Sequential elevation of autoantibodies to thyroglobulin and glutamic acid decarboxylase in type 1 diabetes.

We have previously reported the high levels of glutamic acid decarboxylase 65 autoantibodies (GAD65A) in patients with type 1 diabetes and autoimmune thyroid disease. Here we describe a 32-year-old Japanese female with a thirteen-year history of type 1 diabetes whose levels of GAD65A were elevated just after the emergence of anti-thyroid autoimmunity. At 19 years of age, she developed diabetic ketoacidosis and was diagnosed with type 1 diabetes. She had GAD65A, insulinoma-associated antigen-2 autoantibodies (IA-2A), and zinc transporter-8 autoantibodies (ZnT8A), but was negative for antibodies to thyroid peroxidase (TPOAb) and thyroglobulin (TGAb) at disease onset. ZnT8A and IA-2A turned negative 2-3 years after the onset, whereas GAD65A were persistently positive at lower level (approximately 40 U/mL). However, just after the emergence of TGAb at disease duration of 12.5 years, GAD65A levels were reelevated up to 5717 U/mL in the absence of ZnT8A and IA-2A. Her thyroid function was normal and TPOAb were consistently negative. She has a HLA-DRB1*03:01/*04:01-DQB1*02:01/*03:02 genotype. Persistent positivity for GAD65A might be associated with increased risk to develop anti-thyroid autoimmunity.

A case of glycogenic hepatopathy developed in a patient with new-onset fulminant type 1 diabetes: the role of image modalities in diagnosing hepatic glycogen deposition including gradient-dual-echo MRI.

Glycogenic hepatopathy (GH) has been reported as a very rare and under recognized complication in long-standing poorly controlled type 1 diabetes (T1D) patients. GH is characterized by transient elevation of liver transaminase and hepatomegaly caused by reversible and excessive glycogen accumulation in hepatocytes. It has been reported that GH is indistinguishable from non-alcoholic fatty liver disease, which is more commonly seen in diabetic patients, even after a history is taken and a physical examination or imaging studies have been performed. GH can only be diagnosed by liver biopsy. We here demonstrate a 21-year-old male patient with new-onset fulminant T1D complicated with diabetic ketoacidosis who subsequently developed GH just after the initiation of insulin treatment. The marked liver dysfunction (serum levels of aspartate aminotransferase 769 IU/L and alanine aminotransferase 1348 IU/L) and hepatomegaly improved spontaneously via glycemic control without any specific treatments thereafter. Moreover, the insulin requirement dramatically decreased from 168 to 80 units per day as GH improved, suggesting a potential role of GH in insulin resistance. GH was diagnosed based on the histological findings of the liver in our case, but we were able to predict GH before the biopsy based on the findings in the gradient-dual-echo magnetic resonance imaging sequence combined with ultrasound and/or computed tomography examinations of the liver.

Clinical and genetic characteristics of autoimmune polyglandular syndrome type 3 variant in the Japanese population.

OBJECTIVE: Type 1 diabetes (T1D) is commonly associated with autoimmune thyroid disease (AITD), and the occurrence of both T1D and AITD in a patient is defined as autoimmune polyglandular syndrome type 3 variant (APS3v). We aimed to clarify the differences in the clinical and genetic characteristics of APS3v patients and T1D patients without AITD [T1D/AITD(-)] in the Japanese population. DESIGN/PATIENTS: Our subjects were 54 APS3v patients and 143 T1D/AITD(-) patients who were consecutively diagnosed at Nagasaki University Hospital from 1983 to the present. RESULTS: A remarkable female predominance, a slow and older age onset of T1D, and a higher prevalence of glutamic acid decarboxylase autoantibodies were observed in APS3v patients compared to T1D/AITD(-) patients. The older onset age of T1D in APS3v patients was associated with a higher proportion of slow-onset T1D. Among the two major susceptible human leukocyte antigen (HLA) class II haplotypes in Japanese T1D, DRB1*0405-DQB1*0401, but not DRB1*0901-DQB1*0303, was associated with APS3v patients. Furthermore, DRB1*0803-DQB1*0601 was not protective in patients with APS3v. The frequencies of the GG genotype in +49G>A and +6230G>A polymorphism in the CTLA4 gene were significantly higher in T1D/AITD(-) patients, but not in APS3v patients, compared to control subjects. CONCLUSIONS: In conclusion, we found notable differences in the clinical and genetic characteristics of APS3v patients and T1D/AITD(-) patients in the Japanese population, and the differences in the clinical characteristics between the two groups may reflect distinct genetic backgrounds including the HLA DRB1-DQB1 haplotypes and CTLA4 gene polymorphisms.

Zinc transporter 8 autoantibodies in fulminant, acute-onset, and slow-onset patients with type 1 diabetes.

BACKGROUND: The aim of this study was to determine the prevalence and role of autoantibodies to zinc transporter 8 (ZnT8A) in three forms (fulminant, acute-onset, and slow-onset) of Japanese patients with type 1 diabetes. METHODS: One-hundred and ninety-six new-onset patients with type 1 diabetes were studied: 85 were fulminant, 81 acute-onset, and 30 slow-onset type 1 diabetes. ZnT8A were determined by radioimmunoassay using a hybrid ZnT8 carboxy-terminal construct (aa268-369) carrying 325Trp and 325Arg. Furthermore, ZnT8A epitopes were analysed using ZnT8 constructs incorporating the known aa325 variants (Trp, Arg, and Gln). RESULTS: ZnT8A were detected in 58% patients with acute-onset and 20% with slow-onset type 1 diabetes (p<0.0005). In contrast, none of sera from fulminant type 1 diabetes were reactive to ZnT8 construct. Conversion of Arg or Trp to Gln at aa325 abolished reactivity in 59% of patients with an age of onset>10 years, which was significantly higher than that in patients≤10 years of age (33%, p<0.05). CONCLUSIONS: These results suggest that ZnT8A are an additional useful marker for acute-onset type 1 diabetes, but not a diagnostic marker for fulminant type 1 diabetes, and ZnT8A epitope recognition is different according to the onset age.

Differences in the humoral autoreactivity to zinc transporter 8 between childhood- and adult-onset type 1 diabetes in Japanese patients.

The aim of this study was to evaluate the humoral autoreactivity to zinc transporter 8 (ZnT8) depending on the clinical phenotype of type 1 diabetes (T1D). ZnT8 autoantibodies (ZnT8A) were determined by radioimmunoassay using carboxy-terminal ZnT8 constructs in 57 childhood-onset, 97 adult-onset, and 85 fulminant T1D. The ZnT8A frequency was higher in childhood-onset patients and decreased with increasing age of onset from 70% to 24% (P(trend)<0.005). None of the patients with fulminant T1D was positive for ZnT8A. There were at least two distinct ZnT8A epitope patterns associated with the aa325-restriction, childhood-onset patients have aa325-nonrestricted response more frequently compared to the adult-onset group (P<0.05). The level of ZnT8A was inversely associated with the copy number of HLA-DR4 allele (P<0.05). These results suggest differences in the humoral autoreactivity to ZnT8 depending on the clinical phenotype, which should provide strategy for autoantibody measurement in subjects to allow early diagnosis of autoimmune T1D.

Trajectories of anti-islet autoantibodies before development of type 1 diabetes in interferon-treated hepatitis C patients. Case reports and a literature review.

Interferon-alpha (IFN-α) is widely used in the treatment of viral hepatitis, however, it is known that IFN-α therapy may induce type 1 diabetes. We report here on two cases of chronic viral hepatitis C who developed autoimmune type 1 diabetes during Peg-IFN-α plus ribavirin (RBV) therapy. Case 1: a 48-year-old male with chronic hepatitis C with chronic thyroiditis. The patient's plasma glucose level was normal and anti-islet autoantibody tests were negative before Peg-IFN-α+RBV therapy. The emergence of glutamic acid decarboxylase 65 autoantibody (GAD65Ab) was observed after five months of treatment. Autoantibodies to insulin and insulinoma-associated antigen-2 (IA-2) also became positive. Eleven months later, thirst and polydipsia occurred with increased fasting plasma glucose level and the patient was diagnosed with type 1A diabetes. Zinc transporter-8 autoantibody (ZnT8Ab) was not detectable at any point. The patient has type 1 diabetes-susceptible HLA-DRB1-DQB1 haplotypes *0405-*0401 and *0901-*0303. Case 2: a 65-year-old male with chronic hepatitis C with type 2 diabetes on insulin treatment. GAD65Ab and IA-2Ab were negative before Peg-IFN-α+RBV therapy, however, nine months later, a single appearance of GAD65Ab was observed. After twelve months, his plasma glucose control worsened rapidly, and he was diagnosed with type 1A diabetes. IA-2Ab and ZnT8Ab were negative throughout the clinical course. His HLA-DRB1-DQB1 haplotypes were *0410-*0402 and *1407-*0503. Both cases showed a unique GAD65Ab epitope (amino acids 360-442). These clinical courses suggest that IFN-α therapy provoked acute islet autoimmunity and onset of type 1 diabetes. Therefore, during IFN-α therapy, patients should be closely monitored for the occurrence of type 1 diabetes.

Emergence of anti-islet autoantibodies in Japanese patients with type 1 diabetes.

Circulating anti-islet autoantibodies in sera are used as a predictive marker for type 1 diabetes (T1D). We here report two Japanese patients with autoimmune thyroid disease complicated with T1D in whom the time course of anti-islet autoantibodies were observed before the clinical onset of diabetes. Case 1: A woman who had developed Graves' disease at age 25 was diagnosed with type 2 diabetes at age 31; six months later, insulin therapy was started. At age 36 she was diagnosed with T1D due to glutamic acid decarboxylase 65 autoantibodies (GAD65Ab)-positive status and decreased C-peptide levels. With stored sera we retrospectively followed her anti-islet autoantibodies. GAD65Ab, zinc transporter 8 autoantibodies (ZnT8Ab) and insulin autoantibodies (IAA) were found to be positive at age 25. IAA soon turned negative, but GAD65Ab and ZnT8Ab remained positive with high levels. Insulinoma-associated antigen-2 autoantibodies (IA-2Ab) emerged 2 years before the initiation of insulin therapy. She has T1D-susceptible HLA-DRB1-DQB1 haplotypes, (*)0405- (*)0401/(*)0802-(*)0302. Case 2: A 49-year-old woman with hypothyroidism due to 19 years' history of atrophic thyroiditis noticed marked thirst, polyuria and weight loss. On admission she was diagnosed as T1D due to GAD65Ab-positive findings and poor C-peptide response to i.v. glucagon. Retrospective serology revealed the emergence of GAD65Ab and IAA just after the clinical onset. IA-2Ab and ZnT8Ab never developed. She has T1D-susceptible and -resistant HLADRB1- DQB1 haplotypes, (*)0901-(*)0303/(*)1502-(*)0601. The autoantibody profile and the mode of diabetes onset in the two cases were remarkably different. These cases imply that anti-islet autoantibodies do not always precede the onset of T1D.

Autoantibodies to insulin, insulinoma-associated antigen-2, and zinc transporter 8 improve the prediction of early insulin requirement in adult-onset autoimmune diabetes.

OBJECTIVE: The aim of this study was to identify the predictive marker for early insulin requirement in adult-onset autoimmune diabetes in the Japanese populations. DESIGN/PATIENTS: We analyzed insulin autoantibodies (IAA), insulinoma-associated antigen-2 (IA-2) autoantibodies (IA-2icA), and zinc transporter 8 (ZnT8) autoantibodies (ZnT8A) by radioimmunoassay in 47 Japanese patients with adult-onset autoimmune diabetes who were identified by native GAD autoantibody (nGADA) screening of approximately 3000 non-insulin-requiring diabetes patients and 302 nGADA-negative type 2 diabetes patients. Furthermore, GAD65 autoantibody-specific epitopes were also analyzed using GAD65/GAD67 chimeric constructs. RESULTS: The prevalence of IAA, IA-2icA, and ZnT8A in nGADA-positive patients was 26, 15, and 19%, respectively, which was significantly higher than that in nGADA-negative type 2 diabetes (2, 2, and 2%; P < 0.0001). Among nGADA-positive patients, 38% had one or more of IAA, IA-2icA, or ZnT8A, and 15% had two or more of these autoantibodies, compared with none of the nGADA-negative patients (P < 0.0001). Thirty-six percent of nGADA-positive patients subsequently required insulin therapy; and high nGADA titer (log-rank P = 0.003), middle epitope recognition of GAD65A (P = 0.002), and the presence of one or more of IAA, IA-2icA, or ZnT8A (P = 0.002) at diagnosis marked the risk for early requirement of insulin therapy. Multivariate logistic regression analysis showed the multiple islet autoantibodies to be independently associated with the risk for insulin requirement (odds ratio = 13.77; 95% confidence interval, 2.77-68.45; P = 0.001). CONCLUSIONS: These results indicate that the determination of IAA, IA-2icA, and ZnT8A improves the prediction of a future insulin insufficiency in adult-onset autoimmune diabetes, which appears to be superior to GADA titer and GAD65A-specific epitopes.

Induction of human adiponectin gene transcription by telmisartan, angiotensin receptor blocker, independently on PPAR-gamma activation.

Adiponectin, an adipose tissue-specific plasma protein, has been shown to ameliorate insulin resistance and inhibit the process of atherosclerosis. Recently, several reports have stated that angiotensin type 1 receptor blockers (ARBs), increase adiponectin plasma level, and ameliorate insulin resistance. Telmisartan, a subclass of ARBs, has been shown to be a partial agonist of the peroxisome proliferator-activated receptor (PPAR)-gamma, and to increase the plasma adiponectin level. However, the transcriptional regulation of the human adiponectin gene by telmisartan has not been determined yet. To elucidate the effect of telmisartan on adiponectin, the stimulatory regulation of human adiponectin gene by telmisartan was investigated in 3T3-L1 adipocytes, utilizing adenovirus-mediated luciferase reporter gene-transferring technique. This study indicates that telmisartan may stimulate adiponectin transcription independent of PPAR-gamma.

Identification of the promoter region required for human adiponectin gene transcription: Association with CCAAT/enhancer binding protein-beta and tumor necrosis factor-alpha.

Adiponectin, an adipose tissue-specific plasma protein, is involved in insulin sensitizing and has anti-atherosclerotic properties. Plasma levels of adiponectin are decreased in obese individuals and patients with type 2 diabetes with insulin resistance. Tumor necrosis factor-alpha (TNF-alpha) decreases the expression of adiponectin in adipocytes. The aims of the present study were: (1) to identify the promoter region responsible for basal transcription of the human adiponectin gene, and (2) to investigate the mechanism by which adiponectin was regulated by TNF-alpha. The human adiponectin promoter (2.1kb) was isolated and used for luciferase reporter analysis by transient transfection into 3T3-L1 adipocytes. Deletion analysis demonstrated that the promoter region from -676 to +41 was sufficient for basal transcriptional activity. Mutation analysis of putative response elements for sterol regulatory element binding protein (SREBP) (-431 to -423) and CCAAT/enhancer binding protein (C/EBP) (-230 to -224) showed that both elements were required for basal promoter activity. Adiponectin transcription was increased 3-fold in cells that over-expressed constitutively active C/EBP-beta. Electrophoretic mobility shift assay, using nuclear extract from 3T3-L1 cells and the -258 to -199 region as a probe, demonstrated specific DNA-protein binding, which was abolished by TNF-alpha treatment. The present data indicate that the putative response elements for SREBP and C/EBP are required for human adiponectin promoter activity, and that suppression by TNF-alpha may, at least in part, be associated with inactivation of C/EBP-beta.

Association between IL-18 gene promoter polymorphisms and CTLA-4 gene 49A/G polymorphism in Japanese patients with type 1 diabetes.

Interleukin-18 (IL-18) is a potent proinflammatory cytokine which is strongly associated with the development of diabetes in NOD mice. To test the putative involvement of IL-18 gene polymorphism in predisposition to human type 1 diabetes, the SNPs at position -607 (C/A) and -137 (G/C) in the promoter region of IL-18 gene were analyzed by sequence-specific PCR in 116 patients with type 1 diabetes and 114 normal controls. A linkage disequilibrium found only three of the four possible haplotypes defined by these SNPs. The distribution of the IL-18 gene genotypes at position -607 was significantly different between patients with type 1 diabetes and normal controls (P=0.023). Furthermore, there was a significant increase in haplotype 1 (-607C/-137G) in the patients compared with controls (P=0.006). The association study of the susceptible CTLA-4 genotype (GG at nucleotide position 49 in exon 1) or HLA-DR4-DQB1*0401 and type 1 diabetes showed that the predisposing IL-18 gene haplotype modulates the risk on CTLA-4 GG genotype, but not on HLA-DR4-DQB1*0401 haplotype. Among subjects carrying the CTLA-4 GG genotype, the frequency of IL-18 haplotype 1 in patients with type 1 diabetes was significantly higher than that in controls (91% vs. 71%, P=0.012). However, IL-18 haplotype 1 was not frequent in patients who do not exhibit the CTLA-4 high-risk genotype. These results suggest that the IL-18 gene polymorphism is associated with a type 1 diabetes susceptibility, and there might be a gene-gene interaction between IL-18 gene with susceptible CTLA-4 gene.

Stromal cell-derived factor-1 chemokine gene variant in patients with type 1 diabetes and autoimmune thyroid disease.

Type 1 diabetes is a heterogenous autoimmune disease and is frequently associated with other organ-specific autoimmune diseases, including autoimmune thyroid disease (AITD). Type 1 diabetic patients with AITD are known to have clinical and immunological features distinct from patients without AITD. This study investigated whether stromal cell-derived factor (SDF)-1 gene polymorphism is associated with susceptibility to type 1 diabetes and AITD. SDF-1 is a powerful chemokine that upregulates T-cell migration and activation, and the gene for SDF-1 is located near type 1 diabetes susceptibility locus IDDM10. The SDF1-3'A variant (801 G to A in the 3'-untranslated region) was determined by the PCR-RFLP technique in 54 type 1 diabetic patients with AITD, 75 type 1 diabetic patients without AITD, 137 nondiabetic patients with AITD, and 106 healthy subjects in a case-control study. No significant differences on the allele and genotype frequencies of the SDF1 gene polymorphism were found, not only in type 1 diabetic patients with AITD compared with normal controls but also between nondiabetic patients with AITD and healthy control subjects. These results suggest that the SDF1-3'A variant is not associated with genetic susceptibility to type 1 diabetic patients and AITD.

Interleukin-10 gene promoter region polymorphisms in patients with type 1 diabetes and autoimmune thyroid disease.

Type 1 diabetes is a heterogeneous autoimmune disease and is frequently associated with other organ-specific autoimmune diseases, including autoimmune thyroid disease (AITD). Type 1 diabetic patients with AITD are known to show distinct clinical and immunological features from patients without AITD. This study investigated whether interleukin-10 (IL-10) gene promoter region polymorphisms are associated with susceptibility to type 1 diabetes and AITD. The frequency of -1082G/A, -819C/T, and -592C/A polymorphisms was analyzed in 54 type 1 diabetic patients with AITD, 74 type 1 diabetic patients without AITD, 124 nondiabetic patients with AITD, and 107 healthy subjects in a case-control study. No significant differences on the allele and genotype frequencies of three polymorphisms were found not only in type 1 diabetic patients with AITD compared with normal controls, but also between nondiabetic patients with AITD and healthy controls. The distribution of IL-10 gene haplotypes was also similar between both patient groups and normal controls. These results suggest that IL-10 gene promoter region polymorphisms are not associated with genetic susceptibility to type 1 diabetes and AITD.

Association of interleukin-18 gene promoter polymorphisms in type 1 diabetes and autoimmune thyroid disease.

Type 1 diabetes is a heterogeneous autoimmune disease and is often associated with other organ-specific autoimmune diseases, including autoimmune thyroid disease (AITD). IL-18 is a potent proinflammatory cytokine capable of inducing IFN-gamma production that is associated with the development of type 1 diabetes and AITD. The gene for IL-18 is located near Idd2 and has been reported to be associated with a susceptibility to type 1 diabetes. To test the putative involvement of IL-18 gene polymorphism in predisposition to type 1 diabetes and AITD, we conducted a case-control study in Japanese population. The SNPs at position -607 (C/A) and -137 (G/C) in the promoter region of the IL-18 gene were analyzed by sequence-specific PCR in 74 nondiabetic patients with AITD, 47 type 1 diabetic patients with AITD, and 114 normal controls. There was no significant increase in the genotype and allele frequencies not only in nondiabetic patients with AITD compared with normal controls, but also in type 1 diabetic patients with AITD compared with normal controls. The distribution of IL-18 gene haplotypes was also similar between both patient groups and normal controls. These results suggest that polymorphisms of the IL-18 gene are not associated with a susceptibility to AITD and type 1 diabetes coexistent with AITD in Japanese population.

Epitope analysis of GAD65 autoantibodies in Japanese patients with autoimmune diabetes.

Type 1 diabetes is an organ-specific autoimmune disease characterized by T cell-mediated destruction of pancreatic beta cells. In Japanese population, the incidence of type 1 diabetes in children is very low compared to European countries. However, there are more patients with type 1 diabetes in adults, including latent autoimmune diabetes in adults (LADA). The circulating autoantibodies to multiple islet autoantigens including GAD, insulin, and IA-2 are the important immunological features of type 1 diabetes. The prevalences of anti-islet autoantibodies in patients with Japanese type 1 diabetes are 60-70% for GAD autoantibodies, 45-50% for insulin autoantibodies (IAA), and 60-65% for IA-2 autoantibodies at disease onset, which are similar to those reported in Caucasian patients. With combinatorial analysis of these autoantibodies, 90% of patients express at least one of these autoantibodies and are classified as type 1A diabetes. Although the majority of patients with type 1 diabetes are young, lean, and ketosis-prone, there are a number of patients with type 1 diabetes initially diagnosed as having type 2 diabetes at disease onset called LADA. These patients with LADA often progress toward an insulin-deficient state within several years after diagnosis. High levels of GAD autoantibodies have a high predictive value for future insulin deficiency in LADA. Further, epitope analysis of GAD65 autoantibodies may be helpful to predict future insulin dependency in LADA patients. In conclusion, Japanese patients with type 1 diabetes are clinically heterogeneous and the determination of immunological features are helpful to clarify the characteristics of the Japanese type 1 diabetic syndrome.

Intracerebroventricular administration of insulin and glucose inhibits the anorectic action of leptin in rats.

Obese individuals with glucose intolerance present with high serum levels of glucose, insulin, and leptin. These substances are potent inhibitors of feeding in the brain. Obese subjects still present with over-feeding despite elevation of the above factors. To elucidate the mechanism of this paradox, the effects of insulin and glucose on the anorectic action of leptin in the hypothalamus were examined. Adult male Sprague-Dawley rats (weighing 285-320 g) were pretreated with intracerebroventricular injection of insulin, glucose, or saline, followed by leptin (7.5 microg) or phosphate-buffered saline (PBS) injection into the third cerebral ventricle (icv). The cumulative food intakes were measured 24 hr after leptin icv. The tyrosine phosphorylation of signal transducer and activator transcription factor 3 (STAT3) in the hypothalamus was determined by Western blotting. In rats pretreated with saline and stimulated with leptin (saline/LEPTIN group), food intake diminished to about 50% of that of the saline/PBS group (P < 0.005). Food intake in the insulin/LEPTIN group was significantly higher compared with the saline/LEPTIN group (P < 0.005) and reached the level seen in the saline/PBS group. Similar data were obtained in glucose pretreatment experiments. Insulin and glucose icv resulted in reduction of leptin-induced STAT3 tyrosine phosphorylation compared with saline. Infusion of insulin and glucose icv did not alter peripheral blood glucose levels in all groups. High insulin or glucose levels in the brain could result in leptin resistance as manifested by food intake, which is probably due to the attenuation of STAT3 phosphorylation downstream the leptin receptor.

Stromal-cell derived factor-1 chemokine gene variant is associated with type 1 diabetes age at onset in Japanese population.

Stromal-cell derived factor-1 (SDF-1) is a powerful chemokine that upregulates T-cell migration and activation. The gene for SDF-1 is located near type 1 diabetes susceptibility locus IDDM10, suggesting a contribution by SDF-1 to the induction of diabetes. Recently the role of SDF-1 gene polymorphism in the clinical presentation of type 1 diabetes in French population has been reported. To test the putative involvement of SDF-1 gene polymorphism in predisposition to or clinical heterogeneity of type 1 diabetes in Japanese population, we conducted the case-control study. The SDF1-3'A variant (801 G to A in the 3'-untranslated region) was determined by the polymerase chain reaction-restriction fragment length polymorphism technique in 184 patients with abrupt-onset type 1 diabetes and 106 healthy control subjects. No significant difference in allele and genotype frequencies of SDF1-3'A variant was found between type 1 diabetic patients and healthy controls. However, the SDF1-3'A variant was strongly associated with early-onset diabetes in a recessive model (AA versus AG + GG, p = 0.017). The mean age-at-onset in patients carrying SDF1-3'AA genotype was significantly younger than that in patients with SDF1-3' AG or GG genotype (p = 0.028). The frequencies of SDF1-3' A variant were significantly increased in HLA-DR4/9 patients compared with non-DR4/9 patients (p = 0.008). These results suggest that the SDF-1 gene polymorphism is associated with the age-at-onset of type 1 diabetes in Japanese population.

Insulin attenuates leptin-induced STAT3 tyrosine-phosphorylation in a hepatoma cell line.

Leptin, the 16 kDa protein product of the ob gene, is secreted by adipocytes. The long form leptin receptor (ObRb) is expressed at high levels in the hypothalamus, and regulates appetite and energy expenditure. The fact that serum concentration of leptin is correlated with body mass index (BMI) suggests reduced sensitivity to leptin. Even though hyperinsulinemia and hyperleptinemia could coexist in obese humans, little is known about the interaction of insulin and leptin. In this study, we examined the effect of insulin on leptin signaling using Huh 7 cells transiently transfected with ObRb cDNA. Insulin inhibits leptin-induced STAT3 phosphorylation in a time- and dose-dependent manner without affecting Janus tyrosine kinases (JAKs) JAK2 phosphorylation. Okadaic acid prevents the inhibitory effect of insulin on leptin-induced STAT3 activation.

Vanadate enhances leptin-induced activation of JAK/STAT pathway in CHO cells.

Leptin, the product of the ob gene, is an adipocyte-derived hormone that plays a key role in the control of food intake and energy expenditure. Leptin acts through receptors that belong to a member of the class I cytokine receptor family. It has been demonstrated that the SH2 domain-containing tyrosine phosphatase 2 (SHP-2) negatively regulates STAT3-mediated transcriptional activation through long form leptin receptor (OBRb). Vanadate has been shown to be a potent and selective inhibitor of PTPase activity in vitro. In this study, we have demonstrated that vanadate increases leptin-induced JAK2 and STAT3 phosphorylation in CHO cells expressing OBRb. The increased leptin-dependent luciferase activity of SOCS3 gene was also seen in vanadate-treated cell. Furthermore, vanadate reversed the inhibitory effects of SOCS3 on leptin-induced STAT3 phosphorylation. The present findings suggest that PTP inhibitors including vanadate and vanadate-derived compounds could be used as a therapeutic agent in the treatment of obesity.

Ethanol inhibits leptin-induced STAT3 activation in Huh7 cells.

Leptin, an adipocyte-derived hormone, regulates food intake and energy expenditure in the hypothalamus via its receptor, member of the class I cytokine receptor family. Leptin resistance has been observed in rodents and in humans. However, the mechanisms could not be explained in most cases of human obesity, except for rare cases with mutations in the leptin receptor. Recent reports demonstrated that ethanol inhibited the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway activated by some members of the class I cytokine receptor family. In this study, we examined the effects of ethanol on the leptin-induced JAK/STAT signaling pathway using human hepatoma cell lines transiently expressing long form of the leptin receptor. A 30 min pretreatment with ethanol dose-dependently inhibited the leptin-induced STAT3 phosphorylation. Furthermore, to determine the time course of ethanol inhibitory effects, the cells were incubated in 10 mM ethanol for various times. Partial inhibition of leptin-induced STAT3 activation was seen after 1 min of treatment with ethanol and completely inhibited after 30 min pretreatment. SB 202190, a p38 mitogen-activated protein kinase (MAPK) inhibitor, partly prevented this inhibition by ethanol of leptin-induced STAT3 activation. These findings suggest that ethanol time- and dose-dependently inhibits the leptin action, in part via p38 MAPK.