Microbiome and pregnancy: focus on microbial dysbiosis coupled with maternal obesity

Obesity is becoming a worldwide pandemic with over one billion people affected. Of women in the United States, who are of childbearing age, two-thirds of them are considered overweight/obese. Offspring of women with obesity have a greater likelihood of developing cardiometabolic disease later in life, therefore making obesity a transgenerational issue. Emerging topics such as maternal microbial dysbiosis with altered levels of bacterial phyla and maternal obesity programming offspring cardiometabolic disease are a novel area of research discussed in this review. In the authors' opinion, beneficial therapeutics will be developed from knowledge of bacterial-host interactions at the most specific level possible. Although there is an abundance of obesity-related microbiome research, it is not concise, readily available, nor easy to interpret at this time. This review details the current knowledge regarding the relationship between obesity and the gut microbiome, with an emphasis on maternal obesity.

Metagenetic Analysis of the Pregnant Microbiome in Horses

Placentitis is the leading cause of infectious abortion in the horse. Additionally, it can result in weak and/or growth restricted offspring. While the etiology of ascending placentitis is well described in mares, less is known regarding the pathogenesis of other types, such as nocardioform placentitis. This study aims to identify the microbial communities in different body sites of the pregnant mare in early gestation to establish a core microbiome that may be perturbed in pathologic pregnancies such as placentitis. We hypothesize that the equine placenta harbors a distinct resident microbiome in early pregnancy when characterized by metagenetics and that there will be a disparity in bacterial communities from the oral, vaginal, and fecal microbiome. Samples were collected from the oral cavity, vagina, anus, and the allantoic portion of the allantochorion ("placenta") from five pregnant mares between 96 and 120 days of gestation. The V4 region of the 16S rRNA gene was amplified for Illumina MiSeq sequencing to examine core bacterial communities present in the different body sites. Microbial community composition of the pregnant ponies by body site was significantly different (Bray-Curtis dissimilarity). The placenta was significantly different from the feces, oral cavity, and vagina. Alpha diversity measuring the Shannon diversity matrix was significant, with the body sites being a compounding variable, meaning there was a difference in richness and evenness in the different microbial communities. Feces had the greatest alpha diversity, while the oral cavity and placenta similarly had the least. In conclusion, metagenetics did reveal distinct community differences in the oral, fecal, vaginal, and placenta cavities of the horse. The equine placenta does show similarities in its microbial communities to the oral cavity. Further research needs to be completed to investigate how bacteria may be translocated to the placenta from these other body sites and how they contribute to the development of placentitis.

Effects of fenbendazole on fecal microbiome in BPH/5 mice, a model of hypertension and obesity, a brief report

Fenbendazole (FBZ) is a common antiparasitic treatment used in research rodent colonies for biosecurity purposes. The effect of this compound has been studied in C57 mice, but never before in a strain of mice that has co-morbidities, such as the blood pressure high (BPH)/5. The BPH/5 mouse is an inbred genetic model of hypertension. While both male and female BPH/5 have high blood pressure, there is a metabolic sexual dimorphism with females displaying key features of obesity. The obese gut microbiome has been linked to hypertension. Therefore, we hypothesized that fenbendazole treatment will alter the gut microbiome in hypertensive mice in a sex dependent manner. To test the influence of FBZ on the BPH/5 gut microbiota, fecal samples were collected pre- and post-treatment from adult BPH/5 mice (males and non-pregnant females). The mice were treated with fenbendazole impregnated feed for five weeks. Post-treatment feces were collected at the end of the treatment period and DNA was extracted, and the V4 region of 16S rRNA was amplified and sequenced using the Illumina MiSeq system. The purpose was to analyze the fecal microbiome before and after FBZ treatment, the results demonstrate changes with treatment in a sex dependent manner. More specifically, differences in community composition were detected in BPH/5 non-pregnant female and males using Bray-Curtis dissimilarity as a measure of beta-diversity (treatment p = 0.002). The ratio of Firmicutes to Bacteroidetes, which has been identified in cases of obesity, was not altered. Yet, Verrucomicrobia was increased in BPH/5 males and females post-treatment and was significantly different by sex (treatment p = 5.85e-05, sex p = 0.0151, and interaction p = 0.045), while Actinobacteria was decreased in the post-treatment mice (treatment p = 0.00017, sex p = 0.5, interaction p = 0.2). These results are indicative of gut dysbiosis compared to pre-treatment controls. Lactobacillus was decreased with FBZ treatment in BPH/5 females only. In conclusion, fenbendazole does alter the gut microbial communities, most notable in the male rather than female BPH/5 mouse. This provides evidence that caution should be taken when providing any gut altering treatments before or during mouse experiments.

Sexually dimorphic pubertal development and adipose tissue kisspeptin dysregulation in the obese and preeclamptic-like BPH/5 mouse model offspring

Preeclampsia (PE) is a devastating hypertensive disorder of pregnancy closely linked to obesity. Long-term adverse outcomes may occur in offspring from preeclamptic pregnancies. Accordingly, sex-specific changes in pubertal development have been described in children from preeclamptic women, but the underlying mechanisms remain vastly unexplored. Features of PE are spontaneously recapitulated by the blood pressure high subline 5 (BPH/5) mouse model, including obesity and dyslipidemia in females before and throughout pregnancy, superimposed hypertension from late gestation to parturition and fetal growth restriction. A sexually dimorphic cardiometabolic phenotype has been described in BPH/5 offspring: while females are hyperphagic, hyperleptinemic, and overweight, with increased reproductive white adipose tissue (rWAT), males have similar food intake, serum leptin concentration, body weight and rWAT mass as controls. Herein, pubertal development and adiposity were further investigated in BPH/5 progeny. Precocious onset of puberty occurs in BPH/5 females, but not in male offspring. When reaching adulthood, the obese BPH/5 females display hypoestrogenism and hyperandrogenism. Kisspeptins, a family of peptides closely linked to reproduction and metabolism, have been previously shown to induce lipolysis and inhibit adipogenesis. Interestingly, expression of kisspeptins (Kiss1) and their cognate receptor (Kiss1r) in the adipose tissue seem to be modulated by the sex steroid hormone milieu. To further understand the metabolic-reproductive crosstalk in the BPH/5 offspring, Kiss1/Kiss1r expression in male and female rWAT were investigated. Downregulation of Kiss1/Kiss1r occurs in BPH/5 females when compared to males. Interestingly, dietary weight loss attenuated circulating testosterone concentration and rWAT Kiss1 downregulation in BPH/5 females. Altogether, the studies demonstrate reproductive abnormalities in offspring gestated in a PE-like uterus, which appear to be closely associated to the sexually dimorphic metabolic phenotype of the BPH/5 mouse model.

Kisspeptin Is Upregulated at the Maternal-Fetal Interface of the Preeclamptic-like BPH/5 Mouse and Normalized after Synchronization of Sex Steroid Hormones

Insufficient invasion of conceptus-derived trophoblast cells in the maternal decidua is a key event in the development of early-onset preeclampsia (PE), a subtype of PE associated with high maternal and fetal morbidity and mortality. Kisspeptins, a family of peptides previously shown to inhibit trophoblast cell invasion, have been implicated in the pathogenesis of early-onset PE. However, a role of kisspeptin signaling during the genesis of this syndrome has not been elucidated. Herein, we used the preeclamptic-like BPH/5 mouse model to investigate kisspeptin expression and potential upstream regulatory mechanisms in a PE-like syndrome. Expression of the kisspeptin encoding gene, Kiss1, and the 10-amino-acid kisspeptide (Kp-10), are upregulated in the non-pregnant uterus of BPH/5 females during diestrus and in the maternal-fetal interface during embryonic implantation and decidualization. Correspondingly, the dysregulation of molecular pathways downstream to kisspeptins also occurs in this mouse model. BPH/5 females have abnormal sex steroid hormone profiles during early gestation. In this study, the normalization of circulating concentrations of 17β-estradiol (E2) and progesterone (P4) in pregnant BPH/5 females not only mitigated Kiss1 upregulation, but also rescued the expression of multiple molecules downstream to kisspeptin and ameliorated adverse fetoplacental outcomes. Those findings suggest that uterine Kiss1 upregulation occurs pre-pregnancy and persists during early gestation in a PE-like mouse model. Moreover, this study highlights the role of sex steroid hormones in uteroplacental Kiss1 dysregulation and the improvement of placentation by normalization of E2, P4 and Kiss1.

Abstract P097: Effect Of Maternal Fecal Microbiome And Adverse Pregnancy Outcomes In The Obese BPH/5 Female Mice

Obesity is a worldwide pandemic and of women childbearing age in the US, two-thirds are considered overweight/obese. Maternal microbial dysbiosis associated with obesity may play a role in adverse pregnancy outcomes. To better understand the relationship of microbiome and adverse pregnancy outcomes, we utilized the obese hypertensive BPH/5 mouse model of preeclampsia (PE). We hypothesized that the maternal fecal microbiome during pregnancy will differ in the BPH/5 mice compared to lean normotensive C57 controls as well as non-pregnant (NP) BPH/5 females. We have shown that adult BPH/5 female mice have an adverse cardiometabolic phenotype: hypertension and obesity that is exaggerated by pregnancy and phenocopies PE. To test our hypothesis, fecal samples were collected from NP and pregnant (P) BPH/5 and C57 control females in late gestation and Illumina sequencing of 16S v4 rRNA amplicon libraries were used to compare microbiomes. Microbial community composition of BPH/5 compared to C57 P mice were significantly different (variance of 33.59% in PCo1 and Pco2 11.48%, n=9-17, p=0.001, PERMANOVA with Bray-Curtis dissimilarity of 16S Amplicon Sequence Variant’s relative abundance). Alpha diversity was increased in BPH/5 compared to C57 P mice (n=9-17, p=0.005). There was a difference in beta diversity within the communities in BPH5 P mice compared to BPH5 NP mice, suggesting that the fecal microbiome was altered with pregnancy (n=9-17, p=0.006), but no difference was seen in the alpha diversity meaning that the richness and evenness were similar (n=9-17, p=0.115). The most abundant phyla are represented by 49.39% Firmicutes, 38.54% Bacteroidetes, and 7.48% Epsilonbacteraeota. The most abundant genera including 22.59% Alistipes, 19.57% Lachnospiraceae genus unknown, and 9.85% Helicobacter within the BPH5 samples. Muribaculum spp (p=1.58e-06) and Lachnospiraceae_NK4A136_unclassified (p=2.46e-03) showing significant decreases with pregnancy. In conclusion, obese BPH5 dams have altered fecal microbial communities associated with obesity and adverse pregnancy outcomes. Further investigations are necessary to further understand the importance of these microbial community changes and how they play a role in maternal hypertension and offspring.

Sex-specific effects of maternal weight loss on offspring cardiometabolic outcomes in the obese preeclamptic-like mouse model, BPH/5

AbstractPreeclampsia (PE) is a hypertensive disorder that impacts 2-8% of pregnant women worldwide. It is characterized by new onset hypertension during the second half of gestation and is a leading cause of maternal and fetal morbidity/mortality. Maternal obesity increases the risk of PE and is a key predictor of childhood obesity and potentially offspring cardiometabolic complications in a sex-dependent manner. The influence of the maternal obesogenic environment, with superimposed PE, on offspring development into adulthood is unknown. Obese BPH/5 mice spontaneously exhibit late-gestational hypertension, fetal demise and growth restriction, and excessive gestational weight gain. BPH/5 females have improved pregnancy outcomes when maternal weight loss via pair-feeding is imposed beginning at conception. We hypothesized that phenotypic differences between female and male BPH/5 offspring can be influenced by pair feeding BPH/5 dams during pregnancy. BPH/5 pair-fed dams have improved litter sizes and increased fetal body weights. BPH/5 offspring born to ad libitum dams have similar sex ratios, body weights, and fecal microbiome as well as increased blood pressure that is reduced in the dam pair-fed offspring. Both BPH/5 male and female offspring born to pair-fed dams have a reduction in adiposity and an altered gut microbiome, while only female offspring born to pair-fed dams have decreased circulating leptin and white adipose tissue inflammatory cytokines. These sexually dimorphic results suggest that reduction in the maternal obesogenic environment in early pregnancy may play a greater role in female BPH/5 sex-dependent cardiometabolic outcomes than males. Reprograming females may mitigate the transgenerational progression of cardiometabolic disease.

Cardiometabolic Phenotypic Differences in Male Offspring Born to Obese Preeclamptic-Like BPH/5 Mice

Preeclampsia (PE) is a hypertensive disorder of pregnancy occurring in approximately 10% of women worldwide. While it is life threatening to both the mother and baby, the only effective treatment is delivery of the placenta and fetus, which is often preterm. Maternal obesity is a risk factor for PE, and the effects of both on offspring are long standing with increased incidence of cardiometabolic disease in adulthood. Obese BPH/5 mice spontaneously exhibit excessive gestational weight gain and late-gestational hypertension, similar to women with PE, along with fetal growth restriction and accelerated compensatory growth in female offspring. We hypothesized that BPH/5 male offspring will demonstrate cardiovascular and metabolic phenotypes similar to BPH/5 females. As previously described, BPH/5 females born to ad libitum-fed dams are overweight with hyperphagia and increased subcutaneous, peri-renal, and peri-gonadal white adipose tissue (WAT) and cardiomegaly compared to age-matched adult female controls. In this study, BPH/5 adult male mice have similar body weights and food intake compared to age-matched control mice but have increased inflammatory subcutaneous and peri-renal WAT and signs of cardiovascular disease: left ventricular hypertrophy and hypertension. Therefore, adult male BPH/5 do not completely phenocopy the cardiometabolic profile of female BPH/5 mice. Future investigations are necessary to understand the differences observed in BPH/5 male and female mice as they age. In conclusion, the impact of fetal programming due to PE has a transgenerational effect on both male and female offspring in the BPH/5 mouse model. The maternal obesogenic environment may play a role in PE pregnancy outcomes, including offspring health as they age.

Maternal microbiome and the hypertensive disorder of pregnancy, preeclampsia

Preeclampsia (PE) is a pregnancy-specific disorder that can be life threatening for both mother and baby. It is characterized by a new onset hypertension during the second half of pregnancy and affects ~300,000 women in the United States every year. There is no cure for PE, and the only effective treatment is delivery of the placenta and the fetus, which is often preterm. PE is believed to be a severe manifestation of placental dysfunction due to early angiogenic imbalances and inflammatory disturbances; however, the cause of this is unknown. The once thought "sterile" placenta now has been proposed to have a unique microbiome of its own. Under ideal conditions, the microbiome represents a balanced bacterial community that is important to the maintenance of a healthy environment. Dysbiosis of these communities may lead to inflammation that potentially contributes to adverse pregnancy outcomes, such as preterm birth and PE. Thus far, the female reproductive tract microbiome has been found to be influenced by periodontal disease, cardiometabolic complications, and maternal obesity, all of which have been identified as contributors to PE. This review will look at the maternal reproductive tract microbiome, evidence for and against, and its role in pregnancy and PE-related events as well as data from relevant mouse models that could be useful for further investigating the influence of the reproductive tract microbiome on the pathogenesis of PE.

Dyslipidemia and the role of adipose tissue in early pregnancy in the BPH/5 mouse model for preeclampsia

The hypertensive pregnancy disorder preeclampsia (PE) is a leading cause of fetal and maternal morbidity/mortality. Obesity increases the risk to develop PE, presumably via the release of inflammatory mediators from the adipose tissue, but the exact etiology remains largely unknown. Using obese PE-like blood pressure high subline 5 (BPH/5) and lean gestational age-matched C57Bl6 mice, we aimed to obtain insight into differential reproductive white adipose tissue (rWAT) gene expression, circulating lipids and inflammation at the maternal-fetal interface during early pregnancy. In addition, we investigated the effect of 7 days 25% calorie restriction (CR) in early pregnancy on gene expression in rWAT and implantation sites. Compared with C57Bl6, female BPH/5 are dyslipidemic before pregnancy and show an amplification of rWAT mass, circulating cholesterol, free fatty acids, and triacylglycerol levels throughout pregnancy. RNA sequencing showed that pregnant BPH/5 mice have elevated gene enrichment in pathways related to inflammation and cholesterol biosynthesis at embryonic day (e) 7.5. Expression of cholesterol-related HMGCS1, MVD, Cyp51a1, and DHCR was validated by quantitative reverse-transcription-polymerase chain reaction. CR during the first 7 days of pregnancy restored the relative mRNA expression of these genes to a level comparable to C57Bl6 pregnant females and reduced the expression of circulating leptin and proinflammatory prostaglandin synthase 2 in both rWAT and implantation sites in BPH/5 mice at e7.5. Our data suggest a possible role for rWAT in the dyslipidemic state and inflammatory uterine milieu that might underlie the pathogenesis of PE. Future studies should further address the physiological functioning of the adipose tissue in relation to PE-related pregnancy outcomes.

Rapid regrowth and detection of microbial contaminants in equine fecal microbiome samples

Advances have been made to standardize 16S rRNA gene amplicon based studies for inter-study comparisons, yet there are many opportunities for systematic error that may render these comparisons improper and misleading. The fecal microbiome of horses has been examined previously, however, no universal horse fecal collection method and sample processing procedure has been established. This study was initialized in large part to ensure that samples collected by different individuals from different geographical areas (i.e., crowdsourced) were not contaminated due to less than optimal sampling or holding conditions. In this study, we examined the effect of sampling the surface of fecal pellets compared to homogenized fecal pellets, and also the effect of time of sampling after defecation on ‘bloom’ taxa (bloom taxa refers to microbial taxa that can grow rapidly in horse feces post-defecation) using v4 16S rRNA amplicon libraries. A total of 1,440,171 sequences were recovered from 65 horse fecal samples yielding a total of 3,422 OTUs at 97% similarity. Sampling from either surface or homogenized feces had no effect on diversity and little effect on microbial composition. Sampling at various time points (0, 2, 4, 6, 12 h) had a significant effect on both diversity and community composition of fecal samples. Alpha diversity (Shannon index) initially increased with time as regrowth taxa were detected in the amplicon libraries, but by 12 h the diversity sharply decreased as the community composition became dominated by a few bloom families, including Bacillaceae, Planococcaeae, and Enterococcaceae, and other families to a lesser extent. The results show that immediate sampling of horse feces must be done in order to ensure accurate representation of horse fecal samples. Also, several of the bloom taxa found in this study are known to occur in human and cattle feces post defecation. The dominance of these taxa in feces shortly after defecation suggests that the feces is an important habitat for these organisms, and horse fecal samples that were improperly stored can be identified by presence of bloom taxa.