Results of a global research project published in the prestigious Nature journal today shows there is a genetic link between birth weight and susceptibility to adult diseases, such as type 2 diabetes and cardiovascular disease.
Director of the University of South Australia’s Centre for Population Health, Professor Elina Hypponen, was a senior collaborator in this ground-breaking study that also identifies the genetic differences that help to explain why some babies are born bigger or smaller than others.
The study - Genome-wide associations for birth weight and correlations with adult disease - involved more than 160 international researchers from 17 countries who are members of the Early Growth Genetics (EGG) Consortium and found a substantial proportion (at least one-sixth) of the variation in birth weight is due to genetic differences.
This is seven to eight times more variation than can be explained by environmental factors already known to influence birthweight, such as the mother smoking during pregnancy or her body mass index (a measure of obesity) before pregnancy starts.
“The role of maternal factors is well-known, however, this study has shown that genetic effects on birth weight are also very important,” Prof Hypponen says.
“Early life nutritional environment has an influence on long term health, for example babies who are born very small are at increased risk of diabetes and heart disease later in life.
“In other words, risk of disease can be ‘programmed’ by events in early life.
“These types of long term health effects of birth weight have been typically taken to reflect the impact of the nutritional environment in which the fetus develops. Our study suggests that the link between birth weight and later risk of disease will actually be, at least in part, due to shared genetic factors.
“It is interesting that this study also showed, that those genes which are imprinted, were enriched among the genetic signals influencing birth weight. These are genes which the mother can turn on or off in order to regulate the allocation of her ‘resources’ to the developing fetus.
“According to so called ‘parental conflict hypothesis’ genes from the father aim at maximising fetal growth, while the mother will aim to restrict the use of her valuable resources.
“This is the first time we have large scale, systematic evidence to suggest that these influences will affect normal variation in birth weight,” Prof Hypponen says.
The genetic differences throughout the genomes of nearly 154,000 people from across the world were analysed and by matching their genetic profiles to information on birth weight the team of researchers found sixty genomic regions associated with birth weight, most of which had not previously been identified.
As well as providing vital new information, Prof Hypponen says the study highlights the value of large-scale international research collaborations.
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