This article offers a personal account of a remarkable journey spanning over 30 years of applied mass spectrometry in a clinical setting. It begins with the author's inspiration from a clinician's ...story of rescuing a child from near death with a revolutionary therapeutic intervention. Motivated by this experience, the author delved into the field of chemistry and mass spectrometry to solve an analytical challenge. The breakthrough came with the development of the first front-line diagnostic test performed by MS/MS, which focused on analyzing acylcarnitines to detect and diagnose inherited disorders related to fatty acid and branched-chain amino acid catabolism. Building upon this success, the author expanded the application of the method to dried blood spots, incorporating additional analytical components such as essential amino acids. The result was a groundbreaking multiplex assay capable of screening newborns for more than 30 inherited metabolic conditions with just one test. This novel approach laid the foundation for a targeted metabolomics platform that facilitated the identification of new animal models of metabolic disease through screening the offspring of genetically modified adults. The development and utilization of MS/MS with UPLC has led to the creation of new assays for biomarkers of metabolic disease, benefiting both the diagnosis and therapeutic monitoring of these conditions. The article provides compelling examples from the author's laboratory, highlighting the value and vast applications of these methods in the field of metabolic disease research.
It has recently been announced that the Secretary of the U.S. Department of Health and Human Services has approved the recommendation by the Advisory Committee on Heritable Disorders in Newborns and ...Children (ACHDNC) to add mucopolysaccharidosis type II (MPS-II, Hunter Syndrome) to the recommended uniform screening panel (RUSP) in the United States ...
The lack of biomarkers to identify target populations greatly limits the promise of precision medicine for major depressive disorder (MDD), a primary cause of ill health and disability. The ...endogenously produced molecule acetyl-L-carnitine (LAC) is critical for hippocampal function and several behavioral domains. In rodents with depressive-like traits, LAC levels are markedly decreased and signal abnormal hippocampal glutamatergic function and dendritic plasticity. LAC supplementation induces rapid and lasting antidepressant-like effects via epigenetic mechanisms of histone acetylation. This mechanistic model led us to evaluate LAC levels in humans. We found that LAC levels, and not those of free carnitine, were decreased in patients with MDD compared with age- and sex-matched healthy controls in two independent study centers. Secondary exploratory analyses showed that the degree of LAC deficiency reflected both the severity and age of onset of MDD. Moreover, these analyses showed that the decrease in LAC was larger in patients with a history of treatment-resistant depression (TRD), among whom childhood trauma and, specifically, a history of emotional neglect and being female, predicted the decreased LAC. These findings suggest that LAC may serve as a candidate biomarker to help diagnose a clinical endophenotype of MDD characterized by decreased LAC, greater severity, and earlier onset as well as a history of childhood trauma in patients with TRD. Together with studies in rodents, these translational findings support further exploration of LAC as a therapeutic target that may help to define individualized treatments in biologically based depression subtype consistent with the spirit of precision medicine.
Dear Readers: welcome to the second issue of the Editor’s Choice, continuing the tradition started by Peter Schielen’s appraisal of Issue 4 of Volume 6 of IJNS, published in this issue ...
Mucopolysaccharidoses (MPS) are complex storage disorders that result in the accumulation of glycosaminoglycans (GAGs) in urine, blood, brain and other tissues. Symptomatic patients are typically ...screened for MPS by analysis of GAG in urine. Current screening methods used in clinical laboratories are based on colorimetric assays that lack the sensitivity and specificity to reliably detect mild GAG elevations that occur in some patients with MPS. We have developed a straightforward, reliable method to quantify chondroitin sulfate (CS), dermatan sulfate (DS) and heparan sulfate (HS) in urine by stable isotope dilution tandem mass spectrometry. The GAGs were methanolyzed to uronic acid-N-acetylhexosamine or iduronic acid-N-glucosamine dimers and mixed with stable isotope labeled internal standards derived from deuteriomethanolysis of GAG standards. Specific dimers derived from HS, DS and CS were separated by ultra-performance liquid chromatography and analyzed by electrospray ionization tandem mass spectrometry using selected reaction monitoring for each targeted GAG product and its corresponding internal standard. The method was robust with a mean inaccuracy from 1 to 15%, imprecision below 11%, and a lower limit of quantification of 0.4mg/L for CS, DS and HS. We demonstrate that the method has the required sensitivity and specificity to discriminate patients with MPS III, MPS IVA and MPS VI from those with MPS I or MPS II and can detect mildly elevated GAG species relative to age-specific reference intervals. This assay may also be used for the monitoring of patients following therapeutic intervention. Patients with MPS IVB are, however, not detectable by this method.
•New clinical assay with improved sensitivity and specificity to quantify urinary Glycosaminoglycans (GAG).•Application of UPLC-MS/MS with stable isotope dilution.•Control values for different age groups for each GAG.•Differentiation of MPS type I, II, III, IVA, VI and VII from age matched controls.
The Role of Technology in Newborn Screening Millington, David S
North Carolina medical journal (Durham, N.C.),
2019 Jan-Feb, 2019-01-00, 20190101, Volume:
80, Issue:
1
Journal Article
Peer reviewed
Open access
This commentary traces the expansion of newborn screening for inherited metabolic disorders during the past 55 years, from the first simple test for phenylketonuria to the current panel of over 35 ...conditions. Emphasis is placed on the role played by technology and the contributions made by researchers in North Carolina.
•This study was to assess whether three symptomatically defined phenotypes of MDD, (core depression, neurovegetative of melancholia and anxiety), could be differentiated based on acylcarnitine ...profiles at baseline, after eight weeks of citalopram/escitalopram treatment.•The current data demonstrated that these phenotypes have distinct patterns of acylcarnitine levels at baseline and after eight weeks of antidepressant treatment.•These findings may help to develop a metabolomic profile of MDD patients with the aim of improving subtype classification of the MDD syndrome.
Acylcarnitines have important functions in mitochondrial energetics and β-oxidation, and have been implicated to play a significant role in metabolic functions of the brain. This retrospective study examined whether plasma acylcarnitine profiles can help biochemically distinguish the three phenotypic subtypes of major depressive disorder (MDD): core depression (CD+), anxious depression (ANX+), and neurovegetative symptoms of melancholia (NVSM+).
Depressed outpatients (n = 240) from the Mayo Clinic Pharmacogenomics Research Network were treated with citalopram or escitalopram for eight weeks. Plasma samples collected at baseline and after eight weeks of treatment with citalopram or escitalopram were profiled for short-, medium- and long-chain acylcarnitine levels using AbsoluteIDQ®p180-Kit and LC-MS. Linear mixed effects models were used to examine whether acylcarnitine levels discriminated the clinical phenotypes at baseline or eight weeks post-treatment, and whether temporal changes in acylcarnitine profiles differed between groups.
Compared to ANX+, CD+ and NVSM+ had significantly lower concentrations of short- and long-chain acylcarnitines at both baseline and week 8. In NVSM+, the medium- and long-chain acylcarnitines were also significantly lower in NVSM+ compared to ANX+. Short-chain acylcarnitine levels increased significantly from baseline to week 8 in CD+ and ANX+, whereas medium- and long-chain acylcarnitines significantly decreased in CD+ and NVSM+.
In depressed patients treated with SSRIs, β-oxidation and mitochondrial energetics as evaluated by levels and changes in acylcarnitines may provide the biochemical basis of the clinical heterogeneity of MDD, especially when combined with clinical characteristics.
New therapies for lysosomal storage diseases (LSDs) have generated interest in screening newborns for these conditions. We present performance validation data on a digital microfluidic platform that ...performs multiplex enzymatic assays for Pompe, Fabry, Hunter, Gaucher, and Hurler diseases.
We developed an investigational disposable digital microfluidic cartridge that uses a single dried blood spot (DBS) punch for performing a 5-plex fluorometric enzymatic assay on up to 44 DBS samples. Precision and linearity of the assays were determined by analyzing quality control DBS samples; clinical performance was determined by analyzing 600 presumed normal and known affected samples (12 for Pompe, 7 for Fabry and 10 each for Hunter, Gaucher and Hurler).
Overall coefficient of variation (CV) values between cartridges, days, instruments, and operators ranged from 2 to 21%; linearity correlation coefficients were ≥0.98 for all assays. The multiplex enzymatic assay performed from a single DBS punch was able to discriminate presumed normal from known affected samples for 5 LSDs.
Digital microfluidic technology shows potential for rapid, high-throughput screening for 5 LSDs in a newborn screening laboratory environment. Sample preparation to enzymatic activity on each cartridge is less than 3h.
•Five-plex assay performed on a disposable cartridge capable of handling up to 44 samples•Multiplex analysis validated for Pompe, Fabry, Hunter, Gaucher and Hurler•All 5 enzymatic assays are completed from a single dried blood spot punch.•Punch to results within 3h for rapid and high throughput analysis
Metabolomic profiling of obese versus lean humans reveals a branched-chain amino acid (BCAA)-related metabolite signature that is suggestive of increased catabolism of BCAA and correlated with ...insulin resistance. To test its impact on metabolic homeostasis, we fed rats on high-fat (HF), HF with supplemented BCAA (HF/BCAA), or standard chow (SC) diets. Despite having reduced food intake and a low rate of weight gain equivalent to the SC group, HF/BCAA rats were as insulin resistant as HF rats. Pair-feeding of HF diet to match the HF/BCAA animals or BCAA addition to SC diet did not cause insulin resistance. Insulin resistance induced by HF/BCAA feeding was accompanied by chronic phosphorylation of mTOR, JNK, and IRS1
Ser307 and by accumulation of multiple acylcarnitines in muscle, and it was reversed by the mTOR inhibitor, rapamycin. Our findings show that in the context of a dietary pattern that includes high fat consumption, BCAA contributes to development of obesity-associated insulin resistance.
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