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Title:Effect of dietary protein source on satiety, postprandial blood biomarkers, and metabolism
Author(s):Du, Kristy
Director of Research:Rhodes, Justin S; Dailey, Megan J
Doctoral Committee Chair(s):Pan, Yuan-Xiang
Doctoral Committee Member(s):Liang, Nu-Chu
Department / Program:Nutritional Sciences
Discipline:Nutritional Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Dietary protein
egg white protein
wheat gluten protein
protein source
satiety
food intake
energy expenditure
plasma amino acids
insulin
postprandial
Abstract:High protein diets have become an increasingly popular dieting strategy, but the extent to which different protein sources are similarly anorexigenic and the mechanisms involved are less certain. It was previously observed that male Sprague-Dawley rats given a 35% egg white protein meal at the first meal of the day were more satiated in the initial hours following the meal than when provided a 35% wheat gluten protein meal. The objective of this study was to examine the effect of the source and level of protein on subsequent feeding behavior, metabolism, and changes in plasma amino acids and insulin levels in order to identify possible mechanisms involved in differences of satiety. Rats were entrained to a meal-feeding schedule, which included an overnight fast before being provided a 30-minute treatment meal. The treatment meals consisted of one of four isocaloric diets equivalent to 10-20% of average daily intake and were administered one hour into the dark phase: 20% egg white protein (20EW), 20% wheat gluten protein (20WG), 35% egg white protein (35EW), or 35% wheat gluten protein (35WG). Ad libitum access to a control diet was made available later in the dark phase. Blood plasma was collected from rats surgically implanted with jugular catheters at baseline and at 30-minute intervals for two hours following test meal ingestion, and analyzed for amino acid and insulin concentrations. Separate cohorts of rats were assessed for feeding behavior and metabolism following acute and chronic treatment paradigms. Egg white meals increased total amino acids, as well as specific amino acids including lysine, isoleucine, valine, and tryptophan more than wheat gluten meals (P<0.005). Insulin levels reflected level of protein rather than source. Rats fed egg white displayed decreased food intake at the subsequent meal compared to wheat gluten, regardless of protein level or sex (both P<0.005). The respiratory exchange ratio following ingestion of 35EW was lower than the other treatment meals for several hours following ingestion (P<0.001), however, energy expenditure did not differ among treatments groups. When administered over the course of 30 days, the treatments had no effect on changes in body weight, body composition, energy intake, or energy expenditure. Results confirmed that meals containing egg white protein induced greater satiety than wheat gluten protein, which corresponded to increased postprandial plasma amino acids and lowered respiratory exchange ratio following egg white protein meals. Although dietary source of protein has significant short term implications for satiety and metabolism, manipulation of the protein component of a single meal of the day has minimal long term effects on body weight and composition. Altogether, these results emphasize the importance of considering protein source when designing diets to control appetite.
Issue Date:2017-05-31
Type:Thesis
URI:http://hdl.handle.net/2142/98219
Rights Information:Copyright 2017 Kristy Du
Date Available in IDEALS:2017-09-29
Date Deposited:2017-08


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