Metabolomic profiling of CSF in multiple sclerosis and neuromyelitis optica spectrum disorder by nuclear magnetic resonance.

Multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) are inflammatory diseases of the central nervous system. Although several studies have characterized the metabolome in the cerebrospinal fluid (CSF) from MS and NMOSD patients, comparative analyses between them and between the relapse and the remission of each disease have not been performed. Both univariate and multivariate analyses were used to compare 1H-NMR spectra of CSF from MS, NMOSD, and healthy controls (HCs). The statistical analysis showed alterations of eight metabolites that were dependent on the disease. Levels of 2-hydroxybutyrate, acetone, formate, and pyroglutamate were higher and levels of acetate and glucose were lower in both MS and NMOSD. Citrate was lower in MS patients, whereas lactate was higher in only NMOSD specifically. The shared feature of metabolic changes between MS and NMOSD may be related to altered energy metabolism and fatty acid biosynthesis in the brain. Another analysis to characterize relapse and remission status showed that isoleucine and valine were down-regulated in MS relapse compared to MS remission. The other metabolites identified in the disease comparison showed the same alterations regardless of disease activity. These findings would be helpful in understanding the biological background of these diseases, and distinguishing between MS and NMOSD, as well as determining the disease activity.

Characterizing concentrations of diethylene glycol and suspected metabolites in human serum, urine, and cerebrospinal fluid samples from the Panama DEG mass poisoning.

CONTEXT: Diethylene glycol (DEG) mass poisoning is a persistent public health problem. Unfortunately, there are no human biological data on DEG and its suspected metabolites in poisoning. If present and associated with poisoning, the evidence for use of traditional therapies such as fomepizole and/or hemodialysis would be much stronger. OBJECTIVE: To characterize DEG and its metabolites in stored serum, urine, and cerebrospinal fluid (CSF) specimens obtained from human DEG poisoning victims enrolled in a 2006 case-control study. METHODS: In the 2006 study, biological samples from persons enrolled in a case-control study (42 cases with new-onset, unexplained AKI and 140 age-, sex-, and admission date-matched controls without AKI) were collected and shipped to the Centers for Disease Control and Prevention (CDC) in Atlanta for various analyses and were then frozen in storage. For this study, when sufficient volume of the original specimen remained, the following analytes were quantitatively measured in serum, urine, and CSF: DEG, 2-hydroxyethoxyacetic acid (HEAA), diglycolic acid, ethylene glycol, glycolic acid, and oxalic acid. Analytes were measured using low resolution GC/MS, descriptive statistics calculated and case results compared with controls when appropriate. Specimens were de-identified so previously collected demographic, exposure, and health data were not available. The Wilcoxon Rank Sum test (with exact p-values) and bivariable exact logistic regression were used in SAS v9.2 for data analysis. RESULTS: The following samples were analyzed: serum, 20 case, and 20 controls; urine, 11 case and 22 controls; and CSF, 11 samples from 10 cases and no controls. Diglycolic acid was detected in all case serum samples (median, 40.7 mcg/mL; range, 22.6-75.2) and no controls, and in all case urine samples (median, 28.7 mcg/mL; range, 14-118.4) and only five (23%) controls (median, < Lower Limit of Quantitation (LLQ); range, < LLQ-43.3 mcg/mL). Significant differences and associations were identified between case status and the following: 1) serum oxalic acid and serum HEAA (both OR = 14.6; 95% C I = 2.8-100.9); 2) serum diglycolic acid and urine diglycolic acid (both OR > 999; exact p < 0.0001); and 3) urinary glycolic acid (OR = 0.057; 95% C I = 0.001-0.55). Two CSF sample results were excluded and two from the same case were averaged, yielding eight samples from eight cases. Diglycolic acid was detected in seven (88%) of case CSF samples (median, 2.03 mcg/mL; range, < LLQ, 7.47). DISCUSSION: Significantly elevated HEAA (serum) and diglycolic acid (serum and urine) concentrations were identified among cases, which is consistent with animal data. Low urinary glycolic acid concentrations in cases may have been due to concurrent AKI. Although serum glycolic concentrations among cases may have initially increased, further metabolism to oxalic acid may have occurred thereby explaining the similar glycolic acid concentrations in cases and controls. The increased serum oxalic acid concentration results in cases versus controls are consistent with this hypothesis. CONCLUSION: Diglycolic acid is associated with human DEG poisoning and may be a biomarker for poisoning. These findings add to animal data suggesting a possible role for traditional antidotal therapies. The detection of HEAA and diglycolic acid in the CSF of cases suggests a possible association with signs and symptoms of DEG-associated neurotoxicity. Further work characterizing the pathophysiology of DEG-associated neurotoxicity and the role of traditional toxic alcohol therapies such as fomepizole and hemodialysis is needed.

Saturable transport of gabapentin at the blood-brain barrier.

Gabapentin readily crosses the blood-brain barrier and concentrates in brain tissue via an active transport process believed to be system-L. Blood-brain barrier system-L has a low K(m), making it particularly susceptible to substrate saturation. The purpose of this study was to determine whether the fraction of gabapentin crossing the blood-brain barrier remains constant over a broad range of doses. Using a rat model, microdialysis techniques were employed to determine if fluctuations in gabapentin concentrations in the brain extracellular fluid (ECF) coincided with proportional changes in plasma concentrations. Area under the concentration-time curve was calculated for plasma (AUCplasma) and brain extracellular fluid (AUCECF). The ratios of AUFECF to AUCplasma (AUCratio) and brain extracellular fluid to midpoint plasma gabapentin concentration for each collection interval (Cratio) were determined to provide indicators of the relative (i.e. fractional) amount of gabapentin crossing the blood-brain barrier. Analysis of the association between AUCECF and AUCplasma using linear regression analysis revealed a small, but significant relationship (r = 0.62; p < 0.01). Although higher AUCECF values were obtained with higher AUCplasma values, changes in AUCECF were less than proportional to observed changes in AUCplasma. Blood-brain barrier saturation of gabapentin transport was evident as the AUCratio decreased with increased AUCplasma. Collectively, these results support a trend towards saturation at higher plasma concentrations of the carrier-mediated transport mechanism of gabapentin through the blood-brain barrier.

Seizure frequency and CSF parameters in a double-blind placebo controlled trial of gabapentin in patients with intractable complex partial seizures.

Gabapentin (GBP) is a non-protein-bound gamma amino acid which is not subjected to metabolic degradation in man. As part of a placebo-controlled double-blind study, patients suffering from intractable complex partial seizures with or without secondary generalization were followed with lumbar punctures at baseline and after three months of GBP treatment (900 mg/day or 1200 mg/day). Cerebrospinal fluid (CSF) was analyzed for concentrations of GBP, amino acids including GABA, homovanillic acid (HVA), and 5 hydroxyindoleacetic acid (5-HIAA). The results indicate that there were no changes in the selected amino acids, HVA, or 5-HIAA after GBP treatment. At steady state the CSF/plasma ratios of GBP ranged from 0.056 to 0.34, indicating that there may be some type of active out-transport of GBP across the blood-brain barrier. No linear relationship was observed between plasma and CSF levels in these patients.

Selected CSF biochemistry and gabapentin concentrations in the CSF and plasma in patients with partial seizures after a single oral dose of gabapentin.

Gabapentin (GBP) is a neutral amino acid and a GABA analog which in animal experimental models has shown a broad anticonvulsant spectrum. To evaluate the penetration of GBP into the CSF in humans as well as its possible effects on free and total GABA, homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA), a special investigation was performed as part of a placebo controlled add-on study of GBP in partial epilepsy. At the end of the 3-month double-blind period, 5 patients on placebo were given a single oral dose of GBP. Four patients received 600 mg and 1 patient 1200 mg GBP. CSF was collected immediately before and at 6, 24 and 72 h after the single dose. 5 ml of plasma was collected at 1, 2, 3, 6, 12, 24, 48 and 72 h. Plasma concentrations and plasma elimination half-life (4-6 h) of GBP were in agreement with the results of previous studies. The CSF/plasma concentration ratio of GBP 6 h after drug was 0.1. After 24 h, GBP could only be recovered in the CSF of the patient given 1200 mg. The CSF/plasma ratio at that time was 0.3. Free and total GABA concentrations did not change, but CSF 5-HIAA and HVA increased at 24 and 72 h post dose. The CSF/plasma ratio of gabapentin is similar to that of other amino acids.

Alterations of ventricular pH alter water intake and food consumption in rats.

The pH of third ventricular CSF was altered by infusing acidic or alkaline solution of artificial cerebrospinal fluid (aCSF) through chronically implanted stainless steel cannula. In two separate group of rats (n = 18 each) water and food consumptions were recorded 30 min, 1 hr, and 24 hr after intraventricular infusions of the modified aCSF solutions having pH 6.0, 8.0 and 7.4 (control). On raising the CSF pH, water intake increased in all three observations. Feeding was not affected in the observations taken after 30 min and 1 hr, but significantly reduced food consumption was observed 24 hr after the infusions. Lowering of pH had no effect either on dipsogenic or feeding response. The CSF pH correlated positively with drinking in all three observations. Since dipsogenic and feeding responses are centrally regulated by ion sensitive cells, it may be presumed that altered CSF pH influenced the activities of the sensors by altering ionic conductance across their membranes.

High resolution proton nuclear magnetic resonance studies of human cerebrospinal fluid.

One- and two-dimensional (correlated shift spectroscopy) high resolution proton n.m.r. spectra of human cerebrospinal fluid (CSF) are reported. The merits of water suppression by freeze drying or irradiation, and spectral simplification by spin-echo methods, are discussed. Well-resolved resonances for a range of low molecular weight metabolites such as lactate, 3-D-hydroxybutyrate, alanine, acetate, citrate, glucose, valine and formate were observed. Resonances for glutamine were observed only from freeze dried samples. Concentrations determined by n.m.r. were in reasonable agreement with those from conventional methods. The n.m.r. spectra of CSF were related to the clinical conditions of the subjects. No resonances for citrate were present in spectra of CSF from subjects (three infants) with bacterial meningitis; high lactate and lowered glucose levels were observed. Strong resonances for glucose and glycine were observed for mildly diabetic subjects. Both the aromatic and the aliphatic regions of the CSF spectra from subjects suffering from liver failure contained distinctive features characteristic for hepatic coma: Intense resonances for lactate, alanine, valine, methionine, tyrosine, phenylalanine and histidine. In some cases guanine was also present, which does not appear to have been reported previously. The two-dimensional spectrum suggested the presence of abnormally high levels of a number of endogenous metabolites. Such assignments were not possible using one-dimensional spectra alone because of signal overlap.

CSF acid-base regulation and ventilation in iso- and hypocapnic Hacetate acidosis.

Intravenous infusion in conscious rabbits of Hacetate decreases both arterial CO2 partial pressure PaCO2 and cerebrospinal fluid (CSF) HCO3- more than observed with HCl or HNO3 infusion. These acids did not affect CSF HCO3- in isocapnic conditions, and this study asks whether Hacetate infusion will do so. Arterial, central venous, and cisterna magna catheters were implanted in pentobarbital-anesthetized rabbits and all subsequent measurements were performed in the conscious state. Hacetate was infused intravenously over 6 h to decrease plasma HCO3- the same amount in a group allowed to decrease its PaCO2 in response to the acid (hypocapnic) and one in which PaCO2 was maintained at control levels (isocapnic). CSF HCO3- decreased significantly in isocapnia, although the change was less than in hypocapnia. Stoichiometrically by 6 h the measured CSF HCO3- change was balanced by an increase in acetate in hypocapnia and the sum of an increase in acetate and a decrease in chloride in isocapnia. Mechanistically, net acetate entry into CSF appears to involve an exchange for chloride as proposed for NO3-/Cl- and a process that lowers CSF HCO3-. This process could be competitive replacement of HCO3- by acetate in the CSF production mechanism or nonionic diffusive entry of Hacetate into CSF with subsequent titration of HCO3-. The decreases in CSF HCO3- result from the acetate mechanism and the hypocapnic effect on Cl- and HCO3-. The greater ventilatory response results from the greater CSF acidification or a specific effect of acetate per se.

CSF and plasma ions and blood gases during organic metabolic acidosis in conscious rabbits.

In conscious rabbits with arterial, central venous, and cisterna magna catheters, we infused HCl, Hlactate, and Hacetate so as to lower and maintain plasma [HCO3-] at the same mean values in all three groups over 6 h. The hypothesis was that the cerebrospinal fluid (CSF) [HCO3-] will depend on the changes in CO2 partial pressure (PCO2) and be determined by the net increase in the CSF concentration of the strong anion of the acid. The delta CSF [HCO3-] did correlate strongly with the delta PCO2, with the largest decrease in CSF [HCO3-] and PCO2 being in the Hacetate group, a response we attribute to a greater stimulatory effect of Hacetate on the alveolar ventilation relative to CO2 production. However, the delta CSF [HCO3-] was not simply determined in all cases by the increase in the CSF concentration of the strong anion of the acid. In HCl acidosis, statistically delta CSF [HCO3-] was equal to delta CSF [Cl-]. In H lactate acidosis delta CSF [HCO3-] was equal to the sum of a small positive delta CSF [lactate] and a small positive delta CSF [Cl-]. In Hacetate acidosis, delta CSF [HCO3-] was equal to the sum of a large positive delta CSF [acetate] and a small negative delta CSF [Cl-]. We hypothesize that in metabolic acidosis the changes in large cavity CSF [HCO3-] depend on changes in the PCO2. The strong anion regulated by the PCO2 changes is Cl-.(ABSTRACT TRUNCATED AT 250 WORDS)