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GRK 1482 Jahrbuch 2011-2014

Publications [1] Phillips MI, Speakman EA, Kimura B., Levels of angio- tensin and molecular biology of the tissue renin angio- tensin systems. Regul Pept. 1993, 43: 1-20. [2] Elliot W.J., Meyer P.M., Incident diabetes in clinical trials of antihypertensive drugs: a network meta-analysis. The Lancet. 2007, 369(9572):1518. [3] Baggio, L.L., and Drucker, D.J., Biology of incretins: GLP-1 and GIP. Gastroenterology. 2007, 132:2131-2157. [4] Vilsbøll, T., Krarup, J. Sonne et al., “Incretin secretion in relation to meal size and body weight in healthy subjects and people with type 1 and type 2 diabetes mellitus,” The Journal of Clinical Endocrinology and Metabolis. 1993, vol. 88, no. 6, pp. PhD FELLOWS GRK Progress Report 2011-2014 | Page 59 Aim Preliminary experiments showed the presence of the AT1 recep- tor on GLP-1 secreting NCI-H716 cells. The aims of this project are 1) the investigation of the effect of Ang II on enteroendocrine cells and 2) the identification of the intracellular pathways involved. Additionally a human study is planned to determine the effects of Angiotensin receptor blockade on glucose, GLP-1 and insulin levels in pre-diabetic mildly hypertensive subjects. Methods and Results Results from Western Blot and qPCR analysis showed expres- sion of the AT1 receptor, but not of AT2 in the human entero- endocrine cell line NCI-H716. Uptake experiments with αMDG were performed with Ang II treated mouse intestinal rings. The uptake of radioactively labeled αMDG, a substrate for the glu- cose transporter SGLT1 was reduced by almost 30% in Ang II treated mice. Furthermore, pro-glucagon mRNA, the precursor of GLP-1, was reduced by almost 50% in intestinal cells of Ang II treated mice compared to PBS treated littermates upon glu- cose stimulation. To determine the effects of Ang II on GLP-1 secretion from L-cells, mouse crypt cells were prepared from murine small intestine and grown in cell culture. Cells were in- cubated with various concentrations of Ang II and were subse- quently stimulated with various effectors (isoprenalin, glucose) and GLP-1 secretion determined by ELISA. GLP-1 secretion could be detected from cells, which were co- treated with Ang II and Isoprenalin, a beta adrenergic agonist, but not from glu- cose treated cells. (see figure 1). It is planned to investigate this effect in more detail by blockade of the AT1 receptor, inhibiting different pathways of intracellular signaling and determine the effect of various Ang II concentrations and other components of the RAS. Furthermore a human study will be conducted to investigate possible beneficial effects of Ang II receptor blockade in mildly hypertensive, drug naive, pre-diabetic subjects. Patients will be treated with an angiotensin receptor blocker for several weeks. Prior to AT1 blocker treatment and at the end of the study blood samples will be drawn to determine the effects of angiotensin receptor blockade on GLP-1, insulin and glucose levels in the blood. Outlook Current cell culture experiments showed a substantial modu- lation of GLP-1 secretion after 24h pre-incubation with Ang II. Further experiments will therefore focus on the intracellular pathways involved in GLP-1 secretion. Various pathways from L-cells and from AT1 receptor signalling are known and will be targeted with available inhibitors to determine the interface of angiotensin and GLP-1 secretion. In the proposed human study we try to elucidate a putative mechanism which might explain the beneficial role of ACEi/AT1 receptor blockade on the diabe- tes risk. Figure 1:GLP1 secretion (secreted GLP-1/total GLP-1) from murine small intestinal crypt cells; Ang II cells were treated for 24 hrs with Ang II; all other effectors were incubated for 2h prior to sampling Supervisors Prof. Dr. Hans Hauner I TUM I Nutritional Medicine PD Dr. Thomas Skurk I TUM I Nutritional Medicine Prof. Dr. Hannelore Daniel I TUM I Physiology of Human Nutrition Start of project: September 2011 Academic background: Studies of Cell and Molecular Biology at Friedrich-Alexander-Universität-Erlangen-Nürnberg