Lipid order, saturation and surface property relationships: A study of human meibum saturation

Mudgil, Poonam; Borchman, Douglas; Yappert, Marta C.; Duran, D.; Cox, Gregory W.; Smith, Ryan J.; Bhola, Rahul; Dennis, Gary R.; Whitehall, John

doi:10.1016/j.exer.2013.08.012

Cited by 31 publications

(38 citation statements)

References 51 publications

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“…Namely, with the increase of lipid tail saturation, the spreading of MGS films was impaired, as manifested by (i) the increase in the lift off area, (ii) the shift of the saturated films’ isotherms to lower π values at ≥20% of the initial film area, and (iii) the heterogeneous structure of the meibomian layers (containing large dark regions separating the thick bright islands) at π ≤ 10 mN/m. Such observations align with the supposed qualitative deficiencies of MGD meibum [8,14,15,16,17,18], namely abnormally high melting temperature resulting in high bulk viscosity, which in physiological conditions hampers the expression of MGS from the orifices of the meibomian gland ducts and also suppresses the spreading of meibum over the aqueous tear layer at the ocular surface.…”

Section: Discussionsupporting

confidence: 78%

“…The presence of double bonds (unsaturation) in the hydrocarbon chains of lipids affects the conformational order (fluidity) of meibum [13,14,15,16,17,18,19] and its acyl chain-melting phase transition temperature [18,19,20], which is supposed to have major physiological impact. The TF of infants, with a noninvasive breakup time (NIBUT) of 32.5 ± 5.2 s [21,22] is more saturated than that of adults with a less stable TF (NIBUT = 15.73 ± 8.89 s) [23,24].…”

Section: Introductionmentioning

confidence: 99%

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Effects of Lipid Saturation on the Surface Properties of Human Meibum Films

Nencheva

Ramasubramanian

Eftimov

et al. 2018

IJMS

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Elevated levels of acyl chain saturation of meibomian lipids are associated with vastly different effects: from enhanced tear film (TF) stability in infants to shortened TF breakup time in meibomian gland disease patients. Thus it is important to study the effect of saturation on the surface properties of human meibum (MGS). Therefore, MGS films (1, 2, 3, 4, 5, 10, 25, 50, 67, and 100% saturation) were spread at the air/water interface of a Langmuir surface balance. The layers’ capability to reorganize during dynamic area changes was accessed via the surface pressure (π)-area (A) compression isotherms and step/relaxation dilatational rheology studies. Film structure was monitored with Brewster angle microscopy. The raise in the % (at ≥10%) of saturation resulted in the formation of stiffer, thicker, and more elastic films at π ≥ 12 mN/m with the effects being proportional to the saturation level. At the same time, at low (≤10 mN/m) π the raise in saturation resulted in altered spreading and heterogeneous structure of MGS layers. The strong impact of saturation on MGS surface properties correlates with our recent spectroscopy study, which demonstrated that saturation induced increase of MGS acyl chain order, phase transition temperature, and cooperativity.

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Section: Discussionsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Effects of Lipid Saturation on the Surface Properties of Human Meibum Films

Nencheva

Ramasubramanian

Eftimov

et al. 2018

IJMS

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“…In another Langmuir trough/infrared spectroscopy study we showed that the major factor affecting the conformation (fluidity) of many lipid systems including meibum was hydrocarbon chain saturation. 73 As confirmed in this study, meibum from adults were less ordered than meibum from children 69 largely due to hydrocarbon chain saturation. 73 Although hydrocarbon chain saturation is likely to contribute to the difference in lipid order between sebum and meibum from children, it has yet to be determined.…”

Section: Discussionsupporting

confidence: 66%

Sebum/Meibum Surface Film Interactions and Phase Transitional Differences

Mudgil

Borchman

Gerlach

et al. 2016

Invest. Ophthalmol. Vis. Sci.

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PurposeSebum may contribute to the composition of the tear film lipid layer naturally or as a contaminant artifact from collection. The aims of this study were to determine: if sebum changes the rheology of meibum surface films; if the resonance near 5.2 ppm in the 1H-NMR spectra of sebum is due to squalene (SQ); and if sebum or SQ, a major component of sebum, interacts with human meibum.MethodsHuman meibum was collected from the lid margin with a platinum spatula. Human sebum was collected using lipid absorbent tape. Langmuir trough technology was used to measure the rheology of surface films. Infrared spectroscopy was used to measure lipid conformation and phase transitions. We used 1H-NMR to measure composition and confirm the primary structure of SQ.ResultsThe NMR resonance near 5.2 ppm in the spectra of human sebum was from SQ which composed 28 mole percent of sebum. Both sebum and SQ lowered the lipid order of meibum. Sebum expanded meibum films at lower concentrations and condensed meibum films at higher concentrations. Sebum caused meibum to be more stable at higher pressures (greater maximum surface pressure).ConclusionsPhysiological levels of sebum would be expected to expand or fluidize meibum making it spread better and be more surface active (qualities beneficial for tear film stability). Sebum would also be expected to stabilize the tear film lipid layer, which may allow it to withstand the high shear pressure of a blink.

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“…Malondialdehyde, a proxy of lipid oxidation, has been found to be higher in adult human tears than in younger ones; this agrees with the elevated protein level and C=C bonds in elderly people, that is more susceptible to oxidative attack. In general, the PTF stability decreases with age due to compositional and structural changes of the PTF . For instance, tears of children are more stable than those of adults .…”

Section: Resultsmentioning

confidence: 99%

External eye symptoms in indoor environments

Wolkoff

2016

Indoor Air

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Eye irritation, for example dry or irritated eyes, is generally among top three reported symptoms in office-like environments, in particular among workplaces with cognitive demanding visual display unit (VDU) work. The symptoms are especially among middle and advanced ages and particularly among women more than men. The symptoms are also among the most commonly reported complaints in the eye clinic. To be in a position to interpret the high prevalence of eye symptoms, a multidisciplinary and integrated approach is necessary that involves the external eye physiology (separate from internal eye effects), eye diseases (evaporative dry eye (DE), aqueous-deficient DE, and gland dysfunctions), and risk factors that aggravate the stability of precorneal tear film (PTF) resulting in hyperosmolarity and initiation of inflammatory reactions. Indoor environmental, occupational and personal risk factors may aggravate the PTF stability; factors such as age, contact lenses, cosmetics, diet, draft, gender, low humidity and high temperature, medication, outdoor and combustion pollutants, and VDU work.Psychological stressors may further influence the reporting behavior of eye symptoms.The impact of the risk factors may occur in a combined and exacerbating manner. The symptoms are also among the most commonly reported complaints in the eye clinic, 8 and dry eye disease (DED) is the most common cause of chronic eye irritation in patients over age of 50. 9,10 These external symptoms, as opposed to internal symptoms such as tired or strained eyes (asthenopia) as already described by Dante in 1304-1307, 11 are categorized as dry eye (DE)-like symptoms.12 The symptoms are especially among middle and advanced ages throughout the world and expected to increase due to visually highly demanding workplaces increase continuously and so does the average age of the workforce.Indoor air pollution and low relative humidity (RH) have been proposed to explain the external DE symptoms; furthermore, a number of occupational and personal risk factors have been suggested to exacerbate the symptom reporting. 13 For instance, high ozone concentrations, especially in aircraft, have been proposed to initiate both gas (homogeneous) and surface (heterogeneous) reactions with reactive substances to produce a complex host of gas-and particle-phase products, for example formaldehyde. 14-16 The key question in search of causality for DE symptoms in office workers is how important indoor air pollution is in comparison with occupational, environmental, and personal risk factors. For instance, reported DE symptoms among young and middle-aged Japanese office workers were significantly higher among those with clinically diagnosed DED (12%) than in those with probable (54%) or undiagnosed DED (34%);

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Lipid order, saturation and surface property relationships: A study of human meibum saturation

Cited by 31 publications

References 51 publications

Effects of Lipid Saturation on the Surface Properties of Human Meibum Films

Effects of Lipid Saturation on the Surface Properties of Human Meibum Films

Sebum/Meibum Surface Film Interactions and Phase Transitional Differences

External eye symptoms in indoor environments

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