Influence of phenylketonuria's diet on dimethylated arginines and methylation cycle

Homocysteine and methylmalonic acid in Phenylketonuria patients

Hyperhomocysteinemia and vitamin B12 deficiency have been reported in patients with phenylketonuria. In this study, total homocysteine (tHcy) and methylmalonic acid (MMA) levels were analyzed in samples from 25 phenylketonuria (PKU) patients. Comparisons were made between pre- and post-treatment values (n= 3); on treatment values, between periods with high and normal/low phenylalanine (Phe) levels (n= 20); and in women before, during and after pregnancy (n= 3). THcy levels decreased after treating PKU with metabolic formula (p=0.014). Except for a pregnant woman before pregnancy, none of the patients had tHcy values above the normal range. In fact, tHcy was < 5 μmol/L in 34% of the samples. We observed a decrease in Phe, tHcy, and tyrosine levels during pregnancy. MMA levels did not differ significantly, with values remaining in the normal range. These data indicate that there was no B12 deficiency in patients who adhere to the diet. In conclusion, in PKU patients treated with metabolic formula, tHcy is frequently not elevated, remaining even in the lower normal range in some patients. Thus, clinical follow-up and adherence to dietary treatment are crucial to prevent B12 deficiency.

Phenylketonuria (PKU) Urinary Metabolomic Phenotype Is Defined by Genotype and Metabolite Imbalance: Results in 51 Early Treated Patients Using Ex Vivo 1H-NMR Analysis

Phenylketonuria (PKU) is a rare metabolic disorder caused by mutations in the phenylalanine hydroxylase gene. Depending on the severity of the genetic mutation, medical treatment, and patient dietary management, elevated phenylalanine (Phe) may occur in blood and brain tissues. Research has recently shown that high Phe not only impacts the central nervous system, but also other organ systems (e.g., heart and microbiome). This study used ex vivo proton nuclear magnetic resonance (¹H-NMR) analysis of urine samples from PKU patients (mean 14.9 ± 9.2 years, n = 51) to identify the impact of elevated blood Phe and PKU treatment on metabolic profiles. Our results found that 24 out of 98 urinary metabolites showed a significant difference (p < 0.05) for PKU patients compared to age-matched healthy controls (n = 51) based on an analysis of urinary metabolome. These altered urinary metabolites were related to Phe metabolism, dysbiosis, creatine synthesis or intake, the tricarboxylic acid (TCA) cycle, end products of nicotinamide-adenine dinucleotide degradation, and metabolites associated with a low Phe diet. There was an excellent correlation between the metabolome and genotype of PKU patients and healthy controls of 96.7% in a confusion matrix model. Metabolomic investigations may contribute to a better understanding of PKU pathophysiology.

Protein status in phenylketonuria: A scoping review

BACKGROUND & AIMS

The physical and functional outcomes of lifelong treatment with a phenylalanine restricted diet for the management of Phenylketonuria (PKU) remain unknown. Given that the mainstay of dietary management consists of modifying the sources of ingested protein, various aspects of body protein status could be compromised.

OBJECTIVES

To examine the existing evidence regarding the protein status of people with PKU and identify nutritional and lifestyle variables that influence protein status.

ELIGIBILITY CRITERIA

Studies reporting anthropometric, biochemical and/or functional measurements of body protein status in people with PKU were eligible.

SOURCE OF EVIDENCE

MEDLINE (Ovid), Embase (Ovid), CENTRAL, Web of Science and Scopus, and conference abstracts.

RESULTS

Seventy studies were included in the review. The majority of studies assessing protein status based on anthropometric measurements observed no differences between people with PKU and controls, although deficits in muscle mass were reported within PKU cohorts. Findings for biochemical assessment of protein status were mixed and limited studies assessed protein status using functional measures. Factors such as participant age, sex, metabolic control, protein source, type of protein substitute, and pharmacological treatments were found to modulate protein status of people with PKU.

CONCLUSIONS

Findings were inconclusive regarding body protein status in people with PKU. The relationship between diet and protein status outcomes remains unclear and further research is warranted to determine the impact of dietary regimens on physical and functional outcomes, and to understand the best clinical assessments to reliably monitor the protein status in people with PKU.

Phenylketonuria Patients' and Their Caregivers' Perception of the Pandemic Lockdown: The Results of a National Online Survey

The first pandemic lockdown dramatically impacted many aspects of everyday life, including healthcare systems. The purpose of this study was to identify problems of patients with phenylketonuria (PKU) and their parents/caregivers during that time. We aimed to analyse potential differences in the self-reported compliance and characteristics of contacts with a doctor/dietitian before and during the pandemic lockdown and the perception of access to special food and opinions on remote contacts between a particular group of respondents. All participants (n = 614) were asked to complete an online questionnaire that consisted of 31 questions on pandemic-related events and circumstances which may have directly or indirectly impacted health and treatment. The people who completed the survey were divided into three groups: parents of PKU children (n = 403), parents of PKU adults (n = 58) and PKU patients older than 16 years (n = 153). The differences among the three analysed groups were found in the number of contacts, the way of contacting a doctor/dietitian during the pandemic and satisfaction with remote contact. Caregivers of children with PKU reported better therapy compliance, more frequent contacts with specialists and more satisfaction with remote visits than adult patients. We also observed a relationship between satisfaction from remote contact and self-reported frequency of contacts with a doctor/dietitian, as well as a relationship between satisfaction from remote contact and recommended blood Phe levels reported by both patients and caregivers. Travel time exceeding three hours from the respondents’ location to their doctor was associated with higher odds of their recognition of remote contact as a method of PKU treatment only in the group of caregivers. In the caregiver groups, the reported worse access to low-Phe products during the lockdown was linked to the perceived difficulty of maintaining the diet. However, such a relationship was not found among patients. In conclusion, significant differences in the perception of the pandemic lockdown and its impact on health and treatment-related issues were found.

Hypohomocysteinemia may increases the risk of dementia and Alzheimer's disease: A nationwide population-based prospective cohort study

BACKGROUND

Hyperhomocysteinemia has been repeatedly found to increase the risk of dementia. However, the effects of hypohomocysteinemia on the risk of dementia have been barely investigated. If hypohomocysteinemia, like hyperhomocysteinemia, increases the risk of dementia, misuse or overuse of homocysteine-lowing agents such as vitamin supplements may increase the risk of dementia.

AIMS

To investigate whether hypohomocysteinemia, like hyperhomocysteinemia, could increase the risk of dementia and Alzheimer's disease (AD) in a large population-based cohort of older adults.

METHODS

This prospective cohort study followed 2655 randomly sampled, community-dwelling, non-demented individuals aged 60 years or older from 2010 to 2018. We measured baseline serum total homocysteine (tHcy) levels and examined the effect of serum tHcy on the risks of dementia and AD using Cox proportional hazards models.

RESULTS

During the follow-up period (mean = 5.4 years, SD = 0.9), dementia and AD developed in 85 and 64 participants, respectively. Not only the participants with high serum tHcy (≥10.6 μmol/L) but also those with low serum tHcy (≤8.9 μmol/L) were 4-5 times more likely to develop dementia and AD compared to those with serum tHcy levels between 9.0 and 10.5 μmol/L. With the increase in serum tHcy concentration, the use of vitamin supplements decreased, and 41.2% of the participants with low serum tHcy (≤8.9 μmol/L) were taking vitamin supplements.

CONCLUSIONS

Not only hyperhomocysteinemia but also hypohomocysteinemia considerably increased the risk of dementia and AD in older adults. The risk of dementia that results from overuse or misuse of vitamin supplements should be acknowledged and homocysteine-lowering health policies should be tailored to consider dementia risks that are associated with hypohomocysteinemia.

Generation of urine-derived induced pluripotent stem cells from a patient with phenylketonuria

The aim of the study was to establish an induced pluripotent stem cell line from urine-derived cells (UiPSCs) from a patient with phenylketonuria (PKU) in order to provide a useful research tool with which to examine the pathology of this rare genetic metabolic disease. Urine-derived epithelial cells (UCs) from a 15-year-old male patient with PKU were isolated and reprogrammed with integration-free episomal vectors carrying an OCT4, SOX2, KLF4, and miR-302-367 cluster. PKU-UiPSCs were verified as correct using alkaline phosphatase staining. Pluripotency markers were detected with real-time PCR and flow cytometry. Promoter methylation in two pluripotent genes, NANOG and OCT4, was analyzed using bisulphite sequencing. An embryoid body (EB) formation assay was also performed. An induced pluripotent stem cell line (iPSC) was generated from epithelial cells in urine from a patient with PKU. This cell line had increased expression of stem cell biomarkers, it efficiently formed EBs, it stained positive for alkaline phosphatase (ALP), and it had a marked decrease in promoter methylation in the NANOG and OCT4 genes. The PKU-UiPSCs created here had typical characteristics and are suitable for further differentiation.

Metabolomic Insights into the Nutritional Status of Adults and Adolescents with Phenylketonuria Consuming a Low-Phenylalanine Diet in Combination with Amino Acid and Glycomacropeptide Medical Foods

BACKGROUND

Nutrient status in phenylketonuria (PKU) requires surveillance due to the restrictive low-Phe diet in combination with amino acid medical foods (AA-MF) or glycomacropeptide medical foods (GMP-MF). Micronutrient profiles of medical foods are diverse, and optimal micronutrient supplementation in PKU has not been established.

METHODS

In a crossover design, 30 participants with PKU were randomized to consume AA-MF and Glytactin™ GMP-MF in combination with a low-Phe diet for 3 weeks each. Fasting venipunctures, medical food logs, and 3-day food records were obtained. Metabolomic analyses were completed in plasma and urine by Metabolon, Inc.

RESULTS

The low-Phe diets in combination with AA-MF and GMP-MF were generally adequate based on Dietary Reference Intakes, clinical measures, and metabolomics. Without micronutrient supplementation of medical foods, >70% of participants would have inadequate intakes for 11 micronutrients. Despite micronutrient supplementation of medical foods, inadequate intakes of potassium in 93% of participants and choline in >40% and excessive intakes of sodium in >63% of participants and folic acid in >27% were observed. Sugar intake was excessive and provided 27% of energy.

CONCLUSIONS

Nutrient status was similar with AA-MF and Glytactin GMP-MF. More research related to micronutrient supplementation of medical foods for the management of PKU is needed.