NAD+, as a key coenzyme in eukaryotic organisms, determines hundreds of enzymatic reactions. The coenzyme NAD is involved in oxidation–reduction reactions critical for glycolysis, fatty acid oxidation, the TCA cycle, and complex I of the mitochondrial respiratory chain and also is a key regulator of autophagy. In addition, NAD+ can also indirectly regulate the process of anti-stress, cell growth, anti-inflammatory and anti-aging processes by regulating the function of Sirtuins factor which has NAD+ dependent protein deacetylation activity. The decline of NAD+ level will also lead to heart failure and Alzheimer's disease.