3-Hydroxy-3-methylglutaric, adipic, and 2-oxoglutaric acids measured by HPLC in the plasma from diabetic patients

Rapid evaluation of PHD2 inhibitory activity of natural products based on capillary electrophoresis online stacking strategy

Prolyl hydroxylase domain 2 (PHD2) is an important enzyme in the human body that perceives changes in oxygen concentration and regulates response in hypoxic environments. Evaluation of PHD2 inhibitory activity of natural products is crucial for drug development of hypoxia related diseases. At present, the detection of low concentration of α-ketoglutaric acid (the substrate of PHD2 enzymatic reaction) requires derivatization reactions or sample pretreatment, which undoubtedly increases the workload of PHD2 inhibitory activity evaluation. In this paper, a direct detection approach of α-ketoglutaric acid was established by using the online stacking strategy of capillary electrophoresis to evaluate the PHD2 inhibitory activity of natural products. Under optimized conditions, detection of a single sample can be achieved within 2 min. By calculation, the intraday precision RSD of the apparent electrophoretic mobility and peak areas of α-ketoglutaric acid are 0.92 % and 0.79 %, respectively, and the interday RSD were 1.27 % and 0.96 % respectively. The recoveries of the present approach were 97.9-105.2 %, and the LOQ and LOD were 2.0 μM and 5.0 μM, respectively. Furthermore, this approach was applied for the evaluation of inhibitory activity of PHD2 for 13 natural products, and PHD2 inhibitory activity of salvianolic acid A was firstly reported. The present work not only realizes evaluation of PHD2 inhibitory activity through direct detection of α-ketoglutaric acid, but also provides technical support for the discovery of potential drug molecules in hypoxia related diseases.

Newborn screening for 3-hydroxy-3-methylglutaric aciduria using direct analysis in real-time mass spectrometry

A novel method utilizing ambient thermal desorption ionization with a direct analysis in real-time source integrated with mass spectrometry (DART-MS) was established and applied to the rapid analysis of 3-hydroxy-3-methylglutaric (3-HMG) acid in the neonatal urine. Instrument parameter settings were optimized to obtain high sensitive and accurate determination of 3-HMG acid. The use of helium gas heated to temperature of 400°C was observed to permit deprotonation, 3-HMG acid producing an abundant (M-H)^- (m/z 161) in the negative ion mode. The calibration curve was determined to be linear over the range of 0.05-5 mg/L, with the correlation coefficient r = 0.9988 and the relative standard deviations (n = 6) in the range of 1.5-11.8%. The limit of detection was 0.002 mg/L, and the limit of quantitation was 0.007 mg/L. The recoveries ranged from 88.0% to 123.1%. Four urine samples from patients and four simulated urine samples were investigated. The results of DART-MS were in agreement with the values determined using established methods at the hospitals. The proposed method demonstrated significant potential in the application of the high-throughput screening in newborn screening.

Maternal obesity and increased neonatal adiposity correspond with altered infant mesenchymal stem cell metabolism

Maternal obesity is a global health problem that increases offspring obesity risk. The metabolic pathways underlying early developmental programming in human infants at risk for obesity remain poorly understood, largely due to barriers in fetal/infant tissue sampling. Utilizing umbilical cord-derived mesenchymal stem cells (uMSC) from offspring of normal weight and obese mothers, we tested whether energy metabolism and gene expression differ in differentiating uMSC myocytes and adipocytes, in relation to maternal obesity exposures and/or neonatal adiposity. Biomarkers of incomplete β-oxidation were uniquely positively correlated with infant adiposity and maternal lipid levels in uMSC myocytes from offspring of obese mothers only. Metabolic and biosynthetic processes were enriched in differential gene expression analysis related to maternal obesity. In uMSC adipocytes, maternal obesity and lipids were associated with downregulation in multiple insulin-dependent energy-sensing pathways including PI3K and AMPK. Maternal lipids correlated with uMSC adipocyte upregulation of the mitochondrial respiratory chain but downregulation of mitochondrial biogenesis. Overall, our data revealed cell-specific alterations in metabolism and gene expression that correlated with maternal obesity and adiposity of their offspring, suggesting tissue-specific metabolic and regulatory changes in these newborn cells. We provide important insight into potential developmental programming mechanisms of increased obesity risk in offspring of obese mothers.

Plasma acylcarnitine profiling indicates increased fatty acid oxidation relative to tricarboxylic acid cycle capacity in young, healthy low birth weight men

We hypothesized that an increased, incomplete fatty acid beta‐oxidation in mitochondria could be part of the metabolic events leading to insulin resistance and thereby an increased type 2 diabetes risk in low birth weight (LBW) compared with normal birth weight (NBW) individuals. Therefore, we measured fasting plasma levels of 45 acylcarnitine species in 18 LBW and 25 NBW men after an isocaloric control diet and a 5‐day high‐fat, high‐calorie diet. We demonstrated that LBW men had higher C2 and C4‐OH levels after the control diet compared with NBW men, indicating an increased fatty acid beta‐oxidation relative to the tricarboxylic acid cycle flux. Also, they had higher C6‐DC, C10‐OH/C8‐DC, and total hydroxyl‐/dicarboxyl‐acylcarnitine levels, which may suggest an increased fatty acid omega‐oxidation in the liver. Furthermore, LBW and NBW men decreased several acylcarnitine levels in response to overfeeding, which is likely a result of an upregulation of fatty acid oxidation due to the dietary challenge. Moreover, C10‐OH/C8‐DC and total hydroxyl‐/dicarboxyl‐acylcarnitine levels tended to be negatively associated with the serum insulin level, and the total hydroxyl‐/dicarboxyl‐acylcarnitine level additionally tended to be negatively associated with the hepatic insulin resistance index. This indicates that an increased fatty acid omega‐oxidation could be a compensatory mechanism to prevent an accumulation of lipid species that impair insulin signaling.

Simultaneous quantitation of alpha-ketoglutaric acid and 5-hydroxymethylfurfural in plasma by HPLC with UV and fluorescence detection

Alpha-ketoglutaric acid (KG) and hydroxymethylfurfural (HMF) are currently being investigated in clinical trials as an approach in targeted cancer therapy. Hence, a method for the simultaneous determination of KG and HMF in plasma has been developed. Due to the strongly discriminative chemical properties of KG and HMF, SPE purification is performed using an ion-exchange cartridge to separate KG, and a hydrophobic polymeric cartridge to separate HMF. The cartridges are connected together for several steps, thus resulting in a quicker approach for the purification of plasma samples. The derivatization step is based on the reaction of the carbonyl groups of KG and HMF with dansylhydrazine (DNSH) catalyzed by trifluoroacetic acid. The formed derivatives could be separated by reversed-phase LC on a C8-column, and analyzed by UV and fluorescence detection in a single run using a gradient program. The obtained results show good reproducibility, specificity, and detection limits down to the low picomole range.

Development and validation of a liquid chromatographic method for the determination of hydroxymethylfurfural and alpha-ketoglutaric acid in human plasma

Hydroxymethylfurfural (HMF) and alpha-ketoglutaric acid (KG) have been recently investigated as potential cancer cell damaging agents. We herein report for the first time a validated quantitative assay for their simultaneous determination in human plasma which is amenable to be applied in the future screening of the target compounds in human probands in order to properly design a targeted chemotherapeutic regimen for certain types of malignant tumors. A simple liquid chromatographic method in conjunction to derivatization after a two-step optimized solid phase clean-up procedure is described. The method is based on the reaction of HMF and KG with 2-nitrophenylhydrazine or 2,4-dinitrophenylhydrazine in an aqueous environment. Reaction conditions were studied with respect to pH, reagent volume, reaction temperature and time. Exact testing of such parameters beside careful selection of the mobile phase composition rendered feasible the quantification of the chemically significantly differing analytes along a single chromatographic run. The formed derivatives could be separated isocratically by reversed-phase LC on a C(8)-column. Detection in the UV and in the visible range is possible. Results showed good recovery and reproducibility with detection limits (S/N=3) down to 2 picomoles analyte on column. Resolution of the syn and anti geometric isomers of the HMF and KG derivatives is possible. The isomeric ratio in relation to the reaction pH is discussed.

Analysis of aliphatic dicarboxylic acids in pharmaceuticals and cosmetics by liquid chromatography (HPLC) with fluorescence detection

2-Bromoacetyl-6-methoxynaphthalene has been found to be a useful prechromatographic fluorescent labelling reagent for the analysis of dicarboxylic acids. The derivatization reaction of azelaic acid and meglutol with this reagent yieded stable and highly fluorescent diesters which could be analysed by reversed-phase HPLC with fluorescence detection. According to the nature of the sample, the derivatization reaction could be carried out in acetonitrile or in an aqueous micellar system. The proposed methods proved to be suitable for the quality control of various complex pharmaceutical and cosmetic formulations of the azelaic acid and meglutol.

Determination of glutamine and alpha-ketoglutarate concentration and specific activity in plasma using high-performance liquid chromatography

A method is described for measuring glutamine (GLN) and alpha-ketoglutarate (KG) concentration and specific activity (SA) using high-performance liquid chromatography (HPLC). Plasma GLN and KG are separated on miniature ion-exchange columns. KG is derivatized with O-phenylene diamine, the derivative is extracted in ethyl acetate, dried, and dissolved in pH 7 phosphate buffer. The isolated GLN is enzymatically converted to KG and analysed as such. Derivatized samples are stable for weeks at -20 degrees C. Samples are injected onto a reversed-phase HPLC column. Absolute standards are injected to determine the nmol content of unknown samples. alpha-Ketoadipate and [3H]-glutamine are used as internal standards to quantitate KG and GLN concentrations, respectively. Collection of the entire peak of interest permits determination of the radioactivity in the GLN and KG peaks; this together with the determination of the nanomoles injected permits the calculation of the SA. Typical precision is 3.5 and 4.6% for GLN and KG concentrations and 5.3 and 3.3% for GLN and KG SA, respectively. Analysis time is ca. 7 min. Using this method, the turnover rate of GLN carbon was determined during a 5-h infusion of L-[U-14C]glutamine in a human subject.