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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oral administration of disease-specific autoantigens can prevent or delay the onset of autoimmune disease symptoms. We have generated transgenic potato plants that synthesize human insulin, a major insulin-dependent diabetes mellitus autoantigen, at levels up to 0.05% of total soluble protein. To direct delivery of plant-synthesized insulin to the gut-associated lymphoid tissues, insulin was linked to the C-terminus of the cholera toxin B subunit (CTB). Transgenic potato tubers produced 0.1% of total soluble protein as the pentameric CTB-insulin fusion, which retained GM1-ganglioside binding affinity and native antigenicity of both CTB and insulin. Nonobese diabetic mice fed transformed potato tuber tissues containing microgram amounts of the CTB-insulin fusion protein showed a substantial reduction in pancreatic islet inflammation (insulitis), and a delay in the progression of clinical diabetes. Feeding transgenic potato tissues producing insulin or CTB protein alone did not provide a significant reduction in insulitis or diabetic symptoms. The experimental results indicate that food plants are feasible production and delivery systems for immunotolerization against this T cell-mediated autoimmune disease.
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PMID:A plant-based cholera toxin B subunit-insulin fusion protein protects against the development of autoimmune diabetes. 978 49

Traveller's Diarrhea (TD, turista) is the most common health disturbance in travellers, affecting 20-50% of two-week travellers depending on their origin, destination and eating habits. The etiological agents most frequently isolated from the stools are enterotoxinogenic Escherichia coli (ETEC), Salmonella spp., Shigella spp., but the rate of isolation of Campylobacter spp. and non cholera vibrios is also high in Asia. Preventive measures in eating habits should in principle be able to curb the incidence of TD but compliance of travellers is usually poor. Antibiotic chemoprophylaxis has proved effective, but economic, safety and microbiological (drug resistance) considerations discourage its widespread use. Any treatment strategy should consider that TD is usually a self-limiting, benign illness in most travellers, even though infants, elderly people or persons with severe baseline diseases (heart diseases, diabetes, immunocompromised hosts, etc...) may sometimes suffer severe consequences. Adequate rehydration is the cornerstone of treatment and intestinal motility inhibitors may be used in adults (not in children) with severe diarrhea during the first 24 hours if the suspicion of invasive pathogen has been ruled out. Routine antibiotic treatment of TD is controversial, due to the benign nature of the syndrome and to the impossibility to ascertain its causative agent. It should be limited to severe and disabling cases. Among the many antibiotics tested, quinolones are now considered first-choice treatment worldwide, even though disturbing reports of the increasing prevalence of quinolone-resistant Campylobacter spp. from Asia have been recently published. Cotrimoxazole is efficient in Central America. The role of non absorbed antibiotics and probiotics is still to be fully elucidated.
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PMID:[Principles and management of the ambulatory treatment of traveller's diarrhea]. 1007 85

The aetio-pathogenetic sequences and the physio-pathological patterns of diabetes, emphysema, cholera, circulatory shock and thrombosis have been analysed with respect to an evolutionary interpretation. The diseases, although reflecting alterations of processes that can always be described in physico-chemical language, occur only at the level of biological systems which reflects the decodification of genomic project: the teleonomic projects that have been developed during evolution. The concepts of evolutionary emergence and of downward causation have been used to discuss the relationship between the molecular events responsible for the initiation of the disease, and the subsequent events responsible for the aetio-pathogenesis, for the systemic disarrangement and for the additional alterations of tissues and cells independent of the initial molecular events. In diabetes the systemic disarrangement, glycosuria and hyperglycemia, reflect the evolutionary emergence of the processes regulating carbohydrate metabolism, whereas the cardiovascular and neurological alterations are effects of the systemic disarrangement by a mechanism of downward causation. The complexity of the aetio-pathogenesis and of the physio-pathological patterns of diseases is due to the generation of information during the evolution of multi-hierarchical entities. The evolutionary epistemology approach is useful to explain the behaviour of complex systems.
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PMID:The cement of medical thought. Evolutionary emergence and downward causation. 1032 31

Restoration of peripheral tolerance to target autoantigens during autoimmune diseases has met with several limitations because of the limited efficacy of this approach in an already immune host. To optimize the induction of tolerance, we have shown that feeding insulin conjugated to cholera toxin B-subunit (CTB), a potent mucosal adjuvant, reduced by 5,000 the amounts of antigen necessary for delaying diabetes onset in NOD mice. To analyze these protective mechanisms, we have performed cotransfer experiments using splenocytes from young females fed once with 10 microg of CTB-insulin, mixed with diabetogenic T-cells, and intravenously injected into irradiated syngeneic male recipients. We demonstrated that the delayed onset of diabetes relied on CD4+ T-cells. We studied the cytokine production from plate-bound anti-CD3-stimulated cells. Higher interleukin (IL)-4 amounts were observed in both splenocytes and pancreatic lymph node (PLN) cell cultures from CTB-insulin-fed mice as soon as 4 h after the feeding. An increase in the levels of transforming growth factor-beta was seen after 24 h only in the mesenteric lymph nodes (MLN). In both of these organs, a reduction of gamma-interferon (IFN-gamma) production occurred after CTB-insulin treatment, at 24 h in the PLN and at 7 days in the MLN. Reverse transcription-polymerase chain reaction analysis indicated an increase in the level of IL-4 and a reduction in IFN-gamma transcripts in the PLN of mice treated orally with CTB-insulin and of the recipients of regulatory T-cells. Using different strains of congenic NOD mice at the Thy1 locus, we showed that protection was associated with the accumulation of T-cells from CTB-insulin-fed mice in the lymph nodes from draining sites containing functional islets, i.e., the PLN in normal mice and the renal lymph nodes after a syngeneic islet graft under the kidney capsule of streptozotocin-treated mice. Taken together, our results clearly indicate that oral administration of CTB-insulin conjugates in NOD mice produced a shift from a T-helper type 1 to a type 2 profile with the induction of antigen-specific regulatory CD4+ T-cells in the vicinity of the mucosal barrier and close to the inflamed islets.
Diabetes 1999 Nov
PMID:Oral administration of cholera toxin B-insulin conjugates protects NOD mice from autoimmune diabetes by inducing CD4+ regulatory T-cells. 1053 48

Model systems of human type 1 diabetes have revealed an important role of cellular immune reactions involving macrophages and T cells in the destruction of autologous insulin-producing pancreatic beta cells. Recently, the cholera toxin B chain (CTB) was found to suppress T cell-dependent autoimmune diseases including autoimmune diabetes of nonobese diabetic mice. Therefore, we tested the hypothesis that CTB exerts much of its immunomodulatory activity by targeting macrophages. These studies are reviewed here. Cells of the human monocyte line Mono Mac 6 were exposed to CTB and subsequently tested for proinflammatory immunoreactivity in response to challenge with endotoxin (LPS from Escherichia coli, 10 ng/ml for 5 h). Incubation of monocytes with CTB (10 microgram/ml) suppressed a later proinflammatory response to LPS as demonstrated by suppression of TNFalpha release from 6.7 +/- 0.7 ng/ml in cultures without CTB preexposure to 1.8 +/- 1.1 ng/ml in CTB-pretreated cells (p < 0.001). In contrast, the release of IL-10 remained inducible after CTB pretreatment. RT-PCR analysis showed that the suppression of TNFalpha production occurred at the level of mRNA formation. Control experiments excluded a role of possible contamination of CTB by endotoxin or the intact cholera toxin. Tolerance induction was maximal after 5 h of CTB exposure and persisted for 24 h. The suppressive effect of CTB was dose-dependent and no more recognizable at </=1 microgram/ml. Incubation with IL-10- and TGFbeta-neutralizing antibodies during CTB pretreatment prevented tolerization of macrophages. IFNgamma (1,200 U/ml) was found to antagonize actions of CTB. In contrast to desensitization by low doses of LPS, tolerance induction by CTB occurred 'silently', i.e. in the absence of a measurable proinflammatory response. In view of the potent instructive role of the innate immune system on T cell responses these findings are important in understanding how CTB prevents the development of autoimmune diabetes and improves tolerance to islet autoantigens.
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PMID:Induction of tolerance in macrophages by cholera toxin B chain. 1072 11

Vast changes are taking place in vaccinology consequent to the introduction of new technologies. Amongst the vaccines included in the Expanded Programme of Immunization (EPI), the pertussis vaccine has been replaced by acellular purified fractions devoid of side-effects. Non-pathogenic but immunogenic mutants of tetanus and diptheria toxins are likely to replace the toxoids. An effective vaccine against hepatitis B prepared by recombinant technology is in large-scale use. Conjugated vaccines against Haemophilus influenzae b, S. pneumococcus and meningococcus are now available, as also vaccines against mumps, rubella and measles. Combination vaccines have been devised to limit the number of injections. Vaccine delivery systems have been developed to deliver multiple doses of the vaccine at a single contact point. A genetically-engineered oral vaccine for typhoid imparts better and longer duration of immunity. Oral vaccines for cholera and other enteric infections are under clinical trials. The nose as a route for immunization is showing promise for mucosal immunity and for anti-inflammatory experimental vaccines against multiple sclerosis and insulin-dependent diabetes mellitus. The range of vaccines has expanded to include pathogens resident in the body such as Helicobacter pylori (duodenal ulcer), S. mutans (dental caries), and human papilloma virus (carcinoma of the cervix). An important progress is the recognition that DNA alone can constitute the vaccines, inducing both humoral and cell-mediated immune responses. A large number of DNA vaccines have been made and shown interesting results in experimental animals. Live recombinant vaccines against rabies and rinderpest have proven to be highly effective for controlling these infections in the field, and those for AIDS are under clinical trial. Potent adjuvants have added to the efficacy of the vaccines. New technologies have emerged to 'humanize' mouse monoclonals by genetic engineering and express these efficiently in plants. These recombinant antibodies are opening out an era of highly specific and safe therapeutic interventions. Human recombinant antibodies would be invaluable for treating patients with terminal tetanus and rabies. Antibodies are already in use for treatment of cancer, rheumatoid arthritis and allergies. An advantage of preformed antibodies directed at a defined target and given in adequate amounts is the certainty of efficacy in every recipient, in contrast to vaccines, where the quality and quantum of immune response varies from individual to individual.
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PMID:The impact of new technologies on vaccines. 1073 30

In HIT-T15 insulinoma B-cells incubated in presence of [(32)P]NAD, we identified by autoradiography and immunoblotting ADP-ribosylation (ADP-R) of the trimeric G-protein Galpha(s) and Galpha(olf) subunits (45 kDa) induced by cholera toxin in M1 (120,000g) and M2 (70,000g) subcellular fractions containing plasma membranes, insulin granules, and mitochondria. This ADP-R indicates that these two fractions contain functionally competent Galpha subunits for adenylyl cyclase activation. Prolonged exposure of HIT-T15 cells to high glucose (25 mM instead of 6 mM) specifically reduced the ADP-R in Galpha(s) and Galpha(olf) subunits in the M1 fraction only, despite the clear increase of their accumulation in this compartment. A similar alteration in the ADP-R of the M1-associated Galpha(s) and Galpha(olf) subunits was observed in pancreatic islets isolated from fasted and fed rats. These results may explain, at least in part, the undesirable effects of sustained hyperglycemia on the cAMP-dependent process of insulin secretion in diabetes.
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PMID:Decreased ADP-ribosylation of the Galpha(olf) and Galpha(s) subunits by high glucose in pancreatic B-cells. 1077 86

Cholera toxin (Ctx) from Vibrio cholerae and the closely related Escherichia coli heat-labile enterotoxin (Etx) are the primary virulence factors responsible for causing cholera and traveller's diarrhea, respectively. Studies on the mode of action of these toxins on gut epithelial cells have revealed important insights into the mechanisms of toxin uptake and trafficking in eukaryotic cells. However, of perhaps even greater fascination have been the discoveries that Ctx and Etx exhibit remarkable immunological properties. When either of these toxins is administered via mucosal routes, it triggers a potent mucosal and systemic anti-toxin immune response. By contrast, local or systemic immunization with other soluble protein antigens usually stimulates only a meagre immune response, or results in a state of immunological tolerance. Even more striking are the findings that when Ctx or Etx are mixed with heterologous antigens, they function as adjuvants, leading to stimulation of mucosal responses to the admixed antigen, and the abrogation of oral tolerance. In addition, recent observations have shown that the receptor-binding component of these toxins can down-regulate inflammatory diseases associated with the induction of autoimmune disorders such as rheumatoid arthritis, diabetes, and multiple sclerosis. While the underlying mechanisms responsible for these remarkable properties have yet to be resolved, it is clear that the toxins' ability to bind to cell surface receptors plays an important role in their potent immunogenicity, adjuvanticity, and immunotherapeutic properties. This review provides an overview of the latest developments within the Ctx/Etx field, with a special emphasis on the cell entry mechanisms and immunomodulatory action of Ctx/Etx and their component subunits.
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PMID:Cholera toxin and related enterotoxins: a cell biological and immunological perspective. 1099 30

Because insulin resistance/diabetes may cause inordinate vascular complications in females, we have investigated the effects of insulin and insulin-like growth factor (IGF-1) on vascular reactivity in 12-week-old female Zucker obese (Ob) rats, a rodent model of insulin resistance and its lean (Ln) age-matched counterpart. Endothelium intact aortic rings from Ob animals and their Ln littermates (12 weeks of age) were subjected to contractile concentration responses to phenylephrine (PE) followed by relaxation to isoproterenol (Iso), with and without preincubation for 2 hours with cholera toxin (CTX; 1 microg/mL) or pertussis toxin (PTX; 2 microg/mL) and before and after incubation with either insulin or IGF-1 (100 nmol/L) for 1 hour. Systolic blood pressure was higher (138 +/- 3 v. 109 +/- 4 mm Hg; P <.0001) in the 12-week-old Ob rats. Contractile responses to PE were similar in both groups; however, both insulin and IGF-1 induced a paradoxical increase (P <.001) in contraction in Ob vasculature (929 +/- 92 v. 679 +/- 25 mg, respectively). CTX alone decreased contraction in the Ob (P <.02) and PTX in the Ln (P <.02), but there were no interactions between either IGF-1 or insulin and the toxins. Marked impairment of relaxation to Iso was seen in aortic rings of these female Ob rats (ED(50) = 2.6 micromol/L v. 418 nmol/L, P =.0002), an effect exacerbated by preincubation with either insulin or IGF-1 (P =.0001). Again, no role for G-proteins could be demonstrated. Insulin-dependent glucose uptake was severely impaired (P <.05) in aortic segments of the Ob insulin-resistant rats. Insulin receptor binding, tyrosine kinase activity (TKA), and abundance of several G-protein alpha subunits (inhibitory and stimulatory) in solubilized arterial membrane preparations (assessed by Western blot) were comparable in the 2 groups. These results indicate that resistance to the vascular actions of insulin/IGF-1 in female Ob rats is a postreceptor event that parallels glucose uptake resistance and is independent of G-proteins.
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PMID:Vascular insulin/insulin-like growth factor-1 resistance in female obese Zucker rats. 1131 26

Resistin was recently identified as a hormone secreted by adipocytes which leads to insulin resistance in vivo and in vitro and might therefore be an important link between obesity and diabetes. To clarify the regulation of resistin gene expression, 3T3-L1 adipocytes were treated with various agents known to modulate insulin sensitivity, and resistin mRNA was measured by quantitative real-time reverse transcription-polymerase chain reaction. Interestingly, isoproterenol treatment reduced the level of resistin mRNA to 20% of non-treated control cells. This effect was dose-dependent with significant inhibition occurring at concentrations as low as 10 nM isoproterenol. Moreover, pretreatment of adipocytes with the beta-adrenergic antagonist propranolol almost completely reversed the inhibitory effect of isoproterenol, whereas addition of the alpha-adrenergic antagonist phentolamine did not have any effect. Furthermore, the effect of isoproterenol could be mimicked by activation of G(S)-proteins and adenylyl cyclase. Thus, both cholera toxin and forskolin decreased resistin mRNA expression in a dose-dependent fashion by up to 90% of control levels. Taken together, these results suggest that resistin gene expression is regulated by a protein kinase A-dependent pathway in 3T3-L1 adipocytes.
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PMID:Isoproterenol inhibits resistin gene expression through a G(S)-protein-coupled pathway in 3T3-L1 adipocytes. 1143 27


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