Autoantibody-negative Type Research Articles

Screening of Mutations in Maturity-onset Diabetes of the Young-related Genes and RFX6 in Children with Autoantibody-negative Type 1 Diabetes Mellitus

Maturity-onset diabetes of the young (MODY) is the most common type of monogenic diabetes. To date, mutations have been identified in 14 different genes of patients with a clinical diagnosis of MODY. This study screened mutations in 14 MODY-related genes and the regulator factor X6 (RFX6) gene in children. The presence of clinical features of MODY and negative results for three autoantibody markers of type 1 diabetes mellitus (T1DM) in children and adolescents were used as inclusion criteria for genetic testing. The screening panel for next-generation sequencing included 14 MODY-related genes (GCK, HNF4A, HNF1A, HNF1B, PDX1, NEUROD1, KLF11, CEL, PAX4, INS, BLK, ABCC8, KCNJ11, and APPL1) and the RFX6 gene. Twenty-four different variants in MODY-related genes were identified in 49 children diagnosed with autoantibody-negative T1DM. Twelve variants were classified as pathogenic/likely pathogenic (P/LP) while 12 were interpreted as variant of unknown significance. Nine of the P/LP variants were found in GCK, two in HNF1B, and one in ABCC8. Three variants were novel, and one was a de novo variant. All but one of the variants exhibited heterozygotic inheritance. The frequencies of the MODY subtypes differed from previous reports. Although GCK-MODY was the most frequent mutation in Turkish children, similar to previous studies, the second most prevalent MODY subtype was HNF1B-MODY. This study also established three additional novel mutations in different MODY genes.

IDF2022-0830 Clinical Characteristics of Autoantibody-Negative Type 1 Diabetes Onset in Children During the COVID-19 Era in Kuwait

IDF2022-0830 Clinical Characteristics of Autoantibody-Negative Type 1 Diabetes Onset in Children During the COVID-19 Era in Kuwait

Frequency of Autoantibody-Negative Type 1 Diabetes in Children, Adolescents, and Young Adults During the First Wave of the COVID-19 Pandemic in Germany.

The aim of this study was to investigate the frequency of newly diagnosed type 1 diabetes without evidence of autoimmunity and the respective frequencies of ketoacidosis in children, adolescents, and young adults during the coronavirus disease 2019 (COVID-19) pandemic in Germany compared with the previous decade. Based on data from the German Diabetes Prospective Follow-up Registry (DPV), we compared data from 715 children, adolescents, and young adults, newly diagnosed with type 1 diabetes during the COVID-19 pandemic in Germany between 1 March and 30 June 2020, with data from 5,428 children, adolescents, and young adults of the same periods from 2011 to 2019. Adjusted differences and relative risks (RRs) of negative β-cell autoantibody test results and diabetic ketoacidosis were estimated using multivariable log-binomial regression analysis. An upper noninferiority test (margin 1%) was applied to evaluate whether the autoantibody-negativity rate in 2020 was not higher than that in 2011 to 2019. The estimated frequencies of autoantibody negativity in 2020 and 2011-2019 were 6.6% (95% CI 5.1-8.4) and 7.2% (95% CI 6.5-8.0), respectively, with an absolute difference of -0.68% (90% CI -2.07 to 0.71; P upper noninferiority = 0.023). The increase of the estimated frequency of diabetic ketoacidosis during the COVID-19 pandemic was similar between autoantibody-negative and -positive type 1 diabetes (adjusted RRs 1.28 [95% CI 0.80-2.05] and 1.57 [1.41-1.75], respectively). This study found no evidence that the COVID-19 pandemic leads to a significantly increased number of new cases with autoantibody-negative type 1 diabetes in children, adolescents, and young adults. In addition, autoantibody-negative type 1 diabetes showed no particular susceptibility to ketoacidosis, neither before nor during the pandemic.

A case report with functional characterization of a HNF1B mutation (p.Leu168Pro) causing MODY5.

. We previously performed next-generation sequencing-based genetic screening in patients with autoantibody-negative type 1 diabetes, and identified the p.Leu168Pro mutation in HNF1B. Here,we report the clinical course of the patient and the results of functional characterization of this mutation. The proband had bilateral renal hypodysplasia and developed insulin-dependent diabetes during childhood. The pathogenicity of Leu168Pro-HNF1B was evaluated with three-dimensional structure modeling, Western blotting, immunofluorescence analysis and luciferase reporter assays using human embryonic kidney 293 cells. Three-dimensional structure modeling predicted that the Leu168 residue is buried in the DNA-binding Pit-Oct-Unc-specific (POUS) domain and forms a hydrophobic core. Western blotting showed that the protein expression level of Leu168Pro-HNF1B was lower than that of wild-type (WT) HNF1B. Immunofluorescence staining showed that both WT- and Leu168Pro-HNF1B were normally localized in the nucleus. The cells transfected with WT-HNF1B exhibited 5-fold higher luciferase reporter activity than cells transfected with an empty vector. The luciferase activities were comparable between WT-HNF1B/Leu168Pro-HNF1B and WT-HNF1B/empty vector co-transfection. In conclusion, Leu168Pro is a protein-destabilizing HNF1B mutation, and the destabilization is likely due to the structural changes involving the hydrophobic core of POUS. The disease-causing Leu168Pro HNF1B mutation is a loss-of-function mutation without a dominant-negative effect.

1286-P: Identification of Atypical Pediatric Diabetes Using Electronic Medical Records (EMR)

We aimed to identify cases of rare or atypical pediatric diabetes who may be candidates for studies to understand their etiology and pathogenesis. We tested two strategies in a large pediatric hospital in Southwestern USA. STRATEGY 1: We designed a questionnaire that would allow a health-care provider to rule out typical diabetes types by manual EMR review. This questionnaire was first applied to the EMR of 50 youth (0-21 years old [y/o]) consecutively seen in the diabetes outpatient clinic, then modified to address problems identified, and tested in a second iteration, and on 50 additional cases (n=100). STRATEGY 2: In collaboration with local EMR analysts, we built three queries to generate periodic, automated reports of possible pediatric atypical diabetes cases: unknown type, type 2 diabetes (T2D) diagnosed <10 y/o, and autoantibody-negative type 1 diabetes (T1D). Diabetes type (i.e., unknown, T1D or T2D) was determined by the treating pediatric endocrinologist, through a customized flowchart embedded in the EMR. STRATEGY 1: We found 6 cases (6%) of atypical diabetes (mean age at diagnosis 11 y/o [SD 2.64], 16.6% male, 33% non-Hispanic White [NHW] and 66.6% Hispanic [Hisp]). STRATEGY 2: Unknown diabetes type: 67 cases (15, out of 6676 total diabetes cases), with mean age at diagnosis 12.6 y/o (SD 3.3), 32.8% male, 23.8% NHW, 47.6% Hisp, 25.4% African-American (AA), 3.2% other. Out of 1142 children with T2D, 64 (6.6%) cases were diagnosed <10 y/o, with mean age at diagnosis 8.6 y/o (SD 1.6), 20.3% male, 4.7% NHW, 65.6% Hisp, 28.1% AA, 1.6% other. Out of 680 cases of new onset T1D, 38 (5.6%) were negative for islet autoantibodies (IAA, GAD, IA-2), with mean age at diagnosis 11.3 y/o (SD3.8); 57.9% male, 50% NHW, 19.4% Hisp, 22.3% AA, 8.3% other. In sum, we designed and tested two strategies that use EMR to identify possible atypical pediatric diabetes cases for further studies that may shed light on the heterogeneity of pediatric diabetes, possibly opening new opportunities for diagnosis, treatment and prevention. Disclosure M. Astudillo: None. M. Tosur: None. A.F. Siller: None. A. Balasubramanyam: None. M.J. Redondo: None.

Low prevalence of maternal microchimerism in peripheral blood of Japanese children with type 1 diabetes.

To clarify the prevalence and degree of maternal microchimerism in Japanese children with type 1 diabetes, as well as its effect on phenotypic variation. We studied 153 Japanese children with type 1 diabetes, including 124 children positive for β-cell autoantibodies, and their 71 unaffected siblings. The number of circulating microchimeric cells per 105 host cells was estimated by the use of quantitative-polymerase chain reaction targeting non-transmitted maternal human leukocyte antigen alleles. The results were compared to previous data from white European people. Phenotypic comparison was performed between maternal microchimerism carriers and non-carriers with diabetes. Maternal microchimerism was detected in 15% of children with autoantibody-positive type 1 diabetes, 28% of children with autoantibody-negative type 1 diabetes, and 16% of unaffected siblings. There were no differences in the prevalence or levels of maternal microchimerism among the three groups or between the children with type 1 diabetes and their unaffected siblings. Furthermore, maternal microchimerism carriers and non-carriers exhibited similar phenotypes. Maternal microchimerism appears to be less common in Japanese children with type 1 diabetes than in white European people. Our data indicate that maternal microchimerism is unlikely to be a major trigger or a phenotypic determinant of type 1 diabetes in Japanese children and that the biological significance of maternal microchimerism in type 1 diabetes may differ among ethnic groups.

28-OR: Genetic Landscape of Diabetes in the Swiss Population

Background/Introduction: Diabetes represents a heterogeneous group of metabolic disorders and monogenic diabetes is thought to affect 1- 5% of the diabetes population. Monogenic diabetes causes neonatal diabetes (ND), maturity-onset diabetes of the young (MODY), and syndromic diabetes. The identification of the gene underlying diabetes remains crucial. In many cases, it will instruct a personalized treatment regime, thus improving metabolic control. The aim of the study was to identify mutations causing genetic diabetes. Methods: Inclusion criteria for testing were ND, autoantibody negative type 1 diabetes (T1D), presumed MODY, type 2 diabetes (T2D) diagnosed before the age of forty-five without metabolic features and syndromic diabetes. Haloplex technology was used to perform targeted next-generation sequencing (NGS) for 323 genes known to be involved in glucose homeostasis. Results: We have analyzed 234 diabetic individuals (137 females, 97 males) living in Switzerland by NGS. The mean age at diabetes diagnosis was 27.7 ±15.4 years. We identified variants in the MODY genes 1-13 in 41% (95/234) of the patients, of which 7 had variants in two, and one in three genes. The most frequent variants involved GCK in 58% (55/95), followed by HNF1A 19%, HNF4A 7%, ABCC8 6%, HNF1B/KCNJ11/KLF11 3%, NEUROD1 2% and PAX4 1%. When mapped to age at diabetes onset, MODY variants were most frequent in the neonatal group (50%, 2/4), and declined with age to reach 36% (13/36) in the >45 year group. In the group with variants in other than MODY genes (n=111) diabetes onset was 30 ±16 years; in 39% of the individuals we identified one genetic variant with a maximum of up to six in 1.8% of the probands. Conclusion: NGS is now a feasible method to diagnose monogenic diabetes, as we identified variants in MODY genes in 41% of probands in our cohort. We detected potential digenic and oligogenic diabetes forms in 61% of the probands with variants in other than MODY genes. The discovery of additional diabetes genes may lead to novel, rational treatment strategies. Disclosure V. Schwitzgebel: None. J. Blouin: None. F. Santoni: None. Funding Swiss National Science Foundation

Comprehensive screening for monogenic diabetes in 89 Japanese children with insulin-requiring antibody-negative type 1 diabetes.

Mutations in causative genes for neonatal diabetes or maturity-onset diabetes of the young have been identified in multiple patients with autoantibody-negative type 1 diabetes (T1D). We aimed to clarify the prevalence and phenotypic characteristics of monogenic abnormalities among 89 children with autoantibody-negative insulin-requiring T1D. Mutations in 30 genes were screened using next-generation sequencing, and copy-number alterations of 4 major causative genes were examined using multiplex-ligation-dependent probe amplification. We compared the clinical characteristics between mutation carriers and non-carriers. We identified 11 probable pathogenic substitutions (6 in INS , 2 in HNF1A , 2 in HNF4A , and 1 in HNF1B ) in 11 cases, but no copy-number abnormalities. Only 2 mutation carriers had affected parents. De novo occurrence was confirmed for 3 mutations. The non-carrier group, but not the carrier group, was enriched with susceptible HLA alleles. Mutation carriers exhibited comparable phenotypes to those of non-carriers, except for a relatively normal body mass index (BMI) at diagnosis. This study demonstrated significant genetic overlap between autoantibody-negative T1D and monogenic diabetes. Mutations in INS and HNF genes, but not those in GCK and other monogenic diabetes genes, likely play critical roles in children with insulin-requiring T1D. This study also suggests the relatively high de novo rates of INS and HNF mutations, and the etiological link between autoimmune abnormalities and T1D in the non-carrier group. Carriers of monogenic mutations show non-specific phenotypes among all T1D cases, although they are more likely to have a normal BMI at diagnosis than non-carriers.

Role of anti-GAD, anti-IA2 antibodies and C-peptide in differentiating latent autoimmune diabetes in adults from type 2 diabetes mellitus

Latent autoimmune diabetes in adults (LADA) is a form of autoimmune diabetes affecting adult patients who do not require insulin at diagnosis, positive for circulating islet autoantibodies and characterized by slower beta cell destruction. The study was aimed to identify and characterize LADA patients from clinically diagnosed type 2 diabetes mellitus (DM). We estimated anti-glutamic acid decarboxylase (anti-GAD), anti-tyrosine phosphatase-like insulinoma antigen 2 (anti-IA2) antibodies, fasting connecting peptide (C-peptide) and other clinical and biochemical parameters in 297 clinically diagnosed type 2 DM patients. The diagnosis of LADA was made by the presence of at least one pancreatic autoantibody, and thereafter LADA groups were compared with those of autoantibody-negative type 2 DM groups. The prevalence of LADA was found to be 15.2 % among patients presumed to have type 2 DM. There was significant difference concerning age of patients (p < 0.001), body mass index (p < 0.001), serum levels of C-peptide (p < 0.001), insulin (p < 0.001), total cholesterol (p < 0.001), triglycerides (p = 0.025), high-density lipoprotein cholesterol (HDL-C; p = 0.004), low-density lipoprotein cholesterol (LDL-C; p = 0.001) as well as insulin resistance (p < 0.001) between LADA group and type 2 DM patients. In conclusion, anti-GAD antibody and C-peptide level determination can be considered as confirmatory diagnostic markers for LADA, along with anti-IA2 assay, while other clinical and biochemical parameters can be useful for further characterizing LADA patients.

Adult-onset autoimmune diabetes in Europe is prevalent with a broad clinical phenotype: Action LADA 7.

OBJECTIVESpecific autoantibodies characterize type 1 diabetes in childhood but are also found in adult-onset diabetes, even when initially non–insulin requiring, e.g., with latent autoimmune diabetes (LADA). We aimed to characterize adult-onset autoimmune diabetes.RESEARCH DESIGN AND METHODSWe consecutively studied 6,156 European diabetic patients attending clinics within 5 years of diagnosis (age range, 30–70 years) examined cross-sectionally clinically and for GAD antibodies (GADA) and antibodies to insulinoma-associated antigen-2 (IA-2A) and zinc-transporter 8 (ZnT8A).RESULTSOf 6,156 patients, 541 (8.8%) had GADA and only 57 (0.9%) IA-2A or ZnT8A alone. More autoantibody-positive than autoantibody-negative patients were younger, leaner, on insulin (49.5 vs. 13.2%), and female (P < 0.0001 for each), though LADA patients (9.7% of total) did not show categorically distinct clinical features from autoantibody-negative type 2 diabetes. Similarly, more GADA patients with high (>200 World Health Organization IU) (n = 403) compared with low (n = 138) titer were female, lean, and insulin treated (54.6 vs. 39.7%) (P < 0.02 for each). Autoantibody-positive patients usually had GADA (541 of 598; 90.5%) and had LADA more often than type 1 autoimmune diabetes (odds ratio 3.3).CONCLUSIONSAdult-onset autoimmune diabetes emerges as a prevalent form of autoimmune diabetes. Our results indicate that adult-onset autoimmune diabetes in Europe encompasses type 1 diabetes and LADA in the same broad clinical and autoantibody-positive spectrum. At diagnosis, patients with adult-onset autoimmune diabetes are usually non–insulin requiring and clinically indistinguishable from patients with type 2 diabetes, though they tend to be younger and leaner. Only with screening for autoantibodies, especially GADA, can they be identified with certainty.

Persistently autoantibody-negative type 1 diabetes: Rich pickings or much ado about nothing?

Pediatric DiabetesVolume 12, Issue 3pt1 p. 139-141 Persistently autoantibody-negative type 1 diabetes: Rich pickings or much ado about nothing? Leonard C. Harrison MD, DSc, FRACP, FRCPA, Leonard C. Harrison MD, DSc, FRACP, FRCPA Professor Walter and Eliza Hall Institute of Medical ResearchBurnet Clinical Research UnitPostal address:1G Royal ParadeParkville, 3052VictoriaAustraliaTel: (61-3) 93452461Fax: (61-3) 93470852e-mail: harrison@wehi.edu.auwww.wehi.edu.auSearch for more papers by this author Leonard C. Harrison MD, DSc, FRACP, FRCPA, Leonard C. Harrison MD, DSc, FRACP, FRCPA Professor Walter and Eliza Hall Institute of Medical ResearchBurnet Clinical Research UnitPostal address:1G Royal ParadeParkville, 3052VictoriaAustraliaTel: (61-3) 93452461Fax: (61-3) 93470852e-mail: harrison@wehi.edu.auwww.wehi.edu.auSearch for more papers by this author First published: 26 April 2011 https://doi.org/10.1111/j.1399-5448.2011.00786.xCitations: 1Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume12, Issue3pt1May 2011Pages 139-141 RelatedInformation

Insulin gene mutations and diabetes.

Some mutations of the insulin gene cause hyperinsulinemia or hyperproinsulinemia. Replacement of biologically important amino acid leads to defective receptor binding, longer half-life and hyperinsulinemia. Three mutant insulins have been identified: (i) insulin Chicago (F49L or PheB25Leu); (ii) insulin Los Angeles (F48S or PheB24Ser); (iii) and insulin Wakayama (V92L or ValA3Leu). Replacement of amino acid is necessary for proinsulin processing results in hyperproinsulinemia. Four types have been identified: (i) proinsulin Providence (H34D); (ii) proinsulin Tokyo (R89H); (iii) proinsulin Kyoto (R89L); and (iv) proinsulin Oxford (R89P). Three of these are processing site mutations. The mutation of proinsulin Providence, in contrast, is thought to cause sorting abnormality. Compared with normal proinsulin, a significant amount of proinsulin Providence enters the constitutive pathway where processing does not occur. These insulin gene mutations with hyper(pro)insulinemia were very rare, showed only mild diabetes or glucose intolerance, and hyper(pro)insulinemia was the key for their diagnosis. However, this situation changed dramatically after the identification of insulin gene mutations as a cause of neonatal diabetes. This class of insulin gene mutations does not show hyper(pro)insulinemia. Mutations at the cysteine residue or creating a new cysteine will disturb the correct disulfide bonding and proper conformation, and finally will lead to misfolded proinsulin accumulation, endoplasmic reticulum stress and apoptosis of pancreatic β-cells. Maturity-onset diabetes of the young (MODY) or an autoantibody-negative type 1-like phenotype has also been reported. Very recently, recessive mutations with reduced insulin biosynthesis have been reported. The importance of insulin gene mutation in the pathogenesis of diabetes will increase a great deal and give us a new understanding of β-cell biology and diabetes. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2011.00100.x, 2011).

Genetic and clinical characteristics of patients with HNF1A gene variations from the German–Austrian DPV database

To determine prevalence, genetic and phenotype characteristics of patients with hepatocyte nuclear factor-1α (HNF1A) variants in the Diabetes Patienten Verlaufsdokumenation (DPV) multicentre database and to examine the influence of HNF1A mutation type, or location on clinical phenotypes. Seventy-one DPV patients were labelled as HNF1A-MODY (MODY3). Forty-four patients carried HNF1A mutations, while 27 patients were found to have HNF1A polymorphisms only. Associations between mutation type/position and age at disease onset, HbAlc, body mass index (BMI), diagnosis, family history and treatment modality were analysed using non-parametric statistics (Wilcoxon test). Patients with HNF1A mutations were 36% male, aged 14.1±5.8 years at diagnosis, and slightly overweight (BMI-SDS: +0.8±1.1). Treatment was lifestyle intervention (20.5%), insulin (35.3%), oral anti-diabetic (OAD, 43%) and both insulin+OAD (15.9%). More patients with missense mutations (60%) than patients with nonsense mutations/frameshift (23.8%) did not use insulin (P=0.03). No differences were found with regard to mutation types, isoform or domain. We identified several previously undescribed mutations in the cohort including c.-158insGGGTTGG in the promoter region, G31X, E41X, Q130X, L162P, R245I, A269P, S355X, Q398X, Q473X, Q495X, E508X, P588fs-insGCCA and P588fs-delAC. Patients carrying HNF1A polymorphisms were significantly younger at diagnosis than patients with HNF1A mutations (10.9±4.2 vs 14.19±5.8 years; P=0.027), and all carried I27L, S487N and A98V (n=3). HNF1A-MODY is the second most frequent MODY diagnosis registered in the DPV database, and previously undescribed HNF1A mutations account for about one-third of HNF1A-MODY cases. Patients with HNF1A polymorphisms documented as HNF1A-MODY were misclassified. They may have autoantibody-negative type 1B or type 2 diabetes or may have other MODY types.

Comparison of clinical and laboratory characteristics in children with type 1 diabetes according to pancreatic autoantibodies

Purpose : The purpose of this study was to determine whether there is any difference in the clinical and laboratory characteristics of patients with autoantibody-positive and patients with autoantibody-negative type 1 diabetes at initial presentation. Methods : We analyzed 96 patients under 18 years of age with newly diagnosed type 1 diabetes. One or both of the pancreatic autoantibodies-glutamic acid decarboxylase autoantibodies (GADA) and insulin autoantibody (IAA)-were measured in all patients, and we reviewed clinical and laboratory characteristics according to the presence of these autoantibodies. Results : GADA was examined in 48 of 87 patients, and 55.2% of patients were positive. IAA was checked in 88 patients, and 39.8% were positive. Both GADA and IAA were measured in 83 patients, and 22.8% had both antibodies. The patients who had one or both autoantibodies (autoantibody-positive group) were younger than those not having any autoantibody (autoantibody-negative group). The autoantibody-positive group had lower BMI, corrected sodium level, and serum effective osmolarity, compared to the autoantibody-negative group (P

The Prevalence of Autoimmune Diabetes Among Diabetes Mellitus Patients in Kumasi, Ghana

This study investigate the occurrence and the prevalence of autoantibodies and the metabolic characteristics of autoimmune and antibody-negative type 2, diabetes in recently diagnosed diabetes mellitus patients in Kumasi, Ghana. This study involved a total of 120 recently diagnosed (< 1 year) Ghanaian diabetes mellitus patients (17 insulin-requiring and 103 non insulin-requiring) and 60 controls. A standardized questionnaire was used. Blood pressure and anthropometric measurements were taken. Fasting glucose, lipid and lipoprotein concentrations were measured by enzymatic methods and HbA(1C) levels by agglutination test. Serum insulin level and autoantibodies (ICA, GAD ab and IAA) were analyzed by enzyme-linked immunosorbent assay (ELISA). Out of the 17 insulin-requiring, six were positive for either GAD ab or ICA or both. Out of the 103 non insulin-requiring, 16.5% were positive for ICA and/or GAD ab and/or IAA. The prevalence of Latent Auto-immune Diabetes of Adults (LADA) in the non-insulin requiring and in the total diabetic patients, were 13.5 and 11.7%, respectively. The prevalence of autoimmune type 1 diabetes in the studied population was 7.5% and that of autoimmune diabetes in the total diabetic population was 19.2%. Autoimmune and autoantibody-negative type 2, diabetes did not differ (p = ns) in the mean values of clinical and metabolic parameters, except hypertension, central obesity and HbA(1C) values. Autoimmune diabetes occurs in recently diagnosed diabetic patients in Ghana at prevalence comparable to that in developed countries. Both ICA and GAD ab tests are required to identify autoimmune diabetes.

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 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. 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)). 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. 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.

Mutations in the Insulin Gene Can Cause MODY and Autoantibody-Negative Type 1 Diabetes

Mutations in the insulin (INS) gene can cause neonatal diabetes. We hypothesized that mutations in INS could also cause maturity-onset diabetes of the young (MODY) and autoantibody-negative type 1 diabetes. We screened INS in 62 probands with MODY, 30 probands with suspected MODY, and 223 subjects from the Norwegian Childhood Diabetes Registry selected on the basis of autoantibody negativity or family history of diabetes. Among the MODY patients, we identified the INS mutation c.137G>A (R46Q) in a proband, his diabetic father, and a paternal aunt. They were diagnosed with diabetes at 20, 18, and 17 years of age, respectively, and are treated with small doses of insulin or diet only. In type 1 diabetic patients, we found the INS mutation c.163C>T (R55C) in a girl who at 10 years of age presented with ketoacidosis and insulin-dependent, GAD, and insulinoma-associated antigen-2 (IA-2) antibody-negative diabetes. Her mother had a de novo R55C mutation and was diagnosed with ketoacidosis and insulin-dependent diabetes at 13 years of age. Both had residual beta-cell function. The R46Q substitution changes an invariant arginine residue in position B22, which forms a hydrogen bond with the glutamate at A17, stabilizing the insulin molecule. The R55C substitution involves the first of the two arginine residues localized at the site of proteolytic processing between the B-chain and the C-peptide. Our findings extend the phenotype of INS mutation carriers and suggest that INS screening is warranted not only in neonatal diabetes, but also in MODY and in selected cases of type 1 diabetes.

Equivalent insulin resistance in latent autoimmune diabetes in adults (LADA) and type 2 diabetic patients

Insulin resistance is a primary component in the pathophysiology of type 2 diabetes. In latent autoimmune diabetes in adults (LADA), insulin resistance has been reported to be significantly lower than in autoantibody-negative type 2 diabetes (T2DM), but whether this might be related to differences in body mass index (BMI) has not been excluded. Furthermore, previous studies have used limiting inclusive criteria for LADA, requiring only the presence of GADA or IA-2A. To apply more inclusive criteria for LADA, consistent with recent recommendations, we defined LADA by clinical manifestations characteristic of T2DM, but with the presence of any combination of GADA, IA-2A, ICA, or IAA. We recruited 43 LADA patients, 70 T2DM patients, and 150 non-diabetic controls. Insulin resistance was assessed by both the homeostasis model assessment and the quantitative insulin sensitivity check index, and BMI was calculated. We found that insulin resistance in LADA is equivalent to that of T2DM. When insulin resistance is assessed as a function of BMI, both diabetic populations demonstrated an insulin resistance equally greater than normal controls. The interaction between insulin resistance and BMI in the two diabetic groups was significantly different from that demonstrated in non-diabetic controls. In summary, LADA demonstrates insulin resistance of similar magnitude to T2DM, but with the concurrent component of an immune attack against the pancreatic beta-cells. LADA patients may be at significant risk for metabolic consequences of insulin resistance other than glucose metabolism, such as those described in the metabolic syndrome. As complications and treatment regimens specific to LADA are realized, improved means of identification of LADA will become increasingly important.

Is Latent Autoimmune Diabetes in Adults Distinct From Type 1 Diabetes or Just Type 1 Diabetes at an Older Age?

Diabetes is classified clinically into two types: type 1 and type 2 diabetes. Type 1 diabetes is an autoimmune diabetes, whereas, in contrast, type 2 diabetes is nonautoimmune. However, there is a group of phenotypic adult type 2 diabetic patients ( approximately 10%) who have islet autoantibodies similar to type 1 diabetes. These patients are said to have latent autoimmune diabetes in adults (LADA) or type 1.5 diabetes. T-cells reacting with islet proteins have been demonstrated in type 1 and type 1.5 diabetic patients. In contrast, classic autoantibody-negative type 2 diabetic patients are also negative for T-cell responses to islet proteins. Therefore, we questioned whether type 1 and type 1.5 diabetes are similar or different autoimmune diseases. We have investigated the immunological and metabolic differences between type 1, type 1.5, and classic type 2 diabetic patients. We have identified autoantibody differences, differences in islet proteins recognized by T-cells, and differences in insulin resistance. We have also identified a small group of patients who have T-cells responsive to islet proteins but who are autoantibody negative. These patients appear to be similar to type 1.5 patients in having decreased stimulated C-peptide values. These immunological differences between type 1 and type 1.5 diabetes suggest at least partially distinct disease processes.

T Cell Proliferative and Cytokine Responses to Islet Proteins in Autoantibody Negative Type 2 Patients

T Cell Proliferative and Cytokine Responses to Islet Proteins in Autoantibody Negative Type 2 Patients