Race-specific differences in antioxidant enzyme activity in patients with type 2 diabetes: a potential association with the risk of developing nephropathy.
OBJECTIVE
Lipid hydroperoxide, a marker of oxidative stress, is linked to the development of nephropathy and is reportedly higher in patients of African origin compared with Caucasians. This may be relevant to race-specific differences in susceptibility to nephropathy. We investigated whether alterations in antioxidant enzyme activity could account for this biochemical phenotype and examined the relationship with conventional markers of renal disease.


METHODS
Two hundred seventeen individuals were studied. Patients with type 2 diabetes (n = 75) of African and Caucasian origin were matched by sex and racial origin with healthy control subjects (n = 142). Plasma total superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity were spectrophotometrically measured, and total cholesterol and triglycerides were measured by enzymatic methods.


RESULTS
SOD activity was higher and GPx activity lower in patients with diabetes than in healthy control subjects (573 +/- 515 vs. 267 +/- 70 units/l, P < 0.001 and 150 +/- 93 vs. 178 +/- 90 units/l, P = 0.019, respectively). Patients of African origin with diabetes had lower GPx and higher SOD activity compared with Caucasian patients (126 +/- 82 vs. 172 +/- 97 units/l, P = 0.03 and 722 +/- 590 vs. 445 +/- 408 units/l, P = 0.002, respectively). Patients of African origin with normal urinary albumin excretion had significantly higher plasma creatinine concentrations (100.7 +/- 14.2 vs. 88.1 +/- 14.9 micromol/l, P = 0.007) and lower GPx activity (99.0 +/- 72.4 vs. 173.7 +/- 107.4 units/l, P = 0.02) compared with those of Caucasian origin. African origin was an independent predictor of elevated SOD (P = 0.007) and reduced GPx activity (P = 0.02) in regression analysis.


CONCLUSIONS
SOD and GPx enzyme activities vary according to race and could account for differences in lipid hydroperoxide. In patients of African origin, susceptibility to renal disease may be associated with lowered GPx activity.
Zitouni
Karima
K
Department of Cellular and Molecular Medicine, St. George's Hospital NHS Trust, Thomas Addison Diabetes Centre, London SW17 ORE, UK.
Nourooz-Zadeh
Jaffar
J
Harry
Diane
D
Kerry
Sally M
SM
Betteridge
D John
DJ
Cappuccio
Francesco P
FP
Earle
Kenneth A
KA
D044383:Black People; D001794:Blood Pressure; D015992:Body Mass Index; D002784:Cholesterol / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000201:enzymology*; D003928:Diabetic Nephropathies / Q000453:epidemiology*; D005260:Female; D005979:Glutathione Peroxidase / Q000097:blood*; D006801:Humans; D008131:London; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013482:Superoxide Dismutase / Q000097:blood*; D014280:Triglycerides / Q000097:blood; D044465:White People
D014280:Triglycerides; D002784:Cholesterol; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase