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

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

Copper-dependent activation of hypoxia-inducible factor (HIF)-1: implications for ceruloplasmin regulation

Cellular oxygen partial pressure is sensed by a family of prolyl-4-hydroxylase domain (PHD) enzymes that modify hypoxia-inducible factor (HIF)alpha subunits. Upon hydroxylation under normoxic conditions, HIFalpha is bound by the von Hippel-Lindau tumor suppressor protein and targeted for proteasomal destruction. Since PHD activity is dependent on oxygen and ferrous iron, HIF-1 mediates not only oxygen- but also iron-regulated transcriptional gene expression. Here we show that copper (CuCl(2)) stabilizes nuclear HIF-1alpha under normoxic conditions, resulting in hypoxia-response element (HRE)-dependent reporter gene expression. In in vitro hydroxylation assays CuCl(2) inhibited prolyl-4-hydroxylation independently of the iron concentration. Ceruloplasmin, the main copper transport protein in the plasma and a known HIF-1 target in vitro, was also induced in vivo in the liver of hypoxic mice. Both hypoxia and CuCl(2) increased ceruloplasmin (as well as vascular endothelial growth factor [VEGF] and glucose transporter 1 [Glut-1]) mRNA levels in hepatoma cells, which was due to transcriptional induction of the ceruloplasmin gene (CP) promoter. In conclusion, our data suggest that PHD/HIF/HRE-dependent gene regulation can serve as a sensory system not only for oxygen and iron but also for copper metabolism, regulating the oxygen-, iron- and copper-binding transport proteins hemoglobin, transferrin, and ceruloplasmin, respectively

Ferritin-Mediated Iron Sequestration Stabilizes Hypoxia-Inducible Factor-1α upon LPS Activation in the Presence of Ample Oxygen

SummaryBoth hypoxic and inflammatory conditions activate transcription factors such as hypoxia-inducible factor (HIF)-1α and nuclear factor (NF)-κB, which play a crucial role in adaptive responses to these challenges. In dendritic cells (DC), lipopolysaccharide (LPS)-induced HIF1α accumulation requires NF-κB signaling and promotes inflammatory DC function. The mechanisms that drive LPS-induced HIF1α accumulation under normoxia are unclear. Here, we demonstrate that LPS inhibits prolyl hydroxylase domain enzyme (PHD) activity and thereby blocks HIF1α degradation. Of note, LPS-induced PHD inhibition was neither due to cosubstrate depletion (oxygen or α-ketoglutarate) nor due to increased levels of reactive oxygen species, fumarate, and succinate. Instead, LPS inhibited PHD activity through NF-κB-mediated induction of the iron storage protein ferritin and subsequent decrease of intracellular available iron, a critical cofactor of PHD. Thus, hypoxia and LPS both induce HIF1α accumulation via PHD inhibition but deploy distinct molecular mechanisms (lack of cosubstrate oxygen versus deprivation of co-factor iron)

The Role of PAS Kinase in PASsing the Glucose Signal

PAS kinase is an evolutionarily conserved nutrient responsive protein kinase that regulates glucose homeostasis. Mammalian PAS kinase is activated by glucose in pancreatic beta cells, and knockout mice are protected from obesity, liver triglyceride accumulation, and insulin resistance when fed a high-fat diet. Yeast PAS kinase is regulated by both carbon source and cell integrity stress and stimulates the partitioning of glucose toward structural carbohydrate biosynthesis. In our current model for PAS kinase regulation, a small molecule metabolite binds the sensory PAS domain and activates the enzyme. Although bona fide PAS kinase substrates are scarce, in vitro substrate searches provide putative targets for exploration

TLR9-Dependent and Independent Pathways Drive Activation of the Immune System by Propionibacterium Acnes

Propionibacterium acnes is usually a relatively harmless commensal. However, under certain, poorly understood conditions it is implicated in the etiology of specific inflammatory diseases. In mice, P. acnes exhibits strong immunomodulatory activity leading to splenomegaly, intrahepatic granuloma formation, hypersensitivity to TLR ligands and endogenous cytokines, and enhanced resistance to infection. All these activities reach a maximum one week after P. acnes priming and require IFN-γ and TLR9. We report here the existence of a markedly delayed (1–2 weeks), but phenotypically similar TLR9-independent immunomodulatory response to P. acnes. This alternative immunomodulation is also IFN-γ dependent and requires functional MyD88. From our experiments, a role for MyD88 in the IFN-γ-mediated P. acnes effects seems unlikely and the participation of the known MyD88-dependent receptors, including TLR5, Unc93B-dependent TLRs, IL-1R and IL-18R in the development of the alternative response has been excluded. However, the crucial role of MyD88 can partly be attributed to TLR2 and TLR4 involvement. Either of these two TLRs, activated by bacteria and/or endogenously generated ligands, can fulfill the required function. Our findings hint at an innate immune sensitizing mechanism, which is potentially operative in both infectious and sterile inflammatory disorders