Management of inborn errors of metabolism during pregnancy

Maternal PKU: Defining phenylalanine tolerance and its variation during pregnancy, according to genetic background

BACKGROUND AND AIMS

Phenylketonuria (PKU)-affected women may become pregnant, and dietary phenylalanine (Phe) intake must be adjusted according to Phe tolerance. We report our experience with maternal PKU in relation to genotype PKU heterogeneity.

METHODS AND RESULTS

A total of 10 pregnancies in 7 PKU women (7 different genotypes) were followed up as part of personalized care. Phe tolerance during preconception and pregnancy was assessed by strict dietary control and weekly Phe measurement (blood spots) in relation to genotype. Most women had stopped PKU diet during childhood or adolescence and six pregnancies were unplanned; a phenylalanine-restricted diet was reinstituted soon after conception. Women were classified according to their Phe levels at birth screening and genotype. Phe tolerance increased systematically in the course of pregnancy in all cases, but the increase was different in subjects with classic PKU (cPKU) when compared with cases with mild hyperphenylalaninemia (mHPA), both on average (+297 mg/day in cPKU vs. 597 in mHPA; P = 0.017) and as percentage (+107% in cPKU vs. +17% in mHPA). Notably, Phe tolerance also varied in the same women in the course of different pregnancies, when body weight gain was also different. Two newborns from the same cPKU mother (unplanned pregnancies on free diet) were affected by congenital alterations.

CONCLUSIONS

Several factors influence metabolic phenotype in maternal PKU, to an unpredictable extent even in the same woman. The number of maternal PKU cases is growing in dedicated Nutrition Units, and the burden associated with careful management of this condition for the health care system should be adequately considered.

Dietary management of maternal phenylketonuria with glycomacropeptide and amino acids supplements: A case report

BACKGROUND

In maternal PKU, protein substitute (PS) is provided by phenylalanine (PHE)-free l-amino acids (AA), but glycomacropeptide-based protein substitute (GMP) is an alternative consideration.

OBJECTIVE

To describe the first Portuguese Maternal Phenylketonuria (MPKU) partially managed with GMP.

CASE REPORT

A 31 year old MPKU female with classical PKU (mutations P281L/P281L), diagnosed by newborn screening, had a lifelong history of poor metabolic control. She has a history of partial bicornuate uterus and had a previous miscarriage in the first trimester. Pre-conception, her median blood PHE was 462 μmol/L but throughout pregnancy the median reduced to 258 μmol/L. GMP provided 30 g/day protein equivalent (46 mg/day PHE). Total protein equivalent from PS increased from 58 to 86 g/day during pregnancy but AA provided all additional protein equivalent intake. Both GMP and AA were well tolerated with no morning sickness. Normal morphologic evaluation and adequate fetal growth with cephalic biometry near the 5th percentile was determined. The infant was born at 39.3 weeks: weight 2570 g (3rd percentile), length 47.5 cm (10th percentile) and head circumference (HC) of 31.5 cm (1st percentile). In the neonatal period, the infant had craniofacial dimorphism with metopic suture prominence. Father also had bitemporal narrowing. By 12 months of age, the infant's weight (15th percentile), length (50th percentile) and HC (10th-50th percentile) were normal although bitemporal narrowing persisted.

CONCLUSIONS

This is the first case reporting the use of GMP in MPKU. Its PHE content did not adversely affect metabolic control although it only provided part of the PS intake. Some intrauterine development delay occurred in the last trimester, although we consider that this is unlikely to be associated with MPKU syndrome or the use of GMP. More published data is essential to examine the impact of using GMP in MPKU on morning sickness severity and aversion, maternal weight gain, blood amino acid concentrations and variability of blood PHE concentrations.

The complete European guidelines on phenylketonuria: diagnosis and treatment

Phenylketonuria (PKU) is an autosomal recessive inborn error of phenylalanine metabolism caused by deficiency in the enzyme phenylalanine hydroxylase that converts phenylalanine into tyrosine. If left untreated, PKU results in increased phenylalanine concentrations in blood and brain, which cause severe intellectual disability, epilepsy and behavioural problems. PKU management differs widely across Europe and therefore these guidelines have been developed aiming to optimize and standardize PKU care. Professionals from 10 different European countries developed the guidelines according to the AGREE (Appraisal of Guidelines for Research and Evaluation) method. Literature search, critical appraisal and evidence grading were conducted according to the SIGN (Scottish Intercollegiate Guidelines Network) method. The Delphi-method was used when there was no or little evidence available. External consultants reviewed the guidelines. Using these methods 70 statements were formulated based on the highest quality evidence available. The level of evidence of most recommendations is C or D. Although study designs and patient numbers are sub-optimal, many statements are convincing, important and relevant. In addition, knowledge gaps are identified which require further research in order to direct better care for the future.

Key European guidelines for the diagnosis and management of patients with phenylketonuria

We developed European guidelines to optimise phenylketonuria (PKU) care. To develop the guidelines, we did a literature search, critical appraisal, and evidence grading according to the Scottish Intercollegiate Guidelines Network method. We used the Delphi method when little or no evidence was available. From the 70 recommendations formulated, in this Review we describe ten that we deem as having the highest priority. Diet is the cornerstone of treatment, although some patients can benefit from tetrahydrobiopterin (BH4). Untreated blood phenylalanine concentrations determine management of people with PKU. No intervention is required if the blood phenylalanine concentration is less than 360 μmol/L. Treatment is recommended up to the age of 12 years if the phenylalanine blood concentration is between 360 μmol/L and 600 μmol/L, and lifelong treatment is recommended if the concentration is more than 600 μmol/L. For women trying to conceive and during pregnancy (maternal PKU), untreated phenylalanine blood concentrations of more than 360 μmol/L need to be reduced. Treatment target concentrations are as follows: 120-360 μmol/L for individuals aged 0-12 years and for maternal PKU, and 120-600 μmol/L for non-pregnant individuals older than 12 years. Minimum requirements for the management and follow-up of patients with PKU are scheduled according to age, adherence to treatment, and clinical status. Nutritional, clinical, and biochemical follow-up is necessary for all patients, regardless of therapy.

Maternal administration of the herbal medicine toki-shakuyaku-san promotes fetal growth and placental gene expression in normal mice

Toki-shakuyaku-san (TSS), an herbal formula based on traditional Chinese medicine, is commonly used in obstetrics. To examine the effects of TSS on the normal mouse fetus and placenta, TSS was administered to normal pregnant mice and their placentas and fetuses were studied. First, the effects of maternal TSS treatment on implantation were investigated. Administration of TSS from gestation day 0.5 (G0.5) to G6.5 showed that litter size was not altered at embryonic day 11.5 (E11.5), but the number of resorbed fetuses was slightly decreased. Then, to investigate effects on fetal and placental growths after implantation, TSS was administered from G5.5. At E14.5, the body weight of fetuses from TSS-treated dams was significantly increased. Gene expression of insulin-like growth factor 2 (Igf2), one of the most important modulators of fetal growth, was significantly increased in the placentas and fetuses of TSS-treated dams. In addition, the expression of particular placental developmental genes and nutrient transporter genes was significantly increased in TSS-treated placentas. At E18.5, after longer-term administration of TSS, fetal and placental weights were not altered, but the expression of the placental developmental and nutrient transporter genes remained elevated compared with controls. These results suggest that maternal TSS treatment in normal mice enhances the expression of Igf2, placental developmental genes and nutrient transporter genes, resulting in increased fetal weight. No obvious changes were observed in the expression of these genes after longer-term maternal TSS treatment.