Metabolomic and Lipidomic Profiling of Preoperative CSF in Elderly Hip Fracture Patients With Postoperative Delirium

Abstract

Objective: To investigate dysregulated molecules in preoperative cerebrospinal fluid (CSF) of elderly hip fracture patients with postoperative delirium (POD), in order to identify potential pathological mechanisms and biomarkers for pre-stage POD.

Materials and methods: This nested case control study used untargeted metabolomic and lipidomic analysis to profile the preoperative CSF of patients (n = 40) who developed POD undergone hip fracture surgery (n = 10) and those who did not (n = 30). Thirty Non-POD patients were matched to 10 POD patients by age (± 2 years) and Mini Mental State Examination score (± 2 points). CSF was collected after successful spinal anesthesia and banked for subsequent analysis. On the first two postoperative days, patients were assessed twice daily using the Confusion Assessment Method-Chinese Revision. CSF samples from the two groups were analyzed to investigate possible relevant pathological mechanisms and identify candidate biomarkers.

Results: Demographic characteristics of the groups were matched. Eighteen metabolites and thirty-three lipids were dysregulated in the preoperative CSF of POD patients. Pathway enrichment analysis revealed perturbations in D-glutamine and D-glutamate metabolism; glycerophospholipid metabolism; alanine, aspartate and glutamate metabolism; sphingolipid metabolism; histidine metabolism; and arginine biosynthesis at the pre-delirium stage. Receiver operating characteristic curve analysis indicated that phosphatidylethanolamine (PE, 40:7e), with an area under the curve value of 0.92, is a potential biomarker for POD.

Conclusion: Multiple pathological mechanisms in the POD group were involved before surgery, including neuroinflammation, oxidative stress, and energy metabolism disorders induced by hypoxia, as well as neurotransmitter imbalances such as increased dopamine and glutamate, and decreased glutamine. These metabolic abnormalities potentially increase the fragility of the brain, thus contributing to POD. PE (40:7e) might be a potential biomarker for POD. Not only do our results provide potential biomarkers for POD, but also provide information for deep pathological research.

Clinical trial registration: www.ClinicalTrials.gov, identifier ChiCTR1900021533.

Keywords: cerebrospinal fluid; hip fracture; lipidomics; metabolomics; postoperative delirium.

FIGURE 1

Flow diagram showing the recruiting criterion. One hundred and ten patients were initially screened for the study, and 40 patients were finally included in the data analysis. CSF, cerebrospinal fluid; POD, postoperative delirium; MMSE, mini-mental state examination.

FIGURE 2

Untargeted metabolic profiling of CSF samples in POD patients and Non-POD patients. PCA (A: positive-ion mode; B: negative-ion mode) and PLS-DA (C: positive-ion mode; D: negative-ion mode) analyses of the DDA-based metabolomics data. The indicated groups are presented by different colors (green: POD; red: Non-POD; blue: QC).

FIGURE 3

Untargeted lipidomics profiling of CSF samples in POD patients and Non-POD patients. PCA (A: positive-ion mode; B: negative-ion mode) and PLS-DA (C: positive-ion mode; D: negative-ion mode) analyses of the DDA-based lipidomics data. The indicated groups are presented by different colors (green: POD; red: Non-POD; blue: QC).

FIGURE 4

Pathway analysis of the dysregulated metabolites and lipids in the CSF of POD patients. Fifteen selected metabolites and lipids were involved in the D-Glutamine and D-glutamate metabolism (2 hit), Glycerophospholipid metabolism (4 hits), Alanine, aspartate and glutamate metabolism (3 hits), Sphingolipid metabolism (2 hits), Histidine metabolism (2 hits) and Arginine biosynthesis (2 hits). The color gradient indicates the significance of the pathway ranked by p-value (y-axis; yellow: higher p-values, red: lower p-values), and circle size indicates the pathway impact score (x-axis; the larger circle, the higher impact score). Significantly affected pathways with low p-values and high pathway impact scores are labeled.

FIGURE 5

ROC curve analysis of potential CSF biomarker for differentiating the POD group from the Non-POD group. PE, phosphatidylethanolamine. The area under the curve for the prediction of POD via PE (40:7e) was 0.92 (95% CI = 0.84–1.00).