First MTP joint injuries: MR imaging findings in surgically managed patients

OBJECTIVES

Determine whether MR imaging findings or demographics predict surgical management in patients with first MTP joint injuries.

MATERIALS AND METHODS

Retrospective study of 161 forefoot MRs for traumatic first MTP injury (M:F 92:69, mean age 33 ± 13 yrs.). Two radiologists reviewed imaging for ligamentous, osseous, and tendinous injuries. Ligaments and tendons were graded as 0:normal, 1:sprain or strain, 2:partial tear, 3:complete tear. Osseous injuries were classified as edema, fracture, or cartilage injury. Clinical data obtained included sex, age, injury acuity, sport participation, level of sport, and treatment. Imaging findings and demographic data were assessed to determine predictive factors for surgical management. Statistics included kappa, chi-squared, Fisher's exact, and logistic regression.

RESULTS

Logistic regression (odds ratio [95% CI], p-value) showed that grade 2 or 3 injuries of the plantar ligamentous complex (2.87, [1.10, 7.48], p = 0.031), grade 2 or 3 injuries of the medial collateral ligament (3.24, [1.16, 9.08], p = 0.025), and participation in collegiate or professional sports (4.34 [1.64, 11.52], p = 0.003) were associated with an increased rate of surgical intervention. k = ligamentous injury (0.71-0.83), osseous trauma (0.88-0.95), and tendon injury (0.78). All other imaging findings and demographic factors were not significant predictors of surgery (p > 0.05).

CONCLUSION

Participation in collegiate or professional sports and tears of the plantar ligamentous complex or medial collateral ligament predicted surgical management in patients with first MTP trauma.

Vegetation associations of the endangered fountain darter Etheostoma fonticola

Aquatic vegetation provides many services for aquatic habitats and fish communities. The federally listed fountain darter Etheostoma fonticola, found only in spring systems of the San Marcos and Comal rivers in central Texas, is reported to associate with vegetation for feeding, reproduction, and refuge. Descriptions of associations with vegetation range from preferred to exclusive, whereas other studies describe fountain darters found outside of vegetation. The purposes of this study were to quantify fountain darter occurrences and abundances among vegetated habitats using the concept of obligate and facultative habitat use. Wadeable and non-wadeable habitats among multiple reaches of the San Marcos and Comal rivers were sampled with seines and SCUBA diving methods in the spring and fall from 2014 to 2019. Fountain darters were often associated with aquatic vegetation but demonstrated both obligate and facultative tendencies. Fountain darters occurred in vegetation more than expected among wadeable and non-wadeable habitats in the majority of reaches within the San Marcos and Comal rivers. Among vegetation taxa, they were positively associated with bryophytes and negatively associated with Texas wild rice, but associations with other vegetation taxa varied by river and were possibly influenced by other variables. Current vegetation management in both rivers includes the removal of non-native species and restoration of native vegetation, so understanding the patterns of fountain darter associations with vegetation can guide future management and restoration efforts of these spring systems.

Domain-focused CRISPR screen identifies HRI as a fetal hemoglobin regulator in human erythroid cells

Increasing fetal hemoglobin (HbF) levels in adult red blood cells provides clinical benefit to patients with sickle cell disease and some forms of β-thalassemia. To identify potentially druggable HbF regulators in adult human erythroid cells, we employed a protein kinase domain-focused CRISPR-Cas9-based genetic screen with a newly optimized single-guide RNA scaffold. The screen uncovered the heme-regulated inhibitor HRI (also known as EIF2AK1), an erythroid-specific kinase that controls protein translation, as an HbF repressor. HRI depletion markedly increased HbF production in a specific manner and reduced sickling in cultured erythroid cells. Diminished expression of the HbF repressor BCL11A accounted in large part for the effects of HRI depletion. Taken together, these results suggest HRI as a potential therapeutic target for hemoglobinopathies.

Ultrasonographic Evaluation of the Effect of Osteopathic Manipulative Treatment on Sacral Base Asymmetry

Context

Patients with low back pain (LBP) may receive osteopathic manipulative treatment (OMT) to resolve or manage their pain. The indication for OMT for patients with LBP is the presence of somatic dysfunction, diagnosed using palpatory examination. Because palpatory findings commonly have poor interexaminer reliability, the current study used ultrasonography (US) to establish pre-OMT and post-OMT musculoskeletal measurements of relative asymmetry between pelvic and sacral bony landmarks.

Objective

To document objective musculoskeletal changes that occur in response to OMT using US and to compare palpatory assessment of landmark asymmetry with US assessment.

Methods

Sixty men and women aged 20 to 55 years with at least 1 episode of LBP in the past 2 weeks were assigned to a seated control, walking control, or OMT group (20 participants per group). Participants received an initial, bilateral US measurement of the skin to posterior superior iliac spine (SPSIS), skin to sacral base position (SBP), and sacral sulcus depth (SSD). Participants in seated control and OMT groups received a palpatory assessment of SBP and SSD prior to initial US assessment. After assessment, the seated control group sat in a waiting room for 30 minutes, the walking control group walked for 5 minutes, and the OMT group received OMT to address sacral base asymmetry using predominantly direct techniques for a maximum of 20 minutes. Participants then received a second US assessment of the same structures.

Results

Body mass index (BMI) was correlated with SPSIS (r=0.5, P=.001) and SBP (r=0.6, P<.001). More participants in seated control (75%) and OMT (65%) groups had an increase in asymmetry from first to second US assessment for SPSIS compared with participants in the walking control group (35%, P=.05). No significant differences were found between groups for absolute asymmetry or total change in asymmetry (all P>.10). The κ was −0.1 (95% CI, −0.2 to 0.03) for SBP and −0.01 (95% CI, −0.1 to 0.1) for SSD.

Conclusion

Musculoskeletal changes in SPSIS and SBP measurements related to OMT could not be readily identified using US. The SPSIS and SBP measurements were dependent on BMI, which may have affected the accuracy of US to detect small changes in asymmetry. Qualitative palpatory assessments did not correlate with US measurements. Further study is needed to identify US measurements that demonstrate change with OMT. (ClinicalTrials.gov number NCT02820701)

IDH mutation impairs histone demethylation and results in a block to cell differentiation

Recurrent mutations in isocitrate dehydrogenase 1 (IDH1) and IDH2 have been identified in gliomas, acute myeloid leukaemias (AML) and chondrosarcomas, and share a novel enzymatic property of producing 2-hydroxyglutarate (2HG) from α-ketoglutarate. Here we report that 2HG-producing IDH mutants can prevent the histone demethylation that is required for lineage-specific progenitor cells to differentiate into terminally differentiated cells. In tumour samples from glioma patients, IDH mutations were associated with a distinct gene expression profile enriched for genes expressed in neural progenitor cells, and this was associated with increased histone methylation. To test whether the ability of IDH mutants to promote histone methylation contributes to a block in cell differentiation in non-transformed cells, we tested the effect of neomorphic IDH mutants on adipocyte differentiation in vitro. Introduction of either mutant IDH or cell-permeable 2HG was associated with repression of the inducible expression of lineage-specific differentiation genes and a block to differentiation. This correlated with a significant increase in repressive histone methylation marks without observable changes in promoter DNA methylation. Gliomas were found to have elevated levels of similar histone repressive marks. Stable transfection of a 2HG-producing mutant IDH into immortalized astrocytes resulted in progressive accumulation of histone methylation. Of the marks examined, increased H3K9 methylation reproducibly preceded a rise in DNA methylation as cells were passaged in culture. Furthermore, we found that the 2HG-inhibitable H3K9 demethylase KDM4C was induced during adipocyte differentiation, and that RNA-interference suppression of KDM4C was sufficient to block differentiation. Together these data demonstrate that 2HG can inhibit histone demethylation and that inhibition of histone demethylation can be sufficient to block the differentiation of non-transformed cells.

Histone H4 lysine 20 of Saccharomyces cerevisiae is monomethylated and functions in subtelomeric silencing

Histones undergo post-translational modifications that are linked to important biological processes. Previous studies have indicated that lysine methylation correlating with closed or repressive chromatin is absent in the budding yeast Saccharomyces cerevisiae, including at H4 lysine 20 (K20). Here we provide functional evidence for H4 K20 monomethylation (K20me1) in budding yeast. H4 K20me1 is detectable on endogenous H4 by western analysis using methyl-specific antibodies, and the signal is abrogated by H4 K20 substitutions and by competition with H4 K20me1 peptides. Using chromatin immunoprecipitation, we show that H4 K20me1 levels are highest at heterochromatic locations, including subtelomeres, the silent mating type locus, and rDNA repeats, and lowest at centromeres within euchromatin. Further, an H4 K20A substitution strongly reduced heterochromatic reporter silencing at telomeres and the silent mating type locus and led to an increase in subtelomeric endogenous gene expression. The correlation between the location of H4 K20me1 and the effect of the H4 K20A substitution suggests that this modification plays a repressive function. Our findings reveal the first negative regulatory histone methylation in budding yeast and indicate that H4 K20me1 is evolutionarily conserved from simple to complex eukaryotes.

Characteristics of in vivo radiotherapy dosimetry

The recent discussion and debate about the use of in vivo dosimetry as a routine component of the radiotherapy treatment process has not included the limitations introduced by the physical characteristics of the detectors. Although a robust calibration procedure will ensure acceptable uncertainties in the measurements of tumour dose, further work is required to confirm the accuracy of critical organ measurements with a diode or a thermoluminescent dosemeter outside the main field owing to limitations caused by a non-uniform X-ray energy response of the detector, differences between the X-ray energy spectrum inside and outside the main field, and contaminating electrons.

An update survey of UK in vivo radiotherapy dosimetry practice

A questionnaire was distributed in 2004 to 59 radiotherapy physics departments in the UK to determine whether in vivo dosimetry practice had changed since a similar survey conducted 10 years earlier. The number of centres carrying out central axis dosimetry had increased slightly from 17 centres in 1994 to 22 centres in 2004, with a diode alone being the most commonly used detector. Twice as many centres (43) carried out critical organ dosimetry compared with those carrying out central axis measurements, and this number had also increased slightly above the 1994 value (38). A diode was used by most centres carrying out central axis dosimetry and by about 50% of centres carrying out critical organ dosimetry. The action level adopted by each centre for central axis measurements varied from >+/-3% to >+/-10% difference between the measured and the prescribed dose, with >+/-5% being the most frequent value. It was concluded that there had been little change in in vivo dosimetry practice during the time between the two surveys, and that guidance on the method and applications for in vivo dosimetry is required before recent recommendations for its widespread adoption for routine use can be satisfied.

Neighboring Group-Controlled Hydrolysis: Towards “Designer” Drug Release Biomaterials

To give the first demonstration of neighboring group-controlled drug delivery rates, a series of novel, polymerizable ester drug conjugates was synthesized and fully characterized. The monomers are suitable for copolymerization in biomaterials where control of drug release rate is critical to prophylaxis or obviation of infection. The incorporation of neighboring group moieties differing in nucleophilicity, geometry, and steric bulk in the conjugates allowed the rate of ester hydrolysis, and hence drug liberation, to be rationally and widely controlled. Solutions (2.5 x 10-5 mol dm-3) of ester conjugates of nalidixic acid incorporating pyridyl, amino, and phenyl neighboring groups hydrolyzed according to first-order kinetics, with rate constants between 3.00 +/- 0.12 x 10-5 s -1 (fastest) and 4.50 +/- 0.31 x 10- 6 s-1 (slowest). The hydrolysis was characterized using UV-visible spectroscopy. When copolymerized with poly(methyl methacrylate), free drug was shown to elute from the resulting materials, with the rate of release being controlled by the nature of the conjugate, as in solution. The controlled molecular architecture demonstrated by this system offers an attractive class of drug conjugate for the delivery of drugs from polymeric biomaterials such as bone cements in terms of both sustained, prolonged drug release and minimization of mechanical compromise as a result of release. We consider these results to be the rationale for the development of "designer" drug release biomaterials, where the rate of required release can be controlled by predetermined molecular architecture.

Effect of electron contamination of a 6 MV x-ray beam on near surface diode dosimetry

In critical organ in vivo x-ray dosimetry, the relative contaminating electron contribution to the total dose and total detector response outside the field will be different to the corresponding contributions at the central axis detector calibration position, mainly due to the effects of shielding in the linear accelerator head on the electron and x-ray energy spectrum. To investigate these contributions, the electron energy response of a Scanditronix PFD diode was measured using electrons with mean energies from 0.45 to 14.6 MeV, and the Monte Carlo code MCNP-4C was used to calculate the electron energy spectra on the central axis, and at 1 and 10 cm outside the edge of a 4 x 4, 10 x 10 and a 15 x 15 cm(2) 6 MV x-ray field. The electron contribution to the total dose varied from about 8% on the central axis of the smallest field to about 76% at 10 cm outside the edge of the largest field. The electron contribution to the total diode response varied from about 7-8% on the central axis of all three fields to about 58% at 10 cm outside the edge of the smallest field. The results indicated that a near surface x-ray dose measurement with a diode outside the treatment field has to be interpreted with caution and requires knowledge of the relative electron contribution specific to the measurement position and field size.

The low energy X-ray response of the LiF:Mg:Cu:P thermoluminescent dosemeter: a comparison with LiF:Mg:Ti

LiF:Mg:Cu:P thermoluminescent dosemeters (TLD) can be used for the same X-ray dosimetry applications as LiF:Mg:Ti, with each type having the disadvantage of a response dependent on energy, particularly at low energies. Measurements were made of the response per unit air kerma of LiF:Mg:Cu:P and LiF:Mg:Ti to nine quasi-monoenergetic X-ray beams with mean energies from 12 keV to 208 keV. Each measurement was normalized to the value produced by 6 MV X-rays. LiF:Mg:Cu:P was found to under-respond to a majority of these radiations whereas LiF:Mg:Ti over-responded to a majority. Their smallest relative measured response was produced by the lowest energy beam, and the maximum measured relative response of 1.15+/-0.07 and 1.21+/-0.07 for LiF:Mg:Cu:P and LiF:Mg:Ti, respectively, occurred at 33 keV. Energy response coefficients were derived from these measurements to estimate the error introduced by using either type of TLD to measure the dose from an X-ray spectrum different to that used for its absolute response calibration. It was calculated that if the response of either type of TLD was calibrated at 100 kVp, then an error of no more than +/-2% would be introduced into measurements of tube output at potentials of 50-130 kVp. LiF:Mg:Cu:P was found to introduce a larger error (up to 30%) into the measurement of body exit dose than LiF:Mg:Ti at tube potentials of 40-150 kVp, if its absolute response was calibrated using the corresponding body entrance beam. The method should allow this type of error to be estimated in other dosimetry applications for either type of TLD.

Near surface photon energy spectra outside a 6 MV field edge

The purpose of this study was to investigate the difference between a 6 MV linear accelerator x-ray energy spectrum outside the field edge near a phantom surface, and the corresponding spectrum on the central axis. The Monte Carlo code MCNP-4A was used to calculate the spectra on the central axis and at 1, 2, 5 and 10 cm from the edge of a 4 x 4 cm2, 10 x 10 cm2 and 15 x 15 cm2 field. Compared to the spectrum on the central axis, the spectra outside the field edge showed two distinct regions: a broad peak below about 0.5 MeV, and a lower amplitude, less rapidly changing region at higher energies from 0.5 to 6 MeV. The lower energy peak was due to scattered photons, and the higher energy component was due mainly to primary photons transmitted through the jaws of the secondary collimator. The potential impact of these spectral differences on critical organ photon dosimetry was determined by calculating the ratio of the sensitivity of a Scanditronix EDD-5 diode and of a LiF:Mg:Ti thermoluminescent dosimeter (TLD) outside the field edge to their respective sensitivity at the calibration position on the central axis. The lower energy peak combined with the non-uniform energy sensitivity of each detector produced up to a two-thirds overestimate of x-ray dose outside the field by the diode, whereas the response ratio of the TLD was about unity. These results indicated that a similar evaluation was required for profile measurements of a dynamic wedged field and measurements in an intensity modulated beam with either type of detector.

Functional localization of single active ion channels on the surface of a living cell

The spatial distribution of ion channels in the cell plasma membrane has an important role in governing regional specialization, providing a precise and localized control over cell function. We report here a novel technique based on scanning ion conductance microscopy that allows, for the first time, mapping of single active ion channels in intact cell plasma membranes. We have mapped the distribution of ATP-regulated K+ channels (KATP channels) in cardiac myocytes. The channels are organized in small groups and anchored in the Z-grooves of the sarcolemma. The distinct pattern of distribution of these channels may have important functional implications.

Hybrid scanning ion conductance and scanning near-field optical microscopy for the study of living cells

We have developed a hybrid scanning ion conductance and scanning near-field optical microscope for the study of living cells. The technique allows quantitative, high-resolution characterization of the cell surface and the simultaneous recording of topographic and optical images. A particular feature of the method is a reliable mechanism to control the distance between the probe and the sample in physiological buffer. We demonstrate this new method by recording near-field images of living cells (cardiac myocytes).

Cell volume measurement using scanning ion conductance microscopy

We report a novel scanning ion conductance microscopy (SICM) technique for assessing the volume of living cells, which allows quantitative, high-resolution characterization of dynamic changes in cell volume while retaining the cell functionality. The technique can measure a wide range of volumes from 10(-19) to 10(-9) liter. The cell volume, as well as the volume of small cellular structures such as lamelopodia, dendrites, processes, or microvilli, can be measured with the 2.5 x 10(-20) liter resolution. The sample does not require any preliminary preparation before cell volume measurement. Both cell volume and surface characteristics can be simultaneously and continuously assessed during relatively long experiments. The SICM method can also be used for rapid estimation of the changes in cell volume. These are important when monitoring the cell responses to different physiological stimuli.

Hypertension in mice lacking 11beta-hydroxysteroid dehydrogenase type 2

Deficiency of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) in humans leads to the syndrome of apparent mineralocorticoid excess (SAME), in which cortisol illicitly occupies mineralocorticoid receptors, causing sodium retention, hypokalemia, and hypertension. However, the disorder is usually incompletely corrected by suppression of cortisol, suggesting additional and irreversible changes, perhaps in the kidney. To examine this further, we produced mice with targeted disruption of the 11beta-HSD2 gene. Homozygous mutant mice (11beta-HSD2(-/-)) appear normal at birth, but approximately 50% show motor weakness and die within 48 hours. Both male and female survivors are fertile but exhibit hypokalemia, hypotonic polyuria, and apparent mineralocorticoid activity of corticosterone. Young adult 11beta-HSD2(-/-) mice are markedly hypertensive, with a mean arterial blood pressure of 146 +/- 2 mmHg, compared with 121 +/- 2 mmHg in wild-type controls and 114 +/- 4 mmHg in heterozygotes. The epithelium of the distal tubule of the nephron shows striking hypertrophy and hyperplasia. These histological changes do not readily reverse with mineralocorticoid receptor antagonism in adulthood. Thus, 11beta-HSD2(-/-) mice demonstrate the major features of SAME, providing a unique rodent model to study the molecular mechanisms of kidney resetting leading to hypertension.

The X-ray and electron benchmarking of the Monte Carlo codes MCNP-4A and 4B on different computers

MCNP (Monte Carlo N-Particle) is a Monte Carlo transport code which has been of widespread use in modelling the dosimetry of ionizing radiations. The most recent version (4B) features improved electron transport compared with the previous version 4A. The processing time required by a number of computing systems to carry out X-ray and electron transport calculations using both versions of the code was compared. Version 4A was installed onto a Dec Alpha Server 8200, a personal computer (Pentium 90 MHz), and a Sun Sparc20, 10, 4 and 1+. MCNP-4B was also installed onto the Sun Sparc20. The benchmark tests consisted of determining the transmission of 2 MeV X-rays and 30 MeV electrons through lead. It was found that the Dec Alpha Server 8200 was the fastest computing platform, and the Sun Sparc1+ was the slowest for both tests. The difference in computational speed between different platforms was not matched by the corresponding differences in price. The time required by version 4B to complete the X-ray and electron benchmark tests was found to be 1.4 and 2.3 times greater than version 4A, respectively, without any difference in the results of the calculation for each type of radiation. This suggests that in cases where computing time is important, it may be preferable to use version 4A instead of 4B.

Measuring the progression of foreign-body reaction to silicone implants using in vivo MR microscopy

We used in vivo magnetic resonance (MR) microscopy to follow the growth of fibrous capsule as a foreign body reaction to silicone implants in rats. Anesthetized rats were imaged 1, 7, 14, and 28 days after silicone-coated MR imaging coils were sutured to their neck muscles. On the twenty-eighth day, rats were sacrificed and coils and adjacent tissues were removed en bloc and fixed in formalin, reimaged with MR, and sectioned for conventional histology. Three-dimensional (3-D) spin-echo [3DFT] acquisition gave in-plane resolution of 32 x 32 microns in vivo and 16 x 16 microns ex vivo. All MR images showed a diffuse band of elevated signal intensity between the silicone of the coil and adjacent tissue. The border of the hyperintense band was thin and not well defined at seven days post-implantation. From 7-28 days, the band showed relatively homogeneous signal intensity and its thickness increased 44% on the rectus muscle side and 78% on the subcutaneous side. The capsule thickness determined either by MR in vivo and ex vivo microscopy or conventional histology was not significantly different, and there was a significant correlation between thickness measurements among those methods. MR in vivo microscopy provides sufficient resolution and spatial information to serially evaluate the growth of the foreign body fibrous capsule over time, thus achieving greater accuracy and consistency in measurements.

11Beta-hydroxysteroid dehydrogenase 1 in adipocytes: expression is differentiation-dependent and hormonally regulated

11Beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1) catalyses the reversible metabolism of physiological glucocorticoids (cortisol, corticosterone) to inactive metabolites (cortisone, 11-dehydrocorticosterone), thus regulating glucocorticoid access to receptors. 11Beta-HSD-1 expression is regulated during development and by hormones in a tissue specific manner. The enzyme is highly expressed in liver, where it may influence glucocorticoid action on fuel metabolism, processes also important in adipose tissue. Here we show that 11beta-HSD-1 is expressed in white adipose tissue, in both the adipocyte and stromal/vascular compartments, and in the adipocyte cell lines 3T3-F442A and 3T3-L1. In these cells, 11beta-HSD-1 expression is induced upon differentiation into adipocytes and is characteristic of a 'late differentiation' gene, with maximal expression 6-8 days after confluence is reached. In intact 3T3-F442A adipocytes the enzyme direction is predominantly 11beta-reduction, activating inert glucocorticoids. The expression of 11beta-HSD-1 mRNA is altered in fully differentiated 3T3-F442A adipocytes treated with insulin, dexamethasone or a combination of the hormones, in an identical manner to glycerol-3-phosphate dehydrogenase (GPDH) mRNA (encoding a key enzyme in triglyceride synthesis and a well-characterised marker of adipocyte differentiation). The demonstration of 11beta-HSD-1 expression in adipocytes and its predominant reductase activity in intact 3T3-F442A adipocytes suggests that 11beta-HSD-1 may play an important role in potentiating glucocorticoid action in these cells. 3T3-F442A and 3T3-L1 represent useful model systems in which to examine the factors which regulate 11beta-HSD-1 gene expression and the role of 11beta-HSD-1 in modulating glucocorticoid action in adipose tissue.

Characterization of mutations in patients with multiple endocrine neoplasia type 1

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by tumors of the parathyroids, pancreatic islets, and anterior pituitary. The MEN1 gene, on chromosome 11q13, has recently been cloned, and mutations have been identified. We have characterized such MEN1 mutations, assessed the reliability of SSCP analysis for the detection of these mutations, and estimated the age-related penetrance for MEN1. Sixty-three unrelated MEN1 kindreds (195 affected and 396 unaffected members) were investigated for mutations in the 2,790-bp coding region and splice sites, by SSCP and DNA sequence analysis. We identified 47 mutations (12 nonsense mutations, 21 deletions, 7 insertions, 1 donor splice-site mutation, and 6 missense mutations), that were scattered throughout the coding region, together with six polymorphisms that had heterozygosity frequencies of 2%-44%. More than 10% of the mutations arose de novo, and four mutation hot spots accounted for >25% of the mutations. SSCP was found to be a sensitive and specific mutational screening method that detected >85% of the mutations. Two hundred and one MEN1 mutant-gene carriers (155 affected and 46 unaffected) were identified, and these helped to define the age-related penetrance of MEN1 as 7%, 52%, 87%, 98%, 99%, and 100% at 10, 20, 30, 40, 50, and 60 years of age, respectively. These results provide the basis for a molecular-genetic screening approach that will supplement the clinical evaluation and genetic counseling of members of MEN1 families.

11beta-hydroxysteroid dehydrogenase type 1 knockout mice show attenuated glucocorticoid-inducible responses and resist hyperglycemia on obesity or stress

Glucocorticoid hormones, acting via nuclear receptors, regulate many metabolic processes, including hepatic gluconeogenesis. It recently has been recognized that intracellular glucocorticoid concentrations are determined not only by plasma hormone levels, but also by intracellular 11beta-hydroxysteroid dehydrogenases (11beta-HSDs), which interconvert active corticosterone (cortisol in humans) and inert 11-dehydrocorticosterone (cortisone in humans). 11beta-HSD type 2, a dehydrogenase, thus excludes glucocorticoids from otherwise nonselective mineralocorticoid receptors in the kidney. Recent data suggest the type 1 isozyme (11beta-HSD-1) may function as an 11beta-reductase, regenerating active glucocorticoids from circulating inert 11-keto forms in specific tissues, notably the liver. To examine the importance of this enzyme isoform in vivo, mice were produced with targeted disruption of the 11beta-HSD-1 gene. These mice were unable to convert inert 11-dehydrocorticosterone to corticosterone in vivo. Despite compensatory adrenal hyperplasia and increased adrenal secretion of corticosterone, on starvation homozygous mutants had attenuated activation of the key hepatic gluconeogenic enzymes glucose-6-phosphatase and phosphoenolpyruvate carboxykinase, presumably, because of relative intrahepatic glucocorticoid deficiency. The 11beta-HSD-1 -/- mice were found to resist hyperglycamia provoked by obesity or stress. Attenuation of hepatic 11beta-HSD-1 may provide a novel approach to the regulation of gluconeogenesis.

The response of a MOSFET, p-type semiconductor and LiF TLD to quasi-monoenergetic x-rays

A metal oxide semiconductor field effect transistor (MOSFET), p-type semiconductor and a TLD can all be used for x-ray dosimetry, with each system having the common disadvantage of a response which is dependent upon the incident photon energy, particularly for energies < 1 MeV. A Pantak HF-320 quasi-monoenergetic x-ray unit was used to determine the response of two Thomson and Nielson TN-502RD MOSFETs, a Scanditronix EDP-10 semiconductor (build-up cap 10 mm: tissue equivalence), an EDD-5 semiconductor (build-up cap 4.5 mm: tissue equivalence) and an Lif:Mg:Ti TLD over the energy range 12-208 keV. The sensitivity of each detector was normalized to the value produced by exposure to 6 MV x-rays. The maximum relative sensitivities of the two MOSFET detectors were 4.19 +/- 0.25 and 4.44 +/- 0.26 respectively, occurring at an incident x-ray energy of 33 keV. The maximum relative sensitivity of the Scanditronix EDP-10 of 2.24 +/- 0.13 occurred at 65 keV, and for the EDD-5, it was 7.72 +/- 0.45 at 48 keV. The TLD produced a maximum relative sensitivity of 1.31 +/- 0.09 at 33 keV. Compared with available data based on heteroenergetic x-ray sources, these measurements have identified a more representative response for each detector to low-energy x-rays.

The integrated concentration of cortisone is reduced in obese children

We evaluated the possibility that there is enhanced conversion of cortisol (F) to cortisone (E) in obese children. IC-E was measured from 15 lean children aged 12.7 +/- 2.2 years, body mass index Z-score (BMI-SD) = -0.35 +/- 0.82, IC-F = 197 +/- 70 nM/l and 9 obese children aged 12.3 +/- 3.2 years, BMI-SD = + 4.7 +/- 2.1, IC-F = 149 +/- 53 nM/l. IC-E was higher in lean children 76 +/- 25 nM/l compared to obese 60 +/- 11 nM/l (p < 0.04). There was no difference in the ratio of IC-E/IC-F between lean 0.40 +/- 0.10 and obese subjects 0.42 +/- 0.09 (p < 0.06). IC-E was directly correlated with IC-F: IC-E = 0.25 x IC-F + 26 (n = 24, r2 = 0.57, p < 0.0001). In a multiple regression model (overall r2 = 0.32, p < 0.02), IC-E was related to BMI-SD inversely (p < 0.0054) and influenced as well by interaction of BMI-SD with sex (p < 0.043), IC-E being lower in boys with increasing body mass. In childhood, obesity is associated with decreased plasma IC-E and IC-F levels, the ratio of IC-E/IC-F is independent of body mass. Reduced IC-E levels in obese children are most likely due to the impact of body mass on IC-F.

Correlation of clinical, endocrine and molecular abnormalities with in vivo responses to high-dose testosterone in patients with partial androgen insensitivity syndrome

OBJECTIVE

To investigate the responses of two patients previously diagnosed as Reifenstein's syndrome to graded high-dose testosterone in terms of hormone levels, nitrogen balance and sebum secretion and to attempt to correlate these parameters with the properties of their androgen receptors and mutations in the androgen receptor gene.

DESIGN

Nitrogen balance was determined by comparing controlled nitrogen intake to the amount excreted. Sebum excretion was measured on the forehead. Patients were studied during control periods (no treatment) and during administration of testosterone propionate. Blood samples were used as a source of genomic DNA and to measure peripheral hormone levels; androgen receptor binding was determined using genital skin fibroblasts.

PATIENTS

Two patients of XY karyotype, with ambiguous external genitalia and problems of testicular descent who had required mastectomy as teenagers. Normal male controls of proven fertility.

MEASUREMENTS

Nitrogen balance, sebum excretion rate and peripheral hormone levels (testosterone, dihydrotestosterone, LH and FSH) were studied before and after testosterone therapy (1 or 5 mg/kg/day). Genomic DNA was extracted from peripheral blood leucocytes and regions of the androgen receptor gene amplified by polymerase chain reaction using pairs of specific primers. Mobility of amplified DNA from patients was analysed on denaturing gradient acrylamide gels and fragments differing in mobility from those of normal controls were sequenced. Fibroblasts were cultured from scrotal skin biopsies and androgen receptor binding parameters, subcellular localization and up-regulation were determined.

RESULTS

Testosterone therapy resulted in raised plasma testosterone, dihydrotestosterone and oestradiol in both patients. In patient 1 (lesser genital abnormality), LH was suppressed by 5 mg/kg/day testosterone to the upper limit of the normal range but FSH remained low normal. Both LH and FSH were suppressed by testosterone treatment in patient 2 (greater genital abnormality). Nitrogen retention was increased in both patients (4.2 and 3.0 g/24 h respectively); sebum excretion rate increased to normal in patient 1 but showed no change in patient 2. Mutations in the androgen receptor gene were identified in both patients. In patient 1 a single nucleotide change from adenosine to guanosine resulted in the substitution of glycine for glutamic acid at position 772 within the hormone binding domain of the receptor. In patient 2 a single nucleotide mutation from guanosine to adenosine resulted in the substitution of lysine for arginine at position 608 (exon 3) situated in the second zinc finger of the DNA binding domain. Both patients had a normal number of androgen binding sites in genital skin fibroblasts but those in patient 1 showed reduced binding affinity and rapid dissociation of receptor/ligand complexes while those in patient 2 showed defective nuclear localization.

CONCLUSION

In patients with partial androgen insensitivity syndrome the type of androgen receptor mutation and responses to short-term androgen treatment can be correlated with the individual's potential to virilize. If there is a mutation in the androgen receptor DNA binding domain the patient may show little ability to virilize either spontaneously at puberty or after androgen treatment. Sebum excretion appears to be more discriminating than nitrogen balance or gonadotrophin suppression as an index of tissue response to androgens.

A survey of current in vivo radiotherapy dosimetry practice

A questionnaire was sent out to 57 radiotherapy physics departments in the United Kingdom to determine the type of dosemeters used for in vivo measurements inside and outside X-ray treatment fields, and whether any correction is made for energy dependence when the dose to critical organs outside the main beam is estimated. 44 responses were received. 11 centres used a semi-conductor for central axis dosimetry compared with only two centres which used thermoluminescent dosimetry (TLD). 37 centres carried out dosimetry measurements outside the main beam; 25 centres used TLD and 12 centres used a semi-conductor detector. Of the 16 centres measuring the dose at both sites. 11 used a semi-conductor for the central axis measurement, but only four of those 11 changed to TLD for critical organ dosimetry despite the latter's lower variation in energy response. None of the centres stated that they made a correction for the variation in detector energy response when making measurements outside the main beam, indicating a need for a more detailed evaluation of the energy response of these detectors and the energy spectra outside the main beam.

Placental 11 beta-hydroxysteroid dehydrogenase: a key regulator of fetal glucocorticoid exposure

OBJECTIVE

Placental 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), which converts active cortisol to inactive cortisone, has been proposed to be the mechanism guarding the fetus from the growth retarding effects of maternal glucocorticoids; however, other placental enzymes have also been implicated. Placental 11 beta-HSD is unstable in vitro, and enzyme activity thus detected may not be relevant to the proposed barrier role. We have therefore examined placental glucocorticoid metabolism in dually perfused freshly isolated intact human placentas.

DESIGN

Placentas were obtained from randomly selected normal term deliveries. The maternal circuit was perfused with physiological concentration of cortisol, the fetal effluent collected and steroid metabolites separated and quantified using silica columns (Sep-pak Plus) and HPLC.

RESULTS

Most of the maternally administered cortisol was metabolized to cortisone, and no conversion of cortisone to cortisol was detected. Cortisone was the only product of cortisol metabolism. Inhibition of 11 beta-HSD with glycyrrhetinic acid allowed cortisol to gain direct access to the fetal circulation.

CONCLUSION

We conclude that human placental 11 beta-HSD plays a crucial role in controlling glucocorticoid access to the fetus. Other enzymes are not significant contributors at physiologically relevant cortisol concentrations.

Clinical studies of multiple endocrine neoplasia type 1 (MEN1)

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by the combined occurrence of parathyroid, pancreatic islet and anterior pituitary tumours. To facilitate a screening programme for MEN1, we investigated 709 people (364 males and 345 females, age range 1-84 years) from 62 MEN1 families, and 36 non-familial MEN1 patients. Of those investigated, 220 (95 males and 125 females, age range 8-79 years) suffered from MEN1. Parathyroid, pancreatic and pituitary tumours occurred in 95%, 41% and 30% of the patients, respectively. Parathyroid tumours were the first manifestation of MEN1 in 87% of patients, and amongst the pituitary and pancreatic tumours, somatotrophinomas and gastrinomas were more common in patients above the age of 40 years, whilst insulinomas occurred more frequently in patients below the age of 40 years. Biochemical screening indicated that the penetrance of MEN1 by the ages of 20, 35 and 50 years was 43%, 85% and 94%, respectively, and that the development of MEN1 was confined to first-degree relatives in 91% of patients and to second-degree relatives in 9% of patients. These findings have helped to define a proposed screening programme for MEN1.

11 beta-hydroxysteroid dehydrogenase type 1 expression in 2S FAZA hepatoma cells is hormonally regulated: a model system for the study of hepatic glucocorticoid metabolism

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) is a key enzyme in glucocorticoid metabolism, catalysing the conversion of active glucocorticoids into their inactive 11-keto metabolites, thus regulating glucocorticoid access to intracellular receptors. The type 1 isoform (11 beta-HSD 1) (EC 1.1.1.146) is widely distributed, with particularly high levels in liver, where accumulating evidence suggests that it acts as an 11 beta-reductase, regenerating active glucocorticoids. Investigation of the function and regulation of 11 beta-HSD 1 in liver has been hampered by the lack of hepatic cell lines which express 11 beta-HSD 1. Here, we describe 11 beta-HSD 1 mRNA expression and activity in 2S FAZA cells, a continuously cultured rat liver cell line. In intact 2S FAZA cells 11 beta-HSD 1 acts predominantly as a reductase, with very low dehydrogenase activity. In 2S FAZA cells 11 beta-HSD 1 activity and mRNA expression are regulated by hormones, with dexamethasone increasing activity and insulin, forskolin and insulin-like growth factor 1 decreasing it. Transfection of 2S FAZA cells with a luciferase reporter gene driven by the proximal promoter of the rat 11 beta-HSD 1 gene demonstrates that sequences which can mediate the responses to insulin, dexamethasone and forskolin all lie within 1800 bp of the transcription start site.

Inhibition of 11-beta-hydroxysteroid dehydrogenase in pregnant rats and the programming of blood pressure in the offspring

Recent epidemiological studies have linked low birth weight with the later occurrence of cardiovascular and metabolic disorders, particularly hypertension. We have proposed that fetal exposure to excess maternal glucocorticoids may underpin this association. Normally, the fetus is protected from maternal glucocorticoids by placental 11beta-hydroxysteroid dehydrogenase (11beta-HSD). We have previously shown that treatment of pregnant rats with dexamethasone, a synthetic glucocorticoid that is poorly metabolized by the enzyme, reduces birth weight and produces elevated blood pressure in the adult offspring. Moreover, low activity of placental 11beta-HSD correlates with low birth weight in rats. Here, we show that maternal administration of carbenoxolone, a potent inhibitor of 11 beta-HSD, throughout pregnancy leads to reduced birth weight (mean 20 percent decrease) and elevated blood pressures (increase in mean arterial pressure, 9 mm Hg in males, 7 mm Hg in females) in the adult offspring of carbenoxolone-treated rats. This effect requires the presence of maternal adrenal products, as carbenoxolone given to adrenalectomized pregnant rats had no effect on birth weight or blood pressure. These data support the hypothesis that excess exposure of the fetoplacental unit to maternal glucocorticoids reduces birth weight and programs subsequent hypertension and indicate a key role for placental 11beta-HSD in controlling such exposure.

11 beta-Hydroxysteroid dehydrogenases: key enzymes in determining tissue-specific glucocorticoid effects

Recent studies have demonstrated that the interconversion of active and inactive glucocorticoids plays a key role in determining the specificity of the mineralocorticoid receptor and controlling local tissue glucocorticoid receptor activation. Two distinct isoforms of the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) have been identified. 11 beta-HSD1 is NADPH-dependent and at its major site of action (the liver) is a reductase, converting cortisone to cortisol (11-dehydrocorticosterone to corticosterone in the rat). 11 beta-HSD2 is NAD-dependent, is present in tissues such as the kidney and placenta, and converts cortisol to cortisone (corticosterone to 11-dehydrocorticosterone in the rat). Congenital or acquired deficiency of 11 beta-HSD2 produces the syndrome of apparent mineralocorticoid excess (SAME) in which cortisol gains access to the unprotected nonspecific mineralocorticoid receptor. The congenital deficiency is associated with mutations in the gene encoding the kidney isoform of 11 beta-HSD2; the acquired form results from inhibition of the enzyme by licorice, carbenoxolone, ACTH-dependent steroids in the ectopic ACTH syndrome, and possibly circulating inhibitors of the enzyme. This paper focuses on recent evidence, which suggest that low levels of placental 11 beta-HSD2 result in increased exposure of the fetus to maternal glucocorticoid and low birth weight. In animal studies using the rat we have shown that birth weight is correlated positively and placental weight negatively with the level of placental 11 beta-HSD. Thus animals with low birth weight and large placentae were those likely to be exposed to the highest level of maternal glucocorticoid. In man a similar relationship was found with birth weight being significantly correlated either with placental 11 beta-HSD activity or with the extent of cortisol inactivation by isolated perfused placental cotyledons. Administration of dexamethasone (which is poorly metabolized by placental 11 beta-HSD2) to pregnant rats resulted in decreased birth weight and the development of hypertension in the pups when adult. The same results were obtained when pregnant rats were given carbenoxolone, an inhibitor of placental 11 beta-HSD2. Low protein diet during pregnancy in the rat resulted in low birth weight of the pups, increased placental weight but decreased placental 11 beta-HSD activity, and adult hypertension. Thus increased glucocorticoid exposure of the fetus secondary to a failure of the normal inactivation of maternal glucocorticoid by the placental may be an important mechanism linking changes in the in utero environment and common adult diseases.

Protein intake in pregnancy, placental glucocorticoid metabolism and the programming of hypertension in the rat

Hypertension is strongly predicted by a low birthweight:placental weight ratio. Two independent models have been described to explain this association; less than optimal maternal protein nutrition leading to fetal undernutrition, or glucocorticoid excess. Pregnant rats were fed diets containing 18 per cent casein (control) or 9 per cent casein, balanced for energy. On day 20 of gestation the pregnancies were terminated and placentae collected for determination of 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) activity. Placental 11 beta HSD normally protects the fetus from the effects of maternal glucocorticoids. Activity was specifically attenuated by mild protein restriction (33 per cent in activity), whilst activities of glucocorticoid-insensitive control enzymes were unchanged and glucocorticoid-inducible glutamine synthetase activity was increased (27 per cent), relative to activity in placentae from control animals. The nutritional manipulation during pregnancy significantly increased systolic blood pressure (17 mmHg) in the resulting offspring in early adulthood. A possible common pathway whereby maternal environmental factors may influence fetal and placental growth and programme disease is inferred.

Cloning and production of antisera to human placental 11 beta-hydroxysteroid dehydrogenase type 2

By inactivating potent glucocorticoid hormones (cortisol and corticosterone), 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2) plays an important role in the placenta by controlling fetal exposure to maternal glucocorticoids, and in aldosterone target tissues by controlling ligand access to co-localized glucocorticoid and mineralocorticoid receptors. Amino acid sequence from homogeneous human placental 11 beta-HSD2 was used to isolate a 1897 bp cDNA encoding this enzyme (predicted M(r) 44126; predicted pI 9.9). Transfection into mammalian (CHO) cells produces 11 beta-HSD2 activity which is NAD(+)-dependent, is without reductase activity, avidly metabolizes glucocorticoids (Km values for corticosterone, cortisol and dexamethasone of 12.4 +/- 1.5, 43.9 +/- 8.5 and 119 +/- 15 nM respectively) and is inhibited by glycyrrhetinic acid and carbenoxolone (IC50 values 10-20 nM). Rabbit antisera recognizing 11 beta-HSD2 have been raised to an 11 beta-HSD2-(370--383)-peptide-carrier conjugate. Recombinant 11 beta-HSD2, like native human placental 11 beta-HSD2, is detectable with affinity labelling and anti-11 beta-HSD2 antisera, and appears to require little post-translational processing for activity. 11 beta-HSD2 mRNA (approximately 1.9 kb transcript) is expressed in placenta, aldosterone target tissues (kidney, parotid, colon and skin) and pancreas. In situ hybridization and immunohistochemistry localize abundant 11 beta-HSD2 expression to the distal nephron in human adult kidney and to the trophoblast in the placenta. 11 beta-HSD2 transcripts are expressed in fetal kidney (but not lung, liver or brain) at 21-26 weeks, suggesting that an 11 beta-HSD2 distribution resembling that in the adult is established by this stage in human development.

Purification of 11 beta-hydroxysteroid dehydrogenase type 2 from human placenta utilizing a novel affinity labelling technique

11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2) efficiently inactivates potent glucocorticoid hormones (cortisol and corticosterone), leaving aldosterone unmetabolized. Abundant 11 beta-HSD2 activity in human placenta plays a central role in controlling fetal glucocorticoid exposure, which if excessive is harmful and may predispose to low birth weight and hypertension in adulthood. Similar 11 beta-HSD2 activity in the distal nephron protects mineralocorticoid receptors from glucocorticoids and appears to be important in normal blood pressure control. We have purified human placental 11 beta-HSD2 16000-fold, to homogeneity, and determined over 100 residues of the internal amino acid sequence. Purification was assisted by a novel technique allowing highly specific (single spot on two-dimensional electrophoresis) photoaffinity labelling of active 11 beta-HSD2 in crude tissue extracts by its glucocorticoid substrates. This work reveals that 11 beta-HSD2 is a member of the short-chain alcohol dehydrogenase superfamily (apparent monomer M(r) approximately 40,000). It is a very basic (apparent pI = 9.1) intrinsic membrane protein, requiring as yet undefined membrane constituents for full stability. Affinity chromatography and affinity labelling studies suggest that 11 beta-HSD2 has a compulsory ordered mechanism, with NAD+ binding first, followed by a conformational change allowing glucocorticoid binding with high affinity.

Increased vasoconstrictor sensitivity to glucocorticoids in essential hypertension

Glucocorticoids raise blood pressure but were thought not to play a pathophysiological role in essential hypertension when it was demonstrated that cortisol secretion rates and circulating concentrations are normal in this disease. However, recent observations suggest that increased tissue sensitivity to cortisol, mediated by either abnormal glucocorticoid receptors or impaired inactivation of cortisol by 11 beta-dehydrogenase, may allow cortisol to raise blood pressure despite normal circulating concentrations. We studied 11 patients with essential hypertension and 11 matched normotensive control subjects. Dermal vasoconstriction after topical application of both cortisol (16 +/- 4 versus 32 +/- 5 U, control subjects versus hypertensive patients; P < .02) and beclomethasone dipropionate (75 +/- 10 versus 100 +/- 7 U; P < .05) was increased in the hypertensive patients. Hypothalamic-pituitary glucocorticoid receptor sensitivity was normal, as judged by basal cortisol secretion rates and suppression of plasma cortisol during sequential overnight dexamethasone suppression tests. 11 beta-Dehydrogenase activity was impaired in essential hypertension, as judged by prolonged half-lives of [11 alpha-3H]cortisol (44 +/- 4 versus 58 +/- 4 minutes, control subjects versus hypertensive patients; P < .02). However, this did not correlate with the dermal vasoconstrictor response. We conclude that vasoconstrictor sensitivity to glucocorticoids is increased in essential hypertension and that this may initiate and/or sustain the increased peripheral vascular resistance that characterizes this disease. The mechanism of increased sensitivity remains uncertain, but it will be important to establish whether it relates to genetic abnormalities of the glucocorticoid receptor that have been observed in animal models and young individuals who are predisposed to essential hypertension.

11 beta-Hydroxysteroid dehydrogenases: tissue-specific dictators of glucocorticoid action

11 beta-HSD catalyses the interconversion of active and inactive corticosteroids and exists as two isoforms with less than 30% amino acid homology. The bi-directional NADP-dependent type 1 enzyme appears to function as a tissue-specific glucocorticoid provider. The uni-directional NAD-dependent type 2 enzyme functions as a tissue-specific glucocorticoid protector. The syndrome of AME is caused by mutations in the gene of 11 beta-HSD2. Placental 11 beta-HSD2 is a barrier to growth-retarding maternal glucocorticoids and may play a key role in prenatal programming of hypertension.

11 beta-Hydroxysteroid dehydrogenase in cultured hippocampal cells reactivates inert 11-dehydrocorticosterone, potentiating neurotoxicity

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) catalyzes the conversion of the glucocorticoid corticosterone (cortisol in humans) to inert 11-dehydrocorticosterone (cortisone). 11 beta-HSD activity is present in the hippocampus, where it is induced by glucocorticoids and stress in vivo, prompting suggestions that the enzyme may attenuate the deleterious effects of chronic glucocorticoid excess on neuronal function and survival. Two isoforms exist: 11 beta-HSD1, a bidirectional NADPH-dependent enzyme, and 11 beta-HSD2, an NAD(+)-dependent exclusive 11 beta-dehydrogenase (corticosterone-inactivating enzyme). In this study, 11 beta-HSD1 activity and mRNA synthesis were demonstrated in primary fetal hippocampal cell cultures. Unexpectedly, the reaction direction in intact hippocampal cells was 11 beta-reduction (reactivation of inert 11-dehydrocorticosterone), although homogenization revealed that the enzyme was capable of 11 beta-dehydrogenation when removed from its normal cellular context. Dexamethasone (10(-7) M) increased 11 beta-HSD activity in homogenates of hippocampal cultures (102% increase). In intact hippocampal cells, dexamethasone induced 11 beta reductase, not dehydrogenase. To determine the functional relevance of hippocampal 11 beta-reductase, glucocorticoid potentiation of kainic acid neurotoxicity was examined. Pretreatment of hippocampal cells with corticosterone reduced survival on kainate exposure. Hippocampal cell 11 beta-HSD activity was potently inhibited by carbenoxolone. Carbenoxolone had no effect on cell survival after kainate alone and did not alter the effect of corticosterone. 11-Dehydrocorticosterone also potentiated kainate neurotoxicity; this effect was lost, however, if 11 beta-HSD was inhibited with carbenoxolone. Thus, hippocampal 11 beta-HSD seems to be a functional 11 beta-reductase in intact cells. Measures to attenuate hippocampal 11 beta-reductase may reduce neuronal vulnerability to glucocorticoid toxicity.

LLC-PK1 cells model 11 beta-hydroxysteroid dehydrogenase type 2 regulation of glucocorticoid access to renal mineralocorticoid receptors

Mineralocorticoid receptors (MRs) are nonselective in vitro, binding corticosterone, cortisol, and aldosterone with similar affinity. In the distal nephron in vivo, MRs are selectively activated by aldosterone despite much higher glucocorticoid levels. This has been suggested to reflect the action of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), which catalyzes rapid inactivation of corticosterone to 11-dehydrocorticosterone (cortisol to cortisone). However, cellular models of this effect have not been reported, and a recent study suggested that properties intrinsic to MR contribute to aldosterone selectivity. We have screened clonal mammalian cell lines for 11 beta-HSD activity. Pig kidney epithelial LLC-PK1 cells expressed by far the greatest 11 beta-HSD activity. In cell homogenates, this was NAD-dependent, with Km for corticosterone of 34.4 nM and cortisol of 89.7 nM. Intact LLC-PK1 cells showed similar apparent Km for corticosterone (13.9 nM) and cortisol (79.4 nM); only 11 beta-dehydrogenation was detected. These biochemical data indicate the expression of the type 2 isoform, 11 beta-HSD2. Using primers to conserved regions of 11 beta-HSD2, a reverse transcriptase-polymerase chain reaction product was obtained from LLC-PK1 cell RNA. Sequence analysis revealed close homology to previously cloned 11 beta-HSD2 cDNAs from several species. LLC-PK1 cell 11 beta-HSD activity was inhibited by carbenoxolone (IC50 approximately 10(-8) M) and high concentrations of estradiol or progesterone (10(-7) and 10(-6) M), but was induced at lower estradiol concentrations (10(-8) and 10(-9) M). To examine whether the 11 beta-HSD2 activity in LLC-PK1 cells regulates corticosterone access to MR, cells were transfected with the corticosteroid-inducible mouse mammary tumor virus long terminal repeat-luciferase reporter construct. Cell transfection by a lipofection method did not alter 11 beta-HSD activity in LLC-PK1 cells. LLC-PK1 cells expressed low levels of MR (13.9 fmol/mg protein, dissociation constant (Kd) 0.3 x 10(-9) M for aldosterone) and glucocorticoid receptors (GR; 18.5 fmol/mg protein, Kd 0.3 x 10(-9) M for dexamethasone). Transfection with mouse mammary tumor virus long terminal repeat-luciferase reporter construct alone suggested that the endogenous levels of MR and GR were insufficient to affect transcription. However, cotransfection of LLC-PK1 cells with pRShMR, an MR expression plasmid, allowed at least 50-fold induction of luciferase with 10(-8) M aldosterone; the ED50 0.3 x 10(-9) M closely reflects the in vitro affinity of MR for aldosterone. Corticosterone only weakly induced luciferase (maximum of 6-fold induction).(ABSTRACT TRUNCATED AT 400 WORDS)

Carbenoxolone increases hepatic insulin sensitivity in man: a novel role for 11-oxosteroid reductase in enhancing glucocorticoid receptor activation

In the kidney, conversion of cortisol to cortisone by the enzyme 11 beta-hydroxysteroid dehydrogenase protects mineralocorticoid receptors from cortisol. In the liver, a different isoform of the enzyme favors 11 beta-reductase conversion of cortisone to cortisol. We have tested the hypothesis that hepatic 11 beta-reductase enhances glucocorticoid receptor activation in the liver by inhibiting the enzyme with carbenoxolone and observing effects on insulin sensitivity. Seven healthy males took part in a double blind randomized cross-over study in which oral carbenoxolone (100 mg every 8 h) or placebo was administered for 7 days. Euglycemic hyperinsulinemic clamp studies were then performed, including measurement of forearm glucose uptake. Carbenoxolone increased whole body insulin sensitivity (M values for dextrose infusion rates, 41.1 +/- 2.4 mumol/kg.min for placebo vs. 44.6 +/- 2.3 for carbenoxolone; P < 0.03), but had no effect on forearm insulin sensitivity. We infer that carbenoxolone, by inhibiting hepatic 11 beta-reductase and reducing intrahepatic cortisol concentration, increases hepatic insulin sensitivity and decreases glucose production. Thus, plasma cortisone provides an inactive pool that can be converted to active glucocorticoids at sites where 11 beta-reductase is expressed, abnormal hepatic 11 beta-reductase activity might be important in syndromes of insulin resistance, and manipulation of hepatic 11 beta-reductase may be useful in treating insulin resistance.

11 beta-hydroxysteroid dehydrogenase is an exclusive 11 beta- reductase in primary cultures of rat hepatocytes: effect of physicochemical and hormonal manipulations

11 beta-Hydroxysteroid dehydrogenase (11 beta HSD) catalyzes the conversion of corticosterone to inert 11-dehydrocorticosterone, thus regulating glucocorticoid access to intracellular receptors. This type 1 isoform (11 beta HSD-1) is a bidirectional NADPH(H)-dependent enzyme in vitro and is highly expressed in liver, where it is regulated by glucocorticoids, thyroid hormones, estrogen, and GH in vivo. In humans in vivo, enzyme inhibition alters glucose homeostasis, an effect thought to be mediated in the liver. However, detailed investigation of the biology of 11 beta HSD-1 in liver, its function, regulation, and indeed even reaction direction, has been hampered by the lack of clonal hepatic cell lines that express 11 beta HSR-1. Studies of nonhepatic cell lines have suggested that 11 beta HSD-1 is directly regulated by hormones, and transfection of nonhepatic cell lines has sown that reaction direction varies between cell types, possibly reflecting intracellular cosubstrate (NADP+/NADPH) ratios or PH. To investigate reaction direction and gene regulation of 11 beta HSD-1 in hepatocytes, we defined conditions for primary culture of adult rat hepatocytes that maintain high 11 beta HSR-1 messenger RNA expression. In intact primary hepatocytes over a wide range of steroid concentrations (2.5-250 nM), 11 beta-reduction was the predominant reaction direction [33.5 +/- 0.5% conversion of 11-dehydrocorticosterone (25 nM) to corticosterone after 30 min], with undetectable 11 beta-dehydrogenation. However, homogenates of hepatocyte cultures showed plentiful 11 beta-dehydrogenase activity. Treatment of hepatocyte cultures with the metabolic inhibitors sodium azide (5 nM) and KCN (1 nM) altered cellular NADP+/NADPH ratios from 0.244 +/- 0.042 in controls to 0.020 +/- 0.001 and 0.152 +/- 0.009, respectively, but had no effect on 11 beta-reductase or 11 beta- dehydrogenase activity. High concentrations of KCN (10 mM) modestly increased 11 beta-reductase activity (32.4 +/- 1.7% to 48.8 +/- 0.5%, whereas 11 beta-dehydrogenation remained at the limit of detection. Manipulation of culture medium pH (6.2-8.0) had no effect on enzyme activity. Dexamethasone (10-7 M) induced hepatocyte 11 beta-reductase activity from 23.4 +/- 0.7% to only weakly affects reaction direction. Glucocorticoid and insulin regulation of hepatic 11 beta HSD-1 is directly mediated, but other hormonal controls are either lost in culture or mediated indirectly. This primary hepatocyte culture system will allow investigation of the control of 11 beta-reductase activity and its implications for glucocorticoid-regulated hepatic functions.

Fetal osteocalcin levels are related to placental 11 beta-hydroxysteroid dehydrogenase activity in humans

OBJECTIVE

Overexposure to glucocorticoids in utero reduces birth weight and, in animals, leads to persistent hypertension in the offspring. The fetus is normally protected from maternal glucocorticoids by placental 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) which catalyses the conversion of cortisol to inert cortisone. In adult humans, osteocalcin is a sensitive marker of glucocorticoid exposure. The aim of this study was to determine whether cord blood osteocalcin levels were related to the ability of placental 11 beta-HSD to inactivate maternal cortisol.

DESIGN

Cross-sectional study examining the relation between cord blood levels of osteocalcin and placental glucocorticoid metabolism at term.

PATIENTS

Twenty-one women attending for delivery at the Simpson Memorial Maternity Pavilion in Edinburgh had cord venous and arterial blood samples collected at delivery.

MEASUREMENTS

Cord plasma levels of osteocalcin, cortisol and cortisone were measured by radioimmunoassay and indices of placental 11 beta-HSD activity were calculated.

RESULTS

All indices of placental 11 beta-hydroxysteroid dehydrogenase activity correlated directly and significantly with cord blood osteocalcin levels. For cord blood osteocalcin and the placental 11 beta-HSD Activity Index, Pearson's r was +0.58, r2 = 0.33 and P < 0.02.

CONCLUSION

We conclude that term cord blood osteocalcin level reflects the effectiveness of placental glucocorticoid inactivation, and may be a marker for the development of adult hypertension.

11 beta-Hydroxysteroid dehydrogenase and its inhibitors in hypertensive pregnancy

Preeclampsia is accompanied by amplification of the sodium retention that is a feature of normal pregnancy. Recent evidence suggests that mineralocorticoid receptor activation is increased in preeclampsia, but classic mineralocorticoids (aldosterone, 11-deoxycorticosterone) are not present in excess. Cortisol can act as a mineralocorticoid receptor agonist only when its renal inactivation to cortisone by 11 beta-hydroxy-steroid dehydrogenase is impaired, for example, in congenital enzyme deficiency and after administration of exogenous inhibitors (eg, licorice). Endogenous inhibitors of this enzyme have been detected in human urine and are increased in pregnancy. To establish whether cortisol causes mineralocorticoid excess in hypertensive pregnancy and whether endogenous inhibitors of 11 beta-hydroxysteroid dehydrogenase are responsible, we studied 25 hypertensive pregnant patients (13 with preeclampsia and 12 with gestational hypertension), 16 normotensive pregnant subjects, and 13 nonpregnant control subjects. Concentrations of plasma renin and aldosterone were increased in pregnancy, but less so in hypertensive pregnancy. Plasma potassium and urinary electrolytes were not different between the groups. Plasma cortisol was increased in pregnancy but not different in hypertensive pregnancy, and urinary cortisol, plasma and urinary cortisone, and urinary tetrahydrocortisol and tetrahydrocortisone were not different between the groups. Endogenous inhibitors of 11 beta-hydroxysteroid dehydrogenase were more active in urine from pregnant women but were not increased further in hypertensive pregnancy. There were no differences in these parameters between patients with preeclampsia and gestational hypertension. We conclude that deficient inactivation of cortisol to cortisone does not contribute to the sodium retention of normotensive or hypertensive pregnancy and that endogenous inhibitors of 11 beta-hydroxysteroid dehydrogenase have no evident pathophysiological significance in pregnancy.

Cloning, sequencing and tissue-distribution of mouse 11 beta-hydroxysteroid dehydrogenase-1 cDNA

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) reversibly converts physiological glucocorticoids (cortisol, corticosterone) to inactive 11-dehydro forms, and thus controls glucocorticoid access to receptors in a variety of tissues. We have cloned a cDNA encoding 'liver-type' 11 beta-HSD (11 beta-HSD1) from the mouse using PCR, and have determined its nucleotide sequence. Mouse 11 beta-HSD1 cDNA showed 91% identity to rat 11 beta-HSD1 cDNA. There was 87% amino acid identity with rat 11 beta-HSD1 with conservation of the putative cofactor and substrate binding domains. Northern blot analysis of mouse tissues demonstrated abundant 11 beta-HSD1 message in the liver, kidney and lung, with lower expression in brain subregions and gonads. 11 beta-HSD1 mRNA was below the level of detection in the murine colon. 11 beta-HSD1 mRNA levels in kidney was higher in males than in females, but in contrast to the rat, there was no sexual dimorphism in the mouse liver. Although males and females showed different mRNA levels in the kidney, there was no sex difference in 11 beta-HSD enzyme activity. Thus, despite the high inter-species conservation of 11 beta-HSD1, there are clear species and tissue-specific differences in its expression.

Endogenous inhibitors of 11 beta-hydroxysteroid dehydrogenase in hypertension

Exogenous inhibitors of 11 beta-hydroxysteroid dehydrogenase (e.g. glycyrrhetinic acid, a constituent of licorice) raise blood pressure by allowing cortisol to activate mineralocorticoid receptors. Endogenous 11 beta-dehydrogenase inhibitors called glycyrrhetinic acid-like factors (GALFs), have been extracted from urine. Increased GALFs could explain the impairment of 11 beta-dehydrogenase in essential hypertension and ectopic ACTH syndrome. We extracted urine on Sep-Paks and quantified GALFs by their inhibition of 11 beta-dehydrogenase bioactivity in microsomes from rat liver. GALFs have no diurnal rhythm and were no different after dexamethasone treatment, in patients with low ACTH, on in 4 patients with ectopic ACTH secretion. In 79 subjects, GALF excretion did not correlate with blood pressure. In 17 subjects, GALF excretion did not correlate with indices of mineralocorticoid receptor activation on 11 beta-dehydrogenase activity. We conclude that GALFs are not ACTH dependent and have no measurable effect on 11 beta-dehydrogenase in vivo. In hypertension associated with impaired 11 beta-dehydrogenase activity GALFs are unlikely to play a pathophysiological role.

Alcohol inhibits 11-beta-hydroxysteroid dehydrogenase activity in rat kidney and liver

Male Wistar rats were treated with different ethanol concentrations diluted in drinking water in order to evaluate the effect of acute ethanol intoxication on 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) activity in liver and kidney tissue homogenates. Rats with the highest ethanol consumption (15% ethanol supplementation) showed a significant decrease in both hepatic and renal 11 beta-OHSD activity as compared to the control group (p < 0.005). In the same group, aldosterone plasma levels were significantly lower than in controls (p < 0.01), while corticosterone (B) plasma levels were slightly higher, suggesting that the increase in intrarenal B concentrations, probably related to the acute ethanol consumption, might be responsible for a nonspecific B mineralocorticoid activity.

Cellular selectivity of aldosterone action: role of 11 beta-hydroxysteroid dehydrogenase

Mineralocorticoid receptors in the distal nephron have no intrinsic specificity for mineralocorticoids over glucocorticoids (cortisol in humans; corticosterone in rodents), but are protected from glucocorticoids by the enzyme 11 beta-hydroxysteroid dehydrogenase, which inactivates these steroids to cortisone and 11-dehydrocorticosterone, respectively. Recent work has demonstrated that the enzyme is expressed as multiple tissue-specific isoforms, some of which catalyse the reverse conversion of cortisone to cortisol. These isoforms may allow 11 beta-hydroxysteroid dehydrogenase to modulate access of ligands to glucocorticoid and mineralocorticoid receptors, as well as to amplify and attenuate tissue responses. 11 beta-hydroxysteroid dehydrogenase-mediated protection of mineralocorticoid receptors fails in congenital 11 beta-hydroxysteroid dehydrogenase deficiency and after inhibition of the enzyme by liquorice. In these circumstances, cortisol-dependent mineralocorticoid excess and hypertension ensue. Recent studies suggest that similar deficiencies of 11 beta-dehydrogenase activity may contribute to pathophysiology in common clinical syndromes, illustrating the potential significance of this novel mechanism for development of hypertension.

Sexual dimorphism of hepatic 11 beta-hydroxysteroid dehydrogenase in the rat: the role of growth hormone patterns

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) catalyses the reversible metabolism of corticosterone to inert 11-dehydrocorticosterone. At least two isoforms exist. 11 beta-HSD-1, the first to be characterised and the only isoform for which a cDNA has been isolated, is highly expressed in liver, kidney and hippocampus. The activity of 11 beta-HSD in rat liver is higher in males, due to oestrogen repression of 11 beta-HSD-1 gene transcription in females. Sexual dimorphism in rodent liver proteins is frequently mediated indirectly via sex-specific patterns of GH release (continuous in females, pulsatile in males). We have now investigated whether this applies to 11 beta-HSD, using dwarf rats (congenitally deficient in GH) and hypophysectomised animals. 11 beta-HSD activity and 11 beta-HSD-1 mRNA expression in liver was significantly lower in control female than male rats (50% and 72% of male levels respectively). These sex differences in the liver were attenuated in dwarf rats, with both males and females showing similar levels of 11 beta-HSD activity to control males. Administration of continuous (female pattern) GH to dwarf male rats decreased hepatic 11 beta-HSD activity (30% fall) and mRNA expression (77% fall), whereas the same total daily dose of GH given in the male (pulsatile) pattern had no effect on hepatic 11 beta-HSD in female dwarf rats. Continuous GH also attenuated hepatic 11 beta-HSD activity (25% fall) and 11 beta-HSD-1 mRNA expression (82% fall) in hypophysectomised animals.(ABSTRACT TRUNCATED AT 250 WORDS)

'Liver-type' 11 beta-hydroxysteroid dehydrogenase cDNA encodes reductase but not dehydrogenase activity in intact mammalian COS-7 cells

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) catalyses the metabolism of corticosterone to inert 11-dehydrocorticosterone, thus preventing glucocorticoid access to otherwise non-selective renal mineralocorticoid receptors (MRs), producing aldosterone selectivity in vivo. At least two isoforms of 11 beta-HSD exist. One isoform (11 beta-HSD1) has been purified from rat liver and an encoding cDNA cloned from a rat liver library. Transfection of rat 11 beta-HSD1 cDNA into amphibian cells with a mineralocorticoid phenotype encodes 11 beta-reductase activity (activation of inert 11-dehydrocorticosterone) suggesting that 11 beta-HSD1 does not have the necessary properties to protect renal MRs from exposure to glucocorticoids. This function is likely to reside in a second 11 beta-HSD isoform. 11 beta-HSD1 is co-localized with glucocorticoid receptors (GRs) and may modulate glucocorticoid access to this receptor type. To examine the predominant direction of 11 beta-HSD1 activity in intact mammalian cells, and the possible role of 11 beta-HSD in regulating glucocorticoid access to GRs, we transfected rat 11 beta-HSD1 cDNA into a mammalian kidney-derived cell system (COS-7) which has little endogenous 11 beta-HSD activity or mRNA expression. Homogenates of COS-7 cells transfected with increasing amounts of 11 beta-HSD cDNA exhibited a dose-related increase in 11 beta-dehydrogenase activity. In contrast, intact cells did not convert corticosterone to 11-dehydrocorticosterone over 24 h, but showed a clear dose-related 11 beta-reductase activity, apparent within 4 h of addition of 11-dehydrocorticosterone to the medium.(ABSTRACT TRUNCATED AT 250 WORDS)