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C Boitard

Publications and source records attributed to C Boitard.

At least 55 records · Page 3Linked to original sources
PubMed1997

Insulin-dependent diabetes mellitus in non-DR3/non-DR4 subjects.

Five to 20% insulin-dependent diabetes mellitus (IDDM) patients do not bear the classical HLA class II DR3 or DR4 susceptibility haplotypes. We have studied the clinical characteristics, anti-islet cell antibodies (Ab) and HLA class II genotypes in 72 non-DR3/non-DR4 Caucasian patients, mainly adults, presenting with clinically typical IDDM. The DRB1*08-DQB1*0402-DQA1*0401 haplotype frequency was increased in the patients compared to 272 non-DR3/non-DR4 controls (OR = 5.9, Pc < 0.005). This association was even stronger in the Ab-positive patients (DRB1*08: OR = 7.2, Pc < 0.005; DQB1*0402: OR = 9.2, Pc < 0.005; DQA1*0401: OR = 9, Pc < 0.02). In those subjects the DRB1*15 allele was less frequent than in controls (OR = 0.1, Pc = 0.05). By contrast, IDDM patients with no Ab showed no particular association with HLA class II allele although they had clinical and metabolic characteristics similar to that of Ab-positive subjects. The genetic basis for IDDM predisposition in the Ab-positive subgroup remains elusive since the DRB1*08-DQB1*0402 haplotype encodes an Asp57-positive DQ beta chain. However, all DR8 patients had a non-Asp57 encoding DQB1 allele on the second haplotype. Thus, trans-complementation leading to peculiar predisposing DQ alpha beta heterodimers may occur. Alternatively, a direct role of the DRB1*08 allele cannot be excluded. These results show that autoimmune type 1 diabetes occurs in non-DR3/non-DR4 subjects, mainly adults. They further support that IDDM, when defined on a clinical basis, encompass different pathogenetic entities.

Adolescent↗
PubMed1997

[Emphysematous pyelonephritis in diabetics].

Emphysematous pyelonephritis is a rare, life-threatening complication of upper urinary tract infections, characterized by the presence of gas in renal parenchyma and perirenal space. It occurs in 90% of cases in diabetic patients and E coli is the most common causative germ. The pathogenesis probably involves several factors including enhanced proliferation of microorganisms due to altered immune defences, mixed acid fermentation of glucose leading to gas production, and decreased elimination of the gas because of impaired tissue perfusion. Diagnosis is often delayed because the symptoms may be non-specific, as illustrated by the two cases we report herein. In patients with diabetes and febrile urinary tract infection, obstruction of the urinary tract should first be eliminated by echography. Then, if the infection does not rapidly respond to antimicrobial therapy, a scan should be performed. Aggressive management including correction of hemodynamics, parenteral antimicrobial therapy, and diabetes control with insulin therapy is mandatory, but a surgical procedure (nephrectomy or drainage) is almost always required.

Diabetes Mellitus, Type 2↗
PubMed1997

Immune mechanisms leading to type 1 insulin-dependent diabetes mellitus.

Insulin-dependent diabetes mellitus (IDDM) results from the autoimmune destruction of the endocrine (beta) cells responsible for the secretion of insulin. Experimental and human studies have resulted in unpredicted developments over the past ten years. Against most predictions, a long list of possible autoantigens has been defined, most of which are not beta-cell specific. Seemingly, up to 10 to 20 genetic regions, rather than 2 to 3 as initially predicted, carry markers that associate them with IDDM. Finally, there is accumulating evidence that beta cells are not a passive bystander in the event that leads to the activation of the diabetes autoimmune reaction. Whether the immune system or the islet, or both, are at the initiation of the disease process is a challenge for the near future.

Animals↗
PubMed1997

Insulin responses to intravenous glucose, intravenous arginine and a hyperglycaemic clamp in ICA-positive subjects with different degrees of glucose tolerance.

The relationship between altered insulin secretion and impaired glucose tolerance was studied in 32 non-obese subjects aged 14-49 years with islet-cell antibodies (ICA) and fasting blood glucose below 7.9 mmol/l, using oral (OGTT) and intravenous (IVGTT) glucose tolerance tests. Glucose tolerance was normal in 19 subjects, impaired (IGT) in 4 and satisfied diabetic criteria in 9. Fifteen of these subjects and 8 ICA-negative controls also underwent a hyperglycaemic clamp (10 mmol/l) and a glucose-potentiated IV arginine bolus. Acute insulin response to IVGTT and insulin and C-peptide responses to the hyperglycaemic clamp and the arginine bolus were dramatically lower (p < 0.001) in diabetic and IGT subjects than in ICA-positive patients with normal glucose tolerance and control subjects. Insulin responses to the three tests were inversely correlated with plasma glucose levels and the area under the curve of OGTT. The correlations between the degree of glucose tolerance and insulin responses to IVGTT, the hyperglycaemic clamp and the arginine bolus were virtually identical. It is concluded that insulin responses to the three stimuli were severely altered in ICA-positive patients with impaired glucose tolerance or asymptomatic diabetes, normal in normotolerant ICA-positive subjects, and correlated with glucose tolerance.

Administration, Oral↗
PubMed1997

Insulin-dependent diabetes and human leucocyte antigens.

The association of diabetes with HLA class I alleles in the early 1970s and with HLA class II alleles in the late 1970s provided a crucial, though indirect, indication of the role of immune phenomena in the development of insulin-dependent diabetes mellitus (IDDM). Genotyping of HLA alleles in the mid-1980s opened up a new era. The very precise definition of susceptibility and protection alleles proved to be an important diagnostic factor in predicting IDDM and was also the first step towards an understanding of the role of class II antigen-presenting molecules in the development of the autoimmune reaction responsible for the destruction of insulin-secreting cells and the subsequent onset of diabetes. Animal models have been instrumental in studying the possible relations between the development of IDDM autoimmunity and the expression of particular major histocompatibility complex alleles on a multigenic susceptibility background.

Alleles↗
PubMed1997

Insulin and the prevention of insulin-dependent diabetes mellitus.

Insulin deficiency due to autoimmune destruction of pancreatic beta cells (insulin is an autoantigen) is responsible for insulin-dependent diabetes mellitus. Since 1923, substitutive administration of insulin has been used to treat the disease. Surprisingly, initial usage of insulin is associated with partial resumption of insulin secretion in most patients. This phenomenon is intensified by aggressive insulin therapy. When observed at a late phase of destruction, it has been interpreted as an immunomodulatory effect of insulin which is presumed to act either by masking the target of effector cells in the autoimmune reaction (beta cells at rest because of glycaemic normalisation would expose fewer antigens) or by direct action on autoreactive T lymphocytes (which are rich in insulin receptors). There could also be a direct beneficial effect on anti-apoptotic or pro-regenerative beta cells. Efficient prevention of diabetes has been achieved by administration of parenteral insulin to non-obese diabetic (NOD) mice. Certain sequences of the B chain appear to be responsible for this effect, which seems to be immunomediated. Some preliminary data from the groups of G. Eisenbarth and N. MacLaren have suggested that this effect could be obtained in man by administering small doses of subcutaneous insulin to prediabetic patients. Two trials have been under way since 1994: DPT1 (a non-randomised trial concerning children and adults at high risk) in the United States, and EPP-SCIT (a randomised trial concerning children at very high risk) in Europe. Another approach has also been attempted in diabetes as well as other diseases with an organ-specific autoimmune reaction (SEP, PR) i.e. oral administration of an antigen present at the reaction site. A positive effect has been shown by the group of H. Weiner in the NOD mouse in which islet infiltration was reduced and diabetes prevented by "oral tolerisation" with insulin. Oral insulin is easy to use in therapeutic studies and is currently being administered in two trials: DPT1 (prediabetic children and adults at moderate risk) in the United States, and DIOR (recently diabetic children and adults) in France. However, recent experimental data suggest that oral administration of an antigen in certain artificial circumstances can trigger an autoimmune reaction in the animal, which would indicate that due caution should be exercised in trials involving prediabetic patients.

Animals↗
PubMed1997

T-cell regulation in murine and human autoimmune diabetes: the role of TH1 and TH2 cells.

Insulin-dependent diabetes mellitus (IDDM) results from the destruction of pancreatic insulin-secreting cells by a T-cell-mediated autoimmune reaction. Distinct types of T helper cells (TH1 and TH2) have been characterised based on their cytokine secretion profiles following activation. Evidence from animal models favours the hypothesis that autoimmune diabetes is a TH1 response. However, there is no clear indication that a primary imbalance between protective TH2 and deleterious TH1 cells at early stages can trigger the autoimmune process. Protective CD4 + cells detected in nondiabetic young non-obese diabetic mice have not been shown to work through TH2 cytokines. In humans, there is little evidence that IDDM results from a TH1 response. Indeed, efficient experimental systems are lacking in humans to study the regulation of the autoimmune response in vitro. Interestingly, several immunotherapy strategies have aimed at inducing a TH2 response, even though TH2 cells have not been implicated in spontaneous disease development. However, recent ongoing trials in humans using oral administration of insulin to prevent diabetes are based on a protective mechanism which seems to depend essentially on transforming growth factor-beta. This cytokine is not dependent on TH1/TH2 dichotomy. Thus, although several attempts have been made to induce a TH1/TH2 switch to obtain a protective effect, a different and more complex mechanism probably (and paradoxically) accounts for the oral protection actually tested in animal models and humans.

Animals↗
PubMed1996

[Immunological prospects in the treatment of type 1 diabetes mellitus].

The first therapeutical trials using conventional immunosuppressive agents in recent onset type-1 diabetes mellitus have shown that such an approach can be efficient. However, remissions have remained inconstant and, when induced, transient. New approaches are being developed in experimental models in animals. Some, especially attempts to induce immune tolerance per os, could find rapid applications in the human.

Animals↗
PubMed1996

Contribution of DRB1*04 variants to predisposition to or protection from insulin dependent diabetes mellitus is independent of dq.

Certain DQ alpha/beta dimeric molecules have been shown to play a major role in determining susceptibility or resistance to IDDM. Whether or not predisposition associated with DR4 haplotypes is exclusively due to linkage to DQB1*0302 and DQA1*0301 alleles is still a controversial issue. A modifying effect of certain DRB1*04 subtypes on the susceptibility encoded by DQ alleles is possible, since not all DRB1*04-DQB1*0302 haplotypes are associated with the disease. The distribution of DRB1*04 subtypes was analysed in 240 DR4-positive Caucasian IDDM patients and 110 DR4-positive healthy controls using allele-specific hybridization after genomic amplification. Although an important contribution to IDDM predisposition was encoded by the DQB1*0302 allele which was found in the majority of patients (94.2% vs 64.7% in controls, Odd's ratio OR = 8.8, P < 0.0001), differences between DRB1*04 variants persisted after the effect of the DQB1 locus was removed by matching patients and controls for DQB1*0302. Thus, the DRB1*0402 allele conferred a strong IDDM-predisposing effect (OR = 3.1, P < 0.02) which was highly significant in the absence of DR3 on the second haplotype (OR = 5.6, P < 0.0001) but was not visible among DR3/4 heterozygote individuals. Conversely, the DRB1*0404 allele conferred a strong protective effect (OR = 0.26, P < 0.0001) which was dominant even in the presence of the associated high risk DR3 haplotype (OR = 0.21, P < 0.03). These data indicate that DQ molecules are not the sole contributors to the DR4-associated IDDM predisposition, and that peculiar DR4 subtypes play a significant role in susceptibility to or protection from the disease. DRB1*0402 differs from DRB1*0404 by only two acidic residues at positions 70 and 71 within the peptide binding groove, instead of amide and basic amino acids. This might induce changes of peptide binding specificity that correlate with the genetic linkage of IDDM predisposition.

Alleles↗
PubMed1996

Cyclosporine delays but does not prevent clinical onset in glucose intolerant pre-type 1 diabetic children.

We conducted a pilot study of immunosuppression with low dose cyclosporine in first degree relatives of diabetic patients with immunologic and metabolic criteria for preclinical diabetes: islet cell antibodies (ICA) > or = 20 Juvenile Diabetes Foundation (JDF) units, first phase insulin response < 10th percentile and impaired glucose tolerance. Cyclosporine was given at an initial dose of 7.5 mg/kg*d and tapered after the end of the first year. Six cyclosporine-treated relatives were compared to nine historical controls followed at the same or at different centres. All untreated patients developed diabetes within 12 months (5.9 +/- 1.1 months). Four of the cyclosporine-treated subjects developed diabetes at 5, 24, 24 and 47 months while the other two are non diabetic 47 and 57 months after entry into the trial (time to diabetes > 34 +/- 8 months, P < 0.001 vs the control group; Mann-Whitney test). First phase insulin response increased to normal values in two patients. These results suggest that reversible functional impairment, in association with beta-cell destruction, contributes to the failure of insulin secretion in preclinical type 1 diabetes.

Adolescent↗
PubMed1996

Absence of primary association between DM gene polymorphism and insulin-dependent diabetes mellitus or celiac disease.

The DMA and DMB genes encode class II-like heterodimetric molecules located in a specialized endocytic compartment, where they facilitate efficient loading of antigenic peptides on HLA class II molecules. Both genes are located within the MHC class II region and present a limited allelic polymorphism. Here we report the distribution of DM alleles in a group of 75 IDDM patients, 72 CD patients, and 162 random controls. We found a pronounced decreased frequency of DMA*0102 in both patient groups relative to controls. This difference was, however, mainly secondary to a strong negative linkage disequilibrium (LD) between this allele and the IDDM and CD-associated DRB1*03 allele. The DMB phenotype frequencies were similar in CD patients and controls. By contrast, we observed a decreased frequency of DMB*0101 and an increased frequency of DMB*0102 and DMB*0104 in IDDM patients. These differences disappeared when matching individuals for DRB1*03 or DRB1*04 alleles, which was in accordance with strong negative LD between DMB*0101 and DRB1*04 or DQB1*0302 alleles, and positive LD between DMB*0104 and DQB1*0201. Our data suggest that the apparent associations of IDDM or CD with given DM alleles are mostly secondary to primary associations with alleles at the DRB and DQB loci.

Celiac Disease↗
PubMed1996

Angiotensin converting enzyme inhibition and chronic cyclosporine-induced renal dysfunction in type 1 diabetes.

AIM: This study was designed to evaluate whether the angiotensin converting enzyme inhibitor enalapril could prevent cyclosporine-induced renal dysfunction in diabetic patients treated with CsA in monotherapy. DESIGN: Twenty-four recent onset insulin-dependent diabetic patients without prior renal involvement were randomized to receive a 3 month course of either cyclosporine (CsA) alone (7.5 mg/kg. b.i.d. in olive oil) or CsA+enalapril (20mg p.o. oad.). END POINTS: were mean arterial pressure, plasma creatinine, GFR, renal plasma flow, renal vascular resistance, sodium and lithium clearances measured before and after 3 months of treatment. RESULTS: Baseline values were identical in both groups except for mean arterial pressure which was slightly higher in the subjects subsequently receiving CsA + enalapril. Three month treatment with CsA increased significantly mean arterial pressure and renal vascular resistance by 9 and 24% respectively, while decreasing significantly glomerular filtration rate and renal plasma flow by 17 and 14% respectively. Enalapril was able to prevent the decline in GFR and the increase in blood pressure induced by CsA. This effect was demonstrated despite a similar increase in renal vascular resistance suggesting a dissociation between changes in glomerular filtration rate and renal vascular resistance during angiotensin converting-enzyme inhibition. CONCLUSION: Chronic angiotensin converting-enzyme inhibition could afford some degree of protection against CsA-induced renal dysfunction. Whether these results can be extrapolated to transplant recipients in whom CsA is usually associated to treatment by glucocorticosteroids deserves further evaluation.

Adult↗
PubMed1996

Long-term results of early cyclosporin therapy in juvenile IDDM.

In juvenile IDDM patients, immunosuppression with cyclosporin A allows partial beta-cell function recovery and transient remissions of insulin dependency. The effects of this therapeutic approach, however, have not been evaluated in the long-term, since no reported trial exceeded 1 year. Here we analyze 130 diabetic children followed at our institution during the first years of their disease. Cyclosporin was given to 83 of them at an initial dose of 7.2 +/- 0.1 mg.kg-1.day-1, which was decreased stepwise then interrupted after 6-62 months, depending on the response to therapy. A total of 47 diabetic children, who served as control subjects in two trials, were pooled for comparison. Over 4 years, the cyclosporin-treated group kept plasma C-peptide approximately twice as high as the control group (P < 0.02). It took 5.8 +/- 0.6 years for C-peptide secretion stimulated by glucagon to become undetectable in the cyclosporin group versus 3.2 +/- 0.6 years in the control group (P < 0.02). Average insulin dose remained lower by 0.2-0.4 U.kg-1.day-1 and glycated hemoglobin by approximately 1% in cyclosporin-treated patients (P < 0.02), who also had less hypoglycemia than the diabetic control subjects (P < 0.05). After 4 years, differences between the groups became nonsignificant. We observed no significant secondary effects of cyclosporin. In conclusion, positive effects of low-dose cyclosporin in recently diagnosed clinical IDDM patients are prolonged beyond interruption of the drug. The magnitude and duration of the benefit, however, do not appear sufficient to justify this immunosuppressive treatment in clinical practice.

Autoantibodies↗
PubMed1995

Pancreatic islet beta cells drive T cell-immune responses in the nonobese diabetic mouse model.

The role of autoantigens and that of target organs in which tissue lesions develop remains elusive in most spontaneous models of autoimmune diseases. Whether the presence of target autoantigens is required for the recruitment of autoreactive lymphocytes is unknown in most cases. To evaluate the importance of islet cells in the development of autoimmunity in the nonobese diabetic (NOD) mouse, we generated beta cell-deprived mice by injecting a high dose of alloxan, a toxic agent specific for beta cells. In contrast with spleen cells from 6-mo-old naive NOD mice which transfer diabetes in irradiated 8-mo-old male recipients, spleen cells from age-matched NOD mice which received a single injection of alloxan at 3 wk of age did not transfer diabetes. With the exception of the ability to transfer diabetes, beta cell-deprived NOD mice showed maintained immune competence. Furthermore, sialitis developed with the expected intensity and prevalence in beta cell-deprived mice. Already committed "diabetogenic" spleen cells collected from spontaneously diabetic mice also showed a reduced capacity to transfer diabetes after their removal from the diabetic mice and transient "parking" in beta cell-deprived mice. Taken together, our data bring evidence that involvement of autoreactive T cells detected by the capacity to transfer diabetes requires the presence of target beta cells.

Animals↗
PubMed1995

Lack of L-selectin expression by cells transferring diabetes in NOD mice: insights into the mechanisms involved in diabetes prevention by Mel-14 antibody treatment.

The process of mononuclear cell extravasation from the blood into the islets of Langerhans in nonobese diabetic (NOD) mice is dependent on the expression of a set of molecules, most of which remain to be defined. The observation that vascular addressins are expressed in inflamed islets raises the issue of the involvement of one of their ligands, L-selectin, in the pathogenesis of autoimmune diabetes. Treatment of NOD females with Mel-14, an antibody specific for L-selectin, reduced the spontaneous development of both insulitis and diabetes. Pretreatment of diabetic donors with Mel-14 decreased the capacity of their splenocytes to transfer the disease. However, the treatment of recipients had no effect on the transfer of diabetes by untreated diabetogenic splenocytes. To reconcile these apparently conflicting results, we fractionated spleen T cells from diabetic mice according to L-selectin expression. Diabetogenic cells were found only in the L-selectin subpopulation. Thus, diabetogenic cells in adult mice share phenotypic characteristics with activated/memory cells, and enter the pancreas using L-selectin-independent migratory pathways.

Animals↗