Differential scanning calorimetric evaluation of human meibomian gland secretions and model lipid mixtures: Transition temperatures and cooperativity of melting

Hua Lu, Jadwiga C. Wojtowicz, Igor A. Butovich

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Meibomian gland secretions (or meibum) are produced by holocrine meibomian glands and are secreted in melted form onto the ocular surface of humans and animals to form a protective tear film lipid layer (TFLL). Its protective effect strongly depends on the composition and, hence, thermotropic behavior of meibum. The goal of our study was to quantitatively evaluate the melting characteristics of human meibum and model lipid mixtures using differential scanning microcalorimetry. Standard calorimetric parameters, e.g. changes in calorimetric enthalpy, transition temperatures Tm, cooperativity of melting, etc. were assessed. We found that thermotropic behavior of meibum resembled that of relatively simple mixtures of unsaturated wax esters, but showed a lower change in calorimetric enthalpy, which can be indicative of a looser packing of lipids in meibum compared with pure standards and their simple mixtures. The cooperativity of melting of meibomian lipids was comparable to that of an equimolar mixture of four oleic-acid based wax esters. We demonstrated that the phase transitions in meibum start at about 10-15 C and end at 35-36 C, with Tm being about 30 C. The highly asymmetrical shape of the thermotropic peak of meibum is important for the physiology and biophysics of TFLL.

Original languageEnglish (US)
Pages (from-to)55-64
Number of pages10
JournalChemistry and Physics of Lipids
Volume170-171
DOIs
StatePublished - May 1 2013

Keywords

  • Cooperativity
  • Meibum
  • Melting
  • Microcalorimetry Wax esters
  • Phase transitions

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Organic Chemistry
  • Cell Biology

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