Distinctive subpopulations of the intestinal microbiota are present in women with unexplained chronic anovulation

Impact of Physiological Fluctuations of Sex Hormones During the Menstrual Cycle on Glucose Metabolism and the Gut Microbiota

Diabetes mellitus is one of the most prevalent chronic diseases. Previous studies have shown differences in glucose metabolism between males and females. Moreover, difficulties in medication adherence have been reported in females with type 2 diabetes. These observations are believed to be caused by fluctuations in sex hormone concentrations during the menstrual cycle. Furthermore, gut microbiota is linked to female host metabolism and sex hormone production. Understanding the interactions between fluctuating hormone concentrations during the menstrual cycle, gut microbiota, and glucose metabolism in humans is significant because of the increasing prevalence of diabetes and the consequent need to expand preventive efforts. A literature search was performed to determine and summarize the existing evidence, deduce future research needs to maintain female health, and investigate the relationship between the physiological menstrual cycle and glucose metabolism. Studies from 1967 to 2020 have already examined the relationship between variations during the menstrual cycle and glucose metabolism in healthy female subjects using an oral-glucose tolerance test or intravenous glucose tolerance test. However, the overall number of studies is rather small and the results are contradictory, as some studies detected differences in glucose concentrations depending on the different cycle phases, whereas others did not. Some studies reported lower glucose levels in the follicular phase than in the luteal phase, whereas another study detected the opposite. Data on gut microbiota in relation to the menstrual cycle are limited. Conflicting results exist when examining the effect of hormonal contraceptives on the gut microbiota and changes in the course of the menstrual cycle. The results indicate that the menstrual cycle, especially fluctuating sex hormones, might impact the gut microbiota composition.The menstrual cycle may affect the gut microbiota composition and glucose metabolism. These results indicate that glucose tolerance may be the greatest in the follicular phase; however, further well-conducted studies are needed to support this assumption.

Comprehensive Analysis of Gut Microbiota Alteration in the Patients and Animal Models with Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a common disease of endocrine-metabolic disorder, and its etiology remains largely unknown. The gut microbiota is possibly involved in PCOS, while the association remains unclear. The comprehensive analysis combining gut microbiota with PCOS typical symptoms was performed to analyze the role of gut microbiota in PCOS in this study. The clinical patients and letrozole-induced animal models were determined on PCOS indexes and gut microbiota, and fecal microbiota transplantation (FMT) was conducted. Results indicated that the animal models displayed typical PCOS symptoms, including disordered estrous cycles, elevated testosterone levels, and ovarian morphological change; meanwhile, the symptoms were improved after FMT. Furthermore, the microbial diversity exhibited disordered, and the abundance of the genus Ruminococcus and Lactobacillus showed a consistent trend in PCOS rats and patients. The microbiota diversity and several key genera were restored subjected to FMT, and correlation analysis also supported relevant conclusions. Moreover, LEfSe analysis showed that Gemmiger, Flexispira, and Eubacterium were overrepresented in PCOS groups. Overall, the results indicate the involvement of gut microbiota in PCOS and its possible alleviation of endocrinal and reproductive dysfunctions through several special bacteria taxa, which can function as the biomarker or potential target for diagnosis and treatment. These results can provide the new insights for treatment and prevention strategies of PCOS.

Association of Gut Microbiota Enterotypes with Blood Trace Elements in Women with Infertility

Infertility is defined as failure to achieve pregnancy within 12 months of unprotected intercourse in women. Trace elements, a kind of micronutrient that is very important to female reproductive function, are affected by intestinal absorption, which is regulated by gut microbiota. Enterotype is the classification of an intestinal microbiome based on its characteristics. Whether or not Prevotella-enterotype and Bacteroides-enterotype are associated with blood trace elements among infertile women remains unclear. The study aimed to explore the relationship between five main whole blood trace elements and these two enterotypes in women with infertility. This retrospective cross-sectional study recruited 651 Chinese women. Whole blood copper, zinc, calcium, magnesium, and iron levels were measured. Quantitative real-time PCR was performed on all fecal samples. Patients were categorized according to whole blood trace elements (low levels group, <5th percentile; normal levels group, 5th‒95th percentile; high levels group, >95th percentile). There were no significant differences in trace elements between the two enterotypes within the control population, while in infertile participants, copper (P = 0.033), zinc (P < 0.001), magnesium (P < 0.001), and iron (P < 0.001) in Prevotella-enterotype was significantly lower than in Bacteroides-enterotype. The Chi-square test showed that only the iron group had a significant difference in the two enterotypes (P = 0.001). Among infertile patients, Prevotella-enterotype (Log(P/B) > −0.27) predicted the low levels of whole blood iron in the obesity population (AUC = 0.894; P = 0.042). For the high levels of iron, Bacteroides-enterotype (Log(P/B) <−2.76) had a predictive power in the lean/normal group (AUC = 0.648; P = 0.041) and Log(P/B) <−3.99 in the overweight group (AUC = 0.863; P = 0.013). We can infer that these two enterotypes may have an effect on the iron metabolism in patients with infertility, highlighting the importance of further research into the interaction between enterotypes and trace elements in reproductive function.

Interplay between PCOS and microbiome: The road less travelled

Polycystic ovarian syndrome (PCOS) is a complicated neuro-endocrinal, reproductive, and metabolic condition. It encompasses patterns such as hyperandrogenism, recurrent cysts triggered by steroidogenic functional aberrations in the ovaries, overweight, chronic inflammation, and more. The underlying cause of this heterogeneous illness is obscure, although it is suspected to be driven by a blend of environmental and hereditary factors. In recent years, the connection between the microbiome and PCOS has been acknowledged and is thought to be involved in the genesis of the syndrome's emergence. Microbiota vary in different pathological features of PCOS, and fundamental pathways linked to their involvement in the commencement of diverse clinical presentations in PCOS open up a new avenue for its management. Prebiotic, probiotic, synbiotic, and fecal-microbiota-transplant, by promoting eubiosis and nullifying the effect caused by the altered microbial profile in PCOS women, can aid in management of diverse phenotypes associated with the syndrome. These microbiota-mediated treatments improve PCOS women's metabolic, inflammatory, and hormonal profiles. However, more studies are needed to elucidate the mechanisms that drive this positive effect.

Constant light exposure alters gut microbiota and short-/medium-chain fatty acids and aggravates PCOS-like traits in HFD-fed rats

OBJECTIVE

This study investigated the effects of constant light exposure on polycystic ovary syndrome (PCOS)-like endocrine and metabolic changes in high-fat diet (HFD)-fed rats and to elucidate the related microbiotic mechanisms.

METHODS

A total of 32 female Sprague-Dawley rats were divided into four groups (n = 8 each): rats on a normal chow diet with standard light-dark cycle, rats on a normal chow diet with constant light exposure, rats on an HFD with standard light-dark cycle, and rats on an HFD with constant light exposure. After 16 weeks of treatment, changes in anthropometric parameters, estrous cycle, hormone profiles, ovarian pathology, and gut microbiota and short-/medium-chain fatty acids in colon contents were assessed.

RESULTS

Constant light exposure aggravated PCOS-like phenotypes in HFD-fed rats, such as hyperandrogenism, disrupted estrous cycle, and polycystic ovaries. Additionally, constant light exposure and an HFD synergized to decrease α-diversity of gut microbiota, create a reduced abundance of Ruminococcus genus, and create an increased abundance of Firmicutes and the Firmicutes/Bacteroidetes ratio. In HFD-fed rats, the group with constant light exposure had an increase in propionate acid and a decrease in total medium-chain fatty acids in colon contents compared with the standard light-dark cycle group.

CONCLUSIONS

Constant light exposure causes gut dysbiosis, alters production of short- and medium-chain fatty acids, and aggravates PCOS-like traits in HFD-fed rats.

Comparative analysis of gut microbial composition and potential functions in captive forest and alpine musk deer

Gut microbiota forms a unique microecosystem and performs various irreplaceable metabolic functions for ruminants. The gut microbiota is important for host health and provides new insight into endangered species conservation. Forest musk deer (FMD) and alpine musk deer (AMD) are typical small ruminants, globally endangered due to excessive hunting and habitat loss. Although nearly 60 years of captive musk deer breeding has reduced the hunting pressure in the wild, fatal gastrointestinal diseases restrict the growth of captive populations. In this study, 16S rRNA high-throughput sequencing revealed the differences in gut microbiota between FMD and AMD based on 166 fecal samples. The alpha diversity was higher in FMD than in AMD, probably helping FMD adapt to different and wider habitats. The ß-diversity was higher between adult FMD and AMD than juveniles and in winter than late spring. The phylum Firmicutes and the genera Christensenellaceae R7 group, Ruminococcus, Prevotellaceae UCG-004, and Monoglobus were significantly higher in abundance in FMD than in AMD. However, the phylum Bacteroidetes and genera Bacteroides, UCG-005, Rikenellaceae RC9 gut group, and Alistipes were significantly higher in AMD than FMD. The expression of metabolic functions was higher in AMD than in FMD, a beneficial pattern for AMD to maintain higher energy and substance metabolism. Captive AMD may be at higher risk of intestinal diseases than FMD, with higher relative abundances of most opportunistic pathogens and the expression of disease-related functions. These results provide valuable data for breeding healthy captive musk deer and assessing their adaptability in the wild. KEY POINTS: • Alpha diversity of gut microbiota was higher in FMD than that in AMD • Expression of metabolic and disease-related functions was higher in AMD than in FMD.

Irritable bowel syndrome in midlife women: a narrative review

Midlife women between the ages of 40 and 65 years have reported multiple challenges due to menopausal, developmental, and situational transitions from younger to older adulthood. During the midlife period, many women seek health care for gastrointestinal symptoms and irritable bowel syndrome (IBS). Multiple factors including stress, poor sleep, diet, and physical inactivity may contribute to IBS or gastrointestinal symptoms in midlife women. As such, a comprehensive assessment and treatment approach is needed for midlife women suffering gastrointestinal symptoms. This article reviews the main aspects of the menopausal transition, sex hormonal changes, abdominal and pelvic surgery, psychosocial distress, behavioral factors, and gut microbiome, as well as their relevance on IBS and gastrointestinal symptoms in midlife women. Also, management strategies for IBS in midlife women are discussed. To date, gastrointestinal symptoms during midlife years remain a critical area of women’s health. Additional research is needed to better understand the contributors to gastrointestinal symptoms in this group. Such efforts may provide a new window to refine or develop treatments of gastrointestinal symptoms for midlife women.

Gut microbiota in adolescent girls with polycystic ovary syndrome: Effects of randomized treatments

BACKGROUND

Girls with obesity and polycystic ovary syndrome (PCOS) and women with PCOS have altered gut microbiota.

OBJECTIVE

To study the gut microbiota composition of girls with PCOS without obesity (age, 15.8 years; body mass index [BMI] 25 kg/m² ) and the effects of randomized treatments with an oral contraceptive (OC, N = 15) or with spironolactone-pioglitazone-metformin (SPIOMET, N = 15) for 1 year. Thirty-one age-matched girls served as controls.

METHODS

16S ribosomal subunit gene amplicon sequencing was performed in stool samples from all subjects; samples from 23 out of 30 girls with PCOS (OC, N = 12; SPIOMET, N = 11) were available for analysis post-treatment. Clinical and endocrine-metabolic variables were measured before and after intervention.

RESULTS

Girls with PCOS had decreased diversity alpha, altered microbiota pattern and taxonomic profile with more abundance of Family XI (P = .002), and less abundance of family Prevotellaceae (P = .0006) the genus Prevotella (P = .0001) and Senegalimassilia (P < .0001), as compared to controls. Family XI abundance related positively to hepato-visceral fat (R = 0.453; P = .0003). SPIOMET treatment, but not OC, normalized the abundance of Family XI. Prevotellaceae, Prevotella and Senegalimassilia abundance remained unchanged after either treatment.

CONCLUSION

SPIOMET's spectrum of normalizing effects in girls with PCOS is herewith broadened as to include Family XI abundance in gut microbiota.

Increased Expression of Colonic Mucosal Melatonin in Patients with Irritable Bowel Syndrome Correlated with Gut Dysbiosis

Dysregulation of the gut microbiota/gut hormone axis contributes to the pathogenesis of irritable bowel syndrome (IBS). Melatonin plays a beneficial role in gut motility and immunity. However, altered expression of local mucosal melatonin in IBS and its relationship with the gut microbiota remain unclear. Therefore, we aimed to detect the colonic melatonin levels and microbiota profiles in patients with diarrhea-predominant IBS (IBS-D) and explore their relationship in germ-free (GF) rats and BON-1 cells. Thirty-two IBS-D patients and twenty-eight healthy controls (HCs) were recruited. Fecal specimens from IBS-D patients and HCs were separately transplanted into GF rats by gavage. The levels of colon mucosal melatonin were assessed by immunohistochemical methods, and fecal microbiota communities were analyzed using 16S rDNA sequencing. The effect of butyrate on melatonin synthesis in BON-1 cells was evaluated by ELISA. Melatonin levels were significantly increased and negatively correlated with visceral hypersensitivity in IBS-D patients. GF rats inoculated with fecal microbiota from IBS-D patients had high colonic melatonin levels. Butyrate-producing Clostridium cluster XIVa species, such as Roseburia species and Lachnospira species, were positively related to colonic mucosal melatonin expression. Butyrate significantly increased melatonin secretion in BON-1 cells. Increased melatonin expression may be an adaptive protective mechanism in the development of IBS-D. Moreover, some Clostridium cluster XIVa species could increase melatonin expression via butyrate production. Modulation of the gut hormone/gut microbiota axis offers a promising target of interest for IBS in the future.

Individual and combined toxicogenetic effects of microplastics and heavy metals (Cd, Pb, and Zn) perturb gut microbiota homeostasis and gonadal development in marine medaka (Oryzias melastigma)

Currently, microplastics (MPs) attracted increased attention for their ubiquity and toxic properties. In this study, marine medaka was used to explore the individual and combined toxicity of heavy metals (HMs) and MPs on intestinal bacteria and gonadal development. After exposure to environmentally relevant concentrations of MPs and HMs, significant alterations of intestinal microbiota were found. The MPs treatment reduced the diversity and abundance of intestinal microbiota, while the HMs and MPs-HMs treatments increased them, which were confirmed by the abundance changes of Proteobacteria. According to the KEGG analysis, the metabolism and environmental information processing (EIP) pathways in the microbial community were significantly affected. This study showed that the MPs-HMs treatment caused a higher pollution load on the gut of the marine medaka, and triggered more significant changes of specific bacterial species and gut function in the males. However, during the gonadal development, HMs and MPs-HMs treatments resulted in empty follicles (EF) and follicular atresia (FA), and altered the gene expression levels related to hypothalamic-pituitary-gonadal (HPG) axis. In short, this study demonstrated that the reproductive disturbance was mainly due to HMs, but the combination of MPs and HMs did not strengthen the risk to the gonad development of the marine medaka.

The menstrual cycle may not be limited to the endometrium but also may impact gut permeability

OBJECTIVE

To examine associations between IgA responses to Gram-negative gut commensal bacteria and peri-menstrual symptoms and sex hormone levels during the menstrual cycle in women with and without premenstrual symptoms.

METHODS

Forty women aged 18-45 years completed the Daily Record of Severity of Problems (DRSP) during all 28 consecutive days of the menstrual cycle. We assayed, in plasma, IgA responses to six Gram-negative bacteria, that is, Hafnei alvei, Pseudomonas aeruginosa, Morganella morganii, Klebsiella pneumoniae, Pseudomonas putida and Citobacter koseri, progesterone and oestradiol at days 7, 14, 21 and 28 of the menstrual cycle.

RESULTS

Significant changes in Δ (actual - 1 week earlier) IgA to lipopolysaccharides (LPS) of the six Gram-negative bacteria during the menstrual cycle were observed with peak IgA levels at T4 (day 28) and lows at T1 or T2 (day 7 or 14). The ΔIgA changes in H. alvei, M. Morganii, P. putida during the menstrual cycle were significantly and positively associated with changes in the total DRSP score, and severity of physio-somatic, anxiety and breast-craving, but not depressive, symptoms. The changes in IgA responses to LPS were largely predicted by changes in progesterone and steady-state levels of progesterone averaged over the luteal phase.

DISCUSSION

Menstrual cycle-associated changes in IgA directed against LPS and by inference bacterial translocation may be driven by the effects of progesterone on transcellular, paracellular and vascular pathways (leaky gut) thereby contributing to the severity of physio-somatic and anxiety symptoms as well as fatigue, breast swelling and food cravings.