Aqueous normal phase chromatography improves quantification and qualification of homocysteine, cysteine and methionine by liquid chromatography–tandem mass spectrometry

Commutability assessment of reference materials for homocysteine

OBJECTIVES

Commutability of reference materials is essential for ensuring the traceability of patient measurement results and the technical basis for the use of reference materials. Commutability is only relevant for matrixed reference material; it is a prerequisite for the accuracy and authenticity of calibration methods. In this study, we evaluated the commutability of reference materials for homocysteine.

METHODS

Five conventional measurement methods were applied to simultaneously measure 30 serum samples and seven homocysteine reference materials from the National Institute of Standards and Technology and the National Institute of Metrology. Liquid chromatography tandem-mass spectrometry was used as a reference method. Two methods were used to evaluate the commutability of the seven reference materials according to the Clinical and Laboratory Standards Institute EP30-A and the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) commutability assessment document.

RESULTS

Among 35 combinations of the five conventional methods and seven reference materials, after evaluation in accordance with the EP30-A, the seven reference materials passed the commutability assessment, and 34 combinations were commutable. According to the IFCC, the commutability evaluation of 28 combinations was conclusive (commutable or non-commutable), while results for the remaining seven combinations could not be determined.

CONCLUSIONS

The homocysteine reference materials showed good commutability. The sensitivity of the measurement procedure, measurement deviation and uncertainty, and differences in the "measurand" selected by different methods may affect the evaluation results. Additionally, different judgment standards for different methods may explain the observed variations in evaluation results.

Multiple Micronutrients, Lutein, and Docosahexaenoic Acid Supplementation during Lactation: A Randomized Controlled Trial

Breastfed infants require an adequate supply of critical nutrients for growth, tissue functions, and health. Recommended intakes for several nutrients are considerably higher in lactating than non-lactating women but are not always met with habitual diets. We report a randomized, double-blind clinical trial in 70 healthy lactating women in Germany evaluating the effects of supplementation with multiple micronutrients, lutein, and docosahexaenoic acid (DHA) compared to placebo on maternal nutrient status and milk composition. The primary endpoint was the effect on the change of human milk DHA content (as a proportion of total milk fatty acids) during 12 weeks of supplementation. Maternal blood and milk biomarkers were measured as secondary endpoints. Supplementation increased maternal milk DHA by 30% compared to a decline in the placebo group. Supplementation also increased maternal blood DHA (17%), eicosapentaenoic acid (4%), 25-OH-vitamin D (24%), vitamin B12 (12%), lutein (4%), and beta carotene (49%), while homocysteine decreased. No significant difference in the number of adverse events was observed between supplementation and placebo groups. In conclusion, multi-micronutrient supplementation was safe and increased maternal blood and milk concentrations of selected nutrients in healthy women.

Regioisomer-independent quantification of fatty acid oxidation products by HPLC-ESI-MS/MS analysis of sodium adducts

Despite growing acknowledgement of the role of oxidized fatty acids (oxFA) as cellular signaling molecules and in the pathogenesis of disease, developing methods to measure these species in biological samples has proven challenging. Here we describe a novel method utilizing HPLC-ESI-MS/MS to identify and quantify multiple full-length oxFA species in a regioisomer-independent manner without the need for time-consuming sample preparation or derivatization. Building on recent progress in the characterization of FA and their oxidation products by MS/MS, we employed positive-ion ionization by measuring sodium adducts in conjunction with Differential Energy Qualifier Ion Monitoring to unequivocally verify the presence of the hydroperoxide, hydroxide, and ketone oxidation products of linoleic and arachidonic acid. Our HPLC method achieved separation of these oxidized species from their unoxidized counterparts while maintaining regioisomer-independent elution, allowing quantification over a 5 log10 range with a lower limit of quantification of 0.1 picomoles. With a simple sample preparation and a runtime as low as 11 minutes, our method allows the rapid and facile detection and measurement of full-length oxFA in biological samples. We believe this approach will allow for new insight and further investigation into the role of oxFA in metabolic disease.

The Development of Silica Hydride Stationary Phases for High-Performance Liquid Chromatography from Conception to Commercialization

The development of a stationary phase material for high-performance liquid chromatography based on a surface of silica hydride as opposed to silanols on ordinary silica is discussed including synthetic approaches, characterization, and applications. There are several synthetic approaches available to create a silica hydride surface. Modification of the Si–H moiety on the silica surface can be accomplished through the use of a hydrosilation reaction. Both the intermediate silica hydride and the material modified with an organic moiety can be characterized by a number of spectroscopic as well as a variety of other methods. Further insights into the retention mechanism are provided through chromatographic measurements. The ultimate utility of any chromatographic stationary phase material is determined by its success in solving challenging analytical problems. A broad range of applications is reviewed to illustrate the versatility and usefulness of silica hydride-based stationary phases.

Current Trends in Cancer Biomarker Discovery Using Urinary Metabolomics: Achievements and New Challenges

BACKGROUND

The development of effective screening methods for early cancer detection is one of the foremost challenges facing modern cancer research. Urinary metabolomics has recently emerged as a potentially transformative approach to cancer biomarker discovery owing to its noninvasive sampling characteristics and robust analytical feasibility.

OBJECTIVE

To provide an overview of new developments in urinary metabolomics, cover the most promising aspects of hyphenated techniques in untargeted and targeted metabolomics, and to discuss technical and clinical limitations in addition to the emerging challenges in the field of urinary metabolomics and its application to cancer biomarker discovery.

METHODS

A systematic review of research conducted in the past five years on the application of urinary metabolomics to cancer biomarker discovery was performed. Given the breadth of this topic, our review focused on the five most widely studied cancers employing urinary metabolomics approaches, including lung, breast, bladder, prostate, and ovarian cancers.

RESULTS

As an extension of conventional metabolomics, urinary metabolomics has benefitted from recent technological developments in nuclear magnetic resonance, mass spectrometry, gas and liquid chromatography, and capillary electrophoresis that have improved urine metabolome coverage and analytical reproducibility. Extensive metabolic profiling in urine has revealed a significant number of altered metabolic pathways and putative biomarkers, including pteridines, modified nucleosides, and acylcarnitines, that have been associated with cancer development and progression.

CONCLUSION

Urinary metabolomics presents a transformative new approach toward cancer biomarker discovery with high translational capacity to early cancer screening.

Simultaneous determination of sulfur compounds from the sulfur pathway in rat plasma by liquid chromatography tandem mass spectrometry: application to the study of the effect of Shao Fu Zhu Yu decoction

A sensitive, accurate, and time-saving approach was developed for the simultaneous quantification of eight sulfur compounds in the sulfur pathway, which could reflect the status of an organism, including oxidative stress, signal transduction, enzyme reaction, and so on. In order to overcome the instability of highly reactive sulfhydryl compounds, N-ethylmaleimide derivatization was adopted to effectively protect sulfhydryl-containing samples. Using isotope-labeled glutathione (GSH-¹³C₂, ¹⁵N), the validated method was demonstrated to offer satisfactory linearity, accuracy, and precision. Separation was done by UHPLC, using a BEH amide column. Accordingly, 0.1% formic acid acetonitrile was selected as the precipitant. A tandem mass spectrometer was coupled to the chromatographic system and afforded a detection limit of 0.2 ng/mL. Good linearity was maintained over a wide concentration range (r² > 0.994), and the accuracy was in the range of 86.6-114% for all the studied compounds. The precision, expressed in RSD%, ranged from 1.1% to 9.4% as intraday variability and less than 13% as interday precision for all of the analytes. The approach was applied to study the potential therapeutic mechanism of a well-known traditional Chinese medicine, Shao Fu Zhu Yu decoction. The results suggested that Shao Fu Zhu Yu decoction might protect against oxidative damage by increasing the concentrations of sulfhydryl compounds. Graphical abstract An approach to quantitatively determining sulfur compounds in the sulfur pathway simultaneously wasestablished and applied to the study of the effect of Shao Fu Zhu Yu decoction.

Quantification of methionine and selenomethionine in biological samples using multiple reaction monitoring high performance liquid chromatography tandem mass spectrometry (MRM-HPLC-MS/MS)

Quantification of selenated amino-acids currently relies on methods employing inductively coupled plasma mass spectrometry (ICP-MS). Although very accurate, these methods do not allow the simultaneous determination of standard amino-acids, hampering the comparison of the content of selenated versus non-selenated species such as methionine (Met) and selenomethionine (SeMet). This paper reports two approaches for the simultaneous quantification of Met and SeMet. In the first approach, standard enzymatic hydrolysis employing Protease XIV was applied for the preparation of samples. The second approach utilized methanesulfonic acid (MA) for the hydrolysis of samples, either in a reflux system or in a microwave oven, followed by derivatization with diethyl ethoxymethylenemalonate. The prepared samples were then analyzed by multiple reaction monitoring high performance liquid chromatography tandem mass spectrometry (MRM-HPLC-MS/MS). Both approaches provided platforms for the accurate determination of selenium/sulfur substitution rate in Met. Moreover the second approach also provided accurate simultaneous quantification of Met and SeMet with a low limit of detection, low limit of quantification and wide linearity range, comparable to the commonly used gas chromatography mass spectrometry (GC-MS) method or ICP-MS. The novel method was validated using certified reference material in conjunction with the GC-MS reference method.

High-throughput and simultaneous quantitative analysis of homocysteine-methionine cycle metabolites and co-factors in blood plasma and cerebrospinal fluid by isotope dilution LC-MS/MS

The methionine cycle is a key pathway contributing to the regulation of human health, with well-established involvement in cardiovascular diseases and cognitive function. Changes in one-carbon cycle metabolites have also been associated with mild cognitive decline, vascular dementia, and Alzheimer's disease. Today, there is no single analytical method to monitor both metabolites and co-factors of the methionine cycle. To address this limitation, we here report for the first time a new method for the simultaneous quantitation of 17 metabolites in the methionine cycle, which are homocysteic acid, taurine, serine, cysteine, glycine, homocysteine, riboflavin, methionine, pyridoxine, cystathionine, pyridoxamine, S-adenosylhomocysteine, S-adenosylmethionine, betaine, choline, dimethylglycine, and 5-methyltetrahydrofolic acid. This multianalyte method, developed using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), provides a highly accurate and precise quantitation of these 17 metabolites for both plasma and cerebrospinal fluid metabolite monitoring. The method requires a simple sample preparation, which, combined with a short chromatographic run time, ensures a high sample throughput. This analytical strategy will thus provide a novel metabolomics approach to be employed in large-scale observational and intervention studies. We expect such a robust method to be particularly relevant for broad and deep molecular phenotyping of individuals in relation to their nutritional requirements, health monitoring, and disease risk management.

Quantitation of sulfur-containing amino acids, homocysteine, methionine and cysteine in dried blood spot from newborn baby by HPLC-fluorescence detection

Sulfur-containing amino acids (SAAs), homocysteine (Hcy), methionine (Met) and cysteine (Cys) in blood are related to homocystinuria, an inborn error of metabolism. In this study, an assay method with HPLC-fluorescence detection to quantify the SAAs in a dried blood spot was established and applied to samples from newborn babies (n=200). Sample pretreatment involving reduction, derivatization with 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole, and liquid-liquid extraction with ethyl acetate gave the separation of the derivatives with retention times within 12 min. The method was enough sensitive to determine the SAAs in a dried blood spot with 0.04-0.14 µm as the limit of detection at a signal-to-noise ratio of 3. However, the absolute recoveries were very low (5.7% for Hcy, 4.6% for Cys) except for Met (105.4%) owing to inefficient recovery of Hcy and Cys from the blood matrix. Other validation parameters such as accuracy (93.5-106.2%) and intra- (≤ 9.0%) and inter-day precisions (≤ 8.7%) were acceptable. The reliability of a dried blood spot as an analytical sample was estimated. Furthermore, the proposed method was successfully applied to dried blood spots prepared from newborn babies.

Safranin and cysteine capped gold nanoparticles: spectroscopic qualitative and quantitative studies

The interaction between cysteine and safranin with citrate capped gold nanoparticles was studied.

Regulation of early human growth: impact on long-term health

Growth and development are central characteristics of childhood. Deviations from normal growth can indicate serious health challenges. The adverse impact of early growth faltering and malnutrition on later health has long been known. In contrast, the impact of rapid early weight and body fat gain on programming of later disease risk have only recently received increased attention. Numerous observational studies related diet in early childhood and rapid early growth to the risk of later obesity and associated disorders. Causality was confirmed in a large, double-blind randomised trial testing the 'Early Protein Hypothesis'. In this trial we found that attenuation of protein supply in infancy normalized early growth and markedly reduced obesity prevalence in early school age. These results indicate the need to describe and analyse growth patterns and their regulation through diet in more detail and to characterize the underlying metabolic and epigenetic mechanisms, given the potential major relevance for public health and policy. Better understanding of growth patterns and their regulation could have major benefits for the promotion of public health, consumer-orientated nutrition recommendations, and the development of improved food products for specific target populations.

The Power of Programming and the EarlyNutrition project: opportunities for health promotion by nutrition during the first thousand days of life and beyond

At The Power of Programming 2014 Conference, researchers from multiple disciplines presented and discussed the effects of early nutrition and other environmental cues during the first thousand days of life and beyond on the lifelong risk of noncommunicable diseases. This paper aims to summarize the concepts and some of the first achievements of the EarlyNutrition research project that initiated the conference. The EarlyNutrition consortium is a multinational, multidisciplinary research collaboration of researchers from Europe, the USA, and Australia. A focus is placed on exploration of the developmental origins of obesity, adiposity, and related health outcomes. Here we report on the first findings of experimental approaches, cohort studies, randomized clinical trials, and systematic reviews of current information, as well as position papers, which have all been developed with the involvement of project partners. We conclude that the EarlyNutrition project has successfully established itself during the first 2 project years as a very strong platform for collaborative research on early programming effects. The first results, available already at this early stage of the project, point to great opportunities for health prevention strategies via the implementation of dietary and lifestyle modifications, with large effect sizes. Further results are expected which should support improved recommendations and related policies for optimized nutrition and lifestyle choices before and during pregnancy, in infancy, and in early childhood.

Determination of cysteine and glutathione based on the inhibition of the dinuclear Cu(II)-catalyzed luminol-H2O2 chemiluminescence reaction

The catalyzed luminol chemiluminescent reaction has received a great amount of attention because of its high sensitivity and low background signal which make the reaction an attractive analytical chemistry tool. The present study, introduces the beneficial catalytic effects of dinuclear Cu(II) complex [Cu2L2(TAE)]X2, where TAE=tetraacetylethane; L=N,N(')-dibenzylethylenediamine and X=ClO4 on the luminol chemiluminescent reaction as a novel probe for the determination of glutathione (GSH) and L-cysteine (CySH) in human serum and urine. The [Cu2L2(TAE)]X2 has exhibited highly efficient catalytic activity of luminol CL as an artificial peroxidase model at pH as low as 7.5 in water in the presence of H2O2⋅GSH and CySH can induce a sharp decrease in CL intensity from the [Cu2L2(TAE)]X2-catalyzed luminol system. Under the selected experimental conditions, a linear relationship was obtained between the CL intensity and the concentrations of GSH and CySH in the range of 1.0×10(-7)-1.0×10(-4) M, with detection limits (S/N=3) of 2.7×10(-8) and 6.8×10(-8) M and RSD<4.2% (n=7) for GSH and CySH, respectively.

Three-month B vitamin supplementation in pre-school children affects folate status and homocysteine, but not cognitive performance

BACKGROUND

Suboptimal vitamin B status might affect cognitive performance in early childhood. We tested the hypothesis that short-term supplementation with folic acid and selected B vitamins improves cognitive function in healthy children in a population with relatively low folate status.

METHODS

We screened 1,002 kindergarten children for suboptimal folate status by assessing the total urinary para-aminobenzoylglutamate excretion. Two hundred and fifty low ranking subjects were recruited into a double blind, randomized, controlled trial to receive daily a sachet containing 220 μg folic acid, 1.1 mg vitamin B2, 0.73 mg B6, 1.2 μg B12 and 130 mg calcium, or calcium only for 3 months. Primary outcomes were changes in verbal IQ, short-term memory and processing speed between baseline and study end. Secondary outcomes were urinary markers of folate and vitamin B12 status, acetyl-para-aminobenzoylglutamate and methylmalonic acid, respectively, and, in a subgroup of 120 participants, blood folate and plasma homocysteine.

RESULTS

Pre- and post-intervention cognitive measurements were completed by 115 children in the intervention and 122 in the control group. Compared to control, median blood folate increased by about 50% (P for difference, P < 0.0001). Homocysteine decreased by 1.1 μmol/L compared to baseline, no change was seen in the control group (P for difference P < 0.0001) and acetyl-para-aminobenzoylglutamate was 4 nmol/mmol higher compared to control at the end of the intervention (P < 0.0001). We found no relevant differences between the groups for the cognitive measures.

CONCLUSION

Short-term improvement of folate and homocysteine status in healthy children does not appear to affect cognitive performance.

Quantification of urinary folate catabolites using liquid chromatography-tandem mass spectrometry

Folate catabolites p-aminobenzoylglutamate (pABG) and p-acetamidobenzoylglutamate (apABG) in human urine result from break-down of endogenous folate pools and are potential biomarkers of folate status. There is growing interest in analysis of these non-invasive indicators of folate status, since widespread diseases such as cancer, arteriosclerosis and dementia may be linked to disturbed availability of folates. Determination of pABG and apABG in human urine is challenging due to their low urinary concentrations and due to interferences with other urinary compounds. To address these analytical difficulties, we developed an improved LC-MS/MS method with chemical derivatization for fast, selective and sensitive quantification of pABG and apABG in human urine. Forming butyl esters of urinary folate catabolites pABG and apABG improves ionization efficiency as well as enables selective chromatographic separation on standard C18 reversed-phase column material. In contrast to some previously proposed methods for folate catabolites, the new method allows precise differentiation of apABG from pABG. Partial degradation of apABG during derivatization is exactly accounted for using a second differentially labeled stable isotope internal standard. This method is highly sensitive and covers the full range of physiologically occurring concentrations (from 2 to 1000nmol/L), with volume requirements of only 80μL urine. Method performance has been validated according to widely accepted standard recommendations. Use of two stable isotope-labeled internal standards and qualifier ion monitoring for both analytes ensure correct identification and unbiased quantification. With run times of less than 2.5min per sample and cost-efficient sample preparation, this method allows exact quantitation of urinary folate catabolites pABG and apABG for large-scale non-invasive screening of folate status in clinical and epidemiological trials.

Aqueous normal phase liquid chromatography coupled with tandem time-of-flight quadrupole mass spectrometry for determination of zanamivir in human serum

An aqueous normal phase (ANP) liquid chromatography coupled with a hybrid quadrupole time-of-flight mass spectrometry (ANP-LC-micrOTOFQ) method was used for the determination of zanamivir in human serum. Zanamivir was extracted with methanol from protein-precipitated human serum samples and further purified with SCX solid-phase extraction cartridges. Scherzo SM-C18, Agilent Zorbax SB-Aq, Cogent Diamond Hydride, Cogent Bidentate and Luna HILIC columns were compared and optimized for the retention and separation of zanamivir and the Luna HILIC and Diamond Hydride columns exhibited the best retention of zanamivir. The former provided a shorter retention time, a sharper peak and relatively high sensitivity, whereas the latter exhibited a longer retention time and less matrix interference. The analytical range of the calibration curve was between 5 and 1000 ng/mL.

A dietary resveratrol-rich grape extract prevents the developing of atherosclerotic lesions in the aorta of pigs fed an atherogenic diet

The presence of grape and wine polyphenol resveratrol (RES) in the diet is negligible. Therefore, the cardiovascular benefits of this molecule, in a dietary context, remain to be established. We aimed to investigate, through dietary intervention, the effects of a resveratrol-rich grape extract (GE-RES) on the prevention of early aortic lesions in pigs fed an atherogenic diet (AD). These effects were compared with those produced by a grape extract lacking RES (GE) or RES alone. Pigs fed the AD for 4 months showed early atherosclerotic lesions in the thoracic aorta: degeneration and fragmentation of elastic fibers, increase of intima thickness, subendothelial fibrosis, and accumulation of fatty cells and anion superoxide radicals. GE-RES was the most effective treatment and prevented the disruption of aortic elastic fibers, decreased their alteration (57%), and reduced the intima thickness (33%) and the accumulation of fatty cells (42%) and O(2)(•-) (38%) in aortic tissue. In addition, GE-RES moderately downregulated the expression of the suppressors of cytokine signaling 1 (SOCS1) and 3 (SOCS3), key regulators of vascular cell responses, in peripheral mononuclear blood cells. Our results suggest that the consumption of this GE-RES nutraceutical, in a dietary prevention context, could prevent early atherosclerotic events. The presence of RES in the grape extract strengthened these effects.

Quantification of homocysteine-related metabolites and the role of betaine-homocysteine S-methyltransferase in HepG2 cells

We optimized and validated a rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of six metabolites of homocysteine metabolism: homocysteine, methionine, cysteine, S-adenosylmethionine, S-adenosylhomocysteine and betaine. The detection limits for these metabolites were in the nanomolar range, and the intra- and inter-day precisions were lower than 20% of the relative standard deviations. The method was specifically designed for the determination of the intracellular concentrations of the metabolites in cultured cells. To study the role of betaine-homocysteine S-methyltransferase (BHMT), HepG2 cells and HepG2 cells that were stably transfected with BHMT ((BHMT) HepG2) were treated with homocysteine or with a specific inhibitor of BHMT, and metabolite levels were subsequently measured. Severely compromised methyl group metabolism in the HepG2 cells, which is typical of cancer-derived cells, prevented clear evaluation of the changes caused by the external manipulations of homocysteine metabolism. However, the ease of handling these cells and the almost unlimited source of experimental material supplied by cells in permanent culture allowed us to develop a reliable methodology. The precautions concerning intracellular metabolite determinations using LC-MS/MS in cultured cells that are expressed in this work will have global validity for future metabolomics studies.

Nonesterified fatty acid determination for functional lipidomics: comprehensive ultrahigh performance liquid chromatography-tandem mass spectrometry quantitation, qualification, and parameter prediction

Despite their central importance for lipid metabolism, straightforward quantitative methods for determination of nonesterified fatty acid (NEFA) species are still missing. The protocol presented here provides unbiased quantitation of plasma NEFA species by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Simple deproteination of plasma in organic solvent solution yields high accuracy, including both the unbound and initially protein-bound fractions, while avoiding interferences from hydrolysis of esterified fatty acids from other lipid classes. Sample preparation is fast and nonexpensive, hence well suited for automation and high-throughput applications. Separation of isotopologic NEFA is achieved using ultrahigh-performance liquid chromatography (UPLC) coupled to triple quadrupole LC-MS/MS detection. In combination with automated liquid handling, total assay time per sample is less than 15 min. The analytical spectrum extends beyond readily available NEFA standard compounds by a regression model predicting all the relevant analytical parameters (retention time, ion path settings, and response factor) of NEFA species based on chain length and number of double bonds. Detection of 50 NEFA species and accurate quantification of 36 NEFA species in human plasma is described, the highest numbers ever reported for a LC-MS application. Accuracy and precision are within widely accepted limits. The use of qualifier ions supports unequivocal analyte verification.

Absolute quantification of free glutathione and cysteine in aquatic insects using isotope dilution and selected reaction monitoring

A simple and robust isotope dilution mass spectrometry-based assay was developed for the determination of free cysteine and glutathione (GSH) in aquatic insects. Several experimental parameters were evaluated and optimized to provide specific and sensitive detection of both compounds by in situ derivatization with N-ethylmaleimide followed by acid alkylation quenching and reverse-phased liquid chromatography coupled with selected reaction monitoring. For both targets, the assay was evaluated over a concentration range of 0.313 to 320 μM and was demonstrated to have a quantitative dynamic range spanning nearly three orders of magnitude, with lower limits of quantification being 0.330 μM for GSH and 0.370 μM for cysteine. Additionally, measurements were observed to be highly reproducible over the course of several days. When applied to the analysis of four different species of insects, large biological variation between and within species was observed. Different feeding regimens were also tested within two species of insects but statistical comparisons revealed no significant difference in the levels of either compound.