Increased circulating sclerostin and accumulation of advanced glycation end‐products (AGEs) are two potential mechanisms underlying low bone turnover and increased fracture risk in type 2 diabetes (T2D). Whether the expression of the sclerostin‐encoding SOST gene is altered in T2D, and whether it is associated with AGEs accumulation or regulation of other bone formation‐related genes is unknown. We hypothesized that AGEs accumulate and SOST gene expression is upregulated in bones from subjects with T2D, leading to downregulation of bone forming genes (RUNX2 and osteocalcin) and impaired bone microarchitecture and strength. We obtained bone tissue from femoral heads of 19 T2D postmenopausal women (mean glycated hemoglobin [HbA1c] 6.5%) and 73 age‐ and BMI‐comparable nondiabetic women undergoing hip replacement surgery. Despite similar bone mineral density (BMD) and biomechanical properties, we found a significantly higher SOST (p = .006) and a parallel lower RUNX2 (p = .025) expression in T2D compared with non‐diabetic subjects. Osteocalcin gene expression did not differ between T2D and non‐diabetic subjects, as well as circulating osteocalcin and sclerostin levels. We found a 1.5‐fold increase in total bone AGEs content in T2D compared with non‐diabetic women (364.8 ± 78.2 versus 209.9 ± 34.4 μg quinine/g collagen, respectively; p < .001). AGEs bone content correlated with worse bone microarchitecture, including lower volumetric BMD (r = −0.633; p = .02), BV/TV (r = −0.59; p = .033) and increased trabecular separation/spacing (r = 0.624; p = .023). In conclusion, our data show that even in patients with good glycemic control, T2D affects the expression of genes controlling bone formation (SOST and RUNX2). We also found that accumulation of AGEs is associated with impaired bone microarchitecture. We provide novel insights that may help understand the mechanisms underlying bone fragility in T2D. © 2020 American Society for Bone and Mineral Research (ASBMR).

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Background and objective Bone fragility has been linked to COVID-19 severity. The objective of this study was to evaluate whether a diagnosis of vertebral fracture (VF) increased mortality risk in COVID-19 patients and whether this effect was greater than in those without COVID-19. Methods We assessed VFs by computed tomography (CT) in a cohort of 501 patients consecutively admitted to the emergency department (ED) for clinical suspicion of SARS-CoV-2 infection during the first wave of pandemic emergency. Of those, 239 had a confirmed diagnosis of COVID-19. Results VF prevalence was similar between COVID-19 and non-COVID-19 groups (22.2 vs. 19%; p = 0.458). Death rates were similar between COVID-19 and non-COVID-19 groups at both 30 (15.8 vs. 12.2%; p = 0.234) and 120 days (21.8 vs. 17.6%; p = 0.236). The mortality risk was higher in COVID-19 patients either with one or multiple fractures compared to those without VFs, at 30 and 120 days, but statistical significance was reached only in those with multiple VFs (30-day HR 3.03, 95% CI 1.36-6.75; 120-day HR 2.91, 95% CI 1.43-5.91). In the non-COVID-19 group, the 30-day mortality risk was significantly higher in patients either with one (HR 7.46, 95% CI 3.12-17.8) or multiple fractures (HR 6.2, 95% CI 2.75-13.98) compared to those without VFs. A similar effect was observed at 120 days. After adjustment for age, sex and bone density, mortality risk remained associated with VFs in the non-COVID-19 group only. Conclusions VFs were not independently associated with short-term mortality in patients with COVID-19, but they strongly increased mortality risk in those without COVID-19. Keywords Vertebral fractures • Osteoporosis • COVID-19 • Viral pneumonia • Bone metabolism

High fracture rate and high circulating levels of the Wnt inhibitor, sclerostin, have been reported in diabetic patients. We studied the effects of Wnt signaling activation on bone health in a mouse model of insulin-deficient diabetes. We introduced the sclerostinresistant Lrp5 A214V mutation, associated with high bone mass, in mice carrying the Ins2 Akita mutation (Akita), which results in loss of beta cells, insulin deficiency, and diabetes in males. Akita mice accrue less trabecular bone mass with age relative to wild type (WT). Double heterozygous Lrp5 A214V /Akita mutants have high trabecular bone mass and cortical thickness relative to WT animals, as do Lrp5 A214V single mutants. Likewise, the Lrp5 A214V mutation prevents deterioration of biomechanical properties occurring in Akita mice. Notably, Lrp5 A214V /Akita mice develop fasting hyperglycemia and glucose intolerance with a delay relative to Akita mice (7 to 8 vs. 5 to 6 weeks, respectively), despite lack of insulin production in both groups by 6 weeks of age. Although insulin sensitivity is partially preserved in double heterozygous Lrp5 A214V /Akita relative to Akita mutants up to 30 weeks of age, insulin-dependent phosphorylated protein kinase B (pAKT) activation in vitro is not altered by the Lrp5 A214V mutation. Although white adipose tissue depots are equally reduced in both compound and Akita mice, the Lrp5 A214V mutation prevents brown adipose tissue whitening that occurs in Akita mice. Thus, hyperactivation of Lrp5-dependent signaling fully protects bone mass and strength in prolonged hyperglycemia and improves peripheral glucose metabolism in an insulin independent manner. Wnt signaling activation represents an ideal therapeutic approach for diabetic patients at high risk of fracture.