Recent advances in our understanding of protein and amino acid metabolism in the human fetus

Association of serum levels of phenylalanine and tyrosine with hip fractures and frailty in older adults: The cardiovascular health study

This study examined if the amino acids phenylalanine or tyrosine contribute to risk of hip fracture or frailty in older adults. We determined that neither phenylalanine nor tyrosine are important predictors of hip fracture or frailty. We suggest advice on protein intake for skeletal health consider specific amino acid composition.

PURPOSE

Protein is essential for skeletal health, but the specific amino acid compositions of protein may have differential associations with fracture risk. The aim of this study was to determine the association of serum levels of the aromatic amino acids phenylalanine and tyrosine with risk for incident hip fractures over twelve years of follow-up and cross sectional associations with frailty.

METHODS

We included 131 older men and women from the Cardiovascular Health Study (CHS) who sustained a hip fracture over twelve years of follow-up and 131 men and women without an incident hip fracture over this same period of time. 42% of this cohort were men and 95% were Caucasian. Weighted multivariable Cox hazards molecules were used to estimate the hazard ratios (HR) and 95% confidence intervals (CI) of incident hip fracture associated with a one standard deviation (SD) higher serum level of phenylalanine or tyrosine. Relative risk regression was used to determine the cross-sectional association of these amino acids with Freid's frailty index.

RESULTS

Neither serum levels of phenylalanine (HR 0.85 (95% CI 0.62-1.16) or tyrosine (HR 0.82 (95% CI 0.62-1.1) were significantly associated with incident hip fractures or cross sectionally with frailty (frail compared with prefrail/not frail) (HR 0.92 (95% CI 0.48-1.76) and HR (0.86 (95% CI 0.46-1.61) respectively.

CONCLUSION

Phenylalanine and tyrosine are not significant contributors to hip fractures or frailty in older men and women.

Early Amino Acids in Extremely Preterm Infants and Neurodisability at 2 Years

BACKGROUND

Whether higher parenteral amino acid intake improves outcomes in infants with extremely low birth weight is unclear.

METHODS

In this multicenter, parallel-group, double-blind, randomized, placebo-controlled trial, we assigned infants with birth weights of less than 1000 g at 8 neonatal intensive care units to receive amino acids at a dose of 1 g per day (intervention group) or placebo in addition to usual nutrition for the first 5 days after birth. The primary outcome was survival free from neurodisability as assessed with the Bayley Scales of Infant and Toddler Development and neurologic examination at 2 years, corrected for gestational age at birth. Secondary outcomes were the components of the primary outcome as well as the presence or absence of neonatal disorders, the rate of growth, and nutritional intake.

RESULTS

We enrolled 434 infants (217 per group) in this trial. Survival free from neurodisability was observed in 97 of 203 children (47.8%) in the intervention group and in 102 of 205 (49.8%) in the placebo group (adjusted relative risk, 0.95; 95% confidence interval [CI], 0.79 to 1.14; P = 0.56). Death before the age of 2 years occurred in 39 of 217 children (18.0%) in the intervention group and 42 of 217 (19.4%) in the placebo group (adjusted relative risk, 0.93; 95% CI, 0.63 to 1.36); neurodisability occurred in 67 of 164 children (40.9%) in the intervention group and 61 of 163 (37.4%) in the placebo group (adjusted relative risk, 1.16; 95% CI, 0.90 to 1.50). Neurodisability was moderate to severe in 27 children (16.5%) in the intervention group and 14 (8.6%) in the placebo group (adjusted relative risk, 1.95; 95% CI, 1.09 to 3.48). More children in the intervention group than in the placebo group had patent ductus arteriosus (adjusted relative risk, 1.65; 95% CI, 1.11 to 2.46). In a post hoc analysis, refeeding syndrome occurred in 42 of 172 children in the intervention group and 26 of 166 in the placebo group (adjusted relative risk, 1.64; 95% CI, 1.09 to 2.47). Eight serious adverse events occurred.

CONCLUSIONS

In infants with extremely low birth weight, extra parenteral amino acids at a dose of 1 g per day for 5 days after birth did not increase the number who survived free from neurodisability at 2 years. (Funded by the New Zealand Health Research Council and others; ProVIDe Australian New Zealand Clinical Trials Registry number, ACTRN12612001084875.).

Protein intakes to optimize outcomes for preterm infants

Proteins are key structural components of all human cells and are also involved in key physiologic processes through their roles as enzymes, hormones and transport proteins. Protein requirements are substantially higher in preterm infants than those born at term, yet inadequate protein intakes are a common problem on many neonatal units. Very preterm infants (VPT, <32 weeks) commonly receive parenteral amino acid solutions which are typically commenced on admission, and increased over the next few days. Several recent studies have explored differing parenteral amino acid intakes in the first few days, and recommendations have recently been updated. Parenteral nutrition intakes are decreased as enteral feeds are tolerated, but human milk alone will not meet protein needs in most VPT and supplementation or fortification will be required. This review paper considers basic protein and amino acid physiology in the newborn period, and the evidence base for current recommendations.

Investigating the changes in amino acid values in premature infants: a pilot study

BACKGROUND

The objective of the study was to investigate the changes in amino acid (AAs) values in premature infants.

METHODS

A total of 2159 premature and/or low birth weight infants were recruited for this study. They were divided into three groups: premature infants with normal birth weight (G1), simple low birth weight infants (G2) and premature combined with low birth weight infants (G3). The tandem mass spectrometry technique was used to detect the levels of 11 AAs in neonatal blood.

RESULTS

Compared with normal babies, there were eight and five AAs that significantly changed in G1 and G2, respectively. It was worth noting that the changes greatly exacerbated when the babies were both premature and of low birth weight. All the levels of AAs demonstrated significant changes in G3 compared with the normal control group (G4). With the increase in gestational age, the AAs in premature infants tended to the levels in normal newborns. Meanwhile, there was a correlation between AAs and birth weight. Four AAs significantly changed with the increase in body weight. Among normal newborns, the levels of AAs in girls were significantly higher than in boys. However, if the newborns were premature or had low birth weight, the differences between AA values and sexual distinction would decrease. In the end, we established the specific reference ranges of AAs for premature and/or low birth weight infants.

CONCLUSIONS

There were significant differences in AAs in the premature and/or low birth weight infants. Gestational age and birth weight were two important factors inflecting the AAs metabolism.

Therapeutic applications of dichloroacetate and the role of glutathione transferase zeta-1

Dichloroacetate (DCA) has several therapeutic applications based on its pharmacological property of inhibiting pyruvate dehydrogenase kinase. DCA has been used to treat inherited mitochondrial disorders that result in lactic acidosis, as well as pulmonary hypertension and several different solid tumors, the latter through its ability to reverse the Warburg effect in cancer cells and restore aerobic glycolysis. The main clinically limiting toxicity is reversible peripheral neuropathy. Although administration of high doses to rodents can result in liver cancer, there is no evidence that DCA is a human carcinogen. In all studied species, including humans, DCA has the interesting property of inhibiting its own metabolism upon repeat dosing, resulting in alteration of its pharmacokinetics. The first step in DCA metabolism is conversion to glyoxylate catalyzed by glutathione transferase zeta 1 (GSTZ1), for which DCA is a mechanism-based inactivator. The rate of GSTZ1 inactivation by DCA is influenced by age, GSTZ1 haplotype and cellular concentrations of chloride. The effect of DCA on its own metabolism complicates the selection of an effective dose with minimal side effects.

Effects of Pinellia ternata (Thunb.) Berit. on the metabolomic profiles of placenta and amniotic fluid in pregnant rats

ETHNOPHARMACOLOGICAL RELEVANCE

Banxia (BX) is the root of Pinellia ternata (Thunb.) Berit. Its processed products, such as Jiang Banxia (JBX), have been clinically used in traditional Chinese medicine to treat vomiting, coughing, and inflammation. However, data for their safety for pregnant women are contradictory and confusing.

AIM OF THE STUDY

To further explore the safety of BX, an ultra-performance liquid chromatography coupled with liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) metabolomics approach was used to evaluate the metabolic perturbation in pregnant rats caused by BX and JBX.

MATERIALS AND METHODS

Placenta and amniotic fluid samples were collected from control Sprague-Dawley pregnant rats and exposed to BX suspension and JBX decoction (1.434g/kg/day). Samples were analyzed using LC-MS and GC-MS. The acquired MS data of above samples were further subjected to multivariate data analysis, and the significantly altered metabolites were identified. The associated pathways were constructed using MetaboAnalyst 3.0.

RESULTS

The weight and histopathology of the placenta from each group of rats had no definite difference. However, we found 20 differential endogenous metabolites that changed significantly in the placenta and amniotic fluid samples. The alterations of identified metabolites indicated a perturbation in glycerophospholipid metabolism, amino acid metabolism, and carbohydrate metabolism in pregnant rats exposed to BX and JBX.

CONCLUSION

In summary, this work suggested that oral administration of BX and JBX may induce disturbances in the intermediary metabolism in pregnant rats. This work contributes to further understanding the safety of BX and its processed products.

Inverse association between maternal 25OHD level and cord GLP-1/GIP concentrations

BACKGROUND

Because vitamin D may have beneficial effects on glucose metabolism in pregnant women with gestational diabetes mellitus, we explored whether maternal 25-hydroxyvitamin D (25OHD) levels in normal pregnancy have association with diabetes-related hormone levels and glycated albumin (GA).

METHODS

A prospective cohort study was performed to collect serum samples from 612 pairs of pregnant women and cord blood of their offspring. Levels of 25OHD and GA in maternal and cord blood were measured by radioimmunoassay and enzyme assay, respectively. Using cord serum, 12 diabetes-related hormones were assayed. Spearman's rank correlation coefficient was used to quantify the strength of association between biomarkers.

RESULTS

A prominent association between maternal and cord 25OHD levels (r = 0.76, 95% confidence intervals (CIs): 0.73-0.79, P < 0.0001) and weak association between maternal and cord GA (r = 0.22, 95% CIs: 0.14-0.30, P < 0.0001) were shown. Among the 12 diabetes-related hormones, both maternal and cord 25OHD levels showed prominent negative associations with glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP).

CONCLUSIONS

These results suggest that decreased maternal 25OHD may be associated with decreased cord 25OHD and increased cord GLP-1 and GIP levels, which may be involved with the transfer of maternal glucose to the fetus.

Albumin synthesis in very low birth weight infants is enhanced by early parenteral lipid and high-dose amino acid administration

BACKGROUND & AIMS

Albumin is one of the most important plasma proteins and plays a key role in many physiologic processes, such as preserving colloid osmotic pressure, scavenging radicals, and binding and transporting bilirubin, hormones, and drugs. However, albumin concentrations are often low in preterm infants during the first days of life. We hypothesized that early parenteral lipid and high-dose amino acid (AA) administration to very low birth weight (VLBW) infants from birth onwards increases hepatic albumin synthesis rates.

METHODS

Inborn VLBW infants were randomized to receive from birth onwards either 2.4 g amino acids/(kg(·)d) (control group), 2.4 g amino acids/(kg(·)d) plus 2 g lipids/(kg(·)d) (AA + lipid group), or 3.6 g amino acids/(kg(·)d) plus 2 g lipids/(kg(·)d) (high AA + lipid group). On postnatal day 2, infants received a primed continuous infusion of [U-(13)C6,(15)N]leucine. Mass spectrometry was used to determine the fractional and absolute albumin synthesis rates (FSR and ASR, respectively).

RESULTS

In total, 28 infants (median gestational age 27 weeks (IQR 25-28), median birth weight 810 g (IQR 679-998) were studied. The median FSR was 6.5%/d in the control group, 10.6%/d in the AA group, and 12.3%/d in the high AA + lipid group, while the median was 84 mg/(kg(·)d) in the control group, 138 mg/(kg(·)d) in the AA group, and 160 mg/(kg(·)d) in the high AA + lipid group.

CONCLUSION

A group of VLBW infants given parenteral nutrition containing lipids and high-dose amino acids showed a higher rate of albumin synthesis compared to infants receiving no lipids and standard amounts of amino acids during the first two days of life.

Increased consumption of salmon during pregnancy partly prevents the decline of some plasma essential amino acid concentrations in pregnant women

BACKGROUND & AIMS

Oily fish is a good source of n-3 long-chain polyunsaturated fatty acids. Since these fatty acids may change efficiency of amino acid (AA) absorption, we determined whether increased salmon consumption influences plasma AA concentrations in pregnant women and their newborns.

METHODS

Pregnant women were randomly allocated to remain on their habitual diet (n = 61; control group) or to consume two 150 g farmed salmon portions per week from 20 weeks pregnancy until birth (n = 62; salmon group). Plasma AA concentrations were determined in women at w20, w34 and w38 of pregnancy and in umbilical cord at delivery.

RESULTS

Concentrations of arginine, valine, leucine and lysine were affected by both time of pregnancy and salmon intake (p < 0.05), with a smaller gestation-associated decrease in the salmon group. Total essential AA concentrations were similar in both groups at w20, but at w38 were higher in salmon group (p < 0.05). Cord plasma AA concentrations, higher than in maternal plasma (p < 0.01), were similar in the two groups (p > 0.05).

CONCLUSIONS

Two portions/wk of oily fish increased plasma essential AA concentrations during pregnancy and could contribute to a maternal health benefit. Two portions/wk of salmon did not affect plasma AA concentrations in the newborn.

CLINICAL TRIALS IDENTIFIER

NCT00801502.

Robust reference intervals for liver function test (LFT) analytes in newborns and infants

Background

Reference intervals (RIs) are ranges of upper and lower limits of a given analyte which are used for a laboratory test to determine whether a disease is present or absent or to know if the patient is at risk for future disease states. In Ethiopia, a country with highly diversified population groups and geographical sites, there are no established RIs to metabolic analytes including the liver function test (LFT) analytes for the pediatric population though it has been known that liver function assessment in this population is vital as a result of varied vulnerability to both endogenous and xenobiotic substances.

Methods

A cross sectional study was conducted in Tikur Anbessa Specialized Hospital (TASH) and Teklehaymanot Health Center (THC) from November 2010 to April 2011. 117 cord blood (from newborns) and venous blood samples (from infants) were collected and analyzed using HumaStar 300. All pre-analytical, analytical and post-analytical aspects were thoroughly controlled. A robust, CLSI/ IFCC recommended, method was used for the determination of upper and lower end points covering 95% of the reference values of each analyte with respective 90% CIs using MedCalc® software.

Results

Combined RIs for newborns and infants were established for albumin, AST, ALP, direct bilirubin and total bilirubin to be 3.88-5.82 g/dl, 16.1-55.4U/l, 130-831U/l, <0.41 mg/dl and <1.37 mg/dl respectively. But, separated RIs were indicated for ALT and GGT as 1.2-23.1U/l and 6.94-24.8U/l ALT; and 30.6-160.7U/L and 10–28.2U/l GGT for newborns and infants respectively. Some maternal and infantile factors were identified to affect the values of analytes.

Conclusion

Almost all analytes were different from previously reported values for other target population of similar age group, kit insert values and adult values. So, interpretation of values of these analytes in newborns and infants of Ethiopian population sounds better to be performed by using such RIs taking the effect of some maternal and infantile factors in to account.

High-precision mass spectrometric analysis using stable isotopes in studies of children

The use of stable isotopes combined with mass spectrometry (MS) provides insight into metabolic processes within the body. Herein, an overview on the relevance of stable isotope methodology in pediatric research is presented. Applications for the use of stable isotopes with MS cover carbohydrate, fat, and amino acid metabolism as well as body composition, energy expenditure, and the synthesis of specific peptides and proteins, such as glutathione and albumin. The main focus of these studies is on the interactions between nutrients and the endogenous metabolism within the body and how these factors affect the health of a growing infant. Considering that the early imprinting of metabolic processes hugely impacts metabolism (and thus functional outcome) later in life, research in this area is important and is advancing rapidly. The major fluxes on a metabolic level are the synthesis and breakdown rates. They can be quantified using kinetic tracer analysis and mathematical modeling. Organic MS and isotope ratio mass spectrometry (IRMS) are the two most mature techniques for the isotopic analysis of compounds. Introduction of the samples is usually done by coupling gas chromatography (GC) to either IRMS or MS because it is the most robust technique for specific isotopic analysis of volatile compounds. In addition, liquid chromatography (LC) is now being used more often as a tool for sample introduction of both volatile and non-volatile compounds into IRMS or MS for (13)C isotopic analyses at natural abundances and for (13)C-labeled enriched compounds. The availability of samples is often limited in pediatric patients. Therefore, sample size restriction is important when developing new methods. Also, the availability of stable isotope-labeled substrates is necessary for measurements of the kinetics and concentrations in metabolic studies, which can be a limiting factor. During the last decade, the availability of these substrates has increased. Furthermore, improvements in the accuracy, precision, and sensitivity of existing techniques (such as GC/IRMS) and the development of new techniques (such as LC/IRMS) have opened up new avenues for tackling these limitations.

Inflammatory-induced hibernation in the fetus: priming of fetal sheep metabolism correlates with developmental brain injury

Prenatal inflammation is considered an important factor contributing to preterm birth and neonatal mortality and morbidity. The impact of prenatal inflammation on fetal bioenergetic status and the correlation of specific metabolites to inflammatory-induced developmental brain injury are unknown. We used a global metabolomics approach to examine plasma metabolites differentially regulated by intrauterine inflammation. Preterm-equivalent sheep fetuses were randomized to i.v. bolus infusion of either saline-vehicle or LPS. Blood samples were collected at baseline 2 h, 6 h and daily up to 10 days for metabolite quantification. Animals were killed at 10 days after LPS injection, and brain injury was assessed by histopathology. We detected both acute and delayed effects of LPS on fetal metabolism, with a long-term down-regulation of fetal energy metabolism. Within the first 3 days after LPS, 121 metabolites were up-regulated or down-regulated. A transient phase (4–6 days), in which metabolite levels recovered to baseline, was followed by a second phase marked by an opposing down-regulation of energy metabolites, increased pO₂ and increased markers of inflammation and ADMA. The characteristics of the metabolite response to LPS in these two phases, defined as 2 h to 2 days and at 6–9 days, respectively, were strongly correlated with white and grey matter volumes at 10 days recovery. Based on these results we propose a novel concept of inflammatory-induced hibernation of the fetus. Inflammatory priming of fetal metabolism correlated with measures of brain injury, suggesting potential for future biomarker research and the identification of therapeutic targets.

Nutritional support for extremely low-birth weight infants: abandoning catabolism in the neonatal intensive care unit

PURPOSE OF REVIEW

Obviously, the ultimate goal in neonatology is to achieve a functional outcome in premature infants that is comparable to healthy term-born infants. As nutrition is one of the key factors for normal cell growth, providing the right amount and quality of nutrients could prove pivotal for normal development. However, many premature infants are catabolic during the first week of life, which has directly been linked to growth failure, disease, and suboptimal long-term outcome. This review describes the progress in research on parenteral nutrition for premature infants with a focus on amino acids and the influence of nutrition on later outcome.

RECENT FINDINGS

Although randomized clinical trials on early nutrition for premature infants remain relatively sparse, evidence is accumulating on its beneficial effects both on the short-term and long-term. However, some research also warns for adverse effects.

SUMMARY

Despite the fact that substantially improved nutritional therapies for preterm neonates have been implemented, still, some reluctance exists when it comes to providing high amounts of nutrition to the most immature infants. Pros and cons are outlined, as well as deficits in knowledge, when it comes to providing the optimal nutrient strategy in the first postnatal phase.