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  • 1
    Online Resource
    Online Resource
    MicroRNA-494 regulates mitochondrial biogenesis in skeletal muscle through mitochondrial transcription factor A and Forkhead box j3
    American Physiological Society ; 2012
    In:  American Journal of Physiology-Endocrinology and Metabolism Vol. 303, No. 12 ( 2012-12-15), p. E1419-E1427
    Details
    In: American Journal of Physiology-Endocrinology and Metabolism, American Physiological Society, Vol. 303, No. 12 ( 2012-12-15), p. E1419-E1427
    Abstract: MicroRNAs (miRNAs) are important posttranscriptional regulators of various biological pathways. In this study, we focused on the role of miRNAs during mitochondrial biogenesis in skeletal muscle. The expression of miR-494 was markedly decreased in murine myoblast C 2 C 12 cells during myogenic differentiation, accompanied by an increase in mtDNA. Furthermore, the expression of predicted target genes for miR-494, including mitochondrial transcription factor A (mtTFA) and Forkhead box j3 (Foxj3), was posttranscriptionally increased during myogenic differentiation. Knockdown of miR-494 resulted in increased mitochondrial content and upregulation of mtTFA and Foxj3 at the protein level. A 3′-untranslated region reporter assay revealed that miR-494 knockdown directly upregulated the luciferase activity of mtTFA and Foxj3. All of these observations were reversed by overexpression of miR-494. Furthermore, the miR-494 content significantly decreased after endurance exercise in C57BL/6J mice, accompanied by an increase in expression of mtTFA and Foxj3 proteins. These results suggest that miR-494 regulates mitochondrial biogenesis by downregulating mtTFA and Foxj3 during myocyte differentiation and skeletal muscle adaptation to physical exercise.
    Type of Medium: Online Resource
    ISSN: 0193-1849 , 1522-1555
    URL: Article
    DOI: 10.1152/ajpendo.00097.2012
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2012
    detail.hit.zdb_id: 1477331-4
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  • 2
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    Online Resource
    Bidirectional regulation of monocyte chemoattractant protein-1 gene at distinct sites of its promoter by nitric oxide in vascular smooth muscle cells
    American Physiological Society ; 2005
    In:  American Journal of Physiology-Cell Physiology Vol. 289, No. 3 ( 2005-09), p. C582-C590
    Details
    In: American Journal of Physiology-Cell Physiology, American Physiological Society, Vol. 289, No. 3 ( 2005-09), p. C582-C590
    Abstract: We have previously reported that chronic activation of phosphatidylinositol 3-kinase (PI3-kinase) by the overexpression of membrane-targeted p110CAAX induced proinflammatory gene expression in rat vascular smooth muscle cells (VSMCs) through the induction of CCAAT/enhancer binding protein-β (C/EBP-β) and C/EBP-δ. To examine the anti-inflammatory effect of nitric oxide (NO) on proinflammatory gene expression, we have investigated the effects of sodium nitroprusside (SNP) on the monocyte chemoattractant protein-1 (MCP-1) gene expression in VSMCs under chronic activation of PI3-kinase. At low concentrations (0.05 mM) of SNP, but not at high concentrations (0.5–1.0 mM), MCP-1 mRNA and protein expression as well as its transcriptional activity were significantly reduced. We found that SNP induced C/EBP homologous protein (CHOP) expression, which inhibited C/EBP binding activity and reduced the C/EBP activity induced by chronic activation of PI3-kinase in a dose-dependent manner up to 1.0 mM. Consistently, the increase in CHOP expression significantly reduced the MCP-1 promoter activity induced by PI3-kinase. However, the overexpression of CHOP alone upregulated MCP-1 promoter activity in a dose-dependent manner up to high concentrations. Deletion analysis of MCP-1 promoter and electrophoretic mobility shift assay identified the CHOP-response element (CHOP-RE) at the region between −190 and −179 bp of MCP-1 promoter. By using CHOP-RE as a decoy, we significantly suppressed the increase in promoter activity of MCP-1 induced by either CHOP or SNP. Thus CHOP induced by an NO donor has bidirectional effects on MCP-1 gene expression: it decreases gene expression by inhibition of C/EBPs, and it increases the gene expression through CHOP-RE.
    Type of Medium: Online Resource
    ISSN: 0363-6143 , 1522-1563
    URL: Article
    DOI: 10.1152/ajpcell.00558.2004
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2005
    detail.hit.zdb_id: 1477334-X
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  • 3
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    Online Resource
    Ezetimibe prevents hepatic steatosis induced by a high-fat but not a high-fructose diet
    American Physiological Society ; 2013
    In:  American Journal of Physiology-Endocrinology and Metabolism Vol. 305, No. 2 ( 2013-07-15), p. E293-E304
    Details
    In: American Journal of Physiology-Endocrinology and Metabolism, American Physiological Society, Vol. 305, No. 2 ( 2013-07-15), p. E293-E304
    Abstract: Nonalcoholic fatty liver disease is the most frequent liver disease. Ezetimibe, an inhibitor of intestinal cholesterol absorption, has been reported to ameliorate hepatic steatosis in human and animal models. To explore how ezetimibe reduces hepatic steatosis, we investigated the effects of ezetimibe on the expression of lipogenic enzymes and intestinal lipid metabolism in mice fed a high-fat or a high-fructose diet. CBA/JN mice were fed a high-fat diet or a high-fructose diet for 8 wk with or without ezetimibe. High-fat diet induced hepatic steatosis accompanied by hyperinsulinemia. Treatment with ezetimibe reduced hepatic steatosis, insulin levels, and glucose production from pyruvate in mice fed the high-fat diet, suggesting a reduction of insulin resistance in the liver. In the intestinal analysis, ezetimibe reduced the expression of fatty acid transfer protein-4 and apoB-48 in mice fed the high-fat diet. However, treatment with ezetimibe did not prevent hepatic steatosis, hyperinsulinemia, and intestinal apoB-48 expression in mice fed the high-fructose diet. Ezetimibe decreased liver X receptor-α binding to the sterol regulatory element-binding protein-1c promoter but not expression of carbohydrate response element-binding protein and fatty acid synthase in mice fed the high-fructose diet, suggesting that ezetimibe did not reduce hepatic lipogenesis induced by the high-fructose diet. Elevation of hepatic and intestinal lipogenesis in mice fed a high-fructose diet may partly explain the differences in the effect of ezetimibe.
    Type of Medium: Online Resource
    ISSN: 0193-1849 , 1522-1555
    URL: Article
    DOI: 10.1152/ajpendo.00442.2012
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2013
    detail.hit.zdb_id: 1477331-4
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  • 4
    Online Resource
    Online Resource
    Endothelium-specific activation of NAD(P)H oxidase in aortas of exogenously hyperinsulinemic rats
    American Physiological Society ; 1999
    In:  American Journal of Physiology-Endocrinology and Metabolism Vol. 277, No. 6 ( 1999-12-01), p. E976-E983
    Details
    In: American Journal of Physiology-Endocrinology and Metabolism, American Physiological Society, Vol. 277, No. 6 ( 1999-12-01), p. E976-E983
    Abstract: To examine the effects of chronic hyperinsulinemia on vascular tissues, we examined the production of superoxide anion ([Formula: see text]) in the aortic tissues of control and exogenously hyperinsulinemic rats performed by the implantation of an insulin pellet for 4 wk. [Formula: see text] production by aortic segments from hyperinsulinemic rats was 2.4-fold (lucigenin chemiluminescence method) and 1.7-fold (cytochrome c method) of that of control rats without any differences in [Formula: see text]degrading activities in aortic tissues, respectively ( P 〈 0.025). The increment was completely abolished in the presence of either 100 μmol/l apocynin (an inhibitor of NADPH oxidase) or 10 μmol/l diphenyleneiodonium (an inhibitor of flavin-containing enzyme) and was exclusively endothelium dependent. Consistently, NAD(P)H oxidase activities in endothelial homogenate in hyperinsulinemic rats were dose dependently stimulated above the values of control rats, although these activities in nonendothelial homogenate were not significantly stimulated by insulin. Furthermore, an insulin effect was also demonstrated 1 h after exposing aortic tissues to insulin. These results indicate that[Formula: see text] production specifically increases in endothelium of aortic tissues in chronic hyperinsulinemic rats through the activation of NAD(P)H oxidase.
    Type of Medium: Online Resource
    ISSN: 0193-1849 , 1522-1555
    URL: Article
    DOI: 10.1152/ajpendo.1999.277.6.E976
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1999
    detail.hit.zdb_id: 1477331-4
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  • 5
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    Online Resource
    Sumoylation of Pdx1 is associated with its nuclear localization and insulin gene activation
    American Physiological Society ; 2003
    In:  American Journal of Physiology-Endocrinology and Metabolism Vol. 284, No. 4 ( 2003-04-01), p. E830-E840
    Details
    In: American Journal of Physiology-Endocrinology and Metabolism, American Physiological Society, Vol. 284, No. 4 ( 2003-04-01), p. E830-E840
    Abstract: Pancreatic duodenal homeobox-1 (Pdx1) is a transcription factor, and its phosphorylation is thought to be essential for activation of insulin gene expression. This phosphorylation is related to a concomitant shift in molecular mass from 31 to 46 kDa. However, we found that Pdx1 was modified by SUMO-1 (small ubiquitin-related modifier 1) in β-TC-6 and COS-7 cells, which were transfected with Pdx1 cDNA. This modification contributed to the increase in molecular mass of Pdx1 from 31 to 46 kDa. Additionally, sumoylated Pdx1 localized in the nucleus. The reduction of SUMO-1 protein by use of RNA interference (SUMO-iRNAs) resulted in a significant decrease in Pdx1 protein in the nucleus. A 34-kDa form of Pdx1 was detected by the cells exposed to SUMO-iRNAs in the presence of lactacystin, a proteasome inhibitor. Furthermore, the reduced nuclear sumoylated Pdx1 content was associated with significant lower transcriptional activity of the insulin gene. These findings indicate that SUMO-1 modification is associated with both the localization and stability of Pdx1 as well as its effect on insulin gene activation.
    Type of Medium: Online Resource
    ISSN: 0193-1849 , 1522-1555
    URL: Article
    DOI: 10.1152/ajpendo.00390.2002
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2003
    detail.hit.zdb_id: 1477331-4
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  • 6
    Online Resource
    Online Resource
    Reduced activity of mtTFA decreases the transcription in mitochondria isolated from diabetic rat heart
    American Physiological Society ; 2002
    In:  American Journal of Physiology-Endocrinology and Metabolism Vol. 282, No. 4 ( 2002-04-01), p. E778-E785
    Details
    In: American Journal of Physiology-Endocrinology and Metabolism, American Physiological Society, Vol. 282, No. 4 ( 2002-04-01), p. E778-E785
    Abstract: To evaluate abnormalities in the mitochondrial transcription factor A (mtTFA) function as a cause of mitochondrial dysfunction in diabetes, we measured the mRNA contents of the proteins consisting of the mitochondrial respiratory chain as well as transcriptional and translational activities in the mitochondria isolated from controls and streptozotocin-induced diabetic rat hearts. Using Northern blot analysis, we found 40% reduced mRNA contents of mitochondrial-encoded cytochrome b and ATP synthase subunit 6 in diabetic rat hearts compared with control rats ( P 〈 0.05). These abnormalities were completely recovered by insulin treatment. Furthermore, the mitochondrial activities of transcription and translation were decreased significantly in mitochondria isolated from diabetic rats by 60% ( P 〈 0.01) and 71% ( P 〈 0.01), respectively, compared with control rats. The insulin treatment also completely normalized these abnormalities in diabetic rats. Consistently, gel retardation assay showed a reduced binding of mtTFA to the D-loop of mitochondrial DNA in diabetic rats, although there was no difference in the mtTFA mRNA and protein content between the two groups. On the basis of these findings, a reduced binding activity of mtTFA to the D-loop region in the hearts of diabetic rats may contribute to the decreased mitochondrial protein synthesis.
    Type of Medium: Online Resource
    ISSN: 0193-1849 , 1522-1555
    URL: Article
    DOI: 10.1152/ajpendo.00255.2001
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2002
    detail.hit.zdb_id: 1477331-4
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  • 7
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    Online Resource
    Amelioration of high fructose-induced metabolic derangements by activation of PPARα
    American Physiological Society ; 2002
    In:  American Journal of Physiology-Endocrinology and Metabolism Vol. 282, No. 5 ( 2002-05-01), p. E1180-E1190
    Details
    In: American Journal of Physiology-Endocrinology and Metabolism, American Physiological Society, Vol. 282, No. 5 ( 2002-05-01), p. E1180-E1190
    Abstract: To elucidate molecular mechanisms of high fructose-induced metabolic derangements and the influence of peroxisome proliferator-activated receptor-α (PPARα) activation on them, we examined the expression of sterol regulatory element binding protein-1 (SREBP-1) and PPARα as well as its nuclear activation and target gene expressions in the liver of high fructose-fed rats with or without treatment of fenofibrate. After 8-wk feeding of a diet high in fructose, the mRNA contents of PPARα protein and its activity and gene expressions of fatty acid oxidation enzymes were reduced. In contrast, the gene expressions of SREBP-1 and lipogenic enzymes in the liver were increased by high fructose feeding. Similar high fructose effects were also found in isolated hepatocytes exposed to 20 mM fructose in the media. The treatment of fenofibrate (30 mg · kg −1 · day −1 ) significantly improved high fructose-induced metabolic derangements such as insulin resistance, hypertension, hyperlipidemia, and fat accumulation in the liver. Consistently, the decreased PPARα protein content, its activity, and its target gene expressions found in high fructose-fed rats were all improved by fenofibrate treatment. Furthermore, we also found that the copy number of mitochondrial DNA, the expressions of mitochondrial transcription factor A, ATPase-6 subunit, and uncoupling protein-3 were increased by fenofibrate treatment. These findings suggest that the metabolic syndrome in high fructose-fed rats is reversed by fenofibrate treatment, which is associated with the induction of enzyme expression related to β-oxidation and the enhancement of mitochondrial gene expression.
    Type of Medium: Online Resource
    ISSN: 0193-1849 , 1522-1555
    URL: Article
    DOI: 10.1152/ajpendo.00471.2001
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2002
    detail.hit.zdb_id: 1477331-4
    SSG: 12
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