Abstract
Purpose :
The meibomian gland is a hormone target organ and has sex-associated differences in its anatomy and physiology. We previously reported that meibomian gland physiology changes during the menstrual cycle (IOVS, 2017). In this study, we assessed cyclic change of the fatty acid composition of meibum during the menstrual cycle in normal subjects.
Methods :
Six female subjects (age range: 30-39 years) with a normal 25 to 28-day menstrual cycle were enrolled. The menstrual cycle was divided into 6 periods; i.e., 2 days before menstruation (Phase VI), the first 2 days of menstruation (Phase I), and the remaining time divided into 4 periods (Phases II-V). After a warm compress of the eye, meibum was obtained via spatula after gently squeezing the eyelid margin with a Yoshitomi meibomian gland compressor. The meibum was then transmethylated and analyzed using gas chromatography/mass spectrometry (GC/MS). Saliva hormone concentrations (estradiol, progesterone, free-testosterone, and dehydroepiandrosterone sulfate) were also evaluated. From the GC/MS results, the peak area of each fatty acid was divided by total peak area of all the fatty acids, and principal component analysis (PCA) and hierarchical clustering analysis (HCA) was performed on each value. Moreover, a histogram was prepared for each fatty acid and summarized for each category of Saturated, Branched, Unsaturated, Polyunsaturated, and Branched Unsaturated.
Results :
As a result of PCA, 36 samples were classified into two groups on PC1. The contribution ratio (i.e., the proportion of the main component using all data) in PC1 was as high as 75.5%. One consisted of the Phase I ~ III group, in which the lipid component of meibum seemed to have changed, and another consisted of the Phase IV ~ VI group, suggesting that each group has a distinctive nature. The compounds strongly contributing to PC1 were C14:0, C16:0, and C18:0 in the positive correlation, and C18:1n9 in the negative correlation. C18:1n9 was inversely correlated with the behavior of C14:0, C16:0, and C18:0 at each sampling point, and these components strongly contribute to physiological cycle and composition change.
Conclusions :
Fatty acid composition showed a cyclic change during the menstrual cycle. This may have an impact on tear film stability and be related to dry eye, contact lens intolerance, and meibomitis-related keratoconjunctivitis in premenopausal women.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.