Muscle carnitine in hypo- and hyperthyroidism

Weakness is common in both hyper- and hypothyroidism, and skeletal muscle L-carnitine may play a role in this regard, as suggested by studies indicating abnormal levels of carnitine in serum and urine of patients with thyroid dysfunction. Skeletal muscle samples were obtained for carnitine analysis from control subjects, and from hyperthyroid and hypothyroid patients before and after treatment. There was a significant reduction in carnitine, especially the esterified portion, in hyperthyroid individuals, with a return to normal as euthyroid status was regained. In hypothyroid patients, there was a trend for carnitine to be lower than normal and for improvement once euthyroid status was attained. Our data indicate that muscle carnitine levels are affected by both hypo- and hyperthyroidism. A decrease in muscle carnitine in both conditions may contribute to thyroid myopathy.     

Familial systemic carnitine deficiency

Two sisters with systemic carnitine deficiency showed the heterogenicity of this condition and a lack of correlation between measurable carnitine levels and clinical manifestations. One child experienced recurrent metabolic encephalopathy, which was diagnosed as Reye's syndrome. The older child, despite lower carnitine concentrations, was asymptomatic. Lipid inclusion myopathy was shown in both children. Serum, muscle, and liver carnitine levels were reduced. The parents had normal serum carnitine concentrations. Both children had significantly abnormal renal handling of carnitine, and their mother, a mild alteration. This family provided evidence for genetic transmission and presumed autosomal recessive inheritance in this disease. Both children were treated with carnitine without clear benefit; no side effects were noted. Previously reported cases of systemic carnitine deficiency were reviewed.     

Carnitine in muscle, serum, and urine of nonprofessional athletes: effects of physical exercise, training, and L-carnitine administration

Efficient utilization of fatty acids to sustain prolonged physical efforts is thought to be dependent on the carnitine shuttle of muscle. A study has been carried out in 24 athletes (13 long-distance runners and 11 sprinters). These subjects received placebo or L-carnitine (1 g/orally b.i.d.) during a 6-month period of training. In endurance athletes, training induced lowering of total and free muscle carnitine. Increase of esterified muscle carnitine was also observed. Post-exertional overflow of acetylcarnitine and long-chain acylcarnitine, as well as reduction of the free fraction was also noticed in the blood. Fasting plasma carnitine levels, however, were not affected in carnitine-treated athletes at rest. These changes were likely related with the significantly increased urinary excretion of esterified and total carnitine which occurred after physical exercise. In the sprinters only, a decrease in free and total carnitine of muscle was detected after training. Both these potentially unfavorable effects were prevented by oral administration of L-carnitine. Our data suggest that training in endurance athletes, and to a lesser extent, in sprinters, is associated with a decrease in free and total carnitine of muscle, due to an increased overflow of short-chain carnitine esters in urine.     

Primary carnitine deficiency: adult onset lipid storage myopathy with a mild clinical course

We studied two adult patients with myalgia and muscular fatigability during prolonged physical exercise. Serum creatine kinase was increased and muscle biopsy revealed a lipid storage myopathy affecting predominantly the type I fibres. Skeletal muscle carnitine content was reduced to 15% and 21% of the normal mean values, while serum carnitine levels were either normal or decreased. Four months of oral therapy with L-carnitine (3 g per day) resolved the clinical symptoms completely in both patients, and a subsequent muscle biopsy confirmed a marked reduction of lipid storage, along with increased muscle carnitine levels. The analysis of renal carnitine excretion and the exclusion of possible secondary carnitine deficiencies in both patients are compatible with mild defects of the carnitine transporter in one patient and of carnitine biosynthesis in the other. Since myalgia and muscular fatigue are frequent but unspecified complaints of otherwise clinically unremarkable adult patients, it is important to identify myopathies associated with primary carnitine deficiency because they may be amenable to treatment.     

Melatonin excretion in normal children and in tuberous sclerosis complex with sleep disorder responsive to melatonin

To determine normal melatonin excretion patterns in healthy children without sleep disorder and to compare these with those of patients with tuberous sclerosis complex and sleep disorder responsive to exogenous melatonin, we measured 6-sulfatoxymelatonin excretion in 21 healthy children and in 7 patients with tuberous sclerosis complex and sleep disorder responsive to melatonin (a 5 mg oral dose increasing total sleep time). Total excretion, cosinor percentage, and acrophase time of 6-sulfatoxymelatonin excretion were estimated. In normal children, total 6-sulfatoxymelatonin excretion was range 11.1 to 40.2 microg (mean 19.0 microg, SD 7.4 microg); cosinor percentage rhythm range was 52.9% to 100% (mean 87%, median 94%); and acrophase time range was 23 hours, 54 minutes to 10 hours, 42 minutes (mean 5 hours, 54 minutes; median 4 hours, 12 minutes). Fifth and 95th percentiles were 11.1 to 29.0 microg, 57.8% to 99.9%, and 2 hours, 1 minute to 10 hours, 4 minutes. In tuberous sclerosis, normal patterns of melatonin excretion were seen in responders. Circadian patterns of melatonin excretion were similar in children and adults. We propose that exogenous melatonin can act by a simple sedative action.     

Vigabatrin, lamotrigine, topiramate and serum carnitine levels

Clinical studies indicate a decrease in free and total carnitine in children treated with old-generation antiepileptic drugs (especially valproate). Here, we studied the effect of new-generation antiepileptic drugs on serum carnitine levels. Serum carnitine levels were measured in 91 children: 24 treated with vigabatrin, 28 treated with lamotrigine, and 21 treated with topiramate. These drugs were given as monotherapy (54 children) or polytherapy (19 children). Eighteen additional children treated with valproate served as control subjects. Reduced mean serum carnitine level was evident only in children treated with valproate, with mean free and total carnitine level of 26.9 +/- 8.6 micromol/L and 29.1 +/- 10.4 micromol/L, respectively. In contrast, the mean serum carnitine levels of children treated with vigabatrin, lamotrigine, or topiramate were similar and normal. In these children, the free carnitine levels were 38.5 +/- 7.8 micromol/L, 37.2 +/- 7.7 microg/mL, and 40.4 +/- 8.7 micromol/L, respectively, and total carnitine levels were 43.5 +/- 8.8 micromol/L, 44.4 +/- 9.2 micromol/L, and 45.5 +/- 9.8 micromol/L (+/-S.D.), respectively. Only 4 children (treated with valproate) exhibited considerably lower serum carnitine levels. None of these children had significant clinical adverse effects attributable to carnitine deficiency. In conclusion, these new-generation antiepileptic drugs probably do not cause carnitine deficiency. In contrast, valproate may induce carnitine deficiency, but most cases are asymptomatic.     

Riboflavin-responsive lipid-storage myopathy and glutaric aciduria type II of early adult onset

A 17-year-old girl with progressive lipid-storage myopathy for 2 years had low muscle carnitine levels. There was no therapeutic response to prednisone and DL-carnitine-HCl. Chemical findings indicated glutaric aciduria type II. Riboflavin therapy and a fat-restricted, carbohydrate-enriched diet resulted in dramatic improvement. Low carnitine concentrations in plasma and muscle were observed in three asymptomatic sisters who had normal urinary excretion patterns. There was impaired mitochondrial beta-oxidation in cultured skin fibroblasts from the index patient and all three siblings.     

Carnitine metabolism and morphometric change of liver mitochondria in valproate-treated rats

The effect of the administration for 7 or 28 days of 50 mg/kg/day valproate (VPA) on carnitine metabolism and morphological changes of liver mitochondria in immature rats was evaluated. The dose of VPA was almost the same as that we clinically used. Carnitine concentrations in serum, red blood cells (RBC), muscle, liver and urine were measured. The rats treated with VPA for 7 days showed no significant change in carnitine concentration in each tissue examined or by morphology. In the serum, RBC and muscle of rats treated with VPA for 28 days, free carnitine levels decreased, while acylcarnitine levels and the ratio of acylcarnitine to free carnitine (acyl/free ratio) increased. Mitochondrial enlargement was also induced and urinary acyl/free ratio of VPA treated rats was higher than that of control rats after the 14th day of the treatment. These results suggest that carnitine deficiency and morphometric changes in mitochondria occur time dependent even if the dose of VPA is clinically appropriate.     

Serial CSF corticotropin-releasing hormone levels and adrenocortical activity in combat veterans with posttraumatic stress disorder

OBJECTIVE: The authors sought to carefully test, by using a technique of continuous CSF sampling, the hypothesis that basal elevations in CSF corticotropin-releasing hormone (CRH) concentrations exist in patients with posttraumatic stress disorder (PTSD). They also sought to assess the relationship among PTSD symptoms, adrenocortical activity, and CSF CRH levels. METHOD: CSF was withdrawn by means of a flexible, indwelling subarachnoid catheter over a 6-hour period, and hourly CSF concentrations of CRH were determined for 11 well-characterized combat veterans with PTSD and 12 matched normal volunteers. Twenty-four-hour urinary-free cortisol excretion was also determined. PTSD and depressive symptoms were correlated with the neuroendocrine data. RESULTS: Mean CSF CRH levels were significantly greater in PTSD patients than in normal subjects (55.2 [SD = 16.4] versus 42.3 pg/ml [SD = 15.6]). No correlation was found between CSF CRH concentrations and PTSD symptoms. While there was no significant difference between groups in 24-hour urinary-free cortisol excretion, the correlation between 24-hour urinary-free cortisol excretion and PTSD symptoms was negative and significant. CONCLUSIONS: By using a serial CSF sampling technique, the authors found high basal CSF CRH concentrations and normal 24-hour urinary-free cortisol excretion in combat veterans with PTSD, a combination that appears to be unique among psychiatric conditions studied to date.     

Rhabdomyolysis and acute encephalopathy in late onset medium chain acyl-CoA dehydrogenase deficiency.

A previously asymptomatic 30 year old man presented with rhabdomyolysis, muscle weakness, and acute encephalopathy after strenuous exertion in the cold without adequate food intake. Serum and muscle carnitine concentrations were decreased. Urinary excretion of carnitine and glycine esters and biochemical examination of skeletal muscle and fibroblasts led to the diagnosis of medium chain acyl-CoA dehydrogenase (MCAD) deficiency. A point mutation at nucleotide position 985 of the coding region of the MCAD gene was found. The MCAD protein was synthesised in the patient's fibroblasts at a normal rate, but was unstable. In general, patients in whom the 985 point mutation has been established show much more severe clinical symptoms and other symptoms than those seen in this patient. The relation of the 985 point mutation and the residual MACD activity to the symptoms is not as straightforward as previously thought.     

Plasma free carnitine in epilepsy children, adolescents and young adults treated with old and new antiepileptic drugs with or without ketogenic diet

This study was performed to evaluate carnitine deficiency in a large series of epilepsy children and adolescents treated with old and new antiepileptic drugs with or without ketogenic diet. Plasma free carnitine was determined in 164 epilepsy patients aged between 7 months and 30 years (mean 10.8 years) treated for a mean period of 7.5 years (range 1 month-26 years) with old and new antiepileptic drugs as mono or add-on therapy. In 16 patients on topiramate or lamotrigine and in 11 on ketogenic diet, plasma free carnitine was prospectively evaluated before starting treatment and after 3 and 12 months, respectively. Overall, low plasma levels of free carnitine were found in 41 patients (25%); by single subgroups, 32 out of 84 patients (38%) taking valproic acid and 13 of 54 (24%) on carbamazepine, both as monotherapy or in combination, showed low free carnitine levels. A higher though not statistically significant risk of hypocarnitinemia resulted to be linked to polytherapy (31.5%) versus monotherapy (17.3%) (P=.0573). Female sex, psychomotor or mental retardation and abnormal neurological examination appeared to be significantly related with hypocarnitinemia, as well. As to monotherapy, valproic acid was associated with a higher risk of hypocarnitinemia (27.3%) compared with carbamazepine group (14.3%). Neither one of the patients on topiramate (10), lamotrigine (5) or ketogenic diet (11) developed hypocarnitinemia during the first 12 months of treatment. Carnitine deficiency is not uncommon among epilepsy children and adolescents and is mainly linked to valproate therapy; further studies are needed to better understand the clinical significance of serum carnitine decline.     

Carnitine status in Reye and Reye-like syndromes

Fourteen children with the following Reye and Reye-like syndromes were studied to determine each patient's carnitine status: valproate-induced Reye-like attack, ornithine transcarbamylase deficiency, systemic carnitine deficiency, methylmalonic acidemia, and propionic acidemia. Reduced free carnitine and increased serum and urine acylcarnitine levels were found in all patients except for 2 with Reye syndrome, in whom serum creatinine levels were mildly elevated and serum free carnitine levels were not reduced. The renal free carnitine reabsorption rate was reduced in all cases. The free carnitine content of autopsied liver samples were reduced in 2 Reye syndrome patients, 2 OTC deficiency patients, and in a single systemic carnitine deficiency patient. The observed secondary free carnitine deficiency may be a factor in the pathogenesis of Reye and Reye-like syndromes.     

Altered tissue carnitine levels in animals with hereditary muscular dystrophy

Low levels of muscle carnitine have been found in patients with Duchenne dystrophy, a case possibly of Becker dystrophy, and limb-girdle syndrome as well as in patients with the recently described muscle carnitine deficiency syndrome. Tissues of the mouse, hamster, and chicken were analyzed to determine whether tissue carnitine levels were altered in the animal models of muscular dystrophy. Significantly higher levels of carnitine were found in dystrophic mouse muscle, but carnitine levels in plasma, liver and heart were normal. Histological changes in the skeletal muscle of dystrophic hamsters were relatively mild, and both skeletal muscle and plasma levels were normal. The liver carnitine level was higher than normal levels. The dystrophic hamster also had an inherited cardiomyopathy, and interestingly its heart carnitine level was much lower than normal. The red muscle of the normal chicken contained 5 times the level of carnitine found in white muscle. The dystrophic chicken had higher than normal levels of carnitine in the white muscle, but normal levels in the red muscle. Although all 3 animal models of muscular dystrophy studied have altered levels of carnitine in some tissue, none of the animal models had the same pattern of altered tissue carnitine levels seen in human patients.     

Lipid storage myopathies

Summary Various cases of lipid storage myopathies have been described. The biochemical defect could be determined in only some of these cases. The syndromes identified to date are as follows: carnitine deficiency (type I lipid storage myopathy), carnitine-palmityltransferase (CPT) deficiency and pyruvate-decarboxylase deficiency. In the last two diseases the vacuolization in muscle is not marked.The case of a 10 year old carnitine deficient patient with a history of insidious muscle weakness in the proximal limb and neck muscles is presented. The patient was treated with oral carnitine and a medium chain triglyceride diet for 18 months and her clinical status has remained improved. In other lipid storage patients prednisone treatment resulted in improvement.In cases of suspected lipid storage myopathy the following studies are indicated: 1) examination of ketone bodies in serum and urine during fasting, long chain and medium chain triglyceride diets; 2) serum triglyceride and serum carnitine; 3) study on fresh muscle and fibroblasts with labeled substrates, biochemical determination of carnitine and CPT in muscle.This paper was presented at the meeting of the Swiss Neurological Society and the Swiss Society of Muscular Disease in November 1975, Zürich, Switzerland     

Depression and anxiety symptoms are related to increased 24-hour urinary norepinephrine excretion among healthy middle-aged women

OBJECTIVE: Depression is a risk factor for morbidity and mortality in a variety of populations, and anxiety has also been associated with risk of mortality among cardiac patients. Dysfunction of the autonomic nervous system may be involved in this risk. The primary goal of this study was to evaluate the relationship between levels of self-reported symptoms of depression and anxiety and 24-hour urinary catecholamine excretion. METHOD: Ninety-one women aged 47-55 years were evaluated. Depression symptoms were assessed with the Beck Depression Inventory (BDI) and state anxiety was assessed with the state anxiety portion (SAI) of the Spielberger State-Trait Anxiety Inventory (STAI). Twenty-four hour urine collections were assayed for epinephrine (EPI), norepinephrine (NE) and cortisol (CORT). EPI, NE and CORT were indexed by body surface area to control for individual differences in body size. RESULTS: Higher levels of depression symptoms were associated with increased 24-hour NE excretion (r=.27, P=.009), with depressed women (n=17, BDI scores >/=10) exhibiting an approximately 25% higher rate of urinary NE excretion than women with BDI scores <10 (n=74), P=.007. Higher levels of state anxiety were also related to greater NE excretion (r=.28, P=.01), and CORT excretion was related to both depression (r=.23, P=.02) and anxiety (r=.22, P=.04). Depression and anxiety symptoms were unrelated to urinary EPI excretion. CONCLUSIONS: The current findings that higher levels of depression and anxiety symptoms are related to increased 24-hour urinary NE and CORT excretion among women suggests that depression and anxiety may be associated with increased sympathetic nervous system (SNS) activity, and are consistent with the possibility that SNS activity may play a role in the increased mortality associated with depression in community-dwelling older adults.     

Serum carnitine levels during oxcarbazepine and carbamazepine monotherapies in children with epilepsy

Prolonged antiepilepsy drug treatment can result in secondary carnitine deficiency. The effect of oxcarbazepine on carnitine metabolism has not been reported previously. In this study, serum concentrations of total and free carnitine were measured in 20 children with epilepsy treated with oxcarbazepine monotherapy and were compared with 20 children with epilepsy who were taking carbamazepine as monotherapy. The assays were performed between 3 and 6 months of anticonvulsant treatment. The mean values of serum total and free carnitine levels in patients receiving carbamazepine monotherapy were 63.0 +/- 20.7 micromol/L and 49.1 +/- 16.7 micromol/L, respectively. The mean values of serum total and free carnitine levels in patients receiving oxcarbazepine monotherapy were 64.2 +/- 17.4 micromol/L and 50.3 +/- 13.7 micromol/L, respectively. The values were all between normal ranges. No significant difference was observed in the level of total and free carnitine levels between the two groups. Our results suggest that neither oxcarbazepine nor carbamazepine as monotherapy causes carnitine deficiency in otherwise healthy children with primary idiopathic epilepsy.     

Combined partial deficiency of muscle carnitine palmitoyltransferase and carnitine with autosomal dominant inheritance.

The authors studied a 53 year old woman and her 22 year old son with episodes of paroxysmal muscle cramps and dark urines lasting several hours related to high fat diet and strenuous physical exercise beginning on both at age 14 years. The father, paternal uncle, paternal grandfather and another son of the mother also had paroxysmal muscle cramps. The two studied cases showed normal findings for physical evaluation, blood lactate after ischemic exercise, and muscle histology (light and electron microscopy). The serum creatine kinase was elevated in the son and normal in the mother. However, 72 hour fasting significantly raised the serum creatine kinase level in both cases. Plasma concentration of ketone bodies and acid soluble acyl-carnitine increased normally with prolonged fasting. The biochemical evaluation of the muscle tissue revealed intact anaerobic glycolysis and normal glycogen content but combined partial deficiency of muscle carnitine palmitoyltransferase and carnitine in both cases.     

Relative Carnitine Deficiency in Autism

A random retrospective chart review was conducted to document serum carnitine levels on 100 children with autism. Concurrently drawn serum pyruvate, lactate, ammonia, and alanine levels were also available in many of these children. Values of free and total carnitine (p < 0.001), and pyruvate (p=0.006) were significantly reduced while ammonia and alanine levels were considerably elevated (p < 0.001) in our autistic subjects. The relative carnitine deficiency in these patients, accompanied by slight elevations in lactate and significant elevations in alanine and ammonia levels, is suggestive of mild mitochondrial dysfunction. It is hypothesized that a mitochondrial defect may be the origin of the carnitine deficiency in these autistic children.     

Cytochrome c oxidase deficiency in muscle with dicarboxylic aciduria and renal tubular acidosis

A patient with deficient activity of cytochrome c oxidase in muscle presented at 1 year of age with extreme failure to thrive. He was found to have dicarboxylic aciduria, renal tubular acidosis, and deficiency of carnitine. Treatment with sodium bicarbonate, riboflavin, and carnitine led to considerable improvement in growth and a significant reduction in the dicarboxylic aciduria.     

The syndrome of systemic carnitine deficiency. Clinical, morphologic, biochemical, and pathophysiologic features.

An 11-year old boy had had recurrent episodes of hepatic and cerebral dysfunction and underdeveloped musculature. Overt weakness developed at age 10. Lipid excess, especially in type I fibers, was found in muscle. Hypertrophied smooth endoplasmic reticulum and excessive microbodies were present in liver. Marked carnitine deficiency was shown in skeletal muscle, plasma, and liver. Ketogenesis was impaired on a high fat diet, but omega oxidation of fatty acids was enhanced. There was excessive glucose uptake and essentially no oxidation of labeled long-chain fatty acids by perfused forearm muscles in vivo. Oral replacement therapy restored plasma carnitine levels to normal, but not liver or muscle carnitine levels, and was accompanied by clinical improvement.