Insulin resistence in adult type-2 diabetic skeletal muscle : the effects of exercise and dietary-protein induced skeletal mucscle plasticity controlling microvascular blood flow and glucose transport : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Sport and Exercise Science), Massey University, Wellington, New Zealand

Abstract

Introduction: Insulin-stimulated skeletal muscle glucose uptake is impaired in Type-2 Diabetes Mellitus (T2DM). Insulin resistance leads to reduced skeletal muscle microvascular function and insulin signalling. The purpose of the thesis was to evaluate and compare the effect of chronic intake of a novel keratin-derived protein (WDP) and whey protein, in conjunction with exercise training, on glucose homeostasis and skeletal muscle glucose uptake in T2DM. Methods: In a randomized, double-blinded clinical trial, thirty-five men and women with T2DM completed a 14-week exercise intervention but were randomly assigned to ingest either post-exercise and evening supplements of 20 g WDP-whey protein blend (WDP, n = 11), whey protein (WHEY, n = 12) or isocaloric maltodextrin (CON, n = 12). Before and after the intervention, fasting HbA1c and glucose clearance rate (GCR) during a hyperinsulinaemic isoglycaemic clamp were measured. Insulin-stimulated skeletal muscle blood flow and volume were measured during the clamps via near -infrared spectroscopy. Muscle from the m. vastus lateralis was harvested prior to and at 1-h into the clamps to determine skeletal muscle insulin signalling proteins. Results: Substantially bigger improvements in WDP compared to WHEY or CON were found for GCR, insulin-stimulated GLUT4 translocation and insulin-stimulated blood flow. Fasting eNOSser1177/eNOS possibly increased in WDP and WHEY compared to CON. Capillarization improved in all groups with unclear differences between groups. Conclusion: WDP-whey blend ingestion during 14 weeks of exercise training improved skeletal muscle plasticity and some processes involved in insulin-stimulated glucose uptake to a greater magnitude compared to whey protein or an exercise-only group in T2DM. WDP protein holds the potential to be an additional therapy to exercise as a treatment in T2DM.