Behavioral recovery from acute hypoxia is reliant on leptin

Individuals affected by hypoxia experience a variety of immune-associated sickness symptoms including malaise, fatigue, lethargy and loss of interest in the physical and social environment. Recently, we demonstrated that the interleukin (IL-1 beta arm of the neuroimmune system was critical to the sickness symptoms caused by hypoxia, and that IL-1 receptor antagonist (IL-1RA), IL-1 beta's endogenous inhibitor, was critical to promoting sickness recovery, Here, we report that leptin is key to recovery from hypoxia because it dramatically augmented IL-1RA production in mice. We found that hypoxia increased leptin in white adipose tissue (WAT) which in turn, caused a marked rise in serum IL-1RA. Interestingly, in-vitro, leptin was a more potent inducer of IL-RA, in macrophages, than hypoxia. In leptin receptor defective (db/db) and leptin deficient (ob/ob) mice, sickness recovery from hypoxia was delayed 3-fold. Importantly, in ob/ob mice, leptin administration completely reversed this delayed recovery and induced a marked increase in serum IL-1 RA. Finally, leptin administration to normal mice reduced hypoxia recovery time by 113 and dramatically increased WAT and serum IL-1RA. Leptin did not after recovery from hypoxia in IL-1RA knock out mice. These results show that by enhancing IL-1RA production leptin promoted sickness recovery from hypoxia. (C) 2008 Elsevier Inc. All rights reserved.