Browsing by Author "Gu, Zhiliang"

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    Expression of miR-33 from an SREBF2 Intron Targets the FTO Gene in the Chicken
    Shao, Fang; Wang, Xingguo; Yu, Jianfeng; Jiang, Honglin; Zhu, Bin; Gu, Zhiliang (PLOS, 2014-03-13)
    The sterol regulatory element binding transcription factor 2 (SREBF2) gene encodes a transcription factor that activates the expression of many genes involved in the synthesis and uptake of cholesterol, fatty acids, triglycerides, and phospholipids. Through bioinformatics, we found that intron 16 of the chicken SREBF2 gene might encode the chicken miR-33. Using quantitative RT-PCR, we detected the expression of miR-33 in a variety of chicken tissues including skeletal muscle, adipose tissue, and liver. Three hundred and seventy eight genes were predicted to be potential targets of miR-33 in chickens via miRNA target prediction programs “miRanda” and “TargetScan”. Among these targets, the gene FTO (fat mass and obesity associated) encodes a Fe(II)- and 2-oxoglutarate-dependent nucleic acid demethylase that regulates lipid metabolism, and the possibility that its expression is negatively regulated by miR-33 in the chicken liver was therefore further studied. Co-transfection and dual-luciferase reporter assays showed that the expression of luciferase reporter gene linked to the 3′-untranslated region (3′UTR) of the chicken FTO mRNA was down-regulated by overexpression of the chicken miR-33 in the C2C12 cells (P<0.05). Furthermore, this down-regulation was completely abolished when the predicted miR-33 target site in the FTO 3′UTR was mutated. In contrast, the expression of FTO mRNA in the primary chicken hepatocytes was up-regulated after transfection with the miR-33 inhibitor LNA-anti-miR-33. Using quantitative RT-PCR, we also found that the expression of miR-33 was increased in the chicken liver from day 0 to day 49 of age, whereas that of the FTO mRNA was decreased during the same age period. These data together suggest that miR-33 might play an important role in lipid metabolism in the chicken liver by negatively regulating the expression of the FTO gene.
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    Growth hormone regulation of insulin-like growth factor-I gene expression may be mediated by multiple distal signal transducer and activator of transcription 5 binding sites
    Eleswarapu, Satyanarayana; Gu, Zhiliang; Jiang, Honglin (Endocrine Society, 2008-05)
    The transcription factor signal transducer and activator of transcription (STAT)-5 mediates GH stimulation of IGF-I gene expression in the liver. Previous studies suggested that STAT5 might exert this effect by binding to an IGF-I intron 2 region and a distal 5' -flanking region each containing two STAT5 binding sites. Here we report the identification of three additional chromosomal regions containing a total of five putative STAT5 binding sites that may mediate GH-induced STAT5 activation of IGF-I gene expression in the mouse liver. By comparing an 170-kb mouse genomic DNA containing the IGF-I gene with the corresponding human sequence, we identified 19 putative STAT5 binding sites that bear the consensus sequence of STAT5 binding site and are conserved across the two species. Chromatin immunoprecipitation assays indicated that five chromosomal regions containing a total of nine of the 19 putative STAT5 binding sites were bound by STAT5 in the mouse liver in response to GH administration and that these bindings preceded or coincided with GH-increased IGF-I gene transcription. Two of the five chromosomal regions correspond to those previously identified in other species, and the three new chromosomal regions that contain a total of five putative STAT5 binding sites are IGF-I intron 3 regions located at least 26 kb from the transcription start site. Gelshift assays confirmed the binding of the five new putative STAT5 binding sites as well as three of the four previously identified STAT5 binding sites to GH-activated STAT5 from the mouse liver. Cotransfection analyses indicated that, although each of the five chromosomal regions was able to mediate STAT5 activation of reporter gene expression, together they mediated greater STAT5 activation of reporter gene expression in response to GH. Overall, these results suggest that GH-induced STAT5 activation of IGF-I gene expression in the mouse liver might be collectively mediated by at least eight STAT5 binding sites located located in distal intronic and 5' -flanking regions of the IGF-I gene.
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    Growth hormone stimulates hepatic expression of bovine growth hormone receptor messenger ribonucleic acid through signal transducer and activator of transcription 5 activation of a major growth hormone receptor gene promoter
    Jiang, Honglin; Wang, Ying; Wu, Miaozong; Gu, Zhiliang; Frank, Stuart J.; Torres-Diaz, Roberto (Endocrine Society, 2007-07)
    The objective of this study was to determine whether and how GH regulates hepatic expression of GH receptor (GHR) mRNA in cattle. Ribonuclease protection assays revealed that injection of GH in a slow-release formula increased both hepatic GHR and IGF-I mRNAs 1 wk after the injection. The increases in GHR and IGF-I mRNAs were highly correlated. Western blot analysis showed that the injection also increased liver GHR protein level. In cattle and other mammals, hepatic GHR mRNA is expressed as variants that differ in the 5'-untranslated region due to the use of different promoters in transcription and/or alternative splicing. We found that GH increased the expression of the liver-specific GHR mRNA variant GHR1A without affecting the other two major GHR mRNA variants in the bovine liver, GHR1B and GHR1C. In transient transfection analyses, GH could robustly activate reporter gene expression from a 2.7-kb GHR1A promoter, suggesting that GH augmentation of GHR1A mRNA expression in the liver is at least partially mediated at the transcriptional level. Additional transfection analyses of serially 5'-truncated fragments of this promoter narrowed the GH-responsive sequence element down to a 210-bp region that contained a putative signal transducer and activator of transcription 5 (STAT5) binding site. EMSAs demonstrated that this putative STAT5 binding site was able to bind to STAT5b protein. In cotransfection assays, deletion of this putative STAT5 binding site abolished most of the GH response of the GHR1A promoter. Like 1-wk GH action, 6-h (i.e. short-term) GH action also increased liver expression of GHR1A and total GHR mRNAs in cattle. These observations together suggest that GH directly stimulates the expression of one GHR mRNA variant, GHR1A, through binding STAT5 to its promoter, thereby increasing GHR mRNA and protein expression in the bovine liver.
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    Growth Hormone-Regulated mRNAs and miRNAs in Chicken Hepatocytes
    Wang, Xingguo; Yang, Lei; Wang, Huijuan; Shao, Fang; Yu, Jianfeng; Jiang, Honglin; Han, Yaoping; Gong, Daoqing; Gu, Zhiliang (PLOS, 2014-11-11)
    Growth hormone (GH) is a key regulatory factor in animal growth, development and metabolism. Based on the expression level of the GH receptor, the chicken liver is a major target organ of GH, but the biological effects of GH on the chicken liver are not fully understood. In this work we identified mRNAs and miRNAs that are regulated by GH in primary hepatocytes from female chickens through RNA-seq, and analyzed the functional relevance of these mRNAs and miRNAs through GO enrichment analysis and miRNA target prediction. A total of 164 mRNAs were found to be differentially expressed between GH-treated and control chicken hepatocytes, of which 112 were up-regulated and 52 were down-regulated by GH. A total of 225 chicken miRNAs were identified by the RNA-Seq analysis. Among these miRNAs 16 were up-regulated and 1 miRNA was down-regulated by GH. The GH-regulated mRNAs were mainly involved in growth and metabolism. Most of the GH-upregulated or GH-downregulated miRNAs were predicted to target the GH-downregulated or GH-upregulated mRNAs, respectively, involved in lipid metabolism. This study reveals that GH regulates the expression of many mRNAs involved in metabolism in female chicken hepatocytes, which suggests that GH plays an important role in regulating liver metabolism in female chickens. The results of this study also support the hypothesis that GH regulates lipid metabolism in chicken liver in part by regulating the expression of miRNAs that target the mRNAs involved in lipid metabolism.
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    Tetrahydrocurcumin protects against nonalcoholic fatty liver disease by improving lipid metabolism and redox homeostasis
    Gao, Feng; Chen, Manyu; Yu, Jianfeng; Xu, Lu; Yu, Lisha; Jiang, Honglin; Gu, Zhiliang (Elsevier, 2022-02)
    Nonalcoholic fatty liver disease (NAFLD) is the most common liver metabolic disease in the world. In this study we investigated the effect of tetrahydrocurcumin (THC), a potent antioxidant, on NAFLD. We found that THC significantly reduced the body weight, serum and liver lipids, serum malondialdehyde (MDA) and fasting blood glucose (FBG) of male NAFLD mice induced by feeding a high-fat diet (HFD) for 8 weeks. A RNA-seq analysis revealed that THC also affected the expression of many genes involved in lipid metabolism in the liver of NAFLD mice, including increasing the mRNA expression of CYP51 and FOXQ1. Moreover, THC significantly reduced sodium oleate-induced lipid accumulation, activated the NRF2 pathway, and up-regulated the mRNA expression of FGF21 in HepG2 cells. Overall, our study showed that THC can improve the antioxidant capacity of liver, which suggests that dietary THC may be used to treat NAFLD.