title: Glycation of human high density lipoprotein by methylglyoxal: effect on HDL-paraoxonase activity.
abstract: OBJECTIVE
  Methylglyoxal (MG), a reactive carbonyl compound formed primarily from triose phosphates, appears to be involved in the molecular mechanisms of diabetes, end-stage renal disease and neurodegenerative diseases. Methylglyoxal exerts several biological activities. Among these it promotes advanced glycation end products (AGEs), which are crucial in pathogenesis of human disease. Previous studies have demonstrated that MG reacts with proteins and compositional modifications reflect loss of biological activity. The aim of the study was to investigate the effect of in vitro MG-induced glycation on human high density lipoprotein (HDL) and on the activity of the enzyme paraoxonase-1 (PON1).
  
  
  METHODS
  HDL was incubated in the absence or in the presence of MG (0.2mmol/L and 1.0mmol/L) (MG-HDL) for different times (3, 6, 24h) at 37° C. We evaluated apoprotein compositional changes, in both control and MG treated HDL, using intrinsic fluorescence of tryptophan and monitoring the decrease of free amino groups. Furthermore we evaluated fluorescent advanced glycation end products (Ex=370nm, Em=440nm) and the activity of HDL-paraoxonase.
  
  
  RESULTS
  We demonstrated that human HDL is susceptible to glycation by MG (0.2mmol/L and 1mmol/L). The decrease of free amino groups and of intrinsic fluorescence of tryptophan demonstrates HDL apoprotein modifications in HDL incubated with MG. The compositional changes are associated with a significant increase in fluorescent advanced glycation end products and with a significant decrease of paraoxonase-1 enzyme activity associated with the HDL surface.
  
  
  CONCLUSIONS
  HDL-associated paraoxonase is responsible for the anti-inflammatory and anti-oxidative properties of HDL and detoxification against homocysteine-thiolactone. Therefore, modifications of apoprotein composition and the decrease of paraoxonase-1 activity in MG-treated HDL could affect the protective effect exerted by HDL against oxidative damage and could contribute to complications in patients affected by diseases associated with aging and oxidative stress.
authors.affiliation: Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Bacchetti
authors.affiliation: Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Masciangelo
authors.affiliation: Department of Clinical Experimental Science and Odontostomatology, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Armeni
authors.affiliation: Italian Auxologic Institute (IRCCS), Ospedale S. Giuseppe, Piancavallo (VB), Italy.
authors.forename: Virginia
authors.initials: V
authors.lastname: Bicchiega
authors.affiliation: Department of Clinical Experimental Science and Odontostomatology, Polytechnic University of Marche, Ancona, Italy. Electronic address: g.ferretti@univpm.it.
authors.forename: Gianna
authors.initials: G
authors.lastname: Ferretti
mesh_terms: D001059:Apoproteins / Q000378:metabolism; D043303:Aryldialkylphosphatase / Q000378:metabolism*; D017127:Glycation End Products, Advanced / Q000378:metabolism; D006031:Glycosylation / Q000187:drug effects*; D006801:Humans; D008075:Lipoproteins, HDL / Q000097:blood / Q000378:metabolism*; D011765:Pyruvaldehyde / Q000494:pharmacology*
chemical_list: D001059:Apoproteins; D017127:Glycation End Products, Advanced; D008075:Lipoproteins, HDL; D011765:Pyruvaldehyde; D043303:Aryldialkylphosphatase; C468406:PON1 protein, human
keywords: Glycation; High density lipoprotein; Methylglyoxal; Paraoxonase-1