Publication Date

5-2015

Advisor(s) - Committee Chair

Noah Ashley (Director), Cheryl Davis, Nancy Rice

Degree Program

Department of Biology

Degree Type

Master of Science

Abstract

Sleep fragmentation induces acute inflammation and increases glucocorticosteroids in vertebrates. Obesity and sleep fragmentation are often concurrent pro-inflammatory conditions in patients with obstructive sleep apnea. Despite the association between the two, their simultaneous effects on immune and endocrine profiles have not been explored. In the first experiment, we investigated changes in proinflammatory (IL-1β, TNF-α) and anti-inflammatory (TGF-β1) cytokine gene expression in the periphery (liver, spleen, fat, and heart) and brain (hypothalamus, prefrontal cortex, and hippocampus) in mice exposed to various intervals of sleep fragmentation. Serum corticosterone concentration was also assessed. Sleep was disrupted in male C57BL/6J mice using an automated sleep fragmentation chamber (Lafayette Industries), which involved movement of a sweeping bar at specified intervals. Mice were exposed to bar sweeps every 20 sec (high sleep fragmentation; HSF), 120 sec (low sleep fragmentation; LSF), or the bar remained stationary (control). Trunk blood and tissue samples were collected after 24 h of SF. It was found that HSF is a potent inducer of inflammation in the periphery (IL-1β: adipose, heart, and hypothalamus), but leads to upregulation of antiinflammatory cytokines in the brain (TGF-β1: hypothalamus and hippocampus), despite elevated serum corticosterone. Due to the association between obesity and SF, this experiment was replicated in male C57BL/6J mice (lean) and ob/ob KO mice (obese) using the previously described methods. We predicted the acute inflammatory response resulting from HSF would be different for the lean and the obese mice, with the greatest cytokine gene expression levels in the OB HSF group, due to a summative effect of the pro-inflammatory conditions. Obesity was the factor that most affected cytokine gene expression profiles. Additionally, the pro- vs anti-inflammatory gene expression profile varied with tissue type. While obesity resulted in neuroinflammation (hypothalamus, prefrontal cortex, hippocampus), it led to decreases in pro-inflammatory cytokine gene expression in the periphery (spleen, fat, heart). Serum corticosterone concentration was significantly elevated due to SF, but was not affected by obesity. As a result, the obese mice likely had neuroendocrine adaptations to combat the pre-existing pro-inflammatory condition of obesity, which impacted the acute inflammatory response to sleep loss.

Disciplines

Biology | Biotechnology

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