Resting MAPK expression in chronically trained endurance runners.

Area of Science:

• Exercise physiology
• Molecular biology
• Skeletal muscle research

Background:

• Mitogen-activated protein kinases (MAPK) are crucial signaling pathways involved in cellular responses to stress and stimuli.
• Understanding MAPK expression in chronically trained (CT) athletes is essential for elucidating mechanisms of muscle adaptation and performance enhancement.
• Limited research exists on MAPK expression, specifically extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38-MAPK (p38), in CT individuals.

Purpose of the Study:

• To investigate differences in total and phosphorylated MAPK protein expression between sedentary (SED) and CT runners.
• To determine the specific roles of ERK1/2, JNK, and p38-MAPK in muscle adaptation to chronic endurance training.

Main Methods:

• Muscle biopsy samples were obtained from sedentary (n=5) and CT (n=5) runners.
• Western blotting was used to analyze total and phosphorylated levels of ERK1/2, JNK, and p38-MAPK.
• Statistical analysis included Mann-Whitney U tests and effect sizes to compare protein expression between groups.

Main Results:

• No significant differences were observed in total MAPK protein expression between SED and CT groups.
• A trend towards increased phosphorylated p38-MAPK (p-p38-MAPK) was noted in CT runners compared to SED individuals (p=0.07).
• CT runners exhibited decreased pERK/total-ERK (d=-0.69) and increased pJNK/total-JNK (d=0.54) ratios. A positive correlation was found between p-p38-MAPK and type I fiber percentage (r=0.73, p=0.016).

Conclusions:

• Chronic endurance training does not significantly alter total MAPK protein expression in skeletal muscle.
• Resting phosphorylation of p38-MAPK may be associated with enhanced oxidative metabolism in CT athletes.
• These MAPK signaling alterations likely contribute to physiological adaptations underlying long-term training and high-level athletic performance.