DHCR7 Expression Predicts Poor Outcomes and Mortality From Sepsis

Abstract

This is a study of lipid metabolic gene expression patterns to discover precision medicine for sepsis.

Objectives: Sepsis patients experience poor outcomes including chronic critical illness (CCI) or early death (within 14 d). We investigated lipid metabolic gene expression differences by outcome to discover therapeutic targets.

Design setting and particitpants: Secondary analysis of samples from prospectively enrolled sepsis patients (first 24 hr) and a zebrafish endotoxemia model for drug discovery. Patients were enrolled from the emergency department or ICU at an urban teaching hospital. Enrollment samples from sepsis patients were analyzed. Clinical data and cholesterol levels were recorded. Leukocytes were processed for RNA sequencing and reverse transcriptase polymerase chain reaction. A lipopolysaccharide zebrafish endotoxemia model was used for confirmation of human transcriptomic findings and drug discovery.

Main outcomes and measures: The derivation cohort included 96 patients and controls (12 early death, 13 CCI, 51 rapid recovery, and 20 controls) and the validation cohort had 52 patients (6 early death, 8 CCI, and 38 rapid recovery).

Results: The cholesterol metabolism gene 7-dehydrocholesterol reductase (DHCR7) was significantly up-regulated in both derivation and validation cohorts in poor outcome sepsis compared with rapid recovery patients and in 90-day nonsurvivors (validation only) and validated using RT-qPCR analysis. Our zebrafish sepsis model showed up-regulation of dhcr7 and several of the same lipid genes up-regulated in poor outcome human sepsis (dhcr24, sqlea, cyp51, msmo1, and ldlra) compared with controls. We then tested six lipid-based drugs in the zebrafish endotoxemia model. Of these, only the Dhcr7 inhibitor AY9944 completely rescued zebrafish from lipopolysaccharide death in a model with 100% lethality.

Conclusions: DHCR7, an important cholesterol metabolism gene, was up-regulated in poor outcome sepsis patients warranting external validation. This pathway may serve as a potential therapeutic target to improve sepsis outcomes.

Keywords: genetics; lipids; sepsis; transcriptomics; zebrafish.

Figure 1.

Transcriptomic data analysis methodology and results by outcome and mortality. A, Methodologic flow for transcriptomic data analysis for derivation and validation groups. B, Differentially expressed genes for derivation and validation groups by outcomes of chronic critical illness (CCI)/early death compared with rapid recovery. C, Differentially expressed genes for derivation and validation groups by 90-day mortality. ED = early death, RAP = rapid recovery.

Figure 2.

Heatmaps of differentially expressed genes for derivation (A) and validation (B) groups by outcomes of chronic critical illness (CCI)/early death compared with rapid recovery.

Figure 3.

Drug testing in zebrafish model of endotexemia. A, Methodology for zebrafish experiments. Zebrafish are treated with a lethal dose of lipopolysaccharide or maintained in control embryo medium at 3 (days postfertilization) dpf and examined for survival at 4, 5, and 6 dpf. B, Reverse transcriptase polymerase chain reaction (RT-qPCR) of cholesterol related genes from lipopolysaccharide-treated fish versus controls 3 hours after treatment at 3 dpf. Data represented as fold change lipopolysaccharide/controls. A value of 1 would signify no change, value greater than 1 is up-regulation in lipopolysaccharide treated versus controls, and value less than 1 is down-regulation. Individual dots represent separate experiments. The graph bars represent mean and sd. C, Differential expression analysis of RNA sequencing (RNA-seq) data from three lipopolysaccharide-treated zebrafish and three controls identified 12 lipid metabolism genes that were up-regulated in lipopolysaccharide-treated zebrafish compared with controls. D, Overlap of significantly differentially expressed genes between derivation, validation, and zebrafish groups.