A Preliminary Study Of The Relationship Between Plasma Amino Acids And Carnitine And Primary Angle-closure Glaucoma Based On Metabolomics Analysis

Purpose: Glaucoma is a blinding eye disease that causes irreversible loss of vision and progressive damage to retinal ganglion cells(RGCs)and is one of the major causes of blindness in the world.It is predicted that by 2040,118 million people will have glaucoma.Among Asians and Africans,primary angle-closure glaucoma(PACG)is the most prevalent type of glaucoma.Due to the complex pathophysiological mechanism of PACG,there is no clear early biomarker assisted diagnosis,and the treatment for PACG is also very limited.Metabolomics technology can detect metabolites in biological samples and provide biomarkers that are helpful for disease diagnosis.At present,metabolomics technology has made certain achievements in the diagnosis and treatment of glaucoma.As the main metabolites in human body,amino acids and carnitine have also received extensive attention in the research of PACG.Therefore,the purpose of this study is to detect the concentration of amino acids and carnitine in plasma of PACG patients and non-PACG patients by metabolomics technology,screen the metabolites with differential expression by statistical methods,and analyze the impact of differential metabolites on PACG.Methods: In this study,a total of 487 ophthalmic patients who were admitted to the Second Affiliated Hospital of Dalian Medical University were collected,including 147 patients in the experimental group and 340 patients in the control group.After receiving the same caloric diet for three days,2ml venous blood was drawn from all patients and metabonomic analysis was performed.The target of metabolomics was 21 amino acids and 26 carnitine.SIMCA-P software was used for further grouping processing of principal components analysis(PCA)and orthogonal partial least squares discriminant analysis(OPLS-DA).SPSS 27 software was used for statistical analysis,t test and Wilcoxon rank sum test were used to compare continuous variables,chi-square test was used to compare categorical variables,logistic regression analysis was used to compare the correlation between differential metabolites and PACG,Spearman rank correlation test was used to compare the correlation between eye biometric data and differential metabolites,Finally,the receiver operating characteristic curve(ROC)was used to evaluate the predictive value of different metabolites on PACG.Results:1.A total of 21 amino acids were detected in this study.The concentrations of arginine(Arg)and ornithine(Orn)in PACG group decreased significantly(p<0.05).In the amino acid ratio of PACG group,the Arg/Orn ratio and Orn/Cit ratio decreased,while the Cit/Arg ratio increased,the difference was statistically significant(p<0.05).2.A total of 26 kinds of carnitine were detected in this study,and there was no statistical difference between the carnitine metabolic molecular groups.In the carnitine ratio of PACG group,the C26/C20 ratio and C5DC/C8 ratio decreased,and the C4/C2 ratio and C8/C2 ratio increased,the difference was statistically significant(p<0.05).3.In the single-factor logistic regression analysis of amino acids,Orn(p=0.029),Arg/Orn ratio(p=0.027)and Orn/Cit ratio(p=0.010)were negatively correlated with PACG.The ratio of Cit/Arg(p=0.006)was positively correlated with PACG.4.In the multivariate logistic regression analysis of amino acids,Orn(p=0.049)and Orn/Cit ratio(p=0.030)were negatively correlated with PACG.5.In the single-factor logistic regression analysis of carnitine,palmitoyl carnitine(C16;p=0.049),C5/C0 ratio(p=0.044)and C5-OH/C8 ratio(p=0.032)were negatively correlated with PACG.6.In the multivariate logistic regression analysis of carnitine,C5/C0 ratio(p=0.028)was negatively correlated with PACG.7.In Spearman’s rank correlation test,Orn was negatively correlated with the cup/disc ratio of the optic nerve,Arg was negatively correlated with intraocular pressure and the cup/disc ratio of the optic nerve,Arg and C16 were positively correlated with the length of the eye axis.8.In ROC curve,differential metabolite Model A can predict PACG,and the difference is statistically significant(p<0.001).AUC value is 0.656.Model C integrates demographic factors(age,gender,history of diabetes,history of hypertension),ophthalmological factors(intraocular pressure,eye axis length),and differential metabolite.Compared with Model B(only integrating demographic factors and ophthalmic factors),the AUC value of model C increased from 0.860 to 0.891,with a statistically significant difference(p<0.001).Conclusion:1.Through metabonomics technology,this study detected the decrease of Arg and Orn concentrations in plasma of patients with PACG,and speculated that the retinal function damage caused by Orn metabolism abnormality and the decrease of NO level caused by Arg metabolism abnormality were related to the pathogenesis of PACG;2.Logistic regression analysis showed that Orn and C16 were negatively correlated with PACG,and speculated that lipid peroxidation and mitochondrial oxidative damage caused by C16 reduction were related to the pathogenesis of PACG.3.The ROC curve proved that the combination of differentially expressed amino acids and carnitine may have certain predictive value for PACG,in which Arg,Orn and C16 may be biomarkers for PACG.