Genetic heterogeneity in latent autoimmune diabetes is linked to various degrees of autoimmune activity: results from the Nord-Trøndelag Health Study

Alcohol consumption is associated with reduced risk of Type 2 diabetes and autoimmune diabetes in adults: results from the Nord-Trøndelag health study

AIMS

We investigated the influence of different aspects of alcohol consumption on the risk of Type 2 diabetes and autoimmune diabetes in adults.

METHODS

We used data from the Nord-Trøndelag Health Survey (HUNT) study, in which all adults aged ≥ 20 years from Nord-Trondelag County were invited to participate in three surveys in 1984-1986, 1995-1997 and 2006-2008. Patients with diabetes were identified using self-reports, and participants with onset age ≥ 35 years were classified as having Type 2 diabetes if they were negative for anti-glutamic acid decarboxylase (n = 1841) and as having autoimmune diabetes if they were positive for anti-glutamic acid decarboxylase (n = 140). Hazard ratios of amount and frequency of alcohol use, alcoholic beverage choice, and binge drinking and alcohol use disorders were estimated.

RESULTS

Moderate alcohol consumption (adjusted for confounders) was associated with a reduced risk of Type 2 diabetes in men, but not in women (hazard ratio for men 10-15 g/day 0.48, 95% CI 0.28-0.77; hazard ratio for women ≥ 10 g/day 0.81, 95% CI 0.33-1.96). The reduced risk was primarily linked to consumption of wine [hazard ratio 0.93, 95% CI 0.87-0.99 (per g/day)]. No increased risk was seen in participants reporting binge drinking or in problem drinkers. The results were also compatible with a reduced risk of autoimmune diabetes associated with alcohol consumption [hazard ratio 0.70, 95% CI 0.45-1.08 (frequent consumption) and hazard ratio 0.36, 95% CI 0.13-0.97 (2-7 g/day)].

CONCLUSIONS

Moderate alcohol consumption associates with reduced risk of both Type 2 diabetes and autoimmune diabetes. A protective effect of alcohol intake may be limited to men. High alcohol consumption does not seem to carry an increased risk of diabetes.

Prevalence of ZnT8 antibody in relation to phenotype and SLC30A8 polymorphism in adult autoimmune diabetes: results from the HUNT study, Norway

Zinc transporter 8 (ZnT8), a product of the SLC30A8 gene, is a target-antigen in autoimmune diabetes. Associations between ZnT8 antibody (ZnT8A), phenotype and the genetic variant rs13266634 in the SLC30A8 gene have primarily been studied in patients with young-onset diabetes. We explored such associations in adult-onset autoimmune diabetes identified from the all-population based Nord-Trøndelag health Study (HUNT) ZnT8A (assayed by a fusion probe of C-terminal Arg325 and Trp325), and antibodies against glutamic decarboxylase (GADA) and tyrosine phosphatase-like protein insulinoma antigen-2 (IA-2A) were analysed in 266 subjects classified as having adult-onset autoimmune diabetes ( ≥ 25 years of age at diagnosis). Of these, 161 subjects fulfilled the criteria of latent autoimmune diabetes in adults (LADA), whereas 105 subjects were termed "classical" type 1 diabetes. Ten out of 161 LADA (6.2%) and 23 out of 105 adult-onset "classical" type 1 diabetic patients (22%) were ZnT8A positive. Adult-onset diabetic subjects positive both for GADA and IA-2A (n = 17), had lower waist circumference (p = 0.024) and higher fasting glucose levels (p = 0.023) than those positive both for GADA and ZnT8A (n = 13). Genotyping results of rs13266634 (available in 178 adult-onset diabetic subjects), showed a tendency for association between ZnT8A positivity and the TT- and CC genotypes of SNP rs13266634 (p = 0.101) using the standard cut-off level of 0.06ai, and a significant association at a lower cut-off level of 0.01ai (p = 0.005). We conclude that ZnT8A positivity in a population of adult-onset autoimmune diabetes is a less strong marker of autoimmunity than IA-2A. Further, positivity could be influenced by polymorphism of the SLC30A8 gene.

Sleep disturbances and low psychological well-being are associated with an increased risk of autoimmune diabetes in adults. Results from the Nord-Trøndelag Health Study

AIMS

To investigate whether sleep disturbances and low psychological well-being are associated with an increased risk of autoimmune diabetes in adults (including LADA and type 1 diabetes) and type 2 diabetes.

METHODS

We used data from the Norwegian HUNT Study (n = 53,394) and estimated the risk of developing autoimmune diabetes in adults (n = 138) and type 2 diabetes (n = 1895) between 1984 and 2008 in relation to baseline self-reported psychological well-being and sleep problems.

RESULTS

Sleep disturbances and low psychological well-being were associated with an increased risk of autoimmune diabetes (hazard ratio 1.84, 95% confidence interval 1.10-3.09), primarily linked to poor sleep in men (1.83, 1.05-3.20) and low well-being in women (2.50, 1.03-6.54). Similar associations were seen with type 2 diabetes in relation to sleep problems (1.25, 1.08-1.44) in men and low well-being (1.34, 1.16-1.54), in both men and women. In autoimmune diabetes, these factors were associated with lower anti-GAD levels (177 vs. 306 WHO units/ml, p = 0.04).

CONCLUSIONS

Our findings indicate that psychosocial factors influence the risk of autoimmune diabetes in adults, possibly through mechanisms related to insulin resistance. This supports the notion that the aetiology of autoimmune diabetes with adult onset in some respects is similar to that of type 2 diabetes.

Cohort Profile: the HUNT Study, Norway

The HUNT Study includes large total population-based cohorts from the 1980ies, covering 125 000 Norwegian participants; HUNT1 (1984-86), HUNT2 (1995-97) and HUNT3 (2006-08). The study was primarily set up to address arterial hypertension, diabetes, screening of tuberculosis, and quality of life. However, the scope has expanded over time. In the latest survey a state of the art biobank was established, with availability of biomaterial for decades ahead. The three population based surveys now contribute to important knowledge regarding health related lifestyle, prevalence and incidence of somatic and mental illness and disease, health determinants, and associations between disease phenotypes and genotypes. Every citizen of Nord-Trøndelag County in Norway being 20 years or older, have been invited to all the surveys for adults. Participants may be linked in families and followed up longitudinally between the surveys and in several national health- and other registers covering the total population. The HUNT Study includes data from questionnaires, interviews, clinical measurements and biological samples (blood and urine). The questionnaires included questions on socioeconomic conditions, health related behaviours, symptoms, illnesses and diseases. Data from the HUNT Study are available for researchers who satisfy some basic requirements (www.ntnu.edu/hunt), whether affiliated in Norway or abroad.

Time dynamics of autoantibodies are coupled to phenotypes and add to the heterogeneity of autoimmune diabetes in adults: the HUNT study, Norway

AIMS

The aetiology of latent autoimmune diabetes in adults (LADA), assessed by autoimmune markers, is insufficiently clarified. We cross-sectionally investigated the prevalence and prospectively the prediabetic and postdiabetic presence of antibodies to glutamic acid decarboxylase (GADA), insulinoma-associated protein 2 and zinc transporter 8 in LADA and in type 1 diabetes.

METHODS

We included 208 'classic' type 1, 161 LADA and 302 type 2 diabetic cases from the second (HUNT2: 1995–1997) and third (HUNT3: 2006–2008) Nord-Trøndelag health surveys. Prospective data were available for 59 type 1, 44 LADA and 302 type 2 diabetic cases followed from HUNT2 to HUNT3. From HUNT3, 24 type 1 diabetic and 31 LADA incident cases were available.

RESULTS

Cross-sectionally, 90% of LADA cases were positive for only one antibody (10% multiple-antibodypositive). Prospectively, 59% of GADA-positive LADA patients in HUNT2 were no longer positive in HUNT3. LADA patients who became negative possessed less frequently risk HLA haplotypes and were phenotypically more akin to those with type 2 diabetes than to those who stayed positive. Still, those losing positivity differed from those with type 2 diabetes by lower C-peptide levels (p = 0.009). Of incident LADA cases in HUNT3, 64% were already antibody-positive in HUNT2, i.e. before diabetes diagnosis. These incident LADA cases were phenotypically more akin to type 1 diabetes than were those who did not display positivity in HUNT2.

CONCLUSION/INTERPRETATION

The pattern of antibodies, the postdiabetic loss or persistence as well as the prediabetic absence or presence of antibodies influence LADA phenotypes. Time-dependent presence or absence of antibodies adds new modalities to the heterogeneity of LADA.

The type 2 diabetes-associated variant in TCF7L2 is associated with latent autoimmune diabetes in adult Europeans and the gene effect is modified by obesity: a meta-analysis and an individual study

AIMS/HYPOTHESIS

The variants of transcription factor 7-like 2 (TCF7L2) gene have been proposed to be associated with latent autoimmune diabetes in adults (LADA). We sought to confirm the possible association in Europeans and to examine the interaction between one gene variant and clinical data.

METHODS

The TCF7L2 rs7903146 C-to-T polymorphism was genotyped in 211 LADA, 1,297 type 2 diabetic, 545 type 1 diabetic and 1,497 control individuals from Hungary. A meta-analysis of our and previously published studies was performed to evaluate the size and the heterogeneity of the gene effect.

RESULTS

The meta-analysis yielded a significant effect of TCF7L2 T allele (OR 1.28; p < 0.0001) on LADA risk without heterogeneity among Europeans. The T allele conferred equally strong susceptibility to LADA and type 2 diabetes. In the Hungarian dataset, the T allele was associated with LADA and type 2 diabetes, but not with type 1 diabetes. T allele carriers had significantly lower BMI than patients with the CC genotype in the LADA and type 2 diabetes groups (p = 0.0021 and p = 0.0013, respectively). In both diseases, the diabetes risk was significantly higher in the non-overweight than in the overweight BMI category (p = 0.0013 and p < 0.0001, respectively); susceptibility to LADA was increased by 2.84-fold in non-overweight individuals compared with overweight ones.

CONCLUSIONS/INTERPRETATION

The meta-analysis demonstrates that TCF7L2 rs7903146 polymorphism is a population-independent susceptibility locus for LADA in Europeans. The effect size is similar for LADA and type 2 diabetes. The gene effect on diabetes risk may be modulated by BMI, such that the lower the BMI, the higher the gene effect.

Genetic analysis of adult-onset autoimmune diabetes

OBJECTIVE

In contrast with childhood-onset type 1 diabetes, the genetics of autoimmune diabetes in adults are not well understood. We have therefore investigated the genetics of diabetes diagnosed in adults positive for autoantibodies.

RESEARCH DESIGN AND METHODS

GAD autoantibodies (GADAs), insulinoma-associated antigen-2 antibodies (IA-2As), and islet cell autoantibodies were measured at time of diagnosis. Autoantibody-positive diabetic subjects (n = 1,384) and population-based control subjects (n = 2,235) were genotyped at 20 childhood-onset type 1 diabetes loci and FCRL3, GAD2, TCF7L2, and FTO.

RESULTS

PTPN22 (1p13.2), STAT4 (2q32.2), CTLA4 (2q33.2), HLA (6p21), IL2RA (10p15.1), INS (11p15.5), ERBB3 (12q13.2), SH2B3 (12q24.12), and CLEC16A (16p13.13) were convincingly associated with autoimmune diabetes in adults (P ≤ 0.002), with consistent directions of effect as reported for pediatric type 1 diabetes. No evidence of an HLA-DRB1*03/HLA-DRB1*04 (DR3/4) genotype effect was obtained (P = 0.55), but it remained highly predisposing (odds ratio 26.22). DR3/4 was associated with a lower age at diagnosis of disease, as was DR4 (P = 4.67 × 10(-6)) but not DR3. DR3 was associated with GADA positivity (P = 6.03 × 10(-6)) but absence of IA-2A (P = 3.22 × 10(-7)). DR4 was associated with IA-2A positivity (P = 5.45 × 10(-6)).

CONCLUSIONS

Our results are consistent with the hypothesis that the genetics of autoimmune diabetes in adults and children are differentiated by only relatively few age-dependent genetic effects. The slower progression toward autoimmune insulin deficiency in adults is probably due to a lower genetic load overall combined with subtle variation in the HLA class II gene associations and autoreactivity.

Worldwide distribution of type II diabetes-associated TCF7L2 SNPs: evidence for stratification in Europe

Type II diabetes is a multifactorial disease with a complex etiology. Numerous genes have been implicated in disease pathogenesis. In particular, SNPs at the TCF7L2 locus have consistently shown strong associations with type II diabetes. This study characterizes the global distribution of type II diabetes-associated TCF7L2 SNPs utilizing HapMap, HGDP-CEPH, and Alfred databases and the literature. High frequencies of rs7903146(T), rs12255372(T), and rs7901695(C) SNPs are observed in Africa, Europe, and the Middle East, but they are reduced and almost absent in Southeast Asian and Native American populations. In contrast, rs11196218(A) has the highest frequency in Eurasia but is reduced in sub-Saharan African and Native American populations. Regional variations in rs7903146(T) follow a gradient of decreasing frequency from southern into northeastern Europe. These findings demonstrate extensive global and regional variations in the frequencies of TCF7L2 SNPs, which may contribute to differences in the incidence of type II diabetes worldwide.

No effect by the common gene variant rs10830963 of the melatonin receptor 1B on the association between sleep disturbances and type 2 diabetes: results from the Nord-Trøndelag Health Study

AIMS/HYPOTHESIS

Genetic variation in the melatonin receptor 1B (MTNR1B) is associated with type 2 diabetes. Melatonin contributes to the regulation of sleep, and sleep problems are a documented risk factor for type 2 diabetes. The aim of this study was to investigate whether the MTNR1B gene variant rs10830963 is associated with sleep problems and whether this variant contributes to the association between sleep disturbances and type 2 diabetes.

METHODS

This was a case-control study nested within the population-based Nord-Trøndelag Health Study, including 1,322 prevalent cases of type 2 diabetes and 1,447 controls. In addition, prospective data were available for 838 incident cases and 1,133 controls. Genotyping was done by TaqMan single-nucleotide polymorphism allelic discrimination analysis. ORs and 95% CIs were calculated using logistic regression models.

RESULTS

Our findings confirm an association between sleep disturbances and type 2 diabetes (OR 1.69, 95% CI 1.22-2.33, p = 0.0016) and between the risk allele of rs10830963 and type 2 diabetes (OR 1.12, 95% CI 1.00-1.27, p = 0.0579). There was a tendency for an association between the risk allele and prevalence of sleep problems (specifically early awakening). However, the risk allele did not influence the association of sleep problems with diabetes, which was unaltered after adjustment for the MTNR1B risk allele (OR 1.69, 95% CI 1.23-2.34, p = 0.0014). Results based on prospective data were similar, although non-significant.

CONCLUSIONS/INTERPRETATION

Our findings do not support participation of the MTNR1B gene variant rs10830963 in the well documented association between sleep disturbances and type 2 diabetes.

High levels of education are associated with an increased risk of latent autoimmune diabetes in adults: results from the Nord-Trøndelag health study

OBJECTIVE

To investigate whether the risk for autoimmune diabetes in adults differs between socioeconomic groups and to compare such risk with that for type 2 diabetes.

RESEARCH DESIGN AND METHODS

The inhabitants of the Norwegian county of Nord-Trøndelag were investigated by questionnaires and clinical examinations on three occasions during 1984-2008. We used information from a subset consisting of 56,296 subjects (participating in at least two surveys), including 122 incident cases of autoimmune diabetes in adults (aged ≥35 and anti-GAD positive) and 1,555 cases of type 2 diabetes (aged ≥35 and anti-GAD negative). Hazard ratios (HRs) of diabetes associated with self-reported education and occupation were estimated by Cox proportional hazards models.

RESULTS

High levels of education (university versus primary school) were associated with an increased risk of autoimmune diabetes (HR 1.98 [95% CI 1.21-3.26]), after adjustment for BMI, lifestyle factors, and family history of diabetes. Case subjects with high levels of education had lower levels of C-peptide, tended to have higher levels of anti-GAD, and were more often treated with insulin. Conversely, these subjects had a reduced risk of type 2 diabetes (HR 0.69 [95% CI 0.57-0.82]), a risk that was partly explained by lower BMI and more physical activity (adjusted HR 0.89 [95% CI 0.74-1.06]).

CONCLUSIONS

High levels of education are associated with an increased risk of autoimmune diabetes in adults, a finding that may be mediated by effects on autoimmune activity. Because the association is not explained by traditional risk factors, other, currently unidentified, environmental factors are likely to be involved.

Latent autoimmune diabetes in adults differs genetically from classical type 1 diabetes diagnosed after the age of 35 years

OBJECTIVE

We studied differences between patients with latent autoimmune diabetes in adults (LADA), type 2 diabetes, and classical type 1 diabetes diagnosed after age 35 years.

RESEARCH DESIGN AND METHODS

Polymorphisms in HLA-DQB1, INS, PTPN22, and CTLA4 were genotyped in patients with LADA (n = 213), type 1 diabetes diagnosed at >35 years of age (T1D(>35y); n = 257) or <20 years of age (T1D(<20y); n = 158), and type 2 diabetes.

RESULTS

Although patients with LADA had an increased frequency of HLA-DQB1 and PTPN22 risk genotypes and alleles compared with type 2 diabetic subjects, the frequency was significantly lower compared with T1D(>35y) patients. Genotype frequencies, measures of insulin secretion, and metabolic traits within LADA differed according to GAD antibody (GADA) quartiles, but even the highest quartile differed from type 1 diabetes. Having two or more risk genotypes was associated with lower C-peptide concentrations in LADA.

CONCLUSIONS

LADA patients differed genetically and phenotypically from both T1D(>35y) and type 2 diabetic patients in a manner dependent on GADA levels.