Oxytocin stimulates colonic motor activity in healthy women

Analysis of differentially expressed lncRNAs and mRNAs associated with slow‑transit constipation

Slow transit constipation (STC) is a refractory gastrointestinal disease, accounting for approximately 13 ∼ 37 % of chronic constipation. However, the molecular mechanism of STC remains poorly understood. Herein, this study aims to identify the key mRNAs and lncRNAs associated with STC. To this end, we performed high-throughput RNA sequencing to identify differentially expressed (DE) mRNAs and lncRNAs in the whole-layer sigmoid intestinal tissues from 4 STC patients and 4 non-STC patients. The identified DE lncRNAs and mRNAs were validated through quantitative real-time PCR. Weighted gene co-expression network analysis (WGCNA) and Pearson correlation analysis were conducted to determine the significantly correlated DE mRNA-lncRNA pairs. A total of 1420 DE lncRNAs and 1634 DE mRNAs were identified. Kyoto Encyclopedia of Genes and Genomes analysis of DE mRNAs indicated that these DE mRNAs might be associated with systemic lupus erythematosus, alcoholism, intestinal immune network for IgA production, inflammatory bowel disease, NF-kappa B signaling pathway. WGCNA and Pearson correlation analyses jointly identified 16,577 significantly correlated DE mRNA-lncRNA pairs. Furthermore, lncRNAs LINC00641, LINC02268, LINC03013 were identified as hub lncRNAs. The protein-protein interaction (PPI) network of proteins encoded by DE mRNAs was established, and PPI-based analysis revealed that Interleukin 2(IL2), CD80 molecule (CD80), interleukin-17A (IL-17A) might play significant roles in the development of STC. This study analyzes the expression profiles of lncRNAs and mRNAs associated with STC. Our findings will contribute to further understanding of the molecular mechanism of STC and provide potential diagnostic or therapeutic biomarkers for STC.

Protective effect of oxytocin on vincristine-induced gastrointestinal dysmotility in mice

Aims: Vincristine (VCR), an antineoplastic drug, induces peripheral neuropathy characterized by nerve damage, limiting its use and reducing the quality of life of patients. VCR causes myenteric neuron damage, inhibits gastrointestinal motility, and results in constipation or paralytic ileus in patients. Oxytocin (OT) is an endogenous neuropeptide produced by the enteric nerve system, which regulates gastrointestinal motility and exerts neuroprotective effects. This study aimed to investigate whether OT can improve VCR-induced gastrointestinal dysmotility and evaluate the underlying mechanism. Methods: Mice were injected either with saline or VCR (0.1 mg/kg/d, i. p.) for 14 days, and OT (0.1 mg/kg/d, i.p.) was applied 1 h before each VCR injection. Gastrointestinal transit and the contractile activity of the isolated colonic segments were assessed. The concentration of OT in plasma was measured using ELISA. Immunofluorescence staining was performed to analyze myenteric neurons and reactive oxygen species (ROS) levels. Furthermore, the indicators of oxidative stress were detected. The protein expressions of Nrf2, ERK1/2, P-ERK1/2, p38, and P-p38 in the colon were tested using Western blot. Results: VCR reduced gastrointestinal transit and the responses of isolated colonic segments to electrical field stimulation and decreased the amount of neurons. Furthermore, VCR reduced neuronal nitric oxide synthase and choline acetyltransferase immunopositive neurons in the colonic myenteric nerve plexus. VCR increased the concentration of OT in plasma. Exogenous OT pretreatment ameliorated the inhibition of gastrointestinal motility and the injury of myenteric neurons caused by VCR. OT pretreatment also prevented the decrease of superoxide dismutase activity, glutathione content, total antioxidative capacity, and Nrf2 expression, the increase of ROS levels, and the phosphorylation of ERK1/2 and p38 MAPK following VCR treatment. Conclusion: Our results suggest that OT pretreatment can protect enteric neurons from VCR-induced injury by inhibiting oxidative stress and MAPK pathways (ERK1/2, p38). This may be the underlying mechanism by which it alleviates gastrointestinal dysmotility.

Phloroglucinol inhibits oxytocin-induced contraction in rat gastric circular muscle and uterine smooth muscle

Phloroglucinol is commonly used to alleviate dysmenorrhoea and stomach cramps. However, there is little evidence of phloroglucinol in the mechanism of primary dysmenorrhoea (PD) development. In this study, a PD rat model was established. The effects of phloroglucinol on the contraction of rat gastric circular muscle and uterine smooth muscle induced by oxytocin (OT) were investigated. The writhing response, and levels of oestradiol (E2), prostaglandin e2 (PGE2), and prostaglandin f2α (PGF2α) were determined. The protein and mRNA levels of OT receptor (OTR) were detected. OT showed a significant promoting effect on gastric circular muscle and uterine smooth muscle contraction. However, phloroglucinol strongly inhibited the contraction induced by 10^-6mol/L of OT. We also found that phloroglucinol reduced writhing response and attenuated uterine damage. Compared to the blank group, E2 and PGF2α were significantly increased, but PGE2 was significantly decreased in the PD model group. Phloroglucinol was found to reverse the changes of E2, PGF2α and PGE2. Moreover, phloroglucinol reduced the protein and mRNA levels of OTR. In conclusion, phloroglucinol could attenuate PD and inhibit the contraction of rat gastric circular muscle and uterine smooth muscle induced by OT. The mechanism might be related with the regulation of OTR expression.IMPACT STATEMENTWhat is already known on this subject? Phloroglucinol is commonly used to alleviate dysmenorrhoea and stomach cramps. However, there is little evidence of phloroglucinol in the mechanism of primary dysmenorrhoea (PD) development.What do the results of this study add? Phloroglucinol could attenuate PD and inhibit the contraction of rat gastric circular muscle and uterine smooth muscle induced by OT. The underlying mechanisms of phloroglucinol for PD treatment may be associated with OTR.What are the implications of these findings for clinical practice and/or further research? These findings provide novel ideas for the role of phloroglucinol in PD development.

Risk factors for acute colonic pseudo-obstruction after caesarean section: A retrospective case-control study

BACKGROUND

Pregnancy and caesarean section are known to predispose to the development of acute colonic pseudo-obstruction (ACPO), a rare form of functional ileus of the distal large bowel. Pathogenesis of ACPO is likely influenced by pregnancy and childbirth and subsequent changes to hormonal, autonomic and metabolic physiology. Identifying pregnancy risk factors will assist with early identification, as the insidious onset postpartum often leads to delayed diagnosis and bowel ischaemia, perforation and sepsis.

AIMS

To establish pregnancy risk factors associated with the development of ACPO after caesarean section.

MATERIALS AND METHODS

A retrospective case-control study included 19 121 women undergoing caesarean between 1 January 2008 and 31 December 2016 at a tertiary referral hospital. Twenty-three cases of computerised tomography (CT)-diagnosed ACPO post-caesarean were identified from hospital medical records and imaging databases. Controls were matched for gestational and maternal age within one week of delivery with a ratio of 1:3.

RESULTS

The incidence of ACPO was one in 800 caesarean sections. ACPO was significantly more likely to occur in women who had been administered opioid analgesia in labour (odds ratio (OR) 4.67, P = 0.04), and a trend for increased estimated blood loss (OR 1.01, P = 0.01). There was no increased risk associated with emergency or elective caesarean classification, previous abdominal surgery, type of anaesthesia, duration of labour, oxytocin augmentation, intrapartum fever, hypertensive disorders, diabetes in pregnancy, antepartum haemorrhage, multiple gestation, fetal presentation or birthweight.

CONCLUSIONS

Risk factors for developing ACPO post-caesarean include opioid analgesia in labour and a trend for increased blood loss.

Mechanism of Oxytocin-Induced Contraction in Rat Gastric Circular Smooth Muscle

Oxytocin produces an excitatory effect on gastric muscle through the activation of receptors present on stomach smooth muscle cells. However, the intracellular mechanisms that mediate oxytocin excitatory effects are still largely unknown. Therefore, we aimed to investigate the signaling pathways involved in oxytocin-induced contractions in gastric smooth muscle, shedding light on phospholipase C (PLC)-β1 signaling and its downstream molecules, including inositol 1,4,5- trisphosphate (IP₃) and myosin light chain kinase (MLCK). The contractions of gastric smooth muscle from male rats were measured in an organ bath set up in response to exogenous oxytocin 10^-7 M, in the presence and absence of inhibitors of the indicated signaling molecules. Oxytocin (10^-9-10^-5 M) induced dose-dependent stomach smooth muscle contraction. Pre-incubation with atosiban, an oxytocin receptor inhibitor, abolished the oxytocin-induced contraction. Moreover, PLC β1 inhibitor (U73122) and IP₃ inhibitor Xestospongin C inhibited oxytocin-induced muscle contraction to various degrees. Verapamil, a calcium channel blocker, inhibited oxytocin-induced contraction, and pre-incubation of the strips, with both verapamil and Xestospongin C, further inhibited the excitatory effect of oxytocin. Chelation of intracellular calcium with BAPT-AM (1,2-bis-(o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid) significantly inhibited the effect of oxytocin on muscle contraction. Finally, pre-incubation of the strips with the Ca²⁺/calmodulin-dependent protein kinase selective inhibitor STO-609 significantly inhibited the contraction induced by oxytocin. These results suggest that oxytocin directly stimulates its cell surface receptor to activate PLC β1, which in turn liberates IP₃, which eventually elevates intracellular calcium, the prerequisite for smooth muscle contraction.

The effect of intra-vaginal oxytocin on sexual function in breastfeeding mothers: a randomized triple-blind placebo-controlled trial

BACKGROUND

Considering the importance of sexual function, high prevalence of sexual dysfunction (especially dyspareunia caused by atrophic vaginitis) in breastfeeding women, and lack of effective interventions, the present research aimed to determine the effect of oxytocin (OXT) vaginal gel on sexual function (primary outcome), sexual satisfaction, and depression (secondary outcomes) in the breastfeeding women.

METHODS

This randomized triple-blind controlled trial was conducted on 64 breastfeeding women who referred to health centers in the city of Tabriz, Iran, in 2020-21. Participants were equally assigned to intervention/control groups using block randomization. 200 IU of OXT vaginal gel was given to the participants in the intervention group daily for eight week and the same protocol was carried out for the control group with placebo. Standard questionnaires of Female Sexual Function Index (FSFI), Edinburgh Postpartum Depression Scale (EPDS) and Sexual satisfaction scale for women (SSSW) were completed at baseline and 8 weeks after intervention. ANCOVA test was used to compare post-intervention mean score of the groups, adjusted for the baseline values.

RESULTS

After intervention, there was no statistically significant difference between groups in terms of mean total score of FSFI (Adjusted Mean Difference (AMD): 1.14; 95% Confidence Interval (95% CI): -1.28 to 9.16; P= 0.349) and sexual satisfaction (AMD: 5.01; 95% CI: -0.53 to 10.56; P= 0.075). However, there was statistically significant difference between the groups in terms of mean scores of sexual contentment (AMD: 1.56; 95% CI: 0.29 to 2.83; P = 0.017) and depression (AMD: -1.90; 95% CI: -1.27 to -2.54; P < 0.001). One participant in the OXT group and one participant in the placebo group reported mild uterine contraction and one person in the placebo group reported vaginal burning sensations.

CONCLUSIONS

No evidence was found for the effects of OXT gel in the improvement of FSFI, even though, OXT significantly improved sexual satisfaction in the domain of contentment, and improved the symptoms of depression in comparison to the placebo group. However, a definite conclusion requires more research in this regard.

TRIAL REGISTRATION

the Iranian Registry of Clinical Trials (IRCT), code: IRCT20120718010324N55 , Date of registration: 27/05/2020, URL: https://en.irct.ir/user/trial/44986/view .

Oxytocin and Related Peptide Hormones: Candidate Anti-Inflammatory Therapy in Early Stages of Sepsis

Sepsis is a potentially life-threatening systemic inflammatory syndrome characterized by dysregulated host immunological responses to infection. Uncontrolled immune cell activation and exponential elevation in circulating cytokines can lead to sepsis, septic shock, multiple organ dysfunction syndrome, and death. Sepsis is associated with high re-hospitalization and recovery may be incomplete, with long term sequelae including post-sepsis syndrome. Consequently, sepsis continues to be a leading cause of morbidity and mortality across the world. In our recent review of human chorionic gonadotropin (hCG), we noted that its major properties including promotion of fertility, parturition, and lactation were described over a century ago. By contrast, the anti-inflammatory properties of this hormone have been recognized only more recently. Vasopressin, a hormone best known for its anti-diuretic effect, also has anti-inflammatory actions. Surprisingly, vasopressin's close cousin, oxytocin, has broader and more potent anti-inflammatory effects than vasopressin and a larger number of pre-clinical studies supporting its potential role in limiting sepsis-associated organ damage. This review explores possible links between oxytocin and related octapeptide hormones and sepsis-related modulation of pro-inflammatory and anti-inflammatory activities.

Effects of oxytocin and antagonist antidote atosiban on body weight and food intake of female mice, Mus musculus

Growing evidence suggests that oxytocin (OT) plays an important factor for the control of food intake, body weight, and energy metabolism in human and non-human animals. It has reported previously, the downregulation in oxytocin receptors (OTRs) expression is linked with the development of obesity, but exogenous OT reverse body weight and food intake in obese animal model. It is important to know that, whether intraperitoneal administration crosses blood brain barrier. Therefore, in the present experiment, we study the impact of intraperitoneal administration of synthetic OT 0.0116 mg/kg and antagonist atosiban (OTA) 1 mg/kg on food intake, and body weight of female mice, Mus musculus for different duration i.e. 30, 60, and 90 days. In this study, it was observed that there was significant decrease (p<0.001, one-way analysis of variance [ANOVA]) in the body weight (BW), food intake, and gonadosmatic indices (GSI) after the intraperitoneal exposure of OT at dose 0.0116 mg/kg up to 90 days and inhibits via antagonist atosiban. These results indicates that intraperitoneal administration of OT can be used for treatment for longer duration without any side effects and maintains homeostasis in physiologic system regulates body weight and gonadal weight in female mice, which represent an important therapeutic tool for the obesity and metabolic disorder in female.

Can intravenous oxytocin infusion counteract hyperinflammation in COVID-19 infected patients?

OBJECTIVES

Based on its well-documented anti-inflammatory and restorative properties we propose trials with the natural hormone oxytocin for treatment of hospitalised Covid-19 patients.

METHODS

We searched for, retrieved, and commented on specific literature regarding multiple functions of oxytocin with a special focus on its modulation of inflammatory, immune, and restorative functions.

RESULTS

Available data gathered in animals and humans support the anti-inflammatory properties of oxytocin. The multiple anti-inflammatory effects of oxytocin have been demonstrated in vitro and in vivo in various animal models and also in humans in response to intravenous infusion of oxytocin. Furthermore, oxytocin has been documented to activate several types of protective and restorative mechanisms and to exert positive effects on the immune system.

CONCLUSIONS

In addition, to being anti-inflammatory, it may be hypothesised, that oxytocin may be less suppressive on adaptive immune systems, as compared with glucocorticoids. Finally, by its restorative effects coupled with its anti-stress and healing properties, oxytocin may shorten the recovery period of the Covid-19 patients.

The efficacy and safety of intravaginal oxytocin on vaginal atrophy: A systematic review

Genitourinary syndrome of menopause is a major issue in menopausal health. Because unlike vasomotor symptoms, it has a progressive trend. In this regard we conducted a systematic review to evaluate the efficacy of intravaginal oxytocin on postmenopausal vaginal atrophy. A search was performed for published studies in Cochrane Library, MEDLINE, Web of Science, Embase, Scopus, ProQuest, Google Scholar and Persian databases without time and language limitations. Only randomized controlled trials that compared intravaginal oxytocin with placebos were included. The outcome measures were objective and subjective assessed symptoms of vaginal atrophy. Statistical heterogeneity was evaluated using the I². The standardized mean differences were pooled the fixed effects model. Of the five included studies, four studies meta-analysed. The meta-analysis in terms of the cytological analysis (standardized mean difference: 35.13, 95% confidence interval: 32.59-37.67, n = 218, I² = 96%) was statistically significant. In terms of histological assessments (standardized mean difference: -0.38, 95% confidence interval: -0.94 to 0.17, n = 38, I² = 0%) and endometrial thickness (standardized mean difference: 0.05, 95% confidence interval: -0.20 to -0.31, n = 95, I² = 0%), there were no statistically significant differences between the groups. Three studies reported a statistically significant improvement in the subjective symptoms; however, we were unable to perform a meta-analysis. Four of the included studies assessed side effects, but only two studies reported them. Oxytocin as a nonestrogenic compound can be a suitable alternative for the treatment of vaginal atrophy, especially in women with contraindications for using estrogenic compounds. Further good quality clinical trials with long-term follow-ups are recommended to demonstrate the effects of intravaginal gel in the treatment of vaginal atrophy.

Relevance of Sex and Subtype in Patients With IBS: An Exploratory Study of Gene Expression

BACKGROUND

Psychological state, stress level, and gastrointestinal function are intricately related and relevant to symptom exacerbation in patients with irritable bowel syndrome (IBS), but genetic contributors to this brain-gut connection are not fully understood. The purpose of this exploratory study was to compare gene expression in participants with IBS to that of healthy controls (HC) and to examine patterns of expression in participants with IBS by sex and IBS subtype.

METHOD

Participants were recruited to an ongoing protocol at the National Institutes of Health. Differences in demographic and clinical characteristics were assessed using descriptive statistics and Mann-Whitney U tests. Expression levels of 84 genes were evaluated in peripheral whole blood using Custom RT2 Profiler polymerase chain reaction (PCR) Arrays, and data analysis was performed through GeneGlobe Data Analysis Center.

RESULTS

Participants with IBS (n = 27) reported greater levels of perceived stress (p = .037) and differed in expression values of ±2 for the genes ADIPOR1, ADIPOR2, CNR2, COMT, OXTR, and PPARA compared to HC (n = 43). Further analyses by sex and IBS subtype revealed differential patterns of gene expression related to the endocannabinoid system, cytokines, stress, and sex steroid hormones.

CONCLUSIONS

Diverse yet interconnected processes such as metabolism, inflammation, immunity, social behavior, and pain are associated with differences in gene expression between participants with IBS and HC. These findings lend support for genomic associations with the brain-gut connection in patients with IBS and highlight the relevance of sex and IBS subtype in performing such analyses.

The effects of oxytocin on eating behaviour and metabolism in humans

Oxytocin, a hypothalamic hormone that is secreted directly into the brain and enters the peripheral circulation through the posterior pituitary gland, regulates a range of physiologic processes, including eating behaviour and metabolism. In rodents and nonhuman primates, chronic oxytocin administration leads to sustained weight reduction by reducing food intake, increasing energy expenditure and inducing lipolysis. Oxytocin might improve glucose homeostasis, independently of its effects on weight. Clinical studies are beginning to translate these important preclinical findings to humans. This Review describes key data linking oxytocin to eating behaviour and metabolism in humans. For example, a single intranasal dose of oxytocin can reduce caloric intake, increase fat oxidation and improve insulin sensitivity in men. Furthermore, a pilot study of 8 weeks of oxytocin treatment in adults with obesity or overweight led to substantial weight loss. Together, these data support further investigation of interventions that target pathways involving oxytocin as potential therapeutics in metabolic disorders, including obesity and diabetes mellitus. Therapeutic considerations and areas for further research are also discussed.

Oxytocin system dysfunction as a common mechanism underlying metabolic syndrome and psychiatric symptoms in schizophrenia and bipolar disorders

There is growing interest in using intranasal oxytocin (OT) to treat social dysfunction in schizophrenia and bipolar disorders (i.e., psychotic disorders). While OT treatment results have been mixed, emerging evidence suggests that OT system dysfunction may also play a role in the etiology of metabolic syndrome (MetS), which appears in one-third of individuals with psychotic disorders and associated with increased mortality. Here we examine the evidence for a potential role of the OT system in the shared risk for MetS and psychotic disorders, and its prospects for ameliorating MetS. Using several studies to demonstrate the overlapping neurobiological profiles of metabolic risk factors and psychiatric symptoms, we show that OT system dysfunction may be one common mechanism underlying MetS and psychotic disorders. Given the critical need to better understand metabolic dysregulation in these disorders, future OT trials assessing behavioural and cognitive outcomes should additionally include metabolic risk factor parameters.

Oxytocin hyperpolarizes cultured duodenum myenteric intrinsic primary afferent neurons by opening BK(Ca) channels through IP₃ pathway

Oxytocin (OT) is clinically important in gut motility and constitutively reduces duodenum contractility. Intrinsic primary afferent neurons (IPANs), whose physiological classification is as AH cells, are the 1st neurons of the peristaltic reflex pathway. We set out to investigate if this inhibitory effect is mediated by IPANs and to identify the ion channel(s) and intracellular signal transduction pathway that are involved in this effect. Myenteric neurons were isolated from the longitudinal muscle myenteric plexus (LMMP) preparation of rat duodenum and cultured for 16-24 h before electrophysiological recording in whole cell mode and AH cells identified by their electrophysiological characteristics. The cytoplasmic Ca²⁺ concentration ([Ca²⁺](i) ) of isolated neurons was measured using calcium imaging. The concentration of IP(3) in the LMMP and the OT secreted from the LMMP were measured using ELISA. The oxytocin receptor (OTR) and large-conductance calcium-activated potassium (BK(Ca)) channels, as well as the expression of OT and the IPAN marker calbindin 28 K, on the myenteric plexus neurons were localized using double-immunostaining techniques. We found that administration of OT (10⁻⁷ to 10⁻⁵ M) dose dependently hyperpolarized the resting membrane potential and increased the total outward current. The OTR antagonist atosiban or the BK(Ca) channel blocker iberiotoxin (IbTX) blocked the effects of OT suggesting that the increased outward current resulted from BK(Ca) channel opening. OTR and the BK(Ca) α subunit were co-expressed on a subset of myenteric neurons at the LMMP. NS1619 (10⁻⁵ M, a BK(Ca) channel activator) increased the outward current similar to the effect of OT. OT administration also increased [Ca²⁺](i) and the OT-evoked outward current was significantly attenuated by thapsigargin (10⁻⁶ M) or CdCl₂. The effect of OT on the BK(Ca) current was also blocked by pre-treatment with the IP₃ receptor antagonist 2-APB (10⁻⁴ M) or the PLC inhibitor U73122 (10⁻⁵ M). OT (10⁻⁶ M) also increased the IP₃ concentration within the LMMP. Both of the spontaneous and KCl-induced secretion of OT was enhanced by atosiban. Most of OT-immunoreactive cells are also immunoreactive for calbindin 28 K. In summary, we concluded that OT hyperpolarized myenteric IPANs by activating BK(Ca) channels via the OTR-PLC-IP₃-Ca²⁺ signal pathway. OT might modulate IPANs mediated ENS reflex by an autocrine and negative feedback manner.

Topical oxytocin reverses vaginal atrophy in postmenopausal women: a double-blind randomized pilot study

Introduction

Oxytocin is a peptide hormone produced in the hypothalamus and it is best known for its role in labour and lactation. This double-blind, randomized study was performed at Huddinge Hospital of Karolinska Institutet, Stockholm in order to test the effectiveness of topical oxytocin gel in women with postmenopausal vaginal atrophy.

Methods

Twenty postmenopausal women (at least two years after menopause) with symptoms of vaginal atrophy such as vaginal dryness, pain, itching, discomfort and bleeding during intercourse were enrolled in the study when visual inspection of the vagina had confirmed that their mucosa was atrophic. The participants were randomized to intravaginal treatment with either oxytocin or placebo gel for seven days. Before and after treatment, a gynaecological examination and a visual and colposcopic inspection of the vagina were performed, biopsies from the vaginal mucosa were taken and blood samples were collected for analysis of circulating levels of estradiol and oxytocin.

Results

Prior to treatment, visual and colposcopic inspection showed that all of the 20 participants had an atrophic vaginal mucosa. After treatment with the oxytocin gel, the examination showed that the vaginal epithelium of seven of the 10 participants in the oxytocin group had become healthier and normalized. No change in these parameters was observed among the 10 participants in the placebo group. This difference between the oxytocin and placebo groups was significant ( P= 0.003). Seven participants in the active group and four in the placebo group reported relief of symptoms of vaginal atrophy after seven days of applying the gel. The effect of oxytocin to normalize the morphological appearance of the vaginal mucosa was almost significant when compared with the placebo group ( P= 0.07). There was no significant difference between the circulating levels of estradiol and oxytocin in both the oxytocin and placebo groups before and after treatment. None of the participants reported any side-effects.

Conclusion

Topical treatment with oxytocin appears to improve vaginal atrophy in postmenopausal women. A limitation of this pilot study is that it was based on a small study population hence the results should be regarded with caution. Larger studies are in progress to establish the possibility of using oxytocin as a clinical treatment for vaginal atrophy.

Oxytocin reduces satiety scores without affecting the volume of nutrient intake or gastric emptying rate in healthy subjects

BACKGROUND

Oxytocin is expressed throughout the gastrointestinal tract and is released in response to a fatty meal. Administration of an oxytocin receptor antagonist prolongs the gastric emptying rate. The aim of this study was to examine the effect of oxytocin on gastric accommodation, gastric emptying time, and satiety after food intake.

METHODS

Ten healthy subjects participated in a slow satiety drinking test with a liquid meal. Every 5 min the subjects scored their sensation of satiety using a visual analogue scale (VAS) until maximum satiety was reached and the amount of liquid intake was determined. Twelve subjects participated in a gastric emptying test. They were given a standardized meal containing 20 radio-opaque markers, after which fluoroscopy was performed and VAS was scored every hour. Both tests were performed four times during infusions of saline and three different oxytocin concentrations. Blood was collected for oxytocin concentration measurements.

KEY RESULTS

There were no differences in the volume of nutrient intake at maximum satiety between the three doses of oxytocin and saline. However, lower satiety scores at maximum satiety were seen after oxytocin infusion (P = 0.031), with 40 mU min(-1) being the most effective dosage (P = 0.013), and this was also true 30 min after finishing the meal (P = 0.032). There was no difference in gastric emptying time between saline and oxytocin. The oxytocin concentration in plasma was increased proportional to the oxytocin infusions.

CONCLUSIONS & INFERENCES

Infusion of oxytocin reduces satiety without affecting the volume of nutrient intake or gastric emptying in healthy subjects.

CCK mediated the inhibitory effect of oxytocin on the contraction of longitudinal muscle strips of duodenum in male rats

The aim of the present study was to investigate the effect of oxytocin (OT) on duodenum motility in rats and the possibility that cholecystokinin (CCK) was involved in this process. The isometric contraction of longitudinal muscle strips of duodenum was monitored by polygraph. ELISA was used to measure the concentration of CCK and OT in duodenum. CCK mRNA was assayed by RT-PCR. Oxytocin receptor (OTR) and CCK in duodenum were located by immunohistochemistry and immunofluorescence staining. OT (10⁻⁵ and 10⁻⁶ M) inhibited the spontaneous contraction of the muscle strips. On the contrary, atosiban (OT receptor antagonist), lorglumide (CCK₁ receptor antagonist), and tetrodotoxin (TTX, blocker of voltage-dependent Na(+) channel on nerve fiber) excited the contraction. The inhibitory effect of OT on duodenal motility was reversed by pretreatment of atosiban, lorglumide, or TTX. Exogenous OT did not influence the expression of OT mRNA in duodenum but increased the concentration of CCK in the culture medium of the cells isolated from longitudinal muscle myenteric plexus. The OTR and CCK were co-expressed in the neurons of the myenteric plexus in duodenum. We concluded that OT inhibited the contraction of the LD spontaneous contraction of rats in vitro. This effect was mediated by the CCK released from the neurons of the myenteric plexus in duodenum.

Polymorphism in the oxytocin promoter region in patients with lactase non-persistence is not related to symptoms

Background

Oxytocin and the oxytocin receptor have been demonstrated in the gastrointestinal (GI) tract and have been shown to exert physiological effects on gut motility. The role for oxytocin in the pathophysiology of GI complaints is unknown. The aim of this study was to examine genetic variations or polymorphism of oxytocin (OXT) and its receptor (OXTR) genes in patients with GI complaints without visible organic abnormalities.

Methods

Genetic variants in the OXT promoter region, and in the OXTR gene in DNA samples from 131 rigorously evaluated patients with Irritable Bowel Syndrome (IBS), 408 homozygous subjects referred for lactase (LCT-13910 C>T, rs4988235) genotyping, and 299 asymptomatic blood donors were compared. One polymorphism related to the OXT gene (rs6133010 A>G) and 4 related to the OXTR gene (rs1465386 G>T, rs3806675 G>A, rs968389 A>G, rs1042778 G>T) were selected for genotyping using Applied Biosystems 7900 HT allele discrimination assays.

Results

There were no statistically significant differences in the genotype or allele frequencies in any of the SNPs when IBS patients were compared to healthy controls. Among subjects referred for lactase genotyping, the rs6133010 A>G OXT promoter A/G genotype tended to be more common in the 154 non-persistent (27.3%) subjects than in the 254 lactase persistant (18.1%) subjects and in the healthy controls (19.4%) (p = 0.08). When direct comparing, the A/G genotype was less common in the OXT promoter region in controls (p = 0.09) and in subjects with lactase persistence (p = 0.03) compared to subjects with lactase non-persistence. When healthy controls were viewed according to their own LCT-13910 genotypes, the C/C lactase non-persistent controls had a higher frequency for the OXT promoter A/G genotype than LCT-13910 T/T lactase persistent controls (41.2% vs 13.1%).

No significant differences in frequencies of the investigated OXTR SNPs were noted in this study.

Conclusion

The results suggest that polymorphism in the promoter region of the OXT gene is most common in subjects with lactase non-persistence. This polymorphism may not be related to GI symptoms, as it is related to lactase non-persistence also in healthy controls.

Estradiol upregulates the expression of oxytocin receptor in colon in rats

The study was designed to investigate the effect of estradiol on the excitatory effect of oxytocin (OT) on colon motility. Female Wistar rats were used, and some of them were ovariectomized (OVX) and treated with vehicle or estradiol (E(2)). A plastic balloon made of condom was inserted into colon to monitor the change of colonic pressure in vivo. Longitudinal muscle strips of distal colon were prepared to monitor the spontaneous contraction of colon in vitro. Expression of OT receptor (OTR) was investigated by Western blot analysis. Expression of OTR mRNA was detected by RT-PCR. Immunohistochemistry was used to locate OTR. In OVX rats, pretreatment of E(2) (4-100 microg/kg sc) dose-dependently increased the excitatory effect of OT on colon motility both in vivo and in vitro and increased the expression of OTR and OTR mRNA in colon. Systemic administration of OT excited the colon motility in vivo in rats at perioda of proestrus and estrus but did not influence it at diestrus period, when the concentration of plasma E(2) was lowest in the estrous cycle. Pretreatment of atosiban, the specific OTR antagonist, and TTX, the blocker of voltage-dependent sodium channel on nerve fiber, attenuated the excitatory effect of OT on colon motility. OTR was located in myenteric plexus of colon. These results suggested that E(2) increased the excitatory effect of OT on colon motility by upregulating the expression of OTR in myenteric plexus.

Gastroparesis is associated with oxytocin deficiency, oesophageal dysmotility with hyperCCKemia, and autonomic neuropathy with hypergastrinemia

Background

Gastrointestinal (GI) dysmotility and autonomic neuropathy are common problems among diabetics with largely unknown aetiology. Many peptides are involved in the autonomic nervous system regulating the GI tract. The aim of this study was to examine if concentrations of oxytocin, cholecystokinin (CCK), gastrin and vasopressin in plasma differ between diabetics with normal function and dysfunction in GI motility.

Methods

Nineteen patients with symptoms from the GI tract who had been examined with gastric emptying scintigraphy, oesophageal manometry, and deep-breathing test were included. They further received a fat-rich meal, after which blood samples were collected and plasma frozen until analysed for hormonal concentrations.

Results

There was an increase in postprandial oxytocin plasma concentration in the group with normal gastric emptying (p = 0.015) whereas subjects with delayed gastric emptying had no increased oxytocin secretion (p = 0.114). Both CCK and gastrin levels increased after the meal, with no differences between subjects with normal respective delayed gastric emptying. The concentration of vasopressin did not increase after the meal. In patients with oesophageal dysmotility the basal level of CCK tended to be higher (p = 0.051) and those with autonomic neuropathy had a higher area under the curve (AUC) of gastrin compared to normal subjects (p = 0.007).

Conclusion

Reduced postprandial secretion of oxytocin was found in patients with delayed gastric emptying, CCK secretion was increased in patients with oesophageal dysmotility, and gastrin secretion was increased in patients with autonomic neuropathy. The findings suggest that disturbed peptide secretion may be part of the pathophysiology of digestive complications in diabetics.

Proximal colon distension induces Fos expression in oxytocin-, vasopressin-, CRF- and catecholamines-containing neurons in rat brain

Little is known about the chemical coding of the brain neuronal circuitry activated by nociceptive signals of visceral origin. We characterized brain nuclei activated during isovolumetric phasic distension of the proximal colon (10 ml, 30 s on/off for 10 min) in conscious male rats, using Fos as a marker of neuronal activation and dual immunohistochemistry to visualize co-localization of Fos expression and oxytocin (OT), arginine-vasopressin (AVP), corticotrophin-releasing factor (CRF) or tyrosine hydroxylase (TH). Proximal colon distension, compared with sham distension, induced a robust increase in Fos-like immunoreactive (IR) neurons in the paraventricular nucleus (PVN), supraoptic nucleus (SON) and accessory neurosecretory nuclei of the hypothalamus, nucleus of the solitary tract (NTS) and ventrolateral medulla (VLM), and to a lower extent, in the locus coeruleus (LC) and Barrington nucleus. Fos-IR neurons in the PVN after colon distension were identified in 81% of OT-IR, 18% AVP-IR and 16% CRF-IR neurons, while in the SON it represented 36% of OT-IR and 16% AVP-IR. Catecholaminergic cell groups in the pons (LC) and medulla (VLM, NTS) were also activated by proximal colon distension. Of the TH-IR neurons in VLM and NTS, 74% and 42% respectively were double labeled. These results indicate that colon distension stimulates OT-, AVP- and CRF-containing hypothalamic neurons, likely involved in the integration of colonic sensory information to modulate autonomic outflow and pain-related responses. Activation of medullary catecholaminergic centers might reflect the afferent and efferent limbs of the functional responses associated to visceral pain.

Oxytocin alleviates the neuroendocrine and cytokine response to bacterial endotoxin in healthy men

Oxytocin is a hormone and neurotransmitter found to have anti-inflammatory functions in rodents. Here we used experimental bacterial endotoxinemia to examine the role of exogenous oxytocin administration on innate immune responses in humans. Ten healthy men received, in a randomized, placebo-controlled, crossover design, placebo, oxytocin, LPS, and LPS + oxytocin. Oxytocin treatment resulted in a transient or prolonged reduction of endotoxin-induced increases in plasma ACTH, cortisol, procalcitonin, TNF-alpha, IL-1 receptor antagonist, IL-4, IL-6, macrophage inflammatory protein-1alpha, macrophage inflammatory protein-1beta, monocyte chemoattractant protein-1 (MCP-1), interferon-inducible protein 10, and VEGF. In vitro, oxytocin had no impact on LPS effects in releasing TNF-alpha, IL-6, and MCP-1 in monocytes and peripheral blood mononuclear cells from healthy human donors. In summary, oxytocin decreases the neuroendocrine and cytokine activation caused by bacterial endotoxin in men, possibly due to the pharmacological modulation of the cholinergic anti-inflammatory pathway. Oxytocin might be a candidate for the therapy of inflammatory diseases and conditions associated with high cytokine and VEGF levels.

Systemic oxytocin and vasopressin excite gastrointestinal motility through oxytocin receptor in rabbits

The aim of the present study was to investigate the effect of systemic oxytocin (OT) and vasopressin (VP) on the motility of stomach and duodenum. Two plastic balloons made of condom were inserted into stomach and duodenum to monitor the change of mean pressure. Intravenous injection of OT (0.1-0.8 microg kg(-1)) or VP (0.02-0.08 IU kg(-1)) dose-dependently increased the stomach and duodenum pressure. Pretreatment of atosiban (1 microg kg(-1)), the specific OT receptor (OTR) antagonist, attenuated the excitatory effect of OT or VP on the pressure of stomach and duodenum. Pretreatment of V1880 (1 microg kg(-1)), the specific V1 receptor blocker, did not influence this effect. So we conclude that both of OT and VP injected systemically increased the gastric and duodenum motility via OTR.

Vasopressin receptor mRNA expression in the human gastrointestinal tract

BACKGROUND/AIM

Vasopressin and oxytocin are closely related peptides, and both exert effects on the gastrointestinal function. In the present study, we wanted to map the expression of vasopressin receptor mRNAs (V1a, V1b/V3, and V2) in nontumorous tissue biopsy specimens of human gastrointestinal tract and surrounding tissues.

METHODS

Total and polyA+ RNAs were isolated from human tissue biopsy specimens using an automated nucleic acid extractor and, subsequently, converted into single-stranded cDNA. Semi-nested PCR amplifications were carried out, using gene-specific V1a, V1b/V3, and V2 receptor primers. The PCR amplicons were partially sequenced to confirm their identity.

RESULTS

The present study demonstrated the expression of vasopressin receptor mRNAs in human gastrointestinal tract, pancreas, kidney, lung, brain, and ovary. The expression pattern varied between different parts of the gastrointestinal tract. In the colon ascendens, V1a receptor mRNA expression could not be detected in 3 out of 4 analyzed tissue biopsy specimens. On the other hand, all the vasopressin receptor mRNAs were expressed in all colon transversum biopsy samples.

CONCLUSIONS

V1a, V1b/V3, and V2 receptor mRNAs are widely expressed throughout human gastrointestinal tract and surrounding tissues. The data obtained provide information for further mapping and determination of the physiological role of the vasopressin receptor mRNA expression in normal and tumorous tissues.

Lactational state modifies alcohol pharmacokinetics in women

BACKGROUND

Given the physiological adaptations of the digestive system during lactation, the present study tested the hypothesis that lactation alters alcohol pharmacokinetics.

METHODS

Lactating women who were exclusively breastfeeding a 2- to 5-month-old infant and 2 control groups of nonlactating women were studied. The first control group consisted of women who were exclusively formula-feeding similarly aged infants, whereas the other consisted of women who had never given birth. A within-subjects design study was conducted such that women drank a 0.4 g/kg dose of alcohol following a 12-hour overnight fast during one test session (fasted condition) or 60 minutes after consuming a standard breakfast during the other (fed condition). Blood alcohol concentration (BAC) levels and mood states were obtained at fixed intervals before and after alcohol consumption.

RESULTS

Under both conditions, the resultant BAC levels at each time point were significantly lower and the area under the blood alcohol time curve were significantly smaller in lactating women when compared with the 2 groups of nonlactating women. That such changes were due to lactation per se and not due to recent parturient events was suggested by the finding that alcohol pharmacokinetics of nonlactating mothers, who were tested at a similar time postpartum, were no different from women who had never given birth. Despite lower BAC levels in lactating mothers, there were no significant differences among the 3 groups of women in the stimulant effects of alcohol. However, lactating women did differ in the sedative effects of alcohol when compared with nulliparous but not formula-feeding mothers. That is, both groups of parous women felt sedated for shorter periods of time when compared with nulliparous women.

CONCLUSIONS

The systemic availability of alcohol was diminished during lactation. However, the reduced availability of alcohol in lactating women did not result in corresponding changes in the subjective effects of alcohol.

Oxytocin is expressed throughout the human gastrointestinal tract

BACKGROUND/AIM

Several studies have described that oxytocin exerts stimulatory or inhibitory effects on gut functions. Recently, mRNA for oxytocin and its receptor was found throughout the entire human gastrointestinal (GI) tract. The aim of this study was to examine the cellular localization and distribution of the corresponding proteins.

MATERIAL AND METHODS

Full-thickness biopsies from 24 patients, covering the entire GI tract, were collected during operations at the Department of Surgery in Malmö and Lund. The biopsies were taken from non_affected margins. The biopsies were fixed by immersion, rinsed in buffered sucrose, and kept frozen at 70 degrees C. Indirect immunofluorescence with primary antibodies to oxytocin and its receptor was used.

RESULTS

Oxytocin was expressed in nerve cell bodies and nerve fibres in the myenteric and submucous ganglia all along the GI tract. Immunoreactive nerve cell bodies in myenteric ganglia predominated in the proximal (antrum and duodenum) and distal gut, while those in the submucous ganglia were more numerous in the ileum and colon. The oxytocin receptor was not detectable by two different antibodies in any tissue in the GI tract.

CONCLUSION

Oxytocin is expressed in the myenteric and submucous ganglia and nerve fibres along the entire human GI tract. The role for oxytocin in the physiology and pathophysiology of the bowel remains to be settled.

The oxytocin/vasopressin receptor antagonist atosiban delays the gastric emptying of a semisolid meal compared to saline in human

BACKGROUND

Oxytocin is released in response to a meal. Further, mRNA for oxytocin and its receptor have been found throughout the gastrointestinal (GI) tract. The aim of this study was therefore to examine whether oxytocin, or the receptor antagonist atosiban, influence the gastric emptying.

METHODS

Ten healthy volunteers (five men) were examined regarding gastric emptying at three different occasions: once during oxytocin stimulation using a pharmacological dose; once during blockage of the oxytocin receptors (which also blocks the vasopressin receptors) and thereby inhibiting physiological doses of oxytocin; and once during saline infusion. Gastric emptying rate (GER) was assessed and expressed as the percentage reduction in antral cross-sectional area from 15 to 90 min after ingestion of rice pudding. The assessment was performed by real-time ultrasonography. At the same time, the feeling of satiety was registered using visual satiety scores.

RESULTS

Inhibition of the binding of endogenous oxytocin by the receptor antagonist delayed the GER by 37 % compared to saline (p = 0.037). In contrast, infusion of oxytocin in a dosage of 40 mU/min did not affect the GER (p = 0.610). Satiation scores areas in healthy subjects after receiving atosiban or oxytocin did not show any significant differences.

CONCLUSION

Oxytocin and/or vasopressin seem to be regulators of gastric emptying during physiological conditions, since the receptor antagonist atosiban delayed the GER. However, the actual pharmacological dose of oxytocin in this study had no effect. The effect of oxytocin and vasopressin on GI motility has to be further evaluated.

The inhibitory effects of oxytocin on distal colonic contractile activity in rabbits are enhanced by ovarian steroids

AIMS

To study the effects of oxytocin on isolated rabbit distal colon and the regulation of ovarian steroids by its action.

METHODS

Muscle strips parallel to either the circular or the longitudinal fibres were excised and suspended in tissue chambers containing 5 mL Krebs solution (37 degrees C) and bubbled continuously with 95% O(2) and 5% CO(2). The effects of oxytocin on isometric spontaneous contractile responses were recorded. The effects of atosiban, tetrodotoxin, Mg(2+), progesterone and oestradiol on the oxytocin-induced response were also examined.

RESULTS

Oxytocin (1, 10 and 100 nmol L(-1)) dose dependently decreased the area under the contraction curve of distal colonic smooth muscle strips. The oxytocin receptor antagonist atosiban blocked the oxytocin (10 nmol L(-1))-caused responses in a dose-dependent manner. Tetrodotoxin (10 micromol L(-1)) had no effect on the oxytocin-induced response. Mg(2+)-free Krebs solution attenuated the oxytocin-induced response, but oestradiol (0.1 micromol L(-1)) or progesterone (0.1 micromol L(-1)) increased the oxytocin-induced response.

CONCLUSION

These results suggest that oxytocin inhibits the contractile motility of the distal colon, which is regulated by Mg(2+) and ovarian steroids.

Effects of long-term treatment with oxytocin in chronic constipation; a double blind, placebo-controlled pilot trial

BACKGROUND

Oxytocin and its receptor have been found throughout the gastrointestinal (GI) tract, where it affects gut function. Clinically, we have noticed an improvement of bowel habits during lactation in constipated women. The aim of this study was to examine whether oxytocin has an effect on bowel symptoms and psychological well being in women with refractory constipation.

METHODS

Fifty-nine women with refractory constipation were included in a double blind, multicentre study. After a 2-week run-in period, they were randomly allocated to nasal inhalation of either placebo or oxytocin treatment twice daily for 13 weeks, followed by a 2 weeks, posttreatment period. The patients completed a questionnaire every day concerning bowel habits, abdominal pain and discomfort, and Gastrointestinal Symptoms Rating Scale (GSRS) and Psychological General Well-being (PGWB) twice during the study; namely, during the baseline period and at the end of the treatment period.

RESULTS

Both oxytocin and placebo led to improvement of the constipation according to the GSRS and led to improvement in the sensation of incomplete evacuation and anorectal obstruction, without significant differences between the groups. Abdominal pain and discomfort responded weakly to oxytocin, with no effect of the placebo. In a subgroup of patients with IBS and concomitant depression, a weak improvement in depressed mood was observed after oxytocin administartion.

CONCLUSION

Nasal administration of oxytocin had no significant advantage over placebo concerning an effect on constipation. However, it seems to have a positive effect on abdominal pain and discomfort and depressed mood. These findings should be further explored.

Oxytocin ameliorates oxidative colonic inflammation by a neutrophil-dependent mechanism

Oxytocin (OT), a nonapeptide produced in the paraventricular and the supraoptical nuclei in the hypothalamus has a wide range of effects in the body. However, the role of OT on the gastrointestinal (GI) tract has to be settled. OT may participate in the regulation of motility, secretion, blood flow, cell turnover and release of neurotransmitters and/or peptides in the GI tract, possesses antisecretory and antiulcer effects, facilitates wound healing and is involved in the modulation of immune and inflammatory processes. The present work was conducted to assess the possible therapeutic effects of OT against the acetic acid-induced colonic injury in the rat.

METHODS

Colitis was induced by intracolonic administration of acetic acid (5%) in Sprague-Dawley rats (200-250 g). Either saline or OT (0.5 mg/kg) was injected subcutaneously, immediately after the induction of colitis and repeated two times a day for 4 days. On the 4th day, rats were decapitated and distal 8 cm of the colon were removed for the macroscopic and microscopic damage scoring, determination of tissue wet weight index (WI), malondialdehyde (MDA) levels, an end product of lipid peroxidation; glutathione (GSH) levels, a key antioxidant; and myeloperoxidase (MPO) activity, as an indirect index of neutrophil infiltration. Colonic collagen content, as a fibrosis marker was also determined. Lactate dehydrogenase (LDH) and tumor necrosis factor-alpha (TNF-alpha) levels were assayed in serum samples. In the acetic acid-induced colitis, macroscopic and microscopic damage scores, WI, MDA and MPO levels were significantly increased, while GSH levels were decreased when compared to control group (p <0.05-<0.001). Treatment with OT abolished the colitis-induced elevations in damage scores, WI, MDA and MPO levels and restored the GSH levels (p <0.05-0.001). Similarly, acetic acid increased the collagen content of colonic tissues and OT-treatment reduced this value to the level of the control group. Serum LDH and TNF-alpha levels were also elevated in the acetic acid-induced colitis group as compared to control group, while this increase was significantly decreased by OT treatment. The results suggest that OT, which improves the antioxidative state of the colonic tissue and ameliorates oxidative colonic injury via a neutrophil-dependent mechanism, requires further investigation as a potential therapeutic agent in colonic inflammation.

Oxytocin and cholecystokinin secretion in women with colectomy

Background

Cholecystokinin (CCK) concentrations in plasma have been shown to be significantly higher in colectomised subjects compared to healthy controls. This has been ascribed to reduced inhibition of CCK release from colon. In an earlier study CCK in all but one woman who was colectomised, induced release of oxytocin, a peptide present throughout the gastrointestinal (GI) tract. The aim of this study was thus to examine if colectomised women had a different oxytocin response to CCK compared to healthy controls.

Methods

Eleven women, mean age 34.4 ± 2.3 years, who had undergone colectomy because of ulcerative colitis or constipation were studied. Eleven age-matched healthy women served as controls. All subjects were fasted overnight and given 0.2 μg/kg body weight of CCK-8 i.v. in the morning. Samples were taken ten minutes and immediately before the injection, and 10, 20, 30, 45, 60, 90 and 120 min afterwards. Plasma was collected for measurement of CCK and oxytocin concentrations.

Results

The basal oxytocin and CCK concentrations in plasma were similar in the two groups. Intravenous injection of CCK increased the release of oxytocin from 1.31 ± 0.12 and 1.64 ± 0.19 pmol/l to 2.82 ± 0.35 and 3.26 ± 0.50 pmol/l in controls and colectomised women, respectively (p < 0.001). Given the short half-life of CCK-8 in plasma, the increased concentration following injection could not be demonstrated in the controls. On the other hand, in colectomised women, an increase of CCK in plasma was observed for up to 20 minutes after the injection, concentrations increasing from 1.00 ± 0.21 to a maximum of 1.81 ± 0.26 pmol/l (p < 0.002).

Conclusion

CCK stimulates the release of oxytocin in women. There is no difference in plasma concentrations between colectomised and controls. However, colectomy seems to reduce the metabolic clearance of CCK. The hyperCCKemia in patients who had undergone colectomy is consequently not only dependent on CCK release, but may also depend on reduced clearance.