The Postprandial Metabolic and Appetite Effects of Pre-Meal Whey Protein Supplementation: Implications for the Treatment of Type 2 Diabetes

Abstract

For people with and without type 2 diabetes [T2D], the regulation of postprandial glycaemia [PPG] is critical to optimising glycaemic control and reducing the risk of cardiovascular complications. Proof-of-concept studies have demonstrated that consuming whey protein [WP] before meals reduces PPG excursions via several pancreatic and gastrointestinal mechanisms. However, the extent by which these results can be translated into practice and be used for everyday care remains unclear. The studies presented in this thesis examined the real-world applicability and acceptability of a bespoke-made, pre-meal WP shot, and delineated some of its glucose lowering mechanisms in a population deemed at risk of cardio metabolic complications and in people with overt T2D. Chapter 3 studied the effects of pre-meal WP in centrally obese adult males and compared these responses to lean comparators during a laboratory-based feeding test. This study revealed a marked reduction in PPG in both cohorts with pre-meal WP supplementation, which were accompanied with the sustained release of glucagon-like peptide 1 and the slowing of gastric emptying. Chapter 4 highlighted that the prevalence of daily hyperglycaemia remains an underestimated problem for people with T2D. However, the daily time spent in hyperglycaemia can be reduced by consuming a small dose of WP before each main meal during 7days of free-living. In Chapter 5, the glucose lowering mechanisms associated with pre-meal WP in people with T2D were investigated during a mixed-meal tolerance test. This study revealed that pre-meal WP integrates an enhancement in β-cell function with a reduction in insulin clearance to produce an effective plasma insulin profile to reduce PPG. Lastly, in Chapter 6, barriers and facilitators to pre-meal WP supplementation as a viable treatment for T2D were explored, demonstrating the importance of supplement palatability and ease of consumption, as well as the influence of social factors on treatment uptake. Collectively, this thesis shows that pre-meal consumption of WP stimulates several coordinated mechanisms to reduce PPG excursions. Presenting a nutrient preload in the format of a discrete, ready-to-drink shot containing a low dose of a palatable WP ingredient is an effective way to implement this strategy in the free-living community, which could hold therapeutic significance at a time where public health budgets are constrained.