A study of mice found that obesity can change the genes in a father's sperm, which results in the delayed development of their daughter's breast tissue - and can eventually lead to cancer.
One of the study's lead authors, Sonia de Assis, said: "Of course our study was done in mice, but it recapitulates recent findings in humans which show that obese men have significant epigenetic alterations in their sperm compared to lean men."
This is one of the first animal studies to investigate a link between paternal obesity and breast cancer in offspring.
Obese male mice and normal weight female mice produce female offspring that are overweight at birth. This results in delayed development of their offspring's breast tissue and increased rates of breast cancer, scientists said.
Georgetown Lombardi Comprehensive Cancer Center researchers found evidence that obesity changes the microRNA (miRNA) signature — epigenetic regulators of gene expression — in both the dad’s sperm and the daughter’s breast tissue.
Epigenetic regulators can switch genes on or off. They enable external or environmental factors - such as the effects of a person's lifestyle - to be passed on to offspring.
Gene expression is the process by which specific genes are activated to produce a required protein.
Researchers believe miRNAs may carry epigenetic information from obese dads to their daughters.
According to scientists, these miRNAs can affect alterations in body weight and other molecular pathways linked to cancer development.
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"This study provides evidence that, in animals, a fathers’ body weight at the time of conception affects both their daughters’ body weight both at birth and in childhood as well as their risk of breast cancer later in life," said Sonia de Assis, an assistant professor in the department of oncology at Georgetown Lombardi.
"Of course our study was done in mice, but it recapitulates recent findings in humans which show that obese men have significant epigenetic alterations in their sperm compared to lean men.
"Our animal study suggests that those epigenetic alterations in sperm may have consequences for next generation cancer risk."
The next step is to see if the same associations regarding breast cancer risk hold for daughters of human fathers who are overweight around the time of conception.
de Assis added: "Until we know about this association in men, we should stick to what we all know is good advice: women — and men — should eat a balanced diet, keep a healthy body weight and life-style not only for their own benefit but also to give their offspring’s the best chances of being healthy."
The study is published online in the journal Nature.