N-Acetyltyrosine as a Biomarker of Parenteral Nutrition Administration in First-Tier Newborn Screening Assays.

Parenteral nutrition (PN) is a nutrient solution administered intravenously (IV) to premature babies. PN causes elevations of some amino acids in blood samples that are also biomarkers used in newborn screening (NBS). Therefore, PN status must be annotated by clinicians on dried blood spot (DBS) cards to reduce NBS laboratory burdens associated with potential false results; however, NBS laboratories continue to receive DBSs with misannotated PN status.

Repurposing dried blood spot device technology to examine bile acid profiles in human dried fecal spot samples.

Dried blood spot (DBS) analysis has existed for >50 years, but application of this technique to fecal analysis remains limited. To address whether dried fecal spots (DFS) could be used to measure fecal bile acids, we collected feces from five subjects for each of the following cohorts: ) healthy individuals, ) individuals with diarrhea, and ) infected patients. Homogenized fecal extracts were loaded onto quantitative DBS (qDBS) devices, dried overnight, and shipped to the bioanalytical lab at ambient temperature.

Quantitation of phenylalanine and tyrosine from dried Blood/Plasma spots with impregnated stable isotope internal standards (SIIS) by FIA-SRM.

Background: Dried Blood Spot (DBS) analysis has been used for identification and quantification of diseases and disorders in large populations. Simply collecting blood or plasma samples on cotton paper, followed with an organic solvent extraction, many small molecules can be detected and quantified. In a typical procedure of DBS analysis in newborn screening, stable isotope internal standards (SIIS) are added to extraction solvent as a reference.

Progressive Metabolic Abnormalities Associated with the Development of Neonatal Bronchopulmonary Dysplasia.

Objective: To assess the longitudinal metabolic patterns during the evolution of bronchopulmonary dysplasia (BPD) development. Methods: A case-control dataset of preterm infants (<32-week gestation) was obtained from a multicenter database, including 355 BPD cases and 395 controls. A total of 72 amino acid (AA) and acylcarnitine (AC) variables, along with infants’ calorie intake and growth outcomes, were measured on day of life 1, 7, 28, and 42.

Progressive Metabolic Dysfunction and Nutritional Variability Precedes Necrotizing Enterocolitis.

Necrotizing Enterocolitis (NEC) is associated with prematurity, enteral feedings, and enteral dysbiosis. Accordingly, we hypothesized that along with nutritional variability, metabolic dysfunction would be associated with NEC onset. We queried a multicenter longitudinal database that included 995 preterm infants (<32 weeks gestation) and included 73 cases of NEC.

Impact of vaccination during pregnancy and staphylococci concentration on the presence of Bacillus cereus in raw human milk.

Objective: This study aimed to determine whether vaccination during pregnancy, prematurity, and staphylococci concentration influenced the presence of B. cereus or staphylococcal enterotoxins (SEs) in raw human milk from healthy mothers.

Study Design: Human milk samples were collected from 152 healthy women.

Impact of l-carnitine supplementation on metabolic profiles in premature infants.

Objective: To describe the influence that of l-carnitine supplementation on acylcarnitine (AC) profiles and hospital outcomes in premature infants.

Study Design: This study is a secondary analysis of previously reported work. Metabolic profiles were obtained using standard newborn techniques on infants born between 23 and 31 completed weeks of gestation.

Heptadecanoylcarnitine (C17) a novel candidate biomarker for newborn screening of propionic and methylmalonic acidemias.

Background: 3-Hydroxypalmitoleoyl-carnitine (C16:1-OH) has recently been reported to be elevated in acylcarnitine profiles of patients with propionic acidemia (PA) or methylmalonic acidemia (MMA) during expanded newborn screening (NBS). High levels of C16:1-OH, combined with other hydroxylated long chain acylcarnitines are related to long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) and trifunctional protein (TFP) deficiency.

Methods: The acylcarnitine profile of two LCHADD patients was evaluated using liquid chromatography-tandem mass spectrometric method.

Gestational age and age at sampling influence metabolic profiles in premature infants.

Objective: To describe the influence that gestational age and chronological age have on amino acid and acylcarnitine profiles in an at-risk population of premature infants.

Methods: Metabolic profiles (15 amino acids and 35 acylcarnitines) were obtained by using standard newborn techniques on infants born between 23 and 31 completed weeks of gestation. The profiles were drawn within the first 24 hours after birth and on approximately days 7, 28, and 42 of life or at discharge.

Microsample analyses via DBS: challenges and opportunities.

The use of DBS is an appealing approach to employing microsampling techniques for the bioanalysis of samples, as has been demonstrated for the past 50 years in the metabolic screening of metabolites and diseases. In addition to its minimally invasive sample collection procedures and its economical merits, DBS microsampling benefits from the very high sensitivity, selectivity and multianalyte capabilities of LC-MS, which has been especially well demonstrated in newborn screening applications. Only a few microliters of a biological fluid are required for analysis, which also translates to significantly reduced demands on clinical samples from patients or from animals.

Elaidate, an 18-carbon trans-monoenoic fatty acid, inhibits β-oxidation in human peripheral blood macrophages.

Consumption of trans-unsaturated fatty acids promotes atherosclerosis, but whether degradation of fats in macrophages is altered by trans-unsaturated fatty acids is unknown. We compared the metabolism of oleate (C18:1Δ9-10 cis; (Z)-octadec-9-enoate), elaidate (C18:Δ9-10 trans; (E)-octadec-9-enoate), and stearate (C18:0, octadecanoate) in adherent peripheral human macrophages. Metabolism was followed by measurement of acylcarnitines in cell supernatants by MS/MS, determination of cellular fatty acid content by GC/MS, and assessment of β-oxidation rates using radiolabeled fatty acids.

Metabolomic profiling of amino acids and β-cell function relative to insulin sensitivity in youth.

Context: In longitudinal studies of adults, elevated amino acid (AA) concentrations predicted future type 2 diabetes mellitus (T2DM).

Objective: The aim of the present investigation was to examine whether increased plasma AA concentrations are associated with impaired β-cell function relative to insulin sensitivity [i.e.

Evaluation of asymmetric dimethylarginine, arginine, and carnitine metabolism in pediatric sepsis.

Objective: Increased plasma concentrations of the endogenous nitric oxide synthase inhibitor, asymmetric dimethylarginine, decreased arginine bioavailability, and mitochondrial dysfunction have been reported in adult sepsis. We studied whether asymmetric dimethylarginine, arginine, and carnitine metabolism (a measure of mitochondrial dysfunction) are altered in pediatric sepsis and whether these are clinically useful biomarkers.

Design: : Prospective, observational study.

Metabolomic profiling of fatty acid and amino acid metabolism in youth with obesity and type 2 diabetes: evidence for enhanced mitochondrial oxidation.

Objective: We compared acylcarnitine (AcylCN) species, common amino acid and fat oxidation (FOX) byproducts, and plasma amino acids in normal weight (NW; n = 39), obese (OB; n = 64), and type 2 diabetic (n = 17) adolescents.

Research Design And Methods: Fasting plasma was analyzed by tandem mass spectrometry, body composition by dual energy X-ray absorptiometry and computed tomography, and total-body lipolysis and substrate oxidation by [(2)H(5)]glycerol and indirect calorimetry, respectively. In vivo insulin sensitivity (IS) was assessed with a 3-h hyperinsulinemic-euglycemic clamp.

Detection of TPN contamination of dried blood spots used in newborn and metabolic screening and its impact on quantitative measurement of amino acids.

Background: Markers derived from dextrose (d-glucose) are observed in the MS/MS-based acylcarnitine profiles from dried-blood spots of some premature infants receiving intravenous nutrition. The presence of these markers at m/z 325, 399 and 473 are thought to arise from contamination of blood by total parenteral nutrition (TPN) solutions during specimen collection from premature infants. These solutions contain high concentrations of amino acids and as a result, false-positive screening results for amino acid disorders may occur.

Altered metabolism and newborn screening using tandem mass spectrometry: lessons learned from the bench to bedside.

The use of tandem mass spectrometry (MS/MS) for screening of inherited metabolic disease in newborns has afforded many unique opportunities in the understanding of the benefits early their early detection, diagnosis and treatment. From the standpoint of the laboratory and modern analytical methods, the use of MS based analysis demonstrated that a multiple metabolite-multiple disease screen-one method approach expanded screening significantly. MS/MS and newborn screening has served as a model of one type of approach in preventative health care that has shown proven benefits.

Proficiency testing outcomes of 3-hydroxyisovalerylcarnitine measurements by tandem mass spectrometry in newborn screening.

Background: The use of tandem mass spectrometry (MS/MS) for the analysis of amino acids and acylcarnitines from dried-blood spots (DBS) has become routine practice in newborn screening laboratories. The Newborn Screening Quality Assurance Program (NSQAP) added 3-hydroxyisovalerylcarnitine (C5OH) into its routine quality control and proficiency testing (PT) DBS materials for MS/MS to assure the quality of C5OH screening. We report the results from NSQAP evaluations for C5OH-enriched DBS, and summarize participant screening practices based on their analytical methods.

Tandem mass spectrometric identification of dextrose markers in dried-blood spots from infants receiving total parenteral nutrition.

Background: The false positive rate for the newborn screening of disorders of amino acid metabolism for premature infants is higher than full term infants. This may be due to very low birth weight infants receiving high concentrations of amino acids from total parenteral nutrition (TPN) administration and/or immature metabolism. An investigation of the possible influence of TPN on screening of premature infants resulted in the detection of three unusual peaks in the tandem mass spectrometry (MS/MS) acylcarnitine profile.

Potential loss of methionine following extended storage of newborn screening samples prepared for tandem mass spectrometry analysis.

Background: Methionine (Met) is a key metabolite used in the newborn screening of homocystinuria by tandem mass spectrometry (MS/MS). Recently, a loss of ion counts in both Met and its deuterium-labeled internal standard ((2)H(3)-Met) was observed by the CDC's Newborn Screening Quality Assurance Program laboratory. We report on the stability of labeled and unlabeled Met solutions and their storage in two types of 96 well microtiter plates to illustrate the potential loss of Met following storage of samples prior to MS/MS analysis.

Comparison of amino acids and acylcarnitines assay methods used in newborn screening assays by tandem mass spectrometry.

Background: The analysis of amino acids (AA) and acylcarnitines (AC) by tandem mass spectrometry (MS/MS) is performed in newborn screening laboratories worldwide. While butyl esterification assays are routine, it is possible to detect AAs and ACs as their native free acids (underivatized). The Centers for Disease Control and Prevention's Newborn Screening Quality Assurance Program provides dried blood spot (DBS) quality control (QC) and proficiency testing (PT) programs for numerous MS/MS analytes.

Increased levels of plasma acylcarnitines in obesity and type 2 diabetes and identification of a marker of glucolipotoxicity.

Dysregulation of fatty acid oxidation (FAO) is recognized as important in the pathophysiology of obesity and insulin resistance (IR). However, demonstrating FAO defects in vivo in humans has entailed complex and invasive methodologies. Recently, the identification of genetic blocks in FAO has been vastly simplified by using tandem mass spectrometry (MS/MS) of dried bloodspots to specify acylcarnitine (AcylCN) alterations characteristic for each disorder.