Leucine and citrulline modulate muscle function in malnourished aged rats

Area of Science:

• Gerontology
• Nutritional Science
• Muscle Physiology

Background:

• Protein energy malnutrition in the elderly leads to muscle mass loss and functional decline.
• Leucine and citrulline are known to stimulate muscle protein synthesis in aged rats.
• Previous research has not evaluated the impact of leucine and citrulline on muscle function in aged individuals.

Purpose of the Study:

• To investigate the effects of leucine and citrulline supplementation on muscle mass, motor activity, and muscle function in aged rats.
• To determine if leucine and citrulline can reverse functional deficits associated with malnutrition in the elderly.

Main Methods:

• Sprague-Dawley male rats (23 months old) were subjected to dietary restriction for 12 weeks.
• Rats were then refed for 1 week with either a leucine-supplemented, citrulline-supplemented, or standard diet.
• Muscle mass, motor activity, and maximal tetanic isometric force were measured.

Main Results:

• Leucine and citrulline supplementation significantly increased muscle mass (+51% and +37%, respectively) and motor activity.
• Improvements in muscle mass and activity were strongly correlated with maximal tetanic isometric force.
• Leucine supplementation uniquely enhanced maximal tetanic isometric force by 101%.

Conclusions:

• Leucine and citrulline supplementation can improve muscle mass, motor activity, and muscle function in aged rats.
• This is the first study to demonstrate the muscle function-modulating effects of leucine and citrulline.
• These findings suggest potential therapeutic applications for amino acid supplementation in combating age-related muscle decline.