Disclosed herein are novel compositions and methods for the treatment of age-related diseases, mitochondrial diseases, the improvement of stress resistance, the improvement of resistance to hypoxia and the extension of life span. Also described herein are methods for the identification of agents useful in the foregoing methods. Methods and compositions are provided for the treatment of diseases or disorders associated with mitochondrial dysfunction. The invention relates to methods for treatment and prevention of disorders associated with inflammation by administering agents that increase levels of NAD+, such as NAD+ precursors or agents involved in NAD+ biosynthesis.
