Total ginsenosides and ginsenoside Rb2 delay hepatocyte senescence by regulating NAD metabolism and promoting IDO2/QPRT expression.

Background: Imbalances in nicotinamide adenine dinucleotide (NAD) homeostasis accelerate aging, and targeting NAD metabolism is a potential strategy for delaying aging. Ginsenoside, as the main active ingredient of Panax ginseng Meyer, exert age-delaying effects. However, the potential molecular mechanism by which total ginsenosides (GS) affect NAD metabolism remains unclear.

Methods: The ability of GS to improve the health status of aging mice was evaluated by water maze, new object recognition, cardiac ultrasound, biochemical analysis, and H&E staining. LC-MS was used to detect NAD metabolites. Senescence-associated secretory phenotypes (SASPs), NAD level and mitochondrial function were used to assess cellular senescence status. Screening of active components of GS in mouse hepatocytes (AML12) based on serum metabolites of GS. Targeted knockdown of IDO2 further validated the molecular mechanism.

Results: GS administration significantly improved the health status of aging mice, as evidenced by improvements in body weight maintenance, skeletal muscle function, neurological performance, and hepatic/cardiac function. Furthermore, GS treatment effectively ameliorated age-associated pathological alterations in multiple organs, including the liver, lung, heart, and brain. In addition, GS affects mainly the biosynthesis pathway in the liver. After performing a phenotype screen, ginsenoside Rb2 (Rb2) was found to promote NAD metabolism, improve mitochondrial function and relieve AML12 cell senescence. The results attributed to IDO2 knockdown were reversed by GS and Rb2.

Conclusion: GS and Rb2 enhance mitochondrial function and delay hepatocyte senescence by modulating the IDO2/QPRT-mediated NAD   biosynthesis pathway. This discovery provides new insights into the role of ginsenosides in antiaging.