Serum d- and l-lactate, pyruvate and glucose levels in individuals with at-risk mental state and correlations with clinical symptoms

Aim: Little information exists on the peripheral metabolite levels in individuals with at-risk mental state who meet the criteria for a high-risk state of psychosis. Here, we aimed to investigate serum levels of glucose, pyruvate and d- and l-lactate, which may act as a signalling molecule for learning and memory in neuronal cells.

Methods: High performance liquid chromatography or commercial kits were used to assess serum metabolites in individuals with attenuated psychosis symptoms of at-risk mental state (n = 24, men = 12) who were not receiving antipsychotics. The metabolite levels of these individuals were compared with those of age- and sex-matched healthy individuals (controls, n = 23, men = 11). Correlations between the metabolites and clinical symptoms of at-risk mental state were also examined.

Results: Individuals with at-risk mental state had higher serum glucose levels than did controls (P = 2.18 × 10^-3 ), while no significant difference in pyruvate levels were observed between the groups. Individuals with at-risk mental state had significantly lower serum l-lactate levels than did controls (P = 6.31 × 10^-5 ), while no differences in d-lactate levels were observed. Furthermore, a negative correlation was identified between serum l-lactate levels and Positive and Negative Syndrome Scale negative symptoms scores (r = -0.5651, P = 4.01 × 10^-3 ) in individuals with at-risk mental state.

Conclusions: We found that, compared with controls, individuals with at-risk mental state have reduced serum l-lactate levels, which may predate psychosis onset, and may be involved in the related negative symptoms.