Function of Estrogen on Bone and the Characterization of the Skeletal Phenotype of Steroid Receptor Coactivator (SRC)-1 KO Mice

Estrogen is known to have important effects on both reproductive and non-reproductive tissues. In this study it was demonstrated that an E2 dose of as little as 5µg/kg/d completely prevented loss of cancellous bone (at the lumbar spine and tibial metaphysis), and it had no stimulatory effects on the uterus in 6 month old C57BL/6 mice. By contrast, when 3 month old C56BL/6 mice were administered the same doses of E2 and studied after 1 month; the 5 g/kg/d dose resulted in uterine hypertrophy, but was not able to prevent loss of cancellous bone. These results, thus, a) provide data on the dose response for E2 effects on mouse bone; and b) indicate that the relative effects of E2 on bone versus the uterus are highly dependent on the particular experimental conditions used. This issue needs to be considered in evaluating agents with potential ?selective? effects on bone versus reproductive tissues. 2. Steroid receptor coactivator (SRC)-1 is an important nuclear receptor coactivator that enhances estrogen action in a number of tissues. The presented study has established that SRC-1 KO female and male mice have a comparable skeletal phenotype to their WT littermates at 3 and 5 months of age. The treatment of ovariectomized SRC-1 KO female mice with a physiological concentration of E2 led to a predominant defect in estrogen action in cancellous bone, with a relative preservation of estrogen effects on cortical bone. However, the deficit in estrogen action in the female SRC-1 KO mice was overcome by using a higher dose of E2, consistent with estrogen resistance in bone. The differential expression of the interacting nuclear receptors, ER- and -, in cancellous versus cortical bone and the specific interactions of these receptor isoforms with SRC-1 may, in part, explain why cancellous bone is more susceptible to loss of SRC-1 than cortical bone. 3. In contrast, the SRC-1 male mice lack the defect in estrogen action on bone. These findings are consistent with a gender-related difference that in male mice ER-α but not ER- is mediating the estrogen action on bone. The treatment of SRC-1 KO male mice with 5α-DHT resulted in a significant better response of the cortical bone from the KO male mice compared to the WT mice. The findings lead to the suggestion that in male WT mice SRC-1 might inhibit the action of 5α-DHT on bone. 4. Peripheral tissues including bone are dependent on circulating active sex steroids, but also synthesize estrogen from circulating C19 precursor locally. The conversion of the precursors to estrogen is mediated by aromatase. In this work it has been shown that human and rodent osteoblastic cells at different stages of differentiation express aromatase. Furthermore, the expression and activity has been demonstrated in bone tissues of mice and rats. Although a regulation of the aromatase by E2 was reported by other investigators in certain tissues, such as breast tissue and mammary glands, I did not find a change of aromatase expression and activity in the various bone cell lines and bone tissue under estrogen deficiency and estrogen exposure

Function of Estrogen on Bone and the Characterization of the Skeletal Phenotype of Steroid Receptor Coactivator (SRC)-1 KO Mice

Estrogen is known to have important effects on both reproductive and non-reproductive tissues. In this study it was demonstrated that an E2 dose of as little as 5µg/kg/d completely prevented loss of cancellous bone (at the lumbar spine and tibial metaphysis), and it had no stimulatory effects on the uterus in 6 month old C57BL/6 mice. By contrast, when 3 month old C56BL/6 mice were administered the same doses of E2 and studied after 1 month; the 5 g/kg/d dose resulted in uterine hypertrophy, but was not able to prevent loss of cancellous bone. These results, thus, a) provide data on the dose response for E2 effects on mouse bone; and b) indicate that the relative effects of E2 on bone versus the uterus are highly dependent on the particular experimental conditions used. This issue needs to be considered in evaluating agents with potential ?selective? effects on bone versus reproductive tissues. 2. Steroid receptor coactivator (SRC)-1 is an important nuclear receptor coactivator that enhances estrogen action in a number of tissues. The presented study has established that SRC-1 KO female and male mice have a comparable skeletal phenotype to their WT littermates at 3 and 5 months of age. The treatment of ovariectomized SRC-1 KO female mice with a physiological concentration of E2 led to a predominant defect in estrogen action in cancellous bone, with a relative preservation of estrogen effects on cortical bone. However, the deficit in estrogen action in the female SRC-1 KO mice was overcome by using a higher dose of E2, consistent with estrogen resistance in bone. The differential expression of the interacting nuclear receptors, ER- and -, in cancellous versus cortical bone and the specific interactions of these receptor isoforms with SRC-1 may, in part, explain why cancellous bone is more susceptible to loss of SRC-1 than cortical bone. 3. In contrast, the SRC-1 male mice lack the defect in estrogen action on bone. These findings are consistent with a gender-related difference that in male mice ER-α but not ER- is mediating the estrogen action on bone. The treatment of SRC-1 KO male mice with 5α-DHT resulted in a significant better response of the cortical bone from the KO male mice compared to the WT mice. The findings lead to the suggestion that in male WT mice SRC-1 might inhibit the action of 5α-DHT on bone. 4. Peripheral tissues including bone are dependent on circulating active sex steroids, but also synthesize estrogen from circulating C19 precursor locally. The conversion of the precursors to estrogen is mediated by aromatase. In this work it has been shown that human and rodent osteoblastic cells at different stages of differentiation express aromatase. Furthermore, the expression and activity has been demonstrated in bone tissues of mice and rats. Although a regulation of the aromatase by E2 was reported by other investigators in certain tissues, such as breast tissue and mammary glands, I did not find a change of aromatase expression and activity in the various bone cell lines and bone tissue under estrogen deficiency and estrogen exposure

Die Wirkung von Orexin B auf die Hormonsekretion ( Insulin, Glukagon und Somatostatin ) des isoliert perfundierten Rattenpankreas

Nachdem 1998 die Orexine entdeckt wurden, sind primär zahlreiche Untersuchungen weltweit bezüglich ihrer Wirksamkeit auf das zentrale Nervensystem durchgeführt worden. Die Identifizierung der Orexinrezeptoren sowie vermehrte Hinweise auf eine mögliche auch peripher existierende Wirkung der Orexine führten zur Zielsetzung dieser Arbeit. Untersucht werden sollte der periphere Einfluss von Orexin B auf die Hormonsekretion des Pankreas. Hierzu wurde ein etabliertes Perfusionssystem an männlichen Wistar-Ratten verwendet. Nach 24 stündiger Nahrungskarenz wurde bei den Ratten das Pankreas operativ isoliert und zwischen Truncus coeliacus und Vena portae mit einem abgestimmten Perfusionsmedium perfundiert. Zu Beginn wurde das Pankreas nur „basal“ perfundiert, dann mit 10 mM Glukose die Sekretionsaktivität stimuliert. Nacheinander wurde nun der Einfluss der verschiedenen Substanzen auf das Rattenpankreas durch Hinzugeben zum Perfusionsmedium überprüft. So wurden sukzessive verschiedene Orexin B Konzentrationen sowie die Wirkung von Leptin, GLP-I und Arginin auf das Pankreas untersucht. Die Probengewinnung des Perfusats aus der Vena portae fand in verschiedenen Zeitabständen fraktioniert statt, so dass die Früh- und die Spätphase der Pankreasaktivität separat beurteilbar waren. Diese Proben wurden dann auf ihren Gehalt an Insulin, Glukagon und teilweise auch an Somatostatin mittels Radioimmunoassay untersucht. Die resultierenden Daten wurden in drei Phasen aufbereitet: eine basale, sowie die eigentlich entscheidenden erste und zweite Sekretionsphasen des Rattenpankreas. Die Ergebnisse zeigten, dass Orexin B in hohen Konzentrationen eine deutliche Stimulation der Insulinsekretion des Pankreas bewirkt, die in der Spätphase stärker ausgeprägt ist. Die Wirkungsweise von Leptin als Inhibitor der Insulinsekretion konnte auch in diesen Untersuchungen nachgewiesen werden. Es wirkt als funktioneller Antagonist des Orexin B, wenn auch dieses in der verwendeten Konzentration von 10-8 M den Leptineffekt nicht vollständig ausgleichen konnte. Die Untersuchungen bezüglich des Einflusses von Orexin B auf die GLP-1 stimulierte Insulinsekretion, zeigten eine geringe Steigerung derselben. Jedoch wurde klar, dass die verwendete Dosierung von Orexin B mit 10-8 M die starke Wirkung des 10-9 M GLP-1 nur gering verstärken konnte, der insulinsteigernde Effekt jedoch maßgeblich auf das GLP-1 zurückzuführen ist. Die singuläre Perfusion mit Arginin zeigte merkwürdigerweise keinen statistisch relevanten Einfluss auf die Insulinsekretion des Pankreas. Im Gegensatz hierzu zeigte sich bei der kombinierten Applikation von Orexin B und Arginin eine deutliche Steigerung des Insulinsekretion, so dass von einer gegenseitigen Verstärkung beider Substanzen hinsichtlich der Stimulation der Insulinsekretion ausgegangen werden muss. Hinsichtlich der Glukagonsekretion des Pankreas zeigt Orexin B einen deutlichen inhibierenden Effekt auf die α-Zellen. Dieser Effekt vermag jedoch nicht die sekretionsstimulierende Wirkung des Leptin auf das Rattenpankreas zu relativieren; es vermindert in der verwendeten 10-8 M Konzentrationen die Sekretionsmenge nur geringgradig. Ähnlich sieht es bei der Interaktion von Orexin B und Arginin aus. Arginin als bekannter potenter Stimulator der Glukagonsekretion wird in seiner Wirkung durch Orexin B eingeschränkt. Aber auch hier vermag das mit 10-8 M dosierte Orexin B die Argininwirkung (10 mM) nicht vollständig aufheben. Die orientierenden Untersuchungen hinsichtlich der Beeinflussung der Somatostatinsekretion zeigten hingegen keine erkennbare Wirksamkeit von Orexin B auf die Funktion der D-Zellen. Weitere Untersuchungen hinsichtlich der detaillierten Einflussnahme des Orexin B’s im Hormonhaushalt müssten folgen, v.a. mit noch höheren Dosierungen desselben. Zum anderen wären Nachforschungen bzgl. der Rezeptorwirkung und auch der Rezeptorendichte auf den Pankreaszellen aufschlussreich, die die genaue Funktion sowie die zahlenmäßige und regionale Verteilung der OX-2-Rezeptoren verdeutlichen. Wichtige Hinweise für die Wirkungsweise des Orexin B’s würden auch die (konkurrierende) Situation der verschiedenen Substanzen am Orexinrezeptor darstellende Untersuchungen geben

Controlled engineering of extended states in disordered systems

We describe how to engineer wavefunction delocalization in disordered systems modelled by tight-binding Hamiltonians in d>1 dimensions. We show analytically that a simple product structure for the random onsite potential energies, together with suitably chosen hopping strengths, allows a resonant scattering process leading to ballistic transport along one direction, and a controlled coexistence of extended Bloch states and anisotropically localized states in the spectrum. We demonstrate that these features persist in the thermodynamic limit for a continuous range of the system parameters. Numerical results support these findings and highlight the robustness of the extended regime with respect to deviations from the exact resonance condition for finite systems. The localization and transport properties of the system can be engineered almost at will and independently in each direction. This study gives rise to the possibility of designing disordered potentials that work as switching devices and band-pass filters for quantum waves, such as matter waves in optical lattices.Comment: 14 pages, 11 figure

Deciphering the properties of the medium produced in heavy ion collisions at RHIC by a pQCD analysis of quenched large p⊥p_{\perp} π0\pi^0 spectra

We discuss the question of the relevance of perturbative QCD calculations for analyzing the properties of the dense medium produced in heavy ion collisions. Up to now leading order perturbative estimates have been worked out and confronted with data for quenched large $p_{\perp}$ hadron spectra. Some of them are giving paradoxical results, contradicting the perturbative framework and leading to speculations such as the formation of a strongly interacting quark-gluon plasma. Trying to bypass some drawbacks of these leading order analysis and without performing detailed numerical investigations, we collect evidence in favour of a consistent description of quenching and of the characteristics of the produced medium within the pQCD framework.Comment: 10 pages, 3 figure

The emerging plasma biomarker Dickkopf-3 (DKK3) and its association with renal and cardiovascular disease in the general population

Dickkopf-3 (DKK3) is an emerging biomarker for cardiovascular disease (CVD) and chronic kidney disease (CKD). Herein, baseline DKK3 plasma levels were measured in 8420 subjects from the Prevention of Renal and Vascular ENd-stage Disease (PREVEND) cohort, a large general population cohort, using enzyme-linked immunosorbent assays. Associations with clinical variables and outcomes were analysed. Median DKK3 level was 32.8 ng/ml (28.0-39.0). In multivariable linear regression analysis, the strongest correlates for plasma DKK3 were age, body mass index and estimated glomerular filtration rate (eGFR). At baseline, 564 (6.7%) subjects had CVD (defined as a myocardial infarction and/or cerebrovascular accident) and 1361 (16.2%) subjects had CKD (defined as eGFR 30 mg/24 h). Of subjects with known CVD and CKD follow-up status (respectively 7828 and 5548), 669 (8.5%) developed CVD and 951 (17.1%) developed CKD (median follow-up respectively 12.5 and 10.2 years). Crude logistic regression analysis revealed that DKK3 levels were associated with prevalent CVD (Odds ratio: 2.14 [1.76-2.61] per DKK3 doubling,