Serotonin dysregulation in adolescents with major depression: hormone response to meta-chlorophenylpiperazine (mCPP) infusion

Hormonal Imbalance as a Prognostic Factor of Physical Development of Children with Intellectual Disability

INTRODUCTION

The purpose was to study the indicators of physical development of primary-school-aged children with intellectual disability by observing the type of autonomic nervous regulation and their levels of catecholamines and serotonin.

METHODS

A total of 168 primary school age children were examined, of which 54 had intellectual disability. The autonomic nervous system was assessed using cardiointervalography; anthropometric parameters were applied in accordance with recommendations. The contents of serotonin and catecholamines in blood plasma and lymphocytes were assessed using enzyme immunoassay and luminescent histochemical methods.

RESULTS AND CONCLUSIONS

Delayed physical and mental development in children with intellectual disability were associated with low serotonin levels in this group of children. The optimal option for the physical development of children with intellectual disability is a sympathetic type of autonomic nervous regulation, while negative-type vagotonic nervous regulation was associated with the maximum delay in physical development. The hypersympathetic type of nervous regulation was accompanied by minimal changes in physical development, despite the hormonal imbalance in the ratio of catecholamines and serotonin. The level of the neurotransmitter serotonin is a prognostic marker of the physical development of children of primary school age. The total amount of catecholamines and serotonin in blood plasma has a direct relationship with the amount of these neurotransmitters in blood lymphocytes; the more hormones in plasma, the more of them in lymphocytes. Therefore, the determination of the contents of catecholamines and serotonin in lymphocytes can be used as a model for studying neurotransmitters in humans.

Identification of Key Modules and Genes Associated with Major Depressive Disorder in Adolescents

Major depressive disorder (MDD) is a leading cause of disability worldwide. Adolescence is a crucial period for the occurrence and development of depression. There are essential distinctions between adolescent and adult depression patients, and the etiology of depressive disorder is unclear. The interactions of multiple genes in a co-expression network are likely to be involved in the physiopathology of MDD. In the present study, RNA-Seq data of mRNA were acquired from the peripheral blood of MDD in adolescents and healthy control (HC) subjects. Co-expression modules were constructed via weighted gene co-expression network analysis (WGCNA) to investigate the relationships between the underlying modules and MDD in adolescents. In the combined MDD and HC groups, the dynamic tree cutting method was utilized to assign genes to modules through hierarchical clustering. Moreover, functional enrichment analysis was conducted on those co-expression genes from interested modules. The results showed that eight modules were constructed by WGCNA. The blue module was significantly associated with MDD after multiple comparison adjustment. Several Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways associated with stress and inflammation were identified in this module, including histone methylation, apoptosis, NF-kappa β signaling pathway, and TNF signaling pathway. Five genes related to inflammation, immunity, and the nervous system were identified as hub genes: CNTNAP3, IL1RAP, MEGF9, UBE2W, and UBE2D1. All of these findings supported that MDD was associated with stress, inflammation, and immune responses, helping us to obtain a better understanding of the internal molecular mechanism and to explore biomarkers for the diagnosis or treatment of depression in adolescents.

Cortisol and development of depression in adolescence and young adulthood - a systematic review and meta-analysis

INTRODUCTION

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been implicated in the development of major depressive disorder (MDD) in adulthood. Less work has focused on the role of the HPA axis in depression in adolescence and young adulthood globally. The aim of this study was to conduct a systematic review and meta-analysis of worldwide research investigating the relationship between cortisol, a measure of HPA axis activity, and MDD in adolescence and young adulthood.

METHOD

We searched MEDLINE, PsycINFO, Cochrane Database of Systematic Reviews, Web of Science, Lilacs, African Journals Online, and Global Health for studies which examined the relationship between cortisol and MDD in global youth (10-24 years old).

RESULTS

Twenty-six studies were included in the systematic review and 14 were eligible for the meta-analysis, but only one study included young adults in their sample. Results from the meta-analysis demonstrated that elevated morning, but not evening, cortisol levels was prospectively associated with later MDD development in adolescence and young adulthood. However, morning cortisol levels did not significantly differ between healthy controls and individuals with MDD in cross-sectional studies. Afternoon cortisol and cortisol stress response also did not differ between adolescents with MDD and healthy controls. Qualitative synthesis of the three studies examining nocturnal cortisol showed higher nocturnal cortisol was both longitudinally and cross-sectionally associated with MDD in adolescence.

CONCLUSION

Our findings suggest elevated morning cortisol precedes depression in adolescence. Despite this, we did not find any differences in other cortisol measures in association with MDD in cross-sectional studies. Taken together, these findings suggest that elevated morning and nocturnal cortisol are risk factors for depression in adolescence rather than a biomarker of existing MDD. This supports a role for the hyperactivity of the HPA axis in the development of MDD in adolescence. Most of the studies were from high-income-countries (HICs) and thus further work would need to be conducted in low- and middle-income countries (LMICs) to understand if our findings are generalisable also to these populations.

Serotonin transporter gene promoter methylation status correlates with in vivo prefrontal 5-HTT availability and reward function in human obesity

A polymorphism in the promoter region of the human serotonin transporter (5-HTT)-coding SLC6A4 gene (5-HTTLPR) has been implicated in moderating susceptibility to stress-related psychopathology and to possess regulatory functions on human in vivo 5-HTT availability. However, data on a direct relation between 5-HTTLPR and in vivo 5-HTT availability have been inconsistent. Additional factors such as epigenetic modifications of 5-HTTLPR might contribute to this association. This is of particular interest in the context of obesity, as an association with 5-HTTLPR hypermethylation has previously been reported. Here, we tested the hypothesis that methylation rates of 14 cytosine-phosphate-guanine (CpG) 5-HTTLPR loci, in vivo central 5-HTT availability as measured with [¹¹C]DASB positron emission tomography (PET) and body mass index (BMI) are related in a group of 30 obese (age: 36±10 years, BMI>35 kg/m²) and 14 normal-weight controls (age 36±7 years, BMI<25 kg/m²). No significant association between 5-HTTLPR methylation and BMI overall was found. However, site-specific elevations in 5-HTTLPR methylation rates were significantly associated with lower 5-HTT availability in regions of the prefrontal cortex (PFC) specifically within the obese group when analyzed in isolation. This association was independent of functional 5-HTTLPR allelic variation. In addition, negative correlative data showed that CpG10-associated 5-HTT availability determines levels of reward sensitivity in obesity. Together, our findings suggest that epigenetic mechanisms rather than 5-HTTLPR alone influence in vivo 5-HTT availability, predominantly in regions having a critical role in reward processing, and this might have an impact on the progression of the obese phenotype.

Controversies on the role of 5-HT(2C) receptors in the mechanisms of action of antidepressant drugs

Evidence from the various sources indicates alterations in 5-HT2C receptor functions in anxiety, depression and suicide, and other stress-related disorders treated with antidepressant drugs. Although the notion of a 5-HT2C receptor desensitization following antidepressant treatments is rather well anchored in the literature, this concept is mainly based on in vitro assays and/or behavioral assays (hypolocomotion, hyperthermia) that have poor relevance to anxio-depressive disorders. Our objective herein is to provide a comprehensive overview of the studies that have assessed the effects of antidepressant drugs on 5-HT2C receptors. Relevant molecular (second messengers, editing), neurochemical (receptor binding and mRNA levels), physiological (5-HT2C receptor-induced hyperthermia and hormone release), behavioral (5-HT2C receptor-induced changes in feeding, anxiety, defense and motor activity) data are summarized and discussed. Setting the record straight about drug-induced changes in 5-HT2C receptor function in specific brain regions should help to determine which pharmacotherapeutic strategy is best for affective and anxiety disorders.

RNA splicing and editing modulation of 5-HT(2C) receptor function: relevance to anxiety and aggression in VGV mice

Changes in serotonin(2C) receptor (5-HTR2c) editing, splicing and density were found in conditions such as depression and suicide, but mechanisms explaining the changes in 5-HTR2c function are unknown. Thus, mice expressing only the fully edited VGV isoform of 5-HTR2c, in which clinically relevant behavioral changes are associated with alterations in splicing and receptor density, were studied. VGV mice displayed enhanced anxiety-like behavior in response to a preferential 5-HTR2c agonist in the social interaction test. Nearly half of interactions between pairs of VGV congeners consisted of fighting behaviors, whereas no fighting occurred in wild-type (WT) mice. VGV mice also exhibited a striking increase in freezing behaviors in reaction to an innately aversive ultrasonic stimulus. This behavioral phenotype occurred in conjunction with decreased brain 5-HT turnover during stress. These functional data were put in relation with the 5-HTR2c mRNA splicing process generating a truncated protein (5-HTR2c-Tr) in addition to the full-length receptor (5-HTR2c-Fl). 5-HTR2c-Tr mRNA was less abundant in many brain regions of VGV mice, which concomitantly had more 5-HTR2c than WT mice. Fluorescence resonance energy transfer and bioluminescence resonance energy transfer studies in transfected living HEK293T cells showed that 5-HTR2c-Tr interacts with 5-HTR2c-Fl. The 5-HTR2c-Tr was localized in the endoplasmic reticulum where it retained 5-HTR2c-Fl, preventing the latter to reach the plasma membrane. Consequently, 5-HTR2c-Tr decreased (3)H-mesulergine binding to 5-HTR2c-Fl at the plasma membrane in a concentration-dependent manner and more strongly with edited 5-HTR2c-Fl. These results suggest that 5-HTR2c pre-mRNA editing and splicing are entwined processes determining increased 5-HTR2c levels in pathological conditions through a deficit in 5-HTR2c-Tr.

Neurobiology of depression in children and adolescents

This article reviews classical and updated studies of the neurobiology of depressive disorders in children and adolescents. Most studies of childhood and adolescent depression and suicide have followed up the observations and methods used in studies in adults. These studies include neuroendocrine studies, which particularly look at the hypothalamic-pituitary-adrenal axis, the serotonergic system, peripheral blood and cerebrospinal fluid biologic markers, genetics, gene-environment interactions and sleep studies, and neuroimaging and postmortem studies, although in these areas the number of studies is limited.

Central serotonergic effects of m-chlorophenylpiperazine (mCPP) among normal control adolescents

Central serotonin function was studied among 21 adolescents (12 males, 9 females), mean age 14.4+/-1.5 years. A placebo-controlled design was used to measure three neuroendocrine hormones (prolactin, cortisol and growth hormone) following a challenge with the central serotonergic agonist m-chlorophenylpiperazine (mCPP). Infusion of mCPP resulted in augmented prolactin, cortisol and growth hormone release. Gender effects were significant for prolactin, cortisol and growth hormone. Females had higher baseline prolactin without significant interactions with infusion or time, cortisol levels were higher in males than in females at all time points without significant interactions with infusion or time, and the augmented growth hormone response to mCPP was limited to males. Systolic and diastolic blood pressure, heart rate and temperature were all mildly elevated following mCPP infusion. Side effects to mCPP infusion were mild and lasted approximately 20 min. We conclude that mCPP is useful in the study of serotonergic neuroendocrine hormones in adolescents, is well tolerated, and the levels of prolactin, cortisol and growth hormone are influenced by gender.