Direct analysis of sterols from dried plasma/blood spots by an atmospheric pressure thermal desorption chemical ionization mass spectrometry (APTDCI-MS) method for a rapid screening of Smith-Lemli-Opitz syndrome

Newborn screening for lipid disorders

PURPOSE OF REVIEW

Newborn screening is one of the most successful public health programs of the last century and offers unparalleled access to universal screening for a variety of metabolic and other disorders. Interest in development of newborn screening for lipid disorders has intensified in recent years. Screening newborns for lipid disorders has important implications for the health of the newborn as well as their relatives, and in the case of more common lipid disorders like familial hypercholesterolemia, could have important public health implications.

RECENT FINDINGS

Recent studies have demonstrated feasibility of measuring biomarkers for heterozygous familial hypercholesterolemia from newborn screening dried blood spot specimens. Another lipid disorder, cerebrotendinous xanthomatosis, is currently amenable to newborn screening utilizing currently available assays. New research in next-generation sequencing as a primary screen in newborns will also identify both common and rare lipid disorders in newborns.

SUMMARY

Historically, newborn screening for lipid disorders was not done for many reasons, but new research has developed testing methods that may successfully identify common and rare lipid disorders. This will impact the health of the newborn but could also impact family members and public health.

Revolutionizing Blood Collection: Innovations, Applications, and the Potential of Microsampling Technologies for Monitoring Metabolites and Lipids

Blood serves as the primary global biological matrix for health surveillance, disease diagnosis, and response to drug treatment, holding significant promise for personalized medicine. The diverse array of lipids and metabolites in the blood provides a snapshot of both physiological and pathological processes, with many routinely monitored during conventional wellness checks. The conventional method involves intravenous blood collection, extracting a few milliliters via venipuncture, a technique limited to clinical settings due to its dependence on trained personnel. Microsampling methods have evolved to be less invasive (collecting ≤150 µL of capillary blood), user-friendly (enabling self-collection), and suitable for remote collection in longitudinal studies. Dried blood spot (DBS), a pioneering microsampling technique, dominates clinical and research domains. Recent advancements in device technology address critical limitations of classical DBS, specifically variations in hematocrit and volume. This review presents a comprehensive overview of state-of-the-art microsampling devices, emphasizing their applications and potential for monitoring metabolites and lipids in blood. The scope extends to diverse areas, encompassing population studies, nutritional investigations, drug discovery, sports medicine, and multi-omics research.

VAMS-Based Blood Capillary Sampling for Mass Spectrometry-Based Human Metabolomics Studies

Volumetric absorptive microsampling (VAMS) is a recently developed sample collection method that enables single-drop blood collection in a minimally invasive manner. Blood biomolecules can then be extracted and processed for analysis using several analytical platforms. The integration of VAMS with conventional mass spectrometry (MS)-based metabolomics approaches is an attractive solution for human studies representing a less-invasive procedure compared to phlebotomy with the additional potential for remote sample collection. However, as we recently demonstrated, VAMS samples require long-term storage at -80 °C. This study investigated the stability of VAMS samples during short-term storage and compared the metabolome obtained from capillary blood collected from the fingertip to those of plasma and venous blood from 22 healthy volunteers. Our results suggest that the blood metabolome collected by VAMS samples is stable at room temperature only for up to 6 h requiring subsequent storage at -80 °C to avoid significant changes in the metabolome. We also demonstrated that capillary blood provides better coverage of the metabolome compared to plasma enabling the analysis of several intracellular metabolites presented in red blood cells. Finally, this work demonstrates that with the appropriate pre-analytical protocol capillary blood can be successfully used for untargeted metabolomics studies.

Thermal desorption bridged the gap between dielectric barrier discharge ionization and dried plasma spot samples for sensitive and rapid detection of fentanyl analogs in mass spectrometry

Guided by finite element simulations and 3D-printing, we constructed a semi-covered flat-TD surface for sufficient thermal desorption and ionization of fentanyl analogs from dried plasma/blood spot samples.

Results of the first and second British Mass Spectrometry Society interlaboratory studies on ambient mass spectrometry

RATIONALE

As the popularity of ambient ionisation grows, so too does the importance of understanding its capabilities and limitations. The British Mass Spectrometry Society Special Interest Group on Ambient Ionisation has carried out two studies into the use of ambient ionisation, the results of which are presented here.

METHODS

The first study (study 1) examined the detection and quantitation capabilities of ambient ionisation while the second examined repeatability and robustness. For study 1 participants were sent a range of samples including two calibration sample sets and asked to analyse them. For study 2, two samples containing the same eight-component mixture were provided (one in solvent, one in matrix); participants were asked to analyse these samples multiple times, over multiple days to allow assessment of repeatability.

RESULTS

Study 1 showed that small, polar compounds were well detected by the participants while lower polarity compounds were less well detected. For many samples the introduction method appeared to be a significant factor in the observed spectra. The quantitation study gave good results but revealed significant variability. For study 2 the mean repeatabilities were 65% in solvent and 88% in matrix. The inclusion of an internal standard was shown to greatly improve repeatability.

CONCLUSIONS

Ambient ionisation is capable of ionising a wide range of compounds with good precision and excellent repeatability; however, in order to obtain such data care must be taken with the experimental design. The data can be significantly improved with a well-chosen internal standard.

Metabolic Signature of Dietary Iron Overload in a Mouse Model

Iron is an essential co-factor for several metabolic processes, including the Krebs cycle and mitochondrial oxidative phosphorylation. Therefore, maintaining an appropriate iron balance is essential to ensure sufficient energy production and to avoid excessive reactive oxygen species formation. Iron overload impairs mitochondrial fitness; however, little is known about the associated metabolic changes. Here we aimed to characterize the metabolic signature triggered by dietary iron overload over time in a mouse model, where mice received either a standard or a high-iron diet. Metabolic profiling was assessed in blood, plasma and liver tissue. Peripheral blood was collected by means of volumetric absorptive microsampling (VAMS). Extracted blood and tissue metabolites were analyzed by liquid chromatography combined to high resolution mass spectrometry. Upon dietary iron loading we found increased glucose, aspartic acid and 2-/3-hydroxybutyric acid levels but low lactate and malate levels in peripheral blood and plasma, pointing to a re-programming of glucose homeostasis and the Krebs cycle. Further, iron loading resulted in the stimulation of the urea cycle in the liver. In addition, oxidative stress was enhanced in circulation and coincided with increased liver glutathione and systemic cysteine synthesis. Overall, iron supplementation affected several central metabolic circuits over time. Hence, in vivo investigation of metabolic signatures represents a novel and useful tool for getting deeper insights into iron-dependent regulatory circuits and for monitoring of patients with primary and secondary iron overload, and those ones receiving iron supplementation therapy.

Liver and the defects of cholesterol and bile acids biosynthesis: Rare disorders many diagnostic pitfalls

In recent decades, biotechnology produced a growth of knowledge on the causes and mechanisms of metabolic diseases that have formed the basis for their study, diagnosis and treatment. Unfortunately, it is well known that the clinical features of metabolic diseases can manifest themselves with very different characteristics and escape early detection. Also, it is well known that the prognosis of many metabolic diseases is excellent if diagnosed and treated early. In this editorial we briefly summarized two groups of inherited metabolic diseases, the defects of cholesterol biosynthesis and those of bile acids. Both groups show variable clinical manifestations but some clinical signs and symptoms are common in both the defects of cholesterol and bile acids. The differential diagnosis can be made analyzing sterol profiles in blood and/or bile acids in blood and urine by chromatographic techniques (GC-MS and LC-MS/MS). Several defects of both biosynthetic pathways are treatable so early diagnosis is crucial. Unfortunately their diagnosis is made too late, due either to the clinical heterogeneity of the syndromes (severe, mild and very mild) that to the scarcity of scientific dissemination of these rare diseases. Therefore, the delay in diagnosis leads the patient to the medical observation when the disease has produced irreversible damages to the body. Here, we highlighted simple clinical and laboratory descriptions that can potentially make you to suspect a defect in cholesterol biosynthesis and/or bile acids, as well, we suggest appropriate request of the laboratory tests that along with common clinical features can help to diagnose these defects.

Sterols and oxysterols in plasma from Smith-Lemli-Opitz syndrome patients

Smith-Lemli-Opitz syndrome (SLOS) is a severe autosomal recessive disorder resulting from defects in the cholesterol synthesising enzyme 7-dehydrocholesterol reductase (Δ⁷-sterol reductase, DHCR7, EC 1.3.1.21) leading to a build-up of the cholesterol precursor 7-dehydrocholesterol (7-DHC) in tissues and blood plasma. Although the underling enzyme deficiency associated with SLOS is clear there are likely to be multiple mechanisms responsible for SLOS pathology. In an effort to learn more of the aetiology of SLOS we have analysed plasma from SLOS patients to search for metabolites derived from 7-DHC which may be responsible for some of the pathology. We have identified a novel hydroxy-8-dehydrocholesterol, which is either 24- or 25-hydroxy-8-dehydrocholesterol and also the known metabolites 26-hydroxy-8-dehydrocholesterol, 4-hydroxy-7-dehydrocholesterol, 3β,5α-dihydroxycholest-7-en-6-one and 7α,8α-epoxycholesterol. None of these metabolites are detected in control plasma at quantifiable levels (0.5ng/mL).

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.

Ambient ionization MS for bioanalysis: recent developments and challenges

Ambient ionization MS has become very popular in analytical science and has now evolved as an effective analytical tool in metabolomics, biological tissue imaging, protein and small molecule drug analysis, where biological samples are probed in a rapid and direct fashion with minimal sample preparation at ambient conditions. However, certain inherent challenges continue to hinder the vibrant prospects of these methods for in situ analyses or to replace conventional methods in bioanalysis. This review provides an introduction to the field and its application in bioanalysis, with an emphasis on the most recent developments and applications. Furthermore, ongoing challenges or limitations related to quantitation, sensitivity, selectivity, instrumentation and mass range of these ambient methods will also be discussed.

Applications of ion-mobility mass spectrometry for lipid analysis

The high chemical complexity of the lipidome is one of the major challenges in lipidomics research. Ion-mobility spectrometry (IMS), a gas-phase electrophoretic technique, makes possible the separation of ions in the gas phase according to their charge, shape, and size. IMS can be combined with mass spectrometry (MS), adding three major benefits to traditional lipidomic approaches. First, IMS-MS allows the determination of the collision cross section (CCS), a physicochemical measure related to the conformational structure of lipid ions. The CCS is used to improve the confidence of lipid identification. Second, IMS-MS provides a new set of hybrid fragmentation experiments. These experiments, which combine collision-induced dissociation with ion-mobility separation, improve the specificity of MS/MS-based approaches. Third, IMS-MS improves the peak capacity and signal-to-noise ratio of traditional analytical approaches. In doing so, it allows the separation of complex lipid extracts from interfering isobaric species. Developing in parallel with advances in instrumentation, informatics solutions enable analysts to process and exploit IMS-MS data for qualitative and quantitative applications. Here we review the current approaches for lipidomics research based on IMS-MS, including liquid chromatography-MS and direct-MS analyses of "shotgun" lipidomics and MS imaging.

Next steps for birth defects research and prevention: The birth defects study to evaluate pregnancy exposures (BD-STEPS)

BACKGROUND

The Birth Defects Study To Evaluate Pregnancy exposureS (BD-STEPS) is a population-based, multi-Center case-control study of modifiable risk factors for selected birth defects in the United States. BD-STEPS is the second major research effort of the Centers for Birth Defects Research and Prevention, which extends and expands the initial research effort, the National Birth Defects Prevention Study (NBDPS).

METHODS

BD-STEPS focuses on 17 categories of structural birth defects selected based on severity, prevalence, consistent ascertainment, and previous findings that warrant additional research. Cases are identified through existing birth defects surveillance programs; controls are from vital records or birth hospital logs from the same catchment area. BD-STEPS uses a standardized computer-assisted telephone interview to collect information from case and control mothers on topics including demographics, health conditions, and medication use. Following the maternal interview, selected Centers request permission to sample residual newborn screening blood spots from state repositories for genetic analyses. New components planned for BD-STEPS include linkages with external datasets and use of online questionnaires to collect in-depth information on selected exposures.

RESULTS

BD-STEPS extends NBDPS by continuing to collect data on many exposures that were assessed in NBDPS, allowing data from both studies to be combined and providing an unprecedented sample size to analyze rare exposures. BD-STEPS expands upon NBDPS by collecting more detailed information on existing exposures as well as new exposures.

CONCLUSION

The goal of BD-STEPS is to provide women and healthcare providers with information they need to make decisions to promote the healthiest pregnancy possible.

Autism spectrum disorder: an omics perspective

Current directions in autism spectrum disorder (ASD) research may require moving beyond genetic analysis alone, based on the complexity of the disorder, heterogeneity and convergence of genetic alterations at the cellular/functional level. Mass spectrometry (MS) has been increasingly used to study CNS disorders, including ASDs. Proteomic research using MS is directed at understanding endogenous protein changes that occur in ASD. This review focuses on how MS has been used to study ASDs, with particular focus on proteomic analysis. Other neurodevelopmental disorders have been investigated using MS, including fragile X syndrome (FXS) and Smith-Lemli-Opitz Syndrome (SLOS), genetic syndromes highly associated with ASD comorbidity.

Mass spectrometry for the study of autism and neurodevelopmental disorders

Mass spectrometry (MS) has been increasingly used to study central nervous system disorders, including autism spectrum disorders (ASDs). The first studies of ASD using MS focused on the identification of external toxins, but current research is more directed at understanding endogenous protein changes that occur in ASD (ASD proteomics). This chapter focuses on how MS has been used to study ASDs, with particular focus on proteomic analysis. Other neurodevelopmental disorders have been investigated using this technique, including genetic syndromes associated with autism such as fragile X syndrome and Smith-Lemli-Opitz syndrome.

Evaluating Atmospheric pressure Solids Analysis Probe (ASAP) mass spectrometry for the analysis of low molecular weight synthetic polymers

Atmospheric pressure Solids Analysis Probe (ASAP) mass spectrometry has facilitated the ionisation of oligomers from low molecular weight synthetic polymers, poly(ethylene glycol) (PEG: M(n) = 1430) and poly(styrene) (PS: M(n) = 1770), directly from solids, providing a fast and efficient method of identification. Ion source conditions were evaluated and it was found that the key instrument parameter was the ion source desolvation temperature which, when set to 600 °C was sufficient to vapourise the heavier oligomers for ionisation. PS, a non-polar polymer that is very challenging to analyse by MALDI or ESI without the aid of metal salts to promote cationisation, was ionised promptly by ASAP resulting in the production of radical cations. A small degree of in-source dissociation could be eliminated by control of the instrument ion source voltages. The fragmentation observed through in-source dissociation could be duplicated in a controlled manner through Collision-Induced Dissociation (CID) of the radical cations. PEG, which preferentially ionises through adduction with alkali metal cations in MALDI and ESI, was observed as a protonated molecular ion by ASAP. In-source dissociation could not be eliminated entirely and the fragmentation observed resulted from cleavage of the C-C and C-O backbone bonds, as opposed to only C-O bond cleavage observed from tandem mass spectrometry.

A routine method for cholesterol and 7-dehydrocholesterol analysis in dried blood spot by GC-FID to diagnose the Smith-Lemli-Opitz syndrome

This work was aimed to implement a fast and simple method to quantify cholesterol (CHOL) and 7-dehydrocholesterol (7-DHC) in dried blood spot (DBS) to diagnose the Smith-Lemli-Opitz syndrome (SLOS), an inborn error of CHOL biosynthesis. We developed and validated a GC-FID method for separation and quantification of underivatized CHOL and 7-DHC using a DBS disc of 6mm with a run time of 9 min. Correlation coefficients (r) of calibration curves ranged from 0.998 to 0.999 for CHOL and from 0.997 to 0.998 for 7-DHC. Within-day and between-day imprecision (CV%), accuracy (%), carry-over, and extraction efficacy (%) were also evaluated for validation. CHOL and 7-DHC were analyzed in DBS and plasma samples from 8 SLOS patients and 30 unaffected subjects. In SLOS patients, 7-DHC/CHOL ratios in DBS and plasma samples ranged from 0.035 to 1.448 and from 0.012 to 0.926, respectively. Results from calibration curves, quality controls and patient samples reveal that the method is suitable to analyze DBS to screen patients affected by SLOS.

Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive, multiple congenital malformation and intellectual disability syndrome, with clinical characteristics that encompass a wide spectrum and great variability. Elucidation of the biochemical and genetic basis for SLOS, specifically understanding SLOS as a cholesterol deficiency syndrome caused by mutation in DHCR7, opened up enormous possibilities for therapeutic intervention. When cholesterol was discovered to be the activator of sonic hedgehog, cholesterol deficiency with inactivation of this developmental patterning gene was thought to be the cause of SLOS malformations, yet this explanation is overly simplistic. Despite these important research breakthroughs, there is no proven treatment for SLOS. Better animal models are needed to allow potential treatment testing and the study of disease pathophysiology, which is incompletely understood. Creation of human cellular models, especially models of brain cells, would be useful, and in vivo human studies are also essential. Biomarker development will be crucial in facilitating clinical trials in this rare condition, because the clinical phenotype can change over many years. Additional research in these and other areas is critical if we are to make headway towards ameliorating the effects of this devastating condition.

Profiling of acylcarnitines and sterols from dried blood or plasma spot by atmospheric pressure thermal desorption chemical ionization (APTDCI) tandem mass spectrometry

Free carnitine and acylcarnitines play an important role in the metabolism of fatty acids. Sterols are structural lipids found in the membranes of many eukaryotic cells, and they also have functional roles such as the regulation of membrane permeability and fluidity, activity of membrane-bound enzymes and signals transduction. Abnormal profiles of these compounds in biological fluids may be useful markers of metabolic changes. In this review, we describe the subset of the lipidome represented by acylcarnitines and sterols, and we summarize how these compounds have been analyzed in the past. Over the last 50years, lipid mass spectrometry (MS) has evolved to become one of the most useful techniques for metabolic analysis. Today, the introduction of new ambient ionization techniques coupled to MS (AMS), which are characterized by the direct desorbing/ionizing of molecules from solid samples, is generating new possibilities for in situ analysis. Recently, we developed an AMS approach called APTDCI to desorb/ionize using a heated gas flow and an electrical discharge to directly analyze sterols and indirectly investigate acylcarnitines in dried blood or plasma spot samples. Here, we also describe the APTDCI method and some of its clinical applications, and we underline the common complications and issues that remain to be resolved.

Diagnosis of tetrahydrobiopterin deficiency using filter paper blood spots: further development of the method and 5 years experience

In every newborn with even mild hyperphenylalaninemia (HPA) tetrahydrobiopterin (BH(4)) deficiencies need to be excluded as soon as possible. Differential diagnosis is most commonly performed by analysis of urinary neopterin and biopterin. In 2005 a new method for the measurement of neopterin, biopterin and other pterins in dried blood spot (DBS) on filter paper was introduced. In order to evaluate the usefulness of this method as a standard tool for differential diagnosis of HPAs we analyzed neopterin, biopterin, pterin and dihydropteridine reductase activity in DBS from 362 patients with HPA over the period of five years. Age-dependent reference values were established for the HPA population. Sixty-four patients with BH(4) deficiency (27 patients with 6-pyruvoyl-tetrahydropterin synthase deficiency, seven with GTP cyclohydrolase I deficiency, and 30 with dihydropteridine reductase) were identified. Reference values for neopterin and biopterin in DBS were calculated for each of the variants. 6-pyruvoyl-tetrahydropterin synthase and GTP cyclohydrolase I deficiency can be diagnosed by neopterin and biopterin analysis alone, while for diagnosis of dihydropteridine reductase deficiency additional determination of enzyme activity from the same DBS is essential. Regarding test sensitivity, the interpretation of neopterin and biopterin concentration per hemoglobin is more valid than the interpretation of neopterin and biopterin per liter. Percentage of biopterin, of the sum of neopterin and biopterin should always be calculated. In addition, determination of hemoglobin concentration is essential as a measure for efficient extraction of neopterin and biopterin. Although the measurement of neopterin and biopterin in urine is more sensitive due to the higher concentrations present, our data prove the usefulness of their measurement from DBS for the routine diagnosis of BH(4) deficiencies.

A powerful couple in the future of clinical biochemistry: in situ analysis of dried blood spots by ambient mass spectrometry

Since the early 1960s, dried blood spots (DBS) on filter paper have been used in clinical applications. The first key milestone in the use of DBS was the screening of phenylketonuria and other inborn errors of metabolism using microbiological and enzymatic analytical methods. 20 years after its introduction, advanced mass spectrometers and new soft ionization techniques have permitted the coupling of liquid chromatography with MS and tandem MS (MS/MS) and since the 1990s, DBS analysis by LC-MS/MS expanded screening to many inborn errors of metabolism simultaneously. Recently, DBS-LC-MS/MS analysis has been used in other fields such as pharmacology, toxicology and forensic sciences. Today, new ambient ionization techniques, coupled to MS, directly desorb/ionize molecules from solid samples. This presents new opportunities for the in situ analysis of DBS. Most likely, ambient MS methods will be used to analyze DBS, increasing the clinical applications of MS within the next 10 years.

Sensitive determination of a drug candidate in dried blood spots using a TLC–MS interface integrated into a column-switching LC–MS/MS system

Background: A thin-layer chromatography–mass spectrometry interface was previously reported to extract compounds from dried blood spots online. Here, we integrated this interface into a column-switching LC–MS/MS system for online solid-phase extraction and addressed internal standard addition. Results: A drug was analyzed in dried blood spots with a lower limit of quantitation of 50 pg/ml. The internal standard was added via an autosampler to the extraction solvent. The method featured online aqueous dilution of the dried blood spots extract with subsequent trapping and gradient analytical separation. Good precision, accuracy and recovery were obtained. Conclusion: The thin-layer chromatography–mass spectrometry interface provided high reproducibility and good extraction efficiency. Although manually operated, it significantly reduced sample preparation efforts. The combination with online solid-phase extraction allowed enrichment of larger sample/extract volumes and efficient clean-up.