Diet therapy and metabolic control among Chilean adults with a neonatal diagnosis of Phenylketonuria

Abstract Phenylketonuria (PKU) is an autosomal recessive defect affecting the metabolic pathway of phenylalanine (Phe), causing hyperphenylalaninemia and neurotoxicity. Diagnosis must occur in the neonatal period and treatment should begin as early as possible. Evidence implies that treatment adherence declines as age advances. The aim was to describe the diet of a subgroup of Chilean adults with PKU currently in follow-up. Fifty-three subjects (49% women) followed up between January 2021 to April 2023 were considered. The concentration of Phe (PheC) in dried blood spots measured by fluorometry and 24-hour dietary recalls were analyzed. The median PheC of the sample was 438µmol/L (interquartile range(IQR):351-585µmol/L). A protein intake of 1.35±0.3 gr/Kg/d was observed of which 87% came from the protein substitute without Phe. Participants had a median Phe intake of 459mg/d (IQR:327-976) and 13.1g/d of fiber intake. Most participants, 51% and 92% reported consuming fruits and vegetables, respectively, and 32% consumed Low-Protein foods. Regarding micronutrients, all participants exceeded 90% adequacy according to recommendations. For vitamin-D and vitamin-B12, 100% is provided by the protein substitute. According to our results, it is mandatory to establish transition programs toward adulthood, to constantly maintain good metabolic control, and to adapt diet therapy to their new lifestyle.

25 Hydroxy Vitamin D Level, Bone Health, Vitamin D and Calcium Intake in Chilean Patients with Phenylketonuria and Hyperphenylalaninemias

Abstract It has been shown that there is a decrease in the concentrations of 25 hydroxyvitamin D (25-OHD) and bone mineral density (BMD) in patients with phenylketonuria (PKU) in their follow-up. Our objective was to determine concentrations of 25-OHD in subjects with PKU and hyperphenylalaninemia (HPA). Transversal analytical study considered three groups: G1-PKU with neonatal diagnosis and formula intake without Phe; G2-HPA, without specific treatment and G3-C control group. Sixteen patients per group (aged 6-23) were included. Levels of 25-OHD, lumbar spine (L2-L4), femur and total BMD, intact parathormone (PTH) and vitamin D (VitD) and calcium intake were calculated. The Kruskal-Wallis statistical test was applied (p-value<0,05). Significant differences were detected in concentrations of 25-OHD between G1-PKU and G2-HPA (38.9 ng/mL; 28 ng/mL, respectively) (NV: >30 ng/mL). G1-PKU had a higher intake of VitD, with differences among groups. There were no significant differences among groups in relation to BMD and intact PTH. In conclusion, G1-PKU under treatment and with good adherence, does not present VitD deficiency and no BMD alterations are observed. In contrast, G2-HPA had a lower intake of VitD and decreased 25-OHD concentrations which could affect the bone architecture in the long term. Further studies on the G2-HPA are suggested.

Update on Dietary Compliance, Nutritional Status, and Neuropsychological Functioning in the Chilean Phenylketonuria cohort

Abstract Since 1992, Chile has had a Newborn Screening Program for Phenylketonuria (PKU), which currently has an incidence of 1:18,916 newborns. The objective of the current study was to describe the 2020 follow up of the Chilean PKU cohort. The variables analyzed were: nutritional status, dietary compliance and neuropsychological functioning. We conducted a descriptive cross-sectional statistical analysis. The 271 subjects with PKU had an average age of diagnosis of 17±8 days and a phenylalanine (Phe) level of 1122±546 umol/L. Approximately 80% of protein requirement came from a protein substitute. For those <18 years of age, 80% had good dietary compliance with Phe level between 120-360 umol/L and those >18 years had a median of 522 umol/L (95%CI 468 - 636). Forty-four percent of the active PKU cohort had overweight/obesity. Eighty-five percent of the cohort >4 years of age had a normal intelligence quotient (IQ) (score 80-120). We observed a negative correlation (p <0.001; 95% CI: - 0.5, -0.2) between IQ score and Phe level. The Chilean protocol and protein substitute subsidy for life, together with the follow-up and continuous education carried out by the clinical team has encouraged compliance.

Characterization of Phenyalanine Hydroxylase Gene Mutations in Chilean PKU Patients.

Phenylketonuria (PKU, OMIM 261600) is an autosomal recessive disease, caused by mutations in the Phenylalanine Hydroxylase (PAH) gene situated in chromosome 12q22-q24.2. This gene has 13 exons. To date, 991 mutations have been described. The genotype is one of the main factors that determine the phenotype of this disease. OBJECTIVE: Characterize PKU genotype and phenotype seen in Chilean PKU patients. METHODS: We studied the PAH gene by restriction fragment length polymorphism (RFLP) and/or sequencing techniques to identify pathogenic mutations in 71 PKU subjects. We classified the phenotype according to Guldberg predicted value. RESULTS: We identified 26 different mutations in 134 of the 142 alleles studied (94.4%), 88.7% of the subjects had biallelic pathogenic mutations while 11.3% had only one pathogenic mutation identified. Compound heterozygous represented 85.9% of the cases. Exon 7 included the majority of mutations (26.9%) and 50% of mutations were missense. The most frequent mutations were c.1066-11G > A, c.442-?_509+?del and p.Val388Met. The majority of subjects (52.3%) had the classic phenotype. CONCLUSIONS: The most frequent mutations in our Chilean PKU population were p.Val388Met, c.442?_509+?del and c.1066-11G > A. It is possible to predict phenotype by detecting the genotype, and use this information to determine disease prognosis and adjust patient's medical and nutritional management accordingly.

Past, present and future of newborn screening in Chile.

The history of the Newborn Screening Program in Chile begins in 1984, when a pilot plan was developed that demonstrated the feasibility of its implementation. In 1992, the Ministry of Health started a national newborn screening program for phenylketonuria (PKU) and congenital hypothyroidism (CH), and in 1998, this was extended to the entire country. Throughout this period, a total of 2,478,123 newborns (NB) have been analyzed, obtaining initial coverage of 48.8%, which was later increased to 87.7%, and at present it is at 98.7% of all NB of our country. During this period, 131 cases with PKU have been diagnosed, resulting in an incidence of 1:18,916 NB, an average age of diagnosis of 18 ± 10.2 days and average phenylalanine level of 19,9 ± 8.8 mg/dl. In relation to CH, 783 cases have been confirmed, arriving at an incidence of 1:3,163 NB, with average age of diagnosis of 12.5 ± 6.9 days. Due to the good results of the program, the government is evaluating the initiation of an extended pilot program, to introduce other pathologies.

Binding of microtubules to transitional elements in oligodendrocytes of the myelin mutant taiep rat.

The presence of microtubules physically bound to smooth endoplasmic reticulum profiles of oligodendrocytes constitutes the most conspicuous feature observed in the myelin mutant taiep rat. The endoplasmic reticulum membranes associated with microtubules were morphologically characterized as transitional elements that constitute the intermediate compartment according to their topographic location close to the cis-Golgi apparatus. The development of this surprising microtubular defect appears to be associated with the early events of myelination. Transitional elements associated with microtubules operate in protein transport from endoplasmic reticulum to cis-Golgi. This microtubular defect could explain the dysmyelination and neurologic alterations observed in taiep rats. Moreover, these findings allow us to propose that there is a blockage of protein traffic at the intermediate compartment of taiep oligodendrocytes, a situation that could explain the hypomyelinated axons observed in this myelin mutant. The binding of microtubules to membranous organelles promotes the stabilization of microtubules, a feature that has important implications regarding its accumulation within the cytoplasm of oligodendrocytes during the temporal evolution of this neurologic disorder. The taiep rat is a myelin mutant with a long survival and could be a useful model for understanding dysmyelinating diseases in which the intracellular transport of myelin components is affected.