July 2019
Volume 60, Issue 9
Free
ARVO Annual Meeting Abstract  |   July 2019
Side-by-side comparison of branching and elongation patterns of cholesteryl esters of human and mouse meibum
Author Affiliations & Notes
  • Seher Yuksel
    Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
  • Nita Bhat
    Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
  • Amber Wilkerson
    Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
  • Anne McMahon
    Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
  • Jadwiga Wojtowicz
    Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
    Centro Oftalmologico de Valencia, Valencia, Carabobo, Venezuela, Bolivarian Republic of
  • Igor A Butovich
    Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
    Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, United States
  • Footnotes
    Commercial Relationships   Seher Yuksel, None; Nita Bhat, None; Amber Wilkerson, None; Anne McMahon, None; Jadwiga Wojtowicz, None; Igor Butovich, None
  • Footnotes
    Support  NIH R01 Grant R01EY027349, NIH R01 Grant R01EY024324, Unrestricted Grant from Research to Prevent Blindness, New York, NY.
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 4175. doi:
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    • Get Citation

      Seher Yuksel, Nita Bhat, Amber Wilkerson, Anne McMahon, Jadwiga Wojtowicz, Igor A Butovich; Side-by-side comparison of branching and elongation patterns of cholesteryl esters of human and mouse meibum. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4175.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Branching of lipids strongly influences their packing, melting, and fluidity. As human meibum is formed predominantly of wax esters (40%, w/w, WE) and cholesteryl esters (30%, CE), the effect of branching on properties of meibum and its physiological behavior could be high. Previously, we evaluated the composition of intact WE of human and mouse meibum using gas chromatography-mass spectrometry and demonstrated their extensive branching. However, another major class of meibum lipids – CE – remained insufficiently characterized. Our goal was to evaluate branching and elongation patterns of intact CE of human and mouse meibum.

Methods : Meibum samples were collected from normal human subjects (n=8) and C57BL/6J wild-type mice (n=12). Intact CE were analyzed using liquid chromatography (LC) and mass spectrometry (MS). Authentic chemical standards of straight-chain saturated (SCE) and unsaturated CE (UCE) were used to detect and quantitate them in meibum samples. The compounds were identified using their LC retention times and a common analytical ion m/z 369.3521 (M–fatty acid+H)+, as well as compound-specific ions (M+H)+, (M+NH4)+, (M+K)+, (M–cholesterol), and their fragments generated in MS/MS experiments.

Results : The overall balance of major UCE to SCE was found to be, respectively, 24% and 76% (mol/mol) in humans, and 21% and 79% – in mice. All tested UCE (C16:1 to C32:1) were based on straight, even numbered mono- and di-unsaturated fatty acids (FA). In both species, the majority of SCE were branched (73%). Straight chain SCE with even-numbered FA chains (C12:0 to C32:0) were found to comprise ≤3% of total CE, while their branched counterparts gave 41%. Odd numbered SCE (from C11:0 to C27:0) comprised about 32% of all CE and were almost exclusively branched. Other members of the homolog series of SCE and UCE, and other structural isomers were present in trace amounts, if any, and were below the limit of detection and/or quantitation.

Conclusions : The majority of CE of human and mouse meibum are either branched or unsaturated. A large quantity of CE had odd-numbered FA residues. These features are known to decrease the packing order and lower melting points of lipids, compared with their saturated counterparts with straight chain, even-numbered FA residues. The balance between these features may have a strong impact on rheological and physiological characteristics of meibum in vivo.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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