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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., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The C57BL/6:Slc23a13(-/-);Gpd2(-/-) double-knockout (a.k.a., citrin/mitochondrial glycerol 3-phosphate dehydrogenase double knockout or Ctrn/mGPD-KO) mouse displays phenotypic attributes of both neonatal intrahepatic cholestasis (NICCD) and adult-onset type II citrullinemia (CTLN2), making it a suitable model of human citrin deficiency. In the present study, we show that when mature Ctrn/mGPD-KO mice are switched from a standard chow diet (CE-2) to a purified maintenance diet (AIN-93M), this resulted in a significant loss of body weight as a result of reduced food intake compared to littermate mGPD-KO mice. However, supplementation of the purified maintenance diet with additional protein (from 14% to 22%; and concomitant reduction or corn starch), or with specific supplementation with alanine, sodium glutamate, sodium pyruvate or medium-chain triglycerides (MCT), led to increased food intake and body weight gain near or back to that on chow diet. No such effect was observed when supplementing the diet with other sources of fat that contain long-chain fatty acids. Furthermore, when these supplements were added to a sucrose solution administered enterally to the mice, which has been shown previously to lead to elevated blood ammonia as well as altered hepatic metabolite levels in Ctrn/mGPP-KO mice, this led to metabolic correction. The elevated hepatic glycerol 3-phosphate and citrulline levels after sucrose administration were suppressed by the administration of sodium pyruvate, alanine, sodium glutamate and MCT, although the effect of MCT was relatively small. Low hepatic citrate and increased lysine levels were only found to be corrected by sodium pyruvate, while alanine and sodium glutamate both corrected hepatic glutamate and aspartate levels. Overall, these results suggest that dietary factors including increased protein content, supplementation of specific amino acids like alanine and sodium glutamate, as well as sodium pyruvate and MCT all show beneficial effects on citrin deficiency by increasing the carbohydrate tolerance of Ctrn/mGPD-KO mice, as observed through increased food intake and maintenance of body weight., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background: The most common causes of cholestatic jaundice are biliary atresia and idiopathic neonatal hepatitis (INH). Specific disorders underlying INH, such as various infectious and metabolic causes, including neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) especially, in East Asian populations are increasingly being identified. Since most NICCD infants recovered from liver disease by 1 year of age, they often are misdiagnosed with INH, leading to difficulty in determining the true prevalence of NICCD. Mutation(s) of human SLC25A13 gene encoding a mitochondrial aspartate/glutamate carrier isoform 2 (AGC2), can lead to AGC2 deficiency, resulting in NICCD and an adult-onset fatal disease namely citrullinemia type II (CTLN2). To study the prevalence of NICCD and SLC25A13 mutations in Thai infants, and to compare manifestations of NICCD and non-NICCD, infants with idiopathic cholestatic jaundice or INH were enrolled. Clinical and biochemical data were reviewed. Urine organic acid and plasma amino acids profiles were analyzed. PCR-sequencing of all 18 exons of SLC25A13 and gap PCR for the mutations IVS16ins3kb and Ex16+74&#95;IVS17-32del516 were performed. mRNA were analyzed in selected cases with possible splicing error., Results: Five out of 39 (12.8%) unrelated infants enrolled in the study were found to have NICCD, of which three had homozygous 851del4 (GTATdel) and two compound heterozygous 851del4/IVS16ins3kb and 851del4/1638ins23, respectively. Two missense mutations (p.M1? and p.R605Q) of unknown functional significance were identified. At the initial presentation, NICCD patients had higher levels of alkaline phosphatase (ALP) and alpha-fetoprotein (AFP) and lower level of alanine aminotransferase (ALT) than those in non-NICCD patients (p< 0.05). NICCD patients showed higher citrulline level and threonine/serine ratio than non-NICCD infants (p< 0.05). Fatty liver was found in 2 NICCD patients. Jaundice resolved in all NICCD and in 87.5% of non-NICCD infants at the median age of 9.5 and 4.0 months, respectively., Conclusion: NICCD should be considered in infants with idiopathic cholestasis. The preliminary estimated prevalence of NICCD was calculated to be 1/48,228 with carrier rate of 1/110 among Thai infants. However, this number may be underestimated and required further analysis with mutation screening in larger control population to establish the true prevalence of NICCD and AGC2 deficiency.

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., (Copyright © 2011 Elsevier Inc. All rights reserved.)

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.

Citrin deficiency, aetiologically linked to mutations of SLC25A13 gene, has two clinical phenotypes, namely adult-onset type II citrullinaemia (CTLN2) and neonatal/infantile intrahepatic cholestasis, caused by citrin deficiency (NICCD). Malaysian patients with NICCD, especially of Malay and East Malaysian indigenous descent, have never been reported in the literature. We present the clinical features, biochemical findings and results of molecular analysis in 11 Malaysian children with NICCD. In this case series, all patients manifested prolonged cholestatic jaundice and elevated citrulline levels. The other more variable features included failure to thrive, bleeding diathesis, hypoproteinaemia, abnormal liver enzymes, prolonged coagulation profile, hyperammonaemia, hypergalactosaemia, multiple aminoacidaemia, elevated α-feto protein and urinary orotic acid as well as liver biopsies showing hepatitis and steatosis. DNA analysis of SLC25A13 revealed combinations of 851del4(Ex9), IVS16ins3kb and 1638ins23. Most of our patients recovered completely by the age of 22 months. However, one patient had ongoing symptoms at the time of reporting and one had died of liver failure. Since a small percentage of children with NICCD will develop CTLN2 and the mechanisms leading to this is yet to be defined, ongoing health surveillance into adulthood is essential.

Adult-onset type II citrullinemia (CTLN2) is an autosomal recessive disease characterized by highly elevated plasma levels of citrulline and ammonia due to the urea cycle dysfunction associated with citrin deficiency. Patients with CTLN2 show various neurological symptoms with hyperammonemia closely resembling those of hepatic encephalopathy. Since 1990, 26 CTLN2 patients (17 males and 9 females) have been admitted and treated at Shinshu University Hospital. Twelve of the 26 patients received living related partial liver transplantation (LRLT). After LRLT, neurological symptoms soon disappeared, and all patients returned to their previous social lives. Among the 14 patients that did not undergo LRLT, 6 died of intractable encephalopathy or the development of hepatic cancer, but 8 patients have had relatively good clinical courses (follow-up range 0.5-8 years) with oral intake of L-arginine and low-carbohydrate and relatively protein-rich diet. Six patients have been also given sodium pyruvate and the frequency of attacks of encephalopathy markedly decreased in 5 of 6 patients. Our observations indicated that liver transplantation is a very promising type of therapy but that other therapeutic approaches, including low-carbohydrate diet and pyruvate, are being established.

Citrin deficiency is an autosomal recessive disorder caused by mutation in the SLC25AJ3 gene. It has two major phenotypes: adult-onset type II citrullinemia (CTLN2) and neonatal intrahepatic cholestatic caused by citrin deficiency (NICCD). NICCD is characterized by neonatal/infantile-onset cholestatic hepatitis syndrome associated with multiple amino acidemia and hypergalactosemia. NICCD is self-limiting in most patients. However, some patients may develop CTLN2 years later, which manifests as fatal hyperammonemia coma. We report three unrelated Malay children with genetically confirmed NICCD characterised by an insertion mutation IVS16ins3kb in SLC25A13 gene. All 3 patients presented with prolonged neonatal jaundice which resolved without specific treatment between 5 to 10 months. Of note was the manifestation of a peculiar dislike of sweet foods and drinks. Elevated plasma citrulline was an important biochemical marker. NICCD should be considered in the differential diagnosis of cholestatic jaundice in Malaysian infants regardless of ethnic origin.

Citrin deficiency caused by SLC25A13 gene mutations develops into adult-onset type II citrullinemia (CTLN2) presenting with hepatic encephalopathy. Recent studies have suggested that excessive loading of carbohydrates is harmful in citrin-deficient individuals. Here we report a CTLN2 patient who showed further deterioration of encephalopathy after the employment of conventional low-protein diet therapy for chronic liver failure. Owing to the high carbohydrate content, the conventional low-protein diet therapy should be avoided in patients with hepatic encephalopathy associated with citrin deficiency. In addition, our observation may suggest that carbohydrate-restricted diet in which the content of carbohydrate is below 50% of daily energy intake can have therapeutic efficacy in CTLN2 patients.

Adult-onset type II citrullinemia (CTLN2) is a hereditary metabolic disorder characterized by highly elevated plasma citrulline and ammonia. Recent studies have identified the "citrin gene" (SLC25A13) as the causative gene for CTLN2. Various neurobehavioral symptoms seen in this disease, such as unconsciousness, disorientation, abnormal behavior, and epilepsy, are thought to be caused by encephalopathy mostly due to hyperammonemia. A 47-year-old woman presented with repeated unconsciousness and abnormal behavior. The high plasma anmonia level was not always associated with her neurobehavioral symptoms (unconsciousness, disorientation, abnormal behavior, and epilepsy), but paroxysmal EEG discharges were invariably associated with these symptoms. Her symptoms and abnormal EEG discharges were sometimes treated with diazepam simultaneously. Based on these findings, we considered that her symptoms were caused by nonconvulsive status epilepticus (NCSE). Until date, neurobehavioral symptoms of CTLN2 are considered to be caused by hyperammonemia or other metabolic factors. We suggest that encephalopathy of CTLN2 is caused not only by hyperammonemia but also by NCSE. Therefore, repeated EEG monitoring is recommended in the follow up of patients with CTLN2.

Neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) shows diverse metabolic abnormalities such as urea cycle dysfunction together with citrullinemia, galactosemia, and suppressed gluconeogenesis. Such abnormalities apparently resolve during the first year of life. However, metabolic profiles of the silent period remain unknown. We analyzed oxidative stress markers and profiles of amino acids, carbohydrates, and lipids in 20 asymptomatic children with aspartate/glutamate carrier isoform 2-citrin-deficiency aged 1-10 years, for whom tests showed normal liver function. Despite normal plasma ammonia levels, the affected children showed higher blood levels of ornithine (p<0.001) and citrulline (p<0.01)--amino acids involved in the urea cycle--than healthy children. Blood levels of nitrite/nitrate, metabolites of nitric oxide (NO), and asymmetric dimethylarginine inhibiting NO production from arginine were not different between these two groups. Blood glucose, galactose, pyruvate, and lactate levels after 4-5h fasting were not different between these groups, but the affected group showed a significantly higher lactate to pyruvate ratio. Low-density and high-density lipoprotein cholesterol levels in the affected group were 1.5 times higher than those in the controls. Plasma oxidized low-density lipoprotein apparently increased in the affected children; their levels of urinary oxidative stress markers such as 8-hydroxy-2'-deoxyguanosine and acrolein-lysine were significantly higher than those in the controls. Results of this study showed, even during the silent period, sustained hypercitrullinemia, hypercholesterolemia, and augmented oxidative stress in children with citrin deficiency.

Adult-onset type II citrullinemia (CTLN2) is a rare disorder of the urea cycle resulting in hyperammonemia, with a poor prognosis. Here we report a 48-year-old Japanese man who showed abnormal nocturnal behavior. Laboratory data indicated raised plasma concentrations of ammonia and citrulline, and a definitive diagnosis of CTLN2 was made by DNA analysis. Hyperammonemia was not improved by oral intake of branched-chain amino acids (BCAA), whereas venous infusion of BCAA was effective. Western blotting revealed heterozygotic expression of citrin protein in a liver biopsy specimen from the patient's brother. However, as symptomatic CTLN2 is very unusual in a heterozygotic carrier, we considered the brother suitable as a living-donor liver transplantation (LDLT) donor. The recipient's entire liver was removed, and replaced with the left liver graft. The plasma ammonia level remained low without infusion of BCAA after liver transplantation. From this case we conclude that venous infusion, rather than oral administration, of BCAA is useful for conservative treatment of CTLN2. However, liver transplantation is the only effective therapeutic option for CTLN2, and should be performed before irreversible encephalopathy occurs. Use of a graft from heterozygotic donors is permissible treatment for CTLN2.

Background/aims: Citrin deficiency caused by SLC25A13 gene mutations develops into adult-onset type II citrullinemia (CTLN2) and may be accompanied with hepatic steatosis and steatohepatitis. As its clinical features remain unclear, we aimed to explore the characteristics of fatty liver disease associated with citrin deficiency., Methods: The prevalence of hepatic steatosis in 19 CTLN2 patients was examined, and clinical features were compared with those of non-alcoholic fatty liver disease (NAFLD) patients without known SLC25A13 gene mutations., Results: Seventeen (89%) CTLN2 patients had steatosis, and 4 (21%) had been diagnosed as having NAFLD before appearance of neuropsychological symptoms. One patient had steatohepatitis. Citrin deficiency-associated fatty livers showed a considerably lower prevalence of accompanying obesity and metabolic syndrome, higher prevalence of history of pancreatitis, and higher serum levels of pancreatic secretory trypsin inhibitor (PSTI) than fatty livers without the mutations. Receiver operating characteristic curve analyses revealed that a body mass index < 20kg/m(2) and serum PSTI>29ng/mL were associated with citrin deficiency., Conclusions: Patients presenting with non-alcoholic fatty liver unrelated to obesity and metabolic syndrome might have citrin deficiency, and serum PSTI may be a useful indicator for distinguishing this from conventional NAFLD.

We report a 50-year-old male patient with primary liver carcinoma exhibiting dual hepatocellular and biliary epithelial differentiations associated with citrin deficiency (asymptomatic adult-onset type II citrullinemia, CTLN2). Although so far 14 CTLN2 patients with hepatocellular carcinoma have been reported, this report describes a unique case of liver carcinoma showing the features of both hepatocellular and cholangiocellular carcinoma. In addition to the clinical data of the 14 patients reported previously, the findings in our patient suggest that the citrin deficiency might be one of the key disorders causing hepatocellular carcinoma especially at younger ages and can also play an important role in hepatocarcinogenesis of the hepatic progenitor cells, which have the bipotential to differentiate into both hepatocytes and cholangiocytes.

Objective: Neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD, MIM#605814) is an inherited metabolic disease resulting from mutations of the gene SLC25A13, which encodes citrin, a liver-type mitochondrial aspartate-glutamate carrier. Mutation analysis is necessary for definitive diagnosis of NICCD patients. So far (March, 2007), 36 kinds of mutation, including 7 nonsense, 10 missense, 11 abnormal splicing, 4 insertion and 4 deletion, have been identified by Kobayashi's group, who cloned the gene in Kagoshima, Japan. To date, most of the NICCD patients reported in the world are Japanese. This study aimed to explore the gene diagnosis procedure of two known SLC25A13 mutations in a pedigree with an NICCD patient from China., Methods: DNA was extracted from dried blood spots collected with filter papers from the proband and other 9 members in a NICCD pedigree from China, and then PCR amplification and agarose gel electrophoresis were performed, revealing two mutations preliminarily, which were further proved by Genescan, a procedure established in our laboratory already. Furthermore, the positions and characteristics of the mutations were finally confirmed by DNA sequencing., Results: The proband is a compound heterozygote of two mutations, 851-854del in exon 9 and 1638-1660dup in exon 16 of SLC25A13 gene. His mother and brother carry the former mutation, which predicts a frameshift and introduction of a stop codon at position 286, while his father, one aunt and her son carry the latter, resulting in a frameshift at codon 554, and introducing a stop codon at position 570., Conclusion: A deletion mutation 851-854del in exon 9 and an insertion mutation 1638-1660dup in exon 16 of SLC25A13 gene were identified in the pedigree, providing reliable evidences for both diagnostic confirmation of the patient and the genetic counseling from other members in the pedigree.

Hepatic myelopathy is a rare neurological complication in patients with chronic liver failure and most patients who suffered from this disorder were demonstrated to have portal-systemic shunt. A 31-year-old man who was diagnosed as having adult-onset type II citrullinemia (CTLN2) and had a six-year history of recurrent hepatic encephalopathy showed progressive spastic paraparesis with no involvement of sensation and sphincter function. Examinations of cerebrospinal fluid and spinal MRI were normal. He suddenly died of acute exacerbation of hepatic encephalopathy with severe brain edema. The pathology of the spinal cord disclosed a localized degeneration of both lateral columns, the lesion being more remarkable in the lower segments of the cord. These clinical and pathological findings of hepatic myelopathy have not been noted in the many patients with CTLN2 previously reported, and our patient is unique in developing hepatic myelopathy without porto-caval shunting. Thus, repeated attacks of encephalopathy with hyperammonemia might secondarily have induced the myelopathy in this patient.

Citrin deficiency causes autosomal recessive disorders including adult-onset type II citrullinemia (CTLN2) and neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD). The responsive gene of citrin deficiency, SLC25A13, locates on chromosome 7q21.3 and encodes citrin as a liver-type mitochondrial aspartate/glutamate carrier (AGC). The mutations on SLC25A13 will result in deficiency of citrin and CTLN2 or NICCD. Citrin deficiency was found at first in Japan. However, recently, some of cases were identified in China, Korea, Vietnam, Israel, Czech, United States and England, and racial differences of the SLC25A13 mutations were found, suggesting the patients with citrin deficiency maybe exist worldwide. In this article, authors reviewed the progresses in the study on citrin deficiency up to now and put forward authors' considerations for further research on it.

Background/aims: Mutations in SLC25A13, encoding the mitochondrial aspartate-glutamate carrier citrin, cause adult-onset type II citrullinemia (CTLN2) in humans. We have previously reported that although citrin-knockout (Ctrn-/-) mice fail to display symptoms of CTLN2, liver perfusion revealed a deficit in ureogenesis from ammonia accompanied by an increase in the perfusate lactate-to-pyruvate (L/P) ratio. The present study explores the effects of pyruvate, aspartate and citrate on improving the abnormalities observed in the Ctrn-/- liver., Methods: We measured the rate of ureogenesis from ammonium chloride using the liver-perfusion system., Results: Pyruvate infusion lowered the L/P ratio and corrected the deficit in ureogenesis in the Ctrn-/- liver. This effect was found to be dose-dependent in both instances. Phenazine methosulfate, a cytosolic oxidant, also improved the rate of ureogenesis in the Ctrn-/- liver and led to a fall in the L/P ratio. The addition of aspartate or citrate did not change either the rate of ureogenesis or the L/P ratio in the Ctrn-/- liver., Conclusions: Citrin deficiency disturbs urea synthesis primarily as a result of an elevated cytosolic NADH/NAD+ ratio owing to limited reoxidation of reducing equivalents. Clinically, pyruvate may have a therapeutic benefit for CTLN2 patients.

Background: Adult-onset type II citrullinemia (CTLN2) is an autosomal recessive disorder caused by mutations of SLC25A13 gene encoding citrin and is characterized by recurrent encephalopathy with hyperammonemia. Factors affecting disease progression remain unknown. We report a case with CTLN2, whose clinical course was rapidly worsened by the administration of Glyceol, a hyperosmotic diuretic solution consisting of 10% glycerol and 5% fructose in saline., Case Report: A 34-year-old man was admitted in coma after repeated episodes of altered consciousness. His plasma ammonia level was markedly elevated without any evidence of liver diseases. Brain MRI revealed high signal intensities at the bilateral cingulate gyri and insular cortices, suggesting hepatic encephalopathy. We administered Glyceol. intravenously to alleviate brain edema, however, he developed intractable seizures along with steep increase in plasma ammonia levels (from 808 to 2210 microg/dL) and died. The diagnosis of CTLN2 was confirmed by elevations of plasma citrulline level (384.3 nmol/mL; normal 17-43 nmol/mL) and serum pancreatic secretory trypsin inhibitor (PSTI) (110 ng/mL; normal 4.6-12.2 ng/mL), decrease in hepatic argininosuccinate synthetase activity (5.5% of control), lack of hepatic citrin protein expression and mutations in SLC25A13 gene (compound heterozygote with S225X and Ex1-1G>A)., Conclusions: Physicians should take CTLN2 into consideration as a differential diagnosis in Asian patients with a history of repeated unconsciousness with hyperammonemia and use D-mannitol but not glycerol to treat brain edema in patients with CTLN2.

Adult onset type II citrullinemia (CTLN2) is an autosomal recessive disease accompanied with hyperammonemia and a sudden onset of psychiatric disorders. We demonstrated three male patients with CTLN2 having a liver histology of non-alcoholic steatohepatitis (NASH). Patients with NASH were analyzed for the causative gene of CTLN2, SLC25A13 and discussed.

Unlabelled: Classical citrullinaemia is caused by the inherited deficiency of argininosuccinate synthetase. Although varying degrees of liver involvement have been observed in urea cycle defects, including classical citrullinaemia, the co-existence of liver failure in a patient heterozygous for the disease has not been reported before. A female infant was investigated to find out the aetiology of early infantile liver failure. She was later found to be a heterozygote for the G390R mutation found in severe citrullinaemia patients., Conclusion: Classical citrullinaemia is a phenotypically heterogeneous disease, and observations for signs of its presence should be made even in heterozygotes.

Objective: We report a risk of worsening of encephalopathy by glycerol infusion when this osmotic agent is used for the treatment of brain edema in patients with adult-onset type II citrullinemia (CTLN2) caused by citrin deficiency., Patients and Methods: We performed a retrospective investigation of 3 patients with CTLN2 treated for brain edema at our institute: a 31-year-old male patient and a 40-year-old female patient received treatment for encephalopathy-related brain edema with 10% glycerol infusion and 20% D-mannitol, and a 40-year-old male patient received only 20% D-mannitol infusion. In addition, we also performed a retrospective study in 11 CTLN2 patients reported previously (8 patients treated with 10% glycerol, 2 treated with 10% glycerol and 20% mannitol, and 1 treated with 20% mannitol)., Results: The 12 patients treated with 10% glycerol, including 2 of our patients, died due to rapidly deteriorating encephalopathy and brain edema. On the other hand, the 2 patients who received only 20% D-mannitol, including one of our patients, recovered with the disappearance of brain edema., Conclusion: In CTLN2 patients, glycerol infusion seems to be associated with exacerbation of encephalopathy itself and only mannitol should be used for the treatment of brain edema in patients with this disorder.

Deficiency of citrin, a liver-type mitochondrial aspartate-glutamate carrier (AGC), encoded by the SLC25A13 gene on chromosome 7q21.3, causes autosomal recessive disorders: adult-onset type II citrullinemia (CTLN2) and neonatal hepatitis associated with intrahepatic cholestasis (NICCD). So far, we have described 12 SLC25A13 mutations: 11 were from Japan and one from Israel. Three mutations found in Chinese and Vietnamese patients were the same as those in Japanese patients. In the present study, we identified a novel mutation IVS6+1G>C in a Japanese CTLN2 patient and widely screened 12 SLC25A13 mutations found in Japanese patients in control individuals from East Asia to confirm our preliminary results that the carrier frequency was high in Asian populations. Mutations 851-854del and 1638-1660dup were found in all Asian countries tested, and 851-854del associated with 290-haplotype in microsatellite marker D7S1812 was especially frequent. Other mutations frequently detected were IVS11+1G>A in Japanese and Korean, S225X in Japanese, and IVS6+5G>A in Chinese populations. We found a remarkable difference in carrier rates in China (including Taiwan) between north (1/940) and south (1/48) of the Yangtze River. We detected many carriers in Chinese (64/4169 = 1/65), Japanese (20/1372 = 1/69) and Korean (22/2455 = 1/112) populations, suggesting that over 80,000 East Asians are homozygotes with two mutated SLC25A13 alleles.

Deficiency of citrin due to mutations of the SLC25A13 gene causes adult-onset type II citrullinemia (CTLN2) and one type of neonatal intrahepatic cholestasis (NICCD). About half of the NICCD patients are detected based on high galactose, phenylalanine, and/or methionine concentrations on newborn mass screening (NMS). To clarify the perinatal and neonatal effects and the inconsistent results on NMS, we examined aminograms, the levels of bile acids and galactose in dried blood spots for NMS from 20 patients with NICCD. Birth weight was low for gestational age (-1.4 +/- 0.7 SD). Affected fetuses may have suffered intrauterine citrin deficiency. The first abnormality detected after birth was citrullinemia, and 19 of 20 patients had citrulline levels higher than +2 SD of controls. Tyrosine, phenylalanine, methionine, galactose, and bile acids were less affected than citrulline on d 5 after birth. Galactose and bile acids levels were increased at 1 mo in comparison with d 5 after birth due to impairment of the cytosolic NADH reducing-equivalent supply into mitochondria of hepatocytes. Patients with negative findings on NMS had low levels of total 20 amino acids. Citrulline/serine, citrulline /leucine plus isoleucine, and citrulline/total amino acids ratios, controlled for the confounding effect of low amount of total amino acids, were higher in all patients than +2 SD, +2 SD, and +3 SD of controls, respectively. NMS for citrin deficiency (frequency of homozygote with SLC25A13 mutation: 1/10,000-1/38,000 in East Asia) will be useful for clarification of the clinical course, treatment, and prevention of this disease.

We report the clinical and biochemical data on a second successful pregnancy in a woman with citrullinemia due to argininosuccinate synthetase deficiency (CTLN1). Despite very elevated plasma and urine citrulline and little or no measurable argininosuccinate synthetase enzyme activity on cultured skin fibroblasts, this 29-year-old woman, who was identified through newborn screening, has remained asymptomatic throughout her life. Mutation analysis has recently revealed that she is a compound heterozygote for a known and a novel mutation (IVS15-1G > C and K310Q, respectively). Many newborn screening programs have recently been expanded to include citrullinemia and numerous asymptomatic hypercitrullinemic infants and children have been identified. It is now important to define prognostic indicators that will help with treatment decisions and genetic counseling for these patients. This patient, as the only citrullinemic adult who has been followed prospectively, contributes important information in this regard. In addition, her child was unaffected by the high citrulline levels demonstrated in amniotic fluid and breast milk suggesting that citrulline is not teratogenic. Although pregnancy is an important risk factor for women with CTLN1, it appears that females with citrullinemia can have normal pregnancy outcomes, as long as metabolic crisis is avoided.

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.

More than 20 patients with adult-onset type II citrullinemia have undergone liver transplantation, showing dramatic therapeutic effects. In Japan, living donor liver transplantation is the standard technique of liver transplantation because of the rare availability of cadaveric donors. The feasibility of auxiliary partial orthotopic liver transplantation (APOLT) for adult-onset type II citrullinemia to overcome the problem of a small-for-size graft in living donor liver transplantation has not been defined. We recently performed APOLT for patients with type II citrullinemia. Here, we present 2 patients: patient 1 was a 32-year-old man and patient 2 was a 43-year-old woman. Both patients suffered from hepatic encephalopathy, and laboratory data showed highly elevated plasma levels of ammonia and citrulline. In patient 1, the liver graft was obtained from a patient with familial amyloid polyneuropathy as a domino liver transplant. In patient 2, APOLT was performed after graft donation from her husband. The postoperative clinical courses of both patients were uneventful, and the neurological symptoms were completely resolved. The plasma concentrations of ammonia and citrulline normalized rapidly in both patients. APOLT can provide an adequate hepatocyte mass to correct the underlying enzyme deficiency in adult patients with type II citrullinemia. In addition, APOLT can be carried out safely to overcome the limitation of graft volume in living donor liver transplantation.

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.

Deficiency of citrin encoded by SLC25A13 causes adult-onset type II citrullinemia (CTLN2) and idiopathic neonatal hepatitis (NICCD). So far we have diagnosed 126 (3) CTLN2 and 103 (4) NICCD patients in Japan (and other countries). From preliminary population analysis of the known nine SLC25A13 mutations, we found that the carrier frequency is high in China (1/79), Taiwan (1/98), and Korea (1/50) as well as Japan (1/69), suggesting that many patients with citrin deficiency exist in East Asia.

A 40-year-old woman was admitted with altered consciousness and hyperammonemia after she had delivered her first baby. DNA analysis of the citrin gene and enzymatic assay of argininosuccinate synthetase in the liver led to a diagnosis of adult-onset type II citrullinemia (CTLN2). She was also found to have hepatocellular carcinoma (HCC) and underwent palliative surgery consisting of partial liver section of the HCC. Delivery may be a trigger for the development of CTLN2, while certain pathologic conditions associated with citrin gene abnormality are likely to induce hepatocellular carcinoma in patients with this disorder.

Classical citrullinemia (CTLN1), a rare autosomal recessive disorder, is caused by mutations of the argininosuccinate synthetase (ASS) gene, localized on chromosome 9q34.1. ASS functions as a rate-limiting enzyme in the urea cycle. Previously, we identified 32 mutations in the ASS gene of CTLN1 patients mainly in Japan and the United States, and to date 34 different mutations have been described in 50 families worldwide. In the present study, we report ASS mutations detected in 35 additional CTLN1 families from 11 countries. By analyzing the entire coding sequence and the intron-exon boundaries of the ASS gene using RT-PCR and/or genomic DNA-PCR, we have identified 16 novel mutations (two different 1-bp deletions, a 67-bp insertion, and 13 missense) and have detected 12 known mutations. Altogether, 50 different mutations (seven deletion, three splice site, one duplication, two nonsense, and 37 missense) in 85 CTLN1 families were identified. On the basis of primary sequence comparisons with the crystal structure of E. coli ASS protein, it may be concluded that any of the 37 missense mutations found at 30 different positions led to structural and functional impairments of the human ASS protein. It has been found that three mutations are particularly frequent: IVS6-2A>G in 23 families (Japan: 20 and Korea: three), G390R in 18 families (Turkey: six, U.S.: five, Spain: three, Israel: one, Austria: one, Canada: one, and Bolivia: one), and R304W in 10 families (Japan: nine and Turkey: one). Most mutations of the ASS gene are "private" and are distributed throughout the gene, except for exons 5 and 12-14. It seems that the clinical course of the patients with truncated mutations or the G390R mutation is early-onset/severe. The phenotype of the patients with certain missense mutations (G362V or W179R) is more late-onset/mild. Eight patients with R86H, A118T, R265H, or K310R mutations were adult/late-onset and four of them showed severe symptoms during pregnancy or postpartum. However, it is still difficult to prove the genotype-phenotype correlation, because many patients were compound heterozygotes (with two different mutations), lived in different environments at the time of diagnosis, and/or had several treatment regimes or various knowledge of the disease., (Copyright 2003 Wiley-Liss, Inc.)

Unlabelled: Adult-onset type II citrullinaemia, caused by deficiency of the citrin protein encoded by the SLC25A13 gene, is characterised by a liver-specific argininosuccinate synthetase deficiency. DNA analysis for citrin deficiency revealed that SLC25A13 mutations are the cause of a particular type of neonatal intrahepatic cholestasis. We retrospectively investigated nine infants with cholestatic jaundice of unknown origin, detected by newborn screening over a period of 17 years, to determine the role of SLC25A13 defects in children. The results of the newborn screening were varied; four neonates were positive for hypermethioninaemia, two for hyperphenylalaninaemia, one for hypergalactosaemia and two for both hypermethioninaemia and hypergalactosaemia. Clinical characteristics of the patients were severe intrahepatic cholestasis, hypercitrullinaemia, and fatty liver. The symptoms resolved in all patients by 12 months of age without special treatment other than nutritional management. Although five patients were lost to follow-up, we detected SLC25A13 mutations in the remaining four patients examined., Conclusion: the differential diagnosis of cholestatic jaundice of unknown origin in infants should therefore include citrin deficiency. In this paper, we stress the importance of newborn screening to detect infants with neonatal intrahepatic cholestasis caused by citrin deficiency.

In a patient with microcephaly, feeding problems and restlessness, moderately increased serum and urine citrulline concentrations were observed. Protein and allopurinol loading did not result in additional indications for a urea cycle defect. The diagnosis of citrullinaemia was made at both the enzyme and DNA level, resulting from a novel mutation in the argininosuccinate synthetase gene. The fact that the patient has not suffered from severe deterioration, and that there were only minor abnormalities in metabolite concentrations, suggests that the argininosuccinate synthetase capacity was less affected in vivo than in vitro. In vitro nuclear magnetic resonance investigation suggested an active acetylation mechanism for citrulline. This case illustrates the importance of performing extensive biochemical and molecular investigations in order to reach a definitive diagnosis, particularly in instances of moderate citrullinaemia.

In an infant who suffered from prolonged icterus and hepatocellular dysfunction we detected an increase of citrulline and dibasic amino acids in plasma and urine. The amino acid levels along with all the abnormal liver tests normalized upon replacing breast-milk by formula feeding; there was no relapse after human milk was tentatively reintroduced. A novel mutation, a approximately 9.5-kb genomic duplication, was identified in the citrin gene (SLC25A13) resulting in the insertion of exon 15. No mutation was detected in the CAT2A specific exon of the SLC7A2 gene which encodes for the liver transporter of cationic amino acids. This is the first report of infantile citrin deficiency in non-Asian patients.

Unlabelled: Adult-onset type 2 citrullinaemia (CTLN2) is caused by a deficiency of the citrin protein encoded by the SLC25A13 gene. Citrin, an aspartate glutamate carrier in mitochondria, is an essential component of the malate-aspartate NADH shuttle. Recently, citrin deficiency has been reported to manifest as neonatal intrahepatic cholestasis. We report here five cases with neonatal intrahepatic cholestasis caused by citrin deficiency. Genetic diagnosis revealed compound heterozygotes of 851del4/IVS11 + 1G-->A in two patients, IVS11 + 1G-->A/E601X, and IVS11 + 1G-->A/unknown in each one patient and homozygote for S225X in one patient. All cases revealed high levels of alpha-fetoprotein, which are not observed in CTLN2 patients. The condition was self-limiting and spontaneously disappeared after 5-7 months of age in four patients. However, one patient developed hepatic dysfunction from the age of 6 months and required a living-related liver transplantation at the age of 10 months. The patient showed complete recovery after transplantation, and now at the age of 3 years, shows normal growth and mental development., Conclusion: we report the first case of neonatal intrahepatic cholestasis caused by citrin deficiency with severe hepatic dysfunction requiring a living-related liver transplantation. Patients with this disorder should be followed up carefully, even during infancy.

A 21-year-old woman was admitted with altered consciousness and hyperammonemia. She was diagnosed as having adult-onset type II citrullinemia (CTLN2) by DNA analysis. The patient had mutations of the SLC25A13 gene, which were compound heterozygotes of 851 del 4 and IVS11+1G>A. CTLN2 has a poor prognosis, in spite of various intensive medications, and we performed a living related partial liver transplantation (LRLT). Over a 2-year follow-up, the patient has been well. CTLN2 can be diagnosed by the DNA analysis and can be treated by LRLT.

We have recently identified SLC25A13 on chromosome 7q21.3 as the gene responsible for adult-onset type II citrullinemia (CTLN2) and found seven mutations in the SLC25A13 gene of CTLN2 patients. Most recently, the SLC25A13 mutations have been detected in neonatal/infantile patients with a type of neonatal hepatitis associated with cholestasis (NICCD). In the present study, we identified a novel mutation, E601X, in the SLC25A13 gene and established multiple DNA diagnosis methods for eight mutations by using a genetic analyzer with GeneScan and the single primer extension procedure (SNaPshot). An additional novel missense mutation (variation), E601K, was detected by SNaPshot analysis and was indistinguishable from the mutation E601X detected by the PCR/RFLP method. Multiple DNA diagnoses for the nine mutations revealed that 100 (male/female: 70/30) out of 115 CTLN2 and 38 (14/24) out of 45 NICCD patients tested were homozygotes or compound heterozygotes. The frequency of homozygotes carrying SLC25A13 mutations in both alleles is estimated to be minimally 1 in 21,000 from carrier detection (18 in 1,315 individuals tested) in the Japanese population. The differences in the gender ratio and in mutation types between CTLN2 and NICCD patients are significant. It is, however, unknown whether all homozygotes with mutated SLC25A13 in both alleles suffer from NICCD, CTLN2, both, or neither., (Copyright 2002 Wiley-Liss, Inc.)

A 40-year-old woman was referred for several episodes of coma lasting from 2 hours to 2 days. She had been on maintenance hemodialysis for polycystic kidney disease for 9 months. Laboratory findings showed high serum levels of ammonia and citrulline, and a diagnosis of adult-onset type II citrullinemia was made. Multiple areas of focal brain edema were shown by magnetic resonance imaging. The clinical manifestations of coma and abnormal behavior were resolved with intensified dialysis (ie, four 5-hour sessions per week with glycerol and continuous ambulatory peritoneal dialysis). No abnormal shadow was present on follow-up magnetic resonance imaging. Such intensified dialysis therapy may be effective for adult-onset type II citrullinemia and may be applicable even in patients who do not have end-stage renal disease if liver transplant is not an option., (Copyright 2002 by the National Kidney Foundation, Inc.)

By using homozygosity mapping and positional cloning, we have shown that adult-onset type II citrullinemia (CTLN2) is caused by mutations of the SLC25A13 gene, which is localized on chromosome 7q21.3 and encodes a mitochondrial solute carrier protein named citrin. So far, we have reported nine mutations, most of which cause loss of citrin, and we have established several methods for DNA diagnosis. These methods have shown that more than 90% of the patients diagnosed as suffering from CTLN2 by enzymatic analysis carry SLC25A13 mutations in both alleles, indicating that CTLN2 is caused by citrin deficiency. Furthermore, by using the same DNA diagnosis methods, we discovered that 70 neonates or infants suffering from a particular type of neonatal hepatitis carry the same SLC25A13 mutations. Since the symptoms of the neonates are different from those of the more severe CTLN2 and usually ameliorate without special treatment, we designated the neonatal disease neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD). We conclude that citrin deficiency causes NICCD in neonates and CTLN2 in adults through the additional effects of genetic or environmental modifiers. Since the function of citrin, together with that of an isoform, aralar, was found to be as a mitochondrial aspartate glutamate carrier, the various symptoms of NICCD and CTLN2 may be understood as caused by defective aspartate export from the mitochondria to the cytosol and defects in the malate aspartate shuttle. It is, however, still difficult to understand the cause of the hepatic deficiency of argininosuccinate synthetase protein in CTLN2.

Aim: To characterize the histological features of the livers of patients with neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD), we studied specimens from 30 patients diagnosed with NICCD by genetically analyzing the SLC25A13 gene. Methods: Liver biopsy specimens were subjected to hematoxylin–eosin, Azan, and Berlin-blue staining. Results: Most specimens showed varying degrees of fibrosis. The degree of inflammation varied among the specimens, with half showing moderate or severe inflammatory changes. Fat deposition in hepatocytes was observed in almost all of the specimens, and severe fatty liver was noted in 20 (67%) of them. There was a mixture of two types of hepatocytes with macrovesicular or microvesicular fat droplets, and cholestasis was observed at a rate of 77%. Hemosiderin deposition, mostly mild and localized in periportal hepatocytes and macrophages in portal areas, was observed in 57% of the specimens. Conclusion: A combination of mixed macrovesicular and microvesicular fatty hepatocytes and the above-described findings, such as fatty liver, cholestasis, necroinflammatory reaction and iron deposition, are almost never observed in other liver diseases in infants and adults. We believe that NICCD is a disease with characteristic hepatopathological features. [ABSTRACT FROM AUTHOR]

Abstract: A deficiency of citrin, which is encoded by the SLC25A13 gene, causes both adult-onset type II citrullinemia (CTLN2) and neonatal intrahepatic cholestasis (NICCD). We analyzed 16 patients with NICCD to clarify the clinical features of the disease. Severe intrahepatic cholestasis with fatty liver was the most common symptom, but the accompanying clinical features were variable, namely; suspected cases of neonatal hepatitis or biliary atresia, positive results from newborn screening, tyrosinemia, failure to thrive, hemolytic anemia, bleeding tendencies and ketotic hypoglycemia. Laboratory data showed elevated serum bile acid levels, hypoproteinemia, low levels of vitamin K-dependent coagulation factors, and hypergalactosemia. Hypercitrullinemia was detected in 11 out of 15 patients examined. Most of the patients were given a lactose-free and/or medium chain triglycerides-enriched formula and lipid-soluble vitamins. The prognosis of the 16 patients is going fairy well at present, but we should observe these patients carefully to see if they manifest any symptom of CTLN2 in the future. [Copyright &y& Elsevier]

Abstract: Citrin is a mitochondrial aspartate–glutamate carrier primarily expressed in liver. Adult-onset type II citrullinemia is caused by mutations in the SLC25A13 gene that encodes for citrin, and patients with this condition do not express citrin. We found apoptotic hepatocytes in one such patient. This finding prompted us to investigate the role of citrin in hepatocyte survival. Knockdown of citrin by a vector-based short-hairpin RNA technique reduced cell viability and induced apoptosis of a hepatocellular carcinoma cell line, Hep3B cells. Caspase-3/7 and caspase-9 were activated, and PARP was cleaved. Citrin knockdown also increased the expression of Bax and Bak, and reduced expression of Bcl-xL and Bcl-2. These alterations resulted in the release of cytochrome c from the mitochondria. Our results indicated that citrin downregulation induces apoptosis of hepatocytes through the mitochondrial death pathway, highlighting the importance of citrin in survival of hepatocytes and maintenance of liver function. [Copyright &y& Elsevier]