Relative Metabolite Ratios Research Articles

Urinary di(2-ethylhexyl)phthalate metabolite ratios in obese children of South Korea.

Phthalate exposure has been reported to be more associated with obesity in children than in adults. The concentration of di(2-ethylhexyl)phthalate (DEHP) was high temporal variability in spot urine, so additional tools of assessing DEHP exposure were required. Therefore, we used relative metabolite ratios (RMRs) as well as concentrations, and RMRs did not need to be corrected to the creatinine concentration. We aimed to evaluate the levels of urinary DEHP metabolites and their RMRs in obese children in South Korea, and to investigate the potential of RMRs for assessing the risks for childhood obesity. We analyzed the four urinary DEHP metabolites (mono-2-ethylhexyl phthalate (MEHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), and mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP)) in 240 children aged 5-16 years, using isotope dilution GC-MS/MS. The children were placed into three groups ("normal weight," "overweight," and "obese") according to body mass index (BMI) percentiles. We statistically compared the concentrations and RMRs of DEHP metabolites among these groups. The obese group had lower MEHP levels, and higher secondary metabolite (MEHHP, MEOHP, and MECPP) levels, than the normal weight group. DEHP metabolite levels did not differ significantly between the normal weight and obese groups, whereas RMRA2 (as the ratio of the molar concentrations of MEOHP to MEHHP) was found to be negatively associated with BMI percentile (β= -0.236, p <0.01) and weight percentile (β= -0.282, p<0.001). Therefore, we suggest that RMRs are an additional tool for assessing the health risks of DEHP.

Analysis of magnetic resonance spectroscopy relative metabolite ratios in mild traumatic brain injury and normative controls

We evaluated magnetic resonance spectroscopy (MRS) in United States military personnel with persistent symptoms after mild traumatic brain injury (mTBI), comparing over time two groups randomized to receive hyperbaric oxygen or sham chamber sessions and a third group of normative controls. Active-duty or veteran military personnel and normative controls underwent MRS outcome measures at baseline, 13 weeks (mTBI group only), and six months. Participants received 3.0 Tesla brain MRS for analysis of water-suppressed two-dimensional (2D) multivoxel 1H-MRS of the brain using point resolved spectroscopy (PRESS) with volume selection localized above the lateral ventricles and within the brain parenchyma, of which one voxel was chosen in each hemisphere without artifact. Script-based automatic data processing was used to assess N-acetylaspartate (NAA), creatine (Cr), and choline (Cho). Metabolite ratios for white matter were then calculated for NAA/Cr (Area), Cho/Cr (Area), and Cho/NAA (Area). These ratios were compared using standard analysis methodology. There were no observable differences between participants with mTBI and normative controls nor any observable changes over time in the NAA/Cr (area), Cho/Cr (area), and Cho/NAA (area) ratios. Similarly, the control and injured participants were indistinguishable. While participants with mild TBI showed no difference in MRS compared to normative controls, our results are limited by the few voxels chosen and potentially by less sensitive MRS markers.

Evaluating metabolites in patients with major depressive disorder who received mindfulness-based cognitive therapy and healthy controls using shortecho MRSI at 7 Tesla.

ObjectivesOur aim was to evaluate differences in metabolite levels between unmedicated patients with major depressive disorder (MDD) and healthy controls, to assess changes in metabolites in patients after they completed an 8-week course of mindfulness-based cognitive therapy (MBCT), and to exam the correlation between metabolites and depression severity.Materials and methodsSixteen patients with MDD and ten age- and gender-matched healthy controls were studied using 3D short echo-time (20 ms) magnetic resonance spectroscopic imaging (MRSI) at 7 Tesla. Relative metabolite ratios were estimated in five regions of interest corresponding to insula, anterior cingulate cortex (ACC), caudate, putamen, and thalamus.ResultsIn all cases, MBCT reduced severity of depression. The ratio of total choline-containing compounds/total creatine (tCr) in the right caudate was significantly increased compared to that in healthy controls, while ratios of N-acetyl aspartate (NAA)/tCr in the left ACC, myo-inositol/tCr in the right insula, and glutathione/tCr in the left putamen were significantly decreased. At baseline, the severity of depression was negatively correlated with my-inositol/tCr in the left insula and putamen. The improvement in depression severity was significantly associated with changes in NAA/tCr in the left ACC.ConclusionsThis study has successfully evaluated regional differences in metabolites for patients with MDD who received MBCT treatment and in controls using 7 Tesla MRSI.

Abstract 547: Diagnosis of lung tumor types based on metabolomic profiles in lymph node aspirates

Abstract Lung cancer is the leading cause of cancer-related deaths in the US and worldwide. The majority of lung cancer patients are diagnosed with an advanced stage, precluding curable surgical resection, and therapy is limited to thoracic radiation and chemotherapy. The efficacies have improved in recent years due to patient pre-selection based on the cytology of fine needle aspirates of lymph nodes, which harbor circulating tumor cells. We report herein the evaluation of lymph node aspirates for the presence of metabolite features that are suitable to distinguish patients with lung cancer from patients without malignancies and to separate patients with adenocarcinoma from patients with squamous cell carcinoma. The results provide evidence that patient groups can be separated based on their metabolite profiles. Multivariate statistical analyses (PLS and OPLS) produce a set of consensus features that can be further developed into clinical biomarkers. Two of the features were identified as kynurenine and oxidized glutathione, and their identities were confirmed in a second larger sample set. In addition, the accompanying metabolites glutamate, glutamine and tryptophan were included in the validation experiment to utilize relative metabolite ratios as indicators for corresponding enzyme activities. The validation results demonstrate significant differences in metabolites and metabolite ratios between lymph node aspirates harboring a circulating tumor cell and aspirates negative for malignancy. Subsequently, a second set of lymph node samples were analyzed for an extended panel of metabolites and of these 42 were suitable biomarker to be statistically significant to distinguish between at least one of the pair wise comparisons. Together the results demonstrate that metabolite profiles in lymph node aspirates are suitable to differentiate patients with adenocarcinoma from patients with squamous cell carcinoma. Citation Format: Daniel R. Sappington, Scott A. Helms, Eric Siegel, Susanne K. Jeffus, Teka Bartter, Thaddeus Bartter, Gunnar Boysen. Diagnosis of lung tumor types based on metabolomic profiles in lymph node aspirates. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 547. doi:10.1158/1538-7445.AM2015-547

Short-echo three-dimensional H-1 MR spectroscopic imaging of patients with glioma at 7 Tesla for characterization of differences in metabolite levels.

The purpose of this study was to evaluate the feasibility of using a short echo time, three-dimensional H-1 magnetic resonance spectroscopic imaging (MRSI) sequence at 7 Tesla (T) to assess the metabolic signature of lesions for patients with glioma. Twenty-nine patients with glioma were studied. MRSI data were obtained using CHESS water suppression, spectrally selective adiabatic inversion-recovery pulses and automatically prescribed outer-volume-suppression for lipid suppression, and spin echo slice selection (echo time = 30 ms). An interleaved flyback echo-planar trajectory was applied to shorten the total acquisition time (∼10 min). Relative metabolite ratios were estimated in tumor and in normal-appearing white and gray matter (NAWM, GM). Levels of glutamine, myo-inositol, glycine, and glutathione relative to total creatine (tCr) were significantly increased in the T2 lesions for all tumor grades compared with those in the NAWM (P < 0.05), while N-acetyl aspartate to tCr were significantly decreased (P < 0.05). In grade 2 gliomas, level of total choline-containing-compounds to tCr was significantly increased (P = 0.0137), while glutamate to tCr was significantly reduced (P = 0.0012). The improved sensitivity of MRSI and the increased number of metabolites that can be evaluated using 7T MR scanners is of interest for evaluating patients with glioma. This study has successfully demonstrated the application of a short-echo spin-echo MRSI sequence to detect characteristic differences in regions of tumor versus normal appearing brain.

In vivo enzymatic activity of acetylCoA synthetase in skeletal muscle revealed by 13C turnover from hyperpolarized [1-13C]acetate to [1-13C]acetylcarnitine

BackgroundAcetate metabolism in skeletal muscle is regulated by acetylCoA synthetase (ACS). The main function of ACS is to provide cells with acetylCoA, a key molecule for numerous metabolic pathways including fatty acid and cholesterol synthesis and the Krebs cycle. MethodsHyperpolarized [1-13C]acetate prepared via dissolution dynamic nuclear polarization was injected intravenously at different concentrations into rats. The 13C magnetic resonance signals of [1-13C]acetate and [1-13C]acetylcarnitine were recorded in vivo for 1min. The kinetic rate constants related to the transformation of acetate into acetylcarnitine were deduced from the 3s time resolution measurements using two approaches, either mathematical modeling or relative metabolite ratios. ResultsAlthough separated by two biochemical transformations, a kinetic analysis of the 13C label flow from [1-13C]acetate to [1-13C]acetylcarnitine led to a unique determination of the activity of ACS. The in vivo Michaelis constants for ACS were KM=0.35±0.13mM and Vmax=0.199±0.031μmol/g/min. ConclusionsThe conversion rates from hyperpolarized acetate into acetylcarnitine were quantified in vivo and, although separated by two enzymatic reactions, these rates uniquely defined the activity of ACS. The conversion rates associated with ACS were obtained using two analytical approaches, both methods yielding similar results. General significanceThis study demonstrates the feasibility of directly measuring ACS activity in vivo and, since the activity of ACS can be affected by various pathological states such as cancer or diabetes, the proposed method could be used to non-invasively probe metabolic signatures of ACS in diseased tissue.

The influence of the menstrual cycle on the result of brain examination with hydrogen magnetic resonance spectroscopy – a pilot study

Background and purposeHydrogen magnetic resonance spectroscopy (1HMRS) is nowadays one of the basic tools for noninvasive brain metabolism assessment. The study focuses on the important problem of the influence of hormone fluctuation during the menstrual cycle on brain metabolism, assessed by 1HMRS for clinical diagnostics. Material and methodsIn 11 healthy regularly menstruating women, 1HMRS was performed at the start (phase I), in the middle (phase II) and at the end (phase III) of the menstrual cycle. The relative concentration ratios of 12 brain metabolites in every woman in all cycle phases were examined, in 6 different volumes of interest (VOIs). Finally, statistically significant differences in relative metabolite ratios between the phases examined in given locations were sought. ResultsStatistically significant relations between menstrual cycle phases and relative ratios of 4 metabolites – Lac/Cr, NAA/Cr, Glx1/Cr and Glx2/Cr – in different brain locations were found. In all locations, mean NAA/Cr ratios were greater in phase I compared to the other phases. A similar relationship was found for Glx1/Cr ratio in one location (left occipital lobe). For Lac/Cr and Glx2/Cr ratios, a higher mean ratio value was obtained in phase II compared to phases I and III in the right occipital lobe and left basal ganglia, respectively. ConclusionsMenstrual cycle phase should be considered in planning a date and interpretation of 1HMRS examination, performed for the verification of a disease manifesting as brain metabolite disturbances in the 1HMRS spectrum.

Correlates of cognitive impairment in patients with leukoaraiosis by magnetic resonance spectroscopy

To explore the pathological changes in patients with leukoaraiosis (LA) by magnetic resonance spectroscopy (MRS) and examine its relationship with cognitive function. Twenty-three LA patients and 23 age and gender-matched healthy subjects were recruited from the Department of Neurology, Beijing Chaoyang Hospital, Capital Medical University between August 2010 and November 2010. All participants underwent the neuropsychological tests. Multi-voxel chemical shift imaging was performed and the regions of interest were positioned in bilateral frontal white matter. The relative metabolite ratios, involving N-acetyl aspartate/choline ratio (NAA/Cho), N-acetyl aspartate/creatine (NAA/Cr) and choline/creatine (Cho/Cr), were estimated. The correlation of the MRS data and the performance of cognitive function was analyzed. The LA patients were associated with a worse performance of mini mental state examination (MMSE) versus the healthy controls (24 ± 3 vs 28 ± 1, P < 0.05). Univariate analysis of the MRS data revealed the ratios of NAA/Cho and NAA/Cr significantly decreased in bilateral frontal white matter lesions in the LA group versus the control group (1.72 ± 0.20 vs 1.96 ± 0.36, 1.67 ± 0.17 vs 1.85 ± 0.21, P < 0.05). The values of NAA/Cr and NAA/Cho in normal appearing white matter increased versus the LA group (1.83 ± 0.24 vs 1.72 ± 0.20, 1.78 ± 0.28 vs 1.67 ± 0.17) and decreased versus the control group (1.83 ± 0.24 vs 1.96 ± 0.36, 1.78 ± 0.28 vs 1.85 ± 0.21). But no significant differences were found (P > 0.05). The ratio of Cho/Cr did not differ among 3 groups (P > 0.05). The pathological change of NAA/Cr in white matter lesion in LA patients was markedly correlated with the performance of MMSE (r = 0.47, P < 0.05). NAA may be a marker of axonal loss/dysfunction in LA patients. And the changes of NAA/Cr have a positive correlation with cognitive impairment.

Structural and neurochemical evaluation of the brain and pons in patients with Wilson’s disease

The aim of this study was to examine the structural-neurochemical abnormalities of the frontal white matter (FWM), deep gray matter nuclei, and pons in patients with Wilson's disease (WD) using proton magnetic resonance spectroscopy (MRS) and diffusion-weighted imaging (DWI). Nine patients with WD and 14 age-matched controls were examined with MRS. N-Acetylaspartate (NAA), choline (Cho), and creatine (Cr) peaks were calculated. DWI scans from six WD patients and six controls were also obtained. The relative metabolite ratios and apparent diffusion coefficient (ADC) values of the WD patients were compared to those of the control subjects by using statistical measures. Measurements in the thalamus and pons showed significantly lower NAA/Cho and NAA/Cr ratios in the WD group than in the control group (P < 0.05). Thalamic and pontine Cho/Cr ratios in the patient group were significantly higher than those of the control group (P < 0.05). No statistically significant relation was found between the patient and control groups as a result of the MRS examinations of FWM and all ADC measurements (P > 0.05). MRS is a noninvasive, valuable modality for detecting structural-neurochemical changes of the brain stem and deep gray matter in patients with WD. The contribution of DWI in these patients is limited.

A hierarchical spectral clustering and nonlinear dimensionality reduction scheme for detection of prostate cancer from magnetic resonance spectroscopy (MRS)

Magnetic resonance spectroscopy (MRS) has been shown to have great clinical potential as a supplement to magnetic resonance imaging in the detection of prostate cancer (CaP). MRS provides functional information in the form of changes in the relative concentration of specific metabolites including choline, creatine, and citrate which can be used to identify potential areas of CaP. With a view to assisting radiologists in interpretation and analysis of MRS data, some researchers have begun to develop computer-aided detection (CAD) schemes for CaP identification from spectroscopy. Most of these schemes have been centered on identifying and integrating the area under metabolite peaks which is then used to compute relative metabolite ratios. However, manual identification of metabolite peaks on the MR spectra, and especially via CAD, is a challenging problem due to low signal-to-noise ratio, baseline irregularity, peak overlap, and peak distortion. In this article the authors present a novel CAD scheme that integrates nonlinear dimensionality reduction (NLDR) with an unsupervised hierarchical clustering algorithm to automatically identify suspicious regions on the prostate using MRS and hence avoids the need to explicitly identify metabolite peaks. The methodology comprises two stages. In stage 1, a hierarchical spectral clustering algorithm is used to distinguish between extracapsular and prostatic spectra in order to localize the region of interest (ROI) corresponding to the prostate. Once the prostate ROI is localized, in stage 2, a NLDR scheme, in conjunction with a replicated clustering algorithm, is used to automatically discriminate between three classes of spectra (normal appearing, suspicious appearing, and indeterminate). The methodology was quantitatively and qualitatively evaluated on a total of 18 1.5 T in vivo prostate T2-weighted (w) and MRS studies obtained from the multisite, multi-institutional American College of Radiology (ACRIN) trial. In the absence of the precise ground truth for CaP extent on the MR imaging for most of the ACRIN studies, probabilistic quantitative metrics were defined based on partial knowledge on the quadrant location and size of the tumor. The scheme, when evaluated against this partial ground truth, was found to have a CaP detection sensitivity of 89.33% and specificity of 79.79%. The results obtained from randomized threefold and fivefold cross validation suggest that the NLDR based clustering scheme has a higher CaP detection accuracy compared to such commonly used MRS analysis schemes as z score and PCA. In addition, the scheme was found to be robust to changes in system parameters. For 6 of the 18 studies an expert radiologist laboriously labeled each of the individual spectra according to a five point scale, with 1/2 representing spectra that the expert considered normal and 3/4/5 being spectra the expert deemed suspicious. When evaluated on these expert annotated datasets, the CAD system yielded an average sensitivity (cluster corresponding to suspicious spectra being identified as the CaP class) and specificity of 81.39% and 64.71%, respectively.

1H-MR Spectroscopy of brain tumors in the course of radiation therapy: Use of fast spectroscopic imaging and single-voxel spectroscopy for diagnosing recurrence

To improve differential diagnosis of residual or recurrent tumor vs. tissue necrosis in the course of radiation therapy of neurosurgically-treated brain tumors by application of fast (1)H-MR spectroscopic imaging in combination with single-voxel spectroscopy (SVS). 54 patients after with malignant brain tumor (44 cases of glioblastoma, 10 other high-grade gliomas) were examined post-surgically in a total of 140 proton MRS examinations in the course of radiotherapy and in follow-up controls. Fast SI acquisition was performed as single-slice or double-slice TSI sequence with 32 x 32 phase encodings within 11 or 15 minutes, respectively. SVS with TR/TE 2000/272 ms yielded relative metabolite ratios, and in 15 patients the time courses of the absolute concentrations of brain metabolites were also determined. In the group of 44 patients that could be tracked by MRS until therapy completion, TSI localized in 23 patients a persistent or newly arisen distinct choline accumulation indicating residual or recurrent tumor after radiation therapy. In all these cases MRS diagnosis was confirmed histologically or by short-term follow-up. However, in 6 of 15 patients showing a normal choline pattern in the TSI acquisition, tumor recurrence appeared within three months. SVS provided early recognition of recurrent tumor when detecting characteristic alterations of metabolite concentrations oin therapy follow-up. TSI and SVS represent complementary MRS techniques and are able to diagnose tumor recurrence early and unambiguously in cases where focal choline accumulation is detected.

1H MR Spectroscopy of the Normal Human Brains: Comparison of Automated Prescan Method with Manual Method

Purpose : To evaluate regional differences in relative metabolite ratios in the normal human brain by 1H MRspectroscopy (MRS), and compare the spectral quality obtained by the automated prescan method (PROBE) and themanual method. Materials and Methods : Localized 1H MRS was performed on a GE 1.5T SIGNA MRI/MRS system (version5.5) with active shielded gradients. For 20 normal volunteers aged 8-47 years, spectral parameters were adjustedby the auto-prescan routine provided by a PROBE package(N=34)and manually (N=33). Five regions of the human brainwere examined (N=PROBE,manual): frontal white matter(N=6,10), parietal white matter(N=8,9), basal ganglia(N=6,5),thalamus(N=4,5), and cerebellum(N=4,4). For all spectra, a STEAM localization sequence with three-pulse CHESS H2Osuppression was used, with the following acquisition parameters: TR=3.0 sec, TE=30 msec, TM=13,7 msec, SW=2500Hz,SI=2048 pts, AVG=48, and NEX=2. Results : A total of 61 reliable spectra were obtained by PROBE (28/34=82%success) and by the manual method (33/33=100% success). Regional differences in the spectral patterns of the fiveregions were clearly demonstrated by both PROBE and the manual methods. For prescanning, the manual method tookslightly longer than PROBE (3-5 mins and 2 mins,respectively). There were no significant differences in spectralpatterns and relative metabolic ratios between the two methods. However, auto-prescan by PROBE seemed to be veryvulnerable to slight movement by patients, and in three cases, an acceptable spectrum was thus not obtained.Conclusion : PROBE is a highly practical and reliable method for single voxel 1H MRS of the human brain; the twomethods of prescanning do not result in significantly different spectral patterns and the relative metaboliteratios. PROBE, however, is vulnerable to slight movement by patients, and if the success rate for obtainingquality spectra is to be increased, regardless of the patient's condition and the region of the brain, it must beused in conjunction with the manual method.

Identification of metoclopramide metabolites in the urine of cattle by gas chromatography-mass spectrometry and high-performance liquid chromatography-photodiode array detection.

The urinary metabolites of metoclopramide (4-amino-5-chloro-N-[2-diethylaminoethyl]-2-methoxybenzamide) were identified in cows. The drug was administered intravenously, voided urine was collected, and individual urine extracts were analysed by gas chromatography-mass spectrometry and high-performance liquid chromatography-photodiode array detection. The parent compound and one major metabolite (4-amino-5-chloro-N-[2-(ethylamino)ethyl]-2-methoxybenzamide) were common to all individuals. In addition to the parent and major metabolite, a second, minor metabolite was identified in two cows as 4-amino-5-chloro-N-[2-(diethylamino)ethyl]-2-hydroxybenzamide. The identity of the minor metabolite was confirmed by comparison with a standard synthesized by a new method. Metabolite identification and characterization in food animal species allows the design of safety and environmental impact studies and relative metabolite ratios between dose treatment groups.