Leucine is an amino acid involved in the formation of proteins. It is an essential amino acid i.e. one that cannot be synthesized by the body so must be obtained from food.
In overweight mice, leucine supplementation for 2 months resulted in improved mitochondrial function by significantly increasing levels of NAD+ and SIRT1 [R].
In muscle and fat cells, leucine increased mitochondrial mass by 30% and 53% respectively. As above, both increases were probably caused by leucine’s ability to increase SIRT1 [R].
Leucine was found to increase mitochondrial density and improve mitochondrial function in skeletal muscle [R].