Effects of Low Sodium Intake on the Anti-proteinuric Efficacy in Hypertensive Patient With Olmesartan

1. Background

   A. The chronic kidney disease (CKD) is the one of the main burden of chronic diseases and the prevalence of CKD is increasing in worldwide. In Korea, the prevalence of CKD was reported as 13.7% among urban Korean adults in 2008 by our study group.

   B. It is well known the CKD is the most important risk factor to cardiovascular events, cardiovascular mortality, all cause-mortality, and hospitalization. The cost of the management for the CKD was high and it took 3.25% of all budgets for medical reimbursement in 2004 for all Koreans, which was ranked on the top of expenditure for single disease category.

   C. The most popular risk factors to CKD progression are aging, obesity, hyperlipidemia, diabetes mellitus, hypertension, and proteinuria. The hypertension and proteinuria also cause the cardiovascular events and increase the mortality rate.

   D. The inhibitors for renin-angiotensin aldosterone system, angiotensin II type I receptor blocker (ARB) and angiotensin converting enzyme inhibitor (ACEI), are well known medications to prevent cardiovascular events and renal functional deterioration to end stage renal disease(ESRD) in patients with hypertension, non-diabetic CKD, or diabetic nephropathy. One of the adverse events of ARB is the decrease of hemoglobin. Inoue et al reported the level of hemoglobin was decreased in amount of 0.45 ±0.89 g/dL after prescription of ARB and valsartan decreased the erythropoietin in 6 days after medication. The exact mechanism of decrease of hemoglobin by ARB was not fully verified but it is related to decrease effects of angiotensin II on aggravating hypoxia in the kidney and on the activation of hypoxia-inducible factor 1α (HIF1a) and then decrease the production of erythropoietin as in the report of Durmus et al. Considering that the relationships between ARB usage and decrease of proteinuria in transplanted kidney, between aggravation of hypoxia or HIF1a and CKD, and between ARB and the decrease of HIF1a or erythropoietin(EPO), we could postulate that the decrease of hemoglobin would not be a adverse effect of ARB to deteriorate patients' condition but a co-phenomenon of ARB's anti-RAS effect and a marker of ARB's effectiveness.

   E. The anti-proteinuric effect of ARB is decreased by high salt intake. For example, ARB treatment without low salt intake decreased proteinuria by 30% in patients with proteinuria 2-10g/day compared to baseline value and addition of low salt diet to ARB treatment further decreased proteinuria up to 25%. But, using slow salt tablets, increase of daily intake of sodium diminished the anti-proteinuric effect of ARB in diabetic nephropathy.

   F. The previous studies for the effect of ARB on proteinuria affected by sodium intake took the methods of controlled diet by researcher or using slow salt tablet but these method are not practical to adopt in real clinical practice.

   G. The moderate and mild decrease of daily sodium intake which lower the daily excretion of sodium by 55 mEq/day had an effect of decrease of proteinuria by 11% in hypertensive patients.

   H. The mean amount of sodium of Korean diets was reported as high as 208 mmol/day in Intersalt study, which is more than 11 g of salt. The recent reports also showed the trend of high salt-intake by Koreans.

2. Rationale So, It is worth to do this study because

   • high salt intake is prevalent in Koreans,
   • high salt diet diminishes the effect of ARB on proteinuria
   • the methods used in previous studies were not suitable to apply to clinical practice,
   • and there were no study to reveal the decrease of hemoglobin would the marker for the effect of ARB and not be a adverse event of ARB.

3. Objectives

   1. Primary objective: The difference between amount of albuminuria after usage of Olmesartan and amount of albuminuria after prescription of Olmesartan with intensive diet education in intervention group is higher than the difference of albuminuria in control group.
   2. Secondary objective:

   Item 1: In all patients, Olmesartan decreases the albuminuria. Item 2: In all patients, the change of hemoglobin after prescription of Olmesartan is proportional to the change of albuminuria and serum erythropoietin.

   Item 3: Intensive education for low salt diet induces the significant decrease of daily sodium excretion in Intervention group compared to control group.

   Item 4: Intensive education for low salt diet induces the significant decrease of blood pressure in Intervention group compared to control group.

4. Study Flow

   • Period

     1. Washout period (-8 weeks;Point 0 to 0 weeks; Point 1)
     2. Olmesartan Period ( 0 week; point 1 to 8 weeks; point 2)
     3. Intervention period (8 week ; point 2 to 16 weeks; point 3)
   • For patients with taking ACEI, other ARB, diuretics, or renin inhibitor, already; Initial wash-out period for 8 weeks, and then (point 1) prescription of Olmesartan 40 mg qd for 8 weeks, and then (point 2) allocation to Intensive group or control group for 8 weeks, and then the study will be over (point 3).
   • For patients without taking ACEI, other ARB, diuretics, or renin inhibitor; For initial 8 weeks, adjust the blood pressures around 140/90 mmHg, and then (point 1) prescription of Olmesartan 40 mg qd for 8 weeks, and then (point 2) allocation to Intensive group or control group for 8 weeks, and then the study will be over (point 3).
   • Blood pressure control Adjust the blood pressures around 140/90 mmHg with other hypertensive drugs except ACEI, other ARB, diuretics, or renin inhibitor during whole period.
   • Intensive diet education:

For 8 weeks, dietitian will call patients to take the information according to pre-defined questionnaire, to check the daily diet habit and daily food taken, and to guide how to lessen sodium intake for 30 min at each call. The call will be done once a week for 8 weeks.