Download to read offline
GH and IGF Research 2012 OR09-5
- 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