Plasma sphingolipids, dopaminergic degeneration and clinical progression in idiopathic Parkinson's disease

Sphingolipid dysregulation in Parkinson's disease (PD) may affect the release and uptake of striatal dopamine. However, the longitudinal relationship between sphingolipids, striatal dopaminergic degeneration, and clinical correlates in idiopathic PD (iPD) remain unclear.

To investigate the relationship between plasma sphingolipids, striatal dopamine transporter specific binding ratio (DAT-SBR) and clinical symptoms in iPD.

We included 283 iPD patients and 121 healthy controls (HC) from the Parkinson's Progression Markers Initiative (PPMI), utilizing available data on plasma sphingolipids (sphingomyelin [SM] and ceramide [CER]), striatal DAT-SBR and clinical assessments. Linear mixed models and mediation analyses were used to examine the relationship between sphingolipids, DAT-SBR, and clinical progression in iPD.

Lower baseline SM levels were significantly associated with a faster decline in DAT-SBR in both the caudate (p = 0.015) and putamen (p = 0.002), with the putamen association remaining significant after Bonferroni correction (p = 0.015). No significant association was found for CER. Patients in the lowest quartile of baseline SM showed faster progression in MDS-UPDRS I (p = 0.013) and II (p = 0.011), while those in the lowest quartile of baseline CER showed faster progression in MDS-UPDRS II (p = 0.013) and III (p = 0.033). The progression rate of caudate DAT-SBR partially mediated the relationships between SM and progression in MDS-UPDRS I and II (p < 0.01).

Sphingolipids are associated with worse dopaminergic degeneration and potentially linked to faster progression in iPD, holding the promise for identifying individuals with faster progression in iPD.