Dietary Intake of Proteins and Calories Is Inversely Associated With The Oxidation State of Plasma Thiols in End-Stage Renal Disease Patients

Objectives Oxidative stress contributes to the pathogenesis of protein-energy wasting in maintenance hemodialysis (MHD) patients, but knowledge of specific effectors and mechanisms remains fragmented. Aim of the study was to define whether and how food intake is involved in the causal relationship between oxidative stress and protein-energy wasting. Methods Seventy-one adult MHD patients and 24 healthy subjects (control) were studied cross-sectionally with analyses of diet record and of oxidative stress, as measured by a battery of plasma thiols including the protein sulfhydryl (-SH) group (PSH) levels (a marker of total protein–SH reducing capacity), the protein thiolation index (PTI, the ratio between disulfide, i.e., oxidized and reduced –SH groups in proteins), low molecular mass (LMM) thiols, LMM disulfides, and mixed LMM-protein disulfides. In addition, interleukin-6 (IL-6), albumin, C-reactive protein, and neutrophil gelatinase-associated lipocalin (NGAL) were measured as markers of inflammation. Results The patients showed low energy (22.0 ± 8.4 kcal/kg/day) and adequate protein (1.0 ± 0.4 g/kg/day) intakes, high levels of cystine (CySS; patients vs. control: 113.5 [90.9-132.8] vs. 68.2 [56.2-75.7] μM), cysteinylated proteins (CySSP; 216.0 [182.8-254.0] vs. 163.5 [150.0-195.5] μM), and high PTI (0.76 [0.61-0.88] vs. 0.43 [0.40-0.54]; P