Thymosin beta-4 was identified as the most upregulated exercise-released peptide from contracting muscle, with levels also acutely increased in exercising humans regardless of insulin resistance status.
Most upregulated exerkineThymosin beta-4 was the single most upregulated secreted protein from contracting muscle cells, positioning it as a key mediator of exercise benefits
What the researchers found
TMSB4X was the most upregulated secreted protein from contracting C2C12 myotubes by MS-based proteomics, and was acutely increased in plasma of exercising humans irrespective of insulin resistance status.
Why it matters
Identifying thymosin beta-4 as a major exerkine could explain how exercise promotes tissue repair, cardiovascular health, and brain protection. It opens the possibility of using TMSB4X therapeutically as an "exercise mimetic" for people who cannot exercise.
The numbers in context
Most upregulated secreted protein; acutely elevated in human plasma; increased osteoblast proliferation; promoted neurite outgrowth; no metabolic benefit in obese mice
How the study worked
Proteomics study. MS-based secretome analysis of contracting C2C12 myotubes in vitro. Human plasma TMSB4X levels measured during exercise in subjects with and without insulin resistance.
Who was studied
Exercising humans (with and without insulin resistance), C2C12 myotubes, obese mice, osteoblasts, neurons
What this study cannot tell us
Initial discovery from in vitro muscle cell model. Human plasma measurements were acute (exercise session), not chronic. Functional significance of exercise-induced TMSB4X increase needs further investigation. Dose-response and tissue-specific effects unknown.
How to read the evidence
Moderate evidence: combines in vitro proteomics discovery with human exercise validation. Functional significance needs further study.
When this study was published
Published 2021. The exerkine field is rapidly growing with increasing interest in exercise-released peptides.
The bigger picture
Thymosin beta-4 is already known for wound healing and tissue repair. Identifying it as a major exercise-released factor connects these regenerative properties to the systemic benefits of physical activity, potentially explaining exercise's protective effects across multiple organ systems.
Questions still open
- Could thymosin beta-4 supplementation replicate some benefits of exercise for sedentary or immobile individuals?
- Which organs and tissues are most responsive to exercise-released thymosin beta-4?
- Does chronic exercise training increase baseline thymosin beta-4 levels?
Common questions
What is an exerkine?
Could thymosin beta-4 supplements replace exercise?
Read the original research
Discovery of thymosin β4 as a human exerkine and growth factor.
American journal of physiology. Cell physiology, 321(5), C770-C778
Citation
Gonzalez-Franquesa, Alba; Stocks, Ben; Borg, Melissa L; Kuefner, Michael; Dalbram, Emilie; Nielsen, Thomas S; Agrawal, Ankita; Pankratova, Stanislava; Chibalin, Alexander V; Karlsson, Håkan K R; Gheibi, Sevda; Björnholm, Marie; Jørgensen, Niklas Rye; Clemmensen, Christoffer; Hostrup, Morten; Treebak, Jonas T; Krook, Anna; Zierath, Juleen R; Deshmukh, Atul S. (2021). Discovery of thymosin β4 as a human exerkine and growth factor.. American journal of physiology. Cell physiology, 321(5), C770-C778. https://doi.org/10.1152/ajpcell.00263.2021