Analysis of blood carnitine profile and SLC22A5 gene variants in 17 neonates with Primary carnitine deficiency / 中华医学遗传学杂志

OBJECTIVE@#To analyze the blood free carnitine (C0) level and SLC22A5 gene variants in 17 neonates with Primary carnitine deficiency (PCD) and to determine its incidence in local area and explore the correlation between C0 level and genotype.@*METHODS@#148 043 newborns born in 9 counties (cities and districts) of Ningde city from September 2016 to June 2021 were selected as study subjects. Blood free carnitine and acyl carnitine of 148 043 neonates were analyzed. Variants of the SLC22A5 gene were screened in those with blood C0 < 10 µmol/L, or C0 between 10 ∼ 15 µmol/L. Correlation between the free carnitine level and genetic variants was analyzed.@*RESULTS@#In total 17 neonates were diagnosed with PCD, which yielded a prevalence of 1/8 707 in the region. Twelve variants of the SLC22A5 gene were identified, with the common ones including c.760C>T, c.1400C>G and c.51C>G. Compared with those carrying other variants of the gene, children carrying the c.760C>T variant had significantly lower C0 values (P < 0.01).@*CONCLUSION@#The prevalence of PCD is relatively high in Ningde area, and intervention measures should be taken to prevent and control the disease. The c. 760C>T variant is associated with lower level of C0, which can provide a clue for the diagnosis.

A prospective study of genetic screening of 2 060 neonates by high-throughput sequencing / 中华医学遗传学杂志

OBJECTIVE@#To assess the value of genetic screening by high-throughput sequencing (HTS) for the early diagnosis of neonatal diseases.@*METHODS@#A total of 2 060 neonates born at Ningbo Women and Children's Hospital from March to September 2021 were selected as the study subjects. All neonates had undergone conventional tandem mass spectrometry metabolite analysis and fluorescent immunoassay analysis. HTS was carried out to detect the definite pathogenic variant sites with high-frequency of 135 disease-related genes. Candidate variants were verified by Sanger sequencing or multiplex ligation-dependent probe amplification (MLPA).@*RESULTS@#Among the 2 060 newborns, 31 were diagnosed with genetic diseases, 557 were found to be carriers, and 1 472 were negative. Among the 31 neonates, 5 had G6PD, 19 had hereditary non-syndromic deafness due to variants of GJB2, GJB3 and MT-RNR1 genes, 2 had PAH gene variants, 1 had GAA gene variants, 1 had SMN1 gene variants, 2 had MTTL1 gene variants, and 1 had GH1 gene variants. Clinically, 1 child had Spinal muscular atrophy (SMA), 1 had Glycogen storage disease II, 2 had congenital deafness, and 5 had G6PD deficiency. One mother was diagnosed with SMA. No patient was detected by conventional tandem mass spectrometry. Conventional fluorescence immunoassay had revealed 5 cases of G6PD deficiency (all positive by genetic screening) and 2 cases of hypothyroidism (identified as carriers). The most common variants identified in this region have involved DUOX2 (3.93%), ATP7B (2.48%), SLC26A4 (2.38%), GJB2 (2.33%), PAH (2.09%) and SLC22A5 genes (2.09%).@*CONCLUSION@#Neonatal genetic screening has a wide range of detection and high detection rate, which can significantly improve the efficacy of newborn screening when combined with conventional screening and facilitate secondary prevention for the affected children, diagnosis of family members and genetic counseling for the carriers.

Analysis of metabolic profile and genetic variants for newborns with primary carnitine deficiency from Guangxi / 中华医学遗传学杂志

OBJECTIVE@#To analyze the metabolic profile and genetic variants for newborns with primary carnitine deficiency (PCD) from Guangxi, China.@*METHODS@#From January 2014 to December 2019, 400 575 newborns from the jurisdiction of Guangxi Zhuang Autonomous Region Newborn Screening Center were subjected to tandem mass spectrometry (MS/MS) analysis. Newborns with positive results for PCD and their mothers were recalled for retesting. Those who were still positive were subjected to sequencing of the SLC22A5 gene.@*RESULTS@#Twenty-two newborns and 9 mothers were diagnosed with PCD, which gave a prevalence rate of 1/18 208. Sequencing of 18 newborns and 4 mothers have identified 14 types of SLC22A5 gene variants, with the common ones including c.51C>G (10/44, 22.7%), c.1195C>T (9/44, 20.5%) and c.1400C>G (7/44, 15.9%), The c.517delC(p.L173Cfs*3) and c.1031C>T(p.T344I) were unreported previously and predicted to be pathogenic (PVS1+PM2_supporting+PM3+PP4) and likely pathogenic (PM1+PM2_supporting+PM3+PP3+PP4) based on the American College of Medical Genetics and Genomics standards and guidelines.@*CONCLUSION@#c.51C>G, c.1195C>T and c.1400C>G are the most common variants underlying PCD in Guangxi.

Biochemical and genetic characteristics of 40 neonates with carnitine deficiency / 中南大学学报(医学版)

OBJECTIVES@#Primary carnitine deficiency (PCD) is a rare fatty acid metabolism disorder that can cause neonatal death. This study aims to analyze carnitine levels and detect SLC22A5 gene in newborns with carnitine deficiency, to provide a basis for early diagnosis of PCD, and to explore the relationship between carnitine in blood and SLC22A5 genotype.@*METHODS@#A total of 40 neonates with low free carnitine (C0G (p.Y251C), c.495 C>A (p.R165E), and c.1298T>C (p.M433T). We found 14 PCD patients including 2 homozygous mutations and 12 heterozygous mutations, 14 with 1 mutation, and 12 with no mutation among 40 children. The C0 concentration of children with SLC22A5 gene homozygous or complex heterozygous mutations was (4.95±1.62) μmol/L in the initial screening, and (3.90±1.33) μmol/L in the second screening. The C0 concentration of children with no mutation was (7.04±2.05) μmol/L in the initial screening, and (8.02±2.87) μmol/L in the second screening. There were significant differences between children with homozygous or compound heterozygous mutations and with no mutation in C0 concentration of the initial and the second screening (both @*CONCLUSIONS@#There are 5 new mutations which enriched the mutation spectrum of SLC22A5 gene. C0<5 μmol/L is highly correlated with SLC22A5 gene homozygous or compound heterozygous mutations. Children with truncated mutation may have lower C0 concentration than that with untruncated mutation in the initial screening.

SLC22A5 gene mutation analysis and prenatal diagnosis for a family with primary carnitine deficiency / 中华医学遗传学杂志

OBJECTIVE@#To carry out mutation analysis and prenatal diagnosis for a family affected with primary carnitine deficiency.@*METHODS@#Genomic DNA of the proband was extracted from peripheral blood sample 10 days after birth. The 10 exons and intron/exon boundaries of the SLC22A5 gene were subjected to PCR amplification and Sanger sequencing. The proband's mother was pregnant again two years after his birth. Fetal DNA was extracted from amniocytes and subjected to PCR and Sanger sequencing.@*RESULTS@#Tandem mass spectrometric analysis of the proband revealed low level of plasma-free carnitine whilst organic acids in urine was normal. Compound heterozygous SLC22A5 mutations c.1195C>T (inherited from his father) and c.517delC (inherited from his mother) were detected in the proband. Prenatal diagnosis has detected no mutation in the fetus. The plasma-free carnitine was normal after birth.@*CONCLUSION@#Appropriate genetic testing and prenatal diagnosis can prevent further child with carnitine deficiency. The identification of c.517delC, a novel mutation, enriched the spectrum of SLC22A5 mutations.

Clinical and genetic characteristics of primary carnitine deficiency identified by neonatal screening / 中华医学遗传学杂志

OBJECTIVE@#To study the prevalence, clinical and genetic characteristics of primary carnitine deficiency (PCD).@*METHODS@#From January 2013 to December 2017, 720 667 newborns and their mothers were tested for PCD by tandem mass spectrometry. Potential mutations of carnitine transporter gene SLC22A5 among suspected PCD patients were analyzed. Dietary guidance and L-carnitine supplementation were provided to the parents. Growth and intelligence development were surveyed during follow-up.@*RESULTS@#In total 21 neonates and 6 mothers were diagnosed with PCD, which yielded an incidence of 1 in 34 317. Eighteen SLC22A5 mutations were detected, which included 4 novel mutations, namely c.1484T>C, c.394-1G>T, c.431T>C and c.265-266insGGCTCGCCACC. Eighteen patients were found to carry compound heterozygous mutations and 3 have carried homozygous SLC22A5 mutations. Three mothers carried compound heterozygous mutations and 2 carried homozygous mutations. Common mutations included c.1400C>G (42.3%), c.760C>T (11.5%) and c.51C>G (7.7%). During the 8-42 month follow-up, neonates with PCD showed no clinical symptoms but normal growth. Blood level of free carnitine was raised in all mothers after the treatment.@*CONCLUSION@#The incidence of neonatal PCD in Henan is 1 in 34 317, with the most common mutation being c.1400C>G. Above finding has enriched the spectrum of SLC22A5 gene mutations.

Mutational analysis of SLC22A5 gene in eight patients with systemic primary carnitine deficiency / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To investigate the mutations of SLC22A5 gene in patients with systemic primary carnitine deficiency (CDSP).</p><p><b>METHODS</b>High liquid chromatography tandem mass spectrometry (HPLC/MS/MS) was applied to screen congenital genetic metabolic disease and eight patients with CDSP were diagnosed among 77 511 samples. The SLC22A5 gene mutation was detected using massarray technology and sanger sequencing. Using SIFT and PolyPhen-2 to predict the function of protein for novel variations.</p><p><b>RESULTS</b>Total detection rate of gene mutation is 100% in the eight patients with CDSP. Seven patients had compound heterozygous mutations and one patient had homozygous mutations. Six different mutations were identified, including one nonsense mutation [c.760C>T(p.R254X)] and five missense mutations[c.51C>G(p.F17L), c.250T>A(p.Y84N), c.1195C>T(p.R399W), c.1196G>A(p.R399Q), c.1400C>G(p.S467C)]. The c.250T>A(p.Y84N) was a novel variation, the novel variation was predicted to have affected protein structure and function. The c.760C>T (p.R254X)was the most frequently seen mutation, which was followed by the c.1400C>G(p.S467C).</p><p><b>CONCLUSION</b>This study confirmed the diagnosis of eight patients with CDSP on the gene level. Six mutations were found in the SLC22A5 gene, including one novel mutation which expanded the mutational spectrum of the SLC22A5 gene.</p>

Genetic diagnosis of 10 neonates with primary carnitine deficiency / 中国当代儿科杂志

<p><b>OBJECTIVE</b>To study the gene mutation profile of primary carnitine deficiency (PCD) in neonates, and to provide a theoretical basis for early diagnosis and treatment, genetic counseling, and prenatal diagnosis of PCD.</p><p><b>METHODS</b>Acylcarnitine profile analysis was performed by tandem mass spectrometry using 34 167 dry blood spots on filter paper. The SLC22A5 gene was sequenced and analyzed in neonates with free carnitine (C0) levels lower than 10 μmol/L as well as their parents.</p><p><b>RESULTS</b>In the acylcarnitine profile analysis, a C0 level lower than 10 μmol/L was found in 10 neonates, but C0 level was not reduced in their mothers. The 10 neonates had 10 types of mutations at 20 different sites in the SLC22A5 gene, which included 4 previously unreported mutations: c.976C>T, c.919delG, c.517delC, and c.338G>A. Bioinformatics analysis showed that the four new mutations were associated with a risk of high pathogenicity.</p><p><b>CONCLUSIONS</b>Tandem mass spectrometry combined with SLC22A5 gene sequencing may be useful for the early diagnosis of PCD. Identification of new mutations enriches the SLC22A5 gene mutation profile.</p>

Genetic and prenatal diagnosis for a Chinese family with primary carnitine deficiency / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify potential mutation of SLC22A5 gene in a 5-month-old boy affected with primary carnitine deficiency and provide genetic counseling and prenatal diagnosis for the members of his family.</p><p><b>METHODS</b>DNA was extracted from peripheral blood samples derived from the proband, his parents and elder sister, as well as amniotic fluid from his pregnant mother. All of the 10 exons of the SLC22A5 gene were amplified by PCR and subjected to Sanger sequencing. The amniotic fluid sample was also subjected to G-banded karyotyping and multiplex ligation-dependent probe amplification (MLPA).</p><p><b>RESULTS</b>A homozygous mutation c.760C>T (p.R254X) of the SLC22A5 gene was detected in the proband. Heterozygous mutation c.760C>T (p.R254X) was also found in other family members including the fetus. The karyotyping and chromosomal microdeletion testing for the amniotic fluid sample were both normal.</p><p><b>CONCLUSION</b>The newly identified homozygous nonsense c.760C>T (p.R254X) mutation of the SLC22A5 gene probably underlies the primary carnitine deficiency of the proband. Genetic counseling and prenatal diagnosis have been provided for this family.</p>

Genetics and pedigree analysis of primary carnitine deficiency cardiomyopathy in 6 cases / 中华儿科杂志

<p><b>OBJECTIVE</b>To investigate the mutation and background of SLC22A5 in 6 patients with primary carnitine deficiency (PCD) who only presented as cardiomyopathy.</p><p><b>METHOD</b>Genomic DNA were abstracted from the blood of the patients and their parents. Using high-throughput sequencing to determine the mutation site.Using Sanger method to confirm the mutated alleles in PCD patients and detect the corresponding sequences in their patients. Using SIFT and PolyPhen to predict the function of protein for detected missense mutations.</p><p><b>RESULT</b>Three different mutations were identified, including 2 nonsense mutations (R254X and R289X), 1 missense mutation (C113Y), R254X was the most frequently seen mutation. Four patients had compound heterozygous mutations and 2 patients had homozygous mutations. Their parents were found to have heterozygous mutations in corresponding alleles.</p><p><b>CONCLUSION</b>R254X, R289X and C113Y might be associated with primary carnitine deficiency.</p>

Mutation analysis for a family affected with riboflavin responsive-multiple acyl-CoA dehydrogenase deficiency / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify pathogenic mutation in a boy affected with riboflavin responsive-multiple acyl-CoA dehydrogenase deficiency (RR-MADD).</p><p><b>METHODS</b>The patient was initially diagnosed as primary carnitine deficiency (PCD) and has been treated with carnitine supplementation for 7 years. Clinical manifestations and characteristics of fibula muscle specimen were analyzed. Potential mutation in electron transfer flavoprotein dehydrogenase (ETFDH) gene (for the patient and his parents) and carnitine transfer protein gene (SLC22A5) (for the patient) was screened.</p><p><b>RESULTS</b>Electronic microscopy of the muscle specimen has suggested lipid storage myopathy. Mutation analysis has found that the patient carried compound heterozygous mutations, c.250G>A and c.380T>C, in exon 3 of the ETFDH gene, whilst his father and mother were heterozygous for the c.380T>C and c.250G>A mutations, respectively. Screening of the SLC22A5 gene has yielded no clinically meaningful result. After the establishment of diagnosis of RR-MADD, the condition of the patient has improved greatly with supplementation of high doses of riboflavin along with continuous carnitine supplement.</p><p><b>CONCLUSION</b>The c.250G>A (p.Ala84Thr) mutation of exon 3 of the ETFDH gene has been a hot spot in Southern Chinese population, whilst the c.380T>C (p.Leu127Pro) is rarely reported. Our case has suggested that therapeutic diagnosis cannot substitute genetic testing. The mechanism for having stabilized the patient with only carnitine supplementation for 7 years needs further investigation.</p>

Mangiferin promotes uric acid excretion and kidney function improvement and modulates related renal transporters in hyperuricemic mice / 药学学报

The effects of mangiferin on uric acid excretion, kidney function and related renal transporters were investigated in hyperuricemic mice induced by potassium oxonate. Mice were divided into normal control group, and 5 hyperuricemic groups with model control, 50, 100, and 200 mg x kg(-1) mangiferin, and 5 mg x kg(-1) allopurinol. Mice were administered by gavage once daily with 250 mg x kg(-1) potassium oxonate for seven consecutive days to create the model. And 3 doses of mangiferin were orally initiated on the day 1 h after potassium oxonate was given, separately. Serum uric acid, creatinine and urea nitrogon levels, as well as urinary uric acid creatinine levels were measured. Mouse uromodulin (mUMOD) levels in serum, urine and kidney were determined by ELISA method. The mRNA and protein levels of related renal transporters were assayed by RT-PCR and Western blotting methods, respectively. Compared to model group, mangiferin significantly reduced serum uric acid, creatinine and urea nitrogon levels, increased 24 h uric acid and creatinine excretion, and fractional excretion of uric acid in hyperuricemic mice, exhibiting uric acid excretion enhancement and kidney function improvement. Mangiferin was found to down-regulate mRNA and protein levels of urate transporter 1 (mURAT1) and glucose transporter 9 (mGLUT9), as well as up-regulate organic anion transporter 1 (mOAT1) in the kidney of hyperuricemic mice. These findings suggested that mangiferin might enhance uric acid excretion and in turn reduce serum uric acid level through the decrease of uric acid reabsorption and the increase of uric acid secretion in hyperuricemic mice. Moreover, mangiferin remarkably up-regulated expression levels of renal organic cation and carnitine transporters (mOCT1, mOCT2, mOCTN1 and mOCTN2), increased urine mUMOD levels, as well as decreased serum and kidney mUMOD levels in hyperuricemic mice, which might be involved in mangiferin-mediated renal protective action.

Advances in the study of regulation of novel organic cation transporter-2 / 药学学报

Novel organic cation transporter-2 (OCTN2), a member of the organic cation transporter family, may transport carnitine and multiple organic cationic drugs. Thus OCTN2 possesses substantial roles in physiology and pharmacology. A number of researches have proven that many factors can regulate the expression and/or function of OCTN2 via different pathways, and then may affect the homeostasis and disposition of drugs. This paper reviews recent progresses in this field.

Diagnóstico in vitro de la deficiencia primaria de carnitina / In vitro diagnosis of primary carnitine deficiency

El transportador de carnitina (OCTN2) es fundamental para el metabolismo mitocondrial de los ácidos grasos de cadena larga. Su carencia produce la deficiencia primaria de carnitina. El presente estudio tuvo como objetivo el análisis de los ácidos grasos producidos por fibroblastos incubados en presencia de sustratos deuterados, mediante cromatografía de gases acoplada a espectrometría de masas (GC - MS) como herramienta diagnóstica de la deficiencia primaria de carnitina. Se encontró un perfil característico en esta deficiencia, lo que permite su diagnóstico in vitro.

Carnitine transporter (OCTN2) is required for the mitochondrial metabolism of long-chain fatty acids. Primary carnitine deficiency is a consequence of its deficiency. The objective of the present study was to analyse the fatty acids produced by fibroblasts incubated with deuterated substrates, using gas chromatography-mass spectrometry as a diagnostic tool for the diagnosis of VLCAD deficiency. A characteristic profile for this deficiency was found using this technique which enables its in vitro diagnosis.

Expression of OCTN2 mRNA in the human epididymis and its significance / 中华男科学杂志

<p><b>OBJECTIVE</b>To explore the mechanism of L-Carnitine transport and the expression of OCTN2 mRNA in the human epididymis so as to provide a theoretical basis for male contraception.</p><p><b>METHODS</b>We collected specimens from human epididymides and determined the expressions of OCTN2 mRNA in the caput, corpus and cauda of the epididymis by RT-PCR.</p><p><b>RESULTS</b>OCTN2 mRNA was expressed in the caput, corpus and cauda of the epididymis.</p><p><b>CONCLUSION</b>The human epididymis may rely on OCTN2 for transporting L-Carnitine into the epididymal duct to promote sperm maturation. With the accumulation of information on OCTN2 in the human epididymis, OCTN2 will become a new molecular target for researches on male contraception.</p>