Necrotizing Enterocolitis: The Role of Hypoxia, Gut Microbiome, and Microbial Metabolites.

Necrotizing enterocolitis (NEC) is a life-threatening disease that predominantly affects very low birth weight preterm infants. Development of NEC in preterm infants is accompanied by high mortality. Surgical treatment of NEC can be complicated by short bowel syndrome, intestinal failure, parenteral nutrition-associated liver disease, and neurodevelopmental delay. Issues surrounding pathogenesis, prevention, and treatment of NEC remain unclear. This review summarizes data on prenatal risk factors for NEC, the role of pre-eclampsia, and intrauterine growth retardation in the pathogenesis of NEC. The role of hypoxia in NEC is discussed. Recent data on the role of the intestinal microbiome in the development of NEC, and features of the metabolome that can serve as potential biomarkers, are presented. The Pseudomonadota phylum is known to be associated with NEC in preterm neonates, and the role of other bacteria and their metabolites in NEC pathogenesis is also discussed. The most promising approaches for preventing and treating NEC are summarized.

SIGIRR gene variants in term newborns with congenital heart defects and necrotizing enterocolitis.

Background: Necrotizing enterocolitis (NEC) is a common gastrointestinal emergency among neonates which is characterized by acute intestinal inflammation and necrosis. The main risk factors for NEC are prematurity, low birth weight, and some preexisting health conditions such as congenital heart defects (CHDs). Investigation of the potential genetic predisposition to NEC is a promising approach that might provide new insights into its pathogenesis. One of the most important proteins that play a significant role in the pathogenesis of NEC is Toll-like receptor 4 (TLR4) which recognizes lipopolysaccharide found in Gram-negative bacteria. In intestinal epithelial cells, a protein encoded by the SIGIRR gene is a major inhibitor of TLR4 signaling. A few SIGIRR variants, including rare p.Y168X and p.S80Y, have already been identified in preterm infants with NEC, but their pathogenic significance remains unclear. This study aimed to investigate the spectrum of SIGIRR genetic variants in term newborns with CHD and to assess their potential association with NEC. Methods and Results: A total of 93 term newborns with critical CHD were enrolled in this study, 33 of them developed NEC. SIGIRR genetic variants were determined by Sanger sequencing of all exons. In total, eight SIGIRR genetic variants were identified, two of which were found only in newborns with NEC (P = 0.12). The rare missense p.S80Y (rs117739035) variant in exon 4 was found in two infants with NEC stage IIA. Two infants with NEC stage III and stage IB carried a novel duplication c. 102_121dup (rs552367848) variant in exon 10 that has not been previously associated with any clinical phenotype. Conclusions: The presence of both variants only in neonates who developed NEC, together with earlier published data, may suggest their potential contribution to the risk of developing NEC in term infants with CHD and allow planning larger cohort studies to clarify their relevance.

Intestinal microbiome changes in an infant with right atrial isomerism and recurrent necrotizing enterocolitis: A case report and review of literature.

BACKGROUND: Necrotizing enterocolitis (NEC) is a multifactorial disease that predominantly affects premature neonates. Intestinal dysbiosis plays a critical role in NEC pathogenesis in premature neonates. The main risk factor for NEC in term infants is mesenteric hypoperfusion associated with ductal-dependent congenital heart disease (CHD) that eventually leads to intestinal ischemia. The incidence of NEC in neonates with critical CHD is 6.8%-13%. However, the role of the intestinal microbiome in NEC pathogenesis in infants with ductal-dependent CHD remains unclear. CASE SUMMARY: A male term neonate with right atrial isomerism underwent modified Blalock-Taussig shunt placement on the 14th day of life and had persistent mesenteric hypoperfusion after surgery. The patient had episodes of NEC stage IIA on the 1st and 28th days after cardiac surgery. Fecal microbial composition was analyzed before and after cardiac surgery by sequencing region V4 of the 16S rRNA gene. Before surgery, species belonging to genera Veillonella and Clostridia and class Gammaproteobacteria were detected, Bifidobacteriaceae showed a low abundance. The first NEC episode was associated with postoperative hemodynamic instability, intestinal ischemia-reperfusion injury during cardiopulmonary bypass, and a high abundance of Clostridium paraputrificum (Clostridium sensu stricto I) (56.1%). Antibacterial therapy after the first NEC episode resulted in increased abundance of Gammaproteobacteria, decreased abundance of Firmicutes, and low alpha diversity. These changes in the microbial composition promoted the growth of Clostridium sensu stricto I (72.0%) before the second NEC episode. CONCLUSION: A high abundance of Clostridium sensu stricto I and mesenteric hypoperfusion may have contributed to NEC in the present case.