Season of birth, the dopamine D4 receptor gene and emotional eating in males and females. Evidence of a genetic plasticity factor?

Life-course effects of early life adversity exposure on eating behavior and metabolism

Environmental variations in early life influence brain development, making individuals more vulnerable to psychiatric and metabolic disorders. Early life stress (ELS) has a strong impact on the development of eating behavior. However, eating is a complex behavior, determined by an interaction between signals of energy homeostasis, neuronal circuits involved in its regulation, and circuits related to rewarding properties of the food. Although mechanisms underlying ELS-induced altered feeding behavior are not completely understood, evidence suggest that the effects of ELS on metabolic, mood, and emotional disorders, as well as reward system dysfunctions can contribute directly or indirectly to altered feeding behavior. The focus of this chapter is to discuss the effects of ELS on eating behavior and metabolism, considering different factors that control appetite such as energy homeostasis, hedonic properties of the food, emotional and cognitive status. After highlighting classic studies on the association between ELS and eating behavior alterations, we discuss how exposure to adversity can interact with genetics characteristics to predict variable outcomes.

Underlying Susceptibility to Eating Disorders and Drug Abuse: Genetic and Pharmacological Aspects of Dopamine D4 Receptors

The dopamine D4 receptor (DRD4) has a predominant expression in the prefrontal cortex (PFC), brain area strictly involved in the modulation of reward processes related to both food and drug consumption. Additionally, the human DRD4 gene is characterized by a variable number of tandem repeats (VNTR) in the exon 3 and, among the polymorphic variants, the 7-repeat (7R) allele appears as a contributing factor in the neurobiological mechanisms underlying drug abuse, aberrant eating behaviors and related comorbidities. The 7R variant encodes for a receptor with a blunted intracellular response to dopamine, and carriers of this polymorphism might be more tempted to enhance dopamine levels in the brain, through the overconsumption of drugs of abuse or palatable food, considering their reinforcing properties. Moreover, the presence of this polymorphism seems to increase the susceptibility of individuals to engage maladaptive eating patterns in response to negative environmental stimuli. This review is focused on the role of DRD4 and DRD4 genetic polymorphism in these neuropsychiatric disorders in both clinical and preclinical studies. However, further research is needed to better clarify the complex DRD4 role, by using validated preclinical models and novel compounds more selective for DRD4.

Genetically predicted gene expression of prefrontal DRD4 gene and the differential susceptibility to childhood emotional eating in response to positive environment

Genetic differential susceptibility states that individuals may vary both by exhibiting poor responses when exposed to adverse environments, and disproportionally benefiting from positive settings. The dopamine D4 receptor gene (DRD4) may be particularly implicated in these effects, including disturbed eating behaviors that might lead to obesity. Here, we explore differential susceptibility to positive environments according to the predicted genetically regulated gene expression of prefrontal cortex DRD4 gene. Using MAVAN as the discovery cohort (Maternal Adversity, Vulnerability and Neurodevelopment) and GUSTO as the replication cohort (Growing Up in Singapore Towards Healthy Outcomes), we analyzed the interaction between a) a Positive postnatal environmental score, that accounts for positive outcomes in the postnatal period and b) the genetically regulated gene expression of prefrontal DRD4, computed using a machine learning prediction method (PrediXcan). The outcome measures were the pro-intake domains (Emotional over-eating, Food Responsiveness, Food Enjoyment and Desire to Drink) from the Child Eating Behavior Questionnaire at 48 months of age (MAVAN) and 60 months of age (GUSTO). The interaction between the positive environment and the predicted prefrontal DRD4 gene expression was significant for emotional over-eating in MAVAN (β = -0.403, p < 0.02), in which the high gene expression group had more or less emotional eating according to the exposure to lower or higher positive environment respectively, showing evidence of differential susceptibility criteria. In the replication cohort, a similar result was found with the pro-intake domain Desire to drink (β = -0.583, p < 0.05). These results provide further evidence for the genetic differential susceptibility, accounting for the benefit of positive environments.

Child body mass index, genotype and parenting in the prediction of restrictive feeding

BACKGROUND

Restrictive feeding is implicated in pediatric obesity, and caregivers increase controlling feeding practices on the basis of higher child weight status. However, few studies have examined how child genetic and parenting characteristics together impact restrictive feeding.

OBJECTIVES

We examined whether child body mass index (BMI) status predicts caregiver use of restrictive feeding and if this association is moderated by (i) caregiver strategies to manage their children's distress and (ii) child variations in the catechol-O-methyltransferase (COMT) gene (Val¹⁵⁸ Met, rs4680).

METHODS

Participants included 126 Caucasian children (50% girls) and their caregivers who were participating in a larger study in the USA. Caregivers reported on their feeding practices and responses to child distress when children were 2.5-3.5 years of age. Child anthropometric measurements were also obtained. Restrictive feeding was assessed again 1-1.5 years later. Genomic DNA was obtained from saliva samples, and COMT-rs4680 was genotyped using TaqMan® methodology.

RESULTS

Child BMI percentile predicted subsequent caregiver restrictive feeding for children who were Met/Met and who had caregivers reporting higher use of negative responses to child distress. For Val carriers, BMI percentile predicted restrictive feeding when caregivers were below the mean on these responses.

CONCLUSIONS

Caregivers are at risk for use of restrictive feeding practices when their children are at higher BMI percentiles, and this association increases when caregivers use more ineffective stress regulation practices and their children are homozygous for the Met allele. Prevention programmes might focus on parenting behaviours that foster emotion regulation and consider variation in child responses to parenting.

Higher BMI is associated with stronger effects of social cues on everyday snacking behaviour

Discretionary food choices (snacks) contribute up to a third of the daily energy intake and potentially contribute to energy imbalance and weight gain. Individual snack intake behaviour is guided by internal and external cues, with social cues (seeing others eat, being alone) consistently showing large effects. A wide body of (mainly laboratory-based) research suggests marked differences in people's response to eating cues based on BMI. Here, we show that these BMI differences in cue responsiveness also pertain to everyday snacking behaviour. In two combined ecological momentary assessment studies, 122 participants with BMIs ranging from 18.34 to 45.71 kg/m² logged their everyday snacking behaviour in real-time over two weeks along with the presence or absence of social cues. Random-effects modelling showed that people with higher BMI were more likely to consume high-energy snacks when alone, and were more likely to consume low-energy snacks in the presence of others eating. This suggests BMI differences in cue responsiveness that are in line with impression management theory and underlines the importance of social cues for snacking behaviour and provides avenues for both theory and intervention development.

Fat Tissue Accretion in Children and Adolescents: Interplay between Food Responsiveness, Gender, and the Home Availability of Snacks

The appetitive trait “food responsiveness” is assumed to be a risk factor for adiposity gain primarily in obesogenic environments. So far, the reported results are inconsistent in school-aged children, possibly because these studies did not take into account important moderators such as gender and the food-environment. In order to better inform caregivers, clinicians and the developers of targeted obesity-prevention interventions on the conditions in which food responsiveness precedes adiposity gain, the current study investigated if this relationship is stronger in girls and in children exposed to a higher home availability of energy-dense snacks. Age- and sex-independent Fat and Lean Mass Index z-scores were computed based on air-displacement plethysmography at baseline and after 2 years in a community sample of 129 children (48.8% boys) aged 7.5–14 years at baseline. Parents reported at baseline on children's food responsiveness and the home availability of energy-dense snacks. Food responsiveness was a significant predictor of increases in Fat Mass Index z-scores over 2 years in girls but not boys. The home availability of energy-dense snacks did not significantly moderate the relation of food responsiveness with Fat Mass Index z-score changes. The results suggest that food responsiveness precedes accelerated fat tissue accretion in girls, and may inform targeted obesity-prevention interventions. Further, future research should investigate to which food-environmental parameters children high in food responsiveness mainly respond.

The association of eating styles with weight change after an intensive combined lifestyle intervention for children and adolescents with severe obesity

The main purpose of this prospective intervention study was to determine whether eating styles after an intensive, partly inpatient, one year combined lifestyle intervention are associated with weight change in the following year in severely obese children and adolescents. A total of 120 participants (8-19 years) with an average SDS-BMI of 3.41 (SD = 0.38) was included. Measurements were conducted at baseline (T0), at the end of treatment (T12) and at the end of follow up two years after baseline (T24). The primary outcome measurement was the ΔSDS-BMI between T12 and T24. As primary determinant of weight change after treatment, the participants eating styles were evaluated with the Dutch Eating Behavior Questionnaire - child report that measures external, emotional and restraint eating. The association between outcome and determinant was assessed in linear regression analyses. Complete data were available for 76 of the 120 participants. This study shows that for girls a higher score on restraint eating at T12 and a higher score on external eating at T12 were associated with more weight (re)gain in the year after treatment. No statistically significant association with emotional eating at T12 was found. In addition for girls a higher score on external eating at T0 was associated with more weight (re)gain in the year after treatment. Furthermore, the observed changes in eating styles suggest that on average it is possible to influence these with treatment, although the detected changes were different for girls and boys and for the different eating styles. More generally, this study indicates that for girls the levels of restraint and external eating after treatment were associated with the weight change during the following year.

TRIAL REGISTRATION

Netherlands Trial Register (NTR1678, registered 20-Feb-2009).