1. Oral Presentations / Growth Hormone & IGF Research 22 (2012) S1–S31 S25
lines and/or cancer types in their investigation of the role of these
signaling pathways in carcinogenesis.
OR09-5
Signal tranducer and activator of transcription 5 mediates
the anti-obesity actions of growth hormone
C.N. Nelson1
, J.L. Barclay1
, M.J. Waters1
. 1
University of Queensland,
Institute for Molecular Bioscience, Brisbane, Australia
Aims: Growth hormone (GH) is a well established as having anti-
obesity actions. Growth hormone receptor (GHR) mouse mutants
with abrogated GH activation of signal transducer and activator of
transcription (STAT) 5 (ghr-391) develop late onset obesity, with
the most dramatic difference seen in the inguinal subcutaneous
fat pads (iWAT). The obesity is apparent by 4 months of age. Here
the ghr-391 mice have been used to investigate the mechanism
by which GH-activated STAT5 mediates the anti-obesity actions of
GH.
Method: Transcript analysis of genes involved in fatty acid
metabolism and adipogenesis in iWAT of 4 month old ghr-391
and wt controls (n = 4–6) was performed by using qPCR arrays to
identify any putative genes regulated by GHR-STAT5. Histological
analysis was performed on iWAT sections to determine if adipocyte
size or number was affected.
Results: Adipocyte hypertrophy was observed in ghr-391 mice
iWAT with a 3 fold increase in the iWAT weight (normalized to
body weight) at 4 months of age. Transcript analysis revealed
several brown adipose markers such as Prdm16, Ppara, Pgc1a
and Pgc1b were down-regulated, the latter trio also well known
to promote fatty acid b-oxidation. Conversely, Bmp2 and Bmp4,
transcripts promoting white adipose differentiation, were up-
regulated. Expression of classic adipogenic markers Pparg, Cebpb,
Cebpd, Fabp4 and Srebf1 were either unaltered or decreased. E2f1,
a negative regulator of oxidative metabolism, was up-regulated.
Several enzymes involved in the fatty acid b-oxidation pathway
were down-regulated: carnitine transferases, Cpt1b and Cpt2; acyl-
CoA dehydrogenases Acadl and Acadvl; acyl-CoA synthetase, Acsm3
and the inorganic pyrophosphatase, Ppa1.
Conclusions: Adipocyte hypertrophy, the lack of change in classic
adipogenic markers and the reduction in expression of genes
involved in b-oxidation of fatty acids in the ghr-391 mice suggests
that loss of GH-activated STAT5 predominantly results in an
inability to mobilize fat stores. Adipose tissue traditionally exists as
two types of stores: white and brown. White predominately being
used to store excess energy and brown for thermogenesis. White
adipose, particularly iWAT in rodents, has been shown to have
plasticity under cold stress and b-adrenergic stimulation that allows
it to take on brown-like adipose characteristics. The increase of this
intermediate “beige” or “brite” adipose profile in white adipose
has been correlated with decreased body fat and resistance to diet
induced obesity. The transcript profile of the iWAT has revealed a
number of brown or “beige” adipose markers down-regulated in
the ghr-391 mutants, indicating that GH-activated STAT5 has an
important role in the “browning” of white adipose tissue.
Funded by NHMRC (Australia).
OR09-6
Placental growth hormone (GHV) is the predominant growth
hormone transcript in MCF7 breast cancer cells
J. Herpy1
, E.S. Gosney1,2
, J.J. Kopchick1,3
. 1
Ohio University, Edison
Biotechnology Institute, Athens, United States; 2
Ohio University,
Dept of BIOS, MCB Program, Athens, United States; 3
Ohio University
Heritage College of Osteopathic Medicine, Dept of Biomedical Sciences,
Athens, United States
Abnormal regulation of hormones can alter the cellular
environment in a way that permits and/or promotes the growth of
certain cancers. Many hormones, including growth hormone (GH),
prolactin, insulin and insulin-like growth factors appear to promote
carcinogenesis. For example, research suggests that individuals with
acromegaly (high circulating GH due to a pituitary adenoma) have
been shown to be at an increased risk to develop certain types of
cancer, while Laron patients, who are dwarf and GH-insensitive,
rarely develop tumors. Existing research evaluating GH expression
in cancer biopsies or cell lines has largely neglected to address the
fact that there are five homologous genes in the GH gene cluster
that share high sequence conservation. Adding further complexity,
four genes in the cluster express multiple transcript variants that
arise due to alternative splicing. We have established a method
to identify expression of these transcript variants using RT qPCR
coupled with agarose gel extraction and DNA sequencing. This
method was validated using RNA from MCF7 breast cancer cells.
qPCR was performed with primers that amplify multiple mRNA
variants from all five related GH genes. We detected expression
of a transcript from the GH gene family in these breast cancer
cells. By gel isolation and sequencing of the PCR product, we
identified the transcript to be placental GH (GHV, also known
as GH2) transcript variant 1. Following this validation, we have
begun analysis of all 60 cell lines included in the National Cancer
Institute’s NCI60 human cancer panel (RNA provided by NCI). All
cell lines that express detectable levels of GH will be profiled to
determine the specific GH variant(s) present. We hope this work
will reveal new information about the role of the GH gene family
in cancer.
OR10: IGFs: Biomarkers & clinical outcomes
OR10-1
Bioactive IGF-I and IGFBP-1 in Danish children and adolescents
3 to 5 years after onset of type 1 diabetes. Effect of residual
b-cell function
J. Frystyk1
, J.S. Sørensen2
, M. Bjerre1
, N.H. Birkebæk2
. 1
Medical
Research Laboratory, Institute of Clinical Medicine, Faculty of Health
Sciences, Aarhus University, Aarhus, Denmark; 2
Department of
Pediatrics, Aarhus University Hospital, Aarhus, Denmark
Background: Patients with type 1 diabetes (T1D) show
abnormalities in the GH-IGF-I axis, which may influence
growth, body composition, metabolic control and development of
complications. Portal insulin stimulates the hepatic IGF-I generation
and adults with T1D and a residual b-cell function (RBCF) have
higher levels of IGF-I than patients without RBCF. Therefore, we
hypothesized that RBCF positive children have higher IGF-I levels
than RBCF negative children.
Objective: To compare overnight fasting serum levels of bioactive
IGF-I, total IGF-I, IGFBP-1 and IGFBP-3 in RBCF positive and negative
T1D children/adolescents and healthy controls.
Methods: The study cohort included 336 children/adolescents (167
females) with a median age of 13.6 years (range 4.8–18.9) and T1D
for 3 to 5 years, and 70 (40 females) healthy controls with a median
age of 12.1 years (range 7.4–16.9). Bioactive IGF-I was determined
by a cell-based IGF-I kinase receptor activation assay, IGFBP-1 by
in-house immunoassay and IGF-I and IGFBP-3 by iSYS (from IDS).
A positive RBCF was defined as a meal-stimulated C-peptide level
>100 pM.
Results: Patients had lower (p < 0.001) bioactive IGF-I (Mean±SD)
(1.56±0.96 vs. 2.36±1.02 mg/l) and total IGF-I (251±108 vs.
302±137mg/l), whereas IGFBP-1 was higher (342±251 vs. 200±91
mg/l; p < 0.001). There was no difference (p = 0.37) in IGFBP-3
(5162±1085 vs. 5285±863 mg/l). RBCF positive patients had higher
bioactive IGF-I, total IGF-I and IGFBP-3, but lower IGFBP-1 as
compared to RBCF negative patients (p < 0.05). In regards to pubertal
status, prepubertal RBCF positive children had significantly higher
bioactive IGF-I, total IGF-I and IGFBP-3, but lower IGFBP-1 as com-
pared to prepubertal RBCF negative children. Similar differences