Genetic predisposition and environmental factors leading to the development of insulin-dependent diabetes mellitus in Chilean children

The genetic association between LMP2 and LMP7 polymorphisms and susceptibility of insulin dependent diabetes mellitus: A meta-analysis

BACKGROUND

Insulin dependent diabetes mellitus (IDDM) is a kind of heterogeneous disease caused by the interaction of polygene inheritance and environmental factors. The LMP2 and LMP7 are 2 loci in LMP gene, and although genetic association between LMP2 and LMP7 polymorphisms were reported, the results are inconclusive. The aim of this study was to investigate the association between LMP2 and LMP7 polymorphisms and IDDM risk.

METHODS

An exhaustive search was performed out through the electronic databases including PubMed, Embase, and Chinese National Knowledge Infrastructure (CNKI). The pooled odds ratio (OR) and 95% confidence interval (CI) were used to assess the strength association between LMP2 CfoI and LMP7 G37360T polymorphisms and IDDM risk.

RESULTS

A total of 7 studies with 707 cases and 821 controls were included in the present study. The results indicated that the dominant model of LMP2 CfoI was significantly associated with IDDM in Asian population (OR = 1.96, 95% CI: 1.24-3.10, P = .004). In addition, the allelic and dominant models of LMP7 G37360T were associated with IDDM in Caucasian population (allelic model: OR = 0.69, 95% CI: 0.56-0.85, P = .0005; dominant model: OR = 0.67, 95% CI: 0.50-0.89, P = .007).

CONCLUSIONS

The dominant model of LMP2 CfoI might be a risk factor for IDDM in Asian population. Whereas, the allelic and dominant models of LMP7 G37360T might be protective factors for IDDM in Caucasian population.

Vitamin D Supplementation Is Associated with Increased Glutathione Peroxidase-1 Levels in Arab Adults with Prediabetes

Vitamin D supplementation may be used to lower oxidative stress. This interventional study aimed to investigate the effects of vitamin D supplementation on glutathione peroxidase 1 (GPx1) levels and other parameters in Arab adults with prediabetes. A total of 203 Saudi adults with prediabetes and vitamin D deficiency [intervention group, N = 146 (53 males and 93 females); control group, N = 57 (25 males and 32 females)] were included in this non-randomized, six-month intervention study. The intervention group received 50,000 international units (IU) cholecalciferol tablets once a week for two months, then twice a month for the next two months, followed by 1000 IU daily for the last two months. The control group received no supplementation. Serum 25(OH)D, lipid profile, glucose, C-reactive protein (CRP) and GPx1 were measured at baseline and after six months. Post-intervention, GPx1 concentrations increased significantly in the intervention group [17.3 (11.5–59.0) vs 26.7 (11.4–59.9) p < 0.01] while no changes were observed in the control group (p = 0.15). This significant increase in 25(OH)D and GPx1 levels persisted after adjusting for age and BMI. Stratification according to sex revealed that this favourable increase in GPx1 was true only for males (p = 0.002). In all groups, baseline GPx1 was inversely correlated with low density lipoprotein (LDL)-cholesterol (r = −0.26, p < 0.01) and body mass index (BMI) (r = −0.20, p < 0.05), while positively correlated with age (r = 0.18, p < 0.05) and systolic blood pressure (r = 0.19, p < 0.05). In conclusion, vitamin D supplementation favourably enhanced GPx1 levels in adult Arabs with prediabetes, particularly in males.

Appropriate age range for introduction of complementary feeding into an infant's diet

Following a request from the European Commission, the Panel on Nutrition, Novel Foods and Food Allergens (NDA) revised its 2009 Opinion on the appropriate age for introduction of complementary feeding of infants. This age has been evaluated considering the effects on health outcomes, nutritional aspects and infant development, and depends on the individual's characteristics and development. As long as foods have an age-appropriate texture, are nutritionally appropriate and prepared following good hygiene practices, there is no convincing evidence that at any age investigated in the included studies (< 1 to < 6 months), the introduction of complementary foods (CFs) is associated with adverse health effects or benefits (except for infants at risk of iron depletion). For nutritional reasons, the majority of infants need CFs from around 6 months of age. Infants at risk of iron depletion (exclusively breastfed infants born to mothers with low iron status, or with early umbilical cord clamping (< 1 min after birth), or born preterm, or born small-for-gestational age or with high growth velocity) may benefit from earlier introduction of CFs that are a source of iron. The earliest developmental skills relevant for consuming pureed CFs can be observed between 3 and 4 months of age. Skills for consuming finger foods can be observed in some infants at 4 months, but more commonly at 5-7 months. The fact that an infant may be ready from a neurodevelopmental perspective to progress to a more diversified diet before 6 months of age does not imply that there is a need to introduce CFs. There is no reason to postpone the introduction of potentially allergenic foods (egg, cereals, fish and peanut) to a later age than that of other CFs as far as the risk of developing atopic diseases is concerned. Regarding the risk of coeliac disease, gluten can be introduced with other CFs.

Infant milk-feeding practices and diabetes outcomes in offspring: a systematic review

BACKGROUND

During the Pregnancy and Birth to 24 Months Project, the US Departments of Agriculture and Health and Human Services initiated a review of evidence on diet and health in these populations.

OBJECTIVES

The aim of these systematic reviews was to examine the relation of 1) never versus ever feeding human milk, 2) shorter versus longer durations of any human milk feeding, 3) shorter versus longer durations of exclusive human milk feeding, and 4) feeding a lower versus higher intensity of human milk to mixed-fed infants with type 1 and type 2 diabetes in offspring.

METHODS

The Nutrition Evidence Systematic Review team conducted systematic reviews with external experts. We searched CINAHL, Cochrane, Embase, and PubMed for articles published January 1980-March 2016, dual-screened the results according to predetermined criteria, extracted data from and assessed the risk of bias for each included study, qualitatively synthesized the evidence, developed conclusion statements, and graded the strength of the evidence.

RESULTS

The 4 systematic reviews included 21, 37, 18, and 1 articles, respectively. Observational evidence suggests that never versus ever feeding human milk (limited evidence) and shorter versus longer durations of any (moderate evidence) and exclusive (limited evidence) human milk feeding are associated with higher type 1 diabetes risk. Insufficient evidence examined type 2 diabetes. Limited evidence suggests that the durations of any and exclusive human milk feeding are not associated with intermediate outcomes (e.g., fasting glucose, insulin resistance) during childhood.

CONCLUSIONS

Limited to moderate evidence suggests that feeding less or no human milk is associated with higher risk of type 1 diabetes in offspring. Limited evidence suggests no associations between the durations of any and exclusive human milk feeding and intermediate diabetes outcomes in children. Additional research is needed on infant milk-feeding practices and type 2 diabetes and intermediate outcomes in US populations, which may have distinct metabolic risk.

Apoptosis of beta cells in diabetes mellitus

Diabetes mellitus is a multifactorial metabolic disorder characterized by hyperglycemia. Apoptosis in beta cells has been observed in response to diverse stimuli, such as glucose, cytokines, free fatty acids, leptin, and sulfonylureas, leading to the activation of polyol, hexosamine, and diacylglycerol/protein kinase-C (DAG/PKC) pathways that mediate oxidative and nitrosative stress causing the release of different cytokines. Cytokines induce the expression of Fas and tumor necrosis factor-alpha (TNF-α) by activating the transcription factor, nuclear factor-κb, and signal transducer and activator of transcription 1 (STAT-1) in the β cells in the extrinsic pathway of apoptosis. Cytokines produced in beta cells also induce proapoptotic members of the intrinsic pathway of apoptosis. The genetic alterations in apoptosis signaling machinery and the pathogenesis of diabetes include Fas, FasL, Akt, caspases, calpain-10, and phosphatase and tensin homolog (Pten). The other gene products that are involved in diabetes are nitric oxide synthase-2 (NOS2), small ubiquitin-like modifier (SUMO), apolipoprotein CIII (ApoCIII), forkhead box protein O1 (FOXO1), and Kruppel-like zinc finger protein Gli-similar 3 (GLIS3). The gene products having antiapoptotic nature are Bcl-2 and Bcl-XL. Epigenetic mechanisms play an important role in type I and type II diabetes. Further studies on the apoptotic genes and gene products in diabetics may be helpful in pharmacogenomics and individualized treatment along with antioxidants targeting apoptosis in diabetes.

Beyond genetics. Influence of dietary factors and gut microbiota on type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease ultimately leading to destruction of insulin secreting β-cells in the pancreas. Genetic susceptibility plays an important role in T1D etiology, but even mono-zygotic twins only have a concordance rate of around 50%, underlining that other factors than purely genetic are involved in disease development. Here we review the influence of dietary and environmental factors on T1D development in humans as well as animal models. Even though data are still inconclusive, there are strong indications that gut microbiota dysbiosis plays an important role in T1D development and evidence from animal models suggests that gut microbiota manipulation might prove valuable in future prevention of T1D in genetically susceptible individuals.

Role of diabetes in the development of acute respiratory distress syndrome

OBJECTIVES

Diabetes has been associated with decreased development of acute respiratory distress syndrome in some, but not all, previous studies. Therefore, we examined the relationship between diabetes and development of acute respiratory distress syndrome and whether this association was modified by type of diabetes, etiology of acute respiratory distress syndrome, diabetes medications, or other potential confounders.

DESIGN

Observational prospective multicenter study.

SETTING

Four adult ICUs at two tertiary academic medical centers.

PATIENTS

Three thousand eight hundred sixty critically ill patients at risk for acute respiratory distress syndrome from sepsis, pneumonia, trauma, aspiration, or massive transfusion.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Diabetes history was present in 25.8% of patients. Diabetes was associated with lower rates of developing acute respiratory distress syndrome on univariate (odds ratio, 0.79; 95% CI, 0.66-0.94) and multivariate analysis (adjusted odds ratio, 0.76; 95% CI, 0.61-0.95). After including diabetes medications into the model, diabetes remained protective (adjusted odds ratio, 0.75; 95% CI, 0.59-0.94). Diabetes was associated with decreased development of acute respiratory distress syndrome both in the subgroup of patients with sepsis (adjusted odds ratio, 0.77; 95% CI, 0.61-0.97) and patients with noninfectious etiologies (adjusted odds ratio, 0.30; 95% CI, 0.10-0.90). The protective effect of diabetes on acute respiratory distress syndrome development is not clearly restricted to either type 1 (adjusted odds ratio, 0.50; 95% CI, 0.26-0.99; p = 0.046) or type 2 (adjusted odds ratio, 0.77; 95% CI, 0.60-1.00; p = 0.050) diabetes. Among patients in whom acute respiratory distress syndrome developed, diabetes was not associated with 60-day mortality on univariate (odds ratio, 1.11; 95% CI, 0.80-1.52) or multivariate analysis (adjusted odds ratio, 0.81; 95% CI, 0.56-1.18).

CONCLUSIONS

Diabetes is associated with a lower rate of acute respiratory distress syndrome development, and this relationship remained after adjusting for clinical differences between diabetics and nondiabetics, such as obesity, acute hyperglycemia, and diabetes-associated medications. In addition, this association was present for type 1 and 2 diabetics and in all subgroups of at-risk patients.

Infant exposures and development of type 1 diabetes mellitus: The Diabetes Autoimmunity Study in the Young (DAISY)

IMPORTANCE

The incidence of type 1 diabetes mellitus (T1DM) is increasing worldwide, with the most rapid increase among children younger than 5 years of age.

OBJECTIVE

To examine the associations between perinatal and infant exposures, especially early infant diet, and the development of T1DM.

DESIGN

The Diabetes Autoimmunity Study in the Young (DAISY) is a longitudinal, observational study.

SETTING

Newborn screening for human leukocyte antigen (HLA) was done at St. Joseph's Hospital in Denver, Colorado. First-degree relatives of individuals with T1DM were recruited from the Denver metropolitan area.

PARTICIPANTS

A total of 1835 children at increased genetic risk for T1DM followed up from birth with complete prospective assessment of infant diet. Fifty-three children developed T1DM.

EXPOSURES

Early (<4 months of age) and late (≥6 months of age) first exposure to solid foods compared with first exposures at 4 to 5 months of age (referent).

MAIN OUTCOME AND MEASURE

Risk for T1DM diagnosed by a physician.

RESULTS

Both early and late first exposure to any solid food predicted development of T1DM (hazard ratio [HR], 1.91; 95% CI, 1.04-3.51, and HR, 3.02; 95% CI, 1.26-7.24, respectively), adjusting for the HLA-DR genotype, first-degree relative with T1DM, maternal education, and delivery type. Specifically, early exposure to fruit and late exposure to rice/oat predicted T1DM (HR, 2.23; 95% CI, 1.14-4.39, and HR, 2.88; 95% CI, 1.36-6.11, respectively), while breastfeeding at the time of introduction to wheat/barley conferred protection (HR, 0.47; 95% CI, 0.26-0.86). Complicated vaginal delivery was also a predictor of T1DM (HR, 1.93; 95% CI, 1.03-3.61).

CONCLUSIONS AND RELEVANCE

These results suggest the safest age to introduce solid foods in children at increased genetic risk for T1DM is between 4 and 5 months of age. Breastfeeding while introducing new foods may reduce T1DM risk.

Introducing solid foods: validity of report among mothers who do not adhere to recommended US guidelines

BACKGROUND

Introducing solids foods to infants before 6 months has been associated with adverse long-term health outcomes. Studies and surveys frequently use maternal report to identify the age when infants start solid foods.

OBJECTIVE

To address the accuracy of maternal report at 1 year postpartum regarding introduction of solid foods.

METHODS

Between 2008 and 2009, the authors enrolled mothers of healthy term singletons at an urban Boston hospital within 72 hours of giving birth. We called mothers monthly for 6 months and asked if they had given their baby solid foods in the previous month. At 1 year, we contacted mothers again and asked when they first gave solid foods; answers at 1 year were compared with the data collected monthly.

RESULTS

The authors analyzed data on 157 women, all of whom had, according to monthly responses, started solid foods before 6 months. At 1 year, only 14% (22/157) of reports matched data recorded monthly. Although 100% of women introduced solids before 6 months, at 1 year, 41.4% reported starting solids at 6 months.

CONCLUSIONS

Among women who started feeding solids before 6 months, most did not give an accurate response at 1 year. Most said they started giving solids later than they did. Maternal report may not be the best way to collect such data, and health outcomes based on such data may be biased toward the null.

What is the key environmental trigger in type 1 diabetes--is it viruses, or wheat gluten, or both?

Prevention and treatment of type 1 diabetes is hampered by the fact that the key environmental trigger(s) of the disease is still unknown. Much of the data on this subject points to two possibilities, viruses and wheat gluten. Viruses appear to be involved as an etiological agent in some cases of type 1 diabetes, particularly in fulminant type 1 diabetes. Further analysis of the data suggests that viruses are not the sole trigger of type 1 diabetes in humans, and that wheat gluten may play a role in initiating the disease. Viruses may be the key environmental trigger in some cases of type 1 diabetes, and wheat gluten in others. Conceivably, some cases of type 1 diabetes might be caused by viruses and wheat gluten acting together as disease triggers.

Dietary iron intake in the first 4 months of infancy and the development of type 1 diabetes: a pilot study

AIMS

To investigate the impact of iron intake on the development of type 1 diabetes (T1DM).

METHODS

Case-control study with self-administered questionnaire among families of children with T1DM who were less than 10 years old at the time of the survey and developed diabetes between age 1 and 6 years. Data on the types of infant feeding in the first 4 months of life was collected from parents of children with T1DM (n = 128) and controls (n = 67) <10 years old. Because some cases had sibling controls, we used conditional logistic regression models to analyze the data in two ways. First we performed a case-control analysis of all 128 cases and 67 controls. Next, we performed a case-control analysis restricted to cases (n = 59) that had a sibling without diabetes (n = 59). Total iron intake was modeled as one standard deviation (SD) increase in iron intake. The SD for iron intake was 540 mg in the total sample and 539 mg in the restricted sample as defined above.

RESULTS

The median (min, max) total iron intake in the first 4 months of life was 1159 (50, 2399) mg in T1DM cases and 466 (50, 1224) mg among controls (P < 0.001). For each one standard deviation increase in iron intake, the odds ratio (95% confidence interval) for type 1 diabetes was 2.01 (1.183, 3.41) among all participants (128 cases and 67 controls) while it was 2.26 (1.27, 4.03) in a restricted sample of T1 D cases with a control sibling (59 cases and 59 controls) in models adjusted for birth weight, age at the time of the survey, and birth order.

CONCLUSION

In this pilot study, high iron intake in the first 4 months of infancy is associated with T1DM. Whether iron intake is causal or a marker of another risk factor warrants further investigation.

Clustering of cases of type 1 diabetes in high socioeconomic communes in Santiago de Chile: spatio-temporal and geographical analysis

The objective of this study was to describe spatial and space-time patterns of type 1 diabetes in children less than 15 years old, diagnosed between 2000 and 2005 with residence in the Metropolitan Region of Chile. Knox and Mantel tests were used to detect space-time interaction between cases. An ecological Bayesian model adjusted by socioeconomic factor and year was proposed to estimate the incidence by communes. Initially, there was no space-time interaction between cases, but there is evidence of clustering effect in urban areas of the region. The incidence rate for the overall study period was estimated by 6.18/100,000 (95% CI: 5.69-6.70), with a significant annual trend of 8.2% (P < 0.01). The geographical incidence could be explained by the human development index, as a socioeconomic factor. These results suggest that children living in communes with higher socioeconomic levels may be at higher risk of developing type 1 diabetes. Our findings support the hypothesis of an aetiological role of environmental factors in the onset of type 1 diabetes.

Health professional knowledge of breastfeeding: are the health risks of infant formula feeding accurately conveyed by the titles and abstracts of journal articles?

Effective promotion of breastfeeding is constrained if health professionals' knowledge on its importance is deficient. This study asks whether formula feeding is named as the risk factor in published research or whether it is considered the unspoken norm. A systematic analysis is conducted of the information content of titles and abstracts of 78 studies that report poorer health among formula-fed infants. This shows a surprising silence in the studies examined; formula is rarely named in publication titles or abstracts as an exposure increasing health risk. In 30% of cases, titles imply misleadingly that breastfeeding raises health risk. Only 11% of abstracts identify formula feeding as a health risk exposure. Initiatives to increase breastfeeding have described the importance of accurate language and well-informed health professional support. If widespread, this skew in communication of research findings may reduce health professionals' knowledge and support for breastfeeding.

Reliability of reported breastfeeding duration among reproductive-aged women from Mexico

Breastfed children have lower risk of infectious diseases, post-neonatal mortality and chronic diseases later in life. Because epidemiologic studies usually rely on reported history of previous breastfeeding, data on the accuracy and precision of recalled histories allow improved interpretation of the epidemiologic findings. We evaluated the reliability of two reported breastfeeding durations in 567 reproductive-aged women from Mexico using information obtained from nearly identical sets of questions applied at different times after weaning. We compared differences between reports, and examined the intraclass correlation coefficient (ICC) for any and for exclusive breastfeeding (EBF). Logistic regression was used to evaluate the determinants of poor recall (difference between reports of >20%). The reliability of duration of any breastfeeding was high (ICC 0.94). Overall, differences between reports of duration were usually <1 month, and for 385/567, the difference was < or =0.5 months. Predictors of poorer recall were having > or =4 children, and time between reports of >2 months. The only predictor of better recall was greater age of the baby at weaning. The reliability of EBF duration was lower (ICC 0.49). In this population with a relatively long duration of breastfeeding, reliability of any breastfeeding duration was high. Age, education and previous breastfeeding were not important predictors of recall, in contrast to findings in earlier studies. Consistent with previous reports, however, parity and length of recall were associated with poorer recall of duration of any breastfeeding. Future studies that use reported breastfeeding duration may want to consider the effect of these variables on recall.

Interplay between PTPN22 C1858T polymorphism and cow's milk formula exposure in type 1 diabetes

Genetic heterogeneity may affect the analysis of risk factors associated with type 1 diabetes (T1D). We studied the effect of the INS -23A/T, PTPN22 1858C/T, and CTLA-4 +49A/G polymorphisms on the emergence of T1D-associated autoimmunity in children exposed to cow's milk (CM) based formula during early or late infancy. The study comprised of 156 children from the Finnish DIPP cohort who had developed >or= 2 types of autoantibodies (ICA, IAA, GADA or IA-2A) or clinical T1D and 563 control children. The PTPN22 1858T allele was associated with the appearance of the autoantibodies and clinical T1D among children exposed to CM formula before the age of 6 months (PTPN22: for all P <or= 0.001, Log Rank test), but not among children exposed later on. Cox regression analysis showed an interaction between early CM exposure and 1858T allele and enhanced appearance of ICA, IAA and IA-2A (for all P <or= 0.04). Our results imply that the PTPN22 polymorphism affects the development of T1D-associated autoimmunity only if children are exposed to CM formula during early infancy suggesting an interplay between genetic and environmental factors. This may provide an explanation for the contradictory findings on the significance of CM formula exposure in T1D.

Early infant feeding and risk of type 1 diabetes mellitus-a nationwide population-based case-control study in pre-school children

BACKGROUND

The evidence on the role of environmental factors in the development of type 1 diabetes is conflicting. Reducing potential bias and the variety of exposures, we investigated the association between type 1 diabetes risk and nutritional and environmental exposures in pre-school children.

METHODS

This nationwide population-based case-control study included 760 cases under 5 years of age newly diagnosed with type 1 diabetes during 1992-1995. From the general population, 1,871 controls were randomly selected and individually matched on age ( +/- 1 year), sex, and residence. Information on infant diet, foetal, perinatal and socio-economic factors, and familial diabetes was obtained by a parent-administered questionnaire. Data were analysed by multiple conditional logistic regression.

RESULTS

Duration of breastfeeding and age at introduction of bottle-feeding were inversely associated with type 1 diabetes risk according to a dose-response relationship (trend test p < 0.05). Adjusted odd ratios (95% CI) for a long breastfeeding period and a late introduction of bottle-feeding (>or=5 month versus < 2 weeks) were 0.71 (0.54-0.93) and 0.80 (0.62-1.04), respectively. Familial type 1 diabetes, maternal age > 40 years, and low birth weight were found more frequently among diabetic than among control children. Current cow's milk consumption, higher social status, and a larger family were associated with a reduced diabetes risk. Up to one half of the diabetic cases in the population could be attributed to modifiable exposures.

CONCLUSIONS

Our findings indicate that infant feeding is associated with type 1 diabetes risk and that a considerable part of new type 1 diabetic cases is potentially preventable.

Amamentação natural como fonte de prevenção em saúde

A importância da amamentação natural tem sido abordada sob âmbito multiprofissional. O cirurgião dentista como profissional da área de saúde está incluído neste contexto e deve ser capaz de orientar a gestante e as recém-mães visto a forte relação que existe entre amamentação natural e o desenvolvimento do sistema estomatognático. São inúmeros os benefícios gerados tanto para a mãe quanto para o bebê. Baseado nisso, o presente artigo propõe, por meio de uma revisão de literatura discutida, argumentar com informações atuais e esclarecedoras os benefícios da amamentação dando estímulo à conscientização da sua importância e à formulação de políticas e ações, através do SUS, que priorizem a prática da amamentação como meta.

Study design of the Trial to Reduce IDDM in the Genetically at Risk (TRIGR)

The hypothesis for this study is that weaning to an extensively hydrolyzed infant formula will decrease the incidence of type 1 diabetes (T1D), as it does in all relevant animal models for the disease. This will be tested in children who carry risk-associated human leukocyte antigen genotypes and have a first-degree relative with T1D. The trial will use a double-blind, prospective, placebo-controlled intervention protocol, comparing casein hydrolysate with a conventional cow's milk (CM)-based formula. A secondary aim is to determine relationships between CM antibodies, a measure of CM exposure, and diabetes-associated autoantibodies. To achieve an 80% power for the detection of a 40% intervention-induced difference in the development of autoantibodies and subsequent diabetes, the study requires 2032 subjects. A multicenter, international, collaborative effort is necessary to achieve recruitment targets. A collaborative international study group of 78 clinical centers in 15 countries has therefore been assembled for this purpose.

Dietary risk factors for the emergence of type 1 diabetes-related autoantibodies in 2½-year-old Swedish children

We studied dietary risk factors by analysing a questionnaire administered at birth, 1 year and 2½ years of age, as well as the level of glutamic acid decarboxylase autoantibodies (GADA) and tyrosine phosphatase autoantibodies (IA-2A), in 7208 2½-year-old children from the All Babies in Southeast Sweden cohort, using the 95th percentile cut-off for autoantibodies to identify children at risk of type 1 diabetes. A total of 657 children had either IA-2A (n 360) or GADA (n 335), and thirty-eight children had both GADA and IA-2A. In univariate analysis, male gender and maternal coeliac disease implied a risk of possessing IA-2A. Maternal type 2 diabetes, a high consumption of fresh cows milk at the age of 1 year and a late introduction of gluten were associated with a risk of GADA. Early cessation of breast-feeding (≤2 months of age) was associated with a risk of the simultaneous occurrence of both IA-2A and GADA. In logistic regression analysis, a high consumption of milk at the age of 1 year (odds ratio 2·6) represented a risk for GADA, and maternal coeliac disease (odds ratio 2·9) represented a risk for IA-2A. The combination of an early introduction of cows milk formula and a late introduction of gluten-containing food gave an odds ratio of 6·0 for positivity for at least one autoantibody at 1 and 2½ years of age. The induction of autoantibodies by the age of 2½ years has a male preponderance and is more common in children with maternal type 2 diabetes or maternal coeliac disease. Dietary risk factors for the induction of β-cell autoantibodies in 2½-year-old children are a short duration of breast-feeding, an early introduction of cows milk formula and a late introduction of gluten, as well as a high consumption of milk at the age of 1 year.

Increasing incidence of type 1 diabetes in population from Santiago of Chile: trends in a period of 18 years (1986-2003)

STUDY OBJECTIVE AND SETTING: The aim of this study is to determine the incidence rate of type 1 diabetes in the metropolitan region of Santiago, Chile from 1 January 1986 to 31 December 2003.

DESIGN

Population-based incidence study.

PARTICIPANTS

A case must fulfill the following requirements to be included in this study: age at onset: 0 to 14 years, diagnosed with diabetes and placed on insulin, diagnosed within the defined time period, and to be a resident of the metropolitan region of Santiago at the time of the diagnosis. The population 'at risk' is the population less than 15 years of age.

RESULT

The overall rate of type 1 diabetes was estimated as 4.02 cases per 100 000 children per year (95% confidence interval: 2.98-4.83).

CONCLUSION

The incidence of type 1 diabetes in Santiago, Chile has increased during the last years. This data are concordant with the observation that the incidence of type 1 diabetes is increasing in Latin America and worldwide.

Environmental triggers and determinants of type 1 diabetes

Type 1 diabetes is perceived as a chronic immune-mediated disease with a subclinical prodromal period characterized by selective loss of insulin-producing beta-cells in the pancreatic islets in genetically susceptible subjects. A series of evidence supports a critical role of exogenous factors in the development of type 1 diabetes, such as 1) the fact that <10% of individuals with HLA-conferred diabetes susceptibility do progress to clinical disease, 2) a pairwise concordance of type 1 diabetes of <40% among monozygotic twins, 3) a more than 10-fold difference in the disease incidence among Caucasians living in Europe, 4) a several-fold increase in the incidence over the last 50 years, and 5) migration studies indicating that the disease incidence has increased in population groups who have moved from a low-incidence to a high-incidence region. This article discusses the trigger-booster hypothesis claiming that the diabetic disease process is triggered by an exogenous factor with definite seasonal variation and driven by one or several other environmental determinants. In addition, there are a series of modifying factors affecting the fate and pace of the process. Accordingly, progression to clinical type 1 diabetes typically requires the unfortunate combination of genetic disease susceptibility, a diabetogenic trigger, and a high exposure to a driving antigen.

Epidemiological association between some dietary habits and the increasing incidence of type 1 diabetes worldwide

BACKGROUND/AIMS

The variation in incidence of type 1 diabetes (T1D) worldwide is genetically based. However, its increasing incidence is environmentally determined. Our aim was to describe the role of nutritional habits and of gene-nutrient interactions in the rising incidence of TID.

METHODS

We did an ecological study in the 37 world areas were a 3% yearly increase of T1D incidence had been reported, and we calculated through the FAO's Food Balance Sheets the per caput daily supply of milk, meat and cereals from 1961 to 2000 and its correlation with the TID incidence.

RESULTS

The supply of milk and cereals remained almost unchanged, whereas that of meat increased by over 31%. The absolute mean TID increase (number of cases per 100,000 per year) was + 0.32. A significant positive correlation with supply of milk was present from 1961 to 2000, while that with meat and cereals became significant in 1983 and 2000.

CONCLUSION

Our ecological analysis indicates that nutritional factors, and in particular meat consumption, play a role in the incidence of T1D and its increase worldwide. Further experimental and case-control studies are warranted in order to assess the gene-nutrient interactions.

HLA non-class II genes may confer type I diabetes susceptibility in a Mapuche (Amerindian) affected family

A rare case of type I diabetes is studied in an Amerindian (Mapuche) family from Chile, analyzing glutamic acid decarboxylase, islet-cell autoantibodies and human leukocyte antigen (HLA) genes. The affected sib is the only one that has one specific HLA haplotype combination that differs from the other sibs only in the HLA class I genes. It is concluded that HLA diabetes susceptibility factors may be placed outside the class II region or even that susceptibility factors do not exist in the HLA region in this Amerindian family.

Breastfeeding and the use of human milk

Considerable advances have occurred in recent years in the scientific knowledge of the benefits of breastfeeding, the mechanisms underlying these benefits, and in the clinical management of breastfeeding. This policy statement on breastfeeding replaces the 1997 policy statement of the American Academy of Pediatrics and reflects this newer knowledge and the supporting publications. The benefits of breastfeeding for the infant, the mother, and the community are summarized, and recommendations to guide the pediatrician and other health care professionals in assisting mothers in the initiation and maintenance of breastfeeding for healthy term infants and high-risk infants are presented. The policy statement delineates various ways in which pediatricians can promote, protect, and support breastfeeding not only in their individual practices but also in the hospital, medical school, community, and nation.

Infant diet and type 1 diabetes in China

Infant milk and food introduction may be linked to type 1 diabetes risk in high incidence populations. Dietary data through age 12 months was collected for 247 type 1 diabetic cases and 443 controls in China, a low incidence population, to determine if milk and solid food intake differed. Age range at introduction to milk and formulas was similar in cases and controls but solid food introduction more often occurred before age 3 months in cases. Logistic regression analyses showed soy milk formula consumption at 4-6 (OR = 2.0; 95% CI: 1.1-3.4) and 7-12 months of age (OR = 1.5; 95% CI: 1.0-2.1) was associated with a twofold higher risk of type 1 diabetes, while steamed bread consumption (4-6 months, OR = 0.44; 95% CI: 0.28-0.68; 7-12 months, OR = 0.48; 95% CI: 0.34-0.69) and higher SES (4-6 months, OR = 0.55; 95% CI: 0.39-0.78; 7-12 months, OR = 0.57; 95% CI: 0.40-0.83) were negatively associated. Drinking cow's milk at 7-12 months (OR = 0.60; 95% CI: 0.43-0.85) was negatively associated with type 1 diabetes while consuming vegetables at 4-6 months (OR = 1.5; 95% CI: 1.0-2.2) was positively associated. Results suggest that infant milk and solid food intake are associated with type 1 diabetes in China. Prospective studies may determine how these dietary factors impact disease etiology, particularly for at-risk-populations.

The Baby-Friendly way: the best breastfeeding start

In 1991, the World Health Organization and the United Nations Children's Fund launched the Baby-Friendly Hospital Initiative. "Baby-Friendly" is a designation that a hospital or birthing site can receive by demonstrating compliance with the "Ten Steps to Successful Breastfeeding." Baby-Friendly is more than a catchy name or a snappy slogan. With Baby-Friendly policies in place, breastfeeding initiation and duration rates increase and infant illness decreases. This article reviews the development of the Baby-Friendly Hospital Initiative, describes the components of the initiative, and evaluates current data that favor the universal implementation of the Baby-Friendly Hospital Initiative.

Nutritional risk predictors of beta cell autoimmunity and type 1 diabetes at a young age

Type 1 diabetes is an immune-mediated disease characterized by a preclinical prodrome during which beta cell autoimmunity proceeds at a variable rate. Large geographic differences and a conspicuous increase in incidence, especially among young children since the 1950s, and the relatively low concordance in identical twins are factors that favor a critical role of environmental factors in the etiology of this disease. Only approximately 5% or fewer subjects with HLA-conferred genetic susceptibility to type 1 diabetes actually develop the clinical disease. Breastfeeding, nicotinamide, zinc, and vitamins C, D, and E have been reported as possibly protecting against type 1 diabetes, whereas N-nitroso compounds, cow milk, increased linear growth, and obesity may increase the risk. Thus far, only the significance of infant feeding, cow milk, and vitamin D have been studied in both case-control and cohort settings. The major shortcoming of most studies done so far is that only single dietary exposures have been assessed at single time points. Putative nutritional and other confounding factors have received little attention as have the limitations of the dietary methods used. There is little firm evidence of the significance of nutritional factors in the etiology of type 1 diabetes. The availability of good markers of preclinical type 1 diabetes and of genetic risk have decreased the sample sizes needed and made longitudinal cohort studies of the assessment of children's diets feasible.

Duration of breast feeding and bovine serum albumin antibody levels in type 1 diabetes: a case-control study

OBJECTIVE

To compare the levels of bovine serum albumin (BSA) antibodies and their relationship with duration of breast feeding, age of exposure to cow's milk, and human leukocyte antigen (HLA-DQ) genotype in children with and without type 1 diabetes.

METHODS

Serum samples from 143 (0.3-14.7 yr) newly diagnosed children with type 1 diabetes and 107 unrelated control children (0.8-13.5 yr) were evaluated for BSA antibodies. Duration of breast feeding and exposure to cow's milk were recorded on questionnaires. HLA-DQ typing was determined by polymerase chain reaction.

RESULTS

One hundred percent of the diabetic children were positive for BSA antibodies compared to 1.9% for healthy controls (p < 0.001). Diabetic children also had higher levels of immunoglobulin G antibodies than unrelated controls (55.1 vs. 17.8 ng/mL, p < 0.0001). Duration of breast feeding (5.4 vs. 7.6 months, p < 0.02), but not age of exposure to cow's milk (8.3 vs. 9.2 months, p = 0.11), differed between cases and controls. There was no difference in antibody titer by duration of breast feeding or age of exposure to cow's milk in the cases or controls.

CONCLUSION

Higher levels of antibodies to BSA were found in children recently diagnosed with type 1 diabetes compared to the controls, particularly those with high or moderate HLA-DQ genotypes. The BSA profile, however, does not seem to depend on duration of breast feeding or age of exposure to cow's milk in this population.

Genetic fusion of human insulin B-chain to the B-subunit of cholera toxin enhances in vitro antigen presentation and induction of bystander suppression in vivo

The pentameric B-subunit of cholera toxin (CTB) can be used as an efficient mucosal carrier of either immunogenic or tolerogenic T-cell epitopes. In this study a series of fusions was constructed between the genes encoding CTB and the B-chain of human insulin (InsB). The resulting fusion proteins were expressed in Escherichia coli and isolated as cytoplasmic inclusion bodies that were then dissolved and assembled in vitro. GM1 enzyme-linked immunosorbent assay (ELISA), sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analyses showed that the protein construct in which InsB was fused to the C-terminus of a CTB monomer (CI) assembled into structures that both bound to the receptor GM1 ganglioside and reacted with monoclonal antibodies to CTB and insulin. Fusion of InsB to the N-terminus of CTB resulted in protein that could not assemble into pentameric CTB. In vitro assays showed that the CI fusion protein was 300-fold more potent than native insulin at inducing interleukin-2 (IL-2) production by an insulin-specific T-cell hybridoma. When administered orally, the CI fusion protein induced efficient immunological suppression of ovalbumin-specific T-cell responses in mice co-immunized parenterally with insulin and ovalbumin. These results demonstrate the stability, GM1 receptor-binding activity and antigenic authenticity of the CI fusion protein as well as its ability to elicit insulin-specific T-cell responses in vitro. In addition, we demonstrate that the CI fusion protein induces efficient immunosuppression after oral administration, raising the possibility of using such constructs in the treatment of type-1 diabetes.

ICA69(null) nonobese diabetic mice develop diabetes, but resist disease acceleration by cyclophosphamide

ICA69 (islet cell Ag 69 kDa) is a diabetes-associated autoantigen with high expression levels in beta cells and brain. Its function is unknown, but knockout of its Caenorhabditis elegans homologue, ric-19, compromised neurotransmission. We disrupted the murine gene, ica-1, in 129-strain mice. These animals aged normally, but speed-congenic ICA69(null) nonobese diabetic (NOD) mice developed mid-life lethality, reminiscent of NOD-specific, late lethal seizures in glutamic acid decarboxylase 65-deficient mice. In contrast to wild-type and heterozygous animals, ICA69(null) NOD congenics fail to generate, even after immunization, cross-reactive T cells that recognize the dominant Tep69 epitope in ICA69, and its environmental mimicry Ag, the ABBOS epitope in BSA. This antigenic mimicry is thus driven by the endogenous self Ag, and not initiated by the environmental mimic. Insulitis, spontaneous, and adoptively transferred diabetes develop normally in ICA69(null) NOD congenics. Like glutamic acid decarboxylase 65, ICA69 is not an obligate autoantigen in diabetes. Unexpectedly, ICA69(null) NOD mice were resistant to cyclophosphamide (CY)-accelerated diabetes. Transplantation experiments with hemopoietic and islet tissue linked CY resistance to ICA69 deficiency in islets. CY-accelerated diabetes involves not only ablation of lymphoid cells, but ICA69-dependent drug toxicity in beta cells that boosts autoreactivity in the regenerating lymphoid system.

T cells of multiple sclerosis patients target a common environmental peptide that causes encephalitis in mice

Multiple sclerosis (MS) is a chronic autoimmune disease triggered by unknown environmental factors in genetically susceptible hosts. MS risk was linked to high rates of cow milk protein (CMP) consumption, reminiscent of a similar association in autoimmune diabetes. A recent rodent study showed that immune responses to the CMP, butyrophilin, can lead to encephalitis through antigenic mimicry with myelin oligodendrocyte glycoprotein. In this study, we show abnormal T cell immunity to several other CMPs in MS patients comparable to that in diabetics. Limited epitope mapping with the milk protein BSA identified one specific epitope, BSA(193), which was targeted by most MS but not diabetes patients. BSA(193) was encephalitogenic in SJL/J mice subjected to a standard protocol for the induction of experimental autoimmune encephalitis. These data extend the possible, immunological basis for the association of MS risk, CMP, and CNS autoimmunity. To pinpoint the same peptide, BSA(193), in encephalitis-prone humans and rodents may imply a common endogenous ligand, targeted through antigenic mimicry.

Breastfeeding and chronic disease in childhood and adolescence

A growing body of research suggests that infant feeding practices influence the risk for several chronic diseases of childhood and adolescence. Increased risks for type 1 diabetes, celiac disease, some childhood cancers, and inflammatory bowel disease have been associated with artificial infant feeding and short-term breastfeeding. As genetic susceptibility is understood more completely and gene-environment interactions are elucidated, evidence to either confirm or refute these findings will be forthcoming.

Cow's milk and immune-mediated diabetes

Cow's milk-based infant formulas and cow's milk consumption in childhood have been suggested to promote the development of type 1 diabetes mellitus and other immune-mediated or neurological diseases. Epidemiological studies in man have led to the hypothesis that introduction of cow's milk-based infant formula within the first 3 months of life is associated with increased risk of type 1 diabetes mellitus. Furthermore, in animal models of type 1 diabetes mellitus, cow's milk proteins have been proven to be 'diabetogenic'. However, the issue seems far from being resolved. Several epidemiological studies and, more importantly, the first prospective trials did not show an association between early exposure to cow's milk and type 1 diabetes mellitus. In animal models, cow's milk proteins are modestly and variably diabetogenic, wheat or soybean proteins in the diet cause higher rates of autoimmune diabetes. In both man and rodents there is increasing evidence that the gut-associated immune system plays a major role in disease development, probably because of disturbed oral tolerance mechanisms. Oral tolerance depends on immunological homeostasis and normal maturation of the gut. These factors are influenced by growth factors and cytokines from breast milk, normal bacterial colonization, infections and diet. All these factors have been proposed as risk factors for type 1 diabetes mellitus. Hence, cow's milk proteins may provide mimicry epitopes relevant in autoimmunity, as well as destabilizing oral tolerance mechanisms by biologically active peptides. The concept of dietary regulation of autoimmunity does not apply only to cow's milk protein, but also to other dietary proteins.

Celiac disease in a Chilean population carrying Amerindian traits

BACKGROUND

Although clinical manifestations of celiac disease may change throughout life, clinical, histologic, immunologic, and genetic studies show that there are incomplete forms of this condition, making it difficult to define the disease at a given moment. Because there is no information published in the Latin American-Amerindian population, this study was conducted to assess relations between these parameters in Chileans with celiac disease and their first-degree relatives.

METHODS

Sixty-two persons with confirmed celiac disease (mean age, 17.9 +/- 5.1 years; 78.3% females) and 126 relatives (mean age, 27.9 +/- 17.2 years; 65.1% females) were evaluated. Clinical manifestations, antiendomysial antibodies (EMAs), and human leukocyte antigen (HLA) haplotypes were studied in patients. Additionally, jejunal biopsy specimens were assessed (light microscopy) in EMA-positive (EMA+) relatives.

RESULTS

Of the patients, 24.1% adhered to a strict gluten-free diet; 26% were oligosymptomatic, and none were malnourished; 45% were EMA+; 13.8% who ingested gluten were EMA-negative (EMA-); one patient consuming a strict gluten-free diet was EMA+. The DQA1*0501 allele was present in the highest frequency (48%, P < 0.0005), whereas combinations of DQ8 were predominant. Of the relatives, 4.8% were EMA+; they had a significantly higher frequency of diarrhea, weight loss, and anorexia (P < 0.03); and all had abnormal histology in biopsy specimens.

CONCLUSIONS

After childhood, celiac disease is oligosymptomatic and is often unrecognized by patients. Disease in 13.8% of patients and in 4.8% relatives appeared as incomplete forms of celiac disease. Predominance of DQ8 HLA haplotypes reflects the genetic Spanish-Mapuche heritage of this population.

Milk and diabetes

Type 1 diabetes is based on autoimmunity, and its development is in part determined by environmental factors. Among those, milk intake is discussed as playing a pathogenic role. Geographical and temporal relations between type 1 diabetes prevalence and cow's milk consumption have been found in ecological studies. Several case-control studies found a negative correlation between frequency and/or duration of breast-feeding and diabetes, but this was not confirmed by all authors. T-cell and humoral responses related to cow's milk proteins were suggested to trigger diabetes. The different findings of studies in animals and humans as well as the potential underlying mechanisms with regard to single milk proteins (bovine serum albumin, beta-lactoglobulin, casein) are discussed in this review. In contrast to type 1 diabetes, the etiology of type 2 diabetes, characterized by insulin resistance is still unclear. In a population with a high prevalence of type 2 diabetes, the Pima Indians, people who were exclusively breastfed had significantly lower rates of type 2 diabetes than those who were exclusively bottlefed. Studies in lactovegetarians imply that consumption of low fat dairy products is associated with lower incidence and mortality of diabetes and lower blood pressures. In contrast, preference for a diet high in animal fat could be a pathogenic factor, and milk and high fat dairy products contribute considerably to dietary fat intake. Concerning milk fat composition, the opposite effects of various fatty acids (saturated fatty acids, trans-fatty acids, conjugated linoleic acid) in vitro, in animals and in humans have to be considered.

Update on the genetics and pathophysiology of type I diabetes mellitus

Type I diabetes mellitus results from the genetically predetermined autoimmune destruction of pancreatic beta-cells, resulting in gradual, but complete, loss of insulin secretion. There are strong associations with specific HLA haplotypes, but environmental triggers are also required to initiate beta-cell autoimmunity. These could possibly include enteroviral infection, early weaning from breastfeeding, early exposure to cow's milk antigens, and free radical damage. Once initiated, beta-cell autoimmunity does not always lead to clinical diabetes, suggesting that immunomodulators may be important in the control of beta-cell destruction. Current interventions designed to prevent type I diabetes mellitus are based on attempts to alter this immune response and to preserve beta-cell function. It is important for the pediatrician to understand the background of these trials and to be able to answer parents' questions regarding study participation.

Prevention of type 1 diabetes from laboratory to public health

Despite recent progress in immunology and genetics, the causes of type 1 diabetes remain unknown. Prevention of autoimmune diseases through immunomodulation or gene therapy has not yet been successful in humans. In contrast, some autoimmune diseases such as celiac disease, rheumatic fever, and congenital rubella induced diabetes can be avoided through modification of environmental factors. Candidate environmental causes of type 1 diabetes are now being characterized in cohort studies and clinical trials. An alternative approach to prevention of type 1 diabetes may include a "vaccination" in early childhood to induce tolerance to critical autoantigen(s). This paper reviews the status of current diabetes prevention trials in humans and selected new interventions that are being tested in animal models. We estimate the cost of public health implementation of selected screening and intervention scenarios. The ethical, logistic, and funding issues underlying these scenarios are discussed.

Genetic differences in HLA-DQA1* and DQB1* allelic distributions between celiac and control children in Santiago, Chile

Celiac disease is a permanent gluten intolerance strongly associated with HLA class II antigens. The over presentation of particular HLA alleles and haplotypes has been described in several populations. Different lines of evidence obtained during the last years suggest that a particular HLA-DQ heterodimer, encoded by the DQA1*0501 and DQB1*0201 genes in cis or trans conformation, confers the primary disease susceptibility. We report the HLA class II allelic distribution and DQA1/ DQB1 genotypes in 62 Chilean celiac patients compared with 124 control subjects in Santiago, Chile. We found a pronounced increase of the "susceptible" alleles :DQA1*0501 (0.480 vs 0.169, Pc < 0.0005), DQB1*0302 (0.430 vs 0.242, Pc = 0.002) and DQB1*0201 (0.250 vs 0.125, Pc = 0.037) in celiac patients in comparison with control children. As for "protective" alleles, we detected a high frequency of DQA1*0101 (0.310 vs 0.160, Pc = 0.01), DQA1*0201 (0.105 vs 0.010, Pc < 0.0075) and DQB1*0301 (0.250 vs 0.100, Pc = 0.010) in controls. In relation to risk haplotypes, the main combination observed was the conformation DQ8 (DQB1*0302/DQA1*0301) over DQ2 (DQB1*0201/DQA1*0501). In conclusion, results show that celiac disease in Chilean patients is primarily associated with DQ8 conformation. This is concordant with the high frequency of DR4 alleles (in linkage disequilibrium with DQB1*0302) detected in Amerind groups in Chile, where DQB1*0302 is more frequent than DQB1*0201.

Migrant populations and the incidence of type 1 diabetes mellitus: an overview of the literature with a focus on the Spanish-heritage countries in Latin America

Type 1 diabetes mellitus (DM) is a 'chronic' autoimmune disorder leading to the destruction of the pancreatic beta cell. The natural history of diabetes includes a long subclinical (prediabetes) period. The pathogenesis is multifactorial and characterized by the interaction of environmental factors, with predisposing genes, most of which are associated with the HLA DR DQ loci. The relatively recent development of worldwide incidence registries for Type 1 DM has allowed us to compare the epidemiological results obtained in most parts of the world. This approach is particularly valuable in analysing the effects of migration of populations from one area of the world where the incidence of Type 1 DM is different (usually lower) to a new geographic setting. Properly designed migrant studies may be valuable in uncovering whether the genetic background remains more important than the new 'exposure' as illustrated by the Sardinian migration to Lazio and Lombardy. The presence of some putative 'protective' environmental exposures or the absence of those prevalent in the country of origin may explain the usually lower Type 1 DM incidence observed in most countries (Chile, Peru, Mexico) sharing a 'Spanish caucasoid genetic pool', and even in relatively genetically homogeneous groups such as Japanese populations migrating to Hawaii. In fact, the disease is caused by both genetic and environmental factors and to convince the scientific community of this fact is a primary responsibility for epidemiologists.

The ecogenetics of schizophrenia: a review

Schizophrenia is generally thought to arise as a result of interactions between genetic vulnerability and environmental risk factors. However, research methods to actually investigate the pattern of hypothesized interactions have only recently been developed. In this article, we review the evidence that genes increase the risk for schizophrenia by making individuals more sensitive to environmental risk factors (genotype-environment interaction), or by making individuals more likely to select high-risk environments (genotype-environment correlation). It is likely that at least some of the impact of genes on the occurrence of schizophrenia is mediated through (sensitivity for) environmental risk factors such as a dysfunctional early family rearing environment, cannabis, viral infections, complications of birth and pregnancy, stressful life events and unknown environmental risk factors associated with urban birth or residence and membership of certain ethnic groups. With the advent of molecular genetics, further knowledge about possible genotype-environment interactions is urgently required in order to develop and improve strategies for the prevention and early treatment of schizophrenia.

Different statistical models used in the calculation of the prevalence of insulin-dependent diabetes mellitus according to the polymorphism of the HLA-DQ region

The use of three statistical models yielded different estimates of the odds ratio relative to the association between the polymorphism in the HLA-DQ region and insulin-dependent diabetes mellitus (IDDM). The models used were: (1) the allele-dosage model which assumes that the number of susceptibility alleles has a linear effect on the logarithm of the odds; (2) the reference cell coding method used with alleles of susceptibility as a risk factor; or (3) a model that uses a classification of alpha/beta heterodimers as a susceptibility factor. We suggest that models which imply a log-linear relationship between a susceptibility marker and disease such as the first model are not appropriate in the assessment of the HLA-IDDM association. In contrast, although both latter models are valid, the third model is more compatible with current hypotheses of the pathological process of the disease. Once an estimation of the odds ratio is chosen, we use such an estimation to calculate an approximation of the prevalence of IDDM according to the polymorphism in HLA-DQ region using the iterative procedure of Newton-Raphson. These approaches are illustrated with data from a case-control study previously conducted in the city of Santiago, Chile.