Takayuki Ogiwara

Pretranslational Regulation of Rhythmic Type II Iodothyronine Deiodinase Expression by β-Adrenergic Mechanism in the Rat Pineal Gland1

It has been demonstrated that type II iodothyronine deiodinase is present in rat pineal gland, and the deiodinase activity markedly increases during the hours of darkness, primarily throughβ -adrenergic mechanism. We have studied the relationship between pineal type II iodothyronine deiodinase messenger RNA (mRNA) and the deiodinase activity to elucidate the mechanisms involved in the nocturnal rise in pineal deiodinase activity. Northern analysis has demonstrated that type II iodothyronine deiodinase mRNA is expressed in rat pineal gland, and the mRNA markedly increases during the hours of darkness. The nocturnal increase in pineal type II iodothyronine deiodinase activity is preceded by the increase in its mRNA. Daytime isoproterenol administration resulted in a rapid increase in pineal type II iodothyronine deiodinase mRNA followed by the increase in deiodinase activity. Propranolol treatment, bilateral superior cervical ganglionectomy, or constant light exposure significantly suppressed the nocturnal ...

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.

Primary culture of cells from hyperfunctioning thyroid adenoma with an activating mutation of Gαs

We analyzed cultured cells from hyperfunctioning thyroid adenoma and its surrounding thyroid tissue from a Japanese woman and determined the nucleotide sequences of genes encoding the alpha subunit of the stimulatory G-protein 1 (G alphas) and thyrotropin (TSH) receptor in its tumor tissue. Primary culture of cells from hyperfunctioning thyroid adenoma and its surrounding thyroid tissue revealed that cAMP production was constitutively activated while intracellular Ca2+ concentration was suppressed both at the basal level and in the response to TSH stimulation in the cells from tumor tissue compared with those from non-tumor tissue. Nucleotide sequence analysis demonstrated the somatic missense mutation at codon 201 (CGT(Arg)-CAT(His)) of G alphas gene in tumor tissue but not in its surrounding tissue. No mutation was observed in the transmembrane region of TSH receptor. These results suggest that cAMP regulatory cascade is constitutively activated while phospholipase C-Ca2+ signaling cascade is suppressed in hyperfunctioning thyroid adenoma with an activating mutation of G alphas gene in the present case.

Northern analysis of type II iodothyronine deiodinase mRNA in rat harderian gland

It has been known that type II iodothyronine deiodinase activity is present in rat Harderian gland and the activity is significantly increased by isoproterenol administration. We have performed Northern analyses to study whether the transcript for type II iodothyronine deiodinase is expressed in rat Harderian gland and whether the isoproterenol stimulation of type II iodothyronine deiodinase activity in rat Harderian gland is due to the change in its mRNA level. Northern analyses have demonstrated that type II iodothyronine deiodinase mRNA, approximately 7.5 kb in size, is expressed in rat Harderian gland, and the mRNA levels as well as the deiodinase activities are greater in hypothyroid rats than those in euthyroid rats. Type II iodothyronine deiodinase mRNA levels and the deiodinase activities in Harderian gland were increased by isoproterenol administration, and the increase in the mRNA levels preceded that in the deiodinase activities. These results indicate that 7.5 kb transcript for type II iodothyronine deiodinase is expressed in rat Harderian gland and beta-adrenergic stimulation of type II iodothyronine deiodinase activity is due at least in part to the increase in its mRNA level.

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. Pearsons 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.

Expression and nocturnal increase of type II iodothyronine deiodinase mRNA in rat pineal gland.

It has been demonstrated that thyroxine deiodinating activity is present in rat pineal gland, and its activity increases significantly during the night time. We have studied whether mRNA for type II iodothyronine deiodinase is expressed in rat pineal gland and whether the nocturnal rise of pineal T4 deiodinating activity is due to the change in type II iodothyronine deiodinase mRNA level. Reverse transcription-polymerase chain reaction amplification and Northern blot analyses have demonstrated that type II iodothyronine deiodinase mRNA is expressed in rat pineal gland and its mRNA level increases markedly at midnight. These results suggest that the nocturnal rise in pineal T4 deiodinating activity is due to the change in type II iodothyronine deiodinase mRNA level.

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.

Identification of Monoclonal Insulin Autoantibodies in Insulin Autoimmune Syndrome Associated with HLA-DRB1*0401

We have characterized HLA and insulin autoantibodies in a Japanese female patient with insulin autoimmune syndrome. Serological HLA typing demonstrated the patient had HLA-DR4, and DNA typing showed she had HLA-DRB1*0401 which has not been reported in patients with insulin autoimmune syndrome in Japan. A single binding affinity of insulin autoantibodies was demonstrated by Scatchard analysis and immunoglobulin class of insulin autoantibodies was exclusively IgG-ĸ. HLA-DRB1*0406 is strikingly associated with patients with insulin autoimmune syndrome who have polyclonal insulin autoantibodies. The present report demonstrated the first Japanese patient with insulin autoimmune syndrome carrying HLA-DRB1*0401 who was revealed to have monoclonal insulin autoantibodies. The present results indicate that HLA molecules are the major determinants of polyclonal insulin autoantibodies and monoclonal insulin autoantibodies in insulin autoimmune syndrome.

Inhibitory effects of okadaic acid on thyrotropin and prolactin secretion from rat anterior pituitaries.

The present study was undertaken to elucidate the effects of okadaic acid, a potent inhibitor of protein phosphatases, on thyrotropin (TSH) and prolactin (PRL) secretion, and on the hydrolysis of inositol phospholipids in rat anterior pituitaries. Preincubation of anterior pituitaries with okadaic acid caused a dose dependent decrease in TRH- and K(+)-induced TSH secretion, whereas basal secretion of TSH was not affected by pretreatment with okadaic acid. In contrast, okadaic acid resulted in a marked inhibition in both basal, and TRH- and K(+)-stimulated PRL release from anterior pituitaries. In addition, pretreatment with okadaic acid caused a slight, but significant decrease in the formation of [3H]inositol phosphate ([3H]IP) in rat anterior pituitaries. The present study suggests that okadaic acid blocks the release of TSH and PRL by inhibiting Ca2+ influx and that inhibitory effects of okadaic acid on PRL release are, at least in part, due to the inhibition of inositol phospholipid hydrolysis.

Thyroid hormone affects the hydrolysis of inositol phospholipids in the rat hypothalamus

We have attempted to elucidate the effect of thyroid hormone on phospholipase C-linked inositol phospholipid hydrolysis in the rat hypothalamus. Hypothalamic slices of each animal, euthyroid control, hypothyroid, and thyroxine (T4)-supplemented hypothyroid rats were labeled with [3H]myoinositol in the presence of 5 mM LiCl, and then incubated for 60 min in KHG buffer containing either vehicle or 1 mM ouabain, a Na-K ATPase inhibitor. Hypothyroidism caused a significant increase in both basal and ouabain-stimulated accumulation of [3H]inositol phosphate ([3H]IP) in hypothalamic slices, whereas supplement with T4 to hypothyroid rats resulted in a complete restoration of hypothalamic [3H]IP formation to the value of euthyroid control. The present results indicate that thyroid hormone affects phospholipase C-linked inositol phospholipid hydrolysis in the hypothalamus, suggesting that negative feedback action of thyroid hormone may occur at a post-receptor site in the hypothalamus.