| dc.description.abstract | Skeletal muscle is critical for human locomotion, postural control and the regulation of whole-body metabolism. Concomitantly, understanding how the food we eat influences skeletal muscle protein metabolism, and skeletal muscle mass, is vitally important. This is particularly true in those seeking to increase skeletal muscle mass, and for older individuals seeking to mitigate the seemingly inevitable loss of muscle mass. It is exceptionally well evidenced that protein ingestion increases muscle protein synthesis rates, with postprandial elevations in plasma essential amino acids (and leucine in particular) predominately responsible. The foundation of our evidence-base on protein intake and muscle protein synthesis rates in humans has largely been formed by investigating animal-derived protein sources, which are potent stimulators of muscle protein synthesis rates. However, there is relatively little comparative data in non-animal-derived sources. Consequently, given the prevalence of non-animal-derived proteins within the diet, there is a pressing need to develop an evidence base for sustainable alternative non-animal-derived protein sources. Mycoprotein, Fusarium venenatum, is a sustainably produced fungal derived whole food protein source. Accordingly, the purpose of this thesis was to thoroughly characterise the effect that mycoprotein ingestion has on muscle protein synthesis rates and muscle mass, with specific attention afforded to the interaction between mycoprotein ingestion and resistance exercise in younger and older adults. Firstly, I demonstrate the novel finding that the ingestion of a single bolus of mycoprotein (70 g; 31.5 g protein, 2.5 g leucine) stimulates resting and post-exercise muscle protein synthesis rates, and that it does so to a greater extent than a leucine matched bolus of milk protein (Δ 0.040±0.006 vs Δ 0.018±0.005%·h-1, respectively; P<0.01). I followed this by demonstrating that ingesting a smaller, more palatable, dose (35 g) of mycoprotein, enriched with BCAAs, was unable to stimulate resting or post-exercise muscle protein synthesis rates to the same extent as a BCAA matched larger bolus (70 g) of mycoprotein (Δ 0.040±0.006 vs Δ 0.019±0.005%·h-1, respectively; P<0.05). In both cases, greater muscle protein synthesis rates were observed following the ingestion of a 70 g bolus of mycoprotein, despite significantly lower plasma leucine concentrations, perhaps suggesting the presence of a “whole food” potentiating effect. Conjunctively, these data suggested to us that mycoprotein would support skeletal muscle remodelling over a longer period of time. As such, I subsequently transitioned to investigating daily muscle protein synthesis rates in both young and older individuals, who consumed either an omnivorous (OMNI) or non-animal-derived (VEG) high-protein (1.8 g·kg body mass-1·d-1) diet for three days, whilst completing a daily bout of resistance exercise. Omnivorous and non-animal-derived dietary protein sources supported equivalent rested and exercised daily myofibrillar protein synthesis rates in both younger (OMNI 2.19±0.14 vs 2.46±0.11%·d-1, VEG 2.01±0.17 vs 2.39±0.09%·d-1; P>0.05), and older individuals (OMNI 1.59±0.12 vs 1.77±0.12%·d-1, VEG 1.76±0.14 vs 1.93±0.12%·d-1; P>0.05). As such, obtaining dietary protein from animal-derived sources is not an essential prerequisite to support daily myofibrillar protein synthesis rates in healthy younger and older adults. I translated this line of work further, demonstrating that a high-protein (~2 g·kg body mass-1·d-1), mycoprotein-rich, non-animal-derived diet can support equivalent resistance training-induced skeletal muscle adaptation as a high-protein omnivorous diet. After progressively resistance training 5 d/week for 10 weeks, increases in lean mass (OMNI 2.6±0.3 kg, VEG 3.1±0.8 kg; P>0.05), thigh muscle volume (OMNI 8±1%, VEG 8.2±1.4%; P>0.05), muscle fibre CSA (OMNI 33±10%, VEG 32±17%; P>0.05), and various measures of muscle strength (P>0.05) were equivalent, regardless of whether participants consumed an omnivorous or non-animal-derived diet. In turn, this demonstrates that under near-optimal nutritional and exercise-training conditions, non-animal-derived diets have the capacity to facilitate hypertrophic and strength adaptations in healthy young men and women. Collectively this thesis demonstrates that mycoprotein is an anabolic non-animal-derived protein source, capable of stimulating acute postprandial muscle protein synthesis rates, supporting daily muscle protein synthesis rates when incorporated into a non-animal-derived diet, in both young and older individuals, and, as a result, facilitative of considerable resistance training-induced skeletal muscle remodelling. Therefore, herein details a unique and novel body of work characterising the effect of mycoprotein on skeletal muscle tissue, translating from the level of molecular and metabolic minutiae, to the level of functional movement. | en_GB |
