Table 1.

Summary table of human sphingolipidomics. The up arrows refer to an increase in levels compared to the controls, while the down arrows refer to a reduction. The asterisk (*) indicates that the data were not statistically significant. Ceramide (Cer), ceramide 1-phosphate (C1P), sphingomyelin (SM), glucosyl-ceramide (GlcCer) and lactosyl-ceramide (LacCer).

Sphingolipid Species	Levels	Source	Type of PD	Notes	Ref.
Cer	↑	Serum	GBA mutation	Possible early development of PD and worsening of symptoms	[164]
	↑	Post-mortem CSF	Not specified	Correlation with neuropathological staging and disease duration	[202]
	↑	Primary visual cortex	Sporadic	Contribution to neuronal dysfunction	[205]
Long-chain Cer (such as C24:1 and C24:0-Cer)	↓	Anterior cingulate cortex		Impartment of salvage pathway by increased CerS1 expression	[201]
C14:0-Cer	↑	Plasma	PD with dementia	Association with delayed free recall and cognition	[203]
C16:0-Cer	↑	Plasma	Non-GBA mutation	Association with worse cognition	[204]
C18:0-Cer	↑	Plasma	Non-GBA mutation	Association with worse cognition	[204]
	↑ *		PD with dementia	Association with sleep behaviour disturbance	[203]
C18:1-Cer	↓	Frontal cortex	Not specified	Increased formation of diacylglycerols (DAGs)	[210]
C20:0-Cer	↑ *	Plasma	PD with dementia	Association with anxiety	[203]
	↑		Non-GBA mutation	Association with worse cognition	[204]
C22:0-Cer	↑	Plasma	Non-GBA mutation	Association with worse cognition	[204]
	↑ *		PD with dementia	Association with hallucination	[203]
C24:1-Cer	↑	Plasma	PD with dementia	Association with the score of immediate verbal recall and delayed free recall	[203]
	↑		Non-GBA mutation	Association with worse cognition	[204]
GlcCer	↑	Plasma	Non-GBA or Non-LRRK2 G2019S mutation	Association with worse cognition	[204,218]
GlcCer C16:0	↑	Plasma	Non-GBA mutation	Association with worse cognition	[204]
GlcCer C18:0	↑ *	Temporal cortex	Not specified	Correlation with PD severity	[209]
GlcCer C20:0	↑ *	Temporal cortex	Not specified	Correlation with PD severity	[209]
GlcCer C22:0	↑ *	Temporal cortex	Not specified	Correlation with PD severity	[209]
	↑	Plasma	Non-GBA mutation	Tendency to association with worse cognition	[204]
GlcCer C24:0	↑	Plasma	Non-GBA mutation	Association with worse cognition	[204]
	↑ *	Temporal cortex	Not specified	Correlation with PD severity	[209]
GlcCer C24:1	↑ *	Temporal cortex	Not specified	Correlation with PD severity	[209]
	↓	Frontal cortex	Not specified	Increased formation of DAGs	[210]
LacCer	↑	Serum	GBA mutation	Proposed as novel biomarker for increased risk of PD develop	[164]
C1P	↓	Serum	GBA mutation	Proposed as novel biomarker for increased risk of PD develop	[164]
SM	↑	Post-mortem CSF	Not specified	Correlation with neuropathological staging and disease duration	[205]
	↑	Substantia nigra	Male PD	Caused by enrichment in Lewy bodies	[206]
Long-chain SM	↑	Primary visual cortex	Sporadic	Contribution to neuronal dysfunction	[205]
SM d30:1	↓ *	Plasma	Not specified	Due to dysregulation of sphingolipids metabolism. Possibly involved in demyelination	[208]
SM d32:1	↓ *	Plasma	Not specified	Due to dysregulation of sphingolipids metabolism. Possibly involved in demyelination	[208]
SM d39:1	↓ *	Plasma	Not specified	Due to dysregulation of sphingolipids metabolism. Possibly involved in demyelination	[208]
GM1	↓	Substantia nigra dopaminergic neurons	Sporadic	Loss of neuroprotection and acceleration of α-syn formation	[216]
Ganglioside-NANA-3	↑	Plasma	GBA or/and LRRK2 G2019S mutation	Acceleration of α-syn formation	[217]
GM3 d18:1/24:1	↑	Plasma	Non-GBA or Non-LRRK2 G2019S mutation	Acceleration of α-syn formation	[218]
GM3 d18:1/26:0	↑	Plasma	Non-GBA or Non-LRRK2 G2019S mutation	Acceleration of α-syn formation	[218]