Cicrulating markers of retinal and optic nerve lipids

Abstract

Purpose Blood lipids are frequently used as a surrogate of lipid composition of peripheral tissues. Even if it is well accepted such a relationship has never been clearly demonstrated for the eye. The aim of this study was to determine in human samples whether a lipidomic approach based on red blood cells could reveal associations between circulating and ocular lipid profiles. Methods Red blood cells, retinas and optic nerves were collected from 9 human donors. The lipidomic analyses on these tissues consisted in gas chromatography and liquid chromatography coupled to an electrospray ionization source‐mass spectrometer (LC‐ESI‐MS). Results Gas chromatographic approach did not shpw any relevant association between circulating and ocular lipids except for arachidonic acid whose circulating amounts were positively associated with its retinal and optic nerve levels. However, significant associations emerged from LC‐ESI‐MS analyses. Indeed, phospholipid species in red blood cells were positively or negatively associated with representative pools of retinal DHA (docosahexaenoic acid), retinal VLC‐PUFA (very‐long chain polyunsaturated fatty acids) or optic nerve plasmalogens. Conclusion First, our results show that LC‐ESI‐MS methodology is more appropriate than gas chromatography for lipidomics on red blood cells, and further extrapolation to ocular lipids. Second, this study has identified several individual lipid species as good candidates to represent circulating biomarkers of ocular lipids.

Dysfunctional peroxisomal lipid metabolisms and their ocular manifestations

“…Dependent on the polar head group at sn-3 position, compositions of fatty acids at the sn-1 etherlinkage and sn-2 ester-linkage differs. Plasmalogen ethanolamine (PlsEtn) is the predominant subclass in photoreceptor rod inner segment and RPE (Acar et al, 2007;Bretillon et al, 2008;Acar et al, 2012). In the retina and RPE, PlsEtn accounts for 20-40 and 30% of ethanolamine glycerophospholipids, respectively (Heymans et al, 1983;Acar et al, 2007;Acar et al, 2012).…”

“…Plasmalogen ethanolamine (PlsEtn) is the predominant subclass in photoreceptor rod inner segment and RPE (Acar et al, 2007;Bretillon et al, 2008;Acar et al, 2012). In the retina and RPE, PlsEtn accounts for 20-40 and 30% of ethanolamine glycerophospholipids, respectively (Heymans et al, 1983;Acar et al, 2007;Acar et al, 2012). PlsEtn is composed of ether-linked saturated fatty acid (16:0/18:0) or monounsaturated fatty acid (18:1n-9/18:1n-7) at sn-1 position and ester-linked PUFA (DHA/20:4n-6-arachidonic acid, ARA) at sn-2 position (Acar et al, 2012).…”

“…In the retina and RPE, PlsEtn accounts for 20-40 and 30% of ethanolamine glycerophospholipids, respectively (Heymans et al, 1983;Acar et al, 2007;Acar et al, 2012). PlsEtn is composed of ether-linked saturated fatty acid (16:0/18:0) or monounsaturated fatty acid (18:1n-9/18:1n-7) at sn-1 position and ester-linked PUFA (DHA/20:4n-6-arachidonic acid, ARA) at sn-2 position (Acar et al, 2012). Plasmalogen choline (PlsCho) is the predominant subclass in white matter and optic nerve where it accounts for 76 and 36% of total glycerophospholipids, respectively (Han et al, 2001;Acar et al, 2012).…”

“…PlsEtn is composed of ether-linked saturated fatty acid (16:0/18:0) or monounsaturated fatty acid (18:1n-9/18:1n-7) at sn-1 position and ester-linked PUFA (DHA/20:4n-6-arachidonic acid, ARA) at sn-2 position (Acar et al, 2012). Plasmalogen choline (PlsCho) is the predominant subclass in white matter and optic nerve where it accounts for 76 and 36% of total glycerophospholipids, respectively (Han et al, 2001;Acar et al, 2012). PlsCho is composed of ether-linked saturated fatty acid (16:0/18:0) or monounsaturated fatty acid (18:1n-9/18:1n-7) at sn-1 position and ester-linked saturated fatty acid (18:0) at sn-2 position (Han et al, 2001;Acar et al, 2012).…”

“…Plasmalogen choline (PlsCho) is the predominant subclass in white matter and optic nerve where it accounts for 76 and 36% of total glycerophospholipids, respectively (Han et al, 2001;Acar et al, 2012). PlsCho is composed of ether-linked saturated fatty acid (16:0/18:0) or monounsaturated fatty acid (18:1n-9/18:1n-7) at sn-1 position and ester-linked saturated fatty acid (18:0) at sn-2 position (Han et al, 2001;Acar et al, 2012). The concentrated Pls level in RPE is likely to protect against elevated oxidative stress as discussed in previous section.…”