Lipid and fatty acid profile of the retina, retinal pigment epithelium/choroid, and the lacrimal gland, and associations with adipose tissue fatty acids in human subjects

Abstract

Accumulation of lipids within Bruch's membrane (BrM) and between BrM and retinal pigment epithelium (RPE) accounts for one of the biological changes associated with normal aging and may contribute to the development of age-related maculopathies. The origin of these lipids is still being actively investigated. The relative contribution of plasma lipids and lipids coming from the neural retina remains a matter of controversy. Low-density lipoproteins (LDLs) have been reported to significantly participate in the retina's lipid supply, after active remodeling within RPE. Meanwhile, RPE expresses the enzymatic machinery for synthesizing lipoprotein-like particles. The objective of this study was to establish associations between the fatty acid profile of the ocular structures and adipose tissue as a surrogate for the subjects' past dietary intake. Lipids and fatty acids were analyzed from the neural retina, retinal pigment epithelium (RPE)/choroid, the lacrimal gland, and adipose tissue, collected from 27 human donors (19 women, eight men) aged 59-95 years. DHA concentrations in the neural retina were positively associated with the concentrations in cholesteryl esters (CEs) from RPE/choroid and negatively associated with DHA concentrations in phospholipids (PLs) from RPE/choroid. DHA in orbital fat was positively associated with DHA in the lacrimal gland. No significant association was observed in the other ocular structures. Linoleic acid in orbital fat was positively associated with linoleic acid in the lacrimal gland, followed by the neural retina and CEs from RPE/choroid; it was slightly correlated with PLs from RPE/choroid. Other fatty acids that originate exclusively from the diet such as trans fatty acids were detected in orbital fat, the lacrimal gland, PLs, and CEs from RPE/choroid. DHA in the neural retina was poorly associated with its dietary intake, contrary to other fatty acids such as linoleic acid. Within this context, CEs may be important carriers of fatty acids entering the retina. Although epidemiological studies have reported the benefit of DHA in the prevention of age-related macular degeneration, the leading cause of blindness in Western countries, the relevance of supplementing patients with DHA is questioned.