Differential effects of low-phenylalanine protein sources on brain neurotransmitters and behavior in C57Bl/6-Pah(enu2) mice

New findings about neuropathological outcomes in the PKU mouse throughout lifespan

Phenylketonuria (PKU, OMIM 261600) is a genetic disorder caused by a deficiency of the hepatic enzyme phenylalanine hydroxylase (PAH). If left untreated, PKU leads to systemic phenylalanine (Phe) accumulation, which can result in irreversible brain damage and intellectual disabilities. In the last 60 years, early and strict dietary restriction of phenylalanine (Phe) intake proved to prevent the severe clinical phenotype of untreated PKU. While the specific mechanisms through which phenylalanine causes brain damage are still poorly understood, preclinical models have been deeply explored to characterize the neurotoxic effect of Phe on neurodevelopmental processes. At the same time, that on the aging brain still needs to be explored. In the brain of untreated PAHEnu2(-/-) mouse, we previously reported a reduction of myelin basic protein (MBP) during postnatal development up to 60 PND. Later in the diseased mouse's life, a spontaneous and persistent restoration of MBP was detected. In this present longitudinal study, ranging from 14 to 540 post-natal days (PND) of untreated PAHEnu2(-/-) mice, we further investigated: a) the long-life consistency of two Phe-related brain metabolic alterations, such as large neutral amino acids (LNAA) and biogenic amine neurotransmitters' depletion; b) the outcome of locomotor functions during the same life span; c) the integrity of myelin as assessed ex vivo by central (hippocampus) and peripheral (extensor digitorum longus-sciatic nerve) action potential conduction velocities. In contrast with the results of other studies, brain Leu, Ile, and Val concentrations were not significantly altered in the brain PAHEnu2(-/-) mouse. On the other hand, 3-O-Methyldopa (3-OMD, a biomarker of L-DOPA), serotonin, and its associated metabolites were reduced throughout most of the considered time points, with consistent reductions observed prevalently from 14 to 60 PND. Normal saltatory conduction was restored after 60 PND and remained normal at the last examination at 360 PND, resulting nonetheless in a persistent locomotor impairment throughout a lifetime. These new findings contribute to laying the foundations for the preclinical characterization of aging in PKU, confirming neurotransmitter defects as consistent metabolic traits. LNAAs have a minor role, if any, in brain damage pathogenesis. Transient myelin synthesis failure may impact brain connectivity during postnatal development but not nervous signal conduction.

Drosophila as a diet discovery tool for treating amino acid disorders

Amino acid disorders (AADs) are a large group of rare inherited conditions that collectively impact one in 6500 live births, often resulting in rapid neurological decline and death during infancy. For several AADs, including phenylketonuria, dietary modification prevents physiological deterioration and ameliorates symptoms. Despite this remarkable potential for treatment success, dietary therapy for most AADs remains largely unexplored. Although animal models have provided novel insights into AAD mechanisms, few have been used for therapeutic diet discovery. Here, we find that of all the animal models, Drosophila is particularly well suited for nutrigenomic disease modelling, having amino acid pathways conserved with humans, exceptional genetic tractability, and the unique availability of a synthetic customisable diet.

Integrated Metabonomic Study on the Relationship between Medicinal Properties and Efficacy of Rehmanniae Radix

Each Chinese medicine has its own properties and effects. However, the close connection between the medicinal properties and the effects of the medicine remains unclear. To export the scientific connection between the medicinal properties and efficacy of Rehmanniae Radix (RR), this study established a model and evaluated the therapeutic effects of RR on cold-heat syndrome to access the properties of RR, and then established a blood-heat syndrome model through the injection of rats with dry yeast combined with anhydrous ethanol. Related biochemical indicators (coagulation factors and central pyrogenic factor) were measured to assess the efficacy of RR. Finally, metabonomic technology was used to study the blood-cooling mechanism of RR from two aspects: medicinal properties and efficacy. The comprehensive results suggest that RR can significantly reduce the rectal temperature of blood-heat syndrome model rats and increase both the expression levels of coagulation factors (TNF-[Formula: see text], IL-1[Formula: see text], and IL-6) and the central pyrogenic factors (c-AMP, PGE-2). RR also cools the blood through regulating arginine, proline, phenylalanine, taurine, hypotaurine, sulfur, glycerophospholipid, primary bile acid metabolic pathways, and the tricarboxylic acid cycle. Therefore, RR plays the role of cooling blood by virtue of its cold property. The medicinal property of RR has a guiding effect on the clinical application. Moreover, the integrated metabolomic approach is a powerful tool for studying the properties and efficacy of Chinese medicine.

The discovery of combined toxicity effects and mechanisms of hexaconazole and arsenic to mice based on untargeted metabolomics

The high detected frequencies of hexaconazole (Hex) and arsenic (As) increased the probabilities of their co-existence in agricultural products. However, the combined toxicity effect and mechanism of action for these two pollutants were still unclear. In this study, an untargeted metabolomics method with ultra high performance liquid chromatography and tandem mass spectrometry (UPLC-MS/MS) was developed to monitor the changes of endogenous metabolites and metabolism pathways in mice liver. Our study revealed that significant differences in metabolomics profiles were observed after Hex, As, and Hex+As exposure for 90 d. Hex exposure altered 54 metabolites and 11 pathways significantly which were mainly lipid-related. For As exposure, 63 metabolites and 9 pathways were affected most of which were amino acid-related. Hex+As induced 93 metabolites changes with 34% was lipids and lipid-like molecules and 22% was organic acids and derivatives. Hex+As exposure shared the pathways that altered by Hex and As indicated that the interaction of Hex and As might be independent action. The results of this study could provide an important insight for understanding the mechanism of combined toxicity for Hex and As and be helpful for evaluating their health risk to human.

A porcine model of phenylketonuria generated by CRISPR/Cas9 genome editing

Phenylalanine hydroxylase-deficient (PAH-deficient) phenylketonuria (PKU) results in systemic hyperphenylalaninemia, leading to neurotoxicity with severe developmental disabilities. Dietary phenylalanine (Phe) restriction prevents the most deleterious effects of hyperphenylalaninemia, but adherence to diet is poor in adult and adolescent patients, resulting in characteristic neurobehavioral phenotypes. Thus, an urgent need exists for new treatments. Additionally, rodent models of PKU do not adequately reflect neurocognitive phenotypes, and thus there is a need for improved animal models. To this end, we have developed PAH-null pigs. After selection of optimal CRISPR/Cas9 genome-editing reagents by using an in vitro cell model, zygote injection of 2 sgRNAs and Cas9 mRNA demonstrated deletions in preimplantation embryos, with embryo transfer to a surrogate leading to 2 founder animals. One pig was heterozygous for a PAH exon 6 deletion allele, while the other was compound heterozygous for deletions of exon 6 and of exons 6-7. The affected pig exhibited hyperphenylalaninemia (2000-5000 μM) that was treatable by dietary Phe restriction, consistent with classical PKU, along with juvenile growth retardation, hypopigmentation, ventriculomegaly, and decreased brain gray matter volume. In conclusion, we have established a large-animal preclinical model of PKU to investigate pathophysiology and to assess new therapeutic interventions.

Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry-Based Metabolomics Reveals Metabolic Alterations in the Mouse Cerebellum During Toxoplasma gondii Infection

Toxoplasma gondii is a protozoan parasite with a remarkable neurotropism. We recently showed that T. gondii infection can alter the global metabolism of the cerebral cortex of mice. However, the impact of T. gondii infection on the metabolism of the cerebellum remains unknown. Here we apply metabolomic profiling to discover metabolic changes associated with T. gondii infection of the mouse cerebellum using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Multivariate statistics revealed differences in the metabolic profiles between the infected and control mouse groups and between the infected mouse groups as infection advanced. We also detected 10, 22, and 42 significantly altered metabolites (SAMs) in the infected cerebellum at 7, 14, and 21 days post infection (dpi), respectively. Four metabolites [tabersonine, arachidonic acid (AA), docosahexaenoic acid, and oleic acid] were identified as potential biomarker or responsive metabolites to T. gondii infection in the mouse cerebellum. Three of these metabolites (AA, docosahexaenoic acid, and oleic acid) play roles in the regulation of host behavior and immune response. Pathway analysis showed that T. gondii infection of the cerebellum involves reprogramming of amino acid and lipid metabolism. These results showcase temporal metabolomic changes during cerebellar infection by T. gondii in mice. The study provides new insight into the neuropathogenesis of T. gondii infection and reveals new metabolites and pathways that mediate the interplay between T. gondii and the mouse cerebellum.

Of mice and men: Plasma phenylalanine reduction in PKU corrects neurotransmitter pathways in the brain

In phenylketonuria (PKU), mutations of the phenylalanine hydroxylase (PAH) gene decrease the ability of PAH to convert phenylalanine (Phe) to tyrosine (Tyr), resulting in Phe accumulation in the blood and brain and disruption of neurotransmitter (NT) biosynthesis and metabolism. The following translational study explored the relationship between pegvaliase-mediated Phe correction in plasma and the NT biosynthesis and metabolism pathway in mice and humans with PKU. Lower plasma Phe levels were associated with normalization of the NT biosynthesis pathway which correlated with an improvement in inattention symptoms in subjects with PKU.

Coexisting lacertid lizard species Podarcis siculus and Podarcis melisellensis differ in dopamine brain concentrations

In the eastern Adriatic, Podarcis siculus, an invasive species, competitively excludes the native Podarcis melisellensis. Monoamine neurotransmitters-serotonin (5HT), dopamine (DA), and noradrenaline (NA)-are implicated in social behavior, and could lie at the basis of the direct behavioral interference of P. siculus with P. melisellensis. To understand the relationship between social behavior and monoamines, as well as the differences in behavior between P. siculus and P. melisellensis, we developed a high-performance liquid chromatography (UV/VIS detection) method with which we were able to reliably measure concentrations of 5HT, DA, and NA in 32 brains of the two lizard species. We observed no statistically significant influence of species, sex, or their interaction on brain NA and 5HT concentrations. Statistically significant influence of species on dopamine levels were recorded, with P. siculus having twice as much dopamine in their brains. Taking into account that a significant aggressive relationship, with P. siculus dominating over P. melisellensis, has been previously observed, and that dopamine directly influences this behavior, the observed differences in dopamine levels could represent a trait in these species and may contribute to the competitive exclusion of P. melisellensis by P. siculus in the eastern Adriatic.

The significant role of educational status in PKU patients: the beneficial effect of psychological support in depression

INTRODUCTION

Classical Phenylketonuria (PKU) is a metabolic disease characterized by high phenylalanine (phe) levels in blood and brain. PKU patients are commonly treated with low phe diet supplemented with amino acid free formula. High Phe levels minimize brain tryptophan concentration, the pressure of serotonin, which is responsible for the appearance of depression symptoms. Both amino acids share the same pathway for entering CNS via BBB. Aimed to determine the effect of psychological support on different education status depressed PKU patients via adherence to their diet.

METHODS

PKU patients (n = 110) were divided into groups according to their education status: Primary school, High school, University degree. All patients were tasted with a Patient Health Questionnaire (PHQ-9) standardized for Greek population. Psychological support was performed in every depressed patient ones per two weeks for three successive months under the same conditions. Phe blood levels were measured before psychological support and every 15-20 days till the end of the study.

RESULTS

Only 2/110 (1.8%) participance had finished Primary school and were healthy. 72/110 (65.5%) High School, out of them 29 were depressed and 36/110 (32.7%) achieved a University degree, only 6 suffered from depression. High phe blood levels were measured in the depressed patients, which dropped near to normal after the end of their psychological support. Referring to depression symptoms, all participance except one presented amelioration of their mood.

CONCLUSIONS

Psychological support is beneficial on depressed PKU patients graduated with High School or University degree via adherence to their special diet.

The Use of Glycomacropeptide in Patients with Phenylketonuria: A Systematic Review and Meta-Analysis

In phenylketonuria (PKU), synthetic protein derived from L-amino acids (AAs) is essential in a low-phenylalanine (Phe) diet. Glycomacropeptide (GMP), an intact protein, is very low in Phe in its native form. It has been modified and adapted for PKU to provide an alternative protein source through supplementation with rate-limiting amino acids (GMP-AAs), although it still contains residual Phe. This review aims to systematically evaluate published intervention studies on the use of GMP-AAs in PKU by considering its impact on blood Phe control (primary aim) and changes in tyrosine control, nutritional biomarkers, and patient acceptability or palatability (secondary aims). Four electronic databases were searched for articles published from 2007 to June 2018. Of the 274 studies identified, only eight were included. Bias risk was assessed and a quality appraisal of the body of evidence was completed. A meta-analysis was performed with two studies with adequate comparable methodology which showed no differences between GMP-AAs and AAs for any of the interventions analysed. This work underlines the scarcity and nature of studies with GMP-AAs interventions. All were short-term with small sample sizes. There is a need for better-designed studies to provide the best evidence-based recommendations.

Large neutral amino acid supplementation as an alternative to the phenylalanine-restricted diet in adults with phenylketonuria: evidence from adult Pah-enu2 mice

Phenylketonuria treatment mainly consists of a phenylalanine-restricted diet but still results in suboptimal neuropsychological outcome, which is at least partly based on cerebral monoamine deficiencies, while, after childhood, treatment compliance decreases. Supplementation of large neutral amino acids (LNAAs) was previously demonstrated in young phenylketonuria mice to target all three biochemical disturbances underlying brain dysfunction in phenylketonuria. However, both its potential in adult phenylketonuria and the comparison with the phenylalanine-restricted diet remain to be established. To this purpose, several LNAA supplements were compared with a severe phenylalanine-restricted diet with respect to brain monoamine and amino acid concentrations in adult C57Bl/6 Pah-enu2 mice. Adult phenylketonuria mice received a phenylalanine-restricted diet, unrestricted diet supplemented with several combinations of LNAAs or AIN-93M control diet for 6 weeks. In addition, adult wild-type mice on AIN-93M diet served as controls. The severe phenylalanine-restricted diet in adult phenylketonuria mice significantly reduced plasma and brain phenylalanine and restored brain monoamine concentrations, while brain concentrations of most nonphenylalanine LNAAs remained subnormal. Supplementation of eight LNAAs was similarly effective as the severe phenylalanine-restricted diet to restore brain monoamines, while brain and plasma phenylalanine concentrations remained markedly elevated. These results provide biochemical support for the effectiveness of the severe phenylalanine-restricted diet and showed the possibilities of LNAA supplementation being equally effective to restore brain monoamines in adult phenylketonuria mice. Therefore, LNAA supplementation is a promising alternative treatment to phenylalanine restriction in adult phenylketonuria patients to further optimize neuropsychological functioning.

Effects of amino acid supplementations on metabolic and physiological parameters in Atlantic cod (Gadus morhua) under stress

The effects of tryptophan (Trp) and phenylalanine (Phe) diet supplementation on the stress and metabolism of the Atlantic cod have been studied. Fish were fed diet supplemented with Trp or Phe or control diet for 1 week. At the end of the feeding trial, fish were subjected to air exposure or heat shock. Following samples of blood, liver and muscle were taken from the fish and were analyzed for stress and metabolic indicators. After an air exposure, plasma cortisol levels in fish fed with Trp and Phe diets were lower compared to the fish fed the control diet. Diets containing both amino acids increased significantly the liver transaminase activities in juvenile cod. During thermal stress, high Trp contents had significant effects on fructose biphosphatase activity though Phe did not. Overall, activities of glucose 6-phosphate dehydrogenase, pyruvate kinase, and phosphofructokinase increased significantly for both amino acid diets. For the thermal stress, fish had the highest values of those activities for the 3Trp diet. Trp content in the diet had significant effects on the transaminase activity in muscle during air stress compared to fish fed control and Phe diets. Muscle alanine transaminase activity for thermal stress in fish fed any diet was not significantly different from the control. Both Trp and Phe supplementations reduced the stress markers in the cod; hence, they could be used as additives for the stress attenuation. However, they also raised the activity of key enzymes in glycolysis and gluconeogenesis, mainly the Trp diets.

Multicompartment analysis of protein-restricted phenylketonuric mice reveals amino acid imbalances in brain

BACKGROUND

The mainstay of therapy for phenylketonuria (PKU) remains dietary protein restriction. Developmental and neurocognitive outcomes for patients, however, remain suboptimal. We tested the hypothesis that mice with PKU receiving protein-restricted diets would reveal disruptions of brain amino acids that shed light on these neurocognitive deficits.

METHOD

Phenylalanine hydroxylase-deficient (PKU) mice and parallel controls (both wild-type and heterozygous) were fed custom diets containing 18, 6, and 4 % protein for 3 weeks, after which tissues (brain, liver, sera) were collected for amino acid analysis profiling.

RESULTS

Phenylalanine (phe) was increased in all tissues (p < 0.0001) of PKU mice and improved with protein restriction. In sera, decreased tyrosine (p < 0.01) was corrected (defined as not significantly different from the level in control mice receiving 18 % chow) with protein restriction, whereas protein restriction significantly increased many other amino acids. A similar trend for increased amino acid levels with protein restriction was also observed in liver. In brain, the effects of protein restriction on large neutral amino acids (LNAAs) were variable, with some deficit correction (threonine, methionine, glutamine) and no correction of tyrosine under any dietary paradigm. Protein restriction (4 % diet) in PKU mice significantly decreased lysine, arginine, taurine, glutamate, asparagine, and serine which had been comparable to control mice under 18 % protein intake.

CONCLUSION

Depletion of taurine, glutamate, and serine in the brain of PKU mice with dietary protein restriction may provide new insight into neurocognitive deficits of PKU.

Cartilaginous Metabolomic Study Reveals Potential Mechanisms of Osteophyte Formation in Osteoarthritis

Osteophyte is one of the inevitable consequences of progressive osteoarthritis with the main characteristics of cartilage degeneration and endochondral ossification. The pathogenesis of osteophyte formation is not fully understood to date. In this work, metabolomic approaches were employed to explore potential mechanisms of osteophyte formation by detecting metabolic variations between extracts of osteophyte cartilage tissues (n = 32) and uninvolved control cartilage tissues (n = 34), based on the platform of ultraperformance liquid chromatography tandem quadrupole time-of-flight mass spectrometry, as well as the use of multivariate statistic analysis and univariate statistic analysis. The osteophyte group was significantly separated from the control group by the orthogonal partial least-squares discriminant analysis models, indicating that metabolic state of osteophyte cartilage had been changed. In total, 28 metabolic variations further validated by mass spectrum (MS) match, tandom mass spectrum (MS/MS) match, and standards match mainly included amino acids, sulfonic acids, glycerophospholipids, and fatty acyls. These metabolites were related to some specific physiological or pathological processes (collagen dissolution, boundary layers destroyed, self-restoration triggered, etc.) which might be associated with the procedure of osteophyte formation. Pathway analysis showed phenylalanine metabolism (PI = 0.168, p = 0.004) was highly correlative to this degenerative process. Our findings provided a direction for targeted metabolomic study and an insight into further reveal the molecular mechanisms of ostophyte formation.

The Behavioral Consequence of Phenylketonuria in Mice Depends on the Genetic Background

To unravel the role of gene mutations in the healthy and the diseased state, countless studies have tried to link genotype with phenotype. However, over the years, it became clear that the strain of mice can influence these results. Nevertheless, identical gene mutations in different strains are often still considered equals. An example of this, is the research done in phenylketonuria (PKU), an inheritable metabolic disorder. In this field, a PKU mouse model (either on a BTBR or C57Bl/6 background) is often used to examine underlying mechanisms of the disease and/or new treatment strategies. Both strains have a point mutation in the gene coding for the enzyme phenylalanine hydroxylase which causes toxic concentrations of the amino acid phenylalanine in blood and brain, as found in PKU patients. Although the mutation is identical and therefore assumed to equally affect physiology and behavior in both strains, no studies directly compared the two genetic backgrounds to test this assumption. Therefore, this study compared the BTBR and C57Bl/6 wild-type and PKU mice on PKU-relevant amino acid- and neurotransmitter-levels and at a behavioral level. The behavioral paradigms were selected from previous literature on the PKU mouse model and address four domains, namely (1) activity levels, (2) motor performance, (3) anxiety and/or depression-like behavior, and (4) learning and memory. The results of this study showed comparable biochemical changes in phenylalanine and neurotransmitter concentrations. In contrast, clear differences in behavioral outcome between the strains in all four above-mentioned domains were found, most notably in the learning and memory domain. The outcome in this domain seem to be primarily due to factors inherent to the genetic background of the mouse and much less by differences in PKU-specific biochemical parameters in blood and brain. The difference in behavioral outcome between PKU of both strains emphasizes that the consequence of the PAH mutation is influenced by other factors than Phe levels alone. Therefore, future research should consider these differences when choosing one of the genetic strains to investigate the pathophysiological mechanism underlying PKU-related behavior, especially when combined with new treatment strategies.

Impaired Neurotransmission in Early-treated Phenylketonuria Patients

Cerebral neurotransmitter (NT) deficiency has been suggested as a contributing factor in the pathophysiology of brain dysfunction in phenylketonuria (PKU), even in early-treated phenylketonuric patients. The study aimed to review dopamine and serotonin status in PKU, and the effect of the impaired neurotransmission. Several mechanisms are involved in the pathophysiology of PKU, primarily characterized by impaired dopamine and serotonin synthesis. These deficits are related to executive dysfunctions and social-emotional problems, respectively, in early treated patients. Blood phenylalanine is the main biomarker for treatment compliance follow-up, but further investigations and validation of peripheral biomarkers may be performed to monitor NT status. The development of new therapies is needed not only for decreasing blood and brain phenylalanine levels but also to improve NT syntheses.

Disruption of phenylalanine hydroxylase reduces adult lifespan and fecundity, and impairs embryonic development in parthenogenetic pea aphids

Phenylalanine hydroxylase (PAH) is a key tyrosine-biosynthetic enzyme involved in neurological and melanin-associated physiological processes. Despite extensive investigations in holometabolous insects, a PAH contribution to insect embryonic development has never been demonstrated. Here, we have characterized, for the first time, the PAH gene in a hemimetabolous insect, the aphid Acyrthosiphon pisum. Phylogenetic and sequence analyses confirmed that ApPAH is closely related to metazoan PAH, exhibiting the typical ACT regulatory and catalytic domains. Temporal expression patterns suggest that ApPAH has an important role in aphid developmental physiology, its mRNA levels peaking at the end of embryonic development. We used parental dsApPAH treatment to generate successful knockdown in aphid embryos and to study its developmental role. ApPAH inactivation shortens the adult aphid lifespan and considerably affects fecundity by diminishing the number of nymphs laid and impairing embryonic development, with newborn nymphs exhibiting severe morphological defects. Using single nymph HPLC analyses, we demonstrated a significant tyrosine deficiency and a consistent accumulation of the upstream tyrosine precursor, phenylalanine, in defective nymphs, thus confirming the RNAi-mediated disruption of PAH activity. This study provides first insights into the role of PAH in hemimetabolous insects and demonstrates that this metabolic gene is essential for insect embryonic development.

Evaluation of trace element and mineral status and related to levels of amino acid in children with phenylketonuria

The aim of the present study was to examine trace elements (Zn, Cu, Mn, Se, Fe, Co, Cr, Ni, Cd, Pb), minerals (Ca, Mg, K), amino acids status in children with phenylketonuria and also whether they were correlated with each other in phenylketonuric patients. It has been found out that the HPA group was significantly lower than the control group with regards to Zn, Se, K, Ca, Mg and Zn/Cr levels (p<0.001, p<0.01, p<0.001, p<0.01, p<0.01 and p<0.001 respectively). In the patients with HPA, significantly strong positive correlations were observed between magnesium and calcium (r=0.791; p=0.001), also, indicates negative significant correlation between the concentrations of magnesium and phenylalanine (r=-0.591; p=0.026). The results of this study showed that, in the HPA group, phenylalanine-Mg relationship found, the presence of disease will in the evaluation of phenylalanine and other amino acids, together with the value of magnesium is required to consider.

Voluntary Exercise Prevents Oxidative Stress in the Brain of Phenylketonuria Mice

BACKGROUND

High phenylalanine levels in phenylketonuria (PKU) have been associated with brain oxidative stress and amino acid imbalance. Exercise has been shown to improve brain function in hyperphenylalaninemia and neurodegenerative diseases. This study aimed to verify the effects of exercise on coordination and balance, plasma and brain amino acid levels, and brain oxidative stress markers in PKU mice.

METHODS

Twenty wild-type (WT) and 20 PAH(enu2) (PKU) C57BL/6 mice were placed in cages with (exercise, Exe) or without (sedentary, Sed) running wheels during 53 days. At day 43, a balance beam test was performed. Plasma and brain were collected for analyses of amino acid levels and the oxidative stress parameters superoxide dismutase (SOD) activity, sulfhydryl and reduced glutathione (GSH) contents, total radical-trapping antioxidant potential (TRAP), and total antioxidant reactivity (TAR).

RESULTS

SedPKU showed poor coordination (p < 0.001) and balance (p < 0.001), higher plasma and brain phenylalanine (p < 0.001), and increased brain oxidative stress (p < 0.05) in comparison to SedWT. ExePKU animals ran less than ExeWT (p = 0.018). Although no improvement was seen in motor coordination and balance, exercise in PKU restored SOD, sulfhydryl content, and TRAP levels to controls. TAR levels were increased in ExePKU in comparison to SedPKU (p = 0.012). Exercise decreased plasma and brain glucogenic amino acids in ExePKU, but did not change plasma and brain phenylalanine in both WT and PKU.

CONCLUSIONS

Exercise prevents oxidative stress in the brain of PKU mice without modifying phenylalanine levels. Hence, exercise positively affects the brain, demonstrating its value as an intervention to improve brain quality in PKU.

Phenylketonuria Pathophysiology: on the Role of Metabolic Alterations

Phenylketonuria (PKU) is an inborn error of phenylalanine (Phe) metabolism caused by the deficiency of phenylalanine hydroxylase. This deficiency leads to the accumulation of Phe and its metabolites in tissues and body fluids of PKU patients. The main signs and symptoms are found in the brain but the pathophysiology of this disease is not well understood. In this context, metabolic alterations such as oxidative stress, mitochondrial dysfunction, and impaired protein and neurotransmitters synthesis have been described both in animal models and patients. This review aims to discuss the main metabolic disturbances reported in PKU and relate them with the pathophysiology of this disease. The elucidation of the pathophysiology of brain damage found in PKU patients will help to develop better therapeutic strategies to improve quality of life of patients affected by this condition.

Glycomacropeptide is a prebiotic that reduces Desulfovibrio bacteria, increases cecal short-chain fatty acids, and is anti-inflammatory in mice

Glycomacropeptide (GMP) is a 64-amino acid (AA) glycophosphopeptide with application to the nutritional management of phenylketonuria (PKU), obesity, and inflammatory bowel disease (IBD). GMP is a putative prebiotic based on extensive glycosylation with sialic acid, galactose, and galactosamine. Our objective was to determine the prebiotic properties of GMP by characterizing cecal and fecal microbiota populations, short-chain fatty acids (SCFA), and immune responses. Weanling PKU (Pah(enu2)) and wild-type (WT) C57Bl/6 mice were fed isoenergetic AA, GMP, or casein diets for 8 wk. The cecal content and feces were collected for microbial DNA extraction to perform 16S microbiota analysis by Ion Torrent PGM sequencing. SCFA were determined by gas chromatography, plasma cytokines via a Bio-Plex Pro assay, and splenocyte T cell populations by flow cytometry. Changes in cecal and fecal microbiota are primarily diet dependent. The GMP diet resulted in a reduction from 30-35 to 7% in Proteobacteria, genera Desulfovibrio, in both WT and PKU mice with genotype-dependent changes in Bacteroidetes or Firmicutes. Cecal concentrations of the SCFA acetate, propionate, and butyrate were increased with GMP. The percentage of stimulated spleen cells producing interferon-γ (IFN-γ) was significantly reduced in mice fed GMP compared with casein. In summary, plasma concentrations of IFN-γ, TNF-α, IL-1β, and IL-2 were reduced in mice fed GMP. GMP is a prebiotic based on reduction in Desulfovibrio, increased SCFA, and lower indexes of inflammation compared with casein and AA diets in mice. Functional foods made with GMP may be beneficial in the management of PKU, obesity, and IBD.

Hippocampal synaptic connectivity in phenylketonuria

In humans, lack of phenylalanine hydroxylase (Pah) activity results in phenylketonuria (PKU), which is associated with the development of severe mental retardation after birth. The underlying mechanisms, however, are poorly understood. Mutations of the Pah gene in Pah(enu2)/c57bl6 mice result in elevated levels of phenylalanine in serum similar to those in humans suffering from PKU. In our study, long-term potentiation (LTP) and paired-pulse facilitation, measured at CA3-CA1 Schaffer collateral synapses, were impaired in acute hippocampal slices of Pah(enu2)/c57bl6 mice. In addition, we found reduced expression of presynaptic proteins, such as synaptophysin and the synaptosomal-associated protein 25 (SNAP-25), and enhanced expression of postsynaptic marker proteins, such as synaptopodin and spinophilin. Stereological counting of spine synapses at the ultrastructural level revealed higher synaptic density in the hippocampus, commencing at 3 weeks and persisting up to 12 weeks after birth. Consistent effects were seen in response to phenylalanine treatment in cultures of dissociated hippocampal neurones. Most importantly, in the hippocampus of Pah(enu2)/c57bl6 mice, we found a significant reduction in microglia activity. Reorganization of hippocampal circuitry after birth, namely synaptic pruning, relies on elimination of weak synapses by activated microglia in response to neuronal activity. Hence, our data strongly suggest that reduced microglial activity in response to impaired synaptic transmission affects physiological postnatal remodelling of synapses in the hippocampus and may trigger the development of mental retardation in PKU patients after birth.