Nutritional Status and Amino Acids in Granulocytes and Plasma in Patients with Chronic Renal Disease and Varying Residual Renal Function

Abstract

Background: Protein metabolism changes with loss of renal function resulting in deterioration of nutritional status. Whether changes in macroscopic (anthropometry and subjective global nutritional assessment (SGNA)) and cellular (plasma and granulocyte free amino acid concentration) nutritional status with loss of residual renal function are related is not known. Methods: Anthropometric variables, SGNA, and blood samples were measured after a night’s fast in 43 patients (age 57 years, median (range 27–77), 32 males and 11 females) with chronic renal disease. A 24-hour urine sample was collected the day before the study for calculation of creatinine clearance and protein nitrogen appearance rate. The patients were stratified according to creatinine clearance (group I: >35 ml/min/1.73 m², group II 35–15 ml/min/1.73 m², group III <15 ml/min/1.73 m²). Results: In males a significant lower body weight (p < 0.05) and upper mid-arm muscle area (p < 0.05) was found in group III compared to group I. SGNA indicated suboptimal nutritional status in 12 patients. In group I all had normal SGNA while in group II and group III, 26 and 57% respectively were malnourished. SGNA was significantly and negatively correlated to upper mid-arm muscle area (ρ = –0.37, p < 0.05) and percent body fat mass (ρ = –0.46, p < 0.01) and positively correlated to percent ideal body weight (ρ = 0.48, p < 0.01). Nine patients with malnutrition (M) were compared with 9 well-nourished (N) patients. They were comparable with respect to creatinine clearance (M: 13 ± 5 ml/min/1.73 m²; N: 16 ± 7 ml/min/1.73 m²), age and sex. In malnourished patients plasma concentration of nonessential amino acids was higher (23%, p < 0.05). The intracellular concentration was generally not affected except for sulfur amino acid methionine which was increased by a factor of 2.5 (p < 0.05) and taurine decreased by a factor of 1.6 (p < 0.05). Conclusion: Loss of renal residual function worsened both macroscopic and cellular nutritional status. SGNA correlated to objective measures of nutritional status and is clinically usable. In malnourished chronic renal patients, increased plasma concentration of nonessential amino acids was found which might indicate increased protein degradation.