title: Liquid chromatography-mass spectrometric analysis of lipids present in human meibomian gland secretions.
abstract: The purpose of the study was to qualitatively characterize the major lipid species present in human meibomian gland secretions (MGS) by means of high-performance liquid chromatography with atmospheric pressure ionization mass spectrometric detection of the analytes (NP HPLC-MS). Two different NP HPLC-MS methods have been developed to analyze lipid species that were expected to be present in MGS. The first method was optimized for the analysis of relatively nonpolar lipids [wax esters (WE), di- and triacyl glycerols (DAG and TAG), cholesterol (Chl) and its esters (Chl-E), and ceramides (Cer)], while the second method was designed to separate and detect phospholipids. The major lipid species in MGS were found to be WE, Chl-E, and TAG. A minor amount of free Chl (less then 0.5% of the Chl-E fraction) was detected in MGS. No appreciable amounts of DAG and Cer were found in MGS. The second NP HPLC-MS method, capable of analyzing model mixtures of authentic phospholipids (e.g. phosphatidylglycerol, phosphatidylethanolamine, phosphatidic acid, phosphatidylinositol, phosphatidylserine, phosphatidylcholine, and sphingomyelin) in submicrogram/mL concentrations, showed little or no presence of these species in the MGS samples. These observations suggest that MGS are a major source of the nonpolar lipids of the WE and Chl-E families for the tear film lipid layer (TFLL), but not of the previously reported phospholipid components of the TFLL.
authors.affiliation: Department of Ophthalmology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-9057, USA. igor.butovich@utsouthwestern.edu
authors.forename: Igor A
authors.initials: IA
authors.lastname: Butovich
authors.forename: Eduardo
authors.initials: E
authors.lastname: Uchiyama
authors.forename: Mario A
authors.initials: MA
authors.lastname: Di Pascuale
authors.forename: James P
authors.initials: JP
authors.lastname: McCulley
mesh_terms: D000328:Adult; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005260:Female; D006801:Humans; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry*; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D008537:Meibomian Glands / Q000737:chemistry / Q000378:metabolism*; D010743:Phospholipids / Q000032:analysis
chemical_list: D008055:Lipids; D010743:Phospholipids