Sirtuins may mediate temperature-induced metabolic remodeling in threespine stickleback

The molecular pathway governing metabolic remodeling in response to temperature in fishes is unknown. We tested the hypothesis that sirtuins, a family of NAD+ dependent lysine deacetylases, drives an increase in aerobic metabolism in response to cold acclimation in stickleback. Stickleback were acclimated to 5, 12 and 20°C and sirtuin activity measured in liver, oxidative and glycolytic muscles using a Promega SIRT-Glo Assay kit. Protein levels of SIRT1 and SIRT3 were quantified using custom antibodies and capillary western blotting. In a second set of experiments, sirtuin activity was inhibited by feeding with EX-527 or activated by feeding with the NAD+ pre-cursor, nicotinamide mononucleotide (NMN). Standard metabolic rate (SMR) was measured using intermittent flow respirometry. Mitochondrial respiration rates were measured in permeabilized liver tissue using a substrate-uncoupler-inhibitor titration protocol . Sirtuin activity significantly increased in response to cold acclimation in liver and oxidative and glycolytic muscles but SIRT3 protein levels declined and SIRT1 protein was undetectable, suggesting one or more other SIRT isoforms contribute to an increase in sirtuin activity in response to cold acclimation. Inhibiting sirtuin activity with EX-527 decreased SMR and the activity of complex I in liver, providing further support for the role of sirtuins in metabolic remodeling in stickleback.