Altered Levels Of Tricarboxylic Acid Cycle Intermediate Metabolites In Major Depressive Disorder And Genetically High-Risk Individuals

Objective: Major depressive disorder(MDD)is a severe mental disease with unclear pathogenesis.MDD is a complex disease that is interreacted by genetic factors and psychological-social environmental factors.MDD is moderately heritable,with a heritability of 40%.Exploring the role of genetic factors in the pathogenesis of MDD is of great significance for understanding the etiology of the disease.Genetic High Risk for Major Depressive Disorder(GHR-MDD)carries genetic susceptibility factors of MDD,and the inclusion of GHR-MDD individuals and first onset MDD patients is helpful to find the intrinsic biological characteristics related to heredity and the nature of the disease,so as to further understand the pathogenesis of MDD.Previous studies have found that MDD might exist dysregulation of energy metabolism,with tricarboxylic acid cycle as the core.Abnormal DNA in mitochondria,the major subcellular sites of the tricarboxylic acid cycle,has been found many times in MDD genetic studies.Data from multiple biological dimensions of gene,transcription,and protease regulation have demonstrated that the disrupt of tricarboxylic acid cycle and energy metabolism are stable in MDD,independent of other factors such as clinical heterogeneity of samples and disease course.In order to further clarify the relationship between the tricarboxylic acid cycle and the genetic factors of the disease and the important role in the etiology of the disease,this study firstly analyzed the levels of metabolites related to the tricarboxylic acid cycle cycle in GHRMDD population and first-episode untreated MDD patients,further to provide a scientific evidence for understanding the important role of energy metabolism in the pathogenesis of MDD.Methods: A total of 23 first-episode untreated MDD patients,20 GHR-MDD patients and50 Healthy Controls(HC)were collected.All subjects were aged between 18 and 50 years old,and their informed consent was obtained before the study began.All subjects were assessed for demographic data and clinical symptom information,including Hamilton Depression Scale-17 items(HAMD-17 items)and Hamilton Anxiety Scale(HAMA).Blood samples were collected for all subjects between 10:00 and 15:00 on the enrollment day and plasma samples were collected.After the samples were pretreated with metabolome extracts,the levels of intermediate metabolites related to the tricarboxylic acid cycle(pyruvate,citric acid,cis-aconitic acid,α-ketoglutarate,succinic acid,fumaric acid and malic acid)in plasma samples were qualitatively and quantitatively determined based on UHPLC-MS(Ultimate 3000 Ultra-High Performance Liquid Chromatograph coupled with Q Exactive Quadrupole-Orbitrap High Resolution Mass Spectrometer).Based on the collected demographic data,clinical scales and plasma metabolite data,statistical analysis was performed by applying SPSS 26.0.The steps were as follows: 1.Based on the collected demographic data and clinical scales,descriptive analysis,Analysis of Variance(ANOVA)and chi-square test were applied to analyse the differences;2.Based on the collected plasma tricarboxylic acid cycle-related intermediate metabolite data,Analysis of Covariance(ANCOVA)with age,gender and Body Mass Index(BMI)as covariates was conducted for the three groups.The metabolite levels with significant differences among the three groups(first-episode untreated MDD patients,the GHR-MDD group and HC group)were compared in pair by post hoc analysis with Bonferroni correction,and the correction test level was 0.05/3=0.017,i.e.P <0.017 was statistically different;3.Pearson correlation analysis was performed for metabolite levels showing significant differences in ANCOVA and HAMD＿17 total score and HAMA total score in the first-episode untreated MDD patients and GHR-MDD group,respectively,and Pearson correlation coefficient and P value were calculated,and P <0.05 was statistically significant after correction with FDR.Results: 1.The results of ANCOVA analysis showed that there were significant differences in the levels of pyruvate,citric acid,cis-aconitic acid,α-ketoglutarate,succinic acid,fumaric acid and malic acid among the three groups(P <0.05).Pair comparison results showed that the levels of pyruvate,citric acid,cis-aconitic acid,succinic acid,fumaric acid and malic acid in the first-episode untreated MDD patients were significantly lower than those in HC group(P <0.017,Bonferroni correction),and the levels of pyruvate,citric acid,cis-aconitic acid,α-ketoglutarate,succinic acid,fumaric acid and malic acid in GHR-MDD group were significantly lower than those in HC group(P < 0.017,Bonferroni correction),while there was no significant difference in the intermediate metabolite levels of the tricarboxylic acid cycle between the first-episode untreated MDD patients and the GHR-MDD group(P >0.017,Bonferroni correction).2.Correlation analysis of differential metabolite levels and clinical symptoms of HAMD-17 and HAMA in the first untreated MDD group showed that there was no significant correlation between intermediate metabolite levels related to the tricarboxylic acid cycle and total score of HAMD-17 and HAMA(P >0.05,FDR correction).Similarly,there was no significant correlation between the level of intermediate metabolites related to the tricarboxylic acid cycle and the total score of HAMD-17 and HAMA in the GHR-MDD group(P >0.05,FDR correction).Conclusion: Both first-episode untreated MDD patients and GHR-MDD individuals showed the reduction of tricarboxylic acid cycle metabolites level,suggesting the tricarboxylic acid cycle may be genetic-related factors and the attack of molecular mechanism in MDD.The changed tricarboxylic acid cycle may reflect the nature of disease,which manifests irrespective of other factors such as illness stages or the severity of the symptoms.Therefore,it is very valuable for further study to understanding the etiology of MDD from the perspective of the tricarboxylic acid cycle and energy metabolism.