Lipid mediators of inflammation and Resolution in individuals with tuberculosis and tuberculosis-Diabetes

Abstract

Individuals with concurrent tuberculosis (TB) and Type 2 diabetes (DM) have a higher risk of adverse outcomes. To better understand potential immunological differences, we utilized a comprehensive panel to characterize pro-inflammatory and pro-resolving (i.e., mediators involved in the resolution of inflammation) lipid mediators in individuals with TB and TB-DM. A nested cross-sectional study of 40 individuals (20 newly diagnosed DM and 20 without DM) was conducted within a cohort of individuals with active drug-susceptible treatment-naïve pulmonary TB. Lipid mediators were quantified in serum samples through lipid mediator profiling. We conducted correlation-based analysis of these mediators. Overall, the arachidonic acid-derived leukotriene and prostaglandin families were the most abundant pro-inflammatory lipid mediators, while lipoxins and maresins families were the most abundant pro-resolving lipid mediators in individuals with TB and TB-DM. Individuals with TB-DM had increased correlations and connectivity with both pro-inflammatory and pro-resolving lipid mediators compared to those with TB alone. We identified the most abundant lipid mediator metabolomes in circulation among individuals with TB and TB-DM; in addition, our data shows a substantial number of significant correlations between both pro-inflammatory and pro-resolving lipid mediators in individuals with TB-DM, delineating a molecular balance that potentially defines this comorbidity.

Keywords: Diabetes; Inflammation; Leukotrienes; Lipids; Lipoxins; Prostaglandins; Resolvins; Specialized pro-resolving mediators; Tuberculosis.

Figure 1:. Families of lipid mediators of inflammation and their precursor lipids

Eicosapentanoic acid (EPA), Docosahexaenoic acid (DHA), Docosapentaenoic acid (DPA) and arachidonic acid (AA) are the precursor molecules to various families of pro-inflammatory and Specialized Pro-resolving lipid mediators (SPMs). SPMs include resolvins, protectins, maresins and lipoxins while pro-inflammatory lipid mediator families include leukotrienes, prostaglandins and thromboxane.

Figure 2:. Lipid mediator abundance profile of individuals with TB and TB-DM

Heat map showing average abundances of log-transformed data for A) lipid mediators or B) lipid mediator metabolomes for each patient. Hierarchical clustering was performed to test whether they was grouping by DM status based on overall abundance profiles of the lipid mediator (A) or lipid mediator metabolome (B). The color of each mediator or metabolome group is shown in the figure legends. Individuals with TB-DM are represented by purple circles while individuals with TB alone are represented by blue circles. In C), the most abundant lipid mediators and metabolomes are shown, and in D) the relative abundance (log₂ fold-change) of each lipid mediator metabolome group in those with TB-DM relative to TB alone is shown.

Figure 3:. SPM abundance profile of individuals with TB and TB-DM

Heat map showing average abundances of log-transformed data for A) SPMs or B) SPM metabolomes for each patient. Hierarchical clustering was performed to test whether they was grouping by DM status based on overall abundance profiles of the lipid mediator (A) or lipid mediator metabolome (B). The color of each mediator or metabolome group is shown in the figure legends. Individuals with TB-DM are represented by purple circles while individuals with TB alone are represented by blue circles. In C), the most abundant SPMs mediators and metabolomes are shown.

Figure 4:. Individuals with TB and TB-DM have distinct correlation profile of lipid mediator metabolomes

Spearman correlation analyses were used to identify statistically significant associations between the cumulative levels of lipid mediator metabolomes in individuals with TB and TB-DM. The heatmaps only show statistically significant correlations (p<0.05). Colors infer the strength and direction of the correlation. Of note, only positive correlations between the markers were found to be statistically significant.

Figure 5:. Network analysis of the lipid mediator metabolomes in individuals with TB and TB-DM

A) Network analysis based on spearman correlation matrices of circulating concentrations of lipid mediator metabolomes is shown. Only statistically significant correlations (p<0.05) are displayed. Circle sizes are proportional to the number of connections to each node. Circle colors represent distinct subgroups of parameters that exhibited a similar correlation profile. The parameters from each subgroup are linked through lines of the same color. Correlations between markers from different subgroups are highlighted in different colors. B) Network density values were compared between the study groups using permutation test (100 permutations were performed). Data represent mean and SD values of network densities per permutation. C) Node analysis: We quantified the number of connections of each marker in the networks for each study groups. Heatmaps show hierarchical cluster analysis (Ward’s method) of the number of connections of each marker in each study group, red highlights the lipid mediator groups which exhibited the highest number of connections whereas blue identifies those which displayed the lowest number of connections.