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Abstract
Alzheimer’s disease is a neurodegenerative disease characterised by progressive decline in memory. Sirtuins proteins have been shown to deacetylate numerous proteins that regulate pathways implicated in neurodegeneration. However, relatively little is known about the role of sirtuins in the central nervous system and methods for quantification are limited. In this thesis (chapter 2), I describe a targeted mass spectrometric assay developed and validated for the quantification of all mammalian sirtuins (SIRT1-7). All sirtuins were detected in the human brain, with SIRT2 being the most abundant. In chapter 3, I report a significant drop in SIRT1 levels in AD plasma and an increase in SIRT2 in the occipital AD brain. Interestingly, completion of binding partner work for SIRT2 showed association with a number of energy metabolism associated proteins. Increased protein, lipid and nucleic acid oxidation and reduced activities of antioxidants have been reported in AD plasma. In chapter 4, I investigated the effect of plasma from controls, individuals with mild cognitive impairment and AD, on a microglial cell line. I found that AD plasma significantly decreased cell viability and enhanced glycolytic flux in microglia compared to plasma from healthy controls. Proteomic methods found altered levels of complement and other acute phase proteins, in MCI and AD plasma and an upregulation of glycolytic enzymes in cells exposed to AD plasma. It is well established that amyloid aggregation is enhanced by the presence of metals and various polyphenols are thought to have both antioxidant and anti-aggregation properties. In chapter 5, I investigated the ability of copper and iron to enhance amyloid aggregation and the ability of polyphenols such as resveratrol, curcumin and epigallocatechin gallate to prevent aggregation as well as modulate energy metabolism and attenuate cell toxicity in a neuronal cell culture model. In conclusion, I have successfully applied mass spectrometry for the quantification of sirtuins in the CNS. I have also shown that altered expression of acute phase reactants in AD plasma may alter the energy metabolism of glia. Finally, neurons treated with polyphenols were shown to prevent energy deficits and cell toxicity caused by the Aβ peptide aggregates.