[The relationship of vitamin D endocrine system and estrogen receptor expression with bone mineral density in initial systemic lupus erythematosus].

Objective: To study the incidence of osteopenia in patients with initial systemic lupus erythematosus (SLE). Investigate the levels of the vitamin D (VitD) endocrine system in peripheral blood of SLE patients and its relation to bone mineral density (BMD). Analyse the relationship between the estrogen receptor (ER) and BMD and evaluate the role of ER in the pathogenesis osteopenia.

Methods: Serum levels of 25-OH VitD(3) and 1,25-(OH)(2) VitD(3) were detected by enzyme linked immunosorbent assay. The gene expression levels of VitD receptor (VDR) and ER were determined by real-time PCR. BMD measurements in the lumbar spine (L1-L4) and left proximal femur (femoral neck) were performed using dual X-ray absorptiometry before treatment.

Results: The initial SLE patients had significantly lower BMD values, and higher frequency of bone loss at both sites of measurement compared with normal controls (P < 0.05). The levels of 25-OH VitD(3) and 1,25-(OH)(2) VitD(3) were lower in the initial SLE patients than normal controls (P < 0.01 both). There is no difference in the levels of 25-OH VitD(3) and 1,25-(OH)(2) VitD(3) between the osteopenia SLE group and the normal BMD SLE group (P > 0.05, P > 0.05). There are no correlations between the VitD and BMD in initial SLE patients (P > 0.05 both). The expressions of VDR gene were significantly increased in the initial SLE patients compared with the normal controls (P < 0.01). There was no difference in VDR gene expression between osteopenia SLE group and normal BMD SLE group (P > 0.05). The VDR gene expression does not correlate with the bone mass (P > 0.05). The levels of ER-beta gene expression are higher in the initial SLE group than the normal controls (P < 0.01).

Conclusions: The incipient SLE patients may have lower BMD than expected. SLE patients present abnormal VitD endocrine system and higher ER-beta mRNA expression than those in normal controls, but these weren't concerned with osteopenia.