1.
Naturalization of the microbiota developmental trajectory of Cesarean-born neonates after vaginal seeding.
Song, SJ, Wang, J, Martino, C, Jiang, L, Thompson, WK, Shenhav, L, McDonald, D, Marotz, C, Harris, PR, Hernandez, CD, et al
Med (New York, N.Y.). 2021;2(8):951-964.e5
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Studies on model organisms show that foetal development can be modulated by microbial products from the pregnant mother’s microbiota, and early colonisation is critical for immune system development. However, natural transmission and colonisation of maternal microbes is impaired by caesarean section (CS) delivery. The aim of this study was to determine the effect of restoring exposure to maternal vaginal fluids after CS birth. This study is a large observational study of 177 infants born to 174 mothers. Physicians assessed healthy mothers who were set to deliver vaginally or by scheduled CS. Results demonstrate that microbial differences associated with delivery mode can be reduced by exposure to a vaginal microbial source at birth. In fact, birth mode significantly differentiated infant gut and skin microbiome development, and that seeding worked to adjust the trajectory of CS-delivered infants through partial restoration of microbiome features associated with a vaginal delivery. Authors conclude that restoring natural exposures at birth may be one way to reduce the risk of CS-associated diseases such as obesity, asthma, allergies, and immune disfunctions. However, randomised clinical trials on large cohorts are needed to gain conclusive evidence for microbial restoration at birth improving health outcomes.
Abstract
BACKGROUND Early microbiota perturbations are associated with disorders that involve immunological underpinnings. Cesarean section (CS)-born babies show altered microbiota development in relation to babies born vaginally. Here we present the first statistically powered longitudinal study to determine the effect of restoring exposure to maternal vaginal fluids after CS birth. METHODS Using 16S rRNA gene sequencing, we followed the microbial trajectories of multiple body sites in 177 babies over the first year of life; 98 were born vaginally, and 79 were born by CS, of whom 30 were swabbed with a maternal vaginal gauze right after birth. FINDINGS Compositional tensor factorization analysis confirmed that microbiota trajectories of exposed CS-born babies aligned more closely with that of vaginally born babies. Interestingly, the majority of amplicon sequence variants from maternal vaginal microbiomes on the day of birth were shared with other maternal sites, in contrast to non-pregnant women from the Human Microbiome Project (HMP) study. CONCLUSIONS The results of this observational study prompt urgent randomized clinical trials to test whether microbial restoration reduces the increased disease risk associated with CS birth and the underlying mechanisms. It also provides evidence of the pluripotential nature of maternal vaginal fluids to provide pioneer bacterial colonizers for the newborn body sites. This is the first study showing long-term naturalization of the microbiota of CS-born infants by restoring microbial exposure at birth. FUNDING C&D, Emch Fund, CIFAR, Chilean CONICYT and SOCHIPE, Norwegian Institute of Public Health, Emerald Foundation, NIH, National Institute of Justice, Janssen.
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Maternal diet during pregnancy is related with the infant stool microbiome in a delivery mode-dependent manner.
Lundgren, SN, Madan, JC, Emond, JA, Morrison, HG, Christensen, BC, Karagas, MR, Hoen, AG
Microbiome. 2018;6(1):109
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The mechanism by which the maternal diet may influence the gut microbiota of an infant remains unknown. This study aimed to examine the association of maternal diet during pregnancy and mode of delivery on the gut microbiome 6 weeks post-delivery. 976 subjects were enrolled aged of 18 and 45 years old, between 24 and 28 weeks of gestation and their maternal diet during pregnancy was assessed with a validated food frequency questionnaire. Effects of maternal dairy intake on infant gut microbiota showed decreased colonization of milk-digesting bacteria in infants delivered by caesarean section, when compared to those who were born vaginally. The authors concluded that future studies examining the relationship between maternal diet and components of breast milk including microbial and nutritional profiles, may help to offer insight into the mechanism by which maternal diet influences the gut microbiome of an infant.
Abstract
BACKGROUND The gut microbiome has an important role in infant health and immune development and may be affected by early-life exposures. Maternal diet may influence the infant gut microbiome through vertical transfer of maternal microbes to infants during vaginal delivery and breastfeeding. We aimed to examine the association of maternal diet during pregnancy with the infant gut microbiome 6 weeks post-delivery in mother-infant dyads enrolled in the New Hampshire Birth Cohort Study. Infant stool samples were collected from 145 infants, and maternal prenatal diet was assessed using a food frequency questionnaire. We used targeted sequencing of the 16S rRNA V4-V5 hypervariable region to characterize infant gut microbiota. To account for differences in baseline and trajectories of infant gut microbial profiles, we stratified analyses by delivery mode. RESULTS We identified three infant gut microbiome clusters, characterized by increased abundance of Bifidobacterium, Streptococcus and Clostridium, and Bacteroides, respectively, overall and in the vaginally delivered infant stratum. In the analyses stratified to infants born vaginally and adjusted for other potential confounders, maternal fruit intake was associated with infant gut microbial community structure (PERMANOVA, p < 0.05). In multinomial logistic regression analyses, increased fruit intake was associated with an increased odds of belonging to the high Streptococcus/Clostridium group among infants born vaginally (OR (95% CI) = 2.73 (1.36, 5.46)). In infants delivered by Cesarean section, we identified three clusters that differed slightly from vaginally delivered infants, which were characterized by a high abundance of Bifidobacterium, high Clostridium and low Streptococcus and Ruminococcus genera, and high abundance of the family Enterobacteriaceae. Maternal dairy intake was associated with an increased odds of infants belonging to the high Clostridium cluster in infants born by Cesarean section (OR (95% CI) = 2.36 (1.05, 5.30)). Linear models suggested additional associations between maternal diet and infant intestinal microbes in both delivery mode strata. CONCLUSIONS Our data indicate that maternal diet influences the infant gut microbiome and that these effects differ by delivery mode.
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Human Gut Microbiota and Gastrointestinal Cancer.
Meng, C, Bai, C, Brown, TD, Hood, LE, Tian, Q
Genomics, proteomics & bioinformatics. 2018;16(1):33-49
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In this article the authors review research on the influence of the human gut microbiota on the development and progression of gastrointestinal cancers, and go into significant detail about the molecular mechanisms involved. Helicobacter pylori is a known risk factor for gastric cancer (GC) but other dysbiotic changes in the gut microbiota are also observed in GC. On the other hand, H. pylori is associated with a decreased risk for oesophageal cancer (OC). An increase in gram-negative bacteria is associated with OC, whilst gram-positive bacteria are dominant in a healthy oesophagus. Dietary factors are associated with the risk for colorectal cancer (CRC) and may be due to their effect on the bacterial composition of the bowel. The authors explore possible mechanisms for these links. Although the liver is considered sterile, carcinogenesis can be influenced by the gut microbiota through pathogens and bacterial metabolites which can disturb metabolic pathways and immune responses in the liver. In pancreatic cancer (PC), the gut microbiota may influence carcinogenesis by promoting inflammation. In addition to various lifestyle factors, H. pylori is a risk factor for PC. The authors also review the use of prebiotics, probiotics, synbiotics (a combination of pre- and pro-biotics) and Traditional Chinese Medicine as an adjunct to conventional cancer treatment to reduce side effects, as well as their potential preventive mechanisms.
Abstract
Human gut microbiota play an essential role in both healthy and diseased states of humans. In the past decade, the interactions between microorganisms and tumors have attracted much attention in the efforts to understand various features of the complex microbial communities, as well as the possible mechanisms through which the microbiota are involved in cancer prevention, carcinogenesis, and anti-cancer therapy. A large number of studies have indicated that microbial dysbiosis contributes to cancer susceptibility via multiple pathways. Further studies have suggested that the microbiota and their associated metabolites are not only closely related to carcinogenesis by inducing inflammation and immune dysregulation, which lead to genetic instability, but also interfere with the pharmacodynamics of anticancer agents. In this article, we mainly reviewed the influence of gut microbiota on cancers in the gastrointestinal (GI) tract (including esophageal, gastric, colorectal, liver, and pancreatic cancers) and the regulation of microbiota by diet, prebiotics, probiotics, synbiotics, antibiotics, or the Traditional Chinese Medicine. We also proposed some new strategies in the prevention and treatment of GI cancers that could be explored in the future. We hope that this review could provide a comprehensive overview of the studies on the interactions between the gut microbiota and GI cancers, which are likely to yield translational opportunities to reduce cancer morbidity and mortality by improving prevention, diagnosis, and treatment.