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Abstract Background Primary carnitine deficiency (PCD) is a rare autosomal recessive fatty acid oxidation disorder caused by variants in SLC22A5, with its prevalence and SLC22A5 gene mutation spectrum varying across races and regions. This study aimed to systematically analyze the incidence of PCD in China and delineate regional differences in the prevalence of PCD and SLC22A5 gene variants. Methods PubMed, Embase, Web of Science, and Chinese databases were searched up to November 2023. Following quality assessment and data extraction, a meta-analysis was performed on screening results for PCD among Chinese newborns. Results After reviewing 1,889 articles, 22 studies involving 9,958,380 newborns and 476 PCD cases were included. Of the 476 patients with PCD, 469 underwent genetic diagnosis, revealing 890 variants of 934 alleles of SLC22A5, among which 107 different variants were detected. The meta-analysis showed that the prevalence of PCD in China was 0.05‰ [95%CI, (0.04‰, 0.06‰)] or 1/20 000 [95%CI, (1/16 667, 1/25 000)]. Subgroup analyses revealed a higher incidence in southern China [0.07‰, 95%CI, (0.05‰, 0.08‰)] than in northern China [0.02‰, 95%CI, (0.02‰, 0.03‰)] (P G, c.51C > G, c.760C > T, c.338G > A, and c.428C > T were 45% [95%CI, (34%, 59%)], 26% [95%CI, (22%, 31%)], 14% [95%CI, (10%, 20%)], 6% [95%CI, (4%, 8%)], and 5% [95%CI, (4%, 8%)], respectively. Among the subgroup analyses, the variant frequency of c.1400C > G in southern China [39%, 95%CI, (29%, 53%)] was significantly lower than that in northern China [79‰, 95%CI, (47‰, 135‰)] (P

Background: Primary carnitine deficiency (PCD) is a rare autosomal recessive fatty acid oxidation disorder caused by variants in SLC22A5, with its prevalence and SLC22A5 gene mutation spectrum varying across races and regions. This study aimed to systematically analyze the incidence of PCD in China and delineate regional differences in the prevalence of PCD and SLC22A5 gene variants. Methods: PubMed, Embase, Web of Science, and Chinese databases were searched up to November 2023. Following quality assessment and data extraction, a meta-analysis was performed on screening results for PCD among Chinese newborns. Results: After reviewing 1,889 articles, 22 studies involving 9,958,380 newborns and 476 PCD cases were included. Of the 476 patients with PCD, 469 underwent genetic diagnosis, revealing 890 variants of 934 alleles of SLC22A5, among which 107 different variants were detected. The meta-analysis showed that the prevalence of PCD in China was 0.05‰ [95%CI, (0.04‰, 0.06‰)] or 1/20 000 [95%CI, (1/16 667, 1/25 000)]. Subgroup analyses revealed a higher incidence in southern China [0.07‰, 95%CI, (0.05‰, 0.08‰)] than in northern China [0.02‰, 95%CI, (0.02‰, 0.03‰)] (P < 0.001). Furthermore, the result of the meta-analysis showed that the frequency of the variant with c.1400C > G, c.51C > G, c.760C > T, c.338G > A, and c.428C > T were 45% [95%CI, (34%, 59%)], 26% [95%CI, (22%, 31%)], 14% [95%CI, (10%, 20%)], 6% [95%CI, (4%, 8%)], and 5% [95%CI, (4%, 8%)], respectively. Among the subgroup analyses, the variant frequency of c.1400C > G in southern China [39%, 95%CI, (29%, 53%)] was significantly lower than that in northern China [79‰, 95%CI, (47‰, 135‰)] (P < 0.05). Conclusions: This study systematically analyzed PCD prevalence and identified common SLC22A5 gene variants in the Chinese population. The findings provide valuable epidemiological insights and guidance for future PCD screening effects in newborns. [ABSTRACT FROM AUTHOR]

Abstract Background Primary carnitine deficiency (PCD) denotes low carnitine levels with an autosomal recessive pattern of inheritance. Cardiomyopathy is the most common cardiac symptom in patients with PCD, and early diagnosis can prevent complications. Next-generation sequencing can identify genetic variants attributable to PCD efficiently. Objective We aimed to detect the genetic cause of the early manifestations of hypertrophic cardiomyopathy and metabolic abnormalities in an Iranian family. Methods We herein describe an 8-year-old boy with symptoms of weakness and lethargy diagnosed with PCD through clinical evaluations, lab tests, echocardiography, and cardiac magnetic resonance imaging. The candidate variant was confirmed through whole-exome sequencing, polymerase chain reaction, and direct Sanger sequencing. The binding efficacy of normal and mutant protein-ligand complexes were evaluated via structural modeling and docking studies. Results Clinical evaluations, echocardiography, and cardiac magnetic resonance imaging findings revealed hypertrophic cardiomyopathy as a clinical presentation of PCD. Whole-exome sequencing identified a new homozygous variant, SLC22A5 (NM_003060.4), c.821G > A: p.Trp274Ter, associated with carnitine transport. Docking analysis highlighted the impact of the variant on carnitine transport, further indicating its potential role in PCD development. Conclusions The c.821G > A: p.Trp274Ter variant in SLC22A5 potentially acted as a pathogenic factor by reducing the binding affinity of organic carnitine transporter type 2 proteins for carnitine. So, the c.821G > A variant may be associated with carnitine deficiency, metabolic abnormalities, and cardiomyopathic characteristics.

Primary carnitine deficiency (PCD) caused by pathogenic variants in the solute carrier family 22 member 5 (SLC22A5) gene is a rare autosomal recessive disease that results in defective fatty acid oxidation. PCD can be detected through tandem mass spectrometry (MS/MS), but transplacental transport of free carnitine from mothers may cause false negatives or positives during newborn screening (NBS). This study aimed to analyze the genetic characteristics of SLC22A5 and estimate the prevalence of PCD in the Chinese population, providing useful information for NBS and genetic counseling. We manually curated SLC22A5 pathogenic or likely pathogenic (P/LP) variants according to the American College of Medical Genetics and Genomics (ACMG) guidelines and identified 128 P/LP variants. Based on the China Neonatal Genomes Project (CNGP), the estimated PCD prevalence was 1:17,456, which was higher than that in other populations. The genotype-phenotype association analysis showed that patients carrying homozygous c.760C>T and c.844C>Tweremore likely to present cardiomyopathy, whereas those carrying homozygous c.1400C>G were more likely to be asymptomatic (all p-values < 0.05). We found that there was no significant difference in initial C0 concentrations between patients and carriers, but there was a significant difference in the second-tier screening of C0 concentration between them (p-value < 0.05). We established a cost-effective variant panel containing 10 high-frequency sites and developed a screening algorithm incorporating gene panels with MS/MS, which could rescue one more patient who was undetected from MS/MS. In conclusion, the prevalence of PCD in the Chinese population is relatively high. The combination of conventional NBS with genetic sequencing is suggested for early diagnosis of PCD. [ABSTRACT FROM AUTHOR]

Background: Primary carnitine deficiency (PCD) is an autosomal recessive disease caused by mutations in the SLC22A5 gene, which encodes the organic cation transporter 2 (OCTN2). Patients with PCD may be at risk of skeletal or cardiac myopathy, metabolic decompensation, and even sudden death. This study aimed to analyze the biochemical, clinical, and genetic characteristics of PCD patients identified by newborn screening (NBS) in Shanghai. Methods: Dried blood spot (DBS) samples of newborns were analyzed through tandem mass spectrometry (MS/MS) from January 2003 to December 2021. Newborns with low free carnitine (C0) levels were recalled. Mutation in the SLC22A5 gene was analyzed on suspected positive newborns with low C0 levels after recall. Results: 1,247,274 newborns were screened by MS/MS and 40 newborns were diagnosed with PCD, therefore the incidence of PCD in Shanghai was approximately 1:31,200. The mean C0 level in newborns with PCD was 5.37 ± 1.79 µmol/L before treatment and increased to 24.45 ± 10.87 µmol/L after treatment with L-carnitine. Twenty-three different variants were identified in the SLC22A5 gene, including 8 novel variants, of which c.51C>G (p.F17L) was the most frequent (27.27%, 18/66), followed by c.1400C>G (p.S467C) (25.76%, 17/66). Almost all the screened PCD patients were asymptomatic. Conclusion: NBS via MS/MS was a quick and efficient method for the early diagnosis of PCD. The incidence of PCD in Shanghai was 1:31,200. Eight novel variants were identified, which greatly expanded the variant spectrum of SLC22A5. MS/MS combined with genetic testing could effectively improve the diagnostic accuracy of PCD. [ABSTRACT FROM AUTHOR]

Simple Summary: Kidney cancer diagnoses make up over 2% of newly identified cancers each year. SoLute Carrier 22 (SLC22) genes are expressed in normal functioning kidneys and are responsible for transport of myriad metabolites, xenobiotics, antioxidants and other small molecules, but their role in kidney cancer is not well understood. We assessed the relationship between the expression of SLC22 genes and survival in patients with kidney cancer and found expression patterns of multiple SLC22 genes to be associated with overall survival as well as with disease progression. We sought to interpret this data in the context of physiological information from previous studies by us and others. Furthermore, network analysis indicated the importance of SLC22 genes and identified additional genes that might be therapeutic targets. (1) Background: Many transporters of the SLC22 family (e.g., OAT1, OAT3, OCT2, URAT1, and OCTN2) are highly expressed in the kidney. They transport drugs, metabolites, signaling molecules, antioxidants, nutrients, and gut microbiome products. According to the Remote Sensing and Signaling Theory, SLC22 transporters play a critical role in small molecule communication between organelles, cells and organs as well as between the body and the gut microbiome. This raises the question about the potential role of SLC22 transporters in cancer biology and treatment. (2) Results: In two renal cell carcinoma RNA-seq datasets found in TCGA, KIRC and KIRP, there were multiple differentially expressed (DE) SLC22 transporter genes compared to normal kidney. These included SLC22A6, SLC22A7, SLC22A8, SLC22A12, and SLC22A13. The patients with disease had an association between overall survival and expression for most of these DE genes. In KIRC, the stratification of patient data by pathological tumor characteristics revealed the importance of SLC22A2, SLC22A6, and SLC22A12 in disease progression. Interaction networks combining the SLC22 with ADME genes supported the centrality of SLC22 transporters and other transporters (ABCG2, SLC47A1) in disease progression. (3) Implications: The fact that many of these genes are uric acid transporters is interesting because altered uric acid levels have been associated with kidney cancer. Moreover, these genes play key roles in processing metabolites and chemotherapeutic compounds, thus making them potential therapeutic targets. Finally, our analyses raise the possibility that current approaches may undertreat certain kidney cancer patients with low SLC22 expression and only localized disease while possibly overtreating more advanced disease in patients with higher SLC22 expression. Clinical studies are needed to investigate these possibilities. [ABSTRACT FROM AUTHOR]

Competing Interests: All the authors declare no conflict of interest.

Abstract Background Primary carnitine deficiency due to mutations in the SLC22A5 gene is a rare but well-treatable metabolic disorder that puts patients at risk for metabolic decompensations, skeletal and cardiac myopathy and sudden cardiac death. Results We report on a 7-year-old boy diagnosed with primary carnitine deficiency 2 years after successful heart transplantation thanks his younger sister’s having been identified via expanded newborn screening during a pilot study evaluating an extension of the German newborn screening panel. Conclusion As L-carnitine supplementation can prevent and mostly reverse clinical symptoms of primary carnitine deficiency, all patients with cardiomyopathy should be investigated for primary carnitine deficiency even if newborn screening results were unremarkable.

Abstract Background Maternofetal carnitine transport through the placenta is the main route of fetal carnitine uptake. Decreased free carnitine levels discovered by newborn screening has identified many asymptomatic adult women with systemic primary carnitine deficiency (PCD). Here, we presented amplitude integrated electroencephalogram (aEEG) and magnetic resonance imaging (MRI) findings from a neonate with epilepsy whose mother was carnitine deficient. Case presentation A one-day-old female newborn was admitted after experiencing seizures for half a day; status epilepticus was found on the continuous normal voltage background pattern with immature sleep-wake cycling during aEEG monitoring. On T1-weighted, T2-weighted, FLAIR, and DWI head MRI, there were various degrees of hyperintense signals and diffusion restrictions in the deep white matter of the right hemisphere. Tandem mass spectrometry discovered carnitine deficiency on the second day, which elevated to normal by the 9th day before L-carnitine supplementation was started. The patient was treated with phenobarbital after admission. No further seizures were noted by day 5. It was confirmed that the patient’s mother had a low level of serum-free carnitine. Gene analyses revealed that the newborn had heterozygote mutations on c.1400C > G of the SLC22A5 gene, and her mother had homozygous mutations on c.1400C > G. The patient had a good outcome at the 8-month follow up. Conclusions Maternal carnitine deficiency that occurs during the perinatal period may manifest as secondary epilepsy with cerebral injury in neonates. The short-term neurodevelopmental outcomes were good. Early diagnosis of asymptomatic PCD in female patients can provide guidance for future pregnancies.

Primary carnitine deficiency (PCD) is an autosomal recessive disorder that could result in sudden death. It is caused by a defect in the carnitine transporter encoded by SLC22A5 (Solute Carrier Family 22 Member 5, MIM:603377). Currently, a number of variants in SLC22A5 have been identified, however, the PCD prevalence and its variants in Ningbo area are unclear. In this study, we screened 265,524 newborns by using tandem mass spectrometry. Variants in SLC22A5 were further detected by next-generation sequencing in individuals with abnormal free carnitine levels (C0). We identified 53 newborns with abnormal C0 levels and 26 with variants in SLC22A5. Among them, 16 with compound heterozygous or homozygous variants in SLC22A5 were diagnosed with PCD, suggesting the PCD birth prevalence in Ningbo city was 1/16,595. Moreover, the C0 level was significantly (P = 0.013) higher in PCD patients than in those with one variant. Besides, the c.1400C > G (p. S467C) and c.51C > G (p. F17L) variants were the most frequent and six novel variants are all predicted to be damaging. This study reports the largest PCD patients in Ningbo area by newborn screening and expands the variant spectrum of SLC22A5. Our findings demonstrate the clinical value of combining NBS program results with DNA analysis for the diagnosis of PCD.

Primary carnitine deficiency (PCD) is an autosomal recessive disorder that could result in sudden death. It is caused by a defect in the carnitine transporter encoded by SLC22A5 (Solute Carrier Family 22 Member 5, MIM:603377). Currently, a number of variants in SLC22A5 have been identified, however, the PCD prevalence and its variants in Ningbo area are unclear. In this study, we screened 265,524 newborns by using tandem mass spectrometry. Variants in SLC22A5 were further detected by next-generation sequencing in individuals with abnormal free carnitine levels (C0). We identified 53 newborns with abnormal C0 levels and 26 with variants in SLC22A5. Among them, 16 with compound heterozygous or homozygous variants in SLC22A5 were diagnosed with PCD, suggesting the PCD birth prevalence in Ningbo city was 1/16,595. Moreover, the C0 level was significantly (P = 0.013) higher in PCD patients than in those with one variant. Besides, the c.1400C > G (p. S467C) and c.51C > G (p. F17L) variants were the most frequent and six novel variants are all predicted to be damaging. This study reports the largest PCD patients in Ningbo area by newborn screening and expands the variant spectrum of SLC22A5. Our findings demonstrate the clinical value of combining NBS program results with DNA analysis for the diagnosis of PCD. [ABSTRACT FROM AUTHOR]

Gliomas are the most common primary malignant brain tumor in adults, but current treatment for glioblastoma multiforme (GBM) is insufficient. Even though glucose is the primary energetic substrate of glioma cells, they are capable of using fatty acids to generate energy. Fatty acid oxidation (FAO) in mitochondria requires L‐carnitine for the formation of acylcarnitines by carnitine palmitoylotransferase 1 (CPT1) and further transport of acyl carnitine esters to mitochondrial matrix. Carnitine can be delivered to the cell by an organic cation/carnitine transporter—SLC22A5/OCTN2. In this study, we show that SLC22A5 is up‐regulated in glioma cells and that they vary in the amount of SLC22A5 in the plasma membrane. Research on glioma cells (lines U87MG, LN229, T98G) with various expression levels of SLC22A5 demonstrated a correlation between the FAO rate, the level of the transporter, and the carnitine transport. Inhibition of carnitine transport by chemotherapeutics, such as vinorelbine and vincristine, led to inhibition of FAO, which was further intensified by etomoxir—a CPT1 inhibitor. This led to reduced viability and increased apoptosis in glioma cells. Modulation of SLC22A5 level by either silencing or up‐regulation of SLC22A5 also affected glioma cell survival in a FAO‐dependent way. These observations suggest that the survival of glioma cells is heavily reliant on both FAO and SLC22A5 activity, as well as that CPT1 and SLC22A5 might be possible drug targets. [ABSTRACT FROM AUTHOR]

• The incidence of PCD in children in the Quanzhou area was 1:10126. • Eighteen SLC22A5 variants were found, with five novel ones. • The most prevalent variant in neonatal and maternal patients was c.760C > T (p.R254*) • Newborn screening is effective in identification and timely treatment of PCD. Primary carnitine deficiency (PCD) is an autosomal recessive disease caused by functional defects in the carnitine transporter OCTN2 due to mutations in SLC22A5. Here, we aimed to understand the incidence, clinical, biochemical, and molecular features of PCD in Quanzhou, China. Newborn screening (NBS) was performed through tandem mass spectrometry (MS/MS) to detect genetic metabolic diseases. Next-generation sequencing was used to detect SLC22A5 mutations in patients with suspected PCD. From 364,545 newborns screened, 36 were diagnosed with PCD, in addition to five mothers. The incidence of PCD in children in the Quanzhou area was 1:10126. Eighteen SLC22A5 variants were found, with five novel ones. The most prevalent variant in neonatal and maternal patients was c.760C > T (p.R254*). Twenty-five neonatal patients received L-carnitine supplementation; however, one patient discontinued treatment and sudden death occurred. One sibling presented repeated fatigue, hypoglycemia, and coma, but the symptoms disappeared after treatment. Two mothers with PCD claimed to feel weak and easily fatigued. The incidence of PCD is relatively high in the Quanzhou area. Five novel variants were found, broadening the mutation spectrum of SLC22A5. NBS is effective in identifying PCD, and sudden death may be prevented with timely treatment. [ABSTRACT FROM AUTHOR]

• This study reported the largest series of patients with PCD detected by NBS. • The incidence of newborns with PCD in Zhejiang province was 1:30,182. • Thirty-seven distinct variants were identified in SLC22A5 , of which 10 were novel. • c.1400C>G (p.S467C) was the most common variant in newborns and mothers with PCD. • c.760C>T (p.R254*) was rarely detected in the maternal PCD patients. Testing for primary carnitine deficiency (PCD) has been implemented in many newborn screening (NBS) programs, but few large-scale studies on NBS for PCD have been reported in China. This study aimed to assess the incidence and biochemical, clinical, and genetic characteristics of PCD discovered by NBS. Dried blood spots from newborns were analyzed by tandem mass spectrometry (MS/MS) and suspected positive patients were further tested using molecular genetic analysis. Infants who carried two variants in SLC22A5 or those with extremely low free carnitine levels during recall were referred for follow-up and treatment. Over 3.4 million newborns were screened and 113 newborns were diagnosed with PCD, yielding a positive predictive value of 1.93%. In addition, 63 mothers with PCD were identified. The incidence of PCD in newborns and mothers in Zhejiang was 1:30,182 and 1:54,137, respectively. Thirty-seven distinct variants were identified in SLC22A5 of which 10 were novel. c.1400C > G (p.S467C) was the most prevalent variant in both newborns and mothers with PCD, while c.760C > T (p.R254*), which is reportedly common in other Chinese regions, was rarely detected in maternal PCD patients. This study reports the largest series of patients with PCD detected by NBS and identifies 10 novel variants, expanding the variant spectrum of SLC22A5. [ABSTRACT FROM AUTHOR]

Background: Primary carnitine deficiency due to mutations in the SLC22A5 gene is a rare but well-treatable metabolic disorder that puts patients at risk for metabolic decompensations, skeletal and cardiac myopathy and sudden cardiac death.Results: We report on a 7-year-old boy diagnosed with primary carnitine deficiency 2 years after successful heart transplantation thanks his younger sister's having been identified via expanded newborn screening during a pilot study evaluating an extension of the German newborn screening panel.Conclusion: As L-carnitine supplementation can prevent and mostly reverse clinical symptoms of primary carnitine deficiency, all patients with cardiomyopathy should be investigated for primary carnitine deficiency even if newborn screening results were unremarkable. [ABSTRACT FROM AUTHOR]

Carnitine Uptake Defect (CUD) is an autosomal recessive disorder due to mutations in the SLC22A5 gene. Classically patients present in infancy with profound muscle weakness and cardiomyopathy with characteristic EKG findings. Later presentations include recurrent hypoketotic hypoglycemia, proximal limb girdle myopathy, and/or recurrent muscle pain. Newborn screening detects most of these clinical variants but in addition has identified maternal CUD often in asymptomatic women. We describe a family ascertained through 3 newborn screening (NBS) positive infants found to be unaffected themselves but in whom the mothers (sisters) were affected. There were also two affected children born to an affected male and his heterozygous wife who were false negatives on NBS but had increased fractional excretion of free carnitine in the urine. Analysis on a Next Generation Sequencing panel specifically designed to fully cover newborn screening disease targets showed a homozygous change in the five probands (SLC22A5 ; NM_003060:c.-149G > A; p.?). The mutation segregates with the CUD within the family. It is in the 5′ UTR and has a frequency within the gnomAd database of 0.001198. Plasma carnitine was decreased and fractional excretion of free carnitine was increased in all affected individuals. Functional carnitine uptake studies in cultured skin fibroblasts of one proband showed carnitine uptake at the 5 μM concentration to be 6% of controls. Relative expression of OCTN2 mRNA to beta-actin mRNA by qRT-PCR was increased in a proband relative to controls by a factor of 465-fold. Western blotting revealed a 120 kDa protein band, as well as a weaker 240 kDa band in the proband, the significance of which is unknown at this time. [ABSTRACT FROM AUTHOR]

Objectives: Rheumatoid arthritis (RA), the most common autoimmune disease, is thought to be a complex disease in which a combination of risk alleles from different susceptibility genes predisposes to development of the disease, following exposure to as yet unknown environmental factors. An important component of the carnitine system is the plasma membrane carnitine transporters, also called organic cation transporters, i.e. OCTN1 and OCTN2 encoded by the SLC22A4 and SLC22A5 genes, respectively. The aim of this study was to investigate the association between SLC22A5 polymorphism and RA. Material and methods: The study was carried out on 404 patients diagnosed with RA according to the criteria of the American College of Rheumatology and 560 healthy subjects. The single nucleotide polymorphism (SNP) within the SLC22A5 gene - 207C>G (rs 2631367) was genotyped using pre-validated TaqMan genotyping assays. Results: The distribution of SLC22A5 genotypes and alleles in RA patients did not differ significantly from that in healthy controls. Moreover, there were no significant associations between SLC22A5 genotypes and age at time of disease diagnosis, rheumatoid factor, erosive disease and response to treatment with methotrexate. Extra-articular manifestations were diagnosed in 16.7% of SLC22A5 GG homozygous patients, in 9.4% with the GC genotype and in 7.2% of homozygous CC patients. The frequency of extra-articular manifestations was two-fold greater in homozygous GG patients as compared with carriers of the C allele (GG vs. GC + CC), OR = 2.06 (95% CI: 1.11-3.85, p = 0.022). Conclusions: The results of the present study suggest that the SLC22A5 polymorphism may be associated with the development of extra-articular manifestations of RA but the distribution of SLC22A5 genotypes and alleles in studied RA patients did not significantly differ from healthy subjects. [ABSTRACT FROM AUTHOR]

Primary carnitine deficiency (PCD) caused by pathogenic variants in the solute carrier family 22 member 5 ( SLC22A5 ) gene is a rare autosomal recessive disease that results in defective fatty acid oxidation. PCD can be detected through tandem mass spectrometry (MS/MS), but transplacental transport of free carnitine from mothers may cause false negatives or positives during newborn screening (NBS). This study aimed to analyze the genetic characteristics of SLC22A5 and estimate the prevalence of PCD in the Chinese population, providing useful information for NBS and genetic counseling. We manually curated SLC22A5 pathogenic or likely pathogenic (P/LP) variants according to the American College of Medical Genetics and Genomics (ACMG) guidelines and identified 128 P/LP variants. Based on the China Neonatal Genomes Project (CNGP), the estimated PCD prevalence was 1:17,456, which was higher than that in other populations. The genotype-phenotype association analysis showed that patients carrying homozygous c.760C>T and c.844C>T were more likely to present cardiomyopathy, whereas those carrying homozygous c.1400C>G were more likely to be asymptomatic (all p -values < 0.05). We found that there was no significant difference in initial C0 concentrations between patients and carriers, but there was a significant difference in the second-tier screening of C0 concentration between them ( p -value < 0.05). We established a cost-effective variant panel containing 10 high-frequency sites and developed a screening algorithm incorporating gene panels with MS/MS, which could rescue one more patient who was undetected from MS/MS. In conclusion, the prevalence of PCD in the Chinese population is relatively high. The combination of conventional NBS with genetic sequencing is suggested for early diagnosis of PCD., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Ji, Ge, Ni, Xu, Xiong, Yang, Hu, Cao, Lu, Wei, Kang, Zhuang, Zhou and Dong.)

Systemic primary carnitine deficiency (SPCD) is an autosomal recessive inborn error of fatty acid metabolism caused by a defect in the transporter responsible for moving carnitine across plasma membrane. The clinical features of SPCD vary widely based on the age of onset and organs involved. During infancy, patients might show episodes of hypoketotic hypoglycemia, hepatomegaly, elevated transaminases, and hyperammonemia. Skeletal myopathy, elevated creatine kinase, and cardiomyopathy are the main manifestations in children with SPCD, while in adults, the disorder is usually manifested as cardiomyopathy, arrhythmias, or fatigability. Here, we report a 5-year-old boy with SPCD that presented as dilated cardiomyopathy with atypical features, such as anemia, respiratory distress, and proximal muscle weakness. This report supports considering carnitine deficiency treatment in the work-up of unexplained pediatric dilated cardiomyopathy. [ABSTRACT FROM AUTHOR]

Multiple single nucleotide polymorphisms (SNPs) have been found to be highly correlated with colorectal cancer (CRC) risk. However, the variants identified thus far only explain a small part of the cases, suggesting the existence of many uncharacterised genetic determinants. In this study, using the multilevel ‘omics’ data provided in The Cancer Genome Atlas, we systematically performed expression quantitative trait locus (eQTL) analysis for CRC and identified nine SNPs with significant effects on mRNA expression (correlation |r| > 0.3 and FDR < 0.01). Then we conducted a two-stage case–control study consisting of 1528 cases and 1528 controls to examine the associations between candidate SNPs and CRC risk. We found that rs27437 in SLC22A5 was significantly correlated with CRC risk in both stages and the combined study (additive model, OR = 1.31, 95%CI = 1.17–1.47, P = 1.97 × 10 −6 ). eQTL analysis showed that rs27437 GG and GA genotypes were associated with lower expression of SLC22A5 compared with the AA genotype. Dual-luciferase reporter assays confirmed that the G risk allele could decrease the expression of luciferase. SLC22A5 was significantly decreased in CRC tumour tissues compared with adjacent normal tissues, indicating that SLC22A5 may play important roles in CRC, and rs27437 in SLC22A5 might serve as a novel biomarker for early detection and prevention of CRC. [ABSTRACT FROM AUTHOR]

Background: The prevalence of primary carnitine deficiency (PCD) in the Faroe Islands is the highest reported in the world (1:300). Serious symptoms related to PCD, e.g. sudden death, have previously only been associated to the c.95A > G/c.95A > G genotype in the Faroe Islands. We report and characterize novel mutations associated with PCD in the Faroese population and report and compare free carnitine levels and OCTN2 transport activities measured in fibroblasts from PCD patients with different genotypes. Methods: Genetic analyses were used to identify novel mutations, and carnitine uptake analyses in cultured skin fibroblasts from selected patients were used to examine residual OCTN2 transporter activities of the various genotypes. Results: Four different mutations, including the unpublished c.131C > T (p.A44V), the novel splice mutation c.825-52G > A and a novel risk-haplotype (RH) were identified in the Faroese population. The two most prevalent genotypes were c.95A > G/RH (1:600) and c.95A > G/c.95A > G (1:1300). Patients homozygous for the c.95A > G mutation had both the significantly (p G/c.95A > G genotype had the significantly lowest mean free carnitine level and residual OCTN2 transporter activity.

Primary carnitine deficiency is caused by a defect in the OCTN2 carnitine transporter encoded by the SLC22A5 gene. It can cause hypoketotic hypoglycemia or cardiomyopathy in children, and sudden death in children and adults. Fibroblasts from affected patients have reduced carnitine transport. We evaluated carnitine transport in fibroblasts from 358 subjects referred for possible carnitine deficiency. Carnitine transport was reduced to 20% or less of normal in fibroblasts of 140 out of 358 subjects. Sequencing of the 10 exons and flanking regions of the SLC22A5 gene in 95 out of 140 subjects identified causative variants in 84% of the alleles. The missense variants identified in our patients and others previously reported ( n = 92) were expressed in CHO cells. Carnitine transport was impaired by 73 out of 92 variants expressed. Prediction algorithms (Polyphen-2, SIFT) correctly predicted the functional effects of expressed variants in about 80% of cases. These results indicate that mutations in the coding region of the SLC22A5 gene cannot be identified in about 16% of the alleles causing primary carnitine deficiency. Prediction algorithms failed to determine the functional effects of amino acid substitutions in this transmembrane protein in about 20% of cases. Therefore, functional studies in fibroblasts remain the best strategy to confirm or exclude a diagnosis of primary carnitine deficiency. [ABSTRACT FROM AUTHOR]

Background: The objective of the study was to investigate clinical and gene mutation characteristics of primary carnitine deficiency (PCD) patients identified by newborn screening using tandem mass spectrometry (MS/MS). Methods: Tandem mass spectrometry (MS/MS) was applied to screen inherited metabolic disease and seven patients with PCD were diagnosed among 62,568 samples. The SLC22A5 gene was detected by using diagnosis panel of genetic and metabolic diseases based on Ion Torrent Semiconductor Sequencing Technology. Results: The initial free carnitine (C0) concentrations of the patients were 6.43 ± 1.36 μmol/L, and the recall screening concentrations were 5.59 ± 0.89 μmol/L. The patients were treated with oral carnitine, so the levels after treatment were 20.24 ± 3.88 µmol/L. All patients had two pathogenic mutation alleles. Conclusions: The combined application of MS/MS and a next generation sequencing panel could be used for the accurate diagnosis of PCD. The results of genetic diagnosis can guide the assisted reproductive treatment. The prognosis of PCD patients is good after early treatment. [ABSTRACT FROM AUTHOR]

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 B 0,+ . 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. [ABSTRACT FROM AUTHOR]

Background Organic cation transporters transfer solutes with a positive charge across the plasma membrane. The novel organic cation transporter 1 (OCTN1) and 2 (OCTN2) transport ergothioneine and carnitine, respectively. Mutations in the SLC22A5 gene encoding OCTN2 cause primary carnitine deficiency, a recessive disorders resulting in low carnitine levels and defective fatty acid oxidation. Variations in the SLC22A4 gene encoding OCTN1 are associated with rheumatoid arthritis and Crohn disease. Methods Here we evaluate the functional properties of the OCTN1 transporter using chimeric transporters constructed by fusing different portion of the OCTN1 and OCTN2 cDNAs. Their relative abundance and subcellular distribution was evaluated through western blot analysis and confocal microscopy. Results Substitutions of the C-terminal portion of OCTN1 with the correspondent residues of OCTN2 generated chimeric OCTN transporters more active than wild-type OCTN1 in transporting ergothioneine. Additional single amino acid substitutions introduced in chimeric OCTN transporters further increased ergothioneine transport activity. Kinetic analysis indicated that increased transport activity was due to an increased V max , with modest changes in K m toward ergothioneine. Conclusions Our results indicate that the OCTN1 transporter is tolerant to extensive amino acid substitutions. This is in sharp contrast to the OCTN2 carnitine transporter that has been selected for high functional activity through evolution, with almost all substitutions reducing carnitine transport activity. General significance The widespread tolerance of OCTN1 to amino acid substitutions suggests that the corresponding SLC22A4 gene may have derived from a recent duplication of the SLC22A5 gene and might not yet have a defined physiological role. [ABSTRACT FROM AUTHOR]

Primary carnitine deficiency is caused by the defective OCTN2 carnitine transporter encoded by the SLC22A5 gene. A lack of carnitine impairs fatty acid oxidation resulting in hypoketotic hypoglycemia, hepatic encephalopathy, skeletal and cardiac myopathy, and arrhythmia. This condition can be detected by finding low levels of free carnitine (C0) in neonatal screening. Mothers with primary carnitine deficiency can also be identified by low carnitine levels in their infant by newborn screening. Primary carnitine deficiency is rare (1:40,000–1:140,000 newborns) except in the Faroe Islands (1:300) due to a founder effect. A specific mutation (c.95A>G, p.N32S) is prevalent, but not unique, with three additional mutations (c.131C>T/p.A44V, a splice mutation c.825-52G>A, and a risk-haplotype) recently identified in the Faroese population. In the Faroe Islands, several adult patients suffered sudden death from primary carnitine deficiency leading to the implementation of a nationwide population screening (performed after 2 months of age) in addition to universal neonatal screening. While most affected infants can be identified at birth, some patients with primary carnitine deficiency might be missed by the current neonatal screening and could be better identified with a repeated test performed after 2 months of age.

Systemic primary carnitine deficiency (CDSP) is a rare autosomal recessive disorder caused by a defect in plasma membrane uptake of carnitine due to SLC22A5 gene mutations. A nine-mo-old boy presented with hypertrophic cardiomyopathy, massive hepatomegaly and jaundice. Metabolic testing revealed very low free carnitine levels. Genetic analysis using Sanger sequencing method revealed compound heterozygous mutations in SLC22A5 gene, c. 1354 G > A (p. Glu452Lys, previously reported) and c.231_234del (novel frame-shift). Oral carnitine supplementation resulted in improved clinical outcome with ejection fraction to 75 % and normalization of liver size and enzymes after 3 mo. [ABSTRACT FROM AUTHOR]

Systemic primary carnitine deficiency (CDSP) is caused by mutations in SLC22A5 gene, which encodes organic cation transporter 2(OCTN2). CDSP leads to skeletal or cardiac myopathy and hepatic encephalopathy. The present study aimed to identify SLC22A5 gene mutations and analyze the potential relationship between genotype and clinical symptoms in 20 Chinese patients with CDSP. The complete coding region of the SLC22A5 gene including intron-exon boundaries were amplified and sequenced in all patients. Eighteen different mutations were found; of which, nine were novel. The mutations clustering in exons 1 and 4 accounted for 66.7% of all mutant alleles (26/39). The c.760C>T (p. R254X) was the most frequent mutation (25.6%, 10/39), suggesting it as an ethnic founder mutation. The relationship between genotype and phenotype was investigated in patients carrying the R254X mutation. Homozygous patients with R254X were late-onset cases who presented with dilated cardiomyopathy and muscle weakness after 1 year of age. Compound heterozygous patients carrying R254X, combined with other missense mutations occurred in very specific positions, dramatically altered OCTN2 protein function. Based on the analysis of case studies, a clear relationship between free carnitine (C0) level in plasma and OCTN2 genotype was not found in the present work, however, the low plasma C0 level could not indicate disease severity or genotype. Further functional studies with a large sample size are required to understand the relationship between R254X mutation and CDSP. [ABSTRACT FROM AUTHOR]

Solute carrier family 22 member 5 ( SLC22A5) encodes a sodium-dependent ion transporter responsible for shuffling carnitine across the plasma membrane. This process provides energy for the heart, among other organs allowing beta-oxidation of fatty acids. Mutations in SLC22A5 result in primary carnitine deficiency ( PCD), a disorder that manifests with cardiac, skeletal, or metabolic symptoms. We hereby describe two novel mutations in SLC22A5 in two Lebanese families associated exclusively with a cardiac phenotype. The frequency of the cardiac, metabolic and skeletal symptoms in PCD patients remains undefined. All the reported eight PCD patients belonging to five different Lebanese families have an exclusive cardiac phenotype. Carnitine levels appear to be directly linked to the type and position of the mutation and the severity of the phenotypic presentation does not seem to be associated with serum carnitine levels. A comprehensive review of 61 literature-reported PCD cases revealed an exclusive cardiac manifestation frequency at 62.3% with a very low likelihood of simultaneous occurrence of cardiac and metabolic manifestation. [ABSTRACT FROM AUTHOR]