PHÂN TÍCH GEN SLC25A20 VÀ CPT2 TRONG CHẨN ĐOÁN KHIẾM KHUYẾT BETA OXI HOÁ CỦA AXÍT BÉO Ở TI THỂ

Bệnh lí thiếu hụt Carnitine/acylcarnitine transferase (CACT) và bệnh lí thiếu hụt Carnitine palmitoyltransferase II (CPT II) thuộc nhóm bệnh oxi hóa axit béo trong ti thể. CACT và CPT II là các bệnh lí rối loạn chuyển hóa bẩm sinh (RLCHBS) di truyền hiếm gặp – biến thể di truyền lặn nhiễm sắc thể thường do gen SLC25A20 (gen CACT) và gen CPT2 quy định. Đây là các bệnh lí nguy hiểm để lại các di chứng nặng nề và có thể tử vong. Tuy nhiên, CACT và CPT II có các đặc điểm lâm sàng và cận lâm sàng khá giống với các bệnh lí RLCH oxi hóa axit béo khác và không thể phân biệt về đặc điểm cận lâm sàng và lâm sàng giữa hai bệnh lí này do vậy cần có các phương pháp phù hợp, nhanh chóng để xác định biến thể trên gen SLC25A20 và CPT2 nhằm chẩn đoán và điều trị bệnh. Mục tiêu: Xác định 16 biến thể gen SLC25A20 và 35 biến thể gen CPT2; mô tả kiểu hình và kiểu gen của bệnh nhân mắc biến thể gen SLC25A20/CPT2. Phương pháp: Nghiên cứu ca bệnh gồm mô tả triệu chứng lâm sàng, xét nghiệm sinh hóa và phân tích gen dựa trên phương pháp xây dựng được. Kết quả: Bé gái 10 ngày tuổi, xuất hiện tím tái, ngừng tim, ngưng thở và tử vong. Kết quả xét nghiệm sinh hóa và xét nghiệm amio acid cho thấy hạ glucose máu, nhiễm toan chuyển hóa, tăng amoniac máu; tăng C4, C10, C12, C14, C14OH, C16, C16:1, C16:1OH, C18 và C18:1. Bệnh nhân được xác định có biến thể rs541208710, c.199-10T>G dạng đồng hợp tử trên gen SLC25A20 và 2 biến thể lành tính/ có thể lành tính với bệnh CPT II là rs2229291 (F352C) (c.1055T>G (p.Phe352Cys)) và rs1799821 (V368I) (c.1102G>A (p.Val368Ile)) do vậy chẩn đoán bệnh di truyền mắc phải là bệnh CACT. Kết luận: Xác định 16 biến thể gen SLC25A20 và 35 biến thể gen CPT2 cho phép chẩn đoán xác định bệnh lí RLCHBS di truyền CACT và CPT II.

Detection of Early Onset Carnitine Palmitoyltransferase II Deficiency by Newborn Screening. Should CPT II Deficiency Be a Primary Disease Target?

Early-onset carnitine palmitoyltransferase II deficiency (CPT II deficiency) (OMIM 600650) can result in severe outcomes, which are often fatal in the neonatal to infantile period. CPT II deficiency is a primary target in the Maritime Newborn Screening Program. We report a case of neonatal-onset CPT II deficiency identified through expanded newborn screening with tandem mass spectrometry. Identification through newborn screening led to early treatment interventions, avoidance of metabolic decompensation, and a better clinical outcome. Newborn screening for CPT II deficiency is highly sensitive and specific with no false positives identified. The only screen positive case detected identified a true positive case. This experience illustrates the importance of newborn screening for CPT II deficiency and demonstrates why reconsideration should be taken to add this disease as a primary newborn screening target.

Exercise, Nutrition, and Supplements in the Muscle Carnitine Palmitoyl-Transferase II Deficiency: New Theoretical Bases for Potential Applications

Carnitine palmitoyltransferase II (CPTII) deficiency is the most frequent inherited disorder regarding muscle fatty acid metabolism, resulting in a reduced mitochondrial long-chain fatty acid oxidation during endurance exercise. This condition leads to a clinical syndrome characterized by muscle fatigue and/or muscle pain with a variable annual frequency of severe rhabdomyolytic episodes. While since the CPTII deficiency discovery remarkable scientific advancements have been reached in genetic analysis, pathophysiology and diagnoses, the same cannot be said for the methods of treatments. The current recommendations remain those of following a carbohydrates-rich diet with a limited fats intake and reducing, even excluding, physical activity, without, however, taking into account the long-term consequences of this approach. Suggestions to use carnitine and medium chain triglycerides remain controversial; conversely, other potential dietary supplements able to sustain muscle metabolism and recovery from exercise have never been taken into consideration. The aim of this review is to clarify biochemical mechanisms related to nutrition and physiological aspects of muscle metabolism related to exercise in order to propose new theoretical bases of treatment which, if properly tested and validated by future trials, could be applied to improve the quality of life of these patients.

Carnitine Palmitoyltransferase-II Deficiency: Case Presentation and Review of the Literature

Carnitine palmitoyltransferase-II deficiency, an autosomal recessive disorder, is the most common cause of recurrent rhabdomyolysis in adults. Recognition and avoidance of triggers, such as heavy exercise and stress, is key in prevention of further episodes; however, even with preventative measures, many patients will continue to experience periodic symptoms, including rhabdomyolysis. Avoidance of renal failure, correction of electrolyte disturbances and halting further muscle breakdown are the goals of treatment. It is essential for clinicians to recognize the signs and symptoms of acute disease in CPT-II deficiency. We present a case of recurrent rhabdomyolysis requiring hospitalization in a patient with CPT-II deficiency and review the literature for common clinical manifestations, diagnostics, and treatment strategies.

Different Lipid Signature in Fibroblasts of Long-Chain Fatty Acid Oxidation Disorders

Long-chain fatty acid oxidation disorders (lc-FAOD) are a group of diseases affecting the degradation of long-chain fatty acids. In order to investigate the disease specific alterations of the cellular lipidome, we performed undirected lipidomics in fibroblasts from patients with carnitine palmitoyltransferase II, very long-chain acyl-CoA dehydrogenase, and long-chain 3-hydroxyacyl-CoA dehydrogenase. We demonstrate a deep remodeling of mitochondrial cardiolipins. The aberrant phosphatidylcholine/phosphatidylethanolamine ratio and the increased content of plasmalogens and of lysophospholipids support the theory of an inflammatory phenotype in lc-FAOD. Moreover, we describe increased ratios of sphingomyelin/ceramide and sphingomyelin/hexosylceramide in LCHAD deficiency which may contribute to the neuropathic phenotype of LCHADD/mitochondrial trifunctional protein deficiency.

Cardiolipin Stabilizes and Increases Catalytic Efficiency of Carnitine Palmitoyltransferase II and Its Variants S113L, P50H, and Y479F

Muscle carnitine palmitoyltransferase II (CPT II) deficiency is associated with various mutations in CPT2 gene. In the present study, the impact of the two CPT II variants P50H and Y479F were characterized in terms of stability and activity in vitro in comparison to wildtype (WT) and the well investigated variant S113L. While the initial enzyme activity of all variants showed wild-type-like behavior, the activity half-lives of the variants at different temperatures were severely reduced. This finding was validated by the investigation of thermostability of the enzymes using nano differential scanning fluorimetry (nanoDSF). Further, it was studied whether the protein stabilizing diphosphatidylglycerol cardiolipin (CL) has an effect on the variants. CL indeed had a positive effect on the stability. This effect was strongest for WT and least pronounced for variant P50H. Additionally, CL improved the catalytic efficiency for CPT II WT and the investigated variants by twofold when carnitine was the varied substrate due to a decrease in KM. However, there was no influence detected for the variation of substrate palmitoyl-CoA. The functional consequences of the stabilization by CL in vivo remain open.

Nutrition and Exercise in a Case of Carnitine Palmitoyl-Transferase II Deficiency

In the mild subtype of inherited carnitine palmitoyltransferase II (CPTII) deficiency, muscular mitochondrial fatty acid β-oxidation is impaired. In this condition, interventions involve daily dietary restriction of fats and increase of carbohydrates, whereas physical exercise is commonly contraindicated due to the risk of muscle pain and rhabdomyolysis. We present the case of a 14-year-old female with CPTII deficiency who underwent a 1-h session of unsupervised exercise training for 6 months, 3 days per week, including interval and resistance exercises, after diet assessment and correction. Before and after intervention, the resting metabolic rate (RMR) and respiratory quotient (RQ) were measured by indirect calorimetry, and a cardiopulmonary exercise test (CPET, 10 W/30 s to exhaustion) was performed. Interval training consisted of a 1 min run and a 5 min walk (for 15 min progressively increased to 30 min). During these efforts, the heart rate was maintained over 70% HR max corresponding to respiratory exchange ratio (RER) of 0.98. Resistance training included upper/lower split workouts (3 sets of 8 repetitions each, with 2 min rest between sets). Blood CK was checked before and 36 h after two training sessions chosen randomly without significant difference. After training, RMR increased (+8.1%) and RQ lowered into the physiological range (from 1.0 to 0.85). CPET highlighted an increase of peak power output (+16.7%), aerobic performance (VO2 peak, 8.3%) and anaerobic threshold (+5.7%), oxygen pulse (+4.5%) and a much longer isocapnic buffering duration (+335%). No muscle pain or rhabdomyolysis was reported. Results from our study highlight that training based on short-duration high-intensity exercise improves overall metabolism and aerobic fitness, thus being feasible, at least in a case of CPTII deficiency.

Cause of recurrent rhabdomyolysis, carnitine palmitoyltransferase II deficiency and novel pathogenic mutation

Carnitine palmitoyltransferase II (CPT II) deficiency is an autosomal inherited metabolic disorder in which the β-oxidation of the long chain fatty acids is defective. The clinical presentation may be in various forms; it presents itself in the severe form during neonatal and infantile periods and as the less severe myopathic form in the school age and adolescence. While the severity of the rhabdomyolysis attacks varies, occasionally the clinical course may be complicated with acute renal failure. Acylcarnitine analysis may help in the diagnosis of CPT II, but its normality does not indicate the absence of the disease. If there is strong suspicion, genetic analysis should be performed on the cases. In this article, we present a 15-year-old male patient who had two rhabdomyolysis attacks triggered by infection and starvation. Acylcarnitine analysis of the case was normal, CPT II deficiency was considered when the history was evaluated, and CPT II gene c.137A>G (p.Gln46Arg) homozygous novel pathogenic mutation was detected. CPT II deficiency is one of the most common causes of metabolic rhabdomyolysis in patients with recurrent episodes of rhabdomyolysis.

Schizophrenic Psychosis Symptoms in a Background of Mild-To-Moderate Carnitine Palmitoyltransferase II Deficiency: A Case Report

Schizophrenia is a multifaceted mental illness characterized by cognitive and neurobehavioral abnormalities. Carnitine palmitoyltransferase II (CPT II) deficiency is a metabolic disorder resulting in impaired transport of long-chain fatty acids from the cytosol to the mitochondrial inner membrane, where fatty acid β-oxidation takes place. Here, we present an interesting clinical case of an adolescent male that presented with psychosis and a history of mild-to-moderate CPT II deficiency. To identify germline genetic variation that may contribute to the phenotypes observed, we performed whole-exome sequencing on DNA from the proband, unaffected fraternal twin, and biological parents. The proband was identified to be homozygous for the p.Val368Ile and heterozygous for the p.Met647Val variant in CPT2. Each of these variants are benign on their own; however, their combined effect is unclear. Further, variation was identified in the dopamine β-hydroxylase (DBH) gene (c.339+2T>C), which may contribute to decreased activity of DBH; however, based on the patient’s presentation, severe DBH deficiency is unlikely. In conclusion, the variants identified in this study do not clearly explain the observed patient phenotypes, indicating that the complex phenotypes are likely caused by an interplay of genetic and environmental factors that warrant further investigation.