Intradialytic Protein Supplementation & Exercise Training in Dialysis Patients.

Chronic kidney disease (CKD) patients receiving hemodialysis treatment (CKD stage 5) suffer from a variety of co-morbid diseases, many of which may be mechanistically linked. Protein malnutrition, muscle catabolism and wasting are especially common, and these lead to reduced muscle strength, declines in physical function, and low levels of physical activity. Physical inactivity exacerbates these functional declines, and also promotes cardiovascular disease (CVD) and bone disorders. This cycle of disease and disability greatly reduces quality of life (QOL) and increases mortality rates in dialysis patients.

Many factors contribute to the development of these co-morbidities. Chronic inflammation is believed to be a cause and a consequence of the protein malnutrition, CVD and bone disorders in dialysis patients. In addition, abnormalities in mineral metabolism resulting from the deficit in kidney function promote the loss of mineral from bone and the deposition of mineral in the vasculature, a process termed vascular calcification (VC). VC is associated with a variety of CVD-related disorders, including arterial stiffness, increases in arterial wall intima-media thickness (IMT), left ventricular hypertrophy (LVH), and declines in cardiac function. As a result of these abnormalities, cardiovascular events are 10 to 30 times greater in dialysis patients than in age- and sex-matched subjects in the general population.

A variety of pharmacological therapies are commonly used to help prevent or attenuate the progression of CKD co-morbidities; however, morbidity and mortality in this population remain extremely high, indicating that additional therapeutic strategies that may improve the health and QOL in this population are needed. Recently, the National Kidney Foundation recommended that dialysis patients increase their protein intake to 1.2 g/kg/day to help prevent protein malnutrition; however, little is known about the efficacy of this recommendation. Intradialytic (during dialysis) protein supplementation has been shown to increase serum albumin levels11, and also increases amino acid uptake into skeletal muscle, an effect that is potentiated by both resistance and endurance exercise. However, the individual and combined effects of intradialytic protein supplementation and exercise training on lean mass, muscle strength, and physical function is unknown. Furthermore, intradialytic protein supplementation and exercise training improve many risk factors associated with CVD and renal bone disease (e.g., plasma lipids, inflammatory variables), but their effect on functional CVD outcomes (e.g., arterial stiffness, VC, IMT, LVH, myocardial performance) and bone health in dialysis patients is unknown.

The primary objective of the proposed research is to evaluate the efficacy of intradialytic oral protein supplementation, with and without concomitant intradialytic endurance exercise training (cycling), on physical function, CVD risk, and bone health. We will also examine potential mechanisms for these effects, and determine if improvements in these factors lead to improvements in QOL. Hemodialysis patients will be randomized to the following groups for 12 months: 1) usual care/control (CON); 2) intradialytic protein supplementation (PRO); or 3) intradialytic protein supplementation + exercise training (PRO+EX).

Primary Aim #1: Examine the effects of intradialytic oral protein supplementation and exercise training on physical function.