Carnitine-palmityl-transferase deficiency

Exercise testing and prescription in patients with inborn errors of muscle energy metabolism

Skeletal muscle is a dynamic organ requiring tight regulation of energy metabolism in order to provide bursts of energy for effective function. Several inborn errors of muscle energy metabolism (IEMEM) affect skeletal muscle function and therefore the ability to initiate and sustain physical activity. Exercise testing can be valuable in supporting diagnosis, however its use remains limited due to the inconsistency in data to inform its application in IEMEM populations. While exercise testing is often used in adults with IEMEM, its use in children is far more limited. Once a physiological limitation has been identified and the aetiology defined, habitual exercise can assist with improving functional capacity, with reports supporting favourable adaptations in adult patients with IEMEM. Despite the potential benefits of structured exercise programs, data in paediatric populations remain limited. This review will focus on the utilisation and limitations of exercise testing and prescription for both adults and children, in the management of McArdle Disease, long chain fatty acid oxidation disorders, and primary mitochondrial myopathies.

Phase II randomized study of Plitidepsin (Aplidin), alone or in association with L-carnitine, in patients with unresectable advanced renal cell carcinoma

This randomized phase II study evaluated two schedules of the marine compound Plitidepsin with or without co-administration of L-carnitine in patients with renal cell carcinoma. Patients had adequate performance status and organ function. The primary endpoint was the rate of disease control (no progression) at 12 weeks (RECIST). Other endpoints included the response rate and time dependent efficacy measures. The trial also assessed the efficacy of L-carnitine to prevent Plitidepsin-related toxicity. The two regimes given as 24 hour infusion every two weeks showed hints of antitumoral activity. Disease control at 12 weeks was 15.8% in Arm A (5mg/m2, no L-carnitine) and 11,1% in Arm B (7 mg/m2 with L-carnitine). Two partial responses were observed in Arm A (19 patients), none in Arm B (20 patients). Both schedules had the same progression-free interval (2.1 months). The median overall survival was 7.0 and 7.6 months. The safety profile was similar in both arms of the trial and adverse events were mainly mild to moderate (NCI CTC version 2.0). Increasing the dose to 7 mg/m2 did not increase the treatment efficacy but the incidence of transaminase and CPK elevations and serious AEs. Coadministration of L-carnitine did not prevent muscular toxicity or CPK-elevation associated with Plitidepsin.

Carnitine palmitoyltransferase II deficiency: a clinical, biochemical, and molecular review

Congenital deficiency of carnitine palmitoyltransferase (CPT) II has been known for at least 30 years now, and its phenotypic variability remains fascinating. Three distinct clinical entities have been described, the adult, the infantile, and the perinatal, all with an autosomal recessive inheritance pattern. The adult CPT II clinical phenotype is somewhat benign and requires additional external triggers such as high-intensity exercise before the predominantly myopathic symptoms are elicited. The perinatal and infantile forms involve multiple organ systems. The perinatal disease is the most severe form and is invariably fatal. The introduction of mass spectrometry to analyze blood acylcarnitine profiles has revolutionized the diagnosis of fatty acid oxidation disorders including CPT II deficiency. Its use in expanded neonatal screening programs has made presymptomatic diagnosis a reality. An increasing number of mutations are being identified in the CPT II gene with a distinct genotype-phenotype correlation in most cases. However, clinical variability in some patients suggests additional genetic or environmental modifiers. Herein, we present a new case of lethal perinatal CPT II deficiency with a rare missense mutation, R296Q (907G>A) associated with a previously described 25-bp deletion on the second allele. We review the clinical features, the diagnostic protocol including expanded neonatal screening, the treatment, and the biochemical and molecular basis of CPT II deficiency.

Disorders of lipid metabolism in skeletal muscle

Lipid storage myopathies are typically present with recurrent episodes of myoglobinuria and hypoglycemia, triggered by fasting or infection. Dilated cardiomyopathy can occur. This article will discuss an approach to lipid storage myopathies and describes various forms of disorders by fatty acid oxidation.

Carnitine palmitoyltransferase deficiencies

Carnitine palmitoyltransferase (CPT) deficiencies are common disorders of mitochondrial fatty acid oxidation. The CPT system is made up of two separate proteins located in the outer- (CPT1) and inner- (CPT2) mitochondrial membranes. While CPT2 is a ubiquitous protein, two tissue-specific CPT1 isoforms-the so-called "liver" (L) and "muscle" (M) CPT1s-have been shown to exist. Amino acid and cDNA nucleotide sequences have been identified for all of these proteins. L-CPT1 deficiency (13 families reported) presents as recurrent attacks of fasting hypoketotic hypoglycemia. Two L-CPT1 mutations have been reported to date. M-CPT1 deficiency has not been hitherto identified. CPT2 deficiency has several clinical presentations. The "benign" adult form (more than 150 families reported) is characterized by episodes of rhabdomyolysis triggered by prolonged exercise. The prevalent S113L mutation is found in about 50% of mutant alleles. The infantile-type CPT2 deficiency (10 families reported) presents as severe attacks of hypoketotic hypoglycemia, occasionally associated with cardiac damage commonly responsible for sudden death before 1 year of age. In addition to these symptoms, features of brain and kidney dysorganogenesis are frequently seen in the neonatal-onset CPT2 deficiency (13 families reported), almost always lethal during the first month of life. More than 25 CPT2 mutations (private missense or truncating mutations) have hitherto been detected. Treatment is based upon avoidance of fasting and/or exercise, a low-fat diet enriched with medium chain triglycerides and carnitine ("severe" CPT2 deficiency). Prenatal diagnosis may be offered for pregnancies at a 1/4 risk of infantile/severe-type CPT2 deficiency.

Myoglobinuria: the importance of reaching a firm diagnosis--a patient with defective fatty acid oxidation

A 52 year old man presented with myoglobinuria-induced acute renal failure requiring dialysis. Despite renal biopsy, the cause of the myoglobinuria was not established until he re-presented a year later with a milder episode. At this stage investigations, including a muscle biopsy, demonstrated a defect in fatty acid oxidation amenable to dietary and lifestyle advice. This report emphasizes the importance of reaching a definitive diagnosis in myoglobinuria.

Cardiac and skeletal muscle abnormalities in cardiomyopathy: comparison of patients with ventricular tachycardia or congestive heart failure

Results of cardiac muscle and skeletal muscle biopsies were compared in 22 patients with cardiomyopathy; 11 patients presented with symptoms secondary to ventricular tachycardia (Group 1) and 11 had symptoms of severe congestive heart failure (Group 2). No patient had structural or ischemic cardiac disease. In Group 1 patients, hemodynamic abnormalities were subtle, but invasive study demonstrated dilated cardiomyopathy in two patients and restrictive cardiomyopathy in nine. In Group 2, eight patients had dilated cardiomyopathy and three had restrictive cardiomyopathy. Cardiac biopsy results were abnormal in all 22 patients and the abnormalities were similar for the two groups. Cardiac histologic study revealed a spectrum of abnormalities including fibrosis, dilated sarcoplasmic reticulum, increased numbers of intercalated discs and mitochondrial abnormalities. Histologic abnormalities of skeletal muscle were similar in each group, consisting of endomysial fibrosis and increased lipid deposits. Slightly more than half of the Group 1 and Group 2 patients also had a low concentration of skeletal muscle long chain acylcarnitine. These data demonstrate that abnormalities of both cardiac and skeletal muscle are common in patients with cardiomyopathy; abnormalities are similar whether initial symptoms are due to ventricular tachycardia or congestive heart failure. It is suggested that these patients with cardiomyopathy may have a generalized myopathy.

Metabolism of 1-pyrenedecanoic acid and accumulation of neutral fluorescent lipids in cultured fibroblasts of multisystemic lipid storage myopathy

The lipid metabolism in cultured fibroblasts from multisystemic (type 3) lipid storage myopathy and controls has been studied through pulse-chase experiments using 1-pyrenedecanoic acid as precursor. The uptake of 1-pyrenedecanoic acid was not significantly different in multisystemic lipid storage myopathy and control fibroblasts. The amount of fluorescent lipids synthesized by the cells was proportionally increasing with rising 1-pyrenedecanoic acid concentration in the culture medium. The proportion of the various fluorescent lipids does not significantly vary between 17 to 67 nmol/ml. But a 1-pyrenedecanoic acid concentration higher than 70-100 nmol/ml seems to be severely toxic for the cells. When incubated for 24 h in the presence of 1-pyrenedecanoic acid, at any concentration, the neutral lipid content (triacylglycerols, diacylglycerols and cholesterol esters) of cultured multisystemic lipid storage myopathy fibroblasts was higher than that of controls (around 600% of controls). Chase experiments showed that the biosynthesized triacylglycerols were not degraded in multisystemic lipid storage myopathy cells, but on the contrary were increased, probably by acylation of fluorescent fatty acids liberated from phospholipid turnover. In normal fibroblasts all the cellular fluorescence disappeared after 5 days chase and 1-pyrenedecanoic acid was recovered (as free 1-pyrenedecanoic acid) in the culture medium. In contrast, in multisystemic lipid storage myopathy fibroblasts, 40% of the fluorescence was remaining in the cells after 5 days chase; it was contributed by fluorescent triacylglycerols, which appeared as strongly fluorescent cytoplasmic vesicles. This probably results from a defect of the cytoplasmic catabolism of triacylglycerols which are accumulated in a cytoplasmic compartment independent of the lysosomal compartment (since the acid lysosomal lipase is not deficient in the multisystemic lipid storage myopathy cells). Finally, these results suggest a practical diagnostic application of 1-pyrenedecanoic acid, which can be used to differentiate multisystemic lipid storage myopathy from normal cultured fibroblasts.

Therapy of mitochondrial disorders

Mitochondrial disorders, namely defects of fatty acid oxidation, defects of pyruvate metabolism and defects of the respiratory chain are heterogenous in clinical picture and in response to therapeutic attempts. Defects of fatty acid metabolism are amenable to therapy by dietary means, carnitine substitution and in some cases with vitamins. Defects in pyruvate metabolism do not respond to therapy except in some special cases. Therapeutic attempts include dietary measures, vitamins as coenzyme precursors. Defects in the respiratory chain appear to respond to treatment only in exceptional cases. Evaluation of treatment effects appears to be singularly difficult. General measures that can be of benefit to different defects are discussed.

Familial combined deficiency of muscle carnitine and carnitine palmityl transferase (CPT)

Two patients, brother and sister, aged 19 and 16, with combined, partial deficiency of carnitine palmityltransferase (CPT) are reported. Both patients had recurrent exercise-related myoglobinuria. The brother had also experienced an episode of transient renal failure associated with myoglobinuria. Both had elevated CK and myoglobin in plasma between attacks. There was a normal production of lactate in ischaemic forearm exercise, but elevated levels of NH3, resulting in an increased NH3/lactate ratio; 48-h fasting caused no significant changes in cholesterol, triglycerides or glucose, no rise of CK, and a normal ketogenic response, indicating no hepatic enzyme deficiency. Muscle biopsy showed slight changes of myopathy in both patients, with scattered atrophic fibres, but no lipid accumulation or other specific changes. Biochemical analysis of muscle tissue revealed a reduction of carnitine to 48% and 40% and a reduction of CPT to 55% and 59% of normal values, which is similar to the findings in the only previous report of combined partial carnitine and CPT deficiency. The heterogeneity of the laboratory findings in CPT deficiencies and the value of the various diagnostic procedures in metabolic myopathies are discussed.

The difference between non-selective and beta 1-selective beta-blockers in their effect on platelet function in migraine patients

Platelet function has been postulated as playing a role in the pathogenesis of migraine. This study aimed to investigate to what extent beta 1-selective and non-selective beta-blockers interfere with the platelet function in migraine patients. Twelve patients with classical migraine were included. After a 2-week drug-free period, the patients were randomly allocated to either beta 1-selective metoprolol (50 mg b.i.d.) or non-selective propranolol (40 mg b.i.d.) treatment for one month. After a wash-out period, the patients were changed to the corresponding beta-blocker for one month. ADP-induced platelet aggregability, platelet cAMP, ATP and ADP levels, plasma cAMP and TxB2 concentration, as well as the serum production of TxB2 were measured before and after each treatment period. After propranolol treatment, the patients showed lower ADP threshold values for producing irreversible platelet aggregation and lower platelet and plasma cAMP levels as compared to metoprolol. Neither of the beta-blockers induced any change in the plasma concentration or serum production of TxB2. In conclusion, non-selective beta-blockade (propranolol) significantly increases the platelet aggregability compared to beta 1-selective blockade (metoprolol).

Potential role of carnitine in patients with renal insufficiency

Carnitine metabolism is altered in renal insufficiency and influenced by the treatment modalities. Chronically uremic patients with end-stage renal disease under conservative therapy, hemodialysis, or peritoneal dialysis show low, normal, or elevated serum levels of TC and a distorted pattern of FC, SCAC, and LCAC. HD induces a marked depletion of FC, while predialytic elevated SCAC and LCAC are in the normal range at the end of dialysis treatment. All carnitine fractions rapidly return to predialysis levels 6 h after HD due to a transport of carnitine from muscle stores to plasma pool. Muscle carnitine content is elevated in chronic uremic patients under conservative therapy. Normal or decreased levels are observed in patients on long-term HD treatment. In addition, weekly losses of carnitine in patients undergoing HD or peritoneal dialysis do not exceed urinary carnitine excretion of CO. Supplementation with currently recommended doses (1-2 g L-carnitine i.v. at the end of each HD) is followed by a marked rise in plasma carnitine levels, suggesting limited carnitine utilization in uremia. Therefore, lower carnitine doses and modified application regimens should be considered to avoid exaggerated plasma levels of carnitine and carnitine esters. Furthermore, carnitine application has been reported to show beneficial, worsening, or no effect on the deranged lipid metabolism of the uremic patients. In patients undergoing CAPD or IPD predominantly normal serum carnitine levels have been reported. On the other hand, SCAC and LCAC esters are markedly elevated in these patients. After kidney transplantation the pattern of carnitine fractions is fully normalized in patients with plasma creatinine less than or equal to 120 mumol/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulatory properties of a mutant carnitine palmitoyltransferase in human skeletal muscle

Carnitine palmitoyltransferase (EC 2.3.1.21) was studied in sonicated muscle homogenates of seven patients who had recurrent attacks of myoglobinuria and marked deficiency of carnitine palmitoyltransferase in the isotope exchange assay, and in control subjects. When L-palmitoylcarnitine was reduced from 0.5 mM to 0.05 mM in the isotope exchange assay, enzyme activity returned to normal in the patients but was not significantly altered in the controls. When the forward assay was performed in the presence of 80 microM palmitoyl-CoA and 0.1% albumin, all patients showed normal carnitine palmitoyltransferase activity. The apparent Km values for DL-carnitine and palmitoyl-CoA were also normal in the patients. When albumin was omitted from the forward assay, 72-105% of the initial activity was observed in the controls, but only 31-55% in the patients. When the palmitoyl-CoA concentration in the forward assay exceeded 0.08 mM the enzyme activity was inhibited in both patients and controls, but the inhibition was significantly greater in the patients. The addition of either L-palmitoylcarnitine or DL-palmitoylcarnitine to the forward assay progressively inhibited enzyme activity in both patients and controls, but the inhibition was significantly greater in the patients. In the controls but not the patients D-palmitoylcarnitine was less inhibitory than the L-isomer or the DL-racemate. When the forward assay was performed with muscle homogenates preincubated with 0.4% Triton X-100 only 7-21% of the original enzyme activity remained in the patients, but 86-110% was found in the controls. Increasing concentrations of malonyl-CoA inhibited both the forward and the isotope exchange assays. When the inhibition was maximal, only 14-18% of the CPT activity remained in homogenates of patients but 32-47% in homogenates of controls. The I50 (median inhibitory concentration) and Ki values for malonyl-CoA determined in the forward assay were not significantly different in the patients and controls. The data imply that CPT deficiency is caused by altered regulatory properties of a mutant enzyme and/or by altered interaction between the enzyme and its membranous environment rather than lack of catalytically active CPT I, II or both. The mutant CPT would be most vulnerable to inhibition by its substrate and/or product when lipid metabolism is stressed. This could also explain why the symptoms differ from muscle carnitine deficiency, and why so little lipid accumulates in muscle in CPT deficiency.

Cardiac and skeletal myopathy associated with cardiac dysrhythmias

Electrophysiologic studies, echocardiograms, cardiac catheterizations and histologic and biochemical analyses of skeletal muscle biopsies were performed in 10 patients (aged 10 to 37 years, mean 21) who had dysrhythmias as the initial manifestation of cardiomyopathy. Presenting symptoms and signs attributable to dysrhythmias included sudden cardiac arrest in 2 patients, syncope in 3, presyncope in 3 and palpitations in 2. There was no clinical evidence of skeletal muscle weakness in any patient. Multicatheter electrophysiologic evaluation established diagnoses of ventricular tachycardia in 6 patients, primary atrial tachycardia in 2 and third degree infra-Hisian heart block in 1 patient. One patient presenting with palpitations had no inducible arrhythmia or conduction disturbance. Echocardiographic, angiographic and hemodynamic studies demonstrated previously unsuspected dilated cardiomyopathy in 7 patients and restrictive cardiomyopathy in 3. Skeletal muscle histologic characteristics were abnormal in all 10 patients; increases in lipid droplets and endomysial fibrosis were the characteristic findings. Serum free carnitine and short- and long-chain acylcarnitine were normal in 9 patients. However, skeletal muscle long-chain acylcarnitine was reduced in 9 patients. These findings support the concept that in certain patients presenting with dysrhythmias, the dysrhythmia may be a manifestation of cardiac and skeletal (that is, generalized) myopathy.

Selective carnitine palmitoyltransferase deficiency in fibroblasts from a patient with muscle CPT deficiency

A 13-year-old boy developed cramps and myoglobinuria following exertion. Mitochondrial preparations from a skeletal muscle biopsy were deficient in carnitine palmitoyltransferase (CPT) activity when assayed by the hydroxamate and kinetic assays. The patient's fibroblasts were also deficient when assayed by the hydroxamate and kinetic assays, but not when tested by the DTNB (5,5'-dithiobis-[nitrobenzoic acid]) method. This disparity probably indicates a specific deficiency in fibroblasts of one of the two carnitine palmitoyltransferases, presumably CPT II.

Mitochondrial myopathy

Six clinically affected and 18 asymptomatic members of a six-generation family were investigated clinically, by estimation of serum CK levels, and in some cases by quantitative electromyographic techniques and muscle biopsy. It was concluded that the myopathy was probably inherited as an autosomal dominant trait with variable expression and incomplete penetrance although the possibility of mitochondrial inheritance could not be excluded in view of the almost exclusive transmission through the female line. Eight members of the family with myopathy also had diabetes mellitus, and 2 of these also had cerebellar ataxia. It is suggested that the myopathy, the cerebellar disorder and the diabetes may all be manifestations of the same underlying metabolic defect.

Fasting hypoglycemia resulting from hepatic carnitine palmitoyl transferase deficiency

Two sisters developed severe hypoglycemia at 8 months of age, resulting in death in one of them. Metabolic studies of the second revealed decline of blood glucose concentration and low plasma ketone body values during a 20-hour fast, both reversed by administration of medium-chain triglycerides. Carnitine palmitoyl transferase activity was absent in the liver extract of the patient; lack of this enzyme impairs long-chain fatty acid oxidation and ketogenesis. Failure of gluconeogenesis could result from decreased production of acetyl-CoA and NADH.

Disorders of lipid metabolism in muscle

At rest and during sustained exercise, lipids are the main source of energy for muscle. Free fatty acids become available to muscle from plasma free fatty acids and triglycerides, and from intracellular triglycride lipid droplets. Transport of long-chain fatty acyl groups into the mitochondria requires esterification and de-esterification with carnitine by the "twin" enzymes carnitine palmityltransferase (CPT) I and II, bound to the outer and inner faces of the inner mitochondrial membrane. Carnitine deficiency occurs in two clinical syndromes. (1) In the myopathic form, there is weakness; muscle biopsy shows excessive accumulation of lipid droplets; and the carnitine concentration is markedly decreased in muscle but normal in plasma. (2) In the systemic form, there are weakness and recurrent episodes of hepatic encephalopathy; muscle biopsy shows lipid storage; and the carnitine concentration is decreased in muscle, liver, and plasma. The etiology of carnitine deficiency is not known in either the myopathic or the systemic form, but administration of carnitine or corticosteroids has been beneficial in some patients. "Secondary" carnitine deficiency may occur in patients with malnutrition, liver disease, chronic hemodialysis, and, possibly, mitochondrial disorders. CPT deficiency causes recurrent myoglobinuria, usually precipitated by prolonged exercise or fasting. Muscle biopsy may be normal or show varying degrees of lipid storage. Genetic transmission is probably autosomal recessive, but the great male predominance (20/21) remains unexplained. In many cases, lipid storage myopathy is not accompanied by carnitine or CPT deficiency, and the biochemical error remains to be identified.

Multisystem triglyceride storage disorder with impaired long-chain fatty acid oxidation

A five-year-old girl presented with congenital ichthyosis, hepatosplenomegaly, vacuolized granulocytes (Jordans' anomaly), and myopathy. Pathological, ultrastructural, and biochemical studies revealed nonlysosomal, multisystemic triglyceride storage. The cultured fibroblasts had increased uptake but decreased oxidation of labeled oleate. The patient failed to produce ketone bodies on fasting. A medium-chain triglyceride diet reversed the hepatomegaly. These studies are all consistent with a partial defect in the catabolism of long-chain fatty acids. This newly identified syndrome is presumably transmitted as an autosomal recessive trait.

A mitochondrial myopathy with a deficiency of respiratory chain NADH-CoQ reductase activity

This paper presents data on two sisters with a mitochondrial myopathy characterised by weakness, marked exercise intolerance and a fluctuating lactic acidaemia. Both patients also experienced episodes of increased weakness which could be brought on by unaccustomed activity, going without food or by taking small quantities of alcohol. Metabolic studies during exercise showed a marked and sudden rise in blood lactate and pyruvate levels. Biochemical studies in one case showed that mitochondrial respiratory rates were markedly decreased with all NAD-linked substrates tested but were normal with succinate and with TMPD + ascorbate. The mitochondrial cytochrome components were normal as determined by low temperature spectroscopy and the addition of uncoupler did not enhance state 3 respiratory rates utilising NAD-linked substrates. It was concluded, therefore, that the mitochondrial lesion was located at the level of the NADH-CoQ reductase complex.

Defective oxidative metabolism of myodystrophic skeletal muscle mitochondria

A small-scale procedure for preparing tightly coupled intact skeletal muscle mitochondria from myodystrophic (myd/myd) mice is described. Mitochondrial preparations derived from heart, liver, and skeletal muscle of myd/myd and their littermate (+/?) controls are characterized with respect to their cytochrome content and their oxidative and phosphorylative capacities. Our data indicate that there is an impairment in the NADH CoQ region of the respiratory chain of myodystrophic skeletal muscle mitochondria. Both heart and liver mitochondria of myd/myd exhibited normal activities of respiratory chain-linked oxidative phosphorylation.

Cold induced rhabdomyolysis in carnitine palmyityl transferase deficiency

A case of carnitine palmityl transferase deficiency in skeletal muscle is described. The usual symptoms associated with this disease (recurrent muscle cramps or pain and pigmenturia) were observed but sudden exposure to cold precipitate rhabdomyolysis in this patient.

Familial recurrent rhabdomyolysis due to carnitine palmityl transferase deficiency

Muscle carnitine palmityltransferase (CPT) activity was very low (0 to 14 per cent of controls) in two brothers with a syndrome of recurrent rhabdomyolysis and myoglobulinuria. In isolated muscle mitochondria the majority (87.5 per cent) of total measurable CPT enzyme activity could be attributed to external membrane CPT with severe deficiency of inner membrane CPT. By contrast, control mitochondria demonstrated a 1:1 distribution of external membrane CPT to inner membrane CPT. Thus, myoglobinuria may be due to a genetic defect of lipid metabolism in skeletal muscle, with inner membrane CPT deficiency presenting the same clinical features as external membrane CPT deficiency.

Fatal lipid storage myopathy in an infant: case report and autopsy findings

The clinical presentation, muscle biopsy appearances and autopsy findings in a male infant dying at the age of 13 weeks with a lipid storage myopathy are described. The primary metabolic abnormality was not elucidated but was thought not to be carnitine deficiency.

Carnitine palmitoyltransferase II deficiency with normal carnitine palmitoyltransferase I in skeletal muscle and leucocytes

Deficiency of carnitine palmitoyltransferase II (CPT II), was found to be the cause of the syndrome of muscle pain and myoglobinuria following strenuous exercise in an otherwise healthy young man. During fasting, serum creatine kinase remained low and ketogenesis was normal. The clearance of a fat emulsion and the activity of extrahepatic lipoprotein lipase was lowered, while the hepatic lipoprotein lipase was normal. A skeletal muscle biopsy did not show abnormal lipid storage. CPT II was deficient in skeletal muscle and leucocytes, while CPT I activity was normal and exhibited normal kinetic properties. CPT I has a higher affinity for palmitoylcarnitine than CPT II, and is more inhibited at increasing palmitoylcarnitine concentrations. In erythrocytes only CPT I is present.

Muscle carnitine palmityltransferase deficiency: a case with enzyme deficiency in cultured fibroblasts

A further case of carnitine palmityltransferase (CPT) deficiency in a young man is described, the defect being documented by direct enzyme assays of muscle biopsies. The finding of markedly reduced enzyme activity in the patient's cultured fibroblasts supports the concept that CPT deficiency is a systemic rather than an exclusively muscular condition.

Recurrent exertional rhabdomyolysis and stunted growth

A boy with recurrent exertional rhabdomyolysis and stunted growth is described. Fetal movements were few and the boy was small for gestational age. He always experienced easy fatigability, and he noted bouts of pigmenturia associated with episodes of considerable malaise. The change in color of the urine was caused by myoglobin. An electromyogram was myopathic. CPK rose during 60 minutes mild exercise. Prolonged moderate exercise could not be performed. Histopathological examination of muscle biopsy revealed an increase in the number of 11C fibres (20%). Electronmicroscopy revealed the wavy outline of a number of fibres and hypertrophy of sarcoplasmic reticulum elements. No cause for the stunted growth could be detected.

Biochemical and physiologic consequences of carnitine palmityltransferase deficiency

A patient with a long history of exercise-unduced pain developed myoglobinuria and respiratory failure following extensive exercise (football). Although muscle histochemistry was normal, tissue oxidation of 14C-labeled palmitate was decreased, and muscle carnitine palmityltransferase (CPT) activity was one-tenth of normal. During fasting, his creatine kinase (CK) rose from 127 mu/ml to 278 mu/ml and blood ketones failed to exhibit a normal rise. Triglycerides were normal, as was fatty-acid mobilization. Prolonged exercise resulted in an inordinately increased CK with only moderate elevations in lactate. Treatment with medium-chain triglycerides did not alter his symptoms or improve exercise performance. Pain on exercise is a common complaint, but the occurrence of myoglobinuria points to a defect of energy metabolism; Screening for defects of fat utilization may be accomplished by the prolonged-exercise test, invitro oxidation of 14C-labeled substrates, and prolonged fasting.

Experimental lipid storage myopathy. A quantitative ultrastructural and biochemical study

A lipid storage myopathy was induced in rats treated with daily doses of 2.5 g/kg brominated vegetable oil. As in human lipid storage myopathies, type I fibers were selectively severely affected, the lipid deposits were surrounded by mitochondria and the mitochondrial fraction of the affected fibers was increased. The oxidation of [U-14C]palmitate, [1(-14)C]octanoate and beta-[3(-14)C]hydroxybutyrate was significantly depressed but [1(-14)C]palmitate, as well as labeled pyruvate and succinate were oxidized at normal rates. The activities of long-chain, medium-chain and short-chain carnitine acyltransferases and the muscle carnitine levels were normal. The lipid storage is attributed to impaired beta oxidation of medium-chain and short-chain fatty acyl residues. An approach to the investigation of those human lipid storage myopathies not due to defects in the carnitine system is suggested.

Myoglobin: methods and diagnostic uses

Myoglobin is the oxygen-binding protein characteristic of skeletal and cardiac muscle. With muscle disease or dysfunction, myoglobin may enter the circulation, and after renal clearance, it may also appear in the urine. Therefore, the presence of myoglobinemia and myoglobinuria may serve as indicators of the presence and severity of muscle disease. With newly developed methods of detection, myoglobinemia and myoglobinuria are now recognized as complications of trauma, ischemia, surgery, states of exertion and stress, metabolic abnormalities, inherited enzyme disorders, toxin and drug actions, and inflammatory states. Infarction of the heart muscle also can be detected by myoglobin assay. Persistent myoglobinuric states may be complicated by renal failure and electrolyte imbalance. The diagnosis of myoglobinemia and myoglobinuria can be now confirmed with the use of immunoassay techniques. Although not yet widely available, they offer the possibility of the specificity and sensitivity needed for clinical use.