Neurobiology of Aggressive Behavior-Role of Autoantibodies Reactive With Stress-Related Peptide Hormones

Associations of the AVPR1A RS1 Microsatellite Locus with the Level of Hormones of the Anterior Pituitary Gland and Personality Traits

The arginine vasopressin receptor gene (AVPR1A) is one of the genes affecting mental processes. The aim of this study was to search for associations of microsatellite locus RS1, which is related to the AVPR1A expression level, with the level of hormones of the anterior pituitary gland and personality traits. The study sample included Yakut men aged 18-26 years (n = 121). The analysis of RS1 locus was carried out using the PCR method and sequencing of the primary nucleotide sequence. Serum hormonal levels of thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH) and prolactin were determined by the time-resolved fluorescence immunoassay (DELFIA), plasma adrenocorticotropic hormone (ACTH) levels were determined by enzyme-linked immunosorbent assay (ELISA). In the Yakut population "short" (S) alleles of the AVPR1A RS1 locus containing ≤ 10 repeats (63%) and the corresponding SS genotypes (44.6%) were more frequent, while individuals with "long" (LL) and "heterozygous" (SL) genotypes accounted for 18.2 and 37.2%, respectively. The range of concentrations of ACTH and TSH in the group of SS genotype carriers was significantly lower than that observed in the group of LL genotype carriers (p = 0.042 and p = 0.048, respectively); the LH level was significantly higher (p = 0.029). The trend towards higher neuroticism in SS genotype carriers compared to the individuals with LL genotypes (p = 0.05) is revealed. The results obtained indicate the modulating effect of genetic variants of the AVPR1A gene on the level of anterior pituitary hormones, which could slightly affect the level of neuroticism in humans.

Functional role of immunoglobulin G as an oxytocin-carrier protein

It has been long-time known that oxytocin in plasma is bound to a carrier protein, a common feature of circulating peptide hormones, however, the nature of such protein was uncertain. A recent study revealed that about 60% of oxytocin present in plasma is bound to immunoglobulin G (IgG) and that oxytocin-binding IgG plays a role of a functional oxytocin carrier protein. Here, we review the historical background and methodology leading to this discovery. Moreover, we review the data showing the functional role of oxytocin-binding IgG in the modulation of oxytocin signaling relevant to the regulation of motivated behavior and several neuropsychiatric disorders. Furthermore, the possible role of gut microbiota in the origin of such IgG is discussed and the relevant new therapeutic strategies for the enhancement of oxytocin signaling are presented.

Plasma neuropeptide levels in patients with schizophrenia, bipolar disorder, or major depressive disorder and healthy controls: A multiplex immunoassay study

AIM

We aimed to compare neuropeptide levels between patients with major psychiatric disorders and healthy controls and examine their association with symptoms and cognitive function.

METHODS

The participants were 149 patients with schizophrenia, 115 patients with bipolar disorder (BD), 186 unremitted patients with major depressive disorder (MDD), and 350 healthy controls. Psychiatric (schizophrenic, manic, and depressive) symptoms, sleep state, and cognitive (premorbid intelligence quotient, general cognitive, and memory) functions were evaluated. A multiplex immunoassay kit was used to measure cerebrospinal fluid (CSF) and plasma α-melanocyte-stimulating hormone (MSH), β-endorphin, neurotensin, oxytocin, and substance P levels.

RESULTS

The verification assay revealed that CSF α-MSH, β-endorphin, neurotensin, oxytocin, and substance P levels were too low to be reliably measured, while plasma α-MSH, β-endorphin, neurotensin, oxytocin, and substance P levels could be successfully measured. Plasma α-MSH, β-endorphin, neurotensin, oxytocin, and substance P levels were not significantly different between patients with schizophrenia, BD, or MDD and healthy controls. Plasma α-MSH, β-endorphin, neurotensin, oxytocin, and substance P levels were not significantly correlated with psychiatric symptom scores in patients with schizophrenia, BD, or MDD and cognitive function scores in patients or healthy controls.

CONCLUSION

Our data suggest that plasma neuropeptide levels do not elucidate the involvement of neuropeptides in the pathology of schizophrenia, BD, or MDD.

Blood Levels of Neuropeptide 26RFa in Relation to Anxiety and Aggressive Behavior in Humans-An Exploratory Study

26RFa, also referred to as QRFP, is a hypothalamic neuropeptide mainly known for its role in the regulation of appetite and glucose metabolism. Its possible relevance to emotional regulation is largely unexplored. To address this, in the present exploratory study, we analyzed the plasma concentrations of 26RFa in humans characterized by different levels of anxiety and aggressive behavior. For this purpose, the study included 13 prison inmates who have committed violent crimes and 19 age-matched healthy men from the general population as controls. Anxiety, depression and aggressive behavior were evaluated in both groups using standard questionnaires. The inmate group was characterized by increased aggression and anxiety compared to the controls. We found that the mean plasma levels of 26RFa did not significantly differ between the inmates and the controls. However, several high outliers were present only in the inmate group. The plasma levels of 26RFa correlated positively with the anxiety scores in all the studied subjects and controls. After removing the high outliers in the inmate group, positive correlations of 26RFa with anxiety and a subscale of hostility in the aggression scale were also recorded in this group. No significant correlations of 26RFa with depression scores or other parameters of aggressive behavior were found. Thus, the present results did not support an involvement of 26RFa in aggressive behavior in humans but pointed to a link between this neuropeptide and anxiety. Nevertheless, considering the exploratory nature of the present study, this conclusion should be verified in a larger cohort, including the clinical degree of anxiety.

Neuropsychological Characterization of Aggressive Behavior in Children and Adolescents with CD/ODD and Effects of Single Doses of Medications: The Protocol of the Matrics_WP6-1 Study

Aggressive behaviors and disruptive/conduct disorders are some of the commonest reasons for referral to youth mental health services; nevertheless, the efficacy of therapeutic interventions in real-world clinical practice remains unclear. In order to define more appropriate targets for innovative pharmacological therapies for disruptive/conduct disorders, the European Commission within the Seventh Framework Programme (FP7) funded the MATRICS project (Multidisciplinary Approaches to Translational Research in Conduct Syndromes) to identify neural, genetic, and molecular factors underpinning the pathogenesis of aggression/antisocial behavior in preclinical models and clinical samples. Within the program, a multicentre case-control study, followed by a single-blind, placebo-controlled, cross-over, randomized acute single-dose medication challenge, was conducted at two Italian sites. Aggressive children and adolescents with conduct disorder (CD) or oppositional defiant disorder (ODD) were compared to the same age (10–17 y) typically developing controls (TDC) on a neuropsychological tasks battery that included both “cold” (e.g., inhibitory control, decision making) and “hot” executive functions (e.g., moral judgment, emotion processing, risk assessment). Selected autonomic measures (heart rate variability, skin conductance, salivary cortisol) were recorded before/during/after neuropsychological testing sessions. The acute response to different drugs (methylphenidate/atomoxetine, risperidone/aripiprazole, or placebo) was also examined in the ODD/CD cohort in order to identify potential neuropsychological/physiological mechanisms underlying aggression. The paper describes the protocol of the clinical MATRICS WP6-1 study, its rationale, the specific outcome measures, and their implications for a precision medicine approach.

Adrenocortical Activity and Aggressive Behavior in Children: A Longitudinal Study on Risk and Protective Effects

Most research on aggression and delinquency concentrates on risk factors. There has been less attention for protective factors and mechanisms, in particular with regard to biosocial influences. Based on theories of autonomous arousal and stress reactance the present study addresses the influence of adrenocortical activity as a risk and/or protective factor in the development of antisocial behavior in children. We also investigated relations to anxiousness and family stressors. In a prospective longitudinal study of 150 German boys, the first measurement took place at preschool age and contained an assessment of cortisol after waking up and 30 min later. Aggressiveness and anxiousness of the children were assessed by the kindergarten teachers with the Social Behavior Questionnaire. After 6 years, the children's behavior was rated by the teachers in middle school. Variable-oriented data analyses revealed a significant correlation between the total amount of cortisol after waking up and 30 min later (AUC _G ) and anxiousness both cross-sectionally and longitudinally, but not with aggressiveness. A family stress index correlated positively with aggressiveness but neither with cortisol nor with anxiousness. There were significant correlations between aggressiveness and anxiousness at kindergarten age and the respective behavior problems 6 years later. In a linear regression analysis on aggression only family stress had a significant effect but anxiousness not. Moderator analyses on aggressiveness with anxiousness and AUC _G or on AUC _G with anxiousness and aggressiveness did not show any significant interactions. Longitudinally, only aggression significantly predicted aggression 6 years later in a linear regression. In addition to variable-oriented analyses, we also applied a person-oriented approach to investigate specific patterns of behavior. Children who were high in both aggressiveness and anxiousness had the highest cortisol level and those with low anxiousness and high aggressiveness the lowest. The groups with different patterns of externalizing and internalizing problems at preschool age showed significant differences in aggression 6 years later. Our results underline the need for complex pattern analyses on cortisol, aggression, and anxiousness in children and for a differentiated consideration of emotional reactive aggression and unemotional instrumental aggression.