Endocrine Abstracts

Recent findings suggested two-way interaction between bone and adipose tissue. Osteocalcin, a hormone of osteoblasts, was shown to stimulate insulin sensitivity by direct interaction with insulin. Adipose tissue has an important effect on insulin sensitivity by secretion of anti-inflammatory and proinflammatory adipocytokines like adiponectin and monocyte chemoattractant protein-1 (MCP-1). It is unknown whether they are related to bone metabolism.

Aim of this study was to examine the association of MCP-1 and HMW-adiponectin with bone mineral density (BMD) and osteocalcin in postmenopausal women.

In 32 postmenopausal women we determined serum levels of HMW-adoponectin, MCP-1, osteocalcin, insulin, glucose, triglycerides, HDL-cholesterol and C-reactive protein. Anthropometric measurements, body composition analysis and bone densitometry were performed. Participants did not have any metabolic or inflammatory diseases.

Positive correlation was found between femoral BMD and measures of obesity (P<0.05). Negative correlation of HMW-adiponectin with femoral BMD was noted, but it didn’t remain significant after adjusting for body weight. HMW-adiponectin was negatively associated with measures of obesity and insulin (P<0.05), but MCP-1 showed no relationship with these parameters. Osteocalcin was inversely correlated with weight circumference, insulin and MCP-1 (P<0.05). Association between MCP-1 and osteocalcin remained significant even after adjusting for insulin and body weight.

In our results adiponectin did not appear to be among adipocytokines related with bone metabolism but the close association between osteocalcin and insulin was confirmed. Serum levels of MCP-1 in our study did not reflect its presumed role of chemokine secreted in obesity by macrophages in adipose tissue. In fact, the link between MCP-1 and osteocalcin seems to result from a mechanism that is independent from obesity and insulin sensitivity, for instance the previously demonstrated MCP-1 secretion by osteoblasts during administration of parathyroid hormone. This suggests that close links of bone and adipose tissue involve additional mediators with probably simultaneous impact on bone remodeling and energy metabolism.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.