Surgery (Austin & Northern Health) - Research Publications
Now showing items 1-12 of 77
Induction of Gastrin Expression in Gastrointestinal Cells by Hypoxia or Cobalt Is Independent of Hypoxia-Inducible Factor (HIF)
(ENDOCRINE SOC, 2012-07-27)
Gastrin and its precursors have been shown to promote mitogenesis and angiogenesis in gastrointestinal tumors. Hypoxia stimulates tumor growth, but its effect on gastrin gene regulation has not been examined in detail. Here we have investigated the effect of hypoxia on the transcription of the gastrin gene in human gastric cancer (AGS) cells. Gastrin mRNA was measured by real-time PCR, gastrin peptides were measured by RIA, and gastrin promoter activity was measured by dual-luciferase reporter assay. Exposure to a low oxygen concentration (1%) increased gastrin mRNA concentrations in wild-type AGS cells (AGS) and in AGS cells overexpressing the gastrin receptor (AGS-cholecystokinin receptor 2) by 2.1 +/- 0.4-and 4.1 +/- 0.3-fold (P < 0.05), respectively. The hypoxia mimetic, cobalt chloride (300 mu M), increased gastrin promoter activity in AGS cells by 2.4 +/- 0.3-fold (P < 0.05), and in AGS-cholecystokinin receptor 2 cells by 4.0 +/- 0.3-fold (P < 0.05), respectively. The observations that either deletion from the gastrin promoter of the putative binding sites for the transcription factor hypoxia-inducible factor 1 (HIF-1) or knockdown of either the HIF-1 alpha or HIF-1 beta subunit did not affect gastrin promoter inducibility under hypoxia indicated that the hypoxic activation of the gastrin gene is likely HIF independent. Mutational analysis of previously identified Sp1 regulatory elements in the gastrin promoter also failed to abrogate the induction of promoter activity by hypoxia. The observations that hypoxia up-regulates the gastrin gene in AGS cells by HIF-independent mechanisms, and that this effect is enhanced by the presence of gastrin receptors, provide potential targets for gastrointestinal cancer therapy. (Endocrinology 153: 3006-3016, 2012)
Outcomes of contemporary management of gangrenous and non-gangrenous acute cholecystitis
BACKGROUND: Gangrenous cholecystitis (GC) is considered a more severe form of acute cholecystitis. The risk factors associated with this condition and its impact on morbidity and mortality compared with those of non-gangrenous acute cholecystitis (NGAC) are poorly defined and based largely on findings from older studies. METHODS: Patients with histologically confirmed acute cholecystitis treated in specialized units in a tertiary hospital between 2005 and 2010 were identified from a prospectively maintained database. Data were reviewed retrospectively and patients with GC were compared with those with NGAC. RESULTS: A total of 184 patients with NGAC and 106 with GC were identified. The risk factors associated with GC included older age (69 years vs. 57 years; P= 0.001), diabetes (19% vs. 10%; P= 0.049), temperature of >38 °C (36% vs. 16%; P < 0.001), tachycardia (31% vs. 15%; P= 0.002), detection of muscle rigidity on examination (27% vs. 12%; P= 0.01) and greater elevations in white cell count (WCC) (13.4 × 10⁹/l vs. 10.7 × 10⁹/l; P < 0.001), C-reactive protein (CRP) (94 mg/l vs. 17 mg/l; P= 0.001), bilirubin (19 µmol/l vs. 17 µmol/l; P= 0.029), urea (5.3 mmol/l vs. 4.7 mmol/l; P= 0.016) and creatinine (82 µmol/l vs. 74 µmol/l; P= 0.001). The time from admission to operation in days was greater in the GC group (median = 1 day, range: 0-14 days vs. median = 1 day, range: 0-10 days; P= 0.029). There was no overall difference in complication rates between the GC and NGAC groups (22% vs. 14%; P= 0.102). There was a lower incidence of common bile duct stones in the GC group (5% vs. 13%; P= 0.017). Gangrenous cholecystitis was associated with increased mortality (4% vs. 0%; P= 0.017), but this was not an independent risk factor on multivariate analysis. CONCLUSIONS: Gangrenous cholecystitis has certain clinical features and associated laboratory findings that may help to differentiate it from NGAC. It is not associated with an overall increase in complications when treated in a specialized unit.
Bimodal role of Kupffer cells during colorectal cancer liver metastasis
(LANDES BIOSCIENCE, 2013-07-01)
Kupffer cells (KCs) are resident liver macrophages that play a crucial role in liver homeostasis and in the pathogenesis of liver disease. Evidence suggests KCs have both stimulatory and inhibitory functions during tumor development but the extent of these functions remains to be defined. Using KC depletion studies in an orthotopic murine model of colorectal cancer (CRC) liver metastases we demonstrated the bimodal role of KCs in determining tumor growth. KC depletion with gadolinium chloride before tumor induction was associated with an increased tumor burden during the exponential growth phase. In contrast, KC depletion at the late stage of tumor growth (day 18) decreased liver tumor load compared with non-depleted animals. This suggests KCs exhibit an early inhibitory and a later stimulatory effect. These two opposing functions were associated with changes in iNOS and VEGF expression as well as T-cell infiltration. KC depletion at day 18 increased numbers of CD3 (+) T cells and iNOS-expressing infiltrating cells in the tumor, but decreased the number of VEGF-expressing infiltrating cells. These alterations may be responsible for the observed reduction in tumor burden following depletion of pro-tumor KCs at the late stage of metastatic growth. Taken together, our results indicate that the bimodal role of KC activity in liver tumors may provide the key to timing immunomodulatory intervention for the treatment of CRC liver metastases.
Long-Term Persistence of Hormonal Adaptations to Weight Loss
(MASSACHUSETTS MEDICAL SOC, 2011-10-27)
BACKGROUND: After weight loss, changes in the circulating levels of several peripheral hormones involved in the homeostatic regulation of body weight occur. Whether these changes are transient or persist over time may be important for an understanding of the reasons behind the high rate of weight regain after diet-induced weight loss. METHODS: We enrolled 50 overweight or obese patients without diabetes in a 10-week weight-loss program for which a very-low-energy diet was prescribed. At baseline (before weight loss), at 10 weeks (after program completion), and at 62 weeks, we examined circulating levels of leptin, ghrelin, peptide YY, gastric inhibitory polypeptide, glucagon-like peptide 1, amylin, pancreatic polypeptide, cholecystokinin, and insulin and subjective ratings of appetite. RESULTS: Weight loss (mean [±SE], 13.5±0.5 kg) led to significant reductions in levels of leptin, peptide YY, cholecystokinin, insulin (P<0.001 for all comparisons), and amylin (P=0.002) and to increases in levels of ghrelin (P<0.001), gastric inhibitory polypeptide (P=0.004), and pancreatic polypeptide (P=0.008). There was also a significant increase in subjective appetite (P<0.001). One year after the initial weight loss, there were still significant differences from baseline in the mean levels of leptin (P<0.001), peptide YY (P<0.001), cholecystokinin (P=0.04), insulin (P=0.01), ghrelin (P<0.001), gastric inhibitory polypeptide (P<0.001), and pancreatic polypeptide (P=0.002), as well as hunger (P<0.001). CONCLUSIONS: One year after initial weight reduction, levels of the circulating mediators of appetite that encourage weight regain after diet-induced weight loss do not revert to the levels recorded before weight loss. Long-term strategies to counteract this change may be needed to prevent obesity relapse. (Funded by the National Health and Medical Research Council and others; ClinicalTrials.gov number, NCT00870259.).
p-21-Activated kinase 1 mediates gastrin-stimulated proliferation in the colorectal mucosa via multiple signaling pathways
(AMER PHYSIOLOGICAL SOC, 2013-03-01)
Gastrins, including amidated (Gamide) and glycine-extended (Ggly) forms, function as growth factors for the gastrointestinal mucosa. The p-21-activated kinase 1 (PAK1) plays important roles in growth factor signaling networks that control cell motility, proliferation, differentiation, and transformation. PAK1, activated by both Gamide and Ggly, mediates gastrin-stimulated proliferation and migration, and activation of β-catenin, in gastric epithelial cells. The aim of this study was to investigate the role of PAK1 in the regulation by gastrin of proliferation in the normal colorectal mucosa in vivo. Mucosal proliferation was measured in PAK1 knockout (PAK1 KO) mice by immunohistochemistry. The expression of phosphorylated and unphosphorylated forms of the signaling molecules PAK1, extracellular signal-regulated kinase (ERK), and protein kinase B (AKT), and the expression of β-catenin and its downstream targets c-Myc and cyclin D1, were measured in gastrin knockout (Gas KO) and PAK1 KO mice by Western blotting. The expression and activation of PAK1 are decreased in Gas KO mice, and these decreases are associated with reduced activation of ERK, AKT, and β-catenin. Proliferation in the colorectal mucosa of PAK1 KO mice is reduced, and the reduction is associated with reduced activation of ERK, AKT, and β-catenin. In compensation, antral gastrin mRNA and serum gastrin concentrations are increased in PAK1 KO mice. These results indicate that PAK1 mediates the stimulation of colorectal proliferation by gastrins via multiple signaling pathways involving activation of ERK, AKT, and β-catenin.
Increased gastrin gene expression provides a physiological advantage to mice under hypoxic conditions
(AMER PHYSIOLOGICAL SOC, 2015-01-15)
Hypoxia, or a low concentration of O2, is encountered in humans undertaking activities such as mountain climbing and scuba diving and is important pathophysiologically as a limiting factor in tumor growth. Although data on the interplay between hypoxia and gastrins are limited, gastrin expression is upregulated by hypoxia in gastrointestinal cancer cell lines, and gastrins counterbalance hypoxia by stimulating angiogenesis in vitro and in vivo. The aim of this study was to determine if higher concentrations of the gastrin precursor progastrin are protective against hypoxia in vivo. hGAS mice, which overexpress progastrin in the liver, and mice of the corresponding wild-type FVB/N strain were exposed to normoxia or hypoxia. Iron status was assessed by measurement of serum iron parameters, real-time PCR for mRNAs encoding critical iron regulatory proteins, and Perls' stain and atomic absorption spectrometry for tissue iron concentrations. FVB/N mice lost weight at a faster rate and had higher sickness scores than hGAS mice exposed to hypoxia. Serum iron levels were lower in hGAS than FVB/N mice and decreased further when the animals were exposed to hypoxia. The concentration of iron in the liver was strikingly lower in hGAS than FVB/N mice. We conclude that increased circulating concentrations of progastrin provide a physiological advantage against systemic hypoxia in mice, possibly by increasing the availability of iron stores. This is the first report of an association between progastrin overexpression, hypoxia, and iron homeostasis.
The renin angiotensin system regulates Kupffer cells in colorectal liver metastases
(LANDES BIOSCIENCE, 2013-08-01)
Blockade of the renin angiotensin system (RAS) can inhibit tumor growth and this may be mediated via undefined immunomodulatory actions. This study investigated the effects of RAS blockade on liver macrophages (Kupffer cells; KCs) in an orthotopic murine model of colorectal cancer (CRC) liver metastases. Here we showed that pharmacological targeting of the RAS [ANG II (31.25 µg/kg/h i.p.), ANG-(1-7) (24 µg/kg/h i.p.) or the ACE inhibitor; captopril (750 mg/kg/d i.p.)] altered endogenous KC numbers in the tumor-bearing liver throughout metastatic growth. Captopril, and to a lesser extent ANG-(1-7), increased KC numbers in the liver but not tumor. KCs were found to express the key RAS components: ACE and AT1R. Treatment with captopril and ANG II increased the number of AT1R-expressing KCs, although total KC numbers were not affected by ANG II. Captopril (0.1 µM) also increased macrophage invasion in vitro. Additionally, captopril was administered with KC depletion before tumor induction (day 0) or at established metastatic growth (day 18) using gadolinium chloride (GdCl 3; 20 mg/kg). Livers were collected at day 21 and quantitative stereology used as a measure of tumor burden. Captopril reduced growth of CRC liver metastases. However, when captopril was combined with early KC depletion (day 0) tumor growth was significantly increased compared with captopril alone. In contrast, late KC depletion (day 18) failed to influence the anti-tumor effects of captopril. The result of these studies suggests that manipulation of the RAS can alter KC numbers and may subsequently influence progression of CRC liver metastases.
Comparative Evaluation of Crystalloid Resuscitation Rate in a Human Model of Compensated Haemorrhagic Shock
(LIPPINCOTT WILLIAMS & WILKINS, 2016-08-01)
INTRODUCTION: The most effective rate of fluid resuscitation in haemorrhagic shock is unknown. METHODS: We performed a randomized crossover pilot study in a healthy volunteer model of compensated haemorrhagic shock. Following venesection of 15 mL/kg of blood, participants were randomized to 20 mL/kg of crystalloid over 10 min (FAST treatment) or 30 min (SLOW treatment). The primary end point was oxygen delivery (DO2). Secondary end points included pressure and flow-based haemodynamic variables, blood volume expansion, and clinical biochemistry. RESULTS: Nine normotensive healthy adult volunteers participated. No significant differences were observed in DO2 and biochemical variables between the SLOW and FAST groups. Blood volume was reduced by 16% following venesection, with a corresponding 5% reduction in cardiac index (CI) (P < 0.001). Immediately following resuscitation the increase in blood volume corresponded to 54% of the infused volume under FAST treatment and 69% of the infused volume under SLOW treatment (P = 0.03). This blood volume expansion attenuated with time to 24% and 25% of the infused volume 30 min postinfusion. During fluid resuscitation, blood pressure was higher under FAST treatment. However, CI paradoxically decreased in most participants during the resuscitation phase; a finding not observed under SLOW treatment. CONCLUSION: FAST or SLOW fluid resuscitation had no significant impact on DO2 between treatment groups. In both groups, changes in CI and blood pressure did not reflect the magnitude of intravascular blood volume deficit. Crystalloid resuscitation expanded intravascular blood volume by approximately 25%.
Zinc ions upregulate the hormone gastrin via an E-box motif in the proximal gastrin promoter
(BIOSCIENTIFICA LTD, 2014-02-01)
Gastrin and its precursors act as growth factors for the normal and neoplastic gastrointestinal mucosa. As the hypoxia mimetic cobalt chloride upregulates the gastrin gene, the effect of other metal ions on gastrin promoter activity was investigated. Gastrin mRNA was measured by real-time PCR, gastrin peptides by RIA, and gastrin promoter activity by dual-luciferase reporter assay. Exposure to Zn(2)(+) ions increased gastrin mRNA concentrations in the human gastric adenocarcinoma cell line AGS in a dose-dependent manner, with a maximum stimulation of 55 ± 14-fold at 100 μM (P<0.05). Significant stimulation was also observed with Cd(2)(+) and Cu(2)(+), but not with Ca(2)(+), Mg(2)(+), Ni(2)(+), or Fe(3)(+) ions. Activation of MAPK and phosphatidylinositol 3-kinase pathways is necessary but not sufficient for gastrin induction by Zn(2)(+). Deletional mutation of the gastrin promoter identified an 11 bp DNA sequence, which contained an E-box motif, as necessary for Zn(2)(+)-dependent gastrin induction. The fact that E-box binding transcription factors play a crucial role in the epithelial-mesenchymal transition (EMT), together with our observation that Zn(2)(+) ions upregulate the gastrin gene in AGS cells by an E-box-dependent mechanism, suggests that Zn(2)(+) ions may induce an EMT, and that gastrin may be involved in the transition.
Overview of the study protocols and statistical analysis plan for the Saline versus Plasma-Lyte 148 for Intravenous Fluid Therapy (SPLIT) research program
(AUSTRALASIAN MED PUBL CO LTD, 2015-03-01)
BACKGROUND: 0.9% saline is the most commonly used intravenous (IV) fluid in the world but recent data raise the possibility that, compared with buffered crystalloid fluids such as Plasma-Lyte 148, the administration of 0.9% saline might increase the risk of developing acute kidney injury. OBJECTIVE: To provide an overview of the study protocols and statistical analysis plan for the six studies making up the (0.9% Saline v Plasma-Lyte 148 for Intravenous Fluid Therapy (SPLIT) research program. METHODS: The SPLIT study consists of six integrated clinical trials, including a double-blind, cluster, randomised, double-crossover study in intensive care unit patients, incorporating two nested studies within it; an open-label, before-and-after study in emergency department (ED) patients; a single-centre, double-blind, crossover trial in major surgical patients; and a randomised, double-blind study in ICU patients. All studies focus on biochemical and renal outcomes but will also provide preliminary data on patient-centred outcomes including inhospital mortality and requirements for dialysis. RESULTS AND CONCLUSION: The SPLIT study program will provide preliminary data on the comparative effectiveness of using 0.9% saline v Plasma-Lyte 148 for IV fluid therapy in ED, surgical and ICU patients.
Relative hyperlactatemia and hospital mortality in critically ill patients: a retrospective multi-centre study
INTRODUCTION: Higher lactate concentrations within the normal reference range (relative hyperlactatemia) are not considered clinically significant. We tested the hypothesis that relative hyperlactatemia is independently associated with an increased risk of hospital death. METHODS: This observational study examined a prospectively obtained intensive care database of 7,155 consecutive critically ill patients admitted to the Intensive Care Units (ICUs) of four Australian university hospitals. We assessed the relationship between ICU admission lactate, maximal lactate and time-weighted lactate levels and hospital outcome in all patients and also in those patients whose lactate concentrations (admission n = 3,964, maximal n = 2,511, and time-weighted n = 4,584) were under 2 mmol.L-1 (i.e. relative hyperlactatemia). RESULTS: We obtained 172,723 lactate measurements. Higher admission and time-weightedlactate concentration within the reference range was independently associated with increased hospital mortality (admission odds ratio (OR) 2.1, 95% confidence interval (CI) 1.3 to 3.5, P = 0.01; time-weighted OR 3.7, 95% CI 1.9 to 7.00, P < 0.0001). This significant association was first detectable at lactate concentrations > 0.75 mmol.L-1. Furthermore, in patients whose lactate ever exceeded 2 mmol.L-1, higher time-weighted lactate remained strongly associated with higher hospital mortality (OR 4.8, 95% CI 1.8 to 12.4, P < 0.001). CONCLUSIONS: In critically ill patients, relative hyperlactataemia is independently associated with increased hospital mortality. Blood lactate concentrations > 0.75 mmol.L-1 can be used by clinicians to identify patients at higher risk of death. The current reference range for lactate in the critically ill may need to be re-assessed.