Lack of Association of a Functional Polymorphism in the Serotonin Receptor Gene With Body Mass Index and Depressive Symptoms in a Large Meta-Analysis of Population Based Studies

Effect of exposure to endocrine disrupting chemicals in obesity and neurodevelopment: The genetic and microbiota link

Current evidence highlights the importance of the genetic component in obesity and neurodevelopmental disorders (attention-deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD) and intellectual disability (ID)), given that these diseases have reported an elevated heritability. Additionally, environmental stressors, such as endocrine disrupting chemicals (EDCs) have been classified as obesogens, neuroendocrine disruptors, and microbiota disrupting chemicals (MDCs). For this reason, the importance of this work lies in examining two possible biological mechanistic pathways linking obesity and neurodevelopmental/behavioural disorders: EDCs - gene and EDCs - microbiota interactions. First, we summarise the shared mechanisms of action of EDCs and the common genetic profile in the bidirectional link between obesity and neurodevelopment. In relation to interaction models, evidence from the reviewed studies reveals significant interactions between pesticides/heavy metals and gene polymorphisms of detoxifying and neurotransmission systems and metal homeostasis on cognitive development, ASD and ADHD symptomatology. Nonetheless, available literature about obesity is quite limited. Importantly, EDCs have been found to induce gut microbiota changes through gut-brain-microbiota axis conferring susceptibility to obesity and neurodevelopmental disorders. In view of the lack of studies assessing the impact of EDCs - gene interactions and EDCs - mediated dysbiosis jointly in obesity and neurodevelopment, we support considering genetics, EDCs exposure, and microbiota as interactive factors rather than individual contributors to the risk for developing obesity and neurodevelopmental disabilities at the same time.

Serotonin system genes contribute to the susceptibility to obesity in Black adolescents

OBJECTIVE

The importance of the central and peripheral serotonin systems in regulating energy balance and obesity development has been highlighted in animal models. Yet, the role of both serotonin systems has not been systematically assessed in humans. The purpose of this study was to investigate the association of genes within both serotonin systems with obesity outcomes in black adolescents.

METHODS

African-American adolescents (n = 1052) whose mothers participated the Memphis New Mother's Study were assessed. In total, 110 polymorphisms mapped to 10 serotonin genes were examined for their associations with standardized body mass index (BMI-z) scores and waist circumferences using generalized estimating equation models.

RESULTS

Over 39% of adolescents were overweight or had obesity. Three single nucleotide polymorphisms (SNPs) within TPH2, HTR3B, and SLC6A4, were significantly associated with BMI-z scores (p < 1.7 × 10-3). Two SNPs in TPH2 were nominally associated with waist circumferences. One SNP in HTR2C was associated with BMI-z scores (p = 0.001) and waist circumferences (p = 0.005) only in girls. Tissue-specific expression indicates that three identified genes are predominantly expressed in the brain.

CONCLUSION

The central serotonin system may play a key role in obesity development in black adolescents. Future studies are warranted to explore additional serotonin system genes and their potential obesogenic mechanisms in humans.

Systolic Blood Pressure and Socioeconomic Status in a large multi-study population

The present study used harmonized data from eight studies (N = 28,891) to examine the association between socioeconomic status (SES) and resting systolic blood pressure (SBP). The study replicates and extends our prior work on this topic by examining potential moderation of this association by race and gender. We also examined the extent to which body mass index (BMI), waist circumference (WC), and smoking might explain the association between SES and SBP. Data were available from six race/gender groups: 9200 Black women; 2337 Black men; 7248 White women; 6519 White men; 2950 Hispanic women; and 637 Hispanic men. Multivariable regression models showed that greater annual household income was associated with lower SBP in all groups except Hispanic men. The magnitude and form of this negative association differed across groups, with White women showing the strongest linear negative association. Among Black men and Hispanic women, the association was curvilinear: relatively flat among lower income levels, but then negative among higher income ranges. Education also was independently, negatively related to SBP, though evidence was weaker for race and gender differences in the strength of the association. Higher BMI and WC were associated with higher SBP, and current smoking with lower SBP. Inclusion of these risk factors resulted in only a modest change in the magnitude of the SBP and SES relation, accounting on average about 0.4 mmHg of the effect of income and 0.2 mmHg of the effect of education—effects unlikely to be clinically significant. Further understanding of mechanisms underlying the association between SBP and SES may improve risk stratification in clinical settings and potentially inform interventions aimed at reductions in social disparities in health.

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Harmonized data (n = 28,291) examined association between blood pressure and socioeconomic status.

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Replication and extension of prior work by examining potential moderation of this association by race and gender.

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Further understanding of this association inform interventions aimed at reductions in social disparities in health.