Helsinki Eye Lab, Department of Ophthalmology, University of Helsinki, Helsinki, Finland.
PLoS One. 2011 May 5;6(5):e19553. doi: 10.1371/journal.pone.0019553.
We have explored human aqueous tear fluid lipidome with an emphasis to identify the major lipids. We also address the physiological significance of the lipidome. The tears were analysed using thin layer chromatographic, enzymatic and mass spectrometric techniques. To emphasize the physiological aspect of the lipidome, we modelled the spreading of the non-polar tear fluid lipids at air-water interface in macroscopic scale with olive oil and egg yolk phosphatidylcholine. Based on enzymatic analysis the respective concentrations of choline-containing lipids, triglycerides, and cholesteryl esters were 48±14, 10±0, and 21±18 µM. Ultra performance liquid chromatography quadrupole time of flight mass spectrometry analysis showed that phosphatidylcholine and phosphatidylethanolamine were the two most common polar lipids comprising 88±6% of all identified lipids. Triglycerides were the only non-polar lipids detected in mass spectrometric analysis i.e. no cholesteryl or wax esters were identified. The spreading experiments show that the presence of polar lipids is an absolute necessity for a proper spreading of non-polar tear fluid lipids. We provide evidence that polar lipids are the most common lipid species. Furthermore, we provide a physiological rationale for the observed lipid composition. The results open insights into the functional role of lipids in the tear fluid and also aids in providing new means to understand and treat diseases of the ocular surface.
我们研究了人眼水样液中的脂类组，重点是鉴定主要脂质。我们还探讨了脂类组的生理意义。采用薄层色谱、酶和质谱技术分析眼泪。为了强调脂类组的生理方面，我们用橄榄油和蛋黄卵磷脂在宏观尺度上模拟了非极性泪液脂质在气-液界面的铺展。基于酶分析，含有胆碱的脂质、甘油三酯和胆固醇酯的相应浓度分别为 48±14、10±0 和 21±18 µM。超高效液相色谱四极杆飞行时间质谱分析显示，磷脂酰胆碱和磷脂酰乙醇胺是两种最常见的极性脂质，占所有鉴定脂质的 88±6%。甘油三酯是在质谱分析中检测到的唯一非极性脂质，即没有鉴定出胆固醇酯或蜡酯。铺展实验表明，极性脂质的存在是非极性泪液脂质适当铺展的绝对必要条件。我们提供的证据表明，极性脂质是最常见的脂质种类。此外，我们为观察到的脂质组成提供了生理依据。这些结果为了解脂质在泪液中的功能作用提供了新的思路，也为理解和治疗眼表疾病提供了新的方法。
