Decreased Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) Levels Were Linked with Disease Severity of Postmenopausal Osteoporosis

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) has been identified to facilitate osteogenic differentiation and bone formation both in vitro and in vivo. However, whether lack of PACAP is associated with osteoporosis (OP) still remains unknown. The scope of the current study was to examine the potential relationship between serum PACAP concentrations and disease severity in female patients with postmenopausal osteoporosis (PMOP). 123 PMOP females were enrolled in our study. During the same period, BMI and age-matched 120 postmenopausal non-osteoporotic (PMNOP) patients were also recruited as control. Serum PACAP concentrations were determined by Sandwich ELISA. Bone mineral density was examined by dual-energy x-ray absorptiometry (DXA) at the total hip, lumbar 1-4 vertebrae and left femoral neck. Genant grade was utilized for evaluating the degree of vertebral fracture and receiver operating characteristic (ROC) curve was performed to examine the diagnostic value of PACAP with regard to Genant grade. The numerical rating scale (NRS) was applied for test pain and 6-min walking as well as sit-to-stand test was used for functional status. The bone turnover markers including N-terminal propeptide of type I procollagen (PINP) (marker of bone formation) and C-telopeptide of type I collagen (CTX-I) (marker of bone resorption) were also examined. The PMOP women had significantly decreased mean serum PACAP levels in comparison with the PMNOP females. Serum levels of PACAP in vertebrae fracture patients were significantly lower than that in non-fracture patients Serum PACAP concentrations were negatively and significantly related to Genant grade as well as BMD at total hip, lumbar 1-4 vertebrae and left femoral neck. Further ROC analysis indicated that PACAP may act as a decent marker for Genant grade. In addition, serum PACAP levels were negatively associated with NRS and positively related to 6-min walking as well as sit-to-stand test scores. Last, we found PACAP were negatively correlated with increased CTX-I levels and positively related to PINP levels. Attenuated PACAP concentrations were related to disease severity of PMOP, PACAP may act as a protective role during PMOP.