Characteristics of Bone Tissue in Postmenopausal Women with Systemic Lupus Erythematosus

Introduction. The prevalence of low bone mineral density in patients with systemic lupus erythematosus (SLE) is high, compared to the general population: osteopenia is diagnosed in 25.0–75.0 % of patients with SLE and osteoporosis – in 1.4–68.0 % of patients with SLE. Aim. To characterize bone tissue in postmenopausal women with systemic lupus erythematosus. Materials and methods. SLE patients were randomized in the study, stratified by sex and postmenopausal status. 71 women (experimental group) aged 47 to 68 years with SLE diagnosed according to the criteria of the American College of Rheumatology (1982, 1997) were included in the study. The control group comprised 30 almost healthy women aged 49 to 62 years (mean age at the time of the study – 54.67 ± 0.79 years) in postmenopausal status. Two bone formation markers (osteocalcin and P1NP) and one bone resorption biochemical marker (β-crossLaps) were used to assess the rate of bone remodeling. The ultrasound bone densitometry of the calcaneus was conducted in order to evaluate the structural and functional state of bone tissue. Results and discussion. In all patients with SLE (100.0 %), changes in bone tissue were found: the first stage of osteopenia – in 16 patients (22.5 %), the second stage of osteopenia – in 19 patients (26.8 %), the third stage of osteopenia – in 24 patients (33.8 %), osteoporosis – in 12 patients (16.9 %). Osteocalcin levels were significantly elevated (by 19.76 ± 1.11; p < 0.001) in SLE patients, compared to the control group, and P1NP levels were higher, but not statistically significantly. β-crossLaps marker was significantly higher in patients with SLE, compared to the control group (by 0.15 ± 0.03, p < 0.001). Patients of the 1st group had statistically significantly higher levels of bone formation marker – osteocalcin (by 18.94 ± 2.15; p < 0.001) – and bone resorption marker – β-crossLaps (by 0.06 ng/ml ± 0.04, p < 0.05). Patients of the 2nd group had significantly higher levels of two bone remodeling markers – osteocalcin (by 17.96 ng/ml ± 1.87; p < 0.001) and β-crossLaps (by 0.08 ng/ml ± 0.03, p < 0.01); a lower level of bone formation marker – P1NP (by 3.93 mcg/L ± 1.98; p < 0.05). Patients of the 3rd group had significantly increased levels of osteocalcin, P1NP and β-crossLaps (by 21.04 ng/ml ± 4.04, p < 0.001; 0.69 ng/ml ± 6.49, p < 0.05 ; and 0.25 ng/ml ± 0.04, p < 0.001, respectively), compared to the group of almost healthy women. Patients of the 4th group had significantly higher levels of two bone remodeling markers: osteocalcin (by 20.38 ng/ml ± 1.8; p < 0.001) and β-crossLaps (by 0.16 ng/ml ± 0.05, p < 0.001). Conclusions. The results of bone densitometry and the obtained levels of bone remodeling biochemical markers associated with the defects in both osteoblast and osteoclast functions show that all patients with SLE in postmenopausal status who comprised experimental group had indeed changes in bone tissue.