Journal of Inherited Metabolic Disease 13 (1990) 125-136 © SSIEM and Kluwer AcademicPublishers. Printed in the Netherlands
Evaluation of Branched-chain Amino Acid Intake in Children with Maple Syrup Urine Disease and Methylmalonic Aciduria H. G. PARSONS, R. J. CARTER, M. UNRATH and F. F. SNYDER Department of Pediatrics, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N IN4
Summary: The biochemical and growth responses to dietary branched-chain amino acid (BCAA) intake were studied in two children; one with a disorder of branched-chain amino acid metabolism, maple syrup urine disease (MSUD) (McKusick 24860), and another with methylmalonic aciduria (MMA) (McKusick 25100). Biochemical control of MSUD focussed on plasma leucine levels while measurement of plasma ammonia levels was used in MMA. From 0 to 2.75 years both patients exhibited five episodes of toxicity. In each case toxicity was associated with dietary indiscretion or intbction. The quantity of protein tolerated was always less in the MMA patient and was approximately 1 g/kg/day. From 1 to 2.75 years each patient's growth velocity approximated their predicted growth channel except during periods of toxicity. In both cases leucine intake, which gave normal growth without toxicity, was always judged to be less than the FAO/WHO recommendations. The BCAA intake of the MMA patient was remarkably stable from 0.5 to 2.75 years and at 2 years of age isoleucine and valine intake approximated the FAO/WHO recommendations. From 2 to 2.75 years BCAA intake (mg/kg/day) of the MSUD patient was less than that of the MMA patient and well below FAO/WHO recommendations. Neuromotor development in both patients is normal. Prudent management of children with disorders of amino acid metabolism includes restricting the intake of the non-metabolizable amino acids to a sufficient intake which optimizes anabolism, leads to a normal growth pattern, and minimizes the accumulation of toxic metabolites (Committee on Nutrition, 1976). Determination of long-term intakes of essential amino acids in these children, resulting in normal growth without toxicity, permits the calculation of essential amino acid requirements in normal children (Snyderman, 1974). The purpose of this study was to evaluate the need for leucine, isoleucine and ratine in two children with disorders of branchedchain amino acid metabolism, maple syrup urine disease and methytmalonic aciduria. In MSUD the branched-chain amino acids are transaminated to their c~-keto acids, but further metabolism is deficient because of impaired oxidative decarboxylation of
MS received 20.7.89 Accepted 30.7.89 125
126
Parsons et aI.
the e-keto acids (Dancis e t at., 1972; Wendel et al., 1975). Patients with methylmalonic aciduria are unable to convert methylmalonyl-CoA to succinyl-CoA because of deficient activity of methylmalonyl-CoA mutase (EC 5.4.99.2) (Matsui et at., 1983). The branched-chain amino acids isoleucine and valine, and methionine and threonine are the major precursors of methylmalonyl-CoA. We determined the branched-chain amino acid intake, growth velocity and evidence of toxicity in these two patients over 2.75 years and compared these results with previously published limited data. CASE REPORTS Case 1: V.A., a girl, was born on 12.04.85 after an uneventful pregnancy and spontaneous delivery, weighing 3000 g. She was the second child of non-consanguineous parents who had had a previous child die at age 11 months of MSUD. MSUD was diagnosed in the proband at 96 h of age and the early neonatal course has been previously described (Parsons et al., 1986). Briefly, the plasma leucine levels reached 1.6 mmol/L by day 4, at which time peritoneal dialysis was initiated in conjunction with a semisynthetic formula devoid of branched-chain amino acids. By day 7 plasma leucine had returned to acceptable levels ( 75 #mol/L are inserted in the growth curve shown in Figure 2. Urine levels of methylmalonic acid were shown to correlate (r = 0.93) with plasma ammonia levels in our patient (Figure 7). Methylmalonic acid inhibits the first enzyme in the urea cycle, carbamyl phosphate synthetase I (Gruskay and Rosenberg, 1979). From 0.25 to 2.75 years hyperammonaemia (ammonia > 75 #mol/L) was present on four occasions (Figure 2), in association with dietary
& Inher. Metab. Dis. 13 (t990)
BCAA Intake in Children with MSUD and M M A
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Figure 1 Growth chart of female child with maple syrup urine disease. The insert depicts the age when plasma leucine levels were > 1mmol/L indiscretion at 0.76 and 1.41 years, rubella at 1.36 years and otitis media and vomiting at 2.72 years (Figure 2). He has remained otherwise well and has normal neuromotor development. MATERIALS AND METHODS Amino acid, ammonia and MMA determination 3-4 h postprandial venous plasma samples were analysed for amino acids. Plasma leucine, isoleucine and vaIine were determined by column chromatography with an LKB amino acid analyser equipped for physiological amino acid analysis. The normal ranges for controls between 3 months and 5 years of age were for leucine, 0.040.22 mmol/L; isoleucine, 0.02-0.10 mmol/L; and valine 0.08-0.30 mmol/L (Parsons et al., 1986). Plasma ammonia levels were measured by a Dupont ACA analyser
J. Inher. Metab. Dis, 13 (1990)
128
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2 Growth chart of male child with methylmalonic acidaemia. The insert depicts the age when plasma ammonia levels were > 75 ttmol/L
Figure
(Wilminton, Delaware) in which ammonia is condensed with ~-ketoglutarate by glutamate dehydrogenase with the simultaneous oxidation of NADH. Normal plasma ammonia levels for our laboratory are < 45 #mol/L. Urine was collected at the time of measurement of plasma ammonia levels for creatinine and methylmalonic acid quantitation. Deuterated methylmalonic acid ( M S D - - D o r v a t , Canada) was added as an internal standard to each urine sample. The samples were acidified and the urinary organic acids, along with the internal standard, were extracted three times with ethyl acetate, followed by three times with diethylether. The extractions were pooled, evaporated to dryness and derivatized with N-methyl N-trimethyl silyl-trifluoracetamide (Pierce Chemical Co.). The derivatives were separated using a Hewlett Packard 5890 gas chromatograph equipped with a 25m x 0.31 mm H P ultra-2 capillary column coupled to an H P 5970B mass selective detector. Oven temperature was initially set at 50°C, and increased to a final J. Inher. Metab. Dis. 13 (1990)
B C A A Intake in Children with M S U D and M M A
129
temperature of 300°C at a rate of 4°C/rain. The injection port and detector temperatures were 250°C and 280°C, respectively. Helium was used as the carrier gas and the linear flow rate was 36 cm/sec. Data was collected and processed by the HP 900 Model 310 Workstation Computer System. The major mass abundance of MMA and the internal standard were used for quantitation purposes. Diets
The MSUD formula was prepared with a protein-free formula base (Product 80056, Mead-Johnson Laboratories, 490 kcal/100 g), Enfalac powder, and an amino acid mixture lacking the branched-chain amino acids (MSUD-AID, Milner Scientific and Medical Research Co., Liverpool, UK). According to the manufacturer's analysis Enfalac contained 104rag leucine, 61 mg isoleucine and 62rag valine/g protein and 2.2 g protein/100 kcal. The powdered ingredients were weighed on a balance at home and diluted with water to make l L. The formula provided the only nutrient source for the first six months and approximately 90% of the nutrient source since that time. At 0.1 years due to prior variation in dietary intake and large fluxes in plasma leucine levels half the total formula volume was provided by home continuous nocturnal nasogastric feeds and bolus feeds during the day when the formula was not completely ingested. For the MMA infant formula was prepared with Product 80056 (Mead-Johnson Laboratory, 490 keal/100 g), Enfalac powder, and an amino acid mixture lacking isoleucine, valine, methionine and threonine as OS-1 (Milupa). L-carnitine free base (Chemical Dynamics Corporation, South Plainfield, N J) was added to the total formula to provide 200mg/kg/day. Half the formula volume was provided by nocturnal nasogastric feeds for the first year of life; thereafter, it was discontinued on the condition that the child received a 2.00am high carbohydrate snack. The formula continues to provide at least 50% of calories. Dietary prescriptions were modified according to growth velocity and blood amino acid and plasma ammonia levels in the BCAA and MMA patients respectively. One Super-one-a-day (Miles) vitamin tablet was crushed and added to the daily formula. Any change in energy, protein and non-metabolizable amino acids was recorded. Nutrient composition was taken from the manufacturers' analysis or otherwise generated from a computer program (NUTS R., Version 3.0, Quilchena Consulting Ltd., Victoria, B.C.). Growth charts are those published by the National Center for Health Statistics of the United States government (Harnill et al., 1978). The predicted growth channels were extrapolated from the child's anticipated ultimate height as it related to the parental midpointed height. The midpointed height is obtained by averaging the parents' heights after first adding 13 cm to the mother's height if the subject is a boy or subtracting 13 cm from the father's height if the subject is a girl (Kaplan, 1982). RESULTS
The predicted growth velocity of the MSUD patient wasthe 5th percentile (Figure 1). Growth velocity from 0.50 to 0.75 years was below the 5th percentile. Growth J. Inher. Metab. Dis. 13 (1990)
130
Parsons et al.
velocity from 0.75 to 2.75 years was variable; growth fall-off occurred with infection or dietary indiscretion, followed by catch-up growth which then continued along the 5th percentile. The predicted rate of growth velocity of the MMA patient was the 25th percentile (Figure 2). From 0.25 to 1.0 years length velocity followed the 10th percentile. Thereafter, the growth velocity approximated the 25th percentile except during infection or dietary indiscretion. Severe growth fall-off at 2.75 years was associated with otitis media and vomiting and resulted in the only episode of pancytopenia (white blood cell count 0.490 x 109) and thrombocytopenia (platelet count 110 x 109). The BCAA intakes, as mg/kg/day, given in Figures 3, 4 and 5 represent the mean of two to three 3-day dietary records for each 0.25 years. The intake of BCAA at 0.25 years in the MSUD patient was considered low as growth was proceeding below the 5th percentile. Upward adjustment of the BCAA intake at 0.75 years exceeded the tolerance level of these amino acids and plasma leucine rose to 1.98 mmol/L. The intake was reduced between 0.75 and 1.0 years, was stable until 1.75 years and thereafter was decreased to keep the plasma leucine level within our desired range (0.15-0.5 retool/L). The need for all BCAA in the MMA patient declined rapidly in the first 0.5 years. Henceforth the need for these non-metabolizable BCAA declined very slowly and from 0.5 to 2.75 years the intake of BCAA in the MMA patient required little adjustment. The recommended BCAA intake as tabulated from former studies of healthy infants, children (Snyderman et al., 1959; 1961; 1964; Nakagawa et al., 1961; 1965; Fomon et al., 1964) and adults by the FAO/WHO (intakes available for 3-4 months, 2 years, 10-12 years and adults) (Joint FAO/WHO ad hoc Expert Committee, 1985) and one MSUD patient determined by Kindt and Halborsen (1980) are also shown 160
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AGE ( y e a r s ) Figure 3 Leucine intake (mg/kg/day) in two children, one with maple syrup urine disease (MSUD) and one with methylmalonic aciduria (MMA), compared with former studies on requirements of leucine intake J. lnher. Metab. Dis. 13 1.1990)
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AGE (years) Figure 5 Valine intake (mg/kg/day) in two children, one with maple syrup urine disease (MSUD) and one with methylmalonic aciduria (MMA), compared with former studies on requirement of valine intake in Figures 3, 4 and 5. The F A O / W H O leucine recommendations always exceeded the leucine intake of our M S U D patient. Compared to the M S U D patient of Kindt and Halborsen (1980), our M S U D patient's BCAA intake was increased at 0.75 years, in good agreement from 1.0 to 1.75 years and below at 0.25 and 2.0 to 2.75 years.
J. lnher. Metab. Dis.
13(1990)
132
Parsons et al.
Likewise, the FAO/WHO (1985) leucine intake recommendations always exceeded the leucine intake of our MMA patient. The FAO/WHO (1985) isoleucine and valine recommended intakes were greater than those of our MMA patient between 0.25 and 0.5 years and in good agreement at 2 years. Figure 6 compares the teucine, rag/100 kcal intake of our MSUD patient with her weight. The leucine/energy intake of our MSUD patient was in close agreement with the leucine/energy intake of one of two MSUD patients reported by Ruch and Kerr (1982). The decline in leucine/energy intake with increasing weight was not apparent in our MMA patient (data not shown). The BCAA plasma levels (mean + SD) for each 0.25 years and number of samples analysed for each patient are shown in Table 1. Plasma BCAA levels were excluded from this tabulation when plasma leucine was > 1.0 mmol/L or ammonia > 75/tmol/L These rare occasions are identified on the growth charts (Figures 1 and 2). The mean plasma leucine level of the MSUD patient was slightly above our control range from 0.25 to 0.75 years, and thereafter was 2 to 3-fold elevated except at 1.75 years. In general, the plasma isoleucine levels were elevated while the valine levels fell within the acceptable range for our laboratory. The plasma BCAA profiles of the MMA patient, with few exceptions, fell within the normal range. Plasma ammonia levels of the MMA patient, when he was not ill (see Figure 2), were relatively stable and within acceptable limits. Protein (g/kg/day) and energy (kcal/kg/day) intakes of the patients are also shown in Table 1. Throughout the study period the protein intake of the MSUD patient was greater than that of the MMA patient. The protein tolerance of the MMA patient was consistent from 0.5 to 2.75 years and approximated 1 g/kg/day. The caloric intake of the MSUD patient was greater than that of the MMA patient from 0.25 to 2.25 years and was equal to, and greater than that of the MMA patient at 2.5 and 2.75 years respectively. • MSUO
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J. Inher. Metab. Dis. 13 (1990)
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(35) 0.26 _+ 0.18 (11) 0.28 +_ 0.20 (5) 0.23 ___0.20 (22) 0.65 _+ 0.53 (17) 0.45 _+ 0.25 (31) 0.59 ± 0.16 (9) 0,14 _ 0.12 (8) 0.42_+ 0.13 (5) 0.36 + 0.20 (9) 0.43 + 0.23 (5) 0.34 __ 0.04
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0.5 m m o l / L ) each fime. The leudne/energy intake (mgleucine/lOO kcal) decreased as weight increased in a similar manner to one of two classical MSUD patients (Ruch and Kerr, 1982). The increased leucine/energy intake at 1.75 years corresponded to recovery from gastroenteritis and a fractured radius and ulna. We speculate that the improved leucine tolerance resulted from an increase in protein synthesis. Measurement of plasma ammonia levels provides a useful means of assessing toxic levels of plasma methylmalonic (Packman et al., 1978; Shapiro et al., 1978) and propionic (Coude et al., 1982) acids. We extended this finding to show that plasma ammonia also correlates with the urine methylmalonic acid concentration per g of creatinine (Figure 7). Fall-off in growth was associated with poor metabolic control as assessed by hyperammonaemia (>75#mol/L) and returned to normal when protein intake was decreased from 1.5 to 1.0 g/kg/day. The degree of protein restriction has ranged from 0.6 to 1.4 g/kg/day (Nyhan et al., 1973; Whelan et al., 1979; Satoh et al., 1981; Ney et al., 1985). We recommend that optimal protein intake be determined individually in order to permit maximum growth and minimal metabolic complications. As the body has a very limited capacity for storage of amino acids, fluctuations in daily protein intake for patients with amino acid disorders are to be avoided to prevent toxicity or negative nitrogen balance. We have previously shown in meNfed children a protein synthetic rate 19% higher in the evening (20.00h) and breakdown rate 27% greater in the morning (08.00 h) (Parsons et al., 1983). Nocturnal nasogastric feeds and night-time feeds were both tolerated well without complication J. Inher. Metab. Dis. 13 (1990)
135
B C A A Intake in Children with M S U D and M M A 1412. C~ 0
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Evaluation of Branched-chain Amino Acid Intake in Children with Maple Syrup Urine Disease and Methylmalonic Aciduria H. G. PARSONS, R. J. CARTER, M. UNRATH and F. F. SNYDER Department of Pediatrics, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N IN4
Summary: The biochemical and growth responses to dietary branched-chain amino acid (BCAA) intake were studied in two children; one with a disorder of branched-chain amino acid metabolism, maple syrup urine disease (MSUD) (McKusick 24860), and another with methylmalonic aciduria (MMA) (McKusick 25100). Biochemical control of MSUD focussed on plasma leucine levels while measurement of plasma ammonia levels was used in MMA. From 0 to 2.75 years both patients exhibited five episodes of toxicity. In each case toxicity was associated with dietary indiscretion or intbction. The quantity of protein tolerated was always less in the MMA patient and was approximately 1 g/kg/day. From 1 to 2.75 years each patient's growth velocity approximated their predicted growth channel except during periods of toxicity. In both cases leucine intake, which gave normal growth without toxicity, was always judged to be less than the FAO/WHO recommendations. The BCAA intake of the MMA patient was remarkably stable from 0.5 to 2.75 years and at 2 years of age isoleucine and valine intake approximated the FAO/WHO recommendations. From 2 to 2.75 years BCAA intake (mg/kg/day) of the MSUD patient was less than that of the MMA patient and well below FAO/WHO recommendations. Neuromotor development in both patients is normal. Prudent management of children with disorders of amino acid metabolism includes restricting the intake of the non-metabolizable amino acids to a sufficient intake which optimizes anabolism, leads to a normal growth pattern, and minimizes the accumulation of toxic metabolites (Committee on Nutrition, 1976). Determination of long-term intakes of essential amino acids in these children, resulting in normal growth without toxicity, permits the calculation of essential amino acid requirements in normal children (Snyderman, 1974). The purpose of this study was to evaluate the need for leucine, isoleucine and ratine in two children with disorders of branchedchain amino acid metabolism, maple syrup urine disease and methytmalonic aciduria. In MSUD the branched-chain amino acids are transaminated to their c~-keto acids, but further metabolism is deficient because of impaired oxidative decarboxylation of
MS received 20.7.89 Accepted 30.7.89 125
126
Parsons et aI.
the e-keto acids (Dancis e t at., 1972; Wendel et al., 1975). Patients with methylmalonic aciduria are unable to convert methylmalonyl-CoA to succinyl-CoA because of deficient activity of methylmalonyl-CoA mutase (EC 5.4.99.2) (Matsui et at., 1983). The branched-chain amino acids isoleucine and valine, and methionine and threonine are the major precursors of methylmalonyl-CoA. We determined the branched-chain amino acid intake, growth velocity and evidence of toxicity in these two patients over 2.75 years and compared these results with previously published limited data. CASE REPORTS Case 1: V.A., a girl, was born on 12.04.85 after an uneventful pregnancy and spontaneous delivery, weighing 3000 g. She was the second child of non-consanguineous parents who had had a previous child die at age 11 months of MSUD. MSUD was diagnosed in the proband at 96 h of age and the early neonatal course has been previously described (Parsons et al., 1986). Briefly, the plasma leucine levels reached 1.6 mmol/L by day 4, at which time peritoneal dialysis was initiated in conjunction with a semisynthetic formula devoid of branched-chain amino acids. By day 7 plasma leucine had returned to acceptable levels ( 75 #mol/L are inserted in the growth curve shown in Figure 2. Urine levels of methylmalonic acid were shown to correlate (r = 0.93) with plasma ammonia levels in our patient (Figure 7). Methylmalonic acid inhibits the first enzyme in the urea cycle, carbamyl phosphate synthetase I (Gruskay and Rosenberg, 1979). From 0.25 to 2.75 years hyperammonaemia (ammonia > 75 #mol/L) was present on four occasions (Figure 2), in association with dietary
& Inher. Metab. Dis. 13 (t990)
BCAA Intake in Children with MSUD and M M A
127
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Figure 1 Growth chart of female child with maple syrup urine disease. The insert depicts the age when plasma leucine levels were > 1mmol/L indiscretion at 0.76 and 1.41 years, rubella at 1.36 years and otitis media and vomiting at 2.72 years (Figure 2). He has remained otherwise well and has normal neuromotor development. MATERIALS AND METHODS Amino acid, ammonia and MMA determination 3-4 h postprandial venous plasma samples were analysed for amino acids. Plasma leucine, isoleucine and vaIine were determined by column chromatography with an LKB amino acid analyser equipped for physiological amino acid analysis. The normal ranges for controls between 3 months and 5 years of age were for leucine, 0.040.22 mmol/L; isoleucine, 0.02-0.10 mmol/L; and valine 0.08-0.30 mmol/L (Parsons et al., 1986). Plasma ammonia levels were measured by a Dupont ACA analyser
J. Inher. Metab. Dis, 13 (1990)
128
P a r s o n s et at.
105 100 95
50 25
90
5
Length
85
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2 Growth chart of male child with methylmalonic acidaemia. The insert depicts the age when plasma ammonia levels were > 75 ttmol/L
Figure
(Wilminton, Delaware) in which ammonia is condensed with ~-ketoglutarate by glutamate dehydrogenase with the simultaneous oxidation of NADH. Normal plasma ammonia levels for our laboratory are < 45 #mol/L. Urine was collected at the time of measurement of plasma ammonia levels for creatinine and methylmalonic acid quantitation. Deuterated methylmalonic acid ( M S D - - D o r v a t , Canada) was added as an internal standard to each urine sample. The samples were acidified and the urinary organic acids, along with the internal standard, were extracted three times with ethyl acetate, followed by three times with diethylether. The extractions were pooled, evaporated to dryness and derivatized with N-methyl N-trimethyl silyl-trifluoracetamide (Pierce Chemical Co.). The derivatives were separated using a Hewlett Packard 5890 gas chromatograph equipped with a 25m x 0.31 mm H P ultra-2 capillary column coupled to an H P 5970B mass selective detector. Oven temperature was initially set at 50°C, and increased to a final J. Inher. Metab. Dis. 13 (1990)
B C A A Intake in Children with M S U D and M M A
129
temperature of 300°C at a rate of 4°C/rain. The injection port and detector temperatures were 250°C and 280°C, respectively. Helium was used as the carrier gas and the linear flow rate was 36 cm/sec. Data was collected and processed by the HP 900 Model 310 Workstation Computer System. The major mass abundance of MMA and the internal standard were used for quantitation purposes. Diets
The MSUD formula was prepared with a protein-free formula base (Product 80056, Mead-Johnson Laboratories, 490 kcal/100 g), Enfalac powder, and an amino acid mixture lacking the branched-chain amino acids (MSUD-AID, Milner Scientific and Medical Research Co., Liverpool, UK). According to the manufacturer's analysis Enfalac contained 104rag leucine, 61 mg isoleucine and 62rag valine/g protein and 2.2 g protein/100 kcal. The powdered ingredients were weighed on a balance at home and diluted with water to make l L. The formula provided the only nutrient source for the first six months and approximately 90% of the nutrient source since that time. At 0.1 years due to prior variation in dietary intake and large fluxes in plasma leucine levels half the total formula volume was provided by home continuous nocturnal nasogastric feeds and bolus feeds during the day when the formula was not completely ingested. For the MMA infant formula was prepared with Product 80056 (Mead-Johnson Laboratory, 490 keal/100 g), Enfalac powder, and an amino acid mixture lacking isoleucine, valine, methionine and threonine as OS-1 (Milupa). L-carnitine free base (Chemical Dynamics Corporation, South Plainfield, N J) was added to the total formula to provide 200mg/kg/day. Half the formula volume was provided by nocturnal nasogastric feeds for the first year of life; thereafter, it was discontinued on the condition that the child received a 2.00am high carbohydrate snack. The formula continues to provide at least 50% of calories. Dietary prescriptions were modified according to growth velocity and blood amino acid and plasma ammonia levels in the BCAA and MMA patients respectively. One Super-one-a-day (Miles) vitamin tablet was crushed and added to the daily formula. Any change in energy, protein and non-metabolizable amino acids was recorded. Nutrient composition was taken from the manufacturers' analysis or otherwise generated from a computer program (NUTS R., Version 3.0, Quilchena Consulting Ltd., Victoria, B.C.). Growth charts are those published by the National Center for Health Statistics of the United States government (Harnill et al., 1978). The predicted growth channels were extrapolated from the child's anticipated ultimate height as it related to the parental midpointed height. The midpointed height is obtained by averaging the parents' heights after first adding 13 cm to the mother's height if the subject is a boy or subtracting 13 cm from the father's height if the subject is a girl (Kaplan, 1982). RESULTS
The predicted growth velocity of the MSUD patient wasthe 5th percentile (Figure 1). Growth velocity from 0.50 to 0.75 years was below the 5th percentile. Growth J. Inher. Metab. Dis. 13 (1990)
130
Parsons et al.
velocity from 0.75 to 2.75 years was variable; growth fall-off occurred with infection or dietary indiscretion, followed by catch-up growth which then continued along the 5th percentile. The predicted rate of growth velocity of the MMA patient was the 25th percentile (Figure 2). From 0.25 to 1.0 years length velocity followed the 10th percentile. Thereafter, the growth velocity approximated the 25th percentile except during infection or dietary indiscretion. Severe growth fall-off at 2.75 years was associated with otitis media and vomiting and resulted in the only episode of pancytopenia (white blood cell count 0.490 x 109) and thrombocytopenia (platelet count 110 x 109). The BCAA intakes, as mg/kg/day, given in Figures 3, 4 and 5 represent the mean of two to three 3-day dietary records for each 0.25 years. The intake of BCAA at 0.25 years in the MSUD patient was considered low as growth was proceeding below the 5th percentile. Upward adjustment of the BCAA intake at 0.75 years exceeded the tolerance level of these amino acids and plasma leucine rose to 1.98 mmol/L. The intake was reduced between 0.75 and 1.0 years, was stable until 1.75 years and thereafter was decreased to keep the plasma leucine level within our desired range (0.15-0.5 retool/L). The need for all BCAA in the MMA patient declined rapidly in the first 0.5 years. Henceforth the need for these non-metabolizable BCAA declined very slowly and from 0.5 to 2.75 years the intake of BCAA in the MMA patient required little adjustment. The recommended BCAA intake as tabulated from former studies of healthy infants, children (Snyderman et al., 1959; 1961; 1964; Nakagawa et al., 1961; 1965; Fomon et al., 1964) and adults by the FAO/WHO (intakes available for 3-4 months, 2 years, 10-12 years and adults) (Joint FAO/WHO ad hoc Expert Committee, 1985) and one MSUD patient determined by Kindt and Halborsen (1980) are also shown 160
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AGE ( y e a r s ) Figure 3 Leucine intake (mg/kg/day) in two children, one with maple syrup urine disease (MSUD) and one with methylmalonic aciduria (MMA), compared with former studies on requirements of leucine intake J. lnher. Metab. Dis. 13 1.1990)
131
BCAA Intake in Children with MSUD and M M A 100 • MMA A
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AGE (years) Figure 4 Isoleucine intake (mg/kg/day) in two children, one with maple syrup urine disease (MSUD) and one with methylmalonic aciduria (MMA), compared with former studies on requirements of isoleucine intake 100 DO
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AGE (years) Figure 5 Valine intake (mg/kg/day) in two children, one with maple syrup urine disease (MSUD) and one with methylmalonic aciduria (MMA), compared with former studies on requirement of valine intake in Figures 3, 4 and 5. The F A O / W H O leucine recommendations always exceeded the leucine intake of our M S U D patient. Compared to the M S U D patient of Kindt and Halborsen (1980), our M S U D patient's BCAA intake was increased at 0.75 years, in good agreement from 1.0 to 1.75 years and below at 0.25 and 2.0 to 2.75 years.
J. lnher. Metab. Dis.
13(1990)
132
Parsons et al.
Likewise, the FAO/WHO (1985) leucine intake recommendations always exceeded the leucine intake of our MMA patient. The FAO/WHO (1985) isoleucine and valine recommended intakes were greater than those of our MMA patient between 0.25 and 0.5 years and in good agreement at 2 years. Figure 6 compares the teucine, rag/100 kcal intake of our MSUD patient with her weight. The leucine/energy intake of our MSUD patient was in close agreement with the leucine/energy intake of one of two MSUD patients reported by Ruch and Kerr (1982). The decline in leucine/energy intake with increasing weight was not apparent in our MMA patient (data not shown). The BCAA plasma levels (mean + SD) for each 0.25 years and number of samples analysed for each patient are shown in Table 1. Plasma BCAA levels were excluded from this tabulation when plasma leucine was > 1.0 mmol/L or ammonia > 75/tmol/L These rare occasions are identified on the growth charts (Figures 1 and 2). The mean plasma leucine level of the MSUD patient was slightly above our control range from 0.25 to 0.75 years, and thereafter was 2 to 3-fold elevated except at 1.75 years. In general, the plasma isoleucine levels were elevated while the valine levels fell within the acceptable range for our laboratory. The plasma BCAA profiles of the MMA patient, with few exceptions, fell within the normal range. Plasma ammonia levels of the MMA patient, when he was not ill (see Figure 2), were relatively stable and within acceptable limits. Protein (g/kg/day) and energy (kcal/kg/day) intakes of the patients are also shown in Table 1. Throughout the study period the protein intake of the MSUD patient was greater than that of the MMA patient. The protein tolerance of the MMA patient was consistent from 0.5 to 2.75 years and approximated 1 g/kg/day. The caloric intake of the MSUD patient was greater than that of the MMA patient from 0.25 to 2.25 years and was equal to, and greater than that of the MMA patient at 2.5 and 2.75 years respectively. • MSUO
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Figure 6 Leucine intake (rag/100 kcal) in relationship to weight of a child with IVlSUD. Data is compared with the mean of two classical M S U D patients reported by Ruch and Kerr (1982). With the exclusion of periods 0.25 and 0.75 years, when growth was not optimal and leucine intake resulted in toxic plasma leucine levels, the correlation coefficient was r = 0.95
J. Inher. Metab. Dis. 13 (1990)
__+0.03 __. 0.02 _. 0.02 + 0.02
0.04-0.22
(1) 0.16 (1) 0.17 (2) 0.08 + 0.02 (2) 0.09 + 0.05
(13) 0.08 (12) 0,10 (5) 0.06 (3) 0.10 (1) 0.09 (1) 0.08
+_ 0.02 ± 0.01 + 0.01 + 0.01
0.11 0.04 0.04 + 0,01 0.04 + 0.03
0.02 0.02 0,03 0.06 0.05 0.06
MMA
0.02-0.10
0.09 __+0.08 0.12 _+ 0.08 0.11 _ 0.06 0.18 _+ 0.10 0.14__. 0.05 0.16 + 0.08 0.10 + 0.03 0.14_+_ 0.05 0,10 _+ 0.05 0,11 _ 0.05 0.02 + 0.08
MSUD
Valine
__ 0.05 ___0,03 _+ 0.03 + 0.01
0.20 0.10 0.10 + 0.03 0.04 ___0.03
0.04 0.05 0.04 0.06 0.08 0.10
MMA
0.08-0.30
0.13 _+ 0.10 0.17 _%0.10 0.10 _ 0.07 0.18 + 0.10 0.14 _ 0.09 0.27 _+ 0,09 0,07 _+ 0.04 0.20_+ 0.05 0.17 + 0.09 0.17 + 0.06 0.17 + 0.05
MSUD
(mmol/L)
Numbers in parentheses indicate the number of plasma amino acid determinations during the time interval indicated.
Normal range
(35) 0.26 _+ 0.18 (11) 0.28 +_ 0.20 (5) 0.23 ___0.20 (22) 0.65 _+ 0.53 (17) 0.45 _+ 0.25 (31) 0.59 ± 0.16 (9) 0,14 _ 0.12 (8) 0.42_+ 0.13 (5) 0.36 + 0.20 (9) 0.43 + 0.23 (5) 0.34 __ 0.04
0.25 0.50 0.75 1.0 1.25 1,50 1.75 2.0 2.25 2.50 2.75
MMA
(mmol/L)
MSUD
Isoleucine
Leucine
(mmol/L)
(y)
Age
0.5 m m o l / L ) each fime. The leudne/energy intake (mgleucine/lOO kcal) decreased as weight increased in a similar manner to one of two classical MSUD patients (Ruch and Kerr, 1982). The increased leucine/energy intake at 1.75 years corresponded to recovery from gastroenteritis and a fractured radius and ulna. We speculate that the improved leucine tolerance resulted from an increase in protein synthesis. Measurement of plasma ammonia levels provides a useful means of assessing toxic levels of plasma methylmalonic (Packman et al., 1978; Shapiro et al., 1978) and propionic (Coude et al., 1982) acids. We extended this finding to show that plasma ammonia also correlates with the urine methylmalonic acid concentration per g of creatinine (Figure 7). Fall-off in growth was associated with poor metabolic control as assessed by hyperammonaemia (>75#mol/L) and returned to normal when protein intake was decreased from 1.5 to 1.0 g/kg/day. The degree of protein restriction has ranged from 0.6 to 1.4 g/kg/day (Nyhan et al., 1973; Whelan et al., 1979; Satoh et al., 1981; Ney et al., 1985). We recommend that optimal protein intake be determined individually in order to permit maximum growth and minimal metabolic complications. As the body has a very limited capacity for storage of amino acids, fluctuations in daily protein intake for patients with amino acid disorders are to be avoided to prevent toxicity or negative nitrogen balance. We have previously shown in meNfed children a protein synthetic rate 19% higher in the evening (20.00h) and breakdown rate 27% greater in the morning (08.00 h) (Parsons et al., 1983). Nocturnal nasogastric feeds and night-time feeds were both tolerated well without complication J. Inher. Metab. Dis. 13 (1990)
135
B C A A Intake in Children with M S U D and M M A 1412. C~ 0
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