A Higher Abundance of Actinomyces spp. in the Gut Is Associated with Spontaneous Preterm Birth

The causal relationship between gut microbiota and preterm birth: a two-sample Mendelian randomization study

BACKGROUND

Preterm birth, a significant global health concern, has been associated with alterations in the gut microbiota. However, the causal nature of this relationship remains uncertain due to the limitations inherent in observational studies.

PURPOSE

To investigate the potential causal relationship between gut microbiota imbalances and preterm birth.

METHODS

We conducted a two-sample Mendelian randomization (MR) study using genome-wide association study (GWAS) data from the MiBioGen consortium focusing on microbiota and preterm birth. Single nucleotide polymorphisms (SNPs) associated with the microbiota were selected as instrumental variables. The inverse variance weighting (IVW) method was used to estimate causality. We confirmed pleiotropy and identified and excluded outlier SNPs using MR-PRESSO and MR-Egger regression. Cochran's Q test was applied to assess heterogeneity among SNPs, and a leave-one-out analysis was performed to evaluate the influence of individual SNPs on overall estimates.

RESULTS

Our findings provide evidence for a causal link between specific components of the gut microbiota and preterm birth, with the identification of relevant metabolites.

CONCLUSION

This study highlights the causal role of gut microbiota imbalances in preterm birth, offering novel insights into the development of preterm birth and potential targets for prevention strategies.

Correlation Analyses of the Consumption of Artificial Sweeteners During Pregnancy and the Incidence of Gestational Diabetes Mellitus

Background

Pregnant women face a higher risk of developing gestational diabetes mellitus (GDM) due to the poor dietary habits. GDM can influence the health of both mothers and child. As food processing develops, pregnant women inevitably consume artificial sweeteners, among with the three most common are sucralose, aspartame, and sodium saccharin. It is a concern whether artificial sweeteners consumed during pregnancy increases GDM risk.

Purpose

To analyze the association between artificial sweetener consumption during pregnancy and the incidence of GDM.

Methods

422 pregnant women from a Guangdong hospital were surveyed through convenience sampling. The questionnaire collected general information, artificial sweeteners consumption and other GDM related factors. According to the International Association of Diabetes and Pregnancy Study Groups (IADPSG), GDM was diagnosed was met the 75g oral glucose tolerance test (OGTT) at any time of pregnancy. The consumption of artificial sweeteners was categorized into low and high-consumption groups according to a four-point scale. A multifactorial logistic regression model was used to control for confounders and analyze the association between artificial sweetener consumption andGDM.

Results

This study included 422 pregnant women with a mean age of (32 ± 3.73) years and a GDM incidence of 13.74%. The GDM incidence was higher in the high artificial sweeteners consumption group (56.90%), than in the low consumption group (43.10%) (p < 0.05). Increased artificial sweetener consumption was linked to a higher GDM risk (OR=2.66,95% CI: 1.48-1.78). High artificial sweeteners consumption was a GDM risk factor in BMI-stratified analyses.

Conclusion

High consumption of artificial sweeteners, like sucralose, aspartame, and sodium saccharin, is linked to increased risk of GDM in pregnant women. Further research is required to confirm results and explore mechanism, guiding healthy eating habits during pregnancy.

Intestinal flora was associated with occurrence risk of chronic non-communicable diseases

BACKGROUND

The intestinal flora (IF) has been linked to risks of non-communicable diseases, especially various cancers, stroke, and Alzheimer's disease. However, many uncertainties of these associations during different stages of growth, development, and aging still exist. Therefore, further in-depth explorations are warranted.

AIM

To explore the associations of the human IF with disease risks during different stages of growth, development, and aging to achieve more accurate and convincing conclusions.

METHODS

Cohort, cross-sectional, case-control, and Mendelian randomization studies published in the PubMed and Web of Science databases until December 31, 2023 were systematically reviewed to clarify the associations of the IF at the genus level with the risks of various non-communicable diseases, which were grouped in accordance with the 10th revision of the International Classification of Diseases.

RESULTS

In total, 57 studies were included to quantitatively examine the influence of the IF on the risks of 30 non-communicable diseases during different stages of growth, development, and aging. Population studies and Mendelian randomization studies confirmed positive associations of the abundances of Bifidobacterium and Ruminococcus with multiple sclerosis.

CONCLUSION

These findings contribute to a deeper understanding of the roles of the IF and provide novel evidence for effective strategies for the prevention and treatment of non-communicable diseases. In the future, it will be necessary to explore a greater variety of research techniques to uncover the specific mechanisms by which gut microbiota trigger diseases and conduct in-depth studies on the temporal relationship between microbiota alterations and diseases, so as to clarify the causal relationship more accurately.

Pregnancy during COVID 19 pandemic associated with differential gut microbiome composition as compared to pre-pandemic

The first two years of the COVID-19 pandemic and subsequent health mandates resulted in significant disruptions to daily life, creating a period of heightened psychosocial stress in myriad aspects. Understanding the impact of this period on pregnant individuals' bacteriomes is crucial as pregnancy is a period of heightened vulnerability to stress and its sequelae, anxiety and mood disorders, which have been demonstrated to alter gut microbiome composition. In a prospective cohort study (N = 12-26) conducted from February 2019 to August 2021, we examined psychometric responses and rectal microbiome swabs from pregnant individuals. Full-length 16 S rRNA sequencing followed by calculation of diversity metrics and relative abundance values were used to interrogate fecal microbiome community composition across pandemic groups. Distinct shifts in bacterial diversity and composition were observed during early to late pregnancy in the pandemic group, including lower relative abundance of pathogenic and lesser-known taxa. However, distribution of stress and depressive symptoms did not significantly differ from the pre-pandemic period while the correlation between stress and depressive symptoms dissipated during the pandemic. Our findings suggest that living through the COVID-19 pandemic altered the gut microbiome of pregnant individuals, independent of perceived stress.

Carbohydrate-Mediated Pregnancy Gut Microbiota and Neonatal Low Birth Weight

The effects of gut microbiota on the association between carbohydrate intake during pregnancy and neonatal low birth weight (LBW) were investigated. A prospective cohort study was conducted with 257 singleton-born mother-child pairs in Taiwan, and maternal dietary intake was estimated using a questionnaire, with each macronutrient being classified as low, medium, or high. Maternal fecal samples were collected between 24 and 28 weeks of gestation, and gut microbiota composition and diversity were profiled using 16S rRNA amplicon gene sequencing. Carbohydrates were the major source of total energy (56.61%), followed by fat (27.92%) and protein (15.46%). The rate of infant LBW was 7.8%, which was positively correlated with maternal carbohydrate intake. In the pregnancy gut microbiota, Bacteroides ovatus and Dorea spp. were indirectly and directly negatively associated with fetal growth, respectively; Rosenburia faecis was directly positively associated with neonatal birth weight. Maternal hypertension during pregnancy altered the microbiota features and was associated with poor fetal growth. Microbiota-accessible carbohydrates can modify the composition and function of the pregnancy gut microbiota, thus providing a potential marker to modulate deviations from dietary patterns, particularly in women at risk of hypertension during pregnancy, to prevent neonatal LBW.

Stress and depression-associated shifts in gut microbiota: A pilot study of human pregnancy

Background

Psychosocial stress and mood-related disorders, such as depression, are prevalent and vulnerability to these conditions is heightened during pregnancy. Psychosocial stress induces consequences via several mechanisms including the gut microbiota-brain axis and associated signaling pathways. Previous preclinical work indicates that prenatal stress alters maternal gut microbial composition and impairs offspring development. Importantly, although the fecal and vaginal microenvironments undergo alterations across pregnancy, we lack consensus regarding which shifts are adaptive or maladaptive in the presence of prenatal stress and depression. Clinical studies interrogating these relationships have identified unique taxa but have been limited in study design.

Methods

We conducted a prospective cohort study of pregnant individuals consisting of repeated administration of psychometrics (Perceived Stress Scale (PSS) and Center for Epidemiological Studies Depression Scale (CES-D)) and collection of fecal and vaginal microbiome samples. Fecal and vaginal microbial community composition across psychometric responses were interrogated using full-length 16S rRNA sequencing followed by α and β-diversity metrics and taxonomic abundance.

Results

Early pregnancy stress was associated with increased abundance of fecal taxa not previously identified in related studies, and stress from late pregnancy through postpartum was associated with increased abundance of typical vaginal taxa and opportunistic pathogens in the fecal microenvironment. Additionally, in late pregnancy, maternal stress and depression scores were associated with each other and with elevated maternal C-C motif chemokine ligand 2 (CCL2) concentrations. At delivery, concordant with previous literature, umbilical CCL2 concentration was negatively correlated with relative abundance of maternal fecal Lactobacilli. Lastly, participants with more severe depressive symptoms experienced steeper decreases in prenatal vaginal α-diversity.

Conclusion

These findings a) underscore previous preclinical and clinical research demonstrating the effects of prenatal stress on maternal microbiome composition, b) suggest distinct biological pathways for the consequences of stress versus depression and c) extend the literature by identifying several taxa which may serve critical roles in mediating this relationship. Thus, further interrogation of the role of specific maternal microbial taxa in relation to psychosocial stress and its sequelae is warranted.

Unveiling the dynamics of the breast milk microbiome: impact of lactation stage and gestational age

BACKGROUND

Breast milk (BM) provides complete nutrition for infants for the first six months of life and is essential for the development of the newborn's immature immune and digestive systems. While BM was conventionally believed to be sterile, recent advanced high throughput technologies have unveiled the presence of diverse microbial communities in BM. These insights into the BM microbiota have mainly originated from uncomplicated pregnancies, possibly not reflecting the circumstances of mothers with pregnancy complications like preterm birth (PTB).

METHODS

In this article, we investigated the BM microbial communities in mothers with preterm deliveries (before 37 weeks of gestation). We compared these samples with BM samples from healthy term pregnancies across different lactation stages (colostrum, transitional and mature milk) using 16S rRNA gene sequencing.

RESULTS

Our analysis revealed that the microbial communities became increasingly diverse and compositionally distinct as the BM matured. Specifically, mature BM samples were significantly enriched in Veillonella and lactobacillus (Kruskal Wallis; p < 0.001) compared to colostrum. The comparison of term and preterm BM samples showed that the community structure was significantly different between the two groups (Bray Curtis and unweighted unifrac dissimilarity; p < 0.001). Preterm BM samples exhibited increased species richness with significantly higher abundance of Staphylococcus haemolyticus, Propionibacterium acnes, unclassified Corynebacterium species. Whereas term samples were enriched in Staphylococcus epidermidis, unclassified OD1, and unclassified Veillonella among others.

CONCLUSION

Our study underscores the significant influence of pregnancy-related complications, such as preterm birth (before 37 weeks of gestation), on the composition and diversity of BM microbiota. Given the established significance of the maternal microbiome in shaping child health outcomes, this investigation paves the way for identifying modifiable factors that could optimize the composition of BM microbiota, thereby promoting maternal and infant health.