Acta Pzdiatr Scand 64: 215-218, 1975
CYSTINE DEFICIENCY DURING DIETOTHERAPY O F HOMOCYSTINEMIA CLAUDE SANSARICQ, SANTOSH GARG, PATRICIA M. NORTON SADASHIV V. PHANSALKAR and SELMA E. SNYDERMAN' From the Department of Pediatrics, New York University Medical Center, New York, USA
ABSTRACT. Sansaricq, C., Garg, S., Norton, P. M., Phansalkar, S. V. and Snyderman, S. E. (Department of Pediatrics, New York University Medical Center, New York, USA) Cystine deficiency during dletotherapy of homocystinemia. Acta Paediatr S a n d 64:215, 1975.-Cystine deficiency was inadvertently produced in a boy receiving specific dietary therapy for homocystinuria. This was manifested as a loss in weight, the reappearance of significant amounts of homocystine in the plasma and urine, and the elevation of the plasma methionine level. In addition, there was a significant reduction in the level of cystine in the plasma. This reduction in plasma cystine level differentiates cystine deficiency from loss of biochemical control due to failure to keep the prescribed diet. The addition of cystine to the regime of this child, without any other dietary modification, resulted in a complete remission.
KEY WORDS: Homocystinuria, cystine deficiency
In the first definitive study of the amino acid requirements of man, Rose and his group (2, 3) demonstrated that cystine was not an essential amino acid, a finding that has since been confirmed by other observers as well (7). However, it has become increasingly apparent that the "essential" nature of an amino acid may be influenced by a number of factors. One of these influences is age; cystine is required by at least some premature and full-term infants (4, 5). Another is the route of feeding; the fall in plasma level in the adult during complete intravenous alimentation utilizing amino acid mixtures devoid of cystine is indicative of a special requirement a t this time (6). Thirdly, it has been suggested by a number of observers
that cystine must be an essential amino acid for the individual with homocystinemia as a result of the metabolic block which occurs in the normal pathway of the conversion of methionine to cystine (Fig. 1). Brenton et al. (1) did demonstrate negative nitrogen balance when cystine was removed from the diet of a child with homocystinemia, but the effect on plasma amino acid levels was complicated by a simultaneous increase in the methionine intake as well as an inability, for technical reasons, t o determine plasma cystine levels. It is the purpose of this communication to confirm the essentiality of cystine and to report the effect of such deficiency on the plasma amino acid levels of a patient with homocystinemia.
Supported by Project 317, Maternal and Child Health Services, Department of Health, Education and Welfare. ' Career Scientist of the Health Research Council of the City of New York.
CASE REPORT Very little is known about the early history of this child. However, his neonatal course was uneventful and his Apgar score was 10 at one minute. H e first came under Acta PEdiatr Scand 64
216
Cl. Sansaricq et al. Hornocystine
T. .
Methionin-
S-Adenosylmethionine
.
jS-Adenosylhornocysteine#Homocysteine
t,C y s t a t h i o n i n e --$ C y s t e i n e
Fig. 1. A simplified version of the metabolism of me-
thionine demonstrating the block in homocystinemia. medical observation at 3 years of age when he was removed from his home because of neglect, and placed in an institution. On admission, his physical condition was good, his height and weight were within normal limits, but he was obviously retarded, and in addition, he had not developed any intelligent speech. This boy was referred to our center at 4 years ,of age a s a result of a positive urine screening test for “cystine”. At this time his physical examination revealed that he was unusually large for his age, both his height and weight were well over the 97th percentile. Other findings of note were low-set flattened ears, a mild kyphosis (also observed by roentgenographic examination) and a soft systolic murmur. Examination of the eyes, including slit lamp, did not reveal any abnormalities. The presence of retardation was quite apparent. In addition, hyperactivity, clumsiness and a lack of coordination were observed during the hospitalization. The electroencephalogram was abnormal; the bilateral dysfunction was consistent with a seizure disorder. Retardation was confirmed by psychologic testing; he achieved an I.Q. Score of 74 on the Merrill Palmer, and one of 53 on the Stanford Binet. The suspected diagnosis of homocystinemia was confirmed by finding a level of 13.2 mg/ 100 ml of methionine (normal 0.2-0.4), and 1.1 mg/100 ml of half homocystine in the plasma. Urinary excretion of homocystine was 11.5 mg/g of creatinine. Massive doses of pyridoxine, 500 to 1000 mg daily, supplemented with 20 mg of folic acid and 2 mg of cyanocobalamin had no effect o n his plasma amino acid levels. Therefore, after one month on this form of treatment, we considered him to be non-responsive to vitamin therapy and decided to try methionine restriction. Treciimen i
Dietary therapy was initiated by supplying the protein of the diet in the form of an L-amino acid mixture-free of methionine (Table I ) . His methionine requirement was met by the small amounts of protein contained in the permitted low protein foods. The child accepted the diet surprisingly well and biochemical control was rapidly achieved and this was in turn followed by slow clinical improvement. There was less hyperactivity; he was less clumsy and his improved coordination allowed him to d o manual tasks that had previously been impossible for him. He began to speak, and his vocabulary gradually increased. His general behavior improved, he was much more tractible, and he was able to attend an educable class in school. Subsequent testing revealed a gradual improvement in his psychologic tests. Acta P z d i o t r Scond 64
After he had been on this regimen for over a year and a half, we were offered the use of a preparation which had been formulated for the treatment of this disease. According to the list of contents supplied with this new product, it was free of methionine, but contained cystine in an amount quite similar to the mixture we had been using. It also contained carbohydrate, minerals and vitamins. Our usual procedure with any new amino acid mixture is to check on the presumed content by an analysis employing ion exchange column chromatography. This was done with this material and the results very closely approximated the claimed contents with one striking exception; there seemed to be a complete absence of cystine! This finding so surprised us that we considered the most likely possibility to be some error in our technique, that perhaps the cystine was bound in such a way to one of the other constituents of this formula that it was not possible to detect it. Accordingly, we decided to try the new product, but to keep the child under close observation. One week later, his weight was maintained, the plasma cystine level was in the same range as previously, and there was a moderate increase in his plasma methionine and homocystine lev-
Table 1. The composition of the amino acid mixture The patient was given 1.5 g/kg/day. This provided 32 mg/kg of cystine daily Constituents (grams) L-alanine L-arginine L-aspartic acid L-cystine L-glutamic acid Glycine L-histidine L-isoleucine L-leucine L-lysine L-pheny lalanine L-proline L-serine L-threonine L-tyrosine L-tryptop han L-valine
2.67 4.58 8.78 2. I4 17.56 3.72 1.76 6.11 I I .76 7.10 4.89 6.11 5.34 4.58 4.58 1.68 6.64 100
*
Cystine deficiency during dietotherapy of homocystinemia
-0-
1
,
I
1
I
I
2 17
Methionme
-0-'/IHomocyrtine t '/?Cystroe
0
!I0
20
30
40
50
60
70
80
Methronrne Intake
Weeks
els. There was no change in either blood values or the child's clinical condition after 2 weeks. However, definite manifestations of cystine deficiency were apparent 3 weeks after this regimen was instituted. There was a weight loss of 0.8 kg, the plasma methionine had risen to 4 mg/lOO ml, the plasma 1/2 homocystine level was over 2 mg/100 ml. while the plasma 1/2 cystine level had dropped to 0.08 mg/100 ml. There were no changes in any of the other plasma amino acid levels. A supplement of 32 mg/kg/day of cystine was started immediately without any other dieiary change. This resulted in a complete reversal of the biochemical abnormalities and the weight loss was immediately regained (Fig. 2).
DISCUSSION The child manifested the usual signs of an amino acid deficiency-loss in weight and a depression of the plasma level of the deficient amino acid. In addition, there were plasma deviations which occurred as a result of the metabolic block-an elevation of the plasma methionine and homocystine levels, and also the urinary excretion of appreciable amounts of homocystine. These latter deviations can be explained as the result of breakdown of tissues having a normal complement of methionine so that the end result is similar to feeding a normal diet. The biochemical and clinical response to an increase in cystine intake, the only dietary alteration effected at this time, confirmed the cystine deficiency state. Elevations of methionine and homocystine are, of course, also ob-
90
t
1
100
I10
Fig.2. Effect of various dietary regimens on plasma amino acid levels.
served as a result of loss of dietary control, though this can be differentiated from cystine deficiency by determining the level of cystine in the plasma. This complication in the therapy of this patient once again emphasizes the meticulous care that must be taken whenever dietary therapy is instituted in the management of a metabolic disease. The physician must not only prescribe the proper diet, but he must also be certain that there is dependable quality control of the special formulas that are ernp1oyed.l
REFERENCES I . Brenton, D. P., Cusworth, D. C., Dent, C. E. & Jones, E. E.: Homocystinuria, clinical and dietary studies. Q J Med, 139; 325, 1966. 2. Rose, W. C.: The amino acid requirements of man. Fed Prot, 8:546, 1949. 3. Rose, W. C. & Wixom, R. L.: Amino acid requirements of man. Sparing effect of cystine on methionine requirements. J Biol Chern, 216: 763, 1955. 4. Snyderman, S. E. Protein and amino acid requirements of the premature infant, In: Metubolic Processes in the Foetus a n d Newborn Infunt. H. E. Stenfert Kroese, N.Y., Leiden 1971. 5. Snyderman, S. E.: Unpublished data.
' This deficiency was immediately called to the attention of the manufacturer who instituted the necessary procedure to control the amino acid composition of the diet. Artn PrPdiatr Scand 64
218
C1. Sansaricq et al.
6. Stegink. L. D. & Den Besten, L.: Synthesis of cysteine from methionine in normal adult subjects: effect of route of alimentation. Science, 178:514, 1972. 7 . Swendseid, M . D . , Williams, I . & Dunn, M . S.: Amino acid requirements of young woman based on nitrogen balance data. I . The sulfur containing amino acids. J Nutr, 58: 495, 1956.
Acta Paediatr Scand 64
Submitted May 6, 1974 Accepted July 11, 1974
(c.s.)DepartmentofPediatrics New University bkxkal Center 550 First Avenue New York, N.Y. USA
CYSTINE DEFICIENCY DURING DIETOTHERAPY O F HOMOCYSTINEMIA CLAUDE SANSARICQ, SANTOSH GARG, PATRICIA M. NORTON SADASHIV V. PHANSALKAR and SELMA E. SNYDERMAN' From the Department of Pediatrics, New York University Medical Center, New York, USA
ABSTRACT. Sansaricq, C., Garg, S., Norton, P. M., Phansalkar, S. V. and Snyderman, S. E. (Department of Pediatrics, New York University Medical Center, New York, USA) Cystine deficiency during dletotherapy of homocystinemia. Acta Paediatr S a n d 64:215, 1975.-Cystine deficiency was inadvertently produced in a boy receiving specific dietary therapy for homocystinuria. This was manifested as a loss in weight, the reappearance of significant amounts of homocystine in the plasma and urine, and the elevation of the plasma methionine level. In addition, there was a significant reduction in the level of cystine in the plasma. This reduction in plasma cystine level differentiates cystine deficiency from loss of biochemical control due to failure to keep the prescribed diet. The addition of cystine to the regime of this child, without any other dietary modification, resulted in a complete remission.
KEY WORDS: Homocystinuria, cystine deficiency
In the first definitive study of the amino acid requirements of man, Rose and his group (2, 3) demonstrated that cystine was not an essential amino acid, a finding that has since been confirmed by other observers as well (7). However, it has become increasingly apparent that the "essential" nature of an amino acid may be influenced by a number of factors. One of these influences is age; cystine is required by at least some premature and full-term infants (4, 5). Another is the route of feeding; the fall in plasma level in the adult during complete intravenous alimentation utilizing amino acid mixtures devoid of cystine is indicative of a special requirement a t this time (6). Thirdly, it has been suggested by a number of observers
that cystine must be an essential amino acid for the individual with homocystinemia as a result of the metabolic block which occurs in the normal pathway of the conversion of methionine to cystine (Fig. 1). Brenton et al. (1) did demonstrate negative nitrogen balance when cystine was removed from the diet of a child with homocystinemia, but the effect on plasma amino acid levels was complicated by a simultaneous increase in the methionine intake as well as an inability, for technical reasons, t o determine plasma cystine levels. It is the purpose of this communication to confirm the essentiality of cystine and to report the effect of such deficiency on the plasma amino acid levels of a patient with homocystinemia.
Supported by Project 317, Maternal and Child Health Services, Department of Health, Education and Welfare. ' Career Scientist of the Health Research Council of the City of New York.
CASE REPORT Very little is known about the early history of this child. However, his neonatal course was uneventful and his Apgar score was 10 at one minute. H e first came under Acta PEdiatr Scand 64
216
Cl. Sansaricq et al. Hornocystine
T. .
Methionin-
S-Adenosylmethionine
.
jS-Adenosylhornocysteine#Homocysteine
t,C y s t a t h i o n i n e --$ C y s t e i n e
Fig. 1. A simplified version of the metabolism of me-
thionine demonstrating the block in homocystinemia. medical observation at 3 years of age when he was removed from his home because of neglect, and placed in an institution. On admission, his physical condition was good, his height and weight were within normal limits, but he was obviously retarded, and in addition, he had not developed any intelligent speech. This boy was referred to our center at 4 years ,of age a s a result of a positive urine screening test for “cystine”. At this time his physical examination revealed that he was unusually large for his age, both his height and weight were well over the 97th percentile. Other findings of note were low-set flattened ears, a mild kyphosis (also observed by roentgenographic examination) and a soft systolic murmur. Examination of the eyes, including slit lamp, did not reveal any abnormalities. The presence of retardation was quite apparent. In addition, hyperactivity, clumsiness and a lack of coordination were observed during the hospitalization. The electroencephalogram was abnormal; the bilateral dysfunction was consistent with a seizure disorder. Retardation was confirmed by psychologic testing; he achieved an I.Q. Score of 74 on the Merrill Palmer, and one of 53 on the Stanford Binet. The suspected diagnosis of homocystinemia was confirmed by finding a level of 13.2 mg/ 100 ml of methionine (normal 0.2-0.4), and 1.1 mg/100 ml of half homocystine in the plasma. Urinary excretion of homocystine was 11.5 mg/g of creatinine. Massive doses of pyridoxine, 500 to 1000 mg daily, supplemented with 20 mg of folic acid and 2 mg of cyanocobalamin had no effect o n his plasma amino acid levels. Therefore, after one month on this form of treatment, we considered him to be non-responsive to vitamin therapy and decided to try methionine restriction. Treciimen i
Dietary therapy was initiated by supplying the protein of the diet in the form of an L-amino acid mixture-free of methionine (Table I ) . His methionine requirement was met by the small amounts of protein contained in the permitted low protein foods. The child accepted the diet surprisingly well and biochemical control was rapidly achieved and this was in turn followed by slow clinical improvement. There was less hyperactivity; he was less clumsy and his improved coordination allowed him to d o manual tasks that had previously been impossible for him. He began to speak, and his vocabulary gradually increased. His general behavior improved, he was much more tractible, and he was able to attend an educable class in school. Subsequent testing revealed a gradual improvement in his psychologic tests. Acta P z d i o t r Scond 64
After he had been on this regimen for over a year and a half, we were offered the use of a preparation which had been formulated for the treatment of this disease. According to the list of contents supplied with this new product, it was free of methionine, but contained cystine in an amount quite similar to the mixture we had been using. It also contained carbohydrate, minerals and vitamins. Our usual procedure with any new amino acid mixture is to check on the presumed content by an analysis employing ion exchange column chromatography. This was done with this material and the results very closely approximated the claimed contents with one striking exception; there seemed to be a complete absence of cystine! This finding so surprised us that we considered the most likely possibility to be some error in our technique, that perhaps the cystine was bound in such a way to one of the other constituents of this formula that it was not possible to detect it. Accordingly, we decided to try the new product, but to keep the child under close observation. One week later, his weight was maintained, the plasma cystine level was in the same range as previously, and there was a moderate increase in his plasma methionine and homocystine lev-
Table 1. The composition of the amino acid mixture The patient was given 1.5 g/kg/day. This provided 32 mg/kg of cystine daily Constituents (grams) L-alanine L-arginine L-aspartic acid L-cystine L-glutamic acid Glycine L-histidine L-isoleucine L-leucine L-lysine L-pheny lalanine L-proline L-serine L-threonine L-tyrosine L-tryptop han L-valine
2.67 4.58 8.78 2. I4 17.56 3.72 1.76 6.11 I I .76 7.10 4.89 6.11 5.34 4.58 4.58 1.68 6.64 100
*
Cystine deficiency during dietotherapy of homocystinemia
-0-
1
,
I
1
I
I
2 17
Methionme
-0-'/IHomocyrtine t '/?Cystroe
0
!I0
20
30
40
50
60
70
80
Methronrne Intake
Weeks
els. There was no change in either blood values or the child's clinical condition after 2 weeks. However, definite manifestations of cystine deficiency were apparent 3 weeks after this regimen was instituted. There was a weight loss of 0.8 kg, the plasma methionine had risen to 4 mg/lOO ml, the plasma 1/2 homocystine level was over 2 mg/100 ml. while the plasma 1/2 cystine level had dropped to 0.08 mg/100 ml. There were no changes in any of the other plasma amino acid levels. A supplement of 32 mg/kg/day of cystine was started immediately without any other dieiary change. This resulted in a complete reversal of the biochemical abnormalities and the weight loss was immediately regained (Fig. 2).
DISCUSSION The child manifested the usual signs of an amino acid deficiency-loss in weight and a depression of the plasma level of the deficient amino acid. In addition, there were plasma deviations which occurred as a result of the metabolic block-an elevation of the plasma methionine and homocystine levels, and also the urinary excretion of appreciable amounts of homocystine. These latter deviations can be explained as the result of breakdown of tissues having a normal complement of methionine so that the end result is similar to feeding a normal diet. The biochemical and clinical response to an increase in cystine intake, the only dietary alteration effected at this time, confirmed the cystine deficiency state. Elevations of methionine and homocystine are, of course, also ob-
90
t
1
100
I10
Fig.2. Effect of various dietary regimens on plasma amino acid levels.
served as a result of loss of dietary control, though this can be differentiated from cystine deficiency by determining the level of cystine in the plasma. This complication in the therapy of this patient once again emphasizes the meticulous care that must be taken whenever dietary therapy is instituted in the management of a metabolic disease. The physician must not only prescribe the proper diet, but he must also be certain that there is dependable quality control of the special formulas that are ernp1oyed.l
REFERENCES I . Brenton, D. P., Cusworth, D. C., Dent, C. E. & Jones, E. E.: Homocystinuria, clinical and dietary studies. Q J Med, 139; 325, 1966. 2. Rose, W. C.: The amino acid requirements of man. Fed Prot, 8:546, 1949. 3. Rose, W. C. & Wixom, R. L.: Amino acid requirements of man. Sparing effect of cystine on methionine requirements. J Biol Chern, 216: 763, 1955. 4. Snyderman, S. E. Protein and amino acid requirements of the premature infant, In: Metubolic Processes in the Foetus a n d Newborn Infunt. H. E. Stenfert Kroese, N.Y., Leiden 1971. 5. Snyderman, S. E.: Unpublished data.
' This deficiency was immediately called to the attention of the manufacturer who instituted the necessary procedure to control the amino acid composition of the diet. Artn PrPdiatr Scand 64
218
C1. Sansaricq et al.
6. Stegink. L. D. & Den Besten, L.: Synthesis of cysteine from methionine in normal adult subjects: effect of route of alimentation. Science, 178:514, 1972. 7 . Swendseid, M . D . , Williams, I . & Dunn, M . S.: Amino acid requirements of young woman based on nitrogen balance data. I . The sulfur containing amino acids. J Nutr, 58: 495, 1956.
Acta Paediatr Scand 64
Submitted May 6, 1974 Accepted July 11, 1974
(c.s.)DepartmentofPediatrics New University bkxkal Center 550 First Avenue New York, N.Y. USA
