Association of serum 25-hydroxyvitamin D concentration with HLA-B, -DRB1 and -DQB1 genetic polymorphisms.

BACKGROUND/OBJECTIVES: The human leukocyte antigen (HLA) gene region associates with the risk for several autoimmune diseases, including type 1 diabetes. An association between vitamin D deficiency and several autoimmune diseases has been suggested. We tested the association between serum 25-hydroxyvitamin D (25OHD) concentrations and HLA alleles in pregnant Finnish women. SUBJECTS/METHODS: HLA-B (n=395), HLA-DRB1 (n=501) and HLA-DQB1 (n=475) alleles were genotyped in pregnant women (mothers of children who later developed type 1 diabetes and mothers of non-diabetic children). HLA-B alleles were divided into supertypes that share similar peptide-binding specificity. Serum 25OHD concentration had been previously measured in these women from sera collected during the first trimester of pregnancy. Multiple testing was controlled for using the false discovery rate method. RESULTS: An association was found between 25OHD concentration and HLA-B44 supertype (P=0.009); women with HLA-B44 supertype (B*18, B*37, B*40 and B*44 alleles) had lower 25OHD concentrations. No association was found between HLA-DRB1 or -DQB1 alleles and 25OHD concentration. CONCLUSIONS: In this study we found for the first time an association between HLA genetic polymorphisms and 25OHD concentration. In future studies, the mechanistic background of this association and the role of vitamin D in the regulation of HLA gene expression should be investigated.

Serum 25-hydroxyvitamin D level during early pregnancy and type 1 diabetes risk in the offspring.

AIMS/HYPOTHESIS: Vitamin D deficiency during the fetal period or infancy is one of the suggested environmental factors for type 1 diabetes and for its increasing incidence. To test this hypothesis we compared serum 25-hydroxyvitamin D (25(OH)D) levels during early pregnancy in mothers of children who subsequently developed type 1 diabetes (case mothers) with mothers of non-diabetic healthy children (control mothers) of the same age. METHODS: Children with type 1 diabetes were identified from the nationwide prescription register. 25(OH)D concentration was measured from serum samples collected during the first trimester of pregnancy from all Finnish women (Finnish Maternity Cohort). A total of 343 case mothers and 343 control mothers were included in the study. Samples were collected throughout the year. Samples from case and control mothers were matched on the day of collection. RESULTS: Mean 25(OH)D levels in case mothers (43.9 nmol/l) and control mothers (43.7 nmol/l) were not different. Of all mothers, 481 (70.1%) were vitamin D-deficient or -insufficient. CONCLUSIONS/INTERPRETATION: No difference was found in serum 25(OH)D concentrations during first trimester of pregnancy between mothers whose children later on developed type 1 diabetes, and mothers of non-diabetic ' healthy' children of the same age. It is difficult to detect possible effects of mothers' vitamin D deficiency during early pregnancy on the development of type 1 diabetes in the offspring in this population, as such a large proportion of mothers were vitamin D-deficient or -insufficient.

A population-specific diabetogenic haplotype HLA-A2,Cw1,B56,DR4,DQ8 is associated with high birthweight in Finnish diabetic families.

Children with type 1 diabetes (T1D) susceptibility HLA genotypes are shown to have an increased birthweight. We investigated to what extent T1D-predisposing HLA haplotypes were associated with increased birthweight. A total of 1255 Finnish children comprising those with T1D and their non-diabetic siblings were investigated. A total of 342 children and their non-diabetic parents were HLA genotyped. Birthweight data were obtained from the national Medical Birth Registry. The population-specific diabetogenic haplotype HLA-A2,Cw1,B56,DR4,DQ8 was associated with high birthweight (P=0.0280) in families with a diabetic offspring. Other T1D-predisposing HLA haplotypes showed nonsignificant tendency with high birthweight. More infants with a birthweight >or=4000 g were born in families with a T1D offspring than in the general Finnish population (P=0.0139). The previously observed direct association between birthweight and T1D risk may be mediated through the modulating effects that T1D susceptibility HLA genes have on weight. High birthweight and subsequent weight gain may accelerate the ongoing pancreatic autoimmune process in genetically susceptible individuals. The high proportion of infants having a birthweight >or=4000 g in families with a diabetic offspring raises a concern of potential adverse health outcomes that high birthweight can have.

The metabolic syndrome and incident diabetes: assessment of four suggested definitions of the metabolic syndrome in a Chinese population with high post-prandial glucose.

AIMS: To assess the sensitivity and specificity of the four definitions of the metabolic syndrome for incident diabetes in both men and women. METHODS: The screening survey for type 2 diabetes was conducted in 1994. A follow-up study on 627 high-risk non-diabetic individuals at baseline was carried out in 1999 in Beijing area. 70 men and 76 women developed diabetes during the five-year follow-up. Sensitivity and specificity of four definitions of the metabolic syndrome based on the NCEP, WHO, EGIR and AACE recommendations were compared by McNemar's test. RESULTS: The metabolic syndrome based on all four definitions identified men at a 3.7-4.5-fold and women at a 1.6-2.8-fold risk of developing diabetes during 5-year follow-up. The AACE definition had the highest sensitivity for predicting diabetes (men: 0.61; women: 0.58) and lowest specificity (men: 0.71; women: 0.70). The WHO definition identified 53 % of male and 42 % female incident diabetes. The NCEP definition of adiposity as waist girth > 102 cm was the least sensitive, detecting only 27 % of incident diabetes in men; however, it was the most specific (0.91). The EGIR definition identified the lowest number of female cases (28 %) and fewer male cases (28 %) of incident diabetes, but was specific (women: 0.87; men: 0.91). CONCLUSIONS: Further studies on definition of the metabolic syndrome should focus on the potential ethnic differences in insulin resistance and anthropometric indicators for obesity.