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J. P. McCulley, E. Uchiyama, L. Mendiola, S. Agee, I. A. Butovich; High Pressure Liquid Chromatographic Analysis of Lipids Present in the Human Meibomian Gland Secretions. Invest. Ophthalmol. Vis. Sci. 2007;48(13):442.
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© ARVO (1962-2015); The Authors (2016-present)
To qualitatively characterize the major lipid species present in meibomian gland secretions (MGS) of individual human subjects by means of high pressure liquid chromatography (HPLC).
The samples of human MGS and authentic lipid standards were analyzed using normal phase (NP) HPLC with mass spectrometric detection of the analytes. The MGS lipid samples were compared with authentic lipid standards.
Two separate HPLC protocols have been developed to analyze lipid species that were expected to be present in MGS. The first protocol was optimized for the analysis of nonpolar lipids [wax esters (WE), di- and triacylglycerols (DAG and TAG), cholesterol (Chl) and its esters (Chl-E), free fatty acids (FFA) and ceramides (Cer)], while the second protocol was designed to separate phospholipids (PL). Under the conditions of isocratic NP HPLC of the individual human MGS, optimized for the analysis of nonpolar lipids, only one major peak has been systematically detected. It co-eluted with a standard mixture of authentic WE, Chl-E, and TAG. No appreciable amounts of DAG, FFA, and Cer have been found in the human samples. The only other minor HPLC peak detected in the samples has been identified as free Chl. The second HPLC protocol, while being able to adequately separate standard mixtures of authentic PL (e.g. phosphatidylglycerol, phosphatidylethanolamine, phosphatidic acid, phosphatidylcholine, lyso-phosphatidylcholine, and sphingomyelin), did not reveal any presence of them in the MGS samples.
These observations suggest that MGS are a major source of nonpolar lipids for the tear film lipid layer (TFLL), but not of the previously reported PL components of the TFLL.
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