As expected, metformin treatment efficiently reduced SASP factors such as IL-6, IL-1α, IL-1β, MMP3 and MMP9, diminished the p16 INK4a expression, and enhanced nuclear level of lamin B1 in astrocytes of PD mice, but this effect was not observed in astrocytic cGAS deficient mice (Fig. 5K–S). Here, MMP9 is linked to Parkinson disease.