Regulation of kynurenine metabolism by a ketogenic diet.

Ketogenic diets (KDs) are increasingly utilized as treatments for epilepsy, other neurological diseases, and cancer. Despite their long history in suppressing seizures, the distinct molecular mechanisms of action of KDs are still largely unknown. The goal of this study was to identify key metabolites and pathways altered in the hippocampus and plasma of rats fed a KD versus control diet (CD) either ad libitum or calorically restricted to 90% of the recommended intake.

A High-throughput HPLC-MS/MS Assay for the Detection, Quantification and Simultaneous Structural Confirmation of 136 Drugs and Metabolites in Human Urine.

Background: Because of its superior sensitivity and specificity, multianalyte high-performance liquid chromatography coupled with tandem mass spectrometry has become the gold standard in clinical toxicology. Although several qualitative and quantitative liquid chromatography coupled with tandem mass spectrometry assays on various mass spectrometry platforms have been described in the literature, most methods either analyze only a limited number of compounds and/or require tedious and time-consuming sample preparation.

Methods: A major challenge in urine toxicology screening is the minimization of false-negative and false-positive results.

An Atmospheric Pressure Chemical Ionization MS/MS Assay Using Online Extraction for the Analysis of 11 Cannabinoids and Metabolites in Human Plasma and Urine.

Background: Although, especially in the United States, there has been a recent surge of legalized cannabis for either recreational or medicinal purposes, surprisingly little is known about clinical dose-response relationships, pharmacodynamic and toxicodynamic effects of cannabinoids such as Δ9-tetrahydrocannabinol (THC). Even less is known about other active cannabinoids.

Methods: To address this knowledge gap, an online extraction, high-performance liquid chromatography coupled with tandem mass spectrometry method for simultaneous quantification of 11 cannabinoids and metabolites including THC, 11-hydroxy-Δ9-tetrahydrocannabinol, 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid, 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid glucuronide (THC-C-gluc), cannabinol, cannabidiol, cannabigerol, cannabidivarin, Δ9-tetrahydrocannabivarin (THCV), and 11-nor-9-carboxy-Δ9-tetrahydrocannabivarin (THCV-COOH) was developed and validated in human urine and plasma.

Amino acids in a targeted versus a non-targeted metabolomics LC-MS/MS assay. Are the results consistent?

Background: The results of plasma amino acid patterns in samples from kidney transplant patients with good and impaired renal function using a targeted LC-MS/MS amino acid assay and a non-targeted metabolomics assay were compared.

Methods: EDTA plasma samples were prospectively collected at baseline, 1, 2, 4 and 6months post-transplant (n=116 patients, n=398 samples). Each sample was analyzed using both a commercial amino acid LC-MS/MS assay and a non-targeted metabolomics assay also based on MS/MS ion transitions.

Technologies for retrieving sediment cores in Antarctic subglacial settings.

Accumulations of sediment beneath the Antarctic Ice Sheet contain a range of physical and chemical proxies with the potential to document changes in ice sheet history and to identify and characterize life in subglacial settings. Retrieving subglacial sediments and sediment cores presents several unique challenges to existing technologies. This paper briefly reviews the history of sediment sampling in subglacial environments.

A high-performance liquid chromatography-tandem mass spectrometry-based targeted metabolomics kidney dysfunction marker panel in human urine.

Background: Previous studies have examined and documented fluctuations in urine metabolites in response to disease processes and drug toxicity affecting glomerular filtration, tubule cell metabolism, reabsorption, oxidative stress, purine degradation, active secretion and kidney amino acylase activity representative of diminished renal function. However, a high-throughput assay that incorporates metabolites that are surrogate markers for such changes into a kidney dysfunction panel has yet to be described.

Methods: A high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) assay for the quantification of ten metabolites associated with the Krebs cycle, purine degradation, and oxidative stress in human urine was developed and validated.

Endothelial dysfunction and oxidative stress in polycystic kidney disease.

Cardiovascular disease (CVD) is the leading cause of premature mortality in ADPKD patients. The aim was to identify potential serum biomarkers associated with the severity of ADPKD. Serum samples from a homogenous group of 61 HALT study A ADPKD patients [early disease group with estimated glomerular filtration rate (eGFR) >60 ml·min(-1)·1.

Effects of lovastatin treatment on the metabolic distributions in the Han:SPRD rat model of polycystic kidney disease.

Background: We previously demonstrated that lovastatin decreases cyst volume and improves kidney function in the Han:SPRD (Cy/+) rat model of ADPKD. Since endothelial dysfunction and inflammatory activity are evident in patients with ADPKD, we investigated whether lovastatin reduces the inflammation and vascular dysfunction and improves kidney cell energy metabolism of Cy/+ rats.

Methods: Cy/+ and normal littermate control animals (+/+) were treated with either lovastatin (4 mg/kg/day) or vehicle (ethanol) from 3-8 weeks of age.

Mass Spectrometry-Based Multiplexing for the Analysis of Biomarkers in Drug Development and Clinical Diagnostics- How Much is too Much?

Biomarkers, or more specifically molecular markers, can detect biochemical changes associated with disease processes and drug effects before histopathological and pathophysiological changes occur. Multiplexing technologies such as high-performance liquid chromatography/mass spectrometry (LC-MS) allow for the measurement of molecular marker patterns that confer significantly more information than the measurement of a single parameter alone. The use of multiplexing assays for drug development, and as diagnostic tools, is attractive but will require regulatory review and approval and thus requires validation following regulatory guidances.

Development and validation of an LC-MS/MS assay for the quantification of the trans-methylation pathway intermediates S-adenosylmethionine and S-adenosylhomocysteine in human plasma.

Background: Although increased levels of S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) have been implicated as markers for renal and vascular dysfunction, until now there have been no studies investigating their association with clinical post-transplant events such as organ rejection and immunosuppressant nephrotoxicity.

Methods: A newly developed and validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for the quantification of SAM and SAH in human EDTA plasma was used for a clinical proof-of-concept pilot study. Retrospective analysis was performed using samples from a longitudinal clinical study following de novo kidney transplant patients for the first year (n=16).

Proteomics and metabolomics in renal transplantation-quo vadis?

The improvement of long-term transplant organ and patient survival remains a critical challenge following kidney transplantation. Proteomics and biochemical profiling (metabolomics) may allow for the detection of early changes in cell signal transduction regulation and biochemistry with high sensitivity and specificity. Hence, these analytical strategies hold the promise to detect and monitor disease processes and drug effects before histopathological and pathophysiological changes occur.

A high-throughput U-HPLC-MS/MS assay for the quantification of mycophenolic acid and its major metabolites mycophenolic acid glucuronide and mycophenolic acid acyl-glucuronide in human plasma and urine.

Mycophenolic acid (MPA) is used as an immunosuppressant after organ transplantation and for the treatment of immune diseases. There is increasing evidence that therapeutic drug monitoring and plasma concentration-guided dose adjustments are beneficial for patients to maintain immunosuppressive efficacy and to avoid toxicity. The major MPA metabolite that can be found in high concentrations in plasma is MPA glucuronide (MPAG).

Quantitative improvements in peptide recovery at elevated chromatographic temperatures from microcapillary liquid chromatography-mass spectrometry analyses of brain using selected reaction monitoring.

Elevated chromatographic temperatures are well recognized to provide beneficial analytical effects. Previously, we demonstrated that elevated chromatographic temperature enhances the identification of hydrophobic peptides from enriched membrane samples. Here, we quantitatively assess and compare the recovery of peptide analytes from both simple and complex tryptic peptide matrices using selected reaction monitoring (SRM) mass spectrometry.

A new method in applying power spectral statistics to examine cardio-respiratory interactions in fish.

Power spectral analysis (PSA) provides a powerful tool for determining frequency oscillations in time signals, and it is accepted that mammals can show distinct components in the heart rate (fH) spectrum that are synchronous with ventilatory frequency (fV). Using similar signal processing techniques, these fundamental components at fV are not apparent in the spectrum calculated from fish fH. Here we compare conventional PSA on the R-R interval tachogram generated from ECG traces recorded in rats and fish, with PSA on the raw ECG waveform.

Morphological studies in modern teratological investigations.

Despite the variety of modern molecular techniques available, examination of foetal anatomy is still a fundamental part of teratological studies in evaluating the developmental toxicity of xenobiotics or other non-chemical factors. The article presents contemporary methods of embryotoxicity and foetotoxicity assessment. A single alizarin red S and double alcian blue followed by alizarin red S staining, as well as various methods of soft tissue examination are discussed.