups of subjects. On the other hand, examination at rest is sufficient for differentiation between patient groups and verification of severe ischemia.

Differences in Muscle Metabolism Between Triathletes and Normally Active Volunteers Investigated Using Multinuclear Magnetic Resonance Spectroscopy at 7T.

Purpose: The influence of endurance training on skeletal muscle metabolism can currently be studied only by invasive sampling or through a few related parameters that are investigated by either proton (1H) or phosphorus (31P) magnetic resonance spectroscopy (MRS). The aim of this study was to compare the metabolic differences between endurance-trained triathletes and healthy volunteers using multi-parametric data acquired by both, 31P- and 1H-MRS, at ultra-high field (7T) in a single experimental protocol. This study also aimed to determine the interrelations between these MRS-derived metabolic parameters.Methods: Thirteen male triathletes and ten active male volunteers participated in the study. Proton MRS data from the vastus lateralis yielded concentrations of acetylcarnitine, carnosine, and intramyocellular lipids (IMCL). For the measurement of phosphodiesters (PDEs), inorganic phosphate (Pi), phosphocreatine (PCr), and maximal oxidative capacity (Qmax) phosphorus MRS data were acquired at rest, during 6 min of submaximal exercise and following immediate recovery.Results: The triathletes exhibited significantly higher IMCL levels, higher initial rate of PCr resynthesis (VPCr) during the recovery period, a shorter PCr recovery time constant (τPCr), and higher Qmax. Multivariate stepwise regression analysis identified PDE as the strongest independent predictor of whole-body maximal oxygen uptake (VO2max).Conclusion: In conclusion, we cannot suggest a single MRS-based parameter as an exclusive biomarker of muscular fitness and training status. There is, rather, a combination of different parameters, assessable during a single multi-nuclear MRS session that could be useful for further cross-sectional and/or focused interventional studies on skeletal muscle fitness and training effects.

Optimization of signal-to-noise ratio in the in vivo31P magnetic resonance spectra of the human brain

The main problem in 31P magnetic resonance spectroscopy is a low signal-to-noise ratio (SNR) of spectra acquired with clinical magnetic resonance imaging (MRI) scanners. Using spin-spin phosphorus-proton (31P-1H) decoupling and heteronuclear Overhauser effect and taking into account the effect of the longitudinal relaxation time T1 on the SNR, the method for localization and excitation of the region of interest (Image Selected in vivo Spectroscopy pulse sequence) was optimized to increase the SNR in the 31P magnetic resonance spectra of the human brain to ~50% without increasing signal acquisition time.

Skeletal muscle mitochondrial oxidative phosphorylation function in idiopathic pulmonary arterial hypertension: invivo and invitro study.

Mitochondrial dysfunction within the pulmonary vessels has been shown to contribute to the pathology of idiopathic pulmonary arterial hypertension (IPAH). We investigated the hypothesis of whether impaired exercise capacity observed in IPAH patients is in part due to primary mitochondrial oxidative phosphorylation (OXPHOS) dysfunction in skeletal muscle. This could lead to potentially new avenues of treatment beyond targeting the pulmonary vessels. Nine clinically stable participants with IPAH underwent cardiopulmonary exercise testing, in vivo and in vitro assessment of mitochondrial function by 31P-magnetic resonance spectroscopy (31P-MRS) and laboratory muscle biopsy analysis. 31P-MRS showed abnormal skeletal muscle bioenergetics with prolonged recovery times of phosphocreatine and abnormal muscle pH handling. Histochemistry and quadruple immunofluorescence performed on muscle biopsies showed normal function and subunit protein abundance of the complexes within the OXPHOS system. Our findings suggest that there is no primary mitochondrial OXPHOS dysfunction but raises the possibility of impaired oxygen delivery to the mitochondria affecting skeletal muscle bioenergetics during exercise.

12.4 BRAIN LACTATE IS RELATED TO COGNITION IN SCHIZOPHRENIA

Laura Rowland, University of Maryland School of Med: Bioenergetic function may be altered in schizophrenia as supported by post-mortem, preclinical, cerebrospinal fluid, and 31P-magnetic resonance spectroscopy (MRS) research. Impairments in bioenergetic function may lead to cognitive and functional dysfunction, characteristics of the illness. First, a 7T MRS study that tested the hypothesis that frontal lactate concentrations are elevated in schizophrenia and related to cognitive impairments will be presented. Second, recent advances in brain lactate measurements with 3T MRS will be presented.MethodsTwenty-nine controls and 27 participants with schizophrenia completed the study. MRS scanning was conducted on a Philips ‘Achieva’ 7T scanner, and spectra were acquired from a frontal voxel using STEAM (TE/TM/TR=14/33/3000 ms, 128 NEX, 16 NEX water). Participants completed the MATRICS Consensus Cognitive Battery (MCCB) for cognitive function and UCSD Performance-Based Skills Assessment (UPSA) for functional capacity. The relationships between lactate, MCCB, and UPSA were examined. 3T MRS test-retest measures of lactate were conducted on a Siemens Prisma scanner using spectra editing (TE/TR=140/3, editing pulse at 4.1ppm with 30Hz bandwidth, 360 NEX, 16 NEX water).ResultsPatients had significantly higher lactate compared to controls (p = 0.045). Higher lactate was associated with poorer general cognitive function (r=-0.36, p=0.01) Visual learning, processing speed, and reasoning/problem solving cognitive domains showed the strongest relationships with lactate. Poorer functional capacity (r=-0.43, p=0.001) was also related to higher lactate. 3T spectral editing studies showed excellent reproducibility with a mean coefficient of variation of 4%.DiscussionHigher frontal lactate levels in schizophrenia support the hypothesis that brain bioenergetics are altered and related to cognitive and functional impairments in schizophrenia. Higher lactate could be due to inefficient aerobic metabolism causing a shift towards anaerobic metabolism or poor utilization of lactate. Lactate measurements are doable at 3T field strength and may be a useful biomarker of cognition in schizophrenia. Interventions to promote efficient mitochondrial energy metabolism may prove useful for enhancing cognition and alleviating functional impairments in schizophrenia.

THU-217 - Quantification of biliary phosphatidylcholine by non-invasive 31P magnetic resonance spectroscopy imaging suggests differences in cholangiopathies: A pilot study

THU-217 - Quantification of biliary phosphatidylcholine by non-invasive 31P magnetic resonance spectroscopy imaging suggests differences in cholangiopathies: A pilot study

Crystal Structures, Local Atomic Environments, and Ion Diffusion Mechanisms of Scandium-Substituted Sodium Superionic Conductor (NASICON) Solid Electrolytes

The importance of exploring new solid electrolytes for all-solid-state batteries has led to significant interest in NASICON-type materials. Here, the Sc3+-substituted NASICON compositions Na3ScxZr2–x(SiO4)2–x(PO4)1+x (termed N3) and Na2ScyZr2–y(SiO4)1–y(PO4)2+y (termed N2) (x, y = 0–1) are studied as model Na+-ion conducting electrolytes for solid-state batteries. The influence of Sc3+ substitution on the crystal structures and local atomic environments has been characterized by powder X-ray diffraction (XRD) and neutron powder diffraction (NPD), as well as solid-state 23Na, 31P, and 29Si nuclear magnetic resonance (NMR) spectroscopy. A phase transition between 295 and 473 K from monoclinic C2/c to rhombohedral R3̅c is observed for the N3 compositions, while N2 compositions crystallize in a rhombohedral R3̅c unit cell in this temperature range. Alternating current (AC) impedance spectroscopy, molecular dynamics (MD), and high temperature 23Na NMR studies are in good agreement, showing that, with a higher Sc3+ concentration, the ionic conductivity (of about 10–4 S/cm at 473 K) decreases and the activation energy for ion diffusion increases. 23Na NMR experiments indicate that the nature of the Na+-ion motion is two-dimensional on the local atomic scale of NMR although the long-range diffusion pathways are three-dimensional. In addition, a combination of MD, bond valence, maximum entropy/Rietveld, and van Hove correlation methods has been used to reveal that the Na+-ion diffusion in these NASICON materials is three-dimensional and that there is a continuous exchange of sodium ions between Na(1) and Na(2) sites.

Fractionating Wheat Straw via Phosphoric Acid with Hydrogen Peroxide Pretreatment and Structural Elucidation of the Derived Lignin

As a newly-developed method for pretreating lignocellulosic biomass, phosphoric acid plus hydrogen peroxide (PHP) was employed as a pretreatment solvent to fractionate wheat straw. The structural properties of the derived lignin were elucidated in particular. Results indicated that 100.0 g of wheat straw (dry basis) yielded 39.7 g of cellulose-rich fraction, 4.7 g of oligosaccharides, and 4.5 g of lignin at mild conditions of 50 °C within 1.0 h. The resultant cellulose-rich fraction was highly accessible to hydrolytic enzymes with 88–96% cellulose–glucose conversion in 24 h, suggesting a great potential for producing biofuels. The derived lignin was characterized as having high purity (≤1.0% residual carbohydrates) and relatively low molecular weight (Mw < 1436 g mol–1) and being abundant in carboxylic acid functional groups. According to the 31P, 13C, and 2D heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy results on the derived lignin, the degree of condensation was quite l...

Preparation of Preyssler-type Phosphotungstate with One Central Potassium Cation and Potassium Cation Migration into the Preyssler Molecule to form Di-Potassium-Encapsulated Derivative.

A mono-potassium cation-encapsulated Preyssler-type phosphotungstate, [P5W30O110K]14– (1), was prepared as a potassium salt, K14[P5W30O110K] (1a), by heating mono-bismuth- or mono-calcium-encapsulated Preyssler-type phosphotungstates (K12[P5W30O110Bi(H2O)] or K13[P5W30O110Ca(H2O)]) in acetate buffer. Characterization of the potassium salt 1a by single-crystal X-ray structure analysis, 31P and 183W nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy, high-resolution electrospray ionization mass spectroscopy, and elemental analysis revealed that one potassium cation is encapsulated in the central cavity of the Preyssler-type phosphotungstate molecule with a formal D5h symmetry. Density functional theory calculations have confirmed that the potassium cation prefers the central position of the cavity over a side position, in which no water molecules are coordinated to the encapsulated potassium cation. 31P NMR and cyclic voltammetry analyses revealed the rapid protonation–deprotonation of the oxygens in the cavity compared to that of other Preyssler-type compounds. Heating of 1a in the solid state afforded a di-K+-encapsulated compound, K13[P5W30O110K2] (2a), indicating that a potassium counter-cation is introduced in one of the side cavities, concomitantly displacing the internal potassium ion from the center to a second side cavity, thus providing a new method to encapsulate an additional cation in Preyssler compounds.

The Effects of β-Alanine Supplementation on Muscle pH and the Power-Duration Relationship during High-Intensity Exercise.

Purpose: To investigate the influence of β-alanine (BA) supplementation on muscle carnosine content, muscle pH and the power-duration relationship (i.e., critical power and W′).Methods: In a double-blind, randomized, placebo-controlled study, 20 recreationally-active males (22 ± 3 y, V°O2peak 3.73 ± 0.44 L·min−1) ingested either BA (6.4 g/d for 28 d) or placebo (PL) (6.4 g/d) for 28 d. Subjects completed an incremental test and two 3-min all-out tests separated by 1-min on a cycle ergometer pre- and post-supplementation. Muscle pH was assessed using 31P-magnetic resonance spectroscopy (MRS) during incremental (INC KEE) and intermittent knee-extension exercise (INT KEE). Muscle carnosine content was determined using 1H-MRS.Results: There were no differences in the change in muscle carnosine content from pre- to post-intervention (PL: 1 ± 16% vs. BA: −4 ± 25%) or in muscle pH during INC KEE or INT KEE (P > 0.05) between PL and BA, but blood pH (PL: −0.06 ± 0.10 vs. BA: 0.09 ± 0.13) during the incremental test was elevated post-supplementation in the BA group only (P < 0.05). The changes from pre- to post-supplementation in critical power (PL: −8 ± 18 W vs. BA: −6 ± 17 W) and W′ (PL: 1.8 ± 3.3 kJ vs. BA: 1.5 ± 1.7 kJ) were not different between groups. No relationships were detected between muscle carnosine content and indices of exercise performance.Conclusions: BA supplementation had no significant effect on muscle carnosine content and no influence on intramuscular pH during incremental or high-intensity intermittent knee-extension exercise. The small increase in blood pH following BA supplementation was not sufficient to significantly alter the power-duration relationship or exercise performance.

Novel P,P-diphenylphosphinic amide-TEMPO radicals family: Synthesis, crystal structures, spectroscopic characterization, magnetic properties and DFT calculations

A new family of three P,P-diphenylphosphinic amide-TEMPO radicals with general formula (C6H5)2P(X)-NH-TEMPO, X = O (1), S (2) and Se (3) were obtained by reaction of chlorodiphenylphosphine with 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl radical (NH2-TEMPO) and subsequent oxidation with H2O2 and elemental sulfur or selenium. These radicals were characterized by UV–Vis, FT-IR and 1H, 31P and 77Se nuclear magnetic resonance spectroscopy. The crystal structures of all radicals were determined by single-crystal X-ray diffraction. The magnetic study of all diphenylphosphinic amide-TEMPO radicals reveals very weak intermolecular ferromagnetic interactions. Density functional theory (DFT) calculations have been also performed to support the interpretation of magnetic properties and electronic structure.

Magnetic Resonance Spectroscopy Studies of Mouse Models of Cancer.

Magnetic resonance spectroscopy (MRS) or spectroscopic imaging (MRSI) enables the detection of metabolites, amino acids, and lipids, among other biomolecules, in tumors of live mouse models of cancer. Tumor-bearing mice are anesthetized by breathing isoflurane in a magnetic resonance (MR) scanner dedicated to small animal MR. Here we describe the overall setup and steps for measuring 1H and 31P MRS and 1H MRSI of orthotopic breast tumor models in mice with surface coils. This protocol can be adapted to the use of volume coils to measure 1H and 31P MRS(I) of tumor models that grow inside the body. We address issues of animal handling, setting up the measurement, measurement options, and data analysis.

Optimization of 31P magnetic resonance spectroscopy in vivo

The main problem of magnetic resonance spectroscopy on phosphorus nuclei (31P MRS) is low signal-to-noise ratio (SNR) of spectra acquired on clinical (3T) scanners. This makes quantitative processing of spectra difficult. The optimization of method on a single-voxel model reported in current work implicates an impact of the spin-lattice (T1) relaxation on SNR, and also evaluates the effectiveness of Image Selected InVivo Spectroscopy (ISIS) pulse sequence modification for the increase of SNR.

Human Cardiac 31P-MR Spectroscopy at 3 Tesla Cannot Detect Failing Myocardial Energy Homeostasis during Exercise.

Phosphorus-31 magnetic resonance spectroscopy (31P-MRS) is a unique non-invasive imaging modality for probing in vivo high-energy phosphate metabolism in the human heart. We investigated whether current 31P-MRS methodology would allow for clinical applications to detect exercise-induced changes in (patho-)physiological myocardial energy metabolism. Hereto, measurement variability and repeatability of three commonly used localized 31P-MRS methods [3D image-selected in vivo spectroscopy (ISIS) and 1D ISIS with 1D chemical shift imaging (CSI) oriented either perpendicular or parallel to the surface coil] to quantify the myocardial phosphocreatine (PCr) to adenosine triphosphate (ATP) ratio in healthy humans (n = 8) at rest were determined on a clinical 3 Tesla MR system. Numerical simulations of myocardial energy homeostasis in response to increased cardiac work rates were performed using a biophysical model of myocardial oxidative metabolism. Hypertrophic cardiomyopathy was modeled by either inefficient sarcomere ATP utilization or decreased mitochondrial ATP synthesis. The effect of creatine depletion on myocardial energy homeostasis was explored for both conditions. The mean in vivo myocardial PCr/ATP ratio measured with 3D ISIS was 1.57 ± 0.17 with a large repeatability coefficient of 40.4%. For 1D CSI in a 1D ISIS-selected slice perpendicular to the surface coil, the PCr/ATP ratio was 2.78 ± 0.50 (repeatability 42.5%). With 1D CSI in a 1D ISIS-selected slice parallel to the surface coil, the PCr/ATP ratio was 1.70 ± 0.56 (repeatability 43.7%). The model predicted a PCr/ATP ratio reduction of only 10% at the maximal cardiac work rate in normal myocardium. Hypertrophic cardiomyopathy led to lower PCr/ATP ratios for high cardiac work rates, which was exacerbated by creatine depletion. Simulations illustrated that when conducting cardiac 31P-MRS exercise stress testing with large measurement error margins, results obtained under pathophysiologic conditions may still lie well within the 95% confidence interval of normal myocardial PCr/ATP dynamics. Current measurement precision of localized 31P-MRS for quantification of the myocardial PCr/ATP ratio precludes the detection of the changes predicted by computational modeling. This hampers clinical employment of 31P-MRS for diagnostic testing and risk stratification, and warrants developments in cardiac 31P-MRS exercise stress testing methodology.