Phosphomonoesters Research Articles

31P multi-echo MRSI with low B1 + dual-band refocusing RF pulses.

31P magnetic resonance spectroscopy (MRS) can spectrally resolve metabolites involved in phospholipid metabolism whose levels are altered in many cancers. Ultra-high field facilitates the detection of phosphomonoesters (PMEs) and phosphodiesters (PDEs) with increased SNR and spectral resolution. Utilizing multi-echo MR spectroscopic imaging (MRSI) further enhances SNR and enables T2 information estimation per metabolite. To address the specific absorption rate (SAR) challenges associated with high-power demanding adiabatic or composite block pulses in multi-echo phosphorus imaging, we present a dual-band refocusing RF pulse designed for operation at B1 amplitudes of 14.8 μT which holds potential for integration into multi-echo sequences. Phantom and in vivo experiments conducted in the brain at 7Tesla validated the effectiveness of this low-power dual-band RF pulse. Furthermore, we implemented the dual-band RF pulse into a multi-echo MRSI sequence where it offered the potential to increase the number of echo pulses within the same acquisition time compared to high-power adiabatic implementation, demonstrating its feasibility and practicality.

Mapping Age Differences in Brain Energy Metabolites and Metabolic Markers of Cellular Membrane Production and Degradation With 31P Magnetic Resonance Spectroscopy.

Using Phosphorus Magnetic Resonance Spectroscopy (31P MRS), we examined five metabolites associated with brain energy cycle, and cellular membrane production and degradation in 11 brain regions of 48 children (age 6-15), and 80 middle-aged and older adults (age 52-87). Levels of phosphomonoesters (PMEs) and phosphodiesters (PDEs), gamma plus alpha adenosine triphosphate (γαATP), phosphocreatine (PCr) and inorganic phosphate (Pi), were residualized on the total amplitude value. PMEs were greater in children compared to adults, whereas PDEs showed the opposite age difference. Higher γαATP and lower Pi were found in children compared to adults. The age group differences were particularly salient in the association cortices and anterior white matter. Among children, age correlated negatively with PMEs and positively with PDEs in association cortices. Compared to children, adults had lower intracellular pH. The results suggest reduction in membrane synthesis and increase in membrane degradation in adolescents and to a greater degree in adults compared to younger children. Concomitant reduction in γαATP and increase in Pi are consistent with reduced energy consumption in adolescents and further drop in middle-aged and older adults, although it is impossible to distinguish declines in energy supply from reduced demand due to shrinking neuropil, without longitudinal studies.

31P MR Spectroscopy in the Pancreas: Repeatability, Comparison With Liver, and Pilot Pancreatic Cancer Data.

Non-invasive evaluation of phosphomonoesters (PMEs) and phosphodiesters (PDEs) by 31-phosphorus MR spectroscopy (31P MRS) may have potential for early therapy (non-)response assessment in cancer. However, 31P MRS has not yet been applied to investigate the human pancreas in vivo. To assess the technical feasibility and repeatability of 31P MR spectroscopic imaging (MRSI) of the pancreas, compare 31P metabolite levels between pancreas and liver, and determine the feasibility of 31P MRSI in pancreatic cancer. Prospective cohort study. 10 healthy subjects (age 34 ± 12 years, four females) and one patient (73-year-old female) with pancreatic ductal adenocarcinoma. 7-T, 31P FID-MRSI, 1H gradient-echo MRI. 31P FID-MRSI of the abdomen (including the pancreas and liver) was performed with a nominal voxel size of 20 mm (isotropic). For repeatability measurements, healthy subjects were scanned twice on the same day. The patient was only scanned once. Test-retest 31P MRSI data of pancreas and liver voxels (segmented on 1H MRI) of healthy subjects were quantified by fitting in the time domain and signal amplitudes were normalized to γ-adenosine triphosphate. In addition, the PME/PDE ratio was calculated. Metabolite levels were averaged over all voxels within the pancreas, right liver lobe and left liver lobe, respectively. Repeatability of test-retest data from healthy pancreas was assessed by paired t-tests, Bland-Altman analyses, and calculation of the intrasubject coefficients of variation (CoVs). Significant differences between healthy pancreas and right and left liver lobes were assessed with a two-way analysis of variance (ANOVA) for repeated measures. A P-value <0.05 was considered statistically significant. The intrasubject CoVs for PME, PDE, and PME/PDE in healthy pancreas were below 20%. Furthermore, PME and PME/PDE were significantly higher in pancreas compared to liver. In the patient with pancreatic cancer, qualitatively, elevated relative PME signals were observed in comparison with healthy pancreas. In vivo 31P MRSI of the human healthy pancreas and in pancreatic cancer may be feasible at 7 T. 3 TECHNICAL EFFICACY: Stage 2.

Effects of sex and APOE ε4 genotype on brain mitochondrial high-energy phosphates in midlife individuals at risk for Alzheimer's disease: A 31Phosphorus MR spectroscopy study.

Age, female sex, and APOE epsilon 4 (APOE4) genotype are the three greatest risk factors for late-onset Alzheimer's disease (AD). The convergence of these risks creates a hypometabolic AD-risk profile unique to women, which may help explain their higher lifetime risk of AD. Less is known about APOE4 effects in men, although APOE4 positive men also experience an increased AD risk. This study uses 31Phosphorus Magnetic Resonance Spectroscopy (31P-MRS) to examine effects of sex and APOE4 status on brain high-energy phosphates [adenosine triphosphate (ATP), phosphocreatine (PCr), inorganic phosphate (Pi)] and membrane phospholipids [phosphomonoesters (PME), phosphodiesters (PDE)] in 209 cognitively normal individuals at risk for AD, ages 40-65, 80% female, 46% APOE4 carriers (APOE4+). Women exhibited lower PCr/ATP and PCr/Pi levels than men in AD-vulnerable regions, including frontal, posterior cingulate, lateral and medial temporal cortex (multi-variable adjusted p≤0.037). The APOE4+ group exhibited lower PCr/ATP and PCr/Pi in frontal regions as compared to non-carriers (APOE4-) (multi-variable adjusted p≤0.005). Sex by APOE4 status interactions were observed in frontal regions (multi-variable adjusted p≤0.046), where both female groups and APOE4+ men exhibited lower PCr/ATP and PCr/Pi than APOE4- men. Among men, APOE4 homozygotes exhibited lower frontal PCr/ATP than heterozygotes and non-carriers. There were no significant effects of sex or APOE4 status on Pi/ATP and PME/PDE measures. Among midlife individuals at risk for AD, women exhibit lower PCr/ATP (e.g. higher ATP utilization) and lower PCr/Pi (e.g. higher energy demand) than age-controlled men, independent of APOE4 status. However, a double dose of APOE4 allele shifted men's brains to a similar metabolic range as women's brains. Examination of brain metabolic heterogeneity can support identification of AD-specific pathways within at-risk subgroups, further advancing both preventive and precision medicine for AD.

P.31 A multiparametric quantitative NMR study at rest and during exercise in subjects between 22 and 65 years of age: Preliminary results

The progressive decline in muscle strength and performance during ageing negatively affects the quality of life in the elderly and increases the risk of falls, disability and frailty. The age-related loss of muscle mass, strength and quality is a multifactorial process whose mechanisms are incompletely understood. Nuclear magnetic resonance (NMR) allows evaluating anatomical, structural and physiological aspects of muscle tissue non-invasively. Functional NMR also enables, for instance, to image during an exercise paradigm the tissue blood flow (BF) or energy metabolism using ³¹P MR spectroscopy (MRS). Here, we designed a protocol where multiple quantitative and complementary biomarkers were acquired in the lower leg in a single exam. Acquisitions were done at 3 T (Siemens Prisma) on 26 subjects (22 to 65 y.o., 15 women). Variables studied were muscle-specific cross-sectional area (CSA), intramuscular fat fraction (FF), muscle water T1 (T1_H2O) and T2 (T2_H2O ) values; and pH and concentrations of phosphocreatine (PCr), inorganic phosphate (Pi), phosphodiesters (PDE) and phosphomonoesters (PME) in the triceps. Dynamic simultaneous BF, T2* and 31P MRS measurements were done during a 13-min plantar flexion exercise. A linear model and ANOVA using gender and age as fixed factors were used for analysis. Preliminary results showed several statistically significant (p < 0.05) changes related to age: increased T1_H2O and FF in all the lower leg muscles (gastroc. med. & lat., soleus, tibial. ant. & post, peron.); increased PDE/ATP and PME/ATP ratios; and a modest CSA increase of the extensor and fibular muscles (unlike the quadriceps muscles). Pi/PCr at the end of exercise increased with age in male subjects. No other age-related changes were found for functional NMR variables, grip strength or triceps maximal contraction force. Our results show that age-related structural and basal metabolic changes can be observed with a multiparametric NMR approach in the muscle. The ongoing recruitment of additional subjects will allow us to confirm our findings.

Magnetic field therapy enhances muscle mitochondrial bioenergetics and attenuates systemic ceramide levels following ACL reconstruction: Southeast Asian randomized-controlled pilot trial.

BackgroundMetabolic disruption commonly follows Anterior Cruciate Ligament Reconstruction (ACLR) surgery. Brief exposure to low amplitude and frequency pulsed electromagnetic fields (PEMFs) has been shown to promote in vitro and in vivo murine myogeneses via the activation of a calcium–mitochondrial axis conferring systemic metabolic adaptations. This randomized-controlled pilot trial sought to detect local changes in muscle structure and function using MRI, and systemic changes in metabolism using plasma biomarker analyses resulting from ACLR, with or without accompanying PEMF therapy.Methods20 patients requiring ACLR were randomized into two groups either undergoing PEMF or sham exposure for 16 weeks following surgery. The operated thighs of 10 patients were exposed weekly to PEMFs (1 ​mT for 10 ​min) for 4 months following surgery. Another 10 patients were subjected to sham exposure and served as controls to allow assessment of the metabolic repercussions of ACLR and PEMF therapy. Blood samples were collected prior to surgery and at 16 weeks for plasma analyses. Magnetic resonance data were acquired at 1 and 16 weeks post-surgery using a Siemens 3T Tim Trio system. Phosphorus (31P) Magnetic Resonance Spectroscopy (MRS) was utilized to monitor changes in high-energy phosphate metabolism (inorganic phosphate (Pi), adenosine triphosphate (ATP) and phosphocreatine (PCr)) as well as markers of membrane synthesis and breakdown (phosphomonoesters (PME) and phosphodiester (PDE)). Quantitative Magnetization Transfer (qMT) imaging was used to elucidate changes in the underlying tissue structure, with T1-weighted and 2-point Dixon imaging used to calculate muscle volumes and muscle fat content.ResultsImprovements in markers of high-energy phosphate metabolism including reductions in ΔPi/ATP, Pi/PCr and (Pi ​+ ​PCr)/ATP, and membrane kinetics, including reductions in PDE/ATP were detected in the PEMF-treated cohort relative to the control cohort at study termination. These were associated with reductions in the plasma levels of certain ceramides and lysophosphatidylcholine species. The plasma levels of biomarkers predictive of muscle regeneration and degeneration, including osteopontin and TNNT1, respectively, were improved, whilst changes in follistatin failed to achieve statistical significance. Liquid chromatography with tandem mass spectrometry revealed reductions in small molecule biomarkers of metabolic disruption, including cysteine, homocysteine, and methionine in the PEMF-treated cohort relative to the control cohort at study termination. Differences in measurements of force, muscle and fat volumes did not achieve statistical significance between the cohorts after 16 weeks post-ACLR.ConclusionThe detected changes suggest improvements in systemic metabolism in the post-surgical PEMF-treated cohort that accords with previous preclinical murine studies. PEMF-based therapies may potentially serve as a manner to ameliorate post-surgery metabolic disruptions and warrant future examination in more adequately powered clinical trials.The Translational Potential of this ArticleSome degree of physical immobilisation must inevitably follow orthopaedic surgical intervention. The clinical paradox of such a scenario is that the regenerative potential of the muscle mitochondrial pool is silenced. The unmet need was hence a manner to maintain mitochondrial activation when movement is restricted and without producing potentially damaging mechanical stress. PEMF-based therapies may satisfy the requirement of non-invasively activating the requisite mitochondrial respiration when mobility is restricted for improved metabolic and regenerative recovery.

Does Inosine Monophosphate Formation Facilitate the Bioenergetic Response to Incremental Contractions in Human Skeletal Muscle In Vivo?

Traditionally, it has been accepted that working muscle will endeavor to maintain [ATP] near its resting level in order to maintain a favorable free energy of ATP hydrolysis (∆GATP). Recent reports of significant declines in [ATP] during maximal muscular contractions in vivo spark new interest in this concept. ATP is hydrolyzed to adenosine diphosphate (ADP) in the creatine kinase reaction to provide energy directly to working ATPases. As needed, additional energy can be provided by the breakdown of ADP to adenosine monophosphate (AMP), which is rapidly cleared by the formation of inosine monophosphate (IMP), with accompanying loss of total adenine nucleotides. IMP formation has been thought to occur only during very intense muscular work, wherein ATP production does not keep pace with ATP consumption. Here, we propose a role for IMP in managing both ∆GATP and flux through a key energetic pathway during contractions. To test our hypothesis that IMP formation mitigates the accumulation of ADP, 8 males (28.4 + 3.5 yr, mean + SD) performed 8 min of incremental, isotonic knee extension contractions (1 every 2 s, starting at 6% peak torque and incrementing by 3% every 2 min) on a magnetic resonance (MR)‐compatible ergometer in a 3‐Tesla MR system. 31Phosphorus MR spectra were obtained at rest (60‐s average) and throughout the contraction protocol (10‐s temporal resolution). Peaks corresponding to ATP, phosphocreatine (PCr), inorganic phosphate (Pi), and phosphomonoesters (PME) were fit in jMRUI, and concentrations for these metabolites were determined assuming resting [ATP] = 8.2 mM. [ADP], [AMP], [IMP], and the rate of ATP (mM∙s‐1) production by non‐oxidative glycolysis (i.e., wherein the fate of pyruvate is lactate; ATPgly) were also calculated. As expected, [PCr] decreased and [Pi] increased approximately linearly throughout the incremental contraction protocol. Surprisingly, [ATP] decreased and [IMP] increased (to 7.3 + 0.4 mM and 0.8 + 0.56 mM, respectively) steadily from the onset of contractions until the final stage, at which point no further changes were observed. In contrast, both [ADP] and [AMP] increased linearly from the start of contractions until the final stage, when they accumulated more rapidly; ultimately to 109.9 + 52.1 uM and 1.0 + 0.91 uM, respectively. The glycolytic contribution to ATP production was consistent for the first 3 stages, after which ATPgly increased rapidly to 0.102 + 0.14 mM·s‐1 at 480 s. Collectively, the timing and magnitude of these metabolic changes in working muscle suggest a sequence of responses designed to maintain cytosolic [ADP] sufficiently low as to mitigate changes in ∆GATP, but at a level sufficient to stimulate ATPgly as contraction intensity increases. A novel observation in this study was the decrease in [ATP] (and thus increase in [IMP]) from the onset of the contraction protocol, which then leveled off at the highest contraction intensity. The utility and consequences of these responses remain to be determined, but this study supports the concept that IMP formation is important in maintaining the cellular energy state as well as in directing the bioenergetic response to a series of incremental muscular contractions in vivo.

Phosphomonoesterase and phosphodiesterase activities and their regulation during dinoflagellate blooms under different external phosphate conditions

Phosphatases play a crucial role in recycling organic phosphorus and determining primary production and phytoplankton communities in seawater, especially in phosphate-depleted coastal waters. The present study analyzed spatiotemporal variation in phosphomonoesterase (PMEase) activity (PMEA) and phosphodiesterase (PDEase) activity (PDEA) during 2 dinoflagellate blooms occurring in 2 coastal areas of Fujian Province, East China Sea, which differed in external phosphate conditions. Together with environmental variables and with a specific focus on the availability of different phosphorus forms in the seawater, the regulation of both phosphatases was studied. The results showed that dissolved organic phosphorus (DOP) was the major phosphorus source during blooms, especially in phosphate-depleted environments. Labile DOP accounted for more than 50% of DOP, of which phosphomonoester (PME) and phosphodiester (PDE) accounted for 75-94% and 6-25%, respectively. PMEA and PDEA were highly correlated, both increasing during blooms with a fixed PMEA:PDEA ratio of 2.5 under external phosphate conditions at both sites. Both PMEA and PDEA were negatively correlated with dissolved inorganic phosphorus (DIP) when phosphate was depleted, but positively correlated with DOP regardless of external phosphate conditions. During dinoflagellate blooms, temperature and phytoplankton biomass were the dominant variables determining both phosphatase activities under phosphate-depleted conditions, whereas the availability of DOP was the dominant variable determining both phosphatase activities under phosphate-replete conditions. This study suggests the importance of phosphatases in recycling DOP, and indicates similar regulation of PMEA and PDEA during dinoflagellate blooms.

In vivo magnetic resonance spectrometry imaging demonstrates comparable adaptation of brain energy metabolism to metabolic stress induced by 72 h of fasting in depressed patients and healthy volunteers

Major depressive disorder (MDD) is characterized by dysregulation of stress systems and by abnormalities in cerebral energy metabolism. Stress induction has been shown to impact neurometabolism in healthy individuals. Contrarily, neurometabolic changes in response to stress are insufficiently investigated in MDD patients. Metabolic stress was induced in MDD patients (MDD, N = 24) and in healthy individuals (CTRL, N = 22) by application of an established fasting protocol in which calorie intake was omitted for 72 h. Both study groups were comparable regarding age, gender distribution, and body mass index (BMI). Fasting-induced effects on brain high-energy phosphate levels and membrane phospholipid metabolism were assessed using phosphorus-31 magnetic resonance spectroscopy (31P-MRS). Two-way repeated measures ANOVAs did not reveal significant interaction effects (group x fasting) or group differences in adenosine triphosphate (ATP), phosphocreatine (PCr), inorganic phosphate (Pi), phosphomonoesters (PME), phosphodiesters (PDE), or pH levels between MDD and CTRL. Fasting, independent of group, significantly increased ATP and decreased Pi levels and an overall increase in PME/PDE ratio as marker for membrane turnover was observed. Overall these results indicate reactive changes in cerebral energetics and in membrane phospholipid metabolism in response to fasting. The observed effects did not significantly differ between CTRL and MDD, indicating that neurometabolic adaptation to metabolic stress is preserved in MDD patients.

Phosphorous Magnetic Resonance Spectroscopy and Molecular Markers in IDH1 Wild Type Glioblastoma.

Simple SummaryGliobastoma is one of the deadliest tumors overall, yet the most common malignant brain tumor. The new World Health Organization Classification of Brain Tumors brought changes in how we look at this type of malignancy. Now we know that glioblastoma is rather a spectrum of similar tumors, but with some distinct characteristics that include molecular footprint, response to therapy and with that overall survival, among others. We hypothesised that by employing phosphorous magnetic resonance we will be able to show differences in cellular energy metabolism in these various subtypes of glioblastoma. For example, we found indices of faster cell reproduction and tumor growth in MGMT-methylated and EGFR-amplified tumors. These tumors also could have reduced energetic state or tissue oxygenation due to the increased necrosis. Tumors with EGFR-amplification could have increased apoptotic activity regardless of their MGMT status. Our study indicated various differences in energetic metabolism in tumors with different molecular characteristics, which could potentially be important in future therapeutic strategies.The World Health Organisation’s (WHO) classification of brain tumors requires consideration of both histological appearance and molecular characteristics. Possible differences in brain energy metabolism could be important in designing future therapeutic strategies. Forty-three patients with primary, isocitrate dehydrogenase 1 (IDH1) wild type glioblastomas (GBMs) were included in this study. Pre-operative standard MRI was obtained with additional phosphorous magnetic resonance spectroscopy (31-P-MRS) imaging. Following microsurgical resection of the tumors, biopsy specimens underwent neuropathological diagnostics including standard molecular diagnosis. The spectroscopy results were correlated with epidermal growth factor (EGFR) and -Methylguanine-DNA methyltransferase (MGMT) status. EGFR amplified tumors had significantly lower phosphocreatine (PCr) to adenosine triphosphate (ATP)-PCr/ATP and PCr to inorganic phosphate (Pi)-PCr/Pi ratios, and higher Pi/ATP and phosphomonoesters (PME) to phosphodiesters (PDE)-PME/PDE ratio than those without the amplification. Patients with MGMT-methylated tumors had significantly higher cerebral magnesium (Mg) values and PME/PDE ratio, while their PCr/ATP and PCr/Pi ratios were lower than in patients without the methylation. In survival analysis, not-EGFR-amplified, MGMT-methylated GBMs showed the longest survival. This group had lower PCr/Pi ratio when compared to MGMT-methylated, EGFR-amplified group. PCr/Pi ratio was lower also when compared to the MGMT-unmethylated, EGFR not-amplified group, while PCr/ATP ratio was lower than all other examined groups. Differences in energy metabolism in various molecular subtypes of wild-type-GBMs could be important information in future precision medicine approach.

Relationship of parieto‐occipital brain energy phosphate metabolism and cognition using 31P MRS at 7TESLA in preclinical stages of Alzheimer’s disease

AbstractBackgroundNeuroenergetics, a study of brain energy metabolism (BEM), may uncover cues for early disease biomarkers that potentially trigger downstream neuropathological changes in amnestic mild cognitive impairment (aMCI), a transitory stage of Alzheimer’s disease (AD). Advancements in brain imaging modalities, such as in vivo 31phosphorus magnetic resonance spectroscopy (31P MRS) at higher magnetic strength, offer promising platforms to measure energy and membrane phospholipid metabolites, a window to understand BEM. The primary goal was to quantify distinct features of phosphorus metabolites in parieto‐occipital lobes using 31P MRS at 7Tesla in aMCI. Another objective was to examine the clinical significance of the metabolites to brain‐behavior relationships. Specifically, we examined the correspondence across BEM and membrane phospholipid indices in parieto‐occipital regions of the brain with cognitive performance‐ executive functions (EF), memory, attention, and visuospatial skills.Methods19 aMCI participants enrolled in the study. Each participant completed a cognitive assessment and a scan using partial volume‐coil 31P MRS over parieto‐occipital lobes at 7Tesla. BEM indices were measured using three energy indicators: energy reserve (PCr/t‐ATP), energy consumption (intracellular_Pi/t‐ATP), and metabolic state (PCr/intracellular_Pi) along with regulatory co‐factors of BEM‐intracellular Mg2+ and pH; whereas the ratio of phosphomonoesters (PMEs) to phosphodiesters (PDEs) represented membrane phospholipid indicator.Results 31P MRS data over parieto‐occipital lobes showed thirteen well‐resolved peaks of the energy and membrane phospholipid metabolites at 7Tesla. The higher BEM indices were associated with lower cognitive performance of memory [(energy reserve indicator: CVLT p=0.004), (metabolic state indicator: CVLT p=0.007)], executive function [(metabolic state indicator: TOSL (p=0.044)], and attention [(pH: selective auditory task, p=0.044)]. The finding of higher brain energy indices in the parieto‐occipital lobes associated with lower cognition may represent compensatory hypermetabolism during the early stages of brain disturbances in aMCI.ConclusionThe critical contribution of this work was to develop and test a methodology to quantify neurometabolic markers of energy and membrane phospholipid metabolites at 7Tesla in aMCI. Additionally, the study findings implicated the role of BEM as an early neurometabolic marker of brain changes linked to cognitive decline in the preclinical stages of AD.

Growth and phosphatase activities of Ostreopsis cf. ovata biofilms supplied with diverse dissolved organic phosphorus (DOP) compounds

It is becoming increasingly evident that the use of organic nutrients is widespread among many aquatic phototrophic organisms. Simultaneously, incidents of eutrophication of coastal waters are becoming more common due to rises in organic nutrient loads deriving from anthropogenic activities and natural terrestrial processes. In the northern Adriatic Sea, blooms of the toxic dinoflagellate Ostreopsis cf. ovata are reported as a frequent phenomenon linked to particular environmental conditions, including increased organic nutrient loads. Ostreopsis blooms typically produce a mucilaginous biofilm that can cover all benthic substrata. In order to clarify the role of dissolved organic phosphorus (DOP) in the onset and maintenance of an O. cf. ovata bloom, we investigated the growth rates in the presence of a range of phosphomonoesters (PMEs) (D-fructose 1,6-disphosphate, β-glycerophosphate, α-D-glucose 1-phosphate, guanosine 5’-monophosphate and phytic acid) and phosphodiesters (PDEs) (DNA and RNA). Levels of both phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activities were assessed in the O. cf. ovata biofilms. The results showed that O. cf. ovata growth is not inhibited in media containing a wide range of DOP and diverse ratios of PME:PDE compared to those containing inorganic phosphorus. Much of the hydrolytic activity was associated with bacteria and with extracellular polymeric substances (EPSs). Our findings suggest that the success of O. cf. ovata stems from the collective participation of all components of the biofilm (O. cf. ovata, EPSs and bacteria) that allows it to thrive in phosphorus-limited environments, but where the main source of phosphorus is organic.

Relationship of Parieto-Occipital Brain Energy Phosphate Metabolism and Cognition Using 31P MRS at 7-Tesla in Amnestic Mild Cognitive Impairment.

BackgroundThe human brain has high energy requirements that continuously support healthy neuronal activity and cognition. A disruption in brain energy metabolism (BEM) may contribute to early neuropathological changes such as accumulation of β-amyloid and tau in vulnerable populations. One such population is amnestic mild cognitive impairment (aMCI) where some individuals are at risk for developing dementia, i.e. Alzheimer’s disease (AD). Recent advances in imaging technology are providing new avenues to measure BEM accurately using 31phosphorus magnetic resonance spectroscopy (31P MRS) at ultra-high-field (UHF) magnetic strength 7-Tesla. This study investigates whether a methodology using partial volume-coil 31P MRS at 7T over parieto-occipital lobes can accurately quantify high-energy phosphate and membrane phospholipid metabolites in aMCI. A secondary objective was to explore BEM and membrane phospholipid indices’ correspondence with cognitive performance in domains of executive function (EF), memory, attention, and visuospatial skills in aMCI, a heterogeneous population.Methods19 aMCI participants enrolled in the study completed cognitive assessment and 31P MRS scan. BEM indices were measured using three energy indicators: energy reserve (PCr/t-ATP), energy consumption (intracellular_Pi/t-ATP), and metabolic state (PCr/intracellular_Pi) along with regulatory co-factors of BEM-intracellular Mg2 + and pH; whereas the ratio of phosphomonoesters (PMEs) to phosphodiesters (PDEs) – membrane phospholipid indicator.Results31P MRS scan showed thirteen well-resolved peaks with precise quantification of the phosphorus metabolites at UHF. The higher BEM indices were associated with lower cognitive performance of memory [(energy reserve indicator: CVLT p = 0.004), (metabolic state indicator: CVLT p = 0.007)], executive function [(metabolic state indicator: TOSL (p = 0.044)], and attention [(pH: selective auditory task, p = 0.044)]. The finding of an inverse relationship observed in the parieto-occipital lobes suggests an association between neuronal energy markers with cognition in aMCI.ConclusionThe significant contribution of this preliminary research was to establish the feasibility of utilizing a methodology at UHF to accurately measure high-energy phosphate and membrane phospholipid metabolites in a population with heterogeneous outcomes. This work offers a novel approach for future work to further elucidate early dementia biomarkers or precursors to the downstream accumulation of amyloid and tau using the combination of MRS-PET imaging modalities in AD.

Multinuclear MRS at 7T Uncovers Exercise Driven Differences in Skeletal Muscle Energy Metabolism Between Young and Seniors.

Purpose: Aging is associated with changes in muscle energy metabolism. Proton (1H) and phosphorous (31P) magnetic resonance spectroscopy (MRS) has been successfully applied for non-invasive investigation of skeletal muscle metabolism. The aim of this study was to detect differences in adenosine triphosphate (ATP) production in the aging muscle by 31P-MRS and to identify potential changes associated with buffer capacity of muscle carnosine by 1H-MRS.Methods: Fifteen young and nineteen elderly volunteers were examined. 1H and 31P-MRS spectra were acquired at high field (7T). The investigation included carnosine quantification using 1H-MRS and resting and dynamic 31P-MRS, both including saturation transfer measurements of phosphocreatine (PCr), and inorganic phosphate (Pi)-to-ATP metabolic fluxes.Results: Elderly volunteers had higher time constant of PCr recovery (τPCr) in comparison to the young volunteers. Exercise was connected with significant decrease in PCr-to-ATP flux in both groups. Moreover, PCr-to-ATP flux was significantly higher in young compared to elderly both at rest and during exercise. Similarly, an increment of Pi-to-ATP flux with exercise was found in both groups but the intergroup difference was only observed during exercise. Elderly had lower muscle carnosine concentration and lower postexercise pH. A strong increase in phosphomonoester (PME) concentration was observed with exercise in elderly, and a faster Pi:PCr kinetics was found in young volunteers compared to elderly during the recovery period.Conclusion: Observations of a massive increment of PME concentration together with high Pi-to-ATP flux during exercise in seniors refer to decreased ability of the muscle to meet the metabolic requirements of exercise and thus a limited ability of seniors to effectively support the exercise load.

Regionally Distinct Alterations in Membrane Phospholipid Metabolism in Schizophrenia: A Meta-analysis of Phosphorus Magnetic Resonance Spectroscopy Studies

BackgroundExisting data on altered membrane phospholipid metabolism in schizophrenia are diverse. We conducted a meta-analysis of studies of phosphorus magnetic resonance spectroscopy, a noninvasive imaging approach that can assess molecular biochemistry of cortex by measuring phosphomonoester (PME) and phosphodiester (PDE) levels, which can provide evidence of altered biochemical processes involved in neuropil membrane expansion and contraction in schizophrenia. MethodsWe analyzed PME and PDE data in the frontal and temporal lobes in subjects with schizophrenia from 24 peer-reviewed publications using the MAVIS package in R by building random- and fixed-effects models. Heterogeneity of effect sizes, effects of publication bias, and file drawer analysis were also assessed. ResultsSubjects with schizophrenia showed lower PME levels in the frontal regions (p = .008) and elevated PDE levels in the temporal regions (p < .001) with significant heterogeneity. We noted significant publication bias and file drawer effect for frontal PME and PDE and temporal PDE levels, but not for temporal PME levels. Fail-safe analysis estimated that a high number of negative studies were required to provide nonsignificant results. ConclusionsDespite methodological differences, these phosphorus magnetic resonance spectroscopy studies demonstrate regionally specific imbalance in membrane phospholipid metabolism related to neuropil in subjects with schizophrenia compared with control subjects reflecting neuropil contraction. Specifically, decreased PME levels in the frontal regions and elevated PDE levels in the temporal regions provide evidence of decreased synthesis and increased degradation of neuropil membrane, respectively. Notwithstanding significant heterogeneity and publication bias, a large number of negative studies are required to render the results of this meta-analysis nonsignificant. These findings warrant further postmortem and animal studies.

1873-P: NAFLD and Insulin Resistance Is Associated with a Specific Signature in Membrane Phospholipid Metabolites in Adolescents with Polycystic Ovary Syndrome (PCOS)

Obese adolescents with PCOS are at high risk of nonalcoholic Fatty Liver Disease (NAFLD) which contributes to the risk of diabetes. Impaired hepatic energy metabolism is associated with diabetes and characterized by decreased inorganic phosphates (Pi) and ATP hepatic content. Membrane phospholipids measured by magnetic resonance spectroscopy (MRS) may reflect endoplasmic reticulum (ER) stress (phosphodiesters; PDE) or turnover/composition of membrane phospholipids: precursors (phosphomonoesters (PME): phosphoethanolamine (PE) and phosphocholine (PC)) and degradation products (PDE). It is not known if adolescents with PCOS and NAFLD have impaired hepatic energy metabolism or MRS signature associated with insulin sensitivity (Si). Obese adolescents with PCOS (n=25) underwent fasted hepatic 31phosphorus-MRS to measure ATP, Pi, PME and PDE relative to total phosphates (TP). Liver stiffness was measured with MR elastography and hepatic fat fraction (HFF) by MRI-proton density, with an HFF &amp;gt;5.5% classified as NAFLD. A 6h oral sugar tolerance test (OSTT, 25g fructose+75g glucose) was performed. Insulin sensitivity (Si) was calculated with the oral minimal model. 12 girls (BMI 36.4 ±7.3 kg/m2, age 16 (15-17)) had NAFLD and 13 did not (BMI 34.0±4.9 kg/m2, age 16 (14-17)). PME/TP were lower in girls with NAFLD (p=0.007) as well as the ratio of PME/PDE (p=0.002). A lower PE/TP was associated with higher liver stiffness (r= -0.55; p=0.009) and lower Si (r=0.57; p= 0.03). Total ATP/TP, y-ATP/TP and Pi/TP were similar between groups (p&amp;gt;0.15). Obese adolescents with PCOS and NAFLD have a distinct signature in hepatic 31P-MRS that is associated with Si suggesting alterations in membrane phospholipids. However, changes in energetics seen in adults with NAFLD are not present. Further work is needed to understand how these changes in hepatic phospholipids relates to insulin sensitivity and risk for diabetes. Disclosure A. Carreau: Advisory Panel; Self; Pfizer Inc. Y. Garcia Reyes: None. B. Newcomer: None. D.E. Befroy: None. M.S. Brown: None. M. Cree-Green: None. Funding National Institutes of Health (K23DK107871); Doris Duke Charitable Foundation; National Center for Advancing Translational Sciences (UL1TR002535); Diabetes Canada

Effects of Aging on the Human Brain: A Proton and Phosphorus MR Spectroscopy Study at 3T.

To investigate accumulative aging effects on neurometabolism in human brain and to collect a reference dataset. Fifty-four healthy volunteers aged evenly between 22 and 73 years were studied using whole-brain 1 H-MR spectroscopic imaging in combination with 31 P-MRS at 3T. Global metabolite concentrations of brain N-acetylaspartate (NAA), total choline (tCho), and total creatine (tCr), as well as phosphocreatine (PCr), adenosine-5'-triphosphate (ATP), phosphomonoesters (PME), phosphodiesters (PDE), and inorganic phosphate (Pi) were determined. Fractional volumes of brain gray matter (FVGM), white matter (FVWM), and total tissue (FVTB, GM+WM) were also estimated. With age, NAA, ATP, and PME, as well as FVTB and FVGM decreased and tCho and FVWM increased linearly. Positive correlations were found between FVGM and global concentrations of NAA, ATP, PME, and Pi. Age-related accumulative metabolic changes in aging human brain correlated with reduced neuronal metabolic activity and density, reflected by decreased NAA, reduced mitochondrial activity by decreased ATP, and reduced membrane synthesis by decreased PME. These changes are associated with age-related decrease of neuronal volume. Global NAA and ATP might be used as surrogate biomarker for monitoring aging in human brain.

13C/31P MRS Metabolic Biomarkers of Disease Progression and Response to AAV Delivery of hGAA in a Mouse Model of Pompe Disease

The development of therapeutic clinical trials for glycogen storage disorders, including Pompe disease, has called for non-invasive and objective biomarkers. Glycogen accumulation can be measured in vivo with 13C MRS. However, clinical implementation remains challenging due to low signal-to-noise. On the other hand, the buildup of glycolytic intermediates may be detected with 31P MRS. We sought to identify new biomarkers of disease progression in muscle using 13C/31P MRS and 1H HR-MAS in a mouse model of Pompe disease (Gaa−/−). We evaluated the sensitivity of these MR biomarkers in vivo after treatment using an adeno-associated virus vector 2/9 encoding hGAA driven by the desmin promotor. 31P MRS showed significantly elevated phosphomonoesters (PMEs) in Gaa−/− compared to control at 2 (0.06 ± 0.02 versus 0.03 ± 0.01; p = 0.003), 6, 12, and 18 months of age. Correlative 1H HR-MAS measures in intact gastrocnemius muscles revealed high glucose-6-phosphate (G-6-P). After intramuscular AAV injections, glycogen, PME, and G-6-P were decreased within normal range. The changes in PME levels likely partly resulted from changes in G-6-P, one of the overlapping phosphomonoesters in the 31P MR spectra in vivo. Because 31P MRS is inherently more sensitive than 13C MRS, PME levels have greater potential as a clinical biomarker and should be considered as a complementary approach for future studies in Pompe patients.

Ultra-high-field magnetic resonance spectroscopy in non-alcoholic fatty liver disease: Novel mechanistic and diagnostic insights of energy metabolism in non-alcoholic steatohepatitis and advanced fibrosis.

Background & AimsWith the rising prevalence of non‐alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) non‐invasive tools obtaining pathomechanistic insights to improve risk stratification are urgently needed. We therefore explored high‐ and ultra‐high‐field magnetic resonance spectroscopy (MRS) to obtain novel mechanistic and diagnostic insights into alterations of hepatic lipid, cell membrane and energy metabolism across the spectrum of NAFLD.Methods MRS and liver biopsy were performed in 30 NAFLD patients with NAFL (n=8) or NASH (n=22). Hepatic lipid content and composition were measured using 3‐Tesla proton (1H)‐MRS. 7‐Tesla phosphorus (31P)‐MRS was applied to determine phosphomonoester (PME) including phosphoethanolamine (PE), phosphodiester (PDE) including glycerophosphocholine (GPC), phosphocreatine (PCr), nicotinamide adenine dinucleotide phosphate (NADPH), inorganic phosphate (Pi), γ‐ATP and total phosphorus (TP). Saturation transfer technique was used to quantify hepatic ATP flux.ResultsHepatic steatosis in 1H‐MRS highly correlated with histology (P<.001) showing higher values in NASH than NAFL (P<.001) without differences in saturated or unsaturated fatty acid indices. PE/TP ratio increased with advanced fibrosis (F3/4) (P=.002) whereas GPC/PME+PDE decreased (P=.05) compared to no/mild fibrosis (F0‐2). γ‐ATP/TP was lower in advanced fibrosis (P=.049), while PCr/TP increased (P=.01). NADPH/TP increased with higher grades of ballooning (P=.02). Pi‐to‐ATP exchange rate constant (P=.003) and ATP flux (P=.001) were lower in NASH than NAFL.ConclusionsUltra‐high‐field MRS, especially saturation transfer technique uncovers changes in energy metabolism including dynamic ATP flux in inflammation and fibrosis in NASH. Non‐invasive profiling by MRS appears feasible and may assist further mechanistic and therapeutic studies in NAFLD/NASH.

31Phosphorus magnetic resonance spectroscopy of the liver for evaluating inflammation and fibrosis in autoimmune hepatitis

Background: Liver biopsy is the gold standard in evaluating inflammation and fibrosis in autoimmune hepatitis.Aims: In search of non-invasive follow-up tools in autoimmune hepatitis, we evaluated 31phosphorus magnetic resonance spectroscopy (31P MRS).Methods: Twelve consecutive AIH patients (mean age 42.8 years, 10 women) underwent liver biopsy, routine laboratory liver function tests, which were compared to findings in 31P MRS and transient elastography (TE).Results: Phosphoenolpuryvate (PEP) correlated with the grade of inflammation (r = 0.746, p = .005) and thromboplastin time (r = 0.592, p = .043). It also differentiated patients with active inflammation from patients without (t = 3.781, p = .009). There was no correlation between PEP and aminotransferase or immunoglobulin G levels.The phosphoethanolamine (PE)/phosphocholine (PC) ratio, PE/glyserophosphoethanolamine (GPE) ratio and PC/[total phosphomonoester (PME) + phosphodiester (PDE)] ratios correlated with immunoglobulin G (r = 0.764, p = .006; r = 0.618, p = .043; and r= −0.636, p = .035, respectively).PME/PDE and PE/GPE correlated with fibrosis (r = 0.668, p = .018 and r = 0.604, p = .037). PE/GPE also differentiated F3 from F0-2 patients (t = 3.810, p = .003).Phosphorus metabolites did not correlate with TE results and TE did not correlate with liver histology or laboratory parameters.Conclusions: 31P MRS seems to detect active inflammation and advanced fibrosis in AIH patients. TE was ineffective in fibrosis quantification.