The BB rat

Deficiency of Trex1 leads to spontaneous development of type 1 diabetes

BACKGROUND

Type 1 diabetes is believed to be an autoimmune condition, characterized by destruction of insulin-producing cells, due to the detrimental inflammation in pancreas. Growing evidences have indicated the important role of type I interferon in the development of type 1 diabetes.

METHODS

Trex1-deficient rats were generated by using CRISPR-Cas9. The fasting blood glucose level of rat was measured by a Roche Accuchek blood glucose monitor. The levels of insulin, islet autoantibodies, and interferon-β were measured using enzyme-linked immunosorbent assay. The inflammatory genes were detected by quantitative PCR and RNA-seq. Hematein-eosin staining was used to detect the pathological changes in pancreas, eye and kidney. The pathological features of kidney were also detected by Masson trichrome and periodic acid-Schiff staining. The distribution of islet cells, immune cells or ssDNA in pancreas was analyzed by immunofluorescent staining.

RESULTS

In this study, we established a Trex1-deletion Sprague Dawley rat model, and unexpectedly, we found that the Trex1-/- rats spontaneously develop type 1 diabetes. Similar to human diabetes, the hyperglycemia in rats is accompanied by diabetic complications such as diabetic nephropathy and cataract. Mechanistical investigation revealed the accumulation of ssDNA and the excessive production of proinflammatory cytokines, including IFN-β, in Trex1 null pancreas. These are likely contributing to the inflammation in pancreas and eventually leading to the decline of pancreatic β cells.

CONCLUSIONS

Our study links the DNA-induced chronic inflammation to the pathogenesis of type 1 diabetes, and also provides an animal model for type 1 diabetes studies.

Okra [Abelmoschus esculentus (L.) Moench] improved blood glucose and restored histopathological alterations in splenic tissues in a rat model with streptozotocin-induced type 1 diabetes through CD8+ T cells and NF-kβ expression

Diabetes mellitus is a complex metabolic syndrome that involves dysfunction of spleen and other lymphoid organs. Medicinal plants, including okra (Abelmoschus esculentus (L.) Moench), were used widely for diabetes treatment. Scarce data are available about the potential anti-diabetic effects of okra, the histopathological alterations in splenic tissues and the mechanistic pathways underlying this association. The current research investigated the effects of okra pod extract on the biochemical parameters and expression of CD8+ T cells and nuclear factor kappa (NF-k) B and releasing proinflammatory cytokines in spleen in streptozotocin (STZ)-induced diabetic rat models. A total of 50 mature male Wister albino rats were divided into five isolated groups; the first served as control (untreated) animals, the second (DM group) diabetes induced by STZ (at a dose of 45 mg/kg body weight, administered intraperitoneally), the third group (DM + Insulin): diabetic rats administered insulin subcutaneously (10 units/kg bw/day) daily for 4 weeks, the fourth group was administrated 400 mg/kg okra extract daily for 4 weeks, and diabetic induced rats in the fifth group were administrated 400 mg/kg okra extract daily for 4 weeks. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity in Abelmoschus esculentus (L.) Moench was studied, and the content of phenolic compounds in okra pods was estimated using high-performance liquid chromatography. Diabetes induction led to decreased body weight, increased blood glucose levels. Capsular thickness was significantly increased, white pulp was widely dispersed, and mature lymphocytes in the periphery were also drastically decreased, with thick follicular arteries, necrosis, and depletion of lymphocytes in the germinal center. Red pulp revealed severe congestion and degenerative changes, deposition of hemosiderin granules and lymphocytic depletion. In addition, collagen fiber deposition was increased also in this group. The induction of diabetes exaggerated NF-kβ expression and mediated downregulation of the expression of CD8+ T cells in spleen tissue. Interestingly, oral administration of okra extracts post diabetes induction could mitigate and reverse such adverse effects. Altogether, our study points out the potential benefits of okra in improving blood glucose levels and restoring histopathological alterations in splenic tissues through CD8+ T cells and NF-kβ expression in a diabetic rat model.

The Vbeta13 T Cell Receptor Monoclonal Antibody Reduces Hyaluronan and CD68+, CD3+, and CD8+ Cell Infiltrations to Delay Diabetes in Congenic BB DRLyp/Lyp Rats

The depleting Vβ13a T cell receptor monoclonal antibody (mAb) 17D5 prevents both induced and spontaneous autoimmune diabetes in BB rats. Here it was tested in congenic DRLyp/Lyp rats, all of which spontaneously developed diabetes. Starting at 40 days of age, rats were injected once weekly with either saline, His42 Vβ16 mAb, or 17D5 mAb and monitored for hyperglycemia. Diabetes occurred in 100% (n = 5/5) of saline-treated rats (median age, 66 days; range 55-73), and in 100% (n = 6/6) of His42-treated rats (median age, 69 days; range 59-69). Diabetes occurred in fewer (n = 8/11, 73%) 17D5-treated rats at a later age (median 76 days, range 60-92). Three (27%) of the 17D5-treated rats were killed at 101-103 days of age without diabetes (17D5 no-diabetes rats). Survival analysis demonstrated that 17D5 mAb delayed diabetes onset. Saline- and His42-treated rats had severely distorted islets with substantial loss of insulin-positive cells. These rats exhibited prominent hyaluronan (HA) staining, with the intra-islet HA+ accumulations measuring 5,000 ± 2,400 µm2 and occupying 36 ± 12% of islet area, and severe (grade 4) insulitis with abundant infiltration by CD68+, CD3+, and CD8+ cells. The 17D5 mAb-treated rats with delayed diabetes onset exhibited less severe insulitis (predominantly grade 3). In contrast, the 17D5 no-diabetes rats had mostly normal islets, with insulin+ cells representing 76 ± 3% of islet cells. In these rats, the islet HA deposits were significantly smaller than in the diabetic rats; the intra-islet HA+ areas were 1,200 ± 300 µm2 and accounted for 8 ± 1% of islet area. Also, islet-associated CD68+ and CD3+ cells occurred less frequently (on average in 60 and 3% of the islets, respectively) than in the diabetes rats (present in >95% of the islets). No CD8+ cells were detected in islets in all 17D5 no-diabetes rats. We conclude that mAb 17D5 delayed diabetes in DRLyp/Lyp rats and markedly reduced expression of HA and concomitant infiltration of CD68+, CD3+, and CD8+ cells. Our findings underscore the importance of refining immune suppression in prevention or intervention clinical trials to use mAb reagents that are directed against specific T cell receptors.

Rat Models of Human Type 1 Diabetes

Rat models of human type 1 diabetes have been shown to be of great importance for the elucidation of the mechanisms underlying the development of autoimmune diabetes. The three major well-established spontaneous rat models are the BioBreeding (BB) diabetes-prone rat, the Komeda diabetes-prone (KDP) rat, and the IDDM (LEW.1AR1-iddm) rat. Their distinctive features are described with special reference to their pathology, immunology, and genetics and compared with the situation in patients with type 1 diabetes mellitus. For all three established rat models, a distinctive genetic mutation has been identified that is responsible for the manifestation of the diabetic syndrome in these rat strains.

Hyperglycaemia correlates with skeletal muscle capillary regression and is associated with alterations in the murine double minute-2/forkhead box O1/thrombospondin-1 pathway in type 1 diabetic BioBreeding rats

Type 1 diabetes can have deleterious effects on skeletal muscle and its microvasculature. Our laboratory has recently identified murine double minute-2 as a master regulator of muscle microvasculature by controlling expression levels of two key molecular actors of the angio-adaptive process: the pro-angiogenic vascular endothelial growth factor-A and the anti-angiogenic thrombospondin-1. Here, we show for the first time that in the soleus and plantaris muscles of the diabetes-prone BioBreeding rats, a rodent model of autoimmune type 1 diabetes, murine double minute-2 protein levels are significantly decreased, coinciding with elevated protein levels of thrombospondin-1 and its transcription factor forkhead box O1. Significant capillary regression was observed to similar extent in soleus and plantaris muscles of type 1 diabetic rats. Elevated blood glucose levels were correlated with the loss of capillaries, the reduction in murine double minute-2 expression and with the elevations in thrombospondin-1. Vascular endothelial growth factor-A protein levels were unaltered or even increased in diabetic animals, yet type 1 diabetic animals had less vascular endothelial growth factor receptor-2 abundance. The vascular endothelial growth factor-A/thrombospondin-1 ratio, a good indicator of skeletal muscle angio-adaptive environment, was decreased in type 1 diabetic muscle. Our results suggest that the murine double minute-2-forkhead box O1-thrombospondin-1 pathway plays an important role in angio-regulation of the skeletal muscle in the pathophysiological context of type 1 diabetes.

Development of the Nonobese Diabetic Mouse and Contribution of Animal Models for Understanding Type 1 Diabetes

In 1974, the discovery of a mouse and a rat that spontaneously developed hyperglycemia led to the development of 2 autoimmune diabetes models: nonobese diabetic (NOD) mouse and Bio-Breeding rat. These models have contributed to our understanding of autoimmune diabetes, provided tools to dissect autoimmune islet damage, and facilitated development of early detection, prevention, and treatment of type 1 diabetes. The genetic characterization, monoclonal antibodies, and congenic strains have made NOD mice especially useful.Although the establishment of the inbred NOD mouse strain was documented by Makino et al (Jikken Dobutsu. 1980;29:1-13), this review will focus on the not-as-well-known history leading to the discovery of a glycosuric female mouse by Yoshihiro Tochino. This discovery was spearheaded by years of effort by Japanese scientists from different disciplines and dedicated animal care personnel and by the support of the Shionogi Pharmaceutical Company, Osaka, Japan. The history is based on the early literature, mostly written in Japanese, and personal communications especially with Dr Tochino, who was involved in diabetes animal model development and who contributed to the release of NOD mice to the international scientific community. This article also reviews the scientific contributions made by the Bio-Breeding rat to autoimmune diabetes.

Camel whey protein improves oxidative stress and histopathological alterations in lymphoid organs through Bcl-XL/Bax expression in a streptozotocin-induced type 1 diabetic mouse model

Type I diabetes (T1D) is a characterized by the inflammation of pancreatic islets and destruction of β cells. Long and persistent uncontrolled diabetes tends to degenerate the immune system and increase the incidence of infections in diabetic individuals. Most serious diabetic complications are mediated by the free radicals, which damage multiple cellular components through direct effects of the cell cycle regulatory proteins. Camel whey protein (CWP) has antioxidant activity and decreases the effects of free radicals. However, the effects of CWP on lymphoid organs have not been studied in the context of diabetes. Therefore, the present study was designed to investigate the dietary influence of CWP supplementation on the lymphoid organs in streptozotocin (STZ)-induced type 1 diabetic mouse model. Three experimental groups were used: non diabetic control mice, diabetic mice, and diabetic mice treated with CWP. Induction of diabetes was associated with a marked reduction in glutathione (GSH) levels; decreased activities of GSH peroxidase (GSH Px), manganese superoxide dismutase (MnSOD) and catalase; increased reactive oxygen species (ROS) levels and iNOS activity in plasma and lymphoid organs. Furthermore, diabetic mice exhibited alterations in the expression of Bax and Bcl-XL, and subsequently pathological alterations in the architecture of the bone marrow, pancreas, thymus, and spleen. Interestingly, treatment of diabetic mice with CWP robustly restored glucose, insulin, GSH, and ROS levels and the activities of GSH Px, MnSOD, catalase and iNOS. Additionally, supplementation of diabetic mice with CWP improvement in the architecture of lymphoid tissues and rescued from apoptosis through direct effects on the Bax and Bcl-XL proteins. These data revealed the therapeutic potential of CWP against diabetic complications mediated damages of lymphoid organs.

Ghrelin mitigates β-cell mass loss during insulitis in an animal model of autoimmune diabetes mellitus, the BioBreeding/Worcester rat

BACKGROUND

Ghrelin is a peptide hormone with pleiotropic effects. It stimulates cell proliferation and inhibits apoptosis-mediated cell death. It prevents diabetes mellitus in several models of chemical, surgical and biological toxic insults to pancreas in both in vivo and in vitro models and promotes glucose-stimulated insulin secretion under cytotoxic conditions. It has not yet been tested in vivo in an autoimmune model of diabetes with a persistent insult to the β-cell. Given the immunomodulating effects of ghrelin and its trophic effects on β-cells, we hypothesized that ghrelin treatment during the early stages of insulitis would delay diabetes onset.

METHODS

BioBreeding/Worcester male rats received ghrelin (10 ng/kg/day) before insulitis development. Glucose metabolism was characterized by glucose and insulin tolerance tests. β-cell mass, islet area, islet number, β-cell clusters, proliferation and apoptosis and degree of insulitis were analysed by histomorphometry. A Kaplan-Meier survival curve was plotted and analysed applying the log-rank (Mantel-Cox) test.

RESULTS

Ghrelin treatment significantly reduced the probability of developing diabetes in our model (p < 0.0001). It decreased islet infiltration and partially prevented β-cell mass loss, enabling the maintenance of β-cell neogenesis and proliferation rates. Furthermore, ghrelin treatment did not induce any metabolic perturbations.

CONCLUSIONS

These findings support the hypothesis that ghrelin delays the development of autoimmune diabetes by attenuating insulitis and supporting β-cell mass.

GENERAL SIGNIFICANCE

Ghrelin promotes β-cell viability and function through diverse mechanisms that may have significant implications for diabetes prevention, therapy and also transplant success of both islets and complete pancreas. Copyright © 2016 John Wiley & Sons, Ltd.

The beta-cell in type 1 diabetes: What have we learned from proteomic studies?

Pancreatic beta-cells have a crucial role in the regulation of blood glucose homeostasis by the production and secretion of insulin. In type 1 diabetes (T1D), an autoimmune reaction against the beta-cells together with the presence of inflammatory cytokines and ROS in the islets leads to beta-cell dysfunction and death. This review gives an overview of proteomic studies that lead to better understanding of beta-cell functioning in T1D. Protein profiling of isolated islets and beta-cell lines in health and T1D contributed to the unraveling of pathways involved in cytokine-induced cell death. In addition, by studying the serological proteome of T1D patients, new biomarkers and beta-cell autoantigens were discovered, which may improve screening tests and follow-up of T1D development. Interestingly, an important role for PTMs was demonstrated in the generation of beta-cell autoantigens. To conclude, proteomic techniques are of indispensable value to improve the knowledge on beta-cell function in T1D and the search toward therapeutic targets.

Islet infiltration, cytokine expression and beta cell death in the NOD mouse, BB rat, Komeda rat, LEW.1AR1-iddm rat and humans with type 1 diabetes

AIMS/HYPOTHESIS

Research on the pathogenesis of type 1 diabetes relies heavily on good animal models. The aim of this work was to study the translational value of animal models of type 1 diabetes to the human situation.

METHODS

We compared the four major animal models of spontaneous type 1 diabetes, namely the NOD mouse, BioBreeding (BB) rat, Komeda rat and LEW.1AR1-iddm rat, by examining the immunohistochemistry and in situ RT-PCR of immune cell infiltrate and cytokine pattern in pancreatic islets, and by comparing findings with human data.

RESULTS

After type 1 diabetes manifestation CD8(+) T cells, CD68(+) macrophages and CD4(+) T cells were observed as the main immune cell types with declining frequency, in infiltrated islets of all diabetic pancreases. IL-1β and TNF-α were the main proinflammatory cytokines in the immune cell infiltrate in NOD mice, BB rats and LEW.1AR1-iddm rats, as well as in humans. The Komeda rat was the exception, with IFN-γ and TNF-α being the main cytokines. In addition, IL-17 and IL-6 and the anti-inflammatory cytokines IL-4, IL-10 and IL-13 were found in some infiltrating immune cells. Apoptotic as well as proliferating beta cells were observed in infiltrated islets. In healthy pancreases no proinflammatory cytokine expression was observed.

CONCLUSIONS/INTERPRETATION

With the exception of the Komeda rat, the animal models mirror very well the situation in humans with type 1 diabetes. Thus animal models of type 1 diabetes can provide meaningful information on the disease processes in the pancreas of patients with type 1 diabetes.

Bladder dysfunction in patients with diabetes

With diabetes mellitus (DM) reaching epidemic proportions, the identification of voiding dysfunction as a common and burdensome complication of this disease is critical. Research into diabetic voiding dysfunction significantly lags behind other complications of DM, such as retinopathy and nephropathy. Recent studies have revealed that DM predisposes patients to a wide range of lower urinary tract dysfunction, from the classic diabetic cystopathy of incomplete emptying to urgency incontinence. In this review, we discuss the current concepts of diabetic voiding dysfunction with a critical analysis of the available evidence.

Diabetes in Danish bank voles (M. glareolus): survivorship, influence on weight, and evaluation of polydipsia as a screening tool for hyperglycaemia

Background

Previous studies have concluded that the development of polydipsia (PD, a daily water intake ≥21 ml) among captive Danish bank voles, is associated with the development of a type 1 diabetes (T1D), based on findings of hyperglycaemia, glucosuria, ketonuria/-emia, lipemia, destroyed beta cells, and presence of autoantibodies against GAD65, IA-2, and insulin.

Aim and Methods

We retrospectively analysed data from two separate colonies of Danish bank voles in order to 1) estimate survivorship after onset of PD, 2) evaluate whether the weight of PD voles differed from non-PD voles, and, 3), evaluate a state of PD as a practical and non-invasive tool to screen for voles with a high probability of hypeglycaemia. In addition, we discuss regional differences related to the development of diabetes in Scandinavian bank voles and the relevance of the Ljungan virus as proposed etiological agent.

Results

We found that median survival after onset of PD is at least 91 days (lower/upper quartiles = 57/134 days) with a maximum recording of at least 404 days survivorship. The development of PD did not influence the weight of Danish bank voles. The measures of accuracy when using PD as predictor of hyperglycaemia, i.e. sensitivity, specificity, positive predictive value, and negative predictive value, equalled 69%, 97%, 89%, and 89%, respectively.

Conclusion

The relatively long survival of Danish PD bank voles suggests potentials for this model in future studies of the long-term complications of diabetes, of which some observations are mentioned. Data also indicates that diabetes in Danish bank is not associated with a higher body weight. Finally, the method of using measurements of daily water intake to screen for voles with a high probability of hyperglycaemia constitutes a considerable refinement when compared to the usual, invasive, methods.

Lowering apolipoprotein CIII delays onset of type 1 diabetes

Serum levels of apolipoprotein CIII (apoCIII) are increased in type 1 diabetic patients, and when β cells are exposed to these diabetic sera, apoptosis occurs, an effect abolished by an antibody against apoCIII. We have investigated the BB rat, an animal model that develops a human-like type 1 diabetes, and found that apoCIII was also increased in sera from prediabetic rats. This increase in apoCIII promoted β-cell death. The endogenous levels of apoCIII were reduced by treating prediabetic animals with an antisense against this apolipoprotein, resulting in a significantly delayed onset of diabetes. ApoCIII thus serves as a diabetogenic factor, and intervention with this apolipoprotein in the prediabetic state can arrest disease progression. These findings suggest apoCIII as a target for the treatment of type 1 diabetes.

Prolonged survival and improved glycemia in BioBreeding diabetic rats after early sustained exposure to glucagon-like peptide 1

BACKGROUND

Type 1 diabetes (T1D) in both humans and BioBreeding (BB) rats is an autoimmune disease that results in complete destruction of islets and insulin dependency for life. Glucagon-like peptide 1 (GLP-1) promotes beta cell proliferation and neogenesis and has a potent insulinotropic effect. We hypothesized that the expression of GLP-1 before disease onset would increase islet mass, delay diabetes and prolong survival of BB rats.

METHODS

Vascular smooth muscle cells retrovirally transduced to secrete GLP-1 were seeded into TheraCyte encapsulation devices, implanted subcutaneously, and rats were monitored for diabetes.

RESULTS

In untreated control rats, plasma GLP-1 levels were 34.5-39.5 pmol/l, whereas, in treated rats, plasma levels were elevated, in the range 90-250.4 pmol/l. Hypoglycemia was not detected and this was anticipated from the glucose-regulated action of GLP-1. Diabetes onset (mean + or - SEM) in untreated rats occurred at 56.5 + or - 0.6 days (n = 6) and, in GLP-1-treated rats, was delayed until 76.4 + or - 3.3 days (n = 5) (p < 0.001). After disease onset, untreated control rats showed a rapid weight loss and elevated blood glucose (>650 mg/dl) and did not survive beyond 11 days. At 5 days after diabetes onset, insulin-secreting islets were absent in untreated rats. By contrast, treated rats maintained weight for up to 143 days of age and showed insulin-secreting beta cells.

CONCLUSIONS

Sustained GLP-1 expression delivered by encapsulated cells before diabetes onset in BB rats showed an improved clinical outcome, suggesting the potential for treating patients using long lasting GLP-1 analogs.

Decrease in {beta}-cell proliferation precedes apoptosis during diabetes development in bio-breeding/worcester rat: beneficial role of Exendin-4

In autoimmune type 1 diabetes mellitus, proinflammatory cytokine-mediated apoptosis of beta-cells has been considered to be the first event directly responsible for beta-cell mass reduction. In the Bio-Breeding (BB) rat, an in vivo model used in the study of autoimmune diabetes, beta-cell apoptosis is observed from 9 wk of age and takes place after an insulitis period that begins at an earlier age. Previous studies by our group have shown an antiproliferative effect of proinflammatory cytokines on cultured beta-cells in Wistar rats, an effect that was partially reversed by Exendin-4, an analogue of glucagon-like peptide-1. In the current study, the changes in beta-cell apoptosis and proliferation during insulitis stage were also determined in pancreatic tissue sections in normal and thymectomized BB rats, as well as in Wistar rats of 5, 7, 9, and 11 wk of age. Although stable beta-cell proliferation in Wistar and thymectomized BB rats was observed along the course of the study, a decrease in beta-cell proliferation and beta-cell mass from the age of 5 wk, and prior to the commencement of apoptosis, was noted in BB rats. Exendin-4, in combination with anti-interferon-gamma antibody, induced a near-total recovery of beta-cell proliferation during the initial stages of insulitis. This highlights the importance of early intervention and, as well, the possibilities of new therapeutic approaches in preventing autoimmune diabetes by acting, initially, in the insulitis stage and, subsequently, on beta-cell regeneration and on beta-cell apoptosis.

Animal models of diabetic uropathy

PURPOSE

Diabetes mellitus is a group of debilitating and costly diseases with multiple serious complications. Lower urinary tract complications or diabetic uropathy are among the most common complications of diabetes mellitus, surpassing widely recognized complications such as neuropathy and nephropathy. Diabetic uropathy develops in individuals with types 1 and 2 diabetes, and little is known about the natural history of these common and troublesome complications. Animal models have the potential to reveal mechanisms and aid in the development of treatment strategies.

MATERIALS AND METHODS

We present a review of available animal models of diabetes mellitus relative to their use in the study of diabetic uropathy.

RESULTS

Large and small animal models of diabetes mellitus are available. While large animals such as dogs and swine may closely mirror the human disease in size and phenotype, the time between diabetic complication onset and development, and associated husbandry expenditures can make acquiring data on statistically valid sample sizes prohibitively expensive. In contrast, small animal models (rats and mice) have much lower expenditures for a larger number of animals and compressed observation time due to a shorter life span. Also, mice are readily manipulated genetically to facilitate the isolation of the effect of single genes (transgenic and knockout mice). Type 1 diabetes mellitus can be induced chemically with streptozotocin, which is selectively toxic to pancreatic beta cells. Type 2 diabetes mellitus models have been developed by selective breeding for hyperglycemia with or without associated obesity. Diabetic uropathy has been noted in several well characterized, predictable animal models of diabetes mellitus.

CONCLUSIONS

Diabetic uropathy, including diabetic bladder dysfunction, has been more frequently studied in small animals with type I diabetes. The recent availability of transgenic models provides a new opportunity for further studies of diabetic uropathy in mouse models of types I and II diabetes mellitus.

Differential effects of leptin receptor mutation on male and female BBDR Gimap5-/Gimap5- spontaneously diabetic rats

Rodents homozygous for autosomal leptin receptor gene mutations not only become obese, insulin resistant, and hyperleptinemic but also develop a dysregulated immune system. Using marker-assisted breeding to introgress the Koletsky rat leptin receptor mutant (lepr-/lepr-), we developed a novel congenic BBDR.(lepr-/lepr-) rat line to study the development of obesity and type 2 diabetes (T2D) in the BioBreeding (BB) diabetes-resistant (DR) rat. While heterozygous lepr (-/+) or homozygous (+/+) BBDR rats remained lean and metabolically normal, at 3 wk of age all BBDR.(lepr-/lepr-) rats were obese without hyperglycemia. Between 45 and 70 days of age, male but not female obese rats developed T2D. We had previously developed congenic BBDR.(Gimap5-/Gimap5-) rats, which carry an autosomal frameshift mutation in the Gimap5 gene linked to lymphopenia and spontaneous development of type 1 diabetes (T1D) without sex differences. Because the autoimmune-mediated destruction of pancreatic islet beta-cells may be affected not only by obesity but also by the absence of leptin receptor signaling, we next generated BBDR.(lepr-/lepr-,Gimap5-/Gimap5-) double congenic rats carrying the mutation for Gimap5 and T1D as well as the Lepr mutation for obesity and T2D. The hyperleptinemia rescued end-stage islets in BBDR.(lepr-/lepr-,Gimap5-/Gimap5-) congenic rats and induced an increase in islet size in both sexes, while T1D development was delayed and reduced only in females. These results demonstrate that obesity and T2D induced by introgression of the Koletsky leptin receptor mutation in the BBDR rat result in islet expansion associated with protection from T1D in female but not male BBDR.(lepr-/lepr-,Gimap5-/Gimap5-) congenic rats. BBDR.(lepr-/lepr-,Gimap5-/Gimap5-) congenic rats should prove valuable to study interactions between lack of leptin receptor signaling, obesity, and sex-specific T2D and T1D.

Mechanisms Of Complete Freund's Adjuvant Protection Against Diabetes in Bb Rats: Induction Of Non-Specific Suppressor Cells

We have previously reported that a single injection of complete Freund's adjuvant (CFA) can prevent diabetes appearance in diabetes-prone (DP) BB rats. In this study, we investigated further the mechanism of CFA-induced protection from diabetes. We found that adoptive transfer of splenic cells from CFA-treated DP rats into young DP rats protected the latter from diabetes development. This suggested that CFA-induced protection from diabetes resulted from activation of regulatory (suppressor) cells. Cell mixing experiments in vitro indicated that CFA activated splenic cells with antigen-nonspecific suppressor activity (suppression of lymphoproliferative responses to lipopolysaccharide and to allogeneic splenic cells). Fractionation of splenic cells on Percoll revealed that the suppressor activity resided in low density cells relatively depleted of T-cells, B-cells, macrophages and NK cells. These results suggest that non-specific (natural) suppressor cells in CFA-treated BB rats may be responsible for suppressing autoimmune responses and preventing insulitis and diabetes development.

VMAT2 quantitation by PET as a biomarker for beta-cell mass in health and disease

The common pathology underlying both type 1 and type 2 diabetes (T1DM and T2DM) is insufficient beta-cell mass (BCM) to meet metabolic demands. An important impediment to the more rapid evaluation of interventions for both T1DM and T2DM lack of biomarkers of pancreatic BCM. A reliable means of monitoring the mass and/or function of beta-cells would enable evaluation of the progression of diabetes as well as the monitoring of pharmacologic and other interventions. Recently, we identified a biomarker of BCM that is quantifiable by positron emission tomography (PET). PET is an imaging technique which allows for non-invasive measurements of radioligand uptake and clearance, is sensitive in the pico- to nanomolar range and of which the results can be deconvoluted into measurements of receptor concentration. For BCM estimates, we have identified VMAT2 (vesicular monoamine transporter type 2) as a biomarker and [(11)C] DTBZ (dihydrotetrabenazine) as the transporter's ligand. VMAT2 is highly expressed in beta-cells of the human pancreas relative to other cells of the endocrine and exocrine pancreas. Thus measurements of [(11)C] DTBZ in the pancreas provide an indirect measurement of BCM. Here we summarize our ongoing efforts to validate the clinical utility of this non-invasive approach to real-time BCM measurements.

Chorioretinal vascular oxygen tension in spontaneously breathing anesthetized rats

PURPOSE

To establish baseline and variability of oxygen tension (PO(2)) measurements in the choroid, retinal arteries, capillaries, and veins of spontaneously breathing anesthetized rats and determine the effect of a moderate surgical procedure on the chorioretinal PO(2).

METHODS

Our previously established optical section phosphorescence imaging technique was utilized to measure PO(2) in the chorioretinal vasculatures. Imaging was performed in 29 spontaneously breathing rats under ketamine/xylazine anesthesia. In 7 rats, blood was drawn using a surgically implanted femoral arterial catheter and analyzed to determine the systemic arterial PO(2). The PO(2) measurements in 22 rats without surgery (group 1) and 7 surgically instrumented rats (group 2) were statistically compared. The intrasubject variability was calculated by the average standard deviation (SD) of repeated measurements.

RESULTS

The average systemic arterial PO(2) was 52 +/- 7 mm Hg (mean +/- SD) in group 2. In group 1, the average PO(2) measurements in the choroid, retinal arteries, capillaries, and veins were 50 +/- 11, 40 +/- 5, 39 +/- 6, and 30 +/- 5 mm Hg, respectively. No statistically significant PO(2) differences in any of the chorioretinal vasculatures were found between the two groups (p > 0.4). The intrasubject variability was 3 mm Hg in the choroid, retinal arteries, capillaries, and veins.

CONCLUSIONS

Chorioretinal PO(2) measurements in spontaneously breathing anesthetized rats have a relatively low variability, indicating that PO(2) changes due to various physiological alterations can be reliably assessed.

Cystic cholangiomas after transplantation of pancreatic islets into the livers of diabetic rats

Islet transplantation is increasingly used as a therapy for human type 1 diabetes mellitus. In our study, we investigated the effect of the transplantation of a low number (n = 350) of pancreatic islets into the right liver part on the neighboring portal bile ducts. Male streptozotocin- diabetic Lewis or autoimmune-diabetic BB/Pfd rats (n = 1065) were subdivided into 11 experimental groups. A few days after low-number islet transplantation, cholangiocytes adjacent to the grafts showed an increase in proliferative activity. During the next 12-24 months, many peri-insular ductules progressed via tumor-like cystic lesions to large cystic cholangiomas, accompanied by a translocation of the insulin receptor into the cytoplasm and an increase in expression of insulin-related signaling proteins (Insulin-receptor-substrate-1, Raf-1, Mek-1). After 24 months, 53% of rats with low-number transplantation exhibited at least one cholangioma >10 mm, significantly outnumbering tumor development in the transplant-free left liver part and in any control group. No cholangiocarcinomas emerged. A graft cell origin of the tumors was excluded by Y chromosome in situ hybridization in cross-gender transplantations. Conclusively, low-number intrahepatic islet transplantation, most likely acting by permanent local hyperinsulinism, leads to prolonged cholangiocellular proliferation in streptozotocin- and in autoimmune-diabetic rats, resulting in the development of benign cystic cholangiomas.

Hepatocellular neoplasms induced by low-number pancreatic islet transplants in autoimmune diabetic BB/Pfd rats

It has been shown that combined high local hyperinsulinism and hyperglycemia after low-number islet transplantation into the livers of streptozotocin-diabetic rats lead to the development of hepatocellular neoplasms but a substantial cocarcinogenic effect of genotoxic streptozotocin could not be ruled out completely. Thus, we herein investigated this model in BB/Pfd rats (n = 805; nine experimental groups), which develop spontaneous autoimmune diabetes similar to human type 1 diabetes. After low-number islet transplantation (n = 450), the liver acini downstream of the islets show insulin-induced alterations: massive glycogen and/or fat accumulation, translocation of the insulin receptor, decrease in glucose-6-phosphatase activity, increase in expression of insulin-like growth factor (IGF)-I, IGF-II/mannose-6-phosphate receptor, insulin receptor substrate-1, Raf-1, and Mek-1, corresponding to clear cell preneoplastic foci of altered hepatocytes known from chemical hepatocarcinogenesis and identical to that in streptozotocin-diabetic Lewis rats. After 6 months, many altered liver acini progressed to other types of preneoplasias often accompanied by an overexpression of the glutathione-S transferase (placental form), IGF-I receptor, and transforming growth factor (TGF)-alpha. After 12 to 15 and 15 to 18 months, 52% and 100% of the animals showed one or multiple hepatocellular adenomas or hepatocellular carcinomas (HCCs), respectively. Conclusively, this study identifies combined hyperinsulinism and hyperglycemia as a carcinogenic mechanism for the development of HCCs in diabetic rats. Hepatocarcinogenesis is independent from additional genotoxic compounds (i.e., streptozotocin), but is primarily triggered by increased intracellular insulin signaling via pathways associated with cell growth and proliferation, such as the Ras-Raf-mitogen-activated protein kinase pathway and the IGF system, and secondarily involves other growth factors, such as TGF-alpha.

DR.lyp/lyp bone marrow maintains lymphopenia and promotes diabetes in lyp/lyp but not in +/+ recipient DR.lyp BB rats

Lymphopenia is due to a frameshift mutation in Gimap5 on rat chromosome 4 and is linked to type 1 diabetes in the diabetes prone (DP) BB rat. The hypothesis that bone marrow derived cells confer the lymphopenia phenotype was tested by reciprocal bone marrow transplantation in 40-day-old lethally irradiated diabetes resistant (DR) congenic DR.lyp/lyp (lymphopenia and diabetes) and DR.+/+ (no lymphopenia and no diabetes) rats. In two independent series of transplants, all DR.lyp/lyp rats (n=5 and 4) receiving DR.lyp/lyp bone marrow retained lymphopenia and developed insulitis (5/5 and 4/4) as well as diabetes in some (2/5 and 3/4). Both DR.+/+ and DR.lyp/lyp rats receiving DR.+/+ bone marrow cells as well as DR.+/+ rats receiving DR.lyp/lyp bone marrow cells showed no lymphopenia or diabetes. In accordance with earlier studies in non-congenic BB rats, the DR.+/+ rats receiving DR.lyp/lyp bone marrow cells recapitulated an intermediary phenotype rather than the +/+ or lyp/lyp phenotypes. Our data demonstrate that BBDP rat lymphopenia and diabetes are transferred by bone marrow transplantation to syngeneic DR.lyp/lyp but not DR.+/+ recipients. The intermediary recapitulation of DR.lyp/lyp T cells in recipient DR.+/-/+/- rats suggests that radiation resistant +/-/+/- T cells, the Gimap5 mutation in bone marrow cells, or both may not support the development of lymphopenia.

Immune cell infiltration, cytokine expression, and beta-cell apoptosis during the development of type 1 diabetes in the spontaneously diabetic LEW.1AR1/Ztm-iddm rat

The IDDM (LEW.1AR1/Ztm-iddm) rat is a type 1 diabetic animal model characterized by a rapid apoptotic pancreatic beta-cell destruction. Here we have analyzed the time course of islet infiltration, changes in the cytokine expression pattern, and beta-cell apoptosis in the transition from the pre-diabetic to the diabetic state. Transition from normoglycemia to hyperglycemia occurred when beta-cell loss exceeded 60-70%. At the early stages of islet infiltration, macrophages were the predominant immune cell type in the peripherally infiltrated islets. Progression of beta-cell loss was closely linked to a severe infiltration of the whole islet by CD8+ T-cells. With progressive islet infiltration, interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) were expressed in immune cells but not in beta-cells. This proinflammatory cytokine expression pattern coincided with the expression of inducible nitric oxide synthase (iNOS) and procaspase 3 in beta-cells and a peak apoptosis rate of 6.7%. Islet infiltration declined after manifestation of clinical diabetes, yielding end-stage islets devoid of beta-cells and immune cells without any sign of cytokine expression. The observed coincidence of IL-1beta and TNF-alpha expression in the immune cells and the induction of iNOS and procaspase 3 mRNA expression in the beta-cells depicts a sequence of pathological changes leading to apoptotic beta-cell death in the IDDM rat. This chain of events provides a mechanistic explanation for the development of the diabetic syndrome in this animal model of human type 1 diabetes.

Consomic rat model systems for physiological genomics

A consomic rat strain is one in which an entire chromosome is introgressed into the isogenic background of another inbred strain using marker-assisted selection. The development and physiological screening of two inbred consomic rat panels on two genetic backgrounds (44 strains) is well underway. Consomic strains enable one to assign traits and quantitative trait loci (QTL) to chromosomes by surveying the panel of strains with substituted chromosomes. They enable the rapid development of congenic strains over a narrow region and enable one to perform F2 linkage studies to positionally locate QTL on a single chromosome with a fixed genetic background. These rodent model systems overcome many of the problems encountered with segregating crosses where even if linkage is found, each individual in the cross is genetically unique and the combination of genes cannot be reproduced or studied in detail. For physiologists, consomics enable studies to be performed in a replicative or longitudinal manner to elucidate in greater detail the sequential expression of genes responsible for the observed phenotypes of these animals. They often provide the best available inbred control strains for physiological comparisons with the parental strains and they enable one to assess the impact of a causal gene region in a genome by allowing comparisons of the effect of replacement of a specific chromosome on a disease susceptible or a resistant genomic background. Consomic rat strains are proving to be a unique scientific resource that can greatly extend our understanding of genes and their role in the regulation of complex function and disease.

B cell selection defects underlie the development of diabetogenic APCs in nonobese diabetic mice

One mechanism whereby B cells contribute to type 1 diabetes in nonobese diabetic (NOD) mice is as a subset of APCs that preferentially presents MHC class II-bound pancreatic beta cell Ags to autoreactive CD4 T cells. This results from their ability to use cell surface Ig to specifically capture beta cell Ags. Hence, we postulated a diabetogenic role for defects in the tolerance mechanisms normally blocking the maturation and/or activation of B cells expressing autoreactive Ig receptors. We compared B cell tolerance mechanisms in NOD mice with nonautoimmune strains by using the IgHEL and Ig3-83 transgenic systems, in which the majority of B cells recognize one defined Ag. NOD- and nonautoimmune-prone mice did not differ in ability to delete or receptor edit B cells recognizing membrane-bound self Ags. However, in contrast to the nonautoimmune-prone background, B cells recognizing soluble self Ags in NOD mice did not undergo partial deletion and were also not efficiently anergized. The defective induction of B cell tolerance to soluble autoantigens is most likely responsible for the generation of diabetogenic APC in NOD mice.

Application of chromosomal substitution techniques in gene-function discovery

A consomic rat strain is one in which an entire chromosome is introgressed into the isogenic background of another inbred strain using marker assisted selection. The development and initial physiologic screening of two inbred consomic rat panels on two genetic backgrounds (44 strains) is well underway. The primary uses of consomic strains are: (1) to assign traits and quantitative trait loci (QTL) to chromosomes by surveying the panel of strains with substituted chromosomes; (2) to rapidly develop congenic strains over a narrow region using several approaches described in this review and perform F2 linkage studies to positionally locate QTL in a fixed genetic background. In addition, consomic strains overcome many of the problems encountered with segregating crosses where, even if linkage is found, each individual in the cross is genetically unique and the combination of genes cannot be reproduced or studied in detail. Consomic strains provide greater statistical power to detect linkage than traditional F2 crosses because of their fixed genetic backgrounds, and can produce sufficient numbers of genetically identical rats to validate the relationship between a trait and a particular chromosome. These strains allow studies to be performed in a replicative or longitudinal manner to elucidate in greater detail the sequential changes responsible for the observed phenotypes of these animals, and they enable one to assess the impact of a causal gene region in a genome by allowing comparisons of the effect of replacement of a specific chromosome upon a disease susceptible or resistant genomic background. Consomics can be used to quickly develop multiple chromosome substitution models to investigate gene-gene interactions of complex traits or diseases. Finally, they often provide the best available inbred control strain for particular physiological comparisons with the inbred parental strains. Consomic rat strains are proving to be a unique scientific resource that greatly extends our understanding of genes and complex normal and pathological function.

Genomic sequence and organization of the family of CNR/Pcdhα genes in rat

CNR/Pcdhalpha family proteins are known as synaptic cadherins and Reelin receptors. Here we report the complete genomic sequence and organization of the rat CNR. The rat CNR cluster encodes 15 variable and 3 constant exons. The genomic organizations of the rat, mouse, and human CNR/Pcdhalpha are orthologous. The percentage identity of the coding regions between the rat and the mouse is 93.6% on average at the nucleic acid level, and between rat and human it is 82.8%. The rat CNRs (v1-v13) also contain an RGD motif in the extracellular cadherin 1 domains and cysteine repeats that are characteristic of the transmembrane and cytoplasmic domains of CNR proteins. The number of variable exons in the rat CNR cluster is identical to that of the human. The rat CNR cluster has one more variable exon than is found in laboratory mouse strains, because in the mouse a variable exon located between v7 and v8 is divided by the insertion of a retrotransposon. This exon is not disrupted in the rat, in which it is transcribed. By in silico analysis, CNR/Pcdhalpha was also mapped to rat chromosome 18, but the orientation was opposite for the mouse CNR/Pcdhalpha gene cluster. The relative expression profiles of the rat CNRs (v1-v13) show that all the CNRs are transcribed, but there are variations in the expression ratios among the CNRs.

Significant glomerular basement membrane thickening in hyperglycemic and normoglycemic diabetic-prone BB Wistar rats

The diabetic-prone BioBreeding Wistar rat (BB/DP) is an autoimmune model of insulin-dependent diabetes mellitus. Approximately 80-90% of the animals are hyperglycemic (BB/DP(h)) by 90-120 days of age while those that do not become diabetic in adolescence (BB/DP(n)) remain normoglycemic for life. Likewise, rats in the diabetes-resistant (BB/DR) strain are normoglycemic. Although renal morphological studies have been carried out in this model, ultrastructural observations of age- and diabetes-related extracellular matrix (ECM) changes, including glomerular basement membrane (GBM) morphometry, are not available. Moreover, possible renal changes in the relatively uncommon BB/DP(n) control animals have not been reported. The current electron microscopic study was carried out to investigate temporal changes in detergent-treated acellular ECM in BB/DP(h) rats at 2 weeks, 3 months, 6 months, and 1 year postonset of moderate hyperglycemia. Age-matched BB/DR and BB/DP(n) control animals were also examined. Our data demonstrate age- and diabetes-related alterations in mesangial matrix distributions and GBM widths and show for the first time significant increases in GBM thickening in both hyperglycemic (BB/DP(h)) and normoglycemic (BB/DP(n)) rats when compared to age-matched BB/DR controls. Surprisingly, the rate of increase is greatest in BB/DP(n) animals. Although the pathogenesis of diabetic basement membrane disease is not completely understood, GBM thickening is widely regarded as a morphological consequence of hyperglycemia. However, data in the current investigation show that ECM alterations, including significantly increased GBM thickness, may occur in genetically diabetic animals in the absence of hyperglycemia.

Altered Sonic hedgehog signaling is associated with morphological abnormalities in the penis of the BB/WOR diabetic rat

Erectile dysfunction (ED) is a common and debilitating pathological development that affects up to 75% of diabetic males. Neural stimulation is a crucial aspect of the normal erection process. Nerve injury causes ED and disrupts signaling of the Sonic hedgehog (Shh) cascade in the smooth muscle of the corpora cavernosa. Shh and targets of its signaling establish normal corpora cavernosal morphology during postnatal differentiation of the penis and regulate homeostasis in the adult. Interruption of the Shh cascade in the smooth muscle of the corpora cavernosa results in extensive changes in corpora cavernosal morphology that lead to ED. Our hypothesis is that the neuropathy observed in diabetics causes morphological changes in the corpora cavernosa of the penis that result in ED. Disruption of the Shh cascade may be involved in this process. We tested this hypothesis by examining morphological changes in the penis, altered gene and protein expression, apoptosis, and bromodeoxyuridine incorporation in the BB/WOR rat model of diabetes. Extensive smooth muscle and endothelial degradation was observed in the corpora cavernosa of diabetic penes. This degradation accompanied profound ED, significantly decreased Shh protein in the smooth muscle of the corpora cavernosa, and increased penile Shh RNA expression in the intact penis (nerves, corpora, and urethra). Localization and expression of Shh targets were also disrupted in the corpora cavernosa. Increasing our understanding of the molecular mechanisms that regulate Shh signaling may provide valuable insight into improving treatment options for diabetic impotence.

Developmental expression of the type I diabetes related antigen sulfatide and sulfated lactosylceramide in mammalian pancreas

Previous studies have shown that sulfatide is present and functionally involved in beta cells, and that anti-sulfatide antibodies (ASA) exist during development of type I diabetes mellitus. To further explore the possible role of sulfatide in type I diabetes, developmental expression was examined in human pancreas and in pancreas of the type I diabetes models BB rat and NOD mouse compared to Lewis rat and BALB/c mouse, respectively. Sulfatide was not only expressed in adult pancreas, but also in human fetal and rodent neonatal pancreas, i.e., during the growing period of the immunological self. Sulfatide had a different expression pattern in human beings and rodents, concerning both the amounts of sulfatide and expression during development. There was no change in the sulfatide fatty acid isoform expression during development. The pancreatic expression of another sulfated glycosphingolipid, sulfated lactosylceramide, indicated that this molecule is a potential fetal/neonatal marker, which was further expressed in the type I diabetic models. In conclusion, these findings give further support to the possibility that sulfatide is a relevant autoantigen in type I diabetes and that sulfated lactosylceramide might function as a potential risk factor for disease development, at least in the animal models.

Rat genetics: attaching physiology and pharmacology to the genome

During the past five years, the Rat Genome Project has been rapidly gaining momentum, especially since the announcement in August 2000 of plans to sequence the rat genome. Combined with the wealth of physiological and pharmacological data for the rat, the genome sequence should facilitate the discovery of mammalian genes that underlie the physiological pathways that are involved in disease. Most importantly, this combined physiological and genomic information should also lead to the development of better pre-clinical models of human disease, which will aid in the development of new therapeutics.

Oxidative stress as a mechanism of diabetes in diabetic BB prone rats: effect of secoisolariciresinol diglucoside (SDG)

Secoisolariciresinol diglucoside (SDG) isolated from flaxseed has antioxidant activity and has been shown to prevent hypercholesterolemic atherosclerosis. An investigation was made of the effects of SDG on the development of diabetes in diabetic prone BioBreeding rats (BBdp rats), a model of human type I diabetes [insulin dependent diabetes mellitus (IDDM)] to determine if this type of diabetes is due to oxidative stress and if SDG can prevent the incidence of diabetes. The rats were divided into three groups: Group I, BioBreeding normal rats (BBn rats) (n = 10); group II, BBdp untreated (n = 11); and group III, BBdp treated with SDG 22 mg/kg body wt, orally) (n = 14). Oxidative stress was determined by measuring lipid peroxidation product malondialdehyde (MDA) an index of level of reactive oxygen species in blood and pancreas; and pancreatic chemiluminescence (Pancreatic-CL), a measure of antioxidant reserve. Incidence of diabetes was 72.7% in untreated and 21.4% in SDG-treated group as determined by glycosuria and hyperglycemia. SDG prevented the development of diabetes by approximately 71%. Development of diabetes was associated with an increase in serum and pancreatic MDA and a decrease in antioxidant reserve. Prevention in development of diabetes by SDG was associated with a decrease in serum and pancreatic-MDA and an increase in antioxidant reserve. These results suggest that IDDM is mediated through oxidative stress and that SDG prevents the development of diabetes.

Aortic endothelial cell von Willebrand factor content, and circulating plasminogen activator inhibitor-1 are increased, but expression of endothelial leukocyte adhesion molecules is unchanged in insulin-dependent diabetic BB rats

Endothelial cell injury has been implicated in the increased incidence of vascular disease associated with diabetes mellitus. In diabetic humans, elevated plasma von Willebrand Factor (vWF) has been interpreted as an indication of endothelial damage. In contrast, in an animal model of inherited insulin-dependent diabetes, the bio-breeding (BB) rat, plasma vWF levels did not differ from those in age-matched control rats during the first 7 months of diabetes although morphological evidence of mild aortic endothelial alteration or injury was observed. In the present study efforts have been made to define the endothelial alterations in BB diabetic rats compared to controls more precisely over this time period. Thus, adhesion molecules: intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1(VCAM-1) were evaluated by in situ immunohistochemistry, vWF content was determined by biochemical analysis of aortic extracts and by quantitative immunohistochemistry, plasma vWF levels were measured by ELISA and vWF mRNA by RNAse protection assay. Neither age nor diabetic state significantly affected either the expression of adhesion molecules, or the levels of circulating vWF. Endothelial vWF content was significantly increased in the diabetic vessels, as observed by both approaches but the vWF mRNA content was not different from that in control vessels. Plasma plasminogen activator inhibitor (PAI-1) activity was significantly increased in diabetic animals. In conclusion, endothelial alterations in BB rats associated with diabetes, together with the raised plasma PAI-1 levels, promote the thrombogenic potential of the vessel wall, and are consistent with an increased risk for vascular disease.

Molecular basis of bilirubin UDP-glucuronosyltransferase induction in spontaneously diabetic rats, acetone-treated rats and starved rats

The co-ordinated induction of several hepatic drug-metabolizing enzymes is a common feature in the regulation of drug biotransformation under normal and pathological conditions. In the present study the activity and expression of bilirubin UDP-glucuronosyltransferase (UGT1A1) were investigated in livers of BioBreeding/Worcester diabetic, fasted and acetone-treated rats. Bilirubin glucuronidation was stimulated by all three treatments; this was correlated with an increase in the UGT1A1 protein concentration in hepatic microsomes. Transcriptional induction of UGT1A1 was also observed in diabetes and starvation but not with acetone treatment, which apparently caused translational stabilization of the enzyme protein. The hormonal/metabolic alterations in diabetes and starvation might be a model for postnatal development. The sudden interruption of maternal glucose supply signals the enhanced expression of UGT1A1, giving a novel explanation for the physiological induction of bilirubin glucuronidation in newborn infants.

Low dose poly I:C prevents diabetes in the diabetes prone BB rat

Poly I:C, an inducer of IFN-alpha and other cytokines, has been used to study the development of diabetes in both the BioBreeding (BB) diabetes prone rat and non-obese diabetic (NOD) mouse animal models of insulin-dependent diabetes mellitus (IDDM). Surprisingly, poly I:C accelerates the disease in the BB rat while inhibiting it in the NOD mouse. Since cytokines can have dose related opposing effects on immune responses, we hypothesized that the paradoxical effect of polyinosinic polycytidylic acid (poly I:C) on diabetes in the two animal models is dose related. Accordingly, we compared the incidence of diabetes and degree of insulitis in diabetes prone BB rats administered saline and poly I:C at doses (0.05 microg/g body weight and 0.1 microg/g body weight) up to 100-fold lower than doses (poly-5 microg/g) previously found to accelerate diabetes. In addition, the non-specific suppressor activity of mononuclear splenocytes from BB rats administered low dose (poly-0.05 microg/g body weight), high dose (poly-5 microg/g body weight), and saline were compared. The development of diabetes was inhibited in rats treated with each dose of poly I:C. The degree of insulitis in poly-I:C treated animals was also less severe. The total white blood cell count and proportion of RT6+ T-cells and each T-cell subset were unaltered by poly I:C. When compared to splenocytes of control animals, splenocytes from poly I:C (0.05 microg/g body weight) treated rats suppressed responder cell proliferation to concanavalin A and alloantigen. However, spleen cells from high dose poly-I:C did not suppress responder cell proliferation to alloantigen. In adoptive transfer studies, the administration of spleen cells from poly-0.05 treated rats decreased the development of diabetes in recipient BB rats. In vitro studies also demonstrated that poly-I:C inhibits the proliferative response of BB rat spleen cells to concanavalin A. The administration of poly-0.05, but not poly-5.0, decreased TNF-alpha mRNA and IL-10 mRNA content in spleen cells. We conclude that poly I:C, at a dose 100 times lower than that required to accelerate diabetes prevents the development of diabetes in BB rates by interfering with the development of insulitis. The induction of suppressor cell activity induced by low dose poly-I:C in vivo and the inhibition of T-cell responses by poly-I:C in vitro suggests that the diabetes sparing activity of poly I:C is mediated by augmented immunoregulatory cell activity. Further studies with poly I:C may be important in increasing our understanding of the pathogenesis of IDDM and provide a means to prevent it.

Changes in the aortic endothelium and plasma von Willebrand factor levels during the onset and progression of insulin-dependent diabetes in BB rats

Endothelial injury has been implicated in the enhanced vascular disease associated with diabetes mellitus. In diabetic humans elevated plasma von Willebrand factor (vWF) levels have been interpreted as an indication of endothelial damage. Using the BB rat as a model of inherited insulin dependent-diabetes mellitus, plasma vWF and aortic endothelial ultrastructural alterations were examined during the first 7 months of diabetes. Total plasma vWF levels were determined by ELISA and vWF multimeric composition by electrophoresis. vWF was identified immunohistochemically. Following the onset of hyperglycemia, there were progressive alterations in aortic endothelial morphology, which were consistent with injury, and aortic intimal thickening was significantly greater in rats diabetic for 7 months compared to age-matched controls. Significant increases in the Weibel Palade (WP) body content of the endothelial cells were observed after 1 week and 2 months of diabetes, but not at later times. Endothelial alterations associated with the possible release of vWF appeared to involve fusion of WP bodies with other vacuoles rather than direct fusion with the cell membrane. Plasma vWF levels in diabetic rats were varied, but were not significantly different from those of control animals and did not correlate with either glucose or insulin levels. The multimeric composition of plasma vWF was also similar at all times in both diabetic and non-diabetic animals. From these observations, plasma vWF levels do not provide an indicator of the endothelial perturbations which occurs in diabetic rats.

Proglucagon and glucose transporter mRNA is altered by diet and disease susceptibility in 30-day-old biobreeding (BB) diabetes-prone and normal rats

Diet is an important factor influencing the development of diabetes in the Biobreeding (BB) rat. Changes in gut development and absorption of nutrients in the diabetes-prone rat (Bbdp) and the subsequent effect on pancreatic function may play a role in the ultimate development of the disease. BBdp and normal (BBn) dams were fed one of three diets, chow or semipurified diets containing either soy or casein as the protein source. Pups were weaned at 21 d onto the same diet as their respective dam and killed at 30 d. Chow-fed BBn animals weighed significantly more than casein- or soy-fed BBn animals. Chow-fed BBdp had significantly greater small intestine and colon weight when expressed on a per body weight basis than BBn. With all three diets, BBdp animals had significantly lower colonic proglucagon mRNA abundance than did BBn animals. Adjusting for total colonic RNA content resulted in only casein- and soy-fed BBdp animals demonstrating significantly lower colonic proglucagon mRNA abundance than did BBn animals. BBn animals had higher levels of sodium-dependent D-glucose cotransporter (SGLT)-1 and sodium-independent glucose transporter (GLUT) 5 mRNA than did BBdp. Within BBn animals, casein and soy produced significantly lower levels of SGLT-1 and GLUT5 mRNA than did chow. This study demonstrates that BBn and BBdp animals respond differently to chow versus semipurified weaning diets. These differences may explain the differences in growth and intestinal development among the BBdp and BBn strains weaned onto different diets.

Alpha interferon administration paradoxically inhibits the development of diabetes in BB rats

Alpha-interferon (IFN-alpha) is thought to be important in the pathogenesis of insulin dependent diabetes mellitus (IDDM). However, since potent inducers of IFN-alpha, viruses, have been shown to modulate immune function and autoimmunity, we investigated whether administration of recombinant IFN-alpha (rIFN-alpha) would inhibit the diabetic process in BB rats. The development of diabetes was significantly inhibited by injections of either 10(5) units or 4x10(5) units rIFN-alpha. rIFN-alpha was more effective in preventing disease when injections were initiated at an earlier age (28-30 days vs 35-40 days). Histologic examination revealed a markedly lower degree of insulitis in rIFN-alpha treated rats. The mean total peripheral WBC and differential count, T-cell subsets, peripheral blood NK cell number, splenic NK cell activity, and serum cytotoxic beta cell surface antibody levels were unaltered by rIFN-alpha administration. In vitro incubation with rIFN-alpha inhibited the Con A proliferative response of mononuclear splenocytes of BB rats but not of Sprague Dawley rats. These results document that rIFN-alpha treatment potently prevents diabetes by inhibiting the development of insulitis. This paradoxical diabetes sparing effect may have significant implications for the treatment and prevention of IDDM and towards the understanding the autoimmune process.

Mercury-induced autoimmunity in Brown Norway rats: kinetics of changes in RT6+ T lymphocytes correlated with IgG isotypes of circulating autoantibodies to laminin 1

Repeated exposure to mercury causes various autoimmune effects in rats of the Brown Norway (BN) strain. Previous studies from our laboratory have shown that on day 15 of HgCl2 treatment BN rats exhibit a relative decrease in RT6.2+ T cells. At the same time, they produce high levels of autoantibodies to renal antigens and experience a membranous glomerulonephropathy. In contrast, Lewis (LEW) rats are resistant to autoimmunity caused by mercury and do not demonstrate a decrease in RT6+ cells after administration of HgCl2. In the present paper we provide novel information on the correlation between changes in RT6.2+ lymph node T cells and the production of autoantibodies to laminin 1, obtained by detailed kinetic studies of HgCl2-treated BN rats. We have confirmed a decrease in the percentage of RT6.2+ lymphocytes on day 15 of mercury treatment, despite a significant increase in the number of peripheral lymphocytes. No such changes were observed in LEW rats. We have determined that on day 15 the percentage decrease in RT6+ cells is evident in both RT6.2+CD4+ and RT6.2+CD8+ T cell subsets. Kinetic studies demonstrated that significant changes in the percentage of RT6.2+ cells are first observed by day 8 and continue through days 11 and 15. We have also observed a significant percent decrease in CD4+ T lymphocytes as well as an increase in CD4-CD8- cells. The dramatic increase in the percentage of these double negative cells at the level of peripheral lymphoid tissues does not appear to be due to higher thymic output, since there was a decrease in the percentage of TCR+Thy1+ cells, a phenotype that is associated with recent thymic emigrants. Finally, we have demonstrated that 100% of HgCl2-treated BN rats had circulating antibodies that reacted with both mouse and rat laminin 1, i.e. are autoantibodies to laminin 1. These autoantibodies were predominantly of the IgG1 and IgG2a isotype, possibly as the result of a polarized autoimmune response driven by Type 2 cytokines. A kinetic investigation showed that significant levels of IgG1 and IgG2a autoantibodies to laminin 1 were first presentin the circulation by day 11. The inverse correlation between levels of RT6.2+ T lymphocytes and autoantibodies to laminin 1 suggests that mercury may induce autoimmune responses in BN rats by its effects on these immunoregulatory cells.

Gamma interferon prevents diabetes in the BB rat

The BB rat model of human insulin-dependent diabetes mellitus (IDDM) spontaneously develops diabetes through an autoimmune process. Gamma interferon (IFN-gamma) is thought to play an important pathogenic role. This study examined if IFN-gamma administration can, paradoxically, prevent diabetes in BB rats. Diabetes-prone BB rats were initially injected intraperitoneally with murine recombinant IFN-gamma (rIFN-gamma) at doses of 0.5 x 10(4) to 40 x 10(4) U three times a week for 6 weeks beginning at 35 days of age. The effects of altering the duration of treatment (2 to 6 weeks) and the age at which injections were initiated (45 through 65 days) were also assessed. rIFN-gamma administration prevented the development of diabetes in a dose-dependent manner. The optimal treatment condition resulted in a 9.1% incidence of diabetes versus a 90% incidence in control rats. This diabetes-sparing effect was long lasting and continued to 7 months of age. A 4- to 6-week course resulted in maximal inhibition. Treatment initiated as late as 55 days of age, when insulitis is already present, was effective in preventing diabetes. Islet inflammation was dramatically lower in rIFN-gamma- versus saline-injected rats (P < 0.01). Total leukocyte count and subpopulations of peripheral mononuclear cells were unaltered by rIFN-gamma. In summary, rIFN-gamma paradoxically and potently prevents diabetes in BB rats in a dose-dependent fashion by inhibiting islet inflammation. This diabetes-sparing effect occurs even when injections are initiated after evidence of the diabetic process is already present.