Hepatic glucose production (HGP) maintains blood glucose levels during fasting but can also exacerbate diabetic hyperglycemia. HGP is dynamically controlled by a signaling/transcriptional network that regulates the expression/activity of gluconeogenic enzymes. A key mediator of gluconeogenic gene transcription is PGC-1α. PGC-1α's activation of gluconeogenic gene expression is dependent upon its acetylation state, which is controlled by the acetyltransferase GCN5 and the deacetylase Sirt1. Nevertheless, whether other chromatin modifiers-particularly other sirtuins-can modulate PGC-1α acetylation is currently unknown. Herein, we report that Sirt6 strongly controls PGC-1α acetylation. Surprisingly, Sirt6 induces PGC-1α acetylation and suppresses HGP. Sirt6 depletion decreases PGC-1α acetylation and promotes HGP. These acetylation effects are GCN5 dependent: Sirt6 interacts with and modifies GCN5, enhancing GCN5's activity. Leprdb/db mice, an obese/diabetic animal model, exhibit reduced Sirt6 levels; ectopic re-expression suppresses gluconeogenic genes and normalizes glycemia. Activation of hepatic Sirt6 may therefore be therapeutically useful for treating insulin-resistant diabetes.
Bibliographical noteFunding Information:
We thank members of the Puigserver lab for important discussions about this project. J.E.D. was supported in part by an NRSA Kirschstein fellowship from the National Institutes of Health and Y.L. was supported in part by a 21 st Century Leaders scholarship from Ewha Womans University. Research was supported with funds from the DFCI and with grants from the American Diabetes Association, Department of Defense, and NIH/NIDDK (RO1 069966) awarded to P.P., as well as with a grant from NIH (DK059635) awarded to Yale's Mouse Metabolic Phenotyping Center/G.I.S.