Although obesity is an increasing issue, with a multitude of physical and psychological consequences, a detailed psychological (and particularly cognitive) formulation of why adults become and remain obese is lacking. There is also limited evidence for the long term effectiveness of psychological approaches to treating obesity. The first paper reviews literature that presents information about cognitive factors known to be involved in obesity. It applies a metacognitive model of bulimia nervosa and binge eating to organise this data, resulting in a metacognitive model of obesity. This model is evaluated with regard to what constitutes a good model. The second paper assesses whether the multilevel cognitive factors, found to be relevant in explaining eating disorders, are also useful in explaining obesity (measured by body mass index). A community sample of218 women (of all weights) was recruited to take part in an online survey. In addition to demographic and relevant control factors, this survey asked about cognitions at schema, core belief and metacognitive levels. The results showed that obese and healthy weight participants differed significantly on a number of cognitive variables. A hierarchical multiple regression was conducted and it was found that cognitions at all levels significantly predicted body mass index. Once control factors had been entered into the regression model, significant cognitive predictors were; negative thoughts (metacognitions); schemas of abandonment, social isolation, emotional deprivation and failure; and the core belief of high standards for self (negative correlation). These fmdings support the use of a multilevel metacognitive model for understanding obesity; information which could inform treatment. The use of this model and any treatment plan will need to be evaluated in future research.

Background: Adolescence to adulthood is a transition period, identified as a trigger point for weight gain and obesity but an under-researched age. Aims and objectives: This thesis identifies components crucial to 18-25 year olds in order to develop a lifestyle intervention for obesity prevention by identifying existing effective interventions and exploring their lifestyle related to obesity. Methodology: An initial systematic review identified and critically appraised evidence on effective interventions. An explanatory mixed method approach followed, to explore the lifestyle of 18-25 year olds in the Grampian region, using a questionnaire survey (quantitative) and focus groups (qualitative). A health behaviour theory was used to underpin the questionnaire. Seven focus groups were conducted. Results: The systematic review identified possible effective interventions, but these were short-term and conducted in specific groups in controlled environments. Based on 1313 responses, the self-reported prevalence of overweight or obesity was 22% and increased with age. Irregular meal eating patterns, decreasing physical activity levels with age, combined with high levels of snacking when younger (18-19 year olds) were associated with higher BMI. In spite of high intention, explained by attitudes, gender and employment status, translation of intention to actual behaviour was poor. Barriers preventing healthy lifestyle were time, organising skills during stressful periods and cost. Future health was not a major concern, and neither was winning nor impressing others. ‘Appearance’, ‘feel good factor’, ‘have fun’ and ‘get a buzz’ were major motivators. In spite of identifying some of the crucial elements important in this age group, recruitment and determining the ideal time to intervene will be the challenges still to be addressed. Conclusion: Small behavioural changes homing in on the immediate benefits along with sustained support are more likely to produce changes in young people’s lifestyle which in turn, might lead to prevention of obesity in the long-term.

In this thesis the effects of rimonabant, the CB 1 endocannabinoid receptor antagonist, and gender on free fatty acid (FFA) and very-Iow-density lipoprotein (VLDL)-triacylglycerol kinetics, insulin sensitivity and circulating adipokines was examined in obese postmenopausal women and age- and body mass index (BMI)- matched men. In the first study, the effect of rimonabant (20 mg/day for 12 weeks, with energy intake matched for energy requirements) was compared with the effect of a hypocaloric diet (to achieve the same weight loss as on the rimonabant treatment, for 12 weeks). Forteen obese 2 . (BMI=33.0±0.5 kg/m), postmenopausal, aged 57.8±4.7 years Caucasian women were randomised to the 2 treatments and the following was measured at the baseline and after 12 weeks: FF A kinetics, VLDL-triglyceride kinetics; insulin sensitivity; circulating fasting glucose, FF A, glycerol, triglycerides, VLDL1 and VLDL2-triglycerides, total cholesterol, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, leptin, adiponectin and insulin. In the second study, the same variables were compared between 16 obese postmenopausal Caucasian women (57.9±5.4 years, BMI=::32.8±1.8 kg/m2) and 7 age- and BMI- matched men (60.6±6.6 years, BMI=31.5±1.4 kg/m2). Results: Weight loss was not different between 2 treatment groups in the first study (2.6±1.4 kg in the rimonabant group vs. 3.1±2.8 kg in the diet group, p>0.05). Rimonabant treatment increased palmitate rates of appearance (Ra), metabolic clearance rates (MCR) and oxidation rates, while dietary treatment did not influence these variables. The effect of rimonabant on palmitate oxidation rates was significantly different from the effect of the hypocaloric diet, as well as the effect on VLDL1 and VLDL2-triglyceride absolute production rates (APR), circulating fasting triglycerides, VLDL1- and VLDL2-triglycerides, glucose, insulin and homeostasis model assessment (HOMA)-estimates of insulin sensitivity. Both treatments similarly increased adiponectin and decreased leptin. Neither treatment significantly changed insulin sensitivity estimated by hyperinsulinaemic-euglycaemic clamp. In the second study, women had higher palmitate Ra, MCR, non-oxidative disposal and total plasma fatty acid oxidation (TPF AO) rates, VLDLl and VLDL2-triglyceride fractional clearance rates (FeR), circulating leptin, glycerol and FF A. The other variables were not significantly different. In conclusion, the increase in fatty acid tumover and oxidation may be the mechanism by which the weight loss was achieved by rimonabant treatment, without caloric restriction. The effects of rimonabant on FF A and VLDL-kinetics, insulin sensitivity and metabolic parameters, were the opposite from the effects of the hypocaloric diet, although the weight loss was similar. Postmenopausal obese women, compared with age- and BMI-matched men, have higher rates of fatty acid turnover, accounted by both increased metabolic clearance, non-oxidative disposal and increased fatty acid oxidation. However, their metabolic profile was not different from the men. This suggests that women are intrinsically "primed" for increased lipid turnover, without a significant deterioration of metabolic risk.

The accurate measurement of body composition in humans is pivotal to understanding the links between excess adiposity and metabolic abnormalities. The potential mechanisms linking obesity to ill-health have been the focus of obesity research including the more recent investigations between obesity and both vitamin D status and inflammation. The aim of this thesis was to investigate a number of indices of body composition as predictors of immune and inflammatory responses, and their implications for health across different subgroups of the population. The effect of adiposity on vitamin D status was examined in healthy adults in a 22-wk randomised- controlled intervention. Vitamin D status was inversely associated with adiposity at baseline, however, only BMI was inversely associated with the change in vitamin D status following supplementation (151lg vitamin D3/d). These findings were only demonstrated in older adults ~64yrs), but not in younger adults (20 -40yrs). The associations between indices of body composition and metabolic parameters [lipid profile, insulin resistance (Ik) and inflammation] were investigated in two groups of healthy, young adults: men and women (20-40yrs) and men (18-30yrs). Body composition was a strong predictor of lipid profiles and glucose metabolism in these groups, however in terms of inflammation, it was only predictive of CRP and adiponectin. Although the strongest relationships were observed with fat mass index [FMI (kg/m2)], BMI proved in most cases to be almost as strong a predictor of metabolic risk factors in healthy individuals, and therefore remains a useful and appropriate surrogate measure of adiposity. The measurement of FM using more robust techniques should not be discounted, but, it is imperative that this is expressed relative to height, as FML as relying on the more commonly used indices of FM (kg/%) may attenuate results.

Cholecystokinin-8 (CCK-8) is an important gastrointestinal (GI) peptide that is released from endocrine I-cells in response to feeding. CCK-8 promotes satiety, reducing food intake via the CCK1 receptor. It is also responsible for initiating insulin release from pancreatic beta cells. The hypothesis underlying this thesis was that CCK-8 properties may be exploitable for treatment for obesity and type 11 diabetes. CCK-8 is rapidly released by feeding but has a half life of only 1-2 min because of rapid degradation by aminopeptidase A. In the present study, the aminopeptidase A inhibitor, bestatin was shown to prevent N-terminal degradation of CCK-8 in mouse plasma. Furthermore, novel N-terminally modified CCK-S analogues, such as aceylated(Ac)-CCK-8 and pyroglutamyl p(GluGln)-CCK-S, as well as analogues with secondary pegylated[PEG] and palmitate[PAL] modifications, resisted enzyme degradation. These results suggested that amino terminal protection prevented enzymatic breakdown, raising the possibility of prolonged satiety effects in vivo. Indeed, novel N-terminally modified analogues of CCK-8 reduced food intake for a prolonged time and to a greater extent than native CCK-8. Further to this, these analogues significantly increased insulin secretion from clonal pancreatic BRIN-BD11 cells compared to native CCK-8. Acute in vivo studies also showed that CCK-8 and related analogues reduced the plasma glucose excursion when administered with glucose in normal and obese diabetic (ob/ob) mice. Long term studies involving daily injections of the analogue, p(GluGln)CCK- S, in normal, high fat fed and obese diabetic (ob/ob) mice resulted in significant reduction of both food intake and body weight as well as enhanced glucose tolerance and improved insulin sensitivity. Furthermore, intermittent treatment of obese and high fat fed mice with p(GluGln)CCK-8 significantly decreased body weight and improved glucose tolerance. Secondary modifications of this CCK-8 analogue, whereby a PEGylated moiety was attached to the C-terminus to promote binding to plasma proteins and extend the half life, were also assessed in vivo. p(GluGln)CCK- 8[PEG] exerted similar beneficial effects as p(GluGln)CCK-8 but no superior actions were recorded, possibly due to the low doses of analogue administered. The long term effects of p(GluGln)CCK-8 were examined in combination with other peptide therapeutics known to enhance either the secretion or action of insulin. The combination of p(GluGln)CCK-8 with glucagons like peptide (GLP-l) mimetic exendin-4 produced significantly greater benefic ial effects than either peptide alone. In acute studies, this combination significantly improved glucose tolerance in normal and obese diabetic mice (ob/ob) and potently stimulated insulin secretion from clonal pancreatic BRIN-BDll cells. Daily administration of the combination p(GluGln)CCK-8 plus exendin-4 to high fat fed mice decreased food intake, reduced body weight, increased insulin sensitivity and enhanced glucose tolerance. In other experiments, the gastric inhibitory polypeptide (GIP) receptor antagonist, Pro3GIP[PEG] was administered daily in eqimolar doses with p(GluGln)CCK-8 in high fat fed mice. These mice exhibited reduced food intake, decreased body weight and marked improvements in glucose tolerance and insulin sensitivity. However, each peptide alone produced prominent effects with no appreciable additive effects being observed in combination. In conclusion, this thesis has provided evidence that N-terminal modification of CCK-8 confers enzyme resistance, prolonged action and enhanced biological effects in animal models of obesity-diabetes. The ability to decrease food intake, promote weight loss and improve glucose homeostasis suggests that novel analogues, such as p(GluGln)CCK-8, might be exploitable clinically alone or in combination for the treatment of obesity and type 11 diabetes.

No description available.

The chronic illnesses associated with obesity cause over 30,000 deaths annually in the United Kingdom alone (Moon et al 2007). Pessimistic predictions regarding future obesity trends have highlighted that without government intervention, this grave problem is only going to worsen (Foresight 2007). The most recent figures estimate that 23.3% of men and 24.4% of women are currently obese in England (Health Survey for England, 2008a), with this proliferation in levels of obesity often branded the 'obesity epidemic' (BanweH et al 2005). Although it is acknowledged that genetics play some role in the Body Mass Index (BMI) of individuals, there is significant evidence of the influence of environmental factors upon individual health (World Health Organisation 2000; Kipke et al 2007; Frank et al 2004). The 'obesogenic environment' is defined as "the sum of the influences that the surroundings, opportunities, or conditions of life have on promoting obesity in individual's or populations" and is based upon the notion that our surroundings can drive an "automatic, unconscious influence ... [upon our] behaviour" (Swinburn and Egger 2002,292; Brug et a/2006, 528). Contributing to an as yet under-developed UK research evidence-base, within which this work should be seen as a pilot, this study used a multi-level, cross-sectional study design and data from the Health Survey for England (2005-2008, n=2118, aged 16-75), combined with critically appraised area level obesogenic environment metrics (n=30, focusing on access/availability/opportunity/variety of food (consumed within and without of the home), built (walkability related, both putative and innovative, including measures of the public transport landscape) and physical activity (green space and formal leisure facility) environments, constructed from a variety of secondary data sources (including local council's environmental health records», to assess the impact of the obesogenic environment in the former North East Government Office Region upon BMI, dietary patterns (including fruit and vegetable consumption) and physical activity behaviour (walking/sport frequency/duration). Results from adjusted multivariate and unadjusted analyses suggest that there is a modest environmental effect upon these outcome variables, yet results are not robust enough to delineate specific potential public health interventions. ContrOlling for putative individual and household level confounders and other aspects of diet, increased access to 'healthy' food bought out of the home was associated with decreased fruit consumption (r=0.218, p=0.003), whilst increased access to 'unhealthy' food consumed out of the home was associated with increased vegetable consumption (r=-0.141, p=0.032), 2 and increased availability with increased pulse consumption (r=0.193, p=0.022). Increased access to 'healthy' food outlets was associated with significantly higher BMI (r=-0.134, p=0.008). Moreover, many of the relationships discovered are in unexpected directions, resulting in a close scrutiny of the methods used, and a questioning of some established theoretical relationships. This research also aimed to examine the geography of the obesogenic environment within the study area, and to assess the extent to which this geography is related to area level socio-economic status (Index of Multiple Deprivation 2007) and ethnic mix (UK Census 2001) using a-spatial regression, analysis of variance and Geographically Weighted Regression (GWR) methods. Results suggest that the obesogenic environment varies markedly throughout the study area and systematically by socio-economic status and ethnic mix, with these inequities in the geography of the obesogenic environment framed here as an environmental justice concern, especially as these inequalities may not be self-evident to the exposed individuals'. However, deprived/more ethnic minority populations are not a/ways exposed to the most obesogenic environments. Importantly, GWR was able to offer considerably more insight into particularly vulnerable populations than a-spatial analysis methods.

Physiological processes display intrinsic circadian variations which are controlled by an endogenous circadian timing mechanism. Metabolic disease comprising type 2 diabetes and obesity is a recognised risk factor for cardiovascular disease (CVD). The early phase of atherosclerotic CVD is endothelial dysfunction and, like pre- diabetic insulin resistance, is a major focus of study. Metabolic and vascular disease may be linked through insulin resistance, which is now recognised to be a critical risk factor for the development both of endothelial dysfunction and of type 2 diabetes. A circadian component to cardiovascular and metabolic disease is evident from observations of human populations and recently critical animal studies have begun to elucidate the underlying mechanism. It is not known if circadian dysfunction is a central feature of acquired cardiometabolic disease, or if so at which stage in the disease process it develops. The effect of acquired insulin resistance upon circadian variation in insulin sensitivity and insulin signalling is also unclear. In a mouse model of diet-induced obesity, it was hypothesised that obesity is associated with pathological diminution of diurnal rhythms of systemic and cellular homeostasis and that such diminution is particularly associated with the occurrence of insulin resistance. In the cardiovascular system, aortic endothelial vasomotion studies and qPCR showed no loss of rhythm in obese animals despite clear differences in endothelial phenotype between obese and lean. When the focus of investigation was shifted to other insulin-sensitive tissues, the predicted attenuation of rhythm was found, with widespread diurnal abnormalities in obesity of systemic insulin and glucose homeostasis, rhythmic transcription of clock genes and downstream clock-controlled genes important to metabolic homeostasis, including AMPK. A gradient of tissue sensitivity to circadian disruption was seen, with marked disruption in visceral adipose but fully preserved rhythms in liver and aorta. Patterns of circadian disruption closely mirrored those of tissue inflammation but did not correspond to impaired insulin signalling, which was most marked in liver, followed by aorta. These findings put circadian disruption into the context of tissue- specific events in obesity. They suggest that circadian disruption and insulin resistance arise by distinct processes and prompt speculation regarding the cellular mechanism by which circadian disruption may arise in obesity. 3

MUTATED versions of membrane proteins often fail to express at the plasma membrane, but instead are trapped in the secretory pathway, resulting in disease. The retention of these mutant proteins is thought to result from local misfolding, which prevents export from the endoplasmic reticulum (ER), targeting the receptor for degradation via the Ek-associated quality control system. The rhodopsin-like G protein- coupled melanocortin 4 receptor (MC4R) is an example of such a membrane protein. Over a hundred natural MC4R mutations are linked with an obese phenotype and to date represent the most common monogenic cause of severe early-onset obesity. More than 80% of these mutations result in a substantial proportion of MC4R being retained intracellularly. If these receptors were expressed at the plasma membrane, they are likely to be functional, as many mutations occur in domains distinct from those associated with ligand or G-protein binding. The objective of this thesis was to develop high throughput cell culture based assays with which to monitor MC4R cell surface expression, with the view to screening potential pharmacological chaperones for their ability to promote trafficking to the plasma membrane. Subsequently, the rescued receptors were assessed for signalling capability, to investigate whether their cell surface rescue restored functionality. The work presented herein confirms that clinically occurring MC4R mutants V50M, S58C and I137T are intracellularly retained in HEK-293 cells to differing degrees. Whole cell ELISA and 96-well fluorescence-based assays with N-terminally HA-tagged and C-terminally mCherry-tagged mutant MC4R were used to screen a number of MC4R-selective compounds. Compound A had previously been shown to be a potent antagonist of MC4R, and in addition to this compound, three related compounds B, C and D increased the cell surface expression of wild type and mutant MC4R, thus acting as pharmacological chaperones. They appeared to be receptor specific, as ligands for other proteins failed to alter the cell surface expression of wild type or mutant MC4R, and also had an intracellular site of action. There appears to be a unique rescue profile for each drug which did not correlate with potency, suggesting distinct receptor conformations induced by the different mutations. Functionality of V50M and S58C was rescued following their relocation to the cell surface. IV From the computational analysis using an MC4R model, it is evident that such point mutations can result in markedly changed interactions between amino acidside chains, which may alter helical-helical packing and affect receptor stability and/or activation steps, without directly affecting the ligand binding pocket. Following rescue to the plasma membrane, the ECso and Emax values of V50M and S58C increased significantly, indicating that the misfold induced by these mutations have a lesser impact on the overall structure and stability of the receptor than the one induced by I137T. Following cell surface rescue, novel derivatives of Compound A were also shown to act as competitive antagonists of varying potencies. For the most part, there appears to be a clear separation in potency between Compound A and D, and Compound Band C, indicating that exchange of the centre linker azetidine ring for the piperazine ring results in a marked decrease in potency. Investigation into binding modes of Compounds A and B, using our MC4R model, suggests differential binding of the two compounds when the linker ring is exchanged. The rescue of intracellularly retained MC4R mutants using pharmacological chaperones is a promising and exciting concept that could prove to be a novel therapeutic avenue in the treatment of early-onset obesity.

The developed world is currently in the grip of an obesity epidemic. As a result, there is much ongoing research into the development of an effective anti-obesity agent. Peptide YY (PYY) is a 36 amino acid gastro-intestinal hormone released post-prandially by L-cells in the gastro-intestinal tract in proportion to the calorie content of a meal. The predominant form of the hormone found in circulation is the truncated PYY(3-36). Administration of PYY(3-36) at physiological doses to humans has been shown to reduce food intake. However, due to enzymatic degradation these effects are short lived, reducing the hormone’s utility as an anti-obesity pharmaceutical agent. A series of analogues of PYY(3-36) were designed either with amino acid substitutions in specific parts of the peptide sequence and/or with chemical modifications to the native sequence with the aim of increasing resistance to enzymatic activity whilst retaining or even enhancing the peptide’s bioactivity. The analogues were tested for resistance to degradation by different proteolytic enzymes in comparison to natural PYY(3-36). Their affinity to the Y2 receptor, for which PYY(3-36) is a natural agonist was then investigated. Finally, the effects of peripheral administration of selected analogues on food intake in overnight fasted mice were investigated. These studies suggest that PYY(3-36) analogues may be a useful approach for the treatment of obesity, but further development work is required.