23. Lemieux ME, Yang X, Jardine K, He X, Jacobsen KX, et al. (2005) The Sirt1 deacetylase modulates the insulin-like growth factor signaling pathway in mammals. Mech Ageing Dev 126: 1097–1105. 24. Miwa S, Brand MD (2003) Mitochondrial matrix reactive oxygen species production is very sensitive to mild uncoupling. Biochem Soc Trans 31: 1300–1301. 25. Skulachev VP (1998) Uncoupling: new approaches to an old problem of bioenergetics. Biochim Biophys Acta 1363: 100–124. 26. Cohen HY, Miller C, Bitterman KJ, Wall NR, Hekking B, et al. (2004) Calorie restriction promotes mammalian cell survival by inducing the SIRT1 deacetylase. Science 305: 390–392. 27. Chen D, Steele AD, Lindquist S, Guarente L (2005) Increase in activity during calorie restriction requires Sirt1. Science 310: 1641. 28. Nemoto S, Fergusson MM, Finkel T (2005) SIRT1 functionally interacts with the metabolic regulator and transcriptional coactivator PGC-1{alpha}. J Biol Chem 280: 16456–16460. 29. Zhang J (2007) The Direct Involvement of SirT1 in Insulin-induced Insulin Receptor Substrate-2 Tyrosine Phosphorylation. J Biol Chem 282: 34356–34364. 30. Sun C, Zhang F, Ge X, Yan T, Chen X, et al. (2007) SIRT1 improves insulin sensitivity under insulin-resistant conditions by repressing PTP1B. Cell Metab 6: 307–319. 31. Bartke A, Wright JC, Mattison JA, Ingram DK, Miller RA, et al. (2001) Extending the lifespan of long-lived mice. Nature 414: 412. 32. Fukuda R, Zhang H, Kim JW, Shimoda L, Dang CV, et al. (2007) HIF-1 regulates cytochrome oxidase subunits to optimize efficiency of respiration in hypoxic cells. Cell 129: 111–122. SirT1 and Caloric Restriction 33. Schieke SM, Phillips D, McCoy JP Jr, Aponte AM, Shen RF, et al. (2006) The mammalian target of rapamycin (mTOR) pathway regulates mitochondrial oxygen consumption and oxidative capacity. J Biol Chem 281: 27643–27652. 34. Chappell JB, Perry SV (1954) Biochemical and osmotic properties of skeletal muscle mitochondria. Nature 173: 1094–1095. 35. Bevilacqua L, Ramsey JJ, Hagopian K, Weindruch R, Harper ME (2005) Long- term caloric restriction increases UCP3 content but decreases proton leak and reactive oxygen species production in rat skeletal muscle mitochondria. Am J Physiol Endocrinol Metab 289: E429–438. 36. Reynafarje B, Costa LE, Lehninger AL (1985) O2 solubility in aqueous media determined by a kinetic method. Anal Biochem 145: 406–418. 37. Bevilacqua L, Ramsey JJ, Hagopian K, Weindruch R, Harper ME (2004) Effects of short- and medium-term calorie restriction on muscle mitochondrial proton leak and reactive oxygen species production. Am J Physiol Endocrinol Metab 286: E852–861. 38. Kamo N, Muratsugu M, Hongoh R, Kobatake Y (1979) Membrane potential of mitochondria measured with an electrode sensitive to tetraphenyl phosphonium and relationship between proton electrochemical potential and phosphorylation potential in steady state. J Membr Biol 49: 105–121. 39. Bezaire V, Hofmann W, Kramer JK, Kozak LP, Harper ME (2001) Effects of fasting on muscle mitochondrial energetics and fatty acid metabolism in Ucp3(-/-) and wild-type mice. Am J Physiol Endocrinol Metab 281: E975–982. 40. Hyslop PA, Sklar LA (1984) A quantitative fluorimetric assay for the determination of oxidant production by polymorphonuclear leukocytes: its use in the simultaneous fluorimetric assay of cellular activation processes. Anal Biochem 141: 280–286. PLoS ONE | www.plosone.org 12 2008 | Volume 3 | Issue 3 | e1759