Metabolomics of basal tears in amyotrophic lateral sclerosis: A cross-sectional study

Purpose: Amyotrophic lateral sclerosis (ALS) clinical variability, along with the lack of conclusive diagnostic instruments, result in average diagnosis delays of 9 months. This study aimed to assess whether metabolomic profiling of basal tears in ALS patients could act as a biological marker for diagnosing ALS, predicting prognosis, and discriminating between endophenotypes.

Methods: A single-center prospective case-control study was conducted in France from September 2021 to March 2023 including patients with ALS according to the revised EI Escorial criteria. Two microliters of basal tears were collected using microcapillary glass tubes and analyzed with ultra-high performance liquid chromatography coupled with mass spectrometry. Both univariate and multivariate analyses were performed.

Results: Twenty-five patients with ALS and 30 controls were included. No significant differences in metabolite levels were found between ALS and control groups (p > 0.05). The basal tear metabolome significantly discriminated bulbar and spinal forms of ALS based on 6 metabolites, among which 5 were decreased (aniline, trigonelline, caffeine, theophylline and methyl beta-D-galactoside) in the bulbar form and 1 was decreased in the spinal form (dodecanedioic acid).

Conclusion: This study represents the first prospective analysis of basal tear metabolomics in individuals with ALS. Despite the inability to distinguish between ALS patients and controls based on metabolic signatures, these findings could contribute to understanding the phenotypic diversity of ALS. Notably, distinct metabolic profiles were identified that differentiate between the bulbar and spinal forms of the disease.