No abstract

Extrauterine growth restriction in premature infants is largely attributed to reduced lean mass accretion and is associated with long-term morbidities. Previously, we demonstrated that prematurity blunts the feeding-induced stimulation of translation initiation signaling and protein synthesis in skeletal muscle of neonatal pigs. The objective of the current study was to determine whether the blunted feeding response is mediated by reduced responsiveness to insulin, amino acids, or both. Pigs delivered by Cesarean section preterm (PT; 103 d, n = 25) or at term (T; 112 d, n = 26) were subject to euinsulinemic-euaminoacidemic-euglycemic (FAST), hyperinsulinemic-euaminoacidemic-euglycemic (INS), or euinsulinemic-hyperaminoacidemic-euglycemic (AA) clamps 4 d after delivery. Indices of mechanistic target of rapamycin complex 1 (mTORC1) signaling and fractional protein synthesis rates were measured after 2 h. While longissimus dorsi (LD) muscle protein synthesis increased in response to both INS and AA, the increase was 28% lower in PT than T. Upstream of mTORC1, Akt phosphorylation, an index of insulin signaling, was increased with INS but was 40% less in PT than T. The abundances of mTOR·RagA and mTOR·RagC, indices of amino acid signaling, increased with AA but were 25% less in PT than T. Downstream of mTORC1, eIF4E·eIF4G abundance was increased by both INS and AA but attenuated by prematurity. These results suggest that preterm birth blunts both insulin- and amino acid-induced activation of mTORC1 and protein synthesis in skeletal muscle, thereby limiting the anabolic response to feeding. This anabolic resistance likely contributes to the high prevalence of extrauterine growth restriction in prematurity.

Extrauterine growth restriction often occurs in premature infants but may be mitigated by optimizing enteral feeding strategies. We show that intermittent bolus feeding does not increase skeletal muscle protein synthesis, myonuclear accretion, or lean growth more than continuous feeding in preterm pigs. This attenuated anabolic response of muscle to intermittent bolus feeding, compared with previous observations in pigs born at term, may contribute to deficits in lean mass that many premature infants exhibit into adulthood.

<b><i>Background:</i></b> To perform a comprehensive assessment of postnatal gastrointestinal (GI) morbidity and determine the prenatal imaging features and postnatal factors associated with its development in patients with congenital diaphragmatic hernia (CDH). <b><i>Materials and Methods:</i></b> A retrospective review was conducted of all infants evaluated for CDH at a quaternary fetal center from February 2004 to May 2017. Prenatal imaging features and postnatal variables were analyzed. GI morbidity was the primary outcome. The Mann-Whitney U test, the Kruskal-Wallis test with Dunnett’s T3 post hoc analysis and logistic regression, and the χ² test were performed when appropriate. <b><i>Results:</i></b> We evaluated 256 infants; 191 (75%) underwent CDH repair and had at least 6 months of follow-up. Of this cohort, 60% had gastroesophageal reflux disease (GERD), 13% had gastroparesis, 32% received a gastrostomy tube (G-tube), and 17% needed a fundoplication. Large defect, patch repair, extracorporeal membrane oxygenation (ECMO), and prolonged use of mechanical ventilation were significantly associated with having GERD, gastroparesis, G-tube placement, and fundoplication (<i>p</i> &#x3c; 0.05). Fetuses with stomach grades 3 and 4 were most likely to have GERD, a G-tube, and a long-term need for supplemental nutrition than fetuses with stomach grades 1 and 2 (<i>p</i> &#x3c; 0.05). <b><i>Conclusion:</i></b> Survivors of CDH with large defects, prolonged use of mechanical ventilation, or that have received ECMO may be at an increased risk for having GERD, gastroparesis, and major GI surgery. Marked stomach displacement on prenatal imaging is significantly associated with GI morbidity in left-sided CDH.