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Douglas Borchman, Gary N. Foulks, Marta C. Yappert; Differences In Human Meibum Composition With Age, Meibomian Gland Dysfunction And After Treatment With Azithromycin And Doxycycline Using 1H NMR Spectroscopy. Invest. Ophthalmol. Vis. Sci. 2012;53(14):607.
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© ARVO (1962-2015); The Authors (2016-present)
Human tear film stability decreases with increasing age and meibomian gland dysfunction (MGD). It can be restored to some extent with azithromycin or doxycycline treatment. Changes in meibum composition with age, MGD and treatment were measured in search for markers of tear film instability.
Over 29 resonances were quantified using proton nuclear magnetic resonance (1H NMR) spectroscopy. 1H NMR spectra of 43 normal donors aged 1 to 88 years were acquired for age comparisons. Meibum from 34 donors with MGD (Md) and 22 subjects for the azithromycin study and 9 subjects for the doxycycline study were enrolled.
Compared with meibum from adults, meibum from children contained less CH3 and C=C groups as well as more aldehydes per lipid hydroperoxides. Principal component analysis discriminated between Mn and Md with an accuracy of 86 %. When the NMR spectra of Md were compared with those of Mn, three statistically significant decreases were observed in the relative amounts of CH3 moieties at 1.26 ppm, the products of lipid oxidation above 7 ppm and the =CH moieties at 5.2 ppm associated with terpenoids. Topical therapy with azithromycin and doxycycline relieved signs and symptoms and restored the lipid properties of the meibomian gland secretion towards normal. Treatment with doxycycline but not azithromycin restored the relative area of the 1H-NMR resonance at 1.26 ppm. Both doxycycline and azithromycin treatment restored the levels of the relative areas of the 1H-NMR resonances at 5.2 and 7.9 ppm to normal levels.
It is reasonable that tear film stability is higher in infants compared with adults because their meibum contain less CH3 and C=C groups, and higher levels of protein. As a result, the lipid is more ordered due to tighter and stronger lipid-lipid interactions. Lipid saturation could be the critical feature in meibum that stabilizes tears in infants. It is interesting that when carotenoids in meibum are low as in MGD, the tear film is unstable and patients have the signs and symptoms of dry eye. When carotenoids are restored with azithromycin and doxycycline treatment, tear film stability is restored and patients no longer have the signs and symptoms of dry eye.
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