Longitudinal serum uric acid levels are not associated with dopamine transporter binding in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) causes rapid motor decline and severe dopaminergic dysfunction. While uric acid (UA) may act as a neuroprotective antioxidant in some neurodegenerative disorders (like Parkinson’s disease), its role in PSP remains unclear. This study evaluated the relationship between serum UA levels, measured cross-sectionally and longitudinally, and striatal dopamine transporter binding in PSP. A total of 33 PSP patients with repeated pre-[123I]FP-CIT SPECT UA measurements, along with 30 healthy control individuals and 30 patients with Alzheimer’s disease (AD), were retrospectively analyzed. Group and sex effects were analyzed with t tests and ANOVA. Effects of mean UA and longitudinal UA trajectories on FP-CIT SPECT binding in PSP were modeled using linear mixed-effects models and regressed against binding in four regions (caudate and putamen), separated into more-affected and less-affected side for both sexes. A Bayesian two-stage measurement-error model provided sensitivity analysis. UA was significantly lower in PSP (4.98 mg/dl) and AD (4.69 mg/dl) compared to healthy controls (5.71 mg/dL; p = 0.001). Sex had a significant effect on UA (F(1, 89) = 9.38, p = 0.003, partial η2 = 0.10), however, this effect was significant only in PSP (p< 0.001). Within PSP, UA–[123I]FP-CIT SPECT correlations were weak and nonsignificant, and neither UA intercept nor slope predicted [123I]FP-CIT SPECT binding (all p > 0.7). Bayesian estimates corroborated the absence of a credible relationship. In the present cohort, serum UA is reduced in PSP, primarily in females, but neither mean levels nor longitudinal changes are related to striatal [123I]FP-CIT SPECT binding, suggesting no clear association with dopaminergic degeneration in PSP, without precluding a potential role of uric acid at other disease stages.