Lipid Saturation and the Rheology of Human Tear Lipids

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

doi:10.3390/ijms20143431

Cited by 15 publications

(10 citation statements)

References 42 publications

(87 reference statements)

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“…In addition to hydrocarbon chain branching, hydrocarbon chain saturation is a major factor that contributes to lipid order in lens membranes [ 29 ] and human meibum [ 23 , [30] , [31] , [32] ]. Infrared spectroscopy showed that M HSCT and TL HSCT contained fewer double bonds compared M n and TL n [ 15 ].…”

Section: Discussionmentioning

confidence: 99%

Meibum lipid hydrocarbon chain branching and rheology after hematopoietic stem cell transplantation

Mudgil

Ramasubramanian

Borchman

2020

Biochemistry and Biophysics Reports

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Purpose Meibum from donors who have had hematological stem cell transplantations (M HSCT ) are susceptible to severe dry eye symptoms and exhibit very high lipid order (stiffness) compared with meibum from donors without dry eye (M n ). Since lipid order could have functional consequences, we compared the rheology and composition of M n and M HSCT to measure meibum compositional, structural and functional relationships. Methods The rheology and composition was measured using Langmuir trough and 1 H NMR spectroscopy, respectively. Results M HSCT and M n was studied from 16 to 43 donors, respectively, using NMR spectroscopy. M HSCT contained significantly 16% more straight chain and 24% less iso-chain hydrocarbons compared with M n . The cholesteryl ester to wax ester molar ratio, and hydrocarbon chain unsaturation were not significantly different, for M HSCT compared with M n . Surface pressure-area isotherms of meibum from 30 donors without dry-eye were grouped into 4 pools (PC) and meibum from 32 donors with dry eye who had hematopoietic stem cell transplantation (PT) were grouped into 3 pools. Above 15 years of age the П max and (C s −1 ) max increased with age for both the PC and the PT cohorts. (C s −1 ) max values were higher for PT samples compared with age matched PC samples, indicating they had higher elasticity and stiffness. A more ordered lipid could contribute to the formation of a discontinuous patchy tear film lipid layer, which in turn results in deteriorated spreading, and decreased surface elasticity. Conclusions The composition and rheology of meibum from donors with dry eye and who have had HSCT support the idea from other studies that more ordered meibum may contribute to or be a marker of dry eye.

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Section: Discussionmentioning

confidence: 99%

Meibum lipid hydrocarbon chain branching and rheology after hematopoietic stem cell transplantation

Mudgil

Ramasubramanian

Borchman

2020

Biochemistry and Biophysics Reports

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“…Like lens lipids discussed above, tear film lipid structural order has been measured by quantifying hydrocarbon chain conformation and structure using infrared ( 31 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 ), Raman ( 65 ), Brewster’s angle ( 34 , 62 , 66 ), and fluorescence anisotropy ( 50 ) spectroscopies. Meibum lipid hydrocarbons align to maximize van der Waal’s interactions between chains.…”

Section: Structure/conformation Of the Tfllmentioning

confidence: 99%

“…One must note that changes in meibum hydrocarbon chain structural order measured using infrared spectroscopy are not always related to the elasticity or stiffness, (C s −1 ) max , measured in rheological studies. For instance, meibum and tear lipid saturation causes an increase in both the (C s −1 ) max of tear lipid ( 62 ) and meibum ( 66 ) and the phase transition temperature of tear lipid ( 62 ) and meibum ( 48 , 58 ). However, as the phase transition increases above 33.4°C, the lipid order at 33.4°C reaches a maximum value of about 80% ordered and does not change further with saturation.…”

Section: Relationships Between Tfll Structure and Function And The Etmentioning

confidence: 99%

“…15 ), small changes in the phase transition temperature can cause significant changes in hydrocarbon chain order. The effect of catalytic saturation on the surface properties of human meibum and tear lipids was studied using Langmuir trough, and infrared and Brewster’s angle spectroscopies, respectively ( 48 , 58 , 62 , 66 ). The increase in the percentage of saturation resulted in thicker and more elastic meibum and tear lipid films with the effects being proportional to the saturation level.…”

Section: Relationships Between Tfll Composition and Structurementioning

confidence: 99%

“…Saturation concomitantly increased the phase transition temperature, hydrocarbon chain order, phase transition cooperativity, and the change in entropy and enthalpy. Native tear lipids were more ordered and elastic compared with meibum lipids collected from the same individual ( 62 ). Aggregation of lipids on the tear surface due to saturation was not as significant as it was for meibum ( 62 ).…”

Section: Relationships Between Tfll Composition and Structurementioning

confidence: 99%

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Lipid conformational order and the etiology of cataract and dry eye

Borchman¹

2021

Journal of Lipid Research

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Lens and tear film lipids are as unique as the systems they reside in. The major lipid of the human lens is dihydrosphingomylein, found in quantity only in the lens. The lens contains a cholesterol to phospholipid molar ratio as high as 10:1, more than anywhere in the body. Lens lipids contribute to maintaining lens clarity, and alterations in lens lipid composition due to age are likely to contribute to cataract. Lens lipid composition reflects adaptations to the unique characteristics of the lens: no turnover of lens lipids or proteins; the lowest amount of oxygen than any other tissue and contains almost no intracellular organelles. The tear film lipid layer (TFLL) is also unique. The TFLL is a thin, 100 nm layer of lipid on the surface of tears covering the cornea that contributes to tear film stability. The major lipids of the TFLL are wax esters and cholesterol esters that are not found in the lens. The hydrocarbon chains associated with the esters are longer than those found anywhere in the body, as long as 32 carbons, and many are branched. Changes in the composition and structure of the 30,000 different moieties of TFLL contribute to the instability of tears. The focus of the current review is how spectroscopy has been used to elucidate the relationships between lipid composition, conformational order and function and the etiology of cataract and dry eye.

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On modeling tear breakup dynamics with a nematic lipid layer

Taranchuk,

Braun

2024

J Eng Math

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One of the main roles of the lipid layer (LL) of the tear film (TF) is to help prevent evaporation of the aqueous layer (AL). The LL thickness, composition, and structure all contribute to its barrier function. It is believed that the lipid layer is primarily nonpolar with a layer of polar lipids at the LL/AL interface. There is evidence that the nonpolar region of the LL may have liquid crystalline characteristics. We investigate the structure and function of the LL via a model of the tear film with two layers, using extensional flow of a nematic liquid crystal for the LL and shear-dominated flow of a Newtonian AL. Evaporation is taken into account and is affected by the LL thickness, internal arrangement of its rod-like molecules, and external conditions. We conduct a detailed parameter study with a focus on the evaporative resistance parameter, the Marangoni number, and primary liquid crystal parameters including the Leslie viscosities and director angle. This new model responds similarly to previous Newtonian models in some respects; however, incorporating internal structure via the orientation of the liquid crystal molecules affects both evaporation and flow. As a result, we see new effects on TF dynamics and breakup.

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Lipid Saturation and the Rheology of Human Tear Lipids

Cited by 15 publications

References 42 publications

Meibum lipid hydrocarbon chain branching and rheology after hematopoietic stem cell transplantation

Meibum lipid hydrocarbon chain branching and rheology after hematopoietic stem cell transplantation

Lipid conformational order and the etiology of cataract and dry eye

On modeling tear breakup dynamics with a nematic lipid layer

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