Autoimmune diabetes: caught in the causality trap?

Do local immune-neuroendocrine disturbances initiate diabetes?

It has been suggested that there exists a local immune-neuroendocrine self-regulating system in the pancreas. The system consists of β-cells, nerve ganglia, intercellular fluid, connective tissue, and endothelial and immunocompetent cells. The local immune-neuroendocrine system governs the background level of insulin production by intrinsic mechanisms both in normal conditions and in a recovery period after different kinds of stress. The activity of this system by a complex of metabolic, environmental, nerve, and nonspecific immune factors has been determined. The local immune-neuroendocrine system is partially autonomous as a result of local integrative nerve circuits, morphological and functional substrates. Increased or decreased synthesis and release of some cytokines or biologically active substances (neurotransmitters, neuropeptides, γ-aminobutyric acid, metabolites, nitric oxide, ions, etc.) by various cell types in the local immune-neuroendocrine system above usual levels may result in disturbances of sensitivity and functions of β-cells. If the capability of the local immune-neuroendocrine system is insufficient for their compensation, the islet cell autoantigens may occur, the specific immune mechanisms are involved, and the pathological process becomes irreversible. Some ways for prevention of disturbances in the local immune-neuroendocrine system during the early and late phases of diabetes are presented.Key words: β-cells, diabetes, local immuneneuroendocrine system.

Basal concentrations of various steroids in the nonobese diabetic (NOD) mouse and effect of immobilization stress

The progression of type I diabetes in the NOD mouse is modulated by, among other things, stressful events and steroids. We measured in 2-month-old prediabetic NOD mice various circulating steroids (progesterone, corticosterone, dehydroepiandrosterone, delta4-androstenedione, testosterone, estrone and estradiol) under basal and stressful conditions (1.5h immobilization). Basal progesterone concentrations were low but measurable in randomized cycling NOD females and under the detection limit in NOD males. Immobilization increased progesterone concentrations in both sexes. Serum corticosterone concentrations also increased after immobilization but with the sexual dimorphism normally observed in rodents. Dehydroepiandrosterone concentrations were similar in both sexes and remained unaffected by stress. Testosterone and delta4-androstenedione were drastically reduced after immobilization in NOD males. Serum estrone and estradiol were not found to be statistically different in NOD females and males, but slightly higher to that described in the literature, and immobilization increased estrone concentrations in NOD males. In conclusion, while nonspecific to the NOD mouse, the modulation of circulating corticosteroids, estrogens and androgens induced by environmental factors may be part of the mechanism(s) by which these factors modulate the progression of type I diabetes. The hormonal changes may act in a complex manner at different levels: the immune system, the islet of Langerhans and the other structures involved in glucose homeostasis.

Type 1 diabetes: the facts fit a deficient inhibitory signal given by MHC class II

This paper presents a hypothesis regarding the aetiology of Type 1 (autoimmune) diabetes, which suggests that autoimmunity is normally prevented by an inhibitory or negative signal delivered by MHC molecules, and that in Type 1 diabetes it is the inability of beta cells to deliver sufficient negative signal from MHC Class II that drives the underlying autoimmune process. Based on a broad survey of the diabetes literature, a list of clinical, pathological, experimental and epidemiological 'facts' about Type 1 diabetes is presented which are considered to be widely accepted as proven. The new theory is then compared to other recent theories on the aetiology of diabetes with regard to its ability to explain these accepted 'facts'.

Diabetes results from a late change in the autoimmune response of NOD mice

IDDM in the NOD mouse is the result of a chronic autoimmune process. NOD mice are shown to express benign autoimmunity that converts to a state of malignant autoimmunity and the development of IDDM. Young disease-prone NOD mice are in a state of benign autoimmunity that is correlated with a non-destructive response to islet tissue and the preservation of insulin-containing beta-cells. A proportion of mice with benign autoimmunity convert to having malignant autoimmunity. Clinical diabetes is diagnosed approximately 3 weeks from the development of malignant autoimmunity which is correlated with a destructive response to grafted islet tissue and extensive beta-cell destruction. We conclude that the development of clinical disease is correlated with a change in the state of autoimmunity, that is, from benign to malignant autoimmunity.

Regulation of autoimmune diabetes: characteristics of non-islet-antigen specific therapies

Non-islet-antigen specific treatments have been shown to alter the natural history of insulin dependent diabetes in both the non-obese diabetic (NOD) mouse and in recently diagnosed patients. However concerns have been raised regarding the possibility that non-islet-antigen specific therapy may trade cell mediated autoimmunity for antibody dependent autoimmunity. Female NOD mice at approximately 70 days of age were treated with the non-islet-antigen specific agents complete Freund's adjuvant (CFA) and Bacillus Calmette-Guerin (BCG) and assayed for the development of antibody mediated autoimmunity at 300 days of age. Autoantibodies to red cells were not detected in any of the BCG (n = 19) or CFA (n = 15) treated animals, while 2 of 13 age-matched NOD animals had autoantibodies to red cells, shown by a positive direct Coomb's test. Anti-nuclear autoantibodies and complement deposition in the renal glomeruli were not significantly increased in the treated animals as compared to age-matched non-diabetic mice. The relative effectiveness of CFA and BCG treatment was examined in terms of the ability of these agents to preserve insulin containing islets. Complete Freund's adjuvant treatment was found to be more effective in preserving insulin containing islets when compared to BCG treatment. This study demonstrates that it is possible to inhibit the development of autoimmune diabetes without increasing the probability that treated animals will develop antibody dependent autoimmunity.