Food Regime for Phenylketonuria: Presenting Complications and Possible Solutions

Phenylalanine-Free Infant Formula in Patients with Phenylketonuria: A Retrospective Study

The long-term efficacy and use of phenylalanine-free infant amino acid formula (PFIF) is understudied. This retrospective, longitudinal study evaluated PFIF (PKU Start: Vitaflo International) in children with phenylketonuria, collecting data on metabolic control, growth, dietary intake, and symptoms and the child's experience with PFIF. Twenty-five children (12 males, 48%) with a median age of 3.6 years (2.0-6.2 years) were included. During 24 months follow-up, children maintained normal growth and satisfactory metabolic control. The protein intake from protein substitutes increased from 2.7 at 6 months to 2.8 g/kg/day at 24 months, while natural protein decreased from 0.6 to 0.4 g/kg/day. By 24 months, most children (n = 16, 64%) had stopped PFIF, while nine (36%) continued with a median intake of 450 mL/day (Q1:300 mL, Q3: 560 mL). Children who continued PFIF after 24 months of age had higher energy and fat intakes with higher weight/BMI z-scores compared with those who stopped earlier (p < 0.05). Constipation was reported in 44% of infants but improved with age. Initial difficulty with PFIF acceptance was reported in 20% of infants but also improved with time. Prolonged use of PFIF in pre-school children may contribute to poor feeding patterns and overweight; thus, replacing the majority of the protein equivalent provided by PFIF with a weaning protein substitute by 12 months and discontinuing PFIF before 2 years is recommended.

Vitamin Status in Patients with Phenylketonuria: A Systematic Review and Meta-Analysis

The published data on the vitamin status of patients with phenylketonuria (PKU) is contradictory; therefore, this systematic review and meta-analysis evaluated the vitamin status of PKU patients. A comprehensive search of multiple databases (PubMed, Web of Sciences, Cochrane, and Scopus) was finished in March 2024. The included studies compared vitamin levels between individuals diagnosed with early-treated PKU and healthy controls while excluding pregnant and lactating women, untreated PKU or hyperphenylalaninemia cases, control groups receiving vitamin supplementation, PKU patients receiving tetrahydrobiopterin or pegvaliase, and conference abstracts. The risk of bias in the included studies was assessed by the Newcastle-Ottawa scale. The effect sizes were expressed as standardised mean differences. The calculation of effect sizes with 95% CI using fixed-effects models and random-effects models was performed. A p-value < 0.05 was considered statistically significant. The study protocol was registered in the PROSPERO database (CRD42024519589). Out of the initially identified 11,086 articles, 24 met the criteria. The total number of participants comprised 770 individuals with PKU and 2387 healthy controls. The meta-analyses of cross-sectional and case-control studies were conducted for vitamin B12, D, A, E, B6 and folate levels. PKU patients demonstrated significantly higher folate levels (random-effects model, SMD: 1.378, 95% CI: 0.436, 2.320, p = 0.004) and 1,25-dihydroxyvitamin D concentrations (random-effects model, SMD: 2.059, 95% CI: 0.250, 3.868, p = 0.026) compared to the controls. There were no significant differences in vitamin A, E, B6, B12 or 25-dihydroxyvitamin D levels. The main limitations of the evidence include a limited number of studies and their heterogeneity and variability in patients' compliance. Our findings suggest that individuals with PKU under nutritional guidance can achieve a vitamin status comparable to that of healthy subjects. Our study provides valuable insights into the nutritional status of PKU patients, but further research is required to confirm these findings and explore additional factors influencing vitamin status in PKU.

Engineering phenylalanine ammonia lyase to limit feedback inhibition by cinnamate and enhance biotransformation

Phenylalanine ammonia-lyase (PAL) is a crucial enzyme for various biotechnology applications, such as producing phenols, antioxidants, and nutraceuticals. However, feedback inhibition from its product, cinnamic acid, limits its forward reaction rate. Therefore, this study aims to address the feedback inhibition in PAL using enzyme engineering strategies. Random and site-directed mutagenesis approaches were utilized to screen mutant enzymes with ameliorated tolerance against cinnamic acid. A thermotolerant and cinnamate-tolerant mutant was rationally identified using a high throughput screening method and subsequent biochemical characterization. We evaluated cinnamate affinity among the seven rationally selected mutations, and the T102E mutation was identified as the most promising mutant. This mutant showed a six-fold reduction in the affinity of PAL for cinnamic acid and a two-fold increase in operational stability compared with native PAL. Furthermore, the enzyme was immobilized on carbon nanotubes to increase its robustness and reusability. The immobilized mutant PAL showed greater efficiency in the deamination of phenylalanine present in protein hydrolysate than its free form. The rationale behind the enhancement of cinnamate tolerance was validated using molecular dynamic simulations. Overall, the knowledge of the sequence-function relationship of PAL was applied to drive enzyme engineering to develop highly tolerant PAL.

Increased peripheral of brain-derived neurotrophic factor levels in phenylketonuric patients treated with l-carnitine

Phenylketonuria (PKU) is the most common inherited metabolic disorders caused by severe deficiency or absence of phenylalanine hydroxylase activity that converts phenylalanine (Phe) to tyrosine. PKU patients were treated with a Phe restricted diet supplemented with a special formula containing l-carnitine (L-car), well-known antioxidant compound. The lack of treatment can cause neurological and cognitive impairment, as severe mental retardation, neuronal cell loss and synaptic density reduction. Although Phe has been widely demonstrated to be involved in PKU neurotoxicity, the mechanisms responsible for the CNS injury are still not fully known. In this work, we evaluated markers of neurodegeneration, namely BDNF (brain-derived neurotrophic factor), PAI-1 total (Plasminogen activator inhibitor-1 total), Cathepsin D, PDGF AB/BB (platelet-derived growth factor), and NCAM (neuronal adhesion molecule) in plasma of PKU patients at early and late diagnosis and under treatment. We found decreased Phe levels and increased L-car concentrations in PKU patients treated with L-car compared to the other groups, indicating that the proposed treatment was effective. Furthermore, we found increased BDNF levels in the patients under treatment compared to patients at early diagnosis, and a positive correlation between BDNF and L-car and a negative correlation between BDNF and Phe. Our results may indicate that in PKU patients treated with L-car there is an attempt to adjust neuronal plasticity and recover the damage suffered, reflecting a compensatory response to brain injury.

Actions speak louder than words: Home visits and its effect on dietary adherence in patients with phenylketonuria

AIM

Phenylketonuria (PKU) is an inherited metabolic disorder in which accumulation of phenylalanine (Phe) leads to poor neurological outcomes without treatment. Dietary therapy is the main treatment and nonadherence is associated with elevated blood Phe levels and correspondingly poor neuropsychiatric outcomes. This study aimed to examine the effect of home visits on blood Phe levels in PKU patients.

METHODS

Sixty-five paediatric PKU patients who were on low-phenylalanine diet were visited monthly at home for 6 months. At each visit, dietary education was provided, patients' height and weight were measured and blood samples were collected.

RESULTS

Twenty-eight (43.1%) patients had classic PKU and 37 (56.9%) had moderate PKU. Blood Phe levels decreased statistically significant at first, second, fifth, and sixth months compared with screening visit. Blood Phe levels in moderate PKU patients decreased significantly at the last visit unlike classic PKU patients. A significant decrease in blood Phe levels was observed in patients older than 10 years. Anthropometric parameters improved.

CONCLUSIONS

Dietary nonadherence is the main treatment failure in PKU. Home visits for education are a promising way to improve treatment outcomes by providing quality education, better assessment, and correction of mistakes but they should be ongoing and supported by different interventions that address patients' special needs.

Valorization of pistachio industrial waste: Simultaneous recovery of pectin and phenolics, and their application in low-phenylalanine cookies for phenylketonuria

This study introduces a sustainable approach to simultaneously produce pectin and phenolic compounds from pistachio industrial waste and applies them in the formulation of low-phenylalanine cookies. The co-optimization process was performed using the microwave-assisted technique and a Box-Behnken design, considering four variables and two responses: pectin yield and total phenolic content (TPC). The co-optimized condition (microwave power of 700 W, irradiation time of 210 s, pH level of 1.02, and LSR of 20 mL/g) resulted in a pectin yield of 15.85 % and a TPC of 10.12 %. The pectin obtained under co-optimized condition was evaluated for its physicochemical, structural, and thermal properties and the phenolic extract for its antiradical activity. Characterization of the pectin sample revealed a high degree of esterification (44.21 %) and a galacturonic acid-rich composition (69.55 %). The average molecular weight of the pectin was determined to be 640.236 kDa. FTIR and 1H NMR spectroscopies confirmed the structure of pectin, with an amorphous nature and high thermal stability observed through XRD and DSC analysis. Additionally, the extract exhibited significant antiradical activity comparable to butylated hydroxyanisole and ascorbic acid. The isolated ingredients were used to formulate low-protein, low-phenylalanine cookies for phenylketonuria patients. The addition of 0.5 % pectin and 1 mL/g extract led to increased moisture content (from 9.05 to 12.89 %) and specific volume (from 7.28 to 9.90 mL/g), decreased hardness (from 19.44 to 10.39 N × 102), and improved antioxidant properties (from 5.15 % to 44.60 % inhibition) of the cookies. Importantly, there was no significant increase observed in the phenylalanine content of the samples with pectin and extract addition. Furthermore, sensory evaluation scores demonstrated significantly higher scores for taste, odor, texture, and overall acceptability in cookies enriched with 0.5 % pectin and 1 mL/g extract, with scores of 4.53, 3.93, 4.40, and 4.60, respectively.

Evaluation of Decayed, Missing due to Caries, and Filled Teeth Index in Children with Phenylketonuria in Comparison to Normal Population

OBJECTIVE

Management of patients with phenylketonuria mainly includes limiting the content of phenylalanine in the diet. Therefore, the purpose of this study was to investigate oral problems in children with phenylketonuria compared to the healthy population as a case-control study.

MATERIALS AND METHODS

The subjects of the case and control groups were selected according to the inclusion criteria. First, the oral cavity and tooth were examined by a specialist dentist to indicate the decayed, missing due to caries, and filled teeth index in both groups. To inves- tigate the level of phenylalanine and evaluate other laboratory examinations, 2 mL of blood and saliva samples was taken from the subjects. Blood and saliva phenylalanine levels were measured by high-performance liquid chromatography. Phosphorus, calcium, and pH levels were investigated through calorimetric measurement. The data were analyzed using Statistical Package for Social Sciences software.

RESULTS

There was no significant difference between the case and control groups in terms of age and sex. The average level of calcium and phosphorus in the case group was higher than in the control group. Also, the average decayed, missing due to caries, and filled teeth index in the case group was not significantly different compared to the control group. None of the above-investigated indicators had a significant relationship with each other. On the other hand, it was found that there was a positive and significant relationship between phenylalanine in blood, saliva, and pH as well as between saliva phenylalanine with decayed, missing due to caries, and filled teeth.

CONCLUSION

The results of this study indicate a significant effect of phenylketonuria disease on calcium, phosphorus, and oral pH levels in children.