Research On Lipidomics And Oxylipin Analysis Of Primary Open-angle Glaucoma And Its Pathogenesis Mechanism

Background: Glaucoma is a complex optic neuropathy with genetic heterogeneity,which mainly characterized by progressive degeneration of the optic nerve,eventually resulting in severe functional vision loss.Up to now,glaucoma is the second leading cause of irreversible blindness worldwide after cataracts,and its worldwide age-standardised prevalence is about 3.5%.Primary open-angle glaucoma is the most common type,and it often remains asymptomatic.Without adequate early screening and treatment,patients will not realize that they are affected until the disease is so severe and progress to visual disability,which seriously affects the patient’s quality of life.Therefore,it is necessary to utilize the metabolomics methods to explore the potential screening and diagnostic biomarkers for POAG disease.Further functional studies are carried out to elucidate the underlying mechanism.Subjects and methods:A total of 264 participants were included in our research,which were divided into two groups: the discovery phase and validation phase.The discovery phase included 64 POAG patients and 81 controls,and validation phase included 64 POAG patients and 55 controls.Fasting blood samples were obtained for ultra-high performance liquid chromatography-mass spectrometry(UPLC-MS)detection.Analyst 1.6.3 and Multi Quant software were first performed to analyze the raw data and obtain the peak area and total ions current(TIC).Principal component analysis,orthogonal partial least squares discrimination analysis and univariate analysis were executed using SIMCA14.0 software.Both VIP≥1 and P<0.05 suggested the existence of differential metabolic biomarkers.KEGG database was applied to trace the relevant metabolic pathways.The potential diagnostic value of differential metabolites were assessed by receiver operating characteristic(ROC)curve,which could be used to estimate the predictive ability of differential metabolites alone or in combination for POAG.Finally,the functional of the screened differential metabolites was verified by animal experiments.Results:1.Two differential lipid metabolites(3-hydroxy-cis-5-octenoyl-carnitine and Lauroyl-carnitine)were identified in both discovery phase and validation phase by widely targeted lipidomics analysis,and their change trends were consistent.Significant lipid metabolites were up-regulated and were acylcarnitines.2.Using oxylipin analysis,a total of seven oxylipin metabolites were screened and their change trends were consistent in two groups,including 12,13-Ep OME,11,12-EET,14,15-EET,16(17)-Ep DPE,8,9-EET,(±)5-HETE and 5-oxo ETE.(±)5-HETE and5-oxo ETE were down-regulated,and the others were up-regulated.3.Metabolic pathway analysis found that metabolites were mainly enriched in arachidonic acid metabolism,linoleic acid metabolism and ovarian steroidogenesis pathways.Linoleic acid metabolism was affected most.4.ROC curve analysis showed that single differential metabolite a general diagnostic value for POAG,but combination with these seven metabolites significantly improved the diagnostic value.5.After intravitreal injection of 14,15-EET and 16(17)-Ep DPE,the apoptosis of RGCs,and the increasing expression of complement C3 and GFAP were observed in retina.The expression location of GFAP was deep into outer nuclear layer(ONL)and outer plexiform layer(OPL).These results suggested that oxylipin led to RGC death and retinal damage.Conclusion:There were significant differences between POAG patients and controls in lipidomics and oxylipin analysis.Oxylipin mainly affected the linoleic acid metabolism pathway.Seven oxylipin metabolites as a potential biomarker had a good diagnostic value for POAG.