The effect of intravenous l-carnitine on propionic acid excretion in acute propionic acidaemia

A 6-week-old female infant presented in a severe metabolic crisis from propionic acidaemia. The condition was aggravated by pneumonia and heart insufficiency. In addition to the general supportive measures and caloric intake exclusively from glucose, intravenous l-carnitine treatment (2 g l-carnitine/24 h) was started to enhance propionic acid excretion as a carnitine conjugate. Despite the therapeutic efforts the patient died about 48 h after admission in sudden respiratory arrest and bradycardia. Serum propionic acid concentration was increased to 0.3 mol/ml. Propionylcarnitine excretion was measured and about 55% of the overall excretion during the 48 h treatment period was attributed to an effect of carnitine administration. 2-methylcitrate and 2-methyl-3-oxovaleric acid excretion decreased during the same period. Obviously carnitine was not able to prevent metabolic deterioration but may provide some additional buffer capacity during long-term dietary treatment.     

Cardiomyopathy associated with carnitine loss in kidneys and small intestine

A boy was first seen at the age of 1 year on account of congestive cardiomyopathy. Growth and development had been normal. Total plasma carnitine was extremely low (1.8 mol/l; normal range: 25–64 mol/l). No hypoglycaemia, lactic acidaemia or dicarboxylic aciduria were found. Other laboratory findings were unremarkable except for a slight deficiency in iron, vitamin D and vitamin E. Total muscle carnitine was 1.5% of normal; however, no signs or symptoms of myopathy could be detected. After carnitine loading, liver carnitine increased to 24% of normal. Isolated muscle mitochondria showed decreased oxidative capacity with all substrates tested. Stimulation of O₂ uptake by adenosine diphosphate (ADP) was decreased. After loading with both intravenous and oral carnitine, there was a rise in plasma carnitine and a rapid loss in the urine and the faeces. These findings suggest a defect in the brush border carnitine transport system of the kidneys and of the small intestine. Renal clearance of carnitine was abnormally high. Therapy with 1 g oral l-carnitine/kg per day was instituted without any problems and the cardiac disease resolved within 3 months. The parents and the patient's five sibs also had low plasma carnitine but displayed no cardiomyopathy.Abbreviations ADP adenosine diphosphate - ATP adenosine triphosphate - CoA coenzyme A - DNP 2,4-dinitrophenol - TRC tubular reabsorption coefficient     

A case of carbamylphosphate synthetase-I deficiency associated with secondary carnitine deficiency —l-carnitine treatment of CPS-I deficiency

We describe a male infant with congenital hyperammonaemia due to partial carbamylphosphate synthetase-I (CPS-I) deficiency. At 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 ofl-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 ofl-carnitine therapy to prevent secondary carnitine deficiency in patients with CPS-I deficiency as well as ornithine transcarbamylase (OTC) deficiency.     

Urinary excretion of l-carnitine and acylcarnitines by patients with disorders of organic acid metabolism: evidence for secondary insufficiency of l-carnitine

Concentrations of l-carnitine and acylcarnitines have been determined in urine from patients with disorders of organic acid metabolism associated with an intramitochondrial accumulation of acyl-CoA intermediates. These included propionic acidemia, methylmalonic aciduria, isovaleric acidemia, multicarboxylase deficiency, 3-hydroxy-3-methylglutaric aciduria, methylacetoacetyl-CoA thiolase deficiency, and various dicarboxylic acidurias including glutaric aciduria, medium-chain acyl-CoA dehydrogenase deficiency, and multiple acyl-CoA dehydrogenase deficiency. In all cases, concentrations of acylcarnitines were greatly increased above normal with free carnitine concentrations ranging from undetectable to supranormal values. The ratios of acylcarnitine/carnitine were elevated above the normal value of 2.0 +/- 1.1. l-Carnitine was given to three of these patients; in each case, concentrations of plasma and urine carnitines increased accompanied by a marked increase in concentrations of short-chain acylcarnitines. These acylcarnitines have been examined using fast atom bombardment mass spectrometry in some of these diseases and have been shown to be propionylcarnitine in methylmalonic aciduria and propionic acidemia, isovalerylcarnitine in isovaleric acidemia, and hexanoylcarnitine and octanoylcarnitine in medium-chain acyl-CoA dehydrogenase deficiency. The excretion of these acylcarnitines is compatible with the known accumulation of the corresponding acyl-CoA esters in these diseases. In this group of disorders, the increased acylcarnitine/carnitine ratio in urine and plasma indicates an imbalance of mitochondrial mass action homeostasis and, hence, of acyl-CoA/CoA ratios. Despite naturally occurring attempts to increase endogeneous l-carnitine biosynthesis, there is insufficient carnitine available to restore the mass action ratio as demonstrated by the further increase in acylcarnitine excretion when patients were given oral l-carnitine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reversible cardiomyopathy due to carnitine deficiency from renal tubular wasting

The clinical course of a 4-month-old male infant with a dilated cardiomyopathy secondary to renal tubular losses of carnitine is outlined. He was admitted to the hospital with severe congestive heart failure. An echocardiogram demonstrated normal anatomy. The left ventricular shortening fraction measured 10%. A comprehensive cardiomyopathy evaluation was initiated.The total plasma carnitine level was only 25 mol/ml, but the urine carnitine measured 434 nm/mg of creatinine. He was begun on orall-carnitine and weaned from mechanical ventilation and inotropic support 10 days later. Two years later he remains asymptomatic with normal left ventricular function.     

Metabolic response to carnitine in methylmalonic aciduria. An effective strategy for elimination of propionyl groups.

Patients with methylmalonic aciduria have an excessive intramitochondrial accumulation of acylcoenzyme A compounds that may reduce the availability of free coenzyme A (CoA) for normal metabolic requirements, producing profound metabolic disturbances. Giving carnitine to a patient with methylmalonic aciduria produced an increase in hippurate excretion (an index of intramitochondrial adenosine triphosphate (ATP) and CoA availability), a large increase in short chain urinary acylcarnitines, and a reduction in excretion of methylmalonate and methylcitrate. These acylcarnitines were shown by fast atom bombardment and B/E linked scan mass spectrometry to be propionylcarnitine and acetylcarnitine. Carnitine acts by removing (detoxifying) propionyl groups, thereby releasing CoA and restoring ATP biosynthesis and concentrations towards normal. L-carnitine may play a central role in maintenance of mitochondrial and cellular homoeostasis in methylmalonic aciduria and propionic acidaemia. These principles may provide an approach to the treatment of this and other disorders, inherited and acquired, in which accumulation of acyl CoA metabolites results in sequestration of free CoA, thereby perturbing metabolic homoeostasis.     

Propionylcarnitine excretion is not affected by metronidazole administration to patients with disorders of propionate metabolism

Propionylcarnitine (PC) excretion has been measured during a clinical trial of metronidazole therapy in two patients with propionic acidaemia and two patients with methylmalonic aciduria. All patients were in good metabolic control and were receivingl-carnitine. While total propionate excretion was reduced by up to 40% in all four patients during metronidazole therapy, the excretion of propionylcarnitine remained largely unchanged. PC comprised up to 80% of total propionate excretion in patients with propionic acidaemia.     

Glycine therapy in isovaleric acidemia

The therapeutic efficacy of oral glycine was tested in a 3-year-old girl with isovaleric acidemia. An oral leucine load (25 mg/kg) caused a rise of the blood levels of isovaleric, lactic, and pyruvic acids as well as an increase of urinary excretion of the ketone bodies. These changes did not occur when oral glycine (250 mg/kg) was given with the leucine. Glycine supplementation favored the formation of isovalerylglycine, a nontoxic conjugate of isovaleric acid which is excreted rapidly. Excretion of isovalerylglycine rose threefold when leucine and glycine were administered simultaneously. Chronic glycine therapy was tolerated well and may have prevented one episode of ketoacidosis.     

Serum carnitine levels in patients with homozygous beta thalassemia: a possible new role for carnitine?

Carnitine (-hydroxy--trimethylaminobutyric acid) facilitates the transfer of activated long-chain fatty acids from the cytoplasm to the mitochondria, the site of their -oxidation. Carnitine deficiency results in a reduced usage of fatty acids in energy production and therefore the appearance of clinical symptoms such as myalgia and muscle weakness. In the present study, serum carnitine levels were measured in 45 children and 20 adults with homozygous beta thalassemia. A decrease in serum carnitine levels (total, free and acyl) was found, without any evidence of disorder in the process of mitochondrial -oxidation. The possible cause of this finding could be related to a reduced hepatic carnitine biosynthesis. Conclusion:In patients with homozygous beta thalassemia, the reduction of serum carnitine levels might play an important role in the appearance of muscular dysfunction. It is possible that l -carnitine administration in these patients might improve or even resolve the aforementioned symptom.     

The identification and the excretion pattern of isovaleryl glucuronide in the urine of patients with isovaleric acidemia

We identified isovaleryl glucuronide in the urine of patients with isovaleric acidemia by using gas chromatography-mass spectrometry (GC-MS) and by identifying the products of enzymatic hydrolysis. Conjugation of isovaleryl-CoA with glycine, by the action of glycine-N-acylase, is the main detoxification mechanism in isovaleric acidemia. The identification of isovaleryl glucuronide demonstrates a hitherto unknown, additional detoxification mechanism in patients with isovaleric acidemia. Quantitative analysis of 72 urine specimens from four patients with isovaleric acidemia shows that isovaleryl glucuronide is more likely to be excreted when the amount of urinary 3-hydroxyisovaleric acid excretion is high. This suggests that detoxification via glucuronide conjugation plays an important role when the glycine conjugation system is saturated.     

Cardiomyopathy in propionic acidaemia

Following the death of a patient with propionic acidaemia with a cardiomyopathy we reviewed 19 patients with the same disorder for evidence of cardiomyopathy. Six patients were found to meet the diagnostic criteria. Three patients died and in the other three the cardiac diease resolved completely. All patients were treated with standard therapy and some receivedl-carnitine but this did not seem to influence the eventual outcome. Cardiomyopathy is an important complication of propionic acidaemia and may be rapidly fatal.     

Very long-chain fatty acids in Rett syndrome

Rett syndrome (RS), found exclusively in girls, is characterised by a global deceleration of psychomotor development, loss of acquired speech, loss of manual skills and subsequent deceleration of head growth. The cause of this syndrome is so far unknown. To date there are no biological markers for RS; clinical diagnostic criteria were proposed by the Rett Syndrome Diagnostic Criteria Work Group 1988. The first objective of this study was to assay the levels of very long-chain fatty acids (VLCFA), i.e. C22:0, C24:0, C26:0, by gas chromatography in sera of 30 girls with RS. The VLCFA levels in the studied group were lower than the reference range for healthy children and control group. VLCFA levels were again measured after 2 months of l-carnitine administration in the same groups. VLCFA levels had increased. It is possible that the low VLCFA levels have some relation to the lowered carnitine levels. It may be that low carnitine levels impede transportation to mitochondria, thus the oxidation of long-chain fatty acids is inhibited, and compensated to a certain extent by intensified β-oxidation of VLCFA in the peroxisomal system. Raising carnitine levels could improve substrate delivery for mitochondrial β-oxidation of long-chain fatty acids, thus reducing the use of VLCFA as substrates for β-oxidation. We consider VLCFA to be secondary to the pathogenesis of RS, but the possible abnormalities in their levels may provide an insight into the development of this disease. Conclusion Very long-chain fatty acid and carnitine levels are decreased in Rett syndrome l-Carnitine administration increased very long-chain fatty acid levels in serum. Received: 8 April 1998 / Accepted in revised form: 2 September 1998     

Acute and Chronic-Intermittent Isovaleric Acidemia: Diagnosis and Glycine Therapy

Isovaleric acidemia is caused by an inherited defect in isovaleryl-CoA dehydrogenase (E.C. 1.3.99.10). L-leucine restriction and glycine supplementation are used to decrease the toxic accumulation of isovaleric acid (IVA). Supplemental glycine augments conversion of IVA to isovalerylglycine gVG) through the alternate pathway glycine-N-acylase (E.C. 2.3.1.13). Two clinical phenotypes are described, acute and chronic-intermittent, and are differentiated by enzyme activity in cultured fibroblasts. In this study we determined the optimum therapeutic glycine supplement for treating isovaleric acidemia under stable conditions of restricted leucine intake as compared to oral leucine loading. Under stable clinical conditions and on a restricted leucine intake of 55 mg/kg/day a nine year old with chronic intermittent IVA excreted 12.3 ± 5.8 of IVG which rose to 33.6 ± 14.2 mmoles IVG/gm creatinine as glycine supplements were increased from 0 to 50 mg/kg/day at weekly intervals. Excretion of IVC plateaued between glycine intakes of 50–150 mg/kg, but unexpectedly fell to 13.8 ± 0.5 and 16.3 ± 0.9 mmoles/gm creatinine when glycine supplements were further increased to 300 and 600 mglkglday. IVG excretion increased in a two year old with acute IVA while ingesting 45 mg leucine/kg/day from 5.5 ± 2.8 on no glycine supplement to 10.6 ± 0.8 mmoleslgm creatinine on 600 mg/kg glycine supplements. IVG production was compared in the older patient with chronic intermittent IVA. During acute leucine loads, glycine supplements of 190 or 600 mg/kg/day, resulted in urinary IVG of 194 and 419 mmoles/gm creatinine, respectively. These studies demonstrate that: acute and chronic-intermittent isovaleric acidemia are differentiated with [1–¹⁴C] and [2–¹⁴C]-leucine decarboxylation assays by intact fibroblasts; that glycine supplements of 150 to 250 mg/kg/day are optimum in both forms of the disease when patients are clinically stable but additional supplements will increase IVG production during acute leucine load conditions. However increases in glycine supplementation above 150 mg/kg/day may inhibit IVG production in patients with the chronic intermittent form of isovaleric acidemia, when intracellular IVA accumulation is minimized by diet, or if glycine-N-acylase is less competent.     

Inadequate iron availability as a possible cause of low serum carnitine concentrations in patients with phenylketonuria

A previous observation of decreased serum carnitine concentrations in phenylketonuria (PKU) was investigated in 169 patients either on a strict diet (n=107; median: 8.1 years) or off diet (n=62; median: 15.0 years). Fifty-seven metabolically healthy children (median: 8.5 years) served as controls. PKU patients on a strict diet and older than 2 years had significantly lower serum carnitine concentrations (19.4±5.4 mol/l) than those off diet (29.6±6.7 mol/l). PKU patients on diet also had significantly lower concentrations of haemoglobin and serum ferritin than those off diet. A linear correlation existed between total serum carnitine and ferritin concentrations up to 40 g/l (r=0.52;P<0.01). As iron is an essential cofactor of carnitine synthesis we conclude that reduced endogenous carnitine synthesis due to an inadequate availability of iron may be a major cause of low serum carnitine concentrations. The low carnitine content of the strict and highly protein-reduced diet additionally contributes to a decrease in the serum carnitine concentration. Our results show that a further optimization of the PKU diet increasing either iron availability or carnitine intake should be considered.     

Successful carnitine treatment in a non-carnitine-deficient lipid storage myopathy

An 18-month-old boy presented with general hypotonia, decreased muscle strength, retarded motor development and stunted growth. The excretion of dicarboxylic acids was enhanced. EMG was normal. A muscle biopsy revealed a lipid storage myopathy. Oral daily supplementation with 2 g D,L-carnitine resulted in: (1) an increase of the growth velocity; (2) increased muscle strength, and (3) a decrease in the lipid fraction of the fibre volume. The carnitine content of the muscle biopsied prior to treatment appeared to be normal.Supported by a grant from the Prinses Beatrixfonds     

Ethylmalonic/adipic aciduria: effects of oral medium-chain triglycerides, carnitine, and glycine on urinary excretion of organic acids, acylcarnitines, and acylglycines

A 9-y-old girl with ethylmalonic/adipic aciduria was hospitalized to determine the possible therapeutic efficacy of oral carnitine and glycine supplementation. To provoke a mild metabolic stress, her diet was supplemented with 440 mg/kg/d of medium-chain triglycerides. She was treated successively with carnitine (100 mg/kg/d) for 5 d, neither carnitine nor glycine for 2 d, and then glycine (250 mg/kg/d) for 6 d. Consecutive 12-h urine collections were obtained throughout the entire period. The urinary excretion of eight organic acids, four acylglycines, and four acylcarnitines, which accumulate as a result of a metabolic block of five mitochondrial acyl-CoA dehydrogenases, were quantitatively determined by capillary gas chromatography, stable isotope dilution gas chromatography/mass spectrometry, and radioisotopic exchange HPLC, respectively. The excretion of each group of metabolites was calculated as the mean percentage of total output (mumol/24 h) during the four phases of the protocol (organic acids/acylglycines/acylcarnitines = 100.0%): 1) regular diet (3 d); 88.1/10.8/1.1; 2) medium-chain triglyceride supplementation (4); 82.5/15.6/1.9; 3) medium-chain triglycerides plus carnitine (5); 79.2/8.2/12.6; and 4) medium-chain triglycerides plus glycine (6); 81.0/18.7/0.3. Comparison between total and individual excretion of acylglycines and acylcarnitines indicates that oral glycine supplementation enhanced the conjugation and excretion of fatty acyl-CoA intermediates as efficiently as carnitine. We propose that oral glycine supplementation should be considered in the treatment of other inborn errors of metabolism associated with abnormal urinary excretion of acylglycines.     

Carnitine in the treatment of methylmalonic aciduria (MMA)

Carnitine metabolism was studied and a therapeutic trial with L-carnitine was undertaken in 3 patients with methylmalonic aciduria. Prior to carnitine therapy, the concentration of free carnitine was diminished and the contribution of acylated carnitine to total carnitine was increased in both plasma and urine. During a metabolic crisis, in a patient the intravenous administration of L-carnitine greatly increased, the urinary excretion of acylcarnitine and the plasma concentration of methylmalonic acid fell. In all 3 patients, the chronic oral administration of L-carnitine resulted in the normalisation of the plasma free carnitine concentrations and an increased urinary excretion of carnitine esters. One patient clearly showed clinical improvement under carnitine therapy. The administration of L-carnitine to patients with methylmalonic aciduria results in an increased elimination of toxic propionyl groups and thus to a regeneration of intramitochondrial CoA. In conjunction with appropriate dietary measures, this may improve the metabolic situation of these patients.     

异戊酸血症一例临床及异戊酰辅酶A脱氢酶基因突变研究

目的 了解异戊酸血症患儿的临床、实验室特点以及异戊酰辅酶A脱氢酶(IVD)基因突变情况.方法 对1例异戊酸血症患儿的病史、实验室检查以及血串联质谱和尿气相色谱质谱结果进行了分析,对IVD基因12个外显子及两端内含子行PCR扩增和DNA测序,限制性内切酶片段长度多态性分析c.466G＞C(G127A)新突变.结果 患儿男,2岁7个月,生后3 d起出现呕吐和酸中毒,行幽门切开术后仍反复呕吐,伴有酸中毒发作,智力发育明显落后.血串联质谱分析显示C5酰基肉碱水平增高至12.89μmol/L,尿气相色谱质谱分析显示异戊酰甘氨酸明显升高,临床诊断为异戊酸血症.IVD基因DNA测序显示,患儿存在复合杂合突变:c.149G＞A(R21H)和c.466G＞C(G127A),c.466G＞C(G127A)突变在IVD基因第5外显子上,是以往未报道的新突变.结论 报道1例异戊酸血症,新生儿期发病,反复呕吐,酸中毒和智力落后,血C5酰基肉碱明显升高,尿中有异戊酰、甘氨酸大量排出,基因诊断发现1个IVD基因新突变.     

Carnitine Deficiency in Inherited Organic Acid Disorders and Reye Syndrome

A large quantity of propionylcarnitine in the urine of patients with propionic acidemia and methylmalonic aciduria was demonstrated. The amount excreted depended on the administered L-carnitine dose from 25 to 75 mg/kg/day. A high level of propionylcarnitine was also detected in the amniotic fluid of fetuses at risk of methylmalonic aciduria. Glutaric aciduria type 1 was characterized by excessive urinary excretion of glutarylcarnitine. In a neonate with glutaric aciduria type 2, several specific acylcarnitines were detected in the urine. These included isovaleryl-, acetyl-, isobutyryl-, and butyrylcarnitine as major carnitine esters and glutaryl-, and octanoylcarnitine as minor components. However, the pattern of acylcarnitines excreted changed from isovalerylcarnitine (via leucine) to isobutyrylcarnitine (via valine) during early life. In patients diagnosed as Reye syndrome, tissue carnitine deficiency was not always recognized and no decrease in the free/total carnitine ratio was found in the liver or muscle. The clinical and pathophysiological manifestations seen in these disorders are considered to relate to mitochondrial activity. Therefore, it is necessary to measure acylcarnitine fractions in the urine in order to obtain more precise information about mitochondrial function because carnitine and acylcarnitine compounds may express the metabolic state of mitochondria.     

Transient Carnitine-Responsive Medium-Chain Dicarboxylic Aciduria in an Infant with Cholestasis, Hypoglycemia and Cardiac Failure

In a cholestatic infant showing hypoglycemia and cardiac failure, nonketotic mediumchain dicarboxylic aciduria was disclosed by urinary organic acid analysis. As urinary excretion of long-chain fatty acids was also increased, a defect in β-oxidation of longchain fatty acids appeared likely. To try to improve this abnormality, carnitine supplements were given, which led to the complete resolution of clinical and laboratory abnormalities. This is the first reported case of a cholestatic infant who responded to carnitine supplementation. Deficiency of carnitine palmitoyl transferase was suspected as the underlying cause. ( Acta Paediatr Jpn 1989; 31: 211 - 215)