Association between very long chain fatty acids in the meibomian gland and dry eye resulting from n-3 fatty acid deficiency

• We identified the structure of several fatty acids in the meibomian gland (MG).
• Very long chain fatty acids (VLCFAs) in oily tear of MG existed in monoesters.
• VLCFAs (C25-29) existed in monoesters and almost were the branched chain.
• Sum of VLCFAs were markedly decreased in the n-3 fatty acid deficient mice.
• n-3 fatty acid deficiency caused evaporation of tear by low oily tear.

In our previously study, we reported lower tear volume in with an n-3 fatty acid deficient mice and that the docosahexaenoic acid and total n-3 fatty acid levels in these mice are significantly reduced in the meibomian gland, which secretes an oily tear product. Furthermore, we noted very long chain fatty acids (≥25 carbons) in the meibomian gland. To verify the detailed mechanism of the low tear volume in the n-3 fatty acid-deficient mice, we identified the very long chain fatty acids in the meibomian gland, measured the fatty acid composition in the tear product. Very long chain fatty acids were found to exist as monoesters. In particular, very long chain fatty acids with 25–29 carbons existed for the most part as iso or anteiso branched-chain fatty acids. n-3 fatty acid deficiency was decreased the amount of meibum secretion from meibomian gland without change of fatty acid composition. These results suggest that the n-3 fatty acid deficiency causes the enhancement of evaporation of tear film by reducing oily tear secretion along with the decrease of meibomian gland function.