Cited by 45Metabolism, Diabetes, and CancerMuscle metabolism and nutritionPI3K/AKT/mTOR signaling in cancer

A chronic increase in physical activity inhibits fed-state mTOR/S6K1 signaling and reduces IRS-1 serine phosphorylation in rat skeletal muscle

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Glynn, Erin L., Lujan, Heidi L., Kramer, Victoria J., Drummond, Micah J., DiCarlo, Stephen E., Rasmussen, Blake B.·2008·Applied Physiology, Nutrition, and Metabolism

Abstract

A chronic increase in physical activity and (or) endurance training can improve insulin sensitivity in insulin-resistant skeletal muscle. Cellular mechanisms responsible for the development of insulin resistance are unclear, though one proposed mechanism is that nutrient overload chronically increases available energy, over-activating the mammalian target of rapamycin (mTOR) and ribosomal S6 kinase 1 (S6K1) signaling pathway leading to increased phosphorylation of serine residues on insulin receptor substrate-1 (IRS-1). The objective of this study was to determine if increased physical activity would inhibit mTOR/S6K1 signaling and reduce IRS-1 serine phosphorylation in rat skeletal muscle. Soleus muscle was collected from fed male Sprague–Dawley sedentary rats (Inactive) and rats with free access to running wheels for 9 weeks (Active). Immunoblotting methods were used to measure phosphorylation status of mTOR, S6K1, IRS-1, and PKB/Akt (protein kinase B/AKT), and total abundance of proteins associated with the mTOR pathway. Muscle citrate synthase activity and plasma insulin and glucose concentrations were measured. Phosphorylation of mTOR (Ser 2448), S6K1 (Thr 389), and IRS-1 (Ser 636–639) was reduced in Active rats (p < 0.05). Total protein abundance of mTOR, S6K1, IRS-1, 4E-BP1, eEF2, PKB/Akt and AMPKα, and phosphorylation of PKB/Akt were unaffected (p > 0.05). Total SKAR protein, a downstream target of S6K1, and citrate synthase activity increased in Active rats (p < 0.05), though plasma insulin and glucose levels were unchanged (p > 0.05). Reduced mTOR/S6K1 signaling during chronic increases in physical activity may play an important regulatory role in the serine phosphorylation of IRS-1, which should be examined as a potential mechanism for attenuation of insulin resistance associated with increased IRS-1 serine phosphorylation.

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Crossref · 10.1139/h07-149

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  • Endurance training inhibits mTOR/p70 S6K signaling and reduces IRS1 serine phosphorylation in rat skeletal muscle.

    “Endurance training has been shown to inhibit mTOR/p70 S6K signaling and reduce IRS1 serine phosphorylation in rat skeletal muscle [157], and recent studies have demonstrated that AMPK is involved in the suppression of mTOR signaling [39].”

    From AMPK and Exercise: Glucose Uptake and Insulin Sensitivity (2013) · cites this paper as [157]

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  1. Srere PA. Citrate synthase. Methods Enzymol. 1969;13:3–6. [Google Scholar]

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Authors
Glynn, E. L., Lujan, H. L., Kramer, V. J., Drummond, M. J., DiCarlo, S. E., & Rasmussen, B. B.
Affiliations
Wayne State University (US)
Venue
Applied Physiology, Nutrition, and Metabolism
Published
2008-02
Volume
33
Issue
1
Pages
93-101
ISSN
  • 1715-5312 (ISSN-L)
  • 1715-5320
OpenAlex
W2147722362
Cited by
45
References
49
Citations by year
2025: 1 · 2024: 1 · 2023: 1 · 2022: 6 · 2021: 2 · 2020: 1 · 2019: 1 · 2018: 2 · 2017: 1 · 2016: 1 · 2015: 5 · 2014: 3 · 2013: 4 · 2012: 7
FWCI
1.23
Type
journal article
Language
en
Open access
Locations
  • Applied Physiology, Nutrition, and Metabolism (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
Funders
  • National Institutes of Health
  • National Institute on Aging (P30AG024832)
  • National Heart, Lung, and Blood Institute (R01HL074122)
  • National Institute of Arthritis and Musculoskeletal and Skin Diseases (R01AR049877)
  • Eunice Kennedy Shriver National Institute of Child Health and Human Development (T32HD007539)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Metabolism, Diabetes, and Cancer
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › PI3K/AKT/mTOR signaling in cancer
Keywords
physical activity, endurance training, mTOR signaling, S6K1, IRS-1 serine phosphorylation, insulin resistance, skeletal muscle, soleus muscle, insulin sensitivity, citrate synthase, Akt, AMPKα, 4E-BP1, elongation factor 2
MeSH terms
Animals, Blood Glucose, Citrate (si)-Synthase, Insulin, Insulin Resistance, Male, Phosphorylation, Physical Conditioning, Animal, Protein Kinases, Serine, Blotting, Western, Rats, Sprague-Dawley, Muscle, Skeletal, Lactic Acid, Ribosomal Protein S6 Kinases, Adaptor Proteins, Signal Transducing, STAT1 Transcription Factor, Rats, Insulin Receptor Substrate Proteins, TOR Serine-Threonine Kinases

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