Protein, Nutrition and Cardiovascular Disease in Stage 5 Chronic Kidney Disease

Protein Intake, Nutrition and Cardiovascular Disease in Stage 5 Chronic Kidney Disease (CKD)

National Kidney Foundation guidelines recommend a dietary protein intake of 1.2 grams per kilogram per day (g/kg/d) in hemodialysis patients. However, it is unclear whether consumption of high amounts of protein in dialysis patients has beneficial or harmful nutritional and cardiovascular effects in this population. High protein intake might improve nutritional status, but it has been argued that the state of low muscle mass, small body size and low serum protein levels is not the result of decreased dietary intake, rather a result of hypercatabolism induced by metabolic acidosis, inflammation and oxidative stress.

The specific aims of this study are to examine in a prospective cohort of hemodialysis patients the longitudinal associations of absolute total protein intake or dietary protein intake with muscle mass and arterial stiffness.

It is hypothesized that in the dialysis population overall: (1) Protein intake is a major determinant of muscle mass while inflammation, oxidative stress and metabolic acidosis play a lesser role; (2) Malnutrition is not an uremic cardiovascular risk factor hence low protein intake does not cause cardiovascular disease; and (3) In the other extreme, high protein intake is also not a major cause of cardiovascular disease since high serum phosphorus associated with high protein intake can usually be controlled by the use of phosphorus binders in routine clinical practice.

The specific aims of this proposal are to examine in a prospective cohort of hemodialysis patients the longitudinal associations of absolute total protein intake (TPI) in grams/day, or dietary protein intake (DPI) normalized to body weight in grams/kilogram/day) with

1. Nutritional status (mid-thigh muscle mass as measured by Magnetic Resonance Imaging ) and functional status (6-min walk) and
2. Arterial stiffness (aortic pulse wave velocity)

Understanding the relationship between protein intake with body composition (muscle mass) and intermediate cardiovascular outcomes (arterial stiffness) in stage 5 CKD patients in hemodialysis is of great scientific and practical significance

Inclusion Criteria:

• Adult stage 5 chronic kidney disease patients, on dialysis for at least 3 months.
• Urine output > 200 mL/day

Exclusion Criteria:

• Patients with persistent volume overload (substantial pedal edema) despite attempts at achieving dry weight
• Patients with inability to walk or who use a wheel-chair with reduced mid-thigh muscle mass
• Persons with pacemakers, cochlear implants, or other prohibitive conditions for magnetic resonance imaging
• Atrial fibrillation
• Patients who are unlikely or unable (in the opinion of the nephrologists, nurses or dieticians taking care of the patient) to comply with research protocol
• Patients with symptomatic heart failure, current active malignancy (excluding squamous and basal cell skin cancers), active AIDS, chronic lung disease requiring supplemental oxygen therapy and cirrhosis
• Patients enrolled in interventional trials