AMINO ACID LEVELS IN PRADER-WILLI SYNDROME AND OBESE INDIVIDUALS

To determine if certain features (e.g., hypopigmentation) seen in persons with Prader-Willi syndrome (PWS) may be reflected in abnormalities of amino acid metabolism, fasting plasma amino acid levels were measured from 25 patients and compared with those in 17 obese individuals. Thirteen of the patients with PWS were previously identified by high-resolution analysis to have chromosome 15q deletion, while 12 had normal chromosomes. Compared with reference plasma levels, several amino acid levels were elevated in both patients and obese individuals. Aspartic acid, taurine, and glutamic acid levels were elevated (>2 Z score) in 44% of the patients with PWS but were increased in only one obese individual. The average phenylalanine and tyrosine levels were not different in the two groups. Significant differences in taurine, cystine, glutamic acid, citrulline, and aspartic acid levels were found. There was no correlation with age, degree of obesity (percentage of ideal body weight), and the degree of elevation of amino acids in either patients with PWS or obese individuals. Similarly, the degree of obesity in those with PWS was not associated with chromosome status. Several amino acid concentrations were abnormal in patients compared with our laboratory reference ranges, but many of these abnormalities were also present in obese individuals. Whether the amino acid changes simply reflect the altered eating habits of obese individuals or whether the altered profile may play a role in appetite or energy regulation is not known.