​​​Abstract

This study compares the lipid peroxidation marker urinary

thiobarbituric acid reactive substances (TBARS) and

antioxidants including plasma a-tocopherol (vitamin E),

plasma (P-GSH-Px) and erythrocyte glutathione

peroxidase (E-GSH-Px) activities, and plasma selenium

levels in two groups of type 2 diabetic subjects

(both n=20) with a disease duration of £2 (GP1) and

4–6 years (GP2), and non-diabetic age and gender-matched

control subjects (CG, n=20). The mean (standard

deviation [SD]) age of the groups was similar at 41(10)

years. Fasting blood and midstream urine samples were

obtained from diabetic and non-diabetic subjects attending

the diabetic clinic and HbA1c, fructosamine, urine

TBARS, total antioxidant (TAS) levels, P-GSH-Px, E-GSHPx

and plasma selenium and vitamin E concentrations

were measured. HbA1c (%) and fructosamine levels in

the GP1 and GP2 diabetic subjects and the controls were

5.75 (0.67), 11.43 (2.01) and 4.33 (0.47), and 3.09 (0.57),

6.09 (1.15) and 1.67 (0.31), respectively (GP1 vs. GP2,

GP1 vs. GC and GP2 vs. CG, all P<0.001). Elevated

urinary TBARS (μmol/mmol urinary creatinine) in the

GP1, GP2 and GC groups were 2.47 (0.37), 3.73 (0.93)

and 1.18 (0.24), respectively (GP1 vs. GP2, GP1 vs. GC

and GP2 vs. CG, all P<0.001). A significant correlation

between HbA1c and TBARS was also noted (r2=0.894,

P<0.001) but only in the GP2 subjects. TAS levels were

only decreased in the GP2 group compared to control

values (0.59 [0.18] vs. 1.74 [0.21], P<0.001). Plasma

vitamin E concentrations (μmol/L) of 34.11 (3.31), 9.57 (2.20)

and 39.01 (2.91) were observed in the GP1, GP2 and

GC groups, respectively (GP1 vs. CG, P<0.05 and

GP1 vs. GP2 and GP vs. CG, both P<0.001). E-GSH-Px

(U/g Hb) and P-GSH-Px (U/L) activities in GP1, GP2

and CG groups were also decreased at 57.04 (4.31),

24.0 (8.94) and 67.6 (4.29), and 6.16 (1.56), 2.67 (0.47) and

8.72 (0.31), respectively (E-GSH-Px: CG vs. GP1, P<0.01,

CG vs. GP2 and GP1 vs. GP2, both P<0.001; P-GSH-Px:

CG vs. GP1, CG vs. GP2 and GP1 vs. GP2, all P<0.001).

Plasma selenium levels (μmol/L) were only significantly

decreased in GP2 compared to both GP1 and CG values

(0.49 [0.29] vs. 1.67 [0.80] vs. 1.79 [0.26], both P<0.001).

These observations support the suggestion that chronic

hyperglycaemia can influence the generation of free

radicals, which may lead ultimately to increased lipid

peroxidation and depletion of antioxidants, and thereby

enhanced oxidative stress in subjects with type 2 diabetes

mellitus.