Insulin-like growth factor-I stimulates erythropoiesis when administered enterally

Growth Factors. 2006 Sep;24(3):218-23. doi: 10.1080/08977190600783162.

Abstract

Background: Insulin-like growth factors I and II (IGF-I and IGF-II) are potent growth factors involved in development. IGF-I stimulates proliferation of erythropoietic progenitors and parenteral IGF-I administration stimulates in vivo erythropoiesis in animals. IGF-I and IGF-II are both present in mammalian milks and when milk-borne, are resistant to neonatal gastrointestinal degradation. Whether milk-borne IGF-I or IGF-II regulates neonatal erythropoiesis in not known. We hypothesized that physiological doses of enteral IGFs stimulate erythropoiesis in suckling rats.

Methods: Eight day-old Sprague Dawley rats were artificially fed for 4 days with rat milk substitute (RMS) or RMS supplemented with physiological levels of IGF-I or IGF-II. Rats fed IGF-I and IGF-II were compared to control RMS. Blood and marrow were collected; measures of red cell mass, measures of erythropoietic stimulus, and indices of iron status were measured.

Results: Rats fed IGF-I had higher hemoglobin (Hb) levels (100 +/- 10 g/l), compared to those fed RMS (94 +/- 9) or IGF-II (91 +/- 6), p < 0.001. After IGF-I supplementation, red blood cell counts (RBC) (p < 0.04) and hematocrits (p < 0.002) were also higher. Plasma erythropoietin (Epo) levels, reticulocytes, plasma iron and erythrocyte iron incorporation were similar.

Conclusion: Intact enteral IGF-I reaches distal erythropoietic tissue resulting in greater red cell mass, but not by increasing plasma Epo levels or by altering cellular iron transport.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Enteral Nutrition
  • Erythropoiesis / physiology*
  • Erythropoietin / physiology
  • Female
  • Insulin-Like Growth Factor I / administration & dosage
  • Insulin-Like Growth Factor I / physiology*
  • Insulin-Like Growth Factor II / administration & dosage
  • Insulin-Like Growth Factor II / physiology*
  • Iron / physiology
  • Rats
  • Recombinant Proteins

Substances

  • Recombinant Proteins
  • Erythropoietin
  • Insulin-Like Growth Factor I
  • Insulin-Like Growth Factor II
  • Iron