C - Michigan Technological University

condition in renal patients in which bone turnover is dramatically decreased. Otherpossible effectors of low bone turnover during hibernation were discussed in Chapter 3.These include decreased levels of IGF-1 and serotonin in the serum of bears duringhibernation. It is likely that a combination of serum factors down-regulates bonemetabolism in hibernating bears, and any of these serum factors would be interestingsubjects of further study.The second Aim of this study was to evaluate the inter-relationship of OCN andenergy homeostasis hormones. Not only is OCN a vital component of bone’sextracellular matrix, it can also act as an energy hormone—increasing adiponectin andinsulin secretion and promoting glucose uptake in humans and other animals. In mice,this stimulatory effect on adiponectin and glucose is due to ucOCN [152]. Thehypothesis was that total and ucOCN would increase in the serum of hibernating bears,with correlated increases in adiponectin and insulin and a correlated decrease in serumglucose. In Chapter 2, increased serum levels of OCN were reported, but levels ofadiponectin and glucose were inversely correlated to total and ucOCN. Insulin levelslikewise decreased during hibernation, but with no correlation to OCN. These datasuggest that if OCN acts as an energy homeostasis hormone in bears in the monthsimmediately surrounding and encompassing hibernation, then it does so in a previouslyunreported manner. It is possible that the unique physiological state of bears in thisseason is regulated by a unique interaction of OCN with energy homeostasis. Anothersurprising finding reported in Chapter 2 is that total and ucOCN were negativelycorrelated to serum serotonin, and glucose and adiponectin were positively correlated toserotonin. A correlation of serotonin to OCN has not been reported previously, andearlier studies on the relationship between serotonin and adiponectin would suggest aninverse relationship [189, 190]. Therefore, these relationships, too, may be due to theunique physiological state of the weeks surrounding and encompassing hibernation.The third Aim of this study was to evaluate serum concentrations of antiapoptotichormones (e.g. PTH, melatonin) and to determine whether the serum fromhibernating bears had a protective effect on cultured osteoblasts submitted to anapoptotic threat. The hypothesis was that serum levels of these anti-apoptotic hormoneswould increase during hibernation in bears, and that osteoblasts cultured in serum from133