Trabecular bone score in adults with cerebral palsy

CONTEXT

Bone fragility in cerebral palsy (CP) is secondary to a complex interplay of functional, hormonal, and nutritional factors that affect bone remodelling. A greater understanding of bone microarchitectural changes seen in CP should assist therapeutic decision making.

OBJECTIVE

To examine the relationship between trabecular bone score (TBS), BMD and fractures in adults with CP; the influence of clinical factors and body composition on bone microarchitecture were explored.

DESIGN

Retrospective cross-sectional study.

SETTING AND PARTICIPANTS

43 adults (25 male) with CP of median age 25 years (interquartile range 21.4-33.9) who had evaluable dual-energy X-ray absorptiometry imaging of the lumbar spine from a single tertiary hospital between 2005-March 2018.

RESULTS

24/43 (55.8%) of patients had TBS values indicating intermediate or high risk of fracture (<1.31). TBS correlated with areal BMD at the lumbar spine, femoral neck and total body. TBS was significantly associated with arm and leg lean mass, with adjustment for age, gender and height (adjusted R² = 0.18, p = 0.042 for arm lean mass; adjusted R² = 0.19, p = 0.036 for leg lean mass). There was no difference in TBS when patients were grouped by fracture status, anticonvulsant use, gonadal status or use of PEG feeding. TBS was lower in non-ambulatory patients compared with ambulatory patients (1.28 vs 1.37, p = 0.019).

CONCLUSIONS

Abnormal bone microarchitecture, as measured by TBS, was seen in >50% of young adults with CP. TBS correlated with both areal BMD and appendicular lean mass. Maintaining muscle function is likely to be important for bone health in young adults with CP and needs to be confirmed in further studies.

Fractures in spina bifida from childhood to young adulthood

This study assessed the prevalence and types of fractures in spina bifida and examined risk factors for fracture. Fracture prevalence was highest in childhood and reduced in adolescence and young adulthood. The importance of maintaining mobility is highlighted by the increased risk of fracture in those who are non-ambulatory.

INTRODUCTION

The aims of this study are to study the prevalence and types of fractures according to age group in spina bifida and examine risk factors associated with fracture.

METHODS

This is a retrospective cohort study of 146 individuals with spina bifida aged 2 years or older who attended the paediatric or adult spina bifida multidisciplinary clinic at a single tertiary hospital.

RESULTS

Median age at which first fracture occurred was 7 years (interquartile range 4-13 years). Fracture rates in children (ages 2-10), adolescents (ages 11-18) and adults (age > 18) were 10.9/1000 (95 % confidence interval 5.9-18.3), 5.4/1000 (95 % CI 1.5-13.8) and 2.9/1000 (95 % CI 0.6-8.1) patient years respectively. Childhood fractures predominantly involved the distal femur and femoral shaft; these fractures were rarely seen in adulthood. Non-ambulatory status was associated with a 9.8 times higher risk of fracture compared with ambulatory patients (odds ratio 9.8, p = 0.016, 95 % CI 1.5-63.0). Relative risk of re-fracture was 3.1 (95 % CI 1.4-6.8). Urological intervention with intestinal segments was associated with renal calculi (p = 0.037) but neither was associated with fracture.

CONCLUSIONS

The risk of fracture is lower in adults compared with children with spina bifida. The predominant childhood fracture affects the distal femur, and immobility is the most significant risk factor for fracture. Clinical factors contributing to fracture risk need to be elucidated to enable selection of patients who require investigation and treatment of osteoporosis.

Musculoskeletal and Endocrine Health in Adults With Cerebral Palsy: New Opportunities for Intervention

CONTEXT

Cerebral palsy (CP) increases fracture risk through diminished ambulation, nutritional deficiencies, and anticonvulsant medication use. Studies examining bone mineral density (BMD) in adults with CP are limited.

OBJECTIVE

To examine the relationship between body composition, BMD, and fractures in adults with CP. The effect of functional, nutritional, and endocrine factors on BMD and body composition is also explored.

DESIGN

Retrospective cross-sectional study.

SETTING AND PARTICIPANTS

Forty-five adults with CP (mean age, 28.3 ± 11.0 years) who had dual-energy x-ray absorptiometry imaging at a single tertiary hospital between 2005 and 2015.

RESULTS

Seventeen (38%) had a past history of fragility fracture; 43% had a Z-score of ≤ -2.0 at the lumbar spine (LS) and 41% at the femoral neck (FN). In nonambulatory patients, every one unit decrease in FN Z-score increased the risk of fracture 3.2-fold (95% confidence interval, 1.07-9.70; P = .044). Stepwise linear regression revealed that the Gross Motor Function Classification System was the best predictor of LS Z-score (R(2) = 0.550; β = -0.582; P = .002) and FN Z-score (R(2) = 0.428; β = -0.494; P = .004); 35.7% of the variance in BMD was accounted for by lean tissue mass. Hypogonadism, present in 20% of patients, was associated with reduced lean tissue mass and reduced LS BMD. Lean tissue mass positively correlated with BMD in eugonadal patients, but not in hypogonadal patients.

CONCLUSIONS

Low BMD and fractures are common in adults with CP. This is the first study to document hypogonadism in adults with CP with detrimental changes in body composition and BMD.

Mutation profile of differentiated thyroid tumours in an Australian urban population

BACKGROUND

The majority of differentiated thyroid cancers are characterised by one of several point mutations or gene rearrangements. Limited data are available on the prevalence and clinical correlations of these mutations in the Australian population.

AIMS

The aim of the present study was to characterise the mutation profile of differentiated thyroid tumours in the local population.

METHODS

The study involved 148 patients with differentiated thyroid cancer. The following tumours were examined: 109 papillary carcinomas (PTC), 27 follicular carcinomas (FC) and 12 Hurthle cell carcinomas (HCC). Polymerase chain reaction (PCR) was performed for BRAF and RAS mutations (RNA and DNA) as well as for RET/PTC rearrangements and PAX8-PPARγ translocations (RNA). Clinicopathological parameters and outcome data were analysed according to BRAFV600E status in PTC and RAS mutation status in FC.

RESULTS

BRAFV600E was identified in 74/109 (68%) PTC. BRAFV600E was not significantly correlated with clinicopathological features of aggressive disease. At a median follow up of 48 months, there was no significant difference between BRAFV600E and wild-type BRAF PTC with respect to the rates of nodal recurrence, distant metastases or disease-specific death. In FC, RAS mutations (five NRAS and three HRAS) were present in 8/27 (30%) tumours. RAS mutation was significantly associated with widely invasive histology (P = 0.01) and distant metastases (P = 0.01) on follow up.

CONCLUSION

In the present study, BRAF mutation was not associated with negative prognostic indicators or adverse outcomes in PTC. RAS mutation was positively correlated with aggressive features in FC suggesting potential prognostic utility, although confirmation is required from larger studies.

Expression of eight glucocorticoid receptor isoforms in the human preterm placenta vary with fetal sex and birthweight

INTRODUCTION

Administration of betamethasone to women at risk of preterm delivery is known to be associated with reduced fetal growth via alterations in placental function and possibly direct effects on the fetus. The placental glucocorticoid receptor (GR) is central to this response and recent evidence suggests there are numerous isoforms for GR in term placentae. In this study we have questioned whether GR isoform expression varies in preterm placentae in relation to betamethasone exposure, fetal sex and birthweight.

METHODS

Preterm (24-36 completed weeks of gestation, n = 55) and term placentae (>37 completed weeks of gestation, n = 56) were collected at delivery. Placental GR expression was examined using Western Blot and analysed in relation to gestational age at delivery, fetal sex, birthweight and betamethasone exposure. Data was analysed using non-parametric tests.

RESULTS

Eight known isoforms of the GR were detected in the preterm placenta and include GRα (94 kDa), GRβ (91 kDa), GRα C (81 kDa) GR P (74 kDa) GR A (65 kDa), GRα D1-3 (50-55 kDa). Expression varied between preterm and term placentae with a greater expression of GRα C in preterm placentae relative to term placentae. The only sex differences in preterm placentae was that GRα D2 expression was higher in males than females. There were no alterations in preterm placental GR expression in association with betamethasone exposure.

DISCUSSION

GRα C is the isoform involved in glucocorticoid induced apoptosis and suggests that its predominance in preterm placentae may contribute to the pathophysiology of preterm birth.

CCL2-dependent macrophage recruitment is critical for mineralocorticoid receptor-mediated cardiac fibrosis, inflammation, and blood pressure responses in male mice

Recent studies show that mice with selective deletion of the mineralocorticoid receptor (MR) in macrophages are protected from mineralocorticoid-induced cardiac fibrosis and hypertension without altering cardiac macrophage accumulation. However, it is unclear whether preventing macrophages from entering cardiac tissue would provide similar or additional protection in this disease setting. Therefore, we examined mineralocorticoid-induced cardiovascular disease in mice lacking the CCL2 gene (encoding monocyte chemoattractant protein-1), which have a markedly reduced capacity to recruit proinflammatory tissue macrophages. Male wild-type (WT) and CCL2-null mice were treated for 8 days or 8 weeks with either vehicle (control, CON) or deoxycorticosterone (DOC). At both time points, there was a significant reduction in DOC-induced macrophage recruitment (50% at 8 d and 75% at 8 wk) in the heart with a corresponding suppression of cardiac inflammatory markers in the CCL2-null mice. CCL2-null mice given DOC/salt also displayed 35% less cardiac fibrosis at 8 weeks vs WT DOC. Absence of recruited macrophages in CCL2-null mice promotes greater collagen breakdown by matrix metalloproteinase-9 in the heart and also leads to significantly reduced cardiac fibroblast and myofibroblast numbers. Systolic blood pressure (BP) after DOC/salt was significantly lower in CCL2-null than for WT mice. In the aorta at 8 weeks, MR-responsive gene expression remained intact. However, macrophage-mediated proinflammatory gene expression was reduced in the CCL2-null mice and may account for differential regulation of BP. Our data thus demonstrate an important role for CCL2-dependent macrophage recruitment in MR-dependent cardiac inflammation and remodeling and in the regulation of systolic BP.

The effect of gonadal status on body composition and bone mineral density in transfusion-dependent thalassemia

Patients with transfusion-dependent thalassemia have abnormal growth, hormonal deficits, and increased bone loss. We investigated the relationship between skeletal muscle mass, fat mass, and bone mineral density in adult subjects with transfusion-dependent thalassemia based on their gonadal status. Our findings show that hypogonadism attenuates the strength of the muscle-bone relationship in males but strengthens the positive correlation of skeletal muscle mass and fat mass in female subjects.

INTRODUCTION

Transfusion-dependent thalassemia is associated with a high prevalence of fractures. Multiple hormonal complications, in particular hypogonadism, can lead to changes in body composition and bone mineral density (BMD). We investigated for the first time the relationship between skeletal muscle mass (SMM), fat mass, and BMD in adult subjects with transfusion-dependent thalassemia based on their gonadal status.

METHODS

A retrospective cohort study of 186 adults with transfusion-dependent thalassemia was analyzed. Body composition and BMD were measured using dual energy X-ray absorptiometry. The association between skeletal muscle, fat, and BMD was investigated through uni-, multi-, and stepwise regression analyses after adjusting for multicollinearity. SMM was derived using the formula, SMM = 1.19 × ALST-1.65, where ALST is equivalent to the sum of both arm and leg lean tissue mass.

RESULTS

There were 186 subjects, males (43.5 %) and females (56.5 %), with a median age of 36.5. Hypogonadism was reported in 44.4 % of males and 44.7 % of females. SMM and BMD were positively correlated and strongest in eugonadal males (0.36 ≤ R (2) ≤ 0.59), but the association was attenuated in hypogonadal males. SMM (0.27 ≤ R (2) ≤ 0.69) and total fat mass (0.26 ≤ R (2) ≤ 0.55) were positively correlated with BMD in hypogonadal females, but the correlation was less pronounced in eugonadal females. Leg lean tissue mass and arm lean tissue mass in males and females, respectively, were most highly correlated to BMD in the stepwise regression analysis.

CONCLUSION

Hypogonadism attenuates the strength of the muscle-bone relationship in males but strengthens the positive correlation of skeletal muscle mass and fat mass in female subjects. This study supports the notion that exercise is important for maintaining BMD and the need to optimize treatment of hypogonadism in patients with transfusion-dependent thalassemia.

Prolonged hypocalcemia following denosumab therapy in metastatic hormone refractory prostate cancer

Prostate cancer is a leading cause of cancer death, frequently associated with widespread bone metastases. We report two cases of hypocalcemia following the first dose of denosumab in metastatic hormone refractory prostate cancer, the first case requiring 26 days of intravenous calcium therapy. This is the first report of prolonged hypocalcemia following denosumab in a patient with normal renal function.

Thalassemia bone disease: the association between nephrolithiasis, bone mineral density and fractures

Thalassemia bone disease is well described, but the prevalence of nephrolithiasis has not been characterized. The association between nephrolithiasis, reduced bone density, and increased fractures has been demonstrated through this retrospective study of 166 participants with transfusion-dependent thalassemia. The findings support the need for increased vigilance of kidney and bone disease in this cohort.

INTRODUCTION

Previous studies have revealed that thalassemia is associated with reduced bone mineral density (BMD) and fractures. Many causes are implicated including hypogonadism, growth hormone deficiency, marrow expansion, and iron overload. Nephrolithiasis is associated with reduced BMD and increased fractures in the general population. However, the prevalence of nephrolithiasis and its association with bone density and fractures have not been characterized in thalassemia.

METHODS

We have addressed this question by performing a retrospective cohort study of 166 participants with transfusion-dependent thalassemia who had undergone dual-energy X-ray absorptiometry between 2009 and 2011. Logistic regression modeling was used to adjust for potential confounders.

RESULTS

We found a high prevalence of kidney stones (18.1 %) which was greater in males compared to females (28.7 vs 9.7 %, respectively). Renal stones were associated with reduced femoral neck Z-score and fractures in men after adjusting for potential confounders. These results indicate that nephrolithiasis is highly prevalent in patients with transfusion-dependent thalassemia and is significantly associated with reduced BMD and increased fractures.

CONCLUSIONS

The findings from this study strongly support the need for ongoing surveillance of BMD, fractures, and nephrolithiasis in the management of transfusion-dependent thalassemia.

129. OVARIAN PHENOTYPE OF THE IKK CONDITIONAL KNOCKOUT MOUSE

Nuclear factor-κB (NFκB) designates a family of transcription factors that has been shown to modulate antiviral, inflammatory and immune responses and promote tumorigenesis. Activation of NFκB is dependent on IKKβ, a component of the IκB kinase (IKK) complex which promotes degradation of IκB inhibitory proteins and allows nuclear translocation of NFκB. Little is known about the role of NFκB signalling in the ovary. We created a gonadal specific IKKβ conditional knockout mouse to explore NFκB action in the ovary. A transgenic mouse line containing floxed IKKβ alleles (M Karin, UCSD) was crossed with a transgenic mouse line expressing cre-recombinase under the control of the anti-Müllerian hormone receptor (AMHR) promoter (M Matzuk, BCM). Female mice arising from this breeding regime will not express IKKβ in granulosa cells and cannot activate NFκB signalling. Ovaries and serum were collected from mice at 7 and 15 weeks of age. Histological analyses were undertaken and the gonadotrophic hormones, follicle stimulating hormone (FSH) and luteinising hormone (LH) were measured. The ovaries of 7 week old IKKβ null mice contained follicles of all developmental stages although corpora lutea were absent indicating that these mice were infertile. Some follicle subtypes may be under-represented and apoptosis may be enhanced; these studies are ongoing. Serum FSH and LH levels were elevated compared to littermate controls. By 15 weeks of age corpora lutea were present. The fertility of the IKKβ conditional knockout is currently being assessed. In summary, IKKβ conditional knockout mice exhibit a reproductive phenotype which includes delayed ovulation. These results validate the hypothesis that ovulation is an inflammatory-like response. This model will be a valuable tool for reproductive research; the subtlety of the phenotype allowing us to tease out the underlying mechanisms and role of NFκB signalling in ovarian function.

514. THE REPRODUCTIVE PHENOTYPE OF THE IKKβ CONDITIONAL KNOCKOUT MOUSE

Nuclear factor-κB (NF-κB) designates a family of transcription factors that have been shown to modulate antiviral, inflammatory and immune responses. Activation of NF-κB is dependent on IKKβ a component of the IκB kinase (IKK) complex which promotes degradation of IκB inhibitory proteins and allows nuclear translocation of NF-κB. Our studies in ovarian granulosa cell tumour cell lines (COV434 and KGN) indicate that NF-κB signalling is constitutively activated. FSH has been reported to increase XIAP expression through NFκB activity in granulosa cells, but beyond that the role of NFκB signalling in folliculogenesis has not been elucidated. To establish the significance of NF-κB signalling in the ovary (and testis), we have generated a gonadal specific IKKbeta conditional knockout mouse. A transgenic mouse line containing floxed IKKβ alleles (gift of M Karin, UCSD) was crossed with a cre mouse line (gift of M Matzuk, BCM) expressing the recombinase in anti-Müllerian hormone receptor expressing cells (granulosa cells or Sertoli cells). The resulting mice will not express IKKβ in granulosa cells or Sertoli cells and thus cannot activate the classical NFκB signalling pathway. On histological assessment, the ovaries and testes from flox x cre (heterogenous) mice appear normal with follicles of all developmental stages and corpora lutea. Preliminary data suggests that breeding with the heterogenous females resulted in increased litter sizes. The histology of the testes is also unremarkable. The mice homozygous for the deletion of IKKβ in the granulosa cells appear healthy and a preliminary assessment does not reveal gross morphological abnormalities of the ovaries. The results of detailed histological and overall assessment of these mice will be presented. These IKK conditional knockout mice should provide insights into the role of NFκB signalling in gonadal function.

266. Loss of betaglycan expression contributes to malignant properties of human granulosa tumour cells

Betaglycan is a type III TGF-β receptor that binds to both inhibin and TGF-β with high affinity and determines cellular sensitivity to these ligands. Previous studies have suggested that betaglycan acts as a tumour suppressor in certain human epithelial cancers. However, the roles of betaglycan in ovarian granulosa cell tumours (GCTs) are poorly understood. The objective of this study was to determine whether human GCTs exhibit betaglycan expression, and if so, what impact this receptor has on tumour biology. Real-time PCR was used to quantify betaglycan transcripts in human GCTs (n = 18) and normal premenopausal ovaries (n = 11). This analysis established that GCTs exhibited a significant 2-fold reduction in mean betaglycan mRNA levels as compared with the normal ovary (P < 0.05). Similarly, two human GCT cell lines, the KGN and COV434, exhibited low betaglycan expression and poor responsiveness to TGF-β and inhibin in luciferase reporter assays. Stable transfection of GCT cell lines with a wildtype betaglycan (WT-BG) expression plasmid conveyed ligand responsiveness. FACS analysis was used to examine cell cycle progression and cell death in the GCT cell lines. This analysis revealed that WT-BG had no effect on the number of cells cycling or undergoing apoptosis. However, WT-BG significantly increased the adhesion of COV434 (P < 0.05) and KGN (P < 0.0001) cells to collagen IV and fibronectin, decreased cellular invasion through Matrigel COV434 (50%) and KGN (75%), and inhibited wound healing COV434 (70%) and KGN (80%). Collectively, the data establish that betaglycan is an important regulator of granulosa cell biology and suggest that a deficiency in betaglycan contributes to the pathogenesis of granulosa cell cancer. The work further suggests a role for betaglycan in the prevention of tumour invasion, possibly by increasing the adhesion of granulosa cells to matrix components. Supported by: the NHMRC of Australia (RegKeys 338516; 241000; 441101; 388904).

Insulin-like growth factor, insulin-like growth factor-binding protein-4, and pregnancy-associated plasma protein-A gene expression in human granulosa cell tumors

The insulin-like growth factor (IGF) system plays an important role in folliculogenesis. It is also thought to contribute to the pathogenesis of many cancers, including those of the ovarian epithelium. In the human follicle, the predominant IGF is IGF-II and its actions are modulated by insulin-like growth factor-binding protein-4 (IGFBP-4), the IGFBP-4 protease, and the pregnancy-associated plasma protein-A (PAPP-A). These peptide components are synthesized by the granulosa cells of the developing follicle. The aim of this study was to characterize the expression of these components of the IGF system in granulosa cell tumors (GCT) of the ovary. IGF-I, IGF-II, IGFBP-4, and PAPP-A gene expression was determined in a panel of GCT and compared to the levels in normal ovary and in epithelial ovarian tumors. Although both the IGF-I and IGF-II genes were expressed in the GCT, the levels were lower than in the other tissue groups. IGFBP-4 expression was also low in the GCT, whereas PAPP-A gene expression was highest in the GCT. These findings were unexpected given the prominent role this signaling system plays in normal granulosa cells. In conclusion, these observations suggest that the IGF system may have a limited role in the pathogenesis of GCT with PAPP-A subserving a function other than IGFBP-4 proteolysis.

Molecular characterization of sarcomatous change in a granulosa cell tumor

Sarcomatous transformation of a granulosa cell tumor (GCT) is a rare event. We describe the development of a rapidly progressive sarcomatous change in a woman who had initially presented with a classical GCT. A first recurrence occurred 23 months after the initial diagnosis when she was treated with external beam radiotherapy to her pelvis. A second recurrence 76 months following her initial surgery was consistent with a GCT. At 92 months, she presented with a further recurrence, outside of the radiotherapy field. This last recurrence had a different histologic appearance with features of sarcomatous change. Molecular analysis, using both reverse transcription-polymerase chain reaction and complementary DNA microarrays, has been used to analyze tissue obtained before and after the observed change in the tumor. The data show that GCT-specific genes, such as inhibin alpha, estrogen receptor, and follicle-stimulating hormone receptor, have been downregulated in the sarcomatous change. Significant upregulation of genes associated with an inflammatory response was also noted in the sarcoma, and this was consistent with the presence of a marked inflammatory infiltrate seen on histopathology. This study represents the novel application of microarray technology and demonstrates the unexpected finding of expression of the fibroblast activation protein gene in normal ovary. Although tumors such as this may be targets for the novel fibroblast activating protein-directed chemotherapeutic monoclonal antibody sibrotuzumab, the finding of expression in the normal ovary suggests the need for caution.

Expression of nuclear receptor coregulators in ovarian stromal and epithelial tumours

Granulosa cell tumours of the ovary (GCT) exhibit high expression of estrogen receptor beta (ERbeta). A role for estrogen receptors in these tumours may depend on altered co-activator expression. This study examines the expression of the co-activators SRC-1a/e, SRC-2, SRC-3, SRA, and the corepressors NCoR and SMRT in GCT, epithelial ovarian tumours and normal ovary. No significant difference in the expression of SRC-1, SRC-2, SRC-3 or NCoR and SMRT was found. In particular, there was no correlation of co-activator expression with ERbeta expression. There was a significant upregulation in the expression of the novel RNA co-activator SRA in the serous tumours compared with the other tumour types and normal ovary. The findings suggest that ERbeta may require co-activators, other than members of the SRC family for the modulation of transcription in GCT.

Inhibin/activin and ovarian cancer

Inhibin and activin are members of the transforming growth factor beta (TGFbeta) family of cytokines produced by the gonads, with a recognised role in regulating pituitary FSH secretion. Inhibin consists of two homologous subunits, alpha and either betaA or betaB (inhibin A and B). Activins are hetero- or homodimers of the beta-subunits. Inhibin and free alpha subunit are known products of two ovarian tumours (granulosa cell tumours and mucinous carcinomas). This observation has provided the basis for the development of a serum diagnostic test to monitor the occurrence and treatment of these cancers. Transgenic mice with an inhibin alpha subunit gene deletion develop stromal/granulosa cell tumours suggesting that the alpha subunit is a tumour suppressor gene. The role of inhibin and activin is reviewed in ovarian cancer both as a measure of proven clinical utility in diagnosis and management and also as a factor in the pathogenesis of these tumours. In order to place these findings into perspective the biology of inhibin/activin and of other members of the TGFbeta superfamily is also discussed.

Determinants of spironolactone binding specificity in the mineralocorticoid receptor

Spironolactone is a mineralocorticoid receptor (MR) antagonist in clinical use. The compound has a very low affinity for the glucocorticoid receptor (GR). Determinants of binding specificity of spironolactone to the MR were investigated using chimeras created between the ligand-binding domains (LBDs) of the MR and the GR. These chimeras had previously been used to investigate aldosterone binding specificity to the MR. Spironolactone was able to compete strongly for [(3)H]-aldosterone and [(3)H]-dexamethasone binding to a chimera containing amino acids 804-874 of the MR, and weakly for [(3)H]-dexamethasone binding to a chimera containing amino acids 672-803 of the MR. Amino acids 804-874 were also critical for aldosterone binding specificity. Models of the MR LBD bound to aldosterone and spironolactone were created based on the crystal structure of the progesterone receptor LBD. The ligand-binding pocket of the MR LBD model consisted of 23 amino acids and was predominantly hydrophobic in nature. Analysis of this model in light of the experimental data suggested that spironolactone binding specificity is not governed by amino acids in the ligand-binding pocket.

FSH-regulated gene expression profiles in ovarian tumours and normal ovaries

Development, growth and function of the ovary are controlled by endocrine and paracrine signals. These may also influence the development of ovarian cancer. The aim of this study was to identify the key molecular markers of the unregulated growth and hormone synthesis seen in ovarian tumours, particularly in granulosa cell tumours (GCT). Genes used in this study were chosen on the basis of our understanding of growth and differentiation in the normal ovary. We sought to define the patterns of gene expression in a panel of epithelial and stromal ovarian tumours. Expression was determined by RT-PCR using gene-specific primers for the FSH receptor (FSHR); the FSH early response genes: regulatory subunit of protein kinase A (RII-beta), cyclin D2 (cycD2) and sgk; and late response markers: cyclooxygenase-2 (COX-2) and the LH receptor (LHR). The GCT had high expression of FSHR compared with normal ovaries and the other tumours. cycD2 and RII-beta and COX-2 genes were also highly expressed in the GCT. sgk and LHR expression was lower in all of the tumours than in normal ovaries. Serous cystadenocarcinomas also had an unexpectedly high expression of COX-2. Comparison of the gene expression profiles between each tumour group suggests a molecular phenotype for GCT that is similar to that reported for FSH stimulated pre-ovulatory granulosa cells.

Human kallikrein 4 (KLK4) is highly expressed in serous ovarian carcinomas

Previous studies indicated that a new member of the human kallikrein (KLK) gene family, KLK4, was expressed in prostate, breast, and endometrial carcinoma cell lines and may have potential as a tumor marker. The aim of this study was to examine the expression of KLK4 in the normal ovary and ovarian tumors of different histology, stage, and differentiation and to determine its association with ovarian tumor progression. Using reverse transcription-PCR, Southern blot, and densitometry analyses, we found the level of KLK4 expression was higher in late stage serous (SER) epithelial-derived ovarian carcinomas than in normal ovaries, mucinous epithelial tumors, and granulosa cell tumors. KLK4 was highly expressed in all of the SER ovarian carcinoma cell lines (eight of eight), SER epithelial carcinomas (11 of 11), and two adenomas, whereas it was expressed at a lower level (or not at all) in normal ovaries (four of six), mucinous epithelial tumors (three of four), endometrioid carcinomas (four of five), clear cell carcinomas (two of three), or granulosa cell tumors (three of six). Of particular interest, KLK4 mRNA variants were detected in SER ovarian carcinoma cell lines and primary cultured ovarian tumor cells, but they were not present in normal ovaries. In situ hybridization analysis showed that KLK4 mRNA transcripts are localized to adenocarcinoma cells of ovarian tumor tissues. Similarly, immunohistochemical staining of ovarian carcinoma sections showed immunoreactivity to KLK4 protein product (hK4) antipeptide antibodies. In addition, intracellular hK4 levels, as detected on Western blot analysis, were induced by 100 nM estrogen treatment of the estrogen receptor positive ovarian carcinoma cell line OVCAR-3, >8-24 h. Our results show that the level of KLK4 expression and expression of KLK4 mRNA variants are associated with progression of ovarian cancer, particularly late stage SER adenocarcinomas. Moreover, hK4 may be a candidate marker for the diagnosis and/or monitoring of ovarian epithelial carcinomas.

The inhibins and ovarian cancer

Interest in inhibin as a marker of ovarian malignancy was stimulated by the description of elevated immunoreactive inhibin levels in the sera of patients with granulosa cell tumours. Several groups have confirmed the value of serum inhibin in the diagnosis and follow-up of patients with this uncommon malignancy. Immunoreactive inhibin levels are also frequently elevated in patients with mucinous cystadenocarcinoma and less frequently in other forms of ovarian tumour. Assay of sera using the specific dimeric inhibin assays has shown that ovarian tumours are able to secrete dimeric inhibin particularly inhibin B. The less specific alpha-subunit directed assays, however, most frequently show elevated concentrations. Used in combination with CA125 as a dual tumour marker, it appears in principle that inhibin can be a useful diagnostic agent. Immunohistochemistry for the inhibin subunits has been reported with increasing frequency as a helpful method to assess suspected ovarian stromal cell tumours. Its diagnostic accuracy for other types of ovarian adenocarcinoma appears less reliable. Expression of the inhibin subunit mRNAs has been demonstrated in a variety of ovarian malignancies. The observation that inhibin levels are elevated in ovarian cancer has stimulated studies of their relevance to the molecular pathogenesis of these malignancies. Findings to date have been largely negative with no evidence for activating mutations of the FSH receptor or of the post-receptor signalling pathway proteins.

11th International Congress of Endocrinology

The Olympics of endocrinology, the 11th International Congress of Endocrinolgy was held rather appropriately in Sydney, four weeks after the summer games of the XXWIIth Modern Olympiad. Both occasions were a great success and whilst it may be tempting to extend the analogy to the pool or the track or heaven forbid, digress into 'drugs in sport', this review will focus on endocrinology. There were over 3000 participants with ten plenary lectures, 20 meet-the-expert sessions, 41 symposia, 128 oral free communications and 1500 posters. Sydney post-Olympics provided a vibrant, exciting and picturesque setting with outstanding convention facilities. The Congress Party was held at Campbells Cove in the lee of the Harbour Bridge looking toward the Opera House which provided an opportunity for delegates to view the two architectural icons that had become so familiar in the preceding months. Credit must be given both to the Local Organising Committee of Sydney endocrinologists who made it all happen and to the International Program Organising Committee who crafted a pageant of first rate endocrinology. It is self-evident that this report can only hope to give the reader a flavour of a Congress such as this with the choice of topics being largely idiosyncratic. With five concurrent symposia and two concurrent orals each morning and afternoon of the four days, any omissions reflect not on the topic or its importance but on this reviewer's inability to be in more than one place at once!

Humoral factors in intestinal adaptation

The small bowel has a remarkable ability to adapt after injury, inflammation or resection. It has long been suggested that humoral factors, particularly enteroglucagon, epidermal growth factor, neurotensin and growth hormone/insulin-like growth factor I, might stimulate bowel growth. Of particular interest is the recent finding that glucagon-like peptide 2 (GLP-2), a product of the gene encoding proglucagon, exerts a trophic effect on the intestinal epithelium via a specific G-protein-coupled receptor. GLP-2 and/or these other trophic peptides might prove to have a role in the treatment of bowel diseases associated with structural or functional loss of the small bowel.

Acute differential regulation by corticosteroids of epithelial sodium channel subunit and Nedd4 mRNA levels in the distal colon

The molecular mechanisms by which corticosteroids affect fluid and electrolyte balance have yet to be fully elucidated. The apical amiloride-sensitive electrogenic epithelial sodium channel (ENaC) has been shown to have a central role in corticosteroid-mediated sodium transport in the distal colon. The acute response of the alpha-, beta- and gammaENaC subunit genes to a single parenteral dose of aldosterone or dexamethasone was examined in the rat distal colon in vivo. The response of the Nedd4 gene, whose product is involved in channel turnover, was also examined. Whilst the alphaENaC and Nedd4 genes showed no significant response to either steroid, both the beta- and gammaENaC mRNA levels were increased acutely by both aldosterone and dexamethasone. The gammaENaC mRNA appears to have a very short half-life. Use of the highly selective glucocorticoid receptor agonist RU28362 confirmed that the response was mediated by both the mineralocorticoid and glucocorticoid receptors.

Rapid upregulation of serum and glucocorticoid-regulated kinase (sgk) gene expression by corticosteroids in vivo

The molecular mechanisms by which corticosteroids regulate epithelial sodium transport remain to be fully elucidated. Expression of the serum and glucocorticoid-regulated kinase (sgk) has recently been reported to be regulated acutely by corticosteroids in the amphibian A6 cell line and in cortical collecting tubule cells in vitro. In order to extend this observation to a mammalian system in vivo, the acute response of the sgk gene to a single parenteral dose of aldosterone or dexamethasone was examined in the rat kidney and distal colon. The sgk mRNA levels were significantly elevated by both steroids by 30 min in the distal colon, reaching a peak at 2 h. A more modest increase in sgk mRNA levels was also seen in the kidney in response to both steroids. In both tissues, sgk mRNA has a very short half-life. As for other corticosteroid-regulated genes, the response appears to be mediated by both the mineralocorticoid and glucocorticoid receptors. The response to aldosterone in the distal colon in the presence of cycloheximide was superinduced, strongly suggesting that this is a primary response. The responses to both adrenalectomy and carbenoxolone sodium treatment suggest that the observed responses to corticosteroids can occur in the physiological range of endogenous circulating corticosteroids. These studies provide strong evidence that sgk is an aldosterone-induced gene in vivo in a mammalian system.

The distribution of cells containing estrogen receptor-alpha (ERalpha) and ERbeta messenger ribonucleic acid in the preoptic area and hypothalamus of the sheep: comparison of males and females

We have used in situ hybridization to compare the distributions of estrogen receptor alpha (ERalpha) and ERbeta messenger RNA (mRNA)-containing cells in the preoptic area and hypothalamus of ewes and rams. Perfusion-fixed brain tissue was collected from luteal phase ewes and intact rams (n = 4) during the breeding season. Matched pairs of sections were hybridized with sheep-specific, 35S-labeled riboprobes, and semiquantitative image analysis was performed on emulsion-dipped slides. A number of sex differences were observed, with females having a greater density of labeled cells than males (P < 0.001) and a greater number of silver grains per cell (P < 0.01) in the ventromedial nucleus for both ER subtypes. In addition, in the retrochiasmatic area, males had a greater (P < 0.05) cell density for ERalpha mRNA-containing cells than females, whereas in the paraventricular nucleus, females had a greater density (P < 0.05) of ERalpha mRNA-containing cells than males. There was a trend (P = 0.068) in the arcuate nucleus for males to have a greater number of silver grains per cell labeled for ERalpha mRNA. In both sexes, there was considerable overlap in the distributions of ERalpha and ERbeta mRNA-containing cells, but the density of labeled cells within each nucleus differed in a number of instances. Nuclei that contained a higher (P < 0.001) density of ERalpha than ERbeta mRNA-containing cells included the preoptic area, bed nucleus of the stria terminalis, and ventromedial nucleus, whereas the subfornical organ (P < 0.001), paraventricular nucleus (males only, P < 0.05), and retrochiasmatic nucleus (females only, P < 0.05) had a greater density of ERalpha than ERbeta mRNA-containing cells. The anterior hypothalamic area and supraoptic nucleus had similar densities of cells containing both ER subtypes. The lateral septum and arcuate nucleus contained only ERalpha, whereas only ERbeta mRNA-containing cells were seen in the zona incerta. The sex differences in the populations of ER mRNA-containing cells in the ventromedial and arcuate nuclei may explain in part the sex differences in the neuroendocrine and behavioral responses to localized estrogen treatment in these nuclei. Within sexes, the differences between the distributions of ERalpha and ERbeta mRNA-containing cells may reflect differential regulation of the actions of estrogen in the sheep hypothalamus. Low levels of ERbeta mRNA in the preoptic area and ventromedial and arcuate nuclei, regions known to be important for the regulation of reproduction, suggest that ERbeta may not be involved in these functions.

Specificity in mineralocorticoid versus glucocorticoid action

The mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR) share considerable structural and functional homology. Overlapping effects on epithelial sodium transport are observed in vivo; in vitro, both are able to bind and transactivate through a common hormone response element. This has led several investigators to suggest that specificity is conferred primarily by prereceptor mechanisms, and we have addressed this question using both in vitro and in vivo approaches. Although the MR has been regarded as less transcriptionally active than the GR in vitro, significant differences are observed when epithelial rather than fibroblast cell lines are used. These differences are mediated by the N-termini of the receptors. Activation of intracellular signaling pathways differentially modulates MR- versus GR-mediated transactivation. Although these studies identify mechanisms by which specificity may be achieved, they do not prove that this occurs in vivo. Such studies have been limited by an absence of MR-regulated genes. Known candidate aldosterone-responsive genes have been examined in the rat distal colon; the time course and the specificity of the response to a single parenteral dose of corticosteroid has been characterized. The epithelial sodium channel beta and gamma subunit genes are both up-regulated within 60 minutes by either MR or GR activation. Similar responses are observed for the serum and glucocorticoid-regulated kinase and channel-inducing factor genes. All four genes show clear and rapid up-regulation of their mRNA levels by aldosterone, which is paralleled by GR-mediated up-regulation of expression. While they are indeed aldosterone-responsive genes, genes that are uniquely aldosterone-regulated remain to be identified.

Estrogen receptor isoform gene expression in ovarian stromal and epithelial tumors

The factors involved in the pathogenesis of ovarian cancers remain unclear, and the response of these tumors to hormonal therapy is limited. The identification of a second estrogen receptor gene (ERbeta), expressed predominantly in ovarian granulosa cells, led us to explore its possible role in ovarian cancer, particularly in granulosa cell tumors (GCT). Several isoforms of ERbeta have been identified. We sought to define the patterns of both ERalpha and ERbeta gene expression in a panel of ovarian tumors consisting of GCT and serous and mucinous cystadenocarcinomas as well as in normal ovary. Expression was determined by RT-PCR using gene- and isoform-specific primers and probes combined with Southern blot analysis of the PCR products. Widespread expression of ERalpha was observed in all tumor types, but at relatively low levels. ERbeta is expressed predominantly in GCT, with lower levels in mucinous tumors and very low levels in serous tumors. The ERbeta2 splice variant previously reported in rodents was not observed. Only very low levels of the exon 5, exon 6, and exon 5/6 deletion variants were detected. The C-terminal truncation variant ERbeta(cx), however, exhibited widespread expression across all the tumor types. As ERbeta(cx) has been shown to be a ligand-independent antagonist of ERalpha action, the relative ratios of ERbeta(cx), ERalpha, and ERbeta may influence the response of a tumor to antiestrogen therapy.

Mineralocorticoid action

The physiology of mineralocorticoid action, particularly with respect to epithelial sodium transport, is well defined. A full understanding of the molecular basis of mineralocorticoid action has however proven to be more elusive. In the last decade insights into structural and functional aspects of the mineralocorticoid receptor combined with emerging details of the components of the mediators of the sodium flux has resulted in a clearer picture. This review focuses on two aspects of these new developments; the mineralocorticoid receptor and putative aldosterone induced proteins.

Structural determinants of aldosterone binding selectivity in the mineralocorticoid receptor

The structural determinants of aldosterone binding specificity in the mineralocorticoid receptor (MR) have not been determined. The MR has greatest sequence identity with the better characterized glucocorticoid receptor (GR), which is reflected in their overlapping ligand binding specificities. There must be subtle sequence differences that can account for the MR-specific binding of aldosterone and the shared binding of cortisol. To characterize ligand binding specificity, chimeras were made between the human MR and GR ligand-binding domains (LBDs). Three points were chosen as break points to generate a total of 16 different constructs. These chimeric LBDs were placed in a human GR expression vector containing the GR DNA-binding and N-terminal domains and assayed by co-transfection into CV-1 cells with the mouse mammary tumor virus-luciferase reporter plasmid. Binding of [(3)H]aldosterone and [(3)H]dexamethasone was also measured. All of the constructs that are potently activated by aldosterone contain amino acids 804-874 of the MR. The results of the ligand binding experiments using [(3)H]aldosterone were consistent with the transactivation assay. Cortisol activation of the chimeras was surprisingly complex. Constructs that are activated by cortisol contain either amino acids 804-874 and 932-984 of the MR or amino acids 598-668 and 726-777 of the GR. However, all of the chimeras retained the ability to bind the synthetic glucocorticoid [(3)H]dexamethasone, and cortisol was able to displace [(3)H]dexamethasone binding, suggesting that the differential effects of cortisol on transcriptional activation are caused by an effect that occurs downstream of ligand binding. These results identify a subregion of the MR LBD that confers specificity of aldosterone binding, which contrasts with cortisol binding where differential effects between chimeras appear to be mediated by interactions distal to ligand binding.

mRNA levels of dipeptidyl peptidase IV decrease during intestinal adaptation

BACKGROUND

Glucagon-like peptide 2 (GLP-2) has recently been shown to be a potent enterotrophic factor that may mediate mucosal hyperplasia during intestinal adaptation. The intestinal brush-border protease dipeptidyl peptidase IV (DPP IV) cleaves GLP-2 to an inactive form. It has been postulated that DPP IV activity limits the enterotrophic activity of GLP-2 in rats and humans. Massive small bowel resection (MSBR) in rats is an animal model of intestinal adaptation that has been used successfully to characterize factors involved in the modulation of adaptation.

METHODS

Total RNA was extracted from normal terminal ileum or terminal ileum post-MSBR from Sprague-Dawley rats which were sacrificed 2, 4, and 7 days postresection. A partial rat DPP IV clone was isolated by reverse transcription polymerase chain reaction, and Northern blot analysis of rat DPP IV mRNA levels in normal small bowel and small bowel post-MSBR was performed.

RESULTS

Within normal small bowel, DPP IV mRNA levels were greatest in the terminal ileum; levels in the duodenum and jejunum were approximately 50% of those in the terminal ileum. DPP IV mRNA levels decreased in terminal ileum post-MSBR 2, 4, and 7 days after resection.

CONCLUSION

The decreased DPPIV gene expression suggests a novel mechanism by which the effects on mucosal growth of GLP-2 may be further enhanced, and further that GLP-2 may be a more useful therapeutic agent in humans than currently anticipated.

[Inhibin and ovarian cancer]

Previous observations from our laboratory have demonstrated that the levels of immunoreactive inhibin (ir-inh) are elevated in almost all patients with granulosa cell tumors and in the majority of postmenopausal women with mucinous ovarian cancers. The present report confirms these findings in a larger group of post-menopausal women. Immunohistochemistry for the inhibin alpha. beta A and beta B sununits shows predominantly epithelial staining in granulosa cell tumors and in the majority of mucinous cancers. Serous cystadenocarcinomas also frequently show positive staining. Studies seeking to identify G alpha i-2 or FSH receptor mutations have provided negative results in contrast to other reports. Further studies of the roles of the inhibin-related family of peptides in ovarian cancer diagnosis and monitoring are clearly indicated.

Cushing's syndrome secondary to ectopic ACTH secretion from metastatic breast carcinoma

Breast carcinoma is a rare cause of ectopic ACTH syndrome. There are only two previously reported cases in which ACTH secretion is documented. We describe the case of a 56-year-old woman who presented with clinical and biochemical features of ectopic ACTH syndrome in the setting of metastatic breast carcinoma. Despite aggressive management of her ectopic ACTH syndrome, her course was complicated by opportunistic infection, respiratory failure and death. Immunostaining of the breast metastases for ACTH was positive and in situ hybridization revealed proopiomelanocortin gene expression. This is the first reported case of ectopic ACTH syndrome associated with metastatic breast cancer in which the technique of in situ hybridization has been used to confirm the breast cancer metastases as the source of ectopic ACTH secretion.

Inhibin subunit gene expression in ovarian cancer

OBJECTIVE(S)

Granulosa cell tumors (GCT) and mucinous cystadenocarcinoma of the ovary are associated with elevated circulating levels of immunoreactive inhibin. Measurement of serum inhibin levels provides a useful tumor marker in the management of ovarian tumors. Inhibin is a dimeric ovarian glycoprotein hormone consisting of one alpha and one of two beta subunits. The beta subunits can dimerize to form activin. Activin is bound and its action modulated by another gonadal peptide, follistatin. In this study the patterns of expression of the three inhibin subunit genes, the follistatin gene, and the activin receptor type II gene have been determined.

METHODS

Gene expression was analyzed in RNA prepared from 16 primary ovarian tumors using reverse transcriptase-polymerase chain reaction (RT-PCR). Gene-specific primes were used for RT-PCR; the products were analyzed by Southern blot analysis with gene-specific 32P-labeled probes.

RESULTS

Widespread expression of these genes was found in all of the tumor types examined. Abundant expression of the inhibin alpha subunit gene was observed in the GCT and to a lesser extent in the mucinous and serous tumors. beta subunit expression was also present in the GCT and to a lesser extent in the other tumors. Widespread expression of both the activin receptor type II and the follistatin genes was also observed.

CONCLUSIONS

Expression of the inhibin subunit genes in GCT and some epithelial tumors confirms that these tumors are the source of the increased immunoreactive inhibin seen in the circulation of patients with ovarian tumors. Expression of the activin receptor type II and follistatin genes suggests a paracrine role for activin in these tumors which may be modulated by follistatin, particularly in the GCT.

Transcriptional control by corticosteroids of CHIF gene expression in the rat distal colon

1. Previous studies have shown that levels of CHIF mRNA are increased in the distal colon of the rat in response to corticosteroids. We have recently reported that this response occurs within 2 h of a single dose of either dexamethasone or aldosterone and that the response is mediated via both the mineralocorticoid and glucocorticoid receptors. 2. In the present study we sought to further define the nature of the various transcripts detected by a CHIF coding region cRNA probe in northern blot analysis of corticosteroid-stimulated colonic RNA. The identification of an intronic sequence was used to synthesize an intron-specific cDNA probe to characterize the transcripts. 3. The presence of an intronic sequence in the originally published sequence was confirmed using coupled reverse transcriptase-polymerase chain reactions with primers spanning and within the intronic sequence. The intronic cDNA probe hybridized to the higher molecular weight transcripts detected by the cRNA probe. These transcripts are induced in response to both corticosteroids. 4. Taken together with our observations that the increase in CHIF mRNA levels in the distal colon in response to corticosteroids is not blocked by prior cycloheximide treatment, the increase in the levels of the primary transcript and partially spliced forms argues that this is a primary transcriptional response. This is the first clear demonstration of an aldosterone-induced gene in vivo in a mammalian system.

Acute regulation by corticosteroids of channel-inducing factor gene messenger ribonucleic acid in the distal colon

The molecular mechanisms by which corticosteroids affect fluid and electrolyte balance are unclear. Though glucocorticoid-responsive genes have been identified, genes regulated by aldosterone have not. CHIF (channel-inducing factor gene) is a recently identified gene that is up-regulated in the distal colon by chronic corticosteroid exposure, is expressed in the kidney, and induces a K+-specific current in Xenopus oocytes. The predicted protein shows similarity to gammaNa.K-ATPase, phospholemman, and Mat-8; all seem to be involved in ion transport. CHIF thus presents as a potential aldosterone target gene. In this study, CHIF expression was examined in rats in the acute timeframe of 0.5-4 h after corticosteroid administration. CHIF messenger RNA showed up-regulation by both mineralocorticoid and glucocorticoid receptor agonists in the distal colon, which was not diminished by cycloheximide. Corticosteroid regulation was not observed in the kidney. Basal and induced expression was absent in the lung and in all gastrointestinal tissues except colon, with expression increasing proximal to distal. CHIF is the first gene to show acute regulation by aldosterone and thus encodes a candidate aldosterone-induced protein. In addition, gammaNa.K-ATPase gene expression was found to be very low in colon and significantly higher in kidney. Regulation by corticosteroids was not evident in either tissue.

Cautionary note on the use of end-labelling DNA fragments for detection of apoptosis

The gastrointestinal epithelum undergoes a continual process of cell renewal which is partly regulated by apoptosis. The process of growth and differentiation is greatly enhanced in the terminal ileum after massive small bowel resection, a well-established model of intestinal adaptation. We have applied the terminal deoxynucleotidyl transferase (TdT)-mediated UTP nick end-labelling (TUNEL) method to establish the role of apoptosis in intestinal adaption in terminal ileum of control animals after small bowel resection. Healing skin wound and lymph node were used as positive control tissue for apoptotic cells. We report that considerable inter-animal variation was observed in the intestinal tissue. We believe that caution is required in the interpretation of TUNEL staining in intestinal tissue and in its use as a specific marker for apoptosis in this setting.

Inhibin and ovarian cancer

Previous observations from our laboratory have demonstrated that the levels of immunoreactive inhibin (ir-inh) are elevated in almost all patients with granulosa cell tumours and in the majority of postmenopausal women with mucinous ovarian cancers. The present manuscript confirms these findings in a larger group of postmenopausal women. Immunohistochemistry for the inhibin alpha, betaA and betaB subunits shows predominantly epithelial staining in granulosa cell tumours and in the majority of mucinous cancers. Serous cystadenocarcinomas also frequently show positive staining. Studies seeking to identify G alpha(i-2) or FSH receptor mutations have provided negative results in contrast to other reports. Further studies of the roles of the inhibin-related family of peptides in ovarian cancer diagnosis and monitoring are clearly indicated.

Tissue distribution of rat glucagon receptor and GLP-1 receptor gene expression

The regulation of glucose metabolism by glucagon and GLP-1 is well established, but novel functions for these and other proglucagon-derived peptides are less well defined. This paper highlights the diversity of both GLP-1 and glucagon activity by studying the tissue distribution of glucagon and GLP-1 receptor gene expression by both Southern blot analysis of RT-PCR products and nuclease protection assays. By Southern blot analysis of RT-PCR products, GLP-1 receptor mRNA was detected in lung, hypothalamus, hippocampus, cerebral cortex, kidney, pancreas, and throughout the gastrointestinal tract. Glucagon receptor expression was detected in liver, kidney, spleen, thymus, adrenal glands, pancreas, cerebral cortex, lung, and throughout the gastrointestinal tract. Nuclease protection assay revealed glucagon receptor expression to be highest in liver and kidney, whereas GLP-1 receptor expression was only detected by protection assay in lung, stomach, and large bowel. Despite previous evidence that other receptors for proglucagon-derived peptides may exist, no evidence of novel receptors or multiple isoforms of the glucagon and GLP-1 receptors was found, indicating that the two cloned receptors may mediate all the effects of proglucagon-derived peptides, or that novel receptors may share less homology with the glucagon and GLP-1 receptors than previously anticipated.

Structural determinants of cortisol resistance in the guinea pig glucocorticoid receptor

The guinea pig exhibits resistance to glucocorticoids in vivo which results from the guinea pig glucocorticoid receptor (GR) having a lower affinity for cortisol than the human GR. Cloning of the guinea pig GR has revealed that the amino acid sequence of the ligand-binding domain (LBD) differs from the human GR at 24 residues. The present study confirms that the decreased sensitivity and binding affinity of the guinea pig GR are conferred in vitro by the LBD. Further, the substitutions in the LBD do not confer altered relative steroid sensitivity or selectivity compared with the human GR. The altered sensitivity and binding of dexamethasone are confined to the first third of the LBD, which contains 5 nonconservative substitutions in a region that is otherwise highly conserved across several species of GR. These residues, either alone or in combination, were targeted for site-directed mutagenesis in both the human and guinea pig LBD. Trans-activation studies with these mutant GR failed to exclusively implicate or exclude any of the residues in the observed resistance. Rather, the changes, with 1 exception, caused a decrease in sensitivity, suggesting that critical intramolecular interactions involving at least 4 of these residues determine the correct conformation of this region. Recent molecular modeling of the GR LBD structure suggests that although the above region is not part of the core ligand-binding pocket, it is required to maintain the conformation of the binding pocket.

Intracellular signaling pathways confer specificity of transactivation by mineralocorticoid and glucocorticoid receptors

The glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR) bind similar ligands and target genes in vitro yet have distinct roles in vivo. With a single exception, known mechanisms conferring specificity have been limited to prereceptor mechanisms. These alone cannot account for specificity, particularly at a transcriptional level. These studies aimed to determine whether receptor-specific transcriptional regulation via physiological modulators of cellular signaling pathways, and MR-, as well as GR-specific interactions, could be demonstrated. By comparing modulation of GR- and MR-mediated transactivation in renal LLC-PK1 cells, we have identified several activators of intracellular signaling pathways that discriminate between the GR and the MR and demonstrate that differential regulation occurs at relatively specific points in the signaling pathway. The phosphatase inhibitor, okadaic acid, and the protein kinase G activator, sodium nitroprusside, stimulate only GR-mediated transactivation, in contrast to modulators of other protein kinase pathways that act in parallel on both receptors. The GR-specific effect of okadaic acid is observed only at doses where both phosphatases 1 and 2A are inhibited. MR-specific modulators include a centrally active alpha-2 adrenergic agonist and the thyroid receptor. Comparison of the interaction between the thyroid receptor and the GR, or the MR, distinguish two types of repression, only one of which is receptor-specific. These studies identify several signal transduction pathways that can differentially activate either the MR or the GR at a transcriptional level and might play physiological roles in conferring MR- or GR-specific regulation.

No evidence of a role for mutations or polymorphisms of the follicle-stimulating hormone receptor in ovarian granulosa cell tumors

The molecular pathogenesis of granulosa cell tumors of the ovary is not understood, although recent studies have shown that immunoreactive inhibin secretion by these tumors may be used as a tumor marker. Granulosa cell tumors exhibit many features of normal granulosa cells, including a response to FSH and inhibin secretion. FSH levels are suppressed in patients with inhibin-secreting granulosa cell tumors, suggesting FSH-independent growth of these tumors. Activating mutations of the FSH receptor might, therefore, be involved in tumorigenesis. We sought to identify mutations in the FSH receptor genes of these tumors using PCR to amplify the exon encoding the transmembrane and cytoplasmic domains from the tumor DNA. Analysis of the amplicons for single strand conformational polymorphisms and direct sequencing confirmed a previously reported polymorphism in the C-terminal region of the receptor, but did not identify tumor-specific missense mutations and/or polymorphisms. In addition, ribonucleic acid from 3 granulosa cell tumors was used to confirm expression of the FSH receptor; expression was unexpectedly also observed in several ovarian mucinous cystadenocarcinomas used as controls. In conclusion, our failure to identify activating mutations of the FSH receptor in 15 granulosa cell tumors argues against a role for the FSH receptor in tumorigenesis and suggests that some subsequent component of this signal transduction pathway may be activated.

Identification of a splice variant of the rat estrogen receptor beta gene

Recently a second estrogen receptor termed estrogen receptor beta (ERbeta) has been cloned and characterized, and shown to be expressed at the highest levels in ovarian granulosa cells and prostatic epithelium. In the course of amplifying a region of the ligand-binding domain of the rat ERbeta cDNA we identified a second, larger transcript which appears to arise through differential splicing. The second isoform has 54 nucleotides inserted after position 1372 encoding 18 additional amino acids. Both isoforms are expressed at similar relative abundance in a range of tissues.

Insulin gene expression in adult-onset nesidioblastosis

Nesidioblastosis is a well-recognized cause of persistent hypoglycaemia in neonates. We describe the case of a 24-year-old woman who presented with hyperinsulinaemic hypoglycaemia in whom an insulinoma could not be identified at operation which resulted in her undergoing a subtotal distal pancreatectomy. Histological examination revealed the presence of nesidioblastosis. The finding of nesidioblastosis in adults has been reported previously, albeit rarely. We report the use of in situ hybridization to characterize the patterns of insulin and proglucagon gene expression in the resected pancreas. Insulin expression was observed in both the islets and also the isolated nesidioblasts. The alpha-cells of the islets had lost their usual peripheral distribution suggesting that not only is insulin gene expression dysregulated but that the islets are structurally abnormal.

Determinants of specificity of transactivation by the mineralocorticoid or glucocorticoid receptor

Glucocorticoids and mineralocorticoids have distinct in vivo roles despite close structural homology and similarities in vitro. Known mechanisms of specificity focus on factors extrinsic to the receptor; interactions that directly regulate the receptor to confer specificity are less well understood, particularly for the mineralocorticoid receptor (MR). To examine relative MR vs. glucocorticoid receptor (GR) function in a more physiological context, we compared transactivation by GR and MR in the standard experimental fibroblast CV-1 cell line, the renal epithelial LLC-PK1 line, and neuronal medullary raphe RN33B cells. Maximal transactivational activity mediated by MR, relative to that mediated by GR, is enhanced in both of these cell lines and is primarily conferred by an N-terminal-mediated enhancement of the MR response. In addition, the ligand concentration required for maximal transcriptional activity of the GR varies significantly between cell lines. This is independent of binding affinity or 11beta-hydroxysteroid dehydrogenase-mediated inactivation and may contribute to in vivo tissue-specific differences in responses to the GR. Although ligand binding affinity is clearly conferred by the LBD, receptor-specific variations between cell lines in transcriptional sensitivity to ligand appear, rather, to be associated with the N-terminus. These studies demonstrate that the specificity of the MR vs. the GR response may be mediated via unique cellular factors, as well as suggesting a novel means of expanding the cellular response to cortisol.

Absence of the previously reported G protein oncogene (gip2) in ovarian granulosa cell tumors

The molecular pathogenesis of granulosa cell tumors of the ovary is not understood, although recent studies have shown that authentic inhibin secretion by these tumors may be used as a tumor marker. G proteins are heterotrimeric membrane-based polypeptides that mediate signal transduction. Activating mutations of the alpha-subunit have been reported in several tumors in which the resulting constitutively activated signal transduction pathway may be involved in tumorigenesis. Activating mutations of the G protein, G alpha I-2, have been reported to be present in 30% of ovarian sex cord tumors and in adrenocortical tumors; this activated G alpha I-2 has been designated the gip2 oncogene. We sought to explore the frequency of this oncogene in granulosa cell tumors, the most common of the sex cord tumors. Genomic DNA was obtained from either fresh-frozen tumor tissue or paraffin-embedded sections. Using both allele-specific oligonucleotide hybridization and direct sequencing of a PCR-amplified region of the G alpha I-2 gene, we were unable to confirm the presence of the previously reported mutation in any of the 13 tumors examined. The gip2 oncogene does not appear to be present at high frequency in ovarian granulosa cell tumors.