Analysis of 2-methylcitric acid, methylmalonic acid, and total homocysteine in dried blood spots by LC-MS/MS for application in the newborn screening laboratory: A dual derivatization approach

Inborn errors of propionate, cobalamin and methionine metabolism are targets for Newborn Screening (NBS) in most programs world-wide, and are primarily screened by analyzing for propionyl carnitine (C3) and methionine in dried blood spot (DBS) cards using tandem mass spectrometry (MS/MS). Single-tier NBS approaches using C3 and methionine alone lack specificity, which can lead to an increased false-positive rate if conservative cut-offs are applied to minimize the risk of missing cases. Implementation of liquid chromatography tandem mass spectrometry (LC-MS/MS) second-tier testing for 2-methylcitric acid (MCA), methylmalonic acid (MMA), and homocysteine (HCY) from the same DBS card can improve disease screening performance by reducing the false-positive rate and eliminating the need for repeat specimen collection. However, DBS analysis of MCA, MMA, and HCY by LC-MS/MS is challenging due to limited specimen size and analyte characteristics leading to a combination of low MS/MS sensitivity and poor reverse-phase chromatographic retention. Sufficient MS response and analytical performance can be achieved for MCA by amidation using DAABD-AE and by butylation for MMA and HCY. Herein we describe the validation of a second-tier dual derivatization LC-MS/MS approach to detect elevated MCA, MMA, and HCY in DBS cards for NBS. Clinical utility was demonstrated by retrospective analysis of specimens, an interlaboratory method comparison, and assessment of external proficiency samples. Imprecision was <10.8% CV, with analyte recoveries between 90.2 and 109.4%. Workflows and analytical performance characteristics of this second-tier LC-MS/MS approach are amenable to implementation in the NBS laboratory.

Diagnosis and the importance of early treatment of tyrosinemia type 1: A case report

Tyrosinemia type 1 is an autosomal recessive aminoacidopathy caused by fumarylacetoacetate hydrolase (FAH) deficiency. Consequently, tyrosine and its metabolites accumulate, resulting in liver and kidney toxicity. Symptoms of the disease usually manifest after three weeks of life and include vomiting, failure to thrive, hepatomegaly, jaundice, bleeding diathesis, rickets and renal tubular dysfunction. Untreated, the disease eventually progresses to liver or kidney failure and generally results in a fatal outcome. Expedient diagnosis is critical because an early start of treatment can increase the likelihood of a positive outcome. Here, we report on a male newborn with a family history positive for tyrosinemia type 1 who was subjected to a metabolic work-up immediately after birth. Amino acids were quantified by tandem mass spectrometry coupled with ultra performance liquid chromatography. Urinary organic acids were analyzed on capillary gas chromatography coupled with mass spectrometry. DNA analysis of the FAH gene was performed by Sanger sequencing. On the first day of life, the patient's plasma amino acids showed an increased tyrosine concentration, while urine organic acids detected succinylacetone, a tyrosine metabolite specific for tyrosinemia type 1. The patient's DNA analysis revealed homozygosity of the c.554-1G > T mutation in the FAH gene, which was consistent with the diagnosis. Nitisinone treatment, combined with a dietary restriction of tyrosine and phenylalanine, was introduced immediately. Regular visits and measurement of amino acid concentrations, which enables therapy adjustment and treatment efficiency monitoring in patients with tyrosinemia type 1, has continued over the past 4+ years, and is expected to continue.

Bortezomib alters sour taste sensitivity in mice

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Bortezomib administration increase sour taste sensitivity in mice.

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Protein expression of PKD2L1 increases in circumvallate papillae of bortezomib-administered mice.

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Increased sour taste sensitivity induced by bortezomib returned to the control level on cessation of its administration.

Chemotherapy-induced taste disorder is one of the critical issues in cancer therapy. Bortezomib, a proteasome inhibitor, is a key agent in multiple myeloma therapy, but it induces a taste disorder. In this study, we investigated the characteristics of bortezomib-induced taste disorder and the underlying mechanism in mice. Among the five basic tastes, the sour taste sensitivity of mice was significantly increased by bortezomib administration. In bortezomib-administered mice, protein expression of PKD2L1 was increased. The increased sour taste sensitivity induced by bortezomib returned to the control level on cessation of its administration. These results suggest that an increase in protein expression of PKD2L1 enhances the sour taste sensitivity in bortezomib-administered mice, and this alteration is reversed on cessation of its administration.

Development and evaluation of Desvenlafaxine loaded PLGA-chitosan nanoparticles for brain delivery

Depression is a debilitating psychiatric condition that remains the second most common cause of disability worldwide. Currently, depression affects more than 4 per cent of the world’s population. Most of the drugs intended for clinical management of depression augment the availability of neurotransmitters at the synapse by inhibiting their neuronal reuptake. However, the therapeutic efficacy of antidepressants is often compromised as they are unable to reach brain by the conventional routes of administration. The purpose of the present study was to reconnoiter the potential of mucoadhesive PLGA-chitosan nanoparticles for the delivery of encapsulated Desvenlafaxine to the brain by nose to brain delivery route for superior pharmacokinetic and pharmacodynamic profile of Desvenlafaxine. Desvenlafaxine loaded PLGA-chitosan nanoparticles were prepared by solvent emulsion evaporation technique and optimized for various physiochemical characteristics. The antidepressant efficacy of optimized Desvenlafaxine was evaluated in various rodent depression models together with the biochemical estimation of monoamines in their brain. Further, the levels of Desvenlafaxine in brain and blood plasma were determined at various time intervals for calculation of different pharmacokinetic parameters. The optimized Desvenlafaxine loaded PLGA-chitosan nanoparticles (∼172 nm/+35 mV) on intranasal administration significantly reduced the symptoms of depression and enhanced the level of monoamines in the brain in comparison with orally administered Desvenlafaxine. Nose to brain delivery of Desvenlafaxine PLGA-chitosan nanoparticles also enhanced the pharmacokinetic profile of Desvenlafaxine in brain together with their brain/blood ratio at different time points. Thus, intranasal mucoadhesive Desvenlafaxine PLGA-chitosan nanoparticles could be potentially used for the treatment of depression.

Is bone equally responsive to calcium and vitamin D intake from food vs. supplements? Use of (41)calcium tracer kinetic model

Background

Few interventions directly compare equivalent calcium and vitamin D from dairy vs. supplements on the same bone outcomes. The radioisotope calcium-41 (⁴¹Ca) holds promise as a tracer method to directly measure changes in bone resorption with differing dietary interventions.

Objective

Using ⁴¹Ca tracer methodology, determine if 4 servings/day of dairy foods results in greater ⁴¹Ca retention than an equivalent amount of calcium and vitamin D from supplements. Secondary objective was to evaluate the time course for the change in ⁴¹Ca retention.

Methods

In this crossover trial, postmenopausal women (n = 12) were dosed orally with 100 nCi of ⁴¹Ca and after a 180 day equilibration period received dairy (4 servings/day of milk or yogurt; ~ 1300 mg calcium, 400 IU cholecalciferol (vitamin D₃/day)) or supplement treatments (1200 mg calcium carbonate/day and 400 IU vitamin D₃/day) in random order. Treatments lasted 6 weeks separated by a 6 week washout (WO). Calcium was extracted from weekly 24 h urine collections; accelerator mass spectrometry (AMS) was used to determine the ^41/40Ca ratio. Primary outcome was change in ^41/40Ca excretion. Secondary outcome was the time course for change in ⁴¹Ca excretion during intervention and WO periods.

Results

The ^41/40Ca ratio decreased significantly over time during both treatments; there was no difference between treatments. Both treatments demonstrated a significant retention of ⁴¹Ca within 1–2 weeks (p = 0.0007 and p < 0.001 for dairy and supplements, respectively). WO demonstrated a significant decrease (p = 0.0024) in ⁴¹Ca retention within 1–2 weeks, back to pre-intervention levels.

Conclusion

These data demonstrate that urinary ⁴¹Ca retention is increased with an increase in calcium and vitamin D intake regardless of the source of calcium, and the increased retention occurs within 1–2 weeks.

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Investigated, using ⁴¹Ca tracer, whether bone response to calcium and vitamin D differed based on the source of nutrients, foods vs. supplements.

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There was no difference in the bone response by treatment group.

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Both dairy foods and supplements resulted in reduce ⁴¹Ca excretion in urine.

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Reduction in ⁴¹Ca excretion occurred with 2 weeks of initiating the interventions.

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Removal of interventions resulted in 41Ca excretion returning to pre-intervention levels

The pH of chemistry assays plays an important role in monoclonal immunoglobulin interferences

Objectives

Immunoglobulin paraproteins can interfere with multiple chemistry assays. We want to investigate the mechanisms of immunoglobulin interference.

Design and methods

Serum samples containing paraproteins from the index patient and eight additional patients were used to investigate the interference with the creatinine and total protein assays on the Beckman Coulter AU5400/2700 analyzer, and to determine the effects of pH and ionic strength on the precipitation of different immunoglobulins in these patient samples.

Results

The paraprotein interference with the creatinine and total protein assays was caused by the precipitation of IgM paraprotein in the index patient's samples under alkaline assay conditions. At extremely high pH (12–13) and extremely low pH (1–2) and low ionic strength, paraprotein formed large aggregates in samples from the index patient but not from other patients.

Conclusions

The pH and ionic strength are the key factors that contribute to protein aggregation and precipitation which interfere with the creatinine and total protein measurements on AU5400/2700. The different amino acid sequence of each monoclonal paraprotein will determine the pH and ionic strength at which the paraprotein will precipitate.

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Investigation of the cause of IgM paraprotein interference with creatinine assay.

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Paraprotein precipitation under assay conditions caused the interference.

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Identified The pH of chemistry assays is a key factor causing paraprotein precipitation.

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Results showed that not all paraproteins precipitate under the same assay conditions.

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Different paraproteins react differently to changes in pH and ionic strength.

Design of a novel bilayered gastric mucoadhesive system for localized and unidirectional release of lamotrigine

Lamotrigine is a BCS class II drug with pH dependent solubility. The bilayered gastric mucoadhesive tablets of lamotrigine were designed such that the drug and controlled release polymers were incorporated in the upper layer and the lower layer had the mucoadhesive polymers. The major ingredients selected for the upper layer were the drug and control release polymer (either HPMC K15M or polyox) while the lower MA layer predominantly comprised of Carbopol 974P. A 2(3) full factorial design was constructed for this study and the tablets were optimized for parameters like tablet size, shape, ex vivo mucoadhesive properties and unidirectional drug release. Oval tablets with an average size of 14 mm diameter were set optimum. Maximum mucoadhesive bond strength of 79.3 ± 0.91 * 10(3) dyn/cm(2) was achieved with carbopol when used in combination with a synergistic resin polymer. All the tested formulations presented a mucoadhesion time of greater than 12 h. The incorporation of methacrylic polymers in the lower layer ensured unidirectional drug release from the bilayered tablets. The unidirectional drug release was confirmed after comparing the dissolution results of paddle method with those of a modified basket method. Model independent similarity and dissimilarity factor methods were used for the comparison of dissolution results. Controlled drug release profiles with zero order kinetics were obtained with polyox and HPMC K15M which reported t 90% at 6th and 12th hours, respectively. The "n" value with polyox was 0.992 and that with HPMC K15M was 0.946 indicating an approximate case II transport. These two formulations showed the potential for oral administration of lamotrigine as bilayered gastric mucoadhesive tablets by yielding highest similarity factor values, 96.06 and 92.47, respectively, between the paddle and modified basket method dissolution release profiles apart from reporting the best tablet physical properties and maximum mucoadhesive strength.