16S Ribosomal RNA-based Gut Microbiome Composition Analysis in Infants with Breast Milk Jaundice

Breast Milk Constituents and the Development of Breast Milk Jaundice in Neonates: A Systematic Review

Breast milk is tailored for optimal growth in all infants; however, in some infants, it is related to a unique phenomenon referred to as breast milk jaundice (BMJ). BMJ is a type of prolonged unconjugated hyperbilirubinemia that is often late onset in otherwise healthy-appearing newborns, and its occurrence might be related to breast milk itself. This review aims to systematically evaluate evidence regarding breast milk composition and the development of BMJ in healthy neonates. PubMed, Scopus and Embase were searched up to 13 February 2023 with key search terms, including neonates, hyperbilirubinemia, and breastfeeding. A total of 678 unique studies were identified and 12 were ultimately included in the systematic review with narrative synthesis. These included studies covered both nutritional compositions (e.g., fats and proteins) and bioactive factors (e.g., enzymes and growth factors) of breast milk and formally assessed the difference in the concentration (or presence) of various endogenous components of breast milk collected from mothers of BMJ infants and healthy infants. The results were inconsistent and inconclusive for most of the substances of interest, and there was only a single study available (e.g., total energy and mineral content, bile salts and cytokines); conflicting or even contradictory results arose when there were two or more studies on the subject matter (e.g., fats and free fatty acids contents and epidermal growth factor). The etiology of BMJ is likely multifactorial, and no single constituent of breast milk could explain all the BMJ cases observed. Further well-designed studies are warranted to investigate the complex interaction between maternal physiology, the breast milk system and infant physiology before this field could be progressed to uncover the etiology of BMJ.

Breast milk jaundice affects breastfeeding: From the perspective of intestinal flora and SCFAs-GPR41/43

Breast milk jaundice (BMJ) is one of the main factors leading to interruption or early termination of breastfeeding. Interrupting breastfeeding to treat BMJ may increase the adverse consequences for infant growth and disease prevention. The Intestinal flora and metabolites are increasingly recognized as a potential therapeutic target in BMJ. First, dysbacteriosis can lead to a decrease in the metabolite short-chain fatty acids. At the same time, SCFA can act on specific G protein-coupled receptors 41 and 43 (GPR41/43), and a decrease in SCFA downregulates the GPR41/43 pathway, leading to a diminished inhibition of intestinal inflammation. In addition, intestinal inflammation leads to a decrease in intestinal motility and a large amount of bilirubin enters the enterohepatic circulation. Ultimately, these changes will result in the development of BMJ. In this review, we will describe the underlying pathogenetic mechanism of the intestinal flora effects on BMJ.

Association of Neonatal Jaundice with Gut Dysbiosis Characterized by Decreased Bifidobacteriales

Neonatal jaundice, caused by excess serum bilirubin levels, is a common condition in neonates. Imbalance in the gut microbiota is believed to play a role in the development of neonatal jaundice. Thus, we aimed to reveal the gut microbiota characteristics in neonates with jaundice. 16S rRNA gene sequencing was performed on stool samples collected on day 4 from 26 neonates with jaundice (serum total bilirubin > 15.0 mg/dL) and 17 neonates without jaundice (total serum bilirubin < 10.0 mg/dL). All neonates were born full term, with normal weight, by vaginal delivery, and were breastfed. Neonates who were administered antibiotics, had serum direct bilirubin levels above 1 mg/dL, or had conditions possibly leading to hemolytic anemia were excluded. The median serum bilirubin was 16.0 mg/dL (interquartile range: 15.5-16.8) and 7.4 mg/dL (interquartile range: 6.8-8.3) for the jaundice and non-jaundice groups, respectively. There was no difference in the alpha diversity indices. Meanwhile, in the jaundice group, linear discriminant analysis effect size revealed that Bifidobacteriales were decreased at the order level, while Enterococcaceae were increased and Bifidobacteriaceae were decreased at the family level. Bifidobacteriaceae may act preventatively because of their suppressive effect on beta-glucuronidase, leading to accelerated deconjugation of conjugated bilirubin in the intestine. In summary, neonates with jaundice had dysbiosis characterized by a decreased abundance of Bifidobacteriales.

Deterministic transition of enterotypes shapes the infant gut microbiome at an early age

BACKGROUND

The succession of the gut microbiota during the first few years plays a vital role in human development. We elucidate the characteristics and alternations of the infant gut microbiota to better understand the correlation between infant health and microbiota maturation.

RESULTS

We collect 13,776 fecal samples or datasets from 1956 infants between 1 and 3 years of age, based on multi-population cohorts covering 17 countries. The characteristics of the gut microbiota are analyzed based on enterotype and an ecological model. Clinical information (n = 2287) is integrated to understand outcomes of different developmental patterns. Infants whose gut microbiota are dominated by Firmicutes and Bifidobacterium exhibit typical characteristics of early developmental stages, such as unstable community structure and low microbiome maturation, while those driven by Bacteroides and Prevotella are characterized by higher diversity and stronger connections in the gut microbial community. We further reveal a geography-related pattern in global populations. Through ecological modeling and functional analysis, we demonstrate that the transition of the gut microbiota from infants towards adults follows a deterministic pattern; as infants grow up, the dominance of Firmicutes and Bifidobacterium is replaced by that of Bacteroides and Prevotella, along with shifts in specific metabolic pathways.

CONCLUSIONS

By leveraging the extremely large datasets and enterotype-based microbiome analysis, we decipher the colonization and transition of the gut microbiota in infants from a new perspective. We further introduce an ecological model to estimate the tendency of enterotype transitions, and demonstrated that the transition of infant gut microbiota was deterministic and predictable.

Characterization of gut microbiota and short-chain fatty acid in breastfed infants with or without breast milk jaundice

This study aims to investigate the gut microbiota and metabolites in breastfed infants with breast milk jaundice (BMJ) using gut microbiome-metabolomics. Breastfed newborns diagnosed with BMJ and those without BMJ (control group) were enrolled. Faecal samples were collected from the participants and subjected to high-throughput sequencing of the 16s rDNA V3 and V4 regions of the gut flora and metabolomics of short-chain fatty acids (SCFAs). Proteobacteria, Fimicutes and Actinobacteria were the main bacteria at the phylum level. Eshcerichia-Shigella and Enterobacteriacea were the main bacteria at the genus level. The difference between the two groups was compared. Compared to the control group, the amount of Streptococcus was significantly increased while the amount of Enterococcus was significantly decreased in the faeces from infants with BMJ. Functional prediction analysis of 16S found that biosynthesis of penicillin and cephalosporin significantly increased in the BMJ group. Gas chromatography-mass spectrometry detection of SCFAs revealed that levels of acetic acid and propionic acid were significantly lower in the BMJ group than in the control group. The reduced levels of acetic acid and propionic acid may be related to the increase in Streptococcus and decrease in Enterococcus, both of which may contribute to BMJ.

Changes in Intestinal Flora and Metabolites in Neonates With Breast Milk Jaundice

Background: Breast milk jaundice (BMJ) is the first cause of neonatal jaundice; however, its underlying mechanism is yet to be deciphered. We conducted a study to investigate intestinal flora in neonates with BMJ and used metabolomics to decipher the possible mechanisms by which intestinal flora induces jaundice. Methods: Microbiota collected from the feces of BMJ patients and jaundice-free breastfeeding newborns was used for 16S rRNA sequencing. In addition, differences in fecal metabolites were analyzed using gas chromatography mass spectrometry (GC/MS). The relationship between intestinal microbiota and the differences in fecal metabolites was then analyzed. Results: There was no significant difference in the richness and diversity of intestinal flora between BMJ and the control group; however, there were differences in the structure. At the phylum level, the relative abundance of Firmicutes was higher in the control group compared to the BMJ group, whereas Proteobacteria was higher in the infants with BMJ. Additionally, at the genus level, the relative abundance of Haemophilus was higher in the control group, whereas the relative abundances of Escherichia, Morganella, and Rothia were lower. More remarkably, the major differences in metabolites between the two groups were glyceric acid, succinic acid, and phenylalanine. Additionally, the abundance of Escherichia was positively correlated with succinic acid and cadaverine levels. Conclusions: The intestinal flora colonization status in BMJ patients is immature. This study reports for the first time that the study of intestinal flora, especially Escherichia, plays an important role in BMJ, and found that it may be associated with the regulation of succinic acid metabolic pathways.