SLC6A3 and Parkinson disease: This was identified as a protein of interest by a screening method for candidate plasma proteins in a cohort study, and lower levels of ApoA1 were associated with an earlier age at PD onset.10 They also reported lower ApoA1 correlating with dopamine transporter (DAT) deficit using an enriched cohort of people at high risk of developing PD.10 Mechanisms by which circulating ApoA1 levels may affect progression are speculative but may include an immunomodulatory effect11 or even its effect on cardiovascular or cerebrovascular risk.12, 13, 14