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.

The primary goal of this cross-sectional in vivo study was to assess peripheral bone microarchitecture, bone strength, and bone remodeling in adult type 1 diabetes (T1D) patients with and without diabetic microvascular disease (MVDþ and MVD-, respectively) and to compare them with age-, gender-, and height-matched healthy control subjects (CoMVDþ and CoMVD-, respectively). The secondary goal was to assess differences in MVD-and MVDþ patients. Fifty-five patients with T1DM (MVDþ group: n ¼ 29) were recruited from the Funen Diabetes Database. Dual-energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HRpQCT) of the ultradistal radius and tibia, and biochemical markers of bone turnover were performed in all participants. There were no significant differences in HR-pQCT parameters between MVD-and CoMVD-subjects. In contrast, MVDþ patients had larger total and trabecular bone areas (p ¼ 0.04 and p ¼ 0.02, respectively), lower total, trabecular, and cortical volumetric bone mineral density (vBMD) (p < 0.01, p < 0.04, and p < 0.02, respectively), and thinner cortex (p ¼ 0.03) at the radius, and lower total and trabecular vBMD (p ¼ 0.01 and p ¼ 0.02, respectively) at the tibia in comparison to CoMVDþ. MVDþ patients also exhibited lower total and trabecular vBMD (radius p ¼ 0.01, tibia p < 0.01), trabecular thickness (radius p ¼ 0.01), estimated bone strength, and greater trabecular separation (radius p ¼ 0.01, tibia p < 0.01) and network inhomogeneity (radius p ¼ 0.01, tibia p < 0.01) in comparison to MVD-patients. These differences remained significant after adjustment for age, body mass index, gender, disease duration, and glycemic control (average glycated hemoglobin over the previous 3 years). Although biochemical markers of bone turnover were significantly lower in MVDþ and MVD-groups in comparison to controls, they were similar between the MVDþ and MVD-groups. The results of our study suggest that the presence of MVD was associated with deficits in cortical and trabecular bone vBMD and microarchitecture that could partly explain the excess skeletal fragility observed in these patients.

Objective and design: Patients with type 2 diabetes mellitus (T2D) have an increased fracture risk despite a normal or elevated bone mineral density (BMD). The aim of this cross-sectional in vivo study was to assess parameters of peripheral bone microarchitecture, estimated bone strength and bone remodeling in T2D patients with and without diabetic microvascular disease (MVDC and MVDK respectively) and to compare them with healthy controls. Methods: Fifty-one T2D patients (MVDC group: nZ25) were recruited from Funen Diabetic Database and matched for age, sex and height with 51 healthy subjects. High-resolution peripheral quantitative tomography (HR-pQCT) was used to assess bone structure at the non-dominant distal radius and tibia. Estimated bone strength was calculated using finite element analysis. Biochemical markers of bone turnover were measured in all participants. Results: After adjusting for BMI, MVDC patients displayed lower cortical volumetric BMD (PZ0.02) and cortical thickness (PZ0.02) and higher cortical porosity at the radius (PZ0.02) and a trend towards higher cortical porosity at the tibia (PZ0.07) compared to controls. HR-pQCT parameters did not differ between MVDK and control subjects. Biochemical markers of bone turnover were significantly lower in MVDC and MVDK patients compared to controls (all P!0.01). These were no significant correlations between disease duration, glycemic control (average glycated hemoglobin over the previous 3 years) and HR-pQCT parameters. Conclusion: Cortical bone deficits are not a characteristic of all T2D patients but of a subgroup characterized by the presence of microvascular complications. Whether this influences fracture rates in these patients needs further investigation.

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