Age-related accumulation of free polyunsaturated fatty acids in human retina

The present study reports composition of free (nonesterified) as well as total (sum of free and esterified) fatty acids (FAs) in human retina (n = 13). For free fatty acid (FFA) analysis, retina tissue was homogenized, total lipids were partitioned with ethyl acetate and subsequently applied onto a aminopropyl (NH2) cartridge to isolate FFAs from the bulk of other lipids. FFAs were converted to methyl ester derivatives and analysed by gas chromatography using flame ionization detector. Analysis of FFAs revealed that the mean percentage composition of the major components including palmitic acid (PA), stearic acid (SA), oleic acid (OA), arachidonic acid (AA) and docosahexaenoic acid (DHA) were 17.2, 36.7, 15.6, 8.8 and 14.2%, respectively. There were significant correlations between age of the donors' and the content of both free AA and DHA (rPearson = 0.69, p = 0.005, and rPearson = 0.64, p = 0.009). The mean percentage of total PA, SA, OA, AA and DHA were 22.6, 23.2, 17.7, 11.4 and 21.9%, respectively. There was no association between age and any of the major FAs. The present study provides the first evidence for the presence of FFAs in the human retina as well as an age-related accumulation of polyunsaturated fatty acids (PUFAs). The latter finding suggests an alteration in the metabolism of retinal PUFAs which can be due to an increase of oxidative stress and/or decrease of antioxidant defences during ageing.