HLA-class II and class I genotypes among Japanese children with Type 1A diabetes and their families.

OBJECTIVE: To determine the HLA-DRB1, DQB1, DPB1, A, C, and B genotypes among Japanese children with autoimmune type 1 diabetes. METHODS: Four hundred and thirty patients who were GADAb and/or IA-2Ab-positive (Type 1A) were recruited from 37 medical centers as part of a nationwide multicenter collaborative study. DNA samples from 83 siblings of the children with Type 1A diabetes and 149 parent-child trios were also analyzed. A case-control study and a transmission disequilibrium test (TDT) were then performed. RESULTS: The susceptible and protective DRB1 and DQB1 alleles and haplotypes were confirmed. DPB1 alleles unique to the Japanese population and those common to multiple ethnic groups were also present. A linkage disequilibrium (LD) analysis showed both susceptible and protective haplotypes. The TDT did not reveal any alleles that were transmitted preferentially from the mother or father to children with Type 1A. Homozygosity for DRB1-09:01-DQB1-03:03 and heterozygosity for DRB1-04:05-DQB1-04:01 and DRB1-08:02-DQB1-03:02 were associated with an extremely high risk of Type 1A. A comparison of children with Type 1A and their parents and siblings suggested a dose effect of susceptible DRB1-DQB1 haplotypes and an effect of protective alleles on immunological pathogenesis. DRB1-09:01 appeared to be strongly associated with an early onset in preschool children with Type 1A diabetes. CONCLUSIONS: This study demonstrated the characteristic association of HLA-class II and class I genes with Type 1A diabetes among Japanese children. A TDT did not reveal the genomic imprinting of HLA-class II and class I genes in Type 1A diabetes.

Improvement of glucose tolerance by nateglinide occurs through enhancement of early phase insulin secretion.

Nateglinide is a new, fast-onset, short-acting hypoglycemic agent, which increases early phase insulin secretion and the total amount of insulin secreted. However, it is not clear which of these effects contribute more to the decrease in postprandial plasma glucose (PG). To further clarify the pharmacologic actions of nateglinide, we investigated the changes in PG and insulin levels during meal tolerance tests with and without nateglinide. Subjects were 10 newly diagnosed and untreated inpatients with type 2 diabetes. After diet and exercise therapy for 1 week, nateglinide at 270 mg divided 3 times a day, was started. Meal tolerance tests were performed before (baseline) and after a single nateglinide administration (day 1), after 7 days of repeated administration (day 7), and after cessation of nateglinide on day 8. Mean fasting PG was 146 +/- 6 mg/dl (mean +/- SEM) at baseline and 130 +/- 6 mg/dL on day 7 (P =.0004). The 2-hour postprandial PG level was 226 +/- 10 mg/dL at baseline, 145 +/- 11 mg/dL on day 1 (P =.0008), and 190 +/- 15 mg/dL on day 8 (P =.08, baseline; P =.01, day 7). The mean fasting insulin level was 5.4 +/- 1.0 microU/mL at baseline and did not change significantly during the study. The 30-minute postprandial insulin level was 14.4 +/- 1.9 microU/mL at baseline, 39.5 +/- 4.5 microU/mL on day 1 (P =.0004), and 23.6 +/- 3.6 microU/mL on day 8 (P =.045, baseline; P =.010, day 7). The total insulin amount, in terms of area under the curve (AUC. IRI), was 3.99 +/- 0.7 x 10(3) microU/mL. min at baseline, 5.47 +/- 0.8 microU/mL. min on day 1 (P =.029), and 6.01 +/- 1.9 microU/mL. min on day 8 (P =.047 v baseline). The early phase of insulin secretion, based on the ratio of delta IRI to delta PG from fasting to 30 minutes after a meal was 0.15 +/- 0.13 at baseline, 1.44 +/- 0.26 on day 1 (P =.0009) and 0.26 +/- 0.06 on day 8 (P =.05 v day 1). After cessation of nateglinide, the postprandial PG level increased immediately. Although early phase insulin secretion returned nearly to the baseline level, total insulin secretion remained at a high level. These results suggested that early phase insulin secretion contributes more than total insulin secretion to the improvement of postprandial hyperglycemia in type 2 diabetes.