¹H NMR‐based metabolomics exploring urinary biomarkers correlated with proteinuria in focal segmental glomerulosclerosis: a pilot study

Abstract

Focal segmental glomerulosclerosis (FSGS) is a common glomerulonephritis, and its rates of occurrence are increasing worldwide. Proteinuria is a clinical defining feature of FSGS which correlates with the severity of podocyte injury in patients with nephrotic-range protein excretion. Metabolite biomarkers corresponding with the level of proteinuria could be considered as non-invasive complementary prognostic factors to proteinuria. The urine samples of 15 patients (n = 6 women and n = 9 men) with biopsy-proven FSGS were collected and subjected to nuclear magnetic resonance (NMR) analysis for metabolite profiling. Multivariate statistical analyses, including principal component analysis and orthogonal projection to latent structure discriminant analysis, were applied to construct a predictive model based on patients with proteinuria >3000 mg/day and <3000 mg/day. In addition, random forest was performed to predict differential metabolites, and pathway analysis was performed to find the defective pathways responsible for proteinuria. Ten metabolites, significant in both statistical methods (orthogonal projection to latent structure discriminant analysis and random forest), were considered as prognostic biomarkers for FSGS: citrulline, dimethylamine, proline, acetoacetate, alpha-ketoisovaleric acid, valine, isobutyrate, D-Palmitylcarnitine, histidine, and N-methylnicotinamide. Pathway analysis revealed impairment of the branched-chain amino acid degradation pathways in patients with massive proteinuria. This study shows that metabolomics can reveal the molecular changes corresponding with disease progression in patients with FSGS and provide a new insight for pathogenic pathways. Copyright © 2016 John Wiley & Sons, Ltd.

The metabolomic quest for a biomarker in chronic kidney disease

“…However, caution should be employed as there is evidence to suggest that urinary metabolites fluctuate throughout the day suggesting vigilance should be taken when interpreting results from such studies [ 49 , 50 ]. Kalantari et al [ 15 ] collected urine samples over 24 h from 15 patients with focal segmental glomerulosclerosis to identify 10 metabolites using NMR spectroscopy and ProMetab software, that were deemed to be prognostic when compared with kidney biopsy results. This study implemented a diet on its participants for 24 h prior to collecting urine as a mitigating measure to control for dietary influences on the urinary metabolome.…”

Application of metabolomics to preeclampsia diagnosis

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The Metabolomics Signature Associated with Responsiveness to Steroid Therapy in Focal Segmental Glomerulosclerosis: A Pilot Study

“…Preparation of urine samples for metabolomics analysis using 1 H nuclear magnetic resonance (1HNMR) was performed according to Kalantari et al 16 In brief, 450 µl of urine thawed at room temperature was mixed with 60 µl of buffer containing 300 mM potassium phosphate buffer (KH 2 PO 4 ), 20% deuterium oxide, and 0.2% of 3-(trimethylsilyl) propionic acid-d4 sodium salt at pH 7.4. Subsequently, 510 µl of the mixture of samples and buffer were transferred to separate 5 mm tubes and subjected to NMR spectroscopy.…”