Expression cloning of the pancreatic beta cell receptor for the gluco-incretin hormone glucagon-like peptide 1.

Glucagon-like peptide 1 (GLP-1) is a hormone derived from the preproglucagon molecule and is secreted by intestinal L cells. It is the most potent stimulator of glucose-induced insulin secretion and also suppresses in vivo acid secretion by gastric glands. A cDNA for the GLP-1 receptor was isolated by transient expression of a rat pancreatic islet cDNA library into COS cells; this was followed by binding of radiolabeled GLP-1 and screening by photographic emulsion autoradiography. The receptor transfected into COS cells binds GLP-1 with high affinity and is coupled to activation of adenylate cyclase. The receptor binds specifically GLP-1 and does not bind peptides of related structure and similar function, such as glucagon, gastric inhibitory peptide, vasoactive intestinal peptide, or secretin. The receptor is 463 amino acids long and contains seven transmembrane domains. Sequence homology is found only with the receptors for secretin, calcitonin, and parathyroid hormone, which form a newly characterized family of G-coupled receptors.

Glucose competence of the hepatoportal vein sensor requires the presence of an activated glucagon-like peptide-1 receptor.

Activation of the hepatoportal glucose sensors by portal glucose infusion leads to increased glucose clearance and induction of hypoglycemia. Here, we investigated whether glucagon-like peptide-1 (GLP-1) could modulate the activity of these sensors. Mice were therefore infused with saline (S-mice) or glucose (P-mice) through the portal vein at a rate of 25 mg/kg. min. In P-mice, glucose clearance increased to 67.5 +/- 3.7 mg/kg. min as compared with 24.1 +/- 1.5 mg/kg. min in S-mice, and glycemia decreased from 5.0 +/- 0.1 to 3.3 +/- 0.1 mmol/l at the end of the 3-h infusion period. Coinfusion of GLP-1 with glucose into the portal vein at a rate of 5 pmol/kg. min (P-GLP-1 mice) did not increase the glucose clearance rate (57.4 +/- 5.0 ml/kg. min) and hypoglycemia (3.8 +/- 0.1 mmol/l) observed in P-mice. In contrast, coinfusion of glucose and the GLP-1 receptor antagonist exendin-(9-39) into the portal vein at a rate of 0.5 pmol/kg. min (P-Ex mice) reduced glucose clearance to 36.1 +/- 2.6 ml/kg. min and transiently increased glycemia to 9.2 +/- 0.3 mmol/l at 60 min of infusion before it returned to the fasting level (5.6 +/- 0.3 mmol/l) at 3 h. When glucose and exendin-(9-39) were infused through the portal and femoral veins, respectively, glucose clearance increased to 70.0 +/- 4.6 ml/kg. min and glycemia decreased to 3.1 +/- 0.1 mmol/l, indicating that exendin-(9-39) has an effect only when infused into the portal vein. Finally, portal vein infusion of glucose in GLP-1 receptor(-/-) mice failed to increase the glucose clearance rate (26.7 +/- 2.9 ml/kg. min). Glycemia increased to 8.5 +/- 0.5 mmol/l at 60 min and remained elevated until the end of the glucose infusion (8.2 +/- 0.4 mmol/l). Together, our data show that the GLP-1 receptor is part of the hepatoportal glucose sensor and that basal fasting levels of GLP-1 sufficiently activate the receptor to confer maximum glucose competence to the sensor. These data demonstrate an important extrapancreatic effect of GLP-1 in the control of glucose homeostasis.

Patient satisfaction after biofeedback for constipation and pelvic floor dyssynergia.

Patients referred for chronic constipation frequently report symptoms of straining, feeling of incomplete evacuation, or the need to facilitate defecation digitally (dyschezia). When such patients show manometric evidence of inappropriate contraction or failure to relax the pelvic floor muscles during attempts to defecate, they are diagnosed as having pelvic floor dyssynergia (Rome I). To evaluate long-term satisfaction of patients with pelvic floor dyssynergia after biofeedback. Forty-one consecutive patients referred for chronic constipation at an outpatient gastrointestinal unit and diagnosed as having pelvic floor dyssynergia who completed a full course of biofeedback. Data have been collected using a standardised questionnaire. A questionnaire survey of patients' satisfaction rate and requirement of aperients was undertaken. Mean age and symptom duration were respectively 41 and 20 years. Half of patients reported fewer than 3 bowel motions per week. Patients were treated with a mean of 5 biofeedback sessions. At the end of the therapy pelvic floor dyssynergia was alleviated in 85% of patients and 49% were able to stop all aperients. Satisfaction was maintained at follow-up telephone interviews undertaken after a mean period of 2 years, as biofeedback was helpful for 79% of patients and 47% still abstained from intake of aperients. Satisfaction after biofeedback is high for patients referred for chronic constipation and diagnosed with pelvic floor dyssynergia. Biofeedback improves symptoms related to dyschezia and reduces use of aperients.

Effects of gastric bypass and gastric banding on glucose kinetics and gut hormone release.

BACKGROUND: Bariatric surgery markedly improves glucose homeostasis in patients with type 2 diabetes even before any significant weight loss is achieved. Procedures that involve bypassing the proximal small bowel, such as Roux-en-Y gastric bypass (RYGBP), are more efficient than gastric restriction procedures such as gastric banding (GB). OBJECTIVE: To evaluate the effects of RYGBP and GB on postprandial glucose kinetics and gastro-intestinal hormone secretion after an oral glucose load. METHODS AND PROCEDURES: This study was a cross-sectional comparison among non-diabetic, weight-stable women who had undergone RYGBP (n = 8) between 9 and 48 months earlier or GB (n = 6) from 25 to 85 months earlier, and weight- and age-matched control subjects (n = 8). The women were studied over 4 h following ingestion of an oral glucose load. Total glucose and meal glucose kinetics were assessed using glucose tracers and plasma insulin, and gut hormone concentrations were simultaneously monitored. RESULTS: Patients who had undergone RYGBP showed a a more rapid appearance of exogenous glucose in the systemic circulation and a shorter duration of postprandial hyperglycemia than patients who had undergone GB and C. The response in RYGBP patients was characterized by early and accentuated insulin response, enhanced postprandial levels of glucagon-like peptide-1 (GLP-1) and polypeptide YY (PYY), and greater postprandial suppression of ghrelin. DISCUSSION: These findings indicate that RYGBP is associated with alterations in glucose kinetics and glucoregulatory hormone secretion. These alterations are probably secondary to the anatomic rearrangement of the foregut, given the fact that they are not observed after GB. Increased PYY and GLP-1 concentrations and enhanced ghrelin suppression are compatible with reduced food intake after RYGBP.

Appropriateness of colonoscopy in Europe (EPAGE II). Surveillance after polypectomy and after resection of colorectal cancer.

BACKGROUND AND STUDY AIMS: To summarize the published literature on assessment of appropriateness of colonoscopy for surveillance after polypectomy and after curative-intent resection of colorectal cancer (CRC), and report appropriateness criteria developed by an expert panel, the 2008 European Panel on the Appropriateness of Gastrointestinal Endoscopy, EPAGE II. METHODS: A systematic search of guidelines, systematic reviews and primary studies regarding the evaluation and management of surveillance colonoscopy after polypectomy and after resection of CRC was performed. The RAND/UCLA Appropriateness Method was applied to develop appropriateness criteria for colonoscopy for these conditions. RESULTS: Most CRCs arise from adenomatous polyps. The characteristics of removed polyps, especially the distinction between low-risk adenomas (1 or 2, small [< 1 cm], tubular, no high-grade dysplasia) vs. high-risk adenomas (large [> or = 1 cm], multiple [> 3], high-grade dysplasia or villous features), have an impact on advanced adenoma recurrence. Most guidelines recommend a 3-year follow-up colonoscopy for high-risk adenomas and a 5-year colonoscopy for low-risk adenomas. Despite the lack of evidence to support or refute any survival benefit for follow-up colonoscopy after curative-intent CRC resection, surveillance colonoscopy is recommended by most guidelines. The timing of the first surveillance colonoscopy differs. The expert panel considered that 56 % of the clinical indications for colonoscopy for surveillance after polypectomy were appropriate. For surveillance after CRC resection, it considered colonoscopy appropriate 1 year after resection. CONCLUSIONS: Colonoscopy is recommended as a first-choice procedure for surveillance after polypectomy by all published guidelines and by the EPAGE II criteria. Despite the limitations of the published studies, colonoscopy is also recommended by most of the guidelines and by EPAGE II criteria for surveillance after curative-intent CRC resection.

The Nlrp3 inflammasome regulates acute graft-versus-host disease.

The success of allogeneic hematopoietic cell transplantation is limited by acute graft-versus-host disease (GvHD), a severe complication accompanied by high mortality rates. Yet, the molecular mechanisms initiating this disease remain poorly defined. In this study, we show that, after conditioning therapy, intestinal commensal bacteria and the damage-associated molecular pattern uric acid contribute to Nlrp3 inflammasome-mediated IL-1β production and that gastrointestinal decontamination and uric acid depletion reduced GvHD severity. Early blockade of IL-1β or genetic deficiency of the IL-1 receptor in dendritic cells (DCs) and T cells improved survival. The Nlrp3 inflammasome components Nlrp3 and Asc, which are required for pro-IL-1β cleavage, were critical for the full manifestation of GvHD. In transplanted mice, IL-1β originated from multiple intestinal cell compartments and exerted its effects on DCs and T cells, the latter being preferentially skewed toward Th17. Compatible with these mouse data, increased levels of active caspase-1 and IL-1β were found in circulating leukocytes and intestinal GvHD lesions of patients. Thus, the identification of a crucial role for the Nlrp3 inflammasome sheds new light on the pathogenesis of GvHD and opens a potential new avenue for the targeted therapy of this severe complication.

The Role of Secretory Immunoglobulin A in the Natural Sensing of Commensal Bacteria by Mouse Peyer's Patch Dendritic Cells.

The mammalian gastrointestinal (GI) tract harbors a diverse population of commensal species collectively known as the microbiota, which interact continuously with the host. From very early in life, secretory IgA (SIgA) is found in association with intestinal bacteria. It is considered that this helps to ensure self-limiting growth of the microbiota and hence participates in symbiosis. However, the importance of this association in contributing to the mechanisms ensuring natural host-microorganism communication is in need of further investigation. In the present work, we examined the possible role of SIgA in the transport of commensal bacteria across the GI epithelium. Using an intestinal loop mouse model and fluorescently labeled bacteria, we found that entry of commensal bacteria in Peyer's patches (PP) via the M cell pathway was mediated by their association with SIgA. Preassociation of bacteria with nonspecific SIgA increased their dynamics of entry and restored the reduced transport observed in germ-free mice known to have a marked reduction in intestinal SIgA production. Selective SIgA-mediated targeting of bacteria is restricted to the tolerogenic CD11c(+)CD11b(+)CD8(-) dendritic cell subset located in the subepithelial dome region of PPs, confirming that the host is not ignorant of its resident commensals. In conclusion, our work supports the concept that SIgA-mediated monitoring of commensal bacteria targeting dendritic cells in the subepithelial dome region of PPs represents a mechanism whereby the host mucosal immune system controls the continuous dialogue between the host and commensal bacteria.

Continuous monitoring of liver oxygenation with near infrared spectroscopy during naso-gastric tube feeding in neonates.

Near infrared spectroscopy (NIRS) is a non-invasive method of estimating the haemoglobin concentration changes in certain tissues. It is frequently used to monitor oxygenation of the brain in neonates. At present it is not clear whether near infrared spectroscopy of other organs (e.g. the liver as a corresponding site in the splanchnic region, which reacts very sensitively to haemodynamic instability) provides reliable values on their tissue oxygenation. The aim of the study was to test near infrared spectroscopy by measuring known physiologic changes in tissue oxygenation of the liver in newborn infants during and after feeding via a naso-gastric tube. The test-retest variability of such measurements was also determined. On 28 occasions in 25 infants we measured the tissue oxygenation index (TOI) of the liver and the brain continuously before, during and 30 minutes after feeding via a gastric tube. Simultaneously we measured arterial oxygen saturation (SaO2), heart rate (HR) and mean arterial blood pressure (MAP). In 10 other newborn infants we performed a test-retest analysis of the liver tissue oxygenation index to estimate the variability in repeated intra-individual measurements. The tissue oxygenation index of the liver increased significantly from 56.7 +/- 7.5% before to 60.3 +/- 5.6% after feeding (p < 0.005), and remained unchanged for the next 30 minutes. The tissue oxygenation index of the brain (62.1 +/- 9.7%), SaO2 (94.4 +/- 7.1%), heart rate (145 +/- 17.3 min-1) and mean arterial blood pressure (52.8 +/- 10.2 mm Hg) did not change significantly. The test-retest variability for intra-individual measurements was 2.7 +/- 2.1%. After bolus feeding the tissue oxygenation index of the liver increased as expected. This indicates that near infrared spectroscopy is suitable for monitoring changes in tissue oxygenation of the liver in newborn infants.

Gut-derived signaling molecules and vagal afferents in the control of glucose and energy homeostasis.

PURPOSE OF REVIEW: The control of glucose and energy homeostasis, including feeding behaviour, is tightly regulated by gut-derived peptidic and nonpeptidic endocrine mediators, autonomic nervous signals, as well as nutrients such as glucose. We will review recent findings on the role of the gastrointestinal tract innervation and of portal vein glucose sensors; we will review selected data on the action of gastrointestinally released hormones. RECENT FINDINGS: The involvement of mechanosensory vagal afferents in postprandial meal termination has been clarified using mouse models with selective impairments of genes required for development of mechanosensory fibres. These activate central glucogen-like peptide-1/glucogen-like peptide-2 containing ascending pathways linking the visceroceptive brainstem neurons to hypothalamic nuclei. Mucosal terminals comprise the chemosensory vagal afferents responsive to postprandially released gastrointestinal hormones. The mechanism by which the hepatoportal glucose sensor stimulates glucose utilization by muscles was demonstrated, using genetically modified mice, to be insulin-independent but to require GLUT4 and AMP-kinase. This sensor is a key site of glucogen-like peptide-1 action and plays a critical role in triggering first phase insulin secretion. PeptideYY and ghrelin target intracerebral receptors as they are bidirectionally transported across the blood brain barrier. The anorectic functions of peripherally released peptideYY may however be mediated both via vagal afferents and intracerebral Y2 receptors in the brainstem and arcuate nucleus. SUMMARY: These recent findings demonstrate that the use of improved anatomical and physiological techniques and animal models with targeted gene modifications lead to an improved understanding of the complex role of gastrointestinal signals in the control of energy homeostasis.

Anti-angiogenic therapies for metastatic colorectal cancer.

BACKGROUND: Angiogenesis inhibitors have been developed to block tumour angiogenesis and target vascular endothelial cells. While some of them have already been approved by the health authorities and are successfully integrated into patient care, many others are still under development, and the clinical value of this approach has to be established. OBJECTIVES: To assess the efficacy and toxicity of targeted anti-angiogenic therapies, in addition to chemotherapy, in patients with metastatic colorectal cancer. Primary endpoints are both progression-free and overall survival. Response rates, toxicity and secondary resectability were secondary endpoints. Comparisons were first-line chemotherapy in combination with angiogenesis inhibitor, to the same chemotherapy without angiogenesis inhibitor; and second-line chemotherapy, to the same chemotherapy without angiogenesis inhibitor. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials, MEDLINE, as well as proceedings from ECCO, ESMO and ASCO until November 2008. In addition, reference lists from trials were scanned, experts in the field and drug manufacturers were contacted to obtain further information. SELECTION CRITERIA: Randomized controlled trials on targeted anti-angiogenic drugs in metastatic colorectal cancer (MCRC). DATA COLLECTION AND ANALYSIS: Data collection and analysis was performed, according to a previously published protocol. Because individual patient data was not provided, aggregate data had to be used for the analysis. Summary statistics for the primary endpoints were hazard ratios (HR's) and their 95% confidence intervals. MAIN RESULTS: At present, eligible first line trials for this meta-analysis were available for bevacizumab (5 trials including 3101 patients) and vatalanib (1 trial which included 1168 patients). The overall HR s for PFS (0.61, 95% CI 0.45 - 0.83) and OS (0.81, 95% 0.73 - 0.90) for the comparison of first-line chemotherapy, with or without bevacizumab, confirms significant benefits in favour of the patients treated with bevacizumab. However, the effect on PFS shows significant heterogeneity. For second-line chemotherapy, with or without bevacizumab, a benefit in both PFS (HR 0.61, 95% CI 0.51 - 0.73) and OS (HR 0.75, 95% CI 0.63-0.89) was demonstrated in a single, randomized trial. While differences in treatment-related deaths and 60-day mortality were not significant, higher incidences in grade III/IV hypertension, arterial thrombembolic events and gastrointestinal perforations were observed in the patients treated with bevacizumab. For valatanib, currently available data showed a non-significant benefit in PFS and OS. AUTHORS' CONCLUSIONS: The addition of bevacizumab to chemotherapy of metastatic colorectal cancer prolongs both PFS and OS in first-and second-line therapy.

Regulation of membrane trafficking and organ separation by the NEVERSHED ARF-GAP protein.

Cell separation, or abscission, is a highly specialized process in plants that facilitates remodeling of their architecture and reproductive success. Because few genes are known to be essential for organ abscission, we conducted a screen for mutations that alter floral organ shedding in Arabidopsis. Nine recessive mutations that block shedding were found to disrupt the function of an ADP-ribosylation factor-GTPase-activating protein (ARF-GAP) we have named NEVERSHED (NEV). As predicted by its homology to the yeast Age2 ARF-GAP and transcriptional profile, NEV influences other aspects of plant development, including fruit growth. Co-localization experiments carried out with NEV-specific antiserum and a set of plant endomembrane markers revealed that NEV localizes to the trans-Golgi network and endosomes in Arabidopsis root epidermal cells. Interestingly, transmission electron micrographs of abscission zone regions from wild-type and nev flowers reveal defects in the structure of the Golgi apparatus and extensive accumulation of vesicles adjacent to the cell walls. Our results suggest that NEV ARF-GAP activity at the trans-Golgi network and distinct endosomal compartments is required for the proper trafficking of cargo molecules required for cell separation.

Comprehensive clinical and molecular analysis of 12 families with type 1 recessive cutis laxa.

Autosomal recessive cutis laxa type I (ARCL type I) is characterized by generalized cutis laxa with pulmonary emphysema and/or vascular complications. Rarely, mutations can be identified in FBLN4 or FBLN5. Recently, LTBP4 mutations have been implicated in a similar phenotype. Studying FBLN4, FBLN5, and LTBP4 in 12 families with ARCL type I, we found bi-allelic FBLN5 mutations in two probands, whereas nine probands harbored biallelic mutations in LTBP4. FBLN5 and LTBP4 mutations cause a very similar phenotype associated with severe pulmonary emphysema, in the absence of vascular tortuosity or aneurysms. Gastrointestinal and genitourinary tract involvement seems to be more severe in patients with LTBP4 mutations. Functional studies showed that most premature termination mutations in LTBP4 result in severely reduced mRNA and protein levels. This correlated with increased transforming growth factor-beta (TGFβ) activity. However, one mutation, c.4127dupC, escaped nonsense-mediated decay. The corresponding mutant protein (p.Arg1377Alafs(*) 27) showed reduced colocalization with fibronectin, leading to an abnormal morphology of microfibrils in fibroblast cultures, while retaining normal TGFβ activity. We conclude that LTBP4 mutations cause disease through both loss of function and gain of function mechanisms.

Response evaluation in third- and fourth-line treatment of GIST: the role of PET

Background: Response evaluation in gastrointestinal stromal tumors is difficult. Computed tomography and size-based assessments have been found inadequate to draw prognostic conclusions in patients treated with tyrosine kinase inhibitors (TKI). Density criteria (CHOI) have recently been shown to better define prognostic subsets of patients evaluated with CT. Still, positron emission tomography (PET) might be better at identifying responders with good outcome early, as shown for first and recently second-line treatment in GIST (Prior et al.; J Clin Oncol 2009). We wanted to evaluate the role of PET in third- and fourth-line TKI treatment of GIST. Methods: We retrospectively reviewed patients with GIST who had received third- or fourth-line treatment with TKI and had undergone PET for response evaluation. Patient needed to have a baseline and at least one subsequent PET. Results of the first "early" PET after treatment start have been used throughout this analysis and EORTC PET Study Group criteria applied. Results: Twelve treatment courses were evaluable, seven with Nilotinib in third- and five with Sorafenib in fourth-line treatment, in 8 patients, median age 60 y (range 36−78 y), who had all failed prior Imatinib and Sunitinib treatment due to disease progession. Baseline and follow-up PET were performed within a median of 34 days (range 9−84 days). Median progression-free survival (PFS) was 262 days in patients responding to PET versus 76 days in patients with stable or progressing disease (p = 0.15). Conclusions: This small series suggests that PET retains its value for outcome prediction in third- and fourth-line TKI treatment of GIST. This could be of particular clinical value in these vulnerable patients with large tumour masses. Early PET may help in stopping ineffective, but toxic therapy and help switching to a more effective therapy. PET should be evaluated further in this patient population.