Early structural remodeling and deuterium oxide-derived protein metabolic responses to eccentric and concentric loading in human skeletal muscle

Franchi, Martino V. and Wilkinson, Daniel J. and Quinlan, Jonathan I. and Mitchell, William K. and Lund, Jonathan N. and Williams, John P. and Reeves, Neil D. and Smith, Kenneth and Atherton, Philip J. and Narici, Marco V. (2015) Early structural remodeling and deuterium oxide-derived protein metabolic responses to eccentric and concentric loading in human skeletal muscle. Physiological Reports, 3 (11). e12593/1-e12593/11. ISSN 2051-817X

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Abstract

We recently reported that the greatest distinguishing feature between eccentric (ECC) and concentric (CON) muscle loading lays in architectural adaptations: ECC favors increases in fascicle length (Lf), associated with distal vastus lateralis muscle (VL) hypertrophy, and CON increases in pennation angle (PA). Here, we explored the interactions between structural and morphological remodeling, assessed by ultrasound and dual x‐ray absorptiometry (DXA), and long‐term muscle protein synthesis (MPS), evaluated by deuterium oxide (D2O) tracing technique. Ten young males (23 ± 4 years) performed unilateral resistance exercise training (RET) three times/week for 4 weeks; thus, one‐leg trained concentrically while the contralateral performed ECC exercise only at 80% of either CON or ECC one repetition maximum (1RM). Subjects consumed an initial bolus of D2O (150 mL), while a 25‐mL dose was thereafter provided every 8 days. Muscle biopsies from VL midbelly (MID) and distal myotendinous junction (MTJ) were collected at 0 and 4‐weeks. MPS was then quantified via GC–pyrolysis–IRMS over the 4‐week training period. Expectedly, ECC and CON RET resulted in similar increases in VL muscle thickness (MT) (7.5% vs. 8.4%, respectively) and thigh lean mass (DXA) (2.3% vs. 3%, respectively), albeit through distinct remodeling: Lf increasing more after ECC (5%) versus CON (2%) and PA increasing after CON (7% vs. 3%). MPS did not differ between contractile modes or biopsy sites (MID‐ECC: 1.42 vs. MID‐CON: 1.4% day−1; MTJ‐ECC: 1.38 vs. MTJ‐CON: 1.39% day−1). Muscle thickness at MID site increased similarly following ECC and CON RET, reflecting a tendency for a contractile mode‐independent correlation between MPS and MT (P = 0.07; R2 = 0.18). We conclude that, unlike MT, distinct structural remodeling responses to ECC or CON are not reflected in MPS; the molecular mechanisms of distinct protein deposition, and/or the role of protein breakdown in mediating these responses remain to be defined.

Item Type: Article
Keywords: Exercise; hypertrophy; metabolism; muscle architecture; protein synthesis
Schools/Departments: University of Nottingham, UK > Faculty of Medicine and Health Sciences > School of Medicine > Division of Medical Sciences and Graduate Entry Medicine
Identification Number: 10.14814/phy2.12593
Depositing User: Eprints, Support
Date Deposited: 01 Aug 2017 09:45
Last Modified: 12 Oct 2017 23:10
URI: http://eprints.nottingham.ac.uk/id/eprint/44533

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