European Journal of
Eur J Pediatr (1990) 149 : 272-274
Pediatrics
9 Springer-Verlag 1990
A case of carbamylphosphate synthetase-I deficiency associated with secondary carnitine deficiency L-carnitine treatment of CPS-I deficiency T. Mori 1, A. Tsuchiyama ~, K. Nagai 1, M. Nagao 1, K. Oyanagi 1, and S.Tsugawa ~ 1Department of Paediatrics, Sapporo Medical College, Chuo-ku $1 WI6 Sapporo 060, 2Department of Paediatrics, National Sanatorium Otaru Hospital, Nagahashi 3-24-1, Otaru, 047 Japan
Abstract. We describe a male infant with congenital hyperammonaemia due to partial carbamylphosphate synthetase-I (CPS-I) deficiency. A t 21 days of age, he had convulsions and at 53 days of age hyperammonaemic coma. Therapy with sodium benzoate, L-arginine, essential amino acids, L-carnitine and peritoneal dialysis lowered the blood ammonia levels, and his clinical manifestations improved. The CPS-I activity in liver tissue obtained by open biopsy was about 25.6% of normal values. The serum and urine free carnitine levels in the patient decreased during the hyperammonaemic crisis and were low at 7 months of age. After oral administration of L-carnitine (10 mg/kg per day) at 7 months of age, the mean blood ammonia levels decreased significantly, accompanied by an increase in serum and urine free carnitine levels. We propose the use of L-carnitine therapy to prevent secondary carnitine deficiency in patients with CPS-I deficiency as well as ornithine transcarbamylase (OTC) deficiency.
Key words: CPS-I deficiency - Carnitine - Hyperammonaemia
Introduction Inherited deficiency of carbamylphosphate synthetase-I (CPS-I) is a rare cause of congenital hyperammonaemia. In general, the clinical severity of inborn errors of urea cycle are affected by the residual enzyme activities. CPS-I deficiency is classified as either a lethal neonatal type or a delayed onset type according to the levels of residual enzyme activity [12]. We here report a patient with delayed onset type of CPS-I deficiency, who was admitted to our hospital at 53 days of age because of hyperammonaemic coma. Recently, secondary carnitine deficiency in hyperammonaemic attacks of ornithine transcarbamylase (OTC) deficiency has been reported [8]. It was suggested that reduced carnitine was one of the aggravating factors. However, to our knowledge, there has been no previous report on the carnitine status in CPS-I deficiency. In this paper, we evaluate the carnitine status in a patient with CPS-I deficiency and the effect of oral L-carnitine administration on blood ammonia levels. Possibilities of carnitine therapy in CPS-I deficiency are discussed. Offprint requests to: T. Mori Abbreviations: CPS-I = carbamylphosphate synthetase-I; OTC =
ornithine transcarbamylase; RRFC = renal reabsorption of free carnitine
Case report The patient, a 53-day-old boy, was the first child of unrelated and healthy Japanese parents. He was born after an uneventful delivery with a birth weight of 3358 g. He was healthy until, at 21 days of age, a generalized tonic-clonic seizure developed. After another week, seizures occurred twice a week which were controlled by sodium valproate therapy. A t 50 days of age, he again had a seizure, with frequent vomiting, feeding difficulties and apathy. On the next day, he was admitted to a local hospital in a somnolent state. Frequent vomiting and seizures continued. Two days after admission, he became stuporous, laboratory findings showed hyperammonaemia ( > 400 gg/dl) and he was transferred to our hospital. On admission, the patient was comatose and did not respond to painful stimulii. The pupils were mydriatic and responded poorly to light. The cardiovascular and respiratory systems were normal. The liver edge was palpable 2 cm below the right costal margin. The muscles were hypotonic and the bilateral deep tendon reflexes were weak, but no pathological reflexes were elicited. Laboratory studies showed normal leucocyte, erythrocyte and platelet counts, normal serum electrolytes, hepatocellular enzymes, bilirubin, total protein, blood glucose, creatinine and blood urea nitrogen. Routine urinalysis showed no abnormalities. There was a mild metabolic acidosis (pH7.358, bicarbonate 17.4mM/1, base excess -6.9mM/1). The blood ammonia level was elevated to 741 gg/dl (normal, < 70 gg/dl). Urinary orotic acid excretion was slightly elevated (11.3 gg/mg creatinine; controls: 3.4 to 5.9 gg/mg creatinine). Analysis of urinary organic acids by gas-chromatography and mass spectrometry showed no abnormalities except for valproate metabolites. Serum concentrations of amino acids showed the following levels: citrulline, trace (normal, 32.2+ ll.2gmol/1); glutamic acid, 252.5 gmol/1 (normal, 100.7 + 47.6 gmol/1); glutamine, 942.1 gmol/1 (normal, 555.2 _+237.6 gmol/1); alanine, 424.7gmol/1 (normal, 378.2 + 129.9gmol/1); arginine, 54.8grnol/1 (normal, 88.2+31.6gmol/1); lysine, 320.5grnol/1 (normal, 170.2 + 54.7 gmol/1). Other amino acids were normal. Argininosuccinic acid was not detected. Administration of sodium valproate was stopped because it aggravated the hyperammonaemia and carnitine deficiency. Therapy was started with L-arginine, sodium benzoate, essential amino acids, peritoneal dialysis and L-carnitine (20 mg/kg per day). After peritoneal dialysis, his mental status began to improve and gradually normalised over the next 24h along with a decrease in blood ammonia levels (Fig. 1). He was then put on a low-protein diet (1.5 to 1.7 g/kg per day). Adminis-
273 Essential amino acids
L- carnitine [ (20 mg/kg/day, perOs)
Arginine (0.8g/kg/day) Sodium benzoate (250mg/kg/day)
10,000-
91.3
Peritoneal dialysis ]
[
L-carnitine (20 mg/kg/daY)
800
95.4
g= o 5, 000~
98.3
200 0
0.48 o
60. O.21
I. 65
O.83
g ,0.
98.4
I
c
=o
At
I 12
I
24
I 96
admission
20
Time (hour) after admission E
0
At
I
/ 12
I 24
I 48
admission
Time (hours) after admission
Fig.1. Clinical course and serum carnitine concentrations in the patient after admission. Open columns, free carnitine; closed columns, acyl carnitine; numbers, acyl free ratio tration of L-arginine and sodium benzoate was stopped, but oral administration of L-carnitine was continued for another 20 days. A t 3 months of age, an open liver biopsy was performed with the informed consent of his parents. The CPS-I and OTC activities in the liver specimen, measured by the method of Schimke [10] were 0.011 pmol product/rag protein/rain, 25.6% of normal, (normal= 0.043_+ 0.014, n = 14) and 0.69 grnol product/mg protein/min (normal = 0.66 -+ 0.24, n = 14), respectively.
Methods
Free and acyl carnitine in serum and urine were measured according to McGary and Foster [5]. The rate of renal reabsorption of free carnitine (RRFC) was calculated according to the method of Mastuda et al. [4]. The first monitoring period of blood ammonia levels was 5 months between termination and initiation of L-carnitine therapy, and the second period was 4 months after L-carnitine therapy. The Student t-test was used for statistical analysis. Results
Serum free carnitine was normal on admission, but decreased markedly 12h later. This was accompanied by an increased ratio of acyl/free carnitine. After L-carnitine treatment, the serum free carnitine increased to normal levels (Fig. 1). Changes in urinary free carnitine excretion were similar to those serum. Urinary acyl carnitine excretion increased markedly after initiation of L-carnitine therapy. R R F C was within normal values (Fig. 2). Free carnitine was also deteced in the peritoneal dialysis fluid. Serum free carnitine levels determined at 35 days and 60 days after termination of the i.-carnitine treatment were within normal values. However, at 7 months of age
Fig. 2. Urinary carnitine concentrations in the patient after admission. Open columns, free carnitine; closed columns, acyl carnitine; numbers rate of renal reabsorption of free carnitine
and whilst asymptomatic, his serum free carnitine level decreased again together with an increase of an acyl/free carnitine ratio. Urinary free carnitine was not detected (Table 1). Laboratory findings at this time were normal, including blood gas analysis, blood sugar, hepatocellular enzymes and free fatty acid. L-carnitine administration (10mg/kg per day) was initiated and continued for the last 4 months. Mean blood ammonia concentrations obtained before and after L-carnitine therapy were 135.2 + 42.5 pg/dl (n = 74) and 103.1 + 19.0 pg/dl (n = 22), respectively (P < 0.01). Protein restrictions before and after L-carnitine therapy were 1.5 to 1.7 g/kg per day and 1.8 to 2.0 g/kg per day, respectively. A t 11 months of age, blood ammonia levels were well controlled under the low-protein diet (1.8 to 2.0 g/kg per day). Body weight, motor development, E E G and computed tomography of the brain were all normal.
Discussion
Carnitine is essential for the transport of fatty acids into mitochondria where they undergo ~-oxidation. Another function of carnitine is the buffering of toxic acyl-CoA compounds [11]. Therefore, secondary carnitine deficiency can lead to deterioration of multiple mitochondrial processes and to biochemical abnormalities including hyperammonaemia. Recently, carnitine deficiency secondary to a variety of genetic defects of intermediate metabolism or other disorders has been recognized [2]. In animal experiments, Costell et al. [1] and O'Conner et al. [6] showed that L-carnitine is an excellent protective agent against acute ammonia intoxication in mice, reducing mortality and preventing the manifestations of toxicity. They suggested that secondary carnitine deficiency aggravated hyperammonaemia clue to inborn errors of urea cycle. Ohtani et al. [8] reported secondary carnitine deficiency in hyperammonaemic attacks of OTC deficiency and stated that administration of i.-carnitine lowered the elevated blood ammonia levels in patients. However, as far as we know, the carnitine status in CPS-I deficiency has not been described before. The defini-
274 Table 1. Carnitine concentrations in serum, urine, and peritoneal dialysis fluid in the patient and controls
Serum carnitine (nmol/ml) Free After termination of L-carnitine therapy 35 days 60 days 5 months 3 months after L-carnitine therapy (10 mg/kg/day) Controls 1-11months (n = 51)
35.7 37.7 11.5 55.0 37.4 +
Acyl
9.9
22.7 10.6 16.5 23.8 21.3 _+ 8.9
Total 58.4 48.3 28.0 78.8 58.7 + 14.8
A/F ratio 0.64 0.28 1.44 0.43 0.60 + 0.31
Urine carnitine (nmol/mg creatinine)
5 months after termination of L-carnitine therapy 3 months after L-carnitine therapy (10 mg/kg/day) Controls (n = 30)
Free
Acyl
Total
RRFC (%)
ND 885.1 685.3 + 438.0
98.4 454.1 854.7 + 350.2
98.4 1339.2 1540.3 + 528.7
98.4 99.5 + 0.4 (n = 17)
Peritoneal dialysis fluid (nmol/ml) Free 4.6
Acyl 37.6
Total 42.2
ND = not detectable tion of carnitine deficiency is variable. Some authors imply a deficiency of total carnitine in serum or tissue. Others use the term to indicate reduced levels of free carnitine. The principle issue, according to Stumpf et al. [11] is not carnitine deficiency per se, but the increased acyl/free carnitine ratio. Therefore, our patient with CPS-I deficiency would possibly be included in the category of carnitine deficiency. Administration of sodium benzoate was thought to be one cause of carnitine deficiency in our patient, because benzoylcarnitine is metabolized from accumulated benzoyl-CoA [7]. A second factor was thought to be peritoneal dialysis. It is well established that during haemodialysis, serum flee carnifine levels fall sharply, and carnitine losses due to dialysis are not fully compensated by endogenous synthesis [9], especially in early infancy. Matsuda and Ohtani [3] stated that excess urinary loss of free and acyl carnitine in association with decreased RRFC was one cause of carnitine deficiency in Reye syndrome and Reye-like attacks. However, our patient's RRFC was within normal values, and suggested normal mitochondrial function in the renal tubule. Carnitine is synthesized from lysine molecules in protein, and the endogenous synthesis of carnitine is inadequate in early infancy. Dietary carnifine is necessary for maintenance of normal carnitine status. Also protein restriction using low protein formula containing no carnitine may have been a factor in the carnitine deficiency in our patient at 7 months of age. Oral L-carnitine (100 to 150mg/kg per day divided into three or four doses) has been recommended in systemic carnifine deficiency [11]. Ohtani et al. [8] reported the therapeutic efficacy of oral administration of L-carnitine (50 to 100 mg/kg per day) in two patients with OTC deficiency. Our dosage of L-carnitine of 10 to 20 mg/kg per day was relatively low, but the mean blood ammonia levels decreased significantly, accompanied with an increase in serum free carnitine levels. Although no clinical symptoms of carnitine deficiency were observed in our patient at 7 months of age, the administration of L-carnitine seemed to reduce the elevated blood ammonia levels. Thus, L-carnitine might be useful to prevent hyperammonaemic attacks in CPS-I deficiency as in OTC deficiency.
Acknowledgements. We thank Drs. M. Yokozawa and M. Hiraki who reffered the patient, Dr. U. Kusunoki for performing the organic acid analysis, and Dr. T. Saheki for measuring the CPS-I activity and OTC activity in liver tissue. This work was supported by Grant 62304042 from the Ministry of Education, Science and Culture of Japan.
References
1. CosteU M, O'Connor JE, Miquez MP, Grisolia S (1984) Effects of L-carnitine on urea synthesis following acute ammonia intoxication in mice. Biochem Biophys Res Commun 120: 726-733 2. Engel AG, Rebouche CJ (1984) Carnitine metabolism and inborn errors. J Inherited Metab Dis 7 [Suppl] : 38-43 3. Matsuda I, Ohtani Y (1986) Camitine status in Reye and Reyelike syndrome. Pediatr Neurol 2: 90-94 4. Matsuda I, Ohtani Y, Ninomiya N (1986) Renal handling of carnitine in children with carnitine deficiency and hyperammonemia associated with valproate therapy. J Pediatr 109 : 131-134 5. McGarry JD, Foster DW (1976) An improved and simplified radioisotopic assay for the determination of free and esterified carnitine. J Lipid Res 17:277-281 6. O'Connor JE, Costell M, Grisolia S (1984) Protective effect of L-carnitine on hyperammonemia. FEBS Lett 166 : 331-334 7. O'Connor JE, Costell M, Grisolia S (1987) The potentiation of ammonia toxicity by sodium benzoate is prevented by L-carnitine. Biochem Biophys Res Commun 145 : 817-824 8. Ohtani Y, Ohyanagi K, Yamamoto S, Matsuda I (1988) Secondary carnitine deficiency in hyperammonemic attacks of ornithine transcarbamylase deficiency. J Pediatr 112: 409-414 9. Rodriguez-Segade S, Alonso de la Pena C, Paz JM, Novoa D, Arcocha V, Romero R, Del Rio R (1986) Carnitine deficiency in haemodialysed patients. Clin ClaimActa 159 : 249-256 i0. Schimke RT (1962) Adaptive characteristics of urea cycle enzymes in rat liver. J Biol Chem 237: 459-468 11. Stumpf DE, Parker WD, Angelini C (1985) Carnitine deficiency, organic acidemias and Reye's syndrome. Neurology 35:1041-1045 12. Walser M (1983) Urea cycle disorders and other hereditary hyperammonemic syndromes. In: Stanbury JB, Wyngaarden JB, Fredrickson DS, Goldstein JL, Brown MS (eds) The metabolic basis of inherited disease. McGraw-Hill, New York, pp 402-438
Received February 23, 1989 / Accepted June 15, 1989
Eur J Pediatr (1990) 149 : 272-274
Pediatrics
9 Springer-Verlag 1990
A case of carbamylphosphate synthetase-I deficiency associated with secondary carnitine deficiency L-carnitine treatment of CPS-I deficiency T. Mori 1, A. Tsuchiyama ~, K. Nagai 1, M. Nagao 1, K. Oyanagi 1, and S.Tsugawa ~ 1Department of Paediatrics, Sapporo Medical College, Chuo-ku $1 WI6 Sapporo 060, 2Department of Paediatrics, National Sanatorium Otaru Hospital, Nagahashi 3-24-1, Otaru, 047 Japan
Abstract. We describe a male infant with congenital hyperammonaemia due to partial carbamylphosphate synthetase-I (CPS-I) deficiency. A t 21 days of age, he had convulsions and at 53 days of age hyperammonaemic coma. Therapy with sodium benzoate, L-arginine, essential amino acids, L-carnitine and peritoneal dialysis lowered the blood ammonia levels, and his clinical manifestations improved. The CPS-I activity in liver tissue obtained by open biopsy was about 25.6% of normal values. The serum and urine free carnitine levels in the patient decreased during the hyperammonaemic crisis and were low at 7 months of age. After oral administration of L-carnitine (10 mg/kg per day) at 7 months of age, the mean blood ammonia levels decreased significantly, accompanied by an increase in serum and urine free carnitine levels. We propose the use of L-carnitine therapy to prevent secondary carnitine deficiency in patients with CPS-I deficiency as well as ornithine transcarbamylase (OTC) deficiency.
Key words: CPS-I deficiency - Carnitine - Hyperammonaemia
Introduction Inherited deficiency of carbamylphosphate synthetase-I (CPS-I) is a rare cause of congenital hyperammonaemia. In general, the clinical severity of inborn errors of urea cycle are affected by the residual enzyme activities. CPS-I deficiency is classified as either a lethal neonatal type or a delayed onset type according to the levels of residual enzyme activity [12]. We here report a patient with delayed onset type of CPS-I deficiency, who was admitted to our hospital at 53 days of age because of hyperammonaemic coma. Recently, secondary carnitine deficiency in hyperammonaemic attacks of ornithine transcarbamylase (OTC) deficiency has been reported [8]. It was suggested that reduced carnitine was one of the aggravating factors. However, to our knowledge, there has been no previous report on the carnitine status in CPS-I deficiency. In this paper, we evaluate the carnitine status in a patient with CPS-I deficiency and the effect of oral L-carnitine administration on blood ammonia levels. Possibilities of carnitine therapy in CPS-I deficiency are discussed. Offprint requests to: T. Mori Abbreviations: CPS-I = carbamylphosphate synthetase-I; OTC =
ornithine transcarbamylase; RRFC = renal reabsorption of free carnitine
Case report The patient, a 53-day-old boy, was the first child of unrelated and healthy Japanese parents. He was born after an uneventful delivery with a birth weight of 3358 g. He was healthy until, at 21 days of age, a generalized tonic-clonic seizure developed. After another week, seizures occurred twice a week which were controlled by sodium valproate therapy. A t 50 days of age, he again had a seizure, with frequent vomiting, feeding difficulties and apathy. On the next day, he was admitted to a local hospital in a somnolent state. Frequent vomiting and seizures continued. Two days after admission, he became stuporous, laboratory findings showed hyperammonaemia ( > 400 gg/dl) and he was transferred to our hospital. On admission, the patient was comatose and did not respond to painful stimulii. The pupils were mydriatic and responded poorly to light. The cardiovascular and respiratory systems were normal. The liver edge was palpable 2 cm below the right costal margin. The muscles were hypotonic and the bilateral deep tendon reflexes were weak, but no pathological reflexes were elicited. Laboratory studies showed normal leucocyte, erythrocyte and platelet counts, normal serum electrolytes, hepatocellular enzymes, bilirubin, total protein, blood glucose, creatinine and blood urea nitrogen. Routine urinalysis showed no abnormalities. There was a mild metabolic acidosis (pH7.358, bicarbonate 17.4mM/1, base excess -6.9mM/1). The blood ammonia level was elevated to 741 gg/dl (normal, < 70 gg/dl). Urinary orotic acid excretion was slightly elevated (11.3 gg/mg creatinine; controls: 3.4 to 5.9 gg/mg creatinine). Analysis of urinary organic acids by gas-chromatography and mass spectrometry showed no abnormalities except for valproate metabolites. Serum concentrations of amino acids showed the following levels: citrulline, trace (normal, 32.2+ ll.2gmol/1); glutamic acid, 252.5 gmol/1 (normal, 100.7 + 47.6 gmol/1); glutamine, 942.1 gmol/1 (normal, 555.2 _+237.6 gmol/1); alanine, 424.7gmol/1 (normal, 378.2 + 129.9gmol/1); arginine, 54.8grnol/1 (normal, 88.2+31.6gmol/1); lysine, 320.5grnol/1 (normal, 170.2 + 54.7 gmol/1). Other amino acids were normal. Argininosuccinic acid was not detected. Administration of sodium valproate was stopped because it aggravated the hyperammonaemia and carnitine deficiency. Therapy was started with L-arginine, sodium benzoate, essential amino acids, peritoneal dialysis and L-carnitine (20 mg/kg per day). After peritoneal dialysis, his mental status began to improve and gradually normalised over the next 24h along with a decrease in blood ammonia levels (Fig. 1). He was then put on a low-protein diet (1.5 to 1.7 g/kg per day). Adminis-
273 Essential amino acids
L- carnitine [ (20 mg/kg/day, perOs)
Arginine (0.8g/kg/day) Sodium benzoate (250mg/kg/day)
10,000-
91.3
Peritoneal dialysis ]
[
L-carnitine (20 mg/kg/daY)
800
95.4
g= o 5, 000~
98.3
200 0
0.48 o
60. O.21
I. 65
O.83
g ,0.
98.4
I
c
=o
At
I 12
I
24
I 96
admission
20
Time (hour) after admission E
0
At
I
/ 12
I 24
I 48
admission
Time (hours) after admission
Fig.1. Clinical course and serum carnitine concentrations in the patient after admission. Open columns, free carnitine; closed columns, acyl carnitine; numbers, acyl free ratio tration of L-arginine and sodium benzoate was stopped, but oral administration of L-carnitine was continued for another 20 days. A t 3 months of age, an open liver biopsy was performed with the informed consent of his parents. The CPS-I and OTC activities in the liver specimen, measured by the method of Schimke [10] were 0.011 pmol product/rag protein/rain, 25.6% of normal, (normal= 0.043_+ 0.014, n = 14) and 0.69 grnol product/mg protein/min (normal = 0.66 -+ 0.24, n = 14), respectively.
Methods
Free and acyl carnitine in serum and urine were measured according to McGary and Foster [5]. The rate of renal reabsorption of free carnitine (RRFC) was calculated according to the method of Mastuda et al. [4]. The first monitoring period of blood ammonia levels was 5 months between termination and initiation of L-carnitine therapy, and the second period was 4 months after L-carnitine therapy. The Student t-test was used for statistical analysis. Results
Serum free carnitine was normal on admission, but decreased markedly 12h later. This was accompanied by an increased ratio of acyl/free carnitine. After L-carnitine treatment, the serum free carnitine increased to normal levels (Fig. 1). Changes in urinary free carnitine excretion were similar to those serum. Urinary acyl carnitine excretion increased markedly after initiation of L-carnitine therapy. R R F C was within normal values (Fig. 2). Free carnitine was also deteced in the peritoneal dialysis fluid. Serum free carnitine levels determined at 35 days and 60 days after termination of the i.-carnitine treatment were within normal values. However, at 7 months of age
Fig. 2. Urinary carnitine concentrations in the patient after admission. Open columns, free carnitine; closed columns, acyl carnitine; numbers rate of renal reabsorption of free carnitine
and whilst asymptomatic, his serum free carnitine level decreased again together with an increase of an acyl/free carnitine ratio. Urinary free carnitine was not detected (Table 1). Laboratory findings at this time were normal, including blood gas analysis, blood sugar, hepatocellular enzymes and free fatty acid. L-carnitine administration (10mg/kg per day) was initiated and continued for the last 4 months. Mean blood ammonia concentrations obtained before and after L-carnitine therapy were 135.2 + 42.5 pg/dl (n = 74) and 103.1 + 19.0 pg/dl (n = 22), respectively (P < 0.01). Protein restrictions before and after L-carnitine therapy were 1.5 to 1.7 g/kg per day and 1.8 to 2.0 g/kg per day, respectively. A t 11 months of age, blood ammonia levels were well controlled under the low-protein diet (1.8 to 2.0 g/kg per day). Body weight, motor development, E E G and computed tomography of the brain were all normal.
Discussion
Carnitine is essential for the transport of fatty acids into mitochondria where they undergo ~-oxidation. Another function of carnitine is the buffering of toxic acyl-CoA compounds [11]. Therefore, secondary carnitine deficiency can lead to deterioration of multiple mitochondrial processes and to biochemical abnormalities including hyperammonaemia. Recently, carnitine deficiency secondary to a variety of genetic defects of intermediate metabolism or other disorders has been recognized [2]. In animal experiments, Costell et al. [1] and O'Conner et al. [6] showed that L-carnitine is an excellent protective agent against acute ammonia intoxication in mice, reducing mortality and preventing the manifestations of toxicity. They suggested that secondary carnitine deficiency aggravated hyperammonaemia clue to inborn errors of urea cycle. Ohtani et al. [8] reported secondary carnitine deficiency in hyperammonaemic attacks of OTC deficiency and stated that administration of i.-carnitine lowered the elevated blood ammonia levels in patients. However, as far as we know, the carnitine status in CPS-I deficiency has not been described before. The defini-
274 Table 1. Carnitine concentrations in serum, urine, and peritoneal dialysis fluid in the patient and controls
Serum carnitine (nmol/ml) Free After termination of L-carnitine therapy 35 days 60 days 5 months 3 months after L-carnitine therapy (10 mg/kg/day) Controls 1-11months (n = 51)
35.7 37.7 11.5 55.0 37.4 +
Acyl
9.9
22.7 10.6 16.5 23.8 21.3 _+ 8.9
Total 58.4 48.3 28.0 78.8 58.7 + 14.8
A/F ratio 0.64 0.28 1.44 0.43 0.60 + 0.31
Urine carnitine (nmol/mg creatinine)
5 months after termination of L-carnitine therapy 3 months after L-carnitine therapy (10 mg/kg/day) Controls (n = 30)
Free
Acyl
Total
RRFC (%)
ND 885.1 685.3 + 438.0
98.4 454.1 854.7 + 350.2
98.4 1339.2 1540.3 + 528.7
98.4 99.5 + 0.4 (n = 17)
Peritoneal dialysis fluid (nmol/ml) Free 4.6
Acyl 37.6
Total 42.2
ND = not detectable tion of carnitine deficiency is variable. Some authors imply a deficiency of total carnitine in serum or tissue. Others use the term to indicate reduced levels of free carnitine. The principle issue, according to Stumpf et al. [11] is not carnitine deficiency per se, but the increased acyl/free carnitine ratio. Therefore, our patient with CPS-I deficiency would possibly be included in the category of carnitine deficiency. Administration of sodium benzoate was thought to be one cause of carnitine deficiency in our patient, because benzoylcarnitine is metabolized from accumulated benzoyl-CoA [7]. A second factor was thought to be peritoneal dialysis. It is well established that during haemodialysis, serum flee carnifine levels fall sharply, and carnitine losses due to dialysis are not fully compensated by endogenous synthesis [9], especially in early infancy. Matsuda and Ohtani [3] stated that excess urinary loss of free and acyl carnitine in association with decreased RRFC was one cause of carnitine deficiency in Reye syndrome and Reye-like attacks. However, our patient's RRFC was within normal values, and suggested normal mitochondrial function in the renal tubule. Carnitine is synthesized from lysine molecules in protein, and the endogenous synthesis of carnitine is inadequate in early infancy. Dietary carnifine is necessary for maintenance of normal carnitine status. Also protein restriction using low protein formula containing no carnitine may have been a factor in the carnitine deficiency in our patient at 7 months of age. Oral L-carnitine (100 to 150mg/kg per day divided into three or four doses) has been recommended in systemic carnifine deficiency [11]. Ohtani et al. [8] reported the therapeutic efficacy of oral administration of L-carnitine (50 to 100 mg/kg per day) in two patients with OTC deficiency. Our dosage of L-carnitine of 10 to 20 mg/kg per day was relatively low, but the mean blood ammonia levels decreased significantly, accompanied with an increase in serum free carnitine levels. Although no clinical symptoms of carnitine deficiency were observed in our patient at 7 months of age, the administration of L-carnitine seemed to reduce the elevated blood ammonia levels. Thus, L-carnitine might be useful to prevent hyperammonaemic attacks in CPS-I deficiency as in OTC deficiency.
Acknowledgements. We thank Drs. M. Yokozawa and M. Hiraki who reffered the patient, Dr. U. Kusunoki for performing the organic acid analysis, and Dr. T. Saheki for measuring the CPS-I activity and OTC activity in liver tissue. This work was supported by Grant 62304042 from the Ministry of Education, Science and Culture of Japan.
References
1. CosteU M, O'Connor JE, Miquez MP, Grisolia S (1984) Effects of L-carnitine on urea synthesis following acute ammonia intoxication in mice. Biochem Biophys Res Commun 120: 726-733 2. Engel AG, Rebouche CJ (1984) Carnitine metabolism and inborn errors. J Inherited Metab Dis 7 [Suppl] : 38-43 3. Matsuda I, Ohtani Y (1986) Camitine status in Reye and Reyelike syndrome. Pediatr Neurol 2: 90-94 4. Matsuda I, Ohtani Y, Ninomiya N (1986) Renal handling of carnitine in children with carnitine deficiency and hyperammonemia associated with valproate therapy. J Pediatr 109 : 131-134 5. McGarry JD, Foster DW (1976) An improved and simplified radioisotopic assay for the determination of free and esterified carnitine. J Lipid Res 17:277-281 6. O'Connor JE, Costell M, Grisolia S (1984) Protective effect of L-carnitine on hyperammonemia. FEBS Lett 166 : 331-334 7. O'Connor JE, Costell M, Grisolia S (1987) The potentiation of ammonia toxicity by sodium benzoate is prevented by L-carnitine. Biochem Biophys Res Commun 145 : 817-824 8. Ohtani Y, Ohyanagi K, Yamamoto S, Matsuda I (1988) Secondary carnitine deficiency in hyperammonemic attacks of ornithine transcarbamylase deficiency. J Pediatr 112: 409-414 9. Rodriguez-Segade S, Alonso de la Pena C, Paz JM, Novoa D, Arcocha V, Romero R, Del Rio R (1986) Carnitine deficiency in haemodialysed patients. Clin ClaimActa 159 : 249-256 i0. Schimke RT (1962) Adaptive characteristics of urea cycle enzymes in rat liver. J Biol Chem 237: 459-468 11. Stumpf DE, Parker WD, Angelini C (1985) Carnitine deficiency, organic acidemias and Reye's syndrome. Neurology 35:1041-1045 12. Walser M (1983) Urea cycle disorders and other hereditary hyperammonemic syndromes. In: Stanbury JB, Wyngaarden JB, Fredrickson DS, Goldstein JL, Brown MS (eds) The metabolic basis of inherited disease. McGraw-Hill, New York, pp 402-438
Received February 23, 1989 / Accepted June 15, 1989
