Accurate measurement of free carnitine in dried blood spots by isotope-dilution electrospray tandem mass spectrometry without butylation

UPLC-Q-TOF/MS-Based Serum Metabolomics Reveals Potential Anti-tumor Mechanism of Banxia Xiexin Decoction in Colorectal Cancer Mice

OBJECTIVE

To clarify the potential mechanism of Banxia Xiexin Decoction (BXD) on colorectal cancer (CRC) from the perspective of metabolomics.

METHODS

Forty male C57BL/6 mice were randomly divided into normal control (NC), azoxymethane/dextran sulfate sodium (AOM/DSS) model, low-dose BXD (L-BXD), high-dose BXD (H-BXD) and mesalamine (MS) groups according to a random number table, 8 mice in each group. Colorectal cancer model was induced by AOM/DSS. BXD was administered daily at doses of 3.915 (L-BXD) and 15.66 g/kg (H-BXD) by gavage for consecutive 21 days, and 100 mg/kg MS was used as positive control. Following the entire modeling cycle, colon length of mice was measured and quantity of colorectal tumors were counted. The spleen and thymus index were determined by calculating the spleen/thymus weight to body weight. Inflammatory cytokine and changes of serum metabolites were analyzed by enzyme-linked immunosorbent assay kits and ultra performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UPLC-Q/TOF-MS), respectively.

RESULTS

Notably, BXD supplementation protected against weight loss, mitigated tumor formation, and diminished histologic damage in mice treated with AOM/DSS (P<0.05 or P<0.01). Moreover, BXD suppressed expression of serum inflammatory enzymes, and improved the spleen and thymus index (P<0.05). Compared with the normal group, 102 kinds of differential metabolites were screened in the AOM/DSS group, including 48 potential biomarkers, involving 18 main metabolic pathways. Totally 18 potential biomarkers related to CRC were identified, and the anti-CRC mechanism of BXD was closely related to D-glutamine and D-glutamate metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, arginine biosynthesis, nitrogen metabolism and so on.

CONCLUSION

BXD exerts partial protective effects on AOM/DSS-induced CRC by reducing inflammation, protecting organism immunity ability, and regulating amino acid metabolism.

Use of on-line supercritical fluid extraction-supercritical fluid chromatography/tandem mass spectrometry to analyze disease biomarkers in dried serum spots compared with serum analysis using liquid chromatography/tandem mass spectrometry

RATIONALE

The analytical stability and throughput of biomarker assays based on dried serum spots (DSS) are strongly dependent on the extraction process and determination method. In the present study, an on-line system based on supercritical fluid extraction-supercritical fluid chromatography coupled with tandem mass spectrometry (SFE-SFC/MS/MS) was established for analyzing the levels of disease biomarkers in DSS.

METHODS

The chromatographic conditions were investigated using the ODS-EP, diol, and SIL-100A columns. Then, we optimized the SFE-SFC/MS/MS method using the diol column, focusing on candidate biomarkers of oral, colorectal, and pancreatic cancer that were identified using liquid chromatography (LC)/MS/MS.

RESULTS

By using this system, four hydrophilic metabolites and 17 hydrophobic metabolites were simultaneously detected within 15 min. In an experiment involving clinical samples, PC 16:0-18:2/16:1-18:1 exhibited 93.8% sensitivity and 64.3% specificity, whereas PC 17:1-18:1/17:0-18:2 showed 81.3% sensitivity and 92.9% specificity for detecting oral cancer. In addition, assessments of the creatine levels demonstrated 92.3% sensitivity and 78.6% specificity for detecting colorectal cancer.

CONCLUSIONS

The results of this study indicate that our method has great potential for clinical diagnosis and would be suitable for large-scale screening. Copyright © 2017 John Wiley & Sons, Ltd.

Innovations in health and demographic surveillance systems to establish the causal impacts of HIV policies

PURPOSE OF REVIEW

Health and demographic surveillance systems (HDSS), in conjunction with HIV treatment cohorts, have made important contributions to our understanding of the impact of HIV treatment and treatment-related interventions in sub-Saharan Africa. The purpose of this review is to describe and discuss innovations in data collection and data linkage that will create new opportunities to establish the impacts of HIV treatment, as well as policies affecting the treatment cascade, on population health and economic and social outcomes.

RECENT FINDINGS

Novel approaches to routine collection of biomarkers, behavioural data, spatial data, social network information, migration events and mobile phone records can significantly strengthen the potential of HDSS to generate exposure and outcome data for causal analysis of HIV treatment impact and policies affecting the HIV treatment cascade. Additionally, by linking HDSS data to health service administration, education and welfare service records, researchers can substantially broaden opportunities to establish how HIV treatment affects health and economic outcomes when delivered through public sector health systems and at scale.

SUMMARY

As the HIV treatment scaleup in sub-Saharan Africa enters its second decade, it is becoming increasingly important to understand the long-term causal impacts of large-scale HIV treatment and related policies on broader population health outcomes, such as noncommunicable diseases, as well as on economic and social outcomes, such as family welfare and children's educational attainment. By collecting novel data and linking existing data to public sector records, HDSS can create near-unique opportunities to contribute to this research agenda.

The use of mass spectrometry to analyze dried blood spots

Dried blood spots (DBS) typically consist in the deposition of small volumes of capillary blood onto dedicated paper cards. Comparatively to whole blood or plasma samples, their benefits rely in the fact that sample collection is easier and that logistic aspects related to sample storage and shipment can be relatively limited, respectively, without the need of a refrigerator or dry ice. Originally, this approach has been developed in the sixties to support the analysis of phenylalanine for the detection of phenylketonuria in newborns using bacterial inhibition test. In the nineties tandem mass spectrometry was established as the detection technique for phenylalanine and tyrosine. DBS became rapidly recognized for their clinical value: they were widely implemented in pediatric settings with mass spectrometric detection, and were closely associated to the debut of newborn screening (NBS) programs, as a part of public health policies. Since then, sample collection on paper cards has been explored with various analytical techniques in other areas more or less successfully regarding large-scale applications. Moreover, in the last 5 years a regain of interest for DBS was observed and originated from the bioanalytical community to support drug development (e.g., PK studies) or therapeutic drug monitoring mainly. Those recent applications were essentially driven by improved sensitivity of triple quadrupole mass spectrometers. This review presents an overall view of all instrumental and methodological developments for DBS analysis with mass spectrometric detection, with and without separation techniques. A general introduction to DBS will describe their advantages and historical aspects of their emergence. A second section will focus on blood collection, with a strong emphasis on specific parameters that can impact quantitative analysis, including chromatographic effects, hematocrit effects, blood effects, and analyte stability. A third part of the review is dedicated to sample preparation and will consider off-line and on-line extractions; in particular, instrumental designs that have been developed so far for DBS extraction will be detailed. Flow injection analysis and applications will be discussed in section IV. The application of surface analysis mass spectrometry (DESI, paper spray, DART, APTDCI, MALDI, LDTD-APCI, and ICP) to DBS is described in section V, while applications based on separation techniques (e.g., liquid or gas chromatography) are presented in section VI. To conclude this review, the current status of DBS analysis is summarized, and future perspectives are provided.

Validated method for the quantification of free and total carnitine, butyrobetaine, and acylcarnitines in biological samples

A validated quantitative method for the determination of free and total carnitine, butyrobetaine, and acylcarnitines is presented. The versatile method has four components: (1) isolation using strong cation-exchange solid-phase extraction, (2) derivatization with pentafluorophenacyl trifluoromethanesulfonate, (3) sequential ion-exchange/reversed-phase (ultra) high-performance liquid chromatography [(U)HPLC] using a strong cation-exchange trap in series with a fused-core HPLC column, and (4) detection with electrospray ionization multiple reaction monitoring (MRM) mass spectrometry (MS). Standardized carnitine along with 65 synthesized, standardized acylcarnitines (including short-chain, medium-chain, long-chain, dicarboxylic, hydroxylated, and unsaturated acyl moieties) were used to construct multiple-point calibration curves, resulting in accurate and precise quantification. Separation of the 65 acylcarnitines was accomplished in a single chromatogram in as little as 14 min. Validation studies were performed showing a high level of accuracy, precision, and reproducibility. The method provides capabilities unavailable by tandem MS procedures, making it an ideal approach for confirmation of newborn screening results and for clinical and basic research projects, including treatment protocol studies, acylcarnitine biomarker studies, and metabolite studies using plasma, urine, tissue, or other sample matrixes.

Current and future use of "dried blood spot" analyses in clinical chemistry

The analysis of blood spotted and dried on a matrix (i.e., "dried blood spot" or DBS) has been used since the 1960s in clinical chemistry; mostly for neonatal screening. Since then, many clinical analytes, including nucleic acids, small molecules and lipids, have been successfully measured using DBS. Although this pre-analytical approach represents an interesting alternative to classical venous blood sampling, its routine use is limited. Here, we review the application of DBS technology in clinical chemistry, and evaluate its future role supported by new analytical methods such as mass spectrometry.

Carnitine levels in 26,462 individuals from the nationwide screening program for primary carnitine deficiency in the Faroe Islands

BACKGROUND

Primary carnitine deficiency (PCD) is an autosomal recessive disorder of fatty acid oxidation and has been associated to episodes of sudden death in the Faroe Islands. Data are presented from the nationwide population based Faroese screening program to find people with low carnitine levels indicating PCD.

METHODS

Whole blood samples from dried blood spots were analysed by tandem mass spectrometry with and without butylation. Genetic analyses were performed in all people with non-butylated free carnitine (fC0) below 7 μmol/L.

RESULTS

55 % (n = 26,462) of the entire population was screened and 89 PCD patients were identified, yielding an overall prevalence of 1:297 of PCD in the Faroe Islands. Carnitine levels were positively correlated to age in both males and females (p < 0.003) although levels decreased in females when reaching fertile age. The gender difference in mean carnitine levels was significant during female fertile age (4.71 μmol/L fC0 in the age group 25-30 years, p < 0.01). A lower cut-off of 5 μmol/L in fC0 identified all homozygous for the severe genotype c.95A > G (p.N32S) (n = 20).

CONCLUSION

Carnitine levels differ by gender and age. A lower cut-off of 5 μmol/L in fC0 was appropriate to identify c.95A > G homozygotes. The prevalence of PCD in the Faroe Islands is the highest reported in the world (1:297).

Quantification of carnitine and acylcarnitines in biological matrices by HPLC electrospray ionization-mass spectrometry

BACKGROUND

Analysis of carnitine and acylcarnitines by tandem mass spectrometry (MS/MS) has limitations. First, preparation of butyl esters partially hydrolyzes acylcarnitines. Second, isobaric nonacylcarnitine compounds yield false-positive results in acylcarnitine tests. Third, acylcarnitine constitutional isomers cannot be distinguished.

METHODS

Carnitine and acylcarnitines were isolated by ion-exchange solid-phase extraction, derivatized with pentafluorophenacyl trifluoromethanesulfonate, separated by HPLC, and detected with an ion trap mass spectrometer. Carnitine was quantified with d(3)-carnitine as the internal standard. Acylcarnitines were quantified with 42 synthesized calibrators. The internal standards used were d(6)-acetyl-, d(3)-propionyl-, undecanoyl-, undecanedioyl-, and heptadecanoylcarnitine.

RESULTS

Example recoveries [mean (SD)] were 69.4% (3.9%) for total carnitine, 83.1% (5.9%) for free carnitine, 102.2% (9.8%) for acetylcarnitine, and 107.2% (8.9%) for palmitoylcarnitine. Example imprecision results [mean (SD)] within runs (n = 6) and between runs (n = 18) were, respectively: total carnitine, 58.0 (0.9) and 57.4 (1.7) micromol/L; free carnitine, 44.6 (1.5) and 44.3 (1.2) micromol/L; acetylcarnitine, 7.74 (0.51) and 7.85 (0.69) micromol/L; and palmitoylcarnitine, 0.12 (0.01) and 0.11 (0.02) micromol/L. Standard-addition slopes and linear regression coefficients were 1.00 and 0.9998, respectively, for total carnitine added to plasma, 0.99 and 0.9997 for free carnitine added to plasma, 1.04 and 0.9972 for octanoylcarnitine added to skeletal muscle, and 1.05 and 0.9913 for palmitoylcarnitine added to skeletal muscle. Reference intervals for plasma, urine, and skeletal muscle are provided.

CONCLUSIONS

This method for analysis of carnitine and acylcarnitines overcomes the observed limitations of MS/MS methods.

Determination of 3-hydroxyisovalerylcarnitine and other acylcarnitine levels using liquid chromatography-tandem mass spectrometry in serum and urine of a patient with multiple carboxylase deficiency

Due to its increased concentration in blood, 3-hydroxyisovalerylcarnitine (C5OH-I) is an important indicator for the diagnosis of organic acidemias in newborns. However, C5OH-I has not been used as a standard in tandem mass spectrometric (MS/MS) assays because its isolation is difficult. We developed a new synthesis of C5OH-I and investigated its behavior by MS/MS. A method using the multiple reaction monitoring (MRM) mode of MS/MS with HPLC was developed which provides high accuracy, precision and reproducibility. Acylcarnitine profiles in the serum and urine of a patient with multiple carboxylase deficiency (MCD) showed increased levels compared to a healthy patient.

Determination of carnitine ester patterns during the second half of pregnancy, at delivery, and in neonatal cord blood by tandem mass spectrometry: complex and dynamic involvement of carnitine in the intermediary metabolism

We studied plasma concentrations of free carnitine and 30 carnitine esters by electron spray ionization (ESI) tandem mass spectrometry in 37 pregnant women at the 20th and 30th weeks of gestation and at delivery, and in their neonates at birth, and in 22 age-matched nonpregnant women. The plasma levels of acetylcarnitine and carnitine esters with more than five carbons were significantly higher, whereas the concentration of free carnitine was significantly lower at term than at the 20th week of pregnancy (16.75 +/- 0.89 versus 19.61 +/- 1.25). Almost all of C2- to C12-carnitine esters were significantly lower, whereas C16- and C18-carnitines with in-chain modifications were significantly higher in mothers at delivery compared with nonpregnant women. Plasma levels of free carnitine and C2-, C3-, C4-, C5-, C6-, and C16-carnitines were significantly lower, while concentrations of carnitine esters with 8, 10, 12 and 18 carbons in the acyl chain as well as C14:1-, C14:2-, and C16:1-OH-carnitines were significantly higher in mothers at term than in their neonates. The data of the present study clearly show dynamic features of plasma carnitine profile during pregnancy and indicate an extraordinarily active participation of the carnitine in the intermediary metabolism both in the pregnant woman and in the neonate.

Simultaneous quantification of acylcarnitine isomers containing dicarboxylic acylcarnitines in human serum and urine by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry

Tandem mass spectrometry (MS/MS) has become a prominent method for screening newborns for diseases such as organic acidemia and fatty acid oxidation defects, although current methods cannot separate acylcarnitine isomers. Accurate determination of dicarboxylic acylcarnitines such as methylmalonylcarnitine and glutarylcarnitine has not been carried out, because obtaining standards of these acylcarnitines is difficult. We attempted the individual determinations of acylcarnitines with isomers and dicarboxylic acylcarnitines by applying high-performance liquid chromatography (HPLC). Chromatographic separation was performed by gradient elution using a mixture of 0.08% aqueous ion-pairing agent and acetonitrile as the mobile phase. Mass transitions of m/z 161.8-->84.8 for carnitine and m/z 164.8-->84.8 for deuterated carnitine were monitored in positive ion electrospray ionization mode. One carnitine and 16 acylcarnitines were quantified. The limit of quantitation (LOQ) was 0.1 micromol/L for methylmalonylcarnitine and 0.05 micromol/L for the other acylcarnitines. Intra-day and inter-day coefficients of variance (CVs) were <8.3% and <8.8%, respectively, for all acylcarnitines in serum, and both were <9.2% in urine. Mean recoveries were >90% for all acylcarnitines. Human samples were quantified by this method. After addition of deuterated acylcarnitines as internal standards, acylcarnitines in serum or urine were extracted using a solid-phase extraction cartridge. In healthy adult individuals, isobutyryl-, 2-methylbutyryl- and isovalerylcarnitine were detected in serum and urine. Dicarboxylic acylcarnitines were detected in urine. High concentrations of methylmalonylcarnitine and propionylcarnitine were found in both the serum and the urine of a patient with methylmalonic acidemia. The described HPLC/MS/MS method could separate most acylcarnitine isomers and quantify them, potentially allowing detailed diagnoses and follow-up treatment for those diseases.

Effects of Valproate on Acylcarnitines in Children with Epilepsy Using ESI-MS/MS

PURPOSE

To determine the influence of valproate (VPA) treatment on acylcarnitines in children with epilepsy.

METHODS

Determination of acylcarnitines (including free carnitine and acylcarnitines from C2 to C18) in dried blood spot specimens using tandem-mass spectrometry. Longitudinal study of changes in acylcarnitines in children under VPA treatment without pretreatment (group 1) or with pretreatment with other antiepileptic drugs (group 2) before the start of VPA treatment at an early and a late treatment interval (12-66, 90-260 days after the beginning of treatment, respectively). Cross-sectional comparison of these two VPA groups and of a group receiving carbamazepine monotherapy (group 3) with controls.

RESULTS

Acylcarnitines in epileptic patients before VPA therapy did not differ from control values. In group 1, decreases of C0 (-26%), C2 (-12%), C16 (-31%), C18 (-41%), C(total) (-10%), increases of C5OH (+31%), C8 (+33%) in the early treatment interval, and decreases of C16 (-21%), C18 (-42%), and increases of C2 (+26%), C5OH (+44%) in the late treatment interval were significant. In group 2, both in the longitudinal and the cross-sectional study, only a decrease of C18 (-41%, -43%, respectively) in the late treatment interval was found. In group 3, no significant changes have been observed.

CONCLUSIONS

We could prove changes in acylcarnitine subspecies, which were associated with VPA treatment in children with epilepsy. The treatment interval with the most marked changes coincides with the interval of highest risk for VPA-induced hepatotoxicity. The observed specific acylcarnitine pattern might point to the impaired intermediary metabolism that is responsible for VPA-induced hepatotoxicity.