Dietary Sodium Restriction in Renal Transplant Recipients.

Rationale:

Hypertension is present in >70% of renal transplant recipients and a known risk factor for cardiovascular morbidity, cardiovascular mortality, and graft failure. Volume expansion caused by high sodium intake might play an important role in the development and maintenance of hypertension in renal transplant recipients. Although the effects of dietary sodium restriction have been investigated in healthy subjects and patients with chronic kidney disease, this has not yet been studied in RTR.



Objectives:

Primary Objective:

1. To investigate the effect of dietary sodium restriction on blood pressure in renal transplant recipients.

Secondary Objective(s):

1. To investigate the effect of dietary sodium restriction on extracellular volume as measured by volume parameters such as NT-proBNP;

2. To investigate the effect of dietary sodium restriction on renal damage as measured by urinary protein and albumin excretion and excretion of tubulointerstitial damage markers.



Study design:

The study is designed as a 12 week randomized crossover clinical trial with two parallel groups.



Study population:

The study population will consist of male and female renal transplant recipients who are one year after transplantation or beyond.



Intervention:

Patients will be symmetrically randomized to a liberal sodium diet aimed at 150 mmol (9 grams) daily or a low sodium diet aimed at 50 mmol (3 grams) daily.



Main study parameters/endpoints:

1. Blood pressure and use of antihypertensive medication;

2. Plasma NT-proBNP;

3. Urinary protein and albumin excretion, and urinary excretion of tubulointerstitial damage markers.



Nature and extent of the burden and risks associated with participation, benefit and group relatedness:

Patients are asked to visit the outpatient clinic 4 times. Prior to these visits patients have to collect 24-hour urine of the previous day and fill in dietary questionnaires the three days prior to their visits. The potential benefit of a low sodium diet may be a reduction of blood pressure, with subsequent reduction of cardiovascular risk and local renal damage. It may furthermore be accompanied by decreased tendency for plasma volume expansion with a reduction in the tendency for development of heart failure. Participation in the study is on a free-will base. Patients will not receive any financial support or priority for treatment of other diseases in the clinic during this study. All costs that subjects need for transportation in order to attend the clinic for the study purpose will be reimbursed completely.

Reduction in dietary sodium intake decreases blood pressure, extracellular volume and renal damage in renal transplant recipients.

4 timepoints.

Low dietary sodium intake (~50 mmol/day = 3 grams salt/day) vs liberal dietary sodium intake (~150 mmol/dayg = 9 grams salt/day). This is a crossover design with an intervention period of 6 weeks each.