Circulating Lipids and Acute Pain Sensitization: An Exploratory Analysis

Abstract

Background: In individuals with low back pain, higher lipid levels have been documented and were associated with increased risk for chronic low back pain.

Objectives: The purpose of this research was to identify plasma lipids that discriminate participants with acute low back pain with or without pain sensitization as measured by quantitative sensory testing.

Methods: This exploratory study was conducted as part of a larger parent randomized controlled trial. A cluster analysis of 30 participants with acute low back pain revealed two clusters: one with signs of peripheral and central sensitivity to mechanical and thermal stimuli and the other with an absence of peripheral and central sensitivity. Lipid levels were extracted from plasma and measured using mass spectroscopy.

Results: Triacylglycerol 50:2 was significantly higher in participants with peripheral and central sensitization compared to the nonsensitized cluster. The nonsensitized cluster had significantly higher levels of phosphoglyceride 34:2, plasmenyl phosphocholine 38:1, and phosphatidic acid 28:1 compared to participants with peripheral and central sensitization. Linear discriminant function analysis was conducted using the four statistically significant lipids to test their predictive power to classify those in the sensitization and no-sensitization clusters; the four lipids accurately predicted cluster classification 58% of the time (R = .58, -2 log likelihood = 14.59).

Discussion: The results of this exploratory study suggest a unique lipidomic signature in plasma of patients with acute low back pain based on the presence or absence of pain sensitization. Future work to replicate these preliminary findings is underway.

FIGURE 1

Pain sensitivity cluster analysis. Quantitative sensory testing results were used to determine the underlying clustering of the pain sensitivity profiles. Two major clusters were identified and classified as the non-sensitized (NS) and pain sensitized (PS) clusters. The figure above shows the two clusters using heat pain threshold (HPT) with temperature in Celsius at the low back site, pressure pain at the control (remote) site in kPa, and mechanical pain sensitivity of the low back site as measured by the numerical pain rating score.

FIGURE 2

Score plots of the pain sensitivity clusters applied to the lipidomic data. Panel A shows how the partial least squares discriminant analysis (PLSDA) defined two clusters with overlapping lipid profile scores. Lipids that were most important for discriminating between the pain sensitized (PS; dashed line) and nonsensitized (NS; solid line) clusters were identified. The lipidomic analysis detected 176 lipids with consistent values across the two clusters. Panel B shows how orthogonal projections-to-latent structures discriminant analysis (OPLSDA) defined group separation without overlap by separating cluster-predictive variation from cluster-uncorrelated variation in lipid scores.