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Stephanie Cox, Jason J Nichols; Does the concentration of neuropeptides in tears differ based on extent of meibomian gland drop out?. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6177. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To determine if there is a difference in the concentration of vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), or substance P (SP) in tears of subjects with varying amounts of meibomian gland (MG) drop out.
Subjects were recruited and assigned to a group based on extent of MG drop out (worse of two eyes). Those with a MG drop out score of 0 or 1 on the Arita scale (less than 33% MG drop out) for the lower eyelid were assigned to group 1, and those with a score of 2 or 3 (33% or greater) were assigned to group 2. Tears were collected from the inferior tear meniscus of the eye with the most drop out using a microcapillary tube and stored in glass amber vials at -80 degrees Celsius until analysis. Each sample was optimized for peptide testing using C18 spin columns, and the retrieved peptides were split into four for use in the four neuropeptide ELISA kits. The concentration of each neuropeptide in each sample was found using and standard curve and multiplied by four to find concentration in the entire sample. The maximum likelihood method was used to account for concentrations beneath the limits of detection. The concentrations of the various neuropeptides were normalized by dividing each concentration by the amount of sample collected for each subject. Group neuropeptide concentrations were compared using a Mann-Whitney U test.
Subjects had an average age of 34.9 ± 15.5 years and 63% were female. Group 1 included 29 samples and group 2 included 31 samples. For VIP, the median normalized concentrations (interquartile ranges) were 35.12 ng/mL/mL (46.92) and 29.61 ng/mL/mL (26.25) for groups 1 and 2, respectively (p = 0.70). The median normalized concentrations of CGRP were 159.16 ng/mL/mL (479.51) and 91.97 ng/mL/mL (252.92) for groups 1 and 2, respectively (p = 0.05). For NPY, the median normalized concentrations were 34.53 ng/mL/mL (62.84) and 30.87 ng/mL/mL (36.03) for groups 1 and 2, respectively (p = 0.42). For SP, the median normalized concentrations were 58.90 ng/mL/mL (229.16) and 27.48 ng/mL/mL (116.66) for groups 1 and 2, respectively (p = 0.21).
A statistically significant difference between groups based on extent of MG drop out was not found. This suggests that tear film associated neuropeptides related to sympathetic, parasympathetic, or sensory nervous systems may not be related to MG drop out.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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