Correlations of serum prolidase activity between bone turnover markers and mineral density in postmenopausal osteoporosis

Prolidase is a specific imidodipeptidase involved in collagen degradation. The increase in the enzyme activity is believed to be correlated with the increased intensity of collagen degradation. The aim of this study was to evaluate the serum prolidase activity and its relationship between bone turnover markers and bone mineral density (BMD) in postmenopausal osteoporosis. The study included 45 postmenopausal osteoporotic, 55 postmenopausal nonosteoporotic and 38 premenopausal healthy women. BMD was measured at the femoral neck and lumbar spine with DEXA. T score was more than 2.5 SD below the normal at the lumbar spine or femoral neck in postmenopausal osteoporotic patients. Serum levels of prolidase, C-terminal telopeptide of type I collagen (C-telopeptide), total alkaline phosphatase (ALP), osteocalcin (OC), urinary deoxypyridinoline (Dpd) and urinary creatinine were also assayed. C-telopeptide, total ALP, OC, urinary Dpd levels were significantly higher in postmenopausal osteoporotic group compared with premenopausal women. However, there was no statistical difference in serum prolidase activity between the three groups. There were also no significant correlations between serum prolidase and any biomarkers of bone turnover as well as BMD. To conclude, in postmenopausal osteoporotic women with increased bone turnover, serum prolidase concentration was not correlated with the biomarkers of bone formation or bone resorption and with BMD.