Shinsuke Noso

Prevention and Treatment of Obesity, Insulin Resistance, and Diabetes by Bile Acid–Binding Resin

Bile acid–binding resins, such as cholestyramine and colestimide, have been clinically used as cholesterol-lowering agents. These agents bind bile acids in the intestine and reduce enterohepatic circulation of bile acids, leading to accelerated conversion of cholesterol to bile acids. A significant improvement in glycemic control was reported in patients with type 2 diabetes whose hyperlipidemia was treated with bile acid–binding resins. To confirm the effect of such drugs on glucose metabolism and to investigate the underlying mechanisms, an animal model of type 2 diabetes was given a high-fat diet with and without colestimide. Diet-induced obesity and fatty liver were markedly ameliorated by colestimide without decreasing the food intake. Hyperglycemia, insulin resistance, and insulin response to glucose, as well as dyslipidemia, were markedly and significantly ameliorated by the treatment. Gene expression of the liver indicated reduced expression of small heterodimer partner, a pleiotropic regulator of diverse metabolic pathways, as well as genes for both fatty acid synthesis and gluconeogenesis, by treatment with colestimide. This study provides a molecular basis for a link between bile acids and glucose metabolism and suggests the bile acid metabolism pathway as a novel therapeutic target for the treatment of obesity, insulin resistance, and type 2 diabetes.

Age-related association of MHC class I chain-related gene A (MICA) with type 1 (insulin-dependent) diabetes mellitus

To assess the contribution of the HLA class I region to susceptibility to and heterogeneity of type 1 diabetes, we investigated the association of polymorphism of MHC class I chain-related gene A (MICA) with age-at-onset as well as susceptibility to type 1 diabetes. One hundred one Japanese patients and 110 healthy control subjects were studied. The frequency of A4 allele was significantly higher and that of A6 allele was significantly lower in patients than in control subjects. The frequency of A5.1 allele was highest in early-onset patients (23.0%), intermediate in intermediate-onset patients (9.2%) and lowest in late-onset patients (7.7%) (trend chi-squared test, p = 0.0098). A5. 1 allele was strongly associated with HLA-B7 and Cw7, suggesting that MICA*A5.1-B7-Cw7 haplotype contains a gene responsible for age-at-onset. A4 allele was associated with a susceptible haplotype, DR4-DQB1*0401, and A6 allele was associated with a protective haplotype, DR2-DQB1*0601, suggesting that the association of MICA with type 1 diabetes susceptibility may be due to linkage disequilibrium with class II haplotypes. These data suggest that MICA gene is associated with age-at-onset and that a gene (or genes) responsible for age-at-onset of type 1 diabetes is located in the HLA class I region, probably near the region of MICA-B-C.

Development of autoimmune diabetes in glutamic acid decarboxylase 65 (GAD65) knockout NOD mice

Aims/hypothesisType 1 diabetes mellitus, a T-cell-mediated autoimmune disease, results from the selective destruction of insulin-producing pancreatic beta cells. Autoantibodies against beta-cell components are used clinically as sensitive markers of this disease; however, their physiological role has not been clear. To investigate the role of glutamic acid decarboxylase 65 (GAD65) in the development of the Type 1 diabetes of non-obese diabetic (NOD) mice, we analysed and characterised NOD mice with targeted disruption of the GAD65 gene.MethodsGAD65-deficient mice were previously established. After backcrossing the knockout mutation onto the NOD genetic background for up to eight generations, female littermates of the three resulting genotypes were produced by intercrossing: GAD65 +/+ (n=23), GAD65 +/− (n=62), and GAD65 −/− (n=31).ResultsThe cumulative incidence of autoimmune diabetes showed no significant difference among the three groups in longitudinal studies using the Kaplan-Meier method. Islet morphology showed that the progression of islet infiltration did not differ significantly between the three groups.Conclusion/interpretationThe cumulative incidence of autoimmune diabetes was not influenced by the GAD65 deficiency. These data suggest that GAD65 is not a major regulatory target of beta-cell autoimmunity in NOD mice.

Genetics of Type 1 Diabetes: Similarities and Differences between Asian and Caucasian Populations

Abstract:  Transracial studies are a powerful tool for genetic association studies of multifactorial diseases, such as type 1 diabetes. We therefore studied the association of candidate genes, HLA, INS, CTLA4, PTPN22, and SUMO4, with type 1 diabetes in Asian populations in comparison with Caucasian populations. Class II HLA was strongly associated with type 1 diabetes in both Asian and Caucasian populations, but alleles associated with type 1 diabetes are different among different ethnic groups due to difference in allele distribution in general populations. INS was associated with type 1 diabetes in both Japanese and Caucasian populations, but frequency of disease‐associated haplotype was markedly higher in Japanese than in Caucasian populations. CTLA4 association was reported for both type 1 diabetes and autoimmune thyroid diseases (AITD) in Caucasian populations, but the association with type 1 diabetes was concentrated in a subset of patients with AITD in Japanese. A variant (R620W) of PTPN22 was consistently associated with type 1 diabetes in Caucasian populations, but the variant was absent in Asian populations including Japanese. M55V variant of SUMO4 was significantly associated with type 1 diabetes in Asians, but genetic heterogeneity between Asian and Caucasian populations was suggested. These data indicate the importance of transracial studies with a large number of samples in each ethnic group in genetic dissection of type 1 diabetes.

Association of plasma fibrinogen level and blood pressure with diabetic retinopathy, and renal complications associated with proliferative diabetic retinopathy, in Type 2 diabetes mellitus

Aim To clarify the association of several clinical parameters, including plasma fibrinogen level, with diabetic retinopathy in patients with Type 2 diabetes mellitus (DM).

Low programmed cell death‐1 (PD‐1) expression in peripheral CD4+ T cells in Japanese patients with autoimmune type 1 diabetes

Programmed cell death‐1 (PD‐1) is a co‐stimulatory molecule that inhibits T cell proliferation. We aimed to clarify PD‐1 expression in CD4+ T cells and the association between PD‐1 expression and the 7785C/T polymorphism of PDCD1, with a focus on the two subtypes of type 1 diabetes, type 1A diabetes (T1AD) and fulminant type 1 diabetes (FT1D), in the Japanese population. We examined 22 patients with T1AD, 15 with FT1D, 19 with type 2 diabetes (T2D) and 29 healthy control (HC) subjects. Fluorescence‐activated cell sorting (FACS) and real‐time PCR were utilized to analyse PD‐1 expression quantitatively. Genotyping of 7785C/T in PDCD1 was performed using the TaqMan method in a total of 63 subjects (21 with T1AD, 15 with FT1D and 27 HC). FACS revealed a significant reduction in PD‐1 expression in CD4+ T cells in patients with T1AD (mean: 4·2 vs. 6·0% in FT1D, P = 0·0450; vs. 5·8% in T2D, P = 0·0098; vs. 6·0% in HC, P = 0·0018). PD‐1 mRNA expression in CD4+ T cells was also significantly lower in patients with T1AD than in the HC subjects. Of the 63 subjects, PD‐1 expression was significantly lower in individuals with the 7785C/C genotype than in those with the C/T and T/T genotypes (mean: 4·1 vs. 5·9%, P = 0·0016). Our results indicate that lower PD‐1 expression in CD4+ T‐cells might contribute to the development of T1AD through T cell activation.

Genetic Basis of Type 1 Diabetes: Similarities and Differences between East and West

Type 1 diabetes is a multifactorial disease caused by a complex interaction of genetic and environmental factors. The genetic factors involved consist of multiple susceptibility genes, at least five of which, HLA, INS, CTLA4, PTPN22 and IL2RA/CD25, have been shown to be associated with type 1 diabetes in Caucasian (Western) populations, as has recently been confirmed by genome-wide association studies. It has been proposed, however, that the contribution of these genes to type 1 diabetes susceptibility may be different in Asian (Eastern) populations. HLA and INS genes are consistently associated with type 1 diabetes in both Caucasian and Asian populations, but apparent differences in disease-associated alleles and haplotypes are observed between Japanese and Caucasian subjects. The association of CTLA4 with type 1 diabetes is concentrated in a subset of patients with autoimmune thyroid disease (AITD) in both Japanese and Caucasian populations, while the association of PTPN22 with type 1 diabetes in Japanese and most Asian populations is not as clear as in Caucasians. IL2RA/CD25 genes seem to be similarly distributed in type 1 diabetes patients in the two populations, whereas genetic heterogeneity may exist regarding SUMO4, with an association of the M55V variant with type 1 diabetes observed in Asians, but not in Caucasians. Genome-wide association studies (GWA) are largely outstanding for Asian populations but they are now underway in Japan. This review reports on the discovered similarities and differences in susceptibility genes for type 1 diabetes between East and West and discusses the most recent observations made by the involved investigators.

Insulin Transactivator MafA Regulates Intrathymic Expression of Insulin and Affects Susceptibility to Type 1 Diabetes

OBJECTIVE Tissue-specific self-antigens are ectopically expressed within the thymus and play an important role in the induction of central tolerance. Insulin is expressed in both pancreatic islets and the thymus and is considered to be the primary antigen for type 1 diabetes. Here, we report the role of the insulin transactivator MafA in the expression of insulin in the thymus and susceptibility to type 1 diabetes. RESEARCH DESIGN AND METHODS The expression profiles of transcriptional factors (Pdx1, NeuroD, Mafa, and Aire) in pancreatic islets and the thymus were examined in nonobese diabetic (NOD) and control mice. Thymic Ins2 expression and serum autoantibodies were examined in Mafa knockout mice. Luciferase reporter assay was performed for newly identified polymorphisms of mouse Mafa and human MAFA. A case-control study was applied for human MAFA polymorphisms. RESULTS Mafa, Ins2, and Aire expression was detected in the thymus. Mafa expression was lower in NOD thymus than in the control and was correlated with Ins2 expression. Targeted disruption of MafA reduced thymic Ins2 expression and induced autoantibodies against pancreatic islets. Functional polymorphisms of MafA were newly identified in NOD mice and humans, and polymorphisms of human MAFA were associated with susceptibility to type 1 diabetes but not to autoimmune thyroid disease. CONCLUSIONS These data indicate that functional polymorphisms of MafA are associated with reduced expression of insulin in the thymus and susceptibility to type 1 diabetes in the NOD mouse as well as human type 1 diabetes.

Allelic variation in class I K gene as candidate for a second component of MHC-linked susceptibility to Type 1 diabetes in non-obese diabetic mice

Aims/hypothesisRecent studies have revealed that MHC-linked susceptibility to Type 1 diabetes is determined by multiple components. In the non-obese diabetic (NOD) mouse, a second component (Idd16) has been mapped to a region adjacent to, but distinct from Idd1 in the class II region. In this study, we investigated the class I K gene as a candidate gene for Idd16.MethodsWe determined the genomic sequences of the class I K gene as well as the reactivity of K molecules with monoclonal antibodies in the NOD mouse, the Cataract Shionogi (CTS) mouse, and the NOD.CTS-H-2 congenic strain, which possesses a resistance allele to Type 1 diabetes at the Idd16 on the NOD genetic background genes.ResultsWhile the K sequence of the NOD mouse was identical to that of Kd type, ten nucleotide substitutions were identified in the CTS mouse compared with the NOD mouse. Of these, three were in exon 4, giving two amino acid substitutions, which were identical to those seen in KK type. These characteristics were retained in the NOD.CTS-H-2 congenic strain, which had a lower incidence and delayed onset of Type 1 diabetes owing to a resistance allele at Idd16. Lymphocytes from NOD.CTS-H2 congenic mice reacted with anti-Kd and anti-Kk monoclonal antibodies, reflecting the unique sequence of the K gene. The nucleotide sequence of the K gene in the non-obese non-diabetic (NON) mouse was also unique, consisting of a combination of Kk- and Kb-like sequences.Conclusions/interpretationThese data suggest that H2-K is unique in CTS and NON mice, and that allelic variation of the class I K gene may be responsible for Idd16.

High-level expression of interleukin-4 following electroporation-mediated gene transfer accelerates Type 1 diabetes in NOD mice

Nonobese diabetic (NOD) mice develop T cell-dependent autoimmune disease. Administration of interleukin-4 (IL-4), one of the T helper 2 (Th2) cytokines, is reported to prevent either insulitis or diabetes or both in NOD mice. We examined the effect of transferring an IL-4-expressing plasmid vector into muscle by in vivo electroporation on the progression of diabetes in NOD mice. Plasmid DNA expressing murine IL-4 (pCAGGS-IL-4) was introduced into the muscles of 4- and 6-week-old female NOD mice using an in vivo electroporation technique we developed previously. The serum IL-4 levels reached 2000-8000 pg/ml 3 days after the delivery of pCAGGS-IL-4 and remained detectable (>5 pg/ml) for over 4 weeks. In contrast to the previous reports, 88% of the mice treated with pCAGGS-IL-4 developed overt diabetes by 30 weeks of age, while only 25% of nontreated mice and 19% of the mice treated with control pCAGGS developed overt diabetes by then (p<0.01). Therefore, highly expressed IL-4 introduced by in vivo electroporation may have caused a Th1 shift, resulting in the promotion of diabetes in NOD mice. The high serum concentration of cytokines attained by our method is likely to unveil previously unknown cytokine functions.