Carbohydrate metabolism and the skeleton: picking a bone with the beta-cell.

Novel data show that the bone protein, undercarboxylated osteocalcin, increases islet cell growth and insulin and adiponectin synthesis and enhances glucose metabolism in mice. Human studies, in which undercarboxylated osteocalcin concentrations have been perturbed, show no effect (or a very minor effect) on fasting glucose or insulin concentrations. More extensive and detailed experiments in humans are needed to definitively establish the role of undercarboxylated osteocalcin in human carbohydrate metabolism.