Bone mineral density (BMD) is the most important predictor of fracture risk. We performed the largest meta-analysis to date on lumbar spine and femoral neck BMD, including 17 genome-wide association studies and 32,961 individuals of European and East Asian ancestry. We tested the top-associated BMD markers for replication in 50,933 independent subjects and for risk of low-trauma fracture in 31,016 cases and 102,444 controls. We identified 56 loci (32 novel)associated with BMD atgenome-wide significant level (P<5×10−8). Several of these factors cluster within the RANK-RANKL-OPG, mesenchymal-stem-cell differentiation, endochondral ossification and the Wnt signalling pathways. However, we also discovered loci containing genes not known to play a role in bone biology. Fourteen BMD loci were also associated with fracture risk (P<5×10−4, Bonferroni corrected), of which six reached P<5×10−8 including: 18p11.21 (C18orf19), 7q21.3 (SLC25A13), 11q13.2 (LRP5), 4q22.1 (MEPE), 2p16.2 (SPTBN1) and 10q21.1 (DKK1). These findings shed light on the genetic architecture and pathophysiological mechanisms underlying BMD variation and fracture susceptibility.

Factors involved in inflammation are linked with those critical for bone remodeling. We examined the association between serum high sensitivity C-reactive protein (hsCRP) levels and bone mineral density (BMD) in healthy women. Serum concentrations of hsCRP and total alkaline phosphatase (ALP) were measured in premenopausal ( n =3,662) and postmenopausal ( n =1,031) women aged 30 years or older. BMD was measured at the femoral neck and lumbar spine using dual energy X-ray absorptiometry. According to the WHO definition, osteopenia was diagnosed at -2.5< T -score < -1.0 SD, and osteoporosis was diagnosed at T -score < or = -2.5 SD at any sites. Compared with normal subjects, log-transformed serum hsCRP levels were higher in osteopenic and osteoporotic subjects (all, P < 0.001) with linearity ( P for trend <0.001), after adjustment for age, BMI and menopausal status. Menopausal status did not have a significant interaction on the association ( P =0.457). In both premenopausal and postmenopausal women, serum total ALP levels were higher in the subjects with higher hsCRP quintiles than those with the lowest quintile (all, P for trend < 0.001). Multivariate-adjusted odds ratio (OR) for osteoporosis and osteopenia were 1.35 (95% CI, 1.08 to 1.68) in the highest hsCRP quintile of premenopausal women, and OR for osteoporosis was 1.54 (95% CI, 1.10 to 2.53) in the highest hsCRP quintile of postmenopausal women. These findings suggest that subclinical systemic inflammation may be associated with bone turnover rate and bone mass in healthy women.

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