T-cell responses to islet antigens improves detection of autoimmune diabetes and identifies patients with more severe beta-cell lesions in phenotypic type 2 diabetes

Heterogeneity of circulating CXCR5-PD-1hiTph cells in patients of type 2 and type 1 diabetes in Chinese population

AIMS

Circulating peripheral helper T (Tph) cells are shown to promote the progression of autoimmune diseases. However, the role of Tph cells in inflammatory diseases such as type 2 diabetes mellitus (T2DM) and the differences between T2DM and autoimmune diabetes remain unclear.

METHODS

We recruited 92 T2DM patients, 106 type 1 diabetes mellitus (T1DM) patients and 84 healthy control individuals. Peripheral blood mononucleated cells were isolated and examined by multicolor flow cytometry. We further evaluated the correlations between circulating Tph cells and clinical biochemical parameters, islet function, disease progression and islet autoantibodies.

RESULTS

Circulating Tph cells were significantly higher in both T2DM and T1DM patients than in healthy control individuals. A significant positive correlation was observed between Tph cells and B cells in T1DM patients and overweight T2DM patients. Furthermore, Tph cells were negatively correlated with the area under the C-peptide curve (C-PAUC), and Tph cells were significantly positively correlated with fasting glucose and glycated hemoglobin levels in T2DM patients. However, no correlation was found between Tph cells and the above clinical indicators in T1DM patients. The frequency of Tph cells positively correlated with the titer of GAD autoantibodies and duration of disease in T1DM patients. In addition, we demonstrated that the frequency of Tph cells was decreased after rituximab therapy in T1DM patients.

CONCLUSIONS

Circulating Tph cells are associated with blood glucose levels and islet function in T2DM patients. In T1DM patients, circulating Tph cells are associated with B cells and islet autoantibodies. This may suggest that Tph cells have different pathogenic mechanisms in the two types of diabetes.

CLINICAL TRIAL INFORMATION

http://ClinicalTrials.gov NCT01280682 (registered July, 2010).

Adult-onset autoimmune diabetes

Adult-onset autoimmune (AOA) diabetes pathophysiology starts with immune changes, followed by dysglycaemia and overt disease. AOA diabetes can occur as classic type 1 diabetes when associated with severe loss of insulin secretion. More frequently, it is diagnosed as latent autoimmune diabetes in adults, a slowly progressing form with late onset, a long period not requiring insulin, and it is often misdiagnosed as type 2 diabetes. As its clinical presentation varies remarkably and immune markers often lack specificity, it is challenging to classify each case ad hoc, especially when insulin treatment is not required at diagnosis. Proper care of AOA diabetes aims to prevent complications and to improve quality of life and life expectancy. To achieve these goals, attention should be paid to lifestyle factors, with the aid of pharmacological therapies properly tailored to each individual clinical setting. Given the heterogeneity of the disease, choosing the right therapy for AOA diabetes is challenging. Most of the trials testing disease-modifying therapies for autoimmune diabetes are conducted in people with childhood onset, whereas non-insulin diabetes therapies have mostly been studied in the larger population with type 2 diabetes. More randomized controlled trials of therapeutic agents in AOA diabetes are needed.

Latent autoimmune diabetes in adults in China

Latent autoimmune diabetes in adults (LADA) is a type of diabetes caused by slow progression of autoimmune damage to pancreatic beta cells. According to the etiological classification, LADA should belong to the autoimmune subtype of type 1 diabetes (T1D). Previous studies have found general immune genetic effects associated with LADA, but there are also some racial differences. Multicenter studies have been conducted in different countries worldwide, but it is still unclear how the Chinese and Caucasian populations differ. The epidemiology and phenotypic characteristics of LADA may vary between Caucasian and Chinese diabetic patients as lifestyle, food habits, and body mass index differ between these two populations. The prevalence of LADA in China has reached a high level compared to other countries. The prevalence of LADA in China has reached a high level compared to other countries, and the number of patients with LADA ranks first in the world. Previous studies have found general immune genetic effects associated with LADA, but some racial differences also exist. The prevalence of LADA among newly diagnosed type 2 diabetes patients over the age of 30 years in China is 5.9%, and LADA patients account for 65% of the newly diagnosed T1D patients in the country. As a country with a large population, China has many people with LADA. A summary and analysis of these studies will enhance further understanding of LADA in China. In addition, comparing the similarities and differences between the Chinese and the Caucasian population from the perspectives of epidemiology, clinical, immunology and genetics will help to improve the understanding of LADA, and then promote LADA studies in individual populations.

Clinical Significance of Insulin Peptide-specific Interferon-γ-related Immune Responses in Ketosis-prone Type 2 Diabetes

CONTEXT

Unprovoked A-β+ ketosis-prone type 2 diabetes (KPD) is characterized by the sudden onset of diabetic ketosis/ketoacidosis (DK/DKA) without precipitating factors, negative anti-islet autoantibodies ("A-"), and preservation of β-cell function ("β+") after recovery from DKA. Although this phenotype often appears with acute hyperglycemia and DK/DKA just like acute-onset type 1 diabetes (AT1D), the involvement of anti-islet immune responses remains unknown.

OBJECTIVE

We sought to clarify the immunological role of insulin-associated molecules in unprovoked A-β+ KPD.

METHODS

In this cross-sectional study, blood samples from 75 participants (42 with AT1D and 33 with KPD) were evaluated for interferon (IFN)-γ-secreting peripheral blood mononuclear cells (PBMCs) reactive to 4 insulin B-chain amino acid 9-23-related peptides (B:9-23rPep) using an enzyme-linked immunospot (ELISpot) assay.

RESULTS

Overall, 36.4% (12/33) of KPD participants showed positive IFN-γ ELISpot assay results; the positivity rate in KPD was similar to that in AT1D (38.1%; 16/42) and statistically significantly higher than the previously reported rate in type 2 diabetes (8%; 2/25; P < .0167). Moreover, B:9-23rPep-specific IFN-γ-producing PBMC frequency was negatively correlated with age and ad lib serum C-peptide levels in all KPD participants and positively correlated with glycated hemoglobin A1c level in KPD participants with positive IFN-γ ELISpot results.

CONCLUSION

These findings suggest the involvement of B:9-23rPep-specific IFN-γ-related immunoreactivity in the pathophysiology of some unprovoked A-β+ KPD. Moreover, increased immunoreactivity may reflect transiently decreased β-cell function and increased disease activity at the onset of DK/DKA, thereby playing a key role in DK/DKA development in this KPD phenotype.

Islet Autoimmunity is Highly Prevalent and Associated With Diminished β-Cell Function in Patients With Type 2 Diabetes in the Grade Study

Islet autoimmunity may contribute to β-cell dysfunction in type 2 diabetes (T2D). Its prevalence and clinical significance have not been rigorously determined. In this ancillary study to the Glycemia Reduction Approaches in Diabetes-A Comparative Effectiveness (GRADE) Study, we investigated the prevalence of cellular and humoral islet autoimmunity in patients with T2D duration 4·0±3·0 y, HbA1c 7·5±0·5% on metformin alone. We measured T cell autoreactivity against islet proteins, islet autoantibodies against GAD65, IA2, ZnT8, and β-cell function. Cellular islet autoimmunity was present in 41·3%, humoral islet autoimmunity in 13·5%, and both in 5·3%. β-cell function calculated as iAUC-CG and ΔC-peptide(0- 30)/Δglucose(0-30) from an oral glucose tolerance test was lower among T cell-positives (T+) than T cell-negatives (T-) using two different adjustments for insulin sensitivity (iAUC-CG: 13·2% [95% CI 0·3, 24·4%] or 11·4% [95% CI 0·4, 21·2%] lower; ΔC-peptide(0-30)/Δglucose(0-30)) 19% [95% CI 3·1, 32·3%] or 17·7% [95% CI 2·6, 30·5%] lower). T+ patients had 17% higher HbA1c (95% CI 0·07, 0·28) and 7·7 mg/dL higher fasting plasma glucose levels (95% CI 0·2,15·3) than T- patients. We conclude that islet autoimmunity is much more prevalent in T2D patients than previously reported. T cell-mediated autoimmunity is associated with diminished β-cell function and worse glycemic control.

Autoimmune Inflammation and Insulin Resistance: Hallmarks So Far and Yet So Close to Explain Diabetes Endotypes

PURPOSE OF REVIEW

Diabetes mellitus can be categorized into two major variants, type 1 and type 2. A number of traits such as clinical phenotype, age at disease onset, genetic background, and underlying pathogenesis distinguish the two forms.

RECENT FINDINGS

Recent evidence indicates that type 1 diabetes can be accompanied by insulin resistance and type 2 diabetes exhibits self-reactivity. These two previously unknown conditions can influence the progression and outcome of the disease. Unlike most conventional considerations, diabetes appears to consist of a spectrum of intermediate phenotypes that includes monogenic and polygenic loci linked to inflammatory processes including autoimmunity, beta cell impairment, and insulin resistance. Here we discuss why a shift of the classical bi-modal view of diabetes (autoimmune vs. non-autoimmune) is necessary in favor of a model of an immunological continuum of endotypes lying between the two extreme "insulin-resistant" and "autoimmune beta cell targeting," shaped by environmental and genetic factors which contribute to determine specific immune-conditioned outcomes.

β-Cell Death in Diabetes: Past Discoveries, Present Understanding, and Potential Future Advances

β-cell death is regarded as a major event driving loss of insulin secretion and hyperglycemia in both type 1 and type 2 diabetes mellitus. In this review, we explore past, present, and potential future advances in our understanding of the mechanisms that promote β-cell death in diabetes, with a focus on the primary literature. We first review discoveries of insulin insufficiency, β-cell loss, and β-cell death in human diabetes. We discuss findings in humans and mouse models of diabetes related to autoimmune-associated β-cell loss and the roles of autoreactive T cells, B cells, and the β cell itself in this process. We review discoveries of the molecular mechanisms that underlie β-cell death-inducing stimuli, including proinflammatory cytokines, islet amyloid formation, ER stress, oxidative stress, glucotoxicity, and lipotoxicity. Finally, we explore recent perspectives on β-cell death in diabetes, including: (1) the role of the β cell in its own demise, (2) methods and terminology for identifying diverse mechanisms of β-cell death, and (3) whether non-canonical forms of β-cell death, such as regulated necrosis, contribute to islet inflammation and β-cell loss in diabetes. We believe new perspectives on the mechanisms of β-cell death in diabetes will provide a better understanding of this pathological process and may lead to new therapeutic strategies to protect β cells in the setting of diabetes.

The β Cell in Diabetes: Integrating Biomarkers With Functional Measures

The pathogenesis of hyperglycemia observed in most forms of diabetes is intimately tied to the islet β cell. Impairments in propeptide processing and secretory function, along with the loss of these vital cells, is demonstrable not only in those in whom the diagnosis is established but typically also in individuals who are at increased risk of developing the disease. Biomarkers are used to inform on the state of a biological process, pathological condition, or response to an intervention and are increasingly being used for predicting, diagnosing, and prognosticating disease. They are also proving to be of use in the different forms of diabetes in both research and clinical settings. This review focuses on the β cell, addressing the potential utility of genetic markers, circulating molecules, immune cell phenotyping, and imaging approaches as biomarkers of cellular function and loss of this critical cell. Further, we consider how these biomarkers complement the more long-established, dynamic, and often complex measurements of β-cell secretory function that themselves could be considered biomarkers.

The role of autoimmunity in the pathophysiology of type 2 diabetes: Looking at the other side of the moon

Efforts to unravel the pathophysiological mechanisms of type 2 diabetes (T2D) have been traditionally trapped into a metabolic perspective. However, T2D is a phenotypically and pathophysiologically heterogenous disorder, and the need for a tailored approach in its management is becoming increasingly evident. There is emerging evidence that irregular immune responses contribute to the development of hyperglycemia in T2D and, inversely, that insulin resistance is a component of the pathogenesis of autoimmune diabetes. Nevertheless, it has not yet been fully elucidated to what extent the presence of conventional autoimmune markers, such as autoantibodies, in subjects with T2D might affect the natural history of the disease and particularly each response to various treatments. The challenge for future research in the field is the discovery of novel genetic, molecular, or phenotypical indicators that would enable the characterization of specific subpopulations of people with T2D who would benefit most from the addition of immunomodulatory therapies to standard glucose-lowering treatment. This narrative review aims to discuss the plausible mechanisms through which the immune system might be implicated in the development of metabolic disturbances in T2D and obesity and explore a potential role of immunotherapy in the future management of the disorder and its complications.

Islet Autoimmunity in Adults With Impaired Glucose Tolerance and Recently Diagnosed, Treatment Naïve Type 2 Diabetes in the Restoring Insulin SEcretion (RISE) Study

The presence of islet autoantibodies and islet reactive T cells (T+) in adults with established type 2 diabetes (T2D) have been shown to identify those patients with more severe β-cell dysfunction. However, at what stage in the progression toward clinical T2D does islet autoimmunity emerge as an important component influencing β-cell dysfunction? In this ancillary study to the Restoring Insulin SEcretion (RISE) Study, we investigated the prevalence of and association with β-cell dysfunction of T+ and autoantibodies to the 65 kDa glutamic acid decarboxylase antigen (GADA) in obese pre-diabetes adults with impaired glucose tolerance (IGT) and recently diagnosed treatment naïve (Ndx) T2D. We further investigated the effect of 12 months of RISE interventions (metformin or liraglutide plus metformin, or with 3 months of insulin glargine followed by 9 months of metformin or placebo) on islet autoimmune reactivity. We observed GADA(+) in 1.6% of NdxT2D and 4.6% of IGT at baseline, and in 1.6% of NdxT2D and 5.3% of IGT at 12 months, but no significant associations between GADA(+) and β-cell function. T(+) was observed in 50% of NdxT2D and 60.4% of IGT at baseline, and in 68.4% of NdxT2D and 83.9% of IGT at 12 months. T(+) NdxT2D were observed to have significantly higher fasting glucose (p = 0.004), and 2 h glucose (p = 0.0032), but significantly lower steady state C-peptide (sscpep, p = 0.007) compared to T(-) NdxT2D. T(+) IGT participants demonstrated lower but not significant (p = 0.025) acute (first phase) C-peptide response to glucose (ACPRg) compared to T(-) IGT. With metformin treatment, T(+) participants were observed to have a significantly lower Hemoglobin A1c (HbA1c, p = 0.002) and fasting C-peptide (p = 0.002) compared to T(-), whereas T(+) treated with liraglutide + metformin had significantly lower sscpep (p = 0.010) compared to T(-) participants. In the placebo group, T(+) participants demonstrated significantly lower ACPRg (p = 0.001) compared to T(-) participants. In summary, T(+) were found in a large percentage of obese pre-diabetes adults with IGT and in recently diagnosed T2D. Moreover, T(+) were significantly correlated with treatment effects and β-cell dysfunction. Our results demonstrate that T(+) are an important component in T2D.

Diabetes education in pediatrics: How to survive diabetes

Diabetes mellitus is the most common abnormal carbohydrate metabolism disorder affecting millions of people worldwide. It is characterized by hyperglycemia as a result of ß-cell destruction or dysfunction by both genetic and environmental factors. Over time chronic hyperglycemia leads to microvascular (i.e., retinopathy, nephropathy and neuropathy) and macrovascular (i.e., ischemic heart disease, peripheral vascular disease, and cerebrovascular disease) complications of diabetes. Diabetes complication trials showed the importance of achieving near-normal glycemic control to prevent and/or reduce diabetes-related morbidity and mortality. There is a staggering rate of increased incidence of diabetes in youth, raising concerns for future generations' health, quality of life and its enormous economic burden. Despite advancements in the technology, diabetes management remains cumbersome. Training individuals with diabetes to gain life-long survival skills requires a comprehensive and ongoing diabetes education by a multidisciplinary team. Diabetes education and training start at the time of diagnosis of diabetes and should be continuous throughout the course of disease. The goal is to empower the individuals and families to gain diabetes self-management skills. Diabetes education must be individualized depending on the individual's age, education, family dynamics, and support. In this article, we review the history of diabetes, etiopathogenesis and clinical presentation of both type 1 and type 2 diabetes in children as well as adolescents. We then focus on diabetes management with education methods and materials.

Past, present and future of latent autoimmune diabetes in adults

Latent autoimmune diabetes in adults (LADA) is the most common form of autoimmune diabetes diagnosed in adults. Similar to type 1 diabetes, the prevalence of LADA is impacted by ethnicity and geography. LADA is characterized by β cell loss due to autoimmunity and insulin resistance and has highly heterogeneous clinical features, autoimmunity, and genetics in a glutamic acid decarboxylase antibody (GADA) titre-dependent manner, suggesting LADA is part of a continuum spectrum between type 1 and type 2 diabetes. Although LADA is the most frequent form of autoimmune diabetes diagnosed in adults, clinical trials involving LADA are scarce. Here we review the recent advancements in LADA epidemiology, clinical features, pathogenesis, and interventions. We also highlight the environmental factors that are thought to play an important role in addition to genetics in the pathogenesis of LADA. In the future, high-throughput molecular profiles might shed light on the nature of LADA among the wide spectrum of diabetes and offer new opportunities to identify novel LADA-specific biomarkers.

Setting the Stage for Islet Autoimmunity in Type 2 Diabetes: Obesity-Associated Chronic Systemic Inflammation and Endoplasmic Reticulum (ER) Stress

Islet autoimmunity has been identified as a component of both type 1 (T1D) and type 2 (T2D) diabetes, but the pathway through which islet autoimmunity develops in T1D and T2D may be different. Acknowledging the presence of islet autoimmunity in the pathophysiology of T2D, a historically nonautoimmune metabolic disease, would pave the way for important changes in classifications of and therapeutic options for T2D. In order to fully appreciate the importance of islet autoimmunity in T2D, the underlying mechanisms for immune system activation need to be explored. In this review, we focus on the potential origin of immune system activation (innate and adaptive) leading to the development of islet autoimmunity in T2D.

Prevalence of positive islet autoantibody in type 2 diabetes patients: a cross-sectional study in a Chinese community

BACKGROUND

Islet autoantibodies occur in type 2 diabetes. Our study aimed to investigate the prevalence of positive islet autoimmunity in community patients with type 2 diabetes.

METHODS

A total of 495 community patients with type 2 diabetes were recruited using the method of cluster sampling in this cross-sectional study. Three islet autoantibodies including glutamic acid decarboxylase antibody (GADA), insulin autoantibody (IAA) and islet cell antibody (ICA) were measured, and clinical characteristics involved in those individuals were evaluated.

RESULTS

The positive rate of islet autoantibodies was 28.5% in total, while combinations of different autoantibodies were rarely seen. Compared with GADA-negative group, positive counterparts significantly tended to have lower levels of body mass index (BMI), waist-hip ratio (WHR), and urinary microalbumin (mALB) (P < 0.05). Adjusted for confounding factors, WHR, triglycerides (TG), and mALB seemed to be negative independent predictors of GADA (OR < 1, P < 0.05). Patients with positive IAA tended to receive insulin treatment (P < 0.0001). Besides, fasting blood glucose (FBG), serum levels of high-density lipoprotein cholesterol (HDL-CH), aspartate transaminase (AST), and γ-glutamyltransferase (GGT) were more likely to be higher in IAA positive subgroup in comparison with the negative counterparts. While after AST was adjusted by unconditional logistic regression analysis, history of insulin treatment, FBG, HDL-CH, and GGT were confirmed as positive predictors of IAA. Furthermore, in patients who were IAA positive, those treated with exogenous insulin tended to have longer duration of diabetes than non-insulin treatment counterparts (P < 0.0001). With regard to ICA, however, there were no significant differences between the two subgroups, except that serum level of AST/ALT seemed to be slightly different (P = 0.064).

CONCLUSION

These data suggested that type 2 diabetic community patients with positive GADA tended to be lean and were able to maintain normal lipid metabolism, while patients with positivity of IAA were frequently accompanied with insulin treatment and more closely associated with diabetic liver damage.

Clinical manifestation and islet β-cell function of a subtype of latent autoimmune diabetes in adults (LADA): positive for T cell responses in phenotypic type 2 diabetes

AIMS

To investigate the possibility of identifying a subtype of latent autoimmune diabetes in adults (LADA), T-LADA (T cell responses-positive and autoantibody-negative) from patients with phenotypic type 2 diabetes (T2D) by enzyme-linked immunospot (ELISPOT).

METHODS

Eighty-two patients with phenotypic T2D were studied. Autoantibodies against glutamic acid decarboxylase (GAD), insulinoma-associated protein-2 and zinc transporter 8 were measured by radioligand assay. Thirty-nine Ab⁺ and 43 Ab^- patients with phenotypic T2D were enrolled for T cell assay of responses to GAD65 and C-peptide antigen by ELISPOT.

RESULTS

(1) Eleven of 43 Ab^- participants with phenotypic T2D were demonstrated interferon (IFN)-γ secreting T cells by ELISPOT, while 13 of 39 Ab⁺ patients with phenotypic T2D were positive for T cells responses to islet antigens. (2) The onset ages of T cell⁺ people with phenotypic T2D were younger than that of T cell^- individuals (42.7 ± 9.3 vs. 48.2 ± 10.2 years, P = 0.025). Moreover, T cell⁺ patients with T2D displayed a significantly lower fasting C-peptide (FCP) compared with T cell^- participants [0.28 (0.02-0.84) vs. 0.42 (0.05-1.26) nmol/L, P = 0.013]. (3) Ab^-T⁺ group had a significantly lower FCP compared with Ab^-T^- group [0.31 (0.13-0.84) vs. 0.51 (0.07-1.26) nmol/L, P = 0.023].

CONCLUSIONS

By measuring T cell responses to islet antigens in patients with phenotypic T2D, we identified a specific subtype of LADA who may be associated with worse basal β-cell function than classic T2D (Ab^-T^-).

Autoantibody-positivity in lean type II diabetes patients was associated with elevated Th17-like CD4+CXCR5+ T cell responses

The pathophysiology of type II diabetes (T2D) in patients with normal body-mass index (BMI) remains unclear. In this study, we investigated the circulating CD4⁺CXCR5⁺ T cells in lean T2D patients. Compared with age-, gender-, and BMI-matched healthy controls, the lean T2D patients presented similar frequency and number of CD4⁺CXCR5⁺ T cells; however, the composition of CD4⁺CXCR5⁺ T subsets was altered. The CD4⁺CXCR5⁺ T cells in lean T2D patients were enriched with a Th17-like subset, characterized by an increase in the frequency of IL-17-secreting cells, and an increase in the frequency of CCR6⁺ cells. Compared to CCR6^- CD4⁺CXCR5⁺ T cells, CCR6⁺ CD4⁺CXCR5⁺ T cells secreted significantly higher IL-17. Neither the frequency of IL-17-secreting CD4⁺CXCR5⁺ T cells, nor the frequency of CCR6⁺ CD4⁺CXCR5⁺ T cells, was associated with the BMI of the T2D patients. Interestingly, 10 out of 30 lean T2D patients in our cohort presented islet-reactive autoantibodies. Compared to the autoantibody-negative T2D patients, the autoantibody-positive T2D patients had significantly higher levels of IL-17-secreting CD4⁺CXCR5⁺ T cells and CCR6⁺ CD4⁺CXCR5⁺ T cells. In addition, compared to the CCR6^- CD4⁺CXCR5⁺ T cells, the CCR6⁺ CD4⁺CXCR5⁺ T cells were more effective at promoting Ig secretion from autologous B cells. Together, this study demonstrated that an upregulation of Th17-like CD4⁺CXCR5⁺ T cells was present in lean T2D patients and was associated with autoantibody positivity.

Expansion of Islet-Resident Macrophages Leads to Inflammation Affecting β Cell Proliferation and Function in Obesity

The nature of obesity-associated islet inflammation and its impact on β cell abnormalities remains poorly defined. Here, we explore immune cell components of islet inflammation and define their roles in regulating β cell function and proliferation. Islet inflammation in obese mice is dominated by macrophages. We identify two islet-resident macrophage populations, characterized by their anatomical distributions, distinct phenotypes, and functional properties. Obesity induces the local expansion of resident intra-islet macrophages, independent of recruitment from circulating monocytes. Functionally, intra-islet macrophages impair β cell function in a cell-cell contact-dependent manner. Increased engulfment of β cell insulin secretory granules by intra-islet macrophages in obese mice may contribute to restricting insulin secretion. In contrast, both intra- and peri-islet macrophage populations from obese mice promote β cell proliferation in a PDGFR signaling-dependent manner. Together, these data define distinct roles and mechanisms for islet macrophages in the regulation of islet β cells.

Type 2 Diabetes: How Much of an Autoimmune Disease?

Type 2 diabetes (T2D) is characterized by a progressive status of chronic, low-grade inflammation (LGI) that accompanies the whole trajectory of the disease, from its inception to complication development. Accumulating evidence is disclosing a long list of possible "triggers" of inflammatory responses, many of which are promoted by unhealthy lifestyle choices and advanced age. Diabetic patients show an altered number and function of immune cells, of both innate and acquired immunity. Reactive autoantibodies against islet antigens can be detected in a subpopulation of patients, while emerging data are also suggesting an altered function of specific T lymphocyte populations, including T regulatory (Treg) cells. These observations led to the hypothesis that part of the inflammatory response mounting in T2D is attributable to an autoimmune phenomenon. Here, we review recent data supporting this framework, with a specific focus on both tissue resident and circulating Treg populations. We also propose that selective interception (or expansion) of T cell subsets could be an alternative avenue to dampen inappropriate inflammatory responses without compromising immune responses.

Islet Autoantibody Patterns in Patients With Type 2 Diabetes Aged 60 and Higher: A Cross-Sectional Study in a Chinese Hospital

BACKGROUND

Some elderly citizens with a clinical diagnosis of type 2 diabetes had evidence of positive islet autoantibodies. We aimed to discover their islet autoantibody patterns and independent correlative factors that might lead to a better understanding of significance of islet autoimmunity in the progression of elderly diabetes.

METHODS

A total of 541 inpatients of clinically diagnosed type 2 diabetes aged 60 and over were recruited. Three islet autoantibodies including insulin autoantibody (IAA), islet cell antibody (ICA), and glutamic acid decarboxylase antibody (GADA) as well as clinical and biochemical characteristics were tested and collected in Huashan Hospital. Associations between these antibodies and clinical features were analyzed by Spearman correlation and binary logistic analyses.

RESULTS

In our current study, total positive rate of islet autoantibodies (IAA, ICA, and GADA) was 35.67% with 26.62% for individual IAA, 5.55% for ICA, and 5.91% for GADA, in elderly with type 2 diabetes. None of combinations of such autoantibodies were observed, with the exception of IAA + ICA (0.74%, n = 4), IAA + GADA (1.48%, n = 8), and ICA + GADA (0.18%, n = 1). Compared with GADA negative group, patients in positive group tended to have lower level of fasting and postprandial C peptide, fasting blood glucose (FBG), and body mass index (BMI). After adjusted for the BMI, FBG, and postprandial C peptide, fasting C peptide seemed to be an independent factor related to GADA positivity (OR = 0.52, p = 0.02). As for patients with positive IAA, they were more likely to have insulin treatment with longer duration of diabetes, higher level of BMI, and lower level of postprandial C peptide. After adjusted for the duration of diabetes, BMI, and postprandial C peptide, insulin treatment was a significant predictor for IAA positivity (OR = 5.20, p < 0.0001). Furthermore, hs-CRP was positively related to ICA positivity, and hs-CRP appeared to be an independent indicator for ICA (OR = 3.43, p = 0.008).

CONCLUSION

In elderly with type 2 diabetes, high prevalence rate of IAA was frequently accompanied with insulin treatment, while ICA and GADA were more closely associated with the systemic inflammation and beta-cell failure, respectively.

HLA-DRB1*15:01-DQA1*01:02-DQB1*06:02 Haplotype Protects Autoantibody-Positive Relatives From Type 1 Diabetes Throughout the Stages of Disease Progression

The HLA-DRB1*15:01-DQA1*01:02-DQB1*06:02 haplotype is linked to protection from the development of type 1 diabetes (T1D). However, it is not known at which stages in the natural history of T1D development this haplotype affords protection. We examined a cohort of 3,358 autoantibody-positive relatives of T1D patients in the Pathway to Prevention (PTP) Study of the Type 1 Diabetes TrialNet. The PTP study examines risk factors for T1D and disease progression in relatives. HLA typing revealed that 155 relatives carried this protective haplotype. A comparison with 60 autoantibody-negative relatives suggested protection from autoantibody development. Moreover, the relatives with DRB1*15:01-DQA1*01:02-DQB1*06:02 less frequently expressed autoantibodies associated with higher T1D risk, were less likely to have multiple autoantibodies at baseline, and rarely converted from single to multiple autoantibody positivity on follow-up. These relatives also had lower frequencies of metabolic abnormalities at baseline and exhibited no overall metabolic worsening on follow-up. Ultimately, they had a very low 5-year cumulative incidence of T1D. In conclusion, the protective influence of DRB1*15:01-DQA1*01:02-DQB1*06:02 spans from autoantibody development through all stages of progression, and relatives with this allele only rarely develop T1D.

T-cell receptor repertoire variation may be associated with type 2 diabetes mellitus in humans

BACKGROUND

Recent work in Pima Indians, a population with high rates of obesity and type 2 diabetes mellitus (T2DM), demonstrated that human leukocyte antigen haplotype DRB1*02 carriers have an increased acute insulin response and decreased risk for the development of T2DM, implicating loss of self-tolerance in the pathogenesis of T2DM. Advances in genomic sequencing have made T-cell receptor repertoire analysis a practical mode of investigation.

METHODS

High-throughput sequencing of T-cell receptor complementarity-determining region 3 was carried out in male Pima Indians with normal glucose regulation (n = 11; age = 31 ± 8 years; %fat = 30.2 ± 8.7%) and the protective DRB1*02 haplotype versus those with T2DM without DRB1*02 (n = 7; age = 34 ± 8 years; %fat = 31.2 ± 4.7%). Findings were partially replicated in another cohort by assessing the predictive ability of T-cell receptor variation on risk of T2DM in Pima Indian men (n = 27; age = 28.9 ± 7.1 years; %fat = 28.8 ± 7.1%) and women (n = 20; age = 29 ± 7.0 years; %fat = 37.1 ± 6.8%) with baseline normal glucose regulation but without the protective haplotype who were invited to follow-up examinations as frequently as every 2 years where diabetes status was assessed by a 75-g oral glucose tolerance test. Of these subjects, 13 developed diabetes.

RESULTS

T-cell receptor complementarity-determining region 3 length was shorter in those with T2DM, and a one-nucleotide decrease in complementarity-determining region 3 length was associated with a nearly threefold increase in risk for future diabetes. The frequency of one variable gene, TRBV7-8, was higher in those with T2DM. A 1% increase in TRBV7-8 frequency was associated with a greater than threefold increase in diabetes risk.

CONCLUSIONS

These results indicate that T-cell autoimmunity may be an important component in progression to T2DM in Pima Indians.

Diabetes at the crossroads: relevance of disease classification to pathophysiology and treatment

Diabetes is not a single homogeneous disease but composed of many diseases with hyperglycaemia as a common feature. Four factors have, historically, been used to identify this diversity: the age at onset; the severity of the disease, i.e. degree of loss of beta cell function; the degree of insulin resistance and the presence of diabetes-associated autoantibodies. Our broad understanding of the distinction between the two major types, type 1 diabetes mellitus and type 2 diabetes mellitus, are based on these factors, but it has become apparent that they do not precisely capture the different disease forms. Indeed, both major types of diabetes have common features, encapsulated by adult-onset autoimmune diabetes and maturity-onset diabetes of the young. As a result, there has been a repositioning of our understanding of diabetes. In this review, drawing on recent literature, we discuss the evidence that autoimmune type 1 diabetes has a broad clinical phenotype with diverse therapeutic options, while the term non-autoimmune type 2 diabetes obscures the optimal management strategy because it encompasses substantial heterogeneity. Underlying these developments is a general progression towards precision medicine with the need for precise patient characterisation, currently based on clinical phenotypes but in future augmented by laboratory-based tests.

Use of a High-Density Protein Microarray to Identify Autoantibodies in Subjects with Type 2 Diabetes Mellitus and an HLA Background Associated with Reduced Insulin Secretion

New biomarkers for type 2 diabetes mellitus (T2DM) may aid diagnosis, drug development or clinical treatment. Evidence is increasing for the adaptive immune system’s role in T2DM and suggests the presence of unidentified autoantibodies. While high-density protein microarrays have emerged as a useful technology to identify possible novel autoantigens in autoimmune diseases, its application in T2DM has lagged. In Pima Indians, the HLA haplotype (HLA-DRB1*02) is protective against T2DM and, when studied when they have normal glucose tolerance, subjects with this HLA haplotype have higher insulin secretion compared to those without the protective haplotype. Possible autoantibody biomarkers were identified using microarrays containing 9480 proteins in plasma from Pima Indians with T2DM without the protective haplotype (n = 7) compared with those with normal glucose regulation (NGR) with the protective haplotype (n = 11). A subsequent validation phase involving 45 cases and 45 controls, matched by age, sex and specimen storage time, evaluated 77 proteins. Eleven autoantigens had higher antibody signals among T2DM subjects with the lower insulin-secretion HLA background compared with NGR subjects with the higher insulin-secretion HLA background (p<0.05, adjusted for multiple comparisons). PPARG2 and UBE2M had lowest p-values (adjusted p = 0.023) while PPARG2 and RGS17 had highest case-to-control antibody signal ratios (1.7). A multi-protein classifier involving the 11 autoantigens had sensitivity, specificity, and area under the receiver operating characteristics curve of 0.73, 0.80, and 0.83 (95% CI 0.74–0.91, p = 3.4x10^-8), respectively. This study identified 11 novel autoantigens which were associated with T2DM and an HLA background associated with reduced insulin secretion. While further studies are needed to distinguish whether these antibodies are associated with insulin secretion via the HLA background, T2DM more broadly, or a combination of the two, this study may aid the search for autoantibody biomarkers by narrowing the list of protein targets.

Impact of islet autoimmunity on the progressive β-cell functional decline in type 2 diabetes

OBJECTIVE

Cross-sectional studies have suggested that islet autoimmunity may be more prevalent in type 2 diabetes (T2D) than previously appreciated and may contribute to the progressive decline in β-cell function. In this study, we longitudinally evaluated the effect of islet autoimmune development on the progressive β-cell dysfunction in T2D patients.

RESEARCH DESIGN AND METHODS

Twenty-three T2D patients negative for islet autoantibodies (GAD antibody and insulinoma-associated protein 2) and islet-specific T cells were evaluated prospectively for up to 36 months. We investigated the percentage of patients who developed islet autoantibodies (Ab+) and/or islet-reactive T cells (T+) and the effect of the islet autoimmunity on fasting and glucagon-stimulated C-peptide responses. We defined positive islet autoimmunity as Ab+ and/or T+ for at least two study visits.

RESULTS

Of the 23 patients, 6 (26%) remained negative for islet autoimmunity (Ab-T-), 14 (61%) developed Ab+ and/or T+, and 3 (13%) were unclassifiable because they developed islet autoimmunity at only one study visit. Islet Ab+ was observed to be less stable than islet-specific T-cell responses. Development of islet autoimmunity was significantly associated with a more rapid decline in fasting (P < 0.0001) and glucagon-stimulated (P < 0.05) C-peptide responses.

CONCLUSIONS

These pilot data suggest that the development of islet autoimmunity in T2D is associated with a significantly more rapid β-cell functional decline.

Islet-specific T-cell responses and proinflammatory monocytes define subtypes of autoantibody-negative ketosis-prone diabetes

OBJECTIVE

Ketosis-prone diabetes (KPD) is characterized by diabetic ketoacidosis (DKA) in patients lacking typical features of type 1 diabetes. A validated classification scheme for KPD includes two autoantibody-negative ("A-") phenotypic forms: "A-β-" (lean, early onset, lacking β-cell functional reserve) and "A-β+" (obese, late onset, with substantial β-cell functional reserve after the index episode of DKA). Recent longitudinal analysis of a large KPD cohort revealed that the A-β+ phenotype includes two distinct subtypes distinguished by the index DKA episode having a defined precipitant ("provoked," with progressive β-cell function loss over time) or no precipitant ("unprovoked," with sustained β-cell functional reserve). These three A- KPD subtypes are characterized by absence of humoral islet autoimmune markers, but a role for cellular islet autoimmunity is unknown.

RESEARCH DESIGN AND METHODS

Islet-specific T-cell responses and the percentage of proinflammatory (CD14+CD16+) blood monocytes were measured in A-β- (n = 7), provoked A-β+ (n = 15), and unprovoked A-β+ (n = 13) KPD patients. Genotyping was performed for type 1 diabetes-associated HLA class II alleles.

RESULTS

Provoked A-β+ and A-β- KPD patients manifested stronger islet-specific T-cell responses (P < 0.03) and higher percentages of proinflammatory CD14+CD16+ monocytes (P < 0.01) than unprovoked A-β+ KPD patients. A significant relationship between type 1 diabetes HLA class II protective alleles and negative T-cell responses was observed.

CONCLUSIONS

Provoked A-β+ KPD and A-β- KPD are associated with a high frequency of cellular islet autoimmunity and proinflammatory monocyte populations. In contrast, unprovoked A-β+ KPD lacks both humoral and cellular islet autoimmunity.

Islet autoimmunity in phenotypic type 2 diabetes patients

Historically, type 2 diabetes (T2D) was considered a metabolic disease of ageing. However, recent discoveries have demonstrated the role of chronic systemic inflammation in the development of insulin resistance and subsequent progression to T2D. Over the years, investigations into the pathophysiology of T2D have identified the presence of islet-specific T cells and islet autoimmune disease in T2D patients. Moreover, the cell-mediated islet autoimmunity has also been correlated with the progressive loss of β-cell function associated with T2D disease pathogenesis. In this manuscript, the involvement of cell-mediated islet autoimmune disease in the progression of T2D disease and the similarities in islet-specific T-cell reactivity between type 1 diabetes (T1D) and T2D are discussed.

Latent autoimmune diabetes in adults in Asians: similarities and differences between East and West

Latent autoimmune diabetes in adults (LADA) is a form of autoimmune diabetes with features of both type 1 and type 2 diabetes and in the middle of the diabetes spectrum. Scientists clash on the question of whether this type of diabetes is a unique diabetes subtype. Multicenter studies have been performed in different countries, including the Korea National Diabetes Program (KNDP) collaboratory group, the Ehime study in Japan, the Not Insulin-Requiring Autoimmune Diabetes (NIRAD) study in Italy, the Nord-Trøndelag Health (HUNT) study in Norway, the UK Prospective Diabetes Study (UKPDS) in the UK, the Action LADA study in Europe and the LADA China study in China. These studies found universal immunogenetic effects associated with LADA, but with some ethnic differences. Herein we summarize those multicenter studies and compare the ethnic similarities and differences between East and West from epidemiological, clinical, immune, and genetic viewpoints.

Attenuation of islet-specific T cell responses is associated with C-peptide improvement in autoimmune type 2 diabetes patients

The clinical efficacy of peroxisome proliferator-activated receptor gamma (PPAR-γ) agonists in cell-mediated autoimmune diseases results from down-regulation of inflammatory cytokines and autoimmune effector cells. T cell islet autoimmunity has been demonstrated to be common in patients with phenotypic type 2 diabetes mellitus (T2DM) and islet-specific T cells (T(+) ) to be correlated positively with more severe beta cell dysfunction. We hypothesized that the beneficial effects of the PPAR-γ agonist, rosiglitazone, therapy in autoimmune T2DM patients is due, in part, to the immunosuppressive properties on the islet-specific T cell responses. Twenty-six phenotypic T2DM patients positive for T cell islet autoimmunity (T(+) ) were identified and randomized to rosiglitazone (n = 12) or glyburide (n = 14). Beta cell function, islet-specific T cell responses, interleukin (IL)-12 and interferon (IFN)-γ responses and islet autoantibodies were followed for 36 months. Patients treated with rosiglitazone demonstrated significant (P < 0·03) down-regulation of islet-specific T cell responses, although no change in response to tetanus, a significant decrease (P < 0·05) in IFN-γ production and significantly (P < 0·001) increased levels of adiponectin compared to glyburide-treated patients. Glucagon-stimulated beta cell function was observed to improve significantly (P < 0·05) in the rosiglitazone-treated T2DM patients coinciding with the down-regulation of the islet-specific T cell responses. In contrast, beta cell function in the glyburide-treated T2DM patients was observed to drop progressively throughout the study. Our results suggest that down-regulation of islet-specific T cell autoimmunity through anti-inflammatory therapy may help to improve beta cell function in autoimmune phenotypic T2DM patients.

The outliers become a stampede as immunometabolism reaches a tipping point

Obesity and Type 2 diabetes mellitus (T2D) are characterized by pro-inflammatory alterations in the immune system including shifts in leukocyte subset differentiation and in cytokine/chemokine balance. The chronic, low-grade inflammation resulting largely from changes in T-cell, B-cell, and myeloid compartments promotes and/or exacerbates insulin resistance (IR) that, together with pancreatic islet failure, defines T2D. Animal model studies show that interruption of immune cell-mediated inflammation by any one of several methods almost invariably results in the prevention or delay of obesity and/or IR. However, anti-inflammatory therapies have had a modest impact on established T2D in clinical trials. These seemingly contradictory results indicate that a more comprehensive understanding of human IR/T2D-associated immune cell function is needed to leverage animal studies into clinical treatments. Important outstanding analyses include identifying potential immunological checkpoints in disease etiology, detailing immune cell/adipose tissue cross-talk, and defining strengths/weaknesses of model organism studies to determine whether we can harness the promising new field of immunometabolism to curb the global obesity and T2D epidemics.

The multiple origins of Type 1 diabetes

It is widely accepted that Type 1 diabetes is a complex disease. Genetic predisposition and environmental factors favour the triggering of autoimmune responses against pancreatic β-cells, eventually leading to β-cell destruction. Over 40 susceptibility loci have been identified, many now mapped to known genes, largely supporting a dominant role for an immune-mediated pathogenesis. This role is also supported by the identification of several islet autoantigens and antigen-specific responses in patients with recent onset diabetes and subjects with pre-diabetes. Increasing evidence suggests certain viruses as a common environmental factor, together with diet and the gut microbiome. Inflammation and insulin resistance are emerging as additional cofactors, which might be interrelated with environmental factors. The heterogeneity of disease progression and clinical manifestations is likely a reflection of this multifactorial pathogenesis. So far, clinical trials have been mostly ineffective in delaying progression to overt diabetes in relatives at increased risk, or in reducing further loss of insulin secretion in patients with new-onset diabetes. This limited success may reflect, in part, our incomplete understanding of key pathogenic mechanisms, the lack of truly robust biomarkers of both disease activity and β-cell destruction, and the inability to assess the relative contributions of various pathogenic mechanisms at various time points during the course of the natural history of Type 1 diabetes. Emerging data and a re-evaluation of histopathological, immunological and metabolic findings suggest the hypothesis that unknown mechanisms of β-cell dysfunction may be present at diagnosis, and may contribute to the development of hyperglycaemia and clinical symptoms.

Immunology in the Clinic Review Series; focus on metabolic diseases: development of islet autoimmune disease in type 2 diabetes patients: potential sequelae of chronic inflammation

Historically, the development of type 2 diabetes has been considered not to have an autoimmune component, in contrast to the autoimmune pathogenesis of type 1 diabetes. In this review we will discuss the accumulating data supporting the concept that islet autoreactivity and inflammation is present in type 2 diabetes pathogenesis, and the islet autoimmunity appears to be one of the factors associated with the progressive nature of the type 2 diabetes disease process.

Beyond the hormone: insulin as an autoimmune target in type 1 diabetes

Insulin is not only the hormone produced by pancreatic β-cells but also a key target antigen of the autoimmune islet destruction leading to type 1 diabetes. Despite cultural biases between the fields of endocrinology and immunology, these two facets should not be regarded separately, but rather harmonized in a unifying picture of diabetes pathogenesis. There is increasing evidence suggesting that metabolic factors (β-cell dysfunction, insulin resistance) and immunological components (inflammation and β-cell-directed adaptive immune responses) may synergize toward islet destruction, with insulin standing at the crossroad of these pathways. This concept further calls for a revision of the classical dichotomy between type 1 and type 2 diabetes because metabolic and immune mechanisms may both contribute to different extents to the development of different forms of diabetes. After providing a background on the mechanisms of β-cell autoimmunity, we will explain the role of insulin and its precursors as target antigens expressed not only by β-cells but also in the thymus. Available knowledge on the autoimmune antibody and T-cell responses against insulin will be summarized. A unifying scheme will be proposed to show how different aspects of insulin biology may lead to β-cell destruction and may be therapeutically exploited. We will argue about possible reasons why insulin remains the mainstay of metabolic control in type 1 diabetes but has so far failed to prevent or halt β-cell autoimmunity as an immune modulatory reagent.

Validation of the Diabetes Prevention Trial-Type 1 Risk Score in the TrialNet Natural History Study

OBJECTIVE

We assessed the accuracy of the Diabetes Prevention Trial-Type 1 Risk Score (DPTRS), developed from the Diabetes Prevention Trial-Type 1 (DPT-1), in the TrialNet Natural History Study (TNNHS).

RESEARCH DESIGN AND METHODS

Prediction accuracy of the DPTRS was assessed with receiver-operating characteristic curve areas. The type 1 diabetes cumulative incidence within the DPTRS intervals was compared between the TNNHS and DPT-1 cohorts.

RESULTS

Receiver-operating characteristic curve areas for the DPTRS were substantial in the TNNHS (P < 0.001 at both 2 and 3 years). The type 1 diabetes cumulative incidence did not differ significantly between the TNNHS and DPT-1 cohorts within DPTRS intervals. In the TNNHS, 2-year and 3-year risks were low for DPTRS intervals <6.50 (<0.10 and <0.20, respectively). Thresholds ≥7.50 were indicative of high risk in both cohorts (2-year risks: 0.49 in the TNNHS and 0.51 in DPT-1).

CONCLUSIONS

The DPTRS is an accurate and robust predictor of type 1 diabetes in autoantibody-positive populations.

Identification of autoantibody-negative autoimmune type 2 diabetic patients

OBJECTIVE

Islet autoimmunity has long been recognized in the pathogenesis of type 1 diabetes and is becoming increasingly acknowledged as a component in the pathogenesis of type 2 diabetes. Islet reactive T cells and autoantibodies have been demonstrated in type 1 diabetes, whereas islet autoimmunity in type 2 diabetes has been limited to islet autoantibodies. In this study, we investigated whether islet reactive T cells might also be present in type 2 diabetic patients and how islet reactive T cells correlate with β-cell function.

RESEARCH DESIGN AND METHODS

Adult phenotypic type 2 diabetic patients (n = 36) were screened for islet reactive T-cell responses using cellular immunoblotting and five islet autoantibodies (islet cell antibody, GADA, insulin autoantibody, insulinoma-associated protein-2 autoantibody, and zinc transporter autoantibody).

RESULTS

We identified four subgroups of adult phenotypic type 2 diabetic patients based on their immunological status (Ab(-)T(-), Ab(+)T(-), Ab(-)T(+), and Ab(+)T(+)). The Ab(-)T(+) type 2 diabetic patients demonstrated T-cell responses similar to those of the Ab(+)T(+) type 2 diabetic patients. Data were adjusted for BMI, insulin resistance, and duration of diabetes. Significant differences (P < 0.02) were observed among groups for fasting and glucagon-stimulated C-peptide responses. T-cell responses to islet proteins were also demonstrated to fluctuate less than autoantibody responses.

CONCLUSIONS

We have identified a group of adult autoimmune phenotypic type 2 diabetic patients who are Ab(-)T(+) and thus would not be detected using autoantibody testing alone. We conclude that islet autoimmunity may be more prevalent in adult phenotypic type 2 diabetic patients than previously estimated.

Is diabetes mellitus a continuous spectrum?

BACKGROUND

Diabetes mellitus has been historically divided into type 1 and type 2 diabetes, with type 1 being an autoimmune disease and type 2 being primarily a metabolic disease.

CONTENT

The current diabetes classification scheme needs to be reevaluated because of the accumulating evidence of immune system involvement in the pathophysiology of type 2 diabetes.

SUMMARY

There are similarities and differences between type 1 and type 2 diabetes with regard to pathogenesis, pathophysiology, and genetics. We propose a resolution to the dilemma of the current classification scheme.

Current approaches to measuring human islet-antigen specific T cell function in type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease caused by the T cell-mediated destruction of the pancreatic insulin-producing beta cells. Currently there are no widely accepted and standardized assays available to analyse the function of autoreactive T cells involved in T1D. The development of such an assay would greatly aid efforts to understand the pathogenesis of T1D and is also urgently required to guide the development of antigen-based therapies intended to prevent, or cure, T1D. Here we describe some of the assays used currently to detect autoreactive T cells in human blood and review critically their strengths and weaknesses. The challenges and future prospects for the T cell assays are discussed.

Latent autoimmune diabetes in adults: A distinct but heterogeneous clinical entity

Latent autoimmune diabetes in adults (LADA) accounts for 2%-12% of all cases of diabetes. Patients are typically diagnosed after 35 years of age and are often misdiagnosed as type II Diabetes Mellitus (DM). Glycemic control is initially achieved with sulfonylureas but patients eventually become insulin dependent more rapidly than with type II DM patients. Although they have a type II DM phenotype, patients have circulating beta (β) cell autoantibodies, a hallmark of type I DM. Alternative terms that have been used to describe this condition include type 1.5 diabetes, latent type I diabetes, slowly progressive Insulin Dependent Diabetes Mellitus, or youth onset diabetes of maturity. With regards to its autoimmune basis and rapid requirement for insulin, it has been suggested that LADA is a slowly progressive form of type I DM. However, recent work has revealed genetic and immunological differences between LADA and type I DM. The heterogeneity of LADA has also led to the proposal of criteria for its diagnosis by the Immunology of Diabetes Society. Although many workers have advocated a clinically oriented approach for screening of LADA, there are no universally accepted criteria for autoantibody testing in adult onset diabetes. Following recent advances in immunomodulatory therapies in type I DM, the same strategy is being explored in LADA. This review deals with the contribution of the genetic, immunological and metabolic components involved in the pathophysiology of LADA and recent approaches in screening of this distinct but heterogeneous clinical entity.

Latent autoimmune diabetes in adults

CONTEXT

Autoantibodies that are reactive to islet antigens are present at the time of diagnosis in most patients with type 1 diabetes. Additionally, approximately 10% of phenotypic type 2 diabetic patients are positive for at least one of the islet autoantibodies, and this group is often referred to as "latent autoimmune diabetes in adults (LADA)." These patients share many genetic and immunological similarities with type 1 diabetes, suggesting that LADA, like type 1 diabetes, is an autoimmune disease. However, there are differences in autoantibody clustering, T cell reactivity, and genetic susceptibility and protection between type 1 diabetes and LADA, implying important differences in the underlying disease processes.

EVIDENCE ACQUISITION AND SYNTHESIS

In this clinical review, we will summarize the current understanding of LADA based on the MEDLINE search of all peer-reviewed publications (original articles and reviews) on this topic between 1974 and 2009.

CONCLUSIONS

In LADA, diabetes occurs earlier in the beta-cell-destructive process because of the greater insulin resistance. Complexities arise also because of variable definitions of LADA and type 1 diabetes in adults. As immunomodulatory therapies that slow or halt the type 1 diabetes disease process are discovered, testing these therapies in LADA will be essential.

Improved T cell assay for identification of type 1 diabetes patients

Diabetes mellitus is comprised primarily of two clinically separate diseases: type 1 (T1D) and type 2 diabetes (T2D). T1D is a cell-mediated autoimmune disease directed against the beta cells and characterized by autoantibody (Ab) and T cell reactivity to islet proteins whereas, T2D is non-autoimmune. Despite the fact that the pathological process in autoimmune diabetes involves T cells, immune markers of diabetes have primarily centered on the presence of circulating serum islet autoantibodies. In two masked NIH sponsored workshops, our cellular immunoblotting T cell assay, which uses isolated human islets separated into 18 molecular weight fractions, has been validated to be able to distinguish T1D patients from controls with excellent specificity and sensitivity. In this study, we utilized the first workshop to select eight molecular weight fractions of human islets that were the most discriminatory between T1D patients and controls. Using these eight molecular weight fractions identified in the first workshop, we validated the preferential recognition of these 8 blot sections in a second workshop. We then re-calculated the sensitivity and specificity of the cellular immunoblotting assay for both workshops using only the data from these 8 blot sections.We observed increases in both sensitivity and specificity compared to the original workshop data for both workshops. The use of 8 instead of 18 molecular weight regions allows for a significant reduction in the amount of blood needed from patients, thus allowing cellular immunoblotting to be performed on pediatric patients participating in immunomodulatory studies. This improved T cell assay, which directly measures islet reactive T cell responses in autoimmune diabetes patients with excellent sensitivity and specificity, will likely improve patient follow-up during intervention studies.

Identification of tyrosine phosphatase 2(256-760) construct as a new, sensitive marker for the detection of islet autoimmunity in type 2 diabetic patients: the non-insulin requiring autoimmune diabetes (NIRAD) study 2

OBJECTIVE

The presence of autoantibodies to islet antigens GAD and/or tyrosine phosphatase 2 (IA-2) in type 2 diabetic patients (latent autoimmune diabetes in adults [LADA]) identifies subjects at high risk to develop insulin dependency. The aim of this study was to dissect humoral anti-IA-2 immune response in Caucasian LADA patients, identifying the most sensitive construct to evaluate IA-2 immunoreactivity and comparing LADA IA-2 epitope specificities to those found in type 1 diabetes.

RESEARCH DESIGN AND METHODS

We analyzed 177 LADA and 978 type 2 diabetic patients with different disease duration, collected in a nationwide Italian survey, the Non-Insulin Requiring Autoimmune Diabetes (NIRAD) study aimed at assessing prevalence and characteristics of autoimmune diabetes in type 2 diabetic patients and 106 newly diagnosed type 1 diabetic patients (53 children, 53 adults). By radioimmunoassay, we analyzed humoral immunoreactivity to seven IA-2 constructs: IA-2(PTP (687-979)), IA-2((761-964)), IA-2((256-760)), IA-2(JM (601-630)), IA-2(IC (605-979)), IA-2(BDC (256-556:630-979)), and IA-2(FL (1-979)).

RESULTS

IA-2((256-760)) fragment was identified as the marker with the highest sensitivity for detection of humoral IA-2 immunoreactivity in LADA patients, identifying IA-2 autoantibodies in approximately 30% of GAD antibody (GADA)-positive LADA patients and in 3.4% of GADA-negative type 2 diabetic patients. LADA IA-2((256-760))A positivity was associated with an increased frequency of autoimmune diabetes HLA-susceptible genotypes and with a higher risk for developing thyroid autoimmunity compared with autoantibody-negative type 2 diabetic patients. At disease diagnosis, adult-onset type 1 diabetic and LADA patients showed a lower IA-2 COOH-terminal immunoreactivity compared with childhood-onset type 1 diabetic patients.

CONCLUSIONS

IA-2 immunoreactivity in LADA patients has thus far been underestimated, and IA-2((256-760)) autoantibody detection may represent a novel diagnostic tool for the identification of islet autoimmunity in these patients.

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.

Interleukin 22 receptor 1 expression in pancreas islets

OBJECTIVES

Interleukin (IL) 22 is a recently identified T-cell-derived cytokine. IL-22 binds at the cell surface to a heterodimer receptor complex composed of IL-22 receptor (R) 1 and IL-10R2. In this study, we performed immunohistochemical analyses for IL-22R1 expression in human pancreatic tissue.

METHODS

Normal human pancreatic tissue (n = 8) was immunostained with antihuman IL-22R1 antibodies following standard immunohistochemical procedures.

RESULTS

In the normal human pancreas, IL-22R1 was expressed in the islets of Langerhans. IL-22R1 was not expressed by the acinar cells and ductal epithelium. Double-immunostaining experiments showed that the majority of insulin-expressing beta cells and glucagon-expressing alpha cells were immunopositive for IL-22R1.

CONCLUSIONS

The islets of Langerhans are the local site for IL-22R1 expression in the human pancreas. It may be that the T-cell-mediated immune response modulates cell islet function through IL-22 signaling.