Skip to content

Study · Measured the body's own peptide · 2026

2 results

Intrinsic exercise capacity is associated with skeletal muscle clock gene and IGF-1 signaling in aged low- and high-running capacity rats.

Kim HK, Kawamura T, Bori Z, Koch LG, Britton SL, Radak Z

Frontiers in physiology9 Jun 2026

PMID42344272 (opens in a new tab)PMCIDPMC13286783 (opens in a new tab)DOI10.3389/fphys.2026.1818866 (opens in a new tab)PepBankPUB-42344272
Download PDFPubMedAsk about this study
Jump to 2 results

Summary

BackgroundIntrinsic exercise capacity is a strong predictor of health and longevity and is independently associated with aging- and disease-related outcomes. Although previous studies using low- and high-capacity runner (LCR and HCR) rats have demonstrated organ-specific patterns of epigenetic aging, the molecular mechanisms linking intrinsic aerobic capacity to skeletal muscle signaling remain incompletely understood.ObjectiveThis study investigated whether intrinsic exercise capacity is associated with alterations in skeletal muscle clock gene expression and insulin-like growth factor-1 (IGF-1)-related signaling pathways.MethodsFemale LCR and HCR rats (23-24 months old, 44th generation) underwent maximal oxygen uptake (VO2max) testing, followed by molecular analyses of plantaris and soleus muscles using quantitative PCR and Western blotting.ResultsVO2max was significantly higher in HCR rats. In skeletal muscle, LCR rats exhibited higher mRNA expression levels of Cry1, Bmal1, Igf1, and Igf1Ec measured at ZT2-ZT3, whereas expression of Cry2, Pdk4, and MuRF-1 did not differ between phenotypes. Despite increased Igf1 expression in LCR rats, the phosphorylated-to-total JAK2 ratio was reduced, while STAT5 phosphorylation was unchanged. Correlation analyses demonstrated significant negative associations between VO2max and Igf1, Igf1Ec, Cry1, and Bmal1 expression.ConclusionThese findings indicate that low intrinsic exercise capacity is associated with coordinated alterations in skeletal muscle clock gene expression and IGF-1- related signaling, suggesting altered IGF-1-related signaling balance in aging skeletal muscle. These results provide mechanistic insight into how intrinsic aerobic capacity may influence muscle biology and health trajectories during aging.
CC BYText from Europe PMC. Highlighted sentences are the source of results.

Results from this study2

No result from this study comes from a test of the peptide.

Natural levels measured2

These results measure the body's own peptide. Nobody was given the peptide. They are not evidence about taking it. They are left out of key results, evidence counts and charts.

  1. 01AnimalEndogenous levelAnimal study (in vivo)Mechanism

    In aged rats, skeletal muscle Igf1Ec mRNA expression was higher in low-capacity runner rats than in high-capacity runner rats.

    In plain wordsIn aged rats, the body's own Igf1Ec in muscle was higher in rats bred for low running capacity than in high-capacity rats.

    Peptide
    MGF / PEG-MGF
    Outcome
    IncreaseSkeletal muscle Igf1Ec mRNA expression, LCR versus HCR rats
    Study

    ratn: not reported in source

    Aged female low- and high-running capacity rats
    Comparator
    HCR rats
    Outcome group
    Aging markers · Musculoskeletal

    Source sentences

    Summary
    LCR rats exhibited higher mRNA expression levels of Cry1, Bmal1, Igf1, and Igf1Ec
    1 context sentence
    Summary · context
    Female LCR and HCR rats (23-24 months old, 44th generation) underwent maximal oxygen uptake (VO2max) testing, followed by molecular analyses of plantaris and soleus muscles using quantitative PCR and Western blotting.

    This result measures the body's own MGF / PEG-MGF. Nobody was given the peptide. It is not evidence about taking it.

  2. 02AnimalEndogenous levelAnimal study (in vivo)Mechanism

    In aged rats, maximal oxygen uptake correlated negatively with skeletal muscle Igf1Ec expression.

    In plain wordsIn aged rats, higher fitness was linked to lower natural Igf1Ec levels in muscle.

    Peptide
    MGF / PEG-MGF
    Outcome
    DecreaseCorrelation of VO2max with Igf1Ec expression
    Study

    ratn: not reported in source

    Aged female low- and high-running capacity rats
    Outcome group
    Aging markers · Musculoskeletal

    Source sentences

    Summary
    Correlation analyses demonstrated significant negative associations between VO2max and Igf1, Igf1Ec, Cry1, and Bmal1 expression.
    1 context sentence
    Summary · context
    Female LCR and HCR rats (23-24 months old, 44th generation) underwent maximal oxygen uptake (VO2max) testing, followed by molecular analyses of plantaris and soleus muscles using quantitative PCR and Western blotting.

    This result measures the body's own MGF / PEG-MGF. Nobody was given the peptide. It is not evidence about taking it.

AI wrote and checked these results. AI can make mistakes, so check important results against the source.

Version history

PepBank keeps every version of the data on this study. Status changes from Retraction Watch, Europe PMC and Crossref are listed with their source.

  1. Version 2Current

    13 Oct 2026, 21:44 UTC

    Study results updated

  2. Version 1

    13 Oct 2026, 16:31 UTC

    First added · source update from Europe PMC

Subjects

Terms as the source lists them.

PepBank is a research reference. Talk to a doctor before you use any peptide.