Benoît Bédat

Glucose-Dependent Insulinotropic Peptide Stimulates Glucagon-Like Peptide 1 Production by Pancreatic Islets via Interleukin 6, Produced by α Cells

BACKGROUND & AIMS Glucose-dependent insulinotropic peptide (GIP) induces production of interleukin 6 (IL6) by adipocytes. IL6 increases production of glucagon-like peptide (GLP)-1 by L cells and α cells, leading to secretion of insulin from β cells. We investigated whether GIP regulates GLP1 and glycemia via IL6. METHODS We obtained samples of human pancreatic islets and isolated islets from mice; human α cells and β cells were sorted by flow cytometry and incubated with GIP. Islets were analyzed by quantitative polymerase chain reaction and immunohistochemistry. BKS.Cg-Dock7m+/+ Leprdb/J db/db mice (diabetic mice) and db/+ mice, as well as C57BL/6J IL6-knockout mice (IL6-KO) and C57BL/6J mice with the full-length Il6 gene (controls), were fed a chow or a high-fat diet; some mice were given injections of recombinant GIP, IL6, GLP, a neutralizing antibody against IL6 (anti-IL6), lipopolysaccharide, and/or IL1B. Mice were given a glucose challenge and blood samples were collected and analyzed. RESULTS Incubation of mouse and human pancreatic α cells with GIP induced their production of IL6, leading to production of GLP1 and insulin secretion from pancreatic islets. This did not occur in islets from IL6-KO mice or in islets incubated with anti-IL6. Incubation of islets with IL1B resulted in IL6 production but directly reduced GLP1 production. Incubation of mouse islets with the sodium glucose transporter 2 inhibitor dapagliflozin induced production of GLP1 and IL6. Injection of control mice with GIP increased plasma levels of GLP1, insulin, and glucose tolerance; these effects were amplified in mice given lipopolysaccharide but reduced in IL6-KO mice or in mice given anti-IL6. Islets from diabetic mice had increased levels of IL1B and IL6, compared with db/+ mice, but injection of GIP did not lead to production of GLP1 or reduce glycemia. CONCLUSIONS In studies of pancreatic islets from human beings and mice, we found that GIP induces production of IL6 by α cells, leading to islet production of GLP1 and insulin. This process is regulated by inflammation, via IL1B, and by sodium glucose transporter 2. In diabetic mice, increased islet levels of IL6 and IL1B might increase or reduce the production of GLP1 and affect glycemia.

Cadherin Engagement Improves Insulin Secretion of Single Human β-Cells

The aim of this study was to assess whether cadherin-mediated adhesion of human islet cells was affected by insulin secretagogues and explore the role of cadherins in the secretory activity of β-cells. Experiments were carried out with single islet cells adherent to chimeric proteins made of functional E-, N-, or P-cadherin ectodomains fused to the Fc fragment of immunoglobulin (E-cad/Fc, N-cad/Fc, and P-cad/Fc) and immobilized on an inert substrate. We observed that cadherin expression in islet cells was not affected by insulin secretagogues. Adhesion tests showed that islet cells attached to N-cad/Fc and E-cad/Fc acquired, in a time- and secretagogue-dependent manner, a spreading form that was inhibited by blocking cadherin antibodies. By reverse hemolytic plaque assay, we showed that glucose-stimulated insulin secretion of single β-cells was increased by N-cad/Fc and E-cad/Fc adhesion compared with control. In the presence of E-cad/Fc and after glucose stimulation, we showed that total insulin secretion was six times higher in spreading β-cells compared with round β-cells. Furthermore, cadherin-mediated adhesion induced an asymmetric distribution of cortical actin in β-cells. Our results demonstrate that adhesion of β-cells to E- and N-cadherins is regulated by insulin secretagogues and that E- and N-cadherin engagement promotes stimulated insulin secretion.

Angiotensin II Induces Interleukin-1β–Mediated Islet Inflammation and β-Cell Dysfunction Independently of Vasoconstrictive Effects

Pathological activation of the renin-angiotensin system (RAS) is associated with the metabolic syndrome, and the new onset of type 2 diabetes can be delayed by RAS inhibition. In animal models of type 2 diabetes, inhibition of the RAS improves insulin secretion. However, the direct effects of angiotensin II on islet function and underlying mechanisms independent of changes in blood pressure remain unclear. Here we show that exposure of human and mouse islets to angiotensin II induces interleukin (IL)-1–dependent expression of IL-6 and MCP-1, enhances β-cell apoptosis, and impairs mitochondrial function and insulin secretion. In vivo, mice fed a high-fat diet and treated with angiotensin II and the vasodilator hydralazine to prevent hypertension showed defective glucose-stimulated insulin secretion and deteriorated glucose tolerance. Application of an anti–IL-1β antibody reduced the deleterious effects of angiotensin II on islet inflammation, restored insulin secretion, and improved glycemia. We conclude that angiotensin II leads to islet dysfunction via induction of inflammation and independent of vasoconstriction. Our findings reveal a novel role for the RAS and an additional rationale for the treatment of type 2 diabetic patients with an IL-1β antagonist.

Impact of recipient body mass index on short-term and long-term survival of pancreatic grafts.

Background The impact of recipient body mass index on graft and patient survival after pancreas transplantation is not well known. Methods We have analyzed data from all pancreas transplant recipients reported in the Scientific Registry of Transplant Recipients between 1987 and 2011. Recipients were categorized into BMI classes, as defined by the World Health Organization. Short-term (90 days) and long-term (90 days to 5 years) patient and graft survivals were analyzed according to recipient BMI class using Kaplan-Meier estimates. Hazard ratios were estimated using Cox proportional hazard models. Results A total of 21,075 adult recipients were included in the analysis. Mean follow-up was 5±1.1 years. Subjects were overweight or obese in 39%. Increasing recipient BMI was an independent predictor of pancreatic graft loss and patient death in the short term (P<0.001), especially for obese class II patient survival (hazard ratio, 2.07; P=0.009). In the long term, obesity, but not overweight, was associated with higher risk of graft failure (P=0.01). Underweight was associated with a higher risk of long-term death (P<0.001). Conclusion These results question the safety of pancreas transplantation in obese patients and suggest that they may be directed to alternate therapies, such as behavioral modifications or bariatric surgery, before pancreas transplantation is considered.

Enhancement of islet engraftment and achievement of long-term islet allograft survival by Toll-like receptor 4 blockade.

Background Toll-like receptors are key players in sterile inflammation phenomena and can link the innate and adaptive immune systems by enhancing graft immunogenicity. They are also considered mediators of types 1 and 2 diabetes development. The aim of the present study was to assess the role of Toll-like receptor-4 (TLR4) in mediating the inflammatory and immune responses to pancreatic islets, thereby promoting inflammatory destruction and immune rejection of islet grafts. Methods Experiments were conducted in murine and human in vitro systems and in vivo murine islet transplant models, using species-specific anti-TLR4 monoclonal antibodies. In vitro, mixed lymphocyte-islet reaction experiments were performed to assess T-cell activation and proliferation. In vivo, both a syngeneic (B6-to-B6) marginal mass islet transplant model to assess the impact of TLR4 blockade on islet engraftment and an allogeneic (DBA1-to-B6) model were used. Results In vitro TLR4 blockade decreased lipopolysaccharide-mediated &bgr;-cell apoptosis and T-cell activation and proliferation against allogeneic islets. In vivo, TLR4 blockade resulted in significantly better syngeneic marginal mass islet engraftment and in indefinite allogeneic islet graft survival. Tolerance was not observed because donor-specific skin graft rechallenge in nonrejecting animals resulted in rejection of both skin and islets, but without accelerated rejection as compared to naive animals. Conclusion Taken together, our data indicate that TLR4 blockade leads to a significant improvement of syngeneic islet engraftment and of allogeneic islet graft survival. A mechanism of graft accommodation with concurrent inhibition of donor-specific immune memory is likely to be involved.

Association between lymphoepithelial cysts of the pancreas and HIV infection

BACKGROUND & AIMS To report the association of lymphoepithelial cysts (LEC) of the pancreas with Human Immunodeficiency Virus (HIV) infection. An association between LEC and HIV infection is already established in the parotid gland (PG). METHODS Report of the first two cases of LEC of the pancreas associated with HIV infection and comparison of the clinical and histopathological aspects of LECs of the pancreas and of the PG. RESULTS LECs of the pancreas were discovered by CT imaging in 2 patients with a history of HIV infection. Notably, LEC completely resolved in one patient after initiation of antiretroviral therapy. CONCLUSION This is the first report of an association of LEC of the pancreas and HIV infection. In the presence of LEC of the pancreas, we propose a systematic screening for HIV infection and associated lesions in the PG. Antiretroviral therapy should be initiated in untreated patients. Surgery should be reserved for symptomatic patients in whom medical therapy has failed.

Pancreas preservation fluid microbial contamination is associated with poor islet isolation outcomes - a multi-centre cohort study

The microbiological safety of islet preparations is paramount. Preservation medium contamination is frequent, and its impact on islet yield and function remains unclear. Microbiological samples collected during islet isolations from 2006 to 2016 were analyzed and correlated to isolation and allo‐ and autotransplantation outcomes. Microbial contamination of preservation medium was found in 64.4% of processed donor pancreases (291/452). We identified 464 microorganisms including Staphylococcus (253/464, 54.5%), Streptococcus (31/464, 6.7%), and Candida species (25/464, 5.4%). Microbial contamination was associated with longer warm and cold ischemia times and lower numbers of postpurification islet equivalents, purity, transplant rate, and stimulation index (all P < 0.05). Six percent of the preparations accepted for transplantation showed microbial contamination after isolation (12/200); 9 of 12 were Candida species. Six patients were transplanted with a sample with late microbial growth discovered after the infusion. Insulin independence rate was not affected. This risk of transplanting a contaminated islets preparation was reduced by half following the implementation of an additional sampling after 24 h of islet culture. Pancreas preservation fluid microbial contamination is associated with lower transplant rate and poorer in vitro function, but not with changes in graft survival. Culture medium testing 1 day after isolation reduces the risk of incidental transplantation with contaminated islets.

Impact of near-infrared angiography on the quality of anatomical resection during video-assisted thoracic surgery segmentectomy

Background The aim of the present study was to assess the impact of near-infrared angiography in guiding intraoperatively sublobar anatomical resection by video-assisted thoracic surgery (VATS). Methods We retrospectively analyzed data from 67 patients who underwent segmentectomy by VATS from November 2014 to November 2017 at the University Hospitals of Geneva, Switzerland. The need to modify arterial or parenchymal resection based on intraoperative near-infrared imaging was considered the primary study outcome. Results A total of 67 patients (28 men, 39 women, mean age 66±10 years) underwent anatomical pulmonary segmentectomy by VATS. Histological analysis revealed a primary lung tumor in 59 patients. The mean ± standard deviation (SD) operation time was 154±51 minutes. Identification of the intersegmental plane (ISP) with near-infrared angiography was achieved in 88% of patients and led to modification of the resection during segmentectomy in 7 patients (10%), avoiding inappropriate resection; 2 patients had distant tumor recurrences (3%). Conclusions Near-infrared angiography during VATS segmentectomy is effective for identifying ISPs, with respect to the oncological margins, as well as for correcting the anatomical resection.

Clinical outcome and risk factors for complications after pulmonary segmentectomy by video-assisted thoracoscopic surgery: results of an initial experience

Background Pulmonary anatomical segmentectomies are increasingly being done via video-assisted thoracoscopic surgery (VATS). We analyzed clinical outcomes and risk factors for post-operative complications after pulmonary segmentectomy by VATS was introduced in two institutions. Methods We retrospectively reviewed records of all patients who underwent anatomical pulmonary segmentectomy by VATS from 2014 to 2016 at the university hospitals of Geneva and Lausanne in Switzerland. Results One hundred twenty-nine patients (64 men; median age 68 years, range, 29-85 years) underwent anatomical VATS segmentectomy for primary lung tumors (n=100), metastases (n=16) and benign lesions (n=13). The overall 30-day mortality and morbidity rates were 0.8% and 31%, respectively. The reoperation rate was 4.7% [indications: hemothorax 2, prolonged air leak (PAL) 2, segmental torsion 1, empyema 1]. Chest drainage lasted for a median of 2 days (range, 1-33 days) and patients were discharged from the hospital after a median of 6 days (range, 2-37 days). Postoperative complications were mainly associated with chronic obstructive pulmonary disease (COPD) [odds ratio (OR) 2.54 and 95% confidence interval (95% CI), 1.18-5.47], and smoking pack-years >50 units (OR 5.27; 95% CI, 1.68-16.55). Nine patients (9%) presented with distant recurrences. Nodule size >2 cm was associated with decreased disease-free survival (DFS) (P=0.04). There was no association between surgical experience in VATS segmentectomy and DFS or postoperative complications. Conclusions Segmentectomies can be safely performed by VATS in an initial experience and result in favorable clinical outcome. COPD and smoking pack-years are associated with an increased risk of complications.

Nationwide multicenter study on the management of pulmonary neuroendocrine (carcinoid) tumors.

Background and aim To analyze the management and outcome of patients with primary typical (TC) and atypical lung carcinoids (AC) in Switzerland. Methods Retrospective analysis of patients selected from a neuroendocrine tumor (NET) registry. Patients were divided into TC and AC according to pathology reports, and surgical procedures were grouped as wedge/segmentectomy, lobectomy/bilobectomy and pneumectomy. Survival analysis was performed using the Kaplan–Meier method and log-rank test. Results Over 7 years, 113 pulmonary carcinoids (61.9% females, mean age 59.4 years) were included from 19 hospitals, with pathology data on Ki67 and necrosis incomplete in 16 cases. Eighty-three TC and 14 AC underwent surgical resection with a primary tumor size of median 14.5 (range 1–80) mm and diagnosis was established in 55.8% at surgery. Mean follow-up was 30.2 ± 23.1 months. Lobectomy was performed in 54.2% and wedge resection in 17.7% of cases. Six patients received additional systemic therapy. There was a trend for larger primary lesion size and a significantly higher rate of N2–N3 status in AC. Mean survival tended to be increased in patients with TC compared to AC (86.1 vs 48.4 months, P = 0.06) and mean disease-free interval after surgical resection was 74.1 and 48.3 months for TC and AC, respectively (P = 0.74). Conclusion AC of the lung has a more malignant behavior and a trend to a worse outcome. The results of this registry reinforce the need for standardized histological diagnosis and inter-disciplinary therapeutic decision making to improve the quality of care of patients with TC and AC.