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Targeting Anti-Insulin B Cell Receptors Improves Receptor Editing in Type 1 Diabetes-Prone Mice.

ABSTRACT: Autoreactive B lymphocytes that commonly arise in the developing repertoire can be salvaged by receptor editing, a central tolerance mechanism that alters BCR specificity through continued L chain rearrangement. It is unknown whether autoantigens with weak cross-linking potential, such as insulin, elicit receptor editing, or whether this process is dysregulated in related autoimmunity. To resolve these issues, we developed an editing-competent model in which anti-insulin V?125 was targeted to the Ig? locus and paired with anti-insulin VH125Tg. Physiologic, circulating insulin increased RAG-2 expression and was associated with BCR replacement that eliminated autoantigen recognition in a proportion of developing anti-insulin B lymphocytes. The proportion of anti-insulin B cells that underwent receptor editing was reduced in the type 1 diabetes-prone NOD strain relative to a nonautoimmune strain. Resistance to editing was associated with increased surface IgM expression on immature (but not transitional or mature) anti-insulin B cells in the NOD strain. The actions of mAb123 on central tolerance were also investigated, because selective targeting of insulin-occupied BCR by mAb123 eliminates anti-insulin B lymphocytes and prevents type 1 diabetes. Autoantigen targeting by mAb123 increased RAG-2 expression and dramatically enhanced BCR replacement in newly developed B lymphocytes. Administering F(ab')2123 induced IgM downregulation and reduced the frequency of anti-insulin B lymphocytes within the polyclonal repertoire of VH125Tg/NOD mice, suggesting enhanced central tolerance by direct BCR interaction. These findings indicate that weak or faulty checkpoints for central tolerance can be overcome by autoantigen-specific immunomodulatory therapy.

SUBMITTER: Bonami RH

PROVIDER: S-EPMC4637270 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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Targeting Anti-Insulin B Cell Receptors Improves Receptor Editing in Type 1 Diabetes-Prone Mice.

Bonami Rachel H RH Thomas James W JW

Journal of immunology (Baltimore, Md. : 1950) 20151002 10

Autoreactive B lymphocytes that commonly arise in the developing repertoire can be salvaged by receptor editing, a central tolerance mechanism that alters BCR specificity through continued L chain rearrangement. It is unknown whether autoantigens with weak cross-linking potential, such as insulin, elicit receptor editing, or whether this process is dysregulated in related autoimmunity. To resolve these issues, we developed an editing-competent model in which anti-insulin Vκ125 was targeted to th ...[more]

PMID: 26432895

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Project description:Aims/hypothesisTreatment with the α3β4 nicotinic acetylcholine receptor (nAChR) agonist, 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP), improves glucose tolerance in diet-induced obese (DIO) mice, but the physiological and molecular mechanisms are unknown.MethodsDMPP (10 mg/kg body weight, s.c.) was administered either in a single injection (acute) or daily for up to 14 days (chronic) in DIO wild-type (WT) and Chrnb4 knockout (KO) mice and glucose tolerance, tissue-specific tracer-based glucose metabolism, and insulin signalling were assessed.ResultsIn WT mice, but not in Chrnb4 KO mice, single acute treatment with DMPP induced transient hyperglycaemia, which was accompanied by high plasma adrenaline (epinephrine) levels, upregulated hepatic gluconeogenic genes, and decreased hepatic glycogen content. In contrast to these acute effects, chronic DMPP treatment in WT mice elicited improvements in glucose tolerance already evident after three consecutive days of DMPP treatment. After seven days of DMPP treatment, glucose tolerance was markedly improved, also in comparison with mice that were pair-fed to DMPP-treated mice. The glycaemic benefit of chronic DMPP was absent in Chrnb4 KO mice. Chronic DMPP increased insulin-stimulated glucose clearance into brown adipose tissue (+69%), heart (+93%), gastrocnemius muscle (+74%) and quadriceps muscle (+59%), with no effect in white adipose tissues. After chronic DMPP treatment, plasma adrenaline levels did not increase following an injection with DMPP. In glucose-stimulated skeletal muscle, we detected a decreased phosphorylation of the inhibitory Ser640 phosphorylation site on glycogen synthase and a congruent increase in glycogen accumulation following chronic DMPP treatment.Conclusions/interpretationOur data suggest that DMPP acutely induces adrenaline release and hepatic glycogenolysis, while chronic DMPP-mediated activation of β4-containing nAChRs improves peripheral insulin sensitivity independently of changes in body weight via mechanisms that could involve increased non-oxidative glucose disposal into skeletal muscle.

Project description:Background: The prevalence of type 2 diabetes has increased dramatically in recent decades. Increasing brown adipose tissue (BAT) mass and activity has recently emerged as an interesting approach to not only increase energy expenditure, but also improve glucose homeostasis. BAT can be recruited by prolonged cold exposure in lean, healthy humans. Here, we tested whether cold acclimation could have therapeutic value for patients with type 2 diabetes by improving insulin sensitivity. Methods: Eight type 2 diabetic patients (age 59.3±5.8 years, BMI 29.8±3.2 kg/m2) followed a cold acclimation protocol, consisting of intermittent cold exposure (6 hours/day, 14-14.5 °C) for 12 consecutive days. Before and after cold acclimation, cold-induced BAT activity was assessed by [18F]FDG-PET/CT scanning, insulin sensitivity at thermoneutrality by a hyperinsulinemic-euglycemic clamp, and muscle and WAT biopsies were taken. Results: Cold-induced BAT activity was low, but increased in all patients upon cold acclimation (SUV from 0.40±0.29 to 0.63±0.78, p<0.05). Interestingly, insulin sensitivity showed a very pronounced 40% increase upon cold acclimation (glucose rate of disappearance from 14.9±4.1 to 20.5±6.9 μmol kg-1 min-1, p<0.05). A 40% increase in insulin sensitivity cannot be explained by BAT glucose uptake, in fact basal skeletal muscle GLUT4 content and translocation was markedly increased after cold acclimation, without effects on insulin signaling or AMPk activation. Conclusions: Regular mild cold exposure has marked effects on insulin sensitivity, which are accompanied by small increases in BAT activity and more pronounced effects on skeletal muscle. These data suggest a novel therapeutic option for the treatment of type 2 diabetes. Microarray analysis was performed on abdominal subcutaneous white adipose tissue samples from human type 2 diabetic patients before, and after 10 days of cold acclimation. A total of 14 samples, from 7 subjects, were used for the microarray analysis.

Dataset Information

Targeting Anti-Insulin B Cell Receptors Improves Receptor Editing in Type 1 Diabetes-Prone Mice.

Publications

Targeting Anti-Insulin B Cell Receptors Improves Receptor Editing in Type 1 Diabetes-Prone Mice.

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