Abstract 241: Acetylomic and Metabolomic Alterations in Aged Hearts: Role for Silent Information Regulator (SIRT) 3
Introduction: SIRT3 is a mitochondrial metabolic regulator, and a decline in function of SIRT3 may play a role in age-related mitochondrial alterations. The aim of this study was to investigate the possible down-regulation of SIRT3 activity in aged hearts, and to identify which metabolic pathways in aged hearts may be impaired due to SIRT3 dysfunction.
Methods: Mitochondria were isolated from WT adult (7 mo.), SIRT3-/- adult (7 mo.) and WT aged (18 mo.) hearts. Acetylated proteins in mitochondrial samples were identified using 2D gels and mass spectrometry. Metabolite concentrations and carbon fluxes through core metabolic pathways were determined using 13C-labeled substrates and LC-MS/MS.
Results: Mitochondrial acetylation patterns in the SIRT3-/- adult group matched those found in the WT aged group; the level of acetylation was significantly higher than in WT adult. While the SIRT3-/- samples exhibited zero SIRT3 protein content, no difference in SIRT3 protein level was seen between adult and aged WT hearts. Mechanistically, this suggests that alterations in mitochondrial acetylation during aging were not caused by lower SIRT3 protein levels, but rather by a lower SIRT3 enzymatic activity. Furthermore, aged myocardium exhibited 40% lower NAD+ levels, which may underlie compromised SIRT3 activity.
ATP levels were decreased in both SIRT3-/- and WT aged hearts, suggesting possible defects in energy metabolism. Using metabolomics, we demonstrated that alterations of TCA cycle intermediates were similar in SIRT3-/- and WT aged hearts (relative to WT adult), and included a substantial decline of carbon flux through α-ketoglutarate and malate. Furthermore, regulation of energy production might also be impaired at the level of the electron transport chain, where Complex I was significantly inhibited in both SIRT3 deficient and aged hearts.
Conclusions: Collectively these data suggested that acetylomic and metabolomic fingerprints observed in SIRT3-/- hearts were recapitulated in aged hearts.
Author Disclosures: J. Zhang: None. W.R. Urciuoli: None. P.S. Brookes: None. G.A. Porter: None. S.M. Nadtochiy: None.
This research has received full or partial funding support from the American Heart Association, Founders Affiliate (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, Vermont).
- © 2015 by American Heart Association, Inc.