Biochemical markers in menopausal women

Role of adiponectin in mediating the association of osteocalcin with insulin resistance and type 2 diabetes: a cross sectional study in pre- and post-menopausal women

OBJECTIVE

To analyse the association of osteocalcin with insulin resistance and type 2 diabetes and assess the role of adiponectin in these relationships.

METHODS

This study comprised 98 newly diagnosed type 2 diabetic women (51 pre-menopausal and 47 post-menopausal) and 102 age and BMI matched controls (53 pre-menopausal and 49 post-menopausal). Insulin resistance was calculated by homeostasis model assessment-insulin resistance (HOMA-IR).

RESULTS

Osteocalcin was significantly positively correlated with adiponectin in both pre-menopausal (p = 0.0026) and post-menopausal diabetic women (p = 0.0357). Significant negative association between osteocalcin and HOMA-IR was observed only in pre-menopausal diabetic women (p = 0.0019), but the association was partially reduced (p = 0.0219) after additional adjustment for adiponectin. Adiponectin slightly attenuated the inverse association between osteocalcin and presence of type 2 diabetes in both pre- and post-menopausal women.

CONCLUSION

The protective action of osteocalcin against the development of insulin resistance and type 2 diabetes in women may be partially mediated through up-regulation of adiponectin secretion.

Biomarkers of bone health and osteoporosis risk

The assay features of biochemical markers of bone turnover have markedly improved in the past few years. The most sensitive and specific markers of bone formation include serum bone alkaline phosphatase, total osteocalcin (including the intact molecule and the large N-mid fragment) and the procollagen type I N-terminal propeptide assay. Among the various markers of bone resorption, measurements of the urinary excretion of N- and C-terminal cross-linked telopeptides) and of serum C-terminal cross-linked telopeptides are the most sensitive and specific. Markers of bone turnover can be used to predict the rate of bone loss in post-menopausal women and can also be used to assess the risk of fractures. In osteoporosis-treatment studies (with alendronate, risedronate, raloxifene) markers of bone turnover appear even more strongly associated with fracture risk reduction than bone mineral density (BMD). These observations support the use of markers of bone turnover as surrogates for fracture risk reduction, perhaps even more so than BMD. Bone markers can also be used to monitor the efficacy of antiresorptive therapy such as hormone-replacement therapy, raloxifene and bisphosphonates in individual patients. Furthermore, they have also proved to be helpful in monitoring the response to nutritional interventions and have the advantage over BMD in that they provide information about mechanism of effect and changes are often observed much more rapidly.