Link between plasma ceramides, inflammation and insulin resistance: Association with serum IL-6 concentration in patients with coronary heart disease

Aims/hypothesis: Ceramides and IL-6 have a role in immune–inflammatory responses and cardiovascular diseases, and are suggested to be involved in insulin and glucose metabolism. We sought to assess the associations of circulating levels of IL-6, TNF-α and high-sensitivity C reactive protein (hsCRP), which are inflammatory markers related to insulin resistance (IR), with the plasma lipid metabolites ceramides and diacylglycerols (DAG) in patients with CHD. Methods: Cross-sectional analyses were carried out on data from 33 patients with CHD. Serum levels of the inflammatory markers and plasma lipid metabolites (lipidomics approach performed by ultra-performance liquid chromatography coupled to electrospray ionisation MS) were measured at the same time point as insulin resistance (IR) (HOMA-IR index). Results: Serum circulating levels of IL-6 were strongly correlated with plasma ceramide concentrations (r = 0.59, p < 0.001). Adjustments for serum TNF-α or hsCRP levels, smoking, BMI, age, sex or HOMA-IR did not change the results (p < 0.001). After adjustments for the effect of serum inflammatory markers (TNF-α or hsCRP), HOMA-IR and BMI the correlation between plasma DAG and serum IL-6 (r = 0.33) was also significant (p < 0.03). In a linear regression model, circulating levels of both ceramides and TNF-α had a significant independent influence on circulating levels of IL-6, altogether accounting for 41% of its variation (p < 0.001). Conclusions/interpretation: Our results strongly suggest that the link between ceramides, IR and inflammation is related to the inflammatory marker IL-6. Ceramides may contribute to the induction of inflammation involved in IR states that frequently coexist with CHD.