Microbial endocrinology: the mechanisms by which the microbiota influences host sex steroids

Gut microbiome-driven regulation of sex hormone homeostasis: a potential neuroendocrine connection

The gut microbiome is known to have a bidirectional relationship with sex hormone homeostasis; however, its role in mediating interactions between the primary regulatory axes of sex hormones and their productions is yet to be fully understood. We utilized both conventionally raised and gnotobiotic mouse models to investigate the regulatory role of the gut microbiome on the hypothalamic-pituitary-gonadal (HPG) axis. Male and female conventionally raised mice underwent surgical modifications as follows: (1) hormonally intact controls; (2) gonadectomized males and females; (3) gonadectomized males and females supplemented with testosterone and estrogen, respectively. Fecal samples from these mice were used to colonize sex-matched, intact, germ-free recipient mice through fecal microbiota transplant (FMT). Serum gonadotropins, gonadal sex hormones, cecal microbiota, and the serum global metabolome were assessed. FMT recipients of gonadectomized-associated microbiota showed lower circulating gonadotropin levels than recipients of intact-associated microbiota, opposite to that of FMT donors. FMT recipients of gonadectomized-associated microbiota also had greater testicular weights compared to recipients of intact-associated microbiota. The gut microbiota composition of recipient mice differed significantly based on the FMT received, with the male microbiota having a more concerted impact in response to changes in the HPG axis. Network analyses showed that multiple metabolically unrelated pathways may be involved in driving differences in serum metabolites due to sex and microbiome received in the recipient mice. In sum, our findings indicate that the gut microbiome responds to the HPG axis and subsequently modulates its feedback mechanisms. A deeper understanding of interactions between the gut microbiota and the neuroendocrine-gonadal system may contribute to the development of therapies for sexually dimorphic diseases.

The microbiome in endometrial cancer: vaginal milieu matters

Endometrial cancer remains one of the most common malignancies in women, and its incidence is particularly increasing in developed countries. Despite the well-known promotive role of excessive exposure to estrogen, many other details of the pathogenesis of endometrial cancer remain unknown. Recent studies have elucidated the emerging role of the resident microbiota in the progression of various diseases, including cancer. Next-generation sequencing demonstrated that the uterine cavity, previously considered sterile, contains a composition-rich microbiota. In this work, we determined the differences in the composition of the intrauterine microbiota between patients with endometrial cancer and its precursor-endometrial hyperplasia.

Long-term soy dietary fiber diet modifies the intestinal internal environment: Focus on chronic ulcerative colitis

Okara is a major by-product of soybean processing, which not only has negative impacts on the environment but also leads to resource waste. Soybean residue is rich in insoluble dietary fiber, which is known to have a positive effect on ulcerative colitis. This study aimed to investigate whether long-term consumption of high-purity soy isolate dietary fiber (HPSIDF) promotes the proliferation of beneficial intestinal substances, thereby alleviating intestinal damage caused by chronic ulcerative colitis (CUC). This study induced CUC using 2 % dextran sulfate sodium (DSS) and conducted a three-phase (9-week) intervention experiment. The study showed that long-term consumption of HPSIDF can regulate the level of inflammatory factors in mice and relieve damage to intestinal tissue. In addition, long-term intake of HPSIDF inhibited the degradation of Lactobacillus intestinalis and promoted the proliferation of Oscillospira and the production of beneficial substances such as Agmatine and Betaine, which played an important role in the maintenance of intestinal bacterial flora and the improvement of the internal environment. This study clarified that long-term intake of HPSIDF not only changes the intestinal self-properties but also promotes the proliferation of beneficial flora and metabolites, providing a solution strategy for the high-value utilization of okara.

The Neuroimmune Axis in Gastrointestinal Disorders - An Underrecognized Problem

PURPOSE OF REVIEW

We present an introduction to the neuroimmune axis with a focus on the gastrointestinal system, its role in numerous chronic multisystem disorders, and emerging tools and therapies to diagnose and treat these conditions.

RECENT FINDINGS

There have recently been tremendous breakthroughs in our understanding of how the nervous, immune, and endocrine systems, as well as the extracellular matrix and microbiota, interact within the gastrointestinal system to modulate health and disease.

Gut microbiome in patients with early-stage and late-stage endometriosis

BACKGROUND

Endometriosis is a chronic inflammatory gynecological disease. Previous studies have explored relationships between endometriosis and the microbiota, but none have focused on differences in gut microbiota between early-stage and late-stage endometriosis patients or their connections to dysmenorrhea symptoms. This study compared gut microbiota compositions between early-stage and late-stage endometriosis patients using amplicon sequencing and further analyzed their dysmenorrhea symptoms.

METHODS

To minimize seasonal and dietary impacts, we recruited Guangdong residents hospitalized for surgery at Zhujiang Hospital. Participants underwent preoperative screening based on enrollment criteria and fecal samples were collected. Endometriosis was classified according to the American Society for Reproductive Medicine (ASRM) staging system based on surgincal and pathological findings. Stage I-II cases were designated as early-stage endometriosis, and Stage III-IV as late-stage endometriosis.

RESULTS

A total of 112 patient fecal samples were collected, with 75 (median age, 32 years [range, 18-49 years]) meeting the enrollment criteria, including 39 early-stage (32 Stage I and 7 Stage II) and 36 late-stage (16 Stage III and 20 Stage IV) patients. The gut microbiota structure and functions in early-stage patients significantly differed from those in late-stage cases. Dysmenorrhea was associated with specific microbial traits. Late-stage patients with dysmenorrhea displayed distinctly different gut profiles compared to other endometriosis groups. Bartonella, Snodgrassella, and other taxa were enriched in late-stage cases, while Bacteroides, and Prevotella were decreased.

CONCLUSION

The gut microbial community structure in early-stage endometriosis patients significantly differs from that in late-stage cases, with late-stage patients experiencing dysmenorrhea displaying particularly distinct gut profiles. Predicted functional analysis indicated suppressed steroid biosynthesis pathways in the gut of late-stage endometriosis patients. In conclusion, it is plausible that the multiple effects of steroids on the lower gastrointestinal tract may involve microbiota alterations, suggesting the need for further investigations.

The estrobolome: Estrogen-metabolizing pathways of the gut microbiome and their relation to breast cancer

Increasing evidence links the gut microbiome to carcinogenesis. Disruptions in estrogen regulation by the estrobolome-gut microbiota with estrogen-related functions-may promote breast cancer. However, precise information on estrobolome targets and their underlying mechanisms is limited. This review identifies relevant targets for measuring the estrobolome, focusing on enzymes and microbial taxa involved in processing estrogens, precursors, metabolites, and phytoestrogens, to facilitate the exploration of potential links to breast cancer. Evidence from breast cancer case-control studies is synthesized to assess alignment with these targets, highlight gaps in the evidence, and suggest new paths forward. Findings from case-control studies were heterogeneous and showed limited alignment with estrobolome targets, with only Escherichia coli and Roseburia inulinivorans identified as differentially abundant and functionally relevant between cases and controls. The lack of compelling evidence for estrobolome-specific mechanisms may reflect measurement challenges or may suggest that broader ecological changes in the microbiome, which influence a network of interacting mechanisms, are more influential for carcinogenesis. To clarify the estrobolome's role in breast cancer, future research should use advanced sequencing techniques and methods such as metabolomics and transcriptomics, while considering clinical and behavioral factors that may modify estrobolome mechanisms.

Early-life gut inflammation drives sex-dependent shifts in the microbiome-endocrine-brain axis

Despite recent advances in understanding the connection between the gut microbiota and the adult brain, significant knowledge gaps remain regarding how gut inflammation affects brain development. We hypothesized that gut inflammation during early life would negatively affect neurodevelopment by disrupting microbiota communication to the brain. We therefore developed a novel pediatric chemical model of inflammatory bowel disease (IBD), an incurable condition affecting millions of people worldwide. IBD is characterized by chronic intestinal inflammation, and is associated with comorbid symptoms such as anxiety, depression and cognitive impairment. Notably, 25% of patients with IBD are diagnosed during childhood, and the effects of chronic inflammation during this critical developmental period remain poorly understood. This study investigated the effects of early-life gut inflammation induced by DSS (dextran sulfate sodium) on a range of microbiota, endocrine, and behavioral outcomes, focusing on sex-specific impacts. DSS-treated mice exhibited increased intestinal inflammation and altered microbiota membership, which correlated with changes in microbiota-derived circulating metabolites. The majority of behavioral measures were unaffected, with the exception of impaired mate-seeking behaviors in DSS-treated males. DSS-treated males also showed significantly smaller seminal vesicles, lower circulating androgens, and decreased intestinal hormone-activating enzyme activity compared to vehicle controls. In the brain, DSS treatment led to chronic, sex-specific alterations in microglial morphology. These results suggest that early-life gut inflammation causes changes in gut microbiota composition, affecting short-chain fatty acid (SCFA) producers and glucuronidase (GUS) activity, correlating with altered SCFA and androgen levels. The findings highlight the developmental sensitivity to inflammation-induced changes in endocrine signalling and emphasize the long-lasting physiological and microbiome changes associated with juvenile IBD.

Sex-specific effects of gastrointestinal microbiome disruptions on Helicobacter pylori-induced gastric carcinogenesis in INS-GAS mice

BACKGROUND

Accumulating evidence indicates that the dysbiosis of gastrointestinal microbiota is associated with the development of gastric carcinogenesis. However, the sex-specific traits of gastrointestinal microbiota and their correlation with the sexually dimorphic response to gastric cancer remain poorly understood.

METHODS

Male and female transgenic FVB/N insulin-gastrin (INS-GAS) mice as a model of gastric cancer were randomly administered Brucella Broth or Helicobacter pylori (H. pylori). Stomachs were evaluated by histopathology. The gastric inflammation was examined by immunohistochemical and immunofluorescence staining. Gastric mucosal and fecal samples were collected for microbiota analysis using 16S rRNA gene sequencing.

RESULTS

Following H. pylori infection, male mice showed heightened inflammatory infiltration and notably greater intestinal metaplasia compared to female mice. The structure of gastrointestinal microbiota was different between male and female mice, with relative higher diversity in females than males. Notably, we found gender disparities in the alterations of gastric and intestinal microbiota in mice post H. pylori infection. While the enrichment of Bifidobacterium and Lachnospiraceae was observed in female mice, Escherichia_Shigella and Akkermansia were more abundant in males. Furthermore, the microbial profile was distinct in estrogen-deficient ovariectomized (OVX) mice, including the overgrowth of Akkermansia and the loss of Butyricicoccus. Infected OVX females developed significantly more severe gastric lesions, which was normalized through co-housing with intact females.

CONCLUSIONS

We have identified a novel microbiome-based mechanism that provides insight into the sexual dimorphism in the development of H. pylori-associated gastric cancer.

The microbiome as a modulator of neurological health across the maternal-offspring interface

The maternal microbiome is emerging as an important factor that influences the neurological health of mothers and their children. Recent studies highlight how microbial communities in the maternal gut can shape early-life development in ways that inform long-term health trajectories. Research on the neurodevelopmental effects of maternal microbiomes is expanding our understanding of the microbiome-gut-brain axis to include signaling across the maternal-offspring unit during the perinatal period. In this Review, we synthesize existing literature on how the maternal microbiome modulates brain function and behavior in both mothers and their developing offspring. We present evidence from human and animal studies showing that the maternal microbiome interacts with environmental factors to impact risk for neurodevelopmental abnormalities. We further discuss molecular and cellular mechanisms that facilitate maternal-offspring crosstalk for neuromodulation. Finally, we consider how advancing understanding of these complex interactions could lead to microbiome-based interventions for promoting maternal and offspring health.

Gut feeling: Exploring the intertwined trilateral nexus of gut microbiota, sex hormones, and mental health

The complex interplay between the gut microbiota, sex hormones, and mental health is emerging as a pivotal factor in understanding and managing psychiatric disorders. Beyond their traditional roles, sex hormones exert profound effects on various physiological systems including the gut microbiota. Fluctuations in sex hormone levels, notably during the menstrual cycle, influence gut physiology and barrier function, shaping gut microbiota composition and immune responses. Conversely, the gut microbiota actively modulates sex hormone levels via enzymatic processes. This bidirectional relationship underscores the significance of the gut-brain axis in maintaining mental well-being. This review explores the multifaceted interactions between sex hormones, the gut microbiota, and mental health outcomes. We highlight the potential of personalized interventions in treating psychiatric disorders, particularly in vulnerable populations such as premenopausal women and individuals with depressive disorders. By elucidating these complex interactions, we aim to provide insights for future research into targeted interventions, enhancing mental health outcomes.

Steroid sulfatase and sulfotransferases in the estrogen and androgen action of gynecological cancers: current status and perspectives

Sulfatase (STS) and sulfotransferases (SULT) have important role in the biosynthesis and action of steroid hormones. STS catalyzes the hydrolysis of estrone-sulfate (E1-S) and dehydroepiandrosterone-sulfate (DHEA-S), while sulfotransferases catalyze the reverse reaction and require 3-phosphoadenosine-5-phosphosulfate as a sulfate donor. These enzymes control the concentration of active estrogens and androgens in peripheral tissues. Aberant expression of STS and SULT genes has been found in both, benign hormone-dependent diseases and hormone-dependent cancers. The aim of this review is to present the current knowledge on the role of STS and SULT in gynecological cancers, endometrial (EC) and ovarian cancer (OC). EC is the most common and OC the most lethal gynecological cancer. These cancers primarily affect postmenopausal women and therefore rely on the local production of steroid hormones from inactive precursors, either DHEA-S or E1-S. Following cellular uptake by organic anion transporting polypeptides (OATP) or organic anion transporters (OAT), STS and SULT regulate the formation of active estrogens and androgens, thus disturbed balance between STS and SULT can contribute to the onset and progression of cancer. The importance of these enzymes in peripheral estrogen biosynthesis has long been recognized, and this review provides new data on the important role of STS and SULT in the formation and action of androgens, their regulation and inhibition, and their potential as prognostic biomarkers.

Assessment of the Cutaneous Hormone Landscapes and Microbiomes in Vulvar Lichen Sclerosus

Vulvar lichen sclerosus (VLS) is a progressive skin disease of unknown etiology. In this longitudinal case-control exploratory study, we evaluated the hormonal and microbial landscapes in 18 postmenopausal females (mean [SD] age: 64.4 [8.4] years) with VLS and controls. We reevaluated the patients with VLS after 10-14 weeks of daily topical class I steroid. We found that groin cutaneous estrone was lower in VLS than in controls (-22.33, 95% confidence interval [CI] = -36.96 to -7.70; P = .006); cutaneous progesterone was higher (5.73, 95% CI = 3.74-7.73; P < .0001). Forehead 11-deoxycortisol (-0.24, 95% CI = -0.42 to -0.06; P = .01) and testosterone (-7.22, 95% CI = -12.83 to -1.62; P = .02) were lower in disease. With treatment, cutaneous estrone (-7.88, 95% CI = -44.07 to 28.31; P = .62), progesterone (2.02, 95% CI = -2.08 to 6.11; P = .29), and 11-deoxycortisol (-0.13, 95% CI = -0.32 to 0.05; P = .15) normalized; testosterone remained suppressed (-7.41, 95% CI = -13.38 to -1.43; P = .02). 16S ribosomal RNA V1-V3 and ITS1 amplicon sequencing revealed bacterial and fungal microbiome alterations in disease. Findings suggest that cutaneous sex hormone and bacterial microbiome alterations may be associated with VLS in postmenopausal females.

Evaluation of fecal microbiota of late gestation sows in relation to pelvic organ prolapse risk

Introduction

Sow mortality in the U.S. swine industry has increased in recent years, for which pelvic organ prolapse (POP) is a major contributor, accounting for 21% of all sow mortality. Dysbiosis of microbial communities has been associated with disease and reproductive dysfunction in several species, and previous studies have shown changes in vaginal microbiota in sows with increased risk for POP during late gestation. However, there is insufficient knowledge surrounding the potential relationship between fecal microbiota and POP in sows. Therefore, the study objective was to identify differences in sow fecal microbiota and determine if fecal and vaginal microbial communities are correlated in relation to POP risk.

Methods

Sows were evaluated for POP risk using an established perineal scoring system, with a perineal score (PS) of 1 (PS1) presuming little to no risk of POP to a PS of 3 (PS3) presuming high risk of POP. In the current study, 2,864 sows were scored during gestation week 15, and 1.0%, 2.7%, and 23.4% of PS1, PS2, and PS3 sows, respectively, subsequently experienced POP. Fecal swabs (n = 215) were collected between gestation days 108-115, DNA was extracted, and 16S rRNA gene amplicon sequencing libraries were analyzed using mothur, phyloseq and SAS in reference to PS and POP outcome. Additionally, co-occurrence networks were constructed using CoNet to compare fecal and vaginal microbiota from the same cohort of sows and identify correlations between different taxa.

Results

Differences in fecal community composition (PERMANOVA; P < 0.05), structure (alpha diversity measurements; P < 0.05), and 13 individual operational taxonomic units (OTUs) were revealed between PS1 and PS3 assigned sows. No differences in fecal microbiota were detected as a result of POP outcome. However, the abundances of several taxa were correlated across sample collection sites, suggesting the fecal and vaginal microbial communities may be related to one another.

Discussion

Collectively, fewer differences in the fecal microbiota exist in sows with differing risk for POP compared to the vaginal microbiota, suggesting the vaginal microbiome may be more relevant in relation to POP outcome, although correlations between fecal and vaginal communities may provide insight for strategies to combat POP.

Adolescent gut microbiome imbalance and its association with immune response in inflammatory bowel diseases and obesity

BACKGROUND

Recently, there has been an increase in the number of studies focusing on the association between the gut microbiome and obesity or inflammatory diseases, especially in adults. However, there is a lack of studies investigating the association between gut microbiome and gastrointestinal (GI) diseases in adolescents.

METHOD

We obtained 16S rRNA-seq datasets for gut microbiome analysis from 202 adolescents, comprising ulcerative colitis (UC), Crohn's disease (CD), obesity (Ob), and healthy controls (HC). We utilized Quantitative Insights Into Microbial Ecology (QIIME) and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) to acquire Operational Taxonomic Units (OTUs). Subsequently, we analyzed Kyoto Encyclopedia of Genes and Genomes (KEGG) Orthology (KO) terms and pathway enrichment for the identified OTUs.

RESULTS

In this study, we investigated the difference between the gut microbiomes in adolescents with GI diseases and those in healthy adolescents using 202 samples of 16S rRNA sequencing data. The distribution of the six main gut microbiota (i.e., unclassified Dorea, unclassified Lachnospiraceae, unclassified Ruminococcus, Faecalibacterium prausnitzii, Prevotella copri, unclassified Sutterella) was different based on the status of obesity and inflammatory diseases. Dysbiosis was observed within Lachnospiraceae in adolescents with inflammatory diseases (i.e., UC and CD), and in adolescents with obesity within Prevotella and Sutterella. More specifically, our results showed that the relative abundance of Faecalibacterium prausnitzii and unclassified Lachnospiraceae was more than 10% and 8% higher, respectively, in the UC group compared to the CD, Ob, and HC groups. Additionally, the Ob group had over 20% and over 3% higher levels of Prevotella copri and unclassified Sutterella, respectively, compared to the UC, CD, and HC groups. Also, inspecting associations between the six specific microbiota and KO terms, we found that the six microbiota -relating KO terms were associated with NOD-like receptor signaling. These six taxa differences may affect the immune system and inflammatory response by affecting NOD-like receptor signaling in the host during critical adolescence.

CONCLUSION

In this study, we discovered that dysbiosis of the microbial community had varying degrees of influence on the inflammatory and immune response pathways in adolescents with inflammatory diseases and obesity.

Immune Cells, Gut Microbiota, and Vaccines: A Gender Perspective

The development of preventive and therapeutic vaccines has played a crucial role in preventing infections and treating chronic and non-communicable diseases, respectively. For a long time, the influence of sex differences on modifying health and disease has not been addressed in clinical and preclinical studies. The interaction of genetic, epigenetic, and hormonal factors plays a role in the sex-related differences in the epidemiology of diseases, clinical manifestations, and the response to treatment. Moreover, sex is one of the leading factors influencing the gut microbiota composition, which could further explain the different predisposition to diseases in men and women. In the same way, differences between sexes occur also in the immune response to vaccines. This narrative review aims to highlight these differences, focusing on the immune response to vaccines. Comparative data about immune responses, vaccine effectiveness, and side effects are reviewed. Hence, the intricate interplay between sex, immunity, and the gut microbiota will be discussed for its potential role in the response to vaccination. Embracing a sex-oriented perspective in research may improve the efficacy of the immune response and allow the design of tailored vaccine schedules.

Temporal changes in ewe vaginal microbiota throughout gestation

Introduction

Numerous factors are known to influence reproductive efficiency in ewes, but few studies have investigated the potential role of vaginal microbiota in sheep reproductive success. The objective of this study was to thoroughly characterize the ewe vaginal microbiota throughout the course of pregnancy.

Methods

Vaginal samples were collected from 31 pregnant Hampshire and Hampshire X Suffolk crossbred ewes on a weekly basis from pre-breeding to pregnancy testing and then biweekly until just after lambing. To characterize the vaginal microbial communities, DNA was extracted and 16S rRNA gene Illumina MiSeq amplicon sequencing was performed.

Results and Discussion

Alpha diversity metrics indicated an increase in species richness, evenness, and overall diversity throughout gestation. Distinct shifts in the bacterial communities were observed during gestation and were segregated into three periods: early gestation, a transitional period and mid/late gestation. During early gestation, Actinobacillus, Histophilus, and unclassified Leptotrichiaceae were found in greater relative abundance. During the transitional period, a population shift occurred characterized by increasing relative abundance of Streptococcus and Staphylococcus. During mid/late gestation, Staphylococcus, Streptococcus, and Ureaplasma had the greatest relative abundance. These shifts in the microbial population throughout the ewe's gestation are likely related to hormonal changes triggered by the growing conceptus, specifically increasing blood concentration of progesterone. The transitional period shift in vaginal microbial communities potentially aligns with the placental take-over of progesterone production from the corpus luteum at approximately day 50 after conception (gestational week 7). Understanding the observed variability of the vaginal microbiota throughout pregnancy will allow for future comparison of ewes that did not become pregnant or had abnormal pregnancies, which could lead to the discovery of potential bacterial biomarkers for pregnancy outcome; this understanding could also lead to development of probiotics to improve sheep reproductive success.

Analysis of progesterone and estrone-sulfate in feces of American Bison using liquid chromatography coupled to mass spectrometry: Technical validation and correlation with blood levels

American Bison's wild nature limits blood sample availability to study its endocrinology. This report describes progesterone (P4) and estrone-sulfate (E1S) assays in American Bison feces using Liquid Chromatography coupled with Mass Spectrometry (LC-MS). In 2 ranches, samples of feces (n = 73) and serum (n = 93) were collected in pregnant and nonpregnant American Bison. Feces samples (250 mg) were extracted with methanol, purified, and concentrated. Then, feces and serum samples were assayed using LC-MS, according to our previously described technique. Fecal matrix homogeneity was determined by measuring steroids in different areas of the sample and concentration evolutions were evaluated after storage at room temperature. During the validation process, lower limits of quantification were 20 pg/g (E1S) and 4 ng/g (P4) by meeting the following criteria: relative standard deviation <15% and relative bias <15%. By measuring hormones in different spots from the same sample, a moderate variability for E1S (coefficient of variation [CV] up to 21.3%) and a high variability for P4 (CV up to 85.5%) were highlighted. Correlation between concentrations in feces and in serum was higher for E1S (r = 0.77) than for P4 (r = 0.65) and P4 could be assayed in pregnant and nonpregnant animals whereas E1S was only present in pregnant. Feces storage at room temperature induced modification of steroid concentrations. The quantification of E1S and, at a lower level, of P4 in feces is an interesting alternative to serum assay to describe the pregnancy-related evolution of these steroids in American Bisons, with feces ideally stored frozen and mixed before the LC-MS procedures.

Adolescence and the Microbiome: Implications for Healthy Growth and Maturation

The gut microbiota was initially thought to develop into a stable, adult-like profile during early postnatal life. The formation of the gut microbiota during early life has been shown to contribute to healthy growth and has lifelong implications for host health. Adolescence, the developmental period between childhood and adulthood, is a critical window for healthy growth and maturation. The composition of the gut microbiota in adolescents is distinct from that of children and adults, which supports the premise that the gut microbiota continues to develop during adolescence toward an adult-like profile. Research has begun to shift its focus from understanding the gut microbiome at the extremes of the life span to evaluating the importance of the gut microbiome during adolescence and its role in healthy development. This article provides an overview of adolescent development, host-microbiota interactions, and experimental models used to discern effects of gut microbiota on health and disease. Herein, the role of the gut microbiota is reviewed as it relates to adolescent: i) brain development, cognition, and behavior; ii) metabolism and adiposity; and iii) skeletal growth and bone mass accrual. Future directions are addressed, including omics investigations defining mechanisms through which the gut microbiota influences adolescent development. Furthermore, we discuss advancing noninvasive interventions targeting the adolescent gut microbiota that could be employed to support healthy growth and maturation.

Variations in the Relative Abundance of Gut Bacteria Correlate with Lipid Profiles in Healthy Adults

The gut microbiome is a versatile system regulating numerous aspects of host metabolism. Among other traits, variations in the composition of gut microbial communities are related to blood lipid patterns and hyperlipidaemia, yet inconsistent association patterns exist. This study aims to assess the relationships between the composition of the gut microbiome and variations in lipid profiles among healthy adults. This study used data and samples from 23 adult participants of a previously conducted dietary intervention study. Circulating lipid measurements and whole-metagenome sequences of the gut microbiome were derived from 180 blood and faecal samples collected from eight visits distributed across an 11-week study. Lipid-related variables explained approximately 4.5% of the variation in gut microbiome compositions, with higher effects observed for total cholesterol and high-density lipoproteins. Species from the genera Odoribacter, Anaerostipes, and Parabacteroides correlated with increased serum lipid levels, whereas probiotic species like Akkermansia muciniphila were more abundant among participants with healthier blood lipid profiles. An inverse correlation with serum cholesterol was also observed for Massilistercora timonensis, a player in regulating lipid turnover. The observed correlation patterns add to the growing evidence supporting the role of the gut microbiome as an essential regulator of host lipid metabolism.