The present invention relates to compositions and methods for altering cell function. In particular, the present invention provides compositions comprising selenium (e.g., SEL-PLEX) and methods of using the same (e.g., as a therapeutic and/or prophylactic treatment for neurodegenerative disease). Additionally, the present invention demonstrates that specific forms of selenium (e.g., SEL-PLEX) possess the ability to alter expression of genes associated with disease and/or aging while other forms of selenium (e.g., selenomethionine) do not.