title: AMP-activated protein kinase acts as a negative regulator of high glucose-induced RANKL expression in human periodontal ligament cells.
abstract: BACKGROUND
  It is well known that the function of periodontal ligament cells may be affected by high glucose levels. This study investigated the direct effect of high glucose on the expression of receptor activator of nuclear factor-kappa B ligand (RANKL) in human PDL (hPDL) cells. In addition, we examined whether this effect was mediated via AMPK activation.
  
  
  METHODS
  We examined the expression of osteoprotegerin in hPDL cells cultured at different concentrations of glucose using real-time polymerase chain reaction (PCR), and Western blotting analysis. AMPK phosphorylation in hPDL cells was studied using immunoprecipitate kinase assay and Western blotting. The effect of AMPK activation on RANKL expression in hPDL cells was investigated by real-time PCR and Western blotting.
  
  
  RESULTS
  High glucose levels caused an increase in RANKL mRNA and protein expression in hPDL cells. Moreover, the amount of p-AMPK and AMPK activity was lower in hPDL cells exposed to high glucose levels than in cells exposed to normal glucose levels. Suppression of AMPK by Compound C augmented RANKL expression, and AMPK activation by metformin significantly decreased RANKL expression in hPDL cells. Additionally, metformin down-regulated RANKL expression in hPDL cells exposed to high glucose via AMPK activation.
  
  
  CONCLUSIONS
  High glucose-induced up-regulation of RANKL could be due to decreased AMPK activity, and AMPK activation may be involved in regulating of RANKL expression in hPDL cells.
authors.affiliation: Department of Stomatology, Chinese People's Liberation Army General Hospital, Beijing, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Feng
authors.forename: Jia-Qiang
authors.initials: JQ
authors.lastname: Liu
authors.forename: Hong-Chen
authors.initials: HC
authors.lastname: Liu
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D008687:Metformin / Q000494:pharmacology; D053244:Osteoprotegerin / Q000235:genetics / Q000378:metabolism; D010513:Periodontal Ligament / Q000166:cytology*; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D053244:Osteoprotegerin; D053245:RANK Ligand; D008687:Metformin; D055372:AMP-Activated Protein Kinases; D005947:Glucose