A clinical screening tool identifies autoimmune diabetes in adults

OBJECTIVE: Latent autoimmune diabetes in adults (LADA) is defined as adult-onset diabetes with circulating islet antibodies but not requiring insulin therapy initially. Diagnosing LADA has treatment implications because of the high risk of progression to insulin dependency. Currently, there are no recommendations for islet antibody testing in adult-onset diabetes. In this study, we aimed to develop a clinical screening tool to identify adults at high risk of LADA who require islet antibody testing. RESEARCH DESIGN AND METHODS: Subjects with LADA (n = 102, GAD antibody [GADA]+) and type 2 diabetes (n = 111, GADA-) (aged 30-75 years) were interviewed retrospectively. The clinical features documented were age of onset, acute symptoms of hyperglycemia, BMI, and personal and family history of autoimmune disease. Any clinical feature that was significantly more frequent in LADA was designated as a distinguishing clinical feature. In each subject, a "LADA clinical risk score," based on the total number of distinguishing features, was calculated. A prospective study of adults with newly diagnosed diabetes (n = 130) was used to determine whether the LADA clinical risk score could identify LADA. RESULTS: In the retrospective study, five clinical features were more frequent in LADA compared with type 2 diabetes at diagnosis: 1) age of onset <50 years (P < 0.0001), 2) acute symptoms (P < 0.0001), 3) BMI <25 kg/m2 (P = 0.0004), 4) personal history of autoimmune disease (P = 0.011), and 5) family history of autoimmune disease (P = 0.024). In the prospective study, the presence of at least two of these distinguishing clinical features (LADA clinical risk score > or =2) had a 90% sensitivity and 71% specificity for identifying LADA and a negative predictive value for a LADA clinical risk score < or =1 of 99%. CONCLUSIONS: At least two distinguishing clinical features are found in a majority of patients with LADA at diagnosis and can be used to identify adults with diabetes at higher risk for LADA.     

Latent Autoimmune Diabetes of Adults (LADA) Is Likely to Represent a Mixed Population of Autoimmune (Type 1) and Nonautoimmune (Type 2) Diabetes

Latent autoimmune diabetes of adults (LADA) is typically defined as a new diabetes diagnosis after 35 years of age, presenting with clinical features of type 2 diabetes, in whom a type 1 diabetes–associated islet autoantibody is detected. Identifying autoimmune diabetes is important since the prognosis and optimal therapy differ. However, the existing LADA definition identifies a group with clinical and genetic features intermediate between typical type 1 and type 2 diabetes. It is unclear whether this is due to 1) true autoimmune diabetes with a milder phenotype at older onset ages that initially appears similar to type 2 diabetes but later requires insulin, 2) a disease syndrome where the pathophysiologies of type 1 and type 2 diabetes are both present in each patient, or 3) a heterogeneous group resulting from difficulties in classification. Herein, we suggest that difficulties in classification are a major component resulting from defining LADA using a diagnostic test—islet autoantibody measurement—with imperfect specificity applied in low-prevalence populations. This yields a heterogeneous group of true positives (autoimmune type 1 diabetes) and false positives (nonautoimmune type 2 diabetes). For clinicians, this means that islet autoantibody testing should not be undertaken in patients who do not have clinical features suggestive of autoimmune diabetes: in an adult without clinical features of type 1 diabetes, it is likely that a single positive antibody will represent a false-positive result. This is in contrast to patients with features suggestive of type 1 diabetes, where false-positive results will be rare. For researchers, this means that current definitions of LADA are not appropriate for the study of autoimmune diabetes in later life. Approaches that increase test specificity, or prior likelihood of autoimmune diabetes, are needed to avoid inclusion of participants who have nonautoimmune (type 2) diabetes. Improved classification will allow improved assignment of prognosis and therapy as well as an improved cohort in which to analyze and better understand the detailed pathophysiological components acting at onset and during disease progression in late-onset autoimmune diabetes.     

Metabolic syndrome and autoimmune diabetes: action LADA 3

OBJECTIVE—The purpose of this study was to estimate whether prevalence of metabolic syndrome in adult European diabetic patients is associated with type of diabetes.RESEARCH DESIGN AND METHODS—A consecutive series of patients attending hospital-based diabetes clinics were assessed for the frequency of metabolic syndrome and compared with population-based control subjects as part of the Action LADA study. In total, 2,011 subjects (aged 30–70 years) were studied, including 1,247 patients with recent-onset type 2 diabetes without glutamic acid decarboxylase autoantibodies (GADAs), 117 non–insulin-requiring patients with GADAs who had not received insulin therapy for at least 6 months after diagnosis (designated latent autoimmune diabetes of adults [LADA]), 288 type 1 diabetic patients, and 359 normal subjects.RESULTS—Frequency of metabolic syndrome was significantly different in patients with type 1 diabetes (31.9%) and LADA (41.9%) (P = 0.015) and in both conditions was less frequent than in type 2 diabetic patients (88.8%) (P < 0.0001 for each). Eliminating glucose as a variable, the prevalence of metabolic syndrome was similar in patients with autoimmune diabetes (type 1 diabetes and/or LADA) (17.3%) and control subjects (23.7%) but remained more common in type 2 diabetic patients (47.8%) (P = 0.001 for all groups). In both type 1 diabetic patients and those with LADA, individual components of metabolic syndrome were similar but less common than in type 2 diabetic patients (P < 0.0001 for each).CONCLUSIONS—The prevalence of metabolic syndrome is significantly higher in type 2 diabetic patients than in patients with LADA or adults with type 1 diabetes. Excluding glucose as a variable, metabolic syndrome is not more prevalent in patients with autoimmune diabetes than in control subjects. Metabolic syndrome is not a characteristic of autoimmune diabetes.Type 1 diabetes is an autoimmune disease in which insulin deficiency results from immune-mediated destruction of insulin-secreting islet cells. The majority of patients with type 1 diabetes have autoantibodies in their peripheral blood, and these autoantibodies can predict the disease. Autoimmune diabetes, as characterized by these autoantibodies, such as glutamic acid decarboxylase autoantibodies (GADAs), is the most prevalent form of diabetes in children and also occurs in a proportion of patients who initially present with adult-onset non–insulin-requiring diabetes, also called latent adult-onset autoimmune diabetes (LADA) (1).Because glucose disposal and blood glucose are determined by both insulin secretion and insulin action, it follows that insulin sensitivity could be important in the pathogenesis of autoimmune diabetes. Insulin sensitivity has not been studied in detail in autoimmune diabetes, although studies suggest that its loss may occur in established disease as well as in the pre-diabetic phase (2–5). Loss of insulin sensitivity is difficult to assess epidemiologically but is reflected in the cluster of metabolically related cardiovascular risk factors that together comprise the metabolic syndrome and include altered glucose levels, central obesity, dyslipidemia, and hypertension. Several groups, including the International Diabetes Federation (IDF) and the National Cholesterol Education Program (NCEP), with Adult Treatment Panel III (6), have proposed their own definitions for the metabolic syndrome.LADA is clearly distinct from type 2 diabetes, in that LADA is associated with histocompatability (HLA) genes, diabetes-associated autoantibodies, reduced insulin secretion, no need for insulin therapy initially after diagnosis, and less prevalence of metabolic syndrome (7–9). The key question is whether LADA is distinct from type 1 diabetes (1,10,11), that is, whether LADA is one end of a rainbow of pathophysiological variations encompassing autoimmune diabetes with a frequency of metabolic syndrome similar to that of childhood-onset type 1 diabetes or whether LADA is a distinct form of autoimmune diabetes that resembles type 2 diabetes, showing evidence of insulin resistance with a high frequency of metabolic syndrome (1). Therefore, the aim of this study was to test whether individuals with type 2 diabetes and autoimmune diabetes (incorporating type 1 diabetes and LADA) have a higher frequency of metabolic syndrome than normal subjects, and our hypothesis was that they would.     

GAD65 autoantibody responses in Japanese latent autoimmune diabetes in adult patients

OBJECTIVE—To determine whether development of insulin requirement in patients with latent autoimmune diabetes in adults (LADA) is accompanied with the emergence of a type 1 diabetes–like autoimmune response.RESEARCH DESIGN AND METHODS—We correlated β-cell–specific autoimmunity reflected in autoantibodies to the 65-kDa isoform of GAD (GAD65) with insulin requirement. We determined GAD65Ab epitope specificities in type 1 diabetic patients, LADA patients without insulin requirement (nonprogressed), and LADA patients that had developed insulin requirement (progressed).RESULTS—Recognition of a type 1 diabetes–specific GAD65Ab epitope was more pronounced in type 1 diabetic patients than in nonprogressed (P < 0.001) or progressed (P < 0.01) LADA patients, with no significant differences between the two LADA cohorts. These differences were particularly pronounced in samples with GAD65Ab titers <1,000 units/ml, with no differences in epitope specificities in samples with higher GAD65Ab titers. Disease duration (initial diabetes diagnosis until sample collection or development of insulin requirement) in nonprogressed and progressed LADA patients, respectively, was not correlated with epitope specificity, suggesting lack of epitope maturation. This was supported by epitope analyses of longitudinal samples from LADA patients during progression to insulin requirement.CONCLUSIONS—First, the GAD65Ab-specific autoimmune reaction in type 1 diabetic patients with low and moderate GAD65Ab titers differs from that in LADA patients, irrespective of insulin requirement. Second, the GAD65Ab-specific autoimmune response in LADA patients does not change after their initial diabetes diagnosis. Finally, LADA patients with high GAD65Ab titers resemble type 1 diabetic patients in their GAD65Ab epitope specificity.Latent autoimmune diabetes in adults (LADA) consists of a subgroup (∼10%) of adult patients initially diagnosed with type 2 diabetes, who show signs of β-cell autoimmunity and eventually develop insulin requirement (1,2). Signs of β-cell autoimmunity, such as the well-characterized insulin autoantibodies, glutamate decarboxylase (GAD65), and the tyrosine phosphatase–like protein insulinoma-associated protein-2, indicate significant damage of the β-cells and subsequent development of insulin requirement in these patients (1). While autoantibodies to insulin and insulinoma-associated protein-2 antibody (Ab) are inversely correlated with age at onset, GAD65Ab shows no, and in some studies even a positive, correlation with age at onset and is therefore a particularly attractive marker for autoimmune diabetes in the adult population (3,4). Moreover, GAD65Ab can be detected years after the clinical onset of the disease, indicating that these autoantibodies may be permanent markers for the autoimmune response (5,6).Notably, not all LADA patients progress to insulin requirement, raising the possibility that the autoimmune response in these patients resembles that in autoantibody-positive healthy individuals, with no significant risk for development of insulin requirement (7,8). A better understanding of the autoimmune response is necessary to predict insulin requirement in LADA patients, which is important to prevent escalation of blood glucose levels and subsequent complications.In previous studies, we have investigated the humoral immune response toward GAD65 as a reflection of islet cell destruction (9). It remains unclear whether the autoimmune response in LADA patients and type 1 diabetic patients differs or whether only the duration of the prodomal period distinguishes between the two groups (10). Therefore, we compared the GAD65-specific humoral autoimmune response in type 1 diabetic patients with that in LADA patients who had or had not progressed to insulin requirement.     

Crucial points at diagnosis. Type 2 diabetes or slow type 1 diabetes

Two major types of diabetes have been recognized since the late 1930s. However, in recent times there have been major changes in classification and understanding of these types, including improved knowledge of maturity-onset diabetes in the young, with the identification of mutations relating to impaired insulin secretion and the recognition of slow-onset type 1 diabetes in adults now designated as latent autoimmune diabetes in adults (LADA). A major problem area in diabetes classification concerns cases of slowly progressive forms of type 1 and type 2 diabetes, particularly in adults aged 25-50 years. This is a more contemporary problem because cases of type 2 diabetes are presenting at an increasingly younger age. In the landmark U.K. Prospective Diabetes Study of type 2 diabetes, islet cell antibodies (ICAs) and antibodies to glutamic acid decarboxylase (anti-GAD) were measured at diagnosis in 3,672 patients. The overall proportion with ICAs was 6%, and anti-GADs was 10%. These subjects clearly had type 1 diabetes or LADA by both phenotypic and genotypic features. The presence of auto antibodies correlated particularly with a younger age and phenotypic features consistent with type 1 diabetes (e.g., early age at diagnosis, lower BMI, and reduced beta-cell function). Overall, of patients requiring insulin by 6 years, 38% were anti-GAD+ at baseline compared with 5.3% of those not on insulin at 6 years. Antibodies to GAD indicate an underlying autoimmune process and have a high positive predictive value for type 1 diabetes and future insulin dependency in adults.     

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.     

Hyperproinsulinemia segregates young adult patients with newly diagnosed autoimmune (type 1) and non-autoimmune (type 2) diabetes

OBJECTIVE: To investigate whether measurements of proinsulin and/or intermediate proinsulin degradation products could be used to differentiate between autoimmune (type 1) and non-autoimmune (type 2) diabetes in young adults. MATERIAL AND METHODS: Total proinsulin, intact proinsulin and 32,33 split proinsulin concentrations were measured in 25 patients aged 15-34 years with type 1 diabetes, as defined by the presence of at least two positive islet autoantibodies, and in 23 antibody-negative patients of similar age with type 2 diabetes, at the time of clinical onset of diabetes and at 3-4 months thereafter. Comparisons were made with data from 25 healthy subjects matched for gender and age. RESULTS: Plasma levels of total proinsulin, intact proinsulin and 32,33 split proinsulin were significantly increased 2-3-fold in the patients with newly diagnosed type 2 diabetes as compared with the controls, both in absolute terms (p<0.0001) and when related to circulating insulin (p<0.01-0.0002). In contrast, absolute proinsulin and 32,33 split proinsulin concentrations were significantly lower in patients with onset of type 1 diabetes than in controls. When proinsulin and split proinsulin release were related to plasma insulin, however, similar ratios were found in the type 1 diabetes patients and in controls. Using the 90th percentile for total proinsulin in the control group as the cut-off, the sensitivity and specificity for differentiation between autoimmune and non-autoimmune diabetes were 87% and 92%, respectively. At 3-4 months after clinical onset of diabetes, proinsulin secretion was still 2-3 times higher in type 2 than in type 1 diabetes patients (p<0.001). CONCLUSIONS: Young adult patients with newly diagnosed type 2 diabetes display disproportionate hyperproinsulinemia, whereas proinsulin secretion appears to be normal in patients with clinical onset of type 1 diabetes. Evaluation of proinsulin and 32,33 split proinsulin concentrations may be useful as a diagnostic tool in differentiating between autoimmune and non-autoimmune diabetes in young adults, particularly in those lacking islet autoantibodies at diagnosis.     

Prediction and diagnosis of type 1 diabetes using beta-cell autoantibodies

The clinical manifestation of type 1 diabetes is the endpoint of a long-lasting immune-mediated destruction process of the B-cells. Autoantibodies originating from this process can be applied in the diagnosis and clinical discrimination of autoimmune diabetes as well as in the prediction of this disease. At clinical diagnosis between 80-90% of patients with type 1 diabetes are positive for antibodies to B-cell antigens, such as ICA and antibodies to glutamic acid decarboxylase or IA2. These antibodies can also be detected in the presymptomatic period before onset of the disease, and can thus be used to predict type 1 diabetes. Using a combination of antibodies, diabetes can be predicted in 70-80% of future cases of diabetes, with a positive predictive value between 30-80%, depending on the type of antibody tested for and the population studied. Between 5 and 30% of patients initially diagnosed with type 2 diabetes will show progression to insulin dependency and turn out to have type 1 within three years of diagnosis. It is clinically relevant to identify these patients early in the course of disease, as deterioration of metabolic control results in an increased risk for macro- and micro-vascular complications. Autoantibodies to glutamic acid decarboxylase or ICA are of high diagnostic sensitivity in these cases and are better predictors for future insulin dependency than biochemical or clinical parameters. Increasing knowledge on the applicability of antibodies for diabetes prediction and diagnosis and the development of commercial assays for antibodies to glutamic acid decarboxylase and IA2 antibodies has enabled the implementation of B-cell autoantibodies in routine diagnostic settings.     

The evolution of beta-cell dysfunction and insulin resistance in type 2 diabetes

Insulin resistance and beta-cell dysfunction have important roles in the pathogenesis and evolution of type 2 diabetes. The development of precise methods to measure these factors has helped us to define the relationship between them and evidence is reviewed that changes in insulin sensitivity are compensated by inverse changes in beta-cell responsiveness such that the product of insulin sensitivity and insulin secretion (the disposition index) remains constant. While the disposition index promises to be a useful tool to predict individuals at high risk of developing type 2 diabetes, other factors that contribute to beta-cell dysfunction and mark disease onset and progression include impairments in proinsulin processing and insulin secretion, decreased beta-cell mass and islet amyloid deposition. Emerging data indicate that anti-diabetic agents, such as the thiazolidinediones that simultaneously target insulin resistance and beta-cell dysfunction, may have a beneficial impact on disease onset and progression. Several landmark clinical studies are underway to investigate if their initial promise is supported by data from large-scale trials.     

A Case Report of LADA in the Primary Care Setting

Latent autoimmune diabetes in adults (LADA), a slowly progressing form of autoimmune diabetes, accounts for 2%–12% of all diabetes. Pancreatic beta cell function eventually deteriorates, rendering the patient insulin dependent and at risk for serious complications. All newly presenting adult persons with diabetes should be screened for LADA. In particular, consider LADA in those adults with a personal or family history of autoimmune conditions or those persons diagnosed with type 2 diabetes initially controlled on evidence-based therapies but then become difficult to manage and exhibit signs, such as unintended weight loss, that are more typical of persons with type 1 diabetes.     

Prevention of type 2 diabetes

The importance of type 2 diabetes is due to its high prevalence, the difficulties in achieving optimal glucose control (financial, time, quality of life) and the high frequency of chronic microvascular and macrovascular complications that add very significantly to the morbidity, mortality and overall cost of the disease. Numerous risk factors have been identified that predict the future onset of type 2 diabetes in individuals and an early stage of the disease (impaired glucose tolerance) can often be identified. Insulin resistance is central to the pathogenesis and is initially compensated by an increased insulin secretion. Over time, insulin secretion progressively fails and diabetes appears. Several approaches have been proposed for the prevention of diabetes. Lifestyle changes (nutritional therapy and physical activity) have been shown to reduce the frequency of diabetes in small studies and are being assessed in the NIH-funded Diabetes Prevention Trial. Metformin, which reduces insulin resistance and hyperinsulinaemia, is being assessed in this same trial. Acarbose, which has been shown to reduce post-prandial insulin secretion and improve insulin resistance, is being assessed in the STOP-NIDDM trial. The ACE inhibitor ramipril has been shown in the HOPE study to reduce the appearance of diabetes by one third when given to patients with vascular disorders and this class of agents has been shown to improve insulin resistance. Another very promising approach is the use of thiazolidinediones (rosiglitazone, pioglitazone) to improve the insulin resistance and possibly preserve the beta cells by reducing the need for increased insulin secretion. These lifestyle changes and medications have been shown to be safe in the treatment of type 2 diabetes. There is a high probability that one of these approaches will be effective in delaying or preventing type 2 diabetes, and prevention may become a clinical reality in the near future.     

Latent autoimmune diabetes of adulthood (LADA): An often misdiagnosed type of diabetes mellitus

Purpose: The purpose of this article is to raise awareness about a frequently misdiagnosed form of diabetes, latent autoimmune diabetes of adulthood (LADA), to describe its clinical and epidemiological characteristics, and to compare them to those of the more common and widely known types of diabetes, type 1 diabetes mellitus (DM) and type 2 DM.
Data sources: A review of the pertinent literature describing the features of LADA from 2000–2007 is summarized.
Conclusions: LADA is a rather common and often underrecognized form of diabetes whose clinical presentation falls somewhere between that of type 1 DM and type 2 DM. From a pathophysiological perspective, it is more closely related to type 1 DM, and some have even used the term type 1.5 diabetes to refer to it; however, it is most often misdiagnosed and treated as type 2 DM.
Implications for practice: Nurse practitioners (NPs) should always consider alternate diagnoses when patients with newly or previously identified adult-onset diabetes mellitus do not fit the traditional stereotype of type 2 DM (i.e., overweight with signs of insulin resistance and a significant family history of diabetes). Statistically, strong consideration must be given to the diagnosis of LADA, especially in those who are of normal weight, show little evidence of insulin resistance, and have hardly any family history of diabetes. Knowing the patient's exact diabetes type can give the NP a much greater understanding of the natural history of the patient's disease, the changes that may occur as the patient ages, and how to optimally manage their diabetes to minimize complications. Likewise, when a patient is correctly diagnosed, they can be empowered to manage their diabetes with the appropriate therapies.     

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.     

Hyperproinsulinemia segregates young adult patients with newly diagnosed autoimmune (type 1) and non‐autoimmune (type 2) diabetes

ObjectiveTo investigate whether measurements of proinsulin and/or intermediate proinsulin degradation products could be used to differentiate between autoimmune (type 1) and non‐autoimmune (type 2) diabetes in young adults. Material and methods Total proinsulin, intact proinsulin and 32,33 split proinsulin concentrations were measured in 25 patients aged 15–34 years with type 1 diabetes, as defined by the presence of at least two positive islet autoantibodies, and in 23 antibody‐negative patients of similar age with type 2 diabetes, at the time of clinical onset of diabetes and at 3–4 months thereafter. Comparisons were made with data from 25 healthy subjects matched for gender and age. Results Plasma levels of total proinsulin, intact proinsulin and 32,33 split proinsulin were significantly increased 2–3‐fold in the patients with newly diagnosed type 2 diabetes as compared with the controls, both in absolute terms (p<0.0001) and when related to circulating insulin (p<0.01–0.0002). In contrast, absolute proinsulin and 32,33 split proinsulin concentrations were significantly lower in patients with onset of type 1 diabetes than in controls. When proinsulin and split proinsulin release were related to plasma insulin, however, similar ratios were found in the type 1 diabetes patients and in controls. Using the 90th percentile for total proinsulin in the control group as the cut‐off, the sensitivity and specificity for differentiation between autoimmune and non‐autoimmune diabetes were 87% and 92%, respectively. At 3–4 months after clinical onset of diabetes, proinsulin secretion was still 2–3 times higher in type 2 than in type 1 diabetes patients (p<0.001). Conclusions. Young adult patients with newly diagnosed type 2 diabetes display disproportionate hyperproinsulinemia, whereas proinsulin secretion appears to be normal in patients with clinical onset of type 1 diabetes. Evaluation of proinsulin and 32,33 split proinsulin concentrations may be useful as a diagnostic tool in differentiating between autoimmune and non‐autoimmune diabetes in young adults, particularly in those lacking islet autoantibodies at diagnosis.     

Diamyd, an alum-formulated recombinant human GAD65 for the prevention of autoimmune diabetes

Diamyd Medical AB is developing Diamyd (GAD-65), an alum formulation of a full-length recombinant human glutamic acid decarboxylase 65 for subcutaneous injection, for the potential prevention and treatment of type 1 diabetes (T1DM) or latent autoimmune diabetes (LADA) in adults. Phase II clinical trials indicated that Diamyd was safe and well tolerated in patients with T1DM or LADA. Diamyd is currently in phase II/III and III clinical trials for T1DM.     

Zinc Transporter 8 Antibodies Complement GAD and IA-2 Antibodies in the Identification and Characterization of Adult-Onset Autoimmune Diabetes: Non Insulin Requiring Autoimmune Diabetes (NIRAD) 4

OBJECTIVE

Zinc transporter 8 (ZnT8) is an islet β-cell secretory granule membrane protein recently identified as an autoantibody antigen in type 1 diabetes. The aim of this study was to determine the prevalence and role of antibodies to ZnT8 (ZnT8As) in adult-onset diabetes.

RESEARCH DESIGN AND METHODS

ZnT8As were measured by a radioimmunoprecipitation assay using recombinant ZnT8 COOH-terminal or NH²-terminal proteins in 193 patients with adult-onset autoimmune diabetes having antibodies to either GAD (GADAs) or IA-2 (IA-2As) and in 1,056 antibody-negative patients with type 2 diabetes from the Non Insulin Requiring Autoimmune Diabetes (NIRAD) study.

RESULTS

ZnT8As-COOH were detected in 18.6% patients with autoimmune diabetes and 1.4% with type 2 diabetes. ZnT8As-NH² were rare. ZnT8As were associated with younger age and a high GADA titer. The use of GADAs, IA-2As, and ZnT8As in combination allowed a stratification of clinical phenotype, with younger age of onset of diabetes and characteristics of more severe insulin deficiency (higher fasting glucose and A1C, lower BMI, total cholesterol, and triglycerides) in patients with all three markers, with progressive attenuation in patients with two, one, and no antibodies (all P^trend < 0.001). Autoantibody titers, association with high-risk HLA genotypes, and prevalence of thyroid peroxidase antibodies followed the same trend (all P < 0.001).

CONCLUSIONS

ZnT8As are detectable in a proportion of patients with adult-onset autoimmune diabetes and seem to be a valuable marker to differentiate clinical phenotypes.Zinc transporter 8 (ZnT8) is a pancreatic β-cell secretory granule membrane protein that has been recently identified as a target of humoral immunity in type 1 diabetes (1). Autoantibodies to ZnT8 (ZnT8As) constitute an additional marker of autoimmune diabetes, which complement the established antibodies to insulin (IAAs) (2), GAD (GADAs) (3), and protein tyrosine IA-2 (IA-2As) (4). In the first report, ZnT8As were detected in 63% of young patients at onset of disease, overlapping with, but also independent of, GADAs, IAAs, and IA-2As, and the combined use of these four antibody markers raised the detection rate of autoimmunity to 94% in new-onset cases of type 1 diabetes. Moreover, ZnT8As could be detected also in the preclinical phase of type 1 diabetes, showing a trend to a later appearance relative to IAAs, GADAs, and IA-2As but with the ability to identify individuals with a more rapid progression to clinical disease. Although islet autoimmunity is responsible for the large majority of childhood- and adolescent-onset diabetes, it can be found also in 4–10% of adult-onset diabetes. This subgroup of patients test positive for humoral markers of islet autoreactivity, despite having clinical features indistinguishable from those of classic type 2 diabetes, and are characterized as having latent autoimmune diabetes of adult (LADA). Patients with LADA are identified solely by the detection of circulating islet autoantibodies, with islet cell antibodies (ICAs) and GADAs being the antibody markers with the highest prevalence (5,6), followed by IA-2As, which are detected in a minority of case subjects and are almost invariably associated with GADAs (7), whereas insulin autoantibodies, which constitute a specific marker of juvenile diabetes inversely related to age and rare in adults, are unlikely to be useful for LADA screening (8–10). The aim of this study was to evaluate the prevalence of ZnT8As in adult-onset diabetes and establish their potential use as an additional marker of autoimmunity and phenotype characterization in this patient population.     

Heterogeneity of Patients With Latent Autoimmune Diabetes in Adults: Linkage to Autoimmunity Is Apparent Only in Those With Perceived Need for Insulin Treatment: Results from the Nord-Tr?ndelag Health (HUNT) study

OBJECTIVE—Subjects with the diagnosis of latent autoimmune diabetes in adults (LADA) are more prone to need insulin treatment than those with type 2 diabetes. However, not all patients with LADA develop the need for insulin treatment, indicating the heterogeneity of LADA. We investigated this heterogeneity by comparing phenotypes of LADA with and without perceived need for insulin treatment (data obtained at times when diagnosis of LADA was not investigated) and also compared LADA and type 2 diabetes phenotypes.RESEARCH DESIGN AND METHODS—We used data from the all population–based Nord-Trøndelag Health study (n = 64,931), performed in 1995–1997. Data were assembled for individuals with LADA (n = 106) and type 2 diabetes (n = 943).RESULTS—In the comparison of individuals with LADA both with and without the need for insulin, insulin-treated subjects had higher titers of GAD antibodies (P < 0.001) and lower fasting C-peptide levels (P < 0.001). GAD antibodies and C-peptide correlated negatively (r = −0.40; P = 0.009). In the comparison of individuals with LADA and type 2 diabetes, all without the need for insulin, markers of metabolic syndrome were equally prevalent and pronounced. Age, C-peptide, and glucose levels were also similar. In the comparison of insulin-treated individuals with LADA and type 2 diabetes, more patients with LADA received insulin (40 vs. 22%, P < 0.001) and C-peptide levels were lower (P < 0.001). Patients with LADA were leaner but were still overweight (mean BMI 28.7 vs. 30.9 kg/m² in type 2 diabetes, P < 0.001). In the comparison of type 2 diabetic patients with and without insulin, insulin-treated subjects were more obese and had higher A1C and lower C-peptide levels (P < 0.001).CONCLUSIONS—Our conclusions are that 1) the need for insulin treatment in LADA is linked to the degree of autoimmunity and β-cell failure, 2) subjects with LADA and type 2 diabetes without the need for insulin treatment are phenotypically similar, and 3) insulin treatment in type 2 diabetic patients is associated with both insulin resistance and β-cell insufficiency.Autoimmunity is the major cause of type 1 diabetes. Autoimmunity is also assumed to be the major cause of latent autoimmune diabetes in adults (LADA) because this category of diabetes shares biochemical markers of β-cell–directed autoimmunity with “classic” type 1 diabetes. In clinical practice, autoimmunity in classic type 1 diabetes as well as in LADA is usually documented by antibodies against GAD.LADA is considered a “mild” form of type 1 diabetes. Mild indicates the fact that patients with LADA do not by clinical judgment need insulin from the time of diagnosis. However, within the first few years after the diagnosis of diabetes a need for insulin treatment develops in many patients with LADA. This distinguishes patients with LADA from those with nonautoimmune type 2 diabetes in whom a need for insulin treatment develops later than in those with LADA (1). An early need for insulin treatment in patients with LADA points to ongoing autoimmune-mediated destruction of β-cells in these patients.Risk factors for type 2 diabetes, such as age, obesity, and lack of physical activity, are associated with the development of LADA (2). In fact, odds ratios in terms of risk for diabetes for these factors of insulin resistance were the same for LADA and type 2 diabetes. This raises the question of the relative importance of autoimmunity vis-à-vis insulin resistance for the etiology of LADA and whether etiology differs among patients with LADA. Support for etiological heterogeneity comes from the large UK Prospective Diabetes Study (UKPDS), in which only a minority of patients with the diagnosis of LADA, when defined solely as GAD antibody positivity, developed the need for insulin treatment during 6 years of follow-up (1). The heterogeneity of LADA is also evident when one compares phenotypes of patients with LADA in different studies (3–6).Heterogeneity of patients with LADA could be further elucidated by comparing phenotypes of insulin-treated patients with LADA with those not treated with insulin. However, several conditions have to be met for such comparisons to be valid. First, groups of diabetic subjects to be compared must be drawn from the same geographically defined population. A population-based study is necessary to avoid the possible biases incurred by studying referral patients or patients selected for inclusion in clinical intervention studies. Second, the perceived need for insulin treatment has to be unbiased by LADA classification, because it has been shown that insulin treatment is initiated earlier when prior knowledge of autoimmunity, measured as GAD antibodies, is available (7). Third, valid comparison groups of insulin-treated and non–insulin-treated type 2 diabetic patients from the same population must be at hand.We had the opportunity to study patients with LADA and type 2 diabetes fulfilling the above-mentioned conditions, who were identified and characterized in the Nord-Trøndelag (HUNT) study. The HUNT study was performed between 1995 and 1997. The study was open to all adult subjects (∼90,000) living in a geographically defined area and had a high attendance rate (70%). To our knowledge, the patients with LADA and type 2 diabetes defined in the HUNT study did not participate in any study at the time of diagnosis and initiation of treatment, thereby minimizing any deviation from standard clinical practice and obviating increased attentiveness for signs of insufficient metabolic control and insulin requirement. Further, autoantibodies, such as GAD antibodies, were not measured by doctors (general practitioners) responsible for treatment in the region as part of the diabetes workup before and at the time of assembling data in 1995–1997. Thus, patients with autoimmune diabetes not requiring insulin at time of diagnosis were regarded and treated as type 2 diabetic patients. This assumption provided a unique opportunity to use the need for insulin as clinically perceived as a parameter for subclassifying patients with LADA and to compare phenotypes of insulin-treated and non–insulin-treated patients with LADA with respective groups of type 2 diabetic patients. Specifically, we wished to assess the influence of autoimmunity and β-cell insufficiency vis-à-vis insulin resistance factors for the perceived need for insulin treatment in patients with LADA.     

Predicting type I diabetes

Currently, there are three markers that are being studied with the potential to give a high positive predictive value for the development of type I diabetes (insulin-dependent diabetes caused by autoimmune beta-cell destruction) and that can be utilized to predict the disease in susceptible relatives: 1) high-titer cytoplasmic islet cell antibodies, 2) insulin autoantibodies detected with fluid-phase radiobinding assays, and 3) first-phase insulin release after intravenous glucose less than 1st percentile. With the combination of these assays, it seems to be possible to identify first-degree relatives with a high probability of developing type I diabetes within a limited time span (i.e., less than 10 yr). The ability to predict type I diabetes with selected assays will allow trials for prevention of diabetes and trials to assess whether prediction will decrease morbidity and mortality at onset of diabetes.     

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.