Plasma Phenylalanine Levels Research Articles

Impact of complicated intra-abdominal infection on albumin synthesis rate

To study the impact of complicated intra-abdominal infections on albumin synthesis rate. Eight patients with complicated intra-abdominal infections associated with intestinal fistula were admitted to the Research Institute of General Surgery at the Jinling Hospital between December 2009 and October 2010. Eight healthy volunteers matched for age, sex, and body mass index were enrolled as controls. All the subjects were given a primed, constant infusion of sterile L-[ring-(2)H(5)]-phenylalanine solution (priming dose: 4 μmol/kg, infusion rate: 6 μmol·kg(-1)·min(-1)) via peripheral venous lines in fast state. Arterial blood samples(3 ml) were drawn before and throughout the infusion at hourly intervals. The enrichment of L-[ring-(2)H(5)]-phenylalanine from the plasma free amino acid pool and from albumin were determined by gas chromatography/mass spectrometry analysis. Both plasma total protein concentration(62.2±1.0) g/L and plasma albumin concentration (32.5±4.0) g/L in patients with complicated intra-abdominal infection were lower compared with controls[(74.2±1.7) g/L and (46.1±2.6) g/L, both P<0.05]. Body temperature, neutrophil count and plasma C-reactive protein concentration in patients with infection were significantly greater than the levels in control subjects(P<0.05). Albumin synthesis rate in patients with intra-abdominal infection was significantly lower than that in the control group [(5.3±1.6)%/d and (7.8±1.2)%/d respectively, P<0.05]. The measurement of plasma free amino acid concentration showed that plasma glutamic acid level was greater than that in control subjects, and that plasma phenylalanine and proline levels were lower than those in controls. Complicated intra-abdominal infection inhibits albumin synthesis rate in patients with intestinal fistula, which may partially contribute to the decrease of plasma albumin concentration.

Evaluation of orally administered PEGylated phenylalanine ammonia lyase in mice for the treatment of Phenylketonuria

Phenylketonuria (PKU), a Mendelian autosomal recessive phenotype (OMIM 261600), is an inborn error of metabolism causing impaired postnatal cognitive development in the absence of treatment. We used the Pahenu2/enu2 PKU mouse model to study oral enzyme substitution therapy with various chemically modified formulations of phenylalanine ammonia lyase (Av-p.C503S/p.C565S/p.F18A PAL). In vivo studies with the most therapeutically effective formulation (5kDa PEG-Av-p.C503S/p.C565S/p.F18A PAL) revealed that this conjugate, given orally, yielded statistically significant (p=0.0029) and therapeutically relevant reduction (~40%) in plasma phenylalanine (Phe) levels. Phe reduction occurred in a dose- and loading-dependent manner; sustained clinically and statistically significant reduction of plasma Phe levels was observed with treatment ranging between 0.3 IU and 9 IU and with more frequent and smaller dosings. Oral PAL therapy could potentially serve as an adjunct therapy, perhaps with dietary treatment, and will work independently of phenylalanine hydroxylase (PAH), correcting such forms of hyperphenylalaninemias regardless of the PAH mutations carried by the patient.

Sapropterin hydrochloride: enzyme enhancement therapy for phenylketonuria

Phenylketonuria (PKU) is an inherited disorder of amino acid metabolism caused by deficiency of the enzyme phenylalanine hydroxylase (PAH). Historically PKU was a common genetic cause of severe learning difficulties and developmental delay, but with the introduction of newborn screening and early dietary management, it has become a treatable disease and people born with PKU should now have IQs and achievements similar to their peers. Dietary treatment, however, involves lifestyle changes that pervade most aspects of daily life for an individual and their family. A simple pharmacological treatment for PKU would have a great appeal. Sapropterin hydrochloride is a synthetic form of tetrahydrobiopterin, the cofactor for PAH. A proportion of mutant PAH enzymes show enhanced activity in the presence of pharmacological doses of sapropterin and, for some patients with milder forms of PKU, sapropterin can effectively lower plasma phenylalanine levels. This article discusses the potential place for sapropterin in the management of PKU and how this expensive orphan drug is being integrated into patient care in different healthcare systems.

Introduction of sapropterin dihydrochloride as standard of care in patients with phenylketonuria

Sapropterin dihydrochloride, a synthetic, stable form of the tetrahydrobiopterin cofactor of phenylalanine hydroxylase, has been shown to reduce plasma phenylalanine (Phe) levels in a significant portion of patients with phenylketonuria (PKU). When we undertook introducing this medication to our PKU clinic population, the challenges of recalling and reconnecting with a variably treated and variably compliant patient population became apparent. We offered a trial of sapropterin to all of our clinic patients with PKU. In order to determine responsiveness, we used a two tier dose escalation protocol. After diet records were taken, and baseline plasma Phe levels were established, a 7-day trial of sapropterin at 10 mg/kg/day was started. At day 8, plasma phenylalanine levels were measured. Patients were considered to be responders if they had a 30% reduction in plasma Phe. If they did not respond, the dose of sapropterin was increased to 20 mg/kg/day, and levels were rechecked again in 8 days. Patients who were not responders at this time continued sapropterin for a total of 30 days and had Phe levels checked one last time. Patients who were responders and who were on a Phe-restricted diet underwent gradual liberalization of their diet to the maximum tolerated natural protein intake while still maintaining plasma levels in the acceptable treatment range of 120–360 μmol/L. In our population, 36/39 patients with hyperphenylalaninemia (HPA) who were offered a trial of sapropterin elected to start sapropterin. Five of 36 patients were non-adherent with diet records and/or medication doses and we were unable to determine if they were responders. We were unable to categorize 2 of 31 of the patients who completed the trial as responders due to dietary issues, though they were probably responders. Of the 29 patients who completed the sapropterin trial and we could categorize, 18/29 (62%) were determined to be responders. Patients were classified based on their off-diet diagnostic plasma phenylalanine levels as classical PKU (>1200 μmol/L) and variant PKU (>400 and <1200 μmol/L). The group with variant PKU had a 100% response rate, and patients with classical PKU had a 27% response rate. For the patients in the responder group who were on Phe-restricted diet, we were able to liberalize most diets, in two cases to unrestricted protein intake. We also had unexpected beneficial findings in our clinic experience, including positive behavioral improvements in an adult severely affected by untreated PKU. Even in patients who were not considered to be responders, the introduction of sapropterin provided a tool to reconnect with patients and re-introduce beneficial dietary measures.

Plasma phenylalanine level in dopa‐responsive dystonia

Movement DisordersVolume 24, Issue 15 p. 2289-2290 Letter to the Editor Plasma phenylalanine level in dopa-responsive dystonia† Hiroki Fujioka MD, PhD, Corresponding Author Hiroki Fujioka MD, PhD hfujioka@msic.med.osaka-cu.ac.jp Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, JapanDepartment of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, JapanSearch for more papers by this authorHaruo Shintaku MD, Haruo Shintaku MD Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, JapanSearch for more papers by this authorSatoshi Kudo PhD, Satoshi Kudo PhD Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, JapanSearch for more papers by this authorTsunekazu Yamano MD, Tsunekazu Yamano MD Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, JapanSearch for more papers by this authorHiroki Fujioka MD, PhD, Hiroki Fujioka MD, PhD Osaka City Fukushima-Ward, Public Health and Welfare Center, Fukushima-Ward Office, Osaka, JapanSearch for more papers by this author Hiroki Fujioka MD, PhD, Corresponding Author Hiroki Fujioka MD, PhD hfujioka@msic.med.osaka-cu.ac.jp Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, JapanDepartment of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, JapanSearch for more papers by this authorHaruo Shintaku MD, Haruo Shintaku MD Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, JapanSearch for more papers by this authorSatoshi Kudo PhD, Satoshi Kudo PhD Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, JapanSearch for more papers by this authorTsunekazu Yamano MD, Tsunekazu Yamano MD Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka, JapanSearch for more papers by this authorHiroki Fujioka MD, PhD, Hiroki Fujioka MD, PhD Osaka City Fukushima-Ward, Public Health and Welfare Center, Fukushima-Ward Office, Osaka, JapanSearch for more papers by this author First published: 20 October 2009 https://doi.org/10.1002/mds.22774 † Potential conflict of interest: Hiroki Fujioka received the Grants-in-Aid for Scientific Research by the Ministry of Education, Culture, Sports, Science and Technology of Japan (No. 20790771). Hiroki Fujioka and Haruo Shintaku received Grants-in-Aid for Scientific Research by the Ministry of Education, Culture, Sports, Science and Technology of Japan (No. 17591109). Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume24, Issue1515 November 2009Pages 2289-2290 RelatedInformation

Large neutral amino acids supplementation in phenylketonuric patients

Phenylketonuria is an inborn error of amino acid metabolism that results in severe mental retardation if not treated early and appropriately. The traditional treatment, consisting of a low-phenylalanine diet, is usually difficult to maintain throughout adolescence and adulthood, resulting in undesirable levels of blood phenylalanine and consequent neurotoxicity. The neurotoxicity of phenylalanine is enhanced by its transport mechanism across the blood-brain barrier, which has the highest affinity for phenylalanine compared with the other large neutral amino acids that share the same carrier. The supplementation of large neutral amino acids in phenylketonuric patients has been showing interesting results. Plasma phenylalanine levels can be reduced, which may guarantee important metabolic and clinical benefits to these patients. Although long-term studies are needed to determine the efficacy and safety of large neutral amino acids supplements, the present state of knowledge seems to recommend their prescription to all phenylketonuric adult patients who are non-compliant with the low-phenylalanine diet.

New approaches to the treatment of phenylketonuria.

Phenylketonuria (PKU) is the most common of all aminoacidopathies and is caused by autosomal recessive deficiency of the hepatic phenylalanine hydroxylase system. The diagnosis of PKU should be multifactorial and based on a protein overload test that reveals increased plasma phenylalanine levels during the ingestion of a normal diet, a phenylalanine tolerance test, and in vitro and in vivo activity of the liver enzyme. An individualized diagnosis that characterizes the severity of the disease in each patient provides objective and effective criteria for the dietary treatment of each particular case.

Acrodermatitis Enteropathica‐Like Eruption in Metabolic Disorders: Acrodermatitis Dysmetabolica Is Proposed as a Better Term

Acrodermatitis acidemica is a recently proposed term for the rash that is similar to acrodermatitis enteropathica, which is encountered in organic acidemias. However, acrodermatitis enteropathica-like eruption may be seen in metabolic disorders other than organic acidemias. The aim of this study was to evaluate the clinical features of acrodermatitis enteropathica-like eruption secondary to metabolic disorders. Clinical and demographic features of 12 patients with acrodermatitis enteropathica-like eruption were prospectively evaluated between 2004 and 2006 in this single-center study. Among the 12 patients, underlying metabolic disorders included maple syrup urine disease (n = 5), methylmalonic acidemia (n = 3), phenylketonuria (n = 2), ornithine transcarbamylase deficiency (n = 1), and propionic acidemia (n = 1). Mean age at first presentation was 29.9 months. Mean duration of acrodermatitis enteropathica-like eruption at the time of presentation was 25.2 days. The diaper area was involved in all presentations. Plasma zinc level was measured in 62.5% (n = 10) of the presentations and all had normal levels. All phenylketonuria cases had a low plasma phenylalanine level, and a low plasma isoleucine level was observed in the propionic acidemia case and all maple syrup urine disease cases. The rash responded dramatically to appropriate diet management in all cases. In this study, acrodermatitis enteropathica-like eruption was noted in various metabolic disorders, including organic acidemias. We suggest that acrodermatitis dysmetabolica might be a better term for acrodermatitis enteropathica-like eruption occurring secondary to metabolic disorders other than acquired zinc deficiency.

Disorders of biopterin metabolism

Defects in the metabolism or regeneration of tetrahydrobiopterin (BH4) were initially discovered in patients with hyperphenylalaninaemia who had progressive neurological deterioration despite optimal metabolic control (malignant hyperphenylalaninaemia). BH4 is an essential cofactor not only for phenylalanine hydroxylase, but also for tyrosine and two tryptophan hydroxylases, three nitric oxide synthases, and glyceryl-ether monooxygenase. Defective activity of tyrosine and tryptophan hydroxylases explains the neurological deterioration in patients with BH4 deficiency with progressive mental and physical retardation, central hypotonia and peripheral spasticity, seizures and microcephaly. Five separate genetic conditions affect BH4 synthesis or regeneration: deficiency of GTP cyclohydrolase I, 6-pyruvoyl tetrahydropterin synthase, sepiapterin reductase, dihydropteridine reductase (DHPR) and pterin-4alpha-carbinolamine dehydratase. Only the latter of these conditions is relatively benign and is associated with transient hyperphenylalaninaemia. All these conditions can be identified in newborns by an elevated phenylalanine, with the exception of sepiapterin reductase and the dominant form of GTP cyclohydrolase I deficiency that results in biopterin deficiency/insufficiency only in the brain. Diagnosis relies on the measurement of pterin metabolites in urine, dihydropteridine reductase in blood spots, neurotransmitters and pterins in the CSF and on the demonstration of reduced enzyme activity (red blood cells or fibroblasts) or causative mutations in the relative genes. The outcome of BH4 deficiency is no longer malignant if therapy is promptly initiated to reduce plasma phenylalanine levels and replace missing neurotransmitters. This is accomplished by a special diet and/or BH4 supplements and administration of L-dopa, carbidopa, 5-hydroxytryptophan, and, in certain cases, a MAO-B inhibitor. Patients with DHPR deficiency also require folinic acid supplements, since DHPR may help in maintaining folate in the tetrahydro form. Several patients with BH4 deficiency treated since the newborn period have reached adult age with good outcome.

Carcinogenic Effects in a Phenylketonuria Mouse Model

Phenylketonuria (PKU) is a metabolic disorder caused by impaired phenylalanine hydroxylase (PAH). This condition results in hyperphenylalaninemia and elevated levels of abnormal phenylalanine metabolites, among which is phenylacetic acid/phenylacetate (PA). In recent years, PA and its analogs were found to have anticancer activity against a variety of malignancies suggesting the possibility that PKU may offer protection against cancer through chronically elevated levels of PA. We tested this hypothesis in a genetic mouse model of PKU (PAHenu2) which has a biochemical profile that closely resembles that of human PKU. Plasma levels of phenylalanine in homozygous (HMZ) PAHenu2 mice were >12-fold those of heterozygous (HTZ) littermates while tyrosine levels were reduced. Phenylketones, including PA, were also markedly elevated to the range seen in the human disease. Mice were subjected to 7,12 dimethylbenz[a]anthracene (DMBA) carcinogenesis, a model which is sensitive to the anticancer effects of the PA derivative 4-chlorophenylacetate (4-CPA). Tumor induction by DMBA was not significantly different between the HTZ and HMZ mice, either in total tumor development or in the type of cancers that arose. HMZ mice were then treated with 4-CPA as positive controls for the anticancer effects of PA and to evaluate its possible effects on phenylalanine metabolism in PKU mice. 4-CPA had no effect on the plasma concentrations of phenylalanine, phenylketones, or tyrosine. Surprisingly, the HMZ mice treated with 4-CPA developed an unexplained neuromuscular syndrome which precluded its use in these animals as an anticancer agent. Together, these studies support the use of PAHenu2 mice as a model for studying human PKU. Chronically elevated levels of PA in the PAHenu2 mice were not protective against cancer.

Carcinogenicity of Aspartame in Rats Not Proven

Carcinogenicity of Aspartame in Rats Not Proven

Effects of Sex Steroids on the Neurotransmitter-Specific Aromatic Amino Acids Phenylalanine, Tyrosine, and Tryptophan in Transsexual Subjects

Background/Aims: Phenylalanine, tyrosine and tryptophan are essential aromatic amino acids and precursors of dopamine, norepinephrine, epinephrine and serotonin. The aim of this study was to assess whether sex steroids affect plasma levels of these aromatic amino acids. Methods: 15 male-to-female (M-F) transsexuals were treated with 100 µg/day ethinyl estradiol and 100 mg/day cyproterone acetate, and 14 female-to-male (F-M) transsexuals were treated with testosterone esters 250 mg i.m. per 2 weeks. Plasma levels of hormones and amino acids were measured at baseline and after 4 and 12 months of cross-sex hormone administration, and analyzed by general linear models for repeated measures. Results: Plasma phenylalanine decreased by 7.5% (SD 3.0; p = 0.01); tyrosine by 18.3% (SD 4.6; p < 0.001), and tryptophan by 7.8% (SD 4.7; p = 0.03) after 12 months of estrogen + anti-androgen administration to M-F transsexuals. Administration of testosterone in F-M transsexuals did not induce significant changes in plasma levels of phenylalanine and tyrosine, but increased plasma tryptophan by 18.2% (SD 20.6; p = 0.001). Conclusion: Estrogens and anti-androgens reduce circulating levels of phenylalanine, tyrosine, and tryptophan in men, whereas testosterone administration increases plasma tryptophan levels in women. Sex steroids may influence the availability of neurotransmitter precursors.

Evaluation of neonatal BH4 loading test in neonates screened for hyperphenylalaninemia

Background The outcome in phenylketonuria is related to the early diagnosis and management due to neonatal screening. Aims To assess the interest of tetrahydrobiopterin (BH4) loading test and phenylalanine hydroxylase (PAH) genotyping in the management of neonates with hyperphenylalaninemia (HPA). Study design We evaluate the effectiveness of a BH4 loading test (20 mg/kg) in ten neonates screened for HPA. We evaluated the time required to reach a target plasma Phenylalanine (Phe) level below 300 µmol/l. We compared these ten BH4-loaded patients to the 10 previous neonates non-loaded with BH4. In all these patients, the PAH genotype was determined. Results One loaded patient had biopterin synthesis deficiency and has been retrieved from statistical analysis. All others patients have PAH deficiency. Between the BH4 loaded group (L) and the BH4 non-loaded group (NL), a statistically significant difference was observed in the average time required to reached the target Phe level (13.56 ± 4.30 (L) vs. 20.6 ± 7.59 days (NL) [ p < 0.02]). Results of the genotyping from all but one of these 19 patients indicated that among all mutations present in this patient population, there were 4 known PAH mutations associated with BH4 responsiveness (p.R261Q, the p.V388 M, the p.E390G and the p.Y414C). These mutations were found in 4 non-loaded and 6 loaded patients. Two patients had a more than 90% reduction in their plasma Phe level within 24 h after the load. One of these patients had a PTPS deficiency. The other fully responsive patient (p.Y414C and IVS10-11G > A) has been treated with BH4 from birth with an excellent metabolic control for three years now. Conclusion BH4 loading test improves the management of HPA. It allows an immediate identification of the children fully responsive to BH4. Our results therefore suggest the incorporation of BH4 loading test in the management of neonates screened for HPA.

Treating Phenylketonuria: A Single Centre Experience

Hyperphenylalaninaemia (HPA) is an inherited disorder that results in raised plasma phenylalanine levels with a range of severities, including phenylketonuria (PKU). Since the first attempts at treatment using a low-phenylalanine diet and after more than 50 years of research, considerable progress has been made so we are now at a stage where mental retardation caused by high plasma phenylalanine can be prevented. We must, however, be aware of the new challenges we face in managing PKU. These include: maintaining optimal growth by providing enough phenylalanine without jeopardizing the child's psychomotor development; providing an optimal nutritional status that ensures other essential nutrients, such as long chain polyunsaturated fatty acids, are not excluded from the diet; ensuring optimal compliance to the dietary intervention; and considering patients' quality of life. New strategies, such as tetrahydrobiopterin (BH4) supplementation, need to be evaluated with regard to safety, efficacy and expected outcomes in specific types of HPA.

Noninvasive measurement of phenylalanine by iontophoretic extraction in patients with phenylketonuria

Phenylketonuria is an autosomal recessive disorder characterized by elevated concentrations of phenylalanine. Elevated phenylalanine concentrations can impair intellectual functions and the disease is treated with a lifelong diet and frequent monitoring of plasma phenylalanine concentrations. Previous in vitro studies have demonstrated the feasibility of iontophoretically enhanced transdermal transport of phenylalanine. Here we evaluate the feasibility of transdermal iontophoretic extraction of phenylalanine in vivo. Phenylalanine was iontophoretically extracted from the skin of healthy volunteers and of patients with phenylketonuria for up to 6 h and concentrations were compared with those measured in plasma. The amount of phenylalanine iontophoretically extracted from the skin declined over time, suggesting contribution of phenylalanine from the skin in the initial extraction. Phenylalanine iontophoretically extracted from skin correlated with plasma phenylalanine levels at plasma levels above 300 micromol/L. This correlation supports the feasibility of iontophoretic phenylalanine extraction for monitoring phenylketonuria.

A Novel Approach for Enzyme Replacement Therapy: THE USE OF PHENYLALANINE HYDROXYLASE-BASED FUSION PROTEINS FOR THE TREATMENT OF PHENYLKETONURIA

Metabolic diseases arise from mutations in key enzymes of major metabolic pathways. One promising approach for the treatment of such diseases is based on the administration of a wild-type enzyme to substitute the activity of the impaired enzyme by the use of enzyme replacement therapy, yet it is important to deliver this enzyme to the specific deficient tissue. We suggest a new concept for the treatment of metabolic diseases using fusion proteins. We examined the feasibility of this concept in the well characterized metabolic disease, phenylketonuria (PKU), which results from a mutation in the liver enzyme phenylalanine hydroxylase (PAH). PAH is a key enzyme in the metabolic pathway of phenylalanine. Deficiency in PAH leads to high and persistent levels of this amino acid in the plasma of PKU patients, causing permanent neurological damage. Currently a low protein diet is still considered the only effective treatment for most PKU patients. To restore PAH activity in the liver of PKU patients, we constructed PAH-based fusion proteins with delivery moieties based on the HIV-transactivator of transcription peptide, and fragments of human hepatocyte growth factor aiming to specifically target PAH to the liver. We show that these new fusion proteins can be delivered into a variety of human liver cell lines and retain PAH activity after being internalized. We also show that plasma phenylalanine levels were dramatically lowered in mice treated with PAH-based fusion proteins after intravenous administration. We therefore suggest an alternative concept for the treatment of PKU using targeted fusion proteins, which may also be applied to the treatment of other metabolic diseases.

Fish oil supplements and PKU

For patients with phenylketonuria (PKU), dietary treatment requires a limited natural protein intake and, therefore, a low intake of long-chain omega-3 polyunsaturated fatty acids (LC-PUFA). Despite the restricted phenylalanine intake, patients with PKU have demonstrable neurological deficits and may have impaired specific motor function. The mechanisms behind these less than perfect outcomes may, in part, be related to fluctuations in plasma phenylalanine levels. However, an unintended consequence of the diet may be to induce metabolic imbalance, specifically LC-PUFA deficiencies.

The effects of large neutral amino acid supplements in PKU: An MRS and neuropsychological study

Objective To determine the effects of large neutral amino acid (LNAA) supplements on brain and plasma phenylalanine (Phe) levels and other metabolites in early treated subjects with classical phenylketonuria (PKU), and to investigate the relationship between these metabolites and neuropsychological performance. Methods This was a prospective, double blind, cross over study consisting of four two-week phases with a 4 week washout period. Sixteen subjects (7 males), with classical PKU were recruited into the study and completed all 4 phases. Each phase consisted of either the LNAA supplement or placebo, and either the patient’s usual medical product or not. Subjects were instructed to follow their usual Phe restricted diet, maintain energy intake and complete a 3-day food record during each phase. At the end of each phase, brain Phe and other metabolites were measured by proton magnetic resonance spectroscopy (MRS), and plasma amino acids quantified. A detailed neuropsychological assessment was performed on the same day as the MRS and plasma collection. Results There was no correlation between plasma and brain Phe, but few of the plasma Phe readings were over 1200 μmol/L. Plasma Phe decreased with LNAA supplementation when patients were not taking their medical formula. LNAA supplementation had a specific impact on executive functions particularly in verbal generativity and cognitive flexibility. Measures of attention were better on medical product, with or without LNAA supplements. Conclusions LNAA supplementation was associated with a trend to a lowering of plasma Phe levels. LNAA supplementation had a specific impact on executive functions particularly in verbal generativity and flexibility. For individuals already complying with diet and PKU medical product, additional supplementation with LNAA is of limited value. LNAA supplementation may be of benefit to those unable to comply with PKU medical product by reducing plasma Phe, perhaps by competing with Phe at the level of transport across the gut.

Gene therapy for phenylketonuria mouse model using pseudotyped adeno‐associated virus vector

Phenylketonuria (PKU) is an inherited metabolic disorder caused by a deficiency of phenylalanine hydroxylase. The accumulation of phenylalanine leads to severe mental and psychomotor retardation. Phenylalanine restriction diet can prevent irreversible damage if instituted from birth. Recently, we reported the cognitive outcome of biochemical and phenotypic reversal of PKU mouse model, Pahenu2, by the AAV 2-mediated gene delivery of a human PAH transgene (Pediatr Res 56:–284, 2004). However, the therapeutic effectiveness had been observed only in male PKU mice. No normalization in coat color or plasma phenylalanine level was observed in gene therapy on female PKU mice. In this study, we generated pseudotyped AAV2/8 vector encoding the human PAH gene. The rAAV2/8-hPAH vector was infused into female PKU mice via the hepatic portal vein. Six weeks after injection, the coat color change to black was clearly observed in female PKU as in male. Plasma phenylalanine level in female PKU mice decreased to 120_μM/L. The PAH enzyme activities of treated mouse liver increased to 65–70% of wild-type in female PKU mice, to 90–95% in male PKU mice. These corrections were sustained over 6 month. Furthermore, we observed rAAV2/8-hPAH treated female PKU mice can overcome maternal PKU syndrome. These results indicate that recombinant AAV 2/8 mediated gene therapy can be a useful therapeutic candidate for patients with PKU.

Aspartame: A Safety Evaluation Based on Current Use Levels, Regulations, and Toxicological and Epidemiological Studies

Aspartame is a methyl ester of a dipeptide used as a synthetic nonnutritive sweetener in over 90 countries worldwide in over 6000 products. The purpose of this investigation was to review the scientific literature on the absorption and metabolism, the current consumption levels worldwide, the toxicology, and recent epidemiological studies on aspartame. Current use levels of aspartame, even by high users in special subgroups, remains well below the U.S. Food and Drug Administration and European Food Safety Authority established acceptable daily intake levels of 50 and 40 mg/kg bw/day, respectively. Consumption of large doses of aspartame in a single bolus dose will have an effect on some biochemical parameters, including plasma amino acid levels and brain neurotransmitter levels. The rise in plasma levels of phenylalanine and aspartic acid following administration of aspartame at doses less than or equal to 50 mg/kg bw do not exceed those observed postprandially. Acute, subacute and chronic toxicity studies with aspartame, and its decomposition products, conducted in mice, rats, hamsters and dogs have consistently found no adverse effect of aspartame with doses up to at least 4000 mg/kg bw/day. Critical review of all carcinogenicity studies conducted on aspartame found no credible evidence that aspartame is carcinogenic. The data from the extensive investigations into the possibility of neurotoxic effects of aspartame, in general, do not support the hypothesis that aspartame in the human diet will affect nervous system function, learning or behavior. Epidemiological studies on aspartame include several case-control studies and one well-conducted prospective epidemiological study with a large cohort, in which the consumption of aspartame was measured. The studies provide no evidence to support an association between aspartame and cancer in any tissue. The weight of existing evidence is that aspartame is safe at current levels of consumption as a nonnutritive sweetener.