DQA1 and DQB1 heterodimers in insulin-dependent diabetes mellitus: a genetic-epidemiological study in Finland. DiMe Study Group.

Susceptibility to insulin-dependent diabetes mellitus (IDDM) correlates with the absence of aspartic acid in position 57 of the DQB1 and/or the presence of arginine in position 52 of the DQA1. It has been postulated that transcomplementation between the DQ alpha and beta chains of the two haplotypes could create new molecules conferring susceptibility to IDDM. Finland has the highest incidence of IDDM in the world (35/100,000). In a nationwide study of IDDM in childhood (DiMe study) HLA genotyping using conventional serology was carried out according to genetic-epidemiological principles. We simulated DQA1 and DQB1 alleles in 707 consecutively diagnosed IDDM probands and 98 non-diabetic children based on serology, restriction fragment length polymorphism results and sequence data assuming no recombination between DQ and DR. In 34% of Finnish children with IDDM all four combinations (two in cis and two in trans) could lead to SS heterodimers. Two-thirds of these combinations were explained by DR3,DR4 heterozygotes. In 50% of IDDM children half and in 11% a quarter of the combinations could lead to heterodimers. In 38 IDDM patients (5%) the formation of hybrid molecules was not possible. In 59% of the controls SS heterodimers were possible and should therefore have an underlying genetic susceptible for IDDM assuming the theory of transcomplementation is correct. These findings, together with the fact that the lowest frequency of DR3,DR4 heterozygosity (21%) was seen in Finland, show that heterozygosity for DQ and DR cannot explain the differences seen in IDDM incidence.     

HLA-DQB1-defined genetic susceptibility, beta cell autoimmunity, and metabolic characteristics in familial and nonfamilial insulin-dependent diabetes mellitus. Childhood Diabetes in Finland (DiMe) Study Group.

Familial aggregation of insulin-dependent diabetes mellitus (IDDM) is a common phenomenon, but the reasons behind it are poorly understood. To investigate whether there is heterogeneity between familial and nonfamilial forms of IDDM we compared genetic, immunological, and clinical characteristics of diabetic children with and without an affected first-degree relative in a population-based series of Finnish children with IDDM. The frequencies of HLA-DQB1 genotypes known to be associated with high (DQB1*0302/0201) or moderate (*0302/x) IDDM risk in the Finnish population were increased, while the proportions of DQB1 genotypes associated with low or decreased risk for IDDM were reduced in the 121 familial cases as compared with the 574 nonfamilial cases (32.7 vs. 21.3%, 41.3 vs. 35.9%, 18.3 vs. 31.4%, and 7.7 vs. 11.4%, respectively; P = 0.002). The frequencies and serum concentrations of islet cell antibodies, insulin autoantibodies, and antibodies to the 65-kD isoform of glutamic acid decarboxylase were similar at diagnosis in the familial and nonfamilial cases. The 31 first-affected cases in the multiple case families were younger at diagnosis than the nonfamilial cases (6.9 vs. 8.5 yr; P < 0.05). The 90 second-affected familial cases had less severe metabolic decompensation at diagnosis than either the first-affected familial or nonfamilial cases. In conclusion, familial aggregation of IDDM in Finland is at least partly explained by a higher frequency of IDDM susceptibility genes in families with multiple affected individuals. The lack of differences in autoantibody levels between the familial and nonfamilial cases indicates homogeneity rather than heterogeneity in the pathogenetic process of beta cell destruction.     

Clinical, autoimmune, and genetic characteristics of very young children with type 1 diabetes. Childhood Diabetes in Finland (DiMe) Study Group

OBJECTIVE: To study the characteristics of type 1 diabetes in very young children. RESEARCH DESIGN AND METHODS: Clinical outcome, islet cell antibodies (ICA), insulin autoantibodies (IAA), antibodies against GAD (GADA), IA-2 antibodies (IA-2A), and HLA-DQB1-defined genetic risk were analyzed in 35 children diagnosed with type 1 diabetes before 2 years of age and compared with those in 146 children who were diagnosed between 2.0 and 4.9 years of age and with those in 620 children diagnosed between 5.0 and 14.9 years of age. RESULTS: The youngest age-group had severer metabolic decompensation at clinical onset, and their serum C-peptide levels, compared with those of older children, were lower at the time of diagnosis and during the first 2 years after the diagnosis. The levels of ICA and IAA were highest in children < 2 years of age, but there were no differences in GADA levels among the three age-groups. The youngest age-group had the lowest IA-2A levels. The HLA DQB1*02/*0302 genotype associated with strong genetic susceptibility was more frequent in children diagnosed < 5 years of age, whereas the proportion of children carrying a genotype, which includes protective alleles, was higher among those diagnosed at > or = 5 years of age. CONCLUSIONS: The clinical presentation of type 1 diabetes at a very young age is associated with severe metabolic decompensation, poorly preserved residual beta-cell function, strong humoral autoimmunity against islet cells and insulin, and strong HLA-defined disease susceptibility.     

Plasma fructosamine assay in children with insulin-dependent diabetes mellitus

Plasma concentrations of fructosamine, an indicator of glycated plasma proteins, were measured in non-diabetic children and children with insulin-dependent diabetes mellitus (IDDM) to see if they also correlate with glycemic control in children as well as in adults. Non-diabetic children aged less than 4 yr had significantly lower plasma fructosamine than non-diabetic children aged 4 or more. Total plasma protein in these children was slightly lower or close to that of older children. There was no difference in fructosamine between non-diabetic children aged 4 or more and healthy adult subjects. Plasma fructosamine in children with IDDM was twofold that of age-matched controls. In children with IDDM, correlations between fructosamine and HbAI (r = 0.799) or HbAIc (r = 0.841) were high. The measurement of plasma fructosamine, which is practical in children because of the small sample volume needed and no influence of HbF, is useful in the management of children with IDDM.     

Infant feeding in Finnish children less than 7 yr of age with newly diagnosed IDDM. Childhood Diabetes in Finland Study Group

OBJECTIVE: We studied associations between the type of feeding in infancy and the incidence of insulin-dependent diabetes mellitus (IDDM). RESEARCH DESIGN AND METHODS: We studied 103 newly diagnosed diabetic children less than 7 yr of age and 103 age- and sex-matched population-based control children in a countrywide study. Results: The risk of IDDM was decreased (P less than 0.05) among children breast-fed for at least 7 mo (odds ratio [OR] 0.45, 95% confidence interval [CI] 0.24-0.85) or exclusively breast-fed for at least 3 (OR 0.33, 95% CI 0.13-0.84) or 4 (OR 0.43, 95% CI 0.22-0.84) mo. Also, children who were greater than or equal to 4 mo old at the time of introduction of supplementary milk feeding had a lower risk of diabetes (OR 0.48, 95% CI 0.26-0.91). CONCLUSIONS: The protective effects of a long duration of breast-feeding and a late introduction of dairy products on the risk of IDDM remained significant after adjusting for the mother's education.     

Pre-conception diabetes care in insulin-dependent diabetes mellitus.

Prospective studies of pre-conception diabetes care have confirmed its positive impact on the incidence of malformations by improving glycaemic control. Less information is available on the impact of pre-conception care on maternal and neonatal morbidity. This audit addresses its impact on timing and mode of delivery, incidence of macrosomia and rate of admission to neonatal unit care in addition to sociodemographic factors which may influence attendance at such a service. Attenders were more likely to be in a stable relationship and be non-smokers. They were more likely to book for antenatal care earlier and with a lower glycated haemoglobin. There were no early deliveries (i.e. < 30 weeks) or small for gestational age (SGA) babies in those who attended for pre-conception care and no neonatal deaths. Admission to NNU care was reduced by 50% in those who attended for pre-conception care. Although the rate of macrosomia was reduced, there was no impact on the Caesarian section rate. A pre-conception diabetes clinic may have a positive impact on neonatal morbidity.     

Measurement of glomerular filtration rate in children with insulin-dependent diabetes mellitus

51Cr-EDTA, inulin and creatinine clearances were measured simultaneously in 11 diabetic children and 12 healthy young adults. The clearances in all individuals were 115 +/- 24 ml/min per 1.73 m2SA for 51Cr-EDTA, 118 +/- 25 ml/min per 1.73 m2SA for inulin and 157 +/- 35 ml/min per 1.73 m2SA for creatinine. Values were higher in the diabetic children but the differences were not significant. 51Cr-EDTA clearance significantly underestimated that of inulin by a mean of -7.4 +/- 2.5 (SEM) ml/min per 1.73 m2SA (p less than 0.01) and creatinine clearance significantly overestimated that of inulin by 37.6 +/- 3.3 (SEM) ml/min per 1.73 m2SA (p less than 0.0001). Similarly, the mean ratio of 51Cr-EDTA to inulin clearance was 0.94 (95% CI 0.90-0.98) and that of creatinine to inulin clearance was 1.32 (95% CI 1.27-1.37); the differences between diabetics and controls were not significant. Correlation coefficients were 0.93 between 51Cr-EDTA and inulin clearances, and 0.95 between inulin and creatinine clearances. The pooled coefficient of variation between clearances within an individual was higher with inulin, 10.3 +/- 6.5% (SD), than 51Cr-EDTA, 7.3 +/- 5.1% (p less than 0.001, t test). These results show that 51Cr-EDTA clearance underestimates that of inulin to a similar extent in both diabetic children and healthy controls and creatinine clearance overestimates inulin clearance to a greater but similar extent in both groups. The methodological variation in 51Cr-EDTA measurement is less than with the other 2 methods. Therefore, we recommend the use of the renal clearance of 51Cr-EDTA for the measurement of GFR in diabetic children.     

Factors affecting insulin antibody binding in children with insulin-dependent diabetes mellitus

We measured insulin antibody binding in 2 groups of patients: Study 1, 32 children with newly diagnosed IDDM before onset of insulin therapy, and, in 20 of these, 10 days, 1, 3, and 6 months after beginning therapy; and Study 2, 35 children with long-standing IDDM, 20 of whom had free insulin concentrations measured before, and for 2 hours following subcutaneous injection of 0.25 U/kg regular insulin. Almost 35% of new onset subjects had insulin antibody binding above control levels. In those studied prospectively, binding increased significantly with time. Pre-treatment binding did not correlate with later insulin antibody binding nor metabolic control. In Study 1 we have confirmed previous studies showing abnormally high insulin antibody binding in children with IDDM pre-treatment. We have been unable to demonstrate a relationship between this binding and that found 6 months after initiation of therapy. In Study 2, we have shown that insulin antibody binding is not related to either the level of metabolic control or the rate of rise of free insulin levels in children with IDDM.     

Autonomic nerve function in children and adolescents with insulin-dependent diabetes mellitus

Autonomic nerve function was assessed in 67 insulin-dependent diabetic children and adolescents and in 30 control subjects of the same age. The heart rate and blood pressure reactions to a deep breathing test (E/I ratio) and a tilt table test (acceleration and brake indices) were used. The E/I ratio, 1·54 +0·21, and the acceleration index, 25 ± 7·7, in the diabetic children were not significantly different from those of the control children, 1·51 ± 0·16 and 24 ± 7·5, respectively. Neither was any difference observed between the mean brake index values; 24·3 ± 14·6 vs 23·5 ± 7·5. However, the variance of the brake index in diabetic children was significantly higher than in control children (P< 0·005). The brake index was negatively correlated to age in the healthy control children (r= -0·48, P <0·1). The acceleration index, but not the E/I ratio, also tended to be age related (r= -0·32, P<0·01 NS). No correlation was observed between sex, glycaemic control or duration of diabetes and the autonomic nerve function. Neither were severe hypoglycaemic episodes in diabetic children related to the autonomic nerve function. It is concluded that autonomic neuropathy is uncommon in diabetic children and adolescents and that age-related index values should be used when autonomic nerve function is evaluated in children of different ages.     

The onset age of type 1 diabetes in Finnish children has become younger. The Finnish Childhood Diabetes Registry Group.

OBJECTIVE: To analyze the change in the age distribution at onset of type 1 diabetes in boys and girls aged 1-14 years during a 32-year period (from 1965 to 1996). RESEARCH DESIGN AND METHODS: Data on the incidence of type 1 diabetes in Finland were obtained from the Central Drug Registry of the Social Insurance Institution for 1965-1986 (6,195 cases) and from the Prospective Childhood Diabetes Registry for 1987-1996 (3,613 cases). The change in age- and sex-specific incidence was estimated by fitting the linear regression with the logarithm of the annual incidence data. Analysis of variance was used to compare the trends between the various age-groups (1-4, 5-9, and 10-14 years) and sexes. RESULTS: The incidence of type 1 diabetes increased predominantly in the younger age-groups. In children aged 1-4 years, the increase was 4.2% per year, and the overall 32-year relative increase was 338%. For children aged 5-9 and 10-14 years, the increase was 2.5 and 1.3% per year, respectively, and the overall relative increase was 116 and 49%, respectively. In boys aged 1-9 years, the increase was greatest from 1965 to 1984, whereas in girls aged 1-9 years, the statistically significant increase occurred between 1985 and 1996. In children aged 10-14 years, the only significant increase was seen in boys from 1965 to 1974 (3.7% per year). CONCLUSIONS: The greatest increase in the incidence of type 1 diabetes mainly occurred in children aged < 5 years. The incidence in young boys has been increasing since the mid-1960s, whereas in young girls, the significant increase began later, around the mid-1970s. In children aged 10-14 years, the increase in incidence has leveled off.     

Infant feeding, early weight gain, and risk of type 1 diabetes. Childhood Diabetes in Finland (DiMe) Study Group

OBJECTIVE: To evaluate whether the increased risk of type 1 diabetes conferred by an early introduction of cow's milk supplements can be mediated by accelerated growth in formula-fed infants. RESEARCH DESIGN AND METHODS: All children < or = 14 years of age who were diagnosed with type 1 diabetes from September 1986 to April 1989 were invited to participate in the study. Birth date- and sex-matched control children were randomly selected from the Finnish Population Registry. At least three weight measurements from the first year of life were obtained for 435 full-term diabetic subjects and 386 control subjects from well-baby clinics and school health care units. RESULTS: Increase in body weight was greater in the diabetic girls than in the control girls, and the difference increased from 111 g (95% CI 0-218, P = 0.04) at 1 month of age to 286 g (95% CI 123-450, P = 0.0006) at 7 months. For boys, the difference in weight between the diabetic subjects and the control subjects remained stable during infancy (difference 95 g, 95% CI-2-205, P = 0.09). Increased weight was associated on average with a 1.5-fold risk of type 1 diabetes. Early introduction of formula feeding (< 3 vs. > or = 3 months) was also associated with an increased risk of type 1 diabetes after adjustment for the individual weight gain curve (adjusted odds ratio 1.53, 95% CI 1.1-2.2). No evidence for interaction was observed. CONCLUSIONS: These observations indicate that an early exposure to cow's milk formula-feeding and rapid growth in infancy are independent risk factors of childhood type 1 diabetes.     

The epidemiology of insulin-dependent diabetes mellitus

Diabetes mellitus is a uniquely interesting disorder to study from an epidemiologic perspective. Information that can be gathered from carefully designed and executed epidemiologic studies carried out on a population-based group of individuals with insulin-dependent diabetes mellitus (IDDM) provides insight into this disorder that cannot be obtained by traditional methods of basic or clinical research. The application of epidemiology as an investigative tool can be illustrated in 3 important areas of diabetes mellitus: (1) the etiology of IDDM, (2) the natural history or clinical course of IDDM, and (3) long-term complications of IDDM.     

HLA antigens in insulin-dependent diabetes mellitus.

Diabetes mellitus is largely determined by genetic factors but environmental factors are necessary to convert genetic susceptibility into overt disease. Studies of twins show that the genetic impact in non-insulin-dependent diabetes mellitus is stronger than in insulin-dependent diabetes mellitus. The genetic factors involved in non-insulin-dependent diabetes mellitus are not known and the outcome of molecular genetic research has so far been disappointing. The major genetic susceptibility to insulin-dependent diabetes mellitus is conferred by genes in the HLA region on chromosome 6. Despite many advances in molecular genetics in insulin-dependent diabetes mellitus the serologically detectable HLA antigens and haplotypes are still the best available markers. This review describes the important developments in immunogenetics in insulin-dependent diabetes mellitus and summarises the main findings from earlier studies. Genetically the potential for primary prevention of insulin-dependent diabetes mellitus already exists and will become a reality as soon as the environmental determinants are identified. A wide application of immunogenetic methods will be needed in the prevention of insulin-dependent diabetes mellitus.     

Beta-adrenoceptor regulation in insulin-dependent diabetes mellitus.

The study was performed to determine whether the regulation of mononuclear leukocyte beta-adrenergic receptors and responses was changed in insulin-dependent diabetes mellitus (IDDM). The concentrations of noradrenaline, the beta-adrenoceptor densities, basal cAMP levels and maximal isoprenaline-induced cAMP responses were the same in the diabetic and healthy subjects. After isoprenaline-promoted receptor internalization and uncoupling, the receptor densities and the responsiveness did not differ. In the control group, a highly significant correlation existed between the number of beta-adrenoceptors and maximal isoprenaline responses, before (r = 0.99, p less than 0.01) and after (r = 0.96, p less than 0.01) receptor internalization and uncoupling. This correlation between receptor densities and responses was not present in the IDDM group, which also showed elevated levels of plasma adrenaline. This study demonstrates that IDDM subjects have an unaltered mechanism of agonist-promoted beta-adrenoceptor internalization, but indicates a partial dysfunction of the beta-adrenoceptor-coupling to adenylate cyclase.     

Intellectual deficits associated with early onset of insulin-dependent diabetes mellitus in children

Twenty-seven children with early-onset (less than 4 yr) diabetes (EOD), 24 children with late-onset (greater than 4 yr) diabetes (LOD), and 30 sibling controls were compared in their performance on tests of intellectual functioning and school achievement. The results indicated that children with EOD, particularly girls, scored lower than the other groups of diabetic children and siblings on tests of visuospatial (P less than .05) but not verbal ability. Many of the girls with EOD were also having difficulty at school, and several were receiving special education. Children with EOD had more hypoglycemic convulsions than those with LOD. Both convulsions and age of onset were associated with poorer performance on spatial tasks. Girls with EOD had lower spatial test scores regardless of convulsion history, whereas boys with EOD scored lower only if they had had a convulsion.     

Platelet antioxidant enzymes in insulin-dependent diabetes mellitus.

BACKGROUND: The measurement of the peroxidase scavenging system represented by the activities of superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-Px) in blood cells of diabetic patients has, in the past, given equivocal results. Likewise, the role of these intracellular enzymatic scavengers against the oxidative stress of diabetes-associated microangiopathic complications is unknown. METHODS: Choosing platelets as cell model (as commonly done in previous studies), the aim of this study was to relate the platelet content of SOD, catalase and GSH-Px to the presence of diabetes, as well as to the presence of nephropathy and retinopathy in 35 insulin-dependent diabetic patients, as compared to 10 age-matched control subjects. RESULTS: The enzymatic activities were not changed in diabetic patients in comparison with healthy controls. After stratifying patients according to presence of nephropathy (24-h urinary albumin excretion rate persistently > or =20 microg min(-1)) or retinopathy, the group of albuminuric patients was characterized by a significant decrease in SOD activity as compared to those in the normoalbuminuric range (4.36+/-1.06 vs. 6.81+/-2.26 mU 10(-9) platelets; p=0.01). Catalase and GSH-Px did not change. No modification in platelet enzyme activities has been found in diabetic subjects with retinopathy. CONCLUSIONS: These results suggest that diabetic nephropathy, at least in its early stage, may be related to an altered redox state of platelets, as tested by the reduction in SOD activity, thus, indicating that the renal damage in these patients may be associated to a selective increase in platelet susceptibility to variation in the redox state.     

The cardiovascular risk profile of adolescents with insulin-dependent diabetes mellitus

Cardiovascular risk factors including blood pressure, lipoprotein concentrations, physical activity, and diet were assessed in 149 diabetic adolescents and 45 nondiabetic siblings. All diabetic subjects had had insulin-dependent diabetes mellitus (IDDM) for a minimum of 2 yr and were currently attending the Children's Hospital of Pittsburgh Diabetes Clinic. For both boys and girls, cardiovascular risk profiles were mildly disturbed among diabetic subjects compared with nondiabetic siblings. These disturbances included higher systolic (P = 0.002) and diastolic (P = 0.024) blood pressures and higher HDL3 cholesterol concentrations. The diabetic girls showed higher total cholesterol concentrations during adolescence in contrast to the usual fall seen in nondiabetic adolescents (and evidenced in the siblings studied). In addition, the diabetic girls' mean pulse rate was 12 bpm higher than that of the sibling girls, a finding not seen in the boys. Multiple linear regression analyses showed that neither glycemic control (worse in diabetic girls), diet, nor physical activity were important explanatory variables for any of the lipoprotein or blood pressure measures. These results suggest that the cardiovascular risk profile of diabetic girls may be relatively more disturbed than that of diabetic boys. This difference could not be explained by the slightly higher glycosylated hemoglobin levels in the girls. The loss of the sex differential in the risk for cardiovascular disease experienced by adults with IDDM may partly relate to these adolescent risk factor differences.