A Study On The Potential Mechanism Of Ammonia And Arginine Vasopressin In Sepsis-associated Encephalopathy

BackgroundSepsis-associated encephalopathy(SAE)is one of the most common encephalopathies in critical care medicine,with an incidence rate of 70%and a hospital mortality rate of about 60%.At Present,there is still a lack of potential biomarkers to evaluate the occurrence of SAE,and the pathogenesis is not clear.The previous study on this subject found that Patients with sepsis were prone to an increase in serum ammonia levels for non-liver reasons.With the increase in serum ammonia level,the degree of consciousness disorder gradually increased.Arginine Vasopressin(AVP)has been proved in other encephalopathies that it can regulate the entry of serum ammonia into the brain and upregulate astrocyte aquaporin 4(AQP4)together with ammonia in the brain and promote the occurrence of brain edema.The relationship between serum ammonia,AVP,and SAE and the potential mechanism of SAE are unclear.Objectives1.To explore the relationship between serum ammonia and the occurrence,and prognosis of SAE through the intensive care medical information Mart Ⅳ(mimic Ⅳ)database.2.Evaluate the expression level of the AVP gene in SAE mice and explore its biological function through SAE mouse genomics data.3.Further explore and verify the relationship between serum ammonia,AVP,and SAE and the possible mechanism of SAE through a prospective two-center cohort study.4.Explore the potential mechanism of elevated serum ammonia levels in sepsis.MethodsPart I The effect of serum ammonia on patients with sepsis associated encephalopathy The relationship between serum ammonia level and SAE was determined by a generalized additive model.Multiple logistic regression analysis was used to find the risk factors of SAE occurrence and death.The survival package in R language was used to observe the relationship between serum ammonia level and mortality,and incidence of SAE.Kruskal Wallis rank-sum and Wilcoxon tests were used to analyzing the relationship between serum ammonia levels and prognostic indicators of SAE Patients.Part Ⅱ The study of the gene expression level and biological function of arginine Vasopressin in mice with sepsis associated encephalopathyThe data were retrieved from the gene expression synthesis(GEO)microarray data set gse167610 to obtain the intersection of differentially expressed genes for data analysis.To observe the expression level of AVP in SAE mice and explore the biological function of AVP in SAE mice through gene ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG).Part Ⅲ The study on the potential mechanism of serum ammonia and arginine Vasopressin in patients with sepsis associated encephalopathyThe data were collected from January 2020 to August 2021 in the emergency department of hospital of the Chinese Academy of Medical Sciences and the Department of critical medicine of hospital.Enzyme-linked immunosorbent assay was used to detect the biomarkers ammonia and AVP in the blood and cerebrospinal fluid of patients with SAE;The Possible mechanism of ammonia and AVP entering the brain leading to encephalopathy of the biomarkers:AQP4,glial fibrillary acidic protein(GFAP).Detect the potential mechanism of elevated serum ammonia:ornithine,arginine,citrulline,and aspartic acid,which are important amino acids in the ornithine cycle;Detect glutamine.Main resultPart 1 The effect of serum ammonia on patients with sepsis associated encephalopathy1.After adjusting for other risk factors,serum ammonia level≥45 umol/L[odds ratio(OR):3.508,95%confidence interval(CI):2.336-5.269,P<0.001]is an independent risk factor for SAE.With the increase in serum ammonia levels,the incidence of SAE Patients increases gradually.2.There was no significant correlation between serum ammonia and mortality in patients with SAE.Patients with SAE with serum ammonia ≥ 45 umol/L had higher SAPS Ⅱ and SOFA scores.Part Ⅱ The study of the gene expression level and biological function of arginine Vasopressin in mice with sepsis associated encephalopathy1.AVP was significantly up-regulated in SAE mice(LogFc:1.899)2.Through the exploration of go and KEGG regulatory Pathways,it is found that AVP regulates amino acid and amine transport.Part Ⅲ:The study on the potential mechanism of serum ammonia and arginine Vasopressin in patients with sepsis associated encephalopathy1.The results of this study confirmed the findings of Part Ⅰ and Part Ⅱ Parts of this subject.The levels of serum ammonia and AVP and cerebrospinal fluid of SAE patients were significantly higher than those of non-SAE patients.Correlation analysis showed that the level of serum AVP was positively correlated with the level of ammonia in cerebrospinal fluid.2.AVP in cerebrospinal fluid was positively correlated with GFAP and AQP4(R:0.44;R:0.38).Ammonia in cerebrospinal fluid was positively correlated with GFAP,AQP4,and glutamine(R:0.68;R:0.49;R:061).3.Ammonia in serum is negatively correlated with arginine and aspartic acid in serum.Conclusion1.Serum ammonia and AVP are potential biomarkers of sepsis associated encephalopathy.2.Serum AVP promotes the transport of ammonia to the brain.3.AVP and ammonia entering the brain jointly regulate the expression of AQP4 in astrocytes,resulting in astrocyte injury,which may be the Potential mechanism of sepsis associated encephalopathy.4.The increase in serum ammonia levels in patients with sepsis may be related to the deficiency of arginine and aspartate in the ornithine cycle.