Bone Sialoprotein (BSP), synthesized by osteoblasts and osteoclasts, is a highly glycosylated and phosphorylated
protein, accounting for approximately 5-10% of noncollagenous
proteins of bone extracellular matrix. The present study investigates possible correlations between serum values of immunoreactive
Bone Sialoprotein in relation to established bone turnover markers like
osteocalcin (OC), bone
alkaline phosphatase (B-ALP) and the c-terminal extension
peptide of
type-I-Procollagen (
PICP) in 170
osteoporosis patients (female n = 144, male n = 26) in order to evaluate the usefulness of BSP in the diagnosis of
bone disease. Fasting venous blood samples were collected from our
osteoporosis outpatients in the morning and stored at -80 degrees C until processing. Serum levels of BSP were determined by RIA, OC and B-ALP were measured by IRMA, and
PICP was assessed employing an ELISA technique. A significant correlation was found between BSP serum values and B-ALP (r = 0.532, p = 0.0001). Median serum BSP levels were 8.0 micrograms/l, median B-ALP values were 22.39 U/ml in these patients. Also a significant correlation was observed between BSP and OC (r = 0.588, p = 0.0001), more pronounced in the female patient group (r = 0.632, p < 0.0001). A weak association between BSP and
PICP in the female group was detected (r = 0.398, p = 0.0001). In the female group BSP was inversely related to serum
estradiol levels (r = -0.274, p = 0.002) as to BMD (DEXA) at the lumbar spine and femoral neck. In conclusion, BSP might be a useful marker of non-collagenous organic bone matrix in laboratory assessment of bone turnover, being inversely related to BMD at lumbar spine and femoral neck and showing significant correlations to established markers of bone turnover like B-ALP and OC.