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ABSTRACT: Dietary n-3 polyunsaturated fatty acids (n-3 PUFAs) have well-documented protective effects against obesity-induced insulin resistance and hepatic steatosis. Here, we investigated the effects of endogenous n-3 PUFAs on diet-induced fatty liver disease using fat-1 transgenic mice (fat-1) capable of converting n-6 to n-3 PUFAs. Wild-type (WT) and fat-1 mice were maintained on a high-fat diet (HFD) for 5months. HFD-induced weight gain and fatty liver were more prominent in WT mice than fat-1 mice. Histological analysis indicated that WT mice fed the HFD developed moderate-to-severe macrovesicular steatosis, whereas fat-1 mice developed very mild steatosis. In addition, HFD-induced hepatocyte ballooning and fibrosis were ameliorated in fat-1 mice. Serum alanine transaminase (ALT) and aspartate transaminase (AST) levels were within the respective normal ranges in HFD-fed fat-1 mice, whereas both were significantly elevated in HFD-fed WT mice. The fat-1 mice showed significantly decreased serum lipid levels, including triglycerides, total cholesterol (TC), HDL-C, and LDL-C, compared to WT mice regardless of diet. Specifically, the increases in very low-density lipoprotein cholesterol (VLDL-C) and chylomicrons detected in HFD-fed WT mice were completely blunted in HFD-fed fat-1 mice. Gene expression analysis showed that hepatic Cyp7a1 mRNA and protein expression levels were markedly increased in HFD-fed fat-1 mice. In addition, genes involved in cholesterol uptake (Ldlr) and bile acid excretion (Abcg5 and Abcg8) were increased in the livers of fat-1 mice. These data suggest that n-3 PUFAs ameliorate diet-induced hyperlipidemia and fatty liver through induction of CYP7A1 expression and activation of cholesterol catabolism to bile acid.
Biochemical pharmacology 09/2012; 84(10):1359-65. · 4.25 Impact Factor
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ABSTRACT: A two-component system comprising GacS and GacA affects a large number of traits in many Gram-negative bacteria. However, the signals to which GacS responds, the regulation mechanism for GacA expression, and the genes GacA controls are not yet clear. In this study, several phenotypic tests and tobacco-leaf pathogenicity assays were conducted using a gacA deletion mutant strain (BL473) of Pseudomonas syringae pv. tabaci 11528. To determine the regulation mechanism for gacA gene expression and to identify GacA-regulated genes, we conducted quantitative RT-PCR and electrophoretic mobility shift assay (EMSA) experiments. The results indicated that virulence traits related to the pathogenesis of P. syringae pv. tabaci 11528 are regulated coordinately by GacA and iron availability. They also revealed that several systems coordinately regulate gacA gene expression in response to iron concentration and bacterial cell density and that GacA and iron together control the expression of several virulence genes. EMSA results provided genetic and molecular evidence for direct control of virulence genes by GacA.
Biochemical and Biophysical Research Communications 12/2011; 417(2):665-72. · 2.48 Impact Factor
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ABSTRACT: Pseudomonas syringae pv. tabaci causes wildfire disease in tobacco plants. The hrp pathogenicity island (hrp PAI) of P. syringae pv. tabaci encodes a type III secretion system (TTSS) and its regulatory system, which are required for pathogenesis in plants. Three important regulatory proteins-HrpR, HrpS, and HrpL-have been identified to activate hrp PAI gene expression. The bacterial Lon protease regulates the expression of various genes. To investigate the regulatory mechanism of the Lon protease in P. syringae pv. tabaci 11528, we cloned the lon gene, and then a Δlon mutant was generated by allelic exchange. lon mutants showed increased UV sensitivity, which is a typical feature of such mutants. The Δlon mutant produced higher levels of tabtoxin than the wild-type. The lacZ gene was fused with hrpA promoter and activity of β-galactosidase was measured in hrp-repressing and hrp-inducing media. The Lon protease functioned as a negative regulator of hrp PAI under hrp-repressing conditions. We found that strains with lon disruption elicited the host defense system more rapidly and strongly than the wild-type strain, suggesting that the Lon protease is essential for systemic pathogenesis.
Molecules and Cells 09/2011; 32(4):317-23. · 2.18 Impact Factor
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Yun-Seung Jeong,
Deokhoon Kim,
Yong Seok Lee,
Ha-Jung Kim,
Jung-Youn Han,
Seung-Soon Im,
Hansook Kim Chong,
Je-Keun Kwon,
Yun-Ho Cho,
Woo Kyung Kim,
Timothy F Osborne,
Jay D Horton,
Hee-Sook Jun,
Yong-Ho Ahn,
Sung-Min Ahn, Ji-Young Cha
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ABSTRACT: The carbohydrate response element binding protein (ChREBP), a basic helix-loop-helix/leucine zipper transcription factor, plays a critical role in the control of lipogenesis in the liver. To identify the direct targets of ChREBP on a genome-wide scale and provide more insight into the mechanism by which ChREBP regulates glucose-responsive gene expression, we performed chromatin immunoprecipitation-sequencing and gene expression analysis. We identified 1153 ChREBP binding sites and 783 target genes using the chromatin from HepG2, a human hepatocellular carcinoma cell line. A motif search revealed a refined consensus sequence (CABGTG-nnCnG-nGnSTG) to better represent critical elements of a functional ChREBP binding sequence. Gene ontology analysis shows that ChREBP target genes are particularly associated with lipid, fatty acid and steroid metabolism. In addition, other functional gene clusters related to transport, development and cell motility are significantly enriched. Gene set enrichment analysis reveals that ChREBP target genes are highly correlated with genes regulated by high glucose, providing a functional relevance to the genome-wide binding study. Furthermore, we have demonstrated that ChREBP may function as a transcriptional repressor as well as an activator.
PLoS ONE 01/2011; 6(7):e22544. · 4.09 Impact Factor
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Sung-Min Ahn,
Tae-Hyung Kim,
Sunghoon Lee,
Deokhoon Kim,
Ho Ghang,
Dae-Soo Kim,
Byoung-Chul Kim,
Sang-Yoon Kim,
Woo-Yeon Kim,
Chulhong Kim, [......],
Yong Seok Lee,
Sangsoo Kim,
Rohit Reja,
Sungwoong Jho,
Chang Geun Kim, Ji-Young Cha,
Kyung-Hee Kim,
Bonghee Lee,
Jong Bhak,
Seong-Jin Kim
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ABSTRACT: We present the first Korean individual genome sequence (SJK) and analysis results. The diploid genome of a Korean male was sequenced to 28.95-fold redundancy using the Illumina paired-end sequencing method. SJK covered 99.9% of the NCBI human reference genome. We identified 420,083 novel single nucleotide polymorphisms (SNPs) that are not in the dbSNP database. Despite a close similarity, significant differences were observed between the Chinese genome (YH), the only other Asian genome available, and SJK: (1) 39.87% (1,371,239 out of 3,439,107) SNPs were SJK-specific (49.51% against Venter's, 46.94% against Watson's, and 44.17% against the Yoruba genomes); (2) 99.5% (22,495 out of 22,605) of short indels (< 4 bp) discovered on the same loci had the same size and type as YH; and (3) 11.3% (331 out of 2920) deletion structural variants were SJK-specific. Even after attempting to map unmapped reads of SJK to unanchored NCBI scaffolds, HGSV, and available personal genomes, there were still 5.77% SJK reads that could not be mapped. All these findings indicate that the overall genetic differences among individuals from closely related ethnic groups may be significant. Hence, constructing reference genomes for minor socio-ethnic groups will be useful for massive individual genome sequencing.
Genome Research 07/2009; 19(9):1622-9. · 13.61 Impact Factor
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ABSTRACT: Liver glucokinase (LGK) plays an essential role in controlling blood glucose levels and maintaining cellular metabolic functions. Expression of LGK is induced mainly regulated by insulin through sterol regulatory element-binding protein-1c (SREBP-1c) as a mediator. Since LGK expression is known to be decreased in the liver of liver X receptor (LXR) knockout mice, we have investigated whether LGK might be directly activated by LXRalpha. Furthermore, we have studied interrelationship between transcription factors that control gene expression of LGK. In the current studies, we demonstrated that LXRalpha increased LGK expression in primary hepatocytes and that there is a functional LXR response element in the LGK gene promoter as shown by electrophoretic mobility shift and chromatin precipitation assay. In addition, our studies demonstrate that LXRalpha and insulin activation of the LGK gene promoter occurs through a multifaceted indirect mechanism. LXRalpha increases SREBP-1c expression and then insulin stimulates the processing of the membrane-bound precursor SREBP-1c protein, and it activates LGK expression through SREBP sites in its promoter. LXRalpha also activates the LGK promoter by increasing the transcriptional activity and induction of peroxisome proliferator-activated receptor (PPAR)-gamma, which also stimulates LGK expression through a peroxisome proliferator-responsive element. This activation is tempered through a negative mechanism, where a small heterodimer partner (SHP) decreases LGK gene expression by inhibiting the transcriptional activity of LXRalpha and PPARgamma by directly interacting with their common heterodimer partner RXRalpha. From these data, we propose a mechanism for LXRalpha in controlling the gene expression of LGK that involves activation through SREBP-1c and PPARgamma and inhibition through SHP.
Journal of Biological Chemistry 05/2009; 284(22):15071-83. · 4.77 Impact Factor
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ABSTRACT: Hepatic glucokinase (LGK) plays an essential role in controlling blood glucose levels and maintaining cellular metabolic functions
in liver. Expression of LGK is induced mainly regulated by insulin through sterol regulatory element binding protein-1c (SREBP-1c)
as a mediator. Since glucokinase expression is known to be decreased in the liver of liver X receptor (LXR) knock out mice,
we have investigated whether glucokinase might be directly activated by LXRα. Furthermore, we have studied interrelationship
between transcription factors that control gene expression of LGK. In the current studies, we demonstrated that LXRα increased
LGK expression in primary hepatocytes and that there is a functional LXRE in the LGK gene promoter as shown by EMSA and ChIP
assay. In addition, our studies demonstrate that LXRα and insulin activation of the LGK gene promoter occurs through a multi-faceted
indirect mechanism. LXRα increases SREBP-1c expression and then insulin stimulates the processing of the membrane bound precursor
SREBP-1c protein and it activates LGK expression through SREBP sites in its promoter. LXRα also activates the LGK promoter
by increasing the transcriptional activity and induction of peroxisome proliferators-activated receptor (PPAR)-γ, which also
stimulates LGK expression through a PPRE. This activation is tempered through a negative mechanism where small heterodimer
partner (SHP) decreases LGK gene expression by inhibiting the transcriptional activity of LXRα and PPARγ by directly interacting
with their common heterodimer partner RXRα. From these data, we propose a mechanism for LXRα in controlling the gene expression
of LGK that involves activation through SREBP-1c and PPARγ and inhibition through SHP.
Journal of Biological Chemistry 04/2009; · 4.77 Impact Factor
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ABSTRACT: In this paper, we have suggested a novel method to monitor respiration and heart rate using a PPG pillow during sleep. The proposed method employs a pillow containing a reflective type PPG sensor and a simple extraction algorithm. The PPG pillow was placed under the back of a neck to acquire PPG signal on the assumption that the subjects hardly change their position. The results showed considerable coincidence between the extracted respiratory rhythm and the reference signal in case of either a medium or a high respiration speed, while it was hard to extract the rhythm based on the trace line formed by linear interpolating the detected valleys under the condition of a low respiration speed. HRV could be alternative to the interpolated trace line in the case. This study shows the proposed method has an advantage of processing simplicity so as to be used easily in unconstrained respiration and heart rate monitoring.
Engineering in Medicine and Biology Society, 2008. EMBS 2008. 30th Annual International Conference of the IEEE; 09/2008
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ABSTRACT: In most bacteria, Fur (ferric uptake regulator) is a crucial global regulator known to operate not only in the regulation of iron homeostasis but also in a variety of other cellular processes. In an effort to characterize the role of Fur in the virulence of plant pathogens, a fur homolog was isolated from Pseudomonas syringae pv. tabaci 11528. Phenotype assays showed that a fur deletion mutant (BL33) constitutively produced siderophore(s) and exhibited decreases in swarming motility as well as the synthesis of tabtoxin and N-acyl homoserine lactones. Consistent with the results of TLC, quantitative real-time RT-PCR of the QS associated genes psyR and psyI demonstrated that Fur up-regulates these genes at the transcriptional level. Finally, the effects of a fur mutation on plant virulence indicated that Fur-regulated traits are relevant to plant-pathogen interactions.
Biochemical and Biophysical Research Communications 03/2008; 366(2):281-7. · 2.48 Impact Factor
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ABSTRACT: In this paper, we have suggested a novel method to monitor respiration and heart rate using a PPG pillow during sleep. The proposed method employs a pillow containing a reflective type PPG sensor and a simple extraction algorithm. The PPG pillow was placed under the back of a neck to acquire PPG signal on the assumption that the subjects hardly change their position. The results showed considerable coincidence between the extracted respiratory rhythm and the reference signal in case of either a medium or a high respiration speed, while it was hard to extract the rhythm based on the trace line formed by linear interpolating the detected valleys under the condition of a low respiration speed. HRV could be alternative to the interpolated trace line in the case. This study shows the proposed method has an advantage of processing simplicity so as to be used easily in unconstrained respiration and heart rate monitoring.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2008; 2008:3224-6.
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Cheol Won Park,
Young Mi Park,
Geun Taek Lee,
Yongho Lee,
Seonock Woo, Ji-Young Cha,
Chul Woo Ahn,
Bong Soo Cha,
Kyung-Sup Kim,
Yong-ho Ahn,
Hyun Chul Lee
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ABSTRACT: To achieve the liver-directed expression in sufficient amounts of therapeutic genes for successful and safe gene therapy, natural liver-specific promoters can be used to direct the expression of therapeutic genes in the liver, whereas strong viral enhancers were used to obtain sufficient amounts of expressed therapeutic gene products. However, very often use of either the former or the latter does not guarantee both potent and liver-specific therapeutic gene expression. Here we conglomerate them and thus create a potent tissue-specific promoter by characterizing and using the liver-type pyruvate kinase proximal promoter (LPKPP) harboring its TATA box and a HNF-1alpha binding site. Alone it hardly activated its reporter gene expression in non-hepatocytes or hepatocytes. However, in the presence of the SV40 viral enhancer (SV40VE), which is active in multiple cell types, it was able to potently activate its reporter gene expression specifically in hepatocytes. The tissue-specific activation of the LPKPP by the viral enhancer was attributed to HNF-1alpha binding to the LPKPP. Taken together, these results support the idea that the constitutively active SV40VE could be used to activate the LPKPP in a tissue-specific manner in the presence of HNF-1alpha. To our knowledge, this is the first study to utilize HNF-1alpha and its binding site, in the context of the LPKPP, to generate a basal promoter that is transcriptionally activated potently in a tissue-specific manner by a viral enhancer that is active in multiple cell types.
Biochemical and Biophysical Research Communications 02/2004; 314(1):131-7. · 2.48 Impact Factor
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ABSTRACT: Thiazolidinediones, synthetic ligands of peroxisomal proliferator-activated receptor-gamma (PPAR-gamma), improve peripheral insulin sensitivity and glucose-stimulated insulin secretion in pancreatic beta-cells. To explore the role of PPAR-gamma in glucose sensing of beta-cells, we have dissected the beta-cell-specific glucokinase (betaGK) promoter, which constitutes glucose-sensing apparatus in pancreatic beta-cells, and identified a peroxisomal proliferator response element (PPRE) in the promoter. The betaGK-PPRE is located in the region between +47 and +68 bp. PPAR-gamma/retinoid X receptor-alpha heterodimer binds to the element and activates the betaGK promoter. The betaGK promoter lacking or having mutations in PPRE cannot be activated by PPAR-gamma. PPAR-gamma activates the betaGK promoter in beta-cells as well as non-beta-cells. Furthermore, troglitazone increases endogenous GK expression and its enzyme activity in beta-cell lines. These results indicate that PPAR-gamma can regulate GK expression in beta-cells. Taking these results together with our previous work, we conclude that PPAR-gamma regulates gene expression of glucose-sensing apparatus and thereby improves glucose-sensing ability of beta-cells, contributing to the restoration of beta-cell function in type 2 diabetic subjects by troglitazone.
Diabetes 04/2002; 51(3):676-85. · 8.29 Impact Factor
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ABSTRACT: Glucose transporter type 2 (GLUT2), along with glucokinase, has been implicated to participate in glucose-induced insulin secretion in pancreatic beta-cells. Recently, several sequence variations in the promoter of GLUT2 have been identified in patients with non-insulin dependent diabetes mellitus (NIDDM), but the functional effects of these polymorphisms on promoter activity have not previously been studied. We compared the incidence of sequence variations in the GLUT2 promoter in 100 normal subjects and 100 NIDDM patients. Sequencing of the promoter region (-294 to +301) revealed that an A --> G variant at position -44 was found in 45 of 100 NIDDM patients, but only in 23 of 100 normal subjects. In addition, -269 A --> C and + 103 A --> G mutations were identified in a single diabetic patient. Electrophoretic mobility shift assays using double-stranded oligonucleotide containing -44A as a probe showed a clearly shifted band of DNA-protein. To examine whether the sequence variation at position -44 affects the promoter activity, we carried out in vitro transfection experiments. Site-specific mutagenesis at position -44 region from A to C, T, or G resulted in reductions of CAT activity by 52.3%, 63.8%, and 63.6%, respectively. The -269 A --> C and + 103 A --> G mutations also decreased the promoter activity. These results suggest that polymorphisms at positions -269, -44, or + 103 may affect GLUT2 gene transcription, possibly associated with reduced expression of the GLUT2 gene in NIDDM patients.
Annals of clinical and laboratory science 01/2002; 32(2):114-22. · 0.96 Impact Factor
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ABSTRACT: We investigated transacting factors binding to the cis-element important in tissue-specific expression of the human glucose
transporter type 2 isoform (GLUT2) gene. By transient transfection assay, we determined that the 227-base pair fragment upstream
of the ATG start site contained promoter activity and that the region from +87 to +132 (site C) was responsible for tissue-specific
expression. DNase I footprinting and electrophoretic mobility shift assay indicated that site C contained one binding site
for hepatocyte nuclear factor 1 (HNF1) and two binding sites for HNF3. The mutations at positions +101 and +103, which are
considered to be critical in binding HNF1 and HNF3, resulted in a 53% decrease in promoter activity, whereas the mutation
of the proximal HNF3 binding site (+115 and +117) reduced promoter activity by 28%. The mutations of these four sites resulted
in marked decrease (70%) in promoter activity as well as diminished bindings of HNF1 and HNF3. A to G mutation, which causes
conversion of the HNF1 and HNF3 binding sequence to the NF-Y binding site, resulted in a 22% decrease in promoter activity.
We identified that both HNF1 and HNF3 function as transcriptional activators in GLUT2 gene expression. Coexpression of the
pGL+74 (+74 to +301) construct with the HNF1α and HNF3β expression vectors in NIH 3T3 cells showed the synergistic effect
on GLUT2 promoter activity compared with the expression of HNF1α, HNF3β, or a combination of HNF1β and HNF3β. These data suggest
that HNF1α and HNF3β may be the most important players in the tissue-specific expression of the human GLUT2 gene.
Journal of Biological Chemistry 06/2000; 275(24):18358-18365. · 4.77 Impact Factor
