Self-injury in autism spectrum disorder: an effect of serotonin transporter gene promoter variants

A Systematic Review on Autism and Hyperserotonemia: State-of-the-Art, Limitations, and Future Directions

Hyperserotonemia is one of the most studied endophenotypes in autism spectrum disorder (ASD), but there are still no unequivocal results about its causes or biological and behavioral outcomes. This systematic review summarizes the studies investigating the relationship between blood serotonin (5-HT) levels and ASD, comparing diagnostic tools, analytical methods, and clinical outcomes. A literature search on peripheral 5-HT levels and ASD was conducted. In total, 1104 publications were screened, of which 113 entered the present systematic review. Of these, 59 articles reported hyperserotonemia in subjects with ASD, and 26 presented correlations between 5-HT levels and ASD-core clinical outcomes. The 5-HT levels are increased in about half, and correlations between hyperserotonemia and clinical outcomes are detected in a quarter of the studies. The present research highlights a large amount of heterogeneity in this field, ranging from the characterization of ASD and control groups to diagnostic and clinical assessments, from blood sampling procedures to analytical methods, allowing us to delineate critical topics for future studies.

Understanding Challenging Behaviors in Autism Spectrum Disorder: A Multi-Component, Interdisciplinary Model

A multi-component, interdisciplinary model is described which explains the presence of, and in other cases the lack of, many challenging behaviors associated with autism spectrum disorder (ASD). More specifically, the model expands the operant behavioral conditioning paradigm by taking into account medical comorbidities and interoceptive processing.

Self-injury as a predominant challenging behavior in epilepsy: A study in a residential facility for profoundly disabled patients

BACKGROUND

The association between challenging behavior (CB) and epilepsy in people with intellectual disability (ID) remains largely controversial.

AIM

To clarify the correlation between CB and epilepsy, we investigated the clinical characteristics of CB in both people with and without epilepsy among individuals with ID hospitalized in our residential facility.

METHODS AND PROCEDURES

A total of 63 individuals with CB was retrospectively investigated using the Behavior Problems Inventory, and the following items were collected from the medical records: sex, age, hospitalization period, etiology and risk factors, level of ID, type of CB, administration of psychotropic drugs, presence or absence of epilepsy and clinical features of epilepsy.

OUTCOMES AND RESULTS

Almost all individuals with CB showed profound ID. There was no significant difference in the rate of CB between people with and without epilepsy. A type analysis of CB revealed that self-injurious behavior was observed more frequently in epilepsy cases (66.7 %) than in cases without epilepsy (36.4 %) (p =  0.015), and self-injurious behavior was the predominant clinical form in people with epilepsy among the three subgroups of CB (self-injurious, aggressive and self-injurious and aggressive behavior).

CONCLUSIONS AND IMPLICATIONS

The high incidence of self-injurious behavior in epilepsy with profound disabilities may imply the presence of common pathological basis of self-injurious behavior and epilepsy.

Evidence that ITGB3 promoter variants increase serotonin blood levels by regulating platelet serotonin transporter trafficking

Elevated serotonin (5-HT) blood levels, the first biomarker identified in autism research, has been consistently found in 20-30% of patients with Autism Spectrum Disorder (ASD). Hyperserotonemia is mainly due to greater 5-HT uptake into platelets, mediated by the 5-HT transporter (SERT) located at the platelet plasma membrane. The protein complex involved in platelet SERT trafficking and externalization includes integrin β3, the beta subunit of the platelet membrane adhesive GP IIb/IIIa. Integrin β3 is encoded by the ITGB3 gene, previously identified as a quantitative trait locus (QTL) for 5-HT blood levels in ASD at single nucleotide polymorphism (SNP) rs2317385. The present study aims to identify the functional ITGB3 gene variants contributing to hyperserotonemia. ITGB3 gene sequencing in 20 individuals selected on the basis of rs2317385 genotypes defined four haplotypes encompassing six SNPs located in the ITGB3 gene promoter region, all in linkage disequilibrium with rs2317385. Luciferase assays in two hematopoietic cell lines, K-562 and HEL 92.1.7, demonstrate that ITGB3 gene promoter activity is enhanced by the presence of the C allele at rs55827077 specifically during differentiation into megakaryocytes (P < 0.01), with modulatory effects by flanking SNPs. This same allele is strongly associated with (a) higher 5-HT blood levels in 176 autistic individuals (P < 0.001), (b) greater platelet integrin β3 protein expression (P < 0.05) and (c) enhanced SERT trafficking from the cytosol toward the platelet plasma membrane (P = 4.05 × 10-11). Our results support rs55827077 as the functional ITGB3 gene promoter variant contributing to elevated 5-HT blood levels in ASD and define a mechanistic chain of events linking ITGB3 to hyperserotonemia.

Citalopram attenuates social behavior deficits in the BTBR T+Itpr3tf/J mouse model of autism

Autism spectrum disorder (ASD) is diagnosed by two core symptoms: impaired social communication and the presence of repetitive, stereotyped behaviors and/or restricted interests. Alterations in serotonergic signaling are involved in the genesis of ASD. Selective serotonin reuptake inhibitors (SSRIs) have been reported to reduce repetitive behaviors and rescue social deficits in ASD mouse models and patients. In the present study, we examined the potential of citalopram (a representative selective serotonin reuptake inhibitor) on sociability and repetitive behaviors in the BTBR T⁺Itpr3^tf/J (BTBR) mouse model of ASD. We found that the deficits of sociability in the BTBR mice were reversed by a 20 mg/kg dose of citalopram treatment without any adverse effects on locomotor activity or anxiety level. In addition, both high (20 mg/kg) and low (10 mg/kg) doses decreased the repetitive behavior of marble burying but did not affect self-grooming behavior. Furthermore, both doses were shown to have antidepressant-like activity in both the B6 and the BTBR mice in the tail suspension test. Taken together, these findings further demonstrate that citalopram can alleviate behavioral abnormalities in the BTBR autism model and lend support to the hypothesis that SSRIs may be potential therapeutic drugs for the treatment of behavioral dysfunctions in ASD.

Lurasidone for the Treatment of Irritability Associated with Autistic Disorder

The aim of this study was to evaluate the short-term efficacy and safety of lurasidone in treating irritability associated with autistic disorder. In this multicenter trial, outpatients age 6–17 years who met DSM-IV-TR criteria for autistic disorder, and who demonstrated irritability, agitation, and/or self-injurious behaviors were randomized to 6 weeks of double-blind treatment with lurasidone 20 mg/day (N = 50), 60 mg/day (N = 49), or placebo (N = 51). Efficacy measures included the Aberrant Behavior Checklist Irritability subscale (ABC-I, the primary endpoint) and the Clinical Global Impressions, Improvement (CGI-I) scale, and were analyzed using a likelihood-based mixed model for repeated measures. Least squares (LS) mean (standard error [SE]) improvement from baseline to Week 6 in the ABC-I was not significantly different for lurasidone 20 mg/day (−8.8 [1.5]) and lurasidone 60 mg/day (−9.4 [1.4]) versus placebo (−7.5 [1.5]; p = 0.55 and 0.36, respectively). CGI-I scores showed significantly greater LS mean [SE] improvement at Week 6 for lurasidone 20 mg/day versus placebo (2.8 [0.2] vs. 3.4 [0.2]; p = 0.035) but not for lurasidone 60 mg/day (3.1 [0.2]; p = 0.27). Discontinuation rates due to adverse events were: lurasidone 20 mg/day, 4.1 %; 60 mg/day, 3.9 %; and placebo, 8.2 %. Adverse events with an incidence ≥10 % (lurasidone combined, placebo) included vomiting (18.0, 4.1 %) and somnolence (12.0, 4.1 %). Modest changes were observed in weight and selected metabolic parameters. In this study, once-daily, fixed doses of 20 and 60 mg/day of lurasidone were not demonstrated to be efficacious compared to placebo for the short-term treatment of children and adolescents with moderate-to-severe irritability associated with autistic disorder.