Characteristics of Bone Tissue in Postmenopausal Women with Systemic Lupus Erythematosus

Introduction. Osteoporosis is one of the most common systemic diseases of the skeletal system that is characterized by decreased bone mass per unit volume, increased bone fragility and risk of fractures. 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. According to the results of prospective studies, it was found that the combination of increases in bone resorption markers or bone formation markers in postmenopausal women with low bone mineral density (BMD) is associated with the increased risk of fractures – by a factor of 2.0–2.5. 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 (mean age at the time of the study – 54.08 ± 0.72 years) with SLE diagnosed according to the criteria set by the American College of Rheumatology (1982, 1997) were included in the study. The mean disease (SLE) duration was 13.83 ± 0.97 years; all the women at the time of the study were in postmenopausal status. 100.0 % of the patients received methylprednisolone at a dose of 8.0 to 24.0 mg/day (mean dose – 11.94 ± 0.55 mg/day) and calcium supplements at a daily dose of 1000.0 mg in conjunction with vitamin D supplement at a daily dose of 400.0 IU. The mean duration of glucocorticoid treatment in conjunction with calcium and vitamin D supplements corresponded to the mean duration of disease. 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. The densitometry was performed using the ultrasound bone densitometer SONOST–2000 (OsteoSys Co., Ltd, Seoul, Korea). The statistical analysis was performed using Statistica 6.0 package (Stat Soft Inc, USA). 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). According to the results of ultrasound densitometry, all patients with SLE were divided into four groups depending on the degree of BMD loss: the first group included patients with the first stage of osteopenia; the second group included patients with the second stage of osteopenia; the third group included patients with the third stage of osteopenia; and the fourth group – patients with osteoporosis. 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), compared to the control group. 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), compared to the control group. 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), compared to the control group. 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