The relation of oxidative DNA damage to hypertension and other cardiovascular risk factors in Tanzania

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Abstract
To clarify the mechanism of involvement of oxidative stress in hypertensives, we investigated the relationship between the marker of oxidative DNA damage, urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG), and cardiovascular risk factors, such as hypertension and serum glycosylated hemoglobin (HbA1c), among Tanzanians aged 46–58 years who were not on antihypertensive medication. Sixty subjects (males/females, 28/32) were selected randomly from the subjects who completed a 24h urine collection in our epidemiological study at Dar es Salaam, Tanzania in 1998. The subjects were divided into two groups, hypertensive subjects (systolic blood pressure (SBP) ≥ 140 mmHg and/or diastolic blood pressure (DBP) ≥90 mmHg) and normotensive subjects (SBP <140 mmHg and DBP <90 mmHg) or hyperglycemic subjects (HbA1c ≥ 6.0%) and normoglycemic subjects (HbA1c < 6.0%). Biological markers from urine and blood were analyzed centrally in the WHO Collaborating Center. The mean levels of HbA1c and 8-OHdG were significantly higher in the hypertensive subjects than in the normotensive subjects (P < 0.05). Urinary 8-OHdG was significantly higher in hyperglycemic subjects than in normoglycemic subjects. HbA1c was positively correlated with the 24-h urinary 8-OHdG excretions (r = 0.698, P < 0.0001). These findings suggest oxidative DNA damage is increased in hypertensive subjects, and there is a positive correlation between the level of blood glucose estimated as HbA1c and oxidative DNA damage. Hyperglycemia related to insulin resistance in hypertension in Tanzania is associated with increased urinary 8-OHdG.