Elaine Holmes

Background
Evidence increasingly suggests a connection between cardiovascular disease and brain health in later life; however, the mechanistic pathways from human studies remain unclear. This study aimed to investigate whether urinary metabolites account for part of the association between cognition and cardiometabolic risk.

Methods
Data from 606 participants (aged 48–60; 55% female; 45.5% Black/African American) in the Year 30 follow-up of the Coronary Artery Risk Development in Young Adults Study were analyzed. Urinary metabolites were profiled using nuclear magnetic resonance spectroscopy and liquid chromatography-mass spectrometry; brain magnetic resonance imaging data were available for 281 participants. Structural equation models were used to assess pathways linking cardiometabolic factors to cognitive outcome, with urinary metabolites and brain MRI-derived parameters as mediators.

Results
Fasting glucose showed a negative association with cognition. Valine, isoleucine, leucine, and phenylalanine were positively associated with fasting glucose. Valine and aminoadipic acid also showed positive associations between fasting glucose and cognition, while tryptophan was correlated with both fasting glucose and cognition. Indole-3-acetic acid showed negative associations with systolic blood pressure and fasting glucose. Brain MRI-derived parameters in memory-related medial temporal areas were associated with waist circumference.

Conclusions
Urinary metabolites and brain imaging markers were linked with hyperglycemia, obesity, and cognitive performance, highlighting multimodal biomarkers relevant to global cognitive function in individuals with cardiometabolic risk.

Broad-spectrum viral biomarkers offer a promising approach to distinguishing viral from bacterial infections, thereby reducing inappropriate antibiotic use and improving diagnostic response during emerging infectious disease outbreaks. Among these, the deoxydidehydronucleoside (ddhN) class of nucleoside derivatives has emerged as a potential tool for early detection of viral infections in settings where pathogen-specific diagnostics are unavailable. To assess the clinical utility of these compounds, we investigated the metabolism and excretion rates of four principal ddhN metabolites, 3'-deoxy-3',4'-didehydrocytidine (ddhC), 3'-deoxy-3',4'-didehydrocytidine-5'-carboxylate (ddhC-5'CA), 3'-deoxy-3',4'-didehydrouridine (ddhU), and 3'-deoxy-3',4'-didehydrocytidine-5'-homocysteine (ddhC-5'Hcy), in the Sprague-Dawley rat model following a single intravenous dose. Time-resolved biological sampling was used to characterize urinary excretion and downstream biotransformation. All four metabolites exhibited rapid urinary clearance, ranging from approximately 3 to 8 h, consistent with a transient acute-phase profile. Notably, ddhC-5'Hcy underwent extensive biotransformation, with key metabolites produced via functionalization and conjugation identified following integration of nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) analyses. No adverse clinical signs were observed in any treatment group at any time point. These findings support further research into the ddhN series as markers of active viral infection for clinical application, particularly in critical care environments, where timely differentiation of infectious etiology is essential.

Paediatric burn injuries are a global health concern with long-term health consequences, such as psychological, immune, and cardiovascular complications, that can persist even after non-severe injuries. Emerging evidence suggests that biological sex may influence post-burn outcomes in children, as female burn survivors have been shown to experience higher mortality, scarring, anxiety, depression, and poorer quality of life compared to males. This study addresses a critical research gap by examining sex-specific lipidomic and inflammatory responses following paediatric non-severe burn injury. Children under five years were recruited as a part of the Childhood Burn Injury Biobank at hospital admission, with longitudinal follow-ups, and non-burn controls aged 1 and 3 were collected from the ORIGINS cohort. Plasma lipid profiling and acute-phase glycoprotein systemic inflammatory markers (GlycA and GlycB) were quantified using metabolic phenotyping with hair cortisol provided as a longitudinal measure of stress. Lipidomic analysis revealed acute-phase disruptions in fatty acids and lysophospholipids in both sexes but only females demonstrated a persistent increase of arachidonic acid (FA 20:4) and depletion of monoacylglycerols more than a year post-injury. Females also had significantly higher acute-phase GlycA/GlycB levels around the time of injury and exhibited increasing variability in hair cortisol over time, while male burn survivors did not. These findings highlight a sex-specific response between lipid metabolism, systemic inflammation and stress in paediatric recovery from non-severe burns. Understanding these differences may guide the development of targeted psychological and physiological strategies to improve long-term outcomes for young burn survivors.

Methoxyacetic acid (MAA) is a testicular toxin that targets spermatocytes and round spermatids by disrupting mitochondrial function, leading to cellular energy depletion. Male Sprague-Dawley rats were given single oral doses of MAA (150 or 650 mg/kg), resulting in no mortality but transient toxicity signs and modest body weight effects, especially at the higher dose. Histopathology revealed dose- and time-dependent testicular damage, with selective germ cell necrosis by 48 h and extensive germ cell loss, spermatic giant cells, and epididymal inflammation observed in high-dose animals by 168 h. Metabolic analysis using high resolution 1H NMR spectroscopy and OPLS-DA identified elevated urinary excretion of N-butyryl glycine, a marker of mitochondrial dysfunction and impaired β-oxidation. The persistence of N-butyryl glycine and altered energy metabolites up to 168 h indicates sustained mitochondrial stress and disruption of ATP-dependent processes essential for spermatogenesis. Moreover, the close structural similarity between MAA and butyrate raises the possibility that MAA interacts directly with enzymes involved in butyryl-CoA turnover during the terminal steps of β-oxidation in rodents.

The Consortium for Metabonomic Toxicology (COMET) studies was designed to model metabolic responses to organ-and mechanism-specific toxins to predict acute drug toxicity in rats. A range of clinical chemical parameters were measured in 7-day toxicology studies for 86 toxins eliciting a range of organ-and mechanism-specific effects. Additionally, 21 surgical or physiological stressors were evaluated to identify physiological or metabolic responses that might confound the interpretation of observed toxicity profiles. From these studies on a total of 3473 rats measured at six pharmaceutical companies, we provide a set of 12 serum and 5 urine physical and clinical chemistry parameters. Samples were collected at 24 h, 48 h and 168 h post-dose for each animal and are presented as a downloadable database file. We also summarise the main observations based on the group response at the level of the individual toxin. We demonstrate that correlations between parameters, such as serum bilirubin and aspartate aminotransferase (AST), provide a more nuanced profile of organ-specific toxicity than consideration of individual parameters alone. In addition, we highlight the variability in the measured parameters across the dataset attributable to inter-laboratory differences, and the heterogeneity of metabolic responses to particular compounds or differences in temporal patterns of response. This clinical chemistry atlas of toxicity serves as a valuable reference tool for evaluating the potential toxicity of novel drug candidates.

The nutritional benefits of Extra Virgin Olive Oils (EVOOs) depend on their chemical composition. Currently, there is no simple way to compare the health benefits of different EVOOs. Samples from Australia, Greece, Italy, Spain and Tunisia (N = 423) were analyzed using proton nuclear magnetic resonance spectroscopy to screen against six quality parameters (free acidity, peroxides, K270, K232, Delta K, wax) and measure fat compositions. These fat compositions were compared against healthy eating guidelines to produce five binary descriptors, which were weighted by evidence to create an accessible Nutritional Quality Index (NQI). EVOOs were differentiated by saturated fat and balance between monounsaturated (MUFA) and polyunsaturated fat (PUFA). Most samples (56.4 %) showed poor SFA, poor PUFA and good MUFA (NQI = 56), 21 % had good SFA, poor PUFA and good MUFA (NQI = 81), and 19.4 % exhibited poor SFA, good PUFA and poor MUFA (NQI = 64). The NQI identifies EVOOs with superior nutritional value, enabling informed consumer choices.

Dried blood spot (DBS) sample collections can offer a minimally invasive, cost-effective alternative to traditional venepuncture for remote sampling and high-frequency metabolic profiling. We present an optimised protocol for DBS-based extraction and comprehensive untargeted 4D lipid profiling using ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry, designed to support large-scale applications in population-wide lipidomics research. Inclusion of stable isotopically labelled internal standards allowed for semi-quantitative subclass-level correction for 10 μL DBS samples, enhancing the number of reproducible lipids within our curated target list (focussed on 432 unique rule-based lipid annotations out of 6845 features) across positive and negative heated electrospray ionisation modes. The reproducibility of unique lipid features detected in replicate DBS (n = 6) was assessed on both peak areas (351 lipids < 25 % CV) and calculated concentrations relative to internal standards (432 lipids < 25 % CV), underscoring the benefit of internal standard addition. Storage conditions for DBS were also evaluated to determine short-term lipid stability at different temperatures (-20 ˚C, 4 ˚C, room temperature, and 45 ˚C). The majority of lipid subclasses, excluding a minority of glycerophospholipids and oxylipins, were stable up to 1 week at -20 ˚C and 4 ˚C (log2-fold change < 30 % difference), which supports the short-term storage capacity for DBS in field and clinical settings. Similar stability was observed within a week at room temperature, excluding phosphatidylethanolamines and phosphatidylglycerols (log2-fold change > 30 % difference). Application of the optimised workflow to a microsampling device (n = 6) identified 432 lipid features (CV < 25 %) with three repeated samplings over an hour showing minimal impact on lipid profiles by principal component analysis, showing promise for high-frequency, longitudinal DBS monitoring in population health. This work represents a significant advance, highlighting the potential for reliable lipid analysis from DBS samples with short-term stability under various storage conditions, an important logistical benefit for remote or resource-limited settings.
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•Dried blood spots enable minimally invasive, cost-effective sampling in lipidomics•The developed untargeted 4D-lipidomic method annotates 432 lipids in 10 μL DBS•Majority of lipid subclasses are stable on DBS up to 1 week, ideal at -20°C and 4°C•Commercial microsampling devices suit remote, high-frequency lipid profiling

Pooled quality control (PQC) samples are the gold standard for data quality monitoring in metabolic phenotyping studies. Typically composed of equal parts from all study samples, PQCs can be challenging to generate in large cohorts or when sample volumes are low. As an alternative, externally sourced matrix-matched surrogate QCs (sQC) have been proposed. This study evaluates the performance of sQCs against PQCs for assessing analytical variation, data pre-processing, and downstream data analysis in a targeted lipidomics workflow.
Plasma samples (n = 701) from the Microbiome Understanding in Maternity Study, along with PQC (n = 80) and sQC (n = 80) samples, were analyzed using a lipidomics assay targeting 1162 lipids. QC samples were injected throughout acquisition, and data pre-processing was performed using each strategy. For simplicity, a subset (n = 381) of the study samples was used to assess differences in downstream statistical analyses.
Both QC approaches demonstrated high analytical repeatability. While PQC and sQC compositions differed, use of PQCs retained less than 4 % more lipid species during pre-processing. Univariate analysis identified more statistically significant lipids with PQC-based pre-processing, but multivariate model performance was similar between datasets.
This study provides a comprehensive comparison of QC strategies and emphasizes the importance of careful QC workflow selection. While PQCs offer advantages, sQCs serve as a suitable alternative for quality assessment and pre-processing. Their commercial availability also supports use as intra- and inter-laboratory long-term references, aiding data harmonization across studies and laboratories.
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•Comparison of two quality control workflows; pooled study and surrogate QC samples.•In-depth assessment of lipid composition, precision, and filtering.•OPLS-DA model predictive power maintained with both QC pre-processing strategies.•Surrogate QC samples are a robust alternative to a pooled QC in targeted lipidomics.

Background
Robust tissue pre-treatment and lipid extraction workflows are crucial to metabolic phenotyping studies and accurate interpretation of lipid profiles. Numerous methods for lipid extraction from tissues have been developed, and the choice of technique influences analysis. This study provides a comprehensive evaluation of six liquid-liquid extraction methods (three biphasic and three monophasic) used for lipidomic tissue analysis by liquid chromatography-mass spectrometry. Extraction methods were assessed for their suitability for comprehensive lipid profiling across diverse tissue types: adipose, liver, and heart. These techniques were compared using lyophilised and fresh frozen samples.

Results
The study revealed significant differences in the coverage and reliability of lipid species extracted using each technique, dependent on the tissue type. The optimal extraction method for adipose tissue was butanol:methanol (BUME) (3:1) which achieved the highest lipid coverage, yield and reproducibility (886 lipids with a coefficient of variation (CV) < 30 %); methyl tert-butyl ether (MTBE) with ammonium acetate was most effective for liver tissue (707 lipids CV < 30 %) and BUME (1:1) for heart tissue (311 lipids CV < 30 %). These findings showed that the most effective lipid extraction methods are highly tissue-specific, underscoring the critical need for bespoke protocols tailored to each tissue type. The optimised tissue-specific methods were validated using an intervention study in C57BL/6 mice to investigate diet-induced metabolic changes. The results demonstrated distinct discriminating lipid profiles unique to each tissue type, with 374 lipid species from 13 subclasses significantly different between high-fat diet (HFD) and normal diet (ND) in adipose tissue, while 485 lipid species from 17 subclasses were significantly different between HFD and ND in liver tissue.

Significance and novelty
This study presents a new approach to studying lipid profiles derived from diverse tissues that substantially improve comprehensive lipid species’ detection sensitivity and reliability. Our systematic evaluation provides evidence that tailored tissue-specific extraction protocols are highly valuable in comprehensive lipidomics studies, offering robust tools for reliably identifying lipid changes and facilitates a deeper understanding of tissue-specific metabolic processes in diverse research and clinical applications.
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