Socioeconomic Disparities in Childhood Obesity Risk: Association With an Oxytocin Receptor Polymorphism

Abstract

IMPORTANCE Pediatricians are paying increased attention to the effects of socioeconomic status (SES) on children's health. Low SES is a robust predictor of obesity across the life course and may interact with genes affecting metabolism to influence obesity risk. Recent animal literature and burgeoning human research suggest that the hormone oxytocin (OT) may be important for metabolic regulation. To date, this association has not been examined in children.OBJECTIVES To examine whether an OT receptor polymorphism (rs53576) interacts with SES, potentially exacerbating and buffering the effects of stress, to predict anthropometry during childhood, and based on differential neurobiological susceptibility theory, to test whether carriers of the A allele of the OXTR gene, compared with GG genotyped individuals, would be most sensitive to the effects of SES on anthropometry for better or for worse. DESIGN, SETTING, AND PARTICIPANTSIn this observational study, families were recruited from public school classrooms and enrolled in the Peers and Wellness Study (PAWS), which examined the effects of social status on health. Families were assessed during children's kindergarten year (fall semester of 2003, 2004, and 2005) and again during middle childhood (2009-2011) for a follow-up assessment that included anthropometric measures and DNA collection. The dates of the analysis were January 2015 to June 2016. EXPOSURES Socioeconomic disparities.MAIN OUTCOMES AND MEASURES Child body mass index z score (BMIz) and triceps skinfold thickness. Family SES was collected through questionnaires mailed to homes. Body measurements and DNA were collected in homes by trained research assistants. RESULTSFrom the original community sample of 338 typically developing children, participants were 186 socioeconomically and racially/ethnically diverse children (mean age, 10.3 years; age range, 9.4-11.3 years; 93 females [50%]) who had sufficient data at the follow-up assessment for inclusion in this study. Among 97 A allele carriers, a 1-SD increase in SES was associated with a decrease in BMIz of 0.28 (95% CI, −0.47 to −0.09) and a decrease in skinfold thickness of 0.95 (95% CI, −1.77 to −0.12) mm, such that they exhibited the highest BMIz and skinfold thickness in contexts of low SES but exhibited the lowest BMIz and skinfold thickness in contexts of high SES. Socioeconomic status was unrelated to BMIz (95% CI, −0.21 to 0.26) or skinfold thickness (95% CI, −0.42 to 1.45) for 89 GG genotyped children. CONCLUSIONS AND RELEVANCEThese findings advance etiologic understanding of childhood obesity, highlighting complex effects of SES on child health and adding to growing evidence that OT relates to human obesity risk. The results also support differential neurobiological susceptibility theory, suggesting that the A allele renders individuals more sensitive to both positive and negative health effects of socioecological context.

The effects of oxytocin on eating behaviour and metabolism in humans

“…In these patients, fairly low levels of oxytocin have been reported in the CSF 99 , and post-mortem studies have identified a reduced number of oxytocin-expressing neurons in the PVN of the hypothalamus 100 . In addition, polymorphisms of the oxytocin receptor (A-allele of rs53576) are associated with increased risk of obesity in children of low socioeconomic status 101 .…”

Current findings on the role of oxytocin in the regulation of food intake

“…It has been speculated that the relatively elevated cholesterol levels in obesity may boost highaffinity binding of oxytocin to the OXTR [27,141]. Support for the assumption that oxytocin signaling is altered in obesity comes from studies linking the OXTR gene to body weight [142,143] and the observation that overweight subjects as well as newly diagnosed diabetic patients display lower circulating concentrations of oxytocin when compared to normalweight controls [144]. Patients with Prader-Willi syndrome, who suffer from hyperphagic obesity as a consequence of persistent food craving, display a 40% reduction in the number and size of oxytocin neurons [145].…”

Racial Disparities in Obesity Treatment

“…When raised in high SES environments, lower BMIs were observed. The obesity risk for children with the GG genotype was not influenced by SES [29]. Similarly, the National Health Interview Survey (1997—2005) found that foreign born men and women from Africa have a lower likelihood of obesity than African American’s born in the USA [30].…”

“…Similarly, the National Health Interview Survey (1997—2005) found that foreign born men and women from Africa have a lower likelihood of obesity than African American’s born in the USA [30]. It is evident that health outcomes can be affected by certain genetic predispositions, but there is also an interplay between genetics and environmental factors [29]. …”