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R. W. Beuerman, L. Zhou, T. Cafaro, E. Urrets-Zavalia, J. Urrets-Zavalia, H. Serra; Metabolomic and Proteomic Analysis of Tears From Climatic Droplet Keratopathy Patients in Argentina. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1899.
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© ARVO (1962-2015); The Authors (2016-present)
Climatic droplet keratopathy (CDK) is an acquired, often bilateral degenerative corneal disease with a high prevalence in certain regions, characterized by progressive opacity. Although CDK’s etiology is unknown, it is considered a multifactorial disease related to environmental factors. In this study, we examined the metabolomic and proteomic profiles in tears of CDK patients.
In total 12 CDK patients and 12 controls were recruited in this study. Tears were collected using glass capillary microtubes. For tear metabolomic profiling experiments, tear metabolites were extracted after precipitating proteins. NanoLC-MS/MS was used to analyze the tear metabolites. Principal component analysis (PCA) was used to detect patterns in tear metabolites that correspond to CDK. For tear proteomic analysis, iTRAQ combined with 2D-nanoLC-MS/MS was performed to determine quantitative changes of tear proteins from CDK and controls.
Tear metabolomic profiles showed distinct patterns between CDK and controls revealed by PCA analysis. Classification of CDK and controls is possible using this approach. The levels of tear metabolites with molecular weight of 109.0, 192.0, 335.1, 339.1, 343.2, 361.1, 362.2, 383.1, 384.1, 385.1, 395.1, 399.1, 412.2, 452.2, 456.2, and 481.1 showed significant differences between CDK and controls. Quantitative tear protein profiles also showed different patterns between CDK, dry eye (data from our previous study) and controls by using a 15-protein biomarker panel. Inflammation associated proteins S100 A8 and A9 were found to be up-regulated in tears in both CDK and dry eye. However, no statistical change of levels of prolatin-inducible protein and lysozyme in CDK tears were observed whereas the levels of these two proteins were found to be down-regulated in dry eye tears.
This study is a preliminary exploration of human tear metabolomics using nanoLC-MS/MS. The tear metabolite profiles reflected the altered disease status of the ocular surface tissues. Metabolomics combined with proteomics is a powerful tool for disease biomarker discovery and for further understanding the pathogenesis of the disease.
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