Shared and Distinct Lipid Profiles in amygdala from Sporadic and GBA-associated Parkinson’s Diseases

Parkinson’s Disease (PD) is a neurodegenerative disorder characterised by the deposition of protein-lipid inclusions, containing alpha-synuclein, neuronal cell loss and disruptions in lipid metabolism such as those associated with GBA mutations. GBA mutations are together an important genetic risk factor for PD and are associated with a decrease in glucocerebrosidase, a lysosomal glycoprotein encoded by GBA , increase in alpha-synuclein and changes in sphingolipids levels and composition. However, the extent of lipid metabolism disruptions associated to PD and their contributions to disease progression remain unclear.

In this study, we used a combination of biochemical and lipidomic analyses of amygdala from healthy controls (HC) and people with sporadic (sPD) or GBA-associated PD (PD-GBA) to investigate the correlation between alpha-synuclein, glucocerebrosidase and lipids.

We found extensive metabolic remodelling of brain lipids, including increased free cholesterol, diacylglycerides, sphingolipids and specific glycerophospholipids in amygdala from people with sPD and disease duration above 30 years (sPD _>30y ) and from people with PD carriers of a GBA risk mutation (PD-GBA _risk ) relative to HC. The levels of free cholesterol, diacylglycerides, sphingolipids and specific glycerophospholipids all correlated positively with pathological αS and negatively with GCase activity. In contrast, the levels of phosphatidylethanolamine and cardiolipin only correlated positively with GCase activity. Moreover, we observed changes in the distribution of species for sphingolipids and glycerophospholipids in opposite directions for two categories of PD cases. We found a shift from short to long sphingomyelin and ceramide and from long to short phosphatidylserine and phosphatidylethanolamine in sPD _>30y and PD-GBA _risk cases and the opposite in sPD _<10y and PD-GBA _severe cases. The relative proportion of lipid species affected in these samples all correlated with glucocerebrosidase activity and pathological alpha-synuclein levels.

Together, these findings highlight the correlation between glucocerebrosidase, pathological alpha-synuclein and lipid levels in PD. Moreover, the identified opposite changes in lipid distribution for two categories of people with sPD and PD-GBA underscore the importance of patient stratification in clinical trials aiming at reverting PD-related lipid changes.