Date of Award

January 2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Sciences

First Advisor

Thad A. Rosenberger

Abstract

Acetate supplementation increases brain acetyl-CoA levels that influence inflammation, energy production, histone and non-histone protein acetylation, and purinergic signaling. Interestingly, acetate significantly increases fatty acid content in lipopolysaccharide (LPS)-stimulated BV2 (immortalized murine cell line) microglia compared to control-treated LPS-stimulated cells. This suggests that increasing brain acetyl-CoA metabolism may also influence lipid synthesis. We wanted to determine if treatment with glyceryl triacetate alters central nervous system (CNS) lipid content in mice subjected to experimental autoimmune encephalomyelitis (EAE), an autoimmune multiple sclerosis model. In addition, we performed experiments to determine whether treatment had an effect on disease progression, protein levels of enzymes involved in lipid metabolism, cytoskeletal structure, and myelin structure. We found acetate supplementation attenuated the onset of clinical symptoms in EAE mice based on a clinical score and hang time test. These experiments also showed treatment altered spinal cord phospholipid, fatty acid, cholesterol, and ganglioside content in mice subjected to EAE. In addition, treatment significantly increased total brain phosphatidylserine and choline glycerophospholipid as well as GD3 ganglioside levels in EAE mice compared to control-treated EAE mice. We also determined how treatment altered brain lipid levels within the myelin fraction, the membrane fraction lost in EAE. Acetate supplementation significantly increased brain myelin phosphatidylinositol and GM1 ganglioside levels in EAE mice compared to control-treated EAE mice. These data showed that increasing

acetyl-CoA metabolism altered CNS lipid content in mice subject to EAE to suggest that treatment may alter CNS lipid metabolism in this model. To test this hypothesis, we used Western blot analysis to measure protein levels of enzymes involved in lipid synthesis and lipid breakdown. EAE resulted in a significant increase of cytosolic phospholipase A2 protein levels, but treatment returned those levels back to control to suggest treatment may modulate cytosolic phospholipase A2-mediated lipid breakdown. In addition, we found treatment significantly decreased phosphorylated acetyl-CoA carboxylase protein levels in EAE mice, an enzyme involved in fatty acid synthesis. The phosphorylated acetyl-CoA carboxylase is the inactive form of the enzyme, which suggests acetate may shift this enzyme from the inactive to active form to promote fatty acid synthesis.

These data test the hypothesis that treatment may alter CNS lipid metabolism in mice subjected to EAE. This is significant regarding the treatment of demyelinating diseases because developing a therapy to promote lipid synthesis and/or reduce lipid breakdown may prevent, possibly replace, the lipid loss found in EAE. As well, we determined how acetate supplementation altered EAE-induced increases in cytoskeletal structure and myelin inhibiting protein levels. We found EAE injury resulted in a significant increase in cytoskeletal associated proteins, β-actin and merlin, but treatment was unable to return these levels to control. This suggests treatment may not alter all EAE disease pathologies. In addition, there was a significant increase in oligodendrocyte myelin glycoprotein, a myelin inhibiting protein, and acetate supplementation returned this protein back to control levels. This suggests treatment may alter myelin structure, and this was also shown in the FluoroMyelinTM staining. Treatment slightly increased FluoroMyelinTM intensity in EAE compared to control-treated EAE mice but not to same extent as control levels. These studies demonstrate that acetate supplementation reduced disease progression, altered CNS and myelin lipid content, and influenced CNS and myelin protein content in mice subjected to EAE.

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