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Ely, Isabel (2024) The impact of leucine-enriched whey protein on skeletal muscle anabolism. PhD thesis, University of Nottingham.

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Abstract

The preservation of skeletal muscle (SKM) throughout the lifespan is vital for maintaining health and well-being. SKM is tightly regulated and maintained by the dynamic relationship between muscle protein synthesis (MPS) and muscle protein breakdown (MPB), with SKM protein turnover occurring at a rate of ~1– 2% per day in healthy younger adults. Protein feeding and exercise are the most potent stimulators of MPS with synergistic action occurring to promote SKM mass through increased MPS and suppressed MPB. However, rates of MPS and MPB are also influenced by physical inactivity and ageing, contributing to SKM atrophy and functional declines.

Sarcopenia, the age-related decline in muscle mass and function, is a significant predictor of age-related disability and mortality, and impacts every individual across the globe. Although inevitable and inescapable, performing physical activity/exercise and maintaining a balanced healthy diet throughout life significantly alters the rate at which this functional decline progresses and the presence of disease. As sarcopenia is a multifaceted condition, we specifically focus on the role of SKM anabolic resistance in older age and how dietary protein and exercise interventions can maximise healthy ageing throughout this project.

Following consumption of dietary protein and/or amino acids (AA), MPS is increased temporally and transiently. Regardless of protein source, SKM is receptive to the essential amino acid (EAA) component of a protein meal, in particular leucine (LEU), which is thought to be the most potent AA for stimulating MPS. Interestingly, LEU can stimulate MPS in isolation and through the consumption of low-dose LEU-enriched protein. In some instances, suboptimal doses of LEU-enriched protein have matched the anabolic response of larger doses of protein. b-lactoglobulin (BLG) is the most abundant whey protein (WP) in bovine milk and is rich in EAA and LEU. There has yet to be a thorough investigation of the effects of BLG supplementation on SKM anabolism in both younger and older individuals. Therefore, this thesis is divided into a narrative review and three research chapters aiming to determine the impact of LEU-enriched WP on SKM anabolism.

We initially focus on the importance of LEU supplementation for SKM anabolism in differing physiological states, through our narrative review (Chapter 3). We then aimed to investigate the efficacy of BLG supplementation on SKM anabolism at rest and following acute resistance exercise (RE), using stable isotope tracers. Chapters 4 and 5 focus on the anabolic effects of BLG compared to an isonitrogenous whey protein isolate (WPI) in young and older individuals, respectively. Chapter 6 explores different doses of BLG on SKM anabolism in older adults only. We demonstrate throughout this thesis that BLG is an effective nutritional supplement to stimulate SKM anabolism in differing populations and may be an effective intervention, alongside RE, in offsetting sarcopenia in advancing age.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Atherton, Philip Phillips, Bethan Larsen, Mads Breen, Leigh
Keywords:	Skeletal muscle; Sarcopenia; Anabolic resistance; Dietary protein; Exercise interventions; Muscle protein synthesis; Nutritional supplements
Subjects:	W Medicine and related subjects (NLM Classification) > WE Muscoskeletal system
Faculties/Schools:	UK Campuses > Faculty of Medicine and Health Sciences > School of Medicine
Item ID:	79403
Depositing User:	Ely, Isabel
Date Deposited:	11 Dec 2024 04:40
Last Modified:	11 Dec 2024 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/79403

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