Integrative physiology of the skeleton

In the 21st century, two sharply contrasting disorders of body composition, obesity and osteoporosis, have reached near epidemic proportions and challenged the scientific resources. This chapter focuses on several advances in adipose and bone biology that have revised the thinking about the role of the skeleton in whole body homeostasis. Bone marrow surrounds trabecular elements in the skeleton and is composed of multiple cells that are pluripotent. Bone and adipose tissue remodeling are functionally related through a complex neuroendocrine circuit that involves the brain, adipose depots, and the skeleton. Leptin is an adipokine produced by fat cells. The circulating levels of leptin are directly related to total fat mass. Adiponectin can induce insulin sensitivity and is thought to be a modulator of glucose transport. Several lines of evidence point towards an efferent sympathetic pathway from the brain controlling skeletal metabolism.