BB Rats Research Articles

Identification and Characterization of Secretagogin Promoter Activity

Secretagogin is a newly identified calcium-binding protein selectively expressed in neuroendocrine tissue and pancreatic beta-cells. The function of secretagogin is unknown, but it has been suggested in beta-cells to influence calcium-influx, insulin secretion and proliferation, and has been observed downregulated in diabetes-prone BB rat islets exposed to cytokines. In the present study, we identified and characterized promoter activity of a human 1498 bp sequence upstream the transcription start site. The promoter sequence showed subtle but significant regulation by glucose within the normo-physiological range. Glucose also led to changes in expression of secretagogin protein in INS-1e cells, but not in primary cells from non-diabetes-prone Wistar Furth rats. No effects of cytokines neither on promoter activity nor protein expression were observed. The promoter region was furthermore screened by direct sequencing, and 11 polymorphisms were identified. Genotyping in a large homogenous Type 1 diabetes (T1D) family collection did not reveal association with T1D.

Characteristics of Rat CD4+CD25+ T Cells and Their Ability to Prevent Not Only Diabetes But Also Insulitis in an Adoptive Transfer Model in BB Rats

Human and mouse CD4(+)CD25(+) T cells have been intensively studied through the last decade. However, little is known about this subset in other species. This study describes the phenotype of rat CD4(+)CD25(+) Foxp3(+) T cells and the site in which they exert regulation in a transfer-induced autoimmune diabetes model. Several proteins and mRNAs are up-regulated in unstimulated rat CD4(+)CD25(+) T cells compared with CD4(+)CD25(-) T cells, including Foxp3, Lag-3, CD80, interleukin 10 (IL-10) and CTLA-4. To investigate CD4(+)CD25(+) T cells in vivo, we transferred three million diabetogenic T cells either alone or in combination with two million CD4(+)CD25(+) T cells to 30-day-old BB rats. The pancreas and the pancreatic lymph nodes were examined as two potential regulatory sites. Time-course analysis of pancreatic histology following diabetogenic T-cell transfers revealed insulitis from about 14 days after transfer. By contrast, rats receiving both diabetogenic T cells and CD4(+)CD25(+) T cells had no insulitis at any time. Moreover, the frequency of diabetogenic T cells in the pancreatic lymph nodes 2 days after transfer was significantly reduced in rats receiving both subsets. These data indicate that the primary site of T-cell regulation is in the draining lymph nodes and not the pancreas in our model.

Costimulation and Autoimmune Diabetes in BB Rats

Costimulatory signals regulate T-cell activation. To investigate the role of costimulation in autoimmunity and transplantation, we studied the BB rat model of type 1 diabetes. Diabetes-prone BB (BBDP) rats spontaneously develop disease when 55-120 days of age. We observed that two anti-CD28 monoclonal antibodies (mAb) with different functional activities completely prevented diabetes in BBDP rats. Anti-CD154 mAb delayed diabetes, whereas treatment with CTLA4-Ig or anti-CD80 mAb accelerated disease. Anti-CD86 or anti-CD134L mAbs had no effect. Diabetes resistant BB (BBDR) rats are disease-free, but >95% of them develop diabetes after treatment with polyinosinic-polycytidylic acid and an mAb that depletes Treg cells. In the induced BBDR model, anti-CD154 mAb delayed onset of diabetes, whereas CTLA4-Ig, anti-CD134L or either of the anti-CD28 mAbs had little or no effect. In contrast, blockade of the CD134-CD134L pathway was highly effective for preventing autoimmune recurrence against syngeneic islet grafts in diabetic BBDR hosts. Blockade of the CD40-CD154 pathway was also effective, but less so. These data suggest that the effectiveness of costimulation blockade in the treatment of type 1 diabetes is dependent on both the costimulatory pathway targeted and the mechanism of induction, stage, intensity and duration of the pathogenic process.

Increased galanin expression in the celiac ganglion of BB diabetic rats

BB rats lose >50% of their islet sympathetic nerve terminals soon after diabetes onset, markedly impairing the glucagon response to activation of these nerves. In this study, we sought evidence that this degree of disease-induced nerve terminal damage affected their neuronal cell bodies. Increased galanin expression was used as a marker of the change of phenotype that occurs in neuronal cell bodies when their axons are severely damaged. The celiac ganglion (CG) was analyzed because it is a major source of the sympathetic nerves that project to the pancreatic islets. But we first needed to determine if damaging nerve terminals could increase galanin expression in this ganglion and, if so, when that expression was maximal. Severe, global nerve terminal damage produced a dramatic increase of CG galanin expression which was maximal 5 days later. We next determined if a global, but partial, nerve terminal loss would also increase galanin expression and found a significant increase of galanin mRNA and its peptide in the CG. Finally, we determined if the disease-induced, partial and islet-selective loss of nerve terminals seen in BB diabetic rats was sufficient to increase galanin: we, again, found a significant increase of galanin mRNA and its peptide in their CG. These increases did not occur in their superior cervical ganglia. We conclude that the selective damage to islet sympathetic nerve terminals seen in BB diabetic rats, rather than the systemic factors of diabetic hyperglycemia or insulin deficiency, causes the increased galanin expression observed in the CG of this animal model of type 1 diabetes.

Physiological genomics in PG and beyond: October to December 2005

physiological genomics ( PG ) publishes, on a quarterly basis, brief editorial perspectives entitled “Physiological genomics in PG and beyond.” These editorial perspectives provide brief, accessible highlights of the studies published in PG in the most recent quarter, and relate those studies to

Gene expression studies support obesity related sub-phenotypes in BB.4S and BB.4W rats

Aim: There are two congenic BB rat strains carring a SHR segment (D4Got41-Tacr1; BB.4S) or a WOKW segment (D4Got41-Fabp1; BB.4W) of chromosome 4 into BB/OK background. Both congenics develop obesity with hyperinsulinemia (BB.4W) or with hyperleptinemia (BB.4S) representing two sub-phenotypes related to obesity. Therefore, we studied the gene expression in adipose tissues and hypothalamus of BB.4S and BB.4W rats.

Cardiac function and ischaemic tolerance during acute loss of metabolic control in the diabetic BB Wor rat

The effect of loss of metabolic control, by with-holding insulin treatment, on reperfusion recovery of cardiac function following ischaemia was studied in the spontaneously diabetic "BB" Wor rat. The study involved a group of insulin-treated diabetic BB rats (insulin-treated) and diabetic BB rats in which insulin treatment was withheld 24 h prior to study (insulin-withdrawn). Hearts were isolated and perfused at a constant left atrial filling pressure of 15 cm H(2)O and aortic afterload resistances of 100 and 140 cm H(2)O. Hearts were then subjected to 20 min of ischaemia followed by 30 min of reperfusion. Withdrawing insulin treatment from the BB Wor rat resulted in a dramatic increase in the levels of plasma glucose and free fatty acids. Hearts from these rats perfused under aerobic conditions demonstrated reductions in heart rate, positive and negative dP/dt, cardiac output and left ventricular minute work, whereas diastolic pressure was elevated. Following ischaemia, recovery of cardiac function in the insulin-treated BB Wor rat returned to preischaemic levels, whereas hearts from insulin-withdrawn rats displayed impaired recovery. Throughout reperfusion, heart rate, positive dP/dt, cardiac output and left ventricular minute work remained significantly lower in hearts from insulin-withdrawn rats compared to treated rats. Our results indicate that acute loss of metabolic control increases the sensitivity of the heart to ischaemia, even in the acutely diabetic BB Wor rat.

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.

Is there an autoimmune process in bone? Gene expression studies in diabetic and nondiabetic BB rats as well as BB rat-related and -unrelated rat strains

It is well known that type 1 diabetes is associated with a decrease in bone mass and delayed healing of fractures in human and in animal models of type 1 diabetes. Using well- and poorly compensated diabetic BB/O(ttawa) K(arlsburg) rats spontaneously developing insulin-dependent type 1 diabetes, it was recently shown that, in contrast to all other tissues studied, bone is most influenced by metabolic state and seems to be regulated in a manner different from other organs. Therefore, we studied the expression of additional genes (Bmp-1, Bmp-4, Vegf, Bglap, Il-1b, Infg, Tnfa, Calca, Sp1, Yy1) in bone of nondiabetic BB rats compared with newly diagnosed and well- and poorly compensated diabetic rats as well as two nondiabetes-prone congenic BB.SHR rats, BB rat-related (WOKW) and -unrelated rat strains (F344). Six males of each group were euthanized, the tibial bone was removed, and total RNA was extracted, transcribed in complementary DNA, and used for real-time PCR. In a comparison of nondiabetic with diabetic groups, the relative gene expression was reduced by >80% in newly diagnosed and in well-compensated diabetic BB/OK rats. The gene expression in poorly compensated rats increased significantly in 7 of 10 genes and was comparable with those of nondiabetic BB/OK rats. In a comparison of gene expression between diabetes-prone BB/OK and nondiabetes-prone BB.1K, BB.4S, WOKW, and F344 rats, there were no significant differences between newly diagnosed and well-compensated BB/OK diabetic rats and nondiabetic BB.1K, BB.4S, WOKW, and F344 rats. On the basis of these findings, we concluded that spontaneous diabetes influences bone gene expression in BB/OK rats, which may be attributed to the genetically determined autoimmune process not only affecting pancreatic beta-cells but also bone formation and resorption.

Aldosterone increases urine production and decreases apical AQP2 expression in rats with diabetes insipidus

Vasopressin and aldosterone are essential hormones in the regulation of water and sodium balance. Aldosterone regulates sodium reabsorption, although synergistic effects on collecting duct water permeability have been shown. We investigated the effects of 7-day aldosterone infusion or oral spironolactone treatment on water balance and aquaporin (AQP) 2 expression in rats with 21 days of lithium-induced nephrogenic diabetes insipidus (Li-NDI). In rats with Li-NDI, aldosterone markedly increased (271 +/- 14 ml/24 h), whereas spironolactone decreased (74 +/- 11 ml/24 h) urine production compared with rats treated with lithium only (120 +/- 11 ml/24 h). Aldosterone increased free-water clearance and creatinine clearance, whereas spironolactone caused a decreased creatinine clearance but unchanged free-water clearance. Immunoblotting showed unchanged AQP2 expression in cortex/outer stripe of the outer medulla and inner medulla. In the inner stripe of the outer medulla aldosterone caused a decreased AQP2 expression, whereas spironolactone caused an increase compared with rats treated with lithium only. Semiquantitative confocal immunofluorescence microscopy of AQP2 immunolabeling showed reduced AQP2 expression in the apical plasma membrane domain in connecting tubule (CNT) and initial cortical collecting ducts (iCCD) in response to aldosterone-treated rats compared with rats treated with lithium only. Spironolactone significantly increased apical AQP2 expression in the iCCD compared with rats treated with lithium only. We also tested whether similar changes could be observed in vasopressin-deficient BB rats and found similar changes in urine production and subcellular AQP2 expression in the CNT and iCCD in response to aldosterone and spironolactone. This study shows that aldosterone treatment perturbs diabetes insipidus and is associated with AQP2 redistribution in CNT and iCCD likely mediated by the spironolactone-sensitive mineralocorticoid receptor.

Aberrancies in the differentiation and maturation of dendritic cells from bone-marrow precursors are linked to various genes on chromosome 4 and other chromosomes of the BB-DP rat

BB-Diabetes Prone (BB-DP) rats, a model for endocrine autoimmune diseases, are severely lymphopenic, especially lacking ART2 + regulatory T cells. BB-Diabetes Resistant (DR) rats are not lymphopenic and do not develop autoimmunity. BB-DP and BB-DR rats only differ at the lymphopenia ( lyp) gene ( iddm2) on chromosome 4. Since BB-DP rats also show aberrancies in the differentiation of dendritic cells (DC) from bone-marrow precursors, we tested the hypothesis that F344 rats congenic for a BB-DP chromosome 4 region (42.5–93.6 Mb; including the lyp gene, but also iddm4) display an in vitro DC differentiation different from normal F344 rats. Here we show that the 42.5–93.6 Mb BB-DP chromosome 4 region is linked to an increased DC precursor apoptosis, a low MHC class II expression, a reduced IL-10 production and a reduced T cell stimulatory capacity of DC. From our previous report on DC differentiation defects in BB rats (only differing in iddm2) and the present report, we deduce that the abnormal apoptosis and low MHC class II expression is linked to iddm2. The reduced T cell stimulatory capacity is linked to other genes on chromosome 4 (candidate gene: iddm4). The reduced IL-10 production has a complex linkage pattern.

Anaesthesia-induced hyperglycaemia early in life is not predictive for development of diabetes in diabetes-prone BB rats

Type 1 diabetes (T1D) is an autoimmune disease in genetically predisposed individuals characterised by selective destruction of the beta-cells. Development of diabetes is in the asymptomatic pre-diabetic period characterised by impaired first-phase insulin response and the first clinical symptom is elevated blood glucose (BG). It is still uncertain whether stress or incidental hyperglycaemia can be regarded as predictors for development of T1D or not, even when immunologic and genetic markers for T1D are considered. The aim of this study was to investigate if there was any relationship between elevated BG in 30-day-old anaesthetised pre-diabetic diabetes-prone Bio Breeding (BB-DP) rats and later development of diabetes. Rats anaesthetised by intraperitoneal (ip) injection for islet transplantation displayed significantly higher BG values (Delta1.27 mmol/l, p=8.27x10(-12)) compared to non-anaesthetised non-transplanted rats, indicating that ip injection and/or anaesthesia induce a higher BG level. Linear regression analysis of BG and time of onset of diabetes in transplanted and non-transplanted BB-DP rats revealed no correlation (R(2) at 0.0075 and 0.0324 and p-values at 0.56 and 0.23 respectively). We were not able to identify any association or correlation between the induced temporary hyperglycaemia in 30-day-old BB-DP rats and later development of diabetes.

Defects in differentiation of bone-marrow derived dendritic cells of the BB rat are partly associated with IDDM2 (the lyp gene) and partly associated with other genes in the BB rat background

BB rats develop various organ-specific autoimmune diseases, e.g. autoimmune diabetes and thyroiditis and have proven important to dissect genetic factors that govern autoimmune disease development. The lymphopenia ( lyp) gene ( iddm2) is linked to autoimmune disease development and is a major genetic difference between diabetes-resistant (DR) and diabetes-prone (DP) BB rats. To study the effects of the lyp gene and other genes on dendritic cell (DC) differentiation from bone-marrow precursors, such differentiation was studied in BB-DP, BB-DR, Wistar and F344 control rats. DC of BB-DP rats showed a lower MHC class II expression as compared to BB-DR, Wistar and F344 rats. LPS-maturation did not restore this low MHC class II expression. DC of BB-DP rats also showed a poor capability to terminally differentiate into mature T cell stimulatory DC under the influence of LPS and produced significantly lower quantities of IL-10, yet these aberrancies were also found in BB-DR rats but did not occur in control rats. This study thus shows that various aberrancies exist in the differentiation of myeloid DC from bone-marrow precursors in the BB rat model of organ-specific autoimmunity. These aberrancies are multigenically determined and partly associated with iddm2 ( lyp gene) and partly associated with other genes in the BB rat.

Tubular complexes as a source for islet neogenesis in the pancreas of diabetes-prone BB rats

Tubular complexes (TC) in the pancreas contain duct-like structures with low cuboidal or flattened cells surrounding a large lumen and are thought to be a response to pancreatic injury. TC have been studied in animal models of chemical or surgically induced pancreatic damage but their occurrence has not been reported in rodent models of spontaneous autoimmune type I diabetes. We hypothesized that TC would be increased during the active phase of islet destruction in autoimmune diabetes and could contain islet progenitor cells. We analyzed TC in pancreas of Wistar Furth (WF), control (BBc) and diabetes-prone BioBreeding (BBdp) rats using immunohistochemistry and morphometry. TC were observed in all rat strains during active pancreas remodeling (∼13 days). They increased between 60 and 93 days only in BBdp rats coincident with the increase in diabetes cases. Most TC were infiltrated with CD3+ T-cells. Duct-like cells in the TC had low expression of the exocrine marker amylase, increased expression of epithelial cell markers, keratin and vimentin, and remarkably high cell proliferation and cell death. TC islets contained cells stained positive for insulin, glucagon, somatostatin, pancreatic polypeptide, as well as PDX-1, chromogranin, and hepatocyte-derived growth factor receptor, c-met. Transitional cells that were keratin+/insulin+ and keratin+/amylase+ cells were present in TC. The stem cell marker, nestin was upregulated in the TC region. Duct-like cells in TC of BBdp rats expressed markers of committed endocrine precursors: PDX-1, neurogenin 3 and protein gene product 9.5. This study demonstrates that TC are upregulated during β-cell destruction and contain potential endocrine progenitors.

Impaired Post-Thymic Development of Regulatory CD4+25+ T Cells Contributes to Diabetes Pathogenesis in BB Rats

One of the BB rat diabetes (diabetes mellitus (DM)) susceptibility genes is an Ian5 mutation resulting in premature apoptosis of naive T cells. Impaired differentiation of regulatory T cells has been suggested as one possible mechanism through which this mutation contributes to antipancreatic autoimmunity. Using Ian5 congenic inbred rats (wild-type (non-lyp BB) and mutated (BB)), we assessed the development of BB regulatory CD8(-)4(+)25(+)T cells and their role in the pathogenesis of DM. BB rats have normal numbers of functional CD8(-)4(+)25(+)Foxp3(+) thymocytes. The proportion of CD25(+) cells among CD8(-)4(+) recent thymic emigrants is also normal while it is increased among more mature CD8(-)4(+) T cells. However, BB CD8(-)4(+)25(+)Foxp3(+) thymocytes fail to undergo homeostatic expansion and survive upon transfer to nude BB rats while Foxp3 expression is reduced in mature CD8(-)4(+)25(+) T cells suggesting that these cells are mostly activated cells. Consistent with this interpretation, peripheral BB CD8(-)4(+)25(+) T cells do not suppress anti-TCR-mediated activation of non-lyp BB CD8(-)4(+)25(-) T cells but rather stimulate it. Furthermore, adoptive transfer of unfractionated T cells from diabetic BB donors induces DM in 71% of the recipients while no DM occurred when donor T cells are depleted of CD8(-)4(+)25(+) cells. Adoptive transfer of 10(6) regulatory non-lyp BB CD8(-)4(+)25(+) T cells to young BB rats protects the recipients from DM. Taken together, these results demonstrate that the BB rat Ian5 mutation alters the survival and function of regulatory CD8(-)4(+)25(+) T cells at the post-thymic level, resulting in clonal expansion of diabetogenic T cells among peripheral CD8(-)4(+)25(+) cells.

Unraveling the Pathogenesis of Type 1 Diabetes with Proteomics: Present And Future Directions

Type 1 diabetes (T1D) is the result of selective destruction of the insulin-producing beta-cells in the pancreatic islets of Langerhans. T1D is due to a complex interplay between the beta-cell, the immune system, and the environment in genetically susceptible individuals. The initiating mechanism(s) behind the development of T1D are largely unknown, and no genes or proteins are specific for most T1D cases. Different pro-apoptotic cytokines, IL-1 beta in particular, are present in the islets during beta-cell destruction and are able to modulate beta-cell function and induce beta-cell death. In beta-cells exposed to IL-1 beta, a race between destructive and protective events are initiated and in susceptible individuals the deleterious events prevail. Proteins are involved in most cellular processes, and it is thus expected that their cumulative expression profile reflects the specific activity of cells. Proteomics may be useful in describing the protein expression profile and thus the diabetic phenotype. Relatively few studies using proteomics technologies to investigate the T1D pathogenesis have been published to date despite the defined target organ, the beta-cell. Proteomics has been applied in studies of differentiating beta-cells, cytokine exposed islets, dietary manipulated islets, and in transplanted islets. Although that the studies have revealed a complex and detailed picture of the protein expression profiles many functional implications remain to be answered. In conclusion, a rather detailed picture of protein expression in beta-cell lines, islets, and transplanted islets both in vitro and in vivo have been described. The data indicate that the beta-cell is an active participant in its own destruction during diabetes development. No single protein alone seems to be responsible for the development of diabetes. Rather the cumulative pattern of changes seems to be what favors a transition from dynamic stability in the unperturbed beta-cell to dynamic instability and eventually to beta-cell destruction.

Gut Permeability and Intestinal Mucins, Invertase, and Peroxidase in Control and Diabetes-Prone BB Rats Fed Either a Protective or a Diabetogenic Diet

This study deals with the enteropathy recently identified in diabetes-prone BB rats (BBdp). Diabetes-resistant BB rats (BBc) and BBdp rats were fed from days 32-39 onward either a protective diabetes-retardant hydrolyzed casein diet (HC) or a plant-based diabetogenic (NTP) diet. The NTP diet decreased body weight and plasma insulin in BBc and BBdp rats. The BBdp rats displayed low intestinal invertase and increased intestinal peroxidase activity. In the BBdp rats fed the HC diet, the mucin content 30-35 cm below the pylorus was higher and the gut permeability lower than in the other three rat groups. There was a significant inverse correlation between gut permeability and the insulinogenic index in the BBdp rats fed the HC or NTP diet. Thus, in BBdp rats, the HC diet somehow prevents the increase in gut permeability and the decrease in the insulinogenic index otherwise found in some of these diabetes-prone animals.

Cardiac dysfunction in the euglycemic diabetic-prone BB Wor rat

The purpose of this study was to examine cardiac function in the diabetic-prone BB Wor rat. The study involved 2 groups: diabetic resistant control littermates of BB rats and diabetic-prone BB rats that had yet to demonstrate overt signs of diabetes. Hearts from these animals were isolated and cardiac function examined in response to incremental increases in left atrial filling pressure. Hearts were also perfused at an increased aortic afterload resistance with buffer consisting of glucose alone or glucose in the presence of palmitate. Hearts from diabetic-prone rats exhibited depressed contractility and ventricular relaxation at high filling pressures. Ventricular function, expressed as cardiac output, was also depressed in diabetic-prone rats perfused at increased afterload resistance, but only in the presence of palmitate. Our results indicate that hearts from diabetic-prone BB Wor rats demonstrate abnormalities in contractile performance and thus may be a useful model for the study of cardiac function in the prediabetic state.

GTP cyclohydrolase I gene transfer reverses tetrahydrobiopterin deficiency and increases nitric oxide synthesis in endothelial cells and isolated vessels from diabetic rats.

Nitric oxide (NO) synthesis in endothelial cells is impaired in diabetes. We previously showed that impaired NO synthesis in the spontaneously diabetic BB (BBd) rat is due to decreased levels of tetrahydrobiopterin (BH4), secondary to decreased expression of GTP cyclohydrolase I (GTPCH). The aim of this study was to utilize adenoviral GTPCH gene transfer to reverse BH4 deficiency and repair the ability of endothelial cells to produce NO. GTPCH gene transfer increased BH4 levels in BBd endothelial cells from 0.17 +/- 0.02 (mean +/-SE) to 73.37 +/- 14.42 pmol/million cells and NO production from 0.77 +/- 0.07 to 18.74 +/- 5.52 nmol/24 h/million cells. To demonstrate a functional effect of increasing BH4 concentrations in tissues, we transferred GTPCH into aortic rings from BBd and Zucker diabetic fatty (ZDF) rats, models of human type I and type II diabetes, respectively. GTPCH gene transfer led to a dose-dependent increase in acetylcholine-induced vasorelaxation, preventable by inhibiting NO synthase. Maximal relaxation of virus-treated rings (10(10) virus particles/ml) to acetylcholine was significantly higher than sham-treated rings (BBd 64% vs. 37%, P<0.005; ZDF 80% vs. 44%, P<0.05). This study demonstrates that GTPCH gene transfer can reverse BH4 deficiency in both type I and type II diabetes and provides an experimental basis for using gene therapy to treat cardiovascular complications in diabetic patients.

Insulin-dependent diabetes and gut dysfunction: the BB rat model.

Accumulating data indicate that intestinal dysfunction and dysregulation of the gut immune system may play a role in the development of type 1 diabetes. This review deals with the occurrence of gut damage and dysfunction in BB rats, an animal model of spontaneous immune type 1 diabetes, placing special emphasis on the effect of diet on the incidence of diabetes in BB rats, the identification of a type 1 diabetes-related protein from wheat, and preliminary observations documenting anomalies in the inductive tissues of the gut immune system (Peyer's patch cells and mesenteric lymph node cells) and pancreatic lymph node cells of diabetes-prone BB rats. In addition to histological evidence of gut damage, the review will also draw attention to altered intestinal disaccharidase activity, changes in intestinal peroxidase activity, glucagon-like peptide 1 anomalies, and perturbation of both intestinal permeability and mucin content in BB rats. In all these cases, the findings in rats fed a diabetes-promoting diet are compared to those collected in animals receiving a protective diabetes-retardant diet.