Kopchick JJ et al. Deletion, but not antagonism, of the mouse growth hormone receptor results in severely decreased body weights, insulin, and insulin-like growth factor I levels and increased life span. Endocrinology 2003; 144: 3799–3810. 5 Fontana L, Weiss EP, Villareal DT, Klein S, Holloszy JO. Long-term effects of calorie or protein restriction on serum IGF-1 and IGFBP-3 concentration in humans. Aging Cell 2008; 7: 681–687. 6 Bartke A. Can growth hormone (GH) accelerate aging? Evidence from GH-transgenic mice. Neuroendocrinology 2003; 78: 210–216. 7 Ikeno Y, Hubbard GB, Lee S, Cortez LA, Lew CM, Webb CR et al. Reduced incidence and delayed occurrence of fatal neoplastic diseases in growth hormone receptor/binding protein knockout mice. J Gerontol A Biol Sci Med Sci 2009; 64: 522–529. 8 Russell SJ, Kahn CR. Endocrine regulation of ageing. Nat Rev Mol Cell Biol 2007; 8: 681–691. 9 Ratajczak J, Zhang Q, Pertusini E, Wojczyk BS, Wasik MA, Ratajczak MZ. The role of insulin (INS) and insulin-like growth factor-I (IGF-I) in regulating human erythropoiesis. Studies in vitro under serum-free conditionsFcomparison to other cytokines and growth factors. Leukemia 1998; 12: 371–381. 10 Reik W, Walter J. Genomic imprinting: parental influence on the genome. Nat Rev Genet 2001; 2: 21–32. 11 Kucia M, Reca R, Campbell FR, Zuba-Surma E, Majka M, Ratajczak J et al. A population of very small embryonic-like (VSEL) CXCR4+SSEA-1+Oct-4+ stem cells identified in adult bone marrow. Leukemia 2006; 20: 857–869. 12 Ratajczak J, Wysoczynski M, Zuba-Surma E, Wan W, Kucia M, Yoder MC et al. Adult murine bone marrow-derived very small embryoniclike stem cells (VSELs) differentiate into the hematopoietic lineage after co-culture over op9 stromal cells. Exp Hematol 2011; 39: 225–237. 13 Shin DM, Zuba-Surma EK, Wu W, Ratajczak J, Wysoczynski M, Ratajczak MZ et al. Novel epigenetic mechanisms that control pluripotency and quiescence of adult bone marrow-derived Oct4+ very small embryonic-like stem cells. Leukemia 2009; 23: 2042–2051. 14 Ratajczak MZ, Shin DM, Ratajczak J, Kucia M, Bartke A. A novel insight into aging: are there pluripotent very small embryonic-like stem cells (VSELs) in adult tissues overtime depleted in an Igf-1dependent manner? Aging 2010; 2: 875–883. 15 Ratajczak J, Shin DM, Wan W, Liu R, Masternak MM, Piotrowska K, et al. Higher number of stem cells in the bone marrow of circulating low Igf-1 level Laron dwarf mice-novel view on Igf-1, stem cells and aging. Leukemia 2011; 25: 729–733. 16 Westbrook R, Bonkowski MS, Strader AD, Bartke A. Alterations in oxygen consumption, respiratory quotient, and heat production in long-lived GHRKO and Ames dwarf mice, and short-lived bGH transgenic mice. J Gerontol A Biol Sci Med Sci 2009; 64: 443–451. 17 Feinberg AP. Phenotypic plasticity and the epigenetics of human disease. Nature 2007; 447: 433–440.