Reproductive and Behavior Dysfunction Induced by Maternal Androgen Exposure and Obesity Is Likely Not Gut Microbiome-Mediated

The Gut Microbiome and Female Health

The possession of two X chromosomes may come with the risk of various illnesses, females are more likely to be affected by osteoarthritis, heart disease, and anxiety. Given the reported correlations between gut microbiome dysbiosis and various illnesses, the female gut microbiome is worthy of exploration. Herein, we discuss the composition of the female gut microbiota and its dysbiosis in pathologies affecting the female population. Using PubMed, we performed a literature search, using key terms, namely: "gut microbiome", "estrogen", "menopause", "polycystic ovarian syndrome", "pregnancy", and "menstruation". In polycystic ovarian syndrome (PCOS), the abundance of Bacteroides vulgatus, Firmicutes, Streptococcus, and the ratio of Escherichia/Shigella was found to be increased while that of Tenericutes ML615J-28, Tenericutes 124-7, Akkermansia, Ruminococcaceae, and Bacteroidetes S24-7 was reduced. In breast cancer, the abundance of Clostridiales was enhanced, while in cervical cancer, Prevotella, Porphyromonas, and Dialister were enhanced but Bacteroides, Alistipes, and members of Lachnospiracea, were decreased. In ovarian cancer, Prevotella abundance was increased. Interestingly, the administration of Lactobacillus acidophilus, Bifidobacterium bifidum, Lactobacillus reuteri, and Lactobacillus fermentum ameliorated PCOS symptoms while that of a mix of Bifidobacterium lactis W51, Bifidobacterium bifidum W23, Lactobacillus brevis W63, Bifidobacterium lactis W52, Lactobacillus salivarius W24, Lactobacillus acidophilus W37, Lactococcus lactis W19, Lactobacillus casei W56, and Lactococcus lactis W58 alleviated vascular malfunction and arterial stiffness in obese postmenopausal women, and finally, while further research is needed, Prevotella maybe protective against postmenopausal bone mass loss. As several studies report the therapeutic potential of probiotics and since the gut microbiota of certain female pathological states has been relatively characterized, we speculate that the administration of certain bacterial species as probiotics is warranted, as novel independent or adjunct therapies for various female pathologies.

The interplay between PCOS pathology and diet on gut microbiota in a mouse model

The gut microbiome has been implicated in polycystic ovary syndrome (PCOS) pathophysiology. PCOS is a disorder with reproductive, endocrine and metabolic irregularities, and several studies report that PCOS is associated with a decrease in microbial diversity and composition. Diet is an important regulator of the gut microbiome, as alterations in macronutrient composition impact the balance of gut microbial communities. This study investigated the interplay between macronutrient balance and PCOS on the gut microbiome of control and dihydrotestosterone (DHT)-induced PCOS-like mice exposed to diets that varied in protein (P), carbohydrate (C) and fat (F) content. The amount of dietary P, C and F consumed significantly altered alpha (α) and beta (β) diversity of the gut microbiota of control and PCOS-like mice. However, α-diversity between control and PCOS-like mice on the same diet did not differ significantly. In contrast, β-diversity was significantly altered by PCOS pathology. Further analysis identified an operational taxonomic unit (OTU) within Bacteroides (OTU3) with 99.2% similarity to Bacteroides acidifaciens, which is inversely associated with obesity, to be significantly decreased in PCOS-like mice. Additionally, this study investigated the role of the gut microbiome in the development of PCOS traits, whereby PCOS-like mice were transplanted with healthy fecal microbiota from control mice. Although the PCOS gut microbiome shifted toward that of control mice, PCOS traits were not ameliorated. Overall, these findings demonstrate that while diet exerts a stronger influence over gut microbiota diversity than PCOS pathology, overall gut microbiota composition is affected by PCOS pathology.

Maternal and early life exposures and their potential to influence development of the microbiome

At the dawn of the twentieth century, the medical care of mothers and children was largely relegated to family members and informally trained birth attendants. As the industrial era progressed, early and key public health observations among women and children linked the persistence of adverse health outcomes to poverty and poor nutrition. In the time hence, numerous studies connecting genetics ("nature") to public health and epidemiologic data on the role of the environment ("nurture") have yielded insights into the importance of early life exposures in relation to the occurrence of common diseases, such as diabetes, allergic and atopic disease, cardiovascular disease, and obesity. As a result of these parallel efforts in science, medicine, and public health, the developing brain, immune system, and metabolic physiology are now recognized as being particularly vulnerable to poor nutrition and stressful environments from the start of pregnancy to 3 years of age. In particular, compelling evidence arising from a diverse array of studies across mammalian lineages suggest that modifications to our metagenome and/or microbiome occur following certain environmental exposures during pregnancy and lactation, which in turn render risk of childhood and adult diseases. In this review, we will consider the evidence suggesting that development of the offspring microbiome may be vulnerable to maternal exposures, including an analysis of the data regarding the presence or absence of a low-biomass intrauterine microbiome.

Pathophysiology of polycystic ovary syndrome revisited: Current understanding and perspectives regarding future research

Background

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder among reproductive-age women and has lifelong effects on health.

Methods

In this review, I discuss the pathophysiology of PCOS. First, I summarize our current understanding of the etiology and pathology of PCOS, then, discuss details of two representative environmental factors involved in the pathogenesis of PCOS. Finally, I present perspectives regarding the directions of future research.

Main findings

The pathophysiology of PCOS is heterogeneous and shaped by the interaction of reproductive dysfunction and metabolic disorders. Hyperandrogenism and insulin resistance exacerbate one another during the development of PCOS, which is also affected by dysfunction of the hypothalamus-pituitary-ovarian axis. PCOS is a highly heritable disorder, and exposure to certain environmental factors causes individuals with predisposing genetic factors to develop PCOS. The environmental factors that drive the development of PCOS pathophysiology make a larger contribution than the genetic factors, and may include the intrauterine environment during the prenatal period, the follicular microenvironment, and lifestyle after birth.

Conclusion

On the basis of this current understanding, three areas are proposed to be subjects for future research, with the ultimate goals of developing therapeutic and preventive strategies and providing appropriate lifelong management, including preconception care.

Temporal relationship between alterations in the gut microbiome and the development of polycystic ovary syndrome-like phenotypes in prenatally androgenized female mice

It has been recently recognized that prenatal androgen exposure is involved in the development of polycystic ovary syndrome (PCOS) in adulthood. In addition, the gut microbiome in adult patients and rodents with PCOS differs from that of healthy individuals. Moreover, recent studies have suggested that the gut microbiome may play a causative role in the pathogenesis of PCOS. We wondered whether prenatal androgen exposure induces gut microbial dysbiosis early in life and is associated with the development of PCOS in later life. To test this hypothesis, we studied the development of PCOS-like phenotypes in prenatally androgenized (PNA) female mice and compared the gut microbiome of PNA and control offspring from 4 to 16 weeks of age. PNA offspring showed a reproductive phenotype from 6 weeks and a metabolic phenotype from 12 weeks of age. The α-diversity of the gut microbiome of the PNA group was higher at 8 weeks and lower at 12 and 16 weeks of age, and the β-diversity differed from control at 8 weeks. However, a significant difference in the composition of gut microbiome between the PNA and control groups was already apparent at 4 weeks. Allobaculum and Roseburia were less abundant in PNA offspring, and may therefore be targets for future interventional studies. In conclusion, abnormalities in the gut microbiome appear as early as or even before PCOS-like phenotypes develop in PNA mice. Thus, the gut microbiome in early life is a potential target for the prevention of PCOS in later life.

How biological sex of the host shapes its gut microbiota

The gut microbiota is a complex system, consisting of a dynamic population of microorganisms, involved in the regulation of the host's homeostasis. A vast number of factors are driving the gut microbiota composition including diet, antibiotics, environment, and lifestyle. However, in the past decade, a growing number of studies also focused on the role of sex in relationship to changes in the gut microbiota composition in animal experiments as well as in human beings. Despite the progress in investigation techniques, still little is known about the mechanism behind the observed sex-related differences. In this review, we summarized current knowledge on the sex-dependent differences of the intestinal commensals and discuss the probable direct impact of sex hormones and more indirect effects such as dietary habits or antibiotics. While we have to conclude limited data on specific developmental stages, a clear role for sexual hormones and most probably for testosterone emerges.

Investigating causality with fecal microbiota transplantation in rodents: applications, recommendations and pitfalls

In recent years, studies investigating the role of the gut microbiota in health and diseases have increased enormously - making it essential to deepen and question the research methodology employed. Fecal microbiota transplantation (FMT) in rodent studies (either from human or animal donors) allows us to better understand the causal role of the intestinal microbiota across multiple fields. However, this technique lacks standardization and requires careful experimental design in order to obtain optimal results. By comparing several studies in which rodents are the final recipients of FMT, we summarize the common practices employed. In this review, we document the limitations of this method and highlight different parameters to be considered while designing FMT Studies. Standardizing this method is challenging, as it differs according to the research topic, but avoiding common pitfalls is feasible. Several methodological questions remain unanswered to this day and we offer a discussion on issues to be explored in future studies.

Maternal Testosterone Excess Contributes to Reproductive System Dysfunction of Female Offspring Mice

Hyperandrogenism is considered 1 of the most important characteristics of polycystic ovary syndrome, which affects more than 10% of females of reproductive age and is a common cause of infertility. In addition to the effects on patients themselves, maternal androgen excess has also been reported to impair the growth and development of offspring. In our current study, we found that maternal testosterone (T) treatment during different gestational stages increased the percentage of atretic follicle and decreased corpus luteum formation in female offspring. In addition, decreased serum estradiol and increased T levels were also observed in female offspring of T-treated mice during late gestational stage. Further studies revealed that Forkhead box protein L2 (FOXL2) and Cytochrome P450 family 19 subfamily a member 1 (CYP19A1) expression in granulosa cells of these female offspring mice were decreased. By using mouse primary granulosa cells and the KGN cell line, we demonstrated that decreasing FOXL2 and CYP19A1 levels in ovarian granulosa cells partially may contribute to disturbed sex hormone synthesis in female offspring of T-treated mice during the late gestational stage. Findings from our current study highlight a critical role of excess maternal T exposure, especially during the late gestational stage, which could further lead to aberrant ovary development and sex hormone synthesis in female offspring.