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Publication date: January 2014 Source:Peptides, Volume 51

Author(s): Omar Echeverría-Rodríguez , Leonardo Del Valle-Mondragón , Enrique Hong

The renin–angiotensin system (RAS) regulates skeletal muscle insulin sensitivity through different mechanisms. The overactivation of the ACE (angiotensin-converting enzyme)/Ang (angiotensin) II/AT1R (Ang II type 1 receptor) axis has been associated with the development of insulin resistance, whereas the stimulation of the ACE2/Ang 1–7/MasR (Mas receptor) axis improves insulin sensitivity. The in vivo mechanisms by which this axis enhances skeletal muscle insulin sensitivity are scarcely known. In this work, we investigated whether rat soleus muscle expresses the ACE2/Ang 1–7/MasR axis and determined the effect of Ang 1–7 on rat skeletal muscle glucose uptake in vivo. Western blot analysis revealed the expression of ACE2 and MasR, while Ang 1–7 levels were detected in rat soleus muscle by capillary zone electrophoresis. The euglycemic clamp exhibited that Ang 1–7 by itself did not promote glucose transport, but it increased insulin-stimulated glucose disposal in the rat. In a similar manner, captopril (an ACE inhibitor) enhanced insulin-induced glucose uptake and this effect was blocked by the MasR antagonist A-779. Our results show for the first time that rat soleus muscle expresses the ACE2/Ang 1–7/MasR axis of the RAS, and Ang 1–7 improves insulin sensitivity by enhancing insulin-stimulated glucose uptake in rat skeletal muscle in vivo. Thus, endogenous (systemic and/or local) Ang 1–7 could regulate insulin-mediated glucose transport in vivo.

Publication date: February 2014 Source:Peptides, Volume 52

Author(s): Allyson C. Marshall , Hossam A. Shaltout , Nancy T. Pirro , James C. Rose , Debra I. Diz , Mark C. Chappell

We previously identified angiotensin converting enzyme (ACE) and an endopeptidase activity that degraded angiotensin-(1–7) [Ang-(1–7)] to Ang-(1–5) and Ang-(1–4), respectively, in the cerebrospinal fluid (CSF) of 6-month old male sheep. The present study undertook a more comprehensive analysis of the CSF peptidase that converts Ang-(1–7) to Ang-(1–4) in control and in utero betamethasone-exposed sheep (BMX). Characterization of the Ang-(1–7) peptidase revealed that the thiol agents 4-aminophenylmercuric acetate (APMA) and p-chloromercuribenzoic acid (PCMB), as well as the metallo-chelators o-phenanthroline and EDTA essentially abolished the enzyme activity. Additional inhibitors for serine, aspartyl, and cysteine proteases, as well as selective inhibitors against the endopeptidases neprilysin, neurolysin, prolyl and thimet oligopeptidases did not attenuate enzymatic activity. Competition studies against the peptidase revealed similar IC50s for Ang-(1–7) (5μM) and Ang II (3μM), but lower values for Ala¹-Ang-(1–7) and Ang-(2–7) of 1.8 and 2.0μM, respectively. In contrast, bradykinin exhibited a 6-fold higher IC50 (32μM) than Ang-(1–7) while neurotensin was a poor competitor. Mean arterial pressure (78±1 vs. 94±2mmHg, N =4–5, P <0.01) and Ang-(1–7) peptidase activity (14.2±1 vs 32±1.5fmol/min/ml CSF, N =5, P <0.01) were higher in the BMX group, and enzyme activity inversely correlated with Ang-(1–7) content in CSF. Lower Ang-(1–7) expression in brain is linked to baroreflex impairment in hypertension and aging, thus, increased activity of an Ang-(1–7) peptidase may contribute to lower CSF Ang-(1–7) levels, elevated blood pressure and impaired reflex function in this model of fetal programming.

Publication date: January 2014 Source:Peptides, Volume 51

Author(s): Kazunori Kageyama , Keiichi Itoi , Yasumasa Iwasaki , Kanako Niioka , Yutaka Watanuki , Satoshi Yamagata , Yuki Nakada , Gopal Das , Toshihiro Suda , Makoto Daimon

The Fos- and Jun family proteins are immediate-early gene products, and the Fos/Jun heterodimer, activator protein-1 (AP-1), may be involved in the regulation of corticotropin-releasing factor (CRF) gene expression. FosB is a member of the Fos family proteins that is expressed in the paraventricular nucleus of the hypothalamus upon stress exposure, but it has not been clear whether FosB participates in the regulation of CRF gene expression. This study aimed to explore the effect of the FosB and cJun proteins on CRF gene expression in rat hypothalamic 4B cells. The levels of FosB mRNA and cJun mRNA increased following treatment with forskolin, phorbol-12-myristate-13-acetate (PMA), or A23187 in the hypothalamic cells. Overexpression of FosB or cJun potently increased CRF mRNA levels. Furthermore, downregulation of FosB or cJun suppressed the CRF gene expression induced by forskolin, PMA, or A23187. In addition, the basal CRF mRNA levels were partially reduced by cJun downregulation. These findings suggest that FosB, together with cJun, may mediate CRF gene expression in the hypothalamic cells.

Publication date: February 2014 Source:Peptides, Volume 52

Author(s): Fernand Gobeil Jr. , Pierre Sirois , Domenico Regoli

We previously showed that R-954 (AcOrn[Oic²,(αMe)Phe⁵,dβNal⁷,Ile⁸]desArg⁹-bradykinin) is a potent, selective and stable peptide antagonist of the inducible GPCR kinin B1 receptor. This compound shows potential applications for the treatment of several diseases, including cancer and neurological disturbances of diabetes. To enable clinical translation, more information regarding its pharmacological, pharmacokinetics (PK) and toxicological properties at preclinical stage is warranted. This was the principal objective of the present study. Herein, specificity of R-954 was characterized in binding studies on 133 human molecular targets to reveal minor cross-reactivities against the angiotensin AT2 and the bombesin receptors (110- and 330-fold lower affinity than for B1R, respectively). The pharmacokinetic of R-954 was studied in both normal and streptozotocin-diabetic anaesthetized rats providing half-lives of 1.9–2.7h. R-954 does not appear to be metabolized in the rat circulation and in several rat tissue homogenates, as the kidney, lung and liver. It appears to be excreted as parent drug in the bile (21%) and in urine. A preliminary toxicological profile of R-954 was obtained in rats under various administration routes. R-954 appears to be well tolerated. Overall, these results indicate that R-954 exhibits favorable preclinical pharmacological/PK characteristics and encouraging safety profiles, suitable for early studies in humans.

Publication date: January 2014 Source:Peptides, Volume 51

Author(s): Xiao-Yang Li , Shao-Hua Tang , Xiao-Cong Zhou , Ying-Hai Ye , Xue-Qin Xu , Ri-Zeng Li

Visfatin is identified a pro-inflammatory cytokine and its serum level is increased in various cancers. This study aimed to evaluate the prognostic value of preoperative serum visfatin level in breast cancers. Preoperative serum visfatin levels of 248 patients with breast cancer and serum visfatin levels of 100 healthy individuals and 100 benign women controls were determined using enzyme-linked immunosorbent assay. Unfavorable outcome was defined as first local recurrence, distant metastasis, second primary cancer of another organ, or death from any cause. Disease-free survival was defined as the time between surgery and the date of unfavorable outcome whichever appeared first. Overall survival was defined from surgery to death for any cause. The association of serum visfatin level with outcomes including mortality, unfavorable outcome, disease-free survival and overall survival was investigated by univariate and multivariate analyses. Preoperative serum visfatin level was substantially higher in patients than in healthy subjects and benign controls respectively. Elevated preoperative serum level of visfatin was identified an independent predictor of mortality, unfavorable outcome, disease-free survival and overall survival. Receiver operating characteristic curve analysis showed that serum level visfatin had high predictive value for mortality and unfavorable outcome. Thus, our results suggest that high preoperative serum visfatin level is associated with poor patient outcomes as well as may play a role as prognostic biomarker in breast cancer survival.

Publication date: February 2014 Source:Peptides, Volume 52

Author(s): Nashwa N. Kabil , Hanan A. Seddiek , Nadia A. Yassin , Maha M. Gamal-Eldin

Recent studies have revealed that ghrelin may be an antioxidant and anti-inflammatory agent in many organs, however its role in chronic liver injury (CLI) remains unclear. The role of nitric oxide (NO) in CLI is controversial as evidence suggests that NO is either a primary mediator of liver cell injury or exhibits a protective effect against injurious stimuli. Recent evidence demonstrated that the therapeutic potential for ghrelin was through eNOS activation and increase in NO production. However, its role on NO production in the liver has not been previously investigated. The aim of this study was to investigate the role of ghrelin in treatment of CLI, and whether this action is mediated through NO. Forty male rats were divided into four groups: Group I: Control; Group II: chronic liver injury (CLI); Group III: CLI+Ghrelin; and Group IV: CLI+Ghrelin+ l-NAME. Liver enzymes and tumor necrosis factor alpha (TNF-α), were measured to assess hepatocellular injury. Liver tissue collagen content, malondialdehyde (MDA), gene expression of Bax, Bcl-2, and eNOS were assessed to determine the mechanism of ghrelin action. Results showed that ghrelin decreased serum liver enzymes and TNF-α levels. Ghrelin also reduced liver tissue collagen, MDA, and Bax gene expression, and increased Bcl-2 and eNOS gene expression. The effects on TNF-α, collagen, MDA, Bax, and eNOS were partially reversed in Group IV, suggesting that ghrelin's action could be through modulation of NO levels. Therefore, ghrelin's hepatoprotective effect is partially mediated by NO release.

Publication date: Available online 22 January 2014 Source:Peptides

Author(s): Zheng Ruipan , Meng Xiangzhi , Liu li , Zhang Ying , Qiao Mingliang , Jing Peng , Liu jingwei , Zhao zijun , Gao Yan

Neuropeptide Y (NPY) inhibits insulin secretion. Increased numbers of pancreatic islet cells expressing NPY has been observed in type 1 diabetic rats. To understand the functional significance of NPY expression in islet cells, we investigated the effects of high fat feeding and diabetic conditions on the expression and location of NPY expressing cells in normal and diabetic rats. Twenty rats were maintained on either normal chow (ND) or a high fat dietary regimen (HFD) for 4 weeks. In half of each group, type 1 or type 2 diabetes (groups T1DM and T2DM, respectively) was induced by injection of streptozotocin. At 8 weeks rats were euthanized and the pancreases were processed for immunofluorescence labeling (NPY/insulin, NPY/glucagon, NPY/somatostatin, and NPY/pancreatic polypeptide). Compared with the ND group, HFD rats had significantly fewer alpha cells, but beta cells were similar, while T1DM and T2DM rats showed significant increases in the proportions of alpha, delta, and PP cells. Robust increases in NPY-positive islet cells were found in the HFD, T1DM, and T2DM rats compared with ND controls. In ND rats, 99.7% of the NPY-positive cells were PP cells. However, high fat feeding and diabetes resulted in significant increases in NPY-positive delta cells, with concomitant decreases in NPY-positive PP cells. In summary, high-fat feeding and diabetes resulted in changes in the hormonal composition of pancreatic islet and increased number of NPY-expressing islet cells. Under diabetic conditions NPY expression switched from predominantly a characteristic of PP cells to predominantly that of delta cells. This may be a factor in reduced pancreatic hormone secretion during diabetes.

Publication date: February 2014 Source:Peptides, Volume 52

Author(s): Kazuhisa Honda , Takaoki Saneyasu , Takuya Yamaguchi , Tomohiko Shimatani , Koji Aoki , Kiwako Nakanishi , Hiroshi Kamisoyama

Glucagon-related peptides such as glucagon, glucagon-like peptide-1, and oxyntomodulin suppress food intake in mammals and birds. Recently, novel glucagon-like peptide (GCGL) was identified from chicken brain, and a comparatively high mRNA expression level of GCGL was detected in the hypothalamus. A number of studies suggest that the hypothalamus plays a critical role in the regulation of food intake in mammals and birds. In the present study, we investigated whether GCGL is involved in the central regulation of food intake in chicks. Male 8-day-old chicks (Gallus gallus) were used in all experiments. Intracerebroventricular administration of GCGL in chicks significantly suppressed food intake. Plasma glucose level was significantly decreased by GCGL, whereas plasma corticosterone level was not affected. Central administration of a corticotrophin-releasing factor (CRF) receptor antagonist, α-helical CRF, attenuated GCGL-suppressed food intake. It seems likely that CRF receptor is involved in the GCGL-induced anorexigenic pathway. All our findings suggest that GCGL functions as an anorexigenic peptide in the central nervous system of chicks.

Publication date: Available online 20 January 2014 Source:Peptides

Author(s): Chuan-Liu Wang , Hai-Yan Lin , Jian-Wei Xu , Fei-Fei Jiang , Ming Yang , Jin-Hua Wang , Xiu-Qing Huang

Increased plasma Adrenomedullin level has been associated with critical illness. This study aimed to investigate the correlations of plasma adrenomedullin concentration with 3-month clinical outcomes and early neurological deterioration of patients with acute intracerebral hemorrhage. One hundred fourteen patients and 112 healthy controls were recruited. Relationships of plasma adrenomedullin concentrations with early neurological deterioration, 3-month mortality and unfavorable outcome (modified Rankin Scale score>2) were evaluated. Plasma adrenomedullin concentrations were increased in patients than in healthy individuals and were highly associated with National Institutes of Health Stroke Scale scores. A multivariate analysis selected plasma adrenomedullin concentration as an independent predictor for 3-month clinical outcomes and early neurological deterioration. A receiver operating characteristic curve analysis showed plasma adrenomedullin concentration predicted 3-month clinical outcomes and early neurological deterioration with high area under curves. The predictive value of adrenomedullin was similar to that of National Institutes of Health Stroke Scale score. In a combined logistic-regression model, adrenomedullin did not improve the predictive value of National Institutes of Health Stroke Scale score. Thus, elevated plasma adrenomedullin concentration is highly associated with 3-month clinical outcomes and early neurological deterioration of patients with acute intracerebral hemorrhage.

Publication date: February 2014 Source:Peptides, Volume 52

Author(s): Renzhi Cai , Andrew V. Schally , Tengjiao Cui , Luca Szalontay , Gabor Halmos , Wei Sha , Magdolna Kovacs , Miklos Jaszberenyi , Jinlin He , Ferenc G. Rick , Petra Popovics , Rosemeire Kanashiro-Takeuchi , Joshua M. Hare , Norman L. Block , Marta Zarandi

In view of the recent findings of stimulatory effects of GHRH analogs, JI-34, JI-36 and JI-38, on cardiomyocytes, pancreatic islets and wound healing, three series of new analogs of GHRH(1–29) have been synthesized and evaluated biologically in an endeavor to produce more potent compounds. “Agmatine analogs”, MR-356 (N-Me-Tyr¹-JI-38), MR-361(N-Me-Tyr¹, D-Ala²-JI-38) and MR-367(N-Me-Tyr¹, D-Ala², Asn⁸-JI-38), in which Dat in JI-38 is replaced by N-Me-Tyr¹, showed improved relative potencies on GH release upon subcutaneous administration in vivo and binding in vitro. Modification with N-Me-Tyr¹ and Arg²⁹-NHCH3 as in MR-403 (N-Me-Tyr¹, D-Ala², Arg²⁹-NHCH3-JI-38), MR-406 (N-Me-Tyr¹, Arg²⁹-NHCH3-JI-38) and MR-409 (N-Me-Tyr¹, D-Ala², Asn⁸, Arg²⁹-NHCH3-JI-38), and MR-410 (N-Me-Tyr¹, D-Ala², Thr⁸, Arg²⁹-NHCH3-JI-38) resulted in dramatically increased endocrine activities. These appear to be the most potent GHRH agonistic analogs so far developed. Analogs with Apa³⁰-NH2 such as MR-326 (N-Me-Tyr¹, D-Ala², Arg²⁹, Apa³⁰-NH2-JI-38), and with Gab³⁰-NH2, as MR-502 (D-Ala², 5F-Phe⁶, Ser²⁸, Arg²⁹,Gab³⁰-NH2-JI-38) also exhibited much higher potency than JI-38 upon i.v. administration. The relationship between the GH-releasing potency and the analog structure is discussed. Fourteen GHRH agonists with the highest endocrine potencies were subjected to cardiologic tests. MR-409 and MR-356 exhibited higher potency than JI-38 in activating myocardial repair in rats with induced myocardial infarction. As the previous class of analogs, exemplified by JI-38, had shown promising results in multiple fields including cardiology, diabetes and wound healing, our new, more potent, GHRH agonists should manifest additional efficacy for possible medical applications.