Yoshihiko Fujioka

The NSY mouse: a new animal model of spontaneous NIDDM with moderate obesity

SummaryThe NSY (Nagoya-Shibata-Yasuda) mouse was established as an inbred strain of mouse with spontaneous development of diabetes mellitus, by selective breeding for glucose intolerance from outbred Jcl∶ICR mice. NSY mice spontaneously develop diabetes mellitus in an age-dependent manner. The cumulative incidence of diabetes is 98% in males and 31% in females at 48 weeks of age. Neither severe obesity nor extreme hyperinsulinaemia is observed at any age in these mice. Glucose-stimulated insulin secretion was markedly impaired in NSY mice after 24 weeks of age. In contrast, fasting plasma insulin level was higher in male NSY mice than that in male C3H/He mice (545±73 vs 350±40 pmol/l, p<0.05, at 36 weeks of age). Pancreatic insulin content was higher in male NSY mice than that in male C3H/He mice (76±8 vs 52±5 ng/mg wet weight, p<0.05, at 36 weeks of age). Morphologically, no abnormal findings, such as hypertrophy or inflammatory changes in the pancreatic islets, were observed in NSY mice at any age. These data suggest that functional changes of insulin secretion in response to glucose from pancreatic beta cells may contribute to the development of non-insulin-dependent diabetes mellitus (NIDDM) in the NSY mouse. Although insulin sensitivity was not measured, fasting hyperinsulinaemia in NSY mice suggests that insulin resistance may also contribute to the pathogenesis of NIDDM. Since these findings are similar to the pathophysiologic features of human NIDDM patients, the NSY mouse is considered to be useful for investigating the pathogenesis and genetic predisposition to NIDDM.

Absence of association of TAP and LMP genes with type 1 (insulin-dependent) diabetes mellitus

Although one of the major genes which cause type 1 (insulin-dependent) diabetes mellitus is located in the class II HLA region in humans, its precise location is still unknown. In order to investigate whether TAP (Transporter associated with Antigen Processing) and LMP (Low Molecular Weight Polypeptide) genes, which are located in the class II HLA region, are HLA-linked diabetogenic genes, the association of TAP1, TAP2 and LMP2 genes with type 1 diabetes was analyzed in the Japanese population. No difference in allele frequencies of these genes was detected between diabetic patients and control subjects. On the other hand, DQA1 and DQB1 genes showed significant association with type 1 diabetes. These data suggest that the diabetogenic gene in the class II HLA region may be located near the DQA1 and DQB1 loci, rather than the TAP and LMP loci.

Polymorphism of HSP70 gene is not associated with type 1 (insulin-dependent) diabetes mellitus in Japanese

Heat shock protein (HSP) 70 is one of the stress-induced proteins and a candidate for islet autoantigen of Type 1 (insulin-dependent) diabetes mellitus. Association of PstI-8.5 kb allele of HSP70 gene with Type 1 diabetes was previously reported in the Caucasian population. Since HSP70 gene is located in the class III region of HLA, the association may be due to the linkage disequilibrium between class II HLA and HSP70 genes. To study whether HSP70 gene is associated with Type 1 diabetes independent of class II HLA genes, we analyzed both HSP70 gene and class II HLA genes in 32 Japanese patients with Type 1 diabetes and 31 control subjects. By Southern blot hybridization with restriction enzyme PstI and HSP70 genomic probe, two allelic bands, 9.0 kb and 8.5 kb, were detected as reported in the Caucasian population. The allele frequencies of 8.5 kb in Type 1 diabetic patients and normal controls were 0.39 and 0.44, respectively. There was no significant difference between the two groups. On the other hand, by PCR-RFLP analysis, DQA1*0301, DQB1*0303 and DQB1*0401 alleles were positively associated with Type 1 diabetes and DQA1*01 was negatively associated with Type 1 diabetes. These data suggest that the polymorphism of HSP70 gene was not associated with Type 1 diabetes in the Japanese population, and that association of PstI-8.5 kb allele with Type 1 diabetes observed in Caucasian population appears to be due to the linkage disequilibrium between this allele and HLA-DR3.

Carrier Detection of Werner′s Syndrome Using a Microsatellite That Exhibits Linkage Disequilibrium with the Werner′s Syndrome Locus

SummaryWerners syndrome (WS) is a rare autosomal recessive disorder, one of the progeroid syndromes, characterized by features of premature aging. The genetic defect in WS is unknown but recently the genetic linkage of WS to several markers on the short arm of chromosome 8 has been reported. Genetic analysis of 25 families with WS demonstrated that D8S339 was the closest marker linked to the gene locus for Werners syndrome (WRN), with a peak lod score of 18.29 at recombination frequency 0.001, and showed a linkage disequilibrium with the WRN locus. We studied two unrelated families with WS using ANK1, D8S339, and D8S360. The mutative haplotype identified through the generations in pedigrees provides a means of carrier detection and presymptomatic diagnosis.

A microsatellite polymorphism in the human insulin receptor gene: a highly informative marker for linkage analysis

To study genetic susceptibility to non-insulin dependent diabetes mellitus (NIDDM), association of insulin receptor gene, a candidate gene for NIDDM, with NIDDM was studied. A microsatellite polymorphism located in intron 2 of the human insulin receptor gene was detected by the polymerase chain reaction and used as a genetic marker. Eight different alleles were observed, indicating highly polymorphic nature of this marker. Although no association of this marker with NIDDM was observed in Japanese subjects, this marker will be useful for linkage studies of insulin receptor gene and genes located close to this gene on chromosome 19.