Plasma amino acid concentrations in newborn infants breast-fed ad libitum

Plasma amino acid concentrations were measured in peripheral venous blood of 40 newborn infants breast-fed ad libitum. When these data are compared with amino acid concentrations of umbilical cord artery plasma, only lysine and threonine show a striking decrease after birth: the concentrations of hydroxyproline, asparagine, glutamine, proline, cystine, leucine, tyrosine, and ornithine significantly increase during the first days of life. The high-protein concentration of colostrum and transitional milk may explain this observation.     

Plasma concentrations of vitamin D metabolites in unsupplemented breast-fed infants

Plasma concentrations of the vitamin D metabolites 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, 24,25-dihydroxyvitamin D and 25,26-dihydroxyvitamin D were determined in 12 solely breast-fed infants 4 days and 6 weeks after birth. They were not exposed to sunlight, but the mothers received an average of 600 IU vitamin D2 per day during the study period. The mothers' 25-hydroxyvitamin D levels did not change significantly (medians 42 and 58 nmol/l), but the median level dropped from 26 to 15 nmol/l in the infants (P less than 0.001). There was a close correlation between maternal and infant levels at 4 days (r = 0.95). The babies with the highest initial levels showed the most marked decrease by 6 weeks. The median concentrations of 24,25-dihydroxyvitamin D and 25,26-dihydroxyvitamin D decreased similarly from 1.7 to 0.8 and 0.63 to 0.35 nmol/l respectively, (P less than 0.001). The 1,25-dihydroxyvitamin D levels were within normal limits as were plasma calcium, phosphorus, and alkaline phosphatase. The data suggest that fetal stores of vitamin D may be rapidly depleted, and that breast milk may be inadequate as the only source of vitamin D, even for breast-fed infants of vitamin D-supplemented mothers.     

Reduced serum amino acid concentrations in infants with necrotizing enterocolitis

OBJECTIVE: To determine whether premature infants who have necrotizing enterocolitis (NEC) have deficiencies in glutamine (GLN) and arginine (ARG), which are essential to intestinal integrity. STUDY DESIGN: A 4-month prospective cohort study of serum amino acid and urea levels in premature infants was done. Serum amino acid and urea levels were measured by high-pressure liquid chromatography and enzymatic methods, respectively, on samples obtained on days of life 3, 7, 14, and 21. RESULTS: Infants in the control (n = 32) and NEC groups (n = 13) were comparable for birth weight, gestational age, and Apgar scores. NEC began on mean day of life 14.5 (95% CI, day of life 11 to 18). Median values of GLN were 37% to 57% lower in the NEC group on days 7, 14, and 21 compared with those in the control group (P <.05). On days 7 and 14, median values of ARG, GLN, alanine, lysine, ornithine, and threonine were decreased 36% to 67% (P <.05) in the NEC group. Total nonessential amino and total essential amino acids were 35% to 50% lower in the NEC group on days 7 and 14 (P <.05). Infants in the NEC group had significant reductions in GLN and ARG 7 days before the onset of NEC. CONCLUSIONS: Infants who have NEC have selective amino acid deficiencies including reduced levels of GLN and ARG that may predispose to the illness.     

Plasma amino acid concentrations in children receiving long-term parenteral nutrition

Plasma amino acid concentrations were measured in 15 children aged 4-65 months who received home parenteral nutrition (PN) and in 10 normal controls. In seven patients (Group I), PN was the only source of nutrition. Eight patients (Group II) ingested 30%-70% of their total energy requirements and received the remainder intravenously. Group I and Group II patients received PN for 25.6 +/- 14.4 (SD) and 25.7 +/- 19.1 months, respectively. In comparison to controls, Group I had significantly decreased plasma concentrations of total essential amino acids, the three branched chain amino acids, cystine, tyrosine, and the three major urea cycle amino acids. Group II children displayed decreased plasma concentrations of two branched chain amino acids, leucine and valine, as well as cystine and tyrosine. Taurine was decreased in both groups. The presence of liver disease did not have a major effect on amino acid levels. These data indicate that children receiving long-term parenteral nutrition will develop abnormalities in their plasma amino acid concentrations even though they appear to receive adequate amounts of amino acids in their intravenous solutions. Further studies will be necessary to assess whether modifying the intravenous intake of amino acids will normalize plasma amino acid concentrations in these children.     

Plasma amino acid concentrations in umbilical cord vein and artery of newborn infants after elective cesarean section or spontaneous delivery

Twenty-four infants delivered by elective cesarean section and 23 spontaneously born infants were studied for plasma amino acid concentrations of the umbilical cord vein and artery. Normal labor was not found to influence plasma amino acid concentrations. In both spontaneously and operatively born infants, similar venous-arterial gradients were found for all essential and five nonessential amino acids. Based on the differences of venous and arterial concentrations and the umbilical cord blood flow, the daily fetal retention of single amino acids was calculated.     

Sunshine exposure and serum 25-hydroxyvitamin D concentrations in exclusively breast-fed infants

The relationship between serum 25-hydroxyvitamin D (25-OHD) concentrations and sunshine exposure in 61 term, exclusively breast-fed infants younger than 6 months of age was investigated. Sunshine exposure was quantitated using a sunshine and clothing diary, which was verified by infant-adapted ultraviolet dosimetry. By multiple regression techniques, infant serum 25-OHD concentrations were significantly related to UV exposure and maternal serum 25-OHD concentrations. Infant 25-OHD concentrations correlated with sunshine exposure in infants whose mothers had low (less than 35 ng/ml) or high (greater than 35 ng/ml) serum concentrations of 25-OHD (r = 0.70, P less than 0.001 and r = 0.53, P = 0.004, respectively). Estimates were made to determine sunshine exposure conditions necessary to maintain serum 25-OHD concentrations above the lower limit of the normal range (11 ng/ml). A conservative estimate would be 30 minutes per week wearing only a diaper or 2 hours a week fully clothed without a hat.     

Fecal bilirubin excretion and serum bilirubin concentrations in breast-fed and bottle-fed infants

To assess the rate of excretion of bilirubin in the stools and its effects on serum bilirubin concentrations, we studied 24 breast-fed and 13 bottle-fed infants during the first 3 days after birth. Bottle-fed infants passed significantly more stool (3-day totals, 82 vs 58 gm, P less than 0.001), excreted more bilirubin (3-day totals, 23.8 vs 15.7 mg, P less than 0.05), and had lower serum bilirubin values (day 3, 6.8 vs 9.5 mg/dl, P less than 0.02). Among the breast-fed infants, greater stool output was associated with greater fecal bilirubin excretion (r = 0.56, P less than 0.05) and lower serum bilirubin concentrations (r = 0.66, P less than 0.001). Our data suggest that hyperbilirubinemia in breast-fed infants may be related to a delay in bilirubin clearance resulting from low stool output.     

Blood glucose and plasma amino acid concentrations in infants of diabetic mothers.

Postnatal blood glucose and individual plasma free amino acid levels were measured in 14 newborn infants of diabetic mothers. All infants had a significantly lower blood glucose concentration than normal controls but no significant correlation was observed between the blood glucose values and any of the amino acids determined. As regards the quantitative and qualitative changes of the plasma aminogram, the total concentration of amino acids and the level of a few individual amino acids (glycine, alanine, taurine, and valine) were significantly elevated in full-term babies. However, no significant difference was found in the total plasma concentration of amino acids between premature infants of diabetic mothers and premature control infants, but the plasma alanine level was higher in the former. It is of interest that total plasma amino acid, alanine, and glycine levels were elevated in the asphyxiated babies. This suggests that the postnatal hyperaminoacidemia observed in infants of diabetic mothers was due to birth asphyxia rather than to impaired gluconeogenesis. The possible role of a defective gluconeogenesis in the etiology of postnatal hypoglycemia in infants of diabetic mothers is not supported by these data.     

Cholic acid,chenodeoxycholic acid,alpha-1-fetoprotein and alpha-1-antitrypsin serum concentrations in breast-fed infants with prolonged jaundice

Thirteen breast-fed one-month-old infants with prolonged jaundice not due to known causes were included in this study. All infants were investigated at one and twelve months of age. Serum concentrations of total (TB) and conjugated bilirubin (CB), aspartate (ASAT) and alanine aminotransferase (ALAT), alkaline phosphatase (AP), -1-antitrypsin (-1-AT), -1-fetoprotein (AFP) and the two primary bile acids; cholic (CA) and chenodeoxycholic acid (CDCA) were determined at both ages. The Pi-phenotype of -1-AT was determined at the age of twelve months. The serum concentrations of TB, CB, AP and AFP were elevated at the age of one month but were normal at the age of twelve months. No changes in the serum concentrations of ASAT or ALAT were observed between one and twelve months of age, and the values were within the reference ranges. The serum concentrations of -1-AT were within the reference range at both ages. Two infants were heterozygous for MZ, and they had normal serum -1-AT concentrations. The serum concentrations of CA and CDCA were elevated at the age of one month and were still significantly elevated at the age of twelve months indicating that the infants had slight cholestasis at the age of one month, and that the cholestasis had largely subsided by the end of the first year of life.     

Plasma homocysteine concentrations of preterm infants.

Mild hyperhomocysteinemia in adults is associated with an increased risk of vascular disease. Although information is available about plasma homocysteine concentrations in childhood, data are entirely lacking for preterm infants despite their known abnormalities of sulfur amino acid metabolism. We measured plasma total homocysteine concentrations of 9 preterm infants (gestational age 23-31 weeks) within 48 h of birth and over the subsequent 14 days of life, and 4 term infants (gestational age 36-39 weeks) on a single occasion within 72 h of birth. As measured within 48 h of birth, average plasma homocysteine and cysteine concentrations of the preterm infants were 3.8 +/- 0.3 and 122 +/- 8 microM, both significantly less than those of the term infants (6.1 +/- 1.3 and 187 +/- 39) and of normal adults (8.2 +/- 0.5 and 232 +/- 6). Plasma homocysteine (but not cysteine) appeared to gradually increase during the first 2 weeks of life (p = 0.053). Our results indicate that hyperhomocysteinemia does not normally occur in preterm infants.