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BS1-B Xenotransplantation update
S4
DIABETES RESEARCH A N D CLINICAL PRACTICE
with replication they regressed to a less differentiated phenotype and then could differentiate to form new acini and islets. Using pancreatic digests remaining after human islet isolation, we and others have shown that human pancreatic epithelial cells can be expanded in vitro and differentiated into islet tissue. When purified ducts from these preparations were expanded and then transplanted under the kidney capsule, differentiated beta cells are found in the grafts, supporting that the progenitors were in the ductal population. To test our dedifferentiation hypothesis, we took a direct approach of genetically marking ductal cells using carbonic anhydrase II (CAII) as a duct cell-specific promoter to drive cre recombinase in Cre-lox lineage tracing experiments. We show that CAII-expressing pancreatic duct cells act as progenitors that give rise to both new islets and acini after birth and after injury. This identification of a differentiated pancreatic cell type as in vivo progenitor for all differentiated pancreatic cell types has implications for a potential in vivo or ex vivo expandable source for new islets for replenishment therapy for diabetes.
BS1-B Xenotransplantation update R.B. Elliott Medical Director, Living Cell Technologies, New Zealand Pig islet xenotransplantation in Type 1 diabetic humans has been attempted using four systems: -intraportal injection of foetal or adult pig islets using immune suppression; intraperitoneal piglet islets without immune suppression; intraperitoneal microencapsulated piglet islets without immune suppression, and subcutaneous piglet islets and Sertoli cells without other immune suppression. Other systems have been tried in preclinical experiments in non-human primates. Of these variants some have been tried in human clinical trials. Only microencapsulated piglet islets have resulted in prolonged insulin independence or substantial insulin dose reduction with good diabetes control, and evidence of pig insulin production. Whatever the system employed no adverse effects related to pig viruses have been encountered, nor has there been any evidence of transmission of pig endogenous retroviruses in the total of 43 patients transplanted as of December 2007. Essential for safety are a closed herd of defined pathogen free pigs, GMP licensed manufacturing facility, and careful certified microbiological monitoring of the pigs, their tissues, the derived islets, the recipients and their immediate close contacts. Evidence of efficacy include reduction of HbA1c or maintenance of a normal level, substantial insulin dose reduction, normalisation of blood glucose excursions, and reduction in hypoglycemic events, following implantation compared with a two month preimplantation observation period. Direct evidence of pig insulin secretion and if possible histological evidence of islet survival are helpful in confirming the results. Foreign species cells other than islets have been successfully transplanted into experimental animals. There has been a trial of pig neural cell transplantation in Parkinson’s disease.
BS2-A Relevance of incretins in the treatment of Asian patients with Type 2 diabetes Yutaka Seino Kansai Electric Power Hospital, Osaka, Japan Type 2 diabetes is characterized by various degrees of insulin resistance and pancreatic β-cell dysfunction. In Europe and the USA, insulin resistance with obesity is the predominant pathological manifestation of diabetes; in Asia, impaired insulin secre-
79 (2008) S1 – S127
tion is predominant. The incretins are hormones released from the gut upon ingestion of meal to stimulate insulin secretion. Both GLP-1 and GIP have been well-characterized using KO mice. While both Asian and Western Type 2 diabetes patients generally exhibit incretin defects, they may be more dramatic in Asian patients. In addition, it has recently been demonstrated that both GIP and GLP-1 have extra pancreatic effects. We have found that GIP stimulates nutrient uptake into adipocytes, and that inhibition of the GIP signal reduces meal-induced adiposity. On the other hand, GLP-1 suppresses glucagon secretion and food intake, and slows gastric emptying in human and promotes beta cell neogenesis and proliferation in animal models. Thus, GLP-1 and GIP receptor agonists and dipeptidy1-IV (DPP-IV) inhibitors that enhance endogenous incretin activity may be therapeutically useful in Type 2 diabetes with impaired insulin secretion. It is noteworthy is that while the effectiveness of GLP-1 is generally preserved, that of GIP is markedly reduced in Type 2 diabetes in Asia. We have confirmed this phenomenon in isolated islets of GK rats, a model of non-obese Type 2 diabetes. The reasons for the failure of GIP to stimulate insulin secretion under certain conditions remain to be clarified. Because native GLP-1 is degradated immediately by DPPIV, both GLP receptor agonists (also called GLP-1 mimetics) or analogues and DPP-IV inhibitors have been developed. GLP-1 analogues/agonists in comparison with DPP-IV inhibitors have been found to achieve a greater insulin response with superior glycaemic control, improved weight loss, and comparable levels of adverse effects. Moreover, the beneficial effects of DPP-IV inhibitors are dependent on the endogenous GLP-1 level, which may render them less effective than GLP-1 analogues/mimetics that elicit higher pharmacological GLP-levels. However, GLP1 mimetics and analogues require administration by injection while DPP-IV inhibitors can be administered orally. Recently, the results of a clinical trial of GLP-1 derivatives in Japanese has appeared that allows comparison of the effects of DPP-IV inhibitors with those in Caucasians. Sitagliptin and vildagliptin improves HbA1c in both Caucasian and Japanese diabetic patients, but the reduction in HbA1c at the same dosages is 1.5 greater in Japanese. The use of the GLP-1 analogue, liraglutide, in Japanese Type 2 diabetes patients revealed that monotherapy with oncedaily administration achieved significant improvements in glycaemic control, with HbA1c reductions of 1.9% compared to placebo. While the dosage used was less than half that used in Caucasians, the reduction in HbA1c was more prominent in Japanese Type 2 diabetes patients. These findings indicate that GLP-1 agents may be more effective in Asian than in Caucasian Type 2 diabetes patients possibly due to their improvement of early phase insulin secretion.
BS2-B Beta cell lipotoxicity in Type 2 diabetes Trevor J. Biden Garvan Institute of Medical Research, Sydney, Australia Type 2 diabetes represents a failure of pancreatic beta cells to secrete sufficient insulin to compensate for peripheral insulin resistance. Beta cell failure is manifest as both a relative loss of cellular mass due to apoptosis, and a number of secretory defects including loss of responsiveness to glucose stimulation. Lipid oversupply induces both beta cell apoptosis and the secretory defects, consistent with the association between obesity and Type 2 diabetes. Recent insights from our laboratory into the mechanisms underlying this beta cell lipotoxicity will be presented. Firstly, we show that endoplasmic reticulum (ER) stress is a major determinant of beta cell apoptosis as revealed by analysis of gene and protein expression in lipid exposed cells in vitro, pan-
DIABETES RESEARCH A N D CLINICAL PRACTICE
with replication they regressed to a less differentiated phenotype and then could differentiate to form new acini and islets. Using pancreatic digests remaining after human islet isolation, we and others have shown that human pancreatic epithelial cells can be expanded in vitro and differentiated into islet tissue. When purified ducts from these preparations were expanded and then transplanted under the kidney capsule, differentiated beta cells are found in the grafts, supporting that the progenitors were in the ductal population. To test our dedifferentiation hypothesis, we took a direct approach of genetically marking ductal cells using carbonic anhydrase II (CAII) as a duct cell-specific promoter to drive cre recombinase in Cre-lox lineage tracing experiments. We show that CAII-expressing pancreatic duct cells act as progenitors that give rise to both new islets and acini after birth and after injury. This identification of a differentiated pancreatic cell type as in vivo progenitor for all differentiated pancreatic cell types has implications for a potential in vivo or ex vivo expandable source for new islets for replenishment therapy for diabetes.
BS1-B Xenotransplantation update R.B. Elliott Medical Director, Living Cell Technologies, New Zealand Pig islet xenotransplantation in Type 1 diabetic humans has been attempted using four systems: -intraportal injection of foetal or adult pig islets using immune suppression; intraperitoneal piglet islets without immune suppression; intraperitoneal microencapsulated piglet islets without immune suppression, and subcutaneous piglet islets and Sertoli cells without other immune suppression. Other systems have been tried in preclinical experiments in non-human primates. Of these variants some have been tried in human clinical trials. Only microencapsulated piglet islets have resulted in prolonged insulin independence or substantial insulin dose reduction with good diabetes control, and evidence of pig insulin production. Whatever the system employed no adverse effects related to pig viruses have been encountered, nor has there been any evidence of transmission of pig endogenous retroviruses in the total of 43 patients transplanted as of December 2007. Essential for safety are a closed herd of defined pathogen free pigs, GMP licensed manufacturing facility, and careful certified microbiological monitoring of the pigs, their tissues, the derived islets, the recipients and their immediate close contacts. Evidence of efficacy include reduction of HbA1c or maintenance of a normal level, substantial insulin dose reduction, normalisation of blood glucose excursions, and reduction in hypoglycemic events, following implantation compared with a two month preimplantation observation period. Direct evidence of pig insulin secretion and if possible histological evidence of islet survival are helpful in confirming the results. Foreign species cells other than islets have been successfully transplanted into experimental animals. There has been a trial of pig neural cell transplantation in Parkinson’s disease.
BS2-A Relevance of incretins in the treatment of Asian patients with Type 2 diabetes Yutaka Seino Kansai Electric Power Hospital, Osaka, Japan Type 2 diabetes is characterized by various degrees of insulin resistance and pancreatic β-cell dysfunction. In Europe and the USA, insulin resistance with obesity is the predominant pathological manifestation of diabetes; in Asia, impaired insulin secre-
79 (2008) S1 – S127
tion is predominant. The incretins are hormones released from the gut upon ingestion of meal to stimulate insulin secretion. Both GLP-1 and GIP have been well-characterized using KO mice. While both Asian and Western Type 2 diabetes patients generally exhibit incretin defects, they may be more dramatic in Asian patients. In addition, it has recently been demonstrated that both GIP and GLP-1 have extra pancreatic effects. We have found that GIP stimulates nutrient uptake into adipocytes, and that inhibition of the GIP signal reduces meal-induced adiposity. On the other hand, GLP-1 suppresses glucagon secretion and food intake, and slows gastric emptying in human and promotes beta cell neogenesis and proliferation in animal models. Thus, GLP-1 and GIP receptor agonists and dipeptidy1-IV (DPP-IV) inhibitors that enhance endogenous incretin activity may be therapeutically useful in Type 2 diabetes with impaired insulin secretion. It is noteworthy is that while the effectiveness of GLP-1 is generally preserved, that of GIP is markedly reduced in Type 2 diabetes in Asia. We have confirmed this phenomenon in isolated islets of GK rats, a model of non-obese Type 2 diabetes. The reasons for the failure of GIP to stimulate insulin secretion under certain conditions remain to be clarified. Because native GLP-1 is degradated immediately by DPPIV, both GLP receptor agonists (also called GLP-1 mimetics) or analogues and DPP-IV inhibitors have been developed. GLP-1 analogues/agonists in comparison with DPP-IV inhibitors have been found to achieve a greater insulin response with superior glycaemic control, improved weight loss, and comparable levels of adverse effects. Moreover, the beneficial effects of DPP-IV inhibitors are dependent on the endogenous GLP-1 level, which may render them less effective than GLP-1 analogues/mimetics that elicit higher pharmacological GLP-levels. However, GLP1 mimetics and analogues require administration by injection while DPP-IV inhibitors can be administered orally. Recently, the results of a clinical trial of GLP-1 derivatives in Japanese has appeared that allows comparison of the effects of DPP-IV inhibitors with those in Caucasians. Sitagliptin and vildagliptin improves HbA1c in both Caucasian and Japanese diabetic patients, but the reduction in HbA1c at the same dosages is 1.5 greater in Japanese. The use of the GLP-1 analogue, liraglutide, in Japanese Type 2 diabetes patients revealed that monotherapy with oncedaily administration achieved significant improvements in glycaemic control, with HbA1c reductions of 1.9% compared to placebo. While the dosage used was less than half that used in Caucasians, the reduction in HbA1c was more prominent in Japanese Type 2 diabetes patients. These findings indicate that GLP-1 agents may be more effective in Asian than in Caucasian Type 2 diabetes patients possibly due to their improvement of early phase insulin secretion.
BS2-B Beta cell lipotoxicity in Type 2 diabetes Trevor J. Biden Garvan Institute of Medical Research, Sydney, Australia Type 2 diabetes represents a failure of pancreatic beta cells to secrete sufficient insulin to compensate for peripheral insulin resistance. Beta cell failure is manifest as both a relative loss of cellular mass due to apoptosis, and a number of secretory defects including loss of responsiveness to glucose stimulation. Lipid oversupply induces both beta cell apoptosis and the secretory defects, consistent with the association between obesity and Type 2 diabetes. Recent insights from our laboratory into the mechanisms underlying this beta cell lipotoxicity will be presented. Firstly, we show that endoplasmic reticulum (ER) stress is a major determinant of beta cell apoptosis as revealed by analysis of gene and protein expression in lipid exposed cells in vitro, pan-