title: Expression patterns of atrogenic and ubiquitin proteasome component genes with exercise: effect of different loading patterns and repeated exercise bouts.
abstract: Unaccustomed exercise is known to produce strength loss, soreness, and myocellular disruption. With repeated application of exercise stimuli, the appearance of these indexes of muscle damage is attenuated, the so-called "repeated bout effect." No direct connection has been established between this repeated bout effect and exercise-induced increases in protein turnover, but it appears that a degree of tolerance is developed toward exercise for both. The present study sought to investigate markers of protein degradation by determining the expression of components related to the ubiquitin-proteasome system (UPS) with repeated exercise bouts. Healthy men carried out 30 min of bench stepping, performing eccentric work with one and concentric work with the other leg (n = 14), performing a duplicate exercise bout 8 wk later. A nonexercising control group was included (n = 6). RNA was extracted from muscle biopsies representing time points preexercise, +3 h, +24 h, and +7 days, and selected mRNA species were quantified using Northern blotting. The exercise model proved sufficient to produce a repeated bout effect in terms of strength and soreness. For forkhead box O transcription factor 1 (FOXO1) and muscle RING finger protein-1 (MURF1), strong upregulations were seen exclusively with concentric loading (P < 0.001), while atrogin-1 displayed a strong downregulation exclusively in response to eccentric exercise (P < 0.001). For MURF1 transcription, the first bout produced a downregulation that persisted until the second bout (P < 0.01). In conclusion, the UPS is modulated differentially in response to varying loading modalities and with different time frames in a way that to some extent reflects changes in protein metabolism known to take place with exercise.
authors: Institute of Sports Medicine, Bispebjerg Hospital, Copenhagen, Denmark. incognito@kropogkraft.dk
authors: A
authors: A
authors: Nedergaard
authors: K
authors: K
authors: Vissing
authors: K
authors: K
authors: Overgaard
authors: M
authors: M
authors: Kjaer
authors: P
authors: P
authors: Schjerling
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000328:Adult; D015444:Exercise; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism; D053580:Muscle Strength; D009135:Muscular Diseases / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D046988:Proteasome Endopeptidase Complex / Q000235:genetics* / Q000378:metabolism; D052097:Quadriceps Muscle / Q000378:metabolism* / Q000503:physiopathology; D012333:RNA, Messenger / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D000070584:Tripartite Motif Proteins; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D009124:Muscle Proteins; D012333:RNA, Messenger; D000070584:Tripartite Motif Proteins; D025801:Ubiquitin; C440907:FBXO32 protein, human; D044843:SKP Cullin F-Box Protein Ligases; C440908:TRIM63 protein, human; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex