|Image 1: The yellow bone marrrow fat |
turns out to be more than a filler.
In a comprehensive review of the latest findings on bone metabolism (Fulzele. 2011) Keertik Fulzele and Thomas L. Clemens state that the "contemporary model [which] assigns IGFs [insulin like growth factor] as central regulators of cell profileration, survival, and organism growth" and reduces the influence of insulin to the "level of regulation fuel utilization, storage, and energy expenditure" is too simplistic to to accommodate the overlapping roles of IGF and insulin in several physiologic processes, one of which is the recently discovered and previously unappreciated skeletal action of insulin. Via skeletal insulin receptors, the latter is intricately involved in
- osteablast [=bone cells] bone acquisition
- osteocalcin production
|Figure 1: Metabolic and endocrine functions of white (WAT) and brown (BAT) adipocytes in your bone marrow|
(based on Czernik. 2011)
Answers to these questions will expand our understanding of the biology of the skeleton and should have implications in the diagnosis and management of patients with metabolic diseases, including osteoporosis and diabetes.More information on the underlying mechanisms by which your bones directly influence your metabolic rate, and thus your weight, can be found in a Special Issue of the Journal 'Bone', entitled "Bone and Fat". In her paper (Czernik. 2011), Beata Lecka-Czernik elaborates on the possible influence the yellow bone fat, which - believe it or not - occupies a significant portion of your bone marrow cavity, could have on your metabolism, both locally, as well as systemically.
Did you know? The fat distribution in your skeleton is site, age, and gender specific (men have more bone fat than women). In adults the bone marrow cavity of long bone, for example, is entirely filled with fat, while the ileac crest marrow contains only ~40% fat. The overall amount of bone fat can double in the course of your life and the WAT- and BAT-like adipocytes appear to have similar metabolic and endocrine functions as their white (WAT) and brown (BAT) analogues on your hips, your belly and your neck.In this context, the integrative models of Ferron et al and Fulzele et al. are of particular interest, as they could help elucidate the link between the anabolic effects of insulin signaling in osteoblasts and the regulation of insulin sensitivity in peripheral organs. And who knows, even if its not the "heavy bones" that contribute to the obesity pandemic,"fat bones" could well become a novel target in its prevention and treatment.