Low Serum Carnitine Research Articles

Low serum carnitine level is associated with increased urinary carnitine excretion in late pregnancy.

Carnitine is essential for fatty acid metabolism. Free carnitine (FCA) is excreted in the urine in the glomerulus, but is partly reabsorbed by a carnitine transporter. The mechanism underlying the decrease in serum carnitine level during pregnancy is unclear. To investigate whether low carnitine level is associated with increased renal excretion in pregnant women. We recruited 43 healthy pregnant and 25 non-pregnant women. Total carnitine (TCA) and FCA levels were measured using the enzymatic cycling method, and the acylcarnitine (ACA) level was calculated. Fractional excretion (FE) was calculated as carnitine clearance divided by creatinine clearance. The mean TCA, FCA, and ACA levels were lower at 12weeks of gestation in pregnant than non-pregnant women (P < .001); the levels decreased further at 36weeks, reaching 39%, 36%, and 52% of those in non-pregnant women, respectively (P < .001). The FEs were 3-4-fold higher in pregnant women than non-pregnant women. Pregnant women had a lower serum FCA/TCA ratio than non-pregnant women (0.788±0.098 vs 0.830±0.074, respectively; P < .05), whereas the urine FCA/TCA ratio was similar between the groups. Low carnitine level is associated with increased renal excretion during late pregnancy.

The effect of levocarnitine supplementation on dialysis-related hypotension: A systematic review, meta-analysis, and trial sequential analysis.

Dialysis patients have been shown to have low serum carnitine due to poor nutrition, deprivation of endogenous synthesis from kidneys, and removal by hemodialysis. Carnitine deficiency leads to impaired cardiac function and dialysis-related hypotension which are associated with increased mortality. Supplementing with levocarnitine among hemodialysis patients may diminish incidence of intradialytic hypotension. Data on this topic, however, lacks consensus. We conducted electronic searches in PubMed, Embase and Cochrane Central Register of Controlled Trials from January 1960 to 19th November 2021 to identify randomized controlled studies (RCTs), which examined the effects of oral or intravenous levocarnitine (L-carnitine) on dialysis-related hypotension among hemodialysis patients. The secondary outcome was muscle cramps. Study results were pooled and analyzed utilizing the random-effects model. Trial sequential analysis (TSA) was performed to assess the strength of current evidence. Eight trials with 224 participants were included in our meta-analysis. Compared to control group, L-carnitine reduced the incidence of dialysis-related hypotension among hemodialysis patients (pooled OR = 0.26, 95% CI [0.10-0.72], p = 0.01, I2 = 76.0%). TSA demonstrated that the evidence was sufficient to conclude the finding. Five studies with 147 participants showed a reduction in the incidence of muscle cramps with L-carnitine group (pooled OR = 0.22, 95% CI [0.06-0.81], p = 0.02, I2 = 74.7%). However, TSA suggested that further high-quality studies were required. Subgroup analysis on the route of supplementation revealed that only oral but not intravenous L-carnitine significantly reduced dialysis-related hypotension. Regarding dose and duration of L-carnitine supplementation, the dose > 4,200 mg/week and duration of at least 12 weeks appeared to prevent dialysis-related hypotension. Supplementing oral L-carnitine for at least three months above 4,200 mg/week helps prevent dialysis-related hypotension. L-carnitine supplementation may ameliorate muscle cramps. Further well-powered studies are required to conclude this benefit.

Serum Carnitine Levels in Preterm Infants with Respiratory Distress Syndrome

Background: Respiratory distress syndrome [RDS] is among the most common diseases in preterm infants. Numerous causes of RDS have been recently diagnosed and researchers have identified the presence of low serum carnitine in preterm infants with RDS.The aim of this study: to evaluate serum carnitine levels in preterm infants with RDS.Patients and methods: Eighty preterm infants were divided into two groups; group 1 consisted of 50 preterm with RDS in the first 6h of life constituted Group [A] as they were preterm infants with RDS with normal serum carnitine levels while Group [B] represented infants with carnitine deficiency. Control group 2 consisted of 30 preterm infants without RDS in the first 6 h of life. All cases and their mothers included in the study were subjected to a thorough history taking, thorough clinical examination and measurement of serum carnitine.Results: The cases groups had significantly lower serum L-carnitine than the controls group [25.56 ± 11.14 vs. 34.53 ± 2.54], and carnitine deficiency in RDS cases [32%]. Concerning weight, cases with carnitine deficiency had higher weight than cases with normal carnitine and control. With regard to clinical manifestations, there was a statistically significant difference between the cases subgroups in Down score indicting severe RDS in cases with carnitine deficiency. There was a statistically significant difference among cases subgroups regarding radiological findings. The cases with carnitine deficiency had worse X-ray, more need for surfactant therapy and MV than the cases with normal carnitine.Conclusion: Preterm neonates with RDS were demonstrated to be associated with a significant reduction in carnitine level compared to RDS- free preterm ones.

Primary Carnitine Deficiency and Autism Spectrum Disorder is there a Relationship?

Carnitine plays essential role in energy metabolism .Systemic primary carnitine deficiency is a genetic disorder caused by decreased or absent organic cation transporter type 2 (OCTN2) carnitine transporter activity, resulting in low serum carnitine levels and decreased carnitine accumulation inside cells. The decrease carnitine results in impaired fatty acid oxidation. Primary carnitine deficiency presents a hypoketotic, hypoglycemia and hepatic encephalopathy. Recently, primary carnitine deficiency has been associated with neurodevelopmental disorders including autism spectrum disorders. A seven year-old schoolgirl with intellectual deficit, autistic features and primary carnitine deficiency has been reported. A significant decrease in carnitine levels has been shown in patients with autism and this has been related to the existence of a mitochondrial disease and more severe autism. The early identification of patients with low levels of carnitine or primary carnitine deficiency, with the different methods of measuring free carnitine, including tandem mass spectrometry could help to identify these patients early and achieve an early treatment and better neurological prognosis, because autism spectrum disorders may be preventable in this subgroup. We hope that this paper is useful to neurologists and pediatricians, and may give them more reason to suspect a diagnosis of PCD and autism.

First Case Report of Primary Carnitine Deficiency Manifested as Intellectual Disability and Autism Spectrum Disorder

Systemic primary carnitine deficiency (PCD) is a genetic disorder caused by decreased or absent organic cation transporter type 2 (OCTN2) carnitine transporter activity, resulting in low serum carnitine levels and decreased carnitine accumulation inside cells. In early life, PCD is usually diagnosed as a metabolic decompensation, presenting as hypoketotic hypoglycemia, Reye syndrome, or sudden infant death; in childhood, PCD presents with skeletal or cardiac myopathy. However, the clinical presentation of PCD characterized by autism spectrum disorder (ASD) with intellectual disability (ID) has seldom been reported in the literature. In this report, we describe the clinical features of a seven-year-old girl diagnosed with PCD who presented atypical features of the disease, including a developmental delay involving language skills, concentration, and attention span, as well as autistic features and brain alterations apparent in magnetic resonance imaging. We aim to highlight the difficulties related to the diagnostic and therapeutic approaches used to diagnose such patients. The case reported here presented typical signs of PCD, including frequent episodes of hypoglycemia, generalized muscle weakness, decreased muscle mass, and physical growth deficits. A molecular genetic study confirmed the definitive diagnosis of the disease (c.1345T>G (p.Y449D)) in gene SLC22A5, located in exon 8. PCD can be accompanied by less common clinical signs, which may delay its diagnosis because the resulting global clinical picture can closely resemble other metabolic disorders. In this case, the patient was prescribed a carnitine-enriched diet, as well as oral carnitine at a dose of 100 mg/kg/day. PCD has a better prognosis if it is diagnosed and treated early; however, a high level of clinical suspicion is required for its timely and accurate diagnosis.

Renal dysfunction is rare in Fukuyama congenital muscular dystrophy

BackgroundThe leading cause of death in patients with Fukuyama congenital muscular dystrophy (FCMD) is congestive heart failure or respiratory dysfunction, which is same as that in Duchenne muscular dystrophy (DMD). Recent studies reported that renal dysfunction is a common complication and an increasing cause of death in advanced DMD. It can be attributable to circulatory instability or inappropriate use of drugs for treating cardiac dysfunction. MethodsWe retrospectively evaluated renal function in 38 genetically diagnosed patients with FCMD (range, 1.3–32.9 years; mean age, 13.7 ± 6.9 years) using cystatin C. We examined possible relationships of cystatin C with blood natriuretic peptide and creatinine levels along with cardiac echocardiography findings. ResultsTwenty-five patients were treated for cardiac dysfunction. Elevated cystatin C level was detected only in two, who also showed proteinuria, glycosuria, hematuria, and extremely high β2-microglobulin levels on urine tests, and were thus diagnosed with renal tubular cell damage. Because both patients were treated for intractable epilepsy with various antiepileptic drugs, including valproic acid (VPA), and had low serum carnitine levels, renal tubular cell damage was considered as an adverse effect of VPA. Unlike patients with DMD, no patient with FCMD had renal dysfunction. Such a rare occurrence of renal dysfunction can be attributable to mild cardiac dysfunction, short disease duration, and careful and early fluid management. ConclusionRenal dysfunction is rare in patients with FCMD; however, renal tubular cell damage should be ascertained, particularly in those undergoing VPA treatment for epilepsy.

Relationship of Serum Carnitine Level with Falls and Gait Disturbance in the Elderly.

Gait disturbance and falls are serious events that can impair activities of daily living (ADL) in the elderly. On the other hand, carnitine plays essential roles in energy production, and carnitine deficiency leads to low activity levels. We examined whether a lower serum carnitine concentration was correlated with falls and gait disturbances in the elderly. We performed a cross-sectional study. One hundred and ninety-eight elderly patients (male, 83; female, 115; 81 ± 6 years old) were enrolled in this study. Physical performance (hand grip strength, leg strength, walking speed, one-leg standing time, and tandem gait steps) and frailty status (The Edmonton Frail Scale: EFS) were evaluated. The serum total, free, and acylated carnitine levels were measured using an enzyme cycling method. We then investigated the associations between the serum carnitine level, history of falls, and the results of these physical examinations. Of the 198 subjects, 56 (28%) had a history of falls within the past one year. The patients with a history of falls had lower serum total carnitine and free carnitine levels than those without a history of falls. Regarding the physical performance results, the patients with a history of falls had higher EFS scores, a weaker hand grip strength, a slower walking speed, a shorter one-leg standing time, and a smaller number of tandem gait steps than those without a history of falls. A logistic regression analysis showed that the low serum total carnitine concentration was identified as an independent factor associated with a history of falls, a slow walking speed after adjustments for age, sex and modified EFS. A low serum carnitine level is associated with a history of falls and gait disturbances in elderly people.

L-Carnitine Deficiency Causing Hypoxic Respiratory Failure Due to Recurrent Flash Pulmonary Edema

SESSION TITLE: Student/Resident Case Report Poster - Pulmonary Manifestations of Systemic Disease I SESSION TYPE: Student/Resident Case Report Poster PRESENTED ON: Tuesday, October 25, 2016 at 01:30 PM - 02:30 PM INTRODUCTION: We present a unique case of recurrent flash pumonary edema associated with L-carnitine deficiency. The purpose of our case is to establish clinical significance of L-carnitine replacement, since its deficiency causes pulmonary edema, especially in chronic hepatitis patients. CASE PRESENTATION: 45-y/o African American female with history of cirrhosis from chronic Hepatitis B on Lamivudine was admitted with one week of productive cough with pleuritic pain, nausea and lethargy. On physical exam there were decreased breath sounds bilaterally. ProBNP was elevated at 5297 ng/L. Chest X-ray (pic 1) and CT chest (pic 2) showed bilateral pulmonary vascular congestion without pleural effusions. 2D Transthoracic ECHO showed LVEF-60% with diastolic dysfunction. Upon admission, patient was intubated for acute hypoxic respiratory failure secondary to pulmonary edema. HIV-PCR, PCP, Urine for Legionella Antigen, and AFB cultures were negative. Patient was started on antibiotics for pneumonia based on BAL cultures that grew ESBL E.coli. Patient's severe sepsis significantly improved, but failed multiple weaning trials. She developed recurrent flash pulmonary edema, as noticed on CXR, at the time of weaning from mechanical ventilation that prompted us to check serum carnitine level. Her carnitine levels were extremely low. Despite multiple aggressive attempts to diurese the patient, her clinical condition continued to deteriorate, due to recurrent flash pulmonary edema, requiring hemodialysis until carnitine was replaced. Following carnitine replacement patient’s clinical condition significantly improved, recurrent pulmonary edema completely resolved and hemodialysis was discontinued. DISCUSSION: Serum carnitine is readily measurable and can easily be substituted, but there are no guidelines yet for adults (1). Carnitine levels in patients with chronic hepatitis are lower than in healthy individuals. There are case reports that suggest secondary carnitine deficiency due to some medications like Valproate, Adefovir and Zidovudine. In our patient, carnitine deficiency could be due to chronic hepatitis or even Lamivudine (2,3). CONCLUSIONS: We can clearly establish from our case that carnitine deficiency must be considered as a reversible cause for recurrent flash pulmonary edema in chronic hepatitis patients. Prompt recognition and replacement of carnitine reverses the clinical symptoms. Reference #1: E. Gilbert. Carnitine deficiency. Pathology, 1985;17(2):161-71. Reference #2: M. Vilaseca, R. Artuch, C. Sierra, et al. Low serum carnitine in HIV-infected children on antiretroviral treatment. European Journal of Clinical Nutrition, 2003;57:1317-1322. Reference #3: L. Jansen, A. Niet, F. Stelma, et al. HBsAg loss in patients treated with peginterferon alfa-2a and adefovir is associated with SLC16A9 gene variation and lower plasma carnitine levels. Journal of Hepatology, 2014;61(4):730-737. DISCLOSURE: The following authors have nothing to disclose: Alexandra Sokolova, Shruti Patel, Jagadish Akella No Product/Research Disclosure Information

Carnitine transport and fatty acid oxidation

Carnitine is essential for the transfer of long-chain fatty acids across the inner mitochondrial membrane for subsequent β-oxidation. It can be synthesized by the body or assumed with the diet from meat and dairy products. Defects in carnitine biosynthesis do not routinely result in low plasma carnitine levels. Carnitine is accumulated by the cells and retained by kidneys using OCTN2, a high affinity organic cation transporter specific for carnitine. Defects in the OCTN2 carnitine transporter results in autosomal recessive primary carnitine deficiency characterized by decreased intracellular carnitine accumulation, increased losses of carnitine in the urine, and low serum carnitine levels. Patients can present early in life with hypoketotic hypoglycemia and hepatic encephalopathy, or later in life with skeletal and cardiac myopathy or sudden death from cardiac arrhythmia, usually triggered by fasting or catabolic state. This disease responds to oral carnitine that, in pharmacological doses, enters cells using the amino acid transporter B0,+. Primary carnitine deficiency can be suspected from the clinical presentation or identified by low levels of free carnitine (C0) in the newborn screening. Some adult patients have been diagnosed following the birth of an unaffected child with very low carnitine levels in the newborn screening. The diagnosis is confirmed by measuring low carnitine uptake in the patients' fibroblasts or by DNA sequencing of the SLC22A5 gene encoding the OCTN2 carnitine transporter. Some mutations are specific for certain ethnic backgrounds, but the majority are private and identified only in individual families. Although the genotype usually does not correlate with metabolic or cardiac involvement in primary carnitine deficiency, patients presenting as adults tend to have at least one missense mutation retaining residual activity. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.

Related factor of serum carnitine deficiency and influence of its deficiency on the length of hospital stay in critical ill patients

To investigate the related factors of serum carnitine deficiency in critical ill patients, and the influence of its deficiency on the length of hospital stay. A prospective study was conducted. Critical ill patients with acute physiology and chronic health evaluation II (APACHEII) score>12 admitted to Department of Critical Care Medicine of the First Affiliated Hospital of Sun Yat-sen University from March 2013 to September 2013 were enrolled. Serum carnitine concentration and indexes of organ function were determined, and the tolerance of enteral nutrition within 5 days, the length of hospital stay, the length of intensive care unit (ICU) stay, and the hospital mortality were recorded. The relationship between serum carnitine and indexes mentioned above was analyzed. Thirty critically ill patients were enrolled. Serum carnitine concentration was very low in all critically ill patients, i.e. (8.92 ± 5.05) μmol/L (normal reference value at 43.5 μmol/L) at hospital admission. Serum carnitine concentration in patients with APACHEII score>23 (7 cases) was significantly lower than that in those with APACHEII score 12-23 (23 cases, μmol/L: 5.33 ± 1.72 vs. 10.02 ± 5.24, t=2.300, P=0.001). Serum carnitine concentration in patients with serum total bilirubin(TBil)>19 μmol/L (9 cases) was significantly lower than that in those with TBil≤19 μmol/L (21 cases, μmol/L: 5.54 ± 2.70 vs. 9.84 ± 5.08, t=2.750, P=0.014). Serum carnitine concentration was negatively correlated with the APACHEII score and the TBil (r=-0.387, P=0.035; r=-0.346, P=0.048). During the 5-day observation period, enteral feeding amount [(5 134 ± 1 173) mL] was positively correlated with serum carnitine concentration(r=0.430, P=0.022). In 30 critical patients, the incidence of abdominal distension was 40.0% (12/30), and the serum carnitine concentration of patients with abdominal distension was lower compared with that of patients without abdominal distension (μmol/L: 7.83 ± 4.98 vs. 9.12 ± 5.35, t=0.707, P=0.383). The incidence of diarrhea was 26.7% (8/30), and the serum carnitine concentration of diarrhea patients was lower compared with that of patients without diarrhea (μmol/L: 8.27 ± 5.78 vs. 9.73 ± 4.78, t=0.607, P=0.576). The mean length of hospital stay was (34.72 ± 16.66) days. The serum carnitine concentrations in patients with hospital stay ≥ 45 days (8 cases) were lower compared with those in those <45 days (22 cases, μmol/L: 5.71 ± 3.23 vs. 9.95 ± 5.26, t=1.627, P=0.020). No correlation was found between serum carnitine concentrations and the hospital stay (r=-0.165, P=0.385). The length of ICU stay was (18.60 ± 10.72) days. Serum carnitine concentration in patients with the length of ICU stay>7 days (27 cases) was slightly lower than that in those with the length of ICU stay ≤ 7 days (3 cases, μmol/L: 8.44 ± 5.00 vs. 13.24 ± 3.65, t=1.610, P=0.119). No correlation was found between serum carnitine concentrations and the length of ICU stay (r=-0.019, P= 0.293). In-hospital mortality was 26.67% (8/30). No significant difference in serum carnitine concentrations was found between the death group and the survival group (μmol/L: 12.24 ± 6.52 vs. 7.72 ± 3.91, t=-1.846, P=0.098). No correlation was found between serum carnitine concentrations and in-hospital mortality (r=0.340, P=0.066). Carnitine deficiency is significant in critically ill patients, and it is correlated with disease severity and serum TBil. The total amount of lenteral feeding was lower, and hospital stay was prolonged in critically ill patients with low serum carnitine level.

G.P.317: Renal dysfunction in patients with Fukuyama congenital muscular dystrophy

Fukuyama congenital muscular dystrophy (FCMD), characterized by intellectual deficits and epilepsy with cortical migration defects, is the most common congenital muscular dystrophy in Japan. Most patients die of congestive heart failure or respiratory dysfunction, as in Duchenne muscular dystrophy (DMD), in the second decade of life. Recent studies have found that renal dysfunction is a common complication of advanced DMD and is the third leading cause of death in these patients. Circulatory instability caused by cardiac dysfunction is thought to result in renal dysfunction, especially prerenal failure. We retrospectively evaluated renal function in 37 genetically diagnosed FCMD patients (1.3–32.9 years, mean age 13.7 ± 6.9 years) using Cystatin C. We examined possible relationships of Cystatin with the levels of blood natriuretic peptide and creatinine, as well as the cardiac echo results. Twenty-four patients were treated for cardiac dysfunction, but elevated Cystatin C was detected in only two. These two patients also showed proteinuria, glycosuria, hematuria and extremely high levels of β2-microglobulin on urine tests and were thus diagnosed as having kidney tubule cell damage. Since both patients were treated for intractable epilepsy with many types of antiepileptic drugs, including valproic acid (VPA), and had low serum carnitine levels, kidney tubule cell damage was thought to be an adverse effect of VPA. One patient improved in response to a reduced VPA dose, but the other developed Fanconi syndrome. Unlike DMD patients, none of our FCMD patients progressed to prerenal failure. Though FCMD patients also have cardiac dysfunction, careful fluid management is instituted early because dysphagia emerges in the early stage. In DMD patients, inadequate fluid management may also cause circulatory instability, which can progress to prerenal failure. On the other hand, kidney tubule cell damage should be noted in FCMD patients especially with VPA treatment for epilepsy.

Serum carnitine levels and levocarnitine supplementation in institutionalized Huntington’s disease patients

Along with antioxidant properties, carnitine is an important regulator of lipid metabolism in humans. While beneficial effects of carnitine have been demonstrated in animal models of Huntington's disease (HD), metabolism of carnitine has not been studied in humans with this illness. In this retrospective database review from 23 patients admitted to a HD-specialized nursing home unit, we found a relatively high prevalence of hypocarnitinemia (6 cases, 26%). Our review suggests that catabolism and chronic valproate use predisposed our patients to develop hypocarnitinemia. The patients with low serum carnitine levels who received levocarnitine supplementation, during a mean period of 7.3 months, showed improvement in motor, cognitive and behavioral measures. We hypothesize that observed improvement related to the resolution of reversible metabolic encephalopathy and myopathy associated with secondary carnitine deficiency. In conclusion, notwithstanding its limitations, this is the first study to report measurements of carnitine levels in HD patients, revealing relatively high prevalence of hypocarnitinemia in our population. Our findings suggest that HD patients with hypocarnitinemia may benefit from low-dose levocarnitine supplementation. Further studies of carnitine metabolism and supplementation in HD patients are warranted.

L‐carnitine and cancer cachexia: Clinical and experimental aspects

Cancer cachexia is a multifaceted syndrome characterized, among many symptoms, by extensive muscle wasting. Chronic systemic inflammation, partly triggered and sustained by cytokines, as well as increased oxidative stress contributes to the pathogenesis of this complex metabolic disorder. l-carnitine plays a central role in the metabolism of fatty acids and shows important antioxidant and anti-inflammatory properties. Systemic carnitine depletion has been described in several diseases, and it is characterized by fatigue, muscle weakness, and decreased tolerance to metabolic stress. In cachectic cancer patients, low serum carnitine levels have been reported, and this change has been suggested to play an important contributory role in the development of cachexia. Based on these data, carnitine supplementation has been tested in preliminary studies concerning human cachexia, resulting in improved fatigue and quality of life. We present here a review of clinical and experimental evidence regarding the use of carnitine supplementation in the management of cancer cachexia.

Clinical Outcomes and Low-Dose Levocarnitine Supplementation in Psychiatric Inpatients With Documented Hypocarnitinemia: A Retrospective Chart Review

Metabolic encephalopathy is one of the crucial manifestations of carnitine deficiency. In psychiatric patients, low serum carnitine levels may result from chronic valproate therapy. Despite the widespread use of valproate in psychiatry, neither carnitine deficiency nor supplementation has been studied in a psychiatric population. To describe clinical outcomes in hospitalized psychiatric patients with documented hypocarnitinemia who were receiving oral levocarnitine supplementation. Retrospective chart review. In 38 patients with hypocarnitinemia, a low-dose oral levocarnitine supplementation, in association with comprehensive psychiatric therapy, did not result in any adverse psychiatric or medical outcomes, and was associated with overall improved behavioral, cognitive, and motor functioning. Initially all patients had some degree of cognitive impairment, but after correction of carnitine serum levels, scores on the Mini-Mental State Examination (MMSE) improved in most of the patients (mean improvement 5.5 points, P <0.0001), and normalized in 11 cases. This allowed a correction of the diagnosis in 8 of 14 patients who had initially been diagnosed with dementia. African-American patients achieved significantly lower serum carnitine levels and MMSE scores than Caucasian patients with comparable therapy. We hypothesize that correction of carnitine depletion, either by levocarnitine supplementation or by valproate dose reduction, may enhance recovery from hypocarnitinemia-associated encephalopathy in psychiatric patients. Our findings also suggest that ethnic traits may affect carnitine bioavailability as well as cognitive outcomes in this clinical context. Further studies of carnitine metabolism and supplementation in psychiatric patients are warranted.

Deficiency of the carnitine transporter (OCTN2) with partial N‐acetylglutamate synthase (NAGS) deficiency

A patient with recurrent episodes of hyperammonaemia (highest ammonia level recorded 229 micromol/L, normal 9-33) leading to altered levels of consciousness was diagnosed with partial N-acetylglutamate synthase (NAGS) deficiency (9% residual activity) at age 5 years and was treated with ammonia-conjugating agents (Ucephan 250 mg/kg per day and later sodium phenylbutyrate 200-250 mg/kg per day) for 15 years. A chronically low serum carnitine level (pretreatment plasma free carnitine 4 nmol/L, normal 37 +/- 8 nmol/L; total carnitine 8 nmol/L, normal 46 +/- 10) was assumed to be secondary and was treated with supplemental carnitine (30-50 mg/kg per day). Hypoglycaemia (blood sugar 35 mg/dl, normal 70-100), cardiomegaly, and fatty liver were also noted at diagnosis. The patient died unexpectedly at age 20 years. In retrospect, it was learned that the patient had stopped his carnitine without medical consultation several weeks prior to his death. Additional molecular investigations identified two mutations (R254X and IVS3 + 1G > A) in the patient's OCTN2 (SLC22A5) gene, consistent with a diagnosis of primary carnitine deficiency due to carnitine transporter defect. R245X is a founder mutation in Southern Chinese populations. It is unknown whether the original NAGS deficiency was primary or secondary, but molecular analysis of the NAGS gene failed to identify mutations. Urea cycle enzyme expression may be affected by fatty acid suppression of an AP-1 binding site in the promoter enhancer region of the urea cycle gene. Regardless, it is clear that the NAGS abnormality has led to delay of recognition of the OCTN2 defect, and modified the clinical course in this patient.

Diabetes-induced bradycardia is an intrinsic metabolic defect reversed by carnitine

Rats with streptozotocin-induced diabetes (STZ-D) have reduced serum carnitine levels and bradycardia. Heart rates (HRs) of 24nondiabetic rats (NRs) and 24 STZ-D rats were compared. l-Carnitine (C) was added to the drinking water of rats (12 STZ-D + C) to raise their serum carnitine level. The intrinsic HR for each animal was determined after parasympathetic and sympathetic blockade. The HRs of STZ-D rats (278 ± 15 beats per minute) were less than those of NRs (348 ± 8 beats per minute) ( P < .01). STZ-D rats had low serum carnitine compared with control and STZ-D + C rats. The difference in HR of STZ-D rats and NRs continued after blockade, indicating that the bradycardia ofdiabetes is intrinsic to the heart. The metabolic milieu reflected in the rats' urinary organic acid profiles differed between the control and STZ-D rats. The HR of STZ-D + C rats (326 ± 5 beats per minute) did not differ from those of NRs. Increasing either the insulin dose or the serum free carnitine reduced urinary organic acids, but normal HRs were associated only with elevated serum carnitine levels. When glucose is compromised as a myocardial energy source (diabetes mellitus), we propose that elevated levels of serum carnitine may increase myocardial fatty acid metabolism sufficiently to correct the bradycardia of STZ-D rats.

Relationship Between Serum Carnitine, Acylcarnitines, and Renal Function in Patients With Chronic Renal Disease

Serum free carnitine is decreased and serum acylcarnitines are increased in maintenance hemodialysis (MHD) patients, and the causes for these abnormalities are not known. This study examined the role of renal failure in the occurrence of low serum carnitine and increased acylcarnitines in patients with advanced chronic kidney disease (CKD) by assessing the relationship between these compounds and renal function in normal individuals and patients with CKD. If these compounds decrease as glomerular filtration rate (GFR) decreases, this suggests that decreased intake or impaired synthesis in kidneys explain the low serum values. If serum compounds increase as GFR decreases, this suggests that impaired excretion may predispose to these values. The study, conducted in Lyon, France (part A), and Los Angeles, California (part B), compared serum free carnitine and acylcarnitines to renal function in 20 normal patients, 65 CKD patients, and 29 MHD patients. GFR was measured using inulin (A) and iothalamate (B) clearances. Carnitine compounds were measured by tandem mass spectrometry (A) and electron spray mass spectrometry (B). There was no relationship between serum total carnitine or free carnitine and GFR in the normal subjects and CKD patients. In contrast, serum acylcarnitines were inversely correlated with GFR in these 2 groups. Serum free carnitine was significantly lower in MHD patients than in CKD patients and normal controls in study B, whereas acylcarnitines were significantly greater than controls in studies A and B and than in CKD patients in study A. Serum free carnitine is not reduced in CKD and decreases in MHD patients. Serum acylcarnitines increase in CKD and MHD patients primarily because of impaired excretory function in the failing kidney.

Decrease of serum carnitine levels in patients with or without gastrointestinal cancer cachexia

To evaluate the levels of serum carnitine in patients with cancer in digestive organs and to compare them with other cancers in order to provide new insights into the mechanisms of cachexia. Fifty-five cachectic patients with or without gastrointestinal cancer were enrolled in the present study. They underwent routine laboratory investigations, including examination of the levels of various forms of carnitine present in serum (i.e., long-chain acylcarnitine, short-chain acylcarnitine, free carnitine, and total carnitine). These values were compared with those found in 60 cancer patients in good nutritional status as well as with those of 30 healthy control subjects. When the cachectic patients with gastro-intestinal cancer were compared with the cachectic patients without gastrointestinal cancer, the difference was -6.8 micromol/L in free carnitine (P < 0.005), 0.04 micromol/L in long chain acylcarnitine (P < 0.05), 8.7 micromol/L in total carnitine (P < 0.001). In the cachectic patients with or without gastrointestinal cancer, the difference was 12.2 micromol/L in free carnitine (P < 0.001), 4.60 micromol/L in short chain acylcarnitine (P < 0.001), and 0.60 micromol /L in long-chain acylcarnitine (P < 0.005) and 17.4 micromol/L in total carnitine (P < 0.001). In the cachectic patients with gastrointestinal cancer and the healthy control subjects, the difference was 15.5 micromol/L in free carnitine (P < 0.001), 5.2 micromol /L in short-chain acylcarnitine (P < 0.001), 1.0 micromol/L in long chain acylcarnitine (P < 0.001), and 21.8 micromol/L in total carnitine (P < 0.001). Low serum levels of carnitine in terminal neoplastic patients are decreased greatly due to the decreased dietary intake and impaired endogenous synthesis of this substance. These low serum carnitine levels also contribute to the progression of cachexia in cancer patients.

SERUM CARNITINE LEVELS IN CHILDREN WITH IRON-DEFICIENCY ANEMIA WITH OR WITHOUT PICA

Carnitine is ingested through animal-derived foods as well as synthesized in vivo. It plays an important role in the energy metabolism of many tissues. Iron acts as a co-factor for the synthesis of carnitine. However, the importance of iron deficiency as a cause of secondary carnitine deficiency is not well established. The aim of this study was to investigate the serum levels of carnitine in children with iron-deficiency anemia compared to those of healthy children and to determine if serum carnitine levels in with or without pica differ. The mean serum carnitine concentration in the iron-deficiency group was significantly lower than that in healthy children (12.44± 5.09 and 32.48 ± 7.92 μmol/L, respectively, p <. 001). In the iron-deficient group, serum carnitine levels, ferritin levels, and other hematological parameters were lowest in patients with pica (p <. 001). Pearson correlation test indicated a positive correlation between serum carnitine and ferritin levels in iron-deficient patients. Based on the evidence about the effect of low iron on carnitine stores in animal studies, the authors propose that low serum carnitine levels in these children may be secondary to iron-deficiency anemia. However, further large-scale studies are needed to establish the frequency of carnitine deficiency in children with iron-deficiency anemia.

Serum carnitine levels in patients with tumoral cachexia

Background Cachexia is a serious complication of many cancers that is common in cancer and AIDS patients. However, the key factors and mechanisms involved in the development of cachexia are not yet understood. There is little data currently available regarding carnitine metabolism in patients with neoplasm and cachexia. Methods Forty-six neoplastic patients with different localizations of their primary disease gave signed, informed consent before enrolling in the present study. They underwent routine laboratory investigation, including examination of the levels of the various forms of carnitine present in serum (i.e., long-chain acylcarnitine, short-chain acylcarnitine, soluble acid acylcarnitine, free carnitine, and total carnitine). These values were compared with those found in 30 cancer patients in good nutritional status as well as with those of 30 healthy control subjects. Results In the comparison of serum plasma carnitine of cachectic patients versus controls, the difference in free carnitine was − 8.20 μmol/L ( p = 0.000); the difference in short-chain acylcarnitine − 2.60 μmol/L ( p = 0.029); the difference in soluble acid carnitine − 10.80 μmol/L ( p = 0.000); the difference in long-chain acylcarnitine − 0.40 μmol/L ( p = 0.036); and the difference in total carnitine −11.20 μmol/L ( p = 0.000). In the comparison of serum plasma carnitine of cachectic versus neoplastic patients in good nutritional status, the difference in free carnitine was −5.80 μmol/L ( p = 0.006); the difference in soluble acid carnitine − 7.20 μmol/L ( p = 0.000); and the difference in total carnitine − 7.50 μmol/L ( p = 0.000). Conclusion Our study showed that, in the multifactorial pathogenesis of cachexia, the low serum levels of carnitine in terminal neoplastic patients, which are due to a decreased dietary intake as well as to an impaired endogenous synthesis of this substance, could play an important role. These low serum carnitine levels may also contribute to the development of cachexia in cancer patients.