Albumin antioxidant capacity is modified by methylglyoxal.
OBJECTIVE
Oxidative stress seems to play a major role in diabetic vascular complication development. Plasma albumin, via its thiol groups, is the main extracellular antioxidant molecule. Methylglyoxal (MG) is a very reactive dicarbonyl compound increased in diabetes which strongly modifies proteins by non-enzymatic glycosylation. The aim of this work was to study if MG could modify albumin antioxidant capacity.


METHODS
Bovine serum albumin was incubated with 1 mM MG at 37 degrees C for 7 days (MG-BSA). Albumin physico-chemical changes were evaluated by tryptophan autofluorescence measurement in the presence or in the absence of a quencher (acrylamide). Albumin antioxidant capacity was determined by thiol measurement using Ellman's reagent as well as in a cellular system (HeLa cells stressed by H2O2).


RESULTS
MG-BSA exhibited important modifications as shown by conformational changes, decreased tryptophan autofluorescence (30%) and significant thiol loss (40%). MG-BSA led to important modifications resulting in oxidation and loss of albumin antioxidant capacity. MG-BSA modifications were close to the one observed in albumin isolated from diabetic patients.


CONCLUSIONS
Our results suggest that deleterious effects induced by carbonyl stress in diabetes could also originate from a loss of albumin antioxidant capacity by dicarbonyl compound attack. The biological consequences of these findings have now to be investigated.
Faure
P
P
Laboratoire HP2, Faculté de Médecine et Pharmacie, Domaine de la Merci, 38700 La Tronche, France. patrice.faure@ujf-grenoble.fr
Troncy
L
L
Lecomte
M
M
Wiernsperger
N
N
Lagarde
M
M
Ruggiero
D
D
Halimi
S
S
D000818:Animals; D000975:Antioxidants; D002417:Cattle; D003920:Diabetes Mellitus / Q000097:blood*; D006801:Humans; D011765:Pyruvaldehyde / Q000494:pharmacology*; D012016:Reference Values; D012709:Serum Albumin / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000187:drug effects* / Q000502:physiology*; D013438:Sulfhydryl Compounds / Q000097:blood
D000975:Antioxidants; D012709:Serum Albumin; D013438:Sulfhydryl Compounds; D012710:Serum Albumin, Bovine; D011765:Pyruvaldehyde