Role of estrogen and stress on the brain-gut axis

Gastrointestinal dysfunction in the valproic acid induced model of social deficit in rats

Autism spectrum disorder (ASD) has increased in incidence over the past several decades, and is associated with a range of co-morbidities including gastrointestinal (GI) dysfunctions including gastroesophageal reflux, abdominal pain, bloating, constipation and/or diarrhea. Several animal models have been used that replicate several aspects of ASD but no single model has been able to replicate the entire disease pathophysiology. In humans, prenatal exposure to valproic acid (VPA) has been identified as a significant risk factor and rodent models have shown that in utero VPA exposure leads to behavioral deficits in offspring. The present study aimed to investigate whether in utero exposure to VPA induces GI dysfunction in rats. Timed pregnant Sprague-Dawley rats were injected with a single dose of VPA at embryonic day 12.5. Both male and female offspring subsequently underwent behavioral studies and assessment of GI function in adulthood. In utero VPA treatment induced social deficits in both male and female offspring, decreasing sociability and social novelty. Histological examination showed that VPA treated offspring had decreased thickness of GI muscle and mucosa, while immunohistochemical studies showed a decrease in myenteric neuron number in the fundus. Functional studies showed that both male and female VPA offspring had a delay in gastric emptying compared to vehicle treated offspring. Results of the current study suggest that the rat VPA model of behavioral deficits may be a convenient model by which both mechanistic and functional insights into GI dysfunction may be studied.

Olanzapine-induced weight gain and lipid dysfunction in mice between different gender

As one of the most common antipsychotics, olanzapine may cause metabolic-related adverse effects, but it is still unknown how olanzapine alters lipid metabolism. In this study, we found that olanzapine-treated mice showed varying degrees of dyslipidemia, which was particularly pronounced in female mice. Based on ultra-performance liquid chromatography-quadrupole time-of-flight-MS (UPLC-Q-TOF-MS) technology and lipid metabolomics, we mapped the changes in lipid metabolism in olanzapine-treated mice and then compared the changes in lipid metabolism between male and female mice. There were 98 metabolic differentiators between the olanzapine-treated and control groups in females and 79 in males. These metabolites were glycerolipids, glycerophospholipids, fatty amides, and sphingolipids, which are involved in glycerolipid metabolism, glycerophospholipid metabolism, and fatty acid metabolism. These results suggest that olanzapine-induced changes in the levels of lipid metabolites are closely associated with disturbances in lipid metabolic pathways, which may underlie lipemia. This lipidome profiling study not only visualizes changes in lipid metabolism in liver tissue but also provides a foundation for understanding the regulatory pathways and mechanisms involved in olanzapine-induced lipid metabolism disorders. Furthermore, this study demonstrates differences in lipid metabolism between males and females, providing a reference for clinical treatment regimen selection.

The relationship between gender differences in dietary habits, neuroinflammation, and Alzheimer's disease

Neurocognitive decline is one of the foremost dire issues in medicine today. The mechanisms by which dementia pathogenesis ensues are complicated and multifactorial, particularly in the case of Alzheimer's disease (AD). One irrefutable, yet unexplained factor is the gender disparity in AD, in which women are disproportionately affected by AD, both in the rate and severity of the disease. Examining the multifaceted contributing causes along with unique gender dynamics in modifiable risk factors, such as diet, may lend some insight into why this disparity exists and potential paths forward. The aim of this brief narrative review is to summarize the current literature of gender differences in dietary habits and how they may relate to neuroinflammatory states that contribute to AD pathogenesis. As such, the interplay between diet, hormones, and inflammation will be discussed, along with potential interventions to inform care practices.

Dorsal motor vagal neurons can elicit bradycardia and reduce anxiety-like behavior

Cardiovagal neurons (CVNs) innervate cardiac ganglia through the vagus nerve to control cardiac function. Although the cardioinhibitory role of CVNs in nucleus ambiguus (CVNNA) is well established, the nature and functionality of CVNs in dorsal motor nucleus of the vagus (CVNDMV) is less clear. We therefore aimed to characterize CVNDMV anatomically, physiologically, and functionally. Optogenetically activating cholinergic DMV neurons resulted in robust bradycardia through peripheral muscarinic (parasympathetic) and nicotinic (ganglionic) acetylcholine receptors, but not beta-1-adrenergic (sympathetic) receptors. Retrograde tracing from the cardiac fat pad labeled CVNNA and CVNDMV through the vagus nerve. Using whole-cell patch-clamp, CVNDMV demonstrated greater hyperexcitability and spontaneous action potential firing ex vivo despite similar resting membrane potentials, compared to CVNNA. Chemogenetically activating DMV also caused significant bradycardia with a correlated reduction in anxiety-like behavior. Thus, DMV contains uniquely hyperexcitable CVNs and is capable of cardioinhibition and robust anxiolysis.

Gut Microbiome-Estrobolome Profile in Reproductive-Age Women with Endometriosis

Microbiota is associated with our bodily functions and microenvironment. A healthy, balanced gut microbiome not only helps maintain mucosal integrity, prevents translocation of bacterial content, and contributes to immune status, but also associates with estrogen metabolism. Gut dysbiosis and estrobolome dysfunction have hence been linked to certain estrogen-dependent diseases, including endometriosis. While prior studies on microbiomes and endometriosis have shown conflicting results, most of the observed microbial differences are seen in the genital tract. This case-control study of reproductive-age women utilizes their fecal and urine samples for enzymatic, microbial, and metabolic studies to explore if patients with endometriosis have distinguishable gut microbiota or altered estrogen metabolism. While gut β-glucuronidase activities, microbial diversity, and abundance did not vary significantly between patients with or without endometriosis, fecal samples of patients with endometriosis were more enriched by the Erysipelotrichia class and had higher folds of four estrogen/estrogen metabolites. Further studies are needed to elucidate what these results imply and whether there indeed is an association or causation between gut microbiota and endometriosis.

Functional Gastrointestinal Disorders and Abdominal Visceral Fat in Children and Adolescents

Purpose

Few reports have investigated the correlation between functional gastrointestinal disorders (FGIDs) and the degree of obesity in children and adolescents. Thus, this study aimed to examine the relationship between FGIDs and the degree of obesity in children and adolescents.

Methods

Children and adolescents (<19 years old) who had undergone abdominopelvic computed tomography and had been diagnosed with FGIDs from 2015 to 2016 were included in this retrospective case-control study in a ratio of 1:2. Abdominal visceral fat was measured using an image analysis software.

Results

The mean age of all 54 FGID patients was 12.9±3.4 years, and the male: female ratio was 1:1.2. We observed no difference in body mass index (BMI) between the FGID and control groups (19.5±4.6 vs. 20.6±4.3 kg/m2, p=0.150). However, the FGID group had less abdominal visceral fat than that of the control group (26.2±20.0 vs. 34.4±26.9 cm2, p=0.048). Boys in the FGID group had lower BMI (18.5±3.5 vs. 20.9±4.3 kg/m2, p=0.019) and less abdominal visceral fat (22.8±15.9 vs. 35.9±31.8 cm2, p=0.020) than those of boys in the control group. However, we found no difference in BMI (20.5±5.3 vs. 20.4±4.2 kg/m2, p=0.960) and abdominal visceral fat (29.0±22.9 vs. 33.1±22.1 cm2, p=0.420) between girls in both groups.

Conclusion

Our study revealed a difference in the relationship between FGID and the degree of obesity according to sex, which suggests that sex hormones influence the pathogenesis of FGIDs. Multicenter studies with larger cohorts are required to clarify the correlation between FGID subtypes and the degree of obesity.

Gender-based research underscores sex differences in biological processes, clinical disorders and pharmacological interventions

Earlier research has presumed that the male and female biology is similar in most organs except the reproductive system, leading to major misconceptions in research interpretations and clinical implications, with serious disorders being overlooked or misdiagnosed. Careful research has now identified sex differences in the cardiovascular, renal, endocrine, gastrointestinal, immune, nervous, and musculoskeletal systems. Also, several cardiovascular, immunological, and neurological disorders have shown differences in prevalence and severity between males and females. Genetic variations in the sex chromosomes have been implicated in several disorders at young age and before puberty. The levels of the gonadal hormones estrogen, progesterone and testosterone and their receptors play a role in the sex differences between adult males and premenopausal women. Hormonal deficiencies and cell senescence have been implicated in differences between postmenopausal and premenopausal women. Specifically, cardiovascular disorders are more common in adult men vs premenopausal women, but the trend is reversed with age with the incidence being greater in postmenopausal women than age-matched men. Gender-specific disorders in females such as polycystic ovary syndrome, hypertension-in-pregnancy and gestational diabetes have attained further research recognition. Other gender-related research areas include menopausal hormone therapy, the "Estrogen Paradox" in pulmonary arterial hypertension being more predominant but less severe in young females, and how testosterone may cause deleterious effects in the kidney while having vasodilator effects in the coronary circulation. This has prompted the National Institutes of Health (NIH) initiative to consider sex as a biological variable in research. The NIH and other funding agencies have provided resources to establish state-of-the-art centers for women health and sex differences in biology and disease in several academic institutions. Scientific societies and journals have taken similar steps to organize specialized conferences and publish special issues on gender-based research. These combined efforts should promote research to enhance our understanding of the sex differences in biological systems beyond just the reproductive system, and provide better guidance and pharmacological tools for the management of various clinical disorders in a gender-specific manner.

Perinatal high-fat diet exposure alters oxytocin and corticotropin releasing factor inputs onto vagal neurocircuits controlling gastric motility

Perinatal high-fat diet (pHFD) exposure alters the development of vagal neurocircuits that control gastrointestinal (GI) motility and reduce stress resiliency in offspring. Descending oxytocin (OXT; prototypical anti-stress peptide) and corticotropin releasing factor (CRF; prototypical stress peptide) inputs from the paraventricular nucleus (PVN) of the hypothalamus to the dorsal motor nucleus of the vagus (DMV) modulate the GI stress response. How these descending inputs, and their associated changes to GI motility and stress responses, are altered following pHFD exposure are, however, unknown. The present study used retrograde neuronal tracing experiments, cerebrospinal fluid extraction, in vivo recordings of gastric tone, motility and gastric emptying rates, and in vitro electrophysiological recordings from brainstem slice preparations to investigate the hypothesis that pHFD alters descending PVN-DMV inputs and dysregulates vagal brain-gut responses to stress. Compared to controls, rats exposed to pHFD had slower gastric emptying rates and did not respond to acute stress with the expected delay in gastric emptying. Neuronal tracing experiments demonstrated that pHFD reduced the number of PVNOXT neurons that project to the DMV, but increased PVNCRF neurons. Both in vitro electrophysiology recordings of DMV neurons and in vivo recordings of gastric motility and tone demonstrated that, following pHFD, PVNCRF -DMV projections were tonically active, and that pharmacological antagonism of brainstem CRF1 receptors restored the appropriate gastric response to brainstem OXT application. These results suggest that pHFD exposure disrupts descending PVN-DMV inputs, leading to a dysregulated vagal brain-gut response to stress. KEY POINTS: Maternal high-fat diet exposure is associated with gastric dysregulation and stress sensitivity in offspring. The present study demonstrates that perinatal high-fat diet exposure downregulates hypothalamic-vagal oxytocin (OXT) inputs but upregulates hypothalamic-vagal corticotropin releasing factor (CRF) inputs. Both in vitro and in vivo studies demonstrated that, following perinatal high-fat diet, CRF receptors were tonically active at NTS-DMV synapses, and that pharmacological antagonism of these receptors restored the appropriate gastric response to OXT. The current study suggests that perinatal high-fat diet exposure disrupts descending PVN-DMV inputs, leading to a dysregulated vagal brain-gut response to stress.

Role of Estrogen Receptor α in Aging and Chronic Disease

Estrogen receptor alpha (ERα) plays a crucial role in reproductive function in both sexes. It also mediates cellular responses to estrogens in multiple nonreproductive organ systems, many of which regulate systemic metabolic homeostasis and inflammatory processes in mammals. The loss of estrogens and/or ERα agonism during aging is associated with the emergence of several comorbid conditions, particularly in females undergoing the menopausal transition. Emerging data also suggests that male mammals likely benefit from ERα agonism if done in a way that circumvents feminizing characteristics. This has led us, and others, to speculate that tissue-specific ERα agonism may hold therapeutic potential for curtailing aging and chronic disease burden in males and females that are at high-risk of cancer and/or cardiovascular events with traditional estrogen replacement therapies. In this mini-review, we emphasize the role of ERα in the brain and liver, summarizing recent evidence that indicates these two organs systems mediate the beneficial effects of estrogens on metabolism and inflammation during aging. We also discuss how 17α-estradiol administration elicits health benefits in an ERα-dependent manner, which provides proof-of-concept that ERα may be a druggable target for attenuating aging and age-related disease burden.

Targeting the endocannabinoid system for the treatment of abdominal pain in irritable bowel syndrome

The management of visceral pain in patients with disorders of gut-brain interaction, notably irritable bowel syndrome, presents a considerable clinical challenge, with few available treatment options. Patients are increasingly using cannabis and cannabinoids to control abdominal pain. Cannabis acts on receptors of the endocannabinoid system, an endogenous system of lipid mediators that regulates gastrointestinal function and pain processing pathways in health and disease. The endocannabinoid system represents a logical molecular therapeutic target for the treatment of pain in irritable bowel syndrome. Here, we review the physiological and pathophysiological functions of the endocannabinoid system with a focus on the peripheral and central regulation of gastrointestinal function and visceral nociception. We address the use of cannabinoids in pain management, comparing them to other treatment modalities, including opioids and neuromodulators. Finally, we discuss emerging therapeutic candidates targeting the endocannabinoid system for the treatment of pain in irritable bowel syndrome.

Clinical Pharmacological Considerations in Transgender Medicine

Transgender medicine is a growing clinical field. Hormone therapy (testosterone or estrogen treatment) is part of the standard of gender-affirming medical care, yet clinical pharmacological knowledge in transgender medicine is lacking. Herein, we summarize available clinical and pharmacologic data for hormone therapy among transgender and gender diverse people.

The lack of transcriptionally active Nrf2 triggers colon dysfunction in female mice - The role of estrogens

BACKGROUND AND AIM

The proper functioning of the gastrointestinal system relies on an intricate crosstalk between a plethora of cell types and signaling pathways. Recently we identified that the lack of NRF2 transcriptional activity (NRF2 tKO) triggers significant colon microscopical alterations, still they do not affect the general functioning of mice. Therefore, in this study, we aimed to address the gender-dependent impact of NRF2 transcriptional deficiency on colon function, and relate them to an established model of inflammatory bowel disease (IBD).

METHODS

In the study we subjected 3- and 6-month old mice deficient in IL-10 and NRF2 transcriptional activity and wild-type counterparts to tests assessing colon functionality, and histological analyses. To address the role of estrogens, we attempted to rescue the phenotype by the delivery of 17β-estradiol through subcutaneous implants.

RESULTS

In females, NRF2 transcriptional abrogation, like IL-10 deficiency, triggers a functional and microscopic phenotype, that resembles IBD. The females are significantly more affected by the dysfunctional phenotype, and the functional impairmentdecreases with age. We found that NRF2 transcriptional activity influences 17β-estradiol level and the estrogen receptors expression and location. Exogenous delivery of 17β-estradiol normalized colon motility in the NRF2 tKO mice, which is related to enhanced ERβ signaling.

CONCLUSIONS

Summing up, in this study, we underline that NRF2 transcriptional deficiency or the lack of IL-10 results in pronounced GI functional decline in young females. Mechanistically, we show that the impaired distal colon motility is dependent on ERβ signaling. Targeting estrogen signaling seems a promising therapeutic strategy to counteract colonic dysfunction.

Estrogen-gut microbiota interactions and irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder with a complex pathogenesis that has a serious impact on the quality of life of patients. Abnormal visceral sensation, disordered gut motility, dysregulated immunity, and damaged intestinal barrier are thought to be involved in the pathogenesis of IBS. Female predisposition to IBS strongly suggests that sex hormones such as estrogen are involved in the development of IBS. In addition, dysbiosis of the intestinal flora is closely related to IBS. The interaction between estrogen and gut microbiota in IBS has not been fully elucidated. This review summarizes and evaluates the progress of related studies. Based on the new findings and shortcomings of current studies, we discuss the directions and issues that need to be resolved in future research.

Stress-induced neuroplasticity in the gastric response to brainstem oxytocin in male rats

Previous studies have shown that pharmacological manipulations with stress-related hormones such as corticotropin-releasing factor and thyrotropin-releasing hormone induce neuroplasticity in brainstem vagal neurocircuits, which modulate gastric tone and motility. The prototypical antistress hormone oxytocin (OXT) has been shown to modulate gastric tone and motility via vagal pathways, and descending hypothalamic oxytocinergic inputs play a major role in the vagally dependent gastric-related adaptations to stress. The aim of this study was to investigate the possible cellular mechanisms through which OXT modulates central vagal brainstem and peripheral enteric neurocircuits of male Sprague-Dawley rats in response to chronic repetitive stress. After chronic (5 consecutive days) of homotypic or heterotypic stress load, the response to exogenous brainstem administration of OXT was examined using whole cell patch-clamp recordings from gastric-projecting vagal motoneurons and in vivo recordings of gastric tone and motility. GABAergic currents onto vagal motoneurons were decreased by OXT in stressed, but not in naïve rats. In naïve rats, microinjections of OXT in vagal brainstem nuclei-induced gastroinhibition via peripheral release of nitric oxide (NO). In stressed rats, however, the OXT-induced gastroinhibition was determined by the release of both NO and vasoactive intestinal peptide (VIP). Taken together, our data indicate that stress induces neuroplasticity in the response to OXT in the neurocircuits, which modulate gastric tone and motility. In particular, stress uncovers the OXT-mediated modulation of brainstem GABAergic currents and alters the peripheral gastric response to vagal stimulation.NEW & NOTEWORTHY The prototypical antistress hormone, oxytocin (OXT), modulates gastric tone and motility via vagal pathways, and descending hypothalamic-brainstem OXT neurocircuits play a major role in the vagally dependent adaptation of gastric motility and tone to stress. The current study suggests that in the neurocircuits, which modulate gastric tone and motility, stress induces neuroplasticity in the response to OXT and may reflect the dysregulation observed in stress-exacerbated functional motility disorders.

Abdominal Aortic Endothelial Dysfunction Occurs in Female Mice With Dextran Sodium Sulfate-Induced Chronic Colitis Independently of Reactive Oxygen Species Formation

Background and Objective

Inflammatory bowel disease (IBD) produces significant local and systemic inflammation with increased reactive oxygen species (ROS) formation. IBD Patients are at an increased risk for developing endothelial dysfunction and cardiovascular diseases. The present study tested the hypothesis that IBD impairs aortic endothelial function via ROS formation and investigate potential sex-related differences.

Methods and Results

Acute and chronic colitis models were induced in male and female C57BL/6 mice with dextran sodium sulfate (DSS) treatment. Aortic wall stiffness, endothelial function, and ROS levels, as well as serum levels of pro-inflammatory cytokines were evaluated. Acetylcholine (Ach)-induced endothelium-dependent relaxation of abdominal aorta without perivascular adipose tissue (PVAT) was significantly reduced in female mice, not males, with chronic colitis without a change in nitroglycerin-induced endothelium-independent relaxation. PVAT effectively preserved Ach-induced relaxation in abdominal aorta of female mice with chronic colitis. Aortic peak velocity, maximal intraluminal diameters, pulse wave velocity, distensibility and radial strain were preserved in mice with both acute and chronic colitis. Although pro-inflammatory cytokines levels were increased in mice with acute and chronic colitis, aortic ROS levels were not increased.

Conclusion

The data demonstrate that abdominal aortic endothelial function was attenuated selectively in female mice with chronic colitis independent of ROS formation. Further, PVAT played an important role in preserving endothelial function in female mice with chronic colitis.

Tissue engineering of the gastrointestinal tract: the historic path to translation

The gastrointestinal (GI) tract is imperative for multiple functions including digestion, nutrient absorption, and timely waste disposal. The central feature of the gut is peristalsis, intestinal motility, which facilitates all of its functions. Disruptions in GI motility lead to sub-optimal GI function, resulting in a lower quality of life in many functional GI disorders. Over the last two decades, tissue engineering research directed towards the intestine has progressed rapidly due to advances in cell and stem-cell biology, integrative physiology, bioengineering and biomaterials. Newer biomedical tools (including optical tools, machine learning, and nuanced regenerative engineering approaches) have expanded our understanding of the complex cellular communication within the GI tract that lead to its orchestrated physiological function. Bioengineering therefore can be utilized towards several translational aspects: (i) regenerative medicine to remedy/restore GI physiological function; (ii) in vitro model building to mimic the complex physiology for drug and pharmacology testing; (iii) tool development to continue to unravel multi-cell communication networks to integrate cell and organ-level physiology. Despite the significant strides made historically in GI tissue engineering, fundamental challenges remain including the quest for identifying autologous human cell sources, enhanced scaffolding biomaterials to increase biocompatibility while matching viscoelastic properties of the underlying tissue, and overall biomanufacturing. This review provides historic perspectives for how bioengineering has advanced over time, highlights newer advances in bioengineering strategies, and provides a realistic perspective on the path to translation.

Antipsychotic medication for women with schizophrenia spectrum disorders

There are significant differences between men and women in the efficacy and tolerability of antipsychotic drugs. Here, we provide a comprehensive overview of what is currently known about the pharmacokinetics and pharmacodynamics of antipsychotics in women with schizophrenia spectrum disorders (SSDs) and translate these insights into considerations for clinical practice. Slower drug absorption, metabolism and excretion in women all lead to higher plasma levels, which increase the risk for side-effects. Moreover, women reach higher dopamine receptor occupancy compared to men at similar serum levels, since oestrogens increase dopamine sensitivity. As current treatment guidelines are based on studies predominantly conducted in men, women are likely to be overmedicated by default. The risk of overmedicating generally increases when sex hormone levels are high (e.g. during ovulation and gestation), whereas higher doses may be required during low-hormonal phases (e.g. during menstruation and menopause). For premenopausal women, with the exceptions of quetiapine and lurasidone, doses of antipsychotics should be lower with largest adjustments required for olanzapine. Clinicians should be wary of side-effects that are particularly harmful in women, such as hyperprolactinaemia which can cause oestrogen deficiency and metabolic symptoms that may cause cardiovascular diseases. Given the protective effects of oestrogens on the course of SSD, oestrogen replacement therapy should be considered for postmenopausal patients, who are more vulnerable to side-effects and yet require higher dosages of most antipsychotics to reach similar efficacy. In conclusion, there is a need for tailored, female-specific prescription guidelines, which take into account adjustments required across different phases of life.

Precocious puberty and microbiota: The role of the sex hormone-gut microbiome axis

Puberty is a critical phase of life associated with physiological changes related to sexual maturation, and represents a complex process regulated by multiple endocrine and genetic controls. Puberty is driven by hormones, and it can impact the gut microbiome (GM). GM differences between sex emerge at puberty onset, confirming a relationship between microbiota and sex hormones. In this narrative review, we present an overview of precocious pubertal development and the changes in the GM in precocious puberty (PP) in order to consider the role of the sex hormone-gut microbiome axis from the perspective of pediatric endocrinology. Bidirectional interactions between the GM and sex hormones have been proposed in different studies. Although the evidence on the interaction between microbiota and sex hormones remains limited in pediatric patients, the evidence that GM alterations may occur in girls with central precocious puberty (CPP) represents an interesting finding for the prediction and prevention of PP. Deepening the understanding of the connection between the sex hormones and the role of microbiota changes can lead to the implementation of microbiota-targeted therapies in pubertal disorders by offering a pediatric endocrinology perspective.

Diminished androgen levels are linked to irritable bowel syndrome and cause bowel dysfunction in mice

Functional gastrointestinal disorders (FGIDs) have prominent sex differences in incidence, symptoms, and treatment response that are not well understood. Androgens are steroid hormones present at much higher levels in males than females and could be involved in these differences. In adults with irritable bowel syndrome (IBS), a FGID that affects 5-10% of the population worldwide, we found that free testosterone levels were lower than those in healthy controls and inversely correlated with symptom severity. To determine how this diminished androgen signaling could contribute to bowel dysfunction, we depleted gonadal androgens in adult mice and found that this caused a profound deficit in gastrointestinal transit. Restoring a single androgen hormone was sufficient to rescue this deficit, suggesting that circulating androgens are essential for normal bowel motility in vivo. To determine the site of action, we probed androgen receptor expression in the intestine and discovered, unexpectedly, that a large subset of enteric neurons became androgen-responsive upon puberty. Androgen signaling to these neurons was required for normal colonic motility in adult mice. Taken together, these observations establish a role for gonadal androgens in the neural regulation of bowel function and link altered androgen levels with a common digestive disorder.

Altered Fecal Metabolites and Colonic Glycerophospholipids Were Associated With Abnormal Composition of Gut Microbiota in a Depression Model of Mice

The microbiota–gut–brain axis has been considered to play an important role in the development of depression, but the underlying mechanism remains unclear. The gastrointestinal tract is home to trillions of microbiota and the colon is considered an important site for the interaction between microbiota and host, but few studies have been conducted to evaluate the alterations in the colon. Accordingly, in this study, we established a chronic social defeated stress (CSDS) mice model of depression. We applied 16S rRNA gene sequencing to assess the gut microbial composition and gas and liquid chromatography–mass spectroscopy to identify fecal metabolites and colonic lipids, respectively. Meanwhile, we used Spearman’s correlation analysis method to evaluate the associations between the gut microbiota, fecal metabolites, colonic lipids, and behavioral index. In total, there were 20 bacterial taxa and 18 bacterial taxa significantly increased and decreased, respectively, in the CSDS mice. Further, microbial functional prediction demonstrated a disturbance of lipid, carbohydrate, and amino acid metabolism in the CSDS mice. We also found 20 differential fecal metabolites and 36 differential colonic lipids (in the category of glycerolipids, glycerophospholipids, and sphingolipids) in the CSDS mice. Moreover, correlation analysis showed that fecal metabolomic signature was associated with the alterations in the gut microbiota composition and colonic lipidomic profile. Of note, three lipids [PC(16:0/20:4), PG(22:6/22:6), and PI(18:0/20:3), all in the category of glycerophospholipids] were significantly associated with anxiety- and depression-like phenotypes in mice. Taken together, our results indicated that the gut microbiota might be involved in the pathogenesis of depression via influencing fecal metabolites and colonic glycerophospholipid metabolism.

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.

Risk of cause-specific death, its sex and age differences, and life expectancy in post-pancreatitis diabetes mellitus

AIMS

The aim was to investigate sex- and age-stratified risks of cause-specific death and life expectancy in individuals with post-pancreatitis diabetes mellitus (PPDM).

METHODS

Nationwide data on mortality in New Zealand were obtained. For two head-to-head comparisons (PPDM versus type 2 diabetes mellitus [T2DM]; PPDM versus type 1 diabetes mellitus [T1DM]), the groups were matched on age, sex, and calendar year of diabetes diagnosis. Multivariable Cox regression analyses were conducted to estimate risks of vascular, cancer, and non-vascular non-cancer mortality. Remaining life expectancy at age of diabetes diagnosis was estimated using the Chiang II method.

RESULTS

A total of 15,848 individuals (1,132 PPDM, 3,396 T1DM, and 11,320 T2DM) were included. The risks of vascular mortality and non-vascular non-cancer mortality did not differ significantly between PPDM and T2DM or T1DM. PPDM was associated with a significantly higher risk of cancer mortality compared with T2DM (adjusted hazard ratio, 1.32; 95% confidence interval, 1.08-1.63) or T1DM (adjusted hazard ratio, 1.65; 95% confidence interval, 1.27-2.13). The risk of cancer mortality associated with PPDM (versus T2DM) was significantly higher in women than in men (p for interaction = 0.003). This sex difference in cancer mortality risk was also significant in the comparison between PPDM and T1DM (p for interaction = 0.006). Adults of both sexes with PPDM had the lowest remaining life expectancy (in comparison with T2DM or T1DM) up to 64 years of age.

CONCLUSIONS

People with PPDM have a higher risk of cancer mortality compared with those with T2DM or T1DM. This is especially pronounced in women. Young and middle-aged adults with PPDM have a lower life expectancy compared with their counterparts with T2DM or T1DM.

Irritable bowel syndrome in midlife women: a narrative review

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

Central Neurocircuits Regulating Food Intake in Response to Gut Inputs-Preclinical Evidence

The regulation of energy balance requires the complex integration of homeostatic and hedonic pathways, but sensory inputs from the gastrointestinal (GI) tract are increasingly recognized as playing critical roles. The stomach and small intestine relay sensory information to the central nervous system (CNS) via the sensory afferent vagus nerve. This vast volume of complex sensory information is received by neurons of the nucleus of the tractus solitarius (NTS) and is integrated with responses to circulating factors as well as descending inputs from the brainstem, midbrain, and forebrain nuclei involved in autonomic regulation. The integrated signal is relayed to the adjacent dorsal motor nucleus of the vagus (DMV), which supplies the motor output response via the efferent vagus nerve to regulate and modulate gastric motility, tone, secretion, and emptying, as well as intestinal motility and transit; the precise coordination of these responses is essential for the control of meal size, meal termination, and nutrient absorption. The interconnectivity of the NTS implies that many other CNS areas are capable of modulating vagal efferent output, emphasized by the many CNS disorders associated with dysregulated GI functions including feeding. This review will summarize the role of major CNS centers to gut-related inputs in the regulation of gastric function with specific reference to the regulation of food intake.

Metoclopramide nasal spray for management of symptoms of acute and recurrent diabetic gastroparesis in adults

Introduction: Gastroparesis (GP) is characterized by delayed gastric emptying in the absence of mechanical obstruction. About 75% of GP patients are females. Diabetes and idiopathic are the two commonest etiologies of GP. Up to two-thirds of the GP patients do not have significant symptom responses to medical therapies, and there is a paucity of available oral prokinetic agents with only one medication approved by the U.S. Food and Drug Administration (FDA) for this indication. The oral and parenteral formulations of metoclopramide were FDA approved in 1979 to treat symptoms of acute and recurrent diabetic GP. Now, more than 40 years later, a nasal preparation of metoclopramide (Gimoti^TM) was approved in June 2020 for the same indication.Areas covered: PubMed search using the keywords 'nasal metoclopramide' and 'diabetic gastroparesis.' This article aims to provide a concise review of the pharmacology, clinical efficacy, and tolerability of nasal metoclopramide.Expert opinion: The nasal formulation can be systemically absorbed without relying on the passage through a poorly emptying stomach, thus assuring the delivery of a therapeutic dose of metoclopramide, even during episodes of vomiting. Hence, metoclopramide nasal spray has the potential to be used during an acute flare, potentially avoiding hospitalizations.

Hypothalamic-vagal oxytocinergic neurocircuitry modulates gastric emptying and motility following stress

KEY POINTS

Stress triggers and exacerbates the symptoms of functional gastrointestinal disorders, such as delayed gastric emptying and impaired gastric motility. Understanding the mechanisms by which the neural circuits, impaired by stress, are restored may help to identify potential targets for more effective therapeutic interventions. Oxytocin administration or release ameliorates the stress-induced delayed gastric emptying and motility. However, is it unclear whether the effects are mediated via the hypothalamic-pituitary-adrenocortical axis or the oxytocinergic projections from the paraventricular nucleus of the hypothalamus to brainstem neurones of the dorsal vagal complex. We used Cre-inducible designer receptors exclusively activated by designer drugs to demonstrate the fundamental role of the oxytocinergic hypothalamic-vagal projections in the gastric adaptation to stress.

ABSTRACT

Stress triggers and exacerbates the symptoms of functional gastrointestinal (GI) disorders, such as delayed gastric emptying and impaired gastric motility. The prototypical anti-stress hormone, oxytocin (OXT), plays a major role in the modulation of gastric emptying and motility following stress. It is not clear, however, whether the amelioration of dysregulated GI functions by OXT is mediated via an effect on the hypothalamic-pituitary-adrenocortical axis or the oxytocinergic projections from the paraventricular nucleus of the hypothalamus (PVN) to neurones of the dorsal vagal complex (DVC). In the present study we tested the hypothesis that the activity of hypothalamic-vagal oxytocinergic neurocircuits plays a major role in the gastric adaptation to stress. Cre-inducible designer receptors exclusively activated by designer drugs (DREADDs) were injected into the DVC of rats and retrogradely transported to allow selective expression in OXT neurones in the PVN. Following acute stress and either chronic heterotypic (CHe) or chronic homotypic (CHo) stress, gastric emptying was assessed via the [13 C]-octanoic acid breath test, and gastric tone and motility were assessed via strain gauges sewn on the surface of the stomach. Activation of the hypothalamic-vagal oxytocinergic neurocircuitry, by DREADD agonist clozapine-N-oxide (CNO), prevented the delayed gastric emptying observed following acute or CHe stress, and 4th ventricular administration of CNO increased gastric tone and motility. Conversely, CNO-mediated inhibition of the hypothalamic-vagal oxytocinergic neurocircuitry prevented the CHo-induced adaptation in gastric emptying, and an increase in gastric tone and motility. Taken together, the data support the hypothesis that hypothalamic-vagal oxytocinergic neurocircuits play a major role in the modulation of gastric emptying and motility following stress.

Cytokine Levels and Symptoms Among Women with Irritable Bowel Syndrome: Considering the Role of Hormonal Contraceptive Use

BACKGROUND

Young to middle-aged women are more likely than men to be diagnosed with irritable bowel syndrome (IBS). Immune dysfunction may be present in IBS, however, few studies have tested whether hormonal contraceptive use is linked to inflammatory markers. The purpose of this study was to compare cytokine levels between women (ages 18-45) with and without IBS and with and without hormonal contraceptive use and to examine the relationships of cytokine levels to IBS gastrointestinal (GI) and non-GI symptoms within those using and not using hormonal contraceptives.

METHODS

Seventy-three women with IBS and 47 healthy control women completed questionnaires (demographics, hormonal contraceptive use) and kept a 28-day symptom diary. Fasting plasma and LPS-stimulated pro-inflammatory (IL-1β, IL-6, IL-12p40, IL-12p70, IL-8, and TNF-α) and anti-inflammatory (IL-10) cytokines were assayed.

RESULTS

No differences were found in plasma or stimulated cytokine levels between IBS and control women. Levels of IL-1β (p = 0.04) and TNF-α (p = 0.02) were higher among women who did not use hormonal contraceptives compared to women who used hormonal contraceptives. Among women with IBS, significant correlations were found between daily psychological distress and plasma IL-10, IL-12p70, IL-1β, IL-6, and IL-8 cytokine levels.

CONCLUSIONS

These results suggest that hormonal contraceptive use might reduce IL-1β and TNF-α cytokine levels in women with IBS. The impact of hormonal contraceptive use on innate immune activation among women with IBS requires further research.

Peripheral mechanisms contribute to comorbid visceral hypersensitivity induced by preexisting orofacial pain and stress in female rats

BACKGROUND

Stress exacerbates many chronic pain syndromes including irritable bowel syndrome (IBS). Among these patient populations, many suffer from comorbid or chronic overlapping pain conditions and are predominantly female. Nevertheless, basic studies investigating chronic psychological stress-induced changes in pain sensitivity have been mostly carried out in male rodents. Our laboratory developed a model of comorbid pain hypersensitivity (CPH) (stress in the presence of preexisting orofacial pain inducing chronic visceral pain hypersensitivity that significantly outlasts transient stress-induced pain hypersensitivity (SIH)) facilitating the study of pain associated with IBS. Since CPH and SIH are phenotypically similar until SIH resolves and CPH persists, it is unclear if underlying mechanisms are similar.

METHODS

In the present study, the visceromotor response (VMR) to colorectal distention was recorded in the SIH and CPH models in intact females and ovariectomized rats plus estradiol replacement (OVx + E2). Over several months, rats were determined to be susceptible or resilient to stress and the role of peripheral corticotrophin-releasing factor (CRF) underlying in the pain hypersensitivity was examined.

KEY RESULTS

Stress alone induced transient (3-4 weeks) visceral hypersensitivity, though some rats were resilient. Comorbid conditions increased susceptibility to stress prolonging hypersensitivity beyond 13 weeks. Both models had robust peripheral components; hypersensitivity was attenuated by the CRF receptor antagonist astressin and the mast cell stabilizer disodium cromoglycate (DSCG). However, DSCG was less effective in the CPH model compared to the SIH model.

CONCLUSIONS AND INFERENCES

The data indicate many similarities but some differences in mechanisms contributing to comorbid pain conditions compared to transient stress-induced pain.

Sex-steroid-dependent plasticity of brain-stem autonomic circuits

In the central nervous system (CNS), nuclei of the brain stem play a critical role in the integration of peripheral sensory information and the regulation of autonomic output in mammalian physiology. The nucleus tractus solitarius of the brain stem acts as a relay center that receives peripheral sensory input from vagal afferents of the nodose ganglia, integrates information from within the brain stem and higher central centers, and then transmits autonomic efferent output through downstream premotor nuclei, such as the nucleus ambiguus, the dorsal motor nucleus of the vagus, and the rostral ventral lateral medulla. Although there is mounting evidence that sex and sex hormones modulate autonomic physiology at the level of the CNS, the mechanisms and neurocircuitry involved in producing these functional consequences are poorly understood. Of particular interest in this review is the role of estrogen, progesterone, and 5α-reductase-dependent neurosteroid metabolites of progesterone (e.g., allopregnanolone) in the modulation of neurotransmission within brain-stem autonomic neurocircuits. This review will discuss our understanding of the actions and mechanisms of estrogen, progesterone, and neurosteroids at the cellular level of brain-stem nuclei. Understanding the complex interaction between sex hormones and neural signaling plasticity of the autonomic nervous system is essential to elucidating the role of sex in overall physiology and disease.