Chelikani, Prasanth K.Zapata, Rizaldy C.2018-08-212018-08-212018-08-16http://hdl.handle.net/1880/107640The protein leverage hypothesis posits that protein restriction triggers a compensatory hyperphagia to facilitate the acquirement of the animal's protein needs whereas protein excess elicit hypophagia as the animal's protein requirement is met at a lesser calorie intake. However, the effects of dietary protein on energy expenditure and the underlying mechanisms are not well-established. Moreover, the domestic cat has potential to more closely model human obesity and diabetes; however, the role of dietary protein in the secretion of metabolic hormones has not been well-studied in cats. In this thesis, the effects of protein-restricted diets, tryptophan or histidine-restricted diets, and diets with excess protein on energy intake, energy expenditure, body weight and composition, gut hormones, glucose clearance, key protein and glucose metabolism markers and thermogenesis were determined in rodent models of diet-induced obesity. In addition, the tissue distribution of the transcripts for proglucagon, glucose-dependent insulinotropic peptide, peptide YY and their cognate receptors in feline peripheral tissues and the effects of the consumption of high-protein diets on the concentrations of circulating metabolites and metabolic hormones were determined in lean, overweight and diabetic cats. Using diet-induced obese rats and a clinical population of domestic cats, this work provided important insights on the mechanisms by which dietary protein regulates energy balance. First, moderately restricting dietary protein transiently promoted hyperphagia yet robustly increased energy expenditure. Second, tryptophan restriction partially recapitulates the age-dependent effects of moderate protein restriction on energy intake and expenditure. Third, the protein source has a significant contribution on the hypophagic and thermogenic effects of high-protein diets, with the increased PYY signaling and reduced diet preference mediating this reduction in energy intake, but not thermogenesis. Finally, although there were inherent differences in plasma concentrations of metabolic hormones between lean, overweight and diabetic cats, protein consumption alone did not alter weight or the secretion of these hormones. Collectively, dietary protein greatly influences energy balance in rodent models of human obesity, but has minimal impact in domestic cats.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.energy balanceprotein restrictionhigh protein dietswhey proteinslactalbuminlactoferrinpeptide YYdomestic catsfibroblast growth factor 21protein leverage hypothesistryptophanhistidineenergy expenditureAnimal PhysiologyVeterinary ScienceNutritiondoctoral thesis10.11575/PRISM/32820