Clinical Phenotypes And Transcriptional Metabolic Profiles Of Sepsis-associated Encephalopathy

BackgroundSepsis-associated encephalopathy(SAE)is the brain dysfunction secondary to systemic infection in patients with sepsis without central nervous system(CNS)infection.SAE is highly heterogeneous,with clinical manifestations including inattention,disorientation,and delirium,even coma.Long-term cognitive impairment may remain in SAE patients.The pathophysiology of SAE is complex,involving neuroinflammation,disruption of the blood-brain barrier,metabolic disorders of neurotransmitters,ischemia and hypoxia,and mitochondrial dysfunction.Previous clinical studies and animal experiments have described sepsis extensively.However,there is a lack of in-depth comparative analyses of SAE and Non-SAE.Some studies suggest that metabolic disorders of the tryptophan metabolism play an essential role in SAE,but there is no targeted population validation.The study intended to use critical care databases for clinical phenotype of SAE patients;then explore the potential metabolic mechanism of SAE through transcriptomics and targeted metabolomics.Methods1.The Medical Information Mart for Intensive Care Ⅳ(MIMIC-Ⅳ)database and eICU Collaborative Research Database(eICU)were employed to conduct the retrospective cohort study.Adult patients meeting the sepsis 3.0 criteria were enrolled.SAE was defined as Glasgow coma scale(GCS)of less than 15 or delirium.According to previous literature and potential mechanisms,four clinical phenotypes were defined,including ischemichypoxic,metabolic,mixed and unclassified phenotype.The primary outcome was inhospital mortality.2.We conducted a prospective study of sepsis patients admitted to the emergency room of our hospital.The preliminary study period was from February 2021 to July 2022.The inclusion criteria were sepsis patients defined with sepsis-3.0 criteria.The exclusion criteria included primary craniocerebral diseases,neuropsychiatric diseases with chronic consciousness changes,and consciousness disorders caused by primary metabolic disorders and organ dysfunction.The diagnostic criteria for SAE were a GCS score of less than 15 or delirium.According to GCS and delirium assessment,patients with sepsis were divided into the SAE group and Non-SAE group.Peripheral blood samples were collected within 24 hours after admission for mRNA sequencing.The criterion for determining differential expression genes was | log2(fold change)|>1.5 and false discovery rate<0.05.Gene Ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)were used for functional enrichment analysis.3.The overall prospective study was conducted from February 2021 to November 2022.Patients with sepsis were screened based on the above criteria.At the same time,patients with non-infectious diseases in the rescue room were selected as the control group.Peripheral blood and cerebral spinal fluid(CSF)samples were collected within 24 hours after admission,and clinical variables were collected.Clinical outcomes included 28-day mortality,length of intensive care unit(ICU)stay and hospital stay.We used the ultra-high performance liquid chromatography-MS/MS analysis for targeted neurotransmitter metabolomics and tryptophan pathway metabolites.At the same time,Luminex liquid phase suspension chips were used to detect cytokines.Metabolites and cytokines levels were compared among SAE,Non-SAE,and control groups.Correlation analysis was used to assess the degree of correlation between variables.The receiver operating characteristic(ROC)curves were drawn to evaluate the biomarkers’ diagnostic and prognostic efficacy in SAE patients.Subgroup analysis was based on SAE clinical phenotypes developed in our study.Results1.The study included 4120 sepsis patients,2239 from MIMIC-Ⅳ(SAE 67%)and 1881 from eICU(SAE 69%).The SAE cohort enrolled 2780 patients,with a median GCS score of 12,interquartile range(IQR)[8,14],median sequential organ failure assessment(SOFA)score of 6[4,9].The SAE phenotype distribution of the cohort from MIMIC-Ⅳ was similar to eICU(ischemic-hypoxic:39%vs.35%,p=0.043;metabolic:38%vs.40%,p=0.239;mixed:15%vs.15%,p=0.972;unclassified:38%vs.40%,p=0.471).For the overall cohort,the in-hospital mortality of patients in ischemic-hypoxic,metabolic,mixed,and unclassified phenotypes was 33.9%,28.4%,41.5%and 14.2%,respectively.In the multivariable logistic analysis,the mixed phenotype was associated with the highest risk of in-hospital mortality after adjusting for age,gender,GCS and modified SOFA score.2.A total of 73 sepsis patients were assigned to the preliminary study,including 37 SAE patients and 36 Non-SAE patients.In the transcriptomics analysis of peripheral blood,there were 87 differential expression genes between the SAE group and Non-SAE group,including 83 up-regulated genes and 4 down-regulated genes.The differential expression genes were mainly associated with inflammation,synapse function and solute carrier family.After the GO and KEGG enrichment,the most relative pathways were amino acid transport and metabolism,coagulation,metabolic pathways and pathways of neurodegeneration-multiple disease.3.The overall prospective study enrolled 127 sepsis patients(62 SAE patients and 65 Non-SAE patients)and 10 patients in control group.The patients in SAE group were more severe than Non-SAE group,having higher SOFA scores.For the outcomes,the SAE group had a higher mechanical ventilation rate.There was no significant difference for hospital stay and 28-day mortality.The plasma cytokines in sepsis patients were significantly higher than control group.However,there was no significant difference for common cytokines between SAE and Non-SAE group.Compared to the Non-SAE group,the neural injury biomarkers like glial fibrillary acidic protein(GFAP),neurofilament light chain(NFL)and ubiquitin C-terminal hydrolase-L1(UCH-L1)were significantly increased in the SAE patients.NFL had the highest diagnostic efficacy for SAE.For the plasma metabolites,the 5-hydroxyindoleacetic acid(5-HIAA)and kynurenine(Kyn)in the sepsis group were significantly higher than those in the control group.The levels of 5hydroxytryptophan(5-HTP),5-HIAA and kynurenic acid(KYNA)in the SAE group were significantly higher than those in the Non-SAE group.There was no significant statistical difference in CSF metabolites between the SAE and Non-SAE group.Kyn,5-HTP,and tryptophan in CSF were correlated with plasma levels.Metabolite levels in SAE patients with metabolic and mixed phenotype were significantly higher than those in unclassified phenotype.Conclusion1.The four SAE clinical phenotypes have different clinical outcomes,with mixed phenotype having the worst outcome.2.The gene enrichment pathways in SAE patients are related to amino acid transport,metabolic and synaptic function.3.Tryptophan/serotonin and tryptophan/kynurenine pathway are associated with SAE,which may provide a potential target for the early identification and management of SAE in clinical practice.