Gordon C. Weir

Current methods for glucose-stimulated insulin secretion (GSIS) in rodents involve ex vivo perifusion or static incubation of pancreatic islets and pancreatic slices. Ex vivo perfusion and static incubation allow for multiple samples to be taken quickly with efficiency. However, these procedures subject the islets to trauma, intermittent hypoxia, and reduced paracrine insulin signaling, all of which can affect GSIS. These negative effects can be minimized via perfusion through the mice vasculature with an intact pancreas, which provides another comparison method for the different GSIS models. The backbone of this perfusion procedure involved i) vessel ligation to isolate the pancreas and ii) cannulation of the pancreatic vasculature. This model involved seven ligation points and two cannulations. The resultant perfused vasculature included the lower abdominal aorta, the celiac and superior mesenteric artery, the branching tributaries, and the portal vein. The perfusate was introduced to the vasculature at ~2 mL/min via a peristaltic pump to PE-50 tubing that cannulates the lower abdominal aorta. The perfusates ran through the isolated vasculature and were collected through the portal vein via a cannulation with PE-30 tubing. Perfusate was collected over 3 min intervals in rounds of 30 min for each perfusate solution of 2.6 mM glucose, 16.8 mM glucose, and 2.6 mM glucose with 3-isobutyl-1-methylxanthine (IBMX) in Krebs-Ringer bicarbonate buffer (KRB, 16 mM HEPES and 0.1% BSA, pH 7.4). The IBMX solution was preceded by a normal 2.6 mM glucose solution as a wash cycle. Total time was ~1 h for the surgical procedure and 2 h for perfusate collection. Perfusates were frozen until an ELISA was performed to measure insulin secretion. This method list hopes to provide a detailed procedural basis for insulin secretion measurement through pancreas perfusion through the vasculature, which will allow researchers to perform intact pancreas perfusion successfully in their laboratories.

Current methods for glucose-stimulated insulin secretion (GSIS) in rodents involve ex vivo perifusion or static incubation of pancreatic islets and pancreatic slices. Ex vivo perfusion and static incubation allow for multiple samples to be taken quickly with efficiency. However, these procedures subject the islets to trauma, intermittent hypoxia, and reduced paracrine insulin signaling, all of which can affect GSIS. These negative effects can be minimized via perfusion through the mice vasculature with an intact pancreas, which provides another comparison method for the different GSIS models. The backbone of this perfusion procedure involved i) vessel ligation to isolate the pancreas and ii) cannulation of the pancreatic vasculature. This model involved seven ligation points and two cannulations. The resultant perfused vasculature included the lower abdominal aorta, the celiac and superior mesenteric artery, the branching tributaries, and the portal vein. The perfusate was introduced to the vasculature at ~2 mL/min via a peristaltic pump to PE-50 tubing that cannulates the lower abdominal aorta. The perfusates ran through the isolated vasculature and were collected through the portal vein via a cannulation with PE-30 tubing. Perfusate was collected over 3 min intervals in rounds of 30 min for each perfusate solution of 2.6 mM glucose, 16.8 mM glucose, and 2.6 mM glucose with 3-isobutyl-1-methylxanthine (IBMX) in Krebs-Ringer bicarbonate buffer (KRB, 16 mM HEPES and 0.1% BSA, pH 7.4). The IBMX solution was preceded by a normal 2.6 mM glucose solution as a wash cycle. Total time was ~1 h for the surgical procedure and 2 h for perfusate collection. Perfusates were frozen until an ELISA was performed to measure insulin secretion. This method list hopes to provide a detailed procedural basis for insulin secretion measurement through pancreas perfusion through the vasculature, which will allow researchers to perform intact pancreas perfusion successfully in their laboratories.

In type 1 diabetes, the reduced glucagon response to insulin-induced hypoglycemia has been used to argue that β-cell secretion of insulin is required for the full glucagon counterregulatory response. For years, the concept has been that insulin from the β-cell core flows downstream to suppress glucagon secretion from the α-cells in the islet mantle. This core–mantle relationship has been supported by perfused pancreas studies that show marked increases in glucagon secretion when insulin was neutralized with antisera. Additional support comes from a growing number of studies focused on vascular anatomy and blood flow. However, in recent years this core–mantle view has generated less interest than the argument that optimal insulin secretion is due to paracrine release of glucagon from α-cells stimulating adjacent β-cells. This mechanism has been evaluated by knockout of β-cell receptors and impairment of α-cell function by inhibition of Gi designer receptors exclusively activated by designer drugs. Other studies that support this mechanism have been obtained by pharmacological blocking of glucagon-like peptide 1 receptor in humans. While glucagon has potent effects on β-cells, there are concerns with the suggested paracrine mechanism, since some of the supporting data are from isolated islets. The study of islets in static incubation or perifusion systems can be informative, but the normal paracrine relationships are disrupted by the isolation process. While this complicates interpretation of data, arguments supporting paracrine interactions between α-cells and β-cells have growing appeal. We discuss these conflicting views of the relationship between pancreatic α-cells and β-cells and seek to understand how communication depends on blood flow and/or paracrine mechanisms.

As diabetes continues to grow as major health problem, there has been great progress in understanding the important role of pancreatic beta-cells in its pathogenesis. Diabetes develops when the normal interplay between insulin secretion and the insulin sensitivity of target tissues is disrupted. With type 2 diabetes (T2D), glucose levels start to rise when beta-cells are unable to meet the demands of insulin resistance. For type 1 diabetes (T1D) glucose levels rise as beta-cells are killed off by autoimmunity. In both cases the increased glucose levels have a toxic effect on beta-cells. This process, called glucose toxicity, has a major inhibitory effect on insulin secretion. This beta-cell dysfunction can be reversed by therapies that reduce glucose levels. Thus, it is becoming increasingly apparent that an opportunity exists to produce a complete or partial remission for T2D, both of which will provide health benefit.

Gordon C Weir; Islet inflammation can be linked to the disruption of proinsulin processing in type 1 diabetes but not in type 2 diabetes, The Journal of Clinica

During progression to both types 1 and 2 diabetes (T1D, T2D), there is a striking loss of glucose-induced first-phase insulin release (FPIR), which is known to predict the onset of T1D. The contribution of reduced β cell mass to the onset of hyperglycemia remains unclear. In this issue of the JCI, Mezza et al. report on their study of patients with pancreatic neoplasms before and after partial pancreatectomy to evaluate the impact of reduced β cell mass on the development of diabetes. The authors found that reduced FPIR predicted diabetes when 50% of the pancreas was removed. These findings suggest that low or absent FPIR indicates that β cell mass can no longer compensate for increased insulin needs. Notably, clinicians may use reduction of FPIR as a warning that progression to T2D is underway.

There are strong reasons to say that pancreatic islets are organs before they are isolated and that they should be considered to be organs once transplanted. Thus, taking into account how much we have learned about the structure and function of islet micro-organs, it seems highly illogical to on one hand consider autologous islets be regulated as organ transplants and alloislets to be regulated with the very restrictive rules used for cell transplantation. It is particularly problematic that this policy has led to restrictions that have made it next to impossible for transplants of alloislets to be carried out in the US, which is a very sad situation for the country that made so many of the advances that brought islet transplantation to the clinic.