Reviewed by Benedette Cuffari, M.Sc.

A recent Nature Communications study evaluates the effect of social disadvantages and psychological stressors on the gut microbiome (GM) and circulating proinflammatory cytokines of mothers and their infants.

Study: Social and psychological adversity are associated with distinct mother and infant gut microbiome variations. Image Credit: Kseniya Maruk / Shutterstock.com

Background

Socially disadvantaged (SD) populations experience significant health inequities. This group of individuals is also subjected to psychological stressors (PS) at an early phase of their lives. Previous studies have indicated that the prenatal environment profoundly affects fetal and infant outcomes.

It is important to understand how SD and PS cause differential health outcomes. Notably, multiple SD and PS-related morbidities are linked with the manifestation of chronic inflammation.

Several studies have indicated that GM is associated with immune system functions, as well as the manifestation of systemic inflammation and autoimmune diseases. Interestingly, these clinical manifestations are also linked with the SD population.

Environmental factors, along with diet, hardship, and stress linked to SD, contribute to the diversity and abundance of GM. To date, limited studies have evaluated the effect of psychosocial inequities and SD on microbial community structure and function, particularly in the prenatal period.

Most studies related to GM have focused on maternal psychological state or socioeconomic status, with few studies considering both factors in fetal outcomes. It is essential to understand the dynamics between GM and social determinants of health, as these factors could be exploited to reduce GM-related health impacts.

About the study

A total of 395 pregnant women were recruited between 2017 and 2020 for the Early Life Adversity Biological Embedding and Risk for Developmental Precursors of Mental Disorders Study (eLABE). All women recruited in this study were 18 years of age or older, English-speaking, and delivered at Barnes Jewish Hospital in St. Louis.

The current study used a prospective birth cohort whose mothers were enrolled during gestation. Participants with multiple gestations, premature birth, congenital malformations and infections, and alcohol or drug abuse during pregnancy were excluded. Stool samples of mothers in their third trimester (T3) and four-month-old infants were collected.

SD was evenly distributed throughout the cohort. At each trimester of pregnancy, important information regarding maternal depression measures, stresses, and clinical information was recorded.

The Diet History Questionnaire (DHQII) was used to assess the nutrition and eating patterns of the participants. Maternal psychosocial stressors were evaluated using the Edinburgh Postnatal Depression Scale (EPDS).

Study findings

A total of 121 mother-child dyads were selected from the eLABE study based on the eligibility criteria. Both mother and their infants were classified as "high" or "low" SD and PS based on the score distribution across samples. Their unique GM structure was identified using the whole metagenomic shotgun (WMS) sequencing method.

To generate GM profiles, 16 S ribosomal ribonucleic acid (rRNA) gene sequencing was performed. SD and PS scores were significantly but only moderately correlated across the study cohort.

To identify differences in the overall microbiome profiles, the Dirichlet Multinomial Mixtures (DMM) clustering approach was adopted. To this end, high SD and PS scores were associated with unique GM profiles in children but not mothers.

Reduced α-diversity was associated with lower socioeconomic status (SES) in mothers. Comparatively, in children, α-diversity was significantly and positively correlated with low SD.

This could be attributed to a lower frequency of breastfeeding among high SD mothers than low SD mothers. Previous studies have shown that breastfed infants have lower GM α-diversity as compared to formula-fed infants.

Twelve genomes were detected across all samples, including six Bifidobacteria species, two Bacteroides species, two Faecalicatena species, Flavonifractor plautii, and Eggerthella lenta. Although taxonomic differences prevailed between the GM of mothers and children, 87.2% of the metabolic pathways were common in both mother's and children's GMs.

Phylogenetically distinct predictors were found in mothers linked to high SD and high PS conditions. For example, Bacteroides A mediterraneensis was the most common predictor of low PS in mothers, whereas S. thermophilus was one predictor of low SD. Although an abundance of Blautia in the GM was consistent across mothers, three specific species were identified as predictors of PS.

High SD in children was predicted with the presence of Enterobacter nimipressuralis and Klebsiella pneumoniae, whereas low SD was predicted by B. infantis. Low SD and PS in children were predicted by the presence of Veillonella parvula A and Collinsella spp.

Carbohydrate degradation associated with sucrose degradation IV, glycogen degradation I, and starch degradation III are important predictive pathways associated with high SD in mothers. In children, L-glutamate and L-glutamine synthesis is strongly associated with high SD in the children. B. adolescents, followed by B. pseudocatenulatum, are significantly associated with high maternal interleukin 6 (IL-6) levels in children.

Conclusions

The current study established a distinct association between exposure to PS/SD and GM structure and function for mothers and their infants. Unique features of the maternal and infant GMs were identified and significantly associated with SD and PS at the time of sampling. More research is needed to assess the stability of these GM signatures from early life to early childhood.

Journal reference:

• Warner, B. B., Rosa, B. A., Ndao, I. M., et al. (2023) Social and psychological adversity are associated with distinct mother and infant gut microbiome variations. Nature Communications 14(1);1-19. doi:10.1038/s41467-023-41421-4