Diabetes In Japanese Research Articles

The association of Ala45Thr polymorphism in NeuroD with child-onset Type 1a diabetes in Japanese

Recently Iwata et al. reported that the polymorphism in NeuroD exon 2(Ala45Thr) was associated with adult-onset Type 1 diabetes in Japanese. Furthermore, the mutations in the NeuroD as a regulator of insulin transcription have been reported to result in Type 2 diabetes. We, therefore, aimed to clarify the role of this Ala45Thr polymorphism in the susceptibility to Type 1a, immune-mediated, diabetes of child-onset Japanese patients. Eighty patients with child-onset Type 1 diabetes were examined along with 121 non-diabetic subjects as the controls. The polymorphism in Ala45Thr was defined using the PCR-RFLP method. The GAD Ab, IA-2 Ab, HLA-DRB1 genotypes and residual β-cell function at 3 years from onset were evaluated in relation to the difference in this polymorphism. The frequency of the Ala45Thr heterozygotes was significantly higher in the Type 1 diabetic patients than in the controls (21.3 versus 9.9%, P=0.0252). The frequency of loss of β-cell function was higher in heterozygotes patients than in wild type homozygotes patients ( P=0.0112). Type 1 diabetic patients with DRB1*0901 allele showed a significantly higher frequency, 27.9%, of the Ala45Thr variant than the controls ( P=0.0041). In conclusion, the Ala45Thr polymorphism contributes to the risk of development of, and to the early deterioration of β-cell function, in Type 1a diabetes among the Japanese population.

A missense mutation of Pax4 gene (R121W) is associated with type 2 diabetes in Japanese.

Pax4 is one of the transcription factors that play an important role in the differentiation of islet beta-cells. We scanned the Pax4 gene in 200 unrelated Japanese type 2 diabetic patients and found a missense mutation (R121W) in 6 heterozygous patients and 1 homozygous patient (mutant allele frequency 2.0%). The mutation was not found in 161 nondiabetic subjects. The R121W mutation was located in the paired domain and was thought to affect its transcription activity through lack of DNA binding. Six of seven patients had family history of diabetes or impaired glucose tolerance, and four of seven had transient insulin therapy at the onset. One of them, a homozygous carrier, had relatively early onset diabetes and slowly fell into an insulin-dependent state without an autoimmune-mediated process. This is the first report of a Pax4 gene mutation that exhibits loss of function and seems to be associated with type 2 diabetes. This work provides significant implications for the Pax4 gene as one of the predisposing genes for type 2 diabetes in the Japanese.

NeuroD/beta2 gene G-->A polymorphism may affect onset pattern of type 1 diabetes in Japanese.

The majority of type 1 diabetes is considered to be autoimmune with, for the most part, abrupt development. However, type 1 diabetes with slow onset, or the so-called slowly progressive type 1 diabetes or latent autoimmune diabetes in adults, has been recently recognized and is considered to be autoimmune-related. Although some investigators tried to explain the difference in onset pattern by the genetic background, including HLA type, it has not been established thus far. We hypothesized that the difference in onset pattern may relate to regeneration or differentiation of pancreatic beta-cells, and we therefore focused on the NeuroD/BETA2 gene, which encodes a transcription factor for the insulin gene and beta-cell differentiation. We examined the NeuroD/BETA2 gene polymorphism in 105 Japanese type 1 diabetic patients and in 122 nondiabetic Japanese subjects in a case-control study, and we stratified the patients according to their onset pattern and islet-associated autoantibody positivity. Regardless of the existence of islet-associated autoantibody, we found a significant difference in A allele frequency between type 1 diabetic patients with acute-onset type and control subjects. However, no difference was found between type 1 slow-onset diabetic patients and control subjects. These results support our hypothesis that NeuroD/BETA2 may affect the ability of regeneration of beta-cells, leading to a difference in the onset pattern and clinical course of type 1 diabetes.

Lack of association of the Ala45Thr variant in the BETA2/NEUROD1 with type 1 diabetes in Japanese

To evaluate the role of the Ala45Thr variant of BETA2/NEUROD1 in the development of type 1 or type 2 diabetes, we studied a Japanese population consisting of 383 control subjects, 234 type 1 diabetes patients and 160 type 2 diabetes patients. Both genotypewise and allelewise, there was no significant association of the variant with type 1 diabetes or type 2 diabetes in Japanese. Also, there were no significant differences in clinical characteristics with and without the variant. Our present results do not support a recent report which described an association of the Ala45Thr variant with type 1 diabetes in Japanese.

Analysis of tumor necrosis factor-alpha promoter polymorphism in type 1 diabetes: HLA-B and -DRB1 alleles are primarily associated with the disease in Japanese.

Polymorphisms in the 5'-flanking region of the tumor necrosis factor (TNF)-alpha gene were examined to study the genetic background of type 1 diabetes in Japanese. Five different biallelic polymorphisms were examined in 136 type 1 diabetic patients and 300 control subjects. The frequencies of individuals carrying TNF-alpha-857T allele (designated as TNFP-D allele) or -863A/-1,031C allele (designated as TNFP-B allele) were significantly increased in the patients as compared with the controls. Since these TNF-alpha alleles are in linkage disequilibria with certain DRB1 and HLA-B alleles, two-locus analyses were carried out. The TNFP-D allele did not increase the risk in either the presence or absence of the DRB1*0405 or HLA-B54 allele, while the DRB1*0405 and HLA-B54 alleles per se could confer susceptibility in both the TNFP-D allele-positive and -negative populations. Moreover, an odds ratio was remarkably elevated in the population carrying both DRB1*0405 and HLA-B54. Similarly, the TNFP-B allele did not show significant association with the disease in either the HLA-B61-positive or -negative population, while the HLA-B61 allele could significantly increase the risk in the TNFP-B allele-positive population. These data suggest that the associations of TNFP-D and -B alleles may be secondary to their linkage disequilibria with the susceptible HLA class I and class II alleles. Because HLA-B and DRB1 genes were independently associated, both of these genes may be contributed primarily to the pathogenesis of type 1 diabetes in Japanese.

IgG1 is the dominant subclass of antibody against glutamic acid decarboxylase among type 1 diabetes in Japanese.

Autoantibody against glutamic acid decarboxylase (GADA) is a highly sensitive predictor of insulin-dependency in adult diabetic patients as well as young individuals. A considerable number of diabetics who do not reach the insulin-dependent stage have this antibody. Recently, type 1 diabetes has been thought to be caused by T helper 1 (Thl)-type autoimmunity based on studies in non-obese diabetic mice, but it is still difficult to investigate antigen-specific T-cell function in human type 1 diabetes. We therefore assessed an IgG subclass assay for GADA, which should reflect T-helper function against GAD. Sera from 14 type 1 diabetic patients positive for GADA by radioligand binding assay were tested for the IgG subclass of GADA. The assay was based on an enzyme-linked immunosorbent assay, which showed a good correlation with radioligand binding assay. The sera of all but one of the 14 type 1 diabetic patients (93%) were positive for the IgG1 subclass of GADA. The IgG2 and IgG3 subclasses of GADA were also detected in one diabetic patient each who were also positive for IgG1. The IgG4 subclass was not detected in any of the sera we tested. We concluded that IgG1 is the dominant subclass of GADA in Japanese type 1 diabetic patients.

Molecular scanning for mutations in the melanocortin-4 receptor gene in obese/diabetic Japanese.

Decreased function of the melanocortin-4 receptor (MC4R) was reported to cause late-onset obesity and insulin resistance in rodents. Thus mutations in the MC4R gene drew strong attention as a possible cause of obesity and diabetes. We screened for mutations in the MC4R gene in extremely obese [body mass index (BMI) > or = 35 kg/m2] Japanese with diabetes by direct sequencing. A heterozygous mutation (V103I) was detected in one case (2.0 %), however the frequency was not significantly different from that in non-obese (BMI < or = 24 kg/m2) and non-diabetic subjects (2.7 %). No other mutations were detected. These results suggest that mutations including V103I in the MC4R gene are not a major cause of obesity or diabetes in Japanese.

Molecular scanning for mutations in the melanocortin‐4 receptor gene in obese/diabetic Japanese

Decreased function of the melanocortin‐4 receptor (MC4R) was reported to cause late‐onset obesity and insulin resistance in rodents. Thus mutations in the MC4R gene drew strong attention as a possible cause of obesity and diabetes. We screened for mutations in the MC4R gene in extremely obese [body mass index (BMI) ≥ 35 kg/m2] Japanese with diabetes by direct sequencing. A heterozygous mutation (V103I) was detected in one case (2.0 %), however the frequency was not significantly different from that in non‐obese (BMI ≤ 24 kg/m2) and non‐diabetic subjects (2.7 %). No other mutations were detected. These results suggest that mutations including V103I in the MC4R gene are not a major cause of obesity or diabetes in Japanese.

Antibody to the M(r) 65,000 isoform of glutamic acid decarboxylase are detected in non-insulin-dependent diabetes in Japanese.

It was recently reported that antibodies against glutamic acid decarboxylase (GADAb) have a high positive predictive value for insulin-dependency in non-insulin-dependent diabetic (NIDDM) patients. We studied 289 patients classified at onset as having NIDDM. Patients positive for GAD65Ab had a disease onset at a younger age, lower body mass index (BMI) and lower serum C-peptide concentration, and were more often treated with insulin. Among 73 insulin-treated patients, patients with lower C-peptide level (n = 30, C-peptide < or = 0.9 ng/ml) showed a higher frequency of GAD65Ab (46.7%) than patients with normal C-peptide (n = 53, C-peptide > 0.9; 7.5%, P < 0.0001). The 206 remaining non-insulin-treated patients were divided into 48 short-duration (less than 5 years from diagnosis) and 158 long-duration patients. Frequency of GAD65Ab in short-duration patients (10.4%) was significantly higher than that in long-duration patients (3.2%, P < 0.05). Among short-duration patients, there was no significant difference in C-peptide levels between GAD65-positive and negative patients (2.175 and 2.226 ng/ml). In conclusion, GAD65Ab, a marker of insulin deficiency, may predict the development of insulin dependency in non-insulin-dependent Japanese diabetic patients before serum C-peptide concentration decreases.

Genetic markers for insulin-dependent diabetes mellitus in Japanese

Although the HLA class II genes are clearly associated with insulin-dependent diabetes mellitus (IDDM) in all ethnic groups, considerable variation in the associated haplotypes is observed amoag the ethnic groups. In Japanese, DRB1∗ 0405-DQA1∗ 0301-DQB1∗0401, DRB1∗0901-DQA1∗0301-DQB1∗0303 and DRB1*0802-DQA1∗0301-DQB1∗0302 are the major susceptibility haplotypes to IDDM, while DRB1∗1501-DQA1∗0102-DQB1∗0602 and DRB1∗1502-DQA1∗0103-DQB1∗0601 are the major resistance haplotypes. The hypothesis that alleles encoding amino acids other than aspartic acid at the DQB1 position 57 contribute to IDDM susceptibility is not applicable to the Japanese, mainly because the first and second susceptibility haplotypes listed above have aspartic acid at DQB1 position 57. In the 5′ insulin gene polymorphism, the shorter insertion (class 1 allele) is predominant, and is not associated with diabetes in Japanese. Subdivision of the class 1 alleles also failed to show an association with IDDM in Japanese. The insulin gene region appeared to be of less value as a genetic marker for IDDM in Japanese. Little is known about other genetic markers.

Early-onset type 2 (non-insulin-dependent) diabetes mellitus is associated with glucokinase locus, but not with adenosine deaminase locus, in the Japanese population

To investigate the possible contribution of glucokinase (GCK) and adenosine deaminase (ADA) loci to the genetic susceptibility to type 2 (non-insulin-dependent) diabetes mellitus, we studied the association of these loci with type 2 diabetes in the Japanese population. Fifty patients with type 2 diabetes and 50 control subjects were analyzed for microsatellite polymorphism 3′ to the GCK gene and PstI polymorphism in the ADA gene by polymerase chain reaction. The frequency of the most common GCK allele (Z) was significantly lower in type 2 diabetic patients than that in control subjects and a longer Z + 2 allele was more common in type 2 diabetic patients (26% vs. 15%, P = 0.053), particularly in those with younger age of onset (33% vs. 15%, younger onset type 2 diabetes vs. control, P = 0.014). The frequency of genotypes containing at least one Z + 2 allele was significantly more common in type 2 diabetic patients (46% vs. 28%, P < 0.05), particularly in those with younger age of onset (61% vs. 28%, relative risk 4.00, P < 0.01). In contrast, there was no difference in allelic or genotypic frequencies of PstI polymorphism in the ADA gene between the two groups. Despite the association between the GCK locus and type 2 diabetes, none of the patients had known mutations (Glu 265 → AM 265, Glu 279 → AM 279, Gly 299 → Arg 299, Glu 300 → Gln 300, Leu 309 → Pro 309). These results suggest that the GCK locus, but not the ADA locus, contributes to the genetic susceptibility to type 2 diabetes in Japanese. The low frequencies of known GCK mutations shown in this and other studies suggest that the association of the GCK locus with type 2 diabetes observed in this study is due to the presence of an unknown common mutation in exons or a mutation in the regulatory region of the GCK gene.

Lack of association of the insulin gene region with Type 1 (insulin-dependent) diabetes mellitus in Japanese subjects

Although the insulin gene region is implicated in susceptibility to Type 1 (insulin-dependent) diabetes mellitus in Caucasians, significance of this region to Type 1 diabetes in Japanese remains unclear because the class 1 alleles (shorter insertion) of the variable number of tandem repeat in the 5' region of the insulin gene are predominant in both diabetic and non-diabetic subjects. The 5' insulin gene polymorphism was analysed in 75 Japanese patients and 69 control subjects with a precise method using PvuII and a polymorphism specific probe, which enabled us to divide class 1 alleles into four subclasses. Allelic frequencies were not significantly different between Type 1 diabetic patients and control subjects. The polymorphism in the 3' untranslated region of the insulin gene (1127/PstI) was also analysed and found to be tightly linked to the 5' insulin gene polymorphism, and thus was not associated with diabetes. Interaction between HLA-DR and the insulin gene region, which was reported in the French study, was not observed in Japanese. These results suggest that the insulin gene region is not a valuable genetic risk factor for Type 1 diabetes in Japanese.

Genetic analysis of HLA class II alleles and susceptibility to type 1 (insulin-dependent) diabetes mellitus in Japanese subjects.

Although HLA-DQB1 alleles encoding aspartic acid at position 57 (Asp-57) are protective against Type 1 (insulin-dependent) diabetes mellitus in Caucasians, most Japanese Type 1 diabetic patients carry at least one Asp-57 DQB1 allele. We analysed the DRB1, DQA1 and DQB1 genes of 99 Japanese patients and 86 control subjects with polymerase chain reaction and sequence-specific oligonucleotide hybridization. We found that (1) the DQA1*0301 allele was significantly increased in Type 1 diabetic patients (RR7.8, pc less than 0.0001); (2) the DRB1*0405 (Dw15) allele, which is a subtype of DR4 haplotype, was significantly increased in DR4-positive patients (RR 12.0, pc less than 0.001); and (3) although the DRw8-DQw8 haplotype was positively associated with Type 1 diabetes, the DRB1*0406-DQw8 haplotype was decreased in the diabetic patients. These data indicate that DRB1 and DQA1 genes also confer susceptibility to Type 1 diabetes in Japanese.

The A3 allele of the HLA-DQA1 locus is associated with susceptibility to type 1 diabetes in Japanese.

Analysis of the frequencies of class II HLA-DR and HLA-DQ alleles by serological and DNA typing in 49 Japanese patients with type 1 (insulin-dependent) diabetes and 31 Japanese controls indicates the following. (i) Susceptibility is more strongly associated with the HLA-DQ subregion than with the HLA-DR subregion. (ii) Of the class II alleles detected, the A3 allele of the DQA1 locus was the most strongly associated with disease. Ninety-six percent of the patients were positive for the A3 allele compared to 53% of the controls (P = 0.001; relative risk = 19.7; confidence limits = 3.72-188.64). (iii) The DQw8 allele of the DQB1 locus, which is associated with susceptibility to type 1 diabetes in Caucasians and Blacks, was not increased in frequency in Japanese patients (22%) versus controls (19%). (iv) Asp-57-encoding DQB1 alleles are associated with reduced susceptibility to type 1 diabetes in Caucasians. The major predisposing haplotypes in Japanese are DR4 and DR9. By DNA sequence analysis, both of these Japanese haplotypes have Asp-57-encoding DQB1 alleles. Oligonucleotide dot blot analysis showed that all, except 1, of the 49 Japanese patients and all of the 31 controls have at least one Asp-57-encoding DQB1 allele. In addition, 40% of the patients were homozygous for Asp-57-encoding DQB1 alleles versus 35% of the controls. The high frequencies of Asp-57-encoding DQB1 alleles in this ethnic group may account for the rarity of type 1 diabetes in Japan.

Complications of Diabetes in Japanese

Complications of Diabetes in Japanese

The polymorphism linked to the human insulin gene: its lack of association with either IDDM or NIDDM in Japanese.

Polymorphism of 5' portion of the human insulin gene was examined in 188 unrelated Japanese subjects (49 normal, 71 with IDDM, and 68 with NIDDM) using restriction endonuclease analysis. Restriction fragments were classified according to the insertion size: Class 1 (600 base pairs), Class 2 (1300 base pairs), and Class 3 (2000 base pairs). We found a very high frequency of Class 1 alleles (96.8%) and a low frequency of both Class 2 (0.8%) and Class 3 alleles (2.4%) and that approximately 94% of the genotypes were Class 1/Class 1 homozygote. In addition, there was no correlation of allelic or genotypic frequency with NIDDM or IDDM. We conclude that length polymorphism of the human insulin gene cannot be a useful marker for diabetes in Japanese.

Comparison of the distribution of properdin factor B (Bf) genotypes between type I and type II diabetes in Japanese

Comparison of the distribution of properdin factor B (Bf) genotypes between type I and type II diabetes in Japanese