High-sensitivity cardiac troponin T in essential hypertension.

BACKGROUND: Myocyte injury might be involved in the progression of essential hypertension (EHT) toward heart failure (HF). However, in the absence of high-sensitivity (hs) assay, cardiac troponin T (TnT) in EHT has not been measurable. METHODS AND RESULTS: We studied 236 consecutive ambulatory patients (mean age=65.5 years; 110 men) with treated EHT (mean systolic blood pressure=134.3 mmHg, mean serum N-terminal pro-B-type natriuretic peptide=86.6 pg/ml) for mean 65.6 months. Patients with a history of HF were excluded. Single and multiple variable analyses were performed in search of clinical correlates of elevated hs-TnT (≥0.003 ng/ml). Serum concentration of hs-TnT was ≥0.003 ng/ml (mean=0.008 ng/ml) in 184 patients. By single variable analysis, age, uric acid, log-transformed N-terminal pro-B-type natriuretic peptide, brachial-ankle pulse wave velocity, Cornell electrocardiographic (ECG) voltage, and number of antihypertensive medications were associated with log-transformed hs-TnT, while hemoglobin and estimated glomerular filtration rate (eGFR) were inversely correlated with log-transformed hs-TnT. By multivariate analysis, age, eGFR and Cornell voltage were independent correlates of log-transformed hs-TnT, even after adjustment for clinical backgrounds including known prognostic biomarkers of EHT. CONCLUSIONS: hs-TnT was ≥0.003 ng/ml in 78% of patients presenting with treated EHT and independently correlated with age, renal function, and ECG voltage of hypertrophy.

W194XProp1 and S156insTProp1, both of which have intact DNA-binding domain, show a different DNA-binding activity to the Prop1-binding element in human Pit-1 gene.

Prop1 activates POU1F1 (Pit-1) gene expression, which in turn stimulates GH, PRL, TSHbeta and GHRH receptor gene expressions. Therefore the patients with Prop1 mutation show GH, PRL, and TSH deficiency. The mutation of Prop1 is a major abnormality causing combined pituitary hormone deficiency (CPHD). However, DNA-binding and activating functions of mutant Prop1 have not been examined fully because Prop1-binding elements (PBEs) in human POU1F1 gene were not identified until 2008. The aim of this study is to test DNA-binding and transcriptional activities of two mutant Prop1s (W194XProp1 and S156insTProp1, both of them were found in the patients with CPHD) whose mutation is located in putative transactivating domain but not in DNA-binding domain. W194XProp1 showed a marked DNA-binding to PBE as well as a consensus element of paired-like transcription factors (PRDQ9). Activating function for POU1F1 reporter genes expression was lost or decreased in W194XProp1 but still preserved for PRDQ9 reporter gene. S156insTProp1 did not bind PBE but bound PRDQ9. Consistent with the result, S156insTProp1 did not stimulate POU1F1 reporter gene but stimulated PRDQ9 reporter gene. These results support the inference that W194XProp1 is unable to increase POU1F1 gene expression by the defect of transactivating domain and that S156insTProp1 is unable to increase due to the loss of DNA-binding activity. DNA-binding domain that has been assumed is not sufficient to provide full DNA-binding activity of Prop1 and transactivating domain of Prop1 is likely to affect DNA binding to PBE.

Correlates of NT-proBNP concentration in patients with essential hypertension in absence of congestive heart failure.

BACKGROUND: N-terminal proBNP (NT-proBNP) is widely used as a diagnostic biomarker and for the risk stratification of patients with heart failure (HF). Its role in the evaluation of patients with essential hypertension (EHT) is less clear. We examined the relationship between NT-proBNP concentrations and various clinical characteristics in hypertensive patients without HF. METHODS: This study included 186 consecutive patients with EHT and no history of HF, ischemic heart disease, or atrial fibrillation. Single and multiple variable regression analyses were performed in search of clinical correlates of NT-proBNP concentrations. RESULTS: In patients with EHT, median serum concentration of NT-proBNP was 73 pg/ml, and interquartile range (IQR) was 40-128 pg/ml. NT-proBNP was significantly higher (P<0.001) in women (87 pg/ml; IQR 55-137 pg/ml) than in men (52 pg/ml; IQR 24-115 pg/ml). Age (r=0.371, P<0.001), precordial QRS voltage (r=0.223, P<0.001), hemoglobin (Hgb) concentration, (r=-0.208, P=0.023) and estimated glomerular filtration rate (r=-0.139, P=0.044) were correlated with log-transformed NT-proBNP by multiple variable analysis. In men, age (r=0.453, P<0.001) and QRS voltage (r=0.283, P=0.004), and in women age (r=0.299, P=0.006), QRS voltage (r=0.212, P=0.019), Hgb (r=-0.182, P=0.049), and estimated glomerular filtration rate (r=-0.272, P=0.009) were correlated with serum concentrations of NT-proBNP. CONCLUSIONS: Age, gender, Hgb, left ventricular hypertrophy and renal function were correlated with NT-proBNP in patients with EHT.

Identification and analysis of prophet of Pit-1-binding sites in human Pit-1 gene.

Prophet of Pit-1 (Prop1) is a transcription factor that regulates Pit-1 gene expression. Because Pit-1 regulates the differentiation of pituitary cells and the expressions of GH, prolactin and TSHbeta genes, Prop1 mutation results in combined pituitary hormone deficiency in humans. However, Prop1-binding sites in human Pit-1 gene and the mechanism leading to combined pituitary hormone deficiency have remained unclear. In this study, we identified and analyzed Prop1-binding elements of the human Pit-1 gene. Prop1 stimulated the expression of the reporter plasmid containing Pit-1 gene from translation start site to -1340 dose dependently in GH3 cells. The activation by Prop1 was observed in GH3 and TtT/GF cells but not COS7, HeLa, JEG3, and HuH7 cells. Deletion analysis of Pit-1 gene showed that the Prop1-responsive elements were present within the -257-bp region. Within the -257-bp region, there are four elements similar to consensus sequence of paired-like transcription factors. Because Prop1 is a member of paired-like transcription factors, we assessed the elements. EMSA and transient transfection assay using the mutation of the elements revealed that the element from -63 to -53 (the proximal Prop1 binding element) was essential to Prop1-binding and Prop1-induced activation of Pit-1 reporter plasmid. A region at -8kb of human Pit-1 gene is similar to the distal region containing Prop1-binding elements in mouse Pit-1 gene. We showed the region functioned as an enhancer. Furthermore, chromatin immunoprecipitation assay showed that the proximal element could bind Prop1 in vivo cultured cells. Taken together, these findings indicated the novel functioning binding elements of Prop1 in human Pit-1 gene.

GHRP-2, a GHS-R agonist, directly acts on myocytes to attenuate the dexamethasone-induced expressions of muscle-specific ubiquitin ligases, Atrogin-1 and MuRF1.

Recent reports suggest that Atrogin-1 and MuRF1, E3 ubiquitin ligases, play a pivotal role in muscle atrophy. In the present study, effect of Growth Hormone Releasing Peptide-2 (GHRP-2), a GH secretagogue receptor (GHS-R) agonist, on the expressions of Atrogin-1 and MuRF1 in vivo rat muscles was examined. Dexamethasone administration increased Atrogin-1 mRNA level in rat soleus muscle. The increased mRNA level of Atrogin-1 was significantly attenuated by GHRP-2. In addition, GHRP-2 decreased MuRF1 mRNA level irrespective of the presence of dexamethasone. Although IGF-I is a well-known protective factor for muscle atrophy, GHRP-2 did not influence plasma IGF-I levels and IGF-I mRNA levels in muscles. To clarify a direct effect of GHRP-2, differentiated C2C12 myocytes were used. Ten micrometer dexamethasone increased both Atrogin-1 and MuRF1 mRNA levels in C2C12 cells. GHRP-2 attenuated dexamethasone-induced expression of them dose-dependently and decreased the basal level of MuRF1 mRNA. The suppressive effect on the expressions of Atrogin-1 and MuRF1 by GHRP-2 was blocked by [D-Lys(3)]-GHRP-6, a GHS-R1a blocker, suggesting the effect of GHRP-2 was mediated through GHS-R1a. Taken together, GHRP-2 directly attenuates Atrogin-1 and MuRF1 mRNA levels through ghrelin receptors in myocytes.

Involvement of mPOU (Brn-5), a class VI POU protein, in the gene expression of Pit-1 as well as PRL.

PRL is mainly expressed in the pituitary and its gene expression is regulated by a variety of transcription factors including Pit-1. Brn-5 is a transcription factor that binds to Pit-1 binding elements and stimulates PRL reporter gene expression. In this study, the role of Brn-5 was examined. RNA interference (RNAi) against Brn-5 leaded to reduction in PRL content of GH3 cells, indicating endogenous Brn-5 may play a role in PRL gene expression. Furthermore Brn-5 RNAi decreased Pit-1 mRNA. Transfection of expression vectors for mPOU (human ortholog of Brn-5) modestly but significantly stimulated activities of PRL-Luc and Pit-1-Luc reporter genes in GH3 and HEK 293 cells. In addition, mPOU showed synergistic action with Pit-1 and CBP on PRL-Luc expression. mPOU-FL, a splicing variant of mPOU, showed weaker activity than mPOU. Chip assay suggested binding of mPOU to PRL and Pit-1 promoters of genomic DNA. Taken together, these results suggest that mPOU (Brn-5) enhances PRL gene expression directly in association with Pit-1 and CBP, and indirectly via the activation of Pit-1 gene expression.

Neither intravenous nor intracerebroventricular administration of obestatin affects the secretion of GH, PRL, TSH and ACTH in rats.

To examine the effect of obestatin, a recently identified peptide derived from preproghrelin, on pituitary hormone secretion, obestatin was administered in anesthetized male rats. Intravenous administration of obestatin did not show any effect on plasma GH, PRL, ACTH and TSH levels. Since obestatin has been reported to have opposite effects of ghrelin in regulating food intake, gastric emptying and intestinal contractility, GH suppressive effect, which is opposite effect of ghrelin, was tested. Intravenous administration of GHRH or GHRP-2, a ghrelin receptor ligand, resulted in a marked plasma GH elevation. However obestatin did not show any effect on GHRH- or GHRP-2-induced GH rise. Furthermore intracerebroventricular administration of obestatin also did not influence plasma GH, PRL, ACTH and TSH levels. These findings suggest that obestatin has no effect on pituitary hormone secretions despite the presence of GPR39, a receptor for obestatin, in the pituitary.