TABLE 2.

Summary of studies that investigated the impact of Etn and lyso-Etn supplementation on PL homeostasis.

Supplement	References	Organism	Genetic variant	Treatment	Impact
Etn	Riekhof and Voelker (12).	Yeast	psd1Δpsd2Δ	5 mM	Normal growth, shows that Kennedy pathway can supply sufficient PE when supplemented with Etn.
			psd1Δpsd2Δect1Δ	5 mM	Insufficient PL biosynthesis due to inactive Kennedy pathway, strain not viable.
	Girisha et al. (136).	Human Fibroblasts	Homozygous PISD missense variant: [p.Cys266Tyr]	1 mM	No increase in viability.
				1 mM + 20μM MG-132	Increased viability compared to treatment with MG-132 only, indicates ability for Etn supplementation to reduce activity of apoptotic proteases.
Lyso-PE	Riekhof and Voelker (12).	Yeast	psd1Δpsd2Δ	0.5 mM	Normal growth, mitochondrial pool of PE replenished better than treatment with Etn.
			psd1Δpsd2Δect1Δ	0.5 mM	Normal growth, shows that lyso-PE use is independent of the Kennedy pathway.
	Tasseva et al. (4).	Chinese Hamster Ovary	Deficiency in Ptdss2 resulting in 95% decrease in PS synthesis and chronically reduced mitochondrial PE synthesis	0.1 mM	Improvement in cell growth, mitochondrial morphology, and ATP production.
	Zhao et al. (10).	Human Fibroblasts	PISD splicing variant in intron 5: [p.(?)] PISD missense variant in exon 8: [p.Arg277Gln]	0.05 mM	Mitochondrial and lysosomal morphology restored.