Abstract
Fragility fractures are skeletal complications associated with type 2 diabetes (T2D) causing disability, hospitalization, impaired quality of life, and increased mortality. Increased circulating sclerostin and accumulation of advanced glycation end-products (AGEs) are two potential mechanisms underlying low bone turnover and increased fracture risk. We have recently shown that T2D affects the expression of genes controlling bone formation (SOST and RUNX2) and that accumulation of AGEs is associated with impaired bone formation in T2D. We hypothesized that Wnt/B- catenin target genes are down-regulated in bone of T2D subjects as a consequence of decreased SOST and AGEs accumulation. To this end, we studied gene expression in extracts of bone samples obtained from femoral heads of 14 subjects with relatively well-controlled T2D (HbA1c 6.5±1.7%) and 21 control, non-diabetic postmenopausal women (age >65 years) undergoing hip replacement. There were no differences in age (73.2± .8 vs. 75.2±8.5 years) or BMI (27.7±5.6 vs. 29.9±5.4 kg/m2) between control and T2D groups, respectively. Expression of LEF1 mRNA was significantly lower in T2D compared to non-diabetic subjects (p=0.002), while DKK1 was not different between groups (p=0.108). Correlation analysis showed that DKK1 (r2=0.038; p=0.043) and HbA1c (r2=0.503; p=0.048) increased with age in T2D. COL1A1 mRNA trended lower in T2D compared to controls (p=0.056). Bone volume (9,333 ± 1,443 vs. 15,53 ± 2,442 mm2; p=0.048), mineralized volume (9,278 ± 1,418 vs. 15,45 ± 2,444 mm2; p=0.048) and BV/TV (0,2125 ± 0,03114 vs. 0,3719 ± 0,03196 %; p=0.002) measured by bone histomorphometry were lower in T2D compared to controls. Our data show that even in patients with relatively good glycemic control, T2D decreases expression of Wnt/B-catenin target genes andCOL1A1, associated with decreased bone density. These results may help understand the mechanisms underlying bone fragility in T2D.
