Association between serum soluble membrane type matrix metalloproteinase-1 (MT1-MMP) levels and bone mineral density, and biochemical markers in postmenopausal women.

Background: Recently, membrane type matrix metalloproteinase-1 (MT1-MMP) was found to participate in bone metabolism. We investigated the relationship between serum MT1-MMP and bone mineral density (BMD) as well as bone metabolic markers in 206 Chinese postmenopausal women aged 43-80 years.
Methods: Western analysis and ELISA were performed to detect serum soluble MT1-MMP levels. BMD was measured by dual energy X-ray absorptiometry (DXA). Serum alkaline phosphatase (BAP) and N-telopeptides of type I collagen (NTX) were assayed using ELISA.
Results: We found that soluble MT1-MMP abundantly existed in human serum as protein lack of transmembrane domain. Serum MT1-MMP levels were detectable in all participants and the range of value was 221.2-863.0 ng/ml (435.6+/-98.2 ng/ml). We found a significant negative weaker correlation between MT1-MMP and BMD at lumbar spine, total hip (Thip), and femoral neck (FN) (all P<0.05). After adjustment for age and BMI, the correlation with BMD at FN and Thip disappeared (all P>0.05). Multiple linear stepwise regression analysis showed that MT1-MMP was not a determinant factor for BMD. The significant positive correlations between MT1-MMP and BAP, NTX were found, and remained significant after adjustment for age and BMI (all P<0.05). Moreover, serum MT1-MMP, BAP, and NTX decreased in response to alendronate therapy.
Conclusion: Circulating MT1-MMP and bone turnover markers are correlated, and serum MT1-MMP levels may rise with increase in bone turnover.