Plasma oxytocin levels in autistic children

Hypomethylation of miR-142 promoter and upregulation of microRNAs that target the oxytocin receptor gene in the autism prefrontal cortex

Background

MicroRNAs are small RNA molecules that regulate the translation of protein from gene transcripts and are a powerful mechanism to regulate gene networks. Next-generation sequencing technologies have produced important insights into gene transcription changes that occur in the brain of individuals diagnosed with autism spectrum disorder (asd). However, these technologies have not yet been employed to uncover changes in microRNAs in the brain of individuals diagnosed with asd.

Methods

Small RNA next-generation sequencing was performed on RNA extracted from 12 human autism brain samples and 12 controls. Real-time PCR was used to validate a sample of the differentially expressed microRNAs, and bioinformatic analysis determined common pathways of gene targets. MicroRNA expression data was correlated to genome-wide DNA methylation data to determine if there is epigenetic regulation of dysregulated microRNAs in the autism brain. Luciferase assays, real-time PCR, and Western blot analysis were used to determine how dysregulated microRNAs may regulate the expression and translation of an autism-related gene transcript.

Results

We determined that miR-142-5p, miR-142-3p, miR-451a, miR-144-3p, and miR-21-5p are overexpressed in the asd brain. Furthermore, the promoter region of the miR-142 gene is hypomethylated in the same brain samples, suggesting that epigenetics plays a role in dysregulation of microRNAs in the brain. Bioinformatic analysis revealed that these microRNAs target genes that are involved in synaptic function. Further bioinformatic analysis, coupled with in vitro luciferase assays, determined that miR-451a and miR-21-5p can target the oxytocin receptor (OXTR) gene. OXTR gene expression is increased in these same brain samples, and there is a positive correlation between miR-21-5p and OXTR expression. However, miR-21-5p expression negatively correlates to production of OXTR protein from the OXTR transcript. Therefore, we suggest that miR-21-5p may attenuate OXTR expression in the human autism brain.

Conclusions

Our data suggests that dysregulation of microRNAs may play a biological role in the brain of individuals of autism. In addition, we suggest an interaction between epigenetic mechanisms and microRNA dysregulation in the brain. Overall, this data adds an important link in our understanding of the molecular events that are dysregulated in the brain of individuals diagnosed with autism.

Electronic supplementary material

The online version of this article (doi:10.1186/s13229-015-0040-1) contains supplementary material, which is available to authorized users.

Investigation of Oxytocin Secretion in Anorexia Nervosa and Bulimia Nervosa: Relationships to Temperament Personality Dimensions

Published studies suggested an implication of oxytocin in some temperament characteristics of personality. Therefore, we measured oxytocin secretion in 23 women with anorexia nervosa (AN), 27 with bulimia nervosa (BN) and 19 healthy controls and explored the relationships between circulating oxytocin and patients' personality traits. Plasma oxytocin levels were significantly reduced in AN women but not in BN ones. In healthy women, the attachment subscale scores of the reward dependence temperament and the harm avoidance (HA) scores explained 82% of the variability in circulating oxytocin. In BN patients, plasma oxytocin resulted to be negatively correlated with HA, whereas no significant correlations emerged in AN patients. These findings confirm a dysregulation of oxytocin production in AN but not in BN and show, for the first time, a disruption of the associations between hormone levels and patients' temperament traits, which may have a role in certain deranged behaviours of eating disorder patients.

Prolyl endopeptidase and dipeptidyl peptidase IV are associated with externalizing and aggressive behaviors in normal and autistic adolescents

AIMS

Peptides and a dysregulated immune system play a role in the pathophysiology of autism. Dysfunctions in prolyl endopeptidase (PEP) and dipeptidyl peptidase IV (DPP-IV) may underpin both the peptidergic and immune alterations in autism. The aims of this study are to: (i) delineate serum PEP and DPP-IV enzyme activities in autism, and (ii) examine the associations between both peptidases and behavioral characteristics or immune variables.

MAIN METHODS

We included 18 autistic patients and 22 healthy controls and measured the Child Behavior Checklist (CBCL), serum PEP and DPP-IV and immune biomarkers, i.e. the serum protein fractions α1, α2 and γ, and immunoglobulins, i.e. IgG1, IgG2, IgG3 and IgG4. Results were adjusted for possible effects of age and body mass index (BMI).

KEY FINDINGS

There were no significant differences in PEP or DPP-IV between the autistic patients and controls. DPP-IV was significantly and positively associated with the CBCL attention problems, aggressive and externalizing behavior subscales. PEP was significantly and positively associated with the CBCL delinquent, aggressive, externalizing and internalizing behavior subscales. There was a negative correlation between both peptidases and age and Tanner stage. DPP-IV was associated with α2-globulin (positively) and IgG3 (inversely) levels, while PEP activity was correlated with IgG2 levels (inversely). BMI was significantly associated with aggressive and externalizing behaviors.

SIGNIFICANCE

These findings demonstrate an association between peptidases and aggressive and externalizing behaviors, which may be explained by effects of these peptidases cleaving behavioral neuropeptides. Both peptidases are associated with immune biomarkers suggesting multiple bidirectional effects.

Social Neuroscience: Progress and Implications for Mental Health

Social neuroscience is a new, interdisciplinary field devoted to understanding how biological systems implement social processes and behavior. Social neuroscience capitalizes on biological concepts and methods to inform and refine theories of social behavior, and it uses social and behavioral constructs and data to inform and refine theories of neural organization and function. We focus here on the progress and potential of social neuroscience in the area of mental health. Research in social neuroscience has grown dramatically in recent years. Among the most active areas of research we found are brain-imaging studies in normal children and adults; animal models of social behavior; studies of stroke patients; imaging studies of psychiatric patients; and research on social determinants of peripheral neural, neuroendocrine, and immunological processes. We also found that these areas of research are proceeding along largely independent trajectories. Our goals in this article are to review the development of this field, examine some currently promising approaches, identify obstacles and opportunities for future advances and integration, and consider how this research can inform work on the diagnosis and treatment of mental disorders.

Inhibition-Based Biomarkers for Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a behaviorally defined and heterogeneous disorder. Biomarkers for ASD offer the opportunity to improve prediction, diagnosis, stratification by severity and subtype, monitoring over time and in response to interventions, and overall understanding of the underlying biology of this disorder. A variety of potential biomarkers, from the level of genes and proteins to network-level interactions, is currently being examined. Many of these biomarkers relate to inhibition, which is of particular interest because in many cases ASD is thought to be a disorder of imbalance between excitation and inhibition. Abnormalities in inhibition at the cellular level lead to emergent properties in networks of neurons. These properties take into account a more complete genetic and cellular background than findings at the level of individual genes or cells, and are able to be measured in live humans, offering additional potential as diagnostic biomarkers and predictors of behaviors. In this review we provide examples of how altered inhibition may inform the search for ASD biomarkers at multiple levels, from genes to cells to networks.

The oxytocin receptor gene (OXTR) is associated with autism spectrum disorder: a meta-analysis

The oxytocin receptor gene (OXTR) has been studied as a risk factor for autism spectrum disorder (ASD) owing to converging evidence from multiple levels of analysis that oxytocin (OXT) has an important role in the regulation of affiliative behavior and social bonding in both nonhuman mammals and humans. Inconsistency in the effect sizes of the OXTR variants included in association studies render it unclear whether OXTR is truly associated with ASD, and, if so, which OXTR single-nucleotide polymorphisms (SNPs) are associated. Thus, a meta-analytic review of extant studies is needed to determine whether OXTR shows association with ASD, and to elucidate which specific SNPs have a significant effect on ASD. The current meta-analysis of 16 OXTR SNPs included 3941 individuals with ASD from 11 independent samples, although analyses of each individual SNP included a subset of this total. We found significant associations between ASD and the SNPs rs7632287, rs237887, rs2268491 and rs2254298. OXTR was also significantly associated with ASD in a gene-based test. The current meta-analysis is the largest and most comprehensive investigation of the association of OXTR with ASD and the findings suggest directions for future studies of the etiology of ASD.

The influence of early life sexual abuse on oxytocin concentrations and premenstrual symptomatology in women with a menstrually related mood disorder

Oxytocin (OT), associated with affiliation and social bonding, social salience, and stress/pain regulation, may play a role in the pathophysiology of stress-related disorders, including menstrually-related mood disorders (MRMD's). Adverse impacts of early life sexual abuse (ESA) on adult attachment, affective regulation, and pain sensitivity suggest ESA-related OT dysregulation in MRMD pathophysiology. We investigated the influence of ESA on plasma OT, and the relationship of OT to the clinical phenomenology of MRMD's. Compared to MRMD women without ESA (n=40), those with ESA (n=20) displayed significantly greater OT [5.39pg/mL (SD, 2.4) vs. 4.36pg/mL (SD, 1.1); t (58)=-2.26, p=0.03]. In women with ESA, OT was significantly, inversely correlated with premenstrual psychological and somatic symptoms (r's=-0.45 to -0.64, p's<0.05). The relationship between OT and premenstrual symptomatology was uniformly low and non-significant in women without ESA. In women with ESA, OT may positively modulate MRMD symptomatology.

Plasma oxytocin explains individual differences in neural substrates of social perception

The neuropeptide oxytocin plays a critical role in social cognition and behavior. A number of studies using intranasal administration have demonstrated that oxytocin improves social perception. However, little is known about the relationship between individual differences in endogenous levels of oxytocin and social cognition. In the current study, we assessed the relationship between endogenous oxytocin and brain activity during an animacy perception paradigm. Thirty-seven male participants underwent scanning and provided a blood sample for oxytocin analysis. In line with previous research, perception of animacy was associated with activations in superior temporal sulcus, inferior frontal gyrus, and medial prefrontal cortex (mPFC). Notably, participants’ levels of plasma oxytocin robustly predicted activation in areas critical for social cognitive processes, such that higher oxytocin levels were related to increased activity in dorsal mPFC, ventral mPFC, dorsolateral PFC, superior temporal gyrus, and temporoparietal junction (TPJ), suggesting differential processing of social stimuli. Together these results show that stable variations in endogenous oxytocin levels explain individual differences in social perception.

Genetic variant rs17225178 in the ARNT2 gene is associated with Asperger Syndrome

BACKGROUND

Autism Spectrum Conditions (ASC) are neurodevelopmental conditions characterized by difficulties in communication and social interaction, alongside unusually repetitive behaviours and narrow interests. Asperger Syndrome (AS) is one subgroup of ASC and differs from classic autism in that in AS there is no language or general cognitive delay. Genetic, epigenetic and environmental factors are implicated in ASC and genes involved in neural connectivity and neurodevelopment are good candidates for studying the susceptibility to ASC. The aryl-hydrocarbon receptor nuclear translocator 2 (ARNT2) gene encodes a transcription factor involved in neurodevelopmental processes, neuronal connectivity and cellular responses to hypoxia. A mutation in this gene has been identified in individuals with ASC and single nucleotide polymorphisms (SNPs) have been nominally associated with AS and autistic traits in previous studies.

METHODS

In this study, we tested 34 SNPs in ARNT2 for association with AS in 118 cases and 412 controls of Caucasian origin. P values were adjusted for multiple comparisons, and linkage disequilibrium (LD) among the SNPs analysed was calculated in our sample. Finally, SNP annotation allowed functional and structural analyses of the genetic variants in ARNT2. We tested the replicability of our result using the genome-wide association studies (GWAS) database of the Psychiatric Genomics Consortium (PGC).

RESULTS

We report statistically significant association of rs17225178 with AS. This SNP modifies transcription factor binding sites and regions that regulate the chromatin state in neural cell lines. It is also included in a LD block in our sample, alongside other genetic variants that alter chromatin regulatory regions in neural cells.

CONCLUSIONS

These findings demonstrate that rs17225178 in the ARNT2 gene is associated with AS and support previous studies that pointed out an involvement of this gene in the predisposition to ASC.

Oxytocin, vasopressin, and Williams syndrome: epigenetic effects on abnormal social behavior

Williams syndrome (WS) is a condition caused by a deletion of ∼26-28 genes on chromosome 7q11.23 often characterized by abnormal social behavior and disrupted oxytocin (OT) and vasopressin (AVP) functioning. The observation that individuals with WS exhibit OT and AVP dysregulation is compelling. There is currently a lack of evidence that any of the genes typically deleted in WS have any direct effect on either OT or AVP. In this perspective article, we present a novel epigenetic model describing how DNA methylation may impact the expression of key genes within the OT and AVP systems, which may ultimately influence the social behavior observed in WS. We draw support from data pooled from a prior empirical research study (Henrichsen et al., 2011), demonstrating that OXTR is overexpressed in WS. These preliminary findings may create new opportunities to target the OT and AVP systems with the specific goal of improving outcomes in WS and other psychiatric conditions.

A systematic review of molecular imaging (PET and SPECT) in autism spectrum disorder: current state and future research opportunities

Non-invasive positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are techniques used to quantify molecular interactions, biological processes and protein concentration and distribution. In the central nervous system, these molecular imaging techniques can provide critical insights into neurotransmitter receptors and their occupancy by neurotransmitters or drugs. In recent years, there has been an increase in the number of studies that have investigated neurotransmitters in autism spectrum disorder (ASD), while earlier studies mostly focused on cerebral blood flow and glucose metabolism. The underlying and contributing mechanisms of ASD are largely undetermined and ASD diagnosis relies on the behavioral phenotype. Discovery of biochemical endophenotypes would represent a milestone in autism research that could potentially lead to ASD subtype stratification and the development of novel therapeutic drugs. This review characterizes the prior use of molecular imaging by PET and SPECT in ASD, addresses methodological challenges and highlights areas of future opportunity for contributions from molecular imaging to understand ASD pathophysiology.

An attempt to identify single nucleotide polymorphisms contributing to possible relationships between personality traits and oxytocin-related genes

BACKGROUND

The neuropeptides oxytocin and vasopressin play a central role in social behavior. Trials with intranasal oxytocin have been conducted and many indicate that the hormone facilitates affiliative behavior and trust. Intranasal oxytocin administration is suggested as a treatment option for psychiatric illnesses with altered sociability as a core symptom and the effects may be due to differences in variants of oxytocin- and vasopressin-related genes. The purpose of the present study was to investigate the endogenous oxytocin system by exploring the relationship between variants in the oxytocin gene factors and personality traits closely related to trust, anxiety and social behavior.

METHODS

72 single nucleotide polymorphisms (SNPs) in the genes coding for oxytocin (OXT), vasopressin (AVP), the oxytocin receptor (OXTR) and CD38 (CD38), including polymorphisms reported earlier to be related to social phenotypes and novel SNPs, were investigated in 196 healthy subjects. Association analysis between these variants and 3 personality traits (agreeableness, neuroticism and extraversion) measured by the Neuroticism-Extraversion-Openness Five-Factor Inventory was performed.

RESULTS

We found 7 nominally significant associations for personality traits: agreeableness [rs857240 (AVP, p = 0.0075), rs2270463 (OXTR, p = 0.047)], neuroticism [rs3756242 (CD38, p = 0.024), rs13104011 (CD38, p = 0.024), rs6816486 (CD38, p = 0.024), rs7655635 (CD38, p = 0.034)] and extraversion [rs237878 (OXTR, p = 0.019)]. None of these associations remained significant after the Bonferroni correction (p threshold = 2.31 × 10(-4)).

CONCLUSION

Our results do not contradict the hypothesis of associations between personality traits and oxytocin-related gene variants; however, there are no statistically significant associations after correcting for multiple testing, warranting replication in larger samples.

Social cognition

Social cognition is a major problem underlying deficiencies in interpersonal relationships in several psychiatric populations. And yet there is currently no gold standard for pharmacological treatment of psychiatric illness that directly targets these social cognitive areas. This chapter serves to illustrate some of the most innovative attempts at pharmacological modulation of social cognition in psychiatric illnesses including schizophrenia, borderline personality disorder, autism spectrum disorders, antisocial personality disorder and psychopathy, social anxiety disorder, and posttraumatic stress disorder. Pharmacological modulation includes studies administering oxytocin, ecstasy (MDMA), modafinil, methylphenidate, and D-cycloserine. Furthermore, some background on social cognition research in healthy individuals, which could be helpful in developing future treatments, is provided as well as the potential for each drug as a long-term treatment option.

Neurobiology of Maternal Stress: Role of Social Rank and Central Oxytocin in Hypothalamic-Pituitary Adrenal Axis Modulation

BACKGROUND

Chronic stress may conceivably require plasticity of maternal physiology and behavior to cope with the conflicting primary demands of infant rearing and foraging for food. In addition, social rank may play a pivotal role in mandating divergent homeostatic adaptations in cohesive social groups. We examined cerebrospinal fluid (CSF) oxytocin (OT) levels and hypothalamic-pituitary adrenal (HPA) axis regulation in the context of maternal social stress and assessed the contribution of social rank to dyadic distance as reflective of distraction from normative maternal-infant interaction.

METHODS

Twelve socially housed mother-infant bonnet macaque dyads were studied after variable foraging demand (VFD) exposure compared to 11 unstressed dyads. Dyadic distance was determined by behavioral observation. Social ranking was performed blindly by two observers. Post-VFD maternal plasma cortisol and CSF OT were compared to corresponding measures in non-VFD-exposed mothers.

RESULTS

High-social rank was associated with increased dyadic distance only in VFD-exposed dyads and not in control dyads. In mothers unexposed to VFD, social rank was not related to maternal cortisol levels, whereas VFD-exposed dominant versus subordinate mothers exhibited increased plasma cortisol. Maternal CSF OT directly predicted maternal cortisol only in VFD-exposed mothers. CSF OT was higher in dominant versus subordinate mothers. VFD-exposed mothers with "high" cortisol specifically exhibited CSF OT elevations in comparison to control groups.

CONCLUSION

Pairing of maternal social rank to dyadic distance in VFD presumably reduces maternal contingent responsivity, with ensuing long-term sequelae. VFD-exposure dichotomizes maternal HPA-axis response as a function of social rank with relatively reduced cortisol in subordinates. OT may serve as a homeostatic buffer during maternal stress exposure.

Autism as a disorder of biological and behavioral rhythms: toward new therapeutic perspectives

There is a growing interest in the role of biological and behavioral rhythms in typical and atypical development. Recent studies in cognitive and developmental psychology have highlighted the importance of rhythmicity and synchrony of motor, emotional, and interpersonal rhythms in early development of social communication. The synchronization of rhythms allows tuning and adaptation to the external environment. The role of melatonin in the ontogenetic establishment of circadian rhythms and the synchronization of the circadian clocks network suggests that this hormone might be also involved in the synchrony of motor, emotional, and interpersonal rhythms. Autism provides a challenging model of physiological and behavioral rhythm disturbances and their possible effects on the development of social communication impairments and repetitive behaviors and interests. This article situates autism as a disorder of biological and behavioral rhythms and reviews the recent literature on the role of rhythmicity and synchrony of rhythms in child development. Finally, the hypothesis is developed that an integrated approach focusing on biological, motor, emotional, and interpersonal rhythms may open interesting therapeutic perspectives for children with autism. More specifically, promising avenues are discussed for potential therapeutic benefits in autism spectrum disorder of melatonin combined with developmental behavioral interventions that emphasize synchrony, such as the Early Start Denver Model.

Convergence of circuit dysfunction in ASD: a common bridge between diverse genetic and environmental risk factors and common clinical electrophysiology

Most recent estimates indicate that 1 in 68 children are affected by an autism spectrum disorder (ASD). Though decades of research have uncovered much about these disorders, the pathological mechanism remains unknown. Hampering efforts is the seeming inability to integrate findings over the micro to macro scales of study, from changes in molecular, synaptic and cellular function to large-scale brain dysfunction impacting sensory, communicative, motor and cognitive activity. In this review, we describe how studies focusing on neuronal circuit function provide unique context for identifying common neurobiological disease mechanisms of ASD. We discuss how recent EEG and MEG studies in subjects with ASD have repeatedly shown alterations in ensemble population recordings (both in simple evoked related potential latencies and specific frequency subcomponents). Because these disease-associated electrophysiological abnormalities have been recapitulated in rodent models, studying circuit differences in these models may provide access to abnormal circuit function found in ASD. We then identify emerging in vivo and ex vivo techniques, focusing on how these assays can characterize circuit level dysfunction and determine if these abnormalities underlie abnormal clinical electrophysiology. Such circuit level study in animal models may help us understand how diverse genetic and environmental risks can produce a common set of EEG, MEG and anatomical abnormalities found in ASD.

Interaction between MAOA and FOXP2 in association with autism and verbal communication in a Korean population

Expression levels of monoamine oxidase A (MAOA), the enzyme that related to monoamine neurotransmitters metabolism such as serotonin, are related to schizophrenia and autism spectrum disorder. Forkhead box protein P2 (FOXP2), a transcription factor, is associated with abnormal language development and is expressed in several areas of the central nervous system in response to serotonin. For this reason, we undertook interaction analysis between MAOA and FOXP2 in autism spectrum disorder, including testing the verbal communication score of the childhood autism rating scale. In interaction analysis, the FOXP2-TCGC (rs12531289-rs1350135-rs10230087-rs2061183) diplotype and MAOA-TCG (rs6323-rs1801291-rs3027407) haplotype were significantly associated with autism spectrum disorder in males. However, when the interaction term was omitted, neither MAOA nor FOXP2 was associated with autism spectrum disorder or verbal communication. These results indicate that language and speech ability is affected by an interaction between FOXP2 and MAOA, but not by either gene separately.

Sevoflurane-induced down-regulation of hippocampal oxytocin and arginine vasopressin impairs juvenile social behavioral abilities

Cumulative evidence indicates that early childhood anesthesia can alter a child's future behavioral performance. Animal researchers have found that sevoflurane, the most commonly used anesthetic for children, can produce damage in the neonatal brains of rodents. To further investigate this phenomenon, we focused on the influence of sevoflurane anesthesia on the development of juvenile social behavioral abilities and the pro-social proteins oxytocin (OT) and arginine vasopressin (AVP) in the neonatal hippocampus. A single 6-h sevoflurane exposure for postnatal day 5 mice resulted in decreased OT and AVP messenger RNA (mRNA) and protein levels in the hippocampus. OT and AVP proteins became sparsely distributed in the dorsal hippocampus after the exposure to sevoflurane. Compared with the air-treated group, mice in the sevoflurane-treated group showed signs of impairment in social recognition memory formation and social discrimination ability. Sevoflurane anesthesia reduces OT and AVP activities in the neonatal hippocampus and impairs social recognition memory formation and social discrimination ability in juvenile mice.

Autism, oxytocin and interoception

Autism is a pervasive developmental disorder characterized by profound social and verbal communication deficits, stereotypical motor behaviors, restricted interests, and cognitive abnormalities. Autism affects approximately 1% of children in developing countries. Given this prevalence, identifying risk factors and therapeutic interventions are pressing objectives—objectives that rest on neurobiologically grounded and psychologically informed theories about the underlying pathophysiology. In this article, we review the evidence that autism could result from a dysfunctional oxytocin system early in life. As a mediator of successful procreation, not only in the reproductive system, but also in the brain, oxytocin plays a crucial role in sculpting socio-sexual behavior. Formulated within a (Bayesian) predictive coding framework, we propose that oxytocin encodes the saliency or precision of interoceptive signals and enables the neuronal plasticity necessary for acquiring a generative model of the emotional and social 'self.' An aberrant oxytocin system in infancy could therefore help explain the marked deficits in language and social communication—as well as the sensory, autonomic, motor, behavioral, and cognitive abnormalities—seen in autism.

Is oxytocin a maternal-foetal signalling molecule at birth? Implications for development

The neuropeptide oxytocin was first noted for its capacity to promote uterine contractions and facilitate delivery in mammals. The study of oxytocin has grown to include awareness that this peptide is a neuromodulator with broad effects throughout the body. Accumulating evidence suggests that oxytocin is a powerful signal to the foetus, helping to prepare the offspring for the extrauterine environment. Concurrently, the use of exogenous oxytocin or other drugs to manipulate labour has become common practice. The use of oxytocin to expedite labour and minimise blood loss improves both infant and maternal survival under some conditions. However, further investigations are needed to assess the developmental consequences of changes in oxytocin, such as those associated with pre-eclampsia or obstetric manipulations associated with birth. This review focuses on the role of endogenous and exogenous oxytocin as a neurochemical signal to the foetal nervous system. We also examine the possible developmental consequences, including those associated with autism spectrum disorder, that arise from exogenous oxytocin supplementation during labour.

Visual attention for social information and salivary oxytocin levels in preschool children with autism spectrum disorders: an eye-tracking study

This study was designed to ascertain the relationship between visual attention for social information and oxytocin (OT) levels in Japanese preschool children with autism spectrum disorder (ASD). We hypothesized that poor visual attention for social information and low OT levels are crucially important risk factors associated with ASD. We measured the pattern of gaze fixation for social information using an eye-tracking system, and salivary OT levels by the Enzyme-Linked Immunosorbent Assay (ELISA). There was a positive association between salivary OT levels and fixation duration for an indicated object area in a finger-pointing movie in typically developing (TD) children. However, no association was found between these variables in children with ASD. Moreover, age decreased an individual's attention to people moving and pointed-at objects, but increased attention for mouth-in-the-face recognition, geometric patterns, and biological motions. Thus, OT levels likely vary during visual attention for social information between TD children and those with ASD. Further, aging in preschool children has considerable effect on visual attention for social information.

Oxytocin and vasopressin systems in genetic syndromes and neurodevelopmental disorders

Oxytocin (OT) and arginine vasopressin (AVP) are two small, related neuropeptide hormones found in many mammalian species, including humans. Dysregulation of these neuropeptides have been associated with changes in behavior, especially social interactions. We review how the OT and AVP systems have been investigated in Autism Spectrum Disorder (ASD), Prader-Willi Syndrome (PWS), Williams Syndrome (WS) and Fragile X syndrome (FXS). All of these neurodevelopmental disorders (NDD) are marked by social deficits. While PWS, WS and FXS have identified genetic mutations, ASD stems from multiple genes with complex interactions. Animal models of NDD are invaluable for studying the role and relatedness of OT and AVP in the developing brain. We present data from a FXS mouse model affecting the fragile X mental retardation 1 (Fmr1) gene, resulting in decreased OT and AVP staining cells in some brain regions. Reviewing the research about OT and AVP in these NDD suggests that altered OT pathways may be downstream from different etiological factors and perturbations in development. This has implications for ongoing studies of the therapeutic application of OT in NDD. This article is part of a Special Issue entitled Oxytocin and Social Behav.

Early involvement in friendships predicts later plasma concentrations of oxytocin and vasopressin in juvenile rhesus macaques (Macaca mulatta)

The neuropeptides oxytocin (OT) and arginine vasopressin (AVP) are involved in social bonding in attachment relationships, but their role in friendship is poorly understood. We investigated whether rhesus macaques' (Macaca mulatta) friendships at age one predicted plasma OT and AVP at two later time points. Subjects were 54 rhesus macaques at the California National Primate Research Center (CNPRC). Blood was drawn during a brief capture-and-release in the home cage, and plasma assayed for OT and AVP using an enzyme immunoassay (EIA). Separate linear mixed models for each sex tested the effects of dominance rank, age, sampling time point, housing condition, parturition status, two blood draw timing measures, and five friendship types: proximity friendships, play friendships, reciprocal friendships (a preference for a peer that also preferred the subject), multiplex friendships (friendships displayed in more than one behavioral domain), and total number of friendships. Females' number of reciprocal and play friendships at age one significantly predicted later OT; additionally, these two friendship types interacted with rank, such that high-ranking females with the fewest friendships had the highest OT concentrations. Friendship did not predict later OT levels in males, however proximity, play, reciprocal, and total number of friendships predicted males' plasma AVP. Play and total number of friendships also tended to predict AVP in females. Our results show that peripheral measures of neuroendocrine functioning in juvenile rhesus monkeys are influenced by early involvement in friendships. Friendships have an especially strong impact on an individual's psychosocial development, and our data suggest OT and AVP as potential underlying mechanisms. Moreover, sex differences in the functioning of the OT and AVP systems, and their relation to friendship, may have important clinical implications for the use of OT as a therapeutic, as well as informing the social context in which it is administered.

Plasma oxytocin concentrations and OXTR polymorphisms predict social impairments in children with and without autism spectrum disorder

The neuropeptide oxytocin (OXT) and its receptor (OXTR) regulate social functioning in animals and humans. Initial clinical research suggests that dysregulated plasma OXT concentrations and/or OXTR SNPs may be biomarkers of social impairments in autism spectrum disorder (ASD). We do not know, however, whether OXT dysregulation is unique to ASD or whether OXT biology influences social functioning more generally, thus contributing to, but not causing, ASD phenotypes. To distinguish between these possibilities, we tested in a child ASD cohort, which included unaffected siblings and unrelated neurotypical controls (ages 3-12 y; n = 193), whether plasma OXT concentrations and OXTR SNPs (i) interact to produce ASD phenotypes, (ii) exert differential phenotypic effects in ASD vs. non-ASD children, or (iii) have similar phenotypic effects independent of disease status. In the largest cohort tested to date, we found no evidence to support the OXT deficit hypothesis of ASD. Rather, OXT concentrations strongly and positively predicted theory of mind and social communication performance in all groups. Furthermore, OXT concentrations showed significant heritability between ASD-discordant siblings (h(2) = 85.5%); a heritability estimate on par with that of height in humans. Finally, carriers of the "G" allele of rs53576 showed impaired affect recognition performance and carriers of the "A" allele of rs2254298 exhibited greater global social impairments in all groups. These findings indicate that OXT biology is not uniquely associated with ASD, but instead exerts independent, additive, and highly heritable influences on individual differences in human social functioning, including the severe social impairments which characterize ASD.

An oxytocin-induced facilitation of neural and emotional responses to social touch correlates inversely with autism traits

Social communication through touch and mutual grooming can convey highly salient socio-emotional signals and has been shown to involve the neuropeptide oxytocin (OXT) in several species. Less is known about the modulatory influence of OXT on the neural and emotional responses to human interpersonal touch. The present randomized placebo (PLC)-controlled within-subject pharmaco-functional magnetic resonance imaging (fMRI) study was designed to test the hypothesis that a single intranasal dose of synthetic OXT (24 IU) would facilitate both neural and emotional responses to interpersonal touch in a context- (female vs male touch) and trait- (autistic trait load) specific manner. Specifically, the experimental rationale was to manipulate the reward value of interpersonal touch independent of the intensity and type of actual cutaneous stimulation administered. Thus, 40 heterosexual males believed that they were touched by either a man or a woman, although in fact an identical pattern of touch was always given by the same female experimenter blind to condition type. Our results show that OXT increased the perceived pleasantness of female, but not male touch, and associated neural responses in insula, precuneus, orbitofrontal, and pregenual anterior cingulate cortex. Moreover, the behavioral and neural effects of OXT were negatively correlated with autistic-like traits. Taken together, this is the first study to show that the perceived hedonic value of human heterosexual interpersonal touch is facilitated by OXT in men, but that its behavioral and neural effects in this context are blunted in individuals with autistic traits.

Biobehavioral profiles of arousal and social motivation in autism spectrum disorders

BACKGROUND

Children with autism spectrum disorder (ASD) are impaired in social communication and interaction with peers, which may reflect diminished social motivation. Many children with ASD show enhanced stress when playing with other children. This study investigated social and stress profiles of children with ASD during play.

METHODS

We utilized a peer interaction paradigm in a natural playground setting with 66 unmedicated, prepubertal, children aged 8-12 years [38 with ASD, 28 with typical development (TD)]. Salivary cortisol was collected before and after a 20-min playground interaction that was divided into periods of free and solicited play facilitated by a confederate child. Statistical analyses included Wilcoxon rank-sum tests, mixed effects models, and Spearman correlations to assess the between-group differences in social and stress functioning, identify stress responders, and explore associations between variables, respectively.

RESULTS

There were no differences between the groups during unsolicited free play; however, during solicited play by the confederate, significant differences emerged such that children with ASD engaged in fewer verbal interactions and more self-play than the TD group. Regarding physiological arousal, children with ASD as a group showed relatively higher cortisol in response to social play; however, there was a broad range of responses. Moreover, those with the highest cortisol levels engaged in less social communication.

CONCLUSIONS

The social interaction of children with ASD can be facilitated by peer solicitation; however, it may be accompanied by increased stress. The children with ASD that have the highest level of cortisol show less social motivation; yet, it is unclear if it reflects an underlying state of heightened arousal or enhanced reactivity to social engagement, or both.

Oxytocin plasma concentrations in children and adolescents with autism spectrum disorder: correlation with autistic symptomatology

Findings from research in animal models and humans have shown a clear role for the neuropeptide oxytocin (OT) on complex social behaviors. This is also true in the context of autism spectrum disorder (ASD). Previous studies on peripheral OT concentrations in children and young adults have reported conflicting results with the initial studies presenting mainly decreased OT plasma levels in ASD compared to healthy controls. Our study therefore aimed to further investigate changes in peripheral OT concentrations as a potential surrogate for the effects observed in the central nervous system (CNS) in ASD. OT plasma concentrations were assessed in 19 male children and adolescents with ASD, all with an IQ > 70 (age 10.7 ± 3.8 years), 17 healthy male children (age 13.6 ± 2.1 years) and 19 young male patients with attention deficit hyperactivity disorder (ADHD) as a clinical control group (age 10.4 ± 1.9 years) using a validated radioimmunoassay. Analysis of covariance revealed significant group differences in OT plasma concentrations (F(2, 48) = 9.574, p < 0.001, η2 = 0.285; plasma concentrations ASD 19.61 ± 7.12 pg/ml, ADHD 8.05 ± 5.49 pg/ml, healthy controls 14.43 ± 9.64 pg/ml). Post hoc analyses showed significantly higher concentrations in children with ASD compared to ADHD (p < 0.001). After Bonferroni correction, there was no significant difference in ASD in comparison with healthy controls (p = 0.132). A significant strong correlation between plasma OT and autistic symptomatology, assessed by the Autism Diagnostic Observation Schedule, was observed in the ASD group (p = 0.013, r = 0.603). Patients with ADHD differed from healthy control children by significantly decreased OT concentrations (p = 0.014). No significant influences of the covariates age, IQ, medication and comorbidity could be seen. Our preliminary results point to a correlation of OT plasma concentrations with autistic symptom load in children with ASD and a modulation of the OT system also in the etiologically and phenotypically overlapping disorder ADHD. Further studies in humans and animal models are warranted to clarify the complex association of the OT system with social impairments as well as stress-related and depressive behavior and whether peripheral findings reflect primary changes of OT synthesis and/or release in relevant areas of the CNS.

Aerosolized oxytocin increases cerebrospinal fluid oxytocin in rhesus macaques

Intranasal (IN) administration is a widely used method for examining the effect of oxytocin (OT) on social behavior and cognition in healthy subjects and psychiatric populations. IN-OT in humans enhances trust, emotional perception, and empathetic behavior and is under investigation as a potential pharmacotherapy to enhance social functioning in a variety of neuropsychiatric disorders, including autism spectrum disorders (ASD). Nonhuman primates (NHP) are an important model for understanding the effect of OT on social cognition, its neural mechanisms, and the development of IN-OT as a pharmacotherapy for treating social deficits in humans. However, NHP and even some human populations, such as very young infants and children, cannot easily follow the detailed self-administration protocol used in the majority of human IN-OT studies. Therefore, we evaluated the efficacy of several OT-administration routes for elevating central OT concentrations in rhesus macaques. First, we examined the effect of IN and intravenous (IV) routes of OT administration on concentrations of OT and vasopressin (AVP) in plasma and lumbar CSF. Second, we examined these same measures in monkeys after an aerosolized (AE) OT delivery route. All three administration routes significantly increased plasma OT concentrations, but only the AE-OT route significantly increased concentrations of CSF OT. No route affected concentrations of AVP in plasma or CSF. This study confirms that the AE route is the most effective method for increasing central OT concentrations in monkeys, and may also be an effective route, alternative to IN, for administering OT to some human populations.

Are maternal social networks and perceptions of trust associated with suspected autism spectrum disorder in offspring? A population-based study in Japan

Objective

To investigate the associations of maternal social networks and perceptions of trust with the prevalence of suspected autism spectrum disorders in 18-month-old offspring in Japan.

Methods

Questionnaires included measurements of maternal social networks (number of relatives or friends they could call upon for assistance), maternal perceptions of trust, mutual assistance (i.e. individual measures of “cognitive social capital”), and social participation (i.e. individual measures of “structural social capital”) as well as the Modified Checklist for Autism in Toddlers to detect suspected autism spectrum disorder (ASD). These tools were mailed to all families with 18-month-old toddlers in Chiba, a city near Tokyo (N = 6061; response rate: 64%). The association between social capital or social network indicators and suspected ASD were analyzed, adjusted for covariates by logistic regression analysis.

Results

Low maternal social trust was found to be significantly positively associated with suspected ASD in toddlers compared with high maternal social trust (adjusted odds ratio [OR]: 1.82, 95% confidence interval [CI]: 1.38 to 2.40); mutual aid was also significantly positively related (low vs. high: OR, 1.82, 95% CI: 1.38 to 2.40). However, maternal community participation showed U-shape association with suspected ASD of offspring. Maternal social network showed consistent inverse associations with suspected ASD of offspring, regardless of the type of social connection (e.g., relatives, neighbors, or friends living outside of their neighborhood).

Conclusions

Mothers' cognitive social capital and social networks, but not structural social capital, might be associated with suspected ASD in offspring.

Oxytocin is an age-specific circulating hormone that is necessary for muscle maintenance and regeneration

The regenerative capacity of skeletal muscle declines with age. Previous studies suggest that this process can be reversed by exposure to young circulation, but systemic age-specific factors responsible for this phenomenon are largely unknown. Here we report that oxytocin- a hormone best known for its role in lactation, parturition, and social behaviors - is required for proper muscle tissue regeneration and homeostasis, and that plasma levels of oxytocin decline with age. Inhibition of oxytocin signaling in young animals reduces muscle regeneration, whereas systemic administration of oxytocin rapidly improves muscle regeneration by enhancing aged muscle stem cell activation/proliferation throughactivation of the MAPK/ERK signalling pathway. We further show that the genetic lack of oxytocin does not cause a developmental defect in muscle, but instead leads to premature sarcopenia. Considering that oxytocin is an FDA approved drug, this work reveals a potential novel and safe way to combat or prevent skeletal muscle aging.

Basal salivary oxytocin level predicts extra- but not intra-personal dimensions of emotional intelligence

A wealth of literature suggests that oxytocin is an important mediator of social cognition, but much of the research to date has relied on pharmaceutical administration methods that can raise oxytocin to artificially high levels. The present study builds upon previous work by examining whether basal oxytocin level predicts intra- and extra-personal (i.e., self- and other-focused) elements of emotional intelligence (EI), independent of shared variance with current mood. The sample included 71 healthy young adults (46 women). Assessment measures included the Mayer-Salovey-Caruso Emotional Intelligence Test Version 2.0 (MSCEIT), the Trait Meta-Mood Scale, and the Profile of Mood States. Peripheral oxytocin levels were examined with enzyme-linked immunosorbent assay from saliva after solid phase extraction. Oxytocin level was unrelated to TMMS scores but was positively associated with performance in the Experiential EI domain of the MSCEIT. However, total mood disturbance was positively related to MSCEIT scores. Hierarchical regression analysis indicated that oxytocin level added unique variance to the prediction of MSCEIT performance beyond that of current mood. These results confirm an association between endogenous levels of oxytocin in healthy adults and a subset of EI abilities, including extra-personal emotion recognition and the channeling of emotions to enhance social proficiency.

Switching brain serotonin with oxytocin

Serotonin (5-HT) and oxytocin (OXT) are two neuromodulators involved in human affect and sociality and in disorders like depression and autism. We asked whether these chemical messengers interact in the regulation of emotion-based behavior by administering OXT or placebo to 24 healthy subjects and mapping cerebral 5-HT system by using 2'-methoxyphenyl-(N-2'-pyridinyl)-p-[(18)F]fluoro-benzamidoethylpiperazine ([(18)F]MPPF), an antagonist of 5-HT1A receptors. OXT increased [(18)F]MPPF nondisplaceable binding potential (BPND) in the dorsal raphe nucleus (DRN), the core area of 5-HT synthesis, and in the amygdala/hippocampal complex, insula, and orbitofrontal cortex. Importantly, the amygdala appears central in the regulation of 5-HT by OXT: [(18)F]MPPF BPND changes in the DRN correlated with changes in right amygdala, which were in turn correlated with changes in hippocampus, insula, subgenual, and orbitofrontal cortex, a circuit implicated in the control of stress, mood, and social behaviors. OXT administration is known to inhibit amygdala activity and results in a decrease of anxiety, whereas high amygdala activity and 5-HT dysregulation have been associated with increased anxiety. The present study reveals a previously unidentified form of interaction between these two systems in the human brain, i.e., the role of OXT in the inhibitory regulation of 5-HT signaling, which could lead to novel therapeutic strategies for mental disorders.

The developmental disruptions of serotonin signaling may involved in autism during early brain development

Autism is a developmental disorder defined by the presence of a triad of communication, social and stereo typical behavioral characteristics with onset before 3years of age. In spite of the fact that there are potential environmental factors for autistic behavior, the dysfunction of serotonin during early development of the brain could be playing a role in this prevalence rise. Serotonin can modulate a number of developmental events, including cell division, neuronal migration, cell differentiation and synaptogenesis. Hyperserotonemia during fetal development results in the loss of serotonin terminals through negative feedback. The increased serotonin causes a decrease of oxytocin in the paraventricular nucleus of the hypothalamus and an increase in calcitonin gene-related peptide (CGRP) in the central nucleus of the amygdale, which are associated with social interactions and vital in autism. However, hyposerotonemia may be also relevant to the development of sensory as well as motor and cognitive faculties. And the paucity of placenta-derived serotonin should have potential importance when the pathogenesis of autism is considered. This review briefly summarized the developmental disruptions of serotonin signaling involved in the pathogenesis of autism during early development of the brain.

An aberrant precision account of autism

Autism is a neurodevelopmental disorder characterized by problems with social-communication, restricted interests and repetitive behavior. A recent and thought-provoking article presented a normative explanation for the perceptual symptoms of autism in terms of a failure of Bayesian inference (Pellicano and Burr, 2012). In response, we suggested that when Bayesian inference is grounded in its neural instantiation—namely, predictive coding—many features of autistic perception can be attributed to aberrant precision (or beliefs about precision) within the context of hierarchical message passing in the brain (Friston et al., 2013). Here, we unpack the aberrant precision account of autism. Specifically, we consider how empirical findings—that speak directly or indirectly to neurobiological mechanisms—are consistent with the aberrant encoding of precision in autism; in particular, an imbalance of the precision ascribed to sensory evidence relative to prior beliefs.

A deletion involving CD38 and BST1 results in a fusion transcript in a patient with autism and asthma

CD38 encodes a ligand in the oxytocin signaling pathway. Some single nucleotide polymorphisms in this gene have been associated with low serum oxytocin levels in autism spectrum disorder (ASD) patients. Oxytocin disruption has been hypothesized to account for features of ASD, including impaired communication and social behavior, based on animal studies. Recent human studies have shown administration of oxytocin improving emotion recognition, promoting social behavior, and improving auditory processing of social stimuli in ASD patients. In addition to its role in oxytocin signaling, CD38 is involved in the regulation of calcium concentration in airway smooth muscle with impairment of CD38 being implicated in airway diseases like asthma. While a number of studies have implicated rare chromosomal deletions and duplications in helping determine genetic risk for autism, there are to our knowledge no reports describing rearrangements involving CD38 or deletions in patients with ASD. Here, we present two sisters diagnosed with autism and with features of regression-previously acquired speech lost in the second year of life. The younger sister, who also had asthma, inherited a maternal deletion of 4p15.32 that results in a BST1-CD38 fusion transcript. Their mother's deletion was mosaic and she was not affected. Although further work is required to assess functional consequences of the fusion transcript, we hypothesize that the proband's deletion may have served as a risk factor for autism that, when combined with other susceptibility variants, resulted in a more severe presentation than her sister.

The need for a comprehensive molecular characterization of autism spectrum disorders

Autism spectrum disorders (ASD) are a heterogeneous group of disorders which have complex behavioural phenotypes. Although ASD is a highly heritable neuropsychiatric disorder, genetic research alone has not provided a profound understanding of the underlying causes. Recent developments using biochemical tools such as transcriptomics, proteomics and cellular models, will pave the way to gain new insights into the underlying pathological pathways. This review addresses the state-of-the-art in the search for molecular biomarkers for ASD. In particular, the most important findings in the biochemical field are highlighted and the need for establishing streamlined interaction between behavioural studies, genetics and proteomics is stressed. Eventually, these approaches will lead to suitable translational ASD models and, therefore, a better disease understanding which may facilitate novel drug discovery efforts in this challenging field.

Associations between oxytocin-related genes and autistic-like traits

Oxytocin has repeatedly been shown to influence human behavior in social contexts; also, a relationship between oxytocin and the pathophysiology of autism spectrum disorder (ASD) has been suggested. In the present study, we investigated single-nucleotide polymorphisms (SNPs) in the oxytocin gene (OXT) and the genes for single-minded 1 (SIM1), aryl hydrocarbon receptor nuclear translocator 2 (ARNT2) and cluster of differentiation 38 (CD38) in a population of 1771 children from the Child and Adolescent Twin Study in Sweden (CATSS). Statistical analyses were performed to investigate any association between SNPs and autistic-like traits (ALTs), measured through ASD scores in the Autism-Tics, ADHD and other Co-morbidities inventory. Firstly, we found a statistically significant association between the SIM1 SNP rs3734354 (Pro352Thr) and scores for language impairment (p = .0004), but due to low statistical power this should be interpreted cautiously. Furthermore, nominal associations were found between ASD scores and SNPs in OXT, ARNT2 and CD38. In summary, the present study lends support to the hypothesis that oxytocin and oxytocin neuron development may have an influence on the development of ALTs and suggests a new candidate gene in the search for the pathophysiology of ASD.

Biomarkers in autism spectrum disorder: the old and the new

RATIONALE

Autism spectrum disorder (ASD) is a complex heterogeneous neurodevelopmental disorder with onset during early childhood and typically a life-long course. The majority of ASD cases stems from complex, 'multiple-hit', oligogenic/polygenic underpinnings involving several loci and possibly gene-environment interactions. These multiple layers of complexity spur interest into the identification of biomarkers able to define biologically homogeneous subgroups, predict autism risk prior to the onset of behavioural abnormalities, aid early diagnoses, predict the developmental trajectory of ASD children, predict response to treatment and identify children at risk for severe adverse reactions to psychoactive drugs.

OBJECTIVES

The present paper reviews (a) similarities and differences between the concepts of 'biomarker' and 'endophenotype', (b) established biomarkers and endophenotypes in autism research (biochemical, morphological, hormonal, immunological, neurophysiological and neuroanatomical, neuropsychological, behavioural), (c) -omics approaches towards the discovery of novel biomarker panels for ASD, (d) bioresource infrastructures and (e) data management for biomarker research in autism.

RESULTS

Known biomarkers, such as abnormal blood levels of serotonin, oxytocin, melatonin, immune cytokines and lymphocyte subtypes, multiple neuropsychological, electrophysiological and brain imaging parameters, will eventually merge with novel biomarkers identified using unbiased genomic, epigenomic, transcriptomic, proteomic and metabolomic methods, to generate multimarker panels. Bioresource infrastructures, data management and data analysis using artificial intelligence networks will be instrumental in supporting efforts to identify these biomarker panels.

CONCLUSIONS

Biomarker research has great heuristic potential in targeting autism diagnosis and treatment.

Psychopharmacological interventions in autism spectrum disorder

After participating in this educational activity, the physician should be better able to1. Prescribe the appropriate psychotropic medication to treat symptoms of ASD.2. Identify the side effects of the psychotropic medications used to treat ASD.Autism spectrum disorders (ASDs) are characterized by core deficits in social communication and language, and restrictive and repetitive behaviors that cause significant functional impairment and distress for affected individuals and their caregivers. The increasing prevalence of ASD, most recently estimated as 1 in 88 children, presents an ever-increasing burden on families, schools, medical systems, and society at large. Individuals with ASD commonly present for treatment of associated emotional and behavioral disturbances that include anxiety, symptoms of ADHD, compulsions and other repetitive behaviors, mood lability, irritability, aggression, and sleep disturbance. Psychotropic medications are widely utilized in alleviating these symptoms, though rigorous clinical trials in ASD are lacking for most areas of impairment. Strong evidence from randomized, placebo-controlled trials supports the use of atypical antipsychotics, particularly risperidone and aripiprazole, for managing severe irritability and aggression in ASD. Serotonin reuptake inhibitors are commonly used to treat anxiety and compulsions, though reports of efficacy in the literature are mixed, and behavioral side effects in children are common. Minimal evidence supports the utility of anticonvulsants and traditional mood stabilizers in managing mood lability and aggression. Stimulant and nonstimulant ADHD medications can be effective for reducing hyperactivity, inattention, and impulsivity, though to a lesser degree than in ADHD populations without ASD and with greater risk of adverse effects. Psychopharmacological interventions in development for core symptoms of autism include those that target the glutamatergic and GABAergic neurotransmitter systems and the neuropeptide oxytocin. Further research is needed to establish evidence-based interventions in ASD populations.

Vitamin D hormone regulates serotonin synthesis. Part 1: relevance for autism

Serotonin and vitamin D have been proposed to play a role in autism; however, no causal mechanism has been established. Here, we present evidence that vitamin D hormone (calcitriol) activates the transcription of the serotonin-synthesizing gene tryptophan hydroxylase 2 (TPH2) in the brain at a vitamin D response element (VDRE) and represses the transcription of TPH1 in tissues outside the blood-brain barrier at a distinct VDRE. The proposed mechanism explains 4 major characteristics associated with autism: the low concentrations of serotonin in the brain and its elevated concentrations in tissues outside the blood-brain barrier; the low concentrations of the vitamin D hormone precursor 25-hydroxyvitamin D [25(OH)D3]; the high male prevalence of autism; and the presence of maternal antibodies against fetal brain tissue. Two peptide hormones, oxytocin and vasopressin, are also associated with autism and genes encoding the oxytocin-neurophysin I preproprotein, the oxytocin receptor, and the arginine vasopressin receptor contain VDREs for activation. Supplementation with vitamin D and tryptophan is a practical and affordable solution to help prevent autism and possibly ameliorate some symptoms of the disorder.

Intranasal oxytocin in the treatment of autism spectrum disorders: a review of literature and early safety and efficacy data in youth

BACKGROUND

There is a paucity of treatments targeting core symptom domains in Autism Spectrum Disorder (ASD). Several animal models and research in typically developing volunteers suggests that manipulation of the oxytocin system may have therapeutic potential for the treatment of social deficits. We review the literature for oxytocin and ASD and report on early dosing, safety and efficacy data of multi-dose oxytocin on aspects of social cognition/function, as well as repetitive behaviors and co-occurring anxiety within ASD.

METHODS

Fifteen children and adolescents with verbal IQs≥70 were diagnosed with ASD using the ADOS and the ADI-R. They participated in a modified maximum tolerated dose study of intranasal oxytocin (Syntocinon). Data were modeled using repeated measures regression analysis controlling for week, dose, age, and sex.

RESULTS

Among 4 doses tested, the highest dose evaluated, 0.4 IU/kg/dose, was found to be well tolerated. No serious or severe adverse events were reported and adverse events reported/observed were mild to moderate. Over 12 weeks of treatment, several measures of social cognition/function, repetitive behaviors and anxiety showed sensitivity to change with some measures suggesting maintenance of effect 3 months past discontinuation of intranasal oxytocin.

CONCLUSIONS

This pilot study suggests that daily administration of intranasal oxytocin at 0.4 IU/kg/dose in children and adolescents with ASD is safe and has therapeutic potential. Larger studies are warranted. This article is part of a Special Issue entitled Oxytocin and Social Behav.