Low Fasting Oxytocin Levels Are Associated With Psychopathology in Anorexia Nervosa in Partial Recovery

Understanding oxytocin in human physiology and pathophysiology: A path towards therapeutics

•Oxytocin is a multifaceted hypothalamic-pituitary hormone involved in energy homeostasis, mental health, and bone metabolism.•Oxytocin deficiency in energy deficit states and in hypopituitarism is associated with worse mental health and bone health.•Oxytocin modulates appetitive neurocircuitry, improves impulse control, and reduces food intake in humans.•Defining the oxytocin system in human physiology and pathophysiology could lead to novel therapeutic strategies.

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.

The use of intranasal oxytocin in the treatment of eating disorders

Oxytocin (OXT) is a hypothalamic peptide that plays a number of roles in the body, being involved in labor and lactation, as well as cognitive-emotional processes and social behavior. In recent years, knowledge of the physiology of OXT has been repeatedly used to explore its potential role in the treatment of numerous diseases, identifying a significant role for OXT in appetite regulation, eating behavior, weight regulation, and food-related beliefs. In this review we provide an overview of publications on this topic, but due to the wealth of research, we have limited our focus to studies based on the use of intranasal OXT in psychiatric diseases, with a particular focus on the role of oxytocin in eating disorders and obesity. Accumulating evidence that OXT intranasal supplementation may provide some therapeutic benefit seems promising. In individuals with autistic spectrum disorders (ASD) and schizophrenia, OXT may affect core deficits, improving social cognition and reducing symptom severity in schizophrenia. Dysregulation of serum and CSF OXT levels, as well as polymorphisms of its genes, may affect emotion perception in patients with eating disorders and correlate with co-occurring depressive and anxiety disorders. Nevertheless, there are still many critical questions regarding the pharmacokinetics and pharmacodynamics of intranasal OXT that can only be answered in larger randomized controlled trials.

Paraventricular nucleus-central amygdala oxytocinergic projection modulates pain-related anxiety-like behaviors in mice

AIMS

Anxiety disorders associated with pain are a common health problem. However, the underlying mechanisms remain poorly understood. We aimed to investigate the role of paraventricular nucleus (PVN)-central nucleus of the amygdala (CeA) oxytocinergic projections in anxiety-like behaviors induced by inflammatory pain.

METHODS

After inflammatory pain induction by complete Freund's adjuvant (CFA), mice underwent elevated plus maze, light-dark transition test, and marble burying test to examine the anxiety-like behaviors. Chemogenetic, optogenetic, and fiber photometry recordings were used to modulate and record the activity of the oxytocinergic projections of the PVN-CeA.

RESULTS

The key results are as follows: inflammatory pain-induced anxiety-like behaviors in mice accompanied by decreased activity of PVN oxytocin neurons. Chemogenetic activation of PVN oxytocin neurons prevented pain-related anxiety-like behaviors, whereas inhibition of PVN oxytocin neurons induced anxiety-like behaviors in naïve mice. PVN oxytocin neurons projected directly to the CeA, and microinjection of oxytocin into the CeA blocked anxiety-like behaviors. Inflammatory pain also decreased the activity of CeA neurons, and optogenetic activation of PVNoxytocin -CeA circuit prevented anxiety-like behavior in response to inflammatory pain.

CONCLUSION

The results of our study suggest that oxytocin has anti-anxiety effects and provide novel insights into the role of PVNoxytocin -CeA projections in the regulation of anxiety-like behaviors induced by inflammatory pain.

Oxytocin response to food intake in avoidant/restrictive food intake disorder

OBJECTIVE

To investigate the response of anorexigenic oxytocin to food intake among adolescents and young adults with avoidant/restrictive food intake disorder (ARFID), a restrictive eating disorder characterized by lack of interest in food or eating, sensory sensitivity to food, and/or fear of aversive consequences of eating, compared with healthy controls (HC).

DESIGN

Cross-sectional.

METHODS

A total of 109 participants (54 with ARFID spectrum and 55 HC) were instructed to eat a ∼400-kcal standardized mixed meal. We sampled serum oxytocin at fasting and at 30-, 60-, and 120-min postmeal. We tested the hypothesis that ARFID would show higher mean oxytocin levels across time points compared with HC using a mixed model ANOVA. We then used multivariate regression analysis to identify the impact of clinical characteristics (sex, age, and body mass index [BMI] percentile) on oxytocin levels in individuals with ARFID.

RESULTS

Participants with ARFID exhibited greater mean oxytocin levels at all time points compared with HC, and these differences remained significant even after controlling for sex and BMI percentile (P = .004). Clinical variables (sex, age, and BMI percentile) did not show any impact on fasting and postprandial oxytocin levels among individuals with ARFID.

CONCLUSIONS

Consistently high oxytocin levels might be involved in low appetite and sensory aversions to food, contributing to food avoidance in individuals with ARFID.

Impact of virtual adjunctive cognitive remediation therapy on cognitive flexibility and treatment outcomes in comorbid anorexia nervosa and exercise dependence as quantified using novel biomarkers: A stage 1 registered report

OBJECTIVE

Anorexia nervosa (AN) is associated with significant individual mental and physical suffering and public health burden and fewer than half of patients recover fully with current treatments. Comorbid exercise dependence (ExD) is common in AN and associated with significantly worse symptom severity and treatment outcomes. Research points to cognitive inflexibility as a prominent executive function inefficiency and transdiagnostic etiologic and maintaining mechanism linking AN and ExD. This study will evaluate the initial efficacy of adjunctive Cognitive Remediation Therapy (CRT), which has been shown to produce cognitive improvements in adults with AN, in targeting cognitive inflexibility in individuals with comorbid AN and ExD. As an exploratory aim, this study also addresses the current lack of quick and cost-effective assessments of cognitive flexibility by establishing the utility of two proposed biomarkers, heart rate variability and salivary oxytocin.

METHOD

We will conduct a single-group, within-subjects trial of an established CRT protocol delivered remotely as an adjunct to inpatient or intensive outpatient treatment as usual (TAU) to adult patients (n = 42) with comorbid AN and ExD. Assessments, including self-report, neuropsychological, and biomarker measurements, will occur at three time points.

RESULTS

We expect CRT to increase cognitive flexibility transdiagnostically and consequently, along with TAU, positively impact AN and ExD compulsivity and symptom severity, including weight gain.

DISCUSSION

Findings will inform the development of more effective integrative interventions for AN and ExD targeting shared mechanisms and facilitate the routine assessment of cognitive flexibility as a transdiagnostic risk and maintaining factor across psychopathologies in clinical and research settings.

PUBLIC SIGNIFICANCE

Patients with anorexia nervosa often engage in excessive exercise, leading to harmful outcomes, including increased suicidal behavior. This study examines the preliminary efficacy of an intervention that fosters flexible and holistic thinking in patients with problematic eating and exercise to, along with routine treatment, decrease harmful exercise symptoms. This study also examines new biological markers of the inflexible thinking style thought to be characteristic of anorexia nervosa and exercise dependence.

Association between serum oxytocin levels and depressive state in community-dwelling older adults: A cross-sectional study

Aim

Identifying peripheral biomarkers related to the prevention or modification of unhealthy mental conditions in older adults would be extremely beneficial. This study aimed to evaluate serum oxytocin levels in older adults living in a rural community and their association with cognitive function, anxiety, depressive state, and well-being.

Methods

This survey was conducted between November 2016 and September 2017 in Kurokawa-cho, Imari, Saga Prefecture, Japan, among people aged ≥65 years. Blood samples were collected from the participants for serum oxytocin level analysis, which was performed using peptide enzyme immunoassay. Participants underwent neuropsychological assessments, including the Mini-Mental State Examination, Clinical Dementia Rating, Frontal Assessment Battery, State-Trait Anxiety Inventory, 15-item Geriatric Depression Scale, and 17-item Philadelphia Geriatric Center Morale Scale. We examined the association between serum oxytocin levels and neuropsychological assessment results.

Results

Out of 94 participants, 25 were men and 69 were women, with mean ages of 78.24 ± 3.85 years and 78.10 ± 5.43 years, respectively. Serum oxytocin levels were negatively associated with 15-item Geriatric Depression Scale scores. Additionally, nondepressive state/depressive state was classified by the 15-item Geriatric Depression Scale (cut-off 5/6). Logistic regression analysis showed that higher serum oxytocin levels tended to be associated with a less depressive state at that time.

Conclusions

Serum oxytocin levels may be associated with depressive state in adults aged ≥65 years.

Oxytocin: An Old Hormone, A Novel Psychotropic Drug And Possible Use In Treating Psychiatric Disorders

BACKGROUND

Oxytocin is a nonapeptide synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Historically, this molecule has been involved as a key factor in the formation of infant attachment, maternal behavior and pair bonding and, more generally, in linking social signals with cognition, behaviors and reward. In the last decades, the whole oxytocin system has gained a growing interest as it was proposed to be implicated in etiopathogenesis of several neurodevelopmental and neuropsychiatric disorders.

METHODS

With the main goal of an in-depth understanding of the oxytocin role in the regulation of different functions and complex behaviors as well as its intriguing implications in different neuropsychiatric disorders, we performed a critical review of the current state of art. We carried out this work through PubMed database up to June 2021 with the search terms: 1) "oxytocin and neuropsychiatric disorders"; 2) "oxytocin and neurodevelopmental disorders"; 3) "oxytocin and anorexia"; 4) "oxytocin and eating disorders"; 5) "oxytocin and obsessive-compulsive disorder"; 6) "oxytocin and schizophrenia"; 7) "oxytocin and depression"; 8) "oxytocin and bipolar disorder"; 9) "oxytocin and psychosis"; 10) "oxytocin and anxiety"; 11) "oxytocin and personality disorder"; 12) "oxytocin and PTSD".

RESULTS

Biological, genetic, and epigenetic studies highlighted quality and quantity modifications in the expression of oxytocin peptide or in oxytocin receptor isoforms. These alterations would seem to be correlated with a higher risk of presenting several neuropsychiatric disorders belonging to different psychopathological spectra. Collaterally, the exogenous oxytocin administration has shown to ameliorate many neuropsychiatric clinical conditions.

CONCLUSION

Finally, we briefly analyzed the potential pharmacological use of oxytocin in patient with severe symptomatic SARS-CoV-2 infection due to its anti-inflammatory, anti-oxidative and immunoregulatory properties.

Peripheral oxytocin concentrations in psychiatric disorders - A systematic review and methanalysis: Further evidence

Increased interest in understanding how changes in the oxytocinergic system are associated with the etiology and progression of psychiatric disorders has currently boosted the publication of studies. We present a systematic literature review followed by meta-analyses assessing whether peripheral oxytocin (OXT) levels among psychiatric patients differ from healthy controls, considering the moderating role of methodological aspects and samples' characteristics. The following electronic databases were searched: PubMed, Web of Science, PsycINFO, SciELO, LILACS, and Scopus. Fifty-five papers were included in the analysis, and nine independent meta-analyses were performed according to the different diagnoses. Lower OXT concentrations were found in groups of specific disorders (i.e., schizophrenia, restricting and binge-eating/purging subtypes of anorexia nervosa, and borderline personality disorder) with medium to large effect sizes. Great heterogeneity was found among the studies, so that caution is needed to interpret the results. High OXT levels with an effect size of the same magnitude were found for bipolar disorder - type I and obsessive disorder. In contrast, no differences were found for bulimia, autism spectrum, depression, or social anxiety. No meta-analyses were performed for body dysmorphic disorder, post-traumatic stress disorder, or trichotillomania because only one study was identified for each of these disorders. Altered endogenous OXT concentrations are found in several disorders addressed and must be analyzed according to each disorder's specificities.

Possible oxytocin-related biomarkers in anxiety and mood disorders

Anxiety and mood disorders are prevalent, disabling, and frequently difficult to treat. Such disorders are often comorbid and share similar characteristics. For more accurate diagnosis and improved treatment, a deeper understanding of the pathophysiology of anxiety and mood disorders is important. Oxytocin, a neuropeptide synthesized in the hypothalamus, affects human psychology and behaviors such as social and affiliative behaviors, fear and emotion processing, and stress regulation. Thus, oxytocin is believed to exert anxiolytic and antidepressant-like effects. This review article provides an overview of clinical studies on relationships between the oxytocin system and anxiety and mood disorders, focusing on oxytocin-related biomarker findings. Biomarkers used in such studies include central and peripheral oxytocin levels, analysis of oxytocin-related genes, and expression levels of oxytocin and oxytocin receptor genes in postmortem brains. Although a growing number of studies support the presence of oxytocinergic effects on anxiety and mood disorders, study results are heterogeneous and inconclusive. Moderating factors such as the characteristics of study populations, including sex, age, context, early life adversity, and attachment styles in patient cohorts, might affect the heterogeneity of the study results. Limitations in existing research such as small sample sizes, large dependence on peripheral sources of oxytocin, and inconsistent results between immunoassay methods complicate the interpretation of existing findings.

Salivary oxytocin in autistic patients and in patients with intellectual disability

BACKGROUND

Assessing the role of oxytocin (OT) in the regulation of social interaction is a promising area that opens up new opportunities for studying the mechanisms of developing autism spectrum disorders (ASD).

AIM

To assess the correlation between the salivary OT level and age-related and psychopathological symptoms of children with intellectual disability (ID) and ASD.

METHODS

We used the clinical and psychopathological method to assess the signs of ASD based on International Classification of Diseases (ICD-10), the severity of ASD was specified by the selected Russian type version "Childhood Autism Rating Scale" (CARS). Patients of both groups had an IQ score below 70 points.

RESULTS

The median and interquartile range of salivary OT levels in patients with ID and ASD were 23.897 [14.260-59.643] pg/mL, and in the group ID without ASD - Me = 50.896 [33.502-83.774] pg/mL (p = 0.001). The severity of ASD on the CARS scale Me = 51.5 [40.75-56.0] score in the group ID with ASD, and in the group ID without ASD-at the level of Me = 32 [27.0-38.0] points (p < 0.001). According to the results of correlation-regression analysis in the main group, a direct correlation was established between salivary OT level and a high degree of severity of ASD Rho = 0.435 (p = 0.005). There was no correlation between the salivary OT level and intellectual development in the group ID with ASD, Rho = 0.013 (p = 0.941) and we have found a relationship between oxytocin and intellectual development in the group ID without ASD, Rho = 0.297 (p = 0.005). There was no correlation between salivary OT and age, ASD and age.

CONCLUSION

The results of this study indicate that patients in the group ID with ASD demonstrated a lower level of salivary OT concentration and a direct relationship between the maximum values of this indicator and the severity of autistic disorders, in contrast to patients in the group ID without ASD.

Low oxytocin levels are broadly associated with more pronounced psychopathology in anorexia nervosa with primarily restricting but not binge/purge eating behavior

OBJECTIVE

Anorexia nervosa (AN) is commonly associated with depression, anxiety, and deficits in socioemotional functioning. Basal levels of oxytocin, a neurohormone with antidepressant, anxiolytic, and prosocial properties, are low in women with AN. However, the relationship between oxytocin and psychopathology of AN/atypical AN has not been examined in individuals with primarily food restriction (AN/AtypAN-R) or those with restriction plus binge/purge behaviors (AN/AtypAN-BP) alone, which is important to further elucidate the neurobiology of different AN presentations. We investigated whether oxytocin levels are related to eating, affective, and socioemotional psychopathology in women with AN/AtypAN-R and separately AN/AtypAN-BP.

METHODS

In a cross-sectional study of 53 women with low-weight AN or atypical AN based on DSM-5 (AN/AtypAN-R: n=21, AN/AtypAN-BP: n=32), we obtained fasting serum oxytocin levels and self-report measures of psychopathology, including the Eating Disorder Examination-Questionnaire (EDE-Q), Beck Depression Inventory-IA (BDI), State-Trait Anxiety Inventory (STAI), and Toronto Alexithymia Scale (TAS-20).

RESULTS

In individuals with AN/AtypAN-R, oxytocin levels were negatively associated with eating psychopathology (EDE-Q Global Score: r=-0.49, p=0.024), depressive and anxiety symptoms (BDI Total Score: r=-0.55, p=0.009; STAI Trait Score: r=-0.63, p=0.002), and socioemotional symptoms (TAS-20 Difficulty Identifying Feelings Score: r=-0.49, p=0.023). In contrast, in those with AN/AtypAN-BP oxytocin levels were negatively associated with depressive symptoms only (BDI Total Score: r=-0.52, p=0.049).

CONCLUSIONS

These findings support the notion that AN/AtypAN-R and AN/AtypAN-BP might have divergent underlying neurobiology. Understanding these differences is crucial to develop targeted treatments for a population with high levels of chronicity, for which no specific pharmacological treatments are currently available.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov, identifier: NCT01121211.

Review of eating disorders and oxytocin receptor polymorphisms

BACKGROUND AND AIMS

Oxytocin, a nine amino acid peptide synthesised in the hypothalamus, has been widely recognised for its role in anxiolysis, bonding, sociality, and appetite. It binds to the oxytocin receptor (OXTR)-a G-protein coupled receptor-that is stimulated by the actions of oestrogen both peripherally and centrally. Studies have implicated OXTR genotypes in conferring either a risk or protective effect in autism, schizophrenia, and eating disorders (ED). There are numerous DNA variations of this receptor, with the most common DNA variation being in the form of the single nucleotide polymorphisms (SNPs). Two OXTR SNPs have been most studied in relation to ED: rs53576 and rs2254298. Each SNP has the same allelic variant that produces genotypes AA, AG, and GG. In this critical review we will evaluate the putative role of rs53576 and rs2254298 SNPs in ED. Additionally, this narrative review will consider the role of gene-environment interactions in the development of ED pathology.

FINDINGS

The OXTR SNPs rs53576 and rs2254298 show independent associations between the A allele and restrictive eating behaviours. Conversely, the G allele of the OXTR rs53576 SNP is associated with binging behaviours, findings that were also evident in neuroanatomy. One study found the A allele of both OXTR SNPs to confer risk for more severe ED symptomatology while the G allele conferred some protective effect. An interaction between poor maternal care and rs2254298 AG/AA genotype conferred increased risk for binge eating and purging in women.

CONCLUSIONS

Individual OXTR SNP are unlikely in themselves to explain complex eating disorders but may affect the expression of and/or effectiveness of the OXTR. A growing body of G x E work is indicating that rs53576G homozygosity becomes disadvantageous for later mental health under early adverse conditions but further research to extend these findings to eating pathology is needed. The GWAS approach would benefit this area of knowledge.

The Female Athlete Triad/Relative Energy Deficiency in Sports (RED-S)

In a healthy athlete, the caloric intake is sufficient for sports energy needs and body physiological functions, allowing a balance between energy availability, bone metabolism, and menstrual cycle. On the other hand, an imbalance caused by low energy availability due to a restrictive diet, eating disorders or long periods of energy expenditure leads to multisystemic deregulation favoring the essential functions of the body. This phenomenon, described as the female athlete triad, occurs in a considerable percentage of high-performance athletes, with harmful consequences for their future. The present review was carried out based on a critical analysis of the most recent publications available and aims to provide a global perception of the topic relative energy deficit in sport (RED-S). The objective is to promote the acquisition of more consolidated knowledge on an undervalued theme, enabling the acquisition of preventive strategies, early diagnosis and/or appropriate treatment.

Oxytocin, eating behavior, and metabolism in humans

The hypothalamic peptide oxytocin has been increasingly recognized as a hormone and neurotransmitter with important effects on energy intake, metabolism, and body weight and is under investigation as a potential novel therapeutic agent for obesity. The main neurons producing oxytocin and expressing the oxytocin receptor are strategically located in brain areas known to be critically involved in homeostatic energy balance as well as hedonic and motivational aspects of eating behavior. In this chapter, we will review the central and peripheral physiology of oxytocin and the interaction of oxytocin with key hormones and neural circuitries that affect food intake and metabolism. Next, we will synthesize the available data on endogenous oxytocin levels related to caloric intake, body weight, and metabolic status. We will then review the effects of exogenous oxytocin administration on eating behavior, body weight, and metabolism in humans, including in healthy individuals as well as specific populations with suspected perturbations involving oxytocin pathways. Finally, we will address the promise and fundamental challenges of translating this line of research to clinical care.

Potential shortcomings in current studies on the effect of intranasal oxytocin in Anorexia Nervosa and healthy controls - A systematic review and meta-analysis

RATIONALE

The psychopathology of anorexia nervosa (AN) includes altered social cognition and information processing of fear and anxiety. Oxytocin, a neuromodulating hormone, may influence these functions and could be valuable for the treatment of AN.

OBJECTIVE

The current study aimed at reviewing the effect of intranasal oxytocin (IN-OT) on attentional bias (AB) and emotion recognition (ER) in AN.

METHODS

A systematic literature review was done for free-text and the MeSH-terms: anorexia nervosa, feeding and eating disorders, and oxytocin. Six publications, reporting from 4 unique clinical trials, were included in this review. A meta-analysis was conducted to examine the effects of IN-OT on AB towards food images and ER on healthy controls (HC) and patients with AN.

RESULTS

Overall, IN-OT did not influence AB towards food images (effect size = 0.20 [- 0.16, 0.57], p = 0.28) and had no effect on ER (effect size = - 0.01 [- 0.27, 0.26], p = 0.97) in patients with AN and healthy control (HC) subjects collectively. Assessing HC and AN separately in subgroup analyses did not show any significant effect on AB and ER in neither of the subgroups. All tests were done between 15 and 55 min post-administration of IN-OT, while peak concentration in the cerebrospinal fluid has been determined to be at 75 min.

CONCLUSION

The current level of evidence is moderate showing no effect of IN-OT on AB or ER in AN. However, brain exposure may not have been sufficient which future studies with IN-OT need to ensure by considering dose and dose-to-task interval.

Oxytocin and elderly MRI-based hippocampus and amygdala volume: a 7-year follow-up study

Oxytocin is deeply involved in human relations. In recent years, it is becoming clear that oxytocin is also involved in social cognition and social behaviour. Oxytocin receptors are also thought to be present in the hippocampus and amygdala, and the relationship between oxytocin and the structure and function of the hippocampus and amygdala has been reported. However, a few studies have investigated oxytocin and its relationship to hippocampus and amygdala volume in elderly people. The aim of this study is to investigate the association between serum oxytocin levels and hippocampus and amygdala volume in elderly people. The survey was conducted twice in Kurokawa-cho, Imari, Saga Prefecture, Japan, among people aged 65 years and older. We collected data from 596 residents. Serum oxytocin level measurements, brain MRI, Mini–Mental State Examination and Clinical Dementia Rating were performed in Time 1 (2009–11). Follow-up brain MRI, Mini–Mental State Examination and Clinical Dementia Rating were performed in Time 2 (2016–17). The interval between Time 1 and Time 2 was about 7 years. Fifty-eight participants (14 men, mean age 72.36 ± 3.41 years, oxytocin 0.042 ± 0.052 ng/ml; 44 women, mean age 73.07 ± 4.38 years, oxytocin 0.123 ± 0.130 ng/ml) completed this study. We analysed the correlation between serum oxytocin levels (Time 1) and brain volume (Time 1, Time 2 and Times 1–2 difference) using voxel-based morphometry implemented with Statistical Parametric Mapping. Analysis at the cluster level (family-wise error; P < 0.05) showed a positive correlation between serum oxytocin levels (Time 1) and brain volume of the region containing the left hippocampus and amygdala (Time 2). This result suggests that oxytocin in people aged 65 years and older may be associated with aging-related changes in hippocampus and amygdala volume.

Methylation of the OXTR gene in women with anorexia nervosa: Relationship to social behavior

DNA methylation allows for the environmental regulation of gene expression and is believed to link environmental stressors to psychiatric disorder phenotypes, such as anorexia nervosa (AN). The oxytocin receptor (OXTR) gene is epigenetically regulated, and studies have shown associations between OXTR and social behaviours in various samples, including women with AN. The present study examined differential levels of methylation at various CG sites of the OXTR gene in 69 women with active AN (AN-Active), 21 in whom AN was in remission (AN-Rem) and 35 with no eating disorder (NED). Within each group, we explored the correlation between methylation and measures of social behaviour such as insecure attachment and social avoidance. Hypermethylation of a number of CG sites was seen in AN-Active participants as compared with AN-Rem and NED participants. In the AN-Rem sample, methylation at CG27501759 was significantly positively correlated with insecure attachment (r = .614, p = .003, permutation Q = 0.008) and social avoidance (r = .588, p = .005, permutation Q = 0.0184). Our results highlight differential methylation of the OXTR gene among women with AN, those in remission from AN, and those who never had AN and provide some evidence of associations between OXTR methylation and social behaviour in women remitted from AN.

Serum oxytocin levels are elevated in body dysmorphic disorder and related to severity of psychopathology

The neurobiological mechanisms underlying the pathophysiology of body dysmorphic disorder (BDD) are not well-understood. Oxytocin is a central nervous system peptide which regulates socioemotional functioning and may mediate physiologic processes in a range of psychiatric disorders, particularly those characterized by interpersonal dysfunction. Examining the role of oxytocin in the development and maintenance of BDD may elucidate new targets for intervention. The present study examined endogenous serum oxytocin levels in BDD. Given the prominent deficits in social functioning in BDD, we expected that BDD would be characterized by low basal serum oxytocin concentrations, relative to healthy controls, and that low oxytocin levels would be associated with BDD symptom severity as well as poor performance on measures of social cognition. Twenty individuals with BDD and 28 healthy controls completed a fasting blood draw consisting of frequent sampling every five minutes for one hour to measure pooled levels of oxytocin. Contrary to our hypotheses, people with BDD displayed higher concentrations of oxytocin, compared to their healthy control counterparts, and their oxytocin levels were positively correlated with BDD symptom severity. There were no associations between oxytocin levels and measures of social cognition. These findings suggest increased production of endogenous oxytocin in BDD. Prospective research is needed to determine whether this contributes to or is a consequence of BDD symptomatology.

Disrupted Oxytocin-Appetite Signaling in Females With Anorexia Nervosa

CONTEXT

In healthy females, oxytocin levels decrease postmeal, corresponding to increased satiety. The postprandial response of oxytocin in females with anorexia nervosa (AN)/atypical AN is unknown.

OBJECTIVES

To determine the pattern of postprandial serum oxytocin levels in females with AN/atypical AN, relationship with appetite, and effect of weight, eating behavior, and endogenous estrogen status.

DESIGN

Cross-sectional.

SETTING

Clinical research center.

PARTICIPANTS

67 women (36 with AN [<85% expected body weight (EBW)]; 31 with atypical AN [≥ 85% EBW)]), age 22.4 ± 0.9 (mean ± SEM) years, categorized by weight, restricting vs binge/purge behavior, and estrogen status.

INTERVENTIONS

Standardized mixed meal.

MAIN OUTCOME MEASUREMENTS

Blood sampling for oxytocin occurred fasting and 30, 60, and 120 minutes postmeal. Subjective appetite was assessed using visual analog scales.

RESULTS

In females with AN/atypical AN, oxytocin levels decreased from fasting to 60 (P = 0.002) and 120 (P = 0.005) minutes postmeal. The decrease in oxytocin from fasting to 120 minutes was greater in females with atypical AN than AN (P = 0.027) and did not differ by restricting vs binge/purge behavior or estrogen status. Controlling for caloric intake, the decrease in oxytocin was inversely related to the decrease in hunger postmeal in females with atypical AN (P = 0.04).

CONCLUSIONS

In females with AN/atypical AN, oxytocin levels decrease postmeal, as established in healthy females. Weight, but not restricting vs binge/purging nor endogenous estrogen status, affects postprandial oxytocin levels. The postprandial change in serum oxytocin levels is related to appetite in females with atypical AN only, suggesting a disconnect between oxytocin secretion and appetite in the undernourished state.

Low Plasma Oxytocin Levels and Increased Psychopathology in Hypopituitary Men With Diabetes Insipidus

CONTEXT

Oxytocin (OT) and vasopressin share anatomical pathways of synthesis and secretion, and patients with central diabetes insipidus (CDI) presumably are at risk for OT deficiency. However, an OT-deficient state in hypopituitary patients has not been established.

OBJECTIVES

We hypothesized that men with CDI compared to patients with similar anterior pituitary deficiencies (APD) but no CDI and healthy controls (HC) of similar age and body mass index, would have lower plasma OT levels, associated with increased psychopathology.

DESIGN

Cross-sectional.

SETTING

Clinical research center.

PARTICIPANTS

Sixty-two men (20 CDI, 20 APD, 22 HC), age 18 to 60 years.

INTERVENTIONS

Frequent sampling of blood every 5 minutes for OT over 1 hour and validated questionnaires to assess psychopathology.

MAIN OUTCOMES

Pooled plasma OT levels; depressive, anxiety, and alexithymia symptoms; and quality of life.

RESULTS

The mean 1-hour pool of fasting OT levels was lower in CDI compared with APD and HC (P = 0.02 and P = 0.009, respectively), with no differences between APD and HC (P = 0.78). Symptoms of depression, anxiety, and alexithymia were more pronounced in CDI than in HC (P = 0.001, P = 0.004, and P = 0.02, respectively). Although CDI and APD reported worse physical health compared with HC (P = 0.001 and P = 0.005) with no differences between APD and CDI, only CDI reported worse mental health compared with HC (P = 0.009).

CONCLUSIONS

We have demonstrated low plasma OT levels and increased psychopathology in hypopituitary men with CDI, suggestive of a possible OT-deficient state. Larger studies of both sexes are required to confirm these findings and clinically characterize hypopituitary patients with OT deficiency.

The effect of intranasal oxytocin on the perception of affective touch and multisensory integration in anorexia nervosa: protocol for a double-blind placebo-controlled crossover study

INTRODUCTION

Anorexia nervosa (AN) is an eating disorder characterised by restriction of energy intake, fears of gaining weight and related body image disturbances. The oxytocinergic system has been proposed as a pathophysiological candidate for AN. Oxytocin is a neuropeptide involved in bodily processes (eg, breast feeding) and in the onset of social behaviours (eg, bonding). Studies investigating the effect of intranasal oxytocin (IN-OT) in AN showed that it can improve attentional bias for high-calorie food and fat bodies stimuli, and related stress. However, less is known about the effect of IN-OT on bodily awareness and body image distortions, key features of the disorder linked to its development, prognosis and maintenance. Here, we aim to investigate the effect of IN-OT on the perception of affective, C-tactile-optimal touch, known to be impaired in AN and on multisensory integration processes underlying a body ownership illusion (ie, rubber hand illusion). For exploratory purposes, we will also investigate the effect of IN-OT on another interoceptive modality, namely cardiac awareness and its relationship with affective touch.

DESIGN, METHODS AND ANALYSIS

Forty women with AN and forty matched healthy controls will be recruited and tested in two separate sessions; self-administering IN-OT (40 IU) or placebo, intranasally, in a pseudo-randomised manner. The data from this double-blind, placebo-controlled, cross-over study will be analysed using linear mixed models that allow the use of both fixed (treatment levels) and random (subjects) effects in the same analysis. To address our main hypotheses, separate analyses will be run for the affective touch task, where the primary outcome dependent variable will be the pleasantness of the touch, and for the rubber hand illusion, where we will investigate multisensory integration quantified as subjective embodiment towards the rubber hand. In the latter, we will manipulate the synchronicity of touch and the size of the hand.

ETHICS AND DISSEMINATION

Ethics approval has been obtained by National Research Ethics Service NRES Committee London (Queen's Square Committee, ref number 14/LO/1593). The results will be disseminated through conference presentations and publication in peer-reviewed journals.

MECHANISMS IN ENDOCRINOLOGY: Anorexia nervosa and endocrinology: a clinical update

Anorexia nervosa is a syndrome, that is collections of symptoms, which is not defined by its etiology. The severe cases are intractable. The syndrome is associated with multiple, profound endocrine alterations which may be adaptive, reactive or etiologic. Adaptive changes potentially may be inappropriate in clinical settings such as inpatient intensive re-nutrition or in a setting with somatic comorbidity. Electrolyte levels must be closely monitored during the refeeding process, and the need for weight gain must be balanced against potentially fatal refeeding complications. An important focus of clinical research should be to identify biomarkers associated with different stages of weight loss and re-nutrition combined with psychometric data. Besides well-established peripheral endocrine actions, several hormones also are released directly to different brain areas, where they may exert behavioral and psychogenic actions that could offer therapeutic targets. We need reliable biomarkers for predicting outcome and to ensure safe re-nutrition, however, first of all we need them to explore the metabolism in anorexia nervosa to open new avenues with therapeutic targets. A breakthrough in our understanding and treatment of this whimsical disease remains. Considering this, the aim of the present review is to provide an updated overview of the many endocrine changes in a clinical perspective.

Brain-Derived Neurotrophic Factor and Oxytocin Signaling in Association With Clinical Symptoms in Adolescent Inpatients With Anorexia Nervosa-A Longitudinal Study

INTRODUCTION

Brain-derived neurotrophic factor (BDNF), as well as oxytocin (OXY), are centrally secreted neuropeptides regulating a range of physiological processes, including food intake and metabolism. Moreover, numerous reports suggest their role in affective and cognitive symptoms of various psychiatric disorders. Thus, the study aimed to measure the serum level of BDNF and its receptor-tropomyosin-related kinase B (TrkB) and OXY in the malnourished anorexia nervosa patients and following partial weight-recovery. The correlations between levels of these proteins with the primary symptoms of the anorexia nervosa (AN) were also analyzed.

METHODOLOGY

Eighty-four adolescent AN patients were recruited into the study, but only forty-two AN patients completed it. The control group comprises of thirty age- and height-matched girls (CG). Serum BDNF, TrkB, and OXY levels were measured in AN group in two time-points-at the beginning of the hospitalization in malnourished patients (AN-T1) and again after partial weight normalization, on the day of discharge (AN-T2). The severity of eating disorders, as well as depressive and obsessive-compulsive symptoms, were assessed at the same two-time points.

RESULTS

Body mass index (BMI) differed significantly between the AN-T1, AN-T2, and CG. BDNF levels for the AN-T2 increased significantly in comparison to the AN-T1, but at two-time points were significantly lower than in the CG. The OXY level did not change with weight gain and in both groups AN-T1 and AN-T2 were statistically significantly higher than in the CG. Statistically significant negative correlations between BDNF and the severity of eating disorders symptoms were found. Depressive and obsessive-compulsive symptoms did not show significant correlations with levels of studied proteins for either malnourished or partially weight recovered AN patients.

CONCLUSIONS

BDNF serum levels were decreased in the malnourished AN patients and tended to normalize with partial weight recovery. OXY serum levels were found to be increased in the malnourished AN patients and did not normalize with partial weight recovery, confirming previous reports about its role in the etiopathogenesis of AN. BDNF can be related to aberrant eating behaviors occurring in AN. Our results do not support the role of serum levels of BDNF, TrkB, or OXY in the modulation of depressive or obsessive-compulsive symptoms.

The Neuropeptide Hormone Oxytocin in Eating Disorders

PURPOSE OF REVIEW

The neurohormone oxytocin (OXT) impacts food intake as well as cognitive, emotional, and social functioning-all of which are central to eating disorder (ED) pathology across the weight spectrum. Here, we review findings on endogenous OXT levels and their relationship to ED pathology, the impact of exogenous OXT on mechanisms that drive ED presentation and chronicity, and the potential role of genetic predispositions in the OXT-ED link.

RECENT FINDINGS

Current findings suggest a role of the OXT system in the pathophysiology of anorexia nervosa. In individuals with bulimia nervosa, endogenous OXT levels were comparable to those of healthy controls, and exogenous OXT reduced food intake. Studies in other ED are lacking. However, genetic studies suggest a broad role of the OXT system in influencing ED pathology. Highlighting findings on why OXT represents a potential biomarker of and treatment target for ED, we advocate for a systematic research approach spanning the entire ED spectrum.

Endocrine Effects of Relative Energy Deficiency in Sport

The term Relative Energy Deficiency in Sport was introduced by the International Olympic Committee in 2014. It refers to the potential health and performance consequences of inadequate energy for sport, emphasizing that there are consequences of low energy availability (EA; typically defined as <30 kcal·kg^-1 fat-free mass·day^-1) beyond the important and well-established female athlete triad, and that low EA affects populations other than women. As the prevalence and consequences of Relative Energy Deficiency in Sport become more apparent, it is important to understand the current knowledge of the hormonal changes that occur with decreased EA. This paper highlights endocrine changes that have been observed in female and male athletes with low EA. Where studies are not available in athletes, results of studies in low EA states, such as anorexia nervosa, are included. Dietary intake/appetite-regulating hormones, insulin and other glucose-regulating hormones, growth hormone and insulin-like growth factor 1, thyroid hormones, cortisol, and gonadal hormones are all discussed. The effects of low EA on body composition, metabolic rate, and bone in female and male athletes are presented, and we identify future directions to address knowledge gaps specific to athletes.

The Oxytocin Receptor: From Intracellular Signaling to Behavior

The many facets of the oxytocin (OXT) system of the brain and periphery elicited nearly 25,000 publications since 1930 (see FIGURE 1 , as listed in PubMed), which revealed central roles for OXT and its receptor (OXTR) in reproduction, and social and emotional behaviors in animal and human studies focusing on mental and physical health and disease. In this review, we discuss the mechanisms of OXT expression and release, expression and binding of the OXTR in brain and periphery, OXTR-coupled signaling cascades, and their involvement in behavioral outcomes to assemble a comprehensive picture of the central and peripheral OXT system. Traditionally known for its role in milk let-down and uterine contraction during labor, OXT also has implications in physiological, and also behavioral, aspects of reproduction, such as sexual and maternal behaviors and pair bonding, but also anxiety, trust, sociability, food intake, or even drug abuse. The many facets of OXT are, on a molecular basis, brought about by a single receptor. The OXTR, a 7-transmembrane G protein-coupled receptor capable of binding to either Gαior Gαqproteins, activates a set of signaling cascades, such as the MAPK, PKC, PLC, or CaMK pathways, which converge on transcription factors like CREB or MEF-2. The cellular response to OXT includes regulation of neurite outgrowth, cellular viability, and increased survival. OXTergic projections in the brain represent anxiety and stress-regulating circuits connecting the paraventricular nucleus of the hypothalamus, amygdala, bed nucleus of the stria terminalis, or the medial prefrontal cortex. Which OXT-induced patterns finally alter the behavior of an animal or a human being is still poorly understood, and studying those OXTR-coupled signaling cascades is one initial step toward a better understanding of the molecular background of those behavioral effects.

Oxytocin-like signaling in ants influences metabolic gene expression and locomotor activity

Ants are emerging model systems to study cellular signaling because distinct castes possess different physiologic phenotypes within the same colony. Here we studied the functionality of inotocin signaling, an insect ortholog of mammalian oxytocin (OT), which was recently discovered in ants. In Lasius ants, we determined that specialization within the colony, seasonal factors, and physiologic conditions down-regulated the expression of the OT-like signaling system. Given this natural variation, we interrogated its function using RNAi knockdowns. Next-generation RNA sequencing of OT-like precursor knock-down ants highlighted its role in the regulation of genes involved in metabolism. Knock-down ants exhibited higher walking activity and increased self-grooming in the brood chamber. We propose that OT-like signaling in ants is important for regulating metabolic processes and locomotion.-Liutkevičiūtė, Z., Gil-Mansilla, E., Eder, T., Casillas-Pérez, B., Di Giglio, M. G., Muratspahić, E., Grebien, F., Rattei, T., Muttenthaler, M., Cremer, S., Gruber, C. W. Oxytocin-like signaling in ants influences metabolic gene expression and locomotor activity.

Toward valid and reliable brain imaging results in eating disorders

Human brain imaging can help improve our understanding of mechanisms underlying brain function and how they drive behavior in health and disease. Such knowledge may eventually help us to devise better treatments for psychiatric disorders. However, the brain imaging literature in psychiatry and especially eating disorders has been inconsistent, and studies are often difficult to replicate. The extent or severity of extremes of eating and state of illness, which are often associated with differences in, for instance hormonal status, comorbidity, and medication use, commonly differ between studies and likely add to variation across study results. Those effects are in addition to the well-described problems arising from differences in task designs, data quality control procedures, image data preprocessing and analysis or statistical thresholds applied across studies. Which of those factors are most relevant to improve reproducibility is still a question for debate and further research. Here we propose guidelines for brain imaging research in eating disorders to acquire valid results that are more reliable and clinically useful.

De-masking oxytocin-deficiency in craniopharyngioma and assessing its link with affective function

Despite the high prevalence of panhypopituitarism and diabetes insipidus in patients with craniopharyngioma (CP), little is known about the functioning of the neuropeptide oxytocin in these patients. This is of special interest as tumor-associated lesions often impair sites critical for oxytocin production and release, and affective dysfunction in CP links with elsewhere reported prosocial, antidepressant and anxiolytic oxytocin effects. Using a prospective study-design, we tested whether oxytocin is reduced in CP-patients, and whether altered oxytocin levels account for affective and emotional dysfunction. 26 adult CP-patients and 26 healthy controls matched in sex and age underwent physical exercise, a stimulus previously shown to induce oxytocin release. Baseline and stimulated salivary oxytocin levels, as well as empathy, depression and anxiety scores were measured. Results showed that patients overall did not present with lower baseline oxytocin levels than controls (F[1,30]=0.21, p=0.649), but baseline oxytocin levels were indeed reduced in patients with hypothalamic damage, as assessed by MRI-based grading (F[2,9.79]=4.54, p=0.040). In response to exercise-induced stimulation, all CP-patients showed a blunted oxytocin-release compared to controls (F[1,30]=9.36, p=0.005). DI was not associated with oxytocin levels. Regarding affective function, unexpectedly, higher baseline oxytocin was related to higher trait anxiety (b=2.885, t(43)=2.421, p=0.020, CI[.478; 5.292]); the positive link with higher depression failed to reach statistical significance (b=1.928, t(43)=1.949, p=0.058, CI[-0.070; 3.927]). A blunted oxytocin-release was linked with higher state anxiety (b=-0.133, t(43)=-2.797, p=0.008, CI[-0.230; -0.037]). Empathy was not associated with oxytocin measures. In conclusion, we observed reduced baseline oxytocin levels only in CP-patients with hypothalamic damage. Exercise-induced stimulation de-masked an oxytocin-deficiency in all CP-patients. Baseline oxytocin levels and stimulated OT-responses might have different effects on affective function, which should be considered in future substitution paradigms.

Oxytocin and Eating Disorders: A Narrative Review on Emerging Findings and Perspectives

BACKGROUND

The hypothalamic neuropeptide oxytocin regulates reproductive behavior and mother-infant interaction, and conclusive studies in humans indicate that oxytocin is also a potent modulator of psychosocial function. Pilot experiments have yielded first evidence that this neuropeptide moreover influences eating behavior.

METHODS

We briefly summarize currently available studies on the involvement of the oxytocin system in the pathophysiology of eating disorders, as well as on the effects of oxytocin administration in patients with these disorders.

RESULTS

Brain administration of oxytocin in animals with normal weight, but also with diet-induced or genetically induced obesity, attenuates food intake and reduces body weight. In normal-weight and obese individuals, acute intranasal oxytocin delivery curbs calorie intake from main dishes and snacks. Such effects might converge with the poignant social and cognitive impact of oxytocin to also improve dysfunctional eating behavior in the therapeutic context. This assumption has received support in first studies showing that oxytocin might play a role in the disease process of anorexia nervosa. In contrast, respective experiments in patients with bulimia nervosa and binge eating disorder are still scarce.

CONCLUSIONS

We propose a framework of oxytocin's role and its therapeutic potential in eating disorders that aims at integrating social and metabolic aspects of its pharmacological profile, and ponder perspectives and limitations of oxytocin use in the clinical setting.

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.

Low oxytocin levels are related to alexithymia in anorexia nervosa

OBJECTIVE

Anorexia nervosa is associated with social-emotional functioning deficits and low levels of the social neurohormone oxytocin, even after weight gain. The relationship between low oxytocin levels and social-emotional functioning impairment has not been studied.

METHOD

We performed a cross-sectional study of 79 women (19 who were less than 85% of ideal body weight [IBW] with anorexia nervosa [AN], 26 who were 90-120% IBW with a history of AN [AN-WR], and 34 who were 90-120% IBW with no eating disorder history [H]). We administered the Eating Disorder Examination-Questionnaire (EDE-Q), Leibowitz Social Anxiety Scale-Self Report (LSAS-SR), Dimensional Assessment of Personality Pathology-Basic Questionnaire (DAPP-BQ; suspiciousness and insecure attachment subscales), and the Toronto Alexithymia Scale (TAS-20). We also analyzed fasting serum oxytocin levels.

RESULTS

Most measures of social-emotional functioning showed impairment in women with AN and AN-WR compared to H. Oxytocin levels were low in AN-WR compared to H. Across groups, low oxytocin levels were associated with difficulty identifying feelings (r = -.45, p = .008) and overall alexithymia (r = -.34, p = .0489).

DISCUSSION

We speculate that low oxytocin levels may contribute to alexithymia in women with anorexia nervosa.

Association Between Oxytocin Receptor Genotype, Maternal Care, and Eating Disorder Behaviours in a Community Sample of Women

This study aimed to investigate associations between oxytocin receptor gene (OXT-R) polymorphisms (rs53576 and rs2254298), their interaction with maternal care (GxE), and ED behaviours in a community sample. We studied 3698 women from the Avon Longitudinal Study of Parents and Children (ALSPAC) who participated in a two-phase prevalence study of lifetime ED and had genotype data. The GG rs53576 genotype was associated with binge eating and purging, and the rs2254298 AG/AA genotype with restrictive eating lifetime. In addition, the rs2254298 AG/AA genotype interacted with poor maternal care to increase the odds of binge eating and purging (odds ratio = 4.40 (95% confidence intervals: 1.11-17.4)). This study replicates previous findings of an association between OXT-R polymorphisms and ED, and it is the first to show an interaction between OXT-R genotype and poor maternal care. As such, these findings highlight the important role of oxytocin in understanding the pathophysiology of ED. © 2016 The Authors European Eating Disorders Review published by Eating Disorders Association and John Wiley & Sons Ltd.