Chronic kidney disease is associated with oxidative stress independent of hypertension

Oxidative stress is implicated in the pathogenesis of chronic kidney disease (CKD) and essential hypertension (EHTN). However, the role of hypertension in causing increased oxidative stress in patients with CKD is unknown.

We performed a case control study in patients with EHTN and those with equal blood pressure assessed by ambulatory blood pressure monitoring but with concomitant CKD. Those with diabetes mellitus and those taking renin angiotensin inhibitors were excluded. Biomarkers of oxidative stress, malondialdehyde (MDA) and protein carbonylation and total glutathione levels were measured.

Average (SD) 24-hour ambulatory blood pressure in 12 patients with CKD was 134 (17)/75 (16) compared to 134 (10)/80 (9) in 11 patients with EHTN (p = NS). Plasma MDA in CKD was 0.89 +/- 0.38 micromol/l compared to 0.68 +/- 0.16 micromol/l in EHTN (p = 0.07). Urinary MDA/creatinine ratio was 1.78 (0.31) in CKD vs 1.43 (0.69) micromol/g in those with EHTN (p = 0.04). Thus, lipid peroxidation was increased in urine of CKD patients. Patients with CKD had higher (1.04 (0.20) nmol) carbonyl/mg protein compared to those with EHTN (0.80 (0.21) nmol carbonyl/mg protein) (p = 0.03). Thus, protein carbonylation was increased in CKD patients. Total glutathione in CKD and EHTN patients was 6.6 (1.8) ng/ml and 7.3 (3.1) ng/ml (p = NS). There was a good correlation between biomarkers of lipid (MDA) and protein oxidation (protein carbonyls) (r = 0.6, p = 0.004).

Biomarkers of lipid and protein oxidation are higher in patients with CKD compared to EHTN despite similar blood pressure. Thus, nonhemodynamic factors such as inflammation and altered cellular redox state may play a greater role in the generation of oxidative stress in CKD.