Glutamic acid decarboxylase antibodies (GADA) is the most important factor for prediction of insulin therapy within 3 years in young adult diabetic patients not classified as Type 1 diabetes on clinical grounds

Characteristics of adult-onset auto-immune type 1 diabetes

BACKGROUND

Classically described as a disease of childhood and adolescence, diabetes mellitus type 1 (T1DM) can occur in adulthood. Adult-onset T1DM is poorly documented and is often misdiagnosed. This study aims to describe the epidemiological aspect of T1DM with adult-onset and detail its clinical, paraclinical, and therapeutic characteristics.

MATERIALS AND METHODS

A 9-year retrospective longitudinal study (2011-2019) was conducted including adult patients (age >20 years) with confirmed diabetes and at least one of the auto-antibodies (auto-Abs) to glutamic-acid-decarboxylase (GAD), to islet-tyrosine-phosphatase 2 (IA2) or islet-cell-antibodies (ICA) positive.

RESULTS

A total of 166 patients were included (sex-ratio M/F: 1.34; mean age: 28.6 years [20-56 years]). At the onset, 50.6% of patients presented with diabetic ketosis and 13.3% with diabetic ketoacidosis. Cardinal symptoms of diabetes were present in 30.7% of patients only at diagnosis, while the discovery was fortuitous in 5.4% of cases. 27.7% of patients developed an additional auto-immune disease mainly autoimmune thyroid disease. The risk of developing another AUTO-IMMUNE DISEASE was highest in females (p = 0.010) and increased with age (p = 0.011). GAD-Abs, IA2-Abs, and ICA were positive in 98.2%, 13.3%, and 17.4% of cases respectively. Only GAD-Abs were found positive in 73.1%. Upon diagnosis, 75.9% of patients were treated with insulin, while 24.1% of patients were initially put on oral anti-diabetic drugs before requiring insulin within an average of 7.42 months.

CONCLUSIONS

Adult-onset T1DM has a different clinical course (slower onset, less abrupt symptoms, more insidious presentation, and more prolonged progression to insulin) that has to be known. Misdiagnosis of adult-onset T1DM can have serious consequences.

Low Bone Turnover Associates With Lower Insulin Sensitivity in Newly Diagnosed Drug-Naïve Persons With Type 2 Diabetes

CONTEXT

Bone turnover markers (BTMs) are lower in type 2 diabetes mellitus (T2D). The relationships between bone turnover, β-cell function, and insulin sensitivity in T2D are uncertain.

OBJECTIVE

To investigate if fasting levels of BTMs in persons with T2D are associated with β-cell function or insulin sensitivity.

METHODS

We defined three T2D phenotypes, the insulinopenic (low β-cell function, high insulin sensitivity), the classical (low β-cell function, low insulin sensitivity), and the hyperinsulinemic (high β-cell function, low insulin sensitivity) phenotypes, in the Danish Centre for Strategic Research T2D cohort using the homeostatic model assessment. We selected age- and gender-matched subgroups to represent the three T2D phenotypes, yielding 326 glucose-lowering treatment-naïve persons with T2D. Median values of BTMs between the three T2D phenotypes were compared. Regression models were applied to assess the association between BTMs, β-cell function, and insulin sensitivity adjusted for potential confounders.

RESULTS

Median serum levels of procollagen type I N-terminal propeptide, C-terminal telopeptide of type I collagen, and osteocalcin were higher in the insulinopenic phenotype (52.3 μg/L, IQR 41.6, 63.3; 259.4 ng/L, IQR 163.4, 347.7; and 18.0 μg/L, IQR 14.4, 25.2, respectively) compared with the classical (41.4, IQR 31.0, 51.4; 150.4 IQR 103.5, 265.1; 13.1, IQR 10.0, 17.6, respectively) and the hyperinsulinemic (43.7, IQR 32.3, 57.3; 163.3, IQR 98.9, 273.1; 15.7 IQR 10.2, 20.8, respectively) phenotypes (all P < .01). These differences persisted after adjustment for age, sex, waist to hip ratio, or fasting plasma glucose (P < .01).

CONCLUSION

BTMs are lower in newly diagnosed persons with T2D characterized by low insulin sensitivity.

Mistaken Identity: The Role of Autoantibodies in Endocrine Disease

BACKGROUND

Autoimmune endocrine diseases can be thought of as a case of mistaken identity. The immune system mistakenly attacks one's own cells, as if they were foreign, which typically results in endocrine gland hypofunction and inadequate hormone production. Type 1 diabetes mellitus and autoimmune thyroid disorders (Hashimoto and Graves diseases) are the most common autoimmune endocrine disorders, while conditions such as Addison disease are encountered less frequently. Autoantibody production can precede clinical presentation, and their measurement may aid verification of an autoimmune process and guide appropriate treatment modalities.

CONTENT

In this review, we discuss type 1 diabetes mellitus, autoimmune thyroid disorders, and Addison disease, emphasizing their associated autoantibodies and methods for clinical detection. We will also discuss efforts to standardize measurement of autoantibodies.

CONCLUSIONS

Autoimmune endocrine disease progression may take months to years and detection of associated autoantibodies may precede clinical onset of disease. Although detection of autoantibodies is not necessary for diagnosis, they may be useful to verify an autoimmune process.

DPVis: Visual Analytics With Hidden Markov Models for Disease Progression Pathways

Clinical researchers use disease progression models to understand patient status and characterize progression patterns from longitudinal health records. One approach for disease progression modeling is to describe patient status using a small number of states that represent distinctive distributions over a set of observed measures. Hidden Markov models (HMMs) and its variants are a class of models that both discover these states and make inferences of health states for patients. Despite the advantages of using the algorithms for discovering interesting patterns, it still remains challenging for medical experts to interpret model outputs, understand complex modeling parameters, and clinically make sense of the patterns. To tackle these problems, we conducted a design study with clinical scientists, statisticians, and visualization experts, with the goal to investigate disease progression pathways of chronic diseases, namely type 1 diabetes (T1D), Huntington's disease, Parkinson's disease, and chronic obstructive pulmonary disease (COPD). As a result, we introduce DPVis which seamlessly integrates model parameters and outcomes of HMMs into interpretable and interactive visualizations. In this article, we demonstrate that DPVis is successful in evaluating disease progression models, visually summarizing disease states, interactively exploring disease progression patterns, and building, analyzing, and comparing clinically relevant patient subgroups.

Treating latent autoimmune diabetes in adults in the era of cardiovascular outcomes trials: Old dog should learn new tricks

BACKGROUND

Latent autoimmune diabetes in adults (LADA) is characterised by pathophysiological and clinical heterogeneity. Hence, the optimal treatment strategy for this type of diabetes remains a clinical challenge.

AIM

To discuss the potential of a modern therapeutic approach for LADA in the context of the novel findings of cardiovascular outcomes trials and stress the controversies surrounding LADA and the barriers in the effective management of people with this type of diabetes.

METHODS

We performed a literature search in major biomedical databases in order to retrieve relevant literature. The results of key studies, along with the authors' clinical experience and perspective, are summarised and discussed in this narrative, mini review article.

RESULTS

Insulin remains the primary treatment choice in individuals with low C-peptide levels. Although cardiovascular outcomes trials have mainly recruited participants with type 2 diabetes, recent data suggest that the cardiorenal protective properties of the new therapies are even present in people without diabetes and thus, the extrapolation of their results on LADA individuals sounds reasonable. Therefore, sodium-glucose co-transporter 2 inhibitors (SGLT2is) and glucagon-like peptide-1 receptor agonists should be considered for the management of people with preserved insulin production being at high cardiovascular risk. The risk of diabetic ketoacidosis with SGLT2is requires increased vigilance by treating physicians.

CONCLUSIONS

Individualisation, preservation of beta-cell mass and function and cardiorenal protection are the new challenges in LADA therapy.

An overview of type 2 diabetes and importance of vitamin D3-vitamin D receptor interaction in pancreatic β-cells

One significant health issue that plagues contemporary society is that of Type 2 diabetes (T2D). This disease is characterised by higher-than-average blood glucose levels as a result of a combination of insulin resistance and insufficient insulin secretions from the β-cells of pancreatic islets of Langerhans. Previous developmental research into the pancreas has identified how early precursor genes of pancreatic β-cells, such as Cpal, Ngn3, NeuroD, Ptf1a, and cMyc, play an essential role in the differentiation of these cells. Furthermore, β-cell molecular characterization has also revealed the specific role of β-cell-markers, such as Glut2, MafA, Ins1, Ins2, and Pdx1 in insulin expression. The expression of these genes appears to be suppressed in the T2D β-cells, along with the reappearance of the early endocrine marker genes. Glucose transporters transport glucose into β-cells, thereby controlling insulin release during hyperglycaemia. This stimulates glycolysis through rises in intracellular calcium (a process enhanced by vitamin D) (Norman et al., 1980), activating 2 of 4 proteinases. The rise in calcium activates half of pancreatic β-cell proinsulinases, thus releasing free insulin from granules. The synthesis of ATP from glucose by glycolysis, Krebs cycle and oxidative phosphorylation plays a role in insulin release. Some studies have found that the β-cells contain high levels of the vitamin D receptor; however, the role that this plays in maintaining the maturity of the β-cells remains unknown. Further research is required to develop a more in-depth understanding of the role VDR plays in β-cell function and the processes by which the beta cell function is preserved.

Latent autoimmune diabetes of adulthood: case report

BACKGROUND

Primary care clinicians will see a higher incidence of type 2 diabetes in adult patients, and the diagnosis and management of an initial presentation of type 1 diabetes can pose challenges to clinicians who see it less frequently. Symptoms of hyperglycemia and risk of ketoacidosis may be missed. Further, endocrine autoimmune disease can run together in patients and families.

CASE PRESENTATION

A 49-year-old Caucasian female with history of pituitary adenoma and Graves' disease with history of thyroid ablation presented in the outpatient setting due to hand tingling of her right middle finger that was worse in the mornings and improved throughout the day. She also complained of excessive thirst, finding herself drinking more water than usual and waking up in the night to urinate. There was no dysuria or haematuria, and no other neurologic symptoms. She did report feeling hungry. She had no family history of diabetes, normal body mass index of 21.7, and reported taking her thyroid replacement medication every day. The differential diagnosis for her thirst included dehydration, psychogenic polydipsia, diabetes mellitus, diabetes insipidus, and anxiety. The patient had normal vital signs and was well appearing; labs were ordered for her on her way home from clinic with no medications. Labs revealed a random blood glucose level of 249 mg/dL, normal renal function, a normal B12 of 996 pg/mL, and an elevated thyroid stimulating hormone level of 25.67 u[iU]/mL. On follow up with her primary care provider 5 days later, additional labs were drawn showing A1C of 11.5%, 1+ ketonuria, a negative Acetest, and a normal basic metabolic panel, except for a fasting glucose of 248 mg/dL, and Free T3 of 2.42 pg/mL, and Free T4 of 1.7 ng/dL. Islet cell antibodies and glutamic acid decarboxylase antibodies were both positive, consistent with type 1 diabetes. She was started on insulin and improved.

CONCLUSION

Given the patient's age, this is a less common presentation of type 1 diabetes mellitus, as a part of polyglandular autoimmune syndrome type IIIa. It serves as a reminder that clinicians should remember that patients with one autoimmune disease (in this case, h/o Graves' disease) are at higher risk for diabetes and other endocrine autoimmune diseases and should be screened appropriately. Clinicians should keep latent type 1 diabetes in the differential in adulthood to ensure proper and timely treatment.

Glutamic acid decarboxylase and islet antigen 2 antibody profiles in people with adult-onset diabetes mellitus: a comparison between mixed ethnic populations in Singapore and Germany

AIM

To gain insight into the presence of islet cell autoimmunity in an ethnic Asian compared with a white European population.

METHODS

For this cross-sectional study we recruited people with adult-onset diabetes (age of diagnosis 20-60 years), at tertiary referral centres in Germany (n=1020) and Singapore (n=1088). Glutamic acid decarboxylase and islet antigen 2 antibodies were measured according to Islet Autoantibody Standardization Program protocols.

RESULTS

The prevalence of glutamic acid decarboxylase antibody positivity was 13.9% (95% CI 12.1-16.0; P<0.001) in the white European cohort compared with 6.8% (95% CI 5.5-8.4; P<0.001) in the Asian cohort. Glutamic acid decarboxylase antibody positivity was 11.4% (95% CI 7.7-16.6) in Indian, 6.0% (95% CI 3.6-9.9) in Malay and 5.8% (95% CI 4.3-7.7; P<0.001) in Chinese participants. In the white European participants, the prevalence of islet antigen 2 antibody positivity was 7.8% (95% CI 6.4-9.4) compared with 14.8% (95% CI 12.8-17.0; P<0.001) in the Asian cohort as a whole, and among the three ethnicities in the Asian cohort it was 12.4% (95% CI 8.6-17.7) in Indian, 16.8% (95% CI 12.6-22.2) in Malay and 15.7% (95% CI 13.2-18.6) in Chinese participants. Double antibody positivity was seen in 5.7% (95% CI 4.5-7.1) of white European participants compared with 1.6% (95% CI 1.0-2.5; P<0.01) of Asian participants. In the white European cohort, those who were glutamic acid decarboxylase autoantibody-positive had a lower BMI than those who were autoantibody-negative, but this trend was absent in the Asian cohort.

CONCLUSIONS

A marked prevalence of islet cell autoimmunity was observed in people with adult-onset diabetes. While glutamic acid decarboxylase antibodies were more frequent in the European cohort, islet antigen 2 antibody positivity was highest in the three ethnic groups in Singapore, suggesting ethnic-specific differences in antibody profiles.

Glutamic acid decarboxylase autoantibodies are dominant but insufficient to identify most Chinese with adult-onset non-insulin requiring autoimmune diabetes: LADA China study 5

AIMS

Adult-onset autoimmune diabetes is prevalent in China, in contrast to childhood-onset type 1 diabetes mellitus. Islet autoantibodies are the most important immune biomarkers to diagnose autoimmune diabetes. We assayed four different islet autoantibodies in recently diagnosed adult non-insulin-requiring diabetes Chinese subjects to investigate the best antibody assay strategy for the correct diagnosis of these subjects.

METHODS

LADA China study is a nation-wide multicenter study conducted in diabetes patients from 46 university-affiliated hospitals in China. Non-insulin-treated newly diagnosed adult diabetes patients (n = 2388) were centrally assayed for glutamic acid decarboxylase autoantibody (GADA), protein tyrosine phosphatase-2 autoantibody (IA-2A), and zinc transporter 8 autoantibody (ZnT8A) by radioligand assay and insulin autoantibody (IAA) by microtiter plate radioimmunoassay. Clinical data were determined locally.

RESULTS

Two hundred and six (8.63 %) subjects were autoantibody positive, of which GADA identified 5.78 % (138/2388) of the total, but only 67 % (138/206) of the autoimmune cases. IA-2A, ZnT8A, and IAA were found in 1.51, 1.84, and 1.26 % of the total study subjects, respectively. When assaying three islet autoantibodies, the most effective strategy was the combination of GADA, ZnT8A, and IAA, which could identify 92.2 % (190/206) autoimmune diabetes patients. The clinical data showed that those subjects with positive GADA had lower random C-peptide than autoantibody negative subjects (P < 0.05).

CONCLUSIONS

As with Europeans, GADA is the dominant autoantibody in this form of autoimmune diabetes in China, but in contrast to Europeans, screening should include other diabetes-associated autoantibodies.

The changing face of diabetes in America

So much has changed in the field of diabetes diagnosis and management in the United States. Unhealthy lifestyle choices have hastened an epidemic of childhood obesity, causing a paradigm shift in how childhood diabetes is conceptualized. Once thought a consequence of obesity, sedentary lifestyle, and genetics, diabetes with onset in adults has been found to have a variant with autoimmunity. As the lines among adult-onset, child-onset, and type 1 and type 2 diabetes mellitus become more blurred, best practices in management and prevention become more complicated. This article highlights key points regarding 2 variants, juvenile-onset type 2 diabetes mellitus and latent autoimmune diabetes of adults.

Long-term sustained autoimmune response to beta cell specific zinc transporter (ZnT8, W, R, Q) in young adult patients with preserved beta cell function at diagnosis of diabetes

The aim of this study was to examine whether autoantibodies to: ZnT8-Tryptophan (ZnT8WA), ZnT8-Arginine (ZnT8RA) or ZnT8-Glutamine (ZnT8QA) correlated with C-peptide or other autoantibodies and to assess diagnostic sensitivity of ZnT8WRQA. Specimens from 270 newly diagnosed diabetic subjects (age 15-34 years) and after 5 years duration of disease were examined. Four linear regression models were used to dissect the importance of different factors from diagnosis for the respective difference of (logZnT8WA), (logZnT8RA) and (logZnT8QA); A) unadjusted model for: initial C-peptide, age, BMI, gender, clinical classification, ICA, GADA, IA-2A, (ZnT8WA/ZnT8RA/ZnT8QA); B) C-peptide corrected for clinical factors; C) C-peptide corrected for autoantibodies; D) C-peptide corrected for all factors. The least decrease of ZnT8WA was observed in patients with high initial C-peptide in all models A) p = 0.054; B) p = 0.021; C) p = 0.047 and D) p = 0.017. A less statistically significant decrease of ZnT8RA was observed in patients with high initial C-peptide in A) p = 0.038 and C) p = 0.047, but this finding was not confirmed in B or D. The decrease of ZnT8QA levels was not related to C-peptide in any model but correlated to age D) p = 0.049. Furthermore, patients with unclassifiable diabetes showed the least decrease in D) p = 0.035. ZnT8WA, ZnT8RA or ZnT8QA were identified as a single autoantibody in 3.8% (10/266) of patients, thereby increasing diagnostic sensitivity from 79.3% (211/266) to 83.1% (221/266). In conclusion, high initial C-peptide was the most important factor even after adjusting for other factors in patients positive for ZnT8WA or ZnT8RA to remain autoantibody positive 5 years after diagnosis.

Excess mortality in middle-aged men with diabetes aged 15-34 years at diagnosis

The aim of this study is to assess mortality risk and the excess of risk in patients with diabetes. Patients were 15-34 years old at diagnosis of diabetes mellitus (n = 879) in 1992 and 1993 in this national cohort from Sweden. Healthy controls were matched for gender and birth on the same day as the index cases (n = 837). The civic registration number was used to link patients and controls to the Swedish Cause of Death Registry. During follow-up, 3.3% (29/879) of patients and 1.1% (9/837; P = 0.002) of controls died. The risk for a patient with diabetes to die was almost threefold increased compared with healthy controls; hazard ratio, 2.9 (95% CI 1.4-6.2). This increased risk was significant in men; hazard ratio, 2.8 (95% CI 1.2-6.5). Diabetes as the underlying cause of death accounted for 38% (11/29) of deaths among patients. Most patients, 55% (16/29), died at home, remaining patients in hospital, 28% (8/29), or elsewhere 17% (5/29) compared to controls of whom 33% (3/9; P = 0.45) died at home, 33% (3/9; P = 1.0) in hospital, and 33% (3/9; P = 0.36) elsewhere. Only 55% (16/29) of patients had a specified day of death on death certificates compared to 100% (9/9; P = 0.016) of controls. Adult men with diabetes had an almost threefold increased risk to die within 15 years of diagnosis compared to healthy men. Most middle-aged patients with diabetes died at home and often without a specified date of death recorded.

Latent Autoimmune Diabetes in Adults: a case report

Latent Autoimmune Diabetes in Adults (LADA) is an autoimmune endocrine disorder in which despite the presence of antipancreatic islets antibodies in the moment of diagnostics, the progression to beta-cell secretory insufficiency is slow. It is often confused with others types of diabetes and therefore the management is frequently inadequate. We report a clinical case of a 23-year-old man with diagnosis of type 2 diabetes since 6 months ago, poorly controlled with a sulfonylurea, who initially presented 2 months ago from polyuria, polydipsia, and asthenia and 6 kg weight loss. History of past illness was negative, however, his mother relates exclusive breastfeeding during the first 15 days of life and later (until the 6 months) he was fed with infant formula (S-26). Family history revealed a first-degree relative (father) with diabetes mellitus secondary to steroid administration due to diagnosis of bone marrow hypoplasia. Also presents second-degree family history (uncle and grandfather) of type 2 diabetes mellitus. There were no pathologic findings at the physical examination. Anthropometry and laboratory tests were as follows: body mass index (BMI) = 19.66 kg/m, basal and postprandial glycemia = 108, and 276 mg/dL respectively, glycated haemoglobin = 8.9%, basal and postprandial C-peptide (2 hours) = 1.9, and 3.2 ng/mL, homeostasis model assessment of beta cell function: 87.5%, homeostasis model assessment of insulin resistance: 1.6. LADA presumptive diagnosis was confirmed with presence of autoantibodies anti-tyrosin-phosphatase and GAD65. At the time of diagnosis, individuals with LADA present an onset age <50, BMI <25 kg/m2, low magnitude postprandial and basal hyperglycemia, normal or close to normal C-peptide values, and thus not occur with acute hyperglycemic crises. Insulin therapy preserves pancreatic b-cell function, at the point that eventually prescribed insulin doses need to be reduced.

The glutamic acid decarboxylase 65 immunoglobulin G subclass profile differs between adult-onset type 1 diabetes and latent autoimmune diabetes in adults (LADA) up to 3 years after clinical onset

Autoantibodies against glutamic acid decarboxylase 65 (GADA) are found frequently in patients with autoimmune diabetes. Immunoglobulin (Ig)G(1) is the most frequent subclass among the GADA IgG subclasses. IgG(4) is a more common subclass in latent autoimmune diabetes in adults (LADA) at clinical onset compared to type 1 diabetes. The aim of this work was to study the different GADA-IgG subclass profiles during a 3-year follow-up in these groups of autoimmune diabetes. Adult-onset subjects, classified as either type 1 (n = 40) or LADA (n = 43), were included in the study. New samples were collected every year from these patients. In addition to conventional GADA analyses, GADA-IgG subclasses were also analysed with a radioimmunoprecipitation assay using biotin-conjugated antibodies (directed against human IgG subclasses and IgM) and streptavidin Sepharose. During 3 years' follow-up, all the IgG subclass levels decreased in type 1 diabetes - IgG(1): P < 0.001; IgG(2): P < 0.001; IgG(3): P < 0.001; IgG(4): P < 0.05 (Friedman's' test) - while levels remained stable for all four subclasses in LADA. GADA IgM, however, decreased in both groups (P < 0.001). Patients with LADA have higher GADA IgG(3) and IgG(4) at clinical onset and seem to maintain the levels and profile of their IgG subclasses up to 3 years after clinical onset, while all the GADA IgG subclass levels decrease in type 1 diabetic patients. This indicates a persistent different immune response in LADA compared to type 1 diabetes and further indicates the difference in pathogenesis.

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.

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.

Latent (slowly progressing) autoimmune diabetes in adults

About 10% of patients with the clinical presentation of type 2 diabetes suffer from an autoimmune form of diabetes associated with a rapid decline of residual beta-cell mass and subsequent development of insulin dependency. In this condition, called latent autoimmune diabetes in adults (LADA), there are clinical and metabolic features intermediate between type 1 and type 2 diabetes. Recent studies provide novel information on the immune markers associated with progressive beta-cell loss in LADA patients. However, LADA pathogenesis is still poorly understood; further studies are needed to establish general recommendation for preventing and treating this subtype of autoimmune diabetes.

Seasonality of month of birth differs between type 1 diabetes patients with pronounced beta-cell autoimmunity and individuals with lesser or no beta-cell autoimmunity

OBJECTIVE

To establish whether children with type 1 diabetes mellitus (T1D) with signs of pronounced beta-cell-specific autoimmunity as reflected by high autoantibody titers or positivity for several beta-cell-specific autoantibodies show a different pattern of month of birth (MOB) compared with children with T1D and low beta-cell autoimmunity and that of the general population.

RESEARCH DESIGN AND METHODS

Cosinor analysis was used to analyze MOB rhythmicity in Swedish children with new onset T1D (n = 572), in whom the glutamate decarboxylase autoantibody (GAD65Ab) titer was determined and compared with that in 833 healthy children, and in 505 children with T1D in Berlin, in whom the titers of autoantibodies to insulin, GAD65, and islet antigen-2 were compared with the MOB pattern in the general population (n = 446 571).

RESULTS

In both cohorts of children with T1D, we found that children with either a high GAD65Ab titer (above the 80th percentile) or positivity for three beta-cell-specific autoantibodies differed in their pattern of MOB from the healthy population.

CONCLUSIONS

Our past and present observations support the hypothesis that the autoimmune process leading to childhood T1D is in part triggered in the perinatal period by viral infections in genetically susceptible individuals. The present study suggests that the process is linked to titer levels of autoantibodies.

Islet cell autoantibody levels after the diagnosis of young adult diabetic patients

AIMS

The aim was to determine the course of islet cell antibodies [glutamate decarboxylase (GADA), tyrosine phosphatase-like islet antigen 2 (IA-2A) and islet cell (ICA)] after the diagnosis of the diabetic patient.

METHODS

The Diabetes Incidence Study in Sweden (DISS) attempted to prospectively enrol all newly diagnosed diabetic patients aged 15-34 years during 1992 and 1993. C-peptide and autoantibody levels were determined from venous blood samples at diagnosis and again at yearly intervals for 6 years.

RESULTS

After the first year, the odds of remaining GADA positive decreased by 9% per year [odds ratio (OR) = 0.91, 95% confidence interval (CI) = 0.85-0.96] while the mean GADA index remained unchanged ( = 0.8, P = 0.37). There was no change in the percentage of subjects testing IA-2A positive after the first year ( = 0.1, P = 0.75). However, the mean index decreased 0.04 per year (95% CI: 0.03-0.05)-a 7.9% decline (95% CI: 5.4-10.4%). The odds of a subject testing positive for ICA decreased by 24% per year (OR = 0.76, 95% CI = 0.70-0.82). The mean ICA levels decreased 0.75 per year (95% CI: 0.66-0.84)-a 16.4% decline (95% CI: 14.1-18.6%). The rate of change in titres for all three autoantibodies was independent of gender, human leucocyte antigen genotype and C-peptide status.

CONCLUSIONS

GADA levels remained high while ICA levels declined. In contrast to a previous study, we found that the proportion of IA-2A subjects remaining positive did not decrease after the first year, while the average index decreased slightly.

Determination of glutamic acid decarboxylase antibodies (GADA) IgG subclasses − comparison of three immunoprecipitation assays (IPAs)

IgG subclasses of glutamic acid decarboxylase (GAD65) antibodies (GADA) may reflect the immunological state in the pancreas of GADA-positive patients with autoimmune diabetes. The use of biotin-conjugated antibodies and streptavidin Sepharose are used commonly in immunoprecipitation assays (IPA) based on 125I- or 35S-labelled antigens to capture IgG subclasses directed against IA-2 or GAD65. We have compared three different immunoprecipitation assays for the determination of GADA IgG subclasses. Two of the assays were based on the biotin and streptavidin systems provided in a solid (immobilized) or liquid (mobilized) phase binding environment. The third assay was based on N-hydroxysuccinimide (immobilized) interaction with primary amines (i.e. lysine residues) on the antibody. We found the liquid phase binding assay (LPBA) to be the most stable assay, with a comparatively low coefficient of variation and background.

Multiple factors affect the loss of measurable C-peptide over 6 years in newly diagnosed 15- to 35-year-old diabetic subjects

OBJECTIVE

The aim of this study is to identify risk factors for the loss of measurable plasma C-peptide in newly diagnosed 15- to 35-year-old diabetic subjects.

METHODS

This Swedish study included 778 subjects. C-peptide levels were obtained each year for 6 years after diagnosis. Loss of measurable C-peptide was defined as a level at or below the lower detection limit of the local assay (0.13 nmol/l). In addition to C-peptide, other baseline covariates included gender, age, body mass index, HLA genotype, and autoantibody levels.

RESULTS

Compared with autoantibody-negative subjects, autoantibody-positive subjects had lower median baseline C-peptide (0.27 vs. 0.50, P<.001), their levels declined over the study period, and the risk of losing measurable C-peptide was significantly higher when more than one autoantibody was present [odds ratio (OR), 4.0; 95% confidence interval (CI), 2.13-7.54]. Among autoantibody-positive individuals, the presence of GAD65Ab (OR, 1.8; 95% CI, 1.24-2.51) and islet cell antibodies (OR, 1.6; 95% CI, 1.19-2.18) conferred a higher risk for loss of measurable C-peptide as did female gender (OR, 1.6; 95% CI, 1.17-2.11) and time after diagnosis (OR, 1.5 for each additional year postdiagnosis; 95% CI, 1.41-1.57). Higher baseline C-peptide levels were protective (OR, 0.5 for each additional log(e) nanomoles per liter; 95% CI, 0.36-0.58).

CONCLUSIONS

This study identified autoantibody status, gender, and baseline C-peptide levels as factors that will be useful for predicting the disease course of 15- to 35-year-old diabetic individuals.

HLA-DQB1 genotypes, islet antibodies and beta cell function in the classification of recent-onset diabetes among young adults in the nationwide Diabetes Incidence Study in Sweden

AIMS/HYPOTHESIS

The World Health Organization considers an aetiological classification of diabetes to be essential. The aim of this study was to evaluate whether HLA-DQB1 genotypes facilitate the classification of diabetes as compared with assessment of islet antibodies by investigating young adult diabetic patients.

SUBJECTS AND METHODS

Blood samples were available at diagnosis for 1,872 (90%) of the 2,077 young adult patients (aged 15-34 years old) over a 5-year period in the nationwide Diabetes Incidence Study in Sweden. Islet antibodies were measured at diagnosis in 1,869 patients, fasting plasma C-peptide (fpC-peptide) after diagnosis in 1,522, while HLA-DQB1 genotypes were determined in 1,743.

RESULTS

Islet antibodies were found in 83% of patients clinically considered to have type 1 diabetes, 23% with type 2 diabetes and 45% with unclassifiable diabetes. After diagnosis, median fpC-peptide concentrations were markedly lower in patients with islet antibodies than in those without (0.24 vs 0.69 nmol/l, p<0.0001). Irrespective of clinical classification, patients with islet antibodies showed increased frequencies of at least one of the risk-associated HLA-DQB1 genotypes compared with patients without. Antibody-negative patients with risk-associated HLA-DQB1 genotypes had significantly lower median fpC-peptide concentrations than those without risk-associated genotypes (0.51 vs 0.74 nmol/l, p=0.0003).

CONCLUSIONS/INTERPRETATION

Assessment of islet antibodies is necessary for the aetiological classification of diabetic patients. HLA-DQB1 genotyping does not improve the classification in patients with islet antibodies. However, in patients without islet antibodies, HLA-DQB1 genotyping together with C-peptide measurement may be of value in differentiating between idiopathic type 1 diabetes and type 2 diabetes.

The prevalence of the 65-kilodalton isoform of glutamic acid decarboxylase autoantibodies by glucose tolerance status in elderly patients from the cardiovascular health study

CONTEXT

Autoantibodies (AA) to glutamic acid decarboxylase (GAD65), a determinant of risk for autoimmune diabetes, have been found in up to 10% of patients with type 2 diabetes. In older adults, this marker may also serve as a determinant of risk for autoimmune diabetes and enhance diabetes classification.

OBJECTIVE

The objective of this study was to evaluate the relationship between GAD65AA and glucose tolerance status, current diabetes treatment, and clinical measures in older adults.

DESIGN

GAD65AA were measured at baseline in 3318 participants from the Cardiovascular Health Study, a cohort study of 5888 individuals 65 or older.

SETTING

The population-based cohort was recruited from four U.S. sites.

PATIENTS

Patients included all Cardiovascular Health Study participants with known diabetes, newly diagnosed diabetes, impaired fasting glucose, impaired glucose tolerance, and a sample of normal glucose-tolerant participants.

MAIN OUTCOME MEASURES

GAD65AA, body mass index, fasting glucose and insulin levels, blood pressure, lipid levels, and diabetes treatment at baseline were measured.

RESULTS

The prevalence of GAD65AA increased with decreasing glucose tolerance in both Blacks (n = 560) and Whites (n = 2730), being more pronounced in known diabetic individuals. GAD65AA were found in 2.3, 5.8, 7.8, and 8.3% of diabetic participants, reporting use of no diabetes medication, oral hypoglycemic agents, insulin only, and both oral hypoglycemic agents and insulin, respectively (P = 0.02, linear trend). Among diabetic participants, GAD65AA positivity was associated with diabetes treatment, higher fasting glucose, and lower body mass index.

CONCLUSIONS

Even among older individuals with diabetes, GAD65AA may be a useful marker in identifying a subgroup of autoimmune diabetes, serve as a marker of insulin requirement, and remain stable over years.

T cells to a dominant epitope of GAD65 express a public CDR3 motif

Non-obese diabetic (NOD) mice spontaneously develop autoimmune diabetes, and serve as a model for type 1 diabetes (T1D) and natural autoimmunity. T cell responses to the pancreatic islet antigen glutamic acid decarboxylase 65 (GAD65) can be detected in the spleens of young prediabetic NOD mice, which display a unique MHC class II molecule. Here, we report that a distinct TcR beta chain and CDR3 motif are utilized by all NOD mice in response to a dominant determinant on GAD65, establishing a public repertoire in the spontaneous autoimmunity to an important islet cell antigen. GAD65 530-543 (p530)-reactive T cells preferentially utilize the Vbeta4, Dbeta2.1 and Jbeta2.7 gene segments, with a CDR3 that is characterized by a triad of amino acids, DWG, preceded by a polar residue. In addition, we used CDR3 length spectratyping, CDR3-specific reverse transcriptase-PCR and direct TcR sequencing to show that the TcR beta chain structural patterns associated with p530-specific T cells consistently appeared in the islets of young NOD mice with insulitis, but not in the inflamed islets of streptozotocin-treated C57BL/6 mice, or in inflamed NOD salivary glands. To our knowledge, this is the first report to demonstrate that a public T cell repertoire is used in spontaneous autoimmunity to a dominant self-determinant. These findings suggest that defined clonotypes and repertoires may be preferentially selected in haplotypes predisposed to spontaneous autoimmunity.

Excess mortality in incident cases of diabetes mellitus aged 15 to 34 years at diagnosis: a population-based study (DISS) in Sweden

AIMS/HYPOTHESIS

The objective of the study was to analyse the mortality, survival and cause of death patterns in incident cases of diabetes in the 15-34-year age group that were reported to the nationwide prospective Diabetes Incidence Study in Sweden (DISS).

MATERIALS AND METHODS

During the study period 1983-1999, 6,771 incident cases were reported. Identification of deaths was made by linking the records to the nationwide Cause of Death Register.

RESULTS

With an average follow-up of 8.5 years, resulting in 59,231 person-years, 159 deaths were identified. Diabetes was reported as the underlying cause of death in 51 patients (32%), and as a contributing cause of death in another 42 patients (26%). The standardised mortality ratio (SMR) was significantly elevated (RR=2.4; 95% CI: 2.0-2.8). The SMR was higher for patients classified by the reporting physician as having type 2 diabetes at diagnosis than for those classified as type 1 diabetic (2.9 and 1.8, respectively). Survival analysis showed significant differences in survival curves between males and females (p=0.0003) as well as between cases with different types of diabetes (p=0.005). This pattern was also reflected in the Cox regression model showing significantly increased hazard for males vs females (p=0.0002), and for type 2 vs type 1 (p=0.015) when controlling for age.

CONCLUSIONS/INTERPRETATION

This study shows a two-fold excess mortality in patients with type 1 diabetes and a three-fold excess mortality in patients with type 2 diabetes. Thus, despite advances in treatment, diabetes still carries an increased mortality in young adults, even in a country with a good economic and educational patient status and easy access to health care.

Oral agents in managing diabetes mellitus in children and adolescents

Type 2 diabetes mellitus is a chronic disease with potentially devastating long-term complications. Despite the tremendous body of research and experience in the adult population, relatively little is established regarding this condition and its optimal management in children and adolescents. The pediatric community awaits results of ongoing trials as well as further study of optimal intervention in children, as they continue to extrapolate management practices from their adult counterparts.

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.

Latent autoimmune diabetes of adulthood. Unique features that distinguish it from types 1 and 2

A number of patients with poor glycemic control receive the diagnosis of type 2 diabetes despite the fact that they do not exhibit some of the traditional characteristics of the disease, such as obesity. A more accurate diagnosis for many of these patients is latent autoimmune diabetes of adulthood (LADA). In this article, Dr Nabhan and coauthors describe features that LADA has in common with type 1 and type 2 diabetes, as well as those that distinguish LADA from these more widely recognized forms of diabetes. The authors also describe the pathogenesis of the disease, potential complications, and treatment options.

Different HLA-DR-DQ and MHC class I chain-related gene A (MICA) genotypes in autoimmune and nonautoimmune gestational diabetes in a Swedish population

The genetic susceptibility for gestational diabetes (GDM) was estimated by comparisons of genotypes within human leukocyte antigen (HLA) and major histocompatibility complex class I chain-related gene A (MICA) in 199 women with GDM and 213 healthy women. At least one of ICA, glutamic acid decarboxylase antibodies, or islet cell antigen-2 antibodies/tyrosine phosphatase antibodies was found in 6.0% (12/199) of women with GDM and were considered as autoimmune GDM, whereas the remaining 187 were considered as nonautoimmune GDM. HLA genotyping was done with polymerase chain reaction and sequence-specific oligonucleotides. MICA polymorphism was determined with polymerase chain reaction and fragment size determination. HLA-DR3-DQ2/x or DR4-DQ8/x and MICA5.0/5.1 were more frequent in autoimmune GDM compared with controls; 92% versus 46% and 42% versus 13% and conferred increased risk (odds ratio [OR] = 13; 95% confidence interval [CI] 1.7-104) and (OR = 4.7; 95%CI 1.4-16). Four other genotypes were more frequent in nonautoimmune GDM compared with controls: HLA-DR7-DQ2/y, 24% versus 14%; DR9-DQ9/y, 9.6% versus 1.9%; DR14-DQ5/y, 7.5% versus 0.94%; and MICA5.0/z, 24% versus 13% and gave increased risk: OR = 2.0; 95%CI 1.2-3.4, OR = 5.6; 95%CI 1.8-17, OR = 8.5; 95%CI 1.9-38, and OR = 2.0; 95%CI 1.2-3.4, respectively. We concluded that autoimmune diabetes with onset during pregnancy is associated with the type 1 diabetes-associated genotypes and also with MICA5.0/5.1, whereas DR7-DQ2/y, DR9-DQ9/y, DR14-DQ5/y, and MICA5.0/z are risk factors for nonautoimmune GDM.

Acquired non-type 1 diabetes in childhood: subtypes, diagnosis, and management

Over the past 30 years it has become apparent that not all diabetes presenting in childhood is autoimmune type 1. Increasingly type 2 diabetes, maturity onset diabetes of the young, iatrogenic diabetes, and rare syndromic forms of diabetes such as Wolfram's syndrome have been identified in children. This review is aimed at the general paediatrician looking after children with diabetes, and aims to provide an algorithm for assessment, investigation, and suggested management for the newly diagnosed child with suspected non-type 1 diabetes. This article will also be relevant to the child with atypical diabetes-that is, on low insulin doses outside the honeymoon period.

IgG4-subclass of glutamic acid decarboxylase antibody is more frequent in latent autoimmune diabetes in adults than in type 1 diabetes

AIMS/HYPOTHESIS

Glutamic acid decarboxylase autoantibodies (GADA) are the most frequent beta-cell-specific autoantibodies in type 1 diabetes and in latent autoimmune diabetes in adults (LADA). The autoimmune attack on pancreatic islet cells is associated with a T helper 1 cell (T(h)1) response, mainly represented by IgG(1)-subclass in humans. It has been proposed that the presence of IgG(4) may be associated with a T(h)2 response. The aim of our study was to compare the GADA IgG-subclass distribution between adult patients with type 1 diabetes and LADA.

METHODS

Patients with type 1 diabetes (n=45) and patients with LADA (n=60) were included. Radioimmunoprecipitation assay with IgG-subclass specific Sepharose (IgG(1), IgG(2), IgG(3) and IgG(4)) was used to precipitate the antibody/antigen-complex.

RESULTS

We only detected IgG(4)-subclass of GADA in subjects with LADA (26.7%; p<0.001). IgG(1) was the most common GADA-subclass in both groups, however IgG(1) as the solely expressed subclass was more common among type 1 diabetic patients (77.8%; p<0.05). The rank order of the frequencies of IgG-subclasses in type 1 diabetes was IgG(1)>IgG(3)>IgG(2)>IgG(4) and in LADA patients IgG(1)>IgG(4)>IgG(2)>IgG(3).

CONCLUSIONS/INTERPRETATION

The difference in GADA IgG-subclasses could indicate a different immune response, possibly an altered balance between T(h)1 and T(h)2 cytokine profile in pancreatic islets. This difference could contribute to the slower rate of beta cell destruction in LADA patients, as reflected by a higher C-peptide level at clinical onset.

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.

Conformation-dependent GAD65 autoantibodies in diabetes

AIMS/HYPOTHESIS

Conformation-dependent autoantibodies directed against GAD65 are markers of Type 1 diabetes. In this study we aimed to determine whether the substitution of GAD65 with GAD67 amino acids would affect the binding of conformation-dependent GAD65 autoantibodies.

METHODS

We used PCR-based site-directed mutagenesis to generate a series of mutated GAD65 cDNA constructs in which specific GAD65 coding sequences for regions of the protein critical for autoantibody binding were replaced with GAD67 coding sequences.

RESULTS

The introduction of a point mutation at position 517, substituting glutamic acid with proline, markedly reduced the binding of disease-associated GAD65 antibodies. The binding of GAD65 antibodies to the E517P mutant was reduced in the sera of all newly diagnosed Type 1 diabetes patients ( n=85) by a mean of 72% ( p<0.0001) compared with binding to wild-type GAD65. Patients with latent autoimmune diabetes in adults ( n=24) showed a similar reduction in binding (79% reduction, p<0.0001). First-degree relatives who subsequently progressed to Type 1 diabetes ( n=12) showed a reduction in binding of 80% compared with a reduction of only 65% among relatives who had not progressed to disease ( n=38; p=0.025). In healthy GAD65Ab-positive individuals who did not progress to diabetes during a 9-year follow-up period ( n=51), binding to GAD65-E517P was reduced by only 28% compared with binding to wild-type GAD65.

CONCLUSIONS/INTERPRETATION

Differences in autoantibody binding to wild-type GAD65 versus GAD65-E517P may provide predictive information about Type 1 diabetes risk beyond that provided by the presence or absence of GAD65 autoantibodies. Lack of binding to mutant GAD65-E517P defines GAD65-positive individuals who are at higher risk of developing diabetes.

Development of glutamic acid decarboxylase 65 (GAD65) autoantibody assay using biotin–GAD65 fusion protein

We evaluated a biotin-glutamic acid decarboxylase 65 (GAD65)-based enzyme-linked immunosorbent assay (B-ELISA) to detect GAD65 autoantibodies (GAD65Ab) in 78 sera from individuals with newly diagnosed type 1 diabetes. The GAD65Ab index of patients with type 1 diabetes (mean value of GAD65Ab index of 1.891) was significantly higher than those in 50 sera from healthy control group (mean value of 0.068). The intra- and inter-assay coefficients of variation (CV) were calculated to be 1.042 and 10.703%, respectively. The specificity of the B-GAD65 ELISA was comparable to the standard radioimmunoassay (RIA) which is routinely used in the laboratory. We describe the optimal conditions of the binding kinetics from each assay-step for the detection of GAD65Ab using the WHO standard serum 97/550 as a model autoantibody serum. We concluded that incubation times of 15, 90, and 90 min for step 1 (pre-incubation of Biotin14-GAD65 with serum), step 2 (binding the Ab/Ag complex to NeutrAvidin plate), and step 3 (incubation with HRPO-anti-human IgG), respectively, along with human serum dilutions of 1:50, would provide an optimal assay signal within a relatively short timeframe.

Islet cell autoimmunity in a triethnic adult population of the Third National Health and Nutrition Examination Survey

Markers of humoral islet cell autoimmunity, such as autoantibodies (AAs) against the 65-kDa isoform of GAD (GAD65), serve as determinants of risk for autoimmune diabetes. Despite the high prevalence of diabetes in U.S. racial and ethnic minority adult populations, little is known concerning the prevalence of GAD65 AA in these groups. We estimated the prevalence of GAD65 AA in 1,064 diabetic and 1,036 nondiabetic participants who were 40-90 years of age from the Third National Health and Nutrition Examination Survey (NHANES III), which provides a representative ethnic sample of the U.S. diabetic population. The prevalence of GAD65 AA was higher in diabetic participants compared with nondiabetic participants in non-Hispanic whites (n = 920; 6.3% vs. 2.0%; P = 0.001) and non-Hispanic blacks (n = 534; 3.7% vs. 1.3%; P = 0.08) but not in Mexican Americans (n = 646; 1.2% vs. 2.6%; P = 0.18). Among diabetic non-Hispanic whites and non-Hispanic blacks, being GAD65 AA positive was associated with lower BMI and C-peptide (P < 0.05). These results may reflect the outcome of an autoimmune process leading to beta-cell destruction/dysfunction in non-Hispanic white and non-Hispanic black adult diabetic patients as it occurs in a similar manner in type 1 diabetes. Among diabetic Mexican Americans, the lower prevalence of GAD65 AA suggests a lower frequency of autoimmune-related diabetes.

C-peptide is the appropriate outcome measure for type 1 diabetes clinical trials to preserve beta-cell function: report of an ADA workshop, 21-22 October 2001

The underlying cause of type 1 diabetes, loss of beta-cell function, has become the therapeutic target for a number of interventions in patients with type 1 diabetes. Even though insulin therapies continue to improve, it remains difficult to achieve normal glycemic control in type 1 diabetes, especially long term. The associated risks of hypoglycemia and end-organ diabetic complications remain. Retention of beta-cell function in patients with type 1 diabetes is known to result in improved glycemic control and reduced hypoglycemia, retinopathy, and nephropathy. To facilitate the development of therapies aimed at altering the type 1 diabetes disease process, an American Diabetes Association workshop was convened to identify appropriate efficacy outcome measures in type 1 diabetes clinical trials. The following consensus emerged: While measurements of immune responses to islet cells are important in elucidating pathogenesis, none of these measures have directly correlated with the decline in endogenous insulin secretion. HbA(1c) is a highly valuable clinical measure of glycemic control, but it is an insensitive measure of beta-cell function, particularly with the currently accepted standard of near-normal glycemic control. Rates of severe hypoglycemia and diabetic complications ultimately will be improved by therapies that are effective at preserving beta-cell function but as primary outcomes require inordinately large and protracted trials. Endogenous insulin secretion is assessed best by measurement of C-peptide, which is cosecreted with insulin in a one-to-one molar ratio but unlike insulin experiences little first pass clearance by the liver. Measurement of C-peptide under standardized conditions provides a sensitive, well accepted, and clinically validated assessment of beta-cell function. C-peptide measurement is the most suitable primary outcome for clinical trials of therapies aimed at preserving or improving endogenous insulin secretion in type 1 diabetes patients. Available data demonstrate that even relatively modest treatment effects on C-peptide will result in clinically meaningful benefits. The development of therapies for addressing this important unmet clinical need will be facilitated by trials that are carefully designed with beta-cell function as determined by C-peptide measurement as the primary efficacy outcome.

Heterozygosity for MICA5.0/MICA5.1 and HLA-DR3-DQ2/DR4-DQ8 are independent genetic risk factors for latent autoimmune diabetes in adults

Major histocompatibility complex class I chain-related gene A (MICA) encodes polymorphic, stress-inducible antigens recognized by gammadelta T cells within the intestinal epithelium. MICA microsatellite polymorphism has been implicated to be related to different autoimmune diseases. Ninety-eight patients with type 1 diabetes (median age, 35 years; range, 9-89 years and 51 patients with latent autoimmune diabetes (LADA; median age, 48 years; range, 19-79 years) were compared with 113 healthy control patients (median age, 35 years; range, 19-65 years) to study the importance of MICA-microsatellite polymorphism and HLA-DR-DQ as genetic risk factors for diabetes. The different factors were compared univariately and by logistic regression analysis. In the logistic regression model, heterozygosity for MICA5.0/5.1 was a significant risk factor for LADA (odds ratio [OR] = 12; 95% confidence interval [95%CI], 2.5-59) as well as heterozygosity for HLA-DR3-DQ2/DR4-DQ8 (OR = 15; 95%CI, 2.7-84). None of the MICA polymorphisms were related to type 1 diabetes. Heterozygosity for HLA-DR3-DQ2/DR4-DQ8 was a risk factor for type 1 diabetes (OR = 14; 95%CI, 2.9-66) as well as DR4-DQ8/x (OR = 2.8; 95%CI, 1.4-5.9). HLA-DR15-DQ6 was protective for type 1 diabetes (OR = 0.12; 95%CI, 0.015-0.96). We concluded that both heterozygosity for MICA5.0/5.1 and HLA-DR3-DQ2/DR4-DQ8 are separate risk factors for LADA, but that heterozygosity for HLA-DR3-DQ2/DR4-DQ8 and DR4-DQ8 alone are most important for type 1 diabetes.

Molecular engineering of biotin-glutamic acid decarboxylase 65 fusion protein (Biotin-GAD65) for non-radioactive GAD65 antibody assay

We constructed biotinylated fusion proteins that linked to three detection tags to GAD65 at the N-terminus, and expressed them in an E. coli expression system. The Biotin14-GAD65 protein exhibited the strongest binding to both the GAD65 antibody and the streptavidin among the three constructs. We describe the optimal conditions using a Biotin14-GAD65-based immunoassay for the detection of GAD65 antibody.

Latent autoimmune diabetes in adults

Latent autoimmune diabetes in adults (LADA) is a special form of diabetes that is clinically similar to type 2 diabetes but with positivity for pancreatic autoantibodies. The frequency of LADA patients among all patients diagnosed as type 2 varies between 6-50% in various populations. The frequency is higher in younger age groups. It is clear, however, that the frequency of autoimmune diabetes among adults is underestimated. Clinical features such as age and severity of symptoms are of no help in identifying these patients. Body mass index and C peptide levels in the general population increase with age, and these parameters are of limited use in identifying LADA patients. Determination of autoantibodies is necessary in order to correctly classify the type of diabetes. Among antibodies, GADA is the most frequently occurring autoantibody, followed by ICA. The natural course of these patients shows that C peptide will decrease with time in parallel with the curve for C peptide in classical type 1 diabetic patients. Most of the LADA patients will require insulin within three years. Our recommendation is that all patients be tested for pancreatic islet autoantibodies at diagnosis of diabetes to enable correct diagnosis and to avoid future failure of hypoglycemic agents and risk of complications due to hyperglycemia. It is still unclear whether early treatment with insulin is beneficial for the remaining beta cells.