Nutritional regulation of gene expression of insulin-like growth factor-binding proteins and the acid-labile subunit in various tissues of rats.
The plasma concentration and liver mRNA content of IGF-I are regulated by the quantity and quality of dietary proteins. To determine whether the synthesis of IGF-binding proteins (BPs) is also affected by protein nutrition, we assessed plasma concentration, tissue mRNA content and liver transcription rate of each BP after rats were fed either a 12% casein or a protein-free diet for 1 week. Protein deprivation reduced the plasma concentration of IGFBP-3 and IGFBP-4 and increased that of IGFBP-1 and IGFBP-2. The mRNA content in tissues and liver transcription rates of IGFBP-3 and IGFBP-4 did not change in response to protein deprivation although their plasma concentrations decreased. The increased plasma IGFBP-1 and IGFBP-2 concentrations were explained by the increased mRNA content and transcription rate of their genes in the liver. Although IGFBP-1 mRNA was increased by protein deprivation not only in liver but also in kidney, IGFBP-2 mRNA was increased only in liver and did not increase in any other tissue examined. In addition, the liver mRNA content of the acid-labile subunit, which can form a ternary complex with IGFs and IGFBP-3, was not affected by protein deprivation. These results show that tissue-specific synthesis of each BP is regulated in a distinct way in response to protein deprivation.
Takenaka
A
A
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Japan.
Mori
M
M
Yamada
S
S
Ohgane
J
J
Takahashi
S
S
Noguchi
T
T
D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics*; D002364:Caseins / Q000008:administration & dosage; D017931:DNA Primers / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology*; D006023:Glycoproteins / Q000235:genetics*; D015151:Immunoblotting; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood / Q000235:genetics*; D008099:Liver / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D011502:Protein-Energy Malnutrition / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D013002:Somatomedins / Q000235:genetics*; D014158:Transcription, Genetic
D002352:Carrier Proteins; D002364:Caseins; D017931:DNA Primers; D006023:Glycoproteins; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D013002:Somatomedins; C075944:insulin-like growth factor binding protein, acid labile subunit