Another study by Zhang et al. (2020) showed that RPE isolated from AMD donor samples had downregulated AMPK/SIRT1 activity and decreased NAD+ which had an impact on reduced PGC-1α levels by increased acetylation and (inactivation of PGC-1α), a master regulator for mitochondrial biogenesis when compared to age-matched control samples. This evidence concerns the gene PPARGC1A and age-related macular degeneration.