Purpose: Salt intake not only elevates the levels of blood pressure, glomerular capillary pressure and proteinuria, but also increases oxidative stress within the renal cortex in animal models. We examined the effect of salt intake on the rate of renal function decline, urinary protein and oxidative stress in patients with chronic kidney disease (CKD).
Methods: Clinical data including systolic blood pressure (SBP)and diastolic blood pressure (DBP), serum creatinine, uric acid, total cholesterol, triglyceride, urinary protein, salt intake, protein intake of non-diabetic CKD 53 patients were observed for one year. At the end of the observation period, we measured 8-hydroxydeoxy guanosine (8-OHdG) in spot urine. We calculated the slope of reciprocal serum creatinine as the rate of renal function decline (delta1/Cr). We then investigated the relationship between those clinical factors and delta1/Cr, and urinary 8-OHdG, and also selected clinical factors that significantly influence delta1/Cr and urinary 8-OHdG by stepwise multiple regression analysis. In addition, we investigated the gender difference in urinary 8-OHdG.
Results: Annual mean SBP and DBP of all patients were 121.5 +/- 9.3 mmHg and 72.5+/- 6.2 mmHg, respectively. delta1/Cr was negatively correlated with salt intake, urinary protein and urinary protein was a significant predictor of delta1/Cr in a multiple regression analysis. Salt intake was positively correlated with protein intake and urinary protein. Urinary 8-OHdG of all patients was positively correlated with urinary protein and it was a significant predictor. Urinary 8-OHdG of male patients was positively correlated with salt intake and was a significant predictor; in female patients, it was positively correlated with urinary protein and total cholesterol and these two factors were significant predictors.
Conclusion: Salt intake increases urinary protein and promotes the progression of renal failure in CKD patients.