Document Detail


Insulin-like growth factor 2 and the insulin receptor, but not insulin, regulate fetal hepatic glycogen synthesis.
MedLine Citation:
PMID:  20032056     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Whether insulin or IGFs regulate glycogen synthesis in the fetal liver remains to be determined. In this study, we used several knockout mouse strains, including those lacking Pdx-1 (pancreatic duodenal homeobox-1), Insr (insulin receptor), and Igf2 (IGF-II) to determine the role of these genes in the regulation of fetal hepatic glycogen synthesis. Our data show that insulin deficiency does not alter hepatic glycogen stores, whereas Insr and Igf2 deficiency do. We found that both insulin receptor isoforms (IR-A and IR-B) are present in the fetal liver, and their expression is gestationally regulated. IR-B is highly expressed in the fetal liver; nonetheless, the percentage of hepatic IR-A isoform, which binds Igf2, was significantly higher in the fetus than the adult. In vitro experiments demonstrate that Igf2 increases phosphorylation of hepatic Insr, insulin receptor substrate-2, and Akt proteins and also the activity of glycogen synthase. Igf2 ultimately increased glycogen synthesis in fetal hepatocytes. This increase could be blocked by the phosphoinositide 3-kinase inhibitor LY294008. Taken together, we propose Igf2 as a major regulator of fetal hepatic glycogen metabolism, the insulin receptor as its target receptor, and phosphoinositide 3-kinase as the signaling pathway leading to glycogen formation in the fetal liver.
Authors:
Li Liang; Wei Hui Guo; Diego R Esquiliano; Masato Asai; Susana Rodriguez; Jodel Giraud; Jake A Kushner; Morris F White; Mary Frances Lopez
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2009-12-23
Journal Detail:
Title:  Endocrinology     Volume:  151     ISSN:  1945-7170     ISO Abbreviation:  Endocrinology     Publication Date:  2010 Feb 
Date Detail:
Created Date:  2010-01-26     Completed Date:  2010-02-26     Revised Date:  2011-07-22    
Medline Journal Info:
Nlm Unique ID:  0375040     Medline TA:  Endocrinology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  741-7     Citation Subset:  AIM; IM    
Affiliation:
Department of Medicine/Endocrine Division, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
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MeSH Terms
Descriptor/Qualifier:
Animals
Cells, Cultured
Crosses, Genetic
DNA Primers
Female
Fetus / drug effects,  physiology
Glycogen Synthase / metabolism
Hepatocytes / cytology,  enzymology,  physiology*
Heterozygote
Homeostasis
Insulin / deficiency,  genetics,  physiology*
Insulin-Like Growth Factor II / deficiency,  genetics,  physiology*
Liver Glycogen / blood*
Male
Mice
Mice, Knockout
RNA, Messenger / genetics
Receptor, Insulin / deficiency,  genetics,  physiology*
Grant Support
ID/Acronym/Agency:
R01 GM071046/GM/NIGMS NIH HHS
Chemical
Reg. No./Substance:
0/DNA Primers; 0/Liver Glycogen; 0/RNA, Messenger; 11061-68-0/Insulin; 67763-97-7/Insulin-Like Growth Factor II; EC 2.4.1.11/Glycogen Synthase; EC 2.7.10.1/Receptor, Insulin
Comments/Corrections

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