Moving towards a novel therapeutic strategy for hyperammonemia that targets glutamine metabolism.

Patients with urea cycle disorders intermittently develop episodes of decompensation with hyperammonemia. Although such an episode is often associated with starvation and catabolism, its molecular basis is not fully understood. First, we attempted to elucidate the mechanism of such starvation-associated hyperammonemia. Using a mouse embryonic fibroblast (MEF) culture system, we found that glucose starvation increases ammonia production, and that this increase is associated with enhanced glutaminolysis. These results led us to focus on α-ketoglutarate (AKG), a glutamate dehydrogenase inhibitor, and a major anaplerotic metabolite. Hence, we sought to determine the effect of dimethyl α-ketoglutarate (DKG), a cell-permeable AKG analog, on MEFs and found that DKG mitigates ammonia production primarily by reducing flux through glutamate dehydrogenase. We also verified that DKG reduces ammonia in an NH4 Cl-challenged hyperammonemia mouse model and observed that DKG administration reduces plasma ammonia concentration to 22.8% of the mean value for control mice that received only NH4 Cl. In addition, we detected increases in ornithine concentration and in the ratio of ornithine to arginine following DKG treatment. We subsequently administered DKG intravenously to a newborn pig with hyperammonemia due to ornithine transcarbamylase deficiency and found that blood ammonia concentration declined significantly over time. We determined that this effect is associated with facilitated reductive amination and glutamine synthesis. Our present data indicate that energy starvation triggers hyperammonemia through enhanced glutaminolysis and that DKG reduces ammonia accumulation via pleiotropic mechanisms both in vitro and in vivo. Thus, cell-permeable forms of AKG are feasible candidates for a novel hyperammonemia treatment.

Novel ARG1 variants identified in a patient with arginase 1 deficiency.

We report a case of a 13-year-old boy with arginase 1 deficiency carrying a new variant in ARG1. Sanger sequencing identified the compound heterozygous variants: NM_000045.4: c.365G>A (p.Trp122*)/c.820G>A (p.Asp274Asn). Although not previously reported, the p.Asp274Asn variant is predicted to have strong pathogenicity because it is located in a highly conserved domain in the protein core and arginase activity in the patient was below measurement sensitivity.

Guide for diagnosis and treatment of hyperphenylalaninemia.

IMPORTANCE: Sapropterin hydrochloride, a natural coenzyme (6R-tetrahydrobiopterin) of phenylalanine hydroxylase, was first approved as a treatment for tetrahydrobiopterin deficiency in 1992 in Japan, and was then approved as a treatment for a tetrahydrobiopterin-responsive hyperphenylalaninemia in 2007 and 2008, in the USA and Japan, respectively. Guidelines are required on the proper use of sapropterin hydrochloride for tetrahydrobiopterin-responsive hyperphenylalaninemia. OBSERVATIONS: It is recommended that tetrahydrobiopterin-responsive hyperphenylalaninemia should be diagnosed in all cases of hyperphenylalaninemia, including phenylketonuria, by tetrahydrobiopterin administration tests rather than by phenotype or blood phenylalanine levels. CONCLUSIONS AND RELEVANCE: If tetrahydrobiopterin-responsive hyperphenylalaninemia is diagnosed, all ages can be treated with sapropterin hydrochloride. Although there are reports that sapropterin hydrochloride is effective and safe for the prevention of maternal phenylketonuria, further investigation is required.

Early intervention for late-onset ornithine transcarbamylase deficiency.

We report the case of a family with late-onset ornithine transcarbamylase deficiency (OTCD). Several family members had died from OTCD, and the c.221G>A, p.Lys221Lys mutation was detected at the 3' end of exon 6 of OTC in the X-chromosome of some members. We provided genetic counseling on pregnancy, delivery, and neonate management to a 4th-generation female carrier and decided on metabolic management of her child from birth. Two male patients were diagnosed with late-onset OTCD on the basis of blood amino acid and genetic analysis, and they received arginine supplementation from the asymptomatic, early neonatal period. These children grew and developed normally, without decompensation. Patients with late-onset OTCD can and should be diagnosed and treated in the early neonatal period, especially those from families already diagnosed with late-onset OTCD, and family members must be provided with genetic counseling.

The first Japanese case of the arthrochalasia type of Ehlers-Danlos syndrome with COL1A2 gene mutation.

This is the first report for a Japanese case of arthrochalasia type of Ehlers-Danlos syndrome (EDS). A 46-year-old woman consulted us for joint hypermobility and skin hyperextensibility that had been present soon after birth. There was no family history of a similar disease. She was diagnosed as having bilateral congenital hip dislocation and bilateral habitual shoulder dislocation at her childhood. Her skin was velvety, doughy and hyperextensible. She showed hypermobility of the joints of the hands and feet and generalized joint laxity, with no evidence of scoliosis. Electrophoretic analysis of collagenous proteins revealed the presence of an additional band in the position of pNα2(I) in the sample from culture medium of the patient fibroblasts. Analysis of the α2 chains of type I collagen gene, COL1A2, showed a heterozygous G to T transition at the +1 position of the exon 6 donor splice site (c.279+1G>T). This mutation resulted in skipping of exon 6, which leads to deficient processing of the amino-terminal end of proα2(I) chains of type I collagen. Based on these findings, we made a diagnosis of the arthrochalasia type of EDS, which corresponds to EDS type VIIB in the former classification.

MLL2 and KDM6A mutations in patients with Kabuki syndrome.

Kabuki syndrome is a congenital anomaly syndrome characterized by developmental delay, intellectual disability, specific facial features including long palpebral fissures and ectropion of the lateral third of the lower eyelids, prominent digit pads, and skeletal and visceral abnormalities. Mutations in MLL2 and KDM6A cause Kabuki syndrome. We screened 81 individuals with Kabuki syndrome for mutations in these genes by conventional methods (n = 58) and/or targeted resequencing (n = 45) or whole exome sequencing (n = 5). We identified a mutation in MLL2 or KDM6A in 50 (61.7%) and 5 (6.2%) cases, respectively. Thirty-five MLL2 mutations and two KDM6A mutations were novel. Non-protein truncating-type MLL2 mutations were mainly located around functional domains, while truncating-type mutations were scattered through the entire coding region. The facial features of patients in the MLL2 truncating-type mutation group were typical based on those of the 10 originally reported patients with Kabuki syndrome; those of the other groups were less typical. High arched eyebrows, short fifth finger, and hypotonia in infancy were more frequent in the MLL2 mutation group than in the KDM6A mutation group. Short stature and postnatal growth retardation were observed in all individuals with KDM6A mutations, but in only half of the group with MLL2 mutations.

Fatigue and quality of life in citrin deficiency during adaptation and compensation stage.

Citrin-deficient children and adolescents between adult-onset type II citrullinemia and neonatal intrahepatic cholestasis by citrin deficiency do not have clear clinical features except for unusual diet of high-fat, high-protein, and low-carbohydrate food. The aims of the present study are to characterize fatigue and quality of life (QOL) in citrin-deficient patients during adaptation and compensation stage, and to define the relationship between fatigue and QOL. The study subjects were 55 citrin-deficient patients aged 1-22years (29 males) and 54 guardians. Fatigue was evaluated by self-reports and proxy-reports of the PedsQL Multidimensional Fatigue Scale. QOL was evaluated by the PedsQL Generic Core Scales. Both scale scores were significantly lower in child self-reports (p<0.01 and p<0.05, respectively) and parent proxy-reports (p<0.01 and p<0.01, respectively) than those of healthy children. Citrin-deficient patients with scores of 50 percentile or less of healthy children constituted 67.5% of the sample for the Fatigue Scale and 68.4% for the Generic Core Scales. The PedsQL Fatigue Scale correlated with the Generic Core Scales for both the patients (r=0.56) and parents reports (r=0.71). Assessments by the patients and their parents showed moderate agreement. Parents assessed the condition of children more favorably than their children. The study identified severe fatigue and impaired QOL in citrin-deficient patients during the silent period, and that such children perceive worse fatigue and poorer QOL than those estimated by their parents. The results stress the need for active involvement of parents and medical staff in the management of citrin-deficient patients during the silent period.

An adult patient with mucolipidosis III alpha/beta presenting with parkinsonism.

A 36-year-old man with mucolipidosis type III alpha/beta presented with hypoactivity, mutism, muscle rigidity, and involuntary movement. The involuntary movement was interpreted to be tremor at rest on physical examination and surface electromyography, which revealed mostly asynchronous contractions at 3-4 Hz of the biceps and triceps brachii muscles. All these symptoms were consistent with abnormalities of parkinsonism, which is caused by an insult to the basal ganglia that permeates the entire basal ganglia-thalamocortical circuitry. This report is the first to present a case of mucolipidosis type III alpha/beta in association with parkinsonism.

Coagulopathy in patients with late-onset ornithine transcarbamylase deficiency in remission state: a previously unrecognized complication.

The late-onset type of ornithine transcarbamylase (OTC) deficiency is almost asymptomatic before an abrupt onset of metabolic crisis in adolescence. This study focused on coagulopathy in OTC deficiency. We collected laboratory data regarding coagulation from OTC-deficient patients in Kyushu University Hospital in Japan or from cases reported from previous articles. Five patients with late-onset OTC deficiency, admitted to Kyushu University Hospital at the first metabolic attack or who presented at the outpatient clinic in the hospital, were analyzed, and 3 additional cases of OTC deficiency with coagulopathy in previous articles were included. As a result, the blood ammonia levels in these patients were remarkably high at the time of the metabolic attack, and prothrombin times were far below the normal level. The prothrombin times remained significantly abnormal on remission, despite almost normal levels of blood ammonia, serum aspartate aminotransferase, and alanine aminotransferase. Coagulation abnormality is a previously unidentified complication of OTC deficiency in remission state. This information will aid in the identification of patients with OTC deficiency before a lethal metabolic crisis occurs during adolescence.

Mutant α-galactosidase A with M296I does not cause elevation of the plasma globotriaosylsphingosine level.

Recently, plasma globotriaosylsphingosine (lyso-Gb3) has attracted attention as a biomarker of Fabry disease. However, we found a subset of Fabry disease patients who did not show any increase in the plasma lyso-Gb3 concentration, although other patients exhibited apparent enhancement of it. This subset predominantly exhibited the clinical phenotype of later-onset Fabry disease, and gene analysis revealed that the patients harbored the M296I mutation common to Japanese Fabry patients. This amino acid substitution is predicted to cause a small conformational change on the surface of the α-galactosidase A molecule, resulting in residual enzyme activity. Plasma lyso-Gb3 is a good biomarker of Fabry disease but care should be taken when it is used for a definitive diagnosis.

Long-term outcome and intervention of urea cycle disorders in Japan.

Urea cycle disorders (UCDs) are one of the most frequently inherited metabolic diseases in Japan, with an estimated prevalence of 1 per 50,000 live births. Here, we investigated the clinical manifestations, treatment, and prognosis of 177 patients with UCDs who were evaluated and treated from January 1999 to March 2009. These included 77 cases of neonatal-onset UCDs and 91 cases of late-onset UCDs. The most common UCD was ornithine transcarbamylase deficiency (OTCD), which accounted for 116 out of 177 patients. This result is similar to a previous study performed between 1978 and 1995 in Japan: OTCD accounted for about two-thirds of the total number of UCD cases. We studied the relationship between prognosis and the peak blood ammonia level at the onset in 151 UCD patients. Compared with a previous survey conducted in Japan, we found that a greater number of patients survived without any mental retardation despite their peak blood ammonia levels being greater than 360 µmol/l. The 5-year survival rate of patients with OTCD improved to 86% for those with the neonatal-onset type and to 92% for those with the late-onset type. We hypothesize that the increased survival rate is due to early diagnosis and better treatments that are now available in Japan. It is very important to diagnose and treat UCDs, especially OTCD, when the blood ammonia levels in patients are low. The outcome in patients with low blood ammonia levels was better than that in patients with high blood ammonia levels.

Zinc monotherapy from time of diagnosis for young pediatric patients with presymptomatic Wilson disease.

In 4 young pediatric patients with presymptomatic Wilson disease, we found zinc monotherapy beginning at time of diagnosis to be safe and highly effective for follow-up intervals between 1 and 2 years. Such maintenance therapy with zinc can maintain urinary copper excretion between 1 and 3 µg · kg(-1) · day.

Cross-sectional study of bone metabolism with nutrition in adult classical phenylketonuric patients diagnosed by neonatal screening.

The mechanism underlying the development of osteopenia or osteoporosis in longstanding phenylketonuria (PKU) remains to be clarified. We investigated the details of bone metabolism in 21 female and 13 male classical PKU patients aged 20-35 years. Vitamin D (VD), parathyroid hormone (PTH), bone turnover markers, and daily nutrient intake were examined. The patients had lower daily energy and protein intake than did the age-matched controls (22 women, 14 men), but their respective fat, VD, and calcium intake did not differ. Serum 1,25-dihydroxy VD and 25-hydroxy VD levels in female and male patient groups were significantly higher and lower than those in respective control groups (females, P < 0.001; males, P < 0.05 and P < 0.01, respectively). Serum intact PTH levels were significantly higher in the female patient group (P < 0.05). Urinary calcium levels in the patient groups were significantly higher than those of the control subjects (females, P < 0.001; males, P < 0.05). Bone resorption markers were significantly higher in patients than in controls, although bone formation markers were not different. Patient serum levels of osteoprotegerin-inhibiting bone resorption were significantly lower (females, P < 0.001; males, P < 0.01). None of the bone parameters correlated significantly with serum phenylalanine or nutrient intake. PKU patients exhibited lower VD status and more rapid bone resorption despite normal calcium-VD intakes.

Laronidase replacement therapy improves myocardial function in mucopolysaccharidosis I.

We assessed whether laronidase (recombinant human α-L-iduronidase) replacement therapy could improve left ventricular (LV) myocardial function in a 49-year-old woman with mucopolysaccharidosis I (MPS I) and valvular heart disease. After 6 months of laronidase treatment, the concentration of urinary uron acid decreased by 78.8%. Hepatosplenomegaly improved and LV weight decreased by 19.6%. LV ejection fraction assessed by two-dimensional echocardiogram did not change after laronidase treatment. However, in two-dimensional ultrasound speckle tracking imaging method, LV myocardial longitudinal strain (shortening ratio) increased from -13.2 to -17.4%. LV myocardial radial strain (thickening ratio) increased from 26.6 to 83.4%. LV myocardial torsion increased from +6 to +18°. These indexes of myocardial function were normalized after laronidase treatment. Thus, our findings were a first report that laronidase treatment had a beneficial effect on LV myocardial function in an adult patient with MPS I.

Experimental evidence that phenylalanine is strongly associated to oxidative stress in adolescents and adults with phenylketonuria.

Few studies have looked at optimal or acceptable serum phenylalanine levels in later life in patients with phenylketonuria (PKU). This study examined the oxidative stress status of adolescents and adults with PKU. Forty PKU patients aged over fifteen years were enrolled, and were compared with thirty age-matched controls. Oxidative stress markers, anti-oxidant enzyme activities in erythrocytes, and blood anti-oxidant levels were examined. Nitric oxide (NO) production was also examined as a measure of oxidative stress. Plasma thiobarbituric acid reactive species and serum malondialdehyde-modified LDL levels were significantly higher in PKU patients than control subjects, and correlated significantly with serum phenylalanine level (P<0.01). Plasma total anti-oxidant reactivity levels were significantly lower in the patient group, and correlated negatively with phenylalanine level (P<0.001). Erythrocyte superoxide dismutase and catalase activities were higher and correlated significantly with phenylalanine level (P<0.01). Glutathione peroxidase activity was lower and correlated negatively with phenylalanine level (P<0.001). The oxidative stress score calculated from these six parameters was significantly higher in patients with serum phenylalanine of 700-800 µmol/l. Plasma anti-oxidant substances, beta-carotene, and coenzyme Q(10) were also lower (P<0.001), although the decreases did not correlate significantly with the phenylalanine level. Serum nitrite/nitrate levels, as stable NO products, were higher together with low serum asymmetric dimethylarginine, as an endogenous NO inhibitor. Oxidative stress status is closely linked with serum phenylalanine levels. Phenylalanine level in should be maintained PKU below 700-800 µmol/l even in adult patients.

A long-term survival case of arginase deficiency with severe multicystic white matter and compound mutations.

Neuropathology and neuroimaging of long-term survival cases of arginase deficiency are rarely reported. The magnetic resonance imaging (MRI) of our case showed severe multicystic white matter lesions with cortical atrophy, which were more severe compared with previous reports. In this patient, low-protein diet successfully reduced hyperammonemia, but hyperargininemia persisted. These severe neurological and MRI findings may be explained by a compound heterozygote, inheriting both of severe mutant alleles from her parents.

A familial case of LEOPARD syndrome associated with a high-functioning autism spectrum disorder.

A connection between LEOPARD syndrome (a rare autosomal dominant disorder) and autism spectrum disorders (ASDs) may exist. Of four related individuals (father and three sons) with LEOPARD syndrome, all patients exhibited clinical symptoms consistent with ASDs. Findings included aggressive behavior and impairment of social interaction, communication, and range of interests. The coexistence of LEOPARD syndrome and ASDs in the related individuals may be an incidental familial event or indicative that ASDs is associated with LEOPARD syndrome. There have been no other independent reports of the association of LEOPARD syndrome and ASDs. Molecular and biochemical mechanisms that may suggest a connection between LEOPARD syndrome and ASDs are discussed.

Levothyroxine replacement therapy and refractory hypotension out of transitional period in preterm infants.

BACKGROUND: Recent studies suggest that refractory hypotension from causes other than septicaemia or cardiac failure is common in extremely preterm infants even out of the transitional period. Marked response to low-dose cortisol suggests underlying adrenal insufficiency, although the exact mechanism remains unknown. METHODS: To investigate potential triggers for and related short-term outcomes of early-onset (

Female heterozygotes for the hypomorphic R40H mutation can have ornithine transcarbamylase deficiency and present in early adolescence: a case report and review of the literature.

INTRODUCTION: Ornithine transcarbamylase deficiency is the most common hereditary urea cycle defect. It is inherited in an X-linked manner and classically presents in neonates with encephalopathy and hyperammonemia in males. Females and males with hypomorphic mutations present later, sometimes in adulthood, with episodes that are frequently fatal. CASE PRESENTATION: A 13-year-old Caucasian girl presented with progressive encephalopathy, hyperammonemic coma and lactic acidosis. She had a history of intermittent regular episodes of nausea and vomiting from seven years of age, previously diagnosed as abdominal migraines. At presentation she was hyperammonemic (ammonia 477 µmol/L) with no other biochemical indicators of hepatic dysfunction or damage and had grossly elevated urinary orotate (orotate/creatinine ratio 1.866 µmol/mmol creatinine, reference range <500 µmol/mmol creatinine) highly suggestive of ornithine transcarbamylase deficiency. She was treated with intravenous sodium benzoate and arginine and made a rapid full recovery. She was discharged on a protein-restricted diet. She has not required ongoing treatment with arginine, and baseline ammonia and serum amino acid concentrations are within normal ranges. She has had one further episode of hyperammonemia associated with intercurrent infection after one year of follow up. An R40H (c.119G>A) mutation was identified in the ornithine transcarbamylase gene (OTC) in our patient confirming the first symptomatic female shown heterozygous for the R40H mutation. A review of the literature and correspondence with authors of patients with the R40H mutation identified one other symptomatic female patient who died of hyperammonemic coma in her late teens. CONCLUSIONS: This report expands the clinical spectrum of presentation of ornithine transcarbamylase deficiency to female heterozygotes for the hypomorphic R40H OTC mutation. Although this mutation is usually associated with a mild phenotype, females with this mutation can present with acute decompensation, which can be fatal. Ornithine transcarbamylase deficiency should be considered in the differential diagnosis of unexplained acute confusion, even without a suggestive family history.

Effects of long-term zinc treatment in Japanese patients with Wilson disease: efficacy, stability, and copper metabolism.

Wilson disease is an autosomal recessive disorder with copper metabolism. In Japan, the standard treatment is the administration of copper chelating agents, such as D-penicillamine and trientine. In this study, the authors used zinc acetate to treat Japanese patients with Wilson disease and investigated its efficacy. The 37 patients that comprise this study were found to have Wilson disease using clinical and biochemical tests and were administrated zinc acetate for 48 weeks. The authors followed the clinical symptoms and laboratory findings of the patients by assessing their complete blood counts, biochemical findings, as well as the results of urinalysis and special laboratory tests for copper and zinc metabolism. We also examined side effects of the treatment. Zinc acetate did not aggravate the hepatic or neurological symptoms of any of the patients. Blood biochemical analysis also did not reveal elevation of alanine aminotransferase, aspartate aminotransferase, and γ-glutamyltranspeptidase levels. Zinc treatment did not aggravate the patients' clinical signs and/or laboratory findings. However, it did improve some clinical symptoms of the Wilson disease patients. Although this agent had some side effects, none of them were severe. The authors measured spot urinary copper excretion, which gave an indication of the efficacy of treatment and of the sufficient dosage of zinc. We recommend maintaining a spot urinary copper excretion less than 0.075-µg/mg creatinine. The authors conclude that zinc acetate is an effective and safe treatment for Japanese patients with Wilson disease.