Search

INTRODUCTION: Analyses of cerebrospinal fluid (CSF) metabolites in large, healthy populations have been limited and potential demographic moderators of brain metabolism are largely unknown. OBJECTIVE: Our objective in this study was to examine sex and race differences in 33 CSF metabolites within a sample of 129 healthy individuals (37 African American women, 29 white women, 38 African American men, and 25 white men). METHODS: CSF metabolites were measured with a targeted electrochemistry-based metabolomics platform. Sex and race differences were quantified with both univariate and multivariate analyses. Type I error was controlled for by using a Bonferroni adjustment (.05/33 = .0015). RESULTS: Multivariate Canonical Variate Analysis (CVA) of the 33 metabolites showed correct classification of sex at an average rate of 80.6% and correct classification of race at an average rate of 88.4%. Univariate analyses revealed that men had significantly higher concentrations of cysteine (p

BackgroundWe aimed at exploring potential pathophysiological processes across psychotic disorders, applying metabolomics in a large and well-characterized sample of patients and healthy controls.MethodsPatients with schizophrenia and bipolar disorders (N = 212) and healthy controls (N = 68) had blood sampling with subsequent metabolomics analyses using electrochemical coulometric array detection. Concentrations of 52 metabolites including tyrosine, tryptophan and purine pathways were compared between patients and controls while controlling for demographic and clinical characteristics. Significant findings were further tested in medication-free subsamples.ResultsSignificantly decreased plasma concentrations in patients compared to healthy controls were found for 3-hydroxykynurenine (3OHKY, p = 0.0008), xanthurenic acid (XANU, p = 1.5×10−5), vanillylmandelic acid (VMA, p = 4.5×10−5) and metanephrine (MN, p = 0.0001). Plasma concentration of xanthine (XAN) was increased in the patient group (p = 3.5×10−5). Differences of 3OHKY, XANU, VMA and XAN were replicated across schizophrenia spectrum disorders and bipolar disorders subsamples of medication-free individuals.ConclusionsAlthough prone to residual confounding, the present results suggest the kynurenine pathway of tryptophan metabolism, noradrenergic and purinergic system dysfunction as trait factors in schizophrenia spectrum and bipolar disorders. Of special interest is XANU, a metabolite previously not found to be associated with bipolar disorders.

Millions of patients suffer from major depressive disorder (MDD), but many do not respond to selective serotonin reuptake inhibitor (SSRI) therapy. We used a pharmacometabolomics-informed pharmacogenomics research strategy to identify genes associated with metabolites that were related to SSRI response. Specifically, 306 MDD patients were treated with citalopram or escitalopram and blood was drawn at baseline, 4 and 8 weeks for blood drug levels, genome-wide single nucleotide polymorphism (SNP) genotyping and metabolomic analyses. SSRI treatment decreased plasma serotonin concentrations (P

Objective: Huntington’s disease (HD) is a rare neurodegenerative disease caused by the expansion of an N-terminal repeat in the huntingtin protein. The protein is expressed in all cells in the body; hence, peripheral tissues, such as blood, may recapitulate processes in the brain. The plasma metabolome may provide a window into active processes that influence brain health and a unique opportunity to noninvasively identify processes that may contribute to neurodegeneration. Alterations in metabolic pathways in brain have been shown to profoundly impact HD. Therefore, identification and quantification of critical metabolomic perturbations could provide novel biomarkers for disease onset and disease progression. Methods: We analyzed the plasma metabolomic profiles from 52 premanifest (PHD), 102 early symptomatic HD, and 140 healthy controls (NC) using liquid chromatography coupled with a highly sensitive electrochemical detection platform. Results: Alterations in tryptophan, tyrosine, purine, and antioxidant pathways were identified, including many related to energetic and oxidative stress and derived from the gut microbiome. Multivariate statistical modeling demonstrated mutually distinct metabolomic profiles, suggesting that the processes that determine onset were likely distinct from those that determine progression. Gut microbiome-derived metabolites particularly differentiated the PHD metabolome, while the symptomatic HD metabolome was increasingly influenced by metabolites that may reflect mutant huntingtin toxicity and neurodegeneration. Interpretation: Understanding the complex changes in the delicate balance of the metabolome and the gut microbiome in HD, and how they relate to disease onset, progression, and phenotypic variability in HD are critical questions for future research.

Major depressive disorder (MDD) is a heterogeneous disease. Efforts to identify biomarkers for sub-classifying MDD and antidepressant therapy by genome-wide association studies (GWAS) alone have generally yielded disappointing results. We applied a metabolomics-informed genomic research strategy to study the contribution of genetic variation to MDD pathophysiology by assaying 31 metabolites, including compounds from the tryptophan, tyrosine, and purine pathways, in plasma samples from 290 MDD patients. Associations of metabolite concentrations with depressive symptoms were determined, followed by GWAS for selected metabolites and functional validation studies of the genes identified. Kynurenine (KYN), the baseline plasma metabolite that was most highly associated with depressive symptoms, was negatively correlated with severity of those symptoms. GWAS for baseline plasma KYN concentrations identified SNPs across the beta-defensin 1 (DEFB1) and aryl hydrocarbon receptor (AHR) genes that were cis-expression quantitative trait loci (eQTLs) for DEFB1 and AHR mRNA expression, respectively. Furthermore, the DEFB1 locus was associated with severity of MDD symptoms in a larger cohort of 803 MDD patients. Functional studies demonstrated that DEFB1 could neutralize lipopolysaccharide-stimulated expression of KYN-biosynthesizing enzymes in monocytic cells, resulting in altered KYN concentrations in the culture media. In addition, we demonstrated that AHR was involved in regulating the expression of enzymes in the KYN pathway and altered KYN biosynthesis in cell lines of hepatocyte and astrocyte origin. In conclusion, these studies identified SNPs that were cis-eQTLs for DEFB1 and AHR and, which were associated with variation in plasma KYN concentrations that were related to severity of MDD symptoms.

Mental stress induced left ventricular dysfunction (LVD) has been associated with a greater risk of adverse events in coronary heart disease (CHD) patients independent of conventional risk indicators. The underlying biochemical mechanisms of this cardiovascular condition are poorly understood. Our objective was to use metabolomics technology to identify biochemical changes that co-occur with mental stress-induced LVD in patients with clinically stable CHD. Participants were adult CHD patients who were recruited for mental stress-induced myocardial ischemia screening. For this study, we randomly selected 30 patients representing the extremes of the mental stress-induced left ventricular ejection fraction (LVEF) change distribution; 15 who showed LVD (i.e. LVEF reduction ≥5) and 15 who showed a normal left ventricular response (NLVR; i.e. a LVEF increase of ≥5) to three mental stressors. An electrochemistry based metabolomics platform was used to profile pre- and post-stress serum samples yielding data for 22 known compounds, primarily within the tyrosine, tryptophan, purine and methionine pathways. There were significant stress-induced changes in several compounds. A comparison between the NLVR and LVD groups showed significant effects for kynurenine (p = .036, N-acetylserotonin (p = .054), uric acid (p = .015), tyrosine (p = .019) and a trend for methionine (p = .065); the NLVR group showed a significantly greater stress-induced reduction in all of those compounds compared to the LVD group. Many of these biochemicals have been implicated in other stress-related phenomena and are plausible candidates for mechanisms underlying LVD in response to mental stress.

Previous research has shown an association between hostility and fasting glucose in African American women. Central nervous system serotonin activity is implicated both in metabolic processes and in hostility related traits.The purpose of this study is to determine whether central nervous system serotonin influences the association between hostility and fasting glucose in African American women.The study consisted of 119 healthy volunteers (36 African American women, 27 White women, 21 White males, and 35 African American males, mean age 34 ± 8.5 years). Serotonin related compounds were measured in cerebrospinal fluid. Hostility was measured by the Cook-Medley Hostility Scale.Hostility was associated with fasting glucose and central nervous system serotonin related compounds in African American women only. Controlling for the serotonin related compounds significantly reduced the association of hostility to glucose.The positive correlation between hostility and fasting glucose in African American women can partly be explained by central nervous system serotonin function.

We measured the levels of mutant huntingtin (mtHtt) and total huntingtin (tHtt) in blood leukocytes from Prospective Huntington At-Risk Observational Study (PHAROS) subjects at 50% risk of carrying the Huntington disease mutation using a homogeneous time-resolved fluorescence (HTRF) assay to assess its potential as a biomarker.Peripheral blood mononuclear cells from consenting PHAROS subjects were analyzed by HTRF using antibodies that simultaneously measured mtHtt and tHtt. mtHtt levels were normalized to tHtt, double-stranded DNA, or protein and analyzed according to cytosine-adenine-guanine repeat length (CAGn), demographics, predicted time to clinical onset or known time since clinical onset, and available clinical measures.From 363 assayed samples, 342 met quality control standards. Levels of mtHtt and mt/tHtt were higher in 114 subjects with expanded CAG repeats (CAG ≥ 37) compared with 228 subjects with nonexpanded CAG repeats (CAG37) (p0.0001). Analysis of relationships to predicted time to onset or to phenoconversion suggested that the HTRF signal could mark changes during the Huntington disease prodrome or after clinical onset.The HTRF assay can effectively measure mtHtt in multicenter sample sets and may be useful in trials of therapies targeting huntingtin.

Huntington disease (HD) is a neurodegenerative disorder that involves preferential atrophy in the striatal complex and related subcortical nuclei. In this article, which is based on a dataset extracted from the PREDICT-HD study, we use statistical shape analysis with deformation markers obtained through "Large Deformation Diffeomorphic Metric Mapping" of cortical surfaces to highlight specific atrophy patterns in the caudate, putamen, and globus pallidus, at different prodromal stages of the disease. On the basis of the relation to cortico-basal ganglia circuitry, we propose that statistical shape analysis, along with other structural and functional imaging studies, may help expand our understanding of the brain circuitry affected and other aspects of the neurobiology of HD, and also guide the most effective strategies for intervention.

A major goal of current clinical research in Huntington's disease (HD) has been to identify preclinical and manifest disease biomarkers, as these may improve both diagnosis and the power for therapeutic trials. Although the underlying biochemical alterations and the mechanisms of neuronal degeneration remain unknown, energy metabolism defects in HD have been chronicled for many years. We report that the brain isoenzyme of creatine kinase (CK-BB), an enzyme important in buffering energy stores, was significantly reduced in presymptomatic and manifest disease in brain and blood buffy coat specimens in HD mice and HD patients. Brain CK-BB levels were significantly reduced in R6/2 mice by approximately 18% to approximately 68% from 21 to 91 days of age, while blood CK-BB levels were decreased by approximately 14% to approximately 44% during the same disease duration. Similar findings in CK-BB levels were observed in the 140 CAG mice from 4 to 12 months of age, but not at the earliest time point, 2 months of age. Consistent with the HD mice, there was a grade-dependent loss of brain CK-BB that worsened with disease severity in HD patients from approximately 28% to approximately 63%, as compared to non-diseased control patients. In addition, CK-BB blood buffy coat levels were significantly reduced in both premanifest and symptomatic HD patients by approximately 23% and approximately 39%, respectively. The correlation of CK-BB as a disease biomarker in both CNS and peripheral tissues from HD mice and HD patients may provide a powerful means to assess disease progression and to predict the potential magnitude of therapeutic benefit in this disorder.

Oral sodium phenylbutyrate (SPB) is currently under investigation as a histone deacetylation (HDAC) inhibitor in Huntington disease (HD). Ongoing studies indicate that symptoms related to HD genetic abnormalities decrease with SPB therapy. In a recently reported safety and tolerability study of SPB in HD, we analyzed overall chromatographic patterns from a method that employs gradient liquid chromatography with series electrochemical array, ultraviolet (UV), and fluorescence (LCECA/UV/F) for measuring SPB and its metabolite phenylacetate (PA). We found that plasma and urine from SPB-treated patients yielded individual-specific patterns of approximately 20 metabolites that may provide a means for the selection of subjects for extended trials of SPB. The structural identification of these metabolites is of critical importance because their characterization will facilitate understanding the mechanisms of drug action and possible side effects. We have now developed an iterative process with LCECA, parallel LCECA/LCMS, and high-performance tandem MS for metabolite characterization. Here we report the details of this method and its use for identification of 10 plasma and urinary metabolites in treated subjects, including indole species in urine that are not themselves metabolites of SPB. Thus, this approach contributes to understanding metabolic pathways that differ among HD patients being treated with SPB.

Mapping metabolic “signatures” can provide new insights into addictive mechanisms and potentially identify biomarkers and therapeutic targets. We examined the differences in metabolites related to the tyrosine, tryptophan, purine, and oxidative stress pathways between cocaine-dependent subjects and healthy controls. Several of these metabolites serve as biological indices underlying the mechanisms of reinforcement, toxicity, and oxidative stress. Metabolomic analysis was performed in 18 DSM-IV-diagnosed cocaine-dependent individuals with at least 2 weeks of abstinence and ten drug-free controls. Plasma concentrations of 37 known metabolites were analyzed and compared using a liquid chromatography electrochemical array platform. Multivariate analyses were used to study the relationship between severity of drug use [Addiction Severity Index (ASI) scores] and biological measures. Cocaine subjects showed significantly higher levels of n-methylserotonin (p

The objective of the study was to establish the safety and pharmacodynamics of escalating dosages of sodium phenylbutyrate (NaPB) in participants with ALS. Transcription dysregulation may play a role in the pathogenesis of ALS. Sodium phenylbutyrate, a histone deacetylase inhibitor, improves transcription and post-transcriptional pathways, promoting cell survival in a mouse model of motor neuron disease. Forty research participants at eight sites enrolled in an open-label study. Study medication was increased from 9 to 21 g/day. The primary outcome measure was tolerability. Secondary outcome measures included adverse events, blood histone acetylation levels, and NaPB blood levels at each dosage. Twenty-six participants completed the 20-week treatment phase. NaPB was safe and tolerable. No study deaths or clinically relevant laboratory changes occurred with NaPB treatment. Histone acetylation was decreased by approximately 50% in blood buffy-coat specimens at screening and was significantly increased after NaPB administration. Blood levels of NaPB and the primary metabolite, phenylacetate, increased with dosage. While the majority of subjects tolerated higher dosages of NaPB, the lowest dose (9 g/day), was therapeutically efficient in improving histone acetylation levels.

Pathological-length polyglutamine (Q(n)) expansions, such as those that occur in the huntingtin protein (htt) in Huntington's disease (HD), are excellent substrates for tissue transglutaminase in vitro, and transglutaminase activity is increased in post-mortem HD brain. However, direct evidence for the participation of tissue transglutaminase (or other transglutaminases) in HD patients in vivo is scarce. We now report that levels of N(epsilon)-(gamma-L-glutamyl)-L-lysine (GGEL)--a 'marker' isodipeptide produced by the transglutaminase reaction--are elevated in the CSF of HD patients (708 +/- 41 pmol/mL, SEM, n = 36) vs. control CSF (228 +/- 36, n = 27); p < 0.0001. These data support the hypothesis that transglutaminase activity is increased in HD brain in vivo.

Transglutaminases (TGases) catalyze several reactions with protein substrates, including formation of gamma-glutamyl-epsilon-lysine cross-links and gamma-glutamylpolyamine residues. The resulting gamma-glutamylamines are excised intact during proteolysis. TGase activity is altered in several diseases, highlighting the importance of in situ enzymatic determinations. Previous work showed that TGase activity (as measured by an in vitro assay) and free gamma-glutamyl-epsilon-lysine levels are elevated in Huntington disease (HD) and that gamma-glutamyl-epsilon-lysine is increased in HD CSF. Although free gamma-glutamyl-epsilon-lysine was used in these studies as an index of in situ TGase activity, gamma-glutamylpolyamines may also be diagnostic. We have devised methods for the simultaneous determination of four gamma-glutamylamines in CSF: gamma-glutamyl-epsilon-lysine, gamma-glutamylspermidine, gamma-glutamylputrescine, and bis-gamma-glutamylputrescine and showed that all are present in normal human CSF at concentrations of approximately 150, 670, 40, and 240 nM, respectively. The high gamma-glutamylspermidine/gamma-glutamylputrescine and gamma-glutamylspermidine/bis-gamma-glutamylputrescine ratios presumably reflect in part the large spermidine to putrescine mole ratio in human brain. We also showed that all four gamma-glutamylamines are elevated in HD CSF. Our findings support the hypotheses that (i) gamma-glutamylpolyamines are reflective of TGase activity in human brain, (ii) polyamination is an important post-translational modification of brain proteins, and (iii) TGase-catalyzed modification of proteins is increased in HD brain.

A novel approach to the parallel coupling of normal-bore high-performance liquid chromatography (LC) with electrochemical-array detection (EC-array) and nanoelectrospray mass spectrometry (MS), based on the use of a nanosplitting interface, is described where both detectors are utilized at their optimal detection mode for parallel configuration. The dual detection platform was shown to maintain full chromatographic integrity with retention times and peak widths at half-height between the EC-array and MS displaying high reproducibility with relative standard deviations of

Parkinson's disease (PD) is a progressive neurodegenerative disorder for which there is no current therapy preventing cumulative neuronal loss. There is substantial evidence that mitochondrial dysfunction, oxidative stress, and associated caspase activity underlie the neurodegeneration observed. One potential drug therapy is the potent free radical scavenger and antioxidant cystamine, which has demonstrated significant clinical potential in models of neurodegenerative disorders and human neurological disease. This study examined the oral efficacy of cystamine in the MPTP and 6-hydroxydopamine neurotoxin models of PD. The neuroprotective effects of cystamine treatment significantly ameliorated nigral neuronal loss, preserved striatal dopaminergic projections, and improved striatal dopamine and metabolite levels, as compared to MPTP alone. Cystamine normalized striatal 8-hydroxy-2′-deoxyguanosine levels and ATP concentrations, consistent with reduced oxidative stress and improved mitochondrial function. Cystamine also protected against MPTP-induced mitochondrial loss, as identified by mitochondrial heat shock protein 70 and superoxide dismutase 2, with concomitant reductions in cytochrome c and caspase-3 activities. The neuroprotective value of cystamine was confirmed in the 6-hydroxydopamine model. Together these findings show cystamine's therapeutic benefit to reduce neuronal loss through attenuation of oxidative stress and mitochondrial dysfunction, providing the rationale for human clinical trials in PD patients.

Huntington's disease (HD) is a progressive neurodegenerative disease caused by a glutamine expansion within huntingtin protein. The exact pathological mechanisms determining disease onset and progression remain unclear. However, aggregates of insoluble mutant huntingtin (mhtt), a hallmark of HD, are readily detected within neurons in HD brain. Although aggregated polyglutamines may not be inherently toxic, they constitute a biomarker for mutant huntingtin useful for developing therapeutics. We previously reported that the small molecule, C2-8, inhibits polyglutamine aggregation in cell culture and brain slices and rescues degeneration of photoreceptors in a Drosophila model of HD. In this study, we assessed the therapeutic potential of C2-8 in the R6/2 mouse model of HD, which has been used to provide proof-of-concept data in considering whether to advance therapies to human HD. We show that, at nontoxic doses, C2-8 penetrates the blood–brain barrier and is present in brain at a high concentration. C2-8-treated mice showed improved motor performance and reduced neuronal atrophy and had smaller huntingtin aggregates. There have been no prior drug-like, non-toxic, brain-penetrable aggregation inhibitors to arise from cell-based high-throughput screens for reducing huntingtin aggregation that is efficacious in preclinical in vivo models. C2-8 provides an essential tool to help elucidate mechanisms of neurodegeneration in HD and a therapeutic lead for further optimization and development.

There is substantial evidence that a bioenergetic defect may play a role in the pathogenesis of Huntington's Disease (HD). A potential therapy for remediating defective energy metabolism is the mitochondrial cofactor, coenzyme Q10 (CoQ10). We have reported that CoQ10 is neuroprotective in the R6/2 transgenic mouse model of HD. Based upon the encouraging results of the CARE-HD trial and recent evidence that high-dose CoQ10 slows the progressive functional decline in Parkinson's disease, we performed a dose ranging study administering high levels of CoQ10 from two commercial sources in R6/2 mice to determine enhanced efficacy. High dose CoQ10 significantly extended survival in R6/2 mice, the degree of which was dose- and source-dependent. CoQ10 resulted in a marked improvement in motor performance and grip strength, with a reduction in weight loss, brain atrophy, and huntingtin inclusions in treated R6/2 mice. Brain levels of CoQ10 and CoQ9 were significantly lower in R6/2 mice, in comparison to wild type littermate control mice. Oral administration of CoQ10 elevated CoQ10 plasma levels and significantly increased brain levels of CoQ9, CoQ10, and ATP in R6/2 mice, while reducing 8-hydroxy-2-deoxyguanosine concentrations, a marker of oxidative damage. We demonstrate that high-dose administration of CoQ10 exerts a greater therapeutic benefit in a dose dependent manner in R6/2 mice than previously reported and suggest that clinical trials using high dose CoQ10 in HD patients are warranted.

Objective interpretation of metabolomics data requires understanding both analytical and biological measurement errors. Here we address analytical measurement errors, the sources of these errors, and how this variability can impact metabolomic profiles. Sources considered include room temperature exposure (which could affect sample stability), spiking with authentic standards, the number of study replicates, the overall temporal design of the experimental series, and the complexity of the biological matrix of the samples (individual or pooled sera). The study focused on the analysis of ∼80 rat sera metabolites by HPLC coupled with coulometric array detectors. Time delay and room temperature exposure had minimal effects on the total relative metabolite concentrations and variability (mean: ∼94–98% of control, CVmedian: ±5–7%), but the concentrations of some specific metabolites were significantly altered. Changes observed in the concentrations of specific metabolites ranged as high as ±7-fold, with changes in variability ranging from 0.3% to 68%. Spiked samples demonstrated more complex behavior when allowed to decay over time than did control samples. The spiking of sera and standards with 43 known metabolites increased variability of the apparent concentrations of metabolites up to ∼24% as opposed to ∼3% in pure sera. Increased variability was metabolite-specific. In both pure and spiked sera, ∼80–95% of metabolites had CVs equivalent to standard analytical CVs for these metabolites. Experimental design, number of replicates, and complexity of the biological matrix had comparable effects. These results suggest that, under carefully controlled conditions, these analytical issues are not significant sources of variability relative to biological variation for most metabolites.

Motor neuron diseases (MND) are a heterogeneous group of disorders that includes amyotrophic lateral sclerosis (ALS) and result in death of motor neurons. These diseases may produce characteristic perturbations of the metabolome, the collection of small-molecules (metabolites) present in a cell, tissue, or organism. To test this hypothesis, we used high performance liquid chromatography followed by electrochemical detection to profile blood plasma from 28 patients with MND and 30 healthy controls. Of 317 metabolites, 50 were elevated in MNDpatients and more than 70 were decreased (p < 0.05). Among the compounds elevated, 12 were associated with the drug Riluzole. In a subsequent study of 19 subjects with MND who were not taking Riluzole and 33 healthy control subjects, six compounds were significantly elevated in MND, while the number of compounds with decreased concentration was similar to study 1. Our data also revealed a distinctive signature of highly correlated metabolites in a set of four patients, three of whom had lower motor neuron (LMN) disease. In both datasets we were able to separate MND patients from controls using multivariate regression techniques. These results suggest that metabolomic studies can be used to ascertain metabolic signatures of disease in a non-invasive fashion. Elucidation of the structures of signature molecules in ALS and other forms of MND should provide insight into aberrant biochemical pathways and may provide diagnostic markers and targets for drug design.

Metabolic serotypes sensitive to caloric intake may enable sera metabolomic profiles to validate epidemiological parameters and predict disease risk in humans. This long-range goal is complicated by the lack of known state markers and the requirement for simultaneous monitoring of multiple small changes. Therefore, analytical precision for appropriate high data density studies using HPLC separations coupled with coulometric array detectors was evaluated over a two month period in pooled rat sera samples (previously collected and stored at −80 °C), and in authentic biochemical standards. In sera, mean coefficients of variation (CV) of retention time and ratio accuracy within the established metabolic serotype varied within ±1% and ±3%, respectively. In sets of purified standards, the same parameters fluctuated, correspondently, in ranges of ±0.1% and ±1%. Median CV of the metabolite concentrations were ~13% in standards and ~11–19% in sera, and varied non-monotonically with the analytical system status and experimental design. These parameters were shown to be sufficiently controlled so as not to dominate intra-group biological variability in serum metabolomics studies. Continuation of experimental runs across an analytical breakpoint (column replacement) was associated with disproportionate changes in metabolite concentrations, independent of maintained analytical precision. These changes were sufficient to shift overall profile localization in megavariate projection analyses. We developed a mathematical approach to normalize this break and use partial least squares projection to latent structure discriminant analysis to confirm validity of this normalization approach. This generally applicable mathematical correction helps enable longer term high data density studies by removing a critical source of systemic variation.

Mitochondrial toxicity of nucleoside analogues has been proposed to be the etiology of a range of side-effects from antiretroviral therapy of HIV infection. In this study, urinary 8-hydroxy-2'-deoxyguanosine (8OH2'dG), a metabolite of oxidized DNA, was measured to determine if antiretroviral therapy leads to oxidative damage to DNA. A cross-sectional study was carried out measuring urinary 8OH2'dG in three groups of HIV-infected patients: (1) antiretroviral medication naïve, (2) patients on antiretroviral medications without lipodystrophy and (3) patients on antiretroviral medications with lipodystrophy. Twenty-five patients were enrolled in each group. The mean spot urinary 8OH2'dG measurements per mg creatinine for the three groups were: antiretroviral naïve 4.27 +/- 0.61 (ng 8OH2'dG/mg creatinine +/- SEM), on antiretroviral medications without lipodystrophy 2.88 +/- 0.26, and on antiretroviral medications with lipodystrophy 3.27 +/- 0.30. The differences between the means of the three groups is not statistically significant (p = 0.055), and these results are not significantly different from reported values for healthy controls [A carbon column-based liquid chromatography electrochemical approach to routine 8-hydroxy-2-deoxyguanosine measurements in urine and other biologic matrices: a one-year evaluation of methods. Free Radical Biology and Medicine 27 (1999) 647-666].

The precise cause of neuronal death in Huntington's disease (HD) is unknown. Proteolytic products of the huntingtin protein can contribute to toxic cellular aggregates that may be formed in part by tissue transglutaminase (Tgase). Tgase activity is increased in HD brain. Treatment in R6/2 transgenic HD mice, using the transglutaminase inhibitor cystamine, significantly extended survival, improved body weight and motor performance, and delayed the neuropathological sequela. Tgase activity and N(Sigma)-(gamma-L-glutamyl)-L-lysine (GGEL) levels were significantly altered in HD mice. Free GGEL, a specific biochemical marker of Tgase activity, was markedly elevated in the neocortex and caudate nucleus in HD patients. Both Tgase and GGEL immunoreactivities colocalized to huntingtin aggregates. Cystamine treatment normalized transglutaminase and GGEL levels in R6/2 mice. These findings are consistent with the hypothesis that transglutaminase activity may play a role in the pathogenesis of HD, and they identify cystamine as a potential therapeutic strategy for treating HD patients.

Our research seeks to identify a serum profile, or serotype, that reflects substantial changes in food intake. Earlier studies demonstrated that a number of low-molecular-weight, redox-active compounds of metabolome were sufficiently stable analytically and biologically to identify biomarkers of dietary restriction (DR, restriction of total food intake) in rats. A second initial requirement is to demonstrate feasibility, i.e., that concentration changes in selected serum metabolites can contain sufficient information to classify rats by diet. The current study distinguished 101 (female) and 112 (male) chromatographically identifiable compounds that differ between ad libitum (AL) consumption and DR 6-mo-old rats. In a cohort of female rats, both hierarchical cluster analysis (HCA) and principal component analyses (PCA) could distinguish dietary groups with 100% efficiency (101 metabolites). Repeating the classification studies using the 63 biologically and analytically most robust metabolites decreased noise without affecting categorical separation. In a cohort of male rats, PCA, but not HCA, distinguished the original dietary groups with 100% accuracy (112 metabolites). A subset of 52 of the 112 metabolites enabled both HCA and PCA to group the male rats with 100% accuracy. These data demonstrate that quantitative analysis of selected serum metabolites can yield sufficient information by which to classify the dietary intake of a group of rats, identify such markers chromatographically and set the stage for validation of these metabolic serotypes in independent datasets.

Objective: To assess the safety and tolerability of high-dose creatine, the feasibility of enrolling premanifest and 50% at-risk subjects in a prevention trial, and the potential of cognitive, imaging, and blood markers. Methods: Sixty-four eligible consenting participants were randomly allocated (1:1) to 15 g twice daily of creatine monohydrate or placebo for a 6-month double-blind phase followed by a 12-month open-label extension. Subjects included premanifest (tested) and at-risk (not tested) individuals without clinical symptoms or signs of Huntington disease (HD). Primary outcomes were safety and tolerability. Exploratory endpoints included fine motor, visuospatial, and memory performance; structural and diffusion MRI; and selected blood markers. Results: Forty-seven HD carriers and 17 non-HD controls were enrolled. Fifteen discontinued treatment (2 assigned to placebo); all were followed for the entire study period. Primary analysis was by intent to treat. The most common adverse events were gastrointestinal. Neuroimaging demonstrated treatment-related slowing of cortical and striatal atrophy at 6 and 18 months. Conclusion: We describe a design that preserves the autonomy of subjects not wanting genetic testing while including controls for assessing the specificity of treatment effects. Our results demonstrate the feasibility of prevention trials for HD and the safety of high-dose creatine, provide possible evidence of disease modification, support future studies of creatine, and illustrate the value of prodromal biomarkers. Classification of evidence: This study provides Class I evidence that high-dose creatine is safe and tolerable.

This report, the first in a series on diet-dependent changes in the serum metabolome (metabolic serotype), describes validation of the use of high performance liquid chromatography (HPLC) separations coupled with Coulometric array detectors to characterize changes in the metabolome. The long-term aim of these studies is to improve understanding of the effects of significant variation in nutritive status on physiology and on disease processes. Initial studies focus on identifying the effects of dietary (or caloric) restriction on the redox-active components of rat serum. Identification of compounds of interest is being carried out using HPLC separations coupled with coulometric array analysis, an approach allowing simultaneous examination of nearly 1200 serum compounds. The technical and practical issues discussed in this report are related to both analytical validity (HPLC running conditions, computer-automated peak identification, mathematical compensation for chromatographic drift, etc.) and biological variability (individual variability, cohort-cohort variability, outliers). Attention to these issues suggests approximately 250 compounds in serum are sufficiently reliable, both analytically and biologically, for potential use in building mathematical models of serotype.

8-Hydroxy-2'-deoxyguanosine (8OH2'dG) is a principal stable marker of hydroxyl radical damage to DNA. It has been related to a wide variety of disorders and environmental insults, and has been proposed as a useful systematic marker of oxidative stress. Analytic procedures for 8OH2'dG in DNA digests are well established; however, routine measurement of free 8OH2'dG in other body fluids such as urine or plasma has been problematic. This has hindered its evaluation as a general clinical, therapeutic monitoring, or environmental assessment tool. Therefore, we developed a liquid chromatography electrochemical column-switching system based on the use of the unique purine selectivity of porous carbon columns that allows routine accurate measurement of 8OH2'dG in a variety of biologic matrices. This paper describes the rationale of the system design and the protocols developed for 8OH2'dG in urine, plasma, cerebrospinal fluid, tissue, DNA, saliva, sweat, kidney dialysis fluid, foods, feces, culture matrix, and microdialysates. Concentrations in both human and animal body fluids and tissues are reported. The system performance is discussed in the context of a 1-year evaluation of the methods applied to approximately 3600 samples, using internal quality control and external blind testing to determine long-term accuracy. The methods are reliable and accurate, and therefore should prove useful in assessing the role and utility of oxidative DNA damage in aging and human illness.

Studies of the interaction between oxidative stress and mitochondrial dysfunction are complicated by analytical limitations, especially the need to assess multiple parameters in relatively small samples. We have addressed this problem by developing a methodology for the simultaneous analysis of the majority of low-molecular-weight, redox-active compounds from mitochondria using HPLC separations followed by coulometric array detection. The method described should also be applicable for the study of redox-active compounds in other subcellular organelles as well as in intact cells and tissues. The protocol described enables simultaneous measurement of antioxidants (e.g., tocopherols, ascorbate, lipoates, uric acid, and glutathione), markers of oxidative stress (e.g., o-tyrosine, m-tyrosine, nitrotyrosine, dityrosine, glutathione disulfide, and 8-hydroxydeoxyguanosine) as well as other metabolites (e.g., purines and indoles). In all, ca. 600 redox active compounds can be detected, most with a limit of detection of approximately 5 pg on column. Results, including analytical parameters, from a study of liver mitochondria from control and diabetic rats are presented to demonstrate utility of this methodology.

Liquid chromatography–coulometric array detection (LC–EC) is a sensitive, quantitative, and robust metabolomics profiling tool that complements the commonly used mass spectrometry (MS) and nuclear magnetic resonance (NMR)-based approaches. However, LC–EC provides little structural information. We recently demonstrated a workflow for the structural characterization of metabolites detected by LC–EC profiling combined with LC–electrospray ionization (ESI)–MS and microNMR. This methodology is now extended to include (i) gas chromatography (GC)–electron ionization (EI)–MS analysis to fill structural gaps left by LC–ESI–MS and NMR and (ii) secondary fractionation of LC-collected fractions containing multiple coeluting analytes. GC–EI–MS spectra have more informative fragment ions that are reproducible for database searches. Secondary fractionation provides enhanced metabolite characterization by reducing spectral overlap in NMR and ion suppression in LC–ESI–MS. The need for these additional methods in the analysis of the broad chemical classes and concentration ranges found in plasma is illustrated with discussion of four specific examples: (i) characterization of compounds for which one or more of the detectors is insensitive (e.g., positional isomers in LC–MS, the direct detection of carboxylic groups and sulfonic groups in 1 H NMR, or nonvolatile species in GC–MS), (ii) detection of labile compounds, (iii) resolution of closely eluting and/or coeluting compounds, and (iv) the capability to harness structural similarities common in many biologically related, LC–EC-detectable compounds.

The pathogenic mechanisms of Alzheimer's disease (AD) remain largely unknown and clinical trials have not demonstrated significant benefit. Biochemical characterization of AD and its prodromal phase may provide new diagnostic and therapeutic insights. We used targeted metabolomics platform to profile cerebrospinal fluid (CSF) from AD (n=40), mild cognitive impairment (MCI, n=36) and control (n=38) subjects; univariate and multivariate analyses to define between-group differences; and partial least square-discriminant analysis models to classify diagnostic groups using CSF metabolomic profiles. A partial correlation network was built to link metabolic markers, protein markers and disease severity. AD subjects had elevated methionine (MET), 5-hydroxyindoleacetic acid (5-HIAA), vanillylmandelic acid, xanthosine and glutathione versus controls. MCI subjects had elevated 5-HIAA, MET, hypoxanthine and other metabolites versus controls. Metabolite ratios revealed changes within tryptophan, MET and purine pathways. Initial pathway analyses identified steps in several pathways that appear altered in AD and MCI. A partial correlation network showed total tau most directly related to norepinephrine and purine pathways; amyloid-β (Ab42) was related directly to an unidentified metabolite and indirectly to 5-HIAA and MET. These findings indicate that MCI and AD are associated with an overlapping pattern of perturbations in tryptophan, tyrosine, MET and purine pathways, and suggest that profound biochemical alterations are linked to abnormal Ab42 and tau metabolism. Metabolomics provides powerful tools to map interlinked biochemical pathway perturbations and study AD as a disease of network failure.

Therapeutic response to selective serotonin (5-HT) reuptake inhibitors in Major Depressive Disorder (MDD) varies considerably among patients, and the onset of antidepressant therapeutic action is delayed until after 2 to 4 weeks of treatment. The objective of this study was to analyze changes within methoxyindole and kynurenine (KYN) branches of tryptophan pathway to determine whether differential regulation within these branches may contribute to mechanism of variation in response to treatment. Metabolomics approach was used to characterize early biochemical changes in tryptophan pathway and correlated biochemical changes with treatment outcome. Outpatients with MDD were randomly assigned to sertraline (n = 35) or placebo (n = 40) in a double-blind 4-week trial; response to treatment was measured using the 17-item Hamilton Rating Scale for Depression (HAMD17). Targeted electrochemistry based metabolomic platform (LCECA) was used to profile serum samples from MDD patients. The response rate was slightly higher for sertraline than for placebo (21/35 [60%] vs. 20/40 [50%], respectively, χ(2)(1) = 0.75, p = 0.39). Patients showing a good response to sertraline had higher pretreatment levels of 5-methoxytryptamine (5-MTPM), greater reduction in 5-MTPM levels after treatment, an increase in 5-Methoxytryptophol (5-MTPOL) and Melatonin (MEL) levels, and decreases in the (KYN)/MEL and 3-Hydroxykynurenine (3-OHKY)/MEL ratios post-treatment compared to pretreatment. These changes were not seen in the patients showing poor response to sertraline. In the placebo group, more favorable treatment outcome was associated with increases in 5-MTPOL and MEL levels and significant decreases in the KYN/MEL and 3-OHKY/MEL; changes in 5-MTPM levels were not associated with the 4-week response. These results suggest that recovery from a depressed state due to treatment with drug or with placebo could be associated with preferential utilization of serotonin for production of melatonin and 5-MTPOL.

Guanine methylation is a ubiquitous process affecting DNA and various RNA species. N-7 guanine methylation (7-MG), although relatively less studied, could have a significant role in normal transcriptional regulation as well as in the onset and development of pathological conditions. The lack of a sensitive method to accurately quantify trace amounts of altered bases such as 7-MG has been a major deterrent in delineating its biological function(s). Here we report the development of methods to detect trace amounts of 7-MG in biological samples using electrochemical detection combined with high-performance liquid chromatography (HPLC) separation of compounds. We further sought to assess global alterations in DNA methylation in Huntington disease (HD), where transcriptional dysregulation is a major factor in pathogenesis. The developed method was used to study guanine methylation in cytoplasmic and nuclear nucleic acids from human and transgenic mouse HD brain and controls. Significant differences were observed in the guanine methylation levels in mouse and human samples, consistent with the known transcriptional pathology of HD. The sensitivity of the method makes it capable of detecting subtle aberrations. Identification of changes in methylation pattern will provide insights into the molecular mechanism changes that translate into onset and/or development of symptoms in diseases such as HD.

Targeted metabolomics provides an approach to quantify metabolites involved in specific molecular pathways. We applied an electrochemistry-based, targeted metabolomics platform to define changes in tryptophan, tyrosine, purine and related pathways in the depressed and remitted phases of major depressive disorder (MDD). Biochemical profiles in the cerebrospinal fluid of unmedicated depressed (n = 14; dMDD) or remitted MDD subjects (n = 14; rMDD) were compared against those in healthy controls (n = 18; HC). The rMDD group showed differences in tryptophan and tyrosine metabolism relative to the other groups. The rMDD group also had higher methionine levels and larger methionine-to-glutathione ratios than the other groups, implicating methylation and oxidative stress pathways. The dMDD sample showed nonsignificant differences in the same direction in several of the metabolic branches assessed. The reductions in metabolites associated with tryptophan and tyrosine pathways in rMDD may relate to the vulnerability this population shows for developing depressive symptoms under tryptophan or catecholamine depletion.

Amyotrophic lateral sclerosis (ALS) is a fatal degenerative motor neuron disease. Approximately 20 percent of familial ALS cases are caused by mutations in the Cu/Zn superoxide dismutase (SOD1) gene. Rodents expressing mutant SOD1 transgenes develop progressive, fatal motor neuron disease and disease onset and progression is dependent on the level of SOD1. We investigated the possibility that a reduction in SOD1 protein may be of therapeutic benefit in ALS and screened 30,000 compounds for inhibition of SOD1 transcription. The most effective inhibitor identified was N-{4-[4-(4-methylbenzoyl)-1-piperazinyl]phenyl}-2-thiophenecarboxamide (Compound ID 7687685), which in PC12 cells showed an EC50 of 10.6 microM for inhibition of SOD1 expression and an LD50 more than 30 microM. This compound was subsequently shown to reduce endogenous SOD1 levels in HeLa cells and to exhibit a modest reduction of SOD1 protein levels in mouse spinal cord tissue. These data suggest that the efficacy of compound 7687685 as an inhibitor of SOD1 gene expression is not likely to be clinically useful, although the strategy reported could be applied broadly to screening for small molecule inhibitors of gene expression.

Background: The antioxidant defense system, which is known to be dysregulated in schizophrenia, is closely linked to the dynamics of purine pathway. Thus, alterations in the homeostatic balance in the purine pathway may be involved in the pathophysiology of schizophrenia. Methodology/Principal Findings: Breakdown products in purine pathway were measured using high-pressure liquid chromatography coupled with a coulometric multi-electrode array system for 25 first-episode neuroleptic-naive patients with schizophrenia at baseline and at 4-weeks following initiation of treatment with antipsychotic medication. Associations between these metabolites and clinical and neurological symptoms were examined at both time points. The ratio of uric acid and guanine measured at baseline predicted clinical improvement following four weeks of treatment with antipsychotic medication. Baseline levels of purine metabolites also predicted clinical and neurological symtpoms recorded at baseline; level of guanosine was associated with degree of clinical thought disturbance, and the ratio of xanthosine to guanosine at baseline predicted degree of impairment in the repetition and sequencing of actions. Conclusions/Significance: Findings suggest an association between optimal levels of purine byproducts and dynamics in clinical symptoms and adjustment, as well as in the integrity of sensory and motor processing. Taken together, alterations in purine catabolism may have clinical relevance in schizophrenia pathology.

Huntington disease (HD) is a progressive neurodegenerative disease that affects 30,000 individuals in North America. Treatments that slow its relentless course are not yet available, and biomarkers that can reliably measure disease activity and therapeutic response are urgently needed to facilitate their development. Here, we interrogated 119 human blood samples for transcripts associated with HD. We found that the dynamic regulator of chromatin plasticity H2A histone family, member Y (H2AFY) is specifically overexpressed in the blood and frontal cortex of patients with HD compared with controls. This association precedes the onset of clinical symptoms, was confirmed in two mouse models, and was independently replicated in cross-sectional and longitudinal clinical studies comprising 142 participants. A histone deacetylase inhibitor that suppresses neurodegeneration in animal models reduces H2AFY levels in a randomized phase II clinical trial. This study identifies the chromatin regulator H2AFY as a potential biomarker associated with disease activity and pharmacodynamic response that may become useful for enabling disease-modifying therapeutics for HD.

One branch of the tryptophan catabolic cascade is the kynurenine pathway, which produces neurotoxic (3-hydroxykynurenine (3-OHKY), quinolinic acid) and neuroinhibitory (kynurenic acid) compounds. Kynurenic acid acts as a competitive antagonist at the glycine site of N-methyl-D-asparate receptors at high concentrations and as a non-competitive antagonist on the a7-nicotinic acetylcholine receptor at low concentrations. Kynurenine compounds also influence cognitive functions known to be disrupted in schizophrenia. Alterations in tryptophan metabolism are therefore of potential significance for the pathophysiology of this disorder. In this paper, tryptophan metabolites were measured from plasma using high-pressure liquid chromatography coupled with electrochemical coulometric array detection, and re- lationships were tested between these metabolic signatures and clinical symptoms for 25 first-episode neuroleptic-naive schizophrenia patients. Blood samples were collected and clinical and neurological symptoms were rated at baseline and again at 4 wk following initiation of treatment. Level of 3-OHKY and total clinical symptom scores were correlated when patients were unmedicated and neuroleptic-naive, and this relationship differed significantly from the correlation observed for patients 4 wk after beginning treatment. Baseline psychosis symptoms were predicted only by neurological symptoms. Moreover, baseline 3-OHKY predicted clinical change at 4 wk, with the lowest concentrations of 3-OHKY being associated with the greatest improvement in symptoms. Taken together, our findings suggest a neurotoxic product of tryptophan metabolism, 3-OHKY, predicts severity of clinical symptoms during the early phase of illness and before exposure to antipsychotic drugs. Baseline level of 3-OHKY may also predict the degree of clinical improvement following brief treatment with antipsychotics.

BackgroundPurine catabolism may be an unappreciated, but important component of the homeostatic response of mitochondria to oxidant stress. Accumulating evidence suggests a pivotal role of oxidative stress in schizophrenia pathology.Methodology/principal findingsUsing high-pressure liquid chromatography coupled with a coulometric multi-electrode array system, we compared 6 purine metabolites simultaneously in plasma between first-episode neuroleptic-naïve patients with schizophrenia (FENNS, n = 25) and healthy controls (HC, n = 30), as well as between FENNS at baseline (BL) and 4 weeks (4w) after antipsychotic treatment. Significantly higher levels of xanthosine (Xant) and lower levels of guanine (G) were seen in both patient groups compared to HC subjects. Moreover, the ratios of G/guanosine (Gr), uric acid (UA)/Gr, and UA/Xant were significantly lower, whereas the ratio of Xant/G was significantly higher in FENNS-BL than in HC. Such changes remained in FENNS-4w with exception that the ratio of UA/Gr was normalized. All 3 groups had significant correlations between G and UA, and Xan and hypoxanthine (Hx). By contrast, correlations of UA with each of Xan and Hx, and the correlation of Xan with Gr were all quite significant for the HC but not for the FENNS. Finally, correlations of Gr with each of UA and G were significant for both HC and FENNS-BL but not for the FENNS-4w.Conclusions/significanceDuring purine catabolism, both conversions of Gr to G and of Xant to Xan are reversible. Decreased ratios of product to precursor suggested a shift favorable to Xant production from Xan, resulting in decreased UA levels in the FENNS. Specifically, the reduced UA/Gr ratio was nearly normalized after 4 weeks of antipsychotic treatment. In addition, there are tightly correlated precursor and product relationships within purine pathways; although some of these correlations persist across disease or medication status, others appear to be lost among FENNS. Taken together, these results suggest that the potential for steady formation of antioxidant UA from purine catabolism is altered early in the course of illness.

Article abstract Increased generation of reactive oxygen species may underlie the pathophysiology of Friedreich ataxia (FRDA). The authors measured concentrations of 8-hydroxy-2’-deoxyguanosine (8OH2’dG), a marker of oxidative DNA damage, in urine and of dihydroxybenzoic acid (DHBA), a marker of hydroxyl radical attack, in plasma of 33 patients with FRDA. They found a 2.6-fold increase in normalized urinary 8OH2’dG but no change in plasma DHBA as compared with controls. Oral treatment with 5 mg/kg/day of the antioxidant idebenone for 8 weeks significantly decreased urinary 8OH2’dG concentrations, indicating that 8OH2’dG may be useful in monitoring therapeutic interventions in patients with FRDA.–1721

Background The risk of Parkinson disease (PD) and its rate of progression may decline with increasing concentration of blood urate, a major antioxidant. Objective To determine whether serum and cerebrospinal fluid concentrations of urate predict clinical progression in patients with PD. Design, Setting, and Participants Eight hundred subjects with early PD enrolled in the Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism (DATATOP) trial. The pretreatment urate concentration was measured in serum for 774 subjects and in cerebrospinal fluid for 713 subjects. Main Outcome Measures Treatment-, age-, and sex-adjusted hazard ratios (HRs) for clinical disability requiring levodopa therapy, the prespecified primary end point of the original DATATOP trial. Results The HR of progressing to the primary end point decreased with increasing serum urate concentrations (HR for highest vs lowest quintile = 0.64; 95% confidence interval [CI], 0.44-0.94; HR for a 1-SD increase = 0.82; 95% CI, 0.73-0.93). In analyses stratified by α-tocopherol treatment (2000 IU/d), a decrease in the HR for the primary end point was seen only among subjects not treated with α-tocopherol (HR for a 1-SD increase = 0.75; 95% CI, 0.62-0.89; vs HR for those treated = 0.90; 95% CI, 0.75-1.08). Results were similar for the rate of change in the Unified Parkinson's Disease Rating Scale score. Cerebrospinal fluid urate concentration was also inversely related to both the primary end point (HR for highest vs lowest quintile = 0.65; 95% CI, 0.44-0.96; HR for a 1-SD increase = 0.89; 95% CI, 0.79-1.02) and the rate of change in the Unified Parkinson's Disease Rating Scale score. As with serum urate concentration, these associations were present only among subjects not treated with α-tocopherol. Conclusions Higher serum and cerebrospinal fluid urate concentrations at baseline were associated with slower rates of clinical decline. The findings strengthen the link between urate concentration and PD and the rationale for considering central nervous system urate concentration elevation as a potential strategy to slow PD progression. Published online October 12, 2009 (doi:10.1001/archneurol.2009.247).

Background Metabolomics, the global science of biochemistry, provides powerful tools to map perturbations in the metabolic network and enables simultaneous quantification of several metabolites to identify metabolic perturbances that might provide insights into disease. Methods In this pilot study, we took a targeted electrochemistry-based metabolomics approach where liquid chromatography followed by coulometric array detection enables quantification of over 30 metabolites within key neurotransmitter pathways (dopamine and serotonin) and pathways involved in oxidative stress. Results Using samples from postmortem ventricular cerebrospinal fluid (15 Alzheimer's disease [AD] and 15 nondemented subjects with autopsy-confirmed diagnoses) and by using regression models, correlations, Wilcoxon rank-sum tests, and t -tests we identified alterations in tyrosine, tryptophan, purine, and tocopherol pathways in patients with AD. Reductions in norepinephrine and its related metabolites were also seen, consistent with previously published data. Conclusions These data support further investigation of metabolomics in larger samples of clinical AD as well as in those with preclinical disease for use as biomarkers.

Background: Mutations in LRRK2 gene represent the most common known genetic cause of Parkinson's disease (PD). Methodology/Principal Findings: We used metabolomic profiling to identify biomarkers that are associated with idiopathic and LRRK2 PD. We compared plasma metabolomic profiles of patients with PD due to the G2019S LRRK2 mutation, to asymptomatic family members of these patients either with or without G2019S LRRK2 mutations, and to patients with idiopathic PD, as well as non-related control subjects. We found that metabolomic profiles of both idiopathic PD and LRRK2 PD subjects were clearly separated from controls. LRRK2 PD patients had metabolomic profiles distinguishable from those with idiopathic PD, and the profiles could predict whether the PD was secondary to LRRK2 mutations or idiopathic. Metabolomic profiles of LRRK2 PD patients were well separated from their family members, but there was a slight overlap between family members with and without LRRK2 mutations. Both LRRK2 and idiopathic PD patients showed significantly reduced uric acid levels. We also found a significant decrease in levels of hypoxanthine and in the ratios of major metabolites of the purine pathway in plasma of PD patients. Conclusions/Significance: These findings show that LRRK2 patients with the G2019S mutation have unique metabolomic profiles that distinguish them from patients with idiopathic PD. Furthermore, asymptomatic LRRK2 carriers can be separated from gene negative family members, which raises the possibility that metabolomic profiles could be useful in predicting which LRRK2 carriers will eventually develop PD. The results also suggest that there are aberrations in the purine pathway in PD which may occur upstream from uric acid. © 2009 Johansen et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Objective More must be learned about metabolic and biochemical alterations that contribute to the development and expression of drug dependence. Experimental opioid administration influences mechanisms and indices of oxidative stress, such as antioxidant compounds and purine metabolism. We examined perturbations of neurotransmitter-related pathways in opioid dependence (OD). Methods In this preliminary study, we used a targeted metabolomics platform to explore whether biochemical changes were associated with OD by comparing OD individuals (n = 14) and non-drug users (n = 10). Results OD patients undergoing short-term methadone detoxification showed altered oxidation–reduction activity, as confirmed by higher plasma levels of α- and γ- tocopherol and increased GSH/GSSG ratio. OD individuals had also altered purine metabolism, showing increased concentration of guanine and xanthosine, with decreased guanosine, hypoxanthine and hypoxanthine/xanthine and xanthine/xanthosine ratios. Other drug use in addition to opioids was associated with partly different biochemical changes. Conclusions This is a preliminary investigation using metabolomics and showing multiple peripheral alterations of metabolic pathways in OD. Further studies should explore the metabolic profile of conditions of opioid abuse, withdrawal and long-term abstinence in relation to agonist and antagonist treatment and investigate biochemical signatures of opioid substances and medications. Copyright © 2009 John Wiley & Sons, Ltd.