Department of Ophthalmology and the Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9057, USA.
Prog Lipid Res. 2011 Jul;50(3):278-301. doi: 10.1016/j.plipres.2011.03.003. Epub 2011 Mar 31.
Human Meibomian gland secretions (MGS) are a complex mixture of diverse lipids that are produced by Meibomian glands that are located in the upper and the lower eyelids. During blinking, MGS are excreted onto the ocular surface, spread and mix with aqueous tears that are produced by lachrymal glands, and form an outermost part of an ocular structure called "the tear film" (TF). The main physiological role of TF is to protect delicate ocular structures (such as cornea and conjunctiva) from desiccating. Lipids that are produced by Meibomian glands are believed to "seal" the aqueous portion of TF by creating a hydrophobic barrier and, thus, retard evaporation of water from the ocular surface, which enhances the protective properties of TF. As lipids of MGS are interacting with underlying aqueous sublayer of TF, the chemical composition of MGS is critical for maintaining the overall stability of TF. There is a consensus that a small, but important part of Meibomian lipids, namely polar, or amphiphilic lipids, is of especial importance as it forms an intermediate layer between the aqueous layer of TF and its upper (and much thicker) lipid layer formed mostly of very nonpolar lipids, such as wax esters and cholesteryl esters. The purpose of this review is to summarize the current knowledge on the lipidomics of human MGS, including the discussions of the most effective modern analytical techniques, chemical composition of MGS, biophysical properties of Meibomian lipid films, and their relevance for the physiology of TF. Previously published results obtained in numerous laboratories, as well as novel data generated in the author's laboratory, are discussed. It is concluded that despite a substantial progress in the area of Meibomian glands lipidomics, there are large areas of uncertainty that need to be addressed in future experiments.
人眼的睑板腺分泌物（MGS）是由位于上下眼睑中的睑板腺产生的复杂脂质混合物。在眨眼过程中，MGS 被排出到眼表面，与由泪腺产生的水性泪液混合并扩散，并形成一个称为“泪膜”（TF）的眼部结构的最外层。TF 的主要生理作用是保护娇嫩的眼部结构（如角膜和结膜）免受干燥。人们认为，睑板腺产生的脂质通过形成疏水性屏障来“密封”TF 的水性部分，从而延缓眼表面的水分蒸发，从而增强 TF 的保护性能。由于 MGS 的脂质与 TF 的下层水性亚层相互作用，因此 MGS 的化学成分对于维持 TF 的整体稳定性至关重要。人们普遍认为，睑板腺脂质的一小部分，但很重要的部分，即极性或两亲性脂质，具有特别重要的意义，因为它在 TF 的水性层与其上层（且厚得多）脂质层之间形成中间层，而该上层脂质层主要由非常非极性的脂质组成，例如蜡酯和胆固醇酯。本综述的目的是总结人眼 MGS 的脂质组学的最新知识，包括讨论最有效的现代分析技术、MGS 的化学组成、睑板腺脂质膜的生物物理特性及其与 TF 生理学的相关性。讨论了以前在众多实验室中获得的已发表结果以及作者实验室中生成的新数据。结论是，尽管在睑板腺脂质组学领域取得了实质性进展，但仍有许多不确定性需要在未来的实验中解决。
