Quantitative analysis of biomarkers of liver and kidney injury in serum and urine using ultra-fast liquid chromatography with tandem mass spectrometry coupled with a hydrophilic interaction chromatography column: Application to monitor injury induced by Euphorbiae pekinensis Radix

Analytical method for sequential determination of persistent herbicides and their metabolites in fish tissues by UPLC-MS/MS

A novel and accurate liquid chromatography-tandem mass spectrometry method was developed to sequentially determine three persistent herbicides (atrazine (ATZ), acetochlor (ACE), and metolachlor (MET)) and seven characteristic metabolites (desethylatrazine (DEA), deisopropylatrazine (DIA), diaminochlorotriazine (DACT), MET-oxanilic acid (MET-OA), MET-ethanesulfonic acid (MET-ESA), ACE-ESA, and ACE-OA) in fresh fish tissues from six fish species. A modified QuEChERS method was conducted to extract the target compounds from fish tissues. Matrix-matched calibrations of the target analytes were carried out at spiking levels of 1, 10, 100, and 1000 ng g^-1. The method was validated in accordance with Codex guidelines (CAC/GL 71-2009). Recoveries for the target analytes were 67-120% with relative standard deviations below 20%, and the matrix effects ranged from -58.7% to 59.3%. The limits of detection and quantitation were 0.01-1.90 and 0.02-6.35 ng g^-1, respectively. Moreover, the method was successfully applied to analyze the concentrations of the target chemicals in fresh tissue samples of six fish species (n = 67) collected from four markets in Nanning City, Guangxi Province, China. The concentrations in all samples were 1.1-140.5 ng g^-1. Interestingly, this study was the first to measure DEA and DIA in fish liver, and their highest concentrations were 10.7 and 14.2 ng g^-1, respectively. This method provides a basis for studying the pathways of biotransformation, bioaccumulation, detoxification, and exposure patterns of ACE, ATZ, MET, and their metabolites in aquatic environments.

LC-MS-based metabolomics analysis to identify meprin-β-associated changes in kidney tissue from mice with STZ-induced type 1 diabetes and diabetic kidney injury

Meprin metalloproteases have been implicated in the pathophysiology of diabetic kidney disease (DKD). Single-nucleotide polymorphisms in the meprin-β gene have been associated with DKD in Pima Indians, a Native American ethnic group with an extremely high prevalence of DKD. In African American men with diabetes, urinary meprin excretion positively correlated with the severity of kidney injury. In mice, meprin activity decreased at the onset of diabetic kidney injury. Several studies have identified meprin targets in the kidney. However, it is not known how proteolytic processing of the targets by meprins impacts the metabolite milieu in kidneys. In the present study, global metabolomics analysis identified differentiating metabolites in kidney tissues from wild-type and meprin-β knockout mice with streptozotocin (STZ)-induced type 1 diabetes. Kidney tissues were harvested at 8 wk post-STZ and analyzed by hydrophilic interaction liquid chromatography ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Principal component analysis identified >200 peaks associated with diabetes. Meprin expression-associated metabolites with strong variable importance of projection scores were indoxyl sulfate, N-γ-l-glutamyl-l-aspartic acid, N-methyl-4-pyridone-3-carboxamide, inosine, and cis-5-decenedioic acid. N-methyl-4-pyridone-3-carboxamide has been previously implicated in kidney injury, and its isomers, 4-PY and 2-PY, are markers of peroxisome proliferation and inflammation that correlate with creatinine clearance and glucose tolerance. Meprin deficiency-associated differentiating metabolites with high variable importance of projection scores were cortisol, hydroxymethoxyphenylcarboxylic acid-O-sulfate, and isovaleryalanine. The data suggest that meprin-β activity enhances diabetic kidney injury in part by altering the metabolite balance in kidneys, favoring high levels of uremic toxins such as indoxyl sulfate and N-methyl-pyridone-carboxamide.

Metabonomics analysis of kidneys in rats administered with chronic low-dose cadmium by ultra-performance liquid chromatography-mass spectrometry

This study aimed to investigate the nephrotoxicity in rats administered with chronic low-dose cadmium (Cd) by ultra-performance liquid chromatography-mass spectrometry. A total of 40 male Sprague-Dawley rats were randomly assigned to four groups, namely: control; low-dose (0.13 mg/kg·body weight [bw]); middle-dose (0.80 mg/kg·bw); and high-dose (4.89 mg/kg·bw). The rats received CdCl₂ daily via drinking water for 24 weeks. Rat kidneys were collected for metabonomics analysis. Principal components analysis and partial least-squares discriminant analysis were used to investigate the metabonomics profile changes in the kidney samples and to screen the potential biomarkers. Ten metabolites were identified in the positive and negative ion modes. Compared with the control group, the intensities of tetranor 12-HETE, uric acid, hypoxanthine, phenylacetylglycine, guanidinosuccinic acid and xanthosine significantly increased (P < 0.01), and those of imidazolelactic acid, lactose 6-phosphate, l-urobilinogen and arachidonic acid significantly decreased (P < 0.01) in the high-dose group. Results showed that exposure to Cd in rats induced oxidative stress to the kidneys and disrupted amino acid metabolism, fatty acid metabolism and energy metabolism.

Serial-omics characterization of equine urine

Horse urine is easily collected and contains molecules readily measurable using mass spectrometry that can be used as biomarkers representative of health, disease or drug tampering. This study aimed at analyzing microliter levels of horse urine to purify, identify and quantify proteins, polar metabolites and non-polar lipids. Urine from a healthy 12 year old quarter horse mare on a diet of grass hay and vitamin/mineral supplements with limited pasture access was collected for serial-omics characterization. The urine was treated with methyl tert-butyl ether (MTBE) and methanol to partition into three distinct layers for protein, non-polar lipid and polar metabolite content from a single liquid-liquid extraction and was repeated two times. Each layer was analyzed by high performance liquid chromatography—high resolution tandem mass spectrometry (LC-MS/MS) to obtain protein sequence and relative protein levels as well as identify and quantify small polar metabolites and lipids. The results show 46 urine proteins, many related to normal kidney function, structural and circulatory proteins as well as 474 small polar metabolites but only 10 lipid molecules. Metabolites were mostly related to urea cycle and ammonia recycling as well as amino acid related pathways, plant diet specific molecules, etc. The few lipids represented triglycerides and phospholipids. These data show a complete mass spectrometry based—omics characterization of equine urine from a single 333 μL mid-stream urine aliquot. These omics data help serve as a baseline for healthy mare urine composition and the analyses can be used to monitor disease progression, health status, monitor drug use, etc.

Targeted metabolomics analysis of aromatic amino acids and their gut microbiota-host cometabolites in rat serum and urine by liquid chromatography coupled with tandem mass spectrometry

Gut microbiota-host cometabolites are closely related to various diseases. Monitoring dynamic changes of cometabolites can provide a more comprehensive understanding of pathophysiology. Here, a novel liquid chromatography-tandem mass spectrometry method was performed for the analysis of aromatic amino acids and their gut microbiota-host cometabolites in rat serum and urine. In the developed method, seven key gut microbiota-host cometabolites were chromatographically separated on a Kinetex Phenyl-Hexyl column by gradient elution, and the run time was 6 min. Serum and urine were extracted by protein precipitation. This method was linear between 10.20 and 1000.00 ng/mL for phenylalanine and p-cresyl sulfate; 25.60-2500.00 ng/mL for tryptophan; 51.20-5000.00 ng/mL for tyrosine, indole, and indoxyl sulfate; and 75.50-7500.00 ng/mL for p-cresol. The linearity, accuracy, precision, and recovery of seven analytes were all satisfactory. The method was sufficiently sensitive and robust. It was successfully applied to characterize the alterations of gut microbiota-host cometabolites in inflammatory disorders. All of these results suggest that the developed method is able to simultaneously monitor aromatic amino acids and their gut microbiota-host cometabolites. This method will be expected to be a valuable tool for clinical researches and comprehensive studies of the pathophysiological roles.