Variations in the fat-mass and obesity-associated gene (FTO) are associated with the obesity phenotype in many Caucasian populations. This association with the obesity phenotype is not clear in the Japanese. To investigate the relationship between the FTO gene and obesity in the Japanese, we genotyped single nucleotide polymorphisms (SNPs) in the FTO genes from severely obese subjects [n = 927, body mass index (BMI) C 30 kg/m 2 ] and normalweight control subjects (n = 1,527, BMI \ 25 kg/m 2 ).A case-control association analysis revealed that 15 SNPs, including rs9939609 and rs1121980, in a linkage disequilibrium (LD) block of approximately 50 kb demonstrated significant associations with obesity; rs1558902 was most significantly associated with obesity. P value in additive mode was 0.0000041, and odds ratio (OR) adjusted for age and gender was 1.41 [95% confidential interval (CI) = 1. rs1558902 genotype. Thus, the SNPs in the FTO gene were found to be associated with obesity, i.e., severe obesity, in the Japanese.

NOD/Lt mice harboring a hybrid rat insulin-promoter/SV40 large T-antigen gene spontaneously develop beta-cell adenomas. NIT-1 is a pancreatic beta-cell line established from one of these transgenic mice. Immunocytochemical staining of passage 18 cells showed most contained insulin, with less than 5% containing glucagon, and none containing pancreatic polypeptide or somatostatin. Glucagon content radioimmunoassayed in cell extracts was only 0.27% of the insulin content. Two-hour insulin secretion at 16.5 mM glucose was 638 ng/10(6) cells (41% of intracellular content) compared to only 1.3 ng glucagon (32% of intracellular content). Stimulated insulin secretion was consistently observed in response to 11 and 16.5 mM glucose between passages 11 and 19. At passage 19, both theophylline and tolbutamide stimulated insulin secretion at 5.5 mM glucose. Northern-blot analysis confirmed high levels of insulin mRNA but only trace glucagon mRNA and undetectable somatostatin mRNA. Interferon-gamma (IFN-gamma)-induced MHC class I RNA expression was correlated with markedly increased antigen expression at the cell surface. Similarly, a MHC-linked "occult" class I-like antigen detected by Cr release assay only after exposure of standard NOD/Lt islet cells to IFN-gamma was strongly induced by IFN-gamma in NIT-1 cells. Cell surface MHC class II antigen was not constitutively expressed on NIT-1 cells and could not be detected after IFN-gamma incubation, despite demonstration of IFN-gamma-induced Aa, Ab, and Li invariant-chain RNA transcripts. Similarly IFN-gamma induction of intercellular adhesion molecule 1 (Icam-1) transcripts was not accompanied by demonstrable cell surface expression of ICAM-1 antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

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Previous studies have indicated that certain alleles of HLA-DR and -DQ genes were strongly associated with susceptibility and resistance to insulin-dependent diabetes mellitus (IDDM), and the role of DQ molecule in IDDM has been suggested. To further clarify the association of DQ alleles with IDDM, we determined the nucleotide sequences of full-length cDNA from 13 DQA1 alleles and 14 DQB1 alleles. The sequencing analysis revealed sequence polymorphisms outside the hypervariable region of DQ genes. We then analyzed the DQA1 and DQB1 polymorphisms along with that of DRB genes in 86 B-lymphoblastoid cell lines (B-LCLs) from various ethnic groups and in healthy unrelated Japanese and Norwegian individuals. The allelic and haplotypic distributions in each population revealed the characteristic haplotypic formation in the HLA class II region. HLA genes in 139 Japanese and 100 Norwegian IDDM patients were analyzed. DQB1*0301 was negatively associated with IDDM in both ethnic groups, irrespective of associated DRB1 and DQA1 alleles. In DQB1*0302 positive populations, which represented a positive association with IDDM in both ethnic groups, DRB1*0401, *0404, *0802 haplotypes increased in the patients, whereas DRB1*0406 haplotype decreased. Considering about the hierarchy in DRB1 alleles with IDDM susceptibility (DRB1*0401>*0404>*0403 in Norwegian and DRB1*0802>*0403>*0406 in Japanese), the genetic predisposition to IDDM is suggested to be defined by the combination of DR-associated susceptibility and DQ-associated susceptibility and by the DQ-associated resistance which is a dominant genetic trait.

Cytokine effects on permanent cell lines of transformed mouse pancreatic alpha- and beta-cells were compared. The beta-tumor cell 1 (beta TC1) line (from an adenoma created in transgenic mice expressing the SV40 large T-antigen oncogene under control of the rat insulin II promoter) produced insulin predominantly, although small quantities of intracellular glucagon (100:1 insulin to glucagon) were detectable by radioimmunoassay. The alpha TC1 line (from an adenoma created in transgenic mice expressing the SV40 large T-antigen oncogene under control of the rat preproglucagon promoter) produced not only glucagon but also considerable quantities of insulin (4:1 glucagon to insulin) and preproinsulin mRNA. We therefore cloned alpha TC1 cells and obtained 12 glucagon-producing clonal cell lines that did not produce levels of insulin detectable by radioimmunoassay. Analysis by Northern blotting of total RNA from two lines, alpha TC1 clones 6 and 9, confirmed the absence of preproinsulin mRNA. No somatostatin or pancreatic polypeptide was detected by immunohistochemical staining in alpha TC1 clones 6 or 9 or beta TC1 cells. Rat recombinant gamma-interferon (IFN-gamma; 5-250 U/ml) or mouse recombinant interleukin 1 (IL-1; 1-25 U/ml) individually inhibited DNA synthesis in beta TC1 cells after 3 days of treatment. The two cytokines in combination acted synergistically to further depress DNA synthesis and increase cytotoxicity. In contrast, alpha TC1 clone 9 cells were not sensitive to inhibition of DNA synthesis by each cytokine individually, although glucagon synthesis was inhibited. The combination of these cytokines caused marked inhibition of DNA and glucagon syntheses in alpha TC1 clone 9 cells. alpha TC1 clone 9 cells were somewhat more resistant to the cytotoxic action of the combined cytokines than were beta TC1 cells. Incubation with 50 U/ml IFN-gamma induced class II MHC molecules (I-Ab, I-Ad, and I-Ed) and enhanced the constitutive expression of class I molecules (H-2Kb and H-2Kd) on the cell surfaces of beta TC1, uncloned alpha TC1, and alpha TC1 clones 6 and 9. Thus, these cell lines are heterozygous for MHC alleles derived from both parental strains used in the construction of the transgenic mice [C57BL/6J (H-2b) and DBA/2J (H-2d)]. Class II gene transcription induced by IFN-gamma was confirmed in beta TC1 and alpha TC1 clone 9 cells by Northern blot analysis with A alpha-, A beta-, E alpha, and E beta-DNA probes.(ABSTRACT TRUNCATED AT 400 WORDS)

BackgroundRecently, natural mutation of Tyrosine kinase 2 (Tyk2) gene has been shown to determine susceptibility to murine virus-induced diabetes. In addition, a previous human genome-wide study suggested the type 1 diabetes (T1D) susceptibility region to be 19p13, where the human TYK2 gene is located (19p13.2).MethodsPolymorphisms of TYK2 gene at the promoter region and exons were studied among 331 healthy controls, and 302 patients with T1D and 314 with type 2 diabetes (T2D) in the Japanese.FindingsA TYK2 promoter haplotype with multiple genetic polymorphisms, which are in complete linkage disequilibrium, named TYK2 promoter variant, presenting decreased promoter activity, is associated with an increased risk of not only T1D (odds ratio (OR), 2.4; 95% confidence interval (CI), 1.2 to 4.6; P = 0.01), but also T2D (OR, 2.1; 95% CI, 1.1 to 4.1; P = 0.03). The risk is high in patients with T1D associated with flu-like syndrome at diabetes onset and also those without anti-glutamic acid decarboxylase autoantibody.InterpretationThe TYK2 promoter variant is associated with an overall risk for diabetes, serving a good candidate as a virus-induced diabetes susceptibility gene in humans.FundingMinistry of Education, Culture, Sports, Science and Technology and of Health, Labor and Welfare of Japan.

The pancreatic P-and a-cells are developmentally related to each other but reveal diverse gene expression patterns. Among the two important transcription factors for insulin gene expression, IEF1 is present both in a-and p-cells, but PDX-1/IPF1/STF-1/IDX-1, a homeodomain-containing transcription factor, is present in P-cells but not in a-cells. To elucidate the function of PDX-1 in the expression of P-cell-specific genes, we established stable aTCl clone 6 (aTC1.6)-derived transfectants expressing PDX-1 and examined the changes in the gene expression patterns in them. The exogenous expression of PDX-1 in aTCl.6 cells alone could induce islet amyloid polypeptide (IAPP) mRNA expression in the cells but not the expression of insulin, glucokinase, or GLUT2 gene. However, when betacellulin was added to the medium, the PDX-1-expressing aTCl.6 cells, but not the control aTCl.6 cells, came to express insulin and glucokinase mRNAs. This did not occur with other growth factors such as epidermal growth factor, transforming growth factor a, and insulin-like growth factor I. GLUT2 mRNA remained undetectable in the PDX-1-expressing aTCl.6 cells. These observations demonstrate the potency of PDX-1 for the expression of the insulin, glucokinase, and IAPP genes and suggest that certain regulatory factors, which can partially be modified by betacellulin, also contribute to the p-cell specificity of gene expression.