Lifelong endurance training attenuates age-related genotoxic stress in human skeletal muscle

James N Cobley,Graeme L Close,Sarah Waldron,James P Morton,Scott Murray,Jatin G Burniston,Warren Gregson,Lesley A Iwanejko,George K Sakellariou

doi:10.1186/2046-2395-2-11

Abstract

BackgroundThe aim of the present study was to determine the influence of age and habitual activity level, at rest and following a single bout of high-intensity exercise, on the levels of three proteins poly(ADP-ribose) polymerase-1 (PARP-1), cleaved-PARP-1 and poly(ADP-ribose) glycohydrolase (PARG), involved in the DNA repair and cell death responses to stress and genotoxic insults. Muscle biopsies were obtained from the vastus lateralis of young trained (22 ± 3 years, n = 6), young untrained (24 ± 4 years, n = 6), old trained (64 ± 3 years, n = 6) and old untrained (65 ± 6 years, n = 6) healthy males before, immediately after and three days following a high-intensity interval exercise bout.ResultsPARP-1, which catalyzes poly(ADP-ribosyl)ation of proteins and DNA in response to a range of intrinsic and extrinsic stresses, was increased at baseline in old trained and old untrained compared with young trained and young untrained participants (P ≤ 0.05). Following exercise, PARP-1 levels remained unchanged in young trained participants, in contrast to old trained and old untrained where levels decreased and young untrained where levels increased (P ≤ 0.05). Interestingly, baseline levels of the cleaved PARP-1, a marker of apoptosis, and PARG, responsible for polymer degradation, were both significantly elevated in old untrained compared with old trained, young trained and young untrained (P ≤ 0.05). Despite this baseline difference in PARG, there was no change in any group following exercise. There was a non-significant statistical trend (P = 0.072) towards increased cleaved-PARP-1 expression post-exercise in younger but not old persons, regardless of training status.ConclusionsCollectively, these results show that exercise slows the progression towards a chronically stressed state but has no impact on the age-related attenuated response to acute exercise. Our findings provide valuable insight into how habitual exercise training could protect skeletal muscle from chronic damage to macromolecules and may reduce sarcopenia in older people.

Highlights

The aim of the present study was to determine the influence of age and habitual activity level, at rest and following a single bout of high-intensity exercise, on the levels of three proteins poly(ADP-ribose) polymerase-1 (PARP-1), cleaved-PARP-1 and poly(ADP-ribose) glycohydrolase (PARG), involved in the DNA repair and cell death responses to stress and genotoxic insults
Post-hoc analysis confirmed that total PARP-1 was significantly increased in the old trained compared with both young trained (P = 0.001) and young untrained (P = 0.001) participants
PARP-1 was significantly increased in the old untrained compared with young untrained (P = 0.001) and there was a trend for an increase in the old untrained compared with young trained (P = 0.086)

Summary

Introduction

The aim of the present study was to determine the influence of age and habitual activity level, at rest and following a single bout of high-intensity exercise, on the levels of three proteins poly(ADP-ribose) polymerase-1 (PARP-1), cleaved-PARP-1 and poly(ADP-ribose) glycohydrolase (PARG), involved in the DNA repair and cell death responses to stress and genotoxic insults. One theory is that mitochondrial dysfunction leads to oxidative stress and can contribute to the ageing process by the accumulation of DNA damage and mutations and via cell depletion, as a consequence of senescence and apoptosis [8]. Recent evidence connects mitochondrial dysfunction with apoptosis in skeletal muscle suggesting that increased DNA damage with age could promote apoptosis and fiber loss [11,12]

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