The objective of this study is to characterize the hormonal and inflammatory responses to hemodialysis, and to determine the effect of a meal versus fast on the metabolic changes in the post-dialytic phase.

Studies show that hemodialysis (HD) is a protein catabolic event per se and probably contributes to the high prevalence of protein-energy wasting among HD patients. The muscle catabolic effect of HD is probably caused by loss of amino acids (10-12 grams per dialysis session) and by exacerbation of the inflammatory and hormonal disorders already present. Activation of the immune system during HD has been linked to the contact of blood cells with the dialyzer membrane and to bacterial-derived DNA fragments in the dialysis fluid. An intradialytic increase in interleukin-6 (IL-6) has been shown to correlate with muscle protein catabolism, and because IL-6 continues to increase for 2 hours after HD has ended, there might be a considerable "carry-over effect" to the post-dialytic period. Moreover, HD induces significant changes in the insulin/insulin-like growth factor I (IGF-I) signaling pathways. Plasma insulin is cleared by HD, and the bioactivity of IGF-I is reduced by 50% during a 4-hr maintenance HD due to an up-regulation of IGF-binding protein 1 (IGFBP-1), the only acutely regulated IGFBP.

Inclusion criteria:

• > 18 years
• stable maintenance hemodialysis for at least 3 months
• well-functioning arteriovenous shunts with recirculation less than 5%
• informed consent

Exclusion criteria:

• diabetes mellitus
• body mass index below 18.5 or above 30.0 kg/m2
• malnutrition (global assessment score C)
• active malignant disease
• immunosuppressive treatment (including glucocorticoid treatment)
• evidence of an ongoing inflammatory disease (including infection and autoimmune disorders)
• pregnancy

Exclusion criteria during the study:

• myocardial infarction or arrythmia with hemodynamic derangements
• permanent thrombosis in the arteriovenous (AV) shunt
• severe infectious disease
• renal transplantation