Age-dependent changes of serum oxygen radical scavenger capacity and haemoglobin glycosylation in non-insulin-dependent diabetic patients.
BACKGROUND
Contradictory results have been reported in the literature concerning the correlation between glycosylated haemoglobin (HbA1c) and peroxidation level in serum of diabetic patients.


OBJECTIVE
To evaluate this correlation in type 2 diabetic patients by comparing the level of HbA1c with the oxygen radical absorbance capacity (ORAC(OH)) of serum.


METHODS
One hundred and five type 2 diabetic patients were enrolled for the study. After having obtained informed consent, venous blood samples were drawn after overnight fast at the time of routine diabetic check-ups. The blood was collected in plain and EDTA (1 mg/ml) tubes. Glycosylated haemoglobin (HbA1c) was determined by cation-exchange chromatography (HPLC), and spectrophotometric detection (Diamat Analyzer, BioRad). Serum was used for biochemical determinations performed by standard laboratory procedures and for ORAC(OH) analysis. This last parameter was determined measuring the loss of beta-phycoerytrin fluorescence due to oxidation by hydroxyl radicals generated by Cu(2+) and H(2)O(2), in the presence and absence of serum. Seventy-eight control age-matched subjects were obtained from the personnel staff of our Research Department and old healthy subjects, selected on the basis of Senieur Protocol, were relatives of the above mentioned personnel.


RESULTS
When the population of diabetic patients was taken as a whole, a decrease of ORAC(OH) has been observed compared to the controls. Moreover, negative correlations were found comparing ORAC(OH) either with HbA1c (r = -0.213; p = 0.029) and with the age of patients (r = -0.27; p = 0.005). To better understand the effect of age, the data were re-examined dividing the diabetics into two populations, i.e. under and over 65 years of age. An age-dependent decrease of ORAC(OH) and an increase in HbA1c levels has been observed comparing these two populations; however, the correlation between the two parameters remained statistically significant only in the oldest group (r = -0.31; p = 0.026).


CONCLUSIONS
Present data point to an involvement of oxidative stress in the glycation of haemoglobin especially in old diabetic patients, and provide support for the potential use of an antioxidant therapy in these patients, irrespective of their glycaemic control.
Pieri
C
C
Center of Cytology, Gerontological Research Department of INRCA N. Masera, Ancona, Italy. c.pieri@incra.it
Testa
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R
Marra
M
M
Bonfigli
A R
AR
Manfrini
S
S
Testa
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I
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000097:blood*; D005260:Female; D016166:Free Radical Scavengers / Q000097:blood*; D006442:Glycated Hemoglobin / Q000378:metabolism; D006031:Glycosylation; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000032:analysis / Q000097:blood*; D012044:Regression Analysis
D016166:Free Radical Scavengers; D006442:Glycated Hemoglobin; D006454:Hemoglobins; D010100:Oxygen