9:00 am - 10:00 am
1-040 Li Ka Shing Centre, University of Alberta, Oborowsky Degner Seminar Hall (1-040) , Edmonton
A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES PhD Final Exam Seminar by Maha Alsaif. This seminar is open to the general public to attend.
Thesis Topic: The Impact of Dietary Protein on Appetite-Regulating Hormones and Energy Metabolism in Children with Prader-Willi Syndrome
PhD with Drs. Carla Prado and Andrea Haqq
Prader-Willi syndrome (PWS) is a unique model of childhood obesity characterized by disordered satiety. The excessive weight gain caused by an imbalance between energy intake and expenditure associated with PWS is of concern to healthcare professionals and caregivers who acknowledge that weight management is an essential but challenging aspect of care for these children. To improve the effectiveness of treatments to curb the development of obesity in children with PWS, a more comprehensive understanding of the underlying mechanisms associated with altered energy balance is needed. Therefore, the overall objective of this research was (1) to determine the impact of food intake (FI), higher protein (HP) meals and standard meals (SM) on postprandial regulation of ghrelin; (2) other satiety factor concentrations; and (3) energy balance in children with PWS.
In study 1, two test meals were compared to a SM meal in 10 children with PWS and 7 body mass index (BMI) z-score matched children in a randomized, crossover study design. The first test meal had a higher protein–lower carbohydrate (HP-LC) content and the second test meal had a higher protein–lower fat (HP-LF) content. Under fasting conditions, the PWS group had higher concentrations of both acyl ghrelin (AG) (p = 0.02) and desacyl ghrelin (DAG) than controls, but a comparable ratio of AG:DAG. AG and DAG were reduced in both groups following all meals, but concentrations of AG and DAG remained higher in PWS across all postprandial time points (p = 0.002 and p < 0.001, respectively). Glucagon-like peptide 1 (GLP-1) concentrations were higher after the HP-LC meal than the SM at 2 and 4 hours (p = 0.027 and p = 0.044, respectively) and at hour 4 (p = 0.02) following the HP-LF in the PWS group only; peptide tyrosine tyrosine (PYY) responses were comparable.
In study 2, in a randomized, crossover study design, 5 youth with PWS were randomly allocated to two isocaloric arms: a) standard diet (SD); b) HP diet. Participants received the prescribed diets (three meals plus two snacks per day accompanied by either a powder supplement (HP) or an extra snack (SD) for one day prior to each study visit and a breakfast meal inside a whole-body calorimetry unit (WBCU). Resting energy expenditure (REE), postprandial energy expenditure (PEE) and respiratory exchange ratio (RER) were assessed. PEE calculated as “fixed REE” was higher after the HP meal compared to SM. A lower RER was observed after the HP diet in comparison to the SD (0.80 ± 0.2 vs 0.86 ± 0.2; p < 0.009). However, no difference in subjective appetite assessment between the HP meal and the SM was found.
The major findings of this research were that higher concentrations of total ghrelin in children with PWS were due to higher concentrations in both AG and DAG, with no change in the AG:DAG ratio. Meal consumption also suppressed both forms of ghrelin to a greater extent in children with PWS. Higher protein meals stimulated greater increases in GLP-1 and PYY in PWS children compared to controls. RER after the HP diet was significantly lower compared to SD. In addition, this research highlights the heterogeneity in PEE in youth with PWS in response to HP diet and will contribute to the design of further research exploring PEE; considering, sex, pubertal status and body composition factors that influence response to energy metabolism in children with and without PWS.