title: Glucose oscillations, more than constant high glucose, induce p53 activation and a metabolic memory in human endothelial cells.
abstract: OBJECTIVE
  Damage persists in HUVECs exposed to a constant high glucose concentration long after glucose normalisation, a phenomenon termed 'metabolic memory'. Evaluation of the effects of exposure of HUVECs to oscillating high glucose on the induction of markers of oxidative stress and DNA damage (phospho-γ-histone H2AX and PKCδ) and onset of metabolic memory, and the possible role of the tumour suppressor transcriptional factor p53 is of pivotal interest.
  
  
  METHODS
  HUVECs were incubated for 3 weeks in 5 or 25 mmol/l glucose or oscillating glucose (24 h in 5 mmol/l glucose followed by 24 h in 25 mmol/l glucose) or for 1 week in constant 5 mmol/l glucose after being exposed for 2 weeks to continuous 25 mmol/l high glucose or oscillating glucose. Transcriptional activity of p53 was also evaluated in the first 24 h after high glucose exposure.
  
  
  RESULTS
  High constant glucose upregulated phospho-γ-histone H2AX and protein kinase C (PKC)δ compared with control. Oscillating glucose was even more effective than both normal and constant high glucose. Both constant and oscillating glucose resulted in a memory effect, which was more pronounced in the oscillating condition. Transcriptional activity of p53 peaked 6 h after glucose exposure, showing a predicted oscillatory behaviour.
  
  
  CONCLUSIONS
  Exposure to oscillating glucose was more deleterious than constant high glucose and induced a metabolic memory after glucose normalisation. Hyperactivation of p53 during glucose oscillation might be due to the absence of consistent feedback inhibition during each glucose spike and might account for the worse outcome of this condition.
authors.affiliation: Clinical Science Research Institute (CSRI), Warwick Medical School, University of Warwick, University Hospital-Walsgrave Campus, Coventry, CV2 2DX, UK.
authors.forename: B
authors.initials: B
authors.lastname: Schisano
authors.forename: G
authors.initials: G
authors.lastname: Tripathi
authors.forename: K
authors.initials: K
authors.lastname: McGee
authors.forename: P G
authors.initials: PG
authors.lastname: McTernan
authors.forename: A
authors.initials: A
authors.lastname: Ceriello
mesh_terms: D015153:Blotting, Western; D002478:Cells, Cultured; D004249:DNA Damage / Q000187:drug effects; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism*; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D018384:Oxidative Stress / Q000187:drug effects; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: C468783:H2AX protein, human; D006657:Histones; D016159:Tumor Suppressor Protein p53; D011493:Protein Kinase C