Lipid Saturation and the Rheology of Human Tear Lipids.

Georgi As Georgiev,Petar Eftimov,Douglas Borchman,Norihiko Yokoi

doi:10.3390/ijms20143431

Abstract

Elevated levels of acyl chain saturation of meibomian lipids are associated with enhanced tear film (TF) stability in infants to shortened TF breakup time with meibomian gland dysfunction. Thus, the effect of saturation on the surface properties of human TF lipids (TFLs) using a Langmuir surface balance and Brewster angle microscopy was studied. Lipid phase transitions were measured using infrared spectroscopy. The raise in the % of saturation resulted in thicker, and more elastic films at π = 12 mN/m, with the effects being proportional to the saturation level. At the same time, at lower (≤10 mN/m) π, the raise in saturation resulted in an altered spreading and modified structure of TFL layers. The strong impact of saturation on TFL surface properties correlated with a saturation induced increase of the TFL acyl chain order, phase transition temperature, and lipid–lipid interactions. The native TFL order and πmax were significantly greater, compared with native meibum collected from the same individual. Aggregation of lipids on the tear surface due to saturation was not as significant as it was for meibum. Although the surface pressure/area isotherms for TFL were similar for meibum, differences in rheology and phase transition parameters warrant the study of both.

Highlights

A thin film of lipids, called the tear film lipid layer (TFLL), covers the surface of the tear film (TF) and serves important functions
The TFLL ensures that the TF has a low surface tension, and an immobile air/TF interface that opposes the outflow of aqueous tears in an open eye [1,2,3,4,5]
It is interesting that tear film stability and meibum lipid hydrocarbon order both increase in the order: Meibum from donors without dry eye between the ages of 0 and 25 years old [18,19] < meibum from donors with meibomian gland dysfunction [18,20,21] < meibum donors who are susceptible to severe dry eye who have dysfunction [18,20,21] < meibum donors who are susceptible to severe dry eye who have had Ihnet.mJ. aMtoolp

Summary

Introduction

A thin film of lipids, called the tear film lipid layer (TFLL), covers the surface of the tear film (TF) and serves important functions. The TFLL ensures that the TF has a low surface tension, and an immobile air/TF interface that opposes the outflow of aqueous tears in an open eye [1,2,3,4,5]. The major source of tear lipids (TLs) are the meibomian glands [6], but other sources may include lipocalin bound phospholipid (citations in reviews [2,7] and others [8,9,10,11,12,13,14]) or by eyelid sebum [15,16,17]. Relationships between TFLL composition, structure, and function could provide insight into the etiology of dry eye. Other factors that may contribute to lipid order include proteins [25], hydrocarbon chainAbsrathnechcoinmgp[o29si]t,icohnoalensdteprhoyl s[3ic0a]l, pchroopleesrtteireysloefsTteLrss a[3re1]d, iafnfedrehnytdthroacnatrhbaotnocfhmaienibluenmgt(hab. ove) and saturAatsiothnecoconmtripboustietsiotno athnedpphhyyssicicaallpprrooppeerrtiteiessooffmTeLibs uamre [d2i6ff–e2r8e,n32t ]thwaenetxhtartacotfedmTeiLbsufmro(mabtoevares) aonndScsahtiurmraetrio’snsctroinptsraibnudtecsattaolythtiecapllhyyssaictualraptreodptehretieTsLosftomdeiebteurmmi[n2e6–if28s,a3t2u]rawtieoenxctorancttreibduTteLsstforothme tpehayrssiocnalSpcrhoirpmeretrie’ss sotfriTpLssaansdict adtoaelystticoamllyeisbautumr.aTtehdetphheyTsLicsatloadnedtethrmerimneodifysnaatumraictipornocpoenrttrieibsuotfeTs Ltos twhiethphaysraicnagleproofpsearttuiersatoifonTLlesvaeslsit wdoeeres tmo emaesuibruedm.uTsihnegpihnyfrsaicreadl asnpdecthtreorsmcoopdyynaanmdicthperior prehretoielos goyf TdLetsewrmitihneadrabnygLeaonfgsmatuuirrattrioonuglehvteelcshwnoerloegmy.easured using infrared spectroscopy and their rheology determined by Langmuir trough technology

Methods

Results

Conclusion