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Examines the role of mutations in the coding region of the insulin promoter factor 1 gene in maturity-onset diabetes of young Japanese. Feature of all forms of diabetes; Pancreatic beta cell dysfunction caused by either immune-mediated beta-cell destruction in type 1 diabetes or failure of the beta cell to compensate to meet the increasing demand for insulin.

Variation in the gene encoding the cysteine protease calpain-10 has been linked and associated with risk of type 2 diabetes. We have examined the effect of three polymorphisms in the calpain-10 gene (SNP-43, Indel-19, and SNP-63) on the development of type 2 diabetes in the Japanese population in a pooled analysis of 927 patients and 929 controls. We observed that SNP-43, Indel-19, and SNP-63 either individually or as a haplotype were not associated with altered risk of type 2 diabetes with the exception of the rare 111/221 haplogenotype (odds ratio (OR) =3.53, P=0.02). However, stratification based on the median age-at-diagnosis in the pooled study population (<50 and > or =50 years) revealed that allele 2 of Indel-19 and the 121 haplotype were associated with reduced risk in patients with later age-at-diagnosis (age-at-diagnosis > or =50 years OR=0.82 and 0.80, respectively; P=0.04 and 0.02). Thus, variation in the calpain-10 gene may affect risk of type 2 diabetes in Japanese, especially in older individuals.

We have carried out an autosomal genome scan for genes contributing to the development of type 2 diabetes and affecting BMI in the Japanese population (164 families, 256 affected sib-pairs). We found 12 regions that showed nominally significant multipoint evidence of linkage with type 2 diabetes (i.e. logarithm of odds [LOD] score >0.59, P < 0.05): chromosome 1 29.9 cM; chromosome 2 169.6 and 236.8 cM; chromosome 4 104.9 cM; chromosome 5 114.8 cM; chromosome 6 42.3 cM; chromosome 8 15.3 and 93.3 cM; chromosome 9 140.0 cM; chromosome 11 131.6 cM; chromosome 17 36.1 cM; and chromosome 21 48.0 cM. Twelve regions showed nominal multipoint evidence for linkage with log-transformed BMI (lnBMI): chromosome 2 167.9 and 210.5 cM; chromosome 3 185.7 cM; chromosome 4 118.9 and 145.6 cM; chromosome 5 131.9 cM; chromosome 7 7.4 cM; chromosome 10 70.0 cM; chromosome 15 12.8 cM; chromosome 16 30.0 cM; and chromosome 17 47.8 and 100.2 cM. Although none of the regions achieved genome-wide levels of significance, simulation studies showed that we observed more linkage signals than expected if there were no loci contributing to type 2 diabetes or BMI. Eight of the regions showing nominal evidence for linkage with type 2 diabetes have been reported in other genome scans, and seven of the regions showing linkage with lnBMI have shown linkage with BMI and BMI-related traits in other studies. Thus, our results may replicate findings in other studies. They may also indicate new regions of the genome that are involved in the regulation of blood glucose levels or body weight.