Amino Acid Profiles in DS
by Dr. Len Leshin, MD, FAAP
Heggarty HJ; Ball R; Smith M; Henderson MJ
Amino acid profile in Down's syndrome.
York District Hospital, York.
Arch Dis Child 1996 Apr;74(4):347-9
Abstract:
"Fasting plasma and urinary amino acid concentrations were studied under carefully controlled conditions in 22 children with Down's syndrome and in age matched controls. The only significant difference between the groups was a higher mean plasma lysine concentration in Down's syndrome patients compared to controls."
From the body of the paper:
"The late Professor Lejeune and his colleagues published a report in 1992 showing that the concentrations of urinary and serum amino acids in patients with Down syndrome differed from those with healthy controls. Their study covered a mixed age range and included many adults. It showed that plasma concentrations of cysteine and lysine were increased in patients with Down syndrome and plasma serine decreased when compared to controls. The urine of the Down syndrome patients also contained raised concentrations of tyrosine, methionine, cysteine and methyl-histidine compared to controls. In the present study, all the patients were children below the age of 18."
"Methods: 22 children with DS provided blood and 21 provided urine samples. The controls were healthy children of comparable age. Twenty controls provided urine samples and 18 provided blood samples. None of the subjects was receiving any medication or special diets during the two weeks before sampling, all of which were done in the fasting state...."
"Results: (Figures 1 and 2, bar graphs comparing labs results.) ...It can be clearly seen that only the plasma lysine concentrations achieve significance in the DS group as compared to controls...."
"Discussion: our results confirm Lejeune's finding only in respect of raised plasma concentrations of lysine in DS. We did not confirm the other findings of his study, namely raised plasma cysteine, reduced plasma serine, and increased urinary tyrosine, methionine, methylhistidine and cysteine. The urinary tyrosine in our DS patients was considerably higher than in controls but the difference did not reach statistical significance."
"In general, hyperlyesinemia is a benign disorder in which the serum lysine concentrations are usually much higher than those found in our DS patients. We feel that the lysine levels in our DS subjects are unlikely to have a significant clinical effect, though they may well indicate a metabolic pathway disequilibrium."
"Lejeune and colleagues had found several different examples of 'enzyme imbalances' in DS which they considered important....Peeters et al reported that some DS subjects were particularly sensitive to 6-mercaptopurine and methotrexate (which involve folate metabolism). Folinic acid therapy seemed to relieve psychoses in some DS patients studied by Lejeune and his colleagues. Other workers in France plan to study the therapeutic affects of increasing serine in the diet plus folic acid supplements in DS children. Lejeune's aims were to link the metabolic consequences of additional chromosomal material with a pathophysiological basis of mental retardation. His theory was that enzyme imbalance may be related to the primary chromosomal abnormality and that intellectual improvement could perhaps follow dietary correction of these biochemical imbalances."
"Our study failed to confirm Lejeune's main findings. Perhaps children have a different amino acid profile from adults. Our subjects were all children, whereas his study contained adults."
"We studied fasting plasma and urinary amino acid concentrations under very well controlled circumstances....Lejeune's paper made no reference to the sample collection conditions....."
"We conclude that when studied under carefully controlled conditions there are no differences in amino acid concentrations between control children and DS patients that would justify dietary supplementation, as recommended by Professor Lejeune."