Pre-treatment untargeted cerebrospinal fluid metabolomic profiling in tuberculous meningitis uncovers pathways associated with mortality.

BACKGROUND: Dysregulation of cerebrospinal fluid (CSF) tryptophan metabolism contributes to the high mortality of tuberculous meningitis (TBM). We aimed to identify novel metabolic pathways associated with TBM mortality through untargeted metabolome-wide analysis.

METHODS: We measured 619 metabolites using untargeted liquid chromatography-mass spectrometry in pre-treatment CSF from adults with TBM from Indonesia (n = 388, 34 HIV positive) and Vietnam (n = 679, 250 HIV positive). Sixty-day mortality was modeled using Cox regression, adjusting for age and HIV status. Metabolites were ranked in a screening subset (n = 194, Indonesia) and validated in the same cohort (n = 194) and externally (n = 679, Vietnam). Secondary analysis included variable selection, clustering to classify associated metabolites into subgroups, comparison with non-infectious controls, and correlation with patient characteristics, CSF cytokines, CSF protein, and serum metabolite concentrations.

FINDINGS: Sixty-day mortality was 21.6% and was associated with the concentration of 10 CSF metabolites, including tryptophan. The strongest association was with 3-hydroxyoctanoate (FA 8:0;3OH), part of a cluster of hydroxylated fatty acids also including hydroxy-isocaproate (FA 6:0;OH), hydroxyisobutyrate (FA 4:0;OH), and C4-OH-carnitine. These fatty acids correlated weakly with CSF tumor necrosis factor alpha, interleukin-6 (IL-6), leukocyte counts, bacterial load, and CSF protein. Mediation analysis showed that the variation in fatty acids was linked directly to mortality rather than through disease severity.

CONCLUSION: We identified and validated nine new metabolites associated with TBM mortality, independent of HIV status, disease severity, and tryptophan. These metabolites suggest that altered fatty acid β-oxidation is linked to TBM-associated mortality. Interventions targeting cerebral fatty acid metabolism may improve survival of TBM.

FUNDING: National Institute of Health; Wellcome Trust, UK.