Age-Related Sex Differences in Glucose Tolerance by 75 g Oral Glucose Tolerance Test in Japanese.

To elucidate the age-related sex difference in glucose tolerance, we conducted 75 g oral glucose tolerance tests in 1156 participants. Participants were divided into four groups, namely, young (22−29) males, young females, middle-aged (>50) males, and middle-aged females. According to the Japanese Clinical Practice Guideline for Diabetes 2019, the prevalence of normal glucose tolerance (NGT) was significantly lower in middle-aged than in young participants. The prevalence of high-normal fasting plasma glucose (FPG) was higher, and NGT was lower in young males (high-normal FPG 15.2%, NGT 82.0%) than young females (high-FPG 3.9%, NGT 94.3%). Combined glucose intolerance (CGI) was higher and NGT was lower in middle-aged males (CGI 10.2%, NGT 25.2%) than in middle-aged females (CGI 3.3%, NGT 39.8%). FPG and body mass index (BMI) were the lowest and Homeostatic model assessment beta cell function (HOMA-ß) was the highest in young females, followed by young males, middle-aged females, and middle-aged males. Multiple linear regression analysis revealed that BMI weakly correlated with HOMA-ß and Matsuda index in all subjects except young females. The superior glucose tolerance in females was apparent in young, but attenuated in middle-aged females. The differences are due to the higher insulin secretion potential and lower BMI in young females.

Association Between Insulin Resistance and Cardinal Rheological Parameters in Young Healthy Japanese Individuals During 75g Oral Glucose Tolerance Test.

BACKGROUND: Insulin resistance is a well-known predictor and risk factor for type 2 diabetes mellitus (T2DM). Higher hematocrit induced by higher insulin resistance affects blood rheology. OBJECTIVE: This study intended to reveal the association between indices of insulin resistance and hemorheological parameters during a 75 g oral glucose tolerance test (75-g OGTT). METHODS: A total of 575 healthy young Japanese participants took 75-g OGTT. We then analyzed the association between insulin resistance indices and hematological parameters. RESULTS: The Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) was significantly correlated with hematocrit (Ht), hemoglobin (Hb), red blood cell (RBC), white blood cell (WBC), platelet count, lipid parameters and body mass index (BMI). The Matsuda index was negatively correlated with RBC count, WBC count, platelet count, total cholesterol (TC), low-density lipoprotein- cholesterol (LDL-C), triglyceride (TG), and positively correlated with high-density lipoprotein- cholesterol (HDL-C). The disposition index was negatively correlated with Hb, RBC count, LDL-C and BMI, and positively correlated with HDL-C. The Homeostasis Model Assessment of beta cell (HOMA-ß) was positively correlated with WBC count, platelet count, TC, LDL-C and TG. The insulinogenic index was positively correlated with WBC count, platelet count and TC. Multiple regression analysis revealed that HOMA-IR was independently associated with TG, and the Matsuda index was independently associated with TG, WBC count, and platelet count. The insulinogenic index was independently associated with WBC count. CONCLUSION: Cardinal rheological parameters reflected insulin resistance and release even in young healthy Japanese individuals within the physiological range of glycemic control.

Prolonged plasma glucose elevation on oral glucose tolerance test in young healthy Japanese individuals.

AIMS: This study aims to assess insulin secretion and resistance through oral glucose tolerance test (OGTT) among young Japanese individuals. SUBJECTS AND METHODS: We enrolled 595 young healthy Japanese individuals aged 22-29 years. They underwent an OGTT, and their results were divided into 4 groups (I-IV), according to the time at which their plasma glucose concentration declined below the fasting glucose concentration (30, 60 or 120 minutes or never as groups I, II, III and IV, respectively). RESULTS: We classified 575 normal glucose-tolerant subjects into 4 groups (I-IV) with I: 28 (4.9%), II: 120 (20.9%), III: 143 (24.9%) and IV: 284 (49.4%) individuals. The Matsuda, insulinogenic and disposition indices were decreased from groups I to IV. ROC curves of disposition index reflecting the composition of insulin secretion and sensitivity classified the prolonged glucose elevation group (group III + IV) from the rapid glucose lowering group (group II; AUC = 0.847). CONCLUSIONS: Even in a young and healthy Japanese individual within the physiological range of glycaemic control, there is a sequential decrease in insulin sensitivity and secretion.

Impaired blood rheology is associated with endothelial dysfunction in patients with coronary risk factors.

To investigate the relationship between blood rheology and endothelial function in patients with coronary risk factors, brachial arterial flow-mediated vasodilatation (FMD), an index of endothelial function and blood passage time (BPT), an index of blood rheology, and fasting blood cell count, glucose metabolism, and plasma fibrinogen, lipid, C-reactive protein, and whole blood viscosity levels were measured in 95 patients with coronary risk factors and 37 healthy controls. Brachial arterial FMD after reactive hyperemia was assessed by ultrasonography. BPT was assessed using the microchannel method. In healthy controls, BPT significantly correlated with FMD (r = - 0.325, p <  0.05), HDL cholesterol (r = - 0.393, p <  0.05), body mass index (BMI; r = 0.530, p <  0.01), and plasma fibrinogen concentration (r = 0.335, p <  0.05). In a multivariate regression analysis adjusted for all clinical variables, BPT remained significantly associated with BMI and fibrinogen, but not with FMD, in healthy controls. In patients with coronary risk factors, BPT significantly correlated with FMD (r = - 0.331, p <  0.01), HDL cholesterol (r = - 0.241, p <  0.05), BMI (r = 0.290, p <  0.01), hematocrit (r = 0.422, p <  0.001), white blood cell count (r = 0.295, p <  0.01), platelet count (r = 0.204, p <  0.05), and insulin (r = 0.210, p <  0.05). In a multivariate regression analysis adjusted for all clinical variables, BPT remained strongly associated with FMD and hematocrit in patients with coronary risk factors. These data indicate that BPT is closely associated with FMD in patients with coronary risk factors and suggest that the measurement of blood rheology using the microchannel method may be useful in evaluating brachial arterial endothelial function as a marker of atherosclerosis in these patients.

[Efficacy of Human Immunodeficiency Virus (HIV) Antigen-Antibody Combination Assay as a Screening Test and Factors Causing False-Positivity].

Purpose: We aimed to evaluate the performance of an HIV antigen-antibody combination assay (fourth-generation) by comparing it with second generation assays that detect anti-HIV. Methods: A total of 105,439 HIV screening tests were performed from January 2004 to March 2015; the second - and fourth generation assays were used for 75,302 and 30,137 samples, respectively. Samples positive on a screening test were confirmed by anti-HIV-1 western blotting (WB) and nucleic acid amplification. By the results of confirmation tests, the efficacies of the second and fourth generation assays were estimated. The clinical backgrounds with false-positive samples were examined. Results: Of 75,302 samples, 136(0.18%) were positive by the second-generation assay; 14 were confirmed positives, and 122 were false positives. Of 30,137 samples, 18(0.06%) were positive by the fourth-generation assay; 6 were confirmed positives, and 12 were false positives. The reliability of the positives by fourth-generation assay was significantly improved (p=0.006) Samples form individuals with malignant neoplasms were frequently false positive by both the second and fourth-generation assays. Of 67 samples performed by WB, 10 samples, including 6 from patients with a malignancy, showed indeterminate results. All indeterminate samples were found to have antibodies responding to HIV core protein. Conclusion: The fourth-generation assay had satisfactory reliability of the positives for HIV screening. Antibodies responding to HIV core protein may result in false positive HIV screening tests. [Original]

Type 2 Iodothyronine Deiodinase Activity Is Required for Rapid Stimulation of PI3K by Thyroxine in Human Umbilical Vein Endothelial Cells.

Thyroid hormones (THs) exert a number of physiological effects on the cardiovascular system. Some of the nongenomic actions of T3 are achieved by cross coupling the TH receptor (TR) with the phosphatidylinositol 3-kinase (PI3K)/protein kinase Akt (Akt) pathway. We observed that both T3 and T4 rapidly stimulated Akt phosphorylation and Ras-related C3 botulinum toxin substrate 1 (Rac1) activation, which resulted in cell migration, in a PI3K-dependent manner in human umbilical vein endothelial cells (HUVECs). We identified the expression of type 2 iodothyronine deiodinase (D2), which converts T4 to T3, and TRα1 in HUVECs. D2 activity was significantly stimulated by (Bu)2cAMP in HUVECs. The blockade of D2 activity through transfection of small interfering RNA (siRNA) specific to D2 as well as by addition of iopanoic acid, a potent D2 inhibitor, abolished Akt phosphorylation, Rac activation, and cell migration induced by T4 but not by T3. The inhibition of TRα1 expression by the transfection of siRNA for TRα1 canceled Akt phosphorylation, Rac activation, and cell migration induced by T3 and T4. These findings suggest that conversion of T4 to T3 by D2 is required for TRα1/PI3K-mediated nongenomic actions of T4 in HUVECs, including stimulation of Akt phosphorylation and Rac activation, which result in cell migration.

Relationship between carotid artery intima-media thickness and small dense low-density lipoprotein cholesterol concentrations measured by homogenous assay in Japanese subjects.

BACKGROUND: Small dense low-density lipoprotein cholesterol (sdLDL-C) concentrations correlate more strongly with coronary heart disease than other LDL-C and large LDL particle concentrations. We investigated the association between carotid artery intima-media thickness (IMT) and sdLDL-C concentrations in Japanese subjects. METHODS: Carotid artery IMT, blood pressure (BP), fasting plasma sdLDL-C, glucose metabolism, lipid, and C-reactive protein concentrations were measured in 97 native Japanese subjects. Carotid artery IMT was assessed by ultrasonography, and sdLDL-C concentrations were measured by a homogenous assay. Pearson's correlation coefficient analyses and multiple regression analyses were used to examine the relationships between carotid artery IMT values, sdLDL-C values, and other clinical variables. RESULTS: After multiple regression analysis, including age, sex, body mass index, systolic BP, diastolic BP, fasting plasma glucose, HbA1c, estimated glomerular filtration rate (eGFR), total-C, high-density lipoprotein (HDL)-C, triglyceride, LDL-C, non-HDL-C, large buoyant LDL-C, and sdLDL-C, carotid artery IMT remained significantly associated with age, systolic BP, diastolic BP, and sdLDL-C, whereas sdLDL-C remained significantly associated with age, total-C, HDL-C, triglycerides, and carotid artery IMT. CONCLUSIONS: When measured by a homogenous assay, carotid artery IMT may have a closer relationship with sdLDL-C concentrations than other lipid parameters in Japanese subjects. sdLDL-C may be a potentially useful risk marker when assessing carotid artery IMT in Japanese subjects.

Glucagon-like peptide-1 stimulates type 3 iodothyronine deiodinase expression in a mouse insulinoma cell line.

AIMS: The pathophysiological roles of thyroid hormones in glucose metabolism remain uncertain. Type 3 iodothyronine deiodinase (D3) converts thyroxine (T4) and 3,5,3'-triiodothyronine (T3) to 3,3',5'-triiodothyronine (rT3) and 3,3'-diiodothyronine (T2), respectively, inactivating thyroid hormones in a cell-specific fashion. In the present study, we identified D3 expression in MIN6 cells derived from a mouse insulinoma cell line and examined the mechanisms regulating D3 expression in these cells. MAIN METHODS: We characterized D3 activity using HPLC analysis, and examined the effect of GLP-1 or exendin-4 on D3 expression and cAMP accumulation in MIN6 cells. We also measured insulin secretion from MIN6 cells exposed to GLP-1 and T3. KEY FINDINGS: We identified enzyme activity that catalyzes the conversion of T3 to T2 in MIN6 cells, which showed characteristics compatible with those for D3. D3 mRNA was identified in these cells using RT-PCR analysis. Forskolin rapidly stimulated D3 mRNA and D3 activity. Glucagon-like peptide-1 (GLP-1) increased D3 expression in a dose-dependent manner, and this effect was inhibited by the protein kinase A (PKA) inhibitor H-89. Exendin-4, a GLP-1 receptor agonist, also stimulated D3 expression in MIN6 cells. These results suggest that a cAMP-PKA-mediated pathway participates in GLP-1-stimulated D3 expression in MIN6 cells. Furthermore, GLP-1 stimulated insulin secretion was suppressed by the addition of T3 in MIN6 cells. SIGNIFICANCE: Our findings indicate that GLP-1 regulates intracellular T3 concentration in pancreatic ß cells via a cAMP-PKA-D3-mediated pathway that may also regulate ß-cell function.

Frequency and clinical implication of the R450H mutation in the thyrotropin receptor gene in the Japanese population detected by Smart Amplification Process 2.

In Japanese pediatric patients with thyrotropin (TSH) resistance, the R450H mutation in TSH receptor gene (TSHR) is occasionally observed. We studied the frequency and clinical implication of the R450H mutation in TSHR in the general population of Japanese adults using smart amplification process 2 (SmartAmp2). We designed SmartAmp2 primer sets to detect this mutation using a drop of whole blood. We analyzed thyroid function, antithyroid antibodies, and this mutation in 429 Japanese participants who had not been found to have thyroid disease. Two cases without antithyroid antibodies were heterozygous for the R450H mutation in TSHR. Thus, the prevalence of this mutation was 0.47% in the general population and 0.63% among those without antithyroid antibodies. Their serum TSH concentrations were higher than the average TSH concentration not only in subjects without antithyroid antibodies but also in those with antithyroid antibodies. The R450H mutation in TSHR is relatively common in the Japanese population and potentially affects thyroid function. The present study demonstrates that the SmartAmp2 method is useful to detect the R450H mutation in TSHR, which is one of the common causes of TSH resistance in the Japanese population.

Seroprevalence of measles- and mumps-specific immunoglobulin G among Japanese healthcare students increased during 2007-2012.

We evaluated the seroprevalence of vaccine-preventable infectious diseases among Japanese healthcare students to create immunization guidelines. Between 2007 and 2012, a total of 1746 Japanese medical, nursing, and paramedical students were serologically screened for measles, mumps, rubella, varicella, and hepatitis B virus (HBV) antibodies at the time of admission. In 2007, the seroprevalence of measles and mumps was 52.7% and 65.6%, respectively. The seroprevalence of measles dramatically increased to 96.6% in 2009 and was then sustained at >90%. The seroprevalence of mumps gradually increased to >80.0% between 2010 and 2012. The seroprevalence of rubella remained at >90% except in 2008 (85.6%), and the seroprevalence of varicella was sustained at >92% throughout 2007-2012. The seroprevalence of HBV antibody remained at <7% during 2007-2012. Although the seroprevalence of vaccine-preventable infectious diseases among Japanese healthcare students increased during the 2007-2012 study period, a substantial number of students were susceptible to vaccine-preventable infectious diseases. Therefore, we propose targeted immunization of Japanese healthcare students using serological screening prior to clinical training.

Tuberculosis screening using a T-cell interferon-γ release assay in Japanese medical students and non-Japanese international students.

Screening of medical students and international students for tuberculosis (TB) at the time of admission is a key strategy to control and prevent the spread of infection on university campus and teaching hospitals because of the high risk of exposure to TB patients. The Mycobacterium tuberculosis antigen-specific T-cell interferon-γ release assays (IGRAs) are specific latent tuberculosis detection methods used in such groups. Currently, in Japan, there are no guidelines and no baseline data on IGRAs to evaluate the risk of TB in these high-risk groups. In order to evaluate TB risk at the time of admission in university campus and medical schools in Japan, a retrospective study was conducted. A total of 969 students (585 Japanese students and 384 international students) were screened for TB using the IGRAs at the time of admission. Eight Japanese students (0.9%) were positive for IGRAs, but none were diagnosed with active TB at the follow-up. In contrast, 30 international students (7.8%) were positive for IGRAs, including two students diagnosed with active TB during follow up. Positive ratio of IGRAs in international students was significantly higher than that of medical students at the time of admission. Here we propose a standard approach for TB screening with IGRAs at the time of admission for medical students and international students in Japan.

A novel mechanism for the inhibition of type 2 iodothyronine deiodinase by tumor necrosis factor α: involvement of proteasomal degradation.

Thyroxine (T4) needs to be converted to 3,5,3'-triiodothyronine (T3) by iodothyronine deiodinase to exert its biological activity. Recent studies revealed the presence of type 2 iodothyronine deiodinase (D2) in human thyroid tissue, human skeletal muscle and other tissues, suggesting that D2 is involved in maintaining plasma T3 level in human. Tumor necrosis factor α (TNFα) is an inflammatory cytokine of which production is elevated in patients with nonthyroidal illness. Although several lines of evidence suggest the causal role of TNFα in nonthyroidal illness, detailed nature of the effect of TNFα on D2 remains unclear. In the present study, we identified D2 activity and D2 mRNA in TCO-1 cells, which were derived from human anaplastic thyroid carcinoma, and studied the mechanisms involved in the regulation of D2 expression by TNFα. The characteristics of the deiodinating activity in TCO-1 cells were compatible with those of D2 and Northern analysis demonstrated that D2 mRNA was expressed in TCO-1cells. D2 activity and D2 mRNA expression were rapidly increased by dibutyryl cAMP ((Bu)2cAMP). TNFα showed an inhibitory effect on (Bu)2cAMP-stimulated D2 activity in spite of little effect on (Bu)2cAMP-stimulated D2 mRNA expression. MG132, a proteasome inhibitor abolished TNFα suppression of D2 activity whereas BAY11-7082 or 6-amino-4-(4-phenoxyphenylethylamino) quinazoline, inhibitors of nuclear factor-κB (NF-κB) failed to attenuate the effect of TNFα on D2 activity. These data suggest that a posttranslational mechanism through proteasomal degradation but not NF-κB activation is involved in the suppression of D2 by TNFα.

Association between accumulation of visceral fat and the combination of ß3 adrenergic receptor Trp64Arg, ß2 adrenergic receptor Arg16Gly and uncoupling protein 1 -3826A>G polymorphisms detected by Smart Amplification Process 2.

ß2 and ß3 adrenergic receptors (ß2AR, ß3AR) and uncoupling protein 1 (UCP1) have been considered as candidate genes for obesity. Although each polymorphism of ß3AR Trp64Arg, ß2AR Arg16Gly and UCP1 -3826A>G is known to be associated with obesity, the interaction among these polymorphisms is not fully understood. We analyzed ß3AR Trp64Arg, ß2AR Arg16Gly and UCP1 -3826A>G polymorphisms by the Smart Amplification Process 2 in 222 Japanese subjects without the medication of hypertension, dyslipidemia or diabetes, and investigated the association between the physical and metabolic characteristics and the combination of these polymorphisms. In analysis of the genotypes combination, only the carriers of both ß2AR Arg/Arg and UCP1 G/G genotypes had significantly higher waist to hip ratio (p=0.014). In analysis of the alleles combination, a significant difference was observed in waist to hip ratio among the groups stratified by the carrying number of the alleles of ß3AR Arg, ß2AR Arg and UCP1 G (p=0.026), and the waist to hip ratio was significantly higher in the carriers of four and five risk alleles than in the carriers from zero to three risk alleles (p=0.005). The present study demonstrated the interaction among ß3AR Trp64Arg, ß2AR Arg16Gly and UCP1 -3826A>G for the accumulation of visceral fat.

Oxidative stress associated with rapid weight reduction decreases circulating adiponectin concentrations.

The effect of stress associated with acute weight reduction on adipocytokine production is incompletely understood. In the present study, we have investigated the changes in circulating adipocytokine concentrations and urinary concentrations of stress markers in male collegiate wrestlers during acute weight reduction for a competition. Twenty healthy Japanese male wrestlers (18-22 years of age) who participated in the national collegiate wrestling tournament were studied. Body weight, body fat amount, serum testosterone, serum leptin, serum adiponectin, urinary 8-hydroxy-2'- deoxyguanosine (8-OHdG) and urinary biopyrrins were analyzed during acute weight reduction for the competition. Body weight, body fat amount and the serum concentrations of testosterone, leptin and adiponectin significantly decreased on the day of weigh-in compared with the levels 12 days before weigh-in. In contrast, urinary concentrations of 8-OHdG and biopyrrins significantly increased on the day of weigh-in compared with the concentrations 12 days before weigh-in. A positive correlation was observed between the serum concentrations of adiponectin and testosterone, and a negative correlation was observed between the concentrations of serum adiponectin and urinary biopyrrins. The present results suggest that rapid weight reduction increases the urinary concentrations of stress markers, which is associated with a decrease in serum concentrations of adiponectin.

[New methods for diagnosis of sepsis].

For the treatment of septic patients, it is important to perform a rapid and accurate identification of the causative microorganisms of the syndrome, and to use appropriate medicine. Blood culture has been an established method for the identification of causative bacteria in patients with sepsis, and the measurement of CRP has been used to estimate the severity of disorders. However, the blood culture method has a low sensitivity for detecting surviving bacteria in patients with sepsis because of the possible administration of antibiotics in advance of the test. Although the identification of causative bacteria must be performed quickly, the method requires several days to detect and identify the bacteria and to test for susceptibility to antibiotics. In addition, CRP measurement is not able to distinguish systemic bacterial infection from nonbacterial infection or non-infectious inflammation. To overcome the disadvantages of these tests for the diagnosis of sepsis, new methods have been developed. In this issue, we introduce two new methods for the diagnosis of sepsis. One involves the detection of the bacterial gene ingested by neutrophils by the in-situ hybridization method, and the other is the measurement of procalcitonin in blood samples. Since these tests have several advantages in comparison with the conventional blood culture method or the measurement of CRP to verify the presence of bacterial infection and identify the causal bacteria in a shorter period, we need to combine these tests with the conventional methods to facilitate an accurate diagnosis and administer appropriate antibiotics to septic patients.

Expression of type 2 iodothyronine deiodinase in human osteoblast is stimulated by thyrotropin.

Thyroid hormones play important roles in bone growth, development, and turnover. To exert its biological activity, T(4) needs to be converted to T(3) by iodothyronine deiodinase. In human thyroid gland as well as rat brown adipose tissue, type 2 iodothyronine deiodinase (D2) expression is regulated by a TSH receptor-cAMP-mediated mechanism. TSH receptor knockout mice demonstrated the direct effects of TSH on bone via TSH receptors found on osteoblast and osteoclast precursors. In the present study we investigated the possible expression and function of iodothyronine deiodinase and TSH receptors in human osteoblast-like osteosarcoma (SaOS-2) cells and normal human osteoblast (NHOst) cells. Iodothyronine deiodinase activity was detected in SaOS-2 cells and NHOst cells, and all of the characteristics of deiodinating activity were compatible with those of D2. Northern analysis demonstrated D2 mRNA expression in SaOS-2 cells and NHOst cells. D2 mRNA levels as well as D2 activities were rapidly increased by dibutyryl cAMP or forskolin in SaOS-2 cells and NHOst cells. TSH receptor mRNA was demonstrated in SaOS-2 cells and NHOst cells, and D2 mRNA and D2 activity were stimulated by TSH in both cells. In addition, all T(3) receptor isoforms were detected by RT-PCR in SaOS-2 cells and NHOst cells. The present results indicate the expression of functional TSH receptors and D2 in human osteoblasts and suggest previously unrecognized roles of TSH receptors and local T(3) production by D2 in the pathophysiology of human osteoblasts.

Association of antipituitary antibody and type 2 iodothyronine deiodinase antibody in patients with autoimmune thyroid disease.

Antipituitary antibody (APA) has been reported to be detected in patients with autoimmune thyroid disease. Type 2 iodothyronine deiodinase (D2) is expressed in both pituitary gland and thyroid gland. We studied the association of APA and D2 peptide antibody in patients with autoimmune thyroid disease. Rat pituitary gland homogenate and D2 peptide were used as antigens in the present study. APA and D2 peptide antibodies were measured by enzyme-linked immunosorbent assay (ELISA) in sera obtained from 42 patients with Hashimoto's disease, 26 patients with Graves' disease and 70 healthy control subjects. Moreover, D2 activity precipitation assay was performed in some patients with Hashimoto's disease. APA and D2 peptide antibody were elevated in patients with Hashimoto's disease and patients with Graves' disease, compared with control subjects. APA was positive in 32.4% (22/68), D2 peptide antibody was positive in 26.5% (18/68) of patients with autoimmune thyroid disease. APA was positive in 31.0% (13/42) of patients with Hashimoto's disease and 34.6% (9/26) of patients with Graves' disease. D2 peptide antibody was positive in 26.2% (11/42) of patients with Hashimoto's disease and 26.9% (7/26) of patients with Graves' disease. D2 peptide antibody was correlated with APA in patients with autoimmune thyroid disease. Moreover, precipitation of D2 activity was increased in some patients with Hashimoto's disease including a patient who also had idiopathic diabetes insipidus, and was correlated with D2 peptide antibody. These results suggest that D2 antibody may be associated with APA in patients with autoimmune thyroid disease.

Expression of type 2 iodothyronine deiodinase in corticotropin-secreting mouse pituitary tumor cells is stimulated by glucocorticoid and corticotropin-releasing hormone.

We identified the presence of iodothyronine deiodinase in AtT-20 mouse pituitary tumor cells that secrete corticotropin. Iodothyronine deiodinating activity in AtT-20 cells fulfills all the characteristics of type 2 iodothyronine deiodinase (D2), including the inhibition by thyroid hormones, the insensitivity to inhibition by 6-propyl-2-thiouracil, and the low Michaelis-Menten constant value for T4. Northern analysis using mouse D2 cRNA probe demonstrated the hybridization signal of approximately 7.0 kb in size in AtT-20 cells. D2 activity and D2 mRNA were stimulated by glucocorticoid in a dose-dependent manner but were not stimulated by testosterone or beta-estradiol. D2 expression was stimulated by (Bu)2cAMP, and CRH in a dose-dependent manner in the presence of dexamethasone. These results suggest the previously unrecognized role of local thyroid hormone activation by D2 in the regulation of pituitary corticotrophs.