The Age Dependent Metabolome

Declined metabolic homeostasis is one of the hallmarks if aging. With age, imbalanced glucose and fat metabolism is developed and a results in an induction of age-related metabolic diseases. Genetic and diet interventions such as calorie restriction (CR) were shown to significantly delay the decline in metabolic homeostasis and to extend lifespan. Similar to CR, mice overexpressing the NAD⁺ dependent protein deacylase SIRT6 live longer with improved health and delayed metabolic dysfunction. However, despite the extensive research on SIRT6 only a few substrates for SIRT6 deacetylase activity have been identified. Therefore, in order to explore the regulation of SIRT6 on age-dependent metabolic dysfunction, we characterize the global and SIRT6-dependent liver acetylomes. To do so, a stable isotope labeling by amino acids (SILAC) based mass spectrometry analysis and a complementary metabolomics analyses were performed. 1755 proteins with 5959 acetylation sites were identified, from all cell compartments. The liver SIRT6-dependent acetylome consists of 291 acetylated sites on 215 proteins. Strikingly, within these we identified most of the methionine cycle and transsulfuration pathway (TSP) enzymes. SIRT6 overexpression results in a significant reduction in TSP enzymes’ acetylation and an increase in the levels of their product, the longevity mediator mediator-H₂S, even in old mice. Similarly, constitutively mimicking deacetylated TSP enzymes also results in an increased H₂S levels. Thus, we suggest that one mechanism by which SIRT6 maintains metabolic homeostasis and extends health and survival is through promoting H₂S production by TSP enzymes.