Whole-body insulin sensitivity and changes in skeletal muscle insulin signalling in response to protein ingestion and exercise

Abstract

This thesis investigated the whole-body and local changes in insulin sensitivity in response to protein ingestion with and without resistance exercise training, in individuals both with obesity (Chapter 3) and those with healthy weight (Chapter 4). Chapter 1 serves as an introduction to the main theme of the thesis, while Chapter 2, delves into the potential mechanisms through which dietary amino acids can modulate insulin signalling. In Chapter 3, we investigated the immediate effects of various protein interventions: moderate protein (50g), high protein (100g), and moderate protein with added fat, serving as a control group. This research demonstrates a decrease in IP6K1 protein content (p=0.048) following the consumption of a high-protein meal. This reduction hints at a possible association with a reduction in insulin resistance. Notably, this IP6K1 decline coincides with an increase in the ratio of phosphorylated AktThr308 to total Akt2 activity (p=0.046). Nevertheless, despite these protein-related changes, no discernible alterations in insulin sensitivity or glucose effectiveness during the IVGTT were observed. In Chapter 4, our focus shifts towards the extended effects of a 10-week protein supplementation regimen, both with and without concurrent exercise interventions. The combined approach of exercise and protein supplementation resulted in a reduction in muscle IP6K1 content. Conversely, exercise without protein supplementation led to an increase in muscle IP6K1 compared to the exercised muscle, accompanied by elevated fasting insulin (p=0.039) and HOMA-2IR (p=0.004) post-exercise training in this group. Additionally, protein supplementation had some additional adverse effects in the non-exercised leg, including a reduction in the ratio of phosphorylated AktSer473 to total Akt2 activity (p=0.046). In summary, our findings indicate that high dietary protein intake leads to notable improvements in IP6K1 content acutely. However, for long-term benefits, our research suggests that protein supplementation is most effective when integrated with exercise.

Date of Award	23 Apr 2024
Original language	English
Awarding Institution	University of Roehampton
Supervisor	Richard Mackenzie (Director of Studies) & Astrid Hauge Evans (Co-Supervisor)