Notch, Numb and Numb-Like Responses to Exercise-Induced Muscle Damage in Human Skeletal Muscle

Exp Physiol, 2022 · DOI: 10.1113/EP090364 · Published: August 1, 2022

Genetics Rehabilitation Musculoskeletal Medicine

Simple Explanation

This study investigates how muscle damage from exercise affects certain proteins (Notch, Numb, and Numb-like) in human muscles. These proteins are important for muscle repair and growth. The study found that one of these proteins, Notch1, showed a slight increase in its gene expression after muscle damage. However, the other proteins didn't change significantly. These findings suggest that muscle repair in humans may be different from what has been observed in animals. The timing of when muscle samples are taken and the amount of muscle damage caused by exercise could affect the results.

Study Duration

Not specified

Participants

12 recreationally active male subjects

Evidence Level

Level 2: Experimental study with repeated measures ANOVA

Key Findings

1
Notch1 mRNA expression trended toward a significant increase from Pre to 2 Days post-muscle damage from baseline measures (p = 0.087).
2
There were no significant differences in protein expression post-muscle damage for any of the proteins (Notch1, Numb, Numbl).
3
Numb (p = 0.804) and Numbl (p = 0.480) expression was unaltered post-muscle damage.

Research Summary

The investigation examined changes in the gene and protein expression of Notch, Numb, and Numb-like (Numbl) in human skeletal muscle after an acute bout of eccentric exercise-induced muscle damage. The results show a trend toward an increase in Notch1 mRNA 2 days (p = 0.09) after eccentric exercise, but no significant differences across other tested outcomes. In conclusion, the current data indicate that Numb and Numbl mRNA and protein expression in humans are unaltered post-muscle damage, while Notch1 mRNA expression is trended toward an increase after muscle damage.

Practical Implications

Timing of Biopsies

The timing of muscle biopsies after exercise-induced muscle damage needs careful consideration, as peak expression levels of target genes may be missed.

Training Status

The training status of participants can influence the results, as chronic training may affect baseline levels of certain proteins like Notch1.

Muscle Damage Protocols

The specific muscle damage protocols used can impact the extent of muscle damage and subsequent signaling pathways, requiring careful selection and standardization.

Study Limitations

1
The changes in SC expression of Numb and NumbL may not be detected against the much larger signal for Notch and Numb in skeletal muscle fibers.
2
Therefore, it is possible that the transient expression of Notch and Numb in muscle fibers overshadows changes within SCs which account for approximately 2–7% of the nuclei in skeletal muscle
3
We may have missed the peak expression levels of our target. Further research is needed to determine the temporal expression of Notch, Numb, and Numbl after an acute bout of exercise designed to induce muscle damage.

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