Decoding the Gut-Immune Connection During Pregnancy

TOPLINE:

The anti-inflammatory shift in mid-pregnancy may be linked to changes in gut microbiota, which, in turn, may wield their influence through fecal and plasma metabolites.

METHODOLOGY:

• Midway through a normal pregnancy, the maternal immune system shifts to a more anti-inflammatory state, which may be linked to changes in the gut microbial community by unknown mechanisms.
• The study explored the associations between the gut microbiota, fecal and plasma metabolites, and cytokine levels of pregnant women and compared them with those of nonpregnant women.
• The study recruited 30 pregnant women (ages 18-34 years; prepregnancy body mass index [BMI], 18.5-21.9) who conceived naturally with a singleton pregnancy and 15 nonpregnant women of similar age and BMI from the First Affiliated Hospital of Jinan University, Guangzhou, China, between February 2019 and August 2020.
• All participants had not used probiotics or antibiotics in the 6 months prior to participating in the study.
• Fecal and blood samples were collected during or after the 37th week of pregnancy in pregnant women until their labor and on the 14th day of the menstrual cycle in nonpregnant women.

TAKEAWAY:

• Pregnant women had more Actinobacteriota than nonpregnant women (9.15% vs 2.98%, respectively; P = .002) in their gut microbiomes, and the most enriched other microbes showed a negative correlation with pro-inflammatory cytokines.
• Pregnant women had differences in 44 fecal and 53 plasma metabolites, with certain enriched metabolites negatively correlated with pro-inflammatory cytokines and certain depleted ones positively correlated.
• Levels of pro-inflammatory plasma cytokines such as interleukins (IL)-1β, IL-2, IL-6, IL-12, interferon gamma, and tumor necrosis factor alpha were reduced, while levels of the anti-inflammatory cytokine IL-4 were elevated in pregnant vs nonpregnant women.
• Researchers identified a total of 46 connections between gut microbes, metabolites, and cytokines, with details suggesting that gut microbes may alter plasma cytokine levels by interacting with host metabolites.

IN PRACTICE:

“Our study revealed complicated associations among gut microbiota, metabolites, and immune system during pregnancy and identified some specific metabolites which may act as mediators between symbiotic microorganisms and immune homeostasis,” the authors wrote.

SOURCE:

The study, led by Ting Huang, Department of Obstetrics and Gynecology, the First Affiliated Hospital of Jinan University, Guangzhou, China, was published online on February 7, 2024, in mSystems.

LIMITATIONS:

The small sample size of the study may have limited capacity to address errors resulting from individual differences. No causal relationships between gut microbiota, metabolites, and immune system response could be confirmed. Researchers were unable to account for the possible effects of confounding variables, such as diet, because of the cross-sectional nature of this study.

DISCLOSURES:

This study was funded by the National Natural Science Foundation of China. The authors declared no conflicts of interest.

A version of this article first appeared on Medscape.com.