Plasma from some patients with amyotrophic lateral sclerosis exhibits elevated formaldehyde levels

Introduction: The aim of this study was to determine whether patients with amyotrophic lateral sclerosis (ALS) exhibit higher plasma levels of formaldehyde (FA) than controls, and to look for alterations in levels of FA precursors.

Methods: We studied 40 heathy controls and 50 ALS patients from the Motor Neuron Disease clinic at the Royal Brisbane & Women's Hospital. Plasma FA levels were quantified using a FA detection assay. Trimethylamine (TMA) and trimethylamine oxide (TMAO) in plasma were quantified by multiple reaction monitoring (MRM) mass spectrometry. Plasma levels in patients and controls were compared using Mann-Whitney U test and Spearman's correlation test was used to assess the correlation between levels of FA, TMA, TMAO and other variables.

Results: The levels of plasma FA were significantly greater in ALS subjects than controls. TMA and TMAO levels were not significantly different between healthy controls and patients, but were greater in ALS subjects with elevated FA levels than those with normal levels. Of note, levels of TMA and TMAO demonstrated a significant positive correlation with plasma FA levels (spearman's correlation coefficients of TMA with FA [r = 0.451, p = 0.010] and TMAO [r = 0.401, p = 0.023]). There was no association of FA levels with disability measured with the ALS functional rating scale, with the duration of disease or with the age of the subjects.

Conclusion: Elevated FA is found in some patients with ALS. FA is neurotoxic and could contribute to disease pathogenesis.