Association studies of variants in the genes involved in pancreatic beta-cell function in type 2 diabetes in Japanese subjects.

Because impaired insulin secretion is characteristic of type 2 diabetes in Asians, including Japanese, the genes involved in pancreatic beta-cell function are candidate susceptibility genes for type 2 diabetes. We examined the association of variants in genes encoding several transcription factors (TCF1, TCF2, HNF4A, ISL1, IPF1, NEUROG3, PAX6, NKX2-2, NKX6-1, and NEUROD1) and genes encoding the ATP-sensitive K(+) channel subunits Kir6.2 (KCNJ11) and SUR1 (ABCC8) with type 2 diabetes in a Japanese cohort of 2,834 subjects. The exon 16 -3c/t variant rs1799854 in ABCC8 showed a significant association (P = 0.0073), and variants in several genes showed nominally significant associations (P < 0.05) with type 2 diabetes. Although the E23K variant rs5219 in KCNJ11 showed no association with diabetes in Japanese (for the K allele, odds ratio [OR] 1.08 [95% CI 0.97-1.21], P = 0.15), 95% CI around the OR overlaps in meta-analysis of European populations, suggesting that our results are not inconsistent with the previous studies. This is the largest association study so far conducted on these genes in Japanese and provides valuable information for comparison with other ethnic groups.

Effect of long-term culture on the expression of antigens and adhesion molecule in single porcine pancreatic endocrine cells.

BACKGROUND: Changes in the expression of galactose (Gal) alpha1-3Gal, swine lymphocyte antigen (SLA) class II and intracellular adhesion molecule (ICAM)-1 of single porcine pancreatic endocrine (PE) cells during the culture period were investigated. METHODS: Cultured porcine PE-cells were fixed in 10% buffered formalin for histological evaluation. At 1, 3, 6, 9 and 12 weeks of culture, mRNA was obtained from porcine PE-cells so that the expression of SLA class II and ICAM-1 genes could be examined by reverse transcriptase-polymerase chain reaction. RESULTS: The rates of Galalpha1-3Gal and SLA class II-positive cells did not decrease during the culture period, but the rates of Galalpha1-3Gal and SLA class II strongly positive cells significantly decreased. ICAM-1-positive cells were scarcely observed during the culture period. SLA class II and ICAM-1 mRNAs were detected at 1 and 3 weeks of culture, but were not detected after 6 weeks of culture. CONCLUSIONS: These results suggest that partial reduction in the expression of these antigens could be obtained by a long-term culture.

Diabetes mellitus: rational basis, clinical approach and future therapy.

Clinical islet transplantation has recently received a strong impulse from the results obtained with the introduction of the Edomonton group. However, islet transplantation is at present a minimally invasive procedure and offers for the future the unique possibility of being performed under donor-specific tolerant conditions because islets may potentially be engineered in vitro. In addition, various approaches such as in vitro islet expansion, or xenogenic islets could make the availability of donor tissues unlimited. Recent advances in tissue engineering (technology) and cell biology may allow for the development of novel strategies for the treatment and cure of type I diabetes. In particular, it is now possible to envisage restoration of insulin secretion by cell-replacement therapy. And it will be necessary to ensure that implanted beta-cells are protected in some way from recognition by the immune system (a bio-artificial endocrine pancreas).

Effect of GLP-1 (glucagon-like peptide 1:7-36 amide) on porcine pancreatic endocrine cell proliferation and insulin secretion.

INTRODUCTION: We have established a method of isolation and primary monolayer culture of porcine pancreatic endocrine (PE) cells using nicotinamide. Recently, several insulin-stimulating factors have been recognized as modifying the function of endocrine cells. Glucagon-like peptide 1 (GLP-1), derived from intestinal cells, is one of the substances that may regulate insulin secretion and cell proliferation. AIM: The aim of the current study was to examine the effect of GLP-1 on PE cell proliferation and insulin secretion in our culture system. METHODOLOGY: The PE cells were prepared by nonenzymatic digestion and cultured in media with or without 10 nmol/L GLP-1 and maintained for 15 days. Basal insulin secretion and the glucose stimulated-response were observed by enzyme assay. PE-cell proliferation was assessed using 5-bromo 2' deoxyuridine (BrdU). beta-Cell specificity was confirmed by double staining with anti-BrdU and insulin antibody. mRNA expression in PE cells for insulin and pancreatic and duodenal homeobox gene 1 (PDX-1), a transcription factor, was semiquantitated by a real-time PCR method. RESULTS: Neither baseline nor glucose-stimulated insulin secretion differed significantly with or without the addition of 10 nmol/L GLP-1. However, significant changes of insulin secretion were observed in doses up to 100 nmol/L of GLP-1. BrdU incorporation increased with 10 nmol/L GLP-1 from 2.35+/- 0.16% to 9.11+/- 0.53% as compared with the control (from 2.17 +/- 0.57% to 6.13 +/- 0.35%). This increase was observed after a 12-day culture period. Double staining identified well-preserved insulin-containing cells, but neither the number of positive cells nor staining intensity differed significantly between the 2 groups during the 15-day culture period. The level of mRNA expression for both insulin and PDX-1 increased slightly but significantly. CONCLUSIONS: GLP-1 has a proliferative effect on PE cells and affects gene expression in short-term culture.

Prevalence of porcine endogenous retrovirus in domestic pigs in Japan and its potential infection in dogs xenotransplanted with porcine pancreatic islet cells.

The prevalence of porcine endogenous retrovirus (PERV) proviral DNA among various pig breeds raised in Japan was investigated by polymerase chain reaction (PCR). Moreover, potential infection of PERV was investigated by PCR and reverse transcriptase-polymerase chain reaction (RT-PCR) in experimentally induced diabetic dogs (n=5) implanted with the diffusion chamber type bio-artificial endocrine pancreas (Bio-AEP) containing porcine pancreatic endocrine (PE) cells. No immunosuppressant was used after the transplantation. PERV gag, pol, env-A and env-B genes were detected in any pigs examined. In two of three Landrace breeds, env-C gene was absent. PERV proviral DNAs and viral RNAs were also detected from the cultured porcine PE-cells. In the peripheral blood mononuclear cells and the spleen obtained at 6, 30, 32, 36, 79 weeks of xenotransplantation in dogs, however, no evidence of microchimerism, infection and viremia were confirmed. These results suggested that the risk of PERV infection through xenotransplantation of Bio-AEP containing porcine islet cells without immunosuppressants may be quite low.

Cytotoxicity for porcine islet cells by complement of six animal species.

Complement-mediated cytotoxicity for porcine islet cells (PICs) was evaluated using sera of six animal species. Then soluble complement receptor type-1 (sCR1) as an anti-complement agent was added to those sera, and the changes in 50% hemolytic unit of complement serum (CH50) and cytotoxic effect of those sera on PICs were examined. All the sera except for that of pig showed cytotoxicity. However, the extent of toxicity was considerably different between species. In the rat and human serum, sCR1 significantly reduced CH50 and cytotoxicity, however in the dog serum, sCR1 had no suppressive effects. These results may suggest that complement contribute to humoral cytotoxicity for PICs as a main factor, and the compatibility of complement with PICs differs between animal species.

Effect of adhesion or collagen molecules on cell attachment, insulin secretion, and glucose responsiveness in the cultured adult porcine endocrine pancreas: a preliminary study.

The effect of either adhesion or collagen molecules on cell attachment, insulin secretion, and glucose responsiveness was investigated in adult porcine pancreatic endocrine (PE) cells that were cultured for a longer term in vitro. Six different types of molecules--laminin, fibronectin, poly-L-lysine (PLL), type I collagen, gelatin, and Matrigel--were used. Approximately 2.0 x 10(5) cells per dish of each molecule type were cultured for 4 weeks. In the laminin group, the insulin accumulation was maintained at a significantly higher level than in the control group at 4 weeks of culture, and glucose-stimulated insulin secretion and the insulin-positive rate were also higher than in the control group. In the Matrigel group, islet-like cell clusters were formed, but insulin accumulation rapidly decreased at 3-4 weeks of culture. A large number of PE cells attached tightly and spread in the fibronectin group until the fourth week of culture, but their function was not better than those in the control group. In the PLL and gelatin groups, the PE cell function was not significantly different from that of the control group. In the type I collagen group, insulin secretion was inferior to that of the other groups. The results of this study suggest that laminin is the most suitable extracellular matrix for the long-term culture preservation of PE cells.

Xenotransplantation of porcine pancreatic endocrine cells to total pancreatectomized dogs.

Xenotransplantation of porcine pancreatic endocrine (PE) cells in a diffusion chamber, a bioartificial endocrine pancreas (Bio-AEP), was conducted to total pancreatectomized dogs. Six pancreatectomized dogs were divided into two groups of 3 dogs each. In three dogs of the control group, exogenous insulin was administered twice a day for 30 weeks to maintain fasting blood glucose (FBG) levels within the normal range. The remaining three dogs were implanted with Bio-AEPs (implantation group), in addition to daily insulin administration. In the implantation group, Bio-AEPs containing 1.3 to 1.8 x 10(7) cells per kg of body weight of the recipient were implanted without fixation into the abdominal cavity. In the control group, exogenous insulin requirements did not decrease during the experimental period, whereas it significantly decreased for a certain period (3, 11, 17 weeks) after implantation in all implanted dogs. In the implantation group, laparotomy was performed after FBG and the exogenous insulin requirement increased again and Bio-AEPs were removed. Two Bio-AEPs were completely destroyed, and the remaining one was encapsulated by thin fibrous tissue. In this dog, effusion was present within the capsule, but the Bio-AEP was not destroyed. Histopathologically, the necrosis, presumably caused by hypoxia, of the PE-cells was observed on transmission electron microscopy. In conclusion, Bio-AEP could function for a certain period after implantation in this study. However, more preclinical researches should be needed to apply this technique for the treatment of diabetic dogs.

Comparative study of adult porcine pancreatic endocrine cell preparation using a technique of multiple injections and pancreatic duct cannulation without a proteolytic enzyme.

INTRODUCTION: A method for isolation and primary monolayer culture of pancreatic endocrine (PE) cells from the porcine pancreas has already been established. It is very important for the PE cell preparation to expand the pancreas to separate PE cells from acinar cells. For this purpose, we developed a pancreatic injection system. AIM: To compare two pancreatic injection methods: perfusion from an accessory pancreatic duct (cannulation method) and the traditional pancreatic tissue injection method (multiple injection method). RESULTS: A comparison of the results of the two methods revealed that the PE cell yield was significantly higher with the cannulation method (2.97 +/- 0.59 x 10(7) cells per pancreas) than with the multiple injection method (0.89 +/- 0.15 x 10(7) cells per pancreas) (p < 0.0001). The number of dithizone-positive cells was significantly higher with the cannulation method (1.64 +/- 0.36 x 10(7) cells per pancreas) than with the multiple injection method (0.36 +/- 0.09 x 10(7) cells per pancreas) (p < 0.0001). The number of adhesion cells after 7 days of culture following isolation was higher with the cannulation method (1.07 +/- 0.26 x 10(7) cells per pancreas) than with the multiple injection method (0.36 +/- 0.03 x 10(7) cells per pancreas) (p < 0.0001). The glucose stimulation index of insulin secretion was higher with the cannulation method than with the multiple injection method (p < 0.01). CONCLUSION: These results indicate that pancreatic duct perfusion is useful for obtaining a high yield of PE cells from porcine pancreases.

Analysis of gene expression and insulin secretion by monolayer-forming adult porcine pancreatic endocrine cells.

INTRODUCTION: We recently established a method of isolation and primary monolayer culture of porcine pancreatic endocrine cells that involves the use of nicotinamide. AIM: To obtain genetic information on cultured porcine endocrine cells and to examine cell function in relation to insulin secretion during long-term culture. METHODOLOGY: Gene expression of insulin and several transcription factors, including PDX-1, Beta2/NeuroD, Pax6, and Nkx6.1, was assessed by reverse transcription-polymerase chain reaction analysis, and the insulin protein level was estimated by immunohistochemistry and enzyme assay during a 12-week period. RESULTS: During the culture period, insulin accumulation in the medium at 5 weeks had decreased by almost half the level of accumulation in the first week. In contrast to the alteration of secretory function, insulin gene expression was maintained for at least 12 weeks, and regulatory transcription factors were expressed at the same levels until 9 weeks. These observations suggest that gene expression is not involved in the cause of decreased baseline insulin secretion. Moreover, although the insulin response to high glucose and potassium loading was maintained, the magnitude of the responses to both stimuli was attenuated in the late period of culture. Insulin secretion tended to decrease in our culture system, and the secretory response to pharmacological stimulation was attenuated despite maintenance of messenger RNA expression of insulin and other islet-specific genes for at least 9 weeks in vitro. CONCLUSION: These findings indicate that cell integrity is maintained and that the alteration in insulin secretion must be explained by another mechanism.

Effect of stimulators such as GLP-1, PACAP, and nicotinamide on glucose-stimulated insulin secretion from porcine pancreatic endocrine cells in long-term culture.

INTRODUCTION: Transplantation of glucose-responsive insulin-secreting cells has the potential to result in a cure for diabetes. AIM: To report the development of a model of adult porcine pancreatic endocrine cells (PE cells) exhibiting glucose-stimulated insulin secretion during a long-term culture period, in vitro. METHODOLOGY: The PE cells were prepared by non-enzymatic digestion and purified by modifying a technique developed in our laboratory. The cells were first cultured for 7 days in RPMI-1640 medium containing 10% fetal bovine serum and 10 mM nicotinamide. On adhesion to the culture flasks, cells were collected by trypsinization, and then cultured in tissue culture dishes in medium with or without stimulators such as glucagon-like peptide-1 (GLP-1), pituitary adenylate cyclase-activating polypeptide (PACAP), and nicotinamide. The ability of the cells to respond to glucose-stimulated insulin secretion was also observed with and without stimulators. The immunocytochemical studies demonstrated pancreatic islets with well-preserved insulin and glucagon-containing cells. The morphologic integrity of cultured porcine cells was observed for up to 5-6 weeks after the purification. RESULTS: At a concentration of 3.3 mM glucose, PACAP and nicotinamide did not affect glucose-dependent insulin secretion, whereas 10 nM GLP-1 stimulated insulin secretion significantly. However, when glucose concentration was increased to 20 mM, 10 nM GLP-1 had no effect on insulin secretion. We also demonstrated that GLP-1 and PACAP could maintain insulin secretion better than control in the culture up to 5 weeks. Also GLP-1 and PACAP increased the number of insulin-secreting cells in culture. CONCLUSION: These results demonstrate that GLP-1 and PACAP increased the number of pancreatic beta-cells in culture.