title: Gluconeogenic signals regulate iron homeostasis via hepcidin in mice.
abstract: OBJECTIVE
  Hepatic gluconeogenesis provides fuel during starvation, and is abnormally induced in obese individuals or those with diabetes. Common metabolic disorders associated with active gluconeogenesis and insulin resistance (obesity, metabolic syndrome, diabetes, and nonalcoholic fatty liver disease) have been associated with alterations in iron homeostasis that disrupt insulin sensitivity and promote disease progression. We investigated whether gluconeogenic signals directly control Hepcidin, an important regulator of iron homeostasis, in starving mice (a model of persistently activated gluconeogenesis and insulin resistance).
  
  
  METHODS
  We investigated hepatic regulation of Hepcidin expression in C57BL/6Crl, 129S2/SvPas, BALB/c, and Creb3l3-/- null mice. Mice were fed a standard, iron-balanced chow diet or an iron-deficient diet for 9 days before death, or for 7 days before a 24- to 48-hour starvation period; liver and spleen tissues then were collected and analyzed by quantitative reverse-transcription polymerase chain reaction and immunoblot analyses. Serum levels of iron, hemoglobin, Hepcidin, and glucose also were measured. We analyzed human hepatoma (HepG2) cells and mouse primary hepatocytes to study transcriptional control of Hamp (the gene that encodes Hepcidin) in response to gluconeogenic stimuli using small interfering RNA, luciferase promoter, and chromatin immunoprecipitation analyses.
  
  
  RESULTS
  Starvation led to increased transcription of the gene that encodes phosphoenolpyruvate carboxykinase 1 (a protein involved in gluconeogenesis) in livers of mice, increased levels of Hepcidin, and degradation of Ferroportin, compared with nonstarved mice. These changes resulted in hypoferremia and iron retention in liver tissue. Livers of starved mice also had increased levels of Ppargc1a mRNA and Creb3l3 mRNA, which encode a transcriptional co-activator involved in energy metabolism and a liver-specific transcription factor, respectively. Glucagon and a cyclic adenosine monophosphate analog increased promoter activity and transcription of Hamp in cultured liver cells; levels of Hamp were reduced after administration of small interfering RNAs against Ppargc1a and Creb3l3. PPARGC1A and CREB3L3 bound the Hamp promoter to activate its transcription in response to a cyclic adenosine monophosphate analog. Creb3l3-/- mice did not up-regulate Hamp or become hypoferremic during starvation.
  
  
  CONCLUSIONS
  We identified a link between glucose and iron homeostasis, showing that Hepcidin is a gluconeogenic sensor in mice during starvation. This response is involved in hepatic metabolic adaptation to increased energy demands; it preserves tissue iron for vital activities during food withdrawal, but can cause excessive iron retention and hypoferremia in disorders with persistently activated gluconeogenesis and insulin resistance.
authors.affiliation: Center for Hemochromatosis and Metabolic Liver Diseases, Department of Medical and Surgical Sciences, University Hospital of Modena, Modena, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Vecchi
authors.affiliation: Center for Hemochromatosis and Metabolic Liver Diseases, Department of Medical and Surgical Sciences, University Hospital of Modena, Modena, Italy.
authors.forename: Giuliana
authors.initials: G
authors.lastname: Montosi
authors.affiliation: Center for Hemochromatosis and Metabolic Liver Diseases, Department of Medical and Surgical Sciences, University Hospital of Modena, Modena, Italy.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Garuti
authors.affiliation: Center for Hemochromatosis and Metabolic Liver Diseases, Department of Medical and Surgical Sciences, University Hospital of Modena, Modena, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Corradini
authors.affiliation: Center for Hemochromatosis and Metabolic Liver Diseases, Department of Medical and Surgical Sciences, University Hospital of Modena, Modena, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Sabelli
authors.affiliation: Center for Hemochromatosis and Metabolic Liver Diseases, Department of Medical and Surgical Sciences, University Hospital of Modena, Modena, Italy.
authors.forename: Susanna
authors.initials: S
authors.lastname: Canali
authors.affiliation: Center for Hemochromatosis and Metabolic Liver Diseases, Department of Medical and Surgical Sciences, University Hospital of Modena, Modena, Italy. Electronic address: antonello.pietrangelo@unimore.it.
authors.forename: Antonello
authors.initials: A
authors.lastname: Pietrangelo
mesh_terms: D000818:Animals; D001665:Binding Sites; D001786:Blood Glucose / Q000378:metabolism; D027682:Cation Transport Proteins / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000172:deficiency / Q000235:genetics; D004195:Disease Models, Animal; D005943:Gluconeogenesis; D006454:Hemoglobins / Q000378:metabolism; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000378:metabolism*; D064451:Hepcidins / Q000097:blood*; D006706:Homeostasis; D006801:Humans; D007333:Insulin Resistance; D007501:Iron / Q000097:blood*; D008099:Liver / Q000378:metabolism*; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D015398:Signal Transduction; D013154:Spleen / Q000378:metabolism; D013217:Starvation / Q000097:blood* / Q000235:genetics; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D015854:Up-Regulation; D000098742:Ferroportin
chemical_list: D001786:Blood Glucose; D027682:Cation Transport Proteins; C500051:Creb3l3 protein, mouse; D017362:Cyclic AMP Response Element-Binding Protein; C579599:Hamp protein, mouse; D006454:Hemoglobins; D064451:Hepcidins; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C485290:Ppargc1a protein, mouse; D014157:Transcription Factors; D000098742:Ferroportin; D007501:Iron; D010729:Phosphoenolpyruvate Carboxykinase (GTP)
keywords: Glucagon; Mouse Model; Peroxisome Proliferator-Activated Receptor-Gamma Co-activator 1-Alpha (PGC1A); cAMP Response Element-Binding Protein-H (CREBH)