Lifestyle or Environmental Influences and Their Interaction With Genetic Susceptibility on the Risk of LADA

BACKGROUND

LADA is a common form of diabetes described as a mix between type 1 and type 2 diabetes. Understanding of how genes and environmental factors interact in the development of LADA is central for future efforts to prevent the disease. This review aims to synthesize the literature on lifestyle factors linked to LADA risk and discuss their potential interaction with genetic susceptibility.

FINDINGS

Current knowledge on environmental risk factors for LADA is primarily based on observational data from Scandinavian populations. Increasing evidence suggest that lifestyle factors promoting type 2 diabetes such as obesity, sedentariness, low birth weight and smoking, is implicated in the risk of LADA. Data from mendelian randomization studies support that the link between LADA and obesity, low birth weight and smoking is causal. Limited evidence indicates that dietary factors including consumption of red meat, coffee and sweetened beverages may increase the risk while consumption of alcohol and omega-3 fatty acids may reduce the risk. Several lifestyle factors, including smoking and obesity, seem to interact with human leukocyte antigen genes associated with autoimmunity, conferring much stronger effects on disease risk among those exposed to both factors.

SUMMARY

Available studies suggest that lifestyle modification has the potential for prevention of LADA, particularly for individuals with high risk of disease such as those with genetic susceptibility. Research into risk factors of LADA is however limited, confirmations are warranted, many factors remain to be explored, and there is a need for intervention studies to assess causality.

Genome-wide association analyses highlight etiological differences underlying newly defined subtypes of diabetes

Type 2 diabetes has been reproducibly clustered into five subtypes with different disease progression and risk of complications; however, etiological differences are unknown. We used genome-wide association and genetic risk score (GRS) analysis to compare the underlying genetic drivers. Individuals from the Swedish ANDIS (All New Diabetics In Scania) study were compared to individuals without diabetes; the Finnish DIREVA (Diabetes register in Vasa) and Botnia studies were used for replication. We show that subtypes differ with regard to family history of diabetes and association with GRS for diabetes-related traits. The severe insulin-resistant subtype was uniquely associated with GRS for fasting insulin but not with variants in the TCF7L2 locus or GRS reflecting insulin secretion. Further, an SNP (rs10824307) near LRMDA was uniquely associated with mild obesity-related diabetes. Therefore, we conclude that the subtypes have partially distinct genetic backgrounds indicating etiological differences.

Dietary factors and risk of islet autoimmunity and type 1 diabetes: a systematic review and meta-analysis

Background

Numerous dietary components have been linked to the development of islet autoimmunity (IA) and type 1 diabetes (T1D); however, no associations are firmly established. This systematic review and meta-analysis aimed to synthesize current knowledge on diet and incidence of IA and T1D.

Methods

Literature search was performed in Medline, Embase, and Cochrane Library, from inception until October 2020. Eligible studies had IA or T1D as outcome; any dietary exposure; case-control, cohort, or randomized controlled trial design; and hazard, risk, or odds ratios as measures of association. Summary relative risks (RR) and 95% confidence intervals (CI) were estimated with random-effects models. Certainty of evidence was assessed with GRADE. PROSPERO registration number: CRD42020212505.

Findings

Among 5935 identified records, 96 were eligible, and pooled estimates could be produced for 26 dietary factors. Evidence with moderate/high certainty indicated lower risk of T1D in relation to longer (≥6-12 vs <6-12 months, RR: 0⋅39, CI: 0⋅26-0⋅58, I²=43%) and exclusive (≥2-3 vs <2-3 months, RR: 0⋅68, CI: 0⋅58-0⋅80, I²=0%) breastfeeding, later introduction to gluten (3-6 vs <3-5 months, RR: 0⋅36, CI: 0⋅17-0⋅75, I²=0%), cow's milk (≥2-3 vs <2-3 months, RR: 0⋅69, CI: 0⋅59-0⋅81, I²=0%), and fruit (4-6 vs <4-5 months, RR: 0⋅47, CI: 0⋅25-0⋅86, I²=0%). Higher childhood intake of cow's milk was associated with increased risk of both IA (per 2-3 portions/day, RR: 1⋅25, CI: 1⋅06-1⋅47, I²=0%) and T1D (≥2-3 vs <2-3 glasses/day, RR: 1⋅81, CI: 1⋅12-2⋅91, I²=31%). For the remaining dietary factors investigated, there was no association, or the evidence was of low certainty.

Interpretation

This study suggests that breastfeeding and late introduction of gluten, fruit, and cow's milk may reduce the risk of T1D, whereas high childhood cow's milk intake may increase it.

Funding

Swedish Research Council, Swedish Research Council for Health, Working Life and Welfare (FORTE), Novo Nordisk Foundation, and Swedish Diabetes Foundation.

Mortality rates and cardiovascular disease burden in type 2 diabetes by occupation, results from all Swedish employees in 2002-2015

Objective

To identify occupations where employees with type 2 diabetes have a high risk of cardiovascular disease (CVD) and mortality, and their prevalence of CVD risk factors. This study can contribute in the creation of targeted interventions at the workplace.

Research design and methods

This nationwide registry-based study included all employees with type 2 diabetes born in Sweden in 1937–1979 (n = 180,620) and followed up in 2002–2015. We calculated age-standardized incidence (per 100,000 person-years) of all-cause and CVD mortality, ischemic heart disease (IHD) and stroke across the 30 most common occupations. Information on prognostic factors was retrieved from the National Diabetes Register.

Results

In males with type 2 diabetes, mortality rates were highest in manufacturing workers (1782) and machine operators (1329), and lowest in specialist managers (633). The risk of death at age 61–70 years was 21.8% in manufacturing workers and 8.5% in managers. In females with type 2 diabetes, mortality rates were highest in manufacturing workers (1150) and cleaners (876), and lowest in writers and artists (458); the risk of death at age 61–70 years was 12.4% in manufacturing workers and 4.3% in writers and artists. The same occupations also had relatively high incidences of CVD mortality, IHD and stroke. Occupational groups with poor prognosis had high prevalence of CVD risk factors including poor glycemic control, smoking and obesity.

Conclusions

Manufacturing workers, machine operators and cleaners with type 2 diabetes have two to three times higher mortality rates than managers, writers and artists with type 2 diabetes. Major health gains would be made if targeted workplace interventions could reduce CVD risk factors in these occupations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01320-8.

Combined lifestyle factors and the risk of LADA and type 2 diabetes - Results from a Swedish population-based case-control study

AIMS

We investigated the risk of latent autoimmune diabetes in adults (LADA) and type 2 diabetes in relation to a healthy lifestyle, the proportion of patients attributable to an unhealthy lifestyle, and the influence of family history of diabetes (FHD) and genetic susceptibility.

METHODS

The population-based study included incident LADA (n = 571), type 2 diabetes (n = 1962), and matched controls (n = 2217). A healthy lifestyle was defined by BMI < 25 kg/m², moderate-to-high physical activity, a healthy diet, no smoking, and moderate alcohol consumption. We estimated odds ratios (OR) with 95% confidence intervals (CIs) adjusted for age, sex, education, and FHD.

RESULTS

Compared to a poor/moderate lifestyle, a healthy lifestyle was associated with a reduced risk of LADA (OR 0.51, CI 0.34-0.77) and type 2 diabetes (OR 0.09, CI 0.05-0.15). A healthy lifestyle conferred a reduced risk irrespective of FHD and high-risk HLA genotypes. Having a BMI < 25 kg/m² conferred the largest risk reduction for both LADA (OR 0.54, CI 0.43-0.66) and type 2 diabetes (OR 0.12, CI 0.10-0.15) out of the individual items.

CONCLUSION

People with a healthy lifestyle, especially a healthy body weight, have a reduced risk of LADA including those with genetic susceptibility to diabetes.

Interaction Between GAD65 Antibodies and Dietary Fish Intake or Plasma Phospholipid n-3 Polyunsaturated Fatty Acids on Incident Adult-Onset Diabetes: The EPIC-InterAct Study

OBJECTIVE

Islet autoimmunity is associated with diabetes incidence. We investigated whether there was an interaction between dietary fish intake or plasma phospholipid n-3 polyunsaturated fatty acid (PUFA) concentration with the 65-kDa isoform of GAD (GAD65) antibody positivity on the risk of developing adult-onset diabetes.

RESEARCH DESIGN AND METHODS

We used prospective data on 11,247 incident cases of adult-onset diabetes and 14,288 noncases from the EPIC-InterAct case-cohort study conducted in eight European countries. Baseline plasma samples were analyzed for GAD65 antibodies and phospholipid n-3 PUFAs. Adjusted hazard ratios (HRs) for incident diabetes in relation to GAD65 antibody status and tertiles of plasma phospholipid n-3 PUFA or fish intake were estimated using Prentice-weighted Cox regression. Additive (proportion attributable to interaction [AP]) and multiplicative interactions between GAD65 antibody positivity (≥65 units/mL) and low fish/n-3 PUFA were assessed.

RESULTS

The hazard of diabetes in antibody-positive individuals with low intake of total and fatty fish, respectively, was significantly elevated (HR 2.52 [95% CI 1.76-3.63] and 2.48 [1.79-3.45]) compared with people who were GAD65 antibody negative and had high fish intake, with evidence of additive (AP 0.44 [95% CI 0.16-0.72] and 0.48 [0.24-0.72]) and multiplicative (P = 0.0465 and 0.0103) interactions. Individuals with high GAD65 antibody levels (≥167.5 units/mL) and low total plasma phospholipid n-3 PUFAs had a more than fourfold higher hazard of diabetes (HR 4.26 [2.70-6.72]) and an AP of 0.46 (0.12-0.80) compared with antibody-negative individuals with high n-3 PUFAs.

CONCLUSIONS

High fish intake or relative plasma phospholipid n-3 PUFA concentrations may partially counteract the increased diabetes risk conferred by GAD65 antibody positivity.

The anatomical SP-CL stem demonstrates a non-progressing migration pattern in the first year: a low dose CT-based migration study in 20 patients

Background and purpose - RSA is the gold standard for evaluation of early implant migration. We report the results of a new CT-based method Sectra CT micromotion analysis (CTMA) applied to assess the migration pattern in 20 patients in the 1st year after surgery, both with and without the use of tantalum beads in the bone. The patients had an SP-CL anatomical stem that uses an S-shape, designed to better fit the curvature of the femur. Patients and methods - 20 THA patients (mean age 61 years, 10 female) received SP-CL stems, tantalum markers in the femur, and low-dose CT scans at 1 day, 3 months and 12 months postoperatively. In addition, precision as well as inter- and intra-observer variability of the 12-month migration was measured. Results - The 3-month subsidence was median 0.5 mm (95% CI 0.3-1.0) and the internal rotation 1.8° (CI 0.9-2.6). At 12 months the corresponding values were 0.6 (CI 0.3-1.6) mm and 1.9° (CI 0.8-2.4). Precision was 0.1 to 0.3 mm and 0.1° to 0.4° at 3 and 12 months. Intra- and inter- observer variability yielded R-values averaging 0.96 and 0.98. Interpretation - The migration mainly took place during the 1st 3 months, in line with other uncemented stems. The number of patients with subsidence over 2 mm in the first year (5) might be due to the design of the prosthesis with an anatomical shape. Alternatively, our results might indicate a challenge when choosing the correct size for these new anatomical stems. CTMA provided precise and highly repeatable measurements of migration without the need for tantalum markers.

Physical Activity, Genetic Susceptibility, and the Risk of Latent Autoimmune Diabetes in Adults and Type 2 Diabetes

PURPOSE

Physical activity (PA) has been linked to a reduced risk of type 2 diabetes by reducing weight and improving insulin sensitivity. We investigated whether PA is associated with a lower incidence of latent autoimmune diabetes in adults (LADA) and whether the association is modified by genotypes of human leukocyte antigen (HLA), transcription factor 7-like 2 (TCF7L2)-rs7903146, or the fat mass and obesity-associated gene, FTO-rs9939609.

METHODS

We combined data from a Swedish case-control study and a Norwegian prospective study including 621 incident cases of LADA and 3596 cases of type 2 diabetes. We estimated adjusted pooled relative risks (RRs) and 95% CI of diabetes in relation to high (≥ 30 minutes of moderate activity 3 times/week) self-reported leisure time PA, compared to sedentariness.

RESULTS

High PA was associated with a reduced risk of LADA (RR 0.61; CI, 0.43-0.86), which was attenuated after adjustment for body mass index (BMI) (RR 0.90; CI, 0.63-1.29). The reduced risk applied only to noncarriers of HLA-DQB1 and -DRB1 (RR 0.49; CI, 0.33-0.72), TCF7L2 (RR 0.62; CI, 0.45-0.87), and FTO (RR 0.51; CI, 0.32-0.79) risk genotypes. Adjustment for BMI attenuated but did not eliminate these associations. For type 2 diabetes, there was an inverse association with PA (RR 0.49; CI, 0.42-0.56), irrespective of genotype.

MAIN CONCLUSIONS

Our findings indicate that high PA is associated with a reduced risk of LADA in individuals without genetic susceptibility.

Pharmacologic treatment and SUDEP risk: A nationwide, population-based, case-control study

Objective

We conducted a nationwide case–control study in Sweden to test the hypothesis that antiepileptic drugs (AEDs) mono- or polytherapy, adherence, antidepressants, neuroleptics, β-blockers, and statins are associated with sudden unexpected death in epilepsy (SUDEP) risk.

Methods

Included were 255 SUDEP cases and 1,148 matched controls. Information on clinical factors and medications came from medical records and the National Patient and Prescription Registers. The association between SUDEP and medications was assessed by odds ratios (ORs) with 95% confidence intervals (CIs) adjusted for potential risk factors including type of epilepsy, living conditions, comorbidity, and frequency of generalized tonic-clonic seizures (GTCS).

Results

Polytherapy, especially taking 3 or more AEDs, was associated with a substantially reduced risk of SUDEP (OR 0.31, 95% CI 0.14–0.67). Combinations including lamotrigine (OR 0.55, 95% CI 0.31–0.97), valproic acid (OR 0.53, 95% CI 0.29–0.98), and levetiracetam (OR 0.49, 95% CI 0.27–0.90) were associated with reduced risk. No specific AED was associated with increased risk. Regarding monotherapy, although numbers were limited, the lowest SUDEP risk was seen in users of levetiracetam (0.10, 95% CI 0.02–0.61). Having nonadherence mentioned in the medical record was associated with an OR of 2.75 (95% CI 1.58–4.78). Statin use was associated with a reduced SUDEP risk (OR 0.34, 95% CI 0.11–0.99) but selective serotonin reuptake inhibitor use was not.

Conclusion

These results provide support for the importance of medication adherence and intensified AED treatment for patients with poorly controlled GTCS in the effort to reduce SUDEP risk and suggest that comedication with statins may reduce risk.

Epilepsy syndromes, etiologies, and the use of next-generation sequencing in epilepsy presenting in the first 2 years of life: A population-based study

OBJECTIVE

Population-based data on epilepsy syndromes and etiologies in early onset epilepsy are scarce. The use of next-generation sequencing (NGS) has hitherto not been reported in this context. The aim of this study is to describe children with epilepsy onset before 2 years of age, and to explore to what degree whole exome and whole genome sequencing (WES/WGS) can help reveal a molecular genetic diagnosis.

METHODS

Children presenting with a first unprovoked epileptic seizure before age 2 years and registered in the Stockholm Incidence Registry of Epilepsy (SIRE) between September 1, 2001 and December 31, 2006, were retrieved and their medical records up to age 7 years reviewed. Children who met the epilepsy criteria were included in the study cohort. WES/WGS was offered in cases of suspected genetic etiology regardless of whether a structural or metabolic diagnosis had been established.

RESULTS

One hundred sixteen children were included, of which 88 had seizure onset during the first year of life and 28 during the second, corresponding to incidences of 139 and 42/100 000 person-years, respectively. An epilepsy syndrome could be diagnosed in 54% of cases, corresponding to a birth prevalence of 1/1100. Structural etiology was revealed in 34% of cases, a genetic cause in 20%, and altogether etiology was known in 65% of children. The highest diagnostic yield was seen in magnetic resonance imaging (MRI) with 65% revealing an etiology. WES/WGS was performed in 26/116 cases (22%), with a diagnostic yield of 58%.

SIGNIFICANCE

Epilepsy syndromes can be diagnosed and etiologies revealed in a majority of early onset cases. NGS can identify a molecular diagnosis in a substantial number of children, and should be included in the work-up, especially in cases of epileptic encephalopathy, cerebral malformation, or metabolic disease without molecular diagnosis. A genetic diagnosis is essential to genetic counselling, prenatal diagnostics, and precision therapy.

Consumption of red meat, genetic susceptibility, and risk of LADA and type 2 diabetes

Purpose

Red meat consumption is positively associated with type 1 (T1D) and type 2 (T2D) diabetes. We investigated if red meat consumption increases the risk of latent autoimmune diabetes in adults (LADA) and T2D, and potential interaction with family history of diabetes (FHD), HLA and TCF7L2 genotypes.

Methods

Analyses were based on Swedish case–control data comprising incident cases of LADA (n = 465) and T2D (n = 1528) with matched, population-based controls (n = 1789; n = 1553 in genetic analyses). Multivariable-adjusted ORs in relation to self-reported processed and unprocessed red meat intake were estimated by conditional logistic regression models. Attributable proportion (AP) due to interaction was used to assess departure from additivity of effects.

Results

Consumption of processed red meat was associated with increased risk of LADA (per one servings/day OR 1.27, 95% CI 1.07–1.52), whereas no association was observed for unprocessed red meat. For T2D, there was no association with red meat intake once BMI was taken into account. The combination of high (> 0.3 servings/day vs. less) processed red meat intake and high-risk HLA-DQB1 and -DRB1 genotypes yielded OR 8.05 (95% CI 4.86–13.34) for LADA, with indications of significant interaction (AP 0.53, 95% CI 0.32–0.73). Results were similar for the combination of FHD-T1D and processed red meat. No interaction between processed red meat intake and FHD-T2D or risk variants of TCF7L2 was seen in relation to LADA or T2D.

Conclusion

Consumption of processed but not unprocessed red meat may increase the risk of LADA, especially in individuals with FHD-T1D or high-risk HLA genotypes.

Electronic supplementary material

The online version of this article (10.1007/s00394-020-02285-2) contains supplementary material, which is available to authorized users.

Incidence and prevalence of type 2 diabetes by occupation: results from all Swedish employees

AIMS/HYPOTHESIS

The workplace is a potentially important arena for prevention of type 2 diabetes and the first step is to identify occupations where the disease is common and/or risk is high. Therefore, our aim was to analyse incidence and prevalence of type 2 diabetes across all occupational groups in Sweden.

METHODS

This nationwide study included all Swedish citizens born between 1937 and 1979 and gainfully employed between 2001 and 2013 (N = 4,550,892), and followed for a diagnosis of diabetes from 2006 to 2015 (n = 201,717) through national registers. Prevalence in 2013 (mean age 51 years; range 35-67) and age-standardised incidence (per 1000 person-years) were analysed across the 30 most common occupations among men and women. Information on BMI, physical fitness and smoking was obtained through the National Conscription (mean age 18) and Medical Birth Registers (mean age 29).

RESULTS

Prevalence of type 2 diabetes was 5.2% in men and 3.2% in women; in men it was highest among motor vehicle drivers (8.8%) and in women it was highest among manufacturing workers (6.4%). Incidence varied dramatically across occupational groups. In men, it was highest among manufacturing workers (9.41) and professional drivers (9.32) and lowest among university teachers (3.44). In women, incidence was highest in manufacturing workers (7.20) and cleaners (6.18) and lowest in physiotherapists (2.20). We found major differences in the prevalence of being overweight and smoking and in the level of physical fitness across these occupational groups even at young ages.

CONCLUSIONS/INTERPRETATION

Professional drivers, manufacturing workers and cleaners have a threefold increased risk of type 2 diabetes compared with university teachers and physiotherapists. These differences most likely reflect dramatic differences in the prevalence of lifestyle risk factors. If workplace interventions could reduce weight and increase physical activity among employees in these occupations, major health gains may be made.

Clinical risk factors in SUDEP: A nationwide population-based case-control study

Objective

We conducted a nationwide case-control study in Sweden to test the hypothesis that specific clinical characteristics are associated with increased risk of sudden unexpected death in epilepsy (SUDEP).

Methods

The study included 255 SUDEP cases (definite and probable) and 1,148 matched controls. Clinical information was obtained from medical records and the National Patient Register. The association between SUDEP and potential risk factors was assessed by odds ratios (ORs) and 95% confidence intervals (CIs) and interaction assessed by attributable proportion due to interaction (AP).

Results

Experiencing generalized tonic-clonic seizures (GTCS) during the preceding year was associated with a 27-fold increased risk (OR 26.81, 95% CI 14.86–48.38), whereas no excess risk was seen in those with exclusively non-GTCS seizures (OR 1.15, 95% CI 0.54–48.38). The presence of nocturnal GTCS during the last year of observation was associated with a 15-fold risk (OR 15.31, 95% CI 9.57–24.47). Living alone was associated with a 5-fold increased risk of SUDEP (OR 5.01, 95% CI 2.93–8.57) and interaction analysis showed that the combination of not sharing a bedroom and having GTCS conferred an OR of 67.10 (95% CI 29.66–151.88), with AP estimated at 0.69 (CI 0.53–0.85). Among comorbid diseases, a previous diagnosis of substance abuse or alcohol dependence was associated with excess risk of SUDEP.

Conclusions

Individuals with GTCS who sleep alone have a dramatically increased SUDEP risk. Our results indicate that 69% of SUDEP cases in patients who have GTCS and live alone could be prevented if the patients were not unattended at night or were free from GTCS.

Interaction Between Overweight and Genotypes of HLA, TCF7L2, and FTO in Relation to the Risk of Latent Autoimmune Diabetes in Adults and Type 2 Diabetes

OBJECTIVE

We investigated potential interactions between body mass index (BMI) and genotypes of human leukocyte antigen (HLA), TCF7L2-rs7903146, and FTO-rs9939609 in relation to the risk of latent autoimmune diabetes in adults (LADA) and type 2 diabetes.

METHODS

We pooled data from two population-based studies: (i) a Swedish study with incident cases of LADA [positive for glutamic acid decarboxylase autoantibodies (GADA); n = 394) and type 2 diabetes (negative for GADA; n = 1290) and matched controls without diabetes (n = 2656) and (ii) a prospective Norwegian study that included incident cases of LADA (n = 131) and type 2 diabetes (n = 1901) and 886,120 person-years of follow-up. Analyses were adjusted for age, sex, physical activity, and smoking. Interaction between overweight (BMI ≥ 25 kg/m2) and HLA/TCF7L2/FTO high-risk genotypes was assessed by attributable proportion due to interaction (AP).

RESULTS

The combination of overweight and high-risk genotypes of HLA, TCF7L2, and FTO was associated with pooled relative risk (RRpooled) of 7.59 (95% CI, 5.27 to 10.93), 2.65 (95% CI, 1.97 to 3.56), and 2.21 (95% CI, 1.60 to 3.07), respectively, for LADA, compared with normal-weight individuals with low/intermediate genetic risk. There was a significant interaction between overweight and HLA (AP, 0.29; 95% CI, 0.10 to 0.47), TCF7L2 (AP, 0.31; 95% CI, 0.09 to 0.52), and FTO (AP, 0.38; 95% CI, 0.15 to 0.61). The highest risk of LADA was seen in overweight individuals homozygous for the DR4 genotype [RR, 26.76 (95% CI, 15.42 to 46.43); AP, 0.58 (95% CI, 0.32 to 0.83) (Swedish data)]. Overweight and TCF7L2 also significantly interacted in relation to type 2 diabetes (AP, 0.26; 95% CI, 0.19 to 0.33), but no interaction was observed with high-risk genotypes of HLA or FTO.

CONCLUSIONS

Overweight interacts with HLA high-risk genotypes but also with genes associated with type 2 diabetes in the promotion of LADA.

Tobacco and type 2 diabetes: is the association explained by genetic factors?

BACKGROUND

Smoking and use of Swedish smokeless tobacco (snus) are associated with increased risk of type 2 diabetes (T2D). Our aim was to estimate the unique and shared genetic components of these traits and to what extent the association is explained by shared genetic factors.

METHODS

We used twins of the Swedish Twin Registry who responded to a questionnaire between 1998 and 2006 (n = 40 247) and were followed until 2015 in the National Prescription and Patient Registries. We estimated hazard ratios (HRs) and odds ratios (ORs) for the association between smoking/snus use and T2D (n = 2130) and used structural equation models to estimate genetic and environmental variance components and genetic correlations.

RESULTS

Current smokers [HR 1.69, 95% confidence interval (CI), 1.49-1.92] and snus users (HR 1.19, 95% CI 1.01-1.41) had an increased risk of T2D. In within-pair analyses of monozygotic twins, corresponding ORs were 1.36, 95% CI 0.75-2.46 (smoking) and 1.54, 95% CI 0.80-2.99 (snus). Heritability was 43% (95% CI 36-51) for ever smoking, 58% (95% CI 44- 70) for ever snus use and 66% (95% CI 59-72) for T2D. The genetic correlation with T2D was 18% (95% CI 1-35) for smoking and -6% (95% CI -24 to 4) for snus use, indicating that only a small fraction of the genetic influence is shared.

CONCLUSIONS

We could confirm that consumers of snus and cigarettes are at increased risk of T2D. Both snus use and smoking have strong genetic components, which appears to be attributable primarily to genes that are distinct from those promoting T2D.

Etiology and Pathogenesis of Latent Autoimmune Diabetes in Adults (LADA) Compared to Type 2 Diabetes

As the heterogeneity of diabetes is becoming increasingly clear, opportunities arise for more accurate assessment of factors influencing disease onset, which may lead to more efficient primary prevention. LADA - latent autoimmune diabetes in adults - is a common, hybrid form of diabetes with features of both type 1 and type 2 diabetes. This review aims to summarize current knowledge on the pathophysiological and etiological overlap and differences between LADA and type 2 diabetes, discuss similarities between LADA and type 1 diabetes and point at future research needs. Studies conducted to date show a clear genetic overlap between LADA and type 1 diabetes with a high risk conferred by variants in the human leukocyte antigen (HLA) region. In contrast, data from the limited number of studies on lifestyle factors available indicate that LADA may share several environmental risk factors with type 2 diabetes including overweight, physical inactivity, alcohol consumption (protective) and smoking. These factors are known to influence insulin sensitivity, suggesting that insulin resistance, in addition to insulin deficiency due to autoimmune destruction of the beta cells, may play a key role in the pathogenesis of LADA. Moreover, this implies that onset of LADA, similar to type 2 diabetes, to some extent could be prevented or postponed by lifestyle modification such as weight reduction and increased physical activity. The preventive potential of LADA is an important topic to elucidate in future studies, preferably intervention studies.

Environmental (Lifestyle) Risk Factors for LADA

BACKGROUND

In order to prevent diabetes it is important to identify common, modifiable risk factors in the population. Such knowledge is extensive for type 2 diabetes but limited for autoimmune forms of diabetes.

OBJECTIVE

This review aims at summarizing the limited literature on potential environmental (lifestyle) risk factors for LADA.

METHODS

A PubMed search identified 15 papers estimating the risk of LADA in relation to lifestyle. These were based on data from two population-based studies; one Swedish case-control study and one Norwegian cohort study.

RESULTS

Studies published to date indicate that the risk of LADA is associated with factors promoting insulin resistance and type 2 diabetes such as overweight, physical inactivity, smoking, low birth weight, sweetened beverage intake and moderate alcohol consumption (protective). Findings also indicate potential effects on autoimmunity exerted by intake of coffee (harmful) and fatty fish (protective). This supports the concept of LADA as being a hybrid form of diabetes with an etiology including factors associated with both insulin resistance and autoimmunity.

CONCLUSION

LADA may in part be preventable through the same lifestyle modifications as type 2 diabetes including weight loss, physical activity and smoking cessation. However, current knowledge is hampered by the small number of studies and the fact that they exclusively are based on Scandinavian populations. There is a great need for additional studies exploring the role of lifestyle factors in the development of LADA.