Training affects muscle phospholipid fatty acid composition in humans

Area of Science:

• Exercise physiology
• Molecular biology
• Nutritional science

Background:

• Exercise training enhances insulin sensitivity, influencing fuel availability and athletic performance.
• Insulin action is associated with specific patterns of skeletal muscle structural lipids.
• Understanding exercise-induced changes in muscle lipid composition is crucial for optimizing training and metabolic health.

Purpose of the Study:

• To investigate the effects of regular endurance exercise training on the phospholipid fatty acid composition of human skeletal muscle membranes.
• To determine if exercise training influences muscle triacylglycerol fatty acid composition.
• To assess the impact of training on citrate synthase activity as a marker of mitochondrial adaptation.

Main Methods:

• Seven male subjects underwent 4 weeks of unilateral knee extensor endurance training.
• Muscle biopsies were collected from the vastus lateralis of both trained and untrained legs at baseline, after 4 days, and after 4 weeks.
• Phospholipid and triacylglycerol fatty acid composition, along with citrate synthase activity, were analyzed.

Main Results:

• After 4 weeks, trained legs showed significantly higher levels of oleic acid (18:1(n-9)) and docosahexaenoic acid (22:6(n-3)) in phospholipids compared to untrained legs.
• The ratio of n-6 to n-3 fatty acids was significantly lower in the trained leg.
• Citrate synthase activity increased by 17% in the trained leg, while triacylglycerol fatty acid composition remained unaffected.

Conclusions:

• Regular exercise training specifically alters skeletal muscle membrane phospholipid fatty acid composition.
• These changes may contribute to improved insulin sensitivity and fuel utilization during exercise.
• Exercise training does not alter the fatty acid composition of muscle triacylglycerols.