Nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD): An evidence- and consensus-based approach.

The nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD) is the fourth in a series of web-based guidelines focusing on the diet treatment for inherited metabolic disorders and follows previous publication of guidelines for maple syrup urine disease (2014), phenylketonuria (2016) and propionic acidemia (2019). The purpose of this guideline is to establish harmonization in the treatment and monitoring of individuals with VLCAD of all ages in order to improve clinical outcomes. Six research questions were identified to support guideline development on: nutrition recommendations for the healthy individual, illness management, supplementation, monitoring, physical activity and management during pregnancy. This report describes the methodology used in its development including review, critical appraisal and abstraction of peer-reviewed studies and unpublished practice literature; expert input through two Delphi surveys and a nominal group process; and external review from metabolic physicians and dietitians. It includes the summary statements of the nutrition management recommendations for each research question, followed by a standardized rating based on the strength of the evidence. Online, open access of the full published guideline allows utilization by health care providers, researchers and collaborators who advise, advocate and care for individuals with VLCAD and their families and can be accessed from the Genetic Metabolic Dietitians International (https://GMDI.org) and Southeast Regional Genetics Network (https://southeastgenetics.org/ngp) websites.

Direct evidence for a pressure-induced nodal superconducting gap in the Ba0.65Rb0.35Fe2As2 superconductor.

The superconducting gap structure in iron-based high-temperature superconductors (Fe-HTSs) is non-universal. In contrast to other unconventional superconductors, in the Fe-HTSs both d-wave and extended s-wave pairing symmetries are close in energy. Probing the proximity between these very different superconducting states and identifying experimental parameters that can tune them is of central interest. Here we report high-pressure muon spin rotation experiments on the temperature-dependent magnetic penetration depth in the optimally doped nodeless s-wave Fe-HTS Ba0.65Rb0.35Fe2As2. Upon pressure, a strong decrease of the penetration depth in the zero-temperature limit is observed, while the superconducting transition temperature remains nearly constant. More importantly, the low-temperature behaviour of the inverse-squared magnetic penetration depth, which is a direct measure of the superfluid density, changes qualitatively from an exponential saturation at zero pressure to a linear-in-temperature behaviour at higher pressures, indicating that hydrostatic pressure promotes the appearance of nodes in the superconducting gap.

Skeletal health in adult patients with classic galactosemia.

SUMMARY: This study evaluated bone health in adults with galactosemia. Associations between bone mineral density (BMD) and nutritional and biochemical variables were explored. Calcium level predicted hip and spine BMD, and gonadotropin levels were inversely associated with spinal BMD in women. These results afford insights into management strategies for these patients. INTRODUCTION: Bone loss is a complication of galactosemia. Dietary restriction, primary ovarian insufficiency in women, and disease-related alterations of bone metabolism may contribute. This study examined relationships between clinical factors and BMD in patients with galactosemia. METHODS: This cross-sectional sample included 33 adults (16 women) with classic galactosemia, mean age 32.0 ± 11.8 years. BMD was measured by dual-energy X-ray absorptiometry, and was correlated with age, height, weight, fractures, nutritional factors, hormonal status, and bone biomarkers. RESULTS: There was a significant difference in hip BMD between women and men (0.799 vs. 0.896 g/cm(2), p = 0.014). The percentage of subjects with BMD-Z <-2.0 was also greater for women than men [33 vs. 18 % (spine), 27 vs. 6 % (hip)], and more women reported sustaining fractures. Bivariate analyses yielded correlations between BMI and BMD-Z [at the hip in women (r = 0.58, p < 0.05) and spine in men (r = 0.53, p < 0.05)]. In women, weight was also correlated with BMD-Z (r = 0.57, p < 0.05 at hip), and C-telopeptides (r = -0.59 at spine and -0.63 hip, p < 0.05) and osteocalcin (r = -0.71 at spine and -0.72 hip, p < 0.05) were inversely correlated with BMD-Z. In final regression models, higher gonadotropin levels were associated with lower spinal BMD in women (p = 0.017); serum calcium was a significant predictor of hip (p = 0.014) and spine (p = 0.013) BMD in both sexes. CONCLUSIONS: Bone density in adults with galactosemia is low, indicating the potential for increased fracture risk, the etiology of which appears to be multifactorial.

Tyrosine supplementation in phenylketonuria: diurnal blood tyrosine levels and presumptive brain influx of tyrosine and other large neutral amino acids.

UNLABELLED: Tyrosine supplementation has not consistently been found to improve neuropsychologic function in phenylketonuria (PKU), possibly because of failure to achieve adequate levels of tyrosine in the brain. OBJECTIVES: To evaluate blood levels achieved after tyrosine supplementation in treated PKU and calculate brain influxes of tyrosine and other large neutral amino acids before and with tyrosine supplementation. STUDY DESIGN: Ten subjects with PKU receiving a phenylalanine-restricted diet were studied over 48 hours; each received tyrosine supplementation (300 mg/kg) on day 2. Plasma phenylalanine and tyrosine were measured every 2 hours, and all free amino acids were measured every 6 hours. Brain influxes of tyrosine and other large neutral amino acids were calculated. RESULTS: Plasma tyrosine levels were low normal at baseline. With supplementation there was a substantial but unsustained rise in plasma tyrosine. Calculated brain influx of tyrosine was 27% +/- 19% of normal before supplementation, increasing to 90% +/- 58% of normal with supplementation. Nevertheless, calculated influx remained less than 70% of normal at 50% of the time points. The calculated brain influxes of all other large neutral amino acids except tryptophan were 20% to 40% of normal before and with tyrosine supplementation. CONCLUSIONS: Tyrosine supplementation in the diet for PKU produces marked but nonsustained increases in plasma tyrosine levels, with calculated brain influx that often remains suboptimal. This could explain the lack of consistent neuropsychologic benefit with tyrosine supplementation.

Tyrosine supplementation in the treatment of maternal phenylketonuria.

Lower than average concentrations of tyrosine could be a factor in the fetal damage produced by maternal phenylketonuria (PKU). Dietary supplementation with L-tyrosine has been inconsistent in these reported pregnancies. Consequently, we studied the response to supplementation with L-tyrosine in five maternal PKU pregnancies. Before supplementation the mean plasma tyrosine concentration during midpregnancy was only 34 micromol/L compared with the expected value of 45 micromol/L in the normal population. A single dose of 1.3 g L-tyrosine was sufficient to raise plasma tyrosine concentrations well above the recommended minimum concentration of 45 micromol/L. The response was rapid and sustained over a 3-h study period in each subject and was associated with a markedly increased ratio of tyrosine to large neutral amino acids. These results indicate that the plasma tyrosine concentration can be increased to normal or above-normal values in maternal PKU pregnancies for a period of > or = 3 h by supplementation of the diet with L-tyrosine. The high ratio of tyrosine to large neutral amino acids indicates that tyrosine might readily cross the placenta and provide sufficient tyrosine to the fetus to support normal protein and catecholamine synthesis in what otherwise might be a tyrosine-poor environment.

Detection of phenylketonuria in the very early newborn blood specimen.

Early hospital discharge of newborns is leading to collection of the newborn screening blood specimen during the first day of life in increasing numbers of newborns. There is concern that neonates with phenylketonuria who are tested this early may be missed. To examine this question, the authors screened specimens collected during the first 24 hours of life from 23 neonates at risk for hyperphenylalaninemia. The blood phenylalanine level in each of the 6 neonates with phenylketonuria and a seventh with mild hyperphenylalaninemia was greater than 2 mg/dL as early as 4 hours of age and 6 mg/dL or greater by 24 hours of age. A newborn screening phenylalanine cutoff level of 2 mg/dL would have identified all of these neonates within the first 24 hours of life, but a cutoff level of 4 mg/dL would have missed 2 of the 6 with phenylketonuria before 24 hours of life. Newborn screening programs should adopt a blood phenylalanine level of 2 mg/dL as the cutoff for suspicion of phenylketonuria and request for a second specimen. Breast-fed affected neonates had higher early blood phenylalanine elevations than formula-fed neonates, perhaps reflecting the higher protein (phenylalanine) content of colostrum.

New England Maternal PKU Project: prospective study of untreated and treated pregnancies and their outcomes.

Four women with classic phenylketonuria (blood phenylalanine greater than 1200 mumol/L) were given a phenylalanine-restricted diet; three also received L-tyrosine supplements. Biochemical measures of nutrition were normal except for iron deficiency anemia, and in one woman folate deficiency. One pregnancy in which treatment began before conception and another treated from 8 weeks gestation, both with blood phenylalanine levels maintained at 120 to 730 mumol/L, resulted in normal newborn infants whose postnatal growth and development have also been normal. A third pregnancy, treated from 6 gestational weeks, was marked by poor dietary compliance until the middle of the second trimester; fetal microcephaly was identified by ultrasonography at 28 weeks but not at 21 weeks. The child has microcephaly and motor delay. The fourth pregnancy, not treated until the third trimester, produced a child with microcephaly, mental retardation, hyperactivity, and neurologic deficits. It is likely that fetal damage from maternal phenylketonuria can be largely and perhaps entirely prevented by dietary therapy, but therapy must begin before conception for the best chance of a normal infant.