Metabolic Health and Disease: A Role of Osteokines?

Maintenance of skeletal health is tightly regulated by osteocytes, osteoblasts, and osteoclasts via coordinated secretion of bone-derived factors, termed osteokines. Disruption of this coordinated process due to aging and metabolic disease promotes loss of bone mass and increased risk of fracture. Indeed, growing evidence demonstrates that metabolic diseases, including type 2 diabetes, liver disease and cancer are accompanied by bone loss and altered osteokine levels. With the persistent prevalence of cancer and the growing epidemic of metabolic disorders, investigations into the role of inter-tissue communication during disease progression are on the rise. While osteokines are imperative for bone homeostasis, work from us and others have identified that osteokines possess endocrine functions, exerting effects on distant tissues including skeletal muscle and liver. In this review we first discuss the prevalence of bone loss and osteokine alterations in patients with type 2 diabetes, non-alcoholic fatty liver disease, non-alcoholic steatohepatitis, cirrhosis, and cancer. We then discuss the effects of osteokines in mediating skeletal muscle and liver homeostasis, including RANKL, sclerostin, osteocalcin, FGF23, PGE, TGF-β, BMPs, IGF-1 and PTHrP. To better understand how inter-tissue communication contributes to disease progression, it is essential that we include the bone secretome and the systemic roles of osteokines.