Depending on a teenage girl’s early living conditions, the same gene variant will influence her to make healthy or unhealthy food choices, a new study suggests.
For girls who are carriers of the variant (DRD4 VNTR with 7 repeats), the crucial element is not the gene variant itself, but the interplay between the gene and the girl’s early socioeconomic environment that determines whether they have increased fat intake or healthier-than-average eating compared to their peers from the same class background.
The DRD4 repeat 7 is found in approximately 20 percent of the population and is known to be associated with obesity, especially in women. Boys who had the same gene variant were not affected in the same way.
“We found that among girls raised in poorer families, those with DRD4 repeat 7 had a higher fat intake than other girls from the same socioeconomic background,” says Laurette Dubé, scientific director of the McGill University Centre for the Convergence of Health and Economics.
“But we also found that girls with exactly the same gene variant who came from wealthier families, compared to these with the same economic conditions, had a lower fat intake. This suggests that it’s not the gene acting by itself, but rather how the gene makes an individual more sensitive to environmental conditions that determines ‘for better or worse’ a child’s preference for fat and consequent obesity as the years pass by.”
For the study, researchers used food diaries kept by the parents of close to 200 young Canadian children (average age of four) from the MAVAN birth cohort in Montreal, Quebec and Hamilton, Ontario. They calculated the percentages of fat, protein, and carbohydrates the children were taking in. They also measured the BMI of the children, and used saliva tests to identify which of the children were carriers of the DRD4 repeat 7 gene.
They then used family income as a way of measuring the quality of the socioeconomic environment in which the children were being raised, and an indirect marker of the food environment as well (availability of fruits and vegetables or fast food in the neighborhood, for instance).
The research, published in JAMA Pediatrics, builds on recent work by others that suggests certain genes, including DRD4 7 repeat, function as “plasticity genes.” This means that those with these gene variants may be more “open” to their environment, in general, than those without them. So that, depending on the environment in which the individual with the gene lives, it can either increase or decrease the risk for certain neurobehavioral conditions.
Because carriers of the DRD4 repeat 7 were already reported to have an increased risk of obesity, the researchers wondered whether it was, instead, a plasticity gene whose effects would vary depending on environment.
“We wondered if the higher fat intake already reported by us in 7-repeat girls could be modified by the social environment—and we showed that it can, as the fat intake will increase or decrease in 7-repeat girls according to their socioeconomic status,” says first author Patricia Silveira of the Universidade Federal do Rio Grande do Sul in Brazil.
“This is important because we change the focus from the gene (previously blamed for the risk for increased fat preference) to the environment, since the effects of the gene will vary according to the conditions in which the child is raised.”
“We previously assumed that the 7-repeat variant caused weight gain in these patients by increasing the rewarding aspects of certain foods. These new results suggest a different way that the gene might affect food choices” says Robert Levitan, a co-investigator on the project who has studied the DRD4 gene in female adult overeater populations.
Interestingly, the researchers found this effect to be true only in the girls that they tested. They speculate that this may be because, from an evolutionary standpoint, it may have been more important for girls to be able to gain weight easily to adapt to adverse conditions in order to reproduce. Another possibility is that at age four, it may simply be too early to see these effects in boys since boys and girls gain weight at different stages and may also have different behavioral responses to hunger and feelings of satiety.
“All we can say with certitude from this research is that the gene variant will influence food choices differently according to the environment, but we do not know how the gene is influencing food preferences,” Silveira says.
“These results underscore the importance of moving beyond a one-size-fits-all approach to childhood obesity prevention,” Dubé says.”We need to move towards targeted approaches that focus on populations that are particularly vulnerable to both genetic and environmental factors. Those who are biologically more vulnerable under adverse environments are those likely to be more responsive to improvements in their conditions.”
The Canadian Institutes of Health Research and National Institutes of Health funded the work.
Source: McGill University