Antibodies to glutamic acid decarboxylase reveal latent autoimmune diabetes mellitus in adults with a non-insulin-dependent onset of disease

Type 1 and type 2 diabetes: what do they have in common?

Type 1 and type 2 diabetes frequently co-occur in the same families, suggesting common genetic susceptibility. Such mixed family history is associated with an intermediate phenotype of diabetes: insulin resistance and cardiovascular complications in type 1 diabetic patients and lower BMI and less cardiovascular complications as well as lower C-peptide concentrations in type 2 diabetic patients. GAD antibody positivity is more common in type 2 diabetic patients from mixed families than from common type 2 diabetes families. The mixed family history is associated with more type 1-like genetic (HLA and insulin gene) and phenotypic characteristics in type 2 diabetic patients, especially in the GAD antibody-positive subgroup. Leaving out the extreme ends of diabetes phenotypes, young children progressing rapidly to total insulin deficiency and strongly insulin-resistant subjects mostly with non-Europid ethnic origin, a large proportion of diabetic patients may have both type 1 and type 2 processes contributing to their diabetic phenotype.

Latent autoimmune diabetes in adults (LADA) should be less latent

'Latent autoimmune diabetes in adults' (LADA) is the term coined to describe adults who have a slowly progressive form of autoimmune or type 1 diabetes that can be treated initially without insulin injections. The diagnosis of LADA is currently based on three clinical criteria: (1) adult age at onset of diabetes; (2) the presence of circulating islet autoantibodies, which distinguishes LADA from type 2 diabetes; and (3) insulin independence at diagnosis, which distinguishes LADA from classic type 1 diabetes. The prevalence of LADA in adults presenting with non-insulin-requiring diabetes is approximately 10%. Recognition of LADA expands the concept and prevalence of autoimmune diabetes, but LADA remains poorly understood at both a clinical and research level. In this perspective, we review the nomenclature, diagnostic criteria, genetics, pathology and therapy of LADA, to arrive at recommendations that might advance knowledge and management of this form of diabetes.

Developments in the prediction of type 1 diabetes mellitus, with special reference to insulin autoantibodies

The prodromal phase of type 1 diabetes is characterised by the appearance of multiple islet-cell related autoantibodies (Aab). The major target antigens are islet-cell antigen, glutamic acid decarboxylase (GAD), protein-tyrosine phosphatase-2 (IA-2) and insulin. Insulin autoantibodies (IAA), in contrast to the other autoimmune markers, are the only beta-cell specific antibodies. There is general consensus that the presence of multiple Aab (> or = 3) is associated with a high risk of developing diabetes, where the presence of a single islet-cell-related Aab has usually a low predictive value. The most commonly used assay format for the detection of Aab to GAD, IA-2 and insulin is the fluid-phase radiobinding assay. The RBA does not identify or measure Aab, but merely detects its presence. However, on the basis of molecular studies, disease-specific constructs of GAD and IA-2 have been employed leading to somewhat improved sensitivity and specificity of the RBA. Serological studies have shown epitope restriction of IAA that can differentiate diabetes-related from unrelated IAA, but current assays do not distinguish between disease-predictive and non-predictive IAA or between IAA and insulin antibodies (IA). More recently, phage display technology has been successful in identifying disease-specific anti-idiotopes of insulin. In addition, phage display has facilitated the in vitro production of antibodies with high affinity. Identification of disease-specific anti-idiotopes of insulin should enable the production of a high affinity reagent against the same anti-idiotope. Such a development would form the basis of a disease-specific radioimmunoassay able to identify and measure particular idiotypes, rather than merely detect and titrate IAA.

Epitope analysis of insulin autoantibodies using recombinant Fab

Autoantibodies to insulin are often the first autoantibodies detected in young children with type 1 diabetes and can be present before the onset of clinical diabetes. These autoantibodies and their epitopes are, however, not well characterized. We explored the use of monoclonal antibodies and their recombinant Fab as reagents for epitope analysis. In this study we cloned and characterized the recombinant Fab of the insulin-specific monoclonal antibody CG7C7. We found the epitope of this antibody to be located predominantly at the A-chain loop of the insulin molecule. The recombinant Fab was then used to compete for insulin binding against insulin autoantibodies present in sera from patients with type 1 or type 1.5 diabetes. In competition experiments with sera positive for autoantibodies to insulin the recombinant Fab significantly reduced the binding to [125I]-insulin by sera of type 1 (n = 35) and type 1.5 diabetes [latent autoimmune diabetes in adults (LADA)] (n = 14) patients (P < 0.0001). We conclude that competition between insulin-specific monoclonal antibodies or their recombinant Fab and insulin autoantibodies should prove useful in the epitope analysis of autoantibodies to insulin.

Six-year follow-up of pancreatic β cell function in adults with latent autoimmune diabetes

AIM: To investigate the characteristics of the progression of islet β cell function in Chinese latent autoimmune diabetes in adult (LADA) patients with glutamic acid decarboxylase antibody (GAD-Ab) positivity, and to explore the prognostic factors for β cell function.

METHODS: Forty-five LADA patients with GAD-Ab positivity screened from phenotypic type 2 diabetic (T2DM) patients and 45 T2DM patients without GAD-Ab matched as controls were followed-up every 6 mo. Sixteen patients in LADA1 and T2DM1 groups respectively have been followed-up for 6 years, while 29 patients in LADA2 and T2DM2 groups respectively for only 1.5 years. GAD-Ab was determined by radioligand assay, and C-peptides (CP) by radioimmune assay.

RESULTS: The percentage of patients whose fasting CP (FCP) decreased more than 50% compared with the baseline reached to 25.0% at 1.5^th year in LADA1 group, and FCP level decreased (395.8±71.5 vs 572.8±72.3 pmol/L, P<0.05) at 2.5^th year and continuously went down to the end of follow-up. No significant changes of the above parameters were found in T2DM1 group. The average decreased percentages of FCP per year in LADA and T2DM patients were 15.8% (4.0-91.0%) and 5.2% (-3.5 to 35.5%, P = 0.000) respectively. The index of GAD-Ab was negatively correlated with the FCP in LADA patients (r_s = -0.483, P = 0.000). The decreased percentage of FCP per year in LADA patients were correlated with GAD-Ab index, body mass index (BMI) and age at onset (r_s = 0.408, -0.301 and -0.523 respectively, P<0.05). Moreover, GAD-Ab was the only risk factor for predicting β cell failure in LADA patients (B = 1.455, EXP (B) = 4.283, P = 0.023).

CONCLUSION: The decreasing rate of islet β cell function in LADA, being highly heterogeneous, is three times that of T2DM patients. The titer of GAD-Ab is an important predictor for the progression of islet β cell function, and age at onset and BMI could also act as the predictors.

IA-2 antibody prevalence and risk assessment of early insulin requirement in subjects presenting with type 2 diabetes (UKPDS 71)

AIMS/HYPOTHESIS

Established autoimmune markers of type 1 diabetes, including islet cell autoantibodies (ICA) and autoantibodies to glutamic acid decarboxylase (GADA) have been used to screen people presenting with type 2 diabetes for latent autoimmune diabetes in adults. We have examined the prevalence of autoantibodies to protein tyrosine phosphatase isoforms IA-2 (IA-2A) and IA-2beta/phogrin (IA-2betaA) in a cohort of adult UKPDS patients thought to have type 2 diabetes, and investigated the possible role of these autoantibodies in predicting requirement for insulin therapy.

METHODS

IA-2A and IA-2betaA were measured by a validated radioimmunoassay with human recombinant autoantigens in 4,169 white Caucasian patients aged 25-65 years and newly diagnosed with type 2 diabetes. The clinical requirement for insulin therapy within 6 years was examined in 2,556 patients not randomised to insulin.

RESULTS

IA-2A and IA-2betaA were present in 2.2 and 1.4%, respectively, of these patients. IA-2A were more prevalent in younger patients (p for trend <0.00001), more often associated with the HLA-DR4 allele (26.3 vs 8.0%, p<0.0001), and their presence increased the likelihood of insulin therapy requirement within 6 years from diagnosis [relative risk (95%CI) 12.2 (9.8-15.3)]. The presence of IA-2A together with GADA increased the relative risk of requiring insulin therapy from 5.4 (4.1-7.1) for GADA alone to 8.3 (3.7-18.8) and the corresponding positive predictive value from 33 to 50%.

CONCLUSIONS/INTERPRETATION

In type 2 diabetes, the presence of IA-2A is infrequent, associated with the HLA-DR4 haplotype, and highly predictive of future need for insulin therapy. The measurement of IA-2betaA does not provide additional information.

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

AIMS/HYPOTHESIS

We 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.

METHODS

Patient 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.

RESULTS

Data 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 14.9 mmol/l and no hyperglycaemic symptoms, 9.4% were autoantibody-positive, compared with 25.1% of 678 patients with FPG values of 15.0 mmol/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/INTERPRETATION

Autoantibody-positive patients can be treated initially with sulphonylurea, but are likely to require insulin earlier than autoantibody-negative patients.

Seroconversion of glutamic acid decarboxylase antibodies in a patient initially diagnosed as having type 2 diabetes mellitus

A 61-year-old man admitted in July 1998 had suffered from thirst, polydipsia and polyuria for three years. Diet and transient insulin therapy had induced good blood glucose control which was maintained by metformin hydrochloride for a year. Although it worsened, conventional insulin treatment re-implemented good blood glucose control. Glutamic acid decarboxylase antibodies (GAD-Ab) had been negative up to this point. After 8 months, blood glucose levels became elevated. To date, the GAD-Ab has been positive (112-120 U/ml), and the serum and urine C-peptide levels are decreased. Seroconversion of GAD-Ab should be noted in patients initially diagnosed as having GAD-Ab negative type 2 diabetes mellitus.

Rosiglitazone combined with insulin preserves islet beta cell function in adult-onset latent autoimmune diabetes (LADA)

BACKGROUND

LADA is thought to result from the chronic autoimmune destruction of the insulin-producing pancreatic beta cells. In addition to antidiabetic effects, the newly developed insulin sensitizer-thiazolidinediones have the potential to increase the insulin content of islet cells by downregulating local inflammation and autoimmune response. Therefore, we hypothesized that LADA patients might benefit from thiazolidinediones treatment.

METHODS

LADA patients, with a fasting C-peptide (FCP) of 0.3 nmol/L or more, were enrolled and randomly assigned to receive subcutaneous insulin alone (insulin group, n = 12) or rosiglitazone plus insulin (insulin + RSG group, n = 11) to compare the impacts on islet beta cell function. Plasma glucose, HbA 1c, fasting C-peptide (FCP) and C-peptide after 2 h 75-g glucose load (PCP) were determined every 6 months. GAD-Ab and C-peptide were measured with radioimmune assays. Islet beta cell function was evaluated by PCP and DeltaCP(DeltaCP = PCP-FCP).

RESULTS

All of the 23 patients have been followed up for 6 months, 17 cases for 12 months and 14 for 18 months. (1) During 6 months' follow-up, there were no significant changes for DeltaCP and PCP levels in both groups. (2) PCP and DeltaCP levels in insulin + RSG group patients stayed steady during the 12 months' observation (P = 0.161 for both PCP and DeltaCP), while in the insulin alone group, both FCP (P = 0.021) and PCP (P = 0.028) levels decreased significantly. Furthermore, PCP (P = 0.004) and DeltaCP(P = 0.015) differences between 12th month and baseline were higher in insulin + RSG group than those in the insulin group. (3) When observed up to 18 months, PCP and DeltaCP levels in insulin + RSG group patients still stayed steady, while PCP and DeltaCP levels decreased more in the insulin alone group.

CONCLUSIONS

This pilot study suggests that rosiglitazone combined with insulin may preserve islet beta cell function in LADA patients.

Glycemic management of type 2 diabetes: an emerging strategy with oral agents, insulins, and combinations

The many antihyperglycemic preparations are best used for type 2 diabetes in a logical sequence, using combinations of agents, with clear targets for glycemic control. On the basis of long familiarity, proven benefit and known side effects, and low cost, the sulfonylureas, metformin, and insulin still deserve to be the standard treatments. As shown in the central shaded area of Fig. 4, standard treatment begins with monotherapy and progresses to oral combination therapy and then to two oral agents plus basal insulin. Several triggers for deviation from the standard methods are identified (see Fig. 4). The incidence of each of the conditions that require early individualized treatment has not been studied, but it seems reasonable to estimate no more than 10% each for a strongly symptomatic presentation, inability to use a sulfonylurea or metformin, inability to use insulin, or an early need for prandial therapy. If this estimate is correct, approximately two thirds of patients who are diagnosed with type 2 diabetes should do well with standard therapy for up to 10 years using the standard methods shown. Eventually, many more will need individualized treatment to maintain glycemic control. This scheme is certain to evolve as further information on the nonglycemic benefits (or hazards) of the various therapies appears and as new treatments are released. Notably, agents that mimic or potentiate the effects of gastrointestinal peptides, such as amylin and GLP- 1 analogues and dipeptidyl peptidase IV inhibitors, are likely to alter the current algorithm. For now, systematic application of the scheme (see Fig. 4) should improve the success of treatment greatly from its currently disappointing level.

Variable number of tandem repeats of the insulin gene determines susceptibility to latent autoimmune diabetes in adults

BACKGROUND

The different clinical presentations of latent autoimmune diabetes in adults (LADA) and type 1 diabetes mellitus may be the result of susceptibility genes in determining the mode of onset. We analyzed the 5' polymorphisms of the insulin mini-satellite region (INS), a variable number of tandem repeats (VNTR) [repeat units; RU]. We evaluated the association of the different INS-VNTR alleles in patient susceptibility to LADA autoimmune diabetes. To our knowledge, this constitutes the first study of this kind performed in a Caucasian population.

METHODS

From an group of 160 Argentinean patients previously characterized as having LADA, we selected 44 patients who presented with humoral autoimmunity for genotyping and compared them to 88 patients with type 1 diabetes and 138 healthy individuals. The INS-VNTR allele classes were determined by Southern blotting (class I: 21-44RU; class III: 138-159RU). Subjects with class I alleles were further studied using PCR amplification to determine the exact length of the alleles (short 1S: 22-37RU; medium 1M: 38-41RU; large 1L: 42-43RU). Allelic and genotype frequencies were estimated by chi(2) tests for independence with 2 x 2 contingency tables and the relative risks (RR) were determined using GraphPad InStat software.

RESULTS

We observed differential associations among the class I alleles when comparing patients with LADA (80.6%) and type 1 diabetes (81.3%) with the controls (70%; p < 0.005). This increase was largely due to the high frequency of the 1S/S genotype (63.6% LADA vs 37% controls, with a p-value of 0.0019 [p1]; 53.4% type 1 diabetes vs 37% controls, with a p-value of 0.0149 [p2]). Remarkably, all LADA patients genotyped as class I homozygous had the shorter (S) class I allele (100%). Differences in the overall 1S distribution were observed: in LADA the 94.4% of the alleles were equal to or smaller than 35RU, while in patients with type 1 diabetes it was 78.3% and in controls 74.1%. Moreover, the relative risks associated with the 1S/S genotype for patients with LADA showed a substantial increase with respect to those with type 1 diabetes (52%) when we compare them to the controls (1S/S LADA/control, 2.282 [RR1] vs type 1 diabetes/control, 1.497 [RR2]).

CONCLUSION

The presence of the 1S allele could be considered a risk factor in LADA patients, as previously reported for type 1 diabetes. The class I INS-VNTR allele in LADA increases genetic susceptibility to disease development.

Belgian consensus on metabolic problems associated with atypical antipsychotics

A workshop was convened by a panel of psychiatrists, diabetologists and pharmacists from major Belgian hospitals to review the latest information relating to the risks with second-generation antipsychotics (SGA) for the development of metabolic disorders, especially impaired glucose tolerance, diabetes mellitus and dyslipidemia. The panelists sought to formulate recommendations for practising psychiatrists when initiating and maintaining therapy with SGA, and for the switch of SGA or initiation of further treatment if metabolic complications occur. In addition, recommendations for counselling of the patient and for the cooperation between the psychiatrist and the general physician or diabetologist, respectively, were provided.

Optimal Cutoff Point of Glutamate Decarboxylase Antibody Titers in Differentiating Two Subtypes of Adult-Onset Latent Autoimmune Diabetes

The optimal cutoff point of glutamate decarboxylase antibody (GAD-Ab) titers for differentiating two latent autoimmune diabetes (LADA) subtypes remains unclear. One hundred and forty-five GAD-Ab-positive patients screened from phenotypic type 2 diabetes were diagnosed as LADA. The clinical features were compared among LADA patients with different GAD-Ab titers. The receiver-operating characteristic (ROC) curve was used to evaluate the diagnostic value of GAD-Ab titers and to define the optimal cutoff point. The heterogeneity of clinical features in LADA could be discriminated by five GAD-Ab titers, with maximal differences at the titer of 175 U/mL. The ROC curve analysis showed that the optimal cutoff point for discriminating two LADA subtypes was at the titer of 175 U/mL, with sensitivity and specificity of 54.5% and 92.1%, respectively. These findings demonstrated that the two clinically distinct subtypes of LADA can be optimally discriminated by the GAD-Ab titers.

Phenotypic characteristics of GAD antibody-positive recently diagnosed patients with type 2 diabetes in North America and Europe

A number of patients with type 2 diabetes are GAD antibody positive. A Diabetes Outcome Progression Trial (ADOPT) is a randomized, double-blind clinical trial in recently diagnosed drug-naive patients with type 2 diabetes that allows for the evaluation of GAD positivity in the context of anthropometric and biochemical characteristics. Of the 4,134 subjects enrolled in ADOPT for whom GAD status was obtained, 174 (4.2%) were GAD positive, with the prevalence of GAD antibodies being similar in North America (4.7%) and Europe (3.7%). Although BMI and age were similar, GAD-positive patients had a lower fasting insulin level, compatible with them being more insulin sensitive. The lower fasting insulin concentration was accompanied by a decreased early insulin response to oral glucose. However, when this insulin response was corrected for the degree of insulin sensitivity, GAD-positive and -negative patients had similar beta-cell function. Consistent with the difference in insulin sensitivity, GAD-positive patients had higher HDL cholesterol and lower triglyceride levels. In the GAD-positive individuals, the prevalence of the metabolic syndrome as defined by NCEP ATP III (National Cholesterol Education Program Adult Treatment Panel III) was also lower (74.1 vs. 83.7%, P = 0.0009). These phenotypic differences may underlie a potential difference in the natural history of hyperglycemia and its clinical outcomes.

Metabolic, immunological and clinical characteristics in newly diagnosed Asian diabetes patients aged 12-40 years

AIM

To describe the clinical, biochemical and immunological characteristics of young-onset diabetes in Asia.

METHODS

Clinical, biochemical and immunological variables were assessed in 919 newly diagnosed (duration less than 12 months) young onset Asian diabetic patients aged between 12 and 40 years. The subjects constituted 57% Chinese, 29% Indians and 14% Malays, recruited from diabetes centres in China, Hong Kong, India, Malaysia and Singapore.

RESULTS

The mean age (+/- sd) was 31.6 +/- 7.2 years, with the majority (66%) in the 31-40 years age group. Mean body mass index (BMI) (+/- sd) was 25.3 +/- 5.0 kg/m2 with 47% exceeding the suggested Asian cut-off point for obesity (BMI > or = 25). Ethnic difference in clinical characteristics included BMI, blood pressure, mode of treatment and degree of insulin resistance. Most patients had a clinical presentation of Type 2 diabetes. About 10% had a classical combination of ketotic presentation, presence of autoimmune-markers and documented insulin deficiency indicative of Type 1 diabetes. Forty-eight percent were receiving oral hypoglycaemic agents (OHAs) while 31% were on diet only, 18% were receiving insulin and 2% were on a combination of insulin and OHA.

CONCLUSION

Young onset diabetes patients in Asia represent a heterogeneous group in terms of their clinical and biochemical characteristics and classical Type 1 diabetes is relatively uncommon. The 5-year follow up study will determine the progress of these patients and help to clarify the natural history.

Low prevalence of autoimmune diabetes markers in a mixed ethnic population of Singaporean diabetics

BACKGROUND

Circulating antibodies to glutamic acid decarboxylase (GADab) and tyrosine phosphatase-like molecule IA-2 (IA-2ab) are major indicators for auto-immune destruction of pancreatic islet cells. They identify a majority of Caucasians with type 1 diabetes and approximately 50% of Asians, providing evidence of an idiopathic aetiology in the latter. The present study investigated these autoantibodies in a mixed ethnic group.

METHODS

Hospital clinic patients with clinically defined type 1 (n = 93) and type 2 (n = 300) diabetes and representing Singapore's major ethnic groups--Chinese, Indians and Malays--were studied. GADab and IA-2ab frequencies, and association of autoimmunity status with clinical and biochemical profiles were analysed.

RESULTS

Radio-immunoprecipitation assays detected either or both antibodies (seropositivity) in 41.9% of subjects with type 1 diabetes. GADab was detected in 36.6% and IA-2ab in 23.7% of type 1 diabetics. Prevalence of IA-2ab showed a reduction in frequency with disease duration (P = 0.026). In clinical type 2 diabetics, seropositivity was 10.0% with higher frequency in Malays (17.5%) than Chinese (9.7%) and Indians (4.5%). Multivariate analysis revealed that low fasting C-peptide was associated with seropositivity (odds ratio (OR) = 0.15; 95% confidence interval (CI) = 0.04-0.58). A significant relationship (OR = 13.5; 95% CI = 5.0-36.7) between insulin requirement and duration (>5 years) was also revealed. In patients with type 2 diabetes there was a trend of gradual progression to insulin dependency. However, there was considerable variation in body mass index between ethnic subgroups of type 2 diabetics, particularly for Chinese (mean (SD) = 26.0 (4.7)) and Malays (mean (SD) = 29.2 (5.9); P < 0.001).

CONCLUSIONS

Presence of both antibodies in our mixed ethnic group of type 1 diabetes patients was much lower than in Caucasians. Significant numbers of patients were seronegative for antibodies. Influences due to ethnicity and adiposity would require further investigations.

A clinically orientated approach increases the efficiency of screening for latent autoimmune diabetes in adults (LADA) in a large clinic-based cohort of patients with diabetes onset over 50 years

AIMS

To assess if a clinically orientated approach improves screening for latent autoimmune diabetes in adults (LADA) in patients developing diabetes over age 50.

METHODS

From a clinic-based cohort of 3327 patients with Type 2 DM diagnosed over age 50 we recruited those with at least one feature suggestive of insulin deficiency: (i) fasting blood glucose > or = 15 mmol/l and/or HbA(1c) > or = 10% in spite of adequate compliance to diet and treatment; (ii) decreasing body weight > or = 10% in the previous 3 months in spite of constant diet; (iii) BMI < 25 mg/kg(2). A control group of 240 patients not presenting any of the previous criteria was randomly selected from the out-patient clinic.

RESULTS

We identified 220 (6.6%) patients, of whom 70 were positive for glutamic acid decarboxylase antibodies (GADA) and/or islet cell antibodies (ICA), giving a prevalence of LADA of 31.8% (95% CI 25.7-38.4). In contrast, no patient randomly selected from the remaining cohort had marker positivities. With respect to patients negative for both ICA and GADA, those who were positive had lower C-peptide values (0.53 +/- 0.51 vs. 0.88 +/- 0.42 nmol/l, P < 0.001); the lowest levels were found in patients in whom both antibodies were positive. In linear regression analysis, variables independently associated with fasting C-peptide were GADA (beta = -0.25, P < 0.001), ICA (beta = -0.15, P = 0.04), BMI (beta = 0.03, P < 0.001) and duration of diabetes (beta = -0.02, P < 0.001).

CONCLUSION

This study shows that: (i) a clinically orientated approach increases the efficiency of a screening programme for LADA, so that one in three screened patients are classified correctly; (ii) ICA and GADA positivity were negatively associated with residual beta-cell function, independent of BMI and duration of the disease; (iii) positivity for both ICA and GADA identifies patients with the lowest residual beta-cell function.

Coronary heart disease risk assessment in diabetes mellitus: comparison of UKPDS risk engine with Framingham risk assessment function and its clinical implications

AIMS

To assess differences between absolute coronary heart disease (CHD) risks calculated by Joint British Societies (JBS) risk calculator and UKPDS risk engine and its impact on CHD primary prevention management in diabetes mellitus (DM).

METHODS

Seven hundred Type 2 DM patients without arterial complications were identified from nine general practices in the Scarborough area. Their absolute 10-year CHD risks were calculated. The differences in the proportion of patients identified for aspirin and statin under JBS and National Institute for Clinical Excellence (NICE) guidelines by these two methods were determined. The proportion of additional patients identified for statin in the Scarborough population as a consequence of CHD risk threshold reduction from 30 to 15% (as recommended by NICE) was also determined.

RESULTS

UKPDS risk engine calculated significantly higher mean 10-year CHD risk (UKPDS vs. JBS, 21.5 vs. 18.3%, P < 0.0001). Both methods identified approximately 65% of patients to be eligible for aspirin and statin if NICE recommendations were followed. At a risk threshold of 30%, the UKPDS risk engine identified more patients for statin. Reducing the CHD risk threshold from 30 to 15% for statin initiation will identify an additional 0.5% of the total population for this treatment.

CONCLUSIONS

Both methods are comparable in identifying at-risk patients under NICE recommendations. A high proportion has risk levels that merits primary CHD prevention. Lowering the risk threshold for statin treatment has a small numerical impact on the whole population.

IA-2 autoantibodies are predominant in latent autoimmune diabetes in adults patients from eastern India

Autoimmune diabetes or latent autoimmune diabetes in adults (LADA) among the clinically diagnosed type 2 diabetes patients from Cuttack in Eastern India was studied. GAD65 and IA-2 autoantibodies were measured by radioligand binding assay using recombinant human GAD65 and IA-2. The frequency of GAD65 was not significantly different between patients and controls. However, IA-2 antibodies were predominant in LADA patients and there were two distinct peaks, one in the age group of 20 to 30 years and another in the age group of 50 to 60 years. The data suggest that LADA is more frequent in Eastern Indian T2DM patients and the IA-2 is the predominant autoantibody in this population.

Frequency of latent autoimmune diabetes in adults in Asian patients diagnosed as type 2 diabetes in Birmingham, United Kingdom

The aims of our study were to measure autoantibodies to glutamic acid decarboxylase and autoantibodies to protein tyrosine phosphatase in patients with type 2 diabetes mellitus, patients with impaired glucose tolerance, and healthy controls of Asian origin from Birmingham, United Kingdom. According to our findings, 27% (9/33) of patients initially diagnosed with type 2 diabetes mellitus carry autoantibodies to GAD65.

The Role of C-Peptide Levels in Screening for Latent Autoimmune Diabetes in Adults

Early detection of latent autoimmune diabetes in adults (LADA) is important in that the earlier insulin therapy is initiated, the greater the preservation of pancreatic beta cells. This study assessed whether a random C-peptide level is an effective screening test for LADA. Random C-peptide levels were measured in 39 subjects with LADA and 39 subjects with type 2 diabetes who were matched for age, race, gender, and duration of diabetes. LADA was definitively diagnosed by the presence of antiglutamic acid decarboxylase antibodies. The mean C-peptide level in the LADA group was 1.0 +/- 0.2 ng/mL and 5.1 +/- 0.4 ng/mL in the group with type 2 diabetes. Only 1 LADA subject had a C-peptide level above the normal range, and all subjects with type 2 diabetes had a C-peptide level within or above the normal range. LADA can be ruled out in adult-onset diabetes by the presence of elevated C-peptide. The more expensive testing for anti-GAD antibodies to definitively diagnose LADA should be reserved for patients who on screening have a low or normal random C-peptide level.

Detection of GAD-Reactive CD4+ Cells in So-Called “Type 1B” Diabetes

OBJECTIVE

Although the majority of type 1 diabetes is considered to be type 1A, some patients with type 1 diabetes have no islet-associated autoantibody in their serum. This type of type 1 diabetes has usually been diagnosed as type 1B on the basis of islet-associated autoantibody-negativity. In this study, we tried to demonstrate the existence of islet-associated antigen-specific T cells in type 1 diabetes without islet-associated autoantibody.

RESEARCH DESIGN AND METHODS

Peripheral blood samples were obtained from 110 Japanese diabetic patients, including 15 type 2 diabetic patients. Measurement of islet-associated antigen-specific cytokine response was performed by intracellular cytokine staining for flow cytometry.

RESULTS

The number of GAD-reactive IFN-gamma-producing CD4+ cells in 50,000 CD4+ cells in diabetics with type 1B (113.6 +/- 34.6, median 45), type 1A (132.4 +/- 33.3, median 25), and LADA (154.4 +/- 44.1, median 20) was higher than that in type 2 diabetics (0.3 +/- 0.3, median 0) and control subjects (3.8 +/- 2.4, median 0). When the normal upper limit of the number of GAD-reactive CD4+ cells was set at the mean + 3SD of values in control subjects, at least half (52.4%) of the so-called "type 1B" patients were positive for GAD-reactive IFN-gamma-producing CD4+ cells, a significantly larger proportion than that in type 2 diabetics (0%; p < 0.001).

CONCLUSIONS

Assessment of T cell reactivity against islet-associated antigen may contribute to the diagnosis of "autoimmune-related" type 1 diabetes.

Ketosis-prone diabetes: dissection of a heterogeneous syndrome using an immunogenetic and beta-cell functional classification, prospective analysis, and clinical outcomes

Ketosis-prone diabetes is heterogeneous. Its causes could include novel beta-cell functional defects. To characterize such defects, 103 patients with diabetic ketoacidosis were evaluated for beta-cell autoimmunity and human leukocyte antigen (HLA) class II alleles, with longitudinal measurements of beta-cell function and biochemical and clinical parameters. They were classified into four A beta groups, based on the presence of glutamic acid decarboxylase (GAD)65, GAD67, or IA-2 autoantibodies (A+ or A-) and beta-cell functional reserve (beta+ or beta-). The group distribution was: 18 A+beta-, 23 A-beta-, 11 A+beta+, and 51 A-beta+. Collectively, the two beta- groups differed from the two beta+ groups in earlier onset and longer duration of diabetes, lower body mass index, less glycemic improvement, and persistent insulin requirement. HLA class II genotyping showed that the A-beta- group differed from the A+beta- group in having lower frequencies of two alleles strongly associated with autoimmune type 1 diabetes susceptibility: DQA*03 and DQB1*02. Similarly, the A-beta+ group differed from the A+beta+ group in having a lower frequency of DQB1*02. Ketosis-prone diabetes comprises at least four etiologically distinct syndromes separable by autoantibody status, HLA genotype, and beta-cell functional reserve. Novel, nonautoimmune causes of beta-cell dysfunction are likely to underlie the A-beta+ and A-beta- syndromes.

Antibodies to glutamic acid decarboxylase in Syrian and Jordanian type I diabetes patients and their siblings

BACKGROUND

Attempts to identify the earliest events in the autoimmune process in type I diabetes mellitus suggests the glutamic acid decarboxylase (GAD) is one of the first and most important autoantigens. We conducted this study to determine the prevalence of antibodies to glutamic acid decarboxylase (anti-GAD) in both Syrian and Jordanian children with Type I diabetes and their siblings.

PATIENTS AND METHODS

sera were obtained from 85 Syrian patients with type I diabetes (mean age 13.6 + 5.9 years), from 45 of their siblings (mean age 11 + 6.1 years), from 78 randomly selected Syrian control subjects (mean age 9.9 + 43 years), and from 95 Jordanian patients with type I diabetes (mean age 13.9 + 65 years), from 78 of their siblings (mean age 12.3 + 7.1 years), and from 100 randomly selected Jordanian control subjects (mean age 7.8 + 4.5 years). Sera were analyzed from anti-GAD using the enzyme linked immunosorbent assay (ELISA) technique.

RESULTS

Prevalence of anti-GAD was 34.1% (29/85) in Syrian type I diabetes patients, 20% (9/45) in their siblings, 1.3% (1/78) in Syrian control subjects, 49.5% (47/95) in Jordanian type I diabetes patients, 23% (18/78) in their siblings, and 2% (2/100) in Jordanian control subjects. Differences between the Syrian and Jordanian type I diabetes groups and their siblings and controls were statistically significant. In patients with less than two years of diabetes duration, the frequency was 88.8% (16/18) for both groups. There was no correlation between sex and anti-GAD levels in their Syrian and Jordanian type I diabetes patients and their siblings. The positivity of anti-GAD tended to be more frequent at the age range of 5 to 8 years in siblings. Anti-GAD titers >90 ng/ml were found in 58.8% of type I diabetes patients and in 38% of siblings who were anti-GAD positive.

CONCLUSION

Syria and Jordan have prevalence rates of anti-GAD among type I diabetes patients and their siblings that are among the highest reported in the world. Therefore, anti-GAD may be valuable as an early predictive marker for type I diabetes.

Relationship of family history of type 2 diabetes, hypoglycemia, and autoantibodies to weight gain and lipids with intensive and conventional therapy in the Diabetes Control and Complications Trial

Intensive therapy for type 1 diabetes results in greater weight gain than conventional therapy. Many factors may predispose to this greater weight gain, including improved glycemic control, genetic susceptibility to obesity, and hypoglycemia. To study this, relationships among family history of type 2 diabetes, frequency of severe hypoglycemia, beta-cell autoantibodies, and weight gain were examined in 1,168 subjects aged > or =18 years at baseline randomized to intensive and conventional therapy groups in the Diabetes Control and Complications Trial. With intensive therapy, subjects with a family history of type 2 diabetes had greater central weight gain and dyslipidemia characterized by higher triglyceride levels and greater cholesterol in VLDLs and intermediate-density lipoproteins compared with subjects with no family history. Neither the frequency of severe hypoglycemia nor positivity to GAD65 and insulinoma-associated protein 2 antibodies was associated with increased weight gain with either intensive or conventional therapy. These data support the hypothesis that increased weight gain with intensive therapy might be explained, in part, by genetic traits.

Non-obese adult onset diabetes with oral hypoglycemic agent failure: islet cell autoantibodies or reversible beta cell refractoriness?

Pancreatic beta cell function and insulin sensitivity, analyzed by the homeostasis model assessment, before and after 24 weeks of insulin therapy were studied and correlated with the presence of autoantibodies against beta cells (islet cell and anti-glutamic acid decarboxylase antibodies), in a group of 18 Brazilian lean adult non-insulin-dependent diabetes mellitus (NIDDM) patients with oral hypoglycemic agent failure (OHAF). Median fasting plasma glucose before and after insulin treatment was 19.1 and 8.5 mmol/l, respectively (P < 0.001); median HbA1c was 11.7% before vs 7.2% after insulin treatment (P < 0.001). Forty-four percent of the patients were positive (Ab+) to at least one autoantibody. Fasting C-peptide levels were lower in Ab+ than Ab- patients, both before (Ab+: 0.16+/-0.09 vs Ab-: 0.41+/-0.35 nmol/l, P < 0.003) and after insulin treatment (Ab+: 0.22+/-0.13 vs Ab-: 0.44+/-0.24 nmol/l, P < 0.03). Improvement of H was seen in Ab- (median before: 7.3 vs after insulin therapy: 33.4%, P = 0.003) but not in Ab+ patients (median before: 6.6 vs after insulin therapy: 20.9%). These results show that the OHAF observed in the 18 NIDDM patients studied was due mainly to two major causes: autoantibodies and beta cell desensitization. Autoantibodies against beta cells could account for 44% of OHAF, but Ab- patients may still present beta cell function recovery, mainly after a period of beta cell rest with insulin therapy. However, the effects of beta cell function recovery on the restoration of the response to oral hypoglycemic agents need to be determined.

Inflammatory mediators and islet beta-cell failure: a link between type 1 and type 2 diabetes

Pancreatic islet beta-cell death occurs in type 1 and 2 diabetes mellitus, leading to absolute or relative insulin deficiency. beta-cell death in type 1 diabetes is due predominantly to autoimmunity. In type 2 diabetes beta-cell death occurs as the combined consequence of increased circulating glucose and saturated fatty acids together with adipocyte secreted factors and chronic activation of the innate immune system. In both diabetes types intra-islet inflammatory mediators seem to trigger a final common pathway leading to beta-cell apoptosis. Therefore anti-inflammatory therapeutic approaches designed to block beta-cell apoptosis could be a significant new development in type 1 and 2 diabetes.

No specific reactivity to E. coli glutamic acid decarboxylase from sera of newly-diagnosed insulin dependent diabetic patients

The 65 kD isoform of Glutamic Acid Decarboxylase (GAD), is one of the major autoantigens in human type 1 diabetes mellitus. This enzyme shares amino acid identity, in select regions already determined as antigenic with its counterpart from E. coli. We tested the reactivity of diabetic and normal sera and an E. coli GAD-specific monoclonal antibody (2D9) to E. coli GAD by solid phase and competition ELISA, as well as immunoblotting to check for cross-reactivity of autoantibodies to the two antigens. Specific antibodies for E. coli GAD are present in diabetics and normal subjects without any differences in frequency and titer. The reactivity of such antibodies in ELISA could be blocked in a dose-dependent manner by the addition of excess antigen in the liquid phase. Furthermore, the monoclonal antibody against E. coli GAD does not recognise human recombinant GAD65 in an ELISA. We conclude that there is no basis for cross-reactivity between the two antigens, and antibody reactivity to GAD65 in man cannot arise from cross-reactivity to the E. coli enzyme.

Prospects for the prevention and reversal of type 1 diabetes mellitus

Type 1 (insulin-dependent) diabetes mellitus results from selective immune-mediated destruction of pancreatic islet beta cells. Strategies to prevent or reverse the development of diabetes can be divided into three groups, depending on whether they focus on beta-cell protection, regeneration or replacement. Prevention of immune beta-cell destruction involves either halting the immune attack directed against beta cells or making beta cells better able to withstand immune attack, for example, by making them resistant to free radical damage. The recent identification of beta-cell growth factors and development of stem cell technologies provides an alternative route to the reversal of diabetes, namely beta-cell regeneration. Interestingly, stem cell-derived islets appear to be less sensitive to recurrent immune destruction that is normally seen in response to islet transplantation. The last alternative is beta-cell replacement or substitution. This covers a wide range of interventions including human whole pancreas transplantation, xenotransplantation, genetically modified beta cells, mechanical insulin sensing and delivery devices, and the artificial pancreas. This review describes recent advances in each of these research areas and aims to provide clinicians with an idea of where and when an effective strategy to prevent or reverse diabetes development will become available.

Similar genetic features and different islet cell autoantibody pattern of latent autoimmune diabetes in adults (LADA) compared with adult-onset type 1 diabetes with rapid progression

OBJECTIVE

To compare the clinical parameters, C-peptide levels, pattern of islet cell-specific autoantibodies, and prevalence of predisposing genotypes in subjects with latent autoimmune diabetes in adults (LADA) and those with adult-onset type 1 diabetes with rapid progression.

RESEARCH DESIGN AND METHODS

We evaluated the clinical parameters, C-peptide levels, and islet cell-specific autoantibodies in 54 LADA, 57 adult-onset type 1 diabetic, and 190 type 2 diabetic patients. Islet cell autoantibodies were also compared between subgroups of newly diagnosed patients with LADA and those with newly diagnosed adult-onset and childhood-onset type 1 diabetes. The genetic study was performed in subjects with LADA and those with adult-onset type 1 diabetes in comparison with a control population.

RESULTS

There were no differences in the clinical parameters between LADA and adult-onset type 1 diabetes. Patients with LADA had lower BMI (P < 0.0001), waist-to-hip ratio (0.0029), total cholesterol (P = 0.001), and triglycerides (P = 0.001); higher HDL cholesterol levels (P < 0.0001); and lower prevalence of hypertension (P = 0.0028) compared with patients with type 2 diabetes. C-peptide levels were similar at onset (P = 0.403) but decreased less rapidly in LADA than in adult-onset type 1 diabetes (P = 0.0253). Single-autoantibody positivity was more often seen in LADA than in type 1 diabetes (P = 0.0001). The prevalence of predisposing HLA-DQB1*0302, -DR4, -DR3, and -DR3/DR4 genotypes and the DR4-DQB1*0302 haplotype were increased in both LADA and adult-onset type 1 diabetic subjects compared with the control population. There were no differences in the frequencies of these risk alleles and haplotypes between the two patient groups.

CONCLUSIONS

Subjects with LADA had clinical characteristics similar to those with adult-onset type 1 diabetes with rapid progression. C-peptide levels did not differ at onset but decreased less rapidly in LADA. Patients with LADA rather had single islet cell-specific autoantibody positivity. The prevalence of HLA-DQB1*0302, -DR4, -DR3, and -DR3/DR4 risk alleles and the DR4-DQB1*0302 high-risk haplotype did not differ in the two forms of autoimmune diabetes.

Heterogeneity of non-insulin-dependent diabetes expressed as variability in insulin sensitivity, beta-cell function and cardiovascular risk profile

AIMS

The present study investigated the variability in insulin sensitivity and beta-cell function and their relationship to anti-glutamic acid decarboxylase (GAD) positivity and the metabolic syndrome in a group of patients with non-insulin-dependent diabetes mellitus (NIDDM).

METHODS

Fifty-four subjects aged 59.5 +/- 6.1 (mean +/- SD) years with NIDDM for 7.9 +/- 3.9 years referred to hospital due to poor glycaemic control, were investigated. Insulin sensitivity was determined by the euglycaemic hyperinsulinaemic glucose clamp technique as the glucose disposal rate relative to the insulin level obtained (GDRI), and also estimated with the homeostasis model assessment (HOMA-S). beta-cell function was measured by assaying the fasting and glucagon-stimulated C-peptide levels and with the HOMA-B.

RESULTS

The insulin sensitivity varied 18-fold between subjects when estimated with the clamp and six-fold when estimated with HOMA-S, and was lower the more criteria for the metabolic syndrome present (P = 0.0001 by anova). The beta-cell function varied four-fold when measured as stimulated C-peptide, and eight-fold when estimated with the HOMA-B. The levels of fasting C-peptide and HOMA-B values tended to be lower in anti-GAD+ (n = 11) than in anti-GAD-subjects (P = 0.06 and P = 0.08, respectively). From previously published coronary risk charts, we estimated the 10-year risk of a coronary heart disease (CHD) event to be > 20% in 17 of 39 patients free from cardiovascular disease at the time of study, 16 of whom qualified for a diagnosis of the metabolic syndrome.

CONCLUSIONS

The wide variations in insulin sensitivity and beta-cell function found among subjects with NIDDM support the notion that the disorder is highly heterogeneous. Reduced insulin sensitivity was clearly related to the metabolic syndrome and an increased risk for CHD.

Glutamic acid decarboxylase and ICA512/IA-2 autoantibodies as disease markers and relationship to residual beta-cell function and glycemic control in young type 1 diabetic patients

Circulating autoantibodies (Ab) to islet autoantigens, glutamic acid decarboxylase (GAD(65)), and tyrosine phosphatase ICA512/IA-2 have been proposed as predictive markers of type 1 diabetes mellitus. To ascertain residual beta-cell function and the clinical relevance for monitoring autoimmunity after clinical manifestation of disease, we studied 63 children at diagnosis of type 1 diabetes (mean SD age 7.5 +/- 4 years) and 91 adolescent patients with type 1 diabetes (age 14.7 +/- 1.6 years) with a mean duration of disease of 7 +/- 3.5) years. Forty-two normal adolescent subjects (age 14.6 +/- 1.8 years) without a family history of diabetes were the control group. Anti-GAD(65) and ICA512/IA-2 Ab were assessed by a quantitative radioimmunoprecipitation assay. The relationship between humoral autoimmunity and clinical parameters was explored. GAD(65) and ICA512/IA-2 Ab were detected in 56% and 63% of newly diagnosed children and the prevalence was not different in relationship to clinical characteristics. Levels of GAD(65) Ab positively correlated with diagnosis age (P <.05). Both Ab were associated with islet cell antibodies (ICA) (P <.05), but one fifth of patients had at least 1 of the 2 Ab and absent ICA. At onset, only age showed a significant relationship to residual C-peptide secretion. Among the cohort of patients with diabetes of short-mid duration, GAD(65) and ICA512/IA-2 Ab were present in 44% and 45% of cases (P >.05 and P <.05 v newly diagnosed children, respectively) and more patients were identified by these Ab (68%) than by ICA alone (34%) (P <.05). In this cohort, levels of ICA512/IA-2 Ab negatively correlated with levels of glycosylated hemoglobin (HbA(1c)) (P <.005) and with daily insulin requirement (P <.05). Moreover, the presence of some residual C-peptide secretion was significantly associated with the presence of ICA512/IA-2 Ab (P <.05). Our findings confirm that positivity for either GAD(65) or ICA512/IA-2 Ab is a highly sensitive marker of type 1 diabetes in the pediatric age group, identifying a group of patients with absent ICA immunofluorescence. The persistence of Ab to islet tyrosine phosphatase possibly represents a marker of better glycemic control and less insulin requirement, indicating residual beta-cell function, thus conferring clinical and prognostic relevance to these Ab, as well as potential usefulness in intervention strategies.

Autoimmune thyroiditis in non-obese subjects with initial diagnosis of Type 2 diabetes mellitus

Autoimmune thyroiditis is often associated with Type 1 diabetes mellitus (T1DM). In non-obese adult-onset diabetes diagnosed initially as Type 2 diabetes mellitus (T2DM), there is a proportion of cases with so far undiagnosed T1DM. The objective of this study was to estimate the frequency of autoimmune thyroiditis (AT) among non-obese (BMI <30.0 kg/m2) patients with T2DM and to compare the frequency of AT in subgroups of patients according to the presence of glutamic acid decarboxylase antibodies (GADA), insulin requirement, and post-breakfast C-peptide levels. The study included 118 adult patients (55 men and 63 women) with the initial diagnosis of T2DM and age at the onset of diabetes > 35 yr. Median of age was 66 yr (range 39-82), and median duration of diabetes was 9 (range 1-27) yr. AT was diagnosed using thyroid peroxidase antibodies, TG-antibodies, US and TSH levels. Nineteen per cent of the subjects were found to have AT, and the frequency of AT did not significantly differ between the groups of GADA+ and GADA- subjects. There was no difference in the frequency of AT between the group treated with hypoglycemic agents and/or diet and the group requiring insulin. The frequency of AT was higher in the group with post-breakfast C-peptide levels < or = 0.8 nmol/l compared to the group with post-breakfast C-peptide levels > 0.8 nmol/l (37% vs 16%), however the group with post-breakfast C-peptide levels < or = 0.8 nmol/l had longer duration of diabetes.

Current knowledge of Japanese type 1 diabetic syndrome

The Japanese have one of the lowest incidence of childhood type 1 diabetes in the world, but the incidence of this disease is clearly increasing within the Japanese population, as reported in several European countries. Latent autoimmune diabetes mellitus in adult (LADA) patients are also likely to have a lower incidence compared to Caucasians. Among the non-autoimmune (type 1B) diabetes in Japanese adults, there exists a novel subtype of type 1 diabetes characterized by extremely rapid onset and pancreatic exocrine inflammation. HLA and non-HLA gene associations to type 1 diabetes may vary depending on ethnic origin. Highly susceptible HLA haplotypes of type 1 diabetes observed in Caucasian patients are not found in Japanese patients, while protective HLA haplotypes are similar. Association studies of non-HLA genes have identified several candidate genes that influence the heterogeneity of disease phenotypes as well as disease susceptibility to type 1 diabetes. The INS-VNTR gene or polymorphisms of MICA gene are associated with susceptibility, whereas a certain allele of MICA gene and IL-10 gene polymorphism are associated with clinical heterogeneity of the disease. An expression of multiple autoantibodies to a biochemically determined autoantigen confers a high risk for progression to type 1 diabetes. The combined evaluation of multiple autoantibodies is more sensitive than is ICA testing for the diagnosis of type 1 diabetes. A high titer of GAD autoantibody has the predictive value of future insulin deficiency in patients with LADA. For accurate predictive strategies of future insulin deficiency, combinational multiple autoantibodies analysis or genetic determination should be considered for effective immune intervention.

Antibodies to GAD in Japanese patients classified as Type 2 diabetes at diagnosis. High titre of GAD Ab is a predictive marker for early insulin treatment--report of west Japan (Kyushu, Yamaguchi, Osaka) study for GAD Ab(+) diabetes

AIM

We evaluated the prevalence of GAD Ab in Japanese Type 2 diabetic patients treated with oral hypoglycaemic agents (OHA) and/or diet and followed GAD Ab(+) patients to assess the usefulness of GAD Ab as a marker for future insulin treatment prospectively.

METHODS

A total of 2658 Japanese Type 2 diabetic patients treated by OHA and/or diet were randomly selected between April 1996 and December 1998. The clinical characteristics at entry were assessed and patients were followed for 1-3 years.

RESULTS

The overall prevalence of GAD Ab among Type 2 diabetic patients was 2.0%. Forty-five had a history of diabetes of < or = 5 years (short history) while those with duration > 5 years (long history) totalled nine. Among them, 47% of patients with a short history did not require insulin in the follow-up period. However, none of those with a long history required insulin treatment within 2 years. Comparison of patients based on GAD titre in those with short history showed that 33% of patients in the high-titre group (> or = 20 U) required no insulin treatment in the first year of follow-up. In contrast, this proportion was 80% in the first and 67% in the second year in the low-titre group (< 20 U).

CONCLUSIONS

The prevalence of GAD Ab in Japanese patients with a short and long history of diabetes was 2.8% and 0.9%, respectively. The presence of GAD Ab in Japanese Type 2 diabetic patients with a short history of diabetes is a marker for early insulin treatment.

Detection of GAD65-reactive T-Cells in type 1 diabetes by immunoglobulin-free ELISPOT assays

OBJECTIVE

To investigate the prevalence of beta-cell autoantigen-reactive peripheral T-cells in type 1 diabetes, we developed an immunoglobulin-free enzyme-linked immunospot (ELISPOT) assay and assessed its usefulness for diagnosing this disease.

RESEARCH DESIGN AND METHODS

Cellular immune responses to beta -cell autoantigens were studied both by immunoglobulin-free proliferation assays and ELISPOT assays in 33 patients with type 1 diabetes and 15 patients with type 2 diabetes, compared with 23 healthy control subjects. Autoantibodies against GAD65 and IA-2 were measured by radioimmunoassay.

RESULTS

Significant proliferative responses to GAD65 were observed in 10 of 31 (32.3%) type 1 diabetic patients (P < 0.05), whereas GAD65-reactive gamma-interferon (IFN-gamma)-secreting cells were detected in 22 of 33 patients (66.7%) by ELISPOT assay (P < 0.001). Of patients negative for both GAD65 and IA-2, five of six (83.3%) showed IFN-gamma positivity in ELISPOT and two of five (40.0%) showed significant proliferation against GAD65.

CONCLUSIONS

Using a newly developed ELISPOT assay, GAD-reactive T-helper 1 cells in PBMC of type 1 diabetic patients could be identified at a higher frequency than by the proliferation assay. Therefore, the immunoglobulin-free ELISPOT assay is an excellent tool for detecting T-cell reactivity to autoantigens with greater specificity and, in combination with beta-cell autoantibody determination, will improve the diagnosis of type 1 diabetes.

Retinopathy in latent autoimmune diabetes of adults: the Fremantle Diabetes Study

AIMS

To determine the prevalence of retinopathy and its associations in patients diagnosed clinically with Type 2 diabetes and serum antibodies to glutamic acid decarboxylase (GADA) from a community-based sample.

METHODS

In a case-control design, 24 GADA-positive Type 2 patients from the Fremantle Diabetes Study (FDS) cohort were recruited and matched as closely as possible for age, sex and diabetes duration with 72 GADA-negative Type 2 patients from the FDS. Each patient had a detailed clinical and biochemical assessment including slit lamp biomicroscopy and colour fundus photography with Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR) grading.

RESULTS

The GADA-positive patients had a significantly higher HbA1c (median (interquartile range); 8.4 (7.3, 9.6)%) than those who were GADA-negative (7.2 (6.5, 8.1)%: P = 0.002). The overall prevalence of retinopathy amongst the 96 subjects was 26.0%. The majority (92%) of the retinopathy detected was mild and non-proliferative. GADA-positive patients had double the retinopathy prevalence of the GADA-negative group (41.7% vs. 20.8%; P = 0.044). In a logistic regression model, diabetes duration, HbA1c, systolic blood pressure and current smoking were each significantly and independently predictive of retinopathy (P < 0.025), but GADA status was not.

CONCLUSIONS

These data show that GADA-positive patients have an increased prevalence of retinopathy compared with GADA-negative controls with Type 2 diabetes from an urban Australian community. This increased prevalence is due mainly to relatively poor glycaemic control in the GADA-positive group.

A 12-year prospective study of the relationship between islet antibodies and beta-cell function at and after the diagnosis in patients with adult-onset diabetes

To clarify the relationships between islet antibodies (islet cell antibody [ICA], GAD antibody [GADA], and IA-2 antibody [IA-2A]) versus the progression of beta-cell dysfunction, we have followed a group of diabetic patients from their diagnosis at 21-73 years of age. Patients with ICA had high levels of GADA and/or IA-2A at diagnosis and a more severe beta-cell dysfunction 5 years after diagnosis than those with only GADA in low concentrations. The aim of the current 12-year follow-up study was to examine the further progression of beta-cell dysfunction in relation to islet antibodies at and after diagnosis. Among 107 patients, complete beta-cell failure 12 years after diagnosis was restricted to those with islet antibodies at diagnosis (16 of 21 [77%] with multiple antibodies and 4 of 5 [80%] with only GADA). In contrast, among antibody-negative patients, fasting P-C-peptide levels were unchanged. Most GADA-positive patients (22 of 27 [81%]) remained GADA positive after 12 years. Associated with decreasing fasting P-C-peptide levels (0.85 nmol/l [0.84] at diagnosis vs. 0.51 nmol/l [0.21] 12 years after diagnosis, P < 0.05), ICA developed after diagnosis in 6 of 105 originally antibody negative mostly overweight patients. In conclusion, multiple islet antibodies or GADA alone at diagnosis of diabetes predict future complete beta-cell failure. After diagnosis, GADA persisted in most patients, whereas ICA development in patients who were antibody negative at diagnosis indicated decreasing beta-cell function.

Genetics of latent autoimmune diabetes in adults

Slowly progressive insulin-dependent diabetes mellitus (IDDM), like classical IDDM, is also associated with genetic markers. HLA-DR3 but not DR4 is associated with latent autoimmune diabetes in adults (LADA). In GAD65 antibody-positive Finnish LADA patients, DQB1*0302 is positively associated with the disease. Alleles of the MHC class I chain-related A (MICA) gene located centromeric to the HLA-B gene is associated with LADA. Allele 5.1 of MICA was associated with both LADA and adult-onset Italian IDDM patients when compared to controls. This finding was also observed in Indian and Latvian patients with LADA. These findings suggest that certain genetic markers distinguish LADA better.

Beta cell rest and recovery--does it bring patients with latent autoimmune diabetes in adults to euglycemia?

Diabetes mellitus in humans is a heterogeneous disorder classified clinically into two main types. The diagnosis of type 1 versus type 2 diabetes is made phenotypically using criteria such as age at onset, abruptness of hyperglycemic symptoms, presence of ketosis, degree of obesity and the perceived need for insulin replacement. The pathogeneses of type 1 and type 2 diabetes are believed to be different. Type 1 diabetes is an autoimmune disease mediated by cellular effector mechanisms; whereas classic type 2 diabetes is not autoimmune but results from insulin resistance and a nonautoimmune insulin secretory defect. Most type 1 diabetes patients are diagnosed in childhood or young adulthood before the age of 35 years. However, there is clearly a subgroup of patients clinically diagnosed with type 2 diabetes who are greater than 35 years of age and have evidence of autoimmunity. The disease of these autoantibody-positive type 2 diabetics is often termed latent autoimmune diabetes in adults (LADA), slowly progressive type 1 diabetes, latent type 1 diabetes, and type 1.5 diabetes. This group of patients comprises approximately 10-15% of Caucasian type 2 diabetes patients. Type 1.5 diabetes patients tend to present with islet cell autoantibodies, islet-reactive T cells, higher HbA(1c) levels, lower C peptide, and a propensity toward insulin dependency compared to autoantibody-negative classic type 2 diabetes subjects.

Autoantibody profile and epitope mapping in latent autoimmune diabetes in adults

The presence of islet cell autoantibodies in adult diabetic subjects who do not require insulin treatment for at least six months after the initial clinical diagnosis identifies the so-called latent autoimmune diabetes in the adult (LADA). Glutamic acid decarboxylase autoantibodies (GAD65Ab) are the best immune marker to identify LADA patients, while other islet autoantibodies, such as IA-2 autoantibodies, have a very low diagnostic sensitivity. Islet cell antibodies, as detected by indirect immunofluorescence, may improve the diagnostic specificity of the immune analysis when detected in GAD65Ab-positive patients. Although the majority of LADA patients progresses towards insulin dependency within a few years after the diagnosis, this form of diabetes is heterogeneous. The presence of high titers of GAD65Ab and/or GAD65Ab directed towards COOH-terminal epitopes of the autoantigen (GAD65-CAb) identifies a subgroup of LADA patients with clinical characteristics similar to those of typical type 1 diabetes and at very high risk of progression toward insulin dependency. On the other hand, low titers of GAD65Ab, or the exclusive presence of GAD65Ab directed to middle epitopes of the autoantigen, characterizes LADA patients with clinical characteristics almost indistinguishable from those of GAD65Ab-negative type 2 diabetic patients. LADA subjects, especially in the presence of high titers of GAD65Ab and/or GAD65-CAb, have an increased risk for other organ-specific autoimmune diseases such as thyroid autoimmune diseases or autoimmune Addison's. LADA should be considered a major component of the autoimmune polyendocrine syndromes, and screening for other autoimmune diseases should be performed in all LADA patients.