Diabetic Transgenic Mice Research Articles

Expression of Transgene Encoded TGF-β in Islets Prevents Autoimmune Diabetes in NOD Mice by a Local Mechanism

To analyse the effects of TGF-β in insulin dependent diabetes mellitus (IDDM), we have developed non-obese diabetic (NOD) transgenic mice expressing TGF-β under the control of the rat insulin II promoter. Pancreata of TGF-β transgenic mice were roughly one twentieth of the size of pancreata of wild-type NOD mice and showed small clusters of micro-islets rather than normal adult islets. However, these islets produced sufficient levels of insulin to maintain normal glucose levels and mice were protected from the diabetes, which developed in their negative littermates. A massive fibrosis was seen in the transgenic pancreata that was accompanied with infiltration of mononuclear cells that decreased with age. Interestingly, these mice showed normal anti-islet immune response in their spleens and remained susceptible to adoptive transfer of IDDM by mature cloned CD8 effector cells. TUNEL assays revealed increased apoptosis of invading cells when compared to non-transgenic NOD mice. Taken together, these results suggest that TGF-β protects islets by a local event.

09 Influence of gender and age on excitation-contraction coupling in cardiac myocytes from calmodulin-induced diabetic transgenic (BIC) mice

09 Influence of gender and age on excitation-contraction coupling in cardiac myocytes from calmodulin-induced diabetic transgenic (BIC) mice

Enhanced diabetogenic effect of streptozotocin in mice overexpressing UCP-3 in skeletal muscle.

Diabetic patients exhibit varying degrees of increased muscle UCP-3 expression in skeletal muscle and, in rodents, the pancreatoxin streptozotocin (STZ) upregulates UCP-3 mRNA in skeletal and cardiac muscles. We have investigated the development of STZ-induced diabetes in transgenic mice overexpressing UCP-3 in skeletal muscle in order to provide further insight on the functional role of muscle UCP-3. UCP-3 transgenic mice treated with STZ (UCP3-STZ) showed a significant increase in blood glucose concentration 3 days after the last dose of STZ with a progressive induction of diabetes, attaining blood glucose concentrations of 24.7 +/- 1.5 mmol/L on day 17. Wild-type mice treated with STZ (WT-STZ) only started to show an increase in blood glucose concentration 6 days after the last dose of STZ and peaked on day 17 at a lower concentration than in the UCP-STZ mice. The pancreatic insulin content of UCP-3 control mice (UCP3-CON) was decreased relative to wild-type control mice (WT-CON), and STZ reduced the total pancreatic insulin content by 72% in WT-STZ mice and by 88% in UCP3-STZ mice. In an insulin tolerance test, blood glucose concentrations declined more in the UCP-3 transgenic mice than in the wild-type mice. Mice overexpressing UCP-3 in skeletal muscle have a lower pancreatic insulin content, but tend to be more insulin-sensitive. These twin actions result in an increased susceptibility to STZ-induced diabetes in UCP-3 transgenic mice.

Counteraction of type 1 diabetic alterations by engineering skeletal muscle to produce insulin: insights from transgenic mice.

Insulin replacement therapy in type 1 diabetes is imperfect because proper glycemic control is not always achieved. Most patients develop microvascular, macrovascular, and neurological complications, which increase with the degree of hyperglycemia. Engineered muscle cells continuously secreting basal levels of insulin might be used to improve the efficacy of insulin treatment. Here we examined the control of glucose homeostasis in healthy and diabetic transgenic mice constitutively expressing mature human insulin in skeletal muscle. Fed transgenic mice were normoglycemic and normoinsulinemic and, after an intraperitoneal glucose tolerance test, showed increased glucose disposal. When treated with streptozotocin (STZ), transgenic mice showed increased insulinemia and reduced hyperglycemia when fed and normoglycemia and normoinsulinemia when fasted. Injection of low doses of soluble insulin restored normoglycemia in fed STZ-treated transgenic mice, while STZ-treated controls remained highly hyperglycemic, indicating that diabetic transgenic mice were more sensitive to the hypoglycemic effects of insulin. Furthermore, STZ-treated transgenic mice presented normalization of both skeletal muscle and liver glucose metabolism. These results indicate that skeletal muscle may be a key target tissue for insulin production and suggest that muscle cells secreting basal levels of insulin, in conjunction with insulin therapy, may permit tight regulation of glycemia.

Multiple roles for tumor necrosis factor-α and lymphotoxin α/β in immunity and autoimmunity

Chapter summaryTumor necrosis factor (TNF)-α and lymphotoxin (LT) α/β play multiple roles in the development and function of the immune system. This article focuses on three important aspects of the effects of these cytokines on the immune response and on autoimmunity. In several experimental systems (Jurkat T cells, murine T-cell hybridomas), TNF-α appears to cause a downregulation of signaling through the TCR, revealed by changes in calcium flux, activation of p21, p23 and ZAP70, and a decrease in nuclear activation of NF-κB. Previous and present results suggest that TNF-α interferes in some manner with signaling through the TCR, at a locus yet to be delineated. Transgenic expression of LTβR-Fc in nonobese diabetic (NOD) transgenic mice results in prevention of type 1 diabetes in NOD mice as long as the level of expression of the fusion protein (under the control of the cytomegalovirus promoter) remains above a level of 2–3 μg/ml. Once the expression levels of the fusion protein have dropped below this critical level, the diabetic process resumes and the animals become diabetic at 40–50 weeks of age, whereas nontransgenic littermates develop diabetes by 25–30 weeks of age. The paradoxical effects of neonatal TNF-α administration in NOD mice in increasing incidence of and hastening onset of type 1 diabetes, while neonatal anti-TNF administration completely prevents all signs of islet cell autoimmunity, are due partly to the low levels of CD4+CD25+ T cells in NOD mice. These low levels are reduced by a further 50% on neonatal administration of nontoxic levels of TNF-α. In contrast, neonatal administration of anti-TNF-α results in a dramatic increase in the levels of CD4+CD25+ regulatory T cells, to levels beyond those seen in wild-type untreated NOD mice. TNF-α and LTα/β thus have pleomorphic regulatory effects on the development and expression of autoimmunity.

Cutting edge: interactions through the IL-10 receptor regulate autoimmune diabetes.

BDC2.5/nonobese diabetic (NOD) transgenic mice express a TCR from a diabetogenic T cell clone yet do not spontaneously develop diabetes at high incidence. Evidence exists showing that in the absence of endogenous TCR alpha-chain rearrangements this transgenic mouse spontaneously develops diabetes and that CTLA-4 negatively regulates diabetes onset. This strongly suggests that onset of diabetes in BDC2.5/NOD mice is governed by T cell regulation. We addressed the mechanism of immune regulation in BDC2.5/NOD mice. We find that activated spleen cells from young, but not old, BDC2.5/NOD mice are able to transfer diabetes to NOD-scid recipients. We have used anti-IL-10R to show that the failure of splenocytes from older mice to transfer diabetes is due to dominant regulation. We furthermore found that diabetes developed following anti-IL-10R treatment of 6-wk old BDC2.5/NOD mice indicating that endogenous IL-10 plays a key role in the regulation of diabetes onset in this transgenic mouse.

Systemic Administration of Agonist Peptide Blocks the Progression of Spontaneous CD8-Mediated Autoimmune Diabetes in Transgenic Mice Without Bystander Damage

Insulin-dependent diabetes is an autoimmune disease targeting pancreatic beta-islet cells. Recent data suggest that autoreactive CD8+ T cells are involved in both the early events leading to insulitis and the late destructive phase resulting in diabetes. Although therapeutic injection of protein and synthetic peptides corresponding to CD4+ T cell epitopes has been shown to prevent or block autoimmune disease in several models, down-regulation of an ongoing CD8+ T cell-mediated autoimmune response using this approach has not yet been reported. Using CL4-TCR single transgenic mice, in which most CD8+ T cells express a TCR specific for the influenza virus hemagglutinin HA512-520 peptide:Kd complex, we first show that i.v. injection of soluble HA512-520 peptide induces transient activation followed by apoptosis of Tc1-like CD8+ T cells. We next tested a similar tolerance induction strategy in (CL4-TCR x Ins-HA)F1 double transgenic mice that also express HA in the beta-islet cells and, as a result, spontaneously develop a juvenile onset and lethal diabetes. Soluble HA512-520 peptide treatment, at a time when pathogenic CD8+ T cells have already infiltrated the pancreas, very significantly prolongs survival of the double transgenic pups. In addition, we found that Ag administration eliminates CD8+ T cell infiltrates from the pancreas without histological evidence of bystander damage. Our data indicate that agonist peptide can down-regulate an autoimmune reaction mediated by CD8+ T cells in vivo and block disease progression. Thus, in addition to autoreactive CD4+ T cells, CD8+ T cells may constitute targets for Ag-specific therapy in autoimmune diseases.

Immunotherapy with dendritic cells directed against tumor antigens shared with normal host cells results in severe autoimmune disease.

Vaccination with dendritic cells (DCs) presenting tumor antigens induces primary immune response or amplifies existing cytotoxic antitumor T cell responses. This study documents that antitumor treatment with DCs may cause severe autoimmune disease when the tumor antigens are not tumor-specific but are also expressed in peripheral nonlymphoid organs. Growing tumors with such shared tumor antigens that were, at least initially, strictly located outside of secondary lymphoid organs were successfully controlled by specific DC vaccination. However, antitumor treatment was accompanied by fatal autoimmune disease, i.e., autoimmune diabetes in transgenic mice expressing the tumor antigen also in pancreatic beta islet cells or by severe arteritis, myocarditis, and eventually dilated cardiomyopathy when arterial smooth muscle cells and cardiomyocytes expressed the transgenic tumor antigen. These results reveal the delicate balance between tumor immunity and autoimmunity and therefore point out important limitations for the use of not strictly tumor-specific antigens in antitumor vaccination with DCs.

Pancreatic beta cell-specific expression of thioredoxin, an antioxidative and antiapoptotic protein, prevents autoimmune and streptozotocin-induced diabetes.

The cytotoxicity of reactive oxygen intermediates (ROIs) has been implicated in the destruction of pancreatic beta cells in insulin-dependent diabetes mellitus (IDDM). Thioredoxin (TRX), a redox (reduction/oxidation)-active protein, has recently been shown to protect cells from oxidative stress and apoptosis. To elucidate the roles of oxidative stress in the development of autoimmune diabetes in vivo, we produced nonobese diabetic transgenic mice that overexpress TRX in their pancreatic beta cells. In these transgenic mice, the incidence of diabetes was markedly reduced, whereas the development of insulitis was not prevented. Moreover, induction of diabetes by streptozotocin, an ROI-generating agent, was also attenuated by TRX overexpression in beta cells. This is the first direct demonstration that an antioxidative and antiapoptotic protein protects beta cells in vivo against both autoimmune and drug-induced diabetes. Our results strongly suggest that oxidative stress plays an essential role in the destruction of beta cells by infiltrating inflammatory cells in IDDM.

Peripheral neuropathy in transgenic diabetic mice: restoration of C-fiber function with human recombinant nerve growth factor.

Mice (Ins.Dd1) with hypoinsulinemic diabetes were created by increased expression of syngeneic major histocompatibility complex (MHC) class I protein in pancreatic beta-cells. The diabetic state was characterized in these mice by high glucose concentrations and islet pathology. To determine whether a neuropathy would develop, motor and sensory conduction velocities (CV) were determined in the sciatic nerves of 2-, 4-, and 7-month-old control and diabetic littermate male mice. Recording bipolar electrodes were placed in the plantar muscles of the hind foot of anesthetized (ketamine/xylazine) mice. Bipolar stimulating electrodes were positioned near the sciatic nerve at the sciatic notch or near the tibial nerve at the ankle. Motor CV from alpha-motor fibers and sensory CV from proprioceptive Aalpha nerves were measured and expressed as meters per second (m/s). Group data are reported as mean +/- SE and compared by analysis of variance. The CVs from nondiabetic mice (controls) were not different across the three ages and averaged 41.3 +/- 1.7 m/s for motor and 38.7 +/- 1.7 m/s for sensory. The motor CVs from diabetic mice at 2 and 4 months were similar to controls. Sensory CVs were unchanged at 2 months but were lower at 4 months (18.9 +/- 2.4 m/s). Both sensory (23.9 +/- 2.1 m/s) and motor (18.9 +/- 1.8 m/s) CVs were significantly reduced at 7 months, which is indicative of a polyneuropathy. NGF has well-known trophic effects on sympathetic and small sensory neurons. To determine whether NGF could influence this neuropathy, 6-month-old control and diabetic mice were divided into the following groups: 1) control + vehicle, 2) diabetic + vehicle, and 3) diabetic + NGF (1 mg/kg, 3x week, s.c.). After 1 month of treatment, motor and sensory CVs were determined. In some mice, the branches of the sciatic nerve were exposed and in situ recordings from the sural nerve were performed to determine compound C-fiber CV, integral, and amplitude. Sensory CV, determined via Hoffmann's reflex (H-reflex) (A-fiber), was decreased in diabetic compared with control animals as expected (P < 0.05), and NGF did not alter this parameter. Continuing diabetes reduced the amplitude (0.9 +/- 0.2 vs. 3.2 +/- 0.7 mV x 10(-2); P < 0.05) and integral (6.9 +/- 1.9 mV/ms vs. 18.8 +/- 4.4 mV/ms; P < 0.05) of the C-fiber response versus control, suggesting fiber loss. NGF treatment normalized C-fiber amplitude (2.9 +/- 0.8 mV x 10(-2)) and integral (21.2 +/- 6.5 mV/ms) in animals with established diabetes, with no effect on blood glucose. The C-fiber CV was similar in all groups, indicating that the animals had some normally conducting small fiber sensory nerves. These studies characterized a motor and sensory polyneuropathy in transgenic diabetic mice and are the first to demonstrate directly that NGF treatment can protect or restore abnormal sensory C-fiber function.

Amelioration of insulin resistance in streptozotocin diabetic mice by transgenic overexpression of GLUT4 driven by an adipose-specific promoter.

In diabetic rodents and humans, glucose transporter 4 (GLUT4) expression is suppressed in adipocytes in association with insulin resistance. Transgenic mice overexpressing GLUT4 selectively in fat have enhanced glucose disposal in vivo and massively increased glucose transport in adipocytes. To determine whether overexpression can be maintained in diabetes and whether it can prevent insulin resistance, we rendered wild-type and transgenic mice diabetic with streptozotocin. After 12-14 days, blood glucose was more than 21.4 mM and plasma insulin was 1.06 ng/ml or less in both diabetic groups in the fed state. Body weight was reduced and gonadal fat pad weight and adipocyte size were 52-75% smaller in both nontransgenic and transgenic diabetic mice, compared with nondiabetic. Basal and maximally-stimulated rates of lipolysis were similar in adipocytes from nontransgenic and transgenic mice, but the ED50 for isoproterenol stimulation was 50% lower in transgenic mice. There was no difference in the sensitivity to insulin to inhibit lipolysis. In adipocytes of nontransgenic diabetic mice, GLUT4 protein was reduced 34%, with a 46% reduction in insulin stimulated glucose transport. In contrast, in adipocytes of transgenic diabetic mice, GLUT4 remained 21-fold overexpressed, resulting in 21-fold increased basal and 10-fold increased insulin stimulated glucose transport. Injection of insulin (0.7 mU/g BW) resulted in a 35% decrease in blood glucose in transgenic diabetic mice (P < 0.05), with no effect in nontransgenic diabetic mice. Thus, high-level overexpression of GLUT4 driven by a fat specific promoter can be maintained with insulinopenic diabetes, even when fat cell metabolism is markedly altered. Overexpression of GLUT4 in adipocytes prevents insulin resistant glucose transport at the cellular level and improves insulin action in vivo, even with overt diabetes.

Ultrastructural and functional analyses of nephropathy in calmodulin‐induced diabetic transgenic mice

Background Previous animal models of diabetic nephropathy have used diabetic animals for which the underlying defect was either uncertain or the diabetes was induced by potentially specific toxins. In this report, we describe the renal abnormalities in a transgenic mouse model that develops early-onset diabetes due to overexpression of calmodulin in pancreatic beta cells. Methods Renal tissues were collected from normal and transgenic mice at 112, 182, and 300 days. These were prepared for light microscopic observation, stained with polyethylenimine (for anionic sites), or rendered acellular by detergent extraction prior to observation by transmission and scanning electron microscopy. Morphometric analysis of glomerular basement membrane thickness was carried out by the “orthogonal intercept” method. Twelve-hour urine samples of fed and fasting mice were collected for urine volume and glucose and protein analyses. Blood glucose, blood urea nitrogen, serum insulin, and creatinine were determined in 60-90-day-old and 255-day-old mice by established methods. Results Morphometric analyses revealed age-related and transgene-related increases in glomerular basement membrane thickness. A 22% increase in transgenic diabetics over controls was seen at 112 days of age that developed to increases of 43% and 37% at 182 and 300 days of age, respectively. Mesangial matrix area was also increased markedly in transgenic mice. Surprisingly, even in the oldest diabetic mice, there was no reduction in anionic sites. Moreover, despite an eightfold increase in urine volume, these mice did not become significantly proteinuric. Conclusions These results indicate that proteinuria of diabetes may be delayed or prevented by maintenance of a normal complement of glomerular basement membrane anionic sites. They also demonstrate that transgenic mice can provide a valuble model for discriminating between different aspects of diabetic nephropathy. Anat. Rec. 247:9–19 © 1997 Wiley-Liss, Inc.

Ultrastructural and functional analyses of nephropathy in calmodulin-induced diabetic transgenic mice.

Previous animal models of diabetic nephropathy have used diabetic animals for which the underlying defect was either uncertain or the diabetes was induced by potentially specific toxins. In this report, we describe the renal abnormalities in a transgenic mouse model that develops early-onset diabetes due to overexpression of calmodulin in pancreatic beta cells. Renal tissues were collected from normal and transgenic mice at 112, 182, and 300 days. These were prepared for light microscopic observation, stained with polyethylenimine (for anionic sites), or rendered acellular by detergent extraction prior to observation by transmission and scanning electron microscopy. Morphometric analysis of glomerular basement membrane thickness was carried out by the "orthogonal intercept" method. Twelve-hour urine samples of fed and fasting mice were collected for urine volume and glucose and protein analyses. Blood glucose, blood urea nitrogen, serum insulin, and creatinine were determined in 60-90-day-old and 255-day-old mice by established methods. Morphometric analyses revealed age-related and transgene-related increases in glomerular basement membrane thickness. A 22% increase in transgenic diabetics over controls was seen at 112 days of age that developed to increases of 43% and 37% at 182 and 300 days of age, respectively. Mesangial matrix area was also increased markedly in transgenic mice. Surprisingly, even in the oldest diabetic mice, there was no reduction in anionic sites. Moreover, despite an eightfold increase in urine volume, these mice did not become significantly proteinuric. These results indicate that proteinuria of diabetes may be delayed or prevented by maintenance of a normal complement of glomerular basement membrane anionic sites. They also demonstrate that transgenic mice can provide a valuable model for discriminating between different aspects of diabetic nephropathy.

Acceleration of spontaneous diabetes in TCR-beta-transgenic nonobese diabetic mice by beta-cell cytotoxic CD8+ T cells expressing identical endogenous TCR-alpha chains.

The role of target cell autoantigens and their repertoire vs those of foreign Ags, superantigens, or non-Ag-specific stimuli in the activation and recruitment of effector T cells in most spontaneous models of autoimmune diseases remains elusive. Here we report on the use of single TCR-beta transgenic mice to study the mechanisms that drive the accumulation of pathogenic T cells in the pancreatic islets of nonobese diabetic (NOD) mice, a model for insulin-dependent diabetes mellitus. Expression of the V(beta)8.1+ TCR-beta rearrangement of a diabetogenic H-2Kd-restricted beta cell cytotoxic CD8+ T cell (beta-CTL) clone in NOD mice caused a 10-fold increase in the peripheral precursor frequency of beta-CTL and a selective acceleration of the recruitment of CD8+ T cells to the pancreatic islets of prediabetic animals. This resulted in an earlier onset and a faster progression of beta cell depletion, and led to a dramatic acceleration of the onset of diabetes. Most islet-derived beta-CTL from diabetic transgenic NOD mice expressed an endogenously-derived TCR-alpha sequence identical to that of the clonotype donating the TCR-beta transgene, and a TCR-alpha-CDR3 sequence homologous to those expressed by most islet-derived beta-CTL from nontransgenic NOD mice. TCR-beta transgene expression did not change the peripheral frequency of beta cell-specific CD4+ T cells, the rate at which these cells accumulated in the pancreatic islets, or the incidence of diabetes. Taken together, our data indicate that retention of CD8+ and CD4+ T cells in the pancreatic islets of NOD mice is driven by beta cell autoantigens, rather than by local superantigens or non-Ag-specific stimuli, and that beta-CTL are major effectors of beta cell damage in spontaneous insulin-dependent diabetes mellitus.

Local expression of transgene encoded TNF alpha in islets prevents autoimmune diabetes in nonobese diabetic (NOD) mice by preventing the development of auto-reactive islet-specific T cells.

Lately, TNF alpha has been the focus of studies of autoimmunity; its role in the progression of autoimmune diabetes is, however, still unclear. To analyze the effects of TNF alpha in insulin-dependent diabetes mellitus (IDDM), we have generated nonobese diabetic (NOD) transgenic mice expressing TNF alpha under the control of the rat insulin II promoter (RIP). In transgenic mice, TNF alpha expression on the islets resulted in massive insulitis, composed of CD4+ T cells, CD8+ T cells, and B cells. Despite infiltration of considerable number of lymphoid cells in islets, expression of TNF alpha protected NOD mice from IDDM. To determine the mechanism of TNF alpha action, splenic cells from control NOD and RIP-TNF alpha mice were adoptively transferred to NOD-SCID recipients. In contrast to the induction of diabetes by splenic cells from control NOD mice, splenic cells from RIP-TNF alpha transgenic mice did not induce diabetes in NOD-SCID recipients. Diabetes was induced however, in the RIP-TNF alpha transgenic mice when CD8+ diabetogenic cloned T cells or splenic cells from diabetic NOD mice were adoptively transferred to these mice. Furthermore, expression of TNF alpha in islets also downregulated splenic cell responses to autoantigens. These data establish a mechanism of TNF alpha action and provide evidence that local expression of TNF alpha protects NOD mice from autoimmune diabetes by preventing the development of autoreactive islet-specific T cells.

Oral insulin treatment suppresses virus-induced antigen-specific destruction of beta cells and prevents autoimmune diabetes in transgenic mice.

Oral administration of self-antigens has been proposed as a therapy to prevent and treat autoimmune diseases. Here we report that oral treatment with insulin prevents virus-induced insulin-dependent diabetes mellitus (IDDM) in a transgenic (tg) mouse model. Such mice express the viral nucleoprotein (NP) of lymphocytic choriomeningitis virus (LCMV) under control of the rat insulin promoter in their pancreatic beta cells and < 2% spontaneously develop diabetes. However, 2 mo after challenge with LCMV, IDDM occurs in > 95% of tg mice but not in controls. Oral treatment with 1 mg of insulin twice per week for 2 mo starting either 1 wk before or 10 d after initiating LCMV infection prevents IDDM in > 50% of the tg mice (observation time 8 mo). Thus, insulin therapy is effective in preventing progression to overt IDDM in prediabetic tg mice with ongoing islet infiltration. Oral administration of insulin does not affect the generation of LCMV-NP-specific anti-self cytotoxic T lymphocytes nor the infiltration of lymphocytes into the pancreas. However, less beta cells are destroyed in insulin-treated mice, upregulation of MHC class I and II molecules does not occur, and antiviral (self) cytotoxic T lymphocytes are not found in the islets, events present in tg mice developing IDDM. The majority of lymphocytes in the islets of insulin-treated tg mice without IDDM produces IL-4, IL-10, and TGF-beta. In contrast, lymphocytes from islets of tg mice developing IDDM mainly make gamma-IFN.

Development of insulitis without diabetes in transgenic mice lacking perforin-dependent cytotoxicity.

It is widely accepted that T cells play an important role in the destruction of beta cells leading to autoimmune type I diabetes, but the involved effector mechanisms have remained unclear. We addressed this issue by testing the role of perforin-dependent cytotoxicity in a disease model involving transgenic mice expressing glycoprotein of lymphocytic choriomeningitis virus (LCMV-GP) in the beta cells of the endocrine pancreas. In such mice, LCMV infection leads to a potent LCMV-GP-specific T cell response resulting in rapid development of diabetes. We report here that in perforin-deficient LCMV-GP transgenic mice, LCMV infection failed to induce diabetes despite the activation of LCMV-GP-specific T cells. Deletion of nu beta 6+ T cells in Mls-1a perforin-deficient mice and the activation of LCMV-GP-specific T cells in perforin-deficient LCMV-GP transgenic mice, however, indicated that thymic tolerance induction by negative selection was not affected by the disruption of the perforin gene and that there is no fundamental difference between the T cell repertoires of normal control and perforin-deficient mice. In addition, adoptive transfer of LCMV-GP-specific TCR transgenic perforin-deficient T cells activated by LCMV-GP recombinant vaccinia virus led to marked insulitis with infiltration of CD4+ and CD8+ T cells without the development of diabetes. These findings indicate that perforin-dependent cytotoxicity is not required for the initiation of insulitis but is crucial for the destruction of beta cells in the later phase of the disease process. Other mechanisms or soluble factors present in the inflammatory islet infiltrate apparently lack the ability to efficiently induce diabetogenic beta cell damage.

Transforming growth factor-beta fails to inhibit allograft rejection or virus-induced autoimmune diabetes in transgenic mice.

Transgenic mice whose pancreata express transforming growth factor-beta (TGF-beta) directed by an insulin promoter (Ins-TGF-beta mice) were used to assess the effect of local TGF-beta1 on allograft rejection and on autoimmune diabetes occurring as a cross-reaction to viral antigens. Pancreatic TGF-beta1 did not delay allograft rejection, nor did it inhibit autoimmune diabetes after lymphocytic choriomeningitis infection of double transgenic mice (LCMV/TGF-beta1 mice). These results suggest that local TGF-beta1 does not serve as an immunosuppressive agent for allograft rejection or virus-mediated autoimmune diabetes.

Improvement of insulin action in diabetic transgenic mice selectively overexpressing GLUT4 in skeletal muscle

Improvement of insulin action in diabetic transgenic mice selectively overexpressing GLUT4 in skeletal muscle

Improvement of Insulin Action in Diabetic Transgenic Mice Selectively Overexpressing GLUT4 in Skeletal Muscle

To investigate the role of glucose transporter expression in whole-body glucose homeostasis, we have created transgenic mice that have a 2.0- to 3.5-fold increase in GLUT4 glucose transporter level in skeletal muscle and heart. This increase is sufficient to significantly improve insulin action and to reduce basal blood glucose levels in transgenic streptozotocin-induced diabetic mice. These results provide the first evidence of a direct causality between skeletal muscle GLUT4 transporter level and overall insulin responsiveness.