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

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-alpha 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. 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). Serum circulating levels of IL-6 were strongly correlated with plasma ceramide concentrations (r = 0.59, p < 0.001). Adjustments for serum TNF-alpha 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-alpha 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-alpha had a significant independent influence on circulating levels of IL-6, altogether accounting for 41% of its variation (p < 0.001). 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. ClinicalTrials.gov NCT00720655 The study was supported by the Finnish Cultural Foundation, the North-Savo Regional Fund of the Finnish Cultural Foundation, the Yrjo Jahnsson Foundation, the Sigrid Juselius Foundation, the Juho Vainio Foundation, the Kuopio University Hospital (grant 510RA07), the Academy of Finland (Projects 117844 and 118590) and by the Nordic Centre of Excellence on 'Systems biology in controlled dietary interventions and cohort studies' (SYSDIET), Project 070014.