title: Mangiferin and its aglycone, norathyriol, improve glucose metabolism by activation of AMP-activated protein kinase.
abstract: BACKGROUND
  Mangiferin has been reported to possess antidiabetic activities. Norathyriol, a xanthone aglycone, has the same structure as mangiferin, except for a C-glucosyl bond. To our best knowledge, no study has been conducted to determine and compare those two compounds on glucose consumption in vitro.
  
  
  OBJECTIVE
  In this study, the effects of norathyriol and mangiferin on glucose consumption in normal and insulin resistance (IR) L6 myotubes were evaluated. Simultaneously, the potential mechanism of this effect was also investigated.
  
  
  METHODS
  Normal or IR L6 myotubes were incubated with norathyriol (2.5 ∼ 10 μM, 0.625 ∼ 2.5 μM), mangiferin (10 ∼ 40 μM, 2.5 ∼ 10 μM) or rosiglitazone (20 μM) and/or 0.05 nM insulin for 24 h, respectively. The glucose consumption was assessed using the glucose oxidase method. Immunoblotting was performed to detect protein kinase B (PKB/Akt) and AMP-activated protein kinase (AMPK) phosphorylation in L6 myotubes cells.
  
  
  RESULTS
  Norathyriol and mangiferin treatment alone increased the glucose consumption 61.9 and 56.3%, respectively, in L6 myotubes and made additional increasing with 0.05 nM insulin. In IR L6 myotubes, norathyriol treatment made increasing with or without insulin, mangiferin treatment also made increasing but only when co-treated with insulin. Immunoblotting results showed that norathyriol and mangiferin produced an increase of 1.9 - and 1.8-fold in the phosphorylation levels of the AMPK, but not in Akt.
  
  
  CONCLUSIONS
  Our findings suggest that norathyriol and mangiferin could improve the glucose utilization and insulin sensitivity by up-regulation of the phosphorylation of AMPK. Norathyriol may be considered as an active metabolite responsible for the antidiabetic activity of mangiferin.
authors.affiliation: Biomedical Engineering Research Center, Kunming Medical University , Kunming , China .
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.forename: Juming
authors.initials: J
authors.lastname: Yan
authors.forename: Yanfen
authors.initials: Y
authors.lastname: Niu
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Hua
authors.initials: H
authors.lastname: Lin
authors.forename: Xu
authors.initials: X
authors.lastname: Liu
authors.forename: Jikai
authors.initials: J
authors.lastname: Liu
authors.forename: Ling
authors.initials: L
authors.lastname: Li
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D005947:Glucose / Q000378:metabolism*; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D015151:Immunoblotting; D007328:Insulin / Q000494:pharmacology; D007333:Insulin Resistance; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D000077154:Rosiglitazone; D045162:Thiazolidinediones / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects; D014966:Xanthenes / Q000008:administration & dosage / Q000494:pharmacology*; D044004:Xanthones / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D045162:Thiazolidinediones; D014966:Xanthenes; D044004:Xanthones; D000077154:Rosiglitazone; C013592:mangiferin; C069053:norathyriol; D051057:Proto-Oncogene Proteins c-akt; D055372:AMP-Activated Protein Kinases; D005947:Glucose