Lumbar spine bone mineral density predicts endothelial reactivity in patients with systemic lupus erythematosus.

OBJECTIVES To explore whether endothelial function is related to bone mineral density (BMD) in patients with systemic lupus erythematosus (SLE). METHODS Consecutive adult SLE patients and age-, sex-, BMI- and smoking-status-matched healthy controls were studied. Subjects with hypertension, hyperlipidemia, diabetes mellitus, renal impairment, dysthyroidism, history of or treatment for cardiovascular and cerebrovascular disorders, antiphospholipid syndrome, positive antiphospholipid antibodies or bone loss were excluded. Endothelial function was assessed by measuring flow-mediated dilatation (FMD) at the brachial artery and carotid intima-media thickness (IMT) by ultrasound. Lumbar and hip BMD were measured by dual-energy x-ray absorptiometry. Fasting blood samples were assayed for atherogenic index and high sensitivity C-reactive protein (hsCRP). Regression models were constructed to study the relationship between FMD and BMD. RESULTS One hundred and ten subjects (55 SLE and 55 matched healthy controls) were studied. While there were no differences between SLE patients and controls in menopausal status, blood pressure, atherogenic index, carotid IMT and BMD, SLE patients had significantly poorer FMD even after adjustment for age, gender, smoking and baseline brachial artery diameter. Also, SLE patients with lumbar osteopenia had significantly lower FMD than those with normal BMD. Multivariate regression revealed that lower FMD was associated with lower lumbar BMD and higher serum hsCRP in SLE patients, but these relationships were absent amongst healthy controls. CONCLUSIONS Lumbar vertebral BMD predicted endothelial reactivity in SLE patients without clinically-overt bone loss and atherosclerosis. Thus, early atherosclerotic disease should be considered in lupus patients especially if vertebral bone loss is evident.