(a) Kaplan-Meier survival curves of mice fed a standard diet (SD) or a high-fat diet (HFD) supplemented with SRT1720 at either a low (HFD-L) or high (HFD-H) dose. Mean and maximum lifespan in weeks and the hazard ratio for mortality are represented below. In the parentheses the increases in maximum lifespan from birth and then diet onset are given. (b) Body weights of the groups over time, with average caloric intake over the course of the feeding study in the inset. Below are images of representative mice to illustrate phenotypic body mass of the groups at 82 weeks of age. (c) SRT1720 maintained normal liver appearance and reduced the onset of fatty liver as depicted by images of whole livers harvested after 12 weeks on diets and subsequent oil red O staining. Quantification of steatosis was performed by a blinded pathologist on livers from 82 week-old mice (26 weeks on diets; n = 6). Serum levels of the aminotransferases ALT and AST were reduced by SRT1720 compared with HFD (n = 6; age = 82 wks; diet = 26 wks). (d) SRT1720 normalized pancreas morphology as illustrated by immunostaining for glucagon-producing cells (α cells, green) and insulin-producing cells (β cells, red) in islets, and quantification of islet area and relative α-cell and β-cell areas within the islets (n = 8; diet = 12 weeks). Data are represented as the mean ± SEM. *P < 0.0083 from SD; ^†P < 0.0083 from HFD.

(a) Organ weights were significantly increased in the HFD mice compared with SD and reduced by SRT1720 (n = 6; age = 82 wks; diet = 26 wks). (b) Fat mass increased in all high fat groups relative to SD, however fat mass was significantly reduced in HFD-H compared with HFD (n = 15 at 64, 80 and 94 weeks of age). HDL cholesterol was increased in sera from HFD-H mice (n = 6; age = 82 wks; diet = 26 wks). While serum glucose was unchanged, serum insulin was increased in HFD but not in HFD-H compared with SD. The HOMA calculation of insulin resistance was likewise increased in the HFD but not the SRT1720-treated group (n = 8; age = 40 weeks; diet = 12 weeks). (c) Circadian rhythm of oxygen intake over 60 h is plotted without error bars for clarity (see Supplementary Fig. 4a for average VO₂ during light and dark cycles with SEM) (n = 14 (SD), 12 (HFD), 10 (HFD-L), 14 (HFD-H); age = 122 wks; diet = 66 wks). (d) Daily locomotor activity represented as total movement along the horizontal plane (X Total), ambulatory movement along the horizontal plane (X Amb) and movement across the vertical axis (Z). Ambulatory and vertical movement was reduced in the HFD groups compared with SD, and the high dose of SRT1720 reversed this effect in ambulatory movement (n = 14 (SD), 12 (HFD), 10 (HFD-L), 14 (HFD-H); age = 122 wks; diet = 66 wks). Data are represented as the mean ± SEM. *P < 0.0083 from SD; ^†P < 0.0083 from HFD.

(a) Two indicators of increased programmed cell death, caspase 3 activity and DNA fragmentation, were increased in the HFD compared with SD. This effect was completely blocked by both doses of SRT1720 (n = 6; age = 82 wks; diet = 26 wks). (b) Parametric analysis of gene-set enrichment (PAGE) comparing every pathway significantly upregulated (red) or downregulated (blue) by HFD (as compared with SD, 349 pathways of 1687 considered), and the corresponding effects of the low and high doses of SRT1720 on those same pathways (n = 3; age = 82 wks; diet = 26 wks). (c) The five most highly upregulated and downregulated named genes, based on fold-change in HFD-R compared to HFD (filtering on a false discovery rate of <0.05). (d) Multiple pro-inflammatory markers including TNF, IL-6, IL-1β and iNOS were increased in the HFD mice relative to SD. No significant increase from SD was seen in the HFD-H group, and there was a significant decrease from HFD in the TNF and iNOS expression of the HFD-H livers (n = 6; age = 82 wks; diet = 26 wks). *P < 0.0083 from SD; ^†P < 0.0083 from HFD.

(a) Relative PGC-1α acetylation was analyzed by immunoprecipitation from nuclear extracts from the liver followed by an immunoblot against acetylated lysine residues (n = 8; age = 40 weeks; diet = 12 weeks). Data are represented as the mean ± SEM. *P < 0.0083 from SD. (b) Oxygen consumption in stimulated, respiration-uncoupled MEFs is expressed as the percent increase over basal respiration. Compared with vehicle-treated cells, only WT MEFs displayed increased capacity for O₂ consumption. *P < 0.05 from 0 µM. (c) Cell survival following oxidative stress by 24 h exposure to H₂O₂ (500 µM) showed increased survival after pretreatment with SRT1720 was confined to the WT MEFs. (d) Increases to mitochondrial membrane potential in HepG2 cells only occurred in cells that were transfected with non-targeting siRNA, and this effect was blocked by siRNAs that targeted PGC-1α 1 and 2. (e) Concurrently an increase in cellular ATP content was dependent on PGC-1a. Data are represented as the mean ± SEM. *P < 0.0083 from 0 µM.

(a) State 3 oxygen consumption by mitochondria isolated from the liver was reduced by HFD. Treatment with SRT1720 in the HFD was protective only in WT mice. (b) Oxygen consumption during state 4 respiration was unchanged by diet or genetic manipulation. (c) The respiratory control ratio was also reduced by HFD and rescued by SRT1720 only in WT mice, as was FCCP-induced respiration (d). n = 4 mice per group; age = 30–32 weeks; diet = 18 weeks. Data are represented as the mean ± SEM. *P < 0.05 from WT SD, ^#P < 0.05 from KO SD, ^&P < 0.05 from WT HFD.