Biomedical subjects

E A Park

Publications and source records attributed to E A Park.

At least 19 recordsLinked to original sources

PubMed2004

Influence of maternal serum levels of vitamins C and E during the second trimester on birth weight and length.

OBJECTIVE: It has been known that maternal oxidative stress during pregnancy plays an important role in fetal growth. However, the association between antioxidant vitamin levels and birth outcomes is not conclusive. We investigated the relationship between maternal serum levels of vitamins C and E during the second trimester and birth weight and length. DESIGN: Prospective cohort study. SETTING: Outpatient-clinic of obstetrics, Ewha Womans University Hospital, South Korea. SUBJECTS AND METHODS: The study subjects were 239 healthy, pregnant women who visited an obstetric clinic for antenatal care, and their singleton live births, in Seoul, Korea, between August 2001 and March 2003. We measured the levels of vitamins C and E in maternal serum during the period 24-28 gestational weeks. Each woman was interviewed for dietary intake by trained interviewers during the second trimester. RESULTS: The serum concentration of maternal vitamin C during the second trimester was significantly associated with birth weight and length in the group of full-term deliveries. An increase of 1 microg/ml in the serum vitamin C level increased the birth weight by 27.2 g and the birth length by 0.17 cm. When we considered the levels of vitamins C and E together in the relationship with birth weight and length, we found that the heaviest birth weight and the longest birth length belonged to the group of upper vitamin C/upper vitamin E. However, dietary intake estimated by 24-h recall method was not a predictor of the levels of serum vitamins C and E. CONCLUSION: We found that maternal serum vitamin C levels during the second trimester were positively correlated with birth weight and length in full-term babies. We also found that birth weight and length were highest when the levels of both vitamins C and E were high. Our results indicate the importance of antioxidant nutrient balance for pregnant women who are exposed to various oxidants through food, drinking water, or inhaled air.

Antioxidants↗

PubMed2001

Long-chain fatty acids regulate liver carnitine palmitoyltransferase I gene (L-CPT I) expression through a peroxisome-proliferator-activated receptor alpha (PPARalpha)-independent pathway.

Liver carnitine palmitoyltransferase I (L-CPT I) catalyses the transfer of long-chain fatty acid (LCFA) for translocation across the mitochondrial membrane. Expression of the L-CPT I gene is induced by LCFAs as well as by lipid-lowering compounds such as clofibrate. Previous studies have suggested that the peroxisome-proliferator-activated receptor alpha (PPARalpha) is a common mediator of the transcriptional effects of LCFA and clofibrate. We found that free LCFAs rather than acyl-CoA esters are the signal metabolites responsible for the stimulation of L-CPT I gene expression. Using primary culture of hepatocytes we found that LCFAs failed to stimulate L-CPT I gene expression both in wild-type and PPARalpha-null mice. These results suggest that the PPARalpha-knockout mouse does not represent a suitable model for the regulation of L-CPT I gene expression by LCFAs in the liver. Finally, we determined that clofibrate stimulates L-CPT I through a classical direct repeat 1 (DR1) motif in the promoter of the L-CPT I gene while LCFAs induce L-CPT I via elements in the first intron of the gene. Our results demonstrate that LCFAs can regulate gene expression through PPARalpha-independent pathways and suggest that the regulation of gene expression by dietary lipids is more complex than previously proposed.

Animals↗

PubMed2001

Differential regulation of carnitine palmitoyltransferase-I gene isoforms (CPT-I alpha and CPT-I beta) in the rat heart.

Carnitine palmitoyltransferase-I (CPT-I) is a major control point for fatty acid oxidation. Two kinetically different isoforms, CPT-I alpha and CPT-I beta, have been identified. Cardiac ventricular myocytes are the only cells known to express both CPT-I isoforms. In this study, we characterized the differential regulation of CPT-I alpha and CPT-I beta expression in the heart. Expression of the CPT-I alpha gene was very high in the fetal heart and declined following birth. CPT-I beta was also highly expressed in fetal myocytes and remained so throughout development. CPT-I alpha mRNA abundance was increased in both the liver and heart of diabetic or fasted rats, but CPT-I beta mRNA levels were not altered in these states. A high fat diet elevated expression of the CPT-I alpha gene in the liver but not in the heart. The fat content of the diet did not affect the expression of CPT-I beta. Cultures of neonatal rat cardiac myocytes were transfected with luciferase reporter genes driven by CPT-I alpha or CPT-I beta promoters. Two regions of the CPT-I alpha promoter, including an upstream region (-1300/-960) and a region in the proximal promoter (-193/-52) contributed equally to basal expression in cardiac myocytes. Basal transcription of CPT-I alpha was dependent on Sp1 sites and a CCAAT box in the proximal promoter. Our data indicate that the CPT-I beta gene is expressed in a tissue specific manner, but that it is not subject to the same developmental or hormonal controls imposed on CPT-I alpha. In addition some aspects of CPT-I alpha expression are confined to the liver. The data presented here thus suggest that two types of differential regulation of CPT-I genes exist: (a) differential control of CPT-I alpha and CPT-I beta gene expression in the heart and (b) differential regulation of CPT-I alpha expression in the heart and liver.

Age Factors↗

PubMed2001

Infantile hemangioendothelioma treated with high dose methylprednisolone pulse therapy.

Infantile hemangioendothelioma is a severe disease with a high mortality. It is characterized by multiple hemangioma affecting the skin and visceral organs. We report that high doses of methylprednisolone pulse therapy improved symptoms and signs of infantile hemangioendothelioma in a male neonate, and completely resolved the hepatic and cutaneous hemangioendothelioma on follow up.

Hemangioendothelioma↗

PubMed2000

Thyroid hormone regulates carnitine palmitoyltransferase Ialpha gene expression through elements in the promoter and first intron.

Carnitine palmitoyltransferase I (CPT-I) catalyzes the transfer of long chain fatty acyl groups from CoA to carnitine for translocation across the mitochondrial inner membrane. CPT-Ialpha is a key regulatory enzyme in the oxidation of fatty acids in the liver. CPT-Ialpha is expressed in all tissues except skeletal muscle and adipose tissue, which express CPT-Ibeta. Expression of CPT-Ialpha mRNA and enzyme activity are elevated in the liver in hyperthyroidism, fasting, and diabetes. CPT-Ialpha mRNA abundance is increased 40-fold in the liver of hyperthyroid compared with hypothyroid rats. Here, we examine the mechanisms by which thyroid hormone (T3) stimulates CPT-Ialpha gene expression. Four potential T3 response elements (TRE), which contain direct repeats separated by four nucleotides, are located 3000-4000 base pairs 5' to the start site of transcription in the CPT-Ialpha gene. However, only one of these elements functions as a TRE. This TRE binds the T3 receptor as well as other nuclear proteins. Surprisingly, the first intron of the CPT-Ialpha gene is required for the T3 induction of CPT-Ialpha expression, but this region of the gene does not contain a TRE. In addition, we show that CPT-Ialpha is induced by T3 in cell lines of hepatic origin but not in nonhepatic cell lines.

Amino Acid Sequence↗

PubMed1999

Expression of the rat liver carnitine palmitoyltransferase I (CPT-Ialpha) gene is regulated by Sp1 and nuclear factor Y: chromosomal localization and promoter characterization.

Carnitine palmitoyltransferase (CPT)-I catalyses the transfer of long-chain fatty acids from CoA to carnitine for translocation across the mitochondrial inner membrane. Expression of the 'liver' isoform of the CPT-I gene (CPT-Ialpha) is subject to developmental, hormonal and tissue-specific regulation. To understand the basis for control of CPT-Ialpha gene expression, we have characterized the proximal promoter of the CPT-Ialpha gene. Here, we report the sequence of 6839 base pairs of the promoter and the localization of the rat CPT-Ialpha gene to region q43 on chromosome 1. Our studies show that the first 200 base pairs of the promoter are sufficient to drive transcription of the CPT-Ialpha gene. Within this region are two sites that bind both Sp1 and Sp3 transcription factors. In addition, nuclear factor Y (NF-Y) binds the proximal promoter. Mutation at the Sp1 or NF-Y sites severely decreases transcription from the CPT-Ialpha promoter. Other protein binding sites were identified within the first 200 base pairs of the promoter by DNase I footprinting, and these elements contribute to CPT-Ialpha gene expression. Our studies demonstrate that CPT-Ialpha is a TATA-less gene which utilizes NF-Y and Sp proteins to drive basal expression.

Animals↗

PubMed1999

Role of CCAAT enhancer-binding protein beta in the thyroid hormone and cAMP induction of phosphoenolpyruvate carboxykinase gene transcription.

Transcription of the gene for phosphoenolpyruvate carboxykinase (PEPCK) is stimulated by thyroid hormone (T3) and cAMP. Two DNA elements in the PEPCK promoter are required for T3 responsiveness including a thyroid hormone response element and a binding site called P3(I) for the CCAAT enhancer-binding protein (C/EBP). Both the alpha and beta isoforms of C/EBP are highly expressed in the liver. C/EBPalpha contributes to the liver-specific expression and cAMP responsiveness of the PEPCK gene. In this study, we examined the ability of C/EBPbeta when bound to the P3(I) site to regulate PEPCK gene expression. We report that C/EBPbeta can stimulate basal expression and participate in the induction of PEPCK gene transcription by T3 and cAMP. The cAMP-responsive element-binding protein and AP1 proteins that contribute to the induction by cAMP are not involved in the stimulation by T3. A small region of the transactivation domain of C/EBPbeta is sufficient for the stimulation of basal expression and cAMP responsiveness. Our results suggest that C/EBPalpha and C/EBPbeta are functionally interchangeable when bound to the P3(I) site of the PEPCK promoter.

Base Sequence↗

PubMed1999

Expression and regulation of carnitine palmitoyltransferase-Ialpha and -Ibeta genes.

Two genes control expression of mitochondrial carnitine palmitoyltransferase-I (CPT-I), the enzyme that catalyzes the primary rate-controlling step in fatty acid oxidation. Two CPT-I isoforms have been found--a "liver" isoform (CPT-Ialpha) expressed in most tissues, but not in skeletal muscles, and a "muscle" isoform (CPT-Ibeta) expressed in muscles and adipocytes. Liver CPT-Ialpha increases dramatically at birth, but heart CPT-Ialpha is abundant in the fetus and diminishes at birth. Insulin, thyroid hormone, and fatty acids regulate expression of CPT-Ialpha in liver, whereas electrical stimulation increases CPT-Ibeta and decreases CPT-Ialpha in cardiac myocytes. Both genes are TATA-less and contain Sp1 transcription factor binding sites upstream of the start site of transcription. Multiple transcripts of both CPT-Ialpha and CPT-Ibeta exist, some of which may have roles in regulating fatty acid oxidation.

Animals↗

PubMed1998

Characterization of CCAAT/enhancer-binding protein alpha as a cyclic AMP-responsive nuclear regulator.

The alpha isoform of CCAAT/enhancer-binding protein (C/EBPalpha) is a transcription factor that regulates expression of genes linked to adipose differentiation and hepatic nutrient metabolism. Recently, our laboratory has characterized a role for C/EBPalpha in mediating hormonal responsiveness. For example, the cAMP responsiveness of the phosphoenolpyruvate carboxykinase gene promoter in liver requires synergism among the cAMP response element-binding protein (CREB), C/EBPalpha, and activator protein-1. In the present study, we show that C/EBPalpha can functionally substitute for CREB in this cAMP response unit, i.e. cAMP responsiveness can occur in the absence of CREB. This observation is physiologically relevant since both CREB and C/EBPalpha have been shown to bind with high affinity to the cAMP response element in this particular promoter. Structure/function analysis of C/EBPalpha identified specific mutations that differentially affected its constitutive and protein kinase A-inducible activities. This finding suggests that the mechanism whereby C/EBPalpha mediates constitutive transactivation is distinct from that whereby it mediates cAMP responsiveness. These data support the hypothesis that C/EBPalpha plays a critical role in metabolism, in part by participating in the hormonal regulation of expression of metabolically important genes.

CCAAT-Enhancer-Binding Proteins↗

PubMed1998

Cloning and characterization of the promoter for the liver isoform of the rat carnitine palmitoyltransferase I (L-CPT I) gene.

Carnitine palmitoyltransferase I (CPTI) catalyses the transfer of long chain fatty acids to carnitine for translocation across the mitochondrial inner membrane. The cDNAs of two isoforms of CPT I, termed the hepatic and muscle isoforms, have been cloned. Expression of the hepatic CPT I gene (L-CPT I) is subject to developmental, hormonal and tissue specific regulation. We have cloned the promoter of the L-CPTI gene from a rat genomic library. In the L-CPTI gene, there are two exons 5' to the exon containing the ATG that initiates translation. Exon 1 and the 5' end of exon 2 contain sequences that were not previously described in the rat L-CPTI cDNA. There is an alternatively spliced form of the L-CPTI mRNA in which exon 2 is skipped. The proximal promoter of the L-CPTI gene is extremely GC rich and does not contain a TATA box. There are several putative Sp1 binding sites near the transcriptional start site. A 190 base pair fragment of the promoter can efficiently drive transcription of luciferase and CAT (chloramphenicol acetyltransferase) reporter genes transiently transfected into HepG2 cells. Sequences in both the first intron and the promoter contribute to basal expression. Our results provide the foundation for further studies into the regulation of L-CPTI gene expression.

Alternative Splicing↗

PubMed1998

Identification of a retinoic acid response domain involved in the activation of the beta 1-adrenergic receptor gene by retinoic acid in F9 teratocarcinoma cells.

The density of beta 1-adrenergic receptors (beta 1-AR) is up-regulated upon differentiation of embryonic F9 teratocarcinoma cells by retinoic acid (RA) to the primitive endodermal phenotype. To identify the domains involved in RA-mediated activation of beta 1-AR gene transcription, three kb of 5'-flanking sequence of the beta 1-AR gene were ligated to a luciferase reporter gene and transiently transfected into F9 cells that were pre-exposed to 100 nM RA for 2 days. By generating deletions in the beta 1-AR promoter, a region between -125 and -100 was found to mediate a 3-fold induction in cells exposed to RA for an additional 2 days. Through site-directed mutagenesis of this region, it was determined that the RA responsive element (RARE) was organized as a direct repeat separated by 5 nucleotides in which the 5'-most AGGTCG half-site was between nucleotides -106 and -101 and the 3'-most AGGTCA half-site was between nucleotides -117 and -112. The RA receptor alpha (RAR alpha) isoform bound to the oligomer representing the sequences between -125 and -100 as a heterodimer complex with the retinoid X receptor alpha (RXR alpha). In a separate study, it was determined that the nucleotides between -125 and -100 are involved in thyroid hormone-mediated activation of the beta 1-AR gene in ventricular myocytes. Therefore, transcriptional activation of the beta 1-AR gene by thyroid hormone or RA involves a single binding site in the promoter.

Animals↗

PubMed1998

Hormone response units: one plus one equals more than two.

The transcription rate of many genes, and particularly those which code for metabolically important proteins, is regulated by various hormones. Detailed analysis of the promoters of these genes has shown that, while functional 'Hormone response elements' exist, the hormonal responsiveness of many promoters is often synergistically mediated by several cis-elements, collectively referred to as a hormone response unit. The utilization of a hormone response unit to mediate a response offers several regulatory advantages, including an expansion of the range of transcriptional responses and modulation of the response by tissue- and developmental-specific cues. Furthermore, the presence of Hormone Response Units may provide a mechanism for the coordination of information from two or more signaling pathways into a single, integrated and exquisitely controlled transcriptional response. The protein-protein interactions that likely mediate many of the synergistic functional characteristics of Hormone Response Units may provide unique targets for therapeutic intervention.

Animals↗

PubMed1998

Differential regulation in the heart of mitochondrial carnitine palmitoyltransferase-I muscle and liver isoforms.

Carnitine palmitoyltransferase-I (CPT-I) plays a crucial role in regulating cardiac fatty acid oxidation which provides the primary source of energy for cardiac muscle contraction. CPT-I catalyzes the transfer of long chain fatty acids into mitochondria and is recognized as the primary rate controlling step in fatty acid oxidation. Molecular cloning techniques have demonstrated that two CPT-I isoforms exist as genes encoding the 'muscle' and 'liver' enzymes. Regulation of fatty acid oxidation rates depends on both short-term regulation of enzyme activity and long-term regulation of enzyme synthesis. Most early investigations into metabolic control of fatty acid oxidation at the CPT-I step concentrated on the hepatic enzyme which can be inhibited by malonyl-CoA and can undergo dramatic amplification or reduction of its sensitivity to inhibition by malonyl-CoA. The muscle CPT-I is inherently more sensitive to malonyl-CoA inhibition but has not been found to undergo any alteration of its sensitivity. Short-term control of activity of muscle CPT-I is apparently regulated by malonyl-CoA concentration in response to fuel supply (glucose, lactate, pyruvate and ketone bodies). The liver isoform is the only CPT-I enzyme present in the mitochondria of liver, kidney, brain and most other tissues while muscle CPT-I is the sole isoform expressed in skeletal muscle as well as white and brown adipocytes. The heart is unique in that it contains both muscle and liver isoforms. Liver CPT-I is highly expressed in the fetal heart, but at birth its activity begins to decline whereas the muscle isoform, which is very low at birth, becomes the predominant enzyme during postnatal development. In this paper, the differential regulation of the two CPT-I isoforms at the protein and the gene level will be discussed.

Amino Acid Sequence↗

PubMed1997

CCAAT-enhancer-binding protein alpha (C/EBP alpha) is required for the thyroid hormone but not the retinoic acid induction of phosphoenolpyruvate carboxykinase (PEPCK) gene transcription.

Transcription of the gene for phosphoenolpyruvate carboxykinase (PEPCK) is stimulated by cAMP, the thyroid hormone tri-iodothyronine (T3) and retinoic acid (RA). Regulation of PEPCK transcription by T3 involves two sites in the promoter including a thyroid-hormone-response element (TRE) and a CCAAT-enhancer-binding protein (C/EBP) binding site called P3I. Mutation of either the TRE or P3I eliminates the T3 response. In this study, we examined the role of C/EBPs in the induction of PEPCK transcription by T3 and RA. PEPCK-CAT vectors were transfected into HepG2 cells. Co-transfection of a dominant negative C/EBP eliminated the T3 stimulation indicating that a member of the C/EBP family is required. To determine which C/EBP isoform was required, Gal4 fusion proteins were created that contained the Gal4 DNA-binding domain ligated to the transcriptional activation domain of C/EBP alpha, C/EBP beta or the cAMP-responsive-element-binding protein. A Gal4 DNA-binding site was introduced into the P3(I) site of the PEPCK-CAT vector. Only co-transfection of the Gal4-C/EBP alpha vector was able to restore T3 responsiveness to the PEPCK-CAT vector. The T3 and RA receptors are members of the nuclear receptor superfamily and bind to repeats of the AGGTCA motif. We found that the RA receptor can bind to sequences within the PEPCK-TRE and contribute to RA responsiveness of the PEPCK gene. However, the RA induction of PEPCK transcription was found to be independent of C/EBPs, further demonstrating the specificity of the involvement of C/EBP alpha in the T3 effect.

Binding Sites↗

PubMed1997

Thyroid hormone induces beta1-adrenergic receptor gene transcription through a direct repeat separated by five nucleotides.

Transcription of the rat gene for the beta1-adrenergic receptor (beta1-AR) is stimulated by thyroid hormone (T3) in ventricular myocytes. To identify the domains involved in the regulation of beta1-AR gene transcription by T3, three kb of 5'-flanking sequence of the rat beta1-AR gene were ligated to a luciferase reporter gene and transiently transfected into ventricular myocytes. By generating deletions in the rat beta1-AR promoter, a region between -125 and -100 was found to mediate a three-fold induction by T3. This element was able to confer T3 responsiveness to a neutral promoter driving the luciferase reporter gene. Through site directed mutagenesis of this region, it was determined that the T3 responsive element (TRE) was organized as a direct repeat separated by five nucleotides in which the 5'-most AGGTCG half-site was between nucleotides -105 to -102 and the 3'-most AGGTCA half-site between nucleotides -116 and -113. Both the thyroid hormone receptor isoforms alpha and beta bound to the oligomer representing the sequences between -125 and -100 most efficiently as heterodimers with the retinoid X receptor. This TRE is unusual in that it is a direct repeat separated by five nucleotides which is located 3' to the transcriptional start site.

Animals↗

PubMed1997

Promoter analysis of the rat beta1-adrenergic receptor gene identifies sequences involved in basal expression.

The beta1-adrenergic receptor (beta1-AR) mediates several functions of catecholamines in the heart, including the stimulation of heart rate and contractility. The expression of the rat beta1-AR gene was assessed by transiently transfecting chimeric genes containing the beta1-AR promoter, driving the luciferase reporter gene into various cell lines. beta1-AR/luciferase vectors containing 3 kb of the 5'-flanking region and extending to -126 relative to the start site of translation were expressed at high levels in ventricular myocytes, SK-N-MC cells, and HepG2 cells. The addition of 26 nucleotides from -125 to -100 to the -3311 beta1-AR/luciferase chimeric gene reduced expression in myocytes and SK-N-MC cells while eliminating expression in HepG2 cells. This element is located 125 base-pairs 3' to the transcriptional start site. The mutation of four nucleotides between -121 and -118 diminished the inhibitory effect of this element. The inhibitory activity of the -125 to -100 sequence was completely dependent on promoter context and positioning. In addition to this 3' element, sequences between -3311 and -2740 in the 5'-flanking region of the beta1-AR gene were required for the full transcriptional suppression. Using DNase I footprinting and gel mobility assays, it was determined that within the 26-bp region, rat heart nuclear proteins bound to two sites between nucleotides -123 and -112 and -106 and -100. Therefore, appropriate basal expression of the beta1-AR gene involves widely separated sequences 3' and 5' to the transcriptional start site.

Animals↗

PubMed1996

Identification of a glucocorticoid repressor domain in the rat beta 1-adrenergic receptor gene.

The expression of the gene encoding the rat beta 1-adrenergic receptor is suppressed by glucocorticoids (Kiely et al., 1994). Within the 3.2-kb 5'-flanking region of the promoter, two potential glucocorticoid response elements (GREs) at -950 and -2791 relative to the translational ATG were identified. Characterization of the glucocorticoid-responsive sequences in the 5'-flanking region of the beta 1-adrenergic receptor gene was explored in rat C6 glioma cells and human HepG2 hepatoma cells using transient expression of beta 1-adrenergic receptor-luciferase fusion genes. The ability of glucocorticoids to suppress luciferase expression was not altered when the most 5'-localized GRE was deleted. Deleting the potential GRE at -950, in contrast, abolished glucocorticoid-induced suppression of the beta 1-adrenergic receptor-luciferase gene transcription. A 25-bp element containing the GRE sequence between nucleotides -950 and -926 confers glucocorticoid-dependent inhibition of transcription to a neutral promoter. Gel mobility shift assays with the alpha-subunit of the human glucocorticoid receptor (hGR alpha) expressed in reticulocyte lysates demonstrated specific binding to the 25-bp sequence harboring the putative GRE. We report an inhibitory GRE in the promoter of the rat beta 1-adrenergic receptor gene that is conserved among the rat, human, and mouse genes.

Animals↗

PubMed1995

Insulin regulates enzyme activity, malonyl-CoA sensitivity and mRNA abundance of hepatic carnitine palmitoyltransferase-I.

The regulation of hepatic mitochondrial carnitine palmitoyltransferase-I (CPT-I) was studied in rats during starvation and insulin-dependent diabetes and in rat H4IIE cells. The Vmax. for CPT-I in hepatic mitochondrial outer membranes isolated from starved and diabetic rats increased 2- and 3-fold respectively over fed control values with no change in Km values for substrates. Regulation of malonyl-CoA sensitivity of CPT-I in isolated mitochondrial outer membranes was indicated by an 8-fold increase in Ki during starvation and by a 50-fold increase in Ki in the diabetic state. Peroxisomal and microsomal CPT also had decreased sensitivity to inhibition by malonyl-CoA during starvation. CPT-I mRNA abundance was 7.5 times greater in livers of 48-h-starved rats and 14.6 times greater in livers of insulin-dependent diabetic rats compared with livers of fed rats. In H4IIE cells, insulin increased CPT-I sensitivity to inhibition by malonyl-CoA in 4 h, and sensitivity continued to increase up to 24 h after insulin addition. CPT-I mRNA levels in H4IIE cells were decreased by insulin after 4 h and continued to decrease so that at 24 h there was a 10-fold difference. The half-life of CPT-I mRNA was 4 h in the presence of actinomycin D or with actinomycin D plus insulin. These results suggest that insulin regulates CPT-I by inhibiting transcription of the CPT-I gene.

Animals↗