PMID- 31593504 OWN - NLM STAT- MEDLINE DCOM- 20200413 LR - 20211204 IS - 1522-1555 (Electronic) IS - 0193-1849 (Linking) VI - 317 IP - 6 DP - 2019 Dec 1 TI - Activation of protein synthesis, regeneration, and MAPK signaling pathways following repeated bouts of eccentric cycling. PG - E1131-E1139 LID - 10.1152/ajpendo.00216.2019 [doi] AB - The aim of this study was to examine the activation of skeletal muscle signaling pathways related to protein synthesis and the gene expression of regeneration/degradation markers following repeated bouts of eccentric cycling. Nine untrained men (25.4 +/- 1.9 yr) performed two 30-min eccentric cycling bouts (ECC1, ECC2) at 85% of maximal concentric workload, separated by 2 wk. Muscle biopsies were taken from the vastus lateralis before and 2 h after each bout. Indirect markers of muscle damage were assessed before and 24-48 h after exercise. Changes in the Akt/mammalian target of rapamycin (mTOR)/rbosomal protein S6 kinase 1 (S6K1)/ribosomal protein S6 (rpS6) and MAPK signaling pathways were measured by Western blot and changes in mRNA expression of IL-6 and IL-1beta, and myogenic regulatory factors (MRFs) were measured by real-time PCR. ECC1 induced greater increases in indirect markers of muscle damage compared with ECC2. Phosphorylation of S6K1 and rpS6 increased after both exercise bouts (P < 0.05), whereas phosphorylation of mTOR increased after ECC2 only (P = 0.03). Atrogin-1 mRNA expression decreased after ECC1 and ECC2 (P < 0.05) without changes in muscle RING-finger protein-1 mRNA. Basal mRNA levels of myoblast determination protein-1 (MyoD), MRF4, and myogenin were higher 2 wk after ECC1 (P < 0.05). MRF4 mRNA increased after ECC1 and ECC2 (P < 0.05), whereas MyoD mRNA expression increased only after ECC1 (P = 0.03). Phosphorylation of JNK and p38 MAPK increased after both exercise bouts (P < 0.05), similar to IL-6 and IL-1beta mRNA expression. All together, these results suggest that differential regulation of the mTOR pathway and MRF expression could mediate the repeated bout effect observed between an initial and secondary bout of eccentric exercise. FAU - Valladares-Ide, Denisse AU - Valladares-Ide D AD - Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine, Universidad Finis Terrae, Santiago, Chile. FAU - Penailillo, Luis AU - Penailillo L AD - Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine, Universidad Finis Terrae, Santiago, Chile. FAU - Collao, Nicolas AU - Collao N AD - Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine, Universidad Finis Terrae, Santiago, Chile. FAU - Marambio, Hugo AU - Marambio H AD - Centro de Salud Deportiva, Clinica Santa Maria, Santiago, Chile. FAU - Deldicque, Louise AU - Deldicque L AD - Institute of Neuroscience, Universite Catholique de Louvain, Louvain-la-Neuve, Belgium. FAU - Zbinden-Foncea, Hermann AU - Zbinden-Foncea H AD - Exercise Science Laboratory, School of Kinesiology, Faculty of Medicine, Universidad Finis Terrae, Santiago, Chile. AD - Centro de Salud Deportiva, Clinica Santa Maria, Santiago, Chile. LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20191008 PL - United States TA - Am J Physiol Endocrinol Metab JT - American journal of physiology. Endocrinology and metabolism JID - 100901226 RN - 0 (IL1B protein, human) RN - 0 (IL6 protein, human) RN - 0 (Interleukin-1beta) RN - 0 (Interleukin-6) RN - 0 (Muscle Proteins) RN - 0 (MyoD Protein) RN - 0 (MyoD1 myogenic differentiation protein) RN - 0 (Myogenic Regulatory Factors) RN - 0 (Myogenin) RN - 0 (Ribosomal Protein S6) RN - 0 (Tripartite Motif Proteins) RN - 0 (myogenic factor 6) RN - EC 2.3.2.27 (FBXO32 protein, human) RN - EC 2.3.2.27 (SKP Cullin F-Box Protein Ligases) RN - EC 2.3.2.27 (TRIM63 protein, human) RN - EC 2.3.2.27 (Ubiquitin-Protein Ligases) RN - EC 2.7.1.1 (MTOR protein, human) RN - EC 2.7.11.1 (Proto-Oncogene Proteins c-akt) RN - EC 2.7.11.1 (Ribosomal Protein S6 Kinases, 90-kDa) RN - EC 2.7.11.1 (TOR Serine-Threonine Kinases) RN - EC 2.7.11.1 (ribosomal protein S6 kinase 1, human) RN - EC 2.7.11.24 (p38 Mitogen-Activated Protein Kinases) RN - EC 2.7.12.2 (MAP Kinase Kinase 4) SB - IM MH - Adult MH - *Bicycling MH - Exercise/*physiology MH - *Gene Expression MH - Humans MH - Interleukin-1beta/genetics MH - Interleukin-6/genetics MH - MAP Kinase Kinase 4/metabolism MH - MAP Kinase Signaling System/*genetics MH - Male MH - Muscle Proteins/genetics MH - Muscle, Skeletal/metabolism/physiology MH - MyoD Protein/genetics MH - Myogenic Regulatory Factors/genetics MH - Myogenin/genetics MH - Protein Biosynthesis/*genetics MH - Proto-Oncogene Proteins c-akt/metabolism MH - Quadriceps Muscle/*metabolism MH - Regeneration/*genetics MH - Ribosomal Protein S6/metabolism MH - Ribosomal Protein S6 Kinases, 90-kDa/metabolism MH - SKP Cullin F-Box Protein Ligases/genetics MH - TOR Serine-Threonine Kinases/metabolism MH - Tripartite Motif Proteins/genetics MH - Ubiquitin-Protein Ligases/genetics MH - Young Adult MH - p38 Mitogen-Activated Protein Kinases/metabolism OTO - NOTNLM OT - ERK OT - MAFbx OT - MyoD OT - lengthening OT - mTOR EDAT- 2019/10/09 06:00 MHDA- 2020/04/14 06:00 CRDT- 2019/10/09 06:00 PHST- 2019/10/09 06:00 [pubmed] PHST- 2020/04/14 06:00 [medline] PHST- 2019/10/09 06:00 [entrez] AID - 10.1152/ajpendo.00216.2019 [doi] PST - ppublish SO - Am J Physiol Endocrinol Metab. 2019 Dec 1;317(6):E1131-E1139. doi: 10.1152/ajpendo.00216.2019. Epub 2019 Oct 8.