Unlike height, body mass index (BMI) and other obesity-related traits are strongly influenced by interactions between an individual’s genetic background and environmental factors.
A study with that finding, “Genotype-by-environment interactions inferred from genetic effects on phenotypic variability in the UK Biobank,” was published in Science Advances.
“Most human traits are complex because they are affected by many genetic and environmental factors as well as potential interactions between them. Despite the long history of effort, there has been limited success in identifying genotype-by-environment interaction (GEI) effects in humans,” the investigators wrote.
This is likely because, for a given individual, it is almost impossible to measure all possible environmental factors that a person has been exposed to that might influence their genetic background. In addition, GEI effects often are too small to be picked up in studies focused on a limited number of individuals.
A group of researchers from the University of Queensland decided to take an alternative approach and use known information from 13 complex traits, including BMI and height, to estimate which genetic variants could possibly explain the variability of those traits in a large group of 348,501 unrelated individuals of European origin.
After analyzing approximately 5.6 million genetic variants and cross-referencing that information with known data from the complex traits, they found that even individuals who had the same genetic variations could have strikingly different BMIs and other characteristics related to obesity (e.g., waist and hip circumference).
These observations suggest that BMI and other obesity-related traits were strongly influenced by environmental factors and their interactions with genetic factors.
On the other hand, even though they discovered a large number of genes that were involved in determining a person’s height, their effects did not vary substantially between people exposed to different environmental factors.
“Height can be affected by environment for sure, and height can also be affected by genes, but these things seem to be independent. It’s important to know this because it can enable us to search for elusive environmental factors that might be interfering with the function of a gene,” Jian Yang, PhD, said in a press release. Yang is a professor at the Institute for Molecular Bioscience at the University of Queensland and senior author of the study.
“It is also informative to design further research to understand why a genetic effect at a particular gene [location] is sensitive to environment — knowing the underlying mechanism will be highly important in terms of biology and medical research,” Yang said.
Investigators also cautioned these findings may be applicable only with complex traits that are influenced by several genes. Other types of traits may require different methodological approaches that should be explored in future studies.