Search PubMed⌕ Search

Biomedical subjects

T Akamizu

Publications and source records attributed to T Akamizu.

At least 37 records · Page 2Linked to original sources
PubMed2000

Hashimoto's thyroiditis with heterogeneous antithyrotropin receptor antibodies: unique epitopes may contribute to the regulation of thyroid function by the antibodies.

Blocking-type TSH-binding inhibitor Igs (TBIIs) are known to cause hypothyroidism and an atrophic thyroid gland in patients with primary myxedema. They can block the activity of thyroid-stimulating antibodies (TSAbs) in Graves' patients as well as the activity of TSH. The majority of the epitopes for these blocking-type TBIIs have been, and are shown herein, to be present on the C-terminal region of the extracellular domain of the human TSH receptor (TSHR), whereas those for Graves' TSAbs are on the N-terminus. We report on a patient with Hashimoto's thyroiditis who suffered from mild hypothyroidism and a moderately sized goiter. Her serum had a potent blocking-type TBII and a weak TSAb in human and porcine TSHR systems. Using human TSHR/lutropin-CG receptor chimeras, we determined that the functional epitope of her blocking-type TBII was uniquely present on the N-terminal, rather than the C-terminal, region of the extracellular domain of the TSHR, unlike the case for blocking-type TBIIs in primary myxedema patients. The epitope of her TSAb was also unusual. Although the functional epitopes of most TSAbs are known to involve the N-terminal region of the receptor, her TSAb epitope did not seem to be present solely on the N- or C-terminus of the extracellular domain of the receptor. Blocking-type TBIIs from patients with primary myxedema blocked her TSAb activity as well as stimulation by TSH; her blocking-type TBII was able to only partially block her TSAb. In contrast, her blocking-type TBII almost completely blocked TSAbs from Graves' patients. Thus, we suggest that the unique epitopes of this patient's heterogeneous population of TSH receptor antibodies, at least in part, contribute to regulation of her thyroid function.

Animals↗
PubMed2000

Hyperthyroid Graves' disease after hemithyroidectomy for papillary carcinoma: report of three cases.

Here we report three cases of hyperthyroid Graves' disease that occurred after partial thyroidectomy for papillary carcinoma. In Case 1, the patient first developed hyperthyroidism 2 years after resection of left thyroid lobe, was treated for 2 years with antithyroid drug which was then discontinued, and relapsed with periodic paralysis after 8 years of remission. In Case 2, a hyperfunctioning remnant thyroid was noted 22 years after right hemithyroidectomy. In Case 3, where thyrotoxic symptoms became evident 7 weeks after right hemithyroidectomy, autoantibodies to thyroglobulin and thyroid microsome were positive in preoperative serum, in line with a report by others detecting these antibodies in 2 out of 3 such cases examined. Later bioassay revealed activity of thyroid stimulating antibodies in that serum, with further increase in titer in the sample taken at the clinical manifestation. Hence in Case 3, surgical stress may have altered immunological homeostasis, promoting a preclinical Graves' disease to full-blown hyperthyroidism.

Adult↗
PubMed1999

Thyrotropin decreases leptin production in rat adipocytes.

Leptin, which is secreted from adipocytes, has a role in the regulation of appetite and energy expenditure. The thyrotropin receptor (TSH-R) was recently found in adipocytes. We examined the effects of TSH on leptin production and lipolysis in rat epididymal adipocytes. TSH decreased the concentration of leptin in the medium time (approximately 24 hours)- and dose (approximately 10(-7) mol/L)-dependently (half-maximal inhibition [IC50] approximately 10(-9) mol/L). TSH also decreased the ob mRNA level approximately 55% in adipocytes. We confirmed the presence of TSH-R mRNA in the adipocytes by reverse transcription-polymerase chain reaction (RT-PCR). TSH stimulated glycerol release dose-dependently (IC50 approximately 10(-8) mol/L) in adipocytes. This TSH-induced glycerol release was further enhanced by adenosine deaminase (ADA). In summary, TSH reduced leptin production and stimulated lipolysis in rat epididymal adipocytes. Although the pathophysiological relevance of the regulation of leptin production and lipolysis by TSH is unknown, we speculate that TSH may affect the regulation of appetite and energy expenditure in pathophysiological states.

Adipocytes↗
PubMed1999

Characterization of recombinant monoclonal antithyrotropin receptor antibodies (TSHRAbs) derived from lymphocytes of patients with Graves' disease: epitope and binding study of two stimulatory TSHRAbs.

Anti-TSH receptor autoantibodies (TSHRAbs) are known to be involved in Graves' disease. To elucidate the molecular mechanism of the pathogenesis of Graves' disease, we previously isolated and reconstituted the Ig genes of two B cell clones (101-2 and B6B7) producing a monoclonal thyroid-stimulating antibody (TSAb), a stimulating type of TSHRAb, obtained from patients with Graves' disease. In the present study, we produced a large amount of recombinant monoclonal TSAbs in eukariotic cells using these genes and characterized them. First, we tried to identify their epitopes in the TSHR, by using a panel of mutants of the extracellular domain of the TSH receptor (TSHR). Substantial cell surface expression level of each mutant was confirmed by fluorescence-activated cell sorter analysis using a TSHRAb. Mutations in the N-terminal (but not C-terminal) region of the extracellular domain of TSHR abrogated or reduced TSAb activities of both antibodies, whereas they had opposite effects on TSH activity; cAMP generation by 101-2 significantly decreased in the receptors mutated in amino acids 52-56 and 58-61, and that by B6B7 decreased in amino acids 34-37 and 58-61. Secondly, purified antibodies were radiolabeled and tested for binding to cells expressing high levels of TSHR. Although their affinities were lower than that of TSH, their binding was not displaced by TSH. The antibody binding was not mutually competitive. These findings suggest that these antibodies interact with the N-terminal region of the receptor and transduce a signal through binding sites different from TSH. We believe that this is the first report of the characterization of human monoclonal TSHRAbs on their epitopes and bindings, confirming previous reports using patient sera or murine monoclonal antibodies.

Amino Acid Sequence↗
PubMed1999

A case of Hashimoto's thyroiditis with markedly elevated serum thyroglobulin and evidence of its influence on the measurement of anti-thyroglobulin antibody by highly sensitive assays.

We present the case of a 66-year-old woman with Hashimoto's thyroiditis, who showed extremely high concentrations of serum thyroglobulin (Tg). Serum Tg levels were markedly elevated following a slight elevation of serum thyrotropin (TSH) (22,000 ng/mL and 11.1 microU/mL, respectively). Although elevated concentrations of serum Tg declined concomitant with decrease of serum TSH one month later, Tg concentrations remained high (> 948 ng/mL) even at normal or suppressed TSH levels. There was no evidence of massive thyroid tissue damage or thyroid tumor. To our knowledge, there have been no case reports of such high concentrations of serum Tg (> 2 x 10(4) ng/mL) in the clinical course of Hashimoto's thyroiditis. Furthermore, we showed evidence that extremely high Tg levels could possibly influence the measurement of anti-Tg autoantibody using highly sensitive radioimmunoassays.

Aged↗
PubMed1999

[Genetic and environmental factors of autoimmune thyroid diseases].

There is a growing consensus that autoimmune thyroid diseases, similar to other autoimmune diseases, is multifactorial: both several genetic and environmental factors interact and produce the clinical phenotype of these disorders. Twin studies and familial aggregation, including clustering within families showed that they are complex diseases with a significant genetic component. Several genetic factors associated with autoimmune thyroid diseases susceptibility have been identified, including the HLA genes, cytotoxic T lymphocyte associated-4 (CTLA-4) gene, TSH receptor and other immunoregulatory genes. Regarding environmental factors, although multiple factors including infection, stress, sex steroids, pregnancy, aging and food, are known as factors precipitating autoimmune thyroid diseases, little progress has been achieved defining them. It will be paradoxically important to identify genetic factors to investigate environmental factors.

Autoimmune Diseases↗
PubMed1998

Endothelial nitric oxide synthase gene is positively associated with essential hypertension.

Essential hypertension has a genetic basis. Accumulating evidence, including findings of elevation of arterial blood pressure in mice lacking the endothelial nitric oxide synthase (eNOS) gene, strongly suggests that alteration in NO metabolism is implicated in hypertension. There are, however, no reports indicating that polymorphism in the eNOS gene is associated with essential hypertension. We have identified a missense variant, Glu298Asp, in exon 7 of the eNOS gene and demonstrated that it is associated with both coronary spastic angina and myocardial infarction. To explore the genetic involvement of the eNOS gene in essential hypertension, we examined the possible association between essential hypertension and several polymorphisms including the Glu298Asp variant, variable number tandem repeats in intron 4 (eNOS4b/4a), and two polymorphisms in introns 18 and 23. We performed a large-scale study of genetic association using two independent populations from Kyoto (n=458; 240 normotensive versus 218 hypertensive subjects) and Kumamoto (n=421; 223 normotensive versus 187 hypertensive subjects), Japan. In both groups, a new coding variant, Glu298Asp, showed a strong association with essential hypertension (Kyoto: odds ratio, 2.3 [95% confidence interval, 1.4 to 3.9]; Kumamoto: odds ratio, 2.4 [95% confidence interval, 1.4 to 4.0]). The allele frequencies of 298Asp in hypertensive subjects were significantly higher than those in normotensive subjects in both groups (Kyoto: 0.103 versus 0.050, P<0.0017; Kumamoto: 0.120 versus 0.058, P<0.0013, respectively). No such disequilibrium between genotypes was significantly associated with any other polymorphisms we examined; the Glu298Asp variant was also not linked to any other polymorphisms. In conclusion, the Glu298Asp missense variant was significantly associated with essential hypertension, which suggests that it is a genetic susceptibility factor for essential hypertension.

Adult↗
PubMed1997

Preferential localization of human CD5+ B cells in the peritoneal cavity.

In a transgenic mouse model of autoimmune haemolytic anaemia, CD5+ B lymphocytes localized in the peritoneal cavity are shown to play an important role in the onset of autoimmune disease. The authors have examined whether CD5+ B cells are present in the peritoneal cavity of 12 human individuals with non-invasive gastrointestinal tumours and found that in humans CD5+ B cells preferentially lodge in the peritoneal cavity as compared to the peripheral blood and spleen while the numbers of the peritoneal B lymphocytes in humans are much lower than in mice and vary widely between individuals.

Animals↗
PubMed1997

Differential expression of thyrotropin receptor mRNA in the porcine heart.

Thyrotropin receptor (TSHR) mRNA expression has previously been detected in human heart, suggesting a possible role for the receptor in cardiac function and pathophysiology. In the present study we examined the regional distribution of TSHR mRNA in pig heart to map potential cardiac sites of TSH action. Polyadenylated mRNA extracted from thyroid, atria, ventricles, aorta, coronary arteries, epicardial fat, and purified preparations of atrial and ventricular cardiomyocytes was subjected to reverse-transcriptase polymerase chain reaction (RT-PCR) using primers designed to amplify a 311 base pair (bp) DNA segment of the human TSHR. After reverse transcription of 100 ng mRNA, cDNA was amplified by PCR using TSHR primers and compared by electrophoresis on 2% agarose gels. Relative levels of TSHR cDNA (normalized to glyceraldehyde 3-phosphate dehydrogenase [GAPDH]) were as follows: Coronary arteries, epicardial fat > right atrium > left atrium > right ventricle, aorta > left ventricle, ventricular cardiocytes. In contrast to ventricular cardiocytes, purified atrial cardiocytes expressed levels of TSHR mRNA readily detectable with RT-PCR. These findings demonstrate that TSHR mRNA expression in porcine heart varies regionally, and furthermore suggest that areas of highest expression (coronary arteries, adipose tissue, right atrium) are potential sites for a functional or pathologic role of the TSHR.

Adipose Tissue↗
PubMed1997

Effectiveness of a short-term steroid treatment on the reduction in goiter size in antithyroid drug-treated patients with Graves' disease.

Reduction of goiter size is one of the criteria necessary to determine clinical remission in antithyroid drug (ATD)-treated Graves' patients. To facilitate goiter reduction or to achieve quick remission, a short-term steroid treatment was administered to 5 Graves' patients. These patients had been treated with ATD for a considerable period of time, had maintained euthyroidism with negative or weak thyrotropin-binding inhibitor immunoglobulin (TBII), but still had an enlarged goiter and remained T3 unsuppressive. Betamethazone was initially given 1.5 mg daily and then gradually tapered to 0 mg for 3 months. Compared to the 6-month observation period or the pre-medication period, goiter reduction exceeding 0.7 cm was achieved in all 5 patients during the steroid treatment. These reductions partly reversed to an extent smaller than pre-treatment levels in 2 patients, but continuous goiter reductions were observed for at least 3 months after steroid cessation in 3 patients. In 2 of these reduced goiter patients, T3 suppressibility was confirmed, and they were diagnosed in remission. During steroid administration, serum T3 and TSH concentrations were lowered but reversed shortly, serum fT4 concentrations did not change, and TBII levels became negative in all patients including the 2 with weak positive values before the treatment. In conclusion, a short-term steroid treatment for goitrous ATD-treated Graves' patients appears promising in achieving goiter reduction or remission.

Adult↗
PubMed1997

Association of autoimmune thyroid disease with a microsatellite marker for the thyrotropin receptor gene and CTLA-4 in a Japanese population.

To examine the genetic contribution of the thyroid-stimulating hormone receptor (TSHR, or thyrotropin receptor) gene to autoimmune thyroid disease (AITD), we identified a dinucleotide repeat polymorphism near the TSHR gene that mapped to an 8.6 cM interval between D14S74 and D14S55 on the long arm of human chromosome 14. Association studies revealed a significant difference (p = 3.8 x 10(-5) between the TSHR microsatellite allele frequency distribution in 81 unrelated Japanese AITD patients and 113 Japanese controls, with a significant increase in the 180 pb allele (allele 1) of the microsatellite sequence (p = 5.8 x 10(-7). The risk for AITD with the 180 bp allele was 3.5, with association highly significant in female patients (p = 1.1 x 10(-5) and less dramatic, but still significant, in male patients (p = .02). These results suggest that the 180 bp allele of the TSHR microsatellite is associated with a susceptibility locus for AITD in Japanese patients. Two additional genetic markers have been evaluated for association in the Japanese AITD patients. The TSHR codon 52 (C52-->A52) transition mutation was not observed in the Japanese. A polymorphism for the CTLA-4 gene was genotyped and, while association with AITD was not observed (p = .15), a significant association was observed between CTLA-4 alleles of 110 bp (p = .01) and 106 bp (p = .004) and susceptibility to primary hypothyroidism or idiopathic myxedema, respectively.

Abatacept↗
PubMed1996

Molecular analysis of stimulatory anti-thyrotropin receptor antibodies (TSAbs) involved in Graves' disease. Isolation and reconstruction of antibody genes, and production of monoclonal TSAbs.

Anti-thyrotropin (TSH) receptor autoantibodies (TRAbs) have been known to be involved in Graves' disease. To understand the molecular mechanism for pathogenesis of TSAbs in Graves' disease, we isolated and reconstituted the Ig genes of EBV-transformed B cell clones producing monoclonal thyroid stimulating Ab (TSAb) obtained from patients with Graves' disease. The V region genes of Ig heavy (H) and light (L) chains of two TSAb clones, IgG clone B6B7 and IgM clone 101-2, were isolated by the PCR. Nucleotide sequencing analysis revealed that germ-line VH and VK segments widely used for autoantibodies including the previously isolated TRAbs were utilized in the two clones. A significant number of somatic mutations were found in V regions of both clones, indicating the involvement of somatic mutations for the TSAb specificity. Reconstituted Ig H and L chain genes of the two clones were stably introduced into myeloma cells for IgG1 production. IgGs purified from cultured supernatants of both transfectants exhibited significant TSAb activities, while they did not inhibit TSH binding to the receptor. The successful expression of recombinant TSAbs in eukaryotic cells will provide opportunities to apply them to various pathophysiologic, diagnostic and therapeutic investigations in autoimmune thyroid diseases.

Antibodies, Monoclonal↗
PubMed1996

Laboratory tests necessary at the first examination of patients with suspected thyroid disorders.

In order to determine what and how many test items are necessary for the initial tests when examining patients with thyroid disorders, a questionnaire was sent to the council members of the Japan Thyroid Association. Thyroid disorders were divided into 4 categories; hyperthyroidism, hypothyroidism, diffuse goiter, and nodular goiter. The questionnaire was designed to assess: 1) tests routinely ordered at the initial examination; 2) minimum test battery necessary; 3) the 5 most important tests in order; and 4) selection of only 2 tests at most. The data on 112 completed questionnaires were collected and analyzed. When the choice was limited to only 2 tests, TSH and fT4 were commonly selected for hyperthyroidism hypothyroidism and diffuse goiter, but these 2 tests would be insufficient for the differentiation of disorders. In the case of nodular goiter, ultrasonogram and fine needle aspiration biopsy (FNA) were selected. The mean number of routinely ordered tests was 6.62 +/- 2.00 (S.D.) for hypothyroidism and 8.06 +/- 2.48 for nodular goiter, but many fewer tests were cited as absolutely necessary. In hyperthyroidism, 4.56 +/- 1.92 tests were required, in hypothyroidism 4.39 +/- 1.92, in diffuse goiter 4.93 +/- 1.75, and in nodular goiter 5.15 +/- 2.13. Most of the function-related tests, ultrasonogram and autoantibodies were commonly selected, while TBII and thyroid 123I or 99mTcO4 uptake in hyperthyroidism, and FNA, Tg and scintigram in nodular goiter were considered to be for specific purposes. Summarizing all these, the authors propose 5 or 6 tests to be necessary as the initial tests when examining patients with 4 individual thyroid disorders.

Autoantibodies↗
PubMed1996

Cardiomyopathy associated with Graves' disease.

Cardiovascular changes associated with Graves' disease are generally considered to be secondary to the increased levels of thyroid hormone. We describe a case of Graves' disease in a 25-year-old man, who developed cardiomyopathy with severe heart failure. Pathological examination of the myocardial biopsies showed fibroblast infiltration and degenerative changes. After the cardiomyopathy subsided the patient developed a goitre and signs of hyperthyroidism, followed by Graves' ophthalmopathy, which was treated successfully with a combination of high-dose corticosteroids and orbital radiotherapy. These findings suggested a common pathogenesis for the cardiomyopathy and ophthalmopathy, and prompted us to investigate the expression of TSH receptor (TSH-R) in human heart. TSH-R mRNA was identified in human heart using the reverse transcriptasepolymerase chain reaction (RT-PCR) and DNA sequencing. Taken together, these data suggest that autoimmunity against the TSH-R might contribute to both the cardiomyopathy and ophthalmopathy in similar cases of Graves' disease.

Adult↗