Anorexia and Plasma Levels of Free Tryptophan, Branched Chain Amino Acids, and Ghrelin in Hemodialysis Patients

Abstract

The aim of the present cross-sectional study was to assess appetite and to examine at the same time the associations between self-reported appetite and orexigen (ghrelin) and anorexigen (free tryptophan, free tryptophan/large neutral amino acid ratios, low branched chain amino acid levels) substances in chronic hemodialysis patients. Cross-sectional study. Patients were recruited from the Catholic University Outpatient Dialysis Clinic. A total of 59 patients (32 men and 27 women) were included in this study. The mean age was 63.7 +/- 13.9 years, and the mean dialytic age was 6.6 +/- 5.1 years. Their mean body mass index of the study population was 25.1 +/- 4.1 kg/m(2). The first question of the Hemodialysis (HEMO) Study Appetite questionnaire was used to assess the appetite of the hemodialysis patients. The multiple-choice answers for the first question, "During the past week, how would you rate your appetite?" were (1) very good, (2) good, (3) fair, (4) poor, or (5) very poor. Plasma amino acid concentrations were measured with the use of liquid chromatography. Ghrelin levels were measured with Ghrelin-RIA (Mediagnost). According to the questionnaire, in 16 of 59 (27.1%) hemodialysis patients, their appetite was very good (group 1); in 15 (25.4%), it was good (group 2); in another 15 (25.4%), it was fair (group 3); in 10 (16.9%), it was poor; and in 3 (5%), it was very poor. For statistical purposes, patients with a poor or very poor appetite were pooled together into a single group (group 4). Body mass index and serum albumin were significantly lower in patients with a fair and poor/very poor appetite than in patients with a very good or good appetite. According to the Subjective Global Assessment, all patients in groups A and B were well-nourished, whereas most patients in groups C (60%) and D (68%) were severely malnourished. Most of the comorbid conditions were significantly higher in patients of groups C and D. Branched chain amino acids were significantly lower in patients with a fair or poor/very poor appetite with respect to patients with a very good or good appetite. Free tryptophan levels were similar in the four groups of patients. The molar sum in plasma of the other large neutral amino acids (valine, leucine, isoleucine, tyrosin, phenylalanine) (large neutral amino acids) tended to be lower in patients with a fair and poor/very poor appetite than in patients with a very good or good appetite. However, the free tryptophan/large neutral amino acid ratio did not change significantly according to the appetite reported by the patients. Mean ghrelin levels were significantly higher in patients of group D than in other groups and in patients of groups B and C than in patients of group A. The present study shows that poor appetite is associated with significantly lower branched chain amino acid levels but not with higher free tryptophan levels and higher free tryptophan/large neutral amino acid ratios in hemodialysis patients. In addition, significantly higher levels of ghrelin have been observed in patients with a poor/very poor appetite.