A Washington State University lab says ancestral exposures to environmental compounds like the insecticide DDT may be a factor in high rates of obesity. The finding comes as DDT is getting a second look as a tool against malaria and aging "Silent Spring" researchers are worried.
"What your great-grandmother was exposed to during pregnancy, like DDT, may promote a dramatic increase in your susceptibility to obesity, and you will pass this on to your grandchildren in the absence of any continued exposures," says Michael Skinner, WSU professor and founder of its Center for Reproductive Biology. He and his colleagues document their finding in BMC Medicine.
When they exposed gestating rats to DDT, they saw no altered rates of obesity in the parent or first generation of offspring. But the disease developed in more than half the third-generation males and females. The researchers say the insecticide may be affecting how genes are turned on and off in the offspring of an exposed animal, even though its DNA sequences remain unchanged.
In other words, they are just guessing that DDT is involved at all, they are invoking unproven transgenerational epigenetic inheritance, which is like epigenetic inheritance where correlation-causation arrows don't exist.
In recent years, the Skinner lab has claimed epigenetic effects from a host of environmental toxicants, including plastics, pesticides, fungicides, dioxins, hydrocarbons and, of course, the plasticizer bisphenol-A or BPA. If they is fad chemical harm, they have written about it.
The frequency of DDT effects on obesity are far greater than other toxicants his lab has reviewed, he says.
He notes that more than 50 years have passed since Rachel Carson's book "Silent Spring" used anecdotal evidence to document DDT's effects on the environment. Its use was banned in the U.S but, says Skinner, "the third generation of people exposed in the 1950s is now of adult age and has a dramatic increase in diseases such as obesity."
Yes, grandkids of rich baby boomers are fat because of DDT, not because of too many pizzas.
Meanwhile, he says, groups like the U.S. Agency for International Development and the World Health Organization are backing the use of DDT to control malaria in developing countries. Both because it works and it is far less harmful than having millions of dead children.
"The potential transgenerational actions of DDT need to be considered in the risk-benefit analysis of its use," says Skinner.
First, let's prove that transgenerational epigenetic obesity due to DDT even exists.
Article: Michael K Skinner, Mohan Manikkam, Rebecca Tracey, Carlos Guerrero-Bosagna, Muksitul Haque and Eric E Nilsson, 'Ancestral dichlorodiphenyltrichloroethane (DDT) exposure promotes epigenetic transgenerational inheritance of obesity', BMC Medicine 2013, 11:228 doi:10.1186/1741-7015-11-228