DNA Methylation of Steroidogenic Enzymes in Benign Adrenocortical Tumors: New Insights in Aldosterone-Producing Adenomas

CONTEXT

DNA methylation has been identified among putative regulatory mechanisms for CYP11B2 expression in primary aldosteronism.

OBJECTIVE

The objective of this work is to investigate DNA methylation and expression of genes encoding steroidogenic enzymes in benign adrenocortical tumors.

DESIGN AND SETTING

This cross-sectional study took place at university hospitals.

PATIENTS

We collected fresh-frozen tissues from patients with benign adrenocortical adenomas (n = 48) (nonfunctioning n = 9, autonomous cortisol secretion n = 9, Cushing syndrome n = 17, aldosterone-producing [APA] n = 13) and adrenal cortex adjacent to APA (n = 12). We collected formalin-fixed, paraffin-embedded (FFPE) specimens of paired APA and concurrent aldosterone-producing cell clusters (APCCs) (n = 6).

INTERVENTION

DNA methylation levels were evaluated by quantitative bisulfite next-generation sequencing in fresh-frozen tissues (CYP11A1, CYP11B1, CYP11B2, CYP17A1, CYP21A2, HSD3B1, HSD3B2, NR5A1, STAR, and TSPO) and FFPE APA/APCC paired samples (CYP11B2). CYP11B1, CYP11B2, CYP17, CYP21, and STAR gene expressions were examined by quantitative real-time polymerase chain reaction.

MAIN OUTCOME MEASURE

The main outcome measure was DNA methylation.

RESULTS

CYP11B2 methylation levels were significantly lower in APA than in other adrenal tissues (P < .001). Methylation levels of the remaining genes were comparable among groups. Overall, CYP11B2 expression and DNA methylation were negatively correlated (ρ = -0.379; P = .003). In FFPE-paired APA/APCC samples, CYP11B2 methylation level was significantly lower in APA than in concurrent APCCs (P = .028).

CONCLUSIONS

DNA methylation plays a regulatory role for CYP11B2 expression and may contribute to aldosterone hypersecretion in APA. Lower CYP11B2 methylation levels in APA than in APCCs may suggest an APCC-to-APA switch via progressive CYP11B2 demethylation. Conversely, DNA methylation seems not to be relevant in regulating the expression of genes encoding steroidogenic enzymes other than CYP11B2.

Statins Reduce Intratumor Cholesterol Affecting Adrenocortical Cancer Growth

Mitotane causes hypercholesterolemia in patients with adrenocortical carcinoma (ACC). We suppose that cholesterol increases within the tumor and can be used to activate proliferative pathways. In this study, we used statins to decrease intratumor cholesterol and investigated the effects on ACC growth related to estrogen receptor α (ERα) action at the nuclear and mitochondrial levels. We first used microarray to investigate mitotane effect on genes involved in cholesterol homeostasis and evaluated their relationship with patients' survival in ACC TCGA. We then blocked cholesterol synthesis with simvastatin and determined the effects on H295R cell proliferation, estradiol production, and ERα activity in vitro and in xenograft tumors. We found that mitotane increases intratumor cholesterol content and expression of genes involved in cholesterol homeostasis, among them INSIG, whose expression affects patients' survival. Treatment of H295R cells with simvastatin to block cholesterol synthesis decreased cellular cholesterol content, and this affected cell viability. Simvastatin reduced estradiol production and decreased nuclear and mitochondrial ERα function. A mitochondrial target of ERα, the respiratory complex IV (COXIV), was reduced after simvastatin treatment, which profoundly affected mitochondrial respiration activating apoptosis. Additionally, simvastatin reduced tumor volume and weight of grafted H295R cells, intratumor cholesterol content, Ki-67 and ERα, COXIV expression and activity and increase terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells. Collectively, these data demonstrate that a reduction in intratumor cholesterol content prevents estradiol production and inhibits mitochondrial respiratory chain-inducing apoptosis in ACC cells. Inhibition of mitochondrial respiration by simvastatin represents a novel strategy to counteract ACC growth.

The effects of mitotane and 1α,25-dihydroxyvitamin D3 on Wnt/beta-catenin signaling in human adrenocortical carcinoma cells

PURPOSE

Mitotane is the only chemotherapeutic agent available for the treatment of adrenocortical carcinoma (ACC), however, the anti-neoplastic efficacy is limited due to several side-effects in vivo. There is, therefore, a need of exploring for new anti-tumoral agents which can be used either alone or in combination with mitotane. The active vitamin D metabolite 1α,25-dihydroxyvitamin D₃ (1α,25(OH)₂D₃) acts as an anti-proliferative agent in human cancer by inhibiting the Wnt/beta-catenin pathway through the vitamin D receptor (VDR). The aim of this study was to study the effects of mitotane and 1α,25(OH)₂D₃, individually or in combination, in an in vitro model with H295R ACC cells, and to elucidate the molecular events behind their effects involving the Wnt/beta-catenin signaling.

METHODS AND RESULTS

Multiple concentrations of mitotane and 1α,25(OH)₂D₃, individually or in combination, were tested on H295R cells for 24-96 h, and the effects analysed by MTT. A reduction in cell growth was observed in a dose/time-dependent manner for both mitotane and 1α,25(OH)₂D₃. In addition, a combination of clinically sub-therapeutic concentrations of mitotane with 1α,25(OH)₂D₃, had an additive anti-proliferative effect (Combination Index = 1.02). In a wound healing assay, individual treatments of both mitotane and 1α,25(OH)₂D₃ reduced the migration ability of H295R cells, with the effect further enhanced on combining both the agents. Western blotting and qRT-PCR analysis showed a modulation of the Wnt/beta-catenin and VDR signaling pathways.

CONCLUSION

Our results show an additive effect of mitotane and 1α,25(OH)₂D₃ on the inhibition of H295R ACC cell growth and viability, and suggest that molecular mechanisms of their effects involve a functional link between VDR and Wnt/beta-catenin pathways.

SUN-044 Methylation Status and Gene Expression of Steroidogenic Enzymes in Benign Adrenocortical Tumors

DNA methylation has been recognized as a putative regulatory mechanism for CYP11B2 in primary hyperaldosteronism. We aimed to investigate the DNA methylation and the expression of a panel of genes encoding several enzymes involved in steroidogenesis in adrenocortical benign tumors. We collected a total of 60 adrenocortical tissues, including 9 non-functioning adrenal adenomas, 9 adenomas associated with autonomous cortisol secretion, 17 adenomas associated with Cushing’s syndrome, 13 Conn’s adenomas and 12 tissues derived from adrenal gland adjacent to the Conn’s adenomas. Non-functioning tumors and autonomous cortisol secretion were defined according to cortisol levels after 1 mg dexamethasone suppression test ≤ or > 50 nmol/L, respectively. The DNA methylation level of CYP11A1, CYP11B1, CYP11B2, CYP17A1, CYP21A2, DHCR24, HSD3B1, HSD3B2, NR5A1, STAR, and TSPO was evaluated by quantitative Bisulfite Next Generation Sequencing (bisulfite-NGS). Bioinformatic analysis was performed in a GalaxyProject environment and processed by BSPAT (Bisulfite Sequencing Pattern Analysis Tool). Spearman correlation coefficients were calculated using IBM SPSS 21 (IBM). CYP11B1, CYP11B2, CYP17, CYP21, STAR and β-actin gene expressions were examined by quantitative Real-Time PCR using a Sybr Green Assay kit (Thermo Fisher Scientific). The equation 2−ΔΔCt was used to calculate the fold changes in gene expression between the categories of samples. CYP11B2 was significantly hypomethylated in Conn’s adenoma, when compared to other adrenal tissues (P<0.001). No difference in methylation status was found among groups for the remaining genes. CYP11B2 mRNA levels were significantly higher in Conn’s adenoma than in the remaining adrenal tissues (P=0.001). CYP21 mRNA was significantly higher in all but Conn’s adenomas, when compared to normal adrenal tissues (P<0.001). Overall, we found a negative correlation between CYP11B2 expression and DNA methylation (rho= -0.379; P=0.003). DNA methylation seems to be a pivotal regulatory mechanism for CYP11B2 expression. It is feasible that epigenetic mechanisms may be responsible for aldosterone hypersecretion in Conn’s adenoma.

Grazing Management and Buffer Strip Impact on Nitrogen Runoff from Pastures Fertilized with Poultry Litter

Nitrogen runoff from pastures fertilized with animal manure, such as poultry litter, can result in accelerated eutrophication. The objective of this study was to evaluate the long-term effects of grazing management and buffer strips on N runoff from pastures fertilized with poultry litter. A 12-yr study was conducted on 15 small watersheds in Booneville, AR, using five management practices: continuous grazing, haying, rotational grazing, rotational grazing with an unfertilized buffer strip, and rotational grazing with a fenced unfertilized riparian buffer. Poultry litter was applied annually at a rate of 5.6 Mg ha. Concentrations and loads of total N, NO-N, NH-N, organic N, and total organic C in runoff varied intra- and interannually and coincided with precipitation trends. Overall, the greatest component of total N in runoff was organic N. Rotational grazing resulted in the highest concentrations and loads of all forms of N in runoff compared with other treatments, including the continuously grazed paddocks, which were grazed almost twice as much. Total organic C concentrations and loads in runoff were also higher from rotationally grazed watersheds than other treatments. Rotational grazing is considered a best management practice that typically reduces soil erosion; hence, the mechanism by which it caused higher N and C runoff is unclear. Nitrogen runoff losses from rotationally grazed pastures were reduced by 44% with unfertilized buffer strips, by 54% with fenced unfertilized riparian buffers, and by 52% by converting pastures to hayfields.

Histopathological and genetic characterization of aldosterone-producing adenomas with concurrent subclinical cortisol hypersecretion: a case series

PURPOSE

Aldosterone-producing adenomas with concurrent subclinical cortisol hypersecretion are reported in an increasing number of patients. Five aldosterone-producing adenomas from patients with primary aldosteronism and subclinical hypercortisolism were examined.

THE AIMS OF OUR STUDY WERE

(1) to analyze pathological features and immunohistochemical expression of CYP11B1 (11β-hydroxylase) and CYP11B2 (aldosterone synthase) in these tumors; (2) to investigate somatic mutations involved in adrenal steroid hypersecretion and/or tumor growth.

METHODS

Archival micro-dissected paraffin-embedded slides from tumor specimens were used for histological and molecular studies. Immunohistochemistry was performed using monoclonal anti-CYP11B1 and anti-CYP11B2 antibodies. Cellular composition was determined by examining for known features of zona fasciculata and zona glomerulosa, and immunoreactivity for CYP11B1 and CYP11B2 by McCarty H-score. Spot regions for mutations in KCNJ5, ATP1A1, ATP2B3, CACNA1D, PRKACA, and CTNNB1 gene sequences were evaluated.

RESULTS

Four APAs showed a predominant (≥50%) zona fasciculata-like cell pattern: one tumor had CYP11B1 H-score = 150, no detectable CYP11B2 expression, and harbored a PRKACA p.Leu206Arg mutation (that we have reported previously elsewhere), one had no CYP11B1 expression, CYP11B2 H-score = 40, and no mutations; the remaining two adenomas had high CYP11B1 H-score (160 and 240, respectively) and low CYP11B2 H-score (30 and 15, respectively), with the latter harboring a CTNNB1 p.Ser45Phe activating mutation. One of five aldosterone-producing adenomas had a predominant zona glomerulosa-like pattern, CYP11B1 H-score = 15, CYP11B2 H-score = 180, and no mutations.

CONCLUSIONS

The majority of aldosterone-producing adenomas with concurrent subclinical cortisol hypersecretion were composed mainly of zona fasciculata-like cells, while CYP11B1 and CYP11B2 immunostaining demonstrated clear heterogeneity. In a subset of cases, different somatic mutations may be involved in hormone excess and tumor formation.

Effects of Grazing Management and Buffer Strips on Metal Runoff from Pastures Fertilized with Poultry Litter

Metal runoff from fields fertilized with poultry litter may pose a threat to aquatic systems. Buffer strips located adjacent to fields may reduce nutrients and solids in runoff. However, scant information exists on the long-term effects of buffer strips combined with grazing management on metal runoff from pastures. The objective of this study was to assess the 12-yr impact of grazing management and buffer strips on metal runoff from pastures receiving poultry litter. The research was conducted using 15 watersheds (25 m wide and 57 m long) with five treatments: hayed (H), continuously grazed (CG), rotationally grazed (R), rotationally grazed with a buffer strip (RB), and rotationally grazed with a fenced riparian buffer strip (RBR). Poultry litter was applied annually in spring at 5.6 Mg ha. Runoff samples were collected after every rainfall event. Aluminum (Al) and iron (Fe) concentrations were strongly and positively correlated with total suspended solids, indicating soil erosion was the primary source. Soluble Al and Fe were not related to total Al and Fe. However, there was a strong positive correlation between soluble and total copper (Cu) concentrations. The majority of total Cu and zinc was in water-soluble form. The CG treatment had the highest metal concentrations and loads of all treatments. The RBR and H treatments resulted in lower concentrations of total Al, Cu, Fe, potassium, manganese, and total organic carbon in the runoff. Rotational grazing with a fenced riparian buffer and converting pastures to hayfields appear to be effective management systems for decreasing concentrations and loads of metals in surface runoff from pastures fertilized with poultry litter.

Long-term Effects of Grazing Management and Buffer Strips on Soil Erosion from Pastures

High grazing pressure can lead to soil erosion in pastures, causing increased sediment delivery to waterways. The objectives of this research were to evaluate the impact of grazing management and buffer strips on soil erosion by assessing soil physical properties, hydrology, and sediment loads from pastures fertilized with broiler litter. Field studies were conducted for 12 yr on 15 small watersheds. Five management strategies were evaluated: hayed (H), continuously grazed (CG), rotationally grazed (R), rotationally grazed with a buffer strip (RB), and rotationally grazed with a fenced riparian buffer (RBR). Broiler litter was applied every year at a rate of 5.6 Mg ha. Bulk density and penetration resistance were highest for CG watersheds. Runoff volumes, sediment concentrations, and loads were lowest for the H and RBR treatments and highest for CG. Average runoff amounts were 48, 84, 77, 60, and 81 mm yr for the H, R, RB, RBR, and CG treatments, respectively. Annual average sediment loads were 25, 30, 58, 71, and 110 kg ha for H, RBR, R, RB, and CG, respectively. The Revised Universal Soil Loss Equation, Version 2 was reasonably effective at predicting soil loss for the R, RB, and RBR treatments, but it greatly overpredicted soil loss from the CG and H treatments. Converting a pasture to a hay field or using rotational grazing in conjunction with a fenced riparian buffer appear to be effective options for reducing soil erosion and runoff to waterways from pasture soils.

Transcriptomic Signature of the CD24hi CD38hi Transitional B Cells Associated With an Immunoregulatory Phenotype in Renal Transplant Recipients

The role of B cells after transplant regarding allograft rejection or tolerance has become a topic of major interest. Recently, in renal transplant recipients, a B cell signature characterized by the overexpression of CD19⁺ CD38^hi CD24^hi transitional B cells has been observed in operationally tolerant patients and in belatacept-treated patients with significantly lower incidence of donor-specific antibodies. The phenotypic and functional characterization of these transitional B cells is far from exhaustive. We present the first transcriptomic and phenotypic analysis associated with this cell phenotype. Three populations were studied and compared: (i) transitional CD24^hi CD38^hi , (ii) CD24⁺ CD38^- , and (iii) CD24^int CD38^int B cells. Transcriptome bioinformatic analysis revealed a particular signature for the CD24^hi CD38^hi population. Phenotypic analysis showed that CD24^hi CD38^hi transitional B cells also expressed CD9, CD10, CD1b and inducible T cell costimulator ligand (ICOS-L) markers. In addition, we found enrichment of IL-10⁺ cells among CD24^hi CD38^hi cells expressing ICOS-L and CD1b, the latter showing regulatory properties. Renal transplant recipients treated with belatacept exhibited significant expression of CD1b. Our results show that transitional CD24^hi CD38^hi B cells exhibit a distinct and specific profile, and this could be helpful for understanding of immune-regulatory mechanisms and immune monitoring in the field of organ transplant and autoimmune disease.

Th-17 Alloimmune Responses in Renal Allograft Biopsies From Recipients of Kidney Transplants Using Extended Criteria Donors During Acute T Cell-Mediated Rejection

Although renal transplantation using expanded criteria donors has become a common practice, immune responses related to immunosenescence in those kidney allografts have not been studied yet in humans. We performed a retrospective molecular analysis of the T cell immune response in 43 kidney biopsies from patients with acute T cell-mediated rejection including 25 from recipients engrafted with a kidney from expanded criteria donor and 18 from recipients grafted with optimal kidney allograft. The clinical, transplant and acute T cell-mediated rejection characteristics of both groups were similar at baseline. The expression of RORγt, Il-17 and T-bet mRNA was significantly higher in the elderly than in the optimal group (p = 0.02, p = 0.036, and p = 0.01, respectively). Foxp3 mRNA levels were significantly higher in elderly patients experiencing successful acute T cell-mediated rejection reversal (p = 0.03). The presence of IL-17 mRNA was strongly associated with nonsuccessful reversal in elderly patients (p = 0.008). Patients with mRNA IL17 expression detection and low mRNA Foxp3 expression experienced significantly more treatment failure (87.5%) than patients with no mRNA IL17 expression and/or high mRNA Foxp3 expression (26.7%; p = 0.017). Our study suggests that the Th17 pathway is involved in pathogenesis and prognosis of acute T cell-mediated rejection in recipients of expanded criteria allograft.

Methylation Status of Vitamin D Receptor Gene Promoter in Benign and Malignant Adrenal Tumors

We previously showed a decreased expression of vitamin D receptor (VDR) mRNA/protein in a small group of adrenocortical carcinoma (ACC) tissues, suggesting the loss of a protective role of VDR against malignant cell growth in this cancer type. Downregulation of VDR gene expression may result from epigenetics events, that is, methylation of cytosine nucleotide of CpG islands in VDR gene promoter. We analyzed methylation of CpG sites in the VDR gene promoter in normal adrenals and adrenocortical tumor samples. Methylation of CpG-rich 5' regions was assessed by bisulfite sequencing PCR using bisulfite-treated DNA from archival microdissected paraffin-embedded adrenocortical tissues. Three normal adrenals and 23 various adrenocortical tumor samples (15 adenomas and 8 carcinomas) were studied. Methylation in the promoter region of VDR gene was found in 3/8 ACCs, while no VDR gene methylation was observed in normal adrenals and adrenocortical adenomas. VDR mRNA and protein levels were lower in ACCs than in benign tumors, and VDR immunostaining was weak or negative in ACCs, including all 3 methylated tissue samples. The association between VDR gene promoter methylation and reduced VDR gene expression is not a rare event in ACC, suggesting that VDR epigenetic inactivation may have a role in adrenocortical carcinogenesis.

Kidney transplant recipients treated with belatacept exhibit increased naïve and transitional B cells

Phase III clinical studies have shown that kidney transplant (KT) recipients treated with the costimulation blocker belatacept exhibited a better renal allograft function and lower donor-specific anti-HLA immunization when compared to recipients treated with calcineurin inhibitors (CNI). We analyzed B cell phenotype in KT recipients treated with belatacept and stable renal function (N = 13). Results were compared to those observed in stable patients treated with CNI (N = 12), or with chronic antibody-mediated rejection (N = 5). Both transcriptional profile and phenotypic characterization of peripheral B cells were performed by real-time polymerase chain reaction and flow cytometry, respectively. In belatacept group, the frequency and absolute number of transitional B cells as defined by both phenotypes: CD19(+) CD24(hi) CD38(hi) and CD19(+) IgD(hi) CD38(hi) CD27(-) , as well as naïve B cells were significantly higher compared with CNI group. B cell activating factor (BAFF) and BAFF receptor mRNA levels were significantly lower in belatacept group than in CNI group. These results show for the first time that belatacept influences B cell compartment by favoring the occurrence of transitional B cells with potential regulatory properties, as described in operational tolerant patients. This role may explain the lower alloimmunization rate observed in belatacept-treated patients.

1α,25-Dihydroxyvitamin D₃ inhibits the human H295R cell proliferation by cell cycle arrest: a model for a protective role of vitamin D receptor against adrenocortical cancer

Using the human H295R adrenocortical carcinoma cell line as a model, we analyzed the role of 1α,25-dihydroxyvitamin D₃ [1α,25(OH)₂D₃)]--vitamin D receptor (VDR) axis in the growth of adrenocortical cancer (ACC). The presence of VDR in various adrenocortical tissues, including ACC, was also investigated. DNA synthesis was evaluated by [³H]thymidine cell incorporation after treatment with 1α,25(OH)₂D₃ at increasing doses. The effect of 1α,25(OH)₂D₃ on cell cycle and apoptosis was analyzed with a flow cytometer. Cyclin-dependent kinase 4 (CDK4) expression, a molecular marker of G1-S cell cycle transition phase, was evaluated in cells treated with 1α,25(OH)₂D₃ before and after VDR gene silencing. 1α,25(OH)₂D₃ treatment inhibited cell proliferation by 20% at a dose of 1 nM, in parallel with steroid secretion decrease. A cell cycle arrest in G1, with no change in apoptotic cell proportion, was observed after 10 nM 1α,25(OH)₂D₃ cell exposure. CDK4 activation was reduced by 10 nM 1α,25(OH)₂D₃ but was not affected by 1α,25(OH)₂D₃ after VDR gene silencing. Expression of VDR mRNA was lower in ACC than in benign adrenocortical tumors. VDR immunostaining was evident in benign tumors but it was weak in ACC tissues.

CONCLUSIONS

Slightly supra-physiological concentrations of 1α,25(OH)₂D₃ have a moderate anti-proliferative effect on H295R cells. Anti-proliferative effect was due to cell cycle arrest in G1 phase, without inducing apoptosis. The low mRNA expression levels at qRT-PCR as well as the weak immunohistochemical expression of VDR in ACC, suggests a protective role of VDR against malignant adrenocortical growth.

Targeting estrogen receptor-α reduces adrenocortical cancer (ACC) cell growth in vitro and in vivo: potential therapeutic role of selective estrogen receptor modulators (SERMs) for ACC treatment

CONTEXT

Adrenocortical carcinoma (ACC) is a rare tumor with a very poor prognosis and no effective treatment. ACC is characterized by an increased production of IGF-II and by estrogen receptor (ER)-α up-regulation.

OBJECTIVE

The objective of this study was to define the role played by ERα in 17β-estradiol (E2)- and IGF-II-dependent ACC growth and evaluate whether selective estrogen receptor modulators are effective in controlling ACC growth in vivo.

EXPERIMENTAL DESIGN

The human adrenocortical cell line H295R was used as an in vitro model and to generate xenograft tumors in athymic nude mice.

RESULTS

In H295R cells IGF-II controlled expression of steroidogenic factor-1 that, in turn, increased aromatase transcription and, consequently, estrogen production, inducing cell proliferation. ERα silencing significantly blocked E2- and IGF-II-dependent cell proliferation. This effect was dependent on the regulation of cyclin D1 expression by ERα, activated in response to both E2 and IGF-II. In fact, IGF-II induced ERα activation by phosphorylating serine 118 and 167. Furthermore, we demonstrated that ERα mediated E2-induced nongenomic signaling that stimulated IGF-I receptor (IGF1R), ERK1/2, and AKT phosphorylation, resulting in a ligand-independent activation of the IGF1R-induced pathway. In addition, E2 potentiated this pathway by up-regulating IGF1R expression as a consequence of increased cAMP-responsive element binding protein activation and binding to IGF1R promoter. The estrogen antagonist, hydroxytamoxifen, the active metabolite of tamoxifen, reduced IGF1R protein levels and both E2- and IGF-II-induced cell proliferation. Moreover, H295R xenograft growth was strongly reduced by tamoxifen.

CONCLUSION

These findings establish a critical role for ERα in E2- and IGF-II-dependent ACC proliferation and provide a rationale for targeting ERα to control the proliferation of ACC.

Primary aldosteronism and metabolic syndrome

Hypertension is frequently associated with interrelated risk factors of metabolic origin, including abdominal obesity, dyslipidemia, and alterations in glucose homeostasis, all promoting the pathogenesis of arteriosclerosis. Clustering of these risk factors, defined as metabolic syndrome, is associated with an overall high cardiovascular risk profile. This article reviews current knowledge regarding the prevalence and characteristics of the metabolic syndrome in primary aldosteronism, and discusses a possible pathophysiological link between aldosterone and its individual components other than hypertension. An abnormal glucose metabolism due to insulin resistance appears to be linked to aldosterone overproduction, and seems the major contributor to metabolic dysfunction in primary aldosteronism. Impairment of insulin action may be also due to concurrent environmental factors (hypokalemia?), and/or it might occur in compartments other than fat tissue (liver? skeletal muscle?). Higher rates of cardiovascular events reported in primary aldosteronism could be due in part to the increased prevalence of the metabolic syndrome in this disorder. Regression of glucometabolic complications after the cure of aldosterone excess should be confirmed by larger studies, and the influence on the natural history of primary aldosteronism by using agents potentially able to correct metabolic abnormalities should be further explored.

Prevalence, Clinical, and Molecular Correlates of KCNJ5 Mutations in Primary Aldosteronism

Primary aldosteronism is the most common form of secondary hypertension. Mutations in the KCNJ5 gene have been described recently in aldosterone-producing adenomas (APAs). The aim of this study was to investigate the prevalence of KCNJ5 mutations in unselected patients with primary aldosteronism and their clinical, biological and molecular correlates. KCNJ5 sequencing was performed on somatic (APA, n=380) and peripheral (APA, n=344; bilateral adrenal hyperplasia, n=174) DNA of patients with primary aldosteronism, collected through the European Network for the Study of Adrenal Tumors. Transcriptome analysis was performed in 102 tumors. Somatic KCNJ5 mutations (p.Gly151Arg or p.Leu168Arg) were found in 34% (129 of 380) of APA. They were significantly more prevalent in females (49%) than males (19%; P <10 −3 ) and in younger patients (42.1±1.0 versus 47.6±0.7 years; P <10 −3 ) and were associated with higher preoperative aldosterone levels (455±26 versus 376±17 ng/L; P =0.012) but not with therapeutic outcome after surgery. Germline KCNJ5 mutations were found neither in patients with APA nor those with bilateral adrenal hyperplasia. Somatic KCNJ5 mutations were specific for APA, because they were not identified in 25 peritumoral adrenal tissues or 16 cortisol-producing adenomas. Hierarchical clustering of transcriptome profiles showed that APAs with p.Gly151Arg or p.Leu168Arg mutations were indistinguishable from tumors without KCNJ5 mutations. In conclusion, although a large proportion of sporadic APAs harbors somatic KCNJ5 mutations, germline mutations are not similarly causative for bilateral adrenal hyperplasia. KCNJ5 mutation carriers are more likely to be females; younger age and higher aldosterone levels at diagnosis suggest that KCNJ5 mutations may be associated with a more florid phenotype of primary aldosteronism.

Effects of type 5-phosphodiesterase inhibition on energy metabolism and mitochondrial biogenesis in human adipose tissue ex vivo

OBJECTIVE

An excess of adipose tissue (AT) in obese individuals is linked to increased cardiovascular risk and mitochondria have been shown to be defective in the muscle and AT of patients with metabolic disorders such as obesity and Type 2 diabetes. Nitric oxide (NO) generated by endothelial NO synthase (eNOS) plays a role in mitochondrial biogenesis through cyclic-GMP (cGMP). AT harbors the whole molecular signaling pathway of NO, together with type 5-phosphodiesterase (PDE- 5), the main cGMP catabolising enzyme.

AIM

Our aim was to evaluate the effect of the modulation of NO pathway, through PDE-5 inhibition, on energy metabolism and mitochondria biogenesis in human omental AT.

METHODS AND MEASUREMENTS

Cultured human omental AT was stimulated with PDE-5 inhibitor, vardenafil, at different concentration for 24 and 72 h. Analysis of the expression of both key-regulator genes of adipocyte metabolism and mitochondria-biogenesis markers was performed.

RESULTS

We found an increased gene expression of peroxisome proliferator-activated receptor-γ (PPAR-γ), adiponectin, and proliferator- activated receptor gamma coactivator-1 α (PGC-1α) after a 24-h stimulation with vardenafil at the lowest concentration employed compared to controls (p<0.05). After 72 h of stimulation, a significant increase of mitochondrial DNA was found compared to control samples (p<0.05).

CONCLUSION

Our data suggest that PDE-5 inhibition could have an impact on mitochondrial content of human AT suggesting a positive effect on energy metabolism and adding new elements in the comprehension of AT pathophysiology.

Insulin signaling in adipose tissue of patients with primary aldosteronism

OBJECTIVE

We studied phosphorylation of insulin-receptors substrate downstream molecules: 1) in the ex-vivo visceral adipose tissue (VAT) of patients with aldosterone-producing adenoma (APA) (no.=7) and non-functioning adenoma (NFA) (no.=7) undergoing laparoscopic adrenalectomy; 2) in aldosterone-treated sc adipocytes of subjects (no.=5) who requested abdominoplasty.

PATIENTS AND METHODS

Western blotting was used to detect phosphorylation of Akt and extracellular signal-regulated kinase (ERK) 1/2 in VAT from APA and NFA patients, and in subcutaneous adipocytes pre-treated with different aldosterone concentrations. Phosphorylation of Akt and ERK1/2 was similar in VAT of patients with APA and NFA. Pre-treatment in adipocytes with both physiological (1 nM) and pharmacological (10 μM) doses of aldosterone did not affect basal or insulin-induced phosphorylation of Akt and ERK1/2.

CONCLUSIONS

Our data give further evidence that insulin signaling in human VAT is not affected by primary aldosterone overproduction.

Analysis of insulin sensitivity in adipose tissue of patients with primary aldosteronism

OBJECTIVE

The objective of the study was to assess the effect of high aldosterone levels on insulin sensitivity of adipose tissue in humans.

METHODS

Visceral adipose tissue (VAT) was obtained from patients with aldosterone-producing adenoma (APA; n=14) and, as controls, nonfunctioning adenoma (NFA; n=14) undergoing laparoscopic adrenalectomy. Homeostasis model assessment index was higher and potassium was lower in APA than NFA (P<0.05). Immunohistochemistry, Western blotting, and real-time PCR were used to detect and quantify mineralocorticoid receptor (MR) expression. Transcript levels of peroxisome proliferative-activated receptor-gamma, insulin receptor, glucose transporter 4, insulin receptor substrate-1 and -2, leptin, adiponectin, IL-6, monocyte chemoattractant protein-1, glucocorticoid receptor (GR)-alpha, 11beta-hydroxysteroid dehydrogenase (HSD11B) type 1, and HSD11B2 were quantified. The effect of increasing aldosterone concentrations on 2-deoxy-[3H]d-glucose uptake was tested in human sc abdominal adipocytes.

RESULTS

Expression of MR was demonstrated in VAT, with no difference between APA and NFA as to mRNA levels of MR, GRalpha, HSD11B1, and glucose metabolism and inflammation factors. In cultured adipocytes, basal and insulin-stimulated glucose uptake were unaffected by 1-100 nM (normal/hyperaldosteronism) and impaired only by much higher, up to 10 microM, aldosterone concentrations. The impairment was prevented by RU486 but not by eplerenone.

CONCLUSIONS

Gene expression of insulin signaling/inflammatory molecules was similar in VAT of APA and NFA patients, not supporting an effect of aldosterone excess on insulin sensitivity of adipose tissues. Only at pharmacological concentrations and through GR activation, aldosterone reduced glucose uptake in adipocytes. Insulin resistance in primary aldosteronism might occur in compartments other than fat and/or depend on concurrent environmental factors.

Evidence for osteocalcin production by adipose tissue and its role in human metabolism

CONTEXT

The adipose tissue (AT), which is an endocrine organ, is linked to several metabolic abnormalities. Undercarboxylated osteocalcin (ucOCN) regulates insulin and adiponectin secretion.

OBJECTIVE

Our objective was to investigate the involvement of OCN in obesity and to evaluate, in vitro and ex vivo, the role of AT in the modulation of this endocrine circuit.

DESIGN, PATIENTS, AND SETTING

This transversal study involved 83 male subjects, divided according to the World Health Organization body mass index classification, evaluated at Padova's Obesity Outpatient Clinic.

METHODS

OCN, both undercarboxylated (ucOCN) and carboxylated (cOCN) forms, was measured in serum by ELISA. OCN mRNA expression and protein production were measured by quantitative RT-PCR and immunohistochemistry during in vitro adipogenesis and in sc AT (SAT) and omental AT (OAT) from normal adult men. cOCN and ucOCN release by AT in a simple growth medium was verified by ELISA.

RESULTS

Overweight and obese patients had a lower ucOCN and ucOC/OCN ratio. In the whole cohort, ucOCN/OCN ratio was negatively correlated to body mass index (rho = -0.233; P < 0.05). OCN mRNA was present in SAT and OAT and during all stages of adipogenesis, with higher expression in the first steps. Immunohistochemistry confirmed the expression of OCN protein. Both SAT and OAT were able to release cOCN and ucOCN.

CONCLUSIONS

Our data support a pathophysiological link between ucOCN and cOCN balance and obesity. OCN is present in the first phases of adipogenesis but also in human AT ex vivo. AT releases, in vitro, both ucOCN and cOCN, suggesting a possible link between AT and OCN in the regulation of metabolism.

Induction of porcine regulatory cells by mycophenolic Acid-treated dendritic cells

Tolerance induction in murine allogeneic transplantation is relatively easy, often by induction of regulatory T cells (Treg). Unfortunately, the implementation of these models in clinical situations has not yielded reliable protocols of tolerance induction in humans. Our project sought to create a preclinical model of tolerance induction in large animals. Our current efforts seek to induce and characterize porcine Treg, obtaining dendritic cells (DC) able to preferentially stimulate them. DCs were differentiated from blood monocytes with porcine recombinant interleukin-4 (IL-4) and granulocyte-macrophage colony-stimulating factor (GM-CSF) for 6 days. These DCs were then stimulated by human CD40 ligand-transfected L cells with or without mycophenolic acid (MPA) for 48 hours. We analyzed surface marker expression, cytokine synthesis, and ability to stimulate allogeneic peripheral blood mononuclear cells (PBMC). The porcine lymphocytes underwent 4 rounds of 1-week stimulation with allogeneic DC treated or not with MPA. At the end of this coculture we analyzed their capacity to suppress allogeneic PBMC proliferation induced by mature DC. Our results showed that porcine DCs pretreated with MPA display a low expression of B7 costimulatory molecules, produce low levels of IL-12, and induce weak proliferation of allogeneic lymphocytes. Moreover, after 4 rounds of stimulation with MPA-treated DCs, PBMCs were able to inhibit an alloreactive response. These preliminary results suggested induction of a regulatory T-cell population that we are currently seeking to characterize.

Loss-of-function mutation of the GPR40 gene associates with abnormal stimulated insulin secretion by acting on intracellular calcium mobilization

BACKGROUND

Free fatty acids (FFAs) acutely stimulate but chronically impair glucose-stimulated insulin secretion from beta-cells. The G protein-coupled transmembrane receptor 40 (GPR40) mediates both acute and chronic effects of FFAs on insulin secretion and plays a role in glucose homeostasis. Limited information is available on the effect of GPR40 genetic abnormalities on insulin secretion and metabolic regulation in human subjects.

STUDY DESIGN AND RESULTS

For in vivo studies, we screened 734 subjects for the coding region of GPR40 and identified a new single-nucleotide mutation (Gly180Ser). The mean allele frequency was 0.75%, which progressively increased (P < 0.05) from nonobese subjects (0.42%) to moderately obese (body mass index = 30-39.9 kg/m2, 1.07%) and severely obese patients (body mass index > or = 40 kg/m2, 2.60%). The relationship between the GPR40 mutation, insulin secretion, and metabolic alterations was studied in 11 Gly/Ser mutation carriers. In these subjects, insulin secretion (insulinogenic index derived from oral glucose tolerance test) was significantly lower than in 692 Gly/Gly carriers (86.0 +/- 48.2 vs. 183.7 +/- 134.4, P < 0.005). Moreover, a case-control study indicated that plasma insulin and C-peptide responses to a lipid load were significantly (P < 0.05) lower in six Gly/Ser than in 12 Gly/Gly carriers. In vitro experiments in HeLa cells cotransfected with aequorin and the mutated Gly/Ser GPR40 indicated that intracellular Ca2+ concentration increase after oleic acid was significantly lower than in Gly/Gly GPR40-transfected cells. This fact was confirmed using fura-2 acetoxymethyl ester.

CONCLUSIONS

This newly identified GPR40 variant results in a loss of function that prevents the beta-cell ability to adequately sense lipids as an insulin secretory stimulus because of impaired intracellular Ca2+ concentration increase.

The endogenous cannabinoid system stimulates glucose uptake in human fat cells via phosphatidylinositol 3-kinase and calcium-dependent mechanisms

BACKGROUND

The endogenous cannabinoid system participates in the regulation of energy balance, and its dysregulation may be implicated in the pathogenesis of obesity. Adipose tissue endocannabinoids may produce metabolic and endocrine effects, but very few data are available in human adipose tissue and in primary human fat cells.

EXPERIMENTAL DESIGN

We measured expression of type 1 and type 2 cannabinoid receptors (CNR), enzymes of cannabinoids synthesis and degradation in human omental, sc abdominal, and gluteal adipose tissue from lean and obese subjects. Furthermore, we assessed the effect of CNR1 stimulation on glucose uptake and intracellular transduction mechanisms in primary human adipocytes. Then we assessed the reciprocal regulation between CNR1 and peroxisome proliferator-activated receptor-gamma (PPARgamma). Finally, we tested whether leptin and adiponectin are regulated by CNR1 in human adipocytes.

RESULTS

We found that most genes of the endocannabinoid system are down-regulated in gluteal fat and up-regulated in visceral and sc abdominal adipose tissue of obese patients. Treatment of adipocytes with rosiglitazone markedly down-regulated CNR1 expression, whereas Win 55,212 up-regulated PPARgamma. Win 55,212 increased (+50%) glucose uptake, the translocation of glucose transporter 4, and intracellular calcium in fat cells. All these effects were inhibited by SR141716 and wortmannin and by removing extracellular calcium. Win 55,212 and SR141716 had no effect on expression of adiponectin and leptin.

CONCLUSIONS

These results indicate a role for the local endocannabinoids in the regulation of glucose metabolism in human adipocytes and suggest a role in channeling excess energy fuels to adipose tissue in obese humans.

The role of 21-hydroxylase in the pathogenesis of adrenal masses: review of the literature and focus on our own experience

An exaggerated response of 17- hydroxyprogesterone (17-OHP) to exogenous ACTH stimulation has been found in 30 to 70% of patients with incidentally discovered adrenal tumors, supporting the concept that congenital 21- hydroxylase deficiency may be a predisposing factor for adrenocortical tumorigenesis. Decreased expression of 21-hydroxylase gene has been observed in sporadic non-functioning adrenocortical adenomas and adrenocortical carcinomas, in agreement with the reduced steroidogenic activity found in these types of tumors. Screening studies for the presence of mutations in CYP21A2 gene, encoding 21-hydroxylase, in patients with sporadic adrenocortical tumors yielded discordant results. Overall, a higher frequency of germline 21-hydroxylase mutation carriers has been found among patients with adrenal tumors, including incidentalomas, than in the general population. However, the presence of mutations did not correlate with endocrine test results and tumor mass features, suggesting that 21-hydroxylase deficiency does not represent a relevant mechanism in adrenal tumorigenesis. Mechanisms leading to reduced 21-hydroxylase expression and activity are still unknown.

Reduced plasma visfatin/pre-B cell colony-enhancing factor in obesity is not related to insulin resistance in humans

CONTEXT

Visfatin was recently identified as a protein highly expressed and secreted in adipose tissue with insulin-mimetic effect and is a candidate hormone to help explain the association among adipose tissue expansion, insulin resistance, and type 2 diabetes.

OBJECTIVE

The objective of the study was to assess expression of visfatin in lean and obese subjects and in sc and visceral adipose tissue and moreover to explore the role of visfatin on insulin resistance in humans.

DESIGN

We measured circulating visfatin and its mRNA expression in sc adipose tissue (SAT) in lean and obese subjects. Furthermore, we measured visfatin mRNA in visceral adipose (VAT) and SAT by quantitative RT-PCR. Finally, plasma visfatin and its mRNA in SAT were measured under free fatty acid-induced insulin resistance in healthy subjects.

RESULTS

Plasma visfatin and its mRNA in SAT were significantly lower in obese subjects, compared with normal-weight controls. Both circulating visfatin and SAT visfatin mRNA were negatively correlated with body mass index, whereas no correlation was found with homeostasis model assessment. Significantly higher visfatin mRNA was found in VAT of obese subjects, compared with lean controls. Interestingly, visfatin mRNA in VAT was positively correlated with BMI. Elevation of free fatty acid induced a condition of insulin resistance but did not affect either circulating visfatin or its mRNA.

CONCLUSIONS

Our findings show that, in human obesity, plasma visfatin is reduced, whereas visfatin mRNA is differentially regulated in SAT and VAT. Visfatin is not related to insulin resistance either as assessed by homeostasis model assessment or during lipid infusion.

Rosiglitazone modifies the adipogenic potential of human muscle satellite cells

AIMS/HYPOTHESIS

Satellite cells are responsible for postnatal skeletal muscle regeneration. It has been demonstrated that mouse satellite cells behave as multipotent stem cells. We studied the differentiation capacities of human satellite cells and evaluated the effect of the insulin sensitiser rosiglitazone, a well known peroxisome proliferative activated receptor gamma (PPARG) agonist, on their adipogenic conversion.

SUBJECTS, MATERIALS AND METHODS

We obtained human satellite cells from human muscle biopsies of healthy subjects by single-fibre isolation and cultured them under myogenic, osteogenic and adipogenic conditions. Moreover, we compared the morphological features and the adipose-specific gene expression profiling, as assessed by quantitative PCR, between adipocytes differentiated from human satellite cells and those obtained from the stromal vascular fraction of human visceral fat.

RESULTS

We proved by morphological analysis, mRNA expression and immunohistochemistry that human satellite cells are able to differentiate into myotubes, adipocytes and osteocytes. The addition of rosiglitazone to the adipogenic medium strongly activated PPARG expression and enhanced adipogenesis in human satellite cells, but did not in itself trigger the complete adipogenic programme. Moreover, we observed a decrease in wingless-type MMTV integration site family member 10B and an upregulation of growth differentiation factor 8 expression, both being independent of PPARG activation.

CONCLUSIONS/INTERPRETATION

Human satellite cells possess a clear adipogenic potential that could explain the presence of mature adipocytes within skeletal muscle in pathological conditions such as obesity, type 2 diabetes and ageing-related sarcopenia. Rosiglitazone treatment, while enhancing adipogenesis, induces a more favourable pattern of adipocytokine expression in satellite-derived fat cells. This could partially counteract the worsening effect of intermuscular adipose tissue depots on muscle insulin sensitivity.

Increased serum resistin in nonalcoholic fatty liver disease is related to liver disease severity and not to insulin resistance

CONTEXT

The recently discovered hormone resistin is linked to the development of insulin resistance, but direct evidence of resistin levels in humans with nonalcoholic fatty liver disease (NAFLD) is lacking.

METHODS

We conducted this study to assess the relationship between serum resistin and NAFLD. We measured serum resistin and biochemical, hormonal, and histological correlates in 28 NAFLD patients, 33 controls, and 30 obese patients [body mass index (BMI), >30 kg/m2] without NAFLD.

RESULTS

Resistin and adiponectin expression were measured in sc adipose tissue by quantitative RT-PCR. Resistin was higher in NAFLD patients compared with controls (5.87 +/- 0.49 vs. 4.30 +/- 0.20 ng/ml; P = 0.002) and obese patients (4.37 +/- 0.27 ng/ml; P = 0.002). Increased resistin mRNA was also found in the adipose tissue of NAFLD patients compared with controls and obese subjects.

CONCLUSIONS

Both NAFLD and obese patients had lower adiponectin levels, whereas leptin was increased only in the obese group. No correlation was found between resistin and high-sensitivity C-reactive protein, BMI, homeostasis model assessment, insulin, glucose, transaminases, and lipid values. A positive correlation was found between resistin and histological inflammatory score. These data report increased resistin in NAFLD patients that is related to the histological severity of the disease, but do not support a link between resistin and insulin resistance or BMI in these patients.

Increased serum resistin in adults with prader-willi syndrome is related to obesity and not to insulin resistance

CONTEXT

Determinants of insulin resistance in Prader-Willi syndrome (PWS) are not completely understood. The discovery of several adipokines with relevant effects on insulin resistance and cardiovascular complications of metabolic syndrome offered new tools of investigation of insulin resistance in PWS.

OBJECTIVE

The purpose of this study was to measure serum resistin and mRNA in adipose tissue of patients with PWS, those with simple obesity, and healthy controls and correlate resistin levels with anthropometric and biochemical features.

DESIGN

Twenty-eight adult PWS patients, 29 obese patients, and 25 healthy controls were studied. Anthropometric variables were measured and fasting serum and plasma were collected for measurement of resistin, adiponectin, leptin, lipid profile, glucose, and insulin.

RESULTS

Serum resistin and resistin mRNA expression in adipose tissue was significantly higher in PWS patients, compared with both healthy lean controls and obese patients. Moreover, on regression analysis resistin was significantly correlated with body mass index, whereas no significant association was found between resistin and homeostasis model assessment index. A weak association between resistin and adiponectin was found in the PWS group only. However, on multivariate analysis only the correlation between resistin and body mass index remained significant.

CONCLUSIONS

These results support a link between circulating resistin and obesity in humans but do not support a role for resistin in human insulin resistance.

Coexistence of different phenotypes in a family with glucocorticoid-remediable aldosteronism

In glucocorticoid-remediable aldosteronism (GRA), there is a large interfamily variation of phenotype. We report three subjects with GRA in a single family (parents, two brothers and two sisters), of whom only one (proband) displayed classical features of the mineralocorticoid excess. The proband was a man found to be hypertensive and hypokalaemic at the age of 24 years. Plasma renin activity was suppressed and plasma aldosterone was repeatedly elevated. Blood pressure and aldosterone levels normalized within 5 days of dexamethasone therapy. The presence of a chimaeric CYP11B1/CYP11B2 gene was demonstrated by long-PCR and Southern blotting (crossover site at the end of intron 3) in the proband, in the younger sister (sibling 1) and in the father. In these patients, sequencing of the chimaeric portion of CYP11B1 did not reveal any mutation, while sequencing of the chimaeric portion of CYP11B2 showed a V386A polymorphism in exon 7, known to cause only a minimal impairment of enzymatic activity. Sibling 1 was normotensive, normokalaemic and had normal PRA and aldosterone. The father had normal blood pressure and potassium, low-normal PRA and normal aldosterone. All three subjects had elevated levels of urinary 18-hydroxycortisol and 18-oxocortisol. Baseline 11-deoxycorticosterone (DOC), corticosterone (B) and aldosterone were high in the proband and normal in the father and sibling 1; 11-deoxycortisol (S) and cortisol (F) were normal. ACTH induced a normal increase of B, DOC, S and F, and an excessive aldosterone increase in all three patients. Abnormalities in the chimaeric portions of CYB11B1 or CYP11B2 genes did not account for the phenotypic disparity of the different members in a single GRA family. Altered regulation of the chimaeric gene may be responsible for differences in its activity.

Changes in muscle myostatin expression in obese subjects after weight loss

Myostatin is a member of transforming growth factor-beta superfamily that plays an important inhibitory role during muscle development; in fact mutations of myostatin gene result in a hypermuscular phenotype. Moreover myostatin-deficient mice have a significant reduction in fat depots and a depression of adipogenesis. Little is known about myostatin function in muscle growth regulation in humans and in particular during caloric restriction. In the present work we quantified by real-time RT-PCR myostatin expression in muscle biopsies of a group of morbidly obese patients before and after weight loss obtained by biliopancreatic diversion (BPD). The patients reduced body weight by 38.9%, mostly due to fat-mass loss, showing also a significant reduction in the 24-hour EE as assessed by the respiratory chamber. Myostatin mRNA levels result clearly decreased after weight loss, suggesting a role in counteracting the progressive decline of muscle mass after BPD. Myostatin may provide therefore another mechanistic explanation for the control of energy partitioning between protein and fat, working against muscle wasting. Our data suggest that myostatin might represent an important regulator of skeletal muscle size also in conditions of food restriction in obese subjects.

Acute and chronic effects of methamphetamine on tele-methylhistamine levels in mouse brain: selective involvement of the D(2) and not D(3) receptor

We have explored the role of endogenous dopamine in the control of histaminergic neuron activity in mouse brain regions evaluated by changes in tele-methylhistamine (t-MeHA) levels. In vitro, methamphetamine released [(3)H]noradrenaline but failed to release [(3)H]histamine from synaptosomes. In vivo, methamphetamine enhanced t-MeHA levels by about 2-fold with ED(50) values of approximately 1 mg/kg in caudate putamen, nucleus accumbens, cerebral cortex, and hypothalamus. This response selectively involved the D(2) and not the D(3) receptor as indicated by its blockade by haloperidol and by its persistence after administration of nafadotride, a D(3) receptor preferential ligand, or in (-/-) D(3) receptor-deficient mice. The t-MeHA response to methamphetamine was delayed compared with the locomotor-activating effect of this drug, suggesting that it is of compensatory nature. In agreement, ciproxifan, an inverse agonist known to enhance histamine neuron activity, decreased the hyperlocomotion induced by methamphetamine. Repeated methamphetamine administration resulted in the expected sensitization to the hyperlocomotor effect of the drug but did not modify either the ED(50) or the E(max) regarding t-MeHA levels. However, it resulted in an enhanced basal t-MeHA level (+30-40%), which was sustained for at least 11 days after withdrawal in hypothalamus, striatum, and cerebral cortex and suppressed by haloperidol. Hence, both the acute and chronic administration of methamphetamine enhance histamine neuron activity, presumably in a compensatory manner. Repeated methamphetamine administration also resulted in a modified balance in the opposite influences of dopamine and serotonin on histaminergic neurons as revealed by the enhanced response to haloperidol and abolished response to ketanserin, respectively.

Dopamine D3 receptors expressed by all mesencephalic dopamine neurons

A polyclonal antibody was generated using synthetic peptides designed in a specific sequence of the rat D(3) receptor (D(3)R). Using transfected cells expressing recombinant D(3)R, but not D(2) receptor, this antibody labeled 45-80 kDa species in Western blot analysis, immunoprecipitated a soluble fraction of [(125)I]iodosulpride binding, and generated immunofluorescence, mainly in the cytoplasmic perinuclear region of the cells. In rat brain, the distribution of immunoreactivity matched that of D(3)R binding, revealed using [(125)I]R(+)trans-7-hydroxy-2-[N-propyl-N-(3'-iodo-2'-propenyl)amino] tetralin ([(125)I]7-trans-OH-PIPAT), with dense signals in the islands of Calleja and mammillary bodies, and moderate to low signals in the shell of nucleus accumbens (AccSh), frontoparietal cortex, substantia nigra (SN), ventral tegmental area (VTA) and lobules 9 and 10 of the cerebellum. Very low or no signals could be detected in other rat brain regions, including dorsal striatum, or in D(3)R-deficient mouse brain. Labeling of perikarya of AccSh and SN/VTA appeared with a characteristic punctuate distribution, mostly at the plasma membrane where it was not associated with synaptic boutons, as revealed by synaptophysin immunoreactivity. In SN/VTA, D(3)R immunoreactivity was found on afferent terminals, arising from AccSh, in which destruction of intrinsic neurons by kainate infusions produced a loss of D(3)R binding in both AccSh and SN/VTA. D(3)R-immunoreactivity was also found in all tyrosine hydroxylase (TH)-positive neurons observed in SN, VTA and A8 retrorubral fields, where it could represent D(3) autoreceptors controlling dopamine neuron activities, in agreement with the elevated dopamine extracellular levels in projection areas of these neurons found in D(3)R-deficient mice.

CYP11B2 gene polymorphisms in idiopathic hyperaldosteronism

Primary aldosteronism is characterized by autonomous production of aldosterone and arterial hypertension, and it occurs in 2 principal forms: aldosterone-producing adenoma (APA) and idiopathic hyperaldosteronism (IHA). APA can be cured through removal of the adenoma, whereas IHA leads to hypertension that must be treated with medication. The origin of the autonomous aldosterone production in IHA is poorly understood, but genetic factors may contribute to its cause. To test the hypothesis that variants of the aldosterone synthase gene may contribute to susceptibility to IHA, we compared genotypes at 3 polymorphic sites in the CYP11B2 gene in patients with IHA (n=90) with those found in patients with APA (n=38), in patients with essential hypertension (n=72), and in normotensive individuals (n=102). We observed significant linkage disequilibrium among the 3 polymorphisms with 2 frequent haplotypes in all groups studied. One haplotype (C2R) was found to be increased in frequency in the IHA group (47%) compared with the other groups, which had a similar haplotype frequency (36%). The 3 polymorphisms studied have been implicated in either essential hypertension or excess aldosterone production in previous studies. Because of the strong linkage disequilibrium, the observed results could be due to the action of any 1 of the 3 alleles or to another allele in linkage disequilibrium with them. Our results suggest that variations in the CYP11B2 gene may contribute to dysregulation of aldosterone synthesis and lead to susceptibility to IHA.

Possible implications of the dopamine D(3) receptor in schizophrenia and in antipsychotic drug actions

The D(3) receptor may represent an important target for antipsychotic drugs which all bind with high affinity and do not induce upon repeated administration either tolerance or receptor upregulation. The D(3) receptor is localized in brain areas, namely the nucleus accumbens and cerebral cortex, implicated in neural circuits believed to display defective functioning in schizophrenia. Overexpression of the D(3) receptor, which accounts for the behavioral sensitization to levodopa in a rodent model of Parkinson's disease, might also be responsible for the sensitization to dopamine agonists observed in schizophrenia. The appearance of the D(3) receptor during brain development, early in proliferating neuroepithelia and later in neurons from limbic areas, suggests further studies to assess its participation in the neurodevelopmental disorders of schizophrenia. Finally, meta-analysis of approximately 30 studies comprising over 2500 patients indicate that a polymorphism in the coding sequence of the D(3) receptor is associated with a small but significant enhancement of vulnerability to the disease.

Role of dopamine D3 receptors in thermoregulation: a reappraisal

Dopamine agonist-induced hypothermia has been proposed to be mediated by the D3 receptor (D3R), as it is elicited by (+)7-OH-DPAT and antagonized by S 14297, two putative D3R-preferential ligands. Here we show, however, that S 14297 is a full and partial agonist at D3R and D2R, respectively. Hypothermia was induced in rats by agonists with potencies correlated with their D3R and D2R functional potencies, and was reversed by antagonists, with a rank order of potency typical of the D2R. Moreover, BP 897, a highly potent and selective but partial D3R agonist was inactive in producing hypothermia or reversing (+)7-OH-DPAT-induced hypothermia. (+)7-OH-DPAT was as potent and efficient in inducing hypothermia in wild-type as in D3R-deficient mice. Hence, our results suggest that hypothermia does not result from a selective stimulation of the D3R.

Mutations in CYP11B1 gene converting 11beta-hydroxylase into an aldosterone-producing enzyme are not present in aldosterone-producing adenomas

In the human adrenal cortex, cortisol and aldosterone are synthesized by the isozymes 11beta-hydroxylase and aldosterone synthase, respectively, encoded by the 93% identical CYP11B1 and CYP11B2 genes. In vitro mutagenesis of CYP11B1 complementary DNA, resulting in the replacement of CYP11B1 codons by those encoding the corresponding amino acid residues of CYP11B2 enzyme (exon 5, Ser288Gly; exon 6, Val320Ala), yields a complementary DNA encoding a mutant enzyme with an efficient aldosterone synthase activity. Identical somatic mutations in the CYP11B1 gene in vivo would produce a gene encoding an enzyme with C18 activity and that would preserve ACTH responsiveness due to the retained 5'-promoter in the mutated CYP11B1 gene. An ACTH-responsive aldosterone synthase activity of this type is commonly seen in patients with aldosterone-producing adenomas (APA). We examined the occurrence of mutations in exons 5 and 6 of the CYP11B1 gene in APA from 10 patients with primary aldosteronism. Patients were selected on preoperative evidence of a 50% or greater plasma aldosterone decrease after short term dexamethasone trial and no aldosterone response to upright posture. DNA from adenomas was amplified by PCR using two pairs of primers spanning the regions of CYP11B1 gene, i.e. exons 3-5 and exons 6-9, where mutations could be located. Targeted regions were screened for mutations by automated sequencing of PCR products. No point mutations of the CYP11B1 gene over the two regions examined were found in APA. This argues against involvement of mutations in the pathogenesis of ACTH-responsive APA.

Health care spending as determinants of health outcomes

This paper revisits the relationship between health care spending and health outcomes. While previous researchers found it difficult to establish such a relationship based on international comparisons, the results based on rather homogenous province-specific Canadian data show that lower health care spending is associated with a statistically significant increase in infant mortality and a decrease in life expectancy in Canada. This relationship is independent of various economic, socio-demographic, nutritional and lifestyle factors, as well as provincial specificity or time trend. It is based on annual data collected from the ten Canadian provinces over 15 years.

Inactivation of the p16 tumor suppressor gene in adrenocortical tumors

The mechanisms of adrenocortical tumorigenesis are still unknown. Evidence that the majority of adrenocortical tumors are monoclonal in origin suggests that a progressive accumulation of genetic aberrations, due to activation of protooncogenes and/or inactivation of tumor suppressor genes, leads to abnormal cell proliferation through a multistep process. Inactivation of the p16 tumor suppressor gene (p16INK4A), which encodes the cell cycle protein p16, was investigated in a series of 14 adrenocortical tumors. Using 11 polymorphic microsatellite markers spanning the short arm of chromosome 9, we demonstrated that three of seven adrenocortical carcinomas and one of seven adrenocortical adenomas had loss of heterozygosity (LOH) within chromosome 9p21, the region containing p16NK4A. Immunohistochemistry showed the absence of p16 nuclear staining in all adrenocortical tumors with LOH within 9p21, and positive staining in all remaining tumors without LOH. In conclusion, LOH within 9p21 associated with lack of p16 expression occurs in a considerable proportion of adrenocortical malignant tumors, but is rare in adenomas. Inactivation of p16INK4A may contribute to the deregulation of cell proliferation in this neoplastic disease.

[Function and therapeutic potential of the dopamine D3 receptor]

The D3 receptor is recognized with high affinity by all antipsychotics and selectively expressed in limbic brain areas participating in the central of emotions, motivation and reward. In transfected cultured cells, stimulation of the D3 receptor inhibits cAMP formation and increases mitogenesis, which, in turn, is potentiated by activation of the cAMP cascade. This suggests that both opposite and synergistic interactions occur between the D3 receptor and the cydic AMP pathway, possibly underlying D1/D3 receptor interactions. In fact, D1 and D3 receptors colocalize in the islands of Calleja, in which they interact in opposition on c-fos mRNA expression, and in the shell of nucleus accumbens, in which they interact in synergy on substance P mRNA expression. The expression of the D3 receptor is highly dependent of the dopamine innervation: lesion of ascending dopamine neurons reduces D3 receptor mRNA and binding in the shell of nudeus accumbens, by deprivation of an unknown factor of dopamine neurons, distinct form dopamine and its cotransmitters. In agreement, expression of the D3 receptor in neurons during rat brain development starts after the settlement of dopamine innervation during the first postnatal week. However, in adult rats with a unilateral lesion of dopamine neurons, repeated treatment with levodopa rescues D3 receptor expression in the shell of nudeus accumbens and induces this expression in the dorsal striatum, a region controlling movements in which the D3 receptor is normally absent. This induction seems responsible for the behavioral sensitisation, i.e. increased responsiveness to levodopa. These observations suggest a role of the D3 receptor in the progressive increase in the therapeutic efficacy of levodopa in the initial treatment of Parkinson's disease, and/or its adversive motor and psychopathological effects during long-term treatment. Finally, various pharmacological and genetic data suggest a role of the D3 receptor in drug addiction and schizophrenia, the treatment of which could benefit from selective D3R agents.

Inhibition of Zac1, a new gene differentially expressed in the anterior pituitary, increases cell proliferation

Zac1 is a new zinc finger protein that concomitantly controls apoptosis and cell cycle arrest through separate pathways. The mouse Zac1 gene is mainly expressed in the pituitary gland and in different brain areas. In this study regional and cellular expression of Zac1 in the pituitary gland was determined by in situ hybridization. Zac1 messenger RNA was abundantly expressed in the anterior pituitary lobe compared with that in the intermediate and posterior lobes. Zac1 transcripts were found in all hormone-secreting cell types, with the highest levels in GH- and PRL-producing cells. To investigate the impact of Zac1 in pituitary cell proliferation, we ablated the endogenous Zac1 gene by antisense treatment in two murine cell types, AtT-20 and TtT/GF, that are representative of granular and agranular cell lineages, respectively. The decline in Zac1 protein levels under antisense treatment was accompanied by increased DNA synthesis in clonal corticotroph and folliculo-stellate cells, as demonstrated by enhanced [3H]thymidine incorporation (36% and 50%, respectively). Antisense oligonucleotides against Zac1 controlled cell proliferation in a dose-dependent way, and mutagenized antisense oligonucleotides were inert. Conclusively, our data provide the first evidence of a role for Zac1 in pituitary growth control.

Diagnosis of glucocorticoid-remediable aldosteronism in primary aldosteronism: aldosterone response to dexamethasone and long polymerase chain reaction for chimeric gene

Aldosterone suppression by dexamethasone, and high 18-hydroxycortisol and 18-oxocortisol levels are used to differentiate glucocorticoid-remediable aldosteronism (GRA) from other forms of primary aldosteronism. These methods are time consuming, expensive, and impractical for large studies. Moreover, diagnosis of GRA requires a confirmatory genetic test. We evaluated 117 patients with primary aldosteronism referred to our centers by the use of a long PCR technique to reveal the chimeric gene of GRA. In 60 of 117 patients, the response of aldosterone to dexamethasone (2 mg/day for 4 days) was also assessed. None of our patients, including 2 pairs of siblings, was positive for the chimeric gene. The results of long PCR were confirmed by Southern blotting. Despite a negative genetic test, 6 patients (1 with aldosterone-producing adenoma and 5 with idiopathic hyperaldosteronism) had plasma aldosterone suppressed by dexamethasone (i.e. < or = 2 ng/dL). Of 117 patients, 43 were identified as having aldosterone-producing adenoma and 74 as having idiopathic hyperaldosteronism. In our experience, the long PCR technique is a reliable and simple test to at least exclude GRA in patients with primary aldosteronism. A short term dexamethasone suppression test of aldosterone can be misleading in identifying GRA. The prevalence of GRA in primary aldosteronism remains to be established.

Functional implications of multiple dopamine receptor subtypes: the D1/D3 receptor coexistence

The D3 dopamine receptor, a D2-like receptor, is selectively expressed in the ventral striatum, particularly in the shell of nucleus accumbens and islands of Calleja, where it is found in medium sized substance P neurons. The latter co-express the D1 receptor whose interaction with the D3 receptor was studied by treating rats with selective agonists and antagonists. In agreement with the opposite cAMP response, they mediate in cultured neuroblastoma cells, the D1 and D3 receptors exerted opposite influences on c-fos expression in islands of Calleja. However, in agreement with the synergistic influence of cAMP on D3 receptor-mediated mitogenesis on the same cultured cells, D1 and D3 receptor stimulation in vivo synergistically enhanced preprotachykinin mRNA in the shell of accumbens. This indicates that the two receptor subtypes may affect neurons in either synergy or opposition according to the cell or signal generated. Levodopa-induced behavioral sensitization in hemiparkinsonian rats is another example of D1/D3 receptor interaction. Hence repeated levodopa administration induces the ectopic appearance of the D3 receptor in substance P/dynorphin, striatonigral neurons of the dorsal striatum. This induction is secondary to D1 receptor stimulation in neurons of the denervated side and fully accounts for the sensitization, i.e. the increased behavioral responsiveness to levodopa. During brain development, a similar process could operate to control the late appearance of the D3 receptor in D1-receptor bearing neurons of the ventral striatum at a time at which they start to be innervated by dopamine neurons. Finally, taking into account a variety of genetic, developmental, neuroimaging and pharmacological data, we postulate that imbalances between the levels of D1 and D3 receptors in the same neurons could be responsible for schizophrenic disorders.