Sex differences in associations of arginine vasopressin and oxytocin with resting-state functional brain connectivity

Correlation Between Cortical Thickness Abnormalities of the Olfactory Sulcus and Olfactory Identification Disorder and Persistent Auditory Verbal Hallucinations in Chinese Patients With Chronic Schizophrenia

BACKGROUND AND HYPOTHESIS

Persistent auditory verbal hallucinations (pAVHs) and olfactory identification impairment are common in schizophrenia (SCZ), but the neuroimaging mechanisms underlying both pAVHs and olfactory identification impairment are unclear. This study aimed to investigate whether pAVHs and olfactory identification impairment in SCZ patients are associated with changes in cortical thickness.

STUDY DESIGN

In this study, cortical thickness was investigated in 78 SCZ patients with pAVHs (pAVH group), 58 SCZ patients without AVHs (non-AVH group), and 83 healthy controls (HC group) using 3T magnetic resonance imaging. The severity of pAVHs was assessed by the Auditory Hallucination Rating Scale. Olfactory identification deficits were assessed using the Odor Stick Identification Test for Japanese (OSIT-J). In addition, the relationship between the severity of pAVHs and olfactory identification disorder and cortical thickness abnormalities was determined.

STUDY RESULTS

Significant reductions in cortical thickness were observed in the right medial orbital sulcus (olfactory sulcus) and right orbital sulcus (H-shaped sulcus) in the pAVH group compared to both the non-AVH and HC groups (P < .003, Bonferroni correction). Furthermore, the severity of pAVHs was found to be negatively correlated with the reduction in cortical thickness in the olfactory sulcus and H-shaped sulcus. Additionally, a decrease in cortical thickness in the olfactory sulcus showed a positive correlation with the OSIT-J scores (P < .05, false discovery rate correction).

CONCLUSIONS

Cortical thickness abnormalities in the olfactory sulcus may be a common neuroimaging mechanism for pAVHs and olfactory identification deficits in SCZ patients.

Age- and gender-related dispersion of brain networks across the lifespan

The effects of age and gender on large-scale resting-state networks (RSNs) reflecting within- and between-network connectivity in the healthy brain remain unclear. This study investigated how age and gender influence the brain network roles and topological properties underlying the ageing process. Ten RSNs were constructed based on 998 participants from the REST-meta-MDD cohort. Multivariate linear regression analysis was used to examine the independent and interactive influences of age and gender on large-scale RSNs and their topological properties. A support vector regression model integrating whole-brain network features was used to predict brain age across the lifespan and cognitive decline in an Alzheimer's disease spectrum (ADS) sample. Differential effects of age and gender on brain network roles were demonstrated across the lifespan. Specifically, cingulo-opercular, auditory, and visual (VIS) networks showed more incohesive features reflected by decreased intra-network connectivity with ageing. Further, females displayed distinctive brain network trajectory patterns in middle-early age, showing enhanced network connectivity within the fronto-parietal network (FPN) and salience network (SAN) and weakened network connectivity between the FPN-somatomotor, FPN-VIS, and SAN-VIS networks. Age - but not gender - induced widespread decrease in topological properties of brain networks. Importantly, these differential network features predicted brain age and cognitive impairment in the ADS sample. By showing that age and gender exert specific dispersion of dynamic network roles and trajectories across the lifespan, this study has expanded our understanding of age- and gender-related brain changes with ageing. Moreover, the findings may be useful for detecting early-stage dementia.

Unified topological inference for brain networks in temporal lobe epilepsy using the Wasserstein distance

Persistent homology offers a powerful tool for extracting hidden topological signals from brain networks. It captures the evolution of topological structures across multiple scales, known as filtrations, thereby revealing topological features that persist over these scales. These features are summarized in persistence diagrams, and their dissimilarity is quantified using the Wasserstein distance. However, the Wasserstein distance does not follow a known distribution, posing challenges for the application of existing parametric statistical models. To tackle this issue, we introduce a unified topological inference framework centered on the Wasserstein distance. Our approach has no explicit model and distributional assumptions. The inference is performed in a completely data driven fashion. We apply this method to resting-state functional magnetic resonance images (rs-fMRI) of temporal lobe epilepsy patients collected from two different sites: the University of Wisconsin-Madison and the Medical College of Wisconsin. Importantly, our topological method is robust to variations due to sex and image acquisition, obviating the need to account for these variables as nuisance covariates. We successfully localize the brain regions that contribute the most to topological differences. A MATLAB package used for all analyses in this study is available at https://github.com/laplcebeltrami/PH-STAT.

Hodge Laplacian of Brain Networks

The closed loops or cycles in a brain network embeds higher order signal transmission paths, which provide fundamental insights into the functioning of the brain. In this work, we propose an efficient algorithm for systematic identification and modeling of cycles using persistent homology and the Hodge Laplacian. Various statistical inference procedures on cycles are developed. We validate the our methods on simulations and apply to brain networks obtained through the resting state functional magnetic resonance imaging. The computer codes for the Hodge Laplacian are given in https://github.com/laplcebeltrami/hodge.

Topological data analysis of human brain networks through order statistics

Understanding the common topological characteristics of the human brain network across a population is central to understanding brain functions. The abstraction of human connectome as a graph has been pivotal in gaining insights on the topological properties of the brain network. The development of group-level statistical inference procedures in brain graphs while accounting for the heterogeneity and randomness still remains a difficult task. In this study, we develop a robust statistical framework based on persistent homology using the order statistics for analyzing brain networks. The use of order statistics greatly simplifies the computation of the persistent barcodes. We validate the proposed methods using comprehensive simulation studies and subsequently apply to the resting-state functional magnetic resonance images. We found a statistically significant topological difference between the male and female brain networks.

Effects of exogenous oxytocin and estradiol on resting-state functional connectivity in women and men

Possible interactions of the neuropeptide oxytocin and the sex hormone estradiol may contribute to previously observed sex-specific effects of oxytocin on resting-state functional connectivity (rsFC) of the amygdala and hippocampus. Therefore, we used a placebo-controlled, randomized, parallel-group functional magnetic resonance imaging study design and measured amygdala and hippocampus rsFC in healthy men (n = 116) and free-cycling women (n = 111), who received estradiol gel (2 mg) or placebo before the intranasal administration of oxytocin (24 IU) or placebo. Our results reveal significant interaction effects of sex and treatments on rsFC of the amygdala and hippocampus in a seed-to-voxel analysis. In men, both oxytocin and estradiol significantly decreased rsFC between the left amygdala and the right and left lingual gyrus, the right calcarine fissure, and the right superior parietal gyrus compared to placebo, while the combined treatment produced a significant increase in rsFC. In women, the single treatments significantly increased the rsFC between the right hippocampus and the left anterior cingulate gyrus, whereas the combined treatment had the opposite effect. Collectively, our study indicates that exogenous oxytocin and estradiol have different region-specific effects on rsFC in women and men and that the combined treatment may produce antagonistic effects.

Culture and gender modulate dlPFC integration in the emotional brain: evidence from dynamic causal modeling

Past research has recognized culture and gender variation in the experience of emotion, yet this has not been examined on a level of effective connectivity. To determine culture and gender differences in effective connectivity during emotional experiences, we applied dynamic causal modeling (DCM) to electroencephalography (EEG) measures of brain activity obtained from Chinese and American participants while they watched emotion-evoking images. Relative to US participants, Chinese participants favored a model bearing a more integrated dorsolateral prefrontal cortex (dlPFC) during fear v. neutral experiences. Meanwhile, relative to males, females favored a model bearing a less integrated dlPFC during fear v. neutral experiences. A culture-gender interaction for winning models was also observed; only US participants showed an effect of gender, with US females favoring a model bearing a less integrated dlPFC compared to the other groups. These findings suggest that emotion and its neural correlates depend in part on the cultural background and gender of an individual. To our knowledge, this is also the first study to apply both DCM and EEG measures in examining culture-gender interaction and emotion.

Early Life Trauma and Social Processing in HIV: The Role of Neuroendocrine Factors and Inflammation

OBJECTIVE

Early life trauma (ELT) and HIV are associated with social processing deficits. In people with HIV (PWH), we examined whether facial emotion identification accuracy differs by ELT and whether neuroendocrine factors including cortisol, oxytocin (OT), and arginine vasopressin, and/or immune system measures play a role in the ELT-performance association.

METHODS

We used secondary data from the placebo condition of a pharmacologic challenge study in PWH. Presence of ELT was measured with the Childhood Trauma Questionnaire (at least moderate experiences of sexual, physical, and/or emotional abuse). Social processing was measured with the Facial Emotion Perception Test (FEPT). Salivary immune system measures and cortisol were sampled across a 5-hour study session. Blood was collected at study session start (12 pm ) to measure OT and arginine vasopressin. We examined the association of ELT with FEPT and five biological moderators (from principal components analysis of 12 biomarkers) of ELT-FEPT associations.

RESULTS

Of 58 PWH (42 men; mean [standard deviation] age = 33.7 [8.9] years), 50% endorsed ELT. ELT-exposed PWH demonstrated lower identification accuracy across all emotional expressions (unstandardized β [ B ] = 0.13; standard error [SE] = 0.05; p = .021, d = 0.63) and had higher OT levels compared with ELT-unexposed PWH ( t(1,56) = 2.12, p = .039; d = 0.57). For total accuracy, an OT/C-reactive protein factor moderated the ELT-FEPT association ( B = 0.14; SE = 0.05; p = .014); accuracy was lower in ELT-exposed PWH versus ELT-unexposed PWH when the factor was low but not when high. Similar results were obtained for fearful, neutral, and happy faces ( p values < .05). Regardless of ELT, a myeloid migration (MCP-1/MMP-9) factor was associated with reduced accuracy ( p values < .05).

CONCLUSIONS

Our pilot findings suggest that ELT may alter social processing in PWH, and OT and C-reactive protein may be a target for improving social processing in ELT-exposed PWH, and myeloid migration markers may be a target in PWH more generally.

Sex-specific alterations of cortical morphometry in treatment-naïve patients with major depressive disorder

Major depressive disorder (MDD) shows sex differences in terms of incidence and symptoms, but the neurobiological basis underlying these sex differences remains to be clarified. High resolution T1-weighted Magnetic Resonance Imaging (MRI) scans were obtained from 123 non-comorbid treatment-naïve individuals with MDD and 81 age-, sex-, and handedness-matched healthy controls (HCs). MRI data were preprocessed with FreeSurfer software and four cortical measures were extracted: cortical thickness (CT), surface area (SA), cortical volume (CV), and local gyrification index (LGI). We tested for both sex-specific and sex-nonspecific patterns of cortical anatomic alterations. Regardless of sex, individuals with MDD showed significantly higher LGI in posterior cortex relative to HCs. Significant sex-by-group interactions were observed, and subsequent post-hoc analyses revealed that female individuals with MDD showed significantly lower SA in left ventrolateral prefrontal cortex (vlPFC), lower CV in right rostromedial prefrontal cortex (rmPFC), and higher LGI in left visual cortex compared with sex-matched HCs, whereas the opposite patterns of significant effects were seen in male individuals with MDD relative to their sex-matched HCs. Thus, sex-nonspecific and specific morphometric differences from HCs were found in posterior cortex, while in PFC alterations were highly sex-specific early in the illness course. This may involve sex-specific alterations in brain development or processes related to illness onset. These findings highlight the presence and regional distribution of generalized as well as sex-specific alterations of brain neurobiology in MDD.

Association between salivary oxytocin levels and the amygdala and hippocampal volumes

Salivary oxytocin levels have been widely measured and studied in relation to social behavior because of procedural simplicity and noninvasiveness. Although the relationship between oxytocin levels in the blood and the hippocampus and amygdala is now becoming clear with reliable blood oxytocin studies, few studies have examined the relationship between salivary oxytocin and the brain function and structure. This study aimed to investigate whether the salivary oxytocin level is associated with the volume of the amygdala and hippocampus in 178 adults (92 women and 86 men) in their third to seventh decade of life. We performed volumetric analysis of the amygdala and hippocampus using FreeSurfer and measured salivary oxytocin levels using enzyme-linked immunosorbent assay. The results showed contradictory effects of the salivary oxytocin level on the amygdala volume by sex and no significant effect on the hippocampal volume. Specifically, men showed a positive correlation between the salivary oxytocin level and amygdala volume, whereas women showed a negative correlation between the salivary oxytocin level and amygdala volume. The present study's finding of sex differences in the association between salivary oxytocin and brain structure supports previous findings that there are sex differences in the oxytocin system.

Differences in Cortical Thickness in Schizophrenia Patients With and Without Auditory Verbal Hallucinations

Auditory verbal hallucinations (AVHs) are one of the most common and severe symptoms of schizophrenia (SCZ), but the neuroanatomical mechanisms underlying AVHs remain unclear. This study aimed to investigate whether persistent AVHs (pAVH) are associated with cortical thinning of certain brain regions in patients with SCZ. With the use of the 3T magnetic resonance imaging (MRI) technology, we acquired and analyzed data from 79 SCZ patients with pAVH (pAVH group), 60 SCZ patients without AVHs (non-AVH group), and 83 healthy controls (HC group). The severity of pAVH was assessed by the P3 hallucination items in the Positive and Negative Syndrome Scale (PANSS) and the Auditory Hallucinations Rating Scale (AHRS). Cortical thickness analysis was used to compare the region of interest (ROI) cortical thickness between the groups. The relationship between the severity of pAVH and cortical thickness was also explored. Compared with the non-AVH and HC groups, the pAVH group exhibited significantly reduced cortical thickness in the bilateral lateral orbitofrontal region (p < 0.0007, after Bonferroni correction); no significant difference was found between the non-AVH group and the HC group. The cortical thickness of the left lateral orbitofrontal cortex (P3: r = −0.44, p < 0.001; AHRS: r = −0.45, p < 0.001) and the right lateral orbitofrontal cortex (P3: r = −0.36, p = 0.002; AHRS: r = −0.33, p = 0.004) were negatively correlated with the severity of pAVH (after Bonferroni correction, p < 0.0125). Therefore, abnormal thickness of the bilateral lateral orbitofrontal cortices might be associated with pAVHs in SCZ patients.

Identifying super-feminine, super-masculine and sex-defining connections in the human braingraph

For more than a decade now, we can discover and study thousands of cerebral connections with the application of diffusion magnetic resonance imaging (dMRI) techniques and the accompanying algorithmic workflow. While numerous connectomical results were published enlightening the relation between the braingraph and certain biological, medical, and psychological properties, it is still a great challenge to identify a small number of brain connections closely related to those conditions. In the present contribution, by applying the 1200 Subjects Release of the Human Connectome Project (HCP) and Support Vector Machines, we identify just 102 connections out of the total number of 1950 connections in the 83-vertex graphs of 1064 subjects, which-by a simple linear test-precisely, without any error determine the sex of the subject. Next, we re-scaled the weights of the edges-corresponding to the discovered fibers-to be between 0 and 1, and, very surprisingly, we were able to identify two graph edges out of these 102, such that, if their weights are both 1, then the connectome always belongs to a female subject, independently of the other edges. Similarly, we have identified 3 edges from these 102, whose weights, if two of them are 1 and one is 0, imply that the graph belongs to a male subject-again, independently of the other edges. We call the former 2 edges superfeminine and the first two of the 3 edges supermasculine edges of the human connectome. Even more interestingly, the edge, connecting the right Pars Triangularis and the right Superior Parietal areas, is one of the 2 superfeminine edges, and it is also the third edge, accompanying the two supermasculine connections if its weight is 0; therefore, it is also a "switching" edge. Identifying such edge-sets of distinction is the unprecedented result of this work.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11571-021-09687-w.

Relation of promoter methylation of the structural oxytocin gene to critical life events in major depression: A case control study

BACKGROUND

Stressful life events (SLEs) are associated with hyper(re-)activity of the HPA-axis. HPA-axis hyper(re-)activity is thought to be a major risk factor for depression development. SLEs may induce changes in an organism's stress system via epigenetic mechanisms. The neuropeptide oxytocin (OT) is able to attenuate the stress response, and OT pathways are dysregulated in individuals suffering from Major Depressive Disorder (MDD). Therefore, the gene coding for oxytocin (OXT) is a possible target for the investigation of depression development.

METHODS

We collected data on SLEs, OXT promoter methylation (Sequenom Epityper MassArray) and depression severity from 90 MDD inpatients and 90 matched healthy controls.

RESULTS

We found MDD inpatients to have a significantly lower OXT methylation than healthy controls. Methylation status was significantly negatively associated with SLEs but only in the group of MDD inpatients. There were no associations between methylation status and depression severity.

LIMITATIONS

Methylation in blood samples is only a proxy for epigenetic profiles in brain tissue. We did not assess mRNA or protein levels and cannot draw conclusions regarding the functionality or specificity of differences in OXT methylation between groups.

CONCLUSION

SLEs leave their traces in the epigenetic profiles of the OT system of MDD inpatients. Alterations in epigenetic profiles of the OXT system could constitute a vulnerability factor predisposing individuals for depression development. Better understanding of DNA methylation profiles of depression-associated genes could serve as basis for a personalized medicine, in which pharmacological or psychotherapeutic treatment of depression is tailored to the patient's individual characteristics.

Estimation of gender-specific connectional brain templates using joint multi-view cortical morphological network integration

The estimation of a connectional brain template (CBT) integrating a population of brain networks while capturing shared and differential connectional patterns across individuals remains unexplored in gender fingerprinting. This paper presents the first study to estimate gender-specific CBTs using multi-view cortical morphological networks (CMNs) estimated from conventional T1-weighted magnetic resonance imaging (MRI). Specifically, each CMN view is derived from a specific cortical attribute (e.g. thickness), encoded in a network quantifying the dissimilarity in morphology between pairs of cortical brain regions. To this aim, we propose Multi-View Clustering and Fusion Network (MVCF-Net), a novel multi-view network fusion method, which can jointly identify consistent and differential clusters of multi-view datasets in order to capture simultaneously similar and distinct connectional traits of samples. Our MVCF-Net method estimates a representative and well-centered CBTs for male and female populations, independently, to eventually identify their fingerprinting regions of interest (ROIs) in four main steps. First, we perform multi-view network clustering model based on manifold optimization which groups CMNs into shared and differential clusters while preserving their alignment across views. Second, for each view, we linearly fuse CMNs belonging to each cluster, producing local CBTs. Third, for each cluster, we non-linearly integrate the local CBTs across views, producing a cluster-specific CBT. Finally, by linearly fusing the cluster-specific centers we estimate a final CBT of the input population. MVCF-Net produced the most centered and representative CBTs for male and female populations and identified the most discriminative ROIs marking gender differences. The most two gender-discriminative ROIs involved the lateral occipital cortex and pars opercularis in the left hemisphere and the middle temporal gyrus and lingual gyrus in the right hemisphere.

Oral oxytocin delivery with proton pump inhibitor pretreatment decreases food intake

Oxytocin (Oxt) is considered as a potential agent to treat multiple neuropsychiatric disorders, obesity and metabolic syndrome. Although the mechanisms underlying these effects remain unclear, nasal administration is considered to be a potential way to deliver Oxt into blood vessels. The development of an easier, more stable and efficient way is expected. A recent study demonstrated that orally administered Oxt can be transmitted into blood if it is prevented from degradation in stomach and reaches the intestinal tract. In this study, we pretreated mice with a proton pump inhibitor (PPI), omeprazole (20 mg/kg), and administered capsulized Oxt (0.25 mg), so that the Oxt can be prevented from degradation by pepsin due to the low pH in stomach and reach the intestinal tract. Functionally, these mice showed a similar decrease in food intake to those who underwent intraperitoneal administration. We also confirmed that this method dramatically increased plasma Oxt levels and the expression of neural activation marker c-Fos protein in the paraventricular and suprachiasmatic nucleus. Our study showed that by pretreating mice with PPI, Oxt in a gelatin-coated capsule can prevent Oxt from degradation by pepsin in stomach, and reach the bloodstream in an effective concentration. These results indicate that our method is a promising oral delivery of Oxt and should be investigated further for other peptide agents based on peripheral injection or nasal administration.

Adolescent sex differences in cortico-subcortical functional connectivity during response inhibition

Numerous lines of evidence have shown that cognitive processes engaged during response inhibition tasks are associated with structure and functional integration of regions within fronto-parietal networks. However, while prior studies have started to characterize how intrinsic connectivity during resting state differs between boys and girls, comparatively less is known about how functional connectivity differs between males and females when brain function is exogenously driven by the processing demands of typical Go/No-Go tasks that assess both response inhibition and error processing. The purpose of this study was to characterize adolescent sex differences and possible changes in sexually dimorphic regional functional connectivity across adolescent development in both cortical and subcortical brain connectivity elicited during a visual Go/No-Go task. A total of 130 healthy adolescents (ages 12-25 years) performed a Go/No-Go task during functional magnetic resonance imaging. High model-order group independent component analysis was used to characterize whole-brain network functional connectivity during response inhibition and then a univariate technique used to evaluate differences related to sex and age. As predicted and similar to previously described findings from non-task-driven resting state connectivity studies, functional connectivity sex differences were observed in several subcortical regions, including the amygdala, caudate, thalamus, and cortical regions, including inferior frontal gyrus engaged most strongly during successful response inhibition and/or error processing. Importantly, adolescent boys and girls exhibited different normative profiles of age-related changes in several default mode networks of regions and anterior cingulate cortex. These results suggest that cortical-subcortical functional networks supporting response inhibition operate differently between sexes during adolescence.

Oxytocin Modulates the Intrinsic Dynamics Between Attention-Related Large-Scale Networks

Attention and salience processing have been linked to the intrinsic between- and within-network dynamics of large-scale networks engaged in internal (default network [DN]) and external attention allocation (dorsal attention network [DAN] and salience network [SN]). The central oxytocin (OXT) system appears ideally organized to modulate widely distributed neural systems and to regulate the switch between internal attention and salient stimuli in the environment. The current randomized placebo (PLC)-controlled between-subject pharmacological resting-state fMRI study in N = 187 (OXT, n = 94; PLC, n = 93; single-dose intranasal administration) healthy male and female participants employed an independent component analysis approach to determine the modulatory effects of OXT on the within- and between-network dynamics of the DAN-SN-DN triple network system. OXT increased the functional integration between subsystems within SN and DN and increased functional segregation of the DN with both attentional control networks (SN and DAN). Whereas no sex differences were observed, OXT effects on the DN-SN interaction were modulated by autistic traits. Together, the findings suggest that OXT may facilitate efficient attention allocation by modulating the intrinsic functional dynamics between DN components and large-scale networks involved in external attentional demands (SN and DAN).

Peripheral oxytocin and vasopressin modulates regional brain activity differently in men and women with schizophrenia

BACKGROUND

Oxytocin (OT) and arginine vasopressin (AVP) exert sexually dimorphic effects on cognition and emotion processing. Abnormalities in these hormones are observed in schizophrenia and may contribute to multiple established sex differences associated with the disorder. Here we examined sex-dependent hormone associations with resting brain activity and their clinical associations in schizophrenia patients.

METHODS

OT and AVP serum concentrations were assayed in 35 individuals with schizophrenia (23 men) and 60 controls (24 men) from the Chicago BSNIP study site. Regional cerebral function was assessed with resting state fMRI by measuring the amplitude of low-frequency fluctuations (ALFF) which are believed to reflect intrinsic spontaneous neuronal activity.

RESULTS

In female patients, lower OT levels were associated with lower ALFF in frontal and cerebellar cortices (p's < 0.05) and in female controls AVP levels were inversely associated with ALFF in the frontal cortex (p = 0.01). In male patients, lower OT levels were associated with lower ALFF in the posterior cingulate and lower AVP levels were associated with lower ALFF in frontal cortex (p's < 0.05). In male controls, lower OT levels were associated with lower ALFF in frontal cortex and higher ALFF in the thalamus (p's < 0.05). There were some inverse ALFF-behavior associations in patients.

CONCLUSIONS

Alterations in peripheral hormone levels are associated with resting brain physiology in a sex-dependent manner in schizophrenia. These effects may contribute to sex differences in psychiatric symptom severity and course of illness in schizophrenia.

Sex-specific association of a common GNAS polymorphism with self-reported cognitive empathy in healthy volunteers

Background

In a recent study, we found associations of a common oxytocin receptor (OXTR) polymorphism with inter-individual differences in empathy, especially with emotional empathy in women. Many other studies found specific associations of oxytocin, arginine-vasopressin, serotonin and dopamine receptor gene polymorphisms with various aspects of trait empathy. As all these receptors belong to the guanine-binding protein (G protein) coupled receptor family, it is a reasonable assumption, that alterations in genes encoding G protein subunits also influence the signal transduction in empathy related circuits. However, to the best of our knowledge, these genomic variations have not yet been studied in genetic research on empathy.

Methods

Here, we analysed associations of a common polymorphism of the GNAS gene (C393T) in a previously characterized sample of 421 healthy blood donors (231 M, 190 F; age 18–74). The GNAS gene encodes the G protein adenylyl cyclase stimulator (Gαs) G protein subunit, which activates cyclic adenosine monophosphate (cAMP)-dependent pathways by stimulating the adenylyl cyclase. Cognitive and emotional aspects of dispositional empathy were tested using Davis’ Interpersonal Reactivity Index (IRI).

Results

In the complete sample, associations of C393T genotype with IRI empathy scores, including cognitive empathy (p = 0.055) and perspective taking (p = 0.057) scores did not reach a level of significance. None of the IRI scores was near to being significantly associated with C393T genotype for men alone. In females, however, genotype was significantly associated with cognitive empathy (r = -.204, p = 0.005) and perspective taking (r = -.209, p = 0.004), accounting for 4.2% and 4.4% of variability. The association of genotype with perspective taking remained significant after adjustment for multiple comparisons (p = 0.045). The 393C-allele, which had been identified as a risk factor in several medical conditions such as hypertension, obesity and diabetes, was associated with higher cognitive empathy compared to the T allele in our sample.

Conclusions

The results suggest a significant association of GNAS C393T genotypes with the cognitive empathic capacity of perspective taking. This association could only be found in female participants.

Impact of sex, fat distribution and initial body weight on oxytocin's body weight regulation

Obesity is considered as a worldwide problem in both males and females. Although many studies have demonstrated the efficiency of oxytocin (Oxt) as an anti-obesity peptide, there is no comparative study of its effect in males and females. This study aims to determine factors (sex, initial body weight, and fat distribution) that may affect the ability of Oxt to regulate body weight (BW). With regard to sex, Oxt reduced BW similarly in males and females under both high fat diet (HFD) and standard chow-fed condition. The BW reduction induced by Oxt correlated with initial BW in male and female mice under HFD conditions. Oxt showed an equal efficacy in fat degradation in both the visceral and subcutaneous fat mass in both males and females fed with HFD. The effect of Oxt on BW reduction was attenuated in standard chow-fed male and female mice. Therefore, our results suggest that administration of Oxt is more effective in reducing BW in subjects with a high initial BW with increased fat accumulation. The present data contains important information for the possible clinical application of Oxt for the treatment of obesity.