The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Takeyori Saheki - One of the best experts on this subject based on the ideXlab platform.
-
agc2 Citrin deficiency from recognition of the disease till construction of therapeutic procedures
Biomolecules, 2020Co-Authors: Takeyori Saheki, Mitsuaki Moriyama, Aki Funahashi, Eishi KurodaAbstract:Can you imagine a disease in which intake of an excess amount of sugars or carbohydrates causes hyperammonemia? It is hard to imagine the intake causing hyperammonemia. AGC2 or Citrin deficiency shows their symptoms following sugar/carbohydrates intake excess and this disease is now known as a pan-ethnic disease. AGC2 (aspartate glutamate carrier 2) or Citrin is a mitochondrial transporter which transports aspartate (Asp) from mitochondria to cytosol in exchange with glutamate (Glu) and H+. Asp is originally supplied from mitochondria to cytosol where it is necessary for synthesis of proteins, nucleotides, and urea. In cytosol, Asp can be synthesized from oxaloacetate and Glu by cytosolic Asp aminotransferase, but oxaloacetate formation is limited by the amount of NAD+. This means an increase in NADH causes suppression of Asp formation in the cytosol. Metabolism of carbohydrates and other substances which produce cytosolic NADH such as alcohol and glycerol suppress oxaloacetate formation. It is forced under Citrin deficiency since Citrin is a member of malate/Asp shuttle. In this review, we will describe history of identification of the SLC25A13 gene as the causative gene for adult-onset type II citrullinemia (CTLN2), a type of Citrin deficiency, pathophysiology of Citrin deficiency together with animal models and possible treatments for Citrin deficiency newly developing.
-
oral aversion to dietary sugar ethanol and glycerol correlates with alterations in specific hepatic metabolites in a mouse model of human Citrin deficiency
Molecular Genetics and Metabolism, 2017Co-Authors: Eishi Kuroda, Takeyori Saheki, Kanako Inoue, Yuki Fujimoto, Hiromi Ono, Sumie Furuie, Ken Ichi Yamamura, Miharu UshikaiAbstract:Mice carrying simultaneous homozygous mutations in the genes encoding Citrin, the mitochondrial aspartate-glutamate carrier 2 (AGC2) protein, and mitochondrial glycerol-3-phosphate dehydrogenase (mGPD), are a phenotypically representative model of human Citrin (a.k.a., AGC2) deficiency. In this study, we investigated the voluntary oral intake and preference for sucrose, glycerol or ethanol solutions by wild-type, Citrin (Ctrn)-knockout (KO), mGPD-KO, and Ctrn/mGPD double-KO mice; all substances that are known or suspected precipitating factors in the pathogenesis of human Citrin deficiency. The double-KO mice showed clear suppressed intake of sucrose, consuming less with progressively higher concentrations compared to the other mice. Similar observations were made when glycerol or ethanol were given. The preference of Ctrn-KO and mGPD-KO mice varied with the different treatments; essentially no differences were observed for sucrose, while an intermediate intake or similar to that of the double-KO mice was observed for glycerol and ethanol. We next examined the hepatic glycerol 3-phosphate, citrate, citrulline, lysine, glutamate and adenine nucleotide levels following forced enteral administration of these solutions. A strong correlation between the simultaneous increased hepatic glycerol 3-phosphate and decreased ATP or total adenine nucleotide content and observed aversion of the mice during evaluation of their voluntary preferences was found. Overall, our results suggest that the aversion observed in the double-KO mice to these solutions is initiated and/or mediated by hepatic metabolic perturbations, resulting in a behavioral response to increased hepatic cytosolic NADH and a decreased cellular adenine nucleotide pool. These findings may underlie the dietary predilections observed in human Citrin deficient patients.
-
SLC25A13 Gene Analysis in Citrin Deficiency: Sixteen Novel Mutations in East Asian Patients, and the Mutation Distribution in a Large Pediatric Cohort in China
2016Co-Authors: Sumito Dateki, Keiko Kobayashi, Takeyori Saheki, Lock-hock Ngu, Takeyori SahekiAbstract:Background: The human SLC25A13 gene encodes Citrin, the liver-type mitochondrial aspartate/glutamate carrier isoform 2 (AGC2), and SLC25A13 mutations cause Citrin deficiency (CD), a disease entity that encompasses different age-dependant clinical phenotypes such as Adult-onset Citrullinemia Type II (CTLN2) and Neonatal Intrahepatic Cholestasis caused by Citrin Deficiency (NICCD). The analyses of SLC25A13 gene and its protein/mRNA products remain reliable tools for the definitive diagnoses of CD patients, and so far, the SLC25A13 mutation spectrum in Chinese CD patients has not been well-characterized yet. Methods and Results: By means of direct DNA sequencing, cDNA cloning and SNP analyses, 16 novel pathogenic mutations, including 9 missense, 4 nonsense, 1 splice-site, 1 deletion and 1 large transposal insertion IVS4ins6kb (GenBan
-
chronic hepatitis without hepatic steatosis caused by Citrin deficiency in a child
Hepatology Research, 2016Co-Authors: Ayano Inui, Takeyori Saheki, Takuji Hashimoto, Tsuyoshi Sogo, Haruki Komatsu, Tomoo FujisawaAbstract:Citrin deficiency manifests as both neonatal intrahepatic cholestasis (NICCD) during early infancy and adult-onset type II citrullinemia during adulthood. Hepatic steatosis is most frequently observed in patients with Citrin deficiency. Thus, non-alcoholic fatty liver disease that is unrelated to being overweight is considered one of the clinical features of Citrin deficiency in children and adults. However, it remains unknown whether Citrin deficiency is a cause of chronic hepatitis in the absence of fatty changes to the liver that occur during childhood. We encountered an 8-year-old girl who showed no clinical features of NICCD during infancy and had persistently elevated transaminase levels for several years. Liver biopsy showed widening of the portal tracts with intense mononuclear cell infiltration and mild fibrosis but no fatty changes. However, she had peculiar dietary habits similar to those that have been observed in many patients with Citrin deficiency. In addition, a slightly elevated plasma citrulline level and a high pancreatic secretory trypsin inhibitor level were detected by blood examination, and she was diagnosed with Citrin deficiency. Analysis of the SLC25A13 gene revealed the presence of the compound heterozygous mutations 851del4 and IVS13 + 1G > A. Thus, Citrin deficiency should be included in the differential diagnosis of chronic hepatitis in children, even in the absence of hepatic steatosis.
-
simple and rapid genetic testing for Citrin deficiency by screening 11 prevalent mutations in slc25a13
Molecular Genetics and Metabolism, 2012Co-Authors: Atsuo Kikuchi, Keiko Kobayashi, Takeyori Saheki, Natsuko Araiichinoi, Osamu Sakamoto, Yoichi Matsubara, Toshihro Ohura, Shigeo KureAbstract:Citrin deficiency is an autosomal recessive disorder caused by mutations in the SLC25A13 gene and has two disease outcomes: adult-onset type II citrullinemia and neonatal intrahepatic cholestasis caused by Citrin deficiency. The clinical appearance of these diseases is variable, ranging from almost no symptoms to coma, brain edema, and severe liver failure. Genetic testing for SLC25A13 mutations is essential for the diagnosis of Citrin deficiency because chemical diagnoses are prohibitively difficult. Eleven SLC25A13 mutations account for 95% of the mutant alleles in Japanese patients with Citrin deficiency. Therefore, a simple test for these mutations is desirable. We established a 1-hour, closed-tube assay for the 11 SLC25A13 mutations using real-time PCR. Each mutation site was amplified by PCR followed by a melting-curve analysis with adjacent hybridization probes (HybProbe, Roche). The 11 prevalent mutations were detected in seven PCR reactions. Six reactions were used to detect a single mutation each, and one reaction was used to detect five mutations that are clustered in a 21-bp region in exon 17. To test the reliability, we used this method to genotype blind DNA samples from 50 patients with Citrin deficiency. Our results were in complete agreement those obtained using previously established methods. Furthermore, the mutations could be detected without difficulty using dried blood samples collected on filter paper. Therefore, this assay could be used for newborn screening and for facilitating the genetic diagnosis of Citrin deficiency, especially in East Asian populations.
Keiko Kobayashi - One of the best experts on this subject based on the ideXlab platform.
-
SLC25A13 Gene Analysis in Citrin Deficiency: Sixteen Novel Mutations in East Asian Patients, and the Mutation Distribution in a Large Pediatric Cohort in China
2016Co-Authors: Sumito Dateki, Keiko Kobayashi, Takeyori Saheki, Lock-hock Ngu, Takeyori SahekiAbstract:Background: The human SLC25A13 gene encodes Citrin, the liver-type mitochondrial aspartate/glutamate carrier isoform 2 (AGC2), and SLC25A13 mutations cause Citrin deficiency (CD), a disease entity that encompasses different age-dependant clinical phenotypes such as Adult-onset Citrullinemia Type II (CTLN2) and Neonatal Intrahepatic Cholestasis caused by Citrin Deficiency (NICCD). The analyses of SLC25A13 gene and its protein/mRNA products remain reliable tools for the definitive diagnoses of CD patients, and so far, the SLC25A13 mutation spectrum in Chinese CD patients has not been well-characterized yet. Methods and Results: By means of direct DNA sequencing, cDNA cloning and SNP analyses, 16 novel pathogenic mutations, including 9 missense, 4 nonsense, 1 splice-site, 1 deletion and 1 large transposal insertion IVS4ins6kb (GenBan
-
simple and rapid genetic testing for Citrin deficiency by screening 11 prevalent mutations in slc25a13
Molecular Genetics and Metabolism, 2012Co-Authors: Atsuo Kikuchi, Keiko Kobayashi, Takeyori Saheki, Natsuko Araiichinoi, Osamu Sakamoto, Yoichi Matsubara, Toshihro Ohura, Shigeo KureAbstract:Citrin deficiency is an autosomal recessive disorder caused by mutations in the SLC25A13 gene and has two disease outcomes: adult-onset type II citrullinemia and neonatal intrahepatic cholestasis caused by Citrin deficiency. The clinical appearance of these diseases is variable, ranging from almost no symptoms to coma, brain edema, and severe liver failure. Genetic testing for SLC25A13 mutations is essential for the diagnosis of Citrin deficiency because chemical diagnoses are prohibitively difficult. Eleven SLC25A13 mutations account for 95% of the mutant alleles in Japanese patients with Citrin deficiency. Therefore, a simple test for these mutations is desirable. We established a 1-hour, closed-tube assay for the 11 SLC25A13 mutations using real-time PCR. Each mutation site was amplified by PCR followed by a melting-curve analysis with adjacent hybridization probes (HybProbe, Roche). The 11 prevalent mutations were detected in seven PCR reactions. Six reactions were used to detect a single mutation each, and one reaction was used to detect five mutations that are clustered in a 21-bp region in exon 17. To test the reliability, we used this method to genotype blind DNA samples from 50 patients with Citrin deficiency. Our results were in complete agreement those obtained using previously established methods. Furthermore, the mutations could be detected without difficulty using dried blood samples collected on filter paper. Therefore, this assay could be used for newborn screening and for facilitating the genetic diagnosis of Citrin deficiency, especially in East Asian populations.
-
the mutation spectrum of the slc25a13 gene in chinese infants with intrahepatic cholestasis and aminoacidemia
Journal of Gastroenterology, 2011Co-Authors: Keiko Kobayashi, Shaoren Zhang, Xiaohong Wang, Takeyori Saheki, Jianshe Wang, Takeyori SahekiAbstract:Background SLC25A13 gene mutations cause Citrin deficiency, which leads to neonatal intrahepatic cholestasis caused by Citrin deficiency (NICCD). Information on the mutation spectrum of SLC25A13 in the Chinese population is limited. The aim of this study was to explore the mutation spectrum of the SLC25A13 gene in Chinese infants with intrahepatic cholestasis and various forms of aminoacidemia.
-
the characteristics of food intake in patients with type ii citrullinemia
Journal of Nutritional Science and Vitaminology, 2011Co-Authors: Mio Nakamura, Keiko Kobayashi, Kazuhiro Fukushima, Masahide Yazaki, Shu-ichi Ikeda, Takeyori Saheki, Yumiko Kobayashi, Yutaka NakayaAbstract:Some patients with Citrin deficiency caused by SLC25A13 gene mutations develop adult-onset type II citrullinemia (CTLN2) with hepatic encephalopathy. A recent nutritional survey of 18 Citrin-deficient subjects (age 1-33 y) confirmed a marked decrease in carbohydrate intake compared to an age-matched general Japanese population. However, a quantitative understanding of food intake in CTLN2 patients remains unclear, although qualitative dietary information has been reported. In order to elucidate the characteristics of daily nutrition of CTLN2 patients, the food intake of 5 male patients (age 39-52 y) was investigated in detail by the Food Frequency Questionnaire. In the present survey, the mean energy ratio of protein : fat : carbohydrate (PFC ratio) of the 5 patients was 19±3% : 44±5% : 37±4%, which was almost identical to previously reported data in younger Citrin-deficient subjects (19±2% : 44±5% : 37±7%). Cereal intake was especially low in all CTLN2 patients at 309±33 g/d (56% of control), compared to that in an age-matched general Japanese population (553±197 g/d). Additionally, CTLN2 patients preferred high fat and protein foods. Commonly, fat intake declines with age in the general Japanese population, but this tendency was not observed in the 5 CTLN2 patients. The present results suggest that intakes of low-carbohydrate, high-protein and high-fat food was characteristic the 5 CTLN2 patients surveyed, as has been previously reported in younger Citrin-deficient subjects, and that the PFC ratio may not be influenced by age or CTLN2-onset.
-
low levels of Citrin slc25a13 expression in adult mouse brain restricted to neuronal clusters
Journal of Neuroscience Research, 2010Co-Authors: Laura Contreras, Keiko Kobayashi, Takeyori Saheki, Almudena Urbieta, Jorgina SatrusteguiAbstract:The mitochondrial aspartate-glutamate carriers (AGC) aralar (SLC25A12) and Citrin (SLC25A13) are components of the malate aspartate shuttle (MAS), a major intracellular pathway to transfer reducing equivalents from NADH to the mitochondrial matrix. Aralar is the main AGC isoform present in the adult brain, and it is expressed mainly in neurons. To search for the other AGC isoform, Citrin, in brain glial cells, we used a Citrin knockout mouse in which the lacZ gene was inserted into the Citrin locus as reporter gene. In agreement with the low Citrin levels known to be present in the adult mouse brain, b-galactosidase expression was very low. Surprisingly, unlike the case with astroglial cultures that express Citrin, no b-galactosidase was found in brain glial cells. It was confined to neuronal cells within discrete neuronal clusters. Double-immunolabelling experiments showed that b-galactosidase colocalized not with glial cell markers but with the pan-neuronal marker NeuN. The deep cerebellar nuclei and a few midbrain nuclei (reticular tegmental pontine nuclei; magnocellular red nuclei) were the regions where b-galactosidase expression was highest, and it was up-regulated in fasted mice, as was also the case for liver b-galactosidase. The results support the notion that glial cells have much lower AGC levels and MAS activity than neurons. V C 2009 Wiley-Liss, Inc.
Mikio Iijima - One of the best experts on this subject based on the ideXlab platform.
-
Citrin mitochondrial glycerol 3 phosphate dehydrogenase double knock out mice recapitulate features of human Citrin deficiency
Journal of Biological Chemistry, 2007Co-Authors: Takeyori Saheki, Mikio Iijima, Keiko Kobayashi, Masahisa Horiuchi, Miharu Ushikai, Fumihiko Okumura, Xiao Jian Meng, Ituro Inoue, Atsushi Tajima, Mitsuaki MoriyamaAbstract:Citrin is the liver-type mitochondrial aspartate-glutamate carrier that participates in urea, protein, and nucleotide biosynthetic pathways by supplying aspartate from mitochondria to the cytosol. Citrin also plays a role in transporting cytosolic NADH reducing equivalents into mitochondria as a component of the malate-aspartate shuttle. In humans, loss-of-function mutations in the SLC25A13 gene encoding Citrin cause both adult-onset type II citrullinemia and neonatal intrahepatic cholestasis, collectively referred to as human Citrin deficiency. Citrin knock-out mice fail to display features of human Citrin deficiency. Based on the hypothesis that an enhanced glycerol phosphate shuttle activity may be compensating for the loss of Citrin function in the mouse, we have generated mice with a combined disruption of the genes for Citrin and mitochondrial glycerol 3-phosphate dehydrogenase. The resulting double knock-out mice demonstrated citrullinemia, hyperammonemia that was further elevated by oral sucrose administration, hypoglycemia, and a fatty liver, all features of human Citrin deficiency. An increased hepatic lactate/pyruvate ratio in the double knock-out mice compared with controls was also further elevated by the oral sucrose administration, suggesting that an altered cytosolic NADH/NAD(+) ratio is closely associated with the hyperammonemia observed. Microarray analyses identified over 100 genes that were differentially expressed in the double knock-out mice compared with wild-type controls, revealing genes potentially involved in compensatory or downstream effects of the combined mutations. Together, our data indicate that the more severe phenotype present in the Citrin/mitochondrial glycerol-3-phosphate dehydrogenase double knock-out mice represents a more accurate model of human Citrin deficiency than Citrin knock-out mice.
-
ca2 activation kinetics of the two aspartate glutamate mitochondrial carriers aralar and Citrin role in the heart malate aspartate nadh shuttle
Journal of Biological Chemistry, 2007Co-Authors: Laura Contreras, Mikio Iijima, Keiko Kobayashi, Takeyori Saheki, Paulino Gomezpuertas, Jorgina SatrusteguiAbstract:Abstract Ca2+ regulation of the Ca2+ binding mitochondrial carriers for aspartate/glutamate (AGCs) is provided by their N-terminal extensions, which face the intermembrane space. The two mammalian AGCs, aralar and Citrin, are members of the malate-aspartate NADH shuttle. We report that their N-terminal extensions contain up to four pairs of EF-hand motifs plus a single vestigial EF-hand, and have no known homolog. Aralar and Citrin contain one fully canonical EF-hand pair and aralar two additional half-pairs, in which a single EF-hand is predicted to bind Ca2+. Shuttle activity in brain or skeletal muscle mitochondria, which contain aralar as the major AGC, is activated by Ca2+ with S0.5 values of 280–350 nm; higher than those obtained in liver mitochondria (100–150 nm) that contain Citrin as the major AGC. We have used aralar- and Citrin-deficient mice to study the role of the two isoforms in heart, which expresses both AGCs. The S0.5 for Ca2+ activation of the shuttle in heart mitochondria is about 300 nm, and it remains essentially unchanged in Citrin-deficient mice, although it undergoes a drastic reduction to about 100 nm in aralar-deficient mice. Therefore, aralar and Citrin, when expressed as single isoforms in heart, confer differences in Ca2+ activation of shuttle activity, probably associated with their structural differences. In addition, the results reveal that the two AGCs fully account for shuttle activity in mouse heart mitochondria and that no other glutamate transporter can replace the AGCs in this pathway.
-
Citrin deficiency a novel cause of failure to thrive that responds to a high protein low carbohydrate diet
Pediatrics, 2007Co-Authors: David Dimmock, Mikio Iijima, Ayako Tabata, Leejun C Wong, Keiko Kobayashi, Fernando ScagliaAbstract:The proband was born at 36 weeks, appropriate for gestational age, to nonconsanguineous white parents. There was no evidence of hyperbilirubinemia or intrahepatic cholestasis in the neonatal period, and she had normal newborn screen results. She presented with 3 episodes of life-threatening bleeding and anemia. The diagnostic evaluation for her bleeding diathesis revealed an abnormal clotting profile with no biochemical evidence for hepatocellular damage. She was incidentally noted to have severe growth deceleration that failed to respond to 502 kJ/kg (120 kcal/kg) per day of protein-hydrolyzed formula. An extensive diagnostic workup for failure to thrive, which was otherwise normal, included plasma amino acid analysis that revealed hyperglutaminemia and citrulline levels within the reference range. Testing of a repeat sample revealed isolated hypercitrullinemia. No argininosuccinic acid was detected. Her ammonia level and urine orotic acid were within the reference ranges. Subsequent plasma amino acid analysis exhibited a profile suggestive of neonatal intrahepatic cholestasis caused by Citrin deficiency with elevations in citrulline, methionine, and threonine. Western blotting of fibroblasts demonstrated Citrin deficiency, and a deletion for exon 3 was found in the patient’s coding DNA of the SLC25A13 gene. On the basis of the experience with adults carrying this condition, the patient was given a high-protein, low-carbohydrate diet. The failure to thrive and bleeding diathesis resolved. When compliance with the dietary prescription was relaxed, growth deceleration was again noted, although significant bleeding did not recur. This is the first report of an infant of Northern European descent with Citrin deficiency. The later age at presentation with failure to thrive and bleeding diathesis and without obvious evidence of neonatal intrahepatic cholestasis expands the clinical spectrum of Citrin deficiency. This case emphasizes the importance of continued dietary control and growth monitoring in children with neonatal intrahepatic cholestasis caused by Citrin deficiency and identifies a new metabolic entity responsible for failure to thrive.
-
novel diagnostic approach to Citrin deficiency analysis of Citrin protein in lymphocytes
Molecular Genetics and Metabolism, 2007Co-Authors: Daisuke Tokuhara, Mikio Iijima, Keiko Kobayashi, Takeyori Saheki, Akiko Tamamori, Toshihiro Ohura, Junji Takaya, Shunichi Maisawa, Tsunekazu Yamano, Yoshiyuki OkanoAbstract:Citrin deficiency induces two clinical features; namely neonatal intrahepatic cholestasis caused by Citrin deficiency (NICCD) and adult-onset type II citrullinemia. Hypercitrullinemia is the most characteristic feature, whereas there are non-citrullinemic individuals. Diagnosis of Citrin deficiency is performed by genetic analysis, although the 12 known mutations in the alleles are not detected in about 15% of cases. Thus, we aimed to examine Citrin protein in lymphocytes isolated from peripheral blood as an alternative diagnostic method. We examined 38 children having an episode of cholestatic liver dysfunction, 8 heterozygotes, and 11 healthy individuals. All subjects were evaluated for Citrin protein by Western blotting and for the 12 known mutations by gene analysis. Citrin protein was detected in 15 of 38 children with cholestatic liver dysfunction. Fourteen of them were negative for 12 known mutations in both alleles, whereas one patient was found to have a known mutation in one allele. Citrin protein was absent in 23 of the 38 patients. Among these 23, gene analysis diagnosed Citrin deficiency in 19, whereas 2 patients were later revealed to be NICCD with novel mutations. In the remaining 2 patients, who exhibit the clinical features of NICCD, a known mutation was detected in one allele but no mutation was identified in another allele. Citrin protein was also detected in the 8 heterozygotes and 11 healthy individuals. We disclosed that Citrin was deficient in lymphocytes among patients with Citrin deficiency. Analysis of Citrin is useful to diagnose Citrin deficiency even in patients without known mutations or hypercitrullinemia.
-
metabolic derangements in deficiency of Citrin a liver type mitochondrial aspartate glutamate carrier
Hepatology Research, 2005Co-Authors: Takeyori Saheki, Mikio Iijima, Keiko Kobayashi, Masahide Yazaki, Yoichi Takei, Mitsuaki Moriyama, Takeyori Saheki, Shu-ichi IkedaAbstract:Citrin, encoded by SLC25A13, is a liver-type mitochondrial aspartate-glutamate carrier (AGC), of which deficiency, in autosomal recessive trait, causes neonatal intrahepatic cholestasis (NICCD) and adult-onset type II citrullinemia (CTLN2). NICCD patients have jaundice, hypoproteinemia, hypoglycemia, galactosemia, growth retardation, fatty liver and multiple aminoacidemia including citrulline, methionine, threonine and tyrosine. Some of the neonates who have experienced NICCD suffer from severe CTLN2 more than 10 years or several decades later. In CTLN2, neuropsychotic symptoms such as disorientation, aberrant behavior, coma and death are observed. Laboratory findings reveal hyperammonemia, citrullinemia, fatty liver and liver-specific decrease in a urea cycle enzyme, argininosuccinate synthetase (ASS). In some cases, hyperlipidemia, pancreatitis and hepatoma are accompanied with CTLN2. Citrin as a liver-type AGC plays a role in supplying aspartate to the cytosol for urea, protein and nucleotide synthesis by exchanging mitochondrial aspartate for cytosolic glutamate and proton, and transporting cytosolic NADH reducing equivalent to mitochondria as a member of malate aspartate shuttle essential for aerobic glycolysis. AGC is also important for gluconeogenesis from lactate. Although it is difficult to explain pathogenesis of the symptoms such as cholestasis in NICCD and liver-specific decrease of ASS protein in CTLN2 from the functions of the AGC, some are understandable by the loss of Citrin functions. Many CTLN2 patients have been treated with a low protein and high carbohydrate diet and glycerol at the hyperammonemic coma. We argue that those treatments may result in fatty liver, hyperlipidemia, hyperammonemia and even death due to loss of the Citrin functions. Loss of Citrin first cause deficiency of aspartate in the cytosol, which results in an increase in cytosolic NADH/NAD(+) ratio and then activation of fatty acid synthesis pathway to compensate the aberrant ratio. This follows inhibition of fatty acid oxidation. The peculiar fondness for food of CTLN2 patients who like protein and dislike carbohydrate and sweets may be related to their metabolic requirements.
Mitsuaki Moriyama - One of the best experts on this subject based on the ideXlab platform.
-
agc2 Citrin deficiency from recognition of the disease till construction of therapeutic procedures
Biomolecules, 2020Co-Authors: Takeyori Saheki, Mitsuaki Moriyama, Aki Funahashi, Eishi KurodaAbstract:Can you imagine a disease in which intake of an excess amount of sugars or carbohydrates causes hyperammonemia? It is hard to imagine the intake causing hyperammonemia. AGC2 or Citrin deficiency shows their symptoms following sugar/carbohydrates intake excess and this disease is now known as a pan-ethnic disease. AGC2 (aspartate glutamate carrier 2) or Citrin is a mitochondrial transporter which transports aspartate (Asp) from mitochondria to cytosol in exchange with glutamate (Glu) and H+. Asp is originally supplied from mitochondria to cytosol where it is necessary for synthesis of proteins, nucleotides, and urea. In cytosol, Asp can be synthesized from oxaloacetate and Glu by cytosolic Asp aminotransferase, but oxaloacetate formation is limited by the amount of NAD+. This means an increase in NADH causes suppression of Asp formation in the cytosol. Metabolism of carbohydrates and other substances which produce cytosolic NADH such as alcohol and glycerol suppress oxaloacetate formation. It is forced under Citrin deficiency since Citrin is a member of malate/Asp shuttle. In this review, we will describe history of identification of the SLC25A13 gene as the causative gene for adult-onset type II citrullinemia (CTLN2), a type of Citrin deficiency, pathophysiology of Citrin deficiency together with animal models and possible treatments for Citrin deficiency newly developing.
-
mechanism for increased hepatic glycerol synthesis in the Citrin mitochondrial glycerol 3 phosphate dehydrogenase double knockout mouse urine glycerol and glycerol 3 phosphate as potential diagnostic markers of human Citrin deficiency
Biochimica et Biophysica Acta, 2015Co-Authors: Mitsuaki Moriyama, Eishi Kuroda, Miharu Ushikai, Yuki Fujimoto, Shizuka Rikimaru, Kenji Kawabe, Katsura Takano, Akihiro Asakawa, Akio InuiAbstract:Abstract The mitochondrial aspartate-glutamate carrier isoform 2 (Citrin) and mitochondrial glycerol-3-phosphate dehydrogenase (mGPD) double-knockout mouse has been a useful model of human Citrin deficiency. One of the most prominent findings has been markedly increased hepatic glycerol 3-phosphate (G3P) following oral administration of a sucrose solution. We aimed to investigate whether this change is detectable outside of the liver, and to explore the mechanism underlying the increased hepatic G3P in these mice. We measured G3P and its metabolite glycerol in plasma and urine of the mice under various conditions. Glycerol synthesis from fructose was also studied using the liver perfusion system. The Citrin/mGPD double-knockout mice showed increased urine G3P and glycerol under normal, fed conditions. We also found increased plasma glycerol under fasted conditions, while oral administration of different carbohydrates or ethanol led to substantially increased plasma glycerol. Fructose infusion to the perfused liver of the double-knockout mice augmented hepatic glycerol synthesis, and was accompanied by a concomitant increase in the lactate/pyruvate (L/P) ratio. Co-infusion of either pyruvate or phenazine methosulfate, a cytosolic oxidant, with fructose corrected the high L/P ratio, leading to reduced glycerol synthesis. Overall, these findings suggest that hepatic glycerol synthesis is cytosolic NADH/NAD + ratio-dependent and reveal a likely regulatory mechanism for hepatic glycerol synthesis following a high carbohydrate load in Citrin-deficient patients. Therefore, urine G3P and glycerol may represent potential diagnostic markers for human Citrin deficiency.
-
Citrin mitochondrial glycerol 3 phosphate dehydrogenase double knock out mice recapitulate features of human Citrin deficiency
Journal of Biological Chemistry, 2007Co-Authors: Takeyori Saheki, Mikio Iijima, Keiko Kobayashi, Masahisa Horiuchi, Miharu Ushikai, Fumihiko Okumura, Xiao Jian Meng, Ituro Inoue, Atsushi Tajima, Mitsuaki MoriyamaAbstract:Citrin is the liver-type mitochondrial aspartate-glutamate carrier that participates in urea, protein, and nucleotide biosynthetic pathways by supplying aspartate from mitochondria to the cytosol. Citrin also plays a role in transporting cytosolic NADH reducing equivalents into mitochondria as a component of the malate-aspartate shuttle. In humans, loss-of-function mutations in the SLC25A13 gene encoding Citrin cause both adult-onset type II citrullinemia and neonatal intrahepatic cholestasis, collectively referred to as human Citrin deficiency. Citrin knock-out mice fail to display features of human Citrin deficiency. Based on the hypothesis that an enhanced glycerol phosphate shuttle activity may be compensating for the loss of Citrin function in the mouse, we have generated mice with a combined disruption of the genes for Citrin and mitochondrial glycerol 3-phosphate dehydrogenase. The resulting double knock-out mice demonstrated citrullinemia, hyperammonemia that was further elevated by oral sucrose administration, hypoglycemia, and a fatty liver, all features of human Citrin deficiency. An increased hepatic lactate/pyruvate ratio in the double knock-out mice compared with controls was also further elevated by the oral sucrose administration, suggesting that an altered cytosolic NADH/NAD(+) ratio is closely associated with the hyperammonemia observed. Microarray analyses identified over 100 genes that were differentially expressed in the double knock-out mice compared with wild-type controls, revealing genes potentially involved in compensatory or downstream effects of the combined mutations. Together, our data indicate that the more severe phenotype present in the Citrin/mitochondrial glycerol-3-phosphate dehydrogenase double knock-out mice represents a more accurate model of human Citrin deficiency than Citrin knock-out mice.
-
metabolic derangements in deficiency of Citrin a liver type mitochondrial aspartate glutamate carrier
Hepatology Research, 2005Co-Authors: Takeyori Saheki, Mikio Iijima, Keiko Kobayashi, Masahide Yazaki, Yoichi Takei, Mitsuaki Moriyama, Takeyori Saheki, Shu-ichi IkedaAbstract:Citrin, encoded by SLC25A13, is a liver-type mitochondrial aspartate-glutamate carrier (AGC), of which deficiency, in autosomal recessive trait, causes neonatal intrahepatic cholestasis (NICCD) and adult-onset type II citrullinemia (CTLN2). NICCD patients have jaundice, hypoproteinemia, hypoglycemia, galactosemia, growth retardation, fatty liver and multiple aminoacidemia including citrulline, methionine, threonine and tyrosine. Some of the neonates who have experienced NICCD suffer from severe CTLN2 more than 10 years or several decades later. In CTLN2, neuropsychotic symptoms such as disorientation, aberrant behavior, coma and death are observed. Laboratory findings reveal hyperammonemia, citrullinemia, fatty liver and liver-specific decrease in a urea cycle enzyme, argininosuccinate synthetase (ASS). In some cases, hyperlipidemia, pancreatitis and hepatoma are accompanied with CTLN2. Citrin as a liver-type AGC plays a role in supplying aspartate to the cytosol for urea, protein and nucleotide synthesis by exchanging mitochondrial aspartate for cytosolic glutamate and proton, and transporting cytosolic NADH reducing equivalent to mitochondria as a member of malate aspartate shuttle essential for aerobic glycolysis. AGC is also important for gluconeogenesis from lactate. Although it is difficult to explain pathogenesis of the symptoms such as cholestasis in NICCD and liver-specific decrease of ASS protein in CTLN2 from the functions of the AGC, some are understandable by the loss of Citrin functions. Many CTLN2 patients have been treated with a low protein and high carbohydrate diet and glycerol at the hyperammonemic coma. We argue that those treatments may result in fatty liver, hyperlipidemia, hyperammonemia and even death due to loss of the Citrin functions. Loss of Citrin first cause deficiency of aspartate in the cytosol, which results in an increase in cytosolic NADH/NAD(+) ratio and then activation of fatty acid synthesis pathway to compensate the aberrant ratio. This follows inhibition of fatty acid oxidation. The peculiar fondness for food of CTLN2 patients who like protein and dislike carbohydrate and sweets may be related to their metabolic requirements.
-
slc25a13 knockout mice harbor metabolic deficits but fail to display hallmarks of adult onset type ii citrullinemia
Molecular and Cellular Biology, 2004Co-Authors: David S Sinasac, Mikio Iijima, Keiko Kobayashi, Mitsuaki Moriyama, Takeyori Saheki, Laila Begum, Masahisa Horiuchi, Abdul M Jalil, Brian H Robinson, Lapchee TsuiAbstract:Adult-onset type II citrullinemia (CTLN2) is an autosomal recessive disease caused by mutations in SLC25A13, the gene encoding the mitochondrial aspartate/glutamate carrier Citrin. The absence of Citrin leads to a liver-specific, quantitative decrease of argininosuccinate synthetase (ASS), causing hyperammonemia and citrullinemia. To investigate the physiological role of Citrin and the development of CTLN2, an Slc25a13-knockout (also known as Ctrn-deficient) mouse model was created. The resulting Ctrn-/- mice were devoid of Slc25a13 mRNA and Citrin protein. Liver mitochondrial assays revealed markedly decreased activities in aspartate transport and the malate-aspartate shuttle. Liver perfusion also demonstrated deficits in ureogenesis from ammonia, gluconeogenesis from lactate, and an increase in the lactate-to-pyruvate ratio within hepatocytes. Surprisingly, Ctrn-/- mice up to 1 year of age failed to show CTLN2-like symptoms due to normal hepatic ASS activity. Serological measures of glucose, amino acid, and ammonia metabolism also showed no significant alterations. Nitrogen-loading treatments produced only minor changes in the hepatic ammonia and amino acid levels. These results suggest that Citrin deficiency alone may not be sufficient to produce a CTLN2-like phenotype in mice. These observations are compatible, however, with the variable age of onset, incomplete penetrance, and strong ethnic bias seen in CTLN2 where additional environmental and/or genetic triggers are now suspected.
Laila Begum - One of the best experts on this subject based on the ideXlab platform.
-
adult onset type ii citrullinemia and idiopathic neonatal hepatitis caused by Citrin deficiency involvement of the aspartate glutamate carrier for urea synthesis and maintenance of the urea cycle
Molecular Genetics and Metabolism, 2004Co-Authors: Takeyori Saheki, Mikio Iijima, Keiko Kobayashi, Md. Abdul Jalil, Laila Begum, Masahisa Horiuchi, Miharu Ushikai, Meng Xian Li, Yao Bang Lu, Ayako TabataAbstract:Abstract Citrin is a mitochondrial aspartate glutamate carrier primarily expressed in the liver, heart, and kidney. We found that adult-onset type II citrullinemia is caused by mutations in the SLC25A13 gene that encodes for Citrin. In this report, we describe the frequency of SLC25A13 mutations, the roles of Citrin as a member of the urea cycle and as a member of the malate–aspartate shuttle, the relationship between its functions and symptoms of Citrin deficiency, and therapeutic issues.
-
slc25a13 knockout mice harbor metabolic deficits but fail to display hallmarks of adult onset type ii citrullinemia
Molecular and Cellular Biology, 2004Co-Authors: David S Sinasac, Mikio Iijima, Keiko Kobayashi, Mitsuaki Moriyama, Takeyori Saheki, Laila Begum, Masahisa Horiuchi, Abdul M Jalil, Brian H Robinson, Lapchee TsuiAbstract:Adult-onset type II citrullinemia (CTLN2) is an autosomal recessive disease caused by mutations in SLC25A13, the gene encoding the mitochondrial aspartate/glutamate carrier Citrin. The absence of Citrin leads to a liver-specific, quantitative decrease of argininosuccinate synthetase (ASS), causing hyperammonemia and citrullinemia. To investigate the physiological role of Citrin and the development of CTLN2, an Slc25a13-knockout (also known as Ctrn-deficient) mouse model was created. The resulting Ctrn-/- mice were devoid of Slc25a13 mRNA and Citrin protein. Liver mitochondrial assays revealed markedly decreased activities in aspartate transport and the malate-aspartate shuttle. Liver perfusion also demonstrated deficits in ureogenesis from ammonia, gluconeogenesis from lactate, and an increase in the lactate-to-pyruvate ratio within hepatocytes. Surprisingly, Ctrn-/- mice up to 1 year of age failed to show CTLN2-like symptoms due to normal hepatic ASS activity. Serological measures of glucose, amino acid, and ammonia metabolism also showed no significant alterations. Nitrogen-loading treatments produced only minor changes in the hepatic ammonia and amino acid levels. These results suggest that Citrin deficiency alone may not be sufficient to produce a CTLN2-like phenotype in mice. These observations are compatible, however, with the variable age of onset, incomplete penetrance, and strong ethnic bias seen in CTLN2 where additional environmental and/or genetic triggers are now suspected.
-
Pathogenesis and Pathophysiology of Citrin (a Mitochondrial Aspartate Glutamate Carrier) Deficiency
Metabolic Brain Disease, 2002Co-Authors: Takeyori Saheki, Mikio Iijima, Keiko Kobayashi, Ikumi Nishi, Tomotsugu Yasuda, Naoki Yamaguchi, Hong Zhi Gao, Md. Abdul Jalil, Laila BegumAbstract:Adult-onset type II citrullinemia (CTLN2), characterized by a liver-specific deficiency of urea cycle enzyme, argininosuccinate synthetase, is caused by mutations in SLC25A13 that encodes a calcium binding mitochondrial solute carrier protein, Citrin. Citrin deficiency causes not only CTLN2 but also neonatal intrahepatic cholestasis caused by Citrin deficiency at neonatal period. Moreover Citrin and its isoform aralar were found to be aspartate glutamate carrier. From the viewpoint of the metabolic functions of Citrin as aspartate glutamate carrier in urea synthesis and NADH shuttle, symptoms of CTLN2 and neonatal intrahepatic cholestasis caused by Citrin deficiency are analyzed.
-
expression of three mitochondrial solute carriers Citrin aralar1 and ornithine transporter in relation to urea cycle in mice
Biochimica et Biophysica Acta, 2002Co-Authors: Laila Begum, Mikio Iijima, Keiko Kobayashi, Tomotsugu Yasuda, Md. Abdul Jalil, Masahisa Horiuchi, Araceli Del Arco, Jorgina Satrustegui, Takeyori SahekiAbstract:The present report describes the expression profiles of different tissues and developmental changes of mouse aspartate/glutamate carrier (AGC) genes, Slc25a13 and Slc25a12, and an ornithine transporter gene, Ornt1, in relation to urea cycle enzyme genes, carbamoylphosphate synthetase I (CPS) and argininosuccinate synthetase (ASS). Slc25a13 encodes Citrin, recently found to be deficient in adult-onset type II citrullinemia and to function as AGC together with its isoform and product of Slc25a12, aralar1. Citrin was broadly distributed, but mainly in the liver, kidney and heart. Aralar1 was expressed in diaphragm, skeletal muscle, heart, brain and kidney, but not in the liver. These distribution profiles are different from the restricted of Ornt1, ASS and CPS. Citrin, ASS, CPS and Ornt1 showed similar patterns of developmental changes in the liver and small intestine, where they play a role in urea and arginine synthesis. Dietary, hormonal and physical manipulations caused varied changes of CPS, ASS and Ornt1 in the liver, but the change of Citrin was not so marked as that of the others. Analysis using RT-PCR and restriction enzyme digestion revealed that the ornithine transporter most expressed is Ornt1, although Ornt2 is detectable at a minute level. All these results suggest that Citrin as AGC plays a role in urea synthesis as well as many fundamental metabolic pathways in the liver, and shares metabolic functions with aralar1 in other tissues, and that Ornt1 is an important component in urea synthesis in the liver and in arginine synthesis in the small intestine during the neonatal period.