Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1762617 (weakness)
 37,932 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two brothers, 29 and 33 years of age, had recurrent myoglobinuria, renal failure and azotemia, but were otherwise normal, without apparent muscle weakness or exercise intolerance. Ischemic exercise resulted in normal lactate production. Muscle glycogen content and activities of phosphorylase and phosphofructokinase were normal. Plasma triglycerides were elevated (500 mg per deciliter) on a regular diet and rose during fasting. During a 72-hour fast, serum creatine phosphokinase rose more than 10 times, and myoglobin was detected in urine. Plasma ketone production was minimal during fasting, but prompt ketonemia ( a normal response) occurred after ingestion of medium-chain triglycerides. Carnitine palmityl transferase activity was virtually absent in crude muscle extracts and mitochondrial fractions. Lack of this enzyme impairs long-chain fatty acid utilization, reflected in increased content of plasma free fatty acids and plasma triglycerides. Depletion of ATP because of this metabolic block in muscle may account for the attacks of myoglobinuria.
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PMID:A disorder of muscle lipid metabolism and myoglobinuria. Absence of carnitine palmityl transferase. 12 38

Three new cases of carnitine palmityl transferase deficiency are described. The syndrome consists of recurrent attacks of muscle cramps, weakness, malaise, and myoglobinuria. These attacks are especially likely to occur during prolonged exercise after fasting, eating a high-fat diet, or during cold weather. Occasionally after fasting alone, spontaneous muscle breakdown may occur. One patient studied in detail was excessively slow in producing ketones when he fasted. His mylagias and weakness appeared to be alleviated by beta-hydroxybutyrate. Of eight other patients thought to have idiopathic recurrent myoglobinuria, three were found to have myophosphorylase deficiency, whereas five did not have deficiency of either enzyme. Carnitine palmityl transferase deficiency may be more common than previously supposed, may be in part amenable to dietary therapy, can be easily distinguished from myophosphorylase deficiency, and may provide insight into the metabolism of fatty acids and ketone bodies as well as energy requirements of skeletal muscle.
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PMID:Recurrent myoglobinuria due to muscle carnitine palmityl transferase deficiency. 64 43

A 16-year-old girl, previously in good health, developed progressive generalized muscle weakness following her first parturition. The neck and proximal limb muscles were especially weak and painful. Carnitine (4-trimethylamino-3-hydroxybutyrate) was markedly decreased in muscle, plasma, and urine. Dietary carnitine supplementation, 2.0 gm daily, was followed by clinical improvement and decreased lipid droplets in muscle biopsy. Together with previously reported cases, 2 fatal, the patient's illness emphasizes the risk of pregnancy in women with carnitine deficiency.
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PMID:Carnitine deficiency: acute postpartum crisis. 74 56

The production of energy in muscle from long-chain fatty acid oxidation is dependent upon the presence of carnitine. An abnormally low level of muscle carnitine, as seen in patients with the carnitine deficiency syndrome, results in marked muscle weakness. Muscle from 83 consecutive patients undergoing diagnostic muscle biopsy was assayed for carnitine. Carnitine levels (mean +/- SEM, expressed as nmoles carnitine per mg noncollagen protein) in muscle from patients with Duchenne dystrophy (8.1 +/- 1.7) and possible Becker dystrophy (10.6 +/- 3.0) were significantly (P less than 0.001) different from histologically normal muscle (24.0 +/- 1.4). Carnitine levels in patients with limb-girdle dystrophy (16.1 +/- 3.1) and polymyositis/dermatomyositis (16.6 +/- 3.2) were also low, although not as low as in Duchenne dystrophy. Carnitine levels from patients with denervation atrophy (22.1 +/- 3.6), nonspecific fiber atrophy (21.3 +/- 1.3), and a group of miscellaneous neuromuscular diseases (20.4 +/- 1.4) were not significantly different from histologically normal muscle. The low values of carnitine seen in Duchenne dystrophy and a group of possible Becker dystrophy patients may be a nonspecific effect, related to severe muscle damage.
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PMID:Muscle carnitine levels in neuromuscular disease. 92 14

It has been suggested that early features of scurvy (fatigue and weakness) may be attributed to carnitine deficiency. Ascorbate is a cofactor for two alpha-ketoglutarate-requiring dioxygenase reactions (epsilon-N-trimethyllysine hydroxylase and gamma-butyrobetaine hydroxylase) in the pathway of carnitine biosynthesis. Carnitine concentrations are variably low in some tissues of scorbutic guinea pigs. Ascorbic acid deficiency in guinea pigs resulted in decreased activity of hepatic gamma-butyrobetaine hydroxylase and renal but not hepatic epsilon-N-trimethyllsine hydroxylase when exogenous substrates were provided. It remains unclear whether vitamin C deficiency has a significant impact on the overall rate of carnitine synthesis from endogenous substrates. Nevertheless, results of studies of enzyme preparations and perfused liver in vitro and of scorbutic guinea pigs in vivo provide compelling evidence for participation of ascorbic acid in carnitine biosynthesis.
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PMID:Ascorbic acid and carnitine biosynthesis. 196 62

Chronic hemodialysis (HD) leads to significant losses of carnitine from plasma and muscle. Because L-carnitine is important in the production of energy from fatty acid oxidation (FAO) in muscle, we examined the role of carnitine replacement by administering therapeutic doses of intravenous carnitine to 14 male patients receiving HD. Placebo or carnitine was given 2 g i.v. 3 times weekly for 6 months in a double-blind manner. To evaluate long-term toxicity of carnitine, all patients subsequently received 1 g i.v. carnitine for 10 months. Patients were rated for muscle strength each week. After 6 months, definite improvement in strength occurred in 4 of 7 carnitine-treated patients and in none of 7 controls. During the subsequent 10 months of carnitine administration, no adverse effects were noted and muscle strength improved in 9 of 14 patients. Muscle biopsy was performed in 13 patients before and after the first 6 months of treatment and in 6 healthy controls. FAO and carnitine were measured in each muscle biopsy. FAO was significantly lower in both carnitine- and placebo-treated HD patients compared to healthy controls. Although carnitine therapy increased the muscle concentration of carnitine 3-fold in muscle of HD patients, muscle FAO did not increase significantly and never reached the level of healthy controls. Muscle histopathology and ultrastructure were not specific for HD myopathy. Carnitine may be useful in treating some patients with muscle weakness related to HD.
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PMID:Evaluation of the effect of intravenous L-carnitine therapy on function, structure and fatty acid metabolism of skeletal muscle in patients receiving chronic hemodialysis. 201 71

A 65-year-old man with progressive muscle weakness and liver dysfunction following massive small bowel resection showed myriad lipid-filled vacuoles in type I muscle fibers. Carnitine was significantly decreased in muscle, serum and urine. Carnitine supplementation was followed by clinical improvement and decreased lipid droplets in biopsied muscle. He had been receiving carnitine-deficient total parenteral nutrition. This form of carnitine deficiency may be due to a defect in carnitine biosynthesis, as well as dietary carnitine deficiency.
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PMID:Carnitine deficiency following massive intestinal resection: a morphological and biochemical study. 221 55

A case of 16-year-old female with myalgia and myoglobinuria following prolonged exercise was reported. Neurological examination revealed mild weakness of proximal muscle in the lower extremities. Serum CK, LDH, myoglobin were significantly increased during the attacks. On biopsy, the muscle fibers contained myriad lipid-filled vacuoles, in predominantly type 1 fibers. Electron microscope examinations revealed numerous lipid droplets adjacent to mitochondria and glycogen particles. Carnitine level in the patient's muscle was markedly reduced (under 5% of control), but the serum carnitine concentration was normal. The muscle carnitine palmityl transferase level was not depressed. A forearm ischemic test resulted in normal lactate production. On exercise tolerance test by a bicycle ergometer, mild exercise (15-30 watts for 15 minutes) induced myalgia and marked elevation in serum CK, lactate and pyruvate, while severe exercise showed no increase in serum CK level. The findings suggest that the energy production system in the skeletal muscle was impaired. However, the enzyme activities of NADH oxidation in mitochondria and the anaerobic glycolysis pathway were within normal limits. During fasting (36 hours), there was a normal production of ketone bodies, suggesting that hepatic metabolism of lipids was normal. She showed good response to L-carnitine therapy.
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PMID:[Muscle carnitine deficiency associated with myalgia and rhabdomyolysis following exercise]. 274 89

l-Carnitine occurs naturally as an essential cofactor of fatty acid metabolism which is synthesised endogenously or obtained from dietary sources. In patients with primary carnitine deficiencies, which may be life-threatening, and some secondary deficiencies such as organic acidurias, the exogenously administered compound is clearly beneficial: by abolishing hypotonia, motor skills are improved, as are muscle weakness and wasting. In preliminary clinical trials in patients with ischaemic cardiac disease, therapy with l-carnitine has shown beneficial effects on myocardial function and metabolism and has improved exercise tolerance in patients with angina pectoris-findings which require further substantiation in larger controlled studies. Moreover, while some interesting evidence suggests that l-carnitine may find potential use in such diverse conditions as carnitine deficiencies secondary to prolonged total parenteral nutrition supplementation or chronic haemodialysis, hyperlipidaemias and the prevention of toxicity induced by anthracyclines and valproate, such findings must be regarded as preliminary. Exogenously administered l-carnitine is very well tolerated. Thus, while its role in primary deficiencies is established, with its profile of negligible toxicity l-carnitine is worthy of further investigation to more clearly define its therapeutic applications in a variety of conditions which may be indirectly related to alterations in fatty acid metabolism.
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PMID:l-Carnitine. A preliminary review of its pharmacokinetics, and its therapeutic use in ischaemic cardiac disease and primary and secondary carnitine deficiencies in relationship to its role in fatty acid metabolism. 330 9

Several clinical entities are associated with disorders of fatty acid oxidation or transfer across the inner mitochondrial membrane. Over 40 cases of the primary carnitine deficiency syndrome have been reported to date and various subtypes have been characterized. This represents a large clinical spectrum. The deficiency of carnitine in muscle is at the basis of a syndrome characterized by muscle weakness and lipid storage myopathy. The systemic form of carnitine deficiency is more generalized and includes recurrent episodes of hepatic encephalopathy as well as lipid storage in muscle, liver and heart. In one subtype, hypoglycemia upon fasting and cardiomyopathy are found. There are also several causes of secondary carnitine deficiency states which are either acquired or associated with inborn errors of metabolism (organic acidurias, defects of acyl-CoA dehydrogenases). Clinically, Carnitine palmitoyltransferase (CPT) deficiency is a rather homogeneous syndrome presenting with recurrent episodes of myoglobinuria provoked by fasting or prolonged exercise. The only exception is an infantile variety associated with severe hypoglycemia and hepatic CPT deficiency. Using malonyl-CoA, a specific inhibitor of CPT-I, we had suggestions in five adult patients with myoglobinuria that CPT-II is lacking in muscle, liver and platelets while CPT-I is above the control level. The enzyme abnormality seems partial and limited to CPT-II or to its binding to the inner mitochondrial membrane.
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PMID:Clinical varieties of carnitine and carnitine palmitoyltransferase deficiency. 355 20


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