Francesco Dotta

Oral probiotic administration induces interleukin-10 production and prevents spontaneous autoimmune diabetes in the non-obese diabetic mouse

Aims/hypothesisRecent observations suggest the involvement of the gastrointestinal tract in the pathogenesis of islet autoimmunity. Thus, the modulation of gut-associated lymphoid tissue may represent a means to affect the natural history of the disease. Oral administration of probiotic bacteria can modulate local and systemic immune responses; consequently, we investigated the effects of oral administration of the probiotic compound VSL#3 on the occurrence of diabetes in non-obese diabetic (NOD) mice.MethodsVSL#3 was administered to female NOD mice three times a week starting from 4 weeks of age. A control group received PBS. Whole blood glucose was measured twice a week. IFN-γ and IL-10 production/expression was evaluated by ELISA in culture supernatants of mononuclear cells isolated from Peyer’s patches and the spleen, and by real-time PCR in the pancreas. Insulitis was characterised by immunohistochemistry and histomorphometric studies.ResultsEarly oral administration of VSL#3 prevented diabetes development in NOD mice. Protected mice showed reduced insulitis and a decreased rate of beta cell destruction. Prevention was associated with an increased production of IL-10 from Peyer’s patches and the spleen and with increased IL-10 expression in the pancreas, where IL-10-positive islet-infiltrating mononuclear cells were detected. The protective effect of VSL#3 was transferable to irradiated mice receiving diabetogenic cells and splenocytes from VSL#3-treated mice.Conclusions/interpretationOrally administered VSL#3 prevents autoimmune diabetes and induces immunomodulation by a reduction in insulitis severity. Our results provide a sound rationale for future clinical trials of the primary prevention of type 1 diabetes by oral VSL#3 administration.

Guidelines for the treatment and management of new-onset diabetes after transplantation.

Abstract:  Although graft and patient survival after solid organ transplantation have improved markedly in recent years, transplant recipients continue to experience an increased prevalence of cardiovascular disease (CVD) compared with the general population. A number of factors are known to impact on the increased risk of CVD in this population, including hypertension, dyslipidemia and diabetes mellitus. Of these factors, new‐onset diabetes after transplantation has been identified as one of the most important, being associated with reduced graft function and patient survival, and increased risk of graft loss. In 2003, International Consensus Guidelines on New‐onset Diabetes after Transplantation were published, which aimed to establish a precise definition and diagnosis of the condition and recommend management strategies to reduce its occurrence and impact. These updated 2004 guidelines, developed in consultation with the International Diabetes Federation (IDF), extend the recommendations of the previous guidelines and encompass new‐onset diabetes after kidney, liver and heart transplantation. It is hoped that adoption of these management approaches pre‐ and post‐transplant will reduce individuals’ risk of developing new‐onset diabetes after transplantation as well as ameliorating the long‐term impact of this serious complication.

Role of caspases in the regulation of apoptotic pancreatic islet beta-cells death

The homeostatic control of beta‐cell mass in normal and pathological conditions is based on the balance of proliferation, differentiation, and death of the insulin‐secreting cells. A considerable body of evidence, accumulated during the last decade, has emphasized the significance of the disregulation of the mechnanisms regulating the apoptosis of beta‐cells in the sequence of events that lead to the development of diabetes. The identification of agents capable of interfering with this process needs to be based on a better understanding of the beta‐cell specific pathways that are activated during apoptosis. The aim of this article is fivefold: (1) a review of the evidence for beta‐cell apoptosis in Type I diabetes, Type II diabetes, and islet transplantation, (2) to review the common stimuli and their mechanisms in pancreatic beta‐cell apoptosis, (3) to review the role of caspases and their activation pathway in beta‐cell apoptosis, (4) to review the caspase cascade and morphological cellular changes in apoptotic beta‐cells, and (5) to highlight the putative strategies for preventing pancreatic beta‐cells from apoptosis.

Upregulation of mitochondrial peripheral benzodiazepine receptor expression by cytokine‐induced damage of human pancreatic islets

Cytokines produced by immune system cells infiltrating pancreatic islets are candidate mediators of islet beta‐cell destruction in autoimmune insulin‐dependent diabetes mellitus. After 72 h exposure of human pancreatic islets to a cytotoxic cytokine combination of interleukin 1 beta (50 U/ml), tumor necrosis factor alpha (1,000 U/ml), and interferon gamma (1,000 U/ml), an increase of cell death vs. control islets was demonstrated by TUNEL and cell death detection ELISA method. Islet death was associated with apoptosis and mitochondrial swelling as evidenced by electron microscopy. This effect was correlated with a marked decrease of Bcl‐2 mRNA expression (without any major change of Bax mRNA) and a marked increase of inducible nitric oxide synthase mRNA. Since peripheral benzodiazepine receptors constitute the aspecific mitochondrial permeability transition pore, and that it has been suggested to be involved in cytokine‐induced cell death, we evaluated the effects of the cytotoxic cytokines on PBR density and mRNA expression. We demonstrated that cytokine treatment of human islets induced an increase of maximum density of 3H1‐(2‐chlorophenyl‐N‐methyl‐1‐methylpropyl)‐3‐ isoquinolinecarboxamide binding sites, (5,110 ± 193 vs. 3,421 ± 336 fmol/mg proteins, P < 0.05) with no significant change in the affinity constant value (9.45 ± 0.869 vs. 8.7 ± 1.159 nM). Moreover, an increase of the expression of peripheral benzodiazepine receptor mRNA was observed, suggesting an increased transcription from the coding gene. These results suggest a possible role of peripheral benzodiazepine receptors in the organism response to tissue damage associated with inflammatory mediator production. J. Cell. Biochem. 84: 636–644, 2002.

Gangliosides and autoimmune diabetes

Gangliosides are sialic acid-containing glycolipids which are formed by a hydrophobic portion, the ceramide, and a hydrophilic part, i.e. the oligosaccharide chain. First described in neural tissue, several studies have shown that gangliosides are almost ubiquitous molecules expressed in all vertebrate tissues. Within cells, gangliosides are usually associated with plasma membranes, where they can act as receptors for a variety of molecules and have been shown to take part in cell-to-cell interaction and in signal transduction. In addition, gangliosides are expressed in cytosol membranes like those of secretory granules of some endocrine cells (adrenal medulla, pancreatic islets). As far as the role of gangliosides in diseases is concerned, there are some cases in which an aberrant ganglioside expression plays a crucial role in the disease pathogenetic process. These diseases include two major forms of ganglioside storage, namely GM2-gangliosidosis (Tay-Sachs and its beta-hexosaminidase deficiency) and GM1-gangliosidosis (beta-galactosidase deficiency), where the most prominent pathological characteristic is the lysosomal ganglioside accumulation in neurons. Other inflammatory or degenerative diseases both within and outside the nervous system have been shown to be associated with an altered pattern of ganglioside expression in the target organ. Since monoclonal antibodies have been discovered and used in immunology, a large variety of ganglioside antigens has been described both as blood group antigens and as tumour-related antigens. Several studies have also indicated that gangliosides can act not only as antigens, but also as autoantigens. As a matter of fact, auto-antibodies to gangliosides, detected by immunostaining methods performed directly on TLC plates or by ELISA, have been described in several autoimmune disorders such as Guillain-Barré syndrome, multiple sclerosis, lupus erythematosus, Hashimotos thyroiditis and, last but not least, insulin-dependent (type 1) diabetes mellitus. This last disease is caused by the autoimmune destruction of insulin-producing pancreatic islet cells in genetically predisposed individuals. Autoantibodies and T lymphocytes directed towards multiple islet autoantigens have been detected in the circulation, well before the clinical onset of the disease, in a prodromal phase during which pancreatic islet beta-cells are presumably destroyed. Among the target autoantigens, some are of protein nature but others are acidic glycolipids such as sulphatides158 and the gangliosides GT3, GD3 and especially GM2-1. This last component is specifically expressed in pancreatic islets and has been shown to represent a target of IgG autoantibodies highly associated with diabetes development in first-degree relatives of type 1 diabetic individuals. In addition, the GM2-1 ganglioside appears to be one of the antigens recognized by cytoplasmic ICA, a heterogeneous group of antibodies which specifically react with islets on pancreatic frozen sections. In conclusion, studies performed in the last decade have clearly indicated that gangliosides represent a heterogeneous class of molecules that are involved in several cellular processes that are of crucial importance in physiological as well as in pathological conditions. Interestingly, these molecules, despite their small size, have been shown to represent not only important antigens in tumour immunology but are also able to elicit a specific autoimmune response, thus representing important autoantigens in some autoimmune disorders. It is of interest that, in addition to neurological autoimmune disorders where autoimmunity to gangliosides is frequent and usually of considerable magnitude, an autoimmune response to this class of molecules has been observed in autoimmune diabetes. (ABSTRACT TRUNCATED)

GM2-1 pancreatic islet ganglioside : identification and characterization of a novel islet-specific molecule

SummaryRecent studies have indicated that GM2-1, a pancreatic islet monosialo-ganglioside, is an islet-specific component whose expression is metabolically regulable and represents one of the target antigens of cytoplasmic islet cell antibodies. In the present study we aimed to biochemically characterize this molecule using a panel of biochemical techniques including gas chromatography, thin layer chromatography, enzymatic digestion and mass spectrometry. GM2-1 ganglioside was extracted from human pancreas and purified by thin-layer chromatography. Fatty acids in the ceramide (the hydrophobic portion of the molecule), identified by gas chromatography ranged from C16:1 to C24:1. The oligosaccharide chain was enzymatically digested by the sequential application of various exoglycosidases (neuraminidase followed by Β-galactosidase, followed by Β-hexosaminidase) and characterized by gas chromatography identification of the liberated sugars. The following structure was deducted from enzymatic studies and confirmed by mass spectrometry analysis: N-acetyl neuraminic acid-galactose-galactosamine-galactosamine-glucose-ceramide. This is a novel ganglioside structure, not yet described, which shares characteristics with a neuronal glycolipid autoantigen: the LM1 ganglioside. Both GM2-1 and LM1 have a single sialic acid residue in the terminal position, the same migration position on thin layer chromatography and the same number of carbohydrate moieties. In conclusion, we have characterized a novel islet-specific ganglioside molecule with unusual characteristics, such as the terminal sialic acid and the galactosamine residues, which may facilitate both its anti-genicity and its involvement in beta-cell autoimmunity.

Determination of gangliosides by high-performance liquid chromatography with photodiode-array detection

Abstract Mixtures of gangliosides were separated by high-performance liquid chromatography (HPLC) on amino-silica columns according to their negative charge and the length of the carbohydrate portion. The use of an on-line variable wave-length diode-array detector allows the identification of gangliosides on the basis of their UV spectra with maximum absorbance at 196 nm. Accurate analytical data acquired with the diode-array detector allow the qualitative and quantitative determination of gangliosides and therefore eliminate the need for thin-layer chromatography after HPLC separation.

Autoantibody negative new onset type 1 diabetic patients lacking high risk HLA alleles in a caucasian population: are these type 1b diabetes cases?

In Caucasians, a small number of Type 1 diabetic patients do not show evidence of humoral islet autoimmunity at disease onset, at least with common screening procedures. In African– and Hispanic–American diabetic children at time of diagnosis, many show no evidence of autoimmunity but have an atypical clinical form of the disease. According to the recent American Diabetes Association classification, this subgroup of autoantibody negative patients is referred to as Type 1b diabetic subjects. In the present study, a homogeneous Caucasian Type 1 diabetic clinic‐based cohort has been evaluated at diagnosis using a large panel of diabetes‐related antibodies and then characterized for various genetic features in order to identify newly diagnosed Type 1 diabetics who are potentially autoantibody negative, i.e. possibly referrable to as idiopathic Type 1b diabetes.

Immunology in diabetic pregnancy: activated T cells in diabetic mothers and neonates.

SummaryLymphocytes bearing surface antigens indicating early and full activation have been evaluated, in addition to T cell subsets, in blood samples from diabetic pregnant patients, neonates from diabetic mothers and control groups. The type of diabetes and the trimester of pregnancy were taken into account. Monoclonal antibodies were used to enumerate total T cells, helper/inducer, cytotoxic/suppressor T lymphocytes and activated mononuclear cells using antibodies binding lymphocyte surface antigens as markers of early lymphocyte activation, and MHC Class II surface antigens as markers of late activation. A decrease in T-helper cells during the third trimester of pregnancy in Type 1 (insulin-dependent) and gestational diabetic patiens (p<0.02) and a decrease in T-suppressor cells in Type 2 (non-insulin-dependent) diabetic pregnant patients during the third trimester (p<0.01) were observed in relation to normal values. As in normal pregnancy, 4F2-positive cells were increased in 48% of diabetic pregnant patients during the second and third trimesters of gestation. Class II-positive cells were increased in almost 60% of Type 1 and gestational diabetic patients during the last trimester of pregnancy in comparison with normal pregnant women and control subjects. A decrease in T-helper cells (p<0.02) and a clear increase in 4F2-positive cells (p<0.001) and Class II-positive lymphocytes (p<0.005) were observed in the infants of diabetic mothers in comparison with control subjects. The maternal cellular immune system, actively alerted in pregnancy, is fully activated in a number of Type 1 and gestational diabetic pregnant patients. Activated lymphocytes are even found in the neonates of diabetic mothers, but these do not trigger the events leading to the onset of diabetes in the short term.

Improved insulin secretory function and reduced chemotactic properties after tissue culture of islets from type 1 diabetic patients

Type 1 diabetes results from the destruction of pancreatic beta‐cell as a consequence of an autoimmune process. To date, information on the properties of islets isolated from type 1 diabetic patients is very scant.