The relationships between bone turnover markers and bone mineral density in postmenopausal type 2 diabetic women

Aim. To determine the relationships between bone remodelling markers and bone mineral density (BMD), metabolic parameters and total body composition (TBC) in postmenopausal women with type 2 diabetes (T2D). Materials and methods. The study included 140 women who were diagnosed with T2D more than five years prior. The control group included 20 postmenopausal nondiabetic women with normal BMD. The BMD and TBC parameters were assessed by dual X-ray absorptiometry. Based on their T-scores, T2D women were divided into the following groups: normal BMD (n = 50), osteopenia (n = 50) and osteoporosis (n = 40). Serum levels of bone formation markers [osteocalcin and type 1 C-terminal collagen propeptide (CICP), osteoprotegerin (an inhibitor of bone resorption), parathyroid hormone (PHT) and urinary excretion of C-terminal telopeptides of type 1 collagen (alpha-CrossLaps, or CTX-I; a bone resorption marker)] were determined by ELISA. Results. Osteocalcin levels were decreased in all groups of T2D women (all P < 0.0002), without any differences between groups. Osteoprotegerin levels were reduced in all patient groups but was significantly lower in diabetic women with osteoporosis and osteopenia compared to those with normal BMD (P = 0.003 and P = 0.01, respectively). Women with osteoporosis had higher urinary CTX-I excretion than control and diabetic women with normal BMD (P = 0.01 and P = 0.01, respectively). CICP levels did not differ between groups. PHT concentrations were increased in diabetic women (P < 0.0001), without any differences between groups. After multiple regression analysis, BMI, age and CTX-I excretion were all associated with lumbar BMD (R2 = 0.38, P = 0.0007), whereas age, BMI, osteoprotegerin levels and CTX-I excretion were all predictive of BMD at the proximal femur (R2 = 0.44, P = 0.00003). There was no relationship between bone remodelling markers and HbA1c, lipid metabolism or TBC. Conclusions. In postmenopausal T2D women, osteoporosis is associated with decreased serum osteoprotegerin levels and enhanced urinary CTX-I excretion. The data do not support the existence of an interrelationship between bone remodelling markers, metabolic parameters and TBC in postmenopausal women with T2D.