Session: OR15-Adipokine Action
Room 303 (Moscone Center)
The discovery of adiponectin preceded a surge of interest into white adipose tissue (WAT), which led to the current appreciation of WAT as a major endocrine organ. In contrast, research has largely neglected another adipose depot: bone marrow adipose tissue (MAT). Bone marrow adipocytes account for up to 70% of marrow volume in humans and, in contrast to WAT, MAT increases in states of leanness such as CR, type I diabetes or anorexia nervosa. Moreover, pharmacological agents such as thiazolidinediones or fibroblast growth factor-21 increase marrow adiposity. Notably, each of these conditions is also associated with increased serum adiponectin.
Based on these observations, we investigated the hypothesis that MAT is a major source of serum adiponectin. We found that, in rabbits or mice, adiponectin protein expression is markedly higher in MAT than in WAT. Although this was not consistently observed in human tissues, a subset of patients showed higher adiponectin secretion from MAT than from WAT. We next investigated if blocking MAT formation affects serum adiponectin levels. To do so we used Ocn-Wnt10b mice, in which the anti-adipogenic effector Wnt10b is transgenically expressed in bone. Although expression of adiponectin in WAT did not differ between Ocn-Wnt10b and control mice, Ocn-Wnt10b mice resisted the increases in MAT and serum adiponectin with CR. Finally, we found that total serum adiponectin negatively correlates with WAT mass or % body fat but positively correlates with MAT volume. These observations support the hypothesis that MAT expansion is required for increased serum adiponectin with CR, suggesting that MAT may be a major source of serum adiponectin. Thus, adiponectin production from MAT may account, at least in part, for the adiponectin paradox.
Disclosure: WPC: Researcher, Eli Lilly & Company. VGK: Employee, Eli Lilly & Company. OAM: Principal Investigator, Eli Lilly & Company. Nothing to Disclose: ELS, BSL, DTB, SSS, JLD, CNL, KAG, JDM, PKF, AK, MCH, CJR
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