Long-term attention deficits combined with subcortical and cortical structural central nervous system alterations in young adults born small for gestational age

Long-Term Neurologic Consequences following Fetal Growth Restriction: The Impact on Brain Reserve

BACKGROUND

Fetal growth restriction (FGR) corresponds to the fetus's inability to achieve an adequate weight gain based on genetic potential and gestational age. It is an important cause of morbidity and mortality.

SUMMARY

In this review, we address the challenges of diagnosis and classification of FGR. We review how chronic fetal hypoxia impacts brain development. We describe recent advances on placental and fetal brain imaging using magnetic resonance imaging and how they offer new noninvasive means to study growth restriction in humans. We go on to review the impact of FGR on brain integrity in the neonatal period, later childhood, and adulthood and review available therapies.

KEY MESSAGES

FGR consequences are not limited to the perinatal period. We hypothesize that impaired brain reserve, as defined by structure and size, may predict some concerning epidemiological data of impaired cognitive outcomes and dementia with aging in this group of patients.

Thyroid hormone analogues: Promising therapeutic avenues to improve the neurodevelopmental outcomes of intrauterine growth restriction

Intrauterine growth restriction (IUGR) is a pregnancy complication impairing fetal growth and development. The compromised development is often attributed to disruptions of oxygen and nutrient supply from the placenta, resulting in a number of unfavourable physiological outcomes with impaired brain and organ growth. IUGR is associated with compromised development of both grey and white matter, predisposing the infant to adverse neurodevelopmental outcomes, including long-lasting cognitive and motor difficulties. Cerebral thyroid hormone (TH) signalling, which plays a crucial role in regulating white and grey matter development, is dysregulated in IUGR, potentially contributing to the neurodevelopmental delays associated with this condition. Notably, one of the major TH transporters, monocarboxylate transporter-8 (MCT8), is deficient in the fetal IUGR brain. Currently, no effective treatment to prevent or reverse IUGR exists. Management strategies involve close antenatal monitoring, management of maternal risk factors if present and early delivery if IUGR is found to be severe or worsening in utero. The overall goal is to determine the most appropriate time for delivery, balancing the risks of preterm birth with further fetal compromise due to IUGR. Drug candidates have shown either adverse effects or little to no benefits in this vulnerable population, urging further preclinical and clinical investigation to establish effective therapies. In this review, we discuss the major neuropathology of IUGR driven by uteroplacental insufficiency and the concomitant long-term neurobehavioural impairments in individuals born IUGR. Importantly, we review the existing clinical and preclinical literature on cerebral TH signalling deficits, particularly the impaired expression of MCT8 and their correlation with IUGR. Lastly, we discuss the current evidence on MCT8-independent TH analogues which mimic the brain actions of THs by being metabolised in a similar manner as promising, albeit underappreciated approaches to promote grey and white matter development and improve the neurobehavioural outcomes following IUGR.

The persistent effects of foetal growth on child and adolescent mental health: longitudinal evidence from a large population-based cohort

Low birth weight for one's gestational age is associated with higher rates of child psychopathology, however, most studies assess psychopathology cross-sectionally. The effect of such foetal growth restriction appears to be strongest for attention problems in childhood, although adult studies have found associations with a range of outcomes, from depression to psychosis. We explore how associations between foetal growth and psychopathology change across age, and whether they vary by sex. We used a large nationally representative cohort of children from Ireland (N ~ 8000). Parents completed the Strengths and Difficulties Questionnaire (SDQ) at 3 time points (age 9, 13 and 17). Outcomes included a total problems scale and subscales measuring attention/hyperactivity, peer, conduct and emotional problems. Foetal growth had significant associations with all problem scales, even after controlling for sex, socioeconomic factors and parental mental health. The magnitude of these effects was small but relatively stable across ages 9-17. In males, foetal growth had the strongest associations with attention/hyperactivity and peer problems, whereas females showed more widespread associations with all four subscales. There was a trend for the association between foetal growth and emotional problems to increase with advancing age, approaching the borderline-abnormal threshold by age 17. Reduced foetal growth predicted persistently higher scores on all measured aspects of child and adolescent psychopathology. Associations with child attention/hyperactivity may generalize to a wider array of adult psychopathologies via adolescent-onset emotional problems. Future studies should explore potential age-dependent effects of foetal growth into the early 20s.

Specific Learning Disorders in Children and Adolescents with Obesity

Specific learning disorders (SLDs) are the most frequently diagnosed developmental disorders in childhood. Different neurocognitive patterns have been found in patients with overweight and obesity, but no data on childhood obesity and SLDs have been reported. To increase our understanding of the relationship between neuropsychological developmental and obesity, we assessed the prevalence of SLD in a pediatric population with obesity. We retrospectively included 380 children and adolescents with obesity. For all participants, auxological, metabolic, demographic features, relationship and social skills, anamnestic data on pregnancy and the perinatal period, stages of development and family medical history were reviewed. SLD was defined according to the DSM-5 criteria. A group of 101 controls of normal weight was included. The overall prevalence of SLD was 10.8%, and SLD was more prevalent in patients with obesity (p < 0.001), with male predominance (p = 0.01). SGA was associated with SLD (p = 0.02). Speech retardation (p < 0.001), limited relationships with peers (p < 0.001) and didactic support (p < 0.001) were noted in the SLD group compared to the group without SLD. A higher prevalence of family history of neuropsychiatric disorders was observed in the SLD group (p = 0.04). A higher fasting glucose level was detected in patients with obesity and SLD compared to subjects without SLD (p = 0.01). An association between obesity and SLD could not be excluded, and an overlap of pathogenic factors for both conditions should be considered.

Neurocognitive function and associations with mental health in adults born preterm with very low birthweight or small for gestational age at term

Objectives

To assess neurocognitive function in adults born with low birthweight compared with controls and to explore associations between neurocognitive function and psychopathology in these groups.

Methods

In this prospective cohort study, one group born preterm with very low birthweight (VLBW: birthweight <1,500 g, n = 53), one group born small for gestational age at term (SGA: birthweight <10th percentile, n = 63) and one term-born control group (birthweight ≥10th percentile, n = 81) were assessed with neurocognitive tests, diagnostic interviews, and self-report questionnaires at 26 years of age.

Results

The VLBW group scored significantly below the control group on several neurocognitive measures, including IQ measures, psychomotor speed, verbal fluency, aspects of visual learning and memory, attention, social cognition, working memory and fine motor speed. The SGA group consistently scored at an intermediate level between the VLBW and the control group and had significantly lower scores than controls on Performance IQ and psychomotor speed, including switching. In the VLBW group, associations were found between lower spatial working memory and the presence of anxiety disorders, internalizing and attention problems, and autistic traits. Furthermore, lower Full scale IQ was associated with attention problems when adjusting for sex and parental socioeconomic status.

Conclusion

Adults born preterm with VLBW or born term SGA displayed neurocognitive difficulties. Spatial working memory was associated with difficulties with attention, anxiety, and social function of VLBW adults. The finding and its clinical applicability should be further explored.

Hippocampal neurogenesis and memory in adolescence following intrauterine growth restriction

Intrauterine growth restriction (IUGR) is associated with hippocampal alterations that can increase the risk of short-term memory impairments later in life. Despite the role of hippocampal neurogenesis in learning and memory, research into the long-lasting impact of IUGR on these processes is limited. We aimed to determine the effects of IUGR on neuronal proliferation, differentiation and morphology, and on memory function at adolescent equivalent age. At embryonic day (E) 18 (term ∼E22), placental insufficiency was induced in pregnant Wistar rats via bilateral uterine vessel ligation to generate IUGR offspring (n = 10); control offspring (n = 11) were generated via sham surgery. From postnatal day (P) 36-44, spontaneous location recognition (SLR), novel object location and recognition (NOL, NOR), and open field tests were performed. Brains were collected at P45 to assess neurogenesis (immunohistochemistry), dendritic morphology (Golgi staining), and brain-derived neurotrophic factor expression (BDNF; Western blot analysis). In IUGR versus control rats there was no difference in object preference in the NOL or NOR, the similar and dissimilar condition of the SLR task, or in locomotion and anxiety-like behavior in the open field. There was a significant increase in the linear density of immature neurons (DCX+) in the subgranular zone (SGZ) of the dentate gyrus (DG), but no difference in the linear density of proliferating cells (Ki67+) in the SGZ, nor in areal density of mature neurons (NeuN+) or microglia (Iba-1+) in the DG in IUGR rats compared to controls. Dendritic morphology of dentate granule cells did not differ between groups. Protein expression of the BDNF precursor (pro-BDNF), but not mature BDNF, was increased in the hippocampus of IUGR compared with control rats. These findings highlight that while the long-lasting prenatal hypoxic environment may impact brain development, it may not impact hippocampal-dependent learning and memory in adolescence.

The Association between Delivery of Small-for-Gestational-Age Neonate and Their Risk for Long-Term Neurological Morbidity

Small-for-gestational-age (SGA) is defined as a birth weight below the 10th or below the 5th percentile for a specific gestational age and sex. Previous studies have demonstrated an association between SGA neonates and long-term pediatric morbidity. In this research, we aim to evaluate the possible association between small-for-gestational-age (SGA) and long-term pediatric neurological morbidity. A population-based retrospective cohort analysis was performed, comparing the risk of long-term neurological morbidities in SGA and non-SGA newborns delivered between the years 1991 to 2014 at a single regional medical center. The neurological morbidities included hospitalizations as recorded in hospital records. Neurological hospitalization rate was significantly higher in the SGA group (3.7% vs. 3.1%, OR = 1.2, 95% CI 1.1–1.3, p < 0.001). A significant association was noted between neonates born SGA and developmental disorders (0.2% vs. 0.1%, OR = 2.5, 95% CI 1.7–3.8, p < 0.001). The Kaplan-Meier survival curve demonstrated a significantly higher cumulative incidence of neurological morbidity in the SGA group (log-rank p < 0.001). In the Cox proportional hazards model, which controlled for various Confounders, SGA was found to be an independent risk factor for long-term neurological morbidity (adjusted hazard ratio( HR) = 1.18, 95% CI 1.07–1.31, p < 0. 001). In conclusion, we found that SGA newborns are at an increased risk for long-term pediatric neurological morbidity.

Community initiated kangaroo mother care and early child development in low birth weight infants in India-a randomized controlled trial

BACKGROUND

In a randomized controlled trial (RCT) with 8402 stable low birthweight (LBW) infants, majority being late preterm or term small for gestational age, community-initiated KMC (ciKMC) showed a significant improvement in survival. However, the effect of ciKMC on neurodevelopment is unclear. This is important to elucidate as children born with low birth weight are at high risk of neurodevelopmental deficits. In the first 552 stable LBW infants enrolled in the above trial, we evaluated the effect of ciKMC on neurodevelopmental outcomes during infancy.

METHOD

This RCT was conducted among 552 stable LBW infants, majorly late preterm or term small for gestational age infants without any problems at birth and weighing 1500-2250 g at birth. The intervention comprised of promotion of skin-to-skin contact and exclusive breastfeeding by trained intervention delivery team through home visits. The intervention group mother-infant-dyads were supported to practice ciKMC till day 28 after birth or until the baby wriggled-out. All infants in the intervention and control groups received Home Based Post Natal Care (HBPNC) visits by government health workers. Cognitive, language, motor and socio-emotional outcomes were assessed at infant-ages 6- and 12-months using Bayley Scale of Infant Development (BSID-III). Other outcomes measured were infant temperament, maternal depression, maternal sense of competence, mother-infant bonding and home-environment. We performed post-hoc equivalence testing using two one-sided tests of equivalence (TOST) to provide evidence that ciKMC does not do harm in terms of neurodevelopment.

RESULTS

In the intervention arm, the median (IQR) time to initiate ciKMC was 48 (48 to 72) hours after birth. The mean (SD) duration of skin-to-skin-contact was 27.9 (3.9) days with a mean (SD) of 8.7 (3.5) hours per day. We did not find significant effect of ciKMC on any of the child developmental outcomes during infancy. The TOST analysis demonstrated that composite scores for cognitive, language and motor domains at 12 months among the study arms were statistically equivalent.

CONCLUSION

Our study was unable to capture any effect of ciKMC on neurodevelopment during infancy in this sample of stable late preterm or term small for gestational age infants. Long term follow-up may provide meaningful insights.

TRIAL REGISTRATION

The trial is registered at clinicaltrials.gov NCT02631343 dated February 17, 2016; Retrospectively registered.

Amygdala 5-HTT Gene Network Moderates the Effects of Postnatal Adversity on Attention Problems: Anatomo-Functional Correlation and Epigenetic Changes

Variations in serotoninergic signaling have been related to behavioral outcomes. Alterations in the genome, such as DNA methylation and histone modifications, are affected by serotonin neurotransmission. The amygdala is an important brain region involved in emotional responses and impulsivity, which receives serotoninergic input. In addition, studies suggest that the serotonin transporter gene network may interact with the environment and influence the risk for psychiatric disorders. We propose to investigate whether/how interactions between the exposure to early life adversity and serotonin transporter gene network in the amygdala associate with behavioral disorders. We constructed a co-expression-based polygenic risk score (ePRS) reflecting variations in the function of the serotonin transporter gene network in the amygdala and investigated its interaction with postnatal adversity on attention problems in two independent cohorts from Canada and Singapore. We also described how interactions between ePRS-5-HTT and postnatal adversity exposure predict brain gray matter density and variation in DNA methylation across the genome. We observed that the expression-based polygenic risk score, reflecting the function of the amygdala 5-HTT gene network, interacts with postnatal adversity, to predict attention and hyperactivity problems across both cohorts. Also, both postnatal adversity score and amygdala ePRS-5-HTT score, as well as their interaction, were observed to be associated with variation in DNA methylation across the genome. Variations in gray matter density in brain regions linked to attentional processes were also correlated to our ePRS score. These results confirm that the amygdala 5-HTT gene network is strongly associated with ADHD-related behaviors, brain cortical density, and epigenetic changes in the context of adversity in young children.

Prefrontal Cortex Dopamine Transporter Gene Network Moderates the Effect of Perinatal Hypoxic-Ischemic Conditions on Cognitive Flexibility and Brain Gray Matter Density in Children

BACKGROUND

Genetic polymorphisms of the dopamine transporter gene (DAT1) and perinatal complications associated with poor oxygenation are risk factors for attentional problems in childhood and may show interactive effects.

METHODS

We created a novel expression-based polygenic risk score (ePRS) reflecting variations in the function of the DAT1 gene network (ePRS-DAT1) in the prefrontal cortex and explored the effects of its interaction with perinatal hypoxic-ischemic-associated conditions on cognitive flexibility and brain gray matter density in healthy children from two birth cohorts-MAVAN from Canada (n = 139 boys and girls) and GUSTO from Singapore (n = 312 boys and girls).

RESULTS

A history of exposure to several perinatal hypoxic-ischemic-associated conditions was associated with impaired cognitive flexibility only in the high-ePRS group, suggesting that variation in the prefrontal cortex expression of genes involved in dopamine reuptake is associated with differences in this behavior. Interestingly, this result was observed in both ethnically distinct birth cohorts. Additionally, parallel independent component analysis (MAVAN cohort, n = 40 children) demonstrated relationships between single nucleotide polymorphism-based ePRS and gray matter density in areas involved in executive (cortical regions) and integrative (bilateral thalamus and putamen) functions, and these relationships differ in children from high and low exposure to hypoxic-ischemic-associated conditions.

CONCLUSIONS

These findings reveal that the impact of conditions associated with hypoxia-ischemia on brain development and executive functions is moderated by genotypes associated with dopamine signaling in the prefrontal cortex. We discuss the potential impact of innovative genomic and environmental measures for the identification of children at high risk for impaired executive functions.