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P.–J. Pisella, C. Joffre, S. Gregoire, N. Acar, M. Passemard, C. Creuzot–Garcher, A.M. Bron, L. Bretillon; Comparison of Fatty Acids in the Tear Film Lipid Layer of Normal Individuals and Patients Suffering From Chronic Blepharitis . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4420.
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Purpose: The aim of this study was to compare the fatty acid composition of tears collected from normal subjects and from patients presenting with chronic blepharitis. Methods: Tears were collected from normal individuals (n=20) and from chronic blepharitis patients after gentle massage of the lid margin (n=20). Tears were harvested with a sterile Schirmer paper test which was directly introduced into a screw–capped reaction tube containing boron trifluoride (7% in methanol) and toluene. Fatty acids were directly transmethylated by heating at 90°C for 18 hours. The lipid esters were extracted and were analyzed on a gas–chromatograph equipped with a flame ionization detector. Fatty acid methyl esters were separated on a polar CPSil–column (100m x 0.25mm) using hydrogen as carrier gas. Representative samples were also analyzed by gas chromatography mass spectrometry for a detailed determination of the chemical structures. Results: Tear lipids from normal patients were as follows: 38% saturated fatty acids, 12% branched–chain fatty acids, 45% monounsaturated fatty acids and 5% polyunsaturated fatty acids (% of identified fatty acids). Consistent amounts of very long chain saturated fatty acids (C24 to C28) were observed (one third of the total saturated fatty acids) Significant differences were identified in blepharitis patients: a decrease in palmitic and stearic fatty acids (13.6 vs 4.6% and 8.1 vs 2%, respectively), and an increase of total branched–chain fatty acids (12 vs 18%). Very long chain saturated fatty acids (C25, C26 and C28) were more frequent and may reflect an increase in waxes and in sphingolipids Conclusions: Our results strongly suggest that branched chain fatty acids are the most prominent components of the tear lipids. Owing to their biophysical properties, they may increase the fluidity of the tears. However, the reason for the accumulation of branched chain fatty acids in blepharitis patients remains unknown but might be attributed to a defect in the peroxisomal alpha–oxidation pathway. The toxicity of branched chain fatty acids as potent inducers of apoptosis, remains to be determined in blepharitis patients.
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