Betatrophin, also known as ANGPTL8, is secreted by liver and adipose tissue and plays an important role in glucose and lipid metabolism, but the mechanisms behind this remain unclear. Betatrophin is highly activated by active triiodothyronine (T3), a key player in metabolic control, which in turn is activated by bile acids (BA) via the BA-G-protein-coupled receptor TGR5-cAMP-deiodinase (D2), mediating the conversion of prohormone thyroxine to T3. We here measured betatrophin by ELISA and also applied GWAS and targeted metabolomic profiling in 233 serum samples of coronary angiographied patients. We found a correlation between betatrophin and BMI (r=0.142, p<0.001), fasting glucose (r=0.133, p=0.002), insulin (r=0.221, p<0.001), triglycerides (r=0.233, p<0.001), HDL (-0.122, p=0.004), and oxLDL (r=0.247, p<0.001). GWAs also found a genome wide-association between betatrophin and genomic variants in sterol transporter genes ABCG5/G8 and ABCA1. In the metabolomic assay we identified BA as the top metabolites to be associated with betatrophin concentration in serum (CDCA, r=0.234, p<0.001; GDCA, r=0.247, p<0.001; GCA, r=0.269, p<0.001; GCDCA, r=0.268, p<0.001; GLCA, r=0.211, p=0.002; TDCA, r=0.184, p=0.006). In conclusion, this study for the first time describes the association between betatrophin and BA. As (i) T3 is activated by BA via the BA-TGR5-cAMP-D2 signalling pathway and (ii) T3 is a strong activator of betatrophin, the link between betatrophin concentration and BA suggests that, at least in part, the impact of BA on energy homeostasis and metabolic control may be mediated via betatrophin. Moreover, TGR5 receptors have also been identified on pancreatic islet α- and β-cells and are stimulating insulin secretion in β-cells and able to restore β-cell mass and function under hyperglycemic conditions. Altogether, this may elucidate the impact of betatrophin on lipid and glucose metabolism. Disclosure A. Leiherer: None. A. Muendlein: None. K. Geiger: None. C.H. Saely: None. E. Brandtner: None. J. Ebner: None. B. Larcher: None. A. Mader: None. P. Fraunberger: None. H. Drexel: None.
FOXO transcription factors control programmed cell death, stress resistance and longevity in normal and malignant cells. We investigated the expression, subcellular localization and phosphorylation of FOXO3 in tumour sections of post chemotherapy neuroblastoma (NB) patients and analysed the effects of FOXO3 in cultured NB cells.
Methods
Paraffin-embedded sections from patients were analysed for FOXO3 expression, localization and phosphorylation. Effects of chemotherapeutics on FOXO3 subcellular shuttling were assessed by live cell fluorescence imaging in ECFP-FOXO3 transgenic cells. To study how FOXO3 modulates survival we generated cell lines expressing a conditional PKB-independent FOXO3 allele (FOXO3(A3)ERtm) that can be activated by 4OH-tamoxifen and studied the effects of FOXO3-activation in vitro by clonagenic survival and propidium iodide FACS-analyses and in vivo by xenograft transplantation into nude mice.
Results
We found that FOXO3 was localised in the nucleus in tumour sections from high-risk NB patients. FOXO3 nuclear localization and phosphorylation significantly correlated with reduced patient survival. The chemotherapeutics etoposide and doxorubicin led to rapid nuclear accumulation and increased phosphorylation of FOXO3. After low activation of FOXO3 increased clonagenic survival was observed in NB8/FOXO3 cells in combination with chemotherapeutic drugs whereas NB15/FOXO3 cells underwent spontaneous apoptosis. When transplanting NB15/FOXO cells into nude mice, basal FOXO3 activity induced angiogenesis of NB tumours in vivo, whereas full activation eradicated the tumour.
Conclusions
The combined data suggest that FOXO3 is activated in high risk NB tumours and depending on the level of its activation, contributes to chemotherapy resistance and tumour angiogenesis or acts as a tumour suppressor.
Abstract Glioblastoma multiforme (GBM) is the most prevalent malignant primary brain tumor in adults. GBM is classified as primary if it is assumed to have arisen de novo or as secondary if it progressed from lower grade astrocytoma. Previous studies have found that primary and secondary GBMs have distinct molecular and mutational profiles. Both have a grim prognosis with survival times of about a year with therapy. Although much progress in delineating the temporal order of mutations and copy number aberrations in the progression of lower grade gliomas was made in the past years, none of the studies have actively followed individual tumors through their progression. Whereas this method can detect aberrations that are prevalent in gliomas, it can miss events that are important in a subset of gliomas or are necessary for progression. The GlioMath-DD consortium is an interdisciplinary collaboration of several groups at the Technische Universität Dresden (TU-Dresden) aiming to study the progression of gliomas and to come up with a mathematical model for gliomagenesis. The work involves analyzing pairs of gliomas obtained from patients who had presented with a low grade glioma and who later had a recurrence of a higher grade glioma. All tumors were checked by pathologists and then high quality DNA and RNA material extracted and used for analysis. The tumors are analyzed for copy number variations (CNV) by array comparative genome hybridization (aCGH), while gene expression changes and small mutations are analyzed using high-throughput sequencing (RNA- and Exome-seq). The data gleaned from these experiments and from in vitro models of cell growth and spheroid formation will be used by bioinformaticians and mathematicians to infer key signaling networks and formulate a mathematical model of glioma progression. The ultimate aim of this work that spans two and a half years is to create a comprehensive model of glioma promotion and progression. Furthermore, it will pinpoint driver mutations and aberrations that contribute to this progression and eventually isolate biomarkers for diagnosis and therapy. During the conference, we will present preliminary genetic data of our ongoing study. Acknowledgements: The GlioMath-DD project (coordinator: Andreas Deutsch; SAB-Number 100098214) is funded by the European Social Fund (ESF) and the Free State of Saxony Citation Format: Evelin Schröck, Khalil Abou-El-Ardat, Ralf Wiedemuth, Michael Seifert, Alvaro Köhn-Luque, Mirjam Ingargiola, Kristin Stirnnagel, Alexander Krüger, Wolfgang Nagel, Kathrin Geiger, Andreas Beyer, Leoni A. Kunz-Schughart, Gabriele Schackert, Achim Temme, Barbara Klink, Andreas Deutsch. GlioMath-DD: A multidisciplinary approach to study glioma evolution and identify targets for individualized therapies. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5341. doi:10.1158/1538-7445.AM2014-5341
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