Effects of leucine-enriched essential amino acid and whey protein bolus dosing upon skeletal muscle protein synthesis at rest and after exercise in older women

Wilkinson, Daniel J. and Bukhari, Syed S.I. and Phillips, Bethan E. and Limb, Marie C. and Cegielski, Jessica and Brook, Matthew S. and Rankin, Debbie and Mitchell, William K. and Kobayashi, Hisamine and Williams, John P. and Lund, Jonathan N. and Greenhaff, Paul L. and Smith, Kenneth and Atherton, Philip J. (2017) Effects of leucine-enriched essential amino acid and whey protein bolus dosing upon skeletal muscle protein synthesis at rest and after exercise in older women. Clinical Nutrition . ISSN 1532-1983 (In Press)

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Abstract

Background & aims: Impaired anabolic responses to nutrition and exercise contribute to loss of skeletal muscle mass with ageing (sarcopenia). Here, we tested responses of muscle protein synthesis (MPS), in the under represented group of older women, to leucine-enriched essential amino acids (EAA) in comparison to a large bolus of whey protein (WP).

Methods: Twenty-four older women (65 ± 1 y) received (N ¼ 8/group) 1.5 g leucine-enriched EAA supplements (LEAA_1.5), 6 g LEAA (LEAA_6) in comparison to 40 g WP. A primed constant I.V infusion of 13C6-phenylalanine was used to determine MPS at baseline and in response to feeding (FED) and feeding-plus-exercise (FED-EX; 6 x 8 unilateral leg extensions; 75%1-RM). We quantified plasma insulin/AA concentrations, leg femoral blood flow (LBF)/muscle microvascular blood flow (MBF), and anabolic signalling via immunoblotting.

Results: Plasma insulineamia and EAAemia were greater and more prolonged with WP than LEAA, although LEAA_6 peaked at similar levels to WP. Neither LEAA or WP modified LBF or MBF. FED increased MPS similarly in the LEAA_1.5, LEAA_6 and WP (P < 0.05) groups over 0e2 h, with MPS significantly higher than basal in the LEAA_6 and WP groups only over 0e4 h. However, FED-EX increased MPS similarly across all the groups from 0 to 4 h (P < 0.05). Only p-p70S6K1 increased with WP at 2 h in FED (P < 0.05), and at 2/4 h in FED-EX (P < 0.05).

Conclusions: In conclusion, LEAA_1.5, despite only providing 0.6 g of leucine, robustly (perhaps maximally) stimulated MPS, with negligible trophic advantage of greater doses of LEAA or even to 40 g WP. Highlighting that composition of EAA, in particular the presence of leucine rather than amount is most crucial for anabolism.

Item Type: Article
Keywords: Muscle protein synthesis; Leucine; Ageing; Low dose amino acid supplementation; Exercise; Human metabolism
Schools/Departments: University of Nottingham, UK > Faculty of Medicine and Health Sciences > School of Medicine
Identification Number: 10.1016/j.clnu.2017.09.008
Depositing User: Eprints, Support
Date Deposited: 07 Nov 2017 14:54
Last Modified: 08 Nov 2017 05:55
URI: http://eprints.nottingham.ac.uk/id/eprint/47938

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