Neuroendocrine Immuno-ontogeny of the Pathogenesis of Autoimmune Diabetes in the Nonobese Diabetic (NOD) Mouse

A novel in vitro approach to test the effectiveness of fish oil in ameliorating type 1 diabetes

Diabetes type 1 (T1D) characterized by destruction of pancreatic β-cells results in inadequate insulin production and hyperglycaemia. Generation of reactive oxygen species and glycosylation end-products stimulates toxic impacts on T1D. Dietary w-3 fatty acids present in Fish oil (FO) might be helpful in the prevention of oxidative stress and lipid peroxidation, thus, beneficial against T1D. But how the cellular secretion from β-cells under influence of FO affects the glucose homeostasis of peri-pancreatic cells is poorly understood. In the current study, we aimed to introduce an in vitro model for T1D and evaluate its effectiveness in respect of alloxan treatment to pancreatic Min6 cells. We use alloxan in the Min6 pancreatic β-cell line to induce cellular damage related to T1D. Further treatment with FO was seen to prevent cell death by alloxan and induce mRNA expression of both insulin 1 and insulin 2 isoforms under low-glucose conditions. From the first part of the study, it is clear that FO is effective to recover Min6 cells from the destructive effect of alloxan, and it worked best when given along with alloxan or given after alloxan treatment regime. FO-induced secretion of molecules from Min6 was clearly shown to regulate mRNA expression of key enzymes of carbohydrate metabolism in peri-pancreatic cell types. This is a pilot study showing that an improved in vitro approach of using Min6 along with muscle cells (C2C12) and adipose tissue cells (3T3-L1) together to understand the crosstalk of molecules could be used to check the efficacy of an anti-diabetic drug.

Exaggerated Increases in Microglia Proliferation, Brain Inflammatory Response and Sickness Behaviour upon Lipopolysaccharide Stimulation in Non-Obese Diabetic Mice

The non-obese diabetic (NOD) mouse, an established model for autoimmune diabetes, shows an exaggerated reaction of pancreas macrophages to inflammatory stimuli. NOD mice also display anxiety when immune-stimulated. Chronic mild brain inflammation and a pro-inflammatory microglial activation is critical in psychiatric behaviour.

OBJECTIVE

To explore brain/microglial activation and behaviour in NOD mice at steady state and after systemic lipopolysaccharide (LPS) injection.

METHODS

Affymetrix analysis on purified microglia of pre-diabetic NOD mice (8-10 weeks) and control mice (C57BL/6 and CD1 mice, the parental non-autoimmune strain) at steady state and after systemic LPS (100 μg/kg) administration. Quantitative PCR was performed on the hypothalamus for immune activation markers (IL-1β, IFNγ and TNFα) and growth factors (BDNF and PDGF). Behavioural profiling of NOD, CD1, BALB/c and C57BL/6 mice at steady state was conducted and sickness behaviour/anxiety in NOD and CD1 mice was monitored before and after LPS injection.

RESULTS

Genome analysis revealed cell cycle/cell death and survival aberrancies of NOD microglia, substantiated as higher proliferation on BrdU staining. Inflammation signs were absent. NOD mice had a hyper-reactive response to novel environments with some signs of anxiety. LPS injection induced a higher expression of microglial activation markers, a higher brain pro-inflammatory set point (IFNγ, IDO) and a reduced expression of BDNF and PDGF after immune stimulation in NOD mice. NOD mice displayed exaggerated and prolonged sickness behaviour after LPS administration.

CONCLUSION

After stimulation with LPS, NOD mice display an increased microglial proliferation and an exaggerated inflammatory brain response with reduced BDNF and PDGF expression and increased sickness behaviour as compared to controls.

Modulation of macrophage inflammatory profile in pregnant nonobese diabetic (NOD) mice

During normal early pregnancy circulating monocytes are recruited to the maternal-placental interface where they differentiate to macrophages expressing different functional phenotypes for the maintenance of tissue homeostasis. Pregnancy in the nonobese diabetic (NOD) mouse model presents some pathological features in the pre-diabetic stage. The aim of this work was to analyze the functional profile of peritoneal macrophages faced with inflammatory and phagocytic stimuli in early pregnant pre-diabetic NOD mice and their modulation by vasoactive intestinal peptide (VIP). Pregnant NOD mouse macrophages showed no basal NFκB activation, lower IL-12 and nitrites production compared with the macrophages from non-pregnant NOD mice. Their pro-inflammatory aberrant response to LPS and apoptotic cell challenge was reduced and VIP inhibited macrophage residual deleterious responses to apoptotic cells. A functional phenotype switch in macrophages during pregnancy in NOD mice and a promoting effect of VIP towards this regulatory phenotype would be in line with the central role of macrophages in the maternal-placental dialogue.

Glucose homeostasis in pre-diabetic NOD and lymphocyte-deficient NOD/SCID mice during gestation

BACKGROUND

Unlike other strains, spontaneously type 1 non-obese diabetic (NOD) experience transient hyperinsulinemia after weaning. The same applies for NOD/SCID mice, which lack functional lymphocytes, and unlike NOD mice, do not develop insulitis and diabetes like NOD mice.

AIMS

Given that beta-cell stimulation is a natural feature of gestation, we hypothesized that glucose homeostasis is disturbed in gestate pre-diabetic NOD and non-diabetic NOD/SCID mice, which may accelerate the onset of diabetes and increase diabetes prevalence.

METHODS

During gestation and postpartum, mice were analyzed under basal feed conditions followed by glucose injection (1 g/kg, i.p.) after overnight fast, using glucose tolerance test (GTT). Glycemia, corticosteronemia, blood and pancreatic insulin, glucagon levels, islet size, and islet morphology were evaluated. Glycemia and mortality were assessed after successive gestations in NOD mice mated for the first time at 2 different ages.

RESULTS

1. Basal glucagonemia rose markedly in first-gestation fed NOD mice. 2. beta-cell hyperactivity was present earlier in first-gestation non-diabetic fasted NOD and NOD/SCID mice than in age-matched C57BL/6 mice, assessed by increased insulin/glucose ratio after GTT. 3. Overnight fasting increased corticosteronemia rapidly and sharply in pre-diabetic gestate NOD and NOD/SCID mice. 4. Islet size increased in non-diabetic gestate NOD mice compared with C57BL/6 mice. 5. Successive gestations accelerated diabetes onset, and contributed to increased mortality in NOD mice.

CONCLUSIONS

First-gestation pre-diabetic NOD and non-diabetic NOD/SCID mice exhibited beta-cell hyperactivity and deregulation of glucagon and/or corticosterone secretion. This amplified normally occurring insulin resistance, further exhausted maternal beta-cells, and accelerated diabetes in NOD mice.

Genistein and daidzein prevent diabetes onset by elevating insulin level and altering hepatic gluconeogenic and lipogenic enzyme activities in non-obese diabetic (NOD) mice

BACKGROUND

Non-obese diabetic (NOD) mice are regarded as being excellent animal models of human type 1 diabetes or insulin dependent diabetes (IDDM). This study investigated the beneficial effects of genistein and daidzein on IDDM, an autoimmune disease.

METHODS

Female NOD mice were divided into control, genistein (0.02%, w/w) and daidzein (0.02%, w/w) groups. Blood glucose level, plasma biomarkers, hepatic glucose and lipid regulating enzyme activities and pancreas immunohistochemistry analysis were examined after a 9-week experimental period.

RESULTS

Blood glucose levels of genistein and daidzein groups were 40 and 36% of control value at the end of study (9th week). The genistein and daidzein supplements increased insulin/glucagon ratio and C-peptide level with preservation of insulin staining beta-cell of pancreas in the NOD mice. In the liver, genistein and daidzein supplements resulted in lowering glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK) activities, while increasing two lipogenic enzymes activities, malic enzyme and glucose-6-phosphate dehydrogenase (G6PD), compared to the control group. Significantly, genistein and daidzein supplementation lowered the activities of fatty acid beta-oxidation and carnitine palmitoyltransferase (CPT) in these mice. Genistein and daidzein also improved plasma triglyceride and free fatty acid (FFA) concentrations compared to the control group.

CONCLUSIONS

These results suggest that genistein and daidzein play important roles in regulation of glucose homeostasis in type 1 diabetic mice by down-regulating G6Pase, PEPCK, fatty acid beta-oxidation and CPT activities, while up-regulating malic enzyme and G6PD activities in liver with preservation of pancreatic beta-cells. The supplementation of genistein and daidzein are seemingly helpful for preventing IDDM onset.

Pancreatic innervation in mouse development and beta-cell regeneration

Pancreatic innervation is being viewed with increasing interest with respect to pancreatic disease. At the same time, relatively little is currently known about innervation dynamics during development and disease. The present study employs confocal microscopy to analyze the growth and development of sympathetic and sensory neurons and astroglia during pancreatic organogenesis and maturation. Our research reveals that islet innervation is closely linked to the process of islet maturation-neural cell bodies undergo intrapancreatic migration/shuffling in tandem with endocrine cells, and close neuro-endocrine contacts are established quite early in pancreatic development. In addition, we have assayed the effects of large-scale beta-cell loss and repopulation on the maintenance of islet innervation with respect to particular neuron types. We demonstrate that depletion of the beta-cell population in the rat insulin promoter (RIP)-cmyc(ER) mouse line has cell-type-specific effects on postganglionic sympathetic neurons and pancreatic astroglia. This study contributes to a greater understanding of how cooperating physiological systems develop together and coordinate their functions, and also helps to elucidate how permutation of one organ system through stress or disease can specifically affect parallel systems in an organism.

‘Sensing’ autoimmunity in type 1 diabetes

Type 1 diabetes (T1D) results from autoimmune-mediated loss of insulin-producing beta-cells. Recent findings suggest that the events controlling T1D development are not only immunological, but also neuronal in nature. In the non-obese diabetic (NOD) mouse model of T1D, a mutant sensory neuron channel, TRPV1, initiates chronic, progressive beta-cell stress, inducing islet cell inflammation. This novel mechanism of organ-specific damage requires a permissive, autoimmune-prone host, but ascribes tissue specificity to the local secretory dysfunction of sensory afferent neurons. In NOD mice, normalizing this neuronal function by administration of the neurotransmitter substance P clears islet cell inflammation, reduces insulin resistance and restores normoglycemia. Here, we discuss this neuro-immuno-endocrine model, its implications and the involvement of sensory neurons in other autoimmune disorders. These developments might provide novel neuronal-based therapeutic interventions, particularly in diabetes.

Sensory neurons link the nervous system and autoimmune diabetes

The initial factors that trigger the autoimmune response against pancreatic islets in the nonobese diabetic (NOD) mouse are still unknown. In this issue of Cell, propose that a defect in a subset of sensory neurons innervating the pancreas plays a major role in initiating the chain of events that will lead to local inflammation, islet destruction, and autoimmune diabetes.

NOD mice exocrinopathy: towards a neuroimmune link

Sjogren's syndrome (SS) is a chronic autoimmune disorder of exocrine glands characterized as an autoimmune exocrinopathy and more specifically as an autoimmune epithelitis. An impaired balance of neuroimmune interactions mediated by vasoactive intestinal peptide (VIP) in the target organ at early stages of disease is explored by means of the nonobese diabetic (NOD) mouse model of SS. We have previously described a reduced salivary secretion and signaling upon VIP stimulation. The effect reflected a differential regulation of the neural isoform of nitric oxide synthase by calcium calmodulin kinase II and occurred prior to the appearance of detectable levels of cytokines in NOD glands. VIP acting on NOD macrophages treated with lipopolysaccharide promoted anti-inflammatory effects by inhibiting nitric oxide synthase induction as well as IL-12 and TNF-alpha production, while stimulating IL-10. Here we present evidence on the ability of apoptotic acinar cells from submandibular glands of NOD mice to stimulate nitric oxide in both peritoneal and glandular macrophage pools to a similar extent as lipopolysaccharide + IFN-gamma. VIP was not effective to prevent nitrite accumulation and modestly increased IL-10 levels in macrophages coincubated with acinar cells. An enhanced nitrite response of NOD glandular macrophages in basal and stimulated conditions compared to peritoneal cells is also shown.

Novel leptin receptor mutation in NOD/LtJ mice suppresses type 1 diabetes progression: I. Pathophysiological analysis

A spontaneous single-base mutation in the leptin receptor of type 1 diabetes-prone NOD/LtJ mice (designated as Lepr(db-5J)) produced a glycine640valine transversion in the extracellular domain. All mutant mice became obese and hyperinsulinemic at weaning, with 70-80% developing early-onset hyperglycemia. However, these obese diabetic mice continued to gain weight without insulin therapy. Spontaneous diabetes remission was observed in all obese females and a subset of obese males. Insulitis was largely limited to islet perimeters, with intraislet insulitis infrequently observed. In 17 obese males (age 39 weeks), we observed phenotypic heterogeneity, including full remission from hyperglycemia (24%), intermediate hyperglycemia with elevated body weight (41%), and severe hyperglycemia and weight loss (35%). The remitting normoglycemic and intermediate hyperglycemic phenotypes were associated with extensive beta-cell hyperplasia. Unlike the extensive intraislet insulitis present in diabetic lean NOD/Lt mice, the severe obese diabetic phenotype was associated with islet atrophy without extensive intraislet insulitis. These results indicated that the manipulation of the leptin/leptin receptor axis may provide a novel means of downregulating autoimmunity in type 1 diabetes and confirmed a role for leptin as a mediator in the development of this disease in NOD mice.

Increased transcriptional preproinsulin II beta-cell activity in neonatal nonobese diabetic mice: in situ hybridization analysis

In the prediabetic nonobese diabetic (NOD) mouse, a spontaneous model of type 1 diabetes, we previously reported transient postweaning hyperinsulinemia followed by progressive islet hyperplasia. A modified in situ hybridization technique was used to determine whether these effects were accompanied by changes in insulin transcriptional activity as a function of age. We found that NOD neonates express higher levels of preproinsulin II primary transcripts than age-matched C57BL/6 mice, but this difference disappeared within the first wk of age. To manipulate insulin transcriptional activity in NOD neonates, NOD mothers were treated with insulin during the last two wk of gestation. A down-regulation of beta-cell hyperactivity was observed in female NOD neonates but not in male neonates. By contrast, the same insulin treatment applied to NODscid (severe combined immunodeficiency) mothers, devoid of functional lymphocytes but showing like NOD mice postweaning hyperinsulinemia, increased transcriptional beta-cell activity in both sexes of neonates. In conclusion, NOD mice exhibit successive and transient signs of beta-cell hyperactivity, reflected as early as birth by high transcriptional preproinsulin II activity and later, from weaning to around 10 wk of age, by hyperinsulinemia. Of note, when thinking in terms of in utero disease programming, the NOD neonatal transcriptional beta-cell hyperactivity could be modulated by environmental (maternal and/or fetal) factors.