Toshiro Usa

Thyroid function is associated with carotid intima-media thickness in euthyroid subjects.

To investigate the relationship between thyroid function and carotid intima-media thickness (CIMT) in a relatively large general population with euthyroid status we initially enrolled 1772 Japanese adults (421 men and 1351 women) who participated in a medical screening program for the general population over 40 years old. To evaluate only euthyroid subjects without vascular diseases and/or its major risk factors, 1129 were excluded and 643 participants (175 men and 468 women) were included for further analysis. Simple and multivariate linear regression analyses were performed to evaluate free thyroxine (fT4) and thyroid-stimulating hormone (TSH) levels and other existing parameters, including carotid intima-media thickness. By multivariate linear regression analysis adjusted for age and sex, free thyroxine was significantly correlated with triglycerides (beta=0.07, p=0.015), carotid intima-media thickness (beta=-0.091, p=0.049), and thyroid-stimulating hormone (beta=-0.091, p=0.003). Thyroid-stimulating hormone was significantly correlated with high-density lipoprotein cholesterol (HDL-C) (beta=-0.001, p=0.015), HbA(1c) (beta=0.038, p=0.045), carotid intima-media thickness (beta=0.27, p=0.001), and free thyroxine (beta=-0.15, p=0.003). When adjusted for confounding factors, free thyroxine was significantly correlated only with carotid intima-media thickness (beta=-0.13, p=0.043) and thyroid-stimulating hormone was significantly correlated with HDL-C (beta=-0.001, p<0.001), HbA(1c) (beta=0.04, p=0.021), and carotid intima-media thickness (beta=0.29, p=0.001). We have demonstrated that carotid intima-media thickness is independently associated with thyroid function within the normal reference range, which suggests an increased cardiovascular risk in subjects with low normal thyroid function.

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.

CD4+ T cell-mediated cytotoxicity toward thyrocytes: the importance of Fas/Fas ligand interaction inducing apoptosis of thyrocytes and the inhibitory effect of thyroid-stimulating hormone.

The accumulation of activated CD4+ T cells and antigen (Ag)-dependent cellular interactions between thyrocytes and CD4+ T cells have been determined in thyroid gland from patients with Graves’ disease. The Fas/Fas ligand (FasL) interaction between antigen-presenting cells and T cells regulates the apoptosis of the former cells triggered by the latter cells. The inhibition of Fas-mediated apoptosis in thyrocytes could be a underlying mechanism of hyperplasia of thyrocytes in patients with Graves’ disease. We investigated the potential role of Fas/FasL interaction between thyrocytes and CD4+ T cells in the induction of Fas-mediated apoptosis of the former cells induced by the latter cells. The presence of only a few specific T cells responsive to a putative autoantigen has hampered the investigation of specific T cell activation toward antigen-presenting cells (APCs). Therefore, we used a superantigen, staphylococcal enterotoxin B (SEB), to examine specific T cell activation toward thyrocytes in vitro since it stimulates a large proportion of T cells with particular Vβ elements. Spontaneous apoptosis of thyrocytes in culture was not found even in the presence of various kinds of cytokines. In contrast, a clear induction of Fas-mediated apoptosis by anti-Fas IgM was determined in interferon-γ (IFN-γ)-stimulated thyrocytes. In addition, a significant cytotoxicity of purified CD4+ T cells toward IFN-γ-stimulated thyrocytes in the presence of SEB was induced, and the addition of anti-HLA-DR and -DQ monoclonal antibodies (mAbs) or blockade of the Fas/FasL interaction reduced this cytotoxicity. FasL expression of CD4+ T cells cocultured with IFN-γ-stimulated thyrocytes in the presence of SEB was clearly induced. Furthermore, the addition of mAbs against CD54 and CD58 inhibited both cytotoxicity and FasL expression of CD4+ T cells. The cytotoxicity of CD4+ T cells toward IFN-γ-stimulated, SEB-pulsed thyrocytes was markedly inhibited when we used thyrocytes cultured with IFN-γ in the presence of thyroid-stimulating hormone (TSH) as target cells. Our results suggest that 1) CD4+ T cells were activated by thyrocytes expressing MHC class II molecules in an SEB-dependent manner and then expressed FasL. 2) These activated FasL+ CD4+ T cells killed thyrocytes by interacting with Fas on thyrocytes and FasL on activated CD4+ T cells. The presence of costimulating molecules such as CD54 and CD58 on thyrocytes was also necessary to generate activated FasL+ CD4+ T cells. 3) Since the actions of thyroid stimulating antibody (TSAb) toward thyrocytes are similar to those of TSH, one goitrogenic activity of TSAb may, in part, be due to the inhibitory effect on Fas-mediated apoptosis of thyrocytes triggered by activated CD4+ T cells.

Metabolic cardiovascular disease risk factors and their clustering in subclinical hypothyroidism

Objective  A possible association between subclinical hypothyroidism and cardiovascular disease (CVD) has been reported. Monitoring of atomic‐bomb survivors for late effects of radiation exposure at the Radiation Effects Research Foundation has provided the opportunity to examine associations between subclinical hypothyroidism and metabolic CVD risk factors. The objective of the study was to evaluate associations between subclinical hypothyroidism and metabolic CVD risk factors, and a cluster of these factors.

Risk for Progression to Overt Hypothyroidism in an Elderly Japanese Population with Subclinical Hypothyroidism

BACKGROUND Few population-based studies report the changes with time in thyroid function tests in patients with subclinical hypothyroidism. We compared the risk for developing overt hypothyroidism in patients with subclinical hypothyroidism and euthyroid controls from the same population of elderly Japanese. We also sought associations of selected parameters with the development of overt hypothyroidism in the subclinical hypothyroid and euthyroid groups. METHODS We measured thyrotropin (TSH) and free thyroxine (T4) levels at baseline examinations performed from 2000 to 2003 in the cohort of Japanese atomic-bomb survivors and identified 71 patients with spontaneous subclinical hypothyroidism (normal free T4 and TSH >4.5 mIU/L without a history of thyroid treatment, mean age 70 year) and 562 euthyroid controls. We re-examined TSH and free T4 levels an average of 4.2 years later (range, 1.9-6.9). RESULTS The risk for progression to overt hypothyroidism was significantly increased in subclinical hypothyroid patients (7.0%) compared with control subjects (1.6%) after adjusting for age and sex (odds ratio, 4.56; p=0.009). Higher baseline TSH levels were associated with progression from subclinical to overt hypothyroidism (p=0.02) in the multivariate analysis, including age, sex, antithyroid peroxidase antibody, and ultrasonography (US) findings. The analysis using binary TSH data suggested that a TSH level >8 mIU/L was a predictive value for development of overt hypothyroidism (p=0.005). On the other hand, serum TSH levels spontaneously normalized in 38 (53.5%) of the patients with subclinical hypothyroidism. In the multivariate analysis, normalization of TSH levels was associated with lower baseline TSH levels (p=0.004) and normal and homogenous thyroid US findings (p=0.04). Atomic-bomb radiation dose was not associated with subclinical hypothyroidism or its course. CONCLUSIONS Subclinical hypothyroidism was four times more likely to be associated with development of overt hypothyroidism than euthyroid controls in the sample population of Japanese elderly. TSH levels in half of the patients normalized spontaneously when assessed after an average follow-up period of 4.2 years. Baseline TSH level and thyroid US findings are potential predictors of future thyroid function in subclinical hypothyroidism.

Impairment of the TSH signal transduction system in human thyroid carcinoma cells

In order to further evaluate the role of TSH in the proliferation and the differentiation of human thyroid carcinoma cells, we have analyzed the function of the TSH receptor in the established thyroid carcinoma cell lines NPA and WRO. The TSH signal transduction system in the carcinoma cells was also compared with that in normal thyroid cells. Although unresponsiveness to bovine and human TSH was demonstrated by measurement of cAMP production and [3H]thymidine incorporation after treatment of TSH, cAMP production was induced after stimulation of these cells by forskolin, cholera toxin, and isoproterenol. Specific binding to 125I-TSH was demonstrated in both NPA and WRO cells in addition to the existence of a TSH receptor mRNA and thyroglobulin mRNA species, although thyroid-specific gene expression in these cells was not regulated by TSH. These findings suggest that the unresponsiveness to TSH in these cells may be due to an abnormality of TSH receptor-G protein coupling rather than to a decreased level of TSH-receptor expression or a Gs protein abnormality.

Spatiotemporal Characteristics of Internal Radiation Exposure In Evacuees and First Responders after the Radiological Accident in Fukushima

After the Tokyo Electric Power Company Fukushima Daiichi nuclear power plant accident on March 11, 2011, the reconstruction of early internal radiation doses in residents of Fukushima plays a major role in evaluating their future heath risk, including thyroid cancer by internal radioiodine. Internal radioactivity was measured using a whole body counter (WBC) at the Nagasaki University Medical School to evaluate the health risks of residents and short term visitors in Fukushima. Measurable 131I, 134Cs and 137Cs were detected altogether in 49 out of 196 people who were in Fukushima prefecture at any time during March 11 and April 20, 2011. In 49 people, the 90 percentile of the thyroid equivalent dose by 131I and the committed effective dose (total effective dose over a lifetime) by the sum of 134Cs and 137Cs was 3 mSv and 0.06 mSv, respectively. The radionuclide intakes in early evacuees who left Fukushima before March 16 were more than five times as high as in the responders who moved to Fukushima later. The intake ratio of 131I/137Cs of the earlier evacuees was approximately three. The spatial analysis of 16 evacuees to the south indicated a reduction of internal radioactivity depending on the distance from the nuclear power plant. Among them, high internal 131I radioactivity in 6 people in a particular evacuation route could be explained by the arrival of a radioactive cloud with a high airborne 131I/137Cs ratio to the environment, as predicted by atmospheric dispersion simulations. Overall, the actual internal radioactivity assessed by a WBC examination comparatively agreed with the predicted airborne radioactivity. These results suggest that the accurate estimation of internal doses in the first week after the radiological accident is critical for the dose reconstruction. The evaluation of internal doses of residents based on their evacuation routes and the advanced estimation of airborne radioactivity from the atmospheric dispersion model should continue to be assessed.

Association of Interleukin-18 Gene Promoter Polymorphisms in Type 1 Diabetes and Autoimmune Thyroid Disease

Abstract: 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‐γ 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.

Growth hormone directly and indirectly stimulates articular chondrocyte cell growth

Although growth hormone (GH) is known to regulate cartilage growth and differentiation during development, it is still unclear whether the cell growth of articular chondrocytes is stimulated directly by GH or mediated by GH-induced insulin-like growth factor-I (IGF-I). In the present study, we focused on whether GH directly or indirectly stimulates articular chondrocyte proliferation. Monolayer articular chondrocytes from 5-week-old male Sprague-Dawley rats were cultured in Hams F-12/Dulbeccos modified essential medium supplemented with 10% fetal bovine serum. Stimulation of DNA synthesis by GH was dose-dependent between 0.1 and 1 microg/ml, and the maximum active concentration of GH was 500 ng/ml, which induced a 3.5-fold increase over control values. Anti-IGF-I antiserum neutralized about 80% of GH-induced DNA synthesis. GH stimulated the secretion of IGF-I into the conditioned medium in a dose-responsive manner. To determine whether GH stimulated DNA synthesis directly, we investigated the time-course changes in mRNA expression of IGF-I and the proto-oncogene c-myc. Induction of IGF-I mRNA occurred at 4 h, and reached a maximum level at 12 h, whereas the expression of c-myc mRNA was induced within 4 h, and continued to increase until 72 h after GH treatment. Furthermore, administration of cycloheximide, an inhibitor of protein synthesis, resulted in the superinduction of both IGF-I and c-myc mRNAs. These results suggest that early induction of c-myc is due to a direct stimulatory effect of GH, and that long-term induction of c-myc was attributable to an indirect effect of GH in which GH-induced secondary proliferative factors may act in an autocrine/paracrine manner. The superinduction of c-myc gene by cycloheximide also indicates that fresh protein synthesis of an intermediate protein was not required for GH-induced c-myc expression. Western ligand blot analysis of IGF-binding proteins revealed that cultured rat articular chondrocytes produced a predominant 41 kDa and a faint 32 kDa form, and that GH significantly stimulated the secretion of the 41 kDa form without affecting expression of the 32 kDa form. Furthermore, a specific IGF-I binding study suggested that the increase in DNA synthesis induced by GH was not associated with changes in affinity or in the number of IGF-I binding sites. These results support the conclusion that the stimulatory effect of GH was mainly mediated by GH-induced IGF-I production in monolayer rat articular chondrocytes. However, it is likely that GH may also have a direct stimulatory effect by inducing c-myc proto-oncogene expression.

A Case of Nonfunctioning Pituitary Carcinoma That Responded to Temozolomide Treatment

Pituitary carcinoma is a rare malignancy and is difficult to manage. Pituitary carcinomas commonly produce either PRL or ACTH, but some do not produce pituitary hormones. The alkylating reagent temozolomide (TMZ) was recently shown to be effective as a treatment for pituitary carcinoma. Most of the published reports of TMZ use in pituitary carcinoma cases were against hormone-producing carcinomas. Only a few patients with a nonfunctioning pituitary carcinoma treated with TMZ have been reported. Here we describe our treatment of a patient with nonfunctioning pituitary carcinoma and a background of multiple endocrine neoplasia type 1. The pituitary carcinoma was accompanied by meningeal dissemination with cerebral and L1 spinal bone metastasis. The patient received continuous dosing of TMZ along with external radiation, followed by standard dosing of TMZ. There was an apparent antitumor response seen in MRI. MGMT, an enzyme antagonized by TMZ, was negative in the tumor. The therapeutic efficacy of TMZ and dosing schedules of TMZ in pituitary carcinoma are discussed.