Hexose-6-phosphate Dehydrogenase Modulates 11β-Hydroxysteroid Dehydrogenase Type 1-Dependent Metabolism of 7-keto- and 7β-hydroxy-neurosteroids

BACKGROUND: The role of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) in the regulation of energy metabolism and immune system by locally reactivating glucocorticoids has been extensively studied. Experiments determining initial rates of enzyme activity revealed that 11beta-HSD1 can catalyze both the reductase and the dehydrogenase reaction in cell lysates, whereas it predominantly catalyzes the reduction of cortisone to cortisol in intact cells that also express hexose-6-phosphate dehydrogenase (H6PDH), which provides cofactor NADPH. Besides its role in glucocorticoid metabolism, there is evidence that 11beta-HSD1 is involved in the metabolism of 7-keto- and 7-hydroxy-steroids; however the impact of H6PDH on this alternative function of 11beta-HSD1 has not been assessed. METHODOLOGY: We investigated the 11beta-HSD1-dependent metabolism of the neurosteroids 7-keto-, 7alpha-hydroxy- and 7beta-hydroxy-dehydroepiandrosterone (DHEA) and 7-keto- and 7beta-hydroxy-pregnenolone, respectively, in the absence or presence of H6PDH in intact cells. 3D-structural modeling was applied to study the binding of ligands in 11beta-HSD1. PRINCIPAL FINDINGS: We demonstrated that 11beta-HSD1 functions in a reversible way and efficiently catalyzed the interconversion of these 7-keto- and 7-hydroxy-neurosteroids in intact cells. In the presence of H6PDH, 11beta-HSD1 predominantly converted 7-keto-DHEA and 7-ketopregnenolone into their corresponding 7beta-hydroxy metabolites, indicating a role for H6PDH and 11beta-HSD1 in the local generation of 7beta-hydroxy-neurosteroids. 3D-structural modeling offered an explanation for the preferred formation of 7beta-hydroxy-neurosteroids. CONCLUSIONS: Our results from experiments determining the steady state concentrations of glucocorticoids or 7-oxygenated neurosteroids suggested that the equilibrium between cortisone and cortisol and between 7-keto- and 7-hydroxy-neurosteroids is regulated by 11beta-HSD1 and greatly depends on the coexpression with H6PDH. Thus, the impact of H6PDH on 11beta-HSD1 activity has to be considered for understanding both glucocorticoid and neurosteroid action in different tissues

Neurosteroid Dehydroepiandrosterone Interacts with Nerve Growth Factor (NGF) Receptors, Preventing Neuronal Apoptosis

The neurosteroid dehydroepiandrosterone (DHEA), produced by neurons and glia, affects multiple processes in the brain, including neuronal survival and neurogenesis during development and in aging. We provide evidence that DHEA interacts with pro-survival TrkA and pro-death p75NTR membrane receptors of neurotrophin nerve growth factor (NGF), acting as a neurotrophic factor: (1) the anti-apoptotic effects of DHEA were reversed by siRNA against TrkA or by a specific TrkA inhibitor; (2) [3H]-DHEA binding assays showed that it bound to membranes isolated from HEK293 cells transfected with the cDNAs of TrkA and p75NTR receptors (KD: 7.4±1.75 nM and 5.6±0.55 nM, respectively); (3) immobilized DHEA pulled down recombinant and naturally expressed TrkA and p75NTR receptors; (4) DHEA induced TrkA phosphorylation and NGF receptor-mediated signaling; Shc, Akt, and ERK1/2 kinases down-stream to TrkA receptors and TRAF6, RIP2, and RhoGDI interactors of p75NTR receptors; and (5) DHEA rescued from apoptosis TrkA receptor positive sensory neurons of dorsal root ganglia in NGF null embryos and compensated NGF in rescuing from apoptosis NGF receptor positive sympathetic neurons of embryonic superior cervical ganglia. Phylogenetic findings on the evolution of neurotrophins, their receptors, and CYP17, the enzyme responsible for DHEA biosynthesis, combined with our data support the hypothesis that DHEA served as a phylogenetically ancient neurotrophic factor

A luteinizing hormone receptor intronic variant is significantly associated with decreased risk of Alzheimer's disease in males carrying an apolipoprotein E ε4 allele

Genetic and biochemical studies support the apolipoprotein E (APOE) ε4 allele as a major risk factor for late-onset Alzheimer's disease (AD), though ~50% of AD patients do not carry the allele. APOE transports cholesterol for luteinizing hormone (LH)-regulated steroidogenesis, and both LH and neurosteroids have been implicated in the etiology of AD. Since polymorphisms of LH beta-subunit (LHB) and its receptor (LHCGR) have not been tested for their association with AD, we scored AD and age-matched control samples for APOE genotype and 14 polymorphisms of LHB and LHCGR. Thirteen gene-gene interactions between the loci of LHB, LHCGR, and APOE were associated with AD. The most strongly supported of these interactions was between an LHCGR intronic polymorphism (rs4073366; lhcgr2) and APOE in males, which was detected using all three interaction analyses: linkage disequilibrium, multi-dimensionality reduction, and logistic regression. While the APOE ε4 allele carried significant risk of AD in males [p = 0.007, odds ratio (OR) = 3.08(95%confidence interval: 1.37, 6.91)], ε4-positive males carrying 1 or 2 C-alleles at lhcgr2 exhibited significantly decreased risk of AD [OR = 0.06(0.01, 0.38); p = 0.003]. This suggests that the lhcgr2 C-allele or a closely linked locus greatly reduces the risk of AD in males carrying an APOE ε4 allele. The reversal of risk embodied in this interaction powerfully supports the importance of considering the role gene-gene interactions play in the etiology of complex biological diseases and demonstrates the importance of using multiple analytic methods to detect well-supported gene-gene interactions

Vom Dreisäulensystem zum Baustein des europäischen Hauses – Wandel von Eigentum und Wettbewerb im deutschen Bankensektor

Der Beitrag untersucht die bisherigen Wirkungen von zwei ordnungspolitischen Veränderungen, mit denen der deutsche Bankensektor konfrontiert ist. Dabei handelt es sich zum einen um die Modifikation der Haftungsregeln für die öffentlich-rechtlichen Kreditinstitute und zum anderen um den Abbau von Hemmnissen für grenzüberschreitende Aktivitäten. Mit der Modifikation der Haftungsregeln für die öffentlich-rechtlichen Kreditinstitute waren im Sommer 2005 die rechtlichen Rahmenbedingungen für die drei Säulen des deutschen Bankensektors, d.h. öffentlichrechtliche Banken, private Kreditinstitute und Genossenschaftsbanken, einander angenähert worden. Es wurde erwartet, dass in der Folge Veränderungen im deutschen Bankensektor angestoßen werden könnten. Hierzu gehören ein potentieller Konsolidierungsschub bei Landesbanken in schwieriger Ertragslage sowie darüber hinaus säulenübergreifende Umgestaltungen bzw. Zusammenschlüsse von Banken, die letztlich Einfluss auf die Ertragslage und den Konzentrationsgrad im deutschen Bankensektor haben könnten. In Kapitel 2 wird gezeigt, dass es bislang wenige rechtlich-organisatorische Umgestaltungen gegeben hat; in Ergänzung zeigt Kapitel 3 die bestehende Situation des deutschen Bankensektors, darunter die im Vergleich zu anderen europäischen Ländern ungünstigere Ertragslage. Anhand der in Kapitel 4 vorgestellten Indikatoren zum Konzentrationsgrad lässt sich zeigen, dass der Konkurrenzdruck für deutsche Banken im europäischen Kontext zwar vergleichsweise hoch ist. Dennoch operieren deutsche Banken unter einer ähnlichen Marktkonstellation (monopolistische Konkurrenz) wie deren europäische Konkurrenten. Die detaillierten Indikatoren geben darüber hinaus Hinweise darauf, dass innerhalb des deutschen Bankensektors das Regionalprinzip den Wettbewerbsdruck für die Sparkassen und Genossenschaftsbanken in Vergleich zu den privaten Kreditbanken mildert. Es bestehen somit für den deutschen Bankensektor nur geringe Anstöße zur Veränderung “von innen“. Gleichzeitig sind grenzüberschreitende Aktivitäten, darunter insbesondere Merger- & Acquisition-Aktivitäten (Kapitel 5), in Deutschland wenig ausgeprägt. Insgesamt ging damit der zögerliche interne Anpassungsprozeß mit einem geringen Anpassungsdruck “von außen“ einher. Abstract The article examines the effects of two changes of the legal and institutional framework for German banks: the modification of state liabilities for public banks and the reduction of barriers for cross-border transactions. The modification of state guarantees for public banks led to a harmonization of the basic conditions for the three pillars of the German banking sector (public bank, private banks, cooperative banks). It was expected, that the harmonization could initiate major changes in the German banking sector, e.g. a stimulus for consolidation for those Landesbanken with a difficult return of equity position or a reorganisation or merger of banks beyond pillar frontiers. This might influence the return on equity situation and the concentration ratio of the German banking sector. However, there has been no substantial reorganisation within the German banking sector (chapter 2). In addition, the current situation in the German banking sector still points to an unfavourable return on equity situation compared to other European countries (chapter 3). The concentration ratio shows that the pressure of competition in German banks is quite high compared to European competitors (chapter 4); however German banks operate under similar market conditions (monopolistic competition). Within the German banking sector the Regionalprinzip, which prohibits savings banks and cooperative banks from operating outside their local areas, reduces the pressure of competition for savings and cooperative banks compared to private banks. All in all, there are few intern attempts to change the existent pillar system. At the same time, in Germany there are few cross-border activities, in particular merger & acquisitions (chapter 5). Thus, a lack of intern reorganisation comes along with a low pressure from the outside

Solar Thermal Decoupled Electrolysis: Long-term Behavior of Electrolytic Cell

The use of Co(OH)2 to facilitate the electrolytic production of H2 from stirred, highly alkaline, aqueous solutions was studied using voltammetry and bulk electrolysis at a rotating disc electrode (RDE). In agreement with theory, convection produced by the RDE increased the mass transfer to the electrode surface, which, lead to the desired increased current density over quiescent solutions. An extended form of our previously developed model was developed and used to predict the shape of cyclic and linear voltammograms for different conditions and to extract critical information and parameters for understanding the reaction mechanism. Unexpectedly, but beneficially, it was also observed that the electrode area increased during the course of bulk electrolysis as material was deposited on the anode

Solar Thermal Decoupled Electrolysis: Long-term Behavior of Electrolytic Cell

The use of Co(OH)2 to facilitate the electrolytic production of H2 from stirred, highly alkaline, aqueous solutions was studied using voltammetry and bulk electrolysis at a rotating disc electrode (RDE). In agreement with theory, convection produced by the RDE increased the mass transfer to the electrode surface, which, lead to the desired increased current density over quiescent solutions. An extended form of our previously developed model was developed and used to predict the shape of cyclic and linear voltammograms for different conditions and to extract critical information and parameters for understanding the reaction mechanism. Unexpectedly, but beneficially, it was also observed that the electrode area increased during the course of bulk electrolysis as material was deposited on the anode

σ- vs π‑Bonding in Manganese(II) Allyl Complexes

Reaction of two equivalents of K­[1,3-(SiMe₃)₂C₃H₃] (= K­[A′]) with MnCl₂ in THF produces the allyl complex A′₂Mn­(thf)₂; if the reaction is conducted in ether, the solvent-free heterometallic manganate species K₂MnA′₄ is isolated instead. With the related allyl K­[1,1′,3-(SiMe₃)₃C₃H₂] (= K­[A″]), reaction with MnCl₂ in THF/TMEDA produces the corresponding adduct A″₂Mn­(tmeda). In the solid state, both A′₂Mn­(thf)₂ and A″₂Mn­(tmeda) are monomeric complexes with σ-bonded allyl ligands (Mn–C = 2.174(2) and 2.189(2) Å, respectively). In contrast, K₂MnA′₄ is a two-dimensional coordination polymer, in which two of the allyl ligands on the Mn cation are σ-bonded (Mn–C = 2.197(6), 2.232(7) Å) and the third is π-bonded (Mn–C = 2.342(7)–2.477(7) Å). Both σ-allyls are π-coordinated to potassium cations, promoting the polymer in two directions; the π-allyl ligand is terminal. Density functional theory (DFT) calculations indicate that isolated high-spin (C₃R₂H₃)₂Mn (R = H, SiMe₃) complexes would possess π-bound ligands. A mixed hapticity (π-allyl)­(σ-allyl)­MnE structure would result with the addition of either a neutral ligand (e.g., THF, MeCN) or one that is charged (Cl, H). Both allyl ligands in a bis­(allyl)manganese complex are expected to adopt a σ-bonded mode if two THF ligands are added, as is experimentally observed in A′₂Mn­(thf)₂. The geometry of allyl–Mn­(II) bonding is readily modified; DFT results predict that [(C₃H₅)­Mn]⁺ and (C₃H₅)­MnCl should be σ-bonded, but the allyl in (C₃H₅)­MnH is found to exhibit a symmetrical π-bonded arrangement. Some of this behavior is reminiscent of that found in bis­(allyl)magnesium chemistry

How to assess communication skills? Development of the rating scale ComOn Check: Evaluation of communication skills

Background: Good communication is a core competency for all physicians. Thus, medical students require adequate preparation in communication skills. For research purposes, as well as for evaluation in teaching, there is a clear need for reliable assessment tools. We analyzed the shortcomings of existing instruments and saw a need for a new rating scale. The aim of this publication is to describe the development process for, and evaluation of, a new rating scale. Methods: First, we developed the rating scale in 10 steps. Then, two raters evaluated the newly developed rating scale by rating 135 videotaped consultations of medical students with standardized patients. Additionally, standardized patients evaluated students’ performance, which was used as an outside criterion to validate ratings. Results: Our rating scale comprises six domains with 13 specific items evaluated on a five-point Likert scale: initiating conversation, patient’s perception, structure of conversation, patient’s emotions, end of conversation, and general communication skills. Item-total correlation coefficients between the checklist items ranged from 0.15 to 0.78. Subscale consistency was calculated for domains comprised of more than one item and Cronbach’s α ≥ 0.77, indicating acceptable consistency. Standardized patients’ global evaluation correlated moderately with overall expert ratings (Spearman’s ρ = .40, p < .001). Conclusion: Our rating scale is a reliable and applicable assessment tool. The rating scale focuses on the evaluation of general communication skills and can be applied in research as well as in evaluations, such as objective structured clinical examinations (OSCE). Abbreviations: CST: Communication skills training; ICC: Intra-class correlation coefficient; OSCE: Objective structured clinical examination; SP: Standardized patients; SD: Standard deviation; M: Mea

σ- vs π‑Bonding in Manganese(II) Allyl Complexes

Reaction of two equivalents of K­[1,3-(SiMe₃)₂C₃H₃] (= K­[A′]) with MnCl₂ in THF produces the allyl complex A′₂Mn­(thf)₂; if the reaction is conducted in ether, the solvent-free heterometallic manganate species K₂MnA′₄ is isolated instead. With the related allyl K­[1,1′,3-(SiMe₃)₃C₃H₂] (= K­[A″]), reaction with MnCl₂ in THF/TMEDA produces the corresponding adduct A″₂Mn­(tmeda). In the solid state, both A′₂Mn­(thf)₂ and A″₂Mn­(tmeda) are monomeric complexes with σ-bonded allyl ligands (Mn–C = 2.174(2) and 2.189(2) Å, respectively). In contrast, K₂MnA′₄ is a two-dimensional coordination polymer, in which two of the allyl ligands on the Mn cation are σ-bonded (Mn–C = 2.197(6), 2.232(7) Å) and the third is π-bonded (Mn–C = 2.342(7)–2.477(7) Å). Both σ-allyls are π-coordinated to potassium cations, promoting the polymer in two directions; the π-allyl ligand is terminal. Density functional theory (DFT) calculations indicate that isolated high-spin (C₃R₂H₃)₂Mn (R = H, SiMe₃) complexes would possess π-bound ligands. A mixed hapticity (π-allyl)­(σ-allyl)­MnE structure would result with the addition of either a neutral ligand (e.g., THF, MeCN) or one that is charged (Cl, H). Both allyl ligands in a bis­(allyl)manganese complex are expected to adopt a σ-bonded mode if two THF ligands are added, as is experimentally observed in A′₂Mn­(thf)₂. The geometry of allyl–Mn­(II) bonding is readily modified; DFT results predict that [(C₃H₅)­Mn]⁺ and (C₃H₅)­MnCl should be σ-bonded, but the allyl in (C₃H₅)­MnH is found to exhibit a symmetrical π-bonded arrangement. Some of this behavior is reminiscent of that found in bis­(allyl)magnesium chemistry