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

Etiological approach to characterization of diabetes type: the SEARCH for Diabetes in Youth Study

OBJECTIVE

To describe an etiologic approach to classification of diabetes types in youth based on the 1997 American Diabetes Association (ADA) framework, using data from the SEARCH for Diabetes in Youth Study.

RESEARCH DESIGN AND METHODS

SEARCH conducted a comprehensive assessment of 2,291 subjects aged <20 years with recently diagnosed diabetes. Using autoimmunity (at least one of two diabetes autoantibodies) and insulin sensitivity (equation validated against hyperinsulinemic-euglycemic clamps) as the main etiologic markers, we described four categories along a bidimensional spectrum: autoimmune plus insulin-sensitive (IS), autoimmune plus insulin-resistant (IR), nonautoimmune plus IS, and nonautoimmune plus IR. We then explored how characteristics, including genetic susceptibility to autoimmunity (HLA genotypes), insulin deficiency, and clinical factors varied across these four categories.

RESULTS

Most subjects fell into either the autoimmune plus IS (54.5%) or nonautoimmune plus IR categories (15.9%) and had characteristics that align with traditional descriptions of type 1 or type 2 diabetes. The group classified as autoimmune plus IR (19.5%) had similar prevalence and titers of diabetes autoantibodies and similar distribution of HLA risk genotypes to those in the autoimmune plus IS group, suggesting that it includes individuals with type 1 diabetes who are obese. The group classified as nonautoimmune plus IS (10.1%) likely includes individuals with undetected autoimmunity but may also include those with monogenic diabetes and thus requires further testing.

CONCLUSIONS

The SEARCH study offers researchers and clinicians a practical application for the etiologic classification of diabetes type and at the same time identifies a group of youths who would benefit from further testing.

The diagnostic value of zinc transporter 8 autoantibody (ZnT8A) for type 1 diabetes in Chinese

BACKGROUND

Zinc transporter-8 (ZnT8) was recently identified as a novel autoantigen in human type 1 diabetes (T1D). Autoantibody to ZnT8 (ZnT8A) was detected in up to 80% of patients with new-onset T1D and 26% of patients with T1D otherwise classified as negative on the basis of existing markers. As no data of ZnT8A in Chinese have been reported, we aim to evaluate the utility of ZnT8A for diagnosis of autoimmune T1D in Chinese relative to other autoantibody markers.

METHODS

Radioligand binding assays were performed on 539 T1D sera using human ZnT8 carboxyterminal 325Arg construct or a dimer incorporating 325Arg and 325Trp alongside antibodies to glutamic acid decarboxylase (GADA) or insulinoma-associated protein 2 (IA-2A). The antigenic specificity was analysed in the context of clinical characteristics of the patients.

RESULTS

ZnT8A were present in 24.1% (130 of 539) of patients with T1D versus 1.8% (10 of 555; P < 0.001) in type 2 diabetes. At diagnosis, ZnT8A and IA-2A were less prevalent in Chinese subjects with T1D than in Caucasian populations (both P < 0.001) but similar to Japanese. The diagnostic sensitivity of combined GADA, IA-2A and ZnT8A measurements reached 65.5% with ZnT8A detected in 13.5% (29 of 215) of GADA and/or IA-2A-negative subjects. ZnT8A prevalence was lower in older and fatter patients. ZnT8A+ alone patients were distinguished from Ab- ones (P < 0.05-0.001) on the basis of higher insulin requirement and lower systolic blood pressure level.

CONCLUSION

ZnT8A is an independent marker for T1D in Chinese and combined with GADA and IA-2A enhances diagnostic sensitivity. ZnT8A may be associated with different clinical phenotypes than GADA or IA-2A.

Long-term detrimental consequences of the onset of type 1 diabetes on annual earnings--evidence from annual registry data in 1990-2005

AIMS/HYPOTHESIS

Young adults in the early stages of their participation in the labour market may be particularly vulnerable to the effects of onset of a chronic disease. Our aim was to quantify the consequences of the onset of type 1 diabetes in young adults on annual earnings, using individual-level longitudinal data before and after the onset of diabetes.

METHODS

The Econ-DISS database contains annual socioeconomic information for 1990-2005 from Statistics Sweden. Econ-DISS includes data for persons with diabetes onset at the age of 15-34 years between 1983 and 2005, registered in the national Diabetes Incidence Study in Sweden (DISS) database, and for controls. Considering the onset of type 1 diabetes as an unanticipated and significant life event, we compared the progression of annual earnings for 3,650 cases born between 1949 and 1970 before and after onset of diabetes with that of 14,629 controls. Possible confounders--education, participation in the labour market, sick leave and parental education--were analysed.

RESULTS

We found no differences between the groups in annual earnings or participation in the labour market before onset of diabetes. After onset, persons with type 1 diabetes gradually lagged behind the controls. Their median annual earnings were lower in each year from 1995 to 2005 (p < 0.01). The difference in 2005 was euro (EUR) 1,411 (5.3%). Controlling for confounders, duration of type 1 diabetes > or = 10 years was associated with 4.2% (men) and 8.1% (women) lower average annual earnings for persons with upper secondary education only who were active in the labour market.

CONCLUSION/INTERPRETATION

The onset of type 1 diabetes in young adults has long-term detrimental consequences on earnings that cannot be attributed to confounders.

Common variants in the TCF7L2 gene help to differentiate autoimmune from non-autoimmune diabetes in young (15-34 years) but not in middle-aged (40-59 years) diabetic patients

AIMS/HYPOTHESIS

Type 1 diabetes in children is characterised by autoimmune destruction of pancreatic beta cells and the presence of certain risk genotypes. In adults the same situation is often referred to as latent autoimmune diabetes in adults (LADA). We tested whether genetic markers associated with type 1 or type 2 diabetes could help to discriminate between autoimmune and non-autoimmune diabetes in young (15-34 years) and middle-aged (40-59 years) diabetic patients.

METHODS

In 1,642 young and 1,619 middle-aged patients we determined: (1) HLA-DQB1 genotypes; (2) PTPN22 and INS variable-number tandem repeat (VNTR) polymorphisms; (3) two single nucleotide polymorphisms (rs7903146 and rs10885406) in the TCF7L2 gene; (4) glutamic acid decarboxylase (GAD) and IA-2-protein tyrosine phosphatase-like protein (IA-2) antibodies; and (5) fasting plasma C-peptide.

RESULTS

Frequency of risk genotypes HLA-DQB1 (60% vs 25%, p = 9.4 x 10(-34); 45% vs 18%, p = 1.4 x 10(-16)), PTPN22 CT/TT (34% vs 26%, p = 0.0023; 31% vs 23%, p = 0.034), INS VNTR class I/I (69% vs 53%, p = 1.3 x 10(-8); 69% vs 51%, p = 8.5 x 10(-5)) and INS VNTR class IIIA/IIIA (75% vs 63%, p = 4.3 x 10(-6); 73% vs 60%, p = 0.008) was increased in young and middle-aged GAD antibodies (GADA)-positive compared with GADA-negative patients. The type 2 diabetes-associated genotypes of TCF7L2 CT/TT of rs7903146 were significantly more common in young GADA-negative than in GADA-positive patients (53% vs 43%; p = 0.0004). No such difference was seen in middle-aged patients, in whom the frequency of the CT/TT genotypes of TCF7L2 was similarly increased in GADA-negative and GADA-positive groups (55% vs 56%).

CONCLUSIONS/INTERPRETATION

Common variants in the TCF7L2 gene help to differentiate young but not middle-aged GADA-positive and GADA-negative diabetic patients, suggesting that young GADA-negative patients have type 2 diabetes and that middle-aged GADA-positive patients are different from their young GADA-positive counterparts and share genetic features with type 2 diabetes.

Progression to type 1 diabetes and autoantibody positivity in relation to HLA-risk genotypes in children participating in the ABIS study

BACKGROUND

Autoantibodies against beta-cell antigens together with human leukocyte antigen (HLA)-risk genotypes are used as predictive markers for type 1 diabetes (T1D). In this study, we have investigated the role of HLA-risk and -protective genotypes for development of beta-cell autoantibodies and progression to T1D in healthy children.

METHODS

T1D-related HLA genotypes and autoantibodies against glutamic acid decarboxylase [glutamic acid decarboxylase antibodies (GADA)] and islet antigen-2 (IA-2A) were studied at 1, 2.5 and 5 yr of age in unselected healthy children and children with T1D participating in the All Babies In Southeast Sweden (ABIS) study.

RESULTS

GADA or IA-2A positivity at 5 yr of age was associated with DR4-DQ8 haplotype and DR3-DQ2/DR4-DQ8 genotype. By the age of 6-7 yr, we identified 32 children with T1D among the 17 055 participants in the ABIS study. Eight of 2329 (0.3%) non-diabetic children had permanent autoantibodies, and 143 of 2329 (6%) children had transient autoantibodies. HLA-risk genotypes associated with T1D, whereas protective genotypes were seldom found in children with T1D. Children with permanent autoantibodies had more often risk-associated DR4-DQ8 haplotype than autoantibody-negative children. No associations with HLA-risk or -protective genotypes were found for transient autoantibodies.

CONCLUSIONS

The strong relation between HLA-risk alleles and T1D once again confirmed that HLA-risk genotypes play an important role for development of T1D. However, HLA genotypes seem not to explain induction of autoantibodies, especially transient autoantibodies, in the general population, emphasizing the role of environmental factors in the initiation of autoimmunity. It seems that HLA-risk genotypes are responsible for maturation of the permanent autoantibody response.

Genetic similarities between latent autoimmune diabetes in adults, type 1 diabetes, and type 2 diabetes

OBJECTIVE

Latent autoimmune diabetes in adults (LADA) is often considered a slowly progressing subtype of type 1 diabetes, although the clinical picture more resembles type 2 diabetes. One way to improve classification is to study whether LADA shares genetic features with type 1 and/or type 2 diabetes.

RESEARCH DESIGN AND METHODS

To accomplish this, we studied whether LADA shares variation in the HLA locus or INS VNTR and PTPN22 genes with type 1 diabetes or the TCF7L2 gene with type 2 diabetes in 361 LADA, 718 type 1 diabetic, and 1,676 type 2 diabetic patients, as well as 1,704 healthy control subjects from Sweden and Finland.

RESULTS

LADA subjects showed, compared with type 2 diabetic patients, increased frequency of risk for the HLA-DQB1 *0201/*0302 genotype (27 vs. 6.9%; P < 1 x 10(-6)), with similar frequency as with type 1 diabetes (36%). In addition, LADA subjects showed higher frequencies of protective HLA-DQB1 *0602(3)/X than type 1 diabetic patients (8.1 vs. 3.2%, P = 0.003). The AA genotype of rs689, referring to the class I allele in the INS VNTR, as well as the CT/TT genotypes of rs2476601 in the PTPN22 gene, were increased both in type 1 diabetic (P = 3 x 10(-14) and P = 1 x 10(-10), respectively) and LADA (P = 0.001 and P = 0.002) subjects compared with control subjects. Notably, the frequency of the type 2 diabetes-associated CT/TT genotypes of rs7903146 in the TCF7L2 were increased in LADA subjects (52.8%; P = 0.03), to the same extent as in type 2 diabetic subjects (54.1%, P = 3 x 10(-7)), compared with control subjects (44.8%) and type 1 diabetic subjects (43.3%).

CONCLUSIONS

LADA shares genetic features with both type 1 (HLA, INS VNTR, and PTPN22) and type 2 (TCF7L2) diabetes, which justifies considering LADA as an admixture of the two major types of diabetes.