Thesis
Seasonal changes in adipokines, fat utilization, and regulation of food intake in grizzly bears (Ursus arctos horribilis)
Washington State University
Master of Science (MS), Washington State University
2015
Handle:
https://hdl.handle.net/2376/102903
Abstract
Many hibernating species have evolved physiological adaptations not found in more active organisms, including the ability to amass enormous adipose deposits. In humans, large amounts of adipose tissue are associated with the onset of metabolic diseases. However, in hibernating grizzly bears (Ursus arctos horribilis), obese animals are not only healthy, they are more reproductively fit than their leaner counterparts. Because we hypothesized that adipokines might reflect adiposity, we determined the annual serum profiles of leptin and adiponectin relative to body fat content. Both adipokines were present at relatively low levels throughout the active season but peaked in mid-October just prior to hibernation. Neither strongly correlated with body fat content throughout the year. Since leptin is an appetite suppressant in other animals, we tested the ability of centrally administered leptin to alter food intake at the beginning (August) and end (October) of the annual hyperphagic period. Bears treated with leptin in October significantly reduced their food intake whereas in August intake was unchanged, suggesting that the brain's sensitivity to leptin varies seasonally. We also cultured adipocytes from the active season and from hibernation under a variety of conditions to measure changes in gene expression and cellular lipolytic ability. Following treatment with bear serum collected at different times of year, leptin and its receptor responded differentially to catecholaminergic stimulation. The expression of genes closely related to lipolysis was significantly higher in hibernation cells, revealing cell autonomous changes. Taken together, the results reveal both cell-specific and systemic seasonal changes in bear adipose physiology.
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Details
- Title
- Seasonal changes in adipokines, fat utilization, and regulation of food intake in grizzly bears (Ursus arctos horribilis)
- Creators
- Jamie Lauren Gehring
- Contributors
- Charles T. Robbins (Degree Supervisor)Heiko T. Jansen (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Sciences, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525130601842
- Language
- English
- Resource Type
- Thesis