Proteomic analysis of rat prefrontal cortex after chronic valproate treatment.

Valproic acid (VPA) is commonly used to treat bipolar disorder (BD), but its therapeutic role has not been clearly elucidated. To gain insights into VPA's mechanism of action, proteomic analysis was used to identify differentially expressed proteins in the rat prefrontal cortex (PFC), a region particularly affected in BD, after 6 weeks of VPA treatment. Proteins from PFCs of control and VPA-treated rats were separated by 2D-DIGE and identified by mass spectrometry. Among the 2,826 protein spots resolved, the abundance of 19 proteins was found to be significantly altered in the VPA-treated group (with the levels of three proteins increasing and 16 decreasing). Seven proteins whose levels were significantly altered after chronic VPA exposure were quantified by Western blot analysis. The 19 identified proteins represent potential new targets for VPA action and should aid in our understanding of the role of VPA in BD.

Maintenance of aerobic metabolism increases immunoisolated islet survival.

The progress of immunoisolation as a treatment for diabetes has been hampered by the diminished long term viability of islets within the immunoisolation device. Chronic hypoxia is greatly responsible for islet cell death within an immunoisolation device and remains an obstacle to the success of this form of islet transplantation. In order to address this problem, isolated rat islets were transfected with a plasmid encoding cytoglobin, an intracellular oxygen binding protein. Untreated or transfected islets were placed in polyacrylonitrile-polyvinychloride hollow fiber and implanted beneath the hepatic capsule in streptozotocin-diabetic rats. Fasting blood glucose was used as an indicator of islet survival and function. Rats receiving fibers containing transfected islets remained normoglycemic through the 60 day trial. Untreated islets failed within two weeks after implantation resulting in elevated blood glucose in the recipient. The fibers were recovered and tested for insulin content. Cytoglobin promoted islet cell survival and insulin synthesis and secretion. The induction of cytoglobin in islets may reduce cell loss from chronic hypoxia and may be a useful method to improve the feasibility of immunoisolation as an islet transplantation modality.

Reduction of ischemic cell death in cultured Islets of Langerhans by the induction of cytoglobin.

Despite the source or mechanism of origin of islets of Langerhans or islet ß-cells, all suffer significant cell loss from ischemia after isolation, thereby reducing the surviving islet mass available for study or transplantation. Methods to reduce beta cell death after islet isolation and transplantation must be developed if islet transplantation is to become an accepted treatment for diabetes. In order to enhance intracellular oxygen delivery and utilization, islets were transfected with a plasmid encoding cytoglobin, an intracellular oxygen binding protein. Oxygen consumption, insulin secretion, and the degree of central islet necrosis were measured in untreated and transfected islets to test the effects of cytoglobin on islet survival and function in vitro. The presence of cytoglobin reduced islet cell loss by reducing hypoxia related central islet necrosis and increased insulin secretion as compared with untreated islets. Cytoglobin treated islets maintained a normal rate of oxygen consumption, while untreated islets increased the rate of oxygen consumption caused by a shift to anaerobic metabolism and increased reactive oxygen specie synthesis. The induction of cytoglobin in islets may reduce cell loss from chronic hypoxia and may be a useful adjunct to islet transplantation.

The pancreas as an islet transplantation site. Confirmation in a syngeneic rodent and canine autotransplant model.

CONTEXT: The availability of islet transplantation is limited by both the number of donor pancreata and the number of islets required for successful transplantation. There is evidence that the liver presents a less than optimal environment for islets that contributes to short- and long-term beta cell destruction or failure. OBJECTIVE: It is our hypothesis that the pancreas is a suitable transplant site and may require fewer islets than standard sites such as the liver or kidney, and could lead to improvements in transplantation outcomes. METHODS: To test this hypothesis both a rodent and a canine model were used. Syngeneic rat islets were transplanted to the pancreas, liver, or kidney of Lewis rats. Fasting blood glucose levels were compared for three months as an index of islet function. Dogs received an islet autotransplant to a pancreatic remnant. Insulin and glucose concentrations were followed for six months. RESULTS: In the rat, normoglycemia was maintained with 600 islets transplanted in the pancreas in contrast to the liver (3,200 islets) or kidney (1,000-2,000 islets). Dogs remained normoglycemic after receiving an intra-pancreatic islet transplant (mean 7,640+/-3,600 islets). There was no evidence of pancreatitis or nutritional deficiency in either species. CONCLUSIONS: The pancreas should be considered as an islet transplant site. The pancreas is the native milieu for islets, and offers the advantage of requiring fewer islets than other conventional sites, thereby increasing the possibility that one donor pancreas may serve one or more recipients.

Remission of digestive insufficiency by islet transplantation to the pancreas.

Pancreatic digestive insufficiency is a common problem in both Type 1 and Type 2 diabetes and remains a serious consequence of diabetes in developing countries. The problem is not corrected by supportive therapies including exogenous insulin injections. It is our hypothesis that digestive insufficiency may be corrected or diminished by the transplantation of islets to the pancreas, thereby supplying islet hormones directly to acinar tissue analogous to the normal pancreas. Diabetic rats received 1000 syngeneic islets and dogs received 7600 autologous islets per kilogram as a transplant to the pancreas. Blood glucose and amylase concentrations were normalized in islet recipients in contrast with controls receiving no islets or islets transplanted to the renal capsule. These results suggest that diabetic digestive insufficiency may be corrected by intrapancreatic islet transplantation.

Local growth factors are beneficial for the autonomic reinnervation of transplanted islets in rats.

INTRODUCTION: Transplanted islets, being avascular and denervated, receive blood vessels and nerves from the recipient. Reinnervation may account in part for the normalization of islet function in islet transplants. Whether reinnervation is possible to augment is not known. AIMS AND METHODOLOGY: To explore whether reinnervation of transplanted islets is augmented by local addition of growth factors to the graft, syngeneic islets were transplanted to the pancreas of streptozotocin-diabetic Lewis rats with or without pellets locally releasing nerve growth factor (NGF) and vascular endothelial growth factor (VEGF), alone or in combination. The pellets released growth factors for 14 days at a rate of 20 ng/day. After 7 weeks, pancreatic tissue was processed for immunofluorescence of insulin and the neural markers neuropeptide Y (NPY) and tyrosine hydroxylase (TH). RESULTS: Islets were larger and more numerous after treatment with NGF (p = 0.024) and with NGF in combination with VEGF (p = 0.044). Similarly, immunostaining for TH and the C-terminal flanking peptide of NPY (C-PON) was more pronounced after treatment with NGF in combination with VEGF than in controls (both p < 0.05). CONCLUSION: Local growth factor treatment has a beneficial effect on autonomic reinnervation as well as islet integrity and survival of the graft after islet transplantation in rats.