Differences in the Gut Microbiota Composition and Metabolites Associated With Feeding Intolerance in VLBW Infants With a Gestational Age of ≤ 30 Weeks: A Pilot Study

Dynamics and Crosstalk between Gut Microbiota, Metabolome, and Fecal Calprotectin in Very Preterm Infants: Insights into Feeding Intolerance

BACKGROUND

Feeding intolerance (FI) is a significant concern in the care of preterm infants, impacting their growth and development. We previously reported that FI is linked to lower fecal calprotectin (FC) levels. This study aims to explore the postnatal dynamics and interplay between microbiota, metabolic profiles, and host immunity in preterm infants with and without FI.

METHODS

Infants with gestational age <32 weeks or birth weight <1500 g were enrolled at the Children's Hospital of Fudan University between January 2018 and October 2020. Weekly fecal samples were analyzed for bacterial profiling, metabolome, and calprotectin levels, exploring their longitudinal development and interrelationships.

RESULTS

Of the 118 very preterm infants studied, 48 showed FI. These infants experienced an interrupted microbial-immune trajectory, particularly at 3-4 weeks of age, marked by a reduced bacterial abundance, alpha diversity, and FC levels. Metabolic changes in FI were pronounced between 3 and 6 weeks. Pantothenic acid and two polyamine metabolites were closely associated with bacterial abundance and FC levels and negatively correlated with the duration to attain full enteral feeding.

CONCLUSIONS

FI infants demonstrated compromised microbiome-immune interactions, potentially influenced by specific metabolites. This research underscored the importance of early microbial and metabolic development in the pathogenesis of FI in very preterm infants.

Postnatal Dynamics and Clinical Associations of Fecal Calprotectin in Very Preterm Infants: Implications for Necrotizing Enterocolitis and Feeding Intolerance

INTRODUCTION

To elucidate the postnatal dynamics and clinical associations of fecal calprotectin (FC) in very preterm infants, with a focus on necrotizing enterocolitis (NEC) and feeding intolerance (FI).

METHODS

We performed a prospective observational cohort study in infants with a gestational age of <32 weeks or birth weight <1,500 g with weekly feces collection. The relationships between FC, NEC, and FI were investigated, adjusting for demographic and clinical factors.

RESULTS

A total of 1,086 fecal samples were collected from 194 preterm infants. Postnatal FC levels of non-NEC infants were highly variable and followed an age-dependent patterned progression. FC levels were elevated in patients with NEC before and at NEC onset, distinguishing them from non-NEC infants and those at sepsis onset. Among infants without NEC or sepsis, those with FI exhibited lower FC concentrations throughout hospitalization and displayed a significant delay in reaching high FC levels after meconium compared with non-FI infants. The age to reach the first high nonmeconial FC levels was positively associated with the time to achieve full enteral feeding.

DISCUSSION

Postnatal FC dynamics among premature infants followed a patterned progression but were disturbed in patients with NEC and FI. Because of the high variations, the use of FC levels in NEC diagnosis should be implemented with caution in clinical practice. FC may help understand FI and feeding progression in very preterm infants. Further research is needed to validate these findings and explore the potential clinical applications of FC in this population.

Characteristics of Gut Microbiota in Small for Gestational Age Infants with Very Low Birth Weight

Small for gestational age (SGA) birth is associated with high rates of mortality and morbidity in preterm infants. The aim of this preliminary observational study was to investigate the difference in gut microbiota between SGA and appropriate for gestational age (AGA) preterm infants with very low birth weight (VLBW). We included 20 VLBW preterm infants (SGA, n = 10; AGA, n = 10) in this study. Stool samples were collected on days 7, 14, and 30 after birth. We performed 16S ribosomal DNA sequencing to compare microbiota composition between both groups. The SGA group exhibited a lower abundance of Klebsiella on day 14 (SGA, 0.57%; AGA, 7.42%; p = 0.037). On day 30, the SGA group exhibited a lower abundance of Klebsiella (SGA 3.76% vs. AGA 16.05%; p = 0.07) and Enterobacter (SGA 5.09% vs. AGA 27.25%; p = 0.011) than the AGA group. Beta diversity demonstrated a separation of the bacterial community structure between both groups on day 30 (p = 0.019). The present study revealed that a distinct gut microbiota profile gradually develops in SGA preterm infants with VLBW during the early days of life. The role of changes in gut microbiota structure warrants further investigation.

Succinate aggravates intestinal injury in mice with necrotizing enterocolitis

Background

Necrotizing enterocolitis (NEC) is the most prevalent gastrointestinal disorder that predominantly threatens preterm newborns. Succinate is an emerging metabolic signaling molecule that was recently studied in relation to the regulation of intestinal immunity and homeostasis. We aimed to investigate the relationship between NEC and gut luminal succinate and preliminarily explored the effect of succinate on NEC pathogenesis.

Methods

Fecal samples from human neonates and mouse pups were analyzed by HPLC - MS/MS and 16S rRNA gene sequencing. C57BL/6 mice were randomly divided into four groups: control, NEC, Lsuc, and Hsuc. The mortality, weight gain, and intestinal pathological changes in four mouse groups were observed. Inflammatory cytokines and markers of macrophages were identified by quantitative real-time PCR. Succinate receptor 1 (SUCNR1) localization was visualized by immunohistochemistry. The protein levels of SUCNR1 and hypoxia-inducible factor 1a (HIF-1a) were quantified by western blotting.

Results

The levels of succinate in feces from NEC patients were higher than those in feces from non-NEC patients (P <0.05). In the murine models, succinate levels in intestinal content samples were also higher in the NEC group than in the control group (P <0.05). The change in succinate level was closely related to intestinal flora composition. In samples from human neonates, relative to the control group, the NEC group showed a higher abundance of Enterobacteriaceae and a lower abundance of Lactobacillaceae and Lactobacillus (P <0.05). In the murine models, relative to the control group, increased abundance was observed for Clostridiaceae, Enterococcaceae, Clostridium_sensu_stricto_1, and Enterococcus, whereas decreased abundance was observed for Lactobacillaceae and Lactobacillus (P <0.05). Increased succinate levels prevented mice from gaining weight, damaged their intestines, and increased their mortality; upregulated the gene expression of interleukin-1β (IL-1β), IL-6, IL-18 and tumor necrosis factor (TNF); and downregulated the gene expression of IL-10 and transforming growth factor (TGF)-β. Exogenous succinic acid increased inducible nitric oxide synthase (iNOS) gene expression but decreased Arginase-1 (Arg1) gene expression; and increased the protein expression of SUCNR1 and HIF-1a.

Conclusion

Succinate plays an important role in the development of necrotizing enterocolitis severity, and the activation of the HIF-1a signaling pathway may lead to disease progression.

Gut microbiota and short-chain fatty acids may be new biomarkers for predicting neonatal necrotizing enterocolitis: A pilot study

Background

Dysbacteriosis is thought to play an important role in the pathogenesis of necrotizing enterocolitis (NEC). We aimed to identify new biomarkers among gut microbiota and short-chain fatty acids (SCFAs) for the early prediction of NEC.

Materials and methods

Thirty-four preterm infants with gestational ages of ≤ 34 weeks who developed gastrointestinal symptoms were divided into the NEC group (n = 17) and non-NEC group (n = 17). In the NEC group, the gut microbiota and SCFAs in feces were assessed when the infants were enrolled (Group P) and when they were diagnosed with NEC (Group N). In the non-NEC group, samples were assessed when the infants were enrolled (Group C).

Results

The Ace and Chao1 indices were higher in Group P than in Group C (P &lt; 0.05), and there was no difference between Groups C and N or between Groups P and N (P &gt; 0.05). There was no significant difference in the Simpson and Shannon indices among Groups C, P and N (P &gt; 0.05). The four main phyla showed no differences (P &gt; 0.05) in composition, while at the genus level, compared with Group C, in Group P, Clostridioides, Blautia and Clostridium_sensu_stricto_1 were increased, while Lactobacillus and Bifidobacterium were decreased (P &lt; 0.05). At the species level, Streptococcus salivarius and Rothia mucilaginosa increased, while Bifidobacterium animals subsp. lactis decreased (P &lt; 0.05). In Group N, at the genus level, Stenotrophomonas, Streptococcus and Prevotella increased (P &lt; 0.05). Compared with those in Group C, the levels of acetic acid, propanoic acid and butyric acid decreased significantly in Groups P and N (P &lt; 0.05), and the areas under the curves (AUCs) of these three SCFAs between groups C and P were 0.73, 0.70, and 0.68, respectively.

Conclusion

The increase in Streptococcus salivarius and Rothia mucilaginosa and decrease in Bifidobacterium_animals_subsp._lactis, as well as the decrease in acetic, propionic and butyric acids, may help in the early prediction of NEC.