Abstract
Pregnancy is accompanied by maternal physiological adaptations including metabolic, endocrine, immune, cardiovascular, skeletomuscular and neurological modifications that facilitate fetal and placental growth and development. Emerging evidence suggests that the maternal intestinal microbiota is modified over the course of healthy pregnancy. We have recently identified a maternal intestinal microbial shift within hours of conception; a shift that continued with advancing gestation. It is possible that maternal gut bacterial profiles might be associated with the known endocrine changes that accompany the female reproductive (estrous) cycle. Methods: To determine whether the estrous cycle influenced the shifts in the maternal intestinal microbiota, time-matched fecal pellets were collected daily for 3 consecutive estrous cycles from individually housed, non-pregnant female C57BL/6J mice (n = 10) fed a control diet. Estrous stage was identified by cell type predominance in vaginal cytological samples. The corresponding fecal pellets for each estrous stage were processed for bacterial 16S rRNA sequencing of the variable 3 (V3) region. Results: Estrous cycle stage accounted for a very small and not statistically significant proportion of the variation in the fecal microbiota according to PERMANOVA testing performed on Bray-Curtis dissimilarity scores. These values displayed no significant clustering of fecal microbial communities by estrous stage. Conclusion: The estrous cycle does not result in any significant shift in the intestinal microbial community in the reproductively mature, regularly cycling female mouse.
Highlights
10 trillion (1013) bacteria reside within the human intestine[1]
We investigated the composition of the fecal microbiota throughout the reproductive estrous cycle in regularly cycling, non-pregnant female mice to understand whether sex-steroid hormones may be a factor influencing the intestinal bacterial community in lean female mice
Each stage in the murine reproductive cycle corresponds to significant alterations in circulating sex-steroid hormones (Fig 1), we used reproductive stage as a non-invasive proxy to investigate the association between reproductive hormones 17β-estradiol and progesterone, and the female intestinal microbiota
Summary
10 trillion (1013) bacteria reside within the human intestine[1]. These microbes constitute the intestinal microbiota, and the genes they encode along with the environment they inhabit are known as our microbiome[2]. These organisms have been coined our “forgotten organ”, living symbiotically with the host, having coevolved with vertebrates over many millennia[3]. Intestinal commensals have been suggested to play a key role in the maintenance of host health: they facilitate the metabolism of indigestible polysaccharides, the production of essential nutrients, participate in energy and fat storage[4], the growth. It has been proposed that intestinal commensals may influence maternal adaptation to pregnancy[9]
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