Gene expression of the GH receptor in subcutaneous and intraabdominal fat in healthy females: relationship to GH-binding protein.
OBJECTIVE
Circulating GH-binding protein (GHBP) is produced by proteolytical cleavage of the extracellular part of the GH receptor (GHR) and is positively correlated to the amount of body fat. To test the hypothesis that adipose tissue may contribute to the production of circulating GHBP, we compared gene expression of two GHR isoforms in adipose tissue with serum GHBP concentrations in healthy females.


METHODS
Twenty-two healthy females undergoing surgery for benign gynecological conditions were included in the study.


METHODS
During surgery, s.c. and intraabdominal fat biopsy samples were taken. Gene expression of the full-length GHR and a truncated GHR (GHRtr) was assessed by RT-PCR relative to the expression of beta-actin.


RESULTS
The full-length GHR was expressed to a much higher level than GHRtr in both tissues. The levels of both GHR and GHRtr mRNA were similar in intraabdominal and s.c. adipose tissues. Surprisingly, concentrations of circulating GHBP were negatively correlated to the levels of mRNA transcripts of both the full-length GHR and GHRtr in intraabdominal fat. Whole body resistance (as a measure of lean body mass) was positively correlated to mRNA levels for both GHRs in intraabdominal fat.


CONCLUSIONS
(i) The full-length GHR is expressed to a much higher level than GHRtr in s.c. as well as visceral abdominal fat; (ii) the observation of a significant correlation between GHR expression and GHBP levels further emphasizes the link between adipose tissue and GHBP; (iii) it remains, however, to be demonstrated whether circulating GHBP is produced to a significant degree by adipose tissue.
Fisker
Sanne
S
Medical Department M (Endocrinology and Diabetes), Aarhus University Hospital, DK-8000 Aarhus C, Denmark. sanne.fisker@dadlnet.dk
Hansen
Betina
B
Fuglsang
Jens
J
Kristensen
Kurt
K
Ovesen
Per
P
Ørskov
Hans
H
Jørgensen
Jens Otto Lunde
JO
D000005:Abdomen; D000273:Adipose Tissue / Q000737:chemistry*; D001706:Biopsy; D001823:Body Composition; D002352:Carrier Proteins / Q000032:analysis*; D005260:Female; D015870:Gene Expression; D006801:Humans; D012333:RNA, Messenger / Q000032:analysis; D011986:Receptors, Somatotropin / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D002352:Carrier Proteins; D012333:RNA, Messenger; D011986:Receptors, Somatotropin; C051815:somatotropin-binding protein