MR imaging-detectable metabolic alterations in attention deficit/hyperactivity disorder: from preclinical to clinical studies

Settling a distracted globe: An overview of psychosocial and psychotherapeutic treatment of attention-deficit/hyperactivity disorder

While the currently prevailing theory of ADHD postulates a neurobiological background and core deficits of behavioural inhibition and executive functioning as the basis of ADHD symptoms, our current conceptualisation also acknowledges the essential contributory role of psychosocial, ecological, and cognitive factors. Considering the multifactorial background of ADHD, its treatment equally needs to be multifactorial involving, besides pharmacotherapy, skill development and psychotherapy as well, especially if we postulate the increasing contribution of social factors in the background of the increasing burden of ADHD. Pharmacotherapies, including stimulants and non-stimulant ADHD medications applied as first-line treatments have a positive effect on core behavioural symptoms, however, they often do not sufficiently remediate several other symptoms and comorbid disorders, which are consequences of ADHD, especially considering that ADHD persists into adulthood and is present over the whole life span. Furthermore, pharmacological treatment is not sufficient to substitute for the skills needed to manage symptoms and adapt well to the environment. As part of a multimodal treatment approach, psychological therapies for ADHD target, besides core ADHD symptoms, other associated features including emotional dysregulation, personality development, neurocognitive dysfunction, depression, anxiety, and sleep problems. Insufficiently treated ADHD may contribute to psychological and personality developmental problems in children, as well as increased health costs and decreased productivity warranting multimodal treatment to address the areas not sufficiently targeted by ADHD-specific pharmacotherapy.

The Role of Choline in Neurodevelopmental Disorders-A Narrative Review Focusing on ASC, ADHD and Dyslexia

Neurodevelopmental disorders appear to be rising in prevalence, according to the recent Global Burden of Disease Study. This rise is likely to be multi-factorial, but the role of certain nutrients known to facilitate neurodevelopment should be considered. One possible contributing factor could be attributed to deficits in choline intake, particularly during key stages of neurodevelopment, which includes the first 1000 days of life and childhood. Choline, a key micronutrient, is crucial for optimal neurodevelopment and brain functioning of offspring. The present narrative review discusses the main research, describing the effect of choline in neurodevelopmental disorders, to better understand its role in the etiology and management of these disorders. In terms of findings, low choline intakes and reduced or altered choline status have been reported in relevant population subgroups: pregnancy (in utero), children with autism spectrum disorders, people with attention deficit hyperactivity disorder and those with dyslexia. In conclusion, an optimal choline provision may offer some neuronal protection in early life and help to mitigate some cognitive effects in later life attributed to neurodevelopmental conditions. Research indicates that choline may act as a modifiable risk factor for certain neurodevelopmental conditions. Ongoing research is needed to unravel the mechanisms and explanations.

Effects of methylphenidate on mismatch negativity and P3a amplitude of initially psychostimulant-naïve, adult ADHD patients

BACKGROUND

Deficient information processing in ADHD theoretically results in sensory overload and may underlie the symptoms of the disorder. Mismatch negativity (MMN) and P3a amplitude reflect an individual's detection and subsequent change in attention to stimulus change in their environment. Our primary aim was to explore MMN and P3a amplitude in adult ADHD patients and to examine the effects of methylphenidate (MPH) on these measures.

METHODS

Forty initially psychostimulant-naïve, adult ADHD patients without comorbid ASD and 42 matched healthy controls (HC) were assessed with an MMN paradigm at baseline. Both groups were retested after 6 weeks, in which patients were treated with MPH.

RESULTS

Neither significant group differences in MMN nor P3a amplitude were found at baseline. Although 6-week MPH treatment significantly reduced symptomatology and improved daily functioning of the patients, it did not significantly affect MMN amplitude; however, it did significantly reduce P3a amplitude compared to the HC. Furthermore, more severe ADHD symptoms were significantly associated with larger MMN amplitudes in the patients, both at baseline and follow-up.

CONCLUSION

We found no evidence for early information processing deficits in patients with ADHD, as measured with MMN and P3a amplitude. Six-week treatment with MPH decreased P3a but not MMN amplitude, although more severe ADHD-symptoms were associated with larger MMN amplitudes in the patients. Given that P3a amplitude represents an important attentional process and that glutamate has been linked to both ADHD and MMN amplitude, future research should investigate augmenting MPH treatment of less responsive adults with ADHD with glutamatergic antagonists.

Fronto-Cerebellar Neurometabolite Alterations After Methylphenidate in Children and Adolescents With ADHD: A Proton Magnetic Resonance Spectroscopy Study

OBJECTIVE

The fronto-cerebellar circuit is involved in ADHD pathophysiology. Methylphenidate, as a first-line medication for ADHD, affects different brain regions, however, its effect on the fronto-cerebellar circuit is not investigated sufficiently. We aimed to investigate the effect of 8-week treatment with methylphenidate on neurometabolite ratios in the fronto-cerebellar circuit in ADHD participants using magnetic resonance spectroscopy (MRS).

METHODS

Fifteen drug-naïve ADHD children and adolescents were enrolled in the present study. Two single-voxel MR spectra were acquired from the right dorsolateral prefrontal cortex (DLPFC) and left Crus 1, before and after the medication. Also, neuropsychological and behavioral assessments were administered.

RESULTS

After medication, the glutamate/creatine in the DLPFC and the choline/creatine in the Crus 1 decreased in the ADHD participants.

CONCLUSION

These findings propose that methylphenidate-induced metabolite changes in the fronto-cerebellar circuit could be associated with improvement in cognitive/behavioral characteristics in ADHD. Also, results highlighted cerebellar engagement in ADHD pathophysiology.

MEF2C gene variations are associated with ADHD in the Chinese Han population: a case-control study

Myocyte enhancer factor 2C (MEF2C) is associated with hyperactivity and might be a novel risk gene for susceptibility to attention deficit hyperactivity disorder (ADHD). Therefore, this study aimed to explore the association between MEF2C genetic variants and ADHD in the Chinese Han population. A total of 215 patients with ADHD and 233 controls were recruited for this study. The Swanson, Nolan, and Pelham version IV questionnaire was used to evaluate the clinical features of ADHD. In silico analysis was used to annotate the biological functions of the promising single nucleotide polymorphisms. Our findings indicated that MEF2C rs587490 was significantly associated with ADHD in the multiplicative model (OR = 0.640, p = 0.002). Participants with the rs587490 TT allele exhibited less hyperactivity/impulsivity than those with the rs587490 CC allele. Furthermore, the expression quantitative trait loci analysis suggested that rs587490 could regulate the gene expression of MEF2C in the hippocampus, putamen, thalamus, and frontal white matter. Our study concluded that the MEF2C rs587490 T allele is significantly associated with a reduced risk of ADHD in the Chinese Han population, which provides new insight into the genetic etiology of ADHD.

Striatal dynamics as determinants of reduced gambling vulnerability in the NHE rat model of ADHD

The Naples High-Excitability (NHE) is a validated rat strain to model for a mesocortical variant of Attention Deficit Hyperactivity Disorder (ADHD). NHE rats' brains have a tuned-down cortical and a potentiated limbic loop (Zoratto et al., 2017). ADHD and comorbid pathological gambling (PG) involve similar deficits of prefrontal-striatal dialogue. This work aimed to understand if NHE rats (compared to normal random-bred rats, NRB) can be a useful model for gambling vulnerability in ADHD. Experiment 1 evaluated gambling proneness in NHE rats, namely attraction/avoidance in nose-poking for a "Large & Luck-Linked" (LLL) reward (versus a "Small & Sure" one, SS), when the probability of LLL delivery was progressively reduced. Experiment 2 assessed (by phMRI) differential responsivity of ventral (vStr) versus dorsal (dStr) striatum following a methylphenidate (MPH, 4 mg/kg I.P.) challenge. In NHE rats, reduced attraction by secondary cues (associated with uncertain, rarefying LLL delivery) comes along with little or no activation of dStr and enhanced activation of vStr by MPH. Together, such evidences from NHE rats indicate distinctive roles of ventral (enhanced value given to actual primary reward) and dorsal (lower encoding of repeated stimulus-reward associations into a habit) striatum. In conclusion, the dynamics of reward systems could link an attention deficit with a decreased vulnerability to pathological gambling.

Neurochemical Correlates of Executive Function in Children with Attention-Deficit/Hyperactivity Disorder

OBJECTIVES

Attention-Deficit/Hyperactivity Disorder (ADHD) is a prevalent neurodevelopmental disorder with no known biomarkers. The objectives of this study were 1) to investigate spectroscopic biomarkers in the right prefrontal cortex (R-PFC) and left striatum; 2) to evaluate Executive Function (EF) performance; and, 3) to examine the clinical relevance of glutamate in EF tasks.

METHODS

A total of 21 children with ADHD (M = 10.41 years, SD = 1.41) and 15 controls without ADHD (M = 9.90 years, SD = 1.54 years) were enrolled. Short echo proton magnetic resonance spectroscopy (1H-MRS; TE = 30ms) was used to study the changes in the R-PFC and left striatum. Both groups completed an EF assessment battery, including working memory, inhibition, cognitive flexibility and verbal fluency tasks.

RESULTS

In the R-PFC, independent t-tests found decreased concentration of glutamate (p = 0.009), NAA (p = 0.029) and choline (p = 0.016) in ADHD participants compared to controls. No significant differences were seen in the left striatum. Multivariate analysis of variance did not indicate overall EF challenges in the ADHD sample (p < .05). Positive correlations with glutamate concentration and EF performance in the control group were observed, however, no such correlations were reported in the ADHD group.

CONCLUSIONS

The results indicated a subgroup of children with ADHD who presented with hypo-glutamatergic signalling in the R-PFC. Additionally, findings suggested a decoupling effect of glutamate in EF related tasks in children with ADHD compared to controls. Thus, glutamate concentration may be a possible ADHD biomarker and novel treatments target.

Hyperactivity and impulsivity in adult attention-deficit/hyperactivity disorder is related to glutamatergic dysfunction in the anterior cingulate cortex

OBJECTIVES

Attention-deficit/hyperactivity disorder (ADHD) is closely linked to the dysregulation of dopaminergic and noradrenergic neurotransmission in the fronto-striatal neural network, including the anterior cingulate cortex (ACC) and the dorsolateral prefrontal cortex (DLPFC). Additionally, increasing evidence supports the involvement of the glutamatergic system in the pathophysiology of ADHD. Impulsivity, a core symptom in patients with ADHD, has been repeatedly associated with glutamatergic neurotransmission, and pharmacological treatment of ADHD has been shown to reduce glutamate levels in the prefrontal cortex.

METHODS

We investigated glutamate levels in the ACC and the DLPFC in 30 adults with ADHD and 30 healthy controls using single-voxel proton magnetic resonance spectroscopy on a 3T scanner.

RESULTS

The ADHD group showed a significant increase in glutamate in the ACC compared to controls, no significant differences in metabolites were observed in the DLPFC. Overall, glutamate levels in the ACC were positively correlated with ADHD symptomatology, especially hyperactivity and impulsivity symptoms.

CONCLUSIONS

Increased levels of glutamate in the ACC, which were positively correlated with hyperactivity and impulsivity, support the hypothesis that dysfunctional glutamatergic neurotransmission is at least partially responsible for ADHD symptomatology. Modulation of glutamatergic neurotransmission might therefore be a promising avenue for future pharmacological interventions.

Treatment Approaches to Attention Deficit Hyperactivity Disorder

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder in children, adolescents, and adults, with a prevalence estimated from 5% to 7% across cultures and approximately 2% to 5% in adults. This lifelong disorder challenges nurses to understand the basis of ADHD, analyze symptoms, differentiate coexisting disorders, gather health information from varied sources, and implement person-centered multimodal treatment. Nurses are poised to plan, and work with patients, families, and teachers in the community and school systems to optimize academic and occupational performance and improve quality of life. Pharmacotherapy, psychoeducation, and behavioral therapies are strong components of multimodal treatment planning.

Biomarkers, Genetics, and Epigenetic Studies to Explore the Neurocognitive Effects of Anesthesia in Children

Exposure to commonly used anesthetic agents causes widespread neuronal degeneration in the developing mammalian brain and has been shown to impair neurodevelopment in a variety of newborn vertebrate animal species. Although retrospective studies have suggested an association between anesthesia exposure in childhood and subsequent neurodevelopmental abnormalities, a causal relationship in humans has yet to be demonstrated. Unfortunately, translation of findings from bench to bedside is limited by several factors and histologic assessment in healthy children following exposure to anesthesia is not possible. Therefore, to prove that anesthesia-induced neurotoxicity occurs in humans, alternative approaches are necessary. Here we present the summary of a focus group discussion regarding the utility of biomarkers in translational studies of anesthetic neurotoxicity as part of The 2016 Pediatric Anesthesia NeuroDevelopmental Assessment (PANDA) Symposium at Columbia University Medical Center. The experts agreed that defining intermediate phenotypes using advanced neuroimaging as a biomarker is a highly feasible and reasonable modality to provide new insights into the deleterious effects of anesthetic exposure in the developing human brain and could illuminate a viable investigative path forward. Ultimately, well-defined intermediate phenotypes may allow us to fully understand the neurodevelopmental impact of anesthesia-induced neurotoxicity and permit us to develop the safest and most effective anesthetic strategies for the infants and children we care for.

Brain metabolite differences in one-year-old infants born small at term and association with neurodevelopmental outcome

OBJECTIVE

We assessed brain metabolite levels by magnetic resonance spectroscopy (MRS) in 1-year-old infants born small at term, as compared with infants born appropriate for gestational age (AGA), and their association with neurodevelopment at 2 years of age.

STUDY DESIGN

A total of 40 infants born small (birthweight <10th centile for gestational age) and 30 AGA infants underwent brain MRS at age 1 year on a 3-T scanner. Small-born infants were subclassified as late intrauterine growth restriction or as small for gestational age, based on the presence or absence of prenatal Doppler and birthweight predictors of an adverse perinatal outcome, respectively. Single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) data were acquired from the frontal lobe at short echo time. Neurodevelopment was evaluated at 2 years of age using the Bayley Scales of Infant and Toddler Development, Third Edition, assessing cognitive, language, motor, social-emotional, and adaptive behavior scales.

RESULTS

As compared with AGA controls, infants born small showed significantly higher levels of glutamate and total N-acetylaspartate (NAAt) to creatine (Cr) ratio at age 1 year, and lower Bayley Scales of Infant and Toddler Development, Third Edition scores at 2 years. The subgroup with late intrauterine growth restriction further showed lower estimated glutathione levels at age 1 year. Significant correlations were observed for estimated glutathione levels with adaptive scores, and for myo-inositol with language scores. Significant associations were also noticed for NAA/Cr with cognitive scores, and for glutamate/Cr with motor scores.

CONCLUSION

Infants born small show brain metabolite differences at 1 year of age, which are correlated with later neurodevelopment. These results support further research on MRS to develop imaging biomarkers of abnormal neurodevelopment.

A 40-bp VNTR polymorphism in the 3'-untranslated region of DAT1/SLC6A3 is associated with ADHD but not with alcoholism

Background

ADHD and alcoholism are psychiatric diseases with pathophysiology related to dopamine system. DAT1 belongs to the SLC6 family of transporters and is involved in the regulation of extracellular dopamine levels. A 40 bp variable number tandem repeat (VNTR) polymorphism in the 3′-untranslated region of DAT1/SLC6A3 gene was previously reported to be associated with various phenotypes involving disturbed regulation of dopaminergic neurotransmission.

Methods

A total of 1312 subjects were included and genotyped for 40 bp VNTR polymorphism of DAT1/SLC6A3 gene in this study (441 alcoholics, 400 non-alcoholic controls, 218 ADHD children and 253 non ADHD children). Using miRBase software, we have performed a computer analysis of VNTR part of DAT1 gene for presence of miRNA binding sites.

Results

We have found significant relationships between ADHD and the 40 bp VNTR polymorphisms of DAT1/SLC6A3 gene (P < 0.01). The 9/9 genotype appeared to reduce the risk of ADHD about 0.4-fold (p < 0.04). We also noted an occurrence of rare genotypes in ADHD (frequency different from controls at p < 0.01). No association between alcoholism and genotype frequencies of 40 bp VNTR polymorphism of DAT1/SLC6A3 gene has been detected.

Conclusions

We have found an association between 40 bp VNTR polymorphism of DAT1/SLC6A3 gene and ADHD in the Czech population; in a broad agreement with studies in other population samples. Furthermore, we detected rare genotypes 8/10, 7/10 and 10/11 present in ADHD boys only and identified miRNAs that should be looked at as potential novel targets in the research on ADHD.

Hyperactivity in the Gunn rat model of neonatal jaundice: age-related attenuation and emergence of gait deficits

BACKGROUND

Neonatal jaundice resulting from elevated unconjugated bilirubin occurs in 60-80% of newborn infants. Although mild jaundice is generally considered harmless, little is known about its long-term consequences. Recent studies have linked mild bilirubin-induced neurological dysfunction (BIND) with a range of neurological syndromes, including attention-deficit hyperactivity disorder. The goal of this study was to measure BIND across the lifespan in the Gunn rat model of BIND.

METHODS

Using a sensitive force plate actometer, we measured locomotor activity and gait in jaundiced (jj) Gunn rats versus their nonjaundiced (Nj) littermates. Data were analyzed for young adult (3-4 mo), early middle-aged (9-10 mo), and late middle-aged (17-20 mo) male rats.

RESULTS

jj rats exhibited lower body weights at all ages and a hyperactivity that resolved at 17-20 mo of age. Increased propulsive force and gait velocity accompanied hyperactivity during locomotor bouts at 9-10 mo in jj rats. Stride length did not differ between the two groups at this age. Hyperactivity normalized, and gait deficits, including decreased stride length, propulsive force, and gait velocity, emerged in the 17-20-mo-old jj rats.

CONCLUSION

These results demonstrate that, in aging, hyperactivity decreases with the onset of gait deficits in the Gunn rat model of BIND.