Endogenous glucagon-like peptide 1 controls endocrine pancreatic secretion and antro-pyloro-duodenal motility in humans

Background: Exogenous use of the intestinal hormone glucagon-like peptide 1 (GLP-1) lowers glycaemia by stimulation of insulin, inhibition of glucagon, and delay of gastric emptying.Aims: To assess the effects of endogenous GLP-1 on endocrine pancreatic secretion and antro-pyloro-duodenal motility by utilising the GLP-1 receptor antagonist exendin(9-39)amide (ex(9-39)NH2).Methods: Nine healthy volunteers underwent four experiments each. In two experiments with and without intravenous infusion of ex(9-39)NH2 300 pmol/kg/min, a fasting period was followed by intraduodenal glucose perfusion at 1 and 2.5 kcal/min, with the higher dose stimulating GLP-1 release. Antro-pyloro-duodenal motility was measured by perfusion manometry. To calculate the incretin effect (that is, the proportion of plasma insulin stimulated by intestinal hormones) the glycaemia observed during the luminal glucose experiments was mimicked using intravenous glucose in two further experiments.Results: Ex(9-39)NH2 significantly increased glycaemia during fasting and duodenal glucose. It diminished plasma insulin during duodenal glucose and significantly reduced the incretin effect by approximately 50%. Ex(9-39)NH2 raised plasma glucagon during fasting and abolished the decrease in glucagon at the high duodenal glucose load. Ex(9-39)NH2 markedly stimulated antroduodenal contractility. At low duodenal glucose it reduced the stimulation of tonic and phasic pyloric motility. At the high duodenal glucose load it abolished pyloric stimulation.Conclusions: Endogenous GLP-1 stimulates postprandial insulin release. The pancreatic \textgreeka cell is under the tonic inhibitory control of GLP-1 thereby suppressing postprandial glucagon. GLP-1 tonically inhibits antroduodenal motility and mediates the postprandial inhibition of antral and stimulation of pyloric motility. We therefore suggest GLP-1 as a true incretin hormone and enterogastrone in humans

Differentielle Regulation der postprandialen Jejunummotilität des Menschen durch CCK und durch das cholinerge Nervensystem

Zusammenfassung der Promotionsarbeit: Differentielle Regulation der Postprandialen Jejunummotilität des Menschen durch CCK und durch das cholinerge Nervensystem Diese Studie untersuchte die Bedeutung des endogenen CCK und des cholinergen neuralen Inputs als physiologische Regulatoren der postprandialen Jejunummotilität und des Dünndarmtransits. Dazu wurden CCKA-Rezeptoren und muskarinerge Rezeptoren mit ihren entsprechenden spezifischen Antagonisten Loxiglumid und Atropin blockiert. Methodik: 9 gesunde männliche Probanden wurden an drei verschiedenen Tagen in randomisierter Reihenfolge unter Einfluss von a) NaCl 0,9%, b) Atropin [5µg / (kg KG x h)] und c) Loxiglumid [10 mg / (kg KG x h)] untersucht. Nach einer interdigestiven Periode von mindestens 20 Minuten wurde eine flüssige Mahlzeit (49% Kohlenhydrate, 35% Fett und 16% Eiweiß) für 240 Minuten mit 2,5 kcal pro Minute durch das proximalste Seitenloch des Manometriekatheters (8 Messpunkte mit 2 cm Zwischenabstand) unmittelbar distal des Treitz?schen Bandes perfundiert. Der Dünndarmtransit wurde mit dem H2-Atemtest (intrajejunaler Bolus von 15 g Lactulose) bestimmt. Ergebnisse: Mittelwert ± SEM ; * : p < 0,05 vs NaCl 0,9% ; # : p< 0,01 Loxiglumid vs Atropin. Die Angaben zu den Messergebnisse erfolgen nachfolgender Reihenfolge der Parameter: NaCL ; Atropin ; Loxiglumid. Summe der Kontraktionen / 240 min: 5434 ±568 ; 5140 ± 768 ; 3414 ± 629*#. mittlere Amplitude (mmHg): 18,9 ± 0,9 ; 23,9 ± 1,1* ; 16,3 ± 1,0 *#. Mittlere Dauer (sek) : 3,7 ± 0,2 ; 3,4 ± 0,1* ; 3,2 ± 0,1*. Motilitätsindex (mmHg x sek/240 min): 229248 ± 28446 ; 261446 ± 46120 ; 117587 ± 30879*#. summe der progressive fortgeleiteten Peaks / 240 min: 3957 ± 448 ; 2798 ± 522* ; 1824 ± 479*. % progressiver Peaks / 240 min: 58,7 ± 2,4 ; 40,2 ± 3,2* ; 39,8± 4,4*. Summe der Fortleitungen über 2 cm: 920 ± 107 ; 785 ± 147 ; 505 ± 130*. Summe der Fortleitungen über 4 ? 6 cm: 423 ± 50 ; 266 ± 56* ; 180 ± 59*. Summe der Fortleitungen über 8 ? 12cm: 117 ± 24 ; 61 ± 10* ; 37 ± 10*. Intestinale Transitzeit (min): 54,4 ± 11,3 ; 123,3 ± 24,8* ; 164,4 ± 24,1*. Diskussion: Beide, das endogene und der cholinerge neurale Input, sind wichtige Determinaten des intestinalen Transits, jedoch beeinflussen sie die postprandiale Jejunummotilität unterschiedlich. Das CCK ist ein wichtiger stimulatorischer Regulator der Aktivität (Frequenz, Amplitude, Dauer) und der zeitlichen und räumlichen Organisation (Fortleitung) der Kontraktionen. Der cholinerge Input stimuliert demgegenüber die Aktivität der Motilität nicht relevant, ist aber entscheidend für die Wellenfortleitung, besonders über lange Strecken. Der Dünndarmtransit hängt eindeutig mehr von der Organisation als von der Aktivität des Motilitätsmusters ab. Die differentiellen Effekte von Atropin und Loxiglumid sprechen dafür, dass CCK am Jejunum primär über CCKA-Rezeptoren auf der glatten Muskulatur statt über Rezeptoren auf cholinergen Neuronen wirkt

Technically advanced and SF6-free 145 kV blue GIS

SF6, the most commonly used arc extinguishing and insulating gas in gas-insulated switchgears (GIS), is a greenhouse gas with high global warming potential, requiring careful handling throughout its life cycle. In order to reduce the GIS-related global warming impact, innovative solutions using alternative gases have been developed by different manufacturers, especially the blue GIS from Siemens – available for 145 kV / 40 kA / 3150 A – with clean air insulation and vacuum switching technology shows many technical advantages

Technically advanced and SF6-free 145 kV blue GIS

SF6, the most commonly used arc extinguishing and insulating gas in gas-insulated switchgears (GIS), is a greenhouse gas with high global warming potential, requiring careful handling throughout its life cycle. In order to reduce the GIS-related global warming impact, innovative solutions using alternative gases have been developed by different manufacturers, especially the blue GIS from Siemens – available for 145 kV / 40 kA / 3150 A – with clean air insulation and vacuum switching technology shows many technical advantages

The HIFα-Stabilizing Drug Roxadustat Increases the Number of Renal Epo-Producing Sca-1+ Cells

Inhibition of the prolyl-4-hydroxylase domain (PHD) enzymes, leading to the stabilization of hypoxia-inducible factor (HIF) α as well as to the stimulation of erythropoietin (Epo) synthesis, is the functional mechanism of the new anti-anemia drug roxadustat. Little is known about the effects of roxadustat on the Epo-producing cell pool. To gain further insights into the function of PHD inhibitors, we characterized the abundance of mesenchymal stem cell (MSC)-like cells after roxadustat treatment of mice. The number of Sca-1+ mesenchymal cells following roxadustat treatment increased exclusively in the kidneys. Isolated Sca-1+ cells demonstrated typical features of MSC-like cells, including adherence to tissue culture plates, trilineage differentiation potential, and expression of MSC markers. Kidney-derived Sca-1+ MSC-like cells were cultured for up to 21 days. Within the first few days in culture, cells stabilized HIF-1α and HIF-2α and temporarily increased Epo production upon incubation in hypoxia. In summary, we have identified a Sca-1+ MSC-like cell population that is involved in renal Epo production and might contribute to the strong anti-anemic effect of the PHD inhibitor roxadustat

Cargo-specific effects of hypoxia on clathrin-mediated trafficking

Clathrin-associated trafficking is a major mechanism for intracellular communication, as well as for cells to communicate with the extracellular environment. A decreased oxygen availability termed hypoxia has been described to influence this mechanism in the past. Mostly biochemical studies were applied in these analyses, which miss spatiotemporal information. We have applied live cell microscopy and a newly developed analysis script in combination with a GFP-tagged clathrin-expressing cell line to obtain insight into the dynamics of the effect of hypoxia. Number, mobility and directionality of clathrin-coated vesicles were analysed in non-stimulated cells as well as after stimulation with epidermal growth factor (EGF) or transferrin in normoxic and hypoxic conditions. These data reveal cargo-specific effects, which would not be observable with biochemical methods or with fixed cells and add to the understanding of cell physiology in hypoxia. The stimulus-dependent consequences were also reflected in the final cellular output, i.e. decreased EGF signaling and in contrast increased iron uptake in hypoxia.</p

Acute cytomegalovirus infection modulates the intestinal microbiota and targets intestinal epithelial cells

Primary and recurrent cytomegalovirus (CMV) infections frequently cause CMV colitis in immunocompromised as well as inflammatory bowel disease (IBD) patients. Additionally, colitis occasionally occurs upon primary CMV infection in patients who are apparently immunocompetent. In both cases, the underlying pathophysiologic mechanisms are largely elusive - in part due to the lack of adequate access to specimens. We employed the mouse cytomegalovirus (MCMV) model to assess the association between CMV and colitis. During acute primary MCMV infection of immunocompetent mice, the gut microbial composition was affected as manifested by an altered ratio of the Firmicutes to Bacteroidetes phyla. Interestingly, these microbial changes coincided with high-titer MCMV replication in the colon, crypt hyperplasia, increased colonic pro-inflammatory cytokine levels, and a transient increase in the expression of the antimicrobial protein Regenerating islet-derived protein 3 gamma (Reg3γ). Further analyses revealed that murine and human intestinal epithelial cell lines, as well as primary intestinal crypt cells and organoids represent direct targets of CMV infection causing increased cell death. Accordingly, in vivo MCMV infection disrupted the intestinal epithelial barrier and increased apoptosis of intestinal epithelial cells. In summary, our data show that CMV transiently induces colitis in immunocompetent hosts by altering the intestinal homeostasis

Neurogenic and pericytic plasticity of conditionally immortalized cells derived from renal erythropoietin‐producing cells

In adult mammals, the kidney is the main source of circulating erythropoietin (Epo), the master regulator of erythropoiesis. In vivo data in mice demonstrated multiple subtypes of interstitial renal Epo-producing (REP) cells. To analyze the differentiation plasticity of fibroblastoid REP cells, we used a transgenic REP cell reporter mouse model to generate conditionally immortalized REP-derived (REPD) cell lines. Under nonpermissive conditions, REPD cells ceased from proliferation and acquired a stem cell-like state, with strongly enhanced hypoxia-inducible factor 2 (HIF-2α), stem cell antigen 1 (SCA-1), and CD133 expression, but also enhanced alpha-smooth muscle actin (αSMA) expression, indicating myofibroblastic signaling. These cells maintained the “on-off” nature of Epo expression observed in REP cells in vivo, whereas other HIF target genes showed a more permanent regulation. Like REP cells in vivo, REPD cells cultured in vitro generated long tunneling nanotubes (TNTs) that aligned with endothelial vascular structures, were densely packed with mitochondria and became more numerous under hypoxic conditions. Although inhibition of mitochondrial oxygen consumption blunted HIF signaling, removal of the TNTs did not affect or even enhance the expression of HIF target genes. Apart from pericytes, REPD cells readily differentiated into neuroglia but not adipogenic, chondrogenic, or osteogenic lineages, consistent with a neuronal origin of at least a subpopulation of REP cells. In summary, these results suggest an unprecedented combination of differentiation features of this unique cell type

Deletion of the non-adjacent genes UL148 and UL148D impairs human cytomegalovirus-mediated TNF receptor 2 surface upregulation

Human cytomegalovirus (HCMV) is a prototypical β-herpesvirus which frequently causes morbidity and mortality in individuals with immature, suppressed, or senescent immunity. HCMV is sensed by various pattern recognition receptors, leading to the secretion of pro-inflammatory cytokines including tumor necrosis factor alpha (TNFα). TNFα binds to two distinct trimeric receptors: TNF receptor (TNFR) 1 and TNFR2, which differ in regard to their expression profiles, affinities for soluble and membrane-bound TNFα, and down-stream signaling pathways. While both TNF receptors engage NFκB signaling, only the nearly ubiquitously expressed TNFR1 exhibits a death domain that mediates TRADD/FADD-dependent caspase activation. Under steady-state conditions, TNFR2 expression is mainly restricted to immune cells where it predominantly submits pro-survival, proliferation-stimulating, and immune-regulatory signals. Based on the observation that HCMV-infected cells show enhanced binding of TNFα, we explored the interplay between HCMV and TNFR2. As expected, uninfected fibroblasts did not show detectable levels of TNFR2 on the surface. Intriguingly, however, HCMV infection increased TNFR2 surface levels of fibroblasts. Using HCMV variants and BACmid-derived clones either harboring or lacking the ULb’ region, an association between TNFR2 upregulation and the presence of the ULb’ genome region became evident. Applying a comprehensive set of ULb’ gene block and single gene deletion mutants, we observed that HCMV mutants in which the non-adjacent genes UL148 or UL148D had been deleted show an impaired ability to upregulate TNFR2, coinciding with an inverse regulation of TACE/ADAM17