#$%^&*AU2019246818A120191031.pdf#####ABSTRACT The present application relates to compositions comprising selenium compounds, such as 5'-Methylselenoadenosine, Se-Adenosyl-L-homocysteine,Gamma-glutamylmethylseleno-cysteine, a compound of formula (I), formula (II), a compound of formula (III) and combinations thereof, and methods of using the same in enhancing mitochondrial function, or treating mitochondrial dysfunction.