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Biomedical subjects

K Dahlman-Wright

Publications and source records attributed to K Dahlman-Wright.

At least 19 recordsLinked to original sources
PubMed2007

Oestrogen receptor alpha gene expression levels are reduced in obese compared to normal weight females.

OBJECTIVE: To determine whether oestrogen receptor (ER)alpha messenger RNA (mRNA) levels or single nucleotide polymorphisms (SNPs) are associated with obesity in Swedish women. DESIGN: ERalpha mRNA expression levels were measured by real-time qPCR in subcutaneous adipose tissue from non-obese (N=16, BMI<30) and obese (N=17, BMI>or=30) women. In addition, ERalpha mRNA expression levels were determined in isolated adipocytes. ERalpha promoter usage was characterized by 5' RACE and by real-time qPCR in subcutaneous adipose tissue from the same non-obese and obese women. Two ERalpha SNPs were scored in 509 non-obese and 489 obese females. RESULTS: ERalpha mRNA expression levels were lower in obese compared to non-obese women in both subcutaneous adipose tissue and in adipocytes. We show that two ERalpha promoters are differentially utilized in obese and non-obese individuals. We did not find any significant association between obesity and the ERalpha SNPs or haplotypes assayed. CONCLUSION: The reduced ERalpha mRNA levels observed in adipose tissue from obese compared to non-obese women support a role for oestrogen signaling via ERalpha, in control of body weight. Mechanistic studies of the role of ERalpha in adipocytes and how its expression is regulated in relation to fat mass should be performed. The latter studies should focus on the two promoters that are used differently in obese and non-obese individuals.

Adipocytes↗
PubMed2006

Evidence that oestrogen receptor-alpha plays an important role in the regulation of glucose homeostasis in mice: insulin sensitivity in the liver.

AIMS/HYPOTHESIS: We used oestrogen receptor-alpha (ERalpha) knockout (ERKO) and receptor-beta (ERbeta) knockout (BERKO) mice to investigate the mechanism(s) behind the effects of oestrogens on glucose homeostasis. METHODS: Endogenous glucose production (EGP) was measured in ERKO mice using a euglycaemic-hyperinsulinaemic clamp. Insulin secretion was determined from isolated islets. In isolated muscles, glucose uptake was assayed by using radiolabelled isotopes. Genome-wide expression profiles were analysed by high-density oligonucleotide microarray assay, and the expression of the genes encoding steroyl-CoA desaturase and the Leptin receptor (Scd1 and Lepr, respectively) was confirmed by RT-PCR. RESULTS: ERKO mice had higher fasting blood glucose, plasma insulin levels and IGT. The plasma leptin level was increased, while the adiponectin concentration was decreased in ERKO mice. Levels of both glucose- and arginine-induced insulin secretion from isolated islets were similar in ERKO and wild-type mice. The euglycaemic-hyperinsulinaemic clamp revealed that suppression of EGP by increased insulin levels was blunted in ERKO mice, which suggests a pronounced hepatic insulin resistance. Microarray analysis revealed that in ERKO mice, the genes involved in hepatic lipid biosynthesis were upregulated, while genes involved in lipid transport were downregulated. Notably, hepatic Lepr expression was decreased in ERKO mice. In vitro studies showed a modest decrease in insulin-mediated glucose uptake in soleus and extensor digitorum longus (EDL) muscles of ERKO mice. BERKO mice demonstrated normal glucose tolerance and insulin release. CONCLUSIONS/INTERPRETATION: We conclude that oestrogens, acting via ERalpha, regulate glucose homeostasis mainly by modulating hepatic insulin sensitivity, which can be due to the upregulation of lipogenic genes via the suppression of Lepr expression.

Adiponectin↗
PubMed2006

Estrogen attenuates vascular expression of inflammation associated genes and adhesion of monocytes to endothelial cells.

OBJECTIVE: Investigate effects of estrogen at gene expression and functional levels in vascular wall cells treated with bacterial lipopolysaccharide (LPS). MATERIALS AND METHODS: Aortic segments from ovariectomized mice were treated with LPS for 24 h in the absence or presence of 17beta-estradiol (E2). Gene activity was determined by Affymetrix microarray analysis and real-time RT-PCR. Adhesion of [3H]-thymidine labelled human THP-1 monocytes to mouse bEnd.3 endothelial cells was determined by measuring radioactivity of DNA from co-culture homogenates. RESULTS: Analysis of global gene expression profiles revealed that 10 nM E2 attenuates LPS-induced (10 ng/ml) expression of genes coding for well-known acute-phase proteins, such as alpha-trypsin inhibitor heavy chain 4, serum amyloid A3 and lipocalin 2. The E2-induced down-regulation of these three genes observed by microarray was confirmed by realtime RT-PCR. Treatment with 500 ng/ml LPS increased adhesion of monocytes to endothelial cells more than two fold. Importantly, LPS-induced monocyte adhesion was fully prevented by 50 nM E2. CONCLUSION: Estrogen reduces expression of acute-phase protein genes and inhibits LPS-induced moncocyte adhesion to endothelial cells, suggesting that estrogen might have a vasculoprotective effect via this mechanism.

Animals↗
PubMed2006

Evidence for associations between common polymorphisms of estrogen receptor beta gene with homocysteine and nitric oxide.

BACKGROUND: Homocysteine and asymmetric dimethylarginine (ADMA) affect nitric oxide (NO) concentration, thereby contributing to cardiovascular disease (CVD). Both amino acids can be reduced in vivo by estrogen. Variation in the estrogen receptor (ER) may influence homocysteine and ADMA, yet no information is available on associations with single nucleotide polymorphisms in the estrogen receptor genes ERalpha (PvuII and XbaI) and ERbeta (1730G-->A and cx + 56 G-->A). OBJECTIVE: To find relationships between common polymorphisms associated with cardiovascular disease and cardiovascular risk factors homocysteine and ADMA. METHODS: In a cross-sectional study with healthy postmenopausal women (n = 89), homocysteine, ADMA, nitric oxide metabolites (NOx), plasma folate and ERalpha and beta polymorphisms ERalpha PvuII, ERalpha XbaI; ERbeta 1730G-->A (AluI), ERbeta cx + 56 G-->A (Tsp509I) were analyzed. RESULTS: Women who are homozygotic for ERbetacx + 56 G-->A A/A exhibited higher homocysteine (p = 0.012) and NOx (p = 0.056) levels than wildtype or heterozygotes. NOx concentration was also significantly affected by ERbeta 1730 G -->A polymorphism (p = 0.025). The ERbeta (p < 0.001) and ERalpha (p < 0.001) polymorphisms were in linkage disequilibrium. CONCLUSIONS: Women who are homozygotic for ERbetacx + 56 G-->A A/A may be at increased risk for cardiovascular disease due to higher homocysteine levels.

Aged↗
PubMed2006

Genes associated with telomerase activity levels in esophageal carcinoma cell lines.

Telomerase activity levels have been shown to correlate with tumor progression in several malignancies. However, the genetic regulation of telomerase activity levels is not fully understood. The aim of the present study has been to identify a gene expression profile, predicting correlation with the telomerase-activity test. Ten human esophageal carcinoma cell lines were investigated using the telomerase activity assay (TRAPeze) Telomerase Detection Kit), followed by further characterization using the GeneChip Human Genome U133A 2.0 Array (Affymetrics Inc., USA), including 14 500 human genes. Telomerase activity levels were detected in all cell lines with a broad range of activity levels. Using a high correlation coefficient, r > 0.90, the following genes were found to be positively correlated with telomerase activity levels: N-myristoyltransferase 2; ribosomal protein L3; retinoblastoma-like 2 (pRb2/p130); and cyclin G2. Only one gene was negatively correlated with telomerase activity levels, zinc finger protein 207. In conclusion, the present microarray data provide primary validation data indicating possible candidates for prognostic and prediction factors in esophageal cancer in relation to telomerase activity.

Acyltransferases↗
PubMed2005

Global analysis of uniparental disomy using high density genotyping arrays.

BACKGROUND: Uniparental disomy (UPD), the inheritance of both copies of a chromosome from a single parent, has been identified as the cause for congenital disorders such as Silver-Russell, Prader-Willi, and Angelman syndromes. Detection of UPD has largely been performed through labour intensive screening of DNA from patients and their parents, using microsatellite markers. METHODS: We applied high density single nucleotide polymorphism (SNP) microarrays to diagnose whole chromosome and segmental UPD and to study the occurrence of continuous or interspersed heterodisomic and isodisomic regions in six patients with Silver-Russell syndrome patients who had maternal UPD for chromosome 7 (matUPD7). RESULTS: We have devised a new high precision and high-throughput computational method to confirm UPD and to localise segments where transitions of UPD status occur. Our method reliably confirmed and mapped the matUPD7 regions in all patients in our study. CONCLUSION: Our results suggest that high density SNP arrays can be reliably used for rapid and efficient diagnosis of both segmental and whole chromosome UPD across the entire genome.

Chromosome Mapping↗
PubMed2004

Association of estrogen receptor beta gene polymorphisms with bulimic disease in women.

In this study, we explored the potential association between estrogen receptor beta (ERbeta) and disease in a group of bulimic women. Eating disorders are much more common in females than in males, suggesting a possible role for female sex hormone signalling in the pathogenesis of these diseases. Furthermore, estrogen has been implicated in appetite regulation. The occurrence of menstrual disturbances is also increased in bulimic women. We studied 76 bulimic women and 60 controls, and found an association between two common polymorphisms in the ERbeta gene with disease in this group of bulimic women. More detailed characterisation of the ERbeta gene identified a novel variant changing the primary structure of ERbeta protein in one bulimic patient. An initial functional characterization of this variant did not reveal any differences compared to the wild-type protein. Our findings point towards a possible role of ERbeta and/or neighboring genes in the etiology of disease in bulimic patients.

Adult↗
PubMed2004

Gene expression profiling identifies liver X receptor alpha as an estrogen-regulated gene in mouse adipose tissue.

Estrogens reduce adipose tissue mass in both humans and animals. The molecular mechanisms for this effect are, however, not well characterized. We took a gene expression profiling approach to study the direct effects of estrogen on mouse white adipose tissue (WAT). Female ovariectomized mice were treated for 10, 24 and 48 h with 17beta-estradiol or vehicle. RNA was extracted from gonadal fat and hybridized to Affymetrix MG-U74Av2 arrays. 17beta-Estradiol was shown to decrease mRNA expression of liver X receptor (LXR) alpha after 10 h of treatment compared with the vehicle control. The expression of several LXRalpha target genes, such as sterol regulatory element-binding protein 1c, apolipoprotein E, phospholipid transfer protein, ATP-binding cassette A1 and ATP-binding cassette G1, was similarly decreased. We furthermore identified a 1.5 kb LXRalpha promoter fragment that is negatively regulated by estrogen. Several genes involved in lipogenesis and lipolysis were identified as novel targets that could mediate estrogenic effects on adipose tissue. Finally, we show that ERalpha is the main estrogen receptor expressed in mouse white adipose tissue (WAT) with mRNA levels several hundred times higher than those of ERbeta mRNA.

Adipose Tissue↗
PubMed2002

Estrogen receptor specificity for the effects of estrogen in ovariectomized mice.

Estrogen exerts a variety of important physiological effects, which have been suggested to be mediated via the two known estrogen receptors (ERs), alpha and beta. Three-month-old ovariectomized mice, lacking one or both of the two estrogen receptors, were given estrogen subcutaneously (2.3 micro g/mouse per day) and the effects on different estrogen-responsive parameters, including skeletal effects, were studied. We found that estrogen increased the cortical bone dimensions in both wild-type (WT) and double ER knockout (DERKO) mice. DNA microarray analysis was performed to characterize this effect on cortical bone and it identified four genes that were regulated by estrogen in both WT and DERKO mice. The effect of estrogen on cortical bone in DERKO mice might either be due to remaining ERalpha activity or represent an ERalpha/ERbeta-independent effect. Other effects of estrogen, such as increased trabecular bone mineral density, thymic atrophy, fat reduction and increased uterine weight, were mainly ERalpha mediated.

Animals↗
PubMed2001

Solution structure of the DNA binding domain of the human forkhead transcription factor AFX (FOXO4).

AFX is a human forkhead transcription factor. Based on results from studies of the orthologous transcription factor DAF-16 in Caenorhabditis elegans, it was suggested that some of the metabolic defects in both type I and type II diabetes may be due to unregulated activity of AFX. In the present study, we report the high-resolution NMR solution structure of the DNA binding domain of AFX. It is the first structure of the DNA binding domain from a small subfamily of forkhead transcription factors (i.e., AFX, FKHR, FKHRL1, FKHRL1P1, and FKHRP1). Despite rather low sequence identity for a protein within the forkhead family, the structure is remarkably similar to those of the DNA binding domains of HNF3-gamma and FREAC-11, and to a lesser extent the DNA binding domain of Genesis which displays a slightly altered orientation of the DNA recognition helix. The high degree of structural similarity between the DNA binding domains of different forkhead transcription factors implies that the repositioning of helix 3, observed for Genesis, cannot be a general feature for modulation of the DNA binding specificity. Other mechanisms that could influence the DNA binding specificity are discussed.

Amino Acid Motifs↗
PubMed1999

Selective activation of the probasin androgen-responsive region by steroid hormones.

Glucocorticoid and androgen receptors have been shown to function through the same palindromic glucocorticoid response element (GRE) and yet have differential effects on gene transcription. In this study, we examined the functional and structural relationship of the androgen and glucocorticoid receptors with the androgen responsive region (ARR) of the probasin (PB) gene containing two androgen receptor binding sites, ARBS-1 and ARBS-2. Transfection studies indicated that one copy of each cis-acting DNA element was essential for maximal androgen-induced chloramphenicol acetyltransferase (CAT) activity and that androgen selectivity was maintained when multiple copies of the minimal wild type (wt) androgen responsive region containing both ARBS-1 and ARBS-2 (-244 to -96) were subcloned in front of the thymidine kinase promoter. Furthermore, replacing the androgen response region with 1, 2 or 3 copies of either ARBS-1 or ARBS-2 restored less than 4% of the biological activity seen with the wt PB ARR. Multiple copies of either ARBS-1 or ARBS-2 did not result in glucocorticoid-induced CAT gene activity. By comparison, 1 or 2 copies of the tyrosine aminotransferase (TAT) GRE, as well as the mouse mammary tumour virus GRE, were strong inducers of CAT activity in response to both androgen and glucocorticoid treatment. In addition, band shift assays demonstrated that although the synthetic glucocorticoid receptor, GR-DNA binding domain (GR-DBD), and the synthetic androgen receptor, AR2, could interact with the TAT GRE (dissociation constants Kd of 63.9 and 14.1 respectively), only AR2 but not GR-DBD binding could be detected on ARBS-1 and ARBS-2. Our findings provide further evidence that androgen-induced regulation of gene transcription can occur through androgen-specific DNA binding sites that are distinct from the common GRE.

Androgen-Binding Protein↗
PubMed1996

Functional interaction of the c-Myc transactivation domain with the TATA binding protein: evidence for an induced fit model of transactivation domain folding.

c-Myc is a member of a family of sequence specific-DNA binding proteins that are thought to regulate the transcription of genes involved in normal cell growth, differentiation, and apoptosis. In order to understand how human c-myc functions as a transcription factor, we have studied the mechanism of action and structure of the N-terminal transactivation domain, amino acids 1-143. In a protein interaction assay, c-myc1-143 bound selectively to two basal transcription factors, the TATA binding protein (TBP) and the RAP74 subunit of TFIIF. Furthermore, the isolated c-myc transactivation domain competed for limiting factors required for the assembly of a functional preinitiation complex. This squelching of basal transcription was reversed in a dose-dependent manner by recombinant TBP. Taken together, these results identify TBP as an important target for the c-myc transactivation domain, during transcriptional initiation. Similar to other transactivation domains, the c-myc1-143 polypeptide showed little or no evidence of secondary structure, when measured by circular dichroism spectroscopy (CD) in aqueous solution. However, significant alpha-helical conformation was observed in the presence of the hydrophobic solvent trifluoroethanol. Strikingly, addition of TBP caused changes in the CD spectra consistent with induction of protein conformation in c-myc1-143 during interaction with the target factor. This change was specific for TBP as a similar effect was not observed in the presence of TFIIB. These data support a model in which target factors induce or stabilize a structural conformation in activator proteins during transcriptional transactivation.

Amino Acid Sequence↗
PubMed1996

Structural studies of mutant glucocorticoid receptor transactivation domains establish a link between transactivation activity in vivo and alpha-helix-forming potential in vitro.

We have previously shown, using circular dichroism spectroscopy, that the tau 1 core peptide has alpha-helix-forming potential in vitro [Dahlman-Wright et al. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 1699-1703]. The tau 1 core peptide is a 58-amino acid peptide, constituting the core of the transactivation activity of the tau 1 major transactivation domain of the human glucocorticoid receptor [Dahlman-Wright et al. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 1619-1623]. Further structural studies of the peptide, using NMR spectroscopy, identified three segments with alpha-helical character. In this report we show that reduced protein expression or stability is not responsible for the reduced in vivo transactivation potential of tau 1 core peptides with proline substitutions in proposed alpha-helical regions. Rather, the reduced alpha-helix propensity of the corresponding purified peptides in vitro suggests that alpha-helices are involved in the molecular mechanism of glucocorticoid receptor mediated changes in gene activity.

Amino Acid Sequence↗
PubMed1996

Modulation of glucocorticoid-inducible gene expression by metal ions.

We examined the effects of various metal ions on the DNA-binding activity of the glucocorticoid receptor. Electrophoretic mobility shift assays demonstrated that the sequence-specific DNA binding activity of the receptor was decreased by metal ions in a dose-dependent fashion. The most potent inhibitor was Au(I). Cu(II), Cd(II), and Zn(II) were, in that order, less potent as inhibitors, whereas Fe(III), Al(III), and Mg(II) had no apparent effect. The inhibitory actions of metal ions were efficiently counteracted by the sulfhydryl reducing reagents 2-mercaptoethanol and N-acetyl-L-cysteine, indicating that metal ions interfere with the DNA binding activity of the glucocorticoid receptor through modification of sulfhydryl groups in the receptor molecule. Modification of sulfhydryls by metals seems to involve neither disulfide bond formation nor permanent destruction of the GR protein and is reversible. We also show that metal ions inhibit glucocorticoid-inducible gene transcription in vivo, presumably by interfering with the interaction between the glucocorticoid receptor and cognate DNA target sequences. In summary, these data demonstrates that metal ions are capable of modulating glucocorticoid receptor mediated intracellular signalling pathways.

Animals↗
PubMed1995

Structural characterization of a minimal functional transactivation domain from the human glucocorticoid receptor.

A 58-amino acid polypeptide containing the functional core region, the tau 1 core, of the major transactivation domain of the human glucocorticoid receptor has been expressed in Escherichia coli and purified to homogeneity. The polypeptide retains 60-70% of the activity of the intact domain when assayed in vivo or in vitro. This report describes a structural characterization of the tau 1 core peptide fragment. Circular dichroism spectroscopy shows that the tau 1 core and a larger fragment encompassing the intact tau 1 domain are largely unstructured in water solution under a variety of pH conditions. The tau 1 core, however, acquires a significant alpha-helical structure when analyzed in the presence of trifluoroethanol, an agent that favors secondary structure formation in regions that have propensity for alpha-helical conformation. Two- and three-dimensional NMR spectroscopy of 15N-labeled tau 1 core, in the presence of trifluoroethanol, has allowed sequential assignment of 1H and 15N resonances and identification of three protein segments with alpha-helical character. Potentially helix-breaking proline substitutions, in proposed alpha-helical regions, lead to reduced activity, suggesting that alpha-helices are important for transactivation in vivo.

Amino Acid Sequence↗
PubMed1995

Mechanisms of transcription activation by nuclear receptors: studies on the human glucocorticoid receptor tau 1 transactivation domain.

Nuclear receptors are important signalling molecules that directly mediate the effects of hormones, vitamins and xenobiotic compounds at the level of gene expression. Several members of this superfamily of proteins have been implicated in receptor-dependent carcinogenesis. In this review, we summarise how these receptors can function as transcription factors with particular emphasis on the mechanism of transcription activation by the human glucocorticoid receptor tau 1 transactivation domain.

Animals↗
PubMed1995

Zinc ions antagonize the inhibitory effect of aurothiomalate on glucocorticoid receptor function at physiological concentrations.

The water-soluble gold preparation aurothiomalate, which contains gold as Au(I), is frequently prescribed for patients with rheumatoid arthritis as a disease-modifying agent. We report that aurothiomalate negatively modulates glucocorticoid hormone action; it represses the ligand- and DNA-binding activities and the transactivation function of the glucocorticoid receptor. We suggested the existence of endogenous titrating activities of Au(I) because otherwise administration of aurothiomalate to a patient with rheumatoid arthritis would be expected to result in peripheral insensitivity to glucocorticoids and worsen the patient's status. Focusing on metal ions that are present in vivo, we found that Zn(II) counteracts the inhibitory effect of Au(I) on glucocorticoid receptor function. This complementary effect of Zn(II) was observed at physiological concentrations. We suggest that Zn(II) preserves glucocorticoid receptor function in target tissues and maintains hormone responsiveness, even with chrysotherapy.

Animals↗