Carnitine-acylcarnitine Translocase Research Articles

Lipid emulsions attenuate the inhibition of carnitine acylcarnitine translocase induced by toxic doses of local anesthetics in rat cardiomyoblasts.

The aim of this study was to examine the effects of lipid emulsions on carnitine palmitoyltransferase I (CPT-I), carnitine acylcarnitine translocase (CACT), carnitine palmitoyltransferase II (CPT-II), and the mitochondrial dysfunctions induced by toxic doses of local anesthetics in H9c2 rat cardiomyoblasts. The effects of local anesthetics and lipid emulsions on the activities of CPT-I, CACT, and CPT-II, and concentrations of local anesthetics were examined. The effects of lipid emulsions, N-acetyl-L-cysteine (NAC), and mitotempo on the bupivacaine-induced changes in cell viability, reactive oxygen species (ROS) levels, mitochondrial membrane potential (MMP), and intracellular calcium levels were examined. CACT, without significantly altering CPT-I and CPT-II, was inhibited by toxic concentration of local anesthetics. The levobupivacaine- and bupivacaine-induced inhibition of CACT was attenuated by all concentrations of lipid emulsion, whereas the ropivacaine-induced inhibition of CACT was attenuated by medium and high concentrations of lipid emulsion. The concentration of levobupivacaine was slightly attenuated by lipid emulsion. The bupivacaine-induced increase of ROS and calcium and the bupivacaine-induced decrease of MMP were attenuated by ROS scavengers NAC and mitotempo, and the lipid emulsion. Collectively, these results suggested that the lipid emulsion attenuated the levobupivacaine-induced inhibition of CACT, probably through the lipid emulsion-mediated sequestration of levobupivacaine.

Carnitine Cycle Defect in Newborn: A Rare Case Report

Carnitine Acylcarnitine Translocase (CACT) deficiency and Carnitine Palmitoyl Transferase (CPT I and II) deficiency comes under a group of disorders called mitochondrial fatty acid oxidation disorders, due to defects in the carnitine cycle. The CPT and CACT enzymes play a pivotal role in the transfer of Long Chain Fatty Acids (LCFA) from the cytoplasm to the mitochondrial matrix, where β-oxidation take place. In the present case, a male baby presented on day 2 of life with chief complaints of respiratory distress, apnoea, lethargy and seizures. The baby had multiple episodes of hypoglycaemia and seizures after admission. Diagnosis was made with the help of extended newborn screening using Tandem Mass Spectrometry (TMS) showing accumulation of hexadecanoyl carnitine due to CACT/CPT II deficiency. Echocardiography showed features of cardiomyopathy with cardiomegaly. Liver Function Test (LFT) and Prothrombin Time-International Normalisation Ratio (PT-INR) of the child was also deranged, with hypotonia of all muscles. Early detection along with carnitine supplementation and further prevention of fasting episodes resulted in generalised improvement of the baby. So, a high degree of suspicion of Inborn Error of Metabolism (IEM) and timely diagnosis can save the baby

Metabolic Flexibility in Canine Mammary Tumors: Implications of the Carnitine System.

Simple SummaryThe process of cell transformation toward a malignant phenotype is generally due to genetic alterations and/or epigenetic changes, as well as rewiring of cellular signaling and reprogramming of metabolic pathways. In addition to glucose metabolism, cancer cells can derive fuel from fatty acid-β-oxidation (FAO), an important alternative bioenergetic pathway that is often dysregulated in cancer. Moreover, FAO enzymes (particularly components of the carnitine system) are overactivated in tumors, suggesting that they serve as metabolic signatures in various cancer cell types. Metabolic changes in carcinogenesis are a focus of current research and have been poorly studied in canine malignancies. We previously reported that CPT1A, the rate-limiting regulator of the FAO process, is deregulated in canine mammary tumor tissues and cells. In the present study, we examined the protein expression of the three remaining components of the carnitine system (CACT, CPT2, and CrAT) and confirmed their expression and deregulation in canine mammary tumor tissues and cells. We also found that low expression of carnitine system components was closely related to the malignancy grade of mammary tumors. Detailed studies to investigate the role of these components in canine mammary tumors are needed to also improve the therapeutic approach in dogs.Deregulation of fatty acid catabolism provides an alternative energy source to glycolysis for cancer cell survival and proliferation. The regulator enzymes of the carnitine system (CS), responsible for the transport of fatty acids across mitochondrial membranes for β-oxidation are deregulated in tumorigenesis. Recently, we found that Carnitine Palmitoyl Transferase 1 (CPT1), a crucial regulator of CS components, is expressed and dysregulated in canine mammary tumor (CMT) tissues and cells. In this study, we examined the protein expression of the three remaining enzymes of CS (Carnitine Acylcarnitine Translocase (CACT), Carnitine Palmitoyl Transferase 2 (CPT2), Carnitine O-acetyltransferase (CrAT), in canine mammary cells and tissues by Western blot and immunohistochemistry. Protein expression of the components of CS was found in normal mammary glands and a concomitant deregulation of expression in CMT tissues that inversely correlated with the degree of tumor differentiation. Moreover, the expression and a different deregulation of CS-related proteins was also observed in CF33, CMT-U27, CMT-U309, and P114 cell lines used as in vitro model. These results demonstrate for the first time the expression of CS components in CMT tissues and cancer cells; however, further studies are needed to elucidate their roles in dogs as well.

Novel mutations associated with carnitine-acylcarnitine translocase and carnitine palmitoyl transferase 2 deficiencies in Malaysia

ObjectiveCarnitine-acylcarnitine Translocase (CACT) deficiency (OMIM 212138) and carnitine palmitoyl transferase 2 (CPT2) deficiency (OMIM 60065050) are rare inherited disorders of mitochondrial long chain fatty acid oxidation. The aim of our study is to review the clinical, biochemical and molecular characteristics in children diagnosed with CACT and CPT2 deficiencies in Malaysia. Design and methodsThis is a retrospective study. We reviewed medical records of six patients diagnosed with CACT and CPT2 deficiencies. They were identified from a selective high-risk screening of 50,579 patients from January 2010 until Jun 2020. ResultsAll six patients had either elevation of the long chain acylcarnitines and/or an elevated (C16 + C18:1)/C2 acylcarnitine ratio. SLC25A20 gene sequencing of patient 1 and 6 showed a homozygous splice site mutation at c.199–10 T > G in intron 2. Two novel mutations at c.109C > T p. (Arg37*) in exon 2 and at c.706C > T p. (Arg236*) in exon 7 of SLC25A20 gene were found in patient 2. Patient 3 and 4 (siblings) exhibited a compound heterozygous mutation at c.638A > G p. (Asp213Gly) and novel mutation c.1073 T > G p. (Leu358Arg) in exon 4 of CPT2 gene. A significant combined prevalence at 0.01% of CACT and CPT2 deficiencies was found in the symptomatic Malaysian patients. ConclusionsThe use of the (C16 + C18:1)/C2 acylcarnitine ratio in dried blood spot in our experience improves the diagnostic specificity for CACT/CPT2 deficiencies over long chain acylcarnitine (C16 and C18:1) alone. DNA sequencing for both genes aids in confirming the diagnosis.

Screening for neonatal inherited metabolic disorders by tandem mass spectrometry in Guangzhou.

To analyze the screening results for inherited metabolic disorders (IMD) in newborns by tandem mass spectrometry (MS/MS) in Guangzhou.A total of 272 117 newborns in Guangzhou from Jan 2015 to Dec 2020 were screened for IMD by MS/MS in Guangzhou Newborn Screening Center. When the primary screening was positive, the newborns and their mothers were recalled. For those with positive in re-examination, the biochemical and related genetic analysis were required for confirmation. The screening results, clinical characteristics and outcomes of the confirmed cases were retrospectively analyzed and the performance was optimized. Among 272 117 neonates, 1808 (0.66%) cases were positive in primary screening, and 1738 cases (96.13%) were recalled for review. The median clinical diagnosis time was 15 d after birth. A total of 79 cases of IMD were diagnosed, including 23 with aminoacidopathy, 17 with disorder of organic acid metabolism and 39 with fatty acid oxidation disorders, involving 21 diseases. The incidence rate was 1/3444 in newborns, and the positive predictive value of 4.5%. Four false negative cases were found, all of them were citrin deficiency. The common diseases were primary carnitine deficiency (26.6%), methylmalonic aciduria (12.7%) and phenylalanine hydroxylase deficiency (11.4%). The mothers of 32 cases were confirmed, including 30 cases of primary carnitine deficiency, 1 case of isobutyl-coenzyme A dehydrogenase deficiency and 1 case of 3-methylcromaryl coenzyme A carboxylase deficiency. The detection rate was 1/2451 in total population. During the follow-up, most patients remain asymptomatic, except for 5 severe cases who died early (1 case of maple syrup urine disease, 2 cases of isolated methylmalonic acidurmia, and 2 cases of carnitine-acylcarnitine translocase deficiency); and 10 cases of organic acid metabolism disorders developed mild psychomotor developmental retardation. After optimizing the screening indicators, the number of initial screening positives dropped to 903, and the positive predictive value increased to 9.1%, and no confirmed cases were missed. The incidence rate of fatty acid oxidation disorders is high in Guangzhou. A variety of IMD can be effectively screened out by MS/MS, and the screening performance can be improved by optimizing screening indicators.

Identification of c.199-10T>G mutation in SLC25A20 gene related to fatty acid oxidation disorders on a Vietnamese patient

Fatty acid oxidation disorders (FAODS) consist of rare diseases which affect the energy production of the mitochrondria by disrupting the β-oxidation of fatty acid, resulting in energy deficiency and toxic acumulation in the patient’s body. Typical clinical symtoms of FAODS include rhabdomyolysis, myoglobinuria, cardiomyopathy, hypoketotic hypoglycemia and liver dysfunction on the newborns and could lead to mortality in most of the cases. Mutations occur in different genes in the enzymatic pathway of the mitochrondria may cause diffirent types of FAODS.The objective of this study was to screen and identify genetic mutations associated with fatty acid oxidation disorders in Vietnamese patients through whole exome sequencing analysis. The result revealed a reported homozygous c.199-10T>G mutation in the position of 10 nucleotides before the exon 3 of the SLC25A20 gene. The SLC25A20 gene encodes the carnitine acylcarnitine translocase (CACT), which plays an important role in transporting acylcarnitine and carnitine in the mitochondria. Genetic mutations in this gene often lead to carnitine-acylcarnitine translocase deficiency (CACTD) - a rare form of FAODs. By in silico analysis, the c.199-10T>G mutation was predicted as a splite site mutation that could lead to exon skipping during the creation of mature mRNA. Genetic analysis of the patient’s family showed that both parents had the mutation c.199-10T>G in heterozygous form. This result suggests that every mutant allele in the patient is inherited from parents. Our finding not only improved our understanding of the c.199-10T>G mutation in SLC25A20 gene of our patient but also provides important information for future research, diagnosis and genetic counseling of FAOS in Vietnamese patients.

Calcitonin Stimulation Tests: Rationale, Technical Issues and Side Effects: A Review.

Calcitonin (CT) stimulation tests have great value and could help to: differentiate thyroid causes of elevated CT apart from non-thyroid sources, determine whether the patients with slightly elevated basal CT could/could not be candidates for surgery, and indicate the right moment for prophylactic thyroidectomy in children with MEN syndromes when with normal basal CT. This triggered the requests for development of CT stimulation tests, taking into consideration their safety and aimed us to write a systematic review of literature regarding the rationale, technical issues, and side effects of CT stimulating tests used for diagnosis of MTC. After a thorough review of the literature, we classified the reported side effects by severity, as defined by United States Food and Drug Administration. A statistical analysis was performed using IBM SPSS Statistics version 20. Various side effects were noticed during stimulation tests that differ by intensity, duration and severity, depending on types of substances and protocols used. The side effects after pentagastrin test were significantly more severe than those reported after calcium stimulation test (p=0.0396). There are also significant gender-specific differences in side effects induced by stimulation tests. In conclusion, we recommend performing Ca CT stimulation test when needed, considering preventive evaluation of some clinical, instrumental, and biochemical aspects of each patient. Precise instructions should be followed before a stimulation test and furthermore continuous cardiac monitoring is essential during and after the test to minimize the possibility of a serious event.

Antitumor effects of local anesthetic agents in vitro and in vivo.

e15091 Background: Local anesthetics (LA) are often used during surgery in order to control postoperative pain. Observational retrospective studies showed a significant and unexpected decrease of relapse and increased overall survival after LA injection during solid cancer removal. We hypothesized that LAs used as stand-alone treatment or combined with conventional anticancer therapy may induce cytotoxic effects on cancer cells and trigger antitumor responses against dead-cell antigens. Methods: Cell stress and cell death modalities were investigated in vitro by means of specific biosensors in human osteosarcoma (U2OS) cells after treatment with LAs such as bupivacaine, chloroprocaine, levobupivacaine, lidocaine, ropivacaine and prilocaine. Moreover tumor growth and overall survival were studied in solid tumor models (MCA 205 fibrosarcoma) established in immunocompetent C57Bl/6 mice treated under general anesthesia with LAs (lidocaine or ropivacaine) alone or combined with immune checkpoint blockade (anti-PD-1). Ethical Committee: CEEA IRCIV/IGR n°26, French Ministry of Research, Ref:16946/2018100309413893v2. Results: In vitro, the tested LAs triggered autophagy and induced all arms of the integrated stress response including the phosphorylation of eIF2alpha, the activation of ATF4, the splicing of XBP1 and the proteolytic cleavage of ATF6. Cell stress was followed by apoptotic cell death, and both were inhibited when eIF2alpha kinase 3 (EIF2AK3) was genetically removed by CRISPR/CAS9, while the removal of EIF2AK1, EIF2AK2 and EIF2AK4 had no effects on cellular demise. LAs also triggered mitochondrial dysfunction, mimicking the effect of mitochondrial uncouplers (such as rotenone and CCCP) characterized by respiratory chain and inhibition of a mitochondrial transmembrane enzyme (carnitine-acylcarnitine translocase). In vivo, LAs induced effective tumor growth reduction and improved survival of immunocompetent but not immunodeficient mice, suggesting the ignition of anticancer immune responses. These anticancer immune effects were significantly potentiated when LAs were combined with PD-1 immune checkpoint blockade. LAs and mitochondrial uncouplers failed to induce anticancer effects in MCA205 tumors that were unable to induce ER stress (due to EIF2AK3 knockout) or autophagy (due to AtG5 KO), suggesting that both premortem stress responses are indispensable for inducing anticancer immunity. Conclusions: LAs induce EIF2AK3-dependent cancer cell stress including autophagy and the integrated stress response, which is followed by mitochondrial toxicity and cell death both in vitro and in cancers established in mice. These effects trigger therapeutically relevant anticancer immune responses that can be further potentiated by means of PD-1 blockade. These preclinical observations suggest that the use of LAs during oncological surgery improves clinical outcome by inducing anticancer immunity.

New insights into carnitine-acylcarnitine translocase deficiency from 23 cases: Management challenges and potential therapeutic approaches.

Carnitine acyl-carnitine translocase deficiency (CACTD) is a rare autosomal recessive disorder of mitochondrial long-chain fatty-acid transport. Most patients present in the first 2 days of life, with hypoketotic hypoglycaemia, hyperammonaemia, cardiomyopathy or arrhythmia, hepatomegaly and elevated liver enzymes. Multi-centre international retrospective chart review of clinical presentation, biochemistry, treatment modalities including diet, subsequent complications, and mode of death of all patients. Twenty-three patients from nine tertiary metabolic units were identified. Seven attenuated patients of Pakistani heritage, six of these homozygous c.82G>T, had later onset manifestations and long-term survival without chronic hyperammonemia. Of the 16 classical cases, 15 had cardiac involvement at presentation comprising cardiac arrhythmias (9/15), cardiac arrest (7/15), and cardiac hypertrophy (9/15). Where recorded, ammonia levels were elevated in all but one severe case (13/14 measured) and 14/16 had hypoglycaemia. Nine classical patients survived longer-term-most with feeding difficulties and cognitive delay. Hyperammonaemia appears refractory to ammonia scavenger treatment and carglumic acid, but responds well to high glucose delivery during acute metabolic crises. High-energy intake seems necessary to prevent decompensation. Anaplerosis utilising therapeutic d,l-3-hydroxybutyrate, Triheptanoin and increased protein intake, appeared to improve chronic hyperammonemia and metabolic stability where trialled in individual cases. CACTD is a rare disorder of fatty acid oxidation with a preponderance to severe cardiac dysfunction. Long-term survival is possible in classical early-onset cases with long-chain fat restriction, judicious use of glucose infusions, and medium chain triglyceride supplementation. Adjunctive therapies supporting anaplerosis may improve longer-term outcomes.

Carnitine-Acylcarnitine Translocase Deficiency Masked by Extreme Prematurity.

Carnitine-acylcarnitine translocase (CACT) deficiency is a rare disorder of long chain fatty acid oxidation with a very high mortality rate due to cardiomyopathy or multiorgan failure. We present the course of a very premature infant with early onset CACT deficiency complicated by multiple episodes of necrotizing enterocolitis, sepsis, and liver insufficiency, followed by eventual demise. The complications of prematurity, potentiated by the overlay of CACT deficiency, contributed to the difficulty of reaching the ultimate diagnosis of CACT deficiency.

Tutorial: Triheptanoin and Nutrition Management for Treatment of Long-Chain Fatty Acid Oxidation Disorders.

Patients with severe long-chain fatty acid oxidation disorders (LC-FAODs) experience serious morbidity and mortality despite traditional dietary management including medium-chain triglyceride (MCT)-supplemented, low-fat diets. Triheptanoin is a triglyceride oil that is broken down to acetyl-coenzyme A (CoA) and propionyl-CoA, which replenishes deficient tricarboxylic acid cycle intermediates. We report the complex medical and nutrition management of triheptanoin therapy initiated emergently for 3 patients with LC-FAOD. Triheptanoin (Ultragenyx Pharmaceutical, Inc, Novato, CA, USA) was administered to 3 patients with LC-FAOD on a compassionate-use basis. Triheptanoin was mixed with non-MCT-containing low-fat formula. Patients were closely followed with regular cardiac and laboratory monitoring. Cardiac ejection fraction normalized after triheptanoin initiation. Patients experienced fewer hospitalizations related to metabolic crises while on triheptanoin. Patient 1 has tolerated oral administration without difficulty since birth. Patients 2 and 3 experienced increased diarrhea. Recurrent breakdown of the silicone gastrostomy tube occurred in patient 3, whereas the polyurethane nasogastric tube for patient 2 remained intact. Patient 3 experiences recurrent episodes of elevated creatine kinase levels and muscle weakness associated with illness. Patient 3 had chronically elevated C10-acylcarnitines while on MCT supplementation, which normalized after initiation of triheptanoin and discontinuation of MCT oil. Triheptanoin can ameliorate acute cardiomyopathy and increase survival in patients with severe LC-FAOD. Substituting triheptanoin for traditional MCT-based treatment improves clinical outcomes. MCT oil might be less effective in carnitine-acylcarnitine translocase deficiency patients compared with other FAODs and needs further investigation.

PPARδ Attenuates Alcohol-Mediated Insulin Resistance by Enhancing Fatty Acid-Induced Mitochondrial Uncoupling and Antioxidant Defense in Skeletal Muscle.

Alcohol consumption leads to the dysfunction of multiple organs including liver, heart, and skeletal muscle. Alcohol effects on insulin resistance in liver are well evidenced, whereas its effects in skeletal muscle remain controversial. Emerging evidence indicates that alcohol promotes adipose tissue dysfunction, which may induce organ dysregulation. We show that consumption of ethanol (EtOH) reduces the activation of 5′AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) as well as the protein of carnitine palmitoyltransferase 1 (CPT1) and glucose transporter type 4 (GLUT4) in C2C12 myotube. We observed that chronic EtOH consumption increases free fatty acid levels in plasma and triglyceride (TG) accumulation in skeletal muscle and that these increases induce insulin resistance and decrease glucose uptake. Hence, ethanol dysregulates metabolic factors and induces TG accumulation. We found peroxisome proliferator-activated receptor β/δ (PPARδ) activation recovers AMPK activation and increases carnitine-acylcarnitine translocase (CACT) protein. These effects may contribute to enhance mitochondrial activation via uncoupling protein 3 (UCP3) when fatty acids are used as a substrate, thus reduces EtOH-induced increases in TG levels in skeletal muscle. In addition, PPARδ activation recovered EtOH-induced loss of protein kinase B (AKT) phosphorylation at serine 473 via rapamycin-insensitive companion of mammalian target of rapamycin (Rictor) activation. Importantly, PPARδ activation enhanced mitochondrial uncoupling via UCP3. Taken together, the study shows PPARδ enhances fatty acid utilization and uncoupled respiration via UCP3 and protects against EtOH-induced lipotoxicity and insulin resistance in skeletal muscle.

A novel homozygous missense SLC25A20 mutation in three CACT-deficient patients: clinical and autopsy data

Carnitine-acylcarnitine translocase (CACT) deficiency is a fatty acid ß-oxidation disorder of the carnitine shuttle in mitochondria, with a high mortality rate in childhood. We evaluated three patients, including two siblings, with neonatal-onset CACT deficiency and revealed identical homozygous missense mutations of p.Arg275Gln within the SLC25A20 gene. One patient died from hypoglycemia and arrhythmia at 26 months; his pathological autopsy revealed increased and enlarged mitochondria in the heart but not in the liver.

Cardiac arrest and ventricular tachycardia in a newborn with carnitine–Acylcarnitine translocase deficiency

We report a female infant who was diagnosed to have carnitine–acylcarnitine translocate deficiency (CACTD) and developed ventricular tachycardia followed by cardiac arrest. Following full feeding, the infant developed significant bradycardia, hypothermia, hypotonia, hypoglycemia, metabolic acidosis, and hyperammonemia. The hyperammonemia was successfully treated with continuous renal replacement therapy (CRRT). One day after the CRRT, she developed ventricular tachycardia that was refractory to medical treatment and synchronized cardioversion. She had cardiac arrest that was unresponsive to full cardiopulmonary resuscitation and died. Raising high index of suspicion of CACTD in the deferential diagnosis of infants present with sudden deterioration, hypoglycemia or hyperammonemia is crucial for early recognition and providing appropriate treatment in this highly lethal disorder.

Continuous renal replacement therapy in a preterm neonate with hyperammonemia secondary to a rare disease

We report a newborn baby girl with a rare cause of hyperammonemia, in which a session of continuous renal replacement therapy (CRRT) was performed successfully despite the child's small size. The baby was born at 34 weeks' gestation with a birth weight of 2.2 kg and was referred on day 4 of life with lethargy, bradycardia, hypothermia, hypoglycemia, and metabolic acidosis associated with hyperammonemia. Following the insertion of the GamCath line, CRRT was performed using continuous venovenous hemodialysis modality, Ultraflux AV Paed dialyzer (Fresenius Medical Care), and multiFiltrate pediatric kit. Over 19 h of therapy, serum ammonia level reduced from >700 μmol/L to 103 μmol/L. Next-generation sequencing revealed a homozygous pathogenic variation in SLC25A20 (NM_000387; exon2; c.109C>T; p.R37X), leading to a diagnosis of carnitine-acylcarnitine translocase deficiency. The child succumbed during a subsequent hospital stay. This case instructively informs on the feasibility and efficacy of CRRT in the management of neonatal hyperammonemia.

Diagnostic contribution of metabolic workup for neonatal inherited metabolic disorders in the absence of expanded newborn screening

Inherited metabolic disorders (IMDs) in neonates are a diagnostic and therapeutic challenge for the neonatologist, with the priority being to rapidly flag the treatable diseases. The objective of this study was to evaluate the contribution of targeted metabolic testing for diagnosing suspected IMDs on the basis of suggestive clinical setting or family history in neonates. We conducted an observational study over five years, from January 1st, 2010 to December 31, 2014 in the neonatal intensive care unit (NICU) at Robert Debré University Hospital, Paris, France. We assessed the number of neonates for whom a metabolic testing was performed, the indication for each metabolic test and the diagnostic yield of this selected metabolic workup for diagnosing an IMD. Metabolic testing comprised at least one of the following testings: plasma, urine or cerebrospinal fluid amino acids, urine organic acids, plasma acylcarnitine profile, and urine mucopolysaccharides and oligosaccharides. 11,301 neonates were admitted at the neonatal ICU during the study period. One hundred and ninety six neonates underwent metabolic testing. Eleven cases of IMDs were diagnosed. This diagnostic approach allowed the diagnosis, treatment and survival of 4 neonates (maple syrup urine disease, propionic acidemia, carnitine-acylcarnitine translocase deficiency and type 1 tyrosinemia). In total, metabolic testing was performed for 1.7% of the total number of neonates admitted in the NICU over the study period. These included 23% finally unaffected neonates with transient abnormalities, 5.6% neonates suffering from an identified IMD, 45.4% neonates suffering from a non-metabolic identified disease and 26% neonates with chronic abnormalities but for whom no final causal diagnosis could be made. In conclusion, as expected, such a metabolic targeted workup allowed the diagnosis of classical neonatal onset IMDs in symptomatic newborns. However, this workup remained normal or unspecific for 94.4% of the tested patients. It allowed excluding an IMD in 68.4% of the tested neonates. In spite of the high rate of normal results, such a strategy seems acceptable due to the severity of the symptoms and the need for immediate treatment when available in neonatal IMDs. However, its cost-effectiveness remains low especially in a clinically targeted population in a country where newborn screening is still unavailable for IMDs except for phenylketonuria in 2019.

Carnitine Inborn Errors of Metabolism.

Carnitine plays essential roles in intermediary metabolism. In non-vegetarians, most of carnitine sources (~75%) are obtained from diet whereas endogenous synthesis accounts for around 25%. Renal carnitine reabsorption along with dietary intake and endogenous production maintain carnitine homeostasis. The precursors for carnitine biosynthesis are lysine and methionine. The biosynthetic pathway involves four enzymes: 6-N-trimethyllysine dioxygenase (TMLD), 3-hydroxy-6-N-trimethyllysine aldolase (HTMLA), 4-N-trimethylaminobutyraldehyde dehydrogenase (TMABADH), and γ-butyrobetaine dioxygenase (BBD). OCTN2 (organic cation/carnitine transporter novel type 2) transports carnitine into the cells. One of the major functions of carnitine is shuttling long-chain fatty acids across the mitochondrial membrane from the cytosol into the mitochondrial matrix for β-oxidation. This transport is achieved by mitochondrial carnitine–acylcarnitine cycle, which consists of three enzymes: carnitine palmitoyltransferase I (CPT I), carnitine-acylcarnitine translocase (CACT), and carnitine palmitoyltransferase II (CPT II). Carnitine inborn errors of metabolism could result from defects in carnitine biosynthesis, carnitine transport, or mitochondrial carnitine–acylcarnitine cycle. The presentation of these disorders is variable but common findings include hypoketotic hypoglycemia, cardio(myopathy), and liver disease. In this review, the metabolism and homeostasis of carnitine are discussed. Then we present details of different inborn errors of carnitine metabolism, including clinical presentation, diagnosis, and treatment options. At the end, we discuss some of the causes of secondary carnitine deficiency.

Resveratrol shifts energy metabolism to increase lipid oxidation in healthy old mice

ObjectivesThe objective of this work was to determine the specific mechanisms by which resveratrol inhibits lipogenesis and stimulates lipolysis. MethodsTwelve male mice were individually introduced into a metabolic cage for 24 h to measure basal metabolic rate, prior to intervention. They were randomly divided into two groups, resveratrol (RSV) and control (C), and administered resveratrol intraperitoneally or vehicle, respectively, for two consecutive days. After 24 h, the metabolic energy expenditure was again determined for 24 h, before mice were sacrificed. Protein and gene expression of different enzymes related to metabolism in the hepatic tissue, adipose tissue and gastrocnemius of mice were analyzed by RT-PCR, western blot or ELISA. ResultsWe report that resveratrol lowers the respiratory quotient in old mice and that this may be due to the activation of fatty acid mobilization from white adipose tissue (because hormone-activated lipase expression is increased) and fatty acid transport into mitochondria and eventual oxidation in muscle and liver (because transport enzymes and beta oxidation enzymes are also increased). Indeed, we have observed that resveratrol in vivo causes an increase in the expression and phosphorylation of AMPKα in liver, muscle and adipose tissue and an increase in the expression of acyl-CoA synthetase, of carnitine palmitoyl transferase 1 and of carnitine acylcarnitine translocase, all enzymes involved in lipid catabolism.On the other hand, the levels of acetyl-CoA carboxylase as well as those its product, i.e. malonyl CoA, are decreased. ConclusionsWe conclude that a controlled dose of resveratrol activates fatty acid mobilization and degradation and inhibits fatty acid synthesis in old mice. This is the first time that these effects of resveratrol in lipid metabolism in healthy old (non-obese) animals are reported.

Clinical and molecular characteristics of carnitine-acylcarnitine translocase deficiency: Experience with six patients in Guangdong China

Carnitine-acylcarnitine translocase deficiency (CACTD) is a rare autosomal recessive disorder of mitochondrial fatty acid oxidation that occurs due to mutations in the SLC25A20 gene. Severe CACTD results in neonatal or infantile sudden death. Herein, we reported six patients with CACTD diagnosed based on biochemical and molecular findings from 5 unrelated families in Guangdong from 2016 to 2017. Among them, five patients presented with hypotonia, nonketotic hypoglycemia, and arrhythmia 2 days after birth, while the other patient presented with respiratory distress, hypotonia, and arrhythmia. Five of the patients died in the neonatal period. Blood acylcarnitine concentrations determination from dried blood spots (DBS) were measured by tandem mass spectrometry (MS/MS). The SLC25A20 and CPT2 gene sequences were analyzed by direct Sanger sequencing. SLC25A20 gene analysis revealed a c.199-10T>G (IVS2-10T>G) homozygous variants in four unrelated patients and a novel mutation c.199-10T>G/c.719-8_c.719-1dupCCCACAG compound heterozygous variants in twins. This report describes the clinical characteristics, biochemical findings and molecular analysis of SLC25A20 gene of patients with CACTD in Guangdong. And our results show that the c.199-10T>G is likely the most common variant of CACTD in Guangdong population as it accounts for 83% (10/12) of the observed mutant alleles. Individuals with the c.199-10T>G genotype had a severe CACTD phenotype.

Carnitine-acylcarnitine translocase deficiency with homozygous mutation of c.199-10T>G: a case report and literature review

Objective To investigate the clinical features of carnitine-acylcarnitine translocase deficiency (CACTD) with c.199-10T>G homozygous mutation and the characteristics of SLC25A20 gene mutation. Methods This study retrospectively analyzed the clinical data, biochemical and genetic features, treatment and outcome of a boy with CACTD with c.199-10T>G homozygous mutation, who admitted to Guangzhou Women and Children's Medical Center in September 2017. Pertinent articles were retrieved from China National Knowledge Infrastructure (CNKI), Wanfang Database, National Center for Biotechnology Information and PubMed from the establishment of these databases to April 2018 using key words including CACT, SLC25A20 and carnitine-acylcarnitine translocase. Clinical information of all affected cases in the retrieved publications was analyzed. Results (1) The full-term boy born vaginally at a local hospital was transferred to neonatal intensive care unit (NICU) of Guangzhou Women and Children's Medical Center at 2 days and 5 hours due to groaning, cyanosis and severe hypoglycemia (0.8 mmol/L) at 15 h after birth. His elder brother with similar symptoms died of unknown reason at 50 days of age. In this case, ammonemia, liver enzyme and creatine kinase were significantly elevated, amino acid analysis suggested liver damage, and high amounts of dicarboxylic aciduria, low free carnitine, markedly increased long-chain acylcarnitine and hypoketotic hypoglycemia were also observed. His electrocardiogram showed atrioventricular block and ventricular tachycardia. After a series of treatments, including repeated electrical cardioversion, lidocaine and amiodarone for arrhythmia, arginine for blood ammonia level reduction, formula supplement containing L-carnitine and medium-chain fatty acid, the patient whose conditions had significantly improved and was discharged at the request of his parents at 29 days old. Two weeks later, he was re-admitted due to diarrhea, and discharged two days later when he was 45 days old. He was lost to follow up since then. (2) A homozygous mutation of c.199-10T>G was detected in this boy in SLC25A20 gene, which was also carried by his parents. (3) Thirty-two publications in English were retrieved, involving 50 cases of CACTD and 100 sequenced alleles. A total of 40 mutations in SLC25A20 gene were found so far, and c.199-10T>G was the most common mutation with a frequency of 22/100. It was identified in 13 patients, including nine homozygous mutations and four compound heterozygous mutations. Symptoms presented within 72 h after birth (25 min-52 h) in all the 13 infants, such as hypoketotic hypoglycemia, hyperammonemia, elevated liver enzyme and creatine kinase, significantly decreased free carnitine level, markedly increased level of long-chain acylcarnitine, dicarboxylic aciduria, arrhythmia and cardiomyopathy. The mortality rate of CACTD was 11/12 (the outcome of one case was not reported). Conclusions c.199-10T>G is the most common SLC25A20 gene mutation reported in Asia population with severe phenotypes and poor outcomes. Early diagnosis and timely treatment of CACTD are crucial. Inborn metabolic diseases such as CACTD should be considered if unexplainable exacerbation of clinical signs in neonatal period, or sudden infant death occurs. Key words: Carnitine acyltransferases; Lipid Metabolism, Inborn Errors; Membrane transport proteins; Mutation