Dietary interventions for phenylketonuria

A highly sensitive colorimetric approach based on tris (bipyridine) Ruthenium (II/III) mediator for the enzymatic detection of phenylalanine

The accurate monitoring of phenylalanine concentration plays a prominent role in the treatment of phenylketonuria (PKU). In this study, we present an enzymatic assay based on Phenylalanine Dehydrogenase/NAD⁺ and tris (bipyridine) Ruthenium (II/III) as a colorimetric mediator for the detection of Phenylalanine concentration. The amount of amino acid was quantitatively recognized by optical absorption measurements at 452 nm through the conversion of Ru (byp)₃ ³⁺ to Ru (byp)₃ ²⁺, which is induced by the neoformed NADH. A detection limit of 0.33 µM, a limit of quantification of 1.01 µM, and a sensitivity of 36.6 a.u nM^-1 were obtained. The proposed method was successfully tested using biological specimens from patients affected by hyperphenylalaninemia. The proposed enzymatic assay showed a high selectivity, making it a promising alternative for the development of versatile assays for the detection of phenylalanine in diluted serums.

Diet therapy in patients with rare diseases: a scoping review

BACKGROUND

This scoping review presents existing research evidence regarding diet therapy in patients with rare diseases (RDs).

METHODS

Using the five-stage scoping review framework proposed by Arksey, O'Malley and Levac, we searched the published literature in PubMed, Web of Science, Royal Society of Chemistry, China National Knowledge Infrastructure, VIP Database and Wan Fang Database from January 2010 to November 2022. We selected diet therapy studies on 121 RDs, as categorised by the National Health Commission of China in 2018. Charts for research analysis were developed and used to categorise the data.

RESULTS

We ultimately included 34 diet therapy studies from 19 countries and territories for 10 RDs and 3 RD groups. RD diet therapy studies have mainly focused on inborn errors of metabolism (92.3%) and are common in Western countries. Most studies focused on diet therapy methods for RDs (44%). In addition, 29% of studies included diet therapy management, 15% included guidelines for diet therapy and 12% included the impact of diet therapy on patients.

CONCLUSIONS

Current diet therapies for RDs lack specificity and present with limited characteristics. Therefore, it is necessary to expand the scope and depth of future research and explore evidence-based recommendations and new diet therapies focused on patient needs and family support to provide a reference for improving the efficacy and safety of diet therapies for RDs.

Nervonic Acid Attenuates Accumulation of Very Long-Chain Fatty Acids and is a Potential Therapy for Adrenoleukodystrophy

Adrenoleukodystrophy (ALD) is an X-linked inherited peroxisomal disorder due to mutations in the ALD protein and characterized by accumulation of very long-chain fatty acids (VLCFA), specifically hexacosanoic acid (C26:0). This can trigger other pathological processes such as mitochondrial dysfunction, oxidative stress, and inflammation, which if involves the brain tissues can result in a lethal form of the disease called childhood cerebral ALD. With the recent addition of ALD to the Recommended Uniform Screening Panel, there is an increase in the number of individuals who are identified with ALD. However, currently, there is no approved treatment for pre-symptomatic individuals that can arrest or delay symptom development. Here, we report our observations investigating nervonic acid, a monounsaturated fatty acid as a potential therapy for ALD. Using ALD patient-derived fibroblasts, we examined whether nervonic acid can reverse VLCFA accumulation similar to erucic acid, the active ingredient in Lorenzo's oil, a dietary intervention believed to alter disease course. We have shown that nervonic acid can reverse total lipid C26:0 accumulation in a concentration-dependent manner in ALD cell lines. Further, we show that nervonic acid can protect ALD fibroblasts from oxidative insults, presumably by increasing intracellular ATP production. Thus, nervonic acid can be a potential therapeutic for individuals with ALD, which can alter cellular biochemistry and improve its function.

Health Related Quality of Life of Caregivers of Children and Adolescents With Phenylketonuria: A Systematic Review

Introduction. Caregivers of children with chronic illness are at risk of having impairment in their quality of life (QOL). We systematically reviewed the available literature related to the Health Related Quality Of Life (HRQOL) of caregivers of children with Phenylketonuria (PKU). Methods. We comprehensively searched in electronic databases including Scopus, Science Direct, CINAHL, Medline, PubMed, Google scholar, and ProQuest. The search criteria included studies with samples more than one, children suffering from PKU, exploring parents or primary caregiver’s HRQOL, published from 2010 to 2020, full article available for download and published in English. Eight studies including 5 cross sectional studies, 1 open label trial, and 2 surveys were systematically reviewed. Results. Seven out of 8 studies have established a negative correlation between PKU and parent’s HRQOL in at least 1 of the domains. In one study, the HRQOL of parents is higher than their population norms. Conclusion. Most of the caregivers had poor to moderate HRQOL. More studies are required to explore HRQOL of caregivers of children with PKU using similar tools and outcome measures addressing all the domains of HRQOL in order to have more clarity on the impact of PKU on caregiver’s HRQOL. Interventional studies might help in improving the HRQOL of caregivers.

Dietary interventions for phenylketonuria

BACKGROUND

Phenylketonuria is an inherited disease treated with dietary restriction of the amino acid phenylalanine. The diet is initiated in the neonatal period to prevent learning disability; however, it is restrictive and can be difficult to follow. Whether the diet can be relaxed or discontinued during adolescence or should be continued for life remains a controversial issue, which we aim to address in this review. This is an updated version of a previously published review.

OBJECTIVES

To assess the effects of a low-phenylalanine diet commenced early in life for people with phenylketonuria. To assess the possible effects of relaxation or termination of the diet on intelligence, neuropsychological outcomes and mortality, growth, nutritional status, eating behaviour and quality of life.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches, handsearches of relevant journals and abstract books of conference proceedings. Most recent search of the Inborn Errors of Metabolism Trials Register: 30 April 2020.

SELECTION CRITERIA

All randomised or quasi-randomised controlled trials comparing a low-phenylalanine diet to relaxation or termination of dietary restrictions in people with phenylketonuria.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study eligibility and methodological quality, and subsequently extracted the data.

MAIN RESULTS

We included four studies in this review (251 participants), and found few significant differences between treatment and comparison groups for the outcomes of interest. Blood phenylalanine levels were significantly lower in participants with phenylketonuria following a low-phenylalanine diet compared to those on a less restricted diet, mean difference (MD) at three months -698.67 (95% confidence interval (CI) -869.44 to -527.89). Intelligence quotient was significantly higher in participants who continued the diet than in those who stopped the diet, MD after 12 months 5.00 (95% CI 0.40 to 9.60). However, these results came from a single study.

AUTHORS' CONCLUSIONS

The results of non-randomised studies have concluded that a low-phenylalanine diet is effective in reducing blood phenylalanine levels and improving intelligence quotient and neuropsychological outcomes. We were unable to find any randomised controlled studies that have assessed the effect of a low-phenylalanine diet versus no diet from diagnosis. In view of evidence from non-randomised studies, such a study would be unethical and it is recommended that low-phenylalanine diet should be commenced at the time of diagnosis. There is uncertainty about the precise level of phenylalanine restriction and when, if ever, the diet should be relaxed. This should be addressed by randomised controlled studies; however, no new studies are expected in this area so we do not plan to update this review.

Quality of life and adherence to treatment in early-treated Brazilian phenylketonuria pediatric patients

Early dietary treatment of phenylketonuria (PKU), an inborn error of phenylalanine (Phe) metabolism, results in normal cognitive development. Although health-related quality of life (HRQoL) of PKU patients has been reported as unaffected in high-income countries, there are scarce data concerning HRQoL and adherence to treatment of PKU children and adolescents from Brazil. The present study compared HRQoL scores in core dimensions of Brazilian early-treated PKU pediatric patients with those of a reference population, and explored possible relationships between adherence to treatment and HRQoL. Early-treated PKU pediatric patient HRQoL was evaluated by self- and parent-proxy reports of the Pediatric Quality of Life Inventory (PedsQL) core scales. Adherence to treatment was evaluated by median Phe levels and percentage of results within the therapeutic target range in two periods. Means for total and core scales scores of PedsQL self- and parent proxy-reports of PKU patients were significantly lower than their respective means for controls. Adequacy of median Phe concentrations and the mean percentage of values in the target range fell substantially from the first year of life to the last year of this study. There was no significant difference in mean total and core scale scores for self- and parent proxy-reports between patients with adequate and those with inadequate median Phe concentrations. The harmful consequences for intellectual capacity caused by poor adherence to dietary treatment could explain the observed decrease in all HRQoL scales, especially in school functioning. Healthcare system and financial difficulties may also have influenced negatively all HRQoL dimensions.

Evidence of Oxidative Stress and Secondary Mitochondrial Dysfunction in Metabolic and Non-Metabolic Disorders

Mitochondrial dysfunction and oxidative stress have been implicated in the pathogenesis of a number of diseases and conditions. Oxidative stress occurs once the antioxidant defenses of the body become overwhelmed and are no longer able to detoxify reactive oxygen species (ROS). The ROS can then go unchallenged and are able to cause oxidative damage to cellular lipids, DNA and proteins, which will eventually result in cellular and organ dysfunction. Although not always the primary cause of disease, mitochondrial dysfunction as a secondary consequence disease of pathophysiology can result in increased ROS generation together with an impairment in cellular energy status. Mitochondrial dysfunction may result from either free radical-induced oxidative damage or direct impairment by the toxic metabolites which accumulate in certain metabolic diseases. In view of the importance of cellular antioxidant status, a number of therapeutic strategies have been employed in disorders associated with oxidative stress with a view to neutralising the ROS and reactive nitrogen species implicated in disease pathophysiology. Although successful in some cases, these adjunct therapies have yet to be incorporated into the clinical management of patients. The purpose of this review is to highlight the emerging evidence of oxidative stress, secondary mitochondrial dysfunction and antioxidant treatment efficacy in metabolic and non-metabolic diseases in which there is a current interest in these parameters.

The personal burden for caregivers of children with phenylketonuria: A cross-sectional study investigating time burden and costs in the UK

INTRODUCTION

Management of phenylketonuria (PKU) is mainly achieved through strict dietary control that aims to limit the intake of phenylalanine (Phe). Adherence to this diet is burdensome due to the need for specially prepared low-Phe meals and regular monitoring of Phe concentrations. A UK cross-sectional study was conducted to identify the personal time and monetary burden associated with aspects of the PKU lifestyle for caregivers of children (aged < 18 years) living with PKU.

METHODS

Caregivers of pediatric patients with PKU attending one of four specialist metabolic centers in the UK were invited to participate in a questionnaire-based survey that evaluated different aspects of PKU management that could potentially present out-of-pocket costs (OOPCs) or time burden. Medical clinicians/dieticians provided patient information on PKU severity and an assessment of blood Phe control.

RESULTS

The survey was completed by 114 caregivers of 106 children having mild or moderate (n = 45; 39%) or classical (n = 60; 53%) PKU (severity data missing for n = 1), among whom 8 (8%) and 87 (82%) reported poorly controlled and controlled blood Phe status, respectively; Phe control data were missing for 11 children. Dietary management of PKU incurred a median time burden of > 19 h per week. OOPCs were incurred via attendance at PKU events, PKU-related equipment, and extra holiday expenditure. 21% of caregivers reduced their working hours (median 18.5 h/week) to care for their child, with a further 24% leaving their paid jobs completely.

DISCUSSION AND CONCLUSIONS

Dietary management of PKU is associated with a considerable time burden for caregivers of pediatric patients with PKU. A personal financial burden also arises from OOPCs and lost earnings.

Health safety aspects of foodstuffs intented for phenylketonurics

Phenylketonuria is a rare metabolic disorder that occurs due to the lack of liver enzyme phenylalanine hydroxylase. Untreated it leads to mental retardation, delayed development of speech, microcephaly, epilepsy, behavioral problems etc. Its treatment consists of strict diet, very low in phenylalanine content. The aim of this study was to determine the health safety and suitability of 17 selected foods labeled as „low in protein" respectively „foods low in phenylalanine". Analyses were focused on their phenylalanine content and aminoacid representation. The other aim was to compare phenylalanine measured with the content declared by the producers on their label. By product origin, the largest amount of foodstuffs originated from Poland (59%), followed by Germany (23%) and equal representation (6%) had Slovakia, Hungary and Sweden. Automatic analyzer AAA 400, using ion exchange chromatography, analyzed the samples. The lowest determined phenylalanine content was 1 mg.100g-1 (in rubber candy) and the highest 299 mg.100g-1 (in paté). Powdered egg alternative was monitored as the second highest source of phenylalanine. Phenylalanine content in the monitored foods ranged from 1 to 299.6 mg. 100 g-1 respectively, and increased in the following order: Gum candies (1 mg.100g-1) < Cherry jelly (1.4 mg. 100g-1) < Flour (5.8 mg.100g-1) < Flour (5.9 mg.100g-1) < Spaghetti (8.7 mg.100g-1) < Pasta (9.9 mg.100g-1) < Waffle (14.2 mg.100g-1) < Salty sticks (23.8 mg.100g-1) < Chocolate (24.1 mg.100g-1) < Bread (26 mg.100g-1) < Breadcrumbs (27.1 mg.100g-1) < Sticks with salt (30.3 mg.100g-1) < Ice Cornets (30.8 mg.100g-1) < Walnut cookie (37.2 mg.100g-1) < Instant soup with noodles (46.1 mg.100g-1) < Powdered egg alternative (58 mg.100g-1) < Pate (299.6 mg.100g-1). Only seven products of 17 observed showed low phenylalanine content, less than 20 mg.100g-1.

A Systematic Review of BH4 (Sapropterin) for the Adjuvant Treatment of Phenylketonuria

CONTEXT

Dietary management is the mainstay of effective treatment in PKU, but dietary restriction is difficult and additional treatment options are needed.

OBJECTIVE

To systematically review evidence regarding sapropterin (BH4) use as an adjunct to dietary restriction in individuals with PKU.

DATA SOURCES

Five databases including MEDLINE up to August 2011.

STUDY SELECTION

Two reviewers independently assessed studies against predetermined inclusion/exclusion criteria.

DATA EXTRACTION

Two reviewers independently extracted data regarding participant and intervention characteristics and outcomes and assigned overall quality and strength of evidence ratings based on predetermined criteria.

RESULTS

BH4 research includes two randomized controlled trials (RCTs) and three uncontrolled open-label trials. Phenylalanine (Phe) levels were reduced by at least 30 % in up to half of treated participants (32-50 %). In one RCT comparing placebo on likelihood of a 30 % reduction in Phe, 9 % of those on placebo achieved this effect, compared with 44 % of the treated group after 6 weeks. Phe tolerance and variability were improved in treated participants in studies assessing those outcomes. No comparative studies assessed long-term outcomes including cognitive effects, nutritional status, or quality of life.

CONCLUSIONS

Adjuvant pharmacologic therapy has the potential to support individuals in achieving optimal Phe levels. BH4 has been shown to reduce Phe levels in some individuals, with significantly greater reductions seen in treated versus placebo groups. The strength of the evidence is moderate for short-term effects on reducing Phe in a subset of initially BH4-responsive individuals, moderate for a lack of significant harms, low for longer-term effects on cognition, and insufficient for all other outcomes.

Carnitine supplementation for inborn errors of metabolism

BACKGROUND

Inborn errors of metabolism are genetic conditions which can lead to abnormalities in the synthesis and metabolism of proteins, carbohydrates, or fats. It has been proposed that in some instances carnitine supplementation should be provided to infants with a suspected metabolic disease as an interim measure, particularly whilst awaiting test results. Carnitine supplementation is used in the treatment of primary carnitine deficiency, and also where the deficiency is a secondary complication of several inborn errors of metabolism, such as organic acidaemias and fatty acid oxidation defects in children and adults.

OBJECTIVES

To assess the effectiveness and safety of carnitine supplementation in the treatment of inborn errors of metabolism.

SEARCH METHODS

We searched the Cystic Fibrosis and Genetic Disorders Group's Inborn Errors of Metabolism Trials Register, the Cochrane Central Register of Controlled Trials (The Cochrane Library 2007, Issue 4) and MEDLINE via Ovid (1950 to July week 4 2007), LILACS (15/05/2008) and Iranmedex (15/05/2008) and also the reference lists of retrieved articles.Date of most recent search of the Group's Inborn Errors of Metabolism Register: 27 October 2011.

SELECTION CRITERIA

Randomised controlled trials and quasi-randomised controlled trials comparing carnitine supplementation (in different dose, frequency, or duration) versus placebo in children and adults diagnosed with an inborn error of metabolism.

DATA COLLECTION AND ANALYSIS

Two authors independently screened and assessed the eligibility of the identified trials.

MAIN RESULTS

No trials were included in the review.

AUTHORS' CONCLUSIONS

There are no published or ongoing randomised controlled clinical trials relevant to this review question. Therefore, in the absence of any high level evidence, clinicians should base their decisions on clinical experience and in conjunction with preferences of the individual where appropriate. This does not mean that carnitine is ineffective or should not be used in any inborn error of metabolism. However, given the lack of evidence both on the effectiveness and safety of carnitine and on the necessary dose and frequency to be prescribed, the current prescribing practice should continue to be observed and monitored with care until further evidence is available. Methodologically sound trials, reported according to the Consolidated Standards of Reporting Trials (CONSORT) statement, are required. It should be considered whether placebo-controlled trials in potentially lethal diseases, e.g. carnitine transporter disorder or glutaric aciduria type I, are ethical.

Adherence to diet and quality of life in patients with phenylketonuria

AIM

To investigate adherence to dietary treatment and quality of life (QoL) in patients with phenylketonuria (PKU).

METHODS

In the setting of a tertiary paediatric hospital, 41 early-treated patients affected by PKU aged more than 3 years old were enrolled in a cross-sectional study. Three-days dietary assessment, QoL questionnaires for patients<18 years old (Child Health Questionnaire) and Short Form for adults were completed.

RESULTS

Of 41 patients, 23 (56.1%) were considered adherent to the dietary prescriptions as their phenylalanine intake was less than prescribed. Phenylalanine intake was significantly in excess of prescribed if mothers had a lower level of education. Adherence was not correlated with age. Metabolic control was obtained in 41.5-51.2% of the patients depending on the target. QoL was reduced in children and adolescents. There was no significant correlation between adherence and QoL, except for the domains of Global Health and Family Activities (ρ=0.42 and 0.46, respectively). The overall agreement between adherence and metabolic control varied according to different targets of metabolic control (51.2-65.9%).

CONCLUSIONS

It is necessary to improve the adherence to diet and the QoL in children and adolescents affected by PKU.