Ascorbic acid transport via choroid plexus measured with 6-deoxy-6-[¹⁸F]fluoro-L-ascorbic acid PET

Ascorbic acid, a crucial antioxidant, is transported from blood to cerebrospinal fluid (CSF) via the choroid plexus (ChP). A noninvasive tool to visualize and quantify ascorbic acid transport process in the human brain is currently lacking. We aimed to determine whether 6-deoxy-6-[¹⁸F]fluoro-L-ascorbic acid ([¹⁸F]FAA) PET can visualize and quantify ascorbic acid transport from blood to CSF via the ChP in humans.

This prospective secondary analysis evaluated participants between May 2024 and September 2024. Eight participants underwent a 45-minute dynamic brain [¹⁸F]FAA PET/CT scan; 153 participants underwent a static [¹⁸F]FAA PET/CT scan. Tracer accumulation in ChP and CSF were measured in the lateral and fourth ventricles. Univariable and multivariable linear regression models were used to investigate the associated factors of [¹⁸F]FAA PET metrics.

One hundred sixty-one participants (mean age, 48.0 years ± 15.7 [SD]; 90 women) were evaluated. Dynamic [¹⁸F]FAA PET showed rapid ChP tracer accumulation in the lateral and fourth ventricles, peaking at about 5 min post-injection followed by declining, while CSF [¹⁸F]FAA standardized uptake value progressively increased. The area under the curve of the time-activity curves from 0 to 40 min was significantly higher in the young group (<60 years, n = 4) than in the elderly group (≥ 60 years, n = 4) in the ChP. Multiple linear regression analyses showed age was independently and negatively associated with [¹⁸F]FAA accumulation in the ChP and CSF.

[¹⁸F]FAA PET is a non-invasive tool for visualizing and assessing choroid plexus ascorbic acid transport in humans.

(ChiCTR2300076126: http://www.chictr.org.cn/ ) with the Clinical Trial Registry (2023-09-25).