Low-density lipoprotein net charge is a risk factor for atherosclerosis in lupus patients independent of lipid concentrations

Aims Patients with systemic lupus erythematosus (SLE) suffer from accelerated atherosclerosis. Their most common cause of death is a cardiovascular disease (CVD), in spite of the presence of moderate lipid alterations and normal cardiovascular risk scores. However, cholesterol still accumulates in the arteries of SLE patients, so we aim to identify additional factors that may help explain the residual risk that exists in these patients. We focus on investigating whether the net charge contributes significantly to both the development and the progression of atherosclerosis in patients with SLE. Methods The lipoproteins from 78 patients with SLE and 32 controls were isolated via sequential ultracentrifugation. Lipoprotein subclasses distributions were analyzed via nuclear magnetic resonance spectroscopy and the net charges of very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) were measured using a Zetasizer Nano-ZS. The degree of atherosclerosis (carotid intima-media thickness [cIMT]) was determined in all the participants. Results Each lipoprotein class exhibited a negative net charge. IDL and LDL net charge correlated negatively with cIMT (r = -0.274, P = 0.034; r = -0.288; P = 0.033, respectively) in patients with SLE. This effect was independent of age, body mass index (BMI), gender, tobacco consumption, high-sensitivity C-reactive protein (hsCRP), lipid concentration and lipoprotein particle number. LDL net charge explained 4% of the cIMT variability among these patients; this contribution was also independent of age, BMI, gender, tobacco consumption, lipids levels, apolipoproteins and hsCRP. Conclusions Low-density lipoprotein net charge may be considered a new independent contributor to subclinical atherosclerosis in SLE patients. The observed relationship was independent of lipid concentrations and extends the prominent role that IDL and LDL play in cardiovascular risk.