Effect of a Functional Phospholipid Metabolome-Protein Association Pathway on the Mechanism of COVID-19 Disease Progression

Abstract

This study aimed to explore the clinical practice of phospholipid metabolic pathways in COVID-19. In this study, 48 COVID-19 patients and 17 healthy controls were included. Patients were divided into mild (n=40) and severe (n=8) according to their severity. Phospholipid metabolites, TCA circulating metabolites, eicosanoid metabolites, and closely associated enzymes and transfer proteins were detected in the plasma of all individuals using metabolomics and proteomics assays, respectively. 30 of the 33 metabolites found differed significantly (P<0.05) between patients and healthy controls (P<0.05), with D-dimmer significantly correlated with all of the lysophospholipid metabolites (LysoPE, LysoPC, LysoPI and LPA). In particular, we found that phosphatidylinositol (PI) and phosphatidylcholine (PC) could identify patients from healthy controls (AUC 0.771 and 0.745, respectively) and that the severity of the patients could be determined (AUC 0.663 and 0.809, respectively). The last measurement before discharge also revealed significant changes in both PI and PC. For the first time, our study explores the significance of the phospholipid metabolic system in COVID-19 patients. Based on molecular pathway mechanisms, three important phospholipid pathways related to Ceramide-Malate acid (Cer-SM), Lysophospholipid (LPs), and membrane function were established. Clinical values discovered included the role of Cer in maintaining the inflammatory internal environment, the modulation of procoagulant LPA by upstream fibrinolytic metabolites, and the role of PI and PC in predicting disease aggravation.

Keywords: COVID-19; eicosanoic acids; metabolomics; phospholipid metabolic pathway.

Figure 1

The Phospholipids, TCA cycle and Eicosanoic acids in COVID-19 patients. (A) PLS-DA score plots. (B) Boxplot of fold change (log10 scale) of all metabolites in COVID-19 patients and health control. (C) Heatmap of all metabolites in different groups. (D) Volcano plot of metabolites.

Figure 2

The trend of the diagnosis performance of phospholipid metabolisms. (A) Comparison of metabolites in blood samples on admission and before discharge. Levels 1: admission, 2: before discharge. (B) The ROC curve for PI and PA to identify COVID-19 patients from healthy controls (upper) and identify severe patients from mild patients (bottom).

Figure 3

Correlation analysis of metabolomics and clinical indicators (Supplementary Table 2)

Figure 4

The pathway of the phospholipid and TCA. OAA: Oxaloacetate acid; CA: Citric acid; α-KGA: α-Ketoglutara acid; Succ: succinate acid; MA: Malate acid; GSLs: Glycosphingolip-ids; PIP2: Phosphatidylinositol-4, 5-diphosphate; LysoPI: Lysophosphatidylinositol; PI-PLC: Phosphoinositol specific phospholipase C; DAG: Diacylglycerol; Sph: Sphingosine; PC: Phosphatidylcholine; PE: Phosphatidylethanolamine; LysoPE: Lysophosphatidylethanolamine; LysoPC: Lysophosphatidylcholine; LCAT: Lecithin cholesterol lipoyl transferase; Cer: Ceramide; Cer-1-P: Ceramide 1-phosphate; SM: Sphingomyelin; DAG: Diacylglycerol; Sph-1-P: Sphingosine 1-phosphate; SphK: Sphingomyelin kinase; CERT: Ceramide transfer protein; CRAC: Endoplasmic reticulum Ca²⁺ release activates Ca²⁺ channels; IP3: Inositol 1,4,5-triphosphate; TCA: tricarboxylic acid cycle.