Osteocalcin: An Endocrine Link Between Bone and Glucose Metabolism

Bu B Yeap

Disclosures

Expert Rev Endocrinol Metab. 2011;6(2):177-185. 

In This Article

Associations of TOC with Diabetes & Cardiovascular Risk in Humans

Human studies of TOC in relation to diabetes and metabolic syndrome are shown in Table 1. Postmenopausal women and men with Type 2 diabetes have lower TOC compared with nondiabetic controls.[23–25] Im et al. reported that postmenopausal women with Type 2 diabetes had reduced serum TOC compared with normal glucose and impaired fasting glucose groups.[23] Zhou et al. reported lower serum TOC levels in men and postmenopausal women with newly diagnosed Type 2 diabetes compared with controls.[24] Kindblom et al. reported lower plasma TOC in older men with diabetes and inverse relationships between TOC level with BMI, fat mass and plasma glucose.[25] Among adults with diabetes, higher TOC correlated with lower fasting plasma glucose levels and better glycemic control.[23,26] TOC correlated inversely with fat mass and BMI[25] and positively with total adiponectin and insulin sensitivity.[26,27] Higher TOC at baseline was associated with a lower rise in fasting glucose after 3 years.[28]

Two recent cross-sectional analyses have extended these observations to examine the association of reduced TOC level with cardiovascular risk, as defined by the presence of metabolic syndrome. Saleem et al. reported inverse correlations of serum TOC with BMI, fasting glucose, insulin resistance and leptin, and a positive association with adiponectin, while higher TOC levels were associated with a lower odds ratio of having metabolic syndrome.[29] In a separate study of a large cohort of community-dwelling older men, men with lower TOC levels had a 1.5–2-fold increased odds of metabolic syndrome compared with those with higher TOC levels.[30] This association was mediated via waist circumference, hyperglycemia and triglyceride levels, but not by hypertension or high-density lipoprotein levels. The association remained significant after adjusting for the individual components of metabolic syndrome.[30] Therefore, there are now human data, albeit from observational studies, which support the association of reduced TOC with diabetes and cardiovascular risk. However, these studies are not sufficient in themselves to determine whether reduced TOC is a mediator or a consequence and hence biomarker of impaired glucose metabolism.

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