Interaction Liquid Chromatography-tandem Mass Spectrometry Research Articles

Comprehensive Coverage of Glycolysis and Pentose Phosphate Metabolic Pathways by Isomer-Selective Accurate Targeted Hydrophilic Interaction Liquid Chromatography-Tandem Mass Spectrometry Assay.

The accurate liquid chromatography-tandem mass spectrometry analysis of phosphorylated isomers from glycolysis and pentose phosphate pathways is a challenging analytical problem in metabolomics due to extraction problems from the biological matrix, adherence to stainless steel surfaces leading to tailing in LC, and incomplete separation of hexose and pentose phosphate isomers. In this study, we present a targeted HILIC-ESI-MS/MS method based on a BEH amide fully porous 1.7 μm particle column with an inert surface coating of column hardware and multiple reaction monitoring (MRM) acquisition fully covering the glycolysis and pentose phosphate pathway metabolites. To minimize contact of the phosphorylated analytes with stainless steel surfaces, a μ-ESI-MS probe with a hybrid electrode made of PEEKsil was employed. Optimized HILIC gradient elution conditions with 100 mM ammonium formate (pH 11) provided the separation of hexose monophosphate and pentose phosphate isomers. To ensure good retention time repeatability in HILIC, perfluoroalkoxy alkane bottles were used for the mobile phase (with sd over 60 runs between 0.01 and 0.02 min). For the quantitative assay, the U-13C-labeled cell extract was spiked prior to extraction by metal oxide-based affinity chromatography (MOAC) with TiO2 beads. The concentrations of the 24 targets were quantified in HeLa and human embryonic kidney (HEK293) cells. Erastin-induced ferroptosis in HEK293 cells was accompanied by enhanced levels of fructose-1,6-bis-phosphate, 2- and 3-phosphoglycerate, and 2,3-bis-phosphoglycerate.

Quantification of amino acids secreted by yeast cells by hydrophilic interaction liquid chromatography-tandem mass spectrometry.

Monitoring the levels of amino acids (AAs) in biological cell cultures provides key information to understand the regulation of cell growth and metabolism. Saccharomyces cerevisiae can naturally excrete AAs, making accurate detection and determination of amino acid levels within the cultivation medium pivotal for gaining insights into this still poorly known process. Given that most AAs lack ultraviolet (UV) chromophores or fluorophores necessary for UV and fluorescence detection, derivatization is commonly utilized to enhance amino acid detectability via UV absorption. Unfortunately, this can lead to drawbacks such as derivative instability, labor intensiveness, and poor reproducibility. Hence, this study aimed to develop an accurate and stable hydrophilic interaction liquid chromatography-tandem mass spectrometry analytical method for the separation of all 20 AAs within a short 17-min run time. The method provides satisfactory linearity and sensitivity for all analytes. The method has been validated for intra- and inter-day precision, accuracy, recovery, matrix effect, and stability. It has been successfully applied to quantify 20 AAs in samples of yeast cultivation medium. This endeavor seeks to enhance our comprehension of amino acid profiles in the context of cell growth and metabolism within yeast cultivation media.

Highly sensitive and accurate measurement of underivatized phosphoenolpyruvate in plasma and serum via EDTA-facilitated hydrophilic interaction liquid chromatography–tandem mass spectrometry

Phosphoenolpyruvate (PEP) is an essential intermediate metabolite that is involved in various vital biochemical reactions. However, achieving the direct and accurate quantification of PEP in plasma or serum poses a significant challenge owing to its strong polarity and metal affinity. In this study, a sensitive method for the direct determination of PEP in plasma and serum based on ethylenediaminetetraacetic acid (EDTA)-facilitated hydrophilic interaction liquid chromatography–tandem mass spectrometry was developed. Superior chromatographic retention and peak shapes were achieved using a zwitterionic stationary-phase HILIC column with a metal-inert inner surface. Efficient dechelation of PEP–metal complexes in serum/plasma samples was achieved through the introduction of EDTA, resulting in a significant enhancement of the PEP signal. A PEP isotopically labelled standard was employed as a surrogate analyte for the determination of endogenous PEP, and validation assessments proved the sensitivity, selectivity, and reproducibility of this method. The method was applied to the comparative quantification of PEP in plasma and serum samples from mice and rats, as well as in HepG2 cells, HEK293T cells, and erythrocytes; the results confirmed its applicability in PEP-related biomedical research. The developed method can quantify PEP in diverse biological matrices, providing a feasible opportunity to investigate the role of PEP in relevant biomedical research.

Simultaneous analysis of acyclovir and its metabolite using hydrophilic interaction liquid chromatography-tandem mass spectrometry.

The antiviral drug acyclovir (ACV) may induce drug-induced neuropsychiatric symptoms as side effects. The detailed pathogenic mechanism remains unclear; however, it is hypothesized that 9-carboxymethoxymethylguanine (CMMG), a metabolite of ACV, is the causative compound. Therefore, the blood concentrations of ACV and CMMG should be analyzed in ACV toxicity studies. However, it is rare to find methods that can sufficiently separate the ACV and CMMG peaks during simultaneous analysis of both compounds. Therefore, we intended to develop a liquid chromatography-tandem mass spectrometry method with improved peak separation of analytes. Samples were deproteinized using methanol/acetonitrile solution (6:4, v/v). Analytes were separated on an InertSustain® Amide column (3 μm, 2.1 mm × 150 mm). The mobile phase consisted of acetonitrile/10 mM ammonium formate (5:95, v/v) (A) and acetonitrile/10 mM ammonium formate (95:5, v/v, pH 5.0) (B) and samples were eluted in the gradient mode. The separation of analytes was satisfactory and the peak shapes were good. Linear regression models weighted 1/x2 were obtained in the range of 0.25-10 μg/mL. The range of quality control (QC) bias was between 3.6% and 19.8%, and the within-run and between-run precisions of QC were within 13.5%. Recovery ranged from 83.6% to 103.7%, but ion suppression was observed. Samples from a patient with ACV encephalopathy were analyzed using this method. The resulting blood ACV and CMMG concentrations were 8.2 and 8.5 μg/mL, respectively. This method, with sufficient separation of ACV and CMMG, proved useful for use in ACV toxicity studies.

Determination of dimethylated nucleosides in serum from colorectal cancer patients by hydrophilic interaction liquid chromatography-tandem mass spectrometry

RNA modifications play a crucial regulatory role in a variety of biological processes and are closely related to numerous diseases, including cancer. The diversity of metabolites in serum makes it a favored biofluid for biomarkers discovery. In this work, a robust and accurate hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) approach was established for simultaneous determination of dimethylated nucleosides in human serum. Using the established method, we were able to accurately quantify the concentrations of N6-2′-O-dimethyladenosine (m6Am), N2,N2-dimethylguanosine (m2,2G), and 5,2′-O-dimethyluridine (m5Um) in serum samples from 53 healthy controls, 57 advanced colorectal adenoma patients, and 39 colorectal cancer (CRC) patients. The results showed that, compared with healthy controls and advanced colorectal adenoma patients, the concentrations of m6Am and m2,2G were increased in CRC patients, while the concentration of m5Um was decreased in CRC patients. These results indicate that these three dimethylated nucleosides could be potential biomarkers for early detection of colorectal cancer. Interestingly, the level of m5Um was gradually decreased from healthy controls to advanced colorectal adenoma patients to CRC patients, indicating m5Um could also be used to evaluate the level of malignancy of colorectal tumor. In addition, this study will contribute to the investigation on the regulatory mechanisms of RNA dimethylation in the onset and development of colorectal cancer.

Quality Evaluation of Gentamicin Sulfate Reference Standards in Japanese Pharmacopoeia Using Hydrophilic Interaction Chromatography Combined With Tandem Mass Spectrometry.

Through the recent development of analytical technology, antibiotics quantification in the Japanese Pharmacopoeia (JP) has changed from traditional microbiological assays to physicochemical methods with high specificity and precision. However, for several multicomponent antibiotics without typical UV absorption, potency cannot be directly determined using instrumental methods such as high-performance liquid chromatography; therefore, traditional microbiological assays are still used. Gentamicin sulfate (GmS), which consists of three major components, C1, C1a, and C2, is such a typical antibiotic, and its antimicrobial potency continues to be assayed using microbiological methods in JP monographs. Introduction of a physicochemical assay for GmS is needed to help ensure its quality and quantity. This study aimed to develop quality control measures for GmS that could be complementary to quantitative assays and purity tests specified in the JP. For each gentamicin C component (C1, C2, and C1a), theoretical potencies were determined based on the quantitative relationship between purity and potency, as measured by quantitative 1H NMR and microbiological assays, respectively. Two lots of the JP reference standard (RS) were used as test samples, with the contents of each component and impurity (sisomicin and garamine) being determined using hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS). The ratios of theoretical potency for C1, C2, and C1a were 1.00, 1.21, and 1.80, respectively. The potencies of the GmS JP RSs, which were estimated based on the contents and theoretical potency of each C component, corresponded well with those determined through microbiological assays. Marked differences in impurities (%) between the two RS lots were highlighted by quantifying sisomicin and garamine. The developed analytical procedure enabled the characterization of two different JP RSs in terms of content ratio, potencies, and impurities. Novel analytical procedures useful for routine quality control of GmS were developed using HILIC-MS/MS.

Development of targeted hydrophilic interaction liquid chromatography-tandem mass spectrometry method for acyl-Coenzyme A covering short- to long-chain species in a single analytical run

Acyl-CoAs play a significant role in numerous physiological and metabolic processes making it important to assess their concentration levels for evaluating metabolic health. Considering the important role of acyl-CoAs, it is crucial to develop an analytical method that can analyze these compounds. Due to the structural variations of acyl-CoAs, multiple analytical methods are often required for comprehensive analysis of these compounds, which increases complexity and the analysis time. In this study, we have developed a method using a zwitterionic HILIC column that enables the coverage of free CoA and short- to long-chain acyl-CoA species in one analytical run. Initially, we developed the method using an LC-QTOF instrument for the identification of acyl-CoA species and optimizing their chromatography. Later, a targeted HILIC-MS/MS method was created in scheduled multiple reaction monitoring mode using a QTRAP MS detector. The performance of the method was evaluated based on various parameters such as linearity, precision, recovery and matrix effect. This method was applied to identify the difference in acyl-CoA profiles in HepG2 cells cultured in different conditions. Our findings revealed an increase in levels of acetyl-CoA, medium- and long-chain acyl-CoA while a decrease in the profiles of free CoA in the starved state, indicating a clear alteration in the fatty acid oxidation process.

Circulating choline and phosphocholine measurement by a hydrophilic interaction liquid chromatography–tandem mass spectrometry

BackgroundGiven the growing interest in studying the role of choline and phosphocholine in the development and progression of tumor pathology, in this study we describe the development and validation of a fast and robust method for the simultaneous analysis of choline and phosphocholine in human plasma. MethodsCholine and phosphocholine quantification in human plasma was obtained using a hydrophilic interaction liquid chromatography–tandem mass spectrometry technique. Assay performance parameters were evaluated using EMA guidelines. ResultsCalibration curve ranged from 0.60 to 38.40 μmol/L (R2 = 0.999) and 0.08–5.43 μmol/L (R2 = 0.998) for choline and phosphocholine, respectively. The Limit Of Detection of the method was 0.06 μmol/L for choline and 0.04 μmol/L for phosphocholine. The coefficient of variation range for intra-assay precision is 2.2–4.1 % (choline) and 3.2–15 % (phosphocholine), and the inter-assay precision range is < 1–6.5 % (choline) and 6.2–20 % (phosphocholine). The accuracy of the method was below the ±20 % benchmarks at all the metabolites concentration levels. In-house plasma pool of apparently healthy adults was tested, and a mean concentration of 15.97 μmol/L for Choline and 0.34 μmol/L for Phosphocholine was quantified. ConclusionsThe developed method shows good reliability in quantifying Choline and Phosphocholine in human plasma for clinical purposes.

Appearance of choline metabolites in plasma and milk when choline is infused into the abomasum with or without methionine

Four lactating, ruminally cannulated Jersey cows, (mean ± standard deviation) 264 ± 54.2 d in milk and 484 ± 24.1 kg of body weight, were arranged in a 4 × 4 Latin square design to measure the effects of abomasal infusion of choline chloride with or without dl-Met on milk and plasma choline metabolites and plasma AA in cows fed a Met-deficient diet. Cows were randomly assigned to 1 of 4 experimental treatments: (1) control; no supplemental Met or choline (CON), (2) 13 g/d of choline ion delivered via abomasal infusion (CHO), (3) 13 g/d of Met delivered via abomasal infusion (MET), and (4) 13 g/d of choline and 13 g/d of Met delivered via abomasal infusion (CHO + MET). Cows received the same basal diet throughout the experiment, which was formulated to be deficient in Met (−5.0 g of Met using the NASEM, 2021, model). Periods were 7 d in length with d 1 to 2 serving as a wash-out period and cows being infused on d 3 to 7. Milk samples were collected twice daily on d 5 to 7 and were analyzed for fat, true protein, lactose, and choline metabolites including betaine, phosphocholine, and free choline using hydrophilic interaction liquid chromatography-tandem mass spectrometry. Blood samples were collected via venipuncture of the coccygeal vein at 1100, 1300, and 1500 h on d 7 of each period and were analyzed for free AA as well as choline metabolites. Plasma Met increased in response to Met infusion and an interaction with choline and Met infusion was observed in the plasma concentration of branched-chain AA. Cows receiving choline exhibited the greatest Cho yield in milk. Milk phosphocholine yield tended to be highest when both choline and Met were infused.

Development of a targeted hydrophilic interaction liquid chromatography-tandem mass spectrometry based lipidomics platform applied to a coronavirus disease severity study

The importance of lipids seen in studies of metabolism, cancer, the recent COVID-19 pandemic and other diseases has brought the field of lipidomics to the forefront of clinical research. Quantitative and comprehensive analysis is required to understand biological interactions among lipid species. However, lipidomic analysis is often challenging due to the various compositional structures, diverse physicochemical properties, and wide dynamic range of concentrations of lipids in biological systems. To study the comprehensive lipidome, a hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS)-based screening method with 1200 lipid features across 19 (sub)classes, including both nonpolar and polar lipids, has been developed. HILIC-MS/MS was selected due to its class separation property and fatty acyl chain level information. 3D models of class chromatographic retention behavior were established and evaluations of cross-class and within-class interferences were performed to avoid over-reporting these features. This targeted HILIC-MS/MS method was fully validated, with acceptable analytical parameters in terms of linearity, precision, reproducibility, and recovery. The accurate quantitation of 608 lipid species in the SRM 1950 NIST plasma was achieved using multi-internal standards per class and post-hoc correction, extending current databases by providing lipid concentrations resolved at fatty acyl chain level. The overall correlation coefficients (R2) of measured concentrations with values from literature range from 0.64 to 0.84. The applicability of the developed targeted lipidomics method was demonstrated by discovering 520 differential lipid features related to COVID-19 severity. This high coverage and targeted approach will aid in future investigations of the lipidome in various disease contexts.

Optimization Strategies for Mass Spectrometry-Based Untargeted Metabolomics Analysis of Small Polar Molecules in Human Plasma.

The untargeted approach to mass spectrometry-based metabolomics has a wide potential to investigate health and disease states, identify new biomarkers for diseases, and elucidate metabolic pathways. All this holds great promise for many applications in biological and chemical research. However, the complexity of instrumental parameters on advanced hybrid mass spectrometers can make the optimization of the analytical method immensely challenging. Here, we report a strategy to optimize the selected settings of a hydrophilic interaction liquid chromatography-tandem mass spectrometry method for untargeted metabolomics studies of human plasma, as a sample matrix. Specifically, we evaluated the effects of the reconstitution solvent in the sample preparation procedure, the injection volume employed, and different mass spectrometry-related operating parameters including mass range, the number of data-dependent fragmentation scans, collision energy mode, duration of dynamic exclusion time, and mass resolution settings on the metabolomics data quality and output. This study highlights key instrumental variables influencing the detection of metabolites along with suggested settings for the IQ-X tribrid system and proposes a new methodological framework to ensure increased metabolome coverage.

Determination of seventeen sugars and sugar alcohols in fruit juice samples using hydrophilic interaction liquid chromatography-tandem mass spectrometry combining response surface methodology design

Carbohydrates are the main source of energy for all organisms to sustain their life activities and probably the most common organic substances in nature, whose main source is grains, starchy vegetables and fruits. To clarify the content and distribution of sugars and sugar alcohols in different fruit species samples accurately, a rapid and sensitive hydrophilic interaction liquid chromatography-electrospray ionization-tandem mass spectrometry (HILIC-ESI-MS/MS) method combining ultrasonic-assisted extraction (UAE) and solid phase extraction (SPE) purification was developed for quantitative determination seventeen sugars and sugar alcohols in fruit juice. In this method, the targets were firstly extracted from 1 g of fruit juice sample using 40 mL double-distilled water by ultrasonic-assisted extraction (UAE) for 10 min according to the optimization of response surface methodology (RSM) design. Then, 1.0 mL of UAE extracted solution was cleaned using an amino (NH2) SPE cartridge in the following SPE procedure. Seventeen compounds were separated in 25 min using the HILIC column by a gradient with 0.1% of ammonium hydroxide and acetonitrile as mobile phase. The HILIC-MS/MS method was validated, with the following studies including limit of detection, linearity range, stability and recovery. The limits of detection (LOD) were between 1.2 and 228 ng/g and linear correlation coefficients (R2) were more than 0.994. The average recoveries of 17 sugars and sugar alcohols ranging from 81.8 to 114.9%. The results showed that inter-day and intra-day precision were found to be within acceptable range. The strategy was successfully used for profiling of sugars and sugar alcohols in various fruit juice matrices.

Analysis of Taurine in Infant Formulas and Adult Nutritionals by Hydrophilic Interaction Liquid Chromatography-Mass Spectrometry: First Action 2022.03.

Taurine is recognized as an essential growth factor and as being critical in the maintenance of functional tissue regulation. To evaluate the analytical performance of a hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) method for compliance with AOAC Standard Method Performance Requirements (SMPR®) for taurine analysis described in SMPR 2014.013. Following protein precipitation with Carrez solutions, taurine is extracted and separated by HILIC with detection by triple quadrupole MS using multiple reaction monitoring (MRM). Stable isotope labeled (SIL) taurine internal standard is used for quantification to correct for losses in extraction and variations in ionization in the ion source. The method was shown to meet the requirements specified in the SMPR with a linear range of 0.27-2700 mg/hg RTF (ready-to-feed), a limit of detection of 0.14 mg/hg RTF, acceptable recovery of 97.2-100.1%, and acceptable repeatability of 1.6-6.4% relative standard deviation. Additionally, the method was found to have no statistically significant bias compared with reference values for National Institute of Standards and Technology (NIST) 1849a certified reference material (CRM) (P-value = 0.95) and 1869 CRM (P-value = 0.31), and with results from AOAC 997.05 (P-value = 0.10). A recent review of the method and validation data by the Stakeholder Program on Infant Formula and Adult Nutritionals (SPIFAN) Expert Review Panel (ERP) found that this method met all the criteria for analysis of taurine specified in SMPR 2014.013 and voted to adopt this method as First Action AOAC Official MethodSM2022.03. A method for the analysis of taurine in infant formulas and adult nutritionals by HILIC-MS/MS is described. A single-laboratory validation (SLV) study demonstrated the applicability of the method to meet requirements of SMPR 2014.013. In December 2022, the SPIFAN ERP voted to adopt this method as First Action AOAC Official Method 2022.03.

High-Throughput Analysis of Underivatized Amino Acids and Acylcarnitines in Infant Serum: A Micromethod Based on Stable Isotope Dilution Targeted HILIC-ESI-MS/MS.

Amino acids and acylcarnitines are important biomarkers of the body's energy state and can be used as diagnostic markers of certain inborn errors of metabolism. Few multianalyte methods for high-throughput analysis in serum exist for these compounds, but micromethods suitable for use in young children and infants are lacking. Therefore, we developed a quantitative high-throughput multianalyte hydrophilic interaction liquid chromatography-tandem mass spectrometry method preceded by a derivatization-free sample preparation using minimum amounts of serum (25 μL). Isotopically labeled standards were utilized for quantification. Forty amino acids and amino acid derivatives and 22 acylcarnitines were detected by applying a multiple reaction monitoring mode within a 20 min run. The method was comprehensively validated, comprising linearity, accuracy, (intraday/interday) precision, and quantitation limits, of which the latter ranged from 0.25 to 50 nM for acylcarnitines and from 0.005 to 1 μM for amino acids and their derivatives. Application of the method to 145 serum samples of three- to four-month-old healthy infants showed excellent reproducibility for multiday analyses and enabled simultaneous amino acid and acylcarnitine profiling in this age group.

Determination of Multiclass Cyanotoxins in Blue-Green Algae (BGA) Dietary Supplements Using Hydrophilic Interaction Liquid Chromatography-Tandem Mass Spectrometry.

In recent years, the consumption of blue-green algae (BGA) dietary supplements is increasing because of their health benefits. However, cyanobacteria can produce cyanotoxins, which present serious health risks. In this work we propose hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry (HILIC-MS/MS) to determine cyanotoxins in BGA dietary supplements. Target toxins, including microcystin-leucine-arginine (MC-LR) and microcystin-arginine-arginine (MC-RR), nodularin, anatoxin-a and three non-protein amino acids, β-N-methylamino-L-alanine (BMAA), 2,4-diaminobutyric acid (DAB) and N-(2-aminoethyl)glycine (AEG), were separated using a SeQuant ZIC-HILIC column. Cyanotoxin extraction was based on solid-liquid extraction (SLE) followed by a tandem-solid phase extraction (SPE) procedure using Strata-X and mixed-mode cation-exchange (MCX) cartridges. The method was validated for BGA dietary supplements obtaining quantification limits from 60 to 300 µg·kg-1. Nine different commercial supplements were analyzed, and DAB, AEG, and MCs were found in some samples, highlighting the relevance of monitoring these substances as precaution measures for the safe consumption of these products.

Analysis of degradation products of Novichok agents in human urine by hydrophilic interaction liquid chromatography–tandem mass spectrometry

PurposeThe detection of hydrolysis products of Novichok agents in biological samples from victims is important for confirming exposure to these agents. However, Novichok agents are new class of nerve agent and there have been only few reports on analyses of Novichok agent degradation products. Here, we developed hydrophilic interaction liquid chromatography (HILIC)–tandem mass spectrometry (MS/MS) methods to detect Novichok agent degradation products in human urine with simple pretreatment and high sensitivity.MethodsA Poroshell 120 HILIC-Z column was used to analyze six Novichok agent degradation products. For urine samples, we used a simple pretreatment method, which consisted of deproteinization with acetonitrile and microfiltration. We calculated the pKa values of the OH groups, the log P values, and the molecular weights to investigate the difference in chromatographic behaviors of the Novichok agent degradation products and the degradation products of conventional nerve agents.ResultsSix Novichok agent degradation products, including N-(bis-(diethylamino)methylidene)-methylphosphonamidic acid (MPGA), which could not be detected by our previous method, could be analyzed with sufficient peak shape and mutual separation. The detection limits of six Novichok agent degradation products were sufficiently low (1–50 ng/mL) and the calibration curves showed sufficient linearity. The physicochemical parameters of Novichok agent degradation products were different from those of conventional nerve agent degradation products, and this explains the difference in chromatographic behaviors.ConclusionSix Novichok agent degradation products were successfully analyzed by HILIC–MS/MS. Due to the absence of a derivatization step, throughput performance was higher than our previous derivatization-liquid chromatography–MS/MS method.

Pan-cancer analysis of DNA epigenetic modifications by hydrophilic interaction liquid chromatography-tandem mass spectrometry

Accumulating evidence in recent years indicates that DNA methylation (5-methyl-2′-deoxycytidine, 5-mdC) and hydroxymethylation (5-hydroxymethyl-2′-deoxycytidine, 5-hmdC) have been implicated in various biological processes, and the aberrations of these DNA cytosine modifications is tightly associated with cancer. N6-methyl-2′-deoxyadenosine (m6dA), as a newly discovered epigenetic modification in genome of mammals, has been demonstrated to play vital regulatory roles in tumorigenesis. However, the content information of m6dA in human tumor tissues is still limited and pan-cancer analysis of these DNA epigenetic modifications is lacked. Herein, we developed a sensitive and robust stable isotope-diluted hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) method for accurate quantification of m6dA, 5-mdC and 5-hmdC in genomic DNA from 82 pairs of human tumor tissues and matched tumor-adjacent normal tissues. The types of tumors included esophagus cancer, lung cancer, breast cancer, liver cancer, pancreatic cancer, gastric cancer, stromal tumor and colorectal cancer. Compared to the normal tissues, we revealed the level of m6dA was increased in tumor tissues of esophagus cancer, lung cancer and liver cancer, whereas the level of m6dA was diminished in tumor tissues of pancreatic cancer and gastric cancer; while the contents of 5-mdC and 5-hmdC exhibited significant decrease in tumor tissues of most types of cancer. It is worth noting that we revealed, for the first time, the content of genomic m6dA in pancreatic cancer, stromal tumor and colorectal cancer. The significant changes of these DNA epigenetic modifications indicate they may serve as indicators of cancers. In addition, this study will benefit for better understanding of the regulatory roles of these DNA epigenetic modifications in cancers.

Targeted profiling of polar metabolites in cancer metabolic reprogramming by hydrophilic interaction liquid chromatography-tandem mass spectrometry

Metabolic reprogramming of cancer cells is a hallmark of cancer, in which the polar metabolites involving aerobic glycolysis, pentose phosphate pathway (PPP), tricarboxylic acid (TCA) cycle, and glutaminolysis play a crucial role in the occurrence and development of cancer. Therefore, targeted analysis of the polar metabolites in these pathways is of great value for understanding cancers, finding diagnostic biomarkers, and identifying therapeutic targets. However, it is still challenging to directly determine polar metabolites in these pathways without derivatization due to their diverse chemical properties, isomers, and strong polarity. Herein, a highly selective and sensitive HILIC-MS/MS method was developed for direct determination of the polar metabolites in aerobic glycolysis, PPP, TCA cycle, and glutaminolysis pathways. Without derivatization, 19 polar metabolites and their isomers with carbonyl, carboxyl, or phosphoryl groups in human plasma and cell extracts of prostate cancer (PC) were determined with strong retention and high resolution. This method has been widely verified by measuring linearity, precision, sensitivity, repeatability, matrix effect, and accuracy. The analysis of plasma samples by HILIC-MS/MS revealed distinct PC-specific metabolic signatures compared to a healthy control. In addition, this method could also be used to screen the targets of metabolic inhibitors at the cellular level. We conclude that the developed HILIC-MS/MS method provides a valuable means to study the cancer metabolic reprogramming or energy metabolism in living organisms.

Hydrophilic Interaction Liquid Chromatography–Tandem Mass Spectrometry of 5-Aminolevulinic Acid for Low Concentration and Small Sample Volumes

Hydrophilic Interaction Liquid Chromatography–Tandem Mass Spectrometry of 5-Aminolevulinic Acid for Low Concentration and Small Sample Volumes

Metabolic profiling workflow for cell extracts by targeted hydrophilic interaction liquid chromatography-tandem mass spectrometry

In this study, a targeted approach with wide metabolite coverage was developed for cellular metabolomic analysis using a UHPLC-QTrap-MS system operated in the scheduled multiple reaction monitoring (sMRM) mode. MRM ion pairs were acquired from HeLa cell samples through untargeted analysis using UHPLC-QTOF-MS with SWATH acquisition complemented by missing metabolites from pathway databases. Four different cell extraction protocols were studied and compared based on an experiment series involving the calculation of individual metabolite recoveries (pre/post extraction spiking U-13C isotope-labeled standards), with a Methanol/Water extraction mixture (1:1; v/v) showing the best results. Two HILIC-MS methods employing a Waters Premier BEH Amide column were developed, utilizing two different chromatographic conditions (20 mM ammonium formate as buffer additive adjusted to a pH = 3.5 with formic acid in ESI+ mode and 20 mM ammonium acetate adjusted to a pH = 7.5 with acetic acid in ESI− mode. One hundred sixty-one (161) metabolites were successfully detected in ESI+ mode, whereas 92 were detected in negative ionization mode, totaling to a number of 253 compounds in three different biological matrices covered by the analytical system employed. Both established HILIC methods were calibrated and validated based on 105 authentic chemical standards and U-13C-labeled Pichia pastoris (Komagataella phaffii) yeast extract as internal standards for cellular matrix (HeLa cells). Within-day and between-day precision was determined on three different QC concentration levels and was below 15% for the entirety of the analytes. Inter- and intra-day accuracies showed values in the range between 85 and 115% (assessed as % recovery) in the entire range. Matrix effects, extraction recoveries and process efficiencies were evaluated following the Matuszewski protocol with U-13C-labeled Pichia pastoris metabolite extract as internal standards. Eventually, the method was utilized to quantify metabolites in HeLa cell extracts.