Identification of Urine Metabolic Markers of Stroke Risk Using Untargeted Nuclear Magnetic Resonance Analysis.

Stroke remains the second leading cause of mortality worldwide, and the third leading cause of death and morbidity combined, affecting more than 12 million people every year. Stroke pathophysiology results from complex interactions of several risk factors related to age, family history, gender, lifestyle, and the presence of cardiovascular and metabolic diseases. Despite all the evidence, it is not possible to fully prevent stroke onset. In recent years, there has been an exploration of innovative methodologies for metabolite analysis aimed at identifying novel stroke biomarkers. Utilizing Nuclear Magnetic Resonance (NMR) spectroscopy, we investigated small molecule variations in urine across different stages of stroke risk. The Framingham Stroke Risk Score was used in people over 63 years of age living in long-term care facilities (LTCFs) to calculate the probability of suffering a stroke: low stroke risk (LSR, control), moderate stroke risk (MSR), and high stroke risk (HSR). Univariate statistical analysis showed that urinary 4-hydroxyphenylacetate levels increased while glycolate levels decreased across the different stroke risk groups, from the LSR to the HSR groups. Trimethylamine N-oxide (TMAO) had average concentration values that were significantly higher in elderly people in the HSR group, while trigonelline levels were significantly lower in the MSR group. These metabolic markers can be used for early detection and to differentiate stages of stroke risk more efficiently.

Pharmacokinetics, safety, and tolerability of sodium phenylacetate and sodium benzoate in healthy Japanese volunteers: A phase I, single-center, open-label study.

TAK-123, a combination of sodium phenylacetate (NaPA) and sodium benzoate (NaBZ), is an intravenously administered drug developed for the treatment of acute hyperammonemia in infants, children, and adults with urea cycle enzyme deficiencies. The aim of the current study was to evaluate the pharmacokinetics, safety, and tolerability after intravenous infusion of TAK-123 in Japanese healthy adult volunteers. Ten volunteers received a 3.75 g/m2 loading dose of TAK-123 over a period of 1.5 h followed by a maintenance infusion of the same dose over 24 h. Phenylacetate (PA) and benzoate (BZ) and their respective metabolites, phenylacetylglutamine (PAG) and hippurate (HIP) were measured over a 24-h period using a high-performance liquid chromatography/tandem mass spectrometry method. Non-compartmental analysis was performed using WinNonlin® Professional. During the loading dose, plasma levels of both PA and BZ peaked at 1.5 h. Plasma PA levels plateaued and were maintained up to 6.5 h, whereas plasma BZ levels declined rapidly after switching to maintenance infusion. Urinary excretion ratios of PAG and HIP at 48 h after the administration were 99.3% and 104%, respectively, suggesting that almost all NaPA and NaBZ were metabolized and excreted into urine. Overall, TAK-123 was well-tolerated in healthy Japanese adults.

Longitudinal metabolic and gut bacterial profiling of pregnant women with previous bariatric surgery.

OBJECTIVE: Due to the global increase in obesity rates and success of bariatric surgery in weight reduction, an increasing number of women now present pregnant with a previous bariatric procedure. This study investigates the extent of bariatric-associated metabolic and gut microbial alterations during pregnancy and their impact on fetal development. DESIGN: A parallel metabonomic (molecular phenotyping based on proton nuclear magnetic resonance spectroscopy) and gut bacterial (16S ribosomal RNA gene amplicon sequencing) profiling approach was used to determine maternal longitudinal phenotypes associated with malabsorptive/mixed (n=25) or restrictive (n=16) procedures, compared with women with similar early pregnancy body mass index but without bariatric surgery (n=70). Metabolic profiles of offspring at birth were also analysed. RESULTS: Previous malabsorptive, but not restrictive, procedures induced significant changes in maternal metabolic pathways involving branched-chain and aromatic amino acids with decreased circulation of leucine, isoleucine and isobutyrate, increased excretion of microbial-associated metabolites of protein putrefaction (phenylacetlyglutamine, p-cresol sulfate, indoxyl sulfate and p-hydroxyphenylacetate), and a shift in the gut microbiota. The urinary concentration of phenylacetylglutamine was significantly elevated in malabsorptive patients relative to controls (p=0.001) and was also elevated in urine of neonates born from these mothers (p=0.021). Furthermore, the maternal metabolic changes induced by malabsorptive surgery were associated with reduced maternal insulin resistance and fetal/birth weight. CONCLUSION: Metabolism is altered in pregnant women with a previous malabsorptive bariatric surgery. These alterations may be beneficial for maternal outcomes, but the effect of elevated levels of phenolic and indolic compounds on fetal and infant health should be investigated further.

Amperometric Detection of the Urinary Disease Biomarker p-HPA by Allosteric Modulation of a Redox Polymer-Embedded Bacterial Reductase.

We report an amperometric biosensor for the urinary disease biomarker para-hydroxyphenylacetate ( p-HPA) in which the allosteric reductase component of a bacterial hydroxylase, C1-hpah, is electrically wired to glassy carbon electrodes through incorporation into a low-potential Os-complex modified redox polymer. The proposed biosensing strategy depends on allosteric modulation of C1-hpah by the binding of the enzyme activator and analyte p-HPA, stimulating oxidation of the cofactor NADH. The pronounced concentration-dependence of allosteric C1-hpah modulation in the presence of a constant concentration of NADH allowed sensitive quantification of the target, p-HPA. The specific design of the immobilizing redox polymer with suitably low working potential allowed biosensor operation without the risk of co-oxidation of potentially interfering substances, such as uric acid or ascorbic acid. Optimized sensors were successfully applied for p-HPA determination in artificial urine, with good recovery rates and reproducibility and sub-micromolar detection limits. The proposed application of the allosteric enzyme C1-hpah for p-HPA trace electroanalysis is the first successful example of simple amperometric redox enzyme/redox polymer biosensing in which the analyte acts as an effector, modulating the activity of an immobilized biocatalyst. A general advantage of the concept of allosterically modulated biosensing is its ability to broaden the range of approachable analytes, through the move from substrate to effector detection.

Metabolic Response in Rabbit Urine to Occurrence and Relief of Unilateral Ureteral Obstruction.

Ureteral obstruction will lead clinically to hydronephrosis, which may further develop into partial or complete loss of kidney function and even cause permanent histological damage. However, there is little knowledge of metabolic responses during the obstructed process and its recoverability. In this study, a complete unilateral ureteral obstruction (CUUO) model was established in the rabbit, and 1H NMR-based metabolomic analysis of urine was used to reveal the metabolic perturbations in rabbits caused by CUUO and the metabolic recovery after the CUUO was relieved. Univariate and multivariate statistical analyses were used to identify metabolic characteristics. The gradually decreased levels of 3-hydroxykynurenine, 3-methylhistidine, creatinine, guanidoacetate, meta- and para-hydroxyphenylacetate, and phenylacetylglycine and the gradually increased levels of acetate, alanine, citrate, glycine, lactate, and methionine in urine could be regarded as potential biomarkers for the occurrence and severity of ureteral obstruction. And the reduced levels of 3-methylhistidine, creatinine, guanidoacetate, hippurate, meta-hydroxyphenylacetate, and methylguanidine and the elevated levels of 2-aminoisobutyrate, acetylcholine, citrate, lactate, lysine, valine, and α-ketoglutarate in urine compared with the obstructed level could characterize the metabolic recovery of ureteral obstruction. Our results depicted the disturbed biochemical pathways involved in ureteral obstruction and demonstrated the practicability of recovering renal functions for the patients with severe hydronephrosis in clinical practice by removing causes for obstruction.

Assessing Exposome Effects on Pregnancy through Urine Metabolomics of a Portuguese (Estarreja) Cohort.

This nuclear magnetic resonance metabolomics study compared the influence of two different central Portugal exposomes, one of which comprised an important source of pollutants (the Estarreja Chemical Complex, ECC), on the urinary metabolic trajectory of a cohort of healthy pregnant women (total n = 107). An exposome-independent description of pregnancy metabolism was found to comprise a set of 18 metabolites reflecting expected changes in branched-chain amino acid catabolism and hormone and lipid metabolisms. In addition, a set of small changes in some metabolites was suggested to be exposome-dependent and characteristic of pregnant subjects from the Estarreja region. These results suggested that the Estarreja exposome may impact to a very low extent pregnancy metabolism, inducing slight changes in amino acid metabolism (alanine, glycine, and 3-hydroxyisobutyrate, possibly involved in valine metabolism), tricarboxylic acid (TCA) cycle (cis-aconitate), diet, or gut microflora (furoylglycine) as well as allantoin, 2-hydroxyisobutyrate, and an unassigned resonance at δ 8.45. Furthermore, the urine of Estarreja subjects was found to generally contain higher levels of 4-hydroxyphenylacetate and lower levels of citrate. However, out of the above metabolites, only glycine and citrate seemed to correlate with the proximity to the ECC, with slightly relative higher levels of these compounds found for subjects living closer to the ECC. This suggested possible small effects of local pollutants on energy metabolism, with the remaining exposome-dependent metabolite changes most probably originating from other aspects of the local exposome such as diet and lifestyle. Despite the limitation of this study regarding the unavailability of objective environmental parameters for the period under study, our results confirm the usefulness of metabolomics of human urine to gauge exposome effects on human health and, particularly, during pregnancy.

Quantitation of phenylbutyrate metabolites by UPLC-MS/MS demonstrates inverse correlation of phenylacetate:phenylacetylglutamine ratio with plasma glutamine levels.

Urea cycle disorders (UCDs) are genetic conditions characterized by nitrogen accumulation in the form of ammonia and caused by defects in the enzymes required to convert ammonia to urea for excretion. UCDs include a spectrum of enzyme deficiencies, namely n-acetylglutamate synthase deficiency (NAGS), carbamoyl phosphate synthetase I deficiency (CPS1), ornithine transcarbamylase deficiency (OTC), argininosuccinate lyase deficiency (ASL), citrullinemia type I (ASS1), and argininemia (ARG). Currently, sodium phenylbutyrate and glycerol phenylbutyrate are primary medications used to treat patients with UCDs, and long-term monitoring of these compounds is critical for preventing drug toxic levels. Therefore, a fast and simple ultra-performance liquid chromatography (UPLC-MS/MS) method was developed and validated for quantification of phenylbutyrate (PB), phenylacetate (PA), and phenylacetylglutamine (PAG) in plasma and urine. The separation of all three analytes was achieved in 2min, and the limits of detection were <0.04µg/ml. Intra-precision and inter-precision were <8.5% and 4% at two quality control concentrations, respectively. Average recoveries for all compounds ranged from 100% to 106%. With the developed assay, a strong correlation between PA and the PA/PAG ratio and an inverse correlation between PA/PAG ratio and plasma glutamine were observed in 35 patients with confirmed UCDs. Moreover, all individuals with a ratio ≥0.6 had plasma glutamine levels<1000µmol/l. Our data suggest that a PA/PAG ratio in the range of 0.6-1.5 will result in a plasma glutamine level<1000µmol/l without reaching toxic levels of PA.

Microbial metabolites are associated with a high adherence to a Mediterranean dietary pattern using a 1H-NMR-based untargeted metabolomics approach.

The study of biomarkers of dietary patterns including the Mediterranean diet (MedDiet) is scarce and could improve the assessment of these patterns. Moreover, it could provide a better understanding of health benefits of dietary patterns in nutritional epidemiology. We aimed to determine a robust and accurate biomarker associated with a high adherence to a MedDiet pattern that included dietary assessment and its biological effect. In this cross-sectional study, we included 56 and 63 individuals with high (H-MDA) and low (L-MDA) MedDiet adherence categories, respectively, all from the Prevención con Dieta Mediterránea trial. A 1H-NMR-based untargeted metabolomics approach was applied to urine samples. Multivariate statistical analyses were conducted to determine the metabolite differences between groups. A stepwise logistic regression and receiver operating characteristic curves were used to build and evaluate the prediction model for H-MDA. Thirty-four metabolites were identified as discriminant between H-MDA and L-MDA. The fingerprint associated with H-MDA included higher excretion of proline betaine and phenylacetylglutamine, among others, and decreased amounts of metabolites related to glucose metabolism. Three microbial metabolites - phenylacetylglutamine, p-cresol and 4-hydroxyphenylacetate - were included in the prediction model of H-MDA (95% specificity, 95% sensitivity and 97% area under the curve). The model composed of microbial metabolites was the biomarker that defined high adherence to a Mediterranean dietary pattern. The overall metabolite profiling identified reflects the metabolic modulation produced by H-MDA. The proposed biomarker may be a better tool for assessing and aiding nutritional epidemiology in future associations between H-MDA and the prevention or amelioration of chronic diseases.

Acute Consumption of Flavan-3-ol-Enriched Dark Chocolate Affects Human Endogenous Metabolism.

Flavan-3-ols and methylxanthines have potential beneficial effects on human health including reducing cardiovascular risk. We performed a randomized controlled crossover intervention trial to assess the acute effects of consumption of flavan-3-ol-enriched dark chocolate, compared with standard dark chocolate and white chocolate, on the human metabolome. We assessed the metabolome in urine and blood plasma samples collected before and at 2 and 6 h after consumption of chocolates in 42 healthy volunteers using a nontargeted metabolomics approach. Plasma samples were assessed and showed differentiation between time points with no further separation among the three chocolate treatments. Multivariate statistics applied to urine samples could readily separate the postprandial time points and distinguish between the treatments. Most of the markers responsible for the multivariate discrimination between the chocolates were of dietary origin. Interestingly, small but significant level changes were also observed for a subset of endogenous metabolites. 1H NMR revealed that flavan-3-ol-enriched dark chocolate and standard dark chocolate reduced urinary levels of creatinine, lactate, some amino acids, and related degradation products and increased the levels of pyruvate and 4-hydroxyphenylacetate, a phenolic compound of bacterial origin. This study demonstrates that an acute chocolate intervention can significantly affect human metabolism.

Urinary Time- or Dose-Dependent Metabolic Biomarkers of Aristolochic Acid-Induced Nephrotoxicity in Rats.

The metabolic mechanisms underlying aristolochic acid (AA)-induced nephrotoxicity are inconclusive. A Gas Chromatography-Mass Spectrometer (GC-MS)-based metabolomic study was performed to analyze urinary metabolites in AA-treated rats at different dosages (10, 20, and 40 mg/kg) and time points (2, 4, and 6 days). Serum blood urea nitrogen (BUN), creatinine, and kidney injury were significantly changed only on the 6th day in 40 mg/kg AA group, whereas metabolic alternation appeared even on the 2nd day in 10 mg/kg AA group. A total of 84 differential metabolites were identified in 40 mg/kg AA groups time-dependently and 81 in 10, 20, and 40 mg/kg AA groups dose-dependently (6 days) compared with control group. Eight metabolites were selected as potential metabolic biomarkers including methylsuccinic acid, nicotinamide, 3-hydroxyphenylacetic acid, citric acid, creatinine, uric acid, glycolic acid, and gluconic acid. Four of them were dose-dependently altered including methylsuccinic acid, citric acid, creatinine, and 3-hydroxyphenylacetic acid, which were defined as "early metabolic biomarker." The alteration of nicotinamide, uric acid, and gluconic acid was time- and dose-dependent, whereas the change of glycolic acid was time- or dose-independent. The latter 4 metabolites were defined as "late metabolic biomarker" because of the obvious reduction on the 6th day in 40 mg/kg AA group. In summary, the urinary metabolic alterations were more sensitive than conventional biomarkers of renal injury. The identified metabolites suggested pathways of energy metabolism, gut microbiota, and purine metabolism were associated with AA-induced nephrotoxicity time- or dose-dependently. Further investigation was warranted to determine the roles of the 8 potential metabolic biomarkers in AA-induced nephrotoxicity.