Association between reduced plasma dopamine β-hydroxylase levels and immediate memory impairment in first-episode...

Dopamine β-hydroxylase (DBH) is an enzyme that catalyzes the conversion of dopamine (DA) to norepinephrine (NE). The dysregulation of these neurotransmitters is implicated in the etiology and cognitive impairments of schizophrenia. However, the relationship between DBH and cognitive impairments of schizophrenia, independent of confounding effects of medication and chronic illness, remains unclear. Thus, this case-control study aimed to investigate plasma DBH levels, cognitive performance, and their association in patients with first-episode drug-naïve schizophrenia (FDS). A total of 56 FDS patients and 56 age- and gender-matched healthy controls (HCs) were enrolled. Cognitive function was assessed using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), and plasma DBH levels were measured via sandwich enzyme-linked immunosorbent assays (ELISAs). After adjusting for covariates, plasma Log₁₀DBH levels were significantly lower in FDS patients compared to HCs (F = 9.17, p = 0.003). Moreover, plasma Log₁₀DBH levels showed a positive correlation with immediate memory score in patients (r = 0.27, p = 0.04). Linear regression further confirmed a significant association between Log₁₀DBH levels and immediate memory score in patients (β = 50.18, t = 2.82, p = 0.008). Additionally, FDS patients scored significantly lower than HCs on the RBANS total score and all subdomains, except visuospatial/constructional score (all, p < 0.001). These findings suggest that reduced plasma DBH levels might be strongly associated with schizophrenia and might contribute to immediate memory impairment in FDS patients.