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At least 235 records · Page 13Linked to original sources

PubMed2003

Hypoglycemia, defective islet glucagon secretion, but normal islet mass in mice with a disruption of the gastrin gene.

BACKGROUND AND AIMS: Both cholecystokinin (CCK)-A and CCK-B receptors are expressed in the pancreas, and exogenous gastrin administration stimulates glucagon secretion from human islets. Although gastrin action has been linked to islet neogenesis, transdifferentiation, and beta-cell regeneration, an essential physiologic role(s) for gastrin in the pancreas has not been established. METHODS: We examined glucose homeostasis, glucagon gene expression, glucagon secretion, and islet mass in mice with a targeted gastrin gene disruption. RESULTS: Gastrin -/- mice exhibit fasting hypoglycemia and significantly reduced glycemic excursion following glucose challenge. Insulin sensitivity was normal and levels of circulating insulin and insulin messenger RNA transcripts were appropriately reduced in gastrin -/- mice. In contrast, levels of circulating glucagon and pancreatic glucagon messenger RNA transcripts were not up-regulated in hypoglycemic gastrin -/- mice. Furthermore, the glucagon response to epinephrine in isolated perifused islets was moderately impaired in gastrin -/- versus gastrin +/+ islets (40% reduction; P < 0.01, gastrin +/+ vs. gastrin -/- mice). Moreover, the glucagon response but not the epinephrine response to hypoglycemia was significantly attenuated in gastrin -/- compared with gastrin +/+ mice (P < 0.05). Despite gastrin expression in the developing fetal pancreas, beta-cell area, islet topography, and the islet proliferative response to experimental injury were normal in gastrin -/- mice. CONCLUSIONS: These findings show an essential physiologic role for gastrin in glucose homeostasis; however, the gastrin gene is not essential for murine islet development or the adaptive islet proliferative response to beta-cell injury.

Animals↗

PubMed2002

Unaltered oxygen tension in rat pancreatic islets despite dissociation of insulin release and islet blood flow.

The present study investigated the importance of a tightly regulated islet blood flow for an optimal oxygenation of the islet tissue during different demands for insulin release. Glucose and/or a non-specific nitric oxide synthase inhibitor (L-NNA) were infused intravenously in non-pretreated or vagotomized rats and the animals were subjected to measurements of islet blood flow, oxygen tension and serum insulin concentrations. Islet blood flow was measured using a non-radioactive microsphere technique, tissue oxygen tension was recorded with Clark microelectrodes and insulin concentrations were determined by enzyme-linked immunosorbent assay technique. Administration of L-NNA (0.3 mg kg(-1) min(-1)) for 10 min halved basal islet blood flow, but did not affect serum insulin concentrations. Glucose administration (10 mg kg(-1) min(-1)) induced a marked increase in islet blood flow, which could be prevented by vagotomy or L-NNA. The serum insulin concentrations increased in all glucose-infused animals. The islet tissue oxygen tension remained similar in all animals despite these interventions. Reasons other than oxygenation of the islet tissue must explain the normally existing tight regulation of islet blood flow.

Animals↗

PubMed1999

In vivo microscopy of murine islets of Langerhans: increased adhesion of transferred lymphocytes to islets depends on macrophage-derived cytokines in a model of organ-specific insulitis.

Environmental factors contribute to the pathogenesis of type 1 diabetes (insulin-dependent diabetes mellitus). Multiple low doses of streptozotocin (MLDS) induce hyperglycaemia and insulitis in mice. Previously we demonstrated that adhesion of lymphocytes to endothelium of islets is only increased when donor animals were diabetic and recipient mice had received 5 mg/kg streptozotocin (STZ). Therefore we used streptozotocin to evaluate the immunological relevance of such an irritation of islets. Lymphocytes, separated from diabetic mice (MLDS), were fluorescently labelled and injected to recipient mice that had received 5 mg/kg STZ. With in vivo microscopy we measured lymphocyte flow and adherence in islets. Expression of vascular cell adhesion molecule-1 (VCAM-1) and intracellular adhesion molecule-1 (ICAM-1) in the pancreas was assessed using immunohistochemistry. Very late antigen-4 (VLA-4) and leucocyte function-associated antigen-1 (LFA-1) expression on transferred lymphocytes was measured with flow cytometry. Pretreatment of recipients with antibodies to cytokines or silica reduced lymphocyte adherence to islet endothelium from 2.04% (goat immunoglobulin G; IgG) or 1.82% (rat IgG) to 0.47, 0.58, 0.39 or 0. 19% for monoclonal antibody (mAb) interferon-gamma (IFN-gamma), polyclonal antibody (pAb) tumour necrosis factor-alpha (TNF-alpha), pAb interleukin (IL)-1alpha or silica, respectively. Reduced adhesion was associated with a decreased expression of VCAM-1 and ICAM-1 in islets of treated recipients compared with mice treated with 5 mg/kg STZ alone. In conclusion, pretreatment of recipients with 5 mg/kg STZ leads to an increased expression of adhesion molecules in the islets and lymphocyte adhesion to islet endothelium in vivo, demonstrating an immune response of the islets. Prevention of increased expression of ICAM-1 or VCAM-1 and reduction of lymphocyte adhesion in islets by silica or antibody indicate an involvement of macrophages and macrophage derived cytokines in the generation of this immune response.

Animals↗

PubMed1997

Beta-cell function abnormalities in islets from an adult subject with nesidioblastosis and autoantibodies against the islet cells.

Human islets from an adult subject with nesidioblastosis were isolated and used to perform in vitro studies. Isolated nesidioblastotic islets showed an increased basal rate of insulin secretion (nesidioblastotic islets, 81.3 +/- 6.4 vs. control islets, from cadaveric organ normal donors, 10.2 +/- 0.9 microU/islet/90 min) without any further release with increasing glucose concentration. In addition, islets isolated from the pancreas with nesidioblastosis contained more insulin than control islets, 1,547.0 +/- 128.7 vs. 935.0 +/- 51.7 microU/islet, and the levels of insulin mRNA were also higher than those measured in controls. Interestingly, the serum of the subject with nesidioblastosis contained autoantibodies that stained brightly and selectively a population of islet cells whose distribution coincided with that expected of alpha cells. In summary, pancreatic islets in nesidioblastosis display beta-cell functional abnormalities. Moreover, the finding of antibodies against islet cells is a common feature in the serum of nesidioblastotic subjects; nevertheless, their pathological significance warrants further investigation.

Adolescent↗

PubMed2004

Expression of the beacon gene in the rat pancreatic islets: opposite effects of beacon (47-73) protein (ubiquitin-like protein 5) on insulin secretion in vivo and insulin release by isolated islets.

OBJECTIVE: Beacon gene expression is elevated in the hypothalamus of the Israeli sand rat (Psammomys obesus), an animal that is used as a polygenic animal model of obesity and NIDDM. We performed studies aimed at investigating the expression of beacon mRNA and protein in pancreatic islets of the rat and the possible beacon protein effects on insulin secretion. METHODS: Rat pancreatic islets were isolated by the collagenase digestion technique. Beacon mRNA expression was demonstrated in isolated islets using RT-PCR and beacon-like immunoreactivity using immunocytochemistry (ICC) on a sections of Bouin-fixed pancreas. Isolated islets were incubated with 1-100 nmol/L beacon (47-73) protein in normoglycemic medium. Adult female rats were subcutaneously injected with beacon (47-73) at doses 0.35 or 0.7 nmol/100 g body weight and killed after 30 and 60 minutes. RESULTS: RT-PCR results indicate the presence of beacon mRNA in isolated rat pancreatic islets. Beacon-like immunoreactivity is present in all cell types of the Langerhans islet. Beacon inhibits insulin secretion from isolated islets. In contrast, a bolus administration of beacon at a lower dose notably stimulates blood insulin concentration at 30 and 60 minutes of the experiment while the higher dose does not change insulinemia. None of the treatment had an effect on blood glucose concentration. CONCLUSION: This study demonstrated the presence of beacon mRNA in isolated rat islets as well as a direct inhibitory effect of beacon protein on insulin secretion by isolated rat pancreatic islets. The data obtained suggest that beacon may be involved in physiologic regulation of insulin secretion.

Animals↗

PubMed2002

Inducing tolerance to MHC-matched allogeneic islet grafts in diabetic NOD mice by simultaneous islet and bone marrow transplantation under nonirradiative and nonmyeloablative conditioning therapy.

BACKGROUND: Human type 1 diabetes is associated with defects in the hematopoietic stem cells. Simultaneous donor islet and bone marrow transplantation may be an ideal therapeutic approach for inducing tolerance to islet allogeneic antigens and restoring self-tolerance to islet autoimmune antigens. METHODS: Using a nonobese diabetic (NOD) mouse model of human type 1 diabetes, we investigated whether tolerance to MHC-matched allogeneic islet grafts from male nonobese diabetes-resistant (NOR) donors can be induced in female NOD recipients by simultaneous islet and bone marrow transplantation under fludarabine phosphate-based nonmyeloablative and irradiation-free conditioning therapy. Donor-specific chimerism in the peripheral blood of tolerant mice (n=7) was measured by semiquantitative polymerase chain reaction for a male-specific marker (SRY). RESULTS: Donor-specific tolerance to NOR islet grafts was induced in all diabetic NOD mice after simultaneous islet and bone marrow transplantation and treated with fludarabine phosphate, cyclophosphamide, anti-mouse lymphocyte serum, and rapamycin. At 100 days and 200 days after transplantation, the average percentage of male NOR marker in DNA derived from the peripheral blood of NOD recipients that had long-term islet graft survival was over 10%. CONCLUSION: Our data suggest that this approach may induce donor-specific tolerance in clinical islet transplantation and living-related donor solid organ transplantation.

Animals↗

PubMed2004

Improvement in islet yield from obese donors for human islet transplants.

BACKGROUND: The feasibility of human islet transplantations has been firmly established. To increase the number of islet transplants, the suitability of pancreases from organ donors considered inappropriate for pancreas transplantations must be evaluated. METHODS: We isolated islets from 114 human cadaver donor pancreases by the automated Ricordi method, followed by purification using continuous-density gradients. We divided the pancreases into two groups by donor body mass index (BMI)--group 1: n=51, BMI of 30 or more; group 2: n=63, BMI of less than 30. We compared the results of human islet isolation, in vitro potency assays, and a nude mouse bioassay. RESULTS: In group 1 (vs. group 2), we found a significantly higher mean pancreas weight (109.5+/-30.7 vs. 90.6+/-24.0 g; P=0.0002); higher mean islet equivalents/pancreas, after digestion (442,565+/-238,741 vs. 289,860+/-158,995; P<0.0001) and after purification (319,129+/-164,002 vs. 215,753+/-126,089; P=0.0002); and a higher islet isolation success rate--defined as isolations yielding more than 300,000 islet equivalents/pancreas, with purities of more than 50% (37.3% [19 of 51 pancreases] vs. 15.9% [10 of 63]; P=0.009). Our in vitro potency assays and bioassay uncovered no differences between the two groups. Notably, all except one of the donor BMIs for the successful isolations in group 2 exceeded 26; the mean donor BMI for the successful isolations (27.3+/-3.0, n=10) was significantly higher than for the unsuccessful isolations (24.8+/-3.3, n=53) (P=0.03). CONCLUSIONS: Pancreases from both overweight (BMI > or = 26 but <30) and obese (BMI > or = 30) cadaver donors are suitable for islet isolation and transplantations. Their use could increase the size of the islet donor pool.

Adult↗

PubMed1995

Islet cell antibodies: variable immunostaining of pancreatic islet cells and carcinoid tissue.

OBJECTIVES: Islet cell antibodies (ICA) in sera of patients with autoimmune diabetes mellitus generally stain not only the insulin-producing beta cells but also the non-beta cells of the islets of Langerhans. The antibodies have been reported to react also with the chromaffin cells of carcinoid tissue. In the present study, we examined in detail the reactivity of 10 ICA-positive sera of patients with new onset insulin-dependent diabetes mellitus (IDDM) and two sera of patients with stiff-man syndrome. DESIGN: The sera were analysed by immunofluorescence and by immunoperoxidase staining of human islets as well as by immunoprecipitations using 35S-methionine labelled rat islet lysates. In addition, immunofluorescence analyses of carcinoid tissues were carried out. RESULTS: Eight of the 10 IDDM-positive sera reacted with all islet endocrine cells, whereas two sera showed staining restricted to the beta cells, as did the two sera of the patients with stiff-man syndrome. All beta cell 'selective' sera, but only 6 of 8 'whole' islet positive sera, immunoprecipitated the 64.kDa glutamic acid decarboxylase (GAD) antigen. The staining of carcinoid tissue was variable and did not correlate with the 'whole' or 'selective' staining pattern of islets. CONCLUSION: The data underline a heterogeneity of ICA and indicate the presence of a separate, non-GAD antigen in islet cells. It is possible that in future studies, a resolution of ICA titres with respect to different types of islet cellular reactivity might provide insights into the pathogenesis of IDDM and improve the prognostic implications of antibody determinations.

Adolescent↗

PubMed2000

Dexamethasone counteracts the effect of prolactin on islet function: implications for islet regulation in late pregnancy.

Islets undergo a number of up-regulatory changes to meet the increased demand for insulin during pregnancy, including increased insulin secretion and beta-cell proliferation. It has been shown that elevated lactogenic hormone is directly responsible for these changes, which occur in a phasic pattern, peaking on day 15 of pregnancy and returning to control levels by day 20 (term). As placental lactogen levels remain elevated through late gestation, it was of interest to determine whether glucocorticoids (which increase during late gestation) could counteract the effects of lactogens on insulin secretion, beta-cell proliferation, and apoptosis. We found that insulin secretion measured over 24 h in culture and acute secretion measured over 1 h in response to high glucose were increased at least 2-fold by PRL treatment after 6 days in culture. Dexamethasone (DEX) treatment had a significant inhibitory effect on secretion in a dose-dependent manner at concentrations greater than 1 nM. At 100 nM, a concentration equivalent to the plasma corticosteroid level during late pregnancy, DEX inhibited secretion to below control levels. The addition of DEX (>1 nM) inhibited secretion from PRL-treated islets to levels similar to those produced by DEX treatment alone. Bromodeoxyuridine (10 microM) staining for the final 24 h of a 6-day culture showed that PRL treatment increased cell proliferation 6-fold over the control level. DEX treatment alone (1-1000 nM) did not reduce cell division below the control level, but significantly inhibited the rate of division in PRL-treated islets. YoYo-1, an ultrasensitive fluorescent nucleic acid stain, was added (1 microM; 8 h) to the medium after 1-3 days of culture to examine cell death. Islets examined under confocal microscopy showed that DEX treatment (100 nM) increased the number of cells with apoptotic nuclear morphologies. This was quantified by counting the number of YoYo-labeled nuclei per islet under conventional epifluorescence microscopy. The numbers of YoYo-1-positive nuclei per islet in control and PRL-treated islets were not different after 3 days of culture. However, DEX treatment increased YoYo-1 labeling 7-fold over that in controls. DEX also increased YoYo-1 labeling in PRL-treated islets 3-fold over the control level. These data show that the increased plasma glucocorticoid levels found during the late stages of pregnancy could effectively reverse PRL-induced up-regulation of islet function by inhibiting insulin secretion and cell proliferation while increasing apoptosis.

Animals↗

PubMed2006

Islet microvasculature in islet hyperplasia and failure in a model of type 2 diabetes.

Gene expression profiling of islets from pre-diabetic male Zucker diabetic fatty (ZDF) rats showed increased expression of hypoxia-related genes, prompting investigation of the vascular integrity of the islets. The islet microvasculature was increased approximately twofold in young male ZDF rats by both morphometric analysis and quantifying mRNA levels of endothelial markers. ZDF rats at 12 weeks of age showed a significant reduction in the number of endothelial cells, which was prevented by pretreatment with pioglitazone. Light and electron microscopy of normoglycemic 7-week-old ZDF rats showed thickened endothelial cells with loss of endothelial fenestrations. By 12 weeks of age, there was disruption of the endothelium and intra-islet hemorrhage. Islets from 7- and 12-week-old ZDF rats showed an approximate three- and twofold increase in vascular endothelial growth factor (VEGF)-A mRNA and VEGF protein secretion, respectively, compared with lean controls. Thrombospondin-1 mRNA increased in 7- and 12-week-old rats by 2- and 10-fold, respectively, and was reduced by 50% in 12-week-old rats pretreated with pioglitazone. Islets from young male control rats induced migration of endothelial cells in a collagen matrix only after pretreatment with matrix metalloproteinase (MMP)-9. Islets from 7-week-old ZDF rats showed a fivefold increase in migration score compared with wild-type controls, even without MMP-9 treatment. Islets from 15-week-old ZDF rats did not induce migration; rather, they caused a significant rounding up of the duct-derived cells, suggesting a toxic effect. These data suggest that in the ZDF rat model of type 2 diabetes, an inability of the islet to maintain vascular integrity may contribute to beta-cell failure.

Animals↗

PubMed1987

Spontaneous reassociation of dispersed adult rat pancreatic islet cells into aggregates with three-dimensional architecture typical of native islets.

Islets of Langerhans consist of four major endocrine cell types assembled in a highly organized manner critical for their function. The molecular forces governing islet cellular architecture are not understood. We determined whether adult rat islet cells carry information necessary for orderly assembly. Dispersed cells from adult rat islets were maintained in static suspension culture for 6 days. During this time the cells reassociated to form numerous aggregates. These aggregates were approximately half the size of native islets with a commensurate reduction in DNA and insulin content. However, both cellular composition and organization were remarkably similar to that of adult rat islets, in which the beta-cells form a central core surrounded by a discontinuous mantle of non-beta-cells. Thus, immunoperoxidase staining showed that in the aggregates, just as in intact islets cultured in parallel, 26% of the cells were non-beta-cells and of these, 94% were clearly peripheral. Non-beta-cells were similarly found to be peripheral, with beta-cells located centrally, even when the ratio of non-beta-cells to beta-cells had been altered. This was achieved by sorting the two cell populations by fluorescence-activated flow cytometry, resulting in aggregates with 79% non-beta-cells and 21% beta-cells. Insulin release from the aggregates was stimulated approximately ninefold by raising glucose from 50 to 300 mg/dl, which was comparable to that found for intact islets. The spontaneous formation of isletlike aggregates displaying appropriate cellular architecture indicates that the signals (molecules) needed for such organization are intrinsic to islet cells and are still expressed by them in adult life.

Animals↗

PubMed1994

Lack of immunohistological changes in the islets of nondiabetic, autoimmune, polyendocrine patients with beta-selective GAD-specific islet cell antibodies.

We examined the pancreases from three nondiabetic, autoimmune, polyendocrine patients with islet cell antibodies (ICAs) and glutamic acid decarboxylase (GAD) antibodies who died without developing insulin-dependent diabetes mellitus (IDDM). All three patients had the beta-selective GAD-specific ICA subtype and antibodies to the GAD-derived 50 kD tryptic fragment. None had whole islet ICA or antibodies to the non-GAD-derived 37k islet antigen, which appear to be more closely associated with IDDM than antibodies to GAD. The three patients also were negative for insulin autoantibodies. Islets within pancreas from patients 1 and 2 appeared well preserved as assessed by hematoxylin and eosin staining. In these two patients, insulin content, as assessed by indirect immunofluorescence on cryostat sections, was normal. Patient 3 had a prolonged postmortem time, and the islet insulin content was reduced slightly. In all three pancreases, no evidence was found of increased human leukocyte antigen class I or de novo class II molecule expression on islet cells, and islet infiltration by T- or B-cells or macrophages was not detected. Islet capillary endothelial cells did not show signs of hypertrophy. No immunoglobulin or complement deposition within or around islets was found. These data indicate that humoral GAD autoimmunity does not necessarily associate with visible beta-cell damage.

Adenocarcinoma↗

PubMed2002

Expression of the vesicular inhibitory amino acid transporter in pancreatic islet cells: distribution of the transporter within rat islets.

gamma-Aminobutyric acid (GABA) is stored in microvesicles in pancreatic islet cells. Because GAD65 and GAD67, which catalyze the formation of GABA, are cytoplasmic, the existence of an islet vesicular GABA transporter has been postulated. Here, we test the hypothesis that the putative transporter is the vesicular inhibitory amino acid transporter (VIAAT), a neuronal transmembrane transporter of GABA and glycine. We sequenced the human VIAAT gene and determined that the human and rat proteins share over 98% sequence identity. In vitro expression of VIAAT and immunoblotting of brain and islet lysates revealed two forms of the protein: an approximately 52-kDa and an approximately 57-kDa form. By immunoblotting and immunohistochemistry, we detected VIAAT in rat but not human islets. Immunohistochemical staining showed that in rat islets, the distribution of VIAAT expression parallels that of GAD67, with increased expression in the mantle. GABA, too, was found to be present in islet non-beta-cells. We conclude that VIAAT is expressed in rat islets and is more abundant in the mantle and that expression in human islets is very low or nil. The rat islet mantle differs from rat and human beta-cells in that it contains only GAD67 and relatively increased levels of VIAAT. Cells that express only GAD67 may require higher levels of VIAAT expression.

Amino Acid Sequence↗

PubMed1993

Effect of syngeneic islet antigen administration on complement-dependent antibody-mediated cytotoxicity to islet cells and diabetes onset in diabetes-prone BB/OK rats.

Diabetes-prone BB/OK rats aged 30 to 35 days were subjected to three sequential intrasplenic injections of unfractionated homogenate prepared from Langerhans' islets of newborn syngeneic BB/OK rats. Syngeneic islet antigen administration resulted in increased complement-dependent antibody-mediated cytotoxicity (C'AMC) to rat pancreatic islet cells in serum, compared to buffer-treated control animals as detected by 51Cr-release assay. However, the increase of anti-islet-cell cytotoxicity neither impaired glucose tolerance nor affected the incidence of diabetes and the age at manifestation. In contrast to BB/OK rats developing diabetes, animals remaining long-term normoglycaemic did not show an enhancement of cytotoxicity to islet cells within twelve days after the first islet antigen injection as revealed retrospectively. In conclusion, humoral mediated anti-islet-cell cytotoxicity is not decisively involved in pancreatic beta-cell destruction and promotion of diabetes development in BB/OK rats, but animals becoming diabetic seem to be characterized by a stronger immunological reactivity upon syngeneic islet antigen challenge as indicated by an increase of anti-islet C'AMC compared to long-term normoglycaemic rats.

Animals↗

PubMed2005

The increase in pancreatic endocrine mass after brief occlusion of the main pancreatic duct is primarily due to islet expansion and does not solely originate from islet neogenesis.

OBJECTIVES: We have developed a method for stimulating an increase in total pancreatic endocrine mass to study the initial signaling events occurring during islet neogenesis and found that brief occlusion of the main pancreatic duct transiently stimulates ERK1/2. As transient activation is predominantly associated with differentiation rather than proliferation, we investigated whether increased mass in this model was derived from neogenesis or from expansion of preexisting islets. METHODS: The main pancreatic duct in rats was briefly occluded, the pancreas excised and weighed, and immunocytochemical analysis performed after 56 days. Changes in endocrine-to-exocrine ratio; the percentage of small, medium, and large islets; and endocrine mass were assessed. Proliferation was measured in islets cells at 3, 7, 14, 21, and 56 days post-occlusion. In vitro kinase assays and Western immunoblot analysis were performed on pancreatic lysates to assess ERK1/2 and JNK activation. RESULTS: Briefly occluding the main pancreatic duct results in rapid transient activation of ERK1/2 and a slower activation of JNK, followed by an 80% increase in endocrine mass 56 days post-occlusion. The majority of this additional endocrine mass was due to an increase in the large (51%) rather than the small (8%) islet population. Islet cell proliferation and islet cell size of occluded pancreata were equivalent to those of unaffected controls. CONCLUSION: Neogenesis makes only a minor contribution to the overall increase in pancreatic endocrine mass. The additional endocrine mass is mainly derived from preexisting islets, but this is unlikely to be due to islet cell proliferation or hypertrophy in this model.

Animals↗

PubMed2006

Maintenance of mouse, rat, and pig pancreatic islet functions by coculture with human islet-derived fibroblasts.

Development of an efficient preculture system of islets is ideal. Toward that goal, we constructed a human pancreatic islet-derived fibroblast cell line MNNK-1 for a source as a coculture system for freshly isolated islets to maintain islet functions. Human pancreatic islet cells were nucleofected with a plasmid vector pYK-1 expressing simian virus 40 large T antigen gene (SV40T) and hygromycin resistance gene (HygroR). One of the transduced cell lines, MNNK-1, was established and served as a feeder cell in the coculture for freshly isolated mouse, rat, and pig islets. Morphology, viability, and glucose-responding insulin secretion were analyzed in the coculture system. MNNK-1 cells were morphologically spindle shaped and were negative for pancreatic endocrine markers. MNNK-1 cells were positive for alpha-smooth muscle actin and collagen type I and produced fibroblast growth factor. Coculture of the mouse, rat, and pig islets with MNNK-1 cells maintained their viability and insulin secretion with glucose responsiveness. A human pancreatic islet-derived fibroblast cell line MNNK-1 was established. MNNK-1 cells were a useful means for maintaining morphology and insulin secretion of islets in the coculture system.

Actins↗

PubMed1990

Beta cell destruction of pancreatic islets transplanted into diabetic BB/OK rats may be reflected by increased antibody-mediated anti-islet cytotoxicity.

Neonatal rat pancreatic islets can be affected in vitro by ADCC mediated by serum and mononuclear cells from diabetic BB/OK rats or complement-dependent antibody-mediated cytotoxicity (C'AMC) of BB rat serum as revealed by enhanced 51Cr-release. Using a syngeneic islet transplantation system in BB/OK rats this study addressed the question whether the destruction of islets of Langerhans in vivo is reflected by the appearance of ADCC or C'AMC in vitro. The frequency of the appearance of enhanced anti-islet ADCC in newly diagnosed diabetic BB/OK rats amounted to 33% whereas ADCC was not detectable in long-term diabetic rats with a diabetes duration in a range between 50 and 90 days. After transplantation of syngeneic islets beneath the kidney capsule of long-term diabetic BB/OK rats held without immunosuppression the destruction of the islet graft and the persistence of hyperglycaemia was accompanied by an increase of anti-islet ADCC in 66.6% of the animals. While only 18.7% of the long-term diabetic BB/OK rats showed C'AMC against islet cells before transplantation this frequency raised after transplantation and 62.8% of the animals exhibited increased C'AMC within a period of 21 days but with a pronounced individual variability of the time-course. Increased anti-islet cytotoxicity (ADCC or C'AMC) parallels newly initiated or reactivated beta-cell destruction after transplantation and thus seems to reflect this process.

Animals↗

PubMed1981

In vitro effects of islet-activating protein on cultured rat pancreatic islets. Enhancement of insulin secretion, adenosine 3':5'-monophosphate accumulation and 45Ca flux.

Pancreatic islets were maintained in culture with or without islet-activating protein (IAP), which is a new protein purified from culture medium of Bordetella pertussis. These cultured islets (IAP-treated or control) were then incubated for 30 min in IAP-free medium with various insulin secretagogues. During incubation, much more insulin was released from IAP-treated islets than control islets in response to glucose, arginine, glucagon, and sulfonylurea. IAP was effective in this regard when added to cultures at concentrations higher than 0.01 ng/ml; the effect was dependent on concentration up to 100 ng/ml. Enhanced insulin secretion was associated with accumulation of cyclic AMP when breakdown of the nucleotide was prevented by a methylxanthine. Epinephrine caused marked inhibitions, via alpha-adrenergic receptors, of glucose-induced insulin release, cyclic AMP accumulation and 45Ca uptake in control islets but did not in IAP-treated islets during incubation. None of these effects of IAP pretreatment were observed unless the medium for incubation was supplemented with Ca ions. 45Ca ion flux through the islet cell membrane was accelerated by the IAP treatment; conceivably, IAP was effective in causing sustained activation of native calcium ionophores on the membrane, which would be responsible for the enhanced insulin and cyclic AMP responses characteristic of IAP-treated islets.

1-Methyl-3-isobutylxanthine↗