Association of serum osteoprotegerin levels with trabecular bone score in post-menopausal women with type 2 diabetes

Introduction. Patients with type 2 diabetes (T2D) have increased fracture risk, despite the relatively preserved or even high bone mineral density (BMD). Bone strength in patients with T2D might be strongly affected by qualitative alterations of bone tissue, which are poorly captured by the BMD assessment. Evidence in literature suggested that increased levels of osteoprotegerin (OPG), a regulator of bone turnover, might be associated with increased fracture risk. Trabecular Bone Score (TBS) is an indicator of bone microarchitecture and lower TBS reflects poorer bone quality despite equal BMD. Aim. The aim of this study was to evaluate serum OPG levels and TBS in post-menopausal women with T2D. Methods. A population of n=102 post-menopausal women was enrolled, n=76 patients with T2D (mean age 67.9 ± 8.2 years, BMI 28.4 ± 4.3 Kg/m2) and n=26 control subjects (mean age 60.7 ± 5.9 years, BMI 25.8 ± 5.4 Kg/m2). Exclusion criteria were: medication influencing bone metabolism (bisphosphonates, corticosteroids, hormonal replacement therapy); osteomalacia; Paget disease; hyperparathyroidism; hyperthyroidism; liver failure; chronic kidney disease; antihyperglycemic agents other than metformin; alcohol or drug abuse; psychiatric diseases. A detailed medical history was obtained. Clinical and biochemical parameters were collected. Serum OPG levels were measured (Bio-Rad Laboratories, Inc, CA, USA) and TBS was calculated using lumbar spine Dual Energy X Ray Absorptiometry (DEXA, Hologic, Canada) images. Results. Serum OPG levels were significantly higher in patients with T2D compared with control subjects (T2D 611.79 ± 244.8 pg/ml vs control subjects 487.82 ± 227.45 pg/ml; p 0.003), even after adjustment for age (T2D 598.04 ± 27.76 pg/ml vs control subjects 479.681 ± 50.10 pg/ml; p=0.04). In the whole population a positive correlation between OPG and age was observed (r=0.343, p=0.001). TBS was lower in T2D patients compared with control subjects, with a trend towards statistical significance (p = 0.051). Only in patients with T2D, a negative correlation between OPG and TBS was observed (r= -0,361, p=0.003), and this association remained significant even after adjustment for age (β -619.5 [-1119.3, -119.6] 95% CI, p=0.016). Conclusions. OPG levels were higher in T2D patients compared with control group and an association of higher values of OPG with worse bone microarchitecture, reflected by lower values of TBS, was observed only in patients with T2D. These findings suggest the importance of using parameters of bone metabolism and quality, other than BMD in patients with T2D.