Regulatory mechanisms of the early phase of white adipocyte differentiation: an overview.

The adipose organ comprises two main fat depots termed white and brown adipose tissues. Adipogenesis is a process leading to newly differentiated adipocytes starting from precursor cells, which requires the contribution of many cellular activities at the genome, transcriptome, proteome, and metabolome levels. The adipogenic program is accomplished through two sequential phases; the first includes events favoring the commitment of adipose tissue stem cells/precursors to preadipocytes, while the second involves mechanisms that allow the achievement of full adipocyte differentiation. While there is a very large literature about the mechanisms involved in terminal adipogenesis, little is known about the first stage of this process. Growing interest in this field is due to the recent identification of adipose tissue precursors, which include a heterogenous cell population within different types of adipose tissue as well as within the same fat depot. In addition, the alteration of the heterogeneity of adipose tissue stem cells and of the mechanisms involved in their commitment have been linked to adipose tissue development defects and hence to the onset/progression of metabolic diseases, such as obesity. For this reason, the characterization of early adipogenic events is crucial to understand the etiology and the evolution of adipogenesis-related pathologies, and to explore the adipose tissue precursors' potential as future tools for precision medicine.

Oil Red O Is a Useful Tool to Assess Donor Liver Steatosis on Frozen Sections During Transplantation.

Oil Red O is a useful tool to assess donor liver steatosis on frozen sections during transplantation. Steatosis is a frequent finding in liver evaluation during transplantation, accounting for 9% to 26% of biopsied donor liver. The degree of macrovesicular steatosis is classified as mild, moderate, and severe; the latter is considered an absolute contraindication to liver transplantation because it is associated with poor allograft outcome. Because of the scarcity of organs, there is a debate whether livers with less severe macrovesicular steatosis are still suitable for transplant. Consequently, tools or methods that allow a more accurate intraoperative assessment of steatosis on frozen sections are mandatory. The aim of this study is to improve intraoperative evaluation of steatosis during transplantation using Oil Red O stain on liver biopsies. METHODS: Twenty consecutive liver biopsies of donors were collected during transplantation procedures from September 2017 to February 2018 at the Institute of Pathology of the University and Hospital Trust of Verona, Italy. Each liver biopsy was cut at a different thickness (3, 5, and 8 µm) and stained with both Oil Red O and conventional hematoxylin and eosin for intraoperative consultation. The degree (percentage of hepatocytes involved) of fatty changes was recorded. The results obtained during the intraoperative consultation were finally compared with the formalin-fixed and paraffin-embedded permanent section. RESULTS: Assessment of steatosis on hematoxylin and eosin frozen sections was reported as mild in 17 cases (85%), moderate in 2 cases (10%) and severe in 1 case (5%). Oil Red O frozen sections reported the following results: mild steatosis in 16 cases (80%), moderate in 2 cases (10%), and severe in 2 cases (10%). The percentage of liver steatosis obtained with Oil Red O was consistent in all cases with that of the permanent sections. The staining procedure for Oil Red O required approximately 18 minutes. CONCLUSIONS: Oil Red O special stain is a fast and inexpensive tool to improve the assessment of steatosis on frozen biopsies during liver transplantation.

Attenuation of diet-induced obesity and induction of white fat browning with a chemical inhibitor of histone deacetylases.

BACKGROUND/OBJECTIVES: In the last decade, a strict link between epigenetics and metabolism has been demonstrated. Histone deacetylases (HDACs) have emerged as key epigenetic regulators involved in metabolic homeostasis in normal and pathologic conditions. Here we investigated the effect of the class I HDAC inhibitor MS-275 in a model of obesity induced by a high-fat diet (HFD). METHODS: C57BL6/J male mice were fed HFD for 17 weeks and then randomized in two groups, treated intraperitoneally with vehicle dimethylsulfoxide (DMSO) or with the class I selective HDAC inhibitor MS-275 every other day for 22 days. Glucose tolerance test and measurement of body temperature during cold exposure were performed. Adipose tissues and liver were phenotypically characterized through histological analysis. Gene and protein expression analysis of brown and white adipose tissues (WATs) were performed. RESULTS: MS-275 treated mice showed 10% reduction of body weight, lower adipocyte size and improved glucose tolerance. Inhibition of class I HDAC determined reduction of adipocyte size and of fat mass, paralleled by higher expression of adipose functionality markers and by increased rate of lipolysis and fatty acid ß-oxidation. MS-275 also promoted thermogenic capacity, related to 'browning' of visceral and subcutaneous WAT, showing increased expression of uncoupling protein 1. In brown adipose tissue, we observed limited effects on gene expression and only reduction of brown adipocyte size. CONCLUSIONS: This study provides evidence that class I HDAC inhibition stimulated functionality and oxidative potential of adipose tissue, improving glucose tolerance and ameliorating the metabolic profile in diet-induced obese mice.

Effects of a blend of essential oils and an enzyme combination on nutrient digestibility, ileum histology and expression of inflammatory mediators in weaned piglets.

The aim of this study was to test the hypothesis of an improved gut environment of post-weaning piglets when administered a blend of essential oils (EO; thymol and cinnamaldehyde) and an enzyme combination (xylanase and ß-glucanase (XB)) either alone or in combination. To assess the effect of dietary treatments, faecal nutrient digestibility and microbial counts, as well as ileum histology and gene expression of inflammatory mediators were evaluated. One hundred and ninety-two weaned piglets were allocated into four experimental treatments, and fed the basal diet (CTRL) either without or with EO, XB or their combination (EO+XB) for a 42-day period. The experiment concerning digestibility was designed with two periods (period I: days 15 to 21; period II: days 29 to 35) and the faeces were collected on days 20, 21, 34 and 35. On day 42, six piglets from each treatment were slaughtered. It was found that EO, XB and EO+XB supplementation did not affect (P>0.05) the growth performance of the piglets from days 0 to 42. Moreover, no dietary effect on faecal score was observed. Faecal digestibility of dry matter, organic matter, ash, dietary fibre, lipid, CP and NDF were increased from period I to period II (P<0.01 to P=0.06), while no effect (P>0.05) of EO, XB or their combination on the faecal digestibility was observed at both periods. Compared with the CTRL diet, dietary XB reduced the faecal Lactobacillus and Escherichia coli counts but increased the Lactobacillus to Coliforms ratio on day 42 (P=0.02, 0.03 and 0.03, respectively), and all the additives supplementations decreased the counts of faecal Coliforms on day 42 (P<0.01). XB supplementation increased the villus to crypt ratio (P=0.04) and reduced the mucosal macrophages number (P<0.01) in the ileum compared with the CTRL group, and dietary EO or EO+XB decreased the number of lymphatic follicles (P=0.01 and P<0.01, respectively) and mucosal macrophages (P=0.02 and P<0.01, respectively). In addition, the interleukin (IL)-1α was downregulated in piglets treated with EO+XB compared with the EO group (P=0.02). In conclusion, the administration of EO, XB or their combination was effective in improving ileum histology, and EO+XB supplementation might benefit the modulation of the expression of ileum inflammatory cytokines in piglets.

Synthesis, characterization and biological evaluation of ureidofibrate-like derivatives endowed with peroxisome proliferator-activated receptor activity.

A series of ureidofibrate-like derivatives was prepared and assayed for their PPAR functional activity. A calorimetric approach was used to characterize PPARγ-ligand interactions, and docking experiments and X-ray studies were performed to explain the observed potency and efficacy. R-1 and S-1 were selected to evaluate several aspects of their biological activity. In an adipogenic assay, both enantiomers increased the expression of PPARγ target genes and promoted the differentiation of 3T3-L1 fibroblasts to adipocytes. In vivo administration of these compounds to insulin resistant C57Bl/6J mice fed a high fat diet reduced visceral fat content and body weight. Examination of different metabolic parameters showed that R-1 and S-1 are insulin sensitizers. Notably, they also enhanced the expression of hepatic PPARα target genes indicating that their in vivo effects stemmed from an activation of both PPARα and γ. Finally, the capability of R-1 and S-1 to inhibit cellular proliferation in colon cancer cell lines was also evaluated.

Expression of sterol 27-hydroxylase in glial cells and its regulation by liver X receptor signaling.

Cholesterol is required in the brain for synaptogenesis and its turnover is critical for cerebral functions. Several proteins involved in cholesterol handling and metabolism are transcriptionally regulated by the nuclear liver X receptor (LXR) alpha and beta. Sterol 27-hydroxylase (CYP27) is a ubiquitously expressed enzyme involved in cholesterol metabolism. Notably, its deficiency causes a disease characterized by progressive neurologic impairment. With the final goal to understand the pathophysiological role of CYP27A1 in the CNS, we studied the expression pattern of Cyp27a1 and other related genes in primary cultures of rat glia and neurons. Secondly, given the pivotal role of LXR in the regulation of cholesterol homeostasis, we investigated the effects of its activation on the expression of Cyp27a1.We found that primary astrocytes express different sterol hydroxylases and are able to uptake exogenous 27-hydroxycholesterol. We found that both microglia and astrocytes express preferentially Lxrbeta. However, despite this similarity, we observed cell-specific responsiveness of known and novel (including Cyp27a1) target genes to LXR activation. The increase of mRNA and protein levels in treated astrocytes is paralleled by transactivation of the proximal Cyp27a1 promoter in transfected astrocytes. We suggest that the astrocyte-restricted up-regulation of Cyp27a1 may be ascribable to differential expression of transcriptional co-activators. Given the role of astrocytes in maintaining brain homeostasis, we hypothesize that impairment of CYP27 activity in these cells may alter critical features of the astrocytes, from the handling and delivery of cholesterol to neurons to the release of signaling molecules.

Bile acids and their signaling pathways: eclectic regulators of diverse cellular functions.

The field of bile acids has witnessed an impulse in the last two decades. This has been the result of cloning the genes encoding enzymes of bile acid synthesis and their transporters. There is no doubt that the identification of Farnesoid X Receptor (FXR, NR1H4) as the bile acid receptor has contributed substantially to attract the interest of scientists in this area. When FXR was cloned by Forman et al. [1], farnesol metabolites were initially considered the physiological ligands. After identifying FXR and other nuclear receptors as bile acid sensors [2-4], it has become clear that bile acids are involved in the regulation of lipid and glucose metabolism and that these molecules are eclectic regulators of diverse cellular functions. In this review, we will summarize the current knowledge of the functions regulated by bile acids and how their physiological receptors mediate the signaling underlying numerous cellular responses.

Age-related changes in bile acid synthesis and hepatic nuclear receptor expression.

BACKGROUND: Recent data highlighted the role of nuclear receptors in the transcriptional regulation of the limiting enzyme of bile acid synthesis, cholesterol 7alpha-hydroxylase, in cellular and animal models. This study was designed to analyze the effects of age on cholesterol 7alpha-hydroxylase and related nuclear receptor expression in human livers. DESIGN: Surgical liver biopsies were obtained in 23 patients requiring operation on the gastrointestinal tract. mRNA levels of cholesterol 7alpha-hydroxylase and related nuclear receptors and co-activators were assayed by quantitative real-time RT-PCR. Serum levels of 7alpha-hydroxy-4-cholesten-3-one, a marker of bile acid synthesis, were assayed by gas-liquid chromatography:mass spectrometry. RESULTS: Ageing was inversely correlated with serum 7alpha-hydroxy-4-cholesten-3-one and with cholesterol 7alpha-hydroxylase mRNA levels (r = -0.44 and r = -0.45 on a semi-log scale, respectively, P < 0.05). Among different nuclear factors, cholesterol 7alpha-hydroxylase mRNA best correlated with hepatocyte nuclear factor-4 (r = 0.55 on a log scale, P < 0.05); hepatocyte nuclear factor-4 levels were also inversely correlated with age (r = -0.64 on a semi-log scale, P < 0.05). Age was inversely correlated with serum insulin-like growth factor-I levels, which were directly correlated with hepatocyte nuclear factor-4 and cholesterol 7alpha-hydroxylase expression. No suppressive effect of short heterodimer partner expression on cholesterol 7alpha-hydroxylase was observed. CONCLUSIONS: Ageing associates with reduced bile acid synthesis, possibly related to decreased hepatic expression of hepatocyte nuclear factor-4 and consequently of cholesterol 7alpha-hydroxylase. Age-related modifications of the growth hormone/insulin-like growth factor axis might play a role. These findings may help to elucidate the pathophysiology of age-related modifications of cholesterol metabolism.

Decreased hepatic expression of PPAR-gamma coactivator-1 in cholesterol cholelithiasis.

BACKGROUND: Cholesterol cholelithiasis (gallstone disease) is a common disease in the Western world. The aim of the present study was to analyze the hepatic expression of a number of nuclear receptors involved in bile acid metabolism in human cholesterol gallstone disease. MATERIALS AND METHODS: Surgical liver biopsies were obtained from 11 patients with untreated cholesterol cholelithiasis and nine gallstone-free subjects; mRNA levels of cholesterol 7alpha-hydroxylase (CYP7A1) and related nuclear receptors and coactivators were assayed by quantitative real-time RT-PCR. RESULTS: No differences between the two groups were detected in mRNA levels of CYP7A1 and related nuclear receptors, with the exception of peroxysome proliferator-activated receptor-gamma coactivator 1 (PGC-1), which was significantly (P < 0.01) less expressed in gallstone subjects. Expression of PGC-1 was linearly correlated with farnesoid X receptor (FXR) in gallstone patients (r = 0.87 on a log scale, P < 0.01), but not in control subjects; in gallstone patients PGC-1 expression was also correlated with hepatocyte nuclear factor 4 (HNF-4) (r = 0.78, P < 0.01). CONCLUSION: These findings suggest that PGC-1 can play a role in the prevention of cholesterol gallstone disease in humans; this might take place via interaction with the bile acid receptor FXR, whose protective role in cholelithiasis has been suggested by recent evidence in animal models and other coactivators. The present data might help to understand the pathophysiology and possibly focus on new therapeutical targets in cholesterol gallstone disease.

High pressure liquid chromatography and electrospray ionization mass spectrometry are advantageously integrated into a two-levels approach to detection and identification of haemoglobin variants.

Detecting and correctly identifying haemoglobin (Hb) variants is typically achieved by a two-levels laboratory approach. We report our experience in dealing with 91 Hb variants, including a number of frequent and a few rare variants. Screening included akaline agarose gel electrophoresis (AGE), ion-exchange automated high-performance liquid chromatography (HPLC) and a test for deoxyhaemoglobin solubility. Identification was based on electrospray ionization-mass spectrometry (ESI-MS). Our results confirmed the advantages of HPLC over AGE for screening, because of the occurrence of some electrophoretically 'silent' variants. ESI-MS permitted the definitive identification of 90 of the 91 variants included in the study, in some cases (e.g. HbS) through the application of a simple protocol (direct injection of the sample), in other cases requiring the application of more demanding procedures (purification of the variant chain and peptide analysis after enzymatic or chemical cleavage). In an additional case (Hb J-Oxford), ESI-MS assay did not lead to definitive identification, but gave indications for designing the appropriate primers to focus DNA sequence analysis on the specific region of the gene. Deoxyhaemoglobin solubility test was positive only in the presence of HbS. We conclude that HPLC and ESI-MS are advantageously integrated into a two-level analytical system for the detection and confirmation of variant Hbs.

LXR (liver X receptor) and HNF-4 (hepatocyte nuclear factor-4): key regulators in reverse cholesterol transport.

Cholesterol homoeostasis is the result of the fine tuning between intake and disposal of this molecule. High levels of cholesterol in the blood are detrimental as they may lead to excessive accumulation in vessel walls, a condition predisposing to the development of atherosclerotic lesions. Cholesterol is removed from the vessel wall and transported to the liver through a process called reverse cholesterol transport. Nuclear receptors are among the most important transcription factors regulating genes involved in different steps of reverse cholesterol transport. Here, we discuss the role of the nuclear receptors LXR (liver X receptor) and HNF-4alpha (hepatocyte nuclear factor-4alpha) in different steps of reverse cholesterol transport. LXR controls the transcription of crucial genes in cholesterol efflux from macrophages and its transport to the liver, such as ABCA1 (ATP binding cassette A1), CYP27A1 (sterol 27-hydroxylase), CLA-1 (scavenger receptor type B1) and apolipoprotein E. Some oxysterols present in oxidized low-density lipoproteins and proinflammatory cytokines modulate the activity of LXR by antagonizing the effect of activators of this receptor, thus contributing to cholesterol accumulation in macrophages. Bile acid synthesis, which represents the final step of reverse cholesterol transport, is transcriptionally regulated by several nuclear receptors at the level of the liver-specific cytochrome P450 cholesterol 7alpha-hydroxylase (CYP7A1), the rate-limiting enzyme of this metabolic pathway. Bile acids returning to the liver through the enterohepatic circulation down-regulate CYP7A1 transcription via the bile acid sensors farnesoid X receptor and HNF-4alpha. Based on this evidence, these nuclear receptors are candidate targets of new drugs for the treatment and prevention of atherosclerotic disease.

Inhibition of metalloproteinase-9 activity and gene expression by polyphenolic compounds isolated from the bark of Tristaniopsis calobuxus (Myrtaceae).

Excessive breakdown of extracellular matrix by metalloproteinases (MMPs) occurs in many pathological conditions, and thus inhibition of MMP activity might have therapeutic potential. The methanolic extract and the identified compounds from the bark of Tristaniopsis calobuxus Brongniart & Gris (Myrtaceae) were tested on the activity, production, and gene expression of MMP-9. The extract produced a concentration-dependent inhibition (50-95% at 10-50 microg/ml) of MMP-9 activity. The inhibitory activity was retained in the ethyl acetate-soluble fraction (50-95% inhibition at 10-50 microg/ml) which also reduced the release of MMP-9 by mouse peritoneal macrophages up to 80%. In the ethyl acetate-soluble fraction, two active fractions, 5A and 5B were identified. HPLC-MS and NMR analyses of these fractions indicated the presence of gallocatechin, ellagic acid, and its glycoside derivatives. Since the absolute configuration of gallocatechin was not determined, in the next experiments both (+)-gallocatechin (2R,3S) and (-)-gallocatechin (2S,3R) were tested, and (-)-epigallocatechin (2R,3R) was included for comparison. 5A and 5B inhibited MMP-9 secretion, an observation which correlated with the decrease of MMP-9 promoter activity and the downregulation of mRNA levels. All compounds decreased MMP-9 mRNA levels and secretion. Ellagic acid, (+)-gallocatechin and (-)-epigallocatechin, but not (-)gallocatechin inhibited promoter-driven transcription. Thus configuration at C2 (R) of the flavanol seem to be critical for the interaction with the promoter.

Suppression of bile acid synthesis, but not of hepatic cholesterol 7alpha-hydroxylase expression, by obstructive cholestasis in humans.

Regulation of bile acid synthesis, a key determinant of cholesterol homeostasis, is still incompletely understood. To elucidate the feedback control exerted on bile acid biosynthesis in humans with obstructive cholestasis, 16 patients with bile duct obstruction were studied. In vivo 7alpha-hydroxylation, reflecting bile acid synthesis, was assayed in 13 of them by tritium release analysis. Serum 27-hydroxycholesterol was determined by gas chromatography-mass spectrometry. In a subgroup, hepatic cholesterol 7alpha-hydroxylase mRNA was assayed by real-time polymerase chain reaction (PCR), enzyme activity was determined by isotope incorporation, and microsomal cholesterol content was assayed by gas chromatography-mass spectrometry. Age-matched control subjects were studied in parallel. Hydroxylation rates were lower in cholestatic patients (108 +/- 33 mg of cholesterol per day, mean +/- SEM; controls: 297 +/- 40 mg/d; P <.01). The reduction was proportional to the severity of cholestasis, and synthetic rates were normalized in 4 subjects restudied after resolution of biliary obstruction. Consistent findings were obtained by analysis of serum 7alpha-hydroxycholesterol levels. On the other hand, hepatic cholesterol 7alpha-hydroxylase mRNA, microsomal enzyme activity, and cholesterol content tended to be increased in cholestasis. Finally, serum 27-hydroxycholesterol levels were slightly reduced in cholestatic subjects and were not related with the severity of the disease. Suppression of in vivo bile acid synthesis with no corresponding reduction in tissue 7alpha-hydroxylase expression and activity is consistent with nontranscriptional, posttranslational levels of regulation; these may play a role in the feedback control of bile acid synthesis in particular conditions. Alteration of the alternate biosynthetic pathway seems unlikely according to the present data.

The negative effects of bile acids and tumor necrosis factor-alpha on the transcription of cholesterol 7alpha-hydroxylase gene (CYP7A1) converge to hepatic nuclear factor-4: a novel mechanism of feedback regulation of bile acid synthesis mediated by nuclear receptors.

Bile acids regulate the cholesterol 7alpha-hydroxylase gene (CYP7A1), which encodes the rate-limiting enzyme in the classical pathway of bile acid synthesis. Here we report a novel mechanism whereby bile acid feedback regulates CYP7A1 transcription through the nuclear receptor hepatocyte nuclear factor-4 (HNF-4), which binds to the bile acid response element (BARE) at nt -149/-118 relative to the transcription start site. Using transient transfection assays of HepG2 cells with Gal4-HNF-4 fusion proteins, we show that chenodeoxycholic acid (CDCA) dampened the transactivation potential of HNF-4. Overexpression of a constitutive active form of MEKK1, an upstream mitogen-activated protein kinase (MAPK) module triggered by stress signals, strongly repressed the promoter activity of CYP7A1 via the consensus sequence for HNF-4 embedded in the BARE. Similarly, MEKK1 inhibited the activity of HNF-4 in the Gal4-based assay. The involvement of the MEKK1-dependent pathway in the bile acid-mediated repression of CYP7A1 was confirmed by co-transfecting a dominant negative form of the stress-activated protein kinase kinase, SEK, which abolished the effect of CDCA upon CYP7A1 transcription. Treatment of transfected HepG2 cells with tumor necrosis factor alpha (TNF-alpha), an activator of the MEKK1 pathway, led to the repression of CYP7A1 via the HNF-4 site in the BARE. TNF-alpha also inhibited the transactivation potential of HNF-4. Collectively, our results demonstrate for the first time that HNF-4, in combination with a MAPK signaling pathway, acts as a bile acid sensor in the liver. Furthermore, the effects of CDCA and TNF-alpha converge to HNF-4, which binds to the BARE of CYP7A1, suggesting a link between the cascades elicited by bile acids and pro-inflammatory stimuli in the liver.

Identification and characterization of cis-acting elements conferring insulin responsiveness on hamster cholesterol 7alpha-hydroxylase gene promoter.

Bile acid biosynthesis occurs primarily through a pathway initiated by the 7alpha-hydroxylation of cholesterol, catalysed by cholesterol 7alpha-hydroxylase (encoded by CYP7A1). Insulin down-regulates CYP7A1 transcription. The aim of our study was to characterize the sequences of hamster CYP7A1 promoter, mediating the response to insulin. We therefore performed transient transfection assays with CYP7A1 promoter/luciferase chimaeras mutated at putative response elements and studied protein-DNA interactions by means of gel electrophoresis mobility-shift assay. Here we show that two sequences confer insulin responsiveness on hamster CYP7A1 promoter: a canonical insulin response sequence TGTTTTG overlapping a binding site for hepatocyte nuclear factor 3 (HNF-3) (at nt -235 to -224) and a binding site for HNF-4 at nt -203 to -191. In particular we show that the hamster CYP7A1 insulin response sequence is part of a complex unit involved in specific interactions with multiple transcription factors such as members of the HNF-3 family; this region does not bind very strongly to HNF-3 and as a consequence partly contributes to the transactivation of the gene. Another sequence located at nt -138 to -128 binds to HNF-3 and is involved in the tissue-specific regulation of hamster CYP7A1. The sequence at nt -203 to -191 is not only essential for insulin effect but also has a major role in the liver-specific expression of CYP7A1; it is the target of HNF-4. Therefore the binding sites for liver-enriched factors, present in the hamster CYP7A1 proximal promoter in close vicinity and conserved between species, constitute a regulatory unit important for basal hepatic expression and tissue restriction of the action of hormones such as insulin.

Transcriptional activation of the cholesterol 7alpha-hydroxylase gene (CYP7A) by nuclear hormone receptors.

The gene encoding cholesterol 7alpha-hydroxylase (CYP7A), the rate-limiting enzyme in bile acid synthesis, is transcriptionally regulated by bile acids and hormones. Previously, we have identified two bile acid response elements (BARE) in the promoter of the CYP7A gene. The BARE II is located in nt -149/-118 region and contains three hormone response element (HRE)-like sequences that form two overlapping nuclear receptor binding sites. One is a direct repeat separated by one nucleotide DR1 (-146- TGGACTtAGTTCA-134) and the other is a direct repeat separated by five nucleotides DR5 (-139-AGTTCAaggccGGG TAA-123). Mutagenesis of these HRE sequences resulted in lower transcriptional activity of the CYP7A promoter/reporter genes in transient transfection assay in HepG2 cells. The orphan nuclear receptor, hepatocyte nuclear factor 4 (HNF-4)1, binds to the DR1 sequence as assessed by electrophoretic mobility shift assay, and activates the CYP7A promoter/reporter activity by about 9-fold. Cotransfection of HNF-4 plasmid with another orphan nuclear receptor, chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII), synergistically activated the CYP7A transcription by 80-fold. The DR5 binds the RXR/RAR heterodimer. A hepatocyte nuclear factor-3 (HNF-3) binding site (-175-TGTTTGTTCT-166) was identified. HNF-3 was required for both basal transcriptional activity and stimulation of the rat CYP7A promoter activity by retinoic acid. Combinatorial interactions and binding of these transcription factors to BAREs may modulate the promoter activity and also mediate bile acid repression of CYP7A gene transcription.

[Prevalence of systemic arterial hypertension in the population of +Passo Fundo (Brazil) metropolitan area]. / Prevalência da hipertensão arterial sistêmica na população urbana de Passo Fundo (RS).

PURPOSE: To evaluate the present prevalence of hypertension in the Passo Fundo metropolitan area. METHODS: This is an observational, descriptive, crossectional design with populational base, of a representative random sample of the adults of this urban region. The criteria for hypertension were blood pressure > or = 160/95 mmHg or antihypertensive treatment. The average of the last three measurements was used in the analysis. Two hundred and six subjects were selected. The interview was made with standardized questionnaires. Blood pressure was corrected for arm diameter. RESULTS: The prevalence of hypertension was 21.9% (CI = 19.3 to 24.5) of 45 hypertensive subjects, 53.3% were using anti-hypertensive drugs regularly, however only 20% had normal BP levels. Among the study population 4.4% were diabetics, 33.0% were smokers, 31.4% of the women were using contraceptives, 2.9% were heavy alcohol users, 29.6% were obese. The following conditions of interest were significantively associated with hypertension: age, obesity and diabetes; there was no association with sex, color, heavy alcohol use, smoking and contraceptive use. CONCLUSION: The prevalence of hypertension in the Passo Fundo metropolitan area is within the expected range, however the level of control in this population is not acceptable.

Identification of a bile acid response element in the cholesterol 7 alpha-hydroxylase gene CYP7A.

The transcriptional activity of the cholesterol 7 alpha-hydroxylase gene CYP7A is repressed by bile acids. Taurine conjugates of chenodeoxycholate and deoxycholate, but not cholate and ursodeoxycholate, inhibited the CYP7A promoter/luciferase reporter activity in transient transfection assays in Hep G2 cells. A region from nucleotide (nt) -74 to -55 was found to mediate bile acid response. However, deletion of this bile acid response element (BARE-I) enhanced reporter activity but did not eliminate the bile acid response. This is due to the presence of another BARE-II located in a conserved region between nt -149 and -128. Deletion or mutations of these sequences reduced promoter activity and abolished bile acid repression. This BARE-II shares an identical AGTTCAAG core sequence with BARE-I. Electrophoretic mobility shift assays of BARE-I and BARE-II probes using Hep G2 nuclear extract and the partially purified binding activity of nt -65/-54 DNA-affinity column revealed that the same or a similar nuclear protein might bind to both BAREs. BARE-II is the major BARE involved in the transcriptional repression of the CYP7A gene by hydrophobic bile acids.

Orphan receptors chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) and retinoid X receptor (RXR) activate and bind the rat cholesterol 7alpha-hydroxylase gene (CYP7A).

The cholesterol 7alpha-hydroxylase gene (CYP7A) is transcriptionally regulated by a number of factors, including hormones, bile acids, and diurnal rhythm. Previous studies have identified a region from nucleotides (nt) -74 to -55 of the rat CYP7A promoter that enhanced bile acid repression of the SV40 early promoter, as assayed with a luciferase reporter gene in transiently transfected HepG2 cells. The rat CYP7A promoter/reporter activity was strongly stimulated by cotransfection with an expression plasmid encoding the nuclear hormone receptor chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) in a dose-dependent manner. Site-directed mutagenesis in the region of nt -74 to -55 altered this stimulation. Recombinant COUP-TFII expressed in HepG2 or COS-1 cells were found to bind to nt -74 -55 and nt -149 -128 probes by electrophoretic mobility shift assay (EMSA) and by supershifting the corresponding band with COUP-TFII-specific antibodies. The region of nt -176 -117 was previously mapped as a retinoic acid response region and was found to bind retinoid X receptor (RXR). EMSA supershift assays of wild-type and mutant oligomers using antibody against RXR revealed that the sequences between nt -145 and -134 were important for RXR binding. We conclude that COUP-TFII stimulates the transcriptional activity of the rat CYP7A promoter by binding to the sequences between nt -74 to -54 and nt -149 to -128. RXR may stimulate CYP7A gene transcription by binding to a direct repeat of the hormone response element separated by one nucleotide located at nt -146 -134.

Regulation of the hamster cholesterol 7 alpha-hydroxylase gene (CYP7A): prevalence of negative over positive transcriptional control.

Cholesterol 7 alpha-hydroxylase plays a crucial role in cholesterol homeostasis. We investigated the regulation of this enzyme in the hamster, a suitable animal model for studying cholesterol metabolism. DNase I hypersensitivity assay revealed the presence of a hypersensitive region in the proximal promoter. Both negative (bile acids, phorbol esters and insulin) and positive (glucocorticoid hormones) effects were mediated through sequences in the region 318 bp upstream of the ATG codon. All-trans-retinoic acid, cAMP, and LDL did not affect transcriptional activity. These findings show that the hamster cholesterol 7 alpha-hydroxylase gene undergoes a predominant negative regulation, as opposed to the rat CYP7A homologous gene.