The past thirty years have seen a dramatic rise in obesity worldwide owing to a change in dietary composition, quantity of food consumed- positive energy balance, and a more sedentary life style. Accompanied with obesity is a chronic low grade inflammatory state defined by increased circulating cytokines and an increase in gene expression promoting inflammation. Multiple health risks are associated with obesity such as cardiovascular disease, insulin resistance, and type II diabetes. Advances in mass spectrometry have made wide scale proteomic studies possible and are redefining cell and molecular biology. One such area of that has become of considerable interest is protein acetylation which is observed in most cellular processes such as cell cycle regulation, gene expression, subcellular localization, metabolism, muscle contraction, protein stability, apoptosis, and more. Metabolic proteins are highly susceptible to acetylation with almost all showing the capacity to be acetylated. Our research, using an obese mouse model fed a chronic high fat diet and a lean control mouse model fed a standard chow diet, showed numerous differences in the acetylome between obese and lean animals in a fasted state. As well as, differences in the acetylome's of both animal models upon receiving a high fat meal. We showed that almost every mitochondrially located metabolic protein in obese animals is hyper-acetylated in a fasted state compared to lean animals and that upon feeding lean animals have a greater response in the change to their metabolic acetylome. We show that in the fed state lean and obese mice have almost completely different acetylomic profiles of mitochondrial and glycolytic metabolic proteins. Furthermore, we have observed possible new regulatory mechanisms utilizing acetylation to 1) determine the fate of the co-factor NADH in glycolysis and 2) control an ATP producing reaction in glycolysis. / Ph. D.

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Daily rhythms in physiology and behaviour are orchestrated by theautonomously rhythmic cells of the suprachiasmatic nucleus (SCN).Restricting food intake to the rest phase of nocturnal rodents, leads to thedevelopment of meal anticipatory behaviour, corticosterone and bodytemperature. Given that lesions to the SCN fail to abolish meal anticipation, asecond oscillator of unknown location, referred to as the food-entrainableoscillator (FEO) is thought to exist. Although the site of the FEO is unknown,several hypothalamus nuclei, including the dorsomedial hypothalamus(DMH) are thought to play a role in meal anticipation. Given thatadrenalectomy is reported to abolish meal anticipation, an intact HPA axis isalso thought to contribute to the functioning of the FEO. Some forms ofobesity are characterised by high basal levels of circulating corticosterone. Inaddition, limited access to high fat diet, fails to induce the development ofrobust meal anticipation in rats. During our initial studies, the effect of a standard and 45% high fat diet onthe development of meal anticipatory behaviour and hypothalamic c-Fosexpression were investigated. Restricted access to high fat diet led toattenuation of meal anticipation compared to those fed standard diet. Thiswas concurrent with a failure to develop an anticipatory rise in DMH c-Fosexpression. A meal anticipatory rise in corticosterone is thought to benecessary for the presence of meal anticipation as well as adaptation ofmetabolism to daily restricted feeding. In the next set of studies, weconfirmed that restricted access to standard diet leads to the development ofa meal anticipatory rise in plasma corticosterone. In contrast we observed adramatic post-anticipatory rise in plasma corticosterone in rats givenrestricted access to the 45% high fat diet. We hypothesised that the highcorticosterone levels resulting from high fat diet were a contributing factor tothe lack of meal anticipation in high fat fed rats. With the aid of apharmacokinetic study, a suitable experiment was designed for daily dosingof a potent glucocorticoid receptor antagonist, RU486, with the aim ofrescuing meal anticipation in high fat fed rats. Interestingly, treatment withRU486 successfully rescued meal anticipation in high fat fed rats, butattenuated meal anticipation in standard diet restricted fed rats. In the finalseries of studies the effect of diet and feeding regime on glucose toleranceand metabolism were investigated. High fat feeding was found to reduceglucose tolerance in both ad lib and restricted fed rats, with RU486 treatmentimproving glucose tolerance in a time dependant manner. Restricted accessto food was found to induce post satiation lipogenesis in both standard dietfed and to a lesser extent in high fat fed rats, an effect which may bebeneficial in reducing obesity. Overall the results provide further insight intothe complex role of corticosterone in promoting or preventing mealanticipatory behaviour. An anticipatory rise in plasma corticosterone isrequired for meal anticipation, as repeated daily dosing of RU486 inhibit mealanticipation. The high basal levels of corticosterone in high fat fed rats mayprevent meal anticipation, insulin secretion and post-satiation lipogenesiswhich may in fact be a homeostatic mechanism to prevent obesity. Nonetheless, treatment with RU486 rescues behavioural meal anticipationand glucose tolerance.

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