Influence of Mechanistic Target of Rapamycin (mTOR)-Regulated Anabolic Pathways on Equine Skeletal Muscle Health.
Authors: Semanchik Pier L, Wesolowski Lauren T, Ryan Patrick J, White-Springer Sarah H, Fluckey James D
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Skeletal muscle development and maintenance depend critically on mTOR (mechanistic target of rapamycin), a regulatory hub that orchestrates protein synthesis in response to nutrition, exercise, and life stage—yet the specifics of how this pathway operates across different equine populations remain poorly understood. Semanchik and colleagues reviewed current evidence on how mTOR signalling is activated by adequate dietary amino acids (particularly leucine and glutamine) working in concert with insulin, and how this activation recruits mTOR to the lysosome to trigger downstream protein synthesis and mitochondrial biogenesis, especially when exercise stimulus is imposed on well-nourished horses. The authors highlight that mTOR function is highly context-dependent: young horses appear to benefit from pathway activation for growth, whilst muscle loss in aged horses seems driven more by increased protein degradation than blunted mTOR signalling itself. Whilst diet, exercise, and age clearly influence mTOR activity, the authors identify a critical gap—we lack quantified functional outcomes (such as measurable changes in muscle mass, strength, or performance) linked to these molecular changes. For farriers, vets, nutritionists, and coaches, this synthesis underscores that optimising amino acid intake and exercise programming should be tailored to life stage, and highlights why age-related muscle loss may require different interventions than failure to develop muscle in young athletes, pending more targeted research to bridge molecular mechanism to practical outcome.
Read the full abstract on PubMed
Practical Takeaways
- •Ensure equine diets contain adequate high-quality protein with sufficient leucine and glutamine to support mTOR activation and muscle protein synthesis, particularly in athletes and young stock
- •Combine balanced nutrition with appropriate exercise programming to maximize anabolic signaling; management strategies should be tailored by age, as young horses need growth support while older horses require anti-degradation interventions
- •Further research is needed to translate mTOR pathway knowledge into specific feeding and exercise recommendations, but current evidence supports prioritizing amino acid adequacy and exercise stimulus as foundational management practices
Key Findings
- •mTOR pathway is a key regulator of protein synthesis in equine skeletal muscle and is activated by adequate amino acid availability (leucine, glutamine) and insulin signaling
- •Diet, exercise, and age significantly influence mTOR pathway function, with growth emphasis in young horses and degradation-related losses in aged horses
- •A well-balanced diet sufficient in essential amino acids combined with appropriate exercise activates mitochondrial biogenesis and protein synthesis in performing horses
- •Age-related muscle loss in horses appears attributable to protein degradation mechanisms rather than mTOR pathway alterations, suggesting different interventions may be needed across life stages