SIRT6 is a key regulator of mitochondrial function in the brain

SIRT6 is implicated in DNA repair, telomere maintenance, glucose and lipid metabolism and, importantly, it has critical roles in the brain ranging from its development to neurodegeneration. In this work, we combined transcriptomics and metabolomics approaches to characterize the functions of SIRT6 in mice brains. Our analysis revealed that SIRT6 is a critical regulator of mitochondrial activity in the brain. In its absence, there is a mitochondrial deficiency with a global downregulation of mitochondria-related genes and pronounced changes in metabolites content. We predict that SIRT6 can affect mitochondrial functions through its interaction with the transcription factor YY1 that, together, regulate mitochondrial gene expression. Moreover, SIRT6 target genes include SIRT3 and SIRT4, which are significantly downregulated in SIRT6-deficient brains. Our results demonstrate that the lack of SIRT6 leads to decreased mitochondrial gene expression and metabolomic changes of TCA cycle byproducts, including increased ROS production, reduced mitochondrial number, and impaired membrane potential that can be partially rescued by restoring SIRT3 and 4 levels. Importantly, the changes observed in SIRT6 deficient brains are observed in brains of aging people, but the overlapping is greater in patients with Alzheimers, Parkinsons, Huntingtons, and Amyotrophic lateral sclerosis disease. Overall, our results suggest that reduced levels of SIRT6 in the aging brain and neurodegeneration could initiate mitochondrial dysfunction by altering gene expression, ROS production and mitochondrial decay.