Degradation products of proteins damaged by glycation, oxidation and nitration in clinical type 1 diabetes.
OBJECTIVE
Hyperglycaemia in diabetes is associated with increased glycation, oxidative stress and nitrosative stress. Proteins modified consequently contain glycation, oxidation and nitration adduct residues, and undergo cellular proteolysis with release of corresponding free adducts. These free adducts leak into blood plasma for eventual renal excretion. The aim of this study was to perform a comprehensive quantitative analysis of protein glycation, oxidation and nitration adduct residues in plasma protein and haemoglobin as well as of free adducts in plasma and urine to quantify increased protein damage and flux of proteolytic degradation products in diabetes.


METHODS
Type 1 diabetic patients (n=21) and normal healthy control subjects (n=12) were studied. Venous blood samples, with heparin anticoagulant, and 24-h urine samples were taken. Samples were analysed for protein glycation, oxidation and nitration adducts by a quantitative comprehensive screening method using liquid chromatography with triple quadrupole mass spectrometric detection.


RESULTS
In type 1 diabetic patients, the concentrations of protein glycation, oxidation and nitration adduct residues increased up to three-fold in plasma protein and up to one-fold in haemoglobin, except for decreases in pentosidine and 3-nitrotyrosine residues in haemoglobin when compared with normal control subjects. In contrast, the concentrations of protein glycation and oxidation free adducts increased up to ten-fold in blood plasma, and urinary excretion increased up to 15-fold in diabetic patients.


CONCLUSIONS
We conclude that there are profound increases in proteolytic products of glycated and oxidised proteins in diabetic patients, concurrent with much lower increases in protein glycation and oxidation adduct residues.
Department of Biological Sciences, University of Essex, Colchester, Essex CO4 3SQ, UK.
N
N
Ahmed
R
R
Babaei-Jadidi
S K
SK
Howell
P J
PJ
Beisswenger
P J
PJ
Thornalley
D000328:Adult; D001798:Blood Proteins / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis / Q000378:metabolism; D017127:Glycation End Products, Advanced / Q000737:chemistry / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged; D009566:Nitrates / Q000378:metabolism*; D010084:Oxidation-Reduction
D001798:Blood Proteins; D006442:Glycated Hemoglobin; D017127:Glycation End Products, Advanced; D006454:Hemoglobins; D009566:Nitrates