Effects of glucose, propionate and splanchnic hormones on neuropeptide mRNA concentrations in the ovine hypothalamus

The capacity for glucose, propionate or hormones of splanchnic origin to influence appetite by directly regulating the expression of neuropeptides in the feeding centres of the hypothalamus of the ruminant is not described. Therefore, our objective was to measure the direct effect of metabolites (glucose and propionate) or hormones [insulin, cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1) and polypeptide YY (PYY)] on hypothalamic mRNA concentrations for neuropeptide Y (NPY), agouti-related peptide (AgRP) and proopiomelanocortin (POMC) following in vitro incubation. Hypothalamic tissue from 4- to 5-month-old lambs was obtained at slaughter and immediately incubated in culture media for 2 h at 36 °C. Treatments included a control Dulbecco’s modified Eagle medium (DMEM) containing 1 mm glucose or DMEM with the following additions: 10 mm glucose, 1 mm propionate, 1 nm insulin, 120 pm GLP-1, 100 pm PYY, 80 pm CCK or 10 mm glucose plus 1 nm insulin. The abundance of mRNA for NPY, AgRP and POMC was measured using quantitative reverse transcriptase PCR. Fisher’s protected LSD test was used to compare changes in relative mRNA concentrations for the hypothalamus incubated in the control media vs. the rest of the treatments. The media containing glucose plus insulin increased POMC mRNA concentration (p < 0.05), but did not affect NPY or AgRP mRNA concentration. There were no effects observed for the other treatments (p > 0.20). Results of the present study are consistent with the concept that effects of propionate on feed intake in ruminants is not mediated through direct effects on the hypothalamus, and that insulin is required for an effect of glucose on hypothalamic POMC expression.

Effects of pentoxifylline and n-acetylcysteine on injuries caused by ischemia and reperfusion splanchnic organs in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Systemic evaluation on ischemia and reperfusion injury of splanchnic organs in rats

OBJETIVO: Avaliar as alterações hemodinâmicas e sistêmicas decorrentes de isquemia e reperfusão (I/R) esplâncnica em ratos. MÉTODOS: Vinte ratos foram divididos em dois grupos: grupo controle: os animais foram submetidos à cirurgia, mas não a I/R e foram tratados com solução fisiológica (5 ml/kg/h) por 150 minutos; grupo I/R: os animais foram submetidos à administração contínua de solução fisiológica e à oclusão do tronco celíaco, artéria mesentérica superior e artéria mesentérica inferior por 30 minutos, seguidos por 120 minutos de reperfusão. Avaliou-se a pressão arterial média, pressão venosa, fluxo sangüíneo na aorta e na artéria mesentérica superior, freqüência cardíaca, temperatura esofágica e hematócrito. RESULTADOS: Durante a reperfusão, no grupo I/R, houve uma diminuição progressiva da pressão arterial média, fluxo sangüíneo na aorta e artéria mesentérica superior, freqüência cardíaca e temperatura esofágica; pressão venosa e hematócrito não sofreram alteração. CONCLUSÃO: O modelo de isquemia provocado por oclusão da artéria mesentérica superior, artéria mesentérica inferior e tronco celíaco por 30 minutos seguidos por 120 minutos de reperfusão provoca alterações sistêmicas evidenciadas por hipotensão, diminuição do fluxo sangüíneo mesentérico, da freqüência cardíaca e da temperatura esofágica.

Effect of α-tocopherol, taurine and selenium on the attenuation of ischemia/reperfusion injury of splanchnic organs

Background: Splanchnic artery occlusion shock is caused by increased capillary permeability and cellular injury precipitated by oxygen derived free radicals following ischemia and reperfusion of splanchnic organs. The purpose of this study was to assess the role of several well-known oxygen- derived free radical scavengers in ameliorating or preventing this syndrome. Study design: Anesthetized rats were subjected to periods of occlusion of the visceral arteries and reperfusion. Tocopherol, taurine, selenium or a 'cocktail' of these three agents was injected subcutaneously for 4 consecutive days prior to operation. Mean arterial blood pressure was measured throughout the experimental period. Fluorometry and technetium-99m pyrophosphate counting of the visceral organs were performed as well as a histologic grading system for intestinal viability. Results: Final mean arterial blood pressure associated with the 'cocktail' and selenium groups was 79.1 ± 27.4 mmHg and 83.6 ± 17.8 mmHg, respectively. These values were significantly higher than the control group, 40.8 ± 11.4 mmHg (P < 0.05). Similar patterns of the benefit of selenium in contrast with the other groups were obtained with fluorescein perfusion, radioisotopic activity and histologic analysis. Conclusion: Pretreatment with selenium of splanchnic ischemia and reperfusion in the rat improves mean arterial blood pressure and microcirculatory visceral perfusion. Further analysis of the precise protective mechanism of selenium for reperfusion injury will enable visceral organs to withstand the consequences of increased capillary leakage and oxidant injury.

Effects of pentoxifylline and n-acetylcysteine on injuries caused by ischemia and reperfusion of splanchnic organs in rats

Aim. Occlusion and reperfusion of splanchnic arteries cause local and systemic changes due to the release of cytotoxic substances and the interaction between neutrophils and endothelial cells. This study evaluated the role of pentoxifylline (PTX) and n-acetylcysteine (NAC) in the reduction of ischemia, reperfusion shock and associated intestinal injury. Methods. Sixty rats were divided into 6 groups of 10 animals. Rats in three groups underwent mesenteric ischemia for 30 minutes followed by 120 minutes of reperfusion, and were treated with saline (SAL-5 mL/kg/ h), pentoxifylline (PTX-50 mg/kg) or n-acetylcysteine (NAC-430 mg/kg/h). The other 3 groups underwent sham ischemia and reperfusion (I/R) and received the same treatments. Hemodynamic, biochemical and histological parameters were evaluated. Results. No significant hemodynamic or intestinal histological changes were seen in any sham group. No histological changes were found in the lung or liver of animals in the different groups. There was a progressive decrease in mean arterial blood pressure, from mean of 111.53 mmHg (30 minutes of ischemia) to 44.30±19.91 mmHg in SAL-I/R. 34.52±17.22 mmHg in PTX-I/R and 33.81±8.39 mmHg in NAC-I/R (P<0.05). In all I/R groups, there was a progressive decrease in: aortic blood flow, from median baseline of 19.00 mL/min to 2.50±5.25 mL/min in SAL-I/ R; 2.95±6.40 mL/min in PTX-I/R and 3.35±3.40 mL/min in NAC-I/R (P<0.05); in the heart rate, from mean baseline of 311.74 bpm to 233.33±83.88 bpm in SAL-I/R, 243.20±73.25 bpm in PTX-I/R and 244.92±76.05 bpm in NAC-I/R (P<0.05); and esophageal temperature, from mean baseline of 33.68°C to 30.53±2.05°C in SAL-I/R, 30.69±2.21°C in PTX-I/R and 31.43±1.03°C in NAC-I/R (P<0.05). In the other hand, there was an attenuation of mucosal damage in the small intestine of the animals receiving PTX, and only in the ileum of the animals receiving NAC. No changes were found in ileum or plasma malondialdehyde levels in any group. Conclusion. PTX was more efficient in reducing histological lesions than NAC, but neither treatment prevented hemodynamic changes during splanchnic organs I/R.

Effect of protective solutions and hydroxyethyl starch in the attenuation of the injuries of ischemia and reperfusion of splanchnic organs

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of volume resuscitation on splanchnic perfusion in canine model of severe sepsis induced by live Escherichia coli infusion

Abstract Introduction We conducted the present study to investigate whether early large-volume crystalloid infusion can restore gut mucosal blood flow and mesenteric oxygen metabolism in severe sepsis. Methods Anesthetized and mechanically ventilated male mongrel dogs were challenged with intravenous injection of live Escherichia coli (6 × 109 colony-forming units/ml per kg over 15 min). After 90 min they were randomly assigned to one of two groups – control (no fluids; n = 13) or lactated Ringer's solution (32 ml/kg per hour; n = 14) – and followed for 60 min. Cardiac index, mesenteric blood flow, mean arterial pressure, systemic and mesenteric oxygen-derived variables, blood lactate and gastric carbon dioxide tension (PCO2; by gas tonometry) were assessed throughout the study. Results E. coli infusion significantly decreased arterial pressure, cardiac index, mesenteric blood flow, and systemic and mesenteric oxygen delivery, and increased arterial and portal lactate, intramucosal PCO2, PCO2 gap (the difference between gastric mucosal and arterial PCO2), and systemic and mesenteric oxygen extraction ratio in both groups. The Ringer's solution group had significantly higher cardiac index and systemic oxygen delivery, and lower oxygen extraction ratio and PCO2 gap at 165 min as compared with control animals. However, infusion of lactated Ringer's solution was unable to restore the PCO2 gap. There were no significant differences between groups in mesenteric oxygen delivery, oxygen extraction ratio, or portal lactate at the end of study. Conclusion Significant disturbances occur in the systemic and mesenteric beds during bacteremic severe sepsis. Although large-volume infusion of lactated Ringer's solution restored systemic hemodynamic parameters, it was unable to correct gut mucosal PCO2 gap.

Effects of lung recruitment maneuvers on splanchnic organ perfusion during endotoxin-induced pulmonary arterial hypertension

Lung recruitment maneuvers (RMs), used to reopen atelectatic lung units and to improve oxygenation during mechanical ventilation, may result in hemodynamic impairment. We hypothesize that pulmonary arterial hypertension aggravates the consequences of RMs in the splanchnic circulation. Twelve anesthetized pigs underwent laparotomy and prolonged postoperative ventilation. Systemic, regional, and organ blood flows were monitored. After 6 h (= baseline), a recruitment maneuver was performed with sustained inflation of the lungs. Thereafter, the pigs were randomly assigned to group C (control, n = 6) or group E with endotoxin-induced pulmonary arterial hypertension (n = 6). Endotoxemia resulted in a normotensive and hyperdynamic state and a deterioration of the oxygenation index by 33%. The RM was then repeated in both groups. Pulmonary artery pressure increased during lipopolysaccharide infusion from 17 ± 2 mmHg (mean ± SD) to 31 ± 10 mmHg and remained unchanged in controls (P < 0.05). During endotoxemia, RM decreased aortic pulse pressure from 37 ± 14 mmHg to 27 ± 13 mmHg (mean ± SD, P = 0.024). The blood flows of the renal artery, hepatic artery, celiac trunk, superior mesenteric artery, and portal vein decreased to 71% ± 21%, 69% ± 20%, 76% ± 16%, 79% ± 18%, and 81% ± 12%, respectively, of baseline flows before RM (P < 0.05 all). Organ perfusion of kidney cortex, kidney medulla, liver, and jejunal mucosa in group E decreased to 65% ± 19%, 77% ± 13%, 66% ± 26%, and 71% ± 12%, respectively, of baseline flows (P < 0.05 all). The corresponding recovery to at least 90% of baseline regional blood flow and organ perfusion lasted 1 to 5 min. Importantly, the decreases in regional blood flows and organ perfusion and the time to recovery of these flows did not differ from the controls. In conclusion, lipopolysaccharide-induced pulmonary arterial hypertension does not aggravate the RM-induced significant but short-lasting decreases in systemic, regional, and organ blood flows.

Splanchnic vasoregulation after major abdominal surgery in pigs

Unrecognized reduction of blood supply to intestinal organs is associated with significant postoperative morbidity in abdominal surgery. The aim of this study was to determine whether--in the absence of hypovolemia--intestinal hypoperfusion as a result of blood flow redistribution occurs after abdominal surgery.

The effects of mechanical ventilation on hepato-splanchnic perfusion

PURPOSE OF REVIEW: Mechanical ventilation is a cornerstone of ICU treatment. Because of its interaction with blood flow and intra-abdominal pressure, mechanical ventilation has the potential to alter hepato-splanchnic perfusion, abdominal organ function and thereby outcome of the most critically ill patients. RECENT FINDINGS: Mechanical ventilation can alter hepato-splanchnic perfusion, but the effects are minimal (with moderate inspiratory pressures, tidal volumes, and positive end-expiratory pressure levels) or variable (with high ones). Routine nursing procedures may cause repeated episodes of inadequate hepato-splanchnic perfusion in critically ill patients, but an association between perfusion and multiple organ dysfunction cannot yet be determined. Clinical research continues to be challenging as a result of difficulties in measuring hepato-splanchnic blood flow at the bedside. SUMMARY: Mechanical ventilation and attempts to improve oxygenation such as intratracheal suctioning and recruitment maneuvers, may have harmful consequences in patients with already limited cardiovascular reserves or deteriorated intestinal perfusion. Due to difficulties in assessing hepato-splanchnic perfusion, such effects are often not detected.

Postoperative splanchnic blood flow redistribution in response to fluid challenges in the presence and absence of endotoxemia in a porcine model

We hypothesized that fluid administration may increase regional splanchnic perfusion after abdominal surgery-even in the absence of a cardiac stroke volume (SV) increase and independent of accompanying endotoxemia. Sixteen anesthetized pigs underwent abdominal surgery with flow probe fitting around splanchnic vessels and carotid arteries. They were randomized to continuous placebo or endotoxin infusion, and when clinical signs of hypovolemia (mean arterial pressure, <60 mmHg; heart rate, >100 beats · min(-1); urine production, <0.5 mL · kg(-1) · h(-1); arterial lactate concentration, >2 mmol · L(-1)) and/or low pulmonary artery occlusion pressure (target 5-8 mmHg) were present, they received repeated boli of colloids (50 mL) as long as SV increased 10% or greater. Stroke volume and regional blood flows were monitored 2 min before and 30 min after fluid challenges. Of 132 fluid challenges, 45 (34%) resulted in an SV increase of 10% or greater, whereas 82 (62%) resulted in an increase of 10% or greater in one or more of the abdominal flows (P < 0.001). During blood flow redistribution, celiac trunk (19% of all measurements) and hepatic artery flow (15%) most often decreased, whereas portal vein (10%) and carotid artery (7%) flow decreased less frequently (P = 0.015, between regions). In control animals, celiac trunk (30% vs. 9%, P = 0.004) and hepatic artery (25% vs. 11%, P = 0.040) flow decreased more often than in endotoxin-infused pigs. Accordingly, blood flow redistribution is a common phenomenon in the postoperative period and is only marginally influenced by endotoxemia. Fluid management based on SV changes may not be useful for improving regional abdominal perfusion.

Amelioration of portal hypertension and the hyperdynamic circulatory syndrome in cirrhotic rats by neuropeptide Y via pronounced splanchnic vasoaction

Splanchnic vasodilation triggers the development of the hyperdynamic circulatory syndrome in portal hypertension. Neuropeptide Y (NPY), a sympathetic co-transmitter of norepinephrine, improves contractility in mesenteric arteries of pre-hepatic portal hypertensive rats. Therefore, we investigated the effect of NPY on mesenteric arterial contractility in vitro and in vivo in cirrhotic ascitic rats, as well as the vasoactive pathways involved.

Membrane microdialysis: Evaluation of a new method to assess splanchnic tissue metabolism

OBJECTIVE: Measuring peritoneal lactate concentrations could be useful for detecting splanchnic hypoperfusion. The aims of this study were to evaluate the properties of a new membrane-based microdialyzer in vitro and to assess the ability of the dialyzer to detect a clinically relevant decrease in splanchnic blood flow in vivo. DESIGN: A membrane-based microdialyzer was first validated in vitro. The same device was tested afterward in a randomized, controlled animal experiment. SETTING: University experimental research laboratory. SUBJECTS: Twenty-four Landrace pigs of both genders. INTERVENTIONS: In vitro: Membrane microdialyzers were kept in warmed sodium lactate baths with lactate concentrations between 2 and 8 mmol/L for 10-120 mins, and microdialysis lactate concentrations were measured repeatedly (210 measurements). In vivo: An extracorporeal shunt with blood reservoir and roller pump was inserted between the proximal and distal abdominal aorta, and a microdialyzer was inserted intraperitoneally. In 12 animals, total splanchnic blood flow (measured by transit time ultrasound) was reduced by a median 43% (range, 13% to 72%) by activating the shunt; 12 animals served as controls. MEASUREMENTS AND MAIN RESULTS: In vitro: The fractional lactate recovery was 0.59 (0.32-0.83) after 60 mins and 0.82 (0.71-0.87) after 90 mins, with no further increase thereafter. At 60 and 90 mins, the fractional recovery was independent of the lactate concentration. In vivo: Abdominal blood flow reduction resulted in an increase in peritoneal microdialysis lactate concentration from 1.7 (0.3-3.8) mmol/L to 2.8 (1.3-6.2) mmol/L (p = .006). At the same time, mesenteric venous-arterial lactate gradient increased from 0.1 (-0.2-0.8) mmol/L to 0.3 (-0.3 -1.8) mmol/L (p = .032), and mesenteric venous-arterial Pco2 gradients increased from 12 (8-19) torr to 21 (11-54) torr (p = .005). CONCLUSIONS: Peritoneal membrane microdialysis provides a method for the assessment of splanchnic ischemia, with potential for clinical application.

Arterio-venous gradients of free energy change for assessment of systemic and splanchnic perfusion in cardiac surgery patients

OBJECTIVE: Adequacy of organ perfusion depends on sufficient oxygen supply in relation to the metabolic needs. The aim of this study was to evaluate the relationship between gradients of free energy change, and the more commonly used parameter for the evaluation of the adequacy of organ perfusion, such as oxygen-extraction in patients undergoing valve replacement surgery using normothermic cardiopulmonary bypass (CPB). METHODS: In 43 cardiac patients, arterial, mixed venous, and hepato-venous blood samples were taken synchronously after induction of anaesthesia (preCPB), during CPB, and 2 and 7 h after admission to the intensive care unit (ICU+2, ICU+7). Blood gas analysis, cardiac output, and hepato-splanchnic blood flow were measured. Free energy change gradients between mixed venous and arterial (-deltadeltaG(v - a)) and hepato-venous and arterial (-deltadeltaG(hv - a)) compartments were calculated. MEASUREMENTS AND RESULTS: Cardiac index (CI) increased from 1.9 (0.7) to 2.8 (1.3) L/min/m (median, inter-quartile range) (p = 0.001), and hepato-splanchnic blood flow index (HBFI) from 0.6 (0.22) to 0.8 (0.53) L/min/m (p = 0.001). Despite increasing flow, systemic oxygen extraction increased after CPB from 24 (10)% to 35 (10)% at ICU+2 (p = 0.002), and splanchnic oxygen extraction increased during CPB from 37 (19)% to 52 (14)% (p = 0.001), and remained high thereafter. After CPB, high splanchnic and systemic gradients of free energy change gradients were associated with high splanchnic and systemic oxygen extraction, respectively (p = 0.001, 0.033, respectively). CONCLUSION: Gradients of free energy change may be helpful in characterising adequacy of perfusion in cardiac surgery patients independently from measurements or calculations of data from oxygen transport.

Apelin signaling modulates splanchnic angiogenesis and portosystemic collateral vessel formation in rats with portal hypertension

BACKGROUND/AIMS: Angiogenesis is a pathological hallmark of portal hypertension. Although VEGF is considered to be the most important proangiogenic factor in neoangiogenesis, this process requires the coordinated action of a variety of factors. Identification of novel molecules involved in angiogenesis is highly relevant, since they may represent potential new targets to suppress pathological neovascularization in angiogenesis-related diseases like portal hypertension. The apelin/APJ signaling pathway plays a crucial role in angiogenesis. Therefore, we determined whether the apelin system modulates angiogenesis-driven processes in portal hypertension. METHODS: Partial portal vein-ligated rats were treated with the APJ antagonist F13A for seven days. Splanchnic neovascularization and expression of angiogenesis mediators (Western blotting) was determined. Portosystemic collateral formation (microspheres), and hemodynamic parameters (flowmetry) were also assessed. RESULTS: Apelin and its receptor APJ were overexpressed in the splanchnic vasculature of portal hypertensive rats. F13A effectively decreased, by 52%, splanchnic neovascularization and expression of proangiogenic factors VEGF, PDGF and angiopoietin-2 in portal hypertensive rats. F13A also reduced, by 35%, the formation of portosystemic collateral vessels. CONCLUSIONS: This study provides the first experimental evidence showing that the apelin/APJ system contributes to portosystemic collateralization and splanchnic neovascularization in portal hypertensive rats, presenting a potential novel therapeutic target for portal hypertension.