Sexually dimorphic characteristics of the small intestine and colon of prepubescent C57BL/6 mice

Exposure of Ldlr-/- Mice to a PFAS Mixture and Outcomes Related to Circulating Lipids, Bile Acid Excretion, and the Intestinal Transporter ASBT

BACKGROUND

Previous epidemiological studies have repeatedly found per- and polyfluoroalkyl substances (PFAS) exposure associated with higher circulating cholesterol, one of the greatest risk factors for development of coronary artery disease. The main route of cholesterol catabolism is through its conversion to bile acids, which circulate between the liver and ileum via enterohepatic circulation. Patients with coronary artery disease have decreased bile acid excretion, indicating that PFAS-induced impacts on enterohepatic circulation may play a critical role in cardiovascular risk.

OBJECTIVES

Using a mouse model with high levels of low-density and very low-density lipoprotein (LDL and VLDL, respectively) cholesterol and aortic lesion development similar to humans, the present study investigated mechanisms linking exposure to a PFAS mixture with increased cholesterol.

METHODS

Male and female L d l r - / - mice were fed an atherogenic diet (Clinton/Cybulsky low fat, 0.15% cholesterol) and exposed to a mixture of 5 PFAS representing legacy, replacement, and emerging subtypes (i.e., PFOA, PFOS, PFHxS, PFNA, GenX), each at a concentration of 2 mg / L , for 7 wk. Blood was collected longitudinally for cholesterol measurements, and mass spectrometry was used to measure circulating and fecal bile acids. Transcriptomic analysis of ileal samples was performed via RNA sequencing.

RESULTS

After 7 wk of PFAS exposure, average circulating PFAS levels were measured at 21.6, 20.1, 31.2, 23.5, and 1.5 μ g / mL in PFAS-exposed females and 12.9, 9.7, 23, 14.3, and 1.7 μ g / mL in PFAS-exposed males for PFOA, PFOS, PFHxS, PFNA, and GenX, respectively. Total circulating cholesterol levels were higher in PFAS-exposed mice after 7 wk (352 mg / dL vs. 415 mg / dL in female mice and 392 mg / dL vs. 488 mg / dL in male mice exposed to vehicle or PFAS, respectively). Total circulating bile acid levels were higher in PFAS-exposed mice (2,978  pg / μ L vs. 8,496  pg / μ L in female mice and 1,960  pg / μ L vs. 4,452  pg / μ L in male mice exposed to vehicle or PFAS, respectively). In addition, total fecal bile acid levels were lower in PFAS-exposed mice (1,797  ng / mg vs. 682  ng / mg in females and 1,622  ng / mg vs. 670  ng / mg in males exposed to vehicle or PFAS, respectively). In the ileum, expression levels of the apical sodium-dependent bile acid transporter (ASBT) were higher in PFAS-exposed mice.

DISCUSSION

Mice exposed to a PFAS mixture displayed higher circulating cholesterol and bile acids perhaps due to impacts on enterohepatic circulation. This study implicates PFAS-mediated effects at the site of the ileum as a possible critical mediator of increased cardiovascular risk following PFAS exposure. https://doi.org/10.1289/EHP14339.

Genetic hypogonadal (Gnrh1hpg) mouse model uncovers influence of reproductive axis on maturation of the gut microbiome during puberty

The gut microbiome plays a key role in human health and gut dysbiosis is linked to many sex-specific diseases including autoimmune, metabolic, and neurological disorders. Activation of the hypothalamic-pituitary-gonadal (HPG) axis during puberty leads to sexual maturation and development of sex differences through the action of gonadal sex steroids. While the gut microbiome also undergoes sex differentiation, the mechanisms involved remain poorly understood. Using a genetic hypogonadal (hpg) mouse model, we sampled the fecal microbiome of male and female wild-type and hpg mutant mice before and after puberty to determine how microbial taxonomy and function are influenced by age, sex, and the HPG axis. We showed that HPG axis activation during puberty is required for sexual maturation of the gut microbiota composition, community structure, and metabolic functions. We also demonstrated that some sex differences in taxonomic composition and amine metabolism developed independently of the HPG axis, indicating that sex chromosomes are sufficient for certain sex differences in the gut microbiome. In addition, we showed that age, independent of HPG axis activation, led to some aspects of pubertal maturation of the gut microbiota community composition and putative functions. These results have implications for microbiome-based treatments, indicating that sex, hormonal status, and age should be considered when designing microbiome-based therapeutics.

XX sex chromosome complement modulates immune responses to heat-killed Streptococcus pneumoniae immunization in a microbiome-dependent manner

BACKGROUND

Differences in male vs. female immune responses are well-documented and have significant clinical implications. While the immunomodulatory effects of sex hormones are well established, the contributions of sex chromosome complement (XX vs. XY) and gut microbiome diversity on immune sexual dimorphisms have only recently become appreciated. Here we investigate the individual and collaborative influences of sex chromosome complements and gut microbiota on humoral immune activation.

METHODS

Male and female Four Core Genotype (FCG) mice were immunized with heat-killed Streptococcus pneumoniae (HKSP). Humoral immune responses were assessed, and X-linked immune-related gene expression was evaluated to explain the identified XX-dependent phenotype. The functional role of Kdm6a, an X-linked epigenetic regulatory gene of interest, was evaluated ex vivo using mitogen stimulation of B cells. Additional influences of the gut microbiome on sex chromosome-dependent B cell activation was also evaluated by antibiotically depleting gut microbiota prior to HKSP immunization. Reconstitution of the depleted microbiome with short-chain fatty acid (SCFA)-producing bacteria tested the impact of SCFAs on XX-dependent immune activation.

RESULTS

XX mice exhibited higher HKSP-specific IgM-secreting B cells and plasma cell frequencies than XY mice, regardless of gonadal sex. Although Kdm6a was identified as an X-linked gene overexpressed in XX B cells, inhibition of its enzymatic activity did not affect mitogen-induced plasma cell differentiation or antibody production in a sex chromosome-dependent manner ex vivo. Enhanced humoral responses in XX vs. XY immunized FCG mice were eliminated after microbiome depletion, indicating that the microbiome contributes to the identified XX-dependent immune enhancement. Reconstituting microbiota-depleted mice with select SCFA-producing bacteria enhanced fecal SCFA concentrations and increased humoral responses in XX, but not XY, FCG mice. However, exposure to the SCFA propionate alone did not enhance mitogenic B cell stimulation in ex vivo studies.

CONCLUSIONS

FCG mice have been used to assess sex hormone and sex chromosome complement influences on various sexually dimorphic traits. The current study indicates that the gut microbiome impacts humoral responses in an XX-dependent manner, suggesting that the collaborative influence of gut bacteria and other sex-specific factors should be considered when interpreting data aimed at delineating the mechanisms that promote sexual dimorphism.

Sex differences in colorectal cancer: with a focus on sex hormone-gut microbiome axis

Sexual dimorphism has been observed in the incidence and prognosis of colorectal cancer (CRC), with men generally exhibiting a slightly higher incidence than women. Research suggests that this difference may be attributed to variations in sex steroid hormone levels and the gut microbiome. The gut microbiome in CRC shows variations in composition and function between the sexes, leading to the concept of 'microgenderome' and 'sex hormone-gut microbiome axis.' Conventional research indicates that estrogens, by promoting a more favorable gut microbiota, may reduce the risk of CRC. Conversely, androgens may have a direct pro-tumorigenic effect by increasing the proportion of opportunistic pathogens. The gut microbiota may also influence sex hormone levels by expressing specific enzymes or directly affecting gonadal function. However, this area remains controversial. This review aims to explore the differences in sex hormone in CRC incidence, the phenomenon of sexual dimorphism within the gut microbiome, and the intricate interplay of the sex hormone-gut microbiome axis in CRC. The objective is to gain a better understanding of these interactions and their potential clinical implications, as well as to introduce innovative approaches to CRC treatment.

XX sex chromosome complement modulates immune responses to heat-killed Streptococcus pneumoniae immunization in a microbiome-dependent manner

Background

Differences in male vs. female immune responses are well-documented and have significant clinical implications. While the immunomodulatory effects of sex hormones are well established, the contributions of sex chromosome complement (XX vs. XY) and gut microbiome diversity on immune sexual dimorphisms have only recently become appreciated. Here we investigate the individual and collaborative influences of sex chromosome complements and gut microbiome bacteria on humoral immune activation.

Methods

Sham-operated and gonadectomized male and female Four Core Genotype (FCG) mice were immunized with heat-killed Streptococcus pneumoniae (HKSP). Humoral immune responses were assessed, and X-linked immune-related gene expression was evaluated to explain the identified XX-dependent phenotypes. Ex vivo studies investigated the functional role of Kdm6a, an X-linked epigenetic regulatory gene of interest, in mitogenic B cell activation. Additionally, we examined whether gut microbiome communities, or their metabolites, differentially influence immune cell activation in a sex chromosome-dependent manner. Endogenous gut microbiomes were antibiotically depleted and reconstituted with select short-chain fatty acid (SCFA)-producing bacteria prior to HKSP immunization and immune responses assessed.

Results

XX mice exhibited higher HKSP-specific IgM-secreting B cells and plasma cell frequencies than XY mice, regardless of gonadal sex. Although Kdm6a was identified as an X-linked gene overexpressed in XX B cells, inhibition of its enzymatic activity did not affect mitogen-induced plasma cell differentiation or antibody production in a sex chromosome-dependent manner ex vivo. Enhanced humoral responses in XX vs. XY immunized FCG mice were eliminated after microbiome depletion, indicating that the microbiome contributes to the identified XX-dependent immune enhancement. Reconstituting microbiota-depleted mice with select SCFA-producing bacteria increased humoral responses in XX, but not XY, FCG mice. This XX-dependent enhancement appears to be independent of SCFA production in males, while female XX-dependent responses relied on SCFAs.

Conclusions

FCG mice have been used to assess the influence of sex hormones and sex chromosome complements on various sexually dimorphic traits. The current study indicates that the gut microbiome impacts humoral responses in an XX-dependent manner, suggesting that the collaborative influence of gut bacteria and other sex-specific factors should be considered when interpreting data aimed at delineating the mechanisms that promote sexual dimorphism.

Optical imaging of the small intestine immune compartment across scales

The limitations of 2D microscopy constrain our ability to observe and understand tissue-wide networks that are, by nature, 3-dimensional. Optical projection tomography (OPT) enables the acquisition of large volumes (ranging from micrometres to centimetres) in various tissues. We present a multi-modal workflow for the characterization of both structural and quantitative parameters of the mouse small intestine. As proof of principle, we evidence its applicability for imaging the mouse intestinal immune compartment and surrounding mucosal structures. We quantify the volumetric size and spatial distribution of Isolated Lymphoid Follicles (ILFs) and quantify the density of villi throughout centimetre-long segments of intestine. Furthermore, we exhibit the age and microbiota dependence for ILF development, and leverage a technique that we call reverse-OPT for identifying and homing in on regions of interest. Several quantification capabilities are displayed, including villous density in the autofluorescent channel and the size and spatial distribution of the signal of interest at millimetre-scale volumes. The concatenation of 3D imaging with reverse-OPT and high-resolution 2D imaging allows accurate localisation of ROIs and adds value to interpretations made in 3D. Importantly, OPT may be used to identify sparsely-distributed regions of interest in large volumes whilst retaining compatibility with high-resolution microscopy modalities, including confocal microscopy. We believe this pipeline to be approachable for a wide-range of specialties, and to provide a new method for characterisation of the mouse intestinal immune compartment.

Sex-Related Effects of Gut Microbiota in Metabolic Syndrome-Related Diabetic Retinopathy

The metabolic syndrome (MetS) is a complex disease of metabolic abnormalities, including obesity, insulin resistance, hypertension and dyslipidaemia, and it is associated with an increased risk of cardiovascular disease (CVD). Diabetic retinopathy (DR) is the leading cause of vision loss among working-aged adults around the world and is the most frequent complication in type 2 diabetic (T2D) patients. The gut microbiota are a complex ecosystem made up of more than 100 trillion of microbial cells and their composition and diversity have been identified as potential risk factors for the development of several metabolic disorders, including MetS, T2D, DR and CVD. Biomarkers are used to monitor or analyse biological processes, therapeutic responses, as well as for the early detection of pathogenic disorders. Here, we discuss molecular mechanisms underlying MetS, the effects of biological sex in MetS-related DR and gut microbiota, as well as the latest advances in biomarker research in the field. We conclude that sex may play an important role in gut microbiota influencing MetS-related DR.

Characterisation of the Paternal Influence on Intergenerational Offspring Cardiac and Brain Lipid Homeostasis in Mice

There is growing evidence that poor paternal diet at the time of conception increase the risk of offspring developing a range of non-communicable metabolic diseases, such as obesity, diabetes and cardiovascular disease, in adulthood. We hypothesise that a paternal low protein-high carbohydrate diet perturbs offspring tissue lipid abundance through both sperm and seminal plasma-mediated mechanisms. To test our hypothesis, we fed male C57BL/6 mice either a control normal protein diet (NPD; 18% protein) or an isocaloric low protein diet (LPD; 9% protein) for a minimum of 8 weeks. We generated offspring through artificial insemination, in combination with vasectomised male mating. Using this approach, we derived offspring from either NPD or LPD sperm but in the presence of NPD or LPD seminal plasma. Using high resolution mass-spectrometry, we found that offspring derived from either LPD sperm or seminal fluid displayed perturbed cardiac and brain lipid abundance from just three weeks of age, typically associated with the altered abundance of tissue triglycerides. We also observed the differential sex-specific patterns of lipids between the control and experimental offspring's hearts and brains. These observations indicate that poor paternal diet at the time of conception affects offspring cardiac and brain lipid profiles in an age-, sex- and generation-specific manner.

Sex hormones, intestinal inflammation, and the gut microbiome: Major influencers of the sexual dimorphisms in obesity

Obesity is defined as the excessive accumulation of body fat and is associated with an increased risk of developing major health problems such as cardiovascular disease, diabetes and stroke. There are clear sexual dimorphisms in the epidemiology, pathophysiology and sequelae of obesity and its accompanying metabolic disorders, with females often better protected compared to males. This protection has predominantly been attributed to the female sex hormone estrogen and differences in fat distribution. More recently, the sexual dimorphisms of obesity have also been attributed to the differences in the composition and function of the gut microbiota, and the intestinal immune system. This review will comprehensively summarize the pre-clinical and clinical evidence for these sexual dimorphisms and discuss the interplay between sex hormones, intestinal inflammation and the gut microbiome in obesity. Major gaps and limitations of this rapidly growing area of research will also be highlighted in this review.

Impact of Age, Sex, and Genetic Diversity in Murine Models of the Hematopoietic Acute Radiation Syndrome (H-ARS) and the Delayed Effects of Acute Radiation Exposure (DEARE)

Purpose of review

Malicious or accidental radiation exposure increases risk for the hematopoietic acute radiation syndrome (H-ARS) and the delayed effects of acute radiation exposure (DEARE). Radiation medical countermeasure (MCM) development relies on robust animal models reflective of all age groups and both sexes. This review details critical considerations in murine H-ARS and DEARE model development including divergent radiation responses dependent on age, sex, and genetic diversity.

Recent findings

Radioresistance increases with murine age from pediatrics through geriatrics. Between sexes, radioresistance is higher in male weanlings, pubescent females, and aged males, corresponding with accelerated myelopoiesis. Jackson diversity outbred (JDO) mice resemble non-human primates in radiation response for modeling human diversity. Weanlings and JDO models exhibit less DEARE than other models.

Summary

Highly characterized age-, sex- and diversity-conscious murine models of H-ARS and DEARE provide powerful and essential tools in MCM development for all radiation victims.

Maternal stress and the maternal microbiome have sex-specific effects on offspring development and aggressive behavior in Siberian hamsters (Phodopus sungorus)

The gut microbiome, a community of commensal, symbiotic and pathogenic bacteria, fungi, and viruses, interacts with many physiological systems to affect behavior. Prenatal experiences, including exposure to maternal stress and different maternal microbiomes, are important sources of organismal variation that can affect offspring development. These physiological systems do not act in isolation and can have long-term effects on offspring development and behavior. Here we investigated the interactive effects of maternal stress and manipulations of the maternal microbiome on offspring development and social behavior using Siberian hamsters, Phodopus sungorus. We exposed pregnant females to either a social stressor, antibiotics, both the social stressor and antibiotics, or no treatment (i.e., control) over the duration of their pregnancy and quantified male and female offspring growth, gut microbiome composition and diversity, stress-induced cortisol concentrations, and social behavior. Maternal antibiotic exposure altered the gut microbial communities of male and female offspring. Maternal treatment also had sex-specific effects on aspects of offspring development and aggressive behavior. Female offspring produced by stressed mothers were more aggressive than other female offspring. Female, but not male, offspring produced by mothers exposed to the combined treatment displayed low levels of aggression, suggesting that alteration of the maternal microbiome attenuated the effects of prenatal stress in a sex-specific manner. Maternal treatment did not affect non-aggressive behavior in offspring. Collectively, our study offers insight into how maternal systems can interact to affect offspring in sex-specific ways and highlights the important role of the maternal microbiome in mediating offspring development and behavior.

Gut Microbiota and Immune Modulatory Properties of Human Breast Milk Streptococcus salivarius and S. parasanguinis Strains

Human breast milk Streptococcus spp. are transferred to infant guts via breast feeding, but their effects on the gut microbiota and immunity remain unclear. In this study, we characterized gut microbiota and immune modulatory properties of human breast milk S. salivarius F286 and S. parasanguinis F278 that had been shown to be able to colonize gut. The two Streptococcus strains were orally administered to mouse pups individually at 1 × 10⁷ cells/day from postnatal Days 1 to 21. At postnatal week 3 (the weaning period), S. salivarius F286 reduced the colonic microbiota α-diversity, increased 21 amplicon sequence variants (ASVs), including bacteria from Akkermansia, Intestinimonas, and Lachnospiraceae, and decreased 52 ASVs, including bacteria from Eubacterium, Bifidobacterium, Escherichia-Shigella, and Turicibacter; however, S. parasanguinis F278 didn't change the colonic microbiota. Both Streptococcus strains reduced the ileal mRNA expression of cytokine/transcription factor representatives of T helper (Th) cells, including IFN-γ (Th1), Gata3 (Th2), and TGF-β (Treg) in 2-week-old suckling mice, and promoted the ileal expression of Foxp3 and TGF-β, which are representatives of anti-inflammatory Treg cells, in 3-week-old weaning mice. The two Streptococcus strains exhibited anti-inflammatory potential when incubated in vitro with human peripheral blood mononuclear cells and TNF-α-treated gut epithelial HT29 cells. In C. elegans, both strains activated immune response genes, which was associated with their lifespan-prolonging effects. Our results suggest that S. salivarius F286 and S. parasanguinis F278 may exert regulatory (anti-inflammatory) roles in gut immunity and S. salivarius F286 can modulate gut microbiota, and highlight the probiotic potential of milk S. salivarius and S. parasanguinis strains.

Female sex as a risk factor for penicillin drug allergy in the inpatient setting

Background: Penicillin is the most common reported drug allergy. Previous literature suggests that there is increased prevalence of penicillin drug allergy in female patients in the outpatient setting. However, this is poorly described in the inpatient setting. Objective: This study was performed to determine whether female sex is an independent risk factor for penicillin allergy in the inpatient setting. Methods: A retrospective review of electronic medical records (January 1, 2001-December 31, 2017) was performed for patients with a history of penicillin allergy who underwent penicillin skin testing (PST). Each chart review included the age at initial skin testing, sex, medications, and medical co-morbidities. The study was approved by the institutional review board. Results: 30,883 patients underwent PST with 29,354 and 1,529 occurring in the outpatient and inpatient setting respectively. 170 patients tested positive with a ≥ 5x5 wheal. Of the 170 positive patients, 122 were female (72%) and 48 were male (28%). 15 patients tested positive in the inpatient setting. Of the 1506 adult patients tested in the inpatient setting, 809 were female and 697 were male. 12 females (92.3%) and 1 one male (7.7%) tested positive with a ≥ 5x5 wheal (OR-10.5; 95% CI-1.4-80.8; p-value=0.02). 23 pediatric patients were tested in the inpatient setting. Two pediatric male patients were positive and no female pediatric patients tested positive (OR-1.7; 95% CI-0.5-5.9; p-value=0.5). Conclusion: In the inpatient setting, adult females are 10 times more likely to have a positive PST compared to males. Female sex may be a potential risk factor for objective penicillin drug allergy in the inpatient setting.

Gut dysbiosis and age-related neurological diseases in females

Historically, females have been underrepresented in biological research. With increased interest in the gut microbiome and the gut-brain axis, it is important for researchers to pursue studies that consider sex as a biological variable. The composition of the gut microbiome is influenced by environmental factors, disease, diet, and varies with age and by sex. Detrimental changes in the gut microbiome, referred to as dysbiosis, is believed to influence the development and progression of age-related neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and stroke. Many are investigating the changes in microbial populations in order or to better understand the role of the gut immunity and the microbiome in neurodegenerative diseases, many of which the exact etiology remains elusive, and no cures exist. Others are working to find diagnostic markers for earlier detection, or to therapeutically modulate microbial populations using probiotics. However, while all these diseases present in reproductively senescent females, most studies only use male animals for their experimental design. Reproductively senescent females have been shown to have differences in disease progression, inflammatory responses, and microbiota composition, therefore, for research to be translational to affected populations it is necessary for appropriate models to be used. This review discusses factors that influence the gut microbiome and the gut brain axis in females, and highlights studies that have investigated the role of dysbiosis in age-related neurodegenerative disorders that have included females in their study design.

The intestine and the microbiota in maternal glucose homeostasis during pregnancy

It is now well established that, beyond its role in nutrient processing and absorption, the intestine and its accompanying gut microbiome constitute a major site of immunological and endocrine regulation that mediates whole-body metabolism. Despite the growing field of host-microbe research, few studies explore what mechanisms govern this relationship in the context of pregnancy. During pregnancy, significant maternal metabolic adaptations are made to accommodate the additional energy demands of the developing fetus and to prevent adverse pregnancy outcomes. Recent data suggest that the maternal gut microbiota may play a role in these adaptations, but changes to maternal gut physiology and the underlying intestinal mechanisms remain unclear. In this review, we discuss selective aspects of intestinal physiology including the role of the incretin hormone, glucagon-like peptide 1 (GLP-1), and the role of the maternal gut microbiome in the maternal metabolic adaptations to pregnancy. Specifically, we discuss how bacterial components and metabolites could mediate the effects of the microbiota on host physiology, including nutrient absorption and GLP-1 secretion and action, and whether these mechanisms may change maternal insulin sensitivity and secretion during pregnancy. Finally, we discuss how these pathways could be altered in disease states during pregnancy including maternal obesity and diabetes.

A Pilot Study of the Effect of Lactobacillus casei Obtained from Long-Lived Elderly on Blood Biochemical, Oxidative, and Inflammatory Markers, and on Gut Microbiota in Young Volunteers

Probiotic intake has been shown to improve certain physiological health indicators. We aimed to examine effects of Lactobacillus casei LTL1879, obtained from long-lived elderly volunteers, on blood biochemical, oxidative, and inflammatory markers and gut microbiota in twenty healthy, young volunteers. Volunteers were randomly divided into equal probiotic and placebo groups and changes in blood biochemical indicators, oxidative and inflammatory markers, and gut microbiota were examined after three weeks of probiotic intervention. The probiotic group’s antioxidant levels were significantly enhanced post-intervention. Total antioxidant capacity (T-AOC) levels were significantly increased (p < 0.0001), while malondialdehyde (MDA) levels decreased (p < 0.05), and total superoxide dismutase (T-SOD) levels increased, but with no significant difference. In addition, Interleukin-10 (IL-10) and tumor necrosis factor-α (TNF-α) levels were significantly up-regulated and down-regulated (p < 0.05, respectively). Escherichia coli, Enterococcus, and Bacteroides expression was significantly reduced (p < 0.05), while Clostridium leptum, Bifidobacterium, and Lactobacillus expression increased (p < 0.05). Volunteer health status was quantified using principal components and cluster analysis, indicating that the probiotic group’s overall score was higher than that of the placebo group. The results of this pilot study suggest L. casei LTL 1879 can significantly improve specific immune, oxidative, and gut microbiota characteristics related to health factors.

Sex differences feed into nuclear receptor signaling along the digestive tract

Sex differences in physiology are noted in clinical and animal studies. However, mechanisms underlying these observed differences between males and females remain elusive. Nuclear receptors control a wide range of physiological pathways and are expressed in the gastrointestinal tract, including the mouth, stomach, liver and intestine. We investigated the literature pertaining to ER, AR, FXR, and PPAR regulation and highlight the sex differences in nutrient metabolism along the digestive system. We chose these nuclear receptors based on their metabolic functions, and hormonal actions. Intriguingly, we noted an overlap in target genes of ER and FXR that modulate mucosal integrity and GLP-1 secretion, whereas overlap in target genes of PPARα with ER and AR modulate lipid metabolism. Sex differences were seen not only in the basal expression of nuclear receptors, but also in activation as their endogenous ligand concentrations fluctuate depending on nutrient availability. Finally, in this review, we speculate that interactions between the nuclear receptors may influence overall metabolic decisions in the gastrointestinal tract in a sex-specific manner.

Association of immune cell subsets with cardiac mechanics in the Multi-Ethnic Study of Atherosclerosis

BackgroundImmunomodulatory therapy may help prevent heart failure (HF). Data on immune cells and myocardial remodeling in older adults with cardiovascular risk factors are limited.MethodsIn the Multi-Ethnic Study of Atherosclerosis cohort, 869 adults had 19 peripheral immune cell subsets measured and underwent cardiac MRI during the baseline exam, of which 321 had assessment of left ventricular global circumferential strain (LV-GCS). We used linear regression with adjustment for demographics, cardiovascular risk factors, and cytomegalovirus serostatus to evaluate the cross-sectional association of immune cell subsets with left ventricular mass index (LVMI) and LV-GCS.ResultsThe average age of the cohort was 61.6 ± 10.0 years and 53% were women. Higher proportions of γ/δ T cells were associated with lower absolute (worse) LV-GCS (-0.105% [95% CI -0.164%, -0.046%] per 1 SD higher proportion of γ/δ T cells, P = 0.0006). This association remained significant after Bonferroni's correction. Higher proportions of classical monocytes were associated with worse absolute LV-GCS (-0.04% [95% CI -0.07%, 0.00%] per 1 SD higher proportion of classical monocytes, P = 0.04). This did not meet significance after Bonferroni's correction. There were no other significant associations with LV-GCS or LVMI.ConclusionPathways associated with γ/δ T cells may be potential targets for immunomodulatory therapy targeted at HF prevention in populations at risk.FundingContracts 75N92020D00001, HHSN268201500003I, N01-HC-95159, 75N92020D00005, N01-HC-95160, 75N92020D00002, N01-HC-95161, 75N92020D00003, N01-HC-95162, 75N92020D00006, N01-HC-95163, 75N92020D00004, N01-HC-95164, 75N92020D00007, N01-HC-95165, N01-HC-95166, N01-HC-95167, N01-HC-95168, and N01-HC-95169 and grant R01 HL98077 from the National Heart, Lung, and Blood Institute/NIH and grants KL2TR001424, UL1-TR-000040, UL1-TR-001079, and UL1-TR-001420 from the National Center for Advancing Translational Sciences/NIH.

Eotaxins and Their Receptor as Biomarkers of Colorectal Cancer

Colorectal cancer (CRC) is one of the most common malignancies. Despite the availability of diagnostic tests, an increasing number of new cases is observed. That is why it is very important to search new markers that would show high diagnostic utility. Therefore, we made an attempt to assess the usefulness of eotaxins, as there are few studies that investigate their significance, in patients with CRC. The study included 80 subjects (CRC patients and healthy volunteers). Serum concentrations of all eotaxins were measured using a multiplexing method (Luminex), while CCR3 was measured by immunoenzymatic assay (ELISA). CRP levels were determined by immunoturbidimetry and classical tumor marker levels (CEA and CA 19-9) and were measured using chemiluminescent microparticle immunoassay (CMIA). The highest usefulness among the proteins tested showed CCR3. Its concentrations were significantly higher in the CRC group than in healthy controls. The diagnostic sensitivity, specificity, positive and negative predictive value, and the area under the ROC curve (AUC) of CCR3 were higher than those of CA 19-9. The maximum values for sensitivity, negative predictive value, and AUC were obtained for a combination of CCR3 and CRP. Our findings suggest the potential usefulness of CCR3 in the diagnosis of CRC, especially in combination with CRP or CEA.

The Interplay between Androgen and Gut Microbiota: Is There a Microbiota-Gut-Testis Axis

The gut microbiota, a large ecosystem interacting with the host, has been shown to affect the health and fitness of the host-microbial superorganism. Increasing evidence suggests that the gut microbiota communicates with distal organs of the host including the brain, liver, and muscle, as well as testis, through various complex mechanisms. So far, we know that the androgen can markedly remodel the gut microbiota and has initiated an interdisciplinary field termed "microgenderome." More recently, the gut microbiota has been found as a major regulator of androgen production and metabolism in turn and even could trespass the blood-testis barrier (BTB) to regulate spermatogenesis, which largely updates the current knowledge on male reproduction. In this review, we provided a brief overview of the context of the gender bias of diseases related to gut microbiota, the sex dimorphism of gut microbiota, and their relationships with androgen. We also summarized the known interaction between the testis and gut microbiota based on published animal studies and tentatively discussed the hypothesis of microbiota-gut-testis axis. Finally, we highlighted the opportunities and challenges underlying the ongoing research. This knowledge may extend our understanding of the role of gut microbiota in male health and microbiota-related diseases.

The Gut Microbiota and Unhealthy Aging: Disentangling Cause from Consequence

The gut microbiota changes with age, but it is not clear to what degree these changes are due to physiologic changes, age-associated inflammation or immunosenescence, diet, medications, or chronic health conditions. Observational studies in humans find that there are profound differences between the microbiomes of long-lived and frail individuals, but the degree to which these differences promote or prevent late-life health is unclear. Studies in model organisms demonstrate that age-related microbial dysbiosis causes intestinal permeability, systemic inflammation, and premature mortality, but identifying causal relationships have been challenging. Herein, we review how physiological and immune changes contribute to microbial dysbiosis and the degree to which microbial dysbiosis contributes to late-life health conditions. We discuss the features of the aging microbiota that make it more amenable to diet and pre- and probiotic interventions. Health interventions that promote a diverse microbiome could influence the health of older adults.

Voluntary binge-patterned alcohol drinking and sex-specific influences on monoamine-related neurochemical signatures in the mouse gut and brain

BACKGROUND

Altered monoamine (i.e., serotonin, dopamine, and norepinephrine) activity following episodes of alcohol abuse plays key roles not only in the motivation to ingest ethanol, but also physiological dysfunction related to its misuse. Although monoamine activity is essential for physiological processes that require coordinated communication across the gut-brain axis (GBA), relatively little is known about how alcohol misuse may affect monoamine levels across the GBA. Therefore, we evaluated monoamine activity across the mouse gut and brain following episodes of binge-patterned ethanol drinking.

METHODS

Monoamine and select metabolite neurochemical concentrations were analyzed by ultra-high-performance liquid chromatography in gut and brain regions of female and male C57BL/6J mice following "Drinking in the Dark" (DID), a binge-patterned ethanol ingestion paradigm.

RESULTS

First, we found that alcohol access had an overall small effect on gut monoamine-related neurochemical concentrations, primarily influencing dopamine activity. Second, neurochemical patterns between the small intestine and the striatum were correlated, adding to recent evidence of modulatory activity between these areas. Third, although alcohol access robustly influenced activity in brain areas in the mesolimbic dopamine system, binge exposure also influenced monoaminergic activity in the hypothalamic region. Finally, sex differences were observed in the concentrations of neurochemicals within the gut, which was particularly pronounced in the small intestine.

CONCLUSION

Together, these data provide insights into the influence of alcohol abuse and biological sex on monoamine-related neurochemical changes across the GBA, which could have important implications for GBA function and dysfunction.

Establishing Pediatric Mouse Models of the Hematopoietic Acute Radiation Syndrome and the Delayed Effects of Acute Radiation Exposure

Medical countermeasures (MCMs) for hematopoietic acute radiation syndrome (H-ARS) should be evaluated in well-characterized animal models, with consideration of at-risk populations such as pediatrics. We have developed pediatric mouse models of H-ARS and delayed effects of acute radiation exposure (DEARE) for efficacy testing of MCMs against radiation. Male and female C57BL/6J mice aged 3, 4, 5, 6, 7 and 8 weeks old (±1 day) were characterized for baseline hematopoietic and gastrointestinal parameters, radiation response, efficacy of a known MCM, and DEARE at six and 12 months after total-body irradiation (TBI). Weanlings (age 3 weeks) were the most radiosensitive age group with an estimated LD50/30 of 712 cGy, while mice aged 4 to 8 weeks were more radioresistant with an estimated LD50/30 of 767-787 cGy. Female weanlings were more radiosensitive than males at 3 and 4 weeks old but became significantly more radioresistant after the pubertal age of 5 weeks. The most dramatic increase in body weight, RBC counts and intestinal circumference length occurred from 3 to 5 weeks of age. The established radiomitigator Neulasta® (pegfilgrastim) significantly increased 30-day survival in all age groups, validating these models for MCM efficacy testing. Analyses of DEARE among pediatric survivors revealed depressed weight gain in males six months post-TBI, and increased blood urea nitrogen at 12 months post-TBI which was more severe in females. Hematopoietic DEARE at six months post-TBI appeared to be less severe in survivors from the 3- and 4-week-old groups but was equally severe in all age groups by 12 months of age. Similar to our other acute radiation mouse models, there was no appreciable effect of Neulasta used as an H-ARS MCM on the severity of DEARE. In summary, these data characterize a pediatric mouse model useful for assessing the efficacy of MCMs against ARS and DEARE in children.

The differences in intestinal growth and microorganisms between male and female ducks

There are great differences in physiological and biological functions between animals of different sexes. However, whether there is a consensus between sexes in duck intestinal development and microorganisms is still unknown. The current study used Nonghua ducks to estimate the effect of sex on the intestine by evaluating differences in intestinal growth indexes and microorganisms. The intestines of male and female ducks were sampled at 2, 5, and 10 wk from the duodenum, jejunum, ileum, and cecum. Then, the intestinal length and weight were measured, the morphology was observed with HE staining, and the intestinal content was analyzed by 16S rRNA sequencing. The results showed that male ducks have shorter intestinal lengths with higher relative weights/relative lengths. The values of jejunal villus height (VH)/crypt depth (CD) of female ducks were significantly higher at 2 wk, whereas the jejunal VH/CD was significantly lower at 10 wk. There was obvious separation of microorganisms in each intestinal segment of ducks of different sexes at the 3 time periods. The dominant phyla at different stages were Firmicutea, Proteobacteria, Bacteroidetes, and Actinobacteria. The duodenal Chao index at the genus level of male ducks was significantly higher at 10 wk than that of female ducks. Significantly different genera were found only in the jejunum, and the abundances of Escherichia_Shigella, Pseudomonas, Clostridium_sensu_stricto_1, Sphingomonas, and Desulfovibrio in male ducks were higher than those in female ducks, whereas the abundance of Rothia was lower, and the abundance of viral infectious diseases, lipid metabolism, metabolism of terpenoids and polyketides, parasitic infectious diseases, xenobiotic biodegradation and metabolism, cardiovascular disease, and metabolism of other amino acids in male ducks were higher than that in female ducks, whereas gene folding, sorting and degradation pathways, and nucleotide metabolism were lower. This study provides a basic reference for the intestinal development and microbial symbiosis of ducks of different sexes.

Sex differences in stroke outcome correspond to rapid and severe changes in gut permeability in adult Sprague-Dawley rats

BACKGROUND

Sex differences in experimental stroke outcomes are well documented, such that adult males have a greater infarct volume, increased stroke-induced mortality, and more severe sensory-motor impairment. Based on recent evidence that the gut is an early responder to stroke, the present study tested the hypothesis that sex differences in stroke severity will be accompanied by rapid and greater permeability of the gut-blood barrier and gut dysbiosis in males as compared to females.

METHOD

Male and female Sprague-Dawley rats (5-7 months of age) were subject to endothelin (ET)-1-induced middle cerebral artery occlusion (MCAo). Sensory-motor tests were conducted pre- and 2 days after MCAo. Gut permeability was assessed in serum samples using biomarkers of gut permeability as well as functional assays using size-graded dextrans. Histological analysis of the gut was performed with H&E staining, periodic acid-Schiff for mucus, and immunohistochemistry for the tight junction protein, ZO-1. Fecal samples obtained pre- and post-stroke were analyzed for bacterial taxa and short-chain fatty acids (SCFAs).

RESULTS

After stroke, males displayed greater mortality, worse sensory-motor deficit, and higher serum levels of proinflammatory cytokines IL-17A, MCP-1, and IL-5 as compared to females. MCAo-induced gut permeability was rapid and severe in males as indicated by dextran extravasation from the gut to the blood in the hyperacute (< 2 h) and early acute (2 days) phase of stroke. This was accompanied by dysmorphology of the gut villi and dysregulation of the tight junction protein ZO-1 in the acute phase. Fecal 16s sequencing showed no differences in bacterial diversity in the acute phase of stroke. Predictive modeling indicated that markers of gut permeability were associated with acute sensory-motor impairment and infarct volume.

CONCLUSIONS

These data show that extensive leakiness of the gut barrier is associated with severe post-stroke disability and suggest that reinforcing this barrier may improve stroke outcomes.

Sex- and age-related trajectories of the adult human gut microbiota shared across populations of different ethnicities

Lifelong sex- and age-related trajectories of the human gut microbiota remain largely unexplored. Using metagenomics, we derived the gut microbial composition of 2,338 adults (26-76 years) from a Han Chinese population-based cohort where metabolic health, hormone levels and aspects of their lifestyles were also recorded. In this cohort, and in three independent cohorts distributed across China, Israel and the Netherlands, we observed sex differences in the gut microbial composition and a shared age-related decrease in sex-dependent differences in gut microbiota. Compared to men, the gut microbiota of premenopausal women exhibited higher microbial diversity and higher abundances of multiple species known to have beneficial effects on host metabolism. We also found consistent sex-independent, age-related gut microbial characteristics across all populations, with the presence of members of the oral microbiota being the strongest indicator of older chronological age. Our findings highlight the existence of sex- and age-related trajectories in the human gut microbiota that are shared between populations of different ethnicities and emphasize the pivotal links between sex hormones, gut microbiota and host metabolism.

The possible role of oral microbiome in autoimmunity

OBJECTIVE

The human microbiome refers to the entire habitat, including microorganisms, their genomes and the surrounding environmental conditions of the microbial ecosystem. When the equilibrium between microbial habitats and host is disturbed, dysbiosis is caused. The oral microbiome (OMB) has been implicated in the manifestation of many intra- and extraoral diseases. Lately, there has been an intense effort to investigate and specify the relationship between microbial complexes, especially that of the oral cavity and intestine and autoimmunity. This study aimed to review the current literature about the possible role of the OMB in the pathogenesis of autoimmune diseases.

METHODS

We searched for published articles in English indexed in PubMed, Medline, Research Gate and Google Scholar using a search strategy that included terms for oral microbiome, autoimmune diseases, dysbiosis and next-generation sequencing.

RESULTS

An important number of articles were gathered and used for the description of the possible impact of dysbiosis of OMB in the pathogenesis of Sjögren's syndrome, systemic lupus erythematosus, rheumatoid arthritis, Behcet's disease, Crohn's disease and psoriasis.

CONCLUSION

This review article draws attention to the relationship between OMB and the triggering of a number of autoimmune diseases. Although this specific topic has been previously reviewed, herein, the authors review recent literature regarding the full list of nosological entities related to the OMB, point out the interaction between the microbiome and sex hormones with regard to their role in autoimmunity and discuss novel and promising therapeutic approaches for systemic autoimmune diseases. Furthermore, the question arises of whether the OMB is associated with oral bullous autoimmune diseases.

Intestinal SALSA/dmbt1 levels are decreased in prematurely born infants

The first months of life represent a crucial time period for an infant. Alongside establishing the early microbiome, the mucosal immunological homeostasis is being developed. Both processes may be perturbed in prematurely born infants. The glycoprotein SALSA plays a role in mucosal inflammation and microbial clearance. It is one of the most abundant molecules on the intestinal mucosal surfaces in early life. SALSA binds to many types of microbes and host defence molecules like IgA, C1q and collectin molecules. We here describe the development in faecal SALSA levels during the first three months of life. During these 90 days, the median SALSA level in full-term babies decreased from 1100 μg/mL (range 49-17 000 μg/mL) to 450 μg/mL (range 33-1000 μg/mL). Lower levels of SALSA were observed in prematurely born infants in the same time period. Our novel observation thus indicates an impact of prematurity on an important component of the infant intestinal immune system. Changes in SALSA in early life may have an effect on the early establishment of the human microbiome.

Intestinal miRNAs regulated in response to dietary lipids

The role of miRNAs in intestinal lipid metabolism is poorly described. The small intestine is constantly exposed to high amounts of dietary lipids, and it is under conditions of stress that the functions of miRNAs become especially pronounced. Approaches consisting in either a chronic exposure to cholesterol and triglyceride rich diets (for several days or weeks) or an acute lipid challenge were employed in the search for intestinal miRNAs with a potential role in lipid metabolism regulation. According to our results, changes in miRNA expression in response to fat ingestion are dependent on factors such as time upon exposure, gender and small intestine section. Classic and recent intestinal in vitro models (i.e. differentiated Caco-2 cells and murine organoids) partially mirror miRNA modulation in response to lipid challenges in vivo. Moreover, intestinal miRNAs might play a role in triglyceride absorption and produce changes in lipid accumulation in intestinal tissues as seen in a generated intestinal Dicer1-deletion murine model. Overall, despite some variability between the different experimental cohorts and in vitro models, results show that some miRNAs analysed here are modulated in response to dietary lipids, hence likely to participate in the regulation of lipid metabolism, and call for further research.

Gut microbiota from androgen-altered donors alter pulmonary responses to ozone in female mice

In mice, both androgens and the gut microbiota modify pulmonary responses to ozone. We hypothesized that androgens affect gut microbiota and thereby impact pulmonary responses to ozone. To address this hypothesis, we transferred cecal microbiota from male castrated or sham castrated C57BL/6J mice into female germ-free recipient C57BL/6J mice. Four weeks later mice were exposed to ozone (2 ppm) or room air for 3 hr. The gut microbiomes of castrated versus sham castrated donors differed, as did those of recipients of microbiota from castrated versus sham castrated donors. In recipients, ozone-induced airway hyperresponsiveness was not affected by donor castration status. However, compared to mice receiving microbiota from sham castrated donors, mice receiving microbiota from castrated donors had elevated numbers of bronchoalveolar lavage (BAL) neutrophils despite evidence of reduced lung injury as measured by BAL protein. Serum concentrations of IL-17A and G-CSF were significantly greater in recipients of castrated versus sham castrated microbiota. Furthermore, BAL neutrophils correlated with both serum IL-17A and serum G-CSF. Our data indicate that androgen-mediated effects on the gut microbiota modulate pulmonary inflammatory responses to ozone and suggest a role for circulating IL-17A and G-CSF in these events.

Distinct Alteration of Gene Expression Programs in the Small Intestine of Male and Female Mice in Response to Ablation of Intestinal Fabp Genes

Fatty acid-binding proteins (Fabps) make up a family of widely distributed cytoplasmic lipid-binding proteins. The small intestine contains three predominant Fabp species, Fabp1, Fabp2, and Fabp6. Our previous studies showed that Fabp2 and Fabp6 gene-disrupted mice exhibited sexually dimorphic phenotypes. In this study, we carried out a systematic comparative analysis of the small intestinal transcriptomes of 10 week-old wild-type (WT) and Fabp gene-disrupted male and female mice. We found that the small intestinal transcriptome of male and female mice showed key differences in the gene expression profiles that affect major biological processes. The deletion of specific Fabp genes induced unique and sex-specific changes in the gene expression program, although some differentially expressed genes in certain genotypes were common to both sexes. Functional annotation and interaction network analyses revealed that the number and type of affected pathways, as well as the sets of interacting nodes in each of the Fabp genotypes, are partitioned by sex. To our knowledge, this is the first time that sex differences were identified and categorized at the transcriptome level in mice lacking different intestinal Fabps. The distinctive transcriptome profiles of WT male and female small intestine may predetermine the nature of transcriptional reprogramming that manifests as sexually dimorphic responses to the ablation of intestinal Fabp genes.

The microbiome: an emerging key player in aging and longevity

Revolutionary advancements of high-throughput sequencing and metagenomic tools have provided new insights to microbiome function, including a bidirectional relationship between the microbiome and host aging. The intestinal tract is the largest surface in the human body that directly interacts with foreign antigens - it is covered with extremely complex and diverse community of microorganisms, known as the gut microbiome. In a healthy gut, microbial communities maintain a homeostatic metabolism and reside within the host in a state of immune tolerance. Abnormal shifts in the gut microbiome, however, have been implicated in the pathogenesis of age-related chronic diseases, including obesity, cardiovascular diseases and neurodegenerative diseases. The gut microbiome is emerging as a key factor in the aging process. In this review, we describe studies of humans and model organisms that suggest a direct causal role of the gut microbiome on host aging. Additionally, we also discuss sex-dimorphism in the gut microbiome and its possible roles in age-related sex-dimorphic phenotypes. We also provide an overview of widely used microbiome analysis methods and tools which could be used to explore the impact of microbiome remodeling on aging.

The Role of Genetic Sex and Mitochondria in Response to COVID-19 Infection

The difference between the female and male immune response to COVID-19 infection, and infections in general, is multifactorial. The well-known determiners of the immune response, such as X and Y chromosomes, sex hormones, and microbiota, are functionally interconnected and influence each other in shaping the organism's immunity. We focus our commentary on the interplay between the genetic sex and mitochondria and how this may affect a sex-dependent immune response in COVID-19 infection. Realizing the existence of these interactions may help in designing novel methods or fine-tuning the existing and routine therapies to fight COVID-19 and other infections.

Eotaxins and Their Receptor in Colorectal Cancer-A Literature Review

Colorectal cancer (CRC) is one of the most common malignancies in the world, with a global incidence of almost 2 million new cases every year. Despite the availability of many diagnostic tests, including laboratory tests and molecular diagnostics, an increasing number of new cases is observed. Thus, it is very important to search new markers that would show high diagnostic sensitivity and specificity in the detection of colorectal cancer in early stages of the disease. Eotaxins are proteins that belong to the cytokine group-small molecules with a variety of applications. Their main role is the activation of basophils and eosinophils involved in inflammatory processes. Therefore, we performed an extensive search of the literature pertaining to our investigation via the MEDLINE/PubMed database. On the basis of available literature, we can assume that eotaxins accumulate in cancer cells in the course of CRC. This leads to a decrease in the chemotaxis of eosinophils, which are effector immune cells with anti-tumor activity. This may explain a decrease in their number as a defense mechanism of cancer cells against their destruction and may be useful when attempting anti-tumor therapy with the use of chemokines.

Widespread sex dimorphism in aging and age-related diseases

Although aging is a conserved phenomenon across evolutionary distant species, aspects of the aging process have been found to differ between males and females of the same species. Indeed, observations across mammalian studies have revealed the existence of longevity and health disparities between sexes, including in humans (i.e. with a female or male advantage). However, the underlying mechanisms for these sex differences in health and lifespan remain poorly understood, and it is unclear which aspects of this dimorphism stem from hormonal differences (i.e. predominance of estrogens vs. androgens) or from karyotypic differences (i.e. XX vs. XY sex chromosome complement). In this review, we discuss the state of the knowledge in terms of sex dimorphism in various aspects of aging and in human age-related diseases. Where the interplay between sex differences and age-related differences has not been explored fully, we present the state of the field to highlight important future research directions. We also discuss various dietary, drug or genetic interventions that were shown to improve longevity in a sex-dimorphic fashion. Finally, emerging tools and models that can be leveraged to decipher the mechanisms underlying sex differences in aging are also briefly discussed.

Faecal microbiota and functional capacity associated with weaning weight in meat rabbits

Weaning weight is an important economic trait in the meat rabbit industry. Evidence has linked the gut microbiota to health and production performance in rabbits. However, the effect of gut microbiota on meat rabbit weaning weight remains unclear. In this study, we performed 16S rRNA gene sequencing analysis of 135 faecal samples from commercial Ira rabbits. We detected 50 OTUs significantly associated with weaning weight. OTUs that showed positive associations with weaning weight were mostly members of the family Ruminococcaceae which are important in degrading dietary fibres and producing butyrate. On the contrary, OTUs annotated to genera Blautia, Lachnoclostridium and Butyricicoccus correlated with fat deposition were negatively associated with weaning weight. Predicted functional capacity analysis revealed that 91 KOs and 26 KEGG pathways exhibited potential correlations with weaning weight. We found that gut microbiota involved in the metabolism of amino acids, butanoate, energy and monosaccharides affected weaning weight. Additionally, cross-validation analysis indicated that 16.16% of the variation in weaning weight was explained by the gut microbiome. Our findings provide important information to improve weaning weight of meat rabbits by modulating their gut microbiome.

Sexual dimorphism in PAR2-dependent regulation of primitive colonic cells

BACKGROUND

Sexual dimorphism in biological responses is a critical knowledge for therapeutic proposals. However, gender differences in intestinal stem cell physiology have been poorly studied. Given the important role of the protease-activated receptor PAR₂ in the control of colon epithelial primitive cells and cell cycle genes, we have performed a sex-based comparison of its expression and of the effects of PAR₂ activation or knockout on cell proliferation and survival functions.

METHODS

Epithelial primitive cells isolated from colons from male and female mice were cultured as colonoids, and their number and size were measured. PAR₂ activation was triggered by the addition of SLIGRL agonist peptide in the culture medium. PAR₂-deficient mice were used to study the impact of PAR₂ expression on colon epithelial cell culture and gene expression.

RESULTS

Colonoids from female mice were more abundant and larger compared to males, and these differences were further increased after PAR₂ activation by specific PAR₂ agonist peptide. The proliferation of male epithelial cells was lower compared to females but was specifically increased in PAR₂ knockout male cells. PAR₂ expression was higher in male colon cells compared to females and controlled the gene expression and activation of key negative signals of the primitive cell proliferation. This PAR₂-dependent brake on the proliferation of male colon primitive cells was correlated with stress resistance.

CONCLUSIONS

Altogether, these data demonstrate that there is a sexual dimorphism in the PAR₂-dependent regulation of primitive cells of the colon crypt.

Machine learning applied to transcriptomic data to identify genes associated with feed efficiency in pigs

BACKGROUND

To date, the molecular mechanisms that underlie residual feed intake (RFI) in pigs are unknown. Results from different genome-wide association studies and gene expression analyses are not always consistent. The aim of this research was to use machine learning to identify genes associated with feed efficiency (FE) using transcriptomic (RNA-Seq) data from pigs that are phenotypically extreme for RFI.

METHODS

RFI was computed by considering within-sex regression on mean metabolic body weight, average daily gain, and average backfat gain. RNA-Seq analyses were performed on liver and duodenum tissue from 32 high and 33 low RFI pigs collected at 153 d of age. Machine-learning algorithms were used to predict RFI class based on gene expression levels in liver and duodenum after adjusting for batch effects. Genes were ranked according to their contribution to the classification using the permutation accuracy importance score in an unbiased random forest (RF) algorithm based on conditional inference. Support vector machine, RF, elastic net (ENET) and nearest shrunken centroid algorithms were tested using different subsets of the top rank genes. Nested resampling for hyperparameter tuning was implemented with tenfold cross-validation in the outer and inner loops.

RESULTS

The best classification was obtained with ENET using the expression of 200 genes in liver [area under the receiver operating characteristic curve (AUROC): 0.85; accuracy: 0.78] and 100 genes in duodenum (AUROC: 0.76; accuracy: 0.69). Canonical pathways and candidate genes that were previously reported as associated with FE in several species were identified. The most remarkable pathways and genes identified were NRF2-mediated oxidative stress response and aldosterone signalling in epithelial cells, the DNAJC6, DNAJC1, MAPK8, PRKD3 genes in duodenum, and melatonin degradation II, PPARα/RXRα activation, and GPCR-mediated nutrient sensing in enteroendocrine cells and SMOX, IL4I1, PRKAR2B, CLOCK and CCK genes in liver.

CONCLUSIONS

ML algorithms and RNA-Seq expression data were found to provide good performance for classifying pigs into high or low RFI groups. Classification was better with gene expression data from liver than from duodenum. Genes associated with FE in liver and duodenum tissue that can be used as predictive biomarkers for this trait were identified.

The microgenderome revealed: sex differences in bidirectional interactions between the microbiota, hormones, immunity and disease susceptibility

Sex differences in immunity are well described in the literature and thought to be mainly driven by sex hormones and sex-linked immune response genes. The gastrointestinal tract (GIT) is one of the largest immune organs in the body and contains multiple immune cells in the GIT-associated lymphoid tissue, Peyer's patches and elsewhere, which together have profound effects on local and systemic inflammation. The GIT is colonised with microbial communities composed of bacteria, fungi and viruses, collectively known as the GIT microbiota. The GIT microbiota drives multiple interactions locally with immune cells that regulate the homeostatic environment and systemically in diverse tissues. It is becoming evident that the microbiota differs between the sexes, both in animal models and in humans, and these sex differences often lead to sex-dependent changes in local GIT inflammation, systemic immunity and susceptibility to a range of inflammatory diseases. The sexually dimorphic microbiome has been termed the 'microgenderome'. Herein, we review the evidence for the microgenderome and contemplate the role it plays in driving sex differences in immunity and disease susceptibility. We further consider the impact that biological sex might play in the response to treatments aimed at manipulating the GIT microbiota, such as prebiotics, live biotherapeutics, (probiotics, synbiotics and bacteriotherapies) and faecal microbial transplant. These alternative therapies hold potential in the treatment of both psychological (e.g., anxiety, depression) and physiological (e.g., irritable bowel disease) disorders differentially affecting males and females.

Sex bias in autoimmunity

PURPOSE OF REVIEW

To give an overview of recently published articles addressing the mechanisms underlying sex bias in autoimmune disease.

RECENT FINDINGS

Recent studies investigating the origins of sex bias in autoimmune disease have revealed an extensive and interconnected network of genetic, hormonal, microbial, and environmental influences. Investigation of sex hormones has moved beyond profiling the effects of hormones on activity and prevalence of immune cell types to defining the specific immunity-related genes driving these changes. Deeper examination of the genetic content of the X and Y chromosomes and genetic escapees of X chromosome inactivation has revealed some key drivers of female-biased autoimmunity. Animal studies are offering further insights into the connections among microbiota, particularly that of the gut, and the immune system.

SUMMARY

Sex bias in autoimmune disease is the manifestation of a complex interplay of the sex chromosomes, sex hormones, the microbiota, and additional environmental and sociological factors.

Sexual Dimorphism in the Response to Broad-spectrum Antibiotics During T Cell-mediated Colitis

BACKGROUND

Broad-spectrum antibiotics [Abx], including combination therapy with ciprofloxacin and metronidazole, are often prescribed during the treatment of inflammatory bowel disease [IBD] to alleviate symptoms, but with varying success. In this pilot study, we studied the effects of Abx on the course of experimental colitis, with a particular focus on sex as a determinant of the microbial and inflammatory responses.

METHODS

The effects of Abx were tested on colonic inflammation and microbiome in male and female Rag-/- mice, using adoptive transfer of naïve T cells to induce colitis in a short-term [2-week] and long-term [9-week] study.

RESULTS

We observed disparities between the sexes in both the response to adoptive T cell transfer and the effects of Abx. At baseline without Abx, female mice displayed a trend toward a more severe colitis than males. In both the short- and the long-term experiments, gut microbiota of some female mice exposed to Abx showed weak, delayed, or negligible shifts. Caecum weight was significantly lower in Abx-treated females. Abx exposure favoured a quick and persistent rise in Enterococcaceae exclusively in females. Males had higher relative abundance of Lactobacillaceae following Abx exposure relative to females. Abx-treated females trended toward higher colitis scores than Abx-treated males, and towards higher levels of IL-17A, NOS2, and IL-22.

CONCLUSIONS

Although preliminary, our results suggest a differential response to both inflammation and Abx between male and female mice, The findings may be relevant to current practice and also as the basis for further studies on the differential gender effects during long-term antibiotic exposure in IBD.

Absence of Intestinal Microbiota during Gestation and Lactation Does Not Alter the Metabolic Response to a Western-type Diet in Adulthood

SCOPE

Microbiota composition in early life is implied to affect the risk to develop obesity in adulthood. It is unclear whether this risk is due to long-lasting microbiome-induced changes in host metabolism. This study aims to identify whether the presence or total absence of early-life microbiota affects host metabolism in adulthood.

METHODS AND RESULTS

The effects of a germ-free (Former GF) versus conventional status during gestation and lactation on the metabolic status in adult offspring are compared. Upon conventionalization at weaning, all mice were metabolically challenged with a Western-type diet (WTD) at 10 weeks age. Between age 10 and 30 weeks, a former GF status does not notably affect overall body weight gain, cholesterol metabolism, glucose tolerance or insulin sensitivity at adult age. However, Former GF mice have lower bile flow and bile acid secretion in adulthood, but similar bile acid composition.

CONCLUSIONS

A germ-free status during gestation and lactation does not substantially affect key parameters of the metabolic status before 10 weeks of age on chow diet or in adulthood following a WTD challenge. These data imply that microbiota in early life does not critically affect adult metabolic plasticity.

Gender Difference and Dietary Supplemental Vitamin B6: Impact on Colon Luminal Environment

Colon diseases can be affected by several factors such as gender difference and dietary supplemental vitamin B₆ (B₆). The nutritional status of B₆ is affected by gender difference, leading us to hypothesize that gender difference affects colon luminal environment, which is dependent on B₆ status. To investigate this hypothesis, we fed male and female rats a diet containing 1 mg, 7 mg, or 35 mg pyridoxine HCl/kg diet for 6 wk. We found significantly higher fecal mucin levels in female rats compared to those in male rats. Supplemental B₆ significantly increased fecal mucins and was particularly profound in the female rats. The abundances of cecal and fecal Akkermansia muciniphila (mucin degrader) were unaffected. The fecal mucin levels were significantly correlated with colonic free threonine and serine and with gene expression of colon MUC16, implying that the combined effect of gender and dietary B₆ on fecal mucins was mediated by the alteration in the levels of such amino acids and MUC16 expression. This study further showed the significant effects of gender difference on colonic free amino acids such as threonine, ornithine, asparagine/aspartate ratio, and glutamine/glutamate ratio, cecal and fecal Lactobacillus spp. levels, and colonic gene expressions of MUC16 and TLR8, the factors relating to colon health and diseases. Therefore, our findings suggest that gender difference and dietary B₆ may have an impact on colon diseases by modulating these parameters.

Sex differences in lipid metabolism are affected by presence of the gut microbiota

Physiological processes are differentially regulated between men and women. Sex and gut microbiota have each been demonstrated to regulate host metabolism, but it is unclear whether both factors are interdependent. Here, we determined to what extent sex-specific differences in lipid metabolism are modulated via the gut microbiota. While male and female Conv mice showed predominantly differential expression in gene sets related to lipid metabolism, GF mice showed differences in gene sets linked to gut health and inflammatory responses. This suggests that presence of the gut microbiota is important in sex-specific regulation of lipid metabolism. Further, we explored the role of bile acids as mediators in the cross-talk between the microbiome and host lipid metabolism. Females showed higher total and primary serum bile acids levels, independent of presence of microbiota. However, in presence of microbiota we observed higher secondary serum bile acid levels in females compared to males. Analysis of microbiota composition displayed sex-specific differences in Conv mice. Therefore, our data suggests that bile acids possibly play a role in the crosstalk between the microbiome and sex-specific regulation of lipid metabolism. In conclusion, our data shows that presence of the gut microbiota contributes to sex differences in lipid metabolism.

Sex and Gender Differences in the Outcomes of Vaccination over the Life Course

Both sex (i.e., biological differences) and gender (i.e., social or cultural influences) impact vaccine acceptance, responses, and outcomes. Clinical data illustrate that among children, young adults, and aged individuals, males and females differ in vaccine-induced immune responses, adverse events, and protection. Although males are more likely to receive vaccines, following vaccination, females typically develop higher antibody responses and report more adverse effects of vaccination than do males. Human, nonhuman animal, and in vitro studies reveal numerous immunological, genetic, hormonal, and environmental factors that differ between males and females and contribute to sex- and gender-specific vaccine responses and outcomes. Herein, we address the impact of sex and gender variables that should be considered in preclinical and clinical studies of vaccines.

Role of Microbiota in Sexually Dimorphic Immunity

Sex differences in peripheral immune responses are well recognized. This is associated with sex differences in many immunological diseases. As the intestinal microbiota is known to influence the immune system, such sex differences in immune responses may be a consequence of sex-specific microbiota. Therefore, this mini-review discusses sex differences in intestinal microbiota and the possible role of microbiota in shaping sexually dimorphic immunity. Sex differences in microbiota composition are clearly found in mice studies and also in human studies. However, the lack of standardization in human studies may mask the sexual dimorphism in microbiota composition in human studies, since many factors such as age, genetic background, BMI, diet, and sex hormones appear to interfere with the sexual dimorphism in microbiota composition. Only a few mice studies found that differences in gut microbiota composition are causative for some aspects of sexually dimorphic immunity. Therefore, future studies should focus on a causal relationship between sexually dimorphic immunity and microbiota, considering the abovementioned interfering confounding factors. This would benefit the development of more sex-specific effective treatment options for immunological diseases.

Plasticity of lifelong calorie-restricted C57BL/6J mice in adapting to a medium-fat diet intervention at old age

Calorie restriction (CR) is a dietary regimen that supports healthy aging. In this study, we investigated the systemic and liver‐specific responses caused by a diet switch to a medium‐fat (MF) diet in 24‐month‐old lifelong, CR‐exposed mice. This study aimed to increase the knowledge base on dietary alterations of gerontological relevance. Nine‐week‐old C57BL/6J mice were exposed either to a control, CR, or MF diet. At the age of 24 months, a subset of mice of the CR group was transferred to ad libitumMF feeding (CR‐MF). The mice were sacrificed at the age of 28 months, and then, biochemical and molecular analyses were performed. Our results showed that, despite the long‐term exposure to the CR regimen, mice in the CR‐MF group displayed hyperphagia, rapid weight gain, and hepatic steatosis. However, no hepatic fibrosis/injury or alteration in CR‐improved survival was observed in the diet switch group. The liver transcriptomic profile of CR‐MF mice largely shifted to a profile similar to the MF‐fed animals but leaving ~22% of the 1,578 differentially regulated genes between the CR and MF diet groups comparable with the expression of the lifelong CR group. Therefore, although the diet switch was performed at an old age, the CR‐MF‐exposed mice showed plasticity in coping with the challenge of a MF diet without developing severe liver pathologies.

A gut feeling: Microbiome-brain-immune interactions modulate social and affective behaviors

The expression of a wide range of social and affective behaviors, including aggression and investigation, as well as anxiety- and depressive-like behaviors, involves interactions among many different physiological systems, including the neuroendocrine and immune systems. Recent work suggests that the gut microbiome may also play a critical role in modulating behavior and likely functions as an important integrator across physiological systems. Microbes within the gut may communicate with the brain via both neural and humoral pathways, providing numerous avenues of research in the area of the gut-brain axis. We are now just beginning to understand the intricate relationships among the brain, microbiome, and immune system and how they work in concert to influence behavior. The effects of different forms of experience (e.g., changes in diet, immune challenge, and psychological stress) on the brain, gut microbiome, and the immune system have often been studied independently. Though because these systems do not work in isolation, it is essential to shift our focus to the connections among them as we move forward in our investigations of the gut-brain axis, the shaping of behavioral phenotypes, and the possible clinical implications of these interactions. This review summarizes the recent progress the field has made in understanding the important role the gut microbiome plays in the modulation of social and affective behaviors, as well as some of the intricate mechanisms by which the microbiome may be communicating with the brain and immune system.