title: Pharmacological evaluation of insulin mimetic novel suppressors of PEPCK gene transcription from Paeoniae Rubra Radix.
abstract: BACKGROUND
  Paeoniae Rubra Radix (root of Paeonia lactiflora) has been frequently employed in Traditional Chinese Medicine (TCM) as and anti-diabetic therapy to enhance blood circulation and dissipate stasis.
  
  
  OBJECTIVE
  Previously, we identified a novel hypoglycemic action of a crude extract from Paeoniae Rubra Radix, which also suppressed phosphoenolpyruvate carboxykinase (PEPCK) gene transcription. Therefore, the current investigation intended to elucidate potential active bio-constituents of this herb and mechanisms of action.
  
  
  METHODS
  Glucocorticoid receptor (GR) nuclear localization, the PEPCK messenger (m)RNA level, pregnane X receptor (PXR) mRNA expression, cAMP-responsive element-binding protein (CREB) serine phosphorylation and DNA binding were evaluated in dexamethasone (Dex) and 8-bromo-cAMP (CA)-stimulated H4IIE cells, while efficacy of agents was assessed in a stable cell line containing a green fluorescent protein (GFP) reporter driven by the PEPCK promoter. HPLC profiling, colorimetric assays, and NMR analysis were employed for chemical characterization purpose.
  
  
  RESULTS
  An extract of Paeoniae Rubra Radix lacking the insulin mimetic compound, 1,2,3,4,6-penta-O-galloyl-beta-d-glucose (PGG), and termed the non-PGG fraction (NPF), consisting of tannin polymers, suppressed PEPCK expression in the presence of an insulin receptor antagonist (HNMPA-AM(3)), suggesting the action of this fraction is independent of the insulin receptor. Furthermore, Dex-stimulated GR nuclear localization and transactivation were prevented by the NPF. Similarly, CA-stimulated CREB serine phosphorylation and DNA binding were also inhibited by the NPF in H4IIE cells. Hence NPF antagonizes both signaling pathways that induce PEPCK gene transcription.
  
  
  CONCLUSIONS
  In conclusion, the current study proposes that the potent suppressive activity on PEPCK gene transcription observed with Paeoniae Rubra Radix extract, can be attributed to at least two distinct components, namely PGG and NPF.
authors.affiliation: Division of Herbal Drugs and Natural Products, National Research Institute of Chinese Medicine, Taipei, Taiwan, ROC.
authors.forename: Yi-Chen
authors.initials: YC
authors.lastname: Juan
authors.forename: Chia-Chuan
authors.initials: CC
authors.lastname: Chang
authors.forename: Wei-Jern
authors.initials: WJ
authors.lastname: Tsai
authors.forename: Yun-Lian
authors.initials: YL
authors.lastname: Lin
authors.forename: Yi-Shin
authors.initials: YS
authors.lastname: Hsu
authors.forename: Hui-Kang
authors.initials: HK
authors.lastname: Liu
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D045744:Cell Line, Tumor; D002851:Chromatography, High Pressure Liquid; D003124:Colorimetry; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004365:Drugs, Chinese Herbal / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D017930:Genes, Reporter; D005938:Glucocorticoids / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics; D047348:Hydrolyzable Tannins / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D007004:Hypoglycemic Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy; D009281:Naphthalenes / Q000494:pharmacology; D063065:Organophosphonates / Q000494:pharmacology; D029596:Paeonia / Q000737:chemistry; D010766:Phosphorylation; D018517:Plant Roots; D000077297:Pregnane X Receptor; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011972:Receptor, Insulin / Q000187:drug effects / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000378:metabolism; D011987:Receptors, Steroid / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013634:Tannins / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection
chemical_list: C508137:Creb1 protein, rat; D017362:Cyclic AMP Response Element-Binding Protein; D004365:Drugs, Chinese Herbal; D005938:Glucocorticoids; D047348:Hydrolyzable Tannins; D007004:Hypoglycemic Agents; D009281:Naphthalenes; D063065:Organophosphonates; D000077297:Pregnane X Receptor; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D011987:Receptors, Steroid; D013634:Tannins; C519736:hydroxy-2-naphthalenyl-methyl phosphonic acid trisacetoxymethylester; D049452:Green Fluorescent Proteins; D015124:8-Bromo Cyclic Adenosine Monophosphate; C435084:pentagalloylglucose; D003907:Dexamethasone; C069767:phosphoenolpyruvate carboxylase kinase; D011972:Receptor, Insulin; D017346:Protein Serine-Threonine Kinases