Thomas. L Clemens
Energy homeostasis in mammals is controlled by the actions of circulating hormones, which coordinate fuel production and utilization between metabolically active tissues. Mounting evidence implicates the osteoblast as an important player in the coordination of global energy utilization through its hormonal interactions with other tissues. Leptin produced by adipocytes controls postnatal bone acquisition by activating sympathetic nerves whose efferent outputs target β2-adrenergic receptor on osteoblasts to regulate their proliferation and differentiation. Insulin stimulates osteocalcin production by the osteoblast, which in turn stimulates insulin secretion by the pancreas. These observations suggest that skeletal cells such as the osteoblast, whose cellular ancestry is common to fat and muscle, evolved pathways to participate in global energy homeostasis. New basic questions arising from these findings will probe the precise nature of the fuel sensing and processing mechanisms in the osteoblast and their relative contribution to overall glucose disposal and utilization. The answers to these questions should improve our ability to diagnose and manage patients with metabolic diseases.