Papers by Philip Britz-mckibbin
Journal of Proteome Research, Dec 3, 2018
Cystic fibrosis (CF) is a complex multi-organ disorder that is among the most common fatal geneti... more Cystic fibrosis (CF) is a complex multi-organ disorder that is among the most common fatal genetic diseases benefiting from therapeutic interventions early in life. Newborn screening (NBS) for pre-symptomatic detection of CF currently relies on a two-stage immunoreactive trypsinogen (IRT) and cystic fibrosis transmembrane conductance regulator (CFTR) mutation panel algorithm that is sensitive, but not specific for identifying affected neonates with a low positive predictive value. For the first time, we report the discovery of a panel of CF-specific metabolites from a single 3.2 mm diameter dried blood spot (DBS) punch when using multisegment injection-capillary electrophoresis-mass spectrometry as a high throughput platform for nontargeted metabolite profiling from volume-restricted/bio-banked specimens with quality control. This retrospective case-control study design identified thirty-two metabolites, including a series of N-glycated amino acids, oxidized glutathione disulfide and nicotinamide that were differentially expressed in normal birth weight CF neonates without meconium ileus (n=36) as compared to gestational age/sex-matched screen-negative controls (n=44) after a false discovery rate adjustment (q < 0.05, FDR). Also, sixteen metabolites from DBS extracts allowed for discrimination of true CF cases from presumptive screen-positive carriers with one identified CFTR mutation and transient neonatal hypertrypsinogenemic neonates (n=72), who were later confirmed as unaffected due to a low sweat chloride (< 29 mM) test result. Importantly, six CFspecific biomarker candidates satisfying a Bonferroni adjustment (p < 7.25 E-5) from three independent batches of DBS specimens included several amino acids depleted in circulation (Tyr, Ser, Thr, Pro, Gly) likely reflecting protein maldigestion/malabsorption. Additionally, CF neonates had lower ophthalmic acid as an indicator of oxidative stress due to impaired glutathione efflux from exocrine/epithelial tissue, and elevation of an unknown trivalent peptide that was directly correlated with IRT (ρ = 0.332, p = 4.55 E-4). Structural elucidation of unknown metabolites was performed by high resolution MS/MS, whereas biomarker validation was realized when comparing a subset of metabolites from matching neonatal DBS specimens independently analyzed by direct infusion-MS/MS at an accredited NBS facility. This work sheds new light into the metabolic phenotype of CF early in life, which is required for better functional understanding of CFTR mutations of unknown clinical consequence and the development of more accurate yet cost effective strategies for CF screening.
Analytical Chemistry, Oct 29, 2013
New methods for quantitative analysis of strong anions are required in clinical practice for diag... more New methods for quantitative analysis of strong anions are required in clinical practice for diagnostic testing of human diseases. Current techniques suffer from poor selectivity and/or long analysis times that are not amenable for labile anions in highly saline or volume-restricted samples. We introduce a rapid assay (< 3-5 min) based on capillary electrophoresis (CE) with indirect UV detection for simultaneous analysis of sulfate, sulfite and chloride in human urine, plasma and sweat specimens. Remarkable selectivity for strong anions is achieved by using an acidic background electrolyte under reversed polarity that results in electrokinetic rejection of matrix interferences at the capillary inlet. A dual co-ion probe system consisting of 5 mM naphthalene disulfonate (NDS) and 5 mM naphthalene trisulfonate (NTS) in 0.4 M formic acid, pH 2.0 is developed for photometric detection of UV transparent anions (S/N ≈ 3, 60 µM with 25 µm inner diameter fused-silica capillary) with good peak symmetry and baseline stability. Due to the chemical reactivity of sulfite, dilute formaldehyde is used as a reagent to form an acid-stable hydroxymethylsulfonate adduct. Method validation confirmed excellent linearity (R 2 > 0.999), good accuracy (mean bias ≈ 7%) and acceptable long-term reproducibility (CV < 10%) over 20 days. The assay allows for artifact-free determination of sulfate and sulfite with consistent results for chloride when compared to standard electrochemical methods (R 2 > 0.975). Preliminary data suggests that kidney stone formers have lower urinary sulfate excretion relative to non-kidney stone patient controls (p = 0.0261). CE offers a selective yet robust platform for routine analysis of strong anions that is needed for confirmatory testing of cystic fibrosis, sulfite oxidase deficiency, urolithiasis and other disorders of sulfur metabolism and/or anion transport.
Journal of Proteome Research, Nov 29, 2010
Thiol homeostasis plays an important role in human health and aging by regulation of cellular res... more Thiol homeostasis plays an important role in human health and aging by regulation of cellular responses to oxidative stress. Due to major constraints that hamper reliable plasma thiol/disulfide redox status assessment in clinical research, we introduce an improved strategy for comprehensive thiol speciation using capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) that overcomes sensitivity, selectivity and dynamic range constraints of conventional techniques. This method integrates both specific and nonspecific approaches toward sensitivity enhancement for artifact-free quantification of labile plasma thiols without complicated sample handling. A multivariate model was developed to predict increases in ionization efficiency for reduced thiols when conjugated to various maleimide analogs based on their intrinsic physicochemical properties. Optimization of maleimide labeling in conjunction with online sample preconcentration allowed for simultaneous analysis of nanomolar levels of reduced thiols and free oxidized thiols as their intact symmetric or mixed disulfides. Identification of low-abundance thiols and various other polar metabolites detected in plasma was supported by prediction of their relative migration times using CE as a qualitative tool complementary to ESI-MS. Plasma thiol redox status determination together with untargeted metabolite profiling offers a systemic approach for elucidation of the causal role of dysregulated thiol metabolism in the etiology of human diseases.
Clinical Biochemistry, Oct 1, 2014
Journal of Proteome Research, Jun 23, 2014
A subgroup of obese individuals, referred to as metabolically healthy obese (MHO), have preserved... more A subgroup of obese individuals, referred to as metabolically healthy obese (MHO), have preserved insulin sensitivity and a normal lipid profile despite being obese. The molecular basis for this improved cardiometabolic profile remains unclear. Our objective was to integrate metabolite and gene expression profiling to elucidate the molecular distinctions between MHO and metabolically unhealthy obese (MUO) phenotypes. A subset of individuals were selected from the Diabetes Risk Assessment study and classified into three groups using anthropometric and clinical measurements: lean healthy (LH), MHO, and MUO. Serum metabolites were profiled using gas chromatography coupled to mass spectrometry. Multivariate data analysis uncovered metabolites that differed between groups, and these were subsequently validated by capillary electrophoresis coupled to mass spectrometry. Subcutaneous adipose tissue (SAT) gene expression profiling using microarrays was performed in parallel. Amino acids were the most relevant class of metabolites distinguishing MHO from MUO individuals. Serum levels of glutamic acid, valine, and isoleucine were positively associated (i.e., LH < MHO < MUO) with homeostasis model assessment-insulin resistance (HOMA-IR) and glycated hemoglobin (HbA1c) values, while leucine was only correlated with HOMA-IR. The glutamine-to-glutamic acid ratio and glycine were inversely correlated (i.e., LH > MHO > MUO) with HbA1c values. Concomitantly, SAT gene expression profiling revealed that genes related to branched-chain amino acid catabolism and the tricarboxylic acid cycle were less down-regulated in MHO individuals compared to MUO individuals. Together, this integrated analysis revealed that MHO individuals have an intermediate amino acid homeostasis compared to LH and MUO individuals.
All in-text references underlined in blue are linked to publications on ResearchGate, letting you... more All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
Analytical Chemistry, Nov 17, 2008
The advent of electrospray-ionization mass spectrometry (ESI-MS) has given rise to expanded newbo... more The advent of electrospray-ionization mass spectrometry (ESI-MS) has given rise to expanded newborn screening programs for the early detection of inborn errors of metabolism (IEM). Despite the benefit of high-throughput screening for disease prognosis, conventional ESI-MS methods are limited by inadequate specificity, complicated sample handling, and low positive predictive outcome that can contribute to a high rate of false-positives. Herein, we report a robust strategy for neonatal screening based on capillary electrophoresis-electrospray ionizationmass spectrometry (CE-ESI-MS) that offers a convenient platform for the direct analysis of amino acids, acylcarnitines, and their stereoisomers from dried blood spot (DBS) extracts without chemical derivatization. On-line sample preconcentration with desalting by CE-ESI-MS allowed for improved concentration sensitivity when detecting poorly responsive metabolites in complex biological samples without ionization suppression or isomeric/ isobaric interferences. Method validation demonstrated that accurate yet precise quantification can be achieved for 20 different amino acid and acylcarnitine biomarkers associated with IEMs when using a single non-deuterated internal standard. CE-ESI-MS represents a promising second-tier method in newborn screening programs that is compatible with ESI-MS/MS technology in cases when improved specificity and sensitivity is warranted for diagnosis confirmation and subsequent monitoring.
Nature Protocols, May 17, 2021
Nicotine and Tobacco Research
Introduction Tobacco smoking is a leading preventable cause of premature death globally. Urinary ... more Introduction Tobacco smoking is a leading preventable cause of premature death globally. Urinary thiocyanate is a biomarker of cyanide exposure from tobacco smoke; however, few studies have evaluated its utility in diverse populations of smokers. Aims and Methods We examined the associations between urinary thiocyanate and self-reported never and current smokers among 1000 participants from 14 countries in the Prospective Urban and Rural Epidemiological study. We analyzed urinary thiocyanate in light and heavy smokers as compared to never-smokers from high- (HICs), middle- (MICs), and low-income countries (LICs) using a validated capillary electrophoresis method in conjunction with standardized questionnaires. Results The median urinary thiocyanate concentration was 31 μM, which ranged from 8.6 μM to 52 μM for never-smokers (n = 335) and current smokers (n = 660), respectively. Urinary thiocyanate was correlated with daily cigarette consumption (r = 0.621) and total nicotine equival...
Journal of the Canadian Association of Gastroenterology
Background Irritable bowel syndrome (IBS) is a disorder of gut-brain axis that manifests with chr... more Background Irritable bowel syndrome (IBS) is a disorder of gut-brain axis that manifests with chronic abdominal pain, altered bowel habits, and frequent psychiatric comorbidities. Despite mounting evidence showing gut microbiota composition and associated metabolites being altered in IBS, the mechanisms by which they drive the symptoms are unclear. We have previously shown that several IBS symptoms co-occur, that their severity vary among IBS subtypes (10.1093/jcag/gwab049.050), and that several bacterial taxa are differentially modulated during periods of symptom flares and remission. Here we investigate whether the changes in gut microbiome and bacterial metabolites are linked to symptom occurrence and severity. Purpose To investigate temporal associations of IBS symptoms with gut microbiota profiles and metabolites. Method 16S rRNA gene sequencing was performed on stool samples of 28 IBS patients (IBS-D n=20, IBS-C n=8) and 10 healthy controls (HC), collected weekly over a period...
Additional file 6: Fig. S2. [Clustering of MetS cases]
Additional file 2. Supplemental Methods [IDEFICS MetS definitions and MSI-CE-MS data processing]
Diet is known to affect the gut microbiome and metabolome composition in adults, but this has not... more Diet is known to affect the gut microbiome and metabolome composition in adults, but this has not been fully explored in infants. Dietary patterns from 1 year-old infants (n=182) from the South Asian Birth Cohort (START) study were compared to gut microbiome alpha and beta diversity and to taxa abundance differences. Diet – serum metabolite associations were identified using multivariate analysis (partial least squares-discriminant analysis, PLS-DA) and univariate analysis (T-Test). Dietary biomarkers identified from START were also examined in a separate cohort of white Caucasian infants (CHILD Cohort Study, n=82). Lastly, the association of diet with gut microbiome and serum biomarkers, considering maternal, perinatal and infant characteristics was investigated using multivariate forward stepwise regression. A dietary pattern characterized by breastfeeding, supplemented by formula and dairy was the strongest predictor of the gut microbiome that also differentiated the serum metabo...
Analytical Science Advances, 2020
Perfluoroalkyl substances (PFASs) are a major contaminant class due to their ubiquitous prevalenc... more Perfluoroalkyl substances (PFASs) are a major contaminant class due to their ubiquitous prevalence, persistence, and putative endocrine disrupting activity that may contribute to chronic disease risk notably with exposures early in life. Herein, multisegment injection‐nonaqueous capillary electrophoresis‐tandem mass spectrometry (MSI‐NACE‐MS/MS) is introduced as a high throughput approach for PFAS screening in serum samples following a simple methyl‐tert‐butyl ether (MTBE) liquid extraction. Separation and ionization conditions were optimized to quantify low nanomolar concentration levels of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) from serum extracts when using multiple reaction monitoring under negative ion mode conditions. Multiplexed separations of PFOA and PFOS were achieved with excellent throughput (<3 min/sample), adequate concentration sensitivity (LOD ∼ 20 nM, S/N = 3) and good technical precision over three consecutive days of analysis (mea...
International Journal of Hygiene and Environmental Health, 2020
The main aim of the study was to assess the relationship between inhalable hexavalent chromium an... more The main aim of the study was to assess the relationship between inhalable hexavalent chromium and "total" hexavalent chromium. Air sampling was conducted at steel passivation operation of a steel manufacturer at a stainless steel welding operation and at two hard chrome electroplaters. Air samples were taken side-by-side for "total" dust using closed-face 37-mm diameter cassette samplers and for inhalable dust using Institute of Occupational Medicine inhalable samplers. A total of 40 pairs of total and inhalable dust samples were collected and later analyzed. The range of "total" dust and inhalable dust concentrations in μg/m 3 measured were 30-410 and 0.02 to 740 respectively for steel passivation; 260 to 1520 and 477 to 6970 for welding; and 0.01 to 1500 and 204 to 2130 for electroplaters. The range of "total" dust hexavalent chromium and inhalable dust hexavalent chromium concentrations in μg/m 3 were 0.02-89 and 0.02 to 150 respectively for steel making; 4.1 to 4.9 and 2.2 to 6.9 for welding and 0.01 to 9.3 and 0.01 to 21 for electroplaters. A linear relationship between inhalable hexavalent chromium and "total" hexavalent chromium was found with a slope of 1.4 (CI:1.3, 1.5) and 0 offset. A ratio of 1.4 can thus be used as a conversion factor to convert previous data of hexavalent chromium taken on "total" dust basis to inhalable hexavalent chromium concentrations.
Journal of Vascular Surgery, 2020
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Papers by Philip Britz-mckibbin