A comparison of high-throughput plasma NMR protocols for comparative untargeted metabolomics.

INTRODUCTION: When analyzing the human plasma metabolome with Nuclear Magnetic Resonance (NMR) spectroscopy, the Carr-Purcell-Meiboom-Gill (CPMG) experiment is commonly employed for large studies. However, this process can lead to compromised statistical analyses due to residual macromolecule signals. In addition, the utilization of Trimethylsilylpropanoic acid (TSP) as an internal standard often leads to quantification issues, and binning, as a spectral summarization step, can result in features not clearly assignable to metabolites. OBJECTIVES: Our aim was to establish a new complete protocol for large plasma cohorts collected with the purpose of describing the comparative metabolic profile of groups of samples. METHODS: We compared the conventional CPMG approach to a novel procedure that involves diffusion NMR, using the Longitudinal Eddy-Current Delay (LED) experiment, maleic acid (MA) as the quantification reference and peak picking for spectral reduction. This comparison was carried out using the ultrafiltration method as a gold standard in a simple sample classification experiment, with Partial Least Squares-Discriminant Analysis (PLS-DA) and the resulting metabolic signatures for multivariate data analysis. In addition, the quantification capabilities of the method were evaluated. RESULTS: We found that the LED method applied was able to detect more metabolites than CPMG and suppress macromolecule signals more efficiently. The complete protocol was able to yield PLS-DA models with enhanced classification accuracy as well as a more reliable set of important features than the conventional CPMG approach. Assessment of the quantitative capabilities of the method resulted in good linearity, recovery and agreement with an established amino acid assay for the majority of the metabolites tested. Regarding repeatability, ~ 85% of all peaks had an adequately low coefficient of variation (< 30%) in replicate samples. CONCLUSION: Overall, our comparison yielded a high-throughput untargeted plasma NMR protocol for optimized data acquisition and processing that is expected to be a valuable contribution in the field of metabolic biomarker discovery.

Serum metabolite profiling of ST-segment elevation myocardial infarction using liquid chromatography quadrupole time-of-flight mass spectrometry.

ST segment elevation myocardial infarction (STEMI) is one of the most common global causes of cardiovascular disease-related death. Several metabolites may change during STEMI. Hence, analysis of metabolites in body fluid may be considered as a rapid and accurate test for initial diagnosis. This study has therefore attempted to determine the variation in metabolites identified in the serum of STEMI patients (n = 20) and 15 controls. Samples collected from the Cardiology Department, Medical Faculty, Ataturk University, were extracted by liquid-liquid extraction and analysed using liquid chromatography quadrupole time-of-flight mass spectrometry. The METLIN database was used for the identification and characterization of metabolites. According to Q-TOF/MS measurements, 231 m/z values, which were significantly different between groups (P < 0.01 and fold analysis >1.5) were detected. Metabolite identification was achieved via the Human Metabolome database. According to the multivariate data analysis, leucine, isoleucine, l-proline, l-alanine, glycine, fumaric acid, citrate, succinate and carnitine levels were decreased, whereas levels of propionic acid, maleic acid, butyric acid, urea, oleic acid, palmitic acid, lysoPC [18:2(9Z)], glycerol, phoshpatidylethanolamine, caffeine and l-lactic acid were increased in STEMI patients compared with controls. In conclusion, malonic acid, maleic acid, fumaric acid and palmitic acid can be used as biomarkers for early risk stratification of patients with STEMI.

Synthesis and evaluation of styrene-maleic acid copolymer conjugated amphotericin B.

Amphotericin B (AmB), which plays a central role in the treatment of systemic fungal infections, is difficult to formulate because it's sparingly soluble in water and organic solvents. We previously prepared AmB-loaded micelles using styrene-maleic acid copolymer (SMA). Although solubilization was achieved by this formulation, stability in the blood circulation was as insufficient as that of Fungizone®, which is a conventional formulation of AmB. Meanwhile, it is well known that polymer-drug conjugates are more stable in circulation than drug-loaded micelles. Therefore, in this study, we developed covalently conjugated SMA-AmB (SMA-AmB conjugate). The SMA-AmB conjugate was found to be soluble and present as micelles in aqueous solution. Furthermore, it was revealed that this micelle behaves as a larger molecule by forming a complex with albumin. The circulation in the blood increased significantly compared to that of Fungizone®, which was suggested to be due to this complex-forming ability. Although in vitro and in vivo antifungal activity of the SMA-AmB conjugate against Saccharomyces cerevisiae was reduced by 1/3 compared to that of Fungizone®, hemolysis decreased to 1/40 or less, and the LD50 decreased to 1/10. In conclusion, it is expected that the SMA-AmB conjugate can be a polymer-therapeutic agent with high antifungal selectivity.

Pharmacokinetics of Maleic Acid as a Food Adulterant Determined by Microdialysis in Rat Blood and Kidney Cortex.

Maleic acid has been shown to be used as a food adulterant in the production of modified starch by the Taiwan Food and Drug Administration. Due to the potential toxicity of maleic acid to the kidneys, this study aimed to develop an analytical method to investigate the pharmacokinetics of maleic acid in rat blood and kidney cortex. Multiple microdialysis probes were simultaneously inserted into the jugular vein and the kidney cortex for sampling after maleic acid administration (10 or 30 mg/kg, i.v., respectively). The pharmacokinetic results demonstrated that maleic acid produced a linear pharmacokinetic phenomenon within the doses of 10 and 30 mg/kg. The area under concentration versus time curve (AUC) of the maleic acid in kidney cortex was 5-fold higher than that in the blood after maleic acid administration (10 and 30 mg/kg, i.v., respectively), indicating that greater accumulation of maleic acid occurred in the rat kidney.

Spectrum of ocular manifestations in cobalamin C and cobalamin A types of methylmalonic acidemia.

BACKGROUND: Cobalamin C disease (cblC), which leads to methylmalonic acidemia with homocystinuria, is the most common inherited disorder of vitamin B12 metabolism. Reported ocular findings associated with cblC have been maculopathy, pigmentary retinopathy, and optic nerve atrophy. Cobalamin A disease (cblA) which causes an isolated methylmalonic acidemia without homocystinuria is rarer than cblC. This is the first detailed report of the ocular findings associated with cblA. We also describe the spectrum of ocular findings in our cblC patients. MATERIALS AND METHODS: A case series describing the ophthalmologic clinical course of six patients with a diagnosis of cobalamin C type and one patient with cobalamin A type of methylmalonic acidemia. Patients were diagnosed through biochemical laboratory testing and genetic analysis was conducted on most patients. Longitudinal fundus findings, optical coherence tomography (OCT), autofluorescence, and electrophysiology were followed in the patients. RESULTS: The cblA patient demonstrated a relatively mild ocular phenotype with late-onset and slowly progressing temporal disc pallor and peripapillary atrophy in the second decade of life. The patient maintained good visual acuity and central vision, without evidence of maculopathy. The six cblC patients demonstrated a range of ocular findings from unremarkable and mild phenotypes to significant retinopathy, including bull's eye maculopathy, severe maculopathy with punched out chorioretinal atrophy, peripheral bone spicules, and optic nerve atrophy. CONCLUSIONS: The spectrum of ocular manifestations seen with inherited disorders of cobalamin metabolism is wide, ranging from mild optic nerve atrophy to severe macular or retinal degeneration. This heterogeneity may in part reflect the associated biochemical phenotype, such as that observed between our cblA and cblC patients. We also observed heterogeneity within the cblC type in agreement with previous reports.

Pharmacokinetics and bioavailability of oral single-dose maleic acid in biofluids of Sprague-Dawley rats.

Maleic acid (MA) was purposefully adulterated in an array of starch-based foods in Taiwan, inciting a food safety incident. Due to limited data on the pharmacokinetics and bioavailability of ingested MA, we studied pharmacokinetic (PK) parameters in serum and urine of Sprague Dawley rats. Three groups of male and female rats were given three doses of MA by oral gavage; biofluid samples were collected accordingly. Data demonstrated that a non-compartment model best described MA's linear kinetic behavior upon ingestion. The mean residence life of maleic acid in serum was 17.58 h and 9.84 h for low-dosed male and female rats, whereas 8.24 h and 4.17 h for high-dosed male and female rats, respectively. Our results revealed oral bioavailability ranged from 30.8 to 41.0% for males and 32.2-39.1% for females. The data confirmed that ingested MA is absorbed and metabolized rapidly, along with low bioavailability. Future pathological studies may determine whether prolonged and low-level exposures of MA produce nephrotoxicity. These data provide additional contribution to current understanding of the kinetics of MA in a rat model and enable the development of a physiologically based model, which is essential to form the basis of evidenced-based food safety guidelines.

Determination of the maleic acid in rat urine and serum samples by isotope dilution-liquid chromatography-tandem mass spectrometry with on-line solid phase extraction.

A rapid and simple on-line solid-phase extraction coupled with isotope dilution-liquid chromatography-tandem mass spectrometry (SPE-ID-LC-MS/MS) method was developed to quantitate maleic acid in serum and urine of SpragueDawley (SD) rats. The aforementioned biological samples were spiked with (13)C2-maleic acid, vigorously vortexed, added with acetonitrile to precipitate proteins, and then injected into the on-line SPE-LC-MS/MS system for quantification. Upon validation, this method demonstrated excellent feasibility and sensitivity: calibration curves for maleic acid in serum and urine display excellent linearity with the coefficient of determination (R(2)) greater than 0.999; the limits of detection and quantitation (LOD and LOQ) for maleic acid were determined at 0.2 and 0.5µg L(-1), respectively. Additionally, intra-day accuracy for maleic acid in serum and urine samples ranged from 94.0% to 100.2% and 101.3% to 104.4%, respectively. Furthermore, inter-day accuracy ranged from 93.6% to 101.0% and from 102.3% to 111.4% in serum and urine samples, respectively. Intra-day precision %RSD of maleic acid in serum and urine samples was 13.8% or less, whereas the inter-day precision was 6.1% or less. The matrix effects were not found to be statistically significant (p=0.9145 and p=0.5378, correspondingly) based on the calculations of recovery functions. The collected serum and urine samples were analyzed using SPE-ID-LC-MS/MS. Our results reveal trace levels of maleic acid in the control rats, demonstrating that this method is capable of analyzing background levels of contaminants in biofluids with excellent sensitivity and specificity at part-per-billion levels concentrations in complex matrices.

Pharmacokinetic comparison of the maleate and free base formulations of LB80380, a novel nucleotide analog, in healthy male volunteers.

OBJECTIVE: LB80380, a dipivoxil ester prodrug of LB80331, is a novel antiviral agent for the treatment of chronic hepatitis B. The aim of this study was to compare the pharmacokinetic differences after single oral administrations of the free base and maleate formulations of LB80380 in healthy male subjects. METHODS: An open-label, single- dose, randomized-sequence, 2-treatment crossover study was conducted in 32 Korean male volunteers. Subjects received either a combination of 60 and 90 mg tablets of the free base LB80380 formulation or a 183 mg (150 mg as a free base) tablet of the maleate LB80380 formulation. Then, after a 14- day washout period, each subject received the other formulation. Plasma and urine concentrations of LB80331 and LB80317 (active metabolites of LB80380) were measured by validated liquid chromatographytandem mass spectrometry assays. A safety assessment, which included vital signs, adverse events, electrocardiograms and clinical laboratory tests, was performed for each subject. RESULTS: A total of 32 healthy subjects was enrolled, and 26 subjects completed the study. Single oral administrations of LB80380 maleate tablets did not result in clinically significant differences in the safety profile compared to the LB80380 free base tablets. The 90% confidence intervals (CIs) for the geometric mean ratios of Cmax and AUClast for LB80331 of the two treatments (maleate versus free base formulation) were 0.986 - 1.1240 and 0.9848 - 1.0533, respectively. The 90% CIs for the geometric mean ratios of Cmax and AUClast for LB80317 were 0.8379 - 0.9696 and 0.7224 - 0.9196. CONCLUSIONS: In healthy male subjects, the 183 mg LB80380 maleate tablet was pharmacokinetically equivalent to the 60 and 90 mg LB80380 free base tablets.

Lymphomatosis cerebri presenting as a rapidly progressive dementia with a high methylmalonic acid.

We report a case of a patient with a rapidly progressive dementing illness and gait disturbance, in whom initial screening demonstrated a high methylmalonic acid level only, suggestive of a functional vitamin B(12) deficiency. Despite B(12) replacement therapy, he continued to decline. Further investigations demonstrated extensive signal change on magnetic resonance imaging involving grey and white matter within the corpus callosum, deep grey matter, brainstem and cerebellar peduncles, and patchy post-contrast enhancement. Laboratory testing revealed a raised erythrocyte sedimentation rate, raised anti-nuclear, intrinsic factor and lupus anticoagulant antibody titres, and a IgG kappa paraprotein. Cerebrospinal fluid was unremarkable. Bone marrow trephine biopsy showed monoclonal gammopathy of unknown significance. The patient initially responded to steroids, and underwent a brain biopsy, which was uninformative. However, 3 weeks following admission, he died due to an aspiration pneumonia. Autopsy findings were consistent with a diffuse primary central nervous system small cell B-cell lymphoma. This has been rarely reported in the medical literature, but our case exhibits typical clinical features, although patchy enhancement on imaging and the high methylmalonic acid have not been previously described. We hypothesise that his functional B(12) deficiency may have resulted from rapid cell turnover, perhaps in conjunction with the presence of intrinsic factor antibodies.

Pharmacokinetics of anti-psoriatic fumaric acid esters in psoriasis patients.

The aim of this study was to evaluate pharmacokinetic parameters of fumaric acid esters (FAE) in psoriasis patients for the first time. For this prupose new HPLC assays were developed. Additionally, physicochemical parameters of FAE were determined, allowing a better interpretation of the in vivo data. In vivo, monomethylfumarate (MMF) and monoethylfumarate (MEF) were detected after t (lag) = 120 min. T (max) and c (max) of MMF were 210 min and 11.2 microM, respectively, 210 min and 5.2 microM for MEF. The half-life of MMF was 38.7 min, and 25.4 min of MEF. The AUC(0-infinity) of MMF was 172 min microg ml(-1) and 63.6 min microg ml(-1) of MEF. Data display median of three subjects. No plasma levels of dimethylfumarate (DMF) or fumaric acid (FA) were detected. The evaluation of physicochemical parameters of FAE showed that only DMF fulfils the criteria of Lipinski's rule of five. The pKa of MMF was determined as 3.63. The data of this study provide evidence that DMF is most likely absorbed out of the duodenum into the presystemic circulation and is not completely hydrolysed to MMF before uptake as assumed by others.

Quantification of henatinib maleate, a novel potent inhibitor of VEGF receptors, in rat plasma by LC-MS/MS.

Henatinib maleate (R,Z)-2-[(5-fluoro-1,2-dihydro-2-oxo-3H-indol-3-ylidene) methyl]-5-(2-hydroxy-3-morpholinopropyl)-3-methyl-5,6,7,8-tetrahydro-1H-pyrrolo[3,2-c] azepin-4-ketone maleate is a potent inhibitor of vascular endothelial growth factor receptors, and is currently under preclinical evaluation as an anticancer drug. A novel method for the quantification of henatinib maleate in rat plasma using high performance liquid chromatography-tandem mass spectrometry has been developed. The analyte (henatinib maleate) and internal standard (papaverine hydrochloride) were extracted from 50 microL of rat plasma by protein precipitation and separated on a C(18) column using a mixture of 25 mm ammonium acetate buffer : methanol : acetonitrile (35 : 50 : 15, v/v/v) as mobile phase with a run time of 4.5 min. The detection was performed by means of triple quadrupole mass spectrometer equipped with an ESI interface operating in the multiple-reaction monitoring mode. A linear response was observed over the concentration range 5.0-1000 ng/mL. The limit of quantification was 5.0 ng/mL. Both intra- and inter-day precision, defined as relative standard deviation, were within 9.7%. Accuracy, defined as relative error, was within +/- 3.1%. The developed method was successfully applied to preclinical pharmacokinetic studies of henatinib maleate in rat after a single oral administration of the drug.

Hyperkalemia after acute metabolic decompensation in two children with vitamin B12-unresponsive methylmalonic acidemia and normal renal function.

The patients affected by vitamin B12-unresponsive methylmalonic acidemia (MMA) on the long run develop chronic renal disease with interstitial nephropathy and progressive renal insufficiency. The mechanism of nephrotoxicity in vitamin B12-unresponsive MMA is not yet known. Chronic hyporeninemic hypoaldosteronism has been found in many cases of methylmalonic acidemia, hyperkalemia and renal tubular acidosis type 4. We report 2 patients affected by B12-unresponsive methylmalonic acidemia diagnosed at the age of 23 months and 5 years, respectively, with normal glomerular filtration and function. They showed hyporeninemic hypoaldosteronism and significant hyperkalemia requiring sodium potassium exchange resin (Kayexalate) therapy after an episode of metabolic decompensation leading to diagnosis of MMA. In both children, hyporeninemic hypoaldosteronism and hyperkalemia disappeared after 6 months of good metabolic control.

A GC-MS/MS method for the quantitative analysis of low levels of the tyrosine metabolites maleylacetone, succinylacetone, and the tyrosine metabolism inhibitor dichloroacetate in biological fluids and tissues.

We developed a sensitive method to quantitate the tyrosine metabolites maleylacetone (MA) and succinylacetone (SA) and the tyrosine metabolism inhibitor dichloroacetate (DCA) in biological specimens. Accumulation of these metabolites may be responsible for the toxicity observed when exposed to DCA. Detection limits of previous methods are 200 ng/mL (1.2 pmol/microL) (MA) and 2.6 microg/mL (16.5 pmol/microL) (SA) but the metabolites are likely present in lower levels in biological specimens. To increase sensitivity, analytes were extracted from liver, urine, plasma and cultured nerve cells before and after dosing with DCA, derivatized to their pentafluorobenzyl esters, and analyzed via GC-MS/MS.

Pharmacokinetics and pharmacological effect of recombinant human granulocyte colony-stimulating factor conjugated to poly(styrene-co-maleic acid) in rats.

A new derivative of recombinant human granulocyte colony-stimulating factor (rhG-CSF) has been synthesized by conjugating rhG-CSF to poly(styrene-co-maleic acid) (poly(styrene-co-maleic acid)-rhG-CSF) to try to avoid glomerular filtration and thus potentiate the neutrophil-proliferating activity of rhG-CSF. Poly(styrene-co-maleic acid)-rhG-CSF was highly bound to bovine serum albumin (BSA) and the molecular weight of the poly(styrene-co-maleic acid)-rhG-CSF-BSA complex was estimated to be about 90000 by gel filtration. Intravenous administration of poly(styrene-co-maleic acid)-rhG-CSF to normal rats resulted in a dose-dependent increase in neutrophil count. The neutrophil-proliferating activity of poly(styrene-co-maleic acid)-rhG-CSF was about 10 times greater than that of rhG-CSF. After intravenous injection at a dose of 5 microg protein kg(-1) the total clearance of rhG-CSF fell from 71.0 to 32.1 mLh(-1) kg(-1) following poly(styrene-co-maleic acid) modification. An isolated perfusion study in rat kidney showed that the filtered fraction of rhG-CSF was reduced by conjugation with poly(styrene-co-maleic acid). These results suggest that poly(styrene-co-maleic acid)-conjugation can potentiate the neutrophil-proliferating activity of rhG-CSF by reducing, at least in part, its renal clearance.

Inhibition of ischemia and reflow-induced liver injury by an SOD derivative that circulates bound to albumin.

Ischemia followed by reflow often results in tissue injury. Although reactive oxygens seem to play an important role in the pathogenesis of postischemic reflow-induced tissue injury, the mechanism and an efficient way to inhibit oxidative injury are not known. We studied the mechanism by which hepatic transport function was inhibited by a transient occlusion followed by reflow of the portal vein and hepatic artery by using a superoxide dismutase (SOD) derivative (SM-SOD) which circulates bound to albumin with a half-life of 6 h. Occlusion of the hepatic vessels for 20 min followed by reflow for 60 min significantly inhibited transhepatic transport of cholephilic ligands, such as bromosulfophthalein (BSP) and taurocholic acid. Intravenous administration of SM-SOD markedly inhibited the reflow-induced decrease in transhepatic transport of these ligands. Thiobarbituric acid - reactive metabolites (TBAR) in the liver and plasma remained unchanged during occlusion and reflow, while TBAR in the bile increased significantly. Intravenous injection of SM-SOD inhibited the reflow-induced increase in biliary TBAR. Xanthine oxidase activity in plasma also increased during occlusion and reflow by an SM-SOD-inhibitable mechanism. Polymorphonuclear leukocyte-dependent chemiluminescence of the peripheral blood remained unchanged during occlusion, but increased markedly with time after reflow. SM-SOD also inhibited the increase in chemiluminescence almost completely. These and other results suggested that the superoxide radical and/or its metabolite(s) might play an important role in the pathogenesis of the reflow-induced liver injury and that SM-SOD might be useful for studying the mechanism for tissue injury caused by oxygen toxicity.