The oxytocin receptor system: structure, function, and regulation

The role of oxytocin in mediating the relationships between social factors and chemotherapy-associated cognitive decline in female patients with breast cancer

While chemotherapy can cause debilitating side effects, social support, particularly that of an intimate partner, can be protective. This study examined the relationships between couple satisfaction and chemotherapy-associated subjective and objective cognitive decline in a cohort of breast cancer patients, in addition to the roles of other social factors. Because of oxytocin's role in social bonding and cognition, circulating oxytocin and oxytocin receptor gene expression in peripheral blood mononuclear cells were investigated as potential mediators. Partnered breast cancer patients (n = 48) completed cognitive assessments and provided blood samples at 3 timepoints: pre-chemotherapy, during chemotherapy, and post-chemotherapy. Participants completed a retrospective couple satisfaction questionnaire, provided information about partner duration as well as other social factors (e.g., number of people in the household, number of dependents under 18), and completed a retrospective perceived general social support questionnaire. Analyses were completed using linear mixed effects and regression models. More satisfaction in an intimate relationship related to both less subjective and objective cognitive decline over chemotherapy. Similarly, higher perceived social support related to less overall objective cognitive decline over chemotherapy, though this relationship was less robust than that observed with high couple satisfaction. Remarkably, circulating oxytocin decreased over chemotherapy but was only associated with partner duration and not with cognitive measures. This study suggests a potential benefit of social-directed interventions for the treatment of cognitive side effects of chemotherapy, either from an intimate partner or more generally. Furthermore, understanding biological mechanisms is important to develop novel preventative and interventional therapies to mitigate the adverse side effects of chemotherapy.

Development and validation of a highly-sensitive, quantitative LC-MS/MS assay to evaluate plasma oxytocin

Introduction

Oxytocin is a 9-amino acid peptide that serves as neuromodulator in the human central nervous system. This peptide is implicated in the regulation of diverse behaviors and plays a significant role in positive social interaction. Currently, oxytocin levels are measured using immunoassays. However, these methods have several limitations that can lead to false results and erroneous interpretation. Given the remarkably low endogenous level of oxytocin in human plasma (low ng/L levels), we developed and rigorously validated a novel and highly sensitive LC-MS/MS method for oxytocin quantification in plasma.

Methods

Oxytocin was initially extracted using solid-phase extraction with an Oasis HLB 30 mg plate and then subjected to LC-MS/MS analysis. PBS-0.1 % BSA served as surrogate matrix for the preparation of validation samples and the calibration curve, ensuring no endogenous interference. The validation design followed the Clinical Laboratory Standards Institute guidelines. Precision, accuracy, and measurement uncertainty were determined using single-nested analysis of variance and e.noval software.

Results

A lower limit of quantification of 1 ng/L was achieved. The method was validated for oxytocin concentrations ranging from 1 ng/L to 75 ng/L, with precision (coefficient of variation) below 10 %, accuracy ranging from 94 % to 108 %, and measurement uncertainty below 15 %.

Conclusion

In this work, we developed and validated a highly sensitive LC-MS/MS method for the quantification of oxytocin in plasma. Our novel methodology is well-suited for clinical applications.

How does oxytocin modulate human behavior?

While the highly evolutionarily conserved hypothalamic neuropeptide, oxytocin (OT) can influence cognitive, emotional and social functions, and may have therapeutic potential in disorders with social dysfunction, it is still unclear how it acts. Here, we review the most established findings in both animal model and human studies regarding stimuli which evoke OT release, its primary functional effects and the mechanisms whereby exogenous administration influences brain and behavior. We also review progress on whether OT administration can improve social symptoms in autism spectrum disorder and schizophrenia and consider possible impediments to translational success. Importantly, we emphasize that OT acting via its extensive central or peripheral receptors primarily influences behavior indirectly through neuromodulatory interactions with classical transmitters and other peptides which themselves can independently influence behavior. We also emphasize that exogenous administration studies increasingly demonstrate peripheral effects of OT may be of greater importance than originally thought, especially involving the vagus. Overall, we propose a hierarchical model whereby OT's neuromodulatory actions influence behavior across interconnected functional domains and ultimately help to promote survival, security and sociability. Initially, OT potently facilitates attention to salient social and other important stimuli and additionally modulates cognitive, emotional and reward processing in a person- and context-dependent manner to promote interpersonal social understanding, attraction and bonds on the one hand and social group cohesion through increased conformity, altruistic punishment and moral emotions on the other. OT also increases co-operation and protection across both social domains. We hope this review and model will promote further research and help aid future translation success.

Intranasal oxytocin blunts amygdala response to negative affective stimuli in males and females with alcohol use disorder: a randomized controlled cross-over trial

RATIONALE

Negative affect plays a prominent role in the maintenance of alcohol use disorder (AUD) and has been identified as a risk factor for relapse to alcohol. To date, however, treatment options that target negative affective states and consecutive relapse risk in AUD are insufficient. Oxytocin (OXY) might be a promising approach for addressing negative affective states and resulting motivation to use alcohol.

OBJECTIVES

We aimed to investigate the acute effects of 24 I.U. OXY, administered intranasally, compared to matched placebo (PLC) on central processing of negative emotional stimuli in the amygdala in individuals with AUD.

METHODS

We conducted a randomized double-blind placebo-controlled crossover study in N = 24 individuals with AUD. Amygdala response to emotional stimuli served as primary outcome and was assessed using a validated functional magnetic resonance imaging emotion-processing task. Alcohol craving served as secondary outcome.

RESULTS

OXY versus PLC attenuated right amygdala reactivity to fearful and angry emotional face stimuli during the fMRI task (t(33) = 3.32, pFWE=0.035), while no effect of OXY on amygdala activation was observed during the presentation of geometric figures. In addition, right amygdala reactivity to fearful and angry emotional face stimuli was positively associated with alcohol craving (r =.332, Bias corrected and accelerated 95% confidence interval [95% BCa CI]=-0.044 to 0.624, p =.042).

CONCLUSIONS

OXY's effects on the neurocircuitry underlying negative affect and craving in AUD support its potential for dampening alcohol craving induced by negative affective states and implicate OXY as a potential future treatment option for AUD.

CLINICALTRIALS REGISTRY

DRKS00026218.

Human social behavior and oxytocin: Molecular and neuronal mechanisms

Oxytocin (OT) is a hormone that is crucial for regulating various human social behaviors, such as maternal instinct, empathy, and trust. Its secretion in the brain is triggered by social stimuli. Recent research demonstrated impaired regulation of OT secretion and reduced social behaviors in patients with arginine vasopressin deficiency (central diabetes insipidus). OT interacts with other hormones to regulate human trust. Moreover, it has been shown to generate feelings of attachment and trust toward other and familiar consumer brands, thereby, potentially impacting personal consumption, which is a significant aspect of economic activity. This review provided insights into the molecular and neural mechanisms of OT in regulating human social behavior, including both social and economic activities.

Reduction of oxytocin plasma levels in borderline personality disorder and normalization induced by psychotherapies

BACKGROUND

Borderline personality disorder (BPD) is a severe mental disorder characterized by emotional dysregulation, impulsive behaviors, and difficulties in interpersonal relationships. Despite the poor understanding of the underlying biological processes, the oxytocin (OXT) system may be involved in and mediate some of BPD's symptomatic and behavioral aspects. To clarify OXT's role in BPD, we assessed its plasma levels and modulations induced by psychotherapies in patients.

METHODS

Fifty BPD patients and 28 healthy controls (HC) participated in the study; patients were randomly assigned to two psychotherapeutic treatments: metacognitive interpersonal therapy and structured clinical management. Clinical and psychometric measures were assessed, and plasma was collected at baseline (T0) and in patients after 6 (T6) and 12 (T12) months of treatment. OXT was quantified by a radioimmunoassay technique.

RESULTS

BPD patients showed lower plasma OXT at T0 than HC (p = 0.002), and a correlation was observed (r = -0.36, p = 0.017) between low OXT concentrations and high Attachment Style Questionnaire - Italian Version-Preoccupation with Relationships subscale scores. OXT changed significantly over time in patients (p = 0.049) with an increase particularly evident from baseline to T6 (p = 0.022), without significant difference between treatment groups. OXT changes (T0 - T12) inversely correlated with symptom improvement as changes in the Zanarini Rating Scale for borderline personality disorder (r = 0.387, p = 0.006) and the Difficulties in Emotion Regulation Scale (r = 0.387, p = 0.005) scores during treatment.

CONCLUSIONS

OXT alteration in BPD patients and the regularizing effect of long-term psychotherapies support an involvement of the OXT system in the disease and in treatment impact. More research is needed to fully understand the underlying causal mechanisms linking OXT with pathogenesis and psychotherapy outcomes.

Subdiaphragmatic vagotomy reduces hypothalamic oxytocin expression and blood levels after oral MDMA administration in male rats

3,4-Methylenedioxymethamphetamine (MDMA) is a widely recognized entactogen frequently used recreationally. It is known for its interaction with the serotonin and oxytocin systems, which underlie its entactogenic effects in humans. Recently, we demonstrated that the gut-brain axis, mediated by the subdiaphragmatic vagus nerve, contributes to MDMA-induced resilience enhancement in rodents. This study investigates whether subdiaphragmatic vagotomy (SDV) affects plasma oxytocin levels and the expression of oxytocin and c-Fos in the hypothalamus following a single oral dose of MDMA in rats. SDV significantly reduced baseline plasma oxytocin levels and oxytocin expression in the paraventricular and supraoptic nuclei of the hypothalamus. Furthermore, SDV markedly attenuated MDMA-induced increases in plasma oxytocin and the expression of oxytocin and c-Fos in these hypothalamic regions. These findings suggest that the subdiaphragmatic vagus nerve plays a critical role in brain-body communication, mediating MDMA's pharmacological effects on the oxytocin system.

Linking oxytocin to nicotine dependence: An experimental study of the brain, behavior, and gut microbiota in rats

Oxytocin (OXT) is a hypothalamic neuropeptide, and numerous studies have indicated that exposure to addictive substances, such as opioids, cocaine, etc., can result in decreased function of the OXT system. The study also found that OXT can reduce addictive behavior for certain drugs, including methamphetamine, alcohol, and cocaine, suggesting a close relationship between the OXT system and drug abuse. Although nicotine is the main addictive substance in tobacco, its interaction with the OXT system is unknown and requires further study. Therefore, OXT levels in plasma and brain regions associated with addiction were measured by enzyme-linked immunosorbent assay (ELISA) using chronic nicotine administration via a slow-release pump. In addition, the effects of OXT injection on nicotine self-administration behavior, motor activity, and intestinal microbiota in rats were examined by nicotine self-administration experiment, open field experiment, and 16S sequencing experiment. By depleting gut microbiota with oral antibiotics, this study aims to investigate whether gut microbiota mediates oxytocin effect on the nicotine self-administration behavior in rats. This study shows that chronic nicotine administration can reduce OXT levels in plasma and brain regions such as the paraventricular nucleus (PVN), ventral tegmental area (VTA), and caudate putamen (CPU). OXT at a dose of 1.0 mg/kg significantly reduced the number of nicotine infusions and the abundance of Lactobacillus in rats. Notably, our findings indicate that other mechanisms besides gut microbes are involved in the effect of peripheral OXT administration on the inhibition of nicotine self-administration.

Effects of systemic oxytocin and beta-3 receptor agonist (CL 316243) treatment on body weight and adiposity in male diet-induced obese rats

Previous studies have implicated hindbrain oxytocin (OT) receptors in the control of food intake and brown adipose tissue (BAT) thermogenesis. We recently demonstrated that hindbrain [fourth ventricle (4V)] administration of oxytocin (OT) could be used as an adjunct to drugs that directly target beta-3 adrenergic receptors (β3-AR) to elicit weight loss in diet-induced obese (DIO) rodents. What remains unclear is whether systemic OT can be used as an adjunct with the β3-AR agonist, CL 316243, to increase BAT thermogenesis and elicit weight loss in DIO rats. We hypothesized that systemic OT and β3-AR agonist (CL 316243) treatment would produce an additive effect to reduce body weight and adiposity in DIO rats by decreasing food intake and stimulating BAT thermogenesis. To test this hypothesis, we determined the effects of systemic (subcutaneous) infusions of OT (50 nmol/day) or vehicle (VEH) when combined with daily systemic (intraperitoneal) injections of CL 316243 (0.5 mg/kg) or VEH on body weight, adiposity, food intake and brown adipose tissue temperature (TIBAT). OT and CL 316243 monotherapy decreased body weight by 8.0 ± 0.9% (P<0.05) and 8.6 ± 0.6% (P<0.05), respectively, but OT in combination with CL 316243 produced more substantial weight loss (14.9 ± 1.0%; P<0.05) compared to either treatment alone. These effects were associated with decreased adiposity, energy intake and elevated TIBAT during the treatment period. The findings from the current study suggest that the effects of systemic OT and CL 316243 to elicit weight loss are additive and appear to be driven primarily by OT-elicited changes in food intake and CL 316243-elicited increases in BAT thermogenesis.

Oxytocin enhances creativity specifically in approach-motivated individuals

Oxytocin (OT), a neuropeptide pivotal in social and reproductive behaviors, has recently gained attention for its potential impact on cognitive processes relevant to creativity. Yet, the direct intricate interplay between OT and creativity, particularly in the context of individual differences in motivational orientations, remains poorly understood. Here, we investigated the effects of intranasal OT on creative thinking in individuals characterized by varying levels of approach and avoidance motivations. The initial study, involving participants with high approach or avoidance motivation, employed the Alternative Uses Task to assess creativity under OT administration. Subsequently, the second study induced different motivational states through a recall task, aiming to validate and extend observed effects. Results revealed a significant enhancement of creativity in individuals with approach motivation following OT administration, while no parallel effect was discerned in those with avoidance motivation. Aligning with behavioral findings, functional connectivity and graph theory analyses of neural data illuminated the coordinated effects of OT on creativity-related neural networks. These outcomes collectively suggest that OT exerts a dissociable influence on creativity contingent upon an individual's motivational tendencies, providing insights into the intricate relationship between OT and human creative behavior.

Epilepsy, compulsion and oxytocin: Insights from behavioral sequences, using neuroethology and complexity systems approaches

Epilepsies are complex neurological entities usually co-existing with neuropsychiatric comorbidities. We already demonstrated that microinjection of oxytocin (OT) into the central nucleus of amygdala (CeA) induces hypergrooming in Wistar rats, a model of compulsion. Furthermore, the Wistar Audiogenic Rat (WAR) strain is a genetic model of generalized tonic-clonic seizures. Here we quantified grooming behavior in WAR, with grooming scores, flowcharts and directed graphs of syntactic and non-syntactic grooming chains, after bilateral administration of OT or saline (SAL) into the CeA. Our current pioneer behavioral description considers that hypergrooming (compulsion) in WARs is a comorbidity because: (1) WARs have the highest grooming scores, when exposed only to novelty (2), WARs have better grooming scores than Wistars after CeA-SAL, (3) Epileptic WARs perform much better than Wistars in OT-CeA-dependent stereotyped behavioral sequences (flowcharts of syntactic/non-syntactic grooming chains). One additional observation is that the behavioral sequences here demonstrated can be modeled as reliable Markov chains. In conclusion we can drive hypergrooming in WARs, defined previously as a model of ritualistic motor behavior in Wistar rats, with OT from CeA, one of the principal amygdala complex outputs. As perspectives, ongoing cellular studies are on their way, to demonstrate the neural network, certainly incorporating cortico-striatal-thalamic-basal ganglia-cortical circuits, driven from CeA OT-dependent grooming pattern, a stereotyped, sequential and complex array of behaviors, and its association with seizure susceptibility.

Emerging medications and pharmacological treatment approaches for substance use disorders

Medications to treat substance use disorders (SUDs) remain suboptimal or, in the case of stimulants and cannabis, non-existent. Many factors have contributed to this paucity, including the biological complexity of addiction, regulatory challenges, and a historical lack of enthusiasm among pharmaceutical companies to commit resources to this disease space. Despite these headwinds, the recent opioid crisis has highlighted the devastating consequences of SUDs for both individuals and society, stimulating urgent efforts to identify novel treatment approaches. In addition, several neurobiological systems have been recently implicated in unique aspects of drug reward, opening the door to candidate medications with novel mechanisms of action. Here, we provide an overview of efforts to target several of these new systems, with a focus on those that are the subject of ongoing clinical trials as well as being areas of interest among the authors' research groups (MHJ, MTB, NAE). Specifically, we discuss new classes of medications targeting the serotonin 2A receptor (i.e., psychedelics), glucagon-like peptide 1 receptor, cannabidiol, dynorphin/kappa opioid receptor, orexin/hypocretin, and oxytocin receptor systems, as well as emergent approaches for modulating the more canonical dopaminergic system via agonist therapies for stimulant use disorders. Collectively, innovations in this space give reason for optimism for an improved therapeutic landscape for substance use disorders in the near future.

Neuropeptide receptor distributions in male and female Eulemur vary between female-dominant and egalitarian species

Aggression and its neurochemical modulators are typically studied in males, leaving the mechanisms of female competitive aggression or dominance largely unexplored. To better understand how competitive aggression is regulated in the primate brain, we used receptor autoradiography to compare the neural distributions of oxytocin and vasopressin receptors in male and female members of female-dominant versus egalitarian/codominant species within the Eulemur genus, wherein dominance structure is a reliable proxy of aggression in both sexes. We found that oxytocin receptor binding in the central amygdala (CeA) was predicted by dominance structure, with the members of three codominant species showing more oxytocin receptor binding in this region than their peers in four female-dominant species. Thus, both sexes in female-dominant Eulemur show a pattern consistent with the regulation of aggression in male rodents. We suggest that derived pacifism in Eulemur stems from selective suppression of ancestral female aggression over evolutionary time via a mechanism of increased oxytocin receptor binding in the CeA, rather than from augmented male aggression. This interpretation implies fitness costs to female aggression and/or benefits to its inhibition. These data establish Eulemur as a robust model for examining neural correlates of male and female competitive aggression, potentially providing novel insights into female dominance.

Oxytocin receptor gene single nucleotide polymorphisms in patients with bipolar disorder

INTRODUCTION

Many studies have reported that psychiatric disorders may be associated with oxytocin receptor (OXTR) gene polymorphisms. The aim of this study was to investigate whether there is a relationship between OXTR gene polymorphisms and bipolar disorder (BPD).

METHODS

The study included 100 patients diagnosed with BPD type 1 (BPD I) and 96 healthy controls. Single nucleotide polymorphisms (SNPs) of the OXTR gene, including rs53576, rs2254298 and rs2268494, were examined via polymerase chain reaction in blood samples taken from the study participants. Based on the BPD determinants, the patients were divided into 4 subgroups, as those with psychotic features, seasonal patterns, rapid cycling and peripartum onset.

RESULTS

The frequency of the rs2268494 A allele was lower in the patients than in the healthy controls (p = .048), that frequency of psychotic mania was higher in patients with the rs53576 GG genotype compared to the A allele carriers (p = .003), and that of the seasonal pattern was higher in those carrying the rs2268494 A allele compared to those carrying the rs2268494 TT genotype (p < .001).

CONCLUSION

OXTR gene polymorphisms may be associated with several clinical determinants of BPD. Multicentre studies involving more subjects are required to verify these findings.

Association of the DRD and OXT Genetic Polymorphisms With Schizophrenia in a Chinese Population

ABSTRACT

The polymorphism of dopamine receptor (DRD) and oxytocin (OXT) may be associated with schizophrenia. A case-control study of 248 schizophrenia patients and 236 controls was conducted using the Sequenom MassARRAY platform. The results showed that DRD2 rs1800497 was a heterozygote (AG vs. GG: adjusted odds ratio [OR] = 1.88; 95% confidence interval [CI]: 1.09-3.25) and DRD3 rs7631540 (TC vs. CC: adjusted OR = 0.60; 95% CI: 0.36-1.02) may be associated with an increased risk of developing schizophrenia. In addition, the DRD2 rs1800497 genotype GA showed a reduced risk of schizophrenia in the male subgroup and the late-onset subgroup (>27 years of age). For DRD3 polymorphisms, the rs7631540 TC genotype was associated with schizophrenia in the female subgroup. In OXT polymorphism analysis, rs2740210 codominant CA/AA was a risk factor for schizophrenia in the male and early-onset subgroup (≤27 years old). This study also concluded that OXT rs2740210 codominant CA/AA is associated with schizophrenia.

Toward effective oxytocin interventions in autism: Overcoming challenges and harnessing opportunities

Intranasal administration of oxytocin is emerging as a potential pharmacological option for mitigating social difficulties and regulating stress in autism spectrum disorder. However, initial single-dose and multiple-dose trials showed mixed results, with some demonstrating improvements in social and repetitive behavior and others showing no benefit over placebo. This perspective aims to elucidate factors contributing to this variability and to highlight pitfalls and opportunities in the field. We identified two major factors: design-related elements and individual participant characteristics. Pertaining to design-related elements, optimal dosing regimens have yet to be established, but appear to favor moderate intervention durations (i.e., 4-6 weeks) with intermittent and intermediate dosing (i.e., 24-32 IU every other day). Also, the context of the intervention seems crucial, as enhanced outcomes are mainly observed when oxytocin administration is paired with a socially stimulating and supporting environment. In addition, more adequate outcome measures have to be established to effectively assess oxytocin's impact, including behavioral scales and objective biophysiological markers tapping into stress and neurophysiological regulation. Future research should also account for individual participant differences in biological sex, developmental stage and cognitive and adaptive functioning, and incorporate (epi)genetic screening to identify responders. Overall, refining study designs and personalizing intervention protocols are essential for optimizing oxytocin's prosocial and anxiolytic effect in autism.

Reduction of Prostate Cancer Risk: Role of Frequent Ejaculation-Associated Mechanisms

Prostate cancer (PCa) accounts for roughly 15% of diagnosed cancers among men, with disease incidence increasing worldwide. Age, family history and ethnicity, diet, physical activity, and chemoprevention all play a role in reducing PCa risk. The prostate is an exocrine gland that is characterized by its multi-functionality, being involved in reproductive aspects such as male ejaculation and orgasmic ecstasy, as well as playing key roles in the regulation of local and systemic concentrations of 5α-dihydrotestosterone. The increase in androgen receptors at the ventral prostate is the first elevated response induced by copulation. The regulation of prostate growth and function is mediated by an androgen-dependent mechanism. Binding 5-DHT to androgen receptors (AR) results in the formation of a 5α-DHT:AR complex. The interaction of the 5α-DHT:AR complex with the specific DNA enhancer element of androgen-regulated genes leads to the regulation of androgen-specific target genes to maintain prostate homeostasis. Consequently, ejaculation may play a significant role in the reduction of PCa risk. Thus, frequent ejaculation in the absence of risky sexual behavior is a possible approach for the prevention of PCa. In this review, we provide an insight into possible mechanisms regulating the impact of frequent ejaculation on reducing PCa risk.

Endocrine Controls of Skin Aging

Skin is the largest organ of the human body and undergoes both intrinsic (chronological) and extrinsic aging. While intrinsic skin aging is driven by genetic and epigenetic factors, extrinsic aging is mediated by external threats such as UV irradiation or fine particular matters, the sum of which is referred to as exposome. The clinical manifestations and biochemical changes are different between intrinsic and extrinsic skin aging, albeit overlapping features exist, eg, increased generation of reactive oxygen species, extracellular matrix degradation, telomere shortening, increased lipid peroxidation, or DNA damage. As skin is a prominent target for many hormones, the molecular and biochemical processes underlying intrinsic and extrinsic skin aging are under tight control of classical neuroendocrine axes. However, skin is also an endocrine organ itself, including the hair follicle, a fully functional neuroendocrine "miniorgan." Here we review pivotal hormones controlling human skin aging focusing on IGF-1, a key fibroblast-derived orchestrator of skin aging, of GH, estrogens, retinoids, and melatonin. The emerging roles of additional endocrine players, ie, α-melanocyte-stimulating hormone, a central player of the hypothalamic-pituitary-adrenal axis; members of the hypothalamic-pituitary-thyroid axis; oxytocin, endocannabinoids, and peroxisome proliferator-activated receptor modulators, are also reviewed. Until now, only a limited number of these hormones, mainly topical retinoids and estrogens, have found their way into clinical practice as anti-skin aging compounds. Further research into the biological properties of endocrine players or its derivatives may offer the development of novel senotherapeutics for the treatment and prevention of skin aging.

Associations between different types of delivery, empathy, aggression, impulsivity and school bullying in children attending public and private schools in Pereira (Colombia)

This study aimed to correlate exposure to oxytocin during childbirth with behavioral determinants in teenage students. The Barratt Questionnaire (BQ), the Buss and Perry Aggression Questionnaire (BPAQ) and the Bryant Empathy Index (BEI), respectively measured impulsivity, aggression and empathy; the results were correlated with the roles of school bullying through the Velásquez and Pineda scale. Mothers were asked about birth circumstances. A total of 401 students were included (mean age 12 ± 1 years, 53,9 % were male, 53,3 % were attending a public school). 41,9 % of students had exogenous oxytocin exposure, 40,1 % had physiological oxytocin exposure, and 18 % had no oxytocin exposure. Regarding bullying, 75,1 % of students were classified as observers, 14,2 % were classified as victims, 6 % were classified as intimidators and 4,7 % exhibited an indifferent role. The mean value of the BPAQ was 78 ± 19, for the BEI was 78 ± 10 and for the BQ was 60 ± 10; all values were considered high. There were no significant differences among the type of delivery, sex and bullying roles or the type of delivery, aggressiveness and impulsivity according to sex; however, males had significantly lower empathy scores. There was no significant association between the type of delivery and the risk of assuming a bullying role. A regression model showed a significant association between attending a private school and a lower risk of developing a victim or intimidator role. This study could contribute to a better understanding of the processes involved in behavioral and emotional outcomes after birth, which can help to design prevention strategies to address increasing mental health problems in youth. Furthermore, this study could help emphasize the importance of promoting physiological delivery and find evidence that helps the scientific community design new work to deepen the relationship between oxytocin and behavior.

Prenatal maternal life adversity impacts on learning and memory in offspring: implication to transgenerational epigenetic inheritance

Maternal stress exposure during pregnancy is known to affect offspring behavior, including learning and memory. We hypothesized that maternal stress-induced changes transmit this effect through maternal line mediated transgenerational epigenetic inheritance. To test our hypothesis, pregnant rats (F0) were undisturbed (Control, Ctrl)/exposed to social stress during gestational days (GD) 16-18 (PMS)/exposed to social stress and treated with oxytocin during GD-16 to 18 (PMS+OXT). Subsequently, F1 female offspring from Ctrl, PMS, and PMS+OXT were mated with Ctrl F1 males to examine maternal line mediated transgenerational impacts. Female animals (F1 and F2) were subjected to behavioral test and the levels of global H3K4me2/H3K4me3 methylation, methylation in the CRH promoter, expression of Crh, Crh receptors (Crhr1, Crhr2), and BDNF were determined. It was found that prenatal maternal stress (PMS) reduced reference and working memory in F1 and F2 offspring, increased global and specific H3K4me2, H3K4me3 methylation in the CRH promoter, expression of Crh, Crh receptors, and corticosterone (CORT), and down-regulated the expression of pro-and mature BDNF by differentially regulating Bdnf transcripts III, IV and VI in the amygdala. Oxytocin exposure reduced PMS-induced global and specific H3K4me2/3 changes, which repressed the expression of Crh, Crh receptors, reduced CORT levels, up-regulated the expression of pro-BDNF and mature BDNF, and improved memory in F1 and F2 offspring. Collectively, our study revealed that PMS reduced reference and working memory performance in F1 and F2 offspring through maternal line transgenerational inheritance of H3K4me2, H3K4me3 methylation, and associated mechanisms that regulate BDNF expression and synaptic plasticity.

The OXT rs6133010 variant modulates susceptibility to psychiatric symptoms during withdrawal in patients with alcohol dependence

BACKGROUND

Alcohol dependence (AD) confers susceptibility to distressing withdrawal symptoms that often lead to relapse. While neuroadaptation during withdrawal influences symptoms, the genetic factors behind it have not been thoroughly investigated. We utilized propensity score matching and investigated connections between AD, OXT rs6133010, and withdrawal symptoms to address confounding variables. By elucidating the OXT rs6133010-AD interaction, we aim to gain insights into alcohol withdrawal variability and contribute to personalized treatment approaches.

METHODS

A cross-sectional study design was employed involving a total of 389 AD patients and 184 healthy controls who were genotyped for the OXT rs6133010 polymorphism. Psychiatric symptoms were evaluated using standardized scales during early withdrawal. Propensity score matching mitigated age and education differences.

RESULTS

A two-way ANOVA demonstrated a significant AD x OXT rs6133010 interaction effect on hostility and anxiety. Further analysis revealed that the regulatory impact of OXT rs6133010 was exclusively in AD patients. Specifically, AD patients with the AA homozygote showed robust protection against hostility and anxiety. Path analysis unveiled the underlying mechanism of OXT symptom regulation.

CONCLUSION

This study presents novel evidence that OXT rs6133010 specifically modulates psychiatric symptoms in AD. The G allele may heighten hostility and anxiety vulnerability during alcohol withdrawal. These findings emphasize considering environmental factors when studying and utilizing oxytocin therapeutically. Additionally, OXT may not directly act as an anxiolytic but instead regulates anxiety by modulating hostility.

How does neurochemistry affect attachment styles in humans? The role of oxytocin and the endogenous opioid system in sociotropy and autonomy - A systematic review

Oxytocin was hypothesised to play a critical role in forming and maintaining secure attachments, shown to confer resilience against affective disorders. The endogenous opioid system has also emerged as a key player in attachment dynamics. In this pre-registered systematic review, we investigated whether individual differences in the functioning of these neurochemical systems are related to attachment styles, following PRISMA guidelines. As predicted, individuals with higher oxytocin function exhibited more secure attachment styles (p = .006, n = 12 studies) and less insecure attachment styles (p = .021, n = 16 studies). Contrary to our hypothesis, we found no association of endogenous opioid function with insecure (p = 0.549, n = 11 studies) or secure attachment styles (p = .065, n = 11 studies). The lack of association between endogenous mu-opioid function and attachment styles remains inconclusive due to inconsistencies in the neurochemical measurements and lack of eligible studies. Therefore, further investigations into the role of the endogenous opioid system in attachment styles are needed. Our findings corroborate the hypothesis that individual differences in oxytocin function relate to differences in attachment styles.

Re-embarking in ART while still breastfeeding: an unresolved question

Infertile women may request to embark on a new course of Assisted Reproductive Technologies (ART) in pursuit of a second child while still breastfeeding their first child. Breastfeeding is a time of profound hormonal changes that may interfere with ovarian physiology and uterine receptivity. Prolactin and oxytocin can mediate a plethora of potential detrimental effects. However, robust evidence to advise in favor or against ART during breastfeeding is lacking. In this narrative review, we reviewed the literature with the intent to shed light on this neglected issue. Possible adverse effects on ART success emerged for ovulatory mechanisms, folliculogenesis, uterine contractions, uterine peristalsis, and early embryo development. A negative impact of exogeneous hormones on infant health might be considered only for stimulation cycles. Overall, most concerns can be claimed for the clinical setting of ovarian stimulation, followed by the one of embryo transfer in a natural cycle and, finally, by the embryo transfer in a hormone replacement treatment preparation. However, in general, it seems wise to wait for breastfeeding to be discontinue before re-embarking on IVF, also considering that a too short interpregnancy interval may be deleterious to pregnancy outcomes. On the other hand, one must also recognize that available evidence is insufficient to deny access to treatments for women requesting earlier access. These women must be informed regarding the non-fully reassuring evidence.

Metabolically stable apelin analogs: development and functional role in water balance and cardiovascular function

Apelin, a (neuro) vasoactive peptide, plays a prominent role in controlling water balance and cardiovascular functions. Apelin and its receptor co-localize with vasopressin in magnocellular vasopressinergic neurons. Apelin receptors (Apelin-Rs) are also expressed in the collecting ducts of the kidney, where vasopressin type 2 receptors are also present. Apelin and vasopressin interact at the brain and renal levels to maintain body fluid homeostasis by regulating diuresis in opposite directions. Apelin and angiotensin II have opposite effects on the regulation of blood pressure (BP). Angiotensin II, by binding to AT1 receptors present in VSMCs, induces intracellular calcium mobilization and vasoconstriction, while apelin, by binding to Apelin-R present on vascular endothelium, increases nitric oxide production and induces vasodilation. Apelin also plays a crucial role in the regulation of cardiac function. Apelin-deficient and Apelin-R-deficient mice develop progressive myocardial dysfunction with ageing and are susceptible to heart failure in response to pressure overload. Since the half-life of apelin is very short in vivo (in the minute range), several metabolically stable apelin analogs and non-peptidic Apelin-R agonists have been developed, with potential applications in diverse diseases. In this review, we highlight the interaction between apelin and vasopressin in the regulation of water balance and that between apelin and angiotensin II in the regulation of BP. Additionally, we underline the protective effects of apelin in cardiac function. Lastly, we discuss the beneficial effects of Apelin-R activation in different pathological states such as hyponatremia, hypertension, and heart failure.

Effects of systemic oxytocin and beta-3 receptor agonist (CL 316243) treatment on body weight and adiposity in male diet-induced obese rats

Previous studies have implicated hindbrain oxytocin (OT) receptors in the control of food intake and brown adipose tissue (BAT) thermogenesis. We recently demonstrated that hindbrain [fourth ventricle (4V)] administration of oxytocin (OT) could be used as an adjunct to drugs that directly target beta-3 adrenergic receptors (β3-AR) to elicit weight loss in diet-induced obese (DIO) rodents. What remains unclear is whether systemic OT can be used as an adjunct with the β3-AR agonist, CL 316243, to increase BAT thermogenesis and elicit weight loss in DIO rats. We hypothesized that systemic OT and β3-AR agonist (CL 316243) treatment would produce an additive effect to reduce body weight and adiposity in DIO rats by decreasing food intake and stimulating BAT thermogenesis. To test this hypothesis, we determined the effects of systemic (subcutaneous) infusions of OT (50 nmol/day) or vehicle (VEH) when combined with daily systemic (intraperitoneal) injections of CL 316243 (0.5 mg/kg) or VEH on body weight, adiposity, food intake and brown adipose tissue temperature (TIBAT). OT and CL 316243 monotherapy decreased body weight by 8.0±0.9% (P<0.05) and 8.6±0.6% (P<0.05), respectively, but OT in combination with CL 316243 produced more substantial weight loss (14.9±1.0%; P<0.05) compared to either treatment alone. These effects were associated with decreased adiposity, energy intake and elevated TIBAT during the treatment period. The findings from the current study suggest that the effects of systemic OT and CL 316243 to elicit weight loss are additive and appear to be driven primarily by OT-elicited changes in food intake and CL 316243-elicited increases in BAT thermogenesis.

Oxytocin levels in response to CRH administration in hypopituitarism and hypothalamic damage: a randomized, crossover, placebo-controlled trial

Increasing evidence supports the presence of oxytocin deficiency (OXT-D) in patients with hypopituitarism and hypothalamic damage (HHD), that might be associated with neuropsychological deficits and sexual dysfunction, leading to worse quality of life (QoL). Therefore, identifying a provocative test to diagnose an OXT-D will be important. Corticotropin-releasing hormone (CRH) is a candidate for such a test as it increases oxytocin secretion in animal models. This study aimed to examine the effects of CRH on oxytocin release in HHD compared to healthy controls (HC) and to describe the psychopathology, sexual function and QoL and their associations with oxytocin. This is a single-blind, randomized, placebo-controlled, proof-of-concept study (NCT04902235) with crossover assignment (CRH vs. placebo). Nineteen HHD patients (10 females) and 20 HC (11 females) completed two visits, receiving CRH or placebo in random order and completed validated questionnaires to assess psychopathology, sexual function and QoL. Samples were collected over 120 min to assess oxytocin. Linear mixed-effects regression model evaluated the change in oxytocin after CRH/placebo in HHD vs. HC. CRH administration did not impact oxytocin concentrations across groups over time (p = 0.97). HHD had greater psychopathology (most ps < 0.05), sexual dysfunction (p < 0.03) and worse QoL (p < 0.001) compared to HC, nevertheless, baseline oxytocin concentrations and area under the curve of oxytocin were not significantly associated with psychopathology, sexual function or QoL, neither in HHD or HC. In conclusion, CRH administration does not appear to be a suitable provocative test for diagnosing OXT-D in HHD. Identifying a reliable diagnostic test for OXT-D remains crucial. Alternative provocative tests or biomarkers should be explored.

The pharmacodynamic modulation effect of oxytocin on resting state functional connectivity network topology

Introduction

Neuroimaging studies have demonstrated that intranasal oxytocin has extensive effects on the resting state functional connectivity of social and emotional processing networks and may have therapeutic potential. However, the extent to which intranasal oxytocin modulates functional connectivity network topology remains less explored, with inconsistent findings in the existing literature. To address this gap, we conducted an exploratory data-driven study.

Methods

We recruited 142 healthy males and administered 24 IU of intranasal oxytocin or placebo in a randomized controlled double-blind design. Resting-state functional MRI data were acquired for each subject. Network-based statistical analysis and graph theoretical approaches were employed to evaluate oxytocin's effects on whole-brain functional connectivity and graph topological measures.

Results

Our results revealed that oxytocin altered connectivity patterns within brain networks involved in sensory and motor processing, attention, memory, emotion and reward functions as well as social cognition, including the default mode, limbic, frontoparietal, cerebellar, and visual networks. Furthermore, oxytocin increased local efficiency, clustering coefficients, and small-world propensity in specific brain regions including the cerebellum, left thalamus, posterior cingulate cortex, right orbitofrontal cortex, right superior frontal gyrus, left inferior frontal gyrus, and right middle orbitofrontal cortex, while decreasing nodal path topological measures in the left and right caudate.

Discussion

These findings suggest that intranasal oxytocin may produce its functional effects through influencing the integration and segregation of information flow within small-world brain networks, particularly in regions closely associated with social cognition and motivation.

Social Bonds Retain Oxytocin-Mediated Brain-Liver Axis to Retard Atherosclerosis

BACKGROUNDS

Social interaction with others is essential to life. Although social isolation and loneliness have been implicated as increased risks of cardiometabolic and cardiovascular diseases and all-cause mortality, the cellular and molecular mechanisms by which social connection maintains cardiometabolic and cardiovascular health remain largely unresolved.

METHODS

To investigate how social connection protects against cardiometabolic and cardiovascular diseases, atherosclerosis-prone, high-fat diet-fed Apoe-/- mouse siblings were randomly assigned to either individual or grouped housing for 12 weeks. Histological, flow cytometric, biochemical, gene, and protein analyses were performed to assess atherosclerotic lesions, systemic metabolism, inflammation, and stress response. The effects of oxytocin on hepatocytes and subsequent cardiometabolic and cardiovascular function were investigated by in vivo and in vitro approaches.

RESULTS

Apoe-/- mice housed individually developed larger vulnerable atherosclerotic lesions by disrupted lipid metabolism compared with those of mice in regular group housing, irrespective of body weight, eating behavior, feeding conditions, sympathetic nervous activity, glucocorticoid response, or systemic inflammation. Mechanistically, the chronic isolation reduced the hypothalamic production of oxytocin, which controls bile acid production and LPL (lipoprotein lipase) activity through the peripheral OXTR (oxytocin receptor) in hepatocytes, whose downstream targets include Cyp7a1, Angptl4, and Angptl8. While hepatocyte-specific OXTR-null mice and mice receiving adeno-associated virus targeting OXTR on hepatocytes led to severe dyslipidemia and aggravated atherosclerosis, oral oxytocin supplementation to socially isolated mice, but not to hepatocyte-specific OXTR conditional knockout mice, improved lipid profiles and retarded atherosclerosis development.

CONCLUSIONS

These results identify a novel brain-liver axis that links sociality to hepatic lipid metabolism, thus proposing a potential therapeutic strategy for loneliness-associated atherosclerosis progression.

Lipids shape brain function through ion channel and receptor modulations: physiological mechanisms and clinical perspectives

Lipids represent the most abundant molecular type in the brain, with a fat content of ∼60% of the dry brain weight in humans. Despite this fact, little attention has been paid to circumscribe the dynamic role of lipids in brain function and disease. Membrane lipids such as cholesterol, phosphoinositide, sphingolipids, arachidonic acid, and endocannabinoids finely regulate both synaptic receptors and ion channels that ensure critical neural functions. After a brief introduction on brain lipids and their respective properties, we review here their role in regulating synaptic function and ion channel activity, action potential propagation, neuronal development, and functional plasticity and their contribution in the development of neurological and neuropsychiatric diseases. We also provide possible directions for future research on lipid function in brain plasticity and diseases.

Circadian copeptin and oxytocin profiles in anorexia nervosa: Exploring the interplay with neurohypophysis opioid tone

CONTEXT

Neurohypophysis (NH) function in eating disorders (ED) remains poorly elucidated. Studies on vasopressin and oxytocin display inconclusive findings regarding their levels and associations with psychological complications in ED. The profile of opioid tone, a crucial NH activity regulator, is also unknown.

OBJECTIVE

To characterise the circadian profile of NH hormones and NH opioid tone using positron emission tomography/MRI (PET/MRI) imaging in patients with ED compared to healthy controls.

METHODS

Twelve-point plasma circadian profiles of copeptin and oxytocin, alongside nutritional and psychological scores, were assessed in age-matched female participants: 13 patients with anorexia nervosa restrictive-type (ANR), 12 patients recovered from AN (ANrec), 14 patients with bulimia nervosa and 12 controls. Neurohypophysis PET/MRI [11C] diprenorphin binding potential (BPND) was evaluated in AN, ANrec and controls.

RESULTS

Results revealed lower copeptin circadian levels in both ANR and ANrec compared to controls, with no oxytocin differences. Bulimia nervosa exhibited elevated copeptin and low oxytocin levels. [11C] diprenorphin pituitary binding was fully localised in NH. Anorexia nervosa restrictive-type displayed lower NH [11C] diprenorphin BPND (indicating higher opioid tone) and volume than controls. In ANR, copeptin inversely correlated with osmolarity. Neurohypophysis [11C] diprenorphin BPND did not correlated with copeptin or oxytocin.

CONCLUSION

Copeptin demonstrated significant group differences, highlighting its potential diagnostic and prognostic value. Oxytocin levels exhibited conflicting results, questioning the reliability of peripheral blood assessment. Increased NH opioid tone in anorexia nervosa may influence the vasopressin or oxytocin release, suggesting potential therapeutic applications.

Oxytocin Analogues for the Oral Treatment of Abdominal Pain

Abdominal pain presents an onerous reality for millions of people affected by gastrointestinal disorders such as irritable bowel syndrome (IBS) and inflammatory bowel diseases (IBD). The oxytocin receptor (OTR) has emerged as a new analgesic drug target with OTR expression upregulated on colon-innervating nociceptors in chronic visceral hypersensitivity states, accessible via luminal delivery. However, the low gastrointestinal stability of OTR's endogenous peptide ligand oxytocin (OT) is a bottleneck for therapeutic development. Here, we report the development of potent and fully gut-stable OT analogues, laying the foundation for a new area of oral gut-specific peptide therapeutics. Ligand optimisation guided by structure-gut-stability-activity relationships yielded highly stable analogues (t1/2>24 h, compared to t1/2<10 min of OT in intestinal fluid) equipotent to OT (~3 nM) and with enhanced OTR selectivity. Intra-colonic administration of the lead ligand significantly reduced colonic mechanical hypersensitivity in a concentration-dependent manner in a mouse model of chronic abdominal pain. Moreover, oral administration of the lead ligand also displayed significant analgesia in this abdominal pain mouse model. The generated ligands and employed strategies could pave the way to a new class of oral gut-specific peptides to study and combat chronic gastrointestinal disorders, an area with substantial unmet medical needs.

A comprehensive review on the effects of sex hormones on chemotherapy-induced cardiotoxicity: are they lucrative or unprofitable?

Chemotherapy is one of the routine treatment for preventing rapid growth of the tumor cells. However, chemotherapeutic agents, especially doxorubicin cause damages to the normal cells especially cardiomyocytes. Cardiotoxicity induced by chemotherapeutic drugs lead to the myocardial cell injury and finally causes left ventricular dysfunction. It seems that there were some differences in the severity of cardiovascular side effects of drugs used in the treatment of cancers. Sex hormones in male and female play crucial roles in cardiovascular development and physiological function of the heart and blood vessels. Gender differences and sex-specific hormones influence various aspects of cardiovascular health, including ventricular function, mitochondrial autophagy, and the development of abdominal aortic aneurysms. The most important gender related hormones are LH, FSH, testosterone, estrogen, progesterone, prolactin and oxytocin. They exert very important cardiovascular effects via different signaling mechanisms. Sex related hormones are also important in the cardiovascular side effects of chemotherapeutic agents, so that chronic cardiotoxicity induced by anthracyclines is more common in women. During different stages of life (before, during, and after sexual life), the levels of these hormones will be changed. This alterations can affect cardiovascular function during physiological conditions and pathological process. Because of the importance of the sex related hormones in the cardiac function, in this review we tried to comprehensively elucidate the role of these physiological hormones in cardiotoxicity induced by chemotherapeutic agents with emphasizing their signaling mechanisms.

Sympathetic innervation of interscapular brown adipose tissue is not a predominant mediator of Oxytocin (OT)-elicited reductions of body weight gain and adiposity in male diet-induced obese rats

Recent studies indicate that central administration of oxytocin (OT) reduces body weight (BW) in high fat diet-induced obese (DIO) rodents by reducing energy intake and increasing energy expenditure (EE). Previous studies in our lab have shown that administration of OT into the fourth ventricle (4V; hindbrain) elicits weight loss and stimulates interscapular brown adipose tissue temperature (TIBAT) in DIO rats. We hypothesized that OT-elicited stimulation of sympathetic nervous system (SNS) activation of IBAT contributes to its ability to activate BAT and reduce BW in DIO rats. To test this, we determined the effect of disrupting SNS activation of IBAT on OT-elicited stimulation of TIBAT and reduction of BW in DIO rats. We first confirmed that bilateral surgical SNS denervation to IBAT was successful based on having achieved ≥ 60% reduction in IBAT norepinephrine (NE) content from DIO rats. NE content was selectively reduced in IBAT by 94.7 ± 2.7, 96.8 ± 1.8 and 85.9 ± 6.1% (P<0.05) at 1, 6 and 7-weeks post-denervation, respectively, and was unchanged in liver or inguinal white adipose tissue. We then measured the impact of bilateral surgical SNS denervation to IBAT on the ability of acute 4V OT (1, 5 μg) to stimulate TIBAT in DIO rats. We found that the high dose of 4V OT (5 μg) stimulated TIBAT similarly between sham and denervated rats (P=NS) and that the effects of 4V OT to stimulate TIBAT did not require beta-3 adrenergic receptor signaling. We subsequently measured the effect of bilateral surgical denervation of IBAT on the effect of chronic 4V OT (16 nmol/day) or vehicle infusion to reduce BW, adiposity, and energy intake in DIO rats. Chronic 4V OT reduced BW gain by -7.2 ± 9.6 g and -14.1 ± 8.8 g in sham and denervated rats (P<0.05 vs vehicle treatment), respectively, and this effect was similar between groups (P=NS). These effects were associated with reductions in adiposity and energy intake (P<0.05). Collectively, these findings support the hypothesis that sympathetic innervation of IBAT is not required for central OT to increase BAT thermogenesis and reduce BW gain and adiposity in male DIO rats.

Evaluation of the effect of delivery type on dynamic thiol-disulfide balance: a prospective randomized controlled study

OBJECTIVE

Thiols play an essential role in eliminating oxidative stress in cells. We aimed to evaluate the oxidative stress occurring during labor with thiol-disulfide balance.

METHODS

A total of 97 healthy pregnant women in the 37th-41st gestational weeks who underwent delivery between June 2021 and August 2022 were included in the study. Elective cesarean section group 1 (n=33), vaginal deliveries group 2 (n=29), and cesarean section due to cephalopelvic disproportion group 3 (n=35) were determined. Blood samples were taken before delivery, and from the umbilical artery just after the fetus and placenta were delivered. Serum native thiol (μmol/L), total thiol (μmol/L), and disulfide (μmol/L) were measured. Disulfide/native thiol (%), disulfide/total thiol (%), and native thiol/total thiol (%) ratios were calculated.

RESULTS

No significant difference was observed in thiol values in maternal blood (p>0.05). There was a significant difference between the groups in terms of native/total thiol (p=0.017), disulfide/total thiol (%) (p=0.018), and disulfide/native thiol (%) (p=0.018) in cord blood.

CONCLUSION

In the literature, evidence concerning the impact of the mode of delivery on the level of neonatal and maternal oxidative stress is inconsistent. It is not clear whether parturition accompanied by pain, as in spontaneous vaginal delivery, poses more oxidative stress than a planned operative delivery. Prospective studies in larger cohorts are needed to better understand the impact of oxidative stress on pregnant women and neonates.

Modulatory effects of oxytocin on normal human cultured melanocyte proliferation, migration, and melanogenesis

Melanocytes are specialized melanin-producing neural crest-derived cells. Melanocyte proliferation and melanin production (i.e., melanogenesis) are crucial for determining skin color. Disruption of these processes can cause pigmentary skin disorders, including hypo-pigmentary disorders such as vitiligo and hyper-pigmentary disorders such as melasma. Understanding these processes is important for discovering new targets to tackle these skin disorders. Therefore, this study aimed to investigate the effects of oxytocin (OXT) on melanocyte functions. Normal Human Cultured Melanocytes (NHCM) were treated with different OXT doses to investigate OXT effects and mechanisms on NHCM proliferation, migration, and on melanogenesis. OXT significantly increased NHCM proliferation and migration in a dose-dependent manner after 72 h of treatment. In addition, OXT dose-dependently upregulated melanogenesis-related microphtalmia-associated transcription factor, tyrosinase, tyrosinase-related protein (TYRP)-1, and TYRP-2 expression accompanied by an increased trend in melanosome number and maturation stage. Furthermore, OXT at concentrations (62.5-125 nM) increased melanin production. These findings suggest the involvement of OXT receptor (OXTR). In addition, this study demonstrates that OXT stimulates melanocyte proliferation, migration, with a tendency toward melanosome maturation, while it modulates melanin production in a dose-dependent manner. Thus, OXT system including its receptor OXTR may be a potential therapeutic target for skin pigmentary disorders.

Contractile responses of engineered human μmyometrium to prostaglandins and inflammatory cytokines

Preterm labor is a prevalent public health problem and occurs when the myometrium, the smooth muscle layer of the uterus, begins contracting before the fetus reaches full term. Abnormal contractions of the myometrium also underlie painful menstrual cramps, known as dysmenorrhea. Both disorders have been associated with increased production of prostaglandins and cytokines, yet the functional impacts of inflammatory mediators on the contractility of human myometrium have not been fully established, in part due to a lack of effective model systems. To address this, we engineered human myometrial microtissues (μmyometrium) on compliant hydrogels designed for traction force microscopy. We then measured μmyometrium contractility in response to a panel of compounds with known contractile effects and inflammatory mediators. We observed that prostaglandin F2α, interleukin 6, and interleukin 8 induced contraction, while prostaglandin E1 and prostaglandin E2 induced relaxation. Our data suggest that inflammation may be a key factor modulating uterine contractility in conditions including, but not limited to, preterm labor or dysmenorrhea. More broadly, our μmyometrium model can be used to systematically identify the functional impact of many small molecules on human myometrium.

Oxytocin attenuates cardiac hypertrophy by improving cardiac glucose metabolism and regulating OXTR/JAK2/STAT3 axis

BACKGROUND

The progress of cardiac hypertrophy is modulated by JAK2/STAT3 signaling pathway. Cardiac glucose metabolism derangement exacerbates the progression of cardiac hypertrophy. Oxytocin (OT) has emerged as a significant hormone involved in cardiovascular homeostasis, especially in protecting against cardiac hypertrophy. The present study aims to explore whether the anti-hypertrophy effect of oxytocin is related to the JAK2/STAT3 signaling pathway and cardiac glucose metablism.

METHODS

Cardiac hypertrophy model was induced by angiotensin II (Ang II) in H9c2 cells and in mice with or without oxytocin treatment. Changes in cardiac histopathology were evaluated by hematoxylin and eosin (H&E), Masson staining, and wheat germ agglutinin (WGA) staining. The hypertrophy-related genes and JAK2/STAT3 pathway signaling molecules were analyzed by qRT-PCR and western blotting. The levels of glucose, pyruvic acid, lactic acid, and lactate dehydrogenase activity in H9c2 cells using the corresponding assay kits.

RESULTS

The results showed that OT inhibited hypertrophic and fibrotic changes. Furthermore, OT increased intracellular levels of glucose and pyruvic acid, and decreased lactate dehydrogenase activity and lactic acid levels. Mechanistically, Ang II decreased oxytocin receptors (OXTR) expression and facilitated JAK2 and STAT3 phosphorylation. OT treatment increased OXTR expression and blocked JAK2 and STAT3 phosphorylation The OXTR-specific siRNA-mediated depleted expression could abrogate OT-induced anti-hypertrophic effects in H9c2 cells following angiotensin II insult. However, the JAK2/STAT3 inhibitor AG490 rescued the protective effects of OT against cardiac hypertrophy under OXTR downregulation.

CONCLUSION

OT exerts its protective effects against cardiac hypertrophy by improving cardiac glucose metabolism and regulating OXTR/JAK2/STAT3 axis.

Structure and function of neurohypophysial hormones

Vasopressin (VP) and oxytocin (OXT) are neuropeptides that are synthesized in the hypothalamus and stored in/secreted from the neurohypophysis. Although VP and OXT were initially characterized as osmoregulatory and reproductive hormones, respectively, these peptides exert versatile actions not only in peripheral organs but also in the central nervous system via multiple G protein-coupled receptors. Orthologous peptides and receptors have been identified in various animal phyla, reflecting an ancient origin of this hormone family. The aim of this review is to provide basic information on this hormone family and to propose matters to be addressed in future studies. In the earlier sections of this review, we summarize the historical aspect of VP/OXT research as well as the basic features of hormonal peptides and corresponding receptors. The latter sections describe VP/OXT family peptides and their receptors in nonmammalian species, including invertebrates, to introduce the evolutionary aspect of this hormone family. By integrating knowledge from both general and comparative endocrinology perspectives, we highlight current and future research trends about the VP/OXT system.

R150S mutation in the human oxytocin receptor: Gain-of-function effects and implication in autism spectrum disorder

This study investigates the rs547238576 (R150S) missense variant in the oxytocin receptor (OXTR) gene, previously observed through screening of rare variants in Japanese individuals with autism spectrum disorders (ASD). Contrary to the anticipated loss-of-function, R150S exhibits gain-of-function effects, enhancing oxytocin (OXT) sensitivity, ligand-binding affinity, and OXT-induced Ca2+ mobilization in vitro. This suggests R150S may alter OXT signaling, potentially contributing to the excitatory/inhibitory imbalance seen in ASD and other psychiatric disorders. Our findings underscore the significance of genetic variations in OXTR on functional activity and highlight the necessity for population-specific genetic study and in vitro analysis to elucidate genetic susceptibilities to neuropsychiatric conditions.

Oxytocin in neurodevelopmental disorders: Autism spectrum disorder and Prader-Willi syndrome

This manuscript reviews recent work on oxytocin and its use in neurodevelopmental disorders including spectrum disorder (ASD) and Prader-Willi syndrome (PWS). Oxytocin is involved in social recognition, bonding, maternal behaviors, anxiety, food motivation, and hyperphagia. While the pathophysiology of ASD and PWS involve abnormalities in the oxytocin system, clinical trials have shown discrepant results in the effectiveness of oxytocin as a treatment for core symptoms associated with these disorders. In this review, we outline oxytocin's clinical pharmacology, safety considerations, and results in recent clinical trials. We propose that oxytocin may be most beneficial in these populations if dosed in a dynamic regimen (PRN) and paired with social interventions.

The alteration in myometrial mRNA transcription of the regulatory genes of DNA methylation in mare with endometrosis

A reduction in myometrial contractile activity can lead to inadequate cleaning of the uterine lumen, resulting in persistent endometritis and potentially endometrosis in mares. Oxytocin (OXT) is a key hormonal regulator of myometrial contraction. While epigenetic regulation of myometrial gene expression has been studied in humans, there is limited information on the expression of DNA methyltransferases (DNMTs) and ten-eleven translocation enzymes (TETs) in the myometrium of mares. This study aimed to evaluate the mRNA transcription of these enzymes and the potential role of DNA methylation in the expression of the OXT receptor (OXTR) gene in the myometrium of mares with endometrosis. Myometrial samples were collected post-mortem during the mid-luteal (n = 23) and follicular (n = 20) phases of the estrous cycle and assessed according to Kenney and Doig endometrial category (I, IIA, IIB, III). mRNA transcription of OXTR, DNMT1, -3A, -3B and TET1, -2, -3 were determined using qPCR. DNA methylation analysis at CpG islands of OXTR exons 1 and 2 was performed using bisulfite pyrosequencing. Myometrial OXTR mRNA transcription and DNA methylation in its promoter region showed no significant differences between categories, although increased methylation was observed at CpG island position 6 in exon 2. DNMT1, TET2, and TET3 mRNA transcription was altered in the equine myometrium depending on the phase of the estrous cycle and the severity of endometrosis (P < 0.05). These findings indicate that DNMTs and TETs were expressed in myometrium in a manner specific to the severity of endometrosis and phases of the estrous cycle, suggesting a potential regulatory role in DNA methylation of myometrial gene expression.

Neuroendocrinology of bone

The past decade has witnessed significant advances in our understanding of skeletal homeostasis and the mechanisms that mediate the loss of bone in primary and secondary osteoporosis. Recent breakthroughs have primarily emerged from identifying disease-causing mutations and phenocopying human bone disease in rodents. Notably, using genetically-modified rodent models, disrupting the reciprocal relationship with tropic pituitary hormone and effector hormones, we have learned that pituitary hormones have independent roles in skeletal physiology, beyond their effects exerted through target endocrine glands. The rise of follicle-stimulating hormone (FSH) in the late perimenopause may account, at least in part, for the rapid bone loss when estrogen is normal, while low thyroid-stimulating hormone (TSH) levels may contribute to the bone loss in thyrotoxicosis. Admittedly speculative, suppressed levels of adrenocorticotropic hormone (ACTH) may directly exacerbate bone loss in the setting of glucocorticoid-induced osteoporosis. Furthermore, beyond their established roles in reproduction and lactation, oxytocin and prolactin may affect intergenerational calcium transfer and therefore fetal skeletal mineralization, whereas elevated vasopressin levels in chronic hyponatremic states may increase the risk of bone loss.. Here, we discuss the interaction of each pituitary hormone in relation to its role in bone physiology and pathophysiology.

The impact of the early environment on oxytocin receptor epigenetics and potential therapeutic implications

Oxytocin research is rapidly evolving and increasingly reveals that epigenetic modifications to the oxytocin receptor gene (OXTR) are functional, plastic, and reliable components of oxytocinergic system function. This review outlines how OXTR epigenetics are shaped by the early life environment, impact social-developmental outcomes, and have strong potential to serve as therapeutic targets. We first establish the malleability of OXTR epigenetics in infancy in both animal models and humans through research demonstrating the impact of the early life environment on OXTR DNA methylation (OXTRm) and subsequent social behavior. Next, we detail how OXTRm serves as a predictive mechanism for neurodevelopmental outcomes in animal models of social behavior such as the prairie vole, and summarize the role of OXTRm in psychiatric disorders, emotional processing, and attachment behavior in humans. We discuss the potential of further OXTRm research to improve oxytocin therapeutics by highlighting how a deeper knowledge of OXTRm could improve the therapeutic potential of exogenous oxytocin, how OXTRm may impact additional cellular mechanisms with therapeutic potential including control of the perinatal GABA switch, and how early life therapies may target the tuning of endogenous OXTRm. Finally, we review limitations of previous oxytocin research and make recommendations for future research. IMPACT: Previous research into oxytocin therapeutics has been hampered by methodological difficulties that may be improved by assay of the oxytocin receptor gene (OXTR) and its methylation (OXTRm) Key sites of OXTRm modification link early life exposures to developmental and behavioral outcomes OXTRm appears to have a critical period of development in early life Epigenetic modification of the oxytocin receptor gene could serve as a powerful target for therapeutic interventions.

Oxytocin and the Role of Fluid Restriction in MDMA-Induced Hyponatremia: A Secondary Analysis of 4 Randomized Clinical Trials

Importance

3,4-Methylenedioxymethamphetamine (MDMA, or ecstasy) is a recreational drug being investigated for the treatment of posttraumatic stress disorder. Acute hyponatremia is a potentially serious complication after even a single dose of MDMA. The assumed etiology has been a vasopressin release inducing the syndrome of inappropriate antidiuresis combined with increased thirst, causing polydipsia and water intoxication.

Objective

To investigate the incidence and severity of hyponatremia after a single dose of MDMA, underlying neuroendocrine mechanisms of action, and the potential effect of fluid restriction on lowering the incidence of hyponatremia.

Design, Setting, and Participants

This ad hoc secondary analysis pooled data from 4 placebo-controlled crossover randomized clinical trials conducted at the University Hospital Basel, Basel, Switzerland. The 96 participants received experimental doses of MDMA between March 1, 2017, and August 31, 2022.

Intervention

A single oral 100- or 125-mg dose of MDMA. Fluid intake was not restricted in 81 participants; it was restricted in 15.

Main Outcomes and Measures

Plasma oxytocin, copeptin (marker of vasopressin), and sodium levels were measured repeatedly within 360 minutes after MDMA intake. The association of plasma oxytocin or copeptin levels with plasma sodium level at 180 minutes (peak concentration of MDMA) was determined.

Results

Among the 96 participants, the mean (SD) age was 29 (7) years, and 62 (65%) were men. A total of 39 participants (41%) received a 100-mg dose of MDMA, and 57 (59%) received a 125-mg dose. At baseline, the mean (SD) plasma sodium level was 140 (3) mEq/L and decreased in response to MDMA by 3 (3) mEq/L. Hyponatremia occurred in 30 participants (31%) with a mean (SD) sodium level of 133 (2) mEq/L. In 15 participants with restricted fluid intake, no hyponatremia occurred, while in the 81 participants with unrestricted fluid intake, hyponatremia occurred in 30 (37%) (P = .002) with a difference in plasma sodium of 4 (95% CI, 2-5) mEq/L (P < .001) between both groups, suggesting that fluid restriction may mitigate the risk of hyponatremia. At baseline, the mean (SD) plasma oxytocin level was 87 (45) pg/mL and increased in response to MDMA by 388 (297) pg/mL (ie, a mean [SD] 433% [431%] increase at 180 minutes), while the mean (SD) copeptin level was 4.9 (3.8) pmol/L and slightly decreased, by 0.8 (3.0) pmol/L. Change in plasma sodium level from baseline to 180 minutes demonstrated a negative correlation with the changes in oxytocin (R = -0.4; P < .001) and MDMA (R = -0.4; P < .001) levels while showing no correlation with the change in copeptin level.

Conclusions and Relevance

In this secondary analysis of 4 randomized clinical trials, a high incidence of acute hyponatremia was observed in response to MDMA, which may be mitigated by fluid restriction. Hyponatremia was associated with acute oxytocin but not copeptin release. This challenges the current hypothesis of direct vasopressin release and rather indicates that oxytocin mimics the effect of vasopressin in the kidneys due to structural homology.

Oxytocin pathway gene variation and corticostriatal resting-state functional connectivity

Genetic variations in single nucleotide polymorphisms (SNPs) within oxytocin pathway genes have been linked to social behavior and neurodevelopmental conditions. However, the neurobiological mechanisms underlying these associations remain elusive. In this study, we investigated the relationship between variations of 10 SNPs in oxytocin pathway genes and resting-state functional connectivity among 55 independent components using a large sample from the UK Biobank (N ≈ 30,000). Our findings revealed that individuals with the GG genotype at rs4813627 within the oxytocin structural gene (OXT) exhibited weaker resting-state functional connectivity in the corticostriatal circuit compared to those with the GA/AA genotypes. Empirical evidence has linked the GG genotype at OXT rs4813627 with a behavioral tendency of insensitivity to others. These results inform the neural mechanisms by which oxytocin-related genetic factors can influence social behavior.

The impact of social partners: investigating mixed-strain housing effects on aging in female mice

Aging is a multifaceted process characterized by the gradual decline of physiological functions and can be modulated by various internal and external factors. While social interactions have been shown to affect behaviors and physiology in different species, the impact of social partners on aging-related phenotypes and lifespan in mice remains understudied. To address this question, we investigated various aging-related traits and lifespan in two mouse strains, C57BL/6J and BALB/c, under two different housing conditions: mixed-strain and same-strain housing. Analyses using a Generalized Linear Model revealed significant differences between the two strains in several phenotypes, including metabolic, anxiety-like, and electrocardiographic traits. However, surprisingly, housing conditions did not significantly affect most of the examined parameters, including overall lifespan. Only 3 out of 25 traits-body weight change in a metabolic cage, running wheel activity, and survival days of a quartiles of mice with middle lifespans-were influenced by housing conditions in a strain-dependent manner. Together, our study suggested a minimal influence of co-housing with social partners from different genetic backgrounds on aging-related phenotypes. This result demonstrates the feasibility of mixed housing for mouse husbandry and, more importantly, provides valuable insights for future research on the social influences on the aging process in mice.

Genome-wide selection signatures address trait specific candidate genes in cattle indigenous to arid regions of India

The peculiarity of Indian cattle lies in milk quality, resistance to diseases and stressors as well as adaptability. The investigation addressed selection signatures in Gir and Tharparkar cattle, belonging to arid ecotypes of India. Double digest restriction-site associated DNA sequencing (ddRAD-seq) yielded nearly 26 million high-quality reads from unrelated seven Gir and seven Tharparkar cows. In all, 19,127 high-quality SNPs were processed for selection signature analysis. An approach involving within-population composite likelihood ratio (CLR) statistics and between-population FST statistics was used to capture selection signatures within and between the breeds, respectively. A total of 191 selection signatures were addressed using CLR and FST approaches. Selection signatures overlapping 86 and 73 genes were detected as Gir- and Tharparkar-specific, respectively. Notably, genes related to production (CACNA1D, GHRHR), reproduction (ESR1, RBMS3), immunity (NOSTRIN, IL12B) and adaptation (ADAM22, ASL) were annotated to selection signatures. Gene pathway analysis revealed genes in insulin/IGF pathway for milk production, gonadotropin releasing hormone pathway for reproduction, Wnt signalling pathway and chemokine and cytokine signalling pathway for adaptation. This is the first study where selection signatures are identified using ddRAD-seq in indicine cattle breeds. The study shall help in conservation and leveraging genetic improvements in Gir and Tharparkar cattle.

Exogenous oxytocin administered to induce or augment labour is positively associated with quality of observed mother-infant bonding

Oxytocin is a key hormone in the transition to motherhood. The maternal endogenous oxytocin system facilitates many physiological and biological adaptations, including breastfeeding, maternal wellbeing, and brain plasticity. Additionally, maternal endogenous oxytocin works as a finetuned orchestrator prior to, during, and after the birth of a child to support birth progression and mother-infant bonding. Exogenous oxytocin may be administered to induce or augment labour when this is not progressing naturally and is a common obstetric intervention worldwide. However, the lasting impact of these widely varying levels of systemic exogenous oxytocin on mother-infant bonding is currently unknown. This study aimed to investigate the association between exogenous oxytocin administered to induce or augment labour and quality of observed mother-infant bonding. Thirty-eight mother and infant dyads participated (mothers aged 24-48 years; infants aged 2-5 months). Mother-infant bonding quality was assessed via the Recorded Interaction Task and hospital birth records were consulted to obtain exogenous oxytocin administration data. Demographic information and possible confounding factors were collected from dyads, and salivary oxytocin concentration was measured for both mother and infant. Mother's perception of infant sleep difficulty was identified as a confounding factor for quality of mother-infant bonding. After controlling for the confounding factor, receiving exogenous oxytocin to induce or augment labour, as opposed to not, was found to be significantly positively associated with higher quality of observed mother-infant bonding (p = 0.029). These novel findings highlight the need for further exploration, both of the impact of the treatment and of the mechanisms of action of intrapartum exogenous oxytocin on the endogenous oxytocin system. It is argued that particular focus be given to investigate action on the central oxytocin receptors, and if this may play a role in subsequent mother-infant bonding outcomes. It is vital to understand the full breadth and the clinical implications of this commonplace procedure.

Role of Sex and Early Life Stress Experience on Porcine Cardiac and Brain Tissue Expression of the Oxytocin and H2S Systems

Early life stress (ELS) significantly increases the risk of chronic cardiovascular diseases and may cause neuroinflammation. This post hoc study, based on the material available from a previous study showing elevated "serum brain injury markers" in male control animals, examines the effect of sex and/or ELS on the cerebral and cardiac expression of the H2S and oxytocin systems. Following approval by the Regional Council of Tübingen, a randomized controlled study was conducted on 12 sexually mature, uncastrated German Large White swine of both sexes. The control animals were separated from their mothers at 28-35 days, while the ELS group was separated at day 21. At 20-24 weeks, animals underwent anesthesia, ventilation, and surgical instrumentation. An immunohistochemical analysis of oxytocin, its receptor, and the H2S-producing enzymes cystathionine-β-synthase and cystathionine-γ-lyase was performed on hypothalamic, prefrontal cortex, and myocardial tissue samples. Data are expressed as the % of positive tissue staining, and differences between groups were tested using a two-way ANOVA. The results showed no significant differences in the oxytocin and H2S systems between groups; however, sex influenced the oxytocin system, and ELS affected the oxytocin and H2S systems in a sex-specific manner. No immunohistochemical correlate to the elevated "serum brain injury markers" in male controls was identified.

Sympathetic innervation of interscapular brown adipose tissue is not a predominant mediator of OT-elicited reductions of body weight gain and adiposity in male diet-induced obese rats

Recent studies indicate that central administration of oxytocin (OT) reduces body weight (BW) in high fat diet-induced obese (DIO) rodents by reducing energy intake and increasing energy expenditure (EE). Previous studies in our lab have shown that administration of OT into the fourth ventricle (4V; hindbrain) elicits weight loss and stimulates interscapular brown adipose tissue temperature (TIBAT) in DIO rats. We hypothesized that OT-elicited stimulation of sympathetic nervous system (SNS) activation of IBAT contributes to its ability to activate BAT and reduce BW in DIO rats. To test this, we determined the effect of disrupting SNS activation of IBAT on OT-elicited stimulation of TIBAT and reduction of BW in DIO rats. We first confirmed that bilateral surgical SNS denervation to IBAT was successful based on having achieved ≥ 60% reduction in IBAT norepinephrine (NE) content from DIO rats. NE content was selectively reduced in IBAT by 94.7 ± 2.7, 96.8 ± 1.8 and 85.9 ± 6.1% (P<0.05) at 1, 6 and 7-weeks post-denervation, respectively, and was unchanged in liver or inguinal white adipose tissue. We then measured the impact of bilateral surgical SNS denervation to IBAT on the ability of acute 4V OT (1, 5 μg) to stimulate TIBAT in DIO rats. We found that the high dose of 4V OT (5 μg) stimulated TIBAT similarly between sham and denervated rats (P=NS) and that the effects of 4V OT to stimulate TIBAT did not require beta-3 adrenergic receptor signaling. We subsequently measured the effect of bilateral surgical denervation of IBAT on the effect of chronic 4V OT (16 nmol/day) or vehicle infusion to reduce BW, adiposity, and energy intake in DIO rats. Chronic 4V OT reduced BW gain by -7.2 ± 9.6 g and -14.1 ± 8.8 g in sham and denervated rats (P<0.05 vs vehicle treatment), respectively, and this effect was similar between groups (P=NS). These effects were associated with reductions in adiposity and energy intake (P<0.05). Collectively, these findings support the hypothesis that sympathetic innervation of IBAT is not required for central OT to increase BAT thermogenesis and reduce BW gain and adiposity in male DIO rats.