C - Michigan Technological University

atios of intact to fragmented OCN may provide further insight into the unique physiologyof hibernating bears. Vitamin K levels were below detectable limits in all serum samplesin this study. Carboxylation of OCN is a vitamin K-dependent mechanism, therefore itwould be interesting to know whether ucOCN increases during hibernation due to avitamin K deficiency, or whether its production is regulated by other mechanisms. Sinceit is unlikely that vitamin K is completely absent in bears, quantification in adipose tissuemay provide further insight into the origin of ucOCN during hibernation. Anotherlimitation of this study is that serum was only collected in the months immediatelysurrounding and encompassing hibernation. Thus, the bears were either preparing forhibernation, hibernating, or recovering from hibernation throughout sample collection.The relationship between OCN and energy may be different during this season than inthe summer months. A last limitation is that serum was collected under anesthesia,which could have an impact on endocrine concentrations during the blood collection;however, the same dose of anesthesia was given each time.In summary, TRACP and BSALP match histomorphometric data [18, 20] tosuggest a reduction in both the resorption and the formation of bone during hibernation.Such a decrease in metabolism would help hibernating bears conserve energy. Thissuppression of bone turnover could be due, in part, to reduced serum adiponectin levelsduring hibernation. The spike in OCN in the winter months should not be interpreted as amarker of bone formation; instead it may have passively built up in serum due toreduced renal function. Alternatively, it could act as an energy homeostasis hormone.The inverse relationship of OCN to glucose levels in bears is similar to those found inprevious studies; however, the current study found an inverse relationship between OCNand adiponectin, which is not found in previous studies. The negative correlationbetween OCN and adiponectin may be due to the unique physiological state ofhibernation (i.e. hypoglycemia, increased triglyceride mobilization, etc.). Finally, serumserotonin had an inverse relationship to osteocalcin and a positive relationship toglucose and adiponectin. These relationships have not been reported previously.Serotonin is known to have an impact on glucose sensitivity and adiponectin secretion,but from these previous studies an inverse relationship between adiponectin andserotonin would be expected. Again, adiponectin activity is complex, and not fullyunderstood. Adiponectin may have a unique relationship with serotonin during33