Proton Spectroscopy Metabolomics in serum and CSF from the BioMOx ALS cohort
Gray E*,Larkin JR*, Claridge TDW, Talbot K, Sibson NR, Turner MR
Poster at 2013 ENCALS meeting, Sheffield, UK (2013)
Background: Candidate 'wet' biomarkers in ALS have been largely based upon small studies, and results have rarely been replicated. Using the highly sensitive technique 1H NMR spectroscopy metabolomics, two studies reported serum glutamate as a marker of disease duration (1) and markers in CSF consistent with altered glucose metabolism (2). We attempted to validate these findings.
Methods: The Oxford Study for Biomarkers in MND (BioMOx) obtained serum and CSF samples in 70 ALS patients across a range of clinical sub-types, many with six-monthly longitudinal collection. Samples were processed within one hour of extraction and centrifuged prior to storage in polypropylene at -80°C. Aliquots (0.15mL CSF or ultracentrifuged serum) were mixed with phosphate buffer in D2O containing 1mM TSP as an internal standard (final volume 0.6mL). 1H NMR spectra were acquired using a 700MHz Bruker spectrometer. Partial least squares discriminant analysis (PLS-DA) was used to investigate differences between the spectra from patients and controls, and between different patient sub-groups.
Results: No significant separation was seen between ALS patients and controls when serum or CSF samples were analysed with our PLS-DA models. An apparently high predictive value within a sub-group of ALS patient CSF was found to be caused by differences in glucose concentration. A model comparing CSF spectra from ALS patients sampled at 24 months and control subjects revealed a higher predictive value but below the level considered significant.
Conclusions: The limitations of this approach are discussed, and wider potential reasons for a generalised failure to validate previously published wet biomarker findings.
References: 1. Kumar A et al. Metabolomic analysis of serum by (1) H NMR spectroscopy in amyotrophic lateral sclerosis. International journal of clinical chemistry 2010:411;563-7.
2. Blasco H et al. 1H-NMR-based metabolomic profiling of CSF in early amyotrophic lateral sclerosis. PloS one 2010:5;e13223.