Emanuele Bosi

Islet autoantibody markers in IDDM : risk assessment strategies yielding high sensitivity

SummaryIdentification of islet autoantigens offers the possibility that antibody tests other than islet cell antibodies may be used for assessing risk of insulin-dependent diabetes mellitus (IDDM). The aim of this study was to determine the combination of islet autoantibody markers that could identify most future cases of IDDM. Islet cell antibodies, antibodies to glutamic acid decarboxylase (GAD)65, 37,000/ 40,000 Mr islet tryptic fragments, carboxypeptidase-H, and islet cell autoantigen (ICA)69 were measured in sera from 100 newly-diagnosed IDDM patients, 27 individuals prior to onset of IDDM, and 83 control subjects. Islet cell antibodies were detected in 88 % of IDDM patients and 81 % with pre-IDDM, GAD65 antibodies in 70 % of IDDM patients and 89 % with pre-IDDM, and antibodies to 37,000/40,000 Mr islet tryptic fragments in 54 % of IDDM patients and in 48 % with pre-IDDM. The latter were found only in conjunction with islet cell antibodies and were more frequent in young onset cases. All 20 IDDM patients and the 3 pre-IDDM subjects who had islet cell antibodies without GAD65 antibodies had antibodies to 37,000/40,000 Mr islet tryptic fragments, and all but one had disease onset before age 15 years. No sera strongly immunoprecipitated in vitro translated ICA69 or carboxypeptidase-H; 4 % of patients had anti-ICA69 and 11 % anti-carboxypeptidase-H levels above those of the control subjects. The findings suggest that none of the single antibody specificities are as sensitive as islet cell antibodies, but that a combination of GAD65 antibodies and antibodies to 37,000/40,000 Mr islet tryptic fragments has the potential to identify more than 90 % of future cases of IDDM. Such a strategy could eventually replace islet cell antibodies in population screening for IDDM risk assessment.

Islet autoantibodies in clinically diagnosed type 2 diabetes: prevalence and relationship with metabolic control (UKPDS 70)

Aims/hypothesisWe examined the prevalence of islet autoantibodies and their relationship to glycaemic control over 10 years in patients diagnosed clinically with new-onset type 2 diabetes.MethodsPatient clinical characteristics and autoantibody status were determined at entry to the UK Prospective Diabetes Study (UKPDS) before randomisation to different glucose control policies. Patients were followed for 10 years.ResultsData available on 4,545 of the 5,102 UKPDS patients showed that 11.6% had antibodies to at least one of three antigens: islet cell cytoplasm, glutamic acid decarboxylase and islet autoantibody 2A (IA-2A). Autoantibody-positive patients were younger, more often Caucasian and leaner, with lower beta cell function and higher insulin sensitivity than autoantibody-negative patients. They also had higher HbA1c, and HDL-cholesterol levels, and lower blood pressure, total cholesterol and plasma triglyceride levels. Despite relative hyperglycaemia, autoantibody-positive patients were less likely to have the metabolic syndrome (as defined by the National Cholesterol Education Program Adult Treatment Program III), reflecting a more beneficial overall risk factor profile. Of 3,867 patients with post-dietary run-in fasting plasma glucose (FPG) values between 6.0 and 14.9xa0mmol/l and no hyperglycaemic symptoms, 9.4% were autoantibody-positive, compared with 25.1% of 678 patients with FPG values of 15.0xa0mmol/l or higher, or hyperglycaemic symptoms. In both groups, no differences were seen between those with and without autoantibodies in changes to HbA1c over time, but autoantibody-positive patients required insulin treatment earlier, irrespective of the allocated therapy (p<0.0001).Conclusions/interpretationAutoantibody-positive patients can be treated initially with sulphonylurea, but are likely to require insulin earlier than autoantibody-negative patients.

Association of IA-2 autoantibodies with HLA DR4 phenotypes in IDDM

SummaryInsulin, glutamate decarboxylase (GAD) and the protein tyrosine phosphatase-like molecule IA-2 are major targets of humoral autoimmunity in insulin-dependent diabetes mellitus (IDDM). These autoantibodies are heterogeneous with respect to age and patient human leukocyte antigen (HLA) phenotype. We have previously demonstrated that GAD and IA-2 antibodies potentially identify different subsets of IDDM patients. The aim of this study was to determine whether GAD and IA-2 autoantibodies were associated with different HLA DR phenotypes. We studied 160 patients with IDDM onset before age 16 years. At disease onset serum was tested for GAD and IA-2 antibodies by immunoprecipitation of in vitro-translated35S-methionine labelled recombinant proteins. IA-2 antibodies were significantly associated with HLA DR4: 67 (86 %) of 78 patients with HLA DR4 vs 31 (38 %) of 82 non-DR4 patients had IA-2 antibodies (pc<0.0001) and IA-2 antibody levels were higher in patients with HLA DR4 (pc<0.0001). In contrast, GAD antibodies were more prevalent (pc<0.05) and antibody levels highest (pc<0.01) in patients with HLA DR3 phenotypes. These data provide further evidence that, in IDDM, production and titre of major autoantibody specificities are associated with HLA class II alleles.

Antibodies to tissue transglutaminase C in Type I diabetes

Aims/hypothesis. Silent coeliac disease is a gluten driven autoimmune disease which is relatively frequent in patients with Type I (insulin-dependent) diabetes mellitus. To determine the extent of gluten associated autoimmunity in Type I diabetes, autoantibodies to tissue transglutaminase C, a major autoantigen in coeliac disease, were measured in patients with new-onset Type I diabetes. Methods. We measured IgG and IgA tissue transglutaminase C autoantibodies using human recombinant antigen and radio-binding assays in a cohort of 287 patients with new-onset Type I diabetes, 119 with Type II (non-insulin-dependent) diabetes mellitus and in 213 control subjects. Results. We found IgA and IgG tissue transglutaminase C antibodies in 24 (8 %) patients with Type I diabetes; 97 (33 %) patients had IgG antibodies only and 1 IgA antibodies only. Antibody concentrations were highest in those with both IgA and IgG antibodies. Only 2 (2 %) patients with Type II diabetes and 2 (1 %) control subjects had either IgG or IgA tissue transglutaminase C antibodies. Patients with HLA DRB1*04 alleles had the highest prevalence of IgG tissue transglutaminase C antibodies. Conclusion/Interpretation. These data show that almost 10 % of patients have autoimmunity typical of coeliac disease and that another 30 % have low level tissue transglutaminase C antibody binding. This high prevalence suggests either involvement of the gut in the pathogenesis of Type I diabetes or that transglutaminase is a secondary autoantigen resulting from beta-cell destruction. [Diabetologia (1999) 42: 1195–1198]

Parameters associated with residual insulin secretion during the first year of disease in children and adolescents with Type 1 diabetes mellitus.

Factors associated with residual insulin secretion and spontaneous remission in Type 1 diabetic patients are important in the evaluation of treatment aimed at modifying the natural history of Type 1 DM. We investigated the effect of parameters at onset on residual beta cell function in 215 Type 1 DM children and adolescents. Blood gas analysis, HLA, GAD and IA‐2 antibodies before the start of insulin treatment were recorded for each patient. Residual C‐peptide secretion was assessed by the glucagon test, and parameters of metabolic control (HbA1c and insulin dose U kg−1 day−1) were examined at disease onset and after 3, 6, and 12 months. Residual C‐peptide secretion throughout the first year of disease was significantly reduced in patients with disease onset before age 5. Multiple regression analysis showed that low pH at onset showed a significant and independent association with reduced C‐peptide at 3 months (p = 0.02) and that the detection of GAD antibodies had a significant independent association with decreased C‐peptide secretion at 6 months of follow‐up (p = 0.02). Insulin requirement was higher in the youngest patients group and in patients with GAD antibodies. Spontaneous insulin remission (HbA1c <6 % and insulin <0.3 U kg−1 day−1) occurred in 22/192 (11 %) patients at 3 months of follow‐up, in 15/190 (8 %) patients at 6 months and in 8/169 (5 %) patient at 12 months. Remission was more prevalent in older patients (p = 0.01) and in patients without detectable GAD antibodies: (14/64 vs 8/128, p = 0.001). Sex, IA‐2 antibodies and HLA DR were not independently associated with C‐peptide secretion, insulin requirement or remission in the first year of Type 1 DM. This study confirms the association of young age, severe acidosis at disease onset, and GAD antibodies with decreased residual beta‐cell function and spontaneous remission during the first year of insulin treatment. These factors should be considered in trials evaluating therapies to retain beta‐cell function and induce remission at and after disease onset.

Autoantibodies to glutamic acid decarboxylase (GAD) detected by an immuno-trapping enzyme activity assay: relation to insulin-dependent diabetes mellitus and islet cell antibodies.

It has recently been proposed that the islet 64,000 Mr protein autoantigen (64K) of insulin-dependent diabetes mellitus (IDDM) is glutamic acid decarboxylase (GAD). We evaluated, by means of a newly developed immunotrapping enzyme activity assay (ITEAA), the prevalence of circulating GAD-autoantibodies (Ab) in a large population of IDDM patients (n = 168), blood donors (n = 87) and non-diabetic autoimmune patients (n = 40). The latter two groups were used as controls. Overall, GAD-Ab were found in 22% of IDDM patients, but in none of the two control groups (P = 0.007). These specificities were invariably associated with islet cell antibodies (ICA) (31.6% in IDDM with ICA vs 0 in IDDM without ICA, P = 0.0001), and this prevalence was higher in sera with high titer ICA (54.5% in IDDM with ICA greater than 80 JDF-units vs 22.6% of IDDM with ICA 5-80 JDF units; P = 0.002). Moreover, GAD-Ab were associated with the female sex (P = 0.002) and the concomitant presence of thyroid and/or gastric antibodies (P = 0.002). No correlation was observed between GAD-Ab and age of the patients, duration of IDDM, or associated non-organ specific antibodies. Our study indicates that GAD-Ab measured by ITEAA are: (1) detected in a proportion of IDDM patients; (2) strongly associated with ICA; (3) preferentially found in IDDM female patients with autoimmune polyendocrine serology; and (4) detected with lower frequency than that reported for 64K-Ab in IDDM.

Low prevalence of islet autoimmunity in adult diabetes and low predictive value of islet autoantibodies in the general adult population of northern Italy

Aims/hypothesis. To assess the prevalence of islet autoimmunity in adult-onset diabetes mellitus and the predictive value of islet autoantibodies in the general adult population of northern Italy. Methods. A sample of 2076 people aged 40 years or more participating in the population-based Cremona Study and classified in 1990 as having diabetes mellitus, impaired and normal glucose tolerance according to WHO criteria after an oral glucose tolerance test, were tested for antibodies to glutamic acid decarboxylase and IA-2. Results. Increased concentrations of glutamic acid decarboxylase antibodies were found in 4 (2.8 %) of 143 participants with known diabetes and none of 50 with previously unknown diabetes, 1 (0.65 %) of 153 with impaired and 18 (1.0 %) of 1718 with normal glucose tolerance. The increased prevalence of these antibodies in subjects with known diabetes was not statistically significant. Protein tyrosine phosphatase IA-2-antibodies were found in only four subjects, two of whom also had glutamic acid decarboxylase antibodies, all with normal glucose tolerance. After 8 years of follow-up, none of 21 non-diabetic subjects with either glutamic acid decarboxylase or IA-2-antibodies had developed diabetes and only a slight deterioration from normal to impaired fasting glucose was observed in 3 of 15 subjects with previous normal glucose tolerance. Conclusion/interpretation. This study has shown that in northern Italy the prevalence of adult autoimmune diabetes in the general adult population is 0.19 % (95 % CI 0.05–0.5); that autoimmune diabetes represents only a minority of all cases of adult diabetes; and that islet autoantibodies are not a high-risk factor for diabetes development in adults with normal glucose tolerance over 8 years of follow-up. [Diabetologia (1999) 42: 840–844]

Endocrine responses of type 1 (insulin-dependent) diabetic patients following successful pancreas transplantation.

SummaryThe aim of the present study was to evaluate the insulin and glucagon responses to various stimuli in patients following pancreatic transplantation. Four Type 1 (insulin-dependent) diabetic patients with end-stage renal failure who had received a cadaveric segmental, neoprene-injected, pancreas transplant, in association with kidney transplantation, were investigated. Free-insulin, pancreatic glucagon, and growth hormone concentrations were measured after both oral and intravenous glucose tolerance tests, and following tolbutamide, arginine and arginine plus somatostatin infusions. Tests were performed 1 month (three cases) and 30 months (one case) after surgery, when no insulin administration was required. Four non-diabetic kidney grafted patients, matched for duration of graft survival and immunosuppressive treatment (steroids, azathioprine and anti-lymphocyte-globulins), served as control subjects. Impaired glucose tolerance was present in all diabetic and control patients. This was possibly related to immunosuppressive treatment. In comparison with control subjects, insulin release was normal in response to arginine and tolbutamide but was reduced in response to oral and intravenous glucose, while glucagon and growth hormone release were similar in both groups. Somatostatin was less effective in diabetic patients than in control subjects in suppressing insulin and glucagon release.

Association of TCF7L2 gene variants with low GAD autoantibody titre in LADA subjects (NIRAD Study 5).

Diabet. Med. 27, 701–704 (2010)

Chronic continuous intraperitoneal insulin infusion (CIPII) in type I diabetic patients non-satisfactorily responsive to continuous subcutaneous insulin infusion (CSII).

SummarySix unstable C-peptide negative type I diabetic patients who had been previously treated with continuous subcutaneous insulin infusion (CSII) for at least one year without achieving satisfactory metabolic control, were admitted to this study and switched to continuous intraperitoneal insulin infusion (CIPII). The results obtained with the two treatments have been compared from the metabolic and clinical points of view. CIPII produced a decrease in HbA1c (p<0.05), in MAGE value (p<0.005), in the percentage of blood glucose determinations above 14 mmol/l (p<0.05) and below 3.9 mmol/l (p<0.05); an increase in serum cholesterol, and a decrease in HDL-cholesterol (p<0.05) due to a reduction of the HDL2 fraction (p<0.01). A mean body weight reduction of 3 kg was observed during CIPII (p<0.01), not related to dietary changes or to a reduction of the daily insulin dose. Twenty-four hour metabolic profiles during CIPII showed lower mean plasma glucose (p<0.001), serum free insulin (p<0.001), blood β-OH-butyrate (p<0.001), and higher serum glycerol (p<0.001) as compared to CSII. It is concluded that CIPII may be of clinical value in the out-patient management of unstable type I diabetic patients, and that metabolic modifications induced by CIPII are not limited to changes in glucose utilization and production, but include changes in triglyceride, cholesterol and lipid metabolism which may have clinical relevance.