Browsing by Author "McMillan, Chantal J."

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    Dietary Protein Interacts with Prebiotic Fiber to Modulate Energy Balance and Body Composition
    (2021-01-05) Avirineni, Bharath Sai Srinivas; Chelikani, Prasanth K.; McMillan, Chantal J.; Pang, Daniel S.; DeVinney, Rebekah
    Background: Incidence of obesity is increasing throughout the world. Dietary supplementation of protein and fiber have been individually demonstrated to promote weight loss. However, less is known, about the underlying mechanisms by which diets containing a combination of protein and fiber interact to improve energy balance and promote weight loss. Objectives: The overall objectives of this dissertation were: 1) to determine the interactive effects of dietary protein and fiber on energy balance, body composition and gut microbiota in obesity prone (OPCD) rats; 2) to determine combined effects of protein and fiber enriched diets along with exercise training on energy balance, body composition, gut microbiota in OPCD rats. Methodology: In experiment-1, rats were randomized into four treatment groups- Egg albumin + Cellulose (EC), Egg albumin + Inulin (EI), Whey protein concentrate + Cellulose (WC), and Whey protein concentrate + Inulin (WI) groups. In experiment 2, the effects of identical treatment groups along with exercise were studied. Food intake, energy expenditure, respiratory quotient, and body composition were measured using CLAMS® metabolic chambers and magnetic resonance imaging. The mRNA abundance of tissue markers and gut microbiota composition were measured using qPCR technique. Results: The primary findings were: 1) supplementation of dietary egg or whey protein with inulin fiber promoted greater hypophagia, in conjunction with an increase in fat oxidation. Whey-inulin group increased cholecystokinin (CCK) and peptide YY (PYY) mRNA abundance in the gut, and CCK-1 receptor antagonist attenuated the hypophagic response of the diets. Egg-cellulose and inulin enriched diets (EI, WI) decreased weight, adiposity gains and selectively modulated gut microbiota by specifically increasing Bacteroidetes or Bifidobacterium and decreased Roseburia. 2) Diets containing egg or whey protein and inulin fibre together with exercise transiently decreased energy intake. Egg-cellulose and inulin enriched diets combined with exercise decreased body weight gains, liver fat and improved glycemic control partly through modulations in plasma concentrations of insulin, leptin and selective gut microbiota. Conclusion: Collectively, our findings provide evidence that consuming diets containing egg or whey protein and inulin fiber together with exercise improves energy balance and body composition with significant implications for preventing and treating obesity.
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    Regulation of Energy Balance by Dietary Protein
    (2018-08-16) Zapata, Rizaldy C.; Chelikani, Prasanth K.; Ambrose, D. J.; Banse, Heidi E.; McMillan, Chantal J.; Vijayan, Mathilakath Madathil; Morrison, Christopher David
    The 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.