Disorders of lipid metabolism in muscle

Rhabdomyolysis in thyroid storm

This is the first reported case of thyroid storm complicated by rhabdomyolysis with acute reversible renal failure. The only possible causes for the rhabdomyolysis were inherent features of thyroid storm. Although hyperthyroid patients characteristically have normal or low serum levels of muscle enzymes, this case report demonstrates that rhabdomyolysis with elevated serum levels of muscle enzymes can occur with hyperthyroidism. An appreciation of the potential for rhabdomyolysis in hyperthyroidism should facilitate prompt initiation of aggressive therapy for myoglobinuria and thereby limit the severity of acute renal failure in these already very sick patients.

[Diagnostic significance of muscle biopsies in metabolic myopathies. I. Myopathology]

The clinical course of metabolic myopathies is dominated by progressive muscle weakness and wasting or aching contraction and recurrent rhabdomyolysis with intense exercise. Vacuolar muscle fibre degeneration is the leading pathological finding on routine histological examination. For further characterization of those histologically empty looking vacuoles, histochemistry and electron microscopy are employed. Increase of glycogen, lipid droplets or mitochondria can often be demonstrated and indicate the need for subsequent biochemical identification of the underlying metabolic defect. Some other metabolic myopathies that cause recurrent rhabdomyolysis lack myopathological abnormalities. These can only be diagnosed biochemically, but additional new histochemical screening methods might be helpful.

[Serum levels and urine excretion of L-carnitine in patients with normal and impaired kidney function]

The influence of age, sex, and renal function on serum levels and urinary excretion of free carnitine was studied in 187 subjects. Sixty-one subjects with normal renal function (creatinine clearance greater than 100 ml/min) showed a serum carnitine level of 72.2 +/- 23.2 mumol/l. The carnitine values of males (76.8 +/- 23.3 mumol/l, n = 39) were higher (p less than 0.05) than those of females (64.0 +/- 21.0 mumol/l, n = 22). Carnitine levels did not correlate with age. Values in patients with normal renal function did not differ from serum carnitine levels in healthy controls (74.7 +/- 17.5 mumol/l, n = 49). The mean urinary carnitine excretion per day was 163.5 mumol (range 63.7-419.6 mumol) in patients with intact renal function. Extreme impairment of glomerular filtration rate (creatinine clearance less than 20 ml/min) resulted in higher carnitine concentrations in serum (108.9 +/- 39.4 mumol/l, n = 18, p less than 0.05), lower carnitine elimination per day (78.5 mumol, range 14.5 - 424.3 mumol, n = 18, p less than 0.05) and a decreased carnitine clearance (0.8 ml/min, range 0.2 - 3.8 ml/min). These data together with earlier results obtained in dialysis patients suggest that carnitine metabolism in renal failure is altered by reduction of both endogenous carnitine biosynthesis and renal carnitine clearance.

Fatal lipid storage disorder

A 12-week-old female infant died from acute encephalopathy mimicking Reye syndrome. Because of positive serum hepatitis B surface antigen (HBs Ag) and perivascular inflammatory cell infiltration in the liver, she was diagnosed as having acute hepatitis. The most striking finding in the present case was extremely excessive lipid accumulation in the striated muscles including biceps brachii, tongue and cardiac muscles. The levels of serum, liver and muscle carnitine were within normal limits, though liver carnitine palmityl transferase (CPT) was markedly decreased in activity. Although the primary metabolic defect has yet to be elucidated, it is assumed that the fulminant hepatic failure induced lipid accumulation in the skeletal muscle by a certain abnormal lipid metabolism.

[Myopathy due to carnitine palmitoyltransferase deficiency. Report of 2 cases with enzymatic analyses on muscle tissue]

We describe two brothers, 25 and 19 years-old, with muscle pain and decreased strength after prolonged exercise; these symptoms are worsened by cold whether of fasting. One of the patients developed recurrent myoglobinuria and had one episode of renal failure. Laboratory investigations were normal between the crises, but during myoglobinuria, serum creatine kinase activity increased 100 times. Electromyography was suggestive of denervation. Muscle biopsy showed increased lipid droplets by the "oil red O" stain and increased activity of succinic dehydrogenase histochemical reaction. Lactate production during ischemia was normal. Biochemical analysis showed decreased carnitine-palmityl-transferase activity in muscle (7.23 and 10.58 nmoles/min/gr; normal range 66.7 +/- 17.3), with normal values for carnitine-octanoyl-transferase and carnitine-acetyl-transferase. The metabolic pathway of fatty acid utilization as an energy source for muscle during exercise in normal and in pathological conditions is discussed.

Kearns-Sayre syndrome with reduced plasma and cerebrospinal fluid folate

A young woman with Kearns-Sayre syndrome and progressive central nervous system deterioration over 15 years had decreased plasma and cerebrospinal fluid folate levels while receiving phenytoin for a seizure disorder. A muscle biopsy showed a "ragged red fiber" myopathy with reduced muscle carnitine and mitochondrial enzymes. Computed tomographic brain scans showed cerebral white matter hypodensities and bilateral calcification of the basal ganglia. The mechanism for the folate deficiency and altered ratio of plasma to cerebrospinal fluid folate is unknown, but the deficiency may be responsive to replacement therapy.

Activation of free fatty acids in subcellular fractions of human skeletal muscle

In human pathology little is known about the activating enzymes for fatty acids of different carbon chain length. In order to have a better insight into disorders of lipid metabolism in human skeletal muscle, we studied the distribution of acyl-CoA synthetases in muscular subcellular fractions. We find that in muscle mainly long chain fatty acids are activated to CoA esters. Distribution of palmityl-CoA synthetase in subcellular fractions compared with marker enzymes suggested that this enzymatic activity is located only in the outer mitochondrial membrane, in contrast to human liver, where this enzyme is also located in the microsomes. In human skeletal muscle we also found low butyryl-CoA formation, which was limited to the mitochondrial matrix. This site of activation implies that short chain fatty acids may not depend on carnitine for their oxidation in the mitochondrial matrix, in contrast to long chain fatty acids activated in the outer mitochondrial membrane.

Acute abdominal rhabdomyolysis after body building exercise: is there a "rectus abdominus syndrome?"

Report of a 19-year-old man who was admitted to the hospital after vigorous exercise with signs of the "acute abdomen" syndrome. Since intestinal reasons for the complaints were excluded, a myocardial infarction was considered. However, the excessively increased serum CK levels indicated a disorder of the voluntary muscles. A biopsy taken from the rectus abdominis revealed typical features of acute rhabdomyolysis, which was obviously restricted to the rectus abdominis. Together with a somewhat later observed autopsy case of a young male with acute abdominal rhabdomyolysis, also restricted to the rectus abdominis, this case gives rise to discuss, whether there exists a "rectus abdominis syndrome" analogous to the anterior tibial syndrome.

Phosphoglycerate kinase deficiency: another cause of recurrent myoglobinuria

A 14-year-old boy had myoglobinuria and renal failure after intense exercise; a year earlier he had experienced a milder episode. There was no consanguinity and no family history of neuromuscular diseases or hemolytic anemia. Strength was normal. Forearm ischemic exercise caused prolonged contracture with no rise of venous lactate. Muscle morphology showed only a mild increase of lipid droplets. Glycogen concentration was normal. Muscle phosphoglycerate kinase (PGK) activity was 5% of the normal mean, and all other glycolytic enzymes were normal. The residual PGK activity of muscle was heat stable but showed slower than normal electrophoretic mobility and decreased Michaelis constants for 3-phosphoglycerate and adenosine triphosphate. The enzyme defect was also expressed in erythrocytes and in fibroblast and muscle cultures. PGK activity was decreased in tissues from the patient's mother but normal in the father. PGK deficiency is an X-linked recessive trait usually associated with hemolytic anemia, mental retardation, and seizures; myopathy had not been recognized previously. Muscle PGK deficiency is now added to two other newly recognized glycolytic defects, phosphoglycerate mutase and lactate dehydrogenase deficiencies, as a cause of recurrent myoglobinuria.

Myoglobinuria in carnitine palmityltransferase deficiency

An 18-year-old male developed recurrent myoglobinuria after prolonged physical exertion. Histochemical analysis of biopsied muscle revealed complete absence of carnitine palmityltransferase. Significant ultrastructural abnormalities of muscle were present, but these could be the result of the recent episode of rhabdomyolysis. Recurrent myoglobinuria can occur in several disorders of glycogen and lipid metabolism in muscle, and such disorders should be suspected in cases of unexplained recurrent myoglobinuria.

Palmitate oxidation in human muscle: comparison to CPT and carnitine

The evaluating of palmitate oxidation in muscle tissue may be a useful screening test for detecting defects in fatty acid metabolism in human neuromuscular disease. If the test is to be useful, it is necessary to obtain data on a wide variety of muscle illnesses for comparative purposes. We report our experience with palmitate oxidation, muscle carnitine, and carnitine palmityl transferase (CPT) activity in 148 muscles biopsies from a variety of illnesses. The efficacy of using total protein, citrate synthase, and (1-14C) pyruvate oxidation as internal references was investigated. Palmitate oxidation was significantly less than normal (P less than or equal to 0.01) in Duchenne muscular dystrophy, congenital nonprogressive myopathy, congenital muscular dystrophy, malignant hyperpyrexia, and denervation, depending on the internal reference used. Muscle carnitine levels followed a similar pattern, however, CPT activity did not. The possibility of these findings being secondary to inactivity is discussed.

Fatal lipid storage myopathy with deficiency of cytochrome-c-oxidase and carnitine. A contribution to the combined cytochemical-finestructural identification of cytochrome-c-oxidase in longterm frozen muscle

Two newborn female siblings fell ill with apathy, failure of suckling and a generalized progressive muscular hypotonia. Death occured at the age of 7 weeks, obviously caused by impairment of respiratory musculature. Biochemical studies in one child revealed carnitine deficiency especially in skeletal muscle; hepatic encephalopathy was absent. Both children had a generalized hyperaminoaciduria, an unusual finding in primary carnitine deficiency. Besides fatty metamorphosis of the liver, bilateral hydroureters and tubular calcifications of both kidneys, morphological studies showed a generalized lipid storage myopathy which predominated in Type-I-fibres and was accentuated in the muscles of the neck. Enzymehistochemical electron microscopy in longterm frozen muscle demonstrated that cytochrome-c-oxidase activity was absent not only in myopathic but also in most of the morphological unchanged muscle fibres. Only some fibres and endothelial cells displayed normal activity of mitochondria. Biochemically no cytochrome aa3 (cytochrome-c-oxidase) could be found in skeletal muscle; cytochrome b was almost undetectable. --In newborns with fatal lipid storage myopathy and carnitine deficiency it seems necessary to look for additional defects in the respiratory chain. Enzyme histochemical electron microscopy is a sensitive method in identifying cytochrome-c-oxidase even after a 12 months period of storage.