Variations due to analysis technique in intracellular pH measurements in simulated and in vivo31P MR spectra of the human brain

Bioenergetic impairment in Gulf War illness assessed via 31P-MRS

Time for post-exercise phosphocreatine-recovery (PCr-R), deemed a robust index of mitochondrial function in vivo, was previously reported to be elevated (signifying impaired ATP production) in veterans with Gulf War illness (GWI). Here we sought to replicate the finding and assess the impact of contravening previous eligibility requirements. The replication sample comprised white males. Cases reported ≥ moderate muscle-weakness to match the organ assessed to an organ affected; controls lacked recent headache or multiple symptoms. The expansion sample added cases without muscle-weakness, controls with recent headache, females, nonwhites. PCr-R, following pedal-depression-exercise, was compared in veterans with GWI versus controls (sample N = 38). In the replication sample, PCr-R results closely matched the prior report: PCr-R veterans with GWI mean(SD) = 47.7(16.5); control mean(SD) = 30.3(9.2), p = 0.017. (Prior-study PCr-R veterans with GWI mean(SD) = 46.1(17.9), control mean(SD) = 29.0(8.7), p = 0.023. Combined replication + prior samples: p = 0.001.) No case-control difference was observed in the expansion sample. In cases, PCr-R related to muscle-weakness: PCr-R = 29.9(7.1), 38.2(8.9), 47.8(15.2) for muscle-weakness rated none/low, intermediate, and high respectively (p for trend = 0.02), validating desirability of matching tissue assessed to tissue affected. In controls, headache/multiple symptoms, sex, and ethnicity each mattered (affecting PCr-R significantly). This study affirms mitochondrial/bioenergetic impairment in veterans with GWI. The importance of careful case/control selection is underscored.

Targeting low- or high-normal Carbon dioxide, Oxygen, and Mean arterial pressure After Cardiac Arrest and REsuscitation: study protocol for a randomized pilot trial

Background

Arterial carbon dioxide tension (PaCO₂), oxygen tension (PaO₂), and mean arterial pressure (MAP) are modifiable factors that affect cerebral blood flow (CBF), cerebral oxygen delivery, and potentially the course of brain injury after cardiac arrest. No evidence regarding optimal treatment targets exists.

Methods

The Carbon dioxide, Oxygen, and Mean arterial pressure After Cardiac Arrest and REsuscitation (COMACARE) trial is a pilot multi-center randomized controlled trial (RCT) assessing the feasibility of targeting low- or high-normal PaCO₂, PaO₂, and MAP in comatose, mechanically ventilated patients after out-of-hospital cardiac arrest (OHCA), as well as its effect on brain injury markers. Using a 2³ factorial design, participants are randomized upon admission to an intensive care unit into one of eight groups with various combinations of PaCO₂, PaO₂, and MAP target levels for 36 h after admission.

The primary outcome is neuron-specific enolase (NSE) serum concentration at 48 h after cardiac arrest. The main feasibility outcome is the between-group differences in PaCO2, PaO2, and MAP during the 36 h after ICU admission. Secondary outcomes include serum concentrations of NSE, S100 protein, and cardiac troponin at 24, 48, and 72 h after cardiac arrest; cerebral oxygenation, measured with near-infrared spectroscopy (NIRS); potential differences in epileptic activity, monitored via continuous electroencephalogram (EEG); and neurological outcomes at six months after cardiac arrest.

Discussion

The trial began in March 2016 and participant recruitment has begun in all seven study sites as of March 2017. Currently, 115 of the total of 120 patients have been included. When completed, the results of this trial will provide preliminary clinical evidence regarding the feasibility of targeting low- or high-normal PaCO₂, PaO₂, and MAP values and its effect on developing brain injury, brain oxygenation, and epileptic seizures after cardiac arrest. The results of this trial will be used to evaluate whether a larger RCT on this subject is justified.

Trial registration

ClinicalTrials.gov, NCT02698917. Registered on 26 January 2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2257-0) contains supplementary material, which is available to authorized users.

PH Measurements of the Brain Using Phosphorus Magnetic Resonance Spectroscopy ((31)PMRS) in Healthy Men - Comparison of Two Analysis Methods

Background

Intracellular pH provides information on homeostatic mechanisms in neurons and glial cells. The aim of this study was to define pH of the brain of male volunteers using phosphorus magnetic resonance spectroscopy (³¹PMRS) and to compare two methods of calculating this value.

Material/Methods

In this study, 35 healthy, young, male volunteers (mean age: 25 years) were examined by ³¹PMRS in 1.5 T MR system (Signa Excite, GE). The FID CSI (Free Induction Decay Chemical Shift Imaging) sequence was used with the following parameters: TR=4000 ms, FA=90°, NEX=2. Volume of interest (VOI) was selected depending on the size of the volunteers’ brain (11–14 cm³, mean 11.53 cm³). Raw data were analyzed using SAGE (GE) software.

Results

Based on the chemical shift of peaks in the ³¹PMRS spectrum, intracellular pH was calculated using two equations. In both methods the mean pH was slightly alkaline (7.07 and 7.08). Results were compared with a t-test. Significant difference (p<0.05) was found between these two methods.

Conclusions

The ³¹PMRS method enables non-invasive in vivo measurements of pH. The choice of the calculation method is crucial for computing this value. Comparing the results obtained by different teams can be done in a fully credible way only if the calculations were performed using the same formula.

Glucose metabolism following human traumatic brain injury: methods of assessment and pathophysiological findings

The pathophysiology of traumatic brain (TBI) injury involves changes to glucose uptake into the brain and its subsequent metabolism. We review the methods used to study cerebral glucose metabolism with a focus on those used in clinical TBI studies. Arterio-venous measurements provide a global measure of glucose uptake into the brain. Microdialysis allows the in vivo sampling of brain extracellular fluid and is well suited to the longitudinal assessment of metabolism after TBI in the clinical setting. A recent novel development is the use of microdialysis to deliver glucose and other energy substrates labelled with carbon-13, which allows the metabolism of glucose and other substrates to be tracked. Positron emission tomography and magnetic resonance spectroscopy allow regional differences in metabolism to be assessed. We summarise the data published from these techniques and review their potential uses in the clinical setting.

Systemic, local, and imaging biomarkers of brain injury: more needed, and better use of those already established?

Much progress has been made over the past two decades in the treatment of severe acute brain injury, including traumatic brain injury and subarachnoid hemorrhage, resulting in a higher proportion of patients surviving with better outcomes. This has arisen from a combination of factors. These include improvements in procedures at the scene (pre-hospital) and in the hospital emergency department, advances in neuromonitoring in the intensive care unit, both continuously at the bedside and intermittently in scans, evolution and refinement of protocol-driven therapy for better management of patients, and advances in surgical procedures and rehabilitation. Nevertheless, many patients still experience varying degrees of long-term disabilities post-injury with consequent demands on carers and resources, and there is room for improvement. Biomarkers are a key aspect of neuromonitoring. A broad definition of a biomarker is any observable feature that can be used to inform on the state of the patient, e.g., a molecular species, a feature on a scan, or a monitoring characteristic, e.g., cerebrovascular pressure reactivity index. Biomarkers are usually quantitative measures, which can be utilized in diagnosis and monitoring of response to treatment. They are thus crucial to the development of therapies and may be utilized as surrogate endpoints in Phase II clinical trials. To date, there is no specific drug treatment for acute brain injury, and many seemingly promising agents emerging from pre-clinical animal models have failed in clinical trials. Large Phase III studies of clinical outcomes are costly, consuming time and resources. It is therefore important that adequate Phase II clinical studies with informative surrogate endpoints are performed employing appropriate biomarkers. In this article, we review some of the available systemic, local, and imaging biomarkers and technologies relevant in acute brain injury patients, and highlight gaps in the current state of knowledge.

Mitochondrial dysfunction in Gulf War illness revealed by 31Phosphorus Magnetic Resonance Spectroscopy: a case-control study

BACKGROUND

Approximately 1/3 of 1990-1 Gulf War veterans developed chronic multisymptom health problems. Implicated exposures bear mechanisms that adversely affect mitochondria. Symptoms emphasize fatigue, cognition and muscle (brain and muscle are aerobically demanding); with protean additional domains affected, compatible with mitochondrial impairment. Recent evidence supports treatments targeting cell bioenergetics (coenzyme10) to benefit Gulf War illness symptoms. However, no evidence has directly documented mitochondrial or bioenergetic impairment in Gulf War illness.

OBJECTIVE

We sought to objectively assess for mitochondrial dysfunction, examining post-exercise phosphocreatine-recovery time constant (PCr-R) using (31)Phosphorus Magnetic Resonance Spectroscopy ((31)P-MRS), in Gulf War veterans with Gulf War illness compared to matched healthy controls. PCr-R has been described as a "robust and practical" index of mitochondrial status.

DESIGN AND PARTICIPANTS

Case-control study from 2012-2013. Fourteen community-dwelling Gulf War veterans and matched controls from the San Diego area comprised 7 men meeting CDC and Kansas criteria for Gulf War illness, and 7 non-deployed healthy controls matched 1:1 to cases on age, sex, and ethnicity.

OUTCOME MEASURE

Calf muscle phosphocreatine was evaluated by (31)P-MRS at rest, through 5 minutes of foot pedal depression exercise, and in recovery, to assess PCr-R. Paired t-tests compared cases to matched controls.

RESULTS

PCr-R was significantly prolonged in Gulf War illness cases vs their matched controls: control values, mean ± SD, 29.0 ± 8.7 seconds; case values 46.1 ± 18.0 seconds; difference 17.1 ± 14.9 seconds; p = 0.023. PCr-R was longer for cases relative to their matched controls for all but one pair; moreover while values clustered under 31 seconds for all but one control, they exceeded 35 seconds (with a spread up to 70 seconds) for all but one case.

DISCUSSION

These data provide the first direct evidence supporting mitochondrial dysfunction in Gulf War illness. Findings merit replication in a larger study and/or corroboration with additional mitochondrial assessment tools.

Assessing bioenergetic compromise in autism spectrum disorder with 31P magnetic resonance spectroscopy: preliminary report

We sought to examine, via Phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS) in a case-control design, whether bioenergetic deficits in autism spectrum disorders extend to the brain and muscle. Six cases with autism spectrum disorder with suspected mitochondrial dysfunction (age 6-18 years) and 6 age/sex-matched controls underwent (31)P magnetic resonance spectroscopy. The outcomes of focus were muscle resting phosphocreatine and intracellular pH as well as postexercise phosphocreatine recovery time constant and frontal brain phosphocreatine. Intracellular muscle pH was lower in each autism spectrum disorder case than their matched control (6/6, P = .03; P = .0048, paired t test). Muscle phosphocreatine (5/6), brain phosphocreatine (3/4), and muscle phosphocreatine recovery time constant (3/3) trends were in the predicted direction (not all participants completed each). This study introduces (31)P magnetic resonance spectroscopy as a noninvasive tool for assessment of mitochondrial function in autism spectrum disorder enabling bioenergetic assessment in brain and provides preliminary evidence suggesting that bioenergetic defects in cases with autism spectrum disorder are present in muscle and may extend to brain.

Phosphorus magnetic resonance spectroscopy in malformations of cortical development

PURPOSE

The aim of this study was to evaluate phospholipid metabolism in patients with malformations of cortical development (MCDs).

METHODS

Thirty-seven patients with MCDs and 31 control subjects were studied using three-dimensional phosphorus magnetic resonance spectroscopy ((31)P-MRS) at 3.0 T. The voxels in the lesions and in the frontoparietal cortex of the control subjects were compared (the effective volumes were 12.5 cm(3)). Robust quantification methods were applied to fit the time-domain data to the following resonances: phosphoethanolamine (PE); phosphocholine (PC); inorganic phosphate (Pi); glycerophosphoethanolamine (GPE); glycerophosphocholine (GPC); phosphocreatine (PCr); and α-, β-, and γ-adenosine triphosphate (ATP). We also estimated the total ATP (ATP(t) = α-+β-+γ-ATP), phosphodiesters (PDE = GPC+GPE), phosphomonoesters (PME = PE+PC), and the PME/PDE, PCr/ATP(t) and PCr/Pi ratios. The magnesium (Mg(2+)) levels and pH values were calculated based on PCr, Pi, and β-ATP chemical shifts.

KEY FINDINGS

Compared to controls and assuming that a p-value < 0.05 indicates statistical significance, the patients with MCDs exhibited significantly lower pH values and higher Mg(2+) levels. In addition, the patients with MCDs had lower GPC and PDE and an increased PME/PDE ratio.

SIGNIFICANCE

Mg(2+) and pH are important in the regulation of bioenergetics and are involved in many electrical activity pathways in the brain. Our data support the idea that neurometabolic impairments occur during seizure onset and propagation. The GPC, PDE, and PME/PDE abnormalities also demonstrate that there are membrane turnover disturbances in patients with MCDs.

Identification of amide protons of glutathione in MR spectra of tumour cells

Signals attributable to amide protons and used in previous studies to measure intracellular pH were observed in the low-field region of the (1)H-MR spectra of four tumour cell lines: T98G, MCF-7, A172 and HeLa. The signals were more intense in the spectra of the two cell lines (T98G and MCF-7) characterised by higher concentrations of glutathione (GSH). After comparison with (1)H-MR spectra of GSH in solution at different pH values, the peaks were attributed to NHs of the Cys and Gly residues of GSH. Modification of the intracellular concentration of GSH by treatment with buthionine sulfoximine produced comparable decreases in the intensity of aliphatic signals of GSH and NHs under examination. The assignment was therefore confirmed.

Targeted screening of cis-regulatory variation in human haplotypes

Regulatory cis-acting variants account for a large proportion of gene expression variability in populations. Cis-acting differences can be specifically measured by comparing relative levels of allelic transcripts within a sample. Allelic expression (AE) mapping for cis-regulatory variant discovery has been hindered by the requirements of having informative or heterozygous single nucleotide polymorphisms (SNPs) within genes in order to assign the allelic origin of each transcript. In this study we have developed an approach to systematically screen for heritable cis-variants in common human haplotypes across >1,000 genes. In order to achieve the highest level of information per haplotype studied, we carried out allelic expression measurements by using both intronic and exonic SNPs in primary transcripts. We used a novel RNA pooling strategy in immortalized lymphoblastoid cell lines (LCLs) and primary human osteoblast cell lines (HObs) to allow for high-throughput AE. Screening hits from RNA pools were further validated by performing allelic expression mapping in individual samples. Our results indicate that >10% of expressed genes in human LCLs show genotype-linked AE. In addition, we have validated cis-acting variants in over 20 genes linked with common disease susceptibility in recent genome-wide studies. More generally, our results indicate that RNA pooling coupled with AE read-out by second generation sequencing or by other methods provides a high-throughput tool for cataloging the impact of common noncoding variants in the human genome.